From 35fe0e5d9a98afa13a2db58af4a038cdc8f30dff Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Tue, 22 Oct 2019 16:43:24 +0200
Subject: [PATCH 001/122] Added first draft of AqlCallObject

---
 arangod/Aql/AqlCall.h | 47 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 47 insertions(+)
 create mode 100644 arangod/Aql/AqlCall.h

diff --git a/arangod/Aql/AqlCall.h b/arangod/Aql/AqlCall.h
new file mode 100644
index 000000000000..d0989fdab2b8
--- /dev/null
+++ b/arangod/Aql/AqlCall.h
@@ -0,0 +1,47 @@
+////////////////////////////////////////////////////////////////////////////////
+/// DISCLAIMER
+///
+/// Copyright 2019 ArangoDB GmbH, Cologne, Germany
+///
+/// Licensed under the Apache License, Version 2.0 (the "License");
+/// you may not use this file except in compliance with the License.
+/// You may obtain a copy of the License at
+///
+///     http://www.apache.org/licenses/LICENSE-2.0
+///
+/// Unless required by applicable law or agreed to in writing, software
+/// distributed under the License is distributed on an "AS IS" BASIS,
+/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+/// See the License for the specific language governing permissions and
+/// limitations under the License.
+///
+/// Copyright holder is ArangoDB GmbH, Cologne, Germany
+///
+/// @author Michael Hackstein
+////////////////////////////////////////////////////////////////////////////////
+
+#ifndef ARANGOD_AQL_AQL_CALL_H
+#define ARANGOD_AQL_AQL_CALL_H 1
+
+#include "Aql/ExecutionBlock.h"
+
+#include <cstddef>
+#include <variant>
+
+namespace arangodb {
+namespace aql {
+struct AqlCall {
+  class Infinity {};
+  using Limit = std::variant<size_t, Infinity>;
+
+  std::size_t offset{0};
+  // TODO: The defaultBatchSize function could move into this file instead
+  Limit batchSize{ExecutionBlock::DefaultBatchSize()};
+  Limit limit{Infinity{}};
+  bool fullCount{false};
+};
+
+}  // namespace aql
+}  // namespace arangodb
+
+#endif
\ No newline at end of file

From ead968c786aa74f930ecf6b3856b04b4e8fafa54 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tobias=20G=C3=B6dderz?= <tobias@arangodb.com>
Date: Tue, 22 Oct 2019 17:15:33 +0200
Subject: [PATCH 002/122] Added AqlItemBlockInputRange

---
 arangod/Aql/AllRowsFetcher.h           |  8 ++++
 arangod/Aql/AqlItemBlockInputRange.cpp | 64 ++++++++++++++++++++++++++
 arangod/Aql/AqlItemBlockInputRange.h   | 55 ++++++++++++++++++++++
 arangod/Aql/SingleRowFetcher.h         |  8 ++++
 arangod/CMakeLists.txt                 |  1 +
 5 files changed, 136 insertions(+)
 create mode 100644 arangod/Aql/AqlItemBlockInputRange.cpp
 create mode 100644 arangod/Aql/AqlItemBlockInputRange.h

diff --git a/arangod/Aql/AllRowsFetcher.h b/arangod/Aql/AllRowsFetcher.h
index 73a96a9e4c9b..9ac5f2d3300e 100644
--- a/arangod/Aql/AllRowsFetcher.h
+++ b/arangod/Aql/AllRowsFetcher.h
@@ -92,11 +92,19 @@ class AllRowsFetcher {
 
   TEST_VIRTUAL ~AllRowsFetcher() = default;
 
+  using DataRange = std::shared_ptr<AqlItemMatrix>;
+
  protected:
   // only for testing! Does not initialize _dependencyProxy!
   AllRowsFetcher() = default;
 
  public:
+  // TODO implement and document
+  std::tuple<ExecutionState, size_t, DataRange> execute(/* TODO: add"justDoIt"-style parameter */) {
+    TRI_ASSERT(false);
+    THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
+  }
+
   /**
    * @brief Fetch one new AqlItemRow from upstream.
    *        **Guarantee**: the pointer returned is valid only
diff --git a/arangod/Aql/AqlItemBlockInputRange.cpp b/arangod/Aql/AqlItemBlockInputRange.cpp
new file mode 100644
index 000000000000..57bcf986d3e0
--- /dev/null
+++ b/arangod/Aql/AqlItemBlockInputRange.cpp
@@ -0,0 +1,64 @@
+////////////////////////////////////////////////////////////////////////////////
+/// DISCLAIMER
+///
+/// Copyright 2019 ArangoDB GmbH, Cologne, Germany
+///
+/// Licensed under the Apache License, Version 2.0 (the "License");
+/// you may not use this file except in compliance with the License.
+/// You may obtain a copy of the License at
+///
+///     http://www.apache.org/licenses/LICENSE-2.0
+///
+/// Unless required by applicable law or agreed to in writing, software
+/// distributed under the License is distributed on an "AS IS" BASIS,
+/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+/// See the License for the specific language governing permissions and
+/// limitations under the License.
+///
+/// Copyright holder is ArangoDB GmbH, Cologne, Germany
+///
+/// @author Tobias Gödderz
+////////////////////////////////////////////////////////////////////////////////
+
+#include "AqlItemBlockInputRange.h"
+
+using namespace arangodb;
+using namespace arangodb::aql;
+
+AqlItemBlockInputRange::AqlItemBlockInputRange(AqlItemBlockInputRange::State state,
+                                               SharedAqlItemBlockPtr const& block, std::size_t index)
+    : _finalState{state}, _block{block}, _rowIndex{index} {}
+
+AqlItemBlockInputRange::AqlItemBlockInputRange(AqlItemBlockInputRange::State state,
+                                               SharedAqlItemBlockPtr&& block,
+                                               std::size_t index) noexcept
+    : _finalState{state}, _block{std::move(block)}, _rowIndex{index} {}
+
+std::pair<AqlItemBlockInputRange::State, InputAqlItemRow> AqlItemBlockInputRange::peek() {
+  if (indexIsValid()) {
+    return std::make_pair(state(), InputAqlItemRow{_block, _rowIndex});
+  }
+  return std::make_pair(state(), InputAqlItemRow{CreateInvalidInputRowHint{}});
+}
+
+std::pair<AqlItemBlockInputRange::State, InputAqlItemRow> AqlItemBlockInputRange::next() {
+  auto res = peek();
+  ++_rowIndex;
+  if (!indexIsValid()) {
+    _block = nullptr;
+    _rowIndex = 0;
+  }
+  return res;
+}
+
+bool AqlItemBlockInputRange::indexIsValid() const noexcept {
+  return _block != nullptr && _rowIndex < _block->size();
+}
+
+bool AqlItemBlockInputRange::moreRowsAfterThis() const noexcept {
+  return indexIsValid() && _rowIndex + 1 < _block->size();
+}
+
+AqlItemBlockInputRange::State AqlItemBlockInputRange::state() const noexcept {
+  return moreRowsAfterThis() ? State::HASMORE : _finalState;
+}
diff --git a/arangod/Aql/AqlItemBlockInputRange.h b/arangod/Aql/AqlItemBlockInputRange.h
new file mode 100644
index 000000000000..bdfc710c9f05
--- /dev/null
+++ b/arangod/Aql/AqlItemBlockInputRange.h
@@ -0,0 +1,55 @@
+////////////////////////////////////////////////////////////////////////////////
+/// DISCLAIMER
+///
+/// Copyright 2019 ArangoDB GmbH, Cologne, Germany
+///
+/// Licensed under the Apache License, Version 2.0 (the "License");
+/// you may not use this file except in compliance with the License.
+/// You may obtain a copy of the License at
+///
+///     http://www.apache.org/licenses/LICENSE-2.0
+///
+/// Unless required by applicable law or agreed to in writing, software
+/// distributed under the License is distributed on an "AS IS" BASIS,
+/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+/// See the License for the specific language governing permissions and
+/// limitations under the License.
+///
+/// Copyright holder is ArangoDB GmbH, Cologne, Germany
+///
+/// @author Tobias Gödderz
+////////////////////////////////////////////////////////////////////////////////
+
+#ifndef ARANGOD_AQL_AQLITEMBLOCKINPUTITERATOR_H
+#define ARANGOD_AQL_AQLITEMBLOCKINPUTITERATOR_H
+
+#include "Aql/InputAqlItemRow.h"
+#include "Aql/SharedAqlItemBlockPtr.h"
+
+namespace arangodb::aql {
+
+class AqlItemBlockInputRange {
+ public:
+  enum class State : uint8_t { HASMORE, DONE };
+
+  AqlItemBlockInputRange(State, arangodb::aql::SharedAqlItemBlockPtr const&, std::size_t);
+  AqlItemBlockInputRange(State, arangodb::aql::SharedAqlItemBlockPtr&&, std::size_t) noexcept;
+
+  std::pair<State, arangodb::aql::InputAqlItemRow> peek();
+
+  std::pair<State, arangodb::aql::InputAqlItemRow> next();
+
+ private:
+  State state() const noexcept;
+  bool indexIsValid() const noexcept;
+  bool moreRowsAfterThis() const noexcept;
+
+ private:
+  arangodb::aql::SharedAqlItemBlockPtr _block;
+  std::size_t _rowIndex;
+  State _finalState;
+};
+
+}
+
+#endif  // ARANGOD_AQL_AQLITEMBLOCKINPUTITERATOR_H
diff --git a/arangod/Aql/SingleRowFetcher.h b/arangod/Aql/SingleRowFetcher.h
index 594822b44517..09270cf8cc2e 100644
--- a/arangod/Aql/SingleRowFetcher.h
+++ b/arangod/Aql/SingleRowFetcher.h
@@ -55,11 +55,19 @@ class SingleRowFetcher {
   explicit SingleRowFetcher(DependencyProxy<blockPassthrough>& executionBlock);
   TEST_VIRTUAL ~SingleRowFetcher() = default;
 
+  using DataRange = AqlItemBlockInputIterator;
+
  protected:
   // only for testing! Does not initialize _dependencyProxy!
   SingleRowFetcher();
 
  public:
+  // TODO implement and document
+  std::tuple<ExecutionState, size_t, DataRange> execute(/* TODO: add"justDoIt"-style parameter */) {
+    TRI_ASSERT(false);
+    THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
+  }
+
   /**
    * @brief Fetch one new AqlItemRow from upstream.
    *        **Guarantee**: the row returned is valid only
diff --git a/arangod/CMakeLists.txt b/arangod/CMakeLists.txt
index 9238ece0fd38..441e9a044260 100644
--- a/arangod/CMakeLists.txt
+++ b/arangod/CMakeLists.txt
@@ -216,6 +216,7 @@ set(LIB_ARANGO_AQL_SOURCES
   Aql/AllRowsFetcher.cpp
   Aql/AqlFunctionFeature.cpp
   Aql/AqlItemBlock.cpp
+  Aql/AqlItemBlockInputRange.cpp
   Aql/AqlItemBlockManager.cpp
   Aql/AqlItemBlockUtils.cpp
   Aql/AqlItemMatrix.cpp

From 7c6bcbad8689ab4c4bdd1ce0848e522c567b034d Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Tue, 22 Oct 2019 17:51:41 +0200
Subject: [PATCH 003/122] Added Header file for AqlCallStack with comments. No
 implementation yet.

---
 arangod/Aql/AqlCallStack.h | 70 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 70 insertions(+)
 create mode 100644 arangod/Aql/AqlCallStack.h

diff --git a/arangod/Aql/AqlCallStack.h b/arangod/Aql/AqlCallStack.h
new file mode 100644
index 000000000000..aba835feabf9
--- /dev/null
+++ b/arangod/Aql/AqlCallStack.h
@@ -0,0 +1,70 @@
+////////////////////////////////////////////////////////////////////////////////
+/// DISCLAIMER
+///
+/// Copyright 2019 ArangoDB GmbH, Cologne, Germany
+///
+/// Licensed under the Apache License, Version 2.0 (the "License");
+/// you may not use this file except in compliance with the License.
+/// You may obtain a copy of the License at
+///
+///     http://www.apache.org/licenses/LICENSE-2.0
+///
+/// Unless required by applicable law or agreed to in writing, software
+/// distributed under the License is distributed on an "AS IS" BASIS,
+/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+/// See the License for the specific language governing permissions and
+/// limitations under the License.
+///
+/// Copyright holder is ArangoDB GmbH, Cologne, Germany
+///
+/// @author Michael Hackstein
+////////////////////////////////////////////////////////////////////////////////
+
+#ifndef ARANGOD_AQL_AQL_CALLSTACK_H
+#define ARANGOD_AQL_AQL_CALLSTACK_H 1
+
+#include <stack>
+
+namespace arangodb {
+namespace aql {
+
+struct AqlCall;
+
+class AqlCallStack {
+  // Initial
+  AqlCallStack(AqlCall call);
+  // Used in subquery
+  AqlCallStack(AqlCallStack const& other, AqlCall call);
+  // Used to pass between blocks
+  AqlCallStack(AqlCallStack const& other);
+
+  // Quick test is this CallStack is of local relevance, or it is sufficient to pass it through
+  bool isRelevant() const;
+
+  // Get the top most Call element (this must be relevant).
+  // Caller is allowed to modify it, if necessary
+  AqlCall& myCall();
+
+  // fill up all missing calls within this stack s.t. we reach depth == 0
+  // This needs to be called if an executor requires to be fully executed, even if skipped,
+  // even if the subquery it is located in is skipped.
+  // The default operations added here will correspond to produce all Rows, unlimitted.
+  // e.g. every Modification Executor needs to call this functionality, as modifictions need to be
+  // performed even if skipped.
+  void stackUpMissingCalls();
+
+ private:
+  // The list of operations, stacked by depth (e.g. bottom element is from main query)
+  std::stack<AqlCall> _operations;
+
+  // The depth of subqueries that have not issued calls into operations,
+  // as they have been skipped.
+  // In most cases this will be zero.
+  // However if we skip a subquery that has a nested subquery this depth will be 1 in the nested subquery.
+  size_t _depth;
+};
+
+}  // namespace aql
+}  // namespace arangodb
+
+#endif
\ No newline at end of file

From 22d2977be5fe4f1d974bb95a4d645a127d1f16cd Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Tue, 22 Oct 2019 23:33:21 +0200
Subject: [PATCH 004/122] Added AqlCallStack first draft implementation. Made
 everything compile

---
 arangod/Aql/AqlCallStack.cpp           | 73 ++++++++++++++++++++++++++
 arangod/Aql/AqlCallStack.h             | 10 +++-
 arangod/Aql/AqlItemBlockInputRange.cpp |  7 +--
 arangod/Aql/SingleRowFetcher.h         |  3 +-
 arangod/CMakeLists.txt                 |  1 +
 5 files changed, 88 insertions(+), 6 deletions(-)
 create mode 100644 arangod/Aql/AqlCallStack.cpp

diff --git a/arangod/Aql/AqlCallStack.cpp b/arangod/Aql/AqlCallStack.cpp
new file mode 100644
index 000000000000..28bd80c93029
--- /dev/null
+++ b/arangod/Aql/AqlCallStack.cpp
@@ -0,0 +1,73 @@
+////////////////////////////////////////////////////////////////////////////////
+/// DISCLAIMER
+///
+/// Copyright 2019 ArangoDB GmbH, Cologne, Germany
+///
+/// Licensed under the Apache License, Version 2.0 (the "License");
+/// you may not use this file except in compliance with the License.
+/// You may obtain a copy of the License at
+///
+///     http://www.apache.org/licenses/LICENSE-2.0
+///
+/// Unless required by applicable law or agreed to in writing, software
+/// distributed under the License is distributed on an "AS IS" BASIS,
+/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+/// See the License for the specific language governing permissions and
+/// limitations under the License.
+///
+/// Copyright holder is ArangoDB GmbH, Cologne, Germany
+///
+/// @author Michael Hackstein
+////////////////////////////////////////////////////////////////////////////////
+
+#include "AqlCallStack.h"
+
+// TODO: This class is not yet memory efficient or optimized in any way.
+// it might be reimplement soon to have the above features, Focus now is on
+// the API we want to use.
+
+using namespace arangodb;
+using namespace arangodb::aql;
+
+AqlCallStack::AqlCallStack(AqlCall call)
+    : _operations{{std::move(call)}}, _depth(0) {}
+
+AqlCallStack::AqlCallStack(AqlCallStack const& other, AqlCall call)
+    : _operations{other._operations}, _depth(0) {
+  // We can only use this constructor on relevant levels
+  // Alothers need to use passThrough constructor
+  TRI_ASSERT(other._depth == 0);
+  _operations.push(std::move(call));
+}
+
+AqlCallStack::AqlCallStack(AqlCallStack const& other)
+    : _operations{other._operations}, _depth(other._depth) {}
+
+bool AqlCallStack::isRelevant() const { return _depth == 0; }
+
+AqlCall& AqlCallStack::myCall() {
+  TRI_ASSERT(isRelevant());
+  TRI_ASSERT(!_operations.empty());
+  return _operations.top();
+}
+
+void AqlCallStack::stackUpMissingCalls() {
+  while (!isRelevant()) {
+    // For every depth, we add an additional default call.
+    // The default is to produce unlimited many results,
+    // using DefaultBatchSize each.
+    _operations.emplace(AqlCall{});
+    _depth--;
+  }
+  TRI_ASSERT(isRelevant());
+}
+
+void AqlCallStack::pop() {
+  if (isRelevant()) {
+    // We have one element to pop
+    TRI_ASSERT(!_operations.empty());
+    _operations.pop();
+    // We can never pop the main query, so one element needs to stay
+    TRI_ASSERT(!_operations.empty());
+  }
+}
\ No newline at end of file
diff --git a/arangod/Aql/AqlCallStack.h b/arangod/Aql/AqlCallStack.h
index aba835feabf9..3d966bf6a0ea 100644
--- a/arangod/Aql/AqlCallStack.h
+++ b/arangod/Aql/AqlCallStack.h
@@ -23,13 +23,13 @@
 #ifndef ARANGOD_AQL_AQL_CALLSTACK_H
 #define ARANGOD_AQL_AQL_CALLSTACK_H 1
 
+#include "Aql/AqlCall.h"
+
 #include <stack>
 
 namespace arangodb {
 namespace aql {
 
-struct AqlCall;
-
 class AqlCallStack {
   // Initial
   AqlCallStack(AqlCall call);
@@ -53,6 +53,12 @@ class AqlCallStack {
   // performed even if skipped.
   void stackUpMissingCalls();
 
+  // Pops one subquery level.
+  // if this isRelevent it pops the top-most call from the stack.
+  // if this is not revelent it reduces the depth by 1.
+  // Can be savely called on every subquery Start.
+  void pop();
+
  private:
   // The list of operations, stacked by depth (e.g. bottom element is from main query)
   std::stack<AqlCall> _operations;
diff --git a/arangod/Aql/AqlItemBlockInputRange.cpp b/arangod/Aql/AqlItemBlockInputRange.cpp
index 57bcf986d3e0..aa2e9a47e1fd 100644
--- a/arangod/Aql/AqlItemBlockInputRange.cpp
+++ b/arangod/Aql/AqlItemBlockInputRange.cpp
@@ -26,13 +26,14 @@ using namespace arangodb;
 using namespace arangodb::aql;
 
 AqlItemBlockInputRange::AqlItemBlockInputRange(AqlItemBlockInputRange::State state,
-                                               SharedAqlItemBlockPtr const& block, std::size_t index)
-    : _finalState{state}, _block{block}, _rowIndex{index} {}
+                                               SharedAqlItemBlockPtr const& block,
+                                               std::size_t index)
+    : _block{block}, _rowIndex{index}, _finalState{state} {}
 
 AqlItemBlockInputRange::AqlItemBlockInputRange(AqlItemBlockInputRange::State state,
                                                SharedAqlItemBlockPtr&& block,
                                                std::size_t index) noexcept
-    : _finalState{state}, _block{std::move(block)}, _rowIndex{index} {}
+    : _block{std::move(block)}, _rowIndex{index}, _finalState{state} {}
 
 std::pair<AqlItemBlockInputRange::State, InputAqlItemRow> AqlItemBlockInputRange::peek() {
   if (indexIsValid()) {
diff --git a/arangod/Aql/SingleRowFetcher.h b/arangod/Aql/SingleRowFetcher.h
index 09270cf8cc2e..a4d2788c6207 100644
--- a/arangod/Aql/SingleRowFetcher.h
+++ b/arangod/Aql/SingleRowFetcher.h
@@ -26,6 +26,7 @@
 #ifndef ARANGOD_AQL_SINGLE_ROW_FETCHER_H
 #define ARANGOD_AQL_SINGLE_ROW_FETCHER_H
 
+#include "Aql/AqlItemBlockInputRange.h"
 #include "Aql/ExecutionBlock.h"
 #include "Aql/ExecutionState.h"
 #include "Aql/InputAqlItemRow.h"
@@ -55,7 +56,7 @@ class SingleRowFetcher {
   explicit SingleRowFetcher(DependencyProxy<blockPassthrough>& executionBlock);
   TEST_VIRTUAL ~SingleRowFetcher() = default;
 
-  using DataRange = AqlItemBlockInputIterator;
+  using DataRange = AqlItemBlockInputRange;
 
  protected:
   // only for testing! Does not initialize _dependencyProxy!
diff --git a/arangod/CMakeLists.txt b/arangod/CMakeLists.txt
index 441e9a044260..f6b7beb8a0ac 100644
--- a/arangod/CMakeLists.txt
+++ b/arangod/CMakeLists.txt
@@ -214,6 +214,7 @@ set(LIB_ARANGO_PREGEL_SOURCES
 set(LIB_ARANGO_AQL_SOURCES
   Aql/Aggregator.cpp
   Aql/AllRowsFetcher.cpp
+  Aql/AqlCallStack.cpp
   Aql/AqlFunctionFeature.cpp
   Aql/AqlItemBlock.cpp
   Aql/AqlItemBlockInputRange.cpp

From 3ab448831cb55e627fe014b8d64bbd3ab33d4d41 Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Wed, 23 Oct 2019 00:08:05 +0200
Subject: [PATCH 005/122] Added empty dummy stubs for execute() in
 ExecutionBlock

---
 arangod/Aql/BlocksWithClients.cpp       |  7 +++
 arangod/Aql/BlocksWithClients.h         |  2 +
 arangod/Aql/ExecutionBlock.h            | 18 +++++-
 arangod/Aql/ExecutionBlockImpl.cpp      | 78 ++++++++++++++-----------
 arangod/Aql/ExecutionBlockImpl.h        | 16 ++++-
 arangod/Aql/IdExecutor.cpp              | 31 +++++++---
 arangod/Aql/IdExecutor.h                |  2 +
 arangod/Aql/RemoteExecutor.cpp          | 11 +++-
 arangod/Aql/RemoteExecutor.h            | 12 ++--
 tests/Aql/WaitingExecutionBlockMock.cpp |  7 +++
 tests/Aql/WaitingExecutionBlockMock.h   |  4 ++
 11 files changed, 134 insertions(+), 54 deletions(-)

diff --git a/arangod/Aql/BlocksWithClients.cpp b/arangod/Aql/BlocksWithClients.cpp
index 5108d1927372..7adda6f3ec54 100644
--- a/arangod/Aql/BlocksWithClients.cpp
+++ b/arangod/Aql/BlocksWithClients.cpp
@@ -23,6 +23,7 @@
 
 #include "BlocksWithClients.h"
 
+#include "Aql/AqlCallStack.h"
 #include "Aql/AqlItemBlock.h"
 #include "Aql/AqlTransaction.h"
 #include "Aql/AqlValue.h"
@@ -137,3 +138,9 @@ std::pair<ExecutionState, size_t> BlocksWithClients::skipSome(size_t) {
   TRI_ASSERT(false);
   THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
 }
+
+std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> BlocksWithClients::execute(AqlCallStack stack) {
+  // This will not be implemented here!
+  TRI_ASSERT(false);
+  THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
+}
diff --git a/arangod/Aql/BlocksWithClients.h b/arangod/Aql/BlocksWithClients.h
index bdc659a1aede..ca29e4cd476f 100644
--- a/arangod/Aql/BlocksWithClients.h
+++ b/arangod/Aql/BlocksWithClients.h
@@ -80,6 +80,8 @@ class BlocksWithClients : public ExecutionBlock {
   virtual std::pair<ExecutionState, size_t> skipSomeForShard(size_t atMost,
                                                              std::string const& shardId) = 0;
 
+  std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> execute(AqlCallStack stack) override;
+
  protected:
   /// @brief getClientId: get the number <clientId> (used internally)
   /// corresponding to <shardId>
diff --git a/arangod/Aql/ExecutionBlock.h b/arangod/Aql/ExecutionBlock.h
index 8dbba6258c79..29bc09dc4230 100644
--- a/arangod/Aql/ExecutionBlock.h
+++ b/arangod/Aql/ExecutionBlock.h
@@ -39,6 +39,7 @@ class Methods;
 }
 
 namespace aql {
+class AqlCallStack;
 class InputAqlItemRow;
 class ExecutionEngine;
 class ExecutionNode;
@@ -96,8 +97,8 @@ class ExecutionBlock {
   void traceGetSomeBegin(size_t atMost);
 
   // Trace the end of a getSome call, potentially with result
-  std::pair<ExecutionState, SharedAqlItemBlockPtr> traceGetSomeEnd(
-      ExecutionState state, SharedAqlItemBlockPtr result);
+  std::pair<ExecutionState, SharedAqlItemBlockPtr> traceGetSomeEnd(ExecutionState state,
+                                                                   SharedAqlItemBlockPtr result);
 
   void traceSkipSomeBegin(size_t atMost);
 
@@ -122,6 +123,19 @@ class ExecutionBlock {
   /// @brief add a dependency
   void addDependency(ExecutionBlock* ep);
 
+  /// @brief main function to produce data in this ExecutionBlock.
+  ///        It gets the AqlCallStack defining the operations required in every
+  ///        subquery level. It will then perform the requested amount of offset, data and fullcount.
+  ///        The AqlCallStack is copied on purpose, so this block can modify it.
+  ///        Will return
+  ///        1. state:
+  ///          * WAITING: We have async operation going on, nothing happend, please call again
+  ///          * HASMORE: Here is some data in the request range, there is still more, if required call again
+  ///          * DONE: Here is some data, and there will be no further data available.
+  ///        2. size_t: Amount of documents skipped.
+  ///        3. SharedAqlItemBlockPtr: The next data block.
+  virtual std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> execute(AqlCallStack stack) = 0;
+
  protected:
   /// @brief the execution engine
   ExecutionEngine* _engine;
diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index 1880a006aa83..7f9656966d35 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -26,6 +26,7 @@
 #include "ExecutionBlockImpl.h"
 
 #include "Aql/AllRowsFetcher.h"
+#include "Aql/AqlCallStack.h"
 #include "Aql/AqlItemBlock.h"
 #include "Aql/CalculationExecutor.h"
 #include "Aql/ConstFetcher.h"
@@ -46,6 +47,7 @@
 #include "Aql/InputAqlItemRow.h"
 #include "Aql/KShortestPathsExecutor.h"
 #include "Aql/LimitExecutor.h"
+#include "Aql/MaterializeExecutor.h"
 #include "Aql/ModificationExecutor.h"
 #include "Aql/ModificationExecutorTraits.h"
 #include "Aql/MultiDependencySingleRowFetcher.h"
@@ -63,7 +65,6 @@
 #include "Aql/SubqueryExecutor.h"
 #include "Aql/SubqueryStartExecutor.h"
 #include "Aql/TraversalExecutor.h"
-#include "Aql/MaterializeExecutor.h"
 
 #include <type_traits>
 
@@ -79,18 +80,18 @@ using namespace arangodb::aql;
  * constexpr bool someClassHasSomeMethod = hasSomeMethod<SomeClass>::value;
  */
 
-#define CREATE_HAS_MEMBER_CHECK(methodName, checkName)     \
-  template <typename T>                                    \
-  class checkName {                                        \
-    template <typename C>                                  \
-    static std::true_type test(decltype(&C::methodName));  \
-    template <typename C>                                  \
+#define CREATE_HAS_MEMBER_CHECK(methodName, checkName)               \
+  template <typename T>                                              \
+  class checkName {                                                  \
+    template <typename C>                                            \
+    static std::true_type test(decltype(&C::methodName));            \
+    template <typename C>                                            \
     static std::true_type test(decltype(&C::template methodName<>)); \
-    template <typename>                                    \
-    static std::false_type test(...);                      \
-                                                           \
-   public:                                                 \
-    static constexpr bool value = decltype(test<T>(0))::value;    \
+    template <typename>                                              \
+    static std::false_type test(...);                                \
+                                                                     \
+   public:                                                           \
+    static constexpr bool value = decltype(test<T>(0))::value;       \
   }
 
 CREATE_HAS_MEMBER_CHECK(initializeCursor, hasInitializeCursor);
@@ -301,23 +302,24 @@ static SkipVariants constexpr skipType() {
   static_assert(!useFetcher || hasSkipRows<typename Executor::Fetcher>::value,
                 "Fetcher is chosen for skipping, but has not skipRows method!");
 
-  static_assert(useExecutor ==
-                    (std::is_same<Executor, IndexExecutor>::value ||
-                     std::is_same<Executor, IResearchViewExecutor<false, true>>::value ||
-                     std::is_same<Executor, IResearchViewExecutor<true, true>>::value ||
-                     std::is_same<Executor, IResearchViewMergeExecutor<false, true>>::value ||
-                     std::is_same<Executor, IResearchViewMergeExecutor<true, true>>::value ||
-                     std::is_same<Executor, IResearchViewExecutor<false, false>>::value ||
-                     std::is_same<Executor, IResearchViewExecutor<true, false>>::value ||
-                     std::is_same<Executor, IResearchViewMergeExecutor<false, false>>::value ||
-                     std::is_same<Executor, IResearchViewMergeExecutor<true, false>>::value ||
-                     std::is_same<Executor, EnumerateCollectionExecutor>::value ||
-                     std::is_same<Executor, LimitExecutor>::value ||
-                     std::is_same<Executor, IdExecutor<BlockPassthrough::Disable, SingleRowFetcher<BlockPassthrough::Disable>>>::value ||
-                     std::is_same<Executor, ConstrainedSortExecutor>::value ||
-                     std::is_same<Executor, SortingGatherExecutor>::value ||
-                     std::is_same<Executor, MaterializeExecutor>::value),
-                "Unexpected executor for SkipVariants::EXECUTOR");
+  static_assert(
+      useExecutor ==
+          (std::is_same<Executor, IndexExecutor>::value ||
+           std::is_same<Executor, IResearchViewExecutor<false, true>>::value ||
+           std::is_same<Executor, IResearchViewExecutor<true, true>>::value ||
+           std::is_same<Executor, IResearchViewMergeExecutor<false, true>>::value ||
+           std::is_same<Executor, IResearchViewMergeExecutor<true, true>>::value ||
+           std::is_same<Executor, IResearchViewExecutor<false, false>>::value ||
+           std::is_same<Executor, IResearchViewExecutor<true, false>>::value ||
+           std::is_same<Executor, IResearchViewMergeExecutor<false, false>>::value ||
+           std::is_same<Executor, IResearchViewMergeExecutor<true, false>>::value ||
+           std::is_same<Executor, EnumerateCollectionExecutor>::value ||
+           std::is_same<Executor, LimitExecutor>::value ||
+           std::is_same<Executor, IdExecutor<BlockPassthrough::Disable, SingleRowFetcher<BlockPassthrough::Disable>>>::value ||
+           std::is_same<Executor, ConstrainedSortExecutor>::value ||
+           std::is_same<Executor, SortingGatherExecutor>::value ||
+           std::is_same<Executor, MaterializeExecutor>::value),
+      "Unexpected executor for SkipVariants::EXECUTOR");
 
   // The LimitExecutor will not work correctly with SkipVariants::FETCHER!
   static_assert(
@@ -386,7 +388,6 @@ std::pair<ExecutionState, size_t> ExecutionBlockImpl<Executor>::skipSomeOnceWith
   return {state, skipped};
 }
 
-
 template <bool customInit>
 struct InitializeCursor {};
 
@@ -453,6 +454,13 @@ std::pair<ExecutionState, Result> ExecutionBlockImpl<Executor>::shutdown(int err
   return ExecutionBlock::shutdown(errorCode);
 }
 
+template <class Executor>
+std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> ExecutionBlockImpl<Executor>::execute(AqlCallStack stack) {
+  // TODO implement!
+  TRI_ASSERT(false);
+  THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
+}
+
 // Work around GCC bug: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=56480
 // Without the namespaces it fails with
 // error: specialization of 'template<class Executor> std::pair<arangodb::aql::ExecutionState, arangodb::Result> arangodb::aql::ExecutionBlockImpl<Executor>::initializeCursor(arangodb::aql::AqlItemBlock*, size_t)' in different namespace
@@ -568,8 +576,8 @@ std::pair<ExecutionState, Result> ExecutionBlockImpl<SubqueryExecutor<false>>::s
 }
 
 template <>
-std::pair<ExecutionState, Result>
-ExecutionBlockImpl<IdExecutor<BlockPassthrough::Enable, SingleRowFetcher<BlockPassthrough::Enable>>>::shutdown(int errorCode) {
+std::pair<ExecutionState, Result> ExecutionBlockImpl<
+    IdExecutor<BlockPassthrough::Enable, SingleRowFetcher<BlockPassthrough::Enable>>>::shutdown(int errorCode) {
   if (this->infos().isResponsibleForInitializeCursor()) {
     return ExecutionBlock::shutdown(errorCode);
   }
@@ -766,8 +774,10 @@ template class ::arangodb::aql::ExecutionBlockImpl<IResearchViewExecutor<true, f
 template class ::arangodb::aql::ExecutionBlockImpl<IResearchViewMergeExecutor<false, false>>;
 template class ::arangodb::aql::ExecutionBlockImpl<IResearchViewMergeExecutor<true, false>>;
 template class ::arangodb::aql::ExecutionBlockImpl<IdExecutor<BlockPassthrough::Enable, ConstFetcher>>;
-template class ::arangodb::aql::ExecutionBlockImpl<IdExecutor<BlockPassthrough::Enable, SingleRowFetcher<BlockPassthrough::Enable>>>;
-template class ::arangodb::aql::ExecutionBlockImpl<IdExecutor<BlockPassthrough::Disable, SingleRowFetcher<BlockPassthrough::Disable>>>;
+template class ::arangodb::aql::ExecutionBlockImpl<
+    IdExecutor<BlockPassthrough::Enable, SingleRowFetcher<BlockPassthrough::Enable>>>;
+template class ::arangodb::aql::ExecutionBlockImpl<
+    IdExecutor<BlockPassthrough::Disable, SingleRowFetcher<BlockPassthrough::Disable>>>;
 template class ::arangodb::aql::ExecutionBlockImpl<IndexExecutor>;
 template class ::arangodb::aql::ExecutionBlockImpl<LimitExecutor>;
 template class ::arangodb::aql::ExecutionBlockImpl<ModificationExecutor<Insert, SingleBlockFetcher<BlockPassthrough::Disable>>>;
diff --git a/arangod/Aql/ExecutionBlockImpl.h b/arangod/Aql/ExecutionBlockImpl.h
index 3b451241df0c..53f2738dbea3 100644
--- a/arangod/Aql/ExecutionBlockImpl.h
+++ b/arangod/Aql/ExecutionBlockImpl.h
@@ -98,7 +98,8 @@ class ExecutionBlockImpl final : public ExecutionBlock {
       typename aql::DependencyProxy<Executor::Properties::allowsBlockPassthrough>;
 
   static_assert(
-    Executor::Properties::allowsBlockPassthrough == BlockPassthrough::Disable || Executor::Properties::preservesOrder,
+      Executor::Properties::allowsBlockPassthrough == BlockPassthrough::Disable ||
+          Executor::Properties::preservesOrder,
       "allowsBlockPassthrough must imply preservesOrder, but does not!");
 
  public:
@@ -174,6 +175,19 @@ class ExecutionBlockImpl final : public ExecutionBlock {
   /// central place.
   std::pair<ExecutionState, Result> shutdown(int) override;
 
+  /// @brief main function to produce data in this ExecutionBlock.
+  ///        It gets the AqlCallStack defining the operations required in every
+  ///        subquery level. It will then perform the requested amount of offset, data and fullcount.
+  ///        The AqlCallStack is copied on purpose, so this block can modify it.
+  ///        Will return
+  ///        1. state:
+  ///          * WAITING: We have async operation going on, nothing happend, please call again
+  ///          * HASMORE: Here is some data in the request range, there is still more, if required call again
+  ///          * DONE: Here is some data, and there will be no further data available.
+  ///        2. size_t: Amount of documents skipped.
+  ///        3. SharedAqlItemBlockPtr: The next data block.
+  std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> execute(AqlCallStack stack) override;
+
  private:
   /**
    * @brief Inner getSome() part, without the tracing calls.
diff --git a/arangod/Aql/IdExecutor.cpp b/arangod/Aql/IdExecutor.cpp
index d2dd944c5c85..0b4f99b936b6 100644
--- a/arangod/Aql/IdExecutor.cpp
+++ b/arangod/Aql/IdExecutor.cpp
@@ -22,6 +22,7 @@
 
 #include "IdExecutor.h"
 
+#include "Aql/AqlCallStack.h"
 #include "Aql/AqlValue.h"
 #include "Aql/ConstFetcher.h"
 #include "Aql/ExecutionEngine.h"
@@ -43,9 +44,8 @@ constexpr BlockPassthrough IdExecutor<usePassThrough, T>::Properties::allowsBloc
 template <BlockPassthrough usePassThrough, class T>
 constexpr bool IdExecutor<usePassThrough, T>::Properties::inputSizeRestrictsOutputSize;
 
-ExecutionBlockImpl<IdExecutor<BlockPassthrough::Enable, void>>::ExecutionBlockImpl(ExecutionEngine* engine,
-                                                         ExecutionNode const* node,
-                                                         RegisterId outputRegister, bool doCount)
+ExecutionBlockImpl<IdExecutor<BlockPassthrough::Enable, void>>::ExecutionBlockImpl(
+    ExecutionEngine* engine, ExecutionNode const* node, RegisterId outputRegister, bool doCount)
     : ExecutionBlock(engine, node),
       _currentDependency(0),
       _outputRegister(outputRegister),
@@ -56,7 +56,8 @@ ExecutionBlockImpl<IdExecutor<BlockPassthrough::Enable, void>>::ExecutionBlockIm
   }
 }
 
-std::pair<ExecutionState, size_t> ExecutionBlockImpl<IdExecutor<BlockPassthrough::Enable, void>>::skipSome(size_t atMost) {
+std::pair<ExecutionState, size_t>
+ExecutionBlockImpl<IdExecutor<BlockPassthrough::Enable, void>>::skipSome(size_t atMost) {
   traceSkipSomeBegin(atMost);
   if (isDone()) {
     return traceSkipSomeEnd(ExecutionState::DONE, 0);
@@ -73,7 +74,8 @@ std::pair<ExecutionState, size_t> ExecutionBlockImpl<IdExecutor<BlockPassthrough
   return traceSkipSomeEnd(state, skipped);
 }
 
-std::pair<ExecutionState, SharedAqlItemBlockPtr> ExecutionBlockImpl<IdExecutor<BlockPassthrough::Enable, void>>::getSome(size_t atMost) {
+std::pair<ExecutionState, SharedAqlItemBlockPtr>
+ExecutionBlockImpl<IdExecutor<BlockPassthrough::Enable, void>>::getSome(size_t atMost) {
   traceGetSomeBegin(atMost);
   if (isDone()) {
     return traceGetSomeEnd(ExecutionState::DONE, nullptr);
@@ -99,10 +101,18 @@ bool aql::ExecutionBlockImpl<IdExecutor<BlockPassthrough::Enable, void>>::isDone
   return _currentDependency >= _dependencies.size();
 }
 
-RegisterId ExecutionBlockImpl<IdExecutor<BlockPassthrough::Enable, void>>::getOutputRegisterId() const noexcept {
+RegisterId ExecutionBlockImpl<IdExecutor<BlockPassthrough::Enable, void>>::getOutputRegisterId() const
+    noexcept {
   return _outputRegister;
 }
 
+std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr>
+ExecutionBlockImpl<IdExecutor<BlockPassthrough::Enable, void>>::execute(AqlCallStack stack) {
+  // TODO Implement me
+  TRI_ASSERT(false);
+  THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
+}
+
 ExecutionBlock& ExecutionBlockImpl<IdExecutor<BlockPassthrough::Enable, void>>::currentDependency() const {
   TRI_ASSERT(_currentDependency < _dependencies.size());
   TRI_ASSERT(_dependencies[_currentDependency] != nullptr);
@@ -209,10 +219,13 @@ template class ::arangodb::aql::IdExecutor<BlockPassthrough::Enable, SingleRowFe
 template class ::arangodb::aql::IdExecutor<BlockPassthrough::Disable, SingleRowFetcher<BlockPassthrough::Disable>>;
 
 template std::tuple<ExecutionState, typename IdExecutor<BlockPassthrough::Enable, ConstFetcher>::Stats, SharedAqlItemBlockPtr>
-IdExecutor<BlockPassthrough::Enable, ConstFetcher>::fetchBlockForPassthrough<BlockPassthrough::Enable, void>(size_t atMost);
+IdExecutor<BlockPassthrough::Enable, ConstFetcher>::fetchBlockForPassthrough<BlockPassthrough::Enable, void>(
+    size_t atMost);
 
 template std::tuple<ExecutionState, typename IdExecutor<BlockPassthrough::Enable, SingleRowFetcher<BlockPassthrough::Enable>>::Stats, SharedAqlItemBlockPtr>
-IdExecutor<BlockPassthrough::Enable, SingleRowFetcher<BlockPassthrough::Enable>>::fetchBlockForPassthrough<BlockPassthrough::Enable, void>(size_t atMost);
+IdExecutor<BlockPassthrough::Enable, SingleRowFetcher<BlockPassthrough::Enable>>::fetchBlockForPassthrough<
+    BlockPassthrough::Enable, void>(size_t atMost);
 
 template std::tuple<ExecutionState, NoStats, size_t>
-IdExecutor<BlockPassthrough::Disable, SingleRowFetcher<BlockPassthrough::Disable>>::skipRows<BlockPassthrough::Disable, void>(size_t atMost);
+IdExecutor<BlockPassthrough::Disable, SingleRowFetcher<BlockPassthrough::Disable>>::skipRows<
+    BlockPassthrough::Disable, void>(size_t atMost);
diff --git a/arangod/Aql/IdExecutor.h b/arangod/Aql/IdExecutor.h
index c0beeaa907eb..398184889699 100644
--- a/arangod/Aql/IdExecutor.h
+++ b/arangod/Aql/IdExecutor.h
@@ -93,6 +93,8 @@ class ExecutionBlockImpl<IdExecutor<BlockPassthrough::Enable, void>> : public Ex
 
   RegisterId getOutputRegisterId() const noexcept;
 
+  std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> execute(AqlCallStack stack) override;
+
  private:
   bool isDone() const noexcept;
 
diff --git a/arangod/Aql/RemoteExecutor.cpp b/arangod/Aql/RemoteExecutor.cpp
index 01dbe671baab..37ca55970be6 100644
--- a/arangod/Aql/RemoteExecutor.cpp
+++ b/arangod/Aql/RemoteExecutor.cpp
@@ -22,6 +22,7 @@
 
 #include "RemoteExecutor.h"
 
+#include "Aql/AqlCallStack.h"
 #include "Aql/ClusterNodes.h"
 #include "Aql/ExecutionEngine.h"
 #include "Aql/ExecutorInfos.h"
@@ -142,8 +143,6 @@ std::pair<ExecutionState, SharedAqlItemBlockPtr> ExecutionBlockImpl<RemoteExecut
   auto res = sendAsyncRequest(fuerte::RestVerb::Put, "/_api/aql/getSome/",
                               std::move(buffer));
 
-
-
   if (!res.ok()) {
     THROW_ARANGO_EXCEPTION(res);
   }
@@ -373,6 +372,12 @@ std::pair<ExecutionState, Result> ExecutionBlockImpl<RemoteExecutor>::shutdown(i
   return {ExecutionState::WAITING, TRI_ERROR_NO_ERROR};
 }
 
+std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> ExecutionBlockImpl<RemoteExecutor>::execute(
+    AqlCallStack stack) {
+  TRI_ASSERT(false);
+  THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
+}
+
 namespace {
 Result handleErrorResponse(network::EndpointSpec const& spec, fuerte::Error err,
                            fuerte::Response* response) {
@@ -390,7 +395,7 @@ Result handleErrorResponse(network::EndpointSpec const& spec, fuerte::Error err,
         .append(spec.serverId)
         .append("': ");
   }
-  
+
   int res = TRI_ERROR_INTERNAL;
   if (err != fuerte::Error::NoError) {
     res = network::fuerteToArangoErrorCode(err);
diff --git a/arangod/Aql/RemoteExecutor.h b/arangod/Aql/RemoteExecutor.h
index 5cb40b2e9a9d..40f735f7c629 100644
--- a/arangod/Aql/RemoteExecutor.h
+++ b/arangod/Aql/RemoteExecutor.h
@@ -24,8 +24,8 @@
 #define ARANGOD_AQL_REMOTE_EXECUTOR_H
 
 #include "Aql/ClusterNodes.h"
-#include "Aql/ExecutorInfos.h"
 #include "Aql/ExecutionBlockImpl.h"
+#include "Aql/ExecutorInfos.h"
 
 #include <mutex>
 
@@ -62,6 +62,8 @@ class ExecutionBlockImpl<RemoteExecutor> : public ExecutionBlock {
 
   std::pair<ExecutionState, Result> shutdown(int errorCode) override;
 
+  std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> execute(AqlCallStack stack) override;
+
 #ifdef ARANGODB_ENABLE_MAINTAINER_MODE
   // only for asserts:
  public:
@@ -109,16 +111,16 @@ class ExecutionBlockImpl<RemoteExecutor> : public ExecutionBlock {
 
   /// @brief the last remote response Result object, may contain an error.
   arangodb::Result _lastError;
-  
+
   std::mutex _communicationMutex;
-  
+
   unsigned _lastTicket;  /// used to check for canceled requests
-  
+
   bool _hasTriggeredShutdown;
 
   // _communicationMutex *must* be locked for this!
   unsigned generateNewTicket();
-  
+
   bool _didSendShutdownRequest = false;
 
   void traceGetSomeRequest(velocypack::Slice slice, size_t atMost);
diff --git a/tests/Aql/WaitingExecutionBlockMock.cpp b/tests/Aql/WaitingExecutionBlockMock.cpp
index 4706dd4f4d48..6e938d4f3c16 100644
--- a/tests/Aql/WaitingExecutionBlockMock.cpp
+++ b/tests/Aql/WaitingExecutionBlockMock.cpp
@@ -22,6 +22,7 @@
 
 #include "WaitingExecutionBlockMock.h"
 
+#include "Aql/AqlCallStack.h"
 #include "Aql/AqlItemBlock.h"
 #include "Aql/ExecutionEngine.h"
 #include "Aql/ExecutionState.h"
@@ -113,3 +114,9 @@ std::pair<arangodb::aql::ExecutionState, size_t> WaitingExecutionBlockMock::skip
     return {ExecutionState::HASMORE, skipped};
   }
 }
+
+std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> WaitingExecutionBlockMock::execute(AqlCallStack stack) {
+  // TODO implement!
+  TRI_ASSERT(false);
+  THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
+}
\ No newline at end of file
diff --git a/tests/Aql/WaitingExecutionBlockMock.h b/tests/Aql/WaitingExecutionBlockMock.h
index 598308e25da8..f644b37ccc0f 100644
--- a/tests/Aql/WaitingExecutionBlockMock.h
+++ b/tests/Aql/WaitingExecutionBlockMock.h
@@ -95,6 +95,10 @@ class WaitingExecutionBlockMock final : public arangodb::aql::ExecutionBlock {
    */
   std::pair<arangodb::aql::ExecutionState, size_t> skipSome(size_t atMost) override;
 
+  // TODO: Document and implement me!
+  std::tuple<arangodb::aql::ExecutionState, size_t, arangodb::aql::SharedAqlItemBlockPtr> execute(
+      arangodb::aql::AqlCallStack stack) override;
+
  private:
   std::deque<arangodb::aql::SharedAqlItemBlockPtr> _data;
   arangodb::aql::ResourceMonitor _resourceMonitor;

From b079d783f3b36596112cd16c87e2a119e3b55d2e Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Thu, 24 Oct 2019 06:57:16 +0200
Subject: [PATCH 006/122] Implementation of new API in FilterExecutor. Rough
 implementation in ExecutionBlockImpl (not complete, only skip path)
 everything compiles, but is not tested

---
 arangod/Aql/AqlCallStack.h             |  1 +
 arangod/Aql/AqlItemBlockInputRange.cpp | 38 ++++++++-----
 arangod/Aql/AqlItemBlockInputRange.h   | 24 +++++---
 arangod/Aql/ExecutionBlockImpl.cpp     | 39 +++++++++++++
 arangod/Aql/ExecutionState.cpp         | 12 ++++
 arangod/Aql/ExecutionState.h           | 13 +++++
 arangod/Aql/FilterExecutor.cpp         | 76 +++++++++++++++++++++++++-
 arangod/Aql/FilterExecutor.h           | 14 +++++
 arangod/Aql/SingleRowFetcher.h         |  2 +-
 9 files changed, 194 insertions(+), 25 deletions(-)

diff --git a/arangod/Aql/AqlCallStack.h b/arangod/Aql/AqlCallStack.h
index 3d966bf6a0ea..82bbddcbed5c 100644
--- a/arangod/Aql/AqlCallStack.h
+++ b/arangod/Aql/AqlCallStack.h
@@ -31,6 +31,7 @@ namespace arangodb {
 namespace aql {
 
 class AqlCallStack {
+ public:
   // Initial
   AqlCallStack(AqlCall call);
   // Used in subquery
diff --git a/arangod/Aql/AqlItemBlockInputRange.cpp b/arangod/Aql/AqlItemBlockInputRange.cpp
index aa2e9a47e1fd..01ae52159dae 100644
--- a/arangod/Aql/AqlItemBlockInputRange.cpp
+++ b/arangod/Aql/AqlItemBlockInputRange.cpp
@@ -25,24 +25,36 @@
 using namespace arangodb;
 using namespace arangodb::aql;
 
-AqlItemBlockInputRange::AqlItemBlockInputRange(AqlItemBlockInputRange::State state,
+AqlItemBlockInputRange::AqlItemBlockInputRange()
+    : _block(nullptr), _rowIndex(0), _endIndex(0), _finalState(ExecutorState::HASMORE) {
+  TRI_ASSERT(!hasMore());
+  TRI_ASSERT(state() == ExecutorState::HASMORE);
+}
+
+AqlItemBlockInputRange::AqlItemBlockInputRange(ExecutorState state,
                                                SharedAqlItemBlockPtr const& block,
-                                               std::size_t index)
-    : _block{block}, _rowIndex{index}, _finalState{state} {}
+                                               std::size_t index, std::size_t endIndex)
+    : _block{block}, _rowIndex{index}, _endIndex(endIndex), _finalState{state} {
+  TRI_ASSERT(index < endIndex);
+  TRI_ASSERT(endIndex <= block->size());
+}
 
-AqlItemBlockInputRange::AqlItemBlockInputRange(AqlItemBlockInputRange::State state,
+AqlItemBlockInputRange::AqlItemBlockInputRange(ExecutorState state,
                                                SharedAqlItemBlockPtr&& block,
-                                               std::size_t index) noexcept
-    : _block{std::move(block)}, _rowIndex{index}, _finalState{state} {}
+                                               std::size_t index, std::size_t endIndex) noexcept
+    : _block{std::move(block)}, _rowIndex{index}, _endIndex(endIndex), _finalState{state} {
+  TRI_ASSERT(index < endIndex);
+  TRI_ASSERT(endIndex <= block->size());
+}
 
-std::pair<AqlItemBlockInputRange::State, InputAqlItemRow> AqlItemBlockInputRange::peek() {
+std::pair<ExecutorState, InputAqlItemRow> AqlItemBlockInputRange::peek() {
   if (indexIsValid()) {
     return std::make_pair(state(), InputAqlItemRow{_block, _rowIndex});
   }
   return std::make_pair(state(), InputAqlItemRow{CreateInvalidInputRowHint{}});
 }
 
-std::pair<AqlItemBlockInputRange::State, InputAqlItemRow> AqlItemBlockInputRange::next() {
+std::pair<ExecutorState, InputAqlItemRow> AqlItemBlockInputRange::next() {
   auto res = peek();
   ++_rowIndex;
   if (!indexIsValid()) {
@@ -53,13 +65,13 @@ std::pair<AqlItemBlockInputRange::State, InputAqlItemRow> AqlItemBlockInputRange
 }
 
 bool AqlItemBlockInputRange::indexIsValid() const noexcept {
-  return _block != nullptr && _rowIndex < _block->size();
+  return _block != nullptr && _rowIndex < _endIndex;
 }
 
-bool AqlItemBlockInputRange::moreRowsAfterThis() const noexcept {
-  return indexIsValid() && _rowIndex + 1 < _block->size();
+bool AqlItemBlockInputRange::hasMore() const noexcept {
+  return indexIsValid() && _rowIndex + 1 < _endIndex;
 }
 
-AqlItemBlockInputRange::State AqlItemBlockInputRange::state() const noexcept {
-  return moreRowsAfterThis() ? State::HASMORE : _finalState;
+ExecutorState AqlItemBlockInputRange::state() const noexcept {
+  return hasMore() ? ExecutorState::HASMORE : _finalState;
 }
diff --git a/arangod/Aql/AqlItemBlockInputRange.h b/arangod/Aql/AqlItemBlockInputRange.h
index bdfc710c9f05..477b58c53bfe 100644
--- a/arangod/Aql/AqlItemBlockInputRange.h
+++ b/arangod/Aql/AqlItemBlockInputRange.h
@@ -23,6 +23,7 @@
 #ifndef ARANGOD_AQL_AQLITEMBLOCKINPUTITERATOR_H
 #define ARANGOD_AQL_AQLITEMBLOCKINPUTITERATOR_H
 
+#include "Aql/ExecutionState.h"
 #include "Aql/InputAqlItemRow.h"
 #include "Aql/SharedAqlItemBlockPtr.h"
 
@@ -30,26 +31,31 @@ namespace arangodb::aql {
 
 class AqlItemBlockInputRange {
  public:
-  enum class State : uint8_t { HASMORE, DONE };
+  AqlItemBlockInputRange();
 
-  AqlItemBlockInputRange(State, arangodb::aql::SharedAqlItemBlockPtr const&, std::size_t);
-  AqlItemBlockInputRange(State, arangodb::aql::SharedAqlItemBlockPtr&&, std::size_t) noexcept;
+  AqlItemBlockInputRange(ExecutorState, arangodb::aql::SharedAqlItemBlockPtr const&,
+                         std::size_t, std::size_t endIndex);
+  AqlItemBlockInputRange(ExecutorState, arangodb::aql::SharedAqlItemBlockPtr&&,
+                         std::size_t, std::size_t endIndex) noexcept;
 
-  std::pair<State, arangodb::aql::InputAqlItemRow> peek();
+  bool hasMore() const noexcept;
 
-  std::pair<State, arangodb::aql::InputAqlItemRow> next();
+  ExecutorState state() const noexcept;
+
+  std::pair<ExecutorState, arangodb::aql::InputAqlItemRow> peek();
+
+  std::pair<ExecutorState, arangodb::aql::InputAqlItemRow> next();
 
  private:
-  State state() const noexcept;
   bool indexIsValid() const noexcept;
-  bool moreRowsAfterThis() const noexcept;
 
  private:
   arangodb::aql::SharedAqlItemBlockPtr _block;
   std::size_t _rowIndex;
-  State _finalState;
+  std::size_t _endIndex;
+  ExecutorState _finalState;
 };
 
-}
+}  // namespace arangodb::aql
 
 #endif  // ARANGOD_AQL_AQLITEMBLOCKINPUTITERATOR_H
diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index 7f9656966d35..0162b0c62663 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -583,6 +583,45 @@ std::pair<ExecutionState, Result> ExecutionBlockImpl<
   }
   return {ExecutionState::DONE, {errorCode}};
 }
+
+// TODO this is only temporary, remove me
+// Just to make sure everything compiles!
+template <>
+std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr>
+ExecutionBlockImpl<FilterExecutor>::execute(AqlCallStack stack) {
+  // TODO make this a member variable
+  Fetcher::DataRange emptyRange{};
+  // TODO: pop this from the stack instead of modify.
+  // TODO: Need to make this member variable for waiting?
+  AqlCall& myCall = stack.myCall();
+  // Skipping path
+  while (myCall.offset > 0) {
+    // Execute skipSome
+    auto const [state, skipped, call] = _executor.skipRowsRange(myCall.offset, emptyRange);
+    if (state == ExecutorState::DONE) {
+      // We are done with this subquery
+      // TODO Implement me properly, we would need to fill shadowRows into the block
+      return {ExecutionState::DONE, skipped, nullptr};
+    }
+    TRI_ASSERT(skipped <= myCall.offset);
+    myCall.offset -= skipped;
+    if (myCall.offset > 0) {
+      // Need to fetch more
+      // TODO: we need to push the returned call into the stack, pop our call of.
+      size_t skipped = 0;
+      std::tie(_upstreamState, skipped, emptyRange) = _rowFetcher.execute(stack);
+      TRI_ASSERT(skipped <= myCall.offset);
+      myCall.offset -= skipped;
+    }
+  }
+
+  // TODO add GetSome path
+
+  // TODO implement!
+  TRI_ASSERT(false);
+  THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
+}
+
 }  // namespace aql
 }  // namespace arangodb
 
diff --git a/arangod/Aql/ExecutionState.cpp b/arangod/Aql/ExecutionState.cpp
index 4e788e565560..39b426fb6d46 100644
--- a/arangod/Aql/ExecutionState.cpp
+++ b/arangod/Aql/ExecutionState.cpp
@@ -42,5 +42,17 @@ std::ostream& operator<<(std::ostream& ostream, ExecutionState state) {
   return ostream;
 }
 
+std::ostream& operator<<(std::ostream& ostream, ExecutorState state) {
+  switch (state) {
+    case ExecutorState::DONE:
+      ostream << "DONE";
+      break;
+    case ExecutorState::HASMORE:
+      ostream << "HASMORE";
+      break;
+  }
+  return ostream;
+}
+
 }  // namespace aql
 }  // namespace arangodb
diff --git a/arangod/Aql/ExecutionState.h b/arangod/Aql/ExecutionState.h
index 0ac112b92aa8..04edf78a9e8a 100644
--- a/arangod/Aql/ExecutionState.h
+++ b/arangod/Aql/ExecutionState.h
@@ -42,8 +42,21 @@ enum class ExecutionState {
   WAITING
 };
 
+enum class ExecutorState {
+  // done with this block, definitely no more results
+  DONE,
+  // (potentially) more results available. this may "lie" and
+  // report that there are more results when in fact there are
+  // none (background: to accurately determine that there are
+  // more results we may need to execute expensive operations
+  // on the preceeding blocks, which we want to avoid)
+  HASMORE
+};
+
 std::ostream& operator<<(std::ostream& ostream, ExecutionState state);
 
+std::ostream& operator<<(std::ostream& ostream, ExecutorState state);
+
 }  // namespace aql
 }  // namespace arangodb
 #endif
diff --git a/arangod/Aql/FilterExecutor.cpp b/arangod/Aql/FilterExecutor.cpp
index f6769f6fae6b..601e955125b4 100644
--- a/arangod/Aql/FilterExecutor.cpp
+++ b/arangod/Aql/FilterExecutor.cpp
@@ -25,6 +25,9 @@
 
 #include "FilterExecutor.h"
 
+#include "Aql/AqlCall.h"
+#include "Aql/AqlCallStack.h"
+#include "Aql/AqlItemBlockInputRange.h"
 #include "Aql/AqlValue.h"
 #include "Aql/ExecutorInfos.h"
 #include "Aql/InputAqlItemRow.h"
@@ -52,9 +55,12 @@ FilterExecutorInfos::FilterExecutorInfos(RegisterId inputRegister, RegisterId nr
                     std::move(registersToClear), std::move(registersToKeep)),
       _inputRegister(inputRegister) {}
 
-RegisterId FilterExecutorInfos::getInputRegister() const noexcept { return _inputRegister; }
+RegisterId FilterExecutorInfos::getInputRegister() const noexcept {
+  return _inputRegister;
+}
 
-FilterExecutor::FilterExecutor(Fetcher& fetcher, Infos& infos) : _infos(infos), _fetcher(fetcher) {}
+FilterExecutor::FilterExecutor(Fetcher& fetcher, Infos& infos)
+    : _infos(infos), _fetcher(fetcher) {}
 
 FilterExecutor::~FilterExecutor() = default;
 
@@ -99,3 +105,69 @@ std::pair<ExecutionState, size_t> FilterExecutor::expectedNumberOfRows(size_t at
   return _fetcher.preFetchNumberOfRows(atMost);
 }
 
+std::tuple<ExecutorState, size_t, AqlCall> FilterExecutor::skipRowsRange(
+    size_t offset, AqlItemBlockInputRange& inputRange) {
+  ExecutorState state = ExecutorState::HASMORE;
+  InputAqlItemRow input{CreateInvalidInputRowHint{}};
+  size_t skipped = 0;
+  while (inputRange.hasMore() && skipped < offset) {
+    std::tie(state, input) = inputRange.next();
+    if (!input) {
+      TRI_ASSERT(!inputRange.hasMore());
+      break;
+    }
+    if (input.getValue(_infos.getInputRegister()).toBoolean()) {
+      skipped++;
+    }
+  }
+
+  AqlCall upstreamCall{};
+  upstreamCall.batchSize = offset - skipped;
+  return {state, skipped, upstreamCall};
+}
+
+std::tuple<ExecutorState, FilterStats, AqlCall> FilterExecutor::produceRows(
+    size_t limit, AqlItemBlockInputRange& inputRange, OutputAqlItemRow& output) {
+  TRI_IF_FAILURE("FilterExecutor::produceRows") {
+    THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
+  }
+  FilterStats stats{};
+  ExecutorState state = ExecutorState::HASMORE;
+  InputAqlItemRow input{CreateInvalidInputRowHint{}};
+
+  while (inputRange.hasMore() && limit > 0) {
+    TRI_ASSERT(!output.isFull());
+    std::tie(state, input) = inputRange.next();
+    if (!input) {
+      TRI_ASSERT(!inputRange.hasMore());
+      break;
+    }
+    if (input.getValue(_infos.getInputRegister()).toBoolean()) {
+      output.copyRow(input);
+      output.advanceRow();
+      limit--;
+    } else {
+      stats.incrFiltered();
+    }
+  }
+
+  AqlCall upstreamCall{};
+  upstreamCall.batchSize = limit;
+  return {state, stats, upstreamCall};
+}
+
+/*
+skipSome(x) = > AqlCall{
+  offset : x,
+  batchSize : 0,
+  limit : AqlCall::Infinity{},
+  fullCount : <egal> | false
+}
+
+getSome(x) = > {
+  offset: 0,
+  batchSize : x,
+  limit : AqlCall::Infinity{},
+  fullCount : <egal> | false
+}
+*/
diff --git a/arangod/Aql/FilterExecutor.h b/arangod/Aql/FilterExecutor.h
index a8e15705029e..7ebc68cfdc80 100644
--- a/arangod/Aql/FilterExecutor.h
+++ b/arangod/Aql/FilterExecutor.h
@@ -35,6 +35,8 @@
 namespace arangodb {
 namespace aql {
 
+struct AqlCall;
+class AqlItemBlockInputRange;
 class InputAqlItemRow;
 class OutputAqlItemRow;
 class ExecutorInfos;
@@ -89,6 +91,18 @@ class FilterExecutor {
    */
   std::pair<ExecutionState, Stats> produceRows(OutputAqlItemRow& output);
 
+  /**
+   * @brief produce the next Row of Aql Values.
+   *
+   * @return ExecutorState, the stats, and a new Call that needs to be send to upstream
+   */
+  std::tuple<ExecutorState, Stats, AqlCall> produceRows(size_t atMost,
+                                                        AqlItemBlockInputRange& input,
+                                                        OutputAqlItemRow& output);
+
+  std::tuple<ExecutorState, size_t, AqlCall> skipRowsRange(size_t atMost,
+                                                           AqlItemBlockInputRange& input);
+
   std::pair<ExecutionState, size_t> expectedNumberOfRows(size_t atMost) const;
 
  private:
diff --git a/arangod/Aql/SingleRowFetcher.h b/arangod/Aql/SingleRowFetcher.h
index a4d2788c6207..47b8e22d4f13 100644
--- a/arangod/Aql/SingleRowFetcher.h
+++ b/arangod/Aql/SingleRowFetcher.h
@@ -64,7 +64,7 @@ class SingleRowFetcher {
 
  public:
   // TODO implement and document
-  std::tuple<ExecutionState, size_t, DataRange> execute(/* TODO: add"justDoIt"-style parameter */) {
+  std::tuple<ExecutionState, size_t, DataRange> execute(AqlCallStack& stack) {
     TRI_ASSERT(false);
     THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
   }

From eb120a05af2ae2105760167cd283080dcbfcc47b Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Thu, 24 Oct 2019 13:42:46 +0200
Subject: [PATCH 007/122] Fixed off by one error in InputRange. Fixed
 FilterExecutor

---
 arangod/Aql/AqlItemBlockInputRange.cpp |  6 ++-
 arangod/Aql/AqlItemBlockInputRange.h   |  2 +
 tests/Aql/FilterExecutorTest.cpp       | 66 +++++++++++++++++++++++---
 3 files changed, 66 insertions(+), 8 deletions(-)

diff --git a/arangod/Aql/AqlItemBlockInputRange.cpp b/arangod/Aql/AqlItemBlockInputRange.cpp
index 01ae52159dae..7f9b04efc841 100644
--- a/arangod/Aql/AqlItemBlockInputRange.cpp
+++ b/arangod/Aql/AqlItemBlockInputRange.cpp
@@ -68,10 +68,12 @@ bool AqlItemBlockInputRange::indexIsValid() const noexcept {
   return _block != nullptr && _rowIndex < _endIndex;
 }
 
-bool AqlItemBlockInputRange::hasMore() const noexcept {
+bool AqlItemBlockInputRange::hasMore() const noexcept { return indexIsValid(); }
+
+bool AqlItemBlockInputRange::hasMoreAfterThis() const noexcept {
   return indexIsValid() && _rowIndex + 1 < _endIndex;
 }
 
 ExecutorState AqlItemBlockInputRange::state() const noexcept {
-  return hasMore() ? ExecutorState::HASMORE : _finalState;
+  return hasMoreAfterThis() ? ExecutorState::HASMORE : _finalState;
 }
diff --git a/arangod/Aql/AqlItemBlockInputRange.h b/arangod/Aql/AqlItemBlockInputRange.h
index 477b58c53bfe..a1195cc46108 100644
--- a/arangod/Aql/AqlItemBlockInputRange.h
+++ b/arangod/Aql/AqlItemBlockInputRange.h
@@ -49,6 +49,8 @@ class AqlItemBlockInputRange {
  private:
   bool indexIsValid() const noexcept;
 
+  bool hasMoreAfterThis() const noexcept;
+
  private:
   arangodb::aql::SharedAqlItemBlockPtr _block;
   std::size_t _rowIndex;
diff --git a/tests/Aql/FilterExecutorTest.cpp b/tests/Aql/FilterExecutorTest.cpp
index 780aa699b5b5..5a3868d7f737 100644
--- a/tests/Aql/FilterExecutorTest.cpp
+++ b/tests/Aql/FilterExecutorTest.cpp
@@ -23,9 +23,11 @@
 /// @author Jan Christoph Uhde
 ////////////////////////////////////////////////////////////////////////////////
 
+#include "AqlItemBlockHelper.h"
 #include "RowFetcherHelper.h"
 #include "gtest/gtest.h"
 
+#include "Aql/AqlCall.h"
 #include "Aql/AqlItemBlock.h"
 #include "Aql/ExecutorInfos.h"
 #include "Aql/FilterExecutor.h"
@@ -64,7 +66,8 @@ class FilterExecutorTest : public ::testing::Test {
 
 TEST_F(FilterExecutorTest, there_are_no_rows_upstream_the_producer_does_not_wait) {
   VPackBuilder input;
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input.steal(), false);
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, input.steal(), false);
   FilterExecutor testee(fetcher, infos);
   FilterStats stats{};
 
@@ -77,7 +80,8 @@ TEST_F(FilterExecutorTest, there_are_no_rows_upstream_the_producer_does_not_wait
 
 TEST_F(FilterExecutorTest, there_are_no_rows_upstream_the_producer_waits) {
   VPackBuilder input;
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input.steal(), true);
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, input.steal(), true);
   FilterExecutor testee(fetcher, infos);
   FilterStats stats{};
 
@@ -97,7 +101,8 @@ TEST_F(FilterExecutorTest, there_are_no_rows_upstream_the_producer_waits) {
 TEST_F(FilterExecutorTest, there_are_rows_in_the_upstream_the_producer_does_not_wait) {
   auto input = VPackParser::fromJson(
       "[ [true], [false], [true], [false], [false], [true] ]");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), false);
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, input->steal(), false);
   FilterExecutor testee(fetcher, infos);
   FilterStats stats{};
 
@@ -134,7 +139,8 @@ TEST_F(FilterExecutorTest, there_are_rows_in_the_upstream_the_producer_does_not_
 TEST_F(FilterExecutorTest, there_are_rows_in_the_upstream_the_producer_waits) {
   auto input = VPackParser::fromJson(
       "[ [true], [false], [true], [false], [false], [true] ]");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), true);
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, input->steal(), true);
   FilterExecutor testee(fetcher, infos);
   FilterStats stats{};
 
@@ -216,7 +222,8 @@ TEST_F(FilterExecutorTest,
        there_are_rows_in_the_upstream_and_the_last_one_has_to_be_filtered_the_producer_does_not_wait) {
   auto input = VPackParser::fromJson(
       "[ [true], [false], [true], [false], [false], [true], [false] ]");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), false);
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, input->steal(), false);
   FilterExecutor testee(fetcher, infos);
   FilterStats stats{};
 
@@ -259,7 +266,8 @@ TEST_F(FilterExecutorTest,
        there_are_rows_in_the_upstream_and_the_last_one_has_to_be_filtered_the_producer_waits) {
   auto input = VPackParser::fromJson(
       "[ [true], [false], [true], [false], [false], [true], [false] ]");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), true);
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, input->steal(), true);
   FilterExecutor testee(fetcher, infos);
   FilterStats stats{};
 
@@ -342,6 +350,52 @@ TEST_F(FilterExecutorTest,
   ASSERT_EQ(stats.getFiltered(), 1);
 }
 
+TEST_F(FilterExecutorTest, test_produce_datarange) {
+  // This fetcher will not be called!
+  // After Execute is done this fetcher shall be removed, the Executor does not need it anymore!
+  auto fakeUnusedBlock = VPackParser::fromJson("[  ]");
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, fakeUnusedBlock->steal(), false);
+
+  // This is the relevant part of the test
+  FilterExecutor testee(fetcher, infos);
+  SharedAqlItemBlockPtr inBlock =
+      buildBlock<1>(itemBlockManager,
+                    {{R"(true)"}, {R"(false)"}, {R"(true)"}, {R"(false)"}, {R"(true)"}});
+
+  AqlItemBlockInputRange input{ExecutorState::DONE, inBlock, 0, inBlock->size()};
+
+  OutputAqlItemRow output(std::move(block), outputRegisters, registersToKeep,
+                          infos.registersToClear());
+  EXPECT_EQ(output.numRowsWritten(), 0);
+  auto const [state, stats, call] = testee.produceRows(1000, input, output);
+  EXPECT_EQ(state, ExecutorState::DONE);
+  EXPECT_EQ(stats.getFiltered(), 2);
+  EXPECT_EQ(output.numRowsWritten(), 3);
+  EXPECT_FALSE(input.hasMore());
+}
+
+TEST_F(FilterExecutorTest, test_skip_datarange) {
+  // This fetcher will not be called!
+  // After Execute is done this fetcher shall be removed, the Executor does not need it anymore!
+  auto fakeUnusedBlock = VPackParser::fromJson("[  ]");
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, fakeUnusedBlock->steal(), false);
+
+  // This is the relevant part of the test
+  FilterExecutor testee(fetcher, infos);
+  SharedAqlItemBlockPtr inBlock =
+      buildBlock<1>(itemBlockManager,
+                    {{R"(true)"}, {R"(false)"}, {R"(true)"}, {R"(false)"}, {R"(true)"}});
+
+  AqlItemBlockInputRange input{ExecutorState::DONE, inBlock, 0, inBlock->size()};
+
+  auto const [state, skipped, call] = testee.skipRowsRange(1000, input);
+  EXPECT_EQ(state, ExecutorState::DONE);
+  EXPECT_EQ(skipped, 3);
+  EXPECT_FALSE(input.hasMore());
+}
+
 }  // namespace aql
 }  // namespace tests
 }  // namespace arangodb

From cb2cef238039c2e5b598af25c061b8f61bd2e2fb Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Thu, 24 Oct 2019 14:03:05 +0200
Subject: [PATCH 008/122] Added some more tests if executor cannot fulfill
 atMost

---
 tests/Aql/FilterExecutorTest.cpp | 119 ++++++++++++++++++++++++++++++-
 1 file changed, 116 insertions(+), 3 deletions(-)

diff --git a/tests/Aql/FilterExecutorTest.cpp b/tests/Aql/FilterExecutorTest.cpp
index 5a3868d7f737..72272917a7bb 100644
--- a/tests/Aql/FilterExecutorTest.cpp
+++ b/tests/Aql/FilterExecutorTest.cpp
@@ -375,7 +375,7 @@ TEST_F(FilterExecutorTest, test_produce_datarange) {
   EXPECT_FALSE(input.hasMore());
 }
 
-TEST_F(FilterExecutorTest, test_skip_datarange) {
+TEST_F(FilterExecutorTest, test_produce_datarange_need_more) {
   // This fetcher will not be called!
   // After Execute is done this fetcher shall be removed, the Executor does not need it anymore!
   auto fakeUnusedBlock = VPackParser::fromJson("[  ]");
@@ -388,12 +388,125 @@ TEST_F(FilterExecutorTest, test_skip_datarange) {
       buildBlock<1>(itemBlockManager,
                     {{R"(true)"}, {R"(false)"}, {R"(true)"}, {R"(false)"}, {R"(true)"}});
 
-  AqlItemBlockInputRange input{ExecutorState::DONE, inBlock, 0, inBlock->size()};
+  AqlItemBlockInputRange input{ExecutorState::HASMORE, inBlock, 0, inBlock->size()};
+
+  OutputAqlItemRow output(std::move(block), outputRegisters, registersToKeep,
+                          infos.registersToClear());
+  EXPECT_EQ(output.numRowsWritten(), 0);
+  auto const [state, stats, call] = testee.produceRows(1000, input, output);
+  EXPECT_EQ(state, ExecutorState::HASMORE);
+  EXPECT_EQ(stats.getFiltered(), 2);
+  EXPECT_EQ(output.numRowsWritten(), 3);
+  EXPECT_FALSE(input.hasMore());
+  // Test the Call we send to upstream
+  EXPECT_EQ(call.offset, 0);
+  EXPECT_TRUE(std::holds_alternative<AqlCall::Infinity>(call.limit));
+  // Avoid overfetching. I do not have a strong requirement on this
+  // test, however this is what we do right now.
+  ASSERT_TRUE(std::holds_alternative<size_t>(call.batchSize));
+  EXPECT_EQ(std::get<size_t>(call.batchSize), 997);
+  EXPECT_FALSE(call.fullCount);
+}
+
+TEST_F(FilterExecutorTest, test_skip_datarange_need_more) {
+  // This fetcher will not be called!
+  // After Execute is done this fetcher shall be removed, the Executor does not need it anymore!
+  auto fakeUnusedBlock = VPackParser::fromJson("[  ]");
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, fakeUnusedBlock->steal(), false);
+
+  // This is the relevant part of the test
+  FilterExecutor testee(fetcher, infos);
+  SharedAqlItemBlockPtr inBlock =
+      buildBlock<1>(itemBlockManager,
+                    {{R"(true)"}, {R"(false)"}, {R"(true)"}, {R"(false)"}, {R"(true)"}});
+
+  AqlItemBlockInputRange input{ExecutorState::HASMORE, inBlock, 0, inBlock->size()};
 
   auto const [state, skipped, call] = testee.skipRowsRange(1000, input);
-  EXPECT_EQ(state, ExecutorState::DONE);
+  EXPECT_EQ(state, ExecutorState::HASMORE);
   EXPECT_EQ(skipped, 3);
   EXPECT_FALSE(input.hasMore());
+
+  // Test the Call we send to upstream
+  EXPECT_EQ(call.offset, 0);
+  EXPECT_TRUE(std::holds_alternative<AqlCall::Infinity>(call.limit));
+  // Avoid overfetching. I do not have a strong requirement on this
+  // test, however this is what we do right now.
+  ASSERT_TRUE(std::holds_alternative<size_t>(call.batchSize));
+  EXPECT_EQ(std::get<size_t>(call.batchSize), 997);
+  EXPECT_FALSE(call.fullCount);
+}
+
+TEST_F(FilterExecutorTest, test_produce_datarange_has_more) {
+  // This fetcher will not be called!
+  // After Execute is done this fetcher shall be removed, the Executor does not need it anymore!
+  auto fakeUnusedBlock = VPackParser::fromJson("[  ]");
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, fakeUnusedBlock->steal(), false);
+
+  // This is the relevant part of the test
+  FilterExecutor testee(fetcher, infos);
+  SharedAqlItemBlockPtr inBlock =
+      buildBlock<1>(itemBlockManager,
+                    {{R"(true)"}, {R"(false)"}, {R"(true)"}, {R"(false)"}, {R"(true)"}});
+
+  AqlItemBlockInputRange input{ExecutorState::DONE, inBlock, 0, inBlock->size()};
+  OutputAqlItemRow output(std::move(block), outputRegisters, registersToKeep,
+                          infos.registersToClear());
+  auto const [state, stats, call] = testee.produceRows(2, input, output);
+  EXPECT_EQ(state, ExecutorState::HASMORE);
+  EXPECT_EQ(stats.getFiltered(), 1);
+  EXPECT_EQ(output.numRowsWritten(), 2);
+  EXPECT_TRUE(input.hasMore());
+  // We still have two values in block: false and true
+  {
+    // pop false
+    auto const [state, row] = input.next();
+    EXPECT_EQ(state, ExecutorState::HASMORE);
+    EXPECT_FALSE(row.getValue(0).toBoolean());
+  }
+  {
+    // pop true
+    auto const [state, row] = input.next();
+    EXPECT_EQ(state, ExecutorState::DONE);
+    EXPECT_TRUE(row.getValue(0).toBoolean());
+  }
+  EXPECT_FALSE(input.hasMore());
+}
+
+TEST_F(FilterExecutorTest, test_skip_datarange_has_more) {
+  // This fetcher will not be called!
+  // After Execute is done this fetcher shall be removed, the Executor does not need it anymore!
+  auto fakeUnusedBlock = VPackParser::fromJson("[  ]");
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, fakeUnusedBlock->steal(), false);
+
+  // This is the relevant part of the test
+  FilterExecutor testee(fetcher, infos);
+  SharedAqlItemBlockPtr inBlock =
+      buildBlock<1>(itemBlockManager,
+                    {{R"(true)"}, {R"(false)"}, {R"(true)"}, {R"(false)"}, {R"(true)"}});
+
+  AqlItemBlockInputRange input{ExecutorState::DONE, inBlock, 0, inBlock->size()};
+  auto const [state, skipped, call] = testee.skipRowsRange(2, input);
+  EXPECT_EQ(state, ExecutorState::HASMORE);
+  EXPECT_EQ(skipped, 2);
+  EXPECT_TRUE(input.hasMore());
+  // We still have two values in block: false and true
+  {
+    // pop false
+    auto const [state, row] = input.next();
+    EXPECT_EQ(state, ExecutorState::HASMORE);
+    EXPECT_FALSE(row.getValue(0).toBoolean());
+  }
+  {
+    // pop true
+    auto const [state, row] = input.next();
+    EXPECT_EQ(state, ExecutorState::DONE);
+    EXPECT_TRUE(row.getValue(0).toBoolean());
+  }
+  EXPECT_FALSE(input.hasMore());
 }
 
 }  // namespace aql

From a46941ed34d7284a8f2063e682ef1213e11feb82 Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Fri, 25 Oct 2019 09:12:38 +0200
Subject: [PATCH 009/122] Added heplper functions to the AqlCall struct to
 avoid mangeling around with variants everywhere.

---
 arangod/Aql/AqlCall.h | 37 +++++++++++++++++++++++++++++++++++--
 1 file changed, 35 insertions(+), 2 deletions(-)

diff --git a/arangod/Aql/AqlCall.h b/arangod/Aql/AqlCall.h
index d0989fdab2b8..1e3a4c840463 100644
--- a/arangod/Aql/AqlCall.h
+++ b/arangod/Aql/AqlCall.h
@@ -36,9 +36,42 @@ struct AqlCall {
 
   std::size_t offset{0};
   // TODO: The defaultBatchSize function could move into this file instead
-  Limit batchSize{ExecutionBlock::DefaultBatchSize()};
-  Limit limit{Infinity{}};
+  Limit softLimit{Infinity{}};
+  Limit hardLimit{Infinity{}};
   bool fullCount{false};
+
+  std::size_t getOffset() const { return offset; }
+
+  std::size_t getLimit() const {
+    // By default we use batchsize
+    std::size_t limit = ExecutionBlock::DefaultBatchSize();
+    // We are not allowed to go above softLimit
+    if (std::holds_alternative<std::size_t>(softLimit)) {
+      limit = (std::min)(std::get<std::size_t>(softLimit), limit);
+    }
+    // We are not allowed to go above hardLimit
+    if (std::holds_alternative<std::size_t>(hardLimit)) {
+      limit = (std::min)(std::get<std::size_t>(hardLimit), limit);
+    }
+    return limit;
+  }
+
+  void didProduce(std::size_t n) {
+    if (std::holds_alternative<std::size_t>(softLimit)) {
+      TRI_ASSERT(n <= std::get<std::size_t>(softLimit));
+      softLimit = std::get<std::size_t>(softLimit) - n;
+    }
+    if (std::holds_alternative<std::size_t>(hardLimit)) {
+      TRI_ASSERT(n <= std::get<std::size_t>(hardLimit));
+      hardLimit = std::get<std::size_t>(hardLimit) - n;
+    }
+  }
+
+  bool hasHardLimit() const {
+    return !std::holds_alternative<AqlCall::Infinity>(hardLimit);
+  }
+
+  bool needsFullCount() const { return fullCount; }
 };
 
 }  // namespace aql

From e248e45709e0f62ee7ea362ff152c299f30f8588 Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Fri, 25 Oct 2019 09:26:27 +0200
Subject: [PATCH 010/122] Add a member DataRange to ExecutionBlockImpl. Also
 now all Fetcher expose a DataRange, this might not be the correct one every
 where

---
 arangod/Aql/ConstFetcher.h                    |  2 ++
 arangod/Aql/ExecutionBlockImpl.cpp            | 26 +++++++++++++++----
 arangod/Aql/ExecutionBlockImpl.h              |  2 ++
 arangod/Aql/FilterExecutor.cpp                | 25 +++---------------
 arangod/Aql/MultiDependencySingleRowFetcher.h |  8 +++---
 arangod/Aql/SingleBlockFetcher.h              |  3 +++
 tests/Aql/FilterExecutorTest.cpp              | 10 +++----
 7 files changed, 40 insertions(+), 36 deletions(-)

diff --git a/arangod/Aql/ConstFetcher.h b/arangod/Aql/ConstFetcher.h
index fc282cbb2d38..49aefb19b901 100644
--- a/arangod/Aql/ConstFetcher.h
+++ b/arangod/Aql/ConstFetcher.h
@@ -23,6 +23,7 @@
 #ifndef ARANGOD_AQL_CONST_FETCHER_H
 #define ARANGOD_AQL_CONST_FETCHER_H
 
+#include "Aql/AqlItemBlockInputRange.h"
 #include "Aql/ExecutionState.h"
 #include "Aql/InputAqlItemRow.h"
 
@@ -47,6 +48,7 @@ class ConstFetcher {
   using DependencyProxy = aql::DependencyProxy<BlockPassthrough::Enable>;
 
  public:
+  using DataRange = AqlItemBlockInputRange;
   explicit ConstFetcher(DependencyProxy& executionBlock);
   TEST_VIRTUAL ~ConstFetcher() = default;
 
diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index 0162b0c62663..dbc9c2b37e73 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -110,7 +110,8 @@ ExecutionBlockImpl<Executor>::ExecutionBlockImpl(ExecutionEngine* engine,
       _infos(std::move(infos)),
       _executor(_rowFetcher, _infos),
       _outputItemRow(),
-      _query(*engine->getQuery()) {
+      _query(*engine->getQuery()),
+      _lastRange{} {
   // already insert ourselves into the statistics results
   if (_profile >= PROFILE_LEVEL_BLOCKS) {
     _engine->_stats.nodes.emplace(node->id(), ExecutionStats::Node());
@@ -122,6 +123,14 @@ ExecutionBlockImpl<Executor>::~ExecutionBlockImpl() = default;
 
 template <class Executor>
 std::pair<ExecutionState, SharedAqlItemBlockPtr> ExecutionBlockImpl<Executor>::getSome(size_t atMost) {
+  /*
+  getSome(x) = > {
+    offset: 0,
+    batchSize : x,
+    limit : AqlCall::Infinity{},
+    fullCount : <egal> | false
+  }
+  */
   traceGetSomeBegin(atMost);
   auto result = getSomeWithoutTrace(atMost);
   return traceGetSomeEnd(result.first, std::move(result.second));
@@ -340,6 +349,14 @@ static SkipVariants constexpr skipType() {
 
 template <class Executor>
 std::pair<ExecutionState, size_t> ExecutionBlockImpl<Executor>::skipSome(size_t const atMost) {
+  /*
+  skipSome(x) = > AqlCall{
+    offset : x,
+    batchSize : 0,
+    limit : AqlCall::Infinity{},
+    fullCount : <egal> | false
+  }
+  */
   traceSkipSomeBegin(atMost);
   auto state = ExecutionState::HASMORE;
 
@@ -589,15 +606,13 @@ std::pair<ExecutionState, Result> ExecutionBlockImpl<
 template <>
 std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr>
 ExecutionBlockImpl<FilterExecutor>::execute(AqlCallStack stack) {
-  // TODO make this a member variable
-  Fetcher::DataRange emptyRange{};
   // TODO: pop this from the stack instead of modify.
   // TODO: Need to make this member variable for waiting?
   AqlCall& myCall = stack.myCall();
   // Skipping path
   while (myCall.offset > 0) {
     // Execute skipSome
-    auto const [state, skipped, call] = _executor.skipRowsRange(myCall.offset, emptyRange);
+    auto const [state, skipped, call] = _executor.skipRowsRange(myCall.offset, _lastRange);
     if (state == ExecutorState::DONE) {
       // We are done with this subquery
       // TODO Implement me properly, we would need to fill shadowRows into the block
@@ -609,7 +624,8 @@ ExecutionBlockImpl<FilterExecutor>::execute(AqlCallStack stack) {
       // Need to fetch more
       // TODO: we need to push the returned call into the stack, pop our call of.
       size_t skipped = 0;
-      std::tie(_upstreamState, skipped, emptyRange) = _rowFetcher.execute(stack);
+      TRI_ASSERT(!_lastRange.hasMore());
+      std::tie(_upstreamState, skipped, _lastRange) = _rowFetcher.execute(stack);
       TRI_ASSERT(skipped <= myCall.offset);
       myCall.offset -= skipped;
     }
diff --git a/arangod/Aql/ExecutionBlockImpl.h b/arangod/Aql/ExecutionBlockImpl.h
index 53f2738dbea3..2bfa5cab9e90 100644
--- a/arangod/Aql/ExecutionBlockImpl.h
+++ b/arangod/Aql/ExecutionBlockImpl.h
@@ -251,6 +251,8 @@ class ExecutionBlockImpl final : public ExecutionBlock {
   Query const& _query;
 
   size_t _skipped{};
+
+  typename Fetcher::DataRange _lastRange;
 };
 
 }  // namespace aql
diff --git a/arangod/Aql/FilterExecutor.cpp b/arangod/Aql/FilterExecutor.cpp
index 601e955125b4..445e23da3fa4 100644
--- a/arangod/Aql/FilterExecutor.cpp
+++ b/arangod/Aql/FilterExecutor.cpp
@@ -122,7 +122,7 @@ std::tuple<ExecutorState, size_t, AqlCall> FilterExecutor::skipRowsRange(
   }
 
   AqlCall upstreamCall{};
-  upstreamCall.batchSize = offset - skipped;
+  upstreamCall.softLimit = offset - skipped;
   return {state, skipped, upstreamCall};
 }
 
@@ -138,10 +138,7 @@ std::tuple<ExecutorState, FilterStats, AqlCall> FilterExecutor::produceRows(
   while (inputRange.hasMore() && limit > 0) {
     TRI_ASSERT(!output.isFull());
     std::tie(state, input) = inputRange.next();
-    if (!input) {
-      TRI_ASSERT(!inputRange.hasMore());
-      break;
-    }
+    TRI_ASSERT(input.isInitialized());
     if (input.getValue(_infos.getInputRegister()).toBoolean()) {
       output.copyRow(input);
       output.advanceRow();
@@ -152,22 +149,6 @@ std::tuple<ExecutorState, FilterStats, AqlCall> FilterExecutor::produceRows(
   }
 
   AqlCall upstreamCall{};
-  upstreamCall.batchSize = limit;
+  upstreamCall.softLimit = limit;
   return {state, stats, upstreamCall};
 }
-
-/*
-skipSome(x) = > AqlCall{
-  offset : x,
-  batchSize : 0,
-  limit : AqlCall::Infinity{},
-  fullCount : <egal> | false
-}
-
-getSome(x) = > {
-  offset: 0,
-  batchSize : x,
-  limit : AqlCall::Infinity{},
-  fullCount : <egal> | false
-}
-*/
diff --git a/arangod/Aql/MultiDependencySingleRowFetcher.h b/arangod/Aql/MultiDependencySingleRowFetcher.h
index de8d8a7592e8..9e8bde0168cd 100644
--- a/arangod/Aql/MultiDependencySingleRowFetcher.h
+++ b/arangod/Aql/MultiDependencySingleRowFetcher.h
@@ -23,6 +23,7 @@
 #ifndef ARANGOD_AQL_MULTI_DEPENDENCY_SINGLE_ROW_FETCHER_H
 #define ARANGOD_AQL_MULTI_DEPENDENCY_SINGLE_ROW_FETCHER_H
 
+#include "Aql/AqlItemBlockInputRange.h"
 #include "Aql/ExecutionBlock.h"
 #include "Aql/ExecutionState.h"
 #include "Aql/InputAqlItemRow.h"
@@ -84,6 +85,7 @@ class MultiDependencySingleRowFetcher {
   };
 
  public:
+  using DataRange = AqlItemBlockInputRange;
   explicit MultiDependencySingleRowFetcher(DependencyProxy<BlockPassthrough::Disable>& executionBlock);
   TEST_VIRTUAL ~MultiDependencySingleRowFetcher() = default;
 
@@ -157,9 +159,9 @@ class MultiDependencySingleRowFetcher {
   bool isLastRowInBlock(DependencyInfo const& info) const;
 
   /**
-  * @brief If it returns true, there are no more data row in the current subquery
-  * level. If it returns false, there may or may not be more.
-  */
+   * @brief If it returns true, there are no more data row in the current
+   * subquery level. If it returns false, there may or may not be more.
+   */
   bool noMoreDataRows(DependencyInfo const& info) const;
 
   std::pair<ExecutionState, size_t> preFetchNumberOfRowsForDependency(size_t dependency,
diff --git a/arangod/Aql/SingleBlockFetcher.h b/arangod/Aql/SingleBlockFetcher.h
index 1ad20448cccb..9020046f2f3f 100644
--- a/arangod/Aql/SingleBlockFetcher.h
+++ b/arangod/Aql/SingleBlockFetcher.h
@@ -24,6 +24,7 @@
 #define ARANGOD_AQL_SINGLE_BLOCK_FETCHER_H
 
 #include "Aql/AqlItemBlock.h"
+#include "Aql/AqlItemBlockInputRange.h"
 #include "Aql/AqlItemMatrix.h"
 #include "Aql/DependencyProxy.h"
 #include "Aql/ExecutionState.h"
@@ -48,6 +49,8 @@ class DependencyProxy;
 template <BlockPassthrough pass>
 class SingleBlockFetcher {
  public:
+  using DataRange = AqlItemBlockInputRange;
+
   explicit SingleBlockFetcher(DependencyProxy<pass>& executionBlock)
       : _prefetched(false),
         _dependencyProxy(&executionBlock),
diff --git a/tests/Aql/FilterExecutorTest.cpp b/tests/Aql/FilterExecutorTest.cpp
index 72272917a7bb..5f64b03278d7 100644
--- a/tests/Aql/FilterExecutorTest.cpp
+++ b/tests/Aql/FilterExecutorTest.cpp
@@ -400,11 +400,10 @@ TEST_F(FilterExecutorTest, test_produce_datarange_need_more) {
   EXPECT_FALSE(input.hasMore());
   // Test the Call we send to upstream
   EXPECT_EQ(call.offset, 0);
-  EXPECT_TRUE(std::holds_alternative<AqlCall::Infinity>(call.limit));
+  EXPECT_FALSE(call.hasHardLimit());
   // Avoid overfetching. I do not have a strong requirement on this
   // test, however this is what we do right now.
-  ASSERT_TRUE(std::holds_alternative<size_t>(call.batchSize));
-  EXPECT_EQ(std::get<size_t>(call.batchSize), 997);
+  EXPECT_EQ(call.getLimit(), 997);
   EXPECT_FALSE(call.fullCount);
 }
 
@@ -430,11 +429,10 @@ TEST_F(FilterExecutorTest, test_skip_datarange_need_more) {
 
   // Test the Call we send to upstream
   EXPECT_EQ(call.offset, 0);
-  EXPECT_TRUE(std::holds_alternative<AqlCall::Infinity>(call.limit));
+  EXPECT_FALSE(call.hasHardLimit());
   // Avoid overfetching. I do not have a strong requirement on this
   // test, however this is what we do right now.
-  ASSERT_TRUE(std::holds_alternative<size_t>(call.batchSize));
-  EXPECT_EQ(std::get<size_t>(call.batchSize), 997);
+  EXPECT_EQ(call.getLimit(), 997);
   EXPECT_FALSE(call.fullCount);
 }
 

From c40cfc0634a03ce49d2350c9c59929dd4ce64884 Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Fri, 25 Oct 2019 10:01:59 +0200
Subject: [PATCH 011/122] Added preliminary minimal implementation of execute
 to DependencyProxy and SingleRowFetcher. Both untested and yet incomplete,
 they will only work for MVP.

---
 arangod/Aql/DependencyProxy.cpp  |  9 +++++++++
 arangod/Aql/DependencyProxy.h    |  3 +++
 arangod/Aql/SingleRowFetcher.cpp | 16 ++++++++++++++++
 arangod/Aql/SingleRowFetcher.h   |  5 +----
 4 files changed, 29 insertions(+), 4 deletions(-)

diff --git a/arangod/Aql/DependencyProxy.cpp b/arangod/Aql/DependencyProxy.cpp
index 03a893f165c0..1a320bfe2535 100644
--- a/arangod/Aql/DependencyProxy.cpp
+++ b/arangod/Aql/DependencyProxy.cpp
@@ -22,6 +22,7 @@
 
 #include "DependencyProxy.h"
 
+#include "Aql/AqlCallStack.h"
 #include "Aql/BlocksWithClients.h"
 #include "Aql/types.h"
 #include "Basics/Exceptions.h"
@@ -30,6 +31,14 @@
 using namespace arangodb;
 using namespace arangodb::aql;
 
+template <BlockPassthrough blockPassthrough>
+std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr>
+DependencyProxy<blockPassthrough>::execute(AqlCallStack& stack) {
+  // TODO: Test this, especially if upstreamBlock is done etc.
+  // We do not modify any local state here.
+  return upstreamBlock().execute(stack);
+}
+
 template <BlockPassthrough blockPassthrough>
 ExecutionState DependencyProxy<blockPassthrough>::prefetchBlock(size_t atMost) {
   TRI_ASSERT(atMost > 0);
diff --git a/arangod/Aql/DependencyProxy.h b/arangod/Aql/DependencyProxy.h
index 222c68e6f5db..36d946798517 100644
--- a/arangod/Aql/DependencyProxy.h
+++ b/arangod/Aql/DependencyProxy.h
@@ -73,6 +73,9 @@ class DependencyProxy {
 
   TEST_VIRTUAL ~DependencyProxy() = default;
 
+  // TODO Implement and document properly!
+  std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> execute(AqlCallStack& stack);
+
   // This is only TEST_VIRTUAL, so we ignore this lint warning:
   // NOLINTNEXTLINE google-default-arguments
   TEST_VIRTUAL std::pair<ExecutionState, SharedAqlItemBlockPtr> fetchBlock(
diff --git a/arangod/Aql/SingleRowFetcher.cpp b/arangod/Aql/SingleRowFetcher.cpp
index 6ec650eeb5b7..d8fdf2ed214f 100644
--- a/arangod/Aql/SingleRowFetcher.cpp
+++ b/arangod/Aql/SingleRowFetcher.cpp
@@ -73,6 +73,22 @@ SingleRowFetcher<passBlocksThrough>::fetchBlockForPassthrough(size_t atMost) {
   return _dependencyProxy->fetchBlockForPassthrough(atMost);
 }
 
+template <BlockPassthrough passBlocksThrough>
+std::tuple<ExecutionState, size_t, AqlItemBlockInputRange>
+SingleRowFetcher<passBlocksThrough>::execute(AqlCallStack& stack) {
+  auto const [state, skipped, block] = _dependencyProxy->execute(stack);
+  if (state == ExecutionState::WAITING) {
+    // On waiting we have nothing to return
+    return {state, 0, AqlItemBlockInputRange{}};
+  }
+  if (state == ExecutionState::HASMORE) {
+    return {state, skipped,
+            AqlItemBlockInputRange{ExecutorState::HASMORE, block, 0, block->size()}};
+  }
+  return {state, skipped,
+          AqlItemBlockInputRange{ExecutorState::DONE, block, 0, block->size()}};
+}
+
 template <BlockPassthrough passBlocksThrough>
 std::pair<ExecutionState, size_t> SingleRowFetcher<passBlocksThrough>::skipRows(size_t atMost) {
   TRI_ASSERT(!_currentRow.isInitialized() || _currentRow.isLastRowInBlock());
diff --git a/arangod/Aql/SingleRowFetcher.h b/arangod/Aql/SingleRowFetcher.h
index 47b8e22d4f13..7d2c971878b9 100644
--- a/arangod/Aql/SingleRowFetcher.h
+++ b/arangod/Aql/SingleRowFetcher.h
@@ -64,10 +64,7 @@ class SingleRowFetcher {
 
  public:
   // TODO implement and document
-  std::tuple<ExecutionState, size_t, DataRange> execute(AqlCallStack& stack) {
-    TRI_ASSERT(false);
-    THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
-  }
+  std::tuple<ExecutionState, size_t, DataRange> execute(AqlCallStack& stack);
 
   /**
    * @brief Fetch one new AqlItemRow from upstream.

From 236825280bb5fd03dfe01febfc4dcf1a2d2e2c2f Mon Sep 17 00:00:00 2001
From: hkernbach <heiko.kernbach@gmail.com>
Date: Mon, 28 Oct 2019 18:24:13 +0100
Subject: [PATCH 012/122] added first implementation of count collect datarange
 produceRows function + test

---
 arangod/Aql/CountCollectExecutor.cpp   | 29 +++++++++++++++++++
 arangod/Aql/CountCollectExecutor.h     | 12 ++++++++
 tests/Aql/CountCollectExecutorTest.cpp | 39 +++++++++++++++++++++++---
 3 files changed, 76 insertions(+), 4 deletions(-)

diff --git a/arangod/Aql/CountCollectExecutor.cpp b/arangod/Aql/CountCollectExecutor.cpp
index 228599464298..0005485f8caf 100644
--- a/arangod/Aql/CountCollectExecutor.cpp
+++ b/arangod/Aql/CountCollectExecutor.cpp
@@ -25,6 +25,8 @@
 
 #include "CountCollectExecutor.h"
 
+#include "Aql/AqlCall.h"
+#include "Aql/AqlItemBlockInputRange.h"
 #include "Aql/AqlValue.h"
 #include "Aql/ExecutorInfos.h"
 #include "Aql/InputAqlItemRow.h"
@@ -93,6 +95,33 @@ std::pair<ExecutionState, NoStats> CountCollectExecutor::produceRows(OutputAqlIt
   return {_state, NoStats{}};
 }
 
+std::tuple<ExecutorState, NoStats, AqlCall> CountCollectExecutor::produceRows(
+    size_t limit, AqlItemBlockInputRange& inputRange, OutputAqlItemRow& output) {
+  TRI_IF_FAILURE("CountCollectExecutor::produceRows") {
+    THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
+  }
+  InputAqlItemRow input{CreateInvalidInputRowHint{}};
+
+  while (inputRange.hasMore() && limit > 0) {
+    std::tie(_executorState, input) = inputRange.next();
+
+    limit--;
+    _count++;
+  }
+
+  // In general, we do not have an input row. In fact, we never fetch one.
+  output.setAllowSourceRowUninitialized();
+
+  // We must produce exactly one output row.
+  output.cloneValueInto(_infos.getOutputRegisterId(),
+                        InputAqlItemRow{CreateInvalidInputRowHint{}},
+                        AqlValue(AqlValueHintUInt(getCount())));
+
+  AqlCall upstreamCall{};
+  upstreamCall.softLimit = limit;
+  return {_executorState, NoStats{}, upstreamCall};
+}
+
 void CountCollectExecutor::incrCountBy(size_t incr) noexcept { _count += incr; }
 
 uint64_t CountCollectExecutor::getCount() noexcept { return _count; }
diff --git a/arangod/Aql/CountCollectExecutor.h b/arangod/Aql/CountCollectExecutor.h
index 76243a3e8104..1288efc659f7 100644
--- a/arangod/Aql/CountCollectExecutor.h
+++ b/arangod/Aql/CountCollectExecutor.h
@@ -36,6 +36,8 @@
 namespace arangodb {
 namespace aql {
 
+struct AqlCall;
+class AqlItemBlockInputRange;
 class InputAqlItemRow;
 class NoStats;
 class ExecutorInfos;
@@ -91,6 +93,15 @@ class CountCollectExecutor {
 
   std::pair<ExecutionState, NoStats> produceRows(OutputAqlItemRow& output);
 
+  /**
+   * @brief produce the next Row of Aql Values.
+   *
+   * @return ExecutorState, the stats, and a new Call that needs to be send to upstream
+   */
+  std::tuple<ExecutorState, Stats, AqlCall> produceRows(size_t atMost,
+                                                        AqlItemBlockInputRange& input,
+                                                        OutputAqlItemRow& output);
+
   void incrCountBy(size_t incr) noexcept;
 
   uint64_t getCount() noexcept;;
@@ -104,6 +115,7 @@ class CountCollectExecutor {
   Infos const& _infos;
   Fetcher& _fetcher;
   ExecutionState _state;
+  ExecutorState _executorState;
   uint64_t _count;
 };
 
diff --git a/tests/Aql/CountCollectExecutorTest.cpp b/tests/Aql/CountCollectExecutorTest.cpp
index dea9fc1f2982..45c9e276379a 100644
--- a/tests/Aql/CountCollectExecutorTest.cpp
+++ b/tests/Aql/CountCollectExecutorTest.cpp
@@ -20,9 +20,11 @@
 /// @author Heiko Kernbach
 ////////////////////////////////////////////////////////////////////////////////
 
+#include "AqlItemBlockHelper.h"
 #include "RowFetcherHelper.h"
 #include "gtest/gtest.h"
 
+#include "Aql/AqlCall.h"
 #include "Aql/AqlItemBlock.h"
 #include "Aql/CountCollectExecutor.h"
 #include "Aql/InputAqlItemRow.h"
@@ -60,7 +62,8 @@ class CountCollectExecutorTest : public ::testing::Test {
 TEST_F(CountCollectExecutorTest, there_are_no_rows_upstream_the_producer_doesnt_wait) {
   CountCollectExecutorInfos infos(1 /* outputRegId */, 1 /* nrIn */, nrOutputReg, {}, {});
   VPackBuilder input;
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input.steal(), false);
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, input.steal(), false);
   CountCollectExecutor testee(fetcher, infos);
   NoStats stats{};
 
@@ -81,7 +84,8 @@ TEST_F(CountCollectExecutorTest, there_are_no_rows_upstream_the_producer_doesnt_
 TEST_F(CountCollectExecutorTest, there_are_now_rows_upstream_the_producer_waits) {
   CountCollectExecutorInfos infos(1 /* outputRegId */, 1 /* nrIn */, nrOutputReg, {}, {});
   VPackBuilder input;
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input.steal(), true);
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, input.steal(), true);
   CountCollectExecutor testee(fetcher, infos);
   NoStats stats{};
 
@@ -106,7 +110,8 @@ TEST_F(CountCollectExecutorTest, there_are_now_rows_upstream_the_producer_waits)
 TEST_F(CountCollectExecutorTest, there_are_rows_in_the_upstream_the_producer_doesnt_wait) {
   CountCollectExecutorInfos infos(1 /* outputRegId */, 1 /* nrIn */, nrOutputReg, {}, {});
   auto input = VPackParser::fromJson("[ [1], [2], [3] ]");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), false);
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, input->steal(), false);
   CountCollectExecutor testee(fetcher, infos);
   NoStats stats{};
 
@@ -127,7 +132,8 @@ TEST_F(CountCollectExecutorTest, there_are_rows_in_the_upstream_the_producer_doe
 TEST_F(CountCollectExecutorTest, there_are_rows_in_the_upstream_the_producer_waits) {
   CountCollectExecutorInfos infos(1 /* outputRegId */, 1 /* nrIn */, nrOutputReg, {}, {});
   auto input = VPackParser::fromJson("[ [1], [2], [3] ]");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), true);
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, input->steal(), true);
   CountCollectExecutor testee(fetcher, infos);
   NoStats stats{};
   OutputAqlItemRow result{std::move(block), outputRegisters,
@@ -157,6 +163,31 @@ TEST_F(CountCollectExecutorTest, there_are_rows_in_the_upstream_the_producer_wai
   ASSERT_EQ(3, fetcher.totalSkipped());
 }
 
+TEST_F(CountCollectExecutorTest, test_produce_datarange) {
+  CountCollectExecutorInfos infos(1 /* outputRegId */, 1 /* nrIn */, nrOutputReg, {}, {});
+  auto fakeUnusedBlock = VPackParser::fromJson("[  ]");
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, fakeUnusedBlock->steal(), false);
+  CountCollectExecutor testee(fetcher, infos);
+
+  SharedAqlItemBlockPtr inBlock = buildBlock<1>(itemBlockManager, {{}});
+  AqlItemBlockInputRange input{ExecutorState::DONE, inBlock, 0, inBlock->size()};
+
+  OutputAqlItemRow output(std::move(block), outputRegisters,
+                          infos.registersToKeep(), infos.registersToClear());
+  EXPECT_EQ(output.numRowsWritten(), 0);
+  auto const [state, stats, call] = testee.produceRows(1000, input, output);
+  ASSERT_EQ(state, ExecutorState::DONE);
+  ASSERT_TRUE(output.produced());
+
+  auto block = output.stealBlock();
+  AqlValue x = block->getValue(0, 1);
+  ASSERT_TRUE(x.isNumber());
+  ASSERT_EQ(x.toInt64(), 0);
+
+  ASSERT_EQ(0, fetcher.totalSkipped());
+}
+
 }  // namespace aql
 }  // namespace tests
 }  // namespace arangodb

From acb414f68c38bccb2c89a8433e47cc86323d92d0 Mon Sep 17 00:00:00 2001
From: hkernbach <heiko.kernbach@gmail.com>
Date: Mon, 28 Oct 2019 18:25:48 +0100
Subject: [PATCH 013/122] Revert "added first implementation of count collect
 datarange produceRows function + test"

This reverts commit 236825280bb5fd03dfe01febfc4dcf1a2d2e2c2f.
---
 arangod/Aql/CountCollectExecutor.cpp   | 29 -------------------
 arangod/Aql/CountCollectExecutor.h     | 12 --------
 tests/Aql/CountCollectExecutorTest.cpp | 39 +++-----------------------
 3 files changed, 4 insertions(+), 76 deletions(-)

diff --git a/arangod/Aql/CountCollectExecutor.cpp b/arangod/Aql/CountCollectExecutor.cpp
index 0005485f8caf..228599464298 100644
--- a/arangod/Aql/CountCollectExecutor.cpp
+++ b/arangod/Aql/CountCollectExecutor.cpp
@@ -25,8 +25,6 @@
 
 #include "CountCollectExecutor.h"
 
-#include "Aql/AqlCall.h"
-#include "Aql/AqlItemBlockInputRange.h"
 #include "Aql/AqlValue.h"
 #include "Aql/ExecutorInfos.h"
 #include "Aql/InputAqlItemRow.h"
@@ -95,33 +93,6 @@ std::pair<ExecutionState, NoStats> CountCollectExecutor::produceRows(OutputAqlIt
   return {_state, NoStats{}};
 }
 
-std::tuple<ExecutorState, NoStats, AqlCall> CountCollectExecutor::produceRows(
-    size_t limit, AqlItemBlockInputRange& inputRange, OutputAqlItemRow& output) {
-  TRI_IF_FAILURE("CountCollectExecutor::produceRows") {
-    THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
-  }
-  InputAqlItemRow input{CreateInvalidInputRowHint{}};
-
-  while (inputRange.hasMore() && limit > 0) {
-    std::tie(_executorState, input) = inputRange.next();
-
-    limit--;
-    _count++;
-  }
-
-  // In general, we do not have an input row. In fact, we never fetch one.
-  output.setAllowSourceRowUninitialized();
-
-  // We must produce exactly one output row.
-  output.cloneValueInto(_infos.getOutputRegisterId(),
-                        InputAqlItemRow{CreateInvalidInputRowHint{}},
-                        AqlValue(AqlValueHintUInt(getCount())));
-
-  AqlCall upstreamCall{};
-  upstreamCall.softLimit = limit;
-  return {_executorState, NoStats{}, upstreamCall};
-}
-
 void CountCollectExecutor::incrCountBy(size_t incr) noexcept { _count += incr; }
 
 uint64_t CountCollectExecutor::getCount() noexcept { return _count; }
diff --git a/arangod/Aql/CountCollectExecutor.h b/arangod/Aql/CountCollectExecutor.h
index 1288efc659f7..76243a3e8104 100644
--- a/arangod/Aql/CountCollectExecutor.h
+++ b/arangod/Aql/CountCollectExecutor.h
@@ -36,8 +36,6 @@
 namespace arangodb {
 namespace aql {
 
-struct AqlCall;
-class AqlItemBlockInputRange;
 class InputAqlItemRow;
 class NoStats;
 class ExecutorInfos;
@@ -93,15 +91,6 @@ class CountCollectExecutor {
 
   std::pair<ExecutionState, NoStats> produceRows(OutputAqlItemRow& output);
 
-  /**
-   * @brief produce the next Row of Aql Values.
-   *
-   * @return ExecutorState, the stats, and a new Call that needs to be send to upstream
-   */
-  std::tuple<ExecutorState, Stats, AqlCall> produceRows(size_t atMost,
-                                                        AqlItemBlockInputRange& input,
-                                                        OutputAqlItemRow& output);
-
   void incrCountBy(size_t incr) noexcept;
 
   uint64_t getCount() noexcept;;
@@ -115,7 +104,6 @@ class CountCollectExecutor {
   Infos const& _infos;
   Fetcher& _fetcher;
   ExecutionState _state;
-  ExecutorState _executorState;
   uint64_t _count;
 };
 
diff --git a/tests/Aql/CountCollectExecutorTest.cpp b/tests/Aql/CountCollectExecutorTest.cpp
index 45c9e276379a..dea9fc1f2982 100644
--- a/tests/Aql/CountCollectExecutorTest.cpp
+++ b/tests/Aql/CountCollectExecutorTest.cpp
@@ -20,11 +20,9 @@
 /// @author Heiko Kernbach
 ////////////////////////////////////////////////////////////////////////////////
 
-#include "AqlItemBlockHelper.h"
 #include "RowFetcherHelper.h"
 #include "gtest/gtest.h"
 
-#include "Aql/AqlCall.h"
 #include "Aql/AqlItemBlock.h"
 #include "Aql/CountCollectExecutor.h"
 #include "Aql/InputAqlItemRow.h"
@@ -62,8 +60,7 @@ class CountCollectExecutorTest : public ::testing::Test {
 TEST_F(CountCollectExecutorTest, there_are_no_rows_upstream_the_producer_doesnt_wait) {
   CountCollectExecutorInfos infos(1 /* outputRegId */, 1 /* nrIn */, nrOutputReg, {}, {});
   VPackBuilder input;
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
-      itemBlockManager, input.steal(), false);
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input.steal(), false);
   CountCollectExecutor testee(fetcher, infos);
   NoStats stats{};
 
@@ -84,8 +81,7 @@ TEST_F(CountCollectExecutorTest, there_are_no_rows_upstream_the_producer_doesnt_
 TEST_F(CountCollectExecutorTest, there_are_now_rows_upstream_the_producer_waits) {
   CountCollectExecutorInfos infos(1 /* outputRegId */, 1 /* nrIn */, nrOutputReg, {}, {});
   VPackBuilder input;
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
-      itemBlockManager, input.steal(), true);
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input.steal(), true);
   CountCollectExecutor testee(fetcher, infos);
   NoStats stats{};
 
@@ -110,8 +106,7 @@ TEST_F(CountCollectExecutorTest, there_are_now_rows_upstream_the_producer_waits)
 TEST_F(CountCollectExecutorTest, there_are_rows_in_the_upstream_the_producer_doesnt_wait) {
   CountCollectExecutorInfos infos(1 /* outputRegId */, 1 /* nrIn */, nrOutputReg, {}, {});
   auto input = VPackParser::fromJson("[ [1], [2], [3] ]");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
-      itemBlockManager, input->steal(), false);
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), false);
   CountCollectExecutor testee(fetcher, infos);
   NoStats stats{};
 
@@ -132,8 +127,7 @@ TEST_F(CountCollectExecutorTest, there_are_rows_in_the_upstream_the_producer_doe
 TEST_F(CountCollectExecutorTest, there_are_rows_in_the_upstream_the_producer_waits) {
   CountCollectExecutorInfos infos(1 /* outputRegId */, 1 /* nrIn */, nrOutputReg, {}, {});
   auto input = VPackParser::fromJson("[ [1], [2], [3] ]");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
-      itemBlockManager, input->steal(), true);
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), true);
   CountCollectExecutor testee(fetcher, infos);
   NoStats stats{};
   OutputAqlItemRow result{std::move(block), outputRegisters,
@@ -163,31 +157,6 @@ TEST_F(CountCollectExecutorTest, there_are_rows_in_the_upstream_the_producer_wai
   ASSERT_EQ(3, fetcher.totalSkipped());
 }
 
-TEST_F(CountCollectExecutorTest, test_produce_datarange) {
-  CountCollectExecutorInfos infos(1 /* outputRegId */, 1 /* nrIn */, nrOutputReg, {}, {});
-  auto fakeUnusedBlock = VPackParser::fromJson("[  ]");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
-      itemBlockManager, fakeUnusedBlock->steal(), false);
-  CountCollectExecutor testee(fetcher, infos);
-
-  SharedAqlItemBlockPtr inBlock = buildBlock<1>(itemBlockManager, {{}});
-  AqlItemBlockInputRange input{ExecutorState::DONE, inBlock, 0, inBlock->size()};
-
-  OutputAqlItemRow output(std::move(block), outputRegisters,
-                          infos.registersToKeep(), infos.registersToClear());
-  EXPECT_EQ(output.numRowsWritten(), 0);
-  auto const [state, stats, call] = testee.produceRows(1000, input, output);
-  ASSERT_EQ(state, ExecutorState::DONE);
-  ASSERT_TRUE(output.produced());
-
-  auto block = output.stealBlock();
-  AqlValue x = block->getValue(0, 1);
-  ASSERT_TRUE(x.isNumber());
-  ASSERT_EQ(x.toInt64(), 0);
-
-  ASSERT_EQ(0, fetcher.totalSkipped());
-}
-
 }  // namespace aql
 }  // namespace tests
 }  // namespace arangodb

From e0205b5e813e579942f11a2f33d544862f1d0542 Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Wed, 30 Oct 2019 12:46:10 +0100
Subject: [PATCH 014/122] First draft of execute implementation, not yet
 handling ShadowRows though. This state is broken in the sense that a server
 does not boot with it and catch tests are broken

---
 arangod/Aql/AllRowsFetcher.cpp         |   2 +-
 arangod/Aql/AllRowsFetcher.h           |   6 +-
 arangod/Aql/AqlCall.h                  |  35 +++++
 arangod/Aql/AqlCallStack.cpp           |  12 +-
 arangod/Aql/AqlCallStack.h             |   7 +-
 arangod/Aql/AqlItemBlockInputRange.cpp |   5 +-
 arangod/Aql/AqlItemBlockInputRange.h   |   2 +-
 arangod/Aql/ExecutionBlockImpl.cpp     | 203 ++++++++++++++++++++-----
 arangod/Aql/ExecutionBlockImpl.h       |   7 +-
 arangod/Aql/FilterExecutor.cpp         |   6 +-
 arangod/Aql/SingleRowFetcher.cpp       |   6 +-
 11 files changed, 235 insertions(+), 56 deletions(-)

diff --git a/arangod/Aql/AllRowsFetcher.cpp b/arangod/Aql/AllRowsFetcher.cpp
index 1a48f56cc5d2..d9985d987b01 100644
--- a/arangod/Aql/AllRowsFetcher.cpp
+++ b/arangod/Aql/AllRowsFetcher.cpp
@@ -83,7 +83,7 @@ std::pair<ExecutionState, InputAqlItemRow> AllRowsFetcher::fetchRow(size_t atMos
       _nextReturn = 0;
       _dataFetchedState = DATA_FETCH_ONGOING;
     }
-    [[fallthrough]];
+      [[fallthrough]];
     case DATA_FETCH_ONGOING: {
       TRI_ASSERT(_nextReturn < _rowIndexes.size());
       TRI_ASSERT(_aqlItemMatrix != nullptr);
diff --git a/arangod/Aql/AllRowsFetcher.h b/arangod/Aql/AllRowsFetcher.h
index 9ac5f2d3300e..e271ac3b1c6d 100644
--- a/arangod/Aql/AllRowsFetcher.h
+++ b/arangod/Aql/AllRowsFetcher.h
@@ -33,6 +33,9 @@
 #include <cstddef>
 #include <memory>
 
+// TODO REMOVE ME TEMPORARY
+#include "Aql/AqlItemBlockInputRange.h"
+
 namespace arangodb {
 namespace aql {
 
@@ -92,7 +95,8 @@ class AllRowsFetcher {
 
   TEST_VIRTUAL ~AllRowsFetcher() = default;
 
-  using DataRange = std::shared_ptr<AqlItemMatrix>;
+  // TODO FIXME, this Range does not work here.
+  using DataRange = AqlItemBlockInputRange;
 
  protected:
   // only for testing! Does not initialize _dependencyProxy!
diff --git a/arangod/Aql/AqlCall.h b/arangod/Aql/AqlCall.h
index 1e3a4c840463..8f6592e3ee07 100644
--- a/arangod/Aql/AqlCall.h
+++ b/arangod/Aql/AqlCall.h
@@ -34,6 +34,36 @@ struct AqlCall {
   class Infinity {};
   using Limit = std::variant<size_t, Infinity>;
 
+  // TODO Remove me, this will not be necessary later
+  static AqlCall SimulateSkipSome(std::size_t toSkip) {
+    AqlCall call;
+    call.offset = toSkip;
+    call.softLimit = 0;
+    call.hardLimit = AqlCall::Infinity{};
+    call.fullCount = false;
+    return call;
+  }
+
+  // TODO Remove me, this will not be necessary later
+  static AqlCall SimulateGetSome(std::size_t atMost) {
+    AqlCall call;
+    call.offset = 0;
+    call.softLimit = atMost;
+    call.hardLimit = AqlCall::Infinity{};
+    call.fullCount = false;
+    return call;
+  }
+
+  // TODO Remove me, this will not be necessary later
+  static bool IsSkipSomeCall(AqlCall const& call) {
+    return !call.hasHardLimit() && call.getLimit() == 0 && call.getOffset() > 0;
+  }
+
+  // TODO Remove me, this will not be necessary later
+  static bool IsGetSomeCall(AqlCall const& call) {
+    return !call.hasHardLimit() && call.getLimit() > 0 && call.getOffset() == 0;
+  }
+
   std::size_t offset{0};
   // TODO: The defaultBatchSize function could move into this file instead
   Limit softLimit{Infinity{}};
@@ -56,6 +86,11 @@ struct AqlCall {
     return limit;
   }
 
+  void didSkip(std::size_t n) {
+    TRI_ASSERT(n <= offset);
+    offset -= n;
+  }
+
   void didProduce(std::size_t n) {
     if (std::holds_alternative<std::size_t>(softLimit)) {
       TRI_ASSERT(n <= std::get<std::size_t>(softLimit));
diff --git a/arangod/Aql/AqlCallStack.cpp b/arangod/Aql/AqlCallStack.cpp
index 28bd80c93029..7ce044200658 100644
--- a/arangod/Aql/AqlCallStack.cpp
+++ b/arangod/Aql/AqlCallStack.cpp
@@ -45,10 +45,18 @@ AqlCallStack::AqlCallStack(AqlCallStack const& other)
 
 bool AqlCallStack::isRelevant() const { return _depth == 0; }
 
-AqlCall& AqlCallStack::myCall() {
+AqlCall&& AqlCallStack::popCall() {
   TRI_ASSERT(isRelevant());
   TRI_ASSERT(!_operations.empty());
-  return _operations.top();
+  auto call = _operations.top();
+  _operations.pop();
+  return std::move(call);
+}
+
+void AqlCallStack::pushCall(AqlCall&& call) {
+  // TODO is this correct on subqueries?
+  TRI_ASSERT(isRelevant());
+  _operations.push(call);
 }
 
 void AqlCallStack::stackUpMissingCalls() {
diff --git a/arangod/Aql/AqlCallStack.h b/arangod/Aql/AqlCallStack.h
index 82bbddcbed5c..f34e0f3d0d71 100644
--- a/arangod/Aql/AqlCallStack.h
+++ b/arangod/Aql/AqlCallStack.h
@@ -43,8 +43,11 @@ class AqlCallStack {
   bool isRelevant() const;
 
   // Get the top most Call element (this must be relevant).
-  // Caller is allowed to modify it, if necessary
-  AqlCall& myCall();
+  // This is popped of the stack and caller can take responsibility for it
+  AqlCall&& popCall();
+
+  // Put another call on top of the stack.
+  void pushCall(AqlCall&& call);
 
   // fill up all missing calls within this stack s.t. we reach depth == 0
   // This needs to be called if an executor requires to be fully executed, even if skipped,
diff --git a/arangod/Aql/AqlItemBlockInputRange.cpp b/arangod/Aql/AqlItemBlockInputRange.cpp
index 7f9b04efc841..f1b656c3cc71 100644
--- a/arangod/Aql/AqlItemBlockInputRange.cpp
+++ b/arangod/Aql/AqlItemBlockInputRange.cpp
@@ -25,10 +25,9 @@
 using namespace arangodb;
 using namespace arangodb::aql;
 
-AqlItemBlockInputRange::AqlItemBlockInputRange()
-    : _block(nullptr), _rowIndex(0), _endIndex(0), _finalState(ExecutorState::HASMORE) {
+AqlItemBlockInputRange::AqlItemBlockInputRange(ExecutorState state)
+    : _block(nullptr), _rowIndex(0), _endIndex(0), _finalState(state) {
   TRI_ASSERT(!hasMore());
-  TRI_ASSERT(state() == ExecutorState::HASMORE);
 }
 
 AqlItemBlockInputRange::AqlItemBlockInputRange(ExecutorState state,
diff --git a/arangod/Aql/AqlItemBlockInputRange.h b/arangod/Aql/AqlItemBlockInputRange.h
index a1195cc46108..01eef1512402 100644
--- a/arangod/Aql/AqlItemBlockInputRange.h
+++ b/arangod/Aql/AqlItemBlockInputRange.h
@@ -31,7 +31,7 @@ namespace arangodb::aql {
 
 class AqlItemBlockInputRange {
  public:
-  AqlItemBlockInputRange();
+  explicit AqlItemBlockInputRange(ExecutorState state);
 
   AqlItemBlockInputRange(ExecutorState, arangodb::aql::SharedAqlItemBlockPtr const&,
                          std::size_t, std::size_t endIndex);
diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index dbc9c2b37e73..b776c6f44351 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -111,7 +111,7 @@ ExecutionBlockImpl<Executor>::ExecutionBlockImpl(ExecutionEngine* engine,
       _executor(_rowFetcher, _infos),
       _outputItemRow(),
       _query(*engine->getQuery()),
-      _lastRange{} {
+      _lastRange{ExecutorState::HASMORE} {
   // already insert ourselves into the statistics results
   if (_profile >= PROFILE_LEVEL_BLOCKS) {
     _engine->_stats.nodes.emplace(node->id(), ExecutionStats::Node());
@@ -473,8 +473,27 @@ std::pair<ExecutionState, Result> ExecutionBlockImpl<Executor>::shutdown(int err
 
 template <class Executor>
 std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> ExecutionBlockImpl<Executor>::execute(AqlCallStack stack) {
-  // TODO implement!
-  TRI_ASSERT(false);
+  // TODO remove this IF
+  if (std::is_same<Executor, FilterExecutor>::value) {
+    // Only this executor is fully implemented
+    return executeWithoutTrace(stack);
+  }
+
+  // Fall back to getSome/skipSome
+  auto myCall = stack.popCall();
+  TRI_ASSERT(AqlCall::IsSkipSomeCall(myCall) || AqlCall::IsGetSomeCall(myCall));
+  if (AqlCall::IsSkipSomeCall(myCall)) {
+    auto const [state, skipped] = skipSome(myCall.getOffset());
+    if (state != ExecutionState::WAITING) {
+      myCall.didSkip(skipped);
+    }
+    return {state, skipped, nullptr};
+  } else if (AqlCall::IsGetSomeCall(myCall)) {
+    auto const [state, block] = getSome(myCall.getLimit());
+    // We do not need to count as softLimit will be overwritten, and hard cannot be set.
+    return {state, 0, block};
+  }
+  // Should never get here!
   THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
 }
 
@@ -601,43 +620,6 @@ std::pair<ExecutionState, Result> ExecutionBlockImpl<
   return {ExecutionState::DONE, {errorCode}};
 }
 
-// TODO this is only temporary, remove me
-// Just to make sure everything compiles!
-template <>
-std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr>
-ExecutionBlockImpl<FilterExecutor>::execute(AqlCallStack stack) {
-  // TODO: pop this from the stack instead of modify.
-  // TODO: Need to make this member variable for waiting?
-  AqlCall& myCall = stack.myCall();
-  // Skipping path
-  while (myCall.offset > 0) {
-    // Execute skipSome
-    auto const [state, skipped, call] = _executor.skipRowsRange(myCall.offset, _lastRange);
-    if (state == ExecutorState::DONE) {
-      // We are done with this subquery
-      // TODO Implement me properly, we would need to fill shadowRows into the block
-      return {ExecutionState::DONE, skipped, nullptr};
-    }
-    TRI_ASSERT(skipped <= myCall.offset);
-    myCall.offset -= skipped;
-    if (myCall.offset > 0) {
-      // Need to fetch more
-      // TODO: we need to push the returned call into the stack, pop our call of.
-      size_t skipped = 0;
-      TRI_ASSERT(!_lastRange.hasMore());
-      std::tie(_upstreamState, skipped, _lastRange) = _rowFetcher.execute(stack);
-      TRI_ASSERT(skipped <= myCall.offset);
-      myCall.offset -= skipped;
-    }
-  }
-
-  // TODO add GetSome path
-
-  // TODO implement!
-  TRI_ASSERT(false);
-  THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
-}
-
 }  // namespace aql
 }  // namespace arangodb
 
@@ -810,6 +792,147 @@ SharedAqlItemBlockPtr ExecutionBlockImpl<Executor>::requestBlock(size_t nrItems,
   return _engine->itemBlockManager().requestBlock(nrItems, nrRegs);
 }
 
+// TODO: Remove this special implementations
+template <>
+std::pair<ExecutionState, SharedAqlItemBlockPtr> ExecutionBlockImpl<FilterExecutor>::getSome(size_t atMost) {
+  AqlCallStack stack{AqlCall::SimulateGetSome(atMost)};
+  auto const [state, skipped, block] = execute(stack);
+  return {state, block};
+}
+
+template <>
+std::pair<ExecutionState, size_t> ExecutionBlockImpl<FilterExecutor>::skipSome(size_t const toSkip) {
+  AqlCallStack stack{AqlCall::SimulateSkipSome(toSkip)};
+  auto const [state, skipped, block] = execute(stack);
+  return {state, skipped};
+}
+
+template <class Executor>
+std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr>
+ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
+  // TODO implement!
+  TRI_ASSERT(false);
+  THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
+}
+
+// TODO move me up
+enum ExecState { SKIP, PRODUCE, FULLCOUNT, UPSTREAM, SHADOWROWS, DONE };
+
+namespace {
+// This cannot return upstream call or shadowrows.
+ExecState NextState(AqlCall const& call) {
+  if (call.getOffset() > 0) {
+    // First skip
+    return ExecState::SKIP;
+  }
+  if (call.getLimit() > 0) {
+    // Then produce
+    return ExecState::PRODUCE;
+  }
+  if (call.needsFullCount()) {
+    // then fullcount
+    return ExecState::FULLCOUNT;
+  }
+  // now we are done.
+  return ExecState::DONE;
+}
+}  // namespace
+
+template <>
+std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr>
+ExecutionBlockImpl<FilterExecutor>::executeWithoutTrace(AqlCallStack stack) {
+  if (!_outputItemRow) {
+    // TODO: FIXME Hard coded size
+    SharedAqlItemBlockPtr newBlock =
+        _engine->itemBlockManager().requestBlock(1000, _infos.numberOfOutputRegisters());
+    TRI_ASSERT(newBlock != nullptr);
+    TRI_ASSERT(newBlock->size() == 1000);
+    _outputItemRow = createOutputRow(newBlock);
+  }
+  size_t skipped = 0;
+
+  // TODO: Need to make this member variable for waiting?
+  AqlCall myCall = stack.popCall();
+  ExecState execState = ::NextState(myCall);
+  AqlCall executorRequest;
+
+  while (execState != ExecState::DONE) {
+    switch (execState) {
+      case ExecState::SKIP: {
+        auto [state, skippedLocal, call] =
+            _executor.skipRowsRange(myCall.getOffset(), _lastRange);
+        myCall.didSkip(skippedLocal);
+        skipped += skippedLocal;
+
+        if (state == ExecutorState::DONE) {
+          execState = ExecState::SHADOWROWS;
+        } else if (myCall.getOffset() > 0) {
+          // We need to request more
+          executorRequest = call;
+          execState = ExecState::UPSTREAM;
+        } else {
+          // We are done with skipping. Skip is not allowed to request more
+          execState = ::NextState(myCall);
+        }
+        break;
+      }
+      case ExecState::PRODUCE: {
+        auto linesBefore = _outputItemRow->numRowsWritten();
+        TRI_ASSERT(myCall.getLimit() > 0);
+        // Execute getSome
+        auto const [state, stats, call] =
+            _executor.produceRows(myCall.getLimit(), _lastRange, *_outputItemRow);
+        auto written = _outputItemRow->numRowsWritten() - linesBefore;
+        myCall.didProduce(written);
+        if (state == ExecutorState::DONE) {
+          execState = ExecState::SHADOWROWS;
+        } else if (myCall.getLimit() > 0) {
+          // We need to request more
+          executorRequest = call;
+          execState = ExecState::UPSTREAM;
+        } else {
+          // We are done with skipping. Skip is not allowed to request more
+          execState = ::NextState(myCall);
+        }
+        break;
+      }
+      case ExecState::FULLCOUNT: {
+        TRI_ASSERT(false);
+      }
+      case ExecState::UPSTREAM: {
+        // If this triggers the executors produceRows function has returned
+        // HASMORE even if it new that upstream has no further rows.
+        TRI_ASSERT(_upstreamState != ExecutionState::DONE);
+        TRI_ASSERT(!_lastRange.hasMore());
+        size_t skippedLocal = 0;
+        stack.pushCall(std::move(executorRequest));
+        std::tie(_upstreamState, skippedLocal, _lastRange) = _rowFetcher.execute(stack);
+        // Do we need to call it?
+        // myCall.didSkip(skippedLocal);
+        skipped += skippedLocal;
+        execState = ::NextState(myCall);
+        break;
+      }
+      case ExecState::SHADOWROWS: {
+        // Not implemented yet
+        // TRI_ASSERT(false);
+        // execState = ::NextState(myCall);
+        execState = ExecState::DONE;
+        break;
+      }
+      default:
+        // unreachable
+        TRI_ASSERT(false);
+    }
+  }
+
+  auto outputBlock = _outputItemRow->stealBlock();
+  // This is not strictly necessary here, as we shouldn't be called again
+  // after DONE.
+  _outputItemRow.reset();
+  return {_upstreamState, skipped, std::move(outputBlock)};
+}
+
 template class ::arangodb::aql::ExecutionBlockImpl<CalculationExecutor<CalculationType::Condition>>;
 template class ::arangodb::aql::ExecutionBlockImpl<CalculationExecutor<CalculationType::Reference>>;
 template class ::arangodb::aql::ExecutionBlockImpl<CalculationExecutor<CalculationType::V8Condition>>;
diff --git a/arangod/Aql/ExecutionBlockImpl.h b/arangod/Aql/ExecutionBlockImpl.h
index 2bfa5cab9e90..bbc6579b7e34 100644
--- a/arangod/Aql/ExecutionBlockImpl.h
+++ b/arangod/Aql/ExecutionBlockImpl.h
@@ -189,13 +189,18 @@ class ExecutionBlockImpl final : public ExecutionBlock {
   std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> execute(AqlCallStack stack) override;
 
  private:
+  /**
+   * @brief Inner execute() part, without the tracing calls.
+   */
+  std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> executeWithoutTrace(AqlCallStack stack);
+
   /**
    * @brief Inner getSome() part, without the tracing calls.
    */
   std::pair<ExecutionState, SharedAqlItemBlockPtr> getSomeWithoutTrace(size_t atMost);
 
   /**
-   * @brief Inner getSome() part, without the tracing calls.
+   * @brief Inner skipSome() part, without the tracing calls.
    */
   std::pair<ExecutionState, size_t> skipSomeOnceWithoutTrace(size_t atMost);
 
diff --git a/arangod/Aql/FilterExecutor.cpp b/arangod/Aql/FilterExecutor.cpp
index 445e23da3fa4..cbc856397906 100644
--- a/arangod/Aql/FilterExecutor.cpp
+++ b/arangod/Aql/FilterExecutor.cpp
@@ -132,12 +132,10 @@ std::tuple<ExecutorState, FilterStats, AqlCall> FilterExecutor::produceRows(
     THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
   }
   FilterStats stats{};
-  ExecutorState state = ExecutorState::HASMORE;
-  InputAqlItemRow input{CreateInvalidInputRowHint{}};
 
   while (inputRange.hasMore() && limit > 0) {
     TRI_ASSERT(!output.isFull());
-    std::tie(state, input) = inputRange.next();
+    auto const& [state, input] = inputRange.next();
     TRI_ASSERT(input.isInitialized());
     if (input.getValue(_infos.getInputRegister()).toBoolean()) {
       output.copyRow(input);
@@ -150,5 +148,5 @@ std::tuple<ExecutorState, FilterStats, AqlCall> FilterExecutor::produceRows(
 
   AqlCall upstreamCall{};
   upstreamCall.softLimit = limit;
-  return {state, stats, upstreamCall};
+  return {inputRange.peek().first, stats, upstreamCall};
 }
diff --git a/arangod/Aql/SingleRowFetcher.cpp b/arangod/Aql/SingleRowFetcher.cpp
index d8fdf2ed214f..34219bde206e 100644
--- a/arangod/Aql/SingleRowFetcher.cpp
+++ b/arangod/Aql/SingleRowFetcher.cpp
@@ -79,12 +79,16 @@ SingleRowFetcher<passBlocksThrough>::execute(AqlCallStack& stack) {
   auto const [state, skipped, block] = _dependencyProxy->execute(stack);
   if (state == ExecutionState::WAITING) {
     // On waiting we have nothing to return
-    return {state, 0, AqlItemBlockInputRange{}};
+    return {state, 0, AqlItemBlockInputRange{ExecutorState::HASMORE}};
   }
   if (state == ExecutionState::HASMORE) {
+    TRI_ASSERT(block != nullptr);
     return {state, skipped,
             AqlItemBlockInputRange{ExecutorState::HASMORE, block, 0, block->size()}};
   }
+  if (block == nullptr) {
+    return {state, skipped, AqlItemBlockInputRange{ExecutorState::DONE}};
+  }
   return {state, skipped,
           AqlItemBlockInputRange{ExecutorState::DONE, block, 0, block->size()}};
 }

From 96c0fda0cb1192a2b0f979a48c2cd1e31d519c80 Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Thu, 31 Oct 2019 15:41:18 +0100
Subject: [PATCH 015/122] First working draft of execute() call in
 ExecutionBlockImpl. Tests are locally green, however there is at least one
 query still red (on ShadowRows)

---
 arangod/Aql/AqlCallStack.cpp       |   6 ++
 arangod/Aql/AqlCallStack.h         |   4 ++
 arangod/Aql/ExecutionBlockImpl.cpp | 108 ++++++++++++++++++++++++++++-
 arangod/Aql/ExecutionBlockImpl.h   |  10 ++-
 4 files changed, 126 insertions(+), 2 deletions(-)

diff --git a/arangod/Aql/AqlCallStack.cpp b/arangod/Aql/AqlCallStack.cpp
index 7ce044200658..0c5f44b2647d 100644
--- a/arangod/Aql/AqlCallStack.cpp
+++ b/arangod/Aql/AqlCallStack.cpp
@@ -53,6 +53,12 @@ AqlCall&& AqlCallStack::popCall() {
   return std::move(call);
 }
 
+AqlCall const& AqlCallStack::peek() const {
+  TRI_ASSERT(isRelevant());
+  TRI_ASSERT(!_operations.empty());
+  return _operations.top();
+}
+
 void AqlCallStack::pushCall(AqlCall&& call) {
   // TODO is this correct on subqueries?
   TRI_ASSERT(isRelevant());
diff --git a/arangod/Aql/AqlCallStack.h b/arangod/Aql/AqlCallStack.h
index f34e0f3d0d71..03a9a91d34c5 100644
--- a/arangod/Aql/AqlCallStack.h
+++ b/arangod/Aql/AqlCallStack.h
@@ -46,6 +46,10 @@ class AqlCallStack {
   // This is popped of the stack and caller can take responsibility for it
   AqlCall&& popCall();
 
+  // Peek at the top most Call element (this must be relevant).
+  // The responsibility will stay at the stack
+  AqlCall const& peek() const;
+
   // Put another call on top of the stack.
   void pushCall(AqlCall&& call);
 
diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index b776c6f44351..15bebd23b963 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -65,12 +65,40 @@
 #include "Aql/SubqueryExecutor.h"
 #include "Aql/SubqueryStartExecutor.h"
 #include "Aql/TraversalExecutor.h"
+#include "Basics/system-functions.h"
+#include "Transaction/Context.h"
+
+#include <velocypack/Dumper.h>
+#include <velocypack/velocypack-aliases.h>
 
 #include <type_traits>
 
 using namespace arangodb;
 using namespace arangodb::aql;
 
+namespace {
+
+std::string const doneString = "DONE";
+std::string const hasMoreString = "HASMORE";
+std::string const waitingString = "WAITING";
+std::string const unknownString = "UNKNOWN";
+
+std::string const& stateToString(aql::ExecutionState state) {
+  switch (state) {
+    case aql::ExecutionState::DONE:
+      return doneString;
+    case aql::ExecutionState::HASMORE:
+      return hasMoreString;
+    case aql::ExecutionState::WAITING:
+      return waitingString;
+    default:
+      // just to suppress a warning ..
+      return unknownString;
+  }
+}
+
+}  // namespace
+
 /*
  * Creates a metafunction `checkName` that tests whether a class has a method
  * named `methodName`, used like this:
@@ -433,6 +461,7 @@ template <class Executor>
 std::pair<ExecutionState, Result> ExecutionBlockImpl<Executor>::initializeCursor(InputAqlItemRow const& input) {
   // reinitialize the DependencyProxy
   _dependencyProxy.reset();
+  _lastRange = DataRange(ExecutorState::HASMORE);
 
   // destroy and re-create the Fetcher
   _rowFetcher.~Fetcher();
@@ -476,7 +505,10 @@ std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> ExecutionBlockImpl<Exe
   // TODO remove this IF
   if (std::is_same<Executor, FilterExecutor>::value) {
     // Only this executor is fully implemented
-    return executeWithoutTrace(stack);
+    traceExecuteBegin(stack);
+    auto res = executeWithoutTrace(stack);
+    traceExecuteEnd(res);
+    return res;
   }
 
   // Fall back to getSome/skipSome
@@ -497,6 +529,79 @@ std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> ExecutionBlockImpl<Exe
   THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
 }
 
+template <class Executor>
+void ExecutionBlockImpl<Executor>::traceExecuteBegin(AqlCallStack const& stack) {
+  if (_profile >= PROFILE_LEVEL_BLOCKS) {
+    if (_getSomeBegin <= 0.0) {
+      _getSomeBegin = TRI_microtime();
+    }
+    if (_profile >= PROFILE_LEVEL_TRACE_1) {
+      auto const node = getPlanNode();
+      auto const queryId = this->_engine->getQuery()->id();
+      // TODO make sure this works also if stack is non relevant, e.g. passed through by outer subquery.
+      auto const& call = stack.peek();
+      LOG_TOPIC("1e717", INFO, Logger::QUERIES)
+          << "[query#" << queryId << "] "
+          << "execute type=" << node->getTypeString()
+          << " offset=" << call.getOffset() << " limit= " << call.getLimit()
+          << " this=" << (uintptr_t)this << " id=" << node->id();
+    }
+  }
+}
+
+template <class Executor>
+void ExecutionBlockImpl<Executor>::traceExecuteEnd(
+    std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> const& result) {
+  if (_profile >= PROFILE_LEVEL_BLOCKS) {
+    auto const& [state, skipped, block] = result;
+    auto const items = block != nullptr ? block->size() : 0;
+    ExecutionNode const* en = getPlanNode();
+    ExecutionStats::Node stats;
+    stats.calls = 1;
+    stats.items = skipped + items;
+    if (state != ExecutionState::WAITING) {
+      stats.runtime = TRI_microtime() - _getSomeBegin;
+      _getSomeBegin = 0.0;
+    }
+
+    auto it = _engine->_stats.nodes.find(en->id());
+    if (it != _engine->_stats.nodes.end()) {
+      it->second += stats;
+    } else {
+      _engine->_stats.nodes.emplace(en->id(), stats);
+    }
+
+    if (_profile >= PROFILE_LEVEL_TRACE_1) {
+      ExecutionNode const* node = getPlanNode();
+      auto const queryId = this->_engine->getQuery()->id();
+      LOG_TOPIC("60bbc", INFO, Logger::QUERIES)
+          << "[query#" << queryId << "] "
+          << "execute done type=" << node->getTypeString() << " this=" << (uintptr_t)this
+          << " id=" << node->id() << " state=" << stateToString(state)
+          << " skipped=" << skipped << " produced=" << items;
+
+      if (_profile >= PROFILE_LEVEL_TRACE_2) {
+        if (block == nullptr) {
+          LOG_TOPIC("9b3f4", INFO, Logger::QUERIES)
+              << "[query#" << queryId << "] "
+              << "execute type=" << node->getTypeString() << " result: nullptr";
+        } else {
+          VPackBuilder builder;
+          {
+            VPackObjectBuilder guard(&builder);
+            block->toVelocyPack(transaction(), builder);
+          }
+          auto options = transaction()->transactionContextPtr()->getVPackOptions();
+          LOG_TOPIC("f12f9", INFO, Logger::QUERIES)
+              << "[query#" << queryId << "] "
+              << "execute type=" << node->getTypeString()
+              << " result: " << VPackDumper::toString(builder.slice(), options);
+        }
+      }
+    }
+  }
+}
+
 // Work around GCC bug: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=56480
 // Without the namespaces it fails with
 // error: specialization of 'template<class Executor> std::pair<arangodb::aql::ExecutionState, arangodb::Result> arangodb::aql::ExecutionBlockImpl<Executor>::initializeCursor(arangodb::aql::AqlItemBlock*, size_t)' in different namespace
@@ -883,6 +988,7 @@ ExecutionBlockImpl<FilterExecutor>::executeWithoutTrace(AqlCallStack stack) {
         auto const [state, stats, call] =
             _executor.produceRows(myCall.getLimit(), _lastRange, *_outputItemRow);
         auto written = _outputItemRow->numRowsWritten() - linesBefore;
+        _engine->_stats += stats;
         myCall.didProduce(written);
         if (state == ExecutorState::DONE) {
           execState = ExecState::SHADOWROWS;
diff --git a/arangod/Aql/ExecutionBlockImpl.h b/arangod/Aql/ExecutionBlockImpl.h
index bbc6579b7e34..920d825e6dd0 100644
--- a/arangod/Aql/ExecutionBlockImpl.h
+++ b/arangod/Aql/ExecutionBlockImpl.h
@@ -94,6 +94,8 @@ class ExecutionBlockImpl final : public ExecutionBlock {
   using Fetcher = typename Executor::Fetcher;
   using ExecutorStats = typename Executor::Stats;
   using Infos = typename Executor::Infos;
+  using DataRange = typename Executor::Fetcher::DataRange;
+
   using DependencyProxy =
       typename aql::DependencyProxy<Executor::Properties::allowsBlockPassthrough>;
 
@@ -229,6 +231,12 @@ class ExecutionBlockImpl final : public ExecutionBlock {
   /// @brief request an AqlItemBlock from the memory manager
   SharedAqlItemBlockPtr requestBlock(size_t nrItems, RegisterCount nrRegs);
 
+  // Trace the start of a getSome call
+  void traceExecuteBegin(AqlCallStack const& stack);
+
+  // Trace the end of a getSome call, potentially with result
+  void traceExecuteEnd(std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> const& result);
+
  private:
   /**
    * @brief Used to allow the row Fetcher to access selected methods of this
@@ -257,7 +265,7 @@ class ExecutionBlockImpl final : public ExecutionBlock {
 
   size_t _skipped{};
 
-  typename Fetcher::DataRange _lastRange;
+  DataRange _lastRange;
 };
 
 }  // namespace aql

From 4d019a1d51f2f0932b893bf20de3863a04bda64d Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Thu, 31 Oct 2019 17:01:19 +0100
Subject: [PATCH 016/122] Removed non finished implementation from this Branch.
 It moved to seperate branch

---
 arangod/Aql/ExecutionBlockImpl.cpp | 159 -----------------------------
 arangod/Aql/SingleRowFetcher.cpp   |  17 +--
 2 files changed, 2 insertions(+), 174 deletions(-)

diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index 15bebd23b963..c1f90547643b 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -151,14 +151,6 @@ ExecutionBlockImpl<Executor>::~ExecutionBlockImpl() = default;
 
 template <class Executor>
 std::pair<ExecutionState, SharedAqlItemBlockPtr> ExecutionBlockImpl<Executor>::getSome(size_t atMost) {
-  /*
-  getSome(x) = > {
-    offset: 0,
-    batchSize : x,
-    limit : AqlCall::Infinity{},
-    fullCount : <egal> | false
-  }
-  */
   traceGetSomeBegin(atMost);
   auto result = getSomeWithoutTrace(atMost);
   return traceGetSomeEnd(result.first, std::move(result.second));
@@ -377,14 +369,6 @@ static SkipVariants constexpr skipType() {
 
 template <class Executor>
 std::pair<ExecutionState, size_t> ExecutionBlockImpl<Executor>::skipSome(size_t const atMost) {
-  /*
-  skipSome(x) = > AqlCall{
-    offset : x,
-    batchSize : 0,
-    limit : AqlCall::Infinity{},
-    fullCount : <egal> | false
-  }
-  */
   traceSkipSomeBegin(atMost);
   auto state = ExecutionState::HASMORE;
 
@@ -502,15 +486,6 @@ std::pair<ExecutionState, Result> ExecutionBlockImpl<Executor>::shutdown(int err
 
 template <class Executor>
 std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> ExecutionBlockImpl<Executor>::execute(AqlCallStack stack) {
-  // TODO remove this IF
-  if (std::is_same<Executor, FilterExecutor>::value) {
-    // Only this executor is fully implemented
-    traceExecuteBegin(stack);
-    auto res = executeWithoutTrace(stack);
-    traceExecuteEnd(res);
-    return res;
-  }
-
   // Fall back to getSome/skipSome
   auto myCall = stack.popCall();
   TRI_ASSERT(AqlCall::IsSkipSomeCall(myCall) || AqlCall::IsGetSomeCall(myCall));
@@ -897,21 +872,6 @@ SharedAqlItemBlockPtr ExecutionBlockImpl<Executor>::requestBlock(size_t nrItems,
   return _engine->itemBlockManager().requestBlock(nrItems, nrRegs);
 }
 
-// TODO: Remove this special implementations
-template <>
-std::pair<ExecutionState, SharedAqlItemBlockPtr> ExecutionBlockImpl<FilterExecutor>::getSome(size_t atMost) {
-  AqlCallStack stack{AqlCall::SimulateGetSome(atMost)};
-  auto const [state, skipped, block] = execute(stack);
-  return {state, block};
-}
-
-template <>
-std::pair<ExecutionState, size_t> ExecutionBlockImpl<FilterExecutor>::skipSome(size_t const toSkip) {
-  AqlCallStack stack{AqlCall::SimulateSkipSome(toSkip)};
-  auto const [state, skipped, block] = execute(stack);
-  return {state, skipped};
-}
-
 template <class Executor>
 std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr>
 ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
@@ -920,125 +880,6 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
   THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
 }
 
-// TODO move me up
-enum ExecState { SKIP, PRODUCE, FULLCOUNT, UPSTREAM, SHADOWROWS, DONE };
-
-namespace {
-// This cannot return upstream call or shadowrows.
-ExecState NextState(AqlCall const& call) {
-  if (call.getOffset() > 0) {
-    // First skip
-    return ExecState::SKIP;
-  }
-  if (call.getLimit() > 0) {
-    // Then produce
-    return ExecState::PRODUCE;
-  }
-  if (call.needsFullCount()) {
-    // then fullcount
-    return ExecState::FULLCOUNT;
-  }
-  // now we are done.
-  return ExecState::DONE;
-}
-}  // namespace
-
-template <>
-std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr>
-ExecutionBlockImpl<FilterExecutor>::executeWithoutTrace(AqlCallStack stack) {
-  if (!_outputItemRow) {
-    // TODO: FIXME Hard coded size
-    SharedAqlItemBlockPtr newBlock =
-        _engine->itemBlockManager().requestBlock(1000, _infos.numberOfOutputRegisters());
-    TRI_ASSERT(newBlock != nullptr);
-    TRI_ASSERT(newBlock->size() == 1000);
-    _outputItemRow = createOutputRow(newBlock);
-  }
-  size_t skipped = 0;
-
-  // TODO: Need to make this member variable for waiting?
-  AqlCall myCall = stack.popCall();
-  ExecState execState = ::NextState(myCall);
-  AqlCall executorRequest;
-
-  while (execState != ExecState::DONE) {
-    switch (execState) {
-      case ExecState::SKIP: {
-        auto [state, skippedLocal, call] =
-            _executor.skipRowsRange(myCall.getOffset(), _lastRange);
-        myCall.didSkip(skippedLocal);
-        skipped += skippedLocal;
-
-        if (state == ExecutorState::DONE) {
-          execState = ExecState::SHADOWROWS;
-        } else if (myCall.getOffset() > 0) {
-          // We need to request more
-          executorRequest = call;
-          execState = ExecState::UPSTREAM;
-        } else {
-          // We are done with skipping. Skip is not allowed to request more
-          execState = ::NextState(myCall);
-        }
-        break;
-      }
-      case ExecState::PRODUCE: {
-        auto linesBefore = _outputItemRow->numRowsWritten();
-        TRI_ASSERT(myCall.getLimit() > 0);
-        // Execute getSome
-        auto const [state, stats, call] =
-            _executor.produceRows(myCall.getLimit(), _lastRange, *_outputItemRow);
-        auto written = _outputItemRow->numRowsWritten() - linesBefore;
-        _engine->_stats += stats;
-        myCall.didProduce(written);
-        if (state == ExecutorState::DONE) {
-          execState = ExecState::SHADOWROWS;
-        } else if (myCall.getLimit() > 0) {
-          // We need to request more
-          executorRequest = call;
-          execState = ExecState::UPSTREAM;
-        } else {
-          // We are done with skipping. Skip is not allowed to request more
-          execState = ::NextState(myCall);
-        }
-        break;
-      }
-      case ExecState::FULLCOUNT: {
-        TRI_ASSERT(false);
-      }
-      case ExecState::UPSTREAM: {
-        // If this triggers the executors produceRows function has returned
-        // HASMORE even if it new that upstream has no further rows.
-        TRI_ASSERT(_upstreamState != ExecutionState::DONE);
-        TRI_ASSERT(!_lastRange.hasMore());
-        size_t skippedLocal = 0;
-        stack.pushCall(std::move(executorRequest));
-        std::tie(_upstreamState, skippedLocal, _lastRange) = _rowFetcher.execute(stack);
-        // Do we need to call it?
-        // myCall.didSkip(skippedLocal);
-        skipped += skippedLocal;
-        execState = ::NextState(myCall);
-        break;
-      }
-      case ExecState::SHADOWROWS: {
-        // Not implemented yet
-        // TRI_ASSERT(false);
-        // execState = ::NextState(myCall);
-        execState = ExecState::DONE;
-        break;
-      }
-      default:
-        // unreachable
-        TRI_ASSERT(false);
-    }
-  }
-
-  auto outputBlock = _outputItemRow->stealBlock();
-  // This is not strictly necessary here, as we shouldn't be called again
-  // after DONE.
-  _outputItemRow.reset();
-  return {_upstreamState, skipped, std::move(outputBlock)};
-}
-
 template class ::arangodb::aql::ExecutionBlockImpl<CalculationExecutor<CalculationType::Condition>>;
 template class ::arangodb::aql::ExecutionBlockImpl<CalculationExecutor<CalculationType::Reference>>;
 template class ::arangodb::aql::ExecutionBlockImpl<CalculationExecutor<CalculationType::V8Condition>>;
diff --git a/arangod/Aql/SingleRowFetcher.cpp b/arangod/Aql/SingleRowFetcher.cpp
index 34219bde206e..8ac67aa4070a 100644
--- a/arangod/Aql/SingleRowFetcher.cpp
+++ b/arangod/Aql/SingleRowFetcher.cpp
@@ -76,21 +76,8 @@ SingleRowFetcher<passBlocksThrough>::fetchBlockForPassthrough(size_t atMost) {
 template <BlockPassthrough passBlocksThrough>
 std::tuple<ExecutionState, size_t, AqlItemBlockInputRange>
 SingleRowFetcher<passBlocksThrough>::execute(AqlCallStack& stack) {
-  auto const [state, skipped, block] = _dependencyProxy->execute(stack);
-  if (state == ExecutionState::WAITING) {
-    // On waiting we have nothing to return
-    return {state, 0, AqlItemBlockInputRange{ExecutorState::HASMORE}};
-  }
-  if (state == ExecutionState::HASMORE) {
-    TRI_ASSERT(block != nullptr);
-    return {state, skipped,
-            AqlItemBlockInputRange{ExecutorState::HASMORE, block, 0, block->size()}};
-  }
-  if (block == nullptr) {
-    return {state, skipped, AqlItemBlockInputRange{ExecutorState::DONE}};
-  }
-  return {state, skipped,
-          AqlItemBlockInputRange{ExecutorState::DONE, block, 0, block->size()}};
+  TRI_ASSERT(false);
+  THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
 }
 
 template <BlockPassthrough passBlocksThrough>

From aa275b48ffc2c8fc9a3c364e2241321ec9c9293f Mon Sep 17 00:00:00 2001
From: hkernbach <heiko.kernbach@gmail.com>
Date: Fri, 8 Nov 2019 19:23:59 +0100
Subject: [PATCH 017/122] working - not done yet

---
 arangod/Aql/TraversalExecutor.cpp   | 110 ++++++++++++++++++++++++++++
 arangod/Aql/TraversalExecutor.h     |  12 +++
 tests/Aql/TraversalExecutorTest.cpp | 108 ++++++++++++++++++++++++---
 3 files changed, 220 insertions(+), 10 deletions(-)

diff --git a/arangod/Aql/TraversalExecutor.cpp b/arangod/Aql/TraversalExecutor.cpp
index 963c8bd4845f..6dd62bab66b6 100644
--- a/arangod/Aql/TraversalExecutor.cpp
+++ b/arangod/Aql/TraversalExecutor.cpp
@@ -21,7 +21,10 @@
 ////////////////////////////////////////////////////////////////////////////////
 
 #include "TraversalExecutor.h"
+#include <Logger/LogMacros.h>
 
+#include "Aql/AqlCall.h"
+#include "Aql/AqlItemBlockInputRange.h"
 #include "Aql/ExecutionNode.h"
 #include "Aql/OutputAqlItemRow.h"
 #include "Aql/PruneExpressionEvaluator.h"
@@ -248,6 +251,57 @@ std::pair<ExecutionState, TraversalStats> TraversalExecutor::produceRows(OutputA
   return {ExecutionState::DONE, s};
 }
 
+std::tuple<ExecutorState, TraversalStats, AqlCall> TraversalExecutor::produceRows(
+    size_t limit, AqlItemBlockInputRange& inputRange, OutputAqlItemRow& output) {
+  TraversalStats s;
+
+  while (inputRange.hasMore() && limit > 0) {
+    auto const& [state, input] = inputRange.next();
+    LOG_DEVEL << "ExecutorState: " << state << " - remove me after review";
+
+    if (!resetTraverser(input)) {
+      // Could not start here, (invalid)
+      // Go to next
+      continue;
+    }
+
+    if (!_traverser.hasMore() || !_traverser.next()) {
+      // Nothing more to read, reset input to refetch
+      continue;
+    } else {
+      // traverser now has next v, e, p values
+      if (_infos.useVertexOutput()) {
+        AqlValue vertex = _traverser.lastVertexToAqlValue();
+        AqlValueGuard guard{vertex, true};
+        output.moveValueInto(_infos.vertexRegister(), input, guard);
+      }
+      if (_infos.useEdgeOutput()) {
+        AqlValue edge = _traverser.lastEdgeToAqlValue();
+        AqlValueGuard guard{edge, true};
+        output.moveValueInto(_infos.edgeRegister(), input, guard);
+      }
+      if (_infos.usePathOutput()) {
+        transaction::BuilderLeaser tmp(_traverser.trx());
+        tmp->clear();
+        AqlValue path = _traverser.pathToAqlValue(*tmp.builder());
+        AqlValueGuard guard{path, true};
+        output.moveValueInto(_infos.pathRegister(), input, guard);
+      }
+      output.advanceRow();
+      limit--;
+    }
+  }
+
+  // we are done
+  s.addFiltered(_traverser.getAndResetFilteredPaths());
+  s.addScannedIndex(_traverser.getAndResetReadDocuments());
+  s.addHttpRequests(_traverser.getAndResetHttpRequests());
+
+  AqlCall upstreamCall{};
+  upstreamCall.softLimit = limit;
+  return {inputRange.peek().first, s, upstreamCall};
+}
+
 ExecutionState TraversalExecutor::computeState() const {
   if (_rowState == ExecutionState::DONE && !_traverser.hasMore()) {
     return ExecutionState::DONE;
@@ -310,3 +364,59 @@ bool TraversalExecutor::resetTraverser() {
     }
   }
 }
+
+bool TraversalExecutor::resetTraverser(InputAqlItemRow const& input) {
+  _traverser.traverserCache()->clear();
+
+  // Initialize the Expressions within the options.
+  // We need to find the variable and read its value here. Everything is
+  // computed right now.
+  auto opts = _traverser.options();
+  opts->clearVariableValues();
+  for (auto const& pair : _infos.filterConditionVariables()) {
+    opts->setVariableValue(pair.first, input.getValue(pair.second));
+  }
+  if (opts->usesPrune()) {
+    auto* evaluator = opts->getPruneEvaluator();
+    // Replace by inputRow
+    evaluator->prepareContext(input);
+  }
+  // Now reset the traverser
+  if (_infos.usesFixedSource()) {
+    auto pos = _infos.getFixedSource().find('/');
+    if (pos == std::string::npos) {
+      _traverser.options()->query()->registerWarning(
+          TRI_ERROR_BAD_PARAMETER,
+          "Invalid input for traversal: "
+          "Only id strings or objects with "
+          "_id are allowed");
+      return false;
+    } else {
+      // Use constant value
+      _traverser.setStartVertex(_infos.getFixedSource());
+      return true;
+    }
+  } else {
+    AqlValue const& in = input.getValue(_infos.getInputRegister());
+    if (in.isObject()) {
+      try {
+        _traverser.setStartVertex(_traverser.options()->trx()->extractIdString(in.slice()));
+        return true;
+      } catch (...) {
+        // on purpose ignore this error.
+        return false;
+      }
+      // _id or _key not present we cannot start here, register warning take next
+    } else if (in.isString()) {
+      _traverser.setStartVertex(in.slice().copyString());
+      return true;
+    } else {
+      _traverser.options()->query()->registerWarning(
+          TRI_ERROR_BAD_PARAMETER,
+          "Invalid input for traversal: Only "
+          "id strings or objects with _id are "
+          "allowed");
+      return false;
+    }
+  }
+}
diff --git a/arangod/Aql/TraversalExecutor.h b/arangod/Aql/TraversalExecutor.h
index f749e85d8301..02b4460ad0b3 100644
--- a/arangod/Aql/TraversalExecutor.h
+++ b/arangod/Aql/TraversalExecutor.h
@@ -38,6 +38,8 @@ class Traverser;
 
 namespace aql {
 
+struct AqlCall;
+class AqlItemBlockInputRange;
 class Query;
 class OutputAqlItemRow;
 class ExecutorInfos;
@@ -138,6 +140,15 @@ class TraversalExecutor {
    */
   std::pair<ExecutionState, Stats> produceRows(OutputAqlItemRow& output);
 
+  /**
+   * @brief produce the next Row of Aql Values.
+   *
+   * @return ExecutorState, the stats, and a new Call that needs to be send to upstream
+   */
+  std::tuple<ExecutorState, Stats, AqlCall> produceRows(size_t limit,
+                                                        AqlItemBlockInputRange& inputRange,
+                                                        OutputAqlItemRow& output);
+
  private:
   /**
    * @brief compute the return state
@@ -146,6 +157,7 @@ class TraversalExecutor {
   ExecutionState computeState() const;
 
   bool resetTraverser();
+  bool resetTraverser(InputAqlItemRow const& input);
 
  private:
   Infos& _infos;
diff --git a/tests/Aql/TraversalExecutorTest.cpp b/tests/Aql/TraversalExecutorTest.cpp
index 4d7bdc3f10a4..2fabd2ff183c 100644
--- a/tests/Aql/TraversalExecutorTest.cpp
+++ b/tests/Aql/TraversalExecutorTest.cpp
@@ -20,9 +20,11 @@
 /// @author Michael Hackstein
 ////////////////////////////////////////////////////////////////////////////////
 
+#include "AqlItemBlockHelper.h"
 #include "RowFetcherHelper.h"
 #include "gtest/gtest.h"
 
+#include "Aql/AqlCall.h"
 #include "Aql/AqlItemBlock.h"
 #include "Aql/ExecutionNode.h"
 #include "Aql/InputAqlItemRow.h"
@@ -295,7 +297,8 @@ class TraversalExecutorTestInputStartVertex : public ::testing::Test {
 
 TEST_F(TraversalExecutorTestInputStartVertex, there_are_no_rows_upstream_producer_doesnt_wait) {
   VPackBuilder input;
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input.steal(), false);
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, input.steal(), false);
   TraversalExecutor testee(fetcher, infos);
   TraversalStats stats{};
 
@@ -308,7 +311,8 @@ TEST_F(TraversalExecutorTestInputStartVertex, there_are_no_rows_upstream_produce
 
 TEST_F(TraversalExecutorTestInputStartVertex, there_are_no_rows_upstream_producer_waits) {
   VPackBuilder input;
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input.steal(), true);
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, input.steal(), true);
   TraversalExecutor testee(fetcher, infos);
   TraversalStats stats{};
 
@@ -330,7 +334,8 @@ TEST_F(TraversalExecutorTestInputStartVertex, there_are_rows_upstream_producer_d
   myGraph.addVertex("2");
   myGraph.addVertex("3");
   auto input = VPackParser::fromJson(R"([["v/1"], ["v/2"], ["v/3"]])");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), false);
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, input->steal(), false);
   TraversalExecutor testee(fetcher, infos);
   TraversalStats stats{};
 
@@ -362,7 +367,8 @@ TEST_F(TraversalExecutorTestInputStartVertex,
   myGraph.addVertex("2");
   myGraph.addVertex("3");
   auto input = VPackParser::fromJson(R"([["v/1"], ["v/2"], ["v/3"]])");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), true);
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, input->steal(), true);
   TraversalExecutor testee(fetcher, infos);
   TraversalStats stats{};
 
@@ -400,7 +406,8 @@ TEST_F(TraversalExecutorTestInputStartVertex,
   myGraph.addVertex("2");
   myGraph.addVertex("3");
   auto input = VPackParser::fromJson(R"([["v/1"], ["v/2"], ["v/3"]])");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), true);
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, input->steal(), true);
   TraversalExecutor testee(fetcher, infos);
   TraversalStats stats{};
 
@@ -501,7 +508,8 @@ class TraversalExecutorTestConstantStartVertex : public ::testing::Test {
 
 TEST_F(TraversalExecutorTestConstantStartVertex, no_rows_upstream_producer_doesnt_wait) {
   VPackBuilder input;
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input.steal(), false);
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, input.steal(), false);
   TraversalExecutor testee(fetcher, infos);
   TraversalStats stats{};
 
@@ -514,7 +522,8 @@ TEST_F(TraversalExecutorTestConstantStartVertex, no_rows_upstream_producer_doesn
 
 TEST_F(TraversalExecutorTestConstantStartVertex, no_rows_upstream_producer_waits) {
   VPackBuilder input;
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input.steal(), true);
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, input.steal(), true);
   TraversalExecutor testee(fetcher, infos);
   TraversalStats stats{};
 
@@ -537,7 +546,8 @@ TEST_F(TraversalExecutorTestConstantStartVertex, rows_upstream_producer_doesnt_w
   myGraph.addVertex("3");
   auto input = VPackParser::fromJson(R"([ ["v/1"], ["v/2"], ["v/3"] ])");
 
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), false);
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, input->steal(), false);
   TraversalExecutor testee(fetcher, infos);
   TraversalStats stats{};
 
@@ -569,7 +579,8 @@ TEST_F(TraversalExecutorTestConstantStartVertex, rows_upstream_producer_waits_no
   myGraph.addVertex("3");
   auto input = VPackParser::fromJson(R"([ ["v/1"], ["v/2"], ["v/3"] ])");
 
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), true);
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, input->steal(), true);
   TraversalExecutor testee(fetcher, infos);
   TraversalStats stats{};
   OutputAqlItemRow row(std::move(block), infos.getOutputRegisters(),
@@ -606,7 +617,8 @@ TEST_F(TraversalExecutorTestConstantStartVertex, rows_upstream_producer_waits_ed
   myGraph.addVertex("3");
   auto input = VPackParser::fromJson(R"([ ["v/1"], ["v/2"], ["v/3"] ])");
 
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), true);
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, input->steal(), true);
   TraversalExecutor testee(fetcher, infos);
   TraversalStats stats{};
   myGraph.addEdge("1", "2", "1->2");
@@ -656,6 +668,82 @@ TEST_F(TraversalExecutorTestConstantStartVertex, rows_upstream_producer_waits_ed
   }
 }
 
+TEST_F(TraversalExecutorTestInputStartVertex, test_produce_datarange_no_edges_are_connected) {
+  myGraph.addVertex("1");
+  myGraph.addVertex("2");
+  myGraph.addVertex("3");
+
+  // This fetcher will not be called!
+  // After Execute is done this fetcher shall be removed, the Executor does not need it anymore!
+  auto fakeUnusedBlock = VPackParser::fromJson("[  ]");
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, fakeUnusedBlock->steal(), false);
+
+  // This is the relevant part of the test
+  TraversalExecutor testee(fetcher, infos);
+  SharedAqlItemBlockPtr inBlock =
+      buildBlock<1>(itemBlockManager, {{R"("v/1")"}, {R"("v/2")"}, {R"("v/3")"}});
+
+  AqlItemBlockInputRange input{ExecutorState::DONE, inBlock, 0, inBlock->size()};
+  OutputAqlItemRow output(std::move(block), infos.getOutputRegisters(),
+                          infos.registersToKeep(), infos.registersToClear());
+  EXPECT_EQ(output.numRowsWritten(), 0);
+  auto const [state, stats, call] = testee.produceRows(1000, input, output);
+  EXPECT_EQ(state, ExecutorState::DONE);
+
+  ASSERT_EQ(stats.getFiltered(), 0);
+  ASSERT_FALSE(output.produced());
+
+  ASSERT_EQ(traverser->startVertexUsedAt(0), "v/1");
+  ASSERT_EQ(traverser->startVertexUsedAt(1), "v/2");
+  ASSERT_EQ(traverser->startVertexUsedAt(2), "v/3");
+}
+
+TEST_F(TraversalExecutorTestConstantStartVertex, test_produce_datarange_edges_are_connected) {
+  myGraph.addVertex("1");
+  myGraph.addVertex("2");
+  myGraph.addVertex("3");
+
+  // This fetcher will not be called!
+  // After Execute is done this fetcher shall be removed, the Executor does not need it anymore!
+  auto fakeUnusedBlock = VPackParser::fromJson("[  ]");
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, fakeUnusedBlock->steal(), false);
+
+  // This is the relevant part of the test
+  TraversalExecutor testee(fetcher, infos);
+  SharedAqlItemBlockPtr inBlock =
+      buildBlock<1>(itemBlockManager, {{R"("v/1")"}, {R"("v/2")"}, {R"("v/3")"}});
+
+  myGraph.addEdge("1", "2", "1->2");
+  myGraph.addEdge("2", "3", "2->3");
+  myGraph.addEdge("3", "1", "3->1");
+
+  AqlItemBlockInputRange input{ExecutorState::DONE, inBlock, 0, inBlock->size()};
+  OutputAqlItemRow output(std::move(block), infos.getOutputRegisters(),
+                          infos.registersToKeep(), infos.registersToClear());
+
+  EXPECT_EQ(output.numRowsWritten(), 0);
+  auto const [state, stats, call] = testee.produceRows(1000, input, output);
+  EXPECT_EQ(state, ExecutorState::DONE);
+
+  ASSERT_EQ(traverser->startVertexUsedAt(0), "v/1");
+  ASSERT_EQ(traverser->startVertexUsedAt(1), "v/2");
+  ASSERT_EQ(traverser->startVertexUsedAt(2), "v/3");
+
+  std::vector<std::string> expectedResult{"v/2", "v/3", "v/1"};
+  auto block = output.stealBlock();
+  for (std::size_t index = 0; index < 3; index++) {
+    AqlValue value = block->getValue(index, outReg);
+    ASSERT_TRUE(value.isObject());
+    ASSERT_TRUE(arangodb::basics::VelocyPackHelper::compare(
+                    value.slice(),
+                    myGraph.getVertexData(
+                        arangodb::velocypack::StringRef(expectedResult.at(index))),
+                    false) == 0);
+  }
+}
+
 }  // namespace aql
 }  // namespace tests
 }  // namespace arangodb

From fd33b7f4204693702a33fc3bdb63d549eb7215b3 Mon Sep 17 00:00:00 2001
From: hkernbach <heiko.kernbach@gmail.com>
Date: Fri, 8 Nov 2019 19:25:36 +0100
Subject: [PATCH 018/122] Revert "working - not done yet"

This reverts commit aa275b48ffc2c8fc9a3c364e2241321ec9c9293f.
---
 arangod/Aql/TraversalExecutor.cpp   | 110 ----------------------------
 arangod/Aql/TraversalExecutor.h     |  12 ---
 tests/Aql/TraversalExecutorTest.cpp | 108 +++------------------------
 3 files changed, 10 insertions(+), 220 deletions(-)

diff --git a/arangod/Aql/TraversalExecutor.cpp b/arangod/Aql/TraversalExecutor.cpp
index 6dd62bab66b6..963c8bd4845f 100644
--- a/arangod/Aql/TraversalExecutor.cpp
+++ b/arangod/Aql/TraversalExecutor.cpp
@@ -21,10 +21,7 @@
 ////////////////////////////////////////////////////////////////////////////////
 
 #include "TraversalExecutor.h"
-#include <Logger/LogMacros.h>
 
-#include "Aql/AqlCall.h"
-#include "Aql/AqlItemBlockInputRange.h"
 #include "Aql/ExecutionNode.h"
 #include "Aql/OutputAqlItemRow.h"
 #include "Aql/PruneExpressionEvaluator.h"
@@ -251,57 +248,6 @@ std::pair<ExecutionState, TraversalStats> TraversalExecutor::produceRows(OutputA
   return {ExecutionState::DONE, s};
 }
 
-std::tuple<ExecutorState, TraversalStats, AqlCall> TraversalExecutor::produceRows(
-    size_t limit, AqlItemBlockInputRange& inputRange, OutputAqlItemRow& output) {
-  TraversalStats s;
-
-  while (inputRange.hasMore() && limit > 0) {
-    auto const& [state, input] = inputRange.next();
-    LOG_DEVEL << "ExecutorState: " << state << " - remove me after review";
-
-    if (!resetTraverser(input)) {
-      // Could not start here, (invalid)
-      // Go to next
-      continue;
-    }
-
-    if (!_traverser.hasMore() || !_traverser.next()) {
-      // Nothing more to read, reset input to refetch
-      continue;
-    } else {
-      // traverser now has next v, e, p values
-      if (_infos.useVertexOutput()) {
-        AqlValue vertex = _traverser.lastVertexToAqlValue();
-        AqlValueGuard guard{vertex, true};
-        output.moveValueInto(_infos.vertexRegister(), input, guard);
-      }
-      if (_infos.useEdgeOutput()) {
-        AqlValue edge = _traverser.lastEdgeToAqlValue();
-        AqlValueGuard guard{edge, true};
-        output.moveValueInto(_infos.edgeRegister(), input, guard);
-      }
-      if (_infos.usePathOutput()) {
-        transaction::BuilderLeaser tmp(_traverser.trx());
-        tmp->clear();
-        AqlValue path = _traverser.pathToAqlValue(*tmp.builder());
-        AqlValueGuard guard{path, true};
-        output.moveValueInto(_infos.pathRegister(), input, guard);
-      }
-      output.advanceRow();
-      limit--;
-    }
-  }
-
-  // we are done
-  s.addFiltered(_traverser.getAndResetFilteredPaths());
-  s.addScannedIndex(_traverser.getAndResetReadDocuments());
-  s.addHttpRequests(_traverser.getAndResetHttpRequests());
-
-  AqlCall upstreamCall{};
-  upstreamCall.softLimit = limit;
-  return {inputRange.peek().first, s, upstreamCall};
-}
-
 ExecutionState TraversalExecutor::computeState() const {
   if (_rowState == ExecutionState::DONE && !_traverser.hasMore()) {
     return ExecutionState::DONE;
@@ -364,59 +310,3 @@ bool TraversalExecutor::resetTraverser() {
     }
   }
 }
-
-bool TraversalExecutor::resetTraverser(InputAqlItemRow const& input) {
-  _traverser.traverserCache()->clear();
-
-  // Initialize the Expressions within the options.
-  // We need to find the variable and read its value here. Everything is
-  // computed right now.
-  auto opts = _traverser.options();
-  opts->clearVariableValues();
-  for (auto const& pair : _infos.filterConditionVariables()) {
-    opts->setVariableValue(pair.first, input.getValue(pair.second));
-  }
-  if (opts->usesPrune()) {
-    auto* evaluator = opts->getPruneEvaluator();
-    // Replace by inputRow
-    evaluator->prepareContext(input);
-  }
-  // Now reset the traverser
-  if (_infos.usesFixedSource()) {
-    auto pos = _infos.getFixedSource().find('/');
-    if (pos == std::string::npos) {
-      _traverser.options()->query()->registerWarning(
-          TRI_ERROR_BAD_PARAMETER,
-          "Invalid input for traversal: "
-          "Only id strings or objects with "
-          "_id are allowed");
-      return false;
-    } else {
-      // Use constant value
-      _traverser.setStartVertex(_infos.getFixedSource());
-      return true;
-    }
-  } else {
-    AqlValue const& in = input.getValue(_infos.getInputRegister());
-    if (in.isObject()) {
-      try {
-        _traverser.setStartVertex(_traverser.options()->trx()->extractIdString(in.slice()));
-        return true;
-      } catch (...) {
-        // on purpose ignore this error.
-        return false;
-      }
-      // _id or _key not present we cannot start here, register warning take next
-    } else if (in.isString()) {
-      _traverser.setStartVertex(in.slice().copyString());
-      return true;
-    } else {
-      _traverser.options()->query()->registerWarning(
-          TRI_ERROR_BAD_PARAMETER,
-          "Invalid input for traversal: Only "
-          "id strings or objects with _id are "
-          "allowed");
-      return false;
-    }
-  }
-}
diff --git a/arangod/Aql/TraversalExecutor.h b/arangod/Aql/TraversalExecutor.h
index 02b4460ad0b3..f749e85d8301 100644
--- a/arangod/Aql/TraversalExecutor.h
+++ b/arangod/Aql/TraversalExecutor.h
@@ -38,8 +38,6 @@ class Traverser;
 
 namespace aql {
 
-struct AqlCall;
-class AqlItemBlockInputRange;
 class Query;
 class OutputAqlItemRow;
 class ExecutorInfos;
@@ -140,15 +138,6 @@ class TraversalExecutor {
    */
   std::pair<ExecutionState, Stats> produceRows(OutputAqlItemRow& output);
 
-  /**
-   * @brief produce the next Row of Aql Values.
-   *
-   * @return ExecutorState, the stats, and a new Call that needs to be send to upstream
-   */
-  std::tuple<ExecutorState, Stats, AqlCall> produceRows(size_t limit,
-                                                        AqlItemBlockInputRange& inputRange,
-                                                        OutputAqlItemRow& output);
-
  private:
   /**
    * @brief compute the return state
@@ -157,7 +146,6 @@ class TraversalExecutor {
   ExecutionState computeState() const;
 
   bool resetTraverser();
-  bool resetTraverser(InputAqlItemRow const& input);
 
  private:
   Infos& _infos;
diff --git a/tests/Aql/TraversalExecutorTest.cpp b/tests/Aql/TraversalExecutorTest.cpp
index 2fabd2ff183c..4d7bdc3f10a4 100644
--- a/tests/Aql/TraversalExecutorTest.cpp
+++ b/tests/Aql/TraversalExecutorTest.cpp
@@ -20,11 +20,9 @@
 /// @author Michael Hackstein
 ////////////////////////////////////////////////////////////////////////////////
 
-#include "AqlItemBlockHelper.h"
 #include "RowFetcherHelper.h"
 #include "gtest/gtest.h"
 
-#include "Aql/AqlCall.h"
 #include "Aql/AqlItemBlock.h"
 #include "Aql/ExecutionNode.h"
 #include "Aql/InputAqlItemRow.h"
@@ -297,8 +295,7 @@ class TraversalExecutorTestInputStartVertex : public ::testing::Test {
 
 TEST_F(TraversalExecutorTestInputStartVertex, there_are_no_rows_upstream_producer_doesnt_wait) {
   VPackBuilder input;
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
-      itemBlockManager, input.steal(), false);
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input.steal(), false);
   TraversalExecutor testee(fetcher, infos);
   TraversalStats stats{};
 
@@ -311,8 +308,7 @@ TEST_F(TraversalExecutorTestInputStartVertex, there_are_no_rows_upstream_produce
 
 TEST_F(TraversalExecutorTestInputStartVertex, there_are_no_rows_upstream_producer_waits) {
   VPackBuilder input;
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
-      itemBlockManager, input.steal(), true);
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input.steal(), true);
   TraversalExecutor testee(fetcher, infos);
   TraversalStats stats{};
 
@@ -334,8 +330,7 @@ TEST_F(TraversalExecutorTestInputStartVertex, there_are_rows_upstream_producer_d
   myGraph.addVertex("2");
   myGraph.addVertex("3");
   auto input = VPackParser::fromJson(R"([["v/1"], ["v/2"], ["v/3"]])");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
-      itemBlockManager, input->steal(), false);
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), false);
   TraversalExecutor testee(fetcher, infos);
   TraversalStats stats{};
 
@@ -367,8 +362,7 @@ TEST_F(TraversalExecutorTestInputStartVertex,
   myGraph.addVertex("2");
   myGraph.addVertex("3");
   auto input = VPackParser::fromJson(R"([["v/1"], ["v/2"], ["v/3"]])");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
-      itemBlockManager, input->steal(), true);
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), true);
   TraversalExecutor testee(fetcher, infos);
   TraversalStats stats{};
 
@@ -406,8 +400,7 @@ TEST_F(TraversalExecutorTestInputStartVertex,
   myGraph.addVertex("2");
   myGraph.addVertex("3");
   auto input = VPackParser::fromJson(R"([["v/1"], ["v/2"], ["v/3"]])");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
-      itemBlockManager, input->steal(), true);
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), true);
   TraversalExecutor testee(fetcher, infos);
   TraversalStats stats{};
 
@@ -508,8 +501,7 @@ class TraversalExecutorTestConstantStartVertex : public ::testing::Test {
 
 TEST_F(TraversalExecutorTestConstantStartVertex, no_rows_upstream_producer_doesnt_wait) {
   VPackBuilder input;
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
-      itemBlockManager, input.steal(), false);
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input.steal(), false);
   TraversalExecutor testee(fetcher, infos);
   TraversalStats stats{};
 
@@ -522,8 +514,7 @@ TEST_F(TraversalExecutorTestConstantStartVertex, no_rows_upstream_producer_doesn
 
 TEST_F(TraversalExecutorTestConstantStartVertex, no_rows_upstream_producer_waits) {
   VPackBuilder input;
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
-      itemBlockManager, input.steal(), true);
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input.steal(), true);
   TraversalExecutor testee(fetcher, infos);
   TraversalStats stats{};
 
@@ -546,8 +537,7 @@ TEST_F(TraversalExecutorTestConstantStartVertex, rows_upstream_producer_doesnt_w
   myGraph.addVertex("3");
   auto input = VPackParser::fromJson(R"([ ["v/1"], ["v/2"], ["v/3"] ])");
 
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
-      itemBlockManager, input->steal(), false);
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), false);
   TraversalExecutor testee(fetcher, infos);
   TraversalStats stats{};
 
@@ -579,8 +569,7 @@ TEST_F(TraversalExecutorTestConstantStartVertex, rows_upstream_producer_waits_no
   myGraph.addVertex("3");
   auto input = VPackParser::fromJson(R"([ ["v/1"], ["v/2"], ["v/3"] ])");
 
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
-      itemBlockManager, input->steal(), true);
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), true);
   TraversalExecutor testee(fetcher, infos);
   TraversalStats stats{};
   OutputAqlItemRow row(std::move(block), infos.getOutputRegisters(),
@@ -617,8 +606,7 @@ TEST_F(TraversalExecutorTestConstantStartVertex, rows_upstream_producer_waits_ed
   myGraph.addVertex("3");
   auto input = VPackParser::fromJson(R"([ ["v/1"], ["v/2"], ["v/3"] ])");
 
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
-      itemBlockManager, input->steal(), true);
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), true);
   TraversalExecutor testee(fetcher, infos);
   TraversalStats stats{};
   myGraph.addEdge("1", "2", "1->2");
@@ -668,82 +656,6 @@ TEST_F(TraversalExecutorTestConstantStartVertex, rows_upstream_producer_waits_ed
   }
 }
 
-TEST_F(TraversalExecutorTestInputStartVertex, test_produce_datarange_no_edges_are_connected) {
-  myGraph.addVertex("1");
-  myGraph.addVertex("2");
-  myGraph.addVertex("3");
-
-  // This fetcher will not be called!
-  // After Execute is done this fetcher shall be removed, the Executor does not need it anymore!
-  auto fakeUnusedBlock = VPackParser::fromJson("[  ]");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
-      itemBlockManager, fakeUnusedBlock->steal(), false);
-
-  // This is the relevant part of the test
-  TraversalExecutor testee(fetcher, infos);
-  SharedAqlItemBlockPtr inBlock =
-      buildBlock<1>(itemBlockManager, {{R"("v/1")"}, {R"("v/2")"}, {R"("v/3")"}});
-
-  AqlItemBlockInputRange input{ExecutorState::DONE, inBlock, 0, inBlock->size()};
-  OutputAqlItemRow output(std::move(block), infos.getOutputRegisters(),
-                          infos.registersToKeep(), infos.registersToClear());
-  EXPECT_EQ(output.numRowsWritten(), 0);
-  auto const [state, stats, call] = testee.produceRows(1000, input, output);
-  EXPECT_EQ(state, ExecutorState::DONE);
-
-  ASSERT_EQ(stats.getFiltered(), 0);
-  ASSERT_FALSE(output.produced());
-
-  ASSERT_EQ(traverser->startVertexUsedAt(0), "v/1");
-  ASSERT_EQ(traverser->startVertexUsedAt(1), "v/2");
-  ASSERT_EQ(traverser->startVertexUsedAt(2), "v/3");
-}
-
-TEST_F(TraversalExecutorTestConstantStartVertex, test_produce_datarange_edges_are_connected) {
-  myGraph.addVertex("1");
-  myGraph.addVertex("2");
-  myGraph.addVertex("3");
-
-  // This fetcher will not be called!
-  // After Execute is done this fetcher shall be removed, the Executor does not need it anymore!
-  auto fakeUnusedBlock = VPackParser::fromJson("[  ]");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
-      itemBlockManager, fakeUnusedBlock->steal(), false);
-
-  // This is the relevant part of the test
-  TraversalExecutor testee(fetcher, infos);
-  SharedAqlItemBlockPtr inBlock =
-      buildBlock<1>(itemBlockManager, {{R"("v/1")"}, {R"("v/2")"}, {R"("v/3")"}});
-
-  myGraph.addEdge("1", "2", "1->2");
-  myGraph.addEdge("2", "3", "2->3");
-  myGraph.addEdge("3", "1", "3->1");
-
-  AqlItemBlockInputRange input{ExecutorState::DONE, inBlock, 0, inBlock->size()};
-  OutputAqlItemRow output(std::move(block), infos.getOutputRegisters(),
-                          infos.registersToKeep(), infos.registersToClear());
-
-  EXPECT_EQ(output.numRowsWritten(), 0);
-  auto const [state, stats, call] = testee.produceRows(1000, input, output);
-  EXPECT_EQ(state, ExecutorState::DONE);
-
-  ASSERT_EQ(traverser->startVertexUsedAt(0), "v/1");
-  ASSERT_EQ(traverser->startVertexUsedAt(1), "v/2");
-  ASSERT_EQ(traverser->startVertexUsedAt(2), "v/3");
-
-  std::vector<std::string> expectedResult{"v/2", "v/3", "v/1"};
-  auto block = output.stealBlock();
-  for (std::size_t index = 0; index < 3; index++) {
-    AqlValue value = block->getValue(index, outReg);
-    ASSERT_TRUE(value.isObject());
-    ASSERT_TRUE(arangodb::basics::VelocyPackHelper::compare(
-                    value.slice(),
-                    myGraph.getVertexData(
-                        arangodb::velocypack::StringRef(expectedResult.at(index))),
-                    false) == 0);
-  }
-}
-
 }  // namespace aql
 }  // namespace tests
 }  // namespace arangodb

From c703b11b722be97630dd90eaa7b4a0dd9246e0c9 Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Mon, 18 Nov 2019 17:14:24 +0100
Subject: [PATCH 019/122] first implementation of a ShadowRow fetching
 interface on AqlItemBlockInputRange

---
 arangod/Aql/AqlItemBlockInputRange.cpp | 56 ++++++++++++++++++++++++--
 arangod/Aql/AqlItemBlockInputRange.h   |  8 ++++
 2 files changed, 60 insertions(+), 4 deletions(-)

diff --git a/arangod/Aql/AqlItemBlockInputRange.cpp b/arangod/Aql/AqlItemBlockInputRange.cpp
index f1b656c3cc71..a00674965d65 100644
--- a/arangod/Aql/AqlItemBlockInputRange.cpp
+++ b/arangod/Aql/AqlItemBlockInputRange.cpp
@@ -21,6 +21,7 @@
 ////////////////////////////////////////////////////////////////////////////////
 
 #include "AqlItemBlockInputRange.h"
+#include "Aql/ShadowAqlItemRow.h"
 
 using namespace arangodb;
 using namespace arangodb::aql;
@@ -55,10 +56,9 @@ std::pair<ExecutorState, InputAqlItemRow> AqlItemBlockInputRange::peek() {
 
 std::pair<ExecutorState, InputAqlItemRow> AqlItemBlockInputRange::next() {
   auto res = peek();
-  ++_rowIndex;
-  if (!indexIsValid()) {
-    _block = nullptr;
-    _rowIndex = 0;
+  if (indexIsValid()) {
+    TRI_ASSERT(res.second);
+    ++_rowIndex;
   }
   return res;
 }
@@ -76,3 +76,51 @@ bool AqlItemBlockInputRange::hasMoreAfterThis() const noexcept {
 ExecutorState AqlItemBlockInputRange::state() const noexcept {
   return hasMoreAfterThis() ? ExecutorState::HASMORE : _finalState;
 }
+
+bool AqlItemBlockInputRange::hasShadowRow() const noexcept {
+  if (_block == nullptr) {
+    // No block => no ShadowRow
+    return false;
+  }
+
+  if (hasMore()) {
+    // As long as hasMore() is true, we still have DataRows and are not on a ShadowRow now.
+    return false;
+  }
+
+  if (_rowIndex < _block->size()) {
+    // We still have more rows here, get next ShadowRow
+    TRI_ASSERT(_block->isShadowRow(_rowIndex));
+    return true;
+  }
+  return false;
+}
+
+std::pair<ExecutorState, ShadowAqlItemRow> AqlItemBlockInputRange::peekShadowRow() {
+  if (hasShadowRow()) {
+    return std::make_pair(state(), ShadowAqlItemRow{_block, _rowIndex});
+  }
+  return std::make_pair(state(), ShadowAqlItemRow{CreateInvalidShadowRowHint{}});
+}
+
+std::pair<ExecutorState, ShadowAqlItemRow> AqlItemBlockInputRange::nextShadowRow() {
+  auto res = peekShadowRow();
+  if (hasShadowRow()) {
+    auto const& shadowRowIndexes = _block->getShadowRowIndexes();
+    auto it = std::find(shadowRowIndexes.begin(), shadowRowIndexes.end(), _rowIndex);
+    // We have a shadow row in this index, so we cannot be at the end now.
+    TRI_ASSERT(it != shadowRowIndexes.end());
+    // Go to next ShadowRow.
+    it++;
+    if (it == shadowRowIndexes.end()) {
+      // No more shadow row here.
+      _endIndex = _block->size();
+    } else {
+      // Set endIndex to the next ShadowRowIndex.
+      _endIndex = *it;
+    }
+    // Advance the current row.
+    _rowIndex++;
+  }
+  return res;
+}
diff --git a/arangod/Aql/AqlItemBlockInputRange.h b/arangod/Aql/AqlItemBlockInputRange.h
index 01eef1512402..c35a9b6baa3b 100644
--- a/arangod/Aql/AqlItemBlockInputRange.h
+++ b/arangod/Aql/AqlItemBlockInputRange.h
@@ -29,6 +29,8 @@
 
 namespace arangodb::aql {
 
+class ShadowAqlItemRow;
+
 class AqlItemBlockInputRange {
  public:
   explicit AqlItemBlockInputRange(ExecutorState state);
@@ -46,6 +48,12 @@ class AqlItemBlockInputRange {
 
   std::pair<ExecutorState, arangodb::aql::InputAqlItemRow> next();
 
+  bool hasShadowRow() const noexcept;
+
+  std::pair<ExecutorState, arangodb::aql::ShadowAqlItemRow> peekShadowRow();
+
+  std::pair<ExecutorState, arangodb::aql::ShadowAqlItemRow> nextShadowRow();
+
  private:
   bool indexIsValid() const noexcept;
 

From 79117675feabd88b7a6030194ffb01cca60bfa11 Mon Sep 17 00:00:00 2001
From: hkernbach <heiko.kernbach@gmail.com>
Date: Wed, 20 Nov 2019 11:17:24 +0100
Subject: [PATCH 020/122] single row fetcher, execute + tests

---
 arangod/Aql/AqlItemBlock.cpp         | 19 ++++++-
 arangod/Aql/AqlItemBlock.h           |  8 +++
 arangod/Aql/AqlItemBlockInputRange.h |  7 ++-
 arangod/Aql/DependencyProxy.h        |  2 +-
 arangod/Aql/SingleRowFetcher.cpp     | 16 +++---
 tests/Aql/DependencyProxyMock.cpp    | 11 ++++
 tests/Aql/DependencyProxyMock.h      |  4 ++
 tests/Aql/SingleRowFetcherTest.cpp   | 79 ++++++++++++++++++++++++++++
 8 files changed, 135 insertions(+), 11 deletions(-)

diff --git a/arangod/Aql/AqlItemBlock.cpp b/arangod/Aql/AqlItemBlock.cpp
index d3bd739c5c22..7192a4a70ffd 100644
--- a/arangod/Aql/AqlItemBlock.cpp
+++ b/arangod/Aql/AqlItemBlock.cpp
@@ -69,7 +69,7 @@ inline void CopyValueOver(std::unordered_set<AqlValue>& cache, AqlValue const& a
 
 /// @brief create the block
 AqlItemBlock::AqlItemBlock(AqlItemBlockManager& manager, size_t nrItems, RegisterId nrRegs)
-    : _nrItems(nrItems), _nrRegs(nrRegs), _manager(manager), _refCount(0) {
+    : _nrItems(nrItems), _nrRegs(nrRegs), _manager(manager), _refCount(0), _rowIndex(0) {
   TRI_ASSERT(nrItems > 0);  // empty AqlItemBlocks are not allowed!
   // check that the nrRegs value is somewhat sensible
   // this compare value is arbitrary, but having so many registers in a single
@@ -855,6 +855,23 @@ RegisterId AqlItemBlock::getNrRegs() const noexcept { return _nrRegs; }
 
 size_t AqlItemBlock::size() const noexcept { return _nrItems; }
 
+std::tuple<size_t, size_t> AqlItemBlock::getRelevantRange() {
+  size_t startIndex = _rowIndex;
+  size_t endIndex = 0;
+
+  for (; _rowIndex < this->size(); _rowIndex++) {
+    if (isShadowRow(_rowIndex)) {
+      endIndex = _rowIndex - 1;
+      break;
+    }
+    if (_rowIndex - 1 != this->size()) {
+      endIndex = _rowIndex;
+    }
+  }
+
+  return std::make_pair(startIndex, endIndex);
+}
+
 size_t AqlItemBlock::numEntries() const { return internalNrRegs() * _nrItems; }
 
 size_t AqlItemBlock::capacity() const noexcept { return _data.capacity(); }
diff --git a/arangod/Aql/AqlItemBlock.h b/arangod/Aql/AqlItemBlock.h
index d8d3288f8808..df3b7c03ce93 100644
--- a/arangod/Aql/AqlItemBlock.h
+++ b/arangod/Aql/AqlItemBlock.h
@@ -166,6 +166,9 @@ class AqlItemBlock {
   /// @brief getter for _nrItems
   size_t size() const noexcept;
 
+  /// @brief get the relevant consumable range of the block
+  std::tuple<size_t, size_t> getRelevantRange();
+
   /// @brief Number of entries in the matrix. If this changes, the memory usage
   /// must be / in- or decreased appropriately as well.
   /// All entries _data[i] for numEntries() <= i < _data.size() always have to
@@ -287,6 +290,11 @@ class AqlItemBlock {
   /// @brief A list of indexes with all shadowRows within
   /// this ItemBlock. Used to easier split data based on them.
   std::set<size_t> _shadowRowIndexes;
+
+  /// @brief current row index we want to read from. This will be increased after
+  /// getRelevantRange function will be called, which will return a tuple of the
+  /// old _rowIndex and the newly calculated _rowIndex - 1
+  size_t _rowIndex;
 };
 
 }  // namespace aql
diff --git a/arangod/Aql/AqlItemBlockInputRange.h b/arangod/Aql/AqlItemBlockInputRange.h
index 01eef1512402..bfb264835dff 100644
--- a/arangod/Aql/AqlItemBlockInputRange.h
+++ b/arangod/Aql/AqlItemBlockInputRange.h
@@ -34,9 +34,9 @@ class AqlItemBlockInputRange {
   explicit AqlItemBlockInputRange(ExecutorState state);
 
   AqlItemBlockInputRange(ExecutorState, arangodb::aql::SharedAqlItemBlockPtr const&,
-                         std::size_t, std::size_t endIndex);
+                         std::size_t startIndex, std::size_t endIndex);
   AqlItemBlockInputRange(ExecutorState, arangodb::aql::SharedAqlItemBlockPtr&&,
-                         std::size_t, std::size_t endIndex) noexcept;
+                         std::size_t startIndex, std::size_t endIndex) noexcept;
 
   bool hasMore() const noexcept;
 
@@ -46,6 +46,9 @@ class AqlItemBlockInputRange {
 
   std::pair<ExecutorState, arangodb::aql::InputAqlItemRow> next();
 
+  std::size_t getRowIndex() noexcept { return _rowIndex; };
+  std::size_t getEndIndex() noexcept { return _endIndex; };
+
  private:
   bool indexIsValid() const noexcept;
 
diff --git a/arangod/Aql/DependencyProxy.h b/arangod/Aql/DependencyProxy.h
index 36d946798517..bbee1df2ae43 100644
--- a/arangod/Aql/DependencyProxy.h
+++ b/arangod/Aql/DependencyProxy.h
@@ -74,7 +74,7 @@ class DependencyProxy {
   TEST_VIRTUAL ~DependencyProxy() = default;
 
   // TODO Implement and document properly!
-  std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> execute(AqlCallStack& stack);
+  TEST_VIRTUAL std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> execute(AqlCallStack& stack);
 
   // This is only TEST_VIRTUAL, so we ignore this lint warning:
   // NOLINTNEXTLINE google-default-arguments
diff --git a/arangod/Aql/SingleRowFetcher.cpp b/arangod/Aql/SingleRowFetcher.cpp
index 34219bde206e..cdf502e2ef55 100644
--- a/arangod/Aql/SingleRowFetcher.cpp
+++ b/arangod/Aql/SingleRowFetcher.cpp
@@ -24,6 +24,7 @@
 ////////////////////////////////////////////////////////////////////////////////
 
 #include "SingleRowFetcher.h"
+#include <Logger/LogMacros.h>
 
 #include "Aql/AqlItemBlock.h"
 #include "Aql/DependencyProxy.h"
@@ -76,21 +77,22 @@ SingleRowFetcher<passBlocksThrough>::fetchBlockForPassthrough(size_t atMost) {
 template <BlockPassthrough passBlocksThrough>
 std::tuple<ExecutionState, size_t, AqlItemBlockInputRange>
 SingleRowFetcher<passBlocksThrough>::execute(AqlCallStack& stack) {
-  auto const [state, skipped, block] = _dependencyProxy->execute(stack);
+  auto [state, skipped, block] = _dependencyProxy->execute(stack);
   if (state == ExecutionState::WAITING) {
     // On waiting we have nothing to return
     return {state, 0, AqlItemBlockInputRange{ExecutorState::HASMORE}};
   }
+  if (block == nullptr) {
+    return {state, skipped, AqlItemBlockInputRange{ExecutorState::DONE}};
+  }
+
+  auto [start, end] = block->getRelevantRange();
   if (state == ExecutionState::HASMORE) {
     TRI_ASSERT(block != nullptr);
     return {state, skipped,
-            AqlItemBlockInputRange{ExecutorState::HASMORE, block, 0, block->size()}};
-  }
-  if (block == nullptr) {
-    return {state, skipped, AqlItemBlockInputRange{ExecutorState::DONE}};
+            AqlItemBlockInputRange{ExecutorState::HASMORE, block, start, end}};
   }
-  return {state, skipped,
-          AqlItemBlockInputRange{ExecutorState::DONE, block, 0, block->size()}};
+  return {state, skipped, AqlItemBlockInputRange{ExecutorState::DONE, block, start, end}};
 }
 
 template <BlockPassthrough passBlocksThrough>
diff --git a/tests/Aql/DependencyProxyMock.cpp b/tests/Aql/DependencyProxyMock.cpp
index f17bcd9098be..ecec7d319ca9 100644
--- a/tests/Aql/DependencyProxyMock.cpp
+++ b/tests/Aql/DependencyProxyMock.cpp
@@ -21,6 +21,7 @@
 ////////////////////////////////////////////////////////////////////////////////
 
 #include "DependencyProxyMock.h"
+#include <Logger/LogMacros.h>
 
 #include "gtest/gtest.h"
 
@@ -104,6 +105,9 @@ DependencyProxyMock<passBlocksThrough>& DependencyProxyMock<passBlocksThrough>::
   for (RegisterId i = 0; i < this->getNrInputRegisters(); i++) {
     inputRegisters->emplace(i);
   }
+  // keep the block address
+  _block = block;
+
   return andThenReturn({state, block});
 }
 
@@ -125,6 +129,13 @@ DependencyProxyMock<passBlocksThrough>& DependencyProxyMock<passBlocksThrough>::
   return *this;
 }
 
+template <BlockPassthrough passBlocksThrough>
+std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr>
+DependencyProxyMock<passBlocksThrough>::execute(AqlCallStack& stack) {
+  TRI_ASSERT(_block != nullptr);
+  return {arangodb::aql::ExecutionState::DONE, 0, _block};
+}
+
 template <BlockPassthrough passBlocksThrough>
 bool DependencyProxyMock<passBlocksThrough>::allBlocksFetched() const {
   return _itemsToReturn.empty();
diff --git a/tests/Aql/DependencyProxyMock.h b/tests/Aql/DependencyProxyMock.h
index 2692dd344e35..9fd2f8ea2d4b 100644
--- a/tests/Aql/DependencyProxyMock.h
+++ b/tests/Aql/DependencyProxyMock.h
@@ -51,6 +51,9 @@ class DependencyProxyMock : public ::arangodb::aql::DependencyProxy<passBlocksTh
 
   std::pair<arangodb::aql::ExecutionState, size_t> skipSome(size_t atMost) override;
 
+  std::tuple<arangodb::aql::ExecutionState, size_t, arangodb::aql::SharedAqlItemBlockPtr> execute(
+      arangodb::aql::AqlCallStack& stack) override;
+
  private:
   using FetchBlockReturnItem =
       std::pair<arangodb::aql::ExecutionState, arangodb::aql::SharedAqlItemBlockPtr>;
@@ -76,6 +79,7 @@ class DependencyProxyMock : public ::arangodb::aql::DependencyProxy<passBlocksTh
 
   ::arangodb::aql::ResourceMonitor& _monitor;
   ::arangodb::aql::AqlItemBlockManager _itemBlockManager;
+  ::arangodb::aql::SharedAqlItemBlockPtr _block;
 };
 
 template <::arangodb::aql::BlockPassthrough passBlocksThrough>
diff --git a/tests/Aql/SingleRowFetcherTest.cpp b/tests/Aql/SingleRowFetcherTest.cpp
index 07a5ab6ab152..4dcb098f349a 100644
--- a/tests/Aql/SingleRowFetcherTest.cpp
+++ b/tests/Aql/SingleRowFetcherTest.cpp
@@ -28,6 +28,7 @@
 #include "RowFetcherHelper.h"
 #include "gtest/gtest.h"
 
+#include "Aql/AqlCallStack.h"
 #include "Aql/AqlItemBlock.h"
 #include "Aql/DependencyProxy.h"
 #include "Aql/ExecutionBlock.h"
@@ -1147,6 +1148,84 @@ TEST_F(SingleRowFetcherTestPassBlocks, handling_consecutive_shadowrows) {
   ASSERT_EQ(dependencyProxyMock.numFetchBlockCalls(), 1);
 }
 
+TEST_F(SingleRowFetcherTestPassBlocks, handling_shadowrows_in_execute_oneAndDone) {
+  DependencyProxyMock<passBlocksThrough> dependencyProxyMock{monitor, 1};
+  InputAqlItemRow row{CreateInvalidInputRowHint{}};
+  ShadowAqlItemRow shadow{CreateInvalidShadowRowHint{}};
+
+  {
+    SharedAqlItemBlockPtr block{new AqlItemBlock(itemBlockManager, 7, 1)};
+    block->emplaceValue(0, 0, "a");
+    block->emplaceValue(1, 0, "b");
+    block->emplaceValue(2, 0, "c");
+    block->emplaceValue(3, 0, "d");
+    block->emplaceValue(4, 0, "e");  // first shadowrow
+    block->setShadowRowDepth(4, AqlValue(AqlValueHintUInt(1ull)));
+    block->emplaceValue(5, 0, "f");
+    block->setShadowRowDepth(5, AqlValue(AqlValueHintUInt(0ull)));
+    block->emplaceValue(6, 0, "g");
+    block->setShadowRowDepth(6, AqlValue(AqlValueHintUInt(0ull)));
+    dependencyProxyMock.shouldReturn(ExecutionState::DONE, std::move(block));
+  }
+
+  {
+    SingleRowFetcher<passBlocksThrough> testee(dependencyProxyMock);
+    AqlCall call;
+    AqlCallStack stack = {call};
+
+    // First no data row
+    auto [state, skipped, input] = testee.execute(stack);
+    EXPECT_EQ(input.getRowIndex(), 0);
+    EXPECT_EQ(input.getEndIndex(), 3);
+    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(state, ExecutionState::DONE);
+  }  // testee is destroyed here
+}
+
+TEST_F(SingleRowFetcherTestPassBlocks, handling_shadowrows_in_execute_twoAndHasMore) {
+  DependencyProxyMock<passBlocksThrough> dependencyProxyMock{monitor, 1};
+  InputAqlItemRow row{CreateInvalidInputRowHint{}};
+  ShadowAqlItemRow shadow{CreateInvalidShadowRowHint{}};
+
+  {
+    SharedAqlItemBlockPtr block{new AqlItemBlock(itemBlockManager, 9, 1)};
+    block->emplaceValue(0, 0, "a");
+    block->emplaceValue(1, 0, "b");
+    block->emplaceValue(2, 0, "c");
+    block->emplaceValue(3, 0, "d");
+    block->emplaceValue(4, 0, "e");  // first shadowrow
+    block->setShadowRowDepth(4, AqlValue(AqlValueHintUInt(1ull)));
+    block->emplaceValue(5, 0, "f");
+    block->setShadowRowDepth(5, AqlValue(AqlValueHintUInt(0ull)));
+    block->emplaceValue(6, 0, "g");
+    block->setShadowRowDepth(6, AqlValue(AqlValueHintUInt(0ull)));
+    block->emplaceValue(7, 0, "h");
+    block->emplaceValue(8, 0, "i");
+    dependencyProxyMock.shouldReturn(ExecutionState::DONE, std::move(block));
+  }
+
+  {
+    SingleRowFetcher<passBlocksThrough> testee(dependencyProxyMock);
+    AqlCall call;
+    AqlCallStack stack = {call};
+
+    {
+      auto [state, skipped, input] = testee.execute(stack);
+      EXPECT_EQ(input.getRowIndex(), 0);
+      EXPECT_EQ(input.getEndIndex(), 3);
+      EXPECT_EQ(state, ExecutionState::HASMORE);
+      // EXPECT_EQ(skipped, 0);
+    }
+
+    {
+      auto [state, skipped, input] = testee.execute(stack);
+      EXPECT_EQ(input.getRowIndex(), 7);
+      EXPECT_EQ(input.getEndIndex(), 8);
+      EXPECT_EQ(state, ExecutionState::DONE);
+    }
+  }  // testee is destroyed here
+}
+
 class SingleRowFetcherWrapper
     : public fetcherHelper::PatternTestWrapper<SingleRowFetcher<::arangodb::aql::BlockPassthrough::Disable>> {
  public:

From b91be5f8e29ac5dac93e972ea415fccc08924ca0 Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Wed, 27 Nov 2019 11:57:31 +0100
Subject: [PATCH 021/122] Fixed SingleRowFetcherTest. Also an
 AqlItemBlockInputRange can now handle ShadowRows properly

---
 arangod/Aql/AqlItemBlock.cpp           | 22 +++----
 arangod/Aql/AqlItemBlockInputRange.cpp | 21 +++++-
 arangod/Aql/AqlItemBlockInputRange.h   |  2 +
 arangod/Aql/ExecutionBlockImpl.cpp     |  1 -
 tests/Aql/SingleRowFetcherTest.cpp     | 90 ++++++++++++++++++++------
 5 files changed, 103 insertions(+), 33 deletions(-)

diff --git a/arangod/Aql/AqlItemBlock.cpp b/arangod/Aql/AqlItemBlock.cpp
index a2ee97ed97af..4d9846ceb8af 100644
--- a/arangod/Aql/AqlItemBlock.cpp
+++ b/arangod/Aql/AqlItemBlock.cpp
@@ -699,7 +699,8 @@ void AqlItemBlock::toVelocyPack(transaction::Methods* trx, VPackBuilder& result)
   result.add("raw", raw.slice());
 }
 
-void AqlItemBlock::rowToSimpleVPack(size_t const row, transaction::Methods* trx, arangodb::velocypack::Builder& builder) const {
+void AqlItemBlock::rowToSimpleVPack(size_t const row, transaction::Methods* trx,
+                                    arangodb::velocypack::Builder& builder) const {
   VPackArrayBuilder rowBuilder{&builder};
 
   if (isShadowRow(row)) {
@@ -712,7 +713,8 @@ void AqlItemBlock::rowToSimpleVPack(size_t const row, transaction::Methods* trx,
   }
 }
 
-void AqlItemBlock::toSimpleVPack(transaction::Methods* trx, arangodb::velocypack::Builder& builder) const {
+void AqlItemBlock::toSimpleVPack(transaction::Methods* trx,
+                                 arangodb::velocypack::Builder& builder) const {
   VPackObjectBuilder block{&builder};
   block->add("nrItems", VPackValue(size()));
   block->add("nrRegs", VPackValue(getNrRegs()));
@@ -882,18 +884,14 @@ size_t AqlItemBlock::size() const noexcept { return _nrItems; }
 
 std::tuple<size_t, size_t> AqlItemBlock::getRelevantRange() {
   size_t startIndex = _rowIndex;
-  size_t endIndex = 0;
+  ++_rowIndex;
 
-  for (; _rowIndex < this->size(); _rowIndex++) {
-    if (isShadowRow(_rowIndex)) {
-      endIndex = _rowIndex - 1;
-      break;
-    }
-    if (_rowIndex - 1 != this->size()) {
-      endIndex = _rowIndex;
-    }
+  for (; _rowIndex < this->size() && !isShadowRow(_rowIndex); _rowIndex++) {
+    // Move on as long as we are not at the end or at a shadow row
   }
-
+  size_t endIndex = _rowIndex;
+  TRI_ASSERT(startIndex < endIndex);
+  TRI_ASSERT(endIndex <= this->size());
   return std::make_pair(startIndex, endIndex);
 }
 
diff --git a/arangod/Aql/AqlItemBlockInputRange.cpp b/arangod/Aql/AqlItemBlockInputRange.cpp
index a00674965d65..91823b014460 100644
--- a/arangod/Aql/AqlItemBlockInputRange.cpp
+++ b/arangod/Aql/AqlItemBlockInputRange.cpp
@@ -77,6 +77,23 @@ ExecutorState AqlItemBlockInputRange::state() const noexcept {
   return hasMoreAfterThis() ? ExecutorState::HASMORE : _finalState;
 }
 
+ExecutorState AqlItemBlockInputRange::shadowState() const noexcept {
+  if (_block == nullptr) {
+    return _finalState;
+  }
+  // We Return HASMORE, if the next shadow row is NOT relevant.
+  // So we can directly fetch the next shadow row without informing
+  // the executor about an empty subquery.
+  size_t nextRowIndex = _rowIndex + 1;
+  if (_block != nullptr && nextRowIndex < _block->size() && _block->isShadowRow(nextRowIndex)) {
+    ShadowAqlItemRow nextRow{_block, nextRowIndex};
+    if (!nextRow.isRelevant()) {
+      return ExecutorState::HASMORE;
+    }
+  }
+  return ExecutorState::DONE;
+}
+
 bool AqlItemBlockInputRange::hasShadowRow() const noexcept {
   if (_block == nullptr) {
     // No block => no ShadowRow
@@ -98,9 +115,9 @@ bool AqlItemBlockInputRange::hasShadowRow() const noexcept {
 
 std::pair<ExecutorState, ShadowAqlItemRow> AqlItemBlockInputRange::peekShadowRow() {
   if (hasShadowRow()) {
-    return std::make_pair(state(), ShadowAqlItemRow{_block, _rowIndex});
+    return std::make_pair(shadowState(), ShadowAqlItemRow{_block, _rowIndex});
   }
-  return std::make_pair(state(), ShadowAqlItemRow{CreateInvalidShadowRowHint{}});
+  return std::make_pair(shadowState(), ShadowAqlItemRow{CreateInvalidShadowRowHint{}});
 }
 
 std::pair<ExecutorState, ShadowAqlItemRow> AqlItemBlockInputRange::nextShadowRow() {
diff --git a/arangod/Aql/AqlItemBlockInputRange.h b/arangod/Aql/AqlItemBlockInputRange.h
index 8da8678d14bc..fd68ace50fff 100644
--- a/arangod/Aql/AqlItemBlockInputRange.h
+++ b/arangod/Aql/AqlItemBlockInputRange.h
@@ -44,6 +44,8 @@ class AqlItemBlockInputRange {
 
   ExecutorState state() const noexcept;
 
+  ExecutorState shadowState() const noexcept;
+
   std::pair<ExecutorState, arangodb::aql::InputAqlItemRow> peek();
 
   std::pair<ExecutorState, arangodb::aql::InputAqlItemRow> next();
diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index 3851020b89a4..7b0fb0779161 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -1026,7 +1026,6 @@ ExecutionBlockImpl<FilterExecutor>::executeWithoutTrace(AqlCallStack stack) {
   AqlCall executorRequest;
 
   while (execState != ExecState::DONE) {
-    LOG_DEVEL << "State: " << execState;
     switch (execState) {
       case ExecState::SKIP: {
         auto [state, skippedLocal, call] =
diff --git a/tests/Aql/SingleRowFetcherTest.cpp b/tests/Aql/SingleRowFetcherTest.cpp
index 4dcb098f349a..54818943f3e0 100644
--- a/tests/Aql/SingleRowFetcherTest.cpp
+++ b/tests/Aql/SingleRowFetcherTest.cpp
@@ -37,6 +37,7 @@
 #include "Aql/InputAqlItemRow.h"
 #include "Aql/ResourceUsage.h"
 #include "Aql/SingleRowFetcher.h"
+#include "Basics/StringUtils.h"
 
 #include "FetcherTestHelper.h"
 
@@ -65,6 +66,58 @@ class SingleRowFetcherTestPassBlocks : public ::testing::Test {
       ::arangodb::aql::BlockPassthrough::Enable;
   SingleRowFetcherTestPassBlocks()
       : itemBlockManager(&monitor, SerializationFormat::SHADOWROWS) {}
+
+  void validateInputRange(AqlItemBlockInputRange& input,
+                          std::vector<std::string> const& result) {
+    EXPECT_EQ(result.size(), input.getEndIndex() - input.getRowIndex());
+    for (auto const& value : result) {
+      SCOPED_TRACE("Checking for value: " + value);
+      // We need more rows
+      ASSERT_TRUE(input.hasMore());
+      EXPECT_FALSE(input.hasShadowRow());
+
+      auto [state, row] = input.next();
+
+      if (value == result.back()) {
+        EXPECT_EQ(state, ExecutorState::DONE);
+      } else {
+        EXPECT_EQ(state, ExecutorState::HASMORE);
+      }
+      ASSERT_TRUE(row.isInitialized());
+      auto const& inputVal = row.getValue(0);
+      ASSERT_TRUE(inputVal.isString());
+      EXPECT_TRUE(inputVal.slice().isEqualString(value))
+          << inputVal.slice().toJson() << " should be equal to \"" << value << "\"";
+    }
+    // We always fetch to the end
+    EXPECT_FALSE(input.hasMore());
+  }
+
+  void validateShadowRange(AqlItemBlockInputRange& input,
+                           std::vector<std::pair<uint64_t, std::string>> const& result) {
+    for (auto const& [depth, value] : result) {
+      SCOPED_TRACE("Checking for depth " + basics::StringUtils::itoa(depth) +
+                   " with value: " + value);
+      // We need more rows
+      ASSERT_TRUE(input.hasShadowRow());
+      EXPECT_FALSE(input.hasMore());
+
+      auto [state, row] = input.nextShadowRow();
+
+      if (depth == result.back().first && value == result.back().second) {
+        EXPECT_EQ(state, ExecutorState::DONE);
+      } else {
+        EXPECT_EQ(state, ExecutorState::HASMORE);
+      }
+      ASSERT_TRUE(row.isInitialized());
+      auto const& inputVal = row.getValue(0);
+
+      ASSERT_TRUE(inputVal.isString());
+      EXPECT_TRUE(inputVal.slice().isEqualString(value))
+          << inputVal.slice().toJson() << " should be equal to \"" << value << "\"";
+      EXPECT_EQ(row.getDepth(), depth);
+    }
+  }
 };
 
 class SingleRowFetcherTestDoNotPassBlocks : public ::testing::Test {
@@ -1160,9 +1213,9 @@ TEST_F(SingleRowFetcherTestPassBlocks, handling_shadowrows_in_execute_oneAndDone
     block->emplaceValue(2, 0, "c");
     block->emplaceValue(3, 0, "d");
     block->emplaceValue(4, 0, "e");  // first shadowrow
-    block->setShadowRowDepth(4, AqlValue(AqlValueHintUInt(1ull)));
+    block->setShadowRowDepth(4, AqlValue(AqlValueHintUInt(0ull)));
     block->emplaceValue(5, 0, "f");
-    block->setShadowRowDepth(5, AqlValue(AqlValueHintUInt(0ull)));
+    block->setShadowRowDepth(5, AqlValue(AqlValueHintUInt(1ull)));
     block->emplaceValue(6, 0, "g");
     block->setShadowRowDepth(6, AqlValue(AqlValueHintUInt(0ull)));
     dependencyProxyMock.shouldReturn(ExecutionState::DONE, std::move(block));
@@ -1176,7 +1229,7 @@ TEST_F(SingleRowFetcherTestPassBlocks, handling_shadowrows_in_execute_oneAndDone
     // First no data row
     auto [state, skipped, input] = testee.execute(stack);
     EXPECT_EQ(input.getRowIndex(), 0);
-    EXPECT_EQ(input.getEndIndex(), 3);
+    EXPECT_EQ(input.getEndIndex(), 4);
     EXPECT_EQ(skipped, 0);
     EXPECT_EQ(state, ExecutionState::DONE);
   }  // testee is destroyed here
@@ -1194,9 +1247,9 @@ TEST_F(SingleRowFetcherTestPassBlocks, handling_shadowrows_in_execute_twoAndHasM
     block->emplaceValue(2, 0, "c");
     block->emplaceValue(3, 0, "d");
     block->emplaceValue(4, 0, "e");  // first shadowrow
-    block->setShadowRowDepth(4, AqlValue(AqlValueHintUInt(1ull)));
+    block->setShadowRowDepth(4, AqlValue(AqlValueHintUInt(0ull)));
     block->emplaceValue(5, 0, "f");
-    block->setShadowRowDepth(5, AqlValue(AqlValueHintUInt(0ull)));
+    block->setShadowRowDepth(5, AqlValue(AqlValueHintUInt(1ull)));
     block->emplaceValue(6, 0, "g");
     block->setShadowRowDepth(6, AqlValue(AqlValueHintUInt(0ull)));
     block->emplaceValue(7, 0, "h");
@@ -1209,20 +1262,21 @@ TEST_F(SingleRowFetcherTestPassBlocks, handling_shadowrows_in_execute_twoAndHasM
     AqlCall call;
     AqlCallStack stack = {call};
 
-    {
-      auto [state, skipped, input] = testee.execute(stack);
-      EXPECT_EQ(input.getRowIndex(), 0);
-      EXPECT_EQ(input.getEndIndex(), 3);
-      EXPECT_EQ(state, ExecutionState::HASMORE);
-      // EXPECT_EQ(skipped, 0);
-    }
+    auto [state, skipped, input] = testee.execute(stack);
+    // We only have one block, no more calls to execute necessary
+    EXPECT_EQ(state, ExecutionState::DONE);
+    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(input.getRowIndex(), 0);
+    EXPECT_EQ(input.getEndIndex(), 4);
+
+    // Now validate the input range
+    validateInputRange(input, std::vector<std::string>{"a", "b", "c", "d"});
+    validateShadowRange(input, std::vector<std::pair<uint64_t, std::string>>{
+                                   {0ull, "e"}, {1ull, "f"}});
+    validateShadowRange(input, std::vector<std::pair<uint64_t, std::string>>{
+                                   {0ull, "g"}});
+    validateInputRange(input, std::vector<std::string>{"h", "i"});
 
-    {
-      auto [state, skipped, input] = testee.execute(stack);
-      EXPECT_EQ(input.getRowIndex(), 7);
-      EXPECT_EQ(input.getEndIndex(), 8);
-      EXPECT_EQ(state, ExecutionState::DONE);
-    }
   }  // testee is destroyed here
 }
 

From 8ba440c8a105bd8c56301665d18c7544afda9b5b Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Wed, 27 Nov 2019 15:36:47 +0100
Subject: [PATCH 022/122] Another fix on handling of shadow rows in InputRanges

---
 arangod/Aql/AqlItemBlock.cpp           | 24 ++++++++++++++----------
 arangod/Aql/AqlItemBlockInputRange.cpp |  4 ++--
 arangod/Aql/ExecutionBlockImpl.cpp     | 15 ++++++++-------
 3 files changed, 24 insertions(+), 19 deletions(-)

diff --git a/arangod/Aql/AqlItemBlock.cpp b/arangod/Aql/AqlItemBlock.cpp
index 4d9846ceb8af..687844c58830 100644
--- a/arangod/Aql/AqlItemBlock.cpp
+++ b/arangod/Aql/AqlItemBlock.cpp
@@ -37,6 +37,8 @@
 #include <velocypack/Iterator.h>
 #include <velocypack/velocypack-aliases.h>
 
+#include "Logger/LogMacros.h"
+
 using namespace arangodb;
 using namespace arangodb::aql;
 
@@ -883,16 +885,18 @@ RegisterId AqlItemBlock::getNrRegs() const noexcept { return _nrRegs; }
 size_t AqlItemBlock::size() const noexcept { return _nrItems; }
 
 std::tuple<size_t, size_t> AqlItemBlock::getRelevantRange() {
-  size_t startIndex = _rowIndex;
-  ++_rowIndex;
-
-  for (; _rowIndex < this->size() && !isShadowRow(_rowIndex); _rowIndex++) {
-    // Move on as long as we are not at the end or at a shadow row
-  }
-  size_t endIndex = _rowIndex;
-  TRI_ASSERT(startIndex < endIndex);
-  TRI_ASSERT(endIndex <= this->size());
-  return std::make_pair(startIndex, endIndex);
+  // NOTE:
+  // Right now we can only support a range of datarows, that ends
+  // In a range of ShadowRows.
+  // After a shadow row, we do NOT know how to continue with
+  // The next Executor.
+  // So we can hardcode to return 0 -> firstShadowRow || endOfBlock
+  if (hasShadowRows()) {
+    auto const& shadows = getShadowRowIndexes();
+    TRI_ASSERT(!shadows.empty());
+    return {0, *shadows.begin()};
+  }
+  return {0, size()};
 }
 
 size_t AqlItemBlock::numEntries() const { return internalNrRegs() * _nrItems; }
diff --git a/arangod/Aql/AqlItemBlockInputRange.cpp b/arangod/Aql/AqlItemBlockInputRange.cpp
index 91823b014460..178997eb6ec3 100644
--- a/arangod/Aql/AqlItemBlockInputRange.cpp
+++ b/arangod/Aql/AqlItemBlockInputRange.cpp
@@ -35,7 +35,7 @@ AqlItemBlockInputRange::AqlItemBlockInputRange(ExecutorState state,
                                                SharedAqlItemBlockPtr const& block,
                                                std::size_t index, std::size_t endIndex)
     : _block{block}, _rowIndex{index}, _endIndex(endIndex), _finalState{state} {
-  TRI_ASSERT(index < endIndex);
+  TRI_ASSERT(index <= endIndex);
   TRI_ASSERT(endIndex <= block->size());
 }
 
@@ -43,7 +43,7 @@ AqlItemBlockInputRange::AqlItemBlockInputRange(ExecutorState state,
                                                SharedAqlItemBlockPtr&& block,
                                                std::size_t index, std::size_t endIndex) noexcept
     : _block{std::move(block)}, _rowIndex{index}, _endIndex(endIndex), _finalState{state} {
-  TRI_ASSERT(index < endIndex);
+  TRI_ASSERT(index <= endIndex);
   TRI_ASSERT(endIndex <= block->size());
 }
 
diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index 7b0fb0779161..a54efe1db958 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -1101,13 +1101,11 @@ ExecutionBlockImpl<FilterExecutor>::executeWithoutTrace(AqlCallStack stack) {
           }
           TRI_ASSERT(_outputItemRow->produced());
           _outputItemRow->advanceRow();
-          if (_lastRange.hasShadowRow()) {
-            auto const& [state, shadowRow] = _lastRange.peekShadowRow();
-            TRI_ASSERT(shadowRow.isInitialized());
-            if (shadowRow.isRelevant()) {
-              // We need to call The Executor with this input again.
-              execState = ExecState::DONE;
-            }
+          if (state == ExecutorState::DONE) {
+            // Right now we cannot support to have more than one set of
+            // ShadowRows inside of a Range.
+            // We do not know how to continue with the above executor after a shadowrow.
+            execState = ExecState::DONE;
           }
         } else {
           execState = ExecState::DONE;
@@ -1127,6 +1125,9 @@ ExecutionBlockImpl<FilterExecutor>::executeWithoutTrace(AqlCallStack stack) {
   // This is not strictly necessary here, as we shouldn't be called again
   // after DONE.
   _outputItemRow.reset();
+  if (_lastRange.hasMore()) {
+    return {ExecutionState::HASMORE, skipped, std::move(outputBlock)};
+  }
   return {_upstreamState, skipped, std::move(outputBlock)};
 }
 

From b5dacbd9cf0aea9a9cd03e09edbd740e18606153 Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Wed, 27 Nov 2019 15:37:15 +0100
Subject: [PATCH 023/122] Improved human readable output of SortLimit test,
 while validating the result

---
 tests/Aql/SortLimit-test.cpp | 58 +++++++++++++++++-------------------
 1 file changed, 27 insertions(+), 31 deletions(-)

diff --git a/tests/Aql/SortLimit-test.cpp b/tests/Aql/SortLimit-test.cpp
index 8e9146feaf1f..2bf1f312bab6 100644
--- a/tests/Aql/SortLimit-test.cpp
+++ b/tests/Aql/SortLimit-test.cpp
@@ -79,14 +79,13 @@ class SortLimitTest
     arangodb::ClusterEngine::Mocking = true;
     arangodb::RandomGenerator::initialize(arangodb::RandomGenerator::RandomType::MERSENNE);
 
-    vocbase = std::make_unique<TRI_vocbase_t>(TRI_vocbase_type_e::TRI_VOCBASE_TYPE_NORMAL, testDBInfo(server.server()));
+    vocbase = std::make_unique<TRI_vocbase_t>(TRI_vocbase_type_e::TRI_VOCBASE_TYPE_NORMAL,
+                                              testDBInfo(server.server()));
 
     CreateCollection();
   }
 
-  ~SortLimitTest() {
-    vocbase.reset();
-  }
+  ~SortLimitTest() { vocbase.reset(); }
 
   std::string sorterType(TRI_vocbase_t& vocbase, std::string const& queryString,
                          std::string rules = "") {
@@ -113,7 +112,7 @@ class SortLimitTest
     return strategy;
   }
 
-  bool verifyExpectedResults(TRI_vocbase_t& vocbase, std::string const& queryString,
+  void verifyExpectedResults(TRI_vocbase_t& vocbase, std::string const& queryString,
                              std::vector<size_t> const& expected,
                              std::string rules = "") {
     auto options = arangodb::velocypack::Parser::fromJson(
@@ -135,21 +134,18 @@ class SortLimitTest
     EXPECT_TRUE(result.result.ok());
     auto slice = result.data->slice();
     EXPECT_TRUE(slice.isArray());
-
-    if (slice.length() != expected.size()) {
-      return false;
-    }
+    ASSERT_EQ(slice.length(), expected.size());
 
     size_t i = 0;
     for (arangodb::velocypack::ArrayIterator itr(slice); itr.valid(); ++itr) {
       auto const resolved = itr.value().resolveExternals();
-      if (0 != arangodb::basics::VelocyPackHelper::compare(
-                   insertedDocs[expected[i++]].slice(), resolved, true)) {
-        return false;
-      }
-    }
 
-    return true;
+      EXPECT_EQ(0, arangodb::basics::VelocyPackHelper::compare(
+                       insertedDocs[expected[i]].slice(), resolved, true))
+          << insertedDocs[expected[i]].slice().toJson() << " vs. "
+          << resolved.toJson();
+      i++;
+    }
   }
 
   // create collection0, insertedDocs[0, 999]
@@ -170,9 +166,9 @@ class SortLimitTest
 
     arangodb::OperationOptions options;
     options.returnNew = true;
-    arangodb::SingleCollectionTransaction trx(arangodb::transaction::StandaloneContext::Create(*vocbase),
-                                              *collection,
-                                              arangodb::AccessMode::Type::WRITE);
+    arangodb::SingleCollectionTransaction trx(
+        arangodb::transaction::StandaloneContext::Create(*vocbase), *collection,
+        arangodb::AccessMode::Type::WRITE);
     EXPECT_TRUE(trx.begin().ok());
 
     for (auto& entry : docs) {
@@ -191,7 +187,7 @@ TEST_F(SortLimitTest, CheckSimpleLimitSortedAscInInsertionOrder) {
       "FOR d IN testCollection0 SORT d.valAsc LIMIT 0, 10 RETURN d";
   std::vector<size_t> expected = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
   EXPECT_EQ(sorterType(*vocbase, query), "constrained-heap");
-  EXPECT_TRUE(verifyExpectedResults(*vocbase, query, expected));
+  verifyExpectedResults(*vocbase, query, expected);
 }
 
 TEST_F(SortLimitTest, CheckLimitWithOffsetSortedAscInInsertionOrder) {
@@ -199,7 +195,7 @@ TEST_F(SortLimitTest, CheckLimitWithOffsetSortedAscInInsertionOrder) {
       "FOR d IN testCollection0 SORT d.valAsc LIMIT 10, 10 RETURN d";
   std::vector<size_t> expected = {10, 11, 12, 13, 14, 15, 16, 17, 18, 19};
   EXPECT_EQ(sorterType(*vocbase, query), "constrained-heap");
-  EXPECT_TRUE(verifyExpectedResults(*vocbase, query, expected));
+  verifyExpectedResults(*vocbase, query, expected);
 }
 
 TEST_F(SortLimitTest, CheckSimpleLimitSortedAscInReverseInsertionOrder) {
@@ -208,7 +204,7 @@ TEST_F(SortLimitTest, CheckSimpleLimitSortedAscInReverseInsertionOrder) {
   std::vector<size_t> expected = {999, 998, 997, 996, 995,
                                   994, 993, 992, 991, 990};
   EXPECT_EQ(sorterType(*vocbase, query), "constrained-heap");
-  EXPECT_TRUE(verifyExpectedResults(*vocbase, query, expected));
+  verifyExpectedResults(*vocbase, query, expected);
 }
 
 TEST_F(SortLimitTest, CheckLimitWithOffsetSortedAscInReverseInsertionOrder) {
@@ -217,7 +213,7 @@ TEST_F(SortLimitTest, CheckLimitWithOffsetSortedAscInReverseInsertionOrder) {
   std::vector<size_t> expected = {989, 988, 987, 986, 985,
                                   984, 983, 982, 981, 980};
   EXPECT_EQ(sorterType(*vocbase, query), "constrained-heap");
-  EXPECT_TRUE(verifyExpectedResults(*vocbase, query, expected));
+  verifyExpectedResults(*vocbase, query, expected);
 }
 
 TEST_F(SortLimitTest, CheckSimpleLimitSortedDscInInsertionOrder) {
@@ -226,7 +222,7 @@ TEST_F(SortLimitTest, CheckSimpleLimitSortedDscInInsertionOrder) {
   std::vector<size_t> expected = {999, 998, 997, 996, 995,
                                   994, 993, 992, 991, 990};
   EXPECT_EQ(sorterType(*vocbase, query), "constrained-heap");
-  EXPECT_TRUE(verifyExpectedResults(*vocbase, query, expected));
+  verifyExpectedResults(*vocbase, query, expected);
 }
 
 TEST_F(SortLimitTest, CheckLimitWithOffsetSortedDscInInsertionOrder) {
@@ -235,7 +231,7 @@ TEST_F(SortLimitTest, CheckLimitWithOffsetSortedDscInInsertionOrder) {
   std::vector<size_t> expected = {989, 988, 987, 986, 985,
                                   984, 983, 982, 981, 980};
   EXPECT_EQ(sorterType(*vocbase, query), "constrained-heap");
-  EXPECT_TRUE(verifyExpectedResults(*vocbase, query, expected));
+  verifyExpectedResults(*vocbase, query, expected);
 }
 
 TEST_F(SortLimitTest, CheckSimpleLimitSortedDscInReverseInsertionOrder) {
@@ -243,7 +239,7 @@ TEST_F(SortLimitTest, CheckSimpleLimitSortedDscInReverseInsertionOrder) {
       "FOR d IN testCollection0 SORT d.valDsc DESC LIMIT 0, 10 RETURN d";
   std::vector<size_t> expected = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
   EXPECT_EQ(sorterType(*vocbase, query), "constrained-heap");
-  EXPECT_TRUE(verifyExpectedResults(*vocbase, query, expected));
+  verifyExpectedResults(*vocbase, query, expected);
 }
 
 TEST_F(SortLimitTest, CheckLimitWithOffsetSortedDscInReverseInsertionOrder) {
@@ -251,7 +247,7 @@ TEST_F(SortLimitTest, CheckLimitWithOffsetSortedDscInReverseInsertionOrder) {
       "FOR d IN testCollection0 SORT d.valDsc DESC LIMIT 10, 10 RETURN d";
   std::vector<size_t> expected = {10, 11, 12, 13, 14, 15, 16, 17, 18, 19};
   EXPECT_EQ(sorterType(*vocbase, query), "constrained-heap");
-  EXPECT_TRUE(verifyExpectedResults(*vocbase, query, expected));
+  verifyExpectedResults(*vocbase, query, expected);
 }
 
 TEST_F(SortLimitTest, CheckLimitWithOffsetCompoundSort) {
@@ -259,7 +255,7 @@ TEST_F(SortLimitTest, CheckLimitWithOffsetCompoundSort) {
       "FOR d IN testCollection0 SORT d.mod, d.valAsc LIMIT 2, 5 RETURN  d";
   std::vector<size_t> expected = {200, 300, 400, 500, 600};
   EXPECT_EQ(sorterType(*vocbase, query), "constrained-heap");
-  EXPECT_TRUE(verifyExpectedResults(*vocbase, query, expected));
+  verifyExpectedResults(*vocbase, query, expected);
 }
 
 TEST_F(SortLimitTest, CheckLimitWithOffsetCompoundSortAgain) {
@@ -268,7 +264,7 @@ TEST_F(SortLimitTest, CheckLimitWithOffsetCompoundSortAgain) {
   std::vector<size_t> expected = {1,   101, 201, 301, 401,
                                   501, 601, 701, 801, 901};
   EXPECT_EQ(sorterType(*vocbase, query), "constrained-heap");
-  EXPECT_TRUE(verifyExpectedResults(*vocbase, query, expected));
+  verifyExpectedResults(*vocbase, query, expected);
 }
 
 TEST_F(SortLimitTest, CheckInterloperFilterMovedUp) {
@@ -278,7 +274,7 @@ TEST_F(SortLimitTest, CheckInterloperFilterMovedUp) {
   std::vector<size_t> expected = {0,   100, 200, 300, 400,
                                   500, 600, 700, 800, 900};
   EXPECT_EQ(sorterType(*vocbase, query), "constrained-heap");
-  EXPECT_TRUE(verifyExpectedResults(*vocbase, query, expected));
+  verifyExpectedResults(*vocbase, query, expected);
 }
 
 TEST_F(SortLimitTest, CheckInterloperFilterNotMoved) {
@@ -289,7 +285,7 @@ TEST_F(SortLimitTest, CheckInterloperFilterNotMoved) {
   std::vector<size_t> expected = {0,   100, 200, 300, 400,
                                   500, 600, 700, 800, 900};
   EXPECT_EQ(sorterType(*vocbase, query, rules), "standard");
-  EXPECT_TRUE(verifyExpectedResults(*vocbase, query, expected, rules));
+  verifyExpectedResults(*vocbase, query, expected, rules);
 }
 
 TEST_F(SortLimitTest, CheckInterloperEnumerateList) {
@@ -298,5 +294,5 @@ TEST_F(SortLimitTest, CheckInterloperEnumerateList) {
       "LIMIT 0, 10 RETURN d";
   std::vector<size_t> expected = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
   EXPECT_EQ(sorterType(*vocbase, query), "standard");
-  EXPECT_TRUE(verifyExpectedResults(*vocbase, query, expected));
+  verifyExpectedResults(*vocbase, query, expected);
 }

From a6281daf9d96cc5dfb12aef3e241d0a1af20565e Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Wed, 27 Nov 2019 15:37:32 +0100
Subject: [PATCH 024/122] Removed debug profile execution of a query

---
 tests/Aql/SpliceSubqueryOptimizerRuleTest.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/Aql/SpliceSubqueryOptimizerRuleTest.cpp b/tests/Aql/SpliceSubqueryOptimizerRuleTest.cpp
index 83b692021999..ba8b1d56f146 100644
--- a/tests/Aql/SpliceSubqueryOptimizerRuleTest.cpp
+++ b/tests/Aql/SpliceSubqueryOptimizerRuleTest.cpp
@@ -263,7 +263,7 @@ TEST_F(SpliceSubqueryNodeOptimizerRuleTest, splice_subquery_plan) {
   verifySubquerySplicing(query, 1);
 
   auto expected = arangodb::velocypack::Parser::fromJson(R"([[1],[2]])");
-  verifyQueryResult(query, expected->slice(), R"({"profile": 5})");
+  verifyQueryResult(query, expected->slice());
 }
 
 TEST_F(SpliceSubqueryNodeOptimizerRuleTest, splice_subquery_in_subquery_plan) {

From 7a8a1dc617b8f4ab72e10d0bc58212bdcf5cd8b9 Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Wed, 27 Nov 2019 15:56:22 +0100
Subject: [PATCH 025/122] Use simpleVPack printing for Trace of Execute, better
 to read by humans

---
 arangod/Aql/ExecutionBlockImpl.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index a54efe1db958..ab96aa34e9b0 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -647,7 +647,7 @@ void ExecutionBlockImpl<Executor>::traceExecuteEnd(
           VPackBuilder builder;
           {
             VPackObjectBuilder guard(&builder);
-            block->toVelocyPack(transaction(), builder);
+            block->toSimpleVPack(transaction(), builder);
           }
           auto options = transaction()->transactionContextPtr()->getVPackOptions();
           LOG_TOPIC("f12f9", INFO, Logger::QUERIES)

From 8307d15ed6e715a131e121723a142774806a43ca Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Fri, 29 Nov 2019 14:03:58 +0100
Subject: [PATCH 026/122] Added tests for AqlItemBlockInputRange and adjusted
 implementation accordingly.

---
 arangod/Aql/AqlItemBlockInputRange.cpp   | 110 ++++++---
 arangod/Aql/AqlItemBlockInputRange.h     |  11 +-
 tests/Aql/AqlItemBlockInputRangeTest.cpp | 292 +++++++++++++++++++++++
 tests/CMakeLists.txt                     |   1 +
 4 files changed, 374 insertions(+), 40 deletions(-)
 create mode 100644 tests/Aql/AqlItemBlockInputRangeTest.cpp

diff --git a/arangod/Aql/AqlItemBlockInputRange.cpp b/arangod/Aql/AqlItemBlockInputRange.cpp
index 178997eb6ec3..2ec4ed2e1aea 100644
--- a/arangod/Aql/AqlItemBlockInputRange.cpp
+++ b/arangod/Aql/AqlItemBlockInputRange.cpp
@@ -23,6 +23,12 @@
 #include "AqlItemBlockInputRange.h"
 #include "Aql/ShadowAqlItemRow.h"
 
+#include "Logger/LogMacros.h"
+
+#include <velocypack/Builder.h>
+#include <velocypack/velocypack-aliases.h>
+#include <numeric>
+
 using namespace arangodb;
 using namespace arangodb::aql;
 
@@ -49,15 +55,16 @@ AqlItemBlockInputRange::AqlItemBlockInputRange(ExecutorState state,
 
 std::pair<ExecutorState, InputAqlItemRow> AqlItemBlockInputRange::peek() {
   if (indexIsValid()) {
-    return std::make_pair(state(), InputAqlItemRow{_block, _rowIndex});
+    return std::make_pair(nextState<LookAhead::NEXT, RowType::DATA>(),
+                          InputAqlItemRow{_block, _rowIndex});
   }
-  return std::make_pair(state(), InputAqlItemRow{CreateInvalidInputRowHint{}});
+  return std::make_pair(nextState<LookAhead::NOW, RowType::DATA>(),
+                        InputAqlItemRow{CreateInvalidInputRowHint{}});
 }
 
 std::pair<ExecutorState, InputAqlItemRow> AqlItemBlockInputRange::next() {
   auto res = peek();
-  if (indexIsValid()) {
-    TRI_ASSERT(res.second);
+  if (res.second) {
     ++_rowIndex;
   }
   return res;
@@ -74,50 +81,29 @@ bool AqlItemBlockInputRange::hasMoreAfterThis() const noexcept {
 }
 
 ExecutorState AqlItemBlockInputRange::state() const noexcept {
-  return hasMoreAfterThis() ? ExecutorState::HASMORE : _finalState;
-}
-
-ExecutorState AqlItemBlockInputRange::shadowState() const noexcept {
-  if (_block == nullptr) {
-    return _finalState;
-  }
-  // We Return HASMORE, if the next shadow row is NOT relevant.
-  // So we can directly fetch the next shadow row without informing
-  // the executor about an empty subquery.
-  size_t nextRowIndex = _rowIndex + 1;
-  if (_block != nullptr && nextRowIndex < _block->size() && _block->isShadowRow(nextRowIndex)) {
-    ShadowAqlItemRow nextRow{_block, nextRowIndex};
-    if (!nextRow.isRelevant()) {
-      return ExecutorState::HASMORE;
-    }
-  }
-  return ExecutorState::DONE;
+  return nextState<LookAhead::NOW, RowType::DATA>();
 }
 
 bool AqlItemBlockInputRange::hasShadowRow() const noexcept {
-  if (_block == nullptr) {
-    // No block => no ShadowRow
-    return false;
-  }
+  return isIndexValid(_rowIndex) && isShadowRowAtIndex(_rowIndex);
+}
 
-  if (hasMore()) {
-    // As long as hasMore() is true, we still have DataRows and are not on a ShadowRow now.
-    return false;
-  }
+bool AqlItemBlockInputRange::isIndexValid(std::size_t index) const noexcept {
+  return _block != nullptr && index < _block->size();
+}
 
-  if (_rowIndex < _block->size()) {
-    // We still have more rows here, get next ShadowRow
-    TRI_ASSERT(_block->isShadowRow(_rowIndex));
-    return true;
-  }
-  return false;
+bool AqlItemBlockInputRange::isShadowRowAtIndex(std::size_t index) const noexcept {
+  TRI_ASSERT(isIndexValid(index));
+  return _block->isShadowRow(index);
 }
 
 std::pair<ExecutorState, ShadowAqlItemRow> AqlItemBlockInputRange::peekShadowRow() {
   if (hasShadowRow()) {
-    return std::make_pair(shadowState(), ShadowAqlItemRow{_block, _rowIndex});
+    return std::make_pair(nextState<LookAhead::NEXT, RowType::SHADOW>(),
+                          ShadowAqlItemRow{_block, _rowIndex});
   }
-  return std::make_pair(shadowState(), ShadowAqlItemRow{CreateInvalidShadowRowHint{}});
+  return std::make_pair(nextState<LookAhead::NOW, RowType::SHADOW>(),
+                        ShadowAqlItemRow{CreateInvalidShadowRowHint{}});
 }
 
 std::pair<ExecutorState, ShadowAqlItemRow> AqlItemBlockInputRange::nextShadowRow() {
@@ -138,6 +124,54 @@ std::pair<ExecutorState, ShadowAqlItemRow> AqlItemBlockInputRange::nextShadowRow
     }
     // Advance the current row.
     _rowIndex++;
+    /*
+    {
+      std::string out = "Depths: [";
+      for (auto const& it : shadowRowIndexes) {
+        ShadowAqlItemRow sr(_block, it);
+        out += std::to_string(sr.getDepth()) + ", ";
+      }
+      LOG_DEVEL << out << "]";
+
+      VPackBuilder hund;
+      _block->toSimpleVPack(nullptr, hund);
+      LOG_DEVEL << hund.toJson();
+    }
+    */
   }
   return res;
 }
+
+template <AqlItemBlockInputRange::LookAhead doPeek, AqlItemBlockInputRange::RowType type>
+ExecutorState AqlItemBlockInputRange::nextState() const noexcept {
+  size_t testRowIndex = _rowIndex;
+  if constexpr (LookAhead::NEXT == doPeek) {
+    // Look ahead one
+    testRowIndex++;
+  }
+  if (!isIndexValid(testRowIndex)) {
+    return _finalState;
+  }
+
+  bool isShadowRow = isShadowRowAtIndex(testRowIndex);
+
+  if constexpr (RowType::DATA == type) {
+    // We Return HASMORE, if the next row is a data row
+    if (!isShadowRow) {
+      return ExecutorState::HASMORE;
+    }
+    return ExecutorState::DONE;
+  } else {
+    TRI_ASSERT(RowType::SHADOW == type);
+    // We Return HASMORE, if the next shadow row is NOT relevant.
+    // So we can directly fetch the next shadow row without informing
+    // the executor about an empty subquery.
+    if (isShadowRow) {
+      ShadowAqlItemRow nextRow{_block, testRowIndex};
+      if (!nextRow.isRelevant()) {
+        return ExecutorState::HASMORE;
+      }
+    }
+    return ExecutorState::DONE;
+  }
+}
diff --git a/arangod/Aql/AqlItemBlockInputRange.h b/arangod/Aql/AqlItemBlockInputRange.h
index fd68ace50fff..85b1cafed5a2 100644
--- a/arangod/Aql/AqlItemBlockInputRange.h
+++ b/arangod/Aql/AqlItemBlockInputRange.h
@@ -44,8 +44,6 @@ class AqlItemBlockInputRange {
 
   ExecutorState state() const noexcept;
 
-  ExecutorState shadowState() const noexcept;
-
   std::pair<ExecutorState, arangodb::aql::InputAqlItemRow> peek();
 
   std::pair<ExecutorState, arangodb::aql::InputAqlItemRow> next();
@@ -61,10 +59,19 @@ class AqlItemBlockInputRange {
   std::pair<ExecutorState, arangodb::aql::ShadowAqlItemRow> nextShadowRow();
 
  private:
+  bool isIndexValid(std::size_t index) const noexcept;
+
   bool indexIsValid() const noexcept;
 
   bool hasMoreAfterThis() const noexcept;
 
+  bool isShadowRowAtIndex(std::size_t index) const noexcept;
+
+  enum LookAhead { NOW, NEXT };
+  enum RowType { DATA, SHADOW };
+  template <LookAhead doPeek, RowType type>
+  ExecutorState nextState() const noexcept;
+
  private:
   arangodb::aql::SharedAqlItemBlockPtr _block;
   std::size_t _rowIndex;
diff --git a/tests/Aql/AqlItemBlockInputRangeTest.cpp b/tests/Aql/AqlItemBlockInputRangeTest.cpp
new file mode 100644
index 000000000000..614c70ea7f64
--- /dev/null
+++ b/tests/Aql/AqlItemBlockInputRangeTest.cpp
@@ -0,0 +1,292 @@
+////////////////////////////////////////////////////////////////////////////////
+/// DISCLAIMER
+///
+/// Copyright 2018 ArangoDB GmbH, Cologne, Germany
+///
+/// Licensed under the Apache License, Version 2.0 (the "License");
+/// you may not use this file except in compliance with the License.
+/// You may obtain a copy of the License at
+///
+///     http://www.apache.org/licenses/LICENSE-2.0
+///
+/// Unless required by applicable law or agreed to in writing, software
+/// distributed under the License is distributed on an "AS IS" BASIS,
+/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+/// See the License for the specific language governing permissions and
+/// limitations under the License.
+///
+/// Copyright holder is ArangoDB GmbH, Cologne, Germany
+///
+/// @author Michael Hackstein
+////////////////////////////////////////////////////////////////////////////////
+
+#include "Aql/AqlItemBlockInputRange.h"
+#include "gtest/gtest.h"
+
+#include "Aql/AqlItemBlockManager.h"
+#include "Aql/InputAqlItemRow.h"
+#include "Aql/ShadowAqlItemRow.h"
+#include "AqlItemBlockHelper.h"
+#include "Basics/VelocyPackHelper.h"
+
+#include <velocypack/Builder.h>
+#include <velocypack/Slice.h>
+#include <velocypack/velocypack-aliases.h>
+
+using namespace arangodb;
+using namespace arangodb::aql;
+using namespace arangodb::basics;
+
+namespace arangodb {
+namespace tests {
+namespace aql {
+
+// Test empty constructor
+class InputRangeTest : public ::testing::TestWithParam<ExecutorState> {
+ protected:
+  ResourceMonitor monitor;
+  AqlItemBlockManager itemBlockManager{&monitor, SerializationFormat::SHADOWROWS};
+
+  AqlItemBlockInputRange createEmpty() {
+    return AqlItemBlockInputRange{GetParam()};
+  }
+
+  AqlItemBlockInputRange createFromBlock(arangodb::aql::SharedAqlItemBlockPtr& block) {
+    auto const [start, end] = block->getRelevantRange();
+    return AqlItemBlockInputRange(GetParam(), block, start, end);
+  }
+
+  void validateEndReached(AqlItemBlockInputRange& testee) {
+    EXPECT_EQ(GetParam(), testee.state());
+    // Test Data rows
+    EXPECT_FALSE(testee.hasMore());
+    {
+      auto const [state, row] = testee.peek();
+      EXPECT_EQ(GetParam(), state);
+      EXPECT_FALSE(row.isInitialized());
+    }
+    {
+      auto const [state, row] = testee.next();
+      EXPECT_EQ(GetParam(), state);
+      EXPECT_FALSE(row.isInitialized());
+    }
+    // Test Shadow Rows
+    EXPECT_FALSE(testee.hasShadowRow());
+    {
+      auto const [state, row] = testee.peekShadowRow();
+      EXPECT_EQ(GetParam(), state);
+      EXPECT_FALSE(row.isInitialized());
+    }
+    {
+      auto const [state, row] = testee.nextShadowRow();
+      EXPECT_EQ(GetParam(), state);
+      EXPECT_FALSE(row.isInitialized());
+    }
+  }
+
+  void validateNextIsDataRow(AqlItemBlockInputRange& testee,
+                             ExecutorState expectedState, int64_t value) {
+    EXPECT_TRUE(testee.hasMore());
+    EXPECT_FALSE(testee.hasShadowRow());
+    // We have the next row
+    EXPECT_EQ(testee.state(), ExecutorState::HASMORE);
+    auto rowIndexBefore = testee.getRowIndex();
+    // Validate that shadowRowAPI does not move on
+    {
+      auto [state, row] = testee.peekShadowRow();
+      EXPECT_EQ(state, ExecutorState::DONE);
+      EXPECT_FALSE(row.isInitialized());
+      ASSERT_EQ(rowIndexBefore, testee.getRowIndex())
+          << "Skipped a non processed row.";
+    }
+    {
+      auto [state, row] = testee.nextShadowRow();
+      EXPECT_EQ(state, ExecutorState::DONE);
+      EXPECT_FALSE(row.isInitialized());
+      ASSERT_EQ(rowIndexBefore, testee.getRowIndex())
+          << "Skipped a non processed row.";
+    }
+    // Validate Data Row API
+    {
+      auto [state, row] = testee.peek();
+      EXPECT_EQ(state, expectedState);
+      EXPECT_TRUE(row.isInitialized());
+      auto val = row.getValue(0);
+      ASSERT_TRUE(val.isNumber());
+      EXPECT_EQ(val.toInt64(), value);
+      ASSERT_EQ(rowIndexBefore, testee.getRowIndex())
+          << "Skipped a non processed row.";
+    }
+
+    {
+      auto [state, row] = testee.next();
+      EXPECT_EQ(state, expectedState);
+      EXPECT_TRUE(row.isInitialized());
+      auto val = row.getValue(0);
+      ASSERT_TRUE(val.isNumber());
+      EXPECT_EQ(val.toInt64(), value);
+      ASSERT_NE(rowIndexBefore, testee.getRowIndex())
+          << "Did not go to next row.";
+    }
+  }
+
+  void validateNextIsShadowRow(AqlItemBlockInputRange& testee, ExecutorState expectedState,
+                               int64_t value, uint64_t depth) {
+    EXPECT_TRUE(testee.hasShadowRow());
+    // The next is a ShadowRow, the state shall be done
+    EXPECT_EQ(testee.state(), ExecutorState::DONE);
+
+    auto rowIndexBefore = testee.getRowIndex();
+    // Validate that inputRowAPI does not move on
+    {
+      auto [state, row] = testee.peek();
+      EXPECT_EQ(state, ExecutorState::DONE);
+      EXPECT_FALSE(row.isInitialized());
+      ASSERT_EQ(rowIndexBefore, testee.getRowIndex())
+          << "Skipped a non processed row.";
+    }
+    {
+      auto [state, row] = testee.next();
+      EXPECT_EQ(state, ExecutorState::DONE);
+      EXPECT_FALSE(row.isInitialized());
+      ASSERT_EQ(rowIndexBefore, testee.getRowIndex())
+          << "Skipped a non processed row.";
+    }
+    // Validate ShadowRow API
+    {
+      auto [state, row] = testee.peekShadowRow();
+      EXPECT_EQ(state, expectedState);
+      EXPECT_TRUE(row.isInitialized());
+      auto val = row.getValue(0);
+      ASSERT_TRUE(val.isNumber());
+      EXPECT_EQ(val.toInt64(), value);
+      EXPECT_EQ(row.getDepth(), depth);
+      ASSERT_EQ(rowIndexBefore, testee.getRowIndex())
+          << "Skipped a non processed row.";
+    }
+    {
+      auto [state, row] = testee.nextShadowRow();
+      EXPECT_EQ(state, expectedState);
+      EXPECT_TRUE(row.isInitialized());
+      auto val = row.getValue(0);
+      ASSERT_TRUE(val.isNumber());
+      EXPECT_EQ(val.toInt64(), value);
+      EXPECT_EQ(row.getDepth(), depth);
+      ASSERT_NE(rowIndexBefore, testee.getRowIndex())
+          << "Did not go to next row.";
+    }
+  }
+};
+
+TEST_P(InputRangeTest, empty_returns_given_state) {
+  auto testee = createEmpty();
+  EXPECT_EQ(GetParam(), testee.state());
+}
+
+TEST_P(InputRangeTest, empty_does_not_have_more) {
+  auto testee = createEmpty();
+  EXPECT_FALSE(testee.hasMore());
+}
+
+TEST_P(InputRangeTest, empty_peek_is_empty) {
+  auto testee = createEmpty();
+  auto const [state, row] = testee.peek();
+  EXPECT_EQ(GetParam(), state);
+  EXPECT_FALSE(row.isInitialized());
+}
+
+TEST_P(InputRangeTest, empty_next_is_empty) {
+  auto testee = createEmpty();
+  auto const [state, row] = testee.next();
+  EXPECT_EQ(GetParam(), state);
+  EXPECT_FALSE(row.isInitialized());
+}
+
+TEST_P(InputRangeTest, empty_does_not_have_more_shadow_rows) {
+  auto testee = createEmpty();
+  EXPECT_FALSE(testee.hasShadowRow());
+}
+
+TEST_P(InputRangeTest, empty_peek_shadow_is_empty) {
+  auto testee = createEmpty();
+  auto const [state, row] = testee.peekShadowRow();
+  EXPECT_EQ(GetParam(), state);
+  EXPECT_FALSE(row.isInitialized());
+}
+
+TEST_P(InputRangeTest, empty_next_shadow_is_empty) {
+  auto testee = createEmpty();
+  auto const [state, row] = testee.nextShadowRow();
+  EXPECT_EQ(GetParam(), state);
+  EXPECT_FALSE(row.isInitialized());
+}
+
+TEST_P(InputRangeTest, no_shadow_rows_in_block) {
+  SharedAqlItemBlockPtr inputBlock =
+      buildBlock<1>(itemBlockManager, {{{1}}, {{2}}, {{3}}, {{4}}}, {});
+  auto testee = createFromBlock(inputBlock);
+
+  // We have 3 internal rows
+  validateNextIsDataRow(testee, ExecutorState::HASMORE, 1);
+  validateNextIsDataRow(testee, ExecutorState::HASMORE, 2);
+  validateNextIsDataRow(testee, ExecutorState::HASMORE, 3);
+  // Last Row needs to return upstream State
+  validateNextIsDataRow(testee, GetParam(), 4);
+  validateEndReached(testee);
+}
+
+TEST_P(InputRangeTest, level_0_shadow_rows_in_block) {
+  SharedAqlItemBlockPtr inputBlock =
+      buildBlock<1>(itemBlockManager, {{{1}}, {{2}}, {{3}}, {{4}}}, {{1, 0}, {3, 0}});
+  auto testee = createFromBlock(inputBlock);
+
+  validateNextIsDataRow(testee, ExecutorState::DONE, 1);
+  validateNextIsShadowRow(testee, ExecutorState::DONE, 2, 0);
+  validateNextIsDataRow(testee, ExecutorState::DONE, 3);
+  // Last Row needs to return upstream State
+  validateNextIsShadowRow(testee, GetParam(), 4, 0);
+  validateEndReached(testee);
+}
+
+TEST_P(InputRangeTest, multi_level_shadow_rows_in_block) {
+  SharedAqlItemBlockPtr inputBlock =
+      buildBlock<1>(itemBlockManager, {{{1}}, {{2}}, {{3}}, {{4}}, {{5}}, {{6}}, {{7}}},
+                    {{3, 0}, {4, 1}, {5, 2}});
+  auto testee = createFromBlock(inputBlock);
+
+  validateNextIsDataRow(testee, ExecutorState::HASMORE, 1);
+  validateNextIsDataRow(testee, ExecutorState::HASMORE, 2);
+  validateNextIsDataRow(testee, ExecutorState::DONE, 3);
+  validateNextIsShadowRow(testee, ExecutorState::HASMORE, 4, 0);
+  validateNextIsShadowRow(testee, ExecutorState::HASMORE, 5, 1);
+  validateNextIsShadowRow(testee, ExecutorState::DONE, 6, 2);
+
+  // Last Row needs to return upstream State
+  validateNextIsDataRow(testee, GetParam(), 7);
+  validateEndReached(testee);
+}
+
+TEST_P(InputRangeTest, multi_shadow_rows_batches_in_block) {
+  SharedAqlItemBlockPtr inputBlock =
+      buildBlock<1>(itemBlockManager, {{{1}}, {{2}}, {{3}}, {{4}}, {{5}}, {{6}}, {{7}}},
+                    {{3, 0}, {4, 1}, {5, 0}, {6, 1}});
+  auto testee = createFromBlock(inputBlock);
+
+  validateNextIsDataRow(testee, ExecutorState::HASMORE, 1);
+  validateNextIsDataRow(testee, ExecutorState::HASMORE, 2);
+  validateNextIsDataRow(testee, ExecutorState::DONE, 3);
+  validateNextIsShadowRow(testee, ExecutorState::HASMORE, 4, 0);
+  validateNextIsShadowRow(testee, ExecutorState::DONE, 5, 1);
+  validateNextIsShadowRow(testee, ExecutorState::HASMORE, 6, 0);
+
+  // Last Row needs to return upstream State
+  validateNextIsShadowRow(testee, GetParam(), 7, 1);
+  validateEndReached(testee);
+}
+
+INSTANTIATE_TEST_CASE_P(AqlItemBlockInputRangeTest, InputRangeTest,
+                        ::testing::Values(ExecutorState::DONE, ExecutorState::HASMORE));
+
+}  // namespace aql
+}  // namespace tests
+}  // namespace arangodb
\ No newline at end of file
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index d49562a28008..145503288127 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -25,6 +25,7 @@ set(ARANGODB_TESTS_SOURCES
   Agency/SupervisionTest.cpp
   Aql/AllRowsFetcherTest.cpp
   Aql/AqlHelper.cpp
+  Aql/AqlItemBlockInputRangeTest.cpp
   Aql/AqlItemBlockTest.cpp
   Aql/AqlItemRowPrinter.cpp
   Aql/AqlItemRowTest.cpp

From c97314907864af2b95ff3d03c81d3b20f84d2666 Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Mon, 2 Dec 2019 10:31:24 +0100
Subject: [PATCH 027/122] Fixed issue where ExecutionBlockImpl returns DONE,
 although there are still rows in the DataRange

---
 arangod/Aql/AqlItemBlockInputRange.cpp | 16 +---------------
 arangod/Aql/ExecutionBlockImpl.cpp     | 25 +++++++++++++++++--------
 arangod/Aql/SingleRowFetcher.h         |  8 ++++----
 3 files changed, 22 insertions(+), 27 deletions(-)

diff --git a/arangod/Aql/AqlItemBlockInputRange.cpp b/arangod/Aql/AqlItemBlockInputRange.cpp
index 2ec4ed2e1aea..974f4c0ee320 100644
--- a/arangod/Aql/AqlItemBlockInputRange.cpp
+++ b/arangod/Aql/AqlItemBlockInputRange.cpp
@@ -124,20 +124,6 @@ std::pair<ExecutorState, ShadowAqlItemRow> AqlItemBlockInputRange::nextShadowRow
     }
     // Advance the current row.
     _rowIndex++;
-    /*
-    {
-      std::string out = "Depths: [";
-      for (auto const& it : shadowRowIndexes) {
-        ShadowAqlItemRow sr(_block, it);
-        out += std::to_string(sr.getDepth()) + ", ";
-      }
-      LOG_DEVEL << out << "]";
-
-      VPackBuilder hund;
-      _block->toSimpleVPack(nullptr, hund);
-      LOG_DEVEL << hund.toJson();
-    }
-    */
   }
   return res;
 }
@@ -174,4 +160,4 @@ ExecutorState AqlItemBlockInputRange::nextState() const noexcept {
     }
     return ExecutorState::DONE;
   }
-}
+}
\ No newline at end of file
diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index 94c89833b791..b3bde87744c6 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -1009,6 +1009,12 @@ ExecutionBlockImpl<FilterExecutor>::executeWithoutTrace(AqlCallStack stack) {
   // TODO: Need to make this member variable for waiting?
   AqlCall myCall = stack.popCall();
   ExecState execState = ::NextState(myCall);
+  if (_lastRange.hasShadowRow()) {
+    // We have not been able to move all shadowRows into the output last time.
+    // Continue from there.
+    // TODO test if this works with COUNT COLLECT
+    execState = ExecState::SHADOWROWS;
+  }
   AqlCall executorRequest;
 
   while (execState != ExecState::DONE) {
@@ -1088,17 +1094,20 @@ ExecutionBlockImpl<FilterExecutor>::executeWithoutTrace(AqlCallStack stack) {
           TRI_ASSERT(_outputItemRow->produced());
           _outputItemRow->advanceRow();
           if (state == ExecutorState::DONE) {
-            // Right now we cannot support to have more than one set of
-            // ShadowRows inside of a Range.
-            // We do not know how to continue with the above executor after a shadowrow.
-            execState = ExecState::DONE;
+            if (_lastRange.hasMore()) {
+              // TODO this state is invalid, and can just show up now if we exclude SKIP
+              execState = ExecState::PRODUCE;
+            } else {
+              // Right now we cannot support to have more than one set of
+              // ShadowRows inside of a Range.
+              // We do not know how to continue with the above executor after a shadowrow.
+              TRI_ASSERT(!_lastRange.hasMore());
+              execState = ExecState::DONE;
+            }
           }
         } else {
           execState = ExecState::DONE;
         }
-        // TRI_ASSERT(false);
-        // execState = ::NextState(myCall);
-
         break;
       }
       default:
@@ -1111,7 +1120,7 @@ ExecutionBlockImpl<FilterExecutor>::executeWithoutTrace(AqlCallStack stack) {
   // This is not strictly necessary here, as we shouldn't be called again
   // after DONE.
   _outputItemRow.reset();
-  if (_lastRange.hasMore()) {
+  if (_lastRange.hasMore() || _lastRange.hasShadowRow()) {
     return {ExecutionState::HASMORE, skipped, std::move(outputBlock)};
   }
   return {_upstreamState, skipped, std::move(outputBlock)};
diff --git a/arangod/Aql/SingleRowFetcher.h b/arangod/Aql/SingleRowFetcher.h
index b4b5521e2caf..2afcaf465eaf 100644
--- a/arangod/Aql/SingleRowFetcher.h
+++ b/arangod/Aql/SingleRowFetcher.h
@@ -101,10 +101,10 @@ class SingleRowFetcher {
   template <BlockPassthrough allowPass = blockPassthrough, typename = std::enable_if_t<allowPass == BlockPassthrough::Enable>>
   [[nodiscard]]
 #else
-  [[nodiscard]]
-  TEST_VIRTUAL
+  [[nodiscard]] TEST_VIRTUAL
 #endif
-  std::pair<ExecutionState, SharedAqlItemBlockPtr> fetchBlockForPassthrough(size_t atMost);
+  std::pair<ExecutionState, SharedAqlItemBlockPtr>
+  fetchBlockForPassthrough(size_t atMost);
 
   [[nodiscard]] std::pair<ExecutionState, size_t> preFetchNumberOfRows(size_t atMost);
 
@@ -172,6 +172,6 @@ class SingleRowFetcher {
 
   [[nodiscard]] ExecutionState returnState(bool isShadowRow) const;
 };
-}  // namespace arangodb
+}  // namespace arangodb::aql
 
 #endif  // ARANGOD_AQL_SINGLE_ROW_FETCHER_H

From d83e3acfc9eb6db15ac53a25f88626eef4715976 Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Mon, 2 Dec 2019 17:02:26 +0100
Subject: [PATCH 028/122] Final modification of ShadowRows in FilterExecutor.
 All but profiling tests pass. This needs some discussion about overfetching
 of data, and propagation of hardLimit

---
 arangod/Aql/AqlItemBlockInputRange.cpp   | 41 ++++++------------------
 arangod/Aql/AqlItemBlockInputRange.h     |  4 ---
 arangod/Aql/ExecutionBlockImpl.cpp       |  7 ++--
 arangod/Aql/FilterExecutor.cpp           |  8 ++++-
 tests/Aql/AqlItemBlockInputRangeTest.cpp |  1 +
 5 files changed, 23 insertions(+), 38 deletions(-)

diff --git a/arangod/Aql/AqlItemBlockInputRange.cpp b/arangod/Aql/AqlItemBlockInputRange.cpp
index 974f4c0ee320..3acf0bd1911b 100644
--- a/arangod/Aql/AqlItemBlockInputRange.cpp
+++ b/arangod/Aql/AqlItemBlockInputRange.cpp
@@ -39,22 +39,20 @@ AqlItemBlockInputRange::AqlItemBlockInputRange(ExecutorState state)
 
 AqlItemBlockInputRange::AqlItemBlockInputRange(ExecutorState state,
                                                SharedAqlItemBlockPtr const& block,
-                                               std::size_t index, std::size_t endIndex)
-    : _block{block}, _rowIndex{index}, _endIndex(endIndex), _finalState{state} {
-  TRI_ASSERT(index <= endIndex);
-  TRI_ASSERT(endIndex <= block->size());
+                                               std::size_t index, std::size_t)
+    : _block{block}, _rowIndex{index}, _endIndex(_block->size()), _finalState{state} {
+  TRI_ASSERT(index <= _block->size());
 }
 
 AqlItemBlockInputRange::AqlItemBlockInputRange(ExecutorState state,
                                                SharedAqlItemBlockPtr&& block,
-                                               std::size_t index, std::size_t endIndex) noexcept
-    : _block{std::move(block)}, _rowIndex{index}, _endIndex(endIndex), _finalState{state} {
-  TRI_ASSERT(index <= endIndex);
-  TRI_ASSERT(endIndex <= block->size());
+                                               std::size_t index, std::size_t) noexcept
+    : _block{std::move(block)}, _rowIndex{index}, _endIndex(_block->size()), _finalState{state} {
+  TRI_ASSERT(index <= _block->size());
 }
 
 std::pair<ExecutorState, InputAqlItemRow> AqlItemBlockInputRange::peek() {
-  if (indexIsValid()) {
+  if (hasMore()) {
     return std::make_pair(nextState<LookAhead::NEXT, RowType::DATA>(),
                           InputAqlItemRow{_block, _rowIndex});
   }
@@ -70,14 +68,8 @@ std::pair<ExecutorState, InputAqlItemRow> AqlItemBlockInputRange::next() {
   return res;
 }
 
-bool AqlItemBlockInputRange::indexIsValid() const noexcept {
-  return _block != nullptr && _rowIndex < _endIndex;
-}
-
-bool AqlItemBlockInputRange::hasMore() const noexcept { return indexIsValid(); }
-
-bool AqlItemBlockInputRange::hasMoreAfterThis() const noexcept {
-  return indexIsValid() && _rowIndex + 1 < _endIndex;
+bool AqlItemBlockInputRange::hasMore() const noexcept {
+  return isIndexValid(_rowIndex) && !isShadowRowAtIndex(_rowIndex);
 }
 
 ExecutorState AqlItemBlockInputRange::state() const noexcept {
@@ -108,20 +100,7 @@ std::pair<ExecutorState, ShadowAqlItemRow> AqlItemBlockInputRange::peekShadowRow
 
 std::pair<ExecutorState, ShadowAqlItemRow> AqlItemBlockInputRange::nextShadowRow() {
   auto res = peekShadowRow();
-  if (hasShadowRow()) {
-    auto const& shadowRowIndexes = _block->getShadowRowIndexes();
-    auto it = std::find(shadowRowIndexes.begin(), shadowRowIndexes.end(), _rowIndex);
-    // We have a shadow row in this index, so we cannot be at the end now.
-    TRI_ASSERT(it != shadowRowIndexes.end());
-    // Go to next ShadowRow.
-    it++;
-    if (it == shadowRowIndexes.end()) {
-      // No more shadow row here.
-      _endIndex = _block->size();
-    } else {
-      // Set endIndex to the next ShadowRowIndex.
-      _endIndex = *it;
-    }
+  if (res.second.isInitialized()) {
     // Advance the current row.
     _rowIndex++;
   }
diff --git a/arangod/Aql/AqlItemBlockInputRange.h b/arangod/Aql/AqlItemBlockInputRange.h
index 85b1cafed5a2..e0a6a5827c35 100644
--- a/arangod/Aql/AqlItemBlockInputRange.h
+++ b/arangod/Aql/AqlItemBlockInputRange.h
@@ -61,10 +61,6 @@ class AqlItemBlockInputRange {
  private:
   bool isIndexValid(std::size_t index) const noexcept;
 
-  bool indexIsValid() const noexcept;
-
-  bool hasMoreAfterThis() const noexcept;
-
   bool isShadowRowAtIndex(std::size_t index) const noexcept;
 
   enum LookAhead { NOW, NEXT };
diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index b3bde87744c6..50eb4f63ffe3 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -1017,7 +1017,7 @@ ExecutionBlockImpl<FilterExecutor>::executeWithoutTrace(AqlCallStack stack) {
   }
   AqlCall executorRequest;
 
-  while (execState != ExecState::DONE) {
+  while (execState != ExecState::DONE && !_outputItemRow->isFull()) {
     switch (execState) {
       case ExecState::SKIP: {
         auto [state, skippedLocal, call] =
@@ -1028,6 +1028,7 @@ ExecutionBlockImpl<FilterExecutor>::executeWithoutTrace(AqlCallStack stack) {
         if (state == ExecutorState::DONE) {
           execState = ExecState::SHADOWROWS;
         } else if (myCall.getOffset() > 0) {
+          TRI_ASSERT(_upstreamState != ExecutionState::DONE);
           // We need to request more
           executorRequest = call;
           execState = ExecState::UPSTREAM;
@@ -1040,15 +1041,17 @@ ExecutionBlockImpl<FilterExecutor>::executeWithoutTrace(AqlCallStack stack) {
       case ExecState::PRODUCE: {
         auto linesBefore = _outputItemRow->numRowsWritten();
         TRI_ASSERT(myCall.getLimit() > 0);
+        auto limit = (std::min)(myCall.getLimit(), _outputItemRow->numRowsLeft());
         // Execute getSome
         auto const [state, stats, call] =
-            _executor.produceRows(myCall.getLimit(), _lastRange, *_outputItemRow);
+            _executor.produceRows(limit, _lastRange, *_outputItemRow);
         auto written = _outputItemRow->numRowsWritten() - linesBefore;
         _engine->_stats += stats;
         myCall.didProduce(written);
         if (state == ExecutorState::DONE) {
           execState = ExecState::SHADOWROWS;
         } else if (myCall.getLimit() > 0) {
+          TRI_ASSERT(_upstreamState != ExecutionState::DONE);
           // We need to request more
           executorRequest = call;
           execState = ExecState::UPSTREAM;
diff --git a/arangod/Aql/FilterExecutor.cpp b/arangod/Aql/FilterExecutor.cpp
index e96a83e0383e..dd40309be60a 100644
--- a/arangod/Aql/FilterExecutor.cpp
+++ b/arangod/Aql/FilterExecutor.cpp
@@ -35,6 +35,8 @@
 #include "Aql/SingleRowFetcher.h"
 #include "Aql/Stats.h"
 
+#include "Logger/LogMacros.h"
+
 #include <utility>
 
 using namespace arangodb;
@@ -143,6 +145,10 @@ std::tuple<ExecutorState, FilterStats, AqlCall> FilterExecutor::produceRows(
   }
 
   AqlCall upstreamCall{};
-  upstreamCall.softLimit = limit;
+  /* We can use this value as a heuristic on overfetching.
+   * by default we do not skip, and do not set any soft or hardLimit
+   * on upstream
+   * upstreamCall.softLimit = limit;
+   */
   return {inputRange.state(), stats, upstreamCall};
 }
diff --git a/tests/Aql/AqlItemBlockInputRangeTest.cpp b/tests/Aql/AqlItemBlockInputRangeTest.cpp
index 614c70ea7f64..c5180e23ec1c 100644
--- a/tests/Aql/AqlItemBlockInputRangeTest.cpp
+++ b/tests/Aql/AqlItemBlockInputRangeTest.cpp
@@ -128,6 +128,7 @@ class InputRangeTest : public ::testing::TestWithParam<ExecutorState> {
       ASSERT_NE(rowIndexBefore, testee.getRowIndex())
           << "Did not go to next row.";
     }
+    EXPECT_EQ(expectedState, testee.state());
   }
 
   void validateNextIsShadowRow(AqlItemBlockInputRange& testee, ExecutorState expectedState,

From 9c8ae9dbbf9a604a7ea73e7c2cda0281b8266bfe Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Mon, 2 Dec 2019 17:08:40 +0100
Subject: [PATCH 029/122] Removed debug log includes

---
 arangod/Aql/AqlItemBlock.cpp           | 2 --
 arangod/Aql/AqlItemBlockInputRange.cpp | 2 --
 arangod/Aql/FilterExecutor.cpp         | 2 --
 arangod/Aql/SingleRowFetcher.cpp       | 1 -
 4 files changed, 7 deletions(-)

diff --git a/arangod/Aql/AqlItemBlock.cpp b/arangod/Aql/AqlItemBlock.cpp
index 21ce81042122..c4527d2a6839 100644
--- a/arangod/Aql/AqlItemBlock.cpp
+++ b/arangod/Aql/AqlItemBlock.cpp
@@ -39,8 +39,6 @@
 #include <velocypack/Iterator.h>
 #include <velocypack/velocypack-aliases.h>
 
-#include "Logger/LogMacros.h"
-
 using namespace arangodb;
 using namespace arangodb::aql;
 
diff --git a/arangod/Aql/AqlItemBlockInputRange.cpp b/arangod/Aql/AqlItemBlockInputRange.cpp
index 3acf0bd1911b..32d2155ce8fb 100644
--- a/arangod/Aql/AqlItemBlockInputRange.cpp
+++ b/arangod/Aql/AqlItemBlockInputRange.cpp
@@ -23,8 +23,6 @@
 #include "AqlItemBlockInputRange.h"
 #include "Aql/ShadowAqlItemRow.h"
 
-#include "Logger/LogMacros.h"
-
 #include <velocypack/Builder.h>
 #include <velocypack/velocypack-aliases.h>
 #include <numeric>
diff --git a/arangod/Aql/FilterExecutor.cpp b/arangod/Aql/FilterExecutor.cpp
index dd40309be60a..54b76c8b05ab 100644
--- a/arangod/Aql/FilterExecutor.cpp
+++ b/arangod/Aql/FilterExecutor.cpp
@@ -35,8 +35,6 @@
 #include "Aql/SingleRowFetcher.h"
 #include "Aql/Stats.h"
 
-#include "Logger/LogMacros.h"
-
 #include <utility>
 
 using namespace arangodb;
diff --git a/arangod/Aql/SingleRowFetcher.cpp b/arangod/Aql/SingleRowFetcher.cpp
index a8f8a867b61e..017c1821973f 100644
--- a/arangod/Aql/SingleRowFetcher.cpp
+++ b/arangod/Aql/SingleRowFetcher.cpp
@@ -24,7 +24,6 @@
 ////////////////////////////////////////////////////////////////////////////////
 
 #include "SingleRowFetcher.h"
-#include <Logger/LogMacros.h>
 
 #include "Aql/AqlItemBlock.h"
 #include "Aql/DependencyProxy.h"

From 292bd2ae5158792a3e60bf6eadf44e42bb98c8f8 Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Tue, 3 Dec 2019 17:43:50 +0100
Subject: [PATCH 030/122] Moved responsibility for the client call into the
 output row. This can precisely count the elements it has written, and forms a
 single source of truth. The output row now works as the requested block by
 client that needs to be filled. Now the FilterExecutorTests are red.

---
 arangod/Aql/ExecutionBlockImpl.cpp | 21 ++++++----------
 arangod/Aql/ExecutionBlockImpl.h   |  7 +++++-
 arangod/Aql/FilterExecutor.cpp     |  7 +++---
 arangod/Aql/FilterExecutor.h       |  2 +-
 arangod/Aql/OutputAqlItemRow.cpp   | 22 ++++++++++++++++-
 arangod/Aql/OutputAqlItemRow.h     | 39 ++++++++++++++++++++++++------
 tests/Aql/FilterExecutorTest.cpp   |  6 ++---
 7 files changed, 75 insertions(+), 29 deletions(-)

diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index 50eb4f63ffe3..84b8057174e1 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -301,13 +301,12 @@ std::pair<ExecutionState, SharedAqlItemBlockPtr> ExecutionBlockImpl<Executor>::g
 }
 
 template <class Executor>
-std::unique_ptr<OutputAqlItemRow> ExecutionBlockImpl<Executor>::createOutputRow(
-    SharedAqlItemBlockPtr& newBlock) const {
+std::unique_ptr<OutputAqlItemRow> ExecutionBlockImpl<Executor>::createOutputRow(SharedAqlItemBlockPtr& newBlock) {
   if /* constexpr */ (Executor::Properties::allowsBlockPassthrough == BlockPassthrough::Enable) {
-    return std::make_unique<OutputAqlItemRow>(newBlock, infos().getOutputRegisters(),
-                                              infos().registersToKeep(),
-                                              infos().registersToClear(),
-                                              OutputAqlItemRow::CopyRowBehavior::DoNotCopyInputRows);
+    return std::make_unique<OutputAqlItemRow>(
+        newBlock, infos().getOutputRegisters(), infos().registersToKeep(),
+        infos().registersToClear(), std::move(AqlCall{}),
+        OutputAqlItemRow::CopyRowBehavior::DoNotCopyInputRows);
   } else {
     return std::make_unique<OutputAqlItemRow>(newBlock, infos().getOutputRegisters(),
                                               infos().registersToKeep(),
@@ -996,6 +995,7 @@ ExecState NextState(AqlCall const& call) {
 template <>
 std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr>
 ExecutionBlockImpl<FilterExecutor>::executeWithoutTrace(AqlCallStack stack) {
+  AqlCall myCall = stack.popCall();
   if (!_outputItemRow) {
     // TODO: FIXME Hard coded size
     SharedAqlItemBlockPtr newBlock =
@@ -1007,7 +1007,7 @@ ExecutionBlockImpl<FilterExecutor>::executeWithoutTrace(AqlCallStack stack) {
   size_t skipped = 0;
 
   // TODO: Need to make this member variable for waiting?
-  AqlCall myCall = stack.popCall();
+
   ExecState execState = ::NextState(myCall);
   if (_lastRange.hasShadowRow()) {
     // We have not been able to move all shadowRows into the output last time.
@@ -1039,15 +1039,10 @@ ExecutionBlockImpl<FilterExecutor>::executeWithoutTrace(AqlCallStack stack) {
         break;
       }
       case ExecState::PRODUCE: {
-        auto linesBefore = _outputItemRow->numRowsWritten();
         TRI_ASSERT(myCall.getLimit() > 0);
-        auto limit = (std::min)(myCall.getLimit(), _outputItemRow->numRowsLeft());
         // Execute getSome
-        auto const [state, stats, call] =
-            _executor.produceRows(limit, _lastRange, *_outputItemRow);
-        auto written = _outputItemRow->numRowsWritten() - linesBefore;
+        auto const [state, stats, call] = _executor.produceRows(_lastRange, *_outputItemRow);
         _engine->_stats += stats;
-        myCall.didProduce(written);
         if (state == ExecutorState::DONE) {
           execState = ExecState::SHADOWROWS;
         } else if (myCall.getLimit() > 0) {
diff --git a/arangod/Aql/ExecutionBlockImpl.h b/arangod/Aql/ExecutionBlockImpl.h
index e90fb11f5ce7..88f410033edf 100644
--- a/arangod/Aql/ExecutionBlockImpl.h
+++ b/arangod/Aql/ExecutionBlockImpl.h
@@ -36,6 +36,7 @@
 
 namespace arangodb::aql {
 
+struct AqlCall;
 class AqlItemBlock;
 class ExecutionEngine;
 class ExecutionNode;
@@ -225,7 +226,7 @@ class ExecutionBlockImpl final : public ExecutionBlock {
   [[nodiscard]] std::pair<ExecutionState, SharedAqlItemBlockPtr> requestWrappedBlock(
       size_t nrItems, RegisterId nrRegs);
 
-  [[nodiscard]] std::unique_ptr<OutputAqlItemRow> createOutputRow(SharedAqlItemBlockPtr& newBlock) const;
+  [[nodiscard]] std::unique_ptr<OutputAqlItemRow> createOutputRow(SharedAqlItemBlockPtr& newBlock);
 
   [[nodiscard]] Query const& getQuery() const;
 
@@ -244,6 +245,10 @@ class ExecutionBlockImpl final : public ExecutionBlock {
   // Trace the end of a getSome call, potentially with result
   void traceExecuteEnd(std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> const& result);
 
+  // Ensure that we have an output block of the desired dimenstions
+  // Will as a side effect modify _outputItemRow
+  void ensureOutputBlock(AqlCall&& call);
+
  private:
   /**
    * @brief Used to allow the row Fetcher to access selected methods of this
diff --git a/arangod/Aql/FilterExecutor.cpp b/arangod/Aql/FilterExecutor.cpp
index 54b76c8b05ab..fe7f81f6394e 100644
--- a/arangod/Aql/FilterExecutor.cpp
+++ b/arangod/Aql/FilterExecutor.cpp
@@ -123,26 +123,27 @@ std::tuple<ExecutorState, size_t, AqlCall> FilterExecutor::skipRowsRange(
 }
 
 std::tuple<ExecutorState, FilterStats, AqlCall> FilterExecutor::produceRows(
-    size_t limit, AqlItemBlockInputRange& inputRange, OutputAqlItemRow& output) {
+    AqlItemBlockInputRange& inputRange, OutputAqlItemRow& output) {
   TRI_IF_FAILURE("FilterExecutor::produceRows") {
     THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
   }
   FilterStats stats{};
 
-  while (inputRange.hasMore() && limit > 0) {
+  while (inputRange.hasMore()) {
     TRI_ASSERT(!output.isFull());
     auto const& [state, input] = inputRange.next();
     TRI_ASSERT(input.isInitialized());
     if (input.getValue(_infos.getInputRegister()).toBoolean()) {
       output.copyRow(input);
       output.advanceRow();
-      limit--;
     } else {
       stats.incrFiltered();
     }
   }
 
   AqlCall upstreamCall{};
+  upstreamCall.softLimit = output.softLimit();
+  upstreamCall.hardLimit = output.hardLimit();
   /* We can use this value as a heuristic on overfetching.
    * by default we do not skip, and do not set any soft or hardLimit
    * on upstream
diff --git a/arangod/Aql/FilterExecutor.h b/arangod/Aql/FilterExecutor.h
index 21cd564aea41..eea47aba7b87 100644
--- a/arangod/Aql/FilterExecutor.h
+++ b/arangod/Aql/FilterExecutor.h
@@ -96,7 +96,7 @@ class FilterExecutor {
    * @return ExecutorState, the stats, and a new Call that needs to be send to upstream
    */
   [[nodiscard]] std::tuple<ExecutorState, Stats, AqlCall> produceRows(
-      size_t atMost, AqlItemBlockInputRange& input, OutputAqlItemRow& output);
+      AqlItemBlockInputRange& input, OutputAqlItemRow& output);
 
   /**
    * @brief skip the next Row of Aql Values.
diff --git a/arangod/Aql/OutputAqlItemRow.cpp b/arangod/Aql/OutputAqlItemRow.cpp
index 079653a618a8..ff62d61a0366 100644
--- a/arangod/Aql/OutputAqlItemRow.cpp
+++ b/arangod/Aql/OutputAqlItemRow.cpp
@@ -23,6 +23,15 @@
 /// @author Jan Christoph Uhde
 ////////////////////////////////////////////////////////////////////////////////
 
+/*
+The following conditions need to hold true, we need to add c++ tests for this.
+
+  output.isFull() == output.numRowsLeft() > 0;
+  output.numRowsLeft() <= output.allocatedRows() - output.numRowsWritten();
+  output.numRowsLeft() <= output.softLimit();
+  output.softLimit() <= output.hardLimit();
+*/
+
 #include "OutputAqlItemRow.h"
 
 #include "Aql/AqlItemBlock.h"
@@ -41,13 +50,14 @@ OutputAqlItemRow::OutputAqlItemRow(
     std::shared_ptr<std::unordered_set<RegisterId> const> outputRegisters,
     std::shared_ptr<std::unordered_set<RegisterId> const> registersToKeep,
     std::shared_ptr<std::unordered_set<RegisterId> const> registersToClear,
-    CopyRowBehavior copyRowBehavior)
+    AqlCall&& clientCall, CopyRowBehavior copyRowBehavior)
     : _block(std::move(block)),
       _baseIndex(0),
       _lastBaseIndex(0),
       _inputRowCopied(false),
       _lastSourceRow{CreateInvalidInputRowHint{}},
       _numValuesWritten(0),
+      _call(std::move(clientCall)),
       _doNotCopyInputRow(copyRowBehavior == CopyRowBehavior::DoNotCopyInputRows),
       _outputRegisters(std::move(outputRegisters)),
       _registersToKeep(std::move(registersToKeep)),
@@ -187,6 +197,12 @@ void OutputAqlItemRow::advanceRow() {
   TRI_ASSERT(produced());
   TRI_ASSERT(allValuesWritten());
   TRI_ASSERT(_inputRowCopied);
+  if (!_block->isShadowRow(_baseIndex)) {
+    // We have written a data row into the output.
+    // Need to count it.
+    _call.didProduce(1);
+  }
+
   ++_baseIndex;
   _inputRowCopied = false;
   _numValuesWritten = 0;
@@ -197,6 +213,10 @@ void OutputAqlItemRow::toVelocyPack(velocypack::Options const* options, VPackBui
   block().rowToSimpleVPack(_baseIndex, options, builder);
 }
 
+AqlCall::Limit OutputAqlItemRow::softLimit() const { return _call.softLimit; }
+
+AqlCall::Limit OutputAqlItemRow::hardLimit() const { return _call.hardLimit; }
+
 SharedAqlItemBlockPtr OutputAqlItemRow::stealBlock() {
   // numRowsWritten() inspects _block, so save this before resetting it!
   auto const numRows = numRowsWritten();
diff --git a/arangod/Aql/OutputAqlItemRow.h b/arangod/Aql/OutputAqlItemRow.h
index 969b06e2e895..835b54e4b78f 100644
--- a/arangod/Aql/OutputAqlItemRow.h
+++ b/arangod/Aql/OutputAqlItemRow.h
@@ -26,6 +26,7 @@
 #ifndef ARANGOD_AQL_OUTPUT_AQL_ITEM_ROW_H
 #define ARANGOD_AQL_OUTPUT_AQL_ITEM_ROW_H
 
+#include "Aql/AqlCall.h"
 #include "Aql/InputAqlItemRow.h"
 #include "Aql/SharedAqlItemBlockPtr.h"
 #include "Aql/types.h"
@@ -54,6 +55,7 @@ class OutputAqlItemRow {
                             std::shared_ptr<std::unordered_set<RegisterId> const> outputRegisters,
                             std::shared_ptr<std::unordered_set<RegisterId> const> registersToKeep,
                             std::shared_ptr<std::unordered_set<RegisterId> const> registersToClear,
+                            AqlCall&& clientCall = AqlCall{},
                             CopyRowBehavior = CopyRowBehavior::CopyInputRows);
 
   ~OutputAqlItemRow() = default;
@@ -95,7 +97,9 @@ class OutputAqlItemRow {
   void copyBlockInternalRegister(InputAqlItemRow const& sourceRow,
                                  RegisterId input, RegisterId output);
 
-  [[nodiscard]] std::size_t getNrRegisters() const { return block().getNrRegs(); }
+  [[nodiscard]] std::size_t getNrRegisters() const {
+    return block().getNrRegs();
+  }
 
   /**
    * @brief May only be called after all output values in the current row have
@@ -105,7 +109,9 @@ class OutputAqlItemRow {
   void advanceRow();
 
   // returns true if row was produced
-  [[nodiscard]] bool produced() const { return _inputRowCopied && allValuesWritten(); }
+  [[nodiscard]] bool produced() const {
+    return _inputRowCopied && allValuesWritten();
+  }
 
   /**
    * @brief Steal the AqlItemBlock held by the OutputAqlItemRow. The returned
@@ -118,7 +124,9 @@ class OutputAqlItemRow {
    */
   SharedAqlItemBlockPtr stealBlock();
 
-  [[nodiscard]] bool isFull() const { return numRowsWritten() >= block().size(); }
+  [[nodiscard]] bool isFull() const {
+    return numRowsWritten() >= block().size();
+  }
 
   /**
    * @brief Returns the number of rows that were fully written.
@@ -131,7 +139,9 @@ class OutputAqlItemRow {
    *        NOTE that we later want to replace this with some "atMost" value
    *        passed from ExecutionBlockImpl.
    */
-  [[nodiscard]] size_t numRowsLeft() const { return block().size() - _baseIndex; }
+  [[nodiscard]] size_t numRowsLeft() const {
+    return block().size() - _baseIndex;
+  }
 
   // Use this function with caution! We need it only for the ConstrainedSortExecutor
   void setBaseIndex(std::size_t index);
@@ -161,6 +171,10 @@ class OutputAqlItemRow {
 
   void toVelocyPack(velocypack::Options const* options, velocypack::Builder& builder);
 
+  AqlCall::Limit softLimit() const;
+
+  AqlCall::Limit hardLimit() const;
+
  private:
   [[nodiscard]] std::unordered_set<RegisterId> const& outputRegisters() const {
     TRI_ASSERT(_outputRegisters != nullptr);
@@ -210,6 +224,13 @@ class OutputAqlItemRow {
    */
   size_t _numValuesWritten;
 
+  /**
+   * @brief Call recieved by the client to produce this outputblock
+   *        It is used for accounting of produced rows and number
+   *        of rows requested by client.
+   */
+  AqlCall _call;
+
   /**
    * @brief Set if and only if the current ExecutionBlock passes the
    * AqlItemBlocks through.
@@ -228,9 +249,13 @@ class OutputAqlItemRow {
   bool _allowSourceRowUninitialized;
 
  private:
-  [[nodiscard]] size_t nextUnwrittenIndex() const noexcept { return numRowsWritten(); }
+  [[nodiscard]] size_t nextUnwrittenIndex() const noexcept {
+    return numRowsWritten();
+  }
 
-  [[nodiscard]] size_t numRegistersToWrite() const { return outputRegisters().size(); }
+  [[nodiscard]] size_t numRegistersToWrite() const {
+    return outputRegisters().size();
+  }
 
   [[nodiscard]] bool allValuesWritten() const {
     // If we have a shadowRow in the output, it counts as written
@@ -260,6 +285,6 @@ class OutputAqlItemRow {
   template <class ItemRowType>
   void adjustShadowRowDepth(ItemRowType const& sourceRow);
 };
-}  // namespace arangodb
+}  // namespace arangodb::aql
 
 #endif  // ARANGOD_AQL_OUTPUT_AQL_ITEM_ROW_H
diff --git a/tests/Aql/FilterExecutorTest.cpp b/tests/Aql/FilterExecutorTest.cpp
index 5f64b03278d7..3d832576e388 100644
--- a/tests/Aql/FilterExecutorTest.cpp
+++ b/tests/Aql/FilterExecutorTest.cpp
@@ -368,7 +368,7 @@ TEST_F(FilterExecutorTest, test_produce_datarange) {
   OutputAqlItemRow output(std::move(block), outputRegisters, registersToKeep,
                           infos.registersToClear());
   EXPECT_EQ(output.numRowsWritten(), 0);
-  auto const [state, stats, call] = testee.produceRows(1000, input, output);
+  auto const [state, stats, call] = testee.produceRows(input, output);
   EXPECT_EQ(state, ExecutorState::DONE);
   EXPECT_EQ(stats.getFiltered(), 2);
   EXPECT_EQ(output.numRowsWritten(), 3);
@@ -393,7 +393,7 @@ TEST_F(FilterExecutorTest, test_produce_datarange_need_more) {
   OutputAqlItemRow output(std::move(block), outputRegisters, registersToKeep,
                           infos.registersToClear());
   EXPECT_EQ(output.numRowsWritten(), 0);
-  auto const [state, stats, call] = testee.produceRows(1000, input, output);
+  auto const [state, stats, call] = testee.produceRows(input, output);
   EXPECT_EQ(state, ExecutorState::HASMORE);
   EXPECT_EQ(stats.getFiltered(), 2);
   EXPECT_EQ(output.numRowsWritten(), 3);
@@ -452,7 +452,7 @@ TEST_F(FilterExecutorTest, test_produce_datarange_has_more) {
   AqlItemBlockInputRange input{ExecutorState::DONE, inBlock, 0, inBlock->size()};
   OutputAqlItemRow output(std::move(block), outputRegisters, registersToKeep,
                           infos.registersToClear());
-  auto const [state, stats, call] = testee.produceRows(2, input, output);
+  auto const [state, stats, call] = testee.produceRows(input, output);
   EXPECT_EQ(state, ExecutorState::HASMORE);
   EXPECT_EQ(stats.getFiltered(), 1);
   EXPECT_EQ(output.numRowsWritten(), 2);

From ba3eea6f6f72edc3c42ebb3193be1ab655599955 Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Wed, 4 Dec 2019 09:46:09 +0100
Subject: [PATCH 031/122] Fixed FilterExecutorTest

---
 tests/Aql/FilterExecutorTest.cpp | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/tests/Aql/FilterExecutorTest.cpp b/tests/Aql/FilterExecutorTest.cpp
index 3d832576e388..8b237d87af9d 100644
--- a/tests/Aql/FilterExecutorTest.cpp
+++ b/tests/Aql/FilterExecutorTest.cpp
@@ -387,11 +387,12 @@ TEST_F(FilterExecutorTest, test_produce_datarange_need_more) {
   SharedAqlItemBlockPtr inBlock =
       buildBlock<1>(itemBlockManager,
                     {{R"(true)"}, {R"(false)"}, {R"(true)"}, {R"(false)"}, {R"(true)"}});
-
+  size_t softLimit = 1000;
   AqlItemBlockInputRange input{ExecutorState::HASMORE, inBlock, 0, inBlock->size()};
-
+  AqlCall limitedCall{};
+  limitedCall.softLimit = softLimit;
   OutputAqlItemRow output(std::move(block), outputRegisters, registersToKeep,
-                          infos.registersToClear());
+                          infos.registersToClear(), std::move(limitedCall));
   EXPECT_EQ(output.numRowsWritten(), 0);
   auto const [state, stats, call] = testee.produceRows(input, output);
   EXPECT_EQ(state, ExecutorState::HASMORE);
@@ -401,9 +402,8 @@ TEST_F(FilterExecutorTest, test_produce_datarange_need_more) {
   // Test the Call we send to upstream
   EXPECT_EQ(call.offset, 0);
   EXPECT_FALSE(call.hasHardLimit());
-  // Avoid overfetching. I do not have a strong requirement on this
-  // test, however this is what we do right now.
-  EXPECT_EQ(call.getLimit(), 997);
+  // We have a given softLimit, so we do not do overfetching
+  EXPECT_EQ(call.getLimit(), softLimit - 3);
   EXPECT_FALSE(call.fullCount);
 }
 
@@ -450,8 +450,10 @@ TEST_F(FilterExecutorTest, test_produce_datarange_has_more) {
                     {{R"(true)"}, {R"(false)"}, {R"(true)"}, {R"(false)"}, {R"(true)"}});
 
   AqlItemBlockInputRange input{ExecutorState::DONE, inBlock, 0, inBlock->size()};
+  block.reset(new AqlItemBlock(itemBlockManager, 2, 1));
   OutputAqlItemRow output(std::move(block), outputRegisters, registersToKeep,
                           infos.registersToClear());
+
   auto const [state, stats, call] = testee.produceRows(input, output);
   EXPECT_EQ(state, ExecutorState::HASMORE);
   EXPECT_EQ(stats.getFiltered(), 1);

From d8f80f94c1b67442eb9da6410b10f5da4182deb9 Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Wed, 4 Dec 2019 09:46:56 +0100
Subject: [PATCH 032/122] Expose required features to AqlCall controlled by the
 output aql item row. Adapted executionBlockImpl to report there

---
 arangod/Aql/ExecutionBlockImpl.cpp | 66 +++++++++++++++++++-----------
 arangod/Aql/ExecutionBlockImpl.h   |  3 +-
 arangod/Aql/FilterExecutor.cpp     |  3 +-
 arangod/Aql/OutputAqlItemRow.cpp   |  4 ++
 arangod/Aql/OutputAqlItemRow.h     |  4 ++
 5 files changed, 52 insertions(+), 28 deletions(-)

diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index 84b8057174e1..a8a6e49f4791 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -202,7 +202,7 @@ std::pair<ExecutionState, SharedAqlItemBlockPtr> ExecutionBlockImpl<Executor>::g
     TRI_ASSERT(newBlock != nullptr);
     TRI_ASSERT(newBlock->size() > 0);
     TRI_ASSERT(newBlock->size() <= atMost);
-    _outputItemRow = createOutputRow(newBlock);
+    _outputItemRow = createOutputRow(newBlock, AqlCall{});
   }
 
   ExecutionState state = ExecutionState::HASMORE;
@@ -301,16 +301,18 @@ std::pair<ExecutionState, SharedAqlItemBlockPtr> ExecutionBlockImpl<Executor>::g
 }
 
 template <class Executor>
-std::unique_ptr<OutputAqlItemRow> ExecutionBlockImpl<Executor>::createOutputRow(SharedAqlItemBlockPtr& newBlock) {
+std::unique_ptr<OutputAqlItemRow> ExecutionBlockImpl<Executor>::createOutputRow(
+    SharedAqlItemBlockPtr& newBlock, AqlCall&& call) {
   if /* constexpr */ (Executor::Properties::allowsBlockPassthrough == BlockPassthrough::Enable) {
-    return std::make_unique<OutputAqlItemRow>(
-        newBlock, infos().getOutputRegisters(), infos().registersToKeep(),
-        infos().registersToClear(), std::move(AqlCall{}),
-        OutputAqlItemRow::CopyRowBehavior::DoNotCopyInputRows);
+    return std::make_unique<OutputAqlItemRow>(newBlock, infos().getOutputRegisters(),
+                                              infos().registersToKeep(),
+                                              infos().registersToClear(), std::move(call),
+                                              OutputAqlItemRow::CopyRowBehavior::DoNotCopyInputRows);
   } else {
     return std::make_unique<OutputAqlItemRow>(newBlock, infos().getOutputRegisters(),
                                               infos().registersToKeep(),
-                                              infos().registersToClear());
+                                              infos().registersToClear(),
+                                              std::move(call));
   }
 }
 
@@ -939,6 +941,17 @@ std::pair<ExecutionState, SharedAqlItemBlockPtr> ExecutionBlockImpl<Executor>::r
       executor(), *_engine, nrItems, nrRegs);
 }
 
+template <class Executor>
+void ExecutionBlockImpl<Executor>::ensureOutputBlock(AqlCall&& call) {
+  if (_outputItemRow->isFull()) {
+    // We need to define the size of this block based on Input / Executor / Subquery depth
+    size_t blockSize = ExecutionBlock::DefaultBatchSize();
+    SharedAqlItemBlockPtr newBlock =
+        _engine->itemBlockManager().requestBlock(blockSize, _infos.numberOfOutputRegisters());
+    _outputItemRow = createOutputRow(newBlock, std::move(call));
+  }
+}
+
 /// @brief request an AqlItemBlock from the memory manager
 template <class Executor>
 SharedAqlItemBlockPtr ExecutionBlockImpl<Executor>::requestBlock(size_t nrItems,
@@ -995,20 +1008,20 @@ ExecState NextState(AqlCall const& call) {
 template <>
 std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr>
 ExecutionBlockImpl<FilterExecutor>::executeWithoutTrace(AqlCallStack stack) {
-  AqlCall myCall = stack.popCall();
+  ensureOutputBlock(stack.popCall());
+  /*
   if (!_outputItemRow) {
     // TODO: FIXME Hard coded size
     SharedAqlItemBlockPtr newBlock =
-        _engine->itemBlockManager().requestBlock(1000, _infos.numberOfOutputRegisters());
-    TRI_ASSERT(newBlock != nullptr);
-    TRI_ASSERT(newBlock->size() == 1000);
-    _outputItemRow = createOutputRow(newBlock);
+        _engine->itemBlockManager().requestBlock(1000,
+  _infos.numberOfOutputRegisters()); TRI_ASSERT(newBlock != nullptr); TRI_ASSERT(newBlock->size()
+  == 1000); _outputItemRow = createOutputRow(newBlock);
   }
+  */
   size_t skipped = 0;
 
-  // TODO: Need to make this member variable for waiting?
-
-  ExecState execState = ::NextState(myCall);
+  TRI_ASSERT(_outputItemRow);
+  ExecState execState = ::NextState(_outputItemRow->getClientCall());
   if (_lastRange.hasShadowRow()) {
     // We have not been able to move all shadowRows into the output last time.
     // Continue from there.
@@ -1020,39 +1033,41 @@ ExecutionBlockImpl<FilterExecutor>::executeWithoutTrace(AqlCallStack stack) {
   while (execState != ExecState::DONE && !_outputItemRow->isFull()) {
     switch (execState) {
       case ExecState::SKIP: {
+        auto const& clientCall = _outputItemRow->getClientCall();
         auto [state, skippedLocal, call] =
-            _executor.skipRowsRange(myCall.getOffset(), _lastRange);
-        myCall.didSkip(skippedLocal);
+            _executor.skipRowsRange(clientCall.getOffset(), _lastRange);
+        _outputItemRow->didSkip(skippedLocal);
         skipped += skippedLocal;
 
         if (state == ExecutorState::DONE) {
           execState = ExecState::SHADOWROWS;
-        } else if (myCall.getOffset() > 0) {
+        } else if (clientCall.getOffset() > 0) {
           TRI_ASSERT(_upstreamState != ExecutionState::DONE);
           // We need to request more
           executorRequest = call;
           execState = ExecState::UPSTREAM;
         } else {
           // We are done with skipping. Skip is not allowed to request more
-          execState = ::NextState(myCall);
+          execState = ::NextState(clientCall);
         }
         break;
       }
       case ExecState::PRODUCE: {
-        TRI_ASSERT(myCall.getLimit() > 0);
+        auto const& clientCall = _outputItemRow->getClientCall();
+        TRI_ASSERT(clientCall.getLimit() > 0);
         // Execute getSome
         auto const [state, stats, call] = _executor.produceRows(_lastRange, *_outputItemRow);
         _engine->_stats += stats;
         if (state == ExecutorState::DONE) {
           execState = ExecState::SHADOWROWS;
-        } else if (myCall.getLimit() > 0) {
+        } else if (clientCall.getLimit() > 0) {
           TRI_ASSERT(_upstreamState != ExecutionState::DONE);
           // We need to request more
           executorRequest = call;
           execState = ExecState::UPSTREAM;
         } else {
           // We are done with producing. Produce is not allowed to request more
-          execState = ::NextState(myCall);
+          execState = ::NextState(clientCall);
         }
         break;
       }
@@ -1067,10 +1082,11 @@ ExecutionBlockImpl<FilterExecutor>::executeWithoutTrace(AqlCallStack stack) {
         size_t skippedLocal = 0;
         stack.pushCall(std::move(executorRequest));
         std::tie(_upstreamState, skippedLocal, _lastRange) = _rowFetcher.execute(stack);
-        // Do we need to call it?
-        // myCall.didSkip(skippedLocal);
         skipped += skippedLocal;
-        execState = ::NextState(myCall);
+        auto const& clientCall = _outputItemRow->getClientCall();
+        // Do we need to call it?
+        // clientCall.didSkip(skippedLocal);
+        execState = ::NextState(clientCall);
         break;
       }
       case ExecState::SHADOWROWS: {
diff --git a/arangod/Aql/ExecutionBlockImpl.h b/arangod/Aql/ExecutionBlockImpl.h
index 88f410033edf..d7d0b3267b09 100644
--- a/arangod/Aql/ExecutionBlockImpl.h
+++ b/arangod/Aql/ExecutionBlockImpl.h
@@ -226,7 +226,8 @@ class ExecutionBlockImpl final : public ExecutionBlock {
   [[nodiscard]] std::pair<ExecutionState, SharedAqlItemBlockPtr> requestWrappedBlock(
       size_t nrItems, RegisterId nrRegs);
 
-  [[nodiscard]] std::unique_ptr<OutputAqlItemRow> createOutputRow(SharedAqlItemBlockPtr& newBlock);
+  [[nodiscard]] std::unique_ptr<OutputAqlItemRow> createOutputRow(SharedAqlItemBlockPtr& newBlock,
+                                                                  AqlCall&& call);
 
   [[nodiscard]] Query const& getQuery() const;
 
diff --git a/arangod/Aql/FilterExecutor.cpp b/arangod/Aql/FilterExecutor.cpp
index fe7f81f6394e..88b20d33382e 100644
--- a/arangod/Aql/FilterExecutor.cpp
+++ b/arangod/Aql/FilterExecutor.cpp
@@ -129,8 +129,7 @@ std::tuple<ExecutorState, FilterStats, AqlCall> FilterExecutor::produceRows(
   }
   FilterStats stats{};
 
-  while (inputRange.hasMore()) {
-    TRI_ASSERT(!output.isFull());
+  while (inputRange.hasMore() && !output.isFull()) {
     auto const& [state, input] = inputRange.next();
     TRI_ASSERT(input.isInitialized());
     if (input.getValue(_infos.getInputRegister()).toBoolean()) {
diff --git a/arangod/Aql/OutputAqlItemRow.cpp b/arangod/Aql/OutputAqlItemRow.cpp
index ff62d61a0366..e281ca9aa094 100644
--- a/arangod/Aql/OutputAqlItemRow.cpp
+++ b/arangod/Aql/OutputAqlItemRow.cpp
@@ -217,6 +217,10 @@ AqlCall::Limit OutputAqlItemRow::softLimit() const { return _call.softLimit; }
 
 AqlCall::Limit OutputAqlItemRow::hardLimit() const { return _call.hardLimit; }
 
+AqlCall const& OutputAqlItemRow::getClientCall() const { return _call; }
+
+void OutputAqlItemRow::didSkip(size_t n) { _call.didSkip(n); }
+
 SharedAqlItemBlockPtr OutputAqlItemRow::stealBlock() {
   // numRowsWritten() inspects _block, so save this before resetting it!
   auto const numRows = numRowsWritten();
diff --git a/arangod/Aql/OutputAqlItemRow.h b/arangod/Aql/OutputAqlItemRow.h
index 835b54e4b78f..d96d51d1a861 100644
--- a/arangod/Aql/OutputAqlItemRow.h
+++ b/arangod/Aql/OutputAqlItemRow.h
@@ -175,6 +175,10 @@ class OutputAqlItemRow {
 
   AqlCall::Limit hardLimit() const;
 
+  AqlCall const& getClientCall() const;
+
+  void didSkip(size_t n);
+
  private:
   [[nodiscard]] std::unordered_set<RegisterId> const& outputRegisters() const {
     TRI_ASSERT(_outputRegisters != nullptr);

From 6d18de707a5fcf7b10bbc37eef8485506e7c19d5 Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Thu, 5 Dec 2019 08:02:19 +0100
Subject: [PATCH 033/122] Fixed bug with AqlCallStack pop operation that
 actually caused invalid memory access

---
 arangod/Aql/AqlCallStack.cpp         |  4 ++--
 arangod/Aql/AqlCallStack.h           |  2 +-
 arangod/Aql/AqlItemBlockInputRange.h |  2 --
 arangod/Aql/ExecutionBlockImpl.cpp   | 15 ++++++++++++---
 arangod/Aql/FilterExecutor.cpp       |  3 +--
 arangod/Aql/OutputAqlItemRow.cpp     |  4 ++++
 arangod/Aql/OutputAqlItemRow.h       |  4 ++++
 tests/Aql/SingleRowFetcherTest.cpp   |  3 ---
 8 files changed, 24 insertions(+), 13 deletions(-)

diff --git a/arangod/Aql/AqlCallStack.cpp b/arangod/Aql/AqlCallStack.cpp
index 0c5f44b2647d..608febad859b 100644
--- a/arangod/Aql/AqlCallStack.cpp
+++ b/arangod/Aql/AqlCallStack.cpp
@@ -45,12 +45,12 @@ AqlCallStack::AqlCallStack(AqlCallStack const& other)
 
 bool AqlCallStack::isRelevant() const { return _depth == 0; }
 
-AqlCall&& AqlCallStack::popCall() {
+AqlCall AqlCallStack::popCall() {
   TRI_ASSERT(isRelevant());
   TRI_ASSERT(!_operations.empty());
   auto call = _operations.top();
   _operations.pop();
-  return std::move(call);
+  return call;
 }
 
 AqlCall const& AqlCallStack::peek() const {
diff --git a/arangod/Aql/AqlCallStack.h b/arangod/Aql/AqlCallStack.h
index 03a9a91d34c5..f9fbec8dd927 100644
--- a/arangod/Aql/AqlCallStack.h
+++ b/arangod/Aql/AqlCallStack.h
@@ -44,7 +44,7 @@ class AqlCallStack {
 
   // Get the top most Call element (this must be relevant).
   // This is popped of the stack and caller can take responsibility for it
-  AqlCall&& popCall();
+  AqlCall popCall();
 
   // Peek at the top most Call element (this must be relevant).
   // The responsibility will stay at the stack
diff --git a/arangod/Aql/AqlItemBlockInputRange.h b/arangod/Aql/AqlItemBlockInputRange.h
index e0a6a5827c35..668113457c15 100644
--- a/arangod/Aql/AqlItemBlockInputRange.h
+++ b/arangod/Aql/AqlItemBlockInputRange.h
@@ -50,8 +50,6 @@ class AqlItemBlockInputRange {
 
   std::size_t getRowIndex() noexcept { return _rowIndex; };
 
-  std::size_t getEndIndex() noexcept { return _endIndex; };
-
   bool hasShadowRow() const noexcept;
 
   std::pair<ExecutorState, arangodb::aql::ShadowAqlItemRow> peekShadowRow();
diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index a8a6e49f4791..a34a76235d67 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -943,12 +943,14 @@ std::pair<ExecutionState, SharedAqlItemBlockPtr> ExecutionBlockImpl<Executor>::r
 
 template <class Executor>
 void ExecutionBlockImpl<Executor>::ensureOutputBlock(AqlCall&& call) {
-  if (_outputItemRow->isFull()) {
+  if (_outputItemRow == nullptr || _outputItemRow->isFull()) {
     // We need to define the size of this block based on Input / Executor / Subquery depth
     size_t blockSize = ExecutionBlock::DefaultBatchSize();
     SharedAqlItemBlockPtr newBlock =
         _engine->itemBlockManager().requestBlock(blockSize, _infos.numberOfOutputRegisters());
     _outputItemRow = createOutputRow(newBlock, std::move(call));
+  } else {
+    _outputItemRow->setCall(std::move(call));
   }
 }
 
@@ -1009,6 +1011,7 @@ template <>
 std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr>
 ExecutionBlockImpl<FilterExecutor>::executeWithoutTrace(AqlCallStack stack) {
   ensureOutputBlock(stack.popCall());
+
   /*
   if (!_outputItemRow) {
     // TODO: FIXME Hard coded size
@@ -1082,11 +1085,17 @@ ExecutionBlockImpl<FilterExecutor>::executeWithoutTrace(AqlCallStack stack) {
         size_t skippedLocal = 0;
         stack.pushCall(std::move(executorRequest));
         std::tie(_upstreamState, skippedLocal, _lastRange) = _rowFetcher.execute(stack);
+        if (_upstreamState == ExecutionState::WAITING) {
+          // We do not return anything in WAITING state, also NOT skipped.
+          // TODO: Check if we need to leverage this restriction.
+          TRI_ASSERT(skipped == 0);
+          return {_upstreamState, 0, nullptr};
+        }
         skipped += skippedLocal;
-        auto const& clientCall = _outputItemRow->getClientCall();
+        ensureOutputBlock(_outputItemRow->stealClientCall());
         // Do we need to call it?
         // clientCall.didSkip(skippedLocal);
-        execState = ::NextState(clientCall);
+        execState = ::NextState(_outputItemRow->getClientCall());
         break;
       }
       case ExecState::SHADOWROWS: {
diff --git a/arangod/Aql/FilterExecutor.cpp b/arangod/Aql/FilterExecutor.cpp
index 88b20d33382e..9ca361a78ad2 100644
--- a/arangod/Aql/FilterExecutor.cpp
+++ b/arangod/Aql/FilterExecutor.cpp
@@ -141,8 +141,7 @@ std::tuple<ExecutorState, FilterStats, AqlCall> FilterExecutor::produceRows(
   }
 
   AqlCall upstreamCall{};
-  upstreamCall.softLimit = output.softLimit();
-  upstreamCall.hardLimit = output.hardLimit();
+  upstreamCall.softLimit = output.hardLimit();
   /* We can use this value as a heuristic on overfetching.
    * by default we do not skip, and do not set any soft or hardLimit
    * on upstream
diff --git a/arangod/Aql/OutputAqlItemRow.cpp b/arangod/Aql/OutputAqlItemRow.cpp
index e281ca9aa094..4c6d358ef13e 100644
--- a/arangod/Aql/OutputAqlItemRow.cpp
+++ b/arangod/Aql/OutputAqlItemRow.cpp
@@ -219,6 +219,10 @@ AqlCall::Limit OutputAqlItemRow::hardLimit() const { return _call.hardLimit; }
 
 AqlCall const& OutputAqlItemRow::getClientCall() const { return _call; }
 
+AqlCall&& OutputAqlItemRow::stealClientCall() { return std::move(_call); }
+
+void OutputAqlItemRow::setCall(AqlCall&& call) { _call = call; }
+
 void OutputAqlItemRow::didSkip(size_t n) { _call.didSkip(n); }
 
 SharedAqlItemBlockPtr OutputAqlItemRow::stealBlock() {
diff --git a/arangod/Aql/OutputAqlItemRow.h b/arangod/Aql/OutputAqlItemRow.h
index d96d51d1a861..28a0127fa141 100644
--- a/arangod/Aql/OutputAqlItemRow.h
+++ b/arangod/Aql/OutputAqlItemRow.h
@@ -177,6 +177,10 @@ class OutputAqlItemRow {
 
   AqlCall const& getClientCall() const;
 
+  AqlCall&& stealClientCall();
+
+  void setCall(AqlCall&& call);
+
   void didSkip(size_t n);
 
  private:
diff --git a/tests/Aql/SingleRowFetcherTest.cpp b/tests/Aql/SingleRowFetcherTest.cpp
index 54818943f3e0..9435cd93979c 100644
--- a/tests/Aql/SingleRowFetcherTest.cpp
+++ b/tests/Aql/SingleRowFetcherTest.cpp
@@ -69,7 +69,6 @@ class SingleRowFetcherTestPassBlocks : public ::testing::Test {
 
   void validateInputRange(AqlItemBlockInputRange& input,
                           std::vector<std::string> const& result) {
-    EXPECT_EQ(result.size(), input.getEndIndex() - input.getRowIndex());
     for (auto const& value : result) {
       SCOPED_TRACE("Checking for value: " + value);
       // We need more rows
@@ -1229,7 +1228,6 @@ TEST_F(SingleRowFetcherTestPassBlocks, handling_shadowrows_in_execute_oneAndDone
     // First no data row
     auto [state, skipped, input] = testee.execute(stack);
     EXPECT_EQ(input.getRowIndex(), 0);
-    EXPECT_EQ(input.getEndIndex(), 4);
     EXPECT_EQ(skipped, 0);
     EXPECT_EQ(state, ExecutionState::DONE);
   }  // testee is destroyed here
@@ -1267,7 +1265,6 @@ TEST_F(SingleRowFetcherTestPassBlocks, handling_shadowrows_in_execute_twoAndHasM
     EXPECT_EQ(state, ExecutionState::DONE);
     EXPECT_EQ(skipped, 0);
     EXPECT_EQ(input.getRowIndex(), 0);
-    EXPECT_EQ(input.getEndIndex(), 4);
 
     // Now validate the input range
     validateInputRange(input, std::vector<std::string>{"a", "b", "c", "d"});

From c84be5942963f3c63b1ff6a506600a76cd2b969d Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Thu, 5 Dec 2019 08:24:18 +0100
Subject: [PATCH 034/122] outputRow now honors limits whan called for isFull.

---
 arangod/Aql/OutputAqlItemRow.h   | 4 ++--
 tests/Aql/FilterExecutorTest.cpp | 6 +++---
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/arangod/Aql/OutputAqlItemRow.h b/arangod/Aql/OutputAqlItemRow.h
index 28a0127fa141..54d09cdb9821 100644
--- a/arangod/Aql/OutputAqlItemRow.h
+++ b/arangod/Aql/OutputAqlItemRow.h
@@ -125,7 +125,7 @@ class OutputAqlItemRow {
   SharedAqlItemBlockPtr stealBlock();
 
   [[nodiscard]] bool isFull() const {
-    return numRowsWritten() >= block().size();
+    return numRowsWritten() >= block().size() && _call.getLimit() > 0;
   }
 
   /**
@@ -140,7 +140,7 @@ class OutputAqlItemRow {
    *        passed from ExecutionBlockImpl.
    */
   [[nodiscard]] size_t numRowsLeft() const {
-    return block().size() - _baseIndex;
+    return (std::min)(block().size() - _baseIndex, _call.getLimit());
   }
 
   // Use this function with caution! We need it only for the ConstrainedSortExecutor
diff --git a/tests/Aql/FilterExecutorTest.cpp b/tests/Aql/FilterExecutorTest.cpp
index 8b237d87af9d..646ad62da2e7 100644
--- a/tests/Aql/FilterExecutorTest.cpp
+++ b/tests/Aql/FilterExecutorTest.cpp
@@ -387,10 +387,10 @@ TEST_F(FilterExecutorTest, test_produce_datarange_need_more) {
   SharedAqlItemBlockPtr inBlock =
       buildBlock<1>(itemBlockManager,
                     {{R"(true)"}, {R"(false)"}, {R"(true)"}, {R"(false)"}, {R"(true)"}});
-  size_t softLimit = 1000;
+  size_t hardLimit = 1000;
   AqlItemBlockInputRange input{ExecutorState::HASMORE, inBlock, 0, inBlock->size()};
   AqlCall limitedCall{};
-  limitedCall.softLimit = softLimit;
+  limitedCall.hardLimit = hardLimit;
   OutputAqlItemRow output(std::move(block), outputRegisters, registersToKeep,
                           infos.registersToClear(), std::move(limitedCall));
   EXPECT_EQ(output.numRowsWritten(), 0);
@@ -403,7 +403,7 @@ TEST_F(FilterExecutorTest, test_produce_datarange_need_more) {
   EXPECT_EQ(call.offset, 0);
   EXPECT_FALSE(call.hasHardLimit());
   // We have a given softLimit, so we do not do overfetching
-  EXPECT_EQ(call.getLimit(), softLimit - 3);
+  EXPECT_EQ(call.getLimit(), hardLimit - 3);
   EXPECT_FALSE(call.fullCount);
 }
 

From 2eb29adfb9948918dde822ba50d967f567ed1860 Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Thu, 5 Dec 2019 08:34:59 +0100
Subject: [PATCH 035/122] Fixed isFull() in OutputAqlItemRow

---
 arangod/Aql/OutputAqlItemRow.h | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/arangod/Aql/OutputAqlItemRow.h b/arangod/Aql/OutputAqlItemRow.h
index 54d09cdb9821..9ece8c61353a 100644
--- a/arangod/Aql/OutputAqlItemRow.h
+++ b/arangod/Aql/OutputAqlItemRow.h
@@ -124,9 +124,7 @@ class OutputAqlItemRow {
    */
   SharedAqlItemBlockPtr stealBlock();
 
-  [[nodiscard]] bool isFull() const {
-    return numRowsWritten() >= block().size() && _call.getLimit() > 0;
-  }
+  [[nodiscard]] bool isFull() const { return numRowsLeft() == 0; }
 
   /**
    * @brief Returns the number of rows that were fully written.

From 715186783f716bfc08113fc6766a2d0c63045018 Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Thu, 5 Dec 2019 18:37:21 +0100
Subject: [PATCH 036/122] Use the inbound call in skipRows for executors, in
 order to do a more precise upstream call

---
 arangod/Aql/ExecutionBlockImpl.cpp |  8 ++++----
 arangod/Aql/FilterExecutor.cpp     |  7 ++++---
 arangod/Aql/FilterExecutor.h       |  2 +-
 arangod/Aql/OutputAqlItemRow.cpp   |  2 ++
 arangod/Aql/OutputAqlItemRow.h     | 16 ++++++++++++++++
 tests/Aql/FilterExecutorTest.cpp   | 10 ++++++++--
 6 files changed, 35 insertions(+), 10 deletions(-)

diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index a34a76235d67..6643026ca185 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -1032,14 +1032,12 @@ ExecutionBlockImpl<FilterExecutor>::executeWithoutTrace(AqlCallStack stack) {
     execState = ExecState::SHADOWROWS;
   }
   AqlCall executorRequest;
-
-  while (execState != ExecState::DONE && !_outputItemRow->isFull()) {
+  while (execState != ExecState::DONE && !_outputItemRow->allRowsUsed()) {
     switch (execState) {
       case ExecState::SKIP: {
         auto const& clientCall = _outputItemRow->getClientCall();
         auto [state, skippedLocal, call] =
-            _executor.skipRowsRange(clientCall.getOffset(), _lastRange);
-        _outputItemRow->didSkip(skippedLocal);
+            _executor.skipRowsRange(_lastRange, _outputItemRow->getModifiableClientCall());
         skipped += skippedLocal;
 
         if (state == ExecutorState::DONE) {
@@ -1144,6 +1142,8 @@ ExecutionBlockImpl<FilterExecutor>::executeWithoutTrace(AqlCallStack stack) {
   // after DONE.
   _outputItemRow.reset();
   if (_lastRange.hasMore() || _lastRange.hasShadowRow()) {
+    // We have skipped or/and return data, otherwise we cannot return HASMORE
+    TRI_ASSERT(skipped > 0 || (outputBlock != nullptr && outputBlock->numEntries() > 0));
     return {ExecutionState::HASMORE, skipped, std::move(outputBlock)};
   }
   return {_upstreamState, skipped, std::move(outputBlock)};
diff --git a/arangod/Aql/FilterExecutor.cpp b/arangod/Aql/FilterExecutor.cpp
index 9ca361a78ad2..4366b71d80b6 100644
--- a/arangod/Aql/FilterExecutor.cpp
+++ b/arangod/Aql/FilterExecutor.cpp
@@ -102,11 +102,11 @@ std::pair<ExecutionState, size_t> FilterExecutor::expectedNumberOfRows(size_t at
 }
 
 std::tuple<ExecutorState, size_t, AqlCall> FilterExecutor::skipRowsRange(
-    size_t offset, AqlItemBlockInputRange& inputRange) {
+    AqlItemBlockInputRange& inputRange, AqlCall& call) {
   ExecutorState state = ExecutorState::HASMORE;
   InputAqlItemRow input{CreateInvalidInputRowHint{}};
   size_t skipped = 0;
-  while (inputRange.hasMore() && skipped < offset) {
+  while (inputRange.hasMore() && skipped < call.getOffset()) {
     std::tie(state, input) = inputRange.next();
     if (!input) {
       TRI_ASSERT(!inputRange.hasMore());
@@ -116,9 +116,10 @@ std::tuple<ExecutorState, size_t, AqlCall> FilterExecutor::skipRowsRange(
       skipped++;
     }
   }
+  call.didSkip(skipped);
 
   AqlCall upstreamCall{};
-  upstreamCall.softLimit = offset - skipped;
+  upstreamCall.softLimit = call.getOffset();
   return {state, skipped, upstreamCall};
 }
 
diff --git a/arangod/Aql/FilterExecutor.h b/arangod/Aql/FilterExecutor.h
index eea47aba7b87..0b5237e08652 100644
--- a/arangod/Aql/FilterExecutor.h
+++ b/arangod/Aql/FilterExecutor.h
@@ -104,7 +104,7 @@ class FilterExecutor {
    * @return ExecutorState, the stats, and a new Call that needs to be send to upstream
    */
   [[nodiscard]] std::tuple<ExecutorState, size_t, AqlCall> skipRowsRange(
-      size_t atMost, AqlItemBlockInputRange& input);
+      AqlItemBlockInputRange& inputRange, AqlCall& call);
 
   [[nodiscard]] std::pair<ExecutionState, size_t> expectedNumberOfRows(size_t atMost) const;
 
diff --git a/arangod/Aql/OutputAqlItemRow.cpp b/arangod/Aql/OutputAqlItemRow.cpp
index 4c6d358ef13e..61c6bce4b719 100644
--- a/arangod/Aql/OutputAqlItemRow.cpp
+++ b/arangod/Aql/OutputAqlItemRow.cpp
@@ -219,6 +219,8 @@ AqlCall::Limit OutputAqlItemRow::hardLimit() const { return _call.hardLimit; }
 
 AqlCall const& OutputAqlItemRow::getClientCall() const { return _call; }
 
+AqlCall& OutputAqlItemRow::getModifiableClientCall() { return _call; };
+
 AqlCall&& OutputAqlItemRow::stealClientCall() { return std::move(_call); }
 
 void OutputAqlItemRow::setCall(AqlCall&& call) { _call = call; }
diff --git a/arangod/Aql/OutputAqlItemRow.h b/arangod/Aql/OutputAqlItemRow.h
index 9ece8c61353a..66b0a513e9ef 100644
--- a/arangod/Aql/OutputAqlItemRow.h
+++ b/arangod/Aql/OutputAqlItemRow.h
@@ -124,8 +124,22 @@ class OutputAqlItemRow {
    */
   SharedAqlItemBlockPtr stealBlock();
 
+  /**
+   * @brief Test if the data-Output is full. This contains checks against
+   *        the client call as well. We are considered full as soon as
+   *        hard or softLimit are reached.
+   */
   [[nodiscard]] bool isFull() const { return numRowsLeft() == 0; }
 
+  /**
+   * @brief Test if all allocated rows are used.
+   *        this does not consider the client call and allows to use
+   *        the left-over space for ShadowRows.
+   */
+  [[nodiscard]] bool allRowsUsed() const {
+    return block().size() <= _baseIndex;
+  }
+
   /**
    * @brief Returns the number of rows that were fully written.
    */
@@ -175,6 +189,8 @@ class OutputAqlItemRow {
 
   AqlCall const& getClientCall() const;
 
+  AqlCall& getModifiableClientCall();
+
   AqlCall&& stealClientCall();
 
   void setCall(AqlCall&& call);
diff --git a/tests/Aql/FilterExecutorTest.cpp b/tests/Aql/FilterExecutorTest.cpp
index 646ad62da2e7..dc37f114c757 100644
--- a/tests/Aql/FilterExecutorTest.cpp
+++ b/tests/Aql/FilterExecutorTest.cpp
@@ -421,10 +421,13 @@ TEST_F(FilterExecutorTest, test_skip_datarange_need_more) {
                     {{R"(true)"}, {R"(false)"}, {R"(true)"}, {R"(false)"}, {R"(true)"}});
 
   AqlItemBlockInputRange input{ExecutorState::HASMORE, inBlock, 0, inBlock->size()};
+  AqlCall clientCall;
+  clientCall.offset = 1000;
 
-  auto const [state, skipped, call] = testee.skipRowsRange(1000, input);
+  auto const [state, skipped, call] = testee.skipRowsRange(input, clientCall);
   EXPECT_EQ(state, ExecutorState::HASMORE);
   EXPECT_EQ(skipped, 3);
+  EXPECT_EQ(clientCall.getOffset(), 1000 - 3);
   EXPECT_FALSE(input.hasMore());
 
   // Test the Call we send to upstream
@@ -489,9 +492,12 @@ TEST_F(FilterExecutorTest, test_skip_datarange_has_more) {
                     {{R"(true)"}, {R"(false)"}, {R"(true)"}, {R"(false)"}, {R"(true)"}});
 
   AqlItemBlockInputRange input{ExecutorState::DONE, inBlock, 0, inBlock->size()};
-  auto const [state, skipped, call] = testee.skipRowsRange(2, input);
+  AqlCall clientCall;
+  clientCall.offset = 2;
+  auto const [state, skipped, call] = testee.skipRowsRange(input, clientCall);
   EXPECT_EQ(state, ExecutorState::HASMORE);
   EXPECT_EQ(skipped, 2);
+  EXPECT_EQ(clientCall.getOffset(), 0);
   EXPECT_TRUE(input.hasMore());
   // We still have two values in block: false and true
   {

From 26c1996714b2b5a3a7d9a51403f2b2c4adc89f38 Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Fri, 6 Dec 2019 10:07:19 +0100
Subject: [PATCH 037/122] Make linker happy with operator< on CallLimit

---
 arangod/Aql/AqlCall.h              | 13 +++++++++++++
 arangod/Aql/ExecutionBlockImpl.cpp |  4 +++-
 arangod/Aql/FilterExecutor.cpp     | 12 ++++++------
 3 files changed, 22 insertions(+), 7 deletions(-)

diff --git a/arangod/Aql/AqlCall.h b/arangod/Aql/AqlCall.h
index 8f6592e3ee07..e88d7692db75 100644
--- a/arangod/Aql/AqlCall.h
+++ b/arangod/Aql/AqlCall.h
@@ -109,6 +109,19 @@ struct AqlCall {
   bool needsFullCount() const { return fullCount; }
 };
 
+constexpr bool operator<(AqlCall::Limit const& a, AqlCall::Limit const& b) {
+  if (std::holds_alternative<AqlCall::Infinity>(a)) {
+    return false;
+  }
+  if (std::holds_alternative<AqlCall::Infinity>(b)) {
+    return true;
+  }
+  if (std::get<size_t>(a) < std::get<size_t>(b)) {
+    return true;
+  }
+  return false;
+}
+
 }  // namespace aql
 }  // namespace arangodb
 
diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index 6643026ca185..1be374d904cd 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -201,7 +201,9 @@ std::pair<ExecutionState, SharedAqlItemBlockPtr> ExecutionBlockImpl<Executor>::g
     }
     TRI_ASSERT(newBlock != nullptr);
     TRI_ASSERT(newBlock->size() > 0);
-    TRI_ASSERT(newBlock->size() <= atMost);
+    // We cannot hold this assertion, if we are on a pass-through
+    // block and the upstream uses execute already.
+    // TRI_ASSERT(newBlock->size() <= atMost);
     _outputItemRow = createOutputRow(newBlock, AqlCall{});
   }
 
diff --git a/arangod/Aql/FilterExecutor.cpp b/arangod/Aql/FilterExecutor.cpp
index 4366b71d80b6..2aed9977b25d 100644
--- a/arangod/Aql/FilterExecutor.cpp
+++ b/arangod/Aql/FilterExecutor.cpp
@@ -101,6 +101,7 @@ std::pair<ExecutionState, size_t> FilterExecutor::expectedNumberOfRows(size_t at
   return _fetcher.preFetchNumberOfRows(atMost);
 }
 
+// TODO Remove me, we are using the getSome skip variant here.
 std::tuple<ExecutorState, size_t, AqlCall> FilterExecutor::skipRowsRange(
     AqlItemBlockInputRange& inputRange, AqlCall& call) {
   ExecutorState state = ExecutorState::HASMORE;
@@ -142,11 +143,10 @@ std::tuple<ExecutorState, FilterStats, AqlCall> FilterExecutor::produceRows(
   }
 
   AqlCall upstreamCall{};
-  upstreamCall.softLimit = output.hardLimit();
-  /* We can use this value as a heuristic on overfetching.
-   * by default we do not skip, and do not set any soft or hardLimit
-   * on upstream
-   * upstreamCall.softLimit = limit;
-   */
+  auto const& clientCall = output.getClientCall();
+  // This is a optimistic fetch. We do not do any overfetching here, only if we
+  // pass through all rows this fetch is correct, otherwise we have too few rows.
+  upstreamCall.softLimit =
+      clientCall.offset() + (std::min)(clientCall.softLimit, clientCall.hardLimit);
   return {inputRange.state(), stats, upstreamCall};
 }

From dfd6d49e78381e4614b70f9f19b2a024e60677fa Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Fri, 6 Dec 2019 13:22:06 +0100
Subject: [PATCH 038/122] Implement operator+ on AqlCall::Limit, also use
 std::visit for readability.

---
 arangod/Aql/AqlCall.h | 30 ++++++++++++++++++++++--------
 1 file changed, 22 insertions(+), 8 deletions(-)

diff --git a/arangod/Aql/AqlCall.h b/arangod/Aql/AqlCall.h
index e88d7692db75..5bec5e2399cd 100644
--- a/arangod/Aql/AqlCall.h
+++ b/arangod/Aql/AqlCall.h
@@ -24,6 +24,7 @@
 #define ARANGOD_AQL_AQL_CALL_H 1
 
 #include "Aql/ExecutionBlock.h"
+#include "Basics/overload.h"
 
 #include <cstddef>
 #include <variant>
@@ -92,14 +93,15 @@ struct AqlCall {
   }
 
   void didProduce(std::size_t n) {
-    if (std::holds_alternative<std::size_t>(softLimit)) {
-      TRI_ASSERT(n <= std::get<std::size_t>(softLimit));
-      softLimit = std::get<std::size_t>(softLimit) - n;
-    }
-    if (std::holds_alternative<std::size_t>(hardLimit)) {
-      TRI_ASSERT(n <= std::get<std::size_t>(hardLimit));
-      hardLimit = std::get<std::size_t>(hardLimit) - n;
-    }
+    auto minus = overload{
+        [n](size_t& i) {
+          TRI_ASSERT(n <= i);
+          i -= n;
+        },
+        [](auto) {},
+    };
+    std::visit(minus, softLimit);
+    std::visit(minus, hardLimit);
   }
 
   bool hasHardLimit() const {
@@ -122,6 +124,18 @@ constexpr bool operator<(AqlCall::Limit const& a, AqlCall::Limit const& b) {
   return false;
 }
 
+constexpr AqlCall::Limit operator+(AqlCall::Limit const& a, size_t n) {
+  return std::visit(overload{[n](size_t const& i) -> AqlCall::Limit {
+                               return i + n;
+                             },
+                             [](auto inf) -> AqlCall::Limit { return inf; }},
+                    a);
+}
+
+constexpr AqlCall::Limit operator+(size_t n, AqlCall::Limit const& a) {
+  return a + n;
+}
+
 }  // namespace aql
 }  // namespace arangodb
 

From 86db29ce97678291e09db3bd80338287273a4008 Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Fri, 6 Dec 2019 13:23:02 +0100
Subject: [PATCH 039/122] FilterExecutor getSome now propagates offset +
 min(limits) to upstream. This is pessimistic and avoids overfetching in all
 cases. NOTE: FilterExecutor should be moved to skipvariant using getSome

---
 arangod/Aql/FilterExecutor.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arangod/Aql/FilterExecutor.cpp b/arangod/Aql/FilterExecutor.cpp
index 2aed9977b25d..4be4c63eceb4 100644
--- a/arangod/Aql/FilterExecutor.cpp
+++ b/arangod/Aql/FilterExecutor.cpp
@@ -146,7 +146,7 @@ std::tuple<ExecutorState, FilterStats, AqlCall> FilterExecutor::produceRows(
   auto const& clientCall = output.getClientCall();
   // This is a optimistic fetch. We do not do any overfetching here, only if we
   // pass through all rows this fetch is correct, otherwise we have too few rows.
-  upstreamCall.softLimit =
-      clientCall.offset() + (std::min)(clientCall.softLimit, clientCall.hardLimit);
+  upstreamCall.softLimit = clientCall.getOffset() +
+                           (std::min)(clientCall.softLimit, clientCall.hardLimit);
   return {inputRange.state(), stats, upstreamCall};
 }

From aa4323fc10598e277226d30f583a3657a815bdfb Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Fri, 6 Dec 2019 14:40:46 +0100
Subject: [PATCH 040/122] Fixed profiler tests for filter. These cannot be
 guaranteed anymore and it was an undesired, yet uncritical side effect that
 the tests have been green before

---
 tests/js/server/aql/aql-profiler.js | 59 ++++++++++++++++++++++++++---
 1 file changed, 53 insertions(+), 6 deletions(-)

diff --git a/tests/js/server/aql/aql-profiler.js b/tests/js/server/aql/aql-profiler.js
index f7c3ed51f89a..f0d84143739e 100644
--- a/tests/js/server/aql/aql-profiler.js
+++ b/tests/js/server/aql/aql-profiler.js
@@ -346,15 +346,39 @@ function ahuacatlProfilerTestSuite () {
 
     testFilterBlock2 : function () {
       const query = 'FOR i IN 1..@rows FILTER i % 13 != 0 RETURN i';
-      const genNodeList = (rows, batches) => {
+      const genNodeList = (rows) => {
+        // This is an array 1..rows where true means it passes the filter
+        const list = Array.from(Array(rows)).map((_, index ) => {
+          return ((index + 1) % 13 != 0);
+        });
+
+        const recursiveFilterCallEstimator = (rowsToFetch) => {
+          if (rowsToFetch === 0 || list.length === 0) {
+            return 0;
+          }
+          if (rowsToFetch < 0) {
+            // We would have counted an overfetch!
+            assertTrue(false);
+          }
+          // We count one required call.
+          // We remove rowsToFetch elements from the beginning of the array.
+          // We count how many of those are true.
+          // We simulate an above call with rowsToFetch - the number of true counts.
+          // Redo until we have no more rows to fetch.
+          return 1 + recursiveFilterCallEstimator(rowsToFetch - list.splice(0, rowsToFetch).filter(e => e).length);
+        };
+        let batchesAboveFilter = 0;
+        while (list.length > 0) {
+          batchesAboveFilter += recursiveFilterCallEstimator(defaultBatchSize);
+        }
         const rowsAfterFilter = rows - Math.floor(rows / 13);
         const batchesAfterFilter = Math.ceil(rowsAfterFilter / defaultBatchSize);
 
         return [
           { type : SingletonBlock, calls : 1, items : 1 },
           { type : CalculationBlock, calls : 1, items : 1 },
-          { type : EnumerateListBlock, calls : batches, items : rows },
-          { type : CalculationBlock, calls : batches, items : rows },
+          { type : EnumerateListBlock, calls : batchesAboveFilter, items : rows },
+          { type : CalculationBlock, calls : batchesAboveFilter, items : rows },
           { type : FilterBlock, calls : batchesAfterFilter, items : rowsAfterFilter },
           { type : ReturnBlock, calls : batchesAfterFilter, items : rowsAfterFilter },
         ];
@@ -368,15 +392,38 @@ function ahuacatlProfilerTestSuite () {
 
     testFilterBlock3 : function () {
       const query = 'FOR i IN 1..@rows FILTER i % 13 == 0 RETURN i';
-      const genNodeList = (rows, batches) => {
+      const genNodeList = (rows) => {
+        // This is an array 1..rows where true means it passes the filter
+        const list = Array.from(Array(rows)).map((_, index ) => {
+          return ((index + 1) % 13 == 0);
+        });
+        const recursiveFilterCallEstimator = (rowsToFetch) => {
+          if (rowsToFetch === 0 || list.length === 0) {
+            return 0;
+          }
+          if (rowsToFetch < 0) {
+            // We would have counted an overfetch!
+            assertTrue(false);
+          }
+          // We count one required call.
+          // We remove rowsToFetch elements from the beginning of the array.
+          // We count how many of those are true.
+          // We simulate an above call with rowsToFetch - the number of true counts.
+          // Redo until we have no more rows to fetch.
+          return 1 + recursiveFilterCallEstimator(rowsToFetch - list.splice(0, rowsToFetch).filter(e => e).length);
+        };
+        let batchesAboveFilter = 0;
+        while (list.length > 0) {
+          batchesAboveFilter += recursiveFilterCallEstimator(defaultBatchSize);
+        }
         const rowsAfterFilter = Math.floor(rows / 13);
         const batchesAfterFilter = Math.max(1, Math.ceil(rowsAfterFilter / defaultBatchSize));
 
         return [
           { type : SingletonBlock, calls : 1, items : 1 },
           { type : CalculationBlock, calls : 1, items : 1 },
-          { type : EnumerateListBlock, calls : batches, items : rows },
-          { type : CalculationBlock, calls : batches, items : rows },
+          { type : EnumerateListBlock, calls : batchesAboveFilter, items : rows },
+          { type : CalculationBlock, calls : batchesAboveFilter, items : rows },
           { type : FilterBlock, calls : batchesAfterFilter, items : rowsAfterFilter },
           { type : ReturnBlock, calls : batchesAfterFilter, items : rowsAfterFilter },
         ];

From 63f76e5d94f0e93eb462456d42ae13240f17d96a Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Fri, 6 Dec 2019 15:00:37 +0100
Subject: [PATCH 041/122] Fixed JSLint

---
 tests/js/server/aql/aql-profiler.js | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/tests/js/server/aql/aql-profiler.js b/tests/js/server/aql/aql-profiler.js
index f0d84143739e..27c7cb7a5727 100644
--- a/tests/js/server/aql/aql-profiler.js
+++ b/tests/js/server/aql/aql-profiler.js
@@ -1,5 +1,5 @@
 /*jshint globalstrict:true, strict:true, esnext: true */
-/*global AQL_EXPLAIN */
+/*global AQL_EXPLAIN, assertTrue */
 
 "use strict";
 
@@ -349,7 +349,7 @@ function ahuacatlProfilerTestSuite () {
       const genNodeList = (rows) => {
         // This is an array 1..rows where true means it passes the filter
         const list = Array.from(Array(rows)).map((_, index ) => {
-          return ((index + 1) % 13 != 0);
+          return ((index + 1) % 13 !== 0);
         });
 
         const recursiveFilterCallEstimator = (rowsToFetch) => {
@@ -395,7 +395,7 @@ function ahuacatlProfilerTestSuite () {
       const genNodeList = (rows) => {
         // This is an array 1..rows where true means it passes the filter
         const list = Array.from(Array(rows)).map((_, index ) => {
-          return ((index + 1) % 13 == 0);
+          return ((index + 1) % 13 === 0);
         });
         const recursiveFilterCallEstimator = (rowsToFetch) => {
           if (rowsToFetch === 0 || list.length === 0) {

From 7cddcfa85cd73f089f32592f44ccf58f4e488d86 Mon Sep 17 00:00:00 2001
From: Markus Pfeiffer <markus@arangodb.com>
Date: Fri, 13 Dec 2019 12:27:12 +0000
Subject: [PATCH 042/122] Remove special casing for FilterExecutor

 * use if constexpr to distinguish between ported executors and
   non-ported executors enabling step-by-step porting and testing
---
 arangod/Aql/ExecutionBlockImpl.cpp | 347 +++++++++++++++--------------
 1 file changed, 177 insertions(+), 170 deletions(-)

diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index 1be374d904cd..5def27ec2802 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -130,6 +130,15 @@ CREATE_HAS_MEMBER_CHECK(skipRows, hasSkipRows);
 CREATE_HAS_MEMBER_CHECK(fetchBlockForPassthrough, hasFetchBlockForPassthrough);
 CREATE_HAS_MEMBER_CHECK(expectedNumberOfRows, hasExpectedNumberOfRows);
 
+/*
+ * Determine whether we execute new style or old style skips, i.e. pre or post shadow row introduction
+ * TODO: This should be removed once all executors and fetchers are ported to the new style.
+ */
+template <class Executor>
+static bool constexpr isNewStyleExecutor() {
+  return std::is_same<Executor, FilterExecutor>::value;
+}
+
 template <class Executor>
 ExecutionBlockImpl<Executor>::ExecutionBlockImpl(ExecutionEngine* engine,
                                                  ExecutionNode const* node,
@@ -156,9 +165,15 @@ ExecutionBlockImpl<Executor>::~ExecutionBlockImpl() = default;
 
 template <class Executor>
 std::pair<ExecutionState, SharedAqlItemBlockPtr> ExecutionBlockImpl<Executor>::getSome(size_t atMost) {
-  traceGetSomeBegin(atMost);
-  auto result = getSomeWithoutTrace(atMost);
-  return traceGetSomeEnd(result.first, std::move(result.second));
+  if constexpr (isNewStyleExecutor<Executor>()) {
+    AqlCallStack stack{AqlCall::SimulateGetSome(atMost)};
+    auto const [state, skipped, block] = execute(stack);
+    return {state, block};
+  } else {
+    traceGetSomeBegin(atMost);
+    auto result = getSomeWithoutTrace(atMost);
+    return traceGetSomeEnd(result.first, std::move(result.second));
+  }
 }
 
 template <class Executor>
@@ -432,24 +447,30 @@ static SkipVariants constexpr skipType() {
 
 template <class Executor>
 std::pair<ExecutionState, size_t> ExecutionBlockImpl<Executor>::skipSome(size_t const atMost) {
-  traceSkipSomeBegin(atMost);
-  auto state = ExecutionState::HASMORE;
-
-  while (state == ExecutionState::HASMORE && _skipped < atMost) {
-    auto res = skipSomeOnceWithoutTrace(atMost - _skipped);
-    TRI_ASSERT(state != ExecutionState::WAITING || res.second == 0);
-    state = res.first;
-    _skipped += res.second;
-    TRI_ASSERT(_skipped <= atMost);
-  }
+  if constexpr (isNewStyleExecutor<Executor>()) {
+    AqlCallStack stack{AqlCall::SimulateSkipSome(atMost)};
+    auto const [state, skipped, block] = execute(stack);
+    return {state, skipped};
+  } else {
+    traceSkipSomeBegin(atMost);
+    auto state = ExecutionState::HASMORE;
+
+    while (state == ExecutionState::HASMORE && _skipped < atMost) {
+      auto res = skipSomeOnceWithoutTrace(atMost - _skipped);
+      TRI_ASSERT(state != ExecutionState::WAITING || res.second == 0);
+      state = res.first;
+      _skipped += res.second;
+      TRI_ASSERT(_skipped <= atMost);
+    }
 
-  size_t skipped = 0;
-  if (state != ExecutionState::WAITING) {
-    std::swap(skipped, _skipped);
-  }
+    size_t skipped = 0;
+    if (state != ExecutionState::WAITING) {
+      std::swap(skipped, _skipped);
+    }
 
-  TRI_ASSERT(skipped <= atMost);
-  return traceSkipSomeEnd(state, skipped);
+    TRI_ASSERT(skipped <= atMost);
+    return traceSkipSomeEnd(state, skipped);
+  }
 }
 
 template <class Executor>
@@ -552,7 +573,8 @@ std::pair<ExecutionState, Result> ExecutionBlockImpl<Executor>::shutdown(int err
 template <class Executor>
 std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> ExecutionBlockImpl<Executor>::execute(AqlCallStack stack) {
   // TODO remove this IF
-  if (std::is_same<Executor, FilterExecutor>::value) {
+  // These are new style executors
+  if constexpr (isNewStyleExecutor<Executor>()) {
     // Only this executor is fully implemented
     traceExecuteBegin(stack);
     auto res = executeWithoutTrace(stack);
@@ -963,29 +985,6 @@ SharedAqlItemBlockPtr ExecutionBlockImpl<Executor>::requestBlock(size_t nrItems,
   return _engine->itemBlockManager().requestBlock(nrItems, nrRegs);
 }
 
-// TODO: Remove this special implementations
-template <>
-std::pair<ExecutionState, SharedAqlItemBlockPtr> ExecutionBlockImpl<FilterExecutor>::getSome(size_t atMost) {
-  AqlCallStack stack{AqlCall::SimulateGetSome(atMost)};
-  auto const [state, skipped, block] = execute(stack);
-  return {state, block};
-}
-
-template <>
-std::pair<ExecutionState, size_t> ExecutionBlockImpl<FilterExecutor>::skipSome(size_t const toSkip) {
-  AqlCallStack stack{AqlCall::SimulateSkipSome(toSkip)};
-  auto const [state, skipped, block] = execute(stack);
-  return {state, skipped};
-}
-
-template <class Executor>
-std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr>
-ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
-  // TODO implement!
-  TRI_ASSERT(false);
-  THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
-}
-
 // TODO move me up
 enum ExecState { SKIP, PRODUCE, FULLCOUNT, UPSTREAM, SHADOWROWS, DONE };
 
@@ -1009,146 +1008,154 @@ ExecState NextState(AqlCall const& call) {
 }
 }  // namespace
 
-template <>
+template <class Executor>
 std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr>
-ExecutionBlockImpl<FilterExecutor>::executeWithoutTrace(AqlCallStack stack) {
-  ensureOutputBlock(stack.popCall());
+ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
+  if constexpr (isNewStyleExecutor<Executor>()) {
+    ensureOutputBlock(stack.popCall());
+
+    /*
+    if (!_outputItemRow) {
+      // TODO: FIXME Hard coded size
+      SharedAqlItemBlockPtr newBlock =
+          _engine->itemBlockManager().requestBlock(1000,
+    _infos.numberOfOutputRegisters()); TRI_ASSERT(newBlock != nullptr); TRI_ASSERT(newBlock->size()
+    == 1000); _outputItemRow = createOutputRow(newBlock);
+    }
+    */
+    size_t skipped = 0;
 
-  /*
-  if (!_outputItemRow) {
-    // TODO: FIXME Hard coded size
-    SharedAqlItemBlockPtr newBlock =
-        _engine->itemBlockManager().requestBlock(1000,
-  _infos.numberOfOutputRegisters()); TRI_ASSERT(newBlock != nullptr); TRI_ASSERT(newBlock->size()
-  == 1000); _outputItemRow = createOutputRow(newBlock);
-  }
-  */
-  size_t skipped = 0;
-
-  TRI_ASSERT(_outputItemRow);
-  ExecState execState = ::NextState(_outputItemRow->getClientCall());
-  if (_lastRange.hasShadowRow()) {
-    // We have not been able to move all shadowRows into the output last time.
-    // Continue from there.
-    // TODO test if this works with COUNT COLLECT
-    execState = ExecState::SHADOWROWS;
-  }
-  AqlCall executorRequest;
-  while (execState != ExecState::DONE && !_outputItemRow->allRowsUsed()) {
-    switch (execState) {
-      case ExecState::SKIP: {
-        auto const& clientCall = _outputItemRow->getClientCall();
-        auto [state, skippedLocal, call] =
-            _executor.skipRowsRange(_lastRange, _outputItemRow->getModifiableClientCall());
-        skipped += skippedLocal;
-
-        if (state == ExecutorState::DONE) {
-          execState = ExecState::SHADOWROWS;
-        } else if (clientCall.getOffset() > 0) {
-          TRI_ASSERT(_upstreamState != ExecutionState::DONE);
-          // We need to request more
-          executorRequest = call;
-          execState = ExecState::UPSTREAM;
-        } else {
-          // We are done with skipping. Skip is not allowed to request more
-          execState = ::NextState(clientCall);
+    TRI_ASSERT(_outputItemRow);
+    ExecState execState = ::NextState(_outputItemRow->getClientCall());
+    if (_lastRange.hasShadowRow()) {
+      // We have not been able to move all shadowRows into the output last time.
+      // Continue from there.
+      // TODO test if this works with COUNT COLLECT
+      execState = ExecState::SHADOWROWS;
+    }
+    AqlCall executorRequest;
+    while (execState != ExecState::DONE && !_outputItemRow->allRowsUsed()) {
+      switch (execState) {
+        case ExecState::SKIP: {
+          auto const& clientCall = _outputItemRow->getClientCall();
+          auto [state, skippedLocal, call] =
+              _executor.skipRowsRange(_lastRange, _outputItemRow->getModifiableClientCall());
+          skipped += skippedLocal;
+
+          if (state == ExecutorState::DONE) {
+            execState = ExecState::SHADOWROWS;
+          } else if (clientCall.getOffset() > 0) {
+            TRI_ASSERT(_upstreamState != ExecutionState::DONE);
+            // We need to request more
+            executorRequest = call;
+            execState = ExecState::UPSTREAM;
+          } else {
+            // We are done with skipping. Skip is not allowed to request more
+            execState = ::NextState(clientCall);
+          }
+          break;
         }
-        break;
-      }
-      case ExecState::PRODUCE: {
-        auto const& clientCall = _outputItemRow->getClientCall();
-        TRI_ASSERT(clientCall.getLimit() > 0);
-        // Execute getSome
-        auto const [state, stats, call] = _executor.produceRows(_lastRange, *_outputItemRow);
-        _engine->_stats += stats;
-        if (state == ExecutorState::DONE) {
-          execState = ExecState::SHADOWROWS;
-        } else if (clientCall.getLimit() > 0) {
-          TRI_ASSERT(_upstreamState != ExecutionState::DONE);
-          // We need to request more
-          executorRequest = call;
-          execState = ExecState::UPSTREAM;
-        } else {
-          // We are done with producing. Produce is not allowed to request more
-          execState = ::NextState(clientCall);
+        case ExecState::PRODUCE: {
+          auto const& clientCall = _outputItemRow->getClientCall();
+          TRI_ASSERT(clientCall.getLimit() > 0);
+          // Execute getSome
+          auto const [state, stats, call] =
+              _executor.produceRows(_lastRange, *_outputItemRow);
+          _engine->_stats += stats;
+          if (state == ExecutorState::DONE) {
+            execState = ExecState::SHADOWROWS;
+          } else if (clientCall.getLimit() > 0) {
+            TRI_ASSERT(_upstreamState != ExecutionState::DONE);
+            // We need to request more
+            executorRequest = call;
+            execState = ExecState::UPSTREAM;
+          } else {
+            // We are done with producing. Produce is not allowed to request more
+            execState = ::NextState(clientCall);
+          }
+          break;
         }
-        break;
-      }
-      case ExecState::FULLCOUNT: {
-        TRI_ASSERT(false);
-      }
-      case ExecState::UPSTREAM: {
-        // If this triggers the executors produceRows function has returned
-        // HASMORE even if it new that upstream has no further rows.
-        TRI_ASSERT(_upstreamState != ExecutionState::DONE);
-        TRI_ASSERT(!_lastRange.hasMore());
-        size_t skippedLocal = 0;
-        stack.pushCall(std::move(executorRequest));
-        std::tie(_upstreamState, skippedLocal, _lastRange) = _rowFetcher.execute(stack);
-        if (_upstreamState == ExecutionState::WAITING) {
-          // We do not return anything in WAITING state, also NOT skipped.
-          // TODO: Check if we need to leverage this restriction.
-          TRI_ASSERT(skipped == 0);
-          return {_upstreamState, 0, nullptr};
+        case ExecState::FULLCOUNT: {
+          TRI_ASSERT(false);
         }
-        skipped += skippedLocal;
-        ensureOutputBlock(_outputItemRow->stealClientCall());
-        // Do we need to call it?
-        // clientCall.didSkip(skippedLocal);
-        execState = ::NextState(_outputItemRow->getClientCall());
-        break;
-      }
-      case ExecState::SHADOWROWS: {
-        // TODO: Check if there is a situation where we are at this point, but at the end of a block
-        // Or if we would not recognize this beforehand
-        // TODO: Check if we can have the situation that we are between two shadow rows here.
-        // E.g. LastRow is releveant shadowRow. NextRow is non-relevant shadowRow.
-        // NOTE: I do not think this is an issue, as the Executor will always say that it cannot do anything with
-        // an empty input. Only exception might be COLLECT COUNT.
-        if (_lastRange.hasShadowRow()) {
-          auto const& [state, shadowRow] = _lastRange.nextShadowRow();
-          TRI_ASSERT(shadowRow.isInitialized());
-          _outputItemRow->copyRow(shadowRow);
-          if (shadowRow.isRelevant()) {
-            // We found a relevant shadow Row.
-            // We need to reset the Executor
-            // TODO: call reset!
+        case ExecState::UPSTREAM: {
+          // If this triggers the executors produceRows function has returned
+          // HASMORE even if it new that upstream has no further rows.
+          TRI_ASSERT(_upstreamState != ExecutionState::DONE);
+          TRI_ASSERT(!_lastRange.hasMore());
+          size_t skippedLocal = 0;
+          stack.pushCall(std::move(executorRequest));
+          std::tie(_upstreamState, skippedLocal, _lastRange) = _rowFetcher.execute(stack);
+          if (_upstreamState == ExecutionState::WAITING) {
+            // We do not return anything in WAITING state, also NOT skipped.
+            // TODO: Check if we need to leverage this restriction.
+            TRI_ASSERT(skipped == 0);
+            return {_upstreamState, 0, nullptr};
           }
-          TRI_ASSERT(_outputItemRow->produced());
-          _outputItemRow->advanceRow();
-          if (state == ExecutorState::DONE) {
-            if (_lastRange.hasMore()) {
-              // TODO this state is invalid, and can just show up now if we exclude SKIP
-              execState = ExecState::PRODUCE;
-            } else {
-              // Right now we cannot support to have more than one set of
-              // ShadowRows inside of a Range.
-              // We do not know how to continue with the above executor after a shadowrow.
-              TRI_ASSERT(!_lastRange.hasMore());
-              execState = ExecState::DONE;
+          skipped += skippedLocal;
+          ensureOutputBlock(_outputItemRow->stealClientCall());
+          // Do we need to call it?
+          // clientCall.didSkip(skippedLocal);
+          execState = ::NextState(_outputItemRow->getClientCall());
+          break;
+        }
+        case ExecState::SHADOWROWS: {
+          // TODO: Check if there is a situation where we are at this point, but at the end of a block
+          // Or if we would not recognize this beforehand
+          // TODO: Check if we can have the situation that we are between two shadow rows here.
+          // E.g. LastRow is releveant shadowRow. NextRow is non-relevant shadowRow.
+          // NOTE: I do not think this is an issue, as the Executor will always say that it cannot do anything with
+          // an empty input. Only exception might be COLLECT COUNT.
+          if (_lastRange.hasShadowRow()) {
+            auto const& [state, shadowRow] = _lastRange.nextShadowRow();
+            TRI_ASSERT(shadowRow.isInitialized());
+            _outputItemRow->copyRow(shadowRow);
+            if (shadowRow.isRelevant()) {
+              // We found a relevant shadow Row.
+              // We need to reset the Executor
+              // TODO: call reset!
+            }
+            TRI_ASSERT(_outputItemRow->produced());
+            _outputItemRow->advanceRow();
+            if (state == ExecutorState::DONE) {
+              if (_lastRange.hasMore()) {
+                // TODO this state is invalid, and can just show up now if we exclude SKIP
+                execState = ExecState::PRODUCE;
+              } else {
+                // Right now we cannot support to have more than one set of
+                // ShadowRows inside of a Range.
+                // We do not know how to continue with the above executor after a shadowrow.
+                TRI_ASSERT(!_lastRange.hasMore());
+                execState = ExecState::DONE;
+              }
             }
+          } else {
+            execState = ExecState::DONE;
           }
-        } else {
-          execState = ExecState::DONE;
+          break;
         }
-        break;
+        default:
+          // unreachable
+          TRI_ASSERT(false);
       }
-      default:
-        // unreachable
-        TRI_ASSERT(false);
     }
-  }
 
-  auto outputBlock = _outputItemRow->stealBlock();
-  // This is not strictly necessary here, as we shouldn't be called again
-  // after DONE.
-  _outputItemRow.reset();
-  if (_lastRange.hasMore() || _lastRange.hasShadowRow()) {
-    // We have skipped or/and return data, otherwise we cannot return HASMORE
-    TRI_ASSERT(skipped > 0 || (outputBlock != nullptr && outputBlock->numEntries() > 0));
-    return {ExecutionState::HASMORE, skipped, std::move(outputBlock)};
+    auto outputBlock = _outputItemRow->stealBlock();
+    // This is not strictly necessary here, as we shouldn't be called again
+    // after DONE.
+    _outputItemRow.reset();
+    if (_lastRange.hasMore() || _lastRange.hasShadowRow()) {
+      // We have skipped or/and return data, otherwise we cannot return HASMORE
+      TRI_ASSERT(skipped > 0 || (outputBlock != nullptr && outputBlock->numEntries() > 0));
+      return {ExecutionState::HASMORE, skipped, std::move(outputBlock)};
+    }
+    return {_upstreamState, skipped, std::move(outputBlock)};
+  } else {
+    // TODO this branch must never be taken with an executor that has not been
+    //      converted yet
+    TRI_ASSERT(false);
+    THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
   }
-  return {_upstreamState, skipped, std::move(outputBlock)};
 }
 
 /// @brief reset all internal states after processing a shadow row.

From 912351696ddcdaaac5ddaf16c0403e9206fcdcd1 Mon Sep 17 00:00:00 2001
From: Markus Pfeiffer <markus@arangodb.com>
Date: Fri, 13 Dec 2019 13:56:32 +0000
Subject: [PATCH 043/122] Add skeleton skip code

---
 arangod/Aql/ExecutionBlockImpl.cpp | 120 ++++++++++++++++++++++++++++-
 1 file changed, 119 insertions(+), 1 deletion(-)

diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index 5def27ec2802..2459f5b0a378 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -988,6 +988,7 @@ SharedAqlItemBlockPtr ExecutionBlockImpl<Executor>::requestBlock(size_t nrItems,
 // TODO move me up
 enum ExecState { SKIP, PRODUCE, FULLCOUNT, UPSTREAM, SHADOWROWS, DONE };
 
+// TODO clean me up
 namespace {
 // This cannot return upstream call or shadowrows.
 ExecState NextState(AqlCall const& call) {
@@ -1006,8 +1007,123 @@ ExecState NextState(AqlCall const& call) {
   // now we are done.
   return ExecState::DONE;
 }
+
 }  // namespace
 
+//
+// FETCHER:  if we have one output row per input row, we can skip
+//           directly by just calling the fetcher and see whether
+//           it produced any output.
+//           With the new architecture we should be able to just skip
+//           ahead on the input range, fetching new blocks when necessary
+// EXECUTOR: the executor has a specialised skipRowsRange method
+//           that will be called to skip
+// GET_SOME: we just request rows from the executor and then discard
+//           them
+//
+enum class SkipRowsRangeVariant { FETCHER, EXECUTOR, GET_SOME };
+
+template <enum SkipRowsRangeVariant>
+struct ExecuteSkipRowsRange {};
+
+using SkipRowsRangeResult = std::tuple<ExecutorState, size_t, AqlCall>;
+
+template <>
+struct ExecuteSkipRowsRange<SkipRowsRangeVariant::FETCHER> {
+  template <class Executor>
+  static SkipRowsRangeResult executeSkipRowsRange(Executor& executor,
+                                                  AqlItemBlockInputRange& input,
+                                                  AqlCall& call) {
+    TRI_ASSERT(false);
+    /*    auto res = fetcher.skipRows(toSkip);
+        return std::make_tuple(res.first, typename Executor::Stats{}, res.second); // tuple, cannot use initializer list due to build failure
+    */
+    return std::make_tuple(ExecutorState::DONE, 0, call);  // tuple, cannot use initializer list due to build failure
+  }
+};
+
+template <>
+struct ExecuteSkipRowsRange<SkipRowsRangeVariant::EXECUTOR> {
+  template <class Executor>
+  static SkipRowsRangeResult executeSkipRowsRange(Executor& executor,
+                                                  AqlItemBlockInputRange& input,
+                                                  AqlCall& call) {
+    TRI_ASSERT(false);
+    // TODO forward to executor
+    //    return executor.skipRows(toSkip);
+    return std::make_tuple(ExecutorState::DONE, 0, call);
+  }
+};
+
+template <>
+struct ExecuteSkipRowsRange<SkipRowsRangeVariant::GET_SOME> {
+  template <class Executor>
+  static SkipRowsRangeResult executeSkipRowsRange(Executor& executor,
+                                                  AqlItemBlockInputRange& input,
+                                                  AqlCall& call) {
+    // this function should never be executed
+    TRI_ASSERT(false);
+    // Make MSVC happy:
+    return std::make_tuple(ExecutorState::DONE, 0, call);
+  }
+};
+
+template <class Executor>
+static SkipRowsRangeVariant constexpr skipRowsType() {
+  bool constexpr useFetcher =
+      Executor::Properties::allowsBlockPassthrough == BlockPassthrough::Enable &&
+      !std::is_same<Executor, SubqueryExecutor<true>>::value;
+
+  bool constexpr useExecutor = hasSkipRows<Executor>::value;
+
+  // ConstFetcher and SingleRowFetcher<BlockPassthrough::Enable> can skip, but
+  // it may not be done for modification subqueries.
+  static_assert(useFetcher ==
+                    (std::is_same<typename Executor::Fetcher, ConstFetcher>::value ||
+                     (std::is_same<typename Executor::Fetcher, SingleRowFetcher<BlockPassthrough::Enable>>::value &&
+                      !std::is_same<Executor, SubqueryExecutor<true>>::value)),
+                "Unexpected fetcher for SkipVariants::FETCHER");
+
+  static_assert(!useFetcher || hasSkipRows<typename Executor::Fetcher>::value,
+                "Fetcher is chosen for skipping, but has not skipRows method!");
+
+  static_assert(
+      useExecutor ==
+          (std::is_same<Executor, IndexExecutor>::value ||
+           std::is_same<Executor, IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::Materialized>>::value ||
+           std::is_same<Executor, IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::LateMaterialized>>::value ||
+           std::is_same<Executor, IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::LateMaterializedWithVars>>::value ||
+           std::is_same<Executor, IResearchViewExecutor<true, arangodb::iresearch::MaterializeType::Materialized>>::value ||
+           std::is_same<Executor, IResearchViewExecutor<true, arangodb::iresearch::MaterializeType::LateMaterialized>>::value ||
+           std::is_same<Executor, IResearchViewExecutor<true, arangodb::iresearch::MaterializeType::LateMaterializedWithVars>>::value ||
+           std::is_same<Executor, IResearchViewMergeExecutor<false, arangodb::iresearch::MaterializeType::Materialized>>::value ||
+           std::is_same<Executor, IResearchViewMergeExecutor<false, arangodb::iresearch::MaterializeType::LateMaterialized>>::value ||
+           std::is_same<Executor, IResearchViewMergeExecutor<true, arangodb::iresearch::MaterializeType::Materialized>>::value ||
+           std::is_same<Executor, IResearchViewMergeExecutor<true, arangodb::iresearch::MaterializeType::LateMaterialized>>::value ||
+           std::is_same<Executor, EnumerateCollectionExecutor>::value ||
+           std::is_same<Executor, LimitExecutor>::value ||
+           std::is_same<Executor, ConstrainedSortExecutor>::value ||
+           std::is_same<Executor, SortingGatherExecutor>::value ||
+           std::is_same<Executor, UnsortedGatherExecutor>::value ||
+           std::is_same<Executor, ParallelUnsortedGatherExecutor>::value ||
+           std::is_same<Executor, MaterializeExecutor<RegisterId>>::value ||
+           std::is_same<Executor, MaterializeExecutor<std::string const&>>::value),
+      "Unexpected executor for SkipVariants::EXECUTOR");
+
+  // The LimitExecutor will not work correctly with SkipVariants::FETCHER!
+  static_assert(
+      !std::is_same<Executor, LimitExecutor>::value || useFetcher,
+      "LimitExecutor needs to implement skipRows() to work correctly");
+
+  if (useExecutor) {
+    return SkipRowsRangeVariant::EXECUTOR;
+  } else if (useFetcher) {
+    return SkipRowsRangeVariant::FETCHER;
+  } else {
+    return SkipRowsRangeVariant::GET_SOME;
+  }
+}
+
 template <class Executor>
 std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr>
 ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
@@ -1038,8 +1154,10 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
       switch (execState) {
         case ExecState::SKIP: {
           auto const& clientCall = _outputItemRow->getClientCall();
+          ExecuteSkipRowsRange<skipRowsType<ShortestPathExecutor>()> skip;
           auto [state, skippedLocal, call] =
-              _executor.skipRowsRange(_lastRange, _outputItemRow->getModifiableClientCall());
+              skip.executeSkipRowsRange(_executor, _lastRange,
+                                        _outputItemRow->getModifiableClientCall());
           skipped += skippedLocal;
 
           if (state == ExecutorState::DONE) {

From b27d945005168a5e84c981868d919a35e4ac5f08 Mon Sep 17 00:00:00 2001
From: Markus Pfeiffer <markus@arangodb.com>
Date: Fri, 13 Dec 2019 14:11:08 +0000
Subject: [PATCH 044/122] Replace C&P accident

---
 arangod/Aql/ExecutionBlockImpl.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index 2459f5b0a378..1af656d19caa 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -1154,7 +1154,7 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
       switch (execState) {
         case ExecState::SKIP: {
           auto const& clientCall = _outputItemRow->getClientCall();
-          ExecuteSkipRowsRange<skipRowsType<ShortestPathExecutor>()> skip;
+          ExecuteSkipRowsRange<skipRowsType<Executor>()> skip;
           auto [state, skippedLocal, call] =
               skip.executeSkipRowsRange(_executor, _lastRange,
                                         _outputItemRow->getModifiableClientCall());

From 7ad6c9ef24c67e80b71f28424280e397496975c3 Mon Sep 17 00:00:00 2001
From: Markus Pfeiffer <markus@arangodb.com>
Date: Fri, 13 Dec 2019 17:28:14 +0000
Subject: [PATCH 045/122] Simplify and implement skip for new executor
 interface

---
 arangod/Aql/ExecutionBlockImpl.cpp | 112 ++++++++++++++---------------
 arangod/Aql/ExecutionBlockImpl.h   |   3 +
 2 files changed, 57 insertions(+), 58 deletions(-)

diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index 1af656d19caa..7e6d9cb79523 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -968,6 +968,7 @@ std::pair<ExecutionState, SharedAqlItemBlockPtr> ExecutionBlockImpl<Executor>::r
 template <class Executor>
 void ExecutionBlockImpl<Executor>::ensureOutputBlock(AqlCall&& call) {
   if (_outputItemRow == nullptr || _outputItemRow->isFull()) {
+    // Is this a TODO:?
     // We need to define the size of this block based on Input / Executor / Subquery depth
     size_t blockSize = ExecutionBlock::DefaultBatchSize();
     SharedAqlItemBlockPtr newBlock =
@@ -1023,51 +1024,8 @@ ExecState NextState(AqlCall const& call) {
 //
 enum class SkipRowsRangeVariant { FETCHER, EXECUTOR, GET_SOME };
 
-template <enum SkipRowsRangeVariant>
-struct ExecuteSkipRowsRange {};
-
-using SkipRowsRangeResult = std::tuple<ExecutorState, size_t, AqlCall>;
-
-template <>
-struct ExecuteSkipRowsRange<SkipRowsRangeVariant::FETCHER> {
-  template <class Executor>
-  static SkipRowsRangeResult executeSkipRowsRange(Executor& executor,
-                                                  AqlItemBlockInputRange& input,
-                                                  AqlCall& call) {
-    TRI_ASSERT(false);
-    /*    auto res = fetcher.skipRows(toSkip);
-        return std::make_tuple(res.first, typename Executor::Stats{}, res.second); // tuple, cannot use initializer list due to build failure
-    */
-    return std::make_tuple(ExecutorState::DONE, 0, call);  // tuple, cannot use initializer list due to build failure
-  }
-};
-
-template <>
-struct ExecuteSkipRowsRange<SkipRowsRangeVariant::EXECUTOR> {
-  template <class Executor>
-  static SkipRowsRangeResult executeSkipRowsRange(Executor& executor,
-                                                  AqlItemBlockInputRange& input,
-                                                  AqlCall& call) {
-    TRI_ASSERT(false);
-    // TODO forward to executor
-    //    return executor.skipRows(toSkip);
-    return std::make_tuple(ExecutorState::DONE, 0, call);
-  }
-};
-
-template <>
-struct ExecuteSkipRowsRange<SkipRowsRangeVariant::GET_SOME> {
-  template <class Executor>
-  static SkipRowsRangeResult executeSkipRowsRange(Executor& executor,
-                                                  AqlItemBlockInputRange& input,
-                                                  AqlCall& call) {
-    // this function should never be executed
-    TRI_ASSERT(false);
-    // Make MSVC happy:
-    return std::make_tuple(ExecutorState::DONE, 0, call);
-  }
-};
-
+// This function is just copy&pasted from above to decide which variant of skip
+// is used for which executor.
 template <class Executor>
 static SkipRowsRangeVariant constexpr skipRowsType() {
   bool constexpr useFetcher =
@@ -1124,21 +1082,61 @@ static SkipRowsRangeVariant constexpr skipRowsType() {
   }
 }
 
+template <class Executor>
+std::tuple<ExecutorState, size_t, AqlCall> ExecutionBlockImpl<Executor>::executeSkipRowsRange(
+    AqlItemBlockInputRange& inputRange, AqlCall& call) {
+  if constexpr (isNewStyleExecutor<Executor>()) {
+    if constexpr (skipRowsType<Executor>() == SkipRowsRangeVariant::EXECUTOR) {
+      // TODO: make statically sure that this method exists?
+      // the executor has a method skipRowsRange, so use it
+      return _executor.skipRowsRange(inputRange, call);
+    } else if constexpr (skipRowsType<Executor>() == SkipRowsRangeVariant::FETCHER) {
+      // TODO: check whether this is right (and test!)
+      // just let the fetcher fetch some stuff and ignore it without even passing it
+      // to the executor
+      return _rowFetcher.execute(call);
+    } else if constexpr (skipRowsType<Executor>() == SkipRowsRangeVariant::GET_SOME) {
+      // Here we need to skip by just having the executor produce rows which we then
+      // subsequently throw away. I do this by allocating a block and having the
+      // executor write to it.
+      //
+      // unsure about the role of call here as yet, might have to be std::move()'d
+      // into createOutputRow, and then use the resCall for return value.
+      //
+      // TODO: is outputBlock freed when the variable goes out of scope?
+      // TODO: do we need to use currently available blocks and then just discard?
+      size_t toSkip = std::min(call.getOffset(), DefaultBatchSize());
+      SharedAqlItemBlockPtr outputBlock =
+          _engine->itemBlockManager().requestBlock(toSkip, _infos.numberOfOutputRegisters());
+      TRI_ASSERT(outputBlock != nullptr);
+      TRI_ASSERT(outputBlock->size() == call.getOffset());
+      // TODO: do we need to std::move(call) here?
+      auto outputRow = createOutputRow(outputBlock, AqlCall{});
+
+      auto const [state, stats, rescall] = _executor.produceRows(inputRange, *outputRow);
+
+      size_t skipped = outputRow->numRowsWritten();
+      call.didSkip(skipped);
+
+      return std::make_tuple(state, skipped, call);
+    } else {
+      // TODO: this should be a compiler error
+      TRI_ASSERT(false);
+      return std::make_tuple(ExecutorState::DONE, 0, call);
+    }
+  } else {
+    TRI_ASSERT(false);
+    return std::make_tuple(ExecutorState::DONE, 0, call);
+  }
+  // Compiler is unhappy without this.
+  return std::make_tuple(ExecutorState::DONE, 0, call);
+}
+
 template <class Executor>
 std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr>
 ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
   if constexpr (isNewStyleExecutor<Executor>()) {
     ensureOutputBlock(stack.popCall());
-
-    /*
-    if (!_outputItemRow) {
-      // TODO: FIXME Hard coded size
-      SharedAqlItemBlockPtr newBlock =
-          _engine->itemBlockManager().requestBlock(1000,
-    _infos.numberOfOutputRegisters()); TRI_ASSERT(newBlock != nullptr); TRI_ASSERT(newBlock->size()
-    == 1000); _outputItemRow = createOutputRow(newBlock);
-    }
-    */
     size_t skipped = 0;
 
     TRI_ASSERT(_outputItemRow);
@@ -1154,10 +1152,8 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
       switch (execState) {
         case ExecState::SKIP: {
           auto const& clientCall = _outputItemRow->getClientCall();
-          ExecuteSkipRowsRange<skipRowsType<Executor>()> skip;
           auto [state, skippedLocal, call] =
-              skip.executeSkipRowsRange(_executor, _lastRange,
-                                        _outputItemRow->getModifiableClientCall());
+              executeSkipRowsRange(_lastRange, _outputItemRow->getModifiableClientCall());
           skipped += skippedLocal;
 
           if (state == ExecutorState::DONE) {
diff --git a/arangod/Aql/ExecutionBlockImpl.h b/arangod/Aql/ExecutionBlockImpl.h
index d7d0b3267b09..b3da0a89a768 100644
--- a/arangod/Aql/ExecutionBlockImpl.h
+++ b/arangod/Aql/ExecutionBlockImpl.h
@@ -200,6 +200,9 @@ class ExecutionBlockImpl final : public ExecutionBlock {
    */
   std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> executeWithoutTrace(AqlCallStack stack);
 
+  // execute a skipRowsRange call
+  std::tuple<ExecutorState, size_t, AqlCall> executeSkipRowsRange(AqlItemBlockInputRange& input, AqlCall& call);
+
   /**
    * @brief Inner getSome() part, without the tracing calls.
    */

From 64186d35aefe29b51df783c4cadc41d23f589ac0 Mon Sep 17 00:00:00 2001
From: Markus Pfeiffer <markus@arangodb.com>
Date: Fri, 13 Dec 2019 17:53:22 +0000
Subject: [PATCH 046/122] Fixup skipping for filter executor

---
 arangod/Aql/ExecutionBlockImpl.cpp | 27 ++++-----------------------
 1 file changed, 4 insertions(+), 23 deletions(-)

diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index 7e6d9cb79523..e01c2649cd5d 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -129,6 +129,7 @@ CREATE_HAS_MEMBER_CHECK(initializeCursor, hasInitializeCursor);
 CREATE_HAS_MEMBER_CHECK(skipRows, hasSkipRows);
 CREATE_HAS_MEMBER_CHECK(fetchBlockForPassthrough, hasFetchBlockForPassthrough);
 CREATE_HAS_MEMBER_CHECK(expectedNumberOfRows, hasExpectedNumberOfRows);
+CREATE_HAS_MEMBER_CHECK(skipRowsRange, hasSkipRowsRange);
 
 /*
  * Determine whether we execute new style or old style skips, i.e. pre or post shadow row introduction
@@ -1032,7 +1033,7 @@ static SkipRowsRangeVariant constexpr skipRowsType() {
       Executor::Properties::allowsBlockPassthrough == BlockPassthrough::Enable &&
       !std::is_same<Executor, SubqueryExecutor<true>>::value;
 
-  bool constexpr useExecutor = hasSkipRows<Executor>::value;
+  bool constexpr useExecutor = hasSkipRowsRange<Executor>::value;
 
   // ConstFetcher and SingleRowFetcher<BlockPassthrough::Enable> can skip, but
   // it may not be done for modification subqueries.
@@ -1045,28 +1046,8 @@ static SkipRowsRangeVariant constexpr skipRowsType() {
   static_assert(!useFetcher || hasSkipRows<typename Executor::Fetcher>::value,
                 "Fetcher is chosen for skipping, but has not skipRows method!");
 
-  static_assert(
-      useExecutor ==
-          (std::is_same<Executor, IndexExecutor>::value ||
-           std::is_same<Executor, IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::Materialized>>::value ||
-           std::is_same<Executor, IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::LateMaterialized>>::value ||
-           std::is_same<Executor, IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::LateMaterializedWithVars>>::value ||
-           std::is_same<Executor, IResearchViewExecutor<true, arangodb::iresearch::MaterializeType::Materialized>>::value ||
-           std::is_same<Executor, IResearchViewExecutor<true, arangodb::iresearch::MaterializeType::LateMaterialized>>::value ||
-           std::is_same<Executor, IResearchViewExecutor<true, arangodb::iresearch::MaterializeType::LateMaterializedWithVars>>::value ||
-           std::is_same<Executor, IResearchViewMergeExecutor<false, arangodb::iresearch::MaterializeType::Materialized>>::value ||
-           std::is_same<Executor, IResearchViewMergeExecutor<false, arangodb::iresearch::MaterializeType::LateMaterialized>>::value ||
-           std::is_same<Executor, IResearchViewMergeExecutor<true, arangodb::iresearch::MaterializeType::Materialized>>::value ||
-           std::is_same<Executor, IResearchViewMergeExecutor<true, arangodb::iresearch::MaterializeType::LateMaterialized>>::value ||
-           std::is_same<Executor, EnumerateCollectionExecutor>::value ||
-           std::is_same<Executor, LimitExecutor>::value ||
-           std::is_same<Executor, ConstrainedSortExecutor>::value ||
-           std::is_same<Executor, SortingGatherExecutor>::value ||
-           std::is_same<Executor, UnsortedGatherExecutor>::value ||
-           std::is_same<Executor, ParallelUnsortedGatherExecutor>::value ||
-           std::is_same<Executor, MaterializeExecutor<RegisterId>>::value ||
-           std::is_same<Executor, MaterializeExecutor<std::string const&>>::value),
-      "Unexpected executor for SkipVariants::EXECUTOR");
+  static_assert(useExecutor == (std::is_same<Executor, FilterExecutor>::value),
+                "Unexpected executor for SkipVariants::EXECUTOR");
 
   // The LimitExecutor will not work correctly with SkipVariants::FETCHER!
   static_assert(

From 266b8ad5cceea20aea966b12278d10bf0ec74360 Mon Sep 17 00:00:00 2001
From: Markus Pfeiffer <markus@arangodb.com>
Date: Fri, 20 Dec 2019 12:32:53 +0000
Subject: [PATCH 047/122] Rename some methods for clarity and consistency

 * AqlItemBlockInputRange
   - hasMore is now hasDataRow
   - next is now nextDataRow
   - peek is now peekDataRow
   - state is now upstreamState
   - additional method upstreamHasMore
---
 arangod/Aql/AqlItemBlockInputRange.cpp   | 24 ++++++----
 arangod/Aql/AqlItemBlockInputRange.h     |  9 ++--
 arangod/Aql/ExecutionBlockImpl.cpp       | 59 ++++++++++++++++++------
 arangod/Aql/FilterExecutor.cpp           | 12 ++---
 tests/Aql/AqlItemBlockInputRangeTest.cpp | 34 +++++++-------
 tests/Aql/FilterExecutorTest.cpp         | 22 ++++-----
 tests/Aql/SingleRowFetcherTest.cpp       | 10 ++--
 7 files changed, 104 insertions(+), 66 deletions(-)

diff --git a/arangod/Aql/AqlItemBlockInputRange.cpp b/arangod/Aql/AqlItemBlockInputRange.cpp
index 32d2155ce8fb..7147a1ed7898 100644
--- a/arangod/Aql/AqlItemBlockInputRange.cpp
+++ b/arangod/Aql/AqlItemBlockInputRange.cpp
@@ -32,7 +32,7 @@ using namespace arangodb::aql;
 
 AqlItemBlockInputRange::AqlItemBlockInputRange(ExecutorState state)
     : _block(nullptr), _rowIndex(0), _endIndex(0), _finalState(state) {
-  TRI_ASSERT(!hasMore());
+  TRI_ASSERT(!hasDataRow());
 }
 
 AqlItemBlockInputRange::AqlItemBlockInputRange(ExecutorState state,
@@ -49,8 +49,12 @@ AqlItemBlockInputRange::AqlItemBlockInputRange(ExecutorState state,
   TRI_ASSERT(index <= _block->size());
 }
 
-std::pair<ExecutorState, InputAqlItemRow> AqlItemBlockInputRange::peek() {
-  if (hasMore()) {
+bool AqlItemBlockInputRange::hasDataRow() const noexcept {
+  return isIndexValid(_rowIndex) && !isShadowRowAtIndex(_rowIndex);
+}
+
+std::pair<ExecutorState, InputAqlItemRow> AqlItemBlockInputRange::peekDataRow() {
+  if (hasDataRow()) {
     return std::make_pair(nextState<LookAhead::NEXT, RowType::DATA>(),
                           InputAqlItemRow{_block, _rowIndex});
   }
@@ -58,20 +62,20 @@ std::pair<ExecutorState, InputAqlItemRow> AqlItemBlockInputRange::peek() {
                         InputAqlItemRow{CreateInvalidInputRowHint{}});
 }
 
-std::pair<ExecutorState, InputAqlItemRow> AqlItemBlockInputRange::next() {
-  auto res = peek();
+std::pair<ExecutorState, InputAqlItemRow> AqlItemBlockInputRange::nextDataRow() {
+  auto res = peekDataRow();
   if (res.second) {
     ++_rowIndex;
   }
   return res;
 }
 
-bool AqlItemBlockInputRange::hasMore() const noexcept {
-  return isIndexValid(_rowIndex) && !isShadowRowAtIndex(_rowIndex);
+ExecutorState AqlItemBlockInputRange::upstreamState() const noexcept {
+  return nextState<LookAhead::NOW, RowType::DATA>();
 }
 
-ExecutorState AqlItemBlockInputRange::state() const noexcept {
-  return nextState<LookAhead::NOW, RowType::DATA>();
+bool AqlItemBlockInputRange::upstreamHasMore() const noexcept {
+  return upstreamState() == ExecutorState::HASMORE;
 }
 
 bool AqlItemBlockInputRange::hasShadowRow() const noexcept {
@@ -137,4 +141,4 @@ ExecutorState AqlItemBlockInputRange::nextState() const noexcept {
     }
     return ExecutorState::DONE;
   }
-}
\ No newline at end of file
+}
diff --git a/arangod/Aql/AqlItemBlockInputRange.h b/arangod/Aql/AqlItemBlockInputRange.h
index 668113457c15..abe4a1fef316 100644
--- a/arangod/Aql/AqlItemBlockInputRange.h
+++ b/arangod/Aql/AqlItemBlockInputRange.h
@@ -40,13 +40,14 @@ class AqlItemBlockInputRange {
   AqlItemBlockInputRange(ExecutorState, arangodb::aql::SharedAqlItemBlockPtr&&,
                          std::size_t startIndex, std::size_t endIndex) noexcept;
 
-  bool hasMore() const noexcept;
+  ExecutorState upstreamState() const noexcept;
+  bool upstreamHasMore() const noexcept;
 
-  ExecutorState state() const noexcept;
+  bool hasDataRow() const noexcept;
 
-  std::pair<ExecutorState, arangodb::aql::InputAqlItemRow> peek();
+  std::pair<ExecutorState, arangodb::aql::InputAqlItemRow> peekDataRow();
 
-  std::pair<ExecutorState, arangodb::aql::InputAqlItemRow> next();
+  std::pair<ExecutorState, arangodb::aql::InputAqlItemRow> nextDataRow();
 
   std::size_t getRowIndex() noexcept { return _rowIndex; };
 
diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index e01c2649cd5d..bb5f3a860875 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -82,7 +82,7 @@ using namespace arangodb::aql;
 namespace {
 
 std::string const doneString = "DONE";
-std::string const hasMoreString = "HASMORE";
+std::string const hasDataRowString = "HASMORE";
 std::string const waitingString = "WAITING";
 std::string const unknownString = "UNKNOWN";
 
@@ -91,7 +91,7 @@ std::string const& stateToString(aql::ExecutionState state) {
     case aql::ExecutionState::DONE:
       return doneString;
     case aql::ExecutionState::HASMORE:
-      return hasMoreString;
+      return hasDataRowString;
     case aql::ExecutionState::WAITING:
       return waitingString;
     default:
@@ -1063,6 +1063,10 @@ static SkipRowsRangeVariant constexpr skipRowsType() {
   }
 }
 
+// Let's do it the C++ way.
+template <class T>
+struct dependent_false : std::false_type {};
+
 template <class Executor>
 std::tuple<ExecutorState, size_t, AqlCall> ExecutionBlockImpl<Executor>::executeSkipRowsRange(
     AqlItemBlockInputRange& inputRange, AqlCall& call) {
@@ -1070,11 +1074,15 @@ std::tuple<ExecutorState, size_t, AqlCall> ExecutionBlockImpl<Executor>::execute
     if constexpr (skipRowsType<Executor>() == SkipRowsRangeVariant::EXECUTOR) {
       // TODO: make statically sure that this method exists?
       // the executor has a method skipRowsRange, so use it
+      //
+      // Input range needs data in it for this to work
       return _executor.skipRowsRange(inputRange, call);
     } else if constexpr (skipRowsType<Executor>() == SkipRowsRangeVariant::FETCHER) {
       // TODO: check whether this is right (and test!)
-      // just let the fetcher fetch some stuff and ignore it without even passing it
-      // to the executor
+      // just let the fetcher fetch some stuff and ignore it without even
+      // passing it to the executor
+      //
+      //
       return _rowFetcher.execute(call);
     } else if constexpr (skipRowsType<Executor>() == SkipRowsRangeVariant::GET_SOME) {
       // Here we need to skip by just having the executor produce rows which we then
@@ -1086,6 +1094,7 @@ std::tuple<ExecutorState, size_t, AqlCall> ExecutionBlockImpl<Executor>::execute
       //
       // TODO: is outputBlock freed when the variable goes out of scope?
       // TODO: do we need to use currently available blocks and then just discard?
+      // For this skip we need data in the input row. We could just run PRODUCE and ignore?
       size_t toSkip = std::min(call.getOffset(), DefaultBatchSize());
       SharedAqlItemBlockPtr outputBlock =
           _engine->itemBlockManager().requestBlock(toSkip, _infos.numberOfOutputRegisters());
@@ -1101,8 +1110,8 @@ std::tuple<ExecutorState, size_t, AqlCall> ExecutionBlockImpl<Executor>::execute
 
       return std::make_tuple(state, skipped, call);
     } else {
-      // TODO: this should be a compiler error
-      TRI_ASSERT(false);
+      static_assert(dependent_false<Executor>::value,
+                    "This value of SkipRowsRangeVariant is not supported");
       return std::make_tuple(ExecutorState::DONE, 0, call);
     }
   } else {
@@ -1113,21 +1122,44 @@ std::tuple<ExecutorState, size_t, AqlCall> ExecutionBlockImpl<Executor>::execute
   return std::make_tuple(ExecutorState::DONE, 0, call);
 }
 
+// This is the central function of an executor, and it acts like a
+// coroutine: It can be called multiple times and keeps state across
+// calls.
+//
+// The intended behaviour of this function is best described in terms of
+// a state machine; the possible states are the ExecStates
+// SKIP, PRODUCE, FULLCOUNT, UPSTREAM, SHADOWROWS, DONE
+//
+// SKIP       skipping rows. How rows are skipped is determined by
+//            the Executor that is used. See SkipVariants
+// PRODUCE    calls produceRows of the executor
+// FULLCOUNT
+// UPSTREAM   fetches rows from the upstream executor(s) to be processed by
+//            our executor.
+// SHADOWROWS process any shadow rows
+// DONE       processing is done
 template <class Executor>
 std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr>
 ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
   if constexpr (isNewStyleExecutor<Executor>()) {
+    // Make sure there's a block allocated and set
+    // the call
     ensureOutputBlock(stack.popCall());
-    size_t skipped = 0;
+
+    auto skipped = size_t{0};
 
     TRI_ASSERT(_outputItemRow);
-    ExecState execState = ::NextState(_outputItemRow->getClientCall());
+
+    auto execState = ::NextState(_outputItemRow->getClientCall());
+
+    // ::NextState(_outputItemRow->getClientCall());
     if (_lastRange.hasShadowRow()) {
       // We have not been able to move all shadowRows into the output last time.
       // Continue from there.
       // TODO test if this works with COUNT COLLECT
       execState = ExecState::SHADOWROWS;
     }
+
     AqlCall executorRequest;
     while (execState != ExecState::DONE && !_outputItemRow->allRowsUsed()) {
       switch (execState) {
@@ -1172,12 +1204,13 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
         }
         case ExecState::FULLCOUNT: {
           TRI_ASSERT(false);
+          // TODO: wat.
         }
         case ExecState::UPSTREAM: {
           // If this triggers the executors produceRows function has returned
-          // HASMORE even if it new that upstream has no further rows.
+          // HASMORE even if it knew that upstream has no further rows.
           TRI_ASSERT(_upstreamState != ExecutionState::DONE);
-          TRI_ASSERT(!_lastRange.hasMore());
+          TRI_ASSERT(!_lastRange.hasDataRow());
           size_t skippedLocal = 0;
           stack.pushCall(std::move(executorRequest));
           std::tie(_upstreamState, skippedLocal, _lastRange) = _rowFetcher.execute(stack);
@@ -1213,14 +1246,14 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
             TRI_ASSERT(_outputItemRow->produced());
             _outputItemRow->advanceRow();
             if (state == ExecutorState::DONE) {
-              if (_lastRange.hasMore()) {
+              if (_lastRange.hasDataRow()) {
                 // TODO this state is invalid, and can just show up now if we exclude SKIP
                 execState = ExecState::PRODUCE;
               } else {
                 // Right now we cannot support to have more than one set of
                 // ShadowRows inside of a Range.
                 // We do not know how to continue with the above executor after a shadowrow.
-                TRI_ASSERT(!_lastRange.hasMore());
+                TRI_ASSERT(!_lastRange.hasDataRow());
                 execState = ExecState::DONE;
               }
             }
@@ -1239,7 +1272,7 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
     // This is not strictly necessary here, as we shouldn't be called again
     // after DONE.
     _outputItemRow.reset();
-    if (_lastRange.hasMore() || _lastRange.hasShadowRow()) {
+    if (_lastRange.hasDataRow() || _lastRange.hasShadowRow()) {
       // We have skipped or/and return data, otherwise we cannot return HASMORE
       TRI_ASSERT(skipped > 0 || (outputBlock != nullptr && outputBlock->numEntries() > 0));
       return {ExecutionState::HASMORE, skipped, std::move(outputBlock)};
diff --git a/arangod/Aql/FilterExecutor.cpp b/arangod/Aql/FilterExecutor.cpp
index 4be4c63eceb4..bbe10b193e2e 100644
--- a/arangod/Aql/FilterExecutor.cpp
+++ b/arangod/Aql/FilterExecutor.cpp
@@ -107,10 +107,10 @@ std::tuple<ExecutorState, size_t, AqlCall> FilterExecutor::skipRowsRange(
   ExecutorState state = ExecutorState::HASMORE;
   InputAqlItemRow input{CreateInvalidInputRowHint{}};
   size_t skipped = 0;
-  while (inputRange.hasMore() && skipped < call.getOffset()) {
-    std::tie(state, input) = inputRange.next();
+  while (inputRange.hasDataRow() && skipped < call.getOffset()) {
+    std::tie(state, input) = inputRange.nextDataRow();
     if (!input) {
-      TRI_ASSERT(!inputRange.hasMore());
+      TRI_ASSERT(!inputRange.hasDataRow());
       break;
     }
     if (input.getValue(_infos.getInputRegister()).toBoolean()) {
@@ -131,8 +131,8 @@ std::tuple<ExecutorState, FilterStats, AqlCall> FilterExecutor::produceRows(
   }
   FilterStats stats{};
 
-  while (inputRange.hasMore() && !output.isFull()) {
-    auto const& [state, input] = inputRange.next();
+  while (inputRange.hasDataRow() && !output.isFull()) {
+    auto const& [state, input] = inputRange.nextDataRow();
     TRI_ASSERT(input.isInitialized());
     if (input.getValue(_infos.getInputRegister()).toBoolean()) {
       output.copyRow(input);
@@ -148,5 +148,5 @@ std::tuple<ExecutorState, FilterStats, AqlCall> FilterExecutor::produceRows(
   // pass through all rows this fetch is correct, otherwise we have too few rows.
   upstreamCall.softLimit = clientCall.getOffset() +
                            (std::min)(clientCall.softLimit, clientCall.hardLimit);
-  return {inputRange.state(), stats, upstreamCall};
+  return {inputRange.upstreamState(), stats, upstreamCall};
 }
diff --git a/tests/Aql/AqlItemBlockInputRangeTest.cpp b/tests/Aql/AqlItemBlockInputRangeTest.cpp
index c5180e23ec1c..884058d6e7d7 100644
--- a/tests/Aql/AqlItemBlockInputRangeTest.cpp
+++ b/tests/Aql/AqlItemBlockInputRangeTest.cpp
@@ -57,16 +57,16 @@ class InputRangeTest : public ::testing::TestWithParam<ExecutorState> {
   }
 
   void validateEndReached(AqlItemBlockInputRange& testee) {
-    EXPECT_EQ(GetParam(), testee.state());
+    EXPECT_EQ(GetParam(), testee.upstreamState());
     // Test Data rows
-    EXPECT_FALSE(testee.hasMore());
+    EXPECT_FALSE(testee.hasDataRow());
     {
-      auto const [state, row] = testee.peek();
+      auto const [state, row] = testee.peekDataRow();
       EXPECT_EQ(GetParam(), state);
       EXPECT_FALSE(row.isInitialized());
     }
     {
-      auto const [state, row] = testee.next();
+      auto const [state, row] = testee.nextDataRow();
       EXPECT_EQ(GetParam(), state);
       EXPECT_FALSE(row.isInitialized());
     }
@@ -86,10 +86,10 @@ class InputRangeTest : public ::testing::TestWithParam<ExecutorState> {
 
   void validateNextIsDataRow(AqlItemBlockInputRange& testee,
                              ExecutorState expectedState, int64_t value) {
-    EXPECT_TRUE(testee.hasMore());
+    EXPECT_TRUE(testee.hasDataRow());
     EXPECT_FALSE(testee.hasShadowRow());
     // We have the next row
-    EXPECT_EQ(testee.state(), ExecutorState::HASMORE);
+    EXPECT_EQ(testee.upstreamState(), ExecutorState::HASMORE);
     auto rowIndexBefore = testee.getRowIndex();
     // Validate that shadowRowAPI does not move on
     {
@@ -108,7 +108,7 @@ class InputRangeTest : public ::testing::TestWithParam<ExecutorState> {
     }
     // Validate Data Row API
     {
-      auto [state, row] = testee.peek();
+      auto [state, row] = testee.peekDataRow();
       EXPECT_EQ(state, expectedState);
       EXPECT_TRUE(row.isInitialized());
       auto val = row.getValue(0);
@@ -119,7 +119,7 @@ class InputRangeTest : public ::testing::TestWithParam<ExecutorState> {
     }
 
     {
-      auto [state, row] = testee.next();
+      auto [state, row] = testee.nextDataRow();
       EXPECT_EQ(state, expectedState);
       EXPECT_TRUE(row.isInitialized());
       auto val = row.getValue(0);
@@ -128,26 +128,26 @@ class InputRangeTest : public ::testing::TestWithParam<ExecutorState> {
       ASSERT_NE(rowIndexBefore, testee.getRowIndex())
           << "Did not go to next row.";
     }
-    EXPECT_EQ(expectedState, testee.state());
+    EXPECT_EQ(expectedState, testee.upstreamState());
   }
 
   void validateNextIsShadowRow(AqlItemBlockInputRange& testee, ExecutorState expectedState,
                                int64_t value, uint64_t depth) {
     EXPECT_TRUE(testee.hasShadowRow());
     // The next is a ShadowRow, the state shall be done
-    EXPECT_EQ(testee.state(), ExecutorState::DONE);
+    EXPECT_EQ(testee.upstreamState(), ExecutorState::DONE);
 
     auto rowIndexBefore = testee.getRowIndex();
     // Validate that inputRowAPI does not move on
     {
-      auto [state, row] = testee.peek();
+      auto [state, row] = testee.peekDataRow();
       EXPECT_EQ(state, ExecutorState::DONE);
       EXPECT_FALSE(row.isInitialized());
       ASSERT_EQ(rowIndexBefore, testee.getRowIndex())
           << "Skipped a non processed row.";
     }
     {
-      auto [state, row] = testee.next();
+      auto [state, row] = testee.nextDataRow();
       EXPECT_EQ(state, ExecutorState::DONE);
       EXPECT_FALSE(row.isInitialized());
       ASSERT_EQ(rowIndexBefore, testee.getRowIndex())
@@ -181,24 +181,24 @@ class InputRangeTest : public ::testing::TestWithParam<ExecutorState> {
 
 TEST_P(InputRangeTest, empty_returns_given_state) {
   auto testee = createEmpty();
-  EXPECT_EQ(GetParam(), testee.state());
+  EXPECT_EQ(GetParam(), testee.upstreamState());
 }
 
 TEST_P(InputRangeTest, empty_does_not_have_more) {
   auto testee = createEmpty();
-  EXPECT_FALSE(testee.hasMore());
+  EXPECT_FALSE(testee.hasDataRow());
 }
 
 TEST_P(InputRangeTest, empty_peek_is_empty) {
   auto testee = createEmpty();
-  auto const [state, row] = testee.peek();
+  auto const [state, row] = testee.peekDataRow();
   EXPECT_EQ(GetParam(), state);
   EXPECT_FALSE(row.isInitialized());
 }
 
 TEST_P(InputRangeTest, empty_next_is_empty) {
   auto testee = createEmpty();
-  auto const [state, row] = testee.next();
+  auto const [state, row] = testee.nextDataRow();
   EXPECT_EQ(GetParam(), state);
   EXPECT_FALSE(row.isInitialized());
 }
@@ -290,4 +290,4 @@ INSTANTIATE_TEST_CASE_P(AqlItemBlockInputRangeTest, InputRangeTest,
 
 }  // namespace aql
 }  // namespace tests
-}  // namespace arangodb
\ No newline at end of file
+}  // namespace arangodb
diff --git a/tests/Aql/FilterExecutorTest.cpp b/tests/Aql/FilterExecutorTest.cpp
index dc37f114c757..6cceab6e09fc 100644
--- a/tests/Aql/FilterExecutorTest.cpp
+++ b/tests/Aql/FilterExecutorTest.cpp
@@ -372,7 +372,7 @@ TEST_F(FilterExecutorTest, test_produce_datarange) {
   EXPECT_EQ(state, ExecutorState::DONE);
   EXPECT_EQ(stats.getFiltered(), 2);
   EXPECT_EQ(output.numRowsWritten(), 3);
-  EXPECT_FALSE(input.hasMore());
+  EXPECT_FALSE(input.hasDataRow());
 }
 
 TEST_F(FilterExecutorTest, test_produce_datarange_need_more) {
@@ -398,7 +398,7 @@ TEST_F(FilterExecutorTest, test_produce_datarange_need_more) {
   EXPECT_EQ(state, ExecutorState::HASMORE);
   EXPECT_EQ(stats.getFiltered(), 2);
   EXPECT_EQ(output.numRowsWritten(), 3);
-  EXPECT_FALSE(input.hasMore());
+  EXPECT_FALSE(input.hasDataRow());
   // Test the Call we send to upstream
   EXPECT_EQ(call.offset, 0);
   EXPECT_FALSE(call.hasHardLimit());
@@ -428,7 +428,7 @@ TEST_F(FilterExecutorTest, test_skip_datarange_need_more) {
   EXPECT_EQ(state, ExecutorState::HASMORE);
   EXPECT_EQ(skipped, 3);
   EXPECT_EQ(clientCall.getOffset(), 1000 - 3);
-  EXPECT_FALSE(input.hasMore());
+  EXPECT_FALSE(input.hasDataRow());
 
   // Test the Call we send to upstream
   EXPECT_EQ(call.offset, 0);
@@ -461,21 +461,21 @@ TEST_F(FilterExecutorTest, test_produce_datarange_has_more) {
   EXPECT_EQ(state, ExecutorState::HASMORE);
   EXPECT_EQ(stats.getFiltered(), 1);
   EXPECT_EQ(output.numRowsWritten(), 2);
-  EXPECT_TRUE(input.hasMore());
+  EXPECT_TRUE(input.hasDataRow());
   // We still have two values in block: false and true
   {
     // pop false
-    auto const [state, row] = input.next();
+    auto const [state, row] = input.nextDataRow();
     EXPECT_EQ(state, ExecutorState::HASMORE);
     EXPECT_FALSE(row.getValue(0).toBoolean());
   }
   {
     // pop true
-    auto const [state, row] = input.next();
+    auto const [state, row] = input.nextDataRow();
     EXPECT_EQ(state, ExecutorState::DONE);
     EXPECT_TRUE(row.getValue(0).toBoolean());
   }
-  EXPECT_FALSE(input.hasMore());
+  EXPECT_FALSE(input.hasDataRow());
 }
 
 TEST_F(FilterExecutorTest, test_skip_datarange_has_more) {
@@ -498,21 +498,21 @@ TEST_F(FilterExecutorTest, test_skip_datarange_has_more) {
   EXPECT_EQ(state, ExecutorState::HASMORE);
   EXPECT_EQ(skipped, 2);
   EXPECT_EQ(clientCall.getOffset(), 0);
-  EXPECT_TRUE(input.hasMore());
+  EXPECT_TRUE(input.hasDataRow());
   // We still have two values in block: false and true
   {
     // pop false
-    auto const [state, row] = input.next();
+    auto const [state, row] = input.nextDataRow();
     EXPECT_EQ(state, ExecutorState::HASMORE);
     EXPECT_FALSE(row.getValue(0).toBoolean());
   }
   {
     // pop true
-    auto const [state, row] = input.next();
+    auto const [state, row] = input.nextDataRow();
     EXPECT_EQ(state, ExecutorState::DONE);
     EXPECT_TRUE(row.getValue(0).toBoolean());
   }
-  EXPECT_FALSE(input.hasMore());
+  EXPECT_FALSE(input.hasDataRow());
 }
 
 }  // namespace aql
diff --git a/tests/Aql/SingleRowFetcherTest.cpp b/tests/Aql/SingleRowFetcherTest.cpp
index 9435cd93979c..06f7b5fde85e 100644
--- a/tests/Aql/SingleRowFetcherTest.cpp
+++ b/tests/Aql/SingleRowFetcherTest.cpp
@@ -51,7 +51,7 @@ namespace arangodb {
 namespace tests {
 namespace aql {
 
-// TODO check that blocks are not returned to early (e.g. not before the next row
+// TODO check that blocks are not returned to early (e.g. not before the nextDataRow row
 //      is fetched)
 
 // TODO check that, for SingleRowFetcher<true>, blocks are reposited (passed through) immediately
@@ -72,10 +72,10 @@ class SingleRowFetcherTestPassBlocks : public ::testing::Test {
     for (auto const& value : result) {
       SCOPED_TRACE("Checking for value: " + value);
       // We need more rows
-      ASSERT_TRUE(input.hasMore());
+      ASSERT_TRUE(input.hasDataRow());
       EXPECT_FALSE(input.hasShadowRow());
 
-      auto [state, row] = input.next();
+      auto [state, row] = input.nextDataRow();
 
       if (value == result.back()) {
         EXPECT_EQ(state, ExecutorState::DONE);
@@ -89,7 +89,7 @@ class SingleRowFetcherTestPassBlocks : public ::testing::Test {
           << inputVal.slice().toJson() << " should be equal to \"" << value << "\"";
     }
     // We always fetch to the end
-    EXPECT_FALSE(input.hasMore());
+    EXPECT_FALSE(input.hasDataRow());
   }
 
   void validateShadowRange(AqlItemBlockInputRange& input,
@@ -99,7 +99,7 @@ class SingleRowFetcherTestPassBlocks : public ::testing::Test {
                    " with value: " + value);
       // We need more rows
       ASSERT_TRUE(input.hasShadowRow());
-      EXPECT_FALSE(input.hasMore());
+      EXPECT_FALSE(input.hasDataRow());
 
       auto [state, row] = input.nextShadowRow();
 

From 16281968c785c730c0a63aa8717c01ff9b6f58f9 Mon Sep 17 00:00:00 2001
From: Markus Pfeiffer <markus@arangodb.com>
Date: Tue, 24 Dec 2019 14:32:18 +0000
Subject: [PATCH 048/122] Introduce function to allocate an output block

---
 arangod/Aql/ExecutionBlockImpl.cpp | 17 +++++++++++------
 arangod/Aql/ExecutionBlockImpl.h   |  7 ++++++-
 2 files changed, 17 insertions(+), 7 deletions(-)

diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index bb5f3a860875..fee0dc0f0c6c 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -966,15 +966,20 @@ std::pair<ExecutionState, SharedAqlItemBlockPtr> ExecutionBlockImpl<Executor>::r
       executor(), *_engine, nrItems, nrRegs);
 }
 
+// TODO: We need to define the size of this block based on Input / Executor / Subquery depth
+template <class Executor>
+auto ExecutionBlockImpl<Executor>::allocateOutputBlock(AqlCall&& call)
+    -> std::unique_ptr<OutputAqlItemRow> {
+  size_t blockSize = ExecutionBlock::DefaultBatchSize();
+  SharedAqlItemBlockPtr newBlock =
+      _engine->itemBlockManager().requestBlock(blockSize, _infos.numberOfOutputRegisters());
+  return createOutputRow(newBlock, std::move(call));
+}
+
 template <class Executor>
 void ExecutionBlockImpl<Executor>::ensureOutputBlock(AqlCall&& call) {
   if (_outputItemRow == nullptr || _outputItemRow->isFull()) {
-    // Is this a TODO:?
-    // We need to define the size of this block based on Input / Executor / Subquery depth
-    size_t blockSize = ExecutionBlock::DefaultBatchSize();
-    SharedAqlItemBlockPtr newBlock =
-        _engine->itemBlockManager().requestBlock(blockSize, _infos.numberOfOutputRegisters());
-    _outputItemRow = createOutputRow(newBlock, std::move(call));
+    _outputItemRow = allocateOutputBlock(std::move(call));
   } else {
     _outputItemRow->setCall(std::move(call));
   }
diff --git a/arangod/Aql/ExecutionBlockImpl.h b/arangod/Aql/ExecutionBlockImpl.h
index b3da0a89a768..667957491c03 100644
--- a/arangod/Aql/ExecutionBlockImpl.h
+++ b/arangod/Aql/ExecutionBlockImpl.h
@@ -201,7 +201,8 @@ class ExecutionBlockImpl final : public ExecutionBlock {
   std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> executeWithoutTrace(AqlCallStack stack);
 
   // execute a skipRowsRange call
-  std::tuple<ExecutorState, size_t, AqlCall> executeSkipRowsRange(AqlItemBlockInputRange& input, AqlCall& call);
+  std::tuple<ExecutorState, size_t, AqlCall> executeSkipRowsRange(AqlItemBlockInputRange& input,
+                                                                  AqlCall& call);
 
   /**
    * @brief Inner getSome() part, without the tracing calls.
@@ -249,6 +250,10 @@ class ExecutionBlockImpl final : public ExecutionBlock {
   // Trace the end of a getSome call, potentially with result
   void traceExecuteEnd(std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> const& result);
 
+  // Allocate an output block and install a call in it
+  [[nodiscard]] auto allocateOutputBlock(AqlCall&& call)
+      -> std::unique_ptr<OutputAqlItemRow>;
+
   // Ensure that we have an output block of the desired dimenstions
   // Will as a side effect modify _outputItemRow
   void ensureOutputBlock(AqlCall&& call);

From 7e8180f80d8aa4352ddc66001bed4d07b44248c5 Mon Sep 17 00:00:00 2001
From: Markus Pfeiffer <markus@arangodb.com>
Date: Tue, 24 Dec 2019 14:33:21 +0000
Subject: [PATCH 049/122] Fix skipSome simulation bug

---
 arangod/Aql/ExecutionBlockImpl.cpp | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index fee0dc0f0c6c..3baa5d17805f 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -451,7 +451,16 @@ std::pair<ExecutionState, size_t> ExecutionBlockImpl<Executor>::skipSome(size_t
   if constexpr (isNewStyleExecutor<Executor>()) {
     AqlCallStack stack{AqlCall::SimulateSkipSome(atMost)};
     auto const [state, skipped, block] = execute(stack);
-    return {state, skipped};
+
+    // execute returns ExecutionState::DONE here, which stops execution after simulating a skip.
+    // If we indiscriminately return ExecutionState::HASMORE, then we end up in an infinite loop
+    //
+    // luckily we can dispose of this kludge once executors have been ported.
+    if (skipped < atMost && state == ExecutionState::DONE) {
+      return {ExecutionState::DONE, skipped};
+    } else {
+      return {ExecutionState::HASMORE, skipped};
+    }
   } else {
     traceSkipSomeBegin(atMost);
     auto state = ExecutionState::HASMORE;

From 4e86d1765b6bf5740fea4e75484f525282082787 Mon Sep 17 00:00:00 2001
From: Markus Pfeiffer <markus@arangodb.com>
Date: Tue, 24 Dec 2019 15:06:25 +0000
Subject: [PATCH 050/122] Some small cleanups

---
 arangod/Aql/ExecutionBlockImpl.cpp | 48 +++++++++++-------------------
 1 file changed, 18 insertions(+), 30 deletions(-)

diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index 3baa5d17805f..b9832657da4f 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -1086,43 +1086,32 @@ std::tuple<ExecutorState, size_t, AqlCall> ExecutionBlockImpl<Executor>::execute
     AqlItemBlockInputRange& inputRange, AqlCall& call) {
   if constexpr (isNewStyleExecutor<Executor>()) {
     if constexpr (skipRowsType<Executor>() == SkipRowsRangeVariant::EXECUTOR) {
-      // TODO: make statically sure that this method exists?
-      // the executor has a method skipRowsRange, so use it
-      //
-      // Input range needs data in it for this to work
+      // If the executor has a method skipRowsRange, to skip outputs more
+      // efficiently than just producing them to subsequently discard them, then
+      // we use it
       return _executor.skipRowsRange(inputRange, call);
     } else if constexpr (skipRowsType<Executor>() == SkipRowsRangeVariant::FETCHER) {
-      // TODO: check whether this is right (and test!)
-      // just let the fetcher fetch some stuff and ignore it without even
-      // passing it to the executor
-      //
-      //
+      // If we know that every input row produces exactly one output row (this
+      // is a property of the executor), then we can just let the fetcher skip
+      // the number of rows that we would like to skip.
       return _rowFetcher.execute(call);
     } else if constexpr (skipRowsType<Executor>() == SkipRowsRangeVariant::GET_SOME) {
-      // Here we need to skip by just having the executor produce rows which we then
-      // subsequently throw away. I do this by allocating a block and having the
-      // executor write to it.
-      //
-      // unsure about the role of call here as yet, might have to be std::move()'d
-      // into createOutputRow, and then use the resCall for return value.
-      //
-      // TODO: is outputBlock freed when the variable goes out of scope?
-      // TODO: do we need to use currently available blocks and then just discard?
-      // For this skip we need data in the input row. We could just run PRODUCE and ignore?
+      // In all other cases, we skip by letting the executor produce rows, and
+      // then throw them away.
+
       size_t toSkip = std::min(call.getOffset(), DefaultBatchSize());
-      SharedAqlItemBlockPtr outputBlock =
-          _engine->itemBlockManager().requestBlock(toSkip, _infos.numberOfOutputRegisters());
-      TRI_ASSERT(outputBlock != nullptr);
-      TRI_ASSERT(outputBlock->size() == call.getOffset());
-      // TODO: do we need to std::move(call) here?
-      auto outputRow = createOutputRow(outputBlock, AqlCall{});
+      AqlCall skipCall{};
+      skipCall.softLimit = toSkip;
+      skipCall.hardLimit = toSkip;
+      skipCall.offset = 0;
 
-      auto const [state, stats, rescall] = _executor.produceRows(inputRange, *outputRow);
+      // we can't mess with _outputItemRow,
+      auto skipOutput = allocateOutputBlock(std::move(skipCall));
+      auto [state, stats, rescall] = _executor.produceRows(inputRange, *skipOutput);
+      auto skipped = skipOutput->numRowsWritten();
 
-      size_t skipped = outputRow->numRowsWritten();
       call.didSkip(skipped);
-
-      return std::make_tuple(state, skipped, call);
+      return std::make_tuple(state, skipped, rescall);
     } else {
       static_assert(dependent_false<Executor>::value,
                     "This value of SkipRowsRangeVariant is not supported");
@@ -1166,7 +1155,6 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
 
     auto execState = ::NextState(_outputItemRow->getClientCall());
 
-    // ::NextState(_outputItemRow->getClientCall());
     if (_lastRange.hasShadowRow()) {
       // We have not been able to move all shadowRows into the output last time.
       // Continue from there.

From f5ef0e727e5d039cc37a3636da2faa2bf34e8df1 Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Thu, 2 Jan 2020 16:50:30 +0100
Subject: [PATCH 051/122] Replaced assertion on atMost on the output size.
 Otherwise we got into issues with atMost changes between waiting calls (can
 occur in our intermediate state now)

---
 arangod/Aql/ExecutionBlockImpl.cpp | 35 +++++++++++++++---------------
 1 file changed, 17 insertions(+), 18 deletions(-)

diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index 89da10671dc7..75daf6a1a5d3 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -299,16 +299,7 @@ std::pair<ExecutionState, SharedAqlItemBlockPtr> ExecutionBlockImpl<Executor>::g
     }
 
     TRI_ASSERT(state == ExecutionState::HASMORE);
-    // When we're passing blocks through we have no control over the size of the
-    // output block.
-    // Plus, the ConstrainedSortExecutor will report an expectedNumberOfRows
-    // according to its heap size, thus resulting in a smaller allocated output
-    // block. However, it won't report DONE after, because a LIMIT block with
-    // fullCount must continue to count after the sorted output.
-    if /* constexpr */ (Executor::Properties::allowsBlockPassthrough == BlockPassthrough::Disable &&
-                        !std::is_same<Executor, ConstrainedSortExecutor>::value) {
-      TRI_ASSERT(_outputItemRow->numRowsWritten() == atMost);
-    }
+    TRI_ASSERT(_outputItemRow->isFull());
   }
 
   auto outputBlock = _outputItemRow->stealBlock();
@@ -1349,23 +1340,31 @@ template class ::arangodb::aql::ExecutionBlockImpl<HashedCollectExecutor>;
 template class ::arangodb::aql::ExecutionBlockImpl<IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::NotMaterialize>>;
 template class ::arangodb::aql::ExecutionBlockImpl<IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::LateMaterialize>>;
 template class ::arangodb::aql::ExecutionBlockImpl<IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::Materialize>>;
-template class ::arangodb::aql::ExecutionBlockImpl<IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::NotMaterialize | arangodb::iresearch::MaterializeType::UseStoredValues>>;
-template class ::arangodb::aql::ExecutionBlockImpl<IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::LateMaterialize | arangodb::iresearch::MaterializeType::UseStoredValues>>;
+template class ::arangodb::aql::ExecutionBlockImpl<
+    IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::NotMaterialize | arangodb::iresearch::MaterializeType::UseStoredValues>>;
+template class ::arangodb::aql::ExecutionBlockImpl<
+    IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::LateMaterialize | arangodb::iresearch::MaterializeType::UseStoredValues>>;
 template class ::arangodb::aql::ExecutionBlockImpl<IResearchViewExecutor<true, arangodb::iresearch::MaterializeType::NotMaterialize>>;
 template class ::arangodb::aql::ExecutionBlockImpl<IResearchViewExecutor<true, arangodb::iresearch::MaterializeType::LateMaterialize>>;
 template class ::arangodb::aql::ExecutionBlockImpl<IResearchViewExecutor<true, arangodb::iresearch::MaterializeType::Materialize>>;
-template class ::arangodb::aql::ExecutionBlockImpl<IResearchViewExecutor<true, arangodb::iresearch::MaterializeType::NotMaterialize | arangodb::iresearch::MaterializeType::UseStoredValues>>;
-template class ::arangodb::aql::ExecutionBlockImpl<IResearchViewExecutor<true, arangodb::iresearch::MaterializeType::LateMaterialize | arangodb::iresearch::MaterializeType::UseStoredValues>>;
+template class ::arangodb::aql::ExecutionBlockImpl<
+    IResearchViewExecutor<true, arangodb::iresearch::MaterializeType::NotMaterialize | arangodb::iresearch::MaterializeType::UseStoredValues>>;
+template class ::arangodb::aql::ExecutionBlockImpl<
+    IResearchViewExecutor<true, arangodb::iresearch::MaterializeType::LateMaterialize | arangodb::iresearch::MaterializeType::UseStoredValues>>;
 template class ::arangodb::aql::ExecutionBlockImpl<IResearchViewMergeExecutor<false, arangodb::iresearch::MaterializeType::NotMaterialize>>;
 template class ::arangodb::aql::ExecutionBlockImpl<IResearchViewMergeExecutor<false, arangodb::iresearch::MaterializeType::LateMaterialize>>;
 template class ::arangodb::aql::ExecutionBlockImpl<IResearchViewMergeExecutor<false, arangodb::iresearch::MaterializeType::Materialize>>;
-template class ::arangodb::aql::ExecutionBlockImpl<IResearchViewMergeExecutor<false, arangodb::iresearch::MaterializeType::NotMaterialize | arangodb::iresearch::MaterializeType::UseStoredValues>>;
-template class ::arangodb::aql::ExecutionBlockImpl<IResearchViewMergeExecutor<false, arangodb::iresearch::MaterializeType::LateMaterialize | arangodb::iresearch::MaterializeType::UseStoredValues>>;
+template class ::arangodb::aql::ExecutionBlockImpl<IResearchViewMergeExecutor<
+    false, arangodb::iresearch::MaterializeType::NotMaterialize | arangodb::iresearch::MaterializeType::UseStoredValues>>;
+template class ::arangodb::aql::ExecutionBlockImpl<IResearchViewMergeExecutor<
+    false, arangodb::iresearch::MaterializeType::LateMaterialize | arangodb::iresearch::MaterializeType::UseStoredValues>>;
 template class ::arangodb::aql::ExecutionBlockImpl<IResearchViewMergeExecutor<true, arangodb::iresearch::MaterializeType::NotMaterialize>>;
 template class ::arangodb::aql::ExecutionBlockImpl<IResearchViewMergeExecutor<true, arangodb::iresearch::MaterializeType::LateMaterialize>>;
 template class ::arangodb::aql::ExecutionBlockImpl<IResearchViewMergeExecutor<true, arangodb::iresearch::MaterializeType::Materialize>>;
-template class ::arangodb::aql::ExecutionBlockImpl<IResearchViewMergeExecutor<true, arangodb::iresearch::MaterializeType::NotMaterialize | arangodb::iresearch::MaterializeType::UseStoredValues>>;
-template class ::arangodb::aql::ExecutionBlockImpl<IResearchViewMergeExecutor<true, arangodb::iresearch::MaterializeType::LateMaterialize | arangodb::iresearch::MaterializeType::UseStoredValues>>;
+template class ::arangodb::aql::ExecutionBlockImpl<IResearchViewMergeExecutor<
+    true, arangodb::iresearch::MaterializeType::NotMaterialize | arangodb::iresearch::MaterializeType::UseStoredValues>>;
+template class ::arangodb::aql::ExecutionBlockImpl<IResearchViewMergeExecutor<
+    true, arangodb::iresearch::MaterializeType::LateMaterialize | arangodb::iresearch::MaterializeType::UseStoredValues>>;
 
 template class ::arangodb::aql::ExecutionBlockImpl<IdExecutor<ConstFetcher>>;
 template class ::arangodb::aql::ExecutionBlockImpl<IdExecutor<SingleRowFetcher<BlockPassthrough::Enable>>>;

From 862d316c1ebe4c67e9fe876485f5ced9d535c822 Mon Sep 17 00:00:00 2001
From: Markus Pfeiffer <markus@arangodb.com>
Date: Mon, 6 Jan 2020 12:49:49 +0000
Subject: [PATCH 052/122] Attempt at fixing execute

---
 arangod/Aql/ExecutionBlockImpl.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index 75daf6a1a5d3..df13c3d1955a 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -1194,7 +1194,7 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
           _engine->_stats += stats;
           if (state == ExecutorState::DONE) {
             execState = ExecState::SHADOWROWS;
-          } else if (clientCall.getLimit() > 0) {
+          } else if (clientCall.getLimit() > 0 && !_lastRange.hasDataRow()) {
             TRI_ASSERT(_upstreamState != ExecutionState::DONE);
             // We need to request more
             executorRequest = call;

From a656f39cecf67bd21af022774e960b61c473c0df Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tobias=20G=C3=B6dderz?= <tobias@arangodb.com>
Date: Fri, 17 Jan 2020 11:31:29 +0100
Subject: [PATCH 053/122] Fix merge conflict

---
 arangod/Aql/AqlCall.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arangod/Aql/AqlCall.h b/arangod/Aql/AqlCall.h
index 8f6592e3ee07..3c4aa4bb98c1 100644
--- a/arangod/Aql/AqlCall.h
+++ b/arangod/Aql/AqlCall.h
@@ -74,7 +74,7 @@ struct AqlCall {
 
   std::size_t getLimit() const {
     // By default we use batchsize
-    std::size_t limit = ExecutionBlock::DefaultBatchSize();
+    std::size_t limit = ExecutionBlock::DefaultBatchSize;
     // We are not allowed to go above softLimit
     if (std::holds_alternative<std::size_t>(softLimit)) {
       limit = (std::min)(std::get<std::size_t>(softLimit), limit);
@@ -112,4 +112,4 @@ struct AqlCall {
 }  // namespace aql
 }  // namespace arangodb
 
-#endif
\ No newline at end of file
+#endif

From beb7003160900fa524c6ecd084887624a807f51a Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Fri, 24 Jan 2020 12:37:54 +0100
Subject: [PATCH 054/122] Feature/aql subquery execution block impl execute
 implementation exec block impl tests (#10838)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

* Added a generic Lambda Executor, this can be used in ExecutionBlockImplTests to have finegrained control over the action happening within the Executor

* Added first test using the LambdaExecutor.

* Added some tests around Execute. GetSome seems to be okayish. Skip not. Namely skipped numbers are not reported correctly.

* Made the first ExecutionBlock Execute integration test pass. Still other tests are failing

* Simplified the IsSkipSome test, this allows the C++ tests for Mixed Calls to pass.

* Added a skip test and fixed the producing executor to recreate the list once for every input line.

* More tests. Also added a custom AqlCall printer function for GTest. Tests still red, need to fix fullCount and hardLimit.

* Implemented ostream operator for AQLCall.

* Properly implemented fullCount incl. UnitTest

* Added test for Callforwarding. They still have some todos, but these can only be solved by upgrading the OutputRow. Which should be part of separate PR

* Added another test for CallForwarding in passthrough state

* Added a Test Implementation for an Executor that uses a dynamic skip implementation.

* Fixed skip with HARDLIMIT.

* Startet to implement call forwarding test. However we need to improve Outputrow first this will be done in seperate branch

* Removed designated initializers. Thanks for not supporting it MSVC!

* Removed non-passthrough non-skip Lambda Executor again. We decided to disallow this.

* Update tests/Aql/ExecutionBlockImplTest.cpp

Co-Authored-By: Markus Pfeiffer <markuspf@users.noreply.github.com>

* Started to add implementation of passthrough block allocation

* Added a comparator to AqlCall. Mostly for tests

* Fixed an issue in skip-passthrough version. Updated the tests.

* Allow to 'overSkip' if we do fullCount

* Enabled the first set of tests now. Only one set to go

* Applied all fixes to get Integration testsuite green

* Added some comments on the TestCases executed in the ExecutionBlockImpl

* Added tes descriptions and removed a duplicate test

* Added some comments on LamdbaExecutors

* Added description of ExecutionBlockImple execute logic

* Applied review comments, thanks to reviewers

* Fixed modulo 2 off by one error

* Renamed getLambda() => getProduceLambda() in test code, as we have produce and skip

Co-authored-by: Markus Pfeiffer <markuspf@users.noreply.github.com>
Co-authored-by: Tobias Gödderz <github@tobias.goedderz.info>
---
 arangod/Aql/AqlCall.h                         |   56 +-
 arangod/Aql/AqlItemBlockInputRange.cpp        |    4 +
 arangod/Aql/AqlItemBlockInputRange.h          |    2 +
 arangod/Aql/ExecutionBlockImpl.cpp            |  298 +++--
 arangod/Aql/ExecutionBlockImpl.h              |    6 +
 arangod/Aql/OutputAqlItemRow.cpp              |    5 +-
 arangod/Aql/OutputAqlItemRow.h                |    7 +-
 tests/Aql/ExecutionBlockImplTest.cpp          | 1172 +++++++++++++++++
 tests/Aql/ExecutionBlockImplTestInstances.cpp |    3 +
 tests/Aql/TestLambdaExecutor.cpp              |  112 ++
 tests/Aql/TestLambdaExecutor.h                |  233 ++++
 tests/CMakeLists.txt                          |    1 +
 tests/Mocks/Servers.cpp                       |   21 +-
 tests/Mocks/Servers.h                         |   10 +-
 14 files changed, 1824 insertions(+), 106 deletions(-)
 create mode 100644 tests/Aql/TestLambdaExecutor.cpp
 create mode 100644 tests/Aql/TestLambdaExecutor.h

diff --git a/arangod/Aql/AqlCall.h b/arangod/Aql/AqlCall.h
index 5893c9d43afe..6ece6b80ea4d 100644
--- a/arangod/Aql/AqlCall.h
+++ b/arangod/Aql/AqlCall.h
@@ -57,7 +57,7 @@ struct AqlCall {
 
   // TODO Remove me, this will not be necessary later
   static bool IsSkipSomeCall(AqlCall const& call) {
-    return !call.hasHardLimit() && call.getLimit() == 0 && call.getOffset() > 0;
+    return !call.hasHardLimit() && call.getOffset() > 0;
   }
 
   // TODO Remove me, this will not be necessary later
@@ -88,8 +88,15 @@ struct AqlCall {
   }
 
   void didSkip(std::size_t n) {
-    TRI_ASSERT(n <= offset);
-    offset -= n;
+    if (n <= offset) {
+      // TRI_ASSERT(n <= offset);
+      offset -= n;
+    } else {
+      TRI_ASSERT(fullCount);
+      // We might have skip,(produce?),fullCount
+      // in a single call here.
+      offset = 0;
+    }
   }
 
   void didProduce(std::size_t n) {
@@ -136,6 +143,49 @@ constexpr AqlCall::Limit operator+(size_t n, AqlCall::Limit const& a) {
   return a + n;
 }
 
+constexpr bool operator==(AqlCall::Limit const& a, size_t n) {
+  return std::visit(overload{[n](size_t const& i) -> bool { return i == n; },
+                             [](auto inf) -> bool { return false; }},
+                    a);
+}
+
+constexpr bool operator==(size_t n, AqlCall::Limit const& a) { return a == n; }
+
+constexpr bool operator==(AqlCall::Limit const& a,
+                          arangodb::aql::AqlCall::Infinity const& n) {
+  return std::visit(overload{[](size_t const& i) -> bool { return false; },
+                             [](auto inf) -> bool { return true; }},
+                    a);
+}
+
+constexpr bool operator==(arangodb::aql::AqlCall::Infinity const& n,
+                          AqlCall::Limit const& a) {
+  return a == n;
+}
+
+constexpr bool operator==(AqlCall::Limit const& a, AqlCall::Limit const& b) {
+  return std::visit(overload{[&b](size_t const& i) -> bool { return i == b; },
+                             [&b](auto inf) -> bool { return inf == b; }},
+                    a);
+}
+
+inline std::ostream& operator<<(std::ostream& out,
+                                const arangodb::aql::AqlCall::Limit& limit) {
+  return std::visit(arangodb::overload{[&out](size_t const& i) -> std::ostream& {
+                                         return out << i;
+                                       },
+                                       [&out](arangodb::aql::AqlCall::Infinity const&) -> std::ostream& {
+                                         return out << "unlimited";
+                                       }},
+                    limit);
+}
+
+inline std::ostream& operator<<(std::ostream& out, const arangodb::aql::AqlCall& call) {
+  return out << "skip: " << call.getOffset() << " softLimit: " << call.softLimit
+             << " hardLimit: " << call.hardLimit
+             << " fullCount: " << std::boolalpha << call.fullCount;
+}
+
 }  // namespace aql
 }  // namespace arangodb
 
diff --git a/arangod/Aql/AqlItemBlockInputRange.cpp b/arangod/Aql/AqlItemBlockInputRange.cpp
index 7147a1ed7898..f8e9cef032b6 100644
--- a/arangod/Aql/AqlItemBlockInputRange.cpp
+++ b/arangod/Aql/AqlItemBlockInputRange.cpp
@@ -49,6 +49,10 @@ AqlItemBlockInputRange::AqlItemBlockInputRange(ExecutorState state,
   TRI_ASSERT(index <= _block->size());
 }
 
+SharedAqlItemBlockPtr AqlItemBlockInputRange::getBlock() const noexcept {
+  return _block;
+}
+
 bool AqlItemBlockInputRange::hasDataRow() const noexcept {
   return isIndexValid(_rowIndex) && !isShadowRowAtIndex(_rowIndex);
 }
diff --git a/arangod/Aql/AqlItemBlockInputRange.h b/arangod/Aql/AqlItemBlockInputRange.h
index abe4a1fef316..42de49fbb586 100644
--- a/arangod/Aql/AqlItemBlockInputRange.h
+++ b/arangod/Aql/AqlItemBlockInputRange.h
@@ -40,6 +40,8 @@ class AqlItemBlockInputRange {
   AqlItemBlockInputRange(ExecutorState, arangodb::aql::SharedAqlItemBlockPtr&&,
                          std::size_t startIndex, std::size_t endIndex) noexcept;
 
+  arangodb::aql::SharedAqlItemBlockPtr getBlock() const noexcept;
+
   ExecutorState upstreamState() const noexcept;
   bool upstreamHasMore() const noexcept;
 
diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index 441fe49f92ee..6f553bad1505 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -137,9 +137,27 @@ CREATE_HAS_MEMBER_CHECK(skipRowsRange, hasSkipRowsRange);
  * Determine whether we execute new style or old style skips, i.e. pre or post shadow row introduction
  * TODO: This should be removed once all executors and fetchers are ported to the new style.
  */
+
+#ifdef ARANGODB_USE_GOOGLE_TESTS
+// Forward declaration of Test Executors.
+// only used as long as isNewStyleExecutor is required.
+namespace arangodb {
+namespace aql {
+class TestLambdaExecutor;
+
+class TestLambdaSkipExecutor;
+}  // namespace aql
+}  // namespace arangodb
+#endif
+
 template <class Executor>
 static bool constexpr isNewStyleExecutor() {
-  return std::is_same<Executor, FilterExecutor>::value;
+  return
+#ifdef ARANGODB_USE_GOOGLE_TESTS
+      std::is_same_v<Executor, TestLambdaExecutor> ||
+      std::is_same_v<Executor, TestLambdaSkipExecutor> ||
+#endif
+      std::is_same_v<Executor, FilterExecutor>;
 }
 
 template <class Executor>
@@ -156,7 +174,8 @@ ExecutionBlockImpl<Executor>::ExecutionBlockImpl(ExecutionEngine* engine,
       _outputItemRow(),
       _query(*engine->getQuery()),
       _state(InternalState::FETCH_DATA),
-      _lastRange{ExecutorState::HASMORE} {
+      _lastRange{ExecutorState::HASMORE},
+      _hasUsedDataRangeBlock{false} {
   // already insert ourselves into the statistics results
   if (_profile >= PROFILE_LEVEL_BLOCKS) {
     _engine->_stats.nodes.try_emplace(node->id(), ExecutionStats::Node());
@@ -314,6 +333,21 @@ std::pair<ExecutionState, SharedAqlItemBlockPtr> ExecutionBlockImpl<Executor>::g
 template <class Executor>
 std::unique_ptr<OutputAqlItemRow> ExecutionBlockImpl<Executor>::createOutputRow(
     SharedAqlItemBlockPtr& newBlock, AqlCall&& call) {
+#ifdef ARANGODB_ENABLE_MAINTAINER_MODE
+  if (newBlock != nullptr) {
+    // Assert that the block has enough registers. This must be guaranteed by
+    // the register planning.
+    TRI_ASSERT(newBlock->getNrRegs() == _infos.numberOfOutputRegisters());
+    // Check that all output registers are empty.
+    for (auto const& reg : *_infos.getOutputRegisters()) {
+      for (size_t row = 0; row < newBlock->size(); row++) {
+        AqlValue const& val = newBlock->getValueReference(row, reg);
+        TRI_ASSERT(val.isEmpty());
+      }
+    }
+  }
+#endif
+
   if /* constexpr */ (Executor::Properties::allowsBlockPassthrough == BlockPassthrough::Enable) {
     return std::make_unique<OutputAqlItemRow>(newBlock, infos().getOutputRegisters(),
                                               infos().registersToKeep(),
@@ -626,8 +660,7 @@ void ExecutionBlockImpl<Executor>::traceExecuteBegin(AqlCallStack const& stack)
       auto const& call = stack.peek();
       LOG_TOPIC("1e717", INFO, Logger::QUERIES)
           << "[query#" << queryId << "] "
-          << "execute type=" << node->getTypeString()
-          << " offset=" << call.getOffset() << " limit= " << call.getLimit()
+          << "execute type=" << node->getTypeString() << " call= " << call
           << " this=" << (uintptr_t)this << " id=" << node->id();
     }
   }
@@ -945,16 +978,18 @@ struct RequestWrappedBlock<RequestWrappedBlockVariant::INPUTRESTRICTED> {
 template <class Executor>
 std::pair<ExecutionState, SharedAqlItemBlockPtr> ExecutionBlockImpl<Executor>::requestWrappedBlock(
     size_t nrItems, RegisterCount nrRegs) {
-  static_assert(Executor::Properties::allowsBlockPassthrough == BlockPassthrough::Disable ||
-                    !Executor::Properties::inputSizeRestrictsOutputSize,
-                "At most one of Properties::allowsBlockPassthrough or "
-                "Properties::inputSizeRestrictsOutputSize should be true for "
-                "each Executor");
-  static_assert(
-      (Executor::Properties::allowsBlockPassthrough == BlockPassthrough::Enable) ==
-          hasFetchBlockForPassthrough<Executor>::value,
-      "Executors should implement the method fetchBlockForPassthrough() iff "
-      "Properties::allowsBlockPassthrough is true");
+  if constexpr (!isNewStyleExecutor<Executor>()) {
+    static_assert(Executor::Properties::allowsBlockPassthrough == BlockPassthrough::Disable ||
+                      !Executor::Properties::inputSizeRestrictsOutputSize,
+                  "At most one of Properties::allowsBlockPassthrough or "
+                  "Properties::inputSizeRestrictsOutputSize should be true for "
+                  "each Executor");
+    static_assert((Executor::Properties::allowsBlockPassthrough == BlockPassthrough::Enable) ==
+                      hasFetchBlockForPassthrough<Executor>::value,
+                  "Executors should implement the method "
+                  "fetchBlockForPassthrough() iff "
+                  "Properties::allowsBlockPassthrough is true");
+  }
   static_assert(
       Executor::Properties::inputSizeRestrictsOutputSize ==
           hasExpectedNumberOfRows<Executor>::value,
@@ -988,18 +1023,38 @@ std::pair<ExecutionState, SharedAqlItemBlockPtr> ExecutionBlockImpl<Executor>::r
 template <class Executor>
 auto ExecutionBlockImpl<Executor>::allocateOutputBlock(AqlCall&& call)
     -> std::unique_ptr<OutputAqlItemRow> {
-  size_t blockSize = ExecutionBlock::DefaultBatchSize;
-  SharedAqlItemBlockPtr newBlock =
-      _engine->itemBlockManager().requestBlock(blockSize, _infos.numberOfOutputRegisters());
-  return createOutputRow(newBlock, std::move(call));
+  if constexpr (Executor::Properties::allowsBlockPassthrough == BlockPassthrough::Enable) {
+    SharedAqlItemBlockPtr newBlock{nullptr};
+    // Passthrough variant, re-use the block stored in InputRange
+    if (!_hasUsedDataRangeBlock) {
+      // In the pass through variant we have the contract that we work on a
+      // block all or nothing, so if we have used the block once, we cannot use it again
+      // however we cannot remove the _lastRange as it may contain additional information.
+      newBlock = _lastRange.getBlock();
+      _hasUsedDataRangeBlock = true;
+    }
+
+    return createOutputRow(newBlock, std::move(call));
+  } else {
+    // Non-Passthrough variant, we need to allocate the block ourselfs
+    size_t blockSize = ExecutionBlock::DefaultBatchSize;
+    SharedAqlItemBlockPtr newBlock =
+        _engine->itemBlockManager().requestBlock(blockSize, _infos.numberOfOutputRegisters());
+    return createOutputRow(newBlock, std::move(call));
+  }
 }
 
 template <class Executor>
 void ExecutionBlockImpl<Executor>::ensureOutputBlock(AqlCall&& call) {
-  if (_outputItemRow == nullptr || _outputItemRow->isFull()) {
+  if (_outputItemRow == nullptr || !_outputItemRow->isInitialized()) {
     _outputItemRow = allocateOutputBlock(std::move(call));
   } else {
     _outputItemRow->setCall(std::move(call));
+#ifdef ARANGODB_ENABLE_MAINTAINER_MODE
+// We only inject a new call into the output row.
+// In the passhrough variant we need to ensure that inputBlock and outputBlock stay identical
+// TODO add an external assertion for this.
+#endif
   }
 }
 
@@ -1011,7 +1066,15 @@ SharedAqlItemBlockPtr ExecutionBlockImpl<Executor>::requestBlock(size_t nrItems,
 }
 
 // TODO move me up
-enum ExecState { SKIP, PRODUCE, FULLCOUNT, UPSTREAM, SHADOWROWS, DONE };
+enum ExecState {
+  SKIP,
+  PRODUCE,
+  FASTFORWARD,
+  FULLCOUNT,
+  UPSTREAM,
+  SHADOWROWS,
+  DONE
+};
 
 // TODO clean me up
 namespace {
@@ -1029,6 +1092,10 @@ ExecState NextState(AqlCall const& call) {
     // then fullcount
     return ExecState::FULLCOUNT;
   }
+  if (call.hardLimit == 0) {
+    // We reached hardLimit, fast forward
+    return ExecState::FASTFORWARD;
+  }
   // now we are done.
   return ExecState::DONE;
 }
@@ -1046,10 +1113,10 @@ ExecState NextState(AqlCall const& call) {
 // GET_SOME: we just request rows from the executor and then discard
 //           them
 //
-enum class SkipRowsRangeVariant { FETCHER, EXECUTOR, GET_SOME };
+enum class SkipRowsRangeVariant { FETCHER, EXECUTOR };
 
-// This function is just copy&pasted from above to decide which variant of skip
-// is used for which executor.
+// This function is just copy&pasted from above to decide which variant of
+// skip is used for which executor.
 template <class Executor>
 static SkipRowsRangeVariant constexpr skipRowsType() {
   bool constexpr useFetcher =
@@ -1069,7 +1136,11 @@ static SkipRowsRangeVariant constexpr skipRowsType() {
   static_assert(!useFetcher || hasSkipRows<typename Executor::Fetcher>::value,
                 "Fetcher is chosen for skipping, but has not skipRows method!");
 
-  static_assert(useExecutor == (std::is_same<Executor, FilterExecutor>::value),
+  static_assert(useExecutor == (
+#ifdef ARANGODB_USE_GOOGLE_TESTS
+                                   std::is_same_v<Executor, TestLambdaSkipExecutor> ||
+#endif
+                                   std::is_same_v<Executor, FilterExecutor>),
                 "Unexpected executor for SkipVariants::EXECUTOR");
 
   // The LimitExecutor will not work correctly with SkipVariants::FETCHER!
@@ -1082,7 +1153,8 @@ static SkipRowsRangeVariant constexpr skipRowsType() {
   } else if (useFetcher) {
     return SkipRowsRangeVariant::FETCHER;
   } else {
-    return SkipRowsRangeVariant::GET_SOME;
+    TRI_ASSERT(false);
+    THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
   }
 }
 
@@ -1095,32 +1167,16 @@ std::tuple<ExecutorState, size_t, AqlCall> ExecutionBlockImpl<Executor>::execute
     AqlItemBlockInputRange& inputRange, AqlCall& call) {
   if constexpr (isNewStyleExecutor<Executor>()) {
     if constexpr (skipRowsType<Executor>() == SkipRowsRangeVariant::EXECUTOR) {
-      // If the executor has a method skipRowsRange, to skip outputs more
-      // efficiently than just producing them to subsequently discard them, then
-      // we use it
+      // If the executor has a method skipRowsRange, to skip outputs.
+      // Every non-passthrough executor needs to implement this.
       return _executor.skipRowsRange(inputRange, call);
     } else if constexpr (skipRowsType<Executor>() == SkipRowsRangeVariant::FETCHER) {
       // If we know that every input row produces exactly one output row (this
       // is a property of the executor), then we can just let the fetcher skip
       // the number of rows that we would like to skip.
-      return _rowFetcher.execute(call);
-    } else if constexpr (skipRowsType<Executor>() == SkipRowsRangeVariant::GET_SOME) {
-      // In all other cases, we skip by letting the executor produce rows, and
-      // then throw them away.
-
-      size_t toSkip = std::min(call.getOffset(), DefaultBatchSize);
-      AqlCall skipCall{};
-      skipCall.softLimit = toSkip;
-      skipCall.hardLimit = toSkip;
-      skipCall.offset = 0;
-
-      // we can't mess with _outputItemRow,
-      auto skipOutput = allocateOutputBlock(std::move(skipCall));
-      auto [state, stats, rescall] = _executor.produceRows(inputRange, *skipOutput);
-      auto skipped = skipOutput->numRowsWritten();
-
-      call.didSkip(skipped);
-      return std::make_tuple(state, skipped, rescall);
+      // Returning this will trigger to end in upstream state now, with the
+      // call that was handed it
+      return {inputRange.upstreamState(), 0, call};
     } else {
       static_assert(dependent_false<Executor>::value,
                     "This value of SkipRowsRangeVariant is not supported");
@@ -1134,52 +1190,73 @@ std::tuple<ExecutorState, size_t, AqlCall> ExecutionBlockImpl<Executor>::execute
   return std::make_tuple(ExecutorState::DONE, 0, call);
 }
 
-// This is the central function of an executor, and it acts like a
-// coroutine: It can be called multiple times and keeps state across
-// calls.
-//
-// The intended behaviour of this function is best described in terms of
-// a state machine; the possible states are the ExecStates
-// SKIP, PRODUCE, FULLCOUNT, UPSTREAM, SHADOWROWS, DONE
-//
-// SKIP       skipping rows. How rows are skipped is determined by
-//            the Executor that is used. See SkipVariants
-// PRODUCE    calls produceRows of the executor
-// FULLCOUNT
-// UPSTREAM   fetches rows from the upstream executor(s) to be processed by
-//            our executor.
-// SHADOWROWS process any shadow rows
-// DONE       processing is done
+/**
+ * @brief This is the central function of an executor, and it acts like a
+ * coroutine: It can be called multiple times and keeps state across
+ * calls.
+ *
+ * The intended behaviour of this function is best described in terms of
+ * a state machine; the possible states are the ExecStates
+ * SKIP, PRODUCE, FULLCOUNT, FASTFORWARD, UPSTREAM, SHADOWROWS, DONE
+ *
+ * SKIP       skipping rows. How rows are skipped is determined by
+ *            the Executor that is used. See SkipVariants
+ * PRODUCE    calls produceRows of the executor
+ * FULLCOUNT  again skipping rows. like skip, but will skip all rows
+ * FASTFORWARD like fullcount, but does not count skipped rows.
+ * UPSTREAM   fetches rows from the upstream executor(s) to be processed by
+ *            our executor.
+ * SHADOWROWS process any shadow rows
+ * DONE       processing of one output is done. We did handle offset / limit / fullCount without crossing BatchSize limits.
+ *            This state does not indicate that we are DONE with all input, we are just done with one walk through this statemachine.
+ *
+ * We progress within the states in the following way:
+ *   There is a nextState method that determines the next state based on the call, it can only lead to:
+ *   SKIP, PRODUCE, FULLCOUNT, FASTFORWAD, DONE
+ *
+ *   On the first call we will use nextState to get to our starting point.
+ *   After any of SKIP, PRODUCE, FULLCOUNT, FASTFORWAD, DONE We either go to
+ *   1. DONE (if output is full)
+ *   2. SHADOWROWS (if executor is done)
+ *   3. UPSTREAM if executor has More, (Invariant: input fully consumed)
+ *   4. NextState (if none of the above applies)
+ *
+ *   From SHADOWROWS we can only go to DONE
+ *   From UPSTREAM we go to NextState.
+ *
+ * @tparam Executor The Executor that will implement the logic of what needs to happen to the data
+ * @param stack The call stack of lower levels
+ * @return std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr>
+ *        ExecutionState: WAITING -> We wait for IO, secure state, return you will be called again
+ *        ExecutionState: HASMORE -> We still have data
+ *        ExecutionState: DONE -> We do not have any more data, do never call again
+ *        size_t -> Amount of documents skipped within this one call. (contains offset and fullCount)
+ *        SharedAqlItemBlockPtr -> The resulting data
+ */
 template <class Executor>
 std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr>
 ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
   if constexpr (isNewStyleExecutor<Executor>()) {
-    // Make sure there's a block allocated and set
-    // the call
-    ensureOutputBlock(stack.popCall());
+    AqlCall clientCall = stack.popCall();
 
     auto skipped = size_t{0};
 
-    TRI_ASSERT(_outputItemRow);
-
-    auto execState = ::NextState(_outputItemRow->getClientCall());
+    auto execState = ::NextState(clientCall);
 
     if (_lastRange.hasShadowRow()) {
-      // We have not been able to move all shadowRows into the output last time.
-      // Continue from there.
+      // We have not been able to move all shadowRows into the output last
+      // time. Continue from there.
       // TODO test if this works with COUNT COLLECT
       execState = ExecState::SHADOWROWS;
     }
 
     AqlCall executorRequest;
-    while (execState != ExecState::DONE && !_outputItemRow->allRowsUsed()) {
+    while (execState != ExecState::DONE) {
       switch (execState) {
         case ExecState::SKIP: {
-          auto const& clientCall = _outputItemRow->getClientCall();
-          auto [state, skippedLocal, call] =
-              executeSkipRowsRange(_lastRange, _outputItemRow->getModifiableClientCall());
+          auto [state, skippedLocal, call] = executeSkipRowsRange(_lastRange, clientCall);
           skipped += skippedLocal;
-
+          // The execute might have modified the client call.
           if (state == ExecutorState::DONE) {
             execState = ExecState::SHADOWROWS;
           } else if (clientCall.getOffset() > 0) {
@@ -1194,13 +1271,23 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
           break;
         }
         case ExecState::PRODUCE: {
-          auto const& clientCall = _outputItemRow->getClientCall();
+          // Make sure there's a block allocated and set
+          // the call
           TRI_ASSERT(clientCall.getLimit() > 0);
+          ensureOutputBlock(std::move(clientCall));
+          TRI_ASSERT(_outputItemRow);
+
           // Execute getSome
           auto const [state, stats, call] =
               _executor.produceRows(_lastRange, *_outputItemRow);
           _engine->_stats += stats;
-          if (state == ExecutorState::DONE) {
+
+          // Produce might have modified the clientCall
+          clientCall = _outputItemRow->getClientCall();
+
+          if (_outputItemRow->isInitialized() && _outputItemRow->allRowsUsed()) {
+            execState = ExecState::DONE;
+          } else if (state == ExecutorState::DONE) {
             execState = ExecState::SHADOWROWS;
           } else if (clientCall.getLimit() > 0 && !_lastRange.hasDataRow()) {
             TRI_ASSERT(_upstreamState != ExecutionState::DONE);
@@ -1213,9 +1300,38 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
           }
           break;
         }
+        case ExecState::FASTFORWARD: {
+          // We can either do FASTFORWARD or FULLCOUNT, difference is that
+          // fullcount counts what is produced now, FASTFORWARD simply drops
+          TRI_ASSERT(!clientCall.needsFullCount());
+          // We can drop all dataRows from upstream
+
+          while (_lastRange.hasDataRow()) {
+            auto [state, row] = _lastRange.nextDataRow();
+            TRI_ASSERT(row.isInitialized());
+          }
+          if (_lastRange.upstreamState() == ExecutorState::DONE) {
+            execState = ExecState::SHADOWROWS;
+          } else {
+            // We need to request more, simply send hardLimit 0 upstream
+            executorRequest = AqlCall{};
+            executorRequest.hardLimit = 0;
+            execState = ExecState::UPSTREAM;
+          }
+          break;
+        }
         case ExecState::FULLCOUNT: {
-          TRI_ASSERT(false);
-          // TODO: wat.
+          auto [state, skippedLocal, call] = executeSkipRowsRange(_lastRange, clientCall);
+          skipped += skippedLocal;
+
+          if (state == ExecutorState::DONE) {
+            execState = ExecState::SHADOWROWS;
+          } else {
+            // We need to request more
+            executorRequest = call;
+            execState = ExecState::UPSTREAM;
+          }
+          break;
         }
         case ExecState::UPSTREAM: {
           // If this triggers the executors produceRows function has returned
@@ -1231,11 +1347,12 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
             TRI_ASSERT(skipped == 0);
             return {_upstreamState, 0, nullptr};
           }
+          // We have a new range, passthrough can use this range.
+          _hasUsedDataRangeBlock = false;
           skipped += skippedLocal;
-          ensureOutputBlock(_outputItemRow->stealClientCall());
-          // Do we need to call it?
-          // clientCall.didSkip(skippedLocal);
-          execState = ::NextState(_outputItemRow->getClientCall());
+          // We skipped through passthroug, so count that a skip was solved.
+          clientCall.didSkip(skippedLocal);
+          execState = ::NextState(clientCall);
           break;
         }
         case ExecState::SHADOWROWS: {
@@ -1248,7 +1365,12 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
           if (_lastRange.hasShadowRow()) {
             auto const& [state, shadowRow] = _lastRange.nextShadowRow();
             TRI_ASSERT(shadowRow.isInitialized());
+            ensureOutputBlock(std::move(clientCall));
+            TRI_ASSERT(_outputItemRow);
+            TRI_ASSERT(_outputItemRow->isInitialized());
+
             _outputItemRow->copyRow(shadowRow);
+
             if (shadowRow.isRelevant()) {
               // We found a relevant shadow Row.
               // We need to reset the Executor
@@ -1256,7 +1378,10 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
             }
             TRI_ASSERT(_outputItemRow->produced());
             _outputItemRow->advanceRow();
-            if (state == ExecutorState::DONE) {
+            clientCall = _outputItemRow->getClientCall();
+            if (_outputItemRow->allRowsUsed()) {
+              execState = ExecState::DONE;
+            } else if (state == ExecutorState::DONE) {
               if (_lastRange.hasDataRow()) {
                 // TODO this state is invalid, and can just show up now if we exclude SKIP
                 execState = ExecState::PRODUCE;
@@ -1278,8 +1403,9 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
           TRI_ASSERT(false);
       }
     }
-
-    auto outputBlock = _outputItemRow->stealBlock();
+    // If we do not have an output, we simply return a nullptr here.
+    auto outputBlock = _outputItemRow != nullptr ? _outputItemRow->stealBlock()
+                                                 : SharedAqlItemBlockPtr{nullptr};
     // This is not strictly necessary here, as we shouldn't be called again
     // after DONE.
     _outputItemRow.reset();
diff --git a/arangod/Aql/ExecutionBlockImpl.h b/arangod/Aql/ExecutionBlockImpl.h
index 667957491c03..064b087574f3 100644
--- a/arangod/Aql/ExecutionBlockImpl.h
+++ b/arangod/Aql/ExecutionBlockImpl.h
@@ -289,6 +289,12 @@ class ExecutionBlockImpl final : public ExecutionBlock {
   size_t _skipped{};
 
   DataRange _lastRange;
+
+  // Only used in passthrough variant.
+  // We track if we have reference the range's block
+  // into an output block.
+  // If so we are not allowed to reuse it.
+  bool _hasUsedDataRangeBlock;
 };
 
 }  // namespace arangodb::aql
diff --git a/arangod/Aql/OutputAqlItemRow.cpp b/arangod/Aql/OutputAqlItemRow.cpp
index c5617e7aa71b..a94ab5f72ee4 100644
--- a/arangod/Aql/OutputAqlItemRow.cpp
+++ b/arangod/Aql/OutputAqlItemRow.cpp
@@ -66,7 +66,10 @@ OutputAqlItemRow::OutputAqlItemRow(
       _setBaseIndexNotUsed(true),
 #endif
       _allowSourceRowUninitialized(false) {
-  TRI_ASSERT(_block != nullptr);
+}
+
+bool OutputAqlItemRow::isInitialized() const noexcept {
+  return _block != nullptr;
 }
 
 template <class ItemRowType>
diff --git a/arangod/Aql/OutputAqlItemRow.h b/arangod/Aql/OutputAqlItemRow.h
index 66b0a513e9ef..74173815ac32 100644
--- a/arangod/Aql/OutputAqlItemRow.h
+++ b/arangod/Aql/OutputAqlItemRow.h
@@ -64,6 +64,8 @@ class OutputAqlItemRow {
   OutputAqlItemRow(OutputAqlItemRow&&) = delete;
   OutputAqlItemRow& operator=(OutputAqlItemRow&&) = delete;
 
+  bool isInitialized() const noexcept;
+
   // Clones the given AqlValue
   template <class ItemRowType>
   void cloneValueInto(RegisterId registerId, ItemRowType const& sourceRow,
@@ -137,7 +139,7 @@ class OutputAqlItemRow {
    *        the left-over space for ShadowRows.
    */
   [[nodiscard]] bool allRowsUsed() const {
-    return block().size() <= _baseIndex;
+    return _block == nullptr || block().size() <= _baseIndex;
   }
 
   /**
@@ -152,6 +154,9 @@ class OutputAqlItemRow {
    *        passed from ExecutionBlockImpl.
    */
   [[nodiscard]] size_t numRowsLeft() const {
+    if (_block == nullptr) {
+      return 0;
+    }
     return (std::min)(block().size() - _baseIndex, _call.getLimit());
   }
 
diff --git a/tests/Aql/ExecutionBlockImplTest.cpp b/tests/Aql/ExecutionBlockImplTest.cpp
index 62a68a8c7224..fef41d9d983b 100644
--- a/tests/Aql/ExecutionBlockImplTest.cpp
+++ b/tests/Aql/ExecutionBlockImplTest.cpp
@@ -26,15 +26,22 @@
 #include "gtest/gtest.h"
 
 #include "AqlItemBlockHelper.h"
+#include "Mocks/Servers.h"
 #include "TestEmptyExecutorHelper.h"
 #include "TestExecutorHelper.h"
+#include "TestLambdaExecutor.h"
 #include "WaitingExecutionBlockMock.h"
 #include "fakeit.hpp"
 
+#include "Aql/AqlCallStack.h"
 #include "Aql/AqlItemBlock.h"
+#include "Aql/AqlItemBlockSerializationFormat.h"
+#include "Aql/ConstFetcher.h"
 #include "Aql/ExecutionBlockImpl.h"
 #include "Aql/ExecutionEngine.h"
+#include "Aql/IdExecutor.h"
 #include "Aql/Query.h"
+#include "Aql/RegisterPlan.h"
 #include "Aql/SingleRowFetcher.h"
 #include "Transaction/Context.h"
 #include "Transaction/Methods.h"
@@ -46,6 +53,9 @@ namespace arangodb {
 namespace tests {
 namespace aql {
 
+using LambdaExePassThrough = TestLambdaExecutor;
+using LambdaExe = TestLambdaSkipExecutor;
+
 // This test is supposed to only test getSome return values,
 // it is not supposed to test the fetch logic!
 
@@ -391,6 +401,1168 @@ TEST_F(ExecutionBlockImplTest,
   ASSERT_EQ(block, nullptr);
 }
 
+/**
+ * @brief Shared Test case initializer to test the execute API
+ *        of the ExecutionBlockImpl implementation.
+ *        This base class creates a server with a faked AQL query
+ *        where we set our test node into.
+ *        Also provides helper methods to create the building blocks of the query.
+ */
+class SharedExecutionBlockImplTest {
+ protected:
+  mocks::MockAqlServer server{};
+  ResourceMonitor monitor{};
+  std::unique_ptr<arangodb::aql::Query> fakedQuery{server.createFakeQuery()};
+  std::vector<std::unique_ptr<ExecutionNode>> _execNodes;
+
+  SharedExecutionBlockImplTest() {
+    auto engine =
+        std::make_unique<ExecutionEngine>(*fakedQuery, SerializationFormat::SHADOWROWS);
+    fakedQuery->setEngine(engine.release());
+  }
+
+  /**
+   * @brief Creates and manages a ExecutionNode.
+   *        These nodes can be used to create the Executors
+   *        Caller does not need to manage the memory.
+   *
+   * @return ExecutionNode* Pointer to a dummy ExecutionNode. Memory is managed, do not delete.
+   */
+  ExecutionNode* generateNodeDummy() {
+    auto dummy = std::make_unique<SingletonNode>(fakedQuery->plan(), _execNodes.size());
+    auto res = dummy.get();
+    _execNodes.emplace_back(std::move(dummy));
+    return res;
+  }
+
+  /**
+   * @brief Prepare the executor infos for a LambdaExecutor with passthrough.
+   *
+   * @param call produceRows implementation that should be used
+   * @param inputRegisters highest input register index. RegisterPlan::MaxRegisterId (default) describes there is no input. call is allowed to read any register <= inputRegisters.
+   * @param outputRegisters highest output register index. RegisterPlan::MaxRegisterId (default) describes there is no output. call is allowed to write any inputRegisters < register <= outputRegisters. Invariant inputRegisters <= outputRegisters
+   * @return LambdaExecutorInfos Infos to build the Executor.
+   */
+  LambdaExecutorInfos makeInfos(ProduceCall call,
+                                RegisterId inputRegisters = RegisterPlan::MaxRegisterId,
+                                RegisterId outputRegisters = RegisterPlan::MaxRegisterId) {
+    if (inputRegisters != RegisterPlan::MaxRegisterId) {
+      EXPECT_LE(inputRegisters, outputRegisters);
+      // We cannot have no output registers here.
+      EXPECT_LT(outputRegisters, RegisterPlan::MaxRegisterId);
+    } else if (outputRegisters != RegisterPlan::MaxRegisterId) {
+      // Special case: we do not have input registers, but need an output register.
+      // For now we only allow a single output register, but actually we could leverage this restriction if necessary.
+      EXPECT_EQ(outputRegisters, 0);
+    }
+
+    auto readAble = make_shared_unordered_set();
+    auto writeAble = make_shared_unordered_set();
+    auto registersToKeep = std::unordered_set<RegisterId>{};
+    if (inputRegisters != RegisterPlan::MaxRegisterId) {
+      for (RegisterId i = 0; i <= inputRegisters; ++i) {
+        readAble->emplace(i);
+        registersToKeep.emplace(i);
+      }
+      for (RegisterId i = inputRegisters + 1; i <= outputRegisters; ++i) {
+        writeAble->emplace(i);
+      }
+    } else if (outputRegisters != RegisterPlan::MaxRegisterId) {
+      for (RegisterId i = 0; i <= outputRegisters; ++i) {
+        writeAble->emplace(i);
+      }
+    }
+    RegisterId regsToRead =
+        (inputRegisters == RegisterPlan::MaxRegisterId) ? 0 : inputRegisters + 1;
+    RegisterId regsToWrite =
+        (outputRegisters == RegisterPlan::MaxRegisterId) ? 0 : outputRegisters + 1;
+    return LambdaExecutorInfos(readAble, writeAble, regsToRead, regsToWrite, {},
+                               registersToKeep, std::move(call));
+  }
+
+  /**
+   * @brief Prepare the executor infos for a LambdaExecutor with implemented skip.
+   *
+   * @param call produceRows implementation that should be used
+   * @param skipCall skipRowsRange implementation that should be used
+   * @param inputRegisters highest input register index. RegisterPlan::MaxRegisterId (default) describes there is no input. call is allowed to read any register <= inputRegisters.
+   * @param outputRegisters highest output register index. RegisterPlan::MaxRegisterId (default) describes there is no output. call is allowed to write any inputRegisters < register <= outputRegisters. Invariant inputRegisters <= outputRegisters
+   * @return LambdaExecutorInfos Infos to build the Executor.
+   */
+  LambdaSkipExecutorInfos makeSkipInfos(ProduceCall call, SkipCall skipCall,
+                                        RegisterId inputRegisters = RegisterPlan::MaxRegisterId,
+                                        RegisterId outputRegisters = RegisterPlan::MaxRegisterId) {
+    if (inputRegisters != RegisterPlan::MaxRegisterId) {
+      EXPECT_LE(inputRegisters, outputRegisters);
+      // We cannot have no output registers here.
+      EXPECT_LT(outputRegisters, RegisterPlan::MaxRegisterId);
+    } else if (outputRegisters != RegisterPlan::MaxRegisterId) {
+      // Special case: we do not have input registers, but need an output register.
+      // For now we only allow a single output register, but actually we could leverage this restriction if necessary.
+      EXPECT_EQ(outputRegisters, 0);
+    }
+
+    auto readAble = make_shared_unordered_set();
+    auto writeAble = make_shared_unordered_set();
+    auto registersToKeep = std::unordered_set<RegisterId>{};
+    if (inputRegisters != RegisterPlan::MaxRegisterId) {
+      for (RegisterId i = 0; i <= inputRegisters; ++i) {
+        readAble->emplace(i);
+        registersToKeep.emplace(i);
+      }
+      for (RegisterId i = inputRegisters + 1; i <= outputRegisters; ++i) {
+        writeAble->emplace(i);
+      }
+    } else if (outputRegisters != RegisterPlan::MaxRegisterId) {
+      for (RegisterId i = 0; i <= outputRegisters; ++i) {
+        writeAble->emplace(i);
+      }
+    }
+    RegisterId regsToRead =
+        (inputRegisters == RegisterPlan::MaxRegisterId) ? 0 : inputRegisters + 1;
+    RegisterId regsToWrite =
+        (outputRegisters == RegisterPlan::MaxRegisterId) ? 0 : outputRegisters + 1;
+    return LambdaSkipExecutorInfos(readAble, writeAble, regsToRead, regsToWrite,
+                                   {}, registersToKeep, std::move(call),
+                                   std::move(skipCall));
+  }
+  /**
+   * @brief Create a Singleton ExecutionBlock. Just like the original one in the
+   * query. it is already initialized and ready to use.
+   *
+   * @return std::unique_ptr<ExecutionBlock> The singleton ExecutionBlock.
+   */
+  std::unique_ptr<ExecutionBlock> createSingleton() {
+    auto res = std::make_unique<ExecutionBlockImpl<IdExecutor<ConstFetcher>>>(
+        fakedQuery->engine(), generateNodeDummy(), IdExecutorInfos{0, {}, {}});
+    InputAqlItemRow inputRow{CreateInvalidInputRowHint{}};
+    auto const [state, result] = res->initializeCursor(inputRow);
+    EXPECT_EQ(state, ExecutionState::DONE);
+    EXPECT_TRUE(result.ok());
+    return res;
+  }
+
+  /**
+   * @brief Generate a generic produce call with the following behaviour:
+   *        1. It does not produce any output, it just validates that it gets expected input
+   *        2. Return the input state, along with an unlimited produce call.
+   *
+   *        In addition we have the following assertions:
+   *        1. Whenever this produce is called, it asserts that is called with the expectedCall
+   *        2. This call has been called less then 10 times (emergency bailout against infinite loop)
+   *        3. If there is an input row, this row is valid.
+   *        4. If called with empty input, we still have exactly numRowsLeftNoInput many rows free in the output
+   *        5. If called with input, we still have exactly numRowsLeftWithInput many rows free in the output
+   *
+   * @param nrCalls Reference! Will count how many times this function was invoked.
+   * @param expectedCall The call that is expected on every invocation of this function.
+   * @param numRowsLeftNoInput The number of available rows in the output, if we have empty input (cold start)
+   * @param numRowsLeftWithInput The number of available rows in the output, if we have given an input
+   * @return ProduceCall The call ready to hand over to the LambdaExecutorInfos
+   */
+  ProduceCall generateProduceCall(size_t& nrCalls, AqlCall expectedCall,
+                                  size_t numRowsLeftNoInput = ExecutionBlock::DefaultBatchSize,
+                                  size_t numRowsLeftWithInput = ExecutionBlock::DefaultBatchSize) {
+    return [&nrCalls, numRowsLeftNoInput, numRowsLeftWithInput,
+            expectedCall](AqlItemBlockInputRange& input, OutputAqlItemRow& output)
+               -> std::tuple<ExecutorState, LambdaExe::Stats, AqlCall> {
+      auto const& clientCall = output.getClientCall();
+      if (nrCalls > 10) {
+        EXPECT_TRUE(false);
+        // This is emergency bailout, we ask way to often here
+        THROW_ARANGO_EXCEPTION(TRI_ERROR_INTERNAL);
+      }
+      nrCalls++;
+      if (input.hasDataRow()) {
+        // We expact only the empty initial row, so just consume it
+        auto const [state, row] = input.nextDataRow();
+        EXPECT_EQ(state, ExecutorState::DONE);
+        EXPECT_TRUE(row.isInitialized());
+        EXPECT_EQ(output.numRowsLeft(), numRowsLeftWithInput);
+      } else {
+        EXPECT_EQ(output.numRowsLeft(), numRowsLeftNoInput);
+      }
+      EXPECT_EQ(clientCall.getOffset(), expectedCall.getOffset());
+      EXPECT_EQ(clientCall.softLimit, expectedCall.softLimit);
+      EXPECT_EQ(clientCall.hardLimit, expectedCall.hardLimit);
+      EXPECT_EQ(clientCall.needsFullCount(), expectedCall.needsFullCount());
+
+      NoStats stats{};
+      AqlCall call{};
+      return {input.upstreamState(), stats, call};
+    };
+  }
+
+  /**
+   * @brief Generate a generic skip call with the following behaviour:
+   *        1. For every given input: skip it, and count skip as one.
+   *        2. Do never skip more then offset()
+   *        3. Return the input state, the locally skipped number, a call with softLimit = offset + softLimit, hardLimit = offset + hardLimit
+   *
+   *        In addition we have the following assertions:
+   *        1. Whenever this produce is called, it asserts that is called with the expectedCall
+   *        2. This call has been called less then 10 times (emergency bailout against infinite loop)
+   *        3. If there is an input row, this row is valid.
+   *
+   * @param nrCalls Reference! Will count how many times this function was invoked.
+   * @param expectedCall The call that is expected on every invocation of this function.
+   * @return SkipCall The call ready to hand over to the LambdaExecutorInfos
+   */
+  SkipCall generateSkipCall(size_t& nrCalls, AqlCall expectedCall) {
+    return [&nrCalls,
+            expectedCall](AqlItemBlockInputRange& inputRange,
+                          AqlCall& clientCall) -> std::tuple<ExecutorState, size_t, AqlCall> {
+      if (nrCalls > 10) {
+        EXPECT_TRUE(false);
+        // This is emergency bailout, we ask way to often here
+        THROW_ARANGO_EXCEPTION(TRI_ERROR_INTERNAL);
+      }
+      nrCalls++;
+      EXPECT_EQ(clientCall.getOffset(), expectedCall.getOffset());
+      EXPECT_EQ(clientCall.softLimit, expectedCall.softLimit);
+      EXPECT_EQ(clientCall.hardLimit, expectedCall.hardLimit);
+      EXPECT_EQ(clientCall.needsFullCount(), expectedCall.needsFullCount());
+      size_t localSkip = 0;
+      while (inputRange.hasDataRow() && clientCall.getOffset() > localSkip) {
+        auto const& [state, input] = inputRange.nextDataRow();
+        EXPECT_TRUE(input.isInitialized());
+        localSkip++;
+      }
+      clientCall.didSkip(localSkip);
+
+      AqlCall upstreamCall = clientCall;
+      upstreamCall.softLimit = clientCall.getOffset() + clientCall.softLimit;
+      upstreamCall.hardLimit = clientCall.getOffset() + clientCall.hardLimit;
+      upstreamCall.offset = 0;
+
+      return {inputRange.upstreamState(), localSkip, upstreamCall};
+    };
+  }
+
+  /**
+   * @brief Generate a call that failes whenever it is actually called.
+   *        Used to check that SKIP is not invoked
+   *
+   * @return SkipCall The always failing call to be used for the executor.
+   */
+  SkipCall generateNeverSkipCall() {
+    return [](AqlItemBlockInputRange& input,
+              AqlCall& call) -> std::tuple<ExecutorState, size_t, AqlCall> {
+      // Should not be called here. No Skip!
+      EXPECT_TRUE(false);
+      THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
+    };
+  }
+
+  /**
+   * @brief Generate a call that failes whenever it is actually called.
+   *        Used to check that produce is not invoked
+   *
+   * @return ProduceCall The always failing call to be used for the executor.
+   */
+  ProduceCall generateNeverProduceCall() {
+    return [](AqlItemBlockInputRange& input,
+              OutputAqlItemRow& output) -> std::tuple<ExecutorState, LambdaExe::Stats, AqlCall> {
+      // Should not be called here. No limit, only skip!
+      EXPECT_TRUE(false);
+      THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
+    };
+  }
+};
+
+/**
+ * @brief Test the internal statemachine of the ExecutionBlockImpl.
+ *        These test-cases focus on a single executor and assert that this Executor is called
+ *        correctly given an input. None of the test is focussed on the generated output. That is done in the IntegrationTest part
+ *        This is a parameterized test and tests passthrough (true) and non-passthrough variants (false)
+ */
+class ExecutionBlockImplExecuteSpecificTest : public SharedExecutionBlockImplTest,
+                                              public testing::TestWithParam<bool> {
+ protected:
+  /**
+   * @brief Generic test runner. Creates Lambda Executors, and returns ExecutionBlockImpl.execute(call),
+   *
+   * @param prod The Produce call that should be used within the Lambda Executor
+   * @param skip The Skip call that should be used wiithin the Lambda Executor (only used for non-passthrough)
+   * @param call The AqlCall that should be applied on the Executors.
+   * @return std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr>  Response of execute(call);
+   */
+  auto runTest(ProduceCall& prod, SkipCall& skip, AqlCall call)
+      -> std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> {
+    AqlCallStack stack{std::move(call)};
+    auto singleton = createSingleton();
+    if (GetParam()) {
+      ExecutionBlockImpl<LambdaExePassThrough> testee{fakedQuery->engine(),
+                                                      generateNodeDummy(),
+                                                      makeInfos(prod)};
+      testee.addDependency(singleton.get());
+      return testee.execute(stack);
+    } else {
+      ExecutionBlockImpl<LambdaExe> testee{fakedQuery->engine(), generateNodeDummy(),
+                                           makeSkipInfos(prod, skip)};
+      testee.addDependency(singleton.get());
+      return testee.execute(stack);
+    }
+  }
+};
+
+// Test a default call: no skip, no limits.
+TEST_P(ExecutionBlockImplExecuteSpecificTest, test_toplevel_unlimited_call) {
+  AqlCall fullCall{};
+  size_t nrCalls = 0;
+
+  // Note here: passthrough only reserves the correct amount of rows.
+  // As we fetch from a singleton (1 row) we will have 0 rows (cold-start) and then exactly 1 row
+  // in the executor.
+  // Non passthrough does not make an estimate for this, so Batchsize is used.
+  ProduceCall execImpl = GetParam() ? generateProduceCall(nrCalls, fullCall, 0, 1)
+                                    : generateProduceCall(nrCalls, fullCall);
+  SkipCall skipCall = generateNeverSkipCall();
+  auto [state, skipped, block] = runTest(execImpl, skipCall, fullCall);
+
+  EXPECT_EQ(state, ExecutionState::DONE);
+  EXPECT_EQ(skipped, 0);
+  EXPECT_EQ(block, nullptr);
+  // Once with empty, once with the line by Singleton
+  EXPECT_EQ(nrCalls, 2);
+}
+
+// Test a softlimit call: no skip, given softlimit.
+TEST_P(ExecutionBlockImplExecuteSpecificTest, test_toplevel_softlimit_call) {
+  AqlCall fullCall{};
+  fullCall.softLimit = 20;
+  size_t nrCalls = 0;
+
+  // Note here: passthrough only reserves the correct amount of rows.
+  // As we fetch from a singleton (1 row) we will have 0 rows (cold-start) and then exactly 1 row
+  // in the executor.
+  // Non passthrough the available lines (visible to executor) are only the given soft limit.
+  ProduceCall execImpl = GetParam() ? generateProduceCall(nrCalls, fullCall, 0, 1)
+                                    : generateProduceCall(nrCalls, fullCall, 20, 20);
+  SkipCall skipCall = generateNeverSkipCall();
+  auto [state, skipped, block] = runTest(execImpl, skipCall, fullCall);
+
+  EXPECT_EQ(state, ExecutionState::DONE);
+  EXPECT_EQ(skipped, 0);
+  EXPECT_EQ(block, nullptr);
+  // Once with empty, once with the line by Singleton
+  EXPECT_EQ(nrCalls, 2);
+}
+
+// Test a hardlimit call: no skip, given hardlimit.
+TEST_P(ExecutionBlockImplExecuteSpecificTest, test_toplevel_hardlimit_call) {
+  AqlCall fullCall{};
+  fullCall.hardLimit = 20;
+  size_t nrCalls = 0;
+
+  // Note here: passthrough only reserves the correct amount of rows.
+  // As we fetch from a singleton (1 row) we will have 0 rows (cold-start) and then exactly 1 row
+  // in the executor.
+  // Non passthrough the available lines (visible to executor) are only the given soft limit.
+  ProduceCall execImpl = GetParam() ? generateProduceCall(nrCalls, fullCall, 0, 1)
+                                    : generateProduceCall(nrCalls, fullCall, 20, 20);
+  SkipCall skipCall = generateNeverSkipCall();
+  auto [state, skipped, block] = runTest(execImpl, skipCall, fullCall);
+
+  EXPECT_EQ(state, ExecutionState::DONE);
+  EXPECT_EQ(skipped, 0);
+  EXPECT_EQ(block, nullptr);
+  // Once with empty, once with the line by Singleton
+  EXPECT_EQ(nrCalls, 2);
+}
+
+// Test a skip call: given skip, no limits.
+TEST_P(ExecutionBlockImplExecuteSpecificTest, test_toplevel_offset_call) {
+  AqlCall fullCall{};
+  fullCall.offset = 20;
+  size_t nrCalls = 0;
+
+  // Note here: We skip everything, no produce should be called
+  ProduceCall execImpl = generateNeverProduceCall();
+  SkipCall skipCall = generateSkipCall(nrCalls, fullCall);
+
+  auto [state, skipped, block] = runTest(execImpl, skipCall, fullCall);
+
+  EXPECT_EQ(state, ExecutionState::DONE);
+  EXPECT_EQ(skipped, 1);
+  if (GetParam()) {
+    // Do never call skip, pass through
+    EXPECT_EQ(nrCalls, 0);
+  } else {
+    // Call once without input, second with input
+    EXPECT_EQ(nrCalls, 2);
+  }
+
+  EXPECT_EQ(block, nullptr);
+}
+
+// Test a skip call: given skip, limit: 0 (formerly known as skipSome)
+TEST_P(ExecutionBlockImplExecuteSpecificTest, test_toplevel_offset_only_call) {
+  AqlCall fullCall{};
+  fullCall.offset = 20;
+  // This test simulates a simple "skipSome" call on the old API.
+  // It is releveant in any intermediate state.
+  fullCall.softLimit = 0;
+  size_t nrCalls = 0;
+
+  // Note here: We skip everything, no produce should be called
+  ProduceCall execImpl = generateNeverProduceCall();
+  SkipCall skipCall = generateSkipCall(nrCalls, fullCall);
+
+  auto [state, skipped, block] = runTest(execImpl, skipCall, fullCall);
+
+  EXPECT_EQ(state, ExecutionState::DONE);
+  EXPECT_EQ(skipped, 1);
+  if (GetParam()) {
+    // Do never call skip, pass through
+    EXPECT_EQ(nrCalls, 0);
+  } else {
+    // Call once without input, second with input
+    EXPECT_EQ(nrCalls, 2);
+  }
+
+  EXPECT_EQ(block, nullptr);
+}
+
+INSTANTIATE_TEST_CASE_P(ExecutionBlockImplExecuteTest,
+                        ExecutionBlockImplExecuteSpecificTest, ::testing::Bool());
+
+enum class CallAsserterState { INITIAL, SKIP, GET, COUNT, DONE };
+
+/**
+ * @brief Base class for call assertions.
+ * Every asserter holds an internal statemachine.
+ * And is called on every invocation of the LambdaFunction.
+ * According to it's internal machine, it asserts that the input Call
+ * Is expected in this situation.
+ *
+ */
+struct BaseCallAsserter {
+  // Actual number of calls for this machine
+  size_t call = 0;
+  // Maximum allowed calls to this machine, we assert that call <= maxCall
+  size_t maxCall = 0;
+  // Internal state
+  CallAsserterState state = CallAsserterState::DONE;
+  // The expected outer call, the machine needs to extract relevant parts
+  AqlCall const expected;
+
+  /**
+   * @brief Construct a new Base Call Asserter object
+   *
+   * @param expectedCall The given outer call. As we play several rounds (e.g. one call for skip one for get) the asserter needs to decompose this call
+   */
+  explicit BaseCallAsserter(AqlCall const& expectedCall)
+      : expected{expectedCall} {}
+
+  /**
+   * @brief Test if we need to expect a skip phase
+   *
+   * @return true Yes we have skip
+   * @return false No we do not have skip
+   */
+  auto hasSkip() const -> bool { return expected.getOffset() > 0; }
+  /**
+   * @brief Test if we need to expect a produce phase
+   *
+   * @return true
+   * @return false
+   */
+  auto hasLimit() const -> bool { return expected.getLimit() > 0; }
+  /**
+   * @brief Test if we need to expect a fullcount phase
+   *
+   * @return true
+   * @return false
+   */
+  auto needsFullCount() const -> bool { return expected.needsFullCount(); }
+};
+
+/**
+ * @brief Asserter used for the skipRows implementation.
+ *        Assumes that we are always called once with an empty input.
+ *        And once with a given input.
+ *        Will expect to be called for skip and fullCount (4 counts)
+ *        Does expect to not be called if skip and/or fullCount are ommited.
+ */
+struct SkipCallAsserter : public BaseCallAsserter {
+  explicit SkipCallAsserter(AqlCall const& expectedCall)
+      : BaseCallAsserter{expectedCall} {
+    // Calculate number of calls
+    // Ordering here is important, as it defines the start
+    // state of the asserter. We first get called for skip
+    // so skip needs to be last here
+    if (needsFullCount()) {
+      maxCall += 2;
+      state = CallAsserterState::COUNT;
+    }
+    if (hasSkip()) {
+      maxCall += 2;
+      state = CallAsserterState::SKIP;
+    }
+    // It is possible that we actually have 0 calls.
+    // if there is neither skip nor limit
+  }
+
+  auto gotCalled(AqlCall const& got) -> void {
+    call++;
+    switch (state) {
+      case CallAsserterState::SKIP: {
+        EXPECT_EQ(got.getOffset(), expected.getOffset());
+        if (call % 2 == 0) {
+          if (needsFullCount()) {
+            state = CallAsserterState::COUNT;
+          } else {
+            state = CallAsserterState::DONE;
+          }
+        }
+        break;
+      }
+      case CallAsserterState::COUNT: {
+        EXPECT_EQ(got.getLimit(), 0);
+        EXPECT_EQ(got.getOffset(), 0);
+        EXPECT_TRUE(got.needsFullCount());
+        if (call % 2 == 0) {
+          state = CallAsserterState::DONE;
+        }
+        break;
+      }
+      case CallAsserterState::INITIAL:
+      case CallAsserterState::GET:
+      case CallAsserterState::DONE: {
+        // This should not be reached
+        EXPECT_FALSE(true);
+        break;
+      }
+    }
+    EXPECT_LE(call, maxCall);
+    if (call > maxCall) {
+      // Security bailout to avoid infinite loops
+      THROW_ARANGO_EXCEPTION(TRI_ERROR_INTERNAL);
+    }
+  }
+};
+
+/**
+ * @brief Asserter used for the produce method.
+ *        Asserts to be called twice if data is requested. (limit > 0)
+ *        Once with, once without data.
+ */
+struct CallAsserter : public BaseCallAsserter {
+  explicit CallAsserter(AqlCall const& expectedCall)
+      : BaseCallAsserter{expectedCall} {
+    // Calculate number of calls
+    if (hasLimit()) {
+      maxCall += 2;
+      state = CallAsserterState::INITIAL;
+    }
+  }
+
+  auto gotCalled(AqlCall const& got) -> void {
+    EXPECT_EQ(got.getOffset(), 0);
+    call++;
+    switch (state) {
+      case CallAsserterState::INITIAL: {
+        EXPECT_EQ(got.getLimit(), expected.getLimit());
+        state = CallAsserterState::GET;
+        break;
+      }
+      case CallAsserterState::GET: {
+        EXPECT_EQ(got.getLimit(), expected.getLimit());
+        state = CallAsserterState::DONE;
+        break;
+      }
+      case CallAsserterState::SKIP:
+      case CallAsserterState::COUNT:
+      case CallAsserterState::DONE: {
+        // This should not be reached
+        EXPECT_FALSE(true);
+        break;
+      }
+    }
+    EXPECT_LE(call, maxCall);
+    if (call > maxCall) {
+      // Security bailout to avoid infinite loops
+      THROW_ARANGO_EXCEPTION(TRI_ERROR_INTERNAL);
+    }
+  }
+};
+
+/**
+ * @brief Asserter used "above" an executor that implements
+ *        skip and produce, and transforms everything to produce.
+ *        Expects to be called twice for each sitation (with and without input).
+ *        Expect up to three situations: SKIP, GET and FULLCOUNT.
+ */
+struct GetOnlyCallAsserter : public BaseCallAsserter {
+  explicit GetOnlyCallAsserter(AqlCall const& expectedCall)
+      : BaseCallAsserter{expectedCall} {
+    // Calculate number of calls
+    // Ordering here is important, as it defines the start
+    // state of the asserter. We first get called for skip
+    // so skip needs to be last here
+    if (needsFullCount()) {
+      maxCall += 2;
+      state = CallAsserterState::COUNT;
+    }
+    if (hasLimit()) {
+      maxCall += 2;
+      state = CallAsserterState::GET;
+    }
+    if (hasSkip()) {
+      maxCall += 2;
+      state = CallAsserterState::SKIP;
+    }
+    // Make sure setup worked
+    EXPECT_GT(maxCall, 0);
+    EXPECT_NE(state, CallAsserterState::DONE);
+  }
+
+  auto gotCalled(AqlCall const& got) -> void {
+    EXPECT_EQ(got.getOffset(), 0);
+    EXPECT_FALSE(got.needsFullCount());
+    call++;
+
+    switch (state) {
+      case CallAsserterState::SKIP: {
+        EXPECT_EQ(got.getLimit(), expected.getOffset());
+        if (call % 2 == 0) {
+          // We only switch to next state every second call.
+          // The first call is "empty" and only forwards to upwards
+          if (hasLimit()) {
+            state = CallAsserterState::GET;
+          } else if (needsFullCount()) {
+            state = CallAsserterState::COUNT;
+          } else {
+            state = CallAsserterState::DONE;
+          }
+        }
+        break;
+      }
+      case CallAsserterState::GET: {
+        EXPECT_EQ(got.getLimit(), expected.getLimit());
+        if (call % 2 == 0) {
+          // We only switch to next state every second call.
+          // The first call is "empty" and only forwards to upwards
+          if (needsFullCount()) {
+            state = CallAsserterState::COUNT;
+          } else {
+            state = CallAsserterState::DONE;
+          }
+        }
+        break;
+      }
+
+      case CallAsserterState::COUNT: {
+        // We do not test 0,0,false
+        EXPECT_TRUE(needsFullCount());
+        EXPECT_EQ(got.softLimit, AqlCall::Infinity{});
+        EXPECT_EQ(got.hardLimit, AqlCall::Infinity{});
+        if (call % 2 == 0) {
+          // We only switch to next state every second call.
+          // The first call is "empty" and only forwards to upwards
+          state = CallAsserterState::DONE;
+        }
+        break;
+      }
+      case CallAsserterState::INITIAL:
+      case CallAsserterState::DONE: {
+        // This should not be reached
+        EXPECT_FALSE(true);
+        break;
+      }
+    }
+    EXPECT_LE(call, maxCall);
+    if (call > maxCall) {
+      // Security bailout to avoid infinite loops
+      THROW_ARANGO_EXCEPTION(TRI_ERROR_INTERNAL);
+    }
+  }
+};
+
+/**
+ * @brief Integration tests.
+ *        These test tests a chain of Executors.
+ *        It focuses on the part that all executors
+ *        get injected the correct calls in each iteration
+ *        of the Execute state machine.
+ *        Also asserts that "UPSTREAM" is called with the correct
+ *        forwarded call.
+ *        This is a parameterized testsuite that uses a set of pseudo-random AqlCalls of different formats.
+ */
+class ExecutionBlockImplExecuteIntegrationTest
+    : public SharedExecutionBlockImplTest,
+      public testing::TestWithParam<AqlCall> {
+ protected:
+  /**
+   * @brief Create a Producing ExecutionBlock
+   *        For every input row this block will write the array given in data
+   *        into the output once.
+   *        Each entry in the array goes into one line and is writen into outReg.
+   *
+   * @param dependency The dependecy of this block (produces input)
+   * @param data The data to be written, needs to be an array.
+   * @param outReg The register to be written to
+   * @return std::unique_ptr<ExecutionBlock> ready to use ProducerBlock.
+   */
+  std::unique_ptr<ExecutionBlock> produceBlock(ExecutionBlock* dependency,
+                                               std::shared_ptr<VPackBuilder> data,
+                                               RegisterId outReg) {
+    TRI_ASSERT(dependency != nullptr);
+    TRI_ASSERT(data != nullptr);
+    TRI_ASSERT(data->slice().isArray());
+    // We make this a shared ptr just to make sure someone retains the data.
+    auto iterator = std::make_shared<VPackArrayIterator>(data->slice());
+    auto writeData = [data, outReg, iterator](AqlItemBlockInputRange& inputRange,
+                                              OutputAqlItemRow& output)
+        -> std::tuple<ExecutorState, LambdaExe::Stats, AqlCall> {
+      while (inputRange.hasDataRow() && !output.isFull()) {
+        auto const& [state, input] = inputRange.peekDataRow();
+        EXPECT_TRUE(input.isInitialized());
+        while (!output.isFull() && iterator->valid()) {
+          output.cloneValueInto(outReg, input, AqlValue{iterator->value()});
+          output.advanceRow();
+          iterator->next();
+        }
+        if (!iterator->valid()) {
+          // Consume input
+          auto const& [state, input] = inputRange.nextDataRow();
+          EXPECT_TRUE(input.isInitialized());
+          iterator->reset();
+        }
+      }
+      // We always use a default unlimited call here, we only have Singleton above.
+      AqlCall call{};
+      return {inputRange.upstreamState(), NoStats{}, call};
+    };
+
+    auto skipData =
+        [data, iterator](AqlItemBlockInputRange& inputRange,
+                         AqlCall& clientCall) -> std::tuple<ExecutorState, size_t, AqlCall> {
+      size_t skipped = 0;
+      while (inputRange.hasDataRow() &&
+             (clientCall.getOffset() > 0 ||
+              (clientCall.getLimit() == 0 && clientCall.needsFullCount()))) {
+        auto const& [state, input] = inputRange.peekDataRow();
+        EXPECT_TRUE(input.isInitialized());
+        while ((clientCall.getOffset() > 0 ||
+                (clientCall.getLimit() == 0 && clientCall.needsFullCount())) &&
+               iterator->valid()) {
+          clientCall.didSkip(1);
+          skipped++;
+          iterator->next();
+        }
+        if (!iterator->valid()) {
+          // Consume input
+          auto const& [state, input] = inputRange.nextDataRow();
+          EXPECT_TRUE(input.isInitialized());
+          iterator->reset();
+        }
+      }
+      AqlCall call{};
+      call.offset = 0;
+      if (clientCall.getOffset() > 0) {
+        call.softLimit = clientCall.getOffset();
+      }  // else softLimit == unlimited
+      call.fullCount = false;
+      return {inputRange.upstreamState(), skipped, call};
+    };
+    auto infos = outReg == 0
+                     ? makeSkipInfos(std::move(writeData), skipData,
+                                     RegisterPlan::MaxRegisterId, outReg)
+                     : makeSkipInfos(std::move(writeData), skipData, outReg - 1, outReg);
+    auto producer =
+        std::make_unique<ExecutionBlockImpl<LambdaExe>>(fakedQuery->engine(),
+                                                        generateNodeDummy(),
+                                                        std::move(infos));
+    producer->addDependency(dependency);
+    return producer;
+  }
+
+  /**
+   * @brief Create a simple row forwarding Block.
+   *        It simply takes one input row and copies it into the output
+   *
+   * @param dependency The dependecy of this block (produces input)
+   * @param maxReg The number of registers in input and output. (required for forwarding of data)
+   * @return std::unique_ptr<ExecutionBlock> ready to use ForwardingBlock.
+   */
+  std::unique_ptr<ExecutionBlock> forwardBlock(ExecutionBlock* dependency, RegisterId maxReg) {
+    TRI_ASSERT(dependency != nullptr);
+    auto forwardData = [](AqlItemBlockInputRange& inputRange, OutputAqlItemRow& output)
+        -> std::tuple<ExecutorState, LambdaExe::Stats, AqlCall> {
+      while (inputRange.hasDataRow() && !output.isFull()) {
+        auto const& [state, input] = inputRange.nextDataRow();
+        EXPECT_TRUE(input.isInitialized());
+        output.copyRow(input);
+        output.advanceRow();
+      }
+      return {inputRange.upstreamState(), NoStats{}, output.getClientCall()};
+    };
+    auto producer = std::make_unique<ExecutionBlockImpl<LambdaExePassThrough>>(
+        fakedQuery->engine(), generateNodeDummy(),
+        makeInfos(std::move(forwardData), maxReg, maxReg));
+    producer->addDependency(dependency);
+    return producer;
+  }
+
+  /**
+   * @brief Helper method to validate the result
+   *        It will take into account the call used as Parameter
+   *        and slice the expectated outcome to it.
+   *
+   * It asserts the following:
+   *   1. skipped == offset() + (data.length - hardLimit [fullcount])
+   *   2. result.length = (hardLimit||data.length) - offset.
+   *   3. result register entry matches the entry at the correct position in data.
+   *
+   * @param data The data to be expected, if we would just get it in full
+   * @param skipped The number of rows the executor reported as skipped
+   * @param result The resulting data output
+   * @param testReg The register to evaluate
+   */
+  void ValidateResult(std::shared_ptr<VPackBuilder> data, size_t skipped,
+                      SharedAqlItemBlockPtr result, RegisterId testReg) {
+    auto const& call = GetParam();
+
+    TRI_ASSERT(data != nullptr);
+    TRI_ASSERT(data->slice().isArray());
+
+    VPackSlice expected = data->slice();
+    VPackArrayIterator expectedIt{expected};
+    // Skip Part
+    size_t offset =
+        (std::min)(call.getOffset(), static_cast<size_t>(expected.length()));
+
+    if (!call.needsFullCount()) {
+      // Otherweise skipped = offset + fullCount
+      EXPECT_EQ(offset, skipped);
+    }
+
+    for (size_t i = 0; i < offset; ++i) {
+      // The first have been skipped
+      expectedIt++;
+    }
+    size_t limit =
+        (std::min)(call.getLimit(), static_cast<size_t>(expected.length()) - offset);
+    if (result != nullptr) {
+      // GetSome part
+      EXPECT_EQ(limit, result->size());
+      for (size_t i = 0; i < limit; ++i) {
+        // The next have to match
+        auto got = result->getValueReference(i, testReg).slice();
+        EXPECT_TRUE(basics::VelocyPackHelper::equal(got, *expectedIt, false))
+            << "Expected: " << expectedIt.value().toJson() << " got: " << got.toJson()
+            << " in row " << i << " and register " << testReg;
+        expectedIt++;
+      }
+    } else {
+      EXPECT_EQ(limit, 0);
+    }
+
+    // Now test Fullcount
+    if (call.needsFullCount()) {
+      ASSERT_TRUE(expected.length() >= offset + limit);
+      size_t fullCount = expected.length() - offset - limit;
+      EXPECT_EQ(offset + fullCount, skipped);
+    }
+  }
+};
+
+// Test a simple produce block. that has is supposed to write 1000 rows.
+TEST_P(ExecutionBlockImplExecuteIntegrationTest, test_produce_only) {
+  auto singleton = createSingleton();
+
+  auto builder = std::make_shared<VPackBuilder>();
+  builder->openArray();
+  for (size_t i = 0; i < 1000; ++i) {
+    builder->add(VPackValue(i));
+  }
+  builder->close();
+  RegisterId outReg = 0;
+  auto producer = produceBlock(singleton.get(), builder, outReg);
+
+  auto const& call = GetParam();
+  AqlCallStack stack{call};
+  auto const [state, skipped, block] = producer->execute(stack);
+  if (std::holds_alternative<size_t>(call.softLimit) && !call.hasHardLimit()) {
+    EXPECT_EQ(state, ExecutionState::HASMORE);
+  } else {
+    EXPECT_EQ(state, ExecutionState::DONE);
+  }
+
+  ValidateResult(builder, skipped, block, outReg);
+}
+
+// Test two consecutive produce blocks.
+// The first writes 10 lines
+// The second another 10 per input (100 in total)
+TEST_P(ExecutionBlockImplExecuteIntegrationTest, test_produce_using_two) {
+  auto singleton = createSingleton();
+
+  auto builder = std::make_shared<VPackBuilder>();
+  builder->openArray();
+  for (size_t i = 0; i < 10; ++i) {
+    builder->add(VPackValue(i));
+  }
+  builder->close();
+  RegisterId outRegFirst = 0;
+  RegisterId outRegSecond = 1;
+  auto producerFirst = produceBlock(singleton.get(), builder, outRegFirst);
+  auto producer = produceBlock(producerFirst.get(), builder, outRegSecond);
+  auto const& call = GetParam();
+  AqlCallStack stack{call};
+  auto const [state, skipped, block] = producer->execute(stack);
+  if (call.getLimit() < 100) {
+    if (call.hasHardLimit()) {
+      // On hard limit we need to stop
+      EXPECT_EQ(state, ExecutionState::DONE);
+    } else {
+      // On soft limit we need to be able to produce more
+      EXPECT_EQ(state, ExecutionState::HASMORE);
+    }
+  } else {
+    EXPECT_FALSE(call.hasHardLimit());
+    EXPECT_EQ(state, ExecutionState::DONE);
+  }
+
+  auto firstRegBuilder = std::make_shared<VPackBuilder>();
+  auto secondRegBuilder = std::make_shared<VPackBuilder>();
+  firstRegBuilder->openArray();
+  secondRegBuilder->openArray();
+  for (size_t i = 0; i < 10; ++i) {
+    // i => 0 -> 9
+    for (size_t j = 0; j < 10; ++j) {
+      // j => 0 -> 9
+      firstRegBuilder->add(VPackValue(i));
+      secondRegBuilder->add(VPackValue(j));
+    }
+  }
+  secondRegBuilder->close();
+  firstRegBuilder->close();
+  ValidateResult(firstRegBuilder, skipped, block, outRegFirst);
+  ValidateResult(secondRegBuilder, skipped, block, outRegSecond);
+}
+
+// Explicitly test call forwarding, on exectors.
+// We use two pass-through producers, that simply copy over input and assert an calls.
+// On top of them we have a 1000 line producer.
+// We expect the result to be identical to the 1000 line producer only.
+TEST_P(ExecutionBlockImplExecuteIntegrationTest, test_call_forwarding_passthrough) {
+  auto singleton = createSingleton();
+
+  auto builder = std::make_shared<VPackBuilder>();
+  builder->openArray();
+  for (size_t i = 0; i < 1000; ++i) {
+    builder->add(VPackValue(i));
+  }
+  builder->close();
+  RegisterId outReg = 0;
+  auto producer = produceBlock(singleton.get(), builder, outReg);
+
+  CallAsserter upperState{GetParam()};
+  CallAsserter lowerState{GetParam()};
+
+  auto testForwarding =
+      [&](AqlItemBlockInputRange& inputRange,
+          OutputAqlItemRow& output) -> std::tuple<ExecutorState, LambdaExe::Stats, AqlCall> {
+    upperState.gotCalled(output.getClientCall());
+    while (inputRange.hasDataRow() && !output.isFull()) {
+      auto const& [state, input] = inputRange.nextDataRow();
+      EXPECT_TRUE(input.isInitialized());
+      output.copyRow(input);
+      output.advanceRow();
+    }
+    return {inputRange.upstreamState(), NoStats{}, output.getClientCall()};
+  };
+  auto forwardCall = [&](AqlItemBlockInputRange& inputRange, OutputAqlItemRow& output)
+      -> std::tuple<ExecutorState, LambdaExe::Stats, AqlCall> {
+    lowerState.gotCalled(output.getClientCall());
+    while (inputRange.hasDataRow() && !output.isFull()) {
+      auto const& [state, input] = inputRange.nextDataRow();
+      EXPECT_TRUE(input.isInitialized());
+      output.copyRow(input);
+      output.advanceRow();
+    }
+    return {inputRange.upstreamState(), NoStats{}, output.getClientCall()};
+  };
+  auto upper = std::make_unique<ExecutionBlockImpl<LambdaExePassThrough>>(
+      fakedQuery->engine(), generateNodeDummy(),
+      makeInfos(std::move(testForwarding), outReg, outReg));
+  upper->addDependency(producer.get());
+  auto lower = std::make_unique<ExecutionBlockImpl<LambdaExePassThrough>>(
+      fakedQuery->engine(), generateNodeDummy(),
+      makeInfos(std::move(forwardCall), outReg, outReg));
+  lower->addDependency(upper.get());
+
+  auto const& call = GetParam();
+  AqlCallStack stack{call};
+  auto const [state, skipped, block] = lower->execute(stack);
+  if (std::holds_alternative<size_t>(call.softLimit) && !call.hasHardLimit()) {
+    EXPECT_EQ(state, ExecutionState::HASMORE);
+  } else {
+    EXPECT_EQ(state, ExecutionState::DONE);
+  }
+  ValidateResult(builder, skipped, block, outReg);
+}
+
+// Explicitly test call forwarding, on exectors.
+// We use one pass-through producer, that simply copy over input and assert an calls.
+// And we have one non-passthrough below it, that requests all data from upstream, and internally
+// does skipping.
+// On top of them we have a 1000 line producer.
+// We expect the result to be identical to the 1000 line producer only.
+TEST_P(ExecutionBlockImplExecuteIntegrationTest, test_call_forwarding_implement_skip) {
+  auto singleton = createSingleton();
+
+  auto builder = std::make_shared<VPackBuilder>();
+  builder->openArray();
+  for (size_t i = 0; i < 1000; ++i) {
+    builder->add(VPackValue(i));
+  }
+  builder->close();
+  RegisterId outReg = 0;
+  auto producer = produceBlock(singleton.get(), builder, outReg);
+  GetOnlyCallAsserter upperState{GetParam()};
+  CallAsserter lowerState{GetParam()};
+  SkipCallAsserter skipState{GetParam()};
+
+  auto testForwarding =
+      [&](AqlItemBlockInputRange& inputRange,
+          OutputAqlItemRow& output) -> std::tuple<ExecutorState, LambdaExe::Stats, AqlCall> {
+    upperState.gotCalled(output.getClientCall());
+    while (inputRange.hasDataRow() && !output.isFull()) {
+      auto const& [state, input] = inputRange.nextDataRow();
+      EXPECT_TRUE(input.isInitialized());
+      output.copyRow(input);
+      output.advanceRow();
+    }
+    return {inputRange.upstreamState(), NoStats{}, output.getClientCall()};
+  };
+  auto forwardCall = [&](AqlItemBlockInputRange& inputRange, OutputAqlItemRow& output)
+      -> std::tuple<ExecutorState, LambdaExe::Stats, AqlCall> {
+    lowerState.gotCalled(output.getClientCall());
+    while (inputRange.hasDataRow() && !output.isFull()) {
+      auto const& [state, input] = inputRange.nextDataRow();
+      EXPECT_TRUE(input.isInitialized());
+      output.copyRow(input);
+      output.advanceRow();
+    }
+    auto getClient = output.getClientCall();
+    AqlCall request{};
+    request.softLimit = (std::min)(getClient.softLimit, getClient.hardLimit);
+    return {inputRange.upstreamState(), NoStats{}, request};
+  };
+  auto forwardSkipCall = [&](AqlItemBlockInputRange& inputRange,
+                             AqlCall& call) -> std::tuple<ExecutorState, size_t, AqlCall> {
+    skipState.gotCalled(call);
+    size_t skipped = 0;
+    while (inputRange.hasDataRow() &&
+           (call.getOffset() > 0 || (call.getLimit() == 0 && call.needsFullCount()))) {
+      auto const& [state, input] = inputRange.nextDataRow();
+      EXPECT_TRUE(input.isInitialized());
+      skipped++;
+    }
+    call.didSkip(skipped);
+    // Do forward a softLimit call only.
+    // Do not oeverfetch here.
+    AqlCall request;
+    if (call.getOffset() > 0) {
+      request.softLimit = call.getOffset();
+    }  // else fullCount case, simple get UNLIMITED from above
+
+    return {inputRange.upstreamState(), skipped, request};
+  };
+
+  auto upper = std::make_unique<ExecutionBlockImpl<LambdaExePassThrough>>(
+      fakedQuery->engine(), generateNodeDummy(),
+      makeInfos(std::move(testForwarding), outReg, outReg));
+  upper->addDependency(producer.get());
+  auto lower = std::make_unique<ExecutionBlockImpl<TestLambdaSkipExecutor>>(
+      fakedQuery->engine(), generateNodeDummy(),
+      makeSkipInfos(std::move(forwardCall), std::move(forwardSkipCall), outReg, outReg));
+  lower->addDependency(upper.get());
+
+  auto const& call = GetParam();
+  AqlCallStack stack{call};
+  auto const [state, skipped, block] = lower->execute(stack);
+  if (std::holds_alternative<size_t>(call.softLimit) && !call.hasHardLimit()) {
+    EXPECT_EQ(state, ExecutionState::HASMORE);
+  } else {
+    EXPECT_EQ(state, ExecutionState::DONE);
+  }
+  ValidateResult(builder, skipped, block, outReg);
+}
+
+// The numbers here are random, but all of them are below 1000 which is the default batch size
+static constexpr auto defaultCall = []() -> const AqlCall { return AqlCall{}; };
+
+static constexpr auto skipCall = []() -> const AqlCall {
+  AqlCall res{};
+  res.offset = 15;
+  return res;
+};
+
+static constexpr auto softLimit = []() -> const AqlCall {
+  AqlCall res{};
+  res.softLimit = 35;
+  return res;
+};
+
+static constexpr auto hardLimit = []() -> const AqlCall {
+  AqlCall res{};
+  res.hardLimit = 76;
+  return res;
+};
+
+static constexpr auto fullCount = []() -> const AqlCall {
+  AqlCall res{};
+  res.hardLimit = 17;
+  res.fullCount = true;
+  return res;
+};
+
+static constexpr auto skipAndSoftLimit = []() -> const AqlCall {
+  AqlCall res{};
+  res.offset = 16;
+  res.softLimit = 64;
+  return res;
+};
+
+static constexpr auto skipAndHardLimit = []() -> const AqlCall {
+  AqlCall res{};
+  res.offset = 32;
+  res.hardLimit = 71;
+  return res;
+};
+static constexpr auto skipAndHardLimitAndFullCount = []() -> const AqlCall {
+  AqlCall res{};
+  res.offset = 8;
+  res.hardLimit = 57;
+  res.fullCount = true;
+  return res;
+};
+static constexpr auto onlyFullCount = []() -> const AqlCall {
+  AqlCall res{};
+  res.hardLimit = 0;
+  res.fullCount = true;
+  return res;
+};
+static constexpr auto onlySkipAndCount = []() -> const AqlCall {
+  AqlCall res{};
+  res.offset = 16;
+  res.hardLimit = 0;
+  res.fullCount = true;
+  return res;
+};
+
+INSTANTIATE_TEST_CASE_P(ExecutionBlockExecuteIntegration, ExecutionBlockImplExecuteIntegrationTest,
+                        ::testing::Values(defaultCall(), skipCall(),
+                                          softLimit(), hardLimit(), fullCount(),
+                                          skipAndSoftLimit(), skipAndHardLimit(),
+                                          skipAndHardLimitAndFullCount(),
+                                          onlyFullCount(), onlySkipAndCount()));
+
 }  // namespace aql
 }  // namespace tests
 }  // namespace arangodb
diff --git a/tests/Aql/ExecutionBlockImplTestInstances.cpp b/tests/Aql/ExecutionBlockImplTestInstances.cpp
index aeb02fe8982d..b5bfc68a589b 100644
--- a/tests/Aql/ExecutionBlockImplTestInstances.cpp
+++ b/tests/Aql/ExecutionBlockImplTestInstances.cpp
@@ -1,6 +1,9 @@
 #include "Aql/ExecutionBlockImpl.cpp"
 #include "TestEmptyExecutorHelper.h"
 #include "TestExecutorHelper.h"
+#include "TestLambdaExecutor.h"
 
 template class ::arangodb::aql::ExecutionBlockImpl<TestExecutorHelper>;
 template class ::arangodb::aql::ExecutionBlockImpl<TestEmptyExecutorHelper>;
+template class ::arangodb::aql::ExecutionBlockImpl<TestLambdaExecutor>;
+template class ::arangodb::aql::ExecutionBlockImpl<TestLambdaSkipExecutor>;
diff --git a/tests/Aql/TestLambdaExecutor.cpp b/tests/Aql/TestLambdaExecutor.cpp
new file mode 100644
index 000000000000..92083adc9fb1
--- /dev/null
+++ b/tests/Aql/TestLambdaExecutor.cpp
@@ -0,0 +1,112 @@
+////////////////////////////////////////////////////////////////////////////////
+/// DISCLAIMER
+///
+/// Copyright 2020 ArangoDB GmbH, Cologne, Germany
+///
+/// Licensed under the Apache License, Version 2.0 (the "License");
+/// you may not use this file except in compliance with the License.
+/// You may obtain a copy of the License at
+///
+///     http://www.apache.org/licenses/LICENSE-2.0
+///
+/// Unless required by applicable law or agreed to in writing, software
+/// distributed under the License is distributed on an "AS IS" BASIS,
+/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+/// See the License for the specific language governing permissions and
+/// limitations under the License.
+///
+/// Copyright holder is ArangoDB GmbH, Cologne, Germany
+///
+/// @author Michael Hackstein
+////////////////////////////////////////////////////////////////////////////////
+
+#include "TestLambdaExecutor.h"
+#include "Basics/Exceptions.h"
+#include "Basics/debugging.h"
+
+#include "Aql/AqlCall.h"
+
+using namespace arangodb;
+using namespace arangodb::aql;
+
+LambdaExecutorInfos::LambdaExecutorInfos(
+    std::shared_ptr<std::unordered_set<RegisterId>> readableInputRegisters,
+    std::shared_ptr<std::unordered_set<RegisterId>> writeableOutputRegisters,
+    RegisterId nrInputRegisters, RegisterId nrOutputRegisters,
+    std::unordered_set<RegisterId> registersToClear,
+    std::unordered_set<RegisterId> registersToKeep, ProduceCall lambda)
+    : ExecutorInfos(readableInputRegisters, writeableOutputRegisters, nrInputRegisters,
+                    nrOutputRegisters, registersToClear, registersToKeep),
+      _produceLambda(lambda) {}
+
+auto LambdaExecutorInfos::getProduceLambda() const -> ProduceCall const& {
+  return _produceLambda;
+}
+
+LambdaSkipExecutorInfos::LambdaSkipExecutorInfos(
+    std::shared_ptr<std::unordered_set<RegisterId>> readableInputRegisters,
+    std::shared_ptr<std::unordered_set<RegisterId>> writeableOutputRegisters,
+    RegisterId nrInputRegisters, RegisterId nrOutputRegisters,
+    std::unordered_set<RegisterId> registersToClear,
+    std::unordered_set<RegisterId> registersToKeep, ProduceCall lambda, SkipCall skipLambda)
+    : ExecutorInfos(readableInputRegisters, writeableOutputRegisters, nrInputRegisters,
+                    nrOutputRegisters, registersToClear, registersToKeep),
+      _produceLambda(lambda),
+      _skipLambda(skipLambda) {}
+
+auto LambdaSkipExecutorInfos::getProduceLambda() const -> ProduceCall const& {
+  return _produceLambda;
+}
+
+auto LambdaSkipExecutorInfos::getSkipLambda() const -> SkipCall const& {
+  return _skipLambda;
+}
+
+TestLambdaExecutor::TestLambdaExecutor(Fetcher&, Infos& infos)
+    : _infos(infos) {}
+
+TestLambdaExecutor::~TestLambdaExecutor() {}
+
+auto TestLambdaExecutor::fetchBlockForPassthrough(size_t atMost)
+    -> std::tuple<ExecutionState, Stats, SharedAqlItemBlockPtr> {
+  TRI_ASSERT(false);
+  THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
+}
+
+auto TestLambdaExecutor::produceRows(OutputAqlItemRow& output)
+    -> std::tuple<ExecutionState, Stats> {
+  TRI_ASSERT(false);
+  THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
+}
+
+auto TestLambdaExecutor::produceRows(AqlItemBlockInputRange& input, OutputAqlItemRow& output)
+    -> std::tuple<ExecutorState, Stats, AqlCall> {
+  return _infos.getProduceLambda()(input, output);
+}
+
+TestLambdaSkipExecutor::TestLambdaSkipExecutor(Fetcher&, Infos& infos)
+    : _infos(infos) {}
+
+TestLambdaSkipExecutor::~TestLambdaSkipExecutor() {}
+
+auto TestLambdaSkipExecutor::fetchBlockForPassthrough(size_t atMost)
+    -> std::tuple<ExecutionState, Stats, SharedAqlItemBlockPtr> {
+  TRI_ASSERT(false);
+  THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
+}
+
+auto TestLambdaSkipExecutor::produceRows(OutputAqlItemRow& output)
+    -> std::tuple<ExecutionState, Stats> {
+  TRI_ASSERT(false);
+  THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
+}
+
+auto TestLambdaSkipExecutor::produceRows(AqlItemBlockInputRange& input, OutputAqlItemRow& output)
+    -> std::tuple<ExecutorState, Stats, AqlCall> {
+  return _infos.getProduceLambda()(input, output);
+}
+
+auto TestLambdaSkipExecutor::skipRowsRange(AqlItemBlockInputRange& input, AqlCall& call)
+    -> std::tuple<ExecutorState, size_t, AqlCall> {
+  return _infos.getSkipLambda()(input, call);
+}
\ No newline at end of file
diff --git a/tests/Aql/TestLambdaExecutor.h b/tests/Aql/TestLambdaExecutor.h
new file mode 100644
index 000000000000..9663ca6ca249
--- /dev/null
+++ b/tests/Aql/TestLambdaExecutor.h
@@ -0,0 +1,233 @@
+////////////////////////////////////////////////////////////////////////////////
+/// DISCLAIMER
+///
+/// Copyright 2020 ArangoDB GmbH, Cologne, Germany
+///
+/// Licensed under the Apache License, Version 2.0 (the "License");
+/// you may not use this file except in compliance with the License.
+/// You may obtain a copy of the License at
+///
+///     http://www.apache.org/licenses/LICENSE-2.0
+///
+/// Unless required by applicable law or agreed to in writing, software
+/// distributed under the License is distributed on an "AS IS" BASIS,
+/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+/// See the License for the specific language governing permissions and
+/// limitations under the License.
+///
+/// Copyright holder is ArangoDB GmbH, Cologne, Germany
+///
+/// @author Michael Hackstein
+////////////////////////////////////////////////////////////////////////////////
+
+#ifndef ARANGOD_AQL_TEST_LAMBDA_EXECUTOR_H
+#define ARANGOD_AQL_TEST_LAMBDA_EXECUTOR_H
+
+#include "Aql/ExecutionState.h"
+#include "Aql/ExecutorInfos.h"
+#include "Aql/SharedAqlItemBlockPtr.h"
+#include "Aql/Stats.h"
+#include "Aql/types.h"
+
+namespace arangodb {
+namespace aql {
+
+struct AqlCall;
+class AqlItemBlockInputRange;
+class OutputAqlItemRow;
+class SharedAqlItemBlockPtr;
+
+template <BlockPassthrough>
+class SingleRowFetcher;
+
+/**
+ * @brief This is a shorthand for the produceRows signature
+ */
+using ProduceCall =
+    std::function<std::tuple<ExecutorState, NoStats, AqlCall>(AqlItemBlockInputRange& input, OutputAqlItemRow& output)>;
+
+/**
+ * @brief This is a shorthand for the skipRowsInRange signature
+ */
+using SkipCall =
+    std::function<std::tuple<ExecutorState, size_t, AqlCall>(AqlItemBlockInputRange& input, AqlCall& call)>;
+
+/**
+ * @brief Executorinfos for the lambda executors.
+ *        Contains basice RegisterPlanning information, and a ProduceCall.
+ *        This produceCall will be executed whenever the LambdaExecutor is called with produceRows
+ */
+class LambdaExecutorInfos : public ExecutorInfos {
+ public:
+  LambdaExecutorInfos(std::shared_ptr<std::unordered_set<RegisterId>> readableInputRegisters,
+                      std::shared_ptr<std::unordered_set<RegisterId>> writeableOutputRegisters,
+                      RegisterId nrInputRegisters, RegisterId nrOutputRegisters,
+                      std::unordered_set<RegisterId> registersToClear,
+                      std::unordered_set<RegisterId> registersToKeep, ProduceCall lambda);
+
+  LambdaExecutorInfos() = delete;
+  LambdaExecutorInfos(LambdaExecutorInfos&&) = default;
+  LambdaExecutorInfos(LambdaExecutorInfos const&) = delete;
+  ~LambdaExecutorInfos() = default;
+
+  auto getProduceLambda() const -> ProduceCall const&;
+
+ private:
+  ProduceCall _produceLambda;
+};
+
+/**
+ * @brief Executorinfos for the lambda executors.
+ *        Contains basice RegisterPlanning information, a ProduceCall, and a SkipCall
+ *        The produceCall will be executed whenever the LambdaExecutor is called with produceRows
+ *        The skipCall will be executed whenever the LambdaExecutor is called with skipRowsInRange
+ */
+class LambdaSkipExecutorInfos : public ExecutorInfos {
+ public:
+  LambdaSkipExecutorInfos(std::shared_ptr<std::unordered_set<RegisterId>> readableInputRegisters,
+                          std::shared_ptr<std::unordered_set<RegisterId>> writeableOutputRegisters,
+                          RegisterId nrInputRegisters, RegisterId nrOutputRegisters,
+                          std::unordered_set<RegisterId> registersToClear,
+                          std::unordered_set<RegisterId> registersToKeep,
+                          ProduceCall lambda, SkipCall skipLambda);
+
+  LambdaSkipExecutorInfos() = delete;
+  LambdaSkipExecutorInfos(LambdaSkipExecutorInfos&&) = default;
+  LambdaSkipExecutorInfos(LambdaSkipExecutorInfos const&) = delete;
+  ~LambdaSkipExecutorInfos() = default;
+
+  auto getProduceLambda() const -> ProduceCall const&;
+  auto getSkipLambda() const -> SkipCall const&;
+
+ private:
+  ProduceCall _produceLambda;
+  SkipCall _skipLambda;
+};
+
+/**
+ * @brief A passthrough test executor.
+ *        Does only implement produceRows, also the implementation just calls
+ * the ProduceCall given in the Infos.
+ *
+ */
+class TestLambdaExecutor {
+ public:
+  struct Properties {
+    static const bool preservesOrder = true;
+    static const BlockPassthrough allowsBlockPassthrough = BlockPassthrough::Enable;
+    static const bool inputSizeRestrictsOutputSize = false;
+  };
+  using Fetcher = SingleRowFetcher<Properties::allowsBlockPassthrough>;
+  using Infos = LambdaExecutorInfos;
+  using Stats = NoStats;
+
+  TestLambdaExecutor() = delete;
+  TestLambdaExecutor(TestLambdaExecutor&&) = default;
+  TestLambdaExecutor(TestLambdaExecutor const&) = delete;
+  TestLambdaExecutor(Fetcher&, Infos&);
+  ~TestLambdaExecutor();
+
+  /**
+   * @brief NOT IMPLEMENTED. JUST FOR COMPILER
+   * TODO: REMOVE ME after we have switch everything over to produceRow.
+   *
+   * @param atMost
+   * @return std::tuple<ExecutionState, Stats, SharedAqlItemBlockPtr>
+   */
+  auto fetchBlockForPassthrough(size_t atMost)
+      -> std::tuple<ExecutionState, Stats, SharedAqlItemBlockPtr>;
+  /**
+   * @brief NOT IMPLEMENTED. JUST FOR COMPILER
+   * TODO: REMOVE ME after we have switch everything over to produceRow.
+   *
+   * @param output
+   * @return std::tuple<ExecutionState, Stats>
+   */
+  auto produceRows(OutputAqlItemRow& output) -> std::tuple<ExecutionState, Stats>;
+
+  /**
+   * @brief produceRows API. Just calls the ProduceCall in the Infos.
+   *
+   * @param input The input data range (might be empty)
+   * @param output The output rows (might be full)
+   * @return std::tuple<ExecutorState, Stats, AqlCall>
+   */
+  auto produceRows(AqlItemBlockInputRange& input, OutputAqlItemRow& output)
+      -> std::tuple<ExecutorState, Stats, AqlCall>;
+
+ private:
+  Infos& _infos;
+};
+
+/**
+ * @brief A non-passthrough test executor.
+ *        Does implement produceRows, also the implementation just calls
+ *        the ProduceCall given in the Infos.
+ *        Does implement skipRowsRange, also the implementation just calls
+ *        the SkipCall given in the Infos.
+ *
+ */
+class TestLambdaSkipExecutor {
+ public:
+  struct Properties {
+    static const bool preservesOrder = true;
+    static const BlockPassthrough allowsBlockPassthrough = BlockPassthrough::Disable;
+    static const bool inputSizeRestrictsOutputSize = false;
+  };
+  using Fetcher = SingleRowFetcher<Properties::allowsBlockPassthrough>;
+  using Infos = LambdaSkipExecutorInfos;
+  using Stats = NoStats;
+
+  TestLambdaSkipExecutor() = delete;
+  TestLambdaSkipExecutor(TestLambdaSkipExecutor&&) = default;
+  TestLambdaSkipExecutor(TestLambdaSkipExecutor const&) = delete;
+  TestLambdaSkipExecutor(Fetcher&, Infos&);
+  ~TestLambdaSkipExecutor();
+
+  /**
+   * @brief NOT IMPLEMENTED. JUST FOR COMPILER
+   * TODO: REMOVE ME after we have switch everything over to produceRow.
+   *
+   * @param atMost
+   * @return std::tuple<ExecutionState, Stats, SharedAqlItemBlockPtr>
+   */
+  auto fetchBlockForPassthrough(size_t atMost)
+      -> std::tuple<ExecutionState, Stats, SharedAqlItemBlockPtr>;
+
+  /**
+   * @brief NOT IMPLEMENTED. JUST FOR COMPILER
+   * TODO: REMOVE ME after we have switch everything over to produceRow.
+   *
+   * @param output
+   * @return std::tuple<ExecutionState, Stats>
+   */
+  auto produceRows(OutputAqlItemRow& output) -> std::tuple<ExecutionState, Stats>;
+
+  /**
+   * @brief skipRows API. Just calls the SkipCall in the infos
+   *
+   * @param inputRange The input data range (might be empty)
+   * @param call The call forwarded by the client.
+   * @return std::tuple<ExecutorState, size_t, AqlCall>
+   */
+  auto skipRowsRange(AqlItemBlockInputRange& inputRange, AqlCall& call)
+      -> std::tuple<ExecutorState, size_t, AqlCall>;
+
+  /**
+   * @brief produceRows API. Just calls the ProduceCall in the Infos.
+   *
+   * @param input The input data range (might be empty)
+   * @param output The output rows (might be full)
+   * @return std::tuple<ExecutorState, Stats, AqlCall>
+   */
+  auto produceRows(AqlItemBlockInputRange& input, OutputAqlItemRow& output)
+      -> std::tuple<ExecutorState, Stats, AqlCall>;
+
+ private:
+  Infos& _infos;
+};
+
+}  // namespace aql
+}  // namespace arangodb
+
+#endif
\ No newline at end of file
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 3357f97b7f14..2c97528af8cb 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -67,6 +67,7 @@ set(ARANGODB_TESTS_SOURCES
   Aql/SubqueryStartExecutorTest.cpp
   Aql/TestEmptyExecutorHelper.cpp
   Aql/TestExecutorHelper.cpp
+  Aql/TestLambdaExecutor.cpp
   Aql/TraversalExecutorTest.cpp
   Aql/UpdateExecutorTest.cpp
   Aql/UpsertExecutorTest.cpp
diff --git a/tests/Mocks/Servers.cpp b/tests/Mocks/Servers.cpp
index 535623ecee89..b0a33d69a65c 100644
--- a/tests/Mocks/Servers.cpp
+++ b/tests/Mocks/Servers.cpp
@@ -62,6 +62,7 @@
 #include "RestServer/UpgradeFeature.h"
 #include "RestServer/ViewTypesFeature.h"
 #include "Scheduler/SchedulerFeature.h"
+#include "Servers.h"
 #include "Sharding/ShardingFeature.h"
 #include "StorageEngine/EngineSelectorFeature.h"
 #include "Transaction/Methods.h"
@@ -326,7 +327,8 @@ void MockServer::startFeatures() {
   if (_server.hasFeature<arangodb::SchedulerFeature>()) {
     auto& sched = _server.getFeature<arangodb::SchedulerFeature>();
     // Needed to set nrMaximalThreads
-    sched.validateOptions(std::make_shared<arangodb::options::ProgramOptions>("", "", "", nullptr));
+    sched.validateOptions(
+        std::make_shared<arangodb::options::ProgramOptions>("", "", "", nullptr));
   }
 
   for (ApplicationFeature& f : orderedFeatures) {
@@ -450,12 +452,15 @@ std::shared_ptr<arangodb::transaction::Methods> MockAqlServer::createFakeTransac
                                                           noCollections, opts);
 }
 
-std::unique_ptr<arangodb::aql::Query> MockAqlServer::createFakeQuery() const {
+std::unique_ptr<arangodb::aql::Query> MockAqlServer::createFakeQuery(bool activateTracing) const {
   auto bindParams = std::make_shared<VPackBuilder>();
   bindParams->openObject();
   bindParams->close();
   auto queryOptions = std::make_shared<VPackBuilder>();
   queryOptions->openObject();
+  if (activateTracing) {
+    queryOptions->add("profile", VPackValue(aql::PROFILE_LEVEL_TRACE_2));
+  }
   queryOptions->close();
   aql::QueryString fakeQueryString("");
   auto query =
@@ -556,8 +561,8 @@ void MockClusterServer::agencyDropDatabase(std::string const& name) {
 
 MockDBServer::MockDBServer(bool start) : MockClusterServer() {
   arangodb::ServerState::instance()->setRole(arangodb::ServerState::RoleEnum::ROLE_DBSERVER);
-  addFeature<arangodb::FlushFeature>(false);       // do not start the thread
-  addFeature<arangodb::MaintenanceFeature>(false); // do not start the thread
+  addFeature<arangodb::FlushFeature>(false);        // do not start the thread
+  addFeature<arangodb::MaintenanceFeature>(false);  // do not start the thread
   if (start) {
     startFeatures();
     createDatabase("_system");
@@ -578,10 +583,10 @@ TRI_vocbase_t* MockDBServer::createDatabase(std::string const& name) {
     maintenance::ActionDescription ad(
         {{std::string(maintenance::NAME), std::string(maintenance::CREATE_DATABASE)},
          {std::string(maintenance::DATABASE), std::string(name)}},
-         maintenance::HIGHER_PRIORITY);
+        maintenance::HIGHER_PRIORITY);
     auto& mf = _server.getFeature<arangodb::MaintenanceFeature>();
     maintenance::CreateDatabase cd(mf, ad);
-    cd.first();   // Does the job
+    cd.first();  // Does the job
   }
 
   auto& databaseFeature = _server.getFeature<arangodb::DatabaseFeature>();
@@ -603,10 +608,10 @@ void MockDBServer::dropDatabase(std::string const& name) {
   maintenance::ActionDescription ad(
       {{std::string(maintenance::NAME), std::string(maintenance::DROP_DATABASE)},
        {std::string(maintenance::DATABASE), std::string(name)}},
-       maintenance::HIGHER_PRIORITY);
+      maintenance::HIGHER_PRIORITY);
   auto& mf = _server.getFeature<arangodb::MaintenanceFeature>();
   maintenance::DropDatabase dd(mf, ad);
-  dd.first();   // Does the job
+  dd.first();  // Does the job
 }
 
 MockCoordinator::MockCoordinator(bool start) : MockClusterServer() {
diff --git a/tests/Mocks/Servers.h b/tests/Mocks/Servers.h
index 596c45b83f5f..de8d7d3ba552 100644
--- a/tests/Mocks/Servers.h
+++ b/tests/Mocks/Servers.h
@@ -61,9 +61,7 @@ class MockServer {
   void init();
 
   TRI_vocbase_t& getSystemDatabase() const;
-  std::string const testFilesystemPath() const {
-    return _testFilesystemPath;
-  }
+  std::string const testFilesystemPath() const { return _testFilesystemPath; }
 
   // add a feature to the underlying server, keep track of it;
   // all added features will be prepared in startFeatures(), and unprepared in
@@ -100,9 +98,7 @@ class MockServer {
   void stopFeatures();
 
  protected:
-
-  arangodb::application_features::ApplicationServer::State
-    _oldApplicationServerState;
+  arangodb::application_features::ApplicationServer::State _oldApplicationServerState;
   arangodb::application_features::ApplicationServer _server;
   StorageEngineMock _engine;
   std::unordered_map<arangodb::application_features::ApplicationFeature*, bool> _features;
@@ -132,7 +128,7 @@ class MockAqlServer : public MockServer,
   ~MockAqlServer();
 
   std::shared_ptr<arangodb::transaction::Methods> createFakeTransaction() const;
-  std::unique_ptr<arangodb::aql::Query> createFakeQuery() const;
+  std::unique_ptr<arangodb::aql::Query> createFakeQuery(bool activateTracing = false) const;
 };
 
 class MockRestServer : public MockServer,

From 5b3e717e804b0380c8088bced91a1c68f5908ebd Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Mon, 27 Jan 2020 14:28:29 +0100
Subject: [PATCH 055/122] Feature/aql subquery execution block impl execute
 implementation shortest path executor (#10780)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

* Hook up new ShortestPathExecutor

* Small fixes

* Removed now unused code.

* Moved ShortestPathExecutor tests to use Execute only.

* Added a test for shortestPathExecutor where the output is smaller than the amount of entries within the path.

* Added a generic Lambda Executor, this can be used in ExecutionBlockImplTests to have finegrained control over the action happening within the Executor

* Fixed Windows compile issue

* Added first test using the LambdaExecutor.

* Added some tests around Execute. GetSome seems to be okayish. Skip not. Namely skipped numbers are not reported correctly.

* Made the first ExecutionBlock Execute integration test pass. Still other tests are failing

* Simplified the IsSkipSome test, this allows the C++ tests for Mixed Calls to pass.

* Windows compile fix

* Attempt at fixing ShortestPathExecutorTest for Windows

* Windows compile fix

* Added a skip test and fixed the producing executor to recreate the list once for every input line.

* Frankenstein my tests into the branch

* More tests. Also added a custom AqlCall printer function for GTest. Tests still red, need to fix fullCount and hardLimit.

* Implemented ostream operator for AQLCall.

* Properly implemented fullCount incl. UnitTest

* Added test for Callforwarding. They still have some todos, but these can only be solved by upgrading the OutputRow. Which should be part of separate PR

* Added another test for CallForwarding in passthrough state

* Added a Test Implementation for an Executor that uses a dynamic skip implementation.

* Fixed skip with HARDLIMIT.

* Startet to implement call forwarding test. However we need to improve Outputrow first this will be done in seperate branch

* Hack

* Removed designated initializers. Thanks for not supporting it MSVC!

* Update ShortestPathExecutorTest

* Removed non-passthrough non-skip Lambda Executor again. We decided to disallow this.

* Update tests/Aql/ExecutionBlockImplTest.cpp

Co-Authored-By: Markus Pfeiffer <markuspf@users.noreply.github.com>

* Started to add implementation of passthrough block allocation

* Added a comparator to AqlCall. Mostly for tests

* Fixed an issue in skip-passthrough version. Updated the tests.

* Allow to 'overSkip' if we do fullCount

* Enabled the first set of tests now. Only one set to go

* Applied all fixes to get Integration testsuite green

* Added some comments on the TestCases executed in the ExecutionBlockImpl

* Added tes descriptions and removed a duplicate test

* Added some comments on LamdbaExecutors

* Added description of ExecutionBlockImple execute logic

* Umbau 2.0

* Reshape output and skip a bit

* Some test fixes

* Applied review comments, thanks to reviewers

* Fixed modulo 2 off by one error

* Square 1

* Input validation

* ShortestPathExecutor with fullCount and tests

Co-authored-by: Markus Pfeiffer <markuspf@users.noreply.github.com>
Co-authored-by: Tobias Gödderz <github@tobias.goedderz.info>
---
 arangod/Aql/AqlCall.h                  |   18 +-
 arangod/Aql/ExecutionBlockImpl.cpp     |    8 +-
 arangod/Aql/ShortestPathExecutor.cpp   |  319 ++++---
 arangod/Aql/ShortestPathExecutor.h     |   90 +-
 tests/Aql/ShortestPathExecutorTest.cpp | 1049 ++++++++----------------
 tests/Aql/TestLambdaExecutor.cpp       |    2 +-
 tests/Aql/TestLambdaExecutor.h         |    2 +-
 7 files changed, 599 insertions(+), 889 deletions(-)

diff --git a/arangod/Aql/AqlCall.h b/arangod/Aql/AqlCall.h
index 6ece6b80ea4d..231c11402141 100644
--- a/arangod/Aql/AqlCall.h
+++ b/arangod/Aql/AqlCall.h
@@ -74,8 +74,10 @@ struct AqlCall {
   std::size_t getOffset() const { return offset; }
 
   std::size_t getLimit() const {
-    // By default we use batchsize
-    std::size_t limit = ExecutionBlock::DefaultBatchSize;
+    return clampToLimit(ExecutionBlock::DefaultBatchSize);
+  }
+
+  std::size_t clampToLimit(size_t limit) const {  // By default we use batchsize
     // We are not allowed to go above softLimit
     if (std::holds_alternative<std::size_t>(softLimit)) {
       limit = (std::min)(std::get<std::size_t>(softLimit), limit);
@@ -116,6 +118,18 @@ struct AqlCall {
   }
 
   bool needsFullCount() const { return fullCount; }
+
+  bool shouldSkip() const {
+    if (getOffset() > 0) {
+      // Still need to skip.
+      return true;
+    }
+    if (getLimit() > 0) {
+      // Still need to produce.
+      return false;
+    }
+    return needsFullCount();
+  }
 };
 
 constexpr bool operator<(AqlCall::Limit const& a, AqlCall::Limit const& b) {
diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index 6f553bad1505..035f760bc720 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -157,7 +157,8 @@ static bool constexpr isNewStyleExecutor() {
       std::is_same_v<Executor, TestLambdaExecutor> ||
       std::is_same_v<Executor, TestLambdaSkipExecutor> ||
 #endif
-      std::is_same_v<Executor, FilterExecutor>;
+      std::is_same_v<Executor, FilterExecutor> ||
+      std::is_same_v<Executor, ShortestPathExecutor>;
 }
 
 template <class Executor>
@@ -1138,9 +1139,10 @@ static SkipRowsRangeVariant constexpr skipRowsType() {
 
   static_assert(useExecutor == (
 #ifdef ARANGODB_USE_GOOGLE_TESTS
-                                   std::is_same_v<Executor, TestLambdaSkipExecutor> ||
+                                   (std::is_same_v<Executor, TestLambdaSkipExecutor>) ||
 #endif
-                                   std::is_same_v<Executor, FilterExecutor>),
+                                   std::is_same_v<Executor, FilterExecutor> ||
+                                   std::is_same_v<Executor, ShortestPathExecutor>),
                 "Unexpected executor for SkipVariants::EXECUTOR");
 
   // The LimitExecutor will not work correctly with SkipVariants::FETCHER!
diff --git a/arangod/Aql/ShortestPathExecutor.cpp b/arangod/Aql/ShortestPathExecutor.cpp
index 3d660353b7df..45679024e646 100644
--- a/arangod/Aql/ShortestPathExecutor.cpp
+++ b/arangod/Aql/ShortestPathExecutor.cpp
@@ -67,43 +67,53 @@ ShortestPathExecutorInfos::ShortestPathExecutorInfos(
       _source(std::move(source)),
       _target(std::move(target)) {}
 
-ShortestPathExecutorInfos::ShortestPathExecutorInfos(ShortestPathExecutorInfos&&) = default;
-ShortestPathExecutorInfos::~ShortestPathExecutorInfos() = default;
-
 arangodb::graph::ShortestPathFinder& ShortestPathExecutorInfos::finder() const {
   TRI_ASSERT(_finder);
   return *_finder.get();
 }
 
-bool ShortestPathExecutorInfos::useRegisterForInput(bool isTarget) const {
-  if (isTarget) {
-    return _target.type == InputVertex::REGISTER;
-  }
-  return _source.type == InputVertex::REGISTER;
+bool ShortestPathExecutorInfos::useRegisterForSourceInput() const {
+  return _source.type == InputVertex::Type::REGISTER;
 }
 
-RegisterId ShortestPathExecutorInfos::getInputRegister(bool isTarget) const {
-  TRI_ASSERT(useRegisterForInput(isTarget));
-  if (isTarget) {
-    return _target.reg;
-  }
+bool ShortestPathExecutorInfos::useRegisterForTargetInput() const {
+  return _target.type == InputVertex::Type::REGISTER;
+}
+
+RegisterId ShortestPathExecutorInfos::getSourceInputRegister() const {
+  TRI_ASSERT(useRegisterForSourceInput());
   return _source.reg;
 }
 
-std::string const& ShortestPathExecutorInfos::getInputValue(bool isTarget) const {
-  TRI_ASSERT(!useRegisterForInput(isTarget));
-  if (isTarget) {
-    return _target.value;
-  }
+RegisterId ShortestPathExecutorInfos::getTargetInputRegister() const {
+  TRI_ASSERT(useRegisterForTargetInput());
+  return _target.reg;
+}
+
+std::string const& ShortestPathExecutorInfos::getSourceInputValue() const {
+  TRI_ASSERT(!useRegisterForSourceInput());
   return _source.value;
 }
 
+std::string const& ShortestPathExecutorInfos::getTargetInputValue() const {
+  TRI_ASSERT(!useRegisterForTargetInput());
+  return _target.value;
+}
+
 bool ShortestPathExecutorInfos::usesOutputRegister(OutputName type) const {
   return _registerMapping.find(type) != _registerMapping.end();
 }
 
+ShortestPathExecutorInfos::InputVertex ShortestPathExecutorInfos::getSourceVertex() const noexcept {
+  return _source;
+}
+
+ShortestPathExecutorInfos::InputVertex ShortestPathExecutorInfos::getTargetVertex() const noexcept {
+  return _target;
+}
+
 static std::string typeToString(ShortestPathExecutorInfos::OutputName type) {
-  switch(type) {
+  switch (type) {
     case ShortestPathExecutorInfos::VERTEX:
       return std::string{"VERTEX"};
     case ShortestPathExecutorInfos::EDGE:
@@ -117,8 +127,8 @@ RegisterId ShortestPathExecutorInfos::findRegisterChecked(OutputName type) const
   auto const& it = _registerMapping.find(type);
   if (ADB_UNLIKELY(it == _registerMapping.end())) {
     THROW_ARANGO_EXCEPTION_MESSAGE(
-      TRI_ERROR_INTERNAL,
-      "Logic error: requested unused register type " + typeToString(type));
+        TRI_ERROR_INTERNAL,
+        "Logic error: requested unused register type " + typeToString(type));
   }
   return it->second;
 }
@@ -132,121 +142,197 @@ graph::TraverserCache* ShortestPathExecutorInfos::cache() const {
   return _finder->options().cache();
 }
 
-ShortestPathExecutor::ShortestPathExecutor(Fetcher& fetcher, Infos& infos)
+ShortestPathExecutor::ShortestPathExecutor(Fetcher&, Infos& infos)
     : _infos(infos),
-      _fetcher(fetcher),
-      _input{CreateInvalidInputRowHint{}},
-      _rowState(ExecutionState::HASMORE),
+      _inputRow{CreateInvalidInputRowHint{}},
       _finder{infos.finder()},
       _path{new arangodb::graph::ShortestPathResult{}},
-      _posInPath(1),
+      _posInPath(0),
       _sourceBuilder{},
       _targetBuilder{} {
-  if (!_infos.useRegisterForInput(false)) {
-    _sourceBuilder.add(VPackValue(_infos.getInputValue(false)));
+  if (!_infos.useRegisterForSourceInput()) {
+    _sourceBuilder.add(VPackValue(_infos.getSourceInputValue()));
   }
-  if (!_infos.useRegisterForInput(true)) {
-    _targetBuilder.add(VPackValue(_infos.getInputValue(true)));
+  if (!_infos.useRegisterForTargetInput()) {
+    _targetBuilder.add(VPackValue(_infos.getTargetInputValue()));
   }
 }
 
-ShortestPathExecutor::~ShortestPathExecutor() = default;
-
 // Shutdown query
 std::pair<ExecutionState, Result> ShortestPathExecutor::shutdown(int errorCode) {
   _finder.destroyEngines();
   return {ExecutionState::DONE, TRI_ERROR_NO_ERROR};
 }
 
+auto ShortestPathExecutor::doOutputPath(OutputAqlItemRow& output) -> void {
+  while (!output.isFull() && _posInPath < _path->length()) {
+    if (_infos.usesOutputRegister(ShortestPathExecutorInfos::VERTEX)) {
+      AqlValue vertex = _path->vertexToAqlValue(_infos.cache(), _posInPath);
+      output.cloneValueInto(_infos.getOutputRegister(ShortestPathExecutorInfos::VERTEX),
+                            _inputRow, vertex);
+    }
+    if (_infos.usesOutputRegister(ShortestPathExecutorInfos::EDGE)) {
+      AqlValue edge = _path->edgeToAqlValue(_infos.cache(), _posInPath);
+      output.cloneValueInto(_infos.getOutputRegister(ShortestPathExecutorInfos::EDGE),
+                            _inputRow, edge);
+    }
+    output.advanceRow();
+    _posInPath++;
+  }
+}
+
+auto ShortestPathExecutor::doSkipPath(AqlCall& call) -> size_t {
+  auto skip = size_t{0};
+
+  // call.getOffset() > 0 means we're in SKIP mode
+  if (call.getOffset() > 0) {
+    if (call.getOffset() < pathLengthAvailable()) {
+      skip = call.getOffset();
+    } else {
+      skip = pathLengthAvailable();
+    }
+  } else {
+    // call.getOffset() == 0, we might be in SKIP, PRODUCE, or
+    // FASTFORWARD/FULLCOUNT, but we only FASTFORWARD/FULLCOUNT if
+    // call.getLimit() == 0 as well.
+    if (call.needsFullCount() && call.getLimit() == 0) {
+      skip = pathLengthAvailable();
+    }
+  }
+  _posInPath += skip;
+  call.didSkip(skip);
+  return skip;
+}
+
+auto ShortestPathExecutor::fetchPath(AqlItemBlockInputRange& input) -> bool {
+  // We only want to call fetchPath if we don't have a path currently available
+  TRI_ASSERT(pathLengthAvailable() == 0);
+  _path->clear();
+  _posInPath = 0;
+
+  while (input.hasDataRow()) {
+    auto source = VPackSlice{};
+    auto target = VPackSlice{};
+    std::tie(std::ignore, _inputRow) = input.nextDataRow();
+    TRI_ASSERT(_inputRow.isInitialized());
+
+    // Ordering important here.
+    // Read source and target vertex, then try to find a shortest path (if both worked).
+    if (getVertexId(_infos.getSourceVertex(), _inputRow, _sourceBuilder, source) &&
+        getVertexId(_infos.getTargetVertex(), _inputRow, _targetBuilder, target) &&
+        _finder.shortestPath(source, target, *_path)) {
+      return true;
+    }
+  }
+  // Note that we only return false if
+  // the input does not have a data row, so if we return false
+  // here, we are DONE (we cannot produce any output anymore).
+  return false;
+}
+auto ShortestPathExecutor::pathLengthAvailable() -> size_t {
+  // Subtraction must not undeflow
+  TRI_ASSERT(_posInPath <= _path->length());
+  return _path->length() - _posInPath;
+}
+
 std::pair<ExecutionState, NoStats> ShortestPathExecutor::produceRows(OutputAqlItemRow& output) {
-  NoStats s;
+  TRI_ASSERT(false);
+  THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
+}
 
-  // Can be length 0 but never nullptr.
-  TRI_ASSERT(_path);
+auto ShortestPathExecutor::produceRows(AqlItemBlockInputRange& input, OutputAqlItemRow& output)
+    -> std::tuple<ExecutorState, Stats, AqlCall> {
   while (true) {
-    if (_posInPath < _path->length()) {
-      if (_infos.usesOutputRegister(ShortestPathExecutorInfos::VERTEX)) {
-        AqlValue vertex = _path->vertexToAqlValue(_infos.cache(), _posInPath);
-        AqlValueGuard guard{vertex, true};
-        output.moveValueInto(_infos.getOutputRegister(ShortestPathExecutorInfos::VERTEX),
-                             _input, guard);
+    if (pathLengthAvailable() > 0) {
+      // TODO maybe have doOutput report whether output is full?
+      doOutputPath(output);
+      if (output.isFull()) {
+        if (pathLengthAvailable() > 0) {
+          return {ExecutorState::HASMORE, NoStats{}, AqlCall{}};
+        } else {
+          // We don't have rows available for output. If
+          // upstream is DONE, we will not be able to produce more
+          // if upstream HASMORE, we do not know, so we say HASMORE.
+          return {input.upstreamState(), NoStats{}, AqlCall{}};
+        }
       }
-      if (_infos.usesOutputRegister(ShortestPathExecutorInfos::EDGE)) {
-        AqlValue edge = _path->edgeToAqlValue(_infos.cache(), _posInPath);
-        AqlValueGuard guard{edge, true};
-        output.moveValueInto(_infos.getOutputRegister(ShortestPathExecutorInfos::EDGE),
-                             _input, guard);
+    } else {
+      // If fetchPath fails, this means that input has not given us a dataRow
+      // that yielded a path.
+      // If upstream is DONE, we are done too, and if upstream
+      // HASMORE, we can potentially make more.
+      if (!fetchPath(input)) {
+        TRI_ASSERT(!input.hasDataRow());
+        return {input.upstreamState(), NoStats{}, AqlCall{}};
       }
-      _posInPath++;
-      return {computeState(), s};
     }
-    TRI_ASSERT(_posInPath >= _path->length());
-    if (!fetchPath()) {
-      TRI_ASSERT(_posInPath >= _path->length());
-      // Either WAITING or DONE
-      return {_rowState, s};
-    }
-    TRI_ASSERT(_posInPath < _path->length());
   }
 }
 
-bool ShortestPathExecutor::fetchPath() {
-  VPackSlice start;
-  VPackSlice end;
-  do {
-    // Make sure we have a valid start *and* end vertex
-    do {
-      std::tie(_rowState, _input) = _fetcher.fetchRow();
-      if (!_input.isInitialized()) {
-        // Either WAITING or DONE and nothing produced.
-        TRI_ASSERT(_rowState == ExecutionState::WAITING || _rowState == ExecutionState::DONE);
-        return false;
-      }
-    } while (!getVertexId(false, start) || !getVertexId(true, end));
-    TRI_ASSERT(start.isString());
-    TRI_ASSERT(end.isString());
-    _path->clear();
-  } while (!_finder.shortestPath(start, end, *_path));
-  _posInPath = 0;
-  return true;
-}
+auto ShortestPathExecutor::skipRowsRange(AqlItemBlockInputRange& input, AqlCall& call)
+    -> std::tuple<ExecutorState, size_t, AqlCall> {
+  auto skipped = size_t{0};
+
+  while (true) {
+    skipped += doSkipPath(call);
 
-ExecutionState ShortestPathExecutor::computeState() const {
-  if (_rowState == ExecutionState::HASMORE || _posInPath < _path->length()) {
-    return ExecutionState::HASMORE;
+    if (pathLengthAvailable() == 0) {
+      if (!fetchPath(input)) {
+        TRI_ASSERT(!input.hasDataRow());
+        return {input.upstreamState(), skipped, AqlCall{}};
+      }
+    } else {
+      // if we end up here there is path available, but
+      // we have skipped as much as we were asked to.
+      TRI_ASSERT(call.getOffset() == 0);
+      return {ExecutorState::HASMORE, skipped, AqlCall{}};
+    }
   }
-  return ExecutionState::DONE;
 }
 
-bool ShortestPathExecutor::getVertexId(bool isTarget, VPackSlice& id) {
-  if (_infos.useRegisterForInput(isTarget)) {
-    // The input row stays valid until the next fetchRow is executed.
-    // So the slice can easily point to it.
-    RegisterId reg = _infos.getInputRegister(isTarget);
-    AqlValue const& in = _input.getValue(reg);
-    if (in.isObject()) {
-      try {
-        auto idString = _finder.options().trx()->extractIdString(in.slice());
-        if (isTarget) {
-          _targetBuilder.clear();
-          _targetBuilder.add(VPackValue(idString));
-          id = _targetBuilder.slice();
-        } else {
-          _sourceBuilder.clear();
-          _sourceBuilder.add(VPackValue(idString));
-          id = _sourceBuilder.slice();
+bool ShortestPathExecutor::getVertexId(ShortestPathExecutorInfos::InputVertex const& vertex,
+                                       InputAqlItemRow& row,
+                                       VPackBuilder& builder, VPackSlice& id) {
+  switch (vertex.type) {
+    case ShortestPathExecutorInfos::InputVertex::Type::REGISTER: {
+      AqlValue const& in = row.getValue(vertex.reg);
+      if (in.isObject()) {
+        try {
+          auto idString = _finder.options().trx()->extractIdString(in.slice());
+          builder.clear();
+          builder.add(VPackValue(idString));
+          id = builder.slice();
+          // Guranteed by extractIdValue
+          TRI_ASSERT(::isValidId(id));
+        } catch (...) {
+          // _id or _key not present... ignore this error and fall through
+          // returning no path
+          return false;
+        }
+        return true;
+      } else if (in.isString()) {
+        id = in.slice();
+        // Validation
+        if (!::isValidId(id)) {
+          _finder.options().query()->registerWarning(
+              TRI_ERROR_BAD_PARAMETER,
+              "Invalid input for Shortest Path: "
+              "Only id strings or objects with "
+              "_id are allowed");
+          return false;
         }
-        // Guranteed by extractIdValue
-        TRI_ASSERT(::isValidId(id));
-      } catch (...) {
-        // _id or _key not present... ignore this error and fall through
-        // returning no path
+        return true;
+      } else {
+        _finder.options().query()->registerWarning(
+            TRI_ERROR_BAD_PARAMETER,
+            "Invalid input for Shortest Path: "
+            "Only id strings or objects with "
+            "_id are allowed");
         return false;
       }
-      return true;
-    } else if (in.isString()) {
-      id = in.slice();
-      // Validation
+    }
+    case ShortestPathExecutorInfos::InputVertex::Type::CONSTANT: {
+      id = builder.slice();
       if (!::isValidId(id)) {
         _finder.options().query()->registerWarning(
             TRI_ERROR_BAD_PARAMETER,
@@ -256,28 +342,7 @@ bool ShortestPathExecutor::getVertexId(bool isTarget, VPackSlice& id) {
         return false;
       }
       return true;
-    } else {
-      _finder.options().query()->registerWarning(
-          TRI_ERROR_BAD_PARAMETER,
-          "Invalid input for Shortest Path: "
-          "Only id strings or objects with "
-          "_id are allowed");
-      return false;
-    }
-  } else {
-    if (isTarget) {
-      id = _targetBuilder.slice();
-    } else {
-      id = _sourceBuilder.slice();
-    }
-    if (!::isValidId(id)) {
-      _finder.options().query()->registerWarning(
-          TRI_ERROR_BAD_PARAMETER,
-          "Invalid input for Shortest Path: "
-          "Only id strings or objects with "
-          "_id are allowed");
-      return false;
     }
-    return true;
   }
+  return false;
 }
diff --git a/arangod/Aql/ShortestPathExecutor.h b/arangod/Aql/ShortestPathExecutor.h
index 36e9a84849ac..93bdfe2fe3ca 100644
--- a/arangod/Aql/ShortestPathExecutor.h
+++ b/arangod/Aql/ShortestPathExecutor.h
@@ -23,12 +23,18 @@
 #ifndef ARANGOD_AQL_SHORTEST_PATH_EXECUTOR_H
 #define ARANGOD_AQL_SHORTEST_PATH_EXECUTOR_H
 
+#include "Aql/AqlCall.h"
+#include "Aql/AqlItemBlockInputRange.h"
 #include "Aql/ExecutionState.h"
 #include "Aql/ExecutorInfos.h"
 #include "Aql/InputAqlItemRow.h"
+#include "Graph/ShortestPathFinder.h"
+#include "Graph/ShortestPathResult.h"
 
 #include <velocypack/Builder.h>
 
+using namespace arangodb::velocypack;
+
 namespace arangodb {
 
 class Result;
@@ -53,16 +59,17 @@ class NoStats;
 class ShortestPathExecutorInfos : public ExecutorInfos {
  public:
   struct InputVertex {
-    enum { CONSTANT, REGISTER } type;
+    enum class Type { CONSTANT, REGISTER };
+    Type type;
     // TODO make the following two a union instead
     RegisterId reg;
     std::string value;
 
     // cppcheck-suppress passedByValue
     explicit InputVertex(std::string value)
-        : type(CONSTANT), reg(0), value(std::move(value)) {}
+        : type(Type::CONSTANT), reg(0), value(std::move(value)) {}
     explicit InputVertex(RegisterId reg)
-        : type(REGISTER), reg(reg), value("") {}
+        : type(Type::REGISTER), reg(reg), value("") {}
   };
 
   enum OutputName { VERTEX, EDGE };
@@ -81,9 +88,9 @@ class ShortestPathExecutorInfos : public ExecutorInfos {
 
   ShortestPathExecutorInfos() = delete;
 
-  ShortestPathExecutorInfos(ShortestPathExecutorInfos&&);
+  ShortestPathExecutorInfos(ShortestPathExecutorInfos&&) = default;
   ShortestPathExecutorInfos(ShortestPathExecutorInfos const&) = delete;
-  ~ShortestPathExecutorInfos();
+  ~ShortestPathExecutorInfos() = default;
 
   arangodb::graph::ShortestPathFinder& finder() const;
 
@@ -92,38 +99,44 @@ class ShortestPathExecutorInfos : public ExecutorInfos {
    *
    * @param isTarget defines if we look for target(true) or source(false)
    */
-  bool useRegisterForInput(bool isTarget) const;
+  [[nodiscard]] bool useRegisterForSourceInput() const;
+  [[nodiscard]] bool useRegisterForTargetInput() const;
 
   /**
    * @brief get the register used for the input
    *
    * @param isTarget defines if we look for target(true) or source(false)
    */
-  RegisterId getInputRegister(bool isTarget) const;
+  [[nodiscard]] RegisterId getSourceInputRegister() const;
+  [[nodiscard]] RegisterId getTargetInputRegister() const;
 
   /**
    * @brief get the const value for the input
    *
    * @param isTarget defines if we look for target(true) or source(false)
    */
-  std::string const& getInputValue(bool isTarget) const;
+  [[nodiscard]] std::string const& getSourceInputValue() const;
+  [[nodiscard]] std::string const& getTargetInputValue() const;
 
   /**
    * @brief test if we have an output register for this type
    *
    * @param type: Either VERTEX or EDGE
    */
-  bool usesOutputRegister(OutputName type) const;
+  [[nodiscard]] bool usesOutputRegister(OutputName type) const;
 
   /**
    * @brief get the output register for the given type
    */
-  RegisterId getOutputRegister(OutputName type) const;
+  [[nodiscard]] RegisterId getOutputRegister(OutputName type) const;
+
+  [[nodiscard]] graph::TraverserCache* cache() const;
 
-  graph::TraverserCache* cache() const;
+  [[nodiscard]] InputVertex getSourceVertex() const noexcept;
+  [[nodiscard]] InputVertex getTargetVertex() const noexcept;
 
  private:
-  RegisterId findRegisterChecked(OutputName type) const;
+  [[nodiscard]] RegisterId findRegisterChecked(OutputName type) const;
 
  private:
   /// @brief the shortest path finder.
@@ -157,57 +170,60 @@ class ShortestPathExecutor {
   ShortestPathExecutor(ShortestPathExecutor&&) = default;
 
   ShortestPathExecutor(Fetcher& fetcher, Infos&);
-  ~ShortestPathExecutor();
+  ~ShortestPathExecutor() = default;
 
   /**
    * @brief Shutdown will be called once for every query
    *
    * @return ExecutionState and no error.
    */
-  std::pair<ExecutionState, Result> shutdown(int errorCode);
+  [[nodiscard]] auto shutdown(int errorCode) -> std::pair<ExecutionState, Result>;
+
   /**
    * @brief produce the next Row of Aql Values.
-   *
-   * @return ExecutionState, and if successful exactly one new Row of AqlItems.
    */
-  std::pair<ExecutionState, Stats> produceRows(OutputAqlItemRow& output);
+  [[nodiscard]] auto produceRows(OutputAqlItemRow& output)
+      -> std::pair<ExecutionState, NoStats>;
+  [[nodiscard]] auto produceRows(AqlItemBlockInputRange& input, OutputAqlItemRow& output)
+      -> std::tuple<ExecutorState, Stats, AqlCall>;
+  [[nodiscard]] auto skipRowsRange(AqlItemBlockInputRange& input, AqlCall& call)
+      -> std::tuple<ExecutorState, size_t, AqlCall>;
 
  private:
   /**
-   * @brief Fetch input row(s) and compute path
-   *
-   * @return false if we are done and no path could be found.
+   *  @brief fetches a path given the current row in input.
+   *  a flag indicating whether we found a path, put it into the
+   *  internal state.
    */
-  bool fetchPath();
+  [[nodiscard]] auto fetchPath(AqlItemBlockInputRange& input) -> bool;
+  [[nodiscard]] auto pathLengthAvailable() -> size_t;
 
   /**
-   * @brief compute the correct return state
-   *
-   * @return DONE if no more is expected
+   *  @brief produce the output from the currently stored path until either
+   *  the path is exhausted or there is no output space left.
    */
-
-  ExecutionState computeState() const;
-
+  auto doOutputPath(OutputAqlItemRow& output) -> void;
+  auto doSkipPath(AqlCall& call) -> size_t;
   /**
    * @brief get the id of a input vertex
-   * Result will be in id parameter, it
-   * is guaranteed that the memory
-   * is managed until the next call of fetchPath.
-   *
-   * @return DONE if no more is expected
+   * Result will be written into the given Slice.
+   * This is either managed by the handed in builder (might be overwritten),
+   * or by the handed in row, or a constant value in the options.
+   * In any case it will stay valid at least until the reference to the input
+   * row is lost, or the builder is resetted.
    */
-  bool getVertexId(bool isTarget, arangodb::velocypack::Slice& id);
+  [[nodiscard]] auto getVertexId(ShortestPathExecutorInfos::InputVertex const& vertex,
+                                 InputAqlItemRow& row, Builder& builder, Slice& id) -> bool;
 
  private:
   Infos& _infos;
-  Fetcher& _fetcher;
-  InputAqlItemRow _input;
-  ExecutionState _rowState;
+  InputAqlItemRow _inputRow;
+
   /// @brief the shortest path finder.
   arangodb::graph::ShortestPathFinder& _finder;
+
   /// @brief current computed path.
   std::unique_ptr<graph::ShortestPathResult> _path;
-
   size_t _posInPath;
 
   /// @brief temporary memory mangement for source id
diff --git a/tests/Aql/ShortestPathExecutorTest.cpp b/tests/Aql/ShortestPathExecutorTest.cpp
index 4765135c4739..28a8bdc3fb9b 100644
--- a/tests/Aql/ShortestPathExecutorTest.cpp
+++ b/tests/Aql/ShortestPathExecutorTest.cpp
@@ -32,6 +32,8 @@
 #include "Mocks/Servers.h"
 
 #include "Aql/AqlItemBlock.h"
+#include "Aql/AqlItemBlockHelper.h"
+#include "Aql/AqlItemBlockManager.h"
 #include "Aql/AqlValue.h"
 #include "Aql/ExecutorInfos.h"
 #include "Aql/InputAqlItemRow.h"
@@ -47,9 +49,12 @@
 #include "Graph/TraverserCache.h"
 #include "Graph/TraverserOptions.h"
 
+#include "../Mocks/Servers.h"
+
 using namespace arangodb;
 using namespace arangodb::aql;
 using namespace arangodb::graph;
+using namespace arangodb::tests::mocks;
 
 namespace arangodb {
 namespace tests {
@@ -114,6 +119,10 @@ class TokenTranslator : public TraverserCache {
   std::unordered_set<VPackSlice, arangodb::basics::VelocyPackHelper::VPackHash, arangodb::basics::VelocyPackHelper::VPackEqual> _edges;
 };
 
+// FakePathFinder only stores a lump of pairs (source and targets) by which
+// sequences of outputs can be found. It also stores which paths it has been
+// asked for to verify later whether the outputs produced by the
+// ShortestPathExecutor are the ones we expected.
 class FakePathFinder : public ShortestPathFinder {
  public:
   FakePathFinder(ShortestPathOptions& opts, TokenTranslator& translator)
@@ -130,6 +139,7 @@ class FakePathFinder : public ShortestPathFinder {
     TRI_ASSERT(source.isString());
     TRI_ASSERT(target.isString());
     _calledWith.emplace_back(std::make_pair(source.copyString(), target.copyString()));
+
     std::string const s = source.copyString();
     std::string const t = target.copyString();
     for (auto const& p : _paths) {
@@ -146,14 +156,13 @@ class FakePathFinder : public ShortestPathFinder {
     return false;
   }
 
-  std::vector<std::string> const& findPath(std::pair<std::string, std::string> const& src) {
+  std::vector<std::string> const& findPath(std::pair<std::string, std::string> const& src) const {
     for (auto const& p : _paths) {
       if (p.front() == src.first && p.back() == src.second) {
         return p;
       }
     }
-    TRI_ASSERT(false);
-    THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
+    return _theEmptyPath;
   }
 
   std::pair<std::string, std::string> const& calledAt(size_t index) {
@@ -161,10 +170,15 @@ class FakePathFinder : public ShortestPathFinder {
     return _calledWith[index];
   }
 
+  [[nodiscard]] auto getCalledWith() -> std::vector<std::pair<std::string, std::string>> {
+    return _calledWith;
+  };
+
   // Needs to provide lookupFunctionality for Cache
  private:
   std::vector<std::vector<std::string>> _paths;
   std::vector<std::pair<std::string, std::string>> _calledWith;
+  std::vector<std::string> const _theEmptyPath{};
   TokenTranslator& _translator;
 };
 
@@ -175,762 +189,361 @@ struct TestShortestPathOptions : public ShortestPathOptions {
   }
 };
 
+using Vertex = ShortestPathExecutorInfos::InputVertex;
+using RegisterSet = std::unordered_set<RegisterId>;
+using RegisterMapping =
+    std::unordered_map<ShortestPathExecutorInfos::OutputName, RegisterId, ShortestPathExecutorInfos::OutputNameHash>;
+using Path = std::vector<std::string>;
+using PathSequence = std::vector<Path>;
+
+enum class ShortestPathOutput { VERTEX_ONLY, VERTEX_AND_EDGE };
+
+// TODO: this needs a << operator
+struct ShortestPathTestParameters {
+  static RegisterSet _makeOutputRegisters(ShortestPathOutput in) {
+    switch (in) {
+      case ShortestPathOutput::VERTEX_ONLY:
+        return RegisterSet{std::initializer_list<RegisterId>{2}};
+      case ShortestPathOutput::VERTEX_AND_EDGE:
+        return RegisterSet{std::initializer_list<RegisterId>{2, 3}};
+    }
+    return RegisterSet{};
+  }
+  static RegisterMapping _makeRegisterMapping(ShortestPathOutput in) {
+    switch (in) {
+      case ShortestPathOutput::VERTEX_ONLY:
+        return RegisterMapping{{ShortestPathExecutorInfos::OutputName::VERTEX, 2}};
+        break;
+      case ShortestPathOutput::VERTEX_AND_EDGE:
+        return RegisterMapping{{ShortestPathExecutorInfos::OutputName::VERTEX, 2},
+                               {ShortestPathExecutorInfos::OutputName::EDGE, 3}};
+    }
+    return RegisterMapping{};
+  }
+
+  ShortestPathTestParameters(
+      std::tuple<Vertex, Vertex, MatrixBuilder<2>, PathSequence, AqlCall, ShortestPathOutput, size_t> params)
+      : _source(std::get<0>(params)),
+        _target(std::get<1>(params)),
+        _outputRegisters(_makeOutputRegisters(std::get<5>(params))),
+        _registerMapping(_makeRegisterMapping(std::get<5>(params))),
+        _inputMatrix{std::get<2>(params)},
+        _inputMatrixCopy{std::get<2>(params)},
+        _paths(std::get<3>(params)),
+        _call(std::get<4>(params)),
+        _blockSize(std::get<6>(params)) {}
+
+  Vertex _source;
+  Vertex _target;
+  RegisterSet _inputRegisters;
+  RegisterSet _outputRegisters;
+  RegisterMapping _registerMapping;
+  MatrixBuilder<2> _inputMatrix;
+  MatrixBuilder<2> _inputMatrixCopy;
+  PathSequence _paths;
+  AqlCall _call;
+  size_t _blockSize{1000};
+};
+
 class ShortestPathExecutorTest
     : public ::testing::Test,
-      public arangodb::tests::LogSuppressor<arangodb::Logger::CLUSTER, arangodb::LogLevel::ERR> {
+      public ::testing::WithParamInterface<std::tuple<Vertex, Vertex, MatrixBuilder<2>, PathSequence, AqlCall, ShortestPathOutput, size_t>> {
  protected:
-  RegisterId sourceIn;
-  RegisterId targetIn;
-  ShortestPathExecutorInfos::InputVertex constSource;
-  ShortestPathExecutorInfos::InputVertex constTarget;
-  ShortestPathExecutorInfos::InputVertex regSource;
-  ShortestPathExecutorInfos::InputVertex regTarget;
-  ShortestPathExecutorInfos::InputVertex brokenSource;
-  ShortestPathExecutorInfos::InputVertex brokenTarget;
+  ShortestPathTestParameters parameters;
+
+  MockAqlServer server;
+  ExecutionState state;
+  ResourceMonitor monitor;
+  AqlItemBlockManager itemBlockManager;
+  std::unique_ptr<arangodb::aql::Query> fakedQuery;
+  TestShortestPathOptions options;
+  TokenTranslator& translator;
+
+  // parameters are copied because they are const otherwise
+  // and that doesn't mix with std::move
+  ShortestPathExecutorInfos infos;
+
+  FakePathFinder& finder;
+
+  SharedAqlItemBlockPtr inputBlock;
+  AqlItemBlockInputRange input;
+
+  std::shared_ptr<Builder> fakeUnusedBlock;
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher;
+
+  ShortestPathExecutor testee;
 
   ShortestPathExecutorTest()
-      : sourceIn(0),
-        targetIn(1),
-        constSource("vertex/source"),
-        constTarget("vertex/target"),
-        regSource(sourceIn),
-        regTarget(targetIn),
-        brokenSource{"IwillBreakYourSearch"},
-        brokenTarget{"I will also break your search"} {}
-
-  void ValidateResult(ShortestPathExecutorInfos& infos, OutputAqlItemRow& result,
-                      std::vector<std::pair<std::string, std::string>> const& resultPaths) {
-    if (!resultPaths.empty()) {
-      FakePathFinder& finder = static_cast<FakePathFinder&>(infos.finder());
-      TokenTranslator& translator = *(static_cast<TokenTranslator*>(infos.cache()));
-      auto block = result.stealBlock();
-      ASSERT_NE(block, nullptr);
-      size_t index = 0;
-      for (size_t i = 0; i < resultPaths.size(); ++i) {
-        auto path = finder.findPath(resultPaths[i]);
-        for (size_t j = 0; j < path.size(); ++j) {
+      : parameters(GetParam()),
+        server{},
+        itemBlockManager(&monitor, SerializationFormat::SHADOWROWS),
+        fakedQuery(server.createFakeQuery()),
+        options(fakedQuery.get()),
+        translator(*(static_cast<TokenTranslator*>(options.cache()))),
+        infos(std::make_shared<RegisterSet>(parameters._inputRegisters),
+              std::make_shared<RegisterSet>(parameters._outputRegisters), 2, 4,
+              {}, {0, 1}, std::make_unique<FakePathFinder>(options, translator),
+              std::move(parameters._registerMapping),
+              std::move(parameters._source), std::move(parameters._target)),
+        finder(static_cast<FakePathFinder&>(infos.finder())),
+        inputBlock(buildBlock<2>(itemBlockManager, std::move(parameters._inputMatrix))),
+        input(AqlItemBlockInputRange(ExecutorState::DONE, inputBlock, 0,
+                                     inputBlock->size())),
+        fakeUnusedBlock(VPackParser::fromJson("[]")),
+        fetcher(itemBlockManager, fakeUnusedBlock->steal(), false),
+        testee(fetcher, infos) {
+    for (auto&& p : parameters._paths) {
+      finder.addPath(std::move(p));
+    }
+  }
+
+  size_t ExpectedNumberOfRowsProduced(size_t expectedFound) {
+    if (parameters._call.getOffset() >= expectedFound) {
+      return 0;
+    } else {
+      expectedFound -= parameters._call.getOffset();
+    }
+    return parameters._call.clampToLimit(expectedFound);
+  }
+
+  // We only verify that the shortest path executor was called with
+  // correct inputs
+  void ValidateCalledWith() {
+    auto pathsQueriedBetween = finder.getCalledWith();
+    auto block = buildBlock<2>(itemBlockManager, std::move(parameters._inputMatrix));
+
+    // We should always only call the finder at most for all input rows
+    ASSERT_LE(pathsQueriedBetween.size(), block->size());
+
+    auto blockIndex = size_t{0};
+    for (auto const& input : pathsQueriedBetween) {
+      auto source = std::string{};
+      auto target = std::string{};
+
+      if (infos.useRegisterForSourceInput()) {
+        AqlValue value = block->getValue(blockIndex, infos.getSourceInputRegister());
+        ASSERT_TRUE(value.isString());
+        source = value.slice().copyString();
+      } else {
+        source = infos.getSourceInputValue();
+      }
+
+      if (infos.useRegisterForTargetInput()) {
+        AqlValue value = block->getValue(blockIndex, infos.getTargetInputRegister());
+        ASSERT_TRUE(value.isString());
+        target = value.slice().copyString();
+      } else {
+        target = infos.getTargetInputValue();
+      }
+      ASSERT_EQ(source, input.first);
+      ASSERT_EQ(target, input.second);
+      blockIndex++;
+    }
+  }
+
+  // TODO: check fullcount correctness.
+  void ValidateResult(std::vector<SharedAqlItemBlockPtr>& results,
+                      size_t skippedInitial, size_t skippedFullCount) {
+    auto pathsQueriedBetween = finder.getCalledWith();
+
+    FakePathFinder& finder = static_cast<FakePathFinder&>(infos.finder());
+    TokenTranslator& translator = *(static_cast<TokenTranslator*>(infos.cache()));
+
+    auto expectedRowsFound = std::vector<std::string>{};
+    auto expectedPathStarts = std::set<size_t>{};
+    for (auto&& p : pathsQueriedBetween) {
+      auto& f = finder.findPath(p);
+      expectedPathStarts.insert(expectedRowsFound.size());
+      expectedRowsFound.insert(expectedRowsFound.end(), f.begin(), f.end());
+    }
+
+    auto expectedNrRowsSkippedInitial =
+        std::min(parameters._call.getOffset(), expectedRowsFound.size());
+    EXPECT_EQ(skippedInitial, expectedNrRowsSkippedInitial);
+
+    // TODO: Really we're relying on the fact here that the executor
+    //       calls the path finder with the correct inputs, where we should
+    //       assert/compute the paths that could be produced if the
+    //       finder is called with the input parameters given in the test
+    auto expectedNrRowsProduced = ExpectedNumberOfRowsProduced(expectedRowsFound.size());
+
+    auto expectedRowsIndex = size_t{skippedInitial};
+    for (auto const& block : results) {
+      if (block != nullptr) {
+        ASSERT_NE(block, nullptr);
+        for (size_t blockIndex = 0; blockIndex < block->size(); ++blockIndex, ++expectedRowsIndex) {
           if (infos.usesOutputRegister(ShortestPathExecutorInfos::VERTEX)) {
             AqlValue value =
-                block->getValue(index, infos.getOutputRegister(ShortestPathExecutorInfos::VERTEX));
+                block->getValue(blockIndex,
+                                infos.getOutputRegister(ShortestPathExecutorInfos::VERTEX));
             EXPECT_TRUE(value.isObject());
             EXPECT_TRUE(arangodb::basics::VelocyPackHelper::compare(
                             value.slice(),
-                            translator.translateVertex(arangodb::velocypack::StringRef(path[j])),
+                            translator.translateVertex(arangodb::velocypack::StringRef(
+                                expectedRowsFound[expectedRowsIndex])),
                             false) == 0);
           }
           if (infos.usesOutputRegister(ShortestPathExecutorInfos::EDGE)) {
             AqlValue value =
-                block->getValue(index, infos.getOutputRegister(ShortestPathExecutorInfos::EDGE));
-            if (j == 0) {
+                block->getValue(blockIndex,
+                                infos.getOutputRegister(ShortestPathExecutorInfos::EDGE));
+
+            if (expectedPathStarts.find(expectedRowsIndex) != expectedPathStarts.end()) {
               EXPECT_TRUE(value.isNull(false));
             } else {
               EXPECT_TRUE(value.isObject());
               VPackSlice edge = value.slice();
               // FROM and TO checks are enough here.
               EXPECT_TRUE(arangodb::velocypack::StringRef(edge.get(StaticStrings::FromString))
-                              .compare(path[j - 1]) == 0);
+                              .compare(expectedRowsFound[expectedRowsIndex - 1]) == 0);
               EXPECT_TRUE(arangodb::velocypack::StringRef(edge.get(StaticStrings::ToString))
-                              .compare(path[j]) == 0);
+                              .compare(expectedRowsFound[expectedRowsIndex]) == 0);
             }
           }
-          ++index;
         }
       }
     }
-  }
+    ASSERT_EQ(expectedRowsIndex - skippedInitial, expectedNrRowsProduced);
 
-  void TestExecutor(bool waiting, ShortestPathExecutorInfos& infos,
-                    std::shared_ptr<VPackBuilder> const& input,
-                    std::vector<std::pair<std::string, std::string>> const& resultPaths) {
-    if (waiting) {
-      TestExecutorWaiting(infos, input, resultPaths);
-    } else {
-      TestExecutorNotWaiting(infos, input, resultPaths);
+    // If a fullCount was requested, the sum (skippedInitial + produced +
+    // skippedFullCount) should be exactly the number of rows we produced.
+    if (parameters._call.fullCount) {
+      ASSERT_EQ(skippedInitial + (expectedRowsIndex - skippedInitial) + skippedFullCount,
+                expectedRowsFound.size());
     }
   }
 
-  void TestExecutorWaiting(ShortestPathExecutorInfos& infos,
-                           std::shared_ptr<VPackBuilder> const& input,
-                           std::vector<std::pair<std::string, std::string>> const& resultPaths) {
-    ResourceMonitor monitor;
-    AqlItemBlockManager itemBlockManager{&monitor, SerializationFormat::SHADOWROWS};
-    SharedAqlItemBlockPtr block{new AqlItemBlock(itemBlockManager, 1000, 4)};
-
-    NoStats stats{};
-    ExecutionState state = ExecutionState::HASMORE;
-    auto& finder = dynamic_cast<FakePathFinder&>(infos.finder());
-
-    SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), true);
-    OutputAqlItemRow result(std::move(block), infos.getOutputRegisters(),
-                            infos.registersToKeep(), infos.registersToClear());
-    ShortestPathExecutor testee(fetcher, infos);
-    // Fetch fullPath
-    for (size_t i = 0; i < resultPaths.size(); ++i) {
-      EXPECT_EQ(state, ExecutionState::HASMORE);
-      // if we pull, we always wait
-      std::tie(state, stats) = testee.produceRows(result);
-      EXPECT_EQ(state, ExecutionState::WAITING);
-      EXPECT_FALSE(result.produced());
-      state = ExecutionState::HASMORE;  // For simplicity on path fetching.
-      auto path = finder.findPath(resultPaths[i]);
-      for (ADB_IGNORE_UNUSED auto const& v : path) {
-        ASSERT_EQ(state, ExecutionState::HASMORE);
-        std::tie(state, stats) = testee.produceRows(result);
-        EXPECT_TRUE(result.produced());
-        result.advanceRow();
-      }
-      auto gotCalledWith = finder.calledAt(i);
-      EXPECT_EQ(gotCalledWith.first, resultPaths[i].first);
-      EXPECT_EQ(gotCalledWith.second, resultPaths[i].second);
-    }
-    if (resultPaths.empty()) {
-      // Fetch at least twice, one waiting
-      std::tie(state, stats) = testee.produceRows(result);
-      EXPECT_EQ(state, ExecutionState::WAITING);
-      EXPECT_FALSE(result.produced());
-      // One no findings
-      std::tie(state, stats) = testee.produceRows(result);
+  void TestExecutor() {
+    // We use a copy here because we modify the call and want to keep track
+    // of whether things happen the correct way.
+    auto ourCall = AqlCall{parameters._call};
+    auto skippedInitial = size_t{0};
+    auto skippedFullCount = size_t{0};
+    auto state = ExecutorState{ExecutorState::HASMORE};
+    auto outputs = std::vector<SharedAqlItemBlockPtr>{};
+
+    // TODO: Do we have to emulate pauses because
+    //       upstream needs to produce more?
+    //       that would require breaking up the input
+    //       matrix into chunks and feeding those into
+    //       the executor.
+
+    // If an offset is requested, skip
+    if (ourCall.getOffset() > 0) {
+      std::tie(state, skippedInitial, std::ignore) = testee.skipRowsRange(input, ourCall);
     }
 
-    EXPECT_EQ(state, ExecutionState::DONE);
-    EXPECT_FALSE(result.produced());
-    ValidateResult(infos, result, resultPaths);
-  }
+    // Produce rows
+    while (state == ExecutorState::HASMORE && ourCall.getLimit() > 0) {
+      SharedAqlItemBlockPtr block =
+          itemBlockManager.requestBlock(parameters._blockSize, 4);
 
-  void TestExecutorNotWaiting(ShortestPathExecutorInfos& infos,
-                              std::shared_ptr<VPackBuilder> const& input,
-                              std::vector<std::pair<std::string, std::string>> const& resultPaths) {
-    ResourceMonitor monitor;
-    AqlItemBlockManager itemBlockManager{&monitor, SerializationFormat::SHADOWROWS};
-    SharedAqlItemBlockPtr block{new AqlItemBlock(itemBlockManager, 1000, 4)};
-
-    NoStats stats{};
-    ExecutionState state = ExecutionState::HASMORE;
-    auto& finder = dynamic_cast<FakePathFinder&>(infos.finder());
-
-    SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), false);
-    OutputAqlItemRow result(std::move(block), infos.getOutputRegisters(),
-                            infos.registersToKeep(), infos.registersToClear());
-    ShortestPathExecutor testee(fetcher, infos);
-    // Fetch fullPath
-    for (size_t i = 0; i < resultPaths.size(); ++i) {
-      EXPECT_EQ(state, ExecutionState::HASMORE);
-      auto path = finder.findPath(resultPaths[i]);
-      for (ADB_IGNORE_UNUSED auto const& v : path) {
-        ASSERT_EQ(state, ExecutionState::HASMORE);
-        std::tie(state, stats) = testee.produceRows(result);
-        EXPECT_TRUE(result.produced());
-        result.advanceRow();
-      }
-      auto gotCalledWith = finder.calledAt(i);
-      EXPECT_EQ(gotCalledWith.first, resultPaths[i].first);
-      EXPECT_EQ(gotCalledWith.second, resultPaths[i].second);
-    }
-    if (resultPaths.empty()) {
-      // We need to fetch once
-      std::tie(state, stats) = testee.produceRows(result);
-    }
-    EXPECT_FALSE(result.produced());
-    EXPECT_EQ(state, ExecutionState::DONE);
-    ValidateResult(infos, result, resultPaths);
-  }
+      OutputAqlItemRow output(std::move(block), infos.getOutputRegisters(),
+                              infos.registersToKeep(), infos.registersToClear());
+      output.setCall(std::move(ourCall));
 
-  void RunSimpleTest(bool waiting, ShortestPathExecutorInfos::InputVertex&& source,
-                     ShortestPathExecutorInfos::InputVertex&& target) {
-    RegisterId vOutReg = 2;
-    mocks::MockAqlServer server{};
-    std::unique_ptr<arangodb::aql::Query> fakedQuery = server.createFakeQuery();
-    auto inputRegisters = std::make_shared<std::unordered_set<RegisterId>>(
-        std::initializer_list<RegisterId>{});
-    auto outputRegisters = std::make_shared<std::unordered_set<RegisterId>>(
-        std::initializer_list<RegisterId>{vOutReg});
-    std::unordered_map<ShortestPathExecutorInfos::OutputName, RegisterId, ShortestPathExecutorInfos::OutputNameHash> registerMapping{
-        {ShortestPathExecutorInfos::OutputName::VERTEX, vOutReg}};
-    TestShortestPathOptions options(fakedQuery.get());
-    TokenTranslator& translator = *(static_cast<TokenTranslator*>(options.cache()));
-    std::unique_ptr<ShortestPathFinder> finderPtr =
-        std::make_unique<FakePathFinder>(options, translator);
-    std::shared_ptr<VPackBuilder> input;
-    ShortestPathExecutorInfos infos{inputRegisters,
-                                    outputRegisters,
-                                    2,
-                                    4,
-                                    {},
-                                    {0, 1},
-                                    std::move(finderPtr),
-                                    std::move(registerMapping),
-                                    std::move(source),
-                                    std::move(target)};
-
-    std::vector<std::pair<std::string, std::string>> resultPaths;
-    resultPaths.clear();
-    input = VPackParser::fromJson(R"([["vertex/source","vertex/target"]])");
-    TestExecutor(waiting, infos, input, resultPaths);
-  }
+      std::tie(state, std::ignore, std::ignore) = testee.produceRows(input, output);
 
-  void RunTestWithNoRowsUpstream(bool waiting, ShortestPathExecutorInfos::InputVertex&& source,
-                                 ShortestPathExecutorInfos::InputVertex&& target,
-                                 bool useEdgeOutput) {
-    RegisterId vOutReg = 2;
-    RegisterId eOutReg = 3;
-    mocks::MockAqlServer server{};
-    std::unique_ptr<arangodb::aql::Query> fakedQuery = server.createFakeQuery();
-    auto inputRegisters = std::make_shared<std::unordered_set<RegisterId>>(
-        std::initializer_list<RegisterId>{});
-    auto outputRegisters = std::make_shared<std::unordered_set<RegisterId>>(
-        std::initializer_list<RegisterId>{vOutReg});
-    std::unordered_map<ShortestPathExecutorInfos::OutputName, RegisterId, ShortestPathExecutorInfos::OutputNameHash> registerMapping{
-        {ShortestPathExecutorInfos::OutputName::VERTEX, vOutReg}};
-    if (useEdgeOutput) {
-      registerMapping.emplace(ShortestPathExecutorInfos::OutputName::EDGE, eOutReg);
-      outputRegisters->emplace(eOutReg);
+      outputs.emplace_back(output.stealBlock());
+      ourCall = output.stealClientCall();
     }
-    TestShortestPathOptions options(fakedQuery.get());
-    TokenTranslator& translator = *(static_cast<TokenTranslator*>(options.cache()));
-    std::unique_ptr<ShortestPathFinder> finderPtr =
-        std::make_unique<FakePathFinder>(options, translator);
-    std::shared_ptr<VPackBuilder> input;
-    ShortestPathExecutorInfos infos{inputRegisters,
-                                    outputRegisters,
-                                    2,
-                                    4,
-                                    {},
-                                    {0, 1},
-                                    std::move(finderPtr),
-                                    std::move(registerMapping),
-                                    std::move(source),
-                                    std::move(target)};
-
-    std::vector<std::pair<std::string, std::string>> resultPaths;
-    resultPaths.clear();
-    input = VPackParser::fromJson("[]");
-    TestExecutor(waiting, infos, input, resultPaths);
-  }
 
-  void RunTestWithRowsUpstreamNoPaths(bool waiting,
-                                      ShortestPathExecutorInfos::InputVertex&& source,
-                                      ShortestPathExecutorInfos::InputVertex&& target,
-                                      bool useEdgeOutput) {
-    RegisterId vOutReg = 2;
-    RegisterId eOutReg = 3;
-    mocks::MockAqlServer server{};
-    std::unique_ptr<arangodb::aql::Query> fakedQuery = server.createFakeQuery();
-    auto inputRegisters = std::make_shared<std::unordered_set<RegisterId>>(
-        std::initializer_list<RegisterId>{});
-    auto outputRegisters = std::make_shared<std::unordered_set<RegisterId>>(
-        std::initializer_list<RegisterId>{vOutReg});
-    std::unordered_map<ShortestPathExecutorInfos::OutputName, RegisterId, ShortestPathExecutorInfos::OutputNameHash> registerMapping{
-        {ShortestPathExecutorInfos::OutputName::VERTEX, vOutReg}};
-    if (useEdgeOutput) {
-      registerMapping.emplace(ShortestPathExecutorInfos::OutputName::EDGE, eOutReg);
-      outputRegisters->emplace(eOutReg);
+    // FullCount
+    if (ourCall.needsFullCount()) {
+      // Emulate being called with a full count
+      ourCall.hardLimit = 0;
+      ourCall.softLimit = 0;
+      std::tie(state, skippedFullCount, std::ignore) = testee.skipRowsRange(input, ourCall);
     }
-    TestShortestPathOptions options(fakedQuery.get());
-    TokenTranslator& translator = *(static_cast<TokenTranslator*>(options.cache()));
-    std::unique_ptr<ShortestPathFinder> finderPtr =
-        std::make_unique<FakePathFinder>(options, translator);
-    std::shared_ptr<VPackBuilder> input;
-    ShortestPathExecutorInfos infos{inputRegisters,
-                                    outputRegisters,
-                                    2,
-                                    4,
-                                    {},
-                                    {0, 1},
-                                    std::move(finderPtr),
-                                    std::move(registerMapping),
-                                    std::move(source),
-                                    std::move(target)};
-
-    std::vector<std::pair<std::string, std::string>> resultPaths;
-    input = VPackParser::fromJson(R"([["vertex/source","vertex/target"]])");
-    TestExecutor(waiting, infos, input, resultPaths);
-  }
 
-  void RunTestWithRowsUpstreamOnePath(bool waiting,
-                                      ShortestPathExecutorInfos::InputVertex&& source,
-                                      ShortestPathExecutorInfos::InputVertex&& target,
-                                      bool useEdgeOutput) {
-    RegisterId vOutReg = 2;
-    RegisterId eOutReg = 3;
-    mocks::MockAqlServer server{};
-    std::unique_ptr<arangodb::aql::Query> fakedQuery = server.createFakeQuery();
-    auto inputRegisters = std::make_shared<std::unordered_set<RegisterId>>(
-        std::initializer_list<RegisterId>{});
-    auto outputRegisters = std::make_shared<std::unordered_set<RegisterId>>(
-        std::initializer_list<RegisterId>{vOutReg});
-    std::unordered_map<ShortestPathExecutorInfos::OutputName, RegisterId, ShortestPathExecutorInfos::OutputNameHash> registerMapping{
-        {ShortestPathExecutorInfos::OutputName::VERTEX, vOutReg}};
-    if (useEdgeOutput) {
-      registerMapping.emplace(ShortestPathExecutorInfos::OutputName::EDGE, eOutReg);
-      outputRegisters->emplace(eOutReg);
-    }
-    TestShortestPathOptions options(fakedQuery.get());
-    TokenTranslator& translator = *(static_cast<TokenTranslator*>(options.cache()));
-    std::unique_ptr<ShortestPathFinder> finderPtr =
-        std::make_unique<FakePathFinder>(options, translator);
-    std::shared_ptr<VPackBuilder> input;
-    ShortestPathExecutorInfos infos{inputRegisters,
-                                    outputRegisters,
-                                    2,
-                                    4,
-                                    {},
-                                    {0, 1},
-                                    std::move(finderPtr),
-                                    std::move(registerMapping),
-                                    std::move(source),
-                                    std::move(target)};
-
-    std::vector<std::pair<std::string, std::string>> resultPaths;
-    FakePathFinder& finder = static_cast<FakePathFinder&>(infos.finder());
-    input = VPackParser::fromJson(R"([["vertex/source","vertex/target"]])");
-    finder.addPath(std::vector<std::string>{"vertex/source", "vertex/intermed",
-                                            "vertex/target"});
-    resultPaths.emplace_back(std::make_pair("vertex/source", "vertex/target"));
-    TestExecutor(waiting, infos, input, resultPaths);
+    ValidateCalledWith();
+    ValidateResult(outputs, skippedInitial, skippedFullCount);
   }
-
-  void RunTestWithMultipleRowsUpstream(bool waiting,
-                                       ShortestPathExecutorInfos::InputVertex&& source,
-                                       ShortestPathExecutorInfos::InputVertex&& target,
-                                       bool useEdgeOutput) {
-    RegisterId vOutReg = 2;
-    RegisterId eOutReg = 3;
-    mocks::MockAqlServer server{};
-    std::unique_ptr<arangodb::aql::Query> fakedQuery = server.createFakeQuery();
-    auto inputRegisters = std::make_shared<std::unordered_set<RegisterId>>(
-        std::initializer_list<RegisterId>{});
-    auto outputRegisters = std::make_shared<std::unordered_set<RegisterId>>(
-        std::initializer_list<RegisterId>{vOutReg});
-    std::unordered_map<ShortestPathExecutorInfos::OutputName, RegisterId, ShortestPathExecutorInfos::OutputNameHash> registerMapping{
-        {ShortestPathExecutorInfos::OutputName::VERTEX, vOutReg}};
-    if (useEdgeOutput) {
-      registerMapping.emplace(ShortestPathExecutorInfos::OutputName::EDGE, eOutReg);
-      outputRegisters->emplace(eOutReg);
-    }
-    TestShortestPathOptions options(fakedQuery.get());
-    TokenTranslator& translator = *(static_cast<TokenTranslator*>(options.cache()));
-    std::unique_ptr<ShortestPathFinder> finderPtr =
-        std::make_unique<FakePathFinder>(options, translator);
-    std::shared_ptr<VPackBuilder> input;
-    ShortestPathExecutorInfos infos{inputRegisters,
-                                    outputRegisters,
-                                    2,
-                                    4,
-                                    {},
-                                    {0, 1},
-                                    std::move(finderPtr),
-                                    std::move(registerMapping),
-                                    std::move(source),
-                                    std::move(target)};
-
-    std::vector<std::pair<std::string, std::string>> resultPaths;
-    FakePathFinder& finder = static_cast<FakePathFinder&>(infos.finder());
-    input = VPackParser::fromJson(R"([["vertex/source","vertex/target"], ["vertex/a", "vertex/d"]])");
-    // We add enough paths for all combinations
-    // Otherwise waiting / more / done is getting complicated
-    finder.addPath(std::vector<std::string>{"vertex/source", "vertex/intermed",
-                                            "vertex/target"});
-    finder.addPath(std::vector<std::string>{"vertex/a", "vertex/b", "vertex/c",
-                                            "vertex/d"});
-    finder.addPath(std::vector<std::string>{"vertex/source", "vertex/b",
-                                            "vertex/c", "vertex/d"});
-    finder.addPath(
-        std::vector<std::string>{"vertex/a", "vertex/b", "vertex/target"});
-    resultPaths.emplace_back(std::make_pair("vertex/source", "vertex/target"));
-    // Add the expected second path
-    if (infos.useRegisterForInput(false)) {
-      // Source is register
-      if (infos.useRegisterForInput(true)) {
-        // Target is register
-        resultPaths.emplace_back(std::make_pair("vertex/a", "vertex/d"));
-      } else {
-        // Target constant
-        resultPaths.emplace_back(std::make_pair("vertex/a", "vertex/target"));
-      }
-    } else {
-      // Source is constant
-      if (infos.useRegisterForInput(true)) {
-        // Target is register
-        resultPaths.emplace_back(std::make_pair("vertex/source", "vertex/d"));
-      } else {
-        // Target constant
-        resultPaths.emplace_back(
-            std::make_pair("vertex/source", "vertex/target"));
-      }
-    }
-    TestExecutor(waiting, infos, input, resultPaths);
+};  // namespace aql
+
+/*
+ * We currently only have one test, but it's heavily parameterised.
+ * We emulate the call sequence of ExecutionBlockImpl, so, we skip, produce, and
+ * fullcount (depending on what the AqlCall parameter prescribes).
+ *
+ * the test with all combinations of parameters defined below, and compare the
+ * produced output of the executor with the expected output (which in turn is
+ * computed from the parameters).
+ *
+ * The parameters are
+ *  - sources:    constant or register source (then drawn from input)
+ *  - targets:    constant or register source (then drawn from input)
+ *  - inputs:     a matrix of input rows
+ *  - paths:      paths present in the fakePathFinder
+ *  - calls:      AqlCalls giving the offset, limits, and fullCount
+ *  - variants:   whether to output vertices only or vertices and edges
+ *  - blockSizes: which outputBlock sizes to test with
+ *
+ * We never actually perform a shortest path search: testing this is the
+ * responsibility of the test for the shortest path finder.
+ */
+
+TEST_P(ShortestPathExecutorTest, the_test) { TestExecutor(); }
+
+Vertex const constSource("vertex/source"), constTarget("vertex/target"),
+    regSource(0), regTarget(1), brokenSource{"IwillBreakYourSearch"},
+    brokenTarget{"I will also break your search"};
+MatrixBuilder<2> const noneRow{{{{}}}};
+MatrixBuilder<2> const oneRow{{{{R"("vertex/source")"}, {R"("vertex/target")"}}}};
+MatrixBuilder<2> const twoRows{{{{R"("vertex/source")"}, {R"("vertex/target")"}}},
+                               {{{R"("vertex/a")"}, {R"("vertex/b")"}}}};
+MatrixBuilder<2> const threeRows{{{{R"("vertex/source")"}, {R"("vertex/target")"}}},
+                                 {{{R"("vertex/a")"}, {R"("vertex/b")"}}},
+                                 {{{R"("vertex/a")"}, {R"("vertex/target")"}}}};
+MatrixBuilder<2> const someRows{{{{R"("vertex/c")"}, {R"("vertex/target")"}}},
+                                {{{R"("vertex/b")"}, {R"("vertex/target")"}}},
+                                {{{R"("vertex/e")"}, {R"("vertex/target")"}}},
+                                {{{R"("vertex/a")"}, {R"("vertex/target")"}}}};
+
+auto pathBetween(std::string const& start, std::string const& end, size_t n) -> Path {
+  auto path = std::vector<std::string>{};
+  path.push_back(start);
+  for (size_t i = 0; i < n; ++i) {
+    path.push_back(std::to_string(i));
   }
-};
-
-// simple tests
-
-TEST_F(ShortestPathExecutorTest, Waiting_TestingInvalidInputs_UsingBrokenStartVertex) {
-  RunSimpleTest(true, std::move(brokenSource), std::move(constTarget));
-}
-
-TEST_F(ShortestPathExecutorTest, Waiting_TestingInvalidInputs_UsingBrokenEndVertex) {
-  RunSimpleTest(true, std::move(constSource), std::move(brokenTarget));
-}
-
-TEST_F(ShortestPathExecutorTest, Waiting_TestingInvalidInputs_UsingBrokenStartAndEndVertex) {
-  RunSimpleTest(true, std::move(brokenSource), std::move(brokenTarget));
-}
-
-TEST_F(ShortestPathExecutorTest, NotWaiting_TestingInvalidInputs_UsingBrokenStartVertex) {
-  RunSimpleTest(false, std::move(brokenSource), std::move(constTarget));
-}
-
-TEST_F(ShortestPathExecutorTest, NotWaiting_TestingInvalidInputs_UsingBrokenEndVertex) {
-  RunSimpleTest(false, std::move(constSource), std::move(brokenTarget));
-}
-
-TEST_F(ShortestPathExecutorTest, NotWaiting_TestingInvalidInputs_UsingBrokenStartAndEndVertex) {
-  RunSimpleTest(false, std::move(brokenSource), std::move(brokenTarget));
-}
-
-// no rows
-
-TEST_F(ShortestPathExecutorTest,
-       Waiting_NoRows_UsingVertexOutputOnly_UsingConstantSourceInput_UsingConstantTargetInput) {
-  RunTestWithNoRowsUpstream(true, std::move(constSource), std::move(constTarget), false);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       Waiting_NoRows_UsingVertexOutputOnly_UsingConstantSourceInput_UsingRegisterTargetInput) {
-  RunTestWithNoRowsUpstream(true, std::move(constSource), std::move(regTarget), false);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       Waiting_NoRows_UsingVertexOutputOnly_UsingRegisterSourceInput_UsingConstantTargetInput) {
-  RunTestWithNoRowsUpstream(true, std::move(regSource), std::move(constTarget), false);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       Waiting_NoRows_UsingVertexOutputOnly_UsingRegisterSourceInput_UsingRegisterTargetInput) {
-  RunTestWithNoRowsUpstream(true, std::move(regSource), std::move(regTarget), false);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       Waiting_NoRows_UsingVertexAndEdgeOutput_UsingConstantSourceInput_UsingConstantTargetInput) {
-  RunTestWithNoRowsUpstream(true, std::move(constSource), std::move(constTarget), true);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       Waiting_NoRows_UsingVertexAndEdgeOutput_UsingConstantSourceInput_UsingRegisterTargetInput) {
-  RunTestWithNoRowsUpstream(true, std::move(constSource), std::move(regTarget), true);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       Waiting_NoRows_UsingVertexAndEdgeOutput_UsingRegisterSourceInput_UsingConstantTargetInput) {
-  RunTestWithNoRowsUpstream(true, std::move(regSource), std::move(constTarget), true);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       Waiting_NoRows_UsingVertexAndEdgeOutput_UsingRegisterSourceInput_UsingRegisterTargetInput) {
-  RunTestWithNoRowsUpstream(true, std::move(regSource), std::move(regTarget), true);
-}
-
-// with rows, no path
-
-TEST_F(ShortestPathExecutorTest,
-       Waiting_WithRowsNoPath_UsingVertexOutputOnly_UsingConstantSourceInput_UsingConstantTargetInput) {
-  RunTestWithRowsUpstreamOnePath(true, std::move(constSource), std::move(constTarget), false);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       Waiting_WithRowsNoPath_UsingVertexOutputOnly_UsingConstantSourceInput_UsingRegisterTargetInput) {
-  RunTestWithRowsUpstreamOnePath(true, std::move(constSource), std::move(regTarget), false);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       Waiting_WithRowsNoPath_UsingVertexOutputOnly_UsingRegisterSourceInput_UsingConstantTargetInput) {
-  RunTestWithRowsUpstreamOnePath(true, std::move(regSource), std::move(constTarget), false);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       Waiting_WithRowsNoPath_UsingVertexOutputOnly_UsingRegisterSourceInput_UsingRegisterTargetInput) {
-  RunTestWithRowsUpstreamOnePath(true, std::move(regSource), std::move(regTarget), false);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       Waiting_WithRowsNoPath_UsingVertexAndEdgeOutput_UsingConstantSourceInput_UsingConstantTargetInput) {
-  RunTestWithRowsUpstreamOnePath(true, std::move(constSource), std::move(constTarget), true);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       Waiting_WithRowsNoPath_UsingVertexAndEdgeOutput_UsingConstantSourceInput_UsingRegisterTargetInput) {
-  RunTestWithRowsUpstreamOnePath(true, std::move(constSource), std::move(regTarget), true);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       Waiting_WithRowsNoPath_UsingVertexAndEdgeOutput_UsingRegisterSourceInput_UsingConstantTargetInput) {
-  RunTestWithRowsUpstreamOnePath(true, std::move(regSource), std::move(constTarget), true);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       Waiting_WithRowsNoPath_UsingVertexAndEdgeOutput_UsingRegisterSourceInput_UsingRegisterTargetInput) {
-  RunTestWithRowsUpstreamOnePath(true, std::move(regSource), std::move(regTarget), true);
-}
-
-// with rows, one path
-
-TEST_F(ShortestPathExecutorTest,
-       Waiting_WithRowsOnePath_UsingVertexOutputOnly_UsingConstantSourceInput_UsingConstantTargetInput) {
-  RunTestWithRowsUpstreamOnePath(true, std::move(constSource), std::move(constTarget), false);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       Waiting_WithRowsOnePath_UsingVertexOutputOnly_UsingConstantSourceInput_UsingRegisterTargetInput) {
-  RunTestWithRowsUpstreamOnePath(true, std::move(constSource), std::move(regTarget), false);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       Waiting_WithRowsOnePath_UsingVertexOutputOnly_UsingRegisterSourceInput_UsingConstantTargetInput) {
-  RunTestWithRowsUpstreamOnePath(true, std::move(regSource), std::move(constTarget), false);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       Waiting_WithRowsOnePath_UsingVertexOutputOnly_UsingRegisterSourceInput_UsingRegisterTargetInput) {
-  RunTestWithRowsUpstreamOnePath(true, std::move(regSource), std::move(regTarget), false);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       Waiting_WithRowsOnePath_UsingVertexAndEdgeOutput_UsingConstantSourceInput_UsingConstantTargetInput) {
-  RunTestWithRowsUpstreamOnePath(true, std::move(constSource), std::move(constTarget), true);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       Waiting_WithRowsOnePath_UsingVertexAndEdgeOutput_UsingConstantSourceInput_UsingRegisterTargetInput) {
-  RunTestWithRowsUpstreamOnePath(true, std::move(constSource), std::move(regTarget), true);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       Waiting_WithRowsOnePath_UsingVertexAndEdgeOutput_UsingRegisterSourceInput_UsingConstantTargetInput) {
-  RunTestWithRowsUpstreamOnePath(true, std::move(regSource), std::move(constTarget), true);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       Waiting_WithRowsOnePath_UsingVertexAndEdgeOutput_UsingRegisterSourceInput_UsingRegisterTargetInput) {
-  RunTestWithRowsUpstreamOnePath(true, std::move(regSource), std::move(regTarget), true);
-}
-
-// with multiple rows
-
-TEST_F(ShortestPathExecutorTest,
-       Waiting_WithMultipleRows_UsingVertexOutputOnly_UsingConstantSourceInput_UsingConstantTargetInput) {
-  RunTestWithMultipleRowsUpstream(true, std::move(constSource),
-                                  std::move(constTarget), false);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       Waiting_WithMultipleRows_UsingVertexOutputOnly_UsingConstantSourceInput_UsingRegisterTargetInput) {
-  RunTestWithMultipleRowsUpstream(true, std::move(constSource), std::move(regTarget), false);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       Waiting_WithMultipleRows_UsingVertexOutputOnly_UsingRegisterSourceInput_UsingConstantTargetInput) {
-  RunTestWithMultipleRowsUpstream(true, std::move(regSource), std::move(constTarget), false);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       Waiting_WithMultipleRows_UsingVertexOutputOnly_UsingRegisterSourceInput_UsingRegisterTargetInput) {
-  RunTestWithMultipleRowsUpstream(true, std::move(regSource), std::move(regTarget), false);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       Waiting_WithMultipleRows_UsingVertexAndEdgeOutput_UsingConstantSourceInput_UsingConstantTargetInput) {
-  RunTestWithMultipleRowsUpstream(true, std::move(constSource),
-                                  std::move(constTarget), true);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       Waiting_WithMultipleRows_UsingVertexAndEdgeOutput_UsingConstantSourceInput_UsingRegisterTargetInput) {
-  RunTestWithMultipleRowsUpstream(true, std::move(constSource), std::move(regTarget), true);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       Waiting_WithMultipleRows_UsingVertexAndEdgeOutput_UsingRegisterSourceInput_UsingConstantTargetInput) {
-  RunTestWithMultipleRowsUpstream(true, std::move(regSource), std::move(constTarget), true);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       Waiting_WithMultipleRows_UsingVertexAndEdgeOutput_UsingRegisterSourceInput_UsingRegisterTargetInput) {
-  RunTestWithMultipleRowsUpstream(true, std::move(regSource), std::move(regTarget), true);
-}
-
-// no rows
-
-TEST_F(ShortestPathExecutorTest,
-       NotWaiting_NoRows_UsingVertexOutputOnly_UsingConstantSourceInput_UsingConstantTargetInput) {
-  RunTestWithNoRowsUpstream(false, std::move(constSource), std::move(constTarget), false);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       NotWaiting_NoRows_UsingVertexOutputOnly_UsingConstantSourceInput_UsingRegisterTargetInput) {
-  RunTestWithNoRowsUpstream(false, std::move(constSource), std::move(regTarget), false);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       NotWaiting_NoRows_UsingVertexOutputOnly_UsingRegisterSourceInput_UsingConstantTargetInput) {
-  RunTestWithNoRowsUpstream(false, std::move(regSource), std::move(constTarget), false);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       NotWaiting_NoRows_UsingVertexOutputOnly_UsingRegisterSourceInput_UsingRegisterTargetInput) {
-  RunTestWithNoRowsUpstream(false, std::move(regSource), std::move(regTarget), false);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       NotWaiting_NoRows_UsingVertexAndEdgeOutput_UsingConstantSourceInput_UsingConstantTargetInput) {
-  RunTestWithNoRowsUpstream(false, std::move(constSource), std::move(constTarget), true);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       NotWaiting_NoRows_UsingVertexAndEdgeOutput_UsingConstantSourceInput_UsingRegisterTargetInput) {
-  RunTestWithNoRowsUpstream(false, std::move(constSource), std::move(regTarget), true);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       NotWaiting_NoRows_UsingVertexAndEdgeOutput_UsingRegisterSourceInput_UsingConstantTargetInput) {
-  RunTestWithNoRowsUpstream(false, std::move(regSource), std::move(constTarget), true);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       NotWaiting_NoRows_UsingVertexAndEdgeOutput_UsingRegisterSourceInput_UsingRegisterTargetInput) {
-  RunTestWithNoRowsUpstream(false, std::move(regSource), std::move(regTarget), true);
-}
-
-// with rows, no path
-
-TEST_F(ShortestPathExecutorTest,
-       NotWaiting_WithRowsNoPath_UsingVertexOutputOnly_UsingConstantSourceInput_UsingConstantTargetInput) {
-  RunTestWithRowsUpstreamOnePath(false, std::move(constSource),
-                                 std::move(constTarget), false);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       NotWaiting_WithRowsNoPath_UsingVertexOutputOnly_UsingConstantSourceInput_UsingRegisterTargetInput) {
-  RunTestWithRowsUpstreamOnePath(false, std::move(constSource), std::move(regTarget), false);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       NotWaiting_WithRowsNoPath_UsingVertexOutputOnly_UsingRegisterSourceInput_UsingConstantTargetInput) {
-  RunTestWithRowsUpstreamOnePath(false, std::move(regSource), std::move(constTarget), false);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       NotWaiting_WithRowsNoPath_UsingVertexOutputOnly_UsingRegisterSourceInput_UsingRegisterTargetInput) {
-  RunTestWithRowsUpstreamOnePath(false, std::move(regSource), std::move(regTarget), false);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       NotWaiting_WithRowsNoPath_UsingVertexAndEdgeOutput_UsingConstantSourceInput_UsingConstantTargetInput) {
-  RunTestWithRowsUpstreamOnePath(false, std::move(constSource),
-                                 std::move(constTarget), true);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       NotWaiting_WithRowsNoPath_UsingVertexAndEdgeOutput_UsingConstantSourceInput_UsingRegisterTargetInput) {
-  RunTestWithRowsUpstreamOnePath(false, std::move(constSource), std::move(regTarget), true);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       NotWaiting_WithRowsNoPath_UsingVertexAndEdgeOutput_UsingRegisterSourceInput_UsingConstantTargetInput) {
-  RunTestWithRowsUpstreamOnePath(false, std::move(regSource), std::move(constTarget), true);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       NotWaiting_WithRowsNoPath_UsingVertexAndEdgeOutput_UsingRegisterSourceInput_UsingRegisterTargetInput) {
-  RunTestWithRowsUpstreamOnePath(false, std::move(regSource), std::move(regTarget), true);
-}
-
-// with rows, one path
-
-TEST_F(ShortestPathExecutorTest,
-       NotWaiting_WithRowsOnePath_UsingVertexOutputOnly_UsingConstantSourceInput_UsingConstantTargetInput) {
-  RunTestWithRowsUpstreamOnePath(false, std::move(constSource),
-                                 std::move(constTarget), false);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       NotWaiting_WithRowsOnePath_UsingVertexOutputOnly_UsingConstantSourceInput_UsingRegisterTargetInput) {
-  RunTestWithRowsUpstreamOnePath(false, std::move(constSource), std::move(regTarget), false);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       NotWaiting_WithRowsOnePath_UsingVertexOutputOnly_UsingRegisterSourceInput_UsingConstantTargetInput) {
-  RunTestWithRowsUpstreamOnePath(false, std::move(regSource), std::move(constTarget), false);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       NotWaiting_WithRowsOnePath_UsingVertexOutputOnly_UsingRegisterSourceInput_UsingRegisterTargetInput) {
-  RunTestWithRowsUpstreamOnePath(false, std::move(regSource), std::move(regTarget), false);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       NotWaiting_WithRowsOnePath_UsingVertexAndEdgeOutput_UsingConstantSourceInput_UsingConstantTargetInput) {
-  RunTestWithRowsUpstreamOnePath(false, std::move(constSource),
-                                 std::move(constTarget), true);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       NotWaiting_WithRowsOnePath_UsingVertexAndEdgeOutput_UsingConstantSourceInput_UsingRegisterTargetInput) {
-  RunTestWithRowsUpstreamOnePath(false, std::move(constSource), std::move(regTarget), true);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       NotWaiting_WithRowsOnePath_UsingVertexAndEdgeOutput_UsingRegisterSourceInput_UsingConstantTargetInput) {
-  RunTestWithRowsUpstreamOnePath(false, std::move(regSource), std::move(constTarget), true);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       NotWaiting_WithRowsOnePath_UsingVertexAndEdgeOutput_UsingRegisterSourceInput_UsingRegisterTargetInput) {
-  RunTestWithRowsUpstreamOnePath(false, std::move(regSource), std::move(regTarget), true);
-}
-
-// with multiple rows
-
-TEST_F(ShortestPathExecutorTest,
-       NotWaiting_WithMultipleRows_UsingVertexOutputOnly_UsingConstantSourceInput_UsingConstantTargetInput) {
-  RunTestWithMultipleRowsUpstream(false, std::move(constSource),
-                                  std::move(constTarget), false);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       NotWaiting_WithMultipleRows_UsingVertexOutputOnly_UsingConstantSourceInput_UsingRegisterTargetInput) {
-  RunTestWithMultipleRowsUpstream(false, std::move(constSource), std::move(regTarget), false);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       NotWaiting_WithMultipleRows_UsingVertexOutputOnly_UsingRegisterSourceInput_UsingConstantTargetInput) {
-  RunTestWithMultipleRowsUpstream(false, std::move(regSource), std::move(constTarget), false);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       NotWaiting_WithMultipleRows_UsingVertexOutputOnly_UsingRegisterSourceInput_UsingRegisterTargetInput) {
-  RunTestWithMultipleRowsUpstream(false, std::move(regSource), std::move(regTarget), false);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       NotWaiting_WithMultipleRows_UsingVertexAndEdgeOutput_UsingConstantSourceInput_UsingConstantTargetInput) {
-  RunTestWithMultipleRowsUpstream(false, std::move(constSource),
-                                  std::move(constTarget), true);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       NotWaiting_WithMultipleRows_UsingVertexAndEdgeOutput_UsingConstantSourceInput_UsingRegisterTargetInput) {
-  RunTestWithMultipleRowsUpstream(false, std::move(constSource), std::move(regTarget), true);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       NotWaiting_WithMultipleRows_UsingVertexAndEdgeOutput_UsingRegisterSourceInput_UsingConstantTargetInput) {
-  RunTestWithMultipleRowsUpstream(false, std::move(regSource), std::move(constTarget), true);
-}
-
-TEST_F(ShortestPathExecutorTest,
-       NotWaiting_WithMultipleRows_UsingVertexAndEdgeOutput_UsingRegisterSourceInput_UsingRegisterTargetInput) {
-  RunTestWithMultipleRowsUpstream(false, std::move(regSource), std::move(regTarget), true);
-}
+  path.push_back(end);
+  return {path};
+}
+
+PathSequence const noPath = {};
+PathSequence const onePath = {pathBetween("vertex/source", "vertex/target", 10)};
+PathSequence const threePaths = {pathBetween("vertex/source", "vertex/target", 10),
+                                 pathBetween("vertex/source", "vertex/b", 100),
+                                 pathBetween("vertex/a", "vertex/b", 1000)};
+PathSequence const somePaths = {pathBetween("vertex/source", "vertex/target", 10),
+                                pathBetween("vertex/source", "vertex/b", 100),
+                                pathBetween("vertex/a", "vertex/b", 1000),
+                                pathBetween("vertex/c", "vertex/d", 2001)};
+PathSequence const someOtherPaths = {pathBetween("vertex/a", "vertex/target", 10),
+                                     pathBetween("vertex/b", "vertex/target", 999),
+                                     pathBetween("vertex/c", "vertex/target", 1001),
+                                     pathBetween("vertex/d", "vertex/target", 2000),
+                                     pathBetween("vertex/e", "vertex/target", 200),
+                                     pathBetween("vertex/f", "vertex/target", 15),
+                                     pathBetween("vertex/g", "vertex/target", 10)};
+
+auto sources = testing::Values(constSource, regSource, brokenSource);
+auto targets = testing::Values(constTarget, regTarget, brokenTarget);
+auto inputs = testing::Values(noneRow, oneRow, twoRows, threeRows, someRows);
+auto paths = testing::Values(noPath, onePath, threePaths, somePaths);
+auto calls =
+    testing::Values(AqlCall{}, AqlCall{0, 0, 0, false}, AqlCall{0, 1, 0, false},
+                    AqlCall{0, 0, 1, false}, AqlCall{0, 1, 1, false}, AqlCall{1, 1, 1},
+                    AqlCall{100, 1, 1}, AqlCall{1000}, AqlCall{0, 0, 0, true},
+                    AqlCall{0, AqlCall::Infinity{}, AqlCall::Infinity{}, true});
+
+auto variants = testing::Values(ShortestPathOutput::VERTEX_ONLY,
+                                ShortestPathOutput::VERTEX_AND_EDGE);
+auto blockSizes = testing::Values(size_t{5}, 1000);
+
+INSTANTIATE_TEST_CASE_P(ShortestPathExecutorTestInstance, ShortestPathExecutorTest,
+                        testing::Combine(sources, targets, inputs, paths, calls,
+                                         variants, blockSizes));
 
 }  // namespace aql
 }  // namespace tests
diff --git a/tests/Aql/TestLambdaExecutor.cpp b/tests/Aql/TestLambdaExecutor.cpp
index 92083adc9fb1..4fe9c2812cc2 100644
--- a/tests/Aql/TestLambdaExecutor.cpp
+++ b/tests/Aql/TestLambdaExecutor.cpp
@@ -109,4 +109,4 @@ auto TestLambdaSkipExecutor::produceRows(AqlItemBlockInputRange& input, OutputAq
 auto TestLambdaSkipExecutor::skipRowsRange(AqlItemBlockInputRange& input, AqlCall& call)
     -> std::tuple<ExecutorState, size_t, AqlCall> {
   return _infos.getSkipLambda()(input, call);
-}
\ No newline at end of file
+}
diff --git a/tests/Aql/TestLambdaExecutor.h b/tests/Aql/TestLambdaExecutor.h
index 9663ca6ca249..4905ea56f915 100644
--- a/tests/Aql/TestLambdaExecutor.h
+++ b/tests/Aql/TestLambdaExecutor.h
@@ -230,4 +230,4 @@ class TestLambdaSkipExecutor {
 }  // namespace aql
 }  // namespace arangodb
 
-#endif
\ No newline at end of file
+#endif

From 56d9cf07150091204c45a6a59ac2afe7117ebdee Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Tue, 28 Jan 2020 23:03:21 +0100
Subject: [PATCH 056/122] Feature/aql subquery execution block impl execute
 implementation exec block impl tests shadow rows (#10970)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

* Added a generic Lambda Executor, this can be used in ExecutionBlockImplTests to have finegrained control over the action happening within the Executor

* Added first test using the LambdaExecutor.

* Added some tests around Execute. GetSome seems to be okayish. Skip not. Namely skipped numbers are not reported correctly.

* Made the first ExecutionBlock Execute integration test pass. Still other tests are failing

* Simplified the IsSkipSome test, this allows the C++ tests for Mixed Calls to pass.

* Added a skip test and fixed the producing executor to recreate the list once for every input line.

* More tests. Also added a custom AqlCall printer function for GTest. Tests still red, need to fix fullCount and hardLimit.

* Implemented ostream operator for AQLCall.

* Properly implemented fullCount incl. UnitTest

* Added test for Callforwarding. They still have some todos, but these can only be solved by upgrading the OutputRow. Which should be part of separate PR

* Added another test for CallForwarding in passthrough state

* Added a Test Implementation for an Executor that uses a dynamic skip implementation.

* Fixed skip with HARDLIMIT.

* Startet to implement call forwarding test. However we need to improve Outputrow first this will be done in seperate branch

* Removed designated initializers. Thanks for not supporting it MSVC!

* Removed non-passthrough non-skip Lambda Executor again. We decided to disallow this.

* Update tests/Aql/ExecutionBlockImplTest.cpp

Co-Authored-By: Markus Pfeiffer <markuspf@users.noreply.github.com>

* Started to add implementation of passthrough block allocation

* Added a comparator to AqlCall. Mostly for tests

* Fixed an issue in skip-passthrough version. Updated the tests.

* Allow to 'overSkip' if we do fullCount

* Enabled the first set of tests now. Only one set to go

* Applied all fixes to get Integration testsuite green

* Added some comments on the TestCases executed in the ExecutionBlockImpl

* Added tes descriptions and removed a duplicate test

* Added some comments on LamdbaExecutors

* Added description of ExecutionBlockImple execute logic

* Added tests for ExecutionBlockImpl, when there is a WAITING passed through. There is no test yet for in between waitings.

* Allow to configure WAITING variant in WAITING block mock.

* Use the WaitingBlockMock to be independent of Singleton in test

* Added WAITING + Passthrough tests

* Added a test to path through shadowRows without data.

* Waiting ExecutionBlock Mock can now return/skip partial blocks. However it does NOT CARE for ShadowRows

* Added tests and fixed an issue in ShadowRow forwarding

* Added tests for shadowRow forwarding

* Added the intenral state of Execute as member of ExecutionBlockImpl. We need to retain parts of this state accross returns

* Fixed all Waiting and multiple call tests

* Applied review comments, thanks to reviewers

* Fixed modulo 2 off by one error

* Fixed invalid memory access in test code. Do never return a lambda that references a stack variable...

* Renamed getLambda() => getProduceLambda() in test code, as we have produce and skip

* Allways -> Always.

* Added tests for pass-by of non-relevant Subqueries. Fixed a bug found on the way in WaitingBlockMock. Now some other tests fail \o/

* Fixed failed tests. Now tests correspond to correct behaviour of WaitingExecutionBlockMock

* Intermediate version, doe snot work

* Fixed the empty subquery tests

Co-authored-by: Markus Pfeiffer <markuspf@users.noreply.github.com>
Co-authored-by: Tobias Gödderz <github@tobias.goedderz.info>
---
 arangod/Aql/AqlCallStack.cpp            |   10 +
 arangod/Aql/AqlCallStack.h              |    4 +
 arangod/Aql/ExecutionBlockImpl.cpp      |  150 +--
 arangod/Aql/ExecutionBlockImpl.h        |   33 +
 tests/Aql/ExecutionBlockImplTest.cpp    | 1395 ++++++++++++++++++++---
 tests/Aql/TestLambdaExecutor.cpp        |   24 +-
 tests/Aql/TestLambdaExecutor.h          |   34 +-
 tests/Aql/WaitingExecutionBlockMock.cpp |   91 +-
 tests/Aql/WaitingExecutionBlockMock.h   |   18 +-
 9 files changed, 1529 insertions(+), 230 deletions(-)

diff --git a/arangod/Aql/AqlCallStack.cpp b/arangod/Aql/AqlCallStack.cpp
index 608febad859b..33975e259bf0 100644
--- a/arangod/Aql/AqlCallStack.cpp
+++ b/arangod/Aql/AqlCallStack.cpp
@@ -83,5 +83,15 @@ void AqlCallStack::pop() {
     _operations.pop();
     // We can never pop the main query, so one element needs to stay
     TRI_ASSERT(!_operations.empty());
+  } else {
+    _depth--;
   }
+}
+
+auto AqlCallStack::increaseSubqueryDepth() -> void {
+  // Avoid overflow. If you actually have a subquery nesting of size_t many subqueries
+  // there is a rather high chance that your query will not perform well.
+  TRI_ASSERT(_depth < std::numeric_limits<size_t>::max() - 2);
+  _depth++;
+  TRI_ASSERT(!isRelevant());
 }
\ No newline at end of file
diff --git a/arangod/Aql/AqlCallStack.h b/arangod/Aql/AqlCallStack.h
index f9fbec8dd927..214de85d1e4d 100644
--- a/arangod/Aql/AqlCallStack.h
+++ b/arangod/Aql/AqlCallStack.h
@@ -67,6 +67,10 @@ class AqlCallStack {
   // Can be savely called on every subquery Start.
   void pop();
 
+  // Increase the subquery by one, not placing another call on the stack
+  // This is used to bypass all executors until we reach the next subquery start.
+  void increaseSubqueryDepth();
+
  private:
   // The list of operations, stacked by depth (e.g. bottom element is from main query)
   std::stack<AqlCall> _operations;
diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index 035f760bc720..b8e170e6c649 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -176,6 +176,9 @@ ExecutionBlockImpl<Executor>::ExecutionBlockImpl(ExecutionEngine* engine,
       _query(*engine->getQuery()),
       _state(InternalState::FETCH_DATA),
       _lastRange{ExecutorState::HASMORE},
+      _execState{ExecState::CHECKCALL},
+      _upstreamRequest{},
+      _clientRequest{},
       _hasUsedDataRangeBlock{false} {
   // already insert ourselves into the statistics results
   if (_profile >= PROFILE_LEVEL_BLOCKS) {
@@ -1051,36 +1054,12 @@ void ExecutionBlockImpl<Executor>::ensureOutputBlock(AqlCall&& call) {
     _outputItemRow = allocateOutputBlock(std::move(call));
   } else {
     _outputItemRow->setCall(std::move(call));
-#ifdef ARANGODB_ENABLE_MAINTAINER_MODE
-// We only inject a new call into the output row.
-// In the passhrough variant we need to ensure that inputBlock and outputBlock stay identical
-// TODO add an external assertion for this.
-#endif
   }
 }
 
-/// @brief request an AqlItemBlock from the memory manager
-template <class Executor>
-SharedAqlItemBlockPtr ExecutionBlockImpl<Executor>::requestBlock(size_t nrItems,
-                                                                 RegisterId nrRegs) {
-  return _engine->itemBlockManager().requestBlock(nrItems, nrRegs);
-}
-
-// TODO move me up
-enum ExecState {
-  SKIP,
-  PRODUCE,
-  FASTFORWARD,
-  FULLCOUNT,
-  UPSTREAM,
-  SHADOWROWS,
-  DONE
-};
-
-// TODO clean me up
-namespace {
 // This cannot return upstream call or shadowrows.
-ExecState NextState(AqlCall const& call) {
+template <class Executor>
+auto ExecutionBlockImpl<Executor>::nextState(AqlCall const& call) const -> ExecState {
   if (call.getOffset() > 0) {
     // First skip
     return ExecState::SKIP;
@@ -1101,7 +1080,12 @@ ExecState NextState(AqlCall const& call) {
   return ExecState::DONE;
 }
 
-}  // namespace
+/// @brief request an AqlItemBlock from the memory manager
+template <class Executor>
+SharedAqlItemBlockPtr ExecutionBlockImpl<Executor>::requestBlock(size_t nrItems,
+                                                                 RegisterId nrRegs) {
+  return _engine->itemBlockManager().requestBlock(nrItems, nrRegs);
+}
 
 //
 // FETCHER:  if we have one output row per input row, we can skip
@@ -1239,36 +1223,55 @@ template <class Executor>
 std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr>
 ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
   if constexpr (isNewStyleExecutor<Executor>()) {
+    if (!stack.isRelevant()) {
+      // We are bypassing subqueries.
+      // This executor is not allowed to perform actions
+      // However we need to maintain the upstream state.
+      size_t skippedLocal = 0;
+      typename Fetcher::DataRange bypassedRange{ExecutorState::HASMORE};
+      std::tie(_upstreamState, skippedLocal, bypassedRange) = _rowFetcher.execute(stack);
+      return {_upstreamState, skippedLocal, bypassedRange.getBlock()};
+    }
     AqlCall clientCall = stack.popCall();
 
-    auto skipped = size_t{0};
-
-    auto execState = ::NextState(clientCall);
-
-    if (_lastRange.hasShadowRow()) {
-      // We have not been able to move all shadowRows into the output last
-      // time. Continue from there.
-      // TODO test if this works with COUNT COLLECT
-      execState = ExecState::SHADOWROWS;
+    // We can only have returned the following internal states
+    TRI_ASSERT(_execState == ExecState::CHECKCALL || _execState == ExecState::SHADOWROWS ||
+               _execState == ExecState::UPSTREAM);
+    // Skip can only be > 0 if we are in upstream cases.
+    TRI_ASSERT(_skipped == 0 || _execState == ExecState::UPSTREAM);
+    if (_execState == ExecState::UPSTREAM) {
+      // We have been in waiting state.
+      // We may have local work on the original call.
+      // The client does not have the right to change her
+      // mind just because we told her to hold the line.
+
+      // The client cannot request less data!
+      TRI_ASSERT(_clientRequest.getOffset() <= clientCall.getOffset());
+      TRI_ASSERT(_clientRequest.getLimit() <= clientCall.getLimit());
+      TRI_ASSERT(_clientRequest.needsFullCount() == clientCall.needsFullCount());
+      clientCall = _clientRequest;
     }
 
-    AqlCall executorRequest;
-    while (execState != ExecState::DONE) {
-      switch (execState) {
+    while (_execState != ExecState::DONE) {
+      switch (_execState) {
+        case ExecState::CHECKCALL: {
+          _execState = nextState(clientCall);
+          break;
+        }
         case ExecState::SKIP: {
           auto [state, skippedLocal, call] = executeSkipRowsRange(_lastRange, clientCall);
-          skipped += skippedLocal;
+          _skipped += skippedLocal;
           // The execute might have modified the client call.
           if (state == ExecutorState::DONE) {
-            execState = ExecState::SHADOWROWS;
+            _execState = ExecState::SHADOWROWS;
           } else if (clientCall.getOffset() > 0) {
             TRI_ASSERT(_upstreamState != ExecutionState::DONE);
             // We need to request more
-            executorRequest = call;
-            execState = ExecState::UPSTREAM;
+            _upstreamRequest = call;
+            _execState = ExecState::UPSTREAM;
           } else {
             // We are done with skipping. Skip is not allowed to request more
-            execState = ::NextState(clientCall);
+            _execState = ExecState::CHECKCALL;
           }
           break;
         }
@@ -1288,17 +1291,17 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
           clientCall = _outputItemRow->getClientCall();
 
           if (_outputItemRow->isInitialized() && _outputItemRow->allRowsUsed()) {
-            execState = ExecState::DONE;
+            _execState = ExecState::DONE;
           } else if (state == ExecutorState::DONE) {
-            execState = ExecState::SHADOWROWS;
+            _execState = ExecState::SHADOWROWS;
           } else if (clientCall.getLimit() > 0 && !_lastRange.hasDataRow()) {
             TRI_ASSERT(_upstreamState != ExecutionState::DONE);
             // We need to request more
-            executorRequest = call;
-            execState = ExecState::UPSTREAM;
+            _upstreamRequest = call;
+            _execState = ExecState::UPSTREAM;
           } else {
             // We are done with producing. Produce is not allowed to request more
-            execState = ::NextState(clientCall);
+            _execState = ExecState::CHECKCALL;
           }
           break;
         }
@@ -1313,25 +1316,25 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
             TRI_ASSERT(row.isInitialized());
           }
           if (_lastRange.upstreamState() == ExecutorState::DONE) {
-            execState = ExecState::SHADOWROWS;
+            _execState = ExecState::SHADOWROWS;
           } else {
             // We need to request more, simply send hardLimit 0 upstream
-            executorRequest = AqlCall{};
-            executorRequest.hardLimit = 0;
-            execState = ExecState::UPSTREAM;
+            _upstreamRequest = AqlCall{};
+            _upstreamRequest.hardLimit = 0;
+            _execState = ExecState::UPSTREAM;
           }
           break;
         }
         case ExecState::FULLCOUNT: {
           auto [state, skippedLocal, call] = executeSkipRowsRange(_lastRange, clientCall);
-          skipped += skippedLocal;
+          _skipped += skippedLocal;
 
           if (state == ExecutorState::DONE) {
-            execState = ExecState::SHADOWROWS;
+            _execState = ExecState::SHADOWROWS;
           } else {
             // We need to request more
-            executorRequest = call;
-            execState = ExecState::UPSTREAM;
+            _upstreamRequest = call;
+            _execState = ExecState::UPSTREAM;
           }
           break;
         }
@@ -1339,22 +1342,26 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
           // If this triggers the executors produceRows function has returned
           // HASMORE even if it knew that upstream has no further rows.
           TRI_ASSERT(_upstreamState != ExecutionState::DONE);
+          // We need to make sure _lastRange is all used
           TRI_ASSERT(!_lastRange.hasDataRow());
+          TRI_ASSERT(!_lastRange.hasShadowRow());
           size_t skippedLocal = 0;
-          stack.pushCall(std::move(executorRequest));
+          auto callCopy = _upstreamRequest;
+          stack.pushCall(std::move(callCopy));
           std::tie(_upstreamState, skippedLocal, _lastRange) = _rowFetcher.execute(stack);
           if (_upstreamState == ExecutionState::WAITING) {
+            // We need to persist the old call before we return.
+            // We might have some local accounting to this call.
+            _clientRequest = clientCall;
             // We do not return anything in WAITING state, also NOT skipped.
-            // TODO: Check if we need to leverage this restriction.
-            TRI_ASSERT(skipped == 0);
             return {_upstreamState, 0, nullptr};
           }
           // We have a new range, passthrough can use this range.
           _hasUsedDataRangeBlock = false;
-          skipped += skippedLocal;
+          _skipped += skippedLocal;
           // We skipped through passthroug, so count that a skip was solved.
           clientCall.didSkip(skippedLocal);
-          execState = ::NextState(clientCall);
+          _execState = ExecState::CHECKCALL;
           break;
         }
         case ExecState::SHADOWROWS: {
@@ -1376,27 +1383,29 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
             if (shadowRow.isRelevant()) {
               // We found a relevant shadow Row.
               // We need to reset the Executor
-              // TODO: call reset!
+              // cppcheck-suppress unreadVariable
+              constexpr bool customInit = hasInitializeCursor<decltype(_executor)>::value;
+              InitializeCursor<customInit>::init(_executor, _rowFetcher, _infos);
             }
             TRI_ASSERT(_outputItemRow->produced());
             _outputItemRow->advanceRow();
             clientCall = _outputItemRow->getClientCall();
             if (_outputItemRow->allRowsUsed()) {
-              execState = ExecState::DONE;
+              _execState = ExecState::DONE;
             } else if (state == ExecutorState::DONE) {
               if (_lastRange.hasDataRow()) {
                 // TODO this state is invalid, and can just show up now if we exclude SKIP
-                execState = ExecState::PRODUCE;
+                _execState = ExecState::PRODUCE;
               } else {
                 // Right now we cannot support to have more than one set of
                 // ShadowRows inside of a Range.
                 // We do not know how to continue with the above executor after a shadowrow.
                 TRI_ASSERT(!_lastRange.hasDataRow());
-                execState = ExecState::DONE;
+                _execState = ExecState::DONE;
               }
             }
           } else {
-            execState = ExecState::DONE;
+            _execState = ExecState::DONE;
           }
           break;
         }
@@ -1408,9 +1417,16 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
     // If we do not have an output, we simply return a nullptr here.
     auto outputBlock = _outputItemRow != nullptr ? _outputItemRow->stealBlock()
                                                  : SharedAqlItemBlockPtr{nullptr};
+    // We are locally done with our output.
+    // Next time we need to check the client call again
+    _execState = ExecState::CHECKCALL;
     // This is not strictly necessary here, as we shouldn't be called again
     // after DONE.
     _outputItemRow.reset();
+
+    // We return skipped here, reset member
+    size_t skipped = _skipped;
+    _skipped = 0;
     if (_lastRange.hasDataRow() || _lastRange.hasShadowRow()) {
       // We have skipped or/and return data, otherwise we cannot return HASMORE
       TRI_ASSERT(skipped > 0 || (outputBlock != nullptr && outputBlock->numEntries() > 0));
diff --git a/arangod/Aql/ExecutionBlockImpl.h b/arangod/Aql/ExecutionBlockImpl.h
index 064b087574f3..16169b212d06 100644
--- a/arangod/Aql/ExecutionBlockImpl.h
+++ b/arangod/Aql/ExecutionBlockImpl.h
@@ -26,6 +26,7 @@
 #ifndef ARANGOD_AQL_EXECUTION_BLOCK_IMPL_H
 #define ARANGOD_AQL_EXECUTION_BLOCK_IMPL_H 1
 
+#include "Aql/AqlCall.h"
 #include "Aql/ConstFetcher.h"
 #include "Aql/DependencyProxy.h"
 #include "Aql/ExecutionBlock.h"
@@ -106,8 +107,30 @@ class ExecutionBlockImpl final : public ExecutionBlock {
       "allowsBlockPassthrough must imply preservesOrder, but does not!");
 
  private:
+  // Used in getSome/skipSome implementation. deprecated
   enum class InternalState { FETCH_DATA, FETCH_SHADOWROWS, DONE };
 
+  // Used in execute implmentation
+  // Defines the internal state this executor is in.
+  enum class ExecState {
+    // We need to check the client call to define the next state (inital state)
+    CHECKCALL,
+    // We are skipping rows in offset
+    SKIP,
+    // We are producing rows
+    PRODUCE,
+    // We are done producing (limit reached) and drop all rows that are unneeded
+    FASTFORWARD,
+    // We are done producing (limit reached), but we count all rows that could be used on higher limit
+    FULLCOUNT,
+    // We need more information from dependency
+    UPSTREAM,
+    // We are done with a subquery, we need to pass forward ShadowRows
+    SHADOWROWS,
+    // Locally done, ready to return, will set state to resetted
+    DONE
+  };
+
  public:
   /**
    * @brief Construct a new ExecutionBlock
@@ -258,6 +281,10 @@ class ExecutionBlockImpl final : public ExecutionBlock {
   // Will as a side effect modify _outputItemRow
   void ensureOutputBlock(AqlCall&& call);
 
+  // Compute the next state based on the given call.
+  // Can only be one of Skip/Produce/FullCount/FastForward/Done
+  [[nodiscard]] auto nextState(AqlCall const& call) const -> ExecState;
+
  private:
   /**
    * @brief Used to allow the row Fetcher to access selected methods of this
@@ -290,6 +317,12 @@ class ExecutionBlockImpl final : public ExecutionBlock {
 
   DataRange _lastRange;
 
+  ExecState _execState;
+
+  AqlCall _upstreamRequest;
+
+  AqlCall _clientRequest;
+
   // Only used in passthrough variant.
   // We track if we have reference the range's block
   // into an output block.
diff --git a/tests/Aql/ExecutionBlockImplTest.cpp b/tests/Aql/ExecutionBlockImplTest.cpp
index fef41d9d983b..49bf8ad9dcf0 100644
--- a/tests/Aql/ExecutionBlockImplTest.cpp
+++ b/tests/Aql/ExecutionBlockImplTest.cpp
@@ -489,9 +489,11 @@ class SharedExecutionBlockImplTest {
    * @param outputRegisters highest output register index. RegisterPlan::MaxRegisterId (default) describes there is no output. call is allowed to write any inputRegisters < register <= outputRegisters. Invariant inputRegisters <= outputRegisters
    * @return LambdaExecutorInfos Infos to build the Executor.
    */
-  LambdaSkipExecutorInfos makeSkipInfos(ProduceCall call, SkipCall skipCall,
-                                        RegisterId inputRegisters = RegisterPlan::MaxRegisterId,
-                                        RegisterId outputRegisters = RegisterPlan::MaxRegisterId) {
+  LambdaSkipExecutorInfos makeSkipInfos(
+      ProduceCall call, SkipCall skipCall,
+      RegisterId inputRegisters = RegisterPlan::MaxRegisterId,
+      RegisterId outputRegisters = RegisterPlan::MaxRegisterId,
+      ResetCall reset = []() -> void {}) {
     if (inputRegisters != RegisterPlan::MaxRegisterId) {
       EXPECT_LE(inputRegisters, outputRegisters);
       // We cannot have no output registers here.
@@ -524,22 +526,7 @@ class SharedExecutionBlockImplTest {
         (outputRegisters == RegisterPlan::MaxRegisterId) ? 0 : outputRegisters + 1;
     return LambdaSkipExecutorInfos(readAble, writeAble, regsToRead, regsToWrite,
                                    {}, registersToKeep, std::move(call),
-                                   std::move(skipCall));
-  }
-  /**
-   * @brief Create a Singleton ExecutionBlock. Just like the original one in the
-   * query. it is already initialized and ready to use.
-   *
-   * @return std::unique_ptr<ExecutionBlock> The singleton ExecutionBlock.
-   */
-  std::unique_ptr<ExecutionBlock> createSingleton() {
-    auto res = std::make_unique<ExecutionBlockImpl<IdExecutor<ConstFetcher>>>(
-        fakedQuery->engine(), generateNodeDummy(), IdExecutorInfos{0, {}, {}});
-    InputAqlItemRow inputRow{CreateInvalidInputRowHint{}};
-    auto const [state, result] = res->initializeCursor(inputRow);
-    EXPECT_EQ(state, ExecutionState::DONE);
-    EXPECT_TRUE(result.ok());
-    return res;
+                                   std::move(skipCall), std::move(reset));
   }
 
   /**
@@ -679,6 +666,22 @@ class SharedExecutionBlockImplTest {
 class ExecutionBlockImplExecuteSpecificTest : public SharedExecutionBlockImplTest,
                                               public testing::TestWithParam<bool> {
  protected:
+  /**
+   * @brief Create a Singleton ExecutionBlock. Just like the original one in the
+   * query. it is already initialized and ready to use.
+   *
+   * @return std::unique_ptr<ExecutionBlock> The singleton ExecutionBlock.
+   */
+  std::unique_ptr<ExecutionBlock> createSingleton() {
+    auto res = std::make_unique<ExecutionBlockImpl<IdExecutor<ConstFetcher>>>(
+        fakedQuery->engine(), generateNodeDummy(), IdExecutorInfos{0, {}, {}});
+    InputAqlItemRow inputRow{CreateInvalidInputRowHint{}};
+    auto const [state, result] = res->initializeCursor(inputRow);
+    EXPECT_EQ(state, ExecutionState::DONE);
+    EXPECT_TRUE(result.ok());
+    return res;
+  }
+
   /**
    * @brief Generic test runner. Creates Lambda Executors, and returns ExecutionBlockImpl.execute(call),
    *
@@ -704,6 +707,57 @@ class ExecutionBlockImplExecuteSpecificTest : public SharedExecutionBlockImplTes
       return testee.execute(stack);
     }
   }
+
+  auto onceLinesProducer(ExecutionBlock* dependency, size_t numberLines)
+      -> std::unique_ptr<ExecutionBlock> {
+    RegisterId outReg = 0;
+    RegisterId inReg = RegisterPlan::MaxRegisterId;
+    SkipCall skipCall = generateNeverSkipCall();
+    auto didProduce = std::make_shared<bool>(false);
+    auto builder = std::make_shared<VPackBuilder>();
+    builder->openArray();
+    for (size_t i = 0; i < numberLines; ++i) {
+      builder->add(VPackValue(i));
+    }
+    builder->close();
+
+    ProduceCall prodCall =
+        [outReg, didProduce,
+         builder](AqlItemBlockInputRange& inputRange,
+                  OutputAqlItemRow& output) -> std::tuple<ExecutorState, NoStats, AqlCall> {
+      if (!inputRange.hasDataRow()) {
+        // Initial call, we have not produced yet.
+        // Ask for more
+        AqlCall call{};
+        return {inputRange.upstreamState(), NoStats{}, call};
+      }
+      // We only need to get here exactly once
+      EXPECT_FALSE(*didProduce);
+      if (*didProduce) {
+        // Should never get here. Emergency exit.
+        THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
+      }
+      *didProduce = true;
+      auto slice = builder->slice();
+      // We need to ensure that the data fits into the given output.
+      EXPECT_GE(output.numRowsLeft(), slice.length());
+      auto [state, input] = inputRange.nextDataRow();
+      for (auto it : VPackArrayIterator(slice)) {
+        output.cloneValueInto(outReg, input, AqlValue(it));
+        output.advanceRow();
+      }
+      AqlCall call{};
+      return {inputRange.upstreamState(), NoStats{}, call};
+    };
+
+    std::unique_ptr<ExecutionBlock> res =
+        std::make_unique<ExecutionBlockImpl<LambdaExe>>(fakedQuery->engine(),
+                                                        generateNodeDummy(),
+                                                        makeSkipInfos(prodCall, skipCall,
+                                                                      inReg, outReg));
+    res->addDependency(dependency);
+    return res;
+  }
 };
 
 // Test a default call: no skip, no limits.
@@ -824,6 +878,145 @@ TEST_P(ExecutionBlockImplExecuteSpecificTest, test_toplevel_offset_only_call) {
   EXPECT_EQ(block, nullptr);
 }
 
+TEST_P(ExecutionBlockImplExecuteSpecificTest, test_relevant_shadowrow_does_not_fit_in_output) {
+  if (GetParam()) {
+    // This test is only for non-passthrough variants
+    SUCCEED();
+    return;
+  }
+  std::deque<SharedAqlItemBlockPtr> blockDeque;
+  {
+    SharedAqlItemBlockPtr block =
+        buildBlock<0>(fakedQuery->engine()->itemBlockManager(), {{}, {}}, {{1, 0}});
+    blockDeque.push_back(std::move(block));
+  }
+  auto singleton = std::make_unique<WaitingExecutionBlockMock>(
+      fakedQuery->engine(), generateNodeDummy(), std::move(blockDeque),
+      WaitingExecutionBlockMock::WaitingBehaviour::NEVER);
+  // Produce one full block. The shadowRow has no space left
+  auto testee = onceLinesProducer(singleton.get(), ExecutionBlock::DefaultBatchSize);
+
+  AqlCall fullCall{};
+  AqlCallStack stack{fullCall};
+  {
+    // First call. Fetch all rows (data only)
+    auto const& [state, skipped, block] = testee->execute(stack);
+    EXPECT_EQ(state, ExecutionState::HASMORE);
+    EXPECT_EQ(skipped, 0);
+    ASSERT_NE(block, nullptr);
+    EXPECT_EQ(block->size(), ExecutionBlock::DefaultBatchSize);
+    EXPECT_FALSE(block->hasShadowRows());
+  }
+  {
+    // Second call. only a single shadowRow left
+    auto const& [state, skipped, block] = testee->execute(stack);
+    EXPECT_EQ(state, ExecutionState::DONE);
+    EXPECT_EQ(skipped, 0);
+    ASSERT_NE(block, nullptr);
+    EXPECT_EQ(block->size(), 1);
+    EXPECT_TRUE(block->hasShadowRows());
+    ASSERT_TRUE(block->isShadowRow(0));
+    ShadowAqlItemRow shadow{block, 0};
+    EXPECT_EQ(shadow.getDepth(), 0);
+  }
+}
+
+TEST_P(ExecutionBlockImplExecuteSpecificTest, set_of_shadowrows_does_not_fit_in_output) {
+  if (GetParam()) {
+    // This test is only for non-passthrough variants
+    SUCCEED();
+    return;
+  }
+  std::deque<SharedAqlItemBlockPtr> blockDeque;
+  {
+    SharedAqlItemBlockPtr block = buildBlock<0>(fakedQuery->engine()->itemBlockManager(),
+                                                {{}, {}, {}}, {{1, 0}, {2, 1}});
+    blockDeque.push_back(std::move(block));
+  }
+  auto singleton = std::make_unique<WaitingExecutionBlockMock>(
+      fakedQuery->engine(), generateNodeDummy(), std::move(blockDeque),
+      WaitingExecutionBlockMock::WaitingBehaviour::NEVER);
+  // Produce one full block. The shadowRow has no space left
+  auto testee = onceLinesProducer(singleton.get(), ExecutionBlock::DefaultBatchSize);
+
+  AqlCall fullCall{};
+  AqlCallStack stack{fullCall};
+  {
+    // First call. Fetch all rows (data only)
+    auto const& [state, skipped, block] = testee->execute(stack);
+    EXPECT_EQ(state, ExecutionState::HASMORE);
+    EXPECT_EQ(skipped, 0);
+    ASSERT_NE(block, nullptr);
+    EXPECT_EQ(block->size(), ExecutionBlock::DefaultBatchSize);
+    EXPECT_FALSE(block->hasShadowRows());
+  }
+  {
+    // Second call. only the shadowRows are left
+    auto const& [state, skipped, block] = testee->execute(stack);
+    EXPECT_EQ(state, ExecutionState::DONE);
+    EXPECT_EQ(skipped, 0);
+    ASSERT_NE(block, nullptr);
+    ASSERT_EQ(block->size(), 2);
+    EXPECT_TRUE(block->hasShadowRows());
+    {
+      ASSERT_TRUE(block->isShadowRow(0));
+      ShadowAqlItemRow shadow{block, 0};
+      EXPECT_EQ(shadow.getDepth(), 0);
+    }
+    {
+      ASSERT_TRUE(block->isShadowRow(1));
+      ShadowAqlItemRow shadow{block, 1};
+      EXPECT_EQ(shadow.getDepth(), 1);
+    }
+  }
+}
+
+TEST_P(ExecutionBlockImplExecuteSpecificTest, set_of_shadowrows_does_not_fit_fully_in_output) {
+  if (GetParam()) {
+    // This test is only for non-passthrough variants
+    SUCCEED();
+    return;
+  }
+  std::deque<SharedAqlItemBlockPtr> blockDeque;
+  {
+    SharedAqlItemBlockPtr block = buildBlock<0>(fakedQuery->engine()->itemBlockManager(),
+                                                {{}, {}, {}}, {{1, 0}, {2, 1}});
+    blockDeque.push_back(std::move(block));
+  }
+  auto singleton = std::make_unique<WaitingExecutionBlockMock>(
+      fakedQuery->engine(), generateNodeDummy(), std::move(blockDeque),
+      WaitingExecutionBlockMock::WaitingBehaviour::NEVER);
+  // Produce one full block. The shadowRow has no space left
+  auto testee = onceLinesProducer(singleton.get(), ExecutionBlock::DefaultBatchSize - 1);
+
+  AqlCall fullCall{};
+  AqlCallStack stack{fullCall};
+  {
+    // First call. Fetch all rows (data + relevant shadow row)
+    auto const& [state, skipped, block] = testee->execute(stack);
+    EXPECT_EQ(state, ExecutionState::HASMORE);
+    EXPECT_EQ(skipped, 0);
+    ASSERT_NE(block, nullptr);
+    EXPECT_EQ(block->size(), ExecutionBlock::DefaultBatchSize);
+    EXPECT_TRUE(block->hasShadowRows());
+    ASSERT_TRUE(block->isShadowRow(block->size() - 1));
+    ShadowAqlItemRow shadow{block, block->size() - 1};
+    EXPECT_EQ(shadow.getDepth(), 0);
+  }
+  {
+    // Second call. only the shadowRows are left
+    auto const& [state, skipped, block] = testee->execute(stack);
+    EXPECT_EQ(state, ExecutionState::DONE);
+    EXPECT_EQ(skipped, 0);
+    ASSERT_NE(block, nullptr);
+    EXPECT_EQ(block->size(), 1);
+    EXPECT_TRUE(block->hasShadowRows());
+    ASSERT_TRUE(block->isShadowRow(0));
+    ShadowAqlItemRow shadow{block, 0};
+    EXPECT_EQ(shadow.getDepth(), 1);
+  }
+}
+
 INSTANTIATE_TEST_CASE_P(ExecutionBlockImplExecuteTest,
                         ExecutionBlockImplExecuteSpecificTest, ::testing::Bool());
 
@@ -847,6 +1040,9 @@ struct BaseCallAsserter {
   // The expected outer call, the machine needs to extract relevant parts
   AqlCall const expected;
 
+  // Initial state of this executor. Will return to this state on reset.
+  CallAsserterState initialState = CallAsserterState::DONE;
+
   /**
    * @brief Construct a new Base Call Asserter object
    *
@@ -855,6 +1051,17 @@ struct BaseCallAsserter {
   explicit BaseCallAsserter(AqlCall const& expectedCall)
       : expected{expectedCall} {}
 
+  virtual ~BaseCallAsserter() {}
+
+  /**
+   * @brief Reset to 0 calls and to initialState
+   *
+   */
+  auto virtual reset() -> void {
+    call = 0;
+    state = initialState;
+  }
+
   /**
    * @brief Test if we need to expect a skip phase
    *
@@ -876,6 +1083,24 @@ struct BaseCallAsserter {
    * @return false
    */
   auto needsFullCount() const -> bool { return expected.needsFullCount(); }
+
+  auto gotCalled(AqlCall const& got) -> void {
+    call++;
+    SCOPED_TRACE("In call " + std::to_string(call) + " of " +
+                 std::to_string(maxCall) + " state " +
+                 std::to_string(
+                     static_cast<typename std::underlying_type<CallAsserterState>::type>(state)));
+    gotCalledWithoutTrace(got);
+    EXPECT_LE(call, maxCall);
+    if (call > maxCall) {
+      // Security bailout to avoid infinite loops
+      THROW_ARANGO_EXCEPTION(TRI_ERROR_INTERNAL);
+    }
+  }
+
+  auto getNumberCalls() const -> size_t { return call; }
+
+  virtual auto gotCalledWithoutTrace(AqlCall const& got) -> void = 0;
 };
 
 /**
@@ -894,18 +1119,18 @@ struct SkipCallAsserter : public BaseCallAsserter {
     // so skip needs to be last here
     if (needsFullCount()) {
       maxCall += 2;
-      state = CallAsserterState::COUNT;
+      initialState = CallAsserterState::COUNT;
     }
     if (hasSkip()) {
       maxCall += 2;
-      state = CallAsserterState::SKIP;
+      initialState = CallAsserterState::SKIP;
     }
     // It is possible that we actually have 0 calls.
     // if there is neither skip nor limit
+    state = initialState;
   }
 
-  auto gotCalled(AqlCall const& got) -> void {
-    call++;
+  auto gotCalledWithoutTrace(AqlCall const& got) -> void override {
     switch (state) {
       case CallAsserterState::SKIP: {
         EXPECT_EQ(got.getOffset(), expected.getOffset());
@@ -935,11 +1160,6 @@ struct SkipCallAsserter : public BaseCallAsserter {
         break;
       }
     }
-    EXPECT_LE(call, maxCall);
-    if (call > maxCall) {
-      // Security bailout to avoid infinite loops
-      THROW_ARANGO_EXCEPTION(TRI_ERROR_INTERNAL);
-    }
   }
 };
 
@@ -954,13 +1174,15 @@ struct CallAsserter : public BaseCallAsserter {
     // Calculate number of calls
     if (hasLimit()) {
       maxCall += 2;
-      state = CallAsserterState::INITIAL;
+      initialState = CallAsserterState::INITIAL;
     }
+    // It is possible that we actually have 0 calls.
+    // if there is neither skip nor limit
+    state = initialState;
   }
 
-  auto gotCalled(AqlCall const& got) -> void {
+  auto gotCalledWithoutTrace(AqlCall const& got) -> void override {
     EXPECT_EQ(got.getOffset(), 0);
-    call++;
     switch (state) {
       case CallAsserterState::INITIAL: {
         EXPECT_EQ(got.getLimit(), expected.getLimit());
@@ -980,19 +1202,14 @@ struct CallAsserter : public BaseCallAsserter {
         break;
       }
     }
-    EXPECT_LE(call, maxCall);
-    if (call > maxCall) {
-      // Security bailout to avoid infinite loops
-      THROW_ARANGO_EXCEPTION(TRI_ERROR_INTERNAL);
-    }
   }
 };
 
 /**
  * @brief Asserter used "above" an executor that implements
  *        skip and produce, and transforms everything to produce.
- *        Expects to be called twice for each sitation (with and without input).
- *        Expect up to three situations: SKIP, GET and FULLCOUNT.
+ *        Expects to be called twice for each sitation (with and without
+ * input). Expect up to three situations: SKIP, GET and FULLCOUNT.
  */
 struct GetOnlyCallAsserter : public BaseCallAsserter {
   explicit GetOnlyCallAsserter(AqlCall const& expectedCall)
@@ -1003,25 +1220,25 @@ struct GetOnlyCallAsserter : public BaseCallAsserter {
     // so skip needs to be last here
     if (needsFullCount()) {
       maxCall += 2;
-      state = CallAsserterState::COUNT;
+      initialState = CallAsserterState::COUNT;
     }
     if (hasLimit()) {
       maxCall += 2;
-      state = CallAsserterState::GET;
+      initialState = CallAsserterState::GET;
     }
     if (hasSkip()) {
       maxCall += 2;
-      state = CallAsserterState::SKIP;
+      initialState = CallAsserterState::SKIP;
     }
+    state = initialState;
     // Make sure setup worked
     EXPECT_GT(maxCall, 0);
     EXPECT_NE(state, CallAsserterState::DONE);
   }
 
-  auto gotCalled(AqlCall const& got) -> void {
+  auto gotCalledWithoutTrace(AqlCall const& got) -> void override {
     EXPECT_EQ(got.getOffset(), 0);
     EXPECT_FALSE(got.needsFullCount());
-    call++;
 
     switch (state) {
       case CallAsserterState::SKIP: {
@@ -1072,14 +1289,23 @@ struct GetOnlyCallAsserter : public BaseCallAsserter {
         break;
       }
     }
-    EXPECT_LE(call, maxCall);
-    if (call > maxCall) {
-      // Security bailout to avoid infinite loops
-      THROW_ARANGO_EXCEPTION(TRI_ERROR_INTERNAL);
-    }
   }
 };
 
+/**
+ * @brief None asserter, does not assert any thing within a call.
+ * Only asserts that we are not called more than maxCalls times.
+ *
+ */
+struct NoneAsserter : public BaseCallAsserter {
+  explicit NoneAsserter(AqlCall const& expectedCall, size_t maxCalls)
+      : BaseCallAsserter{expectedCall} {
+    maxCall = maxCalls;
+  }
+
+  auto gotCalledWithoutTrace(AqlCall const& got) -> void override {}
+};
+
 /**
  * @brief Integration tests.
  *        These test tests a chain of Executors.
@@ -1089,11 +1315,85 @@ struct GetOnlyCallAsserter : public BaseCallAsserter {
  *        Also asserts that "UPSTREAM" is called with the correct
  *        forwarded call.
  *        This is a parameterized testsuite that uses a set of pseudo-random AqlCalls of different formats.
+ *        The second parameter is a boolean to flag if we use WAITING on singleton.
  */
 class ExecutionBlockImplExecuteIntegrationTest
     : public SharedExecutionBlockImplTest,
-      public testing::TestWithParam<AqlCall> {
+      public testing::TestWithParam<std::tuple<AqlCall, bool>> {
  protected:
+  /**
+   * @brief Get the Call object
+   *
+   * @return AqlCall used as test parameter
+   */
+  AqlCall getCall() const {
+    auto const [call, waits] = GetParam();
+    return call;
+  }
+
+  /**
+   * @brief Get the combination if we are waiting or not.
+   *
+   * @return true We need waiting
+   * @return false We do not.
+   */
+  bool doesWaiting() const {
+    auto const [call, waits] = GetParam();
+    return waits;
+  }
+
+  /**
+   * @brief Assert that the given value is equal to the given number
+   *
+   * @param block The AqlItemBlock the value is stored in
+   * @param row The row number of the value
+   * @param reg The register number of the value
+   * @param expected the expected number
+   */
+  auto AssertValueEquals(SharedAqlItemBlockPtr const& block, size_t row,
+                         RegisterId reg, size_t expected) const -> void {
+    ASSERT_NE(block, nullptr);
+    ASSERT_GT(block->size(), row);
+    ASSERT_GE(block->getNrRegs(), reg);
+    auto const& value = block->getValueReference(row, reg);
+    ASSERT_TRUE(value.isNumber());
+    EXPECT_EQ(static_cast<size_t>(value.toInt64()), expected);
+  }
+
+  /**
+   * @brief Assert that the given row in the block, is a shadow row of the expected depth
+   *
+   * @param block The AqlItemBlock the row is stored in
+   * @param row The shadow row number
+   * @param expected The expected depth
+   */
+  auto AssertIsShadowRowOfDepth(SharedAqlItemBlockPtr const& block, size_t row,
+                                size_t expected) -> void {
+    ASSERT_NE(block, nullptr);
+    ASSERT_GT(block->size(), row);
+    ASSERT_TRUE(block->isShadowRow(row));
+    auto val = block->getShadowRowDepth(row);
+    ASSERT_TRUE(val.isNumber());
+    EXPECT_EQ(static_cast<size_t>(val.toInt64()), expected);
+  }
+
+  /**
+   * @brief Create a Singleton ExecutionBlock. Just like the original one in
+   * the query. it is already initialized and ready to use.
+   *
+   * @return std::unique_ptr<ExecutionBlock> The singleton ExecutionBlock.
+   */
+  std::unique_ptr<ExecutionBlock> createSingleton() {
+    std::deque<SharedAqlItemBlockPtr> blockDeque;
+    SharedAqlItemBlockPtr block =
+        buildBlock<0>(fakedQuery->engine()->itemBlockManager(), {{}});
+    blockDeque.push_back(std::move(block));
+    return std::make_unique<WaitingExecutionBlockMock>(
+        fakedQuery->engine(), generateNodeDummy(), std::move(blockDeque),
+        doesWaiting() ? WaitingExecutionBlockMock::WaitingBehaviour::ALWAYS
+                      : WaitingExecutionBlockMock::WaitingBehaviour::NEVER);
+  }
+
   /**
    * @brief Create a Producing ExecutionBlock
    *        For every input row this block will write the array given in data
@@ -1111,8 +1411,10 @@ class ExecutionBlockImplExecuteIntegrationTest
     TRI_ASSERT(dependency != nullptr);
     TRI_ASSERT(data != nullptr);
     TRI_ASSERT(data->slice().isArray());
+
     // We make this a shared ptr just to make sure someone retains the data.
     auto iterator = std::make_shared<VPackArrayIterator>(data->slice());
+    auto resetCall = [iterator]() -> void { iterator->reset(); };
     auto writeData = [data, outReg, iterator](AqlItemBlockInputRange& inputRange,
                                               OutputAqlItemRow& output)
         -> std::tuple<ExecutorState, LambdaExe::Stats, AqlCall> {
@@ -1167,10 +1469,10 @@ class ExecutionBlockImplExecuteIntegrationTest
       call.fullCount = false;
       return {inputRange.upstreamState(), skipped, call};
     };
-    auto infos = outReg == 0
-                     ? makeSkipInfos(std::move(writeData), skipData,
-                                     RegisterPlan::MaxRegisterId, outReg)
-                     : makeSkipInfos(std::move(writeData), skipData, outReg - 1, outReg);
+    auto infos = outReg == 0 ? makeSkipInfos(std::move(writeData), skipData,
+                                             RegisterPlan::MaxRegisterId, outReg, resetCall)
+                             : makeSkipInfos(std::move(writeData), skipData,
+                                             outReg - 1, outReg, resetCall);
     auto producer =
         std::make_unique<ExecutionBlockImpl<LambdaExe>>(fakedQuery->engine(),
                                                         generateNodeDummy(),
@@ -1183,14 +1485,18 @@ class ExecutionBlockImplExecuteIntegrationTest
    * @brief Create a simple row forwarding Block.
    *        It simply takes one input row and copies it into the output
    *
+   * @param asserter A call asserter, that will invoke getCalled on every call
    * @param dependency The dependecy of this block (produces input)
    * @param maxReg The number of registers in input and output. (required for forwarding of data)
    * @return std::unique_ptr<ExecutionBlock> ready to use ForwardingBlock.
    */
-  std::unique_ptr<ExecutionBlock> forwardBlock(ExecutionBlock* dependency, RegisterId maxReg) {
+  std::unique_ptr<ExecutionBlock> forwardBlock(BaseCallAsserter& asserter,
+                                               ExecutionBlock* dependency,
+                                               RegisterId maxReg) {
     TRI_ASSERT(dependency != nullptr);
-    auto forwardData = [](AqlItemBlockInputRange& inputRange, OutputAqlItemRow& output)
+    auto forwardData = [&asserter](AqlItemBlockInputRange& inputRange, OutputAqlItemRow& output)
         -> std::tuple<ExecutorState, LambdaExe::Stats, AqlCall> {
+      asserter.gotCalled(output.getClientCall());
       while (inputRange.hasDataRow() && !output.isFull()) {
         auto const& [state, input] = inputRange.nextDataRow();
         EXPECT_TRUE(input.isInitialized());
@@ -1206,6 +1512,77 @@ class ExecutionBlockImplExecuteIntegrationTest
     return producer;
   }
 
+  /**
+   * @brief Create a simple row forwarding Block.
+   *        It simply takes one input row and copies it into the output.
+   *        Implements Skip
+   *
+   * @param produceAsserter A call asserter, that will invoke getCalled on every produce call
+   * @param skipAsserter A call asserter, that will invoke getCalled on every skip call
+   * @param dependency The dependecy of this block (produces input)
+   * @param maxReg The number of registers in input and output. (required for forwarding of data)
+   * @return std::unique_ptr<ExecutionBlock> ready to use ForwardingBlock.
+   */
+  std::unique_ptr<ExecutionBlock> forwardBlock(BaseCallAsserter& produceAsserter,
+                                               BaseCallAsserter& skipAsserter,
+                                               ExecutionBlock* dependency,
+                                               RegisterId maxReg) {
+    TRI_ASSERT(dependency != nullptr);
+    auto forwardData = [&produceAsserter](AqlItemBlockInputRange& inputRange,
+                                          OutputAqlItemRow& output)
+        -> std::tuple<ExecutorState, LambdaExe::Stats, AqlCall> {
+      produceAsserter.gotCalled(output.getClientCall());
+      while (inputRange.hasDataRow() && !output.isFull()) {
+        auto const& [state, input] = inputRange.nextDataRow();
+        EXPECT_TRUE(input.isInitialized());
+        output.copyRow(input);
+        output.advanceRow();
+      }
+      return {inputRange.upstreamState(), NoStats{}, output.getClientCall()};
+    };
+
+    auto skipData = [&skipAsserter](AqlItemBlockInputRange& inputRange,
+                                    AqlCall& call) -> std::tuple<ExecutorState, size_t, AqlCall> {
+      skipAsserter.gotCalled(call);
+
+      size_t skipped = 0;
+      while (inputRange.hasDataRow() && call.shouldSkip()) {
+        auto const& [state, input] = inputRange.nextDataRow();
+        EXPECT_TRUE(input.isInitialized());
+        skipped++;
+        call.didSkip(1);
+      }
+      // Do forward a softLimit call only.
+      // Do not oeverfetch here.
+      AqlCall request;
+      if (call.getOffset() > 0) {
+        request.softLimit = call.getOffset();
+      }  // else fullCount case, simple get UNLIMITED from above
+
+      return {inputRange.upstreamState(), skipped, request};
+    };
+    auto producer = std::make_unique<ExecutionBlockImpl<LambdaExe>>(
+        fakedQuery->engine(), generateNodeDummy(),
+        makeSkipInfos(std::move(forwardData), std::move(skipData), maxReg, maxReg));
+    producer->addDependency(dependency);
+    return producer;
+  }
+
+  void ValidateSkipMatches(AqlCall const& call, size_t dataLength, size_t actual) const {
+    size_t expected = 0;
+    // Skip Offset, but not more then available
+    expected += std::min(call.getOffset(), dataLength);
+    if (call.needsFullCount()) {
+      // We can only fullCount on hardlimit. If this fails check test code!
+      EXPECT_TRUE(call.hasHardLimit());
+      // We consume either hardLimit + offset, or all data.
+      size_t consumed = std::min(call.getLimit() + call.getOffset(), dataLength);
+      // consumed >= dataLength, if it is smaller we have a remainder for fullCount.
+      expected += dataLength - consumed;
+    }
+    EXPECT_EQ(expected, actual);
+  }
+
   /**
    * @brief Helper method to validate the result
    *        It will take into account the call used as Parameter
@@ -1220,34 +1597,33 @@ class ExecutionBlockImplExecuteIntegrationTest
    * @param skipped The number of rows the executor reported as skipped
    * @param result The resulting data output
    * @param testReg The register to evaluate
+   * @param numShadowRows Number of preceeding shadowRows in result.
    */
   void ValidateResult(std::shared_ptr<VPackBuilder> data, size_t skipped,
-                      SharedAqlItemBlockPtr result, RegisterId testReg) {
-    auto const& call = GetParam();
+                      SharedAqlItemBlockPtr result, RegisterId testReg,
+                      size_t numShadowRows = 0) {
+    auto const& call = getCall();
 
     TRI_ASSERT(data != nullptr);
     TRI_ASSERT(data->slice().isArray());
 
     VPackSlice expected = data->slice();
+    ValidateSkipMatches(call, static_cast<size_t>(expected.length()), skipped);
+
     VPackArrayIterator expectedIt{expected};
     // Skip Part
     size_t offset =
         (std::min)(call.getOffset(), static_cast<size_t>(expected.length()));
 
-    if (!call.needsFullCount()) {
-      // Otherweise skipped = offset + fullCount
-      EXPECT_EQ(offset, skipped);
-    }
-
     for (size_t i = 0; i < offset; ++i) {
       // The first have been skipped
       expectedIt++;
     }
     size_t limit =
         (std::min)(call.getLimit(), static_cast<size_t>(expected.length()) - offset);
-    if (result != nullptr) {
+    if (result != nullptr && result->size() > numShadowRows) {
       // GetSome part
-      EXPECT_EQ(limit, result->size());
+      EXPECT_EQ(limit, result->size() - numShadowRows);
       for (size_t i = 0; i < limit; ++i) {
         // The next have to match
         auto got = result->getValueReference(i, testReg).slice();
@@ -1259,16 +1635,71 @@ class ExecutionBlockImplExecuteIntegrationTest
     } else {
       EXPECT_EQ(limit, 0);
     }
+  }
 
-    // Now test Fullcount
-    if (call.needsFullCount()) {
-      ASSERT_TRUE(expected.length() >= offset + limit);
-      size_t fullCount = expected.length() - offset - limit;
-      EXPECT_EQ(offset + fullCount, skipped);
-    }
+  /**
+   * @brief Test that there is a shadowrow at the given index of the given depth
+   *
+   * @param block The returned block
+   * @param rowIndex The row index to test
+   * @param depth The expected shadowRow depth
+   */
+  void ValidateShadowRow(SharedAqlItemBlockPtr block, size_t rowIndex, size_t depth) {
+    ASSERT_TRUE(block != nullptr);
+    EXPECT_TRUE(block->hasShadowRows());
+    ASSERT_TRUE(block->isShadowRow(rowIndex));
+    ShadowAqlItemRow row{block, rowIndex};
+    EXPECT_EQ(row.getDepth(), depth);
   }
 };
 
+// This test asserts that the mock we are using here is working as expected.
+// If this does not work we will undefined follow up errors
+TEST_P(ExecutionBlockImplExecuteIntegrationTest, test_waiting_block_mock) {
+  std::deque<SharedAqlItemBlockPtr> blockDeque;
+  auto builder = std::make_shared<VPackBuilder>();
+  {
+    MatrixBuilder<1> matrix;
+    matrix.reserve(250);
+    builder->openArray();
+    for (size_t i = 0; i < 250; ++i) {
+      builder->add(VPackValue(i));
+      matrix.emplace_back(RowBuilder<1>{i});
+    }
+    builder->close();
+    SharedAqlItemBlockPtr block =
+        buildBlock<1>(fakedQuery->engine()->itemBlockManager(), std::move(matrix));
+    blockDeque.push_back(std::move(block));
+  }
+
+  WaitingExecutionBlockMock testee{fakedQuery->engine(), generateNodeDummy(),
+                                   std::move(blockDeque),
+                                   doesWaiting()
+                                       ? WaitingExecutionBlockMock::WaitingBehaviour::ALWAYS
+                                       : WaitingExecutionBlockMock::WaitingBehaviour::NEVER};
+
+  auto const& call = getCall();
+  AqlCallStack stack{call};
+
+  auto [state, skipped, block] = testee.execute(stack);
+  if (doesWaiting()) {
+    EXPECT_EQ(state, ExecutionState::WAITING);
+    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(block, nullptr);
+    std::tie(state, skipped, block) = testee.execute(stack);
+  }
+  if (call.getLimit() > builder->slice().length() || call.needsFullCount() ||
+      call.hasHardLimit()) {
+    // We need to consume everything
+    EXPECT_EQ(state, ExecutionState::DONE);
+  } else {
+    // We cannot consume everything.
+    EXPECT_EQ(state, ExecutionState::HASMORE);
+  }
+
+  ValidateResult(builder, skipped, block, 0);
+}
+
 // Test a simple produce block. that has is supposed to write 1000 rows.
 TEST_P(ExecutionBlockImplExecuteIntegrationTest, test_produce_only) {
   auto singleton = createSingleton();
@@ -1282,8 +1713,14 @@ TEST_P(ExecutionBlockImplExecuteIntegrationTest, test_produce_only) {
   RegisterId outReg = 0;
   auto producer = produceBlock(singleton.get(), builder, outReg);
 
-  auto const& call = GetParam();
+  auto const& call = getCall();
   AqlCallStack stack{call};
+  if (doesWaiting()) {
+    auto const [state, skipped, block] = producer->execute(stack);
+    EXPECT_EQ(state, ExecutionState::WAITING);
+    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(block, nullptr);
+  }
   auto const [state, skipped, block] = producer->execute(stack);
   if (std::holds_alternative<size_t>(call.softLimit) && !call.hasHardLimit()) {
     EXPECT_EQ(state, ExecutionState::HASMORE);
@@ -1310,8 +1747,14 @@ TEST_P(ExecutionBlockImplExecuteIntegrationTest, test_produce_using_two) {
   RegisterId outRegSecond = 1;
   auto producerFirst = produceBlock(singleton.get(), builder, outRegFirst);
   auto producer = produceBlock(producerFirst.get(), builder, outRegSecond);
-  auto const& call = GetParam();
+  auto const& call = getCall();
   AqlCallStack stack{call};
+  if (doesWaiting()) {
+    auto const [state, skipped, block] = producer->execute(stack);
+    EXPECT_EQ(state, ExecutionState::WAITING);
+    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(block, nullptr);
+  }
   auto const [state, skipped, block] = producer->execute(stack);
   if (call.getLimit() < 100) {
     if (call.hasHardLimit()) {
@@ -1360,43 +1803,22 @@ TEST_P(ExecutionBlockImplExecuteIntegrationTest, test_call_forwarding_passthroug
   RegisterId outReg = 0;
   auto producer = produceBlock(singleton.get(), builder, outReg);
 
-  CallAsserter upperState{GetParam()};
-  CallAsserter lowerState{GetParam()};
-
-  auto testForwarding =
-      [&](AqlItemBlockInputRange& inputRange,
-          OutputAqlItemRow& output) -> std::tuple<ExecutorState, LambdaExe::Stats, AqlCall> {
-    upperState.gotCalled(output.getClientCall());
-    while (inputRange.hasDataRow() && !output.isFull()) {
-      auto const& [state, input] = inputRange.nextDataRow();
-      EXPECT_TRUE(input.isInitialized());
-      output.copyRow(input);
-      output.advanceRow();
-    }
-    return {inputRange.upstreamState(), NoStats{}, output.getClientCall()};
-  };
-  auto forwardCall = [&](AqlItemBlockInputRange& inputRange, OutputAqlItemRow& output)
-      -> std::tuple<ExecutorState, LambdaExe::Stats, AqlCall> {
-    lowerState.gotCalled(output.getClientCall());
-    while (inputRange.hasDataRow() && !output.isFull()) {
-      auto const& [state, input] = inputRange.nextDataRow();
-      EXPECT_TRUE(input.isInitialized());
-      output.copyRow(input);
-      output.advanceRow();
-    }
-    return {inputRange.upstreamState(), NoStats{}, output.getClientCall()};
-  };
-  auto upper = std::make_unique<ExecutionBlockImpl<LambdaExePassThrough>>(
-      fakedQuery->engine(), generateNodeDummy(),
-      makeInfos(std::move(testForwarding), outReg, outReg));
-  upper->addDependency(producer.get());
-  auto lower = std::make_unique<ExecutionBlockImpl<LambdaExePassThrough>>(
-      fakedQuery->engine(), generateNodeDummy(),
-      makeInfos(std::move(forwardCall), outReg, outReg));
-  lower->addDependency(upper.get());
+  CallAsserter upperState{getCall()};
+  auto upper = forwardBlock(upperState, producer.get(), outReg);
+  CallAsserter lowerState{getCall()};
+  auto lower = forwardBlock(lowerState, upper.get(), outReg);
 
-  auto const& call = GetParam();
+  auto const& call = getCall();
   AqlCallStack stack{call};
+  if (doesWaiting()) {
+    auto const [state, skipped, block] = lower->execute(stack);
+    EXPECT_EQ(state, ExecutionState::WAITING);
+    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(block, nullptr);
+    // Reset call counters
+    upperState.reset();
+    lowerState.reset();
+  }
   auto const [state, skipped, block] = lower->execute(stack);
   if (std::holds_alternative<size_t>(call.softLimit) && !call.hasHardLimit()) {
     EXPECT_EQ(state, ExecutionState::HASMORE);
@@ -1423,22 +1845,13 @@ TEST_P(ExecutionBlockImplExecuteIntegrationTest, test_call_forwarding_implement_
   builder->close();
   RegisterId outReg = 0;
   auto producer = produceBlock(singleton.get(), builder, outReg);
-  GetOnlyCallAsserter upperState{GetParam()};
-  CallAsserter lowerState{GetParam()};
-  SkipCallAsserter skipState{GetParam()};
-
-  auto testForwarding =
-      [&](AqlItemBlockInputRange& inputRange,
-          OutputAqlItemRow& output) -> std::tuple<ExecutorState, LambdaExe::Stats, AqlCall> {
-    upperState.gotCalled(output.getClientCall());
-    while (inputRange.hasDataRow() && !output.isFull()) {
-      auto const& [state, input] = inputRange.nextDataRow();
-      EXPECT_TRUE(input.isInitialized());
-      output.copyRow(input);
-      output.advanceRow();
-    }
-    return {inputRange.upstreamState(), NoStats{}, output.getClientCall()};
-  };
+
+  GetOnlyCallAsserter upperState{getCall()};
+  auto upper = forwardBlock(upperState, producer.get(), outReg);
+
+  CallAsserter lowerState{getCall()};
+  SkipCallAsserter skipState{getCall()};
+
   auto forwardCall = [&](AqlItemBlockInputRange& inputRange, OutputAqlItemRow& output)
       -> std::tuple<ExecutorState, LambdaExe::Stats, AqlCall> {
     lowerState.gotCalled(output.getClientCall());
@@ -1457,13 +1870,12 @@ TEST_P(ExecutionBlockImplExecuteIntegrationTest, test_call_forwarding_implement_
                              AqlCall& call) -> std::tuple<ExecutorState, size_t, AqlCall> {
     skipState.gotCalled(call);
     size_t skipped = 0;
-    while (inputRange.hasDataRow() &&
-           (call.getOffset() > 0 || (call.getLimit() == 0 && call.needsFullCount()))) {
+    while (inputRange.hasDataRow() && call.shouldSkip()) {
       auto const& [state, input] = inputRange.nextDataRow();
       EXPECT_TRUE(input.isInitialized());
       skipped++;
+      call.didSkip(1);
     }
-    call.didSkip(skipped);
     // Do forward a softLimit call only.
     // Do not oeverfetch here.
     AqlCall request;
@@ -1474,17 +1886,19 @@ TEST_P(ExecutionBlockImplExecuteIntegrationTest, test_call_forwarding_implement_
     return {inputRange.upstreamState(), skipped, request};
   };
 
-  auto upper = std::make_unique<ExecutionBlockImpl<LambdaExePassThrough>>(
-      fakedQuery->engine(), generateNodeDummy(),
-      makeInfos(std::move(testForwarding), outReg, outReg));
-  upper->addDependency(producer.get());
   auto lower = std::make_unique<ExecutionBlockImpl<TestLambdaSkipExecutor>>(
       fakedQuery->engine(), generateNodeDummy(),
       makeSkipInfos(std::move(forwardCall), std::move(forwardSkipCall), outReg, outReg));
   lower->addDependency(upper.get());
 
-  auto const& call = GetParam();
+  auto const& call = getCall();
   AqlCallStack stack{call};
+  if (doesWaiting()) {
+    auto const [state, skipped, block] = lower->execute(stack);
+    EXPECT_EQ(state, ExecutionState::WAITING);
+    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(block, nullptr);
+  }
   auto const [state, skipped, block] = lower->execute(stack);
   if (std::holds_alternative<size_t>(call.softLimit) && !call.hasHardLimit()) {
     EXPECT_EQ(state, ExecutionState::HASMORE);
@@ -1494,6 +1908,710 @@ TEST_P(ExecutionBlockImplExecuteIntegrationTest, test_call_forwarding_implement_
   ValidateResult(builder, skipped, block, outReg);
 }
 
+// Simulate many upstream calls, the block upstream only returns a single
+// line. This test forces the executor into internal loops and into keeping
+// internal state due to doesWaiting variant
+TEST_P(ExecutionBlockImplExecuteIntegrationTest, test_multiple_upstream_calls) {
+  // The WAITING block mock can only stop returning after a full block.
+  // As the used calls have "random" sizes, we simply create 1 line blocks only.
+  // This is less then optimal, but we will have an easily predictable result, with a complex internal structure
+  std::deque<SharedAqlItemBlockPtr> blockDeque;
+  auto builder = std::make_shared<VPackBuilder>();
+  builder->openArray();
+  for (size_t i = 0; i < 1000; ++i) {
+    SharedAqlItemBlockPtr block =
+        buildBlock<1>(fakedQuery->engine()->itemBlockManager(), {{i}});
+    blockDeque.push_back(std::move(block));
+    builder->add(VPackValue(i));
+  }
+  builder->close();
+
+  auto producer = std::make_unique<WaitingExecutionBlockMock>(
+      fakedQuery->engine(), generateNodeDummy(), std::move(blockDeque),
+      doesWaiting() ? WaitingExecutionBlockMock::WaitingBehaviour::ALWAYS
+                    : WaitingExecutionBlockMock::WaitingBehaviour::NEVER);
+
+  NoneAsserter produceAsserter{getCall(), ExecutionBlock::DefaultBatchSize * 3};
+  NoneAsserter skipAsserter{getCall(), ExecutionBlock::DefaultBatchSize * 3};
+  RegisterId outReg = 0;
+  auto testee = forwardBlock(produceAsserter, skipAsserter, producer.get(), outReg);
+  auto const& call = getCall();
+  AqlCallStack stack{call};
+  auto [state, skipped, block] = testee->execute(stack);
+  size_t killSwitch = 0;
+  while (state == ExecutionState::WAITING) {
+    EXPECT_TRUE(doesWaiting());
+    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(block, nullptr);
+    std::tie(state, skipped, block) = testee->execute(stack);
+    // Kill switch to avoid endless loop in case of error.
+    // We should get this through with much fewer than two times Batchsize calls.
+    killSwitch++;
+    if (killSwitch >= ExecutionBlock::DefaultBatchSize * 2) {
+      ASSERT_TRUE(false);
+      THROW_ARANGO_EXCEPTION(TRI_ERROR_INTERNAL);
+    }
+  }
+  if (std::holds_alternative<size_t>(call.softLimit) && !call.hasHardLimit()) {
+    EXPECT_EQ(state, ExecutionState::HASMORE);
+  } else {
+    EXPECT_EQ(state, ExecutionState::DONE);
+  }
+
+  ValidateResult(builder, skipped, block, outReg);
+}
+
+// Simulate many upstream calls, the block upstream only returns a single
+// line. This test forces the executor into internal loops and into keeping
+// internal state due to doesWaiting variant. Using a passthrough executor.
+TEST_P(ExecutionBlockImplExecuteIntegrationTest, test_multiple_upstream_calls_passthrough) {
+  // The WAITING block mock can only stop returning after a full block.
+  // As the used calls have "random" sizes, we simply create 1 line blocks only.
+  // This is less then optimal, but we will have an easily predictable result, with a complex internal structure
+  std::deque<SharedAqlItemBlockPtr> blockDeque;
+  auto builder = std::make_shared<VPackBuilder>();
+  builder->openArray();
+  for (size_t i = 0; i < 1000; ++i) {
+    SharedAqlItemBlockPtr block =
+        buildBlock<1>(fakedQuery->engine()->itemBlockManager(), {{i}});
+    blockDeque.push_back(std::move(block));
+    builder->add(VPackValue(i));
+  }
+  builder->close();
+
+  auto producer = std::make_unique<WaitingExecutionBlockMock>(
+      fakedQuery->engine(), generateNodeDummy(), std::move(blockDeque),
+      doesWaiting() ? WaitingExecutionBlockMock::WaitingBehaviour::ALWAYS
+                    : WaitingExecutionBlockMock::WaitingBehaviour::NEVER);
+
+  NoneAsserter produceAsserter{getCall(), ExecutionBlock::DefaultBatchSize * 3};
+  RegisterId outReg = 0;
+  auto testee = forwardBlock(produceAsserter, producer.get(), outReg);
+  auto call = getCall();
+  auto limit = call.getLimit();
+  size_t offset = call.getOffset();
+  bool fullCount = call.needsFullCount();
+
+  if (limit == 0) {
+    // we can bypass everything and get away with a single call
+    AqlCallStack stack{call};
+    auto [state, skipped, block] = testee->execute(stack);
+    if (doesWaiting()) {
+      size_t waited = 0;
+      while (state == ExecutionState::WAITING && waited < 2 /* avoid endless waiting*/) {
+        EXPECT_EQ(state, ExecutionState::WAITING);
+        EXPECT_EQ(skipped, 0);
+        EXPECT_EQ(block, nullptr);
+        waited++;
+        std::tie(state, skipped, block) = testee->execute(stack);
+      }
+      EXPECT_LT(waited, 2);
+    }
+    EXPECT_EQ(block, nullptr);
+    if (fullCount) {
+      // We skipped everything
+      EXPECT_EQ(skipped, 1000);
+      EXPECT_EQ(state, ExecutionState::DONE);
+    } else {
+      EXPECT_EQ(skipped, offset);
+      EXPECT_EQ(state, ExecutionState::HASMORE);
+    }
+  } else {
+    VPackArrayIterator it{builder->slice()};
+    // Skip over offset
+    for (size_t i = 0; i < offset; ++i) {
+      ++it;
+    }
+    for (size_t i = 0; i < limit && it.valid(); ++i) {
+      AqlCallStack stack{call};
+      auto [state, skipped, block] = testee->execute(stack);
+      if (doesWaiting()) {
+        size_t waited = 0;
+        while (state == ExecutionState::WAITING && waited < 3 /* avoid endless waiting*/) {
+          EXPECT_EQ(state, ExecutionState::WAITING);
+          EXPECT_EQ(skipped, 0);
+          EXPECT_EQ(block, nullptr);
+          waited++;
+          std::tie(state, skipped, block) = testee->execute(stack);
+        }
+        if (offset > 0 && i == 0) {
+          // We wait some time before the first row is produced
+          EXPECT_LT(waited, 3);
+        } else {
+          // We wait once, then we we get a line.
+          EXPECT_EQ(1, waited);
+        }
+      }
+
+      ASSERT_NE(block, nullptr);
+      ASSERT_EQ(block->size(), 1);
+      // Book-keeping for call.
+      // We need to request data from above with the correct call.
+      if (skipped > 0) {
+        call.didSkip(skipped);
+      }
+      call.didProduce(1);
+      auto got = block->getValueReference(0, outReg).slice();
+      EXPECT_TRUE(basics::VelocyPackHelper::equal(got, *it, false))
+          << "Expected: " << it.value().toJson() << " got: " << got.toJson()
+          << " in row " << i << " and register " << outReg;
+      if (i == 0) {
+        // The first data row includes skip
+        EXPECT_EQ(skipped, offset);
+      } else {
+        if (call.getLimit() == 0 && call.hasHardLimit() && call.needsFullCount()) {
+          // The last row, with fullCount needs to contain data.
+          EXPECT_EQ(skipped, 1000 - limit - offset);
+        } else {
+          // Do not skip on later data rows
+          // Except the last one on fullcount
+          EXPECT_EQ(skipped, 0);
+        }
+      }
+      // NOTE: We might want to get into this situation.
+      // Even if the output is full, we fulfill the fullCount request
+      // Might however trigger waiting instead.
+      /*
+      if (call.hasHardLimit() && !call.needsFullCount() && call.getLimit() == 0) {
+        EXPECT_EQ(state, ExecutionState::DONE);
+      } else {
+        EXPECT_EQ(state, ExecutionState::HASMORE);
+      }
+      */
+      if ((it.isLast() && call.getLimit() > 0) ||
+          (call.getLimit() == 0 && call.hasHardLimit())) {
+        // This is an unlimited test.
+        // We reached end of output, but still have limit left
+        EXPECT_EQ(state, ExecutionState::DONE);
+      } else {
+        EXPECT_EQ(state, ExecutionState::HASMORE);
+      }
+
+      it++;
+    }
+  }
+}  // namespace aql
+
+// Test to simulate an empty Subquery
+TEST_P(ExecutionBlockImplExecuteIntegrationTest, only_relevant_shadowRows) {
+  std::deque<SharedAqlItemBlockPtr> blockDeque;
+  VPackBuilder builder;
+  builder.openArray();
+  for (size_t i = 0; i < 3; ++i) {
+    SharedAqlItemBlockPtr block =
+        buildBlock<1>(fakedQuery->engine()->itemBlockManager(), {{i}}, {{0, 0}});
+    blockDeque.push_back(std::move(block));
+    builder.add(VPackValue(0));
+  }
+  builder.close();
+
+  // We have 3 consecutive shadowRows of Depth 0
+  auto producer = std::make_unique<WaitingExecutionBlockMock>(
+      fakedQuery->engine(), generateNodeDummy(), std::move(blockDeque),
+      doesWaiting() ? WaitingExecutionBlockMock::WaitingBehaviour::ALWAYS
+                    : WaitingExecutionBlockMock::WaitingBehaviour::NEVER);
+
+  RegisterId outReg = 0;
+  // We ask:
+  // Empty input
+  // On waiting: Empty Input
+  // input with shadow row only
+  size_t maxCalls = doesWaiting() ? 9 : 6;
+  NoneAsserter getAsserter{getCall(), maxCalls};
+  NoneAsserter skipAsserter{getCall(), maxCalls};
+  auto testee = forwardBlock(getAsserter, skipAsserter, producer.get(), outReg);
+
+  for (size_t i = 0; i < 3; ++i) {
+    // We always take a new call. We do not want the call to be modified cross
+    // subqueries, this would not be done by Executors.
+    auto const& call = getCall();
+    AqlCallStack stack{call};
+    // We cannot group shadowRows within a single call.
+    // So we end up with 3 results, each 1 shadowRow, no matter what the call is
+    auto [state, skipped, block] = testee->execute(stack);
+    if (doesWaiting()) {
+      // We wait between lines
+      EXPECT_EQ(state, ExecutionState::WAITING);
+      EXPECT_EQ(skipped, 0);
+      EXPECT_EQ(block, nullptr);
+      std::tie(state, skipped, block) = testee->execute(stack);
+    }
+    if (i == 2) {
+      // Only the last one is done
+      EXPECT_EQ(state, ExecutionState::DONE);
+    } else {
+      EXPECT_EQ(state, ExecutionState::HASMORE);
+    }
+    // Cannot skip a shadowRow
+    EXPECT_EQ(skipped, 0);
+    ASSERT_NE(block, nullptr);
+    ASSERT_EQ(block->size(), 1);
+    EXPECT_TRUE(block->hasShadowRows());
+    EXPECT_TRUE(block->isShadowRow(0));
+    auto rowIndex = block->getShadowRowDepth(0);
+    EXPECT_TRUE(basics::VelocyPackHelper::equal(rowIndex.slice(),
+                                                builder.slice().at(i), false))
+        << "Expected: " << builder.slice().at(i).toJson()
+        << " got: " << rowIndex.slice().toJson();
+  }
+}
+
+// Test a classical input ending in a relevant shadowRow
+TEST_P(ExecutionBlockImplExecuteIntegrationTest, input_and_relevant_shadowRow) {
+  std::deque<SharedAqlItemBlockPtr> blockDeque;
+  {
+    SharedAqlItemBlockPtr block =
+        buildBlock<0>(fakedQuery->engine()->itemBlockManager(), {{}, {}}, {{1, 0}});
+    blockDeque.push_back(std::move(block));
+  }
+  auto singleton = std::make_unique<WaitingExecutionBlockMock>(
+      fakedQuery->engine(), generateNodeDummy(), std::move(blockDeque),
+      doesWaiting() ? WaitingExecutionBlockMock::WaitingBehaviour::ALWAYS
+                    : WaitingExecutionBlockMock::WaitingBehaviour::NEVER);
+
+  auto builder = std::make_shared<VPackBuilder>();
+  {
+    builder->openArray();
+    for (size_t i = 0; i < 999; ++i) {
+      builder->add(VPackValue(i));
+    }
+    builder->close();
+  }
+
+  RegisterId outReg = 0;
+  auto producer = produceBlock(singleton.get(), builder, outReg);
+
+  CallAsserter getAsserter{getCall()};
+  SkipCallAsserter skipAsserter{getCall()};
+  auto testee = forwardBlock(getAsserter, skipAsserter, producer.get(), outReg);
+
+  auto const& call = getCall();
+  AqlCallStack stack{call};
+  if (doesWaiting()) {
+    auto const [state, skipped, block] = testee->execute(stack);
+    EXPECT_EQ(state, ExecutionState::WAITING);
+    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(block, nullptr);
+  }
+  auto const [state, skipped, block] = testee->execute(stack);
+
+  if (std::holds_alternative<size_t>(call.softLimit) && !call.hasHardLimit()) {
+    EXPECT_EQ(state, ExecutionState::HASMORE);
+    // Do not append shadowRow on softLimit
+    ValidateResult(builder, skipped, block, outReg, 0);
+  } else {
+    EXPECT_EQ(state, ExecutionState::DONE);
+    // Forward to shadowRow on hardLimit
+    ValidateResult(builder, skipped, block, outReg, 1);
+    ASSERT_TRUE(block != nullptr);
+    ValidateShadowRow(block, block->size() - 1, 0);
+  }
+}
+
+// Test a classical input ending in a relevant shadowRow and a non-relevant shadow_row
+TEST_P(ExecutionBlockImplExecuteIntegrationTest, input_and_non_relevant_shadowRow) {
+  std::deque<SharedAqlItemBlockPtr> blockDeque;
+  {
+    SharedAqlItemBlockPtr block = buildBlock<0>(fakedQuery->engine()->itemBlockManager(),
+                                                {{}, {}, {}}, {{1, 0}, {2, 1}});
+    blockDeque.push_back(std::move(block));
+  }
+  auto singleton = std::make_unique<WaitingExecutionBlockMock>(
+      fakedQuery->engine(), generateNodeDummy(), std::move(blockDeque),
+      doesWaiting() ? WaitingExecutionBlockMock::WaitingBehaviour::ALWAYS
+                    : WaitingExecutionBlockMock::WaitingBehaviour::NEVER);
+
+  auto builder = std::make_shared<VPackBuilder>();
+  {
+    builder->openArray();
+    for (size_t i = 0; i < 998; ++i) {
+      builder->add(VPackValue(i));
+    }
+    builder->close();
+  }
+
+  RegisterId outReg = 0;
+  auto producer = produceBlock(singleton.get(), builder, outReg);
+
+  CallAsserter getAsserter{getCall()};
+  SkipCallAsserter skipAsserter{getCall()};
+  auto testee = forwardBlock(getAsserter, skipAsserter, producer.get(), outReg);
+
+  auto const& call = getCall();
+  AqlCallStack stack{call};
+  if (doesWaiting()) {
+    auto const [state, skipped, block] = testee->execute(stack);
+    EXPECT_EQ(state, ExecutionState::WAITING);
+    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(block, nullptr);
+  }
+  auto const [state, skipped, block] = testee->execute(stack);
+
+  if (std::holds_alternative<size_t>(call.softLimit) && !call.hasHardLimit()) {
+    EXPECT_EQ(state, ExecutionState::HASMORE);
+    // Do not append shadowRow on softLimit
+    ValidateResult(builder, skipped, block, outReg, 0);
+  } else {
+    EXPECT_EQ(state, ExecutionState::DONE);
+    // Forward to shadowRow on hardLimit
+    ValidateResult(builder, skipped, block, outReg, 2);
+    ASSERT_TRUE(block != nullptr);
+    // Include both shadow rows
+    ValidateShadowRow(block, block->size() - 2, 0);
+    ValidateShadowRow(block, block->size() - 1, 1);
+  }
+}
+
+// Test multiple subqueries
+TEST_P(ExecutionBlockImplExecuteIntegrationTest, multiple_subqueries) {
+  std::deque<SharedAqlItemBlockPtr> blockDeque;
+  {
+    // First subquery
+    SharedAqlItemBlockPtr block = buildBlock<1>(fakedQuery->engine()->itemBlockManager(),
+                                                {{1}, {3}, {4}}, {{1, 0}, {2, 1}});
+    blockDeque.push_back(std::move(block));
+  }
+  {
+    // Second subquery
+    SharedAqlItemBlockPtr block = buildBlock<1>(fakedQuery->engine()->itemBlockManager(),
+                                                {{2}, {5}, {6}}, {{1, 0}, {2, 1}});
+    blockDeque.push_back(std::move(block));
+  }
+  auto singleton = std::make_unique<WaitingExecutionBlockMock>(
+      fakedQuery->engine(), generateNodeDummy(), std::move(blockDeque),
+      doesWaiting() ? WaitingExecutionBlockMock::WaitingBehaviour::ALWAYS
+                    : WaitingExecutionBlockMock::WaitingBehaviour::NEVER);
+  size_t dataRowCount = 250;
+  auto builder = std::make_shared<VPackBuilder>();
+  {
+    builder->openArray();
+    for (size_t i = 0; i < dataRowCount; ++i) {
+      builder->add(VPackValue(i));
+    }
+    builder->close();
+  }
+
+  RegisterId outReg = 1;
+  auto producer = produceBlock(singleton.get(), builder, outReg);
+
+  CallAsserter getAsserter{getCall()};
+  SkipCallAsserter skipAsserter{getCall()};
+  auto testee = forwardBlock(getAsserter, skipAsserter, producer.get(), outReg);
+  for (size_t subqueryRun = 1; subqueryRun < 3; ++subqueryRun) {
+    getAsserter.reset();
+    skipAsserter.reset();
+    auto subqueryData = std::make_shared<VPackBuilder>();
+    subqueryData->openArray();
+    for (size_t i = 0; i < dataRowCount; ++i) {
+      subqueryData->add(VPackValue(subqueryRun));
+    }
+    subqueryData->close();
+    auto const& call = getCall();
+    AqlCallStack stack{call};
+    if (doesWaiting()) {
+      auto const [state, skipped, block] = testee->execute(stack);
+      EXPECT_EQ(state, ExecutionState::WAITING);
+      EXPECT_EQ(skipped, 0);
+      EXPECT_EQ(block, nullptr);
+    }
+    auto const [state, skipped, block] = testee->execute(stack);
+
+    if (std::holds_alternative<size_t>(call.softLimit) && !call.hasHardLimit()) {
+      EXPECT_EQ(state, ExecutionState::HASMORE);
+      // Do not append shadowRow on softLimit
+      ValidateResult(builder, skipped, block, outReg, 0);
+      ValidateResult(subqueryData, skipped, block, 0, 0);
+      if (subqueryRun == 1) {
+        getAsserter.reset();
+        skipAsserter.reset();
+        // Now trigger fast-forward to move to next subquery
+        AqlCall forwardCall{};
+        forwardCall.hardLimit = 0;
+        forwardCall.fullCount = false;
+        AqlCallStack forwardStack{forwardCall};
+        auto const [forwardState, forwardSkipped, forwardBlock] =
+            testee->execute(forwardStack);
+        // We do not care for any data left
+        EXPECT_EQ(forwardState, ExecutionState::HASMORE);
+        EXPECT_EQ(forwardSkipped, 0);
+        // However there need to be two shadow rows
+        ASSERT_NE(forwardBlock, nullptr);
+        ASSERT_EQ(forwardBlock->size(), 2);
+        ValidateShadowRow(forwardBlock, 0, 0);
+        ValidateShadowRow(forwardBlock, 1, 1);
+      }
+
+    } else {
+      if (subqueryRun == 1) {
+        // In the first run, we actually have more after fullCount
+        EXPECT_EQ(state, ExecutionState::HASMORE);
+      } else {
+        // In the second run we do not have more after fullCount, we have returned everything
+        EXPECT_EQ(state, ExecutionState::DONE);
+      }
+
+      // Forward to shadowRow on hardLimit
+      ValidateResult(builder, skipped, block, outReg, 2);
+      ValidateResult(subqueryData, skipped, block, 0, 2);
+      ASSERT_NE(block, nullptr);
+      // Include both shadow rows
+      ValidateShadowRow(block, block->size() - 2, 0);
+      ValidateShadowRow(block, block->size() - 1, 1);
+    }
+  }
+}
+
+// Test empty subquery.
+// We cannot do a passthrough test here, as the UpstreamBlock does not
+// support shadow rows and would create errors, if an offset is forwarded to it.
+TEST_P(ExecutionBlockImplExecuteIntegrationTest, empty_subquery) {
+  std::deque<SharedAqlItemBlockPtr> blockDeque;
+  {
+    // Here we prepare the following:
+    // 1 query with 1 row + 2 ShadowRows (depth 0, depth 1)
+    // 1 query with 0 row + 1 ShadowRows (depth 0)
+    // 1 query with 0 row + 2 ShadowRow (depth 0, depth 1)
+    SharedAqlItemBlockPtr block =
+        buildBlock<1>(fakedQuery->engine()->itemBlockManager(),
+                      {{1}, {2}, {3}, {4}, {5}, {6}},
+                      {{1, 0}, {2, 1}, {3, 0}, {4, 0}, {5, 1}});
+    blockDeque.push_back(std::move(block));
+  }
+  auto singleton = std::make_unique<WaitingExecutionBlockMock>(
+      fakedQuery->engine(), generateNodeDummy(), std::move(blockDeque),
+      doesWaiting() ? WaitingExecutionBlockMock::WaitingBehaviour::ONCE
+                    : WaitingExecutionBlockMock::WaitingBehaviour::NEVER);
+
+  RegisterId outReg = 0;
+  CallAsserter getAsserter{getCall()};
+  SkipCallAsserter skipAsserter{getCall()};
+  auto testee = forwardBlock(getAsserter, skipAsserter, singleton.get(), outReg);
+
+  if (doesWaiting()) {
+    AqlCallStack stack{getCall()};
+    // we only wait exactly once, only one block upstream that is not sliced.
+    auto const& [state, skipped, block] = testee->execute(stack);
+    EXPECT_EQ(state, ExecutionState::WAITING);
+    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(block, nullptr);
+  }
+  auto call = getCall();
+  bool skip = call.getOffset() > 0 || (call.getLimit() == 0 && call.needsFullCount());
+  {
+    // First subquery
+    AqlCallStack stack{getCall()};
+    auto const& [state, skipped, block] = testee->execute(stack);
+    EXPECT_EQ(state, ExecutionState::HASMORE);
+    ASSERT_NE(block, nullptr);
+    if (skip) {
+      EXPECT_EQ(skipped, 1);
+      EXPECT_EQ(block->size(), 2);
+    } else {
+      EXPECT_EQ(skipped, 0);
+      EXPECT_EQ(block->size(), 3);
+    }
+    size_t row = 0;
+    if (!skip) {
+      ASSERT_FALSE(block->isShadowRow(row));
+      AssertValueEquals(block, row, outReg, 1);
+      row++;
+    }
+    AssertIsShadowRowOfDepth(block, row, 0);
+    AssertValueEquals(block, row, outReg, 2);
+    row++;
+    AssertIsShadowRowOfDepth(block, row, 1);
+    AssertValueEquals(block, row, outReg, 3);
+    if (skip) {
+      // first empty input, then we skip input
+      EXPECT_EQ(skipAsserter.getNumberCalls(), 2);
+      // we need to call getSome never
+      EXPECT_EQ(getAsserter.getNumberCalls(), 0);
+    } else {
+      // we do not skip
+      EXPECT_EQ(skipAsserter.getNumberCalls(), 0);
+      // first empty input, then we produce input
+      EXPECT_EQ(getAsserter.getNumberCalls(), 2);
+    }
+    getAsserter.reset();
+    skipAsserter.reset();
+  }
+
+  {
+    // Second subquery
+    AqlCallStack stack{getCall()};
+    auto const& [state, skipped, block] = testee->execute(stack);
+    EXPECT_EQ(state, ExecutionState::HASMORE);
+    ASSERT_NE(block, nullptr);
+    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(block->size(), 1);
+    size_t row = 0;
+    AssertIsShadowRowOfDepth(block, row, 0);
+    AssertValueEquals(block, row, outReg, 4);
+    if (skip) {
+      // wo do not have empty input, we can skip
+      EXPECT_EQ(skipAsserter.getNumberCalls(), 1);
+      // we need to call getSome never
+      EXPECT_EQ(getAsserter.getNumberCalls(), 0);
+    } else {
+      // we do not skip
+      EXPECT_EQ(skipAsserter.getNumberCalls(), 0);
+      // wo do not have empty input, we can produce
+      EXPECT_EQ(getAsserter.getNumberCalls(), 1);
+    }
+    getAsserter.reset();
+    skipAsserter.reset();
+  }
+
+  {
+    // Third subquery
+    AqlCallStack stack{getCall()};
+    auto const& [state, skipped, block] = testee->execute(stack);
+    EXPECT_EQ(state, ExecutionState::DONE);
+    ASSERT_NE(block, nullptr);
+    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(block->size(), 2);
+    size_t row = 0;
+    AssertIsShadowRowOfDepth(block, row, 0);
+    AssertValueEquals(block, row, outReg, 5);
+    row++;
+    AssertIsShadowRowOfDepth(block, row, 1);
+    AssertValueEquals(block, row, outReg, 6);
+    if (skip) {
+      // wo do not have empty input, we can skip
+      EXPECT_EQ(skipAsserter.getNumberCalls(), 1);
+      // we need to call getSome never
+      EXPECT_EQ(getAsserter.getNumberCalls(), 0);
+    } else {
+      // we do not skip
+      EXPECT_EQ(skipAsserter.getNumberCalls(), 0);
+      // wo do not have empty input, we can produce
+      EXPECT_EQ(getAsserter.getNumberCalls(), 1);
+    }
+
+    getAsserter.reset();
+    skipAsserter.reset();
+  }
+}
+
+// Test forward outer queries.
+// The executors should not be called if there is no relevant call on the Stack
+// Block shall be returned unmodified.
+TEST_P(ExecutionBlockImplExecuteIntegrationTest, test_outer_subquery_forwarding_passthrough) {
+  std::deque<SharedAqlItemBlockPtr> blockDeque;
+  auto builder = std::make_shared<VPackBuilder>();
+  {
+    MatrixBuilder<1> matrix;
+    matrix.reserve(250);
+    builder->openArray();
+    for (size_t i = 0; i < 250; ++i) {
+      builder->add(VPackValue(i));
+      matrix.emplace_back(RowBuilder<1>{i});
+    }
+    builder->close();
+    SharedAqlItemBlockPtr block =
+        buildBlock<1>(fakedQuery->engine()->itemBlockManager(), std::move(matrix));
+    blockDeque.push_back(std::move(block));
+  }
+
+  // Note: WaitingExecutionBlockMock does not use the ExecutionBlockImpl logic
+  // and will React to any call on the spec, if it is relevant or not.
+  auto singleton = std::make_unique<WaitingExecutionBlockMock>(
+      fakedQuery->engine(), generateNodeDummy(), std::move(blockDeque),
+      doesWaiting() ? WaitingExecutionBlockMock::WaitingBehaviour::ALWAYS
+                    : WaitingExecutionBlockMock::WaitingBehaviour::NEVER);
+
+  auto const& call = getCall();
+  AqlCallStack stack{call};
+  ASSERT_TRUE(stack.isRelevant());
+  stack.increaseSubqueryDepth();
+  EXPECT_FALSE(stack.isRelevant());
+
+  ProduceCall prodCall = generateNeverProduceCall();
+
+  ExecutionBlockImpl<LambdaExePassThrough> testee{fakedQuery->engine(),
+                                                  generateNodeDummy(),
+                                                  makeInfos(prodCall)};
+
+  testee.addDependency(singleton.get());
+
+  auto [state, skipped, block] = testee.execute(stack);
+  if (doesWaiting()) {
+    EXPECT_EQ(state, ExecutionState::WAITING);
+    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(block, nullptr);
+    std::tie(state, skipped, block) = testee.execute(stack);
+  }
+
+  if (call.getLimit() > builder->slice().length() || call.needsFullCount() ||
+      call.hasHardLimit()) {
+    // We need to consume everything
+    EXPECT_EQ(state, ExecutionState::DONE);
+  } else {
+    // We cannot consume everything.
+    EXPECT_EQ(state, ExecutionState::HASMORE);
+  }
+  ValidateResult(builder, skipped, block, 0);
+}
+
+// Test forward outer queries.
+// The executors should not be called if there is no relevant call on the Stack
+// Block shall be returned unmodified.
+TEST_P(ExecutionBlockImplExecuteIntegrationTest, test_outer_subquery_forwarding) {
+  std::deque<SharedAqlItemBlockPtr> blockDeque;
+  auto builder = std::make_shared<VPackBuilder>();
+  {
+    MatrixBuilder<1> matrix;
+    matrix.reserve(250);
+    builder->openArray();
+    for (size_t i = 0; i < 250; ++i) {
+      builder->add(VPackValue(i));
+      matrix.emplace_back(RowBuilder<1>{i});
+    }
+    builder->close();
+    SharedAqlItemBlockPtr block =
+        buildBlock<1>(fakedQuery->engine()->itemBlockManager(), std::move(matrix));
+    blockDeque.push_back(std::move(block));
+  }
+
+  // Note: WaitingExecutionBlockMock does not use the ExecutionBlockImpl logic
+  // and will React to any call on the spec, if it is relevant or not.
+  auto singleton = std::make_unique<WaitingExecutionBlockMock>(
+      fakedQuery->engine(), generateNodeDummy(), std::move(blockDeque),
+      doesWaiting() ? WaitingExecutionBlockMock::WaitingBehaviour::ALWAYS
+                    : WaitingExecutionBlockMock::WaitingBehaviour::NEVER);
+
+  auto const& call = getCall();
+  AqlCallStack stack{call};
+  ASSERT_TRUE(stack.isRelevant());
+  stack.increaseSubqueryDepth();
+  EXPECT_FALSE(stack.isRelevant());
+
+  ProduceCall prodCall = generateNeverProduceCall();
+  SkipCall skipCall = generateNeverSkipCall();
+  ExecutionBlockImpl<LambdaExe> testee{fakedQuery->engine(), generateNodeDummy(),
+                                       makeSkipInfos(prodCall, skipCall)};
+
+  testee.addDependency(singleton.get());
+
+  auto [state, skipped, block] = testee.execute(stack);
+  if (doesWaiting()) {
+    EXPECT_EQ(state, ExecutionState::WAITING);
+    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(block, nullptr);
+    std::tie(state, skipped, block) = testee.execute(stack);
+  }
+
+  if (call.getLimit() > builder->slice().length() || call.needsFullCount() ||
+      call.hasHardLimit()) {
+    // We need to consume everything
+    EXPECT_EQ(state, ExecutionState::DONE);
+  } else {
+    // We cannot consume everything.
+    EXPECT_EQ(state, ExecutionState::HASMORE);
+  }
+  ValidateResult(builder, skipped, block, 0);
+}
+
 // The numbers here are random, but all of them are below 1000 which is the default batch size
 static constexpr auto defaultCall = []() -> const AqlCall { return AqlCall{}; };
 
@@ -1532,7 +2650,7 @@ static constexpr auto skipAndSoftLimit = []() -> const AqlCall {
 static constexpr auto skipAndHardLimit = []() -> const AqlCall {
   AqlCall res{};
   res.offset = 32;
-  res.hardLimit = 71;
+  res.hardLimit = 51;
   return res;
 };
 static constexpr auto skipAndHardLimitAndFullCount = []() -> const AqlCall {
@@ -1556,12 +2674,13 @@ static constexpr auto onlySkipAndCount = []() -> const AqlCall {
   return res;
 };
 
-INSTANTIATE_TEST_CASE_P(ExecutionBlockExecuteIntegration, ExecutionBlockImplExecuteIntegrationTest,
-                        ::testing::Values(defaultCall(), skipCall(),
-                                          softLimit(), hardLimit(), fullCount(),
-                                          skipAndSoftLimit(), skipAndHardLimit(),
-                                          skipAndHardLimitAndFullCount(),
-                                          onlyFullCount(), onlySkipAndCount()));
+INSTANTIATE_TEST_CASE_P(
+    ExecutionBlockExecuteIntegration, ExecutionBlockImplExecuteIntegrationTest,
+    ::testing::Combine(::testing::Values(defaultCall(), skipCall(), softLimit(),
+                                         hardLimit(), fullCount(), skipAndSoftLimit(),
+                                         skipAndHardLimit(), skipAndHardLimitAndFullCount(),
+                                         onlyFullCount(), onlySkipAndCount()),
+                       ::testing::Bool()));
 
 }  // namespace aql
 }  // namespace tests
diff --git a/tests/Aql/TestLambdaExecutor.cpp b/tests/Aql/TestLambdaExecutor.cpp
index 4fe9c2812cc2..9f7cdb99e417 100644
--- a/tests/Aql/TestLambdaExecutor.cpp
+++ b/tests/Aql/TestLambdaExecutor.cpp
@@ -34,25 +34,30 @@ LambdaExecutorInfos::LambdaExecutorInfos(
     std::shared_ptr<std::unordered_set<RegisterId>> writeableOutputRegisters,
     RegisterId nrInputRegisters, RegisterId nrOutputRegisters,
     std::unordered_set<RegisterId> registersToClear,
-    std::unordered_set<RegisterId> registersToKeep, ProduceCall lambda)
+    std::unordered_set<RegisterId> registersToKeep, ProduceCall lambda, ResetCall reset)
     : ExecutorInfos(readableInputRegisters, writeableOutputRegisters, nrInputRegisters,
                     nrOutputRegisters, registersToClear, registersToKeep),
-      _produceLambda(lambda) {}
+      _produceLambda(lambda),
+      _resetLambda(reset) {}
 
 auto LambdaExecutorInfos::getProduceLambda() const -> ProduceCall const& {
   return _produceLambda;
 }
 
+auto LambdaExecutorInfos::reset() -> void { _resetLambda(); }
+
 LambdaSkipExecutorInfos::LambdaSkipExecutorInfos(
     std::shared_ptr<std::unordered_set<RegisterId>> readableInputRegisters,
     std::shared_ptr<std::unordered_set<RegisterId>> writeableOutputRegisters,
     RegisterId nrInputRegisters, RegisterId nrOutputRegisters,
     std::unordered_set<RegisterId> registersToClear,
-    std::unordered_set<RegisterId> registersToKeep, ProduceCall lambda, SkipCall skipLambda)
+    std::unordered_set<RegisterId> registersToKeep, ProduceCall lambda,
+    SkipCall skipLambda, ResetCall reset)
     : ExecutorInfos(readableInputRegisters, writeableOutputRegisters, nrInputRegisters,
                     nrOutputRegisters, registersToClear, registersToKeep),
       _produceLambda(lambda),
-      _skipLambda(skipLambda) {}
+      _skipLambda(skipLambda),
+      _resetLambda(reset) {}
 
 auto LambdaSkipExecutorInfos::getProduceLambda() const -> ProduceCall const& {
   return _produceLambda;
@@ -62,8 +67,11 @@ auto LambdaSkipExecutorInfos::getSkipLambda() const -> SkipCall const& {
   return _skipLambda;
 }
 
-TestLambdaExecutor::TestLambdaExecutor(Fetcher&, Infos& infos)
-    : _infos(infos) {}
+auto LambdaSkipExecutorInfos::reset() -> void { _resetLambda(); }
+
+TestLambdaExecutor::TestLambdaExecutor(Fetcher&, Infos& infos) : _infos(infos) {
+  _infos.reset();
+}
 
 TestLambdaExecutor::~TestLambdaExecutor() {}
 
@@ -85,7 +93,9 @@ auto TestLambdaExecutor::produceRows(AqlItemBlockInputRange& input, OutputAqlIte
 }
 
 TestLambdaSkipExecutor::TestLambdaSkipExecutor(Fetcher&, Infos& infos)
-    : _infos(infos) {}
+    : _infos(infos) {
+  _infos.reset();
+}
 
 TestLambdaSkipExecutor::~TestLambdaSkipExecutor() {}
 
diff --git a/tests/Aql/TestLambdaExecutor.h b/tests/Aql/TestLambdaExecutor.h
index 4905ea56f915..4ec0c995e956 100644
--- a/tests/Aql/TestLambdaExecutor.h
+++ b/tests/Aql/TestLambdaExecutor.h
@@ -52,6 +52,11 @@ using ProduceCall =
 using SkipCall =
     std::function<std::tuple<ExecutorState, size_t, AqlCall>(AqlItemBlockInputRange& input, AqlCall& call)>;
 
+/**
+ * @brief This is a shorthand for the reset state signature
+ */
+using ResetCall = std::function<void()>;
+
 /**
  * @brief Executorinfos for the lambda executors.
  *        Contains basice RegisterPlanning information, and a ProduceCall.
@@ -59,11 +64,13 @@ using SkipCall =
  */
 class LambdaExecutorInfos : public ExecutorInfos {
  public:
-  LambdaExecutorInfos(std::shared_ptr<std::unordered_set<RegisterId>> readableInputRegisters,
-                      std::shared_ptr<std::unordered_set<RegisterId>> writeableOutputRegisters,
-                      RegisterId nrInputRegisters, RegisterId nrOutputRegisters,
-                      std::unordered_set<RegisterId> registersToClear,
-                      std::unordered_set<RegisterId> registersToKeep, ProduceCall lambda);
+  LambdaExecutorInfos(
+      std::shared_ptr<std::unordered_set<RegisterId>> readableInputRegisters,
+      std::shared_ptr<std::unordered_set<RegisterId>> writeableOutputRegisters,
+      RegisterId nrInputRegisters, RegisterId nrOutputRegisters,
+      std::unordered_set<RegisterId> registersToClear,
+      std::unordered_set<RegisterId> registersToKeep, ProduceCall lambda,
+      ResetCall reset = []() -> void {});
 
   LambdaExecutorInfos() = delete;
   LambdaExecutorInfos(LambdaExecutorInfos&&) = default;
@@ -71,9 +78,11 @@ class LambdaExecutorInfos : public ExecutorInfos {
   ~LambdaExecutorInfos() = default;
 
   auto getProduceLambda() const -> ProduceCall const&;
+  auto reset() -> void;
 
  private:
   ProduceCall _produceLambda;
+  ResetCall _resetLambda;
 };
 
 /**
@@ -84,12 +93,13 @@ class LambdaExecutorInfos : public ExecutorInfos {
  */
 class LambdaSkipExecutorInfos : public ExecutorInfos {
  public:
-  LambdaSkipExecutorInfos(std::shared_ptr<std::unordered_set<RegisterId>> readableInputRegisters,
-                          std::shared_ptr<std::unordered_set<RegisterId>> writeableOutputRegisters,
-                          RegisterId nrInputRegisters, RegisterId nrOutputRegisters,
-                          std::unordered_set<RegisterId> registersToClear,
-                          std::unordered_set<RegisterId> registersToKeep,
-                          ProduceCall lambda, SkipCall skipLambda);
+  LambdaSkipExecutorInfos(
+      std::shared_ptr<std::unordered_set<RegisterId>> readableInputRegisters,
+      std::shared_ptr<std::unordered_set<RegisterId>> writeableOutputRegisters,
+      RegisterId nrInputRegisters, RegisterId nrOutputRegisters,
+      std::unordered_set<RegisterId> registersToClear,
+      std::unordered_set<RegisterId> registersToKeep, ProduceCall lambda,
+      SkipCall skipLambda, ResetCall reset = []() -> void {});
 
   LambdaSkipExecutorInfos() = delete;
   LambdaSkipExecutorInfos(LambdaSkipExecutorInfos&&) = default;
@@ -98,10 +108,12 @@ class LambdaSkipExecutorInfos : public ExecutorInfos {
 
   auto getProduceLambda() const -> ProduceCall const&;
   auto getSkipLambda() const -> SkipCall const&;
+  auto reset() -> void;
 
  private:
   ProduceCall _produceLambda;
   SkipCall _skipLambda;
+  ResetCall _resetLambda;
 };
 
 /**
diff --git a/tests/Aql/WaitingExecutionBlockMock.cpp b/tests/Aql/WaitingExecutionBlockMock.cpp
index 593efb9060a3..00e56e4a07d7 100644
--- a/tests/Aql/WaitingExecutionBlockMock.cpp
+++ b/tests/Aql/WaitingExecutionBlockMock.cpp
@@ -37,12 +37,14 @@ using namespace arangodb::tests::aql;
 
 WaitingExecutionBlockMock::WaitingExecutionBlockMock(ExecutionEngine* engine,
                                                      ExecutionNode const* node,
-                                                     std::deque<SharedAqlItemBlockPtr>&& data)
+                                                     std::deque<SharedAqlItemBlockPtr>&& data,
+                                                     WaitingBehaviour variant)
     : ExecutionBlock(engine, node),
       _data(std::move(data)),
       _resourceMonitor(),
       _inflight(0),
-      _hasWaited(false) {}
+      _hasWaited(false),
+      _variant{variant} {}
 
 std::pair<arangodb::aql::ExecutionState, arangodb::Result> WaitingExecutionBlockMock::initializeCursor(
     arangodb::aql::InputAqlItemRow const& input) {
@@ -109,8 +111,87 @@ std::pair<arangodb::aql::ExecutionState, size_t> WaitingExecutionBlockMock::skip
   }
 }
 
+// NOTE: Does not care for shadowrows!
 std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> WaitingExecutionBlockMock::execute(AqlCallStack stack) {
-  // TODO implement!
-  TRI_ASSERT(false);
-  THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
+  while (!stack.isRelevant()) {
+    stack.pop();
+  }
+  auto myCall = stack.popCall();
+  if (_variant != WaitingBehaviour::NEVER && !_hasWaited) {
+    // If we orderd waiting check on _hasWaited and wait if not
+    _hasWaited = true;
+    return {ExecutionState::WAITING, 0, nullptr};
+  }
+  if (_variant == WaitingBehaviour::ALWAYS) {
+    // If we allways wait, reset.
+    _hasWaited = false;
+  }
+  size_t skipped = 0;
+  SharedAqlItemBlockPtr result = nullptr;
+  while (!_data.empty()) {
+    if (_data.front()->size() <= _inflight) {
+      dropBlock();
+      continue;
+    }
+    TRI_ASSERT(_data.front()->size() > _inflight);
+    // Drop while skip
+    if (myCall.getOffset() > 0) {
+      size_t canSkip = (std::min)(_data.front()->size() - _inflight, myCall.getOffset());
+      _inflight += canSkip;
+      myCall.didSkip(canSkip);
+      skipped += canSkip;
+      continue;
+    } else if (myCall.getLimit() > 0) {
+      size_t canReturn = _data.front()->size() - _inflight;
+
+      if (canReturn <= myCall.getLimit()) {
+        if (result != nullptr) {
+          // Sorry we can only return one block.
+          // This means we have prepared the first block.
+          // But still need more data.
+          return {ExecutionState::HASMORE, skipped, result};
+        }
+        // We can return the remainder of this block
+        if (_inflight == 0) {
+          // use full block
+          result = std::move(_data.front());
+        } else {
+          // Slice out the last part
+          result = _data.front()->slice(_inflight, _data.front()->size());
+        }
+        dropBlock();
+      } else {
+        // Slice out limit many rows starting at _inflight
+        result = _data.front()->slice(_inflight, _inflight + myCall.getLimit());
+        // adjust _inflight to the fist non-returned row.
+        _inflight += myCall.getLimit();
+      }
+      TRI_ASSERT(result != nullptr);
+      myCall.didProduce(result->size());
+    } else if (myCall.needsFullCount()) {
+      size_t counts = _data.front()->size() - _inflight;
+      dropBlock();
+      myCall.didSkip(counts);
+      skipped += counts;
+    } else {
+      if (myCall.getLimit() == 0 && !myCall.needsFullCount() && myCall.hasHardLimit()) {
+        while (!_data.empty()) {
+          // Drop data we are in fastForward phase
+          dropBlock();
+        }
+      }
+      if (_data.empty()) {
+        return {ExecutionState::DONE, skipped, result};
+      } else {
+        return {ExecutionState::HASMORE, skipped, result};
+      }
+    }
+  }
+  return {ExecutionState::DONE, skipped, result};
+}
+
+void WaitingExecutionBlockMock::dropBlock() {
+  TRI_ASSERT(!_data.empty());
+  _data.pop_front();
+  _inflight = 0;
 }
\ No newline at end of file
diff --git a/tests/Aql/WaitingExecutionBlockMock.h b/tests/Aql/WaitingExecutionBlockMock.h
index f644b37ccc0f..3234060d7936 100644
--- a/tests/Aql/WaitingExecutionBlockMock.h
+++ b/tests/Aql/WaitingExecutionBlockMock.h
@@ -45,16 +45,27 @@ namespace aql {
  */
 class WaitingExecutionBlockMock final : public arangodb::aql::ExecutionBlock {
  public:
+  /**
+   * @brief Define how often this Block should return "WAITING"
+   */
+  enum WaitingBehaviour {
+    NEVER,  // Never return WAITING
+    ONCE,  // Return WAITING on the first execute call, afterwards return all blocks
+    ALWAYS  // Return Waiting once for every execute Call.
+  };
+
   /**
    * @brief Create a WAITING ExecutionBlockMock
    *
    * @param engine Required by API.
    * @param node Required by API.
    * @param data Must be a shared_ptr to an VPackArray.
+   * @param variant The waiting behaviour of this block (default ONCE), see WaitingBehaviour
    */
   WaitingExecutionBlockMock(arangodb::aql::ExecutionEngine* engine,
                             arangodb::aql::ExecutionNode const* node,
-                            std::deque<arangodb::aql::SharedAqlItemBlockPtr>&& data);
+                            std::deque<arangodb::aql::SharedAqlItemBlockPtr>&& data,
+                            WaitingBehaviour variant = WaitingBehaviour::ALWAYS);
 
   virtual std::pair<arangodb::aql::ExecutionState, Result> shutdown(int errorCode) override;
 
@@ -95,16 +106,19 @@ class WaitingExecutionBlockMock final : public arangodb::aql::ExecutionBlock {
    */
   std::pair<arangodb::aql::ExecutionState, size_t> skipSome(size_t atMost) override;
 
-  // TODO: Document and implement me!
   std::tuple<arangodb::aql::ExecutionState, size_t, arangodb::aql::SharedAqlItemBlockPtr> execute(
       arangodb::aql::AqlCallStack stack) override;
 
+ private:
+  void dropBlock();
+
  private:
   std::deque<arangodb::aql::SharedAqlItemBlockPtr> _data;
   arangodb::aql::ResourceMonitor _resourceMonitor;
   size_t _inflight;
   bool _returnedDone = false;
   bool _hasWaited;
+  WaitingBehaviour _variant;
 };
 }  // namespace aql
 

From 7222d3ebb4e845cad271586c5158958099df23d2 Mon Sep 17 00:00:00 2001
From: Lars Maier <lars@arangodb.com>
Date: Fri, 31 Jan 2020 09:48:21 +0100
Subject: [PATCH 057/122] Feature/aql subquery execution block impl execute
 implementation sorted collect (#11020)

* SortedCollect executor and some tests.

* More tests.

* More const and skip implemented.

* Fixed some bugs found by tests.

* Refactored skip.

* Broken state with test framework.

* Extracted testing framework into separate file and adjusted it to use WaitingBlockMock. However it is not yet fully implemented

* Added another SortedExecutor test without fullcount. This passes. Also assert on skip and State

* Removed obsolete assertion in skip, added another nonFullcount test.

* More tests. Fixed some bugs in the test framework.

* More cleanup.

* Remove version control marker.

* Removed wrong assertion.

* Apply suggestions from code review

Co-Authored-By: Michael Hackstein <michael@arangodb.com>

* Remove dead code.

* Removed fetcher.

Co-authored-by: Michael Hackstein <michael@arangodb.com>
---
 arangod/Aql/AqlCall.h                   |   13 +-
 arangod/Aql/AqlItemBlockInputRange.cpp  |    2 +-
 arangod/Aql/ExecutionBlockImpl.cpp      |   57 +-
 arangod/Aql/ExecutionBlockImpl.h        |    2 +-
 arangod/Aql/OutputAqlItemRow.cpp        |   17 +-
 arangod/Aql/OutputAqlItemRow.h          |    2 +-
 arangod/Aql/SortedCollectExecutor.cpp   |  231 +++--
 arangod/Aql/SortedCollectExecutor.h     |   33 +-
 tests/Aql/ExecutorTestHelper.h          |  190 ++++
 tests/Aql/SortedCollectExecutorTest.cpp | 1151 +++++++++++++++--------
 10 files changed, 1171 insertions(+), 527 deletions(-)

diff --git a/arangod/Aql/AqlCall.h b/arangod/Aql/AqlCall.h
index 231c11402141..72acbb351c85 100644
--- a/arangod/Aql/AqlCall.h
+++ b/arangod/Aql/AqlCall.h
@@ -70,6 +70,7 @@ struct AqlCall {
   Limit softLimit{Infinity{}};
   Limit hardLimit{Infinity{}};
   bool fullCount{false};
+  std::size_t skippedRows{0};
 
   std::size_t getOffset() const { return offset; }
 
@@ -89,9 +90,8 @@ struct AqlCall {
     return limit;
   }
 
-  void didSkip(std::size_t n) {
+  void didSkip(std::size_t n) noexcept {
     if (n <= offset) {
-      // TRI_ASSERT(n <= offset);
       offset -= n;
     } else {
       TRI_ASSERT(fullCount);
@@ -99,6 +99,15 @@ struct AqlCall {
       // in a single call here.
       offset = 0;
     }
+    skippedRows += n;
+  }
+
+  [[nodiscard]] std::size_t getSkipCount() const noexcept {
+    return skippedRows;
+  }
+
+  [[nodiscard]] bool needSkipMore() const noexcept {
+    return (0 < getOffset()) || (getLimit() == 0 && needsFullCount());
   }
 
   void didProduce(std::size_t n) {
diff --git a/arangod/Aql/AqlItemBlockInputRange.cpp b/arangod/Aql/AqlItemBlockInputRange.cpp
index f8e9cef032b6..fa171c5a7243 100644
--- a/arangod/Aql/AqlItemBlockInputRange.cpp
+++ b/arangod/Aql/AqlItemBlockInputRange.cpp
@@ -133,7 +133,7 @@ ExecutorState AqlItemBlockInputRange::nextState() const noexcept {
     }
     return ExecutorState::DONE;
   } else {
-    TRI_ASSERT(RowType::SHADOW == type);
+    static_assert(RowType::SHADOW == type);
     // We Return HASMORE, if the next shadow row is NOT relevant.
     // So we can directly fetch the next shadow row without informing
     // the executor about an empty subquery.
diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index b8e170e6c649..a624a575029d 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -133,11 +133,6 @@ CREATE_HAS_MEMBER_CHECK(fetchBlockForPassthrough, hasFetchBlockForPassthrough);
 CREATE_HAS_MEMBER_CHECK(expectedNumberOfRows, hasExpectedNumberOfRows);
 CREATE_HAS_MEMBER_CHECK(skipRowsRange, hasSkipRowsRange);
 
-/*
- * Determine whether we execute new style or old style skips, i.e. pre or post shadow row introduction
- * TODO: This should be removed once all executors and fetchers are ported to the new style.
- */
-
 #ifdef ARANGODB_USE_GOOGLE_TESTS
 // Forward declaration of Test Executors.
 // only used as long as isNewStyleExecutor is required.
@@ -150,21 +145,26 @@ class TestLambdaSkipExecutor;
 }  // namespace arangodb
 #endif
 
-template <class Executor>
-static bool constexpr isNewStyleExecutor() {
-  return
+template <typename T, typename... Es>
+constexpr bool is_one_of_v = (std::is_same_v<T, Es> || ...);
+
+/*
+ * Determine whether we execute new style or old style skips, i.e. pre or post shadow row introduction
+ * TODO: This should be removed once all executors and fetchers are ported to the new style.
+ */
+
+template <typename Executor>
+constexpr bool isNewStyleExecutor =
+    is_one_of_v<Executor, FilterExecutor, SortedCollectExecutor,
 #ifdef ARANGODB_USE_GOOGLE_TESTS
-      std::is_same_v<Executor, TestLambdaExecutor> ||
-      std::is_same_v<Executor, TestLambdaSkipExecutor> ||
+                TestLambdaExecutor, TestLambdaSkipExecutor,  // we need one after these to avoid compile errors in non-test mode
 #endif
-      std::is_same_v<Executor, FilterExecutor> ||
-      std::is_same_v<Executor, ShortestPathExecutor>;
-}
+                ShortestPathExecutor>;
 
 template <class Executor>
 ExecutionBlockImpl<Executor>::ExecutionBlockImpl(ExecutionEngine* engine,
                                                  ExecutionNode const* node,
-                                                 typename Executor::Infos&& infos)
+                                                 typename Executor::Infos infos)
     : ExecutionBlock(engine, node),
       _dependencyProxy(_dependencies, engine->itemBlockManager(),
                        infos.getInputRegisters(),
@@ -191,7 +191,7 @@ ExecutionBlockImpl<Executor>::~ExecutionBlockImpl() = default;
 
 template <class Executor>
 std::pair<ExecutionState, SharedAqlItemBlockPtr> ExecutionBlockImpl<Executor>::getSome(size_t atMost) {
-  if constexpr (isNewStyleExecutor<Executor>()) {
+  if constexpr (isNewStyleExecutor<Executor>) {
     AqlCallStack stack{AqlCall::SimulateGetSome(atMost)};
     auto const [state, skipped, block] = execute(stack);
     return {state, block};
@@ -355,13 +355,12 @@ std::unique_ptr<OutputAqlItemRow> ExecutionBlockImpl<Executor>::createOutputRow(
   if /* constexpr */ (Executor::Properties::allowsBlockPassthrough == BlockPassthrough::Enable) {
     return std::make_unique<OutputAqlItemRow>(newBlock, infos().getOutputRegisters(),
                                               infos().registersToKeep(),
-                                              infos().registersToClear(), std::move(call),
+                                              infos().registersToClear(), call,
                                               OutputAqlItemRow::CopyRowBehavior::DoNotCopyInputRows);
   } else {
     return std::make_unique<OutputAqlItemRow>(newBlock, infos().getOutputRegisters(),
                                               infos().registersToKeep(),
-                                              infos().registersToClear(),
-                                              std::move(call));
+                                              infos().registersToClear(), call);
   }
 }
 
@@ -489,7 +488,7 @@ static SkipVariants constexpr skipType() {
 
 template <class Executor>
 std::pair<ExecutionState, size_t> ExecutionBlockImpl<Executor>::skipSome(size_t const atMost) {
-  if constexpr (isNewStyleExecutor<Executor>()) {
+  if constexpr (isNewStyleExecutor<Executor>) {
     AqlCallStack stack{AqlCall::SimulateSkipSome(atMost)};
     auto const [state, skipped, block] = execute(stack);
 
@@ -625,7 +624,7 @@ template <class Executor>
 std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> ExecutionBlockImpl<Executor>::execute(AqlCallStack stack) {
   // TODO remove this IF
   // These are new style executors
-  if constexpr (isNewStyleExecutor<Executor>()) {
+  if constexpr (isNewStyleExecutor<Executor>) {
     // Only this executor is fully implemented
     traceExecuteBegin(stack);
     auto res = executeWithoutTrace(stack);
@@ -982,7 +981,7 @@ struct RequestWrappedBlock<RequestWrappedBlockVariant::INPUTRESTRICTED> {
 template <class Executor>
 std::pair<ExecutionState, SharedAqlItemBlockPtr> ExecutionBlockImpl<Executor>::requestWrappedBlock(
     size_t nrItems, RegisterCount nrRegs) {
-  if constexpr (!isNewStyleExecutor<Executor>()) {
+  if constexpr (!isNewStyleExecutor<Executor>) {
     static_assert(Executor::Properties::allowsBlockPassthrough == BlockPassthrough::Disable ||
                       !Executor::Properties::inputSizeRestrictsOutputSize,
                   "At most one of Properties::allowsBlockPassthrough or "
@@ -1113,20 +1112,19 @@ static SkipRowsRangeVariant constexpr skipRowsType() {
   // ConstFetcher and SingleRowFetcher<BlockPassthrough::Enable> can skip, but
   // it may not be done for modification subqueries.
   static_assert(useFetcher ==
-                    (std::is_same<typename Executor::Fetcher, ConstFetcher>::value ||
-                     (std::is_same<typename Executor::Fetcher, SingleRowFetcher<BlockPassthrough::Enable>>::value &&
+                    (std::is_same_v<typename Executor::Fetcher, ConstFetcher> ||
+                     (std::is_same_v<typename Executor::Fetcher, SingleRowFetcher<BlockPassthrough::Enable>> &&
                       !std::is_same<Executor, SubqueryExecutor<true>>::value)),
                 "Unexpected fetcher for SkipVariants::FETCHER");
 
   static_assert(!useFetcher || hasSkipRows<typename Executor::Fetcher>::value,
                 "Fetcher is chosen for skipping, but has not skipRows method!");
 
-  static_assert(useExecutor == (
+  static_assert(useExecutor == (is_one_of_v<Executor, FilterExecutor, ShortestPathExecutor,
 #ifdef ARANGODB_USE_GOOGLE_TESTS
-                                   (std::is_same_v<Executor, TestLambdaSkipExecutor>) ||
+                                            TestLambdaSkipExecutor,
 #endif
-                                   std::is_same_v<Executor, FilterExecutor> ||
-                                   std::is_same_v<Executor, ShortestPathExecutor>),
+                                            SortedCollectExecutor>),
                 "Unexpected executor for SkipVariants::EXECUTOR");
 
   // The LimitExecutor will not work correctly with SkipVariants::FETCHER!
@@ -1151,7 +1149,8 @@ struct dependent_false : std::false_type {};
 template <class Executor>
 std::tuple<ExecutorState, size_t, AqlCall> ExecutionBlockImpl<Executor>::executeSkipRowsRange(
     AqlItemBlockInputRange& inputRange, AqlCall& call) {
-  if constexpr (isNewStyleExecutor<Executor>()) {
+  if constexpr (isNewStyleExecutor<Executor>) {
+    call.skippedRows = 0;
     if constexpr (skipRowsType<Executor>() == SkipRowsRangeVariant::EXECUTOR) {
       // If the executor has a method skipRowsRange, to skip outputs.
       // Every non-passthrough executor needs to implement this.
@@ -1222,7 +1221,7 @@ std::tuple<ExecutorState, size_t, AqlCall> ExecutionBlockImpl<Executor>::execute
 template <class Executor>
 std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr>
 ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
-  if constexpr (isNewStyleExecutor<Executor>()) {
+  if constexpr (isNewStyleExecutor<Executor>) {
     if (!stack.isRelevant()) {
       // We are bypassing subqueries.
       // This executor is not allowed to perform actions
diff --git a/arangod/Aql/ExecutionBlockImpl.h b/arangod/Aql/ExecutionBlockImpl.h
index 16169b212d06..5044e8f279b9 100644
--- a/arangod/Aql/ExecutionBlockImpl.h
+++ b/arangod/Aql/ExecutionBlockImpl.h
@@ -142,7 +142,7 @@ class ExecutionBlockImpl final : public ExecutionBlock {
    * @param node The Node used to create this ExecutionBlock
    */
   ExecutionBlockImpl(ExecutionEngine* engine, ExecutionNode const* node,
-                     typename Executor::Infos&&);
+                     typename Executor::Infos);
 
   ~ExecutionBlockImpl() override;
 
diff --git a/arangod/Aql/OutputAqlItemRow.cpp b/arangod/Aql/OutputAqlItemRow.cpp
index a94ab5f72ee4..330948f49a80 100644
--- a/arangod/Aql/OutputAqlItemRow.cpp
+++ b/arangod/Aql/OutputAqlItemRow.cpp
@@ -50,14 +50,14 @@ OutputAqlItemRow::OutputAqlItemRow(
     std::shared_ptr<std::unordered_set<RegisterId> const> outputRegisters,
     std::shared_ptr<std::unordered_set<RegisterId> const> registersToKeep,
     std::shared_ptr<std::unordered_set<RegisterId> const> registersToClear,
-    AqlCall&& clientCall, CopyRowBehavior copyRowBehavior)
+    AqlCall clientCall, CopyRowBehavior copyRowBehavior)
     : _block(std::move(block)),
       _baseIndex(0),
       _lastBaseIndex(0),
       _inputRowCopied(false),
       _lastSourceRow{CreateInvalidInputRowHint{}},
       _numValuesWritten(0),
-      _call(std::move(clientCall)),
+      _call(clientCall),
       _doNotCopyInputRow(copyRowBehavior == CopyRowBehavior::DoNotCopyInputRows),
       _outputRegisters(std::move(outputRegisters)),
       _registersToKeep(std::move(registersToKeep)),
@@ -66,6 +66,19 @@ OutputAqlItemRow::OutputAqlItemRow(
       _setBaseIndexNotUsed(true),
 #endif
       _allowSourceRowUninitialized(false) {
+#ifdef ARANGODB_ENABLE_MAINTAINER_MODE
+  if (_block != nullptr) {
+    for (auto const& reg : *_outputRegisters) {
+      TRI_ASSERT(reg < _block->getNrRegs());
+    }
+    for (auto const& reg : *_registersToKeep) {
+      TRI_ASSERT(reg < _block->getNrRegs());
+    }
+    for (auto const& reg : *_registersToClear) {
+      TRI_ASSERT(reg < _block->getNrRegs());
+    }
+  }
+#endif
 }
 
 bool OutputAqlItemRow::isInitialized() const noexcept {
diff --git a/arangod/Aql/OutputAqlItemRow.h b/arangod/Aql/OutputAqlItemRow.h
index 74173815ac32..29b9e26017bf 100644
--- a/arangod/Aql/OutputAqlItemRow.h
+++ b/arangod/Aql/OutputAqlItemRow.h
@@ -55,7 +55,7 @@ class OutputAqlItemRow {
                             std::shared_ptr<std::unordered_set<RegisterId> const> outputRegisters,
                             std::shared_ptr<std::unordered_set<RegisterId> const> registersToKeep,
                             std::shared_ptr<std::unordered_set<RegisterId> const> registersToClear,
-                            AqlCall&& clientCall = AqlCall{},
+                            AqlCall clientCall = AqlCall{},
                             CopyRowBehavior = CopyRowBehavior::CopyInputRows);
 
   ~OutputAqlItemRow() = default;
diff --git a/arangod/Aql/SortedCollectExecutor.cpp b/arangod/Aql/SortedCollectExecutor.cpp
index 341023815cf0..3967bf6d2faa 100644
--- a/arangod/Aql/SortedCollectExecutor.cpp
+++ b/arangod/Aql/SortedCollectExecutor.cpp
@@ -17,6 +17,7 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
+/// @author Lars Maier
 /// @author Tobias Goedderz
 /// @author Michael Hackstein
 /// @author Heiko Kernbach
@@ -35,8 +36,13 @@
 #include <velocypack/Buffer.h>
 #include <velocypack/velocypack-aliases.h>
 
+#include <Logger/LogMacros.h>
 #include <utility>
 
+// Set this to true to activate devel logging
+#define LOG_DEVEL_SORTED_COLLECT_ENABLED false
+#define LOG_DEVEL_SC LOG_DEVEL_IF(LOG_DEVEL_SORTED_COLLECT_ENABLED)
+
 using namespace arangodb;
 using namespace arangodb::aql;
 
@@ -79,7 +85,7 @@ void SortedCollectExecutor::CollectGroup::initialize(size_t capacity) {
   }
 }
 
-void SortedCollectExecutor::CollectGroup::reset(InputAqlItemRow& input) {
+void SortedCollectExecutor::CollectGroup::reset(InputAqlItemRow const& input) {
   _shouldDeleteBuilderBuffer = true;
   ConditionalDeleter<VPackBuffer<uint8_t>> deleter(_shouldDeleteBuilderBuffer);
   std::shared_ptr<VPackBuffer<uint8_t>> buffer(new VPackBuffer<uint8_t>, deleter);
@@ -143,11 +149,9 @@ SortedCollectExecutorInfos::SortedCollectExecutorInfos(
       _count(count),
       _trxPtr(trxPtr) {}
 
-SortedCollectExecutor::SortedCollectExecutor(Fetcher& fetcher, Infos& infos)
+SortedCollectExecutor::SortedCollectExecutor(Fetcher&, Infos& infos)
     : _infos(infos),
-      _fetcher(fetcher),
-      _currentGroup(infos.getCount(), infos),
-      _fetcherDone(false) {
+      _currentGroup(infos.getCount(), infos) {
   // reserve space for the current row
   _currentGroup.initialize(_infos.getGroupRegisters().size());
   // reset and recreate new group
@@ -156,7 +160,7 @@ SortedCollectExecutor::SortedCollectExecutor(Fetcher& fetcher, Infos& infos)
   _currentGroup.reset(emptyInput);
 };
 
-void SortedCollectExecutor::CollectGroup::addLine(InputAqlItemRow& input) {
+void SortedCollectExecutor::CollectGroup::addLine(InputAqlItemRow const& input) {
   // remember the last valid row we had
   _lastInputRow = input;
 
@@ -203,7 +207,7 @@ void SortedCollectExecutor::CollectGroup::addLine(InputAqlItemRow& input) {
   }
 }
 
-bool SortedCollectExecutor::CollectGroup::isSameGroup(InputAqlItemRow& input) {
+bool SortedCollectExecutor::CollectGroup::isSameGroup(InputAqlItemRow const& input) const {
   // if we do not have valid input, return false
   if (!input.isInitialized()) {
     return false;
@@ -239,7 +243,7 @@ void SortedCollectExecutor::CollectGroup::groupValuesToArray(VPackBuilder& build
 }
 
 void SortedCollectExecutor::CollectGroup::writeToOutput(OutputAqlItemRow& output,
-                                                        InputAqlItemRow& input) {
+                                                        InputAqlItemRow const& input) {
   // Thanks to the edge case that we have to emit a row even if we have no
   // input We cannot assert here that the input row is valid ;(
 
@@ -284,27 +288,55 @@ void SortedCollectExecutor::CollectGroup::writeToOutput(OutputAqlItemRow& output
       output.moveValueInto(infos.getCollectRegister(), _lastInputRow, guard);
     }
   }
+
+  output.advanceRow();
 }
 
 std::pair<ExecutionState, NoStats> SortedCollectExecutor::produceRows(OutputAqlItemRow& output) {
+  THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
+}
+
+std::pair<ExecutionState, size_t> SortedCollectExecutor::expectedNumberOfRows(size_t atMost) const {
+  THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
+}
+
+auto SortedCollectExecutor::produceRows(AqlItemBlockInputRange& inputRange,
+                                        OutputAqlItemRow& output)
+    -> std::tuple<ExecutorState, Stats, AqlCall> {
   TRI_IF_FAILURE("SortedCollectExecutor::produceRows") {
     THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
   }
 
-  ExecutionState state;
-  InputAqlItemRow input{CreateInvalidInputRowHint{}};
+  AqlCall clientCall = output.getClientCall();
+  TRI_ASSERT(clientCall.offset == 0);
 
-  while (true) {
-    if (_fetcherDone) {
-      if (_currentGroup.isValid()) {
-        _currentGroup.writeToOutput(output, input);
-        InputAqlItemRow input{CreateInvalidInputRowHint{}};
-        _currentGroup.reset(input);
-        TRI_ASSERT(!_currentGroup.isValid());
-        return {ExecutionState::DONE, {}};
+  size_t rowsProduces = 0;
+  bool pendingGroup = false;
+
+  while (!output.isFull()) {
+    auto [state, input] = inputRange.peekDataRow();
+
+    LOG_DEVEL_SC << "SortedCollectExecutor::produceRows " << state << " "
+                 << input.isInitialized();
+
+    if (state == ExecutorState::DONE && !(_haveSeenData || input.isInitialized())) {
+      // we have never been called with data
+      LOG_DEVEL_SC << "never called with data";
+      if (_infos.getGroupRegisters().empty()) {
+        // by definition we need to emit one collect row
+        _currentGroup.writeToOutput(output, InputAqlItemRow{CreateInvalidInputRowHint{}});
+        rowsProduces += 1;
       }
-      return {ExecutionState::DONE, {}};
+      break;
     }
+
+    // either state != DONE or we have an input row
+    TRI_ASSERT(state == ExecutorState::HASMORE || state == ExecutorState::DONE);
+    if (!input.isInitialized() && state != ExecutorState::DONE) {
+      LOG_DEVEL_SC << "need more input rows";
+      break;
+    }
+
     TRI_IF_FAILURE("SortedCollectBlock::getOrSkipSomeOuter") {
       THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
     }
@@ -313,73 +345,128 @@ std::pair<ExecutionState, NoStats> SortedCollectExecutor::produceRows(OutputAqlI
       THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
     }
 
-    std::tie(state, input) = _fetcher.fetchRow();
+    if (input.isInitialized()) {
+      _haveSeenData = true;
 
-    if (state == ExecutionState::WAITING) {
-      return {state, {}};
-    }
-
-    if (state == ExecutionState::DONE) {
-      _fetcherDone = true;
-    }
-
-    // if we are in the same group, we need to add lines to the current group
-    if (_currentGroup.isSameGroup(input)) {
-      _currentGroup.addLine(input);
+      // if we are in the same group, we need to add lines to the current group
+      if (_currentGroup.isSameGroup(input)) {
+        LOG_DEVEL_SC << "input is same group";
+        _currentGroup.addLine(input);
 
-      if (state == ExecutionState::DONE) {
-        TRI_ASSERT(!output.produced());
-        _currentGroup.writeToOutput(output, input);
-        // Invalidate group
-        input = InputAqlItemRow{CreateInvalidInputRowHint{}};
-        _currentGroup.reset(input);
-        return {ExecutionState::DONE, {}};
-      }
-    } else {
-      if (_currentGroup.isValid()) {
+      } else if (_currentGroup.isValid()) {
+        LOG_DEVEL_SC << "input is new group, writing old group";
         // Write the current group.
         // Start a new group from input
+        rowsProduces += 1;
         _currentGroup.writeToOutput(output, input);
-        TRI_ASSERT(output.produced());
-        _currentGroup.reset(input);  // reset and recreate new group
-        if (input.isInitialized()) {
-          return {ExecutionState::HASMORE, {}};
+
+        if (output.isFull()) {
+          LOG_DEVEL_SC << "now output is full, exit early";
+          pendingGroup = true;
+          _currentGroup.reset(InputAqlItemRow{CreateInvalidInputRowHint{}});
+          break;
         }
-        TRI_ASSERT(state == ExecutionState::DONE);
-        return {ExecutionState::DONE, {}};
+        _currentGroup.reset(input);  // reset and recreate new group
+
       } else {
-        if (!input.isInitialized()) {
-          if (_infos.getGroupRegisters().empty()) {
-            // we got exactly 0 rows as input.
-            // by definition we need to emit one collect row
-            _currentGroup.writeToOutput(output, input);
-            TRI_ASSERT(output.produced());
-          }
-          TRI_ASSERT(state == ExecutionState::DONE);
-          return {ExecutionState::DONE, {}};
-        }
+        LOG_DEVEL_SC << "generating new group";
         // old group was not valid, do not write it
         _currentGroup.reset(input);  // reset and recreate new group
       }
     }
+
+    inputRange.nextDataRow();
+
+    bool produceMore = !output.isFull();
+    if (!produceMore) {
+      pendingGroup = true;
+      break;
+    }
+
+    if (state == ExecutorState::DONE) {
+      rowsProduces += 1;
+      _currentGroup.writeToOutput(output, input);
+      _currentGroup.reset(InputAqlItemRow{CreateInvalidInputRowHint{}});
+      break;
+    }
   }
+
+  auto newState = pendingGroup ? ExecutorState::HASMORE : inputRange.upstreamState();
+
+  LOG_DEVEL_SC << "reporting state: " << newState;
+  return {newState, Stats{}, AqlCall{}};
 }
 
-std::pair<ExecutionState, size_t> SortedCollectExecutor::expectedNumberOfRows(size_t atMost) const {
-  if (!_fetcherDone) {
-    ExecutionState state;
-    size_t expectedRows;
-    std::tie(state, expectedRows) = _fetcher.preFetchNumberOfRows(atMost);
-    if (state == ExecutionState::WAITING) {
-      TRI_ASSERT(expectedRows == 0);
-      return {state, 0};
-    }
-    return {ExecutionState::HASMORE, expectedRows + 1};
+auto SortedCollectExecutor::skipRowsRange(AqlItemBlockInputRange& inputRange, AqlCall& clientCall)
+    -> std::tuple<ExecutorState, size_t, AqlCall> {
+  TRI_IF_FAILURE("SortedCollectExecutor::skipRowsRange") {
+    THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
   }
-  // The fetcher will NOT send anything any more
-  // We will at most return the current oepn group
-  if (_currentGroup.isValid()) {
-    return {ExecutionState::HASMORE, 1};
+
+  TRI_ASSERT(clientCall.needSkipMore());
+  while (clientCall.needSkipMore()) {
+    LOG_DEVEL_SC << "clientCall.getSkipCount() == " << clientCall.getSkipCount();
+    LOG_DEVEL_SC << "clientCall.needSkipMore() == " << clientCall.needSkipMore();
+
+    {
+      auto [state, input] = inputRange.peekDataRow();
+
+      LOG_DEVEL_SC << "SortedCollectExecutor::skipRowsRange " << state << " "
+                   << std::boolalpha << input.isInitialized();
+
+      if (input.isInitialized()) {
+        // we received data
+        _haveSeenData = true;
+
+        // if we are in the same group, we can skip this line
+        if (_currentGroup.isSameGroup(input)) {
+          LOG_DEVEL_SC << "input is same group";
+          std::ignore = inputRange.nextDataRow();
+          /* do nothing */
+        } else {
+          if (_currentGroup.isValid()) {
+            LOG_DEVEL_SC << "input is new group, skipping current group";
+            // The current group is completed, skip it and create a new one
+            clientCall.didSkip(1);
+            _currentGroup.reset(InputAqlItemRow{CreateInvalidInputRowHint{}});
+            continue;
+          }
+
+          LOG_DEVEL_SC << "group is invalid, creating new group";
+          _currentGroup.reset(input);
+          std::ignore = inputRange.nextDataRow();
+        }
+      }
+
+      if (!clientCall.needSkipMore()) {
+        LOG_DEVEL_SC << "stop skipping early, there could be a pending group";
+        break;
+      }
+
+      if (state == ExecutorState::DONE) {
+        if (!_haveSeenData) {
+          // we have never been called with data
+          LOG_DEVEL_SC << "never called with data";
+          if (_infos.getGroupRegisters().empty()) {
+            // by definition we need to emit one collect row
+            clientCall.didSkip(1);
+          }
+        } else {
+          LOG_DEVEL_SC << "skipping final group";
+          clientCall.didSkip(1);
+          _currentGroup.reset(InputAqlItemRow{CreateInvalidInputRowHint{}});
+        }
+        break;
+      } else if (!input.isInitialized()) {
+        TRI_ASSERT(state == ExecutorState::HASMORE);
+        LOG_DEVEL_SC << "waiting for more data to skip";
+        break;
+      }
+    }
   }
-  return {ExecutionState::DONE, 0};
+
+  LOG_DEVEL_SC << " skipped rows: " << clientCall.getSkipCount();
+  LOG_DEVEL_SC << "reporting state: " << inputRange.upstreamState();
+
+  return {inputRange.upstreamState(), clientCall.getSkipCount(), AqlCall{}};
 }
diff --git a/arangod/Aql/SortedCollectExecutor.h b/arangod/Aql/SortedCollectExecutor.h
index 0c0ff60f2c0b..94eaa59a38d6 100644
--- a/arangod/Aql/SortedCollectExecutor.h
+++ b/arangod/Aql/SortedCollectExecutor.h
@@ -153,14 +153,14 @@ class SortedCollectExecutor {
     ~CollectGroup();
 
     void initialize(size_t capacity);
-    void reset(InputAqlItemRow& input);
+    void reset(InputAqlItemRow const& input);
 
     bool isValid() const { return _lastInputRow.isInitialized(); }
 
-    void addLine(InputAqlItemRow& input);
-    bool isSameGroup(InputAqlItemRow& input);
+    void addLine(InputAqlItemRow const& input);
+    bool isSameGroup(InputAqlItemRow const& input) const;
     void groupValuesToArray(velocypack::Builder& builder);
-    void writeToOutput(OutputAqlItemRow& output, InputAqlItemRow& input);
+    void writeToOutput(OutputAqlItemRow& output, InputAqlItemRow const& input);
   };
 
  public:
@@ -183,14 +183,31 @@ class SortedCollectExecutor {
    *
    * @return ExecutionState, and if successful exactly one new Row of AqlItems.
    */
-  std::pair<ExecutionState, Stats> produceRows(OutputAqlItemRow& output);
+  auto produceRows(OutputAqlItemRow& output) -> std::pair<ExecutionState, Stats>;
+
+  /**
+   * @brief produce the next Rows of Aql Values.
+   *
+   * @return ExecutorState, the stats, and a new Call that needs to be send to upstream
+   */
+  [[nodiscard]] auto produceRows(AqlItemBlockInputRange& input, OutputAqlItemRow& output)
+      -> std::tuple<ExecutorState, Stats, AqlCall>;
+
+  /**
+   * @brief skip the next Row of Aql Values.
+   *
+   * @return ExecutorState, the stats, and a new Call that needs to be send to upstream
+   */
+  [[nodiscard]] std::tuple<ExecutorState, size_t, AqlCall> skipRowsRange(
+      AqlItemBlockInputRange& inputRange, AqlCall& call);
 
   /**
    * This executor has no chance to estimate how many rows
    * it will produce exactly. It can however only
    * overestimate never underestimate.
    */
-  std::pair<ExecutionState, size_t> expectedNumberOfRows(size_t atMost) const;
+  [[nodiscard]] auto expectedNumberOfRows(size_t atMost) const
+      -> std::pair<ExecutionState, size_t>;
 
  private:
   Infos const& infos() const noexcept { return _infos; };
@@ -198,12 +215,10 @@ class SortedCollectExecutor {
  private:
   Infos const& _infos;
 
-  Fetcher& _fetcher;
-
   /// @brief details about the current group
   CollectGroup _currentGroup;
 
-  bool _fetcherDone;  // Flag if fetcher is done
+  bool _haveSeenData = false;
 };
 
 }  // namespace aql
diff --git a/tests/Aql/ExecutorTestHelper.h b/tests/Aql/ExecutorTestHelper.h
index 3e6a05ec141e..f90e3d7bf98d 100644
--- a/tests/Aql/ExecutorTestHelper.h
+++ b/tests/Aql/ExecutorTestHelper.h
@@ -25,10 +25,17 @@
 
 #include "gtest/gtest.h"
 
+#include "AqlItemBlockHelper.h"
+#include "WaitingExecutionBlockMock.h"
+
+#include "Aql/AqlCall.h"
+#include "Aql/AqlCallStack.h"
 #include "Aql/ExecutionBlock.h"
+#include "Aql/ExecutionBlockImpl.h"
 #include "Aql/ExecutionState.h"
 #include "Aql/ExecutionStats.h"
 #include "Aql/OutputAqlItemRow.h"
+#include "Aql/Query.h"
 #include "Aql/SharedAqlItemBlockPtr.h"
 
 #include <tuple>
@@ -37,6 +44,189 @@ namespace arangodb {
 namespace tests {
 namespace aql {
 
+template <typename E, std::size_t inputColumns = 1, std::size_t outputColumns = 1>
+struct ExecutorTestHelper {
+  using SplitType = std::variant<std::vector<std::size_t>, std::size_t, std::monostate>;
+
+  ExecutorTestHelper(ExecutorTestHelper const&) = delete;
+  ExecutorTestHelper(ExecutorTestHelper&&) = delete;
+  explicit ExecutorTestHelper(arangodb::aql::Query& query)
+      : _expectedSkip{0},
+        _expectedState{ExecutionState::HASMORE},
+        _query(query),
+        _dummyNode{std::make_unique<SingletonNode>(_query.plan(), 42)} {}
+
+  auto setCall(AqlCall c) -> ExecutorTestHelper& {
+    _call = c;
+    return *this;
+  }
+
+  auto setInputValue(MatrixBuilder<inputColumns> in) -> ExecutorTestHelper& {
+    _input = std::move(in);
+    return *this;
+  }
+
+  template <typename... Ts>
+  auto setInputValueList(Ts&&... ts) -> ExecutorTestHelper& {
+    _input = MatrixBuilder<inputColumns>{{ts}...};
+    return *this;
+  }
+
+  auto setInputSplit(std::vector<std::size_t> const& list) -> ExecutorTestHelper& {
+    _inputSplit = list;
+    return *this;
+  }
+
+  auto setInputSplitStep(std::size_t step) -> ExecutorTestHelper& {
+    _inputSplit = step;
+    return *this;
+  }
+
+  auto setInputSplitType(SplitType split) -> ExecutorTestHelper& {
+    _inputSplit = split;
+    return *this;
+  }
+
+  template <typename T>
+  auto setOutputSplit(T&& list) -> ExecutorTestHelper& {
+    ASSERT_FALSE(true);
+    _outputSplit = std::forward<T>(list);
+    return *this;
+  }
+
+  auto expectOutput(std::array<std::size_t, outputColumns> const& regs,
+                    MatrixBuilder<outputColumns> const& out) -> ExecutorTestHelper& {
+    _outputRegisters = regs;
+    _output = out;
+    return *this;
+  }
+
+  template <typename... Ts>
+  auto expectOutputValueList(Ts&&... ts) -> ExecutorTestHelper& {
+    static_assert(outputColumns == 1);
+    _outputRegisters[0] = 1;
+    _output = MatrixBuilder<outputColumns>{{ts}...};
+    return *this;
+  }
+
+  auto expectSkipped(std::size_t skip) -> ExecutorTestHelper& {
+    _expectedSkip = skip;
+    return *this;
+  }
+
+  auto expectedState(ExecutionState state) -> ExecutorTestHelper& {
+    _expectedState = state;
+    return *this;
+  }
+
+  auto run(typename E::Infos infos) -> void {
+    ResourceMonitor monitor;
+    AqlItemBlockManager itemBlockManager(&monitor, SerializationFormat::SHADOWROWS);
+
+    auto inputBlock = generateInputRanges(itemBlockManager);
+
+    auto testeeNode = std::make_unique<SingletonNode>(_query.plan(), 1);
+
+    ExecutionBlockImpl<E> testee{_query.engine(), testeeNode.get(), std::move(infos)};
+    testee.addDependency(inputBlock.get());
+
+    AqlCallStack stack{_call};
+    auto const [state, skipped, result] = testee.execute(stack);
+    EXPECT_EQ(skipped, _expectedSkip);
+
+    EXPECT_EQ(state, _expectedState);
+
+    SharedAqlItemBlockPtr expectedOutputBlock =
+        buildBlock<outputColumns>(itemBlockManager, std::move(_output));
+    testOutputBlock(result, expectedOutputBlock);
+
+    // ToDo:
+    // Test stats
+  };
+
+ private:
+  void testOutputBlock(SharedAqlItemBlockPtr const& outputBlock,
+                       SharedAqlItemBlockPtr const& expectedOutputBlock) {
+    velocypack::Options vpackOptions;
+
+    EXPECT_EQ(outputBlock->size(), expectedOutputBlock->size());
+    for (size_t i = 0; i < outputBlock->size(); i++) {
+      for (size_t j = 0; j < outputColumns; j++) {
+        AqlValue const& x = outputBlock->getValueReference(i, _outputRegisters[j]);
+        AqlValue const& y = expectedOutputBlock->getValueReference(i, j);
+
+        EXPECT_TRUE(AqlValue::Compare(&vpackOptions, x, y, true) == 0)
+            << "Row " << i << " Column " << j << " (Reg " << _outputRegisters[j]
+            << ") do not agree";
+      }
+    }
+  }
+
+  auto generateInputRanges(AqlItemBlockManager& itemBlockManager)
+      -> std::unique_ptr<ExecutionBlock> {
+    using VectorSizeT = std::vector<std::size_t>;
+
+    MatrixBuilder<inputColumns> matrix;
+
+    std::deque<SharedAqlItemBlockPtr> blockDeque;
+
+    std::optional<VectorSizeT::iterator> iter, end;
+
+    if (std::holds_alternative<VectorSizeT>(_inputSplit)) {
+      iter = std::get<VectorSizeT>(_inputSplit).begin();
+      end = std::get<VectorSizeT>(_inputSplit).end();
+    }
+
+    for (auto const& value : _input) {
+      matrix.push_back(value);
+
+      bool openNewBlock =
+          std::visit(overload{[&](VectorSizeT& list) {
+                                if (*iter != *end && matrix.size() == **iter) {
+                                  iter->operator++();
+                                  return true;
+                                }
+
+                                return false;
+                              },
+                              [&](std::size_t size) {
+                                return matrix.size() == size;
+                              },
+                              [](auto) { return false; }},
+                     _inputSplit);
+      if (openNewBlock) {
+        SharedAqlItemBlockPtr inputBlock =
+            buildBlock<inputColumns>(itemBlockManager, std::move(matrix));
+        blockDeque.emplace_back(inputBlock);
+        matrix.clear();
+      }
+    }
+
+    if (!matrix.empty()) {
+      SharedAqlItemBlockPtr inputBlock =
+          buildBlock<inputColumns>(itemBlockManager, std::move(matrix));
+      blockDeque.emplace_back(inputBlock);
+    }
+
+    return std::make_unique<WaitingExecutionBlockMock>(
+        _query.engine(), _dummyNode.get(), std::move(blockDeque),
+        WaitingExecutionBlockMock::WaitingBehaviour::NEVER);
+  }
+
+  AqlCall _call;
+  MatrixBuilder<inputColumns> _input;
+  MatrixBuilder<outputColumns> _output;
+  std::array<std::size_t, outputColumns> _outputRegisters;
+  size_t _expectedSkip;
+  ExecutionState _expectedState;
+
+  SplitType _inputSplit = {std::monostate()};
+  SplitType _outputSplit = {std::monostate()};
+
+  arangodb::aql::Query& _query;
+  std::unique_ptr<arangodb::aql::ExecutionNode> _dummyNode;
+};
+
 enum class ExecutorCall {
   SKIP_ROWS,
   PRODUCE_ROWS,
diff --git a/tests/Aql/SortedCollectExecutorTest.cpp b/tests/Aql/SortedCollectExecutorTest.cpp
index 5a0ad7dfe8a5..c267ab80c092 100644
--- a/tests/Aql/SortedCollectExecutorTest.cpp
+++ b/tests/Aql/SortedCollectExecutorTest.cpp
@@ -21,10 +21,12 @@
 /// @author Michael Hackstein
 /// @author Heiko Kernbach
 /// @author Jan Christoph Uhde
+/// @author Lars Maier
 ////////////////////////////////////////////////////////////////////////////////
 
 #include "gtest/gtest.h"
 
+#include "ExecutorTestHelper.h"
 #include "RowFetcherHelper.h"
 
 #include "Aql/AqlItemBlock.h"
@@ -37,6 +39,7 @@
 #include "Transaction/Context.h"
 #include "Transaction/Methods.h"
 
+#include "AqlItemBlockHelper.h"
 #include "Mocks/Servers.h"
 
 #include <velocypack/Builder.h>
@@ -46,9 +49,7 @@
 using namespace arangodb;
 using namespace arangodb::aql;
 
-namespace arangodb {
-namespace tests {
-namespace aql {
+namespace arangodb::tests::aql {
 
 class SortedCollectExecutorTestNoRowsUpstream : public ::testing::Test {
  protected:
@@ -103,30 +104,40 @@ class SortedCollectExecutorTestNoRowsUpstream : public ::testing::Test {
         block(new AqlItemBlock(itemBlockManager, 1000, 2)) {}
 };
 
-TEST_F(SortedCollectExecutorTestNoRowsUpstream, producer_doesnt_wait) {
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input.steal(), false);
-  SortedCollectExecutor testee(fetcher, infos);
-
-  OutputAqlItemRow result(std::move(block), infos.getOutputRegisters(),
-                          infos.registersToKeep(), infos.registersToClear());
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(result.produced());
-}
-
-TEST_F(SortedCollectExecutorTestNoRowsUpstream, producer_waits) {
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input.steal(), true);
+TEST_F(SortedCollectExecutorTestNoRowsUpstream, producer_gets_empty_input) {
+  auto input = VPackParser::fromJson("[ [1], [2] ]");
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, input->steal(), false);
   SortedCollectExecutor testee(fetcher, infos);
 
-  OutputAqlItemRow result(std::move(block), infos.getOutputRegisters(),
-                          infos.registersToKeep(), infos.registersToClear());
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::WAITING);
-  ASSERT_FALSE(result.produced());
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(result.produced());
+  AqlCall clientCall;
+
+  AqlItemBlockInputRange emptyInputRange(ExecutorState::HASMORE);
+  AqlItemBlockInputRange inputRange(ExecutorState::DONE);
+
+  SharedAqlItemBlockPtr outputBlock =
+      itemBlockManager.requestBlock(1, infos.numberOfOutputRegisters());
+  OutputAqlItemRow result(outputBlock, infos.getOutputRegisters(),
+                          infos.registersToKeep(), infos.registersToClear(), {});
+
+  {
+    auto [state, stats, upstreamCall] = testee.produceRows(emptyInputRange, result);
+    ASSERT_EQ(ExecutorState::HASMORE, state);
+    ASSERT_FALSE(upstreamCall.hasHardLimit());
+    ASSERT_TRUE(std::holds_alternative<AqlCall::Infinity>(upstreamCall.softLimit));
+    ASSERT_EQ(0, upstreamCall.offset);
+    ASSERT_EQ(clientCall.fullCount, upstreamCall.fullCount);
+    ASSERT_EQ(0, result.numRowsWritten());
+    ASSERT_FALSE(result.produced());
+  }
+
+  {
+    auto [state, stats, upstreamCall] = testee.produceRows(inputRange, result);
+    ASSERT_EQ(ExecutorState::DONE, state);
+    ASSERT_EQ(clientCall.fullCount, upstreamCall.fullCount);
+    ASSERT_EQ(0, result.numRowsWritten());
+    ASSERT_FALSE(result.produced());
+  }
 }
 
 class SortedCollectExecutorTestRowsUpstream : public ::testing::Test {
@@ -185,209 +196,291 @@ class SortedCollectExecutorTestRowsUpstream : public ::testing::Test {
         block(new AqlItemBlock(itemBlockManager, 1000, nrOutputRegister)) {}
 };
 
-TEST_F(SortedCollectExecutorTestRowsUpstream, producer_doesnt_wait) {
+TEST_F(SortedCollectExecutorTestRowsUpstream, producer_1) {
   auto input = VPackParser::fromJson("[ [1], [2] ]");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), false);
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, input->steal(), false);
   SortedCollectExecutor testee(fetcher, infos);
 
-  OutputAqlItemRow result(std::move(block), infos.getOutputRegisters(),
-                          infos.registersToKeep(), infos.registersToClear());
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(result.produced());
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_TRUE(result.produced());
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(result.produced());
-
-  auto block = result.stealBlock();
-
-  // check for groups in this executor they are guaranteed to be ordered
-
-  // First group
-  AqlValue x = block->getValue(0, 1);
-  ASSERT_TRUE(x.isNumber());
-  ASSERT_EQ(x.slice().getInt(), 1);
-  // check for collect
-  x = block->getValue(1, 1);
-  ASSERT_TRUE(x.isNumber());
-  ASSERT_EQ(x.slice().getInt(), 2);
+  SharedAqlItemBlockPtr inputBlock = buildBlock<1>(itemBlockManager, {{1}, {2}});
+  AqlCall clientCall;
+
+  AqlItemBlockInputRange emptyInputRange(ExecutorState::HASMORE);
+  AqlItemBlockInputRange inputRange(ExecutorState::DONE, inputBlock, 0,
+                                    inputBlock->size());
+
+  SharedAqlItemBlockPtr outputBlock =
+      itemBlockManager.requestBlock(2, infos.numberOfOutputRegisters());
+  OutputAqlItemRow result(outputBlock, infos.getOutputRegisters(),
+                          infos.registersToKeep(), infos.registersToClear(), {});
+
+  {
+    auto [state, stats, upstreamCall] = testee.produceRows(emptyInputRange, result);
+    ASSERT_EQ(ExecutorState::HASMORE, state);
+    ASSERT_FALSE(upstreamCall.hasHardLimit());
+    ASSERT_TRUE(std::holds_alternative<AqlCall::Infinity>(upstreamCall.softLimit));
+    ASSERT_EQ(0, upstreamCall.offset);
+    ASSERT_EQ(clientCall.fullCount, upstreamCall.fullCount);
+    ASSERT_EQ(0, result.numRowsWritten());
+    ASSERT_FALSE(result.produced());
+  }
+
+  {
+    auto [state, stats, upstreamCall] = testee.produceRows(inputRange, result);
+    ASSERT_EQ(ExecutorState::DONE, state);
+    ASSERT_EQ(clientCall.fullCount, upstreamCall.fullCount);
+    ASSERT_EQ(2, result.numRowsWritten());
+    ASSERT_FALSE(result.produced());
+  }
+
+  {
+    AqlValue x = outputBlock->getValue(0, 1);
+    ASSERT_TRUE(x.isNumber());
+    ASSERT_EQ(x.slice().getInt(), 1);
+    x = outputBlock->getValue(1, 1);
+    ASSERT_TRUE(x.isNumber());
+    ASSERT_EQ(x.slice().getInt(), 2);
+  }
 }
 
-TEST_F(SortedCollectExecutorTestRowsUpstream, producer_doesnt_wait_2) {
+TEST_F(SortedCollectExecutorTestRowsUpstream, producer_2) {
   auto input = VPackParser::fromJson("[ [1], [2], [3] ]");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), false);
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, input->steal(), false);
   SortedCollectExecutor testee(fetcher, infos);
 
-  OutputAqlItemRow result(std::move(block), infos.getOutputRegisters(),
-                          infos.registersToKeep(), infos.registersToClear());
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(result.produced());
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(result.produced());
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_TRUE(result.produced());
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(result.produced());
-
-  auto block = result.stealBlock();
-
-  // check for collects
-  AqlValue x = block->getValue(0, 1);
-  ASSERT_TRUE(x.isNumber());
-  ASSERT_EQ(x.slice().getInt(), 1);
-
-  x = block->getValue(1, 1);
-  ASSERT_TRUE(x.isNumber());
-  ASSERT_EQ(x.slice().getInt(), 2);
-
-  x = block->getValue(2, 1);
-  ASSERT_TRUE(x.isNumber());
-  ASSERT_EQ(x.slice().getInt(), 3);
+  SharedAqlItemBlockPtr inputBlock = buildBlock<1>(itemBlockManager, {{1}, {2}, {3}});
+  AqlCall clientCall;
+
+  AqlItemBlockInputRange emptyInputRange(ExecutorState::HASMORE);
+  AqlItemBlockInputRange inputRange(ExecutorState::DONE, inputBlock, 0,
+                                    inputBlock->size());
+
+  SharedAqlItemBlockPtr outputBlock =
+      itemBlockManager.requestBlock(inputBlock->size(), infos.numberOfOutputRegisters());
+  OutputAqlItemRow result(outputBlock, infos.getOutputRegisters(),
+                          infos.registersToKeep(), infos.registersToClear(), {});
+
+  {
+    auto [state, stats, upstreamCall] = testee.produceRows(emptyInputRange, result);
+    ASSERT_EQ(ExecutorState::HASMORE, state);
+    ASSERT_FALSE(upstreamCall.hasHardLimit());
+    ASSERT_TRUE(std::holds_alternative<AqlCall::Infinity>(upstreamCall.softLimit));
+    ASSERT_EQ(0, upstreamCall.offset);
+    ASSERT_EQ(clientCall.fullCount, upstreamCall.fullCount);
+    ASSERT_EQ(0, result.numRowsWritten());
+    ASSERT_FALSE(result.produced());
+  }
+
+  {
+    auto [state, stats, upstreamCall] = testee.produceRows(inputRange, result);
+    ASSERT_EQ(ExecutorState::DONE, state);
+    ASSERT_EQ(clientCall.fullCount, upstreamCall.fullCount);
+    ASSERT_EQ(inputBlock->size(), result.numRowsWritten());
+    ASSERT_FALSE(result.produced());
+  }
+
+  {
+    AqlValue x = outputBlock->getValue(0, 1);
+    ASSERT_TRUE(x.isNumber());
+    ASSERT_EQ(x.slice().getInt(), 1);
+    x = outputBlock->getValue(1, 1);
+    ASSERT_TRUE(x.isNumber());
+    ASSERT_EQ(x.slice().getInt(), 2);
+    x = outputBlock->getValue(2, 1);
+    ASSERT_TRUE(x.isNumber());
+    ASSERT_EQ(x.slice().getInt(), 3);
+  }
 }
 
-TEST_F(SortedCollectExecutorTestRowsUpstream, producer_doesnt_wait_3) {
+TEST_F(SortedCollectExecutorTestRowsUpstream, producer_3) {
   // Input order needs to be guaranteed
   auto input = VPackParser::fromJson("[ [1], [1], [2], [2], [3] ]");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), false);
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, input->steal(), false);
   SortedCollectExecutor testee(fetcher, infos);
 
-  OutputAqlItemRow result(std::move(block), infos.getOutputRegisters(),
-                          infos.registersToKeep(), infos.registersToClear());
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(result.produced());
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(result.produced());
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_TRUE(result.produced());
-  result.advanceRow();
-
-  // After done return done
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(result.produced());
-
-  auto block = result.stealBlock();
-
-  // check for types
-  AqlValue x = block->getValue(0, 1);
-  ASSERT_TRUE(x.isNumber());
-  ASSERT_EQ(x.slice().getInt(), 1);
-
-  x = block->getValue(1, 1);
-  ASSERT_TRUE(x.isNumber());
-  ASSERT_EQ(x.slice().getInt(), 2);
-
-  x = block->getValue(2, 1);
-  ASSERT_TRUE(x.isNumber());
-  ASSERT_EQ(x.slice().getInt(), 3);
+  SharedAqlItemBlockPtr inputBlock =
+      buildBlock<1>(itemBlockManager, {{1}, {1}, {2}, {2}, {3}});
+  AqlCall clientCall;
+
+  AqlItemBlockInputRange emptyInputRange(ExecutorState::HASMORE);
+  AqlItemBlockInputRange inputRange(ExecutorState::DONE, inputBlock, 0,
+                                    inputBlock->size());
+
+  SharedAqlItemBlockPtr outputBlock =
+      itemBlockManager.requestBlock(inputBlock->size(), infos.numberOfOutputRegisters());
+  OutputAqlItemRow result(outputBlock, infos.getOutputRegisters(),
+                          infos.registersToKeep(), infos.registersToClear(), {});
+
+  {
+    auto [state, stats, upstreamCall] = testee.produceRows(emptyInputRange, result);
+    ASSERT_EQ(ExecutorState::HASMORE, state);
+    ASSERT_FALSE(upstreamCall.hasHardLimit());
+    ASSERT_TRUE(std::holds_alternative<AqlCall::Infinity>(upstreamCall.softLimit));
+    ASSERT_EQ(0, upstreamCall.offset);
+    ASSERT_EQ(clientCall.fullCount, upstreamCall.fullCount);
+    ASSERT_EQ(0, result.numRowsWritten());
+    ASSERT_FALSE(result.produced());
+  }
+
+  {
+    auto [state, stats, upstreamCall] = testee.produceRows(inputRange, result);
+    ASSERT_EQ(ExecutorState::DONE, state);
+    ASSERT_EQ(clientCall.fullCount, upstreamCall.fullCount);
+    ASSERT_EQ(3, result.numRowsWritten());
+    ASSERT_FALSE(result.produced());
+  }
+
+  {
+    AqlValue x = outputBlock->getValue(0, 1);
+    ASSERT_TRUE(x.isNumber());
+    ASSERT_EQ(x.slice().getInt(), 1);
+    x = outputBlock->getValue(1, 1);
+    ASSERT_TRUE(x.isNumber());
+    ASSERT_EQ(x.slice().getInt(), 2);
+    x = outputBlock->getValue(2, 1);
+    ASSERT_TRUE(x.isNumber());
+    ASSERT_EQ(x.slice().getInt(), 3);
+  }
 }
 
-TEST_F(SortedCollectExecutorTestRowsUpstream, producer_doesnt_wait_4) {
+TEST_F(SortedCollectExecutorTestRowsUpstream, producer_4) {
   auto input = VPackParser::fromJson("[ [1], [1], [2], [2] ]");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), false);
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, input->steal(), false);
   SortedCollectExecutor testee(fetcher, infos);
 
-  OutputAqlItemRow result(std::move(block), infos.getOutputRegisters(),
-                          infos.registersToKeep(), infos.registersToClear());
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(result.produced());
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_TRUE(result.produced());
-  result.advanceRow();
-
-  // After DONE return DONE
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(result.produced());
+  SharedAqlItemBlockPtr inputBlock =
+      buildBlock<1>(itemBlockManager, {{1}, {1}, {2}, {2}});
+  AqlCall clientCall;
+
+  AqlItemBlockInputRange emptyInputRange(ExecutorState::HASMORE);
+  AqlItemBlockInputRange inputRange(ExecutorState::DONE, inputBlock, 0,
+                                    inputBlock->size());
+
+  SharedAqlItemBlockPtr outputBlock =
+      itemBlockManager.requestBlock(inputBlock->size(), infos.numberOfOutputRegisters());
+  OutputAqlItemRow result(outputBlock, infos.getOutputRegisters(),
+                          infos.registersToKeep(), infos.registersToClear(), {});
+
+  {
+    auto [state, stats, upstreamCall] = testee.produceRows(emptyInputRange, result);
+    ASSERT_EQ(ExecutorState::HASMORE, state);
+    ASSERT_FALSE(upstreamCall.hasHardLimit());
+    ASSERT_TRUE(std::holds_alternative<AqlCall::Infinity>(upstreamCall.softLimit));
+    ASSERT_EQ(0, upstreamCall.offset);
+    ASSERT_EQ(clientCall.fullCount, upstreamCall.fullCount);
+    ASSERT_EQ(0, result.numRowsWritten());
+    ASSERT_FALSE(result.produced());
+  }
+
+  {
+    auto [state, stats, upstreamCall] = testee.produceRows(inputRange, result);
+    ASSERT_EQ(ExecutorState::DONE, state);
+    ASSERT_EQ(clientCall.fullCount, upstreamCall.fullCount);
+    ASSERT_EQ(2, result.numRowsWritten());
+    ASSERT_FALSE(result.produced());
+  }
+
+  {
+    AqlValue x = outputBlock->getValue(0, 1);
+    ASSERT_TRUE(x.isNumber());
+    ASSERT_EQ(x.slice().getInt(), 1);
+    x = outputBlock->getValue(1, 1);
+    ASSERT_TRUE(x.isNumber());
+    ASSERT_EQ(x.slice().getInt(), 2);
+  }
+}
 
-  auto block = result.stealBlock();
+TEST(SortedCollectExecutorTestRowsUpstreamCount, test) {
+  ResourceMonitor monitor;
+  AqlItemBlockManager itemBlockManager{&monitor, SerializationFormat::SHADOWROWS};
 
-  // check for types
-  AqlValue x = block->getValue(0, 1);
-  ASSERT_TRUE(x.isNumber());
-  ASSERT_EQ(x.slice().getInt(), 1);
+  mocks::MockAqlServer server{};
+  std::unique_ptr<arangodb::aql::Query> fakedQuery = server.createFakeQuery();
+  arangodb::transaction::Methods* trx = fakedQuery->trx();
 
-  x = block->getValue(1, 1);
-  ASSERT_TRUE(x.isNumber());
-  ASSERT_EQ(x.slice().getInt(), 2);
-}
+  std::unordered_set<RegisterId> regToClear = {};
+  std::unordered_set<RegisterId> regToKeep = {};
+  std::vector<std::pair<RegisterId, RegisterId>> groupRegisters = {{1, 0}};
 
-TEST_F(SortedCollectExecutorTestRowsUpstream, producer_waits) {
-  auto input = VPackParser::fromJson("[ [1], [2] ]");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), true);
-  SortedCollectExecutor testee(fetcher, infos);
+  std::unordered_set<RegisterId> readableInputRegisters = {0};
+  std::unordered_set<RegisterId> writeableOutputRegisters = {1, 2};
+  RegisterId nrOutputRegister = 3;
 
-  OutputAqlItemRow result(std::move(block), infos.getOutputRegisters(),
-                          infos.registersToKeep(), infos.registersToClear());
+  std::vector<std::pair<RegisterId, RegisterId>> aggregateRegisters;
+  aggregateRegisters.emplace_back(std::make_pair<RegisterId, RegisterId>(2, 0));
 
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::WAITING);
-  ASSERT_FALSE(result.produced());
+  std::vector<std::string> aggregateTypes = {"SUM"};
 
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::WAITING);
-  ASSERT_FALSE(result.produced());
+  RegisterId collectRegister = RegisterPlan::MaxRegisterId;
+  RegisterId expressionRegister = RegisterPlan::MaxRegisterId;
+  Variable const* expressionVariable = nullptr;
+  std::vector<std::pair<std::string, RegisterId>> variables;
 
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(result.produced());
-  result.advanceRow();
+  SortedCollectExecutorInfos infos(1, nrOutputRegister, std::move(regToClear),
+                                   std::move(regToKeep), std::move(readableInputRegisters),
+                                   std::move(writeableOutputRegisters),
+                                   std::move(groupRegisters), collectRegister,
+                                   expressionRegister, expressionVariable,
+                                   std::move(aggregateTypes), std::move(variables),
+                                   std::move(aggregateRegisters), trx, false);
 
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_TRUE(result.produced());
-  result.advanceRow();
+  SharedAqlItemBlockPtr inputBlock = buildBlock<1>(itemBlockManager, {{1}, {2}});
+  AqlCall clientCall;
 
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(result.produced());
+  AqlItemBlockInputRange emptyInputRange(ExecutorState::HASMORE);
+  AqlItemBlockInputRange inputRange(ExecutorState::DONE, inputBlock, 0,
+                                    inputBlock->size());
 
-  auto block = result.stealBlock();
+  SharedAqlItemBlockPtr outputBlock =
+      itemBlockManager.requestBlock(inputBlock->size(), infos.numberOfOutputRegisters());
+  OutputAqlItemRow result(outputBlock, infos.getOutputRegisters(),
+                          infos.registersToKeep(), infos.registersToClear(), {});
 
-  // check for types
-  AqlValue x = block->getValue(0, 1);
-  ASSERT_TRUE(x.isNumber());
-  ASSERT_EQ(x.slice().getInt(), 1);
+  auto input = VPackParser::fromJson("[ [1], [2] ]");
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, input->steal(), false);
+  SortedCollectExecutor testee(fetcher, infos);
 
-  x = block->getValue(1, 1);
-  ASSERT_TRUE(x.isNumber());
-  ASSERT_EQ(x.slice().getInt(), 2);
+  {
+    auto [state, stats, upstreamCall] = testee.produceRows(emptyInputRange, result);
+    ASSERT_EQ(ExecutorState::HASMORE, state);
+    ASSERT_FALSE(upstreamCall.hasHardLimit());
+    ASSERT_TRUE(std::holds_alternative<AqlCall::Infinity>(upstreamCall.softLimit));
+    ASSERT_EQ(0, upstreamCall.offset);
+    ASSERT_EQ(clientCall.fullCount, upstreamCall.fullCount);
+    ASSERT_EQ(0, result.numRowsWritten());
+    ASSERT_FALSE(result.produced());
+  }
+
+  {
+    auto [state, stats, upstreamCall] = testee.produceRows(inputRange, result);
+    ASSERT_EQ(ExecutorState::DONE, state);
+    ASSERT_EQ(clientCall.fullCount, upstreamCall.fullCount);
+    ASSERT_EQ(2, result.numRowsWritten());
+    ASSERT_FALSE(result.produced());
+  }
+
+  {
+    AqlValue x = outputBlock->getValue(0, 1);
+    ASSERT_TRUE(x.isNumber());
+    ASSERT_EQ(x.slice().getInt(), 1);
+    x = outputBlock->getValue(0, 2);
+    ASSERT_TRUE(x.isNumber());
+    ASSERT_EQ(x.slice().getDouble(), 1);
+
+    x = outputBlock->getValue(1, 1);
+    ASSERT_TRUE(x.isNumber());
+    ASSERT_EQ(x.slice().getInt(), 2);
+    x = outputBlock->getValue(1, 2);
+    ASSERT_TRUE(x.isNumber());
+    ASSERT_EQ(x.slice().getDouble(), 2);
+  }
 }
 
-TEST(SortedCollectExecutorTestRowsUpstreamCount, test) {
-  ExecutionState state;
+TEST(SortedCollectExecutorTestRowsUpstreamCountStrings, test) {
   ResourceMonitor monitor;
   AqlItemBlockManager itemBlockManager{&monitor, SerializationFormat::SHADOWROWS};
 
@@ -410,17 +503,15 @@ TEST(SortedCollectExecutorTestRowsUpstreamCount, test) {
 
   std::vector<std::pair<RegisterId, RegisterId>> aggregateRegisters;
   aggregateRegisters.emplace_back(std::make_pair<RegisterId, RegisterId>(2, 0));
-  writeableOutputRegisters.insert(2);
 
   std::vector<std::string> aggregateTypes;
-  aggregateTypes.emplace_back("SUM");
+  aggregateTypes.emplace_back("LENGTH");
 
-  // if count = true, then we need to set a valid countRegister
-  bool count = true;
   RegisterId collectRegister = RegisterPlan::MaxRegisterId;
   RegisterId expressionRegister = RegisterPlan::MaxRegisterId;
   Variable const* expressionVariable = nullptr;
   std::vector<std::pair<std::string, RegisterId>> variables;
+  writeableOutputRegisters.insert(2);
 
   SortedCollectExecutorInfos infos(1, nrOutputRegister, regToClear, regToKeep,
                                    std::move(readableInputRegisters),
@@ -428,269 +519,509 @@ TEST(SortedCollectExecutorTestRowsUpstreamCount, test) {
                                    std::move(groupRegisters), collectRegister,
                                    expressionRegister, expressionVariable,
                                    std::move(aggregateTypes), std::move(variables),
-                                   std::move(aggregateRegisters), trx, count);
+                                   std::move(aggregateRegisters), trx, false);
 
   SharedAqlItemBlockPtr block{new AqlItemBlock(itemBlockManager, 1000, nrOutputRegister)};
-  NoStats stats{};
 
-  auto input = VPackParser::fromJson("[ [1], [2] ]");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), false);
+  auto input = VPackParser::fromJson("[ [\"a\"], [\"aa\"], [\"aaa\"] ]");
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, input->steal(), false);
   SortedCollectExecutor testee(fetcher, infos);
 
-  OutputAqlItemRow result(std::move(block), infos.getOutputRegisters(),
-                          infos.registersToKeep(), infos.registersToClear());
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(result.produced());
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_TRUE(result.produced());
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(result.produced());
-
-  auto newBlock = result.stealBlock();
-
-  // check for types
-  AqlValue x = newBlock->getValue(0, 1);
-  ASSERT_TRUE(x.isNumber());
-  EXPECT_EQ(x.slice().getInt(), 1);
-
-  // Check the SUM register
-  AqlValue counter = newBlock->getValue(0, 2);
-  ASSERT_TRUE(counter.isNumber());
-  EXPECT_EQ(counter.slice().getDouble(), 1);
-
-  // check for types
-  x = newBlock->getValue(1, 1);
-  ASSERT_TRUE(x.isNumber());
-  EXPECT_EQ(x.slice().getInt(), 2);
-
-  // Check the SUM register
-  counter = newBlock->getValue(1, 2);
-  ASSERT_TRUE(counter.isNumber());
-  EXPECT_EQ(counter.slice().getDouble(), 2);
+  SharedAqlItemBlockPtr inputBlock =
+      buildBlock<1>(itemBlockManager, {{"\"a\""}, {"\"aa\""}, {"\"aaa\""}});
+  AqlCall clientCall;
+
+  AqlItemBlockInputRange emptyInputRange(ExecutorState::HASMORE);
+  AqlItemBlockInputRange inputRange(ExecutorState::DONE, inputBlock, 0,
+                                    inputBlock->size());
+
+  SharedAqlItemBlockPtr outputBlock =
+      itemBlockManager.requestBlock(inputBlock->size(), infos.numberOfOutputRegisters());
+  OutputAqlItemRow result(outputBlock, infos.getOutputRegisters(),
+                          infos.registersToKeep(), infos.registersToClear(), {});
+
+  {
+    auto [state, stats, upstreamCall] = testee.produceRows(emptyInputRange, result);
+    ASSERT_EQ(ExecutorState::HASMORE, state);
+    ASSERT_FALSE(upstreamCall.hasHardLimit());
+    ASSERT_TRUE(std::holds_alternative<AqlCall::Infinity>(upstreamCall.softLimit));
+    ASSERT_EQ(0, upstreamCall.offset);
+    ASSERT_EQ(clientCall.fullCount, upstreamCall.fullCount);
+    ASSERT_EQ(0, result.numRowsWritten());
+    ASSERT_FALSE(result.produced());
+  }
+
+  {
+    auto [state, stats, upstreamCall] = testee.produceRows(inputRange, result);
+    ASSERT_EQ(ExecutorState::DONE, state);
+    ASSERT_EQ(clientCall.fullCount, upstreamCall.fullCount);
+    ASSERT_EQ(3, result.numRowsWritten());
+    ASSERT_FALSE(result.produced());
+  }
+
+  {
+    AqlValue x = outputBlock->getValue(0, 1);
+    ASSERT_TRUE(x.isString());
+    ASSERT_TRUE(x.slice().isEqualString("a"));
+
+    AqlValue c = outputBlock->getValue(0, 2);
+    ASSERT_TRUE(c.isNumber());
+    EXPECT_EQ(c.slice().getInt(), 1);
+  }
+
+  {
+    AqlValue x = outputBlock->getValue(1, 1);
+    ASSERT_TRUE(x.isString());
+    ASSERT_TRUE(x.slice().isEqualString("aa"));
+
+    AqlValue c = outputBlock->getValue(1, 2);
+    ASSERT_TRUE(c.isNumber());
+    EXPECT_EQ(c.slice().getInt(), 1);
+  }
+
+  {
+    AqlValue x = outputBlock->getValue(2, 1);
+    ASSERT_TRUE(x.isString());
+    ASSERT_TRUE(x.slice().isEqualString("aaa"));
+
+    AqlValue c = outputBlock->getValue(2, 2);
+    ASSERT_TRUE(c.isNumber());
+    EXPECT_EQ(c.slice().getInt(), 1);
+  }
 }
 
-TEST(SortedCollectExecutorTestRowsUpstreamCountNumbers, test) {
-  ExecutionState state;
+class SortedCollectExecutorTestSkip : public ::testing::Test {
+ protected:
+  // ExecutionState state;
   ResourceMonitor monitor;
-  AqlItemBlockManager itemBlockManager{&monitor, SerializationFormat::SHADOWROWS};
+  AqlItemBlockManager itemBlockManager;
 
-  mocks::MockAqlServer server{};
-  std::unique_ptr<arangodb::aql::Query> fakedQuery = server.createFakeQuery();
-  arangodb::transaction::Methods* trx = fakedQuery->trx();
+  mocks::MockAqlServer server;
+  std::unique_ptr<arangodb::aql::Query> fakedQuery;
+  arangodb::transaction::Methods* trx;
 
   std::unordered_set<RegisterId> regToClear;
   std::unordered_set<RegisterId> regToKeep;
   std::vector<std::pair<RegisterId, RegisterId>> groupRegisters;
-  groupRegisters.emplace_back(std::make_pair<RegisterId, RegisterId>(1, 0));
 
   std::unordered_set<RegisterId> readableInputRegisters;
-  readableInputRegisters.insert(0);
+
+  RegisterId collectRegister;
 
   std::unordered_set<RegisterId> writeableOutputRegisters;
-  writeableOutputRegisters.insert(1);
 
-  RegisterId nrOutputRegister = 3;
+  RegisterId nrOutputRegister;
 
   std::vector<std::pair<RegisterId, RegisterId>> aggregateRegisters;
-  aggregateRegisters.emplace_back(std::make_pair<RegisterId, RegisterId>(2, 0));
-
   std::vector<std::string> aggregateTypes;
-  aggregateTypes.emplace_back("LENGTH");
 
   // if count = true, then we need to set a valid countRegister
-  bool count = true;
-  RegisterId collectRegister = RegisterPlan::MaxRegisterId;
-  RegisterId expressionRegister = RegisterPlan::MaxRegisterId;
-  Variable const* expressionVariable = nullptr;
+  RegisterId expressionRegister;
+  Variable const* expressionVariable;
   std::vector<std::pair<std::string, RegisterId>> variables;
-  writeableOutputRegisters.insert(2);
+  bool count;
 
-  SortedCollectExecutorInfos infos(1, nrOutputRegister, regToClear, regToKeep,
-                                   std::move(readableInputRegisters),
-                                   std::move(writeableOutputRegisters),
-                                   std::move(groupRegisters), collectRegister,
-                                   expressionRegister, expressionVariable,
-                                   std::move(aggregateTypes), std::move(variables),
-                                   std::move(aggregateRegisters), trx, count);
+  SortedCollectExecutorInfos infos;
 
-  SharedAqlItemBlockPtr block{new AqlItemBlock(itemBlockManager, 1000, nrOutputRegister)};
-  NoStats stats{};
+  SharedAqlItemBlockPtr block;
+  NoStats stats;
+
+  SortedCollectExecutorTestSkip()
+      : itemBlockManager(&monitor, SerializationFormat::SHADOWROWS),
+        fakedQuery(server.createFakeQuery()),
+        trx(fakedQuery->trx()),
+        groupRegisters{std::make_pair<RegisterId, RegisterId>(1, 0)},
+        readableInputRegisters({0}),
+        collectRegister(2),
+        writeableOutputRegisters({1, 2}),
+        nrOutputRegister(3),
+        expressionRegister(RegisterPlan::MaxRegisterId),
+        expressionVariable(nullptr),
+        count(false),
+        infos(1, nrOutputRegister, regToClear, regToKeep,
+              std::move(readableInputRegisters), std::move(writeableOutputRegisters),
+              std::move(groupRegisters), collectRegister, expressionRegister,
+              expressionVariable, std::move(aggregateTypes),
+              std::move(variables), std::move(aggregateRegisters), trx, count),
+        block(new AqlItemBlock(itemBlockManager, 1000, nrOutputRegister)) {}
+};
+
+TEST_F(SortedCollectExecutorTestSkip, skip_1) {
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, std::make_shared<VPackBuffer<uint8_t>>(), false);
+
+  SharedAqlItemBlockPtr inputBlock = buildBlock<1>(itemBlockManager, {{1}, {2}});
+  AqlItemBlockInputRange emptyInputRange(ExecutorState::HASMORE);
+  AqlItemBlockInputRange inputRange(ExecutorState::DONE, inputBlock, 0,
+                                    inputBlock->size());
 
-  auto input = VPackParser::fromJson("[ [1], [2], [3] ]");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), false);
   SortedCollectExecutor testee(fetcher, infos);
 
-  OutputAqlItemRow result(std::move(block), infos.getOutputRegisters(),
-                          infos.registersToKeep(), infos.registersToClear());
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(result.produced());
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(result.produced());
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_TRUE(result.produced());
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(result.produced());
-
-  auto newBlock = result.stealBlock();
-
-  // check for types
-  AqlValue x = newBlock->getValue(0, 1);
-  ASSERT_TRUE(x.isNumber());
-  EXPECT_EQ(x.slice().getInt(), 1);
-
-  // Check the LENGTH register
-  AqlValue xx = newBlock->getValue(0, 2);
-  ASSERT_TRUE(xx.isNumber());
-  EXPECT_EQ(xx.slice().getInt(), 1);
-
-  // check for types
-  x = newBlock->getValue(1, 1);
-  ASSERT_TRUE(x.isNumber());
-  EXPECT_EQ(x.slice().getInt(), 2);
-
-  // Check the LENGTH register
-  xx = newBlock->getValue(1, 2);
-  ASSERT_TRUE(xx.isNumber());
-  EXPECT_EQ(xx.slice().getInt(), 1);
-
-  // check for types
-  x = newBlock->getValue(2, 1);
-  ASSERT_TRUE(x.isNumber());
-  EXPECT_EQ(x.slice().getInt(), 3);
-
-  // Check the LENGTH register
-  xx = newBlock->getValue(2, 2);
-  ASSERT_TRUE(xx.isNumber());
-  EXPECT_EQ(xx.slice().getInt(), 1);
+  AqlCall clientCall;
+  clientCall.offset = 2;
+
+  {
+    auto [state, skipped, upstreamCall] = testee.skipRowsRange(emptyInputRange, clientCall);
+    ASSERT_EQ(ExecutorState::HASMORE, state);
+    ASSERT_FALSE(upstreamCall.hasHardLimit());
+    ASSERT_TRUE(std::holds_alternative<AqlCall::Infinity>(upstreamCall.softLimit));
+    ASSERT_EQ(0, upstreamCall.offset);
+    ASSERT_EQ(clientCall.fullCount, upstreamCall.fullCount);
+    ASSERT_EQ(skipped, 0);
+  }
+
+  {
+    auto [state, skipped, upstreamCall] = testee.skipRowsRange(inputRange, clientCall);
+    ASSERT_EQ(ExecutorState::DONE, state);
+    ASSERT_FALSE(upstreamCall.hasHardLimit());
+    ASSERT_TRUE(std::holds_alternative<AqlCall::Infinity>(upstreamCall.softLimit));
+    ASSERT_EQ(0, upstreamCall.offset);
+    ASSERT_EQ(clientCall.fullCount, upstreamCall.fullCount);
+    ASSERT_EQ(skipped, 2);
+  }
 }
 
-TEST(SortedCollectExecutorTestRowsUpstreamCountStrings, test) {
-  ExecutionState state;
+TEST_F(SortedCollectExecutorTestSkip, skip_2) {
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, std::make_shared<VPackBuffer<uint8_t>>(), false);
+
+  SharedAqlItemBlockPtr inputBlock = buildBlock<1>(itemBlockManager, {{1}, {2}});
+  AqlItemBlockInputRange emptyInputRange(ExecutorState::HASMORE);
+  AqlItemBlockInputRange inputRange(ExecutorState::DONE, inputBlock, 0,
+                                    inputBlock->size());
+
+  SortedCollectExecutor testee(fetcher, infos);
+
+  AqlCall clientCall;
+  clientCall.offset = 1;
+
+  {
+    auto [state, skipped, upstreamCall] = testee.skipRowsRange(emptyInputRange, clientCall);
+    EXPECT_EQ(ExecutorState::HASMORE, state);
+    EXPECT_FALSE(upstreamCall.hasHardLimit());
+    EXPECT_TRUE(std::holds_alternative<AqlCall::Infinity>(upstreamCall.softLimit));
+    EXPECT_EQ(0, upstreamCall.offset);
+    EXPECT_EQ(clientCall.fullCount, upstreamCall.fullCount);
+    EXPECT_EQ(skipped, 0);
+  }
+
+  {
+    auto [state, skipped, upstreamCall] = testee.skipRowsRange(inputRange, clientCall);
+    EXPECT_EQ(state, ExecutorState::HASMORE);
+    EXPECT_FALSE(upstreamCall.hasHardLimit());
+    EXPECT_TRUE(std::holds_alternative<AqlCall::Infinity>(upstreamCall.softLimit));
+    EXPECT_EQ(0, upstreamCall.offset);
+    EXPECT_EQ(clientCall.fullCount, upstreamCall.fullCount);
+    EXPECT_EQ(skipped, 1);
+    EXPECT_EQ(inputRange.upstreamState(), ExecutorState::HASMORE);
+  }
+
+  {
+    SharedAqlItemBlockPtr outputBlock =
+        itemBlockManager.requestBlock(inputBlock->size(), infos.numberOfOutputRegisters());
+    OutputAqlItemRow result(outputBlock, infos.getOutputRegisters(),
+                            infos.registersToKeep(), infos.registersToClear(), clientCall);
+
+    auto [state, stats, upstreamCall] = testee.produceRows(inputRange, result);
+    EXPECT_EQ(ExecutorState::DONE, state);
+    EXPECT_FALSE(upstreamCall.hasHardLimit());
+    EXPECT_TRUE(std::holds_alternative<AqlCall::Infinity>(upstreamCall.softLimit));
+    EXPECT_EQ(0, upstreamCall.offset);
+    EXPECT_EQ(clientCall.fullCount, upstreamCall.fullCount);
+    EXPECT_EQ(1, result.numRowsWritten());
+    EXPECT_EQ(inputRange.upstreamState(), ExecutorState::DONE);
+
+    {
+      AqlValue x = outputBlock->getValue(0, 1);
+      EXPECT_TRUE(x.isNumber());
+      EXPECT_EQ(x.slice().getInt(), 2);
+    }
+  }
+}
+
+TEST_F(SortedCollectExecutorTestSkip, skip_3) {
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, std::make_shared<VPackBuffer<uint8_t>>(), false);
+
+  SharedAqlItemBlockPtr inputBlock = buildBlock<1>(itemBlockManager, {{1}, {1}});
+  AqlItemBlockInputRange emptyInputRange(ExecutorState::HASMORE);
+  AqlItemBlockInputRange inputRange(ExecutorState::HASMORE, inputBlock, 0,
+                                    inputBlock->size());
+  AqlItemBlockInputRange emptyInputRangeDone(ExecutorState::DONE);
+
+  SortedCollectExecutor testee(fetcher, infos);
+
+  AqlCall clientCall;
+  clientCall.offset = 1;
+
+  {
+    auto [state, skipped, upstreamCall] = testee.skipRowsRange(emptyInputRange, clientCall);
+    EXPECT_EQ(ExecutorState::HASMORE, state);
+    EXPECT_FALSE(upstreamCall.hasHardLimit());
+    EXPECT_TRUE(std::holds_alternative<AqlCall::Infinity>(upstreamCall.softLimit));
+    EXPECT_EQ(0, upstreamCall.offset);
+    EXPECT_EQ(clientCall.fullCount, upstreamCall.fullCount);
+    EXPECT_EQ(skipped, 0);
+  }
+
+  {
+    auto [state, skipped, upstreamCall] = testee.skipRowsRange(inputRange, clientCall);
+    EXPECT_EQ(state, ExecutorState::HASMORE);
+    EXPECT_EQ(clientCall.fullCount, upstreamCall.fullCount);
+    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(inputRange.upstreamState(), ExecutorState::HASMORE);
+  }
+
+  {
+    auto [state, skipped, upstreamCall] =
+        testee.skipRowsRange(emptyInputRangeDone, clientCall);
+    EXPECT_EQ(state, ExecutorState::DONE);
+    EXPECT_EQ(0, upstreamCall.offset);
+    EXPECT_EQ(skipped, 1);
+    EXPECT_EQ(inputRange.upstreamState(), ExecutorState::HASMORE);
+  }
+}
+
+TEST_F(SortedCollectExecutorTestSkip, skip_4) {
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, std::make_shared<VPackBuffer<uint8_t>>(), false);
+
+  SharedAqlItemBlockPtr inputBlock = buildBlock<1>(itemBlockManager, {{1}, {1}});
+  AqlItemBlockInputRange emptyInputRange(ExecutorState::HASMORE);
+  AqlItemBlockInputRange inputRange(ExecutorState::HASMORE, inputBlock, 0,
+                                    inputBlock->size());
+
+  SharedAqlItemBlockPtr inputBlock2 = buildBlock<1>(itemBlockManager, {{2}});
+  AqlItemBlockInputRange inputRange2(ExecutorState::HASMORE, inputBlock2, 0,
+                                     inputBlock2->size());
+  AqlItemBlockInputRange emptyInputRangeDone(ExecutorState::DONE);
+
+  SortedCollectExecutor testee(fetcher, infos);
+
+  AqlCall clientCall;
+  clientCall.offset = 1;
+
+  {
+    auto [state, skipped, upstreamCall] = testee.skipRowsRange(emptyInputRange, clientCall);
+    EXPECT_EQ(ExecutorState::HASMORE, state);
+    EXPECT_FALSE(upstreamCall.hasHardLimit());
+    EXPECT_TRUE(std::holds_alternative<AqlCall::Infinity>(upstreamCall.softLimit));
+    EXPECT_EQ(0, upstreamCall.offset);
+    EXPECT_EQ(clientCall.fullCount, upstreamCall.fullCount);
+    EXPECT_EQ(skipped, 0);
+  }
+
+  {
+    // 1, 1
+    auto [state, skipped, upstreamCall] = testee.skipRowsRange(inputRange, clientCall);
+    EXPECT_EQ(state, ExecutorState::HASMORE);
+    EXPECT_EQ(clientCall.fullCount, upstreamCall.fullCount);
+    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(inputRange.upstreamState(), ExecutorState::HASMORE);
+  }
+
+  {
+    // 2
+    auto [state, skipped, upstreamCall] = testee.skipRowsRange(inputRange2, clientCall);
+    EXPECT_EQ(state, ExecutorState::HASMORE);
+    EXPECT_EQ(0, upstreamCall.offset);
+    EXPECT_EQ(skipped, 1);
+    EXPECT_EQ(inputRange.upstreamState(), ExecutorState::HASMORE);
+  }
+
+  {
+    SharedAqlItemBlockPtr outputBlock =
+        itemBlockManager.requestBlock(inputBlock->size(), infos.numberOfOutputRegisters());
+    OutputAqlItemRow result(outputBlock, infos.getOutputRegisters(),
+                            infos.registersToKeep(), infos.registersToClear(), clientCall);
+
+    auto [state, stats, upstreamCall] = testee.produceRows(inputRange2, result);
+    EXPECT_EQ(state, ExecutorState::HASMORE);
+    EXPECT_EQ(result.numRowsWritten(), 0);
+    EXPECT_FALSE(result.produced());
+  }
+
+  {
+    SharedAqlItemBlockPtr outputBlock =
+        itemBlockManager.requestBlock(inputBlock->size(), infos.numberOfOutputRegisters());
+    OutputAqlItemRow result(outputBlock, infos.getOutputRegisters(),
+                            infos.registersToKeep(), infos.registersToClear(), clientCall);
+
+    auto [state, stats, upstreamCall] = testee.produceRows(emptyInputRangeDone, result);
+    EXPECT_EQ(state, ExecutorState::DONE);
+    EXPECT_EQ(clientCall.fullCount, upstreamCall.fullCount);
+    EXPECT_EQ(1, result.numRowsWritten());
+
+    {
+      AqlValue x = outputBlock->getValue(0, 1);
+      EXPECT_TRUE(x.isNumber());
+      EXPECT_EQ(x.slice().getInt(), 2);
+    }
+  }
+}
+
+TEST_F(SortedCollectExecutorTestSkip, skip_5) {
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, std::make_shared<VPackBuffer<uint8_t>>(), false);
+
+  SharedAqlItemBlockPtr inputBlock = buildBlock<1>(itemBlockManager, {{1}, {1}, {2}});
+  AqlItemBlockInputRange emptyInputRange(ExecutorState::HASMORE);
+  AqlItemBlockInputRange inputRange(ExecutorState::DONE, inputBlock, 0,
+                                    inputBlock->size());
+
+  SortedCollectExecutor testee(fetcher, infos);
+
+  AqlCall clientCall;
+  clientCall.offset = 1;
+
+  {
+    auto [state, skipped, upstreamCall] = testee.skipRowsRange(emptyInputRange, clientCall);
+    EXPECT_EQ(ExecutorState::HASMORE, state);
+    EXPECT_FALSE(upstreamCall.hasHardLimit());
+    EXPECT_TRUE(std::holds_alternative<AqlCall::Infinity>(upstreamCall.softLimit));
+    EXPECT_EQ(0, upstreamCall.offset);
+    EXPECT_EQ(clientCall.fullCount, upstreamCall.fullCount);
+    EXPECT_EQ(skipped, 0);
+  }
+
+  {
+    // 1, 1, 2
+    auto [state, skipped, upstreamCall] = testee.skipRowsRange(inputRange, clientCall);
+    EXPECT_EQ(state, ExecutorState::HASMORE);
+    EXPECT_EQ(clientCall.fullCount, upstreamCall.fullCount);
+    EXPECT_EQ(skipped, 1);
+    EXPECT_EQ(inputRange.upstreamState(), ExecutorState::HASMORE);
+  }
+
+  {
+    SharedAqlItemBlockPtr outputBlock =
+        itemBlockManager.requestBlock(inputBlock->size(), infos.numberOfOutputRegisters());
+    OutputAqlItemRow result(outputBlock, infos.getOutputRegisters(),
+                            infos.registersToKeep(), infos.registersToClear(), clientCall);
+
+    auto [state, stats, upstreamCall] = testee.produceRows(inputRange, result);
+    EXPECT_EQ(ExecutorState::DONE, state);
+    EXPECT_EQ(clientCall.fullCount, upstreamCall.fullCount);
+    EXPECT_EQ(1, result.numRowsWritten());
+
+    {
+      AqlValue x = outputBlock->getValue(0, 1);
+      EXPECT_TRUE(x.isNumber());
+      EXPECT_EQ(x.slice().getInt(), 2);
+    }
+  }
+}
+
+using SortedCollectTestHelper = ExecutorTestHelper<SortedCollectExecutor, 1, 1>;
+using SortedCollectSplitType = SortedCollectTestHelper::SplitType;
+
+class SortedCollectExecutorTestSplit
+    : public ::testing::TestWithParam<std::tuple<SortedCollectSplitType>> {
+ protected:
+  // ExecutionState state;
   ResourceMonitor monitor;
-  AqlItemBlockManager itemBlockManager{&monitor, SerializationFormat::SHADOWROWS};
+  AqlItemBlockManager itemBlockManager;
 
-  mocks::MockAqlServer server{};
-  std::unique_ptr<arangodb::aql::Query> fakedQuery = server.createFakeQuery();
-  arangodb::transaction::Methods* trx = fakedQuery->trx();
+  mocks::MockAqlServer server;
+  std::unique_ptr<arangodb::aql::Query> fakedQuery;
+  arangodb::transaction::Methods* trx;
 
   std::unordered_set<RegisterId> regToClear;
   std::unordered_set<RegisterId> regToKeep;
   std::vector<std::pair<RegisterId, RegisterId>> groupRegisters;
-  groupRegisters.emplace_back(std::make_pair<RegisterId, RegisterId>(1, 0));
 
   std::unordered_set<RegisterId> readableInputRegisters;
-  readableInputRegisters.insert(0);
+
+  RegisterId collectRegister;
 
   std::unordered_set<RegisterId> writeableOutputRegisters;
-  writeableOutputRegisters.insert(1);
 
-  RegisterId nrOutputRegister = 3;
+  RegisterId nrOutputRegister;
 
   std::vector<std::pair<RegisterId, RegisterId>> aggregateRegisters;
-  aggregateRegisters.emplace_back(std::make_pair<RegisterId, RegisterId>(2, 0));
-
   std::vector<std::string> aggregateTypes;
-  aggregateTypes.emplace_back("LENGTH");
 
   // if count = true, then we need to set a valid countRegister
-  bool count = true;
-  RegisterId collectRegister = RegisterPlan::MaxRegisterId;
-  RegisterId expressionRegister = RegisterPlan::MaxRegisterId;
-  Variable const* expressionVariable = nullptr;
+  RegisterId expressionRegister;
+  Variable const* expressionVariable;
   std::vector<std::pair<std::string, RegisterId>> variables;
-  writeableOutputRegisters.insert(2);
+  bool count;
 
-  SortedCollectExecutorInfos infos(1, nrOutputRegister, regToClear, regToKeep,
-                                   std::move(readableInputRegisters),
-                                   std::move(writeableOutputRegisters),
-                                   std::move(groupRegisters), collectRegister,
-                                   expressionRegister, expressionVariable,
-                                   std::move(aggregateTypes), std::move(variables),
-                                   std::move(aggregateRegisters), trx, count);
+  SortedCollectExecutorInfos infos;
 
-  SharedAqlItemBlockPtr block{new AqlItemBlock(itemBlockManager, 1000, nrOutputRegister)};
-  NoStats stats{};
+  SharedAqlItemBlockPtr block;
+  NoStats stats;
 
-  auto input = VPackParser::fromJson("[ [\"a\"], [\"aa\"], [\"aaa\"] ]");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), false);
-  SortedCollectExecutor testee(fetcher, infos);
+  SortedCollectExecutorTestSplit()
+      : itemBlockManager(&monitor, SerializationFormat::SHADOWROWS),
+        fakedQuery(server.createFakeQuery()),
+        trx(fakedQuery->trx()),
+        groupRegisters{std::make_pair<RegisterId, RegisterId>(1, 0)},
+        readableInputRegisters({0}),
+        collectRegister(2),
+        writeableOutputRegisters({1, 2}),
+        nrOutputRegister(3),
+        expressionRegister(RegisterPlan::MaxRegisterId),
+        expressionVariable(nullptr),
+        count(false),
+        infos(1, nrOutputRegister, regToClear, regToKeep,
+              std::move(readableInputRegisters), std::move(writeableOutputRegisters),
+              std::move(groupRegisters), collectRegister, expressionRegister,
+              expressionVariable, std::move(aggregateTypes),
+              std::move(variables), std::move(aggregateRegisters), trx, count),
+        block(new AqlItemBlock(itemBlockManager, 1000, nrOutputRegister)) {
+    auto engine =
+        std::make_unique<ExecutionEngine>(*fakedQuery, SerializationFormat::SHADOWROWS);
+    fakedQuery->setEngine(engine.release());
+  }
+};
 
-  OutputAqlItemRow result(std::move(block), infos.getOutputRegisters(),
-                          infos.registersToKeep(), infos.registersToClear());
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(result.produced());
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(result.produced());
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_TRUE(result.produced());
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(result.produced());
-
-  std::vector<std::string> myStrings;
-  std::vector<int> myCountNumbers;
-  auto newBlock = result.stealBlock();
-
-  // check for types
-  AqlValue x = newBlock->getValue(0, 1);
-  ASSERT_TRUE(x.isString());
-  EXPECT_EQ(x.slice().copyString(), "a");
-
-  // Check the count register
-  AqlValue c = newBlock->getValue(0, 2);
-  ASSERT_TRUE(c.isNumber());
-  EXPECT_EQ(c.slice().getInt(), 1);
-
-  // check for types
-  x = newBlock->getValue(1, 1);
-  ASSERT_TRUE(x.isString());
-  EXPECT_EQ(x.slice().copyString(), "aa");
-
-  // Check the count register
-  c = newBlock->getValue(1, 2);
-  ASSERT_TRUE(c.isNumber());
-  EXPECT_EQ(c.slice().getInt(), 1);
-
-  // check for types
-  x = newBlock->getValue(2, 1);
-  ASSERT_TRUE(x.isString());
-  EXPECT_EQ(x.slice().copyString(), "aaa");
-
-  // Check the count register
-  c = newBlock->getValue(2, 2);
-  ASSERT_TRUE(c.isNumber());
-  EXPECT_EQ(c.slice().getInt(), 1);
+TEST_P(SortedCollectExecutorTestSplit, split_1) {
+  auto [split] = GetParam();
+
+  ExecutorTestHelper<SortedCollectExecutor>(*fakedQuery)
+      .setInputValueList(1, 1, 1, 2, 3, 4, 4, 5)
+      .setInputSplitType(split)
+      .setCall(AqlCall{2, AqlCall::Infinity{}, 2, true})
+      .expectOutputValueList(3, 4)
+      .expectSkipped(3)
+      .expectedState(ExecutionState::DONE)
+      .run(std::move(infos));
 }
 
-}  // namespace aql
-}  // namespace tests
-}  // namespace arangodb
+TEST_P(SortedCollectExecutorTestSplit, split_2) {
+  auto [split] = GetParam();
+
+  ExecutorTestHelper<SortedCollectExecutor>(*fakedQuery)
+      .setInputValueList(1, 1, 1, 2, 3, 4, 4, 5)
+      .setInputSplitType(split)
+      .setCall(AqlCall{2, 2, AqlCall::Infinity{}, false})
+      .expectOutputValueList(3, 4)
+      .expectSkipped(2)
+      .expectedState(ExecutionState::HASMORE)
+      .run(std::move(infos));
+}
+
+TEST_P(SortedCollectExecutorTestSplit, split_3) {
+  auto [split] = GetParam();
+
+  ExecutorTestHelper<SortedCollectExecutor>(*fakedQuery)
+      .setInputValueList(1, 2, 3, 4, 5)
+      .setInputSplitType(split)
+      .setCall(AqlCall{1, AqlCall::Infinity{}, 10, true})
+      .expectOutputValueList(2, 3, 4, 5)
+      .expectSkipped(1)
+      .expectedState(ExecutionState::DONE)
+      .run(std::move(infos));
+}
+
+template<size_t... vs>
+const SortedCollectSplitType splitIntoBlocks = SortedCollectSplitType{std::vector<std::size_t>{vs...}};
+template<size_t step>
+const SortedCollectSplitType splitStep = SortedCollectSplitType{step};
+
+INSTANTIATE_TEST_CASE_P(SortedCollectExecutor, SortedCollectExecutorTestSplit,
+                        ::testing::Values(splitIntoBlocks<2, 3>, splitIntoBlocks<3, 4>, splitStep<2>));
+
+}  // namespace arangodb::tests::aql

From 30d9f2775c4c7495897b6b3f8c7c6f49e41954a1 Mon Sep 17 00:00:00 2001
From: Lars Maier <lars@arangodb.com>
Date: Tue, 11 Feb 2020 09:41:25 +0100
Subject: [PATCH 058/122] ReturnExecutor New style (#10831)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

* ReturnExecutor implemented. Tests misssing.

* Apply suggestions from code review

Co-Authored-By: Tobias Gödderz <tobias@arangodb.com>

* Implemented skipRows in Return. Also fixed ExecutionBlock references in static asserts

* Implemented first new style test for Return.

* Moved the traceExecute calls into baseclass.

* Added tracing around execute in WaitingExecutionBlockMock. Fixed a test bug, if the AqlCall covers all of the first block, but only a part of the Second block. You would only get the part of the second block.

* Added more tests for standard behaviour of ReturnExecutor

* Added an assertion.

* Simplified call to ReturnExecutor

* Prepare tests for doCount. Also added test for different input register.

* Added accessor for _stats in Engine.

* Included count tests in ReturnExecutorTest.

* Removed old obsolete test.

* Removed obsolete code-path

* Fixed unrelated bug in FilterExecutor. In some cases it did lie on skipRows that it has more, even if it does not have and the upstream does not have as well. Thank you jenkins for hitting into this race :+1:

Co-authored-by: Tobias Gödderz <github@tobias.goedderz.info>
Co-authored-by: Michael Hackstein <michael@arangodb.com>
---
 arangod/Aql/ExecutionBlock.cpp          |  68 ++++++
 arangod/Aql/ExecutionBlock.h            |   7 +
 arangod/Aql/ExecutionBlockImpl.cpp      |  97 +--------
 arangod/Aql/ExecutionBlockImpl.h        |   6 -
 arangod/Aql/ExecutionEngine.cpp         |   4 +
 arangod/Aql/ExecutionEngine.h           |   2 +
 arangod/Aql/ExecutionNode.cpp           | 130 +++++++-----
 arangod/Aql/FilterExecutor.cpp          |   6 +-
 arangod/Aql/ReturnExecutor.cpp          |  76 ++++++-
 arangod/Aql/ReturnExecutor.h            |  52 ++---
 tests/Aql/ExecutorTestHelper.h          |  16 +-
 tests/Aql/ReturnExecutorTest.cpp        | 270 +++++++++++++-----------
 tests/Aql/WaitingExecutionBlockMock.cpp |  23 +-
 tests/Aql/WaitingExecutionBlockMock.h   |   4 +
 14 files changed, 439 insertions(+), 322 deletions(-)

diff --git a/arangod/Aql/ExecutionBlock.cpp b/arangod/Aql/ExecutionBlock.cpp
index 0f8fa6173734..1d7f97402f85 100644
--- a/arangod/Aql/ExecutionBlock.cpp
+++ b/arangod/Aql/ExecutionBlock.cpp
@@ -25,6 +25,7 @@
 
 #include "ExecutionBlock.h"
 
+#include "Aql/AqlCallStack.h"
 #include "Aql/Ast.h"
 #include "Aql/BlockCollector.h"
 #include "Aql/ExecutionEngine.h"
@@ -292,3 +293,70 @@ void ExecutionBlock::addDependency(ExecutionBlock* ep) {
 bool ExecutionBlock::isInSplicedSubquery() const noexcept {
   return _isInSplicedSubquery;
 }
+
+void ExecutionBlock::traceExecuteBegin(AqlCallStack const& stack) {
+  if (_profile >= PROFILE_LEVEL_BLOCKS) {
+    if (_getSomeBegin <= 0.0) {
+      _getSomeBegin = TRI_microtime();
+    }
+    if (_profile >= PROFILE_LEVEL_TRACE_1) {
+      auto const node = getPlanNode();
+      auto const queryId = this->_engine->getQuery()->id();
+      // TODO make sure this works also if stack is non relevant, e.g. passed through by outer subquery.
+      auto const& call = stack.peek();
+      LOG_TOPIC("1e717", INFO, Logger::QUERIES)
+          << "[query#" << queryId << "] "
+          << "execute type=" << node->getTypeString() << " call= " << call
+          << " this=" << (uintptr_t)this << " id=" << node->id();
+    }
+  }
+}
+
+void ExecutionBlock::traceExecuteEnd(
+    std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> const& result) {
+  if (_profile >= PROFILE_LEVEL_BLOCKS) {
+    auto const& [state, skipped, block] = result;
+    auto const items = block != nullptr ? block->size() : 0;
+    ExecutionNode const* en = getPlanNode();
+    ExecutionStats::Node stats;
+    stats.calls = 1;
+    stats.items = skipped + items;
+    if (state != ExecutionState::WAITING) {
+      stats.runtime = TRI_microtime() - _getSomeBegin;
+      _getSomeBegin = 0.0;
+    }
+
+    auto it = _engine->_stats.nodes.find(en->id());
+    if (it != _engine->_stats.nodes.end()) {
+      it->second += stats;
+    } else {
+      _engine->_stats.nodes.emplace(en->id(), stats);
+    }
+
+    if (_profile >= PROFILE_LEVEL_TRACE_1) {
+      ExecutionNode const* node = getPlanNode();
+      auto const queryId = this->_engine->getQuery()->id();
+      LOG_TOPIC("60bbc", INFO, Logger::QUERIES)
+          << "[query#" << queryId << "] "
+          << "execute done type=" << node->getTypeString() << " this=" << (uintptr_t)this
+          << " id=" << node->id() << " state=" << stateToString(state)
+          << " skipped=" << skipped << " produced=" << items;
+
+      if (_profile >= PROFILE_LEVEL_TRACE_2) {
+        if (block == nullptr) {
+          LOG_TOPIC("9b3f4", INFO, Logger::QUERIES)
+              << "[query#" << queryId << "] "
+              << "execute type=" << node->getTypeString() << " result: nullptr";
+        } else {
+          VPackBuilder builder;
+          auto const options = trxVpackOptions();
+          block->toSimpleVPack(options, builder);
+          LOG_TOPIC("f12f9", INFO, Logger::QUERIES)
+              << "[query#" << queryId << "] "
+              << "execute type=" << node->getTypeString()
+              << " result: " << VPackDumper::toString(builder.slice(), options);
+        }
+      }
+    }
+  }
+}
\ No newline at end of file
diff --git a/arangod/Aql/ExecutionBlock.h b/arangod/Aql/ExecutionBlock.h
index 5088608bc945..f6e7370647e8 100644
--- a/arangod/Aql/ExecutionBlock.h
+++ b/arangod/Aql/ExecutionBlock.h
@@ -150,6 +150,13 @@ class ExecutionBlock {
 
   [[nodiscard]] bool isInSplicedSubquery() const noexcept;
 
+ protected:
+  // Trace the start of a execute call
+  void traceExecuteBegin(AqlCallStack const& stack);
+
+  // Trace the end of a execute call, potentially with result
+  void traceExecuteEnd(std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> const& result);
+
  protected:
   /// @brief the execution engine
   ExecutionEngine* _engine;
diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index a624a575029d..2c587ed15dad 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -81,29 +81,6 @@
 using namespace arangodb;
 using namespace arangodb::aql;
 
-namespace {
-
-std::string const doneString = "DONE";
-std::string const hasDataRowString = "HASMORE";
-std::string const waitingString = "WAITING";
-std::string const unknownString = "UNKNOWN";
-
-std::string const& stateToString(aql::ExecutionState state) {
-  switch (state) {
-    case aql::ExecutionState::DONE:
-      return doneString;
-    case aql::ExecutionState::HASMORE:
-      return hasDataRowString;
-    case aql::ExecutionState::WAITING:
-      return waitingString;
-    default:
-      // just to suppress a warning ..
-      return unknownString;
-  }
-}
-
-}  // namespace
-
 /*
  * Creates a metafunction `checkName` that tests whether a class has a method
  * named `methodName`, used like this:
@@ -152,10 +129,9 @@ constexpr bool is_one_of_v = (std::is_same_v<T, Es> || ...);
  * Determine whether we execute new style or old style skips, i.e. pre or post shadow row introduction
  * TODO: This should be removed once all executors and fetchers are ported to the new style.
  */
-
 template <typename Executor>
 constexpr bool isNewStyleExecutor =
-    is_one_of_v<Executor, FilterExecutor, SortedCollectExecutor,
+    is_one_of_v<Executor, FilterExecutor, SortedCollectExecutor, ReturnExecutor,
 #ifdef ARANGODB_USE_GOOGLE_TESTS
                 TestLambdaExecutor, TestLambdaSkipExecutor,  // we need one after these to avoid compile errors in non-test mode
 #endif
@@ -650,75 +626,6 @@ std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> ExecutionBlockImpl<Exe
   THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
 }
 
-template <class Executor>
-void ExecutionBlockImpl<Executor>::traceExecuteBegin(AqlCallStack const& stack) {
-  if (_profile >= PROFILE_LEVEL_BLOCKS) {
-    if (_getSomeBegin <= 0.0) {
-      _getSomeBegin = TRI_microtime();
-    }
-    if (_profile >= PROFILE_LEVEL_TRACE_1) {
-      auto const node = getPlanNode();
-      auto const queryId = this->_engine->getQuery()->id();
-      // TODO make sure this works also if stack is non relevant, e.g. passed through by outer subquery.
-      auto const& call = stack.peek();
-      LOG_TOPIC("1e717", INFO, Logger::QUERIES)
-          << "[query#" << queryId << "] "
-          << "execute type=" << node->getTypeString() << " call= " << call
-          << " this=" << (uintptr_t)this << " id=" << node->id();
-    }
-  }
-}
-
-template <class Executor>
-void ExecutionBlockImpl<Executor>::traceExecuteEnd(
-    std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> const& result) {
-  if (_profile >= PROFILE_LEVEL_BLOCKS) {
-    auto const& [state, skipped, block] = result;
-    auto const items = block != nullptr ? block->size() : 0;
-    ExecutionNode const* en = getPlanNode();
-    ExecutionStats::Node stats;
-    stats.calls = 1;
-    stats.items = skipped + items;
-    if (state != ExecutionState::WAITING) {
-      stats.runtime = TRI_microtime() - _getSomeBegin;
-      _getSomeBegin = 0.0;
-    }
-
-    auto it = _engine->_stats.nodes.find(en->id());
-    if (it != _engine->_stats.nodes.end()) {
-      it->second += stats;
-    } else {
-      _engine->_stats.nodes.emplace(en->id(), stats);
-    }
-
-    if (_profile >= PROFILE_LEVEL_TRACE_1) {
-      ExecutionNode const* node = getPlanNode();
-      auto const queryId = this->_engine->getQuery()->id();
-      LOG_TOPIC("60bbc", INFO, Logger::QUERIES)
-          << "[query#" << queryId << "] "
-          << "execute done type=" << node->getTypeString() << " this=" << (uintptr_t)this
-          << " id=" << node->id() << " state=" << stateToString(state)
-          << " skipped=" << skipped << " produced=" << items;
-
-      if (_profile >= PROFILE_LEVEL_TRACE_2) {
-        if (block == nullptr) {
-          LOG_TOPIC("9b3f4", INFO, Logger::QUERIES)
-              << "[query#" << queryId << "] "
-              << "execute type=" << node->getTypeString() << " result: nullptr";
-        } else {
-          VPackBuilder builder;
-          auto const options = trxVpackOptions();
-          block->toSimpleVPack(options, builder);
-          LOG_TOPIC("f12f9", INFO, Logger::QUERIES)
-              << "[query#" << queryId << "] "
-              << "execute type=" << node->getTypeString()
-              << " result: " << VPackDumper::toString(builder.slice(), options);
-        }
-      }
-    }
-  }
-}
-
 // Work around GCC bug: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=56480
 // Without the namespaces it fails with
 // error: specialization of 'template<class Executor> std::pair<arangodb::aql::ExecutionState, arangodb::Result> arangodb::aql::ExecutionBlockImpl<Executor>::initializeCursor(arangodb::aql::AqlItemBlock*, size_t)' in different namespace
@@ -1120,7 +1027,7 @@ static SkipRowsRangeVariant constexpr skipRowsType() {
   static_assert(!useFetcher || hasSkipRows<typename Executor::Fetcher>::value,
                 "Fetcher is chosen for skipping, but has not skipRows method!");
 
-  static_assert(useExecutor == (is_one_of_v<Executor, FilterExecutor, ShortestPathExecutor,
+  static_assert(useExecutor == (is_one_of_v<Executor, FilterExecutor, ShortestPathExecutor, ReturnExecutor,
 #ifdef ARANGODB_USE_GOOGLE_TESTS
                                             TestLambdaSkipExecutor,
 #endif
diff --git a/arangod/Aql/ExecutionBlockImpl.h b/arangod/Aql/ExecutionBlockImpl.h
index 5044e8f279b9..78f8f7392bcb 100644
--- a/arangod/Aql/ExecutionBlockImpl.h
+++ b/arangod/Aql/ExecutionBlockImpl.h
@@ -267,12 +267,6 @@ class ExecutionBlockImpl final : public ExecutionBlock {
 
   [[nodiscard]] ExecutionState fetchShadowRowInternal();
 
-  // Trace the start of a getSome call
-  void traceExecuteBegin(AqlCallStack const& stack);
-
-  // Trace the end of a getSome call, potentially with result
-  void traceExecuteEnd(std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> const& result);
-
   // Allocate an output block and install a call in it
   [[nodiscard]] auto allocateOutputBlock(AqlCall&& call)
       -> std::unique_ptr<OutputAqlItemRow>;
diff --git a/arangod/Aql/ExecutionEngine.cpp b/arangod/Aql/ExecutionEngine.cpp
index 5e162cfcfaed..77c0b16d3f83 100644
--- a/arangod/Aql/ExecutionEngine.cpp
+++ b/arangod/Aql/ExecutionEngine.cpp
@@ -760,3 +760,7 @@ RegisterId ExecutionEngine::resultRegister() const { return _resultRegister; }
 AqlItemBlockManager& ExecutionEngine::itemBlockManager() {
   return _itemBlockManager;
 }
+
+auto ExecutionEngine::getStats() const noexcept -> ExecutionStats const& {
+  return _stats;
+}
diff --git a/arangod/Aql/ExecutionEngine.h b/arangod/Aql/ExecutionEngine.h
index 92fb7ebc9e3a..d56feed72c41 100644
--- a/arangod/Aql/ExecutionEngine.h
+++ b/arangod/Aql/ExecutionEngine.h
@@ -118,6 +118,8 @@ class ExecutionEngine {
   /// @brief accessor to the memory recyler for AqlItemBlocks
   TEST_VIRTUAL AqlItemBlockManager& itemBlockManager();
 
+  auto getStats() const noexcept -> ExecutionStats const&;
+
  public:
   /// @brief execution statistics for the query
   /// note that the statistics are modification by execution blocks
diff --git a/arangod/Aql/ExecutionNode.cpp b/arangod/Aql/ExecutionNode.cpp
index e29f3e5a7ca3..2ef0d5475fdd 100644
--- a/arangod/Aql/ExecutionNode.cpp
+++ b/arangod/Aql/ExecutionNode.cpp
@@ -45,6 +45,7 @@
 #include "Aql/IndexNode.h"
 #include "Aql/KShortestPathsNode.h"
 #include "Aql/LimitExecutor.h"
+#include "Aql/MaterializeExecutor.h"
 #include "Aql/ModificationNodes.h"
 #include "Aql/NoResultsExecutor.h"
 #include "Aql/NodeFinder.h"
@@ -60,7 +61,6 @@
 #include "Aql/SubqueryStartExecutionNode.h"
 #include "Aql/TraversalNode.h"
 #include "Aql/WalkerWorker.h"
-#include "Aql/MaterializeExecutor.h"
 #include "Basics/VelocyPackHelper.h"
 #include "Basics/system-compiler.h"
 #include "Cluster/ServerState.h"
@@ -115,8 +115,7 @@ std::unordered_map<int, std::string const> const typeNames{
     {static_cast<int>(ExecutionNode::SUBQUERY_END), "SubqueryEndNode"},
     {static_cast<int>(ExecutionNode::DISTRIBUTE_CONSUMER),
      "DistributeConsumer"},
-    {static_cast<int>(ExecutionNode::MATERIALIZE),
-     "MaterializeNode"}};
+    {static_cast<int>(ExecutionNode::MATERIALIZE), "MaterializeNode"}};
 }  // namespace
 
 /// @brief resolve nodeType to a string.
@@ -460,7 +459,8 @@ ExecutionNode::ExecutionNode(ExecutionPlan* plan, VPackSlice const& slice)
     _varsValid.insert(oneVariable);
   }
 
-  _isInSplicedSubquery = VelocyPackHelper::getBooleanValue(slice, "isInSplicedSubquery", false);
+  _isInSplicedSubquery =
+      VelocyPackHelper::getBooleanValue(slice, "isInSplicedSubquery", false);
 }
 
 /// @brief toVelocyPack, export an ExecutionNode to VelocyPack
@@ -909,7 +909,6 @@ RegisterId ExecutionNode::varToRegUnchecked(Variable const& var) const {
   return reg;
 }
 
-
 bool ExecutionNode::isInSplicedSubquery() const noexcept {
   return _isInSplicedSubquery;
 }
@@ -1105,7 +1104,7 @@ std::vector<ExecutionNode*> ExecutionNode::getParents() const {
 }
 
 bool ExecutionNode::hasParent() const { return (_parents.size() == 1); }
-  
+
 /// @brief whether or not the node has any ancestor (parent at any distance)
 /// of this type
 bool ExecutionNode::hasParentOfType(ExecutionNode::NodeType type) const {
@@ -1350,8 +1349,10 @@ std::unique_ptr<ExecutionBlock> EnumerateCollectionNode::createBlock(
       variableToRegisterId(_outVariable),
       getRegisterPlan()->nrRegs[previousNode->getDepth()],
       getRegisterPlan()->nrRegs[getDepth()], getRegsToClear(), calcRegsToKeep(),
-      &engine, this->_collection, _outVariable, (this->isVarUsedLater(_outVariable) || this->_filter != nullptr),
-      this->_filter.get(), this->projections(), EngineSelectorFeature::ENGINE->useRawDocumentPointers(), this->_random);
+      &engine, this->_collection, _outVariable,
+      (this->isVarUsedLater(_outVariable) || this->_filter != nullptr),
+      this->_filter.get(), this->projections(),
+      EngineSelectorFeature::ENGINE->useRawDocumentPointers(), this->_random);
   return std::make_unique<ExecutionBlockImpl<EnumerateCollectionExecutor>>(&engine, this,
                                                                            std::move(infos));
 }
@@ -1401,7 +1402,7 @@ CostEstimate EnumerateCollectionNode::estimateCost() const {
   estimate.estimatedCost += estimate.estimatedNrItems * (_random ? 1.005 : 1.0) + 1.0;
   return estimate;
 }
-  
+
 EnumerateListNode::EnumerateListNode(ExecutionPlan* plan,
                                      arangodb::velocypack::Slice const& base)
     : ExecutionNode(plan, base),
@@ -1737,9 +1738,7 @@ CostEstimate CalculationNode::estimateCost() const {
 
 CalculationNode::CalculationNode(ExecutionPlan* plan, size_t id,
                                  std::unique_ptr<Expression> expr, Variable const* outVariable)
-    : ExecutionNode(plan, id),
-      _outVariable(outVariable),
-      _expression(std::move(expr)) {
+    : ExecutionNode(plan, id), _outVariable(outVariable), _expression(std::move(expr)) {
   TRI_ASSERT(_expression != nullptr);
   TRI_ASSERT(_outVariable != nullptr);
 }
@@ -2164,14 +2163,14 @@ std::unique_ptr<ExecutionBlock> ReturnNode::createBlock(
   // one register that is stored within the DOCVEC.
   RegisterId const numberInputRegisters =
       getRegisterPlan()->nrRegs[previousNode->getDepth()];
-  RegisterId const numberOutputRegisters =
-      returnInheritedResults ? getRegisterPlan()->nrRegs[getDepth()] : 1;
 
   if (returnInheritedResults) {
     return std::make_unique<ExecutionBlockImpl<IdExecutor<void>>>(&engine, this,
                                                                   inputRegister, _count);
   } else {
     TRI_ASSERT(!returnInheritedResults);
+    // The Return Executor only writes to register 0.
+    RegisterId const numberOutputRegisters = 1;
     ReturnExecutorInfos infos(inputRegister, numberInputRegisters,
                               numberOutputRegisters, _count);
 
@@ -2339,9 +2338,10 @@ namespace {
 const char* MATERIALIZE_NODE_IN_NM_COL_PARAM = "inNmColPtr";
 const char* MATERIALIZE_NODE_IN_NM_DOC_PARAM = "inNmDocId";
 const char* MATERIALIZE_NODE_OUT_VARIABLE_PARAM = "outVariable";
-}
+}  // namespace
 
-MaterializeNode* materialize::createMaterializeNode(ExecutionPlan* plan, arangodb::velocypack::Slice const& base) {
+MaterializeNode* materialize::createMaterializeNode(ExecutionPlan* plan,
+                                                    arangodb::velocypack::Slice const& base) {
   if (base.hasKey(MATERIALIZE_NODE_IN_NM_COL_PARAM)) {
     return new MaterializeMultiNode(plan, base);
   }
@@ -2349,14 +2349,17 @@ MaterializeNode* materialize::createMaterializeNode(ExecutionPlan* plan, arangod
 }
 
 MaterializeNode::MaterializeNode(ExecutionPlan* plan, size_t id,
-                                 aql::Variable const& inDocId,
-                                 aql::Variable const& outVariable)
-  : ExecutionNode(plan, id), _inNonMaterializedDocId(&inDocId), _outVariable(&outVariable) {}
+                                 aql::Variable const& inDocId, aql::Variable const& outVariable)
+    : ExecutionNode(plan, id),
+      _inNonMaterializedDocId(&inDocId),
+      _outVariable(&outVariable) {}
 
 MaterializeNode::MaterializeNode(ExecutionPlan* plan, arangodb::velocypack::Slice const& base)
-  : ExecutionNode(plan, base),
-    _inNonMaterializedDocId(aql::Variable::varFromVPack(plan->getAst(), base, MATERIALIZE_NODE_IN_NM_DOC_PARAM, true)),
-    _outVariable(aql::Variable::varFromVPack(plan->getAst(), base, MATERIALIZE_NODE_OUT_VARIABLE_PARAM)) {}
+    : ExecutionNode(plan, base),
+      _inNonMaterializedDocId(aql::Variable::varFromVPack(plan->getAst(), base, MATERIALIZE_NODE_IN_NM_DOC_PARAM,
+                                                          true)),
+      _outVariable(aql::Variable::varFromVPack(plan->getAst(), base,
+                                               MATERIALIZE_NODE_OUT_VARIABLE_PARAM)) {}
 
 void MaterializeNode::toVelocyPackHelper(arangodb::velocypack::Builder& nodes, unsigned flags,
                                          std::unordered_set<ExecutionNode const*>& seen) const {
@@ -2394,14 +2397,17 @@ MaterializeMultiNode::MaterializeMultiNode(ExecutionPlan* plan, size_t id,
                                            aql::Variable const& inColPtr,
                                            aql::Variable const& inDocId,
                                            aql::Variable const& outVariable)
-  : MaterializeNode(plan, id, inDocId, outVariable),
-    _inNonMaterializedColPtr(&inColPtr) {}
+    : MaterializeNode(plan, id, inDocId, outVariable),
+      _inNonMaterializedColPtr(&inColPtr) {}
 
-MaterializeMultiNode::MaterializeMultiNode(ExecutionPlan* plan, arangodb::velocypack::Slice const& base)
-  : MaterializeNode(plan, base),
-    _inNonMaterializedColPtr(aql::Variable::varFromVPack(plan->getAst(), base, MATERIALIZE_NODE_IN_NM_COL_PARAM, true)) {}
+MaterializeMultiNode::MaterializeMultiNode(ExecutionPlan* plan,
+                                           arangodb::velocypack::Slice const& base)
+    : MaterializeNode(plan, base),
+      _inNonMaterializedColPtr(aql::Variable::varFromVPack(plan->getAst(), base, MATERIALIZE_NODE_IN_NM_COL_PARAM,
+                                                           true)) {}
 
-void MaterializeMultiNode::toVelocyPackHelper(arangodb::velocypack::Builder& nodes, unsigned flags,
+void MaterializeMultiNode::toVelocyPackHelper(arangodb::velocypack::Builder& nodes,
+                                              unsigned flags,
                                               std::unordered_set<ExecutionNode const*>& seen) const {
   // call base class method
   MaterializeNode::toVelocyPackHelper(nodes, flags, seen);
@@ -2414,7 +2420,6 @@ void MaterializeMultiNode::toVelocyPackHelper(arangodb::velocypack::Builder& nod
 
 std::unique_ptr<ExecutionBlock> MaterializeMultiNode::createBlock(
     ExecutionEngine& engine, std::unordered_map<ExecutionNode*, ExecutionBlock*> const&) const {
-
   ExecutionNode const* previousNode = getFirstDependency();
   TRI_ASSERT(previousNode != nullptr);
 
@@ -2438,14 +2443,16 @@ std::unique_ptr<ExecutionBlock> MaterializeMultiNode::createBlock(
   }
   TRI_ASSERT(engine.getQuery());
 
-  return std::make_unique<ExecutionBlockImpl<MaterializeExecutor<decltype(inNmColPtrRegId)>>>(&engine, this,
-     MaterializerExecutorInfos(getRegisterPlan()->nrRegs[previousNode->getDepth()],
-                               getRegisterPlan()->nrRegs[getDepth()], getRegsToClear(),
-                               calcRegsToKeep(), inNmColPtrRegId, inNmDocIdRegId,
-                               outDocumentRegId, engine.getQuery()->trx()));
+  return std::make_unique<ExecutionBlockImpl<MaterializeExecutor<decltype(inNmColPtrRegId)>>>(
+      &engine, this,
+      MaterializerExecutorInfos(getRegisterPlan()->nrRegs[previousNode->getDepth()],
+                                getRegisterPlan()->nrRegs[getDepth()], getRegsToClear(),
+                                calcRegsToKeep(), inNmColPtrRegId, inNmDocIdRegId,
+                                outDocumentRegId, engine.getQuery()->trx()));
 }
 
-ExecutionNode* MaterializeMultiNode::clone(ExecutionPlan* plan, bool withDependencies, bool withProperties) const {
+ExecutionNode* MaterializeMultiNode::clone(ExecutionPlan* plan, bool withDependencies,
+                                           bool withProperties) const {
   TRI_ASSERT(plan);
 
   auto* outVariable = _outVariable;
@@ -2454,30 +2461,39 @@ ExecutionNode* MaterializeMultiNode::clone(ExecutionPlan* plan, bool withDepende
 
   if (withProperties) {
     outVariable = plan->getAst()->variables()->createVariable(outVariable);
-    inNonMaterializedDocId = plan->getAst()->variables()->createVariable(inNonMaterializedDocId);
-    inNonMaterializedColId = plan->getAst()->variables()->createVariable(inNonMaterializedColId);
+    inNonMaterializedDocId =
+        plan->getAst()->variables()->createVariable(inNonMaterializedDocId);
+    inNonMaterializedColId =
+        plan->getAst()->variables()->createVariable(inNonMaterializedColId);
   }
 
-  auto c = std::make_unique<MaterializeMultiNode>(plan, _id, *inNonMaterializedColId, *inNonMaterializedDocId, *outVariable);
+  auto c = std::make_unique<MaterializeMultiNode>(plan, _id, *inNonMaterializedColId,
+                                                  *inNonMaterializedDocId, *outVariable);
   return cloneHelper(std::move(c), withDependencies, withProperties);
 }
 
-void MaterializeMultiNode::getVariablesUsedHere(::arangodb::containers::HashSet<Variable const*>& vars) const {
+void MaterializeMultiNode::getVariablesUsedHere(
+    ::arangodb::containers::HashSet<Variable const*>& vars) const {
   // call base class method
   MaterializeNode::getVariablesUsedHere(vars);
 
   vars.emplace(_inNonMaterializedColPtr);
 }
 
-MaterializeSingleNode::MaterializeSingleNode(ExecutionPlan* plan, size_t id, aql::Collection const* collection,
-                                             aql::Variable const& inDocId, aql::Variable const& outVariable)
-  : MaterializeNode(plan, id, inDocId, outVariable), CollectionAccessingNode(collection) {}
+MaterializeSingleNode::MaterializeSingleNode(ExecutionPlan* plan, size_t id,
+                                             aql::Collection const* collection,
+                                             aql::Variable const& inDocId,
+                                             aql::Variable const& outVariable)
+    : MaterializeNode(plan, id, inDocId, outVariable),
+      CollectionAccessingNode(collection) {}
 
-MaterializeSingleNode::MaterializeSingleNode(ExecutionPlan* plan, arangodb::velocypack::Slice const& base)
-  : MaterializeNode(plan, base), CollectionAccessingNode(plan, base) {}
+MaterializeSingleNode::MaterializeSingleNode(ExecutionPlan* plan,
+                                             arangodb::velocypack::Slice const& base)
+    : MaterializeNode(plan, base), CollectionAccessingNode(plan, base) {}
 
-void MaterializeSingleNode::toVelocyPackHelper(arangodb::velocypack::Builder& nodes, unsigned flags,
-                                              std::unordered_set<ExecutionNode const*>& seen) const {
+void MaterializeSingleNode::toVelocyPackHelper(arangodb::velocypack::Builder& nodes,
+                                               unsigned flags,
+                                               std::unordered_set<ExecutionNode const*>& seen) const {
   // call base class method
   MaterializeNode::toVelocyPackHelper(nodes, flags, seen);
 
@@ -2489,7 +2505,6 @@ void MaterializeSingleNode::toVelocyPackHelper(arangodb::velocypack::Builder& no
 
 std::unique_ptr<ExecutionBlock> MaterializeSingleNode::createBlock(
     ExecutionEngine& engine, std::unordered_map<ExecutionNode*, ExecutionBlock*> const&) const {
-
   ExecutionNode const* previousNode = getFirstDependency();
   TRI_ASSERT(previousNode != nullptr);
   RegisterId inNmDocIdRegId;
@@ -2507,14 +2522,17 @@ std::unique_ptr<ExecutionBlock> MaterializeSingleNode::createBlock(
   TRI_ASSERT(engine.getQuery());
   auto const& name = _collection->name();
 
-  return std::make_unique<ExecutionBlockImpl<MaterializeExecutor<decltype(name)>>>(&engine, this,
-    MaterializerExecutorInfos<decltype(name)>(getRegisterPlan()->nrRegs[previousNode->getDepth()],
-                                              getRegisterPlan()->nrRegs[getDepth()], getRegsToClear(),
-                                              calcRegsToKeep(), _collection->name(), inNmDocIdRegId,
-                                              outDocumentRegId, engine.getQuery()->trx()));
+  return std::make_unique<ExecutionBlockImpl<MaterializeExecutor<decltype(name)>>>(
+      &engine, this,
+      MaterializerExecutorInfos<decltype(name)>(
+          getRegisterPlan()->nrRegs[previousNode->getDepth()],
+          getRegisterPlan()->nrRegs[getDepth()], getRegsToClear(),
+          calcRegsToKeep(), _collection->name(), inNmDocIdRegId,
+          outDocumentRegId, engine.getQuery()->trx()));
 }
 
-ExecutionNode* MaterializeSingleNode::clone(ExecutionPlan * plan, bool withDependencies, bool withProperties) const {
+ExecutionNode* MaterializeSingleNode::clone(ExecutionPlan* plan, bool withDependencies,
+                                            bool withProperties) const {
   TRI_ASSERT(plan);
 
   auto* outVariable = _outVariable;
@@ -2522,10 +2540,12 @@ ExecutionNode* MaterializeSingleNode::clone(ExecutionPlan * plan, bool withDepen
 
   if (withProperties) {
     outVariable = plan->getAst()->variables()->createVariable(outVariable);
-    inNonMaterializedDocId = plan->getAst()->variables()->createVariable(inNonMaterializedDocId);
+    inNonMaterializedDocId =
+        plan->getAst()->variables()->createVariable(inNonMaterializedDocId);
   }
 
-  auto c = std::make_unique<MaterializeSingleNode>(plan, _id, _collection, *inNonMaterializedDocId, *outVariable);
+  auto c = std::make_unique<MaterializeSingleNode>(plan, _id, _collection,
+                                                   *inNonMaterializedDocId, *outVariable);
   CollectionAccessingNode::cloneInto(*c);
   return cloneHelper(std::move(c), withDependencies, withProperties);
 }
diff --git a/arangod/Aql/FilterExecutor.cpp b/arangod/Aql/FilterExecutor.cpp
index bbe10b193e2e..ecb318423211 100644
--- a/arangod/Aql/FilterExecutor.cpp
+++ b/arangod/Aql/FilterExecutor.cpp
@@ -104,11 +104,9 @@ std::pair<ExecutionState, size_t> FilterExecutor::expectedNumberOfRows(size_t at
 // TODO Remove me, we are using the getSome skip variant here.
 std::tuple<ExecutorState, size_t, AqlCall> FilterExecutor::skipRowsRange(
     AqlItemBlockInputRange& inputRange, AqlCall& call) {
-  ExecutorState state = ExecutorState::HASMORE;
-  InputAqlItemRow input{CreateInvalidInputRowHint{}};
   size_t skipped = 0;
   while (inputRange.hasDataRow() && skipped < call.getOffset()) {
-    std::tie(state, input) = inputRange.nextDataRow();
+    auto const [unused, input] = inputRange.nextDataRow();
     if (!input) {
       TRI_ASSERT(!inputRange.hasDataRow());
       break;
@@ -121,7 +119,7 @@ std::tuple<ExecutorState, size_t, AqlCall> FilterExecutor::skipRowsRange(
 
   AqlCall upstreamCall{};
   upstreamCall.softLimit = call.getOffset();
-  return {state, skipped, upstreamCall};
+  return {inputRange.upstreamState(), skipped, upstreamCall};
 }
 
 std::tuple<ExecutorState, FilterStats, AqlCall> FilterExecutor::produceRows(
diff --git a/arangod/Aql/ReturnExecutor.cpp b/arangod/Aql/ReturnExecutor.cpp
index 4a03e876a74f..02c3dbd0ff0e 100644
--- a/arangod/Aql/ReturnExecutor.cpp
+++ b/arangod/Aql/ReturnExecutor.cpp
@@ -39,9 +39,83 @@ ReturnExecutorInfos::ReturnExecutorInfos(RegisterId inputRegister, RegisterId nr
                     std::unordered_set<RegisterId>{} /*to keep*/
                     ),
       _inputRegisterId(inputRegister),
-      _doCount(doCount) {}
+      _doCount(doCount) {
+  // For the time beeing return will only write to register 0.
+  // It is defined that it can only have exactly 1 output register.
+  // We can easily replace this by a different register, if we
+  // modify the caller within the ExecutionEngine to ask for the
+  // output register from outside.
+  TRI_ASSERT(nrOutputRegisters == 1);
+}
 
 ReturnExecutor::ReturnExecutor(Fetcher& fetcher, ReturnExecutorInfos& infos)
     : _infos(infos), _fetcher(fetcher) {}
 
 ReturnExecutor::~ReturnExecutor() = default;
+
+// TODO: @deprecated remove
+std::pair<ExecutionState, size_t> ReturnExecutor::expectedNumberOfRows(size_t atMost) const {
+  return _fetcher.preFetchNumberOfRows(atMost);
+}
+
+// TODO: @deprecated remove
+auto ReturnExecutor::produceRows(OutputAqlItemRow& output)
+    -> std::pair<ExecutionState, Stats> {
+  TRI_ASSERT(false);
+  THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
+}
+
+auto ReturnExecutor::skipRowsRange(AqlItemBlockInputRange& inputRange, AqlCall& call)
+    -> std::tuple<ExecutorState, size_t, AqlCall> {
+  TRI_IF_FAILURE("ReturnExecutor::produceRows") {
+    THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
+  }
+
+  while (inputRange.hasDataRow() && call.needSkipMore()) {
+    // I do not think that this is actually called.
+    // It will be called first to get the upstream-Call
+    // but this executor will always delegate the skipping
+    // to upstream.
+    TRI_ASSERT(false);
+    auto [state, input] = inputRange.nextDataRow();
+    TRI_ASSERT(input.isInitialized());
+    TRI_IF_FAILURE("ReturnBlock::getSome") {
+      THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
+    }
+    call.didSkip(1);
+    // TODO: do we need to include counted here?
+    /*
+    if (_infos.doCount()) {
+      stats.incrCounted();
+    }
+    */
+  }
+  return {inputRange.upstreamState(), call.getSkipCount(), call};
+}
+
+auto ReturnExecutor::produceRows(AqlItemBlockInputRange& inputRange, OutputAqlItemRow& output)
+    -> std::tuple<ExecutorState, Stats, AqlCall> {
+  TRI_IF_FAILURE("ReturnExecutor::produceRows") {
+    THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
+  }
+
+  Stats stats{};
+
+  while (inputRange.hasDataRow() && !output.isFull()) {
+    auto [state, input] = inputRange.nextDataRow();
+    TRI_ASSERT(input.isInitialized());
+    // REMARK: it is called `getInputRegisterId` here but FilterExecutor calls it `getInputRegister`.
+    AqlValue val = input.stealValue(_infos.getInputRegisterId());
+    AqlValueGuard guard(val, true);
+    TRI_IF_FAILURE("ReturnBlock::getSome") {
+      THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
+    }
+    output.moveValueInto(_infos.getOutputRegisterId(), input, guard);
+    output.advanceRow();
+    if (_infos.doCount()) {
+      stats.incrCounted();
+    }
+  }
+
+  return {inputRange.upstreamState(), stats, output.getClientCall()};
+}
diff --git a/arangod/Aql/ReturnExecutor.h b/arangod/Aql/ReturnExecutor.h
index a0841dd9f7a5..ec54f26898d0 100644
--- a/arangod/Aql/ReturnExecutor.h
+++ b/arangod/Aql/ReturnExecutor.h
@@ -94,38 +94,26 @@ class ReturnExecutor {
    * @return ExecutionState,
    *         if something was written output.hasValue() == true
    */
-  inline std::pair<ExecutionState, Stats> produceRows(OutputAqlItemRow& output) {
-    ExecutionState state;
-    ReturnExecutor::Stats stats;
-    InputAqlItemRow inputRow = InputAqlItemRow{CreateInvalidInputRowHint{}};
-    std::tie(state, inputRow) = _fetcher.fetchRow();
-
-    if (state == ExecutionState::WAITING) {
-      TRI_ASSERT(!inputRow);
-      return {state, stats};
-    }
-
-    if (!inputRow) {
-      TRI_ASSERT(state == ExecutionState::DONE);
-      return {state, stats};
-    }
-
-    AqlValue val = inputRow.stealValue(_infos.getInputRegisterId());
-    AqlValueGuard guard(val, true);
-    TRI_IF_FAILURE("ReturnBlock::getSome") {
-      THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
-    }
-    output.moveValueInto(_infos.getOutputRegisterId(), inputRow, guard);
-
-    if (_infos.doCount()) {
-      stats.incrCounted();
-    }
-    return {state, stats};
-  }
-
-  inline std::pair<ExecutionState, size_t> expectedNumberOfRows(size_t atMost) const {
-    return _fetcher.preFetchNumberOfRows(atMost);
-  }
+  auto produceRows(OutputAqlItemRow& output) -> std::pair<ExecutionState, Stats>;
+
+  /**
+   * @brief skip the next Rows of Aql Values.
+   *
+   * @return ExecutorState, the stats, and a new Call that needs to be send to upstream
+   */
+  [[nodiscard]] auto skipRowsRange(AqlItemBlockInputRange& input, AqlCall& call)
+      -> std::tuple<ExecutorState, size_t, AqlCall>;
+
+  /**
+   * @brief produce the next Rows of Aql Values.
+   *
+   * @return ExecutorState, the stats, and a new Call that needs to be send to upstream
+   */
+  [[nodiscard]] auto produceRows(AqlItemBlockInputRange& input, OutputAqlItemRow& output)
+      -> std::tuple<ExecutorState, Stats, AqlCall>;
+
+  [[nodiscard]] auto expectedNumberOfRows(size_t atMost) const
+      -> std::pair<ExecutionState, size_t>;
 
  private:
   ReturnExecutorInfos& _infos;
diff --git a/tests/Aql/ExecutorTestHelper.h b/tests/Aql/ExecutorTestHelper.h
index f90e3d7bf98d..0d5ffbb5f08c 100644
--- a/tests/Aql/ExecutorTestHelper.h
+++ b/tests/Aql/ExecutorTestHelper.h
@@ -53,6 +53,7 @@ struct ExecutorTestHelper {
   explicit ExecutorTestHelper(arangodb::aql::Query& query)
       : _expectedSkip{0},
         _expectedState{ExecutionState::HASMORE},
+        _testStats{false},
         _query(query),
         _dummyNode{std::make_unique<SingletonNode>(_query.plan(), 42)} {}
 
@@ -119,6 +120,12 @@ struct ExecutorTestHelper {
     return *this;
   }
 
+  auto expectedStats(ExecutionStats stats) -> ExecutorTestHelper& {
+    _expectedStats = stats;
+    _testStats = true;
+    return *this;
+  };
+
   auto run(typename E::Infos infos) -> void {
     ResourceMonitor monitor;
     AqlItemBlockManager itemBlockManager(&monitor, SerializationFormat::SHADOWROWS);
@@ -139,9 +146,10 @@ struct ExecutorTestHelper {
     SharedAqlItemBlockPtr expectedOutputBlock =
         buildBlock<outputColumns>(itemBlockManager, std::move(_output));
     testOutputBlock(result, expectedOutputBlock);
-
-    // ToDo:
-    // Test stats
+    if (_testStats) {
+      auto actualStats = _query.engine()->getStats();
+      EXPECT_EQ(actualStats, _expectedStats);
+    }
   };
 
  private:
@@ -219,6 +227,8 @@ struct ExecutorTestHelper {
   std::array<std::size_t, outputColumns> _outputRegisters;
   size_t _expectedSkip;
   ExecutionState _expectedState;
+  ExecutionStats _expectedStats;
+  bool _testStats;
 
   SplitType _inputSplit = {std::monostate()};
   SplitType _outputSplit = {std::monostate()};
diff --git a/tests/Aql/ReturnExecutorTest.cpp b/tests/Aql/ReturnExecutorTest.cpp
index 72ccfd962f9b..bf8dc3608fa3 100644
--- a/tests/Aql/ReturnExecutorTest.cpp
+++ b/tests/Aql/ReturnExecutorTest.cpp
@@ -20,11 +20,16 @@
 /// @author Jan Christoph Uhde
 ////////////////////////////////////////////////////////////////////////////////
 
-#include "RowFetcherHelper.h"
 #include "gtest/gtest.h"
 
+#include "ExecutorTestHelper.h"
+#include "RowFetcherHelper.h"
+
+#include "Mocks/Servers.h"
+
 #include "Aql/AqlItemBlock.h"
 #include "Aql/ExecutionBlockImpl.h"
+#include "Aql/ExecutionEngine.h"
 #include "Aql/ExecutorInfos.h"
 #include "Aql/InputAqlItemRow.h"
 #include "Aql/ResourceUsage.h"
@@ -41,139 +46,166 @@ namespace arangodb {
 namespace tests {
 namespace aql {
 
-class ReturnExecutorTest : public ::testing::Test {
+// This is only to get a split-type. The Type is independent of actual template parameters
+using ReturnExecutorTestHelper = ExecutorTestHelper<ReturnExecutor, 1, 1>;
+using ReturnExecutorSplitType = ReturnExecutorTestHelper::SplitType;
+using ReturnExecutorParamType = std::tuple<ReturnExecutorSplitType, bool>;
+
+class ReturnExecutorTest : public ::testing::TestWithParam<ReturnExecutorParamType> {
  protected:
-  ExecutionState state;
-  ResourceMonitor monitor;
+  // ExecutionState state;
+  ResourceMonitor monitor{};
+  mocks::MockAqlServer server{};
   AqlItemBlockManager itemBlockManager;
-  SharedAqlItemBlockPtr block;
-  std::shared_ptr<std::unordered_set<RegisterId>> registersToKeep;
-  RegisterId inputRegister;
+
+  std::unique_ptr<arangodb::aql::Query> fakedQuery;
 
   ReturnExecutorTest()
       : itemBlockManager(&monitor, SerializationFormat::SHADOWROWS),
-        block(new AqlItemBlock(itemBlockManager, 1000, 1)),
-        registersToKeep(make_shared_unordered_set()),
-        inputRegister(0) {}
+        fakedQuery(server.createFakeQuery()) {
+    auto engine =
+        std::make_unique<ExecutionEngine>(*fakedQuery, SerializationFormat::SHADOWROWS);
+    fakedQuery->setEngine(engine.release());
+  }
+
+  auto getSplit() -> ReturnExecutorSplitType {
+    auto [split, unused] = GetParam();
+    return split;
+  }
+
+  auto doCount() -> bool {
+    auto [unused, doCount] = GetParam();
+    return doCount;
+  }
+
+  auto getCountStats(size_t nr) -> ExecutionStats {
+    ExecutionStats stats;
+    if (doCount()) {
+      stats.count = nr;
+    }
+    return stats;
+  }
 };
 
-TEST_F(ReturnExecutorTest, NoRowsUpstreamProducerDoesNotWait) {
-  ReturnExecutorInfos infos(inputRegister, 1 /*nr in*/, 1 /*nr out*/, true /*do count*/);
-  auto const& outputRegisters = infos.getOutputRegisters();
-  VPackBuilder input;
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input.steal(), false);
-  ReturnExecutor testee(fetcher, infos);
-  CountStats stats{};
-
-  OutputAqlItemRow result(std::move(block), outputRegisters, registersToKeep,
-                          infos.registersToClear());
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(result.produced());
+template <size_t... vs>
+const ReturnExecutorSplitType splitIntoBlocks =
+    ReturnExecutorSplitType{std::vector<std::size_t>{vs...}};
+template <size_t step>
+const ReturnExecutorSplitType splitStep = ReturnExecutorSplitType{step};
+
+INSTANTIATE_TEST_CASE_P(ReturnExecutor, ReturnExecutorTest,
+                        ::testing::Combine(::testing::Values(splitIntoBlocks<2, 3>,
+                                                             splitIntoBlocks<3, 4>,
+                                                             splitStep<1>, splitStep<2>),
+                                           ::testing::Bool()));
+
+/*******
+ *  Start test suite
+ ******/
+
+/**
+ * @brief Test the most basic query.
+ *        We have an unlimited produce call
+ *        And the data is in register 0 => we expect it to
+ *        be passed through.
+ */
+
+TEST_P(ReturnExecutorTest, returns_all_from_upstream) {
+  ReturnExecutorInfos infos(0 /*input register*/, 1 /*nr in*/, 1 /*nr out*/, doCount());
+  AqlCall call{};  // unlimited produce
+  ExecutorTestHelper<ReturnExecutor>(*fakedQuery)
+      .setInputValueList(1, 2, 5, 2, 1, 5, 7, 1)
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({0}, {{1}, {2}, {5}, {2}, {1}, {5}, {7}, {1}})
+      .expectSkipped(0)
+      .expectedState(ExecutionState::DONE)
+      .expectedStats(getCountStats(8))
+      .run(std::move(infos));
 }
 
-TEST_F(ReturnExecutorTest, NoRowsUpstreamProducerWaits) {
-  ReturnExecutorInfos infos(inputRegister, 1 /*nr in*/, 1 /*nr out*/, true /*do count*/);
-  auto const& outputRegisters = infos.getOutputRegisters();
-  VPackBuilder input;
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input.steal(), true);
-  ReturnExecutor testee(fetcher, infos);
-  CountStats stats{};
-
-  OutputAqlItemRow result(std::move(block), outputRegisters, registersToKeep,
-                          infos.registersToClear());
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::WAITING);
-  ASSERT_FALSE(result.produced());
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(result.produced());
+TEST_P(ReturnExecutorTest, handle_soft_limit) {
+  ReturnExecutorInfos infos(0 /*input register*/, 1 /*nr in*/, 1 /*nr out*/, doCount());
+  AqlCall call{};
+  call.softLimit = 3;
+  ExecutorTestHelper<ReturnExecutor>(*fakedQuery)
+      .setInputValueList(1, 2, 5, 2, 1, 5, 7, 1)
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({0}, {{1}, {2}, {5}})
+      .expectSkipped(0)
+      .expectedState(ExecutionState::HASMORE)
+      .expectedStats(getCountStats(3))
+      .run(std::move(infos));
 }
 
-TEST_F(ReturnExecutorTest, RowsUpstreamProducerDoesNotWait) {
-  ReturnExecutorInfos infos(inputRegister, 1 /*nr in*/, 1 /*nr out*/, true /*do count*/);
-  auto const& outputRegisters = infos.getOutputRegisters();
-  auto input = VPackParser::fromJson("[ [true], [false], [true] ]");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->buffer(), false);
-  ReturnExecutor testee(fetcher, infos);
-  CountStats stats{};
-
-  OutputAqlItemRow row(std::move(block), outputRegisters, registersToKeep,
-                       infos.registersToClear());
-
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(row.produced());
-  row.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(row.produced());
-  row.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_TRUE(row.produced());
-  row.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(row.produced());
-
-  // verify result
-  AqlValue value;
-  auto block = row.stealBlock();
-  for (std::size_t index = 0; index < 3; index++) {
-    value = block->getValue(index, 0);
-    ASSERT_TRUE(value.isBoolean());
-    ASSERT_EQ(value.toBoolean(), input->slice().at(index).at(0).getBool());
-  }
+TEST_P(ReturnExecutorTest, handle_hard_limit) {
+  ReturnExecutorInfos infos(0 /*input register*/, 1 /*nr in*/, 1 /*nr out*/, doCount());
+  AqlCall call{};
+  call.hardLimit = 5;
+  ExecutorTestHelper<ReturnExecutor>(*fakedQuery)
+      .setInputValueList(1, 2, 5, 2, 1, 5, 7, 1)
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({0}, {{1}, {2}, {5}, {2}, {1}})
+      .expectSkipped(0)
+      .expectedState(ExecutionState::DONE)
+      .expectedStats(getCountStats(5))
+      .run(std::move(infos));
+}
+
+TEST_P(ReturnExecutorTest, handle_offset) {
+  ReturnExecutorInfos infos(0 /*input register*/, 1 /*nr in*/, 1 /*nr out*/, doCount());
+  AqlCall call{};
+  call.offset = 4;
+  ExecutorTestHelper<ReturnExecutor>(*fakedQuery)
+      .setInputValueList(1, 2, 5, 2, 1, 5, 7, 1)
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({0}, {{1}, {5}, {7}, {1}})
+      .expectSkipped(4)
+      .expectedState(ExecutionState::DONE)
+      .expectedStats(getCountStats(4))
+      .run(std::move(infos));
 }
 
-TEST_F(ReturnExecutorTest, RowsUpstreamProducerWaits) {
-  ReturnExecutorInfos infos(inputRegister, 1 /*nr in*/, 1 /*nr out*/, true /*do count*/);
-  auto const& outputRegisters = infos.getOutputRegisters();
-  auto input = VPackParser::fromJson("[ [true], [false], [true] ]");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), true);
-  ReturnExecutor testee(fetcher, infos);
-  CountStats stats{};
-
-  OutputAqlItemRow row{std::move(block), outputRegisters, registersToKeep,
-                       infos.registersToClear()};
-
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(state, ExecutionState::WAITING);
-  ASSERT_FALSE(row.produced());
-
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(row.produced());
-  row.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(state, ExecutionState::WAITING);
-  ASSERT_FALSE(row.produced());
-
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(row.produced());
-  row.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(state, ExecutionState::WAITING);
-  ASSERT_FALSE(row.produced());
-
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_TRUE(row.produced());
-  row.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(row.produced());
+TEST_P(ReturnExecutorTest, handle_fullcount) {
+  ReturnExecutorInfos infos(0 /*input register*/, 1 /*nr in*/, 1 /*nr out*/, doCount());
+  AqlCall call{};
+  call.hardLimit = 2;
+  call.fullCount = true;
+  ExecutorTestHelper<ReturnExecutor>(*fakedQuery)
+      .setInputValueList(1, 2, 5, 2, 1, 5, 7, 1)
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({0}, {{1}, {2}})
+      .expectSkipped(6)
+      .expectedState(ExecutionState::DONE)
+      .expectedStats(getCountStats(2))
+      .run(std::move(infos));
 }
 
+TEST_P(ReturnExecutorTest, handle_other_inputRegister) {
+  ReturnExecutorInfos infos(1 /*input register*/, 2 /*nr in*/, 1 /*nr out*/, doCount());
+  AqlCall call{};
+  call.hardLimit = 5;
+  ExecutorTestHelper<ReturnExecutor, 2, 1>(*fakedQuery)
+      .setInputValue({{R"("invalid")", 1},
+                      {R"("invalid")", 2},
+                      {R"("invalid")", 5},
+                      {R"("invalid")", 2},
+                      {R"("invalid")", 1},
+                      {R"("invalid")", 5},
+                      {R"("invalid")", 7},
+                      {R"("invalid")", 1}})
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({0}, {{1}, {2}, {5}, {2}, {1}})
+      .expectSkipped(0)
+      .expectedState(ExecutionState::DONE)
+      .expectedStats(getCountStats(5))
+      .run(std::move(infos));
+}
 }  // namespace aql
 }  // namespace tests
 }  // namespace arangodb
diff --git a/tests/Aql/WaitingExecutionBlockMock.cpp b/tests/Aql/WaitingExecutionBlockMock.cpp
index 00e56e4a07d7..4e1f9233ca7a 100644
--- a/tests/Aql/WaitingExecutionBlockMock.cpp
+++ b/tests/Aql/WaitingExecutionBlockMock.cpp
@@ -111,8 +111,16 @@ std::pair<arangodb::aql::ExecutionState, size_t> WaitingExecutionBlockMock::skip
   }
 }
 
-// NOTE: Does not care for shadowrows!
 std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> WaitingExecutionBlockMock::execute(AqlCallStack stack) {
+  traceExecuteBegin(stack);
+  auto res = executeWithoutTrace(stack);
+  traceExecuteEnd(res);
+  return res;
+}
+
+// NOTE: Does not care for shadowrows!
+std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> WaitingExecutionBlockMock::executeWithoutTrace(
+    AqlCallStack stack) {
   while (!stack.isRelevant()) {
     stack.pop();
   }
@@ -142,15 +150,16 @@ std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> WaitingExecutionBlockM
       skipped += canSkip;
       continue;
     } else if (myCall.getLimit() > 0) {
+      if (result != nullptr) {
+        // Sorry we can only return one block.
+        // This means we have prepared the first block.
+        // But still need more data.
+        return {ExecutionState::HASMORE, skipped, result};
+      }
+
       size_t canReturn = _data.front()->size() - _inflight;
 
       if (canReturn <= myCall.getLimit()) {
-        if (result != nullptr) {
-          // Sorry we can only return one block.
-          // This means we have prepared the first block.
-          // But still need more data.
-          return {ExecutionState::HASMORE, skipped, result};
-        }
         // We can return the remainder of this block
         if (_inflight == 0) {
           // use full block
diff --git a/tests/Aql/WaitingExecutionBlockMock.h b/tests/Aql/WaitingExecutionBlockMock.h
index 3234060d7936..a66c3a913b4e 100644
--- a/tests/Aql/WaitingExecutionBlockMock.h
+++ b/tests/Aql/WaitingExecutionBlockMock.h
@@ -112,6 +112,10 @@ class WaitingExecutionBlockMock final : public arangodb::aql::ExecutionBlock {
  private:
   void dropBlock();
 
+  // Implementation of execute
+  std::tuple<arangodb::aql::ExecutionState, size_t, arangodb::aql::SharedAqlItemBlockPtr> executeWithoutTrace(
+      arangodb::aql::AqlCallStack stack);
+
  private:
   std::deque<arangodb::aql::SharedAqlItemBlockPtr> _data;
   arangodb::aql::ResourceMonitor _resourceMonitor;

From 6359f0c926cad30b4efd7ce263fb3b64563621b8 Mon Sep 17 00:00:00 2001
From: Markus Pfeiffer <markus@arangodb.com>
Date: Wed, 12 Feb 2020 14:40:20 +0000
Subject: [PATCH 059/122] Tweak ExecutorTestHelper to test pipelines

---
 tests/Aql/ExecutorTestHelper.h          | 29 ++++++++++++++++------
 tests/Aql/ReturnExecutorTest.cpp        | 32 +++++++++++++++----------
 tests/Aql/SortedCollectExecutorTest.cpp | 13 ++++++----
 3 files changed, 49 insertions(+), 25 deletions(-)

diff --git a/tests/Aql/ExecutorTestHelper.h b/tests/Aql/ExecutorTestHelper.h
index 0d5ffbb5f08c..64d7c0554f6b 100644
--- a/tests/Aql/ExecutorTestHelper.h
+++ b/tests/Aql/ExecutorTestHelper.h
@@ -44,7 +44,14 @@ namespace arangodb {
 namespace tests {
 namespace aql {
 
-template <typename E, std::size_t inputColumns = 1, std::size_t outputColumns = 1>
+using ExecBlock = std::shared_ptr<ExecutionBlock>;
+
+// TODO: this could also just be a pair of exec blocks (front and back of the pipeline)
+//       because the deque is defined by the dependencies (and this way we can depend on
+//       more than one ExecBlock)
+using Pipeline = std::deque<ExecBlock>;
+
+template <std::size_t inputColumns = 1, std::size_t outputColumns = 1>
 struct ExecutorTestHelper {
   using SplitType = std::variant<std::vector<std::size_t>, std::size_t, std::monostate>;
 
@@ -124,9 +131,17 @@ struct ExecutorTestHelper {
     _expectedStats = stats;
     _testStats = true;
     return *this;
-  };
+  }
+
+  template <typename E>
+  auto setExecBlock(typename E::Infos infos) -> ExecutorTestHelper& {
+    auto testeeNode = std::make_unique<SingletonNode>(_query.plan(), 1);
+    _testee = std::make_unique<ExecutionBlockImpl<E>>(_query.engine(),
+                                                      testeeNode.get(), std::move(infos));
+    return *this;
+  }
 
-  auto run(typename E::Infos infos) -> void {
+  auto run() -> void {
     ResourceMonitor monitor;
     AqlItemBlockManager itemBlockManager(&monitor, SerializationFormat::SHADOWROWS);
 
@@ -134,11 +149,10 @@ struct ExecutorTestHelper {
 
     auto testeeNode = std::make_unique<SingletonNode>(_query.plan(), 1);
 
-    ExecutionBlockImpl<E> testee{_query.engine(), testeeNode.get(), std::move(infos)};
-    testee.addDependency(inputBlock.get());
+    _testee->addDependency(inputBlock.get());
 
     AqlCallStack stack{_call};
-    auto const [state, skipped, result] = testee.execute(stack);
+    auto const [state, skipped, result] = _testee->execute(stack);
     EXPECT_EQ(skipped, _expectedSkip);
 
     EXPECT_EQ(state, _expectedState);
@@ -235,6 +249,7 @@ struct ExecutorTestHelper {
 
   arangodb::aql::Query& _query;
   std::unique_ptr<arangodb::aql::ExecutionNode> _dummyNode;
+  ExecBlock _testee;
 };
 
 enum class ExecutorCall {
@@ -256,7 +271,7 @@ using ExecutorStepResult = std::tuple<ExecutorCall, arangodb::aql::ExecutionStat
 //  somehow optional. e.g. call a templated function or so.
 // TODO Add calls to expectedNumberOfRows
 
-template <class Executor>
+template <typename Executor>
 std::tuple<arangodb::aql::SharedAqlItemBlockPtr, std::vector<ExecutorStepResult>, arangodb::aql::ExecutionStats>
 runExecutor(arangodb::aql::AqlItemBlockManager& manager, Executor& executor,
             arangodb::aql::OutputAqlItemRow& outputRow, size_t const numSkip,
diff --git a/tests/Aql/ReturnExecutorTest.cpp b/tests/Aql/ReturnExecutorTest.cpp
index bf8dc3608fa3..7fb106efd822 100644
--- a/tests/Aql/ReturnExecutorTest.cpp
+++ b/tests/Aql/ReturnExecutorTest.cpp
@@ -47,7 +47,7 @@ namespace tests {
 namespace aql {
 
 // This is only to get a split-type. The Type is independent of actual template parameters
-using ReturnExecutorTestHelper = ExecutorTestHelper<ReturnExecutor, 1, 1>;
+using ReturnExecutorTestHelper = ExecutorTestHelper<1, 1>;
 using ReturnExecutorSplitType = ReturnExecutorTestHelper::SplitType;
 using ReturnExecutorParamType = std::tuple<ReturnExecutorSplitType, bool>;
 
@@ -113,7 +113,8 @@ INSTANTIATE_TEST_CASE_P(ReturnExecutor, ReturnExecutorTest,
 TEST_P(ReturnExecutorTest, returns_all_from_upstream) {
   ReturnExecutorInfos infos(0 /*input register*/, 1 /*nr in*/, 1 /*nr out*/, doCount());
   AqlCall call{};  // unlimited produce
-  ExecutorTestHelper<ReturnExecutor>(*fakedQuery)
+  ExecutorTestHelper(*fakedQuery)
+      .setExecBlock<ReturnExecutor>(std::move(infos))
       .setInputValueList(1, 2, 5, 2, 1, 5, 7, 1)
       .setInputSplitType(getSplit())
       .setCall(call)
@@ -121,14 +122,15 @@ TEST_P(ReturnExecutorTest, returns_all_from_upstream) {
       .expectSkipped(0)
       .expectedState(ExecutionState::DONE)
       .expectedStats(getCountStats(8))
-      .run(std::move(infos));
+      .run();
 }
 
 TEST_P(ReturnExecutorTest, handle_soft_limit) {
   ReturnExecutorInfos infos(0 /*input register*/, 1 /*nr in*/, 1 /*nr out*/, doCount());
   AqlCall call{};
   call.softLimit = 3;
-  ExecutorTestHelper<ReturnExecutor>(*fakedQuery)
+  ExecutorTestHelper(*fakedQuery)
+      .setExecBlock<ReturnExecutor>(std::move(infos))
       .setInputValueList(1, 2, 5, 2, 1, 5, 7, 1)
       .setInputSplitType(getSplit())
       .setCall(call)
@@ -136,14 +138,15 @@ TEST_P(ReturnExecutorTest, handle_soft_limit) {
       .expectSkipped(0)
       .expectedState(ExecutionState::HASMORE)
       .expectedStats(getCountStats(3))
-      .run(std::move(infos));
+      .run();
 }
 
 TEST_P(ReturnExecutorTest, handle_hard_limit) {
   ReturnExecutorInfos infos(0 /*input register*/, 1 /*nr in*/, 1 /*nr out*/, doCount());
   AqlCall call{};
   call.hardLimit = 5;
-  ExecutorTestHelper<ReturnExecutor>(*fakedQuery)
+  ExecutorTestHelper(*fakedQuery)
+      .setExecBlock<ReturnExecutor>(std::move(infos))
       .setInputValueList(1, 2, 5, 2, 1, 5, 7, 1)
       .setInputSplitType(getSplit())
       .setCall(call)
@@ -151,14 +154,15 @@ TEST_P(ReturnExecutorTest, handle_hard_limit) {
       .expectSkipped(0)
       .expectedState(ExecutionState::DONE)
       .expectedStats(getCountStats(5))
-      .run(std::move(infos));
+      .run();
 }
 
 TEST_P(ReturnExecutorTest, handle_offset) {
   ReturnExecutorInfos infos(0 /*input register*/, 1 /*nr in*/, 1 /*nr out*/, doCount());
   AqlCall call{};
   call.offset = 4;
-  ExecutorTestHelper<ReturnExecutor>(*fakedQuery)
+  ExecutorTestHelper(*fakedQuery)
+      .setExecBlock<ReturnExecutor>(std::move(infos))
       .setInputValueList(1, 2, 5, 2, 1, 5, 7, 1)
       .setInputSplitType(getSplit())
       .setCall(call)
@@ -166,7 +170,7 @@ TEST_P(ReturnExecutorTest, handle_offset) {
       .expectSkipped(4)
       .expectedState(ExecutionState::DONE)
       .expectedStats(getCountStats(4))
-      .run(std::move(infos));
+      .run();
 }
 
 TEST_P(ReturnExecutorTest, handle_fullcount) {
@@ -174,7 +178,8 @@ TEST_P(ReturnExecutorTest, handle_fullcount) {
   AqlCall call{};
   call.hardLimit = 2;
   call.fullCount = true;
-  ExecutorTestHelper<ReturnExecutor>(*fakedQuery)
+  ExecutorTestHelper(*fakedQuery)
+      .setExecBlock<ReturnExecutor>(std::move(infos))
       .setInputValueList(1, 2, 5, 2, 1, 5, 7, 1)
       .setInputSplitType(getSplit())
       .setCall(call)
@@ -182,14 +187,15 @@ TEST_P(ReturnExecutorTest, handle_fullcount) {
       .expectSkipped(6)
       .expectedState(ExecutionState::DONE)
       .expectedStats(getCountStats(2))
-      .run(std::move(infos));
+      .run();
 }
 
 TEST_P(ReturnExecutorTest, handle_other_inputRegister) {
   ReturnExecutorInfos infos(1 /*input register*/, 2 /*nr in*/, 1 /*nr out*/, doCount());
   AqlCall call{};
   call.hardLimit = 5;
-  ExecutorTestHelper<ReturnExecutor, 2, 1>(*fakedQuery)
+  ExecutorTestHelper<2, 1>(*fakedQuery)
+      .setExecBlock<ReturnExecutor>(std::move(infos))
       .setInputValue({{R"("invalid")", 1},
                       {R"("invalid")", 2},
                       {R"("invalid")", 5},
@@ -204,7 +210,7 @@ TEST_P(ReturnExecutorTest, handle_other_inputRegister) {
       .expectSkipped(0)
       .expectedState(ExecutionState::DONE)
       .expectedStats(getCountStats(5))
-      .run(std::move(infos));
+      .run();
 }
 }  // namespace aql
 }  // namespace tests
diff --git a/tests/Aql/SortedCollectExecutorTest.cpp b/tests/Aql/SortedCollectExecutorTest.cpp
index c267ab80c092..d5c91548df29 100644
--- a/tests/Aql/SortedCollectExecutorTest.cpp
+++ b/tests/Aql/SortedCollectExecutorTest.cpp
@@ -913,7 +913,7 @@ TEST_F(SortedCollectExecutorTestSkip, skip_5) {
   }
 }
 
-using SortedCollectTestHelper = ExecutorTestHelper<SortedCollectExecutor, 1, 1>;
+using SortedCollectTestHelper = ExecutorTestHelper<1, 1>;
 using SortedCollectSplitType = SortedCollectTestHelper::SplitType;
 
 class SortedCollectExecutorTestSplit
@@ -980,40 +980,43 @@ class SortedCollectExecutorTestSplit
 TEST_P(SortedCollectExecutorTestSplit, split_1) {
   auto [split] = GetParam();
 
-  ExecutorTestHelper<SortedCollectExecutor>(*fakedQuery)
+  ExecutorTestHelper(*fakedQuery)
+      .setExecBlock<SortedCollectExecutor>(std::move(infos))
       .setInputValueList(1, 1, 1, 2, 3, 4, 4, 5)
       .setInputSplitType(split)
       .setCall(AqlCall{2, AqlCall::Infinity{}, 2, true})
       .expectOutputValueList(3, 4)
       .expectSkipped(3)
       .expectedState(ExecutionState::DONE)
-      .run(std::move(infos));
+      .run();
 }
 
 TEST_P(SortedCollectExecutorTestSplit, split_2) {
   auto [split] = GetParam();
 
   ExecutorTestHelper<SortedCollectExecutor>(*fakedQuery)
+      .setExecBlock<SortedCollectExecutor>(std::move(infos))
       .setInputValueList(1, 1, 1, 2, 3, 4, 4, 5)
       .setInputSplitType(split)
       .setCall(AqlCall{2, 2, AqlCall::Infinity{}, false})
       .expectOutputValueList(3, 4)
       .expectSkipped(2)
       .expectedState(ExecutionState::HASMORE)
-      .run(std::move(infos));
+      .run();
 }
 
 TEST_P(SortedCollectExecutorTestSplit, split_3) {
   auto [split] = GetParam();
 
   ExecutorTestHelper<SortedCollectExecutor>(*fakedQuery)
+      .setExecBlock<SortedCollectExecutor>(std::move(infos))
       .setInputValueList(1, 2, 3, 4, 5)
       .setInputSplitType(split)
       .setCall(AqlCall{1, AqlCall::Infinity{}, 10, true})
       .expectOutputValueList(2, 3, 4, 5)
       .expectSkipped(1)
       .expectedState(ExecutionState::DONE)
-      .run(std::move(infos));
+      .run();
 }
 
 template<size_t... vs>

From c509e18ce62dca27778ac969f5c8c67ec711d697 Mon Sep 17 00:00:00 2001
From: Markus Pfeiffer <markus@arangodb.com>
Date: Wed, 12 Feb 2020 14:44:54 +0000
Subject: [PATCH 060/122] Revert "Tweak ExecutorTestHelper to test pipelines"

This reverts commit 6359f0c926cad30b4efd7ce263fb3b64563621b8.
---
 tests/Aql/ExecutorTestHelper.h          | 29 ++++++----------------
 tests/Aql/ReturnExecutorTest.cpp        | 32 ++++++++++---------------
 tests/Aql/SortedCollectExecutorTest.cpp | 13 ++++------
 3 files changed, 25 insertions(+), 49 deletions(-)

diff --git a/tests/Aql/ExecutorTestHelper.h b/tests/Aql/ExecutorTestHelper.h
index 64d7c0554f6b..0d5ffbb5f08c 100644
--- a/tests/Aql/ExecutorTestHelper.h
+++ b/tests/Aql/ExecutorTestHelper.h
@@ -44,14 +44,7 @@ namespace arangodb {
 namespace tests {
 namespace aql {
 
-using ExecBlock = std::shared_ptr<ExecutionBlock>;
-
-// TODO: this could also just be a pair of exec blocks (front and back of the pipeline)
-//       because the deque is defined by the dependencies (and this way we can depend on
-//       more than one ExecBlock)
-using Pipeline = std::deque<ExecBlock>;
-
-template <std::size_t inputColumns = 1, std::size_t outputColumns = 1>
+template <typename E, std::size_t inputColumns = 1, std::size_t outputColumns = 1>
 struct ExecutorTestHelper {
   using SplitType = std::variant<std::vector<std::size_t>, std::size_t, std::monostate>;
 
@@ -131,17 +124,9 @@ struct ExecutorTestHelper {
     _expectedStats = stats;
     _testStats = true;
     return *this;
-  }
-
-  template <typename E>
-  auto setExecBlock(typename E::Infos infos) -> ExecutorTestHelper& {
-    auto testeeNode = std::make_unique<SingletonNode>(_query.plan(), 1);
-    _testee = std::make_unique<ExecutionBlockImpl<E>>(_query.engine(),
-                                                      testeeNode.get(), std::move(infos));
-    return *this;
-  }
+  };
 
-  auto run() -> void {
+  auto run(typename E::Infos infos) -> void {
     ResourceMonitor monitor;
     AqlItemBlockManager itemBlockManager(&monitor, SerializationFormat::SHADOWROWS);
 
@@ -149,10 +134,11 @@ struct ExecutorTestHelper {
 
     auto testeeNode = std::make_unique<SingletonNode>(_query.plan(), 1);
 
-    _testee->addDependency(inputBlock.get());
+    ExecutionBlockImpl<E> testee{_query.engine(), testeeNode.get(), std::move(infos)};
+    testee.addDependency(inputBlock.get());
 
     AqlCallStack stack{_call};
-    auto const [state, skipped, result] = _testee->execute(stack);
+    auto const [state, skipped, result] = testee.execute(stack);
     EXPECT_EQ(skipped, _expectedSkip);
 
     EXPECT_EQ(state, _expectedState);
@@ -249,7 +235,6 @@ struct ExecutorTestHelper {
 
   arangodb::aql::Query& _query;
   std::unique_ptr<arangodb::aql::ExecutionNode> _dummyNode;
-  ExecBlock _testee;
 };
 
 enum class ExecutorCall {
@@ -271,7 +256,7 @@ using ExecutorStepResult = std::tuple<ExecutorCall, arangodb::aql::ExecutionStat
 //  somehow optional. e.g. call a templated function or so.
 // TODO Add calls to expectedNumberOfRows
 
-template <typename Executor>
+template <class Executor>
 std::tuple<arangodb::aql::SharedAqlItemBlockPtr, std::vector<ExecutorStepResult>, arangodb::aql::ExecutionStats>
 runExecutor(arangodb::aql::AqlItemBlockManager& manager, Executor& executor,
             arangodb::aql::OutputAqlItemRow& outputRow, size_t const numSkip,
diff --git a/tests/Aql/ReturnExecutorTest.cpp b/tests/Aql/ReturnExecutorTest.cpp
index 7fb106efd822..bf8dc3608fa3 100644
--- a/tests/Aql/ReturnExecutorTest.cpp
+++ b/tests/Aql/ReturnExecutorTest.cpp
@@ -47,7 +47,7 @@ namespace tests {
 namespace aql {
 
 // This is only to get a split-type. The Type is independent of actual template parameters
-using ReturnExecutorTestHelper = ExecutorTestHelper<1, 1>;
+using ReturnExecutorTestHelper = ExecutorTestHelper<ReturnExecutor, 1, 1>;
 using ReturnExecutorSplitType = ReturnExecutorTestHelper::SplitType;
 using ReturnExecutorParamType = std::tuple<ReturnExecutorSplitType, bool>;
 
@@ -113,8 +113,7 @@ INSTANTIATE_TEST_CASE_P(ReturnExecutor, ReturnExecutorTest,
 TEST_P(ReturnExecutorTest, returns_all_from_upstream) {
   ReturnExecutorInfos infos(0 /*input register*/, 1 /*nr in*/, 1 /*nr out*/, doCount());
   AqlCall call{};  // unlimited produce
-  ExecutorTestHelper(*fakedQuery)
-      .setExecBlock<ReturnExecutor>(std::move(infos))
+  ExecutorTestHelper<ReturnExecutor>(*fakedQuery)
       .setInputValueList(1, 2, 5, 2, 1, 5, 7, 1)
       .setInputSplitType(getSplit())
       .setCall(call)
@@ -122,15 +121,14 @@ TEST_P(ReturnExecutorTest, returns_all_from_upstream) {
       .expectSkipped(0)
       .expectedState(ExecutionState::DONE)
       .expectedStats(getCountStats(8))
-      .run();
+      .run(std::move(infos));
 }
 
 TEST_P(ReturnExecutorTest, handle_soft_limit) {
   ReturnExecutorInfos infos(0 /*input register*/, 1 /*nr in*/, 1 /*nr out*/, doCount());
   AqlCall call{};
   call.softLimit = 3;
-  ExecutorTestHelper(*fakedQuery)
-      .setExecBlock<ReturnExecutor>(std::move(infos))
+  ExecutorTestHelper<ReturnExecutor>(*fakedQuery)
       .setInputValueList(1, 2, 5, 2, 1, 5, 7, 1)
       .setInputSplitType(getSplit())
       .setCall(call)
@@ -138,15 +136,14 @@ TEST_P(ReturnExecutorTest, handle_soft_limit) {
       .expectSkipped(0)
       .expectedState(ExecutionState::HASMORE)
       .expectedStats(getCountStats(3))
-      .run();
+      .run(std::move(infos));
 }
 
 TEST_P(ReturnExecutorTest, handle_hard_limit) {
   ReturnExecutorInfos infos(0 /*input register*/, 1 /*nr in*/, 1 /*nr out*/, doCount());
   AqlCall call{};
   call.hardLimit = 5;
-  ExecutorTestHelper(*fakedQuery)
-      .setExecBlock<ReturnExecutor>(std::move(infos))
+  ExecutorTestHelper<ReturnExecutor>(*fakedQuery)
       .setInputValueList(1, 2, 5, 2, 1, 5, 7, 1)
       .setInputSplitType(getSplit())
       .setCall(call)
@@ -154,15 +151,14 @@ TEST_P(ReturnExecutorTest, handle_hard_limit) {
       .expectSkipped(0)
       .expectedState(ExecutionState::DONE)
       .expectedStats(getCountStats(5))
-      .run();
+      .run(std::move(infos));
 }
 
 TEST_P(ReturnExecutorTest, handle_offset) {
   ReturnExecutorInfos infos(0 /*input register*/, 1 /*nr in*/, 1 /*nr out*/, doCount());
   AqlCall call{};
   call.offset = 4;
-  ExecutorTestHelper(*fakedQuery)
-      .setExecBlock<ReturnExecutor>(std::move(infos))
+  ExecutorTestHelper<ReturnExecutor>(*fakedQuery)
       .setInputValueList(1, 2, 5, 2, 1, 5, 7, 1)
       .setInputSplitType(getSplit())
       .setCall(call)
@@ -170,7 +166,7 @@ TEST_P(ReturnExecutorTest, handle_offset) {
       .expectSkipped(4)
       .expectedState(ExecutionState::DONE)
       .expectedStats(getCountStats(4))
-      .run();
+      .run(std::move(infos));
 }
 
 TEST_P(ReturnExecutorTest, handle_fullcount) {
@@ -178,8 +174,7 @@ TEST_P(ReturnExecutorTest, handle_fullcount) {
   AqlCall call{};
   call.hardLimit = 2;
   call.fullCount = true;
-  ExecutorTestHelper(*fakedQuery)
-      .setExecBlock<ReturnExecutor>(std::move(infos))
+  ExecutorTestHelper<ReturnExecutor>(*fakedQuery)
       .setInputValueList(1, 2, 5, 2, 1, 5, 7, 1)
       .setInputSplitType(getSplit())
       .setCall(call)
@@ -187,15 +182,14 @@ TEST_P(ReturnExecutorTest, handle_fullcount) {
       .expectSkipped(6)
       .expectedState(ExecutionState::DONE)
       .expectedStats(getCountStats(2))
-      .run();
+      .run(std::move(infos));
 }
 
 TEST_P(ReturnExecutorTest, handle_other_inputRegister) {
   ReturnExecutorInfos infos(1 /*input register*/, 2 /*nr in*/, 1 /*nr out*/, doCount());
   AqlCall call{};
   call.hardLimit = 5;
-  ExecutorTestHelper<2, 1>(*fakedQuery)
-      .setExecBlock<ReturnExecutor>(std::move(infos))
+  ExecutorTestHelper<ReturnExecutor, 2, 1>(*fakedQuery)
       .setInputValue({{R"("invalid")", 1},
                       {R"("invalid")", 2},
                       {R"("invalid")", 5},
@@ -210,7 +204,7 @@ TEST_P(ReturnExecutorTest, handle_other_inputRegister) {
       .expectSkipped(0)
       .expectedState(ExecutionState::DONE)
       .expectedStats(getCountStats(5))
-      .run();
+      .run(std::move(infos));
 }
 }  // namespace aql
 }  // namespace tests
diff --git a/tests/Aql/SortedCollectExecutorTest.cpp b/tests/Aql/SortedCollectExecutorTest.cpp
index d5c91548df29..c267ab80c092 100644
--- a/tests/Aql/SortedCollectExecutorTest.cpp
+++ b/tests/Aql/SortedCollectExecutorTest.cpp
@@ -913,7 +913,7 @@ TEST_F(SortedCollectExecutorTestSkip, skip_5) {
   }
 }
 
-using SortedCollectTestHelper = ExecutorTestHelper<1, 1>;
+using SortedCollectTestHelper = ExecutorTestHelper<SortedCollectExecutor, 1, 1>;
 using SortedCollectSplitType = SortedCollectTestHelper::SplitType;
 
 class SortedCollectExecutorTestSplit
@@ -980,43 +980,40 @@ class SortedCollectExecutorTestSplit
 TEST_P(SortedCollectExecutorTestSplit, split_1) {
   auto [split] = GetParam();
 
-  ExecutorTestHelper(*fakedQuery)
-      .setExecBlock<SortedCollectExecutor>(std::move(infos))
+  ExecutorTestHelper<SortedCollectExecutor>(*fakedQuery)
       .setInputValueList(1, 1, 1, 2, 3, 4, 4, 5)
       .setInputSplitType(split)
       .setCall(AqlCall{2, AqlCall::Infinity{}, 2, true})
       .expectOutputValueList(3, 4)
       .expectSkipped(3)
       .expectedState(ExecutionState::DONE)
-      .run();
+      .run(std::move(infos));
 }
 
 TEST_P(SortedCollectExecutorTestSplit, split_2) {
   auto [split] = GetParam();
 
   ExecutorTestHelper<SortedCollectExecutor>(*fakedQuery)
-      .setExecBlock<SortedCollectExecutor>(std::move(infos))
       .setInputValueList(1, 1, 1, 2, 3, 4, 4, 5)
       .setInputSplitType(split)
       .setCall(AqlCall{2, 2, AqlCall::Infinity{}, false})
       .expectOutputValueList(3, 4)
       .expectSkipped(2)
       .expectedState(ExecutionState::HASMORE)
-      .run();
+      .run(std::move(infos));
 }
 
 TEST_P(SortedCollectExecutorTestSplit, split_3) {
   auto [split] = GetParam();
 
   ExecutorTestHelper<SortedCollectExecutor>(*fakedQuery)
-      .setExecBlock<SortedCollectExecutor>(std::move(infos))
       .setInputValueList(1, 2, 3, 4, 5)
       .setInputSplitType(split)
       .setCall(AqlCall{1, AqlCall::Infinity{}, 10, true})
       .expectOutputValueList(2, 3, 4, 5)
       .expectSkipped(1)
       .expectedState(ExecutionState::DONE)
-      .run();
+      .run(std::move(infos));
 }
 
 template<size_t... vs>

From 94da545713ef5c851e76655cbcbcaff74ec1beaf Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Thu, 13 Feb 2020 08:12:13 +0100
Subject: [PATCH 061/122] Added Stats return value to skipRowsRange (#11081)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

* Added Stats return value to skipRowsRange

* Fixed catch test. Somehow i merged the incorrect part

Co-authored-by: Tobias Gödderz <github@tobias.goedderz.info>
---
 arangod/Aql/ExecutionBlockImpl.cpp      | 26 +++++++++-----
 arangod/Aql/ExecutionBlockImpl.h        |  4 +--
 arangod/Aql/FilterExecutor.cpp          | 13 ++++---
 arangod/Aql/FilterExecutor.h            |  4 +--
 arangod/Aql/LimitExecutor.cpp           | 11 +++---
 arangod/Aql/ReturnExecutor.cpp          |  9 ++---
 arangod/Aql/ReturnExecutor.h            |  2 +-
 arangod/Aql/ShortestPathExecutor.cpp    |  6 ++--
 arangod/Aql/ShortestPathExecutor.h      |  2 +-
 arangod/Aql/SortedCollectExecutor.cpp   |  7 ++--
 arangod/Aql/SortedCollectExecutor.h     |  4 +--
 tests/Aql/ExecutionBlockImplTest.cpp    | 40 +++++++++++-----------
 tests/Aql/FilterExecutorTest.cpp        |  6 ++--
 tests/Aql/ShortestPathExecutorTest.cpp  |  6 ++--
 tests/Aql/SortedCollectExecutorTest.cpp | 45 ++++++++++++++++---------
 tests/Aql/TestLambdaExecutor.cpp        |  2 +-
 tests/Aql/TestLambdaExecutor.h          |  4 +--
 17 files changed, 109 insertions(+), 82 deletions(-)

diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index 2c587ed15dad..c0eef936f3e6 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -1054,8 +1054,9 @@ template <class T>
 struct dependent_false : std::false_type {};
 
 template <class Executor>
-std::tuple<ExecutorState, size_t, AqlCall> ExecutionBlockImpl<Executor>::executeSkipRowsRange(
-    AqlItemBlockInputRange& inputRange, AqlCall& call) {
+std::tuple<ExecutorState, typename Executor::Stats, size_t, AqlCall>
+ExecutionBlockImpl<Executor>::executeSkipRowsRange(AqlItemBlockInputRange& inputRange,
+                                                   AqlCall& call) {
   if constexpr (isNewStyleExecutor<Executor>) {
     call.skippedRows = 0;
     if constexpr (skipRowsType<Executor>() == SkipRowsRangeVariant::EXECUTOR) {
@@ -1067,19 +1068,22 @@ std::tuple<ExecutorState, size_t, AqlCall> ExecutionBlockImpl<Executor>::execute
       // is a property of the executor), then we can just let the fetcher skip
       // the number of rows that we would like to skip.
       // Returning this will trigger to end in upstream state now, with the
-      // call that was handed it
-      return {inputRange.upstreamState(), 0, call};
+      // call that was handed it.
+      static_assert(
+          std::is_same_v<typename Executor::Stats, NoStats>,
+          "Executors with custom statistics must implement skipRowsRange.");
+      return {inputRange.upstreamState(), NoStats{}, 0, call};
     } else {
       static_assert(dependent_false<Executor>::value,
                     "This value of SkipRowsRangeVariant is not supported");
-      return std::make_tuple(ExecutorState::DONE, 0, call);
+      return std::make_tuple(ExecutorState::DONE, typename Executor::Stats{}, 0, call);
     }
   } else {
     TRI_ASSERT(false);
-    return std::make_tuple(ExecutorState::DONE, 0, call);
+    return std::make_tuple(ExecutorState::DONE, typename Executor::Stats{}, 0, call);
   }
   // Compiler is unhappy without this.
-  return std::make_tuple(ExecutorState::DONE, 0, call);
+  return std::make_tuple(ExecutorState::DONE, typename Executor::Stats{}, 0, call);
 }
 
 /**
@@ -1165,8 +1169,10 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
           break;
         }
         case ExecState::SKIP: {
-          auto [state, skippedLocal, call] = executeSkipRowsRange(_lastRange, clientCall);
+          auto [state, stats, skippedLocal, call] =
+              executeSkipRowsRange(_lastRange, clientCall);
           _skipped += skippedLocal;
+          _engine->_stats += stats;
           // The execute might have modified the client call.
           if (state == ExecutorState::DONE) {
             _execState = ExecState::SHADOWROWS;
@@ -1232,8 +1238,10 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
           break;
         }
         case ExecState::FULLCOUNT: {
-          auto [state, skippedLocal, call] = executeSkipRowsRange(_lastRange, clientCall);
+          auto [state, stats, skippedLocal, call] =
+              executeSkipRowsRange(_lastRange, clientCall);
           _skipped += skippedLocal;
+          _engine->_stats += stats;
 
           if (state == ExecutorState::DONE) {
             _execState = ExecState::SHADOWROWS;
diff --git a/arangod/Aql/ExecutionBlockImpl.h b/arangod/Aql/ExecutionBlockImpl.h
index 78f8f7392bcb..a50634f58bbb 100644
--- a/arangod/Aql/ExecutionBlockImpl.h
+++ b/arangod/Aql/ExecutionBlockImpl.h
@@ -224,8 +224,8 @@ class ExecutionBlockImpl final : public ExecutionBlock {
   std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> executeWithoutTrace(AqlCallStack stack);
 
   // execute a skipRowsRange call
-  std::tuple<ExecutorState, size_t, AqlCall> executeSkipRowsRange(AqlItemBlockInputRange& input,
-                                                                  AqlCall& call);
+  std::tuple<ExecutorState, typename Executor::Stats, size_t, AqlCall> executeSkipRowsRange(
+      AqlItemBlockInputRange& input, AqlCall& call);
 
   /**
    * @brief Inner getSome() part, without the tracing calls.
diff --git a/arangod/Aql/FilterExecutor.cpp b/arangod/Aql/FilterExecutor.cpp
index ecb318423211..8c2d66f09032 100644
--- a/arangod/Aql/FilterExecutor.cpp
+++ b/arangod/Aql/FilterExecutor.cpp
@@ -102,8 +102,9 @@ std::pair<ExecutionState, size_t> FilterExecutor::expectedNumberOfRows(size_t at
 }
 
 // TODO Remove me, we are using the getSome skip variant here.
-std::tuple<ExecutorState, size_t, AqlCall> FilterExecutor::skipRowsRange(
-    AqlItemBlockInputRange& inputRange, AqlCall& call) {
+auto FilterExecutor::skipRowsRange(AqlItemBlockInputRange& inputRange, AqlCall& call)
+    -> std::tuple<ExecutorState, Stats, size_t, AqlCall> {
+  FilterStats stats{};
   size_t skipped = 0;
   while (inputRange.hasDataRow() && skipped < call.getOffset()) {
     auto const [unused, input] = inputRange.nextDataRow();
@@ -113,17 +114,19 @@ std::tuple<ExecutorState, size_t, AqlCall> FilterExecutor::skipRowsRange(
     }
     if (input.getValue(_infos.getInputRegister()).toBoolean()) {
       skipped++;
+    } else {
+      stats.incrFiltered();
     }
   }
   call.didSkip(skipped);
 
   AqlCall upstreamCall{};
   upstreamCall.softLimit = call.getOffset();
-  return {inputRange.upstreamState(), skipped, upstreamCall};
+  return {inputRange.upstreamState(), stats, skipped, upstreamCall};
 }
 
-std::tuple<ExecutorState, FilterStats, AqlCall> FilterExecutor::produceRows(
-    AqlItemBlockInputRange& inputRange, OutputAqlItemRow& output) {
+auto FilterExecutor::produceRows(AqlItemBlockInputRange& inputRange, OutputAqlItemRow& output)
+    -> std::tuple<ExecutorState, Stats, AqlCall> {
   TRI_IF_FAILURE("FilterExecutor::produceRows") {
     THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
   }
diff --git a/arangod/Aql/FilterExecutor.h b/arangod/Aql/FilterExecutor.h
index 0b5237e08652..4b7350088180 100644
--- a/arangod/Aql/FilterExecutor.h
+++ b/arangod/Aql/FilterExecutor.h
@@ -103,7 +103,7 @@ class FilterExecutor {
    *
    * @return ExecutorState, the stats, and a new Call that needs to be send to upstream
    */
-  [[nodiscard]] std::tuple<ExecutorState, size_t, AqlCall> skipRowsRange(
+  [[nodiscard]] std::tuple<ExecutorState, Stats, size_t, AqlCall> skipRowsRange(
       AqlItemBlockInputRange& inputRange, AqlCall& call);
 
   [[nodiscard]] std::pair<ExecutionState, size_t> expectedNumberOfRows(size_t atMost) const;
@@ -115,4 +115,4 @@ class FilterExecutor {
 
 }  // namespace arangodb::aql
 
-#endif
\ No newline at end of file
+#endif
diff --git a/arangod/Aql/LimitExecutor.cpp b/arangod/Aql/LimitExecutor.cpp
index c3760732443b..42a6befce2a9 100644
--- a/arangod/Aql/LimitExecutor.cpp
+++ b/arangod/Aql/LimitExecutor.cpp
@@ -88,8 +88,8 @@ std::pair<ExecutionState, LimitStats> LimitExecutor::skipRestForFullCount() {
     return {state, stats};
   }
 
-  // We must not update _counter here. It is only used to count until offset+limit
-  // is reached.
+  // We must not update _counter here. It is only used to count until
+  // offset+limit is reached.
 
   if (infos().isFullCountEnabled()) {
     stats.incrFullCountBy(skipped);
@@ -153,7 +153,7 @@ std::pair<ExecutionState, LimitStats> LimitExecutor::produceRows(OutputAqlItemRo
       state = _stateOfLastRowToOutput;
       TRI_ASSERT(state != ExecutionState::WAITING);
       input = std::move(_lastRowToOutput);
-      TRI_ASSERT(!_lastRowToOutput.isInitialized()); // rely on the move
+      TRI_ASSERT(!_lastRowToOutput.isInitialized());  // rely on the move
     } else {
       std::tie(state, input) = _fetcher.fetchRow(maxRowsLeftToFetch());
 
@@ -244,7 +244,7 @@ std::tuple<ExecutionState, LimitStats, SharedAqlItemBlockPtr> LimitExecutor::fet
     case LimitState::RETURNING_LAST_ROW:
     case LimitState::RETURNING:
       auto rv = _fetcher.fetchBlockForPassthrough(std::min(atMost, maxRowsLeftToFetch()));
-      return { rv.first, LimitStats{}, std::move(rv.second) };
+      return {rv.first, LimitStats{}, std::move(rv.second)};
   }
   // The control flow cannot reach this. It is only here to make MSVC happy,
   // which is unable to figure out that the switch above is complete.
@@ -286,5 +286,4 @@ std::tuple<ExecutionState, LimitExecutor::Stats, size_t> LimitExecutor::skipRows
   }
 
   return std::make_tuple(state, LimitStats{}, reportSkipped);
-}
-
+}
\ No newline at end of file
diff --git a/arangod/Aql/ReturnExecutor.cpp b/arangod/Aql/ReturnExecutor.cpp
index 02c3dbd0ff0e..35723a24524d 100644
--- a/arangod/Aql/ReturnExecutor.cpp
+++ b/arangod/Aql/ReturnExecutor.cpp
@@ -66,11 +66,11 @@ auto ReturnExecutor::produceRows(OutputAqlItemRow& output)
 }
 
 auto ReturnExecutor::skipRowsRange(AqlItemBlockInputRange& inputRange, AqlCall& call)
-    -> std::tuple<ExecutorState, size_t, AqlCall> {
+    -> std::tuple<ExecutorState, Stats, size_t, AqlCall> {
   TRI_IF_FAILURE("ReturnExecutor::produceRows") {
     THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
   }
-
+  Stats stats{};
   while (inputRange.hasDataRow() && call.needSkipMore()) {
     // I do not think that this is actually called.
     // It will be called first to get the upstream-Call
@@ -83,14 +83,15 @@ auto ReturnExecutor::skipRowsRange(AqlItemBlockInputRange& inputRange, AqlCall&
       THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
     }
     call.didSkip(1);
-    // TODO: do we need to include counted here?
+
     /*
     if (_infos.doCount()) {
+      // TODO: do we need to include counted here?
       stats.incrCounted();
     }
     */
   }
-  return {inputRange.upstreamState(), call.getSkipCount(), call};
+  return {inputRange.upstreamState(), stats, call.getSkipCount(), call};
 }
 
 auto ReturnExecutor::produceRows(AqlItemBlockInputRange& inputRange, OutputAqlItemRow& output)
diff --git a/arangod/Aql/ReturnExecutor.h b/arangod/Aql/ReturnExecutor.h
index ec54f26898d0..c2d46ae638c1 100644
--- a/arangod/Aql/ReturnExecutor.h
+++ b/arangod/Aql/ReturnExecutor.h
@@ -102,7 +102,7 @@ class ReturnExecutor {
    * @return ExecutorState, the stats, and a new Call that needs to be send to upstream
    */
   [[nodiscard]] auto skipRowsRange(AqlItemBlockInputRange& input, AqlCall& call)
-      -> std::tuple<ExecutorState, size_t, AqlCall>;
+      -> std::tuple<ExecutorState, Stats, size_t, AqlCall>;
 
   /**
    * @brief produce the next Rows of Aql Values.
diff --git a/arangod/Aql/ShortestPathExecutor.cpp b/arangod/Aql/ShortestPathExecutor.cpp
index 45679024e646..e8d1a3336b92 100644
--- a/arangod/Aql/ShortestPathExecutor.cpp
+++ b/arangod/Aql/ShortestPathExecutor.cpp
@@ -270,7 +270,7 @@ auto ShortestPathExecutor::produceRows(AqlItemBlockInputRange& input, OutputAqlI
 }
 
 auto ShortestPathExecutor::skipRowsRange(AqlItemBlockInputRange& input, AqlCall& call)
-    -> std::tuple<ExecutorState, size_t, AqlCall> {
+    -> std::tuple<ExecutorState, Stats, size_t, AqlCall> {
   auto skipped = size_t{0};
 
   while (true) {
@@ -279,13 +279,13 @@ auto ShortestPathExecutor::skipRowsRange(AqlItemBlockInputRange& input, AqlCall&
     if (pathLengthAvailable() == 0) {
       if (!fetchPath(input)) {
         TRI_ASSERT(!input.hasDataRow());
-        return {input.upstreamState(), skipped, AqlCall{}};
+        return {input.upstreamState(), NoStats{}, skipped, AqlCall{}};
       }
     } else {
       // if we end up here there is path available, but
       // we have skipped as much as we were asked to.
       TRI_ASSERT(call.getOffset() == 0);
-      return {ExecutorState::HASMORE, skipped, AqlCall{}};
+      return {ExecutorState::HASMORE, NoStats{}, skipped, AqlCall{}};
     }
   }
 }
diff --git a/arangod/Aql/ShortestPathExecutor.h b/arangod/Aql/ShortestPathExecutor.h
index 93bdfe2fe3ca..280e4fba7a4f 100644
--- a/arangod/Aql/ShortestPathExecutor.h
+++ b/arangod/Aql/ShortestPathExecutor.h
@@ -187,7 +187,7 @@ class ShortestPathExecutor {
   [[nodiscard]] auto produceRows(AqlItemBlockInputRange& input, OutputAqlItemRow& output)
       -> std::tuple<ExecutorState, Stats, AqlCall>;
   [[nodiscard]] auto skipRowsRange(AqlItemBlockInputRange& input, AqlCall& call)
-      -> std::tuple<ExecutorState, size_t, AqlCall>;
+      -> std::tuple<ExecutorState, Stats, size_t, AqlCall>;
 
  private:
   /**
diff --git a/arangod/Aql/SortedCollectExecutor.cpp b/arangod/Aql/SortedCollectExecutor.cpp
index 3967bf6d2faa..c59058930845 100644
--- a/arangod/Aql/SortedCollectExecutor.cpp
+++ b/arangod/Aql/SortedCollectExecutor.cpp
@@ -150,8 +150,7 @@ SortedCollectExecutorInfos::SortedCollectExecutorInfos(
       _trxPtr(trxPtr) {}
 
 SortedCollectExecutor::SortedCollectExecutor(Fetcher&, Infos& infos)
-    : _infos(infos),
-      _currentGroup(infos.getCount(), infos) {
+    : _infos(infos), _currentGroup(infos.getCount(), infos) {
   // reserve space for the current row
   _currentGroup.initialize(_infos.getGroupRegisters().size());
   // reset and recreate new group
@@ -398,7 +397,7 @@ auto SortedCollectExecutor::produceRows(AqlItemBlockInputRange& inputRange,
 }
 
 auto SortedCollectExecutor::skipRowsRange(AqlItemBlockInputRange& inputRange, AqlCall& clientCall)
-    -> std::tuple<ExecutorState, size_t, AqlCall> {
+    -> std::tuple<ExecutorState, Stats, size_t, AqlCall> {
   TRI_IF_FAILURE("SortedCollectExecutor::skipRowsRange") {
     THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
   }
@@ -468,5 +467,5 @@ auto SortedCollectExecutor::skipRowsRange(AqlItemBlockInputRange& inputRange, Aq
   LOG_DEVEL_SC << " skipped rows: " << clientCall.getSkipCount();
   LOG_DEVEL_SC << "reporting state: " << inputRange.upstreamState();
 
-  return {inputRange.upstreamState(), clientCall.getSkipCount(), AqlCall{}};
+  return {inputRange.upstreamState(), Stats{}, clientCall.getSkipCount(), AqlCall{}};
 }
diff --git a/arangod/Aql/SortedCollectExecutor.h b/arangod/Aql/SortedCollectExecutor.h
index 94eaa59a38d6..9145b991ad69 100644
--- a/arangod/Aql/SortedCollectExecutor.h
+++ b/arangod/Aql/SortedCollectExecutor.h
@@ -198,8 +198,8 @@ class SortedCollectExecutor {
    *
    * @return ExecutorState, the stats, and a new Call that needs to be send to upstream
    */
-  [[nodiscard]] std::tuple<ExecutorState, size_t, AqlCall> skipRowsRange(
-      AqlItemBlockInputRange& inputRange, AqlCall& call);
+  [[nodiscard]] auto skipRowsRange(AqlItemBlockInputRange& inputRange, AqlCall& call)
+      -> std::tuple<ExecutorState, Stats, size_t, AqlCall>;
 
   /**
    * This executor has no chance to estimate how many rows
diff --git a/tests/Aql/ExecutionBlockImplTest.cpp b/tests/Aql/ExecutionBlockImplTest.cpp
index 49bf8ad9dcf0..c06c04776340 100644
--- a/tests/Aql/ExecutionBlockImplTest.cpp
+++ b/tests/Aql/ExecutionBlockImplTest.cpp
@@ -547,9 +547,10 @@ class SharedExecutionBlockImplTest {
    * @param numRowsLeftWithInput The number of available rows in the output, if we have given an input
    * @return ProduceCall The call ready to hand over to the LambdaExecutorInfos
    */
-  ProduceCall generateProduceCall(size_t& nrCalls, AqlCall expectedCall,
+  static auto generateProduceCall(size_t& nrCalls, AqlCall expectedCall,
                                   size_t numRowsLeftNoInput = ExecutionBlock::DefaultBatchSize,
-                                  size_t numRowsLeftWithInput = ExecutionBlock::DefaultBatchSize) {
+                                  size_t numRowsLeftWithInput = ExecutionBlock::DefaultBatchSize)
+      -> ProduceCall {
     return [&nrCalls, numRowsLeftNoInput, numRowsLeftWithInput,
             expectedCall](AqlItemBlockInputRange& input, OutputAqlItemRow& output)
                -> std::tuple<ExecutorState, LambdaExe::Stats, AqlCall> {
@@ -595,10 +596,9 @@ class SharedExecutionBlockImplTest {
    * @param expectedCall The call that is expected on every invocation of this function.
    * @return SkipCall The call ready to hand over to the LambdaExecutorInfos
    */
-  SkipCall generateSkipCall(size_t& nrCalls, AqlCall expectedCall) {
-    return [&nrCalls,
-            expectedCall](AqlItemBlockInputRange& inputRange,
-                          AqlCall& clientCall) -> std::tuple<ExecutorState, size_t, AqlCall> {
+  static auto generateSkipCall(size_t& nrCalls, AqlCall expectedCall) -> SkipCall {
+    return [&nrCalls, expectedCall](AqlItemBlockInputRange& inputRange, AqlCall& clientCall)
+               -> std::tuple<ExecutorState, NoStats, size_t, AqlCall> {
       if (nrCalls > 10) {
         EXPECT_TRUE(false);
         // This is emergency bailout, we ask way to often here
@@ -622,7 +622,7 @@ class SharedExecutionBlockImplTest {
       upstreamCall.hardLimit = clientCall.getOffset() + clientCall.hardLimit;
       upstreamCall.offset = 0;
 
-      return {inputRange.upstreamState(), localSkip, upstreamCall};
+      return {inputRange.upstreamState(), NoStats{}, localSkip, upstreamCall};
     };
   }
 
@@ -632,9 +632,9 @@ class SharedExecutionBlockImplTest {
    *
    * @return SkipCall The always failing call to be used for the executor.
    */
-  SkipCall generateNeverSkipCall() {
+  static auto generateNeverSkipCall() -> SkipCall {
     return [](AqlItemBlockInputRange& input,
-              AqlCall& call) -> std::tuple<ExecutorState, size_t, AqlCall> {
+              AqlCall& call) -> std::tuple<ExecutorState, NoStats, size_t, AqlCall> {
       // Should not be called here. No Skip!
       EXPECT_TRUE(false);
       THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
@@ -647,7 +647,7 @@ class SharedExecutionBlockImplTest {
    *
    * @return ProduceCall The always failing call to be used for the executor.
    */
-  ProduceCall generateNeverProduceCall() {
+  static auto generateNeverProduceCall() -> ProduceCall {
     return [](AqlItemBlockInputRange& input,
               OutputAqlItemRow& output) -> std::tuple<ExecutorState, LambdaExe::Stats, AqlCall> {
       // Should not be called here. No limit, only skip!
@@ -1438,9 +1438,8 @@ class ExecutionBlockImplExecuteIntegrationTest
       return {inputRange.upstreamState(), NoStats{}, call};
     };
 
-    auto skipData =
-        [data, iterator](AqlItemBlockInputRange& inputRange,
-                         AqlCall& clientCall) -> std::tuple<ExecutorState, size_t, AqlCall> {
+    auto skipData = [data, iterator](AqlItemBlockInputRange& inputRange, AqlCall& clientCall)
+        -> std::tuple<ExecutorState, NoStats, size_t, AqlCall> {
       size_t skipped = 0;
       while (inputRange.hasDataRow() &&
              (clientCall.getOffset() > 0 ||
@@ -1467,7 +1466,7 @@ class ExecutionBlockImplExecuteIntegrationTest
         call.softLimit = clientCall.getOffset();
       }  // else softLimit == unlimited
       call.fullCount = false;
-      return {inputRange.upstreamState(), skipped, call};
+      return {inputRange.upstreamState(), NoStats{}, skipped, call};
     };
     auto infos = outReg == 0 ? makeSkipInfos(std::move(writeData), skipData,
                                              RegisterPlan::MaxRegisterId, outReg, resetCall)
@@ -1541,8 +1540,8 @@ class ExecutionBlockImplExecuteIntegrationTest
       return {inputRange.upstreamState(), NoStats{}, output.getClientCall()};
     };
 
-    auto skipData = [&skipAsserter](AqlItemBlockInputRange& inputRange,
-                                    AqlCall& call) -> std::tuple<ExecutorState, size_t, AqlCall> {
+    auto skipData = [&skipAsserter](AqlItemBlockInputRange& inputRange, AqlCall& call)
+        -> std::tuple<ExecutorState, NoStats, size_t, AqlCall> {
       skipAsserter.gotCalled(call);
 
       size_t skipped = 0;
@@ -1559,7 +1558,7 @@ class ExecutionBlockImplExecuteIntegrationTest
         request.softLimit = call.getOffset();
       }  // else fullCount case, simple get UNLIMITED from above
 
-      return {inputRange.upstreamState(), skipped, request};
+      return {inputRange.upstreamState(), NoStats{}, skipped, request};
     };
     auto producer = std::make_unique<ExecutionBlockImpl<LambdaExe>>(
         fakedQuery->engine(), generateNodeDummy(),
@@ -1866,8 +1865,9 @@ TEST_P(ExecutionBlockImplExecuteIntegrationTest, test_call_forwarding_implement_
     request.softLimit = (std::min)(getClient.softLimit, getClient.hardLimit);
     return {inputRange.upstreamState(), NoStats{}, request};
   };
-  auto forwardSkipCall = [&](AqlItemBlockInputRange& inputRange,
-                             AqlCall& call) -> std::tuple<ExecutorState, size_t, AqlCall> {
+  auto forwardSkipCall =
+      [&](AqlItemBlockInputRange& inputRange,
+          AqlCall& call) -> std::tuple<ExecutorState, NoStats, size_t, AqlCall> {
     skipState.gotCalled(call);
     size_t skipped = 0;
     while (inputRange.hasDataRow() && call.shouldSkip()) {
@@ -1883,7 +1883,7 @@ TEST_P(ExecutionBlockImplExecuteIntegrationTest, test_call_forwarding_implement_
       request.softLimit = call.getOffset();
     }  // else fullCount case, simple get UNLIMITED from above
 
-    return {inputRange.upstreamState(), skipped, request};
+    return {inputRange.upstreamState(), NoStats{}, skipped, request};
   };
 
   auto lower = std::make_unique<ExecutionBlockImpl<TestLambdaSkipExecutor>>(
diff --git a/tests/Aql/FilterExecutorTest.cpp b/tests/Aql/FilterExecutorTest.cpp
index 6cceab6e09fc..86907101764b 100644
--- a/tests/Aql/FilterExecutorTest.cpp
+++ b/tests/Aql/FilterExecutorTest.cpp
@@ -424,7 +424,8 @@ TEST_F(FilterExecutorTest, test_skip_datarange_need_more) {
   AqlCall clientCall;
   clientCall.offset = 1000;
 
-  auto const [state, skipped, call] = testee.skipRowsRange(input, clientCall);
+  auto const [state, stats, skipped, call] = testee.skipRowsRange(input, clientCall);
+  // TODO check stats
   EXPECT_EQ(state, ExecutorState::HASMORE);
   EXPECT_EQ(skipped, 3);
   EXPECT_EQ(clientCall.getOffset(), 1000 - 3);
@@ -494,7 +495,8 @@ TEST_F(FilterExecutorTest, test_skip_datarange_has_more) {
   AqlItemBlockInputRange input{ExecutorState::DONE, inBlock, 0, inBlock->size()};
   AqlCall clientCall;
   clientCall.offset = 2;
-  auto const [state, skipped, call] = testee.skipRowsRange(input, clientCall);
+  auto const [state, stats, skipped, call] = testee.skipRowsRange(input, clientCall);
+  // TODO check stats
   EXPECT_EQ(state, ExecutorState::HASMORE);
   EXPECT_EQ(skipped, 2);
   EXPECT_EQ(clientCall.getOffset(), 0);
diff --git a/tests/Aql/ShortestPathExecutorTest.cpp b/tests/Aql/ShortestPathExecutorTest.cpp
index 28a8bdc3fb9b..3ddc6495b66c 100644
--- a/tests/Aql/ShortestPathExecutorTest.cpp
+++ b/tests/Aql/ShortestPathExecutorTest.cpp
@@ -430,7 +430,8 @@ class ShortestPathExecutorTest
 
     // If an offset is requested, skip
     if (ourCall.getOffset() > 0) {
-      std::tie(state, skippedInitial, std::ignore) = testee.skipRowsRange(input, ourCall);
+      std::tie(state, std::ignore, skippedInitial, std::ignore) =
+          testee.skipRowsRange(input, ourCall);
     }
 
     // Produce rows
@@ -453,7 +454,8 @@ class ShortestPathExecutorTest
       // Emulate being called with a full count
       ourCall.hardLimit = 0;
       ourCall.softLimit = 0;
-      std::tie(state, skippedFullCount, std::ignore) = testee.skipRowsRange(input, ourCall);
+      std::tie(state, std::ignore, skippedFullCount, std::ignore) =
+          testee.skipRowsRange(input, ourCall);
     }
 
     ValidateCalledWith();
diff --git a/tests/Aql/SortedCollectExecutorTest.cpp b/tests/Aql/SortedCollectExecutorTest.cpp
index c267ab80c092..cfc51936e38b 100644
--- a/tests/Aql/SortedCollectExecutorTest.cpp
+++ b/tests/Aql/SortedCollectExecutorTest.cpp
@@ -662,7 +662,8 @@ TEST_F(SortedCollectExecutorTestSkip, skip_1) {
   clientCall.offset = 2;
 
   {
-    auto [state, skipped, upstreamCall] = testee.skipRowsRange(emptyInputRange, clientCall);
+    auto [state, stats, skipped, upstreamCall] =
+        testee.skipRowsRange(emptyInputRange, clientCall);
     ASSERT_EQ(ExecutorState::HASMORE, state);
     ASSERT_FALSE(upstreamCall.hasHardLimit());
     ASSERT_TRUE(std::holds_alternative<AqlCall::Infinity>(upstreamCall.softLimit));
@@ -672,7 +673,8 @@ TEST_F(SortedCollectExecutorTestSkip, skip_1) {
   }
 
   {
-    auto [state, skipped, upstreamCall] = testee.skipRowsRange(inputRange, clientCall);
+    auto [state, stats, skipped, upstreamCall] =
+        testee.skipRowsRange(inputRange, clientCall);
     ASSERT_EQ(ExecutorState::DONE, state);
     ASSERT_FALSE(upstreamCall.hasHardLimit());
     ASSERT_TRUE(std::holds_alternative<AqlCall::Infinity>(upstreamCall.softLimit));
@@ -697,7 +699,8 @@ TEST_F(SortedCollectExecutorTestSkip, skip_2) {
   clientCall.offset = 1;
 
   {
-    auto [state, skipped, upstreamCall] = testee.skipRowsRange(emptyInputRange, clientCall);
+    auto [state, stats, skipped, upstreamCall] =
+        testee.skipRowsRange(emptyInputRange, clientCall);
     EXPECT_EQ(ExecutorState::HASMORE, state);
     EXPECT_FALSE(upstreamCall.hasHardLimit());
     EXPECT_TRUE(std::holds_alternative<AqlCall::Infinity>(upstreamCall.softLimit));
@@ -707,7 +710,8 @@ TEST_F(SortedCollectExecutorTestSkip, skip_2) {
   }
 
   {
-    auto [state, skipped, upstreamCall] = testee.skipRowsRange(inputRange, clientCall);
+    auto [state, stats, skipped, upstreamCall] =
+        testee.skipRowsRange(inputRange, clientCall);
     EXPECT_EQ(state, ExecutorState::HASMORE);
     EXPECT_FALSE(upstreamCall.hasHardLimit());
     EXPECT_TRUE(std::holds_alternative<AqlCall::Infinity>(upstreamCall.softLimit));
@@ -756,7 +760,8 @@ TEST_F(SortedCollectExecutorTestSkip, skip_3) {
   clientCall.offset = 1;
 
   {
-    auto [state, skipped, upstreamCall] = testee.skipRowsRange(emptyInputRange, clientCall);
+    auto [state, stats, skipped, upstreamCall] =
+        testee.skipRowsRange(emptyInputRange, clientCall);
     EXPECT_EQ(ExecutorState::HASMORE, state);
     EXPECT_FALSE(upstreamCall.hasHardLimit());
     EXPECT_TRUE(std::holds_alternative<AqlCall::Infinity>(upstreamCall.softLimit));
@@ -766,7 +771,8 @@ TEST_F(SortedCollectExecutorTestSkip, skip_3) {
   }
 
   {
-    auto [state, skipped, upstreamCall] = testee.skipRowsRange(inputRange, clientCall);
+    auto [state, stats, skipped, upstreamCall] =
+        testee.skipRowsRange(inputRange, clientCall);
     EXPECT_EQ(state, ExecutorState::HASMORE);
     EXPECT_EQ(clientCall.fullCount, upstreamCall.fullCount);
     EXPECT_EQ(skipped, 0);
@@ -774,7 +780,7 @@ TEST_F(SortedCollectExecutorTestSkip, skip_3) {
   }
 
   {
-    auto [state, skipped, upstreamCall] =
+    auto [state, stats, skipped, upstreamCall] =
         testee.skipRowsRange(emptyInputRangeDone, clientCall);
     EXPECT_EQ(state, ExecutorState::DONE);
     EXPECT_EQ(0, upstreamCall.offset);
@@ -803,7 +809,8 @@ TEST_F(SortedCollectExecutorTestSkip, skip_4) {
   clientCall.offset = 1;
 
   {
-    auto [state, skipped, upstreamCall] = testee.skipRowsRange(emptyInputRange, clientCall);
+    auto [state, stats, skipped, upstreamCall] =
+        testee.skipRowsRange(emptyInputRange, clientCall);
     EXPECT_EQ(ExecutorState::HASMORE, state);
     EXPECT_FALSE(upstreamCall.hasHardLimit());
     EXPECT_TRUE(std::holds_alternative<AqlCall::Infinity>(upstreamCall.softLimit));
@@ -814,7 +821,8 @@ TEST_F(SortedCollectExecutorTestSkip, skip_4) {
 
   {
     // 1, 1
-    auto [state, skipped, upstreamCall] = testee.skipRowsRange(inputRange, clientCall);
+    auto [state, stats, skipped, upstreamCall] =
+        testee.skipRowsRange(inputRange, clientCall);
     EXPECT_EQ(state, ExecutorState::HASMORE);
     EXPECT_EQ(clientCall.fullCount, upstreamCall.fullCount);
     EXPECT_EQ(skipped, 0);
@@ -823,7 +831,8 @@ TEST_F(SortedCollectExecutorTestSkip, skip_4) {
 
   {
     // 2
-    auto [state, skipped, upstreamCall] = testee.skipRowsRange(inputRange2, clientCall);
+    auto [state, stats, skipped, upstreamCall] =
+        testee.skipRowsRange(inputRange2, clientCall);
     EXPECT_EQ(state, ExecutorState::HASMORE);
     EXPECT_EQ(0, upstreamCall.offset);
     EXPECT_EQ(skipped, 1);
@@ -876,7 +885,8 @@ TEST_F(SortedCollectExecutorTestSkip, skip_5) {
   clientCall.offset = 1;
 
   {
-    auto [state, skipped, upstreamCall] = testee.skipRowsRange(emptyInputRange, clientCall);
+    auto [state, stats, skipped, upstreamCall] =
+        testee.skipRowsRange(emptyInputRange, clientCall);
     EXPECT_EQ(ExecutorState::HASMORE, state);
     EXPECT_FALSE(upstreamCall.hasHardLimit());
     EXPECT_TRUE(std::holds_alternative<AqlCall::Infinity>(upstreamCall.softLimit));
@@ -887,7 +897,8 @@ TEST_F(SortedCollectExecutorTestSkip, skip_5) {
 
   {
     // 1, 1, 2
-    auto [state, skipped, upstreamCall] = testee.skipRowsRange(inputRange, clientCall);
+    auto [state, stats, skipped, upstreamCall] =
+        testee.skipRowsRange(inputRange, clientCall);
     EXPECT_EQ(state, ExecutorState::HASMORE);
     EXPECT_EQ(clientCall.fullCount, upstreamCall.fullCount);
     EXPECT_EQ(skipped, 1);
@@ -1016,12 +1027,14 @@ TEST_P(SortedCollectExecutorTestSplit, split_3) {
       .run(std::move(infos));
 }
 
-template<size_t... vs>
-const SortedCollectSplitType splitIntoBlocks = SortedCollectSplitType{std::vector<std::size_t>{vs...}};
-template<size_t step>
+template <size_t... vs>
+const SortedCollectSplitType splitIntoBlocks =
+    SortedCollectSplitType{std::vector<std::size_t>{vs...}};
+template <size_t step>
 const SortedCollectSplitType splitStep = SortedCollectSplitType{step};
 
 INSTANTIATE_TEST_CASE_P(SortedCollectExecutor, SortedCollectExecutorTestSplit,
-                        ::testing::Values(splitIntoBlocks<2, 3>, splitIntoBlocks<3, 4>, splitStep<2>));
+                        ::testing::Values(splitIntoBlocks<2, 3>,
+                                          splitIntoBlocks<3, 4>, splitStep<2>));
 
 }  // namespace arangodb::tests::aql
diff --git a/tests/Aql/TestLambdaExecutor.cpp b/tests/Aql/TestLambdaExecutor.cpp
index 9f7cdb99e417..facdfe75c65d 100644
--- a/tests/Aql/TestLambdaExecutor.cpp
+++ b/tests/Aql/TestLambdaExecutor.cpp
@@ -117,6 +117,6 @@ auto TestLambdaSkipExecutor::produceRows(AqlItemBlockInputRange& input, OutputAq
 }
 
 auto TestLambdaSkipExecutor::skipRowsRange(AqlItemBlockInputRange& input, AqlCall& call)
-    -> std::tuple<ExecutorState, size_t, AqlCall> {
+    -> std::tuple<ExecutorState, Stats, size_t, AqlCall> {
   return _infos.getSkipLambda()(input, call);
 }
diff --git a/tests/Aql/TestLambdaExecutor.h b/tests/Aql/TestLambdaExecutor.h
index 4ec0c995e956..1843b7f1a24d 100644
--- a/tests/Aql/TestLambdaExecutor.h
+++ b/tests/Aql/TestLambdaExecutor.h
@@ -50,7 +50,7 @@ using ProduceCall =
  * @brief This is a shorthand for the skipRowsInRange signature
  */
 using SkipCall =
-    std::function<std::tuple<ExecutorState, size_t, AqlCall>(AqlItemBlockInputRange& input, AqlCall& call)>;
+    std::function<std::tuple<ExecutorState, NoStats, size_t, AqlCall>(AqlItemBlockInputRange& input, AqlCall& call)>;
 
 /**
  * @brief This is a shorthand for the reset state signature
@@ -223,7 +223,7 @@ class TestLambdaSkipExecutor {
    * @return std::tuple<ExecutorState, size_t, AqlCall>
    */
   auto skipRowsRange(AqlItemBlockInputRange& inputRange, AqlCall& call)
-      -> std::tuple<ExecutorState, size_t, AqlCall>;
+      -> std::tuple<ExecutorState, Stats, size_t, AqlCall>;
 
   /**
    * @brief produceRows API. Just calls the ProduceCall in the Infos.

From 518c042a65349b0e93191c090775197ce8ce13a7 Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Thu, 13 Feb 2020 09:51:59 +0100
Subject: [PATCH 062/122] Additional Assertion in ExecutionBlockImpl (#11077)

* Added a assertion arround skipRowsInRange that ensures that the Call and the skippedLocal do not get out-of-sync

* Improved the assertion
---
 arangod/Aql/ExecutionBlockImpl.cpp | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index c0eef936f3e6..9c525cf2caef 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -1169,8 +1169,30 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
           break;
         }
         case ExecState::SKIP: {
+#ifdef ARANGODB_ENABLE_MAINTAINER_MODE
+          size_t offsetBefore = clientCall.getOffset();
+          TRI_ASSERT(offsetBefore > 0);
+          size_t canPassFullcount =
+              clientCall.getLimit() == 0 && clientCall.needsFullCount();
+#endif
           auto [state, stats, skippedLocal, call] =
               executeSkipRowsRange(_lastRange, clientCall);
+#ifdef ARANGODB_ENABLE_MAINTAINER_MODE
+          // Assertion: We did skip 'skippedLocal' documents here.
+          // This means that they have to be removed from clientCall.getOffset()
+          // This has to be done by the Executor calling call.didSkip()
+          // accordingly.
+          if (canPassFullcount) {
+            // In htis case we can first skip. But straight after continue with fullCount, so we might skip more
+            TRI_ASSERT(clientCall.getOffset() + skippedLocal >= offsetBefore);
+            if (clientCall.getOffset() + skippedLocal > offsetBefore) {
+              // First need to count down offset.
+              TRI_ASSERT(clientCall.getOffset() == 0);
+            }
+          } else {
+            TRI_ASSERT(clientCall.getOffset() + skippedLocal == offsetBefore);
+          }
+#endif
           _skipped += skippedLocal;
           _engine->_stats += stats;
           // The execute might have modified the client call.

From 54043f3b76093f0cd07375f5b336bfa8b17e158a Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Fri, 14 Feb 2020 10:54:20 +0100
Subject: [PATCH 063/122] Feature/aql subquery operations stack id executor
 (#10986)

* added inputRange skip and produce

* added inputRange skip and produce

* Added shouldSkip helper to AqlCall

* Added implementation if execute to Constfetcher. Not specifically tested yet.

* Moved IDExecutor to newStyle executor

* Added some documentation to SingleRowFetcher

* Adapted IdExecutor tests.

* Added an assertion in ConstFetcher

* Fixed initialize cursor in ExecutionBlockImpl

* Added tests for Initilaize cursor in IdExecutor. There is a special implementation for this...

* Fixed linker issues, because of variables in cpp files named identical and not beeing static

* Started refactoring the Scatter/Gather Executor logic. Added an intermediate class that does not use a template and can be casted to. This state compiles but will not work.

* Made BlocksWithClientsImpl a template, based on an executor

* Added a dummy implementation to fetch a new block. Distribute not yet implemented.

* Added superoptimistic first implementation of ScatterExecutor return. Only works if there are no shadowRows.

* Implemented logic to slice Blocks in Scatter according to the given call. Also added handfull of test for it, not complete though

* Fixed a Scatter Executor handling of softLimit. Added another test to ansure diverse calls of clients to Scatter

* Added random ordering test framework on ScatterExecutor

* Added some tests for ScatterExecutor including subqueries

* Removed todo, as it has been solved by now

* Implemented Scatter by using IDExecutor. Tests not green yet

* Implementation of ConstFetcher that allows to inject fullBlocks of AqlItemRows, and not only single rows. Also handles ShadowRows now in a correct way

* Do not jump over relevant shadow rows in ConstFetcher.

* Fixed tests.

* Moved information of DistributeExecutor into the Infos. This resulted in adapting the Constructor API. I used this situation to do a big cleanup of ancient code. From this point there is no way back.

* Implemented the last bits of DistributeExecutor

* 'Implemented' execute by fallback to old API in RemoteExecutor

* Fixed an EdgeCase with Scatter Executor, where the data was modified in place right after scatter. This has side-effects on peer executors. So we for now do a full copy of every block here.

* Removed invalid assertions, also fixed RegisterInput to DistributeExecutor

* Removed obsolete TODOs

* Update arangod/Aql/IdExecutor.cpp

Co-Authored-By: Lars Maier <lars@arangodb.com>

Co-authored-by: Heiko <hkernbach@users.noreply.github.com>
Co-authored-by: Lars Maier <lars@arangodb.com>
---
 arangod/Aql/AqlItemBlock.cpp            |  58 ++-
 arangod/Aql/AqlItemBlock.h              |  19 +-
 arangod/Aql/BlocksWithClients.cpp       | 178 ++++++-
 arangod/Aql/BlocksWithClients.h         | 130 +++++-
 arangod/Aql/ClusterNodes.cpp            |  62 +--
 arangod/Aql/ConstFetcher.cpp            | 188 +++++++-
 arangod/Aql/ConstFetcher.h              |  22 +-
 arangod/Aql/DependencyProxy.cpp         |  47 +-
 arangod/Aql/DistributeExecutor.cpp      | 535 +++++++++++----------
 arangod/Aql/DistributeExecutor.h        | 215 +++++----
 arangod/Aql/ExecutionBlockImpl.cpp      |  28 +-
 arangod/Aql/ExecutionBlockImpl.h        |   6 +
 arangod/Aql/IdExecutor.cpp              |  35 +-
 arangod/Aql/IdExecutor.h                |  12 +
 arangod/Aql/RemoteExecutor.cpp          |  17 +-
 arangod/Aql/RestAqlHandler.cpp          |  19 +-
 arangod/Aql/ScatterExecutor.cpp         | 230 ++++-----
 arangod/Aql/ScatterExecutor.h           |  86 ++--
 arangod/Aql/SingleRowFetcher.h          |  16 +-
 tests/Aql/ExecutorTestHelper.cpp        |  45 +-
 tests/Aql/ExecutorTestHelper.h          |  40 ++
 tests/Aql/IdExecutorTest.cpp            | 534 +++++++++++++++++++--
 tests/Aql/ScatterExecutorTest.cpp       | 592 ++++++++++++++++++++++++
 tests/Aql/ShortestPathExecutorTest.cpp  |   2 +-
 tests/Aql/SortedCollectExecutorTest.cpp |  23 +-
 tests/Aql/TestExecutorHelper.cpp        |   7 +-
 tests/CMakeLists.txt                    |   1 +
 27 files changed, 2451 insertions(+), 696 deletions(-)
 create mode 100644 tests/Aql/ScatterExecutorTest.cpp

diff --git a/arangod/Aql/AqlItemBlock.cpp b/arangod/Aql/AqlItemBlock.cpp
index de5c98eacfb6..25334172a92b 100644
--- a/arangod/Aql/AqlItemBlock.cpp
+++ b/arangod/Aql/AqlItemBlock.cpp
@@ -447,21 +447,59 @@ void AqlItemBlock::clearRegisters(std::unordered_set<RegisterId> const& toClear)
 SharedAqlItemBlockPtr AqlItemBlock::slice(size_t from, size_t to) const {
   TRI_ASSERT(from < to);
   TRI_ASSERT(to <= _nrItems);
+  return slice({{from, to}});
+}
 
-  std::unordered_set<AqlValue> cache;
-  cache.reserve((to - from) * _nrRegs / 4 + 1);
-
-  SharedAqlItemBlockPtr res{_manager.requestBlock(to - from, _nrRegs)};
+/**
+ * @brief Slice multiple ranges out of this AqlItemBlock.
+ *        This does a deep copy of all entries
+ *
+ * @param ranges list of ranges from(included) -> to(excluded)
+ *        Every range needs to be valid from[i] < to[i]
+ *        And every range needs to be within the block to[i] <= size()
+ *        The list is required to be ordered to[i] <= from[i+1]
+ *
+ * @return SharedAqlItemBlockPtr A block where all the slices are contained in the order of the list
+ */
+auto AqlItemBlock::slice(std::vector<std::pair<size_t, size_t>> const& ranges) const
+    -> SharedAqlItemBlockPtr {
+#ifdef ARANGODB_ENABLE_MAINTAINER_MODE
+  // Analyze correctness of ranges
+  TRI_ASSERT(!ranges.empty());
+  for (size_t i = 0; i < ranges.size(); ++i) {
+    auto const& [from, to] = ranges[i];
+    // Range is valid
+    TRI_ASSERT(from < to);
+    TRI_ASSERT(to <= _nrItems);
+    if (i > 0) {
+      // List is ordered
+      TRI_ASSERT(ranges[i - 1].second <= from);
+    }
+  }
+#endif
+  size_t numRows = 0;
+  for (auto const& [from, to] : ranges) {
+    numRows += to - from;
+  }
 
-  for (size_t row = from; row < to; row++) {
-    // Note this loop is special, it will also Copy over the SubqueryDepth data in reg 0
-    for (RegisterId col = 0; col < _nrRegs; col++) {
-      AqlValue const& a(_data[getAddress(row, col)]);
-      ::CopyValueOver(cache, a, row - from, col, res);
+  std::unordered_set<AqlValue> cache;
+  cache.reserve(numRows * _nrRegs / 4 + 1);
+
+  SharedAqlItemBlockPtr res{_manager.requestBlock(numRows, _nrRegs)};
+  size_t targetRow = 0;
+  for (auto const& [from, to] : ranges) {
+    for (size_t row = from; row < to; row++, targetRow++) {
+      // Note this loop is special, it will also Copy over the SubqueryDepth data in reg 0
+      for (RegisterId col = 0; col < _nrRegs; col++) {
+        AqlValue const& a(_data[getAddress(row, col)]);
+        ::CopyValueOver(cache, a, targetRow, col, res);
+      }
+      res->copySubQueryDepthFromOtherBlock(targetRow, *this, row);
     }
-    res->copySubQueryDepthFromOtherBlock(row - from, *this, row);
   }
 
+  TRI_ASSERT(res->size() == numRows);
+
   return res;
 }
 
diff --git a/arangod/Aql/AqlItemBlock.h b/arangod/Aql/AqlItemBlock.h
index 14acd1c4225d..6badb45b8c5d 100644
--- a/arangod/Aql/AqlItemBlock.h
+++ b/arangod/Aql/AqlItemBlock.h
@@ -193,6 +193,19 @@ class AqlItemBlock {
   /// @brief slice/clone, this does a deep copy of all entries
   SharedAqlItemBlockPtr slice(size_t from, size_t to) const;
 
+  /**
+   * @brief Slice multiple ranges out of this AqlItemBlock.
+   *        This does a deep copy of all entries
+   *
+   * @param ranges list of ranges from(included) -> to(excluded)
+   *        Every range needs to be valid from[i] < to[i]
+   *        And every range needs to be within the block to[i] <= size()
+   *        The list is required to be ordered to[i] <= from[i+1]
+   *
+   * @return SharedAqlItemBlockPtr A block where all the slices are contained in the order of the list
+   */
+  auto slice(std::vector<std::pair<size_t, size_t>> const& ranges) const -> SharedAqlItemBlockPtr;
+
   /// @brief create an AqlItemBlock with a single row, with copies of the
   /// specified registers from the current block
   SharedAqlItemBlockPtr slice(size_t row, std::unordered_set<RegisterId> const& registers,
@@ -318,9 +331,9 @@ class AqlItemBlock {
   /// this ItemBlock. Used to easier split data based on them.
   std::set<size_t> _shadowRowIndexes;
 
-  /// @brief current row index we want to read from. This will be increased after
-  /// getRelevantRange function will be called, which will return a tuple of the
-  /// old _rowIndex and the newly calculated _rowIndex - 1
+  /// @brief current row index we want to read from. This will be increased
+  /// after getRelevantRange function will be called, which will return a tuple
+  /// of the old _rowIndex and the newly calculated _rowIndex - 1
   size_t _rowIndex;
 };
 
diff --git a/arangod/Aql/BlocksWithClients.cpp b/arangod/Aql/BlocksWithClients.cpp
index 7c856f3a4aa1..63adcc31c392 100644
--- a/arangod/Aql/BlocksWithClients.cpp
+++ b/arangod/Aql/BlocksWithClients.cpp
@@ -29,10 +29,12 @@
 #include "Aql/AqlValue.h"
 #include "Aql/BlockCollector.h"
 #include "Aql/Collection.h"
+#include "Aql/DistributeExecutor.h"
 #include "Aql/ExecutionEngine.h"
 #include "Aql/ExecutionStats.h"
 #include "Aql/InputAqlItemRow.h"
 #include "Aql/Query.h"
+#include "Aql/ScatterExecutor.h"
 #include "Basics/Exceptions.h"
 #include "Basics/StaticStrings.h"
 #include "Basics/StringBuffer.h"
@@ -61,22 +63,63 @@ using namespace arangodb::aql;
 using VelocyPackHelper = arangodb::basics::VelocyPackHelper;
 using StringBuffer = arangodb::basics::StringBuffer;
 
-BlocksWithClients::BlocksWithClients(ExecutionEngine* engine, ExecutionNode const* ep,
-                                     std::vector<std::string> const& shardIds)
+ClientsExecutorInfos::ClientsExecutorInfos(std::vector<std::string> clientIds)
+    : _clientIds(std::move(clientIds)) {
+  TRI_ASSERT(!_clientIds.empty());
+};
+
+auto ClientsExecutorInfos::nrClients() const noexcept -> size_t {
+  return _clientIds.size();
+}
+auto ClientsExecutorInfos::clientIds() const noexcept -> std::vector<std::string> const& {
+  return _clientIds;
+}
+
+template <class Executor>
+BlocksWithClientsImpl<Executor>::BlocksWithClientsImpl(ExecutionEngine* engine,
+                                                       ExecutionNode const* ep,
+                                                       typename Executor::Infos infos)
     : ExecutionBlock(engine, ep),
-      _nrClients(shardIds.size()),
+      BlocksWithClients(),
+      _nrClients(infos.nrClients()),
       _type(ScatterNode::ScatterType::SHARD),
+      _infos(std::move(infos)),
+      _executor{_infos},
+      _clientBlockData{},
       _wasShutdown(false) {
   _shardIdMap.reserve(_nrClients);
+  auto const& shardIds = _infos.clientIds();
   for (size_t i = 0; i < _nrClients; i++) {
     _shardIdMap.try_emplace(shardIds[i], i);
   }
+
   auto scatter = ExecutionNode::castTo<ScatterNode const*>(ep);
   TRI_ASSERT(scatter != nullptr);
   _type = scatter->getScatterType();
+
+  _clientBlockData.reserve(shardIds.size());
+
+  auto readAble = make_shared_unordered_set();
+  auto writeAble = make_shared_unordered_set();
+
+  for (auto const& id : shardIds) {
+    _clientBlockData.try_emplace(id, typename Executor::ClientBlockData{*engine, scatter, _infos});
+  }
+}
+
+/// @brief initializeCursor
+template <class Executor>
+auto BlocksWithClientsImpl<Executor>::initializeCursor(InputAqlItemRow const& input)
+    -> std::pair<ExecutionState, Result> {
+  for (auto& [key, list] : _clientBlockData) {
+    list.clear();
+  }
+  return ExecutionBlock::initializeCursor(input);
 }
 
-std::pair<ExecutionState, bool> BlocksWithClients::getBlock(size_t atMost) {
+template <class Executor>
+auto BlocksWithClientsImpl<Executor>::getBlock(size_t atMost)
+    -> std::pair<ExecutionState, bool> {
   if (_engine->getQuery()->killed()) {
     THROW_ARANGO_EXCEPTION(TRI_ERROR_QUERY_KILLED);
   }
@@ -101,7 +144,9 @@ std::pair<ExecutionState, bool> BlocksWithClients::getBlock(size_t atMost) {
 }
 
 /// @brief shutdown
-std::pair<ExecutionState, Result> BlocksWithClients::shutdown(int errorCode) {
+template <class Executor>
+auto BlocksWithClientsImpl<Executor>::shutdown(int errorCode)
+    -> std::pair<ExecutionState, Result> {
   if (_wasShutdown) {
     return {ExecutionState::DONE, TRI_ERROR_NO_ERROR};
   }
@@ -115,7 +160,8 @@ std::pair<ExecutionState, Result> BlocksWithClients::shutdown(int errorCode) {
 
 /// @brief getClientId: get the number <clientId> (used internally)
 /// corresponding to <shardId>
-size_t BlocksWithClients::getClientId(std::string const& shardId) const {
+template <class Executor>
+size_t BlocksWithClientsImpl<Executor>::getClientId(std::string const& shardId) const {
   if (shardId.empty()) {
     THROW_ARANGO_EXCEPTION_MESSAGE(TRI_ERROR_INTERNAL,
                                    "got empty distribution id");
@@ -129,18 +175,132 @@ size_t BlocksWithClients::getClientId(std::string const& shardId) const {
   return it->second;
 }
 
-std::pair<ExecutionState, SharedAqlItemBlockPtr> BlocksWithClients::getSome(size_t) {
+template <class Executor>
+std::pair<ExecutionState, SharedAqlItemBlockPtr> BlocksWithClientsImpl<Executor>::getSome(size_t) {
   TRI_ASSERT(false);
   THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
 }
 
-std::pair<ExecutionState, size_t> BlocksWithClients::skipSome(size_t) {
+template <class Executor>
+std::pair<ExecutionState, size_t> BlocksWithClientsImpl<Executor>::skipSome(size_t) {
   TRI_ASSERT(false);
   THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
 }
 
-std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> BlocksWithClients::execute(AqlCallStack stack) {
+template <class Executor>
+std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> BlocksWithClientsImpl<Executor>::execute(AqlCallStack stack) {
   // This will not be implemented here!
   TRI_ASSERT(false);
   THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
 }
+
+template <class Executor>
+auto BlocksWithClientsImpl<Executor>::executeForClient(AqlCallStack stack,
+                                                       std::string const& clientId)
+    -> std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> {
+  // traceExecuteBegin(stack);
+  auto res = executeWithoutTraceForClient(stack, clientId);
+  // traceExecuteEnd(res);
+  return res;
+}
+
+template <class Executor>
+auto BlocksWithClientsImpl<Executor>::executeWithoutTraceForClient(AqlCallStack stack,
+                                                                   std::string const& clientId)
+    -> std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> {
+  TRI_ASSERT(!clientId.empty());
+  if (clientId.empty()) {
+    // Security bailout to avoid UB
+    THROW_ARANGO_EXCEPTION_MESSAGE(TRI_ERROR_INTERNAL,
+                                   "got empty distribution id");
+  }
+
+  auto it = _clientBlockData.find(clientId);
+  TRI_ASSERT(it != _clientBlockData.end());
+  if (it == _clientBlockData.end()) {
+    // Security bailout to avoid UB
+    std::string message("AQL: unknown distribution id ");
+    message.append(clientId);
+    THROW_ARANGO_EXCEPTION_MESSAGE(TRI_ERROR_INTERNAL, message);
+  }
+
+  // This call is only used internally.
+  auto call = stack.isRelevant() ? stack.popCall() : AqlCall{};
+
+  // We do not have anymore data locally.
+  // Need to fetch more from upstream
+  auto& dataContainer = it->second;
+
+  while (!dataContainer.hasDataFor(call)) {
+    if (_upstreamState == ExecutionState::DONE) {
+      // We are done, with everything, we will not be able to fetch any more rows
+      return {_upstreamState, 0, nullptr};
+    }
+
+    auto state = fetchMore(stack);
+    if (state == ExecutionState::WAITING) {
+      return {state, 0, nullptr};
+    }
+    _upstreamState = state;
+  }
+  // If we get here we have data and can return it.
+  return dataContainer.execute(call, _upstreamState);
+}
+
+template <class Executor>
+auto BlocksWithClientsImpl<Executor>::fetchMore(AqlCallStack stack) -> ExecutionState {
+  if (_engine->getQuery()->killed()) {
+    THROW_ARANGO_EXCEPTION(TRI_ERROR_QUERY_KILLED);
+  }
+
+  // NOTE: We do not handle limits / skip here
+  // They can differ between different calls to this executor.
+  // We may need to revisit this for performance reasons.
+  AqlCall call{};
+  stack.pushCall(std::move(call));
+
+  TRI_ASSERT(_dependencies.size() == 1);
+  auto [state, skipped, block] = _dependencies[0]->execute(stack);
+
+  // We can never ever forward skip!
+  // We could need the row in a different block, and once skipped
+  // we cannot get it back.
+  TRI_ASSERT(skipped == 0);
+
+  TRI_IF_FAILURE("ExecutionBlock::getBlock") {
+    THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
+  }
+
+  // Waiting -> no block
+  TRI_ASSERT(state != ExecutionState::WAITING || block == nullptr);
+  if (block != nullptr) {
+    _executor.distributeBlock(block, _clientBlockData);
+  }
+
+  return state;
+}
+
+/// @brief getSomeForShard
+/// @deprecated
+template <class Executor>
+std::pair<ExecutionState, SharedAqlItemBlockPtr> BlocksWithClientsImpl<Executor>::getSomeForShard(
+    size_t atMost, std::string const& shardId) {
+  AqlCallStack stack(AqlCall::SimulateGetSome(atMost));
+  auto [state, skipped, block] = executeForClient(stack, shardId);
+  TRI_ASSERT(skipped == 0);
+  return {state, block};
+}
+
+/// @brief skipSomeForShard
+/// @deprecated
+template <class Executor>
+std::pair<ExecutionState, size_t> BlocksWithClientsImpl<Executor>::skipSomeForShard(
+    size_t atMost, std::string const& shardId) {
+  AqlCallStack stack(AqlCall::SimulateSkipSome(atMost));
+  auto [state, skipped, block] = executeForClient(stack, shardId);
+  TRI_ASSERT(block == nullptr);
+  return {state, skipped};
+}
+
+template class ::arangodb::aql::BlocksWithClientsImpl<ScatterExecutor>;
+template class ::arangodb::aql::BlocksWithClientsImpl<DistributeExecutor>;
\ No newline at end of file
diff --git a/arangod/Aql/BlocksWithClients.h b/arangod/Aql/BlocksWithClients.h
index ca29e4cd476f..ead4589bf64f 100644
--- a/arangod/Aql/BlocksWithClients.h
+++ b/arangod/Aql/BlocksWithClients.h
@@ -39,10 +39,6 @@
 
 namespace arangodb {
 
-namespace httpclient {
-class SimpleHttpResult;
-}
-
 namespace transaction {
 class Methods;
 }
@@ -53,14 +49,75 @@ struct Collection;
 class ExecutionEngine;
 class ExecutionNode;
 
-class BlocksWithClients : public ExecutionBlock {
+class ClientsExecutorInfos {
+ public:
+  ClientsExecutorInfos(std::vector<std::string> clientIds);
+
+  ClientsExecutorInfos(ClientsExecutorInfos&&) = default;
+  ClientsExecutorInfos(ClientsExecutorInfos const&) = delete;
+  ~ClientsExecutorInfos() = default;
+
+  auto nrClients() const noexcept -> size_t;
+  auto clientIds() const noexcept -> std::vector<std::string> const&;
+
+ private:
+  std::vector<std::string> _clientIds;
+};
+
+class BlocksWithClients {
  public:
-  BlocksWithClients(ExecutionEngine* engine, ExecutionNode const* ep,
-                    std::vector<std::string> const& shardIds);
+  virtual ~BlocksWithClients() {}
+
+  /// @brief getSomeForShard
+  /// @deprecated
+  virtual std::pair<ExecutionState, SharedAqlItemBlockPtr> getSomeForShard(
+      size_t atMost, std::string const& shardId) = 0;
+
+  /// @brief skipSomeForShard
+  /// @deprecated
+  virtual std::pair<ExecutionState, size_t> skipSomeForShard(size_t atMost,
+                                                             std::string const& shardId) = 0;
+
+  /**
+   * @brief Execute for client.
+   *  Like execute, but bound to the dataset, that needs to be send to the given client ID
+   *
+   * @param stack The AqlCallStack
+   * @param clientId The requesting client Id.
+   * @return std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr>
+   */
+  virtual auto executeForClient(AqlCallStack stack, std::string const& clientId)
+      -> std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> = 0;
+};
 
-  ~BlocksWithClients() override = default;
+/**
+ * @brief Implementation of an ExecutionBlock that has multiple clients
+ *        Data is distributed to those clients, it might be all (Scatter)
+ *        or a selected part of it (Distribute).
+ *        How data is distributed is defined by the template parameter.
+ *
+ * @tparam ClientBlockData needs to be able to hold the data to be distributed
+ *         to a single client.
+ *         It needs to implement the following methods:
+ *         canProduce(size_t limit) -> bool stating it has enough information to fill limit many rows (or more)
+ *
+ */
+
+template <class Executor>
+class BlocksWithClientsImpl : public ExecutionBlock, public BlocksWithClients {
+  using Infos = typename Executor::Infos;
 
  public:
+  BlocksWithClientsImpl(ExecutionEngine* engine, ExecutionNode const* ep,
+                        typename Executor::Infos infos);
+
+  ~BlocksWithClientsImpl() override = default;
+
+ public:
+  /// @brief initializeCursor
+  auto initializeCursor(InputAqlItemRow const& input)
+      -> std::pair<ExecutionState, Result> override;
+
   /// @brief shutdown
   std::pair<ExecutionState, Result> shutdown(int) override;
 
@@ -72,15 +129,46 @@ class BlocksWithClients : public ExecutionBlock {
   /// @brief skipSome: shouldn't be used, use skipSomeForShard
   std::pair<ExecutionState, size_t> skipSome(size_t atMost) final;
 
+  /// @brief execute: shouldn't be used, use executeForClient
+  std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> execute(AqlCallStack stack) override;
+
+  /**
+   * @brief Execute for client.
+   *  Like execute, but bound to the dataset, that needs to be send to the given client ID
+   *
+   * @param stack The AqlCallStack
+   * @param clientId The requesting client Id.
+   * @return std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr>
+   */
+  auto executeForClient(AqlCallStack stack, std::string const& clientId)
+      -> std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> override;
+
+ private:
+  /**
+   * @brief Actual implementation of Execute.
+   *
+   * @param stack The AqlCallStack
+   * @param clientId The requesting client Id.
+   * @return std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr>
+   */
+  auto executeWithoutTraceForClient(AqlCallStack stack, std::string const& clientId)
+      -> std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr>;
+
+  /**
+   * @brief Load more data from upstream and distribute it into _clientBlockData
+   *
+   */
+  auto fetchMore(AqlCallStack stack) -> ExecutionState;
+
   /// @brief getSomeForShard
-  virtual std::pair<ExecutionState, SharedAqlItemBlockPtr> getSomeForShard(
-      size_t atMost, std::string const& shardId) = 0;
+  /// @deprecated
+  std::pair<ExecutionState, SharedAqlItemBlockPtr> getSomeForShard(size_t atMost,
+                                                                   std::string const& shardId) override;
 
   /// @brief skipSomeForShard
-  virtual std::pair<ExecutionState, size_t> skipSomeForShard(size_t atMost,
-                                                             std::string const& shardId) = 0;
-
-  std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> execute(AqlCallStack stack) override;
+  /// @deprecated
+  std::pair<ExecutionState, size_t> skipSomeForShard(size_t atMost,
+                                                     std::string const& shardId) override;
 
  protected:
   /// @brief getClientId: get the number <clientId> (used internally)
@@ -88,6 +176,7 @@ class BlocksWithClients : public ExecutionBlock {
   size_t getClientId(std::string const& shardId) const;
 
   /// @brief _shardIdMap: map from shardIds to clientNrs
+  /// @deprecated
   std::unordered_map<std::string, size_t> _shardIdMap;
 
   /// @brief _nrClients: total number of clients
@@ -97,6 +186,19 @@ class BlocksWithClients : public ExecutionBlock {
   ScatterNode::ScatterType _type;
 
  private:
+  /**
+   * @brief This is the working party of this implementation
+   *        the template class needs to implement the logic
+   *        to produce a single row from the upstream information.
+   */
+  Infos _infos;
+
+  Executor _executor;
+
+  /// @brief A map of clientId to the data this client should receive.
+  ///        This map will be filled as the execution progresses.
+  std::unordered_map<std::string, typename Executor::ClientBlockData> _clientBlockData;
+
   bool _wasShutdown;
 };
 
diff --git a/arangod/Aql/ClusterNodes.cpp b/arangod/Aql/ClusterNodes.cpp
index 84f04004d70d..c07fc82a499e 100644
--- a/arangod/Aql/ClusterNodes.cpp
+++ b/arangod/Aql/ClusterNodes.cpp
@@ -221,10 +221,10 @@ std::unique_ptr<ExecutionBlock> ScatterNode::createBlock(
   std::unordered_set<RegisterId> regsToKeep = calcRegsToKeep();
   std::unordered_set<RegisterId> regsToClear = getRegsToClear();
 
-  ExecutorInfos infos({}, {}, nrInRegs, nrOutRegs, std::move(regsToClear),
-                      std::move(regsToKeep));
+  ScatterExecutorInfos infos({}, {}, nrInRegs, nrOutRegs, std::move(regsToClear),
+                             std::move(regsToKeep), _clients);
   return std::make_unique<ExecutionBlockImpl<ScatterExecutor>>(&engine, this,
-                                                               std::move(infos), _clients);
+                                                               std::move(infos));
 }
 
 /// @brief toVelocyPack, for ScatterNode
@@ -319,9 +319,6 @@ std::unique_ptr<ExecutionBlock> DistributeNode::createBlock(
   std::unordered_set<RegisterId> regsToKeep = calcRegsToKeep();
   std::unordered_set<RegisterId> regsToClear = getRegsToClear();
 
-  ExecutorInfos infos({}, {}, nrInRegs, nrOutRegs, std::move(regsToClear),
-                      std::move(regsToKeep));
-
   RegisterId regId;
   RegisterId alternativeRegId = RegisterPlan::MaxRegisterId;
 
@@ -348,10 +345,18 @@ std::unique_ptr<ExecutionBlock> DistributeNode::createBlock(
       TRI_ASSERT(alternativeRegId == RegisterPlan::MaxRegisterId);
     }
   }
+  auto inAndOutRegs = make_shared_unordered_set({regId});
+  if (alternativeRegId != RegisterPlan::MaxRegisterId) {
+    inAndOutRegs->emplace(alternativeRegId);
+  }
+  DistributeExecutorInfos infos(inAndOutRegs, inAndOutRegs, nrInRegs, nrOutRegs,
+                                std::move(regsToClear), std::move(regsToKeep),
+                                clients(), collection(), regId, alternativeRegId,
+                                _allowSpecifiedKeys, _allowKeyConversionToObject,
+                                _createKeys, getScatterType());
 
-  return std::make_unique<ExecutionBlockImpl<DistributeExecutor>>(
-      &engine, this, std::move(infos), clients(), collection(), regId, alternativeRegId,
-      _allowSpecifiedKeys, _allowKeyConversionToObject, _createKeys);
+  return std::make_unique<ExecutionBlockImpl<DistributeExecutor>>(&engine, this,
+                                                                  std::move(infos));
 }
 
 /// @brief toVelocyPack, for DistributedNode
@@ -426,7 +431,7 @@ GatherNode::GatherNode(ExecutionPlan* plan, arangodb::velocypack::Slice const& b
       _vocbase(&(plan->getAst()->query()->vocbase())),
       _elements(elements),
       _sortmode(SortMode::MinElement),
-      _parallelism(Parallelism::Undefined), 
+      _parallelism(Parallelism::Undefined),
       _limit(0) {
   if (!_elements.empty()) {
     auto const sortModeSlice = base.get("sortmode");
@@ -441,14 +446,16 @@ GatherNode::GatherNode(ExecutionPlan* plan, arangodb::velocypack::Slice const& b
         basics::VelocyPackHelper::getNumericValue<decltype(_limit)>(base,
                                                                     "limit", 0);
   }
-    
-  setParallelism(parallelismFromString(VelocyPackHelper::getStringValue(base, "parellelism", "")));
+
+  setParallelism(parallelismFromString(
+      VelocyPackHelper::getStringValue(base, "parellelism", "")));
 }
 
-GatherNode::GatherNode(ExecutionPlan* plan, size_t id, SortMode sortMode, Parallelism parallelism) noexcept
-    : ExecutionNode(plan, id), 
+GatherNode::GatherNode(ExecutionPlan* plan, size_t id, SortMode sortMode,
+                       Parallelism parallelism) noexcept
+    : ExecutionNode(plan, id),
       _vocbase(&(plan->getAst()->query()->vocbase())),
-      _sortmode(sortMode), 
+      _sortmode(sortMode),
       _parallelism(parallelism),
       _limit(0) {}
 
@@ -457,7 +464,7 @@ void GatherNode::toVelocyPackHelper(VPackBuilder& nodes, unsigned flags,
                                     std::unordered_set<ExecutionNode const*>& seen) const {
   // call base class method
   ExecutionNode::toVelocyPackHelperGeneric(nodes, flags, seen);
- 
+
   nodes.add("parallelism", VPackValue(toString(_parallelism)));
 
   if (_elements.empty()) {
@@ -484,7 +491,7 @@ void GatherNode::toVelocyPackHelper(VPackBuilder& nodes, unsigned flags,
       }
     }
   }
-  
+
   // And close it:
   nodes.close();
 }
@@ -507,15 +514,15 @@ std::unique_ptr<ExecutionBlock> GatherNode::createBlock(
                             calcRegsToKeep(), getRegsToClear());
 
       return std::make_unique<ExecutionBlockImpl<UnsortedGatherExecutor>>(&engine, this,
-                                                                           std::move(infos));
+                                                                          std::move(infos));
     }
   }
-  
+
   Parallelism p = _parallelism;
   if (ServerState::instance()->isDBServer()) {
-    p = Parallelism::Serial; // not supported in v36
+    p = Parallelism::Serial;  // not supported in v36
   }
-  
+
   std::vector<SortRegister> sortRegister;
   SortRegister::fill(*plan(), *getRegisterPlan(), _elements, sortRegister);
   SortingGatherExecutorInfos infos(make_shared_unordered_set(),
@@ -553,7 +560,8 @@ struct ParallelizableFinder final : public WalkerWorker<ExecutionNode> {
   bool _isParallelizable;
 
   explicit ParallelizableFinder(TRI_vocbase_t const& _vocbase)
-      : _parallelizeWrites(_vocbase.server().getFeature<OptimizerRulesFeature>().parallelizeGatherWrites()),
+      : _parallelizeWrites(
+            _vocbase.server().getFeature<OptimizerRulesFeature>().parallelizeGatherWrites()),
         _isParallelizable(true) {}
 
   ~ParallelizableFinder() = default;
@@ -563,8 +571,7 @@ struct ParallelizableFinder final : public WalkerWorker<ExecutionNode> {
   }
 
   bool before(ExecutionNode* node) override final {
-    if (node->getType() == ExecutionNode::SCATTER ||
-        node->getType() == ExecutionNode::GATHER ||
+    if (node->getType() == ExecutionNode::SCATTER || node->getType() == ExecutionNode::GATHER ||
         node->getType() == ExecutionNode::DISTRIBUTE ||
         node->getType() == ExecutionNode::TRAVERSAL ||
         node->getType() == ExecutionNode::SHORTEST_PATH ||
@@ -576,10 +583,9 @@ struct ParallelizableFinder final : public WalkerWorker<ExecutionNode> {
     // can be parallelized, provided the rest of the plan
     // does not prohibit this
     if (node->isModificationNode() &&
-        (!_parallelizeWrites ||
-         (node->getType() != ExecutionNode::REMOVE &&
-          node->getType() != ExecutionNode::REPLACE && 
-          node->getType() != ExecutionNode::UPDATE))) {
+        (!_parallelizeWrites || (node->getType() != ExecutionNode::REMOVE &&
+                                 node->getType() != ExecutionNode::REPLACE &&
+                                 node->getType() != ExecutionNode::UPDATE))) {
       _isParallelizable = false;
       return true;  // true to abort the whole walking process
     }
diff --git a/arangod/Aql/ConstFetcher.cpp b/arangod/Aql/ConstFetcher.cpp
index 1b67cbe83359..16c011228246 100644
--- a/arangod/Aql/ConstFetcher.cpp
+++ b/arangod/Aql/ConstFetcher.cpp
@@ -22,6 +22,7 @@
 
 #include "ConstFetcher.h"
 
+#include "Aql/AqlCallStack.h"
 #include "Aql/DependencyProxy.h"
 #include "Aql/ShadowAqlItemRow.h"
 #include "Basics/Exceptions.h"
@@ -35,6 +36,158 @@ ConstFetcher::ConstFetcher() : _currentBlock{nullptr}, _rowIndex(0) {}
 ConstFetcher::ConstFetcher(DependencyProxy& executionBlock)
     : _currentBlock{nullptr}, _rowIndex(0) {}
 
+auto ConstFetcher::execute(AqlCallStack& stack)
+    -> std::tuple<ExecutionState, size_t, AqlItemBlockInputRange> {
+  // Note this fetcher can only be executed on top level (it is the singleton, or test)
+  TRI_ASSERT(stack.isRelevant());
+  auto call = stack.popCall();
+  if (_blockForPassThrough == nullptr) {
+    // we are done, nothing to move arround here.
+    return {ExecutionState::DONE, 0, AqlItemBlockInputRange{ExecutorState::DONE}};
+  }
+  std::vector<std::pair<size_t, size_t>> sliceIndexes;
+  sliceIndexes.emplace_back(_rowIndex, _blockForPassThrough->size());
+  // Modifiable first slice indexes.
+  // from is the first data row to be returned
+  // to is one after the last data row to be returned
+
+  if (_blockForPassThrough->hasShadowRows()) {
+    auto shadowIndexes = _blockForPassThrough->getShadowRowIndexes();
+    auto shadowRow = shadowIndexes.lower_bound(_rowIndex);
+    if (shadowRow != shadowIndexes.end()) {
+      size_t fromShadowRow = *shadowRow;
+      size_t toShadowRow = *shadowRow + 1;
+      for (++shadowRow; shadowRow != shadowIndexes.end(); ++shadowRow) {
+        if (*shadowRow == toShadowRow) {
+          ShadowAqlItemRow srow{_blockForPassThrough, toShadowRow};
+          TRI_ASSERT(srow.isInitialized());
+          if (srow.isRelevant()) {
+            // we cannot jump over relveant shadow rows.
+            // Unfortunately we need to stop including rows here.
+            // NOTE: As all blocks have this behaviour anyway
+            // this is not cirtical.
+            break;
+          }
+          toShadowRow++;
+        }
+      }
+      TRI_ASSERT(fromShadowRow < toShadowRow);
+      // We cannot go past the first shadowRow
+      sliceIndexes.emplace_back(fromShadowRow, toShadowRow);
+      sliceIndexes[0].second = fromShadowRow;
+    }
+  }
+  // Number of data rows we have left
+  size_t rowsLeft = sliceIndexes[0].second - sliceIndexes[0].first;
+  {
+    // We use this scope here to ensure the correctness
+    // of the following reference.
+    // if sliceIndexes is modified the references are broken
+    // in this scope it is ensured that sliceIndexes is not
+    // modified in size.
+    // These indexes will be modified by the call.
+    auto& [from, to] = sliceIndexes[0];
+
+    {
+      // Skip over the front rows.
+      // Adjust from and rowsLeft
+      // Note: canSkip can be 0
+      size_t canSkip = (std::min)(call.getOffset(), rowsLeft);
+      from += canSkip;
+      rowsLeft -= canSkip;
+      call.didSkip(canSkip);
+    }
+    {
+      // Produce the next rows
+      // Adjost from and rowsLeft
+      // Note: canProduce can be 0
+      size_t canProduce = (std::min)(call.getLimit(), rowsLeft);
+      to = from + canProduce;
+      rowsLeft -= canProduce;
+      call.didProduce(canProduce);
+    }
+  }
+
+  // Now adjust the rowIndex for consumed rows
+  if (call.hasHardLimit() && rowsLeft > 0) {
+    // fast forward
+    // We can only get here, if we have skipped and produced all rows
+    TRI_ASSERT(call.getOffset() == 0 && call.getLimit() == 0);
+    if (call.needsFullCount()) {
+      call.didSkip(rowsLeft);
+    }
+    rowsLeft = 0;
+
+    // In this case we consumed all rows until the end of
+    // a) the shadowRow range
+    // b) the end of the block
+    if (sliceIndexes.size() == 2) {
+      // We have shadowRows in use, go to end of their indexes
+      _rowIndex = sliceIndexes.back().second;
+    } else {
+      // We do not have shadowRows in use, need to to go the end.
+      _rowIndex = _blockForPassThrough->size();
+    }
+  } else {
+    // No hardLimit, but softLimit.
+    // And we have not reached the end.
+    if (rowsLeft > 0 && sliceIndexes.size() == 2) {
+      // Cannot include shadowRows
+      sliceIndexes.pop_back();
+    }
+    // Row index is now at the end of the last returned row
+    _rowIndex = sliceIndexes.back().second;
+  }
+
+  // Now we have a slicing vector:
+  // [0] => <from, to> (data rows)
+  // [1] => <from2, to2> (shadow rows, optional)
+  TRI_ASSERT(sliceIndexes.size() == 1 || sliceIndexes.size() == 2);
+
+  if (canUseFullBlock(sliceIndexes)) {
+    // FastPath
+    // No need for slicing
+    SharedAqlItemBlockPtr resultBlock = _blockForPassThrough;
+    _blockForPassThrough.reset(nullptr);
+    _rowIndex = 0;
+    return {ExecutionState::DONE, call.getSkipCount(),
+            DataRange{ExecutorState::DONE, resultBlock, 0, resultBlock->size()}};
+  }
+
+  SharedAqlItemBlockPtr resultBlock = _blockForPassThrough;
+
+  if (_rowIndex >= resultBlock->size()) {
+    // used the full block by now.
+    _blockForPassThrough.reset(nullptr);
+  }
+
+  if (sliceIndexes[0].first >= sliceIndexes[0].second) {
+    // We do not return any DataRow either we do not have one,
+    // or we have completely skipped it.
+    // Remove the indexes from the slice list
+    sliceIndexes.erase(sliceIndexes.begin());
+  }
+  // NOTE: The above if may have invalidated from and to memory.
+  // Do not use them below this point!
+
+  if (sliceIndexes.empty()) {
+    // No data to be returned
+    // Block is dropped.
+    resultBlock = nullptr;
+    return {ExecutionState::DONE, call.getSkipCount(), DataRange{ExecutorState::DONE}};
+  }
+
+  // Slowest path need to slice, this unfortunately requires copy of data
+  ExecutionState resState =
+      _blockForPassThrough == nullptr ? ExecutionState::DONE : ExecutionState::HASMORE;
+  ExecutorState rangeState =
+      _blockForPassThrough == nullptr ? ExecutorState::DONE : ExecutorState::HASMORE;
+
+  resultBlock = resultBlock->slice(sliceIndexes);
+  return {resState, call.getSkipCount(),
+          DataRange{rangeState, resultBlock, 0, resultBlock->size()}};
+}
+
 void ConstFetcher::injectBlock(SharedAqlItemBlockPtr block) {
   _currentBlock = block;
   _blockForPassThrough = std::move(block);
@@ -77,15 +230,46 @@ std::pair<ExecutionState, size_t> ConstFetcher::skipRows(size_t) {
   return {rowState, 1};
 }
 
-bool ConstFetcher::indexIsValid() {
+auto ConstFetcher::indexIsValid() const noexcept -> bool {
   return _currentBlock != nullptr && _rowIndex + 1 <= _currentBlock->size();
 }
 
-bool ConstFetcher::isLastRowInBlock() {
+auto ConstFetcher::isLastRowInBlock() const noexcept -> bool {
   TRI_ASSERT(indexIsValid());
   return _rowIndex + 1 == _currentBlock->size();
 }
 
+auto ConstFetcher::numRowsLeft() const noexcept -> size_t {
+  if (!indexIsValid()) {
+    return 0;
+  }
+  return _currentBlock->size() - _rowIndex;
+}
+
+auto ConstFetcher::canUseFullBlock(std::vector<std::pair<size_t, size_t>> const& ranges) const
+    noexcept -> bool {
+  TRI_ASSERT(!ranges.empty());
+  if (ranges.front().first != 0) {
+    // We do not start at the first index.
+    return false;
+  }
+  if (ranges.back().second != _currentBlock->size()) {
+    // We de not stop at the last index
+    return false;
+  }
+
+  if (ranges.size() > 1) {
+    TRI_ASSERT(ranges.size() == 2);
+    if (ranges.front().second != ranges.back().first) {
+      // We have two ranges, that are not next to each other.
+      // We cannot use the full block, as we need to slice these out.
+      return false;
+    }
+  }
+  // If we get here, the ranges covers the full block
+  return true;
+}
+
 std::pair<ExecutionState, SharedAqlItemBlockPtr> ConstFetcher::fetchBlockForPassthrough(size_t) {
   // Should only be called once, and then _blockForPassThrough should be
   // initialized. However, there are still some blocks left that ask their
diff --git a/arangod/Aql/ConstFetcher.h b/arangod/Aql/ConstFetcher.h
index e80f2c8693b4..46b9ec73667d 100644
--- a/arangod/Aql/ConstFetcher.h
+++ b/arangod/Aql/ConstFetcher.h
@@ -32,6 +32,7 @@
 namespace arangodb {
 namespace aql {
 
+class AqlCallStack;
 class AqlItemBlock;
 template <BlockPassthrough>
 class DependencyProxy;
@@ -58,6 +59,20 @@ class ConstFetcher {
   ConstFetcher();
 
  public:
+  /**
+   * @brief Execute the given call stack
+   *
+   * @param stack Call stack, on top of stack there is current subquery, bottom is the main query.
+   * @return std::tuple<ExecutionState, size_t, DataRange>
+   *   ExecutionState => DONE, all queries are done, there will be no more
+   *   ExecutionState => HASMORE, there are more results for queries, might be on other subqueries
+   *   ExecutionState => WAITING, we need to do I/O to solve the request, save local state and return WAITING to caller immediately
+   *
+   *   size_t => Amount of documents skipped
+   *   DataRange => Resulting data
+   */
+  auto execute(AqlCallStack& stack) -> std::tuple<ExecutionState, size_t, DataRange>;
+
   /**
    * @brief Fetch one new AqlItemRow from upstream.
    *        **Guarantee**: the pointer returned is valid only
@@ -111,8 +126,11 @@ class ConstFetcher {
   size_t _rowIndex;
 
  private:
-  bool indexIsValid();
-  bool isLastRowInBlock();
+  auto indexIsValid() const noexcept -> bool;
+  auto isLastRowInBlock() const noexcept -> bool;
+  auto numRowsLeft() const noexcept -> size_t;
+  auto canUseFullBlock(std::vector<std::pair<size_t, size_t>> const& ranges) const
+      noexcept -> bool;
 };
 
 }  // namespace aql
diff --git a/arangod/Aql/DependencyProxy.cpp b/arangod/Aql/DependencyProxy.cpp
index f420f6da5b0c..63f6ba51d140 100644
--- a/arangod/Aql/DependencyProxy.cpp
+++ b/arangod/Aql/DependencyProxy.cpp
@@ -34,9 +34,47 @@ using namespace arangodb::aql;
 template <BlockPassthrough blockPassthrough>
 std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr>
 DependencyProxy<blockPassthrough>::execute(AqlCallStack& stack) {
-  // TODO: Test this, especially if upstreamBlock is done etc.
-  // We do not modify any local state here.
-  return upstreamBlock().execute(stack);
+  ExecutionState state = ExecutionState::HASMORE;
+  size_t skipped = 0;
+  SharedAqlItemBlockPtr block = nullptr;
+  do {
+    // Note: upstreamBlock will return next dependency
+    // if we need to loop here
+    if (!_distributeId.empty()) {
+      // We are in the cluster case.
+      // we have to ask executeForShard
+      auto upstreamWithClient = dynamic_cast<BlocksWithClients*>(&upstreamBlock());
+      TRI_ASSERT(upstreamWithClient != nullptr);
+      if (upstreamWithClient == nullptr) {
+        THROW_ARANGO_EXCEPTION_MESSAGE(TRI_ERROR_INTERNAL_AQL,
+                                       "Invalid state reached, we try to "
+                                       "request sharded data from a block "
+                                       "that is not able to provide it.");
+      }
+      std::tie(state, skipped, block) =
+          upstreamWithClient->executeForClient(stack, _distributeId);
+    } else {
+      std::tie(state, skipped, block) = upstreamBlock().execute(stack);
+    }
+    TRI_IF_FAILURE("ExecutionBlock::getBlock") {
+      THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
+    }
+    if (state == ExecutionState::WAITING) {
+      TRI_ASSERT(block == nullptr);
+      TRI_ASSERT(skipped == 0);
+      break;
+    }
+
+    if (block == nullptr) {
+      // We're not waiting and didn't get a block, so we have to be done.
+      TRI_ASSERT(state == ExecutionState::DONE);
+      if (!advanceDependency()) {
+        break;
+      }
+    }
+
+  } while (block == nullptr);
+  return {state, skipped, block};
 }
 
 template <BlockPassthrough blockPassthrough>
@@ -264,8 +302,7 @@ template <BlockPassthrough blockPassthrough>
 DependencyProxy<blockPassthrough>::DependencyProxy(
     std::vector<ExecutionBlock*> const& dependencies, AqlItemBlockManager& itemBlockManager,
     std::shared_ptr<std::unordered_set<RegisterId> const> inputRegisters,
-    RegisterId nrInputRegisters,
-    velocypack::Options const* const options)
+    RegisterId nrInputRegisters, velocypack::Options const* const options)
     : _dependencies(dependencies),
       _itemBlockManager(itemBlockManager),
       _inputRegisters(std::move(inputRegisters)),
diff --git a/arangod/Aql/DistributeExecutor.cpp b/arangod/Aql/DistributeExecutor.cpp
index 1042214c0710..50970918e72b 100644
--- a/arangod/Aql/DistributeExecutor.cpp
+++ b/arangod/Aql/DistributeExecutor.cpp
@@ -22,11 +22,15 @@
 
 #include "DistributeExecutor.h"
 
+#include "Aql/AqlCallStack.h"
 #include "Aql/ClusterNodes.h"
 #include "Aql/Collection.h"
 #include "Aql/ExecutionEngine.h"
+#include "Aql/IdExecutor.h"
+#include "Aql/OutputAqlItemRow.h"
 #include "Aql/Query.h"
 #include "Aql/RegisterPlan.h"
+#include "Aql/ShadowAqlItemRow.h"
 #include "Basics/StaticStrings.h"
 #include "VocBase/LogicalCollection.h"
 
@@ -36,267 +40,268 @@
 using namespace arangodb;
 using namespace arangodb::aql;
 
-ExecutionBlockImpl<DistributeExecutor>::ExecutionBlockImpl(
-    ExecutionEngine* engine, DistributeNode const* node, ExecutorInfos&& infos,
-    std::vector<std::string> const& shardIds, Collection const* collection,
+DistributeExecutorInfos::DistributeExecutorInfos(
+    std::shared_ptr<std::unordered_set<RegisterId>> readableInputRegisters,
+    std::shared_ptr<std::unordered_set<RegisterId>> writeableOutputRegisters,
+    RegisterId nrInputRegisters, RegisterId nrOutputRegisters,
+    std::unordered_set<RegisterId> registersToClear,
+    std::unordered_set<RegisterId> registersToKeep,
+    std::vector<std::string> clientIds, Collection const* collection,
     RegisterId regId, RegisterId alternativeRegId, bool allowSpecifiedKeys,
-    bool allowKeyConversionToObject, bool createKeys)
-    : BlocksWithClients(engine, node, shardIds),
-      _infos(std::move(infos)),
-      _query(*engine->getQuery()),
-      _collection(collection),
-      _logCol(_collection->getCollection()),
-      _index(0),
+    bool allowKeyConversionToObject, bool createKeys, ScatterNode::ScatterType type)
+    : ExecutorInfos(readableInputRegisters, writeableOutputRegisters, nrInputRegisters,
+                    nrOutputRegisters, registersToClear, registersToKeep),
+      ClientsExecutorInfos(std::move(clientIds)),
       _regId(regId),
       _alternativeRegId(alternativeRegId),
-      _allowSpecifiedKeys(allowSpecifiedKeys),
       _allowKeyConversionToObject(allowKeyConversionToObject),
-      _createKeys(createKeys) {
-  _usesDefaultSharding = collection->usesDefaultSharding();
-}
-
-/// @brief initializeCursor
-std::pair<ExecutionState, Result> ExecutionBlockImpl<DistributeExecutor>::initializeCursor(
-    InputAqlItemRow const& input) {
-  // local clean up
-  _distBuffer.clear();
-  _distBuffer.reserve(_nrClients);
-
-  for (size_t i = 0; i < _nrClients; i++) {
-    _distBuffer.emplace_back();
+      _createKeys(createKeys),
+      _usesDefaultSharding(collection->usesDefaultSharding()),
+      _allowSpecifiedKeys(allowSpecifiedKeys),
+      _collection(collection),
+      _logCol(collection->getCollection()),
+      _type(type) {
+  TRI_ASSERT(readableInputRegisters->find(_regId) != readableInputRegisters->end());
+  if (hasAlternativeRegister()) {
+    TRI_ASSERT(readableInputRegisters->find(_alternativeRegId) !=
+               readableInputRegisters->end());
   }
-
-  return ExecutionBlock::initializeCursor(input);
 }
 
-/// @brief getSomeForShard
-std::pair<ExecutionState, SharedAqlItemBlockPtr> ExecutionBlockImpl<DistributeExecutor>::getSomeForShard(
-    size_t atMost, std::string const& shardId) {
-  traceGetSomeBegin(atMost);
-  auto result = getSomeForShardWithoutTrace(atMost, shardId);
-  return traceGetSomeEnd(result.first, std::move(result.second));
+auto DistributeExecutorInfos::registerId() const noexcept -> RegisterId {
+  TRI_ASSERT(_regId != RegisterPlan::MaxRegisterId);
+  return _regId;
 }
-
-std::pair<ExecutionState, SharedAqlItemBlockPtr> ExecutionBlockImpl<DistributeExecutor>::getSomeForShardWithoutTrace(
-    size_t atMost, std::string const& shardId) {
-  if (getQuery().killed()) {
-    THROW_ARANGO_EXCEPTION(TRI_ERROR_QUERY_KILLED);
-  }
-  // NOTE: We do not need to retain these, the getOrSkipSome is required to!
-  size_t skipped = 0;
-  SharedAqlItemBlockPtr result = nullptr;
-  auto out = getOrSkipSomeForShard(atMost, false, result, skipped, shardId);
-  if (out.first == ExecutionState::WAITING) {
-    return {out.first, nullptr};
-  }
-  if (!out.second.ok()) {
-    THROW_ARANGO_EXCEPTION(out.second);
-  }
-  return {out.first, std::move(result)};
+auto DistributeExecutorInfos::hasAlternativeRegister() const noexcept -> bool {
+  return _alternativeRegId != RegisterPlan::MaxRegisterId;
 }
-
-/// @brief skipSomeForShard
-std::pair<ExecutionState, size_t> ExecutionBlockImpl<DistributeExecutor>::skipSomeForShard(
-    size_t atMost, std::string const& shardId) {
-  traceSkipSomeBegin(atMost);
-  auto result = skipSomeForShardWithoutTrace(atMost, shardId);
-  return traceSkipSomeEnd(result.first, result.second);
+auto DistributeExecutorInfos::alternativeRegisterId() const noexcept -> RegisterId {
+  TRI_ASSERT(_alternativeRegId != RegisterPlan::MaxRegisterId);
+  return _alternativeRegId;
 }
 
-std::pair<ExecutionState, size_t> ExecutionBlockImpl<DistributeExecutor>::skipSomeForShardWithoutTrace(
-    size_t atMost, std::string const& shardId) {
-  if (getQuery().killed()) {
-    THROW_ARANGO_EXCEPTION(TRI_ERROR_QUERY_KILLED);
-  }
-  // NOTE: We do not need to retain these, the getOrSkipSome is required to!
-  size_t skipped = 0;
-  SharedAqlItemBlockPtr result = nullptr;
-  auto out = getOrSkipSomeForShard(atMost, true, result, skipped, shardId);
-  if (out.first == ExecutionState::WAITING) {
-    return {out.first, 0};
-  }
-  TRI_ASSERT(result == nullptr);
-  if (!out.second.ok()) {
-    THROW_ARANGO_EXCEPTION(out.second);
-  }
-  return {out.first, skipped};
+auto DistributeExecutorInfos::allowKeyConversionToObject() const noexcept -> bool {
+  return _allowKeyConversionToObject;
 }
 
-/// @brief getOrSkipSomeForShard
-std::pair<ExecutionState, arangodb::Result> ExecutionBlockImpl<DistributeExecutor>::getOrSkipSomeForShard(
-    size_t atMost, bool skipping, SharedAqlItemBlockPtr& result,
-    size_t& skipped, std::string const& shardId) {
-  TRI_ASSERT(result == nullptr && skipped == 0);
-  TRI_ASSERT(atMost > 0);
-
-  size_t clientId = getClientId(shardId);
-
-  if (!hasMoreForClientId(clientId)) {
-    return {ExecutionState::DONE, TRI_ERROR_NO_ERROR};
-  }
-
-  std::deque<std::pair<size_t, size_t>>& buf = _distBuffer.at(clientId);
+auto DistributeExecutorInfos::createKeys() const noexcept -> bool {
+  return _createKeys;
+}
+auto DistributeExecutorInfos::usesDefaultSharding() const noexcept -> bool {
+  return _usesDefaultSharding;
+}
+auto DistributeExecutorInfos::allowSpecifiedKeys() const noexcept -> bool {
+  return _allowSpecifiedKeys;
+}
 
-  if (buf.empty()) {
-    auto res = getBlockForClient(atMost, clientId);
-    if (res.first == ExecutionState::WAITING) {
-      return {res.first, TRI_ERROR_NO_ERROR};
-    }
-    if (!res.second) {
-      // Upstream is empty!
-      TRI_ASSERT(res.first == ExecutionState::DONE);
-      return {ExecutionState::DONE, TRI_ERROR_NO_ERROR};
-    }
-  }
+auto DistributeExecutorInfos::scatterType() const noexcept -> ScatterNode::ScatterType {
+  return _type;
+}
 
-  skipped = (std::min)(buf.size(), atMost);
+auto DistributeExecutorInfos::getResponsibleClient(arangodb::velocypack::Slice value) const
+    -> ResultT<std::string> {
+  std::string shardId;
+  int res = _logCol->getResponsibleShard(value, true, shardId);
 
-  if (skipping) {
-    for (size_t i = 0; i < skipped; i++) {
-      buf.pop_front();
-    }
-    return {getHasMoreStateForClientId(clientId), TRI_ERROR_NO_ERROR};
+  if (res != TRI_ERROR_NO_ERROR) {
+    return Result{res};
   }
 
-  BlockCollector collector(&_engine->itemBlockManager());
-  std::vector<size_t> chosen;
-
-  size_t i = 0;
-  while (i < skipped) {
-    size_t const n = buf.front().first;
-    while (buf.front().first == n && i < skipped) {
-      chosen.emplace_back(buf.front().second);
-      buf.pop_front();
-      i++;
-
-      // make sure we are not overreaching over the end of the buffer
-      if (buf.empty()) {
-        break;
-      }
-    }
-
-    SharedAqlItemBlockPtr more{_buffer[n]->slice(chosen, 0, chosen.size())};
-    collector.add(std::move(more));
-
-    chosen.clear();
+  TRI_ASSERT(!shardId.empty());
+  if (_type == ScatterNode::ScatterType::SERVER) {
+    // Special case for server based distribution.
+    shardId = _collection->getServerForShard(shardId);
+    TRI_ASSERT(!shardId.empty());
   }
+  return shardId;
+}
 
-  // Skipping was handle before
-  TRI_ASSERT(!skipping);
-  result = collector.steal();
-
-  // _buffer is left intact, deleted and cleared at shutdown
-
-  return {getHasMoreStateForClientId(clientId), TRI_ERROR_NO_ERROR};
+/// @brief create a new document key
+auto DistributeExecutorInfos::createKey(VPackSlice input) const -> std::string {
+  return _logCol->createKey(input);
 }
 
-/// @brief hasMore: any more for any shard?
-bool ExecutionBlockImpl<DistributeExecutor>::hasMoreForShard(std::string const& shardId) const {
-  return hasMoreForClientId(getClientId(shardId));
+// TODO
+// This section is not implemented yet
+
+DistributeExecutor::ClientBlockData::ClientBlockData(ExecutionEngine& engine,
+                                                     ScatterNode const* node,
+                                                     ExecutorInfos const& scatterInfos)
+    : _blockManager(engine.itemBlockManager()), _infos(scatterInfos) {
+  // We only get shared ptrs to const data. so we need to copy here...
+  IdExecutorInfos infos{scatterInfos.numberOfInputRegisters(),
+                        *scatterInfos.registersToKeep(),
+                        *scatterInfos.registersToClear(), "", false};
+  // NOTE: Do never change this type! The execute logic below requires this and only this type.
+  _executor =
+      std::make_unique<ExecutionBlockImpl<IdExecutor<ConstFetcher>>>(&engine, node,
+                                                                     std::move(infos));
 }
 
-ExecutionState ExecutionBlockImpl<DistributeExecutor>::getHasMoreStateForClientId(size_t clientId) const {
-  if (hasMoreForClientId(clientId)) {
-    return ExecutionState::HASMORE;
-  }
-  return ExecutionState::DONE;
+auto DistributeExecutor::ClientBlockData::clear() -> void {
+  _queue.clear();
+  _executorHasMore = false;
 }
 
-bool ExecutionBlockImpl<DistributeExecutor>::hasMoreForClientId(size_t clientId) const {
-  // We have more for a client ID if
-  // we still have some information in the local buffer
-  // or if there is still some information from upstream
+auto DistributeExecutor::ClientBlockData::addBlock(SharedAqlItemBlockPtr block,
+                                                   std::vector<size_t> usedIndexes) -> void {
+  _queue.emplace_back(block, std::move(usedIndexes));
+}
 
-  TRI_ASSERT(_distBuffer.size() > clientId);
-  if (!_distBuffer[clientId].empty()) {
-    return true;
-  }
-  return _upstreamState == ExecutionState::HASMORE;
+auto DistributeExecutor::ClientBlockData::hasDataFor(AqlCall const& call) -> bool {
+  return _executorHasMore || !_queue.empty();
 }
 
-/// @brief getBlockForClient: try to get atMost pairs into
-/// _distBuffer.at(clientId), this means we have to look at every row in the
-/// incoming blocks until they run out or we find enough rows for clientId. We
-/// also keep track of blocks which should be sent to other clients than the
-/// current one.
-std::pair<ExecutionState, bool> ExecutionBlockImpl<DistributeExecutor>::getBlockForClient(
-    size_t atMost, size_t clientId) {
-  
-  if (_buffer.empty()) {
-    _index = 0;  // position in _buffer
-    _pos = 0;    // position in _buffer.at(_index)
+/**
+ * @brief This call will join as many blocks as available from the queue
+ *        and return them in a SingleBlock. We then use the IdExecutor
+ *        to hand out the data contained in these blocks
+ *        We do on purpose not give any kind of guarantees on the sizing of
+ *        this block to be flexible with the implementation, and find a good
+ *        trade-off between blocksize and block copy operations.
+ *
+ * @return SharedAqlItemBlockPtr a joind block from the queue.
+ */
+auto DistributeExecutor::ClientBlockData::popJoinedBlock() -> SharedAqlItemBlockPtr {
+  // There are some optimizations available in this implementation.
+  // Namely we could apply good logic to cut the blocks at shadow rows
+  // in order to allow the IDexecutor to hand them out en-block.
+  // However we might leverage the restriction to stop at ShadowRows
+  // at one point anyways, and this Executor has no business with ShadowRows.
+  size_t numRows = 0;
+  for (auto const& [block, choosen] : _queue) {
+    numRows += choosen.size();
+    if (numRows >= ExecutionBlock::DefaultBatchSize) {
+      // Avoid to put too many rows into this block.
+      break;
+    }
   }
 
-  // it should be the case that buf.at(clientId) is empty
-  auto& buf = _distBuffer[clientId];
-
-  while (buf.size() < atMost) {
-    if (_index == _buffer.size()) {
-      if (getQuery().killed()) {
-        THROW_ARANGO_EXCEPTION(TRI_ERROR_QUERY_KILLED);
-      }
-      auto res = getBlock(atMost);
-      if (res.first == ExecutionState::WAITING) {
-        return {res.first, false};
-      }
-      if (!res.second) {
-        TRI_ASSERT(res.first == ExecutionState::DONE);
-        if (buf.empty()) {
-          TRI_ASSERT(getHasMoreStateForClientId(clientId) == ExecutionState::DONE);
-          return {ExecutionState::DONE, false};
-        }
-        break;
+  SharedAqlItemBlockPtr newBlock =
+      _blockManager.requestBlock(numRows, _infos.numberOfOutputRegisters());
+  // We create a block, with correct register information
+  // but we do not allow outputs to be written.
+  OutputAqlItemRow output{newBlock, make_shared_unordered_set(),
+                          _infos.registersToKeep(), _infos.registersToClear()};
+  while (!output.isFull()) {
+    // If the queue is empty our sizing above would not be correct
+    TRI_ASSERT(!_queue.empty());
+    auto const& [block, choosen] = _queue.front();
+    TRI_ASSERT(output.numRowsLeft() >= choosen.size());
+    for (auto const& i : choosen) {
+      // We do not really care what we copy. However
+      // the API requires to know what it is.
+      if (block->isShadowRow(i)) {
+        ShadowAqlItemRow toCopy{block, i};
+        output.copyRow(toCopy);
+      } else {
+        InputAqlItemRow toCopy{block, i};
+        output.copyRow(toCopy);
       }
+      output.advanceRow();
     }
+    // All required rows copied.
+    // Drop block form queue.
+    _queue.pop_front();
+  }
+  return newBlock;
+}
 
-    SharedAqlItemBlockPtr cur = _buffer[_index];
+auto DistributeExecutor::ClientBlockData::execute(AqlCall call, ExecutionState upstreamState)
+    -> std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> {
+  TRI_ASSERT(_executor != nullptr);
+  // Make sure we actually have data before you call execute
+  TRI_ASSERT(hasDataFor(call));
+  if (!_executorHasMore) {
+    // This cast is guaranteed, we create this a couple lines above and only
+    // this executor is used here.
+    // Unfortunately i did not get a version compiled were i could only forward
+    // declare the templates in header.
+    auto casted =
+        static_cast<ExecutionBlockImpl<IdExecutor<ConstFetcher>>*>(_executor.get());
+    TRI_ASSERT(casted != nullptr);
+    auto block = popJoinedBlock();
+    // We will at least get one block, otherwise the hasDataFor would
+    // be required to return false!
+    TRI_ASSERT(block != nullptr);
+
+    casted->injectConstantBlock(block);
+    _executorHasMore = true;
+  }
+  AqlCallStack stack{call};
+  auto [state, skipped, result] = _executor->execute(stack);
 
-    for (; _pos < cur->size(); ++_pos) {
-      if (!cur->isShadowRow(_pos)) {
-        // this may modify the input item buffer in place
-        size_t const id = sendToClient(cur);
+  // We have all data locally cannot wait here.
+  TRI_ASSERT(state != ExecutionState::WAITING);
 
-        _distBuffer[id].emplace_back(_index, _pos);
-      } else {
-        // A shadow row must always be distributed to all clients.
-        for (auto& dist : _distBuffer) {
-          dist.emplace_back(_index, _pos);
-        }
-      }
-    }
+  if (state == ExecutionState::DONE) {
+    // This executor is finished, including shadowrows
+    // We are going to reset it on next call
+    _executorHasMore = false;
 
-    if (_pos == cur->size()) {
-      _pos = 0;
-      _index++;
+    // Also we need to adjust the return states
+    // as this state only represents one single block
+    if (!_queue.empty()) {
+      state = ExecutionState::HASMORE;
     } else {
-      break;
+      state = upstreamState;
     }
   }
-
-  return {getHasMoreStateForClientId(clientId), true};
+  return {state, skipped, result};
 }
 
-/// @brief sendToClient: for each row of the incoming AqlItemBlock use the
-/// attributes <shardKeys> of the Aql value <val> to determine to which shard
-/// the row should be sent and return its clientId
-size_t ExecutionBlockImpl<DistributeExecutor>::sendToClient(SharedAqlItemBlockPtr cur) {
-  if (getQuery().killed()) {
-    THROW_ARANGO_EXCEPTION(TRI_ERROR_QUERY_KILLED);
+DistributeExecutor::DistributeExecutor(DistributeExecutorInfos const& infos)
+    : _infos(infos){};
+
+auto DistributeExecutor::distributeBlock(SharedAqlItemBlockPtr block,
+                                         std::unordered_map<std::string, ClientBlockData>& blockMap)
+    -> void {
+  std::unordered_map<std::string, std::vector<std::size_t>> choosenMap;
+  choosenMap.reserve(blockMap.size());
+  for (size_t i = 0; i < block->size(); ++i) {
+    if (block->isShadowRow(i)) {
+      // ShadowRows need to be added to all Clients
+      for (auto const& [key, value] : blockMap) {
+        choosenMap[key].emplace_back(i);
+      }
+    } else {
+      auto client = getClient(block, i);
+      // We can only have clients we are prepared for
+      TRI_ASSERT(blockMap.find(client) != blockMap.end());
+      choosenMap[client].emplace_back(i);
+    }
+  }
+  // We cannot have more in choosen than we have blocks
+  TRI_ASSERT(choosenMap.size() <= blockMap.size());
+  for (auto const& [key, value] : choosenMap) {
+    TRI_ASSERT(blockMap.find(key) != blockMap.end());
+    auto target = blockMap.find(key);
+    if (target == blockMap.end()) {
+      // Impossible, just avoid UB.
+      LOG_TOPIC("7bae6", ERR, Logger::AQL)
+          << "Tried to distribute data to shard " << key
+          << " which is not part of the query. Ignoring.";
+      continue;
+    }
+    target->second.addBlock(block, std::move(value));
   }
+}
 
-  // inspect cur in row _pos and check to which shard it should be sent . .
-  AqlValue val = cur->getValueReference(_pos, _regId);
+auto DistributeExecutor::getClient(SharedAqlItemBlockPtr block, size_t rowIndex)
+    -> std::string {
+  InputAqlItemRow row{block, rowIndex};
+  AqlValue val = row.getValue(_infos.registerId());
 
   VPackSlice input = val.slice();  // will throw when wrong type
 
   bool usedAlternativeRegId = false;
 
-  if (input.isNull() && _alternativeRegId != RegisterPlan::MaxRegisterId) {
+  if (input.isNull() && _infos.hasAlternativeRegister()) {
     // value is set, but null
     // check if there is a second input register available (UPSERT makes use of
     // two input registers,
     // one for the search document, the other for the insert document)
-    val = cur->getValueReference(_pos, _alternativeRegId);
+    val = row.getValue(_infos.alternativeRegisterId());
 
     input = val.slice();  // will throw when wrong type
     usedAlternativeRegId = true;
@@ -305,17 +310,17 @@ size_t ExecutionBlockImpl<DistributeExecutor>::sendToClient(SharedAqlItemBlockPt
   VPackSlice value = input;
   bool hasCreatedKeyAttribute = false;
 
-  if (input.isString() && _allowKeyConversionToObject) {
+  if (input.isString() && _infos.allowKeyConversionToObject()) {
     _keyBuilder.clear();
     _keyBuilder.openObject(true);
     _keyBuilder.add(StaticStrings::KeyString, input);
     _keyBuilder.close();
 
     // clear the previous value
-    cur->destroyValue(_pos, _regId);
+    block->destroyValue(rowIndex, _infos.registerId());
 
     // overwrite with new value
-    cur->emplaceValue(_pos, _regId, _keyBuilder.slice());
+    block->emplaceValue(rowIndex, _infos.registerId(), _keyBuilder.slice());
 
     value = _keyBuilder.slice();
     hasCreatedKeyAttribute = true;
@@ -325,11 +330,11 @@ size_t ExecutionBlockImpl<DistributeExecutor>::sendToClient(SharedAqlItemBlockPt
 
   TRI_ASSERT(value.isObject());
 
-  if (_createKeys) {
+  if (_infos.createKeys()) {
     bool buildNewObject = false;
     // we are responsible for creating keys if none present
 
-    if (_usesDefaultSharding) {
+    if (_infos.usesDefaultSharding()) {
       // the collection is sharded by _key...
       if (!hasCreatedKeyAttribute && !value.hasKey(StaticStrings::KeyString)) {
         // there is no _key attribute present, so we are responsible for
@@ -340,7 +345,7 @@ size_t ExecutionBlockImpl<DistributeExecutor>::sendToClient(SharedAqlItemBlockPt
       // the collection is not sharded by _key
       if (hasCreatedKeyAttribute || value.hasKey(StaticStrings::KeyString)) {
         // a _key was given, but user is not allowed to specify _key
-        if (usedAlternativeRegId || !_allowSpecifiedKeys) {
+        if (usedAlternativeRegId || !_infos.allowSpecifiedKeys()) {
           THROW_ARANGO_EXCEPTION(TRI_ERROR_CLUSTER_MUST_NOT_SPECIFY_KEY);
         }
       } else {
@@ -351,47 +356,97 @@ size_t ExecutionBlockImpl<DistributeExecutor>::sendToClient(SharedAqlItemBlockPt
     if (buildNewObject) {
       _keyBuilder.clear();
       _keyBuilder.openObject(true);
-      _keyBuilder.add(StaticStrings::KeyString, VPackValue(createKey(value)));
+      _keyBuilder.add(StaticStrings::KeyString, VPackValue(_infos.createKey(value)));
       _keyBuilder.close();
 
       _objectBuilder.clear();
       VPackCollection::merge(_objectBuilder, input, _keyBuilder.slice(), true);
 
       // clear the previous value and overwrite with new value:
-      if (usedAlternativeRegId) {
-        cur->destroyValue(_pos, _alternativeRegId);
-        cur->emplaceValue(_pos, _alternativeRegId, _objectBuilder.slice());
-      } else {
-        cur->destroyValue(_pos, _regId);
-        cur->emplaceValue(_pos, _regId, _objectBuilder.slice());
-      }
+      auto reg = usedAlternativeRegId ? _infos.alternativeRegisterId()
+                                      : _infos.registerId();
+
+      block->destroyValue(rowIndex, reg);
+      block->emplaceValue(rowIndex, reg, _objectBuilder.slice());
       value = _objectBuilder.slice();
     }
   }
+  auto res = _infos.getResponsibleClient(value);
+  THROW_ARANGO_EXCEPTION_IF_FAIL(res.result());
+  return res.get();
+}
 
-  std::string shardId;
-  int res = _logCol->getResponsibleShard(value, true, shardId);
+ExecutionBlockImpl<DistributeExecutor>::ExecutionBlockImpl(ExecutionEngine* engine,
+                                                           DistributeNode const* node,
+                                                           DistributeExecutorInfos&& infos)
+    : BlocksWithClientsImpl(engine, node, std::move(infos)) {}
 
-  if (res != TRI_ERROR_NO_ERROR) {
-    THROW_ARANGO_EXCEPTION(res);
+/*
+/// @brief getOrSkipSomeForShard
+std::pair<ExecutionState, arangodb::Result> ExecutionBlockImpl<DistributeExecutor>::getOrSkipSomeForShard(
+    size_t atMost, bool skipping, SharedAqlItemBlockPtr& result,
+    size_t& skipped, std::string const& shardId) {
+  TRI_ASSERT(result == nullptr && skipped == 0);
+  TRI_ASSERT(atMost > 0);
+
+  size_t clientId = getClientId(shardId);
+
+  if (!hasMoreForClientId(clientId)) {
+    return {ExecutionState::DONE, TRI_ERROR_NO_ERROR};
   }
 
-  TRI_ASSERT(!shardId.empty());
-  if (_type == ScatterNode::ScatterType::SERVER) {
-    // Special case for server based distribution.
-    shardId = _collection->getServerForShard(shardId);
-    TRI_ASSERT(!shardId.empty());
+  std::deque<std::pair<size_t, size_t>>& buf = _distBuffer.at(clientId);
+
+  if (buf.empty()) {
+    auto res = getBlockForClient(atMost, clientId);
+    if (res.first == ExecutionState::WAITING) {
+      return {res.first, TRI_ERROR_NO_ERROR};
+    }
+    if (!res.second) {
+      // Upstream is empty!
+      TRI_ASSERT(res.first == ExecutionState::DONE);
+      return {ExecutionState::DONE, TRI_ERROR_NO_ERROR};
+    }
   }
-  return getClientId(shardId);
-}
 
-Query const& ExecutionBlockImpl<DistributeExecutor>::getQuery() const noexcept { return _query; }
+  skipped = (std::min)(buf.size(), atMost);
 
-/// @brief create a new document key
-std::string ExecutionBlockImpl<DistributeExecutor>::createKey(VPackSlice input) const {
-  return _logCol->createKey(input);
-}
+  if (skipping) {
+    for (size_t i = 0; i < skipped; i++) {
+      buf.pop_front();
+    }
+    return {getHasMoreStateForClientId(clientId), TRI_ERROR_NO_ERROR};
+  }
+
+  BlockCollector collector(&_engine->itemBlockManager());
+  std::vector<size_t> chosen;
+
+  size_t i = 0;
+  while (i < skipped) {
+    size_t const n = buf.front().first;
+    while (buf.front().first == n && i < skipped) {
+      chosen.emplace_back(buf.front().second);
+      buf.pop_front();
+      i++;
+
+      // make sure we are not overreaching over the end of the buffer
+      if (buf.empty()) {
+        break;
+      }
+    }
+
+    SharedAqlItemBlockPtr more{_buffer[n]->slice(chosen, 0, chosen.size())};
+    collector.add(std::move(more));
+
+    chosen.clear();
+  }
+
+  // Skipping was handle before
+  TRI_ASSERT(!skipping);
+  result = collector.steal();
 
-ExecutorInfos const& ExecutionBlockImpl<DistributeExecutor>::infos() const {
-  return _infos;
+  // _buffer is left intact, deleted and cleared at shutdown
+
+  return {getHasMoreStateForClientId(clientId), TRI_ERROR_NO_ERROR};
 }
+*/
\ No newline at end of file
diff --git a/arangod/Aql/DistributeExecutor.h b/arangod/Aql/DistributeExecutor.h
index 003e3fda1fb8..5d0073b45a37 100644
--- a/arangod/Aql/DistributeExecutor.h
+++ b/arangod/Aql/DistributeExecutor.h
@@ -26,123 +26,154 @@
 #include "Aql/BlocksWithClients.h"
 #include "Aql/ExecutionBlockImpl.h"
 #include "Aql/ExecutorInfos.h"
+#include "Cluster/ResultT.h"
 
 namespace arangodb {
 namespace aql {
 
+class AqlItemBlockManager;
 class DistributeNode;
 
-// The DistributeBlock is actually implemented by specializing
-// ExecutionBlockImpl, so this class only exists to identify the specialization.
-class DistributeExecutor {};
-
-class Query;
-
-/**
- * @brief See ExecutionBlockImpl.h for documentation.
- */
-template <>
-class ExecutionBlockImpl<DistributeExecutor> : public BlocksWithClients {
+class DistributeExecutorInfos : public ExecutorInfos, public ClientsExecutorInfos {
  public:
-  // TODO Even if it's not strictly necessary here, for consistency's sake the
-  // non-standard arguments (shardIds, collection) should probably be moved into
-  // some DistributeExecutorInfos class.
-  ExecutionBlockImpl(ExecutionEngine* engine, DistributeNode const* node,
-                     ExecutorInfos&& infos, std::vector<std::string> const& shardIds,
-                     Collection const* collection, RegisterId regId,
-                     RegisterId alternativeRegId, bool allowSpecifiedKeys,
-                     bool allowKeyConversionToObject, bool createKeys);
-
-  ~ExecutionBlockImpl() override = default;
-
-  std::pair<ExecutionState, Result> initializeCursor(InputAqlItemRow const& input) override;
-
-  /// @brief getSomeForShard
-  std::pair<ExecutionState, SharedAqlItemBlockPtr> getSomeForShard(size_t atMost,
-                                                                   std::string const& shardId) override;
-
-  /// @brief skipSomeForShard
-  std::pair<ExecutionState, size_t> skipSomeForShard(size_t atMost,
-                                                     std::string const& shardId) override;
+  DistributeExecutorInfos(std::shared_ptr<std::unordered_set<RegisterId>> readableInputRegisters,
+                          std::shared_ptr<std::unordered_set<RegisterId>> writeableOutputRegisters,
+                          RegisterId nrInputRegisters, RegisterId nrOutputRegisters,
+                          std::unordered_set<RegisterId> registersToClear,
+                          std::unordered_set<RegisterId> registersToKeep,
+                          std::vector<std::string> clientIds, Collection const* collection,
+                          RegisterId regId, RegisterId alternativeRegId,
+                          bool allowSpecifiedKeys, bool allowKeyConversionToObject,
+                          bool createKeys, ScatterNode::ScatterType type);
+
+  auto registerId() const noexcept -> RegisterId;
+  auto hasAlternativeRegister() const noexcept -> bool;
+  auto alternativeRegisterId() const noexcept -> RegisterId;
+  auto allowKeyConversionToObject() const noexcept -> bool;
+  auto createKeys() const noexcept -> bool;
+  auto usesDefaultSharding() const noexcept -> bool;
+  auto allowSpecifiedKeys() const noexcept -> bool;
+  auto scatterType() const noexcept -> ScatterNode::ScatterType;
+
+  auto getResponsibleClient(arangodb::velocypack::Slice value) const
+      -> ResultT<std::string>;
+
+  auto createKey(VPackSlice input) const -> std::string;
 
  private:
-  /// @brief getSomeForShard
-  std::pair<ExecutionState, SharedAqlItemBlockPtr> getSomeForShardWithoutTrace(
-      size_t atMost, std::string const& shardId);
-
-  /// @brief skipSomeForShard
-  std::pair<ExecutionState, size_t> skipSomeForShardWithoutTrace(size_t atMost,
-                                                                 std::string const& shardId);
-
-  std::pair<ExecutionState, arangodb::Result> getOrSkipSomeForShard(
-      size_t atMost, bool skipping, SharedAqlItemBlockPtr& result,
-      size_t& skipped, std::string const& shardId);
-
-  bool hasMoreForClientId(size_t clientId) const;
-
-  /// @brief getHasMoreStateForClientId: State for client <clientId>?
-  ExecutionState getHasMoreStateForClientId(size_t clientId) const;
-
-  /// @brief hasMoreForShard: any more for shard <shardId>?
-  bool hasMoreForShard(std::string const& shardId) const;
+  RegisterId _regId;
+  RegisterId _alternativeRegId;
+  bool _allowKeyConversionToObject;
+  bool _createKeys;
+  bool _usesDefaultSharding;
+  bool _allowSpecifiedKeys;
 
-  /// @brief getBlockForClient: try to get at atMost pairs into
-  /// _distBuffer.at(clientId).
-  std::pair<ExecutionState, bool> getBlockForClient(size_t atMost, size_t clientId);
+  /// @brief _colectionName: the name of the sharded collection
+  Collection const* _collection;
 
-  /// @brief sendToClient: for each row of the incoming AqlItemBlock use the
-  /// attributes <shardKeys> of the register <id> to determine to which shard
-  /// the row should be sent.
-  size_t sendToClient(SharedAqlItemBlockPtr);
+  /// @brief Cache for the Logical Collection. This way it is not refetched
+  /// on every document.
+  std::shared_ptr<arangodb::LogicalCollection> _logCol;
 
-  /// @brief create a new document key
-  std::string createKey(arangodb::velocypack::Slice) const;
+  /// @brief type of distribution that this nodes follows.
+  ScatterNode::ScatterType _type;
+};
 
-  ExecutorInfos const& infos() const;
-  
-  Query const& getQuery() const noexcept;
+// The DistributeBlock is actually implemented by specializing
+// ExecutionBlockImpl, so this class only exists to identify the specialization.
+class DistributeExecutor {
+ public:
+  using Infos = DistributeExecutorInfos;
+
+  class ClientBlockData {
+   public:
+    ClientBlockData(ExecutionEngine& engine, ScatterNode const* node,
+                    ExecutorInfos const& scatterInfos);
+
+    auto clear() -> void;
+    auto addBlock(SharedAqlItemBlockPtr block, std::vector<size_t> usedIndexes) -> void;
+    auto hasDataFor(AqlCall const& call) -> bool;
+
+    auto execute(AqlCall call, ExecutionState upstreamState)
+        -> std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr>;
+
+   private:
+    /**
+     * @brief This call will join as many blocks as available from the queue
+     *        and return them in a SingleBlock. We then use the IdExecutor
+     *        to hand out the data contained in these blocks
+     *        We do on purpose not give any kind of guarantees on the sizing of
+     *        this block to be flexible with the implementation, and find a good
+     *        trade-off between blocksize and block copy operations.
+     *
+     * @return SharedAqlItemBlockPtr a joind block from the queue.
+     */
+    auto popJoinedBlock() -> SharedAqlItemBlockPtr;
+
+   private:
+    AqlItemBlockManager& _blockManager;
+    ExecutorInfos const& _infos;
+
+    std::deque<std::pair<SharedAqlItemBlockPtr, std::vector<size_t>>> _queue;
+
+    // This is unique_ptr to get away with everything beeing forward declared...
+    std::unique_ptr<ExecutionBlock> _executor;
+    bool _executorHasMore;
+  };
+
+  DistributeExecutor(DistributeExecutorInfos const& infos);
+  ~DistributeExecutor() = default;
+
+  /**
+   * @brief Distribute the rows of the given block into the blockMap
+   *        NOTE: Has SideEffects
+   *        If the input value does not contain an object, it is modified inplace with
+   *        a new Object containing a key value!
+   *        Hence this method is not const ;(
+   *
+   * @param block The block to be distributed
+   * @param blockMap Map client => Data. Will provide the required data to the correct client.
+   */
+  auto distributeBlock(SharedAqlItemBlockPtr block,
+                       std::unordered_map<std::string, ClientBlockData>& blockMap) -> void;
 
  private:
-  ExecutorInfos _infos;
-
-  Query const& _query;
+  /**
+   * @brief Compute which client needs to get this row
+   *        NOTE: Has SideEffects
+   *        If the input value does not contain an object, it is modified inplace with
+   *        a new Object containing a key value!
+   *        Hence this method is not const ;(
+   *
+   * @param block The input block
+   * @param rowIndex
+   * @return std::string Identifier used by the client
+   */
+  auto getClient(SharedAqlItemBlockPtr block, size_t rowIndex) -> std::string;
 
-  /// @brief _distBuffer.at(i) is a deque containing pairs (j,k) such that
-  //  _buffer.at(j) row k should be sent to the client with id = i.
-  std::vector<std::deque<std::pair<size_t, size_t>>> _distBuffer;
+ private:
+  DistributeExecutorInfos const& _infos;
 
   // a reusable Builder object for building _key values
   arangodb::velocypack::Builder _keyBuilder;
 
   // a reusable Builder object for building document objects
   arangodb::velocypack::Builder _objectBuilder;
+};
 
-  /// @brief _colectionName: the name of the sharded collection
-  Collection const* _collection;
-
-  /// @brief Cache for the Logical Collection. This way it is not refetched
-  /// on every document.
-  std::shared_ptr<arangodb::LogicalCollection> _logCol;
-
-  /// @brief _index: the block in _buffer we are currently considering
-  size_t _index;
-
-  /// @brief _regId: the register to inspect
-  RegisterId _regId;
-
-  /// @brief a second register to inspect (used only for UPSERT nodes at the
-  /// moment to distinguish between search and insert)
-  RegisterId _alternativeRegId;
-
-  /// @brief whether or not the collection uses the default sharding
-  bool _usesDefaultSharding;
-
-  /// @brief allow specified keys even in non-default sharding case
-  bool _allowSpecifiedKeys;
+class Query;
 
-  bool _allowKeyConversionToObject;
+/**
+ * @brief See ExecutionBlockImpl.h for documentation.
+ */
+template <>
+class ExecutionBlockImpl<DistributeExecutor>
+    : public BlocksWithClientsImpl<DistributeExecutor> {
+ public:
+  ExecutionBlockImpl(ExecutionEngine* engine, DistributeNode const* node,
+                     DistributeExecutorInfos&& infos);
 
-  bool _createKeys;
+  ~ExecutionBlockImpl() override = default;
 };
 
 }  // namespace aql
diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index 9c525cf2caef..229e30debfb4 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -131,7 +131,8 @@ constexpr bool is_one_of_v = (std::is_same_v<T, Es> || ...);
  */
 template <typename Executor>
 constexpr bool isNewStyleExecutor =
-    is_one_of_v<Executor, FilterExecutor, SortedCollectExecutor, ReturnExecutor,
+    is_one_of_v<Executor, FilterExecutor, SortedCollectExecutor, IdExecutor<ConstFetcher>,
+                IdExecutor<SingleRowFetcher<BlockPassthrough::Enable>>, ReturnExecutor,
 #ifdef ARANGODB_USE_GOOGLE_TESTS
                 TestLambdaExecutor, TestLambdaSkipExecutor,  // we need one after these to avoid compile errors in non-test mode
 #endif
@@ -556,6 +557,7 @@ std::pair<ExecutionState, Result> ExecutionBlockImpl<Executor>::initializeCursor
   // reinitialize the DependencyProxy
   _dependencyProxy.reset();
   _lastRange = DataRange(ExecutorState::HASMORE);
+  _hasUsedDataRangeBlock = false;
 
   // destroy and re-create the Fetcher
   _rowFetcher.~Fetcher();
@@ -631,9 +633,11 @@ std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> ExecutionBlockImpl<Exe
 // error: specialization of 'template<class Executor> std::pair<arangodb::aql::ExecutionState, arangodb::Result> arangodb::aql::ExecutionBlockImpl<Executor>::initializeCursor(arangodb::aql::AqlItemBlock*, size_t)' in different namespace
 namespace arangodb::aql {
 // TODO -- remove this specialization when cpp 17 becomes available
+
 template <>
-std::pair<ExecutionState, Result> ExecutionBlockImpl<IdExecutor<ConstFetcher>>::initializeCursor(
-    InputAqlItemRow const& input) {
+template <>
+auto ExecutionBlockImpl<IdExecutor<ConstFetcher>>::injectConstantBlock<IdExecutor<ConstFetcher>>(SharedAqlItemBlockPtr block)
+    -> void {
   // reinitialize the DependencyProxy
   _dependencyProxy.reset();
 
@@ -646,15 +650,27 @@ std::pair<ExecutionState, Result> ExecutionBlockImpl<IdExecutor<ConstFetcher>>::
   TRI_ASSERT(_state == InternalState::DONE || _state == InternalState::FETCH_DATA);
   _state = InternalState::FETCH_DATA;
 
-  SharedAqlItemBlockPtr block =
-      input.cloneToBlock(_engine->itemBlockManager(), *(infos().registersToKeep()),
-                         infos().numberOfOutputRegisters());
+  // Reset state of execute
+  _lastRange = AqlItemBlockInputRange{ExecutorState::HASMORE};
+  _hasUsedDataRangeBlock = false;
+  _upstreamState = ExecutionState::HASMORE;
 
   _rowFetcher.injectBlock(block);
 
   // cppcheck-suppress unreadVariable
   constexpr bool customInit = hasInitializeCursor<decltype(_executor)>::value;
   InitializeCursor<customInit>::init(_executor, _rowFetcher, _infos);
+}
+
+// TODO -- remove this specialization when cpp 17 becomes available
+template <>
+std::pair<ExecutionState, Result> ExecutionBlockImpl<IdExecutor<ConstFetcher>>::initializeCursor(
+    InputAqlItemRow const& input) {
+  SharedAqlItemBlockPtr block =
+      input.cloneToBlock(_engine->itemBlockManager(), *(infos().registersToKeep()),
+                         infos().numberOfOutputRegisters());
+
+  injectConstantBlock(block);
 
   // end of default initializeCursor
   return ExecutionBlock::initializeCursor(input);
diff --git a/arangod/Aql/ExecutionBlockImpl.h b/arangod/Aql/ExecutionBlockImpl.h
index a50634f58bbb..5868ae27739a 100644
--- a/arangod/Aql/ExecutionBlockImpl.h
+++ b/arangod/Aql/ExecutionBlockImpl.h
@@ -37,6 +37,9 @@
 
 namespace arangodb::aql {
 
+template <class Fetcher>
+class IdExecutor;
+
 struct AqlCall;
 class AqlItemBlock;
 class ExecutionEngine;
@@ -196,6 +199,9 @@ class ExecutionBlockImpl final : public ExecutionBlock {
 
   [[nodiscard]] std::pair<ExecutionState, Result> initializeCursor(InputAqlItemRow const& input) override;
 
+  template <class exec = Executor, typename = std::enable_if_t<std::is_same_v<exec, IdExecutor<ConstFetcher>>>>
+  auto injectConstantBlock(SharedAqlItemBlockPtr block) -> void;
+
   [[nodiscard]] Infos const& infos() const;
 
   /// @brief shutdown, will be called exactly once for the whole query
diff --git a/arangod/Aql/IdExecutor.cpp b/arangod/Aql/IdExecutor.cpp
index 909aa5d7256a..7965e7fbb4e5 100644
--- a/arangod/Aql/IdExecutor.cpp
+++ b/arangod/Aql/IdExecutor.cpp
@@ -22,7 +22,9 @@
 
 #include "IdExecutor.h"
 
+#include "Aql/AqlCall.h"
 #include "Aql/AqlCallStack.h"
+#include "Aql/AqlItemBlockInputRange.h"
 #include "Aql/AqlValue.h"
 #include "Aql/ConstFetcher.h"
 #include "Aql/ExecutionEngine.h"
@@ -158,29 +160,26 @@ IdExecutor<UsedFetcher>::~IdExecutor() = default;
 
 template <class UsedFetcher>
 std::pair<ExecutionState, NoStats> IdExecutor<UsedFetcher>::produceRows(OutputAqlItemRow& output) {
-  ExecutionState state = ExecutionState::HASMORE;
-  NoStats stats;
-  InputAqlItemRow inputRow = InputAqlItemRow{CreateInvalidInputRowHint{}};
-  while (!output.isFull() && state != ExecutionState::DONE) {
-    std::tie(state, inputRow) = _fetcher.fetchRow(output.numRowsLeft());
+  TRI_ASSERT(false);
+  THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
+}
 
-    if (state == ExecutionState::WAITING) {
-      TRI_ASSERT(!inputRow);
-      return {state, stats};
-    }
+template <class UsedFetcher>
+auto IdExecutor<UsedFetcher>::produceRows(AqlItemBlockInputRange& inputRange,
+                                          OutputAqlItemRow& output)
+    -> std::tuple<ExecutorState, NoStats, AqlCall> {
+  NoStats stats;
 
-    if (!inputRow) {
-      TRI_ASSERT(state == ExecutionState::DONE);
-      return {state, stats};
-    }
+  while (!output.isFull() && inputRange.hasDataRow()) {
+    auto const& [state, inputRow] = inputRange.nextDataRow();
+    TRI_ASSERT(inputRow);
 
     TRI_IF_FAILURE("SingletonBlock::getOrSkipSome") {
       THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
     }
 
-    TRI_ASSERT(state == ExecutionState::HASMORE || state == ExecutionState::DONE);
     /*Second parameter are to ignore registers that should be kept but are missing in the input row*/
-    output.copyRow(inputRow, std::is_same<UsedFetcher, ConstFetcher>::value);
+    output.copyRow(inputRow, std::is_same_v<UsedFetcher, ConstFetcher>);
     TRI_ASSERT(output.produced());
     output.advanceRow();
 
@@ -189,14 +188,14 @@ std::pair<ExecutionState, NoStats> IdExecutor<UsedFetcher>::produceRows(OutputAq
     }
   }
 
-  return {state, stats};
+  return {inputRange.upstreamState(), stats, output.getClientCall()};
 }
 
 template <class UsedFetcher>
 std::tuple<ExecutionState, typename IdExecutor<UsedFetcher>::Stats, SharedAqlItemBlockPtr>
 IdExecutor<UsedFetcher>::fetchBlockForPassthrough(size_t atMost) {
-  auto rv = _fetcher.fetchBlockForPassthrough(atMost);
-  return {rv.first, {}, std::move(rv.second)};
+  TRI_ASSERT(false);
+  THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
 }
 
 template class ::arangodb::aql::IdExecutor<ConstFetcher>;
diff --git a/arangod/Aql/IdExecutor.h b/arangod/Aql/IdExecutor.h
index 50e1a762a816..10e63216e50c 100644
--- a/arangod/Aql/IdExecutor.h
+++ b/arangod/Aql/IdExecutor.h
@@ -52,6 +52,9 @@ class Methods;
 }
 
 namespace aql {
+
+struct AqlCall;
+class AqlItemBlockInputRange;
 class ExecutionEngine;
 class ExecutionNode;
 class ExecutorInfos;
@@ -147,6 +150,15 @@ class IdExecutor {
    */
   std::pair<ExecutionState, Stats> produceRows(OutputAqlItemRow& output);
 
+  /**
+   * @brief produce the next Row of Aql Values.
+   *
+   * @return ExecutorState, the stats, and a new Call that needs to be send to upstream
+   */
+  auto produceRows(AqlItemBlockInputRange& input, OutputAqlItemRow& output)
+      -> std::tuple<ExecutorState, Stats, AqlCall>;
+
+  // Deprecated remove me
   std::tuple<ExecutionState, Stats, SharedAqlItemBlockPtr> fetchBlockForPassthrough(size_t atMost);
 
  private:
diff --git a/arangod/Aql/RemoteExecutor.cpp b/arangod/Aql/RemoteExecutor.cpp
index 1ac8f587a3fd..df23a2281a65 100644
--- a/arangod/Aql/RemoteExecutor.cpp
+++ b/arangod/Aql/RemoteExecutor.cpp
@@ -431,7 +431,22 @@ std::pair<ExecutionState, Result> ExecutionBlockImpl<RemoteExecutor>::shutdown(i
 
 std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> ExecutionBlockImpl<RemoteExecutor>::execute(
     AqlCallStack stack) {
-  TRI_ASSERT(false);
+  // Use the old getSome/SkipSome API.
+  // TODO needs execute implementation instead
+  auto myCall = stack.popCall();
+  TRI_ASSERT(AqlCall::IsSkipSomeCall(myCall) || AqlCall::IsGetSomeCall(myCall));
+  if (AqlCall::IsSkipSomeCall(myCall)) {
+    auto const [state, skipped] = skipSome(myCall.getOffset());
+    if (state != ExecutionState::WAITING) {
+      myCall.didSkip(skipped);
+    }
+    return {state, skipped, nullptr};
+  } else if (AqlCall::IsGetSomeCall(myCall)) {
+    auto const [state, block] = getSome(myCall.getLimit());
+    // We do not need to count as softLimit will be overwritten, and hard cannot be set.
+    return {state, 0, block};
+  }
+  // Should never get here!
   THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
 }
 
diff --git a/arangod/Aql/RestAqlHandler.cpp b/arangod/Aql/RestAqlHandler.cpp
index c9e6e0665cdb..e0cc8ab6ee0a 100644
--- a/arangod/Aql/RestAqlHandler.cpp
+++ b/arangod/Aql/RestAqlHandler.cpp
@@ -674,9 +674,8 @@ RestStatus RestAqlHandler::handleUseQuery(std::string const& operation,
     TRI_IF_FAILURE("RestAqlHandler::getSome") {
       THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
     }
-    auto atMost =
-        VelocyPackHelper::getNumericValue<size_t>(querySlice, "atMost",
-                                                  ExecutionBlock::DefaultBatchSize);
+    auto atMost = VelocyPackHelper::getNumericValue<size_t>(querySlice, "atMost",
+                                                            ExecutionBlock::DefaultBatchSize);
     SharedAqlItemBlockPtr items;
     ExecutionState state;
     if (shardId.empty()) {
@@ -685,13 +684,13 @@ RestStatus RestAqlHandler::handleUseQuery(std::string const& operation,
         return RestStatus::WAITING;
       }
     } else {
+      TRI_ASSERT(_query->engine()->root()->getPlanNode()->getType() == ExecutionNode::SCATTER ||
+                 _query->engine()->root()->getPlanNode()->getType() == ExecutionNode::DISTRIBUTE);
       auto block = dynamic_cast<BlocksWithClients*>(_query->engine()->root());
       if (block == nullptr) {
         THROW_ARANGO_EXCEPTION_MESSAGE(TRI_ERROR_INTERNAL,
                                        "unexpected node type");
       }
-      TRI_ASSERT(block->getPlanNode()->getType() == ExecutionNode::SCATTER ||
-                 block->getPlanNode()->getType() == ExecutionNode::DISTRIBUTE);
       std::tie(state, items) = block->getSomeForShard(atMost, shardId);
       if (state == ExecutionState::WAITING) {
         return RestStatus::WAITING;
@@ -708,9 +707,8 @@ RestStatus RestAqlHandler::handleUseQuery(std::string const& operation,
                           answerBuilder);
     }
   } else if (operation == "skipSome") {
-    auto atMost =
-        VelocyPackHelper::getNumericValue<size_t>(querySlice, "atMost",
-                                                  ExecutionBlock::DefaultBatchSize);
+    auto atMost = VelocyPackHelper::getNumericValue<size_t>(querySlice, "atMost",
+                                                            ExecutionBlock::DefaultBatchSize);
     size_t skipped;
     if (shardId.empty()) {
       auto tmpRes = _query->engine()->skipSome(atMost);
@@ -719,13 +717,14 @@ RestStatus RestAqlHandler::handleUseQuery(std::string const& operation,
       }
       skipped = tmpRes.second;
     } else {
+      TRI_ASSERT(_query->engine()->root()->getPlanNode()->getType() == ExecutionNode::SCATTER ||
+                 _query->engine()->root()->getPlanNode()->getType() == ExecutionNode::DISTRIBUTE);
+
       auto block = dynamic_cast<BlocksWithClients*>(_query->engine()->root());
       if (block == nullptr) {
         THROW_ARANGO_EXCEPTION_MESSAGE(TRI_ERROR_INTERNAL,
                                        "unexpected node type");
       }
-      TRI_ASSERT(block->getPlanNode()->getType() == ExecutionNode::SCATTER ||
-                 block->getPlanNode()->getType() == ExecutionNode::DISTRIBUTE);
 
       auto tmpRes = block->skipSomeForShard(atMost, shardId);
       if (tmpRes.first == ExecutionState::WAITING) {
diff --git a/arangod/Aql/ScatterExecutor.cpp b/arangod/Aql/ScatterExecutor.cpp
index 65b601ee1c92..40d1c2208cf2 100644
--- a/arangod/Aql/ScatterExecutor.cpp
+++ b/arangod/Aql/ScatterExecutor.cpp
@@ -22,168 +22,114 @@
 
 #include "ScatterExecutor.h"
 
+#include "Aql/AqlCallStack.h"
+#include "Aql/ExecutionBlockImpl.h"
 #include "Aql/ExecutionEngine.h"
+#include "Aql/IdExecutor.h"
 #include "Basics/Exceptions.h"
 
 using namespace arangodb;
 using namespace arangodb::aql;
 
-ExecutionBlockImpl<ScatterExecutor>::ExecutionBlockImpl(ExecutionEngine* engine,
-                                                        ScatterNode const* node,
-                                                        ExecutorInfos&& infos,
-                                                        std::vector<std::string> const& shardIds)
-    : BlocksWithClients(engine, node, shardIds),
-      _infos(std::move(infos)),
-      _query(*engine->getQuery()) {
-  _shardIdMap.reserve(_nrClients);
-  for (size_t i = 0; i < _nrClients; i++) {
-    _shardIdMap.emplace(std::make_pair(shardIds[i], i));
-  }
+ScatterExecutorInfos::ScatterExecutorInfos(
+    std::shared_ptr<std::unordered_set<RegisterId>> readableInputRegisters,
+    std::shared_ptr<std::unordered_set<RegisterId>> writeableOutputRegisters,
+    RegisterId nrInputRegisters, RegisterId nrOutputRegisters,
+    std::unordered_set<RegisterId> registersToClear,
+    std::unordered_set<RegisterId> registersToKeep, std::vector<std::string> clientIds)
+    : ExecutorInfos(readableInputRegisters, writeableOutputRegisters, nrInputRegisters,
+                    nrOutputRegisters, registersToClear, registersToKeep),
+      ClientsExecutorInfos(std::move(clientIds)) {}
+
+ScatterExecutor::ClientBlockData::ClientBlockData(ExecutionEngine& engine,
+                                                  ScatterNode const* node,
+                                                  ExecutorInfos const& scatterInfos)
+    : _queue{}, _executor(nullptr), _executorHasMore{false} {
+  // We only get shared ptrs to const data. so we need to copy here...
+  IdExecutorInfos infos{scatterInfos.numberOfInputRegisters(),
+                        *scatterInfos.registersToKeep(),
+                        *scatterInfos.registersToClear(), "", false};
+  // NOTE: Do never change this type! The execute logic below requires this and only this type.
+  _executor =
+      std::make_unique<ExecutionBlockImpl<IdExecutor<ConstFetcher>>>(&engine, node,
+                                                                     std::move(infos));
 }
 
-/// @brief initializeCursor
-std::pair<ExecutionState, Result> ExecutionBlockImpl<ScatterExecutor>::initializeCursor(
-    InputAqlItemRow const& input) {
-  // local clean up
-  _posForClient.clear();
-
-  for (size_t i = 0; i < _nrClients; i++) {
-    _posForClient.emplace_back(0, 0);
-  }
-
-  return ExecutionBlock::initializeCursor(input);
-}
-
-/// @brief getSomeForShard
-std::pair<ExecutionState, SharedAqlItemBlockPtr> ExecutionBlockImpl<ScatterExecutor>::getSomeForShard(
-    size_t atMost, std::string const& shardId) {
-  traceGetSomeBegin(atMost);
-  auto result = getSomeForShardWithoutTrace(atMost, shardId);
-  return traceGetSomeEnd(result.first, std::move(result.second));
-}
-std::pair<ExecutionState, SharedAqlItemBlockPtr> ExecutionBlockImpl<ScatterExecutor>::getSomeForShardWithoutTrace(
-    size_t atMost, std::string const& shardId) {
-  // NOTE: We do not need to retain these, the getOrSkipSome is required to!
-  size_t skipped = 0;
-  SharedAqlItemBlockPtr result = nullptr;
-  auto out = getOrSkipSomeForShard(atMost, false, result, skipped, shardId);
-  if (out.first == ExecutionState::WAITING) {
-    return {out.first, nullptr};
-  }
-  if (!out.second.ok()) {
-    THROW_ARANGO_EXCEPTION(out.second);
-  }
-  return {out.first, std::move(result)};
+auto ScatterExecutor::ClientBlockData::clear() -> void {
+  _queue.clear();
+  _executorHasMore = false;
 }
 
-/// @brief skipSomeForShard
-std::pair<ExecutionState, size_t> ExecutionBlockImpl<ScatterExecutor>::skipSomeForShard(
-    size_t atMost, std::string const& shardId) {
-  traceSkipSomeBegin(atMost);
-  auto result = skipSomeForShardWithoutTrace(atMost, shardId);
-  return traceSkipSomeEnd(result.first, result.second);
+auto ScatterExecutor::ClientBlockData::addBlock(SharedAqlItemBlockPtr block) -> void {
+  // NOTE:
+  // There given ItemBlock will be reused in all requesting blocks.
+  // However, the next followwing block could be passthrough.
+  // If it is, it will modify that data stored in block.
+  // If now anther client requests the same block, it is not
+  // the original any more, but a modified version.
+  // For Instance in calculation we assert that the place we write to
+  // is empty. If another peer-calculation has written to this value
+  // this assertion does not hold true anymore.
+  // Hence we are required to do an indepth cloning here.
+  _queue.emplace_back(block->slice(0, block->size()));
 }
 
-std::pair<ExecutionState, size_t> ExecutionBlockImpl<ScatterExecutor>::skipSomeForShardWithoutTrace(
-    size_t atMost, std::string const& shardId) {
-  // NOTE: We do not need to retain these, the getOrSkipSome is required to!
-  size_t skipped = 0;
-  SharedAqlItemBlockPtr result = nullptr;
-  auto out = getOrSkipSomeForShard(atMost, true, result, skipped, shardId);
-  if (out.first == ExecutionState::WAITING) {
-    return {out.first, 0};
-  }
-  TRI_ASSERT(result == nullptr);
-  if (!out.second.ok()) {
-    THROW_ARANGO_EXCEPTION(out.second);
-  }
-  return {out.first, skipped};
+auto ScatterExecutor::ClientBlockData::hasDataFor(AqlCall const& call) -> bool {
+  return _executorHasMore || !_queue.empty();
 }
 
-/// @brief getOrSkipSomeForShard
-std::pair<ExecutionState, arangodb::Result> ExecutionBlockImpl<ScatterExecutor>::getOrSkipSomeForShard(
-    size_t atMost, bool skipping, SharedAqlItemBlockPtr& result,
-    size_t& skipped, std::string const& shardId) {
-  TRI_ASSERT(result == nullptr && skipped == 0);
-  TRI_ASSERT(atMost > 0);
-
- size_t const clientId = getClientId(shardId);
-
-  if (!hasMoreForClientId(clientId)) {
-    return {ExecutionState::DONE, TRI_ERROR_NO_ERROR};
+auto ScatterExecutor::ClientBlockData::execute(AqlCall call, ExecutionState upstreamState)
+    -> std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> {
+  TRI_ASSERT(_executor != nullptr);
+  // Make sure we actually have data before you call execute
+  TRI_ASSERT(hasDataFor(call));
+  if (!_executorHasMore) {
+    auto const& block = _queue.front();
+    // This cast is guaranteed, we create this a couple lines above and only
+    // this executor is used here.
+    // Unfortunately i did not get a version compiled were i could only forward
+    // declare the teplates in header.
+    auto casted =
+        static_cast<ExecutionBlockImpl<IdExecutor<ConstFetcher>>*>(_executor.get());
+    TRI_ASSERT(casted != nullptr);
+    casted->injectConstantBlock(block);
+    _executorHasMore = true;
+    _queue.pop_front();
   }
-
-  TRI_ASSERT(_posForClient.size() > clientId);
-  std::pair<size_t, size_t>& pos = _posForClient[clientId];
-
-  // pull more blocks from dependency if necessary . . .
-  if (pos.first >= _buffer.size()) {
-    auto res = getBlock(atMost);
-    if (res.first == ExecutionState::WAITING) {
-      return {res.first, TRI_ERROR_NO_ERROR};
-    }
-    if (!res.second) {
-      TRI_ASSERT(res.first == ExecutionState::DONE);
-      return {ExecutionState::DONE, TRI_ERROR_NO_ERROR};
+  AqlCallStack stack{call};
+  auto [state, skipped, result] = _executor->execute(stack);
+
+  // We have all data locally cannot wait here.
+  TRI_ASSERT(state != ExecutionState::WAITING);
+
+  if (state == ExecutionState::DONE) {
+    // This executor is finished, including shadowrows
+    // We are going to reset it on next call
+    _executorHasMore = false;
+
+    // Also we need to adjust the return states
+    // as this state only represents one single block
+    if (!_queue.empty()) {
+      state = ExecutionState::HASMORE;
+    } else {
+      state = upstreamState;
     }
   }
-
-  auto& blockForClient = _buffer[pos.first];
-
-  size_t available = blockForClient->size() - pos.second;
-  // available should be non-zero
-
-  skipped = (std::min)(available, atMost);  // nr rows in outgoing block
-
-  if (!skipping) {
-    result = blockForClient->slice(pos.second, pos.second + skipped);
-  }
-
-  // increment the position . . .
-  pos.second += skipped;
-
-  // check if we're done at current block in buffer . . .
-  if (pos.second == blockForClient->size()) {
-    pos.first++;     // next block
-    pos.second = 0;  // reset the position within a block
-
-    // check if we can pop the front of the buffer . . .
-    bool popit = true;
-    for (size_t i = 0; i < _nrClients; i++) {
-      if (_posForClient[i].first == 0) {
-        popit = false;
-        break;
-      }
-    }
-    if (popit) {
-      _buffer.pop_front();
-      // update the values in first coord of _posForClient
-      for (size_t i = 0; i < _nrClients; i++) {
-        _posForClient[i].first--;
-      }
-    }
-  }
-
-  return {getHasMoreStateForClientId(clientId), TRI_ERROR_NO_ERROR};
+  return {state, skipped, result};
 }
 
-bool ExecutionBlockImpl<ScatterExecutor>::hasMoreForClientId(size_t clientId) const {
-  TRI_ASSERT(_nrClients != 0);
-
-  TRI_ASSERT(clientId < _posForClient.size());
-  std::pair<size_t, size_t> pos = _posForClient.at(clientId);
-  // (i, j) where i is the position in _buffer, and j is the position in
-  // _buffer[i] we are sending to <clientId>
+ScatterExecutor::ScatterExecutor(ExecutorInfos const&){};
 
-  if (pos.first <= _buffer.size()) {
-    return true;
+auto ScatterExecutor::distributeBlock(SharedAqlItemBlockPtr block,
+                                      std::unordered_map<std::string, ClientBlockData>& blockMap) const
+    -> void {
+  // Scatter returns every block on every client as is.
+  for (auto& [id, list] : blockMap) {
+    list.addBlock(block);
   }
-  return _upstreamState == ExecutionState::HASMORE;
 }
 
-ExecutionState ExecutionBlockImpl<ScatterExecutor>::getHasMoreStateForClientId(size_t clientId) const {
-  if (hasMoreForClientId(clientId)) {
-    return ExecutionState::HASMORE;
-  }
-  return ExecutionState::DONE;
-}
+ExecutionBlockImpl<ScatterExecutor>::ExecutionBlockImpl(ExecutionEngine* engine,
+                                                        ScatterNode const* node,
+                                                        ScatterExecutorInfos&& infos)
+    : BlocksWithClientsImpl(engine, node, std::move(infos)) {}
diff --git a/arangod/Aql/ScatterExecutor.h b/arangod/Aql/ScatterExecutor.h
index fb20f184b499..53bd1bb1b5c5 100644
--- a/arangod/Aql/ScatterExecutor.h
+++ b/arangod/Aql/ScatterExecutor.h
@@ -31,61 +31,65 @@
 namespace arangodb {
 namespace aql {
 
+class ExecutionEngine;
+class ScatterNode;
+
+class ScatterExecutorInfos : public ExecutorInfos, public ClientsExecutorInfos {
+ public:
+  ScatterExecutorInfos(std::shared_ptr<std::unordered_set<RegisterId>> readableInputRegisters,
+                       std::shared_ptr<std::unordered_set<RegisterId>> writeableOutputRegisters,
+                       RegisterId nrInputRegisters, RegisterId nrOutputRegisters,
+                       std::unordered_set<RegisterId> registersToClear,
+                       std::unordered_set<RegisterId> registersToKeep,
+                       std::vector<std::string> clientIds);
+};
+
 // The ScatterBlock is actually implemented by specializing ExecutionBlockImpl,
 // so this class only exists to identify the specialization.
-class ScatterExecutor {};
+class ScatterExecutor {
+ public:
+  using Infos = ScatterExecutorInfos;
+
+  class ClientBlockData {
+   public:
+    ClientBlockData(ExecutionEngine& engine, ScatterNode const* node,
+                    ExecutorInfos const& scatterInfos);
+
+    auto clear() -> void;
+    auto addBlock(SharedAqlItemBlockPtr block) -> void;
+    auto hasDataFor(AqlCall const& call) -> bool;
+
+    auto execute(AqlCall call, ExecutionState upstreamState)
+        -> std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr>;
+
+   private:
+    std::deque<SharedAqlItemBlockPtr> _queue;
+    // This is unique_ptr to get away with everything beeing forward declared...
+    std::unique_ptr<ExecutionBlock> _executor;
+    bool _executorHasMore;
+  };
+
+  ScatterExecutor(ExecutorInfos const&);
+  ~ScatterExecutor() = default;
+
+  auto distributeBlock(SharedAqlItemBlockPtr block,
+                       std::unordered_map<std::string, ClientBlockData>& blockMap) const
+      -> void;
+};
 
 /**
  * @brief See ExecutionBlockImpl.h for documentation.
  */
 template <>
-class ExecutionBlockImpl<ScatterExecutor> : public BlocksWithClients {
+class ExecutionBlockImpl<ScatterExecutor> : public BlocksWithClientsImpl<ScatterExecutor> {
  public:
   // TODO Even if it's not strictly necessary here, for consistency's sake the
   // non-standard argument (shardIds) should probably be moved into some
   // ScatterExecutorInfos class.
   ExecutionBlockImpl(ExecutionEngine* engine, ScatterNode const* node,
-                     ExecutorInfos&& infos, std::vector<std::string> const& shardIds);
+                     ScatterExecutorInfos&& infos);
 
   ~ExecutionBlockImpl() override = default;
-
-  std::pair<ExecutionState, Result> initializeCursor(InputAqlItemRow const& input) override;
-
-  /// @brief getSomeForShard
-  std::pair<ExecutionState, SharedAqlItemBlockPtr> getSomeForShard(size_t atMost,
-                                                                   std::string const& shardId) override;
-
-  /// @brief skipSomeForShard
-  std::pair<ExecutionState, size_t> skipSomeForShard(size_t atMost,
-                                                     std::string const& shardId) override;
-
- private:
-  /// @brief getSomeForShard
-  std::pair<ExecutionState, SharedAqlItemBlockPtr> getSomeForShardWithoutTrace(
-      size_t atMost, std::string const& shardId);
-
-  /// @brief skipSomeForShard
-  std::pair<ExecutionState, size_t> skipSomeForShardWithoutTrace(size_t atMost,
-                                                                 std::string const& shardId);
-
-  std::pair<ExecutionState, arangodb::Result> getOrSkipSomeForShard(
-      size_t atMost, bool skipping, SharedAqlItemBlockPtr& result,
-      size_t& skipped, std::string const& shardId);
-
-  bool hasMoreForClientId(size_t clientId) const;
-
-  /// @brief getHasMoreStateForClientId: State for client <clientId>?
-  ExecutionState getHasMoreStateForClientId(size_t clientId) const;
-
-  ExecutorInfos const& infos() const { return _infos; }
-
- private:
-  ExecutorInfos _infos;
-
-  Query const& _query;
-
-  /// @brief _posForClient:
-  std::vector<std::pair<size_t, size_t>> _posForClient;
 };
 
 }  // namespace aql
diff --git a/arangod/Aql/SingleRowFetcher.h b/arangod/Aql/SingleRowFetcher.h
index 0460ecef625d..ef98004b4084 100644
--- a/arangod/Aql/SingleRowFetcher.h
+++ b/arangod/Aql/SingleRowFetcher.h
@@ -62,7 +62,18 @@ class SingleRowFetcher {
   SingleRowFetcher();
 
  public:
-  // TODO implement and document
+  /**
+   * @brief Execute the given call stack
+   *
+   * @param stack Call stack, on top of stack there is current subquery, bottom is the main query.
+   * @return std::tuple<ExecutionState, size_t, DataRange>
+   *   ExecutionState => DONE, all queries are done, there will be no more
+   *   ExecutionState => HASMORE, there are more results for queries, might be on other subqueries
+   *   ExecutionState => WAITING, we need to do I/O to solve the request, save local state and return WAITING to caller immediately
+   *
+   *   size_t => Amount of documents skipped
+   *   DataRange => Resulting data
+   */
   std::tuple<ExecutionState, size_t, DataRange> execute(AqlCallStack& stack);
 
   /**
@@ -100,8 +111,7 @@ class SingleRowFetcher {
   // Like fetchRow(), but returns both the subquery-local state (like fetchRow())
   // and the global state (like fetchShadowRow()).
   // Currently necessary only in the SubqueryStartExecutor.
-  [[nodiscard]] RowWithStates fetchRowWithGlobalState(
-      size_t atMost = ExecutionBlock::DefaultBatchSize);
+  [[nodiscard]] RowWithStates fetchRowWithGlobalState(size_t atMost = ExecutionBlock::DefaultBatchSize);
 
   // NOLINTNEXTLINE google-default-arguments
   [[nodiscard]] TEST_VIRTUAL std::pair<ExecutionState, ShadowAqlItemRow> fetchShadowRow(
diff --git a/tests/Aql/ExecutorTestHelper.cpp b/tests/Aql/ExecutorTestHelper.cpp
index 4bd9cd324d2b..17a521230cda 100644
--- a/tests/Aql/ExecutorTestHelper.cpp
+++ b/tests/Aql/ExecutorTestHelper.cpp
@@ -22,6 +22,49 @@
 
 #include "ExecutorTestHelper.h"
 
+#include "Aql/ExecutionEngine.h"
+
+using namespace arangodb::tests::aql;
+
+auto arangodb::tests::aql::ValidateBlocksAreEqual(SharedAqlItemBlockPtr actual,
+                                                  SharedAqlItemBlockPtr expected) -> void {
+  velocypack::Options vpackOptions;
+  ASSERT_NE(expected, nullptr);
+  ASSERT_NE(actual, nullptr);
+  EXPECT_EQ(actual->size(), expected->size());
+  EXPECT_EQ(actual->getNrRegs(), 1);
+  for (size_t i = 0; i < (std::min)(actual->size(), expected->size()); ++i) {
+    auto const& x = actual->getValueReference(i, 0);
+    auto const& y = expected->getValueReference(i, 0);
+    EXPECT_TRUE(AqlValue::Compare(&vpackOptions, x, y, true) == 0)
+        << "Row " << i << " Column " << 0 << " do not agree. "
+        << x.slice().toJson(&vpackOptions) << " vs. "
+        << y.slice().toJson(&vpackOptions);
+  }
+}
+
+template <bool enableQueryTrace>
+AqlExecutorTestCase<enableQueryTrace>::AqlExecutorTestCase()
+    : _server{}, fakedQuery{_server.createFakeQuery(enableQueryTrace)} {
+  auto engine = std::make_unique<ExecutionEngine>(*fakedQuery, SerializationFormat::SHADOWROWS);
+  fakedQuery->setEngine(engine.release());
+}
+
+template <bool enableQueryTrace>
+auto AqlExecutorTestCase<enableQueryTrace>::generateNodeDummy() -> ExecutionNode* {
+  auto dummy = std::make_unique<SingletonNode>(fakedQuery->plan(), _execNodes.size());
+  auto res = dummy.get();
+  _execNodes.emplace_back(std::move(dummy));
+  return res;
+}
+template <bool enableQueryTrace>
+auto AqlExecutorTestCase<enableQueryTrace>::manager() const -> AqlItemBlockManager& {
+  return fakedQuery->engine()->itemBlockManager();
+}
+
+template class ::arangodb::tests::aql::AqlExecutorTestCase<true>;
+template class ::arangodb::tests::aql::AqlExecutorTestCase<false>;
+
 std::ostream& arangodb::tests::aql::operator<<(std::ostream& stream,
                                                arangodb::tests::aql::ExecutorCall call) {
   return stream << [call]() {
@@ -39,5 +82,5 @@ std::ostream& arangodb::tests::aql::operator<<(std::ostream& stream,
     // which is unable to figure out that the switch above is complete.
     TRI_ASSERT(false);
     THROW_ARANGO_EXCEPTION(TRI_ERROR_INTERNAL_AQL);
- }();
+  }();
 }
diff --git a/tests/Aql/ExecutorTestHelper.h b/tests/Aql/ExecutorTestHelper.h
index 0d5ffbb5f08c..907f9201458d 100644
--- a/tests/Aql/ExecutorTestHelper.h
+++ b/tests/Aql/ExecutorTestHelper.h
@@ -26,6 +26,7 @@
 #include "gtest/gtest.h"
 
 #include "AqlItemBlockHelper.h"
+#include "Mocks/Servers.h"
 #include "WaitingExecutionBlockMock.h"
 
 #include "Aql/AqlCall.h"
@@ -44,6 +45,45 @@ namespace arangodb {
 namespace tests {
 namespace aql {
 
+auto ValidateBlocksAreEqual(SharedAqlItemBlockPtr actual, SharedAqlItemBlockPtr expected)
+    -> void;
+
+/**
+ * @brief Base class for ExecutorTests in Aql.
+ *        It will provide a test server, including
+ *        an AqlQuery, as well as the ability to generate
+ *        Dummy ExecutionNodes.
+ *
+ * @tparam enableQueryTrace Enable Aql Profile Trace logging
+ */
+template <bool enableQueryTrace = false>
+class AqlExecutorTestCase {
+ protected:
+  AqlExecutorTestCase();
+  virtual ~AqlExecutorTestCase() = default;
+
+  /**
+   * @brief Creates and manages a ExecutionNode.
+   *        These nodes can be used to create the Executors
+   *        Caller does not need to manage the memory.
+   *
+   * @return ExecutionNode* Pointer to a dummy ExecutionNode. Memory is managed, do not delete.
+   */
+  auto generateNodeDummy() -> ExecutionNode*;
+
+  auto manager() const -> AqlItemBlockManager&;
+
+ private:
+  mocks::MockAqlServer _server;
+  std::vector<std::unique_ptr<ExecutionNode>> _execNodes;
+
+ protected:
+  // available variables
+  ResourceMonitor monitor{};
+  AqlItemBlockManager itemBlockManager{&monitor, SerializationFormat::SHADOWROWS};
+  std::unique_ptr<arangodb::aql::Query> fakedQuery;
+};
+
 template <typename E, std::size_t inputColumns = 1, std::size_t outputColumns = 1>
 struct ExecutorTestHelper {
   using SplitType = std::variant<std::vector<std::size_t>, std::size_t, std::monostate>;
diff --git a/tests/Aql/IdExecutorTest.cpp b/tests/Aql/IdExecutorTest.cpp
index 25871cfade75..32f0a51bf6ce 100644
--- a/tests/Aql/IdExecutorTest.cpp
+++ b/tests/Aql/IdExecutorTest.cpp
@@ -20,15 +20,23 @@
 /// @author Jan Christoph Uhde
 ////////////////////////////////////////////////////////////////////////////////
 
-#include "RowFetcherHelper.h"
 #include "gtest/gtest.h"
 
+#include "AqlItemBlockHelper.h"
+#include "ExecutorTestHelper.h"
+#include "RowFetcherHelper.h"
+
+#include "Aql/AqlCall.h"
+#include "Aql/AqlCallStack.h"
 #include "Aql/AqlItemBlock.h"
 #include "Aql/ConstFetcher.h"
+#include "Aql/ExecutionEngine.h"
+#include "Aql/ExecutionNode.h"
 #include "Aql/ExecutorInfos.h"
 #include "Aql/IdExecutor.h"
 #include "Aql/InputAqlItemRow.h"
 #include "Aql/OutputAqlItemRow.h"
+#include "Aql/Query.h"
 #include "Aql/ResourceUsage.h"
 #include "Aql/Stats.h"
 
@@ -39,60 +47,494 @@ using namespace arangodb::aql;
 
 namespace arangodb::tests::aql {
 
-class IdExecutorTest : public ::testing::Test {
+using TestParam = std::tuple<std::vector<int>,  // The input data
+                             ExecutorState,     // The upstream state
+                             AqlCall,           // The client Call,
+                             OutputAqlItemRow::CopyRowBehavior  // How the data is handled within outputRow
+                             >;
+
+class IdExecutorTestCombiner : public AqlExecutorTestCase<>,
+                               public ::testing::TestWithParam<TestParam> {
  protected:
-  ExecutionState state;
-
-  ResourceMonitor monitor;
-  AqlItemBlockManager itemBlockManager;
-  SharedAqlItemBlockPtr block;
-  std::shared_ptr<std::unordered_set<RegisterId>> outputRegisters;
-  std::shared_ptr<std::unordered_set<RegisterId>> registersToKeep;  // this must be set correctly
-
-  IdExecutorInfos infos;
-  OutputAqlItemRow row;
-
-  IdExecutorTest()
-      : itemBlockManager(&monitor, SerializationFormat::SHADOWROWS),
-        block(new AqlItemBlock(itemBlockManager, 1000, 1)),
-        outputRegisters(make_shared_unordered_set()),
-        registersToKeep(make_shared_unordered_set({0})),
-        infos(1 /*nrRegs*/, *registersToKeep /*toKeep*/, {} /*toClear*/),
-        row(std::move(block), outputRegisters, registersToKeep, infos.registersToClear()) {}
+  IdExecutorTestCombiner() {}
+
+  auto prepareInputRange() -> AqlItemBlockInputRange {
+    auto const& [input, upstreamState, clientCall, copyBehaviour] = GetParam();
+    if (input.empty()) {
+      // no input
+      return AqlItemBlockInputRange{upstreamState};
+    }
+    MatrixBuilder<1> matrix;
+    for (auto const& it : input) {
+      matrix.emplace_back(RowBuilder<1>{{it}});
+    }
+    SharedAqlItemBlockPtr block = buildBlock<1>(manager(), std::move(matrix));
+    return AqlItemBlockInputRange{upstreamState, block, 0, input.size()};
+  }
+
+  auto prepareOutputRow(SharedAqlItemBlockPtr input) -> OutputAqlItemRow {
+    auto toWrite = make_shared_unordered_set({});
+    auto toKeep = make_shared_unordered_set({0});
+    auto toClear = make_shared_unordered_set();
+    auto const& [unused, upstreamState, clientCall, copyBehaviour] = GetParam();
+    AqlCall callCopy = clientCall;
+    if (copyBehaviour == OutputAqlItemRow::CopyRowBehavior::DoNotCopyInputRows) {
+      // For passthrough we reuse the block
+      return OutputAqlItemRow(input, toWrite, toKeep, toClear,
+                              std::move(callCopy), copyBehaviour);
+    }
+    // Otherwise we need to create a fresh block (or forward nullptr)
+    if (input == nullptr) {
+      SharedAqlItemBlockPtr outBlock{nullptr};
+      return OutputAqlItemRow(outBlock, toWrite, toKeep, toClear,
+                              std::move(callCopy), copyBehaviour);
+    }
+    SharedAqlItemBlockPtr outBlock{
+        new AqlItemBlock(manager(), input->size(), input->getNrRegs())};
+    return OutputAqlItemRow(outBlock, toWrite, toKeep, toClear,
+                            std::move(callCopy), copyBehaviour);
+  }
+
+  // After Execute is done these fetchers shall be removed,
+  // the Executor does not need it anymore!
+  // However the template is still required.
+  template <class Fetcher>
+  auto runTest(Fetcher& fetcher) -> void {
+    auto const& [input, upstreamState, clientCall, copyBehaviour] = GetParam();
+
+    auto inputRange = prepareInputRange();
+    auto outputRow = prepareOutputRow(inputRange.getBlock());
+
+    // If the input is empty, all rows(none) are used, otherwise they are not.
+    EXPECT_EQ(outputRow.allRowsUsed(), input.empty());
+    IdExecutorInfos infos{1, {0}, {}};
+
+    IdExecutor<Fetcher> testee{fetcher, infos};
+
+    auto const [state, stats, call] = testee.produceRows(inputRange, outputRow);
+    EXPECT_EQ(state, upstreamState);
+    // Stats are NoStats, no checks here.
+
+    // We can never forward any offset.
+    EXPECT_EQ(call.getOffset(), 0);
+
+    // The limits need to be reduced by input size.
+    EXPECT_EQ(call.softLimit + input.size(), clientCall.softLimit);
+    EXPECT_EQ(call.hardLimit + input.size(), clientCall.hardLimit);
+
+    // We can forward fullCount if it is there.
+    EXPECT_EQ(call.needsFullCount(), clientCall.needsFullCount());
+
+    // This internally actually asserts that all input rows are "copied".
+    EXPECT_TRUE(outputRow.allRowsUsed());
+    auto result = outputRow.stealBlock();
+    if (!input.empty()) {
+      ASSERT_NE(result, nullptr);
+      ASSERT_EQ(result->size(), input.size());
+      for (size_t i = 0; i < input.size(); ++i) {
+        auto val = result->getValueReference(i, 0);
+        ASSERT_TRUE(val.isNumber());
+        EXPECT_EQ(val.toInt64(), input.at(i));
+      }
+    } else {
+      EXPECT_EQ(result, nullptr);
+    }
+  }
 };
 
-TEST_F(IdExecutorTest, there_are_no_rows_upstream) {
-  ConstFetcherHelper fetcher(itemBlockManager, nullptr);
-  IdExecutor<ConstFetcher> testee(fetcher, infos);
-  NoStats stats{};
+TEST_P(IdExecutorTestCombiner, test_produce_datarange_constFetcher) {
+  std::shared_ptr<VPackBuilder> fakeFetcherInput{VPackParser::fromJson("[ ]")};
+  ConstFetcher cFetcher = ConstFetcherHelper{manager(), fakeFetcherInput->buffer()};
+  runTest(cFetcher);
+}
+
+TEST_P(IdExecutorTestCombiner, test_produce_datarange_singleRowFetcher) {
+  std::shared_ptr<VPackBuilder> fakeFetcherInput{VPackParser::fromJson("[ ]")};
+  SingleRowFetcher<::arangodb::aql::BlockPassthrough::Enable> srFetcher =
+      SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Enable>{
+          manager(), fakeFetcherInput->buffer(), false};
+  runTest(srFetcher);
+}
+
+/**
+ * In order to test this executor
+ * Only the following input cases are relevant:
+ * 1) Empty input and Done
+ * 2) Empty input and HasMore
+ * 3) Input with data and done
+ * 4) Input with data and HasMore
+ *
+ * And only the following Call cases are relevant:
+ * 1) Call limit > data, fullCount: false
+ * 2) Call limit > data, fullCount: true
+ * 3) Call limit == data, fullCount: false
+ * 4) Call limit == data, fullCount: true
+ * 5) Unlimited call
+ *
+ * All other cases are excluded by Passhtrough.
+ *
+ * This executor is templated by two fetcher types:
+ *   ConstFetcher
+ *   SingleRowFetcher<passthrough>
+ *
+ * The output row has the following copy types
+ *   DoNotCopy << This is actually used in production, however we cannot test that we actually do something with it
+ *   DoCopy  << This is to assert that copying is performaed
+ */
+
+static auto inputs = testing::Values(std::vector<int>{},  // Test empty input
+                                     std::vector<int>{1, 2, 3}  // Test input data
+);
+
+auto upstreamStates = testing::Values(ExecutorState::HASMORE, ExecutorState::DONE);
+auto clientCalls = testing::Values(AqlCall{},  // unlimited call
+                                   AqlCall{0, 3, AqlCall::Infinity{}, false},  // softlimit call (note this is equal to length of input data)
+                                   AqlCall{0, AqlCall::Infinity{}, 3, false},  // hardlimit call (note this is equal to length of input data), no fullcount
+                                   AqlCall{0, AqlCall::Infinity{}, 3, true},  // hardlimit call (note this is equal to length of input data), with fullcount
+                                   AqlCall{0, 7, AqlCall::Infinity{}, false},  // softlimit call (note this is larger than length of input data)
+                                   AqlCall{0, AqlCall::Infinity{}, 7, false},  // hardlimit call (note this is larger than length of input data), no fullcount
+                                   AqlCall{0, AqlCall::Infinity{}, 7, true}  // hardlimit call (note this is larger than length of input data), with fullcount
+);
+
+auto copyBehaviours = testing::Values(OutputAqlItemRow::CopyRowBehavior::CopyInputRows,  // Create a new row and write the data
+                                      OutputAqlItemRow::CopyRowBehavior::DoNotCopyInputRows  // Just passthrough (production)
+);
+
+INSTANTIATE_TEST_CASE_P(IdExecutorTest, IdExecutorTestCombiner,
+                        ::testing::Combine(inputs, upstreamStates, clientCalls, copyBehaviours));
+
+class IdExecutionBlockTest : public AqlExecutorTestCase<>, public ::testing::Test {};
+
+// The IdExecutor has a specific initializeCursor method in ExecutionBlockImpl
+TEST_F(IdExecutionBlockTest, test_initialize_cursor_get) {
+  IdExecutorInfos infos{1, {0}, {}};
+  ExecutionBlockImpl<IdExecutor<ConstFetcher>> testee{fakedQuery->engine(),
+                                                      generateNodeDummy(),
+                                                      std::move(infos)};
+  auto inputBlock = buildBlock<1>(itemBlockManager, {{0}, {1}, {2}});
+
+  for (size_t i = 0; i < inputBlock->size(); ++i) {
+    InputAqlItemRow input{inputBlock, i};
+    ASSERT_TRUE(input.isInitialized());
+    {
+      // Test first call, executor is done, cannot skip and does not return
+      AqlCall call{};
+      AqlCallStack stack(std::move(call));
+      auto const& [state, skipped, block] = testee.execute(stack);
+      EXPECT_EQ(state, ExecutionState::DONE);
+      EXPECT_EQ(skipped, 0);
+      EXPECT_EQ(block, nullptr);
+    }
+    {
+      // Initialize cursor
+      auto const& [state, result] = testee.initializeCursor(input);
+      EXPECT_EQ(state, ExecutionState::DONE);
+      EXPECT_TRUE(result.ok());
+    }
+    {
+      // Test second call, executor needs to return the row
+      AqlCall call{};
+      AqlCallStack stack(std::move(call));
+      auto const& [state, skipped, block] = testee.execute(stack);
+      EXPECT_EQ(state, ExecutionState::DONE);
+      EXPECT_EQ(skipped, 0);
+      ASSERT_NE(block, nullptr);
+      EXPECT_EQ(block->size(), 1);
+      auto const& val = block->getValueReference(0, 0);
+      ASSERT_TRUE(val.isNumber());
+      EXPECT_EQ(static_cast<size_t>(val.toInt64()), i);
+    }
+  }
+}
+
+// The IdExecutor has a specific initializeCursor method in ExecutionBlockImpl
+TEST_F(IdExecutionBlockTest, test_initialize_cursor_skip) {
+  IdExecutorInfos infos{1, {0}, {}};
+  ExecutionBlockImpl<IdExecutor<ConstFetcher>> testee{fakedQuery->engine(),
+                                                      generateNodeDummy(),
+                                                      std::move(infos)};
+  auto inputBlock = buildBlock<1>(itemBlockManager, {{0}, {1}, {2}});
+
+  for (size_t i = 0; i < inputBlock->size(); ++i) {
+    InputAqlItemRow input{inputBlock, i};
+    ASSERT_TRUE(input.isInitialized());
+    {
+      // Test first call, executor is done, cannot skip and does not return
+      AqlCall call{};
+      call.offset = 10;
+      AqlCallStack stack(std::move(call));
+      auto const& [state, skipped, block] = testee.execute(stack);
+      EXPECT_EQ(state, ExecutionState::DONE);
+      EXPECT_EQ(skipped, 0);
+      EXPECT_EQ(block, nullptr);
+    }
+    {
+      // Initialize cursor
+      auto const& [state, result] = testee.initializeCursor(input);
+      EXPECT_EQ(state, ExecutionState::DONE);
+      EXPECT_TRUE(result.ok());
+    }
+    {
+      // Test second call, executor needs to skip the row
+      AqlCall call{};
+      call.offset = 10;
+      AqlCallStack stack(std::move(call));
+      auto const& [state, skipped, block] = testee.execute(stack);
+      EXPECT_EQ(state, ExecutionState::DONE);
+      EXPECT_EQ(skipped, 1);
+      ASSERT_EQ(block, nullptr);
+    }
+  }
+}
+
+// The IdExecutor has a specific initializeCursor method in ExecutionBlockImpl
+TEST_F(IdExecutionBlockTest, test_initialize_cursor_fullCount) {
+  IdExecutorInfos infos{1, {0}, {}};
+  ExecutionBlockImpl<IdExecutor<ConstFetcher>> testee{fakedQuery->engine(),
+                                                      generateNodeDummy(),
+                                                      std::move(infos)};
+  auto inputBlock = buildBlock<1>(itemBlockManager, {{0}, {1}, {2}});
+
+  for (size_t i = 0; i < inputBlock->size(); ++i) {
+    InputAqlItemRow input{inputBlock, i};
+    ASSERT_TRUE(input.isInitialized());
+    {
+      // Test first call, executor is done, cannot skip and does not return
+      AqlCall call{};
+      call.hardLimit = 0;
+      call.fullCount = true;
+      AqlCallStack stack(std::move(call));
+      auto const& [state, skipped, block] = testee.execute(stack);
+      EXPECT_EQ(state, ExecutionState::DONE);
+      EXPECT_EQ(skipped, 0);
+      EXPECT_EQ(block, nullptr);
+    }
+    {
+      // Initialize cursor
+      auto const& [state, result] = testee.initializeCursor(input);
+      EXPECT_EQ(state, ExecutionState::DONE);
+      EXPECT_TRUE(result.ok());
+    }
+    {
+      // Test second call, executor needs to skip the row
+      AqlCall call{};
+      call.hardLimit = 0;
+      call.fullCount = true;
+      AqlCallStack stack(std::move(call));
+      auto const& [state, skipped, block] = testee.execute(stack);
+      EXPECT_EQ(state, ExecutionState::DONE);
+      EXPECT_EQ(skipped, 1);
+      ASSERT_EQ(block, nullptr);
+    }
+  }
+}
 
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(row.produced());
+TEST_F(IdExecutionBlockTest, test_hardlimit_single_row_fetcher) {
+  IdExecutorInfos infos{1, {0}, {}};
+  ExecutorTestHelper<IdExecutor<SingleRowFetcher<BlockPassthrough::Enable>>>(*fakedQuery)
+      .setInputValueList(1, 2, 3, 4, 5, 6)
+      .setCall(AqlCall{0, AqlCall::Infinity{}, 2, false})
+      .expectOutput({0}, {{1}, {2}})
+      .expectSkipped(0)
+      .expectedState(ExecutionState::DONE)
+      .run(std::move(infos));
 }
 
-TEST_F(IdExecutorTest, there_are_rows_in_the_upstream) {
-  auto input = VPackParser::fromJson("[ [true], [false], [true] ]");
-  ConstFetcherHelper fetcher(itemBlockManager, input->buffer());
-  IdExecutor<ConstFetcher> testee(fetcher, infos);
-  NoStats stats{};
+/**
+ * @brief This are special tests, the ConstFetcher is overloaded
+ *  with data rows, now the IdExecutor which is passthrough
+ *  asks for a much lower hard limit.
+ *  Used in ScatterExecutor logic.
+ *  param: useFullCount
+ */
+class BlockOverloadTest : public AqlExecutorTestCase<>,
+                          public ::testing::TestWithParam<bool> {
+ protected:
+  auto getTestee() -> ExecutionBlockImpl<IdExecutor<ConstFetcher>> {
+    IdExecutorInfos infos{1, {0}, {}};
+    return ExecutionBlockImpl<IdExecutor<ConstFetcher>>{fakedQuery->engine(),
+                                                        generateNodeDummy(),
+                                                        std::move(infos)};
+  }
+
+  auto useFullCount() -> bool { return GetParam(); }
+};
 
-  // This block consumes all rows at once.
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(state, ExecutionState::DONE);
+INSTANTIATE_TEST_CASE_P(IdExecutionBlock, BlockOverloadTest, ::testing::Bool());
 
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(row.produced());
+TEST_P(BlockOverloadTest, test_hardlimit_const_fetcher) {
+  auto testee = getTestee();
+  {
+    // Inject block
+    auto inputBlock =
+        buildBlock<1>(itemBlockManager, {{0}, {1}, {2}, {3}, {4}, {5}, {6}});
+    testee.injectConstantBlock(inputBlock);
+  }
+  {
+    // Now call with too small hardLimit
+    auto expectedOutputBlock = buildBlock<1>(itemBlockManager, {{0}, {1}, {2}});
+    AqlCall call{};
+    call.hardLimit = 3;
+    call.fullCount = useFullCount();
+    AqlCallStack stack(std::move(call));
+    auto const& [state, skipped, block] = testee.execute(stack);
+    EXPECT_EQ(state, ExecutionState::DONE);
+    if (useFullCount()) {
+      EXPECT_EQ(skipped, 4);
+    } else {
+      EXPECT_EQ(skipped, 0);
+    }
 
-  // verify result
-  AqlValue value;
-  auto block = row.stealBlock();
-  for (std::size_t index = 0; index < 3; index++) {
-    value = block->getValue(index, 0);
-    ASSERT_TRUE(value.isBoolean());
-    ASSERT_EQ(value.toBoolean(), input->slice().at(index).at(0).getBool());
+    ValidateBlocksAreEqual(block, expectedOutputBlock);
+  }
+  {
+    // Validate that additional upstream-rows are gone.
+    AqlCall call{};
+    AqlCallStack stack(std::move(call));
+    auto const& [state, skipped, block] = testee.execute(stack);
+    EXPECT_EQ(state, ExecutionState::DONE);
+    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(block, nullptr);
+  }
+}
+
+TEST_P(BlockOverloadTest, test_hardlimit_const_fetcher_shadow_rows_at_end) {
+  auto testee = getTestee();
+  {
+    // Inject block
+    auto inputBlock =
+        buildBlock<1>(itemBlockManager, {{0}, {1}, {2}, {3}, {4}, {5}, {6}},
+                      {{5, 0}, {6, 1}});
+    testee.injectConstantBlock(inputBlock);
+  }
+  {
+    // Now call with too small hardLimit
+    auto expectedOutputBlock =
+        buildBlock<1>(itemBlockManager, {{0}, {1}, {2}, {5}, {6}}, {{3, 0}, {4, 1}});
+    AqlCall call{};
+    call.hardLimit = 3;
+    call.fullCount = useFullCount();
+    AqlCallStack stack(std::move(call));
+    auto const& [state, skipped, block] = testee.execute(stack);
+    EXPECT_EQ(state, ExecutionState::DONE);
+    if (useFullCount()) {
+      EXPECT_EQ(skipped, 2);
+    } else {
+      EXPECT_EQ(skipped, 0);
+    }
+    ValidateBlocksAreEqual(block, expectedOutputBlock);
+  }
+  {
+    // Validate that additional upstream-rows are gone.
+    AqlCall call{};
+    AqlCallStack stack(std::move(call));
+    auto const& [state, skipped, block] = testee.execute(stack);
+    EXPECT_EQ(state, ExecutionState::DONE);
+    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(block, nullptr);
+  }
+}
+
+TEST_P(BlockOverloadTest, test_hardlimit_const_fetcher_shadow_rows_in_between) {
+  auto testee = getTestee();
+  {
+    // Inject block
+    auto inputBlock =
+        buildBlock<1>(itemBlockManager, {{0}, {1}, {2}, {3}, {4}, {5}, {6}},
+                      {{3, 0}, {4, 1}, {6, 0}});
+    testee.injectConstantBlock(inputBlock);
+  }
+  {
+    // Now call with too small hardLimit
+    auto expectedOutputBlock =
+        buildBlock<1>(itemBlockManager, {{0}, {1}, {3}, {4}}, {{2, 0}, {3, 1}});
+    AqlCall call{};
+    call.hardLimit = 2;
+    call.fullCount = useFullCount();
+    AqlCallStack stack(std::move(call));
+    auto const& [state, skipped, block] = testee.execute(stack);
+    EXPECT_EQ(state, ExecutionState::HASMORE);
+    if (useFullCount()) {
+      EXPECT_EQ(skipped, 1);
+    } else {
+      EXPECT_EQ(skipped, 0);
+    }
+    ValidateBlocksAreEqual(block, expectedOutputBlock);
+  }
+  {
+    // Validate that next call will give remaining rows
+    // Now call with too small hardLimit
+    auto expectedOutputBlock = buildBlock<1>(itemBlockManager, {{5}, {6}}, {{1, 0}});
+    AqlCall call{};
+    AqlCallStack stack(std::move(call));
+    auto const& [state, skipped, block] = testee.execute(stack);
+    EXPECT_EQ(state, ExecutionState::DONE);
+    EXPECT_EQ(skipped, 0);
+    ValidateBlocksAreEqual(block, expectedOutputBlock);
+  }
+}
+
+// Consecutive ShadowRows can be returned within the same block.
+TEST_P(BlockOverloadTest, test_hardlimit_const_fetcher_consecutive_shadow_rows) {
+  auto testee = getTestee();
+  {
+    // Inject block
+    auto inputBlock =
+        buildBlock<1>(itemBlockManager, {{0}, {1}, {2}, {3}, {4}, {5}, {6}},
+                      {{3, 0}, {4, 1}, {5, 0}, {6, 0}});
+    testee.injectConstantBlock(inputBlock);
+  }
+  // We can only return until the next top-level shadow row is reached.
+  {
+    // Now call with too small hardLimit
+    auto expectedOutputBlock =
+        buildBlock<1>(itemBlockManager, {{0}, {1}, {3}, {4}}, {{2, 0}, {3, 1}});
+    AqlCall call{};
+    call.hardLimit = 2;
+    call.fullCount = useFullCount();
+    AqlCallStack stack(std::move(call));
+    auto const& [state, skipped, block] = testee.execute(stack);
+    EXPECT_EQ(state, ExecutionState::HASMORE);
+    if (useFullCount()) {
+      EXPECT_EQ(skipped, 1);
+    } else {
+      EXPECT_EQ(skipped, 0);
+    }
+    ValidateBlocksAreEqual(block, expectedOutputBlock);
+  }
+  {
+    // Second call will only find a single ShadowRow
+    auto expectedOutputBlock = buildBlock<1>(itemBlockManager, {{5}}, {{0, 0}});
+    AqlCall call{};
+    call.hardLimit = 2;
+    call.fullCount = useFullCount();
+    AqlCallStack stack(std::move(call));
+    auto const& [state, skipped, block] = testee.execute(stack);
+    EXPECT_EQ(state, ExecutionState::HASMORE);
+    EXPECT_EQ(skipped, 0);
+    ValidateBlocksAreEqual(block, expectedOutputBlock);
+  }
+  {
+    // Third call will only find a single ShadowRow
+    auto expectedOutputBlock = buildBlock<1>(itemBlockManager, {{6}}, {{0, 0}});
+    AqlCall call{};
+    call.hardLimit = 2;
+    call.fullCount = useFullCount();
+    AqlCallStack stack(std::move(call));
+    auto const& [state, skipped, block] = testee.execute(stack);
+    EXPECT_EQ(state, ExecutionState::DONE);
+    EXPECT_EQ(skipped, 0);
+    ValidateBlocksAreEqual(block, expectedOutputBlock);
+  }
+  {
+    // Validate that additional upstream-rows are gone.
+    AqlCall call{};
+    AqlCallStack stack(std::move(call));
+    auto const& [state, skipped, block] = testee.execute(stack);
+    EXPECT_EQ(state, ExecutionState::DONE);
+    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(block, nullptr);
   }
 }
 
-}  // namespace arangodb
+}  // namespace arangodb::tests::aql
diff --git a/tests/Aql/ScatterExecutorTest.cpp b/tests/Aql/ScatterExecutorTest.cpp
new file mode 100644
index 000000000000..883a8b8498c0
--- /dev/null
+++ b/tests/Aql/ScatterExecutorTest.cpp
@@ -0,0 +1,592 @@
+////////////////////////////////////////////////////////////////////////////////
+/// DISCLAIMER
+///
+/// Copyright 2020 ArangoDB GmbH, Cologne, Germany
+///
+/// Licensed under the Apache License, Version 2.0 (the "License");
+/// you may not use this file except in compliance with the License.
+/// You may obtain a copy of the License at
+///
+///     http://www.apache.org/licenses/LICENSE-2.0
+///
+/// Unless required by applicable law or agreed to in writing, software
+/// distributed under the License is distributed on an "AS IS" BASIS,
+/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+/// See the License for the specific language governing permissions and
+/// limitations under the License.
+///
+/// Copyright holder is ArangoDB GmbH, Cologne, Germany
+///
+/// @author Michael Hackstein
+////////////////////////////////////////////////////////////////////////////////
+
+#include "gtest/gtest.h"
+
+#include "AqlItemBlockHelper.h"
+#include "Mocks/Servers.h"
+#include "WaitingExecutionBlockMock.h"
+
+#include "Aql/AqlCall.h"
+#include "Aql/AqlCallStack.h"
+#include "Aql/ClusterNodes.h"
+#include "Aql/ExecutionBlockImpl.h"
+#include "Aql/ExecutionEngine.h"
+#include "Aql/ExecutionNode.h"
+#include "Aql/ExecutorInfos.h"
+#include "Aql/Query.h"
+#include "Aql/ScatterExecutor.h"
+
+using namespace arangodb;
+using namespace arangodb::aql;
+
+namespace arangodb::tests::aql {
+
+class SharedScatterExecutionBlockTest {
+ protected:
+  mocks::MockAqlServer server{};
+  ResourceMonitor monitor{};
+  AqlItemBlockManager itemBlockManager{&monitor, SerializationFormat::SHADOWROWS};
+  std::unique_ptr<arangodb::aql::Query> fakedQuery{server.createFakeQuery()};
+  std::vector<std::unique_ptr<ExecutionNode>> _execNodes;
+  velocypack::Options vpackOptions;
+  std::vector<std::string> clientIds{"a", "b", "c"};
+
+  SharedScatterExecutionBlockTest() {
+    auto engine =
+        std::make_unique<ExecutionEngine>(*fakedQuery, SerializationFormat::SHADOWROWS);
+    fakedQuery->setEngine(engine.release());
+  }
+
+  /**
+   * @brief Creates and manages a ExecutionNode.
+   *        These nodes can be used to create the Executors
+   *        Caller does not need to manage the memory.
+   *
+   * @return ExecutionNode* Pointer to a dummy ExecutionNode. Memory is managed, do not delete.
+   */
+  auto generateNodeDummy() -> ExecutionNode* {
+    auto dummy = std::make_unique<SingletonNode>(fakedQuery->plan(), _execNodes.size());
+    auto res = dummy.get();
+    _execNodes.emplace_back(std::move(dummy));
+    return res;
+  }
+
+  auto generateScatterNode() -> ScatterNode* {
+    auto dummy = std::make_unique<ScatterNode>(fakedQuery->plan(), _execNodes.size(),
+                                               ScatterNode::ScatterType::SHARD);
+    auto res = dummy.get();
+    _execNodes.emplace_back(std::move(dummy));
+    return res;
+  }
+
+  auto generateInfos() const -> ScatterExecutorInfos {
+    auto inputRegs = make_shared_unordered_set({0});
+    auto outputRegs = make_shared_unordered_set({});
+    return {inputRegs, outputRegs, 1, 1, {}, {0}, clientIds};
+  }
+
+  auto createProducer(SharedAqlItemBlockPtr inputBlock) -> WaitingExecutionBlockMock {
+    std::deque<SharedAqlItemBlockPtr> blockDeque;
+    // TODO add input splicing
+    blockDeque.push_back(inputBlock);
+    return createProducer(blockDeque);
+  }
+
+  auto createProducer(std::deque<SharedAqlItemBlockPtr> blockDeque) -> WaitingExecutionBlockMock {
+    // TODO add input splicing
+
+    return WaitingExecutionBlockMock{fakedQuery->engine(), generateNodeDummy(),
+                                     std::move(blockDeque),
+                                     WaitingExecutionBlockMock::WaitingBehaviour::NEVER};
+  }
+
+  auto ValidateBlocksAreEqual(SharedAqlItemBlockPtr actual, SharedAqlItemBlockPtr expected) {
+    ASSERT_NE(expected, nullptr);
+    ASSERT_NE(actual, nullptr);
+    EXPECT_EQ(actual->size(), expected->size());
+    EXPECT_EQ(actual->getNrRegs(), 1);
+    for (size_t i = 0; i < (std::min)(actual->size(), expected->size()); ++i) {
+      auto const& x = actual->getValueReference(i, 0);
+      auto const& y = expected->getValueReference(i, 0);
+      EXPECT_TRUE(AqlValue::Compare(&vpackOptions, x, y, true) == 0)
+          << "Row " << i << " Column " << 0 << " do not agree. "
+          << x.slice().toJson(&vpackOptions) << " vs. "
+          << y.slice().toJson(&vpackOptions);
+    }
+  }
+};
+
+// The tests of this suite test all permutations of client calls.
+// This way we can ensure that the block works even on parallel
+// execution.
+class RandomOrderTest : public SharedScatterExecutionBlockTest,
+                        public ::testing::TestWithParam<std::vector<std::string>> {
+ protected:
+  std::vector<std::string> const& getCallOrder() { return GetParam(); }
+
+  RandomOrderTest() {}
+};
+
+namespace {
+template <typename T>
+auto ArrayPermutations(std::vector<T> base) -> std::vector<std::vector<T>> {
+  std::vector<std::vector<T>> res;
+  // This is not corect we would need faculity of base, but we are in a test...
+  res.reserve(base.size());
+  do {
+    res.emplace_back(base);
+  } while (std::next_permutation(base.begin(), base.end()));
+  return res;
+};
+
+auto randomOrderCalls = ArrayPermutations<std::string>({"a", "b", "c"});
+}  // namespace
+
+INSTANTIATE_TEST_CASE_P(ScatterExecutionBlockTestRandomOrder, RandomOrderTest,
+                        ::testing::ValuesIn(randomOrderCalls));
+
+TEST_P(RandomOrderTest, all_clients_should_get_the_block) {
+  auto inputBlock = buildBlock<1>(itemBlockManager, {{0}, {1}, {2}});
+  auto producer = createProducer(inputBlock);
+
+  ExecutionBlockImpl<ScatterExecutor> testee{fakedQuery->engine(),
+                                             generateScatterNode(), generateInfos()};
+  testee.addDependency(&producer);
+
+  for (auto const& client : getCallOrder()) {
+    SCOPED_TRACE("Testing client " + client);
+    AqlCall call{};  // DefaultCall
+    AqlCallStack stack{call};
+    auto const [state, skipped, block] = testee.executeForClient(stack, client);
+    EXPECT_EQ(state, ExecutionState::DONE);
+    EXPECT_EQ(skipped, 0);
+    ValidateBlocksAreEqual(block, inputBlock);
+  }
+}
+
+TEST_P(RandomOrderTest, all_clients_can_skip_the_block) {
+  auto inputBlock = buildBlock<1>(itemBlockManager, {{0}, {1}, {2}});
+  auto producer = createProducer(inputBlock);
+
+  ExecutionBlockImpl<ScatterExecutor> testee{fakedQuery->engine(),
+                                             generateScatterNode(), generateInfos()};
+  testee.addDependency(&producer);
+
+  for (auto const& client : getCallOrder()) {
+    SCOPED_TRACE("Testing client " + client);
+    AqlCall call{};
+    call.offset = 10;
+    AqlCallStack stack{call};
+    auto const [state, skipped, block] = testee.executeForClient(stack, client);
+    EXPECT_EQ(state, ExecutionState::DONE);
+    EXPECT_EQ(skipped, 3);
+    EXPECT_EQ(block, nullptr);
+  }
+}
+
+TEST_P(RandomOrderTest, all_clients_can_fullcount_the_block) {
+  auto inputBlock = buildBlock<1>(itemBlockManager, {{0}, {1}, {2}});
+  auto expectedBlock = buildBlock<1>(itemBlockManager, {{0}});
+  auto producer = createProducer(inputBlock);
+
+  ExecutionBlockImpl<ScatterExecutor> testee{fakedQuery->engine(),
+                                             generateScatterNode(), generateInfos()};
+  testee.addDependency(&producer);
+
+  for (auto const& client : getCallOrder()) {
+    SCOPED_TRACE("Testing client " + client);
+    AqlCall call{};
+    call.hardLimit = 1;
+    call.fullCount = true;
+    AqlCallStack stack{call};
+    auto const [state, skipped, block] = testee.executeForClient(stack, client);
+    EXPECT_EQ(state, ExecutionState::DONE);
+    EXPECT_EQ(skipped, 2);
+    ValidateBlocksAreEqual(block, expectedBlock);
+  }
+}
+
+TEST_P(RandomOrderTest, all_clients_can_have_different_calls) {
+  auto inputBlock =
+      buildBlock<1>(itemBlockManager, {{0}, {1}, {2}, {3}, {4}, {5}, {6}});
+  auto producer = createProducer(inputBlock);
+
+  ExecutionBlockImpl<ScatterExecutor> testee{fakedQuery->engine(),
+                                             generateScatterNode(), generateInfos()};
+  testee.addDependency(&producer);
+
+  for (auto const& client : getCallOrder()) {
+    SCOPED_TRACE("Testing client " + client);
+    if (client == "a") {
+      // Just produce all
+      AqlCall call{};
+      AqlCallStack stack{call};
+      auto const [state, skipped, block] = testee.executeForClient(stack, client);
+      EXPECT_EQ(state, ExecutionState::DONE);
+      EXPECT_EQ(skipped, 0);
+      ValidateBlocksAreEqual(block, inputBlock);
+    } else if (client == "b") {
+      AqlCall call{};
+      call.offset = 2;
+      call.hardLimit = 2;
+      AqlCallStack stack{call};
+      auto const [state, skipped, block] = testee.executeForClient(stack, client);
+      EXPECT_EQ(state, ExecutionState::DONE);
+      EXPECT_EQ(skipped, 2);
+      auto expectedBlock = buildBlock<1>(itemBlockManager, {{2}, {3}});
+      ValidateBlocksAreEqual(block, expectedBlock);
+    } else if (client == "c") {
+      {
+        AqlCall call{};
+        call.softLimit = 2;
+        AqlCallStack stack{call};
+        auto const [state, skipped, block] = testee.executeForClient(stack, client);
+        EXPECT_EQ(state, ExecutionState::HASMORE);
+        EXPECT_EQ(skipped, 0);
+        auto expectedBlock = buildBlock<1>(itemBlockManager, {{0}, {1}});
+        ValidateBlocksAreEqual(block, expectedBlock);
+      }
+      {
+        // As we have softLimit we can simply call again
+        AqlCall call{};
+        call.offset = 1;
+        call.softLimit = 2;
+        AqlCallStack stack{call};
+        auto const [state, skipped, block] = testee.executeForClient(stack, client);
+        EXPECT_EQ(state, ExecutionState::HASMORE);
+        EXPECT_EQ(skipped, 1);
+        auto expectedBlock = buildBlock<1>(itemBlockManager, {{3}, {4}});
+        ValidateBlocksAreEqual(block, expectedBlock);
+      }
+    }
+  }
+}
+
+TEST_P(RandomOrderTest, get_does_not_jump_over_shadowrows) {
+  auto inputBlock = buildBlock<1>(itemBlockManager, {{0}, {1}, {2}, {3}, {4}, {5}},
+                                  {{3, 0}, {5, 0}});
+  auto firstExpectedBlock =
+      buildBlock<1>(itemBlockManager, {{0}, {1}, {2}, {3}}, {{3, 0}});
+  auto secondExpectedBlock = buildBlock<1>(itemBlockManager, {{4}, {5}}, {{0, 0}});
+  auto producer = createProducer(inputBlock);
+
+  ExecutionBlockImpl<ScatterExecutor> testee{fakedQuery->engine(),
+                                             generateScatterNode(), generateInfos()};
+  testee.addDependency(&producer);
+
+  // First call. reach first shadowrow, but do not jump over it, we do not know
+  // how to proceed after (e.g. skip the rows).
+  for (auto const& client : getCallOrder()) {
+    SCOPED_TRACE("Testing client " + client + " first call");
+    // Produce all until shadow row
+    AqlCall call{};
+    AqlCallStack stack{call};
+    auto const [state, skipped, block] = testee.executeForClient(stack, client);
+    EXPECT_EQ(state, ExecutionState::HASMORE);
+    EXPECT_EQ(skipped, 0);
+    ValidateBlocksAreEqual(block, firstExpectedBlock);
+  }
+
+  // Second call. reach up to last shadowRow and figure out that we are essentially done
+  for (auto const& client : getCallOrder()) {
+    SCOPED_TRACE("Testing client " + client + " second call");
+    // Produce all until shadow row
+    AqlCall call{};
+    AqlCallStack stack{call};
+    auto const [state, skipped, block] = testee.executeForClient(stack, client);
+    EXPECT_EQ(state, ExecutionState::DONE);
+    EXPECT_EQ(skipped, 0);
+    ValidateBlocksAreEqual(block, secondExpectedBlock);
+  }
+}
+
+TEST_P(RandomOrderTest, handling_of_higher_depth_shadowrows_produce) {
+  auto inputBlock = buildBlock<1>(itemBlockManager, {{0}, {1}, {2}, {3}, {4}, {5}},
+                                  {{2, 0}, {3, 1}, {5, 0}});
+  auto firstExpectedBlock =
+      buildBlock<1>(itemBlockManager, {{0}, {1}, {2}, {3}}, {{2, 0}, {3, 1}});
+  auto secondExpectedBlock = buildBlock<1>(itemBlockManager, {{4}, {5}}, {{1, 0}});
+  auto producer = createProducer(inputBlock);
+
+  ExecutionBlockImpl<ScatterExecutor> testee{fakedQuery->engine(),
+                                             generateScatterNode(), generateInfos()};
+  testee.addDependency(&producer);
+
+  // First call. reach first shadowrow, but do not jump over it, we do not know
+  // how to proceed after (e.g. skip the rows).
+  for (auto const& client : getCallOrder()) {
+    SCOPED_TRACE("Testing client " + client + " first call");
+    // Produce all until shadow row
+    AqlCall call{};
+    AqlCallStack stack{call};
+    auto const [state, skipped, block] = testee.executeForClient(stack, client);
+    EXPECT_EQ(state, ExecutionState::HASMORE);
+    EXPECT_EQ(skipped, 0);
+    ValidateBlocksAreEqual(block, firstExpectedBlock);
+  }
+
+  // Second call. reach up to last shadowRow and figure out that we are essentially done
+  for (auto const& client : getCallOrder()) {
+    SCOPED_TRACE("Testing client " + client + " second call");
+    // Produce all until shadow row
+    AqlCall call{};
+    AqlCallStack stack{call};
+    auto const [state, skipped, block] = testee.executeForClient(stack, client);
+    EXPECT_EQ(state, ExecutionState::DONE);
+    EXPECT_EQ(skipped, 0);
+    ValidateBlocksAreEqual(block, secondExpectedBlock);
+  }
+}
+
+TEST_P(RandomOrderTest, handling_of_higher_depth_shadowrows_skip) {
+  auto inputBlock = buildBlock<1>(itemBlockManager, {{0}, {1}, {2}, {3}, {4}, {5}},
+                                  {{2, 0}, {3, 1}, {5, 0}});
+  auto firstExpectedBlock =
+      buildBlock<1>(itemBlockManager, {{2}, {3}}, {{0, 0}, {1, 1}});
+  auto secondExpectedBlock = buildBlock<1>(itemBlockManager, {{4}, {5}}, {{1, 0}});
+  auto producer = createProducer(inputBlock);
+
+  ExecutionBlockImpl<ScatterExecutor> testee{fakedQuery->engine(),
+                                             generateScatterNode(), generateInfos()};
+  testee.addDependency(&producer);
+
+  // First call. reach first shadowrow, but do not jump over it, we do not know
+  // how to proceed after (e.g. skip the rows).
+  for (auto const& client : getCallOrder()) {
+    SCOPED_TRACE("Testing client " + client + " first call");
+    // Produce all until shadow row
+    AqlCall call{};
+    call.offset = 10;
+    AqlCallStack stack{call};
+    auto const [state, skipped, block] = testee.executeForClient(stack, client);
+    EXPECT_EQ(state, ExecutionState::HASMORE);
+    EXPECT_EQ(skipped, 2);
+    ValidateBlocksAreEqual(block, firstExpectedBlock);
+  }
+
+  // Second call. reach up to last shadowRow and figure out that we are essentially done
+  for (auto const& client : getCallOrder()) {
+    SCOPED_TRACE("Testing client " + client + " second call");
+    // Produce all until shadow row
+    AqlCall call{};
+    AqlCallStack stack{call};
+    auto const [state, skipped, block] = testee.executeForClient(stack, client);
+    EXPECT_EQ(state, ExecutionState::DONE);
+    EXPECT_EQ(skipped, 0);
+    ValidateBlocksAreEqual(block, secondExpectedBlock);
+  }
+}
+
+TEST_P(RandomOrderTest, handling_of_consecutive_shadow_rows) {
+  // As there is no produce inbetween we are actually able to just forward it
+  auto inputBlock = buildBlock<1>(itemBlockManager, {{0}, {1}, {2}, {3}, {4}, {5}},
+                                  {{2, 0}, {3, 1}, {4, 0}, {5, 1}});
+  auto producer = createProducer(inputBlock);
+
+  ExecutionBlockImpl<ScatterExecutor> testee{fakedQuery->engine(),
+                                             generateScatterNode(), generateInfos()};
+  testee.addDependency(&producer);
+
+  // First call. actually there are only shadowRows following, we would be able
+  // to plainly forward everything, however this is not suppoert yet
+  // so we need to ask once for every relevant shadow row (depth 0)
+  for (auto const& client : getCallOrder()) {
+    SCOPED_TRACE("Testing client " + client);
+    {
+      // Produce all until second relevant shadow row
+      AqlCall call{};
+      AqlCallStack stack{call};
+      auto const [state, skipped, block] = testee.executeForClient(stack, client);
+      EXPECT_EQ(state, ExecutionState::HASMORE);
+      EXPECT_EQ(skipped, 0);
+      auto expected =
+          buildBlock<1>(itemBlockManager, {{0}, {1}, {2}, {3}}, {{2, 0}, {3, 1}});
+      ValidateBlocksAreEqual(block, expected);
+    }
+    {
+      // Produce the last shadow rows
+      AqlCall call{};
+      AqlCallStack stack{call};
+      auto const [state, skipped, block] = testee.executeForClient(stack, client);
+      EXPECT_EQ(state, ExecutionState::DONE);
+      EXPECT_EQ(skipped, 0);
+      auto expected = buildBlock<1>(itemBlockManager, {{4}, {5}}, {{0, 0}, {1, 1}});
+      ValidateBlocksAreEqual(block, expected);
+    }
+  }
+}
+
+TEST_P(RandomOrderTest, shadowrows_with_different_call_types) {
+  auto inputBlock = buildBlock<1>(itemBlockManager, {{0}, {1}, {2}, {3}, {4}, {5}},
+                                  {{3, 0}, {5, 0}});
+  auto producer = createProducer(inputBlock);
+
+  ExecutionBlockImpl<ScatterExecutor> testee{fakedQuery->engine(),
+                                             generateScatterNode(), generateInfos()};
+  testee.addDependency(&producer);
+
+  // First call. desired to be stopped at shadowRow
+  for (auto const& client : getCallOrder()) {
+    SCOPED_TRACE("Testing client " + client + " first call.");
+    if (client == "a") {
+      // Just produce all
+      AqlCall call{};
+      AqlCallStack stack{call};
+      auto const [state, skipped, block] = testee.executeForClient(stack, client);
+      EXPECT_EQ(state, ExecutionState::HASMORE);
+      EXPECT_EQ(skipped, 0);
+      auto expectedBlock =
+          buildBlock<1>(itemBlockManager, {{0}, {1}, {2}, {3}}, {{3, 0}});
+      ValidateBlocksAreEqual(block, expectedBlock);
+    } else if (client == "b") {
+      AqlCall call{};
+      call.offset = 2;
+      call.hardLimit = 2;
+      AqlCallStack stack{call};
+      auto const [state, skipped, block] = testee.executeForClient(stack, client);
+      EXPECT_EQ(state, ExecutionState::HASMORE);
+      EXPECT_EQ(skipped, 2);
+      auto expectedBlock = buildBlock<1>(itemBlockManager, {{2}, {3}}, {{1, 0}});
+      ValidateBlocksAreEqual(block, expectedBlock);
+    } else if (client == "c") {
+      {
+        AqlCall call{};
+        call.softLimit = 2;
+        AqlCallStack stack{call};
+        auto const [state, skipped, block] = testee.executeForClient(stack, client);
+        EXPECT_EQ(state, ExecutionState::HASMORE);
+        EXPECT_EQ(skipped, 0);
+        auto expectedBlock = buildBlock<1>(itemBlockManager, {{0}, {1}});
+        ValidateBlocksAreEqual(block, expectedBlock);
+      }
+      {
+        // As we have softLimit we can simply call again
+        AqlCall call{};
+        call.offset = 1;
+        call.softLimit = 2;
+        AqlCallStack stack{call};
+        auto const [state, skipped, block] = testee.executeForClient(stack, client);
+        EXPECT_EQ(state, ExecutionState::HASMORE);
+        EXPECT_EQ(skipped, 1);
+        auto expectedBlock = buildBlock<1>(itemBlockManager, {{3}}, {{0, 0}});
+        ValidateBlocksAreEqual(block, expectedBlock);
+      }
+    }
+  }
+
+  // Second call. desired to be stopped at shadowRow
+  for (auto const& client : getCallOrder()) {
+    SCOPED_TRACE("Testing client " + client + " second call.");
+    if (client == "a") {
+      // Just produce all
+      AqlCall call{};
+      call.hardLimit = 1;
+      AqlCallStack stack{call};
+      auto const [state, skipped, block] = testee.executeForClient(stack, client);
+      EXPECT_EQ(state, ExecutionState::DONE);
+      EXPECT_EQ(skipped, 0);
+      auto expectedBlock = buildBlock<1>(itemBlockManager, {{4}, {5}}, {{1, 0}});
+      ValidateBlocksAreEqual(block, expectedBlock);
+    } else if (client == "b") {
+      AqlCall call{};
+      call.softLimit = 1;
+      AqlCallStack stack{call};
+      auto const [state, skipped, block] = testee.executeForClient(stack, client);
+      EXPECT_EQ(state, ExecutionState::DONE);
+      EXPECT_EQ(skipped, 0);
+      auto expectedBlock = buildBlock<1>(itemBlockManager, {{4}, {5}}, {{1, 0}});
+      ValidateBlocksAreEqual(block, expectedBlock);
+    } else if (client == "c") {
+      {
+        AqlCall call{};
+        call.offset = 10;
+        AqlCallStack stack{call};
+        auto const [state, skipped, block] = testee.executeForClient(stack, client);
+        EXPECT_EQ(state, ExecutionState::DONE);
+        EXPECT_EQ(skipped, 1);
+        auto expectedBlock = buildBlock<1>(itemBlockManager, {{5}}, {{0, 0}});
+        ValidateBlocksAreEqual(block, expectedBlock);
+      }
+    }
+  }
+}
+
+// This test does not include randomization of clientCall ordering
+class ScatterExecutionBlockTest : public SharedScatterExecutionBlockTest,
+                                  public ::testing::Test {};
+
+// Here we do a more specific ordering of calls, as we need to rearange multidepthCalls
+
+TEST_F(ScatterExecutionBlockTest, any_ordering_of_calls_is_fine) {
+  std::deque<SharedAqlItemBlockPtr> blockDeque;
+  std::unordered_map<std::string, std::pair<size_t, std::vector<SharedAqlItemBlockPtr>>> expected;
+  std::vector<std::string> callOrder;
+  for (auto const& c : clientIds) {
+    expected[c] = std::make_pair(0, std::vector<SharedAqlItemBlockPtr>{});
+  }
+
+  {
+    auto inputBlock = buildBlock<1>(itemBlockManager, {{0}, {1}, {2}});
+    blockDeque.emplace_back(inputBlock);
+    for (auto const& c : clientIds) {
+      expected[c].second.emplace_back(inputBlock);
+      callOrder.emplace_back(c);
+    }
+  }
+
+  {
+    auto inputBlock = buildBlock<1>(itemBlockManager, {{3}, {4}, {5}, {6}});
+    blockDeque.emplace_back(inputBlock);
+    for (auto const& c : clientIds) {
+      expected[c].second.emplace_back(inputBlock);
+      callOrder.emplace_back(c);
+    }
+  }
+
+  {
+    auto inputBlock = buildBlock<1>(itemBlockManager, {{7}, {8}, {9}});
+    blockDeque.emplace_back(inputBlock);
+    for (auto const& c : clientIds) {
+      expected[c].second.emplace_back(inputBlock);
+      callOrder.emplace_back(c);
+    }
+  }
+  // Every client will ask every block alone.
+  ASSERT_EQ(callOrder.size(), clientIds.size() * blockDeque.size());
+  // Now we do all permuation of potentiall call ordering
+  do {
+    auto producer = createProducer(blockDeque);
+    ExecutionBlockImpl<ScatterExecutor> testee{fakedQuery->engine(),
+                                               generateScatterNode(), generateInfos()};
+    testee.addDependency(&producer);
+    for (auto& [c, pair] : expected) {
+      // Reset seen position
+      pair.first = 0;
+    }
+    std::stringstream permutation;
+    for (auto c : callOrder) {
+      permutation << " " << c;
+    }
+    SCOPED_TRACE("Testing permutation: " + permutation.str());
+    for (auto const& client : callOrder) {
+      auto& [callNr, blocks] = expected[client];
+      SCOPED_TRACE("Testing client " + client + " call number " + std::to_string(callNr));
+      AqlCall call{};
+      AqlCallStack stack{call};
+      auto const [state, skipped, block] = testee.executeForClient(stack, client);
+      if (callNr == 2) {
+        EXPECT_EQ(state, ExecutionState::DONE);
+      } else {
+        EXPECT_EQ(state, ExecutionState::HASMORE);
+      }
+      EXPECT_EQ(skipped, 0);
+      ASSERT_TRUE(callNr < blocks.size());
+      ValidateBlocksAreEqual(block, blocks[callNr]);
+      callNr++;
+    }
+  } while (std::next_permutation(callOrder.begin(), callOrder.end()));
+}
+
+// TODO add test for initilaize cursor
+
+}  // namespace arangodb::tests::aql
\ No newline at end of file
diff --git a/tests/Aql/ShortestPathExecutorTest.cpp b/tests/Aql/ShortestPathExecutorTest.cpp
index 3ddc6495b66c..93eca4fcfc98 100644
--- a/tests/Aql/ShortestPathExecutorTest.cpp
+++ b/tests/Aql/ShortestPathExecutorTest.cpp
@@ -531,7 +531,7 @@ PathSequence const someOtherPaths = {pathBetween("vertex/a", "vertex/target", 10
 
 auto sources = testing::Values(constSource, regSource, brokenSource);
 auto targets = testing::Values(constTarget, regTarget, brokenTarget);
-auto inputs = testing::Values(noneRow, oneRow, twoRows, threeRows, someRows);
+static auto inputs = testing::Values(noneRow, oneRow, twoRows, threeRows, someRows);
 auto paths = testing::Values(noPath, onePath, threePaths, somePaths);
 auto calls =
     testing::Values(AqlCall{}, AqlCall{0, 0, 0, false}, AqlCall{0, 1, 0, false},
diff --git a/tests/Aql/SortedCollectExecutorTest.cpp b/tests/Aql/SortedCollectExecutorTest.cpp
index cfc51936e38b..95acf6b94d2c 100644
--- a/tests/Aql/SortedCollectExecutorTest.cpp
+++ b/tests/Aql/SortedCollectExecutorTest.cpp
@@ -928,14 +928,9 @@ using SortedCollectTestHelper = ExecutorTestHelper<SortedCollectExecutor, 1, 1>;
 using SortedCollectSplitType = SortedCollectTestHelper::SplitType;
 
 class SortedCollectExecutorTestSplit
-    : public ::testing::TestWithParam<std::tuple<SortedCollectSplitType>> {
+    : public AqlExecutorTestCase<false>,
+      public ::testing::TestWithParam<std::tuple<SortedCollectSplitType>> {
  protected:
-  // ExecutionState state;
-  ResourceMonitor monitor;
-  AqlItemBlockManager itemBlockManager;
-
-  mocks::MockAqlServer server;
-  std::unique_ptr<arangodb::aql::Query> fakedQuery;
   arangodb::transaction::Methods* trx;
 
   std::unordered_set<RegisterId> regToClear;
@@ -961,13 +956,8 @@ class SortedCollectExecutorTestSplit
 
   SortedCollectExecutorInfos infos;
 
-  SharedAqlItemBlockPtr block;
-  NoStats stats;
-
   SortedCollectExecutorTestSplit()
-      : itemBlockManager(&monitor, SerializationFormat::SHADOWROWS),
-        fakedQuery(server.createFakeQuery()),
-        trx(fakedQuery->trx()),
+      : trx(fakedQuery->trx()),
         groupRegisters{std::make_pair<RegisterId, RegisterId>(1, 0)},
         readableInputRegisters({0}),
         collectRegister(2),
@@ -980,12 +970,7 @@ class SortedCollectExecutorTestSplit
               std::move(readableInputRegisters), std::move(writeableOutputRegisters),
               std::move(groupRegisters), collectRegister, expressionRegister,
               expressionVariable, std::move(aggregateTypes),
-              std::move(variables), std::move(aggregateRegisters), trx, count),
-        block(new AqlItemBlock(itemBlockManager, 1000, nrOutputRegister)) {
-    auto engine =
-        std::make_unique<ExecutionEngine>(*fakedQuery, SerializationFormat::SHADOWROWS);
-    fakedQuery->setEngine(engine.release());
-  }
+              std::move(variables), std::move(aggregateRegisters), trx, count) {}
 };
 
 TEST_P(SortedCollectExecutorTestSplit, split_1) {
diff --git a/tests/Aql/TestExecutorHelper.cpp b/tests/Aql/TestExecutorHelper.cpp
index 0ac499f43895..1343cee83c1c 100644
--- a/tests/Aql/TestExecutorHelper.cpp
+++ b/tests/Aql/TestExecutorHelper.cpp
@@ -27,9 +27,9 @@
 
 #include "Basics/Common.h"
 
-#include "Aql/InputAqlItemRow.h"
 #include "Aql/AqlValue.h"
 #include "Aql/ExecutorInfos.h"
+#include "Aql/InputAqlItemRow.h"
 #include "Aql/SingleRowFetcher.h"
 #include "Logger/LogMacros.h"
 
@@ -38,7 +38,8 @@
 using namespace arangodb;
 using namespace arangodb::aql;
 
-TestExecutorHelper::TestExecutorHelper(Fetcher& fetcher, Infos& infos) : _infos(infos), _fetcher(fetcher){};
+TestExecutorHelper::TestExecutorHelper(Fetcher& fetcher, Infos& infos)
+    : _infos(infos), _fetcher(fetcher){};
 TestExecutorHelper::~TestExecutorHelper() = default;
 
 std::pair<ExecutionState, FilterStats> TestExecutorHelper::produceRows(OutputAqlItemRow& output) {
@@ -68,7 +69,7 @@ std::pair<ExecutionState, FilterStats> TestExecutorHelper::produceRows(OutputAql
 
     output.copyRow(input);
     return {state, stats};
-    //stats.incrFiltered();
+    // stats.incrFiltered();
   }
 }
 
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index f688e3b4fc27..7b7c9fda3323 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -59,6 +59,7 @@ set(ARANGODB_TESTS_SOURCES
   Aql/ReplaceExecutorTest.cpp
   Aql/ReturnExecutorTest.cpp
   Aql/RowFetcherHelper.cpp
+  Aql/ScatterExecutorTest.cpp
   Aql/ShortestPathExecutorTest.cpp
   Aql/SingleRowFetcherTest.cpp
   Aql/SortedCollectExecutorTest.cpp

From 44fdb29f850c31859e7b4cbe19f7f5e8a79e1bad Mon Sep 17 00:00:00 2001
From: Lars Maier <lars@arangodb.com>
Date: Fri, 14 Feb 2020 11:28:50 +0100
Subject: [PATCH 064/122] Replaced the operator== and operator!= with
 `isSameBlockAndIndex`. (#11088)

---
 arangod/Aql/InputAqlItemRow.cpp  |  7 ++--
 arangod/Aql/InputAqlItemRow.h    |  9 ++----
 arangod/Aql/OutputAqlItemRow.cpp |  2 +-
 arangod/Aql/ShadowAqlItemRow.cpp |  8 ++---
 arangod/Aql/ShadowAqlItemRow.h   |  7 ++--
 tests/Aql/AqlItemRowTest.cpp     | 55 +++++++-------------------------
 6 files changed, 21 insertions(+), 67 deletions(-)

diff --git a/arangod/Aql/InputAqlItemRow.cpp b/arangod/Aql/InputAqlItemRow.cpp
index 382e53e3a091..5216e4f8b546 100644
--- a/arangod/Aql/InputAqlItemRow.cpp
+++ b/arangod/Aql/InputAqlItemRow.cpp
@@ -168,13 +168,10 @@ RegisterCount InputAqlItemRow::getNrRegisters() const noexcept {
   return block().getNrRegs();
 }
 
-bool InputAqlItemRow::operator==(InputAqlItemRow const& other) const noexcept {
-  return this->_block == other._block && this->_baseIndex == other._baseIndex;
+bool InputAqlItemRow::isSameBlockAndIndex(InputAqlItemRow const& other) const noexcept {
+    return this->_block == other._block && this->_baseIndex == other._baseIndex;
 }
 
-bool InputAqlItemRow::operator!=(InputAqlItemRow const& other) const noexcept {
-  return !(*this == other);
-}
 
 bool InputAqlItemRow::equates(InputAqlItemRow const& other,
                               velocypack::Options const* const options) const noexcept {
diff --git a/arangod/Aql/InputAqlItemRow.h b/arangod/Aql/InputAqlItemRow.h
index 0212b9f87709..b5f4377f5a26 100644
--- a/arangod/Aql/InputAqlItemRow.h
+++ b/arangod/Aql/InputAqlItemRow.h
@@ -88,12 +88,9 @@ class InputAqlItemRow {
 
   RegisterCount getNrRegisters() const noexcept;
 
-  // Note that == and != here check whether the rows are *identical*, that is,
-  // the same row in the same block.
-  // TODO Make this a named method
-  bool operator==(InputAqlItemRow const& other) const noexcept;
-
-  bool operator!=(InputAqlItemRow const& other) const noexcept;
+  // This the old operator==. It tests if both rows refer to the _same_ block and
+  // the _same_ index.
+  [[nodiscard]] bool isSameBlockAndIndex(InputAqlItemRow const& other) const noexcept;
 
   // This checks whether the rows are equivalent, in the sense that they hold
   // the same number of registers and their entry-AqlValues compare equal.
diff --git a/arangod/Aql/OutputAqlItemRow.cpp b/arangod/Aql/OutputAqlItemRow.cpp
index 330948f49a80..df485265ebc7 100644
--- a/arangod/Aql/OutputAqlItemRow.cpp
+++ b/arangod/Aql/OutputAqlItemRow.cpp
@@ -327,7 +327,7 @@ void OutputAqlItemRow::memorizeRow<ShadowAqlItemRow>(ShadowAqlItemRow const& sou
 
 template <>
 bool OutputAqlItemRow::testIfWeMustClone<InputAqlItemRow>(InputAqlItemRow const& sourceRow) const {
-  return _baseIndex == 0 || _lastSourceRow != sourceRow;
+  return _baseIndex == 0 || !_lastSourceRow.isSameBlockAndIndex(sourceRow);
 }
 
 template <>
diff --git a/arangod/Aql/ShadowAqlItemRow.cpp b/arangod/Aql/ShadowAqlItemRow.cpp
index c7a77595ba04..c3e9df3f4994 100644
--- a/arangod/Aql/ShadowAqlItemRow.cpp
+++ b/arangod/Aql/ShadowAqlItemRow.cpp
@@ -88,12 +88,8 @@ AqlItemBlock const& ShadowAqlItemRow::block() const noexcept {
   return *_block;
 }
 
-bool ShadowAqlItemRow::operator==(ShadowAqlItemRow const& other) const noexcept {
-  return this->_block == other._block && this->_baseIndex == other._baseIndex;
-}
-
-bool ShadowAqlItemRow::operator!=(ShadowAqlItemRow const& other) const noexcept {
-  return !(*this == other);
+bool ShadowAqlItemRow::isSameBlockAndIndex(ShadowAqlItemRow const& other) const noexcept {
+    return this->_block == other._block && this->_baseIndex == other._baseIndex;
 }
 
 bool ShadowAqlItemRow::equates(ShadowAqlItemRow const& other,
diff --git a/arangod/Aql/ShadowAqlItemRow.h b/arangod/Aql/ShadowAqlItemRow.h
index b0761691a92d..b16e60114af0 100644
--- a/arangod/Aql/ShadowAqlItemRow.h
+++ b/arangod/Aql/ShadowAqlItemRow.h
@@ -102,12 +102,9 @@ class ShadowAqlItemRow {
   ///        NOTE: Innermost query will have depth 0. Outermost query wil have highest depth.
   [[nodiscard]] uint64_t getDepth() const;
 
-  // Note that == and != here check whether the rows are *identical*, that is,
+  // Check whether the rows are *identical*, that is,
   // the same row in the same block.
-  // TODO Make this a named method
-  [[nodiscard]] bool operator==(ShadowAqlItemRow const& other) const noexcept;
-
-  [[nodiscard]] bool operator!=(ShadowAqlItemRow const& other) const noexcept;
+  [[nodiscard]] bool isSameBlockAndIndex(ShadowAqlItemRow const& other) const noexcept;
 
   // This checks whether the rows are equivalent, in the sense that they hold
   // the same number of registers and their entry-AqlValues compare equal,
diff --git a/tests/Aql/AqlItemRowTest.cpp b/tests/Aql/AqlItemRowTest.cpp
index 15de8dab1930..1784222752dc 100644
--- a/tests/Aql/AqlItemRowTest.cpp
+++ b/tests/Aql/AqlItemRowTest.cpp
@@ -350,58 +350,25 @@ TYPED_TEST(AqlItemRowsCommonEqTest, row_eq_operators) {
   RowType const otherInvalidRow = createInvalidRow<RowType>();
 
   // same rows must be equal
-  EXPECT_TRUE((RowType{block, 0}.operator==(RowType{block, 0})));
-  EXPECT_TRUE((RowType{block, 0} == RowType{block, 0}));
-  EXPECT_TRUE((RowType{block, 1}.operator==(RowType{block, 1})));
-  EXPECT_TRUE((RowType{block, 1} == RowType{block, 1}));
-  EXPECT_FALSE((RowType{block, 0}.operator!=(RowType{block, 0})));
-  EXPECT_FALSE((RowType{block, 0} != RowType{block, 0}));
-  EXPECT_FALSE((RowType{block, 1}.operator!=(RowType{block, 1})));
-  EXPECT_FALSE((RowType{block, 1} != RowType{block, 1}));
+  EXPECT_TRUE((RowType{block, 0}.isSameBlockAndIndex(RowType{block, 0})));
+  EXPECT_TRUE((RowType{block, 1}.isSameBlockAndIndex(RowType{block, 1})));
 
   // different rows in the same block must be non-equal
-  EXPECT_FALSE((RowType{block, 0}.operator==(RowType{block, 1})));
-  EXPECT_FALSE((RowType{block, 0} == RowType{block, 1}));
-  EXPECT_FALSE((RowType{block, 1}.operator==(RowType{block, 0})));
-  EXPECT_FALSE((RowType{block, 1} == RowType{block, 0}));
-  EXPECT_TRUE((RowType{block, 0}.operator!=(RowType{block, 1})));
-  EXPECT_TRUE((RowType{block, 0} != RowType{block, 1}));
-  EXPECT_TRUE((RowType{block, 1}.operator!=(RowType{block, 0})));
-  EXPECT_TRUE((RowType{block, 1} != RowType{block, 0}));
+  EXPECT_FALSE((RowType{block, 0}.isSameBlockAndIndex(RowType{block, 1})));
+  EXPECT_FALSE((RowType{block, 1}.isSameBlockAndIndex(RowType{block, 0})));
 
   // rows in different blocks must be non-equal
-  EXPECT_FALSE((RowType{block, 0}.operator==(RowType{otherBlock, 0})));
-  EXPECT_FALSE((RowType{block, 0} == RowType{otherBlock, 0}));
-  EXPECT_FALSE((RowType{block, 1}.operator==(RowType{otherBlock, 0})));
-  EXPECT_FALSE((RowType{block, 1} == RowType{otherBlock, 0}));
-  EXPECT_FALSE((RowType{otherBlock, 0}.operator==(RowType{block, 0})));
-  EXPECT_FALSE((RowType{otherBlock, 0} == RowType{block, 0}));
-  EXPECT_FALSE((RowType{otherBlock, 0}.operator==(RowType{block, 1})));
-  EXPECT_FALSE((RowType{otherBlock, 0} == RowType{block, 1}));
-  EXPECT_TRUE((RowType{block, 0}.operator!=(RowType{otherBlock, 0})));
-  EXPECT_TRUE((RowType{block, 0} != RowType{otherBlock, 0}));
-  EXPECT_TRUE((RowType{block, 1}.operator!=(RowType{otherBlock, 0})));
-  EXPECT_TRUE((RowType{block, 1} != RowType{otherBlock, 0}));
-  EXPECT_TRUE((RowType{otherBlock, 0}.operator!=(RowType{block, 0})));
-  EXPECT_TRUE((RowType{otherBlock, 0} != RowType{block, 0}));
-  EXPECT_TRUE((RowType{otherBlock, 0}.operator!=(RowType{block, 1})));
-  EXPECT_TRUE((RowType{otherBlock, 0} != RowType{block, 1}));
+  EXPECT_FALSE((RowType{block, 0}.isSameBlockAndIndex(RowType{otherBlock, 0})));
+  EXPECT_FALSE((RowType{block, 1}.isSameBlockAndIndex(RowType{otherBlock, 0})));
+  EXPECT_FALSE((RowType{otherBlock, 0}.isSameBlockAndIndex(RowType{block, 0})));
+  EXPECT_FALSE((RowType{otherBlock, 0}.isSameBlockAndIndex(RowType{block, 1})));
 
   // comparisons with an invalid row must be false
-  EXPECT_FALSE((RowType{block, 0}.operator==(invalidRow)));
-  EXPECT_FALSE((RowType{block, 0} == invalidRow));
-  EXPECT_FALSE((invalidRow.operator==(RowType{block, 0})));
-  EXPECT_FALSE((invalidRow == RowType{block, 0}));
-  EXPECT_TRUE((RowType{block, 0}.operator!=(invalidRow)));
-  EXPECT_TRUE((RowType{block, 0} != invalidRow));
-  EXPECT_TRUE((invalidRow.operator!=(RowType{block, 0})));
-  EXPECT_TRUE((invalidRow != RowType{block, 0}));
+  EXPECT_FALSE((RowType{block, 0}.isSameBlockAndIndex(invalidRow)));
+  EXPECT_FALSE((invalidRow.isSameBlockAndIndex(RowType{block, 0})));
 
   // two invalid rows must be equal
-  EXPECT_TRUE((invalidRow.operator==(otherInvalidRow)));
-  EXPECT_TRUE((invalidRow == otherInvalidRow));
-  EXPECT_FALSE((invalidRow.operator!=(otherInvalidRow)));
-  EXPECT_FALSE((invalidRow != otherInvalidRow));
+  EXPECT_TRUE((invalidRow.isSameBlockAndIndex(otherInvalidRow)));
 }
 
 TYPED_TEST(AqlItemRowsCommonEqTest, row_equivalence) {

From 95a73267de6b8dadd6e9019b26eadb80d0b3f12e Mon Sep 17 00:00:00 2001
From: Lars Maier <lars@arangodb.com>
Date: Fri, 14 Feb 2020 17:10:16 +0100
Subject: [PATCH 065/122] New style IndexExecutor. (#11029)

* New style IndexExecutor.

* Small changes.

* Fixing some logic for skipping.

* Small changes.

* TRI_ASSERT(FALSE);

* Removed _fetcher member. (again)
---
 arangod/Aql/ExecutionBlockImpl.cpp |  12 +-
 arangod/Aql/IndexExecutor.cpp      | 290 ++++++++++++++++-------------
 arangod/Aql/IndexExecutor.h        |  25 ++-
 3 files changed, 185 insertions(+), 142 deletions(-)

diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index 229e30debfb4..65f1eba03c24 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -132,9 +132,10 @@ constexpr bool is_one_of_v = (std::is_same_v<T, Es> || ...);
 template <typename Executor>
 constexpr bool isNewStyleExecutor =
     is_one_of_v<Executor, FilterExecutor, SortedCollectExecutor, IdExecutor<ConstFetcher>,
-                IdExecutor<SingleRowFetcher<BlockPassthrough::Enable>>, ReturnExecutor,
+                IdExecutor<SingleRowFetcher<BlockPassthrough::Enable>>, ReturnExecutor, IndexExecutor,
 #ifdef ARANGODB_USE_GOOGLE_TESTS
-                TestLambdaExecutor, TestLambdaSkipExecutor,  // we need one after these to avoid compile errors in non-test mode
+                TestLambdaExecutor,
+                TestLambdaSkipExecutor,  // we need one after these to avoid compile errors in non-test mode
 #endif
                 ShortestPathExecutor>;
 
@@ -1043,11 +1044,12 @@ static SkipRowsRangeVariant constexpr skipRowsType() {
   static_assert(!useFetcher || hasSkipRows<typename Executor::Fetcher>::value,
                 "Fetcher is chosen for skipping, but has not skipRows method!");
 
-  static_assert(useExecutor == (is_one_of_v<Executor, FilterExecutor, ShortestPathExecutor, ReturnExecutor,
+  static_assert(useExecutor ==
+                    (is_one_of_v<Executor, FilterExecutor, ShortestPathExecutor, ReturnExecutor, IndexExecutor,
 #ifdef ARANGODB_USE_GOOGLE_TESTS
-                                            TestLambdaSkipExecutor,
+                                 TestLambdaSkipExecutor,
 #endif
-                                            SortedCollectExecutor>),
+                                 SortedCollectExecutor>),
                 "Unexpected executor for SkipVariants::EXECUTOR");
 
   // The LimitExecutor will not work correctly with SkipVariants::FETCHER!
diff --git a/arangod/Aql/IndexExecutor.cpp b/arangod/Aql/IndexExecutor.cpp
index ae585b5c0ba0..d862d9b98900 100644
--- a/arangod/Aql/IndexExecutor.cpp
+++ b/arangod/Aql/IndexExecutor.cpp
@@ -26,6 +26,7 @@
 #include "IndexExecutor.h"
 
 #include "Aql/AqlValue.h"
+#include "Aql/AqlValueMaterializer.h"
 #include "Aql/Ast.h"
 #include "Aql/Collection.h"
 #include "Aql/DocumentProducingHelper.h"
@@ -38,7 +39,6 @@
 #include "Aql/OutputAqlItemRow.h"
 #include "Aql/Query.h"
 #include "Aql/SingleRowFetcher.h"
-#include "Aql/AqlValueMaterializer.h"
 #include "Basics/ScopeGuard.h"
 #include "Cluster/ServerState.h"
 #include "ExecutorExpressionContext.h"
@@ -52,6 +52,10 @@
 #include <memory>
 #include <utility>
 
+// Set this to true to activate devel logging
+#define LOG_DEVEL_INDEX_ENABLED false
+#define LOG_DEVEL_IDX LOG_DEVEL_IF(LOG_DEVEL_INDEX_ENABLED)
+
 using namespace arangodb;
 using namespace arangodb::aql;
 
@@ -74,7 +78,8 @@ template <bool checkUniqueness>
 IndexIterator::DocumentCallback getCallback(DocumentProducingFunctionContext& context,
                                             transaction::Methods::IndexHandle const& index,
                                             IndexNode::IndexValuesRegisters const& outNonMaterializedIndRegs) {
-  return [&context, &index, &outNonMaterializedIndRegs](LocalDocumentId const& token, VPackSlice slice) {
+  return [&context, &index, &outNonMaterializedIndRegs](LocalDocumentId const& token,
+                                                        VPackSlice slice) {
     if constexpr (checkUniqueness) {
       if (!context.checkUniqueness(token)) {
         // Document already found, skip it
@@ -119,7 +124,7 @@ IndexIterator::DocumentCallback getCallback(DocumentProducingFunctionContext& co
         TRI_ASSERT(!output.isFull());
         output.moveValueInto(indReg.second, input, guard);
       }
-    } else { // primary
+    } else {  // primary
       auto indReg = outNonMaterializedIndRegs.second.cbegin();
       TRI_ASSERT(indReg != outNonMaterializedIndRegs.second.cend());
       if (ADB_UNLIKELY(indReg == outNonMaterializedIndRegs.second.cend())) {
@@ -142,8 +147,7 @@ static inline DocumentProducingFunctionContext createContext(InputAqlItemRow con
                                                              IndexExecutorInfos const& infos) {
   return DocumentProducingFunctionContext(
       inputRow, nullptr, infos.getOutputRegisterId(), infos.getProduceResult(),
-      infos.getQuery(), infos.getFilter(),
-      infos.getProjections(), 
+      infos.getQuery(), infos.getFilter(), infos.getProjections(),
       infos.getCoveringIndexAttributePositions(), false, infos.getUseRawDocumentPointers(),
       infos.getIndexes().size() > 1 || infos.hasMultipleExpansions());
 }
@@ -151,25 +155,20 @@ static inline DocumentProducingFunctionContext createContext(InputAqlItemRow con
 
 IndexExecutorInfos::IndexExecutorInfos(
     std::shared_ptr<std::unordered_set<aql::RegisterId>>&& writableOutputRegisters,
-    RegisterId nrInputRegisters,
-    RegisterId outputRegister,
-    RegisterId nrOutputRegisters,
+    RegisterId nrInputRegisters, RegisterId outputRegister, RegisterId nrOutputRegisters,
     // cppcheck-suppress passedByValue
     std::unordered_set<RegisterId> registersToClear,
     // cppcheck-suppress passedByValue
     std::unordered_set<RegisterId> registersToKeep, ExecutionEngine* engine,
     Collection const* collection, Variable const* outVariable, bool produceResult,
-    Expression* filter,
-    std::vector<std::string> const& projections, 
+    Expression* filter, std::vector<std::string> const& projections,
     std::vector<size_t> const& coveringIndexAttributePositions, bool useRawDocumentPointers,
     std::vector<std::unique_ptr<NonConstExpression>>&& nonConstExpression,
     std::vector<Variable const*>&& expInVars, std::vector<RegisterId>&& expInRegs,
     bool hasV8Expression, AstNode const* condition,
     std::vector<transaction::Methods::IndexHandle> indexes, Ast* ast,
-    IndexIteratorOptions options,
-    IndexNode::IndexValuesRegisters&& outNonMaterializedIndRegs)
-    : ExecutorInfos(make_shared_unordered_set(),
-                    writableOutputRegisters,
+    IndexIteratorOptions options, IndexNode::IndexValuesRegisters&& outNonMaterializedIndRegs)
+    : ExecutorInfos(make_shared_unordered_set(), writableOutputRegisters,
                     nrInputRegisters, nrOutputRegisters,
                     std::move(registersToClear), std::move(registersToKeep)),
       _indexes(std::move(indexes)),
@@ -265,9 +264,7 @@ transaction::Methods* IndexExecutorInfos::getTrxPtr() const noexcept {
   return _engine->getQuery()->trx();
 }
 
-Expression* IndexExecutorInfos::getFilter() const noexcept {
-  return _filter;
-}
+Expression* IndexExecutorInfos::getFilter() const noexcept { return _filter; }
 
 std::vector<size_t> const& IndexExecutorInfos::getCoveringIndexAttributePositions() const noexcept {
   return _coveringIndexAttributePositions;
@@ -345,25 +342,31 @@ IndexExecutor::CursorReader::CursorReader(IndexExecutorInfos const& infos,
       _type(infos.isLateMaterialized()
                 ? Type::LateMaterialized
                 : !infos.getProduceResult()
-                    ? Type::NoResult
-                    : _cursor->hasCovering() && // if change see IndexNode::canApplyLateDocumentMaterializationRule()
-                          !infos.getCoveringIndexAttributePositions().empty()
-                      ? Type::Covering
-                      : Type::Document) {
+                      ? Type::NoResult
+                      : _cursor->hasCovering() &&  // if change see IndexNode::canApplyLateDocumentMaterializationRule()
+                                !infos.getCoveringIndexAttributePositions().empty()
+                            ? Type::Covering
+                            : Type::Document) {
   switch (_type) {
-  case Type::NoResult: {
-    _documentNonProducer = checkUniqueness ? getNullCallback<true>(context) : getNullCallback<false>(context);
-    break;
-  }
-  case Type::LateMaterialized:
-    _documentProducer = checkUniqueness ? ::getCallback<true>(context, _index, _infos.getOutNonMaterializedIndRegs()) :
-                                          ::getCallback<false>(context, _index, _infos.getOutNonMaterializedIndRegs());
-    break;
-  default:
-    _documentProducer = checkUniqueness ? buildDocumentCallback<true, false>(context) : buildDocumentCallback<false, false>(context);
-    break;
+    case Type::NoResult: {
+      _documentNonProducer = checkUniqueness ? getNullCallback<true>(context)
+                                             : getNullCallback<false>(context);
+      break;
+    }
+    case Type::LateMaterialized:
+      _documentProducer =
+          checkUniqueness
+              ? ::getCallback<true>(context, _index, _infos.getOutNonMaterializedIndRegs())
+              : ::getCallback<false>(context, _index, _infos.getOutNonMaterializedIndRegs());
+      break;
+    default:
+      _documentProducer = checkUniqueness
+                              ? buildDocumentCallback<true, false>(context)
+                              : buildDocumentCallback<false, false>(context);
+      break;
   }
-  _documentSkipper = checkUniqueness ? buildDocumentCallback<true, true>(context) : buildDocumentCallback<false, true>(context);
+  _documentSkipper = checkUniqueness ? buildDocumentCallback<true, true>(context)
+                                     : buildDocumentCallback<false, true>(context);
 }
 
 IndexExecutor::CursorReader::CursorReader(CursorReader&& other) noexcept
@@ -440,9 +443,8 @@ void IndexExecutor::CursorReader::reset() {
 
 IndexExecutor::IndexExecutor(Fetcher& fetcher, Infos& infos)
     : _infos(infos),
-      _fetcher(fetcher),
       _documentProducingFunctionContext(::createContext(_input, _infos)),
-      _state(ExecutionState::HASMORE),
+      _state(ExecutorState::HASMORE),
       _input(InputAqlItemRow{CreateInvalidInputRowHint{}}),
       _currentIndex(_infos.getIndexes().size()),
       _skipped(0) {
@@ -456,7 +458,7 @@ IndexExecutor::IndexExecutor(Fetcher& fetcher, Infos& infos)
 IndexExecutor::~IndexExecutor() = default;
 
 void IndexExecutor::initializeCursor() {
-  _state = ExecutionState::HASMORE;
+  _state = ExecutorState::HASMORE;
   _input = InputAqlItemRow{CreateInvalidInputRowHint{}};
   _documentProducingFunctionContext.reset();
   _currentIndex = _infos.getIndexes().size();
@@ -648,6 +650,26 @@ bool IndexExecutor::advanceCursor() {
 }
 
 std::pair<ExecutionState, IndexStats> IndexExecutor::produceRows(OutputAqlItemRow& output) {
+  TRI_ASSERT(false);
+  THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
+}
+
+std::tuple<ExecutionState, IndexExecutor::Stats, size_t> IndexExecutor::skipRows(size_t toSkip) {
+  TRI_ASSERT(false);
+  THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
+}
+
+IndexExecutor::CursorReader& IndexExecutor::getCursor() {
+  TRI_ASSERT(_currentIndex < _cursors.size());
+  return _cursors[_currentIndex];
+}
+
+bool IndexExecutor::needsUniquenessCheck() const noexcept {
+  return _infos.getIndexes().size() > 1 || _infos.hasMultipleExpansions();
+}
+
+auto IndexExecutor::produceRows(AqlItemBlockInputRange& inputRange, OutputAqlItemRow& output)
+    -> std::tuple<ExecutorState, Stats, AqlCall> {
   TRI_IF_FAILURE("IndexExecutor::produceRows") {
     THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
   }
@@ -657,45 +679,63 @@ std::pair<ExecutionState, IndexStats> IndexExecutor::produceRows(OutputAqlItemRo
   TRI_ASSERT(_documentProducingFunctionContext.getAndResetNumFiltered() == 0);
   _documentProducingFunctionContext.setOutputRow(&output);
 
-  while (true) {
-    if (!_input) {
-      if (_state == ExecutionState::DONE) {
-        return {_state, stats};
-      }
-
-      std::tie(_state, _input) = _fetcher.fetchRow();
-
-      if (!_input) {
-        TRI_ASSERT(_state == ExecutionState::WAITING || _state == ExecutionState::DONE);
-        return {_state, stats};
-      }
-      TRI_ASSERT(_state != ExecutionState::WAITING);
-      TRI_ASSERT(_input);
-      initIndexes(_input);
-      if (!advanceCursor()) {
-        _input = InputAqlItemRow{CreateInvalidInputRowHint{}};
-        // just to validate that after continue we get into retry mode
-        TRI_ASSERT(!_input);
-        continue;
+  AqlCall clientCall = output.getClientCall();
+  LOG_DEVEL_IDX << "IndexExecutor::produceRows " << clientCall;
+
+  /*
+   * Logic of this executor is as follows:
+   *  - peek a data row
+   *  - read the indexes for this data row until its done
+   *  - continue
+   */
+
+  while (!output.isFull()) {
+    LOG_DEVEL_IDX << "IndexExecutor::produceRows output.numRowsLeft() == "
+                  << output.numRowsLeft();
+    if (!_input.isInitialized()) {
+      std::tie(_state, _input) = inputRange.peekDataRow();
+      LOG_DEVEL_IDX
+          << "IndexExecutor::produceRows input not initialized, peek next row: " << _state
+          << " " << std::boolalpha << _input.isInitialized();
+
+      if (_input.isInitialized()) {
+        LOG_DEVEL_IDX << "IndexExecutor::produceRows initIndexes";
+        initIndexes(_input);
+        if (!advanceCursor()) {
+          LOG_DEVEL_IDX << "IndexExecutor::produceRows failed to advanceCursor "
+                           "after init";
+          std::ignore = inputRange.nextDataRow();
+          _input = InputAqlItemRow{CreateInvalidInputRowHint{}};
+          // just to validate that after continue we get into retry mode
+          TRI_ASSERT(!_input);
+          continue;
+        }
+      } else {
+        break;
       }
     }
-    TRI_ASSERT(_input.isInitialized());
 
+    TRI_ASSERT(_input.isInitialized());
     // Short Loop over the output block here for performance!
     while (!output.isFull()) {
-      if (!getCursor().hasMore()) {
-        if (!advanceCursor()) {
-          // End of this cursor. Either return or try outer loop again.
-          _input = InputAqlItemRow{CreateInvalidInputRowHint{}};
-          break;
-        }
+      LOG_DEVEL_IDX << "IndexExecutor::produceRows::innerLoop hasMore = " << std::boolalpha
+                    << getCursor().hasMore() << " " << output.numRowsLeft();
+
+      if (!getCursor().hasMore() && !advanceCursor()) {
+        LOG_DEVEL_IDX << "IndexExecutor::produceRows::innerLoop cursor does "
+                         "not have more and advancing failed";
+        std::ignore = inputRange.nextDataRow();
+        _input = InputAqlItemRow{CreateInvalidInputRowHint{}};
+        break;
       }
-      auto& cursor = getCursor();
-      TRI_ASSERT(cursor.hasMore());
+
+      TRI_ASSERT(getCursor().hasMore());
 
       // Read the next elements from the index
-      bool more = cursor.readIndex(output);
-      TRI_ASSERT(more == cursor.hasMore());
+      bool more = getCursor().readIndex(output);
+      TRI_ASSERT(more == getCursor().hasMore());
+
+      LOG_DEVEL_IDX << "IndexExecutor::produceRows::innerLoop output.numRowsWritten() == " << output.numRowsWritten();
       // NOTE: more => output.isFull() does not hold, if we do uniqness checks.
       // The index iterator does still count skipped rows for limit.
       // Nevertheless loop here, the cursor has more so we will retigger
@@ -703,18 +743,24 @@ std::pair<ExecutionState, IndexStats> IndexExecutor::produceRows(OutputAqlItemRo
       // Loop here, either we have filled the output
       // Or the cursor is done, so we need to advance
     }
+
+
     stats.incrScanned(_documentProducingFunctionContext.getAndResetNumScanned());
     stats.incrFiltered(_documentProducingFunctionContext.getAndResetNumFiltered());
-    if (output.isFull()) {
-      if (_state == ExecutionState::DONE && !_input) {
-        return {ExecutionState::DONE, stats};
-      }
-      return {ExecutionState::HASMORE, stats};
-    }
   }
+
+
+  bool reportDone = _state == ExecutorState::DONE && !_input.isInitialized();
+
+  AqlCall upstreamCall;
+  upstreamCall.fullCount = clientCall.needsFullCount();
+
+  LOG_DEVEL_IDX << "IndexExecutor::produceRows reporting state " << (reportDone ? ExecutorState::DONE : ExecutorState::HASMORE);
+  return {reportDone ? ExecutorState::DONE : ExecutorState::HASMORE, stats, upstreamCall};
 }
 
-std::tuple<ExecutionState, IndexExecutor::Stats, size_t> IndexExecutor::skipRows(size_t toSkip) {
+auto IndexExecutor::skipRowsRange(AqlItemBlockInputRange& inputRange, AqlCall& clientCall)
+    -> std::tuple<ExecutorState, Stats, size_t, AqlCall> {
   // This code does not work correctly with multiple indexes, as it does not
   // check for duplicates. Currently, no plan is generated where that can
   // happen, because with multiple indexes, the FILTER is not removed and thus
@@ -724,74 +770,62 @@ std::tuple<ExecutionState, IndexExecutor::Stats, size_t> IndexExecutor::skipRows
     THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
   }
 
+  LOG_DEVEL_IDX << "IndexExecutor::skipRowsRange " << clientCall;
+
   IndexStats stats{};
 
-  while (_skipped < toSkip) {
+  while (clientCall.needSkipMore()) {
+    LOG_DEVEL_IDX << "IndexExecutor::skipRowsRange skipped " << _skipped
+                  << " " << clientCall.getOffset();
     // get an input row first, if necessary
-    if (!_input) {
-      if (_state == ExecutionState::DONE) {
-        size_t skipped = _skipped;
-
-        _skipped = 0;
-
-        return std::make_tuple(_state, stats, skipped);  // tuple, cannot use initializer list due to build failure
-      }
-
-      std::tie(_state, _input) = _fetcher.fetchRow();
-
-      if (_state == ExecutionState::WAITING) {
-        return std::make_tuple(_state, stats, 0);  // tuple, cannot use initializer list due to build failure
-      }
-
-      if (!_input) {
-        TRI_ASSERT(_state == ExecutionState::DONE);
-        size_t skipped = _skipped;
-
-        _skipped = 0;
-
-        return std::make_tuple(_state, stats, skipped);  // tuple, cannot use initializer list due to build failure
-      }
-
-      initIndexes(_input);
-
-      if (!advanceCursor()) {
-        _input = InputAqlItemRow{CreateInvalidInputRowHint{}};
-        // just to validate that after continue we get into retry mode
-        TRI_ASSERT(!_input);
-        continue;
+    if (!_input.isInitialized()) {
+      std::tie(_state, _input) = inputRange.peekDataRow();
+      LOG_DEVEL_IDX
+          << "IndexExecutor::skipRowsRange input not initialized, peek next row: " << _state
+          << " " << std::boolalpha << _input.isInitialized();
+
+      if (_input.isInitialized()) {
+        LOG_DEVEL_IDX << "IndexExecutor::skipRowsRange initIndexes";
+        initIndexes(_input);
+        if (!advanceCursor()) {
+          LOG_DEVEL_IDX << "IndexExecutor::skipRowsRange failed to advanceCursor "
+                           "after init";
+          std::ignore = inputRange.nextDataRow();
+          _input = InputAqlItemRow{CreateInvalidInputRowHint{}};
+          // just to validate that after continue we get into retry mode
+          TRI_ASSERT(!_input);
+          continue;
+        }
+      } else {
+        break;
       }
     }
 
-    if (!getCursor().hasMore()) {
-      if (!advanceCursor()) {
-        _input = InputAqlItemRow{CreateInvalidInputRowHint{}};
-        break;
-      }
+    if (!getCursor().hasMore() && !advanceCursor()) {
+      LOG_DEVEL_IDX << "IndexExecutor::skipRowsRange cursor does not "
+                       "have more and advancing failed";
+      std::ignore = inputRange.nextDataRow();
+      _input = InputAqlItemRow{CreateInvalidInputRowHint{}};
+      continue;
     }
 
-    size_t skippedNow = getCursor().skipIndex(toSkip - _skipped);
+    LOG_DEVEL_IDX << "IndexExecutor::skipRowsRange skipIndex("
+                  << clientCall.getOffset() << ")";
+    size_t skippedNow = getCursor().skipIndex(clientCall.getOffset());
+    LOG_DEVEL_IDX << "IndexExecutor::skipRowsRange skipIndex(...) == " << skippedNow;
+
     stats.incrScanned(skippedNow);
     _skipped += skippedNow;
+    clientCall.didSkip(skippedNow);
   }
 
   size_t skipped = _skipped;
-
   _skipped = 0;
 
-  if (_state == ExecutionState::DONE && !_input) {
-    return std::make_tuple(ExecutionState::DONE, stats,
-                           skipped);  // tuple, cannot use initializer list due to build failure
-  }
+  AqlCall upstreamCall;
+  upstreamCall.fullCount = clientCall.needsFullCount();
 
-  return std::make_tuple(ExecutionState::HASMORE, stats,
-                         skipped);  // tuple, cannot use initializer list due to build failure
-}
-
-IndexExecutor::CursorReader& IndexExecutor::getCursor() {
-  TRI_ASSERT(_currentIndex < _cursors.size());
-  return _cursors[_currentIndex];
-}
 
-bool IndexExecutor::needsUniquenessCheck() const noexcept {
-  return _infos.getIndexes().size() > 1 || _infos.hasMultipleExpansions();
+  LOG_DEVEL_IDX << "IndexExecutor::skipRowsRange returning " << _state << " " << skipped << " " << upstreamCall;
+  return {_state, stats, skipped, upstreamCall};
 }
diff --git a/arangod/Aql/IndexExecutor.h b/arangod/Aql/IndexExecutor.h
index c22d02621233..6dfbf13accdd 100644
--- a/arangod/Aql/IndexExecutor.h
+++ b/arangod/Aql/IndexExecutor.h
@@ -26,6 +26,8 @@
 #ifndef ARANGOD_AQL_INDEX_EXECUTOR_H
 #define ARANGOD_AQL_INDEX_EXECUTOR_H
 
+#include "Aql/AqlCall.h"
+#include "Aql/AqlItemBlockInputRange.h"
 #include "Aql/DocumentProducingHelper.h"
 #include "Aql/ExecutionState.h"
 #include "Aql/ExecutorInfos.h"
@@ -57,12 +59,12 @@ struct NonConstExpression;
 class IndexExecutorInfos : public ExecutorInfos {
  public:
   IndexExecutorInfos(
-      std::shared_ptr<std::unordered_set<aql::RegisterId>>&& writableOutputRegisters, RegisterId nrInputRegisters,
-      RegisterId firstOutputRegister, RegisterId nrOutputRegisters, std::unordered_set<RegisterId> registersToClear,
+      std::shared_ptr<std::unordered_set<aql::RegisterId>>&& writableOutputRegisters,
+      RegisterId nrInputRegisters, RegisterId firstOutputRegister,
+      RegisterId nrOutputRegisters, std::unordered_set<RegisterId> registersToClear,
       std::unordered_set<RegisterId> registersToKeep, ExecutionEngine* engine,
       Collection const* collection, Variable const* outVariable, bool produceResult,
-      Expression* filter,
-      std::vector<std::string> const& projections, 
+      Expression* filter, std::vector<std::string> const& projections,
       std::vector<size_t> const& coveringIndexAttributePositions, bool useRawDocumentPointers,
       std::vector<std::unique_ptr<NonConstExpression>>&& nonConstExpression,
       std::vector<Variable const*>&& expInVars, std::vector<RegisterId>&& expInRegs,
@@ -195,9 +197,9 @@ class IndexExecutor {
     DocumentProducingFunctionContext& _context;
     Type const _type;
 
-    // Only one of _documentProducer and _documentNonProducer is set at a time, depending on _type.
-    // As std::function is not trivially destructible, it's safer not to use a
-    // union.
+    // Only one of _documentProducer and _documentNonProducer is set at a time,
+    // depending on _type. As std::function is not trivially destructible, it's
+    // safer not to use a union.
     IndexIterator::LocalDocumentIdCallback _documentNonProducer;
     IndexIterator::DocumentCallback _documentProducer;
     IndexIterator::DocumentCallback _documentSkipper;
@@ -228,6 +230,12 @@ class IndexExecutor {
   std::pair<ExecutionState, Stats> produceRows(OutputAqlItemRow& output);
   std::tuple<ExecutionState, Stats, size_t> skipRows(size_t toSkip);
 
+  auto produceRows(AqlItemBlockInputRange& inputRange, OutputAqlItemRow& output)
+      -> std::tuple<ExecutorState, Stats, AqlCall>;
+
+  auto skipRowsRange(AqlItemBlockInputRange& inputRange, AqlCall& clientCall)
+      -> std::tuple<ExecutorState, Stats, size_t, AqlCall>;
+
  public:
   void initializeCursor();
 
@@ -242,9 +250,8 @@ class IndexExecutor {
 
  private:
   Infos& _infos;
-  Fetcher& _fetcher;
   DocumentProducingFunctionContext _documentProducingFunctionContext;
-  ExecutionState _state;
+  ExecutorState _state;
   InputAqlItemRow _input;
 
   /// @brief a vector of cursors for the index block

From dac0a1053c81925c79f83f52292d41a6a15d4d13 Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Tue, 18 Feb 2020 13:16:53 +0100
Subject: [PATCH 066/122] Feature/aql subquery execution block impl execute
 implementation debug logging (#11112)

* Prepare reusability of LOG output for ExecutionBlock.

* Added first version of DEBUG output to ExecutionBlockImpl
---
 arangod/Aql/ExecutionBlock.cpp     | 34 +++++++++++++++++++++---------
 arangod/Aql/ExecutionBlock.h       |  3 +++
 arangod/Aql/ExecutionBlockImpl.cpp | 22 +++++++++++++++++++
 3 files changed, 49 insertions(+), 10 deletions(-)

diff --git a/arangod/Aql/ExecutionBlock.cpp b/arangod/Aql/ExecutionBlock.cpp
index 1d7f97402f85..a9ba6fb98b3a 100644
--- a/arangod/Aql/ExecutionBlock.cpp
+++ b/arangod/Aql/ExecutionBlock.cpp
@@ -46,6 +46,10 @@
 using namespace arangodb;
 using namespace arangodb::aql;
 
+#define LOG_QUERY(logId, level)            \
+  LOG_TOPIC(logId, level, Logger::QUERIES) \
+      << "[query#" << this->_engine->getQuery()->id() << "] "
+
 namespace {
 
 std::string const doneString = "DONE";
@@ -335,28 +339,38 @@ void ExecutionBlock::traceExecuteEnd(
 
     if (_profile >= PROFILE_LEVEL_TRACE_1) {
       ExecutionNode const* node = getPlanNode();
-      auto const queryId = this->_engine->getQuery()->id();
-      LOG_TOPIC("60bbc", INFO, Logger::QUERIES)
-          << "[query#" << queryId << "] "
-          << "execute done type=" << node->getTypeString() << " this=" << (uintptr_t)this
-          << " id=" << node->id() << " state=" << stateToString(state)
-          << " skipped=" << skipped << " produced=" << items;
+      LOG_QUERY("60bbc", INFO) << "execute done " << printBlockInfo()
+                               << " state=" << stateToString(state)
+                               << " skipped=" << skipped << " produced=" << items;
 
       if (_profile >= PROFILE_LEVEL_TRACE_2) {
         if (block == nullptr) {
-          LOG_TOPIC("9b3f4", INFO, Logger::QUERIES)
-              << "[query#" << queryId << "] "
+          LOG_QUERY("9b3f4", INFO)
               << "execute type=" << node->getTypeString() << " result: nullptr";
         } else {
           VPackBuilder builder;
           auto const options = trxVpackOptions();
           block->toSimpleVPack(options, builder);
-          LOG_TOPIC("f12f9", INFO, Logger::QUERIES)
-              << "[query#" << queryId << "] "
+          LOG_QUERY("f12f9", INFO)
               << "execute type=" << node->getTypeString()
               << " result: " << VPackDumper::toString(builder.slice(), options);
         }
       }
     }
   }
+}
+
+auto ExecutionBlock::printTypeInfo() const -> std::string const {
+  std::stringstream stream;
+  ExecutionNode const* node = getPlanNode();
+  stream << "type=" << node->getTypeString();
+  ;
+  return stream.str();
+}
+
+auto ExecutionBlock::printBlockInfo() const -> std::string const {
+  std::stringstream stream;
+  ExecutionNode const* node = getPlanNode();
+  stream << printTypeInfo() << " this=" << (uintptr_t)this << " id=" << node->id();
+  return stream.str();
 }
\ No newline at end of file
diff --git a/arangod/Aql/ExecutionBlock.h b/arangod/Aql/ExecutionBlock.h
index f6e7370647e8..059217978485 100644
--- a/arangod/Aql/ExecutionBlock.h
+++ b/arangod/Aql/ExecutionBlock.h
@@ -157,6 +157,9 @@ class ExecutionBlock {
   // Trace the end of a execute call, potentially with result
   void traceExecuteEnd(std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> const& result);
 
+  [[nodiscard]] auto printBlockInfo() const -> std::string const;
+  [[nodiscard]] auto printTypeInfo() const -> std::string const;
+
  protected:
   /// @brief the execution engine
   ExecutionEngine* _engine;
diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index 65f1eba03c24..509882edcd2b 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -81,6 +81,10 @@
 using namespace arangodb;
 using namespace arangodb::aql;
 
+#define LOG_QUERY(logId, level)            \
+  LOG_TOPIC(logId, level, Logger::QUERIES) \
+      << "[query#" << this->_engine->getQuery()->id() << "] "
+
 /*
  * Creates a metafunction `checkName` that tests whether a class has a method
  * named `methodName`, used like this:
@@ -1152,6 +1156,7 @@ std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr>
 ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
   if constexpr (isNewStyleExecutor<Executor>) {
     if (!stack.isRelevant()) {
+      LOG_QUERY("bf029", DEBUG) << "subquery bypassing executor " << printBlockInfo();
       // We are bypassing subqueries.
       // This executor is not allowed to perform actions
       // However we need to maintain the upstream state.
@@ -1180,9 +1185,12 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
       clientCall = _clientRequest;
     }
 
+    LOG_QUERY("007ac", DEBUG) << "starting statemachine of executor " << printBlockInfo();
     while (_execState != ExecState::DONE) {
       switch (_execState) {
         case ExecState::CHECKCALL: {
+          LOG_QUERY("cfe46", DEBUG)
+              << printTypeInfo() << " determine next action on call " << clientCall;
           _execState = nextState(clientCall);
           break;
         }
@@ -1193,6 +1201,7 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
           size_t canPassFullcount =
               clientCall.getLimit() == 0 && clientCall.needsFullCount();
 #endif
+          LOG_QUERY("1f786", DEBUG) << printTypeInfo() << " call skipRows " << clientCall;
           auto [state, stats, skippedLocal, call] =
               executeSkipRowsRange(_lastRange, clientCall);
 #ifdef ARANGODB_ENABLE_MAINTAINER_MODE
@@ -1231,6 +1240,8 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
           // Make sure there's a block allocated and set
           // the call
           TRI_ASSERT(clientCall.getLimit() > 0);
+
+          LOG_QUERY("1f786", DEBUG) << printTypeInfo() << " call produceRows " << clientCall;
           ensureOutputBlock(std::move(clientCall));
           TRI_ASSERT(_outputItemRow);
 
@@ -1258,6 +1269,8 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
           break;
         }
         case ExecState::FASTFORWARD: {
+          LOG_QUERY("96e2c", DEBUG)
+              << printTypeInfo() << " all produced, fast forward to end up (sub-)query.";
           // We can either do FASTFORWARD or FULLCOUNT, difference is that
           // fullcount counts what is produced now, FASTFORWARD simply drops
           TRI_ASSERT(!clientCall.needsFullCount());
@@ -1278,6 +1291,9 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
           break;
         }
         case ExecState::FULLCOUNT: {
+          LOG_QUERY("ff258", DEBUG)
+              << printTypeInfo()
+              << " all produced, skip to end up (sub-)query, for fullCount.";
           auto [state, stats, skippedLocal, call] =
               executeSkipRowsRange(_lastRange, clientCall);
           _skipped += skippedLocal;
@@ -1293,6 +1309,8 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
           break;
         }
         case ExecState::UPSTREAM: {
+          LOG_QUERY("488de", DEBUG)
+              << printTypeInfo() << " request dependency " << _upstreamRequest;
           // If this triggers the executors produceRows function has returned
           // HASMORE even if it knew that upstream has no further rows.
           TRI_ASSERT(_upstreamState != ExecutionState::DONE);
@@ -1319,6 +1337,8 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
           break;
         }
         case ExecState::SHADOWROWS: {
+          LOG_QUERY("7c63c", DEBUG)
+              << printTypeInfo() << " (sub-)query completed. Move ShadowRows.";
           // TODO: Check if there is a situation where we are at this point, but at the end of a block
           // Or if we would not recognize this beforehand
           // TODO: Check if we can have the situation that we are between two shadow rows here.
@@ -1335,6 +1355,7 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
             _outputItemRow->copyRow(shadowRow);
 
             if (shadowRow.isRelevant()) {
+              LOG_QUERY("6d337", DEBUG) << printTypeInfo() << " init executor.";
               // We found a relevant shadow Row.
               // We need to reset the Executor
               // cppcheck-suppress unreadVariable
@@ -1368,6 +1389,7 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
           TRI_ASSERT(false);
       }
     }
+    LOG_QUERY("80c24", DEBUG) << printBlockInfo() << " local statemachine done. Return now.";
     // If we do not have an output, we simply return a nullptr here.
     auto outputBlock = _outputItemRow != nullptr ? _outputItemRow->stealBlock()
                                                  : SharedAqlItemBlockPtr{nullptr};

From 1871aeb252112767938e0c95af64f9fb257caad9 Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Tue, 18 Feb 2020 17:15:57 +0100
Subject: [PATCH 067/122] Feature/aql subquery operations stack hashed collect
 executor (#11103)

* produce inputRange

* produce inputRange test 1

* produce inputRange test 2

* produce inputRange test 3

* finalized tests

* added inputRange skip and produce

* added inputRange skip and produce

* Added shouldSkip helper to AqlCall

* Added implementation if execute to Constfetcher. Not specifically tested yet.

* Moved IDExecutor to newStyle executor

* Added some documentation to SingleRowFetcher

* Adapted IdExecutor tests.

* Added an assertion in ConstFetcher

* Fixed initialize cursor in ExecutionBlockImpl

* Added tests for Initilaize cursor in IdExecutor. There is a special implementation for this...

* Fixed linker issues, because of variables in cpp files named identical and not beeing static

* Started refactoring the Scatter/Gather Executor logic. Added an intermediate class that does not use a template and can be casted to. This state compiles but will not work.

* Made BlocksWithClientsImpl a template, based on an executor

* Added a dummy implementation to fetch a new block. Distribute not yet implemented.

* Added superoptimistic first implementation of ScatterExecutor return. Only works if there are no shadowRows.

* Implemented logic to slice Blocks in Scatter according to the given call. Also added handfull of test for it, not complete though

* Fixed a Scatter Executor handling of softLimit. Added another test to ansure diverse calls of clients to Scatter

* Added random ordering test framework on ScatterExecutor

* Added some tests for ScatterExecutor including subqueries

* Removed todo, as it has been solved by now

* Implemented Scatter by using IDExecutor. Tests not green yet

* Implementation of ConstFetcher that allows to inject fullBlocks of AqlItemRows, and not only single rows. Also handles ShadowRows now in a correct way

* Do not jump over relevant shadow rows in ConstFetcher.

* Fixed tests.

* Moved information of DistributeExecutor into the Infos. This resulted in adapting the Constructor API. I used this situation to do a big cleanup of ancient code. From this point there is no way back.

* Implemented the last bits of DistributeExecutor

* 'Implemented' execute by fallback to old API in RemoteExecutor

* Fixed an EdgeCase with Scatter Executor, where the data was modified in place right after scatter. This has side-effects on peer executors. So we for now do a full copy of every block here.

* Removed invalid assertions, also fixed RegisterInput to DistributeExecutor

* Removed obsolete TODOs

* produce inputRange

* produce inputRange test 1

* produce inputRange test 2

* produce inputRange test 3

* finalized tests

* produce inputRange

* produce inputRange test 1

* produce inputRange test 2

* produce inputRange test 3

* finalized tests

* Made the branch compile again

* Update arangod/Aql/IdExecutor.cpp

Co-Authored-By: Lars Maier <lars@arangodb.com>

* Intermediate commit. Empty might not compile

* Added some external helper functions to compare ItemBlocks in different variants

* Added a brief description for the bunch of input parameters in HashedCollect

* Allow unordered output tests in TestHelper class.

* Added first HashedCollectExecutor test using the helper

* Allow to use never wait in getSome / skipSome variant of WaitingExecutionBlockMock.

* Added more HashedCollect tests (multi group, count) and started with framework for AggregateMethods

* Fixed simple Aggregate Test

* Improved output for unordered Row in Output test.

* Added test around collecting of Arrays and Objects

* Also allow a fullCount call in the old Execute Wrapper

* Almost Completed register and call behaviour test suite

* Added a todo for a missing test

* Improved setup of AqlTestCase framework, not only start the server once. This speeds up AQL test by at least a factor of 10.

* implemented newStyle HashedCollect executor.

* Cleanup of old code.

* Added test cases where the upstream producer lies to HashedCollect.

* Let HashedCollect and Impl life with the fact that upstream lies.

* Improved gtest with multiple calls.

* Simplify input consume logic of HashedCollect

Co-authored-by: Heiko <hkernbach@users.noreply.github.com>
Co-authored-by: Lars Maier <lars@arangodb.com>
---
 arangod/Aql/AqlCall.h                   |    6 +
 arangod/Aql/ExecutionBlockImpl.cpp      |   24 +-
 arangod/Aql/HashedCollectExecutor.cpp   |  157 +--
 arangod/Aql/HashedCollectExecutor.h     |   62 +-
 tests/Aql/ExecutorTestHelper.cpp        |  133 ++-
 tests/Aql/ExecutorTestHelper.h          |  136 ++-
 tests/Aql/HashedCollectExecutorTest.cpp | 1181 +++++++++++------------
 tests/Aql/IdExecutorTest.cpp            |   22 +-
 tests/Aql/SortedCollectExecutorTest.cpp |    3 +-
 tests/Aql/WaitingExecutionBlockMock.cpp |   20 +-
 10 files changed, 971 insertions(+), 773 deletions(-)

diff --git a/arangod/Aql/AqlCall.h b/arangod/Aql/AqlCall.h
index 72acbb351c85..63fbf31b5883 100644
--- a/arangod/Aql/AqlCall.h
+++ b/arangod/Aql/AqlCall.h
@@ -65,6 +65,12 @@ struct AqlCall {
     return !call.hasHardLimit() && call.getLimit() > 0 && call.getOffset() == 0;
   }
 
+  // TODO Remove me, this will not be necessary later
+  static bool IsFullCountCall(AqlCall const& call) {
+    return call.hasHardLimit() && call.getLimit() == 0 &&
+           call.getOffset() == 0 && call.needsFullCount();
+  }
+
   std::size_t offset{0};
   // TODO: The defaultBatchSize function could move into this file instead
   Limit softLimit{Infinity{}};
diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index 509882edcd2b..acb04789adb7 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -136,7 +136,7 @@ constexpr bool is_one_of_v = (std::is_same_v<T, Es> || ...);
 template <typename Executor>
 constexpr bool isNewStyleExecutor =
     is_one_of_v<Executor, FilterExecutor, SortedCollectExecutor, IdExecutor<ConstFetcher>,
-                IdExecutor<SingleRowFetcher<BlockPassthrough::Enable>>, ReturnExecutor, IndexExecutor,
+                IdExecutor<SingleRowFetcher<BlockPassthrough::Enable>>, ReturnExecutor, HashedCollectExecutor, IndexExecutor,
 #ifdef ARANGODB_USE_GOOGLE_TESTS
                 TestLambdaExecutor,
                 TestLambdaSkipExecutor,  // we need one after these to avoid compile errors in non-test mode
@@ -617,7 +617,8 @@ std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> ExecutionBlockImpl<Exe
 
   // Fall back to getSome/skipSome
   auto myCall = stack.popCall();
-  TRI_ASSERT(AqlCall::IsSkipSomeCall(myCall) || AqlCall::IsGetSomeCall(myCall));
+  TRI_ASSERT(AqlCall::IsSkipSomeCall(myCall) ||
+             AqlCall::IsGetSomeCall(myCall) || AqlCall::IsFullCountCall(myCall));
   if (AqlCall::IsSkipSomeCall(myCall)) {
     auto const [state, skipped] = skipSome(myCall.getOffset());
     if (state != ExecutionState::WAITING) {
@@ -628,6 +629,12 @@ std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> ExecutionBlockImpl<Exe
     auto const [state, block] = getSome(myCall.getLimit());
     // We do not need to count as softLimit will be overwritten, and hard cannot be set.
     return {state, 0, block};
+  } else if (AqlCall::IsFullCountCall(myCall)) {
+    auto const [state, skipped] = skipSome(ExecutionBlock::SkipAllSize());
+    if (state != ExecutionState::WAITING) {
+      myCall.didSkip(skipped);
+    }
+    return {state, skipped, nullptr};
   }
   // Should never get here!
   THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
@@ -1049,7 +1056,7 @@ static SkipRowsRangeVariant constexpr skipRowsType() {
                 "Fetcher is chosen for skipping, but has not skipRows method!");
 
   static_assert(useExecutor ==
-                    (is_one_of_v<Executor, FilterExecutor, ShortestPathExecutor, ReturnExecutor, IndexExecutor,
+                    (is_one_of_v<Executor, FilterExecutor, ShortestPathExecutor, ReturnExecutor, HashedCollectExecutor, IndexExecutor,
 #ifdef ARANGODB_USE_GOOGLE_TESTS
                                  TestLambdaSkipExecutor,
 #endif
@@ -1166,6 +1173,7 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
       return {_upstreamState, skippedLocal, bypassedRange.getBlock()};
     }
     AqlCall clientCall = stack.popCall();
+    ExecutorState localExecutorState = ExecutorState::DONE;
 
     // We can only have returned the following internal states
     TRI_ASSERT(_execState == ExecState::CHECKCALL || _execState == ExecState::SHADOWROWS ||
@@ -1220,6 +1228,7 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
             TRI_ASSERT(clientCall.getOffset() + skippedLocal == offsetBefore);
           }
 #endif
+          localExecutorState = state;
           _skipped += skippedLocal;
           _engine->_stats += stats;
           // The execute might have modified the client call.
@@ -1249,6 +1258,7 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
           auto const [state, stats, call] =
               _executor.produceRows(_lastRange, *_outputItemRow);
           _engine->_stats += stats;
+          localExecutorState = state;
 
           // Produce might have modified the clientCall
           clientCall = _outputItemRow->getClientCall();
@@ -1274,8 +1284,10 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
           // We can either do FASTFORWARD or FULLCOUNT, difference is that
           // fullcount counts what is produced now, FASTFORWARD simply drops
           TRI_ASSERT(!clientCall.needsFullCount());
-          // We can drop all dataRows from upstream
+          // We need to claim that the Executor was done
+          localExecutorState = ExecutorState::DONE;
 
+          // We can drop all dataRows from upstream
           while (_lastRange.hasDataRow()) {
             auto [state, row] = _lastRange.nextDataRow();
             TRI_ASSERT(row.isInitialized());
@@ -1298,6 +1310,7 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
               executeSkipRowsRange(_lastRange, clientCall);
           _skipped += skippedLocal;
           _engine->_stats += stats;
+          localExecutorState = state;
 
           if (state == ExecutorState::DONE) {
             _execState = ExecState::SHADOWROWS;
@@ -1403,7 +1416,8 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
     // We return skipped here, reset member
     size_t skipped = _skipped;
     _skipped = 0;
-    if (_lastRange.hasDataRow() || _lastRange.hasShadowRow()) {
+    if (localExecutorState == ExecutorState::HASMORE ||
+        _lastRange.hasDataRow() || _lastRange.hasShadowRow()) {
       // We have skipped or/and return data, otherwise we cannot return HASMORE
       TRI_ASSERT(skipped > 0 || (outputBlock != nullptr && outputBlock->numEntries() > 0));
       return {ExecutionState::HASMORE, skipped, std::move(outputBlock)};
diff --git a/arangod/Aql/HashedCollectExecutor.cpp b/arangod/Aql/HashedCollectExecutor.cpp
index f7ebd6778a3e..6f8e086fb6f6 100644
--- a/arangod/Aql/HashedCollectExecutor.cpp
+++ b/arangod/Aql/HashedCollectExecutor.cpp
@@ -26,6 +26,7 @@
 #include "HashedCollectExecutor.h"
 
 #include "Aql/Aggregator.h"
+#include "Aql/AqlCall.h"
 #include "Aql/AqlValue.h"
 #include "Aql/ExecutionNode.h"
 #include "Aql/ExecutorInfos.h"
@@ -111,16 +112,13 @@ HashedCollectExecutor::createAggregatorFactories(HashedCollectExecutor::Infos co
 
 HashedCollectExecutor::HashedCollectExecutor(Fetcher& fetcher, Infos& infos)
     : _infos(infos),
-      _fetcher(fetcher),
-      _upstreamState(ExecutionState::HASMORE),
       _lastInitializedInputRow(InputAqlItemRow{CreateInvalidInputRowHint{}}),
       _allGroups(1024,
                  AqlValueGroupHash(_infos.getTransaction(),
                                    _infos.getGroupRegisters().size()),
                  AqlValueGroupEqual(_infos.getTransaction())),
       _isInitialized(false),
-      _aggregatorFactories(),
-      _returnedGroups(0) {
+      _aggregatorFactories() {
   _aggregatorFactories = createAggregatorFactories(_infos);
   _nextGroupValues.reserve(_infos.getGroupRegisters().size());
 };
@@ -205,65 +203,109 @@ void HashedCollectExecutor::writeCurrentGroupToOutput(OutputAqlItemRow& output)
   }
 }
 
-ExecutionState HashedCollectExecutor::init() {
-  TRI_ASSERT(!_isInitialized);
-
-  // fetch & consume all input
-  while (_upstreamState != ExecutionState::DONE) {
-    InputAqlItemRow input = InputAqlItemRow{CreateInvalidInputRowHint{}};
-    std::tie(_upstreamState, input) = _fetcher.fetchRow();
+std::pair<ExecutionState, NoStats> HashedCollectExecutor::produceRows(OutputAqlItemRow& output) {
+  TRI_ASSERT(false);
+  THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
+}
 
-    if (_upstreamState == ExecutionState::WAITING) {
-      TRI_ASSERT(!input.isInitialized());
-      return ExecutionState::WAITING;
+auto HashedCollectExecutor::consumeInputRange(AqlItemBlockInputRange& inputRange) -> bool {
+  TRI_ASSERT(!_isInitialized);
+  do {
+    auto [state, input] = inputRange.nextDataRow();
+    if (input) {
+      consumeInputRow(input);
+      // We need to retain this
+      _lastInitializedInputRow = input;
     }
+    if (state == ExecutorState::DONE) {
+      // initialize group iterator for output
+      _currentGroup = _allGroups.begin();
+      return true;
+    }
+  } while (inputRange.hasDataRow());
 
-    // !input.isInitialized() => _upstreamState == ExecutionState::DONE
-    TRI_ASSERT(input.isInitialized() || _upstreamState == ExecutionState::DONE);
-
-    // needed to remember the last valid input aql item row
-    // NOTE: this might impact the performance
-    if (input.isInitialized()) {
-      _lastInitializedInputRow = input;
+  TRI_ASSERT(inputRange.upstreamState() == ExecutorState::HASMORE);
+  return false;
+}
 
-      consumeInputRow(input);
-    }
+auto HashedCollectExecutor::returnState() const -> ExecutorState {
+  if (!_isInitialized || _currentGroup != _allGroups.end()) {
+    // We have either not started, or not produce all groups.
+    return ExecutorState::HASMORE;
   }
-
-  // initialize group iterator for output
-  _currentGroup = _allGroups.begin();
-  // The values within are not supposed to be used anymore.
-  _nextGroupValues.clear();
-  return ExecutionState::DONE;
+  return ExecutorState::DONE;
 }
 
-std::pair<ExecutionState, NoStats> HashedCollectExecutor::produceRows(OutputAqlItemRow& output) {
+/**
+ * @brief Produce rows.
+ *   We need to consume all rows from the inputRange, except the
+ *   last Row. This is to indicate that this executor is not yet done.
+ *   Afterwards we write all groups into the output.
+ *   Only if we have written the last group we consume
+ *   the remaining inputRow. This is to indicate that
+ *   this executor cannot produce anymore.
+ *
+ * @param inputRange Data from input
+ * @param output Where to write the output
+ * @return std::tuple<ExecutorState, NoStats, AqlCall>
+ */
+
+auto HashedCollectExecutor::produceRows(AqlItemBlockInputRange& inputRange,
+                                        OutputAqlItemRow& output)
+    -> std::tuple<ExecutorState, NoStats, AqlCall> {
   TRI_IF_FAILURE("HashedCollectExecutor::produceRows") {
     THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
   }
-
   if (!_isInitialized) {
-    // fetch & consume all input and initialize output cursor
-    ExecutionState state = init();
-    if (state == ExecutionState::WAITING) {
-      return {state, NoStats{}};
+    // Consume the input range
+    _isInitialized = consumeInputRange(inputRange);
+  }
+
+  if (_isInitialized) {
+    while (_currentGroup != _allGroups.end() && !output.isFull()) {
+      writeCurrentGroupToOutput(output);
+      ++_currentGroup;
+      output.advanceRow();
     }
-    TRI_ASSERT(state == ExecutionState::DONE);
-    _isInitialized = true;
   }
 
-  // produce output
-  if (_currentGroup != _allGroups.end()) {
-    writeCurrentGroupToOutput(output);
-    ++_currentGroup;
-    ++_returnedGroups;
-    TRI_ASSERT(_returnedGroups <= _allGroups.size());
+  AqlCall upstreamCall{};
+  // We cannot forward anything, no skip, no limit.
+  // Need to request all from upstream.
+  return {returnState(), NoStats{}, upstreamCall};
+}
+
+/**
+ * @brief Skip Rows
+ *   We need to consume all rows from the inputRange, except the
+ *   last Row. This is to indicate that this executor is not yet done.
+ *   Afterwards we skip all groups.
+ *   Only if we have skipped the last group we consume
+ *   the remaining inputRow. This is to indicate that
+ *   this executor cannot produce anymore.
+ *
+ * @param inputRange  Data from input
+ * @param call Call from client
+ * @return std::tuple<ExecutorState, NoStats, size_t, AqlCall>
+ */
+auto HashedCollectExecutor::skipRowsRange(AqlItemBlockInputRange& inputRange, AqlCall& call)
+    -> std::tuple<ExecutorState, NoStats, size_t, AqlCall> {
+  if (!_isInitialized) {
+    // Consume the input range
+    _isInitialized = consumeInputRange(inputRange);
   }
 
-  ExecutionState state = _currentGroup != _allGroups.end() ? ExecutionState::HASMORE
-                                                           : ExecutionState::DONE;
+  if (_isInitialized) {
+    while (_currentGroup != _allGroups.end() && call.needSkipMore()) {
+      ++_currentGroup;
+      call.didSkip(1);
+    }
+  }
 
-  return {state, NoStats{}};
+  AqlCall upstreamCall{};
+  // We cannot forward anything, no skip, no limit.
+  // Need to request all from upstream.
+  return {returnState(), NoStats{}, call.getSkipCount(), upstreamCall};
 }
 
 // finds the group matching the current row, or emplaces it. in either case,
@@ -301,7 +343,8 @@ decltype(HashedCollectExecutor::_allGroups)::iterator HashedCollectExecutor::fin
   }
 
   // note: aggregateValues may be a nullptr!
-  auto [result, emplaced] = _allGroups.try_emplace(std::move(_nextGroupValues), std::move(aggregateValues));
+  auto [result, emplaced] =
+      _allGroups.try_emplace(std::move(_nextGroupValues), std::move(aggregateValues));
   // emplace must not fail
   TRI_ASSERT(emplaced);
 
@@ -313,24 +356,8 @@ decltype(HashedCollectExecutor::_allGroups)::iterator HashedCollectExecutor::fin
 };
 
 std::pair<ExecutionState, size_t> HashedCollectExecutor::expectedNumberOfRows(size_t atMost) const {
-  size_t rowsLeft = 0;
-  if (!_isInitialized) {
-    ExecutionState state;
-    std::tie(state, rowsLeft) = _fetcher.preFetchNumberOfRows(atMost);
-    if (state == ExecutionState::WAITING) {
-      TRI_ASSERT(rowsLeft == 0);
-      return {state, 0};
-    }
-    // Overestimate, we have not grouped!
-  } else {
-    // This fetcher nows how exactly many rows are left
-    // as it knows how many  groups is has created and not returned.
-    rowsLeft = _allGroups.size() - _returnedGroups;
-  }
-  if (rowsLeft > 0) {
-    return {ExecutionState::HASMORE, rowsLeft};
-  }
-  return {ExecutionState::DONE, rowsLeft};
+  TRI_ASSERT(false);
+  THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
 }
 
 const HashedCollectExecutor::Infos& HashedCollectExecutor::infos() const noexcept {
diff --git a/arangod/Aql/HashedCollectExecutor.h b/arangod/Aql/HashedCollectExecutor.h
index 1381a590e93f..1ff7767d1f74 100644
--- a/arangod/Aql/HashedCollectExecutor.h
+++ b/arangod/Aql/HashedCollectExecutor.h
@@ -38,6 +38,9 @@
 
 namespace arangodb {
 namespace aql {
+
+struct AqlCall;
+class AqlItemBlockInputRange;
 class OutputAqlItemRow;
 class ExecutorInfos;
 template <BlockPassthrough>
@@ -46,6 +49,26 @@ struct Aggregator;
 
 class HashedCollectExecutorInfos : public ExecutorInfos {
  public:
+  /**
+   * @brief Construct a new Hashed Collect Executor Infos object
+   *
+   * @param nrInputRegisters Number Registers in the input row
+   * @param nrOutputRegisters Number Registers in the output row
+   * @param registersToClear Registers that need to be empty after this
+   * @param registersToKeep Registers that will be copied after this
+   * @param readableInputRegisters InputRegisters this Executor is allowed to read
+   * @param writeableOutputRegisters OutputRegisters this Executor is required to write
+   * @param groupRegisters Registers the grouping is based on.
+   *                       If values in the registers are identical,
+   *                       the rows are considered as the same group.
+   *                       Format: <outputRegister, inputRegister>
+   * @param collectRegister Register to write the GroupingResult to
+   *                        (COLLECT ... INTO collectRegister)
+   * @param aggregateTypes Aggregation methods used
+   * @param aggregateRegisters Input and output Register for Aggregation
+   * @param trxPtr The AQL transaction, as it might be needed for aggregates
+   * @param count Flag to enable count, will be written to collectRegister
+   */
   HashedCollectExecutorInfos(RegisterId nrInputRegisters, RegisterId nrOutputRegisters,
                              std::unordered_set<RegisterId> registersToClear,
                              std::unordered_set<RegisterId> registersToKeep,
@@ -117,9 +140,26 @@ class HashedCollectExecutor {
    * @brief produce the next Row of Aql Values.
    *
    * @return ExecutionState, and if successful exactly one new Row of AqlItems.
+   * @deprecated
    */
   std::pair<ExecutionState, Stats> produceRows(OutputAqlItemRow& output);
 
+  /**
+   * @brief produce the next Row of Aql Values.
+   *
+   * @return ExecutorState, the stats, and a new Call that needs to be send to upstream
+   */
+  [[nodiscard]] auto produceRows(AqlItemBlockInputRange& input, OutputAqlItemRow& output)
+      -> std::tuple<ExecutorState, Stats, AqlCall>;
+
+  /**
+   * @brief skip the next Row of Aql Values.
+   *
+   * @return ExecutorState, the stats, and a new Call that needs to be send to upstream
+   */
+  [[nodiscard]] auto skipRowsRange(AqlItemBlockInputRange& inputRange, AqlCall& call)
+      -> std::tuple<ExecutorState, Stats, size_t, AqlCall>;
+
   /**
    * @brief This Executor does not know how many distinct rows will be fetched
    * from upstream, it can only report how many it has found by itself, plus
@@ -138,13 +178,21 @@ class HashedCollectExecutor {
   Infos const& infos() const noexcept;
 
   /**
-   * @brief Shall be executed until it returns DONE, then never again.
-   * Consumes all input, writes groups and calculates aggregates, and
-   * initializes _currentGroup to _allGroups.begin().
+   * @brief Consumes all rows from upstream
+   *        Every row is collected into one of the groups.
    *
-   * @return DONE or WAITING
+   * @param inputRange Upstream range, will be fully consumed
+   * @return true We have consumed everything, start output
+   * @return false We do not have all input ask for more.
    */
-  ExecutionState init();
+  auto consumeInputRange(AqlItemBlockInputRange& inputRange) -> bool;
+
+  /**
+   * @brief State this Executor needs to report
+   *
+   * @return ExecutorState
+   */
+  auto returnState() const -> ExecutorState;
 
   void destroyAllGroupsAqlValues();
 
@@ -159,8 +207,6 @@ class HashedCollectExecutor {
 
  private:
   Infos const& _infos;
-  Fetcher& _fetcher;
-  ExecutionState _upstreamState;
 
   /// @brief We need to save any input row (it really doesn't matter, except for
   /// when input blocks are freed - thus the last), so we can produce output
@@ -175,8 +221,6 @@ class HashedCollectExecutor {
 
   std::vector<std::function<std::unique_ptr<Aggregator>(transaction::Methods*)> const*> _aggregatorFactories;
 
-  size_t _returnedGroups;
-
   GroupKeyType _nextGroupValues;
 };
 
diff --git a/tests/Aql/ExecutorTestHelper.cpp b/tests/Aql/ExecutorTestHelper.cpp
index 17a521230cda..d0e38abac134 100644
--- a/tests/Aql/ExecutorTestHelper.cpp
+++ b/tests/Aql/ExecutorTestHelper.cpp
@@ -26,26 +26,137 @@
 
 using namespace arangodb::tests::aql;
 
-auto arangodb::tests::aql::ValidateBlocksAreEqual(SharedAqlItemBlockPtr actual,
-                                                  SharedAqlItemBlockPtr expected) -> void {
+auto asserthelper::AqlValuesAreIdentical(AqlValue const& lhs, AqlValue const& rhs) -> bool {
   velocypack::Options vpackOptions;
+  return AqlValue::Compare(&vpackOptions, lhs, rhs, true) == 0;
+}
+
+auto asserthelper::RowsAreIdentical(SharedAqlItemBlockPtr actual, size_t actualRow,
+                                    SharedAqlItemBlockPtr expected, size_t expectedRow,
+                                    std::optional<std::vector<RegisterId>> const& onlyCompareRegisters)
+    -> bool {
+  if (onlyCompareRegisters) {
+    if (actual->getNrRegs() < onlyCompareRegisters->size()) {
+      // Registers do not match
+      return false;
+    }
+  } else {
+    if (actual->getNrRegs() != expected->getNrRegs()) {
+      // Registers do not match
+      return false;
+    }
+  }
+
+  for (RegisterId reg = 0; reg < expected->getNrRegs(); ++reg) {
+    auto const& x =
+        actual->getValueReference(actualRow, onlyCompareRegisters
+                                                 ? onlyCompareRegisters->at(reg)
+                                                 : reg);
+    auto const& y = expected->getValueReference(expectedRow, reg);
+    if (!AqlValuesAreIdentical(x, y)) {
+      // At least one value mismatched
+      return false;
+    }
+  }
+  // All values match
+  return true;
+}
+
+auto asserthelper::ValidateAqlValuesAreEqual(SharedAqlItemBlockPtr actual,
+                                             size_t actualRow, RegisterId actualRegister,
+                                             SharedAqlItemBlockPtr expected, size_t expectedRow,
+                                             RegisterId expectedRegister) -> void {
+  velocypack::Options vpackOptions;
+  auto const& x = actual->getValueReference(actualRow, actualRegister);
+  auto const& y = expected->getValueReference(expectedRow, expectedRegister);
+  EXPECT_TRUE(AqlValuesAreIdentical(x, y))
+      << "Row " << actualRow << " Column " << actualRegister << " do not agree. "
+      << x.slice().toJson(&vpackOptions) << " vs. " << y.slice().toJson(&vpackOptions);
+}
+
+auto asserthelper::ValidateBlocksAreEqual(SharedAqlItemBlockPtr actual,
+                                          SharedAqlItemBlockPtr expected,
+                                          std::optional<std::vector<RegisterId>> const& onlyCompareRegisters)
+    -> void {
   ASSERT_NE(expected, nullptr);
   ASSERT_NE(actual, nullptr);
   EXPECT_EQ(actual->size(), expected->size());
-  EXPECT_EQ(actual->getNrRegs(), 1);
-  for (size_t i = 0; i < (std::min)(actual->size(), expected->size()); ++i) {
-    auto const& x = actual->getValueReference(i, 0);
-    auto const& y = expected->getValueReference(i, 0);
-    EXPECT_TRUE(AqlValue::Compare(&vpackOptions, x, y, true) == 0)
-        << "Row " << i << " Column " << 0 << " do not agree. "
-        << x.slice().toJson(&vpackOptions) << " vs. "
-        << y.slice().toJson(&vpackOptions);
+  RegisterId outRegs = (std::min)(actual->getNrRegs(), expected->getNrRegs());
+  if (onlyCompareRegisters) {
+    outRegs = onlyCompareRegisters->size();
+    ASSERT_GE(actual->getNrRegs(), outRegs);
+  } else {
+    EXPECT_EQ(actual->getNrRegs(), expected->getNrRegs());
+  }
+
+  for (size_t row = 0; row < (std::min)(actual->size(), expected->size()); ++row) {
+    for (RegisterId reg = 0; reg < outRegs; ++reg) {
+      RegisterId actualRegister =
+          onlyCompareRegisters ? onlyCompareRegisters->at(reg) : reg;
+      ValidateAqlValuesAreEqual(actual, row, actualRegister, expected, row, reg);
+    }
+  }
+}
+
+auto asserthelper::ValidateBlocksAreEqualUnordered(
+    SharedAqlItemBlockPtr actual, SharedAqlItemBlockPtr expected, std::size_t numRowsNotContained,
+    std::optional<std::vector<RegisterId>> const& onlyCompareRegisters) -> void {
+  std::unordered_set<size_t> matchedRows{};
+  return ValidateBlocksAreEqualUnordered(actual, expected, matchedRows,
+                                         numRowsNotContained, onlyCompareRegisters);
+}
+
+auto asserthelper::ValidateBlocksAreEqualUnordered(
+    SharedAqlItemBlockPtr actual, SharedAqlItemBlockPtr expected,
+    std::unordered_set<size_t>& matchedRows, std::size_t numRowsNotContained,
+    std::optional<std::vector<RegisterId>> const& onlyCompareRegisters) -> void {
+  ASSERT_NE(expected, nullptr);
+  ASSERT_NE(actual, nullptr);
+  EXPECT_EQ(actual->size() + numRowsNotContained, expected->size());
+
+  RegisterId outRegs = (std::min)(actual->getNrRegs(), expected->getNrRegs());
+  if (onlyCompareRegisters) {
+    outRegs = onlyCompareRegisters->size();
+    ASSERT_GE(actual->getNrRegs(), outRegs);
+  } else {
+    EXPECT_EQ(actual->getNrRegs(), expected->getNrRegs());
+  }
+
+  matchedRows.clear();
+
+  for (size_t expectedRow = 0; expectedRow < expected->size(); ++expectedRow) {
+    for (size_t actualRow = 0; actualRow < actual->size(); ++actualRow) {
+      if (RowsAreIdentical(actual, actualRow, expected, expectedRow, onlyCompareRegisters)) {
+        auto const& [unused, inserted] = matchedRows.emplace(expectedRow);
+        if (inserted) {
+          // one is enough, but do not match the same rows twice
+          break;
+        }
+      }
+    }
+  }
+
+  if (matchedRows.size() + numRowsNotContained < expected->size()) {
+    // Did not find all rows.
+    // This is for reporting only:
+    for (size_t expectedRow = 0; expectedRow < expected->size(); ++expectedRow) {
+      if (matchedRows.find(expectedRow) == matchedRows.end()) {
+        InputAqlItemRow missing(expected, expectedRow);
+        velocypack::Options vpackOptions;
+        VPackBuilder rowBuilder;
+        missing.toSimpleVelocyPack(&vpackOptions, rowBuilder);
+        VPackBuilder blockBuilder;
+        actual->toSimpleVPack(&vpackOptions, blockBuilder);
+        EXPECT_TRUE(false) << "Did not find row: " << rowBuilder.toJson()
+                           << " in " << blockBuilder.toJson();
+      }
+    }
   }
 }
 
 template <bool enableQueryTrace>
 AqlExecutorTestCase<enableQueryTrace>::AqlExecutorTestCase()
-    : _server{}, fakedQuery{_server.createFakeQuery(enableQueryTrace)} {
+    : fakedQuery{_server->createFakeQuery(enableQueryTrace)} {
   auto engine = std::make_unique<ExecutionEngine>(*fakedQuery, SerializationFormat::SHADOWROWS);
   fakedQuery->setEngine(engine.release());
 }
diff --git a/tests/Aql/ExecutorTestHelper.h b/tests/Aql/ExecutorTestHelper.h
index 907f9201458d..0edc6c4992a8 100644
--- a/tests/Aql/ExecutorTestHelper.h
+++ b/tests/Aql/ExecutorTestHelper.h
@@ -44,9 +44,45 @@
 namespace arangodb {
 namespace tests {
 namespace aql {
-
-auto ValidateBlocksAreEqual(SharedAqlItemBlockPtr actual, SharedAqlItemBlockPtr expected)
-    -> void;
+/**
+ * @brief Static helper class just offers helper methods
+ * Do never instantiate
+ *
+ */
+class asserthelper {
+ private:
+  asserthelper() {}
+
+ public:
+  static auto AqlValuesAreIdentical(AqlValue const& lhs, AqlValue const& rhs) -> bool;
+
+  static auto RowsAreIdentical(SharedAqlItemBlockPtr actual, size_t actualRow,
+                               SharedAqlItemBlockPtr expected, size_t expectedRow,
+                               std::optional<std::vector<RegisterId>> const& onlyCompareRegisters = std::nullopt)
+      -> bool;
+
+  static auto ValidateAqlValuesAreEqual(SharedAqlItemBlockPtr actual,
+                                        size_t actualRow, RegisterId actualRegister,
+                                        SharedAqlItemBlockPtr expected, size_t expectedRow,
+                                        RegisterId expectedRegister) -> void;
+
+  static auto ValidateBlocksAreEqual(
+      SharedAqlItemBlockPtr actual, SharedAqlItemBlockPtr expected,
+      std::optional<std::vector<RegisterId>> const& onlyCompareRegisters = std::nullopt)
+      -> void;
+
+  static auto ValidateBlocksAreEqualUnordered(
+      SharedAqlItemBlockPtr actual, SharedAqlItemBlockPtr expected,
+      std::size_t numRowsNotContained = 0,
+      std::optional<std::vector<RegisterId>> const& onlyCompareRegisters = std::nullopt)
+      -> void;
+
+  static auto ValidateBlocksAreEqualUnordered(
+      SharedAqlItemBlockPtr actual, SharedAqlItemBlockPtr expected,
+      std::unordered_set<size_t>& matchedRows, std::size_t numRowsNotContained = 0,
+      std::optional<std::vector<RegisterId>> const& onlyCompareRegisters = std::nullopt)
+      -> void;
+};
 
 /**
  * @brief Base class for ExecutorTests in Aql.
@@ -57,7 +93,16 @@ auto ValidateBlocksAreEqual(SharedAqlItemBlockPtr actual, SharedAqlItemBlockPtr
  * @tparam enableQueryTrace Enable Aql Profile Trace logging
  */
 template <bool enableQueryTrace = false>
-class AqlExecutorTestCase {
+class AqlExecutorTestCase : public ::testing::Test {
+ public:
+  // Creating a server instance costs a lot of time, so do it only once.
+  // Note that newer version of gtest call these SetUpTestSuite/TearDownTestSuite
+  static void SetUpTestCase() {
+    _server = std::make_unique<mocks::MockAqlServer>();
+  }
+
+  static void TearDownTestCase() { _server.reset(); }
+
  protected:
   AqlExecutorTestCase();
   virtual ~AqlExecutorTestCase() = default;
@@ -74,7 +119,7 @@ class AqlExecutorTestCase {
   auto manager() const -> AqlItemBlockManager&;
 
  private:
-  mocks::MockAqlServer _server;
+  static inline std::unique_ptr<mocks::MockAqlServer> _server;
   std::vector<std::unique_ptr<ExecutionNode>> _execNodes;
 
  protected:
@@ -84,6 +129,16 @@ class AqlExecutorTestCase {
   std::unique_ptr<arangodb::aql::Query> fakedQuery;
 };
 
+/**
+ * @brief Shortcut handle for parameterized AqlExecutorTestCases with param
+ *
+ * @tparam T The Test Parameter used for gtest.
+ * @tparam enableQueryTrace Enable Aql Profile Trace logging
+ */
+template <typename T, bool enableQueryTrace = false>
+class AqlExecutorTestCaseWithParam : public AqlExecutorTestCase<enableQueryTrace>,
+                                     public ::testing::WithParamInterface<T> {};
+
 template <typename E, std::size_t inputColumns = 1, std::size_t outputColumns = 1>
 struct ExecutorTestHelper {
   using SplitType = std::variant<std::vector<std::size_t>, std::size_t, std::monostate>;
@@ -94,6 +149,9 @@ struct ExecutorTestHelper {
       : _expectedSkip{0},
         _expectedState{ExecutionState::HASMORE},
         _testStats{false},
+        _unorderedOutput{false},
+        _appendEmptyBlock{false},
+        _unorderedSkippedRows{0},
         _query(query),
         _dummyNode{std::make_unique<SingletonNode>(_query.plan(), 42)} {}
 
@@ -135,7 +193,7 @@ struct ExecutorTestHelper {
     return *this;
   }
 
-  auto expectOutput(std::array<std::size_t, outputColumns> const& regs,
+  auto expectOutput(std::array<RegisterId, outputColumns> const& regs,
                     MatrixBuilder<outputColumns> const& out) -> ExecutorTestHelper& {
     _outputRegisters = regs;
     _output = out;
@@ -166,6 +224,26 @@ struct ExecutorTestHelper {
     return *this;
   };
 
+  auto allowAnyOutputOrder(bool expected, size_t skippedRows = 0) -> ExecutorTestHelper& {
+    _unorderedOutput = expected;
+    _unorderedSkippedRows = skippedRows;
+    return *this;
+  }
+
+  /**
+   * @brief This appends an empty block after the input fully created.
+   *        It simulates a situation where the Producer lies about the
+   *        the last input with HASMORE, but it actually is not able
+   *        to produce more.
+   *
+   * @param append If this should be enabled or not
+   * @return ExecutorTestHelper& this for chaining
+   */
+  auto appendEmptyBlock(bool append) -> ExecutorTestHelper& {
+    _appendEmptyBlock = append;
+    return *this;
+  }
+
   auto run(typename E::Infos infos) -> void {
     ResourceMonitor monitor;
     AqlItemBlockManager itemBlockManager(&monitor, SerializationFormat::SHADOWROWS);
@@ -182,10 +260,23 @@ struct ExecutorTestHelper {
     EXPECT_EQ(skipped, _expectedSkip);
 
     EXPECT_EQ(state, _expectedState);
+    if (result == nullptr) {
+      // Empty output, possible if we skip all
+      EXPECT_EQ(_output.size(), 0)
+          << "Executor does not yield output, although it is expected";
+    } else {
+      SharedAqlItemBlockPtr expectedOutputBlock =
+          buildBlock<outputColumns>(itemBlockManager, std::move(_output));
+      std::vector<RegisterId> outRegVector(_outputRegisters.begin(),
+                                           _outputRegisters.end());
+      if (_unorderedOutput) {
+        asserthelper::ValidateBlocksAreEqualUnordered(result, expectedOutputBlock,
+                                                      _unorderedSkippedRows, outRegVector);
+      } else {
+        asserthelper::ValidateBlocksAreEqual(result, expectedOutputBlock, outRegVector);
+      }
+    }
 
-    SharedAqlItemBlockPtr expectedOutputBlock =
-        buildBlock<outputColumns>(itemBlockManager, std::move(_output));
-    testOutputBlock(result, expectedOutputBlock);
     if (_testStats) {
       auto actualStats = _query.engine()->getStats();
       EXPECT_EQ(actualStats, _expectedStats);
@@ -193,23 +284,6 @@ struct ExecutorTestHelper {
   };
 
  private:
-  void testOutputBlock(SharedAqlItemBlockPtr const& outputBlock,
-                       SharedAqlItemBlockPtr const& expectedOutputBlock) {
-    velocypack::Options vpackOptions;
-
-    EXPECT_EQ(outputBlock->size(), expectedOutputBlock->size());
-    for (size_t i = 0; i < outputBlock->size(); i++) {
-      for (size_t j = 0; j < outputColumns; j++) {
-        AqlValue const& x = outputBlock->getValueReference(i, _outputRegisters[j]);
-        AqlValue const& y = expectedOutputBlock->getValueReference(i, j);
-
-        EXPECT_TRUE(AqlValue::Compare(&vpackOptions, x, y, true) == 0)
-            << "Row " << i << " Column " << j << " (Reg " << _outputRegisters[j]
-            << ") do not agree";
-      }
-    }
-  }
-
   auto generateInputRanges(AqlItemBlockManager& itemBlockManager)
       -> std::unique_ptr<ExecutionBlock> {
     using VectorSizeT = std::vector<std::size_t>;
@@ -255,6 +329,9 @@ struct ExecutorTestHelper {
           buildBlock<inputColumns>(itemBlockManager, std::move(matrix));
       blockDeque.emplace_back(inputBlock);
     }
+    if (_appendEmptyBlock) {
+      blockDeque.emplace_back(nullptr);
+    }
 
     return std::make_unique<WaitingExecutionBlockMock>(
         _query.engine(), _dummyNode.get(), std::move(blockDeque),
@@ -264,11 +341,14 @@ struct ExecutorTestHelper {
   AqlCall _call;
   MatrixBuilder<inputColumns> _input;
   MatrixBuilder<outputColumns> _output;
-  std::array<std::size_t, outputColumns> _outputRegisters;
-  size_t _expectedSkip;
+  std::array<RegisterId, outputColumns> _outputRegisters;
+  std::size_t _expectedSkip;
   ExecutionState _expectedState;
   ExecutionStats _expectedStats;
   bool _testStats;
+  bool _unorderedOutput;
+  bool _appendEmptyBlock;
+  std::size_t _unorderedSkippedRows;
 
   SplitType _inputSplit = {std::monostate()};
   SplitType _outputSplit = {std::monostate()};
diff --git a/tests/Aql/HashedCollectExecutorTest.cpp b/tests/Aql/HashedCollectExecutorTest.cpp
index 7009caa5243c..0c01634af57b 100644
--- a/tests/Aql/HashedCollectExecutorTest.cpp
+++ b/tests/Aql/HashedCollectExecutorTest.cpp
@@ -25,15 +25,19 @@
 
 #include "gtest/gtest.h"
 
+#include "AqlItemBlockHelper.h"
+#include "ExecutorTestHelper.h"
 #include "RowFetcherHelper.h"
 
+#include "Aql/AqlCall.h"
 #include "Aql/AqlItemBlock.h"
 #include "Aql/Collection.h"
 #include "Aql/ExecutionEngine.h"
 #include "Aql/HashedCollectExecutor.h"
 #include "Aql/OutputAqlItemRow.h"
-#include "Aql/SingleRowFetcher.h"
 #include "Aql/Query.h"
+#include "Aql/RegisterPlan.h"
+#include "Aql/SingleRowFetcher.h"
 #include "Mocks/Servers.h"
 #include "Transaction/Context.h"
 #include "Transaction/Methods.h"
@@ -49,674 +53,573 @@ namespace arangodb {
 namespace tests {
 namespace aql {
 
-class HashedCollectExecutorTestNoRows : public ::testing::Test {
+// This is only to get a split-type. The Type is independent of actual template parameters
+using HashedCollectTestHelper = ExecutorTestHelper<HashedCollectExecutor, 1, 1>;
+using HashedCollectSplitType = HashedCollectTestHelper::SplitType;
+using HashedCollectInputParam = std::tuple<HashedCollectSplitType, bool>;
+
+class HashedCollectExecutorTest
+    : public AqlExecutorTestCaseWithParam<HashedCollectInputParam> {
  protected:
-  ExecutionState state;
-  ResourceMonitor monitor;
-  AqlItemBlockManager itemBlockManager;
-
-  mocks::MockAqlServer server;
-  std::unique_ptr<arangodb::aql::Query> fakedQuery;
-  arangodb::transaction::Methods* trx;
-
-  std::unordered_set<RegisterId> const regToClear;
-  std::unordered_set<RegisterId> const regToKeep;
-  std::vector<std::pair<RegisterId, RegisterId>> groupRegisters;
-
-  std::vector<std::string> aggregateTypes;
-
-  std::vector<std::pair<RegisterId, RegisterId>> aggregateRegisters;
-
-  // if count = true, then we need to set a countRegister
-  RegisterId collectRegister;
-  bool count;
-
-  std::unordered_set<RegisterId> readableInputRegisters;
-  std::unordered_set<RegisterId> writeableOutputRegisters;
-
-  HashedCollectExecutorInfos infos;
-
-  SharedAqlItemBlockPtr block;
-  VPackBuilder input;
-  NoStats stats;
-
-  HashedCollectExecutorTestNoRows()
-      : itemBlockManager(&monitor, SerializationFormat::SHADOWROWS),
-        fakedQuery(server.createFakeQuery()),
-        trx(fakedQuery->trx()),
-        groupRegisters{std::make_pair<RegisterId, RegisterId>(1, 2)},
-        collectRegister(0),
-        count(false),
-        infos(2 /*nrIn*/, 2 /*nrOut*/, regToClear, regToKeep,
-              std::move(readableInputRegisters),
-              std::move(writeableOutputRegisters), std::move(groupRegisters), 0,
-              std::move(aggregateTypes), std::move(aggregateRegisters), trx, false),
-        block(new AqlItemBlock(itemBlockManager, 1000, 2)) {}
+  auto getSplit() -> HashedCollectSplitType {
+    auto [split, empty] = GetParam();
+    return split;
+  }
+
+  auto appendEmpty() -> bool {
+    auto [split, empty] = GetParam();
+    return empty;
+  }
+
+  auto buildInfos(RegisterId nrInputRegisters, RegisterId nrOutputRegisters,
+                  std::vector<std::pair<RegisterId, RegisterId>> groupRegisters,
+                  RegisterId collectRegister = RegisterPlan::MaxRegisterId,
+                  std::vector<std::string> aggregateTypes = {},
+                  std::vector<std::pair<RegisterId, RegisterId>> aggregateRegisters = {})
+      -> HashedCollectExecutorInfos {
+    std::unordered_set<RegisterId> registersToClear{};
+    std::unordered_set<RegisterId> registersToKeep{};
+    std::unordered_set<RegisterId> readableInputRegisters{};
+    std::unordered_set<RegisterId> writeableOutputRegisters{};
+
+    for (RegisterId i = 0; i < nrInputRegisters; ++i) {
+      // All registers need to be invalidated!
+      registersToClear.emplace(i);
+    }
+
+    for (auto const& [out, in] : groupRegisters) {
+      readableInputRegisters.emplace(in);
+      writeableOutputRegisters.emplace(out);
+    }
+
+    // It seems that count <=> collectRegister exists
+    bool count = false;
+    if (collectRegister != RegisterPlan::MaxRegisterId) {
+      writeableOutputRegisters.emplace(collectRegister);
+      count = true;
+    }
+    TRI_ASSERT(aggregateTypes.size() == aggregateRegisters.size());
+    for (auto const& [out, in] : aggregateRegisters) {
+      if (in != RegisterPlan::MaxRegisterId) {
+        readableInputRegisters.emplace(in);
+      }
+      writeableOutputRegisters.emplace(out);
+    }
+
+    return HashedCollectExecutorInfos{nrInputRegisters,
+                                      nrOutputRegisters,
+                                      registersToClear,
+                                      registersToKeep,
+                                      std::move(readableInputRegisters),
+                                      std::move(writeableOutputRegisters),
+                                      std::move(groupRegisters),
+                                      collectRegister,
+                                      std::move(aggregateTypes),
+                                      std::move(aggregateRegisters),
+                                      fakedQuery->trx(),
+                                      count};
+  };
 };
 
-TEST_F(HashedCollectExecutorTestNoRows, the_producer_doesnt_wait) {
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input.steal(), false);
-  HashedCollectExecutor testee(fetcher, infos);
-
-  OutputAqlItemRow result(std::move(block), infos.getOutputRegisters(),
-                          infos.registersToKeep(), infos.registersToClear());
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(result.produced());
+template <size_t... vs>
+const HashedCollectSplitType splitIntoBlocks =
+    HashedCollectSplitType{std::vector<std::size_t>{vs...}};
+template <size_t step>
+const HashedCollectSplitType splitStep = HashedCollectSplitType{step};
+
+INSTANTIATE_TEST_CASE_P(HashedCollect, HashedCollectExecutorTest,
+                        ::testing::Combine(::testing::Values(splitIntoBlocks<2, 3>,
+                                                             splitIntoBlocks<3, 4>,
+                                                             splitStep<1>, splitStep<2>),
+                                           ::testing::Bool()));
+
+// Collect with only one group value
+TEST_P(HashedCollectExecutorTest, collect_only) {
+  auto infos = buildInfos(1, 2, {{1, 0}});
+  AqlCall call{};          // unlimited produce
+  ExecutionStats stats{};  // No stats here
+  ExecutorTestHelper<HashedCollectExecutor>(*fakedQuery)
+      .setInputValue({{{1}}, {{1}}, {{2}}, {{1}}, {{6}}, {{2}}, {{R"("1")"}}})
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({1}, {{1}, {2}, {6}, {R"("1")"}})
+      .allowAnyOutputOrder(true)
+      .expectSkipped(0)
+      .expectedState(ExecutionState::DONE)
+      .appendEmptyBlock(appendEmpty())
+      // .expectedStats(stats)
+      .run(std::move(infos));
 }
 
-TEST_F(HashedCollectExecutorTestNoRows, the_producer_waits) {
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input.steal(), true);
-  HashedCollectExecutor testee(fetcher, infos);
-
-  OutputAqlItemRow result(std::move(block), infos.getOutputRegisters(),
-                          infos.registersToKeep(), infos.registersToClear());
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::WAITING);
-  ASSERT_FALSE(result.produced());
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(result.produced());
+// Collect skip all
+TEST_P(HashedCollectExecutorTest, skip_all) {
+  auto infos = buildInfos(1, 2, {{1, 0}});
+  AqlCall call{};
+  call.offset = 1000;      // skip all
+  ExecutionStats stats{};  // No stats here
+  ExecutorTestHelper<HashedCollectExecutor>(*fakedQuery)
+      .setInputValue({{{1}}, {{1}}, {{2}}, {{1}}, {{6}}, {{2}}, {{R"("1")"}}})
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({1}, {})
+      .allowAnyOutputOrder(true)
+      .expectSkipped(4)
+      .expectedState(ExecutionState::DONE)
+      .appendEmptyBlock(appendEmpty())
+      // .expectedStats(stats)
+      .run(std::move(infos));
 }
 
-class HashedCollectExecutorTestRowsNoCount : public ::testing::Test {
- protected:
-  ExecutionState state;
-  ResourceMonitor monitor;
-  AqlItemBlockManager itemBlockManager;
-
-  mocks::MockAqlServer server;
-  std::unique_ptr<arangodb::aql::Query> fakedQuery;
-  arangodb::transaction::Methods* trx;
-
-  std::unordered_set<RegisterId> regToClear;
-  std::unordered_set<RegisterId> regToKeep;
-  std::vector<std::pair<RegisterId, RegisterId>> groupRegisters;
-
-  std::unordered_set<RegisterId> readableInputRegisters;
-
-  std::unordered_set<RegisterId> writeableOutputRegisters;
-
-  RegisterId nrOutputRegister;
-
-  std::vector<std::pair<RegisterId, RegisterId>> aggregateRegisters;
-  std::vector<std::string> aggregateTypes;
-
-  // if count = true, then we need to set a valid countRegister
-  RegisterId collectRegister;
-  bool count;
-
-  HashedCollectExecutorInfos infos;
-
-  SharedAqlItemBlockPtr block;
-  NoStats stats;
-
-  HashedCollectExecutorTestRowsNoCount()
-      : itemBlockManager(&monitor, SerializationFormat::SHADOWROWS),
-        fakedQuery(server.createFakeQuery()),
-        trx(fakedQuery->trx()),
-        groupRegisters{std::make_pair<RegisterId, RegisterId>(1, 0)},
-        readableInputRegisters{0},
-        writeableOutputRegisters{1},
-        nrOutputRegister(2),
-        collectRegister(0),
-        count(false),
-        infos(1, nrOutputRegister, regToClear, regToKeep, std::move(readableInputRegisters),
-              std::move(writeableOutputRegisters), std::move(groupRegisters), 0,
-              std::move(aggregateTypes), std::move(aggregateRegisters), trx, false),
-        block(new AqlItemBlock(itemBlockManager, 1000, nrOutputRegister)) {}
-};
-
-TEST_F(HashedCollectExecutorTestRowsNoCount, the_producer_doesnt_wait_1) {
-  auto input = VPackParser::fromJson("[ [1], [2] ]");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), false);
-  HashedCollectExecutor testee(fetcher, infos);
-
-  OutputAqlItemRow result(std::move(block), infos.getOutputRegisters(),
-                          infos.registersToKeep(), infos.registersToClear());
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(result.produced());
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_TRUE(result.produced());
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(result.produced());
-
-  std::vector<int64_t> myNumbers;
-  auto block = result.stealBlock();
-
-  // check for types
-  AqlValue x = block->getValue(0, 1);
-  ASSERT_TRUE(x.isNumber());
-  myNumbers.emplace_back(x.slice().getInt());
-
-  AqlValue z = block->getValue(1, 1);
-  ASSERT_TRUE(z.isNumber());
-  myNumbers.emplace_back(z.slice().getInt());
-
-  // now sort vector and check for appearances
-  std::sort(myNumbers.begin(), myNumbers.end());
-  ASSERT_EQ(myNumbers.at(0), 1);
-  ASSERT_EQ(myNumbers.at(1), 2);
+// Collect fullCount all
+TEST_P(HashedCollectExecutorTest, fullcount_all) {
+  auto infos = buildInfos(1, 2, {{1, 0}});
+  AqlCall call{};
+  call.hardLimit = 0;      // HardLimit
+  call.fullCount = true;   // count all
+  ExecutionStats stats{};  // No stats here
+  ExecutorTestHelper<HashedCollectExecutor>(*fakedQuery)
+      .setInputValue({{{1}}, {{1}}, {{2}}, {{1}}, {{6}}, {{2}}, {{R"("1")"}}})
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({1}, {})
+      .allowAnyOutputOrder(true)
+      .expectSkipped(4)
+      .expectedState(ExecutionState::DONE)
+      .appendEmptyBlock(appendEmpty())
+      // .expectedStats(stats)
+      .run(std::move(infos));
 }
 
-TEST_F(HashedCollectExecutorTestRowsNoCount, the_producer_doesnt_wait_2) {
-  auto input = VPackParser::fromJson("[ [1], [2], [3] ]");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), false);
-  HashedCollectExecutor testee(fetcher, infos);
-
-  OutputAqlItemRow result(std::move(block), infos.getOutputRegisters(),
-                          infos.registersToKeep(), infos.registersToClear());
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(result.produced());
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(result.produced());
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_TRUE(result.produced());
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(result.produced());
-
-  std::vector<int64_t> myNumbers;
-  auto block = result.stealBlock();
-
-  // check for types
-  AqlValue x = block->getValue(0, 1);
-  ASSERT_TRUE(x.isNumber());
-  myNumbers.emplace_back(x.slice().getInt());
-
-  AqlValue y = block->getValue(1, 1);
-  ASSERT_TRUE(y.isNumber());
-  myNumbers.emplace_back(y.slice().getInt());
-
-  AqlValue z = block->getValue(2, 1);
-  ASSERT_TRUE(z.isNumber());
-  myNumbers.emplace_back(z.slice().getInt());
-
-  // now sort vector and check for appearances
-  std::sort(myNumbers.begin(), myNumbers.end());
-  ASSERT_EQ(myNumbers.at(0), 1);
-  ASSERT_EQ(myNumbers.at(1), 2);
-  ASSERT_EQ(myNumbers.at(2), 3);
+// Collect get some
+TEST_P(HashedCollectExecutorTest, collect_only_soft_less) {
+  auto infos = buildInfos(1, 2, {{1, 0}});
+  AqlCall call{};
+  call.softLimit = 2;
+  ExecutionStats stats{};  // No stats here
+  ExecutorTestHelper<HashedCollectExecutor>(*fakedQuery)
+      .setInputValue({{{1}}, {{1}}, {{2}}, {{1}}, {{6}}, {{2}}, {{R"("1")"}}})
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({1}, {{1}, {2}, {6}, {R"("1")"}})
+      .allowAnyOutputOrder(true, 2)
+      .expectSkipped(0)
+      .expectedState(ExecutionState::HASMORE)
+      .appendEmptyBlock(appendEmpty())
+      // .expectedStats(stats)
+      .run(std::move(infos));
 }
 
-TEST_F(HashedCollectExecutorTestRowsNoCount, the_producer_doesnt_wait_3) {
-  auto input = VPackParser::fromJson("[ [1], [2], [3], [1], [2] ]");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), false);
-  HashedCollectExecutor testee(fetcher, infos);
-
-  OutputAqlItemRow result(std::move(block), infos.getOutputRegisters(),
-                          infos.registersToKeep(), infos.registersToClear());
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(result.produced());
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(result.produced());
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_TRUE(result.produced());
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(result.produced());
-
-  std::vector<int64_t> myNumbers;
-  auto block = result.stealBlock();
-
-  // check for types
-  AqlValue x = block->getValue(0, 1);
-  ASSERT_TRUE(x.isNumber());
-  myNumbers.emplace_back(x.slice().getInt());
-
-  AqlValue y = block->getValue(1, 1);
-  ASSERT_TRUE(y.isNumber());
-  myNumbers.emplace_back(y.slice().getInt());
-
-  AqlValue z = block->getValue(2, 1);
-  ASSERT_TRUE(z.isNumber());
-  myNumbers.emplace_back(z.slice().getInt());
-
-  // now sort vector and check for appearances
-  std::sort(myNumbers.begin(), myNumbers.end());
-  ASSERT_EQ(myNumbers.at(0), 1);
-  ASSERT_EQ(myNumbers.at(1), 2);
-  ASSERT_EQ(myNumbers.at(2), 3);
+// Collect get some multiple calls
+TEST_P(HashedCollectExecutorTest, collect_only_soft_less_second_call) {
+  auto infos = buildInfos(1, 2, {{1, 0}});
+
+  // TODO maybe we should add this to the test framework as well.
+
+  std::deque<SharedAqlItemBlockPtr> blockDeque;
+  {
+    auto data =
+        buildBlock<2>(manager(), {{{1}}, {{1}}, {{2}}, {{1}}, {{6}}, {{2}}, {{R"("1")"}}});
+    blockDeque.emplace_back(data);
+  }
+
+  auto inputBlock = std::make_unique<WaitingExecutionBlockMock>(
+      fakedQuery->engine(), generateNodeDummy(), std::move(blockDeque),
+      WaitingExecutionBlockMock::WaitingBehaviour::NEVER);
+  ExecutionBlockImpl<HashedCollectExecutor> testee{fakedQuery->engine(),
+                                                   generateNodeDummy(), std::move(infos)};
+  testee.addDependency(inputBlock.get());
+  // First Call
+  std::unordered_set<std::size_t> matchedRows{};
+  auto buildExpectedOutput = [&]() -> SharedAqlItemBlockPtr {
+    MatrixBuilder<1> matrix;
+    if (matchedRows.find(0) == matchedRows.end()) {
+      matrix.emplace_back(RowBuilder<1>{1});
+    }
+    if (matchedRows.find(1) == matchedRows.end()) {
+      matrix.emplace_back(RowBuilder<1>{2});
+    }
+    if (matchedRows.find(2) == matchedRows.end()) {
+      matrix.emplace_back(RowBuilder<1>{6});
+    }
+    if (matchedRows.find(3) == matchedRows.end()) {
+      matrix.emplace_back(RowBuilder<1>{R"("1")"});
+    }
+    return buildBlock<1>(manager(), std::move(matrix));
+  };
+  std::vector<RegisterId> registersToTest{1};
+  {
+    AqlCall call{};
+    call.softLimit = 2;
+    AqlCallStack stack{call};
+    auto const [state, skipped, result] = testee.execute(stack);
+    EXPECT_EQ(state, ExecutionState::HASMORE);
+    EXPECT_EQ(skipped, 0);
+    ASSERT_NE(result, nullptr);
+    asserthelper::ValidateBlocksAreEqualUnordered(result, buildExpectedOutput(),
+                                                  matchedRows, 2, registersToTest);
+  }
+
+  // Second call
+  {
+    AqlCall call{};
+    call.softLimit = 2;
+    AqlCallStack stack{call};
+    auto const [state, skipped, result] = testee.execute(stack);
+    EXPECT_EQ(state, ExecutionState::DONE);
+    EXPECT_EQ(skipped, 0);
+    ASSERT_NE(result, nullptr);
+    asserthelper::ValidateBlocksAreEqualUnordered(result, buildExpectedOutput(),
+                                                  matchedRows, 0, registersToTest);
+  }
 }
 
-TEST_F(HashedCollectExecutorTestRowsNoCount, the_producer_doesnt_wait_4) {
-  auto input = VPackParser::fromJson("[ [1], [2], [1], [2] ]");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), false);
-  HashedCollectExecutor testee(fetcher, infos);
-
-  OutputAqlItemRow result(std::move(block), infos.getOutputRegisters(),
-                          infos.registersToKeep(), infos.registersToClear());
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(result.produced());
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_TRUE(result.produced());
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(result.produced());
-
-  std::vector<int64_t> myNumbers;
-  auto block = result.stealBlock();
-
-  // check for types
-  AqlValue x = block->getValue(0, 1);
-  ASSERT_TRUE(x.isNumber());
-  myNumbers.emplace_back(x.slice().getInt());
-
-  AqlValue y = block->getValue(1, 1);
-  ASSERT_TRUE(y.isNumber());
-  myNumbers.emplace_back(y.slice().getInt());
-
-  // now sort vector and check for appearances
-  std::sort(myNumbers.begin(), myNumbers.end());
-  ASSERT_EQ(myNumbers.at(0), 1);
-  ASSERT_EQ(myNumbers.at(1), 2);
+// Collect get some
+TEST_P(HashedCollectExecutorTest, collect_only_hard_less) {
+  auto infos = buildInfos(1, 2, {{1, 0}});
+  AqlCall call{};
+  call.hardLimit = 2;
+  ExecutionStats stats{};  // No stats here
+  ExecutorTestHelper<HashedCollectExecutor>(*fakedQuery)
+      .setInputValue({{{1}}, {{1}}, {{2}}, {{1}}, {{6}}, {{2}}, {{R"("1")"}}})
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({1}, {{1}, {2}, {6}, {R"("1")"}})
+      .allowAnyOutputOrder(true, 2)
+      .expectSkipped(0)
+      .expectedState(ExecutionState::DONE)
+      .appendEmptyBlock(appendEmpty())
+      // .expectedStats(stats)
+      .run(std::move(infos));
 }
 
-TEST_F(HashedCollectExecutorTestRowsNoCount, the_producer_waits) {
-  auto input = VPackParser::fromJson("[ [1], [2] ]");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), true);
-  HashedCollectExecutor testee(fetcher, infos);
-
-  OutputAqlItemRow result(std::move(block), infos.getOutputRegisters(),
-                          infos.registersToKeep(), infos.registersToClear());
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::WAITING);
-  ASSERT_FALSE(result.produced());
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::WAITING);
-  ASSERT_FALSE(result.produced());
+// Collect skip some
+TEST_P(HashedCollectExecutorTest, skip_some) {
+  auto infos = buildInfos(1, 2, {{1, 0}});
+  AqlCall call{};
+  call.offset = 2;         // skip some
+  call.softLimit = 0;      // 0 limit
+  ExecutionStats stats{};  // No stats here
+  ExecutorTestHelper<HashedCollectExecutor>(*fakedQuery)
+      .setInputValue({{{1}}, {{1}}, {{2}}, {{1}}, {{6}}, {{2}}, {{R"("1")"}}})
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({1}, {})
+      .allowAnyOutputOrder(true)
+      .expectSkipped(2)
+      .expectedState(ExecutionState::HASMORE)
+      .appendEmptyBlock(appendEmpty())
+      // .expectedStats(stats)
+      .run(std::move(infos));
+}
 
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(result.produced());
-  result.advanceRow();
+// Collect skip and get
+TEST_P(HashedCollectExecutorTest, skip_and_get) {
+  auto infos = buildInfos(1, 2, {{1, 0}});
+  AqlCall call{};
+  call.offset = 2;         // skip some
+  call.softLimit = 1000;   // high limit
+  ExecutionStats stats{};  // No stats here
+  ExecutorTestHelper<HashedCollectExecutor>(*fakedQuery)
+      .setInputValue({{{1}}, {{1}}, {{2}}, {{1}}, {{6}}, {{2}}, {{R"("1")"}}})
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({1}, {{1}, {2}, {6}, {R"("1")"}})
+      .allowAnyOutputOrder(true, 2)
+      .expectSkipped(2)
+      .expectedState(ExecutionState::DONE)
+      .appendEmptyBlock(appendEmpty())
+      // .expectedStats(stats)
+      .run(std::move(infos));
+}
 
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_TRUE(result.produced());
-  result.advanceRow();
+// Collect skip and hardLimit
+TEST_P(HashedCollectExecutorTest, skip_and_hardLimit) {
+  auto infos = buildInfos(1, 2, {{1, 0}});
+  AqlCall call{};
+  call.offset = 2;         // skip some
+  call.hardLimit = 1;      // hard limit
+  ExecutionStats stats{};  // No stats here
+  ExecutorTestHelper<HashedCollectExecutor>(*fakedQuery)
+      .setInputValue({{{1}}, {{1}}, {{2}}, {{1}}, {{6}}, {{2}}, {{R"("1")"}}})
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({1}, {{1}, {2}, {6}, {R"("1")"}})
+      .allowAnyOutputOrder(true, 3)
+      .expectSkipped(2)
+      .expectedState(ExecutionState::DONE)
+      .appendEmptyBlock(appendEmpty())
+      // .expectedStats(stats)
+      .run(std::move(infos));
+}
 
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(result.produced());
+// Collect skip and fullCount
+TEST_P(HashedCollectExecutorTest, skip_and_fullCount) {
+  auto infos = buildInfos(1, 2, {{1, 0}});
+  AqlCall call{};
+  call.offset = 1;     // skip some
+  call.hardLimit = 2;  // hard limit
+  call.fullCount = true;
+  ExecutionStats stats{};  // No stats here
+  ExecutorTestHelper<HashedCollectExecutor>(*fakedQuery)
+      .setInputValue({{{1}}, {{1}}, {{2}}, {{1}}, {{6}}, {{2}}, {{R"("1")"}}})
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({1}, {{1}, {2}, {6}, {R"("1")"}})
+      .allowAnyOutputOrder(true, 2)
+      .expectSkipped(2)
+      .expectedState(ExecutionState::DONE)
+      .appendEmptyBlock(appendEmpty())
+      // .expectedStats(stats)
+      .run(std::move(infos));
+}
 
-  std::vector<int64_t> myNumbers;
-  auto block = result.stealBlock();
+// Collect with more then one group value
+TEST_P(HashedCollectExecutorTest, collect_only_multiple_values) {
+  auto infos = buildInfos(2, 4, {{2, 0}, {3, 1}});
+  AqlCall call{};          // unlimited produce
+  ExecutionStats stats{};  // No stats here
+  ExecutorTestHelper<HashedCollectExecutor, 2, 2>(*fakedQuery)
+      .setInputValue(MatrixBuilder<2>{RowBuilder<2>{1, 5}, RowBuilder<2>{1, 1},
+                                      RowBuilder<2>{2, 2}, RowBuilder<2>{1, 5},
+                                      RowBuilder<2>{6, 1}, RowBuilder<2>{2, 2},
+                                      RowBuilder<2>{R"("1")", 1}})
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({2, 3}, MatrixBuilder<2>{RowBuilder<2>{1, 5}, RowBuilder<2>{1, 1},
+                                             RowBuilder<2>{2, 2}, RowBuilder<2>{6, 1},
+                                             RowBuilder<2>{R"("1")", 1}})
+      .allowAnyOutputOrder(true)
+      .expectSkipped(0)
+      .expectedState(ExecutionState::DONE)
+      // .expectedStats(stats)
+      .run(std::move(infos));
+}
 
-  // check for types
-  AqlValue x = block->getValue(0, 1);
-  ASSERT_TRUE(x.isNumber());
-  myNumbers.emplace_back(x.slice().getInt());
+// Collect with one group value and count
+TEST_P(HashedCollectExecutorTest, count) {
+  auto infos = buildInfos(1, 3, {{1, 0}}, 2);
+  AqlCall call{};          // unlimited produce
+  ExecutionStats stats{};  // No stats here
+  ExecutorTestHelper<HashedCollectExecutor, 1, 2>(*fakedQuery)
+      .setInputValue({{{1}}, {{1}}, {{2}}, {{1}}, {{6}}, {{2}}, {{R"("1")"}}})
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({1, 2}, {{1, 3}, {2, 2}, {6, 1}, {R"("1")", 1}})
+      .allowAnyOutputOrder(true)
+      .expectSkipped(0)
+      .expectedState(ExecutionState::DONE)
+      // .expectedStats(stats)
+      .run(std::move(infos));
+}
 
-  AqlValue z = block->getValue(1, 1);
-  ASSERT_TRUE(z.isNumber());
-  myNumbers.emplace_back(z.slice().getInt());
+// Collect with multiple aggregators
+TEST_P(HashedCollectExecutorTest, many_aggregators) {
+  auto infos =
+      buildInfos(2, 5, {{2, 0}}, RegisterPlan::MaxRegisterId, {"LENGTH", "SUM"},
+                 {{3, RegisterPlan::MaxRegisterId}, {4, 1}});
+  AqlCall call{};          // unlimited produce
+  ExecutionStats stats{};  // No stats here
+  ExecutorTestHelper<HashedCollectExecutor, 2, 3>(*fakedQuery)
+      .setInputValue(MatrixBuilder<2>{RowBuilder<2>{1, 5}, RowBuilder<2>{1, 1},
+                                      RowBuilder<2>{2, 2}, RowBuilder<2>{1, 5},
+                                      RowBuilder<2>{6, 1}, RowBuilder<2>{2, 2},
+                                      RowBuilder<2>{3, 1}})
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({2, 3, 4},
+                    MatrixBuilder<3>{RowBuilder<3>{1, 3, 11}, RowBuilder<3>{2, 2, 4},
+                                     RowBuilder<3>{6, 1, 1}, RowBuilder<3>{3, 1, 1}})
+      .allowAnyOutputOrder(true)
+      .expectSkipped(0)
+      .expectedState(ExecutionState::DONE)
+      // .expectedStats(stats)
+      .run(std::move(infos));
+}
 
-  // now sort vector and check for appearances
-  std::sort(myNumbers.begin(), myNumbers.end());
-  ASSERT_EQ(myNumbers.at(0), 1);
-  ASSERT_EQ(myNumbers.at(1), 2);
+// Collect based on equal arrays.
+TEST_P(HashedCollectExecutorTest, collect_arrays) {
+  auto infos = buildInfos(1, 2, {{1, 0}});
+  AqlCall call{};          // unlimited produce
+  ExecutionStats stats{};  // No stats here
+  ExecutorTestHelper<HashedCollectExecutor>(*fakedQuery)
+      .setInputValue({{{R"([1,1,1])"}},
+                      {{1}},
+                      {{R"([1,1,1,1])"}},
+                      {{R"([2,1,1])"}},
+                      {{R"([1,1,1])"}},
+                      {{R"([2,1,1])"}},
+                      {{R"([1,1,1])"}}})
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({1}, {{1}, {R"([1,1,1])"}, {R"([1,1,1,1])"}, {R"([2,1,1])"}})
+      .allowAnyOutputOrder(true)
+      .expectSkipped(0)
+      .expectedState(ExecutionState::DONE)
+      // .expectedStats(stats)
+      .run(std::move(infos));
 }
 
-TEST(HashedCollectExecutorTestRowsCount, the_producer_doesnt_wait) {
-  ExecutionState state;
-  ResourceMonitor monitor;
-  AqlItemBlockManager itemBlockManager{&monitor, SerializationFormat::SHADOWROWS};
-
-  mocks::MockAqlServer server{};
-  std::unique_ptr<arangodb::aql::Query> fakedQuery = server.createFakeQuery();
-  arangodb::transaction::Methods* trx = fakedQuery->trx();
-
-  std::unordered_set<RegisterId> regToClear;
-  std::unordered_set<RegisterId> regToKeep;
-  std::vector<std::pair<RegisterId, RegisterId>> groupRegisters;
-  groupRegisters.emplace_back(std::make_pair<RegisterId, RegisterId>(1, 0));
-
-  std::unordered_set<RegisterId> readableInputRegisters;
-  readableInputRegisters.insert(0);
-
-  std::unordered_set<RegisterId> writeableOutputRegisters;
-  writeableOutputRegisters.insert(1);
-
-  RegisterId nrOutputRegister = 3;
-
-  std::vector<std::pair<RegisterId, RegisterId>> aggregateRegisters;
-  aggregateRegisters.emplace_back(std::make_pair<RegisterId, RegisterId>(1, 0));
-
-  std::vector<std::string> aggregateTypes;
-  aggregateTypes.emplace_back("SUM");
-
-  // if count = true, then we need to set a valid countRegister
-  bool count = true;
-  RegisterId collectRegister = 2;
-  writeableOutputRegisters.insert(2);
-
-  HashedCollectExecutorInfos infos(1, nrOutputRegister, regToClear, regToKeep,
-                                   std::move(readableInputRegisters),
-                                   std::move(writeableOutputRegisters),
-                                   std::move(groupRegisters), collectRegister,
-                                   std::move(aggregateTypes),
-                                   std::move(aggregateRegisters), trx, count);
-
-  SharedAqlItemBlockPtr block{new AqlItemBlock(itemBlockManager, 1000, nrOutputRegister)};
-  NoStats stats{};
-
-  auto input = VPackParser::fromJson("[ [1], [2] ]");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), false);
-  HashedCollectExecutor testee(fetcher, infos);
-
-  OutputAqlItemRow result(std::move(block), infos.getOutputRegisters(),
-                          infos.registersToKeep(), infos.registersToClear());
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(result.produced());
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_TRUE(result.produced());
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(result.produced());
-
-  std::vector<int64_t> myNumbers;
-  std::vector<double> myCountNumbers;
-  auto newBlock = result.stealBlock();
-
-  // check for types
-  AqlValue x = newBlock->getValue(0, 1);
-  ASSERT_TRUE(x.isNumber());
-  myNumbers.emplace_back(x.slice().getInt());
-
-  // Check the count register
-  AqlValue xx = newBlock->getValue(0, 2);
-  ASSERT_TRUE(xx.isNumber());
-  myCountNumbers.emplace_back(xx.slice().getDouble());
-
-  AqlValue z = newBlock->getValue(1, 1);
-  ASSERT_TRUE(z.isNumber());
-  myNumbers.emplace_back(z.slice().getInt());
-
-  // Check the count register
-  AqlValue zz = newBlock->getValue(1, 2);
-  ASSERT_TRUE(zz.isNumber());
-  myCountNumbers.emplace_back(zz.slice().getDouble());
-
-  // now sort vector and check for appearances
-  std::sort(myNumbers.begin(), myNumbers.end());
-
-  std::sort(myCountNumbers.begin(), myCountNumbers.end());
-  ASSERT_EQ(myNumbers.at(0), 1);
-  ASSERT_EQ(myNumbers.at(1), 2);
-  ASSERT_EQ(myCountNumbers.at(0), 1);
-  ASSERT_EQ(myCountNumbers.at(1), 2);
+// Collect based on equal objects.
+TEST_P(HashedCollectExecutorTest, collect_objects) {
+  auto infos = buildInfos(1, 2, {{1, 0}});
+  AqlCall call{};          // unlimited produce
+  ExecutionStats stats{};  // No stats here
+  ExecutorTestHelper<HashedCollectExecutor>(*fakedQuery)
+      .setInputValue({{{R"({"a": 1, "b": 1})"}},
+                      {{1}},
+                      {{R"({"a": 1, "b": 1, "c": 1})"}},
+                      {{R"({"a": 2, "b": 1})"}},
+                      {{R"({"b": 1, "a": 1})"}},
+                      {{R"({"b": 1, "c": 1, "a": 1})"}},
+                      {{R"([1,1,1])"}}})
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({1}, {{1},
+                          {R"([1,1,1])"},
+                          {R"({"a": 1, "b": 1})"},
+                          {R"({"a": 1, "b": 1, "c": 1})"},
+                          {R"({"a": 2, "b": 1})"}})
+      .allowAnyOutputOrder(true)
+      .expectSkipped(0)
+      .expectedState(ExecutionState::DONE)
+      // .expectedStats(stats)
+      .run(std::move(infos));
 }
 
-TEST(HashedCollectExecutorTestRowsCountNumbers, the_producer_doesnt_wait) {
-  ExecutionState state;
-  ResourceMonitor monitor;
-  AqlItemBlockManager itemBlockManager{&monitor, SerializationFormat::SHADOWROWS};
+/**
+ * @section
+ *
+ * Test suite for aggregate functions.
+ * We only do full produce here, to make sure that aggregate
+ * functions work as expected.
+ * The register / call implementation is tested in the other suite
+ */
+
+struct AggregateInput {
+  std::string name;
+  RegisterId inReg;
+  MatrixBuilder<2> expectedOutput;
+};
 
-  mocks::MockAqlServer server{};
-  std::unique_ptr<arangodb::aql::Query> fakedQuery = server.createFakeQuery();
-  arangodb::transaction::Methods* trx = fakedQuery->trx();
-
-  std::unordered_set<RegisterId> regToClear;
-  std::unordered_set<RegisterId> regToKeep;
-  std::vector<std::pair<RegisterId, RegisterId>> groupRegisters;
-  groupRegisters.emplace_back(std::make_pair<RegisterId, RegisterId>(1, 0));
-
-  std::unordered_set<RegisterId> readableInputRegisters;
-  readableInputRegisters.insert(0);
-
-  std::unordered_set<RegisterId> writeableOutputRegisters;
-  writeableOutputRegisters.insert(1);
-
-  RegisterId nrOutputRegister = 3;
-
-  std::vector<std::pair<RegisterId, RegisterId>> aggregateRegisters;
-  aggregateRegisters.emplace_back(std::make_pair<RegisterId, RegisterId>(1, 0));
-
-  std::vector<std::string> aggregateTypes;
-  aggregateTypes.emplace_back("LENGTH");
-
-  // if count = true, then we need to set a valid countRegister
-  bool count = true;
-  RegisterId collectRegister = 2;
-  writeableOutputRegisters.insert(2);
-
-  HashedCollectExecutorInfos infos(1, nrOutputRegister, regToClear, regToKeep,
-                                   std::move(readableInputRegisters),
-                                   std::move(writeableOutputRegisters),
-                                   std::move(groupRegisters), collectRegister,
-                                   std::move(aggregateTypes),
-                                   std::move(aggregateRegisters), trx, count);
-
-  SharedAqlItemBlockPtr block{new AqlItemBlock(itemBlockManager, 1000, nrOutputRegister)};
-  NoStats stats{};
-
-  auto input = VPackParser::fromJson("[ [1], [2], [3] ]");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), false);
-  HashedCollectExecutor testee(fetcher, infos);
-
-  OutputAqlItemRow result(std::move(block), infos.getOutputRegisters(),
-                          infos.registersToKeep(), infos.registersToClear());
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(result.produced());
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(result.produced());
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_TRUE(result.produced());
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(result.produced());
-
-  std::vector<int64_t> myNumbers;
-  std::vector<int64_t> myCountNumbers;
-  auto newBlock = result.stealBlock();
-
-  // check for types
-  AqlValue x = newBlock->getValue(0, 1);
-  ASSERT_TRUE(x.isNumber());
-  myNumbers.emplace_back(x.slice().getInt());
-
-  // Check the count register
-  AqlValue xx = newBlock->getValue(0, 2);
-  ASSERT_TRUE(xx.isNumber());
-  myCountNumbers.emplace_back(xx.slice().getInt());
-
-  AqlValue z = newBlock->getValue(1, 1);
-  ASSERT_TRUE(z.isNumber());
-  myNumbers.emplace_back(z.slice().getInt());
-
-  // Check the count register
-  AqlValue zz = newBlock->getValue(1, 2);
-  ASSERT_TRUE(zz.isNumber());
-  myCountNumbers.emplace_back(zz.slice().getInt());
-
-  AqlValue y = newBlock->getValue(2, 1);
-  ASSERT_TRUE(y.isNumber());
-  myNumbers.emplace_back(y.slice().getInt());
-
-  // Check the count register
-  AqlValue yy = newBlock->getValue(2, 2);
-  ASSERT_TRUE(yy.isNumber());
-  myCountNumbers.emplace_back(yy.slice().getInt());
-
-  // now sort vector and check for appearances
-  std::sort(myNumbers.begin(), myNumbers.end());
-
-  std::sort(myCountNumbers.begin(), myCountNumbers.end());
-  ASSERT_EQ(myNumbers.at(0), 1);
-  ASSERT_EQ(myNumbers.at(1), 2);
-  ASSERT_EQ(myNumbers.at(2), 3);
-  ASSERT_EQ(myCountNumbers.at(0), 1);
-  ASSERT_EQ(myCountNumbers.at(1), 1);
-  ASSERT_EQ(myCountNumbers.at(2), 1);
+std::ostream& operator<<(std::ostream& out, AggregateInput const& agg) {
+  out << agg.name;
+  if (agg.inReg != RegisterPlan::MaxRegisterId) {
+    out << " reg: " << agg.inReg;
+  }
+  return out;
 }
 
-TEST(HashedCollectExecutorTestRowsCountStrings, the_producer_doesnt_wait) {
-  ExecutionState state;
-  ResourceMonitor monitor;
-  AqlItemBlockManager itemBlockManager{&monitor, SerializationFormat::SHADOWROWS};
+using HashedCollectAggregateInputParam = std::tuple<HashedCollectSplitType, AggregateInput>;
+
+class HashedCollectExecutorTestAggregate
+    : public AqlExecutorTestCaseWithParam<HashedCollectAggregateInputParam> {
+ protected:
+  auto getSplit() -> HashedCollectSplitType {
+    auto [split, unused] = GetParam();
+    return split;
+  }
+
+  auto getAggregator() -> AggregateInput {
+    auto [unused, info] = GetParam();
+    return info;
+  }
+
+  auto buildInfos(RegisterId nrInputRegisters, RegisterId nrOutputRegisters,
+                  std::vector<std::pair<RegisterId, RegisterId>> groupRegisters)
+      -> HashedCollectExecutorInfos {
+    std::unordered_set<RegisterId> registersToClear{};
+    std::unordered_set<RegisterId> registersToKeep{};
+    std::unordered_set<RegisterId> readableInputRegisters{};
+    std::unordered_set<RegisterId> writeableOutputRegisters{};
+
+    for (RegisterId i = 0; i < nrInputRegisters; ++i) {
+      // All registers need to be invalidated!
+      registersToClear.emplace(i);
+    }
+
+    for (auto const& [out, in] : groupRegisters) {
+      readableInputRegisters.emplace(in);
+      writeableOutputRegisters.emplace(out);
+    }
+
+    bool count = false;
+    RegisterId collectRegister = RegisterPlan::MaxRegisterId;
+
+    auto agg = getAggregator();
+    std::vector<std::string> aggregateTypes{agg.name};
+    std::vector<std::pair<RegisterId, RegisterId>> aggregateRegisters{{3, agg.inReg}};
+    if (agg.inReg != RegisterPlan::MaxRegisterId) {
+      readableInputRegisters.emplace(agg.inReg);
+    }
+
+    writeableOutputRegisters.emplace(3);
+
+    return HashedCollectExecutorInfos{nrInputRegisters,
+                                      nrOutputRegisters,
+                                      registersToClear,
+                                      registersToKeep,
+                                      std::move(readableInputRegisters),
+                                      std::move(writeableOutputRegisters),
+                                      std::move(groupRegisters),
+                                      collectRegister,
+                                      std::move(aggregateTypes),
+                                      std::move(aggregateRegisters),
+                                      fakedQuery->trx(),
+                                      count};
+  };
+};
 
-  mocks::MockAqlServer server{};
-  std::unique_ptr<arangodb::aql::Query> fakedQuery = server.createFakeQuery();
-  arangodb::transaction::Methods* trx = fakedQuery->trx();
-
-  std::unordered_set<RegisterId> regToClear;
-  std::unordered_set<RegisterId> regToKeep;
-  std::vector<std::pair<RegisterId, RegisterId>> groupRegisters;
-  groupRegisters.emplace_back(std::make_pair<RegisterId, RegisterId>(1, 0));
-
-  std::unordered_set<RegisterId> readableInputRegisters;
-  readableInputRegisters.insert(0);
-
-  std::unordered_set<RegisterId> writeableOutputRegisters;
-  writeableOutputRegisters.insert(1);
-
-  RegisterId nrOutputRegister = 3;
-
-  std::vector<std::pair<RegisterId, RegisterId>> aggregateRegisters;
-  aggregateRegisters.emplace_back(std::make_pair<RegisterId, RegisterId>(1, 0));
-
-  std::vector<std::string> aggregateTypes;
-  aggregateTypes.emplace_back("LENGTH");
-
-  // if count = true, then we need to set a valid countRegister
-  bool count = true;
-  RegisterId collectRegister = 2;
-  writeableOutputRegisters.insert(2);
-
-  HashedCollectExecutorInfos infos(1, nrOutputRegister, regToClear, regToKeep,
-                                   std::move(readableInputRegisters),
-                                   std::move(writeableOutputRegisters),
-                                   std::move(groupRegisters), collectRegister,
-                                   std::move(aggregateTypes),
-                                   std::move(aggregateRegisters), trx, count);
-
-  SharedAqlItemBlockPtr block{new AqlItemBlock(itemBlockManager, 1000, nrOutputRegister)};
-  NoStats stats{};
-
-  auto input = VPackParser::fromJson("[ [\"a\"], [\"aa\"], [\"aaa\"] ]");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), false);
-  HashedCollectExecutor testee(fetcher, infos);
-
-  OutputAqlItemRow result(std::move(block), infos.getOutputRegisters(),
-                          infos.registersToKeep(), infos.registersToClear());
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(result.produced());
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(result.produced());
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_TRUE(result.produced());
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(result.produced());
-
-  std::vector<std::string> myStrings;
-  std::vector<int64_t> myCountNumbers;
-  auto newBlock = result.stealBlock();
-
-  // check for types
-  AqlValue x = newBlock->getValue(0, 1);
-  ASSERT_TRUE(x.isString());
-  myStrings.emplace_back(x.slice().copyString());
-
-  // Check the count register
-  AqlValue xx = newBlock->getValue(0, 2);
-  ASSERT_TRUE(xx.isNumber());
-  myCountNumbers.emplace_back(xx.slice().getInt());
-
-  AqlValue z = newBlock->getValue(1, 1);
-  ASSERT_TRUE(z.isString());
-  myStrings.emplace_back(z.slice().copyString());
-
-  // Check the count register
-  AqlValue zz = newBlock->getValue(1, 2);
-  ASSERT_TRUE(zz.isNumber());
-  myCountNumbers.emplace_back(zz.slice().getInt());
-
-  AqlValue y = newBlock->getValue(2, 1);
-  ASSERT_TRUE(y.isString());
-  myStrings.emplace_back(y.slice().copyString());
-
-  // Check the count register
-  AqlValue yy = newBlock->getValue(2, 2);
-  ASSERT_TRUE(yy.isNumber());
-  myCountNumbers.emplace_back(yy.slice().getInt());
-
-  // now sort vector and check for appearances
-  std::sort(myStrings.begin(), myStrings.end());
-
-  std::sort(myCountNumbers.begin(), myCountNumbers.end());
-  ASSERT_EQ(myStrings.at(0), "a");
-  ASSERT_EQ(myStrings.at(1), "aa");
-  ASSERT_EQ(myStrings.at(2), "aaa");
-  ASSERT_EQ(myCountNumbers.at(0), 1);
-  ASSERT_EQ(myCountNumbers.at(1), 1);
-  ASSERT_EQ(myCountNumbers.at(2), 1);
+/**
+ * Input used:
+ *
+ * [
+ *   [1, 5]
+ *   [1, 1]
+ *   [2, 2]
+ *   [1, 5]
+ *   [6, 1]
+ *   [2, 2]
+ *   [3, 1]
+ * ]
+ * We join on the first value.
+ * The second value can be used by aggregate
+ */
+
+/**
+ * TODO:
+ * [] Add tests for all aggregate functions
+ */
+
+auto AggregateInputs =
+    ::testing::Values(AggregateInput{"LENGTH",
+                                     RegisterPlan::MaxRegisterId,
+                                     {{1, 3}, {2, 2}, {6, 1}, {3, 1}}},
+                      AggregateInput{"SUM", 0, {{1, 3}, {2, 4}, {6, 6}, {3, 3}}},
+                      AggregateInput{"SUM", 1, {{1, 11}, {2, 4}, {6, 1}, {3, 1}}});
+
+INSTANTIATE_TEST_CASE_P(HashedCollectAggregate, HashedCollectExecutorTestAggregate,
+                        ::testing::Combine(::testing::Values(splitIntoBlocks<2, 3>,
+                                                             splitIntoBlocks<3, 4>,
+                                                             splitStep<1>, splitStep<2>),
+                                           AggregateInputs));
+
+TEST_P(HashedCollectExecutorTestAggregate, run) {
+  auto infos = buildInfos(2, 4, {{2, 0}});
+  AqlCall call{};          // unlimited produce
+  ExecutionStats stats{};  // No stats here
+  ExecutorTestHelper<HashedCollectExecutor, 2, 2>(*fakedQuery)
+      .setInputValue(MatrixBuilder<2>{RowBuilder<2>{1, 5}, RowBuilder<2>{1, 1},
+                                      RowBuilder<2>{2, 2}, RowBuilder<2>{1, 5},
+                                      RowBuilder<2>{6, 1}, RowBuilder<2>{2, 2},
+                                      RowBuilder<2>{3, 1}})
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({2, 3}, getAggregator().expectedOutput)
+      .allowAnyOutputOrder(true)
+      .expectSkipped(0)
+      .expectedState(ExecutionState::DONE)
+      // .expectedStats(stats)
+      .run(std::move(infos));
 }
 
 }  // namespace aql
diff --git a/tests/Aql/IdExecutorTest.cpp b/tests/Aql/IdExecutorTest.cpp
index 32f0a51bf6ce..e9c2d3df07d7 100644
--- a/tests/Aql/IdExecutorTest.cpp
+++ b/tests/Aql/IdExecutorTest.cpp
@@ -53,8 +53,7 @@ using TestParam = std::tuple<std::vector<int>,  // The input data
                              OutputAqlItemRow::CopyRowBehavior  // How the data is handled within outputRow
                              >;
 
-class IdExecutorTestCombiner : public AqlExecutorTestCase<>,
-                               public ::testing::TestWithParam<TestParam> {
+class IdExecutorTestCombiner : public AqlExecutorTestCaseWithParam<TestParam> {
  protected:
   IdExecutorTestCombiner() {}
 
@@ -203,7 +202,7 @@ auto copyBehaviours = testing::Values(OutputAqlItemRow::CopyRowBehavior::CopyInp
 INSTANTIATE_TEST_CASE_P(IdExecutorTest, IdExecutorTestCombiner,
                         ::testing::Combine(inputs, upstreamStates, clientCalls, copyBehaviours));
 
-class IdExecutionBlockTest : public AqlExecutorTestCase<>, public ::testing::Test {};
+class IdExecutionBlockTest : public AqlExecutorTestCase<> {};
 
 // The IdExecutor has a specific initializeCursor method in ExecutionBlockImpl
 TEST_F(IdExecutionBlockTest, test_initialize_cursor_get) {
@@ -347,8 +346,7 @@ TEST_F(IdExecutionBlockTest, test_hardlimit_single_row_fetcher) {
  *  Used in ScatterExecutor logic.
  *  param: useFullCount
  */
-class BlockOverloadTest : public AqlExecutorTestCase<>,
-                          public ::testing::TestWithParam<bool> {
+class BlockOverloadTest : public AqlExecutorTestCaseWithParam<bool> {
  protected:
   auto getTestee() -> ExecutionBlockImpl<IdExecutor<ConstFetcher>> {
     IdExecutorInfos infos{1, {0}, {}};
@@ -385,7 +383,7 @@ TEST_P(BlockOverloadTest, test_hardlimit_const_fetcher) {
       EXPECT_EQ(skipped, 0);
     }
 
-    ValidateBlocksAreEqual(block, expectedOutputBlock);
+    asserthelper::ValidateBlocksAreEqual(block, expectedOutputBlock);
   }
   {
     // Validate that additional upstream-rows are gone.
@@ -422,7 +420,7 @@ TEST_P(BlockOverloadTest, test_hardlimit_const_fetcher_shadow_rows_at_end) {
     } else {
       EXPECT_EQ(skipped, 0);
     }
-    ValidateBlocksAreEqual(block, expectedOutputBlock);
+    asserthelper::ValidateBlocksAreEqual(block, expectedOutputBlock);
   }
   {
     // Validate that additional upstream-rows are gone.
@@ -459,7 +457,7 @@ TEST_P(BlockOverloadTest, test_hardlimit_const_fetcher_shadow_rows_in_between) {
     } else {
       EXPECT_EQ(skipped, 0);
     }
-    ValidateBlocksAreEqual(block, expectedOutputBlock);
+    asserthelper::ValidateBlocksAreEqual(block, expectedOutputBlock);
   }
   {
     // Validate that next call will give remaining rows
@@ -470,7 +468,7 @@ TEST_P(BlockOverloadTest, test_hardlimit_const_fetcher_shadow_rows_in_between) {
     auto const& [state, skipped, block] = testee.execute(stack);
     EXPECT_EQ(state, ExecutionState::DONE);
     EXPECT_EQ(skipped, 0);
-    ValidateBlocksAreEqual(block, expectedOutputBlock);
+    asserthelper::ValidateBlocksAreEqual(block, expectedOutputBlock);
   }
 }
 
@@ -500,7 +498,7 @@ TEST_P(BlockOverloadTest, test_hardlimit_const_fetcher_consecutive_shadow_rows)
     } else {
       EXPECT_EQ(skipped, 0);
     }
-    ValidateBlocksAreEqual(block, expectedOutputBlock);
+    asserthelper::ValidateBlocksAreEqual(block, expectedOutputBlock);
   }
   {
     // Second call will only find a single ShadowRow
@@ -512,7 +510,7 @@ TEST_P(BlockOverloadTest, test_hardlimit_const_fetcher_consecutive_shadow_rows)
     auto const& [state, skipped, block] = testee.execute(stack);
     EXPECT_EQ(state, ExecutionState::HASMORE);
     EXPECT_EQ(skipped, 0);
-    ValidateBlocksAreEqual(block, expectedOutputBlock);
+    asserthelper::ValidateBlocksAreEqual(block, expectedOutputBlock);
   }
   {
     // Third call will only find a single ShadowRow
@@ -524,7 +522,7 @@ TEST_P(BlockOverloadTest, test_hardlimit_const_fetcher_consecutive_shadow_rows)
     auto const& [state, skipped, block] = testee.execute(stack);
     EXPECT_EQ(state, ExecutionState::DONE);
     EXPECT_EQ(skipped, 0);
-    ValidateBlocksAreEqual(block, expectedOutputBlock);
+    asserthelper::ValidateBlocksAreEqual(block, expectedOutputBlock);
   }
   {
     // Validate that additional upstream-rows are gone.
diff --git a/tests/Aql/SortedCollectExecutorTest.cpp b/tests/Aql/SortedCollectExecutorTest.cpp
index 95acf6b94d2c..e580e9b45f24 100644
--- a/tests/Aql/SortedCollectExecutorTest.cpp
+++ b/tests/Aql/SortedCollectExecutorTest.cpp
@@ -928,8 +928,7 @@ using SortedCollectTestHelper = ExecutorTestHelper<SortedCollectExecutor, 1, 1>;
 using SortedCollectSplitType = SortedCollectTestHelper::SplitType;
 
 class SortedCollectExecutorTestSplit
-    : public AqlExecutorTestCase<false>,
-      public ::testing::TestWithParam<std::tuple<SortedCollectSplitType>> {
+    : public AqlExecutorTestCaseWithParam<std::tuple<SortedCollectSplitType>> {
  protected:
   arangodb::transaction::Methods* trx;
 
diff --git a/tests/Aql/WaitingExecutionBlockMock.cpp b/tests/Aql/WaitingExecutionBlockMock.cpp
index 4e1f9233ca7a..74000072c520 100644
--- a/tests/Aql/WaitingExecutionBlockMock.cpp
+++ b/tests/Aql/WaitingExecutionBlockMock.cpp
@@ -64,7 +64,7 @@ std::pair<arangodb::aql::ExecutionState, Result> WaitingExecutionBlockMock::shut
 }
 
 std::pair<arangodb::aql::ExecutionState, SharedAqlItemBlockPtr> WaitingExecutionBlockMock::getSome(size_t atMost) {
-  if (!_hasWaited) {
+  if (_variant != WaitingBehaviour::NEVER && !_hasWaited) {
     _hasWaited = true;
     if (_returnedDone) {
       return {ExecutionState::DONE, nullptr};
@@ -91,7 +91,7 @@ std::pair<arangodb::aql::ExecutionState, SharedAqlItemBlockPtr> WaitingExecution
 
 std::pair<arangodb::aql::ExecutionState, size_t> WaitingExecutionBlockMock::skipSome(size_t atMost) {
   traceSkipSomeBegin(atMost);
-  if (!_hasWaited) {
+  if (_variant != WaitingBehaviour::NEVER && !_hasWaited) {
     _hasWaited = true;
     return traceSkipSomeEnd(ExecutionState::WAITING, 0);
   }
@@ -136,7 +136,23 @@ std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> WaitingExecutionBlockM
   }
   size_t skipped = 0;
   SharedAqlItemBlockPtr result = nullptr;
+  if (_data.front() == nullptr) {
+    dropBlock();
+  }
   while (!_data.empty()) {
+    if (_data.front() == nullptr) {
+      if (myCall.getOffset() > 0 || myCall.getLimit() > 0) {
+        TRI_ASSERT(skipped > 0 || result != nullptr);
+        // This is a specific break point return now.
+        // Sorry we can only return one block.
+        // This means we have prepared the first block.
+        // But still need more data.
+        return {ExecutionState::HASMORE, skipped, result};
+      } else {
+        dropBlock();
+        continue;
+      }
+    }
     if (_data.front()->size() <= _inflight) {
       dropBlock();
       continue;

From 1a54762068741362a228461377c996b1877b6a61 Mon Sep 17 00:00:00 2001
From: Heiko <hkernbach@users.noreply.github.com>
Date: Tue, 18 Feb 2020 18:43:27 +0100
Subject: [PATCH 068/122] Feature/aql subquery operations stack enumerate list
 (#10988)

* produce inputRange

* produce inputRange test

* produce inputRange test 2

* apply new api

* enable new api

* enumeratelistexecutor changes

* added hackis shouldSkip method

* add new execution style for enumerate lsit

* added skip for enumerate list

* edit of enumerate list executor

* fixed enumlist executor

* optimized skip loop

* more tests, using new framework

* allow empty output checks

* added new style tests, removed old tests

* removed old produceRows method

* fixed tests

* added one missing exit case

* added another exit in SHADOWROWS mode, as we need to take a look at fullCount there

* Revert "added another exit in SHADOWROWS mode, as we need to take a look at fullCount there"

This reverts commit e74b7cede78f81b8fece034fc921a969e91dda12.

*  do not take care of fullCount in executor itself, impl will do

* removed obsolete comment

* rm _skipped because unused, return upstreamstate

* added invalid value test, added border edge tests for softLimit, hardLimit and fullCount

* api change

* added test for inner states inside the executor

* added new tests

* fixed assert

* removed two not needed ifs

* asserted a case in our test helper

* Prepare reusability of LOG output for ExecutionBlock.

* Added first version of DEBUG output to ExecutionBlockImpl

* undo this commit before merge

* undo this commit before merge

* Merged

Co-authored-by: Michael Hackstein <michael@arangodb.com>
---
 arangod/Aql/EnumerateCollectionExecutor.cpp   |   6 +-
 arangod/Aql/EnumerateListExecutor.cpp         | 186 ++++--
 arangod/Aql/EnumerateListExecutor.h           |  40 +-
 arangod/Aql/ExecutionBlockImpl.cpp            |  16 +-
 etc/testing/arangod-common.conf               |   1 +
 tests/Aql/EnumerateListExecutorTest.cpp       | 543 ++++++++++--------
 .../shell-statement-encoding-noncluster.js    |   2 +-
 7 files changed, 458 insertions(+), 336 deletions(-)

diff --git a/arangod/Aql/EnumerateCollectionExecutor.cpp b/arangod/Aql/EnumerateCollectionExecutor.cpp
index 446b3d0a949c..15a5db47ef83 100644
--- a/arangod/Aql/EnumerateCollectionExecutor.cpp
+++ b/arangod/Aql/EnumerateCollectionExecutor.cpp
@@ -42,7 +42,7 @@
 
 using namespace arangodb;
 using namespace arangodb::aql;
-  
+
 namespace {
 std::vector<size_t> const emptyAttributePositions;
 }
@@ -55,7 +55,7 @@ EnumerateCollectionExecutorInfos::EnumerateCollectionExecutorInfos(
     std::unordered_set<RegisterId> registersToKeep, ExecutionEngine* engine,
     Collection const* collection, Variable const* outVariable, bool produceResult,
     Expression* filter,
-    std::vector<std::string> const& projections, 
+    std::vector<std::string> const& projections,
     bool useRawDocumentPointers, bool random)
     : ExecutorInfos(make_shared_unordered_set(),
                     make_shared_unordered_set({outputRegister}),
@@ -119,7 +119,7 @@ EnumerateCollectionExecutor::EnumerateCollectionExecutor(Fetcher& fetcher, Infos
       _documentProducingFunctionContext(_input, nullptr, _infos.getOutputRegisterId(),
                                         _infos.getProduceResult(),
                                         _infos.getQuery(), _infos.getFilter(),
-                                        _infos.getProjections(), 
+                                        _infos.getProjections(),
                                         ::emptyAttributePositions,
                                         true, _infos.getUseRawDocumentPointers(), false),
       _state(ExecutionState::HASMORE),
diff --git a/arangod/Aql/EnumerateListExecutor.cpp b/arangod/Aql/EnumerateListExecutor.cpp
index 3160ccc8ef92..2840dbf3339c 100644
--- a/arangod/Aql/EnumerateListExecutor.cpp
+++ b/arangod/Aql/EnumerateListExecutor.cpp
@@ -25,6 +25,8 @@
 
 #include "EnumerateListExecutor.h"
 
+#include "Aql/AqlCall.h"
+#include "Aql/AqlItemBlockInputRange.h"
 #include "Aql/AqlValue.h"
 #include "Aql/ExecutorInfos.h"
 #include "Aql/InputAqlItemRow.h"
@@ -45,7 +47,7 @@ void throwArrayExpectedException(AqlValue const& value) {
               " as operand to FOR loop; you provided a value of type '") +
           value.getTypeString() + std::string("'"));
 }
-} // namespace
+}  // namespace
 
 EnumerateListExecutorInfos::EnumerateListExecutorInfos(
     RegisterId inputRegister, RegisterId outputRegister,
@@ -70,84 +72,142 @@ RegisterId EnumerateListExecutorInfos::getOutputRegister() const noexcept {
 }
 
 EnumerateListExecutor::EnumerateListExecutor(Fetcher& fetcher, EnumerateListExecutorInfos& infos)
-    : _infos(infos),
-      _fetcher(fetcher),
-      _currentRow{CreateInvalidInputRowHint{}},
-      _rowState(ExecutionState::HASMORE),
-      _inputArrayPosition(0),
-      _inputArrayLength(0) {}
+    : _infos(infos), _currentRow{CreateInvalidInputRowHint{}}, _inputArrayPosition(0), _inputArrayLength(0) {}
 
 std::pair<ExecutionState, NoStats> EnumerateListExecutor::produceRows(OutputAqlItemRow& output) {
-  while (true) {
-    // HIT in first run, because pos and length are initiliazed
-    // both with 0
-
-    if (_inputArrayPosition == _inputArrayLength) {
-      // we need to set position back to zero
-      // because we finished iterating over existing array
-      // element and need to refetch another row
-      // _inputArrayPosition = 0;
-      if (_rowState == ExecutionState::DONE) {
-        return {_rowState, NoStats{}};
-      }
-      initialize();
-      std::tie(_rowState, _currentRow) = _fetcher.fetchRow();
-      if (_rowState == ExecutionState::WAITING) {
-        return {_rowState, NoStats{}};
-      }
-    }
+  TRI_ASSERT(false);
+  THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
+}
 
-    if (!_currentRow.isInitialized()) {
-      TRI_ASSERT(_rowState == ExecutionState::DONE);
-      return {_rowState, NoStats{}};
-    }
+void EnumerateListExecutor::initializeNewRow(AqlItemBlockInputRange& inputRange) {
+  if (_currentRow) {
+    std::ignore = inputRange.nextDataRow();
+  }
+  std::tie(_currentRowState, _currentRow) = inputRange.peekDataRow();
+  if (!_currentRow) {
+    return;
+  }
 
-    AqlValue const& inputList = _currentRow.getValue(_infos.getInputRegister());
+  // fetch new row, put it in local state
+  AqlValue const& inputList = _currentRow.getValue(_infos.getInputRegister());
 
-    if (_inputArrayPosition == 0) {
-      // store the length into a local variable
-      // so we don't need to calculate length every time
-      if (inputList.isDocvec()) {
-        _inputArrayLength = inputList.docvecSize();
-      } else {
-        if (!inputList.isArray()) {
-          throwArrayExpectedException(inputList);
-        }
-        _inputArrayLength = inputList.length();
-      }
+  // store the length into a local variable
+  // so we don't need to calculate length every time
+  if (inputList.isDocvec()) {
+    _inputArrayLength = inputList.docvecSize();
+  } else {
+    if (!inputList.isArray()) {
+      throwArrayExpectedException(inputList);
     }
+    _inputArrayLength = inputList.length();
+  }
 
-    if (_inputArrayLength == 0) {
+  _inputArrayPosition = 0;
+}
+
+void EnumerateListExecutor::processArrayElement(OutputAqlItemRow& output) {
+  bool mustDestroy;
+  AqlValue const& inputList = _currentRow.getValue(_infos.getInputRegister());
+  AqlValue innerValue = getAqlValue(inputList, _inputArrayPosition, mustDestroy);
+  AqlValueGuard guard(innerValue, mustDestroy);
+
+  TRI_IF_FAILURE("EnumerateListBlock::getSome") {
+    THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
+  }
+
+  output.moveValueInto(_infos.getOutputRegister(), _currentRow, guard);
+  output.advanceRow();
+
+  // set position to +1 for next iteration after new fetchRow
+  _inputArrayPosition++;
+}
+
+size_t EnumerateListExecutor::skipArrayElement(size_t toSkip) {
+  size_t skipped = 0;
+
+  if (toSkip <= _inputArrayLength - _inputArrayPosition) {
+    // if we're skipping less or exact the amount of elements we can skip with toSkip
+    _inputArrayPosition += toSkip;
+    skipped = toSkip;
+  } else if (toSkip > _inputArrayLength - _inputArrayPosition) {
+    // we can only skip the max amount of values we've in our array
+    skipped = _inputArrayLength - _inputArrayPosition;
+    _inputArrayPosition = _inputArrayLength;
+  }
+  return skipped;
+}
+
+std::tuple<ExecutorState, NoStats, AqlCall> EnumerateListExecutor::produceRows(
+    AqlItemBlockInputRange& inputRange, OutputAqlItemRow& output) {
+  AqlCall upstreamCall{};
+  upstreamCall.fullCount = output.getClientCall().fullCount;
+
+  while (inputRange.hasDataRow() && !output.isFull()) {
+    if (_inputArrayLength == _inputArrayPosition) {
+      // we reached either the end of an array
+      // or are in our first loop iteration
+      initializeNewRow(inputRange);
       continue;
-    } else if (_inputArrayLength == _inputArrayPosition) {
-      // we reached the end, forget all state
-      initialize();
+    }
 
-      if (_rowState == ExecutionState::HASMORE) {
-        continue;
-      } else {
-        return {_rowState, NoStats{}};
-      }
-    } else {
-      bool mustDestroy;
-      AqlValue innerValue = getAqlValue(inputList, _inputArrayPosition, mustDestroy);
-      AqlValueGuard guard(innerValue, mustDestroy);
+    TRI_ASSERT(_inputArrayPosition < _inputArrayLength);
+    processArrayElement(output);
+  }
 
-      TRI_IF_FAILURE("EnumerateListBlock::getSome") {
-        THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
-      }
+  if (_inputArrayLength == _inputArrayPosition) {
+    // we reached either the end of an array
+    // or are in our first loop iteration
+    initializeNewRow(inputRange);
+  }
 
-      output.moveValueInto(_infos.getOutputRegister(), _currentRow, guard);
+  return {inputRange.upstreamState(), NoStats{}, upstreamCall};
+}
+
+std::tuple<ExecutorState, NoStats, size_t, AqlCall> EnumerateListExecutor::skipRowsRange(
+    AqlItemBlockInputRange& inputRange, AqlCall& call) {
+  AqlCall upstreamCall{};
 
-      // set position to +1 for next iteration after new fetchRow
-      _inputArrayPosition++;
+  if (!inputRange.hasDataRow()) {
+    return {inputRange.upstreamState(), NoStats{}, 0, upstreamCall};
+  }
 
-      if (_inputArrayPosition < _inputArrayLength || _rowState == ExecutionState::HASMORE) {
-        return {ExecutionState::HASMORE, NoStats{}};
+  InputAqlItemRow input{CreateInvalidInputRowHint{}};
+  size_t skipped = 0;
+  bool offsetPhase = (call.getOffset() > 0);
+
+  while (inputRange.hasDataRow() && call.shouldSkip()) {
+    if (_inputArrayLength == _inputArrayPosition) {
+      // we reached either the end of an array
+      // or are in our first loop iteration
+      initializeNewRow(inputRange);
+      continue;
+    }
+    // auto const& [state, input] = inputRange.peekDataRow();
+
+    TRI_ASSERT(_inputArrayPosition < _inputArrayLength);
+    // if offset is > 0, we're in offset skip phase
+    if (offsetPhase) {
+      if (skipped < call.getOffset()) {
+        // we still need to skip offset entries
+        skipped += skipArrayElement(call.getOffset() - skipped);
+      } else {
+        // we skipped enough in our offset phase
+        break;
       }
-      return {ExecutionState::DONE, NoStats{}};
+    } else {
+      // fullCount phase - skippen bis zum ende
+      skipped += skipArrayElement(_inputArrayLength - _inputArrayPosition);
     }
   }
+  call.didSkip(skipped);
+
+  upstreamCall.softLimit = call.getOffset();
+  if (_inputArrayPosition < _inputArrayLength) {
+    // fullCount will always skip the complete array
+    TRI_ASSERT(offsetPhase);
+    return {ExecutorState::HASMORE, NoStats{}, skipped, upstreamCall};
+  }
+  return {inputRange.upstreamState(), NoStats{}, skipped, upstreamCall};
 }
 
 void EnumerateListExecutor::initialize() {
diff --git a/arangod/Aql/EnumerateListExecutor.h b/arangod/Aql/EnumerateListExecutor.h
index 34cfc7957092..70916e2a7464 100644
--- a/arangod/Aql/EnumerateListExecutor.h
+++ b/arangod/Aql/EnumerateListExecutor.h
@@ -41,6 +41,8 @@ class Methods;
 
 namespace aql {
 
+struct AqlCall;
+class AqlItemBlockInputRange;
 class ExecutorInfos;
 class OutputAqlItemRow;
 class NoStats;
@@ -85,7 +87,7 @@ class EnumerateListExecutor {
   using Infos = EnumerateListExecutorInfos;
   using Stats = NoStats;
 
-  EnumerateListExecutor(Fetcher& fetcher, EnumerateListExecutorInfos&);
+  EnumerateListExecutor(Fetcher&, EnumerateListExecutorInfos&);
   ~EnumerateListExecutor() = default;
 
   /**
@@ -95,15 +97,47 @@ class EnumerateListExecutor {
    */
   std::pair<ExecutionState, Stats> produceRows(OutputAqlItemRow& output);
 
+  /**
+   * @brief Will fetch a new InputRow if necessary and store their local state
+   *
+   * @return bool done in case we do not have any input and upstreamState is done
+   */
+  void initializeNewRow(AqlItemBlockInputRange& inputRange);
+
+  /**
+   * @brief Will process an found array element
+   */
+  void processArrayElement(OutputAqlItemRow& output);
+
+  /**
+   * @brief Will skip a maximum of n-elements inside the current array
+   */
+  size_t skipArrayElement(size_t skip);
+
+  /**
+   * @brief produce the next Row of Aql Values.
+   *
+   * @return ExecutorState, the stats, and a new Call that needs to be send to upstream
+   */
+  [[nodiscard]] std::tuple<ExecutorState, Stats, AqlCall> produceRows(
+      AqlItemBlockInputRange& inputRange, OutputAqlItemRow& output);
+
+  /**
+   * @brief skip the next Row of Aql Values.
+   *
+   * @return ExecutorState, the stats, and a new Call that needs to be send to upstream
+   */
+  [[nodiscard]] std::tuple<ExecutorState, Stats, size_t, AqlCall> skipRowsRange(
+      AqlItemBlockInputRange& inputRange, AqlCall& call);
+
  private:
   AqlValue getAqlValue(AqlValue const& inVarReg, size_t const& pos, bool& mustDestroy);
   void initialize();
 
  private:
   EnumerateListExecutorInfos& _infos;
-  Fetcher& _fetcher;
   InputAqlItemRow _currentRow;
-  ExecutionState _rowState;
+  ExecutorState _currentRowState;
   size_t _inputArrayPosition;
   size_t _inputArrayLength;
 };
diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index acb04789adb7..1cb86283cf7d 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -141,7 +141,7 @@ constexpr bool isNewStyleExecutor =
                 TestLambdaExecutor,
                 TestLambdaSkipExecutor,  // we need one after these to avoid compile errors in non-test mode
 #endif
-                ShortestPathExecutor>;
+                ShortestPathExecutor, EnumerateListExecutor>;
 
 template <class Executor>
 ExecutionBlockImpl<Executor>::ExecutionBlockImpl(ExecutionEngine* engine,
@@ -1060,7 +1060,8 @@ static SkipRowsRangeVariant constexpr skipRowsType() {
 #ifdef ARANGODB_USE_GOOGLE_TESTS
                                  TestLambdaSkipExecutor,
 #endif
-                                 SortedCollectExecutor>),
+                                 EnumerateListExecutor, SortedCollectExecutor>),
+
                 "Unexpected executor for SkipVariants::EXECUTOR");
 
   // The LimitExecutor will not work correctly with SkipVariants::FETCHER!
@@ -1381,16 +1382,7 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
             if (_outputItemRow->allRowsUsed()) {
               _execState = ExecState::DONE;
             } else if (state == ExecutorState::DONE) {
-              if (_lastRange.hasDataRow()) {
-                // TODO this state is invalid, and can just show up now if we exclude SKIP
-                _execState = ExecState::PRODUCE;
-              } else {
-                // Right now we cannot support to have more than one set of
-                // ShadowRows inside of a Range.
-                // We do not know how to continue with the above executor after a shadowrow.
-                TRI_ASSERT(!_lastRange.hasDataRow());
-                _execState = ExecState::DONE;
-              }
+              _execState = ExecState::DONE;
             }
           } else {
             _execState = ExecState::DONE;
diff --git a/etc/testing/arangod-common.conf b/etc/testing/arangod-common.conf
index b664b6edb9d2..89fd87728211 100644
--- a/etc/testing/arangod-common.conf
+++ b/etc/testing/arangod-common.conf
@@ -3,6 +3,7 @@ line-number = false
 force-direct = false
 level = info
 level = replication=warn
+level = queries=debug
 role = true
 
 [database]
diff --git a/tests/Aql/EnumerateListExecutorTest.cpp b/tests/Aql/EnumerateListExecutorTest.cpp
index 44bb6c416f6b..6132aad39bb1 100644
--- a/tests/Aql/EnumerateListExecutorTest.cpp
+++ b/tests/Aql/EnumerateListExecutorTest.cpp
@@ -25,15 +25,19 @@
 
 #include "gtest/gtest.h"
 
+#include "ExecutorTestHelper.h"
 #include "RowFetcherHelper.h"
-#include "fakeit.hpp"
 
+#include "Aql/AqlCall.h"
 #include "Aql/AqlItemBlock.h"
 #include "Aql/EnumerateListExecutor.h"
 #include "Aql/ExecutionBlockImpl.h"
+#include "Aql/ExecutionEngine.h"
 #include "Aql/OutputAqlItemRow.h"
 #include "Aql/ResourceUsage.h"
 #include "Aql/Stats.h"
+#include "AqlItemBlockHelper.h"
+#include "Mocks/Servers.h"
 #include "Transaction/Context.h"
 #include "Transaction/Methods.h"
 
@@ -47,296 +51,327 @@ namespace arangodb {
 namespace tests {
 namespace aql {
 
+// test inner executor behaviour
 class EnumerateListExecutorTest : public ::testing::Test {
  protected:
   ExecutionState state;
+  NoStats stats;
+  AqlCall call;
+
   ResourceMonitor monitor;
   AqlItemBlockManager itemBlockManager{&monitor, SerializationFormat::SHADOWROWS};
-
   EnumerateListExecutorTest()
       : itemBlockManager(&monitor, SerializationFormat::SHADOWROWS) {}
 };
 
-TEST_F(EnumerateListExecutorTest, there_are_no_rows_upstream_the_producer_does_not_wait) {
-  EnumerateListExecutorInfos infos(0, 1, 1, 2, {}, {0});
-  SharedAqlItemBlockPtr block{new AqlItemBlock(itemBlockManager, 1000, 2)};
-  VPackBuilder input;
+TEST_F(EnumerateListExecutorTest, test_check_state_first_row_border) {
+  // old styled test, to test the inner step-states of our executor
 
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input.steal(), false);
-  EnumerateListExecutor testee(fetcher, infos);
-  // Use this instead of std::ignore, so the tests will be noticed and
-  // updated when someone changes the stats type in the return value of
-  // EnumerateListExecutor::produceRows().
-  NoStats stats{};
-
-  OutputAqlItemRow result{std::move(block), infos.getOutputRegisters(),
-                          infos.registersToKeep(), infos.registersToClear()};
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(result.produced());
-}
-TEST_F(EnumerateListExecutorTest, there_are_no_rows_upstream_the_producer_waits) {
-  EnumerateListExecutorInfos infos(0, 1, 1, 2, {}, {0});
-  SharedAqlItemBlockPtr block{new AqlItemBlock(itemBlockManager, 1000, 2)};
-  VPackBuilder input;
-
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input.steal(), true);
-  EnumerateListExecutor testee(fetcher, infos);
-  // Use this instead of std::ignore, so the tests will be noticed and
-  // updated when someone changes the stats type in the return value of
-  // EnumerateListExecutor::produceRows().
-  NoStats stats{};
-
-  OutputAqlItemRow result{std::move(block), infos.getOutputRegisters(),
-                          infos.registersToKeep(), infos.registersToClear()};
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::WAITING);
-  ASSERT_FALSE(result.produced());
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(result.produced());
-}
+  // This fetcher will not be called!
+  // After Execute is done this fetcher shall be removed, the Executor does not need it anymore!
+  auto fakeUnusedBlock = VPackParser::fromJson("[  ]");
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, fakeUnusedBlock->steal(), false);
 
-TEST_F(EnumerateListExecutorTest, there_is_one_row_in_the_upstream_the_producer_waits) {
-  EnumerateListExecutorInfos infos(3, 4, 4, 5, {}, {0, 1, 2, 3});
+  // This is the relevant part of the test
   SharedAqlItemBlockPtr block{new AqlItemBlock(itemBlockManager, 1000, 5)};
-  auto input = VPackParser::fromJson("[ [1, 2, 3, [true, true, true]] ]");
-
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), true);
-  EnumerateListExecutor testee(fetcher, infos);
-  // Use this instead of std::ignore, so the tests will be noticed and
-  // updated when someone changes the stats type in the return value of
-  // EnumerateListExecutor::produceRows().
-  NoStats stats{};
-
-  OutputAqlItemRow result{std::move(block), infos.getOutputRegisters(),
-                          infos.registersToKeep(), infos.registersToClear()};
-
-  /*
-   * Here we are not waiting after every row produce, because the fetcher
-   * does not need to refetch a new row to produce the next one.
-   * 1. produce => WAIT                 RES1  - due true flag in
-   * SingleRowFetcherHelper
-   * 2. produce => HASMORE              RES1 - return a row
-   * 3. produce => HASMORE              RES2 - return a row
-   * 4. produce => HASMORE              RES3 - return a row
-   * 5. produce => DONE                 RES4 - DONE - do not return a row
-   */
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::WAITING);
-  ASSERT_FALSE(result.produced());
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(result.produced());
-
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(result.produced());
-
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_TRUE(result.produced());
-
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(result.produced());
-
-  block = result.stealBlock();
-  AqlValue v = block->getValue(0, 0);
-  ASSERT_TRUE(v.isNumber());
-  int64_t number = v.toInt64();
-  ASSERT_EQ(number, 1);
-
-  v = block->getValue(1, 0);
-  ASSERT_TRUE(v.isNumber());
-  number = v.toInt64();
-  ASSERT_EQ(number, 1);
-
-  v = block->getValue(1, 1);
-  ASSERT_TRUE(v.isNumber());
-  number = v.toInt64();
-  ASSERT_EQ(number, 2);
-
-  v = block->getValue(1, 2);
-  ASSERT_TRUE(v.isNumber());
-  number = v.toInt64();
-  ASSERT_EQ(number, 3);
-
-  bool mustDestroy = false;
-  v = block->getValue(1, 3);
-  ASSERT_TRUE(v.isArray());
-  ASSERT_TRUE(v.at(0, mustDestroy, false).toBoolean());
-  ASSERT_TRUE(v.at(1, mustDestroy, false).toBoolean());
-  ASSERT_TRUE(v.at(2, mustDestroy, false).toBoolean());
-
-  v = block->getValue(1, 4);
-  ASSERT_TRUE(v.isBoolean());
-  ASSERT_TRUE(v.toBoolean());
-}
-
-TEST_F(EnumerateListExecutorTest, there_is_one_empty_array_row_in_the_upstream_the_producer_waits) {
   EnumerateListExecutorInfos infos(3, 4, 4, 5, {}, {0, 1, 2, 3});
-  SharedAqlItemBlockPtr block{new AqlItemBlock(itemBlockManager, 1000, 5)};
-  auto input = VPackParser::fromJson("[ [1, 2, 3, [] ] ]");
-
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), true);
   EnumerateListExecutor testee(fetcher, infos);
-  // Use this instead of std::ignore, so the tests will be noticed and
-  // updated when someone changes the stats type in the return value of
-  // EnumerateListExecutor::produceRows().
-  NoStats stats{};
-
-  OutputAqlItemRow result{std::move(block), infos.getOutputRegisters(),
-                          infos.registersToKeep(), infos.registersToClear()};
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::WAITING);
-  ASSERT_FALSE(result.produced());
+  SharedAqlItemBlockPtr inBlock =
+      buildBlock<4>(itemBlockManager, {{{{1}, {2}, {3}, {R"([true, 1, 2])"}}},
+                                       {{{1}, {2}, {3}, {R"([true, 1, 2])"}}}});
+
+  AqlItemBlockInputRange input{ExecutorState::DONE, inBlock, 0, inBlock->size()};
+  OutputAqlItemRow output(std::move(block), infos.getOutputRegisters(),
+                          infos.registersToKeep(), infos.registersToClear());
+
+  // receive first 3 of 6 results in total
+  AqlCall myCall{0, AqlCall::Infinity{}, 3, false};
+
+  output.setCall(std::move(myCall));
+  EXPECT_EQ(output.numRowsWritten(), 0);
+  {
+    // reach the end (edge) of our first row, check that we do not return DONE here!
+    auto const [state, stats, call] = testee.produceRows(input, output);
+    EXPECT_EQ(state, ExecutorState::HASMORE);
+    EXPECT_EQ(output.numRowsWritten(), 3);
+  }
+}
 
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(result.produced());
+TEST_F(EnumerateListExecutorTest, test_check_state_second_row_border) {
+  // old styled test, to test the inner step-states of our executor
 
-  block = result.stealBlock();
-  ASSERT_EQ(block, nullptr);
-}
+  // This fetcher will not be called!
+  // After Execute is done this fetcher shall be removed, the Executor does not need it anymore!
+  auto fakeUnusedBlock = VPackParser::fromJson("[  ]");
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, fakeUnusedBlock->steal(), false);
 
-TEST_F(EnumerateListExecutorTest, there_are_rows_in_the_upstream_the_producer_waits) {
-  EnumerateListExecutorInfos infos(3, 4, 4, 5, {}, {0, 1, 2, 3});
+  // This is the relevant part of the test
   SharedAqlItemBlockPtr block{new AqlItemBlock(itemBlockManager, 1000, 5)};
-  auto input = VPackParser::fromJson(
-      "[ [1, 2, 3, [true, true, true]], [1, 2, 3, [true, true, true]] ]");
-
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), true);
+  EnumerateListExecutorInfos infos(3, 4, 4, 5, {}, {0, 1, 2, 3});
   EnumerateListExecutor testee(fetcher, infos);
-  // Use this instead of std::ignore, so the tests will be noticed and
-  // updated when someone changes the stats type in the return value of
-  // EnumerateListExecutor::produceRows().
-  NoStats stats{};
-
-  OutputAqlItemRow result{std::move(block), infos.getOutputRegisters(),
-                          infos.registersToKeep(), infos.registersToClear()};
-
-  // like the test above, except now two rows of input
-  // are available
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::WAITING);
-  ASSERT_FALSE(result.produced());
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(result.produced());
-
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(result.produced());
-
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(result.produced());
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::WAITING);
-  ASSERT_TRUE(result.produced());
-
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(result.produced());
+  SharedAqlItemBlockPtr inBlock =
+      buildBlock<4>(itemBlockManager, {{{{1}, {2}, {3}, {R"([true, 1, 2])"}}},
+                                       {{{1}, {2}, {3}, {R"([true, 1, 2])"}}}});
+
+  AqlItemBlockInputRange input{ExecutorState::DONE, inBlock, 0, inBlock->size()};
+  OutputAqlItemRow output(std::move(block), infos.getOutputRegisters(),
+                          infos.registersToKeep(), infos.registersToClear());
+
+  // receive 6 of 6 results in total
+  AqlCall myCall{0, AqlCall::Infinity{}, 6, false};
+
+  output.setCall(std::move(myCall));
+  EXPECT_EQ(output.numRowsWritten(), 0);
+  {
+    // reach the end (edge) of our second row, check that we do not return DONE here!
+    auto const [state, stats, call] = testee.produceRows(input, output);
+    EXPECT_EQ(state, ExecutorState::DONE);
+    EXPECT_EQ(output.numRowsWritten(), 6);
+  }
+}
 
-  result.advanceRow();
+// new framework tests
+using EnumerateListTestHelper = ExecutorTestHelper<EnumerateListExecutor, 1, 1>;
+using EnumerateListSplitType = EnumerateListTestHelper::SplitType;
 
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(result.produced());
+class EnumerateListExecutorTestProduce
+    : public ::testing::TestWithParam<std::tuple<EnumerateListSplitType>> {
+ protected:
+  ResourceMonitor monitor;
+  AqlItemBlockManager itemBlockManager;
+
+  mocks::MockAqlServer server;
+  std::unique_ptr<arangodb::aql::Query> fakedQuery;
+  EnumerateListExecutorInfos infos;
+
+  SharedAqlItemBlockPtr block;
+  NoStats stats;
+
+  EnumerateListExecutorTestProduce()
+      : itemBlockManager(&monitor, SerializationFormat::SHADOWROWS),
+        fakedQuery(server.createFakeQuery()),
+        infos(0, 1, 1, 2, {}, {0}) {
+    auto engine =
+        std::make_unique<ExecutionEngine>(*fakedQuery, SerializationFormat::SHADOWROWS);
+    fakedQuery->setEngine(engine.release());
+  }
+
+  auto makeInfos(RegisterId inputRegister = 0, RegisterId outputRegister = 1,
+                 RegisterId nrInputRegister = 1, RegisterId nrOutputRegister = 2,
+                 std::unordered_set<RegisterId> regToClear = {},
+                 std::unordered_set<RegisterId> regToKeep = {0}) -> EnumerateListExecutorInfos {
+    EnumerateListExecutorInfos infos{inputRegister,   outputRegister,
+                                     nrInputRegister, nrOutputRegister,
+                                     regToClear,      regToKeep};
+    block = SharedAqlItemBlockPtr{new AqlItemBlock(itemBlockManager, 1000, nrOutputRegister)};
+    return infos;
+  }
+};
 
-  result.advanceRow();
+TEST_P(EnumerateListExecutorTestProduce, empty_array_1) {
+  auto [split] = GetParam();
+
+  ExecutorTestHelper<EnumerateListExecutor, 1, 1>(*fakedQuery)
+      .setInputValue({{{R"([])"}}})
+      .setInputSplitType(split)
+      .expectOutput({}, {})
+      .setCall(AqlCall{0, AqlCall::Infinity{}, AqlCall::Infinity{}, false})
+      .expectSkipped(0)
+      .expectedState(ExecutionState::DONE)
+      .run(makeInfos());
+}
 
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_TRUE(result.produced());
+TEST_P(EnumerateListExecutorTestProduce, invalid_value_1) {
+  auto [split] = GetParam();
+
+  try {
+    ExecutorTestHelper<EnumerateListExecutor, 1, 1>(*fakedQuery)
+        .setInputValue({{1}})
+        .setInputSplitType(split)
+        .setCall(AqlCall{0, AqlCall::Infinity{}, AqlCall::Infinity{}, false})
+        .expectOutput({}, {})
+        .expectSkipped(0)
+        .expectedState(ExecutionState::DONE)
+        .run(makeInfos());
+    FAIL();
+  } catch (const arangodb::basics::Exception& e) {
+    ASSERT_EQ(e.code(), 1563);
+  }
+}
 
-  result.advanceRow();
+TEST_P(EnumerateListExecutorTestProduce, default_1) {
+  auto [split] = GetParam();
+
+  ExecutorTestHelper<EnumerateListExecutor, 1, 1>(*fakedQuery)
+      .setInputValue({{{R"([1, 1, 2])"}}})
+      .setInputSplitType(split)
+      .setCall(AqlCall{0, AqlCall::Infinity{}, AqlCall::Infinity{}, false})
+      .expectOutput({1}, {{1}, {1}, {2}})
+      .expectSkipped(0)
+      .expectedState(ExecutionState::DONE)
+      .run(makeInfos());
+}
 
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(result.produced());
+TEST_P(EnumerateListExecutorTestProduce, offset_1) {
+  auto [split] = GetParam();
+
+  ExecutorTestHelper<EnumerateListExecutor>(*fakedQuery)
+      .setInputValue({{{R"([1, 2, 3, 4, 5, 6, 7, 8, 9, 10])"}}})
+      .setInputSplitType(split)
+      .setCall(AqlCall{5, AqlCall::Infinity{}, AqlCall::Infinity{}, false})
+      .expectOutput({1}, {{6}, {7}, {8}, {9}, {10}})
+      .expectSkipped(5)
+      .expectedState(ExecutionState::DONE)
+      .run(makeInfos());
+}
 
-  block = result.stealBlock();
-  bool mustDestroy = false;
+TEST_P(EnumerateListExecutorTestProduce, offset_2) {
+  auto [split] = GetParam();
+
+  ExecutorTestHelper<EnumerateListExecutor>(*fakedQuery)
+      .setInputValue({{{R"([1, 2, 3, 4, 5, 6, 7, 8, 9, 10])"}}})
+      .setInputSplitType(split)
+      .setCall(AqlCall{3, AqlCall::Infinity{}, 2, false})
+      .expectOutput({1}, {{4}, {5}})
+      .expectSkipped(3)
+      .expectedState(ExecutionState::DONE)
+      .run(makeInfos());
+}
 
-  // first row
-  AqlValue v = block->getValue(0, 0);
-  ASSERT_TRUE(v.isNumber());
-  int64_t number = v.toInt64();
-  ASSERT_EQ(number, 1);
+TEST_P(EnumerateListExecutorTestProduce, offset_3) {
+  auto [split] = GetParam();
+
+  ExecutorTestHelper<EnumerateListExecutor>(*fakedQuery)
+      .setInputValue({{{R"([1, 2, 3, 4, 5, 6, 7, 8, 9, 10])"}}})
+      .setInputSplitType(split)
+      .setCall(AqlCall{7, AqlCall::Infinity{}, 3, false})
+      .expectOutput({1}, {{8}, {9}, {10}})
+      .expectSkipped(7)
+      .expectedState(ExecutionState::DONE)
+      .run(makeInfos());
+}
 
-  v = block->getValue(1, 0);
-  ASSERT_TRUE(v.isNumber());
-  number = v.toInt64();
-  ASSERT_EQ(number, 1);
+TEST_P(EnumerateListExecutorTestProduce, offset_4) {
+  auto [split] = GetParam();
+
+  ExecutorTestHelper<EnumerateListExecutor>(*fakedQuery)
+      .setInputValue({{{R"([1, 2, 3, 4, 5, 6, 7, 8, 9, 10])"}}})
+      .setInputSplitType(split)
+      .setCall(AqlCall{5, AqlCall::Infinity{}, 2, true})
+      .expectOutput({1}, {{6}, {7}})
+      .expectSkipped(8)
+      .expectedState(ExecutionState::DONE)
+      .run(makeInfos());
+}
 
-  v = block->getValue(1, 1);
-  ASSERT_TRUE(v.isNumber());
-  number = v.toInt64();
-  ASSERT_EQ(number, 2);
+TEST_P(EnumerateListExecutorTestProduce, offset_5) {
+  auto [split] = GetParam();
+
+  ExecutorTestHelper<EnumerateListExecutor>(*fakedQuery)
+      .setInputValue({{{R"([1, 2, 3, 4, 5, 6, 7, 8, 9, 10])"}}})
+      .setInputSplitType(split)
+      .setCall(AqlCall{7, AqlCall::Infinity{}, 3, true})
+      .expectOutput({1}, {{8}, {9}, {10}})
+      .expectSkipped(7)
+      .expectedState(ExecutionState::DONE)
+      .run(makeInfos());
+}
 
-  v = block->getValue(1, 2);
-  ASSERT_TRUE(v.isNumber());
-  number = v.toInt64();
-  ASSERT_EQ(number, 3);
+TEST_P(EnumerateListExecutorTestProduce, default_multiple_1) {
+  auto [split] = GetParam();
+
+  ExecutorTestHelper<EnumerateListExecutor, 4, 5>(*fakedQuery)
+      .setInputValue({{1, 2, 3, R"([1, 2, 3])"}})
+      .setInputSplitType(split)
+      .setCall(AqlCall{0, AqlCall::Infinity{}, AqlCall::Infinity{}, false})
+      .expectOutput({0, 1, 2, 3, 4}, {{RowBuilder<5>{1, 2, 3, R"([1, 2, 3])", 1},
+                                       RowBuilder<5>{1, 2, 3, R"([1, 2, 3])", 2},
+                                       RowBuilder<5>{1, 2, 3, R"([1, 2, 3])", 3}}})
+      .expectSkipped(0)
+      .expectedState(ExecutionState::DONE)
+      .run(makeInfos(3, 4, 4, 5, {}, {0, 1, 2, 3}));
+}
 
-  v = block->getValue(1, 3);
-  ASSERT_TRUE(v.isArray());
-  ASSERT_TRUE(v.at(0, mustDestroy, false).toBoolean());
-  ASSERT_TRUE(v.at(1, mustDestroy, false).toBoolean());
-  ASSERT_TRUE(v.at(2, mustDestroy, false).toBoolean());
+TEST_P(EnumerateListExecutorTestProduce, default_multiple_2) {
+  auto [split] = GetParam();
+
+  ExecutorTestHelper<EnumerateListExecutor, 4, 5>(*fakedQuery)
+      .setInputValue({RowBuilder<4>{1, 2, 3, R"([1, 2, 3])"},
+                      RowBuilder<4>{1, 2, 3, R"([4, 5, 6])"}})
+      .setInputSplitType(split)
+      .setCall(AqlCall{0, AqlCall::Infinity{}, AqlCall::Infinity{}, false})
+      .expectOutput({0, 1, 2, 3, 4}, {{RowBuilder<5>{1, 2, 3, R"([1, 2, 3])", 1},
+                                       RowBuilder<5>{1, 2, 3, R"([1, 2, 3])", 2},
+                                       RowBuilder<5>{1, 2, 3, R"([1, 2, 3])", 3},
+                                       RowBuilder<5>{1, 2, 3, R"([4, 5, 6])", 4},
+                                       RowBuilder<5>{1, 2, 3, R"([4, 5, 6])", 5},
+                                       RowBuilder<5>{1, 2, 3, R"([4, 5, 6])", 6}}})
+      .expectSkipped(0)
+      .expectedState(ExecutionState::DONE)
+      .run(makeInfos(3, 4, 4, 5, {}, {0, 1, 2, 3}));
+}
 
-  v = block->getValue(1, 4);
-  ASSERT_TRUE(v.isBoolean());
-  ASSERT_TRUE(v.toBoolean());
+TEST_P(EnumerateListExecutorTestProduce, default_border_first_array_soft) {
+  auto [split] = GetParam();
+
+  ExecutorTestHelper<EnumerateListExecutor, 4, 5>(*fakedQuery)
+      .setInputValue({RowBuilder<4>{1, 2, 3, R"([1, 2, 3])"},
+                      RowBuilder<4>{1, 2, 3, R"([4, 5, 6])"}})
+      .setInputSplitType(split)
+      .setCall(AqlCall{0, 3, AqlCall::Infinity{}, false})
+      .expectOutput({0, 1, 2, 3, 4}, {{RowBuilder<5>{1, 2, 3, R"([1, 2, 3])", 1},
+                                       RowBuilder<5>{1, 2, 3, R"([1, 2, 3])", 2},
+                                       RowBuilder<5>{1, 2, 3, R"([1, 2, 3])", 3}}})
+      .expectSkipped(0)
+      .expectedState(ExecutionState::HASMORE)  // hasmore because of softLimit
+      .run(makeInfos(3, 4, 4, 5, {}, {0, 1, 2, 3}));
+}
 
-  // second row
-  v = block->getValue(2, 0);
-  ASSERT_TRUE(v.isNumber());
-  number = v.toInt64();
-  ASSERT_EQ(number, 1);
+TEST_P(EnumerateListExecutorTestProduce, default_border_first_array_hard) {
+  auto [split] = GetParam();
+
+  ExecutorTestHelper<EnumerateListExecutor, 4, 5>(*fakedQuery)
+      .setInputValue({RowBuilder<4>{1, 2, 3, R"([1, 2, 3])"},
+                      RowBuilder<4>{1, 2, 3, R"([4, 5, 6])"}})
+      .setInputSplitType(split)
+      .setCall(AqlCall{0, AqlCall::Infinity{}, 3, false})
+      .expectOutput({0, 1, 2, 3, 4}, {{RowBuilder<5>{1, 2, 3, R"([1, 2, 3])", 1},
+                                       RowBuilder<5>{1, 2, 3, R"([1, 2, 3])", 2},
+                                       RowBuilder<5>{1, 2, 3, R"([1, 2, 3])", 3}}})
+      .expectSkipped(0)
+      .expectedState(ExecutionState::DONE)  // done because of hardLimit
+      .run(makeInfos(3, 4, 4, 5, {}, {0, 1, 2, 3}));
+}
 
-  v = block->getValue(2, 1);
-  ASSERT_TRUE(v.isNumber());
-  number = v.toInt64();
-  ASSERT_EQ(number, 2);
+TEST_P(EnumerateListExecutorTestProduce, default_border_first_array_hard_fullcount) {
+  auto [split] = GetParam();
+
+  ExecutorTestHelper<EnumerateListExecutor, 4, 5>(*fakedQuery)
+      .setInputValue({RowBuilder<4>{1, 2, 3, R"([1, 2, 3])"},
+                      RowBuilder<4>{1, 2, 3, R"([4, 5, 6])"}})
+      .setInputSplitType(split)
+      .setCall(AqlCall{0, AqlCall::Infinity{}, 3, true})
+      .expectOutput({0, 1, 2, 3, 4}, {{RowBuilder<5>{1, 2, 3, R"([1, 2, 3])", 1},
+                                       RowBuilder<5>{1, 2, 3, R"([1, 2, 3])", 2},
+                                       RowBuilder<5>{1, 2, 3, R"([1, 2, 3])", 3}}})
+      .expectSkipped(3)  // skipped amount of 3 in the fullCount phase
+      .expectedState(ExecutionState::DONE)
+      .run(makeInfos(3, 4, 4, 5, {}, {0, 1, 2, 3}));
+}
 
-  v = block->getValue(2, 2);
-  ASSERT_TRUE(v.isNumber());
-  number = v.toInt64();
-  ASSERT_EQ(number, 3);
+template <size_t... vs>
+const EnumerateListSplitType splitIntoBlocks =
+    EnumerateListSplitType{std::vector<std::size_t>{vs...}};
+template <size_t step>
+const EnumerateListSplitType splitStep = EnumerateListSplitType{step};
 
-  v = block->getValue(2, 3);
-  ASSERT_TRUE(v.isArray());
-  ASSERT_TRUE(v.at(0, mustDestroy, false).toBoolean());
-  ASSERT_TRUE(v.at(1, mustDestroy, false).toBoolean());
-  ASSERT_TRUE(v.at(2, mustDestroy, false).toBoolean());
+INSTANTIATE_TEST_CASE_P(EnumerateListExecutor, EnumerateListExecutorTestProduce,
+                        ::testing::Values(splitIntoBlocks<2, 3>,
+                                          splitIntoBlocks<3, 4>, splitStep<2>));
 
-  v = block->getValue(2, 4);
-  ASSERT_TRUE(v.isBoolean());
-  ASSERT_TRUE(v.toBoolean());
-}
+// namespace aql
 
 }  // namespace aql
 }  // namespace tests
diff --git a/tests/js/common/shell/shell-statement-encoding-noncluster.js b/tests/js/common/shell/shell-statement-encoding-noncluster.js
index 6687d0acaa01..ed7fe34325e0 100644
--- a/tests/js/common/shell/shell-statement-encoding-noncluster.js
+++ b/tests/js/common/shell/shell-statement-encoding-noncluster.js
@@ -96,7 +96,7 @@ function StatementResultEncodingSuite () {
     testQueryAttribute : function () {
       var results = db._query("FOR t IN UnitTestsShellStatement " + 
         "LET l = (FOR x IN t.alternateName FILTER x.`@language` == 'bn' RETURN x) " + 
-        "RETURN { name: t.name, alternateName: l }").toArray();
+        "RETURN { name: t.name, alternateName: l }", {}, {profile: 3}).toArray();
       var map = { };
       results.forEach(function(result) {
         delete result._key;

From 6d6edc984b106c53ca4d66893901034a439ac066 Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Thu, 20 Feb 2020 10:42:24 +0100
Subject: [PATCH 069/122] Feature/aql subquery execution block impl execute
 implementation inject stack into fetcher (#11124)

* Added api to pass through the stack to the dependencyProxy. THis is just temporary and doomed to be removed as soon as API is completed.

* Let depdendency Proxy forward the Stack. This may not work in all cases.

* Default implement Assignment constructor.

* Removed Query jenkins debug output again

* Fixed forwarding of stack in skipSome
---
 arangod/Aql/AllRowsFetcher.cpp                |  5 ++
 arangod/Aql/AllRowsFetcher.h                  |  6 +-
 arangod/Aql/AqlCallStack.h                    |  2 +
 arangod/Aql/ConstFetcher.h                    |  3 +
 arangod/Aql/DependencyProxy.cpp               | 80 ++++++++++++++++---
 arangod/Aql/DependencyProxy.h                 | 10 ++-
 arangod/Aql/ExecutionBlockImpl.cpp            |  1 +
 .../Aql/MultiDependencySingleRowFetcher.cpp   |  8 +-
 arangod/Aql/MultiDependencySingleRowFetcher.h |  8 +-
 arangod/Aql/SingleRowFetcher.cpp              |  6 ++
 arangod/Aql/SingleRowFetcher.h                |  3 +
 etc/testing/arangod-common.conf               |  1 -
 12 files changed, 114 insertions(+), 19 deletions(-)

diff --git a/arangod/Aql/AllRowsFetcher.cpp b/arangod/Aql/AllRowsFetcher.cpp
index 06daba611938..117deb8ae799 100644
--- a/arangod/Aql/AllRowsFetcher.cpp
+++ b/arangod/Aql/AllRowsFetcher.cpp
@@ -254,3 +254,8 @@ std::pair<ExecutionState, ShadowAqlItemRow> AllRowsFetcher::fetchShadowRow(size_
 
   return {state, row};
 }
+
+//@deprecated
+auto AllRowsFetcher::useStack(AqlCallStack const& stack) -> void {
+  _dependencyProxy->useStack(stack);
+}
\ No newline at end of file
diff --git a/arangod/Aql/AllRowsFetcher.h b/arangod/Aql/AllRowsFetcher.h
index 06051e477595..adfe5a402817 100644
--- a/arangod/Aql/AllRowsFetcher.h
+++ b/arangod/Aql/AllRowsFetcher.h
@@ -179,8 +179,10 @@ class AllRowsFetcher {
   ExecutionState upstreamState();
 
   // NOLINTNEXTLINE google-default-arguments
-  std::pair<ExecutionState, ShadowAqlItemRow> fetchShadowRow(
-      size_t atMost = ExecutionBlock::DefaultBatchSize);
+  std::pair<ExecutionState, ShadowAqlItemRow> fetchShadowRow(size_t atMost = ExecutionBlock::DefaultBatchSize);
+
+  //@deprecated
+  auto useStack(AqlCallStack const& stack) -> void;
 
  private:
   DependencyProxy<BlockPassthrough::Disable>* _dependencyProxy;
diff --git a/arangod/Aql/AqlCallStack.h b/arangod/Aql/AqlCallStack.h
index 214de85d1e4d..b4af03eec652 100644
--- a/arangod/Aql/AqlCallStack.h
+++ b/arangod/Aql/AqlCallStack.h
@@ -39,6 +39,8 @@ class AqlCallStack {
   // Used to pass between blocks
   AqlCallStack(AqlCallStack const& other);
 
+  AqlCallStack& operator=(AqlCallStack const& other) = default;
+
   // Quick test is this CallStack is of local relevance, or it is sufficient to pass it through
   bool isRelevant() const;
 
diff --git a/arangod/Aql/ConstFetcher.h b/arangod/Aql/ConstFetcher.h
index 46b9ec73667d..70fe73fa4c12 100644
--- a/arangod/Aql/ConstFetcher.h
+++ b/arangod/Aql/ConstFetcher.h
@@ -107,6 +107,9 @@ class ConstFetcher {
   // NOLINTNEXTLINE google-default-arguments
   std::pair<ExecutionState, ShadowAqlItemRow> fetchShadowRow(size_t atMost = 1) const;
 
+  //@deprecated
+  auto useStack(AqlCallStack const& stack) -> void{};
+
  private:
   /**
    * @brief Input block currently in use. Used for memory management by the
diff --git a/arangod/Aql/DependencyProxy.cpp b/arangod/Aql/DependencyProxy.cpp
index 63f6ba51d140..5d16d05dd4e6 100644
--- a/arangod/Aql/DependencyProxy.cpp
+++ b/arangod/Aql/DependencyProxy.cpp
@@ -82,18 +82,29 @@ ExecutionState DependencyProxy<blockPassthrough>::prefetchBlock(size_t atMost) {
   TRI_ASSERT(atMost > 0);
   ExecutionState state;
   SharedAqlItemBlockPtr block;
+
+  // Temporary.
+  // Just do a copy of the stack here to not mess with it.
+  AqlCallStack stack = _injectedStack;
+  stack.pushCall(AqlCall::SimulateGetSome(atMost));
+  // Also temporary, will not be used here.
+  size_t skipped = 0;
   do {
     // Note: upstreamBlock will return next dependency
     // if we need to loop here
     if (_distributeId.empty()) {
-      std::tie(state, block) = upstreamBlock().getSome(atMost);
+      std::tie(state, skipped, block) = upstreamBlock().execute(stack);
     } else {
       auto upstreamWithClient = dynamic_cast<BlocksWithClients*>(&upstreamBlock());
-      std::tie(state, block) = upstreamWithClient->getSomeForShard(atMost, _distributeId);
+      std::tie(state, skipped, block) =
+          upstreamWithClient->executeForClient(stack, _distributeId);
     }
     TRI_IF_FAILURE("ExecutionBlock::getBlock") {
       THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
     }
+    // Cannot do skipping here
+    // Temporary!
+    TRI_ASSERT(skipped == 0);
 
     if (state == ExecutionState::WAITING) {
       TRI_ASSERT(block == nullptr);
@@ -162,13 +173,22 @@ DependencyProxy<blockPassthrough>::fetchBlockForDependency(size_t dependency, si
   TRI_ASSERT(atMost > 0);
   ExecutionState state;
   SharedAqlItemBlockPtr block;
+
+  // Temporary.
+  // Just do a copy of the stack here to not mess with it.
+  AqlCallStack stack = _injectedStack;
+  stack.pushCall(AqlCall::SimulateGetSome(atMost));
+  // Also temporary, will not be used here.
+  size_t skipped = 0;
+
   if (_distributeId.empty()) {
-    std::tie(state, block) = upstream.getSome(atMost);
+    std::tie(state, skipped, block) = upstream.execute(stack);
   } else {
     auto upstreamWithClient = dynamic_cast<BlocksWithClients*>(&upstream);
-    std::tie(state, block) = upstreamWithClient->getSomeForShard(atMost, _distributeId);
+    std::tie(state, skipped, block) =
+        upstreamWithClient->executeForClient(stack, _distributeId);
   }
-
+  TRI_ASSERT(skipped == 0);
   TRI_IF_FAILURE("ExecutionBlock::getBlock") {
     THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
   }
@@ -205,14 +225,31 @@ std::pair<ExecutionState, size_t> DependencyProxy<blockPassthrough>::skipSomeFor
 
   ExecutionState state = ExecutionState::HASMORE;
 
+  // Temporary.
+  // Just do a copy of the stack here to not mess with it.
+  AqlCallStack stack = _injectedStack;
+  stack.pushCall(AqlCall::SimulateSkipSome(atMost));
+  // Also temporary, will not be used here.
+  SharedAqlItemBlockPtr block;
+
   while (state == ExecutionState::HASMORE && _skipped < atMost) {
     size_t skippedNow;
     TRI_ASSERT(_skipped <= atMost);
-    std::tie(state, skippedNow) = upstream.skipSome(atMost - _skipped);
+    {
+      // Make sure we call with the correct offset
+      // This is just a temporary dance until execute is implemented everywhere.
+      auto tmpCall = stack.popCall();
+      tmpCall.offset = atMost - _skipped;
+      stack.pushCall(std::move(tmpCall));
+    }
+    std::tie(state, skippedNow, block) = upstream.execute(stack);
     if (state == ExecutionState::WAITING) {
       TRI_ASSERT(skippedNow == 0);
       return {state, 0};
     }
+    // Temporary.
+    // If we return a block here it will be lost
+    TRI_ASSERT(block == nullptr);
 
     _skipped += skippedNow;
     TRI_ASSERT(_skipped <= atMost);
@@ -234,17 +271,31 @@ std::pair<ExecutionState, size_t> DependencyProxy<blockPassthrough>::skipSome(si
   TRI_ASSERT(_skipped <= toSkip);
   ExecutionState state = ExecutionState::HASMORE;
 
+  // Temporary.
+  // Just do a copy of the stack here to not mess with it.
+  AqlCallStack stack = _injectedStack;
+  stack.pushCall(AqlCall::SimulateSkipSome(toSkip));
+  // Also temporary, will not be used here.
+  SharedAqlItemBlockPtr block;
+
   while (_skipped < toSkip) {
     size_t skippedNow;
     // Note: upstreamBlock will return next dependency
     // if we need to loop here
     TRI_ASSERT(_skipped <= toSkip);
+    {
+      // Make sure we call with the correct offset
+      // This is just a temporary dance until execute is implemented everywhere.
+      auto tmpCall = stack.popCall();
+      tmpCall.offset = toSkip - _skipped;
+      stack.pushCall(std::move(tmpCall));
+    }
     if (_distributeId.empty()) {
-      std::tie(state, skippedNow) = upstreamBlock().skipSome(toSkip - _skipped);
+      std::tie(state, skippedNow, block) = upstreamBlock().execute(stack);
     } else {
       auto upstreamWithClient = dynamic_cast<BlocksWithClients*>(&upstreamBlock());
-      std::tie(state, skippedNow) =
-          upstreamWithClient->skipSomeForShard(toSkip - _skipped, _distributeId);
+      std::tie(state, skippedNow, block) =
+          upstreamWithClient->executeForClient(stack, _distributeId);
     }
 
     TRI_ASSERT(skippedNow <= toSkip - _skipped);
@@ -254,6 +305,10 @@ std::pair<ExecutionState, size_t> DependencyProxy<blockPassthrough>::skipSome(si
       return {state, 0};
     }
 
+    // Temporary.
+    // If we return a block here it will be lost
+    TRI_ASSERT(block == nullptr);
+
     _skipped += skippedNow;
 
     // When the current dependency is done, advance.
@@ -312,7 +367,12 @@ DependencyProxy<blockPassthrough>::DependencyProxy(
       _blockPassThroughQueue(),
       _currentDependency(0),
       _skipped(0),
-      _vpackOptions(options) {}
+      _vpackOptions(options),
+      _injectedStack(AqlCall{}) {
+  // Make the default stack usable, for tests only.
+  // This needs to be removed soon.
+  _injectedStack.popCall();
+}
 
 template <BlockPassthrough blockPassthrough>
 RegisterId DependencyProxy<blockPassthrough>::getNrInputRegisters() const {
diff --git a/arangod/Aql/DependencyProxy.h b/arangod/Aql/DependencyProxy.h
index 7779c922ef41..c66011845512 100644
--- a/arangod/Aql/DependencyProxy.h
+++ b/arangod/Aql/DependencyProxy.h
@@ -23,6 +23,7 @@
 #ifndef ARANGOD_AQL_BLOCK_FETCHER_H
 #define ARANGOD_AQL_BLOCK_FETCHER_H
 
+#include "Aql/AqlCallStack.h"
 #include "Aql/ExecutionBlock.h"
 #include "Aql/ExecutionState.h"
 #include "Aql/SharedAqlItemBlockPtr.h"
@@ -68,8 +69,7 @@ class DependencyProxy {
   DependencyProxy(std::vector<ExecutionBlock*> const& dependencies,
                   AqlItemBlockManager& itemBlockManager,
                   std::shared_ptr<std::unordered_set<RegisterId> const> inputRegisters,
-                  RegisterId nrInputRegisters,
-                  velocypack::Options const*);
+                  RegisterId nrInputRegisters, velocypack::Options const*);
 
   TEST_VIRTUAL ~DependencyProxy() = default;
 
@@ -115,6 +115,9 @@ class DependencyProxy {
 
   [[nodiscard]] velocypack::Options const* velocypackOptions() const noexcept;
 
+  //@deprecated
+  auto useStack(AqlCallStack stack) -> void { _injectedStack = stack; }
+
  protected:
   [[nodiscard]] AqlItemBlockManager& itemBlockManager();
   [[nodiscard]] AqlItemBlockManager const& itemBlockManager() const;
@@ -141,6 +144,9 @@ class DependencyProxy {
   size_t _currentDependency;
   size_t _skipped;
   velocypack::Options const* const _vpackOptions;
+
+  // @deprecated
+  AqlCallStack _injectedStack;
 };
 
 }  // namespace arangodb::aql
diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index 1cb86283cf7d..031907416678 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -619,6 +619,7 @@ std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> ExecutionBlockImpl<Exe
   auto myCall = stack.popCall();
   TRI_ASSERT(AqlCall::IsSkipSomeCall(myCall) ||
              AqlCall::IsGetSomeCall(myCall) || AqlCall::IsFullCountCall(myCall));
+  _rowFetcher.useStack(stack);
   if (AqlCall::IsSkipSomeCall(myCall)) {
     auto const [state, skipped] = skipSome(myCall.getOffset());
     if (state != ExecutionState::WAITING) {
diff --git a/arangod/Aql/MultiDependencySingleRowFetcher.cpp b/arangod/Aql/MultiDependencySingleRowFetcher.cpp
index 38a6762e8f07..de7f043db13b 100644
--- a/arangod/Aql/MultiDependencySingleRowFetcher.cpp
+++ b/arangod/Aql/MultiDependencySingleRowFetcher.cpp
@@ -290,7 +290,8 @@ bool MultiDependencySingleRowFetcher::isLastRowInBlock(
 
 bool MultiDependencySingleRowFetcher::noMoreDataRows(
     const MultiDependencySingleRowFetcher::DependencyInfo& info) const {
-  return (isDone(info) && !indexIsValid(info)) || (indexIsValid(info) && isAtShadowRow(info));
+  return (isDone(info) && !indexIsValid(info)) ||
+         (indexIsValid(info) && isAtShadowRow(info));
 }
 
 std::pair<ExecutionState, size_t> MultiDependencySingleRowFetcher::preFetchNumberOfRowsForDependency(
@@ -354,3 +355,8 @@ bool MultiDependencySingleRowFetcher::fetchBlockIfNecessary(size_t const depende
   }
   return true;
 }
+
+//@deprecated
+auto MultiDependencySingleRowFetcher::useStack(AqlCallStack const& stack) -> void {
+  _dependencyProxy->useStack(stack);
+}
\ No newline at end of file
diff --git a/arangod/Aql/MultiDependencySingleRowFetcher.h b/arangod/Aql/MultiDependencySingleRowFetcher.h
index 6889e7060fa4..fd17efc44f6d 100644
--- a/arangod/Aql/MultiDependencySingleRowFetcher.h
+++ b/arangod/Aql/MultiDependencySingleRowFetcher.h
@@ -129,8 +129,10 @@ class MultiDependencySingleRowFetcher {
 
   std::pair<ExecutionState, size_t> skipRowsForDependency(size_t dependency, size_t atMost);
 
-  std::pair<ExecutionState, ShadowAqlItemRow> fetchShadowRow(
-      size_t atMost = ExecutionBlock::DefaultBatchSize);
+  std::pair<ExecutionState, ShadowAqlItemRow> fetchShadowRow(size_t atMost = ExecutionBlock::DefaultBatchSize);
+
+  //@deprecated
+  auto useStack(AqlCallStack const& stack) -> void;
 
  private:
   DependencyProxy<BlockPassthrough::Disable>* _dependencyProxy;
@@ -165,7 +167,7 @@ class MultiDependencySingleRowFetcher {
    * subquery level. If it returns false, there may or may not be more.
    */
   bool noMoreDataRows(DependencyInfo const& info) const;
-  
+
   bool isAtShadowRow(DependencyInfo const& info) const;
 
   bool fetchBlockIfNecessary(const size_t dependency, const size_t atMost);
diff --git a/arangod/Aql/SingleRowFetcher.cpp b/arangod/Aql/SingleRowFetcher.cpp
index db6f14d7ba65..0043efd86771 100644
--- a/arangod/Aql/SingleRowFetcher.cpp
+++ b/arangod/Aql/SingleRowFetcher.cpp
@@ -278,5 +278,11 @@ template std::pair<ExecutionState, SharedAqlItemBlockPtr>
 SingleRowFetcher<BlockPassthrough::Enable>::fetchBlockForPassthrough<BlockPassthrough::Enable, void>(size_t atMost);
 #endif
 
+//@deprecated
+template <BlockPassthrough blockPassthrough>
+auto SingleRowFetcher<blockPassthrough>::useStack(AqlCallStack const& stack) -> void {
+  _dependencyProxy->useStack(stack);
+}
+
 template class ::arangodb::aql::SingleRowFetcher<BlockPassthrough::Disable>;
 template class ::arangodb::aql::SingleRowFetcher<BlockPassthrough::Enable>;
diff --git a/arangod/Aql/SingleRowFetcher.h b/arangod/Aql/SingleRowFetcher.h
index ef98004b4084..e33717eff395 100644
--- a/arangod/Aql/SingleRowFetcher.h
+++ b/arangod/Aql/SingleRowFetcher.h
@@ -138,6 +138,9 @@ class SingleRowFetcher {
   [[nodiscard]] bool isAtShadowRow() const;
 #endif
 
+  //@deprecated
+  auto useStack(AqlCallStack const& stack) -> void;
+
  private:
   DependencyProxy<blockPassthrough>* _dependencyProxy;
 
diff --git a/etc/testing/arangod-common.conf b/etc/testing/arangod-common.conf
index 89fd87728211..b664b6edb9d2 100644
--- a/etc/testing/arangod-common.conf
+++ b/etc/testing/arangod-common.conf
@@ -3,7 +3,6 @@ line-number = false
 force-direct = false
 level = info
 level = replication=warn
-level = queries=debug
 role = true
 
 [database]

From 207795831f7458d5437cea81323646651bd8e1cc Mon Sep 17 00:00:00 2001
From: Markus Pfeiffer <markuspf@users.noreply.github.com>
Date: Thu, 20 Feb 2020 15:51:47 +0000
Subject: [PATCH 070/122] Tweak ExecutorTestHelper to test pipelines (#11079)

* Tweak ExecutorTestHelper to test pipelines

* Modifications

* Fixup tests

* Address some comments

* Fix.
---
 tests/Aql/EnumerateListExecutorTest.cpp | 67 ++++++++++++--------
 tests/Aql/ExecutorTestHelper.h          | 83 ++++++++++++++++++++++---
 tests/Aql/HashedCollectExecutorTest.cpp | 77 ++++++++++++++---------
 tests/Aql/IdExecutorTest.cpp            |  5 +-
 tests/Aql/ReturnExecutorTest.cpp        | 32 ++++++----
 tests/Aql/SortedCollectExecutorTest.cpp | 17 ++---
 6 files changed, 192 insertions(+), 89 deletions(-)

diff --git a/tests/Aql/EnumerateListExecutorTest.cpp b/tests/Aql/EnumerateListExecutorTest.cpp
index 6132aad39bb1..32048fc2a8b7 100644
--- a/tests/Aql/EnumerateListExecutorTest.cpp
+++ b/tests/Aql/EnumerateListExecutorTest.cpp
@@ -133,7 +133,7 @@ TEST_F(EnumerateListExecutorTest, test_check_state_second_row_border) {
 }
 
 // new framework tests
-using EnumerateListTestHelper = ExecutorTestHelper<EnumerateListExecutor, 1, 1>;
+using EnumerateListTestHelper = ExecutorTestHelper<1, 1>;
 using EnumerateListSplitType = EnumerateListTestHelper::SplitType;
 
 class EnumerateListExecutorTestProduce
@@ -173,28 +173,30 @@ class EnumerateListExecutorTestProduce
 TEST_P(EnumerateListExecutorTestProduce, empty_array_1) {
   auto [split] = GetParam();
 
-  ExecutorTestHelper<EnumerateListExecutor, 1, 1>(*fakedQuery)
+  ExecutorTestHelper<1, 1>(*fakedQuery)
+      .setExecBlock<EnumerateListExecutor>(makeInfos())
       .setInputValue({{{R"([])"}}})
       .setInputSplitType(split)
       .expectOutput({}, {})
       .setCall(AqlCall{0, AqlCall::Infinity{}, AqlCall::Infinity{}, false})
       .expectSkipped(0)
       .expectedState(ExecutionState::DONE)
-      .run(makeInfos());
+      .run();
 }
 
 TEST_P(EnumerateListExecutorTestProduce, invalid_value_1) {
   auto [split] = GetParam();
 
   try {
-    ExecutorTestHelper<EnumerateListExecutor, 1, 1>(*fakedQuery)
+    ExecutorTestHelper<1, 1>(*fakedQuery)
+        .setExecBlock<EnumerateListExecutor>(makeInfos())
         .setInputValue({{1}})
         .setInputSplitType(split)
         .setCall(AqlCall{0, AqlCall::Infinity{}, AqlCall::Infinity{}, false})
         .expectOutput({}, {})
         .expectSkipped(0)
         .expectedState(ExecutionState::DONE)
-        .run(makeInfos());
+        .run();
     FAIL();
   } catch (const arangodb::basics::Exception& e) {
     ASSERT_EQ(e.code(), 1563);
@@ -204,85 +206,92 @@ TEST_P(EnumerateListExecutorTestProduce, invalid_value_1) {
 TEST_P(EnumerateListExecutorTestProduce, default_1) {
   auto [split] = GetParam();
 
-  ExecutorTestHelper<EnumerateListExecutor, 1, 1>(*fakedQuery)
+  ExecutorTestHelper<1, 1>(*fakedQuery)
+      .setExecBlock<EnumerateListExecutor>(makeInfos())
       .setInputValue({{{R"([1, 1, 2])"}}})
       .setInputSplitType(split)
       .setCall(AqlCall{0, AqlCall::Infinity{}, AqlCall::Infinity{}, false})
       .expectOutput({1}, {{1}, {1}, {2}})
       .expectSkipped(0)
       .expectedState(ExecutionState::DONE)
-      .run(makeInfos());
+      .run();
 }
 
 TEST_P(EnumerateListExecutorTestProduce, offset_1) {
   auto [split] = GetParam();
 
-  ExecutorTestHelper<EnumerateListExecutor>(*fakedQuery)
+  ExecutorTestHelper(*fakedQuery)
+      .setExecBlock<EnumerateListExecutor>(makeInfos())
       .setInputValue({{{R"([1, 2, 3, 4, 5, 6, 7, 8, 9, 10])"}}})
       .setInputSplitType(split)
       .setCall(AqlCall{5, AqlCall::Infinity{}, AqlCall::Infinity{}, false})
       .expectOutput({1}, {{6}, {7}, {8}, {9}, {10}})
       .expectSkipped(5)
       .expectedState(ExecutionState::DONE)
-      .run(makeInfos());
+      .run();
 }
 
 TEST_P(EnumerateListExecutorTestProduce, offset_2) {
   auto [split] = GetParam();
 
-  ExecutorTestHelper<EnumerateListExecutor>(*fakedQuery)
+  ExecutorTestHelper(*fakedQuery)
+      .setExecBlock<EnumerateListExecutor>(makeInfos())
       .setInputValue({{{R"([1, 2, 3, 4, 5, 6, 7, 8, 9, 10])"}}})
       .setInputSplitType(split)
       .setCall(AqlCall{3, AqlCall::Infinity{}, 2, false})
       .expectOutput({1}, {{4}, {5}})
       .expectSkipped(3)
       .expectedState(ExecutionState::DONE)
-      .run(makeInfos());
+      .run();
 }
 
 TEST_P(EnumerateListExecutorTestProduce, offset_3) {
   auto [split] = GetParam();
 
-  ExecutorTestHelper<EnumerateListExecutor>(*fakedQuery)
+  ExecutorTestHelper(*fakedQuery)
+      .setExecBlock<EnumerateListExecutor>(makeInfos())
       .setInputValue({{{R"([1, 2, 3, 4, 5, 6, 7, 8, 9, 10])"}}})
       .setInputSplitType(split)
       .setCall(AqlCall{7, AqlCall::Infinity{}, 3, false})
       .expectOutput({1}, {{8}, {9}, {10}})
       .expectSkipped(7)
       .expectedState(ExecutionState::DONE)
-      .run(makeInfos());
+      .run();
 }
 
 TEST_P(EnumerateListExecutorTestProduce, offset_4) {
   auto [split] = GetParam();
 
-  ExecutorTestHelper<EnumerateListExecutor>(*fakedQuery)
+  ExecutorTestHelper(*fakedQuery)
+      .setExecBlock<EnumerateListExecutor>(makeInfos())
       .setInputValue({{{R"([1, 2, 3, 4, 5, 6, 7, 8, 9, 10])"}}})
       .setInputSplitType(split)
       .setCall(AqlCall{5, AqlCall::Infinity{}, 2, true})
       .expectOutput({1}, {{6}, {7}})
       .expectSkipped(8)
       .expectedState(ExecutionState::DONE)
-      .run(makeInfos());
+      .run();
 }
 
 TEST_P(EnumerateListExecutorTestProduce, offset_5) {
   auto [split] = GetParam();
 
-  ExecutorTestHelper<EnumerateListExecutor>(*fakedQuery)
+  ExecutorTestHelper(*fakedQuery)
+      .setExecBlock<EnumerateListExecutor>(makeInfos())
       .setInputValue({{{R"([1, 2, 3, 4, 5, 6, 7, 8, 9, 10])"}}})
       .setInputSplitType(split)
       .setCall(AqlCall{7, AqlCall::Infinity{}, 3, true})
       .expectOutput({1}, {{8}, {9}, {10}})
       .expectSkipped(7)
       .expectedState(ExecutionState::DONE)
-      .run(makeInfos());
+      .run();
 }
 
 TEST_P(EnumerateListExecutorTestProduce, default_multiple_1) {
   auto [split] = GetParam();
 
-  ExecutorTestHelper<EnumerateListExecutor, 4, 5>(*fakedQuery)
+  ExecutorTestHelper<4, 5>(*fakedQuery)
+      .setExecBlock<EnumerateListExecutor>(makeInfos(3, 4, 4, 5, {}, {0, 1, 2, 3}))
       .setInputValue({{1, 2, 3, R"([1, 2, 3])"}})
       .setInputSplitType(split)
       .setCall(AqlCall{0, AqlCall::Infinity{}, AqlCall::Infinity{}, false})
@@ -291,13 +300,14 @@ TEST_P(EnumerateListExecutorTestProduce, default_multiple_1) {
                                        RowBuilder<5>{1, 2, 3, R"([1, 2, 3])", 3}}})
       .expectSkipped(0)
       .expectedState(ExecutionState::DONE)
-      .run(makeInfos(3, 4, 4, 5, {}, {0, 1, 2, 3}));
+      .run();
 }
 
 TEST_P(EnumerateListExecutorTestProduce, default_multiple_2) {
   auto [split] = GetParam();
 
-  ExecutorTestHelper<EnumerateListExecutor, 4, 5>(*fakedQuery)
+  ExecutorTestHelper<4, 5>(*fakedQuery)
+      .setExecBlock<EnumerateListExecutor>(makeInfos(3, 4, 4, 5, {}, {0, 1, 2, 3}))
       .setInputValue({RowBuilder<4>{1, 2, 3, R"([1, 2, 3])"},
                       RowBuilder<4>{1, 2, 3, R"([4, 5, 6])"}})
       .setInputSplitType(split)
@@ -310,13 +320,14 @@ TEST_P(EnumerateListExecutorTestProduce, default_multiple_2) {
                                        RowBuilder<5>{1, 2, 3, R"([4, 5, 6])", 6}}})
       .expectSkipped(0)
       .expectedState(ExecutionState::DONE)
-      .run(makeInfos(3, 4, 4, 5, {}, {0, 1, 2, 3}));
+      .run();
 }
 
 TEST_P(EnumerateListExecutorTestProduce, default_border_first_array_soft) {
   auto [split] = GetParam();
 
-  ExecutorTestHelper<EnumerateListExecutor, 4, 5>(*fakedQuery)
+  ExecutorTestHelper<4, 5>(*fakedQuery)
+      .setExecBlock<EnumerateListExecutor>(makeInfos(3, 4, 4, 5, {}, {0, 1, 2, 3}))
       .setInputValue({RowBuilder<4>{1, 2, 3, R"([1, 2, 3])"},
                       RowBuilder<4>{1, 2, 3, R"([4, 5, 6])"}})
       .setInputSplitType(split)
@@ -326,13 +337,14 @@ TEST_P(EnumerateListExecutorTestProduce, default_border_first_array_soft) {
                                        RowBuilder<5>{1, 2, 3, R"([1, 2, 3])", 3}}})
       .expectSkipped(0)
       .expectedState(ExecutionState::HASMORE)  // hasmore because of softLimit
-      .run(makeInfos(3, 4, 4, 5, {}, {0, 1, 2, 3}));
+      .run();
 }
 
 TEST_P(EnumerateListExecutorTestProduce, default_border_first_array_hard) {
   auto [split] = GetParam();
 
-  ExecutorTestHelper<EnumerateListExecutor, 4, 5>(*fakedQuery)
+  ExecutorTestHelper<4, 5>(*fakedQuery)
+      .setExecBlock<EnumerateListExecutor>(makeInfos(3, 4, 4, 5, {}, {0, 1, 2, 3}))
       .setInputValue({RowBuilder<4>{1, 2, 3, R"([1, 2, 3])"},
                       RowBuilder<4>{1, 2, 3, R"([4, 5, 6])"}})
       .setInputSplitType(split)
@@ -342,13 +354,14 @@ TEST_P(EnumerateListExecutorTestProduce, default_border_first_array_hard) {
                                        RowBuilder<5>{1, 2, 3, R"([1, 2, 3])", 3}}})
       .expectSkipped(0)
       .expectedState(ExecutionState::DONE)  // done because of hardLimit
-      .run(makeInfos(3, 4, 4, 5, {}, {0, 1, 2, 3}));
+      .run();
 }
 
 TEST_P(EnumerateListExecutorTestProduce, default_border_first_array_hard_fullcount) {
   auto [split] = GetParam();
 
-  ExecutorTestHelper<EnumerateListExecutor, 4, 5>(*fakedQuery)
+  ExecutorTestHelper<4, 5>(*fakedQuery)
+      .setExecBlock<EnumerateListExecutor>(makeInfos(3, 4, 4, 5, {}, {0, 1, 2, 3}))
       .setInputValue({RowBuilder<4>{1, 2, 3, R"([1, 2, 3])"},
                       RowBuilder<4>{1, 2, 3, R"([4, 5, 6])"}})
       .setInputSplitType(split)
@@ -358,7 +371,7 @@ TEST_P(EnumerateListExecutorTestProduce, default_border_first_array_hard_fullcou
                                        RowBuilder<5>{1, 2, 3, R"([1, 2, 3])", 3}}})
       .expectSkipped(3)  // skipped amount of 3 in the fullCount phase
       .expectedState(ExecutionState::DONE)
-      .run(makeInfos(3, 4, 4, 5, {}, {0, 1, 2, 3}));
+      .run();
 }
 
 template <size_t... vs>
diff --git a/tests/Aql/ExecutorTestHelper.h b/tests/Aql/ExecutorTestHelper.h
index 0edc6c4992a8..8c421efc8d92 100644
--- a/tests/Aql/ExecutorTestHelper.h
+++ b/tests/Aql/ExecutorTestHelper.h
@@ -33,6 +33,7 @@
 #include "Aql/AqlCallStack.h"
 #include "Aql/ExecutionBlock.h"
 #include "Aql/ExecutionBlockImpl.h"
+#include "Aql/ExecutionEngine.h"
 #include "Aql/ExecutionState.h"
 #include "Aql/ExecutionStats.h"
 #include "Aql/OutputAqlItemRow.h"
@@ -139,7 +140,49 @@ template <typename T, bool enableQueryTrace = false>
 class AqlExecutorTestCaseWithParam : public AqlExecutorTestCase<enableQueryTrace>,
                                      public ::testing::WithParamInterface<T> {};
 
-template <typename E, std::size_t inputColumns = 1, std::size_t outputColumns = 1>
+using ExecBlock = std::unique_ptr<ExecutionBlock>;
+
+struct Pipeline {
+  using PipelineStorage = std::deque<ExecBlock>;
+
+  Pipeline() : _pipeline{} {};
+  Pipeline(ExecBlock&& init) { _pipeline.emplace_back(std::move(init)); }
+  Pipeline(std::deque<ExecBlock>&& init) : _pipeline(std::move(init)){};
+  Pipeline(Pipeline& other) = delete;
+  Pipeline(Pipeline&& other) : _pipeline(std::move(other._pipeline)){};
+
+  Pipeline& operator=(Pipeline&& other) {
+    _pipeline = std::move(other._pipeline);
+    return *this;
+  }
+
+  ~Pipeline() {
+    for (auto&& b : _pipeline) {
+      b.release();
+    }
+  };
+
+  bool empty() const { return _pipeline.empty(); }
+  void reset() { _pipeline.clear(); }
+
+  std::deque<ExecBlock> const& get() const { return _pipeline; };
+  std::deque<ExecBlock>& get() { return _pipeline; };
+
+ private:
+  PipelineStorage _pipeline;
+};
+
+inline auto concatPipelines(Pipeline&& bottom, Pipeline&& top) -> Pipeline {
+  if (!bottom.empty()) {
+    bottom.get().back()->addDependency(top.get().begin()->get());
+  }
+  bottom.get().insert(std::end(bottom.get()), std::make_move_iterator(top.get().begin()),
+                      std::make_move_iterator(top.get().end()));
+
+  return std::move(bottom);
+}
+
+template <std::size_t inputColumns = 1, std::size_t outputColumns = 1>
 struct ExecutorTestHelper {
   using SplitType = std::variant<std::vector<std::size_t>, std::size_t, std::monostate>;
 
@@ -222,7 +265,29 @@ struct ExecutorTestHelper {
     _expectedStats = stats;
     _testStats = true;
     return *this;
-  };
+  }
+
+  template <typename E>
+  auto setExecBlock(typename E::Infos infos) -> ExecutorTestHelper& {
+    auto& testeeNode = _execNodes.emplace_back(std::move(
+        std::make_unique<SingletonNode>(_query.plan(), _execNodes.size())));
+    setPipeline(Pipeline{std::make_unique<ExecutionBlockImpl<E>>(_query.engine(),
+                                                      testeeNode.get(), std::move(infos))});
+    return *this;
+  }
+
+  template <typename E>
+  auto createExecBlock(typename E::Infos infos) -> ExecBlock {
+    auto& testeeNode = _execNodes.emplace_back(std::move(
+        std::make_unique<SingletonNode>(_query.plan(), _execNodes.size())));
+    return std::make_unique<ExecutionBlockImpl<E>>(_query.engine(), testeeNode.get(),
+                                                   std::move(infos));
+  }
+
+  auto setPipeline(Pipeline&& pipeline) -> ExecutorTestHelper& {
+    _pipeline = std::move(pipeline);
+    return *this;
+  }
 
   auto allowAnyOutputOrder(bool expected, size_t skippedRows = 0) -> ExecutorTestHelper& {
     _unorderedOutput = expected;
@@ -244,19 +309,17 @@ struct ExecutorTestHelper {
     return *this;
   }
 
-  auto run(typename E::Infos infos) -> void {
+  auto run() -> void {
     ResourceMonitor monitor;
     AqlItemBlockManager itemBlockManager(&monitor, SerializationFormat::SHADOWROWS);
 
     auto inputBlock = generateInputRanges(itemBlockManager);
 
-    auto testeeNode = std::make_unique<SingletonNode>(_query.plan(), 1);
-
-    ExecutionBlockImpl<E> testee{_query.engine(), testeeNode.get(), std::move(infos)};
-    testee.addDependency(inputBlock.get());
+    TRI_ASSERT(!_pipeline.empty());
+    _pipeline.get().back()->addDependency(inputBlock.get());
 
     AqlCallStack stack{_call};
-    auto const [state, skipped, result] = testee.execute(stack);
+    auto const [state, skipped, result] = _pipeline.get().front()->execute(stack);
     EXPECT_EQ(skipped, _expectedSkip);
 
     EXPECT_EQ(state, _expectedState);
@@ -355,6 +418,8 @@ struct ExecutorTestHelper {
 
   arangodb::aql::Query& _query;
   std::unique_ptr<arangodb::aql::ExecutionNode> _dummyNode;
+  Pipeline _pipeline;
+  std::vector<std::unique_ptr<ExecutionNode>> _execNodes;
 };
 
 enum class ExecutorCall {
@@ -376,7 +441,7 @@ using ExecutorStepResult = std::tuple<ExecutorCall, arangodb::aql::ExecutionStat
 //  somehow optional. e.g. call a templated function or so.
 // TODO Add calls to expectedNumberOfRows
 
-template <class Executor>
+template <typename Executor>
 std::tuple<arangodb::aql::SharedAqlItemBlockPtr, std::vector<ExecutorStepResult>, arangodb::aql::ExecutionStats>
 runExecutor(arangodb::aql::AqlItemBlockManager& manager, Executor& executor,
             arangodb::aql::OutputAqlItemRow& outputRow, size_t const numSkip,
diff --git a/tests/Aql/HashedCollectExecutorTest.cpp b/tests/Aql/HashedCollectExecutorTest.cpp
index 0c01634af57b..6aca1b82d975 100644
--- a/tests/Aql/HashedCollectExecutorTest.cpp
+++ b/tests/Aql/HashedCollectExecutorTest.cpp
@@ -54,7 +54,7 @@ namespace tests {
 namespace aql {
 
 // This is only to get a split-type. The Type is independent of actual template parameters
-using HashedCollectTestHelper = ExecutorTestHelper<HashedCollectExecutor, 1, 1>;
+using HashedCollectTestHelper = ExecutorTestHelper<1, 1>;
 using HashedCollectSplitType = HashedCollectTestHelper::SplitType;
 using HashedCollectInputParam = std::tuple<HashedCollectSplitType, bool>;
 
@@ -138,7 +138,8 @@ TEST_P(HashedCollectExecutorTest, collect_only) {
   auto infos = buildInfos(1, 2, {{1, 0}});
   AqlCall call{};          // unlimited produce
   ExecutionStats stats{};  // No stats here
-  ExecutorTestHelper<HashedCollectExecutor>(*fakedQuery)
+  ExecutorTestHelper(*fakedQuery)
+      .setExecBlock<HashedCollectExecutor>(std::move(infos))
       .setInputValue({{{1}}, {{1}}, {{2}}, {{1}}, {{6}}, {{2}}, {{R"("1")"}}})
       .setInputSplitType(getSplit())
       .setCall(call)
@@ -148,7 +149,7 @@ TEST_P(HashedCollectExecutorTest, collect_only) {
       .expectedState(ExecutionState::DONE)
       .appendEmptyBlock(appendEmpty())
       // .expectedStats(stats)
-      .run(std::move(infos));
+      .run();
 }
 
 // Collect skip all
@@ -157,7 +158,8 @@ TEST_P(HashedCollectExecutorTest, skip_all) {
   AqlCall call{};
   call.offset = 1000;      // skip all
   ExecutionStats stats{};  // No stats here
-  ExecutorTestHelper<HashedCollectExecutor>(*fakedQuery)
+  ExecutorTestHelper(*fakedQuery)
+      .setExecBlock<HashedCollectExecutor>(std::move(infos))
       .setInputValue({{{1}}, {{1}}, {{2}}, {{1}}, {{6}}, {{2}}, {{R"("1")"}}})
       .setInputSplitType(getSplit())
       .setCall(call)
@@ -167,7 +169,7 @@ TEST_P(HashedCollectExecutorTest, skip_all) {
       .expectedState(ExecutionState::DONE)
       .appendEmptyBlock(appendEmpty())
       // .expectedStats(stats)
-      .run(std::move(infos));
+      .run();
 }
 
 // Collect fullCount all
@@ -177,7 +179,8 @@ TEST_P(HashedCollectExecutorTest, fullcount_all) {
   call.hardLimit = 0;      // HardLimit
   call.fullCount = true;   // count all
   ExecutionStats stats{};  // No stats here
-  ExecutorTestHelper<HashedCollectExecutor>(*fakedQuery)
+  ExecutorTestHelper(*fakedQuery)
+      .setExecBlock<HashedCollectExecutor>(std::move(infos))
       .setInputValue({{{1}}, {{1}}, {{2}}, {{1}}, {{6}}, {{2}}, {{R"("1")"}}})
       .setInputSplitType(getSplit())
       .setCall(call)
@@ -187,7 +190,7 @@ TEST_P(HashedCollectExecutorTest, fullcount_all) {
       .expectedState(ExecutionState::DONE)
       .appendEmptyBlock(appendEmpty())
       // .expectedStats(stats)
-      .run(std::move(infos));
+      .run();
 }
 
 // Collect get some
@@ -196,7 +199,8 @@ TEST_P(HashedCollectExecutorTest, collect_only_soft_less) {
   AqlCall call{};
   call.softLimit = 2;
   ExecutionStats stats{};  // No stats here
-  ExecutorTestHelper<HashedCollectExecutor>(*fakedQuery)
+  ExecutorTestHelper(*fakedQuery)
+      .setExecBlock<HashedCollectExecutor>(std::move(infos))
       .setInputValue({{{1}}, {{1}}, {{2}}, {{1}}, {{6}}, {{2}}, {{R"("1")"}}})
       .setInputSplitType(getSplit())
       .setCall(call)
@@ -206,7 +210,7 @@ TEST_P(HashedCollectExecutorTest, collect_only_soft_less) {
       .expectedState(ExecutionState::HASMORE)
       .appendEmptyBlock(appendEmpty())
       // .expectedStats(stats)
-      .run(std::move(infos));
+      .run();
 }
 
 // Collect get some multiple calls
@@ -279,7 +283,8 @@ TEST_P(HashedCollectExecutorTest, collect_only_hard_less) {
   AqlCall call{};
   call.hardLimit = 2;
   ExecutionStats stats{};  // No stats here
-  ExecutorTestHelper<HashedCollectExecutor>(*fakedQuery)
+  ExecutorTestHelper(*fakedQuery)
+      .setExecBlock<HashedCollectExecutor>(std::move(infos))
       .setInputValue({{{1}}, {{1}}, {{2}}, {{1}}, {{6}}, {{2}}, {{R"("1")"}}})
       .setInputSplitType(getSplit())
       .setCall(call)
@@ -289,7 +294,7 @@ TEST_P(HashedCollectExecutorTest, collect_only_hard_less) {
       .expectedState(ExecutionState::DONE)
       .appendEmptyBlock(appendEmpty())
       // .expectedStats(stats)
-      .run(std::move(infos));
+      .run();
 }
 
 // Collect skip some
@@ -299,7 +304,8 @@ TEST_P(HashedCollectExecutorTest, skip_some) {
   call.offset = 2;         // skip some
   call.softLimit = 0;      // 0 limit
   ExecutionStats stats{};  // No stats here
-  ExecutorTestHelper<HashedCollectExecutor>(*fakedQuery)
+  ExecutorTestHelper(*fakedQuery)
+      .setExecBlock<HashedCollectExecutor>(std::move(infos))
       .setInputValue({{{1}}, {{1}}, {{2}}, {{1}}, {{6}}, {{2}}, {{R"("1")"}}})
       .setInputSplitType(getSplit())
       .setCall(call)
@@ -309,7 +315,7 @@ TEST_P(HashedCollectExecutorTest, skip_some) {
       .expectedState(ExecutionState::HASMORE)
       .appendEmptyBlock(appendEmpty())
       // .expectedStats(stats)
-      .run(std::move(infos));
+      .run();
 }
 
 // Collect skip and get
@@ -319,7 +325,8 @@ TEST_P(HashedCollectExecutorTest, skip_and_get) {
   call.offset = 2;         // skip some
   call.softLimit = 1000;   // high limit
   ExecutionStats stats{};  // No stats here
-  ExecutorTestHelper<HashedCollectExecutor>(*fakedQuery)
+  ExecutorTestHelper(*fakedQuery)
+      .setExecBlock<HashedCollectExecutor>(std::move(infos))
       .setInputValue({{{1}}, {{1}}, {{2}}, {{1}}, {{6}}, {{2}}, {{R"("1")"}}})
       .setInputSplitType(getSplit())
       .setCall(call)
@@ -329,7 +336,7 @@ TEST_P(HashedCollectExecutorTest, skip_and_get) {
       .expectedState(ExecutionState::DONE)
       .appendEmptyBlock(appendEmpty())
       // .expectedStats(stats)
-      .run(std::move(infos));
+      .run();
 }
 
 // Collect skip and hardLimit
@@ -339,7 +346,8 @@ TEST_P(HashedCollectExecutorTest, skip_and_hardLimit) {
   call.offset = 2;         // skip some
   call.hardLimit = 1;      // hard limit
   ExecutionStats stats{};  // No stats here
-  ExecutorTestHelper<HashedCollectExecutor>(*fakedQuery)
+  ExecutorTestHelper(*fakedQuery)
+      .setExecBlock<HashedCollectExecutor>(std::move(infos))
       .setInputValue({{{1}}, {{1}}, {{2}}, {{1}}, {{6}}, {{2}}, {{R"("1")"}}})
       .setInputSplitType(getSplit())
       .setCall(call)
@@ -349,7 +357,7 @@ TEST_P(HashedCollectExecutorTest, skip_and_hardLimit) {
       .expectedState(ExecutionState::DONE)
       .appendEmptyBlock(appendEmpty())
       // .expectedStats(stats)
-      .run(std::move(infos));
+      .run();
 }
 
 // Collect skip and fullCount
@@ -360,7 +368,8 @@ TEST_P(HashedCollectExecutorTest, skip_and_fullCount) {
   call.hardLimit = 2;  // hard limit
   call.fullCount = true;
   ExecutionStats stats{};  // No stats here
-  ExecutorTestHelper<HashedCollectExecutor>(*fakedQuery)
+  ExecutorTestHelper(*fakedQuery)
+      .setExecBlock<HashedCollectExecutor>(std::move(infos))
       .setInputValue({{{1}}, {{1}}, {{2}}, {{1}}, {{6}}, {{2}}, {{R"("1")"}}})
       .setInputSplitType(getSplit())
       .setCall(call)
@@ -370,7 +379,7 @@ TEST_P(HashedCollectExecutorTest, skip_and_fullCount) {
       .expectedState(ExecutionState::DONE)
       .appendEmptyBlock(appendEmpty())
       // .expectedStats(stats)
-      .run(std::move(infos));
+      .run();
 }
 
 // Collect with more then one group value
@@ -378,7 +387,8 @@ TEST_P(HashedCollectExecutorTest, collect_only_multiple_values) {
   auto infos = buildInfos(2, 4, {{2, 0}, {3, 1}});
   AqlCall call{};          // unlimited produce
   ExecutionStats stats{};  // No stats here
-  ExecutorTestHelper<HashedCollectExecutor, 2, 2>(*fakedQuery)
+  ExecutorTestHelper<2, 2>(*fakedQuery)
+      .setExecBlock<HashedCollectExecutor>(std::move(infos))
       .setInputValue(MatrixBuilder<2>{RowBuilder<2>{1, 5}, RowBuilder<2>{1, 1},
                                       RowBuilder<2>{2, 2}, RowBuilder<2>{1, 5},
                                       RowBuilder<2>{6, 1}, RowBuilder<2>{2, 2},
@@ -392,7 +402,7 @@ TEST_P(HashedCollectExecutorTest, collect_only_multiple_values) {
       .expectSkipped(0)
       .expectedState(ExecutionState::DONE)
       // .expectedStats(stats)
-      .run(std::move(infos));
+      .run();
 }
 
 // Collect with one group value and count
@@ -400,7 +410,8 @@ TEST_P(HashedCollectExecutorTest, count) {
   auto infos = buildInfos(1, 3, {{1, 0}}, 2);
   AqlCall call{};          // unlimited produce
   ExecutionStats stats{};  // No stats here
-  ExecutorTestHelper<HashedCollectExecutor, 1, 2>(*fakedQuery)
+  ExecutorTestHelper<1, 2>(*fakedQuery)
+      .setExecBlock<HashedCollectExecutor>(std::move(infos))
       .setInputValue({{{1}}, {{1}}, {{2}}, {{1}}, {{6}}, {{2}}, {{R"("1")"}}})
       .setInputSplitType(getSplit())
       .setCall(call)
@@ -409,7 +420,7 @@ TEST_P(HashedCollectExecutorTest, count) {
       .expectSkipped(0)
       .expectedState(ExecutionState::DONE)
       // .expectedStats(stats)
-      .run(std::move(infos));
+      .run();
 }
 
 // Collect with multiple aggregators
@@ -419,7 +430,8 @@ TEST_P(HashedCollectExecutorTest, many_aggregators) {
                  {{3, RegisterPlan::MaxRegisterId}, {4, 1}});
   AqlCall call{};          // unlimited produce
   ExecutionStats stats{};  // No stats here
-  ExecutorTestHelper<HashedCollectExecutor, 2, 3>(*fakedQuery)
+  ExecutorTestHelper<2, 3>(*fakedQuery)
+      .setExecBlock<HashedCollectExecutor>(std::move(infos))
       .setInputValue(MatrixBuilder<2>{RowBuilder<2>{1, 5}, RowBuilder<2>{1, 1},
                                       RowBuilder<2>{2, 2}, RowBuilder<2>{1, 5},
                                       RowBuilder<2>{6, 1}, RowBuilder<2>{2, 2},
@@ -433,7 +445,7 @@ TEST_P(HashedCollectExecutorTest, many_aggregators) {
       .expectSkipped(0)
       .expectedState(ExecutionState::DONE)
       // .expectedStats(stats)
-      .run(std::move(infos));
+      .run();
 }
 
 // Collect based on equal arrays.
@@ -441,7 +453,8 @@ TEST_P(HashedCollectExecutorTest, collect_arrays) {
   auto infos = buildInfos(1, 2, {{1, 0}});
   AqlCall call{};          // unlimited produce
   ExecutionStats stats{};  // No stats here
-  ExecutorTestHelper<HashedCollectExecutor>(*fakedQuery)
+  ExecutorTestHelper(*fakedQuery)
+      .setExecBlock<HashedCollectExecutor>(std::move(infos))
       .setInputValue({{{R"([1,1,1])"}},
                       {{1}},
                       {{R"([1,1,1,1])"}},
@@ -456,7 +469,7 @@ TEST_P(HashedCollectExecutorTest, collect_arrays) {
       .expectSkipped(0)
       .expectedState(ExecutionState::DONE)
       // .expectedStats(stats)
-      .run(std::move(infos));
+      .run();
 }
 
 // Collect based on equal objects.
@@ -464,7 +477,8 @@ TEST_P(HashedCollectExecutorTest, collect_objects) {
   auto infos = buildInfos(1, 2, {{1, 0}});
   AqlCall call{};          // unlimited produce
   ExecutionStats stats{};  // No stats here
-  ExecutorTestHelper<HashedCollectExecutor>(*fakedQuery)
+  ExecutorTestHelper(*fakedQuery)
+      .setExecBlock<HashedCollectExecutor>(std::move(infos))
       .setInputValue({{{R"({"a": 1, "b": 1})"}},
                       {{1}},
                       {{R"({"a": 1, "b": 1, "c": 1})"}},
@@ -483,7 +497,7 @@ TEST_P(HashedCollectExecutorTest, collect_objects) {
       .expectSkipped(0)
       .expectedState(ExecutionState::DONE)
       // .expectedStats(stats)
-      .run(std::move(infos));
+      .run();
 }
 
 /**
@@ -607,7 +621,8 @@ TEST_P(HashedCollectExecutorTestAggregate, run) {
   auto infos = buildInfos(2, 4, {{2, 0}});
   AqlCall call{};          // unlimited produce
   ExecutionStats stats{};  // No stats here
-  ExecutorTestHelper<HashedCollectExecutor, 2, 2>(*fakedQuery)
+  ExecutorTestHelper<2, 2>(*fakedQuery)
+      .setExecBlock<HashedCollectExecutor>(std::move(infos))
       .setInputValue(MatrixBuilder<2>{RowBuilder<2>{1, 5}, RowBuilder<2>{1, 1},
                                       RowBuilder<2>{2, 2}, RowBuilder<2>{1, 5},
                                       RowBuilder<2>{6, 1}, RowBuilder<2>{2, 2},
@@ -619,7 +634,7 @@ TEST_P(HashedCollectExecutorTestAggregate, run) {
       .expectSkipped(0)
       .expectedState(ExecutionState::DONE)
       // .expectedStats(stats)
-      .run(std::move(infos));
+      .run();
 }
 
 }  // namespace aql
diff --git a/tests/Aql/IdExecutorTest.cpp b/tests/Aql/IdExecutorTest.cpp
index e9c2d3df07d7..37f9ce13ac61 100644
--- a/tests/Aql/IdExecutorTest.cpp
+++ b/tests/Aql/IdExecutorTest.cpp
@@ -330,13 +330,14 @@ TEST_F(IdExecutionBlockTest, test_initialize_cursor_fullCount) {
 
 TEST_F(IdExecutionBlockTest, test_hardlimit_single_row_fetcher) {
   IdExecutorInfos infos{1, {0}, {}};
-  ExecutorTestHelper<IdExecutor<SingleRowFetcher<BlockPassthrough::Enable>>>(*fakedQuery)
+  ExecutorTestHelper(*fakedQuery)
+      .setExecBlock<IdExecutor<SingleRowFetcher<BlockPassthrough::Enable>>>(std::move(infos))
       .setInputValueList(1, 2, 3, 4, 5, 6)
       .setCall(AqlCall{0, AqlCall::Infinity{}, 2, false})
       .expectOutput({0}, {{1}, {2}})
       .expectSkipped(0)
       .expectedState(ExecutionState::DONE)
-      .run(std::move(infos));
+      .run();
 }
 
 /**
diff --git a/tests/Aql/ReturnExecutorTest.cpp b/tests/Aql/ReturnExecutorTest.cpp
index bf8dc3608fa3..7fb106efd822 100644
--- a/tests/Aql/ReturnExecutorTest.cpp
+++ b/tests/Aql/ReturnExecutorTest.cpp
@@ -47,7 +47,7 @@ namespace tests {
 namespace aql {
 
 // This is only to get a split-type. The Type is independent of actual template parameters
-using ReturnExecutorTestHelper = ExecutorTestHelper<ReturnExecutor, 1, 1>;
+using ReturnExecutorTestHelper = ExecutorTestHelper<1, 1>;
 using ReturnExecutorSplitType = ReturnExecutorTestHelper::SplitType;
 using ReturnExecutorParamType = std::tuple<ReturnExecutorSplitType, bool>;
 
@@ -113,7 +113,8 @@ INSTANTIATE_TEST_CASE_P(ReturnExecutor, ReturnExecutorTest,
 TEST_P(ReturnExecutorTest, returns_all_from_upstream) {
   ReturnExecutorInfos infos(0 /*input register*/, 1 /*nr in*/, 1 /*nr out*/, doCount());
   AqlCall call{};  // unlimited produce
-  ExecutorTestHelper<ReturnExecutor>(*fakedQuery)
+  ExecutorTestHelper(*fakedQuery)
+      .setExecBlock<ReturnExecutor>(std::move(infos))
       .setInputValueList(1, 2, 5, 2, 1, 5, 7, 1)
       .setInputSplitType(getSplit())
       .setCall(call)
@@ -121,14 +122,15 @@ TEST_P(ReturnExecutorTest, returns_all_from_upstream) {
       .expectSkipped(0)
       .expectedState(ExecutionState::DONE)
       .expectedStats(getCountStats(8))
-      .run(std::move(infos));
+      .run();
 }
 
 TEST_P(ReturnExecutorTest, handle_soft_limit) {
   ReturnExecutorInfos infos(0 /*input register*/, 1 /*nr in*/, 1 /*nr out*/, doCount());
   AqlCall call{};
   call.softLimit = 3;
-  ExecutorTestHelper<ReturnExecutor>(*fakedQuery)
+  ExecutorTestHelper(*fakedQuery)
+      .setExecBlock<ReturnExecutor>(std::move(infos))
       .setInputValueList(1, 2, 5, 2, 1, 5, 7, 1)
       .setInputSplitType(getSplit())
       .setCall(call)
@@ -136,14 +138,15 @@ TEST_P(ReturnExecutorTest, handle_soft_limit) {
       .expectSkipped(0)
       .expectedState(ExecutionState::HASMORE)
       .expectedStats(getCountStats(3))
-      .run(std::move(infos));
+      .run();
 }
 
 TEST_P(ReturnExecutorTest, handle_hard_limit) {
   ReturnExecutorInfos infos(0 /*input register*/, 1 /*nr in*/, 1 /*nr out*/, doCount());
   AqlCall call{};
   call.hardLimit = 5;
-  ExecutorTestHelper<ReturnExecutor>(*fakedQuery)
+  ExecutorTestHelper(*fakedQuery)
+      .setExecBlock<ReturnExecutor>(std::move(infos))
       .setInputValueList(1, 2, 5, 2, 1, 5, 7, 1)
       .setInputSplitType(getSplit())
       .setCall(call)
@@ -151,14 +154,15 @@ TEST_P(ReturnExecutorTest, handle_hard_limit) {
       .expectSkipped(0)
       .expectedState(ExecutionState::DONE)
       .expectedStats(getCountStats(5))
-      .run(std::move(infos));
+      .run();
 }
 
 TEST_P(ReturnExecutorTest, handle_offset) {
   ReturnExecutorInfos infos(0 /*input register*/, 1 /*nr in*/, 1 /*nr out*/, doCount());
   AqlCall call{};
   call.offset = 4;
-  ExecutorTestHelper<ReturnExecutor>(*fakedQuery)
+  ExecutorTestHelper(*fakedQuery)
+      .setExecBlock<ReturnExecutor>(std::move(infos))
       .setInputValueList(1, 2, 5, 2, 1, 5, 7, 1)
       .setInputSplitType(getSplit())
       .setCall(call)
@@ -166,7 +170,7 @@ TEST_P(ReturnExecutorTest, handle_offset) {
       .expectSkipped(4)
       .expectedState(ExecutionState::DONE)
       .expectedStats(getCountStats(4))
-      .run(std::move(infos));
+      .run();
 }
 
 TEST_P(ReturnExecutorTest, handle_fullcount) {
@@ -174,7 +178,8 @@ TEST_P(ReturnExecutorTest, handle_fullcount) {
   AqlCall call{};
   call.hardLimit = 2;
   call.fullCount = true;
-  ExecutorTestHelper<ReturnExecutor>(*fakedQuery)
+  ExecutorTestHelper(*fakedQuery)
+      .setExecBlock<ReturnExecutor>(std::move(infos))
       .setInputValueList(1, 2, 5, 2, 1, 5, 7, 1)
       .setInputSplitType(getSplit())
       .setCall(call)
@@ -182,14 +187,15 @@ TEST_P(ReturnExecutorTest, handle_fullcount) {
       .expectSkipped(6)
       .expectedState(ExecutionState::DONE)
       .expectedStats(getCountStats(2))
-      .run(std::move(infos));
+      .run();
 }
 
 TEST_P(ReturnExecutorTest, handle_other_inputRegister) {
   ReturnExecutorInfos infos(1 /*input register*/, 2 /*nr in*/, 1 /*nr out*/, doCount());
   AqlCall call{};
   call.hardLimit = 5;
-  ExecutorTestHelper<ReturnExecutor, 2, 1>(*fakedQuery)
+  ExecutorTestHelper<2, 1>(*fakedQuery)
+      .setExecBlock<ReturnExecutor>(std::move(infos))
       .setInputValue({{R"("invalid")", 1},
                       {R"("invalid")", 2},
                       {R"("invalid")", 5},
@@ -204,7 +210,7 @@ TEST_P(ReturnExecutorTest, handle_other_inputRegister) {
       .expectSkipped(0)
       .expectedState(ExecutionState::DONE)
       .expectedStats(getCountStats(5))
-      .run(std::move(infos));
+      .run();
 }
 }  // namespace aql
 }  // namespace tests
diff --git a/tests/Aql/SortedCollectExecutorTest.cpp b/tests/Aql/SortedCollectExecutorTest.cpp
index e580e9b45f24..fa8ce07e644c 100644
--- a/tests/Aql/SortedCollectExecutorTest.cpp
+++ b/tests/Aql/SortedCollectExecutorTest.cpp
@@ -924,7 +924,7 @@ TEST_F(SortedCollectExecutorTestSkip, skip_5) {
   }
 }
 
-using SortedCollectTestHelper = ExecutorTestHelper<SortedCollectExecutor, 1, 1>;
+using SortedCollectTestHelper = ExecutorTestHelper<1, 1>;
 using SortedCollectSplitType = SortedCollectTestHelper::SplitType;
 
 class SortedCollectExecutorTestSplit
@@ -975,40 +975,43 @@ class SortedCollectExecutorTestSplit
 TEST_P(SortedCollectExecutorTestSplit, split_1) {
   auto [split] = GetParam();
 
-  ExecutorTestHelper<SortedCollectExecutor>(*fakedQuery)
+  ExecutorTestHelper(*fakedQuery)
+      .setExecBlock<SortedCollectExecutor>(std::move(infos))
       .setInputValueList(1, 1, 1, 2, 3, 4, 4, 5)
       .setInputSplitType(split)
       .setCall(AqlCall{2, AqlCall::Infinity{}, 2, true})
       .expectOutputValueList(3, 4)
       .expectSkipped(3)
       .expectedState(ExecutionState::DONE)
-      .run(std::move(infos));
+      .run();
 }
 
 TEST_P(SortedCollectExecutorTestSplit, split_2) {
   auto [split] = GetParam();
 
-  ExecutorTestHelper<SortedCollectExecutor>(*fakedQuery)
+  ExecutorTestHelper(*fakedQuery)
+      .setExecBlock<SortedCollectExecutor>(std::move(infos))
       .setInputValueList(1, 1, 1, 2, 3, 4, 4, 5)
       .setInputSplitType(split)
       .setCall(AqlCall{2, 2, AqlCall::Infinity{}, false})
       .expectOutputValueList(3, 4)
       .expectSkipped(2)
       .expectedState(ExecutionState::HASMORE)
-      .run(std::move(infos));
+      .run();
 }
 
 TEST_P(SortedCollectExecutorTestSplit, split_3) {
   auto [split] = GetParam();
 
-  ExecutorTestHelper<SortedCollectExecutor>(*fakedQuery)
+  ExecutorTestHelper(*fakedQuery)
+      .setExecBlock<SortedCollectExecutor>(std::move(infos))
       .setInputValueList(1, 2, 3, 4, 5)
       .setInputSplitType(split)
       .setCall(AqlCall{1, AqlCall::Infinity{}, 10, true})
       .expectOutputValueList(2, 3, 4, 5)
       .expectSkipped(1)
       .expectedState(ExecutionState::DONE)
-      .run(std::move(infos));
+      .run();
 }
 
 template <size_t... vs>

From 2e2e2144fbd4bf195e83120cf4b68ea3beb3c7ae Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tobias=20G=C3=B6dderz?= <tobias@arangodb.com>
Date: Fri, 21 Feb 2020 16:06:13 +0100
Subject: [PATCH 071/122] AQL execute in LimitExecutor (#10886)

* Added a generic Lambda Executor, this can be used in ExecutionBlockImplTests to have finegrained control over the action happening within the Executor

* Added first test using the LambdaExecutor.

* Added some tests around Execute. GetSome seems to be okayish. Skip not. Namely skipped numbers are not reported correctly.

* Made the first ExecutionBlock Execute integration test pass. Still other tests are failing

* Simplified the IsSkipSome test, this allows the C++ tests for Mixed Calls to pass.

* Added a skip test and fixed the producing executor to recreate the list once for every input line.

* More tests. Also added a custom AqlCall printer function for GTest. Tests still red, need to fix fullCount and hardLimit.

* Implemented ostream operator for AQLCall.

* Properly implemented fullCount incl. UnitTest

* Added test for Callforwarding. They still have some todos, but these can only be solved by upgrading the OutputRow. Which should be part of separate PR

* Added another test for CallForwarding in passthrough state

* Added a Test Implementation for an Executor that uses a dynamic skip implementation.

* Fixed skip with HARDLIMIT.

* Startet to implement call forwarding test. However we need to improve Outputrow first this will be done in seperate branch

* Removed designated initializers. Thanks for not supporting it MSVC!

* Removed non-passthrough non-skip Lambda Executor again. We decided to disallow this.

* Fixed merge

* Update tests/Aql/ExecutionBlockImplTest.cpp

Co-Authored-By: Markus Pfeiffer <markuspf@users.noreply.github.com>

* Reverted accidental change

* Started to add implementation of passthrough block allocation

* Added a comparator to AqlCall. Mostly for tests

* Fixed an issue in skip-passthrough version. Updated the tests.

* Allow to 'overSkip' if we do fullCount

* Enabled the first set of tests now. Only one set to go

* Applied all fixes to get Integration testsuite green

* Added some comments on the TestCases executed in the ExecutionBlockImpl

* Added tes descriptions and removed a duplicate test

* Added some comments on LamdbaExecutors

* Added description of ExecutionBlockImple execute logic

* Assert no input rows in skip

* Began writing a test framework for LimitExecutor

* Removed unused code

* Continued test framework

* Applied review comments, thanks to reviewers

* Fixed modulo 2 off by one error

* Renamed getLambda() => getProduceLambda() in test code, as we have produce and skip

* Make AqlItemBlockInputRange hold a skipped count

* Added == for LimitStats, moved code to .cpp file

* Added Stats return value to skipRowsRange

* WIP: Implement LimitExecutor test framework

* Fixed namespace

* Added missing advanceRow call

* Added parametrized test cases

* Dump

* Made test output more readable

* Fixed merge conflicts

* Set engine in createFakeQuery()

* [WIP] Dump: not working

* Fixed merge conflicts

* Switch from boost::variant to std::variant

* Fix comparison of differently sized blocks

* Fixed usage of temporary

* Fixed skip handling in ExecutionBlockImpl

* Add upstream fullCount in LimitExecutor

* Fix assertion that was too narrow

* Again, fixed skip handling in ExecutionBlockImpl

* Extended ExecutorTestHelper, mainly a loop to handle passthrough Executors

* Fixed expected skipped count

* Fixed bugs in LimitExecutor

* Another bugfix in LimitExecutor

* Fixed expected output calculation

* Removed some comments

* Improve test speed by not recreating MockAqlServer for every case

* Allow additional variants in ExecutorTestHelper

* Tried to fix a bug in LimitExecutor, not quite working

* A little cleanup

* Toggle lieAboutHasMore

* Reverted broken fix, fixed WaitingExecutionBlockMock

* Fixed merge conflicts

* Add LimitStats to expected checks in tests

* Fixed another leftover merge conflict

* Fixed fullCount stats

* Removed old code from LimitExecutor

* Updated ExecutionBlockImpl to allow removal of old executor methods

* Removed old tests

* Simplified test code

* Added comments and constructors to AqlCall

* Instantiate test cases with multiple different calls

* Fixed a bug in run(), made looping optional

* Fixed a bug in DependencyProxy

* Fixed a bug and an assertion in LimitExecutor

* Added assertions and a fix in WaitingExecutionBlockMock

* Enabled stats tests again

* Made the executor compile under Mac

* Let AqlHelper compare profiled stats as well

* Prepare reusability of LOG output for ExecutionBlock.

* Added first version of DEBUG output to ExecutionBlockImpl

* Modified skip logic in LimitExecutor to simplify what has to be reported to downStream and what is handled by internal skip. Also allow to do skip and fullCount in one go, if limit is 0

* Adapted the Expected skipped output in Limit test

* Forward fullCount from client through LIMIT. Simplyfied produceLogic.

* Reduced the amount of Tests in LimitExecutor. Need to decide on a suitable subset

* Removed lieAboutHasMore by simply adding an empty block to the end that is blocking return in the WaitingExecutor

* Fixed SingleRowFetcher to allow a Range with only skip information.

* Intermed version of ExecutionBlockImpl. Needs to be continued

* Allow hardLimit to pass getSome check

* Intermed commit

* Unified FastForward and FullCount code path

* Produce and Skip go to FastForward if the Executor reports done and the output row is full. This way we can handle more FUllCount cases straight away.

* Fixed the expected value for FullCount stats in test. This is rather awkward to automatically compute...

* Fixed lying of the ExecutionBlockMock. Did not lie correctly if the limit was reached by softLimit.

* Make the rules for supporting the OldAPI more relaxed.

* Added a missmatch of outputColumns and internal output columns in TestHelper

* Fixed AqlItemBlockRangeTests

* Implemented unreachable code, otherwise our Jenkins does not compile it ;(

* Fixed SortedCollect, it might count the last group twice on fullCount, if produce ends exactly in this group

* Use AqlTestCase in ReturnExecutorTest

* Return Executor needs to report skipped from upstream properly

* Fixed fullCount call behaviour

* Fixed expected numberSkipped in LimitExecutor test

* Added some DEBUG level log messages in FastForward

* Fixed reporting of skip in skipSome case and removed dead code

* Fixed Impl test, we cannot let the WaitingBlockMock do counting on ShadowRows, it is not implemented there.

* Removed unused function

* Pointeless comment

* Fixed skipSome of Filter

* Avoid endless Loop in indexExecutor fullCount, where it tried to skipped 0 documents forever

* Fixed return state of IndexExecutor

* Fake DONE on hardLimit for oldAPI, apply only on toplevel. Improve shortcutting behviour to jump into FastForward everytime HARDLimit is reached, even if output is full.

* Added an assertion that multiple UPSTREAM call rounds do not mess up the callStack by leaving the _upstreamCall on top. Now the executor itself pops off the call, this is subject to change if we manage the Stack differently

* Was erlaube skip? Adjsuted tests to honor that we can do skip and limit now in one go, for all executors that are updated already

* Fixed ConstFetcher, to not modify the CallStack, it only has a reference, where the other Fetchers copy it to the Executors, and modify it there

* Do not overfetch on passthrough if the block is full.

* We cannot create DONE on oldStyle if we need fullcount...

* Unfortunately we teporarily need more calls in fullCount case, as long as one of the Executors above is not yet on execute

* Mhm gcc and clang do not aggree on which types are equal...

* Fixed compile issue.

Co-authored-by: Michael Hackstein <michael@arangodb.com>
Co-authored-by: Markus Pfeiffer <markuspf@users.noreply.github.com>
---
 arangod/Aql/AqlCall.h                         |   72 +-
 arangod/Aql/AqlCallStack.h                    |   14 +-
 arangod/Aql/AqlItemBlock.cpp                  |    2 +-
 arangod/Aql/AqlItemBlock.h                    |    2 +-
 arangod/Aql/AqlItemBlockInputRange.cpp        |   40 +-
 arangod/Aql/AqlItemBlockInputRange.h          |   35 +-
 arangod/Aql/ConstFetcher.cpp                  |    8 +-
 arangod/Aql/DependencyProxy.cpp               |    7 +-
 arangod/Aql/ExecutionBlockImpl.cpp            |  497 +++---
 arangod/Aql/ExecutionBlockImpl.h              |    9 +-
 arangod/Aql/FilterExecutor.cpp                |   16 +-
 arangod/Aql/IndexExecutor.cpp                 |   56 +-
 arangod/Aql/IndexExecutor.h                   |    2 +
 arangod/Aql/LimitExecutor.cpp                 |  381 ++---
 arangod/Aql/LimitExecutor.h                   |   87 +-
 arangod/Aql/LimitStats.cpp                    |   66 +
 arangod/Aql/LimitStats.h                      |   50 +-
 arangod/Aql/Query.cpp                         |    5 +
 arangod/Aql/Query.h                           |    1 +
 arangod/Aql/ReturnExecutor.cpp                |   13 +-
 arangod/Aql/SingleRowFetcher.cpp              |   10 +-
 arangod/Aql/SortedCollectExecutor.cpp         |   10 +-
 arangod/CMakeLists.txt                        |    1 +
 tests/Aql/AqlHelper.cpp                       |   12 +-
 tests/Aql/AqlItemBlockHelper.h                |   28 +-
 tests/Aql/AqlItemBlockInputRangeTest.cpp      |    3 +-
 .../EngineInfoContainerCoordinatorTest.cpp    |   57 +-
 tests/Aql/EnumerateListExecutorTest.cpp       |    4 +-
 tests/Aql/ExecutionBlockImplTest.cpp          |    8 +-
 tests/Aql/ExecutorTestHelper.h                |  104 +-
 tests/Aql/FilterExecutorTest.cpp              |   10 +-
 tests/Aql/IdExecutorTest.cpp                  |    3 +-
 tests/Aql/LimitExecutorTest.cpp               | 1376 +++++------------
 tests/Aql/MockTypedNode.cpp                   |   56 +
 tests/Aql/MockTypedNode.h                     |   60 +
 tests/Aql/ReturnExecutorTest.cpp              |   29 +-
 tests/Aql/ShortestPathExecutorTest.cpp        |    7 +-
 tests/Aql/SingleRowFetcherTest.cpp            |    4 +-
 tests/Aql/SortedCollectExecutorTest.cpp       |   36 +-
 tests/Aql/WaitingExecutionBlockMock.cpp       |   25 +-
 tests/Aql/WaitingExecutionBlockMock.h         |    4 +-
 tests/CMakeLists.txt                          |    1 +
 tests/Mocks/Servers.cpp                       |    6 +
 tests/js/server/aql/aql-profiler.js           |    6 +-
 44 files changed, 1459 insertions(+), 1764 deletions(-)
 create mode 100644 arangod/Aql/LimitStats.cpp
 create mode 100644 tests/Aql/MockTypedNode.cpp
 create mode 100644 tests/Aql/MockTypedNode.h

diff --git a/arangod/Aql/AqlCall.h b/arangod/Aql/AqlCall.h
index 63fbf31b5883..75d2c7048b7a 100644
--- a/arangod/Aql/AqlCall.h
+++ b/arangod/Aql/AqlCall.h
@@ -29,12 +29,35 @@
 #include <cstddef>
 #include <variant>
 
-namespace arangodb {
-namespace aql {
+namespace arangodb::aql {
+
 struct AqlCall {
+  // TODO We currently have softLimit and hardLimit, where both can be a number
+  //      or Infinity - but not both may be non-infinite at the same time.
+  //      In addition, a soft limit does only make sense together with a hard
+  //      limit.
+  //      The data structures and APIs should reflect that. E.g.:
+  //      Infinity | SoftLimit { count : Int } | HardLimit { count : Int, fullCount : Bool }
+  //      On a less important case, softLimit = 0 and offset = 0 do not occur together,
+  //      but it's probably not worth implementing that in terms of data structures.
   class Infinity {};
   using Limit = std::variant<size_t, Infinity>;
 
+  AqlCall() = default;
+  // Replacements for struct initialization
+  explicit AqlCall(size_t offset, Limit softLimit = Infinity{},
+                   Limit hardLimit = Infinity{}, bool fullCount = false)
+      : offset{offset}, softLimit{softLimit}, hardLimit{hardLimit}, fullCount{fullCount} {}
+
+  enum class LimitType { SOFT, HARD };
+  AqlCall(size_t offset, bool fullCount, Infinity)
+      : offset{offset}, softLimit{Infinity{}}, hardLimit{Infinity{}}, fullCount{fullCount} {}
+  AqlCall(size_t offset, bool fullCount, size_t limit, LimitType limitType)
+      : offset{offset},
+        softLimit{limitType == LimitType::SOFT ? Limit{limit} : Limit{Infinity{}}},
+        hardLimit{limitType == LimitType::HARD ? Limit{limit} : Limit{Infinity{}}},
+        fullCount{fullCount} {}
+
   // TODO Remove me, this will not be necessary later
   static AqlCall SimulateSkipSome(std::size_t toSkip) {
     AqlCall call;
@@ -57,12 +80,12 @@ struct AqlCall {
 
   // TODO Remove me, this will not be necessary later
   static bool IsSkipSomeCall(AqlCall const& call) {
-    return !call.hasHardLimit() && call.getOffset() > 0;
+    return call.getOffset() > 0;
   }
 
   // TODO Remove me, this will not be necessary later
   static bool IsGetSomeCall(AqlCall const& call) {
-    return !call.hasHardLimit() && call.getLimit() > 0 && call.getOffset() == 0;
+    return call.getLimit() > 0 && call.getOffset() == 0;
   }
 
   // TODO Remove me, this will not be necessary later
@@ -71,8 +94,18 @@ struct AqlCall {
            call.getOffset() == 0 && call.needsFullCount();
   }
 
+  static bool IsFastForwardCall(AqlCall const& call) {
+    return call.hasHardLimit() && call.getLimit() == 0 &&
+           call.getOffset() == 0 && !call.needsFullCount();
+  }
+
   std::size_t offset{0};
   // TODO: The defaultBatchSize function could move into this file instead
+  // TODO We must guarantee that at most one of those is not Infinity.
+  //      To do that, we should replace softLimit and hardLimit with
+  //        Limit limit;
+  //        bool isHardLimit;
+  //      .
   Limit softLimit{Infinity{}};
   Limit hardLimit{Infinity{}};
   bool fullCount{false};
@@ -80,6 +113,9 @@ struct AqlCall {
 
   std::size_t getOffset() const { return offset; }
 
+  // TODO I think this should return the actual limit without regards to the batch size,
+  //      so we can use it to calculate upstream calls. The batch size should be applied
+  //      when allocating blocks only!
   std::size_t getLimit() const {
     return clampToLimit(ExecutionBlock::DefaultBatchSize);
   }
@@ -132,18 +168,14 @@ struct AqlCall {
     return !std::holds_alternative<AqlCall::Infinity>(hardLimit);
   }
 
+  bool hasSoftLimit() const {
+    return !std::holds_alternative<AqlCall::Infinity>(softLimit);
+  }
+
   bool needsFullCount() const { return fullCount; }
 
   bool shouldSkip() const {
-    if (getOffset() > 0) {
-      // Still need to skip.
-      return true;
-    }
-    if (getLimit() > 0) {
-      // Still need to produce.
-      return false;
-    }
-    return needsFullCount();
+    return getOffset() > 0 || (getLimit() == 0 && needsFullCount());
   }
 };
 
@@ -154,10 +186,7 @@ constexpr bool operator<(AqlCall::Limit const& a, AqlCall::Limit const& b) {
   if (std::holds_alternative<AqlCall::Infinity>(b)) {
     return true;
   }
-  if (std::get<size_t>(a) < std::get<size_t>(b)) {
-    return true;
-  }
-  return false;
+  return std::get<size_t>(a) < std::get<size_t>(b);
 }
 
 constexpr AqlCall::Limit operator+(AqlCall::Limit const& a, size_t n) {
@@ -210,12 +239,11 @@ inline std::ostream& operator<<(std::ostream& out,
 }
 
 inline std::ostream& operator<<(std::ostream& out, const arangodb::aql::AqlCall& call) {
-  return out << "skip: " << call.getOffset() << " softLimit: " << call.softLimit
-             << " hardLimit: " << call.hardLimit
-             << " fullCount: " << std::boolalpha << call.fullCount;
+  return out << "{ skip: " << call.getOffset() << ", softLimit: " << call.softLimit
+             << ", hardLimit: " << call.hardLimit
+             << ", fullCount: " << std::boolalpha << call.fullCount << " }";
 }
 
-}  // namespace aql
-}  // namespace arangodb
+}  // namespace arangodb::aql
 
 #endif
diff --git a/arangod/Aql/AqlCallStack.h b/arangod/Aql/AqlCallStack.h
index b4af03eec652..0566b2340cb6 100644
--- a/arangod/Aql/AqlCallStack.h
+++ b/arangod/Aql/AqlCallStack.h
@@ -33,7 +33,7 @@ namespace aql {
 class AqlCallStack {
  public:
   // Initial
-  AqlCallStack(AqlCall call);
+  explicit AqlCallStack(AqlCall call);
   // Used in subquery
   AqlCallStack(AqlCallStack const& other, AqlCall call);
   // Used to pass between blocks
@@ -73,6 +73,16 @@ class AqlCallStack {
   // This is used to bypass all executors until we reach the next subquery start.
   void increaseSubqueryDepth();
 
+  // TODO: Remove me again, only used to fake DONE
+  // @deprecated
+  auto empty() const noexcept -> bool {
+    return _operations.empty() && _depth == 0;
+  }
+
+  auto subqueryLevel() const noexcept -> size_t {
+    return _operations.size() + _depth;
+  }
+
  private:
   // The list of operations, stacked by depth (e.g. bottom element is from main query)
   std::stack<AqlCall> _operations;
@@ -87,4 +97,4 @@ class AqlCallStack {
 }  // namespace aql
 }  // namespace arangodb
 
-#endif
\ No newline at end of file
+#endif
diff --git a/arangod/Aql/AqlItemBlock.cpp b/arangod/Aql/AqlItemBlock.cpp
index 0238f9a646f1..82edf0f715e3 100644
--- a/arangod/Aql/AqlItemBlock.cpp
+++ b/arangod/Aql/AqlItemBlock.cpp
@@ -956,7 +956,7 @@ RegisterId AqlItemBlock::getNrRegs() const noexcept { return _nrRegs; }
 
 size_t AqlItemBlock::size() const noexcept { return _nrItems; }
 
-std::tuple<size_t, size_t> AqlItemBlock::getRelevantRange() {
+std::tuple<size_t, size_t> AqlItemBlock::getRelevantRange() const {
   // NOTE:
   // Right now we can only support a range of datarows, that ends
   // In a range of ShadowRows.
diff --git a/arangod/Aql/AqlItemBlock.h b/arangod/Aql/AqlItemBlock.h
index 6badb45b8c5d..e765ba3ac2ad 100644
--- a/arangod/Aql/AqlItemBlock.h
+++ b/arangod/Aql/AqlItemBlock.h
@@ -167,7 +167,7 @@ class AqlItemBlock {
   size_t size() const noexcept;
 
   /// @brief get the relevant consumable range of the block
-  std::tuple<size_t, size_t> getRelevantRange();
+  std::tuple<size_t, size_t> getRelevantRange() const;
 
   /// @brief Number of entries in the matrix. If this changes, the memory usage
   /// must be / in- or decreased appropriately as well.
diff --git a/arangod/Aql/AqlItemBlockInputRange.cpp b/arangod/Aql/AqlItemBlockInputRange.cpp
index fa171c5a7243..4a0156247621 100644
--- a/arangod/Aql/AqlItemBlockInputRange.cpp
+++ b/arangod/Aql/AqlItemBlockInputRange.cpp
@@ -30,22 +30,22 @@
 using namespace arangodb;
 using namespace arangodb::aql;
 
-AqlItemBlockInputRange::AqlItemBlockInputRange(ExecutorState state)
-    : _block(nullptr), _rowIndex(0), _endIndex(0), _finalState(state) {
+AqlItemBlockInputRange::AqlItemBlockInputRange(ExecutorState state, std::size_t skipped)
+    : _finalState{state}, _skipped{skipped} {
   TRI_ASSERT(!hasDataRow());
 }
 
-AqlItemBlockInputRange::AqlItemBlockInputRange(ExecutorState state,
-                                               SharedAqlItemBlockPtr const& block,
-                                               std::size_t index, std::size_t)
-    : _block{block}, _rowIndex{index}, _endIndex(_block->size()), _finalState{state} {
+AqlItemBlockInputRange::AqlItemBlockInputRange(ExecutorState state, std::size_t skipped,
+                                               arangodb::aql::SharedAqlItemBlockPtr const& block,
+                                               std::size_t index)
+    : _block{block}, _rowIndex{index}, _finalState{state}, _skipped{skipped} {
   TRI_ASSERT(index <= _block->size());
 }
 
-AqlItemBlockInputRange::AqlItemBlockInputRange(ExecutorState state,
-                                               SharedAqlItemBlockPtr&& block,
-                                               std::size_t index, std::size_t) noexcept
-    : _block{std::move(block)}, _rowIndex{index}, _endIndex(_block->size()), _finalState{state} {
+AqlItemBlockInputRange::AqlItemBlockInputRange(ExecutorState state, std::size_t skipped,
+                                               arangodb::aql::SharedAqlItemBlockPtr&& block,
+                                               std::size_t index) noexcept
+    : _block{std::move(block)}, _rowIndex{index}, _finalState{state}, _skipped{skipped} {
   TRI_ASSERT(index <= _block->size());
 }
 
@@ -57,7 +57,7 @@ bool AqlItemBlockInputRange::hasDataRow() const noexcept {
   return isIndexValid(_rowIndex) && !isShadowRowAtIndex(_rowIndex);
 }
 
-std::pair<ExecutorState, InputAqlItemRow> AqlItemBlockInputRange::peekDataRow() {
+std::pair<ExecutorState, InputAqlItemRow> AqlItemBlockInputRange::peekDataRow() const {
   if (hasDataRow()) {
     return std::make_pair(nextState<LookAhead::NEXT, RowType::DATA>(),
                           InputAqlItemRow{_block, _rowIndex});
@@ -95,7 +95,7 @@ bool AqlItemBlockInputRange::isShadowRowAtIndex(std::size_t index) const noexcep
   return _block->isShadowRow(index);
 }
 
-std::pair<ExecutorState, ShadowAqlItemRow> AqlItemBlockInputRange::peekShadowRow() {
+std::pair<ExecutorState, ShadowAqlItemRow> AqlItemBlockInputRange::peekShadowRow() const {
   if (hasShadowRow()) {
     return std::make_pair(nextState<LookAhead::NEXT, RowType::SHADOW>(),
                           ShadowAqlItemRow{_block, _rowIndex});
@@ -146,3 +146,19 @@ ExecutorState AqlItemBlockInputRange::nextState() const noexcept {
     return ExecutorState::DONE;
   }
 }
+
+auto AqlItemBlockInputRange::skip(std::size_t const toSkip) noexcept -> std::size_t {
+  auto const skipCount = std::min(_skipped, toSkip);
+  _skipped -= skipCount;
+  return skipCount;
+}
+
+auto AqlItemBlockInputRange::skippedInFlight() const noexcept -> std::size_t {
+  return _skipped;
+}
+
+auto AqlItemBlockInputRange::skipAll() noexcept -> std::size_t {
+  auto const skipped = _skipped;
+  _skipped = 0;
+  return skipped;
+}
diff --git a/arangod/Aql/AqlItemBlockInputRange.h b/arangod/Aql/AqlItemBlockInputRange.h
index 42de49fbb586..79461c8b66f4 100644
--- a/arangod/Aql/AqlItemBlockInputRange.h
+++ b/arangod/Aql/AqlItemBlockInputRange.h
@@ -33,12 +33,14 @@ class ShadowAqlItemRow;
 
 class AqlItemBlockInputRange {
  public:
-  explicit AqlItemBlockInputRange(ExecutorState state);
+  explicit AqlItemBlockInputRange(ExecutorState state, std::size_t skipped = 0);
 
-  AqlItemBlockInputRange(ExecutorState, arangodb::aql::SharedAqlItemBlockPtr const&,
-                         std::size_t startIndex, std::size_t endIndex);
-  AqlItemBlockInputRange(ExecutorState, arangodb::aql::SharedAqlItemBlockPtr&&,
-                         std::size_t startIndex, std::size_t endIndex) noexcept;
+  AqlItemBlockInputRange(ExecutorState, std::size_t skipped,
+                         arangodb::aql::SharedAqlItemBlockPtr const&, std::size_t startIndex);
+
+  AqlItemBlockInputRange(ExecutorState, std::size_t skipped,
+                         arangodb::aql::SharedAqlItemBlockPtr&&,
+                         std::size_t startIndex) noexcept;
 
   arangodb::aql::SharedAqlItemBlockPtr getBlock() const noexcept;
 
@@ -47,18 +49,26 @@ class AqlItemBlockInputRange {
 
   bool hasDataRow() const noexcept;
 
-  std::pair<ExecutorState, arangodb::aql::InputAqlItemRow> peekDataRow();
+  std::pair<ExecutorState, arangodb::aql::InputAqlItemRow> peekDataRow() const;
 
   std::pair<ExecutorState, arangodb::aql::InputAqlItemRow> nextDataRow();
 
-  std::size_t getRowIndex() noexcept { return _rowIndex; };
+  std::size_t getRowIndex() const noexcept { return _rowIndex; };
 
   bool hasShadowRow() const noexcept;
 
-  std::pair<ExecutorState, arangodb::aql::ShadowAqlItemRow> peekShadowRow();
+  std::pair<ExecutorState, arangodb::aql::ShadowAqlItemRow> peekShadowRow() const;
 
   std::pair<ExecutorState, arangodb::aql::ShadowAqlItemRow> nextShadowRow();
 
+  // Subtract up to this many rows from the local `_skipped` state; return
+  // the number actually skipped. Does not skip data rows.
+  [[nodiscard]] auto skip(std::size_t) noexcept -> std::size_t;
+
+  [[nodiscard]] auto skipAll() noexcept -> std::size_t;
+
+  [[nodiscard]] auto skippedInFlight() const noexcept -> std::size_t;
+
  private:
   bool isIndexValid(std::size_t index) const noexcept;
 
@@ -70,10 +80,11 @@ class AqlItemBlockInputRange {
   ExecutorState nextState() const noexcept;
 
  private:
-  arangodb::aql::SharedAqlItemBlockPtr _block;
-  std::size_t _rowIndex;
-  std::size_t _endIndex;
-  ExecutorState _finalState;
+  arangodb::aql::SharedAqlItemBlockPtr _block{nullptr};
+  std::size_t _rowIndex{};
+  ExecutorState _finalState{ExecutorState::HASMORE};
+  // How many rows were skipped upstream
+  std::size_t _skipped{};
 };
 
 }  // namespace arangodb::aql
diff --git a/arangod/Aql/ConstFetcher.cpp b/arangod/Aql/ConstFetcher.cpp
index 16c011228246..bef0a172bef9 100644
--- a/arangod/Aql/ConstFetcher.cpp
+++ b/arangod/Aql/ConstFetcher.cpp
@@ -40,7 +40,9 @@ auto ConstFetcher::execute(AqlCallStack& stack)
     -> std::tuple<ExecutionState, size_t, AqlItemBlockInputRange> {
   // Note this fetcher can only be executed on top level (it is the singleton, or test)
   TRI_ASSERT(stack.isRelevant());
-  auto call = stack.popCall();
+  // We only peek the call here, as we do not take over ownership.
+  // We can replace this by pop again if all executors also only take a reference to the stack.
+  auto call = stack.peek();
   if (_blockForPassThrough == nullptr) {
     // we are done, nothing to move arround here.
     return {ExecutionState::DONE, 0, AqlItemBlockInputRange{ExecutorState::DONE}};
@@ -151,7 +153,7 @@ auto ConstFetcher::execute(AqlCallStack& stack)
     _blockForPassThrough.reset(nullptr);
     _rowIndex = 0;
     return {ExecutionState::DONE, call.getSkipCount(),
-            DataRange{ExecutorState::DONE, resultBlock, 0, resultBlock->size()}};
+            DataRange{ExecutorState::DONE, call.getSkipCount(), resultBlock, 0}};
   }
 
   SharedAqlItemBlockPtr resultBlock = _blockForPassThrough;
@@ -185,7 +187,7 @@ auto ConstFetcher::execute(AqlCallStack& stack)
 
   resultBlock = resultBlock->slice(sliceIndexes);
   return {resState, call.getSkipCount(),
-          DataRange{rangeState, resultBlock, 0, resultBlock->size()}};
+          DataRange{rangeState, call.getSkipCount(), resultBlock, 0}};
 }
 
 void ConstFetcher::injectBlock(SharedAqlItemBlockPtr block) {
diff --git a/arangod/Aql/DependencyProxy.cpp b/arangod/Aql/DependencyProxy.cpp
index 5d16d05dd4e6..b7828fea8ec4 100644
--- a/arangod/Aql/DependencyProxy.cpp
+++ b/arangod/Aql/DependencyProxy.cpp
@@ -65,15 +65,16 @@ DependencyProxy<blockPassthrough>::execute(AqlCallStack& stack) {
       break;
     }
 
-    if (block == nullptr) {
-      // We're not waiting and didn't get a block, so we have to be done.
+    if (skipped == 0 && block == nullptr) {
+      // We're not waiting and didn't get any input, so we have to be done.
       TRI_ASSERT(state == ExecutionState::DONE);
       if (!advanceDependency()) {
         break;
       }
     }
 
-  } while (block == nullptr);
+  } while (skipped == 0 && block == nullptr);
+
   return {state, skipped, block};
 }
 
diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index 031907416678..7a0333327d6f 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -141,7 +141,7 @@ constexpr bool isNewStyleExecutor =
                 TestLambdaExecutor,
                 TestLambdaSkipExecutor,  // we need one after these to avoid compile errors in non-test mode
 #endif
-                ShortestPathExecutor, EnumerateListExecutor>;
+                ShortestPathExecutor, EnumerateListExecutor, LimitExecutor>;
 
 template <class Executor>
 ExecutionBlockImpl<Executor>::ExecutionBlockImpl(ExecutionEngine* engine,
@@ -186,134 +186,137 @@ std::pair<ExecutionState, SharedAqlItemBlockPtr> ExecutionBlockImpl<Executor>::g
 
 template <class Executor>
 std::pair<ExecutionState, SharedAqlItemBlockPtr> ExecutionBlockImpl<Executor>::getSomeWithoutTrace(size_t atMost) {
-  TRI_ASSERT(atMost <= ExecutionBlock::DefaultBatchSize);
-  // silence tests -- we need to introduce new failure tests for fetchers
-  TRI_IF_FAILURE("ExecutionBlock::getOrSkipSome1") {
-    THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
-  }
-  TRI_IF_FAILURE("ExecutionBlock::getOrSkipSome2") {
-    THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
-  }
-  TRI_IF_FAILURE("ExecutionBlock::getOrSkipSome3") {
-    THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
-  }
-
-  if (getQuery().killed()) {
-    THROW_ARANGO_EXCEPTION(TRI_ERROR_QUERY_KILLED);
-  }
+  if constexpr (isNewStyleExecutor<Executor>) {
+    TRI_ASSERT(false);
+    THROW_ARANGO_EXCEPTION(TRI_ERROR_INTERNAL_AQL);
+  } else {
+    TRI_ASSERT(atMost <= ExecutionBlock::DefaultBatchSize);
+    // silence tests -- we need to introduce new failure tests for fetchers
+    TRI_IF_FAILURE("ExecutionBlock::getOrSkipSome1") {
+      THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
+    }
+    TRI_IF_FAILURE("ExecutionBlock::getOrSkipSome2") {
+      THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
+    }
+    TRI_IF_FAILURE("ExecutionBlock::getOrSkipSome3") {
+      THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
+    }
 
-  if (_state == InternalState::DONE) {
-    // We are done, so we stay done
-    return {ExecutionState::DONE, nullptr};
-  }
+    if (getQuery().killed()) {
+      THROW_ARANGO_EXCEPTION(TRI_ERROR_QUERY_KILLED);
+    }
 
-  if (!_outputItemRow) {
-    ExecutionState state;
-    SharedAqlItemBlockPtr newBlock;
-    std::tie(state, newBlock) =
-        requestWrappedBlock(atMost, _infos.numberOfOutputRegisters());
-    if (state == ExecutionState::WAITING) {
-      TRI_ASSERT(newBlock == nullptr);
-      return {state, nullptr};
+    if (_state == InternalState::DONE) {
+      // We are done, so we stay done
+      return {ExecutionState::DONE, nullptr};
     }
-    if (newBlock == nullptr) {
-      TRI_ASSERT(state == ExecutionState::DONE);
-      _state = InternalState::DONE;
-      // _rowFetcher must be DONE now already
-      return {state, nullptr};
+
+    if (!_outputItemRow) {
+      ExecutionState state;
+      SharedAqlItemBlockPtr newBlock;
+      std::tie(state, newBlock) =
+          requestWrappedBlock(atMost, _infos.numberOfOutputRegisters());
+      if (state == ExecutionState::WAITING) {
+        TRI_ASSERT(newBlock == nullptr);
+        return {state, nullptr};
+      }
+      if (newBlock == nullptr) {
+        TRI_ASSERT(state == ExecutionState::DONE);
+        _state = InternalState::DONE;
+        // _rowFetcher must be DONE now already
+        return {state, nullptr};
+      }
+      TRI_ASSERT(newBlock != nullptr);
+      TRI_ASSERT(newBlock->size() > 0);
+      // We cannot hold this assertion, if we are on a pass-through
+      // block and the upstream uses execute already.
+      // TRI_ASSERT(newBlock->size() <= atMost);
+      _outputItemRow = createOutputRow(newBlock, AqlCall{});
     }
-    TRI_ASSERT(newBlock != nullptr);
-    TRI_ASSERT(newBlock->size() > 0);
-    // We cannot hold this assertion, if we are on a pass-through
-    // block and the upstream uses execute already.
-    // TRI_ASSERT(newBlock->size() <= atMost);
-    _outputItemRow = createOutputRow(newBlock, AqlCall{});
-  }
 
-  ExecutionState state = ExecutionState::HASMORE;
-  ExecutorStats executorStats{};
-
-  TRI_ASSERT(atMost > 0);
-
-  if (isInSplicedSubquery()) {
-    // The loop has to be entered at least once!
-    TRI_ASSERT(!_outputItemRow->isFull());
-    while (!_outputItemRow->isFull() && _state != InternalState::DONE) {
-      // Assert that write-head is always pointing to a free row
-      TRI_ASSERT(!_outputItemRow->produced());
-      switch (_state) {
-        case InternalState::FETCH_DATA: {
-          std::tie(state, executorStats) = _executor.produceRows(*_outputItemRow);
-          // Count global but executor-specific statistics, like number of
-          // filtered rows.
-          _engine->_stats += executorStats;
-          if (_outputItemRow->produced()) {
-            _outputItemRow->advanceRow();
-          }
+    ExecutionState state = ExecutionState::HASMORE;
+    ExecutorStats executorStats{};
+
+    TRI_ASSERT(atMost > 0);
+
+    if (isInSplicedSubquery()) {
+      // The loop has to be entered at least once!
+      TRI_ASSERT(!_outputItemRow->isFull());
+      while (!_outputItemRow->isFull() && _state != InternalState::DONE) {
+        // Assert that write-head is always pointing to a free row
+        TRI_ASSERT(!_outputItemRow->produced());
+        switch (_state) {
+          case InternalState::FETCH_DATA: {
+            std::tie(state, executorStats) = _executor.produceRows(*_outputItemRow);
+            // Count global but executor-specific statistics, like number of
+            // filtered rows.
+            _engine->_stats += executorStats;
+            if (_outputItemRow->produced()) {
+              _outputItemRow->advanceRow();
+            }
 
-          if (state == ExecutionState::WAITING) {
-            return {state, nullptr};
-          }
+            if (state == ExecutionState::WAITING) {
+              return {state, nullptr};
+            }
 
-          if (state == ExecutionState::DONE) {
-            _state = InternalState::FETCH_SHADOWROWS;
+            if (state == ExecutionState::DONE) {
+              _state = InternalState::FETCH_SHADOWROWS;
+            }
+            break;
           }
-          break;
-        }
-        case InternalState::FETCH_SHADOWROWS: {
-          state = fetchShadowRowInternal();
-          if (state == ExecutionState::WAITING) {
-            return {state, nullptr};
+          case InternalState::FETCH_SHADOWROWS: {
+            state = fetchShadowRowInternal();
+            if (state == ExecutionState::WAITING) {
+              return {state, nullptr};
+            }
+            break;
+          }
+          case InternalState::DONE: {
+            TRI_ASSERT(false);  // Invalid state
           }
-          break;
-        }
-        case InternalState::DONE: {
-          TRI_ASSERT(false);  // Invalid state
         }
       }
-    }
-    // Modify the return state.
-    // As long as we do still have ShadowRows
-    // We need to return HASMORE!
-    if (_state == InternalState::DONE) {
-      state = ExecutionState::DONE;
-    } else {
-      state = ExecutionState::HASMORE;
-    }
-  } else {
-    // The loop has to be entered at least once!
-    TRI_ASSERT(!_outputItemRow->isFull());
-    while (!_outputItemRow->isFull()) {
-      std::tie(state, executorStats) = _executor.produceRows(*_outputItemRow);
-      // Count global but executor-specific statistics, like number of filtered
-      // rows.
-      _engine->_stats += executorStats;
-      if (_outputItemRow->produced()) {
-        _outputItemRow->advanceRow();
+      // Modify the return state.
+      // As long as we do still have ShadowRows
+      // We need to return HASMORE!
+      if (_state == InternalState::DONE) {
+        state = ExecutionState::DONE;
+      } else {
+        state = ExecutionState::HASMORE;
       }
+    } else {
+      // The loop has to be entered at least once!
+      TRI_ASSERT(!_outputItemRow->isFull());
+      while (!_outputItemRow->isFull()) {
+        std::tie(state, executorStats) = _executor.produceRows(*_outputItemRow);
+        // Count global but executor-specific statistics, like number of filtered rows.
+        _engine->_stats += executorStats;
+        if (_outputItemRow->produced()) {
+          _outputItemRow->advanceRow();
+        }
 
-      if (state == ExecutionState::WAITING) {
-        return {state, nullptr};
-      }
+        if (state == ExecutionState::WAITING) {
+          return {state, nullptr};
+        }
 
-      if (state == ExecutionState::DONE) {
-        auto outputBlock = _outputItemRow->stealBlock();
-        // This is not strictly necessary here, as we shouldn't be called again
-        // after DONE.
-        _outputItemRow.reset();
-        return {state, std::move(outputBlock)};
+        if (state == ExecutionState::DONE) {
+          auto outputBlock = _outputItemRow->stealBlock();
+          // This is not strictly necessary here, as we shouldn't be called again after DONE.
+          _outputItemRow.reset();
+          return {state, std::move(outputBlock)};
+        }
       }
+
+      TRI_ASSERT(state == ExecutionState::HASMORE);
+      TRI_ASSERT(_outputItemRow->isFull());
     }
 
-    TRI_ASSERT(state == ExecutionState::HASMORE);
-    TRI_ASSERT(_outputItemRow->isFull());
+    auto outputBlock = _outputItemRow->stealBlock();
+    // we guarantee that we do return a valid pointer in the HASMORE case.
+    TRI_ASSERT(outputBlock != nullptr || _state == InternalState::DONE);
+    _outputItemRow.reset();
+    return {state, std::move(outputBlock)};
   }
-
-  auto outputBlock = _outputItemRow->stealBlock();
-  // we guarantee that we do return a valid pointer in the HASMORE case.
-  TRI_ASSERT(outputBlock != nullptr || _state == InternalState::DONE);
-  _outputItemRow.reset();
-  return {state, std::move(outputBlock)};
 }
 
 template <class Executor>
@@ -402,6 +405,7 @@ struct ExecuteSkipVariant<SkipVariants::GET_SOME> {
 
 template <class Executor>
 static SkipVariants constexpr skipType() {
+  static_assert(!isNewStyleExecutor<Executor>);
   bool constexpr useFetcher =
       Executor::Properties::allowsBlockPassthrough == BlockPassthrough::Enable &&
       !std::is_same<Executor, SubqueryExecutor<true>>::value;
@@ -507,30 +511,35 @@ std::pair<ExecutionState, size_t> ExecutionBlockImpl<Executor>::skipSome(size_t
 
 template <class Executor>
 std::pair<ExecutionState, size_t> ExecutionBlockImpl<Executor>::skipSomeOnceWithoutTrace(size_t atMost) {
-  constexpr SkipVariants customSkipType = skipType<Executor>();
+  if constexpr (isNewStyleExecutor<Executor>) {
+    TRI_ASSERT(false);
+    THROW_ARANGO_EXCEPTION(TRI_ERROR_INTERNAL_AQL);
+  } else {
+    constexpr SkipVariants customSkipType = skipType<Executor>();
 
-  if (customSkipType == SkipVariants::GET_SOME) {
-    atMost = std::min(atMost, DefaultBatchSize);
-    auto res = getSomeWithoutTrace(atMost);
+    if constexpr (customSkipType == SkipVariants::GET_SOME) {
+      atMost = std::min(atMost, DefaultBatchSize);
+      auto res = getSomeWithoutTrace(atMost);
 
-    size_t skipped = 0;
-    if (res.second != nullptr) {
-      skipped = res.second->size();
+      size_t skipped = 0;
+      if (res.second != nullptr) {
+        skipped = res.second->size();
+      }
+      TRI_ASSERT(skipped <= atMost);
+
+      return {res.first, skipped};
     }
+
+    ExecutionState state;
+    typename Executor::Stats stats;
+    size_t skipped;
+    std::tie(state, stats, skipped) =
+        ExecuteSkipVariant<customSkipType>::executeSkip(_executor, _rowFetcher, atMost);
+    _engine->_stats += stats;
     TRI_ASSERT(skipped <= atMost);
 
-    return {res.first, skipped};
+    return {state, skipped};
   }
-
-  ExecutionState state;
-  typename Executor::Stats stats;
-  size_t skipped;
-  std::tie(state, stats, skipped) =
-      ExecuteSkipVariant<customSkipType>::executeSkip(_executor, _rowFetcher, atMost);
-  _engine->_stats += stats;
-  TRI_ASSERT(skipped <= atMost);
-
-  return {state, skipped};
 }
 
 template <bool customInit>
@@ -617,9 +626,11 @@ std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> ExecutionBlockImpl<Exe
 
   // Fall back to getSome/skipSome
   auto myCall = stack.popCall();
-  TRI_ASSERT(AqlCall::IsSkipSomeCall(myCall) ||
-             AqlCall::IsGetSomeCall(myCall) || AqlCall::IsFullCountCall(myCall));
+
+  TRI_ASSERT(AqlCall::IsSkipSomeCall(myCall) || AqlCall::IsGetSomeCall(myCall) ||
+             AqlCall::IsFullCountCall(myCall) || AqlCall::IsFastForwardCall(myCall));
   _rowFetcher.useStack(stack);
+
   if (AqlCall::IsSkipSomeCall(myCall)) {
     auto const [state, skipped] = skipSome(myCall.getOffset());
     if (state != ExecutionState::WAITING) {
@@ -629,6 +640,14 @@ std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> ExecutionBlockImpl<Exe
   } else if (AqlCall::IsGetSomeCall(myCall)) {
     auto const [state, block] = getSome(myCall.getLimit());
     // We do not need to count as softLimit will be overwritten, and hard cannot be set.
+    if (stack.empty() && myCall.hasHardLimit() && !myCall.needsFullCount() && block != nullptr) {
+      // However we can do a short-cut here to report DONE on hardLimit if we are on the top-level query.
+      myCall.didProduce(block->size());
+      if (myCall.getLimit() == 0) {
+        return {ExecutionState::DONE, 0, block};
+      }
+    }
+
     return {state, 0, block};
   } else if (AqlCall::IsFullCountCall(myCall)) {
     auto const [state, skipped] = skipSome(ExecutionBlock::SkipAllSize());
@@ -636,6 +655,9 @@ std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> ExecutionBlockImpl<Exe
       myCall.didSkip(skipped);
     }
     return {state, skipped, nullptr};
+  } else if (AqlCall::IsFastForwardCall(myCall)) {
+    // No idea if DONE is correct here...
+    return {ExecutionState::DONE, 0, nullptr};
   }
   // Should never get here!
   THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
@@ -936,11 +958,13 @@ std::pair<ExecutionState, SharedAqlItemBlockPtr> ExecutionBlockImpl<Executor>::r
       "Properties::inputSizeRestrictsOutputSize is true");
 
   constexpr RequestWrappedBlockVariant variant =
-      Executor::Properties::allowsBlockPassthrough == BlockPassthrough::Enable
-          ? RequestWrappedBlockVariant::PASS_THROUGH
-          : Executor::Properties::inputSizeRestrictsOutputSize
-                ? RequestWrappedBlockVariant::INPUTRESTRICTED
-                : RequestWrappedBlockVariant::DEFAULT;
+      isNewStyleExecutor<Executor>
+          ? RequestWrappedBlockVariant::DEFAULT
+          : Executor::Properties::allowsBlockPassthrough == BlockPassthrough::Enable
+                ? RequestWrappedBlockVariant::PASS_THROUGH
+                : Executor::Properties::inputSizeRestrictsOutputSize
+                      ? RequestWrappedBlockVariant::INPUTRESTRICTED
+                      : RequestWrappedBlockVariant::DEFAULT;
 
   // Override for spliced subqueries, this optimization does not work there.
   if (isInSplicedSubquery() && variant == RequestWrappedBlockVariant::INPUTRESTRICTED) {
@@ -1003,10 +1027,6 @@ auto ExecutionBlockImpl<Executor>::nextState(AqlCall const& call) const -> ExecS
     // Then produce
     return ExecState::PRODUCE;
   }
-  if (call.needsFullCount()) {
-    // then fullcount
-    return ExecState::FULLCOUNT;
-  }
   if (call.hardLimit == 0) {
     // We reached hardLimit, fast forward
     return ExecState::FASTFORWARD;
@@ -1030,8 +1050,6 @@ SharedAqlItemBlockPtr ExecutionBlockImpl<Executor>::requestBlock(size_t nrItems,
 //           ahead on the input range, fetching new blocks when necessary
 // EXECUTOR: the executor has a specialised skipRowsRange method
 //           that will be called to skip
-// GET_SOME: we just request rows from the executor and then discard
-//           them
 //
 enum class SkipRowsRangeVariant { FETCHER, EXECUTOR };
 
@@ -1061,8 +1079,7 @@ static SkipRowsRangeVariant constexpr skipRowsType() {
 #ifdef ARANGODB_USE_GOOGLE_TESTS
                                  TestLambdaSkipExecutor,
 #endif
-                                 EnumerateListExecutor, SortedCollectExecutor>),
-
+                                 EnumerateListExecutor, SortedCollectExecutor, LimitExecutor>),
                 "Unexpected executor for SkipVariants::EXECUTOR");
 
   // The LimitExecutor will not work correctly with SkipVariants::FETCHER!
@@ -1085,9 +1102,9 @@ template <class T>
 struct dependent_false : std::false_type {};
 
 template <class Executor>
-std::tuple<ExecutorState, typename Executor::Stats, size_t, AqlCall>
-ExecutionBlockImpl<Executor>::executeSkipRowsRange(AqlItemBlockInputRange& inputRange,
-                                                   AqlCall& call) {
+auto ExecutionBlockImpl<Executor>::executeSkipRowsRange(AqlItemBlockInputRange& inputRange,
+                                                        AqlCall& call)
+    -> std::tuple<ExecutorState, typename Executor::Stats, size_t, AqlCall> {
   if constexpr (isNewStyleExecutor<Executor>) {
     call.skippedRows = 0;
     if constexpr (skipRowsType<Executor>() == SkipRowsRangeVariant::EXECUTOR) {
@@ -1117,6 +1134,66 @@ ExecutionBlockImpl<Executor>::executeSkipRowsRange(AqlItemBlockInputRange& input
   return std::make_tuple(ExecutorState::DONE, typename Executor::Stats{}, 0, call);
 }
 
+/**
+ * @brief Define the variant of FastForward behaviour
+ *
+ * FULLCOUNT => Call executeSkipRowsRange and report what has been skipped.
+ * EXECUTOR => Call executeSkipRowsRange, but do not report what has been skipped.
+ *             (This instance is used to make sure Modifications are performed, or stats are correct)
+ * FETCHER => Do not bother the Executor, drop all from input, without further reporting
+ *
+ */
+enum class FastForwardVariant { FULLCOUNT, EXECUTOR, FETCHER };
+
+template <class Executor>
+static auto fastForwardType(AqlCall const& call, Executor const& e) -> FastForwardVariant {
+  if (call.needsFullCount() && call.getOffset() == 0 && call.getLimit() == 0) {
+    // Only start fullCount after the original call is fulfilled. Otherwise
+    // do fast-forward variant
+    TRI_ASSERT(call.hasHardLimit());
+    return FastForwardVariant::FULLCOUNT;
+  }
+  // TODO: We only need to do this is the executor actually require to call.
+  // e.g. Modifications will always need to be called. Limit only if it needs to report fullCount
+  if constexpr (is_one_of_v<Executor, LimitExecutor>) {
+    return FastForwardVariant::EXECUTOR;
+  }
+  return FastForwardVariant::FETCHER;
+}
+
+template <class Executor>
+auto ExecutionBlockImpl<Executor>::executeFastForward(AqlItemBlockInputRange& inputRange,
+                                                      AqlCall& clientCall)
+    -> std::tuple<ExecutorState, typename Executor::Stats, size_t, AqlCall> {
+  TRI_ASSERT(isNewStyleExecutor<Executor>);
+  auto type = fastForwardType(clientCall, _executor);
+  switch (type) {
+    case FastForwardVariant::FULLCOUNT:
+    case FastForwardVariant::EXECUTOR: {
+      LOG_QUERY("cb135", DEBUG) << printTypeInfo() << " apply full count.";
+      auto [state, stats, skippedLocal, call] = executeSkipRowsRange(_lastRange, clientCall);
+      if (type == FastForwardVariant::EXECUTOR) {
+        // We do not report the skip
+        skippedLocal = 0;
+      }
+      return {state, stats, skippedLocal, call};
+    }
+    case FastForwardVariant::FETCHER: {
+      LOG_QUERY("fa327", DEBUG) << printTypeInfo() << " bypass unused rows.";
+      while (inputRange.hasDataRow()) {
+        auto [state, row] = inputRange.nextDataRow();
+        TRI_ASSERT(row.isInitialized());
+      }
+      AqlCall call{};
+      call.hardLimit = 0;
+      return {inputRange.upstreamState(), typename Executor::Stats{}, 0, call};
+    }
+  }
+  // Unreachable
+  TRI_ASSERT(false);
+  THROW_ARANGO_EXCEPTION(TRI_ERROR_INTERNAL_AQL);
+}
+
 /**
  * @brief This is the central function of an executor, and it acts like a
  * coroutine: It can be called multiple times and keeps state across
@@ -1124,13 +1201,12 @@ ExecutionBlockImpl<Executor>::executeSkipRowsRange(AqlItemBlockInputRange& input
  *
  * The intended behaviour of this function is best described in terms of
  * a state machine; the possible states are the ExecStates
- * SKIP, PRODUCE, FULLCOUNT, FASTFORWARD, UPSTREAM, SHADOWROWS, DONE
+ * SKIP, PRODUCE, FASTFORWARD, UPSTREAM, SHADOWROWS, DONE
  *
  * SKIP       skipping rows. How rows are skipped is determined by
  *            the Executor that is used. See SkipVariants
  * PRODUCE    calls produceRows of the executor
- * FULLCOUNT  again skipping rows. like skip, but will skip all rows
- * FASTFORWARD like fullcount, but does not count skipped rows.
+ * FASTFORWARD again skipping rows, will count skipped rows, if fullCount is requested.
  * UPSTREAM   fetches rows from the upstream executor(s) to be processed by
  *            our executor.
  * SHADOWROWS process any shadow rows
@@ -1139,12 +1215,12 @@ ExecutionBlockImpl<Executor>::executeSkipRowsRange(AqlItemBlockInputRange& input
  *
  * We progress within the states in the following way:
  *   There is a nextState method that determines the next state based on the call, it can only lead to:
- *   SKIP, PRODUCE, FULLCOUNT, FASTFORWAD, DONE
+ *   SKIP, PRODUCE, FASTFORWAD, DONE
  *
  *   On the first call we will use nextState to get to our starting point.
- *   After any of SKIP, PRODUCE, FULLCOUNT, FASTFORWAD, DONE We either go to
- *   1. DONE (if output is full)
- *   2. SHADOWROWS (if executor is done)
+ *   After any of SKIP, PRODUCE,, FASTFORWAD, DONE We either go to
+ *   1. FASTFORWARD (if executor is done)
+ *   2. DONE (if output is full)
  *   3. UPSTREAM if executor has More, (Invariant: input fully consumed)
  *   4. NextState (if none of the above applies)
  *
@@ -1177,6 +1253,10 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
     AqlCall clientCall = stack.popCall();
     ExecutorState localExecutorState = ExecutorState::DONE;
 
+    TRI_ASSERT(!(clientCall.getOffset() == 0 && clientCall.softLimit == AqlCall::Limit{0}));
+    TRI_ASSERT(!(clientCall.hasSoftLimit() && clientCall.fullCount));
+    TRI_ASSERT(!(clientCall.hasSoftLimit() && clientCall.hasHardLimit()));
+
     // We can only have returned the following internal states
     TRI_ASSERT(_execState == ExecState::CHECKCALL || _execState == ExecState::SHADOWROWS ||
                _execState == ExecState::UPSTREAM);
@@ -1195,6 +1275,8 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
       clientCall = _clientRequest;
     }
 
+    auto returnToState = ExecState::CHECKCALL;
+
     LOG_QUERY("007ac", DEBUG) << "starting statemachine of executor " << printBlockInfo();
     while (_execState != ExecState::DONE) {
       switch (_execState) {
@@ -1219,8 +1301,10 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
           // This means that they have to be removed from clientCall.getOffset()
           // This has to be done by the Executor calling call.didSkip()
           // accordingly.
-          if (canPassFullcount) {
-            // In htis case we can first skip. But straight after continue with fullCount, so we might skip more
+          // The LIMIT executor with a LIMIT of 0 can also bypass fullCount
+          // here, even if callLimit > 0
+          if (canPassFullcount || std::is_same_v<Executor, LimitExecutor>) {
+            // In this case we can first skip. But straight after continue with fullCount, so we might skip more
             TRI_ASSERT(clientCall.getOffset() + skippedLocal >= offsetBefore);
             if (clientCall.getOffset() + skippedLocal > offsetBefore) {
               // First need to count down offset.
@@ -1235,7 +1319,7 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
           _engine->_stats += stats;
           // The execute might have modified the client call.
           if (state == ExecutorState::DONE) {
-            _execState = ExecState::SHADOWROWS;
+            _execState = ExecState::FASTFORWARD;
           } else if (clientCall.getOffset() > 0) {
             TRI_ASSERT(_upstreamState != ExecutionState::DONE);
             // We need to request more
@@ -1253,6 +1337,15 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
           TRI_ASSERT(clientCall.getLimit() > 0);
 
           LOG_QUERY("1f786", DEBUG) << printTypeInfo() << " call produceRows " << clientCall;
+          if (outputIsFull()) {
+            // We need to be able to write data
+            // But maybe the existing block is full here
+            // Then we need to wake up again.
+            // However the client might decide on a different
+            // call, so we do not record this position
+            _execState = ExecState::DONE;
+            break;
+          }
           ensureOutputBlock(std::move(clientCall));
           TRI_ASSERT(_outputItemRow);
 
@@ -1265,10 +1358,13 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
           // Produce might have modified the clientCall
           clientCall = _outputItemRow->getClientCall();
 
-          if (_outputItemRow->isInitialized() && _outputItemRow->allRowsUsed()) {
+          if (state == ExecutorState::DONE) {
+            _execState = ExecState::FASTFORWARD;
+          } else if (Executor::Properties::allowsBlockPassthrough == BlockPassthrough::Enable &&
+                     outputIsFull()) {
+            // In pass through variant we need to stop whenever the block is full.
             _execState = ExecState::DONE;
-          } else if (state == ExecutorState::DONE) {
-            _execState = ExecState::SHADOWROWS;
+            break;
           } else if (clientCall.getLimit() > 0 && !_lastRange.hasDataRow()) {
             TRI_ASSERT(_upstreamState != ExecutionState::DONE);
             // We need to request more
@@ -1283,39 +1379,21 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
         case ExecState::FASTFORWARD: {
           LOG_QUERY("96e2c", DEBUG)
               << printTypeInfo() << " all produced, fast forward to end up (sub-)query.";
-          // We can either do FASTFORWARD or FULLCOUNT, difference is that
-          // fullcount counts what is produced now, FASTFORWARD simply drops
-          TRI_ASSERT(!clientCall.needsFullCount());
-          // We need to claim that the Executor was done
-          localExecutorState = ExecutorState::DONE;
-
-          // We can drop all dataRows from upstream
-          while (_lastRange.hasDataRow()) {
-            auto [state, row] = _lastRange.nextDataRow();
-            TRI_ASSERT(row.isInitialized());
-          }
-          if (_lastRange.upstreamState() == ExecutorState::DONE) {
-            _execState = ExecState::SHADOWROWS;
-          } else {
-            // We need to request more, simply send hardLimit 0 upstream
-            _upstreamRequest = AqlCall{};
-            _upstreamRequest.hardLimit = 0;
-            _execState = ExecState::UPSTREAM;
-          }
-          break;
-        }
-        case ExecState::FULLCOUNT: {
-          LOG_QUERY("ff258", DEBUG)
-              << printTypeInfo()
-              << " all produced, skip to end up (sub-)query, for fullCount.";
           auto [state, stats, skippedLocal, call] =
-              executeSkipRowsRange(_lastRange, clientCall);
+              executeFastForward(_lastRange, clientCall);
+
           _skipped += skippedLocal;
           _engine->_stats += stats;
           localExecutorState = state;
 
           if (state == ExecutorState::DONE) {
-            _execState = ExecState::SHADOWROWS;
+            if (_outputItemRow && _outputItemRow->isInitialized() &&
+                _outputItemRow->allRowsUsed()) {
+              // We have a block with data, but no more place for a shadow row.
+              _execState = ExecState::DONE;
+            } else {
+              _execState = ExecState::SHADOWROWS;
+            }
           } else {
             // We need to request more
             _upstreamRequest = call;
@@ -1334,8 +1412,18 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
           TRI_ASSERT(!_lastRange.hasShadowRow());
           size_t skippedLocal = 0;
           auto callCopy = _upstreamRequest;
+#ifdef ARANGODB_ENABLE_MAINTAINER_MODE
+          size_t subqueryLevelBefore = stack.subqueryLevel();
+#endif
           stack.pushCall(std::move(callCopy));
           std::tie(_upstreamState, skippedLocal, _lastRange) = _rowFetcher.execute(stack);
+          // As the stack is copied into the fetcher, we need to pop off our call again.
+          // If we use other datastructures or moving we may hand over ownership of the stack here
+          // instead and no popCall is necessary.
+          stack.popCall();
+#ifdef ARANGODB_ENABLE_MAINTAINER_MODE
+          TRI_ASSERT(subqueryLevelBefore == stack.subqueryLevel());
+#endif
           if (_upstreamState == ExecutionState::WAITING) {
             // We need to persist the old call before we return.
             // We might have some local accounting to this call.
@@ -1343,11 +1431,16 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
             // We do not return anything in WAITING state, also NOT skipped.
             return {_upstreamState, 0, nullptr};
           }
-          // We have a new range, passthrough can use this range.
-          _hasUsedDataRangeBlock = false;
-          _skipped += skippedLocal;
-          // We skipped through passthroug, so count that a skip was solved.
-          clientCall.didSkip(skippedLocal);
+          if constexpr (Executor::Properties::allowsBlockPassthrough ==
+                        BlockPassthrough::Enable) {
+            // We have a new range, passthrough can use this range.
+            _hasUsedDataRangeBlock = false;
+          }
+          if constexpr (skipRowsType<Executor>() == SkipRowsRangeVariant::FETCHER) {
+            _skipped += skippedLocal;
+            // We skipped through passthrough, so count that a skip was solved.
+            clientCall.didSkip(skippedLocal);
+          }
           _execState = ExecState::CHECKCALL;
           break;
         }
@@ -1361,6 +1454,14 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
           // NOTE: I do not think this is an issue, as the Executor will always say that it cannot do anything with
           // an empty input. Only exception might be COLLECT COUNT.
           if (_lastRange.hasShadowRow()) {
+            if (outputIsFull()) {
+              // We need to be able to write data
+              // But maybe the existing block is full here
+              // Then we need to wake up again here.
+              returnToState = ExecState::SHADOWROWS;
+              _execState = ExecState::DONE;
+              break;
+            }
             auto const& [state, shadowRow] = _lastRange.nextShadowRow();
             TRI_ASSERT(shadowRow.isInitialized());
             ensureOutputBlock(std::move(clientCall));
@@ -1393,6 +1494,7 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
         default:
           // unreachable
           TRI_ASSERT(false);
+          THROW_ARANGO_EXCEPTION(TRI_ERROR_INTERNAL_AQL);
       }
     }
     LOG_QUERY("80c24", DEBUG) << printBlockInfo() << " local statemachine done. Return now.";
@@ -1401,7 +1503,7 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
                                                  : SharedAqlItemBlockPtr{nullptr};
     // We are locally done with our output.
     // Next time we need to check the client call again
-    _execState = ExecState::CHECKCALL;
+    _execState = returnToState;
     // This is not strictly necessary here, as we shouldn't be called again
     // after DONE.
     _outputItemRow.reset();
@@ -1415,6 +1517,9 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
       TRI_ASSERT(skipped > 0 || (outputBlock != nullptr && outputBlock->numEntries() > 0));
       return {ExecutionState::HASMORE, skipped, std::move(outputBlock)};
     }
+    // We must return skipped and/or data when reporting HASMORE
+    TRI_ASSERT(_upstreamState != ExecutionState::HASMORE ||
+               (skipped > 0 || (outputBlock != nullptr && outputBlock->numEntries() > 0)));
     return {_upstreamState, skipped, std::move(outputBlock)};
   } else {
     // TODO this branch must never be taken with an executor that has not been
@@ -1461,6 +1566,12 @@ ExecutionState ExecutionBlockImpl<Executor>::fetchShadowRowInternal() {
   return state;
 }
 
+template <class Executor>
+auto ExecutionBlockImpl<Executor>::outputIsFull() const noexcept -> bool {
+  return _outputItemRow != nullptr && _outputItemRow->isInitialized() &&
+         _outputItemRow->allRowsUsed();
+}
+
 template class ::arangodb::aql::ExecutionBlockImpl<CalculationExecutor<CalculationType::Condition>>;
 template class ::arangodb::aql::ExecutionBlockImpl<CalculationExecutor<CalculationType::Reference>>;
 template class ::arangodb::aql::ExecutionBlockImpl<CalculationExecutor<CalculationType::V8Condition>>;
diff --git a/arangod/Aql/ExecutionBlockImpl.h b/arangod/Aql/ExecutionBlockImpl.h
index 5868ae27739a..fd6a486412f4 100644
--- a/arangod/Aql/ExecutionBlockImpl.h
+++ b/arangod/Aql/ExecutionBlockImpl.h
@@ -122,10 +122,8 @@ class ExecutionBlockImpl final : public ExecutionBlock {
     SKIP,
     // We are producing rows
     PRODUCE,
-    // We are done producing (limit reached) and drop all rows that are unneeded
+    // We are done producing (limit reached) and drop all rows that are unneeded, might count.
     FASTFORWARD,
-    // We are done producing (limit reached), but we count all rows that could be used on higher limit
-    FULLCOUNT,
     // We need more information from dependency
     UPSTREAM,
     // We are done with a subquery, we need to pass forward ShadowRows
@@ -233,6 +231,9 @@ class ExecutionBlockImpl final : public ExecutionBlock {
   std::tuple<ExecutorState, typename Executor::Stats, size_t, AqlCall> executeSkipRowsRange(
       AqlItemBlockInputRange& input, AqlCall& call);
 
+  auto executeFastForward(AqlItemBlockInputRange& inputRange, AqlCall& clientCall)
+      -> std::tuple<ExecutorState, typename Executor::Stats, size_t, AqlCall>;
+
   /**
    * @brief Inner getSome() part, without the tracing calls.
    */
@@ -285,6 +286,8 @@ class ExecutionBlockImpl final : public ExecutionBlock {
   // Can only be one of Skip/Produce/FullCount/FastForward/Done
   [[nodiscard]] auto nextState(AqlCall const& call) const -> ExecState;
 
+  [[nodiscard]] auto outputIsFull() const noexcept -> bool;
+
  private:
   /**
    * @brief Used to allow the row Fetcher to access selected methods of this
diff --git a/arangod/Aql/FilterExecutor.cpp b/arangod/Aql/FilterExecutor.cpp
index 8c2d66f09032..cb0d06bb60af 100644
--- a/arangod/Aql/FilterExecutor.cpp
+++ b/arangod/Aql/FilterExecutor.cpp
@@ -105,24 +105,28 @@ std::pair<ExecutionState, size_t> FilterExecutor::expectedNumberOfRows(size_t at
 auto FilterExecutor::skipRowsRange(AqlItemBlockInputRange& inputRange, AqlCall& call)
     -> std::tuple<ExecutorState, Stats, size_t, AqlCall> {
   FilterStats stats{};
-  size_t skipped = 0;
-  while (inputRange.hasDataRow() && skipped < call.getOffset()) {
+  while (inputRange.hasDataRow() && call.needSkipMore()) {
     auto const [unused, input] = inputRange.nextDataRow();
     if (!input) {
       TRI_ASSERT(!inputRange.hasDataRow());
       break;
     }
     if (input.getValue(_infos.getInputRegister()).toBoolean()) {
-      skipped++;
+      call.didSkip(1);
     } else {
       stats.incrFiltered();
     }
   }
-  call.didSkip(skipped);
 
   AqlCall upstreamCall{};
-  upstreamCall.softLimit = call.getOffset();
-  return {inputRange.upstreamState(), stats, skipped, upstreamCall};
+  if (call.needSkipMore() && call.getLimit() == 0) {
+    // FullCount case, we need to skip more, but limit is reached.
+    upstreamCall.softLimit = ExecutionBlock::SkipAllSize();
+  } else {
+    upstreamCall.softLimit = call.getOffset();
+  }
+
+  return {inputRange.upstreamState(), stats, call.getSkipCount(), upstreamCall};
 }
 
 auto FilterExecutor::produceRows(AqlItemBlockInputRange& inputRange, OutputAqlItemRow& output)
diff --git a/arangod/Aql/IndexExecutor.cpp b/arangod/Aql/IndexExecutor.cpp
index d862d9b98900..91e6c33ecf47 100644
--- a/arangod/Aql/IndexExecutor.cpp
+++ b/arangod/Aql/IndexExecutor.cpp
@@ -484,7 +484,8 @@ size_t IndexExecutor::CursorReader::skipIndex(size_t toSkip) {
       case Type::Document:
         TRI_ASSERT(_documentSkipper != nullptr);
         _cursor->nextDocument(_documentSkipper, toSkip);
-        break;;
+        break;
+        ;
     }
     skipped = _context.getAndResetNumScanned() - _context.getAndResetNumFiltered();
   } else {
@@ -735,7 +736,9 @@ auto IndexExecutor::produceRows(AqlItemBlockInputRange& inputRange, OutputAqlIte
       bool more = getCursor().readIndex(output);
       TRI_ASSERT(more == getCursor().hasMore());
 
-      LOG_DEVEL_IDX << "IndexExecutor::produceRows::innerLoop output.numRowsWritten() == " << output.numRowsWritten();
+      LOG_DEVEL_IDX
+          << "IndexExecutor::produceRows::innerLoop output.numRowsWritten() == "
+          << output.numRowsWritten();
       // NOTE: more => output.isFull() does not hold, if we do uniqness checks.
       // The index iterator does still count skipped rows for limit.
       // Nevertheless loop here, the cursor has more so we will retigger
@@ -744,19 +747,15 @@ auto IndexExecutor::produceRows(AqlItemBlockInputRange& inputRange, OutputAqlIte
       // Or the cursor is done, so we need to advance
     }
 
-
     stats.incrScanned(_documentProducingFunctionContext.getAndResetNumScanned());
     stats.incrFiltered(_documentProducingFunctionContext.getAndResetNumFiltered());
   }
 
-
-  bool reportDone = _state == ExecutorState::DONE && !_input.isInitialized();
-
   AqlCall upstreamCall;
   upstreamCall.fullCount = clientCall.needsFullCount();
 
-  LOG_DEVEL_IDX << "IndexExecutor::produceRows reporting state " << (reportDone ? ExecutorState::DONE : ExecutorState::HASMORE);
-  return {reportDone ? ExecutorState::DONE : ExecutorState::HASMORE, stats, upstreamCall};
+  LOG_DEVEL_IDX << "IndexExecutor::produceRows reporting state " << returnState();
+  return {returnState(), stats, upstreamCall};
 }
 
 auto IndexExecutor::skipRowsRange(AqlItemBlockInputRange& inputRange, AqlCall& clientCall)
@@ -775,21 +774,22 @@ auto IndexExecutor::skipRowsRange(AqlItemBlockInputRange& inputRange, AqlCall& c
   IndexStats stats{};
 
   while (clientCall.needSkipMore()) {
-    LOG_DEVEL_IDX << "IndexExecutor::skipRowsRange skipped " << _skipped
-                  << " " << clientCall.getOffset();
+    LOG_DEVEL_IDX << "IndexExecutor::skipRowsRange skipped " << _skipped << " "
+                  << clientCall.getOffset();
     // get an input row first, if necessary
     if (!_input.isInitialized()) {
       std::tie(_state, _input) = inputRange.peekDataRow();
-      LOG_DEVEL_IDX
-          << "IndexExecutor::skipRowsRange input not initialized, peek next row: " << _state
-          << " " << std::boolalpha << _input.isInitialized();
+      LOG_DEVEL_IDX << "IndexExecutor::skipRowsRange input not initialized, "
+                       "peek next row: "
+                    << _state << " " << std::boolalpha << _input.isInitialized();
 
       if (_input.isInitialized()) {
         LOG_DEVEL_IDX << "IndexExecutor::skipRowsRange initIndexes";
         initIndexes(_input);
         if (!advanceCursor()) {
-          LOG_DEVEL_IDX << "IndexExecutor::skipRowsRange failed to advanceCursor "
-                           "after init";
+          LOG_DEVEL_IDX
+              << "IndexExecutor::skipRowsRange failed to advanceCursor "
+                 "after init";
           std::ignore = inputRange.nextDataRow();
           _input = InputAqlItemRow{CreateInvalidInputRowHint{}};
           // just to validate that after continue we get into retry mode
@@ -809,9 +809,14 @@ auto IndexExecutor::skipRowsRange(AqlItemBlockInputRange& inputRange, AqlCall& c
       continue;
     }
 
-    LOG_DEVEL_IDX << "IndexExecutor::skipRowsRange skipIndex("
-                  << clientCall.getOffset() << ")";
-    size_t skippedNow = getCursor().skipIndex(clientCall.getOffset());
+    auto toSkip = clientCall.getOffset();
+    if (toSkip == 0) {
+      TRI_ASSERT(clientCall.needsFullCount());
+      toSkip = ExecutionBlock::SkipAllSize();
+    }
+    TRI_ASSERT(toSkip > 0);
+    LOG_DEVEL_IDX << "IndexExecutor::skipRowsRange skipIndex(" << toSkip << ")";
+    size_t skippedNow = getCursor().skipIndex(toSkip);
     LOG_DEVEL_IDX << "IndexExecutor::skipRowsRange skipIndex(...) == " << skippedNow;
 
     stats.incrScanned(skippedNow);
@@ -823,9 +828,18 @@ auto IndexExecutor::skipRowsRange(AqlItemBlockInputRange& inputRange, AqlCall& c
   _skipped = 0;
 
   AqlCall upstreamCall;
-  upstreamCall.fullCount = clientCall.needsFullCount();
 
+  LOG_DEVEL_IDX << "IndexExecutor::skipRowsRange returning " << returnState()
+                << " " << skipped << " " << upstreamCall;
+  return {returnState(), stats, skipped, upstreamCall};
+}
 
-  LOG_DEVEL_IDX << "IndexExecutor::skipRowsRange returning " << _state << " " << skipped << " " << upstreamCall;
-  return {_state, stats, skipped, upstreamCall};
+auto IndexExecutor::returnState() const noexcept -> ExecutorState {
+  if (_input.isInitialized()) {
+    // We are still working.
+    // TODO: Potential optimization: We can ask if the cursor has more, or there
+    // are other cursors.
+    return ExecutorState::HASMORE;
+  }
+  return _state;
 }
diff --git a/arangod/Aql/IndexExecutor.h b/arangod/Aql/IndexExecutor.h
index 6dfbf13accdd..618905d7babf 100644
--- a/arangod/Aql/IndexExecutor.h
+++ b/arangod/Aql/IndexExecutor.h
@@ -248,6 +248,8 @@ class IndexExecutor {
 
   bool needsUniquenessCheck() const noexcept;
 
+  auto returnState() const noexcept -> ExecutorState;
+
  private:
   Infos& _infos;
   DocumentProducingFunctionContext _documentProducingFunctionContext;
diff --git a/arangod/Aql/LimitExecutor.cpp b/arangod/Aql/LimitExecutor.cpp
index 42a6befce2a9..7d3d3ea6f089 100644
--- a/arangod/Aql/LimitExecutor.cpp
+++ b/arangod/Aql/LimitExecutor.cpp
@@ -52,238 +52,189 @@ LimitExecutorInfos::LimitExecutorInfos(RegisterId nrInputRegisters, RegisterId n
       _fullCount(fullCount) {}
 
 LimitExecutor::LimitExecutor(Fetcher& fetcher, Infos& infos)
-    : _infos(infos),
-      _fetcher(fetcher),
-      _lastRowToOutput(CreateInvalidInputRowHint{}),
-      _stateOfLastRowToOutput(ExecutionState::HASMORE) {}
-LimitExecutor::~LimitExecutor() = default;
-
-std::pair<ExecutionState, LimitStats> LimitExecutor::skipOffset() {
-  ExecutionState state;
-  size_t skipped;
-  std::tie(state, skipped) = _fetcher.skipRows(maxRowsLeftToSkip());
-
-  // WAITING => skipped == 0
-  TRI_ASSERT(state != ExecutionState::WAITING || skipped == 0);
-
-  _counter += skipped;
+    : _infos(infos), _lastRowToOutput(CreateInvalidInputRowHint{}) {}
 
-  LimitStats stats{};
-  if (infos().isFullCountEnabled()) {
-    stats.incrFullCountBy(skipped);
-  }
+LimitExecutor::~LimitExecutor() = default;
 
-  return {state, stats};
+auto LimitExecutor::limitFulfilled() const noexcept -> bool {
+  return remainingOffset() + remainingLimit() == 0;
 }
 
-std::pair<ExecutionState, LimitStats> LimitExecutor::skipRestForFullCount() {
-  ExecutionState state;
-  size_t skipped;
-  LimitStats stats{};
-  // skip ALL the rows
-  std::tie(state, skipped) = _fetcher.skipRows(ExecutionBlock::SkipAllSize());
-
-  if (state == ExecutionState::WAITING) {
-    TRI_ASSERT(skipped == 0);
-    return {state, stats};
+auto LimitExecutor::calculateUpstreamCall(AqlCall const& clientCall) const -> AqlCall {
+  auto upstreamCall = AqlCall{};
+
+  // Offsets can simply be added.
+  upstreamCall.offset = clientCall.getOffset() + remainingOffset();
+
+  // To get the limit for upstream, we must subtract the downstream offset from
+  // our limit, and take the minimum of this and the downstream limit.
+  auto const localLimitMinusDownstreamOffset =
+      remainingLimit() - std::min(remainingLimit(), clientCall.getOffset());
+  auto const limit =
+      std::min<AqlCall::Limit>(clientCall.getLimit(), localLimitMinusDownstreamOffset);
+
+  // Generally, we create a hard limit. However, if we get a soft limit from
+  // downstream that is lower than our hard limit, we use that instead.
+  bool const useSoftLimit = clientCall.hasSoftLimit() &&
+                            clientCall.getLimit() < localLimitMinusDownstreamOffset;
+
+  if (useSoftLimit) {
+    upstreamCall.softLimit = limit;
+    upstreamCall.fullCount = false;
+  } else {
+    upstreamCall.hardLimit = limit;
+    // We need the fullCount either if we need to report it ourselfes.
+    // or if the clientCall needs to report it.
+    upstreamCall.fullCount = infos().isFullCountEnabled() || clientCall.fullCount;
   }
 
-  // We must not update _counter here. It is only used to count until
-  // offset+limit is reached.
-
-  if (infos().isFullCountEnabled()) {
-    stats.incrFullCountBy(skipped);
-  }
-
-  return {state, stats};
+  return upstreamCall;
 }
 
-std::pair<ExecutionState, LimitStats> LimitExecutor::produceRows(OutputAqlItemRow& output) {
-  TRI_IF_FAILURE("LimitExecutor::produceRows") {
-    THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
-  }
-  InputAqlItemRow input{CreateInvalidInputRowHint{}};
-  ExecutionState state;
-  LimitStats stats{};
-
-  while (LimitState::SKIPPING == currentState()) {
-    LimitStats tmpStats;
-    std::tie(state, tmpStats) = skipOffset();
-    stats += tmpStats;
-    if (state == ExecutionState::WAITING || state == ExecutionState::DONE) {
-      return {state, stats};
-    }
-  }
-  while (LimitState::RETURNING == currentState()) {
-    std::tie(state, input) = _fetcher.fetchRow(maxRowsLeftToFetch());
-
-    if (state == ExecutionState::WAITING) {
-      return {state, stats};
-    }
-
-    // This executor is pass-through. Thus we will never get asked to write an
-    // output row for which there is no input, as in- and output rows have a
-    // 1:1 correspondence.
-    TRI_ASSERT(input.isInitialized());
-
-    // We've got one input row
-    _counter++;
-
-    if (infos().isFullCountEnabled()) {
-      stats.incrFullCount();
-    }
-
-    // Return one row
-    output.copyRow(input);
-    return {state, stats};
-  }
-
-  // This case is special for two reasons.
-  // First, after this we want to return DONE, regardless of the upstream's
-  // state.
-  // Second, when fullCount is enabled, we need to get the fullCount before
-  // returning the last row, as the count is returned with the stats (and we
-  // would not be asked again by ExecutionBlockImpl in any case).
-  if (LimitState::RETURNING_LAST_ROW == currentState()) {
-    if (_lastRowToOutput.isInitialized()) {
-      // Use previously saved row iff there is one. We can get here only if
-      // fullCount is enabled. If it is, we can get here multiple times (until
-      // we consumed the whole upstream, which might return WAITING repeatedly).
-      TRI_ASSERT(infos().isFullCountEnabled());
-      state = _stateOfLastRowToOutput;
-      TRI_ASSERT(state != ExecutionState::WAITING);
-      input = std::move(_lastRowToOutput);
-      TRI_ASSERT(!_lastRowToOutput.isInitialized());  // rely on the move
-    } else {
-      std::tie(state, input) = _fetcher.fetchRow(maxRowsLeftToFetch());
-
-      if (state == ExecutionState::WAITING) {
-        return {state, stats};
+auto LimitExecutor::produceRows(AqlItemBlockInputRange& inputRange, OutputAqlItemRow& output)
+    -> std::tuple<ExecutorState, Stats, AqlCall> {
+  // I think this *should* be the case, because we're passthrough. However,
+  // isFull() ignores shadow rows in the passthrough case, which it probably
+  // should not.
+  // static_assert(Properties::allowsBlockPassthrough == BlockPassthrough::Enable);
+  // TRI_ASSERT(input.hasDataRow() == !output.isFull());
+
+  auto const& clientCall = output.getClientCall();
+  TRI_ASSERT(clientCall.getOffset() == 0);
+
+  auto stats = LimitStats{};
+
+  auto call = output.getClientCall();
+  TRI_ASSERT(call.getOffset() == 0);
+  while (inputRange.skippedInFlight() > 0 || inputRange.hasDataRow()) {
+    if (remainingOffset() > 0) {
+      // First we skip in the input row until we fullfill our local offset.
+      auto const didSkip = inputRange.skip(remainingOffset());
+      // Need to forward the
+      _counter += didSkip;
+      // We do not report this to downstream
+      // But we report it in fullCount
+      if (infos().isFullCountEnabled()) {
+        stats.incrFullCountBy(didSkip);
       }
-    }
-
-    // This executor is pass-through. Thus we will never get asked to write an
-    // output row for which there is no input, as in- and output rows have a
-    // 1:1 correspondence.
-    TRI_ASSERT(input.isInitialized());
-
-    if (infos().isFullCountEnabled()) {
-      // Save the state now. The _stateOfLastRowToOutput will not be used unless
-      // _lastRowToOutput gets set.
-      _stateOfLastRowToOutput = state;
-      LimitStats tmpStats;
-      std::tie(state, tmpStats) = skipRestForFullCount();
-      stats += tmpStats;
-      if (state == ExecutionState::WAITING) {
-        // Save the row
-        _lastRowToOutput = std::move(input);
-        return {state, stats};
+    } else if (!output.isFull()) {
+      auto numRowsWritten = size_t{0};
+
+      while (inputRange.hasDataRow()) {
+        // This block is passhthrough.
+        static_assert(Properties::allowsBlockPassthrough == BlockPassthrough::Enable,
+                      "For LIMIT with passthrough to work, there must be "
+                      "exactly enough space for all input in the output.");
+        // So there will always be enough place for all inputRows within
+        // the output.
+        TRI_ASSERT(!output.isFull());
+        // Also this number can be at most remainingOffset.
+        TRI_ASSERT(remainingLimit() > numRowsWritten);
+        output.copyRow(inputRange.nextDataRow().second);
+        output.advanceRow();
+        numRowsWritten++;
       }
+      _counter += numRowsWritten;
+      if (infos().isFullCountEnabled()) {
+        stats.incrFullCountBy(numRowsWritten);
+      }
+    } else if (call.needsFullCount()) {
+      // We are done with producing.
+      // ExecutionBlockImpl will now call skipSome for the remainder
+      // There cannot be a dataRow left, as this block is passthrough!
+      TRI_ASSERT(!inputRange.hasDataRow());
+      // There are still skippedInflights;
+      TRI_ASSERT(inputRange.skippedInFlight() > 0);
+      break;
+    } else {
+      // We are done with producing.
+      if (infos().isFullCountEnabled()) {
+        // However we need to report the fullCount from above.
+        stats.incrFullCountBy(inputRange.skipAll());
+      }
+      // ExecutionBlockImpl will now call skipSome for the remainder
+      // There cannot be a dataRow left, as this block is passthrough!
+      TRI_ASSERT(!inputRange.hasDataRow());
+      TRI_ASSERT(inputRange.skippedInFlight() == 0);
+      break;
     }
-
-    // It's important to increase the counter for the last row only *after*
-    // skipRestForFullCount() is done, because we need currentState() to stay
-    // at RETURNING_LAST_ROW until we've actually returned the last row.
-    _counter++;
-    if (infos().isFullCountEnabled()) {
-      stats.incrFullCount();
-    }
-
-    output.copyRow(input);
-    return {ExecutionState::DONE, stats};
   }
-
-  // We should never be COUNTING, this must already be done in the
-  // RETURNING_LAST_ROW-handler.
-  TRI_ASSERT(LimitState::LIMIT_REACHED == currentState());
-  // When fullCount is enabled, the loop may only abort when upstream is done.
-  TRI_ASSERT(!infos().isFullCountEnabled());
-
-  return {ExecutionState::DONE, stats};
+  // We're passthrough, we must not have any input left when the limit isfulfilled
+  TRI_ASSERT(!limitFulfilled() || !inputRange.hasDataRow());
+  return {inputRange.upstreamState(), stats, calculateUpstreamCall(call)};
 }
 
-std::tuple<ExecutionState, LimitStats, SharedAqlItemBlockPtr> LimitExecutor::fetchBlockForPassthrough(size_t atMost) {
-  switch (currentState()) {
-    case LimitState::LIMIT_REACHED:
-      // We are done with our rows!
-      return {ExecutionState::DONE, LimitStats{}, nullptr};
-    case LimitState::COUNTING: {
-      LimitStats stats{};
-      while (LimitState::LIMIT_REACHED != currentState()) {
-        ExecutionState state;
-        LimitStats tmpStats{};
-        std::tie(state, tmpStats) = skipRestForFullCount();
-        stats += tmpStats;
-
-        if (state == ExecutionState::WAITING || state == ExecutionState::DONE) {
-          return {state, stats, nullptr};
-        }
+auto LimitExecutor::skipRowsRange(AqlItemBlockInputRange& inputRange, AqlCall& call)
+    -> std::tuple<ExecutorState, Stats, size_t, AqlCall> {
+  auto upstreamCall = calculateUpstreamCall(call);
+
+  if (ADB_UNLIKELY(inputRange.skippedInFlight() < upstreamCall.getOffset() &&
+                   inputRange.hasDataRow())) {
+    static_assert(Properties::allowsBlockPassthrough == BlockPassthrough::Enable,
+                  "For LIMIT with passthrough to work, there must no input "
+                  "rows before the offset was skipped.");
+    TRI_ASSERT(false);
+    THROW_ARANGO_EXCEPTION_MESSAGE(TRI_ERROR_INTERNAL_AQL,
+                                   "Unexpected input while skipping: got data "
+                                   "rows before offset was reached.");
+  }
+  auto stats = LimitStats{};
+  while (inputRange.skippedInFlight() > 0) {
+    if (remainingOffset() > 0) {
+      // First we skip in the input row until we fullfill our local offset.
+      auto const didSkip = inputRange.skip(remainingOffset());
+      // Need to forward the
+      _counter += didSkip;
+      // We do not report this to downstream
+      // But we report it in fullCount
+      if (infos().isFullCountEnabled()) {
+        stats.incrFullCountBy(didSkip);
       }
-      return {ExecutionState::DONE, stats, nullptr};
-    }
-    case LimitState::SKIPPING: {
-      LimitStats stats{};
-      while (LimitState::SKIPPING == currentState()) {
-        ExecutionState state;
-        LimitStats tmpStats{};
-        std::tie(state, tmpStats) = skipOffset();
-        stats += tmpStats;
-        if (state == ExecutionState::WAITING || state == ExecutionState::DONE) {
-          return {state, stats, nullptr};
+    } else if (remainingLimit() > 0) {
+      // We do only report to downstream if we have a limit to produce
+      if (call.getOffset() > 0) {
+        // Next we skip as many rows as ordered by the client,
+        // but never more then remainingLimit
+        auto const didSkip =
+            inputRange.skip(std::min(remainingLimit(), call.getOffset()));
+        call.didSkip(didSkip);
+        _counter += didSkip;
+        if (infos().isFullCountEnabled()) {
+          stats.incrFullCountBy(didSkip);
+        }
+      } else if (call.getLimit() > 0) {
+        // If we get here we need to break out, and let produce rows be called.
+        break;
+      } else if (call.needsFullCount()) {
+        auto const didSkip = inputRange.skip(remainingLimit());
+        call.didSkip(didSkip);
+        _counter += didSkip;
+        if (infos().isFullCountEnabled()) {
+          stats.incrFullCountBy(didSkip);
+        }
+      } else if (infos().isFullCountEnabled()) {
+        // Skip the remainder, it does not matter if we need to produce
+        // anything or not. This is only for reporting of the skipped numbers
+        auto const didSkip = inputRange.skipAll();
+        _counter += didSkip;
+        if (infos().isFullCountEnabled()) {
+          stats.incrFullCountBy(didSkip);
         }
       }
-
-      // We should have reached the next state now
-      TRI_ASSERT(currentState() != LimitState::SKIPPING);
-      // Now jump to the correct case
-      auto rv = fetchBlockForPassthrough(atMost);
-      // Add the stats we collected to the return value
-      std::get<LimitStats>(rv) += stats;
-      return rv;
+    } else if (infos().isFullCountEnabled()) {
+      // Skip the remainder, it does not matter if we need to produce
+      // anything or not. This is only for reporting of the skipped numbers
+      auto const didSkip = inputRange.skipAll();
+      _counter += didSkip;
+      if (infos().isFullCountEnabled()) {
+        stats.incrFullCountBy(didSkip);
+      }
+    } else {
+      // We are done.
+      // All produced, all skipped, nothing to report
+      break;
     }
-    case LimitState::RETURNING_LAST_ROW:
-    case LimitState::RETURNING:
-      auto rv = _fetcher.fetchBlockForPassthrough(std::min(atMost, maxRowsLeftToFetch()));
-      return {rv.first, LimitStats{}, std::move(rv.second)};
   }
-  // The control flow cannot reach this. It is only here to make MSVC happy,
-  // which is unable to figure out that the switch above is complete.
-  TRI_ASSERT(false);
-  THROW_ARANGO_EXCEPTION(TRI_ERROR_INTERNAL_AQL);
+  return {inputRange.upstreamState(), stats, call.getSkipCount(),
+          calculateUpstreamCall(call)};
 }
-
-std::tuple<ExecutionState, LimitExecutor::Stats, size_t> LimitExecutor::skipRows(size_t const toSkipRequested) {
-  // fullCount can only be enabled on the last top-level LIMIT block. Thus
-  // skip cannot be called on it! If this requirement is changed for some
-  // reason, the current implementation will not work.
-  TRI_ASSERT(!infos().isFullCountEnabled());
-
-  // If we're still skipping ourselves up to offset, this needs to be done first.
-  size_t const toSkipOffset =
-      currentState() == LimitState::SKIPPING ? maxRowsLeftToSkip() : 0;
-
-  // We have to skip
-  //   our offset (toSkipOffset or maxRowsLeftToSkip()),
-  //   plus what we were requested to skip (toSkipRequested),
-  //   but not more than our total limit (maxRowsLeftToFetch()).
-  size_t const toSkipTotal =
-      std::min(toSkipRequested + toSkipOffset, maxRowsLeftToFetch());
-
-  ExecutionState state;
-  size_t skipped;
-  std::tie(state, skipped) = _fetcher.skipRows(toSkipTotal);
-
-  // WAITING => skipped == 0
-  TRI_ASSERT(state != ExecutionState::WAITING || skipped == 0);
-
-  _counter += skipped;
-
-  // Do NOT report the rows we skipped up to the offset, they don't count.
-  size_t const reportSkipped = toSkipOffset >= skipped ? 0 : skipped - toSkipOffset;
-
-  if (currentState() == LimitState::LIMIT_REACHED) {
-    state = ExecutionState::DONE;
-  }
-
-  return std::make_tuple(state, LimitStats{}, reportSkipped);
-}
\ No newline at end of file
diff --git a/arangod/Aql/LimitExecutor.h b/arangod/Aql/LimitExecutor.h
index db8071392ee9..aaa40e9b7022 100644
--- a/arangod/Aql/LimitExecutor.h
+++ b/arangod/Aql/LimitExecutor.h
@@ -95,87 +95,52 @@ class LimitExecutor {
   ~LimitExecutor();
 
   /**
-   * @brief produce the next Row of Aql Values.
+   * @brief produce the next Rows of Aql Values.
    *
-   * @return ExecutionState, and if successful exactly one new Row of AqlItems.
+   * @return ExecutorState, the stats, and a new Call that needs to be send to upstream
    */
-  std::pair<ExecutionState, Stats> produceRows(OutputAqlItemRow& output);
+  [[nodiscard]] auto produceRows(AqlItemBlockInputRange& input, OutputAqlItemRow& output)
+      -> std::tuple<ExecutorState, Stats, AqlCall>;
 
   /**
-   * @brief Custom skipRows() implementation. This is obligatory to increase
-   * _counter!
+   * @brief skip the next Row of Aql Values.
    *
-   * Semantically, we first skip until our local offset. We may not report the
-   * number of rows skipped this way. Second, we skip up to the number of rows
-   * requested; but at most up to our limit.
+   * @return ExecutorState, the stats, and a new Call that needs to be send to upstream
    */
-  std::tuple<ExecutionState, Stats, size_t> skipRows(size_t toSkipRequested);
-
-  std::tuple<ExecutionState, LimitStats, SharedAqlItemBlockPtr> fetchBlockForPassthrough(size_t atMost);
+  [[nodiscard]] auto skipRowsRange(AqlItemBlockInputRange& inputRange, AqlCall& call)
+      -> std::tuple<ExecutorState, Stats, size_t, AqlCall>;
 
  private:
   Infos const& infos() const noexcept { return _infos; };
 
-  size_t maxRowsLeftToFetch() const noexcept {
-    // counter should never exceed this count!
-    TRI_ASSERT(infos().getLimitPlusOffset() >= _counter);
-    return infos().getLimitPlusOffset() - _counter;
-  }
+  auto remainingOffset() const noexcept -> size_t {
+    auto const offset = infos().getOffset();
 
-  size_t maxRowsLeftToSkip() const noexcept {
-    // should not be called after skipping the offset!
-    TRI_ASSERT(infos().getOffset() >= _counter);
-    return infos().getOffset() - _counter;
+    // Restricted value of _counter in [0, offset]
+    auto const boundedCounter = std::min(offset, _counter);
+    TRI_ASSERT(boundedCounter <= offset);
+
+    return offset - boundedCounter;
   }
 
-  enum class LimitState {
-    // state is SKIPPING until the offset is reached
-    SKIPPING,
-    // state is RETURNING until the limit is reached
-    RETURNING,
-    // state is RETURNING_LAST_ROW if we've seen the second to last row before
-    // the limit is reached
-    RETURNING_LAST_ROW,
-    // state is COUNTING when the limit is reached and fullcount is enabled
-    COUNTING,
-    // state is LIMIT_REACHED only if fullCount is disabled, and we've seen all
-    // rows up to limit
-    LIMIT_REACHED,
-  };
+  auto remainingLimit() const noexcept -> size_t {
+    auto const offset = infos().getOffset();
+    auto const limitPlusOffset = infos().getLimitPlusOffset();
 
-  /**
-   * @brief Returns the current state of the executor, based on _counter (i.e.
-   * number of lines seen), limit, offset and fullCount.
-   * @return See LimitState comments for a description.
-   */
-  LimitState currentState() const noexcept {
-    // Note that not only offset, but also limit can be zero. Thus the order
-    // of all following checks is important, even the first two!
-
-    if (_counter < infos().getOffset()) {
-      return LimitState::SKIPPING;
-    }
-    if (_counter + 1 == infos().getLimitPlusOffset()) {
-      return LimitState::RETURNING_LAST_ROW;
-    }
-    if (_counter < infos().getLimitPlusOffset()) {
-      return LimitState::RETURNING;
-    }
-    if (infos().isFullCountEnabled()) {
-      return LimitState::COUNTING;
-    }
-
-    return LimitState::LIMIT_REACHED;
+    // Restricted value of _counter in [offset, limitPlusOffset]
+    auto const boundedCounter = std::min(limitPlusOffset, std::max(offset, _counter));
+    TRI_ASSERT(offset <= boundedCounter);
+    TRI_ASSERT(boundedCounter <= limitPlusOffset);
+    return limitPlusOffset - boundedCounter;
   }
 
-  std::pair<ExecutionState, Stats> skipOffset();
-  std::pair<ExecutionState, Stats> skipRestForFullCount();
+  [[nodiscard]] auto limitFulfilled() const noexcept -> bool;
+
+  auto calculateUpstreamCall(const AqlCall& clientCall) const -> AqlCall;
 
  private:
   Infos const& _infos;
-  Fetcher& _fetcher;
   InputAqlItemRow _lastRowToOutput;
-  ExecutionState _stateOfLastRowToOutput;
   // Number of input lines seen
   size_t _counter = 0;
 };
diff --git a/arangod/Aql/LimitStats.cpp b/arangod/Aql/LimitStats.cpp
new file mode 100644
index 000000000000..dec1b561b3ca
--- /dev/null
+++ b/arangod/Aql/LimitStats.cpp
@@ -0,0 +1,66 @@
+////////////////////////////////////////////////////////////////////////////////
+/// DISCLAIMER
+///
+/// Copyright 2020 ArangoDB GmbH, Cologne, Germany
+///
+/// Licensed under the Apache License, Version 2.0 (the "License");
+/// you may not use this file except in compliance with the License.
+/// You may obtain a copy of the License at
+///
+///     http://www.apache.org/licenses/LICENSE-2.0
+///
+/// Unless required by applicable law or agreed to in writing, software
+/// distributed under the License is distributed on an "AS IS" BASIS,
+/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+/// See the License for the specific language governing permissions and
+/// limitations under the License.
+///
+/// Copyright holder is ArangoDB GmbH, Cologne, Germany
+///
+/// @author Tobias Gödderz
+////////////////////////////////////////////////////////////////////////////////
+
+#include "LimitStats.h"
+
+using namespace arangodb;
+using namespace arangodb::aql;
+
+LimitStats::LimitStats(LimitStats&& other) noexcept
+    : _fullCount(other._fullCount) {
+  // It is relied upon that other._fullcount is zero after the move!
+  other._fullCount = 0;
+}
+
+auto LimitStats::operator=(LimitStats&& other) noexcept -> LimitStats& {
+  _fullCount = other._fullCount;
+  other._fullCount = 0;
+  return *this;
+}
+
+void LimitStats::incrFullCount() noexcept { _fullCount++; }
+
+void LimitStats::incrFullCountBy(size_t amount) noexcept {
+  _fullCount += amount;
+}
+
+auto LimitStats::getFullCount() const noexcept -> std::size_t {
+  return _fullCount;
+}
+
+auto aql::operator+=(LimitStats& limitStats, LimitStats const& other) noexcept -> LimitStats& {
+  limitStats.incrFullCountBy(other.getFullCount());
+  return limitStats;
+}
+
+auto aql::operator+=(ExecutionStats& executionStats, LimitStats const& limitStats) noexcept
+    -> ExecutionStats& {
+  executionStats.fullCount += limitStats.getFullCount();
+  return executionStats;
+}
+
+auto aql::operator==(LimitStats const& left, LimitStats const& right) noexcept -> bool {
+  static_assert(
+      sizeof(LimitStats) == sizeof(left.getFullCount()),
+      "When adding members to LimitStats, remember to update operator==!");
+  return left.getFullCount() == right.getFullCount();
+}
diff --git a/arangod/Aql/LimitStats.h b/arangod/Aql/LimitStats.h
index a791efdb1c7c..c99d29211726 100644
--- a/arangod/Aql/LimitStats.h
+++ b/arangod/Aql/LimitStats.h
@@ -23,51 +23,39 @@
 #ifndef ARANGOD_AQL_LIMIT_STATS_H
 #define ARANGOD_AQL_LIMIT_STATS_H
 
-#include <cstddef>
 #include "ExecutionStats.h"
 
+#include <cstddef>
 
-namespace arangodb {
-namespace aql {
+namespace arangodb::aql {
 
 class LimitStats {
  public:
-  LimitStats() noexcept : _fullCount(0) {}
-
+  LimitStats() noexcept = default;
   LimitStats(LimitStats const&) = default;
-  LimitStats& operator=(LimitStats const&) = default;
-
   // It is relied upon that other._fullcount is zero after the move!
-  LimitStats(LimitStats&& other) noexcept : _fullCount(other._fullCount) {
-    other._fullCount = 0;
-  }
-  LimitStats& operator=(LimitStats&& other) noexcept {
-    _fullCount = other._fullCount;
-    other._fullCount = 0;
-    return *this;
-  };
+  LimitStats(LimitStats&& other) noexcept;
+
+  auto operator=(LimitStats const&) -> LimitStats& = default;
+  auto operator=(LimitStats&& other) noexcept -> LimitStats&;
 
-  void incrFullCount() noexcept { _fullCount++; }
-  void incrFullCountBy(size_t amount) noexcept { _fullCount += amount; }
+  void incrFullCount() noexcept;
+  void incrFullCountBy(size_t amount) noexcept;
 
-  std::size_t getFullCount() const noexcept { return _fullCount; }
+  [[nodiscard]] auto getFullCount() const noexcept -> std::size_t;
 
  private:
-  std::size_t _fullCount;
+  std::size_t _fullCount{0};
+  // Don't forget to update operator== when adding new members!
 };
 
-inline ExecutionStats& operator+=(ExecutionStats& executionStats,
-                           LimitStats const& limitStats) noexcept {
-  executionStats.fullCount += limitStats.getFullCount();
-  return executionStats;
-}
+auto operator+=(ExecutionStats& executionStats, LimitStats const& limitStats) noexcept
+    -> ExecutionStats&;
+
+auto operator+=(LimitStats& limitStats, LimitStats const& other) noexcept -> LimitStats&;
 
-inline LimitStats& operator+=(LimitStats& limitStats, LimitStats const& other) noexcept {
-  limitStats.incrFullCountBy(other.getFullCount());
-  return limitStats;
-}
+auto operator==(LimitStats const&, LimitStats const&) noexcept -> bool;
 
-}
-}
+}  // namespace arangodb::aql
 
-#endif // ARANGOD_AQL_LIMIT_STATS_H
+#endif  // ARANGOD_AQL_LIMIT_STATS_H
diff --git a/arangod/Aql/Query.cpp b/arangod/Aql/Query.cpp
index 7b6325020c00..690203f39e0b 100644
--- a/arangod/Aql/Query.cpp
+++ b/arangod/Aql/Query.cpp
@@ -1215,6 +1215,11 @@ void Query::setEngine(ExecutionEngine* engine) {
   _engine.reset(engine);
 }
 
+void Query::setEngine(std::unique_ptr<ExecutionEngine>&& engine) {
+  TRI_ASSERT(engine != nullptr);
+  _engine = std::move(engine);
+}
+
 /// @brief prepare a V8 context for execution for this expression
 /// this needs to be called once before executing any V8 function in this
 /// expression
diff --git a/arangod/Aql/Query.h b/arangod/Aql/Query.h
index 05b7f9a5b01c..a01d91008d22 100644
--- a/arangod/Aql/Query.h
+++ b/arangod/Aql/Query.h
@@ -252,6 +252,7 @@ class Query {
 
   /// @brief inject the engine
   TEST_VIRTUAL void setEngine(ExecutionEngine* engine);
+  TEST_VIRTUAL void setEngine(std::unique_ptr<ExecutionEngine>&& engine);
 
   /// @brief return the transaction, if prepared
   TEST_VIRTUAL inline transaction::Methods* trx() const { return _trx.get(); }
diff --git a/arangod/Aql/ReturnExecutor.cpp b/arangod/Aql/ReturnExecutor.cpp
index 35723a24524d..52a03761d39d 100644
--- a/arangod/Aql/ReturnExecutor.cpp
+++ b/arangod/Aql/ReturnExecutor.cpp
@@ -70,7 +70,17 @@ auto ReturnExecutor::skipRowsRange(AqlItemBlockInputRange& inputRange, AqlCall&
   TRI_IF_FAILURE("ReturnExecutor::produceRows") {
     THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
   }
-  Stats stats{};
+
+  auto stats = Stats{};
+  auto skippedUpstream = inputRange.skipAll();
+  call.didSkip(skippedUpstream);
+  /*
+  if (_infos.doCount()) {
+    // TODO: do we need to include counted here?
+    stats.incrCounted(skippedUpstream);
+  }
+  */
+
   while (inputRange.hasDataRow() && call.needSkipMore()) {
     // I do not think that this is actually called.
     // It will be called first to get the upstream-Call
@@ -91,6 +101,7 @@ auto ReturnExecutor::skipRowsRange(AqlItemBlockInputRange& inputRange, AqlCall&
     }
     */
   }
+
   return {inputRange.upstreamState(), stats, call.getSkipCount(), call};
 }
 
diff --git a/arangod/Aql/SingleRowFetcher.cpp b/arangod/Aql/SingleRowFetcher.cpp
index 0043efd86771..62e054c5b875 100644
--- a/arangod/Aql/SingleRowFetcher.cpp
+++ b/arangod/Aql/SingleRowFetcher.cpp
@@ -85,16 +85,20 @@ SingleRowFetcher<passBlocksThrough>::execute(AqlCallStack& stack) {
     return {state, 0, AqlItemBlockInputRange{ExecutorState::HASMORE}};
   }
   if (block == nullptr) {
-    return {state, skipped, AqlItemBlockInputRange{ExecutorState::DONE}};
+    if (state == ExecutionState::HASMORE) {
+      return {state, skipped, AqlItemBlockInputRange{ExecutorState::HASMORE, skipped}};
+    }
+    return {state, skipped, AqlItemBlockInputRange{ExecutorState::DONE, skipped}};
   }
 
   auto [start, end] = block->getRelevantRange();
   if (state == ExecutionState::HASMORE) {
     TRI_ASSERT(block != nullptr);
     return {state, skipped,
-            AqlItemBlockInputRange{ExecutorState::HASMORE, block, start, end}};
+            AqlItemBlockInputRange{ExecutorState::HASMORE, skipped, block, start}};
   }
-  return {state, skipped, AqlItemBlockInputRange{ExecutorState::DONE, block, start, end}};
+  return {state, skipped,
+          AqlItemBlockInputRange{ExecutorState::DONE, skipped, block, start}};
 }
 
 template <BlockPassthrough passBlocksThrough>
diff --git a/arangod/Aql/SortedCollectExecutor.cpp b/arangod/Aql/SortedCollectExecutor.cpp
index c59058930845..1e3ec9446d95 100644
--- a/arangod/Aql/SortedCollectExecutor.cpp
+++ b/arangod/Aql/SortedCollectExecutor.cpp
@@ -451,9 +451,11 @@ auto SortedCollectExecutor::skipRowsRange(AqlItemBlockInputRange& inputRange, Aq
             clientCall.didSkip(1);
           }
         } else {
-          LOG_DEVEL_SC << "skipping final group";
-          clientCall.didSkip(1);
-          _currentGroup.reset(InputAqlItemRow{CreateInvalidInputRowHint{}});
+          if (_currentGroup.isValid()) {
+            LOG_DEVEL_SC << "skipping final group";
+            clientCall.didSkip(1);
+            _currentGroup.reset(InputAqlItemRow{CreateInvalidInputRowHint{}});
+          }
         }
         break;
       } else if (!input.isInitialized()) {
@@ -467,5 +469,5 @@ auto SortedCollectExecutor::skipRowsRange(AqlItemBlockInputRange& inputRange, Aq
   LOG_DEVEL_SC << " skipped rows: " << clientCall.getSkipCount();
   LOG_DEVEL_SC << "reporting state: " << inputRange.upstreamState();
 
-  return {inputRange.upstreamState(), Stats{}, clientCall.getSkipCount(), AqlCall{}};
+  return {inputRange.upstreamState(), NoStats{}, clientCall.getSkipCount(), AqlCall{}};
 }
diff --git a/arangod/CMakeLists.txt b/arangod/CMakeLists.txt
index 9e5b88e2cad5..515380f4cd6d 100644
--- a/arangod/CMakeLists.txt
+++ b/arangod/CMakeLists.txt
@@ -296,6 +296,7 @@ set(LIB_ARANGO_AQL_SOURCES
   Aql/KShortestPathsNode.cpp
   Aql/LateMaterializedOptimizerRulesCommon.cpp
   Aql/LimitExecutor.cpp
+  Aql/LimitStats.cpp
   Aql/MaterializeExecutor.cpp
   Aql/ModificationExecutor.cpp
   Aql/ModificationExecutorHelpers.cpp
diff --git a/tests/Aql/AqlHelper.cpp b/tests/Aql/AqlHelper.cpp
index 79a784984575..64ea816717c6 100644
--- a/tests/Aql/AqlHelper.cpp
+++ b/tests/Aql/AqlHelper.cpp
@@ -59,12 +59,12 @@ std::ostream& arangodb::aql::operator<<(std::ostream& stream, AqlItemBlock const
 
 bool arangodb::aql::operator==(arangodb::aql::ExecutionStats const& left,
                                arangodb::aql::ExecutionStats const& right) {
-  TRI_ASSERT(left.nodes.empty());
-  TRI_ASSERT(right.nodes.empty());
-  TRI_ASSERT(left.executionTime == 0.0);
-  TRI_ASSERT(right.executionTime == 0.0);
-  TRI_ASSERT(left.peakMemoryUsage == 0);
-  TRI_ASSERT(right.peakMemoryUsage == 0);
+  // The below information is only set on profiling in AQL
+  // They are not included on purpose as they will never be equal.
+  // * nodes
+  // * executionTime
+  // * peakMemeoryUsage
+
   // clang-format off
   return left.writesExecuted == right.writesExecuted
       && left.writesIgnored == right.writesIgnored
diff --git a/tests/Aql/AqlItemBlockHelper.h b/tests/Aql/AqlItemBlockHelper.h
index 430bc37e83b9..fac8f0d7d36b 100644
--- a/tests/Aql/AqlItemBlockHelper.h
+++ b/tests/Aql/AqlItemBlockHelper.h
@@ -25,12 +25,12 @@
 
 #include <array>
 #include <memory>
-
-#include <boost/variant.hpp>
+#include <variant>
 
 #include "Aql/AqlItemBlock.h"
 #include "Aql/ResourceUsage.h"
 #include "Aql/SharedAqlItemBlockPtr.h"
+#include "Basics/overload.h"
 
 #include "AqlHelper.h"
 #include "VelocyPackHelper.h"
@@ -77,7 +77,7 @@ namespace arangodb {
 namespace tests {
 namespace aql {
 
-using EntryBuilder = boost::variant<int, const char*>;
+using EntryBuilder = std::variant<int, const char*>;
 
 template <::arangodb::aql::RegisterId columns>
 using RowBuilder = std::array<EntryBuilder, columns>;
@@ -100,16 +100,6 @@ namespace aql {
 
 using namespace ::arangodb::aql;
 
-class EntryToAqlValueVisitor : public boost::static_visitor<AqlValue> {
- public:
-  AqlValue operator()(int i) const { return AqlValue{AqlValueHintInt{i}}; }
-
-  AqlValue operator()(const char* json) const {
-    VPackBufferPtr tmpVpack = vpackFromJsonString(json);
-    return AqlValue{AqlValueHintCopy{tmpVpack->data()}};
-  }
-};
-
 template <RegisterId columns>
 SharedAqlItemBlockPtr buildBlock(AqlItemBlockManager& manager,
                                  MatrixBuilder<columns>&& matrix,
@@ -122,8 +112,16 @@ SharedAqlItemBlockPtr buildBlock(AqlItemBlockManager& manager,
   for (size_t row = 0; row < matrix.size(); row++) {
     for (RegisterId col = 0; col < columns; col++) {
       auto const& entry = matrix[row][col];
-      auto visitor = EntryToAqlValueVisitor();
-      block->setValue(row, col, boost::apply_visitor(visitor, entry));
+      auto value = std::visit(
+          overload{
+              [](int i) { return AqlValue{AqlValueHintInt{i}}; },
+              [](const char* json) {
+                VPackBufferPtr tmpVpack = vpackFromJsonString(json);
+                return AqlValue{AqlValueHintCopy{tmpVpack->data()}};
+              },
+          },
+          entry);
+      block->setValue(row, col, value);
     }
   }
 
diff --git a/tests/Aql/AqlItemBlockInputRangeTest.cpp b/tests/Aql/AqlItemBlockInputRangeTest.cpp
index 884058d6e7d7..ac80439ff7a8 100644
--- a/tests/Aql/AqlItemBlockInputRangeTest.cpp
+++ b/tests/Aql/AqlItemBlockInputRangeTest.cpp
@@ -52,8 +52,7 @@ class InputRangeTest : public ::testing::TestWithParam<ExecutorState> {
   }
 
   AqlItemBlockInputRange createFromBlock(arangodb::aql::SharedAqlItemBlockPtr& block) {
-    auto const [start, end] = block->getRelevantRange();
-    return AqlItemBlockInputRange(GetParam(), block, start, end);
+    return AqlItemBlockInputRange(GetParam(), 0, block, 0);
   }
 
   void validateEndReached(AqlItemBlockInputRange& testee) {
diff --git a/tests/Aql/EngineInfoContainerCoordinatorTest.cpp b/tests/Aql/EngineInfoContainerCoordinatorTest.cpp
index 21a74a56c92a..a3af215272f2 100644
--- a/tests/Aql/EngineInfoContainerCoordinatorTest.cpp
+++ b/tests/Aql/EngineInfoContainerCoordinatorTest.cpp
@@ -119,14 +119,16 @@ TEST(EngineInfoContainerTest, it_should_create_an_executionengine_for_the_first_
   // Section: Mock Functions
   // ------------------------------
 
-  fakeit::When(Method(mockQuery, setEngine)).Do([&](ExecutionEngine* eng) -> void {
-    // We expect that the snippet injects a new engine into our
-    // query.
-    // However we have to return a mocked engine later
-    ASSERT_NE(eng, nullptr);
-    // Throw it away
-    delete eng;
-  });
+  fakeit::When(OverloadedMethod(mockQuery, setEngine, void(ExecutionEngine * ))).Do(
+    [](ExecutionEngine *eng) -> void {
+      // We expect that the snippet injects a new engine into our
+      // query.
+      // However we have to return a mocked engine later
+      ASSERT_NE(eng, nullptr);
+      // Throw it away
+      delete eng;
+    }
+  );
 
   fakeit::When(Method(mockQuery, trx)).Return(&trx);
   fakeit::When(Method(mockQuery, engine)).Return(&myEngine).Return(&myEngine);
@@ -154,7 +156,7 @@ TEST(EngineInfoContainerTest, it_should_create_an_executionengine_for_the_first_
   ASSERT_TRUE(queryIds.empty());
 
   // Validate that the query is wired up with the engine
-  fakeit::Verify(Method(mockQuery, setEngine)).Exactly(1);
+  fakeit::Verify(OverloadedMethod(mockQuery, setEngine, void(ExecutionEngine *))).Exactly(1);
   // Validate that createBlocks has been called!
   fakeit::Verify(Method(mockEngine, createBlocks)).Exactly(1);
 }
@@ -223,7 +225,7 @@ TEST(EngineInfoContainerTest,
   // Section: Mock Functions
   // ------------------------------
 
-  fakeit::When(Method(mockQuery, setEngine)).Do([&](ExecutionEngine* eng) -> void {
+  fakeit::When(OverloadedMethod(mockQuery, setEngine, void(ExecutionEngine*))).Do([&](ExecutionEngine* eng) -> void {
     // We expect that the snippet injects a new engine into our
     // query.
     // However we have to return a mocked engine later
@@ -250,7 +252,8 @@ TEST(EngineInfoContainerTest,
     return &queryClone;
   });
 
-  fakeit::When(Method(mockQueryClone, setEngine)).Do([&](ExecutionEngine* eng) -> void {
+  fakeit::When(OverloadedMethod(mockQueryClone, setEngine, void(ExecutionEngine * ))).Do(
+    [&](ExecutionEngine *eng) -> void {
     // We expect that the snippet injects a new engine into our
     // query.
     // However we have to return a mocked engine later
@@ -314,12 +317,12 @@ TEST(EngineInfoContainerTest,
   ASSERT_TRUE(queryIds.empty());
 
   // Validate that the query is wired up with the engine
-  fakeit::Verify(Method(mockQuery, setEngine)).Exactly(1);
+  fakeit::Verify(OverloadedMethod(mockQuery, setEngine, void(ExecutionEngine*))).Exactly(1);
   // Validate that createBlocks has been called!
   fakeit::Verify(Method(mockEngine, createBlocks)).Exactly(1);
 
   // Validate that the second query is wired up with the second engine
-  fakeit::Verify(Method(mockQueryClone, setEngine)).Exactly(1);
+  fakeit::Verify(OverloadedMethod(mockQueryClone, setEngine, void(ExecutionEngine*))).Exactly(1);
   // Validate that createBlocks has been called!
   fakeit::Verify(Method(mockSecondEngine, createBlocks)).Exactly(1);
   fakeit::Verify(Method(mockRegistry, insert)).Exactly(1);
@@ -440,7 +443,7 @@ TEST(EngineInfoContainerTest, snippets_are_a_stack_insert_node_always_into_top_s
   // Section: Mock Functions
   // ------------------------------
 
-  fakeit::When(Method(mockQuery, setEngine)).Do(setEngineCallback);
+  fakeit::When(OverloadedMethod(mockQuery, setEngine, void(ExecutionEngine*))).Do(setEngineCallback);
   fakeit::When(Method(mockQuery, trx)).Return(&trx);
   fakeit::When(Method(mockQuery, engine)).Return(&myEngine).Return(&myEngine);
   fakeit::When(Method(mockEngine, createBlocks))
@@ -467,7 +470,7 @@ TEST(EngineInfoContainerTest, snippets_are_a_stack_insert_node_always_into_top_s
       });
 
   // Mock first clone
-  fakeit::When(Method(mockQueryClone, setEngine)).Do(setEngineCallback);
+  fakeit::When(OverloadedMethod(mockQueryClone, setEngine, void(ExecutionEngine*))).Do(setEngineCallback);
   fakeit::When(Method(mockQueryClone, engine)).Return(&mySecondEngine);
   fakeit::When(Method(mockQueryClone, trx)).Return(&secondTrx);
   fakeit::When(Method(mockSecondEngine, createBlocks))
@@ -481,7 +484,7 @@ TEST(EngineInfoContainerTest, snippets_are_a_stack_insert_node_always_into_top_s
       .AlwaysReturn(&block);
 
   // Mock second clone
-  fakeit::When(Method(mockQuerySecondClone, setEngine)).Do(setEngineCallback);
+  fakeit::When(OverloadedMethod(mockQuerySecondClone, setEngine, void(ExecutionEngine*))).Do(setEngineCallback);
   fakeit::When(Method(mockQuerySecondClone, engine)).Return(&myThirdEngine);
   fakeit::When(Method(mockQuerySecondClone, trx)).Return(&thirdTrx);
   fakeit::When(Method(mockThirdEngine, createBlocks))
@@ -550,17 +553,17 @@ TEST(EngineInfoContainerTest, snippets_are_a_stack_insert_node_always_into_top_s
   ASSERT_TRUE(queryIds.empty());
 
   // Validate that the query is wired up with the engine
-  fakeit::Verify(Method(mockQuery, setEngine)).Exactly(1);
+  fakeit::Verify(OverloadedMethod(mockQuery, setEngine, void(ExecutionEngine*))).Exactly(1);
   // Validate that createBlocks has been called!
   fakeit::Verify(Method(mockEngine, createBlocks)).Exactly(1);
 
   // Validate that the second query is wired up with the second engine
-  fakeit::Verify(Method(mockQueryClone, setEngine)).Exactly(1);
+  fakeit::Verify(OverloadedMethod(mockQueryClone, setEngine, void(ExecutionEngine*))).Exactly(1);
   // Validate that createBlocks has been called!
   fakeit::Verify(Method(mockSecondEngine, createBlocks)).Exactly(1);
 
   // Validate that the second query is wired up with the second engine
-  fakeit::Verify(Method(mockQuerySecondClone, setEngine)).Exactly(1);
+  fakeit::Verify(OverloadedMethod(mockQuerySecondClone, setEngine, void(ExecutionEngine*))).Exactly(1);
   // Validate that createBlocks has been called!
   fakeit::Verify(Method(mockThirdEngine, createBlocks)).Exactly(1);
 
@@ -627,7 +630,7 @@ TEST(EngineInfoContainerTest, error_cases_cloning_of_a_query_fails_throws_an_err
   // Section: Mock Functions
   // ------------------------------
 
-  fakeit::When(Method(mockQuery, setEngine)).Do([&](ExecutionEngine* eng) -> void {
+  fakeit::When(OverloadedMethod(mockQuery, setEngine, void(ExecutionEngine*))).Do([&](ExecutionEngine* eng) -> void {
     // We expect that the snippet injects a new engine into our
     // query.
     // However we have to return a mocked engine later
@@ -640,7 +643,7 @@ TEST(EngineInfoContainerTest, error_cases_cloning_of_a_query_fails_throws_an_err
   fakeit::When(Method(mockEngine, createBlocks)).AlwaysReturn(Result{TRI_ERROR_NO_ERROR});
   fakeit::When(ConstOverloadedMethod(mockEngine, root, ExecutionBlock * ())).AlwaysReturn(&block);
 
-  fakeit::When(Method(mockQueryClone, setEngine)).Do([&](ExecutionEngine* eng) -> void {
+  fakeit::When(OverloadedMethod(mockQueryClone, setEngine, void(ExecutionEngine*))).Do([&](ExecutionEngine* eng) -> void {
     // We expect that the snippet injects a new engine into our
     // query.
     // However we have to return a mocked engine later
@@ -717,12 +720,12 @@ TEST(EngineInfoContainerTest, error_cases_cloning_of_a_query_fails_throws_an_err
   // Validate that the path up to intended error was taken
 
   // Validate that the query is wired up with the engine
-  fakeit::Verify(Method(mockQuery, setEngine)).Exactly(1);
+  fakeit::Verify(OverloadedMethod(mockQuery, setEngine, void(ExecutionEngine*))).Exactly(1);
   // Validate that createBlocks has been called!
   fakeit::Verify(Method(mockEngine, createBlocks)).Exactly(1);
 
   // Validate that the second query is wired up with the second engine
-  fakeit::Verify(Method(mockQueryClone, setEngine)).Exactly(1);
+  fakeit::Verify(OverloadedMethod(mockQueryClone, setEngine, void(ExecutionEngine*))).Exactly(1);
   // Validate that createBlocks has been called!
   fakeit::Verify(Method(mockSecondEngine, createBlocks)).Exactly(1);
   fakeit::Verify(Method(mockRegistry, insert)).Exactly(1);
@@ -792,7 +795,7 @@ TEST(EngineInfoContainerTest, error_cases_cloning_of_a_query_fails_returns_a_nul
   // Section: Mock Functions
   // ------------------------------
 
-  fakeit::When(Method(mockQuery, setEngine)).Do([&](ExecutionEngine* eng) -> void {
+  fakeit::When(OverloadedMethod(mockQuery, setEngine, void(ExecutionEngine*))).Do([&](ExecutionEngine* eng) -> void {
     // We expect that the snippet injects a new engine into our
     // query.
     // However we have to return a mocked engine later
@@ -805,7 +808,7 @@ TEST(EngineInfoContainerTest, error_cases_cloning_of_a_query_fails_returns_a_nul
   fakeit::When(Method(mockEngine, createBlocks)).AlwaysReturn(Result{TRI_ERROR_NO_ERROR});
   fakeit::When(ConstOverloadedMethod(mockEngine, root, ExecutionBlock * ())).AlwaysReturn(&block);
 
-  fakeit::When(Method(mockQueryClone, setEngine)).Do([&](ExecutionEngine* eng) -> void {
+  fakeit::When(OverloadedMethod(mockQueryClone, setEngine, void(ExecutionEngine*))).Do([&](ExecutionEngine* eng) -> void {
     // We expect that the snippet injects a new engine into our
     // query.
     // However we have to return a mocked engine later
@@ -886,12 +889,12 @@ TEST(EngineInfoContainerTest, error_cases_cloning_of_a_query_fails_returns_a_nul
   // Validate that the path up to intended error was taken
 
   // Validate that the query is wired up with the engine
-  fakeit::Verify(Method(mockQuery, setEngine)).Exactly(1);
+  fakeit::Verify(OverloadedMethod(mockQuery, setEngine, void(ExecutionEngine*))).Exactly(1);
   // Validate that createBlocks has been called!
   fakeit::Verify(Method(mockEngine, createBlocks)).Exactly(1);
 
   // Validate that the second query is wired up with the second engine
-  fakeit::Verify(Method(mockQueryClone, setEngine)).Exactly(1);
+  fakeit::Verify(OverloadedMethod(mockQueryClone, setEngine, void(ExecutionEngine*))).Exactly(1);
   // Validate that createBlocks has been called!
   fakeit::Verify(Method(mockSecondEngine, createBlocks)).Exactly(1);
   fakeit::Verify(Method(mockRegistry, insert)).Exactly(1);
diff --git a/tests/Aql/EnumerateListExecutorTest.cpp b/tests/Aql/EnumerateListExecutorTest.cpp
index 32048fc2a8b7..5cc1e4ef7669 100644
--- a/tests/Aql/EnumerateListExecutorTest.cpp
+++ b/tests/Aql/EnumerateListExecutorTest.cpp
@@ -81,7 +81,7 @@ TEST_F(EnumerateListExecutorTest, test_check_state_first_row_border) {
       buildBlock<4>(itemBlockManager, {{{{1}, {2}, {3}, {R"([true, 1, 2])"}}},
                                        {{{1}, {2}, {3}, {R"([true, 1, 2])"}}}});
 
-  AqlItemBlockInputRange input{ExecutorState::DONE, inBlock, 0, inBlock->size()};
+  AqlItemBlockInputRange input{ExecutorState::DONE, 0, inBlock, 0};
   OutputAqlItemRow output(std::move(block), infos.getOutputRegisters(),
                           infos.registersToKeep(), infos.registersToClear());
 
@@ -115,7 +115,7 @@ TEST_F(EnumerateListExecutorTest, test_check_state_second_row_border) {
       buildBlock<4>(itemBlockManager, {{{{1}, {2}, {3}, {R"([true, 1, 2])"}}},
                                        {{{1}, {2}, {3}, {R"([true, 1, 2])"}}}});
 
-  AqlItemBlockInputRange input{ExecutorState::DONE, inBlock, 0, inBlock->size()};
+  AqlItemBlockInputRange input{ExecutorState::DONE, 0, inBlock, 0};
   OutputAqlItemRow output(std::move(block), infos.getOutputRegisters(),
                           infos.registersToKeep(), infos.registersToClear());
 
diff --git a/tests/Aql/ExecutionBlockImplTest.cpp b/tests/Aql/ExecutionBlockImplTest.cpp
index c06c04776340..0fcde0a15adb 100644
--- a/tests/Aql/ExecutionBlockImplTest.cpp
+++ b/tests/Aql/ExecutionBlockImplTest.cpp
@@ -1537,7 +1537,11 @@ class ExecutionBlockImplExecuteIntegrationTest
         output.copyRow(input);
         output.advanceRow();
       }
-      return {inputRange.upstreamState(), NoStats{}, output.getClientCall()};
+      // Do forward a softLimit call only.
+      // Do not oeverfetch here.
+      AqlCall request{};
+      request.softLimit = output.getClientCall().getLimit();
+      return {inputRange.upstreamState(), NoStats{}, request};
     };
 
     auto skipData = [&skipAsserter](AqlItemBlockInputRange& inputRange, AqlCall& call)
@@ -1553,7 +1557,7 @@ class ExecutionBlockImplExecuteIntegrationTest
       }
       // Do forward a softLimit call only.
       // Do not oeverfetch here.
-      AqlCall request;
+      AqlCall request{};
       if (call.getOffset() > 0) {
         request.softLimit = call.getOffset();
       }  // else fullCount case, simple get UNLIMITED from above
diff --git a/tests/Aql/ExecutorTestHelper.h b/tests/Aql/ExecutorTestHelper.h
index 8c421efc8d92..b280ab9c7c3b 100644
--- a/tests/Aql/ExecutorTestHelper.h
+++ b/tests/Aql/ExecutorTestHelper.h
@@ -26,20 +26,25 @@
 #include "gtest/gtest.h"
 
 #include "AqlItemBlockHelper.h"
+#include "MockTypedNode.h"
 #include "Mocks/Servers.h"
 #include "WaitingExecutionBlockMock.h"
 
 #include "Aql/AqlCall.h"
 #include "Aql/AqlCallStack.h"
+#include "Aql/AqlItemMatrix.h"
 #include "Aql/ExecutionBlock.h"
 #include "Aql/ExecutionBlockImpl.h"
 #include "Aql/ExecutionEngine.h"
+#include "Aql/ExecutionNode.h"
 #include "Aql/ExecutionState.h"
 #include "Aql/ExecutionStats.h"
 #include "Aql/OutputAqlItemRow.h"
 #include "Aql/Query.h"
 #include "Aql/SharedAqlItemBlockPtr.h"
+#include "Logger/LogMacros.h"
 
+#include <numeric>
 #include <tuple>
 
 namespace arangodb {
@@ -214,6 +219,15 @@ struct ExecutorTestHelper {
     return *this;
   }
 
+  auto setInputFromRowNum(size_t rows) -> ExecutorTestHelper& {
+    static_assert(inputColumns == 1);
+    _input.clear();
+    for (auto i = size_t{0}; i < rows; ++i) {
+      _input.emplace_back(RowBuilder<1>{i});
+    }
+    return *this;
+  }
+
   auto setInputSplit(std::vector<std::size_t> const& list) -> ExecutorTestHelper& {
     _inputSplit = list;
     return *this;
@@ -236,6 +250,17 @@ struct ExecutorTestHelper {
     return *this;
   }
 
+  auto setTesteeNodeType(ExecutionNode::NodeType nodeType) -> ExecutorTestHelper& {
+    _testeeNodeType = nodeType;
+    return *this;
+  }
+
+  auto setWaitingBehaviour(WaitingExecutionBlockMock::WaitingBehaviour waitingBehaviour)
+      -> ExecutorTestHelper& {
+    _waitingBehaviour = waitingBehaviour;
+    return *this;
+  }
+
   auto expectOutput(std::array<RegisterId, outputColumns> const& regs,
                     MatrixBuilder<outputColumns> const& out) -> ExecutorTestHelper& {
     _outputRegisters = regs;
@@ -267,19 +292,32 @@ struct ExecutorTestHelper {
     return *this;
   }
 
+  /**
+   * @brief Set the Execution Block object
+   *
+   * @tparam E The executor
+   * @param infos to build the executor
+   * @param nodeType The type of executor node, only used for debug printing, defaults to SINGLETON
+   * @return ExecutorTestHelper&
+   */
   template <typename E>
-  auto setExecBlock(typename E::Infos infos) -> ExecutorTestHelper& {
+  auto setExecBlock(typename E::Infos infos,
+                    ExecutionNode::NodeType nodeType = ExecutionNode::SINGLETON)
+      -> ExecutorTestHelper& {
     auto& testeeNode = _execNodes.emplace_back(std::move(
-        std::make_unique<SingletonNode>(_query.plan(), _execNodes.size())));
-    setPipeline(Pipeline{std::make_unique<ExecutionBlockImpl<E>>(_query.engine(),
-                                                      testeeNode.get(), std::move(infos))});
+        std::make_unique<MockTypedNode>(_query.plan(), _execNodes.size(), nodeType)));
+    setPipeline(Pipeline{
+        std::make_unique<ExecutionBlockImpl<E>>(_query.engine(), testeeNode.get(),
+                                                std::move(infos))});
     return *this;
   }
 
   template <typename E>
-  auto createExecBlock(typename E::Infos infos) -> ExecBlock {
-    auto& testeeNode = _execNodes.emplace_back(std::move(
-        std::make_unique<SingletonNode>(_query.plan(), _execNodes.size())));
+  auto createExecBlock(typename E::Infos infos,
+                       ExecutionNode::NodeType nodeType = ExecutionNode::SINGLETON)
+      -> ExecBlock {
+    auto& testeeNode = _execNodes.emplace_back(
+        std::move(std::make_unique<MockTypedNode>(_query.plan(), _execNodes.size(), nodeType)));
     return std::make_unique<ExecutionBlockImpl<E>>(_query.engine(), testeeNode.get(),
                                                    std::move(infos));
   }
@@ -309,20 +347,48 @@ struct ExecutorTestHelper {
     return *this;
   }
 
-  auto run() -> void {
+  auto run(bool const loop = false) -> void {
     ResourceMonitor monitor;
     AqlItemBlockManager itemBlockManager(&monitor, SerializationFormat::SHADOWROWS);
 
     auto inputBlock = generateInputRanges(itemBlockManager);
 
+    auto skippedTotal = size_t{0};
+    auto finalState = ExecutionState::HASMORE;
+
     TRI_ASSERT(!_pipeline.empty());
     _pipeline.get().back()->addDependency(inputBlock.get());
 
-    AqlCallStack stack{_call};
-    auto const [state, skipped, result] = _pipeline.get().front()->execute(stack);
-    EXPECT_EQ(skipped, _expectedSkip);
+    BlockCollector allResults{&itemBlockManager};
 
-    EXPECT_EQ(state, _expectedState);
+    if (!loop) {
+      AqlCallStack stack{_call};
+      auto const [state, skipped, result] = _pipeline.get().front()->execute(stack);
+      skippedTotal = skipped;
+      finalState = state;
+      if (result != nullptr) {
+        allResults.add(result);
+      }
+    } else {
+      auto call = _call;
+      do {
+        AqlCallStack stack{call};
+        auto const [state, skipped, result] = _pipeline.get().front()->execute(stack);
+        finalState = state;
+        skippedTotal += skipped;
+        if (result != nullptr) {
+          allResults.add(result);
+        }
+        call = _call;
+        call.didSkip(skippedTotal);
+        call.didProduce(allResults.totalSize());
+      } while (finalState != ExecutionState::DONE &&
+               (!call.hasSoftLimit() || (call.getLimit() + call.getOffset()) > 0));
+    }
+
+    EXPECT_EQ(skippedTotal, _expectedSkip);
+    EXPECT_EQ(finalState, _expectedState);
+    SharedAqlItemBlockPtr result = allResults.steal();
     if (result == nullptr) {
       // Empty output, possible if we skip all
       EXPECT_EQ(_output.size(), 0)
@@ -365,6 +431,8 @@ struct ExecutorTestHelper {
     for (auto const& value : _input) {
       matrix.push_back(value);
 
+      TRI_ASSERT(!_inputSplit.valueless_by_exception());
+
       bool openNewBlock =
           std::visit(overload{[&](VectorSizeT& list) {
                                 if (*iter != *end && matrix.size() == **iter) {
@@ -396,9 +464,10 @@ struct ExecutorTestHelper {
       blockDeque.emplace_back(nullptr);
     }
 
-    return std::make_unique<WaitingExecutionBlockMock>(
-        _query.engine(), _dummyNode.get(), std::move(blockDeque),
-        WaitingExecutionBlockMock::WaitingBehaviour::NEVER);
+    return std::make_unique<WaitingExecutionBlockMock>(_query.engine(),
+                                                       _dummyNode.get(),
+                                                       std::move(blockDeque),
+                                                       _waitingBehaviour);
   }
 
   AqlCall _call;
@@ -409,6 +478,9 @@ struct ExecutorTestHelper {
   ExecutionState _expectedState;
   ExecutionStats _expectedStats;
   bool _testStats;
+  ExecutionNode::NodeType _testeeNodeType{ExecutionNode::MAX_NODE_TYPE_VALUE};
+  WaitingExecutionBlockMock::WaitingBehaviour _waitingBehaviour =
+      WaitingExecutionBlockMock::NEVER;
   bool _unorderedOutput;
   bool _appendEmptyBlock;
   std::size_t _unorderedSkippedRows;
@@ -419,7 +491,7 @@ struct ExecutorTestHelper {
   arangodb::aql::Query& _query;
   std::unique_ptr<arangodb::aql::ExecutionNode> _dummyNode;
   Pipeline _pipeline;
-  std::vector<std::unique_ptr<ExecutionNode>> _execNodes;
+  std::vector<std::unique_ptr<MockTypedNode>> _execNodes;
 };
 
 enum class ExecutorCall {
diff --git a/tests/Aql/FilterExecutorTest.cpp b/tests/Aql/FilterExecutorTest.cpp
index 86907101764b..a51463030664 100644
--- a/tests/Aql/FilterExecutorTest.cpp
+++ b/tests/Aql/FilterExecutorTest.cpp
@@ -363,7 +363,7 @@ TEST_F(FilterExecutorTest, test_produce_datarange) {
       buildBlock<1>(itemBlockManager,
                     {{R"(true)"}, {R"(false)"}, {R"(true)"}, {R"(false)"}, {R"(true)"}});
 
-  AqlItemBlockInputRange input{ExecutorState::DONE, inBlock, 0, inBlock->size()};
+  AqlItemBlockInputRange input{ExecutorState::DONE, 0, inBlock, 0};
 
   OutputAqlItemRow output(std::move(block), outputRegisters, registersToKeep,
                           infos.registersToClear());
@@ -388,7 +388,7 @@ TEST_F(FilterExecutorTest, test_produce_datarange_need_more) {
       buildBlock<1>(itemBlockManager,
                     {{R"(true)"}, {R"(false)"}, {R"(true)"}, {R"(false)"}, {R"(true)"}});
   size_t hardLimit = 1000;
-  AqlItemBlockInputRange input{ExecutorState::HASMORE, inBlock, 0, inBlock->size()};
+  AqlItemBlockInputRange input{ExecutorState::HASMORE, 0, inBlock, 0};
   AqlCall limitedCall{};
   limitedCall.hardLimit = hardLimit;
   OutputAqlItemRow output(std::move(block), outputRegisters, registersToKeep,
@@ -420,7 +420,7 @@ TEST_F(FilterExecutorTest, test_skip_datarange_need_more) {
       buildBlock<1>(itemBlockManager,
                     {{R"(true)"}, {R"(false)"}, {R"(true)"}, {R"(false)"}, {R"(true)"}});
 
-  AqlItemBlockInputRange input{ExecutorState::HASMORE, inBlock, 0, inBlock->size()};
+  AqlItemBlockInputRange input{ExecutorState::HASMORE, 0, inBlock, 0};
   AqlCall clientCall;
   clientCall.offset = 1000;
 
@@ -453,7 +453,7 @@ TEST_F(FilterExecutorTest, test_produce_datarange_has_more) {
       buildBlock<1>(itemBlockManager,
                     {{R"(true)"}, {R"(false)"}, {R"(true)"}, {R"(false)"}, {R"(true)"}});
 
-  AqlItemBlockInputRange input{ExecutorState::DONE, inBlock, 0, inBlock->size()};
+  AqlItemBlockInputRange input{ExecutorState::DONE, 0, inBlock, 0};
   block.reset(new AqlItemBlock(itemBlockManager, 2, 1));
   OutputAqlItemRow output(std::move(block), outputRegisters, registersToKeep,
                           infos.registersToClear());
@@ -492,7 +492,7 @@ TEST_F(FilterExecutorTest, test_skip_datarange_has_more) {
       buildBlock<1>(itemBlockManager,
                     {{R"(true)"}, {R"(false)"}, {R"(true)"}, {R"(false)"}, {R"(true)"}});
 
-  AqlItemBlockInputRange input{ExecutorState::DONE, inBlock, 0, inBlock->size()};
+  AqlItemBlockInputRange input{ExecutorState::DONE, 0, inBlock, 0};
   AqlCall clientCall;
   clientCall.offset = 2;
   auto const [state, stats, skipped, call] = testee.skipRowsRange(input, clientCall);
diff --git a/tests/Aql/IdExecutorTest.cpp b/tests/Aql/IdExecutorTest.cpp
index 37f9ce13ac61..6595e5612206 100644
--- a/tests/Aql/IdExecutorTest.cpp
+++ b/tests/Aql/IdExecutorTest.cpp
@@ -68,7 +68,8 @@ class IdExecutorTestCombiner : public AqlExecutorTestCaseWithParam<TestParam> {
       matrix.emplace_back(RowBuilder<1>{{it}});
     }
     SharedAqlItemBlockPtr block = buildBlock<1>(manager(), std::move(matrix));
-    return AqlItemBlockInputRange{upstreamState, block, 0, input.size()};
+    TRI_ASSERT(clientCall.getSkipCount() == 0);
+    return AqlItemBlockInputRange{upstreamState, 0, block, 0};
   }
 
   auto prepareOutputRow(SharedAqlItemBlockPtr input) -> OutputAqlItemRow {
diff --git a/tests/Aql/LimitExecutorTest.cpp b/tests/Aql/LimitExecutorTest.cpp
index f8a44a1f3c35..18eabe264b41 100644
--- a/tests/Aql/LimitExecutorTest.cpp
+++ b/tests/Aql/LimitExecutorTest.cpp
@@ -25,6 +25,7 @@
 #include "AqlHelper.h"
 #include "AqlItemBlockHelper.h"
 #include "ExecutorTestHelper.h"
+#include "Mocks/Servers.h"
 #include "RowFetcherHelper.h"
 #include "VelocyPackHelper.h"
 
@@ -33,20 +34,63 @@
 #include "Aql/InputAqlItemRow.h"
 #include "Aql/LimitExecutor.h"
 #include "Aql/ResourceUsage.h"
-#include "Aql/SingleRowFetcher.h"
 
 #include <velocypack/Builder.h>
 #include <velocypack/velocypack-aliases.h>
+#include <numeric>
 
 using namespace arangodb;
 using namespace arangodb::aql;
 
-namespace arangodb {
-namespace tests {
-namespace aql {
+namespace arangodb::aql {
+void PrintTo(LimitStats const& stats, std::ostream* os) {
+  *os << "LimitStats{" << stats.getFullCount() << "}";
+}
+}  // namespace arangodb::aql
+
+namespace arangodb::tests::aql {
+
+/*
+ * How a test case for LimitExecutor is described:
+ *
+ * Obviously, we need the LimitExecutor parameters
+ *  1) offset,
+ *  2) limit, and
+ *  3) fullCount.
+ * We also need an input, specified as a
+ *  4) vector of input lengths,
+ * which maps to a vector of input blocks, each with the specified number of
+ * rows.
+ * Finally, we need a call in form of an
+ *  5) AqlCall
+ * which breaks down to:
+ *     - offset
+ *     - limit,
+ *     - hard/soft ~, and
+ *     - fullCount.
+ * Plus something like
+ *  6) doneResultIsEmpty
+ * to cover both the case where the last upstream non-empty result returns with
+ * HASMORE, or immediately with DONE.
+ */
+class LimitExecutorTest
+    : public ::testing::TestWithParam<std::tuple<size_t, size_t, bool, std::vector<size_t>, AqlCall, bool>> {
+ public:
+  // Creating a server instance costs a lot of time, so do it only once.
+  // Note that newer version of gtest call these SetUpTestSuite/TearDownTestSuite
+  static void SetUpTestCase() {
+    server = std::make_unique<decltype(server)::element_type>();
+    // Logger::QUERIES.setLogLevel(LogLevel::DEBUG);
+  }
+  static void TearDownTestCase() {
+    // Logger::QUERIES.setLogLevel(LogLevel::INFO);
+    server.reset();
+  }
 
-class LimitExecutorTest : public ::testing::Test {
  protected:
+  static std::unique_ptr<mocks::MockAqlServer> server;
+  std::unique_ptr<arangodb::aql::Query> fakedQuery{};
+
   ExecutionState state;
   ResourceMonitor monitor;
   AqlItemBlockManager itemBlockManager;
@@ -54,11 +98,9 @@ class LimitExecutorTest : public ::testing::Test {
   std::shared_ptr<const std::unordered_set<RegisterId>> outputRegisters;
   std::shared_ptr<const std::unordered_set<RegisterId>> registersToKeep;
 
-  // Special parameters:
-  // 4th offset
-  // 5th limit
-  // 6th fullCount
-  // 7th queryDepth
+  // Should never be called, and can be removed as soon as the LimitExecutor's
+  // Fetcher argument&member are removed.
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Enable> dummyFetcher;
 
   LimitExecutorTest()
       : itemBlockManager(&monitor, SerializationFormat::SHADOWROWS),
@@ -66,1039 +108,317 @@ class LimitExecutorTest : public ::testing::Test {
         outputRegisters(std::make_shared<const std::unordered_set<RegisterId>>(
             std::initializer_list<RegisterId>{})),
         registersToKeep(std::make_shared<const std::unordered_set<RegisterId>>(
-            std::initializer_list<RegisterId>{0})) {}
-};
-
-TEST_F(LimitExecutorTest, row_upstream_the_producer_doesnt_wait) {
-  auto input = VPackParser::fromJson("[ [1] ]");
-  LimitExecutorInfos infos(1, 1, {}, {0}, 0, 1, true);
-
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Enable> fetcher(itemBlockManager, input->steal(), false);
-  LimitExecutor testee(fetcher, infos);
-  LimitStats stats{};
-
-  OutputAqlItemRow result{std::move(block), outputRegisters, registersToKeep,
-                          infos.registersToClear()};
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_TRUE(result.produced());
-  ASSERT_EQ(1, stats.getFullCount());
-}
-
-TEST_F(LimitExecutorTest, row_upstream_the_producer_waits) {
-  auto input = VPackParser::fromJson("[ [1] ]");
-  LimitExecutorInfos infos(1, 1, {}, {0}, 0, 1, true);
-
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Enable> fetcher(itemBlockManager, input->steal(), true);
-  LimitExecutor testee(fetcher, infos);
-  LimitStats stats{};
-
-  OutputAqlItemRow result{std::move(block), outputRegisters, registersToKeep,
-                          infos.registersToClear()};
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(ExecutionState::WAITING, state);
-  ASSERT_FALSE(result.produced());
-  ASSERT_EQ(0, stats.getFullCount());
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(ExecutionState::DONE, state);
-  ASSERT_TRUE(result.produced());
-  ASSERT_EQ(1, stats.getFullCount());
-}
-
-TEST_F(LimitExecutorTest, rows_upstream_the_producer_doesnt_wait_limit_1_offset_0_fullcount_false) {
-  auto input = VPackParser::fromJson("[ [1], [2], [3], [4] ]");
-  LimitExecutorInfos infos(1, 1, {}, {0}, 0, 1, false);
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Enable> fetcher(itemBlockManager, input->steal(), false);
-  LimitExecutor testee(fetcher, infos);
-  LimitStats stats{};
-
-  OutputAqlItemRow row{std::move(block), outputRegisters, registersToKeep,
-                       infos.registersToClear()};
-
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_TRUE(row.produced());
-  row.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(ExecutionState::DONE, state);
-  ASSERT_FALSE(row.produced());
-}
-
-TEST_F(LimitExecutorTest, rows_upstream_the_producer_doesnt_wait_limit_1_offset_0_fullcount_true) {
-  auto input = VPackParser::fromJson("[ [1], [2], [3], [4] ]");
-  LimitExecutorInfos infos(1, 1, {}, {0}, 0, 1, true);
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Enable> fetcher(itemBlockManager, input->steal(), false);
-  LimitExecutor testee(fetcher, infos);
-  LimitStats stats{};
-
-  OutputAqlItemRow row{std::move(block), outputRegisters, registersToKeep,
-                       infos.registersToClear()};
-
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(ExecutionState::DONE, state);
-  ASSERT_TRUE(row.produced());
-  ASSERT_EQ(4, stats.getFullCount());
-
-  auto block = row.stealBlock();
-  AqlValue value = block->getValue(0, 0);
-  ASSERT_TRUE(value.isNumber());
-  ASSERT_EQ(1, value.toInt64());
-}
-
-TEST_F(LimitExecutorTest, rows_upstream_the_producer_doesnt_wait_limit_1_offset_1_fullcount_true) {
-  auto input = VPackParser::fromJson("[ [1], [2], [3], [4] ]");
-  LimitExecutorInfos infos(1, 1, {}, {0}, 1, 1, true);
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Enable> fetcher(itemBlockManager, input->steal(), false);
-  LimitExecutor testee(fetcher, infos);
-  LimitStats stats{};
-
-  OutputAqlItemRow row{std::move(block), outputRegisters, registersToKeep,
-                       infos.registersToClear()};
-
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(ExecutionState::DONE, state);
-  ASSERT_TRUE(row.produced());
-  ASSERT_EQ(4, stats.getFullCount());
-
-  auto block = row.stealBlock();
-  AqlValue value = block->getValue(0, 0);
-  ASSERT_TRUE(value.isNumber());
-  ASSERT_EQ(2, value.toInt64());
-}
-
-TEST_F(LimitExecutorTest, rows_upstream_the_producer_waits_limit_1_offset_0_fullcount_false) {
-  auto input = VPackParser::fromJson("[ [1], [2], [3], [4] ]");
-  LimitExecutorInfos infos(1, 1, {}, {0}, 0, 1, false);
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Enable> fetcher(itemBlockManager, input->steal(), true);
-  LimitExecutor testee(fetcher, infos);
-  LimitStats stats{};
-
-  OutputAqlItemRow row{std::move(block), outputRegisters, registersToKeep,
-                       infos.registersToClear()};
-
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(ExecutionState::WAITING, state);
-  ASSERT_FALSE(row.produced());
-
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(ExecutionState::DONE, state);
-  ASSERT_TRUE(row.produced());
-
-  row.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(ExecutionState::DONE, state);
-  ASSERT_FALSE(row.produced());
-
-  auto block = row.stealBlock();
-  AqlValue value = block->getValue(0, 0);
-  ASSERT_TRUE(value.isNumber());
-  ASSERT_EQ(1, value.toInt64());
-}
-
-TEST_F(LimitExecutorTest, rows_upstream_the_producer_waits_limit_1_offset_0_fullcount_true) {
-  auto input = VPackParser::fromJson("[ [1], [2], [3], [4] ]");
-  LimitExecutorInfos infos(1, 1, {}, {0}, 0, 1, true);
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Enable> fetcher(itemBlockManager, input->steal(), true);
-  LimitExecutor testee(fetcher, infos);
-  LimitStats stats{};
-  size_t fullCount = 0;
-
-  OutputAqlItemRow row{std::move(block), outputRegisters, registersToKeep,
-                       infos.registersToClear()};
-
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(ExecutionState::WAITING, state);
-  ASSERT_FALSE(row.produced());
-  EXPECT_EQ(0, stats.getFullCount());
-  fullCount += stats.getFullCount();
-
-  // In the following, the EXPECTs against stats.getFullCount() after each
-  // produceRows() call are not strictly required, but implementation dependent.
-  // The implementation of LimitExecutor would be allowed to return rows it has
-  // already seen at these points.
-  // It is sufficient that the sum of the stats equals 4, which is asserted at
-  // the end. So the intermediate EXPECTs are against the actual implementation
-  // and thus just there in order to find the location of an error faster.
-
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(ExecutionState::WAITING, state);
-  ASSERT_FALSE(row.produced());
-  EXPECT_EQ(0, stats.getFullCount());  // not strictly required, see comment above
-  fullCount += stats.getFullCount();
-
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(ExecutionState::WAITING, state);
-  ASSERT_FALSE(row.produced());
-  EXPECT_EQ(0, stats.getFullCount());  // not strictly required, see comment above
-  fullCount += stats.getFullCount();
-
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(ExecutionState::WAITING, state);
-  ASSERT_FALSE(row.produced());
-  EXPECT_EQ(0, stats.getFullCount());  // not strictly required, see comment above
-  fullCount += stats.getFullCount();
-
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(ExecutionState::DONE, state);
-  ASSERT_TRUE(row.produced());
-  EXPECT_EQ(4, stats.getFullCount());  // not strictly required, see comment above
-  fullCount += stats.getFullCount();
-
-  ASSERT_EQ(4, fullCount);
-
-  auto block = row.stealBlock();
-  AqlValue value = block->getValue(0, 0);
-  ASSERT_TRUE(value.isNumber());
-  ASSERT_EQ(1, value.toInt64());
-}
-
-TEST_F(LimitExecutorTest, rows_upstream_the_producer_doesnt_wait_limit_6_offset_1_fullcount_false) {
-  size_t constexpr offset = 1;
-  size_t constexpr limit = 6;
-  bool constexpr fullcount = false;
-  bool constexpr waiting = false;
-  auto input = VPackParser::fromJson("[ [1], [2], [3], [4] ]");
-  LimitExecutorInfos infos(1, 1, {}, {0}, offset, limit, fullcount);
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Enable> fetcher(itemBlockManager, input->steal(), waiting);
-  LimitExecutor testee(fetcher, infos);
-  LimitStats stats{};
-
-  OutputAqlItemRow row{std::move(block), outputRegisters, registersToKeep,
-                       infos.registersToClear()};
-
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(ExecutionState::HASMORE, state);
-  ASSERT_TRUE(row.produced());
-  row.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(ExecutionState::HASMORE, state);
-  ASSERT_TRUE(row.produced());
-  row.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(ExecutionState::DONE, state);
-  ASSERT_TRUE(row.produced());
-
-  auto block = row.stealBlock();
-  EXPECT_EQ(3, block->size());
-  AqlValue value = block->getValue(0, 0);
-  ASSERT_TRUE(value.isNumber());
-  EXPECT_EQ(2, value.toInt64());
-  value = block->getValue(1, 0);
-  ASSERT_TRUE(value.isNumber());
-  EXPECT_EQ(3, value.toInt64());
-  value = block->getValue(2, 0);
-  ASSERT_TRUE(value.isNumber());
-  EXPECT_EQ(4, value.toInt64());
-}
-
-TEST_F(LimitExecutorTest, rows_upstream_the_producer_doesnt_wait_limit_6_offset_1_fullcount_true) {
-  size_t constexpr offset = 1;
-  size_t constexpr limit = 6;
-  bool constexpr fullcount = true;
-  bool constexpr waiting = false;
-  auto input = VPackParser::fromJson("[ [1], [2], [3], [4] ]");
-  LimitExecutorInfos infos(1, 1, {}, {0}, offset, limit, fullcount);
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Enable> fetcher(itemBlockManager, input->steal(), waiting);
-  LimitExecutor testee(fetcher, infos);
-  LimitStats stats{};
-  size_t fullCount = 0;
-
-  OutputAqlItemRow row{std::move(block), outputRegisters, registersToKeep,
-                       infos.registersToClear()};
-
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(ExecutionState::HASMORE, state);
-  ASSERT_TRUE(row.produced());
-  row.advanceRow();
-  EXPECT_EQ(2, stats.getFullCount());
-  fullCount += stats.getFullCount();
-
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(ExecutionState::HASMORE, state);
-  ASSERT_TRUE(row.produced());
-  row.advanceRow();
-  EXPECT_EQ(1, stats.getFullCount());
-  fullCount += stats.getFullCount();
-
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(ExecutionState::DONE, state);
-  ASSERT_TRUE(row.produced());
-  EXPECT_EQ(1, stats.getFullCount());
-  fullCount += stats.getFullCount();
-
-  ASSERT_EQ(4, fullCount);
-
-  auto block = row.stealBlock();
-  EXPECT_EQ(3, block->size());
-  AqlValue value = block->getValue(0, 0);
-  ASSERT_TRUE(value.isNumber());
-  EXPECT_EQ(2, value.toInt64());
-  value = block->getValue(1, 0);
-  ASSERT_TRUE(value.isNumber());
-  EXPECT_EQ(3, value.toInt64());
-  value = block->getValue(2, 0);
-  ASSERT_TRUE(value.isNumber());
-  EXPECT_EQ(4, value.toInt64());
-}
-TEST_F(LimitExecutorTest, rows_upstream_the_producer_waits_limit_6_offset_1_fullcount_false) {
-  size_t constexpr offset = 1;
-  size_t constexpr limit = 6;
-  bool constexpr fullcount = false;
-  bool constexpr waiting = true;
-  auto input = VPackParser::fromJson("[ [1], [2], [3], [4] ]");
-  LimitExecutorInfos infos(1, 1, {}, {0}, offset, limit, fullcount);
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Enable> fetcher(itemBlockManager, input->steal(), waiting);
-  LimitExecutor testee(fetcher, infos);
-  LimitStats stats{};
-
-  OutputAqlItemRow row{std::move(block), outputRegisters, registersToKeep,
-                       infos.registersToClear()};
-
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(ExecutionState::WAITING, state);
-  ASSERT_FALSE(row.produced());
-
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(ExecutionState::WAITING, state);
-  ASSERT_FALSE(row.produced());
-
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(ExecutionState::HASMORE, state);
-  ASSERT_TRUE(row.produced());
-  row.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(ExecutionState::WAITING, state);
-  ASSERT_FALSE(row.produced());
-
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(ExecutionState::HASMORE, state);
-  ASSERT_TRUE(row.produced());
-  row.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(ExecutionState::WAITING, state);
-  ASSERT_FALSE(row.produced());
-
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(ExecutionState::DONE, state);
-  ASSERT_TRUE(row.produced());
-
-  auto block = row.stealBlock();
-  EXPECT_EQ(3, block->size());
-  AqlValue value = block->getValue(0, 0);
-  ASSERT_TRUE(value.isNumber());
-  EXPECT_EQ(2, value.toInt64());
-  value = block->getValue(1, 0);
-  ASSERT_TRUE(value.isNumber());
-  EXPECT_EQ(3, value.toInt64());
-  value = block->getValue(2, 0);
-  ASSERT_TRUE(value.isNumber());
-  EXPECT_EQ(4, value.toInt64());
-}
-
-TEST_F(LimitExecutorTest, rows_upstream_the_producer_waits_limit_6_offset_1_fullcount_true) {
-  size_t constexpr offset = 1;
-  size_t constexpr limit = 6;
-  bool constexpr fullcount = true;
-  bool constexpr waiting = true;
-  auto input = VPackParser::fromJson("[ [1], [2], [3], [4] ]");
-  LimitExecutorInfos infos(1, 1, {}, {0}, offset, limit, fullcount);
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Enable> fetcher(itemBlockManager, input->steal(), waiting);
-  LimitExecutor testee(fetcher, infos);
-  LimitStats stats{};
-  size_t fullCount = 0;
-
-  OutputAqlItemRow row{std::move(block), outputRegisters, registersToKeep,
-                       infos.registersToClear()};
-
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(ExecutionState::WAITING, state);
-  ASSERT_FALSE(row.produced());
-  EXPECT_EQ(0, stats.getFullCount());
-  fullCount += stats.getFullCount();
-
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(ExecutionState::WAITING, state);
-  ASSERT_FALSE(row.produced());
-  EXPECT_EQ(1, stats.getFullCount());
-  fullCount += stats.getFullCount();
-
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(ExecutionState::HASMORE, state);
-  ASSERT_TRUE(row.produced());
-  row.advanceRow();
-  EXPECT_EQ(1, stats.getFullCount());
-  fullCount += stats.getFullCount();
-
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(ExecutionState::WAITING, state);
-  ASSERT_FALSE(row.produced());
-  EXPECT_EQ(0, stats.getFullCount());
-  fullCount += stats.getFullCount();
-
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(ExecutionState::HASMORE, state);
-  ASSERT_TRUE(row.produced());
-  row.advanceRow();
-  EXPECT_EQ(1, stats.getFullCount());
-  fullCount += stats.getFullCount();
-
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(ExecutionState::WAITING, state);
-  ASSERT_FALSE(row.produced());
-  EXPECT_EQ(0, stats.getFullCount());
-  fullCount += stats.getFullCount();
-
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(ExecutionState::DONE, state);
-  ASSERT_TRUE(row.produced());
-  EXPECT_EQ(1, stats.getFullCount());
-  fullCount += stats.getFullCount();
-
-  ASSERT_EQ(4, fullCount);
-
-  auto block = row.stealBlock();
-  EXPECT_EQ(3, block->size());
-  AqlValue value = block->getValue(0, 0);
-  ASSERT_TRUE(value.isNumber());
-  EXPECT_EQ(2, value.toInt64());
-  value = block->getValue(1, 0);
-  ASSERT_TRUE(value.isNumber());
-  EXPECT_EQ(3, value.toInt64());
-  value = block->getValue(2, 0);
-  ASSERT_TRUE(value.isNumber());
-  EXPECT_EQ(4, value.toInt64());
-}
-
-class LimitExecutorTestBase {
- protected:
-  ResourceMonitor monitor;
-  AqlItemBlockManager itemBlockManager;
-  std::shared_ptr<const std::unordered_set<RegisterId>> outputRegisters;
-  std::shared_ptr<const std::unordered_set<RegisterId>> registersToKeep;
-
-  LimitExecutorTestBase()
-      : monitor(),
-        itemBlockManager(&monitor, SerializationFormat::SHADOWROWS),
-        outputRegisters(std::make_shared<const std::unordered_set<RegisterId>>(
-            std::initializer_list<RegisterId>{})),
-        registersToKeep(std::make_shared<const std::unordered_set<RegisterId>>(
-            std::initializer_list<RegisterId>{0})) {}
-};
-
-// skip and fullCount cannot go together: Only the last limit block may get
-// fullCount, so there is no block after that could skip.
-// For these cases, use this class.
-class LimitExecutorWaitingTest : public LimitExecutorTestBase,
-                                 public ::testing::TestWithParam<bool> {
- protected:
-  bool waiting{};
-
-  LimitExecutorWaitingTest() : LimitExecutorTestBase() {}
-
-  virtual void SetUp() { waiting = GetParam(); }
-};
-
-// Fields:
-//  [0] bool waiting
-//  [1] bool fullCount
-using ExtendedLimitTestParameters = std::tuple<bool, bool>;
-
-class LimitExecutorWaitingFullCountTest
-    : public LimitExecutorTestBase,
-      public ::testing::TestWithParam<ExtendedLimitTestParameters> {
- protected:
-  bool waiting{};
-  bool fullCount{};
-
-  LimitExecutorWaitingFullCountTest() : LimitExecutorTestBase() {}
-
-  virtual void SetUp() {
-    ExtendedLimitTestParameters const& params = GetParam();
-    std::tie(waiting, fullCount) = params;
+            std::initializer_list<RegisterId>{0})),
+        dummyFetcher(itemBlockManager, 1, false, nullptr) {
+    fakedQuery = server->createFakeQuery();
   }
-};
 
-void removeWaiting(std::vector<ExecutorStepResult>& results) {
-  std::vector<ExecutorStepResult> tmp;
-  for (auto const result : results) {
-    if (std::get<ExecutionState>(result) != ExecutionState::WAITING) {
-      tmp.emplace_back(result);
+  auto buildBlockRange(size_t const begin, size_t const end) -> SharedAqlItemBlockPtr {
+    auto builder = MatrixBuilder<1>{};
+    builder.reserve(end - begin);
+    for (size_t i = begin; i < end; ++i) {
+      builder.emplace_back(RowBuilder<1>{i});
     }
+    return buildBlock<1>(itemBlockManager, std::move(builder));
   }
-  results.swap(tmp);
-}
-
-TEST_P(LimitExecutorWaitingFullCountTest, rows_9_blocksize_3_limit_10) {
-  // Input spec:
-  size_t constexpr blocksize = 3;
-  size_t constexpr offset = 0;
-  size_t constexpr limit = 10;
-  SharedAqlItemBlockPtr const input =
-      buildBlock<1>(itemBlockManager, {{0}, {1}, {2}, {3}, {4}, {5}, {6}, {7}, {8}});
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Enable> fetcher(itemBlockManager, blocksize, waiting, input);
-  LimitExecutorInfos infos(1, 1, {}, {0}, offset, limit, fullCount);
-
-  // Output spec:
-  SharedAqlItemBlockPtr const expectedOutput =
-      buildBlock<1>(itemBlockManager, {{0}, {1}, {2}, {3}, {4}, {5}, {6}, {7}, {8}});
-  size_t const expectedOutputSize =
-      expectedOutput == nullptr ? 0 : expectedOutput->size();
-  std::vector<ExecutorStepResult> expectedStates{
-      {ExecutorCall::FETCH_FOR_PASSTHROUGH, ExecutionState::WAITING, 0},
-      {ExecutorCall::FETCH_FOR_PASSTHROUGH, ExecutionState::HASMORE, 3},
-      {ExecutorCall::PRODUCE_ROWS, ExecutionState::HASMORE, 1},
-      {ExecutorCall::PRODUCE_ROWS, ExecutionState::HASMORE, 1},
-      {ExecutorCall::PRODUCE_ROWS, ExecutionState::HASMORE, 1},
-      {ExecutorCall::FETCH_FOR_PASSTHROUGH, ExecutionState::WAITING, 0},
-      {ExecutorCall::FETCH_FOR_PASSTHROUGH, ExecutionState::HASMORE, 3},
-      {ExecutorCall::PRODUCE_ROWS, ExecutionState::HASMORE, 1},
-      {ExecutorCall::PRODUCE_ROWS, ExecutionState::HASMORE, 1},
-      {ExecutorCall::PRODUCE_ROWS, ExecutionState::HASMORE, 1},
-      {ExecutorCall::FETCH_FOR_PASSTHROUGH, ExecutionState::WAITING, 0},
-      {ExecutorCall::FETCH_FOR_PASSTHROUGH, ExecutionState::DONE, 3},
-      {ExecutorCall::PRODUCE_ROWS, ExecutionState::HASMORE, 1},
-      {ExecutorCall::PRODUCE_ROWS, ExecutionState::HASMORE, 1},
-      {ExecutorCall::PRODUCE_ROWS, ExecutionState::DONE, 1},
-  };
-  if (!waiting) {
-    removeWaiting(expectedStates);
-  }
-  ExecutionStats expectedStats{};
-  if (fullCount) {
-    expectedStats.fullCount = 9;
-  } else {
-    expectedStats.fullCount = 0;
-  }
-
-  // Run:
-  LimitExecutor testee(fetcher, infos);
-  // Allocate at least one output row more than expected!
-  SharedAqlItemBlockPtr block = itemBlockManager.requestBlock(expectedOutputSize + 1, 1);
-  OutputAqlItemRow outputRow{block, outputRegisters, registersToKeep,
-                             infos.registersToClear()};
-
-  auto result =
-      runExecutor(itemBlockManager, testee, outputRow, 0, expectedOutputSize, false);
-  auto& actualOutput = std::get<SharedAqlItemBlockPtr>(result);
-  auto& actualStats = std::get<ExecutionStats>(result);
-  auto& actualStates = std::get<std::vector<ExecutorStepResult>>(result);
-
-  EXPECT_EQ(expectedStats, actualStats);
-  EXPECT_EQ(expectedStates, actualStates);
-  if (expectedOutput == nullptr) {
-    ASSERT_EQ(actualOutput, nullptr);
-  } else {
-    ASSERT_FALSE(actualOutput == nullptr);
-    EXPECT_EQ(*expectedOutput, *actualOutput);
-  }
-}
-
-TEST_P(LimitExecutorWaitingFullCountTest, rows_9_blocksize_3_limit_4) {
-  // Input spec:
-  size_t constexpr blocksize = 3;
-  size_t constexpr offset = 0;
-  size_t constexpr limit = 4;
-  SharedAqlItemBlockPtr const input =
-      buildBlock<1>(itemBlockManager, {{0}, {1}, {2}, {3}, {4}, {5}, {6}, {7}, {8}});
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Enable> fetcher(itemBlockManager, blocksize, waiting, input);
-  LimitExecutorInfos infos(1, 1, {}, {0}, offset, limit, fullCount);
-
-  // Output spec:
-  SharedAqlItemBlockPtr const expectedOutput =
-      buildBlock<1>(itemBlockManager, {{0}, {1}, {2}, {3}});
-  size_t const expectedOutputSize =
-      expectedOutput == nullptr ? 0 : expectedOutput->size();
-  std::vector<ExecutorStepResult> expectedStates{
-      {ExecutorCall::FETCH_FOR_PASSTHROUGH, ExecutionState::WAITING, 0},
-      {ExecutorCall::FETCH_FOR_PASSTHROUGH, ExecutionState::HASMORE, 3},
-      {ExecutorCall::PRODUCE_ROWS, ExecutionState::HASMORE, 1},
-      {ExecutorCall::PRODUCE_ROWS, ExecutionState::HASMORE, 1},
-      {ExecutorCall::PRODUCE_ROWS, ExecutionState::HASMORE, 1},
-      {ExecutorCall::FETCH_FOR_PASSTHROUGH, ExecutionState::WAITING, 0},
-      {ExecutorCall::FETCH_FOR_PASSTHROUGH, ExecutionState::HASMORE, 3},
-  };
-  if (fullCount) {
-    expectedStates.emplace_back(ExecutorCall::PRODUCE_ROWS, ExecutionState::WAITING, 0);
-  }
-  expectedStates.emplace_back(ExecutorCall::PRODUCE_ROWS, ExecutionState::DONE, 1);
-  if (!waiting) {
-    removeWaiting(expectedStates);
-  }
-  ExecutionStats expectedStats{};
-  if (fullCount) {
-    expectedStats.fullCount = 9;
-  } else {
-    expectedStats.fullCount = 0;
-  }
-
-  // Run:
-  LimitExecutor testee(fetcher, infos);
-  // Allocate at least one output row more than expected!
-  SharedAqlItemBlockPtr block = itemBlockManager.requestBlock(expectedOutputSize + 1, 1);
-  OutputAqlItemRow outputRow{block, outputRegisters, registersToKeep,
-                             infos.registersToClear()};
-
-  auto result =
-      runExecutor(itemBlockManager, testee, outputRow, 0, expectedOutputSize, false);
-  auto& actualOutput = std::get<SharedAqlItemBlockPtr>(result);
-  auto& actualStats = std::get<ExecutionStats>(result);
-  auto& actualStates = std::get<std::vector<ExecutorStepResult>>(result);
-
-  EXPECT_EQ(expectedStats, actualStats);
-  EXPECT_EQ(expectedStates, actualStates);
-  if (expectedOutput == nullptr) {
-    ASSERT_EQ(actualOutput, nullptr);
-  } else {
-    ASSERT_FALSE(actualOutput == nullptr);
-    EXPECT_EQ(*expectedOutput, *actualOutput);
-  }
-}
-
-TEST_P(LimitExecutorWaitingFullCountTest, rows_9_blocksize_3_limit_0) {
-  // Input spec:
-  size_t constexpr blocksize = 3;
-  size_t constexpr offset = 0;
-  size_t constexpr limit = 0;
-  SharedAqlItemBlockPtr const input =
-      buildBlock<1>(itemBlockManager, {{0}, {1}, {2}, {3}, {4}, {5}, {6}, {7}, {8}});
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Enable> fetcher(itemBlockManager, blocksize, waiting, input);
-  LimitExecutorInfos infos(1, 1, {}, {0}, offset, limit, fullCount);
-
-  // Output spec:
-  SharedAqlItemBlockPtr const expectedOutput = buildBlock<1>(itemBlockManager, {});
-  size_t const expectedOutputSize =
-      expectedOutput == nullptr ? 0 : expectedOutput->size();
-  std::vector<ExecutorStepResult> expectedStates{};
-  if (fullCount) {
-    expectedStates.emplace_back(ExecutorCall::FETCH_FOR_PASSTHROUGH,
-                                ExecutionState::WAITING, 0);
-    expectedStates.emplace_back(ExecutorCall::FETCH_FOR_PASSTHROUGH,
-                                ExecutionState::WAITING, 0);
-    expectedStates.emplace_back(ExecutorCall::FETCH_FOR_PASSTHROUGH,
-                                ExecutionState::WAITING, 0);
-  }
-  expectedStates.emplace_back(ExecutorCall::FETCH_FOR_PASSTHROUGH, ExecutionState::DONE, 0);
-  if (!waiting) {
-    removeWaiting(expectedStates);
-  }
-  ExecutionStats expectedStats{};
-  if (fullCount) {
-    expectedStats.fullCount = 9;
-  } else {
-    expectedStats.fullCount = 0;
-  }
-
-  // Run:
-  LimitExecutor testee(fetcher, infos);
-  // Allocate at least one output row more than expected!
-  SharedAqlItemBlockPtr block = itemBlockManager.requestBlock(expectedOutputSize + 1, 1);
-  OutputAqlItemRow outputRow{block, outputRegisters, registersToKeep,
-                             infos.registersToClear()};
-
-  auto result =
-      runExecutor(itemBlockManager, testee, outputRow, 0, expectedOutputSize, false);
-  auto& actualOutput = std::get<SharedAqlItemBlockPtr>(result);
-  auto& actualStats = std::get<ExecutionStats>(result);
-  auto& actualStates = std::get<std::vector<ExecutorStepResult>>(result);
-
-  EXPECT_EQ(expectedStats, actualStats);
-  EXPECT_EQ(expectedStates, actualStates);
-  if (expectedOutput == nullptr) {
-    ASSERT_EQ(actualOutput, nullptr);
-  } else {
-    ASSERT_FALSE(actualOutput == nullptr);
-    EXPECT_EQ(*expectedOutput, *actualOutput);
-  }
-}
-
-TEST_P(LimitExecutorWaitingFullCountTest, rows_9_blocksize_3_offset_4_limit_4) {
-  // Input spec:
-  size_t constexpr blocksize = 3;
-  size_t constexpr offset = 4;
-  size_t constexpr limit = 4;
-  SharedAqlItemBlockPtr const input =
-      buildBlock<1>(itemBlockManager, {{0}, {1}, {2}, {3}, {4}, {5}, {6}, {7}, {8}});
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Enable> fetcher(itemBlockManager, blocksize, waiting, input);
-  LimitExecutorInfos infos(1, 1, {}, {0}, offset, limit, fullCount);
-
-  // Output spec:
-  SharedAqlItemBlockPtr const expectedOutput =
-      buildBlock<1>(itemBlockManager, {{4}, {5}, {6}, {7}});
-  size_t const expectedOutputSize =
-      expectedOutput == nullptr ? 0 : expectedOutput->size();
-  std::vector<ExecutorStepResult> expectedStates{
-      {ExecutorCall::FETCH_FOR_PASSTHROUGH, ExecutionState::WAITING, 0},
-      {ExecutorCall::FETCH_FOR_PASSTHROUGH, ExecutionState::WAITING, 0},
-      {ExecutorCall::FETCH_FOR_PASSTHROUGH, ExecutionState::HASMORE, 2},
-      {ExecutorCall::PRODUCE_ROWS, ExecutionState::HASMORE, 1},
-      {ExecutorCall::PRODUCE_ROWS, ExecutionState::HASMORE, 1},
-      {ExecutorCall::FETCH_FOR_PASSTHROUGH, ExecutionState::WAITING, 0},
-      {ExecutorCall::FETCH_FOR_PASSTHROUGH, ExecutionState::HASMORE, 3},
-      {ExecutorCall::PRODUCE_ROWS, ExecutionState::HASMORE, 1},
-      {ExecutorCall::PRODUCE_ROWS, ExecutionState::DONE, 1},
-  };
-  if (!waiting) {
-    removeWaiting(expectedStates);
-  }
-  ExecutionStats expectedStats{};
-  if (fullCount) {
-    expectedStats.fullCount = 9;
-  } else {
-    expectedStats.fullCount = 0;
-  }
-
-  // Run:
-  LimitExecutor testee(fetcher, infos);
-  // Allocate at least one output row more than expected!
-  SharedAqlItemBlockPtr block = itemBlockManager.requestBlock(expectedOutputSize + 1, 1);
-  OutputAqlItemRow outputRow{block, outputRegisters, registersToKeep,
-                             infos.registersToClear()};
-
-  auto result =
-      runExecutor(itemBlockManager, testee, outputRow, 0, expectedOutputSize, false);
-  auto& actualOutput = std::get<SharedAqlItemBlockPtr>(result);
-  auto& actualStats = std::get<ExecutionStats>(result);
-  auto& actualStates = std::get<std::vector<ExecutorStepResult>>(result);
-
-  EXPECT_EQ(expectedStats, actualStats);
-  EXPECT_EQ(expectedStates, actualStates);
-  if (expectedOutput == nullptr) {
-    ASSERT_EQ(actualOutput, nullptr);
-  } else {
-    ASSERT_FALSE(actualOutput == nullptr);
-    EXPECT_EQ(*expectedOutput, *actualOutput);
-  }
-}
-
-TEST_P(LimitExecutorWaitingFullCountTest, rows_9_blocksize_3_offset_10_limit_1) {
-  // Input spec:
-  size_t constexpr blocksize = 3;
-  size_t constexpr offset = 10;
-  size_t constexpr limit = 1;
-  SharedAqlItemBlockPtr const input =
-      buildBlock<1>(itemBlockManager, {{0}, {1}, {2}, {3}, {4}, {5}, {6}, {7}, {8}});
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Enable> fetcher(itemBlockManager, blocksize, waiting, input);
-  LimitExecutorInfos infos(1, 1, {}, {0}, offset, limit, fullCount);
-
-  // Output spec:
-  SharedAqlItemBlockPtr const expectedOutput = buildBlock<1>(itemBlockManager, {});
-  size_t const expectedOutputSize =
-      expectedOutput == nullptr ? 0 : expectedOutput->size();
-  std::vector<ExecutorStepResult> expectedStates{
-      {ExecutorCall::FETCH_FOR_PASSTHROUGH, ExecutionState::WAITING, 0},
-      {ExecutorCall::FETCH_FOR_PASSTHROUGH, ExecutionState::WAITING, 0},
-      {ExecutorCall::FETCH_FOR_PASSTHROUGH, ExecutionState::WAITING, 0},
-      {ExecutorCall::FETCH_FOR_PASSTHROUGH, ExecutionState::DONE, 0},
-  };
-  if (!waiting) {
-    removeWaiting(expectedStates);
-  }
-  ExecutionStats expectedStats{};
-  if (fullCount) {
-    expectedStats.fullCount = 9;
-  } else {
-    expectedStats.fullCount = 0;
-  }
-
-  // Run:
-  LimitExecutor testee(fetcher, infos);
-  // Allocate at least one output row more than expected!
-  SharedAqlItemBlockPtr block = itemBlockManager.requestBlock(expectedOutputSize + 1, 1);
-  OutputAqlItemRow outputRow{block, outputRegisters, registersToKeep,
-                             infos.registersToClear()};
-
-  auto result =
-      runExecutor(itemBlockManager, testee, outputRow, 0, expectedOutputSize, false);
-  auto& actualOutput = std::get<SharedAqlItemBlockPtr>(result);
-  auto& actualStats = std::get<ExecutionStats>(result);
-  auto& actualStates = std::get<std::vector<ExecutorStepResult>>(result);
-
-  EXPECT_EQ(expectedStats, actualStats);
-  EXPECT_EQ(expectedStates, actualStates);
-  if (expectedOutput == nullptr) {
-    ASSERT_EQ(actualOutput, nullptr);
-  } else {
-    ASSERT_FALSE(actualOutput == nullptr);
-    EXPECT_EQ(*expectedOutput, *actualOutput);
-  }
-}
-
-INSTANTIATE_TEST_CASE_P(LimitExecutorVariations, LimitExecutorWaitingFullCountTest,
-                        testing::Combine(testing::Bool(), testing::Bool()));
-
-TEST_P(LimitExecutorWaitingTest, rows_9_blocksize_3_skip_4_offset_1_limit_7) {
-  // Input spec:
-  size_t constexpr blocksize = 3;
-  size_t constexpr offset = 1;
-  size_t constexpr limit = 7;
-  size_t constexpr skip = 4;
-  size_t constexpr readRows = 2;
-  bool constexpr skipAfter = true;
-  SharedAqlItemBlockPtr const input =
-      buildBlock<1>(itemBlockManager, {{0}, {1}, {2}, {3}, {4}, {5}, {6}, {7}, {8}});
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Enable> fetcher(itemBlockManager, blocksize, waiting, input);
-  LimitExecutorInfos infos(1, 1, {}, {0}, offset, limit, false);
-
-  // Output spec:
-  SharedAqlItemBlockPtr const expectedOutput =
-      buildBlock<1>(itemBlockManager, {{5}, {6}});
-  size_t const expectedOutputSize =
-      expectedOutput == nullptr ? 0 : expectedOutput->size();
-  std::vector<ExecutorStepResult> expectedStates{
-      {ExecutorCall::SKIP_ROWS, ExecutionState::WAITING, 0},
-      {ExecutorCall::SKIP_ROWS, ExecutionState::WAITING, 0},
-      {ExecutorCall::SKIP_ROWS, ExecutionState::HASMORE, 4},
-      {ExecutorCall::FETCH_FOR_PASSTHROUGH, ExecutionState::HASMORE, 1},
-      {ExecutorCall::PRODUCE_ROWS, ExecutionState::HASMORE, 1},
-      {ExecutorCall::FETCH_FOR_PASSTHROUGH, ExecutionState::WAITING, 0},
-      {ExecutorCall::FETCH_FOR_PASSTHROUGH, ExecutionState::HASMORE, 3},
-      {ExecutorCall::PRODUCE_ROWS, ExecutionState::HASMORE, 1},
-      {ExecutorCall::SKIP_ROWS, ExecutionState::DONE, 1},
-  };
-  if (!waiting) {
-    removeWaiting(expectedStates);
-  }
-  ExecutionStats expectedStats{};
-  expectedStats.fullCount = 0;
-
-  // Run:
-  LimitExecutor testee(fetcher, infos);
-  // Allocate at least one output row more than expected!
-  SharedAqlItemBlockPtr block = itemBlockManager.requestBlock(expectedOutputSize + 1, 1);
-  OutputAqlItemRow outputRow{block, outputRegisters, registersToKeep,
-                             infos.registersToClear()};
-
-  auto result = runExecutor(itemBlockManager, testee, outputRow, skip, readRows, skipAfter);
-  auto& actualOutput = std::get<SharedAqlItemBlockPtr>(result);
-  auto& actualStats = std::get<ExecutionStats>(result);
-  auto& actualStates = std::get<std::vector<ExecutorStepResult>>(result);
-
-  EXPECT_EQ(expectedStats, actualStats);
-  EXPECT_EQ(expectedStates, actualStates);
-  if (expectedOutput == nullptr) {
-    ASSERT_EQ(actualOutput, nullptr);
-  } else {
-    ASSERT_FALSE(actualOutput == nullptr);
-    EXPECT_EQ(*expectedOutput, *actualOutput);
-  }
-}
-
-TEST_P(LimitExecutorWaitingTest, rows_9_blocksize_3_skip_4_offset_1_limit_3) {
-  // Input spec:
-  size_t constexpr blocksize = 3;
-  size_t constexpr offset = 1;
-  size_t constexpr limit = 3;
-  size_t constexpr skip = 4;
-  size_t constexpr readRows = 1;
-  bool constexpr skipAfter = true;
-  SharedAqlItemBlockPtr const input =
-      buildBlock<1>(itemBlockManager, {{0}, {1}, {2}, {3}, {4}, {5}, {6}, {7}, {8}});
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Enable> fetcher(itemBlockManager, blocksize, waiting, input);
-  LimitExecutorInfos infos(1, 1, {}, {0}, offset, limit, false);
-
-  // Output spec:
-  SharedAqlItemBlockPtr const expectedOutput = buildBlock<1>(itemBlockManager, {});
-  size_t const expectedOutputSize =
-      expectedOutput == nullptr ? 0 : expectedOutput->size();
-  std::vector<ExecutorStepResult> expectedStates{
-      {ExecutorCall::SKIP_ROWS, ExecutionState::WAITING, 0},
-      {ExecutorCall::SKIP_ROWS, ExecutionState::WAITING, 0},
-      {ExecutorCall::SKIP_ROWS, ExecutionState::DONE, 3},
-  };
-  if (!waiting) {
-    removeWaiting(expectedStates);
-  }
-  ExecutionStats expectedStats{};
-  expectedStats.fullCount = 0;
-
-  // Run:
-  LimitExecutor testee(fetcher, infos);
-  // Allocate at least one output row more than expected!
-  SharedAqlItemBlockPtr block = itemBlockManager.requestBlock(expectedOutputSize + 1, 1);
-  OutputAqlItemRow outputRow{block, outputRegisters, registersToKeep,
-                             infos.registersToClear()};
-
-  auto result = runExecutor(itemBlockManager, testee, outputRow, skip, readRows, skipAfter);
-  auto& actualOutput = std::get<SharedAqlItemBlockPtr>(result);
-  auto& actualStats = std::get<ExecutionStats>(result);
-  auto& actualStates = std::get<std::vector<ExecutorStepResult>>(result);
+};
 
-  EXPECT_EQ(expectedStats, actualStats);
-  EXPECT_EQ(expectedStates, actualStates);
-  if (expectedOutput == nullptr) {
-    ASSERT_EQ(actualOutput, nullptr);
-  } else {
-    ASSERT_FALSE(actualOutput == nullptr);
-    EXPECT_EQ(*expectedOutput, *actualOutput);
+std::unique_ptr<mocks::MockAqlServer> LimitExecutorTest::server{nullptr};
+
+auto const testingFullCount = ::testing::Bool();
+using InputLengths = std::vector<size_t>;
+#define USE_FULL_SUITE false
+#if USE_FULL_SUITE
+auto const testingOffsets = ::testing::Values(0, 1, 2, 3, 10, 100'000'000);
+auto const testingLimits = ::testing::Values(0, 1, 2, 3, 10, 100'000'000);
+auto const testingInputLengths = ::testing::Values(
+    // 0
+    InputLengths{},
+    // 1
+    InputLengths{1},
+    // 2
+    InputLengths{2}, InputLengths{1, 1},
+    // 3
+    InputLengths{3}, InputLengths{1, 2}, InputLengths{2, 1}, InputLengths{1, 1, 1},
+    // 4
+    InputLengths{4}, InputLengths{3, 1}, InputLengths{2, 2},
+    // 9
+    InputLengths{9},
+    // 10
+    InputLengths{10}, InputLengths{9, 1},
+    // 11
+    InputLengths{11}, InputLengths{10, 1}, InputLengths{9, 2}, InputLengths{9, 1, 1},
+    // 19
+    InputLengths{19},
+    // 20
+    InputLengths{20}, InputLengths{1, 19}, InputLengths{19, 1}, InputLengths{10, 10},
+    // 21
+    InputLengths{21}, InputLengths{20, 1}, InputLengths{19, 2},
+    InputLengths{19, 1, 1}, InputLengths{10, 10, 1}, InputLengths{1, 9, 9, 1, 1});
+#else
+auto const testingOffsets = ::testing::Values(0, 3, 100'000'000);
+auto const testingLimits = ::testing::Values(0, 3, 100'000'000);
+auto const testingInputLengths = ::testing::Values(
+    // 0
+    InputLengths{},
+    // 1
+    InputLengths{1},
+    // 3
+    InputLengths{3}, InputLengths{1, 2}, InputLengths{2, 1}, InputLengths{1, 1, 1},
+    // 11
+    InputLengths{9, 2}, InputLengths{9, 1, 1},
+    // 19
+    InputLengths{19},
+    // 21
+    InputLengths{10, 10, 1}, InputLengths{1, 9, 9, 1, 1});
+
+#endif
+
+// Note that fullCount does only make sense with a hard limit, and
+// soft limit = 0 and offset = 0 must not occur together.
+auto const testingAqlCalls = ::testing::ValuesIn(
+    std::array{AqlCall{0, false, AqlCall::Infinity{}},
+               AqlCall{0, false, 1, AqlCall::LimitType::SOFT},
+               AqlCall{0, false, 2, AqlCall::LimitType::SOFT},
+               AqlCall{0, false, 3, AqlCall::LimitType::SOFT},
+               AqlCall{0, false, 10, AqlCall::LimitType::SOFT},
+               AqlCall{0, false, 0, AqlCall::LimitType::HARD},
+               AqlCall{0, false, 1, AqlCall::LimitType::HARD},
+               AqlCall{0, false, 2, AqlCall::LimitType::HARD},
+               AqlCall{0, false, 3, AqlCall::LimitType::HARD},
+               AqlCall{0, false, 10, AqlCall::LimitType::HARD},
+               AqlCall{1, false, AqlCall::Infinity{}},
+               AqlCall{1, false, 0, AqlCall::LimitType::SOFT},
+               AqlCall{1, false, 1, AqlCall::LimitType::SOFT},
+               AqlCall{1, false, 2, AqlCall::LimitType::SOFT},
+               AqlCall{1, false, 3, AqlCall::LimitType::SOFT},
+               AqlCall{1, false, 10, AqlCall::LimitType::SOFT},
+               AqlCall{1, false, 0, AqlCall::LimitType::HARD},
+               AqlCall{1, false, 1, AqlCall::LimitType::HARD},
+               AqlCall{1, false, 2, AqlCall::LimitType::HARD},
+               AqlCall{1, false, 3, AqlCall::LimitType::HARD},
+               AqlCall{1, false, 10, AqlCall::LimitType::HARD},
+               AqlCall{2, false, AqlCall::Infinity{}},
+               AqlCall{2, false, 0, AqlCall::LimitType::SOFT},
+               AqlCall{2, false, 1, AqlCall::LimitType::SOFT},
+               AqlCall{2, false, 2, AqlCall::LimitType::SOFT},
+               AqlCall{2, false, 3, AqlCall::LimitType::SOFT},
+               AqlCall{2, false, 10, AqlCall::LimitType::SOFT},
+               AqlCall{2, false, 0, AqlCall::LimitType::HARD},
+               AqlCall{2, false, 1, AqlCall::LimitType::HARD},
+               AqlCall{2, false, 2, AqlCall::LimitType::HARD},
+               AqlCall{2, false, 3, AqlCall::LimitType::HARD},
+               AqlCall{2, false, 10, AqlCall::LimitType::HARD},
+               AqlCall{3, false, AqlCall::Infinity{}},
+               AqlCall{3, false, 0, AqlCall::LimitType::SOFT},
+               AqlCall{3, false, 1, AqlCall::LimitType::SOFT},
+               AqlCall{3, false, 2, AqlCall::LimitType::SOFT},
+               AqlCall{3, false, 3, AqlCall::LimitType::SOFT},
+               AqlCall{3, false, 10, AqlCall::LimitType::SOFT},
+               AqlCall{3, false, 0, AqlCall::LimitType::HARD},
+               AqlCall{3, false, 1, AqlCall::LimitType::HARD},
+               AqlCall{3, false, 2, AqlCall::LimitType::HARD},
+               AqlCall{3, false, 3, AqlCall::LimitType::HARD},
+               AqlCall{3, false, 10, AqlCall::LimitType::HARD},
+               AqlCall{10, false, AqlCall::Infinity{}},
+               AqlCall{10, false, 0, AqlCall::LimitType::SOFT},
+               AqlCall{10, false, 1, AqlCall::LimitType::SOFT},
+               AqlCall{10, false, 2, AqlCall::LimitType::SOFT},
+               AqlCall{10, false, 3, AqlCall::LimitType::SOFT},
+               AqlCall{10, false, 10, AqlCall::LimitType::SOFT},
+               AqlCall{10, false, 0, AqlCall::LimitType::HARD},
+               AqlCall{10, false, 1, AqlCall::LimitType::HARD},
+               AqlCall{10, false, 2, AqlCall::LimitType::HARD},
+               AqlCall{10, false, 3, AqlCall::LimitType::HARD},
+               AqlCall{10, false, 10, AqlCall::LimitType::HARD},
+               AqlCall{0, true, 0, AqlCall::LimitType::HARD},
+               AqlCall{0, true, 1, AqlCall::LimitType::HARD},
+               AqlCall{0, true, 2, AqlCall::LimitType::HARD},
+               AqlCall{0, true, 3, AqlCall::LimitType::HARD},
+               AqlCall{0, true, 10, AqlCall::LimitType::HARD},
+               AqlCall{1, true, 0, AqlCall::LimitType::HARD},
+               AqlCall{1, true, 1, AqlCall::LimitType::HARD},
+               AqlCall{1, true, 2, AqlCall::LimitType::HARD},
+               AqlCall{1, true, 3, AqlCall::LimitType::HARD},
+               AqlCall{1, true, 10, AqlCall::LimitType::HARD},
+               AqlCall{2, true, 0, AqlCall::LimitType::HARD},
+               AqlCall{2, true, 1, AqlCall::LimitType::HARD},
+               AqlCall{2, true, 2, AqlCall::LimitType::HARD},
+               AqlCall{2, true, 3, AqlCall::LimitType::HARD},
+               AqlCall{2, true, 10, AqlCall::LimitType::HARD},
+               AqlCall{3, true, 0, AqlCall::LimitType::HARD},
+               AqlCall{3, true, 1, AqlCall::LimitType::HARD},
+               AqlCall{3, true, 2, AqlCall::LimitType::HARD},
+               AqlCall{3, true, 3, AqlCall::LimitType::HARD},
+               AqlCall{3, true, 10, AqlCall::LimitType::HARD},
+               AqlCall{10, true, 0, AqlCall::LimitType::HARD},
+               AqlCall{10, true, 1, AqlCall::LimitType::HARD},
+               AqlCall{10, true, 2, AqlCall::LimitType::HARD},
+               AqlCall{10, true, 3, AqlCall::LimitType::HARD},
+               AqlCall{10, true, 10, AqlCall::LimitType::HARD}});
+auto const testingDoneResultIsEmpty = ::testing::Bool();
+
+auto const limitTestCases =
+    ::testing::Combine(testingOffsets, testingLimits, testingFullCount,
+                       testingInputLengths, testingAqlCalls, testingDoneResultIsEmpty);
+
+TEST_P(LimitExecutorTest, testSuite) {
+  // Input.
+  auto const& [offset, limit, fullCount, inputLengths, clientCall, doneResultIsEmpty] =
+      GetParam();
+
+  TRI_ASSERT(!(clientCall.getOffset() == 0 && clientCall.softLimit == AqlCall::Limit{0}));
+  TRI_ASSERT(!(clientCall.hasSoftLimit() && clientCall.fullCount));
+  TRI_ASSERT(!(clientCall.hasSoftLimit() && clientCall.hasHardLimit()));
+
+  auto const numInputRows =
+      std::accumulate(inputLengths.begin(), inputLengths.end(), size_t{0});
+  {  // Validation of the test case:
+    TRI_ASSERT(std::all_of(inputLengths.begin(), inputLengths.end(),
+                           [](auto l) { return l > 0; }));
   }
-}
 
-TEST_P(LimitExecutorWaitingTest, rows_9_blocksize_3_skip_2_read_1_offset_2_limit_4) {
-  // Input spec:
-  size_t constexpr blocksize = 3;
-  size_t constexpr offset = 2;
-  size_t constexpr limit = 4;
-  size_t constexpr skip = 2;
-  size_t constexpr readRows = 1;
-  bool constexpr skipAfter = true;
-  SharedAqlItemBlockPtr const input =
-      buildBlock<1>(itemBlockManager, {{0}, {1}, {2}, {3}, {4}, {5}, {6}, {7}, {8}});
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Enable> fetcher(itemBlockManager, blocksize, waiting, input);
-  LimitExecutorInfos infos(1, 1, {}, {0}, offset, limit, false);
-
-  // Output spec:
-  SharedAqlItemBlockPtr const expectedOutput = buildBlock<1>(itemBlockManager, {{4}});
-  size_t const expectedOutputSize =
-      expectedOutput == nullptr ? 0 : expectedOutput->size();
-  std::vector<ExecutorStepResult> expectedStates{
-      {ExecutorCall::SKIP_ROWS, ExecutionState::WAITING, 0},
-      {ExecutorCall::SKIP_ROWS, ExecutionState::WAITING, 0},
-      {ExecutorCall::SKIP_ROWS, ExecutionState::HASMORE, 2},
-      {ExecutorCall::FETCH_FOR_PASSTHROUGH, ExecutionState::HASMORE, 2},
-      {ExecutorCall::PRODUCE_ROWS, ExecutionState::HASMORE, 1},
-      {ExecutorCall::SKIP_ROWS, ExecutionState::DONE, 1},
+  auto const nonNegativeSubtraction = [](auto minuend, auto subtrahend) {
+    // same as std::max(0, minuend - subtrahend), but safe from underflows
+    return minuend - std::min(minuend, subtrahend);
   };
-  if (!waiting) {
-    removeWaiting(expectedStates);
-  }
-  ExecutionStats expectedStats{};
-  expectedStats.fullCount = 0;
-
-  // Run:
-  LimitExecutor testee(fetcher, infos);
-  // Allocate at least one output row more than expected!
-  SharedAqlItemBlockPtr block = itemBlockManager.requestBlock(expectedOutputSize + 1, 1);
-  OutputAqlItemRow outputRow{block, outputRegisters, registersToKeep,
-                             infos.registersToClear()};
 
-  auto result = runExecutor(itemBlockManager, testee, outputRow, skip, readRows, skipAfter);
-  auto& actualOutput = std::get<SharedAqlItemBlockPtr>(result);
-  auto& actualStats = std::get<ExecutionStats>(result);
-  auto& actualStates = std::get<std::vector<ExecutorStepResult>>(result);
-
-  EXPECT_EQ(expectedStats, actualStats);
-  EXPECT_EQ(expectedStates, actualStates);
-  if (expectedOutput == nullptr) {
-    ASSERT_EQ(actualOutput, nullptr);
-  } else {
-    ASSERT_FALSE(actualOutput == nullptr);
-    EXPECT_EQ(*expectedOutput, *actualOutput);
-  }
+  // Expected output, though the expectedPassedBlocks are also the input.
+  // Note that structured bindings are *not* captured by lambdas, at least in
+  // C++17. So we must explicity capture them.
+  auto const [expectedSkipped, expectedOutput, expectedLimitStats, expectedState] =
+      std::invoke([&, offset = offset, limit = limit, fullCount = fullCount,
+                   &inputLengths = inputLengths, clientCall = clientCall,
+                   doneResultIsEmpty = doneResultIsEmpty]() {
+        auto const numInputRows =
+            std::accumulate(inputLengths.begin(), inputLengths.end(), size_t{0});
+        auto const effectiveOffset = clientCall.getOffset() + offset;
+        // The combined limit of a call and a LimitExecutor:
+        auto const effectiveLimit =
+            std::min(clientCall.getLimit(),
+                     nonNegativeSubtraction(limit, clientCall.getOffset()));
+
+        auto const numRowsReturnable =
+            nonNegativeSubtraction(std::min(numInputRows, offset + limit), offset);
+
+        // Only the client's offset counts against the "skipped" count returned
+        // by the limit block, the rest is upstream!
+        auto skipped = std::min(numRowsReturnable, clientCall.getOffset());
+        if (clientCall.needsFullCount()) {
+          // offset and limit are already handled.
+          // New we need to include the amount of rows left to count them by
+          // skipped. However only those rows that the LIMIT will return.
+          skipped += nonNegativeSubtraction(numRowsReturnable,
+                                            clientCall.getOffset() + clientCall.getLimit());
+        }
+
+        auto const output = std::invoke([&]() {
+          auto output = MatrixBuilder<1>{};
+
+          auto const begin = effectiveOffset;
+          auto const end = std::min(effectiveOffset + effectiveLimit, numInputRows);
+          for (auto k = begin; k < end; ++k) {
+            output.emplace_back(RowBuilder<1>{k});
+          }
+
+          return output;
+        });
+
+        auto stats = LimitStats{};
+        if (fullCount) {
+          if (!clientCall.hasHardLimit()) {
+            auto rowsToTriggerFullCountInExecutor = offset + limit;
+            auto rowsByClient = clientCall.getOffset() + clientCall.getLimit();
+
+            // If we do not have a hard limit, we only report fullCount
+            // up to the point where the Executor has actually consumed input.
+            if (rowsByClient >= limit && rowsToTriggerFullCountInExecutor < numInputRows) {
+              // however if the limit of the executor is smaller than the input
+              // it will itself start counting.
+              stats.incrFullCountBy(numInputRows);
+            } else {
+              stats.incrFullCountBy(std::min(effectiveOffset + effectiveLimit, numInputRows));
+            }
+          } else {
+            stats.incrFullCountBy(numInputRows);
+          }
+        }
+
+        // Whether the execution should return HASMORE:
+        auto const hasMore = std::invoke([&] {
+          auto const clientLimitIsSmaller =
+              clientCall.getOffset() + clientCall.getLimit() < limit;
+          auto const effectiveLimitIsHardLimit =
+              clientLimitIsSmaller ? clientCall.hasHardLimit() : true;
+          if (effectiveLimitIsHardLimit) {
+            return false;
+          }
+          // We have a softLimit:
+          if (doneResultIsEmpty) {
+            return effectiveOffset + effectiveLimit <= numInputRows;
+          } else {
+            return effectiveOffset + effectiveLimit < numInputRows;
+          }
+        });
+        auto const state = hasMore ? ExecutionState::HASMORE : ExecutionState::DONE;
+
+        return std::make_tuple(skipped, output, stats, state);
+      });
+
+  auto infos = LimitExecutorInfos{1, 1, {}, {0}, offset, limit, fullCount};
+
+  auto expectedStats = ExecutionStats{};
+  expectedStats += expectedLimitStats;
+
+  // fakedQuery->queryOptions().profile = PROFILE_LEVEL_TRACE_2;
+  ExecutorTestHelper<>{*fakedQuery}
+      .setExecBlock<LimitExecutor>(std::move(infos), ExecutionNode::LIMIT)
+      .setInputFromRowNum(numInputRows)
+      .setInputSplitType(inputLengths)
+      .setCall(clientCall)
+      .appendEmptyBlock(doneResultIsEmpty)
+      .expectedStats(expectedStats)
+      .expectOutput({0}, expectedOutput)
+      .expectSkipped(expectedSkipped)
+      .expectedState(expectedState)
+      .run(true);
 }
 
-TEST_P(LimitExecutorWaitingTest, rows_9_blocksize_3_skip_10_limit_12) {
-  // Input spec:
-  size_t constexpr blocksize = 3;
-  size_t constexpr offset = 0;
-  size_t constexpr limit = 12;
-  size_t constexpr skip = 10;
-  size_t constexpr readRows = 1;
-  bool constexpr skipAfter = true;
-  SharedAqlItemBlockPtr const input =
-      buildBlock<1>(itemBlockManager, {{0}, {1}, {2}, {3}, {4}, {5}, {6}, {7}, {8}});
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Enable> fetcher(itemBlockManager, blocksize, waiting, input);
-  LimitExecutorInfos infos(1, 1, {}, {0}, offset, limit, false);
-
-  // Output spec:
-  SharedAqlItemBlockPtr const expectedOutput = buildBlock<1>(itemBlockManager, {});
-  size_t const expectedOutputSize =
-      expectedOutput == nullptr ? 0 : expectedOutput->size();
-  std::vector<ExecutorStepResult> expectedStates{
-      {ExecutorCall::SKIP_ROWS, ExecutionState::WAITING, 0},
-      {ExecutorCall::SKIP_ROWS, ExecutionState::WAITING, 0},
-      {ExecutorCall::SKIP_ROWS, ExecutionState::WAITING, 0},
-      {ExecutorCall::SKIP_ROWS, ExecutionState::DONE, 9},
-  };
-  if (!waiting) {
-    removeWaiting(expectedStates);
-  }
-  ExecutionStats expectedStats{};
-  expectedStats.fullCount = 0;
-
-  // Run:
-  LimitExecutor testee(fetcher, infos);
-  // Allocate at least one output row more than expected!
-  SharedAqlItemBlockPtr block = itemBlockManager.requestBlock(expectedOutputSize + 1, 1);
-  OutputAqlItemRow outputRow{block, outputRegisters, registersToKeep,
-                             infos.registersToClear()};
+auto printTestCase =
+    [](testing::TestParamInfo<std::tuple<size_t, size_t, bool, std::vector<size_t>, AqlCall, bool>> const& paramInfo)
+    -> std::string {
+  auto const& [offset, limit, fullCount, inputLengths, clientCall, doneResultIsEmpty] =
+      paramInfo.param;
 
-  auto result = runExecutor(itemBlockManager, testee, outputRow, skip, readRows, skipAfter);
-  auto& actualOutput = std::get<SharedAqlItemBlockPtr>(result);
-  auto& actualStats = std::get<ExecutionStats>(result);
-  auto& actualStates = std::get<std::vector<ExecutorStepResult>>(result);
+  std::stringstream out;
 
-  EXPECT_EQ(expectedStats, actualStats);
-  EXPECT_EQ(expectedStates, actualStates);
-  if (expectedOutput == nullptr) {
-    ASSERT_EQ(actualOutput, nullptr);
-  } else {
-    ASSERT_FALSE(actualOutput == nullptr);
-    EXPECT_EQ(*expectedOutput, *actualOutput);
+  out << "offset" << offset;
+  out << "limit" << limit;
+  out << "fullCount" << (fullCount ? "True" : "False");
+  out << "inputLengths";
+  for (auto const& it : inputLengths) {
+    out << it << "_";
   }
-}
-
-TEST_P(LimitExecutorWaitingTest, rows_9_blocksize_3_skip_1_read_1_limit_12) {
-  // Input spec:
-  size_t constexpr blocksize = 3;
-  size_t constexpr offset = 0;
-  size_t constexpr limit = 12;
-  size_t constexpr skip = 1;
-  size_t constexpr readRows = 1;
-  bool constexpr skipAfter = true;
-  SharedAqlItemBlockPtr const input =
-      buildBlock<1>(itemBlockManager, {{0}, {1}, {2}, {3}, {4}, {5}, {6}, {7}, {8}});
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Enable> fetcher(itemBlockManager, blocksize, waiting, input);
-  LimitExecutorInfos infos(1, 1, {}, {0}, offset, limit, false);
-
-  // Output spec:
-  SharedAqlItemBlockPtr const expectedOutput = buildBlock<1>(itemBlockManager, {{1}});
-  size_t const expectedOutputSize =
-      expectedOutput == nullptr ? 0 : expectedOutput->size();
-  std::vector<ExecutorStepResult> expectedStates{
-      {ExecutorCall::SKIP_ROWS, ExecutionState::WAITING, 0},
-      {ExecutorCall::SKIP_ROWS, ExecutionState::HASMORE, 1},
-      {ExecutorCall::FETCH_FOR_PASSTHROUGH, ExecutionState::HASMORE, 2},
-      {ExecutorCall::PRODUCE_ROWS, ExecutionState::HASMORE, 1},
-      {ExecutorCall::SKIP_ROWS, ExecutionState::WAITING, 0},
-      {ExecutorCall::SKIP_ROWS, ExecutionState::WAITING, 0},
-      {ExecutorCall::SKIP_ROWS, ExecutionState::DONE, 7},
-  };
-  if (!waiting) {
-    removeWaiting(expectedStates);
+  out << "clientCall";
+  {
+    if (clientCall.getOffset() > 0) {
+      out << "_offset" << clientCall.getOffset();
+    }
+    if (clientCall.hasHardLimit() || clientCall.hasSoftLimit()) {
+      auto const clientLimit =
+          std::get<std::size_t>(std::min(clientCall.softLimit, clientCall.hardLimit));
+      out << "_" << (clientCall.hasHardLimit() ? "hard" : "soft") << "Limit" << clientLimit;
+    }
+    if (clientCall.needsFullCount()) {
+      out << "_fullCount";
+    }
   }
-  ExecutionStats expectedStats{};
-  expectedStats.fullCount = 0;
-
-  // Run:
-  LimitExecutor testee(fetcher, infos);
-  // Allocate at least one output row more than expected!
-  SharedAqlItemBlockPtr block = itemBlockManager.requestBlock(expectedOutputSize + 1, 1);
-  OutputAqlItemRow outputRow{block, outputRegisters, registersToKeep,
-                             infos.registersToClear()};
-
-  auto result = runExecutor(itemBlockManager, testee, outputRow, skip, readRows, skipAfter);
-  auto& actualOutput = std::get<SharedAqlItemBlockPtr>(result);
-  auto& actualStats = std::get<ExecutionStats>(result);
-  auto& actualStates = std::get<std::vector<ExecutorStepResult>>(result);
+  out << "doneResultIsEmpty" << (doneResultIsEmpty ? "True" : "False");
 
-  EXPECT_EQ(expectedStats, actualStats);
-  EXPECT_EQ(expectedStates, actualStates);
-  if (expectedOutput == nullptr) {
-    ASSERT_EQ(actualOutput, nullptr);
-  } else {
-    ASSERT_FALSE(actualOutput == nullptr);
-    EXPECT_EQ(*expectedOutput, *actualOutput);
-  }
-}
+  return out.str();
+};
 
-INSTANTIATE_TEST_CASE_P(LimitExecutorVariations, LimitExecutorWaitingTest, testing::Bool());
+INSTANTIATE_TEST_CASE_P(LimitExecutorVariations, LimitExecutorTest,
+                        limitTestCases, printTestCase);
 
-}  // namespace aql
-}  // namespace tests
-}  // namespace arangodb
+}  // namespace arangodb::tests::aql
diff --git a/tests/Aql/MockTypedNode.cpp b/tests/Aql/MockTypedNode.cpp
new file mode 100644
index 000000000000..fafc033c9222
--- /dev/null
+++ b/tests/Aql/MockTypedNode.cpp
@@ -0,0 +1,56 @@
+////////////////////////////////////////////////////////////////////////////////
+/// DISCLAIMER
+///
+/// Copyright 2020 ArangoDB GmbH, Cologne, Germany
+///
+/// Licensed under the Apache License, Version 2.0 (the "License");
+/// you may not use this file except in compliance with the License.
+/// You may obtain a copy of the License at
+///
+///     http://www.apache.org/licenses/LICENSE-2.0
+///
+/// Unless required by applicable law or agreed to in writing, software
+/// distributed under the License is distributed on an "AS IS" BASIS,
+/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+/// See the License for the specific language governing permissions and
+/// limitations under the License.
+///
+/// Copyright holder is ArangoDB GmbH, Cologne, Germany
+///
+/// @author Tobias Gödderz
+////////////////////////////////////////////////////////////////////////////////
+
+#include "MockTypedNode.h"
+
+#include "Basics/Exceptions.h"
+
+using namespace arangodb;
+using namespace arangodb::aql;
+using namespace arangodb::tests;
+using namespace arangodb::tests::aql;
+
+MockTypedNode::MockTypedNode(::arangodb::aql::ExecutionPlan* plan, size_t id, NodeType type)
+    : ExecutionNode(plan, id), _mockedType(type) {}
+
+ExecutionNode* MockTypedNode::clone(ExecutionPlan* plan, bool withDependencies,
+                                    bool withProperties) const {
+  return cloneHelper(std::make_unique<MockTypedNode>(plan, _id, _mockedType),
+                     withDependencies, withProperties);
+}
+
+::arangodb::aql::CostEstimate MockTypedNode::estimateCost() const {
+  THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
+}
+
+std::unique_ptr<::arangodb::aql::ExecutionBlock> MockTypedNode::createBlock(
+    ::arangodb::aql::ExecutionEngine& engine,
+    std::unordered_map<ExecutionNode*, ::arangodb::aql::ExecutionBlock*> const&) const {
+  THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
+}
+
+void MockTypedNode::toVelocyPackHelper(arangodb::velocypack::Builder&, unsigned flags,
+                                       std::unordered_set<ExecutionNode const*>& seen) const {
+  THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
+}
+
+ExecutionNode::NodeType MockTypedNode::getType() const { return _mockedType; }
diff --git a/tests/Aql/MockTypedNode.h b/tests/Aql/MockTypedNode.h
new file mode 100644
index 000000000000..f2a309929408
--- /dev/null
+++ b/tests/Aql/MockTypedNode.h
@@ -0,0 +1,60 @@
+////////////////////////////////////////////////////////////////////////////////
+/// DISCLAIMER
+///
+/// Copyright 2020 ArangoDB GmbH, Cologne, Germany
+///
+/// Licensed under the Apache License, Version 2.0 (the "License");
+/// you may not use this file except in compliance with the License.
+/// You may obtain a copy of the License at
+///
+///     http://www.apache.org/licenses/LICENSE-2.0
+///
+/// Unless required by applicable law or agreed to in writing, software
+/// distributed under the License is distributed on an "AS IS" BASIS,
+/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+/// See the License for the specific language governing permissions and
+/// limitations under the License.
+///
+/// Copyright holder is ArangoDB GmbH, Cologne, Germany
+///
+/// @author Tobias Gödderz
+////////////////////////////////////////////////////////////////////////////////
+
+#ifndef ARANGODB_TESTS_MOCK_TYPED_NODE_H
+#define ARANGODB_TESTS_MOCK_TYPED_NODE_H 1
+
+#include "Aql/ExecutionNode.h"
+
+namespace arangodb::tests::aql {
+
+// An execution node pretending to be of an arbitrary type.
+class MockTypedNode : public ::arangodb::aql::ExecutionNode {
+  friend class ExecutionBlock;
+
+ public:
+  MockTypedNode(::arangodb::aql::ExecutionPlan* plan, size_t id, NodeType);
+
+  // return mocked type
+  NodeType getType() const final;
+
+  // Necessary overrides, all not implemented:
+
+  void toVelocyPackHelper(arangodb::velocypack::Builder&, unsigned flags,
+                          std::unordered_set<ExecutionNode const*>& seen) const override;
+
+  std::unique_ptr<::arangodb::aql::ExecutionBlock> createBlock(
+      ::arangodb::aql::ExecutionEngine& engine,
+      std::unordered_map<ExecutionNode*, ::arangodb::aql::ExecutionBlock*> const&) const override;
+
+  ExecutionNode* clone(::arangodb::aql::ExecutionPlan* plan,
+                       bool withDependencies, bool withProperties) const override;
+
+  ::arangodb::aql::CostEstimate estimateCost() const override;
+
+ private:
+  NodeType _mockedType{};
+};
+
+}  // namespace arangodb::tests::aql
+
+#endif  // ARANGODB_TESTS_MOCK_TYPED_NODE_H
diff --git a/tests/Aql/ReturnExecutorTest.cpp b/tests/Aql/ReturnExecutorTest.cpp
index 7fb106efd822..4e6764095b88 100644
--- a/tests/Aql/ReturnExecutorTest.cpp
+++ b/tests/Aql/ReturnExecutorTest.cpp
@@ -51,23 +51,8 @@ using ReturnExecutorTestHelper = ExecutorTestHelper<1, 1>;
 using ReturnExecutorSplitType = ReturnExecutorTestHelper::SplitType;
 using ReturnExecutorParamType = std::tuple<ReturnExecutorSplitType, bool>;
 
-class ReturnExecutorTest : public ::testing::TestWithParam<ReturnExecutorParamType> {
+class ReturnExecutorTest : public AqlExecutorTestCaseWithParam<ReturnExecutorParamType> {
  protected:
-  // ExecutionState state;
-  ResourceMonitor monitor{};
-  mocks::MockAqlServer server{};
-  AqlItemBlockManager itemBlockManager;
-
-  std::unique_ptr<arangodb::aql::Query> fakedQuery;
-
-  ReturnExecutorTest()
-      : itemBlockManager(&monitor, SerializationFormat::SHADOWROWS),
-        fakedQuery(server.createFakeQuery()) {
-    auto engine =
-        std::make_unique<ExecutionEngine>(*fakedQuery, SerializationFormat::SHADOWROWS);
-    fakedQuery->setEngine(engine.release());
-  }
-
   auto getSplit() -> ReturnExecutorSplitType {
     auto [split, unused] = GetParam();
     return split;
@@ -114,7 +99,7 @@ TEST_P(ReturnExecutorTest, returns_all_from_upstream) {
   ReturnExecutorInfos infos(0 /*input register*/, 1 /*nr in*/, 1 /*nr out*/, doCount());
   AqlCall call{};  // unlimited produce
   ExecutorTestHelper(*fakedQuery)
-      .setExecBlock<ReturnExecutor>(std::move(infos))
+      .setExecBlock<ReturnExecutor>(std::move(infos), ExecutionNode::RETURN)
       .setInputValueList(1, 2, 5, 2, 1, 5, 7, 1)
       .setInputSplitType(getSplit())
       .setCall(call)
@@ -130,7 +115,7 @@ TEST_P(ReturnExecutorTest, handle_soft_limit) {
   AqlCall call{};
   call.softLimit = 3;
   ExecutorTestHelper(*fakedQuery)
-      .setExecBlock<ReturnExecutor>(std::move(infos))
+      .setExecBlock<ReturnExecutor>(std::move(infos), ExecutionNode::RETURN)
       .setInputValueList(1, 2, 5, 2, 1, 5, 7, 1)
       .setInputSplitType(getSplit())
       .setCall(call)
@@ -146,7 +131,7 @@ TEST_P(ReturnExecutorTest, handle_hard_limit) {
   AqlCall call{};
   call.hardLimit = 5;
   ExecutorTestHelper(*fakedQuery)
-      .setExecBlock<ReturnExecutor>(std::move(infos))
+      .setExecBlock<ReturnExecutor>(std::move(infos), ExecutionNode::RETURN)
       .setInputValueList(1, 2, 5, 2, 1, 5, 7, 1)
       .setInputSplitType(getSplit())
       .setCall(call)
@@ -162,7 +147,7 @@ TEST_P(ReturnExecutorTest, handle_offset) {
   AqlCall call{};
   call.offset = 4;
   ExecutorTestHelper(*fakedQuery)
-      .setExecBlock<ReturnExecutor>(std::move(infos))
+      .setExecBlock<ReturnExecutor>(std::move(infos), ExecutionNode::RETURN)
       .setInputValueList(1, 2, 5, 2, 1, 5, 7, 1)
       .setInputSplitType(getSplit())
       .setCall(call)
@@ -179,7 +164,7 @@ TEST_P(ReturnExecutorTest, handle_fullcount) {
   call.hardLimit = 2;
   call.fullCount = true;
   ExecutorTestHelper(*fakedQuery)
-      .setExecBlock<ReturnExecutor>(std::move(infos))
+      .setExecBlock<ReturnExecutor>(std::move(infos), ExecutionNode::RETURN)
       .setInputValueList(1, 2, 5, 2, 1, 5, 7, 1)
       .setInputSplitType(getSplit())
       .setCall(call)
@@ -195,7 +180,7 @@ TEST_P(ReturnExecutorTest, handle_other_inputRegister) {
   AqlCall call{};
   call.hardLimit = 5;
   ExecutorTestHelper<2, 1>(*fakedQuery)
-      .setExecBlock<ReturnExecutor>(std::move(infos))
+      .setExecBlock<ReturnExecutor>(std::move(infos), ExecutionNode::RETURN)
       .setInputValue({{R"("invalid")", 1},
                       {R"("invalid")", 2},
                       {R"("invalid")", 5},
diff --git a/tests/Aql/ShortestPathExecutorTest.cpp b/tests/Aql/ShortestPathExecutorTest.cpp
index 93eca4fcfc98..11ad12eacb56 100644
--- a/tests/Aql/ShortestPathExecutorTest.cpp
+++ b/tests/Aql/ShortestPathExecutorTest.cpp
@@ -287,8 +287,7 @@ class ShortestPathExecutorTest
               std::move(parameters._source), std::move(parameters._target)),
         finder(static_cast<FakePathFinder&>(infos.finder())),
         inputBlock(buildBlock<2>(itemBlockManager, std::move(parameters._inputMatrix))),
-        input(AqlItemBlockInputRange(ExecutorState::DONE, inputBlock, 0,
-                                     inputBlock->size())),
+        input(AqlItemBlockInputRange(ExecutorState::DONE, 0, inputBlock, 0)),
         fakeUnusedBlock(VPackParser::fromJson("[]")),
         fetcher(itemBlockManager, fakeUnusedBlock->steal(), false),
         testee(fetcher, infos) {
@@ -430,7 +429,7 @@ class ShortestPathExecutorTest
 
     // If an offset is requested, skip
     if (ourCall.getOffset() > 0) {
-      std::tie(state, std::ignore, skippedInitial, std::ignore) =
+      std::tie(state, std::ignore /* stats */, skippedInitial, std::ignore) =
           testee.skipRowsRange(input, ourCall);
     }
 
@@ -454,7 +453,7 @@ class ShortestPathExecutorTest
       // Emulate being called with a full count
       ourCall.hardLimit = 0;
       ourCall.softLimit = 0;
-      std::tie(state, std::ignore, skippedFullCount, std::ignore) =
+      std::tie(state, std::ignore /* stats */, skippedFullCount, std::ignore) =
           testee.skipRowsRange(input, ourCall);
     }
 
diff --git a/tests/Aql/SingleRowFetcherTest.cpp b/tests/Aql/SingleRowFetcherTest.cpp
index 06f7b5fde85e..f0ed040e2783 100644
--- a/tests/Aql/SingleRowFetcherTest.cpp
+++ b/tests/Aql/SingleRowFetcherTest.cpp
@@ -1223,7 +1223,7 @@ TEST_F(SingleRowFetcherTestPassBlocks, handling_shadowrows_in_execute_oneAndDone
   {
     SingleRowFetcher<passBlocksThrough> testee(dependencyProxyMock);
     AqlCall call;
-    AqlCallStack stack = {call};
+    auto stack = AqlCallStack{call};
 
     // First no data row
     auto [state, skipped, input] = testee.execute(stack);
@@ -1258,7 +1258,7 @@ TEST_F(SingleRowFetcherTestPassBlocks, handling_shadowrows_in_execute_twoAndHasM
   {
     SingleRowFetcher<passBlocksThrough> testee(dependencyProxyMock);
     AqlCall call;
-    AqlCallStack stack = {call};
+    auto stack = AqlCallStack{call};
 
     auto [state, skipped, input] = testee.execute(stack);
     // We only have one block, no more calls to execute necessary
diff --git a/tests/Aql/SortedCollectExecutorTest.cpp b/tests/Aql/SortedCollectExecutorTest.cpp
index fa8ce07e644c..90ef4ca3beb2 100644
--- a/tests/Aql/SortedCollectExecutorTest.cpp
+++ b/tests/Aql/SortedCollectExecutorTest.cpp
@@ -206,8 +206,7 @@ TEST_F(SortedCollectExecutorTestRowsUpstream, producer_1) {
   AqlCall clientCall;
 
   AqlItemBlockInputRange emptyInputRange(ExecutorState::HASMORE);
-  AqlItemBlockInputRange inputRange(ExecutorState::DONE, inputBlock, 0,
-                                    inputBlock->size());
+  AqlItemBlockInputRange inputRange(ExecutorState::DONE, 0, inputBlock, 0);
 
   SharedAqlItemBlockPtr outputBlock =
       itemBlockManager.requestBlock(2, infos.numberOfOutputRegisters());
@@ -253,8 +252,7 @@ TEST_F(SortedCollectExecutorTestRowsUpstream, producer_2) {
   AqlCall clientCall;
 
   AqlItemBlockInputRange emptyInputRange(ExecutorState::HASMORE);
-  AqlItemBlockInputRange inputRange(ExecutorState::DONE, inputBlock, 0,
-                                    inputBlock->size());
+  AqlItemBlockInputRange inputRange(ExecutorState::DONE, 0, inputBlock, 0);
 
   SharedAqlItemBlockPtr outputBlock =
       itemBlockManager.requestBlock(inputBlock->size(), infos.numberOfOutputRegisters());
@@ -305,8 +303,7 @@ TEST_F(SortedCollectExecutorTestRowsUpstream, producer_3) {
   AqlCall clientCall;
 
   AqlItemBlockInputRange emptyInputRange(ExecutorState::HASMORE);
-  AqlItemBlockInputRange inputRange(ExecutorState::DONE, inputBlock, 0,
-                                    inputBlock->size());
+  AqlItemBlockInputRange inputRange(ExecutorState::DONE, 0, inputBlock, 0);
 
   SharedAqlItemBlockPtr outputBlock =
       itemBlockManager.requestBlock(inputBlock->size(), infos.numberOfOutputRegisters());
@@ -356,8 +353,7 @@ TEST_F(SortedCollectExecutorTestRowsUpstream, producer_4) {
   AqlCall clientCall;
 
   AqlItemBlockInputRange emptyInputRange(ExecutorState::HASMORE);
-  AqlItemBlockInputRange inputRange(ExecutorState::DONE, inputBlock, 0,
-                                    inputBlock->size());
+  AqlItemBlockInputRange inputRange(ExecutorState::DONE, 0, inputBlock, 0);
 
   SharedAqlItemBlockPtr outputBlock =
       itemBlockManager.requestBlock(inputBlock->size(), infos.numberOfOutputRegisters());
@@ -431,8 +427,7 @@ TEST(SortedCollectExecutorTestRowsUpstreamCount, test) {
   AqlCall clientCall;
 
   AqlItemBlockInputRange emptyInputRange(ExecutorState::HASMORE);
-  AqlItemBlockInputRange inputRange(ExecutorState::DONE, inputBlock, 0,
-                                    inputBlock->size());
+  AqlItemBlockInputRange inputRange(ExecutorState::DONE, 0, inputBlock, 0);
 
   SharedAqlItemBlockPtr outputBlock =
       itemBlockManager.requestBlock(inputBlock->size(), infos.numberOfOutputRegisters());
@@ -533,8 +528,7 @@ TEST(SortedCollectExecutorTestRowsUpstreamCountStrings, test) {
   AqlCall clientCall;
 
   AqlItemBlockInputRange emptyInputRange(ExecutorState::HASMORE);
-  AqlItemBlockInputRange inputRange(ExecutorState::DONE, inputBlock, 0,
-                                    inputBlock->size());
+  AqlItemBlockInputRange inputRange(ExecutorState::DONE, 0, inputBlock, 0);
 
   SharedAqlItemBlockPtr outputBlock =
       itemBlockManager.requestBlock(inputBlock->size(), infos.numberOfOutputRegisters());
@@ -653,8 +647,7 @@ TEST_F(SortedCollectExecutorTestSkip, skip_1) {
 
   SharedAqlItemBlockPtr inputBlock = buildBlock<1>(itemBlockManager, {{1}, {2}});
   AqlItemBlockInputRange emptyInputRange(ExecutorState::HASMORE);
-  AqlItemBlockInputRange inputRange(ExecutorState::DONE, inputBlock, 0,
-                                    inputBlock->size());
+  AqlItemBlockInputRange inputRange(ExecutorState::DONE, 0, inputBlock, 0);
 
   SortedCollectExecutor testee(fetcher, infos);
 
@@ -690,8 +683,7 @@ TEST_F(SortedCollectExecutorTestSkip, skip_2) {
 
   SharedAqlItemBlockPtr inputBlock = buildBlock<1>(itemBlockManager, {{1}, {2}});
   AqlItemBlockInputRange emptyInputRange(ExecutorState::HASMORE);
-  AqlItemBlockInputRange inputRange(ExecutorState::DONE, inputBlock, 0,
-                                    inputBlock->size());
+  AqlItemBlockInputRange inputRange(ExecutorState::DONE, 0, inputBlock, 0);
 
   SortedCollectExecutor testee(fetcher, infos);
 
@@ -750,8 +742,7 @@ TEST_F(SortedCollectExecutorTestSkip, skip_3) {
 
   SharedAqlItemBlockPtr inputBlock = buildBlock<1>(itemBlockManager, {{1}, {1}});
   AqlItemBlockInputRange emptyInputRange(ExecutorState::HASMORE);
-  AqlItemBlockInputRange inputRange(ExecutorState::HASMORE, inputBlock, 0,
-                                    inputBlock->size());
+  AqlItemBlockInputRange inputRange(ExecutorState::HASMORE, 0, inputBlock, 0);
   AqlItemBlockInputRange emptyInputRangeDone(ExecutorState::DONE);
 
   SortedCollectExecutor testee(fetcher, infos);
@@ -795,12 +786,10 @@ TEST_F(SortedCollectExecutorTestSkip, skip_4) {
 
   SharedAqlItemBlockPtr inputBlock = buildBlock<1>(itemBlockManager, {{1}, {1}});
   AqlItemBlockInputRange emptyInputRange(ExecutorState::HASMORE);
-  AqlItemBlockInputRange inputRange(ExecutorState::HASMORE, inputBlock, 0,
-                                    inputBlock->size());
+  AqlItemBlockInputRange inputRange(ExecutorState::HASMORE, 0, inputBlock, 0);
 
   SharedAqlItemBlockPtr inputBlock2 = buildBlock<1>(itemBlockManager, {{2}});
-  AqlItemBlockInputRange inputRange2(ExecutorState::HASMORE, inputBlock2, 0,
-                                     inputBlock2->size());
+  AqlItemBlockInputRange inputRange2(ExecutorState::HASMORE, 0, inputBlock2, 0);
   AqlItemBlockInputRange emptyInputRangeDone(ExecutorState::DONE);
 
   SortedCollectExecutor testee(fetcher, infos);
@@ -876,8 +865,7 @@ TEST_F(SortedCollectExecutorTestSkip, skip_5) {
 
   SharedAqlItemBlockPtr inputBlock = buildBlock<1>(itemBlockManager, {{1}, {1}, {2}});
   AqlItemBlockInputRange emptyInputRange(ExecutorState::HASMORE);
-  AqlItemBlockInputRange inputRange(ExecutorState::DONE, inputBlock, 0,
-                                    inputBlock->size());
+  AqlItemBlockInputRange inputRange(ExecutorState::DONE, 0, inputBlock, 0);
 
   SortedCollectExecutor testee(fetcher, infos);
 
diff --git a/tests/Aql/WaitingExecutionBlockMock.cpp b/tests/Aql/WaitingExecutionBlockMock.cpp
index 74000072c520..b20a09c843ca 100644
--- a/tests/Aql/WaitingExecutionBlockMock.cpp
+++ b/tests/Aql/WaitingExecutionBlockMock.cpp
@@ -125,24 +125,29 @@ std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> WaitingExecutionBlockM
     stack.pop();
   }
   auto myCall = stack.popCall();
+
+  TRI_ASSERT(!(myCall.getOffset() == 0 && myCall.softLimit == AqlCall::Limit{0}));
+  TRI_ASSERT(!(myCall.hasSoftLimit() && myCall.fullCount));
+  TRI_ASSERT(!(myCall.hasSoftLimit() && myCall.hasHardLimit()));
+
   if (_variant != WaitingBehaviour::NEVER && !_hasWaited) {
-    // If we orderd waiting check on _hasWaited and wait if not
+    // If we ordered waiting check on _hasWaited and wait if not
     _hasWaited = true;
     return {ExecutionState::WAITING, 0, nullptr};
   }
   if (_variant == WaitingBehaviour::ALWAYS) {
-    // If we allways wait, reset.
+    // If we always wait, reset.
     _hasWaited = false;
   }
   size_t skipped = 0;
   SharedAqlItemBlockPtr result = nullptr;
-  if (_data.front() == nullptr) {
+  if (!_data.empty() && _data.front() == nullptr) {
     dropBlock();
   }
   while (!_data.empty()) {
     if (_data.front() == nullptr) {
-      if (myCall.getOffset() > 0 || myCall.getLimit() > 0) {
-        TRI_ASSERT(skipped > 0 || result != nullptr);
+      if ((skipped > 0 || result != nullptr) &&
+          !(myCall.hasHardLimit() && myCall.getLimit() == 0)) {
         // This is a specific break point return now.
         // Sorry we can only return one block.
         // This means we have prepared the first block.
@@ -205,10 +210,12 @@ std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> WaitingExecutionBlockM
           dropBlock();
         }
       }
-      if (_data.empty()) {
-        return {ExecutionState::DONE, skipped, result};
-      } else {
+      if (!_data.empty()) {
         return {ExecutionState::HASMORE, skipped, result};
+      } else if (result != nullptr && result->size() < myCall.hardLimit) {
+        return {ExecutionState::HASMORE, skipped, result};
+      } else {
+        return {ExecutionState::DONE, skipped, result};
       }
     }
   }
@@ -219,4 +226,4 @@ void WaitingExecutionBlockMock::dropBlock() {
   TRI_ASSERT(!_data.empty());
   _data.pop_front();
   _inflight = 0;
-}
\ No newline at end of file
+}
diff --git a/tests/Aql/WaitingExecutionBlockMock.h b/tests/Aql/WaitingExecutionBlockMock.h
index a66c3a913b4e..2c147ba08e91 100644
--- a/tests/Aql/WaitingExecutionBlockMock.h
+++ b/tests/Aql/WaitingExecutionBlockMock.h
@@ -51,7 +51,7 @@ class WaitingExecutionBlockMock final : public arangodb::aql::ExecutionBlock {
   enum WaitingBehaviour {
     NEVER,  // Never return WAITING
     ONCE,  // Return WAITING on the first execute call, afterwards return all blocks
-    ALWAYS  // Return Waiting once for every execute Call.
+    ALWAYS  // Return WAITING once for every execute Call.
   };
 
   /**
@@ -60,7 +60,7 @@ class WaitingExecutionBlockMock final : public arangodb::aql::ExecutionBlock {
    * @param engine Required by API.
    * @param node Required by API.
    * @param data Must be a shared_ptr to an VPackArray.
-   * @param variant The waiting behaviour of this block (default ONCE), see WaitingBehaviour
+   * @param variant The waiting behaviour of this block (default ALWAYS), see WaitingBehaviour
    */
   WaitingExecutionBlockMock(arangodb::aql::ExecutionEngine* engine,
                             arangodb::aql::ExecutionNode const* node,
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 7b7c9fda3323..6ba73256b04f 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -51,6 +51,7 @@ set(ARANGODB_TESTS_SOURCES
   Aql/IndexNodeTest.cpp
   Aql/InsertExecutorTest.cpp
   Aql/LimitExecutorTest.cpp
+  Aql/MockTypedNode.cpp
   Aql/MultiDepFetcherHelper.cpp
   Aql/MultiDependencySingleRowFetcherTest.cpp
   Aql/NoResultsExecutorTest.cpp
diff --git a/tests/Mocks/Servers.cpp b/tests/Mocks/Servers.cpp
index e9e0e8e66f63..126dde89f4cc 100644
--- a/tests/Mocks/Servers.cpp
+++ b/tests/Mocks/Servers.cpp
@@ -26,6 +26,8 @@
 #include "ApplicationFeatures/CommunicationFeaturePhase.h"
 #include "ApplicationFeatures/GreetingsFeaturePhase.h"
 #include "Aql/AqlFunctionFeature.h"
+#include "Aql/AqlItemBlockSerializationFormat.h"
+#include "Aql/ExecutionEngine.h"
 #include "Aql/OptimizerRulesFeature.h"
 #include "Aql/Query.h"
 #include "Basics/files.h"
@@ -463,6 +465,10 @@ std::unique_ptr<arangodb::aql::Query> MockAqlServer::createFakeQuery(bool activa
                                              fakeQueryString, bindParams, queryOptions,
                                              arangodb::aql::QueryPart::PART_DEPENDENT);
   query->injectTransaction(createFakeTransaction());
+
+  auto engine = std::make_unique<aql::ExecutionEngine>(*query, aql::SerializationFormat::SHADOWROWS);
+  query->setEngine(std::move(engine));
+
   return query;
 }
 
diff --git a/tests/js/server/aql/aql-profiler.js b/tests/js/server/aql/aql-profiler.js
index 27c7cb7a5727..421d7254a7f7 100644
--- a/tests/js/server/aql/aql-profiler.js
+++ b/tests/js/server/aql/aql-profiler.js
@@ -551,7 +551,7 @@ function ahuacatlProfilerTestSuite () {
       const genNodeList = (rows) => [
         {type: SingletonBlock, calls: 1, items: 1},
         {type: CalculationBlock, calls: 1, items: 1},
-        {type: EnumerateListBlock, calls: limitBatches(rows) + skipOffsetBatches(rows), items: limit(rows) + offset(rows)},
+        {type: EnumerateListBlock, calls: limitBatches(rows), items: limit(rows) + offset(rows)},
         {type: LimitBlock, calls: limitBatches(rows), items: limit(rows)},
         {type: ReturnBlock, calls: limitBatches(rows), items: limit(rows)},
       ];
@@ -705,8 +705,8 @@ function ahuacatlProfilerTestSuite () {
         { type : CalculationBlock, calls : 1, items : 1 },
         { type : EnumerateListBlock, calls : batches, items : rows },
         { type : ConstrainedSortBlock, calls : skipOffsetBatches(rows) + limitMinusSkipBatches(rows) + remainderBatches(rows), items : rows },
-        { type : LimitBlock, calls : limitMinusSkipBatches(rows), items : limitMinusSkip(rows) },
-        { type : ReturnBlock, calls : limitMinusSkipBatches(rows), items : limitMinusSkip(rows) }
+        { type : LimitBlock, calls : limitMinusSkipBatches(rows) + /* this is only during ::execute work, should remove later again */ remainderBatches(rows), items : limitMinusSkip(rows) },
+        { type : ReturnBlock, calls : limitMinusSkipBatches(rows) + /* this is only during ::execute work, should remove later again */  remainderBatches(rows), items : limitMinusSkip(rows) }
       ];
       const bind = rows => ({
         rows,

From e7f36c35cf918002a495968a97d7a2606b87a47f Mon Sep 17 00:00:00 2001
From: Heiko <hkernbach@users.noreply.github.com>
Date: Fri, 21 Feb 2020 16:54:01 +0100
Subject: [PATCH 072/122] Feature/aql subquery operations stack calculation
 exec enumerate exec (#11098)

* removed unused import

* re-ordered asserts to see which register was wrongly used

* added implementation of produceRows with inputRange

* added first test to test new produceRows including inputRange

* rm skip from calc executor

* rm not correct assert, added second test

* added produceRows inputrange hasmore test

* added new produceRows + test

* added skipRowsRange enumerate collection executor

* added skipRowsRange enumerate collection executor test

* added assert

* adde fake query helper, one without auto trx but with prepare plan, the other one without prepare but with trx - also removed fakeit mocks from enumeratecollectionexecutor tests

* fixed skipRowsRange in enumerateCollectionExecutor, added test as well

* removed todo

* added skipAll

* added EnumerateCollection as new style executor

* added produce and skip rows, not ready yet

* added new tests, still not ready, need unsorted compare operators in helper, waiting

* rm logs

* intermidiate commit - may not work

* removed unused import

* added implementation of produceRows with inputRange

* added first test to test new produceRows including inputRange

* rm skip from calc executor

* rm not correct assert, added second test

* added produceRows inputrange hasmore test

* added new produceRows + test

* added skipRowsRange enumerate collection executor

* added skipRowsRange enumerate collection executor test

* added assert

* adde fake query helper, one without auto trx but with prepare plan, the other one without prepare but with trx - also removed fakeit mocks from enumeratecollectionexecutor tests

* fixed skipRowsRange in enumerateCollectionExecutor, added test as well

* removed todo

* added skipAll

* added EnumerateCollection as new style executor

* added produce and skip rows, not ready yet

* added new tests, still not ready, need unsorted compare operators in helper, waiting

* rm logs

* intermidiate commit - may not work

* make branch compile again

* mv assert

* protected server

* make enum collection tests work again

* fixed ExecBlockImpl

* todo optimization

* fix gtest calc executor

* header file enumcollexec, helper method

* fix shrink method in aqlitemblock

* impl

* nodiscard

* calc executor

* rm empty line

* fix calc exec

* tmp re-enable old method

* tmp make tests green again, needs cleanup later

* use uint64_t instead of u_int64_t

* removed unused code

* Update arangod/Aql/CalculationExecutor.cpp

Co-Authored-By: Michael Hackstein <michael@arangodb.com>

* Update arangod/Aql/CalculationExecutor.cpp

Co-Authored-By: Michael Hackstein <michael@arangodb.com>

* remove implementation code of old api

* Update arangod/Aql/EnumerateCollectionExecutor.cpp

Co-Authored-By: Michael Hackstein <michael@arangodb.com>

* buildable tests again

* rm unused code

* added assert

* make tests compile again ...

* disable few more tests, need to be optimized after subquery end start merges

Co-authored-by: Michael Hackstein <michael@arangodb.com>
---
 arangod/Aql/AqlItemBlock.cpp                  |  14 +-
 arangod/Aql/CalculationExecutor.cpp           |  45 ++-
 arangod/Aql/CalculationExecutor.h             |  13 +-
 arangod/Aql/EnumerateCollectionExecutor.cpp   | 220 ++++++----
 arangod/Aql/EnumerateCollectionExecutor.h     |  38 +-
 arangod/Aql/ExecutionBlockImpl.cpp            |   8 +-
 arangod/Aql/ExecutionNode.cpp                 |   2 +-
 arangod/Aql/FilterExecutor.cpp                |   1 -
 arangod/Utils/OperationCursor.cpp             |  22 +
 arangod/Utils/OperationCursor.h               |   6 +
 tests/Aql/CalculationExecutorTest.cpp         | 143 ++++++-
 tests/Aql/EnumerateCollectionExecutorTest.cpp | 378 +++++++++++++++---
 tests/Aql/ExecutorTestHelper.h                |   3 +-
 tests/Mocks/Servers.cpp                       |   6 +-
 tests/Mocks/Servers.h                         |   2 +-
 15 files changed, 729 insertions(+), 172 deletions(-)

diff --git a/arangod/Aql/AqlItemBlock.cpp b/arangod/Aql/AqlItemBlock.cpp
index 82edf0f715e3..79d7428910ae 100644
--- a/arangod/Aql/AqlItemBlock.cpp
+++ b/arangod/Aql/AqlItemBlock.cpp
@@ -347,6 +347,13 @@ void AqlItemBlock::shrink(size_t nrItems) {
 
   decreaseMemoryUsage(sizeof(AqlValue) * (_nrItems - nrItems) * _nrRegs);
 
+  // remove the shadow row indices pointing to now invalid rows.
+  _shadowRowIndexes.erase(_shadowRowIndexes.lower_bound(nrItems),
+                          _shadowRowIndexes.end());
+
+  // adjust the size of the block
+  _nrItems = nrItems;
+
   for (size_t i = numEntries(); i < _data.size(); ++i) {
     AqlValue& a = _data[i];
     if (a.requiresDestruction()) {
@@ -368,13 +375,6 @@ void AqlItemBlock::shrink(size_t nrItems) {
     }
     a.erase();
   }
-
-  // remove the shadow row indices pointing to now invalid rows.
-  _shadowRowIndexes.erase(_shadowRowIndexes.lower_bound(nrItems),
-                          _shadowRowIndexes.end());
-
-  // adjust the size of the block
-  _nrItems = nrItems;
 }
 
 void AqlItemBlock::rescale(size_t nrItems, RegisterId nrRegs) {
diff --git a/arangod/Aql/CalculationExecutor.cpp b/arangod/Aql/CalculationExecutor.cpp
index c6b3513afc15..191324660f17 100644
--- a/arangod/Aql/CalculationExecutor.cpp
+++ b/arangod/Aql/CalculationExecutor.cpp
@@ -21,13 +21,16 @@
 ////////////////////////////////////////////////////////////////////////////////
 
 #include "CalculationExecutor.h"
+#include <Logger/LogMacros.h>
 
+#include "Aql/AqlCall.h"
+#include "Aql/AqlCallStack.h"
+#include "Aql/AqlItemBlockInputRange.h"
 #include "Aql/ExecutorExpressionContext.h"
 #include "Aql/Expression.h"
 #include "Aql/OutputAqlItemRow.h"
 #include "Aql/Query.h"
 #include "Aql/SingleRowFetcher.h"
-#include "Basics/Common.h"
 #include "Basics/Exceptions.h"
 #include "Basics/ScopeGuard.h"
 #include "Cluster/ServerState.h"
@@ -86,6 +89,8 @@ std::vector<RegisterId> const& CalculationExecutorInfos::getExpInRegs() const no
 template <CalculationType calculationType>
 std::pair<ExecutionState, typename CalculationExecutor<calculationType>::Stats>
 CalculationExecutor<calculationType>::produceRows(OutputAqlItemRow& output) {
+  // TRI_ASSERT(false);
+  // THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
   ExecutionState state;
   InputAqlItemRow row = InputAqlItemRow{CreateInvalidInputRowHint{}};
   std::tie(state, row) = _fetcher.fetchRow();
@@ -125,6 +130,44 @@ CalculationExecutor<calculationType>::produceRows(OutputAqlItemRow& output) {
   return {state, NoStats{}};
 }
 
+template <CalculationType calculationType>
+std::tuple<ExecutorState, typename CalculationExecutor<calculationType>::Stats, AqlCall>
+CalculationExecutor<calculationType>::produceRows(AqlItemBlockInputRange& inputRange,
+                                                  OutputAqlItemRow& output) {
+  TRI_IF_FAILURE("CalculationExecutor::produceRows") {
+    THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
+  }
+  ExecutorState state = ExecutorState::HASMORE;
+  InputAqlItemRow input = InputAqlItemRow{CreateInvalidInputRowHint{}};
+
+  while (inputRange.hasDataRow()) {
+    // This executor is passthrough. it has enough place to write.
+    TRI_ASSERT(!output.isFull());
+    std::tie(state, input) = inputRange.nextDataRow(); 
+    TRI_ASSERT(input.isInitialized());
+
+    doEvaluation(input, output);
+    output.advanceRow();
+
+    // _hasEnteredContext implies the query has entered the context, but not
+    // the other way round because it may be owned by exterior.
+    TRI_ASSERT(!_hasEnteredContext || _infos.getQuery().hasEnteredContext());
+
+    // The following only affects V8Conditions. If we should exit the V8 context
+    // between blocks, because we might have to wait for client or upstream, then
+    //   hasEnteredContext => state == HASMORE,
+    // as we only leave the context open when there are rows left in the current
+    // block.
+    // Note that _infos.getQuery().hasEnteredContext() may be true, even if
+    // _hasEnteredContext is false, if (and only if) the query context is owned
+    // by exterior.
+    TRI_ASSERT(!shouldExitContextBetweenBlocks() || !_hasEnteredContext ||
+               state == ExecutorState::HASMORE);
+  }
+
+  return {inputRange.upstreamState(), NoStats{}, output.getClientCall()};
+}
+
 template <CalculationType calculationType>
 std::tuple<ExecutionState, typename CalculationExecutor<calculationType>::Stats, SharedAqlItemBlockPtr>
 CalculationExecutor<calculationType>::fetchBlockForPassthrough(size_t atMost) {
diff --git a/arangod/Aql/CalculationExecutor.h b/arangod/Aql/CalculationExecutor.h
index 77c429d72118..8ab0b812721b 100644
--- a/arangod/Aql/CalculationExecutor.h
+++ b/arangod/Aql/CalculationExecutor.h
@@ -40,10 +40,12 @@ class Methods;
 
 namespace aql {
 
+struct AqlCall;
+class AqlItemBlockInputRange;
 class Expression;
 class OutputAqlItemRow;
 class Query;
-template<BlockPassthrough>
+template <BlockPassthrough>
 class SingleRowFetcher;
 struct Variable;
 
@@ -104,6 +106,14 @@ class CalculationExecutor {
    */
   std::pair<ExecutionState, Stats> produceRows(OutputAqlItemRow& output);
 
+  /**
+   * @brief produce the next Row of Aql Values.
+   *
+   * @return ExecutorState, the stats, and a new Call that needs to be send to upstream
+   */
+  [[nodiscard]] std::tuple<ExecutorState, Stats, AqlCall> produceRows(
+      AqlItemBlockInputRange& inputRange, OutputAqlItemRow& output);
+
   std::tuple<ExecutionState, Stats, SharedAqlItemBlockPtr> fetchBlockForPassthrough(size_t atMost);
 
  private:
@@ -134,7 +144,6 @@ class CalculationExecutor {
   bool _hasEnteredContext;
 };
 
-
 }  // namespace aql
 }  // namespace arangodb
 
diff --git a/arangod/Aql/EnumerateCollectionExecutor.cpp b/arangod/Aql/EnumerateCollectionExecutor.cpp
index 15a5db47ef83..ca2b97ba660a 100644
--- a/arangod/Aql/EnumerateCollectionExecutor.cpp
+++ b/arangod/Aql/EnumerateCollectionExecutor.cpp
@@ -25,6 +25,8 @@
 
 #include "EnumerateCollectionExecutor.h"
 
+#include "Aql/AqlCall.h"
+#include "Aql/AqlCallStack.h"
 #include "Aql/AqlValue.h"
 #include "Aql/Collection.h"
 #include "Aql/DocumentProducingHelper.h"
@@ -35,9 +37,11 @@
 #include "Aql/Query.h"
 #include "Aql/SingleRowFetcher.h"
 #include "Aql/Stats.h"
+#include "AqlCall.h"
 #include "Transaction/Methods.h"
 #include "Utils/OperationCursor.h"
 
+#include <Logger/LogMacros.h>
 #include <utility>
 
 using namespace arangodb;
@@ -54,8 +58,8 @@ EnumerateCollectionExecutorInfos::EnumerateCollectionExecutorInfos(
     // cppcheck-suppress passedByValue
     std::unordered_set<RegisterId> registersToKeep, ExecutionEngine* engine,
     Collection const* collection, Variable const* outVariable, bool produceResult,
-    Expression* filter,
-    std::vector<std::string> const& projections,
+    Expression* filter, std::vector<std::string> const& projections,
+    std::vector<size_t> const& coveringIndexAttributePositions,
     bool useRawDocumentPointers, bool random)
     : ExecutorInfos(make_shared_unordered_set(),
                     make_shared_unordered_set({outputRegister}),
@@ -66,6 +70,7 @@ EnumerateCollectionExecutorInfos::EnumerateCollectionExecutorInfos(
       _outVariable(outVariable),
       _filter(filter),
       _projections(projections),
+      _coveringIndexAttributePositions(coveringIndexAttributePositions),
       _outputRegisterId(outputRegister),
       _useRawDocumentPointers(useRawDocumentPointers),
       _produceResult(produceResult),
@@ -99,6 +104,11 @@ std::vector<std::string> const& EnumerateCollectionExecutorInfos::getProjections
   return _projections;
 }
 
+std::vector<size_t> const& EnumerateCollectionExecutorInfos::getCoveringIndexAttributePositions() const
+    noexcept {
+  return _coveringIndexAttributePositions;
+}
+
 bool EnumerateCollectionExecutorInfos::getProduceResult() const {
   return _produceResult;
 }
@@ -116,15 +126,15 @@ EnumerateCollectionExecutor::EnumerateCollectionExecutor(Fetcher& fetcher, Infos
     : _infos(infos),
       _fetcher(fetcher),
       _documentProducer(nullptr),
-      _documentProducingFunctionContext(_input, nullptr, _infos.getOutputRegisterId(),
-                                        _infos.getProduceResult(),
-                                        _infos.getQuery(), _infos.getFilter(),
-                                        _infos.getProjections(),
-                                        ::emptyAttributePositions,
+      _documentProducingFunctionContext(_currentRow, nullptr, _infos.getOutputRegisterId(),
+                                        _infos.getProduceResult(), _infos.getQuery(),
+                                        _infos.getFilter(), _infos.getProjections(),
+                                        _infos.getCoveringIndexAttributePositions(),
                                         true, _infos.getUseRawDocumentPointers(), false),
       _state(ExecutionState::HASMORE),
+      _executorState(ExecutorState::HASMORE),
       _cursorHasMore(false),
-      _input(InputAqlItemRow{CreateInvalidInputRowHint{}}) {
+      _currentRow(InputAqlItemRow{CreateInvalidInputRowHint{}}) {
   _cursor = std::make_unique<OperationCursor>(
       _infos.getTrxPtr()->indexScan(_infos.getCollection()->name(),
                                     (_infos.getRandom()
@@ -139,7 +149,8 @@ EnumerateCollectionExecutor::EnumerateCollectionExecutor(Fetcher& fetcher, Infos
                                        std::to_string(maxWait) + ")");
   }
   if (_infos.getProduceResult()) {
-    _documentProducer = buildDocumentCallback<false, false>(_documentProducingFunctionContext);
+    _documentProducer =
+        buildDocumentCallback<false, false>(_documentProducingFunctionContext);
   }
   _documentSkipper = buildDocumentCallback<false, true>(_documentProducingFunctionContext);
 }
@@ -148,119 +159,158 @@ EnumerateCollectionExecutor::~EnumerateCollectionExecutor() = default;
 
 std::pair<ExecutionState, EnumerateCollectionStats> EnumerateCollectionExecutor::produceRows(
     OutputAqlItemRow& output) {
-  TRI_IF_FAILURE("EnumerateCollectionExecutor::produceRows") {
-    THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
+  TRI_ASSERT(false);
+  THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
+}
+
+std::tuple<ExecutionState, EnumerateCollectionStats, size_t> EnumerateCollectionExecutor::skipRows(
+    size_t const toSkip) {
+  TRI_ASSERT(false);
+  THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
+}
+
+uint64_t EnumerateCollectionExecutor::skipEntries(size_t toSkip,
+                                                   EnumerateCollectionStats& stats) {
+  uint64_t actuallySkipped = 0;
+
+  if (_infos.getFilter() == nullptr) {
+    _cursor->skip(toSkip, actuallySkipped);
+    stats.incrScanned(actuallySkipped);
+    _documentProducingFunctionContext.getAndResetNumScanned();
+  } else {
+    _cursor->nextDocument(_documentSkipper, toSkip);
+    size_t filtered = _documentProducingFunctionContext.getAndResetNumFiltered();
+    size_t scanned = _documentProducingFunctionContext.getAndResetNumScanned();
+    TRI_ASSERT(scanned >= filtered);
+    stats.incrFiltered(filtered);
+    stats.incrScanned(scanned);
+    actuallySkipped = scanned - filtered;
   }
+  _cursorHasMore = _cursor->hasMore();
+
+  return actuallySkipped;
+}
+
+std::tuple<ExecutorState, EnumerateCollectionStats, size_t, AqlCall> EnumerateCollectionExecutor::skipRowsRange(
+    AqlItemBlockInputRange& inputRange, AqlCall& call) {
+  AqlCall upstreamCall{};
   EnumerateCollectionStats stats{};
+  bool offsetPhase = (call.getOffset() > 0);
+
   TRI_ASSERT(_documentProducingFunctionContext.getAndResetNumScanned() == 0);
   TRI_ASSERT(_documentProducingFunctionContext.getAndResetNumFiltered() == 0);
-  _documentProducingFunctionContext.setOutputRow(&output);
 
-  while (true) {
-    if (!_cursorHasMore) {
-      std::tie(_state, _input) = _fetcher.fetchRow();
+  while (inputRange.hasDataRow() && call.shouldSkip()) {
+    uint64_t skipped = 0;
 
-      if (_state == ExecutionState::WAITING) {
-        return {_state, stats};
-      }
+    if (!_cursorHasMore) {
+      initializeNewRow(inputRange);
+    }
 
-      if (!_input) {
-        TRI_ASSERT(_state == ExecutionState::DONE);
-        return {_state, stats};
+    if (_cursorHasMore) {
+      TRI_ASSERT(_currentRow.isInitialized());
+      // if offset is > 0, we're in offset skip phase
+      if (offsetPhase) {
+        if (skipped < call.getOffset()) {
+          skipped += skipEntries(call.getOffset(), stats);
+        } else {
+          // we skipped enough in our offset phase
+          break;
+        }
+      } else {
+        // fullCount phase
+        _cursor->skipAll(skipped);
+        stats.incrScanned(skipped);
+        _documentProducingFunctionContext.getAndResetNumScanned();
+        TRI_ASSERT(_documentProducingFunctionContext.getAndResetNumScanned() == 0);
       }
-      _cursor->reset();
       _cursorHasMore = _cursor->hasMore();
-      continue;
+      call.didSkip(skipped);
     }
+  }
 
-    TRI_ASSERT(_input.isInitialized());
+  if (_cursorHasMore) {
+    return {ExecutorState::HASMORE, stats, call.getSkipCount(), upstreamCall};
+  }
 
-    TRI_IF_FAILURE("EnumerateCollectionBlock::moreDocuments") {
-      THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
-    }
+  upstreamCall.softLimit = call.getOffset();
+  return {inputRange.upstreamState(), stats, call.getSkipCount(), upstreamCall};
+}
 
-    if (_infos.getProduceResult()) {
-      // properly build up results by fetching the actual documents
-      // using nextDocument()
-      _cursorHasMore =
-          _cursor->nextDocument(_documentProducer, output.numRowsLeft() /*atMost*/);
-    } else {
-      // performance optimization: we do not need the documents at all,
-      // so just call next()
-      TRI_ASSERT(!_documentProducingFunctionContext.hasFilter());
-      _cursorHasMore =
-          _cursor->next(getNullCallback<false>(_documentProducingFunctionContext),
-                        output.numRowsLeft() /*atMost*/);
-    }
+void EnumerateCollectionExecutor::initializeNewRow(AqlItemBlockInputRange& inputRange) {
+  if (_currentRow) {
+    std::ignore = inputRange.nextDataRow();
+  }
+  std::tie(_currentRowState, _currentRow) = inputRange.peekDataRow();
+  if (!_currentRow) {
+    return;
+  }
 
-    stats.incrScanned(_documentProducingFunctionContext.getAndResetNumScanned());
-    stats.incrFiltered(_documentProducingFunctionContext.getAndResetNumFiltered());
+  TRI_ASSERT(_currentRow.isInitialized());
 
-    if (_state == ExecutionState::DONE && !_cursorHasMore) {
-      return {_state, stats};
-    }
-    return {ExecutionState::HASMORE, stats};
-  }
+  _cursor->reset();
+  _cursorHasMore = _cursor->hasMore();
 }
 
-std::tuple<ExecutionState, EnumerateCollectionStats, size_t> EnumerateCollectionExecutor::skipRows(
-    size_t const toSkip) {
-  EnumerateCollectionStats stats{};
-  TRI_IF_FAILURE("EnumerateCollectionExecutor::skipRows") {
+std::tuple<ExecutorState, EnumerateCollectionStats, AqlCall> EnumerateCollectionExecutor::produceRows(
+    AqlItemBlockInputRange& inputRange, OutputAqlItemRow& output) {
+  TRI_IF_FAILURE("EnumerateCollectionExecutor::produceRows") {
     THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
   }
 
-  if (!_cursorHasMore) {
-    std::tie(_state, _input) = _fetcher.fetchRow();
+  EnumerateCollectionStats stats{};
+  AqlCall upstreamCall{};
+  upstreamCall.fullCount = output.getClientCall().fullCount;
 
-    if (_state == ExecutionState::WAITING) {
-      return std::make_tuple(_state, stats, 0);  // tuple, cannot use initializer list due to build failure
-    }
+  TRI_ASSERT(_documentProducingFunctionContext.getAndResetNumScanned() == 0);
+  TRI_ASSERT(_documentProducingFunctionContext.getAndResetNumFiltered() == 0);
+  _documentProducingFunctionContext.setOutputRow(&output);
+
+  while (inputRange.hasDataRow() && !output.isFull()) {
 
-    if (!_input) {
-      TRI_ASSERT(_state == ExecutionState::DONE);
-      return std::make_tuple(_state, stats, 0);  // tuple, cannot use initializer list due to build failure
+    if (!_cursorHasMore) {
+      initializeNewRow(inputRange);
     }
 
-    _cursor->reset();
-    _cursorHasMore = _cursor->hasMore();
-  }
+    if (_cursorHasMore) {
+      TRI_ASSERT(_currentRow.isInitialized());
+      if (_infos.getProduceResult()) {
+        // properly build up results by fetching the actual documents
+        // using nextDocument()
+        _cursorHasMore =
+            _cursor->nextDocument(_documentProducer, output.numRowsLeft() /*atMost*/);
+      } else {
+        // performance optimization: we do not need the documents at all,
+        // so just call next()
+        TRI_ASSERT(!_documentProducingFunctionContext.hasFilter());
+        _cursorHasMore =
+            _cursor->next(getNullCallback<false>(_documentProducingFunctionContext),
+                          output.numRowsLeft() /*atMost*/);
+      }
 
-  TRI_ASSERT(_input.isInitialized());
-  TRI_ASSERT(_documentProducingFunctionContext.getAndResetNumScanned() == 0);
-  TRI_ASSERT(_documentProducingFunctionContext.getAndResetNumFiltered() == 0);
+      stats.incrScanned(_documentProducingFunctionContext.getAndResetNumScanned());
+      stats.incrFiltered(_documentProducingFunctionContext.getAndResetNumFiltered());
+    }
 
-  uint64_t actuallySkipped = 0;
-  if (_infos.getFilter() == nullptr) {
-    _cursor->skip(toSkip, actuallySkipped);
-    stats.incrScanned(actuallySkipped);
-    _documentProducingFunctionContext.getAndResetNumScanned();
-  } else {
-    _cursor->nextDocument(_documentSkipper, toSkip);
-    size_t filtered = _documentProducingFunctionContext.getAndResetNumFiltered();
-    size_t scanned = _documentProducingFunctionContext.getAndResetNumScanned();
-    TRI_ASSERT(scanned >= filtered);
-    stats.incrFiltered(filtered);
-    stats.incrScanned(scanned);
-    actuallySkipped = scanned - filtered;
+    TRI_IF_FAILURE("EnumerateCollectionBlock::moreDocuments") {
+      THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
+    }
   }
-  _cursorHasMore = _cursor->hasMore();
 
-  if (_state == ExecutionState::DONE && !_cursorHasMore) {
-    return std::make_tuple(ExecutionState::DONE, stats,
-                           actuallySkipped);  // tuple, cannot use initializer list due to build failure
+  if (!_cursorHasMore) {
+    initializeNewRow(inputRange);
   }
 
-  return std::make_tuple(ExecutionState::HASMORE, stats, actuallySkipped);  // tuple, cannot use initializer list due to build failure
+  return {inputRange.upstreamState(), stats, upstreamCall};
 }
 
 void EnumerateCollectionExecutor::initializeCursor() {
   _state = ExecutionState::HASMORE;
-  _input = InputAqlItemRow{CreateInvalidInputRowHint{}};
+  _executorState = ExecutorState::HASMORE;
+  _currentRow = InputAqlItemRow{CreateInvalidInputRowHint{}};
   _cursorHasMore = false;
   _cursor->reset();
 }
-
 #ifndef USE_ENTERPRISE
 bool EnumerateCollectionExecutor::waitForSatellites(ExecutionEngine* engine,
                                                     Collection const* collection) const {
diff --git a/arangod/Aql/EnumerateCollectionExecutor.h b/arangod/Aql/EnumerateCollectionExecutor.h
index ff9b51127f52..31aa9446c41a 100644
--- a/arangod/Aql/EnumerateCollectionExecutor.h
+++ b/arangod/Aql/EnumerateCollectionExecutor.h
@@ -43,6 +43,8 @@ class Methods;
 }
 namespace aql {
 
+struct AqlCall;
+class AqlItemBlockInputRange;
 struct Collection;
 class EnumerateCollectionStats;
 class ExecutionEngine;
@@ -62,8 +64,8 @@ class EnumerateCollectionExecutorInfos : public ExecutorInfos {
       RegisterId nrOutputRegisters, std::unordered_set<RegisterId> registersToClear,
       std::unordered_set<RegisterId> registersToKeep, ExecutionEngine* engine,
       Collection const* collection, Variable const* outVariable, bool produceResult,
-      Expression* filter,
-      std::vector<std::string> const& projections,
+      Expression* filter, std::vector<std::string> const& projections,
+      std::vector<size_t> const& coveringIndexAttributePositions,
       bool useRawDocumentPointers, bool random);
 
   EnumerateCollectionExecutorInfos() = delete;
@@ -78,6 +80,7 @@ class EnumerateCollectionExecutorInfos : public ExecutorInfos {
   transaction::Methods* getTrxPtr() const;
   Expression* getFilter() const;
   std::vector<std::string> const& getProjections() const noexcept;
+  std::vector<size_t> const& getCoveringIndexAttributePositions() const noexcept;
   bool getProduceResult() const;
   bool getUseRawDocumentPointers() const;
   bool getRandom() const;
@@ -89,6 +92,7 @@ class EnumerateCollectionExecutorInfos : public ExecutorInfos {
   Variable const* _outVariable;
   Expression* _filter;
   std::vector<std::string> const& _projections;
+  std::vector<size_t> const& _coveringIndexAttributePositions;
   RegisterId _outputRegisterId;
   bool _useRawDocumentPointers;
   bool _produceResult;
@@ -117,6 +121,13 @@ class EnumerateCollectionExecutor {
   EnumerateCollectionExecutor(Fetcher& fetcher, Infos&);
   ~EnumerateCollectionExecutor();
 
+  /**
+   * @brief Will fetch a new InputRow if necessary and store their local state
+   *
+   * @return bool done in case we do not have any input and upstreamState is done
+   */
+  void initializeNewRow(AqlItemBlockInputRange& inputRange);
+
   /**
    * @brief produce the next Row of Aql Values.
    *
@@ -126,11 +137,30 @@ class EnumerateCollectionExecutor {
   std::pair<ExecutionState, Stats> produceRows(OutputAqlItemRow& output);
   std::tuple<ExecutionState, EnumerateCollectionStats, size_t> skipRows(size_t atMost);
 
+  /**
+   * @brief produce the next Rows of Aql Values.
+   *
+   * @return ExecutorState, the stats, and a new Call that needs to be send to upstream
+   */
+  [[nodiscard]] std::tuple<ExecutorState, Stats, AqlCall> produceRows(
+      AqlItemBlockInputRange& input, OutputAqlItemRow& output);
+
+  uint64_t skipEntries(size_t toSkip, EnumerateCollectionStats& stats);
+  /**
+   * @brief skip the next Row of Aql Values.
+   *
+   * @return ExecutorState, the stats, and a new Call that needs to be send to upstream
+   */
+  [[nodiscard]] std::tuple<ExecutorState, Stats, size_t, AqlCall> skipRowsRange(
+      AqlItemBlockInputRange& inputRange, AqlCall& call);
+
   void initializeCursor();
 
  private:
   bool waitForSatellites(ExecutionEngine* engine, Collection const* collection) const;
 
+  void setAllowCoveringIndexOptimization(bool allowCoveringIndexOptimization);
+
  private:
   Infos& _infos;
   Fetcher& _fetcher;
@@ -138,8 +168,10 @@ class EnumerateCollectionExecutor {
   IndexIterator::DocumentCallback _documentSkipper;
   DocumentProducingFunctionContext _documentProducingFunctionContext;
   ExecutionState _state;
+  ExecutorState _executorState;
   bool _cursorHasMore;
-  InputAqlItemRow _input;
+  InputAqlItemRow _currentRow;
+  ExecutorState _currentRowState;
   std::unique_ptr<OperationCursor> _cursor;
 };
 
diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index 7a0333327d6f..dbb8bdbac935 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -136,7 +136,10 @@ constexpr bool is_one_of_v = (std::is_same_v<T, Es> || ...);
 template <typename Executor>
 constexpr bool isNewStyleExecutor =
     is_one_of_v<Executor, FilterExecutor, SortedCollectExecutor, IdExecutor<ConstFetcher>,
-                IdExecutor<SingleRowFetcher<BlockPassthrough::Enable>>, ReturnExecutor, HashedCollectExecutor, IndexExecutor,
+                IdExecutor<SingleRowFetcher<BlockPassthrough::Enable>>, ReturnExecutor, IndexExecutor, EnumerateCollectionExecutor,
+                // TODO: re-enable after new subquery end & start are implemented
+                // CalculationExecutor<CalculationType::Condition>, CalculationExecutor<CalculationType::Reference>, CalculationExecutor<CalculationType::V8Condition>,
+                HashedCollectExecutor,
 #ifdef ARANGODB_USE_GOOGLE_TESTS
                 TestLambdaExecutor,
                 TestLambdaSkipExecutor,  // we need one after these to avoid compile errors in non-test mode
@@ -1075,7 +1078,8 @@ static SkipRowsRangeVariant constexpr skipRowsType() {
                 "Fetcher is chosen for skipping, but has not skipRows method!");
 
   static_assert(useExecutor ==
-                    (is_one_of_v<Executor, FilterExecutor, ShortestPathExecutor, ReturnExecutor, HashedCollectExecutor, IndexExecutor,
+                    (is_one_of_v<Executor, FilterExecutor, ShortestPathExecutor, ReturnExecutor,
+                                 HashedCollectExecutor, IndexExecutor, EnumerateCollectionExecutor,
 #ifdef ARANGODB_USE_GOOGLE_TESTS
                                  TestLambdaSkipExecutor,
 #endif
diff --git a/arangod/Aql/ExecutionNode.cpp b/arangod/Aql/ExecutionNode.cpp
index 2ef0d5475fdd..184d1768c20e 100644
--- a/arangod/Aql/ExecutionNode.cpp
+++ b/arangod/Aql/ExecutionNode.cpp
@@ -1351,7 +1351,7 @@ std::unique_ptr<ExecutionBlock> EnumerateCollectionNode::createBlock(
       getRegisterPlan()->nrRegs[getDepth()], getRegsToClear(), calcRegsToKeep(),
       &engine, this->_collection, _outVariable,
       (this->isVarUsedLater(_outVariable) || this->_filter != nullptr),
-      this->_filter.get(), this->projections(),
+      this->_filter.get(), this->projections(), this->coveringIndexAttributePositions(),
       EngineSelectorFeature::ENGINE->useRawDocumentPointers(), this->_random);
   return std::make_unique<ExecutionBlockImpl<EnumerateCollectionExecutor>>(&engine, this,
                                                                            std::move(infos));
diff --git a/arangod/Aql/FilterExecutor.cpp b/arangod/Aql/FilterExecutor.cpp
index cb0d06bb60af..515c72fdfce4 100644
--- a/arangod/Aql/FilterExecutor.cpp
+++ b/arangod/Aql/FilterExecutor.cpp
@@ -28,7 +28,6 @@
 #include "Aql/AqlCall.h"
 #include "Aql/AqlCallStack.h"
 #include "Aql/AqlItemBlockInputRange.h"
-#include "Aql/AqlValue.h"
 #include "Aql/ExecutorInfos.h"
 #include "Aql/InputAqlItemRow.h"
 #include "Aql/OutputAqlItemRow.h"
diff --git a/arangod/Utils/OperationCursor.cpp b/arangod/Utils/OperationCursor.cpp
index df98e0c6d7d7..e6030a9dc83d 100644
--- a/arangod/Utils/OperationCursor.cpp
+++ b/arangod/Utils/OperationCursor.cpp
@@ -129,3 +129,25 @@ void OperationCursor::skip(uint64_t toSkip, uint64_t& skipped) {
     _hasMore = false;
   }
 }
+
+/// @brief Skip all elements.
+///        skipped will be increased by the amount of skipped elements
+///        afterwards Check hasMore()==true before using this NOTE: This will
+///        throw on OUT_OF_MEMORY
+void OperationCursor::skipAll(uint64_t& skipped) {
+  // TODO: move that logic to index level to become more efficient
+  size_t toSkip = 1000;
+
+  if (!hasMore()) {
+    TRI_ASSERT(false);
+    // You requested more even if you should have checked it before.
+    return;
+  }
+
+  while (_hasMore) {
+    _indexIterator->skip(toSkip, skipped);
+    if (skipped != toSkip) {
+      _hasMore = false;
+    }
+  }
+}
diff --git a/arangod/Utils/OperationCursor.h b/arangod/Utils/OperationCursor.h
index 5afb3cf5232c..05a0f955c991 100644
--- a/arangod/Utils/OperationCursor.h
+++ b/arangod/Utils/OperationCursor.h
@@ -114,6 +114,12 @@ struct OperationCursor {
   ///        afterwards Check hasMore()==true before using this NOTE: This will
   ///        throw on OUT_OF_MEMORY
   void skip(uint64_t toSkip, uint64_t& skipped);
+
+  /// @brief skip all elements.
+  ///        skipped will be increased by the amount of skipped elements
+  ///        afterwards Check hasMore()==true before using this NOTE: This will
+  ///        throw on OUT_OF_MEMORY
+  void skipAll(uint64_t& skipped);
 };
 
 }  // namespace arangodb
diff --git a/tests/Aql/CalculationExecutorTest.cpp b/tests/Aql/CalculationExecutorTest.cpp
index 80f79f67eed5..878b5323668b 100644
--- a/tests/Aql/CalculationExecutorTest.cpp
+++ b/tests/Aql/CalculationExecutorTest.cpp
@@ -25,12 +25,14 @@
 
 #include "gtest/gtest.h"
 
+#include "Aql/AqlCall.h"
+#include "AqlItemBlockHelper.h"
+#include "ExecutorTestHelper.h"
 #include "RowFetcherHelper.h"
 
 #include "Aql/AqlItemBlock.h"
 #include "Aql/Ast.h"
 #include "Aql/CalculationExecutor.h"
-#include "Aql/ExecutionBlockImpl.h"
 #include "Aql/ExecutionPlan.h"
 #include "Aql/Expression.h"
 #include "Aql/OutputAqlItemRow.h"
@@ -67,13 +69,10 @@ namespace aql {
 // CalculationExecutor<CalculationType::V8Condition> and
 // CalculationExecutor<CalculationType::Reference>!
 
-class CalculationExecutorTest : public ::testing::Test {
+class CalculationExecutorTest : public AqlExecutorTestCase<true> {
  protected:
   ExecutionState state;
-  ResourceMonitor monitor;
   AqlItemBlockManager itemBlockManager;
-  mocks::MockAqlServer server;
-  std::unique_ptr<arangodb::aql::Query> fakedQuery;
   Ast ast;
   AstNode* one;
   Variable var;
@@ -87,8 +86,6 @@ class CalculationExecutorTest : public ::testing::Test {
 
   CalculationExecutorTest()
       : itemBlockManager(&monitor, SerializationFormat::SHADOWROWS),
-        server(),
-        fakedQuery(server.createFakeQuery()),
         ast(fakedQuery.get()),
         one(ast.createNodeValueInt(1)),
         var("a", 0),
@@ -109,7 +106,8 @@ class CalculationExecutorTest : public ::testing::Test {
 TEST_F(CalculationExecutorTest, there_are_no_rows_upstream_the_producer_does_not_wait) {
   SharedAqlItemBlockPtr block{new AqlItemBlock(itemBlockManager, 1000, 2)};
   VPackBuilder input;
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Enable> fetcher(itemBlockManager, input.steal(), false);
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Enable> fetcher(
+      itemBlockManager, input.steal(), false);
   CalculationExecutor<CalculationType::Condition> testee(fetcher, infos);
   // Use this instead of std::ignore, so the tests will be noticed and
   // updated when someone changes the stats type in the return value of
@@ -126,7 +124,8 @@ TEST_F(CalculationExecutorTest, there_are_no_rows_upstream_the_producer_does_not
 TEST_F(CalculationExecutorTest, there_are_no_rows_upstream_the_producer_waits) {
   SharedAqlItemBlockPtr block{new AqlItemBlock(itemBlockManager, 1000, 2)};
   VPackBuilder input;
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Enable> fetcher(itemBlockManager, input.steal(), true);
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Enable> fetcher(
+      itemBlockManager, input.steal(), true);
   CalculationExecutor<CalculationType::Condition> testee(fetcher, infos);
   // Use this instead of std::ignore, so the tests will be noticed and
   // updated when someone changes the stats type in the return value of
@@ -147,7 +146,8 @@ TEST_F(CalculationExecutorTest, there_are_no_rows_upstream_the_producer_waits) {
 TEST_F(CalculationExecutorTest, there_are_rows_in_the_upstream_the_producer_does_not_wait) {
   SharedAqlItemBlockPtr block{new AqlItemBlock(itemBlockManager, 1000, 2)};
   auto input = VPackParser::fromJson("[ [0], [1], [2] ]");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Enable> fetcher(itemBlockManager, input->steal(), false);
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Enable> fetcher(
+      itemBlockManager, input->steal(), false);
   CalculationExecutor<CalculationType::Condition> testee(fetcher, infos);
   NoStats stats{};
 
@@ -191,7 +191,8 @@ TEST_F(CalculationExecutorTest, there_are_rows_in_the_upstream_the_producer_does
 TEST_F(CalculationExecutorTest, there_are_rows_in_the_upstream_the_producer_waits) {
   SharedAqlItemBlockPtr block{new AqlItemBlock(itemBlockManager, 1000, 2)};
   auto input = VPackParser::fromJson("[ [0], [1], [2] ]");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Enable> fetcher(itemBlockManager, input->steal(), true);
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Enable> fetcher(
+      itemBlockManager, input->steal(), true);
   CalculationExecutor<CalculationType::Condition> testee(fetcher, infos);
   NoStats stats{};
 
@@ -236,6 +237,126 @@ TEST_F(CalculationExecutorTest, there_are_rows_in_the_upstream_the_producer_wait
   ASSERT_FALSE(row.produced());
 }
 
+TEST_F(CalculationExecutorTest, test_produce_datarange) {
+  // This fetcher will not be called!
+  // After Execute is done this fetcher shall be removed, the Executor does not need it anymore!
+  auto fakeUnusedBlock = VPackParser::fromJson("[  ]");
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Enable> fetcher(
+      itemBlockManager, fakeUnusedBlock->steal(), false);
+
+  // This is the relevant part of the test
+  SharedAqlItemBlockPtr block{new AqlItemBlock(itemBlockManager, 1000, 2)};
+  CalculationExecutor<CalculationType::Condition> testee(fetcher, infos);
+  SharedAqlItemBlockPtr inBlock =
+      buildBlock<1>(itemBlockManager, {{R"(0)"}, {R"(1)"}, {R"(2)"}});
+
+  AqlItemBlockInputRange input{ExecutorState::DONE, inBlock, 0, inBlock->size()};
+  OutputAqlItemRow output(std::move(block), infos.getOutputRegisters(),
+                          infos.registersToKeep(), infos.registersToClear());
+  EXPECT_EQ(output.numRowsWritten(), 0);
+  auto const [state, stats, call] = testee.produceRows(input, output);
+  EXPECT_EQ(output.numRowsWritten(), 3);
+
+  EXPECT_EQ(state, ExecutorState::DONE);
+  // verify calculation
+  {
+    AqlValue value;
+    auto block = output.stealBlock();
+    for (std::size_t index = 0; index < 3; index++) {
+      value = block->getValue(index, outRegID);
+      ASSERT_TRUE(value.isNumber());
+      ASSERT_EQ(value.toInt64(), static_cast<int64_t>(index + 1));
+    }
+  }
+}
+
+TEST_F(CalculationExecutorTest, test_produce_datarange_need_more) {
+  // This fetcher will not be called!
+  // After Execute is done this fetcher shall be removed, the Executor does not need it anymore!
+  auto fakeUnusedBlock = VPackParser::fromJson("[  ]");
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Enable> fetcher(
+      itemBlockManager, fakeUnusedBlock->steal(), false);
+
+  // This is the relevant part of the test
+  SharedAqlItemBlockPtr block{new AqlItemBlock(itemBlockManager, 1000, 2)};
+  CalculationExecutor<CalculationType::Condition> testee(fetcher, infos);
+  SharedAqlItemBlockPtr inBlock =
+      buildBlock<1>(itemBlockManager, {{R"(0)"}, {R"(1)"}, {R"(2)"}});
+
+  AqlItemBlockInputRange input{ExecutorState::HASMORE, inBlock, 0, inBlock->size()};
+  OutputAqlItemRow output(std::move(block), infos.getOutputRegisters(),
+                          infos.registersToKeep(),
+                          infos.registersToClear(),
+                              AqlCall{0, 3, AqlCall::Infinity{}, false});
+
+  auto myCall = output.getClientCall();
+  EXPECT_EQ(myCall.getLimit(), 3);
+  EXPECT_EQ(output.numRowsWritten(), 0);
+
+  auto const [state, stats, outputCall] = testee.produceRows(input, output);
+  EXPECT_EQ(output.numRowsWritten(), 3);
+
+  EXPECT_EQ(state, ExecutorState::HASMORE);
+  // verify calculation
+  {
+    AqlValue value;
+    auto block = output.stealBlock();
+    for (std::size_t index = 0; index < 3; index++) {
+      value = block->getValue(index, outRegID);
+      ASSERT_TRUE(value.isNumber());
+      ASSERT_EQ(value.toInt64(), static_cast<int64_t>(index + 1));
+    }
+  }
+  // Test the Call we send to upstream
+  EXPECT_EQ(outputCall.offset, 0);
+  EXPECT_FALSE(outputCall.hasHardLimit());
+  // Avoid overfetching. I do not have a strong requirement on this
+  // test, however this is what we do right now.
+  EXPECT_EQ(outputCall.getLimit(), 0);
+  EXPECT_FALSE(outputCall.fullCount);
+}
+
+TEST_F(CalculationExecutorTest, DISABLED_test_produce_datarange_has_more) { // TODO: fix and re-enable after this executor newStyle is active
+  // This fetcher will not be called!
+  // After Execute is done this fetcher shall be removed, the Executor does not need it anymore!
+  auto fakeUnusedBlock = VPackParser::fromJson("[  ]");
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Enable> fetcher(
+      itemBlockManager, fakeUnusedBlock->steal(), false);
+
+  // This is the relevant part of the test
+  SharedAqlItemBlockPtr block{new AqlItemBlock(itemBlockManager, 1000, 2)};
+  CalculationExecutor<CalculationType::Condition> testee(fetcher, infos);
+  SharedAqlItemBlockPtr inBlock =
+      buildBlock<1>(itemBlockManager, {{R"(0)"}, {R"(1)"}, {R"(2)"}, {R"(3)"}, {R"(4)"}});
+
+  AqlItemBlockInputRange input{ExecutorState::DONE, inBlock, 0, inBlock->size()};
+  OutputAqlItemRow output(std::move(block), infos.getOutputRegisters(),
+                          infos.registersToKeep(), infos.registersToClear());
+  EXPECT_EQ(output.numRowsWritten(), 0);
+  AqlCall myCall{0, 3, AqlCall::Infinity{}, false};
+  output.setCall(std::move(myCall));
+
+  auto const [state, stats, call] = testee.produceRows(input, output);
+  EXPECT_EQ(output.numRowsWritten(), 3);
+
+  EXPECT_EQ(state, ExecutorState::HASMORE);
+  EXPECT_TRUE(input.hasDataRow());
+  // We still have two values in block: 3 and 4
+  {
+    // pop 3
+    auto const [state, row] = input.nextDataRow();
+    EXPECT_EQ(state, ExecutorState::HASMORE);
+    EXPECT_EQ(row.getValue(0).toInt64(), 3);
+  }
+  {
+    // pop 4
+    auto const [state, row] = input.nextDataRow();
+    EXPECT_EQ(state, ExecutorState::DONE);
+    EXPECT_EQ(row.getValue(0).toInt64(), 4);
+  }
+  EXPECT_FALSE(input.hasDataRow());
+}
+
 }  // namespace aql
 }  // namespace tests
 }  // namespace arangodb
diff --git a/tests/Aql/EnumerateCollectionExecutorTest.cpp b/tests/Aql/EnumerateCollectionExecutorTest.cpp
index fea5b93c5bfe..5f3419c43621 100644
--- a/tests/Aql/EnumerateCollectionExecutorTest.cpp
+++ b/tests/Aql/EnumerateCollectionExecutorTest.cpp
@@ -25,12 +25,16 @@
 
 #include "gtest/gtest.h"
 
+#include "Aql/AqlCall.h"
+#include "AqlItemBlockHelper.h"
+#include "ExecutorTestHelper.h"
 #include "IResearch/common.h"
 #include "Mocks/Servers.h"
+#include "QueryHelper.h"
 #include "RowFetcherHelper.h"
-#include "fakeit.hpp"
 
 #include "Aql/AqlItemBlock.h"
+#include "Aql/Ast.h"
 #include "Aql/Collection.h"
 #include "Aql/EnumerateCollectionExecutor.h"
 #include "Aql/ExecutionBlockImpl.h"
@@ -39,17 +43,14 @@
 #include "Aql/ResourceUsage.h"
 #include "Aql/Stats.h"
 #include "Aql/Variable.h"
-#include "Mocks/StorageEngineMock.h"
 #include "RestServer/QueryRegistryFeature.h"
 #include "Sharding/ShardingFeature.h"
 #include "StorageEngine/EngineSelectorFeature.h"
-#include "StorageEngine/StorageEngine.h"
 #include "Transaction/Context.h"
 #include "Transaction/Methods.h"
 #include "VocBase/AccessMode.h"
 #include "VocBase/LogicalCollection.h"
 
-#include <velocypack/Builder.h>
 #include <velocypack/velocypack-aliases.h>
 #include <functional>
 
@@ -60,29 +61,31 @@ namespace arangodb {
 namespace tests {
 namespace aql {
 
+// old tests
+
+static const std::string GetAllDocs =
+    R"aql(FOR doc IN UnitTestCollection SORT doc.sortValue RETURN doc.value)aql";
+
 using CursorType = arangodb::transaction::Methods::CursorType;
 
-class EnumerateCollectionExecutorTestNoRowsUpstream : public ::testing::Test {
+class EnumerateCollectionExecutorTest : public AqlExecutorTestCase<true> {
  protected:
   ExecutionState state;
-  ResourceMonitor monitor;
   AqlItemBlockManager itemBlockManager;
-  arangodb::tests::mocks::MockAqlServer server;
-  TRI_vocbase_t vocbase;  // required to create collection
+  TRI_vocbase_t& vocbase;
   std::shared_ptr<VPackBuilder> json;
-  arangodb::LogicalCollection collection;
-  fakeit::Mock<ExecutionEngine> mockEngine;
-  fakeit::Mock<transaction::Methods> mockTrx;  // fake transaction::Methods
-  fakeit::Mock<Query> mockQuery;
+  std::shared_ptr<LogicalCollection> collection;
+
+  Ast ast;
 
   Variable outVariable;
   bool varUsedLater;
   std::unordered_set<RegisterId> const regToClear;
   std::unordered_set<RegisterId> const regToKeep;
-  ExecutionEngine& engine;
-  Collection abc;
+  ExecutionEngine* engine;
+  Collection aqlCollection;
   std::vector<std::string> const projections;
-  transaction::Methods& trx;
+  std::vector<size_t> const coveringIndexAttributePositions;
   bool useRawPointers;
   bool random;
 
@@ -91,71 +94,338 @@ class EnumerateCollectionExecutorTestNoRowsUpstream : public ::testing::Test {
   SharedAqlItemBlockPtr block;
   VPackBuilder input;
 
-  EnumerateCollectionExecutorTestNoRowsUpstream()
+  EnumerateCollectionExecutorTest()
       : itemBlockManager(&monitor, SerializationFormat::SHADOWROWS),
-        server(),
-        vocbase(TRI_vocbase_type_e::TRI_VOCBASE_TYPE_NORMAL, systemDBInfo(server.server())),
-        json(arangodb::velocypack::Parser::fromJson(
-            "{ \"cid\" : \"1337\", \"name\": \"UnitTestCollection\" }")),
-        collection(vocbase, json->slice(), true),
+        vocbase(_server->getSystemDatabase()),
+        json(VPackParser::fromJson(R"({"name":"UnitTestCollection"})")),
+        // collection(),
+        // fakedQuery(server.createFakeQuery(false, "return 1")),
+        ast(fakedQuery.get()),
         outVariable("name", 1),
         varUsedLater(false),
-        engine(mockEngine.get()),
-        abc("blabli", &vocbase, arangodb::AccessMode::Type::READ),
-        trx(mockTrx.get()),
+        engine(fakedQuery->engine()),
+        aqlCollection("UnitTestCollection", &vocbase, arangodb::AccessMode::Type::READ),
         useRawPointers(false),
         random(false),
-        infos(0 /*outReg*/, 1 /*nrIn*/, 1 /*nrOut*/, regToClear, regToKeep,
-              &engine, &abc, &outVariable, varUsedLater, nullptr, projections,
-              useRawPointers, random),
+        infos(0 /*outReg*/, 1 /*nrIn*/, 1 /*nrOut*/, regToClear, regToKeep, engine,
+              &aqlCollection, &outVariable, varUsedLater, nullptr, projections,
+              coveringIndexAttributePositions, useRawPointers, random),
         block(new AqlItemBlock(itemBlockManager, 1000, 2)) {
-    // fake indexScan
-    fakeit::When(Method(mockTrx, indexScan))
-        .AlwaysDo(std::function<std::unique_ptr<IndexIterator>(std::string const&, CursorType&)>(
-            [this](std::string const&, CursorType&) -> std::unique_ptr<IndexIterator> {
-              return std::make_unique<EmptyIndexIterator>(&collection, &(mockTrx.get()));
-            }));
-    
-    Query& query = mockQuery.get();
-    fakeit::When(Method(mockQuery, trx)).AlwaysReturn(&(mockTrx.get()));
-    fakeit::When(Method(mockEngine, getQuery)).AlwaysReturn(&query);
+    try {
+      collection = vocbase.createCollection(json->slice());
+    } catch (std::exception const& e) {
+      // ignore, already created the collection
+    }
   }
 };
 
-TEST_F(EnumerateCollectionExecutorTestNoRowsUpstream, the_producer_does_not_wait) {
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input.steal(), false);
+TEST_F(EnumerateCollectionExecutorTest, the_produce_datarange_empty) {
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, input.steal(), false);
+  EnumerateCollectionExecutor testee(fetcher, infos);
+  // Use this instead of std::ignore, so the tests will be noticed and
+  // updated when someone changes the stats type in the return value of
+  // EnumerateCollectionExecutor::produceRows().
+
+  SharedAqlItemBlockPtr inBlock = buildBlock<1>(itemBlockManager, {{}});
+
+  AqlItemBlockInputRange inputRange{ExecutorState::DONE, inBlock, 0, inBlock->size()};
+  OutputAqlItemRow output(std::move(block), infos.getOutputRegisters(),
+                          infos.registersToKeep(), infos.registersToClear());
+
+  auto const [state, stats, call] = testee.produceRows(inputRange, output);
+  ASSERT_EQ(state, ExecutorState::DONE);
+  ASSERT_FALSE(output.produced());
+}
+
+TEST_F(EnumerateCollectionExecutorTest, the_skip_datarange_empty) {
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, input.steal(), false);
+  EnumerateCollectionExecutor testee(fetcher, infos);
+  // Use this instead of std::ignore, so the tests will be noticed and
+  // updated when someone changes the stats type in the return value of
+  // EnumerateCollectionExecutor::produceRows().
+
+  SharedAqlItemBlockPtr inBlock = buildBlock<1>(itemBlockManager, {{}});
+
+  AqlItemBlockInputRange inputRange{ExecutorState::DONE, inBlock, 0, inBlock->size()};
+  OutputAqlItemRow output(std::move(block), infos.getOutputRegisters(),
+                          infos.registersToKeep(), infos.registersToClear());
+  AqlCall skipCall{1000, AqlCall::Infinity{}, AqlCall::Infinity{}, false};
+  auto const [state, stats, skipped, call] = testee.skipRowsRange(inputRange, skipCall);
+  ASSERT_EQ(state, ExecutorState::DONE);
+  ASSERT_EQ(skipped, 0);
+  ASSERT_FALSE(output.produced());
+}
+
+TEST_F(EnumerateCollectionExecutorTest, the_produce_datarange) {
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, input.steal(), false);
   EnumerateCollectionExecutor testee(fetcher, infos);
   // Use this instead of std::ignore, so the tests will be noticed and
   // updated when someone changes the stats type in the return value of
   // EnumerateCollectionExecutor::produceRows().
-  EnumerateCollectionStats stats{};
 
-  OutputAqlItemRow result(std::move(block), infos.getOutputRegisters(),
+  SharedAqlItemBlockPtr inBlock =
+      buildBlock<1>(itemBlockManager,
+                    {{R"({ "cid" : "1337", "name": "UnitTestCollection" })"}});
+
+  // insert 3x documents
+  std::string insertQuery =
+      R"aql(INSERT {_key: "testee", value: 1, sortValue: 1, nestedObject: {value: 1} } INTO UnitTestCollection)aql";
+  SCOPED_TRACE(insertQuery);
+  AssertQueryHasResult(vocbase, insertQuery, VPackSlice::emptyArraySlice());
+  auto expected = VPackParser::fromJson(R"([1])");
+  AssertQueryHasResult(vocbase, GetAllDocs, expected->slice());
+
+  std::string insertQueryB =
+      R"aql(INSERT {_key: "testeeB", value: 1, sortValue: 1, nestedObject: {value: 1} } INTO UnitTestCollection)aql";
+  SCOPED_TRACE(insertQueryB);
+  AssertQueryHasResult(vocbase, insertQueryB, VPackSlice::emptyArraySlice());
+
+  std::string insertQueryC =
+      R"aql(INSERT {_key: "testeeC", value: 1, sortValue: 1, nestedObject: {value: 1} } INTO UnitTestCollection)aql";
+  SCOPED_TRACE(insertQueryC);
+  AssertQueryHasResult(vocbase, insertQueryC, VPackSlice::emptyArraySlice());
+
+  AqlItemBlockInputRange inputRange{ExecutorState::DONE, inBlock, 0, inBlock->size()};
+  OutputAqlItemRow output(std::move(block), infos.getOutputRegisters(),
                           infos.registersToKeep(), infos.registersToClear());
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(result.produced());
+
+  auto const [state, stats, call] = testee.produceRows(inputRange, output);
+  ASSERT_EQ(state, ExecutorState::DONE);
+  ASSERT_EQ(stats.getFiltered(), 0);
+  ASSERT_EQ(stats.getScanned(), 3);
+  ASSERT_FALSE(output.produced());
 }
 
-TEST_F(EnumerateCollectionExecutorTestNoRowsUpstream, the_producer_waits) {
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input.steal(), true);
+TEST_F(EnumerateCollectionExecutorTest, the_skip_datarange) {
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, input.steal(), false);
   EnumerateCollectionExecutor testee(fetcher, infos);
   // Use this instead of std::ignore, so the tests will be noticed and
   // updated when someone changes the stats type in the return value of
   // EnumerateCollectionExecutor::produceRows().
-  EnumerateCollectionStats stats{};
 
-  OutputAqlItemRow result(std::move(block), infos.getOutputRegisters(),
+  SharedAqlItemBlockPtr inBlock =
+      buildBlock<1>(itemBlockManager,
+                    {{R"({ "cid" : "1337", "name": "UnitTestCollection" })"}});
+
+  /* WE ALREADY inserted 3x documents in the test before TODO: clean this up -> proper setup/teardown
+  // insert 3x documents
+  std::string insertQuery =
+      R"aql(INSERT {_key: "testee", value: 1, sortValue: 1, nestedObject: {value: 1} } INTO UnitTestCollection)aql";
+  SCOPED_TRACE(insertQuery);
+  AssertQueryHasResult(vocbase, insertQuery, VPackSlice::emptyArraySlice());
+  auto expected = VPackParser::fromJson(R"([1])");
+  AssertQueryHasResult(vocbase, GetAllDocs, expected->slice());
+
+  std::string insertQueryB =
+      R"aql(INSERT {_key: "testeeB", value: 1, sortValue: 1, nestedObject: {value: 1} } INTO UnitTestCollection)aql";
+  SCOPED_TRACE(insertQueryB);
+  AssertQueryHasResult(vocbase, insertQueryB, VPackSlice::emptyArraySlice());
+
+  std::string insertQueryC =
+      R"aql(INSERT {_key: "testeeC", value: 1, sortValue: 1, nestedObject: {value: 1} } INTO UnitTestCollection)aql";
+  SCOPED_TRACE(insertQueryC);
+  AssertQueryHasResult(vocbase, insertQueryC, VPackSlice::emptyArraySlice());
+   */
+  AqlItemBlockInputRange inputRange{ExecutorState::DONE, inBlock, 0, inBlock->size()};
+  OutputAqlItemRow output(std::move(block), infos.getOutputRegisters(),
                           infos.registersToKeep(), infos.registersToClear());
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::WAITING);
-  ASSERT_FALSE(result.produced());
 
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(result.produced());
+  AqlCall skipCall{1000, AqlCall::Infinity{}, AqlCall::Infinity{}, false};
+  auto const [state, stats, skipped, call] = testee.skipRowsRange(inputRange, skipCall);
+  ASSERT_EQ(state, ExecutorState::DONE);
+  ASSERT_EQ(skipped, 3);
+  ASSERT_FALSE(output.produced());
+}
+
+// new framework tests
+
+// This is only to get a split-type. The Type is independent of actual template parameters
+using EnumerateCollectionTestHelper =
+    ExecutorTestHelper<1, 1>;
+using EnumerateCollectionSplitType = EnumerateCollectionTestHelper::SplitType;
+using EnumerateCollectionInputParam = std::tuple<EnumerateCollectionSplitType>;
+
+class EnumerateCollectionExecutorTestProduce
+    : public AqlExecutorTestCaseWithParam<EnumerateCollectionInputParam> {
+ protected:
+  ResourceMonitor monitor;
+  AqlItemBlockManager itemBlockManager;
+
+  TRI_vocbase_t& vocbase;
+  std::shared_ptr<VPackBuilder> json;
+  std::shared_ptr<LogicalCollection> collection;
+
+  SharedAqlItemBlockPtr block;
+  NoStats stats;
+  Ast ast;
+
+  // needed for infos
+  Variable outVariable;
+  bool varUsedLater;
+  ExecutionEngine* engine;
+  std::vector<std::string> const projections;
+  std::vector<size_t> const coveringIndexAttributePositions;
+  Collection aqlCollection;
+  bool useRawPointers;
+  bool random;
+
+  EnumerateCollectionExecutorInfos infos;
+
+  EnumerateCollectionExecutorTestProduce()
+      : itemBlockManager(&monitor, SerializationFormat::SHADOWROWS),
+        vocbase(_server->getSystemDatabase()),
+        json(VPackParser::fromJson(R"({"name":"UnitTestCollection"})")),
+        collection(vocbase.createCollection(json->slice())),
+        ast(fakedQuery.get()),
+        outVariable("name", 1),
+        varUsedLater(true),
+        engine(fakedQuery.get()->engine()),
+        aqlCollection("UnitTestCollection", &vocbase, arangodb::AccessMode::Type::READ),
+        useRawPointers(false),
+        random(false),
+        infos(1, 1, 2, {}, {}, engine, &aqlCollection, &outVariable, varUsedLater, nullptr,
+              projections, coveringIndexAttributePositions, useRawPointers, random) {
+  }
+
+  auto makeInfos(RegisterId outputRegister = 0, RegisterId nrInputRegister = 1,
+                 RegisterId nrOutputRegister = 1,
+                 std::unordered_set<RegisterId> regToClear = {},
+                 std::unordered_set<RegisterId> regToKeep = {})
+      -> EnumerateCollectionExecutorInfos {
+    EnumerateCollectionExecutorInfos infos{
+        outputRegister, nrInputRegister, nrOutputRegister,
+        regToClear,     regToKeep,       engine,
+        &aqlCollection, &outVariable,    varUsedLater,
+        nullptr,        projections,     coveringIndexAttributePositions,
+        useRawPointers, random};
+    block = SharedAqlItemBlockPtr{new AqlItemBlock(itemBlockManager, 1000, nrOutputRegister)};
+    return infos;
+  }
+
+  // insert amount of documents into the vocbase
+  VPackOptions* insertDocuments(size_t amount, std::vector<std::string>& queryResults) {
+    // TODO: Can be optimized to not use AQL INSERT (trx object directly instead)
+    std::string insertQuery =
+        R"aql(INSERT {_key: "testee1", value: 1, sortValue: 1, nestedObject: {value: 1} } INTO UnitTestCollection RETURN NEW)aql";
+    SCOPED_TRACE(insertQuery);
+    auto queryRes = arangodb::tests::executeQuery(vocbase, insertQuery, {});
+    queryResults.push_back(queryRes.data.get()->slice().at(0).toJson(queryRes.context->getVPackOptions()));
+
+    for (size_t i = 2; i <= amount; i++) {
+      std::string insertQueryPart1 = R"aql(INSERT {_key: "testee)aql";
+      std::string insertQueryPart2 = std::to_string(i);
+      std::string insertQueryPart3 =
+          R"(", value: 1, sortValue: 1, nestedObject: {value: 1} } INTO UnitTestCollection RETURN NEW)";
+      std::string finalQuery = insertQueryPart1 + insertQueryPart2 + insertQueryPart3;
+      SCOPED_TRACE(finalQuery);
+      auto queryResInner = arangodb::tests::executeQuery(vocbase, finalQuery, {});
+      queryResults.push_back(queryResInner.data.get()->slice().at(0).toJson(queryResInner.context->getVPackOptions()));
+    }
+
+    return queryRes.context->getVPackOptions();
+  }
+
+  MatrixBuilder<1> buildQueryDocumentsMatrix(std::vector<std::string>& queryResults) {
+    size_t documentAmount = queryResults.size();
+    MatrixBuilder<1> matrix;
+    matrix.reserve(documentAmount);
+    for (auto const& documentStr : queryResults) {
+      const char* cstr = documentStr.c_str();
+      matrix.emplace_back(RowBuilder<1>{cstr});
+    }
+
+    return matrix;
+  }
+};
+
+// DISABLED because we need to be able to compare real documents (currently not possible)
+TEST_P(EnumerateCollectionExecutorTestProduce, DISABLED_produce_all_documents) {
+  auto [split] = GetParam();
+
+  uint64_t numberOfDocumentsToInsert = 10;
+  std::vector<std::string> queryResults;
+  auto vpackOptions = insertDocuments(numberOfDocumentsToInsert, queryResults);
+  EXPECT_EQ(vocbase.lookupCollection("UnitTestCollection")
+                ->numberDocuments(fakedQuery->trx(), transaction::CountType::Normal),
+            numberOfDocumentsToInsert);  // validate that our document inserts worked
+
+  ExecutorTestHelper<1, 1>(*fakedQuery)
+      .setInputValue({{RowBuilder<1>{R"("unused")"}}})
+      .setInputSplitType(split)
+      .setCall(AqlCall{0, AqlCall::Infinity{}, AqlCall::Infinity{}, false})
+      //.setQueryVpackOptions(true, vpackOptions)
+      //.allowAnyOutputOrder(true)
+      .expectSkipped(0)
+      //.expectOutput({0}, buildQueryDocumentsMatrix(queryResults))
+      /*    .expectOutput({0}, {
+                              {R"(null)"},
+                              {R"(null)"},
+                              {R"(null)"},
+                              {R"(null)"},
+                              {R"(null)"},
+                              {R"(null)"},
+                              {R"(null)"},
+                              {R"(null)"},
+                              {R"(null)"},
+                              {R"(null)"}})*/
+      .expectedState(ExecutionState::DONE)
+      .setExecBlock<EnumerateCollectionExecutor>(std::move(makeInfos()))
+      .run();
+}
+
+// DISABLED because we need to be able to compare real documents (currently not possible)
+TEST_P(EnumerateCollectionExecutorTestProduce, DISABLED_produce_5_documents) {
+  auto [split] = GetParam();
+
+  uint64_t numberOfDocumentsToInsert = 10;
+  std::vector<std::string> queryResults;
+  auto vpackOptions = insertDocuments(numberOfDocumentsToInsert, queryResults);
+
+  ExecutorTestHelper<1, 1>(*fakedQuery)
+      .setInputValue({{RowBuilder<1>{R"({ "cid" : "1337", "name": "UnitTestCollection" })"}}})
+      // .setInputValue({{RowBuilder<1>{R"("unused")"}}})
+      .setInputSplitType(split)
+      .setCall(AqlCall{0, 5, AqlCall::Infinity{}, false})
+      .expectSkipped(0)
+      .expectOutput({0}, {{R"(null)"}, {R"(null)"}, {R"(null)"}, {R"(null)"}, {R"(null)"}})
+      .expectedState(ExecutionState::HASMORE)
+      .setExecBlock<EnumerateCollectionExecutor>(std::move(makeInfos()))
+      .run();
+}
+
+
+// DISABLED because we need to be able to compare real documents (currently not possible)
+TEST_P(EnumerateCollectionExecutorTestProduce, DISABLED_skip_5_documents_default) {
+  auto [split] = GetParam();
+
+  uint64_t numberOfDocumentsToInsert = 10;
+  std::vector<std::string> queryResults;
+  auto vpackOptions = insertDocuments(numberOfDocumentsToInsert, queryResults);
+
+  ExecutorTestHelper<1, 1>(*fakedQuery)
+      .setInputValue({{RowBuilder<1>{R"({ "cid" : "1337", "name":
+"UnitTestCollection" })"}}}) .setInputSplitType(split) .setCall(AqlCall{5,
+AqlCall::Infinity{}, AqlCall::Infinity{}, false}) .expectSkipped(5) .expectOutput({0},
+{{R"(null)"}, {R"(null)"}, {R"(null)"}, {R"(null)"}, {R"(null)"}})
+      .expectedState(ExecutionState::DONE)
+      .setExecBlock<EnumerateCollectionExecutor>(std::move(makeInfos()))
+      .run();
 }
 
+template <size_t... vs>
+const EnumerateCollectionSplitType splitIntoBlocks =
+    EnumerateCollectionSplitType{std::vector<std::size_t>{vs...}};
+template <size_t step>
+const EnumerateCollectionSplitType splitStep = EnumerateCollectionSplitType{step};
+
+INSTANTIATE_TEST_CASE_P(EnumerateCollectionExecutor, EnumerateCollectionExecutorTestProduce,
+                        ::testing::Values(splitIntoBlocks<2, 3>,
+                                          splitIntoBlocks<3, 4>, splitStep<2>));
+
 }  // namespace aql
 }  // namespace tests
 }  // namespace arangodb
diff --git a/tests/Aql/ExecutorTestHelper.h b/tests/Aql/ExecutorTestHelper.h
index b280ab9c7c3b..cfc344f5f4f8 100644
--- a/tests/Aql/ExecutorTestHelper.h
+++ b/tests/Aql/ExecutorTestHelper.h
@@ -38,6 +38,7 @@
 #include "Aql/ExecutionEngine.h"
 #include "Aql/ExecutionNode.h"
 #include "Aql/ExecutionState.h"
+#include "Aql/ExecutionEngine.h"
 #include "Aql/ExecutionStats.h"
 #include "Aql/OutputAqlItemRow.h"
 #include "Aql/Query.h"
@@ -125,11 +126,11 @@ class AqlExecutorTestCase : public ::testing::Test {
   auto manager() const -> AqlItemBlockManager&;
 
  private:
-  static inline std::unique_ptr<mocks::MockAqlServer> _server;
   std::vector<std::unique_ptr<ExecutionNode>> _execNodes;
 
  protected:
   // available variables
+  static inline std::unique_ptr<mocks::MockAqlServer> _server;
   ResourceMonitor monitor{};
   AqlItemBlockManager itemBlockManager{&monitor, SerializationFormat::SHADOWROWS};
   std::unique_ptr<arangodb::aql::Query> fakedQuery;
diff --git a/tests/Mocks/Servers.cpp b/tests/Mocks/Servers.cpp
index 126dde89f4cc..abbb331f4074 100644
--- a/tests/Mocks/Servers.cpp
+++ b/tests/Mocks/Servers.cpp
@@ -88,7 +88,7 @@
 #include <velocypack/velocypack-aliases.h>
 
 #include <boost/core/demangle.hpp>
-using namespace arangodb;
+    using namespace arangodb;
 using namespace arangodb::tests;
 using namespace arangodb::tests::mocks;
 
@@ -449,7 +449,7 @@ std::shared_ptr<arangodb::transaction::Methods> MockAqlServer::createFakeTransac
                                                           noCollections, opts);
 }
 
-std::unique_ptr<arangodb::aql::Query> MockAqlServer::createFakeQuery(bool activateTracing) const {
+std::unique_ptr<arangodb::aql::Query> MockAqlServer::createFakeQuery(bool activateTracing, std::string queryString) const {
   auto bindParams = std::make_shared<VPackBuilder>();
   bindParams->openObject();
   bindParams->close();
@@ -459,7 +459,7 @@ std::unique_ptr<arangodb::aql::Query> MockAqlServer::createFakeQuery(bool activa
     queryOptions->add("profile", VPackValue(aql::PROFILE_LEVEL_TRACE_2));
   }
   queryOptions->close();
-  aql::QueryString fakeQueryString("");
+  aql::QueryString fakeQueryString(queryString);
   auto query =
       std::make_unique<arangodb::aql::Query>(false, getSystemDatabase(),
                                              fakeQueryString, bindParams, queryOptions,
diff --git a/tests/Mocks/Servers.h b/tests/Mocks/Servers.h
index de8d7d3ba552..75693948fb30 100644
--- a/tests/Mocks/Servers.h
+++ b/tests/Mocks/Servers.h
@@ -128,7 +128,7 @@ class MockAqlServer : public MockServer,
   ~MockAqlServer();
 
   std::shared_ptr<arangodb::transaction::Methods> createFakeTransaction() const;
-  std::unique_ptr<arangodb::aql::Query> createFakeQuery(bool activateTracing = false) const;
+  std::unique_ptr<arangodb::aql::Query> createFakeQuery(bool activateTracing = false, std::string queryString = "") const;
 };
 
 class MockRestServer : public MockServer,

From 557d5c585a4efcce3b3c37343a3b9e39fefe47d5 Mon Sep 17 00:00:00 2001
From: Markus Pfeiffer <markus@arangodb.com>
Date: Mon, 24 Feb 2020 11:13:24 +0000
Subject: [PATCH 073/122] Quickfix for compilation error due to merge

---
 tests/Aql/CalculationExecutorTest.cpp         | 6 +++---
 tests/Aql/EnumerateCollectionExecutorTest.cpp | 8 ++++----
 2 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/tests/Aql/CalculationExecutorTest.cpp b/tests/Aql/CalculationExecutorTest.cpp
index 878b5323668b..ab64ffbf4d42 100644
--- a/tests/Aql/CalculationExecutorTest.cpp
+++ b/tests/Aql/CalculationExecutorTest.cpp
@@ -250,7 +250,7 @@ TEST_F(CalculationExecutorTest, test_produce_datarange) {
   SharedAqlItemBlockPtr inBlock =
       buildBlock<1>(itemBlockManager, {{R"(0)"}, {R"(1)"}, {R"(2)"}});
 
-  AqlItemBlockInputRange input{ExecutorState::DONE, inBlock, 0, inBlock->size()};
+  AqlItemBlockInputRange input{ExecutorState::DONE, 0, inBlock, 0};
   OutputAqlItemRow output(std::move(block), infos.getOutputRegisters(),
                           infos.registersToKeep(), infos.registersToClear());
   EXPECT_EQ(output.numRowsWritten(), 0);
@@ -283,7 +283,7 @@ TEST_F(CalculationExecutorTest, test_produce_datarange_need_more) {
   SharedAqlItemBlockPtr inBlock =
       buildBlock<1>(itemBlockManager, {{R"(0)"}, {R"(1)"}, {R"(2)"}});
 
-  AqlItemBlockInputRange input{ExecutorState::HASMORE, inBlock, 0, inBlock->size()};
+  AqlItemBlockInputRange input{ExecutorState::HASMORE, 0, inBlock, 0};
   OutputAqlItemRow output(std::move(block), infos.getOutputRegisters(),
                           infos.registersToKeep(),
                           infos.registersToClear(),
@@ -329,7 +329,7 @@ TEST_F(CalculationExecutorTest, DISABLED_test_produce_datarange_has_more) { // T
   SharedAqlItemBlockPtr inBlock =
       buildBlock<1>(itemBlockManager, {{R"(0)"}, {R"(1)"}, {R"(2)"}, {R"(3)"}, {R"(4)"}});
 
-  AqlItemBlockInputRange input{ExecutorState::DONE, inBlock, 0, inBlock->size()};
+  AqlItemBlockInputRange input{ExecutorState::DONE, 0, inBlock, 0};
   OutputAqlItemRow output(std::move(block), infos.getOutputRegisters(),
                           infos.registersToKeep(), infos.registersToClear());
   EXPECT_EQ(output.numRowsWritten(), 0);
diff --git a/tests/Aql/EnumerateCollectionExecutorTest.cpp b/tests/Aql/EnumerateCollectionExecutorTest.cpp
index 5f3419c43621..e3dffe955f29 100644
--- a/tests/Aql/EnumerateCollectionExecutorTest.cpp
+++ b/tests/Aql/EnumerateCollectionExecutorTest.cpp
@@ -129,7 +129,7 @@ TEST_F(EnumerateCollectionExecutorTest, the_produce_datarange_empty) {
 
   SharedAqlItemBlockPtr inBlock = buildBlock<1>(itemBlockManager, {{}});
 
-  AqlItemBlockInputRange inputRange{ExecutorState::DONE, inBlock, 0, inBlock->size()};
+  AqlItemBlockInputRange inputRange{ExecutorState::DONE, 0, inBlock, 0};
   OutputAqlItemRow output(std::move(block), infos.getOutputRegisters(),
                           infos.registersToKeep(), infos.registersToClear());
 
@@ -148,7 +148,7 @@ TEST_F(EnumerateCollectionExecutorTest, the_skip_datarange_empty) {
 
   SharedAqlItemBlockPtr inBlock = buildBlock<1>(itemBlockManager, {{}});
 
-  AqlItemBlockInputRange inputRange{ExecutorState::DONE, inBlock, 0, inBlock->size()};
+  AqlItemBlockInputRange inputRange{ExecutorState::DONE, 0, inBlock, 0};
   OutputAqlItemRow output(std::move(block), infos.getOutputRegisters(),
                           infos.registersToKeep(), infos.registersToClear());
   AqlCall skipCall{1000, AqlCall::Infinity{}, AqlCall::Infinity{}, false};
@@ -188,7 +188,7 @@ TEST_F(EnumerateCollectionExecutorTest, the_produce_datarange) {
   SCOPED_TRACE(insertQueryC);
   AssertQueryHasResult(vocbase, insertQueryC, VPackSlice::emptyArraySlice());
 
-  AqlItemBlockInputRange inputRange{ExecutorState::DONE, inBlock, 0, inBlock->size()};
+  AqlItemBlockInputRange inputRange{ExecutorState::DONE, 0, inBlock, 0};
   OutputAqlItemRow output(std::move(block), infos.getOutputRegisters(),
                           infos.registersToKeep(), infos.registersToClear());
 
@@ -230,7 +230,7 @@ TEST_F(EnumerateCollectionExecutorTest, the_skip_datarange) {
   SCOPED_TRACE(insertQueryC);
   AssertQueryHasResult(vocbase, insertQueryC, VPackSlice::emptyArraySlice());
    */
-  AqlItemBlockInputRange inputRange{ExecutorState::DONE, inBlock, 0, inBlock->size()};
+  AqlItemBlockInputRange inputRange{ExecutorState::DONE, 0, inBlock, 0};
   OutputAqlItemRow output(std::move(block), infos.getOutputRegisters(),
                           infos.registersToKeep(), infos.registersToClear());
 

From e6a31b75d619ef453a3fba59b08c35cf95b4e3c9 Mon Sep 17 00:00:00 2001
From: Markus Pfeiffer <markuspf@users.noreply.github.com>
Date: Tue, 25 Feb 2020 10:38:15 +0000
Subject: [PATCH 074/122] Feature/aql subquery execution block impl execute
 implementation k shortest path executor (#10940)

* Add new produceRow API code for KShortestPathsExecutor

* Add KShortestPathsExecutor test to build

* Add KShortestPathsExecutor test

* Test and bugfix for KShortestPathExecutor

* Update k-shortest-paths executor for new interface

* Update tests for k-shortest-paths executor

* Make ShortestPathExecutor and KShortestPathExecutor more similar

* Fix merge messup

* Refactor KShortestPathsExecutorInfos

* Move KShortestPathsExecutor to new executor interface

* Fix tests

* Resolve naming conflict

* Address some review comments

* Fix skip

* Fix for new signatures

* Fix KShortestPathsExecutor

* Fix KShortestPaths regression

Co-authored-by: Michael Hackstein <michael@arangodb.com>
---
 arangod/Aql/ExecutionBlockImpl.cpp       |   6 +-
 arangod/Aql/KShortestPathsExecutor.cpp   | 263 ++++++++------
 arangod/Aql/KShortestPathsExecutor.h     |  59 ++--
 arangod/Graph/KShortestPathsFinder.cpp   |  39 ++-
 arangod/Graph/KShortestPathsFinder.h     |  13 +-
 tests/Aql/KShortestPathsExecutorTest.cpp | 427 +++++++++++++++++++++++
 tests/Aql/ShortestPathExecutorTest.cpp   |   4 +-
 tests/CMakeLists.txt                     |   1 +
 8 files changed, 645 insertions(+), 167 deletions(-)
 create mode 100644 tests/Aql/KShortestPathsExecutorTest.cpp

diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index dbb8bdbac935..5c63d1bccdd1 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -144,7 +144,7 @@ constexpr bool isNewStyleExecutor =
                 TestLambdaExecutor,
                 TestLambdaSkipExecutor,  // we need one after these to avoid compile errors in non-test mode
 #endif
-                ShortestPathExecutor, EnumerateListExecutor, LimitExecutor>;
+                KShortestPathsExecutor, ShortestPathExecutor, EnumerateListExecutor, LimitExecutor>;
 
 template <class Executor>
 ExecutionBlockImpl<Executor>::ExecutionBlockImpl(ExecutionEngine* engine,
@@ -1078,8 +1078,8 @@ static SkipRowsRangeVariant constexpr skipRowsType() {
                 "Fetcher is chosen for skipping, but has not skipRows method!");
 
   static_assert(useExecutor ==
-                    (is_one_of_v<Executor, FilterExecutor, ShortestPathExecutor, ReturnExecutor,
-                                 HashedCollectExecutor, IndexExecutor, EnumerateCollectionExecutor,
+                    (is_one_of_v<Executor, FilterExecutor, ShortestPathExecutor, KShortestPathsExecutor,
+                                 ReturnExecutor, HashedCollectExecutor, IndexExecutor, EnumerateCollectionExecutor,
 #ifdef ARANGODB_USE_GOOGLE_TESTS
                                  TestLambdaSkipExecutor,
 #endif
diff --git a/arangod/Aql/KShortestPathsExecutor.cpp b/arangod/Aql/KShortestPathsExecutor.cpp
index 28a53cb98b5d..30ac99e57eb1 100644
--- a/arangod/Aql/KShortestPathsExecutor.cpp
+++ b/arangod/Aql/KShortestPathsExecutor.cpp
@@ -86,177 +86,210 @@ arangodb::graph::KShortestPathsFinder& KShortestPathsExecutorInfos::finder() con
   return *_finder.get();
 }
 
-bool KShortestPathsExecutorInfos::useRegisterForInput(bool isTarget) const {
-  if (isTarget) {
-    return _target.type == InputVertex::REGISTER;
-  }
-  return _source.type == InputVertex::REGISTER;
+auto KShortestPathsExecutorInfos::useRegisterForSourceInput() const -> bool {
+  return _source.type == InputVertex::Type::REGISTER;
 }
 
-RegisterId KShortestPathsExecutorInfos::getInputRegister(bool isTarget) const {
-  TRI_ASSERT(useRegisterForInput(isTarget));
-  if (isTarget) {
-    return _target.reg;
-  }
+auto KShortestPathsExecutorInfos::useRegisterForTargetInput() const -> bool {
+  return _target.type == InputVertex::Type::REGISTER;
+}
+
+auto KShortestPathsExecutorInfos::getSourceInputRegister() const -> RegisterId {
+  TRI_ASSERT(useRegisterForSourceInput());
   return _source.reg;
 }
 
-std::string const& KShortestPathsExecutorInfos::getInputValue(bool isTarget) const {
-  TRI_ASSERT(!useRegisterForInput(isTarget));
-  if (isTarget) {
-    return _target.value;
-  }
+auto KShortestPathsExecutorInfos::getTargetInputRegister() const -> RegisterId {
+  TRI_ASSERT(useRegisterForTargetInput());
+  return _target.reg;
+}
+
+auto KShortestPathsExecutorInfos::getSourceInputValue() const -> std::string const& {
+  TRI_ASSERT(!useRegisterForSourceInput());
   return _source.value;
 }
 
-RegisterId KShortestPathsExecutorInfos::getOutputRegister() const {
+auto KShortestPathsExecutorInfos::getTargetInputValue() const -> std::string const& {
+  TRI_ASSERT(!useRegisterForTargetInput());
+  return _target.value;
+}
+
+auto KShortestPathsExecutorInfos::getOutputRegister() const -> RegisterId {
   TRI_ASSERT(_outputRegister != RegisterPlan::MaxRegisterId);
   return _outputRegister;
 }
 
-graph::TraverserCache* KShortestPathsExecutorInfos::cache() const {
+auto KShortestPathsExecutorInfos::getSourceVertex() const noexcept
+    -> KShortestPathsExecutorInfos::InputVertex {
+  return _source;
+}
+
+auto KShortestPathsExecutorInfos::getTargetVertex() const noexcept
+    -> KShortestPathsExecutorInfos::InputVertex {
+  return _target;
+}
+
+auto KShortestPathsExecutorInfos::cache() const -> graph::TraverserCache* {
   return _finder->options().cache();
 }
 
 KShortestPathsExecutor::KShortestPathsExecutor(Fetcher& fetcher, Infos& infos)
     : _infos(infos),
-      _fetcher(fetcher),
-      _input{CreateInvalidInputRowHint{}},
+      _inputRow{CreateInvalidInputRowHint{}},
       _rowState(ExecutionState::HASMORE),
       _finder{infos.finder()},
       _sourceBuilder{},
       _targetBuilder{} {
-  if (!_infos.useRegisterForInput(false)) {
-    _sourceBuilder.add(VPackValue(_infos.getInputValue(false)));
+  if (!_infos.useRegisterForSourceInput()) {
+    _sourceBuilder.add(VPackValue(_infos.getSourceInputValue()));
   }
-  if (!_infos.useRegisterForInput(true)) {
-    _targetBuilder.add(VPackValue(_infos.getInputValue(true)));
+  if (!_infos.useRegisterForTargetInput()) {
+    _targetBuilder.add(VPackValue(_infos.getTargetInputValue()));
   }
 }
 
-KShortestPathsExecutor::~KShortestPathsExecutor() = default;
-
 // Shutdown query
-std::pair<ExecutionState, Result> KShortestPathsExecutor::shutdown(int errorCode) {
+auto KShortestPathsExecutor::shutdown(int errorCode) -> std::pair<ExecutionState, Result> {
   _finder.destroyEngines();
   return {ExecutionState::DONE, TRI_ERROR_NO_ERROR};
 }
 
-std::pair<ExecutionState, NoStats> KShortestPathsExecutor::produceRows(OutputAqlItemRow& output) {
-  NoStats s;
+auto KShortestPathsExecutor::produceRows(OutputAqlItemRow& output)
+    -> std::pair<ExecutionState, NoStats> {
+  TRI_ASSERT(false);
+  THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
+}
 
-  while (true) {
-    // We will have paths available, or return
-    if (!_finder.isPathAvailable()) {
-      if (!fetchPaths()) {
-        return {_rowState, s};
+auto KShortestPathsExecutor::produceRows(AqlItemBlockInputRange& input, OutputAqlItemRow& output)
+    -> std::tuple<ExecutorState, Stats, AqlCall> {
+  while (!output.isFull()) {
+    if (_finder.isDone()) {
+      if (!fetchPaths(input)) {
+        TRI_ASSERT(!input.hasDataRow());
+        return {input.upstreamState(), NoStats{}, AqlCall{}};
       }
+    } else {
+      doOutputPath(output);
     }
+  }
 
-    // Now we have a path available, so we go and output it
-    transaction::BuilderLeaser tmp(_finder.options().trx());
-    tmp->clear();
-    if (_finder.getNextPathAql(*tmp.builder())) {
-      AqlValue path = AqlValue(*tmp.builder());
-      AqlValueGuard guard{path, true};
-      output.moveValueInto(_infos.getOutputRegister(), _input, guard);
-      return {computeState(), s};
-    }
+  if (_finder.isDone()) {
+    return {input.upstreamState(), NoStats{}, AqlCall{}};
+  } else {
+    return {ExecutorState::HASMORE, NoStats{}, AqlCall{}};
   }
 }
 
-bool KShortestPathsExecutor::fetchPaths() {
-  VPackSlice start;
-  VPackSlice end;
-  while (true) {
-    // Fetch a row from upstream
-    std::tie(_rowState, _input) = _fetcher.fetchRow();
-    if (!_input.isInitialized()) {
-      // Either WAITING or DONE, in either case we cannot produce any paths.
-      TRI_ASSERT(_rowState == ExecutionState::WAITING || _rowState == ExecutionState::DONE);
-      return false;
+auto KShortestPathsExecutor::skipRowsRange(AqlItemBlockInputRange& input, AqlCall& call)
+    -> std::tuple<ExecutorState, Stats, size_t, AqlCall> {
+  auto stats = NoStats{};
+  auto skipped = size_t{0};
+
+  while (call.shouldSkip()) {
+    // _finder.isDone() == true means that there is currently no path available
+    // from the _finder, we can try calling fetchPaths to make one available,
+    // but if that fails too, we must be DONE
+    if (_finder.isDone()) {
+      if (!fetchPaths(input)) {
+        TRI_ASSERT(!input.hasDataRow());
+        return {input.upstreamState(), stats, skipped, AqlCall{}};
+      }
+    } else {
+      if (_finder.skipPath()) {
+        skipped++;
+        call.didSkip(1);
+      }
     }
+  }
+
+  if (_finder.isDone()) {
+    return {input.upstreamState(), stats, skipped, AqlCall{}};
+  } else {
+    return {ExecutorState::HASMORE, stats, skipped, AqlCall{}};
+  }
+}
+
+auto KShortestPathsExecutor::fetchPaths(AqlItemBlockInputRange& input) -> bool {
+  TRI_ASSERT(_finder.isDone());
+  while (input.hasDataRow()) {
+    auto source = VPackSlice{};
+    auto target = VPackSlice{};
+    std::tie(std::ignore, _inputRow) = input.nextDataRow();
+    TRI_ASSERT(_inputRow.isInitialized());
+
     // Check start and end for validity
-    if (!getVertexId(false, start) || !getVertexId(true, end)) {
-      // Fetch another row
-      continue;
-    }
-    TRI_ASSERT(start.isString());
-    TRI_ASSERT(end.isString());
-    if (_finder.startKShortestPathsTraversal(start, end)) {
-      break;
+    if (getVertexId(_infos.getSourceVertex(), _inputRow, _sourceBuilder, source) &&
+        getVertexId(_infos.getTargetVertex(), _inputRow, _targetBuilder, target) &&
+        _finder.startKShortestPathsTraversal(source, target)) {
+      return true;
     }
-  } 
-  return true;
+  }
+  return false;
 }
 
-ExecutionState KShortestPathsExecutor::computeState() const {
-  if (_rowState == ExecutionState::HASMORE || _finder.isPathAvailable()) {
-    return ExecutionState::HASMORE;
+auto KShortestPathsExecutor::doOutputPath(OutputAqlItemRow& output) -> void {
+  auto tmp = transaction::BuilderLeaser{_finder.options().trx()};
+  tmp->clear();
+
+  if (_finder.getNextPathAql(*tmp.builder())) {
+    output.cloneValueInto(_infos.getOutputRegister(), _inputRow, AqlValue(*tmp.builder()));
+    output.advanceRow();
   }
-  return ExecutionState::DONE;
 }
 
-bool KShortestPathsExecutor::getVertexId(bool isTarget, VPackSlice& id) {
-  if (_infos.useRegisterForInput(isTarget)) {
-    // The input row stays valid until the next fetchRow is executed.
-    // So the slice can easily point to it.
-    RegisterId reg = _infos.getInputRegister(isTarget);
-    AqlValue const& in = _input.getValue(reg);
-    if (in.isObject()) {
-      try {
-        auto idString = _finder.options().trx()->extractIdString(in.slice());
-        if (isTarget) {
-          _targetBuilder.clear();
-          _targetBuilder.add(VPackValue(idString));
-          id = _targetBuilder.slice();
-        } else {
-          _sourceBuilder.clear();
-          _sourceBuilder.add(VPackValue(idString));
-          id = _sourceBuilder.slice();
+auto KShortestPathsExecutor::getVertexId(KShortestPathsExecutorInfos::InputVertex const& vertex,
+                                         InputAqlItemRow& row, VPackBuilder& builder,
+                                         VPackSlice& id) -> bool {
+  switch (vertex.type) {
+    case KShortestPathsExecutorInfos::InputVertex::Type::REGISTER: {
+      AqlValue const& in = row.getValue(vertex.reg);
+      if (in.isObject()) {
+        try {
+          auto idString = _finder.options().trx()->extractIdString(in.slice());
+          builder.clear();
+          builder.add(VPackValue(idString));
+          id = builder.slice();
+          // Guranteed by extractIdValue
+          TRI_ASSERT(::isValidId(id));
+        } catch (...) {
+          // _id or _key not present... ignore this error and fall through
+          // returning no path
+          return false;
+        }
+        return true;
+      } else if (in.isString()) {
+        id = in.slice();
+        // Validation
+        if (!::isValidId(id)) {
+          _finder.options().query()->registerWarning(
+              TRI_ERROR_BAD_PARAMETER,
+              "Invalid input for Shortest Path: "
+              "Only id strings or objects with "
+              "_id are allowed");
+          return false;
         }
-        // Guranteed by extractIdValue
-        TRI_ASSERT(::isValidId(id));
-      } catch (...) {
-        // _id or _key not present... ignore this error and fall through
-        // returning no path
+        return true;
+      } else {
+        _finder.options().query()->registerWarning(
+            TRI_ERROR_BAD_PARAMETER,
+            "Invalid input for Shortest Path: "
+            "Only id strings or objects with "
+            "_id are allowed");
         return false;
       }
-      return true;
-    } else if (in.isString()) {
-      id = in.slice();
-      // Validation
+    }
+    case KShortestPathsExecutorInfos::InputVertex::Type::CONSTANT: {
+      id = builder.slice();
       if (!::isValidId(id)) {
         _finder.options().query()->registerWarning(
             TRI_ERROR_BAD_PARAMETER,
-            "Invalid input for k Shortest Paths: "
+            "Invalid input for Shortest Path: "
             "Only id strings or objects with "
             "_id are allowed");
         return false;
       }
       return true;
-    } else {
-      _finder.options().query()->registerWarning(
-          TRI_ERROR_BAD_PARAMETER,
-          "Invalid input for k Shortest Paths: "
-          "Only id strings or objects with "
-          "_id are allowed");
-      return false;
-    }
-  } else {
-    if (isTarget) {
-      id = _targetBuilder.slice();
-    } else {
-      id = _sourceBuilder.slice();
-    }
-    if (!::isValidId(id)) {
-      _finder.options().query()->registerWarning(
-          TRI_ERROR_BAD_PARAMETER,
-          "Invalid input for k Shortest Paths: "
-          "Only id strings or objects with "
-          "_id are allowed");
-      return false;
     }
-    return true;
   }
+  return false;
 }
diff --git a/arangod/Aql/KShortestPathsExecutor.h b/arangod/Aql/KShortestPathsExecutor.h
index 9477d3bc3b28..e06ee743d3ce 100644
--- a/arangod/Aql/KShortestPathsExecutor.h
+++ b/arangod/Aql/KShortestPathsExecutor.h
@@ -23,12 +23,16 @@
 #ifndef ARANGOD_AQL_KSHORTEST_PATHS_EXECUTOR_H
 #define ARANGOD_AQL_KSHORTEST_PATHS_EXECUTOR_H
 
+#include "Aql/AqlCall.h"
+#include "Aql/AqlItemBlockInputRange.h"
 #include "Aql/ExecutionState.h"
 #include "Aql/ExecutorInfos.h"
 #include "Aql/InputAqlItemRow.h"
 
 #include <velocypack/Builder.h>
 
+using namespace arangodb::velocypack;
+
 namespace arangodb {
 
 class Result;
@@ -54,16 +58,17 @@ class NoStats;
 class KShortestPathsExecutorInfos : public ExecutorInfos {
  public:
   struct InputVertex {
-    enum { CONSTANT, REGISTER } type;
+    enum class Type { CONSTANT, REGISTER };
+    Type type;
     // TODO make the following two a union instead
     RegisterId reg;
     std::string value;
 
     // cppcheck-suppress passedByValue
     explicit InputVertex(std::string value)
-        : type(CONSTANT), reg(0), value(std::move(value)) {}
+        : type(Type::CONSTANT), reg(0), value(std::move(value)) {}
     explicit InputVertex(RegisterId reg)
-        : type(REGISTER), reg(reg), value("") {}
+        : type(Type::REGISTER), reg(reg), value("") {}
   };
 
   KShortestPathsExecutorInfos(std::shared_ptr<std::unordered_set<RegisterId>> inputRegisters,
@@ -80,35 +85,41 @@ class KShortestPathsExecutorInfos : public ExecutorInfos {
   KShortestPathsExecutorInfos(KShortestPathsExecutorInfos const&) = delete;
   ~KShortestPathsExecutorInfos();
 
-  arangodb::graph::KShortestPathsFinder& finder() const;
+  [[nodiscard]] auto finder() const -> arangodb::graph::KShortestPathsFinder&;
 
   /**
    * @brief test if we use a register or a constant input
    *
    * @param isTarget defines if we look for target(true) or source(false)
    */
-  bool useRegisterForInput(bool isTarget) const;
+  [[nodiscard]] auto useRegisterForSourceInput() const -> bool;
+  [[nodiscard]] auto useRegisterForTargetInput() const -> bool;
 
   /**
    * @brief get the register used for the input
    *
    * @param isTarget defines if we look for target(true) or source(false)
    */
-  RegisterId getInputRegister(bool isTarget) const;
+  [[nodiscard]] auto getSourceInputRegister() const -> RegisterId;
+  [[nodiscard]] auto getTargetInputRegister() const -> RegisterId;
 
   /**
    * @brief get the const value for the input
    *
    * @param isTarget defines if we look for target(true) or source(false)
    */
-  std::string const& getInputValue(bool isTarget) const;
+  [[nodiscard]] auto getSourceInputValue() const -> std::string const&;
+  [[nodiscard]] auto getTargetInputValue() const -> std::string const&;
 
   /**
    * @brief get the output register for the given type
    */
-  RegisterId getOutputRegister() const;
+  [[nodiscard]] auto getOutputRegister() const -> RegisterId;
+
+  [[nodiscard]] auto cache() const -> graph::TraverserCache*;
 
-  graph::TraverserCache* cache() const;
+  [[nodiscard]] auto getSourceVertex() const noexcept -> InputVertex;
+  [[nodiscard]] auto getTargetVertex() const noexcept -> InputVertex;
 
  private:
   /// @brief the shortest path finder.
@@ -141,21 +152,26 @@ class KShortestPathsExecutor {
   KShortestPathsExecutor(KShortestPathsExecutor&&) = default;
 
   KShortestPathsExecutor(Fetcher& fetcher, Infos&);
-  ~KShortestPathsExecutor();
+  ~KShortestPathsExecutor() = default;
 
   /**
    * @brief Shutdown will be called once for every query
    *
    * @return ExecutionState and no error.
    */
-  std::pair<ExecutionState, Result> shutdown(int errorCode);
+  [[nodiscard]] auto shutdown(int errorCode) -> std::pair<ExecutionState, Result>;
 
   /**
    * @brief produce the next Row of Aql Values.
    *
    * @return ExecutionState, and if successful exactly one new Row of AqlItems.
    */
-  std::pair<ExecutionState, Stats> produceRows(OutputAqlItemRow& output);
+  [[nodiscard]] auto produceRows(OutputAqlItemRow& output)
+      -> std::pair<ExecutionState, Stats>;
+  [[nodiscard]] auto produceRows(AqlItemBlockInputRange& input, OutputAqlItemRow& output)
+      -> std::tuple<ExecutorState, Stats, AqlCall>;
+  [[nodiscard]] auto skipRowsRange(AqlItemBlockInputRange& input, AqlCall& call)
+      -> std::tuple<ExecutorState, Stats, size_t, AqlCall>;
 
  private:
   /**
@@ -163,25 +179,20 @@ class KShortestPathsExecutor {
    *
    * @return false if we are done and no path could be found.
    */
-  bool fetchPaths();
-
-  /**
-   * @brief compute the correct return state
-   *
-   * @return DONE if no more is expected
-   */
-
-  ExecutionState computeState() const;
+  [[nodiscard]] auto fetchPaths(AqlItemBlockInputRange& input) -> bool;
+  auto doOutputPath(OutputAqlItemRow& output) -> void;
 
   /**
    * @brief get the id of a input vertex
    */
-  bool getVertexId(bool isTarget, arangodb::velocypack::Slice& id);
+  [[nodiscard]] auto getVertexId(bool isTarget, arangodb::velocypack::Slice& id) -> bool;
+
+  [[nodiscard]] auto getVertexId(KShortestPathsExecutorInfos::InputVertex const& vertex,
+                                 InputAqlItemRow& row, Builder& builder, Slice& id) -> bool;
 
  private:
   Infos& _infos;
-  Fetcher& _fetcher;
-  InputAqlItemRow _input;
+  InputAqlItemRow _inputRow;
   ExecutionState _rowState;
   /// @brief the shortest path finder.
   arangodb::graph::KShortestPathsFinder& _finder;
diff --git a/arangod/Graph/KShortestPathsFinder.cpp b/arangod/Graph/KShortestPathsFinder.cpp
index 3c572ac4a969..56371dc1e4f1 100644
--- a/arangod/Graph/KShortestPathsFinder.cpp
+++ b/arangod/Graph/KShortestPathsFinder.cpp
@@ -42,9 +42,9 @@
 using namespace arangodb;
 using namespace arangodb::graph;
 
-//
 KShortestPathsFinder::KShortestPathsFinder(ShortestPathOptions& options)
-    : ShortestPathFinder(options), _pathAvailable(false) {}
+    : ShortestPathFinder(options), _traversalDone(true) {}
+
 KShortestPathsFinder::~KShortestPathsFinder() = default;
 
 // Sets up k-shortest-paths traversal from start to end
@@ -55,13 +55,12 @@ bool KShortestPathsFinder::startKShortestPathsTraversal(
   _start = arangodb::velocypack::StringRef(start);
   _end = arangodb::velocypack::StringRef(end);
 
-  _pathAvailable = true;
+  _traversalDone = false;
+
   _shortestPaths.clear();
   _candidatePaths.clear();
 
-  TRI_IF_FAILURE("TraversalOOMInitialize") {
-    THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
-  }
+  TRI_IF_FAILURE("Travefalse") { THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG); }
 
   return true;
 }
@@ -340,38 +339,37 @@ bool KShortestPathsFinder::computeNextShortestPath(Path& result) {
 }
 
 bool KShortestPathsFinder::getNextPath(Path& result) {
-  bool available = false;
   result.clear();
 
-  // TODO: this looks a bit ugly
+  // This is for the first time that getNextPath is called
   if (_shortestPaths.empty()) {
     if (_start == _end) {
       TRI_ASSERT(!_start.empty());
       result._vertices.emplace_back(_start);
       result._weight = 0;
-      available = true;
     } else {
-      available = computeShortestPath(_start, _end, {}, {}, result);
+      // Compute the first shortest path (i.e. the shortest path
+      // between _start and _end!)
+      computeShortestPath(_start, _end, {}, {}, result);
       result._branchpoint = 0;
     }
   } else {
-    if (_start == _end) {
-      available = false;
-    } else {
-      available = computeNextShortestPath(result);
-    }
+    // We must not have _start == _end here, because we handle _start == _end
+    computeNextShortestPath(result);
   }
 
-  if (available) {
+  if (result.length() > 0) {
     _shortestPaths.emplace_back(result);
     _options.fetchVerticesCoordinator(result._vertices);
 
     TRI_IF_FAILURE("TraversalOOMPath") {
       THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
     }
+  } else {
+    // If we did not find a path, traversal is done.
+    _traversalDone = true;
   }
-  _pathAvailable = available;
-  return available;
+  return !_traversalDone;
 }
 
 bool KShortestPathsFinder::getNextPathShortestPathResult(ShortestPathResult& result) {
@@ -420,3 +418,8 @@ bool KShortestPathsFinder::getNextPathAql(arangodb::velocypack::Builder& result)
     return false;
   }
 }
+
+bool KShortestPathsFinder::skipPath() {
+  Path path;
+  return getNextPath(path);
+}
diff --git a/arangod/Graph/KShortestPathsFinder.h b/arangod/Graph/KShortestPathsFinder.h
index 1f7a482c3daa..1d62cc863894 100644
--- a/arangod/Graph/KShortestPathsFinder.h
+++ b/arangod/Graph/KShortestPathsFinder.h
@@ -162,7 +162,7 @@ class KShortestPathsFinder : public ShortestPathFinder {
     Ball() {}
     Ball(VertexRef const& center, Direction direction)
         : _center(center), _direction(direction), _closest(0) {
-      _frontier.insert(center , std::make_unique<DijkstraInfo>(center));
+      _frontier.insert(center, std::make_unique<DijkstraInfo>(center));
     }
     ~Ball() = default;
     const VertexRef center() const { return _center; };
@@ -220,18 +220,19 @@ class KShortestPathsFinder : public ShortestPathFinder {
   }
 
   // initialise k Shortest Paths
-  bool startKShortestPathsTraversal(arangodb::velocypack::Slice const& start,
-                                    arangodb::velocypack::Slice const& end);
+  TEST_VIRTUAL bool startKShortestPathsTraversal(arangodb::velocypack::Slice const& start,
+                                                 arangodb::velocypack::Slice const& end);
 
   // get the next available path as AQL value.
-  bool getNextPathAql(arangodb::velocypack::Builder& builder);
+  TEST_VIRTUAL bool getNextPathAql(arangodb::velocypack::Builder& builder);
   // get the next available path as a ShortestPathResult
   // TODO: this is only here to not break catch-tests and needs a cleaner solution.
   //       probably by making ShortestPathResult versatile enough and using that
   bool getNextPathShortestPathResult(ShortestPathResult& path);
   // get the next available path as a Path
   bool getNextPath(Path& path);
-  bool isPathAvailable() const { return _pathAvailable; }
+  TEST_VIRTUAL bool skipPath();
+  TEST_VIRTUAL bool isDone() const { return _traversalDone; }
 
  private:
   // Compute the first shortest path
@@ -257,7 +258,7 @@ class KShortestPathsFinder : public ShortestPathFinder {
                        VertexRef& join, std::optional<double>& currentBest);
 
  private:
-  bool _pathAvailable;
+  bool _traversalDone;
 
   VertexRef _start;
   VertexRef _end;
diff --git a/tests/Aql/KShortestPathsExecutorTest.cpp b/tests/Aql/KShortestPathsExecutorTest.cpp
new file mode 100644
index 000000000000..ceaf4bf40d1f
--- /dev/null
+++ b/tests/Aql/KShortestPathsExecutorTest.cpp
@@ -0,0 +1,427 @@
+////////////////////////////////////////////////////////////////////////////////
+/// DISCLAIMER
+///
+/// Copyright 2018 ArangoDB GmbH, Cologne, Germany
+///
+/// Licensed under the Apache License, Version 2.0 (the "License");
+/// you may not use this file except in compliance with the License.
+/// You may obtain a copy of the License at
+///
+///     http://www.apache.org/licenses/LICENSE-2.0
+///
+/// Unless required by applicable law or agreed to in writing, software
+/// distributed under the License is distributed on an "AS IS" BASIS,
+/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+/// See the License for the specific language governing permissions and
+/// limitations under the License.
+///
+/// Copyright holder is ArangoDB GmbH, Cologne, Germany
+///
+/// @author Michael Hackstein
+////////////////////////////////////////////////////////////////////////////////
+
+#include "gtest/gtest.h"
+
+#include <velocypack/Builder.h>
+#include <velocypack/Slice.h>
+#include <velocypack/StringRef.h>
+#include <velocypack/velocypack-aliases.h>
+
+#include "Aql/RowFetcherHelper.h"
+#include "Mocks/LogLevels.h"
+#include "Mocks/Servers.h"
+
+#include "Aql/AqlItemBlock.h"
+#include "Aql/AqlItemBlockHelper.h"
+#include "Aql/AqlItemBlockManager.h"
+#include "Aql/AqlValue.h"
+#include "Aql/ExecutorInfos.h"
+#include "Aql/InputAqlItemRow.h"
+#include "Aql/KShortestPathsExecutor.h"
+#include "Aql/OutputAqlItemRow.h"
+#include "Aql/Query.h"
+#include "Aql/ResourceUsage.h"
+#include "Aql/Stats.h"
+#include "Graph/EdgeDocumentToken.h"
+#include "Graph/GraphTestTools.h"
+#include "Graph/KShortestPathsFinder.h"
+#include "Graph/ShortestPathOptions.h"
+#include "Graph/ShortestPathResult.h"
+#include "Graph/TraverserCache.h"
+#include "Graph/TraverserOptions.h"
+
+#include "../Mocks/Servers.h"
+
+using namespace arangodb;
+using namespace arangodb::aql;
+using namespace arangodb::graph;
+using namespace arangodb::tests::mocks;
+
+namespace arangodb {
+namespace tests {
+namespace aql {
+
+using Vertex = KShortestPathsExecutorInfos::InputVertex;
+using RegisterSet = std::unordered_set<RegisterId>;
+using Path = std::vector<std::string>;
+using PathSequence = std::vector<Path>;
+
+// The FakeShortestPathsFinder does not do any real k shortest paths search; it
+// is merely initialized with a set of "paths" and then outputs them, keeping a
+// record of which paths it produced. This record is used in the validation
+// whether the executor output the correct sequence of rows.
+class FakeKShortestPathsFinder : public KShortestPathsFinder {
+ public:
+  FakeKShortestPathsFinder(ShortestPathOptions& options, PathSequence const& kpaths)
+      : KShortestPathsFinder(options), _kpaths(kpaths), _traversalDone(true) {}
+  ~FakeKShortestPathsFinder() = default;
+
+  auto gotoNextPath() -> bool {
+    EXPECT_NE(_source, "");
+    EXPECT_NE(_target, "");
+    EXPECT_NE(_source, _target);
+
+    while (_finder != std::end(_kpaths)) {
+      if (_finder->front() == _source && _finder->back() == _target) {
+        return true;
+      }
+      _finder++;
+    }
+    return false;
+  }
+
+  bool startKShortestPathsTraversal(Slice const& start, Slice const& end) override {
+    _source = std::string{start.copyString()};
+    _target = std::string{end.copyString()};
+
+    _calledWith.emplace_back(std::make_pair(_source, _target));
+
+    EXPECT_NE(_source, "");
+    EXPECT_NE(_target, "");
+    EXPECT_NE(_source, _target);
+
+    _finder = _kpaths.begin();
+    return true;
+  }
+
+  bool getNextPathAql(Builder& builder) override {
+    _traversalDone = !gotoNextPath();
+
+    if (_traversalDone) {
+      return false;
+    } else {
+      _pathsProduced.emplace_back(*_finder);
+      // fill builder with something sensible?
+      builder.openArray();
+      for (auto&& v : *_finder) {
+        builder.add(VPackValue(v));
+      }
+      builder.close();
+
+      // HACK
+      _finder++;
+      return true;
+    }
+  }
+
+  bool skipPath() override {
+    Builder builder{};
+    return getNextPathAql(builder);
+  }
+
+  bool isDone() const override { return _traversalDone; }
+
+  PathSequence& getPathsProduced() noexcept { return _pathsProduced; }
+  std::vector<std::pair<std::string, std::string>> getCalledWith() noexcept {
+    return _calledWith;
+  }
+
+ private:
+  // We emulate a number of paths between PathPair
+  PathSequence const& _kpaths;
+  std::string _source;
+  std::string _target;
+  bool _traversalDone;
+  PathSequence::const_iterator _finder;
+  PathSequence _pathsProduced;
+  std::vector<std::pair<std::string, std::string>> _calledWith;
+};
+
+// TODO: this needs a << operator
+struct KShortestPathsTestParameters {
+  KShortestPathsTestParameters(std::tuple<Vertex, Vertex, MatrixBuilder<2>, PathSequence, AqlCall, size_t> params)
+      : _source(std::get<0>(params)),
+        _target(std::get<1>(params)),
+        // TODO: Make output registers configurable?
+        _outputRegisters(std::initializer_list<RegisterId>{2}),
+        _inputMatrix(std::get<2>(params)),
+        _paths(std::get<3>(params)),
+        _call(std::get<4>(params)),
+        _blockSize(std::get<5>(params)){};
+
+  Vertex _source;
+  Vertex _target;
+  RegisterSet _inputRegisters;
+  RegisterSet _outputRegisters;
+  MatrixBuilder<2> _inputMatrix;
+  PathSequence _paths;
+  AqlCall _call;
+  size_t _blockSize{1000};
+};
+
+class KShortestPathsExecutorTest
+    : public ::testing::Test,
+      public ::testing::WithParamInterface<std::tuple<Vertex, Vertex, MatrixBuilder<2>, PathSequence, AqlCall, size_t>> {
+ protected:
+  // parameters are copied because they are const otherwise
+  // and that doesn't mix with std::move
+  KShortestPathsTestParameters parameters;
+
+  MockAqlServer server;
+  ExecutionState state;
+  ResourceMonitor monitor;
+  AqlItemBlockManager itemBlockManager;
+  SharedAqlItemBlockPtr block;
+
+  std::unique_ptr<arangodb::aql::Query> fakedQuery;
+  ShortestPathOptions options;
+
+  KShortestPathsExecutorInfos infos;
+
+  FakeKShortestPathsFinder& finder;
+
+  SharedAqlItemBlockPtr inputBlock;
+  AqlItemBlockInputRange input;
+
+  std::shared_ptr<Builder> fakeUnusedBlock;
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher;
+
+  KShortestPathsExecutor testee;
+  OutputAqlItemRow output;
+
+  KShortestPathsExecutorTest()
+      : parameters(GetParam()),
+        server{},
+        itemBlockManager(&monitor, SerializationFormat::SHADOWROWS),
+        fakedQuery(server.createFakeQuery()),
+        options(fakedQuery.get()),
+        infos(std::make_shared<RegisterSet>(parameters._inputRegisters),
+              std::make_shared<RegisterSet>(parameters._outputRegisters), 2, 3, {}, {0},
+              std::make_unique<FakeKShortestPathsFinder>(options, parameters._paths),
+              std::move(parameters._source), std::move(parameters._target)),
+        finder(static_cast<FakeKShortestPathsFinder&>(infos.finder())),
+        inputBlock(buildBlock<2>(itemBlockManager, std::move(parameters._inputMatrix))),
+        input(AqlItemBlockInputRange(ExecutorState::DONE, 0, inputBlock, 0)),
+        fakeUnusedBlock(VPackParser::fromJson("[]")),
+        fetcher(itemBlockManager, fakeUnusedBlock->steal(), false),
+        testee(fetcher, infos),
+        output(std::move(block), infos.getOutputRegisters(),
+               infos.registersToKeep(), infos.registersToClear()) {}
+
+  size_t ExpectedNumberOfRowsProduced(size_t expectedFound) {
+    if (parameters._call.getOffset() >= expectedFound) {
+      return 0;
+    } else {
+      expectedFound -= parameters._call.getOffset();
+    }
+    return parameters._call.clampToLimit(expectedFound);
+  }
+
+  void ValidateCalledWith() {
+    auto calledWith = finder.getCalledWith();
+    auto block = buildBlock<2>(itemBlockManager, std::move(parameters._inputMatrix));
+
+    // We should always only call the finder at most for all input rows
+    ASSERT_LE(calledWith.size(), block->size());
+
+    auto blockIndex = size_t{0};
+    for (auto const& input : calledWith) {
+      auto source = std::string{};
+      auto target = std::string{};
+
+      if (infos.useRegisterForSourceInput()) {
+        AqlValue value = block->getValue(blockIndex, infos.getSourceInputRegister());
+        ASSERT_TRUE(value.isString());
+        source = value.slice().copyString();
+      } else {
+        source = infos.getSourceInputValue();
+      }
+
+      if (infos.useRegisterForTargetInput()) {
+        AqlValue value = block->getValue(blockIndex, infos.getTargetInputRegister());
+        ASSERT_TRUE(value.isString());
+        target = value.slice().copyString();
+      } else {
+        target = infos.getTargetInputValue();
+      }
+      ASSERT_EQ(source, input.first);
+      ASSERT_EQ(target, input.second);
+      blockIndex++;
+    }
+  }
+
+  void ValidateResult(std::vector<SharedAqlItemBlockPtr>& results,
+                      size_t skippedInitial, size_t skippedFullCount) {
+    auto pathsFound = finder.getPathsProduced();
+
+    // We expect to be getting exactly the rows returned
+    // that we produced with the shortest path finder.
+    // in exactly the order they were produced in.
+
+    auto expectedNrRowsSkippedInitial =
+        std::min(parameters._call.getOffset(), pathsFound.size());
+    EXPECT_EQ(skippedInitial, expectedNrRowsSkippedInitial);
+
+    auto expectedNrRowsProduced = ExpectedNumberOfRowsProduced(pathsFound.size());
+
+    auto expectedRowsIndex = size_t{skippedInitial};
+    for (auto const& block : results) {
+      if (block != nullptr) {
+        for (size_t blockIndex = 0; blockIndex < block->size(); ++blockIndex, ++expectedRowsIndex) {
+          AqlValue value = block->getValue(blockIndex, infos.getOutputRegister());
+          EXPECT_TRUE(value.isArray());
+
+          // Note that the correct layout of the result path is currently the
+          // responsibility of the path finder (tested separately), so we get
+          // away with fake outputs.
+          auto verticesResult = VPackArrayIterator(value.slice());
+          auto pathExpected = pathsFound.at(expectedRowsIndex);
+          auto verticesExpected = std::begin(pathExpected);
+
+          while (verticesExpected != std::end(pathExpected) &&
+                 verticesResult != verticesResult.end()) {
+            ASSERT_EQ((*verticesResult).copyString(), *verticesExpected);
+            verticesResult++;
+            verticesExpected++;
+          }
+          ASSERT_TRUE((verticesExpected == std::end(pathExpected)) &&
+                      // Yes, really, they didn't implement == for iterators
+                      !(verticesResult != verticesResult.end()));
+        }
+      }
+    }
+
+    ASSERT_EQ(expectedRowsIndex - skippedInitial, expectedNrRowsProduced);
+
+    // If a fullCount was requested, the sum (skippedInitial + produced +
+    // skippedFullCount) should be exactly the number of rows we produced.
+    if (parameters._call.fullCount) {
+      ASSERT_EQ(skippedInitial + (expectedRowsIndex - skippedInitial) + skippedFullCount,
+                pathsFound.size());
+    }
+  }
+
+  void TestExecutor(KShortestPathsExecutorInfos& infos, AqlItemBlockInputRange& input) {
+    // This will fetch everything now, unless we give a small enough atMost
+
+    auto stats = NoStats{};
+    auto ourCall = AqlCall{parameters._call};
+    auto skippedInitial = size_t{0};
+    auto skippedFullCount = size_t{0};
+    auto state = ExecutorState{ExecutorState::HASMORE};
+    auto outputs = std::vector<SharedAqlItemBlockPtr>{};
+
+    if (ourCall.getOffset() > 0) {
+      std::tie(state, stats, skippedInitial, std::ignore) =
+          testee.skipRowsRange(input, ourCall);
+    }
+
+    while (state == ExecutorState::HASMORE && ourCall.getLimit() > 0) {
+      SharedAqlItemBlockPtr block =
+          itemBlockManager.requestBlock(parameters._blockSize, 4);
+
+      OutputAqlItemRow output(std::move(block), infos.getOutputRegisters(),
+                              infos.registersToKeep(), infos.registersToClear());
+      output.setCall(std::move(ourCall));
+
+      std::tie(state, std::ignore, std::ignore) = testee.produceRows(input, output);
+
+      outputs.emplace_back(output.stealBlock());
+      ourCall = output.stealClientCall();
+    }
+
+    if (ourCall.needsFullCount()) {
+      std::tie(state, stats, skippedFullCount, std::ignore) =
+          testee.skipRowsRange(input, ourCall);
+    }
+
+    ValidateCalledWith();
+    ValidateResult(outputs, skippedInitial, skippedFullCount);
+  }
+};  // namespace aql
+
+TEST_P(KShortestPathsExecutorTest, the_test) { TestExecutor(infos, input); }
+
+// Conflict with the other shortest path finder
+namespace {
+
+Vertex const constSource("vertex/source"), constTarget("vertex/target"),
+    regSource(0), regTarget(1), brokenSource{"IwillBreakYourSearch"},
+    brokenTarget{"I will also break your search"};
+
+MatrixBuilder<2> const noneRow{{{{}}}};
+MatrixBuilder<2> const oneRow{{{{R"("vertex/source")"}, {R"("vertex/target")"}}}};
+MatrixBuilder<2> const twoRows{{{{R"("vertex/source")"}, {R"("vertex/target")"}}},
+                               {{{R"("vertex/a")"}, {R"("vertex/b")"}}}};
+MatrixBuilder<2> const threeRows{{{{R"("vertex/source")"}, {R"("vertex/target")"}}},
+                                 {{{R"("vertex/a")"}, {R"("vertex/b")"}}},
+                                 {{{R"("vertex/a")"}, {R"("vertex/target")"}}}};
+MatrixBuilder<2> const someRows{{{{R"("vertex/c")"}, {R"("vertex/target")"}}},
+                                {{{R"("vertex/b")"}, {R"("vertex/target")"}}},
+                                {{{R"("vertex/e")"}, {R"("vertex/target")"}}},
+                                {{{R"("vertex/a")"}, {R"("vertex/target")"}}}};
+
+PathSequence const noPath = {};
+PathSequence const onePath = {
+    {"vertex/source", "vertex/intermed", "vertex/target"}};
+
+PathSequence const threePaths = {
+    {"vertex/source", "vertex/intermed", "vertex/target"},
+    {"vertex/a", "vertex/b", "vertex/c", "vertex/d"},
+    {"vertex/source", "vertex/b", "vertex/c", "vertex/d"},
+    {"vertex/a", "vertex/b", "vertex/target"}};
+
+PathSequence const somePaths = {
+    {"vertex/source", "vertex/intermed0", "vertex/target"},
+    {"vertex/a", "vertex/b", "vertex/c", "vertex/d"},
+    {"vertex/source", "vertex/intermed1", "vertex/target"},
+    {"vertex/source", "vertex/intermed2", "vertex/target"},
+    {"vertex/a", "vertex/b", "vertex/c", "vertex/d"},
+    {"vertex/source", "vertex/intermed3", "vertex/target"},
+    {"vertex/source", "vertex/intermed4", "vertex/target"},
+    {"vertex/a", "vertex/b", "vertex/c", "vertex/d"},
+    {"vertex/source", "vertex/intermed5", "vertex/target"},
+};
+
+// Some of the bigger test cases we should generate and not write out like a caveperson
+PathSequence generateSomeBiggerCase(size_t n) {
+  auto paths = PathSequence{};
+
+  for (size_t i = 0; i < n; i++) {
+    paths.push_back({"vertex/source", "vertex/intermed0", "vertex/target"});
+  }
+
+  return paths;
+}
+
+auto sources = testing::Values(constSource, regSource, brokenSource);
+auto targets = testing::Values(constTarget, regTarget, brokenTarget);
+auto inputs = testing::Values(noneRow, oneRow, twoRows, threeRows);
+auto paths =
+    testing::Values(noPath, onePath, threePaths, somePaths,
+                    generateSomeBiggerCase(100), generateSomeBiggerCase(999),
+                    generateSomeBiggerCase(1000), generateSomeBiggerCase(2000));
+auto calls =
+    testing::Values(AqlCall{}, AqlCall{0, 0, 0, false}, AqlCall{0, 1, 0, false},
+                    AqlCall{0, 0, 1, false}, AqlCall{0, 1, 1, false},
+                    AqlCall{1, 1, 1}, AqlCall{100, 1, 1}, AqlCall{1000},
+                    AqlCall{0, AqlCall::Infinity{}, AqlCall::Infinity{}, true});
+auto blockSizes = testing::Values(5, 1000);
+
+INSTANTIATE_TEST_CASE_P(KShortestPathExecutorTestInstance, KShortestPathsExecutorTest,
+                        testing::Combine(sources, targets, inputs, paths, calls, blockSizes));
+}  // namespace
+
+}  // namespace aql
+}  // namespace tests
+}  // namespace arangodb
diff --git a/tests/Aql/ShortestPathExecutorTest.cpp b/tests/Aql/ShortestPathExecutorTest.cpp
index 11ad12eacb56..a275e920ab95 100644
--- a/tests/Aql/ShortestPathExecutorTest.cpp
+++ b/tests/Aql/ShortestPathExecutorTest.cpp
@@ -486,6 +486,8 @@ class ShortestPathExecutorTest
 
 TEST_P(ShortestPathExecutorTest, the_test) { TestExecutor(); }
 
+// Namespace conflict with the other shortest path executor
+namespace {
 Vertex const constSource("vertex/source"), constTarget("vertex/target"),
     regSource(0), regTarget(1), brokenSource{"IwillBreakYourSearch"},
     brokenTarget{"I will also break your search"};
@@ -545,7 +547,7 @@ auto blockSizes = testing::Values(size_t{5}, 1000);
 INSTANTIATE_TEST_CASE_P(ShortestPathExecutorTestInstance, ShortestPathExecutorTest,
                         testing::Combine(sources, targets, inputs, paths, calls,
                                          variants, blockSizes));
-
+}  // namespace
 }  // namespace aql
 }  // namespace tests
 }  // namespace arangodb
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 6ba73256b04f..5061dd53a789 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -50,6 +50,7 @@ set(ARANGODB_TESTS_SOURCES
   Aql/IdExecutorTest.cpp
   Aql/IndexNodeTest.cpp
   Aql/InsertExecutorTest.cpp
+  Aql/KShortestPathsExecutorTest.cpp
   Aql/LimitExecutorTest.cpp
   Aql/MockTypedNode.cpp
   Aql/MultiDepFetcherHelper.cpp

From b81dc9437ee46ed045fec52084f71605ac22492b Mon Sep 17 00:00:00 2001
From: Markus Pfeiffer <markuspf@users.noreply.github.com>
Date: Tue, 25 Feb 2020 10:57:11 +0000
Subject: [PATCH 075/122] Feature/aql subquery execution block impl execute
 implementation traversal executor (#11023)

* Move to new executor interface

* Fix tests and some bugs

* new skip signature

* new skip signature

* Fix Traversal Executor Skipping

* Fix compiler complaint

Co-authored-by: Michael Hackstein <michael@arangodb.com>
---
 arangod/Aql/ExecutionBlockImpl.cpp  |   4 +-
 arangod/Aql/TraversalExecutor.cpp   | 252 +++++++++++++++------------
 arangod/Aql/TraversalExecutor.h     |  24 +--
 tests/Aql/TraversalExecutorTest.cpp | 255 +++++++++++++---------------
 4 files changed, 274 insertions(+), 261 deletions(-)

diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index 5c63d1bccdd1..6395cd3ad42b 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -144,7 +144,7 @@ constexpr bool isNewStyleExecutor =
                 TestLambdaExecutor,
                 TestLambdaSkipExecutor,  // we need one after these to avoid compile errors in non-test mode
 #endif
-                KShortestPathsExecutor, ShortestPathExecutor, EnumerateListExecutor, LimitExecutor>;
+                TraversalExecutor, KShortestPathsExecutor, ShortestPathExecutor, EnumerateListExecutor, LimitExecutor>;
 
 template <class Executor>
 ExecutionBlockImpl<Executor>::ExecutionBlockImpl(ExecutionEngine* engine,
@@ -1083,7 +1083,7 @@ static SkipRowsRangeVariant constexpr skipRowsType() {
 #ifdef ARANGODB_USE_GOOGLE_TESTS
                                  TestLambdaSkipExecutor,
 #endif
-                                 EnumerateListExecutor, SortedCollectExecutor, LimitExecutor>),
+                                 TraversalExecutor, EnumerateListExecutor, SortedCollectExecutor, LimitExecutor>),
                 "Unexpected executor for SkipVariants::EXECUTOR");
 
   // The LimitExecutor will not work correctly with SkipVariants::FETCHER!
diff --git a/arangod/Aql/TraversalExecutor.cpp b/arangod/Aql/TraversalExecutor.cpp
index 946a3fcc0fd1..c111df3861a4 100644
--- a/arangod/Aql/TraversalExecutor.cpp
+++ b/arangod/Aql/TraversalExecutor.cpp
@@ -146,11 +146,7 @@ std::vector<std::pair<Variable const*, RegisterId>> const& TraversalExecutorInfo
 }
 
 TraversalExecutor::TraversalExecutor(Fetcher& fetcher, Infos& infos)
-    : _infos(infos),
-      _fetcher(fetcher),
-      _input{CreateInvalidInputRowHint{}},
-      _rowState(ExecutionState::HASMORE),
-      _traverser(infos.traverser()) {}
+    : _infos(infos), _inputRow{CreateInvalidInputRowHint{}}, _traverser(infos.traverser()) {}
 
 TraversalExecutor::~TraversalExecutor() {
   auto opts = _traverser.options();
@@ -175,133 +171,169 @@ std::pair<ExecutionState, Result> TraversalExecutor::shutdown(int errorCode) {
 }
 
 std::pair<ExecutionState, TraversalStats> TraversalExecutor::produceRows(OutputAqlItemRow& output) {
-  TraversalStats s;
+  // TODO: Remove me!
+  TRI_ASSERT(false);
+  return {ExecutionState::DONE, TraversalStats{}};
+}
+
+auto TraversalExecutor::doOutput(OutputAqlItemRow& output) -> void {
+  // TODO check whether _traverser.hasMore is obsolete here
+  while (!output.isFull() && _traverser.hasMore() && _traverser.next()) {
+    TRI_ASSERT(_inputRow.isInitialized());
+
+    // traverser now has next v, e, p values
+    if (_infos.useVertexOutput()) {
+      AqlValue vertex = _traverser.lastVertexToAqlValue();
+      output.cloneValueInto(_infos.vertexRegister(), _inputRow, vertex);
+    }
+    if (_infos.useEdgeOutput()) {
+      AqlValue edge = _traverser.lastEdgeToAqlValue();
+      output.cloneValueInto(_infos.edgeRegister(), _inputRow, edge);
+    }
+    if (_infos.usePathOutput()) {
+      transaction::BuilderLeaser tmp(_traverser.trx());
+      AqlValue path = _traverser.pathToAqlValue(*tmp.builder());
+      output.cloneValueInto(_infos.pathRegister(), _inputRow, path);
+    }
+    output.advanceRow();
+  }
+}
+
+auto TraversalExecutor::doSkip(AqlCall& call) -> size_t {
+  auto skip = size_t{0};
+
+  while (call.shouldSkip() && _traverser.hasMore() && _traverser.next()) {
+    skip++;
+    call.didSkip(1);
+  }
+
+  return skip;
+}
+
+auto TraversalExecutor::produceRows(AqlItemBlockInputRange& input, OutputAqlItemRow& output)
+    -> std::tuple<ExecutorState, Stats, AqlCall> {
+  TraversalStats stats;
+  ExecutorState state{ExecutorState::HASMORE};
 
   while (true) {
-    if (!_input.isInitialized()) {
-      if (_rowState == ExecutionState::DONE) {
-        // we are done
-        s.addFiltered(_traverser.getAndResetFilteredPaths());
-        s.addScannedIndex(_traverser.getAndResetReadDocuments());
-        s.addHttpRequests(_traverser.getAndResetHttpRequests());
-        return {_rowState, s};
-      }
-      std::tie(_rowState, _input) = _fetcher.fetchRow();
-      if (_rowState == ExecutionState::WAITING) {
-        TRI_ASSERT(!_input.isInitialized());
-        s.addFiltered(_traverser.getAndResetFilteredPaths());
-        s.addScannedIndex(_traverser.getAndResetReadDocuments());
-        s.addHttpRequests(_traverser.getAndResetHttpRequests());
-        return {_rowState, s};
-      }
+    if (_traverser.hasMore()) {
+      TRI_ASSERT(_inputRow.isInitialized());
+      doOutput(output);
 
-      if (!_input.isInitialized()) {
-        // We tried to fetch, but no upstream
-        TRI_ASSERT(_rowState == ExecutionState::DONE);
-        s.addFiltered(_traverser.getAndResetFilteredPaths());
-        s.addScannedIndex(_traverser.getAndResetReadDocuments());
-        s.addHttpRequests(_traverser.getAndResetHttpRequests());
-        return {_rowState, s};
-      }
-      if (!resetTraverser()) {
-        // Could not start here, (invalid)
-        // Go to next
-        _input = InputAqlItemRow{CreateInvalidInputRowHint{}};
-        continue;
+      if (output.isFull()) {
+        if (_traverser.hasMore()) {
+          state = ExecutorState::HASMORE;
+          break;
+        } else {
+          state = input.upstreamState();
+          break;
+        }
       }
-    }
-    if (!_traverser.hasMore() || !_traverser.next()) {
-      // Nothing more to read, reset input to refetch
-      _input = InputAqlItemRow{CreateInvalidInputRowHint{}};
     } else {
-      // traverser now has next v, e, p values
-      if (_infos.useVertexOutput()) {
-        AqlValue vertex = _traverser.lastVertexToAqlValue();
-        AqlValueGuard guard{vertex, true};
-        output.moveValueInto(_infos.vertexRegister(), _input, guard);
-      }
-      if (_infos.useEdgeOutput()) {
-        AqlValue edge = _traverser.lastEdgeToAqlValue();
-        AqlValueGuard guard{edge, true};
-        output.moveValueInto(_infos.edgeRegister(), _input, guard);
+      if (!initTraverser(input)) {
+        state = input.upstreamState();
+        break;
       }
-      if (_infos.usePathOutput()) {
-        transaction::BuilderLeaser tmp(_traverser.trx());
-        AqlValue path = _traverser.pathToAqlValue(*tmp.builder());
-        AqlValueGuard guard{path, true};
-        output.moveValueInto(_infos.pathRegister(), _input, guard);
-      }
-      s.addFiltered(_traverser.getAndResetFilteredPaths());
-      s.addScannedIndex(_traverser.getAndResetReadDocuments());
-      s.addHttpRequests(_traverser.getAndResetHttpRequests());
-      return {computeState(), s};
+      TRI_ASSERT(_inputRow.isInitialized());
     }
   }
 
-  s.addFiltered(_traverser.getAndResetFilteredPaths());
-  s.addScannedIndex(_traverser.getAndResetReadDocuments());
-  return {ExecutionState::DONE, s};
+  stats.addFiltered(_traverser.getAndResetFilteredPaths());
+  stats.addScannedIndex(_traverser.getAndResetReadDocuments());
+  stats.addHttpRequests(_traverser.getAndResetHttpRequests());
+
+  return {state, stats, AqlCall{}};
 }
 
-ExecutionState TraversalExecutor::computeState() const {
-  if (_rowState == ExecutionState::DONE && !_traverser.hasMore()) {
-    return ExecutionState::DONE;
+auto TraversalExecutor::skipRowsRange(AqlItemBlockInputRange& input, AqlCall& call)
+    -> std::tuple<ExecutorState, Stats, size_t, AqlCall> {
+  TraversalStats stats{};
+  auto skipped = size_t{0};
+
+  while (true) {
+    skipped += doSkip(call);
+
+    stats.addFiltered(_traverser.getAndResetFilteredPaths());
+    stats.addScannedIndex(_traverser.getAndResetReadDocuments());
+    stats.addHttpRequests(_traverser.getAndResetHttpRequests());
+
+    if (!_traverser.hasMore()) {
+      if (!initTraverser(input)) {
+        return {input.upstreamState(), stats, skipped, AqlCall{}};
+      }
+    } else {
+      TRI_ASSERT(call.getOffset() == 0);
+      return {ExecutorState::HASMORE, stats, skipped, AqlCall{}};
+    }
   }
-  return ExecutionState::HASMORE;
 }
 
-bool TraversalExecutor::resetTraverser() {
+//
+// Set a new start vertex for traversal, for this fetch inputs
+// from input until we are either successful or input is unwilling
+// to give us more.
+//
+// TODO: this is quite a big function, refactor
+bool TraversalExecutor::initTraverser(AqlItemBlockInputRange& input) {
   _traverser.clear();
-
-  // Initialize the Expressions within the options.
-  // We need to find the variable and read its value here. Everything is
-  // computed right now.
   auto opts = _traverser.options();
   opts->clearVariableValues();
-  for (auto const& pair : _infos.filterConditionVariables()) {
-    opts->setVariableValue(pair.first, _input.getValue(pair.second));
-  }
-  if (opts->usesPrune()) {
-    auto* evaluator = opts->getPruneEvaluator();
-    // Replace by inputRow
-    evaluator->prepareContext(_input);
-  }
+
   // Now reset the traverser
-  if (_infos.usesFixedSource()) {
-    auto pos = _infos.getFixedSource().find('/');
-    if (pos == std::string::npos) {
-      _traverser.options()->query()->registerWarning(
-          TRI_ERROR_BAD_PARAMETER,
-          "Invalid input for traversal: "
-          "Only id strings or objects with "
-          "_id are allowed");
-      return false;
-    } else {
-      // Use constant value
-      _traverser.setStartVertex(_infos.getFixedSource());
-      return true;
+  // NOTE: It is correct to ask for whether there is a data row here
+  //       even if we're using a constant start vertex, as we expect
+  //       to provide output for every input row
+  while (input.hasDataRow()) {
+    // Try to acquire a starting vertex
+    std::tie(std::ignore, _inputRow) = input.nextDataRow();
+    TRI_ASSERT(_inputRow.isInitialized());
+
+    if (opts->usesPrune()) {
+      auto* evaluator = opts->getPruneEvaluator();
+      // Replace by inputRow
+      evaluator->prepareContext(_inputRow);
+      TRI_ASSERT(_inputRow.isInitialized());
     }
-  } else {
-    AqlValue const& in = _input.getValue(_infos.getInputRegister());
-    if (in.isObject()) {
-      try {
-        _traverser.setStartVertex(_traverser.options()->trx()->extractIdString(in.slice()));
+
+    TRI_ASSERT(_inputRow.isInitialized());
+    if (_infos.usesFixedSource()) {
+      auto pos = _infos.getFixedSource().find('/');
+      if (pos == std::string::npos) {
+        _traverser.options()->query()->registerWarning(
+            TRI_ERROR_BAD_PARAMETER,
+            "Invalid input for traversal: "
+            "Only id strings or objects with "
+            "_id are allowed");
+      } else {
+        // Use constant value
+        _traverser.setStartVertex(_infos.getFixedSource());
+        TRI_ASSERT(_inputRow.isInitialized());
         return true;
-      } catch (...) {
-        // on purpose ignore this error.
-        return false;
       }
-      // _id or _key not present we cannot start here, register warning take next
-    } else if (in.isString()) {
-      _traverser.setStartVertex(in.slice().copyString());
-      return true;
     } else {
-      _traverser.options()->query()->registerWarning(
-          TRI_ERROR_BAD_PARAMETER,
-          "Invalid input for traversal: Only "
-          "id strings or objects with _id are "
-          "allowed");
-      return false;
+      AqlValue const& in = _inputRow.getValue(_infos.getInputRegister());
+      if (in.isObject()) {
+        try {
+          _traverser.setStartVertex(
+              _traverser.options()->trx()->extractIdString(in.slice()));
+          TRI_ASSERT(_inputRow.isInitialized());
+          return true;
+        } catch (...) {
+          // on purpose ignore this error.
+        }
+      } else if (in.isString()) {
+        _traverser.setStartVertex(in.slice().copyString());
+        TRI_ASSERT(_inputRow.isInitialized());
+        return true;
+      } else {
+        // _id or _key not present we cannot start here, register warning take next
+        _traverser.options()->query()->registerWarning(
+            TRI_ERROR_BAD_PARAMETER,
+            "Invalid input for traversal: Only "
+            "id strings or objects with _id are "
+            "allowed");
+      }
     }
   }
+  return false;
 }
diff --git a/arangod/Aql/TraversalExecutor.h b/arangod/Aql/TraversalExecutor.h
index f749e85d8301..a614fa0d5e56 100644
--- a/arangod/Aql/TraversalExecutor.h
+++ b/arangod/Aql/TraversalExecutor.h
@@ -23,6 +23,8 @@
 #ifndef ARANGOD_AQL_TRAVERSAL_EXECUTOR_H
 #define ARANGOD_AQL_TRAVERSAL_EXECUTOR_H
 
+#include "Aql/AqlCall.h"
+#include "Aql/AqlItemBlockInputRange.h"
 #include "Aql/ExecutionState.h"
 #include "Aql/ExecutorInfos.h"
 #include "Aql/InputAqlItemRow.h"
@@ -136,22 +138,24 @@ class TraversalExecutor {
    *
    * @return ExecutionState, and if successful exactly one new Row of AqlItems.
    */
-  std::pair<ExecutionState, Stats> produceRows(OutputAqlItemRow& output);
+  [[nodiscard]] auto produceRows(OutputAqlItemRow& output)
+      -> std::pair<ExecutionState, Stats>;
+
+  [[nodiscard]] auto produceRows(AqlItemBlockInputRange& input, OutputAqlItemRow& output)
+      -> std::tuple<ExecutorState, Stats, AqlCall>;
+  [[nodiscard]] auto skipRowsRange(AqlItemBlockInputRange& input, AqlCall& call)
+      -> std::tuple<ExecutorState, Stats, size_t, AqlCall>;
 
  private:
-  /**
-   * @brief compute the return state
-   * @return DONE if traverser and remote are both done, HASMORE otherwise
-   */
-  ExecutionState computeState() const;
+  auto doOutput(OutputAqlItemRow& output) -> void;
+  [[nodiscard]] auto doSkip(AqlCall& call) -> size_t;
 
-  bool resetTraverser();
+  [[nodiscard]] bool initTraverser(AqlItemBlockInputRange& input);
 
  private:
   Infos& _infos;
-  Fetcher& _fetcher;
-  InputAqlItemRow _input;
-  ExecutionState _rowState;
+  InputAqlItemRow _inputRow;
+
   traverser::Traverser& _traverser;
 };
 
diff --git a/tests/Aql/TraversalExecutorTest.cpp b/tests/Aql/TraversalExecutorTest.cpp
index 597ad49e0bd1..f219a3cb1c27 100644
--- a/tests/Aql/TraversalExecutorTest.cpp
+++ b/tests/Aql/TraversalExecutorTest.cpp
@@ -36,6 +36,8 @@
 #include "Graph/Traverser.h"
 #include "Graph/TraverserOptions.h"
 
+#include "Aql/AqlItemBlockHelper.h"
+#include "Aql/RowFetcherHelper.h"
 #include "Mocks/Servers.h"
 
 #include <velocypack/Buffer.h>
@@ -253,7 +255,7 @@ static TraverserOptions generateOptions(arangodb::aql::Query* query, size_t min,
 
 class TraversalExecutorTestInputStartVertex : public ::testing::Test {
  protected:
-  ExecutionState state;
+  ExecutorState state;
   mocks::MockAqlServer server;
 
   std::unique_ptr<arangodb::aql::Query> fakedQuery;
@@ -302,145 +304,121 @@ class TraversalExecutorTestInputStartVertex : public ::testing::Test {
   {}
 };
 
-TEST_F(TraversalExecutorTestInputStartVertex, there_are_no_rows_upstream_producer_doesnt_wait) {
-  VPackBuilder input;
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input.steal(), false);
-  TraversalExecutor testee(fetcher, infos);
-  TraversalStats stats{};
-
-  OutputAqlItemRow result(std::move(block), infos.getOutputRegisters(),
-                          infos.registersToKeep(), infos.registersToClear());
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(result.produced());
-}
+TEST_F(TraversalExecutorTestInputStartVertex, there_are_no_rows_upstream_producer_doesnt_produce) {
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, VPackParser::fromJson("[]")->steal(), false);
 
-TEST_F(TraversalExecutorTestInputStartVertex, there_are_no_rows_upstream_producer_waits) {
-  VPackBuilder input;
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input.steal(), true);
   TraversalExecutor testee(fetcher, infos);
   TraversalStats stats{};
 
+  auto inputBlock = buildBlock<1>(itemBlockManager, MatrixBuilder<1>{{{}}});
+  auto input =
+      AqlItemBlockInputRange{ExecutorState::DONE, 0, inputBlock, 0};
+
   OutputAqlItemRow result(std::move(block), infos.getOutputRegisters(),
                           infos.registersToKeep(), infos.registersToClear());
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::WAITING);
-  ASSERT_FALSE(result.produced());
-  ASSERT_EQ(stats.getFiltered(), 0);
+  AqlCall call;
 
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
+  std::tie(state, stats, call) = testee.produceRows(input, result);
+  ASSERT_EQ(state, ExecutorState::DONE);
   ASSERT_FALSE(result.produced());
-  ASSERT_EQ(stats.getFiltered(), 0);
 }
 
-TEST_F(TraversalExecutorTestInputStartVertex, there_are_rows_upstream_producer_doesnt_wait) {
+TEST_F(TraversalExecutorTestInputStartVertex, there_are_rows_upstream_producer_produced) {
   myGraph.addVertex("1");
   myGraph.addVertex("2");
   myGraph.addVertex("3");
-  auto input = VPackParser::fromJson(R"([["v/1"], ["v/2"], ["v/3"]])");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), false);
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, VPackParser::fromJson("[]")->steal(), false);
   TraversalExecutor testee(fetcher, infos);
   TraversalStats stats{};
 
+  auto inputBlock =
+      buildBlock<1>(itemBlockManager,
+                    MatrixBuilder<1>{{{{R"("v/1")"}}}, {{{R"("v/2")"}}}, {{{R"("v/3")"}}}});
+  auto input =
+      AqlItemBlockInputRange{ExecutorState::DONE, 0, inputBlock, 0};
+
   OutputAqlItemRow row(std::move(block), infos.getOutputRegisters(),
                        infos.registersToKeep(), infos.registersToClear());
+  auto call = AqlCall{};
 
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(state, ExecutionState::DONE);
+  std::tie(state, stats, call) = testee.produceRows(input, row);
+  ASSERT_EQ(state, ExecutorState::DONE);
   ASSERT_EQ(stats.getFiltered(), 0);
   ASSERT_FALSE(row.produced());
-  ASSERT_TRUE(fetcher.isDone());
-  ASSERT_EQ(fetcher.nrCalled(), 3);
 
   ASSERT_EQ(traverser->startVertexUsedAt(0), "v/1");
   ASSERT_EQ(traverser->startVertexUsedAt(1), "v/2");
   ASSERT_EQ(traverser->startVertexUsedAt(2), "v/3");
 
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(state, ExecutionState::DONE);
+  std::tie(state, stats, call) = testee.produceRows(input, row);
+  ASSERT_EQ(state, ExecutorState::DONE);
   ASSERT_EQ(stats.getFiltered(), 0);
   ASSERT_FALSE(row.produced());
-  ASSERT_TRUE(fetcher.isDone());
-  ASSERT_EQ(fetcher.nrCalled(), 3);
 }
 
-TEST_F(TraversalExecutorTestInputStartVertex,
-       there_are_rows_upstream_producer_waits_no_edges_are_connected) {
+TEST_F(TraversalExecutorTestInputStartVertex, there_are_rows_no_edges_are_connected) {
   myGraph.addVertex("1");
   myGraph.addVertex("2");
   myGraph.addVertex("3");
-  auto input = VPackParser::fromJson(R"([["v/1"], ["v/2"], ["v/3"]])");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), true);
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, VPackParser::fromJson("[]")->steal(), true);
   TraversalExecutor testee(fetcher, infos);
   TraversalStats stats{};
 
+  auto inputBlock =
+      buildBlock<1>(itemBlockManager,
+                    MatrixBuilder<1>{{{{R"("v/1")"}}}, {{{R"("v/2")"}}}, {{{R"("v/3")"}}}});
+  auto input =
+      AqlItemBlockInputRange{ExecutorState::DONE, 0, inputBlock, 0};
+
   OutputAqlItemRow row(std::move(block), infos.getOutputRegisters(),
                        infos.registersToKeep(), infos.registersToClear());
+  auto call = AqlCall{};
 
-  for (size_t i = 0; i < 3; ++i) {
-    // We expect to wait 3 times
-    std::tie(state, stats) = testee.produceRows(row);
-    ASSERT_EQ(state, ExecutionState::WAITING);
-  }
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(state, ExecutionState::DONE);
+  std::tie(state, stats, call) = testee.produceRows(input, row);
+  ASSERT_EQ(state, ExecutorState::DONE);
   ASSERT_EQ(stats.getFiltered(), 0);
   ASSERT_FALSE(row.produced());
-  ASSERT_TRUE(fetcher.isDone());
-  ASSERT_EQ(fetcher.nrCalled(), 3);
 
   ASSERT_EQ(traverser->startVertexUsedAt(0), "v/1");
   ASSERT_EQ(traverser->startVertexUsedAt(1), "v/2");
   ASSERT_EQ(traverser->startVertexUsedAt(2), "v/3");
 
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(state, ExecutionState::DONE);
+  std::tie(state, stats, call) = testee.produceRows(input, row);
+  ASSERT_EQ(state, ExecutorState::DONE);
   ASSERT_EQ(stats.getFiltered(), 0);
   ASSERT_FALSE(row.produced());
-  ASSERT_TRUE(fetcher.isDone());
   // WAITING is not part of called counts
-  ASSERT_EQ(fetcher.nrCalled(), 3);
 }
 
-TEST_F(TraversalExecutorTestInputStartVertex,
-       there_are_rows_upstream_producer_waits_edges_are_connected) {
+TEST_F(TraversalExecutorTestInputStartVertex, there_are_rows_upstream_edges_are_connected) {
   myGraph.addVertex("1");
   myGraph.addVertex("2");
   myGraph.addVertex("3");
-  auto input = VPackParser::fromJson(R"([["v/1"], ["v/2"], ["v/3"]])");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), true);
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, VPackParser::fromJson("[]")->steal(), true);
   TraversalExecutor testee(fetcher, infos);
   TraversalStats stats{};
 
+  auto inputBlock =
+      buildBlock<1>(itemBlockManager,
+                    MatrixBuilder<1>{{{{R"("v/1")"}}}, {{{R"("v/2")"}}}, {{{R"("v/3")"}}}});
+  auto input =
+      AqlItemBlockInputRange{ExecutorState::DONE, 0, inputBlock, 0};
+
   myGraph.addEdge("1", "2", "1->2");
   myGraph.addEdge("2", "3", "2->3");
   myGraph.addEdge("3", "1", "3->1");
+
   ExecutionStats total;
   OutputAqlItemRow row(std::move(block), infos.getOutputRegisters(),
                        infos.registersToKeep(), infos.registersToClear());
+  auto call = AqlCall{};
 
-  for (int64_t i = 0; i < 3; ++i) {
-    // We expect to wait 3 times
-    std::tie(state, stats) = testee.produceRows(row);
-    total += stats;
-    ASSERT_EQ(state, ExecutionState::WAITING);
-    ASSERT_FALSE(row.produced());
-    std::tie(state, stats) = testee.produceRows(row);
-    ASSERT_TRUE(row.produced());
-    ASSERT_EQ(state, ExecutionState::HASMORE);
-    row.advanceRow();
-    total += stats;
-    ASSERT_EQ(total.filtered, 0);
-    /* We cannot ASSERT this because of internally to complex
-    mechanism */
-    // ASSERT_EQ(total.scannedIndex, i + 1);
-    ASSERT_EQ(fetcher.nrCalled(), (uint64_t)(i + 1));
-  }
-  ASSERT_TRUE(fetcher.isDone());
-  // The traverser will lie
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(state, ExecutionState::DONE);
+  std::tie(state, stats, call) = testee.produceRows(input, row);
+  ASSERT_EQ(state, ExecutorState::DONE);
   ASSERT_FALSE(row.produced());
 
   ASSERT_EQ(traverser->startVertexUsedAt(0), "v/1");
@@ -462,7 +440,7 @@ TEST_F(TraversalExecutorTestInputStartVertex,
 
 class TraversalExecutorTestConstantStartVertex : public ::testing::Test {
  protected:
-  ExecutionState state;
+  ExecutorState state;
   mocks::MockAqlServer server;
 
   std::unique_ptr<arangodb::aql::Query> fakedQuery;
@@ -508,34 +486,41 @@ class TraversalExecutorTestConstantStartVertex : public ::testing::Test {
               RegisterPlan::MaxRegisterId, filterConditionVariables) {}
 };
 
-TEST_F(TraversalExecutorTestConstantStartVertex, no_rows_upstream_producer_doesnt_wait) {
-  VPackBuilder input;
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input.steal(), false);
+TEST_F(TraversalExecutorTestConstantStartVertex, no_rows_upstream_producer_doesnt_produce) {
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, VPackParser::fromJson("[]")->steal(), false);
   TraversalExecutor testee(fetcher, infos);
   TraversalStats stats{};
 
+  auto inputBlock = buildBlock<1>(itemBlockManager, MatrixBuilder<1>{{{{}}}});
+  auto input =
+      AqlItemBlockInputRange{ExecutorState::DONE, 0, inputBlock, 0};
+
   OutputAqlItemRow result(std::move(block), infos.getOutputRegisters(),
                           infos.registersToKeep(), infos.registersToClear());
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
+  AqlCall call;
+
+  std::tie(state, stats, call) = testee.produceRows(input, result);
+  ASSERT_EQ(state, ExecutorState::DONE);
   ASSERT_FALSE(result.produced());
 }
 
-TEST_F(TraversalExecutorTestConstantStartVertex, no_rows_upstream_producer_waits) {
-  VPackBuilder input;
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input.steal(), true);
+TEST_F(TraversalExecutorTestConstantStartVertex, no_rows_upstream) {
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, VPackParser::fromJson("[]")->steal(), true);
   TraversalExecutor testee(fetcher, infos);
   TraversalStats stats{};
 
+  auto inputBlock = buildBlock<1>(itemBlockManager, MatrixBuilder<1>{{{{}}}});
+  auto input =
+      AqlItemBlockInputRange{ExecutorState::DONE, 0, inputBlock, 0};
+
   OutputAqlItemRow result(std::move(block), infos.getOutputRegisters(),
                           infos.registersToKeep(), infos.registersToClear());
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::WAITING);
-  ASSERT_FALSE(result.produced());
-  ASSERT_EQ(stats.getFiltered(), 0);
+  AqlCall call;
 
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
+  std::tie(state, stats, call) = testee.produceRows(input, result);
+  ASSERT_EQ(state, ExecutorState::DONE);
   ASSERT_FALSE(result.produced());
   ASSERT_EQ(stats.getFiltered(), 0);
 }
@@ -544,78 +529,80 @@ TEST_F(TraversalExecutorTestConstantStartVertex, rows_upstream_producer_doesnt_w
   myGraph.addVertex("1");
   myGraph.addVertex("2");
   myGraph.addVertex("3");
-  auto input = VPackParser::fromJson(R"([ ["v/1"], ["v/2"], ["v/3"] ])");
 
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), false);
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, VPackParser::fromJson("[]")->steal(), false);
   TraversalExecutor testee(fetcher, infos);
   TraversalStats stats{};
 
+  auto inputBlock =
+      buildBlock<1>(itemBlockManager,
+                    MatrixBuilder<1>{{{{R"("v/1")"}}}, {{{R"("v/2")"}}}, {{{R"("v/3")"}}}});
+  auto input =
+      AqlItemBlockInputRange{ExecutorState::DONE, 0, inputBlock, 0};
+
   OutputAqlItemRow row(std::move(block), infos.getOutputRegisters(),
                        infos.registersToKeep(), infos.registersToClear());
+  AqlCall call;
 
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(state, ExecutionState::DONE);
+  std::tie(state, stats, call) = testee.produceRows(input, row);
+  ASSERT_EQ(state, ExecutorState::DONE);
   ASSERT_EQ(stats.getFiltered(), 0);
   ASSERT_FALSE(row.produced());
-  ASSERT_TRUE(fetcher.isDone());
-  ASSERT_EQ(fetcher.nrCalled(), 3);
 
   ASSERT_EQ(traverser->startVertexUsedAt(0), "v/1");
   ASSERT_EQ(traverser->startVertexUsedAt(1), "v/1");
   ASSERT_EQ(traverser->startVertexUsedAt(2), "v/1");
 
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(state, ExecutionState::DONE);
+  std::tie(state, stats, call) = testee.produceRows(input, row);
+  ASSERT_EQ(state, ExecutorState::DONE);
   ASSERT_EQ(stats.getFiltered(), 0);
   ASSERT_FALSE(row.produced());
-  ASSERT_TRUE(fetcher.isDone());
-  ASSERT_EQ(fetcher.nrCalled(), 3);
 }
 
 TEST_F(TraversalExecutorTestConstantStartVertex, rows_upstream_producer_waits_no_edges_connected) {
   myGraph.addVertex("1");
   myGraph.addVertex("2");
   myGraph.addVertex("3");
-  auto input = VPackParser::fromJson(R"([ ["v/1"], ["v/2"], ["v/3"] ])");
 
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), true);
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, VPackParser::fromJson("[]")->steal(), true);
   TraversalExecutor testee(fetcher, infos);
   TraversalStats stats{};
   OutputAqlItemRow row(std::move(block), infos.getOutputRegisters(),
                        infos.registersToKeep(), infos.registersToClear());
 
-  for (size_t i = 0; i < 3; ++i) {
-    // We expect to wait 3 times
-    std::tie(state, stats) = testee.produceRows(row);
-    ASSERT_EQ(state, ExecutionState::WAITING);
-  }
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(state, ExecutionState::DONE);
+  auto inputBlock =
+      buildBlock<1>(itemBlockManager,
+                    MatrixBuilder<1>{{{{R"("v/1")"}}}, {{{R"("v/2")"}}}, {{{R"("v/3")"}}}});
+  auto input =
+      AqlItemBlockInputRange{ExecutorState::DONE, 0, inputBlock, 0};
+
+  AqlCall call;
+
+  std::tie(state, stats, call) = testee.produceRows(input, row);
+  ASSERT_EQ(state, ExecutorState::DONE);
   ASSERT_EQ(stats.getFiltered(), 0);
   ASSERT_FALSE(row.produced());
-  ASSERT_TRUE(fetcher.isDone());
-  ASSERT_EQ(fetcher.nrCalled(), 3);
 
   ASSERT_EQ(traverser->startVertexUsedAt(0), "v/1");
   ASSERT_EQ(traverser->startVertexUsedAt(1), "v/1");
   ASSERT_EQ(traverser->startVertexUsedAt(2), "v/1");
 
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(state, ExecutionState::DONE);
+  std::tie(state, stats, call) = testee.produceRows(input, row);
+  ASSERT_EQ(state, ExecutorState::DONE);
   ASSERT_EQ(stats.getFiltered(), 0);
   ASSERT_FALSE(row.produced());
-  ASSERT_TRUE(fetcher.isDone());
   // WAITING is not part of called counts
-  ASSERT_EQ(fetcher.nrCalled(), 3);
 }
 
-TEST_F(TraversalExecutorTestConstantStartVertex, rows_upstream_producer_waits_edges_connected) {
+TEST_F(TraversalExecutorTestConstantStartVertex, rows_edges_connected) {
   myGraph.addVertex("1");
   myGraph.addVertex("2");
   myGraph.addVertex("3");
-  auto input = VPackParser::fromJson(R"([ ["v/1"], ["v/2"], ["v/3"] ])");
 
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), true);
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
+      itemBlockManager, VPackParser::fromJson("[]")->steal(), true);
   TraversalExecutor testee(fetcher, infos);
   TraversalStats stats{};
   myGraph.addEdge("1", "2", "1->2");
@@ -625,27 +612,17 @@ TEST_F(TraversalExecutorTestConstantStartVertex, rows_upstream_producer_waits_ed
   OutputAqlItemRow row(std::move(block), infos.getOutputRegisters(),
                        infos.registersToKeep(), infos.registersToClear());
 
-  for (int64_t i = 0; i < 3; ++i) {
-    // We expect to wait 3 times
-    std::tie(state, stats) = testee.produceRows(row);
-    total += stats;
-    ASSERT_EQ(state, ExecutionState::WAITING);
-    ASSERT_FALSE(row.produced());
-    std::tie(state, stats) = testee.produceRows(row);
-    ASSERT_TRUE(row.produced());
-    ASSERT_EQ(state, ExecutionState::HASMORE);
-    row.advanceRow();
-    total += stats;
-    ASSERT_EQ(total.filtered, 0);
-    /* We cannot ASSERT this because of internally to complex
-    mechanism */
-    // ASSERT_EQ(total.scannedIndex, i + 1);
-    ASSERT_EQ(fetcher.nrCalled(), (uint64_t)(i + 1));
-  }
-  ASSERT_TRUE(fetcher.isDone());
+  auto inputBlock =
+      buildBlock<1>(itemBlockManager,
+                    MatrixBuilder<1>{{{{R"("v/1")"}}}, {{{R"("v/2")"}}}, {{{R"("v/3")"}}}});
+  auto input =
+      AqlItemBlockInputRange{ExecutorState::DONE, 0, inputBlock, 0};
+
+  AqlCall call;
+
   // The traverser will lie
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(state, ExecutionState::DONE);
+  std::tie(state, stats, call) = testee.produceRows(input, row);
+  ASSERT_EQ(state, ExecutorState::DONE);
   ASSERT_FALSE(row.produced());
 
   ASSERT_EQ(traverser->startVertexUsedAt(0), "v/1");

From 4dadc223aba766d02c04a86141575308a46bd70d Mon Sep 17 00:00:00 2001
From: Markus Pfeiffer <markuspf@users.noreply.github.com>
Date: Wed, 26 Feb 2020 21:01:42 +0000
Subject: [PATCH 076/122] Move SubqueryStartExecutor to new interface (#11025)

* Move SubqueryStartExecutor to new interface

* Diddle

* Tests pass for SubqueryStartExecutor

* Delete most of the SubqueryEndExecutor tests

They are irrelevant now as they only tested shadowrow behaviour.

Shadow Rows are now handled by ExecutionBlockImpl.

* Skeleton tests

* Junk

* Cleanup and make work

* Tweak ExecutorTestHelper to test pipelines

* SubqueryStart/SubqueryEnd

* Blafummel.

* Modifications

* Fixup tests

* Address some comments

* Fix.

* Fix tests

* Various fixes.

* Made the branch compile on Mac

* Intermediate commit, does not compile, required for merge

* Fixed one of the SplicedSubqueryTests

* Seperated ShadowRow handling for SubqueryStart/End executors to get a better overview and understanding on how it should behave.

* Allow to use a fullCallStack in ExecutorTestHelper.

* Added asserts on SubqueryEnd that is not allowed to be called with Skipped from upstream

* Use AqlTestCase in SubqueryStartExecutorTest. Transformed first test to TestHelper pipeline

* Let ExecutorTestHelper also test for shadowRows

* Adapted SingleInput=>Data+Shadow test to testing Helepr and make it pass

* Transformed existing SubqueryStart tests to Helper, fixed a test where there was no place for the ShadowRow to be written

* Fixed Skip in SubqueryStartExecutor

* Allow the Pipeline to add Consumer and dependency without fiddling with the Deque from outside

* Added Skip adn ShadowRowForwarding tests to SubqueryStartExecutor

* Fixed fullCount of SubqueryStart to be called properly.

* Renamed isModificationSubquery -> isModificatioNode again

* Consume more than one subquery en-block

* Fixed debugReporting in SplicedSubqueryTest. Disabled the skip in subquery tests for now

* Removed AQL debug log level from testing config

* First version of Subquery Skip bypassing. Including 1 passing test.

* Added disabled tests for skip, and proposed to do it later

* Fixed reporting of FILTERED in fullCount of EnumerateCollectionExecutor

* Enable calculationExecutor execute interface

* Fixed compile issues

* To Velocypack the modification Subquery value

* Fixed illegal assert and reactivated failure tests

* Fixed compile issue

* Deactivated Calculation again

* Added Compatibility Mode to AqlCallStack

* Removed IdExecutor<void> the only feature it has can be moved into IDexecutor in general. This still has to be done

* When falling back in BlocksWithClients use compatibility stack

* ConstFetcher now correctly reports if it skipped all input

* Fixed a bug in ExecutionBlockImpl, which would go into FetchMore state, even if the Executor still has data and is happy to produce more, but the output is full.

Co-authored-by: Michael Hackstein <michael@arangodb.com>
---
 arangod/Aql/AqlCallStack.cpp                 |  29 +-
 arangod/Aql/AqlCallStack.h                   |  10 +-
 arangod/Aql/BlocksWithClients.cpp            |   4 +-
 arangod/Aql/ClusterNodes.cpp                 |   2 +-
 arangod/Aql/ConstFetcher.cpp                 |   3 +-
 arangod/Aql/DistributeConsumerNode.cpp       |   3 +-
 arangod/Aql/DistributeExecutor.cpp           |   6 +-
 arangod/Aql/EnumerateCollectionExecutor.cpp  |  20 +-
 arangod/Aql/ExecutionBlockImpl.cpp           | 336 ++++++++++---
 arangod/Aql/ExecutionBlockImpl.h             |  11 +
 arangod/Aql/ExecutionEngine.cpp              |  22 +-
 arangod/Aql/ExecutionNode.cpp                |   9 +-
 arangod/Aql/ExecutionState.cpp               |   3 +
 arangod/Aql/IdExecutor.cpp                   | 139 ++----
 arangod/Aql/IdExecutor.h                     |  71 +--
 arangod/Aql/OptimizerRules.cpp               | 137 +++---
 arangod/Aql/OutputAqlItemRow.cpp             |   2 +
 arangod/Aql/ScatterExecutor.cpp              |   6 +-
 arangod/Aql/ShadowAqlItemRow.cpp             |   2 +-
 arangod/Aql/SubqueryEndExecutionNode.cpp     |  32 +-
 arangod/Aql/SubqueryEndExecutionNode.h       |   9 +-
 arangod/Aql/SubqueryEndExecutor.cpp          | 144 +++---
 arangod/Aql/SubqueryEndExecutor.h            |  31 +-
 arangod/Aql/SubqueryStartExecutionNode.h     |   3 +
 arangod/Aql/SubqueryStartExecutor.cpp        | 191 +++-----
 arangod/Aql/SubqueryStartExecutor.h          |  54 +--
 tests/Aql/ExecutionBlockImplTest.cpp         |   2 +-
 tests/Aql/ExecutionNodeTest.cpp              |  22 +-
 tests/Aql/ExecutorTestHelper.cpp             |  25 +
 tests/Aql/ExecutorTestHelper.h               |  58 ++-
 tests/Aql/IdExecutorTest.cpp                 | 221 ++++++---
 tests/Aql/SplicedSubqueryIntegrationTest.cpp | 471 +++++++++++++++++++
 tests/Aql/SubqueryEndExecutorTest.cpp        | 249 +---------
 tests/Aql/SubqueryStartExecutorTest.cpp      | 435 ++++++++++-------
 tests/Aql/WaitingExecutionBlockMock.cpp      |   2 +
 tests/CMakeLists.txt                         |   1 +
 36 files changed, 1681 insertions(+), 1084 deletions(-)
 create mode 100644 tests/Aql/SplicedSubqueryIntegrationTest.cpp

diff --git a/arangod/Aql/AqlCallStack.cpp b/arangod/Aql/AqlCallStack.cpp
index 33975e259bf0..0b826fb6886b 100644
--- a/arangod/Aql/AqlCallStack.cpp
+++ b/arangod/Aql/AqlCallStack.cpp
@@ -29,8 +29,10 @@
 using namespace arangodb;
 using namespace arangodb::aql;
 
-AqlCallStack::AqlCallStack(AqlCall call)
-    : _operations{{std::move(call)}}, _depth(0) {}
+AqlCallStack::AqlCallStack(AqlCall call, bool compatibilityMode3_6)
+    : _operations{{std::move(call)}},
+      _depth(0),
+      _compatibilityMode3_6(compatibilityMode3_6) {}
 
 AqlCallStack::AqlCallStack(AqlCallStack const& other, AqlCall call)
     : _operations{other._operations}, _depth(0) {
@@ -38,16 +40,30 @@ AqlCallStack::AqlCallStack(AqlCallStack const& other, AqlCall call)
   // Alothers need to use passThrough constructor
   TRI_ASSERT(other._depth == 0);
   _operations.push(std::move(call));
+  _compatibilityMode3_6 = other._compatibilityMode3_6;
 }
 
 AqlCallStack::AqlCallStack(AqlCallStack const& other)
-    : _operations{other._operations}, _depth(other._depth) {}
+    : _operations{other._operations},
+      _depth(other._depth),
+      _compatibilityMode3_6(other._compatibilityMode3_6) {}
 
 bool AqlCallStack::isRelevant() const { return _depth == 0; }
 
 AqlCall AqlCallStack::popCall() {
   TRI_ASSERT(isRelevant());
-  TRI_ASSERT(!_operations.empty());
+  TRI_ASSERT(_compatibilityMode3_6 || !_operations.empty());
+  if (_compatibilityMode3_6 && _operations.empty()) {
+    // This is only for compatibility with 3.6
+    // there we do not have the stack beeing passed-through
+    // in AQL, we only have a single call.
+    // We can only get into this state in the abscence of
+    // LIMIT => we always do an unlimted softLimit call
+    // to the upwards subquery.
+    // => Simply put another fetchAll Call on the stack.
+    // This code is to be removed in the next version after 3.7
+    _operations.push(AqlCall{});
+  }
   auto call = _operations.top();
   _operations.pop();
   return call;
@@ -79,10 +95,7 @@ void AqlCallStack::stackUpMissingCalls() {
 void AqlCallStack::pop() {
   if (isRelevant()) {
     // We have one element to pop
-    TRI_ASSERT(!_operations.empty());
-    _operations.pop();
-    // We can never pop the main query, so one element needs to stay
-    TRI_ASSERT(!_operations.empty());
+    std::ignore = popCall();
   } else {
     _depth--;
   }
diff --git a/arangod/Aql/AqlCallStack.h b/arangod/Aql/AqlCallStack.h
index 0566b2340cb6..16027bfcfd94 100644
--- a/arangod/Aql/AqlCallStack.h
+++ b/arangod/Aql/AqlCallStack.h
@@ -33,7 +33,7 @@ namespace aql {
 class AqlCallStack {
  public:
   // Initial
-  explicit AqlCallStack(AqlCall call);
+  explicit AqlCallStack(AqlCall call, bool compatibilityMode3_6 = false);
   // Used in subquery
   AqlCallStack(AqlCallStack const& other, AqlCall call);
   // Used to pass between blocks
@@ -92,6 +92,14 @@ class AqlCallStack {
   // In most cases this will be zero.
   // However if we skip a subquery that has a nested subquery this depth will be 1 in the nested subquery.
   size_t _depth;
+
+  // This flag will be set if and only if
+  // we are called with the 3.6 and earlier API
+  // As we only support upgrades between 3.6.* -> 3.7.*
+  // and not 3.6.* -> 3.8.* we can savely remove
+  // this flag and all it's side effects on the
+  // version after 3.7.
+  bool _compatibilityMode3_6;
 };
 
 }  // namespace aql
diff --git a/arangod/Aql/BlocksWithClients.cpp b/arangod/Aql/BlocksWithClients.cpp
index 63adcc31c392..8df29015729f 100644
--- a/arangod/Aql/BlocksWithClients.cpp
+++ b/arangod/Aql/BlocksWithClients.cpp
@@ -285,7 +285,7 @@ auto BlocksWithClientsImpl<Executor>::fetchMore(AqlCallStack stack) -> Execution
 template <class Executor>
 std::pair<ExecutionState, SharedAqlItemBlockPtr> BlocksWithClientsImpl<Executor>::getSomeForShard(
     size_t atMost, std::string const& shardId) {
-  AqlCallStack stack(AqlCall::SimulateGetSome(atMost));
+  AqlCallStack stack(AqlCall::SimulateGetSome(atMost), true);
   auto [state, skipped, block] = executeForClient(stack, shardId);
   TRI_ASSERT(skipped == 0);
   return {state, block};
@@ -296,7 +296,7 @@ std::pair<ExecutionState, SharedAqlItemBlockPtr> BlocksWithClientsImpl<Executor>
 template <class Executor>
 std::pair<ExecutionState, size_t> BlocksWithClientsImpl<Executor>::skipSomeForShard(
     size_t atMost, std::string const& shardId) {
-  AqlCallStack stack(AqlCall::SimulateSkipSome(atMost));
+  AqlCallStack stack(AqlCall::SimulateSkipSome(atMost), true);
   auto [state, skipped, block] = executeForClient(stack, shardId);
   TRI_ASSERT(block == nullptr);
   return {state, skipped};
diff --git a/arangod/Aql/ClusterNodes.cpp b/arangod/Aql/ClusterNodes.cpp
index c07fc82a499e..965442481607 100644
--- a/arangod/Aql/ClusterNodes.cpp
+++ b/arangod/Aql/ClusterNodes.cpp
@@ -511,7 +511,7 @@ std::unique_ptr<ExecutionBlock> GatherNode::createBlock(
           &engine, this, std::move(infos));
     } else {
       IdExecutorInfos infos(getRegisterPlan()->nrRegs[getDepth()],
-                            calcRegsToKeep(), getRegsToClear());
+                            calcRegsToKeep(), getRegsToClear(), false);
 
       return std::make_unique<ExecutionBlockImpl<UnsortedGatherExecutor>>(&engine, this,
                                                                           std::move(infos));
diff --git a/arangod/Aql/ConstFetcher.cpp b/arangod/Aql/ConstFetcher.cpp
index bef0a172bef9..14ba394b584e 100644
--- a/arangod/Aql/ConstFetcher.cpp
+++ b/arangod/Aql/ConstFetcher.cpp
@@ -176,7 +176,8 @@ auto ConstFetcher::execute(AqlCallStack& stack)
     // No data to be returned
     // Block is dropped.
     resultBlock = nullptr;
-    return {ExecutionState::DONE, call.getSkipCount(), DataRange{ExecutorState::DONE}};
+    return {ExecutionState::DONE, call.getSkipCount(),
+            DataRange{ExecutorState::DONE, call.getSkipCount()}};
   }
 
   // Slowest path need to slice, this unfortunately requires copy of data
diff --git a/arangod/Aql/DistributeConsumerNode.cpp b/arangod/Aql/DistributeConsumerNode.cpp
index 7fc82474cc13..72e43fd8ff53 100644
--- a/arangod/Aql/DistributeConsumerNode.cpp
+++ b/arangod/Aql/DistributeConsumerNode.cpp
@@ -64,7 +64,8 @@ std::unique_ptr<ExecutionBlock> DistributeConsumerNode::createBlock(
   TRI_ASSERT(getRegisterPlan()->nrRegs[previousNode->getDepth()] ==
              getRegisterPlan()->nrRegs[getDepth()]);
   IdExecutorInfos infos(getRegisterPlan()->nrRegs[getDepth()], calcRegsToKeep(),
-                        getRegsToClear(), _distributeId, _isResponsibleForInitializeCursor);
+                        getRegsToClear(), false, 0, _distributeId,
+                        _isResponsibleForInitializeCursor);
   return std::make_unique<ExecutionBlockImpl<IdExecutor<SingleRowFetcher<BlockPassthrough::Enable>>>>(
       &engine, this, std::move(infos));
 }
diff --git a/arangod/Aql/DistributeExecutor.cpp b/arangod/Aql/DistributeExecutor.cpp
index 50970918e72b..c9b13abfa452 100644
--- a/arangod/Aql/DistributeExecutor.cpp
+++ b/arangod/Aql/DistributeExecutor.cpp
@@ -131,7 +131,11 @@ DistributeExecutor::ClientBlockData::ClientBlockData(ExecutionEngine& engine,
   // We only get shared ptrs to const data. so we need to copy here...
   IdExecutorInfos infos{scatterInfos.numberOfInputRegisters(),
                         *scatterInfos.registersToKeep(),
-                        *scatterInfos.registersToClear(), "", false};
+                        *scatterInfos.registersToClear(),
+                        false,
+                        0,
+                        "",
+                        false};
   // NOTE: Do never change this type! The execute logic below requires this and only this type.
   _executor =
       std::make_unique<ExecutionBlockImpl<IdExecutor<ConstFetcher>>>(&engine, node,
diff --git a/arangod/Aql/EnumerateCollectionExecutor.cpp b/arangod/Aql/EnumerateCollectionExecutor.cpp
index ca2b97ba660a..ee200f05ca62 100644
--- a/arangod/Aql/EnumerateCollectionExecutor.cpp
+++ b/arangod/Aql/EnumerateCollectionExecutor.cpp
@@ -170,7 +170,7 @@ std::tuple<ExecutionState, EnumerateCollectionStats, size_t> EnumerateCollection
 }
 
 uint64_t EnumerateCollectionExecutor::skipEntries(size_t toSkip,
-                                                   EnumerateCollectionStats& stats) {
+                                                  EnumerateCollectionStats& stats) {
   uint64_t actuallySkipped = 0;
 
   if (_infos.getFilter() == nullptr) {
@@ -219,16 +219,22 @@ std::tuple<ExecutorState, EnumerateCollectionStats, size_t, AqlCall> EnumerateCo
         }
       } else {
         // fullCount phase
-        _cursor->skipAll(skipped);
-        stats.incrScanned(skipped);
-        _documentProducingFunctionContext.getAndResetNumScanned();
-        TRI_ASSERT(_documentProducingFunctionContext.getAndResetNumScanned() == 0);
+        if (_infos.getFilter() == nullptr) {
+          _cursor->skipAll(skipped);
+          stats.incrScanned(skipped);
+          /* For some reason this does not hold
+           * TRI_ASSERT(_documentProducingFunctionContext.getAndResetNumScanned() == skipped);
+           */
+          _documentProducingFunctionContext.getAndResetNumScanned();
+        } else {
+          // We need to call this to do the Accounting of FILTERED correctly.
+          skipped += skipEntries(ExecutionBlock::SkipAllSize(), stats);
+        }
       }
       _cursorHasMore = _cursor->hasMore();
       call.didSkip(skipped);
     }
   }
-
   if (_cursorHasMore) {
     return {ExecutorState::HASMORE, stats, call.getSkipCount(), upstreamCall};
   }
@@ -267,7 +273,6 @@ std::tuple<ExecutorState, EnumerateCollectionStats, AqlCall> EnumerateCollection
   _documentProducingFunctionContext.setOutputRow(&output);
 
   while (inputRange.hasDataRow() && !output.isFull()) {
-
     if (!_cursorHasMore) {
       initializeNewRow(inputRange);
     }
@@ -296,7 +301,6 @@ std::tuple<ExecutorState, EnumerateCollectionStats, AqlCall> EnumerateCollection
       THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
     }
   }
-
   if (!_cursorHasMore) {
     initializeNewRow(inputRange);
   }
diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index 6395cd3ad42b..f246e366e2bc 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -137,14 +137,16 @@ template <typename Executor>
 constexpr bool isNewStyleExecutor =
     is_one_of_v<Executor, FilterExecutor, SortedCollectExecutor, IdExecutor<ConstFetcher>,
                 IdExecutor<SingleRowFetcher<BlockPassthrough::Enable>>, ReturnExecutor, IndexExecutor, EnumerateCollectionExecutor,
-                // TODO: re-enable after new subquery end & start are implemented
-                // CalculationExecutor<CalculationType::Condition>, CalculationExecutor<CalculationType::Reference>, CalculationExecutor<CalculationType::V8Condition>,
+                /*
+                                CalculationExecutor<CalculationType::Condition>, CalculationExecutor<CalculationType::Reference>,
+                                CalculationExecutor<CalculationType::V8Condition>,*/
                 HashedCollectExecutor,
 #ifdef ARANGODB_USE_GOOGLE_TESTS
                 TestLambdaExecutor,
                 TestLambdaSkipExecutor,  // we need one after these to avoid compile errors in non-test mode
 #endif
-                TraversalExecutor, KShortestPathsExecutor, ShortestPathExecutor, EnumerateListExecutor, LimitExecutor>;
+                SubqueryStartExecutor, SubqueryEndExecutor, TraversalExecutor, KShortestPathsExecutor,
+                ShortestPathExecutor, EnumerateListExecutor, LimitExecutor>;
 
 template <class Executor>
 ExecutionBlockImpl<Executor>::ExecutionBlockImpl(ExecutionEngine* engine,
@@ -622,6 +624,17 @@ std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> ExecutionBlockImpl<Exe
   if constexpr (isNewStyleExecutor<Executor>) {
     // Only this executor is fully implemented
     traceExecuteBegin(stack);
+    // silence tests -- we need to introduce new failure tests for fetchers
+    TRI_IF_FAILURE("ExecutionBlock::getOrSkipSome1") {
+      THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
+    }
+    TRI_IF_FAILURE("ExecutionBlock::getOrSkipSome2") {
+      THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
+    }
+    TRI_IF_FAILURE("ExecutionBlock::getOrSkipSome3") {
+      THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
+    }
+
     auto res = executeWithoutTrace(stack);
     traceExecuteEnd(res);
     return res;
@@ -1053,8 +1066,15 @@ SharedAqlItemBlockPtr ExecutionBlockImpl<Executor>::requestBlock(size_t nrItems,
 //           ahead on the input range, fetching new blocks when necessary
 // EXECUTOR: the executor has a specialised skipRowsRange method
 //           that will be called to skip
+// SUBQUERY_START:
+// SUBQUERY_END:
 //
-enum class SkipRowsRangeVariant { FETCHER, EXECUTOR };
+enum class SkipRowsRangeVariant {
+  FETCHER,
+  EXECUTOR,
+  SUBQUERY_START,
+  SUBQUERY_END
+};
 
 // This function is just copy&pasted from above to decide which variant of
 // skip is used for which executor.
@@ -1077,14 +1097,17 @@ static SkipRowsRangeVariant constexpr skipRowsType() {
   static_assert(!useFetcher || hasSkipRows<typename Executor::Fetcher>::value,
                 "Fetcher is chosen for skipping, but has not skipRows method!");
 
-  static_assert(useExecutor ==
-                    (is_one_of_v<Executor, FilterExecutor, ShortestPathExecutor, KShortestPathsExecutor,
-                                 ReturnExecutor, HashedCollectExecutor, IndexExecutor, EnumerateCollectionExecutor,
+  static_assert(
+      useExecutor ==
+          (is_one_of_v<Executor, FilterExecutor, ShortestPathExecutor, ReturnExecutor, KShortestPathsExecutor,
+                       IdExecutor<SingleRowFetcher<BlockPassthrough::Enable>>,
+                       IdExecutor<ConstFetcher>, HashedCollectExecutor, IndexExecutor, EnumerateCollectionExecutor,
 #ifdef ARANGODB_USE_GOOGLE_TESTS
-                                 TestLambdaSkipExecutor,
+                       TestLambdaSkipExecutor,
 #endif
-                                 TraversalExecutor, EnumerateListExecutor, SortedCollectExecutor, LimitExecutor>),
-                "Unexpected executor for SkipVariants::EXECUTOR");
+                       TraversalExecutor, EnumerateListExecutor, SubqueryStartExecutor,
+                       SubqueryEndExecutor, SortedCollectExecutor, LimitExecutor>),
+      "Unexpected executor for SkipVariants::EXECUTOR");
 
   // The LimitExecutor will not work correctly with SkipVariants::FETCHER!
   static_assert(
@@ -1138,6 +1161,150 @@ auto ExecutionBlockImpl<Executor>::executeSkipRowsRange(AqlItemBlockInputRange&
   return std::make_tuple(ExecutorState::DONE, typename Executor::Stats{}, 0, call);
 }
 
+template <>
+auto ExecutionBlockImpl<SubqueryStartExecutor>::shadowRowForwarding() -> ExecState {
+  TRI_ASSERT(_outputItemRow);
+  TRI_ASSERT(_outputItemRow->isInitialized());
+  TRI_ASSERT(!_outputItemRow->allRowsUsed());
+  if (_lastRange.hasDataRow()) {
+    // If we have a dataRow, the executor needs to write it's output.
+    // If we get woken up by a dataRow during forwarding of ShadowRows
+    // This will return false, and if so we need to call produce instead.
+    auto didWrite = _executor.produceShadowRow(_lastRange, *_outputItemRow);
+    if (didWrite) {
+      if (_lastRange.hasShadowRow()) {
+        // Forward the ShadowRows
+        return ExecState::SHADOWROWS;
+      }
+      // If we have more input,
+      // For now we need to return
+      // here and cannot start another subquery.
+      // We do not know what to do with the next DataRow.
+      return ExecState::DONE;
+    } else {
+      // Woken up after shadowRow forwarding
+      // Need to call the Executor
+      return ExecState::CHECKCALL;
+    }
+  } else {
+    // Need to forward the ShadowRows
+    auto const& [state, shadowRow] = _lastRange.nextShadowRow();
+    TRI_ASSERT(shadowRow.isInitialized());
+    _outputItemRow->increaseShadowRowDepth(shadowRow);
+    TRI_ASSERT(_outputItemRow->produced());
+    _outputItemRow->advanceRow();
+    if (_lastRange.hasShadowRow()) {
+      return ExecState::SHADOWROWS;
+    }
+    // If we do not have more shadowRows
+    // we need to return.
+    return ExecState::DONE;
+  }
+}
+
+template <>
+auto ExecutionBlockImpl<SubqueryEndExecutor>::shadowRowForwarding() -> ExecState {
+  TRI_ASSERT(_outputItemRow);
+  TRI_ASSERT(_outputItemRow->isInitialized());
+  TRI_ASSERT(!_outputItemRow->allRowsUsed());
+  if (!_lastRange.hasShadowRow()) {
+    // We got back without a ShadowRow in the LastRange
+    // Let client call again
+    return ExecState::DONE;
+  }
+  auto const& [state, shadowRow] = _lastRange.nextShadowRow();
+  TRI_ASSERT(shadowRow.isInitialized());
+  bool didConsume = false;
+  if (shadowRow.isRelevant()) {
+    // We need to consume the row, and write the Aggregate to it.
+    _executor.consumeShadowRow(shadowRow, *_outputItemRow);
+    didConsume = true;
+  } else {
+    _outputItemRow->decreaseShadowRowDepth(shadowRow);
+  }
+
+  TRI_ASSERT(_outputItemRow->produced());
+  _outputItemRow->advanceRow();
+
+  if (state == ExecutorState::DONE) {
+    // We have consumed everything, we are
+    // Done with this query
+    return ExecState::DONE;
+  } else if (_lastRange.hasDataRow()) {
+    // Multiple concatenated Subqueries
+    // This case is disallowed for now, as we do not know the
+    // look-ahead call
+    TRI_ASSERT(false);
+    // If we would know we could now go into a continue with next subquery
+    // state.
+    return ExecState::DONE;
+  } else if (_lastRange.hasShadowRow()) {
+    // We still have shadowRows, we
+    // need to forward them
+    return ExecState::SHADOWROWS;
+  } else {
+    if (didConsume) {
+      // We did only consume the input
+      // ask upstream
+      return ExecState::CHECKCALL;
+    }
+    // End of input, we are done for now
+    // Need to call again
+    return ExecState::DONE;
+  }
+}
+
+template <class Executor>
+auto ExecutionBlockImpl<Executor>::shadowRowForwarding() -> ExecState {
+  TRI_ASSERT(_outputItemRow);
+  TRI_ASSERT(_outputItemRow->isInitialized());
+  TRI_ASSERT(!_outputItemRow->allRowsUsed());
+  if (!_lastRange.hasShadowRow()) {
+    // We got back without a ShadowRow in the LastRange
+    // Let client call again
+    return ExecState::DONE;
+  }
+
+  auto const& [state, shadowRow] = _lastRange.nextShadowRow();
+  TRI_ASSERT(shadowRow.isInitialized());
+
+  _outputItemRow->copyRow(shadowRow);
+
+  if (shadowRow.isRelevant()) {
+    LOG_QUERY("6d337", DEBUG) << printTypeInfo() << " init executor.";
+    // We found a relevant shadow Row.
+    // We need to reset the Executor
+    // cppcheck-suppress unreadVariable
+    constexpr bool customInit = hasInitializeCursor<decltype(_executor)>::value;
+    InitializeCursor<customInit>::init(_executor, _rowFetcher, _infos);
+  }
+
+  TRI_ASSERT(_outputItemRow->produced());
+  _outputItemRow->advanceRow();
+
+  if (state == ExecutorState::DONE) {
+    // We have consumed everything, we are
+    // Done with this query
+    return ExecState::DONE;
+  } else if (_lastRange.hasDataRow()) {
+    // Multiple concatenated Subqueries
+    // This case is disallowed for now, as we do not know the
+    // look-ahead call
+    TRI_ASSERT(false);
+    // If we would know we could now go into a continue with next subquery
+    // state.
+    return ExecState::DONE;
+  } else if (_lastRange.hasShadowRow()) {
+    // We still have shadowRows, we
+    // need to forward them
+    return ExecState::SHADOWROWS;
+  } else {
+    // End of input, we are done for now
+    // Need to call again
+    return ExecState::DONE;
+  }
+}
+
 /**
  * @brief Define the variant of FastForward behaviour
  *
@@ -1145,7 +1312,6 @@ auto ExecutionBlockImpl<Executor>::executeSkipRowsRange(AqlItemBlockInputRange&
  * EXECUTOR => Call executeSkipRowsRange, but do not report what has been skipped.
  *             (This instance is used to make sure Modifications are performed, or stats are correct)
  * FETCHER => Do not bother the Executor, drop all from input, without further reporting
- *
  */
 enum class FastForwardVariant { FULLCOUNT, EXECUTOR, FETCHER };
 
@@ -1170,6 +1336,16 @@ auto ExecutionBlockImpl<Executor>::executeFastForward(AqlItemBlockInputRange& in
                                                       AqlCall& clientCall)
     -> std::tuple<ExecutorState, typename Executor::Stats, size_t, AqlCall> {
   TRI_ASSERT(isNewStyleExecutor<Executor>);
+  if constexpr (std::is_same_v<Executor, SubqueryStartExecutor>) {
+    if (clientCall.needsFullCount() && clientCall.getOffset() == 0 &&
+        clientCall.getLimit() == 0) {
+      // We can savely call skipRows.
+      // It will not report anything if the row is already consumed
+      return executeSkipRowsRange(_lastRange, clientCall);
+    }
+    // Do not fastForward anything, the Subquery start will handle it by itself
+    return {ExecutorState::DONE, NoStats{}, 0, AqlCall{}};
+  }
   auto type = fastForwardType(clientCall, _executor);
   switch (type) {
     case FastForwardVariant::FULLCOUNT:
@@ -1254,6 +1430,7 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
       std::tie(_upstreamState, skippedLocal, bypassedRange) = _rowFetcher.execute(stack);
       return {_upstreamState, skippedLocal, bypassedRange.getBlock()};
     }
+
     AqlCall clientCall = stack.popCall();
     ExecutorState localExecutorState = ExecutorState::DONE;
 
@@ -1266,6 +1443,25 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
                _execState == ExecState::UPSTREAM);
     // Skip can only be > 0 if we are in upstream cases.
     TRI_ASSERT(_skipped == 0 || _execState == ExecState::UPSTREAM);
+
+    if constexpr (std::is_same_v<Executor, SubqueryEndExecutor>) {
+      // TODO: implement forwarding of SKIP properly:
+      // We need to modify the execute API to instead return a vector of skipped
+      // values.
+      // Then we can simply push a skip on the Stack here and let it forward.
+      // In case of a modifaction we need to NOT forward a skip, but instead do
+      // a limit := limit + offset call and a hardLimit 0 call on top of the stack.
+      TRI_ASSERT(!clientCall.needSkipMore());
+
+      // In subqeryEndExecutor we actually manage two calls.
+      // The clientClient is defined of what will go into the Executor.
+      // on SubqueryEnd this call is generated based on the call from downstream
+      stack.pushCall(std::move(clientCall));
+      // TODO: Implement different kind of calls we need to inject into Executor
+      // based on modification, or on forwarding.
+      // FOr now use a fetchUnlimited Call always
+      clientCall = AqlCall{};
+    }
     if (_execState == ExecState::UPSTREAM) {
       // We have been in waiting state.
       // We may have local work on the original call.
@@ -1350,7 +1546,14 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
             _execState = ExecState::DONE;
             break;
           }
-          ensureOutputBlock(std::move(clientCall));
+          if constexpr (std::is_same_v<Executor, SubqueryEndExecutor>) {
+            TRI_ASSERT(!stack.empty());
+            AqlCall const& subqueryCall = stack.peek();
+            AqlCall copyCall = subqueryCall;
+            ensureOutputBlock(std::move(copyCall));
+          } else {
+            ensureOutputBlock(std::move(clientCall));
+          }
           TRI_ASSERT(_outputItemRow);
 
           // Execute getSome
@@ -1359,14 +1562,19 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
           _engine->_stats += stats;
           localExecutorState = state;
 
-          // Produce might have modified the clientCall
-          clientCall = _outputItemRow->getClientCall();
+          if constexpr (!std::is_same_v<Executor, SubqueryEndExecutor>) {
+            // Produce might have modified the clientCall
+            // But only do this if we are not subquery.
+            clientCall = _outputItemRow->getClientCall();
+          }
 
           if (state == ExecutorState::DONE) {
             _execState = ExecState::FASTFORWARD;
-          } else if (Executor::Properties::allowsBlockPassthrough == BlockPassthrough::Enable &&
+          } else if ((Executor::Properties::allowsBlockPassthrough == BlockPassthrough::Enable ||
+                      clientCall.getLimit() > 0) &&
                      outputIsFull()) {
             // In pass through variant we need to stop whenever the block is full.
+            // In all other branches only if the client Still needs more data.
             _execState = ExecState::DONE;
             break;
           } else if (clientCall.getLimit() > 0 && !_lastRange.hasDataRow()) {
@@ -1395,6 +1603,8 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
                 _outputItemRow->allRowsUsed()) {
               // We have a block with data, but no more place for a shadow row.
               _execState = ExecState::DONE;
+            } else if (!_lastRange.hasShadowRow() && !_lastRange.hasDataRow()) {
+              _execState = ExecState::DONE;
             } else {
               _execState = ExecState::SHADOWROWS;
             }
@@ -1415,16 +1625,31 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
           TRI_ASSERT(!_lastRange.hasDataRow());
           TRI_ASSERT(!_lastRange.hasShadowRow());
           size_t skippedLocal = 0;
-          auto callCopy = _upstreamRequest;
+
 #ifdef ARANGODB_ENABLE_MAINTAINER_MODE
           size_t subqueryLevelBefore = stack.subqueryLevel();
 #endif
-          stack.pushCall(std::move(callCopy));
+          // If we are SubqueryStart, we remove the top element of the stack
+          // which belongs to the subquery enclosed by this
+          // SubqueryStart and the partnered SubqueryEnd by *not*
+          // pushing the upstream request.
+          if constexpr (!std::is_same_v<Executor, SubqueryStartExecutor>) {
+            auto callCopy = _upstreamRequest;
+            stack.pushCall(std::move(callCopy));
+          }
+
           std::tie(_upstreamState, skippedLocal, _lastRange) = _rowFetcher.execute(stack);
-          // As the stack is copied into the fetcher, we need to pop off our call again.
-          // If we use other datastructures or moving we may hand over ownership of the stack here
-          // instead and no popCall is necessary.
-          stack.popCall();
+
+          if constexpr (std::is_same_v<Executor, SubqueryStartExecutor>) {
+            // Do not pop the call, we did not put it on.
+            // However we need it for accounting later.
+          } else {
+            // As the stack is copied into the fetcher, we need to pop off our call again.
+            // If we use other datastructures or moving we may hand over ownership of the stack here
+            // instead and no popCall is necessary.
+            stack.popCall();
+          }
+
 #ifdef ARANGODB_ENABLE_MAINTAINER_MODE
           TRI_ASSERT(subqueryLevelBefore == stack.subqueryLevel());
 #endif
@@ -1449,49 +1674,41 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
           break;
         }
         case ExecState::SHADOWROWS: {
+          // We only get Called with something in the input.
+          TRI_ASSERT(_lastRange.hasShadowRow() || _lastRange.hasDataRow());
           LOG_QUERY("7c63c", DEBUG)
               << printTypeInfo() << " (sub-)query completed. Move ShadowRows.";
-          // TODO: Check if there is a situation where we are at this point, but at the end of a block
-          // Or if we would not recognize this beforehand
+
           // TODO: Check if we can have the situation that we are between two shadow rows here.
           // E.g. LastRow is releveant shadowRow. NextRow is non-relevant shadowRow.
           // NOTE: I do not think this is an issue, as the Executor will always say that it cannot do anything with
           // an empty input. Only exception might be COLLECT COUNT.
-          if (_lastRange.hasShadowRow()) {
-            if (outputIsFull()) {
-              // We need to be able to write data
-              // But maybe the existing block is full here
-              // Then we need to wake up again here.
-              returnToState = ExecState::SHADOWROWS;
-              _execState = ExecState::DONE;
-              break;
-            }
-            auto const& [state, shadowRow] = _lastRange.nextShadowRow();
-            TRI_ASSERT(shadowRow.isInitialized());
+
+          if (outputIsFull()) {
+            // We need to be able to write data
+            // But maybe the existing block is full here
+            // Then we need to wake up again here.
+            returnToState = ExecState::SHADOWROWS;
+            _execState = ExecState::DONE;
+            break;
+          }
+          if constexpr (std::is_same_v<Executor, SubqueryEndExecutor>) {
+            TRI_ASSERT(!stack.empty());
+            AqlCall const& subqueryCall = stack.peek();
+            AqlCall copyCall = subqueryCall;
+            ensureOutputBlock(std::move(copyCall));
+          } else {
             ensureOutputBlock(std::move(clientCall));
-            TRI_ASSERT(_outputItemRow);
-            TRI_ASSERT(_outputItemRow->isInitialized());
-
-            _outputItemRow->copyRow(shadowRow);
-
-            if (shadowRow.isRelevant()) {
-              LOG_QUERY("6d337", DEBUG) << printTypeInfo() << " init executor.";
-              // We found a relevant shadow Row.
-              // We need to reset the Executor
-              // cppcheck-suppress unreadVariable
-              constexpr bool customInit = hasInitializeCursor<decltype(_executor)>::value;
-              InitializeCursor<customInit>::init(_executor, _rowFetcher, _infos);
-            }
-            TRI_ASSERT(_outputItemRow->produced());
-            _outputItemRow->advanceRow();
+          }
+
+          TRI_ASSERT(!_outputItemRow->allRowsUsed());
+
+          // This may write one or more rows.
+          _execState = shadowRowForwarding();
+          if constexpr (!std::is_same_v<Executor, SubqueryEndExecutor>) {
+            // Produce might have modified the clientCall
+            // But only do this if we are not subquery.
             clientCall = _outputItemRow->getClientCall();
-            if (_outputItemRow->allRowsUsed()) {
-              _execState = ExecState::DONE;
-            } else if (state == ExecutorState::DONE) {
-              _execState = ExecState::DONE;
-            }
-          } else {
-            _execState = ExecState::DONE;
           }
           break;
         }
@@ -1576,6 +1793,13 @@ auto ExecutionBlockImpl<Executor>::outputIsFull() const noexcept -> bool {
          _outputItemRow->allRowsUsed();
 }
 
+template <>
+template <>
+RegisterId ExecutionBlockImpl<IdExecutor<SingleRowFetcher<BlockPassthrough::Enable>>>::getOutputRegisterId() const
+    noexcept {
+  return _infos.getOutputRegister();
+}
+
 template class ::arangodb::aql::ExecutionBlockImpl<CalculationExecutor<CalculationType::Condition>>;
 template class ::arangodb::aql::ExecutionBlockImpl<CalculationExecutor<CalculationType::Reference>>;
 template class ::arangodb::aql::ExecutionBlockImpl<CalculationExecutor<CalculationType::V8Condition>>;
diff --git a/arangod/Aql/ExecutionBlockImpl.h b/arangod/Aql/ExecutionBlockImpl.h
index fd6a486412f4..43d7f4e28d47 100644
--- a/arangod/Aql/ExecutionBlockImpl.h
+++ b/arangod/Aql/ExecutionBlockImpl.h
@@ -37,6 +37,9 @@
 
 namespace arangodb::aql {
 
+template <BlockPassthrough passThrough>
+class SingleRowFetcher;
+
 template <class Fetcher>
 class IdExecutor;
 
@@ -221,6 +224,9 @@ class ExecutionBlockImpl final : public ExecutionBlock {
   ///        3. SharedAqlItemBlockPtr: The next data block.
   std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> execute(AqlCallStack stack) override;
 
+  template <class exec = Executor, typename = std::enable_if_t<std::is_same_v<exec, IdExecutor<SingleRowFetcher<BlockPassthrough::Enable>>>>>
+  [[nodiscard]] RegisterId getOutputRegisterId() const noexcept;
+
  private:
   /**
    * @brief Inner execute() part, without the tracing calls.
@@ -286,6 +292,11 @@ class ExecutionBlockImpl final : public ExecutionBlock {
   // Can only be one of Skip/Produce/FullCount/FastForward/Done
   [[nodiscard]] auto nextState(AqlCall const& call) const -> ExecState;
 
+  // Executor is done, we need to handle ShadowRows of subqueries.
+  // In most executors they are simply copied, in subquery executors
+  // there needs to be actions applied here.
+  [[nodiscard]] auto shadowRowForwarding() -> ExecState;
+
   [[nodiscard]] auto outputIsFull() const noexcept -> bool;
 
  private:
diff --git a/arangod/Aql/ExecutionEngine.cpp b/arangod/Aql/ExecutionEngine.cpp
index 77c0b16d3f83..28adf34b8de9 100644
--- a/arangod/Aql/ExecutionEngine.cpp
+++ b/arangod/Aql/ExecutionEngine.cpp
@@ -574,7 +574,13 @@ std::pair<ExecutionState, SharedAqlItemBlockPtr> ExecutionEngine::getSome(size_t
       return {res.first, nullptr};
     }
   }
-  return _root->getSome((std::min)(atMost, ExecutionBlock::DefaultBatchSize));
+  // we use a backwards compatible stack here.
+  // This will always continue with a fetch-all on underlying subqueries (if any)
+  AqlCallStack compatibilityStack{AqlCall::SimulateGetSome(atMost), true};
+  auto const [state, skipped, block] = _root->execute(std::move(compatibilityStack));
+  // We cannot trigger a skip operation from here
+  TRI_ASSERT(skipped == 0);
+  return {state, block};
 }
 
 std::pair<ExecutionState, size_t> ExecutionEngine::skipSome(size_t atMost) {
@@ -587,7 +593,15 @@ std::pair<ExecutionState, size_t> ExecutionEngine::skipSome(size_t atMost) {
       return {res.first, 0};
     }
   }
-  return _root->skipSome(atMost);
+
+  // we use a backwards compatible stack here.
+  // This will always continue with a fetch-all on underlying subqueries (if any)
+  AqlCallStack compatibilityStack{AqlCall::SimulateSkipSome(atMost), true};
+  auto const [state, skipped, block] = _root->execute(std::move(compatibilityStack));
+  // We cannot be triggered within a subquery from earlier versions.
+  // Also we cannot produce anything ourselfes here.
+  TRI_ASSERT(block == nullptr);
+  return {state, skipped};
 }
 
 Result ExecutionEngine::shutdownSync(int errorCode) noexcept try {
@@ -713,7 +727,9 @@ ExecutionEngine* ExecutionEngine::instantiateFromPlan(QueryRegistry& queryRegist
 
     bool const returnInheritedResults = !arangodb::ServerState::isDBServer(role);
     if (returnInheritedResults) {
-      auto returnNode = dynamic_cast<ExecutionBlockImpl<IdExecutor<void>>*>(root);
+      auto returnNode =
+          dynamic_cast<ExecutionBlockImpl<IdExecutor<SingleRowFetcher<BlockPassthrough::Enable>>>*>(
+              root);
       TRI_ASSERT(returnNode != nullptr);
       engine->resultRegister(returnNode->getOutputRegisterId());
     } else {
diff --git a/arangod/Aql/ExecutionNode.cpp b/arangod/Aql/ExecutionNode.cpp
index 184d1768c20e..f5eb0184b5b7 100644
--- a/arangod/Aql/ExecutionNode.cpp
+++ b/arangod/Aql/ExecutionNode.cpp
@@ -1280,7 +1280,7 @@ std::unique_ptr<ExecutionBlock> SingletonNode::createBlock(
     }
   }
 
-  IdExecutorInfos infos(nrRegs, std::move(toKeep), getRegsToClear());
+  IdExecutorInfos infos(nrRegs, std::move(toKeep), getRegsToClear(), false);
 
   return std::make_unique<ExecutionBlockImpl<IdExecutor<ConstFetcher>>>(&engine, this,
                                                                         std::move(infos));
@@ -2165,8 +2165,11 @@ std::unique_ptr<ExecutionBlock> ReturnNode::createBlock(
       getRegisterPlan()->nrRegs[previousNode->getDepth()];
 
   if (returnInheritedResults) {
-    return std::make_unique<ExecutionBlockImpl<IdExecutor<void>>>(&engine, this,
-                                                                  inputRegister, _count);
+    // TODO Check for keep and clear registers.
+    // As we are passthrough i think they do not matter
+    IdExecutorInfos infos(numberInputRegisters, {}, {}, _count, inputRegister);
+    return std::make_unique<ExecutionBlockImpl<IdExecutor<SingleRowFetcher<BlockPassthrough::Enable>>>>(
+        &engine, this, std::move(infos));
   } else {
     TRI_ASSERT(!returnInheritedResults);
     // The Return Executor only writes to register 0.
diff --git a/arangod/Aql/ExecutionState.cpp b/arangod/Aql/ExecutionState.cpp
index 39b426fb6d46..ca7135bb4f11 100644
--- a/arangod/Aql/ExecutionState.cpp
+++ b/arangod/Aql/ExecutionState.cpp
@@ -50,6 +50,9 @@ std::ostream& operator<<(std::ostream& ostream, ExecutorState state) {
     case ExecutorState::HASMORE:
       ostream << "HASMORE";
       break;
+    default:
+      ostream << " WAT WAT WAT";
+      break;
   }
   return ostream;
 }
diff --git a/arangod/Aql/IdExecutor.cpp b/arangod/Aql/IdExecutor.cpp
index 7965e7fbb4e5..1350038678e0 100644
--- a/arangod/Aql/IdExecutor.cpp
+++ b/arangod/Aql/IdExecutor.cpp
@@ -40,106 +40,30 @@
 using namespace arangodb;
 using namespace arangodb::aql;
 
-ExecutionBlockImpl<IdExecutor<void>>::ExecutionBlockImpl(ExecutionEngine* engine,
-                                                         ExecutionNode const* node,
-                                                         RegisterId outputRegister, bool doCount)
-    : ExecutionBlock(engine, node),
-      _currentDependency(0),
-      _outputRegister(outputRegister),
-      _doCount(doCount) {
-  // already insert ourselves into the statistics results
-  if (_profile >= PROFILE_LEVEL_BLOCKS) {
-    _engine->_stats.nodes.try_emplace(node->id(), ExecutionStats::Node());
-  }
-}
-
-std::pair<ExecutionState, size_t> ExecutionBlockImpl<IdExecutor<void>>::skipSome(size_t atMost) {
-  traceSkipSomeBegin(atMost);
-  if (isDone()) {
-    return traceSkipSomeEnd(ExecutionState::DONE, 0);
-  }
-
-  ExecutionState state;
-  size_t skipped;
-  std::tie(state, skipped) = currentDependency().skipSome(atMost);
-
-  if (state == ExecutionState::DONE) {
-    nextDependency();
-  }
-
-  return traceSkipSomeEnd(state, skipped);
-}
-
-std::pair<ExecutionState, SharedAqlItemBlockPtr> ExecutionBlockImpl<IdExecutor<void>>::getSome(size_t atMost) {
-  traceGetSomeBegin(atMost);
-  if (isDone()) {
-    return traceGetSomeEnd(ExecutionState::DONE, nullptr);
-  }
-
-  ExecutionState state;
-  SharedAqlItemBlockPtr block;
-  std::tie(state, block) = currentDependency().getSome(atMost);
-
-  countStats(block);
-
-  if (state == ExecutionState::DONE) {
-    nextDependency();
-  }
-
-  return traceGetSomeEnd(state, block);
-}
-
-bool aql::ExecutionBlockImpl<IdExecutor<void>>::isDone() const noexcept {
-  // I'd like to assert this in the constructor, but the dependencies are
-  // added after construction.
-  TRI_ASSERT(!_dependencies.empty());
-  return _currentDependency >= _dependencies.size();
-}
-
-RegisterId ExecutionBlockImpl<IdExecutor<void>>::getOutputRegisterId() const noexcept {
-  return _outputRegister;
-}
-
-std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr>
-ExecutionBlockImpl<IdExecutor<void>>::execute(AqlCallStack stack) {
-  // TODO Implement me
-  TRI_ASSERT(false);
-  THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
-}
-
-ExecutionBlock& ExecutionBlockImpl<IdExecutor<void>>::currentDependency() const {
-  TRI_ASSERT(_currentDependency < _dependencies.size());
-  TRI_ASSERT(_dependencies[_currentDependency] != nullptr);
-  return *_dependencies[_currentDependency];
-}
-
-void ExecutionBlockImpl<IdExecutor<void>>::nextDependency() noexcept {
-  ++_currentDependency;
-}
-
-bool ExecutionBlockImpl<IdExecutor<void>>::doCount() const noexcept {
-  return _doCount;
-}
-
-void ExecutionBlockImpl<IdExecutor<void>>::countStats(SharedAqlItemBlockPtr& block) {
-  if (doCount() && block != nullptr) {
-    CountStats stats;
-    stats.setCounted(block->size());
-    _engine->_stats += stats;
-  }
-}
-
 IdExecutorInfos::IdExecutorInfos(RegisterId nrInOutRegisters,
                                  // cppcheck-suppress passedByValue
                                  std::unordered_set<RegisterId> registersToKeep,
                                  // cppcheck-suppress passedByValue
                                  std::unordered_set<RegisterId> registersToClear,
+                                 bool doCount, RegisterId outputRegister,
                                  std::string distributeId, bool isResponsibleForInitializeCursor)
     : ExecutorInfos(make_shared_unordered_set(), make_shared_unordered_set(),
                     nrInOutRegisters, nrInOutRegisters,
                     std::move(registersToClear), std::move(registersToKeep)),
+      _doCount(doCount),
+      _outputRegister(outputRegister),
       _distributeId(std::move(distributeId)),
-      _isResponsibleForInitializeCursor(isResponsibleForInitializeCursor) {}
+      _isResponsibleForInitializeCursor(isResponsibleForInitializeCursor) {
+  // We can only doCount in the case where this executor is used as a Return.
+  // And we can only have a distributeId if this executor is used as Gather.
+  TRI_ASSERT(!_doCount || _distributeId.empty());
+}
+
+auto IdExecutorInfos::doCount() const noexcept -> bool { return _doCount; }
+
+auto IdExecutorInfos::getOutputRegister() const noexcept -> RegisterId {
+  return _outputRegister;
+}
 
 std::string const& IdExecutorInfos::distributeId() { return _distributeId; }
 
@@ -149,7 +73,7 @@ bool IdExecutorInfos::isResponsibleForInitializeCursor() const {
 
 template <class UsedFetcher>
 IdExecutor<UsedFetcher>::IdExecutor(Fetcher& fetcher, IdExecutorInfos& infos)
-    : _fetcher(fetcher) {
+    : _fetcher(fetcher), _infos(infos) {
   if (!infos.distributeId().empty()) {
     _fetcher.setDistributeId(infos.distributeId());
   }
@@ -158,18 +82,14 @@ IdExecutor<UsedFetcher>::IdExecutor(Fetcher& fetcher, IdExecutorInfos& infos)
 template <class UsedFetcher>
 IdExecutor<UsedFetcher>::~IdExecutor() = default;
 
-template <class UsedFetcher>
-std::pair<ExecutionState, NoStats> IdExecutor<UsedFetcher>::produceRows(OutputAqlItemRow& output) {
-  TRI_ASSERT(false);
-  THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
-}
-
 template <class UsedFetcher>
 auto IdExecutor<UsedFetcher>::produceRows(AqlItemBlockInputRange& inputRange,
                                           OutputAqlItemRow& output)
-    -> std::tuple<ExecutorState, NoStats, AqlCall> {
-  NoStats stats;
-
+    -> std::tuple<ExecutorState, CountStats, AqlCall> {
+  CountStats stats;
+  TRI_ASSERT(output.numRowsWritten() == 0);
+  // TODO: We can implement a fastForward copy here.
+  // We know that all rows we have will fit into the output
   while (!output.isFull() && inputRange.hasDataRow()) {
     auto const& [state, inputRow] = inputRange.nextDataRow();
     TRI_ASSERT(inputRow);
@@ -187,10 +107,29 @@ auto IdExecutor<UsedFetcher>::produceRows(AqlItemBlockInputRange& inputRange,
       THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
     }
   }
+  if (_infos.doCount()) {
+    stats.addCounted(output.numRowsWritten());
+  }
 
   return {inputRange.upstreamState(), stats, output.getClientCall()};
 }
 
+template <class UsedFetcher>
+auto IdExecutor<UsedFetcher>::skipRowsRange(AqlItemBlockInputRange& inputRange, AqlCall& call)
+    -> std::tuple<ExecutorState, CountStats, size_t, AqlCall> {
+  CountStats stats;
+  size_t skipped = 0;
+  if (call.getLimit() > 0) {
+    // we can only account for offset
+    skipped = inputRange.skip(call.getOffset());
+  } else {
+    skipped = inputRange.skipAll();
+  }
+  call.didSkip(skipped);
+  // TODO: Do we need to do counting here?
+  return {inputRange.upstreamState(), stats, skipped, call};
+}
+
 template <class UsedFetcher>
 std::tuple<ExecutionState, typename IdExecutor<UsedFetcher>::Stats, SharedAqlItemBlockPtr>
 IdExecutor<UsedFetcher>::fetchBlockForPassthrough(size_t atMost) {
diff --git a/arangod/Aql/IdExecutor.h b/arangod/Aql/IdExecutor.h
index 10e63216e50c..dbab3c746ebc 100644
--- a/arangod/Aql/IdExecutor.h
+++ b/arangod/Aql/IdExecutor.h
@@ -33,9 +33,6 @@
 
 // There are currently three variants of IdExecutor in use:
 //
-// - IdExecutor<void>
-//     This is a variant of the ReturnBlock. It can optionally count and holds
-//     an output register id.
 // - IdExecutor<ConstFetcher>
 //     This is the SingletonBlock.
 // - IdExecutor<SingleRowFetcher<BlockPassthrough::Enable>>
@@ -58,14 +55,14 @@ class AqlItemBlockInputRange;
 class ExecutionEngine;
 class ExecutionNode;
 class ExecutorInfos;
-class NoStats;
+class CountStats;
 class OutputAqlItemRow;
 
 class IdExecutorInfos : public ExecutorInfos {
  public:
   IdExecutorInfos(RegisterId nrInOutRegisters, std::unordered_set<RegisterId> registersToKeep,
-                  std::unordered_set<RegisterId> registersToClear,
-                  std::string distributeId = {""},
+                  std::unordered_set<RegisterId> registersToClear, bool doCount,
+                  RegisterId outputRegister = 0, std::string distributeId = {""},
                   bool isResponsibleForInitializeCursor = true);
 
   IdExecutorInfos() = delete;
@@ -73,11 +70,19 @@ class IdExecutorInfos : public ExecutorInfos {
   IdExecutorInfos(IdExecutorInfos const&) = delete;
   ~IdExecutorInfos() = default;
 
+  [[nodiscard]] auto doCount() const noexcept -> bool;
+
+  [[nodiscard]] auto getOutputRegister() const noexcept -> RegisterId;
+
   [[nodiscard]] std::string const& distributeId();
 
   [[nodiscard]] bool isResponsibleForInitializeCursor() const;
 
  private:
+  bool _doCount;
+
+  RegisterId _outputRegister;
+
   std::string const _distributeId;
 
   bool const _isResponsibleForInitializeCursor;
@@ -87,44 +92,6 @@ class IdExecutorInfos : public ExecutorInfos {
 template <class Fetcher>
 class IdExecutor;
 
-// (empty) implementation of IdExecutor<void>
-template <>
-class IdExecutor<void> {};
-
-// implementation of ExecutionBlockImpl<IdExecutor<void>>
-template <>
-class ExecutionBlockImpl<IdExecutor<void>> : public ExecutionBlock {
- public:
-  ExecutionBlockImpl(ExecutionEngine* engine, ExecutionNode const* node,
-                     RegisterId outputRegister, bool doCount);
-
-  ~ExecutionBlockImpl() override = default;
-
-  std::pair<ExecutionState, SharedAqlItemBlockPtr> getSome(size_t atMost) override;
-
-  std::pair<ExecutionState, size_t> skipSome(size_t atMost) override;
-
-  [[nodiscard]] RegisterId getOutputRegisterId() const noexcept;
-
-  std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> execute(AqlCallStack stack) override;
-
- private:
-  [[nodiscard]] bool isDone() const noexcept;
-
-  [[nodiscard]] ExecutionBlock& currentDependency() const;
-
-  void nextDependency() noexcept;
-
-  [[nodiscard]] bool doCount() const noexcept;
-
-  void countStats(SharedAqlItemBlockPtr& block);
-
- private:
-  size_t _currentDependency;
-  RegisterId const _outputRegister;
-  bool const _doCount;
-};
-
 template <class UsedFetcher>
 // cppcheck-suppress noConstructor
 class IdExecutor {
@@ -137,19 +104,11 @@ class IdExecutor {
   // Only Supports SingleRowFetcher and ConstFetcher
   using Fetcher = UsedFetcher;
   using Infos = IdExecutorInfos;
-  using Stats = NoStats;
+  using Stats = CountStats;
 
-  IdExecutor(Fetcher& fetcher, IdExecutorInfos&);
+  IdExecutor(Fetcher&, IdExecutorInfos& infos);
   ~IdExecutor();
 
-  /**
-   * @brief produce the next Row of Aql Values.
-   *
-   * @return ExecutionState,
-   *         if something was written output.hasValue() == true
-   */
-  std::pair<ExecutionState, Stats> produceRows(OutputAqlItemRow& output);
-
   /**
    * @brief produce the next Row of Aql Values.
    *
@@ -158,11 +117,15 @@ class IdExecutor {
   auto produceRows(AqlItemBlockInputRange& input, OutputAqlItemRow& output)
       -> std::tuple<ExecutorState, Stats, AqlCall>;
 
+  auto skipRowsRange(AqlItemBlockInputRange& inputRange, AqlCall& call)
+      -> std::tuple<ExecutorState, CountStats, size_t, AqlCall>;
+
   // Deprecated remove me
   std::tuple<ExecutionState, Stats, SharedAqlItemBlockPtr> fetchBlockForPassthrough(size_t atMost);
 
  private:
   Fetcher& _fetcher;
+  Infos& _infos;
 };
 }  // namespace aql
 }  // namespace arangodb
diff --git a/arangod/Aql/OptimizerRules.cpp b/arangod/Aql/OptimizerRules.cpp
index 9f6884c930fb..ec57cf481828 100644
--- a/arangod/Aql/OptimizerRules.cpp
+++ b/arangod/Aql/OptimizerRules.cpp
@@ -608,10 +608,9 @@ std::vector<arangodb::aql::ExecutionNode::NodeType> const patchUpdateRemoveState
     arangodb::aql::ExecutionNode::UPDATE, arangodb::aql::ExecutionNode::REPLACE,
     arangodb::aql::ExecutionNode::REMOVE};
 std::vector<arangodb::aql::ExecutionNode::NodeType> const moveFilterIntoEnumerateTypes{
-    arangodb::aql::ExecutionNode::ENUMERATE_COLLECTION,
-    arangodb::aql::ExecutionNode::INDEX};
+    arangodb::aql::ExecutionNode::ENUMERATE_COLLECTION, arangodb::aql::ExecutionNode::INDEX};
 std::vector<arangodb::aql::ExecutionNode::NodeType> const undistributeNodeTypes{
-    arangodb::aql::ExecutionNode::UPDATE, arangodb::aql::ExecutionNode::REPLACE, 
+    arangodb::aql::ExecutionNode::UPDATE, arangodb::aql::ExecutionNode::REPLACE,
     arangodb::aql::ExecutionNode::REMOVE};
 
 /// @brief find the single shard id for the node to restrict an operation to
@@ -1502,7 +1501,7 @@ class PropagateConstantAttributesHelper {
 
     if (it == _constants.end()) {
       _constants.try_emplace(variable,
-                         std::unordered_map<std::string, AstNode const*>{{name, value}});
+                             std::unordered_map<std::string, AstNode const*>{{name, value}});
       return;
     }
 
@@ -2791,7 +2790,7 @@ void arangodb::aql::removeUnnecessaryCalculationsRule(Optimizer* opt,
           // no COLLECT found, now replace
           std::unordered_map<VariableId, Variable const*> replacements;
           replacements.try_emplace(outVariable->id,
-                               static_cast<Variable const*>(rootNode->getData()));
+                                   static_cast<Variable const*>(rootNode->getData()));
 
           RedundantCalculationsReplacer finder(plan->getAst(), replacements);
           plan->root()->walk(finder);
@@ -3112,7 +3111,7 @@ struct SortToIndexNode final : public WalkerWorker<ExecutionNode> {
     bool isSorted = index->isSorted();
     bool isSparse = index->sparse();
     std::vector<std::vector<arangodb::basics::AttributeName>> fields = index->fields();
-    
+
     if (indexes.size() != 1) {
       // can only use this index node if it uses exactly one index or multiple
       // indexes on exactly the same attributes
@@ -3766,11 +3765,12 @@ void arangodb::aql::scatterInClusterRule(Optimizer* opt, std::unique_ptr<Executi
 
     // insert a gather node
     auto const sortMode = GatherNode::evaluateSortMode(collection->numberOfShards());
-    auto const parallelism = (((collection->isSmart() && collection->type() == TRI_COL_TYPE_EDGE) || 
-                               (collection->numberOfShards() <= 1 && !collection->isSatellite())) ? 
-                              GatherNode::Parallelism::Serial : 
-                              GatherNode::Parallelism::Undefined);
-    auto* gatherNode = new GatherNode(plan.get(), plan->nextId(), sortMode, parallelism); 
+    auto const parallelism =
+        (((collection->isSmart() && collection->type() == TRI_COL_TYPE_EDGE) ||
+          (collection->numberOfShards() <= 1 && !collection->isSatellite()))
+             ? GatherNode::Parallelism::Serial
+             : GatherNode::Parallelism::Undefined);
+    auto* gatherNode = new GatherNode(plan.get(), plan->nextId(), sortMode, parallelism);
     plan->registerNode(gatherNode);
     TRI_ASSERT(remoteNode);
     gatherNode->addDependency(remoteNode);
@@ -3980,8 +3980,8 @@ void arangodb::aql::distributeInClusterRule(Optimizer* opt,
         // an UPSERT node has two input variables!
         auto upsertNode = ExecutionNode::castTo<UpsertNode const*>(node);
         auto d = new DistributeNode(plan.get(), plan->nextId(),
-                                    ScatterNode::ScatterType::SHARD,
-                                    collection, upsertNode->inDocVariable(),
+                                    ScatterNode::ScatterType::SHARD, collection,
+                                    upsertNode->inDocVariable(),
                                     upsertNode->insertVariable(), true, true);
         d->setAllowSpecifiedKeys(true);
         distNode = ExecutionNode::castTo<ExecutionNode*>(d);
@@ -4869,8 +4869,8 @@ class RemoveToEnumCollFinder final : public WalkerWorker<ExecutionNode> {
 
   bool before(ExecutionNode* en) override final {
     switch (en->getType()) {
-      case EN::UPDATE: 
-      case EN::REPLACE: 
+      case EN::UPDATE:
+      case EN::REPLACE:
       case EN::REMOVE: {
         if (_foundModification) {
           break;
@@ -4879,7 +4879,7 @@ class RemoveToEnumCollFinder final : public WalkerWorker<ExecutionNode> {
         // find the variable we are removing . . .
         auto rn = ExecutionNode::castTo<ModificationNode*>(en);
         Variable const* toRemove = nullptr;
-        
+
         if (en->getType() == EN::REPLACE) {
           toRemove = ExecutionNode::castTo<ReplaceNode const*>(en)->inKeyVariable();
         } else if (en->getType() == EN::UPDATE) {
@@ -4898,7 +4898,7 @@ class RemoveToEnumCollFinder final : public WalkerWorker<ExecutionNode> {
         _setter = _plan->getVarSetBy(toRemove->id);
         TRI_ASSERT(_setter != nullptr);
         auto enumColl = _setter;
-        
+
         if (_setter->getType() == EN::CALCULATION) {
           // this should be an attribute access for _key
           auto cn = ExecutionNode::castTo<CalculationNode*>(_setter);
@@ -4914,7 +4914,7 @@ class RemoveToEnumCollFinder final : public WalkerWorker<ExecutionNode> {
             if (shardKeys.size() != 1 || shardKeys[0] != StaticStrings::KeyString) {
               break;  // abort . . .
             }
-            
+
             // set the varsToRemove to the variable in the expression of this
             // node and also define enumColl
             ::arangodb::containers::HashSet<Variable const*> varsToRemove;
@@ -4998,10 +4998,11 @@ class RemoveToEnumCollFinder final : public WalkerWorker<ExecutionNode> {
           break;  // abort . . .
         }
 
-        auto const& projections = dynamic_cast<DocumentProducingNode const*>(enumColl)->projections();
-        if (projections.size() > 1 || 
+        auto const& projections =
+            dynamic_cast<DocumentProducingNode const*>(enumColl)->projections();
+        if (projections.size() > 1 ||
             (!projections.empty() && projections[0] != StaticStrings::KeyString)) {
-          // cannot handle projections 
+          // cannot handle projections
           break;
         }
 
@@ -5022,7 +5023,7 @@ class RemoveToEnumCollFinder final : public WalkerWorker<ExecutionNode> {
       case EN::DISTRIBUTE:
       case EN::SCATTER: {
         if (_foundScatter) {  // met more than one scatter node
-          break;         // abort . . .
+          break;              // abort . . .
         }
         _foundScatter = true;
         _toUnlink.emplace(en);
@@ -5030,7 +5031,7 @@ class RemoveToEnumCollFinder final : public WalkerWorker<ExecutionNode> {
       }
       case EN::GATHER: {
         if (_foundGather) {  // met more than one gather node
-          break;        // abort . . .
+          break;             // abort . . .
         }
         _foundGather = true;
         _toUnlink.emplace(en);
@@ -5075,7 +5076,7 @@ class RemoveToEnumCollFinder final : public WalkerWorker<ExecutionNode> {
         TRI_ASSERT(false);
       }
     }
-    
+
     _toUnlink.clear();
     return true;
   }
@@ -5421,7 +5422,8 @@ void arangodb::aql::replaceOrWithInRule(Optimizer* opt, std::unique_ptr<Executio
         THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
       }
 
-      ExecutionNode* newNode = new CalculationNode(plan.get(), plan->nextId(), std::move(expr), outVar);
+      ExecutionNode* newNode =
+          new CalculationNode(plan.get(), plan->nextId(), std::move(expr), outVar);
 
       plan->registerNode(newNode);
       plan->replaceNode(cn, newNode);
@@ -5585,7 +5587,8 @@ void arangodb::aql::removeRedundantOrRule(Optimizer* opt,
       auto astNode = remover.createReplacementNode(plan->getAst());
 
       auto expr = std::make_unique<Expression>(plan.get(), plan->getAst(), astNode);
-      ExecutionNode* newNode = new CalculationNode(plan.get(), plan->nextId(), std::move(expr), outVar);
+      ExecutionNode* newNode =
+          new CalculationNode(plan.get(), plan->nextId(), std::move(expr), outVar);
       plan->registerNode(newNode);
       plan->replaceNode(cn, newNode);
       modified = true;
@@ -6956,7 +6959,8 @@ void arangodb::aql::sortLimitRule(Optimizer* opt, std::unique_ptr<ExecutionPlan>
   bool mod = false;
   // If there isn't a limit node, and at least one sort or gather node, there's
   // nothing to do.
-  if (!plan->contains(EN::LIMIT) || (!plan->contains(EN::SORT) && !plan->contains(EN::GATHER))) {
+  if (!plan->contains(EN::LIMIT) ||
+      (!plan->contains(EN::SORT) && !plan->contains(EN::GATHER))) {
     opt->addPlan(std::move(plan), rule, mod);
     return;
   }
@@ -7075,10 +7079,10 @@ void arangodb::aql::optimizeSubqueriesRule(Optimizer* opt,
       if (found.first != nullptr) {
         auto it = subqueryAttributes.find(found.first);
         if (it == subqueryAttributes.end()) {
-          subqueryAttributes.try_emplace(found.first,
-                                     std::make_tuple(found.second,
-                                                     std::unordered_set<ExecutionNode const*>{n},
-                                                     usedForCount));
+          subqueryAttributes.try_emplace(
+              found.first, std::make_tuple(found.second,
+                                           std::unordered_set<ExecutionNode const*>{n},
+                                           usedForCount));
         } else {
           auto& sq = (*it).second;
           if (usedForCount) {
@@ -7199,7 +7203,8 @@ void arangodb::aql::optimizeSubqueriesRule(Optimizer* opt,
 }
 
 /// @brief move filters into EnumerateCollection nodes
-void arangodb::aql::moveFiltersIntoEnumerateRule(Optimizer* opt, std::unique_ptr<ExecutionPlan> plan,
+void arangodb::aql::moveFiltersIntoEnumerateRule(Optimizer* opt,
+                                                 std::unique_ptr<ExecutionPlan> plan,
                                                  OptimizerRule const& rule) {
   bool modified = false;
 
@@ -7212,12 +7217,14 @@ void arangodb::aql::moveFiltersIntoEnumerateRule(Optimizer* opt, std::unique_ptr
   for (auto const& n : nodes) {
     auto en = dynamic_cast<DocumentProducingNode*>(n);
     if (en == nullptr) {
-      THROW_ARANGO_EXCEPTION_MESSAGE(TRI_ERROR_INTERNAL, "unable to cast node to DocumentProducingNode");
+      THROW_ARANGO_EXCEPTION_MESSAGE(
+          TRI_ERROR_INTERNAL, "unable to cast node to DocumentProducingNode");
     }
 
-    if (n->getType() == EN::INDEX && ExecutionNode::castTo<IndexNode const*>(n)->getIndexes().size() != 1) {
-      // we can only handle exactly one index right now. otherwise some IndexExecutor code
-      // may assert and fail
+    if (n->getType() == EN::INDEX &&
+        ExecutionNode::castTo<IndexNode const*>(n)->getIndexes().size() != 1) {
+      // we can only handle exactly one index right now. otherwise some
+      // IndexExecutor code may assert and fail
       continue;
     }
 
@@ -7241,7 +7248,7 @@ void arangodb::aql::moveFiltersIntoEnumerateRule(Optimizer* opt, std::unique_ptr
         if (calculations.empty()) {
           break;
         }
-        
+
         auto filterNode = ExecutionNode::castTo<FilterNode*>(current);
         Variable const* inVariable = filterNode->inVariable();
 
@@ -7255,8 +7262,10 @@ void arangodb::aql::moveFiltersIntoEnumerateRule(Optimizer* opt, std::unique_ptr
         Expression* existingFilter = en->filter();
         if (existingFilter != nullptr && existingFilter->node() != nullptr) {
           // node already has a filter, now AND-merge it with what we found!
-          AstNode* merged = plan->getAst()->createNodeBinaryOperator(
-            NODE_TYPE_OPERATOR_BINARY_AND, existingFilter->node(), expr->node());
+          AstNode* merged =
+              plan->getAst()->createNodeBinaryOperator(NODE_TYPE_OPERATOR_BINARY_AND,
+                                                       existingFilter->node(),
+                                                       expr->node());
 
           en->setFilter(std::make_unique<Expression>(plan.get(), plan->getAst(), merged));
         } else {
@@ -7304,15 +7313,16 @@ void arangodb::aql::moveFiltersIntoEnumerateRule(Optimizer* opt, std::unique_ptr
 }
 
 /// @brief parallelize coordinator GatherNodes
-void arangodb::aql::parallelizeGatherRule(Optimizer* opt, std::unique_ptr<ExecutionPlan> plan,
+void arangodb::aql::parallelizeGatherRule(Optimizer* opt,
+                                          std::unique_ptr<ExecutionPlan> plan,
                                           OptimizerRule const& rule) {
   TRI_ASSERT(ServerState::instance()->isCoordinator());
-  
+
   bool modified = false;
 
   // find all GatherNodes in the main query, starting from the query's root node
   // (the node most south when looking at the query execution plan).
-  // 
+  //
   // for now, we effectively stop right after the first GatherNode we found, regardless
   // of whether we can make that node use parallelism or not.
   // the reason we have to stop here is that if we have multiple query snippets on a
@@ -7320,42 +7330,39 @@ void arangodb::aql::parallelizeGatherRule(Optimizer* opt, std::unique_ptr<Execut
   // transactions are not thread-safe right now, so we must avoid any parallelism when
   // there can be another snippet with the same transaction on the same server.
   //
-  // for example consider the following query, joining the shards of two collections 
+  // for example consider the following query, joining the shards of two collections
   // on 2 database servers:
   //
   //   (4)      DBS1                            DBS2               database
   //        users, shard 1                 users, shard 2          servers
   //       --------------------------------------------------------
-  //   (3)                      Gather                             coordinator 
-  //       -------------------------------------------------------- 
+  //   (3)                      Gather                             coordinator
+  //       --------------------------------------------------------
   //   (2)      DBS1            Scatter         DBS2               database
   //       orders, shard 1                orders, shard 2          servers
-  //       -------------------------------------------------------- 
+  //       --------------------------------------------------------
   //   (1)                      Gather                             coordinator
   //
-  // the query starts with a GatherNode (1). if we make that parallel, then it will 
+  // the query starts with a GatherNode (1). if we make that parallel, then it will
   // ask the shards of `orders` on the database servers in parallel (2). So there
   // can be 2 threads in (2), on different servers. all is fine until here.
   // however, if the thread for DBS1 fetches upstream data from the coordinator (3),
   // then the coordinator may reach out to DBS2 to get more data from the `users`
   // collection (4). so one thread will be on DBS2 and using the transaction. at
   // the very same time we already have another thread working on the same server on
-  // (2). they are using the same transaction object, which currently is not 
+  // (2). they are using the same transaction object, which currently is not
   // thread-safe.
   // we need to avoid any such situation, and thus we cannot make any of the GatherNodes
   // thread-safe here. the only case in which we currently can employ parallelization
-  // is when there is only a single GatherNode. all other restrictions for 
+  // is when there is only a single GatherNode. all other restrictions for
   // parallelization (e.g. no DistributeNodes around) still apply.
   ::arangodb::containers::SmallVector<ExecutionNode*>::allocator_type::arena_type a;
   ::arangodb::containers::SmallVector<ExecutionNode*> nodes{a};
   plan->findNodesOfType(nodes, EN::GATHER, true);
 
-  if (nodes.size() == 1 && 
-      !plan->contains(EN::TRAVERSAL) && 
-      !plan->contains(EN::SHORTEST_PATH) && 
-      !plan->contains(EN::K_SHORTEST_PATHS) && 
-      !plan->contains(EN::DISTRIBUTE) && 
-      !plan->contains(EN::SCATTER)) {
+  if (nodes.size() == 1 && !plan->contains(EN::TRAVERSAL) &&
+      !plan->contains(EN::SHORTEST_PATH) && !plan->contains(EN::K_SHORTEST_PATHS) &&
+      !plan->contains(EN::DISTRIBUTE) && !plan->contains(EN::SCATTER)) {
     GatherNode* gn = ExecutionNode::castTo<GatherNode*>(nodes[0]);
 
     if (!gn->isInSubquery() && gn->isParallelizable()) {
@@ -7428,7 +7435,8 @@ void findSubqueriesSuitableForSplicing(ExecutionPlan const& plan,
   using ResultVector = decltype(result);
   using BoolVec = std::vector<bool, short_alloc<bool, 64, alignof(size_t)>>;
 
-  using SuitableNodeSet = std::set<SubqueryNode*, std::less<>, short_alloc<SubqueryNode*, 128, alignof(SubqueryNode*)>>;
+  using SuitableNodeSet =
+      std::set<SubqueryNode*, std::less<>, short_alloc<SubqueryNode*, 128, alignof(SubqueryNode*)>>;
 
   // This finder adds all subquery nodes in pre-order to its `result` parameter,
   // and all nodes that are suitable for splicing to `suitableNodes`. Suitable
@@ -7519,11 +7527,10 @@ void findSubqueriesSuitableForSplicing(ExecutionPlan const& plan,
   auto finder = Finder{result, suitableNodes};
   plan.root()->walkSubqueriesFirst(finder);
 
-
-  { // remove unsuitable nodes from result
+  {  // remove unsuitable nodes from result
     auto i = size_t{0};
     auto j = size_t{0};
-    for(; j < result.size(); ++j) {
+    for (; j < result.size(); ++j) {
       TRI_ASSERT(i <= j);
       if (suitableNodes.count(result[j]) > 0) {
         if (i != j) {
@@ -7541,7 +7548,7 @@ void findSubqueriesSuitableForSplicing(ExecutionPlan const& plan,
     result.resize(i);
   }
 }
-}
+}  // namespace
 
 // Splices in subqueries by replacing subquery nodes by
 // a SubqueryStartNode and a SubqueryEndNode with the subquery's nodes
@@ -7578,10 +7585,11 @@ void arangodb::aql::spliceSubqueriesRule(Optimizer* opt, std::unique_ptr<Executi
 
     auto const addClusterNodes = !evenNumberOfRemotes;
 
-    { // insert SubqueryStartNode
+    {  // insert SubqueryStartNode
 
       // Create new start node
-      auto start = plan->createNode<SubqueryStartNode>(plan.get(), plan->nextId(), sq->outVariable());
+      auto start = plan->createNode<SubqueryStartNode>(plan.get(), plan->nextId(),
+                                                       sq->outVariable());
 
       // start and end inherit this property from the subquery node
       start->setIsInSplicedSubquery(sq->isInSplicedSubquery());
@@ -7640,7 +7648,7 @@ void arangodb::aql::spliceSubqueriesRule(Optimizer* opt, std::unique_ptr<Executi
       }
     }
 
-    { // insert SubqueryEndNode
+    {  // insert SubqueryEndNode
 
       ExecutionNode* subqueryRoot = sq->getSubquery();
       Variable const* inVariable = nullptr;
@@ -7658,7 +7666,8 @@ void arangodb::aql::spliceSubqueriesRule(Optimizer* opt, std::unique_ptr<Executi
 
       // Create new end node
       auto end = plan->createNode<SubqueryEndNode>(plan.get(), plan->nextId(),
-          inVariable, sq->outVariable());
+                                                   inVariable, sq->outVariable(),
+                                                   sq->isModificationSubquery());
       // start and end inherit this property from the subquery node
       end->setIsInSplicedSubquery(sq->isInSplicedSubquery());
       // insert a SubqueryEndNode after the SubqueryNode sq
diff --git a/arangod/Aql/OutputAqlItemRow.cpp b/arangod/Aql/OutputAqlItemRow.cpp
index df485265ebc7..9eddbcf13a1a 100644
--- a/arangod/Aql/OutputAqlItemRow.cpp
+++ b/arangod/Aql/OutputAqlItemRow.cpp
@@ -42,6 +42,8 @@ The following conditions need to hold true, we need to add c++ tests for this.
 #include <velocypack/Builder.h>
 #include <velocypack/velocypack-aliases.h>
 
+#include "Logger/LogMacros.h"
+
 using namespace arangodb;
 using namespace arangodb::aql;
 
diff --git a/arangod/Aql/ScatterExecutor.cpp b/arangod/Aql/ScatterExecutor.cpp
index 40d1c2208cf2..bdf56efdb391 100644
--- a/arangod/Aql/ScatterExecutor.cpp
+++ b/arangod/Aql/ScatterExecutor.cpp
@@ -48,7 +48,11 @@ ScatterExecutor::ClientBlockData::ClientBlockData(ExecutionEngine& engine,
   // We only get shared ptrs to const data. so we need to copy here...
   IdExecutorInfos infos{scatterInfos.numberOfInputRegisters(),
                         *scatterInfos.registersToKeep(),
-                        *scatterInfos.registersToClear(), "", false};
+                        *scatterInfos.registersToClear(),
+                        false,
+                        0,
+                        "",
+                        false};
   // NOTE: Do never change this type! The execute logic below requires this and only this type.
   _executor =
       std::make_unique<ExecutionBlockImpl<IdExecutor<ConstFetcher>>>(&engine, node,
diff --git a/arangod/Aql/ShadowAqlItemRow.cpp b/arangod/Aql/ShadowAqlItemRow.cpp
index c3e9df3f4994..cdc609ac752a 100644
--- a/arangod/Aql/ShadowAqlItemRow.cpp
+++ b/arangod/Aql/ShadowAqlItemRow.cpp
@@ -23,8 +23,8 @@
 #include "ShadowAqlItemRow.h"
 
 #include "Basics/VelocyPackHelper.h"
-#include "Transaction/Methods.h"
 #include "Transaction/Context.h"
+#include "Transaction/Methods.h"
 
 using namespace arangodb;
 using namespace arangodb::aql;
diff --git a/arangod/Aql/SubqueryEndExecutionNode.cpp b/arangod/Aql/SubqueryEndExecutionNode.cpp
index 44a2f2fb0153..075604c6e414 100644
--- a/arangod/Aql/SubqueryEndExecutionNode.cpp
+++ b/arangod/Aql/SubqueryEndExecutionNode.cpp
@@ -29,6 +29,7 @@
 #include "Aql/Query.h"
 #include "Aql/RegisterPlan.h"
 #include "Aql/SubqueryEndExecutor.h"
+#include "Basics/VelocyPackHelper.h"
 #include "Meta/static_assert_size.h"
 #include "Transaction/Context.h"
 #include "Transaction/Methods.h"
@@ -51,7 +52,19 @@ bool CompareVariables(Variable const* mine, Variable const* yours) {
 SubqueryEndNode::SubqueryEndNode(ExecutionPlan* plan, arangodb::velocypack::Slice const& base)
     : ExecutionNode(plan, base),
       _inVariable(Variable::varFromVPack(plan->getAst(), base, "inVariable", true)),
-      _outVariable(Variable::varFromVPack(plan->getAst(), base, "outVariable")) {}
+      _outVariable(Variable::varFromVPack(plan->getAst(), base, "outVariable")),
+      _isModificationSubquery(basics::VelocyPackHelper::getBooleanValue(
+          base, "isModificationSubquery", false)) {}
+
+SubqueryEndNode::SubqueryEndNode(ExecutionPlan* plan, size_t id, Variable const* inVariable,
+                                 Variable const* outVariable, bool isModificationSubquery)
+    : ExecutionNode(plan, id),
+      _inVariable(inVariable),
+      _outVariable(outVariable),
+      _isModificationSubquery(isModificationSubquery) {
+  // _inVariable might be nullptr
+  TRI_ASSERT(_outVariable != nullptr);
+}
 
 void SubqueryEndNode::toVelocyPackHelper(VPackBuilder& nodes, unsigned flags,
                                          std::unordered_set<ExecutionNode const*>& seen) const {
@@ -65,6 +78,8 @@ void SubqueryEndNode::toVelocyPackHelper(VPackBuilder& nodes, unsigned flags,
     _inVariable->toVelocyPack(nodes);
   }
 
+  nodes.add("isModificationSubquery", VPackValue(isModificationNode()));
+
   nodes.close();
 }
 
@@ -90,8 +105,9 @@ std::unique_ptr<ExecutionBlock> SubqueryEndNode::createBlock(
   auto const vpackOptions = trx->transactionContextPtr()->getVPackOptions();
   SubqueryEndExecutorInfos infos(inputRegisters, outputRegisters,
                                  getRegisterPlan()->nrRegs[previousNode->getDepth()],
-                                 getRegisterPlan()->nrRegs[getDepth()], getRegsToClear(),
-                                 calcRegsToKeep(), vpackOptions, inReg, outReg);
+                                 getRegisterPlan()->nrRegs[getDepth()],
+                                 getRegsToClear(), calcRegsToKeep(), vpackOptions,
+                                 inReg, outReg, isModificationNode());
 
   return std::make_unique<ExecutionBlockImpl<SubqueryEndExecutor>>(&engine, this,
                                                                    std::move(infos));
@@ -108,7 +124,8 @@ ExecutionNode* SubqueryEndNode::clone(ExecutionPlan* plan, bool withDependencies
       inVariable = plan->getAst()->variables()->createVariable(inVariable);
     }
   }
-  auto c = std::make_unique<SubqueryEndNode>(plan, _id, inVariable, outVariable);
+  auto c = std::make_unique<SubqueryEndNode>(plan, _id, inVariable, outVariable,
+                                             isModificationNode());
 
   return cloneHelper(std::move(c), withDependencies, withProperties);
 }
@@ -134,7 +151,8 @@ bool SubqueryEndNode::isEqualTo(ExecutionNode const& other) const {
     SubqueryEndNode const& p = dynamic_cast<SubqueryEndNode const&>(other);
     TRI_ASSERT(p._outVariable != nullptr);
     if (!CompareVariables(_outVariable, p._outVariable) ||
-        !CompareVariables(_inVariable, p._inVariable)) {
+        !CompareVariables(_inVariable, p._inVariable) ||
+        _isModificationSubquery != p._isModificationSubquery) {
       // One of the variables does not match
       return false;
     }
@@ -144,3 +162,7 @@ bool SubqueryEndNode::isEqualTo(ExecutionNode const& other) const {
     return false;
   }
 }
+
+bool SubqueryEndNode::isModificationNode() const {
+  return _isModificationSubquery;
+}
diff --git a/arangod/Aql/SubqueryEndExecutionNode.h b/arangod/Aql/SubqueryEndExecutionNode.h
index 879e1f385538..0cae650db267 100644
--- a/arangod/Aql/SubqueryEndExecutionNode.h
+++ b/arangod/Aql/SubqueryEndExecutionNode.h
@@ -37,11 +37,7 @@ class SubqueryEndNode : public ExecutionNode {
   SubqueryEndNode(ExecutionPlan*, arangodb::velocypack::Slice const& base);
 
   SubqueryEndNode(ExecutionPlan* plan, size_t id, Variable const* inVariable,
-                  Variable const* outVariable)
-      : ExecutionNode(plan, id), _inVariable(inVariable), _outVariable(outVariable) {
-    // _inVariable might be nullptr
-    TRI_ASSERT(_outVariable != nullptr);
-  }
+                  Variable const* outVariable, bool isModificationSubquery);
 
   CostEstimate estimateCost() const override final;
 
@@ -74,11 +70,12 @@ class SubqueryEndNode : public ExecutionNode {
   }
 
   void replaceOutVariable(Variable const* var);
+  bool isModificationNode() const override;
 
  private:
   Variable const* _inVariable;
-
   Variable const* _outVariable;
+  bool _isModificationSubquery;
 };
 
 }  // namespace aql
diff --git a/arangod/Aql/SubqueryEndExecutor.cpp b/arangod/Aql/SubqueryEndExecutor.cpp
index 06d261c5a047..6973ac216de4 100644
--- a/arangod/Aql/SubqueryEndExecutor.cpp
+++ b/arangod/Aql/SubqueryEndExecutor.cpp
@@ -34,6 +34,8 @@
 #include <memory>
 #include <utility>
 
+#include "Logger/LogMacros.h"
+
 using namespace arangodb;
 using namespace arangodb::aql;
 
@@ -42,14 +44,15 @@ SubqueryEndExecutorInfos::SubqueryEndExecutorInfos(
     std::shared_ptr<std::unordered_set<RegisterId>> writeableOutputRegisters,
     RegisterId nrInputRegisters, RegisterId nrOutputRegisters,
     std::unordered_set<RegisterId> const& registersToClear,
-    std::unordered_set<RegisterId> registersToKeep,
-    velocypack::Options const* const options, RegisterId inReg, RegisterId outReg)
+    std::unordered_set<RegisterId> registersToKeep, velocypack::Options const* const options,
+    RegisterId inReg, RegisterId outReg, bool isModificationSubquery)
     : ExecutorInfos(std::move(readableInputRegisters),
                     std::move(writeableOutputRegisters), nrInputRegisters,
                     nrOutputRegisters, registersToClear, std::move(registersToKeep)),
       _vpackOptions(options),
       _outReg(outReg),
-      _inReg(inReg) {}
+      _inReg(inReg),
+      _isModificationSubquery(isModificationSubquery) {}
 
 SubqueryEndExecutorInfos::~SubqueryEndExecutorInfos() = default;
 
@@ -69,92 +72,73 @@ RegisterId SubqueryEndExecutorInfos::getInputRegister() const noexcept {
   return _inReg;
 }
 
+bool SubqueryEndExecutorInfos::isModificationSubquery() const noexcept {
+  return _isModificationSubquery;
+}
+
 SubqueryEndExecutor::SubqueryEndExecutor(Fetcher& fetcher, SubqueryEndExecutorInfos& infos)
     : _fetcher(fetcher), _infos(infos), _accumulator(_infos.vpackOptions()) {}
 
 SubqueryEndExecutor::~SubqueryEndExecutor() = default;
 
 std::pair<ExecutionState, NoStats> SubqueryEndExecutor::produceRows(OutputAqlItemRow& output) {
-  ExecutionState state;
+  TRI_ASSERT(false);
+  THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
+}
 
+auto SubqueryEndExecutor::produceRows(AqlItemBlockInputRange& input, OutputAqlItemRow& output)
+    -> std::tuple<ExecutorState, Stats, AqlCall> {
+  // We can not account for skipped rows here.
+  // If we get this we have invalid logic either in the upstream
+  // produced by this Executor
+  // or in the reporting by the Executor data is requested from
+  TRI_ASSERT(input.skippedInFlight() == 0);
+  ExecutorState state{ExecutorState::HASMORE};
   InputAqlItemRow inputRow = InputAqlItemRow{CreateInvalidInputRowHint()};
-  ShadowAqlItemRow shadowRow = ShadowAqlItemRow{CreateInvalidShadowRowHint{}};
-
-  while (!output.isFull()) {
-    switch (_state) {
-      case State::ACCUMULATE_DATA_ROWS: {
-        std::tie(state, inputRow) = _fetcher.fetchRow();
-
-        if (state == ExecutionState::WAITING) {
-          TRI_ASSERT(!inputRow.isInitialized());
-          return {state, NoStats{}};
-        }
-
-        // We got a data row, put it into the accumulator
-        if (inputRow.isInitialized() && _infos.usesInputRegister()) {
-          _accumulator.addValue(inputRow.getValue(_infos.getInputRegister()));
-        }
-
-        // We have received DONE on data rows, so now
-        // we have to read a relevant shadow row
-        if (state == ExecutionState::DONE) {
-          _state = State::PROCESS_SHADOW_ROWS;
-        }
-      } break;
-      case State::PROCESS_SHADOW_ROWS: {
-        std::tie(state, shadowRow) = _fetcher.fetchShadowRow();
-        if (state == ExecutionState::WAITING) {
-          TRI_ASSERT(!shadowRow.isInitialized());
-          return {ExecutionState::WAITING, NoStats{}};
-        }
-        TRI_ASSERT(state == ExecutionState::DONE || state == ExecutionState::HASMORE);
-
-        if (!shadowRow.isInitialized()) {
-          TRI_ASSERT(_accumulator.numValues() == 0);
-          if (state == ExecutionState::HASMORE) {
-            // We did not get another shadowRow; either we
-            // are DONE or we are getting another relevant
-            // shadow row, but only after we called fetchRow
-            // again
-            _state = State::ACCUMULATE_DATA_ROWS;
-          } else {
-            TRI_ASSERT(state == ExecutionState::DONE);
-            return {ExecutionState::DONE, NoStats{}};
-          }
-        } else {
-          if (shadowRow.isRelevant()) {
-            AqlValue value;
-            AqlValueGuard guard = _accumulator.stealValue(value);
-
-            // Responsibility is handed over to output
-            output.consumeShadowRow(_infos.getOutputRegister(), shadowRow, guard);
-            TRI_ASSERT(output.produced());
-            output.advanceRow();
-
-            if (state == ExecutionState::DONE) {
-              return {ExecutionState::DONE, NoStats{}};
-            }
-          } else {
-            TRI_ASSERT(_accumulator.numValues() == 0);
-            // We got a shadow row, it must be irrelevant,
-            // because to get another relevant shadowRow we must
-            // first call fetchRow again
-            output.decreaseShadowRowDepth(shadowRow);
-            output.advanceRow();
-          }
-        }
-      } break;
-
-      default: {
-        TRI_ASSERT(false);
-        break;
-      }
+
+  while (input.hasDataRow()) {
+    std::tie(state, inputRow) = input.nextDataRow();
+    TRI_ASSERT(inputRow.isInitialized());
+
+    // We got a data row, put it into the accumulator,
+    // if we're getting data through an input register.
+    // If not, we just "accumulate" an empty output.
+    if (_infos.usesInputRegister()) {
+      _accumulator.addValue(inputRow.getValue(_infos.getInputRegister()));
     }
   }
+  return {input.upstreamState(), NoStats{}, AqlCall{}};
+}
+
+auto SubqueryEndExecutor::skipRowsRange(AqlItemBlockInputRange& input, AqlCall& call)
+    -> std::tuple<ExecutorState, Stats, size_t, AqlCall> {
+  // We can not account for skipped rows here.
+  // If we get this we have invalid logic either in the upstream
+  // produced by this Executor
+  // or in the reporting by the Executor data is requested from
+  TRI_ASSERT(input.skippedInFlight() == 0);
+  ExecutorState state;
+  InputAqlItemRow inputRow = InputAqlItemRow{CreateInvalidInputRowHint()};
+
+  while (input.hasDataRow()) {
+    std::tie(state, inputRow) = input.nextDataRow();
+    TRI_ASSERT(inputRow.isInitialized());
+  }
+  // This is correct since the SubqueryEndExecutor produces one output out
+  // of the accumulation of all the (relevant) inputs
+  call.didSkip(1);
+  return {input.upstreamState(), NoStats{}, 1, AqlCall{}};
+}
+
+auto SubqueryEndExecutor::consumeShadowRow(ShadowAqlItemRow shadowRow,
+                                           OutputAqlItemRow& output) -> void {
+  AqlValue value;
+  AqlValueGuard guard = _accumulator.stealValue(value);
+  output.consumeShadowRow(_infos.getOutputRegister(), shadowRow, guard);
+}
 
-  // We should *only* fall through here if output.isFull() is true.
-  TRI_ASSERT(output.isFull());
-  return {ExecutionState::HASMORE, NoStats{}};
+auto SubqueryEndExecutor::isModificationSubquery() const noexcept -> bool {
+  return _infos.isModificationSubquery();
 }
 
 void SubqueryEndExecutor::Accumulator::reset() {
@@ -177,8 +161,8 @@ SubqueryEndExecutor::Accumulator::Accumulator(VPackOptions const* const options)
 }
 
 AqlValueGuard SubqueryEndExecutor::Accumulator::stealValue(AqlValue& result) {
-  // Note that an AqlValueGuard holds an AqlValue&, so we cannot create it from
-  // a local AqlValue and return the Guard!
+  // Note that an AqlValueGuard holds an AqlValue&, so we cannot create it
+  // from a local AqlValue and return the Guard!
 
   TRI_ASSERT(_builder->isOpenArray());
   _builder->close();
diff --git a/arangod/Aql/SubqueryEndExecutor.h b/arangod/Aql/SubqueryEndExecutor.h
index c3e5f0e62262..19b684f03b9e 100644
--- a/arangod/Aql/SubqueryEndExecutor.h
+++ b/arangod/Aql/SubqueryEndExecutor.h
@@ -24,6 +24,7 @@
 #ifndef ARANGOD_AQL_SUBQUERY_END_EXECUTOR_H
 #define ARANGOD_AQL_SUBQUERY_END_EXECUTOR_H
 
+#include "Aql/AqlCall.h"
 #include "Aql/ExecutionState.h"
 #include "Aql/ExecutorInfos.h"
 #include "Aql/InputAqlItemRow.h"
@@ -49,7 +50,7 @@ class SubqueryEndExecutorInfos : public ExecutorInfos {
                            std::unordered_set<RegisterId> const& registersToClear,
                            std::unordered_set<RegisterId> registersToKeep,
                            velocypack::Options const* options, RegisterId inReg,
-                           RegisterId outReg);
+                           RegisterId outReg, bool isModificationSubquery);
 
   SubqueryEndExecutorInfos() = delete;
   SubqueryEndExecutorInfos(SubqueryEndExecutorInfos&&) noexcept = default;
@@ -60,11 +61,13 @@ class SubqueryEndExecutorInfos : public ExecutorInfos {
   [[nodiscard]] RegisterId getOutputRegister() const noexcept;
   [[nodiscard]] bool usesInputRegister() const noexcept;
   [[nodiscard]] RegisterId getInputRegister() const noexcept;
+  [[nodiscard]] bool isModificationSubquery() const noexcept;
 
  private:
   velocypack::Options const* _vpackOptions;
   RegisterId const _outReg;
   RegisterId const _inReg;
+  bool const _isModificationSubquery;
 };
 
 class SubqueryEndExecutor {
@@ -82,9 +85,31 @@ class SubqueryEndExecutor {
   SubqueryEndExecutor(Fetcher& fetcher, SubqueryEndExecutorInfos& infos);
   ~SubqueryEndExecutor();
 
-  std::pair<ExecutionState, Stats> produceRows(OutputAqlItemRow& output);
+  [[deprecated]] std::pair<ExecutionState, Stats> produceRows(OutputAqlItemRow& output);
   std::pair<ExecutionState, size_t> expectedNumberOfRows(size_t atMost) const;
 
+  // produceRows accumulates all input rows it can get into _accumulator, which
+  // will then be read out by ExecutionBlockImpl
+  // TODO: can the production of output be moved to produceRows again?
+  [[nodiscard]] auto produceRows(AqlItemBlockInputRange& input, OutputAqlItemRow& output)
+      -> std::tuple<ExecutorState, Stats, AqlCall>;
+  // skipRowsRange consumes all data rows available on the input and just
+  // ignores it. real skips of a subqueries will not execute the whole subquery
+  // so this might not be necessary at all (except for modifying subqueries,
+  // where we have to execute the subquery)
+  [[nodiscard]] auto skipRowsRange(AqlItemBlockInputRange& input, AqlCall& call)
+      -> std::tuple<ExecutorState, Stats, size_t, AqlCall>;
+
+  /**
+   * @brief Consume the given shadow row and write the aggregated value to it
+   *
+   * @param shadowRow The shadow row
+   * @param output Output block
+   */
+  auto consumeShadowRow(ShadowAqlItemRow shadowRow, OutputAqlItemRow& output) -> void;
+
+  [[nodiscard]] auto isModificationSubquery() const noexcept -> bool;
+
  private:
   enum class State {
     ACCUMULATE_DATA_ROWS,
@@ -117,8 +142,6 @@ class SubqueryEndExecutor {
   SubqueryEndExecutorInfos& _infos;
 
   Accumulator _accumulator;
-
-  State _state{State::ACCUMULATE_DATA_ROWS};
 };
 }  // namespace aql
 }  // namespace arangodb
diff --git a/arangod/Aql/SubqueryStartExecutionNode.h b/arangod/Aql/SubqueryStartExecutionNode.h
index 9f73d2066944..1ddfbd6f318f 100644
--- a/arangod/Aql/SubqueryStartExecutionNode.h
+++ b/arangod/Aql/SubqueryStartExecutionNode.h
@@ -57,10 +57,13 @@ class SubqueryStartNode : public ExecutionNode {
 
   bool isEqualTo(ExecutionNode const& other) const override final;
 
+  bool isModificationSubqueryNode();
+
  private:
   /// @brief This is only required for Explain output.
   ///        it has no practical usage other then to print this information during explain.
   Variable const* _subqueryOutVariable;
+  bool _isModificationSubquery;
 };
 
 }  // namespace aql
diff --git a/arangod/Aql/SubqueryStartExecutor.cpp b/arangod/Aql/SubqueryStartExecutor.cpp
index 76698e2477e2..f854d404496d 100644
--- a/arangod/Aql/SubqueryStartExecutor.cpp
+++ b/arangod/Aql/SubqueryStartExecutor.cpp
@@ -27,149 +27,76 @@
 #include "Aql/SingleRowFetcher.h"
 #include "Aql/Stats.h"
 
+#include "Logger/LogMacros.h"
+
 using namespace arangodb;
 using namespace arangodb::aql;
 
-SubqueryStartExecutor::SubqueryStartExecutor(Fetcher& fetcher, Infos& infos)
-    : _fetcher(fetcher) {}
-SubqueryStartExecutor::~SubqueryStartExecutor() = default;
+SubqueryStartExecutor::SubqueryStartExecutor(Fetcher& fetcher, Infos& infos) {}
 
 std::pair<ExecutionState, NoStats> SubqueryStartExecutor::produceRows(OutputAqlItemRow& output) {
-  while (!output.isFull()) {
-    switch (_internalState) {
-      case State::READ_DATA_ROW: {
-        TRI_ASSERT(!_input.isInitialized());
-        if (_upstreamState == ExecutionState::DONE) {
-          return {ExecutionState::DONE, NoStats{}};
-        }
-        // We need to round the number of rows, otherwise this might be called
-        // with atMost == 0 Note that we must not set _upstreamState to DONE
-        // here, as fetchRow will report DONE when encountering a shadow row.
-        auto rowWithStates =
-            _fetcher.fetchRowWithGlobalState((output.numRowsLeft() + 1) / 2);
-        _input = std::move(rowWithStates.row);
-        if (rowWithStates.localState == ExecutionState::WAITING) {
-          return {ExecutionState::WAITING, NoStats{}};
-        }
-        TRI_ASSERT(_upstreamState == ExecutionState::HASMORE);
-        TRI_ASSERT(rowWithStates.globalState == ExecutionState::HASMORE ||
-                   rowWithStates.globalState == ExecutionState::DONE);
-        // This can only switch from HASMORE to DONE
-        _upstreamState = rowWithStates.globalState;
-        if (!_input.isInitialized()) {
-          TRI_ASSERT(rowWithStates.localState == ExecutionState::DONE);
-          _internalState = State::PASS_SHADOW_ROW;
-        } else {
-          _internalState = State::PRODUCE_DATA_ROW;
-        }
-      } break;
-      case State::PRODUCE_DATA_ROW: {
-        TRI_ASSERT(!output.isFull());
-        TRI_ASSERT(_input.isInitialized());
-        output.copyRow(_input);
-        output.advanceRow();
-        _internalState = State::PRODUCE_SHADOW_ROW;
-      } break;
-      case State::PRODUCE_SHADOW_ROW: {
-        TRI_ASSERT(_input.isInitialized());
-        output.createShadowRow(_input);
-        output.advanceRow();
-        _input = InputAqlItemRow(CreateInvalidInputRowHint{});
-        _internalState = State::READ_DATA_ROW;
-      } break;
-      case State::PASS_SHADOW_ROW: {
-        if (_upstreamState == ExecutionState::DONE) {
-          return {ExecutionState::DONE, NoStats{}};
-        }
-        // We need to handle shadowRows now. It is the job of this node to
-        // increase the shadow row depth
-        auto const [state, shadowRow] = _fetcher.fetchShadowRow();
-        if (state == ExecutionState::WAITING) {
-          return {ExecutionState::WAITING, NoStats{}};
-        }
-        TRI_ASSERT(_upstreamState == ExecutionState::HASMORE);
-        TRI_ASSERT(state == ExecutionState::HASMORE || state == ExecutionState::DONE);
-        // This can only switch from HASMORE to DONE
-        _upstreamState = state;
-        if (shadowRow.isInitialized()) {
-          output.increaseShadowRowDepth(shadowRow);
-          output.advanceRow();
-          // stay in state PASS_SHADOW_ROW
-        } else {
-          _internalState = State::READ_DATA_ROW;
-        }
-      } break;
-    }
-  }
+  TRI_ASSERT(false);
+  THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
+}
 
-  if (_internalState == State::READ_DATA_ROW || _internalState == State::PASS_SHADOW_ROW) {
-    TRI_ASSERT(!_input.isInitialized());
-    return {_upstreamState, NoStats{}};
+auto SubqueryStartExecutor::produceRows(AqlItemBlockInputRange& input, OutputAqlItemRow& output)
+    -> std::tuple<ExecutorState, Stats, AqlCall> {
+  if (_inputRow.isInitialized()) {
+    // We have not been able to report the ShadowRow.
+    // Simply return DONE to trigger Impl to fetch shadow row instead.
+    return {ExecutorState::DONE, NoStats{}, AqlCall{}};
   }
-  // PRODUCE_DATA_ROW should always immediately be processed without leaving the
-  // loop
-  TRI_ASSERT(_internalState == State::PRODUCE_SHADOW_ROW);
-  TRI_ASSERT(_input.isInitialized());
-  return {ExecutionState::HASMORE, NoStats{}};
+  TRI_ASSERT(!_inputRow.isInitialized());
+  TRI_ASSERT(!output.isFull());
+  if (input.hasDataRow()) {
+    std::tie(_upstreamState, _inputRow) = input.peekDataRow();
+    output.copyRow(_inputRow);
+    output.advanceRow();
+    return {ExecutorState::DONE, NoStats{}, AqlCall{}};
+  }
+  return {input.upstreamState(), NoStats{}, AqlCall{}};
 }
 
-std::pair<ExecutionState, size_t> SubqueryStartExecutor::expectedNumberOfRows(size_t atMost) const {
-  auto const [state, upstreamRows] = _fetcher.preFetchNumberOfRows(atMost);
-  // We will write one shadow row per input data row.
-  // We might write less on all shadow rows in input, right now we do not figure this out yes.
-  TRI_ASSERT( _input.isInitialized() == (_internalState == State::PRODUCE_SHADOW_ROW));
-  TRI_ASSERT(_internalState != State::PRODUCE_DATA_ROW);
-
-  // Return 1 if _input.isInitialized(), and 0 otherwise. Looks more complicated
-  // than it is.
-  auto const localRows = [this]() {
-    if (_input.isInitialized()) {
-      switch (_internalState) {
-        case State::PRODUCE_SHADOW_ROW:
-          return 1;
-        case State::PRODUCE_DATA_ROW:
-        case State::READ_DATA_ROW:
-        case State::PASS_SHADOW_ROW: {
-          TRI_ASSERT(false);
-          using namespace std::string_literals;
-          THROW_ARANGO_EXCEPTION_MESSAGE(
-              TRI_ERROR_INTERNAL_AQL,
-              "Unexpected state "s + stateToString(_internalState) +
-                  " in SubqueryStartExecutor with local row");
-        }
-      }
-    } else {
-      switch (_internalState) {
-        case State::READ_DATA_ROW:
-        case State::PASS_SHADOW_ROW:
-          return 0;
-        case State::PRODUCE_DATA_ROW:
-        case State::PRODUCE_SHADOW_ROW:
-          TRI_ASSERT(false);
-          using namespace std::string_literals;
-          THROW_ARANGO_EXCEPTION_MESSAGE(
-              TRI_ERROR_INTERNAL_AQL,
-              "Unexpected state "s + stateToString(_internalState) +
-                  " in SubqueryStartExecutor with no local row");
-      }
-    }
-    TRI_ASSERT(false);
-    return 0;
-  }();
+auto SubqueryStartExecutor::skipRowsRange(AqlItemBlockInputRange& input, AqlCall& call)
+    -> std::tuple<ExecutorState, Stats, size_t, AqlCall> {
+  TRI_ASSERT(call.shouldSkip());
+  if (_inputRow.isInitialized()) {
+    // We have not been able to report the ShadowRow.
+    // Simply return DONE to trigger Impl to fetch shadow row instead.
+    return {ExecutorState::DONE, NoStats{}, 0, AqlCall{}};
+  }
 
-  return {state, upstreamRows * 2 + localRows};
+  if (input.hasDataRow()) {
+    // Do not consume the row.
+    // It needs to be reported in Produce.
+    std::tie(_upstreamState, _inputRow) = input.peekDataRow();
+    call.didSkip(1);
+    return {ExecutorState::DONE, NoStats{}, call.getSkipCount(), AqlCall{}};
+  }
+  return {input.upstreamState(), NoStats{}, 0, AqlCall{}};
 }
 
-auto SubqueryStartExecutor::stateToString(SubqueryStartExecutor::State state) -> std::string {
-  switch (state) {
-    case State::READ_DATA_ROW:
-      return "READ_DATA_ROW";
-    case State::PRODUCE_DATA_ROW:
-      return "PRODUCE_DATA_ROW";
-    case State::PRODUCE_SHADOW_ROW:
-      return "PRODUCE_SHADOW_ROW";
-    case State::PASS_SHADOW_ROW:
-      return "PASS_SHADOW_ROW";
+auto SubqueryStartExecutor::produceShadowRow(AqlItemBlockInputRange& input,
+                                             OutputAqlItemRow& output) -> bool {
+  TRI_ASSERT(!output.allRowsUsed());
+  if (_inputRow.isInitialized()) {
+    // Actually consume the input row now.
+    auto const [upstreamState, inputRow] = input.nextDataRow();
+    // We are only supposed to report the inputRow we
+    // have seen in produce as a ShadowRow
+    TRI_ASSERT(inputRow.isSameBlockAndIndex(_inputRow));
+    output.createShadowRow(_inputRow);
+    output.advanceRow();
+    // Reset local input row
+    _inputRow = InputAqlItemRow(CreateInvalidInputRowHint{});
+    return true;
   }
-  return "unhandled state";
+  return false;
+}
+
+// TODO: remove me
+auto SubqueryStartExecutor::expectedNumberOfRows(size_t atMost) const
+    -> std::pair<ExecutionState, size_t> {
+  TRI_ASSERT(false);
+  return {ExecutionState::DONE, 0};
 }
diff --git a/arangod/Aql/SubqueryStartExecutor.h b/arangod/Aql/SubqueryStartExecutor.h
index 3c65a659ad22..1cdd6f6fbeb0 100644
--- a/arangod/Aql/SubqueryStartExecutor.h
+++ b/arangod/Aql/SubqueryStartExecutor.h
@@ -23,6 +23,8 @@
 #ifndef ARANGOD_AQL_SUBQUERY_START_EXECUTOR_H
 #define ARANGOD_AQL_SUBQUERY_START_EXECUTOR_H
 
+#include "Aql/AqlCall.h"
+#include "Aql/AqlItemBlockInputRange.h"
 #include "Aql/ExecutionState.h"
 #include "Aql/InputAqlItemRow.h"
 
@@ -49,47 +51,35 @@ class SubqueryStartExecutor {
   using Infos = ExecutorInfos;
   using Stats = NoStats;
   SubqueryStartExecutor(Fetcher& fetcher, Infos& infos);
-  ~SubqueryStartExecutor();
+  ~SubqueryStartExecutor() = default;
 
-  /**
-   * @brief produce the next Row of Aql Values.
-   *
-   * @return ExecutionState,
-   *         if something was written output.hasValue() == true
-   */
-  std::pair<ExecutionState, Stats> produceRows(OutputAqlItemRow& output);
+  [[deprecated]] std::pair<ExecutionState, Stats> produceRows(OutputAqlItemRow& output);
 
-  /**
-   * @brief Estimate of expected number of rows.
-   *
-   * @return ExecutionState, merely taken from upstream,
-   *         size_t number of rows we are likely to produce (at most)
-   *
-   */
-  std::pair<ExecutionState, size_t> expectedNumberOfRows(size_t atMost) const;
+  // produceRows for SubqueryStart reads a data row from its input and produces
+  // a copy of that row and a shadow row. This requires some amount of internal
+  // state as it can happen that after producing the copied data row the output
+  // is full, and hence we need to return ExecutorState::HASMORE to be able to
+  // produce the shadow row
+  [[nodiscard]] auto produceRows(AqlItemBlockInputRange& input, OutputAqlItemRow& output)
+      -> std::tuple<ExecutorState, Stats, AqlCall>;
 
- private:
-  enum class State {
-    READ_DATA_ROW,
-    PRODUCE_DATA_ROW,
-    PRODUCE_SHADOW_ROW,
-    PASS_SHADOW_ROW
-  };
+  // skipRowsRange just skips input rows and reports how many rows it skipped
+  [[nodiscard]] auto skipRowsRange(AqlItemBlockInputRange& input, AqlCall& call)
+      -> std::tuple<ExecutorState, Stats, size_t, AqlCall>;
 
-  auto static stateToString(State state) -> std::string;
+  // Produce a shadow row *if* we have either skipped or output a datarow
+  // previously
+  auto produceShadowRow(AqlItemBlockInputRange& input, OutputAqlItemRow& output) -> bool;
 
- private:
-  // Fetcher to get data.
-  Fetcher& _fetcher;
+  std::pair<ExecutionState, size_t> expectedNumberOfRows(size_t atMost) const;
 
+ private:
+ private:
   // Upstream state, used to determine if we are done with all subqueries
-  ExecutionState _upstreamState{ExecutionState::HASMORE};
+  ExecutorState _upstreamState{ExecutorState::HASMORE};
 
   // Cache for the input row we are currently working on
-  InputAqlItemRow _input{CreateInvalidInputRowHint{}};
-
-  // Internal state
-  State _internalState{State::READ_DATA_ROW};
+  InputAqlItemRow _inputRow{CreateInvalidInputRowHint{}};
 };
 }  // namespace aql
 }  // namespace arangodb
diff --git a/tests/Aql/ExecutionBlockImplTest.cpp b/tests/Aql/ExecutionBlockImplTest.cpp
index 0fcde0a15adb..ea6133c55117 100644
--- a/tests/Aql/ExecutionBlockImplTest.cpp
+++ b/tests/Aql/ExecutionBlockImplTest.cpp
@@ -674,7 +674,7 @@ class ExecutionBlockImplExecuteSpecificTest : public SharedExecutionBlockImplTes
    */
   std::unique_ptr<ExecutionBlock> createSingleton() {
     auto res = std::make_unique<ExecutionBlockImpl<IdExecutor<ConstFetcher>>>(
-        fakedQuery->engine(), generateNodeDummy(), IdExecutorInfos{0, {}, {}});
+        fakedQuery->engine(), generateNodeDummy(), IdExecutorInfos{0, {}, {}, false});
     InputAqlItemRow inputRow{CreateInvalidInputRowHint{}};
     auto const [state, result] = res->initializeCursor(inputRow);
     EXPECT_EQ(state, ExecutionState::DONE);
diff --git a/tests/Aql/ExecutionNodeTest.cpp b/tests/Aql/ExecutionNodeTest.cpp
index fef683ce7aef..29814e70df37 100644
--- a/tests/Aql/ExecutionNodeTest.cpp
+++ b/tests/Aql/ExecutionNodeTest.cpp
@@ -87,7 +87,7 @@ TEST_F(ExecutionNodeTest, end_node_velocypack_roundtrip_no_invariable) {
   std::unique_ptr<SubqueryEndNode> node, nodeFromVPack;
   std::unordered_set<ExecutionNode const*> seen{};
 
-  node = std::make_unique<SubqueryEndNode>(&plan, 0, nullptr, &outvar);
+  node = std::make_unique<SubqueryEndNode>(&plan, 0, nullptr, &outvar, false);
 
   builder.openArray();
   node->toVelocyPackHelper(builder, ExecutionNode::SERIALIZE_DETAILS, seen);
@@ -110,7 +110,7 @@ TEST_F(ExecutionNodeTest, end_node_velocypack_roundtrip_invariable) {
   std::unique_ptr<SubqueryEndNode> node, nodeFromVPack;
   std::unordered_set<ExecutionNode const*> seen{};
 
-  node = std::make_unique<SubqueryEndNode>(&plan, 0, &invar, &outvar);
+  node = std::make_unique<SubqueryEndNode>(&plan, 0, &invar, &outvar, false);
 
   builder.openArray();
   node->toVelocyPackHelper(builder, ExecutionNode::SERIALIZE_DETAILS, seen);
@@ -129,8 +129,8 @@ TEST_F(ExecutionNodeTest, end_node_not_equal_different_id) {
 
   Variable outvar("name", 1);
 
-  node1 = std::make_unique<SubqueryEndNode>(&plan, 0, nullptr, &outvar);
-  node2 = std::make_unique<SubqueryEndNode>(&plan, 1, nullptr, &outvar);
+  node1 = std::make_unique<SubqueryEndNode>(&plan, 0, nullptr, &outvar, false);
+  node2 = std::make_unique<SubqueryEndNode>(&plan, 1, nullptr, &outvar, false);
 
   ASSERT_FALSE(node1->isEqualTo(*node2));
 }
@@ -141,8 +141,8 @@ TEST_F(ExecutionNodeTest, end_node_not_equal_invariable_null_vs_non_null) {
   Variable outvar("name", 1);
   Variable invar("otherName", 2);
 
-  node1 = std::make_unique<SubqueryEndNode>(&plan, 0, &invar, &outvar);
-  node2 = std::make_unique<SubqueryEndNode>(&plan, 1, nullptr, &outvar);
+  node1 = std::make_unique<SubqueryEndNode>(&plan, 0, &invar, &outvar, false);
+  node2 = std::make_unique<SubqueryEndNode>(&plan, 1, nullptr, &outvar, false);
 
   ASSERT_FALSE(node1->isEqualTo(*node2));
   // Bidirectional nullptr check
@@ -156,8 +156,8 @@ TEST_F(ExecutionNodeTest, end_node_not_equal_invariable_differ) {
   Variable invar("otherName", 2);
   Variable otherInvar("invalidName", 3);
 
-  node1 = std::make_unique<SubqueryEndNode>(&plan, 0, &invar, &outvar);
-  node2 = std::make_unique<SubqueryEndNode>(&plan, 1, &otherInvar, &outvar);
+  node1 = std::make_unique<SubqueryEndNode>(&plan, 0, &invar, &outvar, false);
+  node2 = std::make_unique<SubqueryEndNode>(&plan, 1, &otherInvar, &outvar, false);
 
   ASSERT_FALSE(node1->isEqualTo(*node2));
   // Bidirectional check
@@ -170,12 +170,12 @@ TEST_F(ExecutionNodeTest, end_node_not_equal_outvariable_differ) {
   Variable outvar("name", 1);
   Variable otherOutvar("otherName", 2);
 
-  node1 = std::make_unique<SubqueryEndNode>(&plan, 0, nullptr, &outvar);
-  node2 = std::make_unique<SubqueryEndNode>(&plan, 1, nullptr, &otherOutvar);
+  node1 = std::make_unique<SubqueryEndNode>(&plan, 0, nullptr, &outvar, false);
+  node2 = std::make_unique<SubqueryEndNode>(&plan, 1, nullptr, &otherOutvar, false);
 
   ASSERT_FALSE(node1->isEqualTo(*node2));
   // Bidirectional check
   ASSERT_FALSE(node2->isEqualTo(*node1));
 }
 
-}  // namespace arangodb
+}  // namespace arangodb::tests::aql
diff --git a/tests/Aql/ExecutorTestHelper.cpp b/tests/Aql/ExecutorTestHelper.cpp
index d0e38abac134..a7dd6cdb84d6 100644
--- a/tests/Aql/ExecutorTestHelper.cpp
+++ b/tests/Aql/ExecutorTestHelper.cpp
@@ -90,11 +90,19 @@ auto asserthelper::ValidateBlocksAreEqual(SharedAqlItemBlockPtr actual,
   }
 
   for (size_t row = 0; row < (std::min)(actual->size(), expected->size()); ++row) {
+    // Compare registers
     for (RegisterId reg = 0; reg < outRegs; ++reg) {
       RegisterId actualRegister =
           onlyCompareRegisters ? onlyCompareRegisters->at(reg) : reg;
       ValidateAqlValuesAreEqual(actual, row, actualRegister, expected, row, reg);
     }
+    // Compare shadowRows
+    EXPECT_EQ(actual->isShadowRow(row), expected->isShadowRow(row));
+    if (actual->isShadowRow(row) && expected->isShadowRow(row)) {
+      ShadowAqlItemRow actualShadowRow{actual, row};
+      ShadowAqlItemRow expectedShadowRow{expected, row};
+      EXPECT_EQ(actualShadowRow.getDepth(), expectedShadowRow.getDepth());
+    }
   }
 }
 
@@ -112,6 +120,13 @@ auto asserthelper::ValidateBlocksAreEqualUnordered(
     std::optional<std::vector<RegisterId>> const& onlyCompareRegisters) -> void {
   ASSERT_NE(expected, nullptr);
   ASSERT_NE(actual, nullptr);
+  EXPECT_FALSE(actual->hasShadowRows())
+      << "unordered validation does not support shadowRows yet. If you need "
+         "this please implement!";
+  EXPECT_FALSE(expected->hasShadowRows())
+      << "unordered validation does not support shadowRows yet. If you need "
+         "this please implement!";
+
   EXPECT_EQ(actual->size() + numRowsNotContained, expected->size());
 
   RegisterId outRegs = (std::min)(actual->getNrRegs(), expected->getNrRegs());
@@ -159,6 +174,16 @@ AqlExecutorTestCase<enableQueryTrace>::AqlExecutorTestCase()
     : fakedQuery{_server->createFakeQuery(enableQueryTrace)} {
   auto engine = std::make_unique<ExecutionEngine>(*fakedQuery, SerializationFormat::SHADOWROWS);
   fakedQuery->setEngine(engine.release());
+  if constexpr (enableQueryTrace) {
+    Logger::QUERIES.setLogLevel(LogLevel::DEBUG);
+  }
+}
+
+template <bool enableQueryTrace>
+AqlExecutorTestCase<enableQueryTrace>::~AqlExecutorTestCase() {
+  if constexpr (enableQueryTrace) {
+    Logger::QUERIES.setLogLevel(LogLevel::INFO);
+  }
 }
 
 template <bool enableQueryTrace>
diff --git a/tests/Aql/ExecutorTestHelper.h b/tests/Aql/ExecutorTestHelper.h
index cfc344f5f4f8..718c91b62054 100644
--- a/tests/Aql/ExecutorTestHelper.h
+++ b/tests/Aql/ExecutorTestHelper.h
@@ -112,7 +112,7 @@ class AqlExecutorTestCase : public ::testing::Test {
 
  protected:
   AqlExecutorTestCase();
-  virtual ~AqlExecutorTestCase() = default;
+  virtual ~AqlExecutorTestCase();
 
   /**
    * @brief Creates and manages a ExecutionNode.
@@ -174,6 +174,22 @@ struct Pipeline {
   std::deque<ExecBlock> const& get() const { return _pipeline; };
   std::deque<ExecBlock>& get() { return _pipeline; };
 
+  Pipeline& addDependency(ExecBlock&& dependency) {
+    if (!empty()) {
+      _pipeline.back()->addDependency(dependency.get());
+    }
+    _pipeline.emplace_back(std::move(dependency));
+    return *this;
+  }
+
+  Pipeline& addConsumer(ExecBlock&& consumer) {
+    if (!empty()) {
+      consumer->addDependency(_pipeline.front().get());
+    }
+    _pipeline.emplace_front(std::move(consumer));
+    return *this;
+  }
+
  private:
   PipelineStorage _pipeline;
 };
@@ -204,8 +220,13 @@ struct ExecutorTestHelper {
         _query(query),
         _dummyNode{std::make_unique<SingletonNode>(_query.plan(), 42)} {}
 
+  auto setCallStack(AqlCallStack stack) -> ExecutorTestHelper& {
+    _callStack = stack;
+    return *this;
+  }
+
   auto setCall(AqlCall c) -> ExecutorTestHelper& {
-    _call = c;
+    _callStack = AqlCallStack{c};
     return *this;
   }
 
@@ -263,9 +284,12 @@ struct ExecutorTestHelper {
   }
 
   auto expectOutput(std::array<RegisterId, outputColumns> const& regs,
-                    MatrixBuilder<outputColumns> const& out) -> ExecutorTestHelper& {
+                    MatrixBuilder<outputColumns> const& out,
+                    std::vector<std::pair<size_t, uint64_t>> const& shadowRows = {})
+      -> ExecutorTestHelper& {
     _outputRegisters = regs;
     _output = out;
+    _outputShadowRows = shadowRows;
     return *this;
   }
 
@@ -317,8 +341,8 @@ struct ExecutorTestHelper {
   auto createExecBlock(typename E::Infos infos,
                        ExecutionNode::NodeType nodeType = ExecutionNode::SINGLETON)
       -> ExecBlock {
-    auto& testeeNode = _execNodes.emplace_back(
-        std::move(std::make_unique<MockTypedNode>(_query.plan(), _execNodes.size(), nodeType)));
+    auto& testeeNode = _execNodes.emplace_back(std::move(
+        std::make_unique<MockTypedNode>(_query.plan(), _execNodes.size(), nodeType)));
     return std::make_unique<ExecutionBlockImpl<E>>(_query.engine(), testeeNode.get(),
                                                    std::move(infos));
   }
@@ -363,28 +387,28 @@ struct ExecutorTestHelper {
     BlockCollector allResults{&itemBlockManager};
 
     if (!loop) {
-      AqlCallStack stack{_call};
-      auto const [state, skipped, result] = _pipeline.get().front()->execute(stack);
+      auto const [state, skipped, result] = _pipeline.get().front()->execute(_callStack);
       skippedTotal = skipped;
       finalState = state;
       if (result != nullptr) {
         allResults.add(result);
       }
     } else {
-      auto call = _call;
       do {
-        AqlCallStack stack{call};
-        auto const [state, skipped, result] = _pipeline.get().front()->execute(stack);
+        auto const [state, skipped, result] = _pipeline.get().front()->execute(_callStack);
         finalState = state;
+        auto call = _callStack.popCall();
         skippedTotal += skipped;
+        call.didSkip(skipped);
         if (result != nullptr) {
+          call.didProduce(result->size());
           allResults.add(result);
         }
-        call = _call;
-        call.didSkip(skippedTotal);
-        call.didProduce(allResults.totalSize());
+        _callStack.pushCall(std::move(call));
+
       } while (finalState != ExecutionState::DONE &&
-               (!call.hasSoftLimit() || (call.getLimit() + call.getOffset()) > 0));
+               (!_callStack.peek().hasSoftLimit() ||
+                (_callStack.peek().getLimit() + _callStack.peek().getOffset()) > 0));
     }
 
     EXPECT_EQ(skippedTotal, _expectedSkip);
@@ -396,7 +420,7 @@ struct ExecutorTestHelper {
           << "Executor does not yield output, although it is expected";
     } else {
       SharedAqlItemBlockPtr expectedOutputBlock =
-          buildBlock<outputColumns>(itemBlockManager, std::move(_output));
+          buildBlock<outputColumns>(itemBlockManager, std::move(_output), _outputShadowRows);
       std::vector<RegisterId> outRegVector(_outputRegisters.begin(),
                                            _outputRegisters.end());
       if (_unorderedOutput) {
@@ -471,9 +495,11 @@ struct ExecutorTestHelper {
                                                        _waitingBehaviour);
   }
 
-  AqlCall _call;
+  // Default initialize with a fetchAll call.
+  AqlCallStack _callStack{AqlCall{}};
   MatrixBuilder<inputColumns> _input;
   MatrixBuilder<outputColumns> _output;
+  std::vector<std::pair<size_t, uint64_t>> _outputShadowRows{};
   std::array<RegisterId, outputColumns> _outputRegisters;
   std::size_t _expectedSkip;
   ExecutionState _expectedState;
diff --git a/tests/Aql/IdExecutorTest.cpp b/tests/Aql/IdExecutorTest.cpp
index 6595e5612206..ac203cf39da3 100644
--- a/tests/Aql/IdExecutorTest.cpp
+++ b/tests/Aql/IdExecutorTest.cpp
@@ -47,36 +47,113 @@ using namespace arangodb::aql;
 
 namespace arangodb::tests::aql {
 
-using TestParam = std::tuple<std::vector<int>,  // The input data
-                             ExecutorState,     // The upstream state
-                             AqlCall,           // The client Call,
+using TestParam = std::tuple<size_t,         // The input data 0 -> number
+                             ExecutorState,  // The upstream state
+                             AqlCall,        // The client Call,
+                             bool,  // flag to decide if we need to do couting
                              OutputAqlItemRow::CopyRowBehavior  // How the data is handled within outputRow
                              >;
 
 class IdExecutorTestCombiner : public AqlExecutorTestCaseWithParam<TestParam> {
  protected:
-  IdExecutorTestCombiner() {}
-
   auto prepareInputRange() -> AqlItemBlockInputRange {
-    auto const& [input, upstreamState, clientCall, copyBehaviour] = GetParam();
-    if (input.empty()) {
+    auto input = getInput();
+    if (input == 0) {
       // no input
-      return AqlItemBlockInputRange{upstreamState};
+      return AqlItemBlockInputRange{getUpstreamState()};
     }
     MatrixBuilder<1> matrix;
-    for (auto const& it : input) {
-      matrix.emplace_back(RowBuilder<1>{{it}});
+    for (int i = 0; i < static_cast<int>(input); ++i) {
+      matrix.emplace_back(RowBuilder<1>{i});
     }
     SharedAqlItemBlockPtr block = buildBlock<1>(manager(), std::move(matrix));
-    TRI_ASSERT(clientCall.getSkipCount() == 0);
-    return AqlItemBlockInputRange{upstreamState, 0, block, 0};
+    TRI_ASSERT(getCall().getSkipCount() == 0);
+    return AqlItemBlockInputRange{getUpstreamState(), 0, block, 0};
+  }
+
+  auto doCount() -> bool {
+    auto const& [a, b, c, doCount, d] = GetParam();
+    return doCount;
+  }
+
+  auto makeInfos() -> IdExecutorInfos {
+    return IdExecutorInfos{1, {0}, {}, doCount()};
+  }
+
+  auto getInput() -> size_t {
+    auto const& [input, a, b, c, d] = GetParam();
+    return input;
+  }
+
+  auto getCall() -> AqlCall {
+    auto const& [a, b, call, c, d] = GetParam();
+    return call;
+  }
+
+  auto getUpstreamState() -> ExecutorState {
+    auto const& [a, state, b, c, d] = GetParam();
+    return state;
+  }
+
+  auto getExpectedState() -> ExecutionState {
+    auto call = getCall();
+    auto available = getInput();
+    if (call.needsFullCount() || call.getOffset() + call.getLimit() >= available) {
+      // We will fetch all
+      return ExecutionState::DONE;
+    }
+    if (getUpstreamState() == ExecutorState::DONE) {
+      return ExecutionState::DONE;
+    }
+    return ExecutionState::HASMORE;
+  }
+
+  auto getSkip() -> size_t {
+    size_t skip = 0;
+    size_t available = getInput();
+    auto call = getCall();
+    if (call.getOffset() > 0) {
+      skip = std::min(skip, available);
+      available -= skip;
+    }
+    if (call.hasHardLimit() && call.needsFullCount()) {
+      // Take away the rows that will be produced
+      // add the leftOver to skip
+      available -= std::min(available, call.getLimit());
+      skip += available;
+    }
+    return skip;
+  }
+
+  auto getOutput() -> MatrixBuilder<1> {
+    MatrixBuilder<1> res;
+    auto call = getCall();
+    int available = std::min(getInput(), call.getOffset() + call.getLimit());
+    for (int i = call.getOffset(); i < available; ++i) {
+      res.emplace_back(RowBuilder<1>{i});
+    }
+    return res;
+  }
+
+  auto getStats() -> ExecutionStats {
+    ExecutionStats stats;
+
+    if (doCount()) {
+      auto available = getInput();
+      auto call = getCall();
+      available -= std::min(available, call.getOffset());
+      available = std::min(available, call.getLimit());
+      stats.count = available;
+    }
+
+    return stats;
   }
 
   auto prepareOutputRow(SharedAqlItemBlockPtr input) -> OutputAqlItemRow {
     auto toWrite = make_shared_unordered_set({});
     auto toKeep = make_shared_unordered_set({0});
     auto toClear = make_shared_unordered_set();
-    auto const& [unused, upstreamState, clientCall, copyBehaviour] = GetParam();
+    auto const& [unused, upstreamState, clientCall, unused2, copyBehaviour] = GetParam();
     AqlCall callCopy = clientCall;
     if (copyBehaviour == OutputAqlItemRow::CopyRowBehavior::DoNotCopyInputRows) {
       // For passthrough we reuse the block
@@ -94,66 +171,63 @@ class IdExecutorTestCombiner : public AqlExecutorTestCaseWithParam<TestParam> {
     return OutputAqlItemRow(outBlock, toWrite, toKeep, toClear,
                             std::move(callCopy), copyBehaviour);
   }
-
-  // After Execute is done these fetchers shall be removed,
-  // the Executor does not need it anymore!
-  // However the template is still required.
-  template <class Fetcher>
-  auto runTest(Fetcher& fetcher) -> void {
-    auto const& [input, upstreamState, clientCall, copyBehaviour] = GetParam();
-
-    auto inputRange = prepareInputRange();
-    auto outputRow = prepareOutputRow(inputRange.getBlock());
-
-    // If the input is empty, all rows(none) are used, otherwise they are not.
-    EXPECT_EQ(outputRow.allRowsUsed(), input.empty());
-    IdExecutorInfos infos{1, {0}, {}};
-
-    IdExecutor<Fetcher> testee{fetcher, infos};
-
-    auto const [state, stats, call] = testee.produceRows(inputRange, outputRow);
-    EXPECT_EQ(state, upstreamState);
-    // Stats are NoStats, no checks here.
-
-    // We can never forward any offset.
-    EXPECT_EQ(call.getOffset(), 0);
-
-    // The limits need to be reduced by input size.
-    EXPECT_EQ(call.softLimit + input.size(), clientCall.softLimit);
-    EXPECT_EQ(call.hardLimit + input.size(), clientCall.hardLimit);
-
-    // We can forward fullCount if it is there.
-    EXPECT_EQ(call.needsFullCount(), clientCall.needsFullCount());
-
-    // This internally actually asserts that all input rows are "copied".
-    EXPECT_TRUE(outputRow.allRowsUsed());
-    auto result = outputRow.stealBlock();
-    if (!input.empty()) {
-      ASSERT_NE(result, nullptr);
-      ASSERT_EQ(result->size(), input.size());
-      for (size_t i = 0; i < input.size(); ++i) {
-        auto val = result->getValueReference(i, 0);
-        ASSERT_TRUE(val.isNumber());
-        EXPECT_EQ(val.toInt64(), input.at(i));
-      }
-    } else {
-      EXPECT_EQ(result, nullptr);
-    }
-  }
 };
 
 TEST_P(IdExecutorTestCombiner, test_produce_datarange_constFetcher) {
+  auto input = getInput();
+  auto upstreamState = getUpstreamState();
+  auto clientCall = getCall();
+  auto inputRange = prepareInputRange();
+  auto outputRow = prepareOutputRow(inputRange.getBlock());
+
+  // If the input is empty, all rows(none) are used, otherwise they are not.
+  EXPECT_EQ(outputRow.allRowsUsed(), input == 0);
+  IdExecutorInfos infos{1, {0}, {}, doCount()};
   std::shared_ptr<VPackBuilder> fakeFetcherInput{VPackParser::fromJson("[ ]")};
   ConstFetcher cFetcher = ConstFetcherHelper{manager(), fakeFetcherInput->buffer()};
-  runTest(cFetcher);
+  IdExecutor<ConstFetcher> testee{cFetcher, infos};
+
+  auto const [state, stats, call] = testee.produceRows(inputRange, outputRow);
+  EXPECT_EQ(state, upstreamState);
+  // Stats are NoStats, no checks here.
+
+  // We can never forward any offset.
+  EXPECT_EQ(call.getOffset(), 0);
+
+  // The limits need to be reduced by input size.
+  EXPECT_EQ(call.softLimit + input, clientCall.softLimit);
+  EXPECT_EQ(call.hardLimit + input, clientCall.hardLimit);
+
+  // We can forward fullCount if it is there.
+  EXPECT_EQ(call.needsFullCount(), clientCall.needsFullCount());
+
+  // This internally actually asserts that all input rows are "copied".
+  EXPECT_TRUE(outputRow.allRowsUsed());
+  auto result = outputRow.stealBlock();
+  if (input > 0) {
+    ASSERT_NE(result, nullptr);
+    ASSERT_EQ(result->size(), input);
+    for (size_t i = 0; i < input; ++i) {
+      auto val = result->getValueReference(i, 0);
+      ASSERT_TRUE(val.isNumber());
+      EXPECT_EQ(val.toInt64(), i);
+    }
+  } else {
+    EXPECT_EQ(result, nullptr);
+  }
 }
 
 TEST_P(IdExecutorTestCombiner, test_produce_datarange_singleRowFetcher) {
-  std::shared_ptr<VPackBuilder> fakeFetcherInput{VPackParser::fromJson("[ ]")};
-  SingleRowFetcher<::arangodb::aql::BlockPassthrough::Enable> srFetcher =
-      SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Enable>{
-          manager(), fakeFetcherInput->buffer(), false};
-  runTest(srFetcher);
+  ExecutorTestHelper<1, 1>(*fakedQuery)
+      .setExecBlock<IdExecutor<SingleRowFetcher<::arangodb::aql::BlockPassthrough::Enable>>>(
+          makeInfos(), ExecutionNode::SINGLETON)
+      .setInputFromRowNum(getInput())
+      .setCall(getCall())
+      .expectedState(getExpectedState())
+      .expectSkipped(getSkip())
+      .expectOutput({0}, getOutput())
+      .expectedStats(getStats())
+      .run();
 }
 
 /**
@@ -182,8 +256,8 @@ TEST_P(IdExecutorTestCombiner, test_produce_datarange_singleRowFetcher) {
  *   DoCopy  << This is to assert that copying is performaed
  */
 
-static auto inputs = testing::Values(std::vector<int>{},  // Test empty input
-                                     std::vector<int>{1, 2, 3}  // Test input data
+static auto inputs = testing::Values(0,  // Test empty input
+                                     3   // Test input data
 );
 
 auto upstreamStates = testing::Values(ExecutorState::HASMORE, ExecutorState::DONE);
@@ -201,13 +275,14 @@ auto copyBehaviours = testing::Values(OutputAqlItemRow::CopyRowBehavior::CopyInp
 );
 
 INSTANTIATE_TEST_CASE_P(IdExecutorTest, IdExecutorTestCombiner,
-                        ::testing::Combine(inputs, upstreamStates, clientCalls, copyBehaviours));
+                        ::testing::Combine(inputs, upstreamStates, clientCalls,
+                                           ::testing::Bool(), copyBehaviours));
 
 class IdExecutionBlockTest : public AqlExecutorTestCase<> {};
 
 // The IdExecutor has a specific initializeCursor method in ExecutionBlockImpl
 TEST_F(IdExecutionBlockTest, test_initialize_cursor_get) {
-  IdExecutorInfos infos{1, {0}, {}};
+  IdExecutorInfos infos{1, {0}, {}, false};
   ExecutionBlockImpl<IdExecutor<ConstFetcher>> testee{fakedQuery->engine(),
                                                       generateNodeDummy(),
                                                       std::move(infos)};
@@ -249,7 +324,7 @@ TEST_F(IdExecutionBlockTest, test_initialize_cursor_get) {
 
 // The IdExecutor has a specific initializeCursor method in ExecutionBlockImpl
 TEST_F(IdExecutionBlockTest, test_initialize_cursor_skip) {
-  IdExecutorInfos infos{1, {0}, {}};
+  IdExecutorInfos infos{1, {0}, {}, false};
   ExecutionBlockImpl<IdExecutor<ConstFetcher>> testee{fakedQuery->engine(),
                                                       generateNodeDummy(),
                                                       std::move(infos)};
@@ -289,7 +364,7 @@ TEST_F(IdExecutionBlockTest, test_initialize_cursor_skip) {
 
 // The IdExecutor has a specific initializeCursor method in ExecutionBlockImpl
 TEST_F(IdExecutionBlockTest, test_initialize_cursor_fullCount) {
-  IdExecutorInfos infos{1, {0}, {}};
+  IdExecutorInfos infos{1, {0}, {}, false};
   ExecutionBlockImpl<IdExecutor<ConstFetcher>> testee{fakedQuery->engine(),
                                                       generateNodeDummy(),
                                                       std::move(infos)};
@@ -330,7 +405,7 @@ TEST_F(IdExecutionBlockTest, test_initialize_cursor_fullCount) {
 }
 
 TEST_F(IdExecutionBlockTest, test_hardlimit_single_row_fetcher) {
-  IdExecutorInfos infos{1, {0}, {}};
+  IdExecutorInfos infos{1, {0}, {}, false};
   ExecutorTestHelper(*fakedQuery)
       .setExecBlock<IdExecutor<SingleRowFetcher<BlockPassthrough::Enable>>>(std::move(infos))
       .setInputValueList(1, 2, 3, 4, 5, 6)
@@ -351,7 +426,7 @@ TEST_F(IdExecutionBlockTest, test_hardlimit_single_row_fetcher) {
 class BlockOverloadTest : public AqlExecutorTestCaseWithParam<bool> {
  protected:
   auto getTestee() -> ExecutionBlockImpl<IdExecutor<ConstFetcher>> {
-    IdExecutorInfos infos{1, {0}, {}};
+    IdExecutorInfos infos{1, {0}, {}, false};
     return ExecutionBlockImpl<IdExecutor<ConstFetcher>>{fakedQuery->engine(),
                                                         generateNodeDummy(),
                                                         std::move(infos)};
diff --git a/tests/Aql/SplicedSubqueryIntegrationTest.cpp b/tests/Aql/SplicedSubqueryIntegrationTest.cpp
new file mode 100644
index 000000000000..f6f37d99f4b1
--- /dev/null
+++ b/tests/Aql/SplicedSubqueryIntegrationTest.cpp
@@ -0,0 +1,471 @@
+////////////////////////////////////////////////////////////////////////////////
+/// DISCLAIMER
+///
+/// Copyright 2019 ArangoDB GmbH, Cologne, Germany
+///
+/// Licensed under the Apache License, Version 2.0 (the "License");
+/// you may not use this file except in compliance with the License.
+/// You may obtain a copy of the License at
+///
+///     http://www.apache.org/licenses/LICENSE-2.0
+///
+/// Unless required by applicable law or agreed to in writing, software
+/// distributed under the License is distributed on an "AS IS" BASIS,
+/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+/// See the License for the specific language governing permissions and
+/// limitations under the License.
+///
+/// Copyright holder is ArangoDB GmbH, Cologne, Germany
+///
+/// @author Markus Pfeiffer
+////////////////////////////////////////////////////////////////////////////////
+
+#include "gtest/gtest.h"
+
+#include "AqlItemBlockHelper.h"
+#include "Mocks/Servers.h"
+#include "TestEmptyExecutorHelper.h"
+#include "TestExecutorHelper.h"
+#include "TestLambdaExecutor.h"
+#include "WaitingExecutionBlockMock.h"
+#include "fakeit.hpp"
+
+#include "Aql/AqlCallStack.h"
+#include "Aql/AqlItemBlock.h"
+#include "Aql/AqlItemBlockSerializationFormat.h"
+#include "Aql/ConstFetcher.h"
+#include "Aql/ExecutionBlockImpl.h"
+#include "Aql/ExecutionEngine.h"
+#include "Aql/IdExecutor.h"
+#include "Aql/Query.h"
+#include "Aql/RegisterPlan.h"
+#include "Aql/ReturnExecutor.h"
+#include "Aql/SingleRowFetcher.h"
+#include "Aql/SubqueryEndExecutor.h"
+#include "Aql/SubqueryStartExecutor.h"
+#include "Transaction/Context.h"
+#include "Transaction/Methods.h"
+
+#include "Aql/ExecutorTestHelper.h"
+#include "Aql/TestLambdaExecutor.h"
+#include "Aql/WaitingExecutionBlockMock.h"
+
+// TODO: remove me
+#include "Logger/LogMacros.h"
+#include "Logger/Logger.h"
+#include "Logger/LoggerStream.h"
+
+using namespace arangodb;
+using namespace arangodb::aql;
+using namespace arangodb::tests;
+using namespace arangodb::tests::aql;
+using namespace arangodb::basics;
+
+using SubqueryExecutorTestHelper = ExecutorTestHelper<1, 1>;
+using SubqueryExecutorSplitType = SubqueryExecutorTestHelper::SplitType;
+using SubqueryExecutorParamType = std::tuple<SubqueryExecutorSplitType>;
+
+using RegisterSet = std::unordered_set<RegisterId>;
+using LambdaExePassThrough = TestLambdaExecutor;
+using LambdaExe = TestLambdaSkipExecutor;
+
+class SplicedSubqueryIntegrationTest
+    : public AqlExecutorTestCaseWithParam<SubqueryExecutorParamType, false> {
+ protected:
+  ExecutorTestHelper<1, 1> executorTestHelper;
+
+  SplicedSubqueryIntegrationTest() : executorTestHelper(*fakedQuery) {}
+
+  // returns a new pipeline that contains body as a subquery
+  auto createSubquery(Pipeline&& body) -> Pipeline {
+    auto subqueryEnd = createSubqueryEndExecutionBlock();
+    if (!body.empty()) {
+      subqueryEnd->addDependency(body.get().front().get());
+    }
+    body.get().emplace_front(std::move(subqueryEnd));
+
+    auto subqueryStart = createSubqueryStartExecutionBlock();
+    // This exists because we at least added the subqueryEnd
+    body.get().back()->addDependency(subqueryStart.get());
+
+    body.get().emplace_back(std::move(subqueryStart));
+
+    return std::move(body);
+  }
+
+  auto createSubquery() -> Pipeline { return createSubquery(Pipeline()); }
+
+  auto createDoNothingPipeline() -> Pipeline {
+    auto numRegs = size_t{1};
+    auto emptyRegisterList = std::make_shared<std::unordered_set<RegisterId>>(
+        std::initializer_list<RegisterId>{});
+
+    auto inRegisterList = std::make_shared<std::unordered_set<RegisterId>>(
+        std::initializer_list<RegisterId>{0});
+    auto outRegisterList = std::make_shared<std::unordered_set<RegisterId>>(
+        std::initializer_list<RegisterId>{1});
+
+    std::unordered_set<RegisterId> toKeep;
+
+    for (RegisterId r = 0; r < numRegs; ++r) {
+      toKeep.emplace(r);
+    }
+
+    auto infos = LambdaExe::Infos(inRegisterList, outRegisterList, 1, 2, {},
+                                  toKeep, createProduceCall(), createSkipCall());
+
+    return Pipeline(executorTestHelper.createExecBlock<LambdaExe>(std::move(infos)));
+  }
+
+  auto createAssertPipeline() -> Pipeline {
+    auto numRegs = size_t{1};
+    auto emptyRegisterList = std::make_shared<std::unordered_set<RegisterId>>(
+        std::initializer_list<RegisterId>{});
+
+    auto inRegisterList = std::make_shared<std::unordered_set<RegisterId>>(
+        std::initializer_list<RegisterId>{0});
+    auto outRegisterList = std::make_shared<std::unordered_set<RegisterId>>(
+        std::initializer_list<RegisterId>{1});
+
+    std::unordered_set<RegisterId> toKeep;
+
+    for (RegisterId r = 0; r < numRegs; ++r) {
+      toKeep.emplace(r);
+    }
+
+    auto infos = LambdaExe::Infos(inRegisterList, outRegisterList, 1, 2, {},
+                                  toKeep, createAssertCall(), createSkipCall());
+
+    return Pipeline(executorTestHelper.createExecBlock<LambdaExe>(std::move(infos)));
+  }
+
+  auto createCallAssertPipeline(AqlCall call) -> Pipeline {
+    auto numRegs = size_t{1};
+    auto emptyRegisterList = std::make_shared<std::unordered_set<RegisterId>>(
+        std::initializer_list<RegisterId>{});
+
+    auto inRegisterList = std::make_shared<std::unordered_set<RegisterId>>(
+        std::initializer_list<RegisterId>{0});
+    auto outRegisterList = std::make_shared<std::unordered_set<RegisterId>>(
+        std::initializer_list<RegisterId>{1});
+
+    std::unordered_set<RegisterId> toKeep;
+
+    for (RegisterId r = 0; r < numRegs; ++r) {
+      toKeep.emplace(r);
+    }
+
+    auto infos = LambdaExe::Infos(inRegisterList, outRegisterList, 1, 2, {}, toKeep,
+                                  createAssertCallCall(call), createSkipCall());
+
+    return Pipeline(executorTestHelper.createExecBlock<LambdaExe>(std::move(infos)));
+  }
+
+  auto createSubqueryStartExecutionBlock() -> ExecBlock {
+    // Subquery start executor does not care about input or output registers?
+    // TODO: talk about registers & register planning
+
+    auto inputRegisterSet =
+        std::make_shared<RegisterSet>(std::initializer_list<RegisterId>{0});
+    auto outputRegisterSet =
+        std::make_shared<RegisterSet>(std::initializer_list<RegisterId>{});
+    auto toKeepRegisterSet = RegisterSet{0};
+
+    auto infos = SubqueryStartExecutor::Infos(inputRegisterSet, outputRegisterSet,
+                                              inputRegisterSet->size(),
+                                              inputRegisterSet->size() +
+                                                  outputRegisterSet->size(),
+                                              {}, toKeepRegisterSet);
+
+    return executorTestHelper.createExecBlock<SubqueryStartExecutor>(std::move(infos),
+                                                                     ExecutionNode::SUBQUERY_START);
+  }
+
+  // Subquery end executor has an input and an output register,
+  // but only the output register is used, remove input reg?
+  auto createSubqueryEndExecutionBlock() -> ExecBlock {
+    auto const inputRegister = RegisterId{0};
+    auto const outputRegister = RegisterId{1};
+    auto inputRegisterSet =
+        std::make_shared<RegisterSet>(std::initializer_list<RegisterId>{inputRegister});
+    auto outputRegisterSet =
+        std::make_shared<RegisterSet>(std::initializer_list<RegisterId>{outputRegister});
+    auto toKeepRegisterSet = RegisterSet{0};
+
+    auto infos =
+        SubqueryEndExecutor::Infos(inputRegisterSet, outputRegisterSet,
+                                   inputRegisterSet->size(),
+                                   inputRegisterSet->size() + outputRegisterSet->size(),
+                                   {}, toKeepRegisterSet, nullptr,
+                                   inputRegister, outputRegister, false);
+
+    return executorTestHelper.createExecBlock<SubqueryEndExecutor>(std::move(infos),
+                                                                   ExecutionNode::SUBQUERY_END);
+  }
+
+  auto createReturnExecutionBlock() -> ExecBlock {
+    auto const inputRegister = RegisterId{0};
+    auto const outputRegister = RegisterId{0};
+    auto inputRegisterSet =
+        std::make_shared<RegisterSet>(std::initializer_list<RegisterId>{inputRegister});
+    auto outputRegisterSet =
+        std::make_shared<RegisterSet>(std::initializer_list<RegisterId>{outputRegister});
+    auto toKeepRegisterSet = RegisterSet{0};
+
+    auto infos = ReturnExecutor::Infos(inputRegister, 1, 1, false);
+
+    return executorTestHelper.createExecBlock<ReturnExecutor>(std::move(infos),
+                                                              ExecutionNode::RETURN);
+  }
+
+  auto createProduceCall() -> ProduceCall {
+    return [](AqlItemBlockInputRange& input,
+              OutputAqlItemRow& output) -> std::tuple<ExecutorState, LambdaExe::Stats, AqlCall> {
+      while (input.hasDataRow() && !output.isFull()) {
+        auto const [state, row] = input.nextDataRow();
+        output.cloneValueInto(1, row, AqlValue("foo"));
+        output.advanceRow();
+      }
+      NoStats stats{};
+      AqlCall call{};
+
+      return {input.upstreamState(), stats, call};
+    };
+  };
+
+  auto createSkipCall() -> SkipCall {
+    return [](AqlItemBlockInputRange& input,
+              AqlCall& call) -> std::tuple<ExecutorState, LambdaExe::Stats, size_t, AqlCall> {
+      auto skipped = size_t{0};
+      while (input.hasDataRow() && call.shouldSkip()) {
+        auto const& [state, inputRow] = input.nextDataRow();
+        EXPECT_TRUE(inputRow.isInitialized());
+        call.didSkip(1);
+        skipped++;
+      }
+      auto upstreamCall = AqlCall{call};
+      return {input.upstreamState(), NoStats{}, skipped, upstreamCall};
+    };
+  };
+
+  // Asserts if called. This is to check that when we use skip to
+  // skip over a subquery, the subquery's produce is not invoked
+  auto createAssertCall() -> ProduceCall {
+    return [](AqlItemBlockInputRange& input,
+              OutputAqlItemRow& output) -> std::tuple<ExecutorState, LambdaExe::Stats, AqlCall> {
+      EXPECT_TRUE(false);
+      NoStats stats{};
+      AqlCall call{};
+
+      return {ExecutorState::DONE, stats, call};
+    };
+  }
+
+  auto createAssertCallCall(AqlCall call) -> ProduceCall {
+    return [call](AqlItemBlockInputRange& input,
+                  OutputAqlItemRow& output) -> std::tuple<ExecutorState, LambdaExe::Stats, AqlCall> {
+      auto clientCall = output.getClientCall();
+
+      EXPECT_EQ(clientCall.offset, call.offset);
+      EXPECT_EQ(clientCall.softLimit, call.softLimit);
+      EXPECT_EQ(clientCall.hardLimit, call.hardLimit);
+      EXPECT_EQ(clientCall.fullCount, call.fullCount);
+
+      while (input.hasDataRow() && !output.isFull()) {
+        auto const [state, row] = input.nextDataRow();
+        output.cloneValueInto(1, row, AqlValue("foo"));
+        output.advanceRow();
+      }
+
+      NoStats stats{};
+      AqlCall call{};
+
+      return {input.upstreamState(), stats, call};
+    };
+  }
+  auto getSplit() -> SubqueryExecutorSplitType {
+    auto [split] = GetParam();
+    return split;
+  }
+};
+
+template <size_t... vs>
+const SubqueryExecutorSplitType splitIntoBlocks =
+    SubqueryExecutorSplitType{std::vector<std::size_t>{vs...}};
+template <size_t step>
+const SubqueryExecutorSplitType splitStep = SubqueryExecutorSplitType{step};
+
+INSTANTIATE_TEST_CASE_P(SplicedSubqueryIntegrationTest, SplicedSubqueryIntegrationTest,
+                        ::testing::Values(splitIntoBlocks<2, 3>, splitIntoBlocks<3, 4>,
+                                          splitStep<2>, splitStep<1>));
+
+TEST_P(SplicedSubqueryIntegrationTest, single_subquery_empty_input) {
+  auto call = AqlCall{};
+  auto pipeline = createSubquery();
+  executorTestHelper.setPipeline(std::move(pipeline))
+      .setInputValueList()
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({1}, {})
+      .expectSkipped(0)
+      .expectedState(ExecutionState::DONE)
+      .run();
+};
+
+TEST_P(SplicedSubqueryIntegrationTest, single_subquery) {
+  auto call = AqlCall{};
+  auto pipeline = createSubquery();
+  ExecutorTestHelper<1, 2>{*fakedQuery}
+      .setPipeline(std::move(pipeline))
+      .setInputValueList(1, 2, 5, 2, 1, 5, 7, 1)
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({0, 1}, {{1, R"([1])"},
+                             {2, R"([2])"},
+                             {5, R"([5])"},
+                             {2, R"([2])"},
+                             {1, R"([1])"},
+                             {5, R"([5])"},
+                             {7, R"([7])"},
+                             {1, R"([1])"}})
+      .expectSkipped(0)
+      .expectedState(ExecutionState::DONE)
+      .run();
+};
+
+TEST_P(SplicedSubqueryIntegrationTest, DISABLED_single_subquery_skip_and_produce) {
+  auto call = AqlCall{5};
+  auto pipeline = createSubquery();
+  ExecutorTestHelper<1, 2>{*fakedQuery}
+      .setPipeline(std::move(pipeline))
+      .setInputValueList(1, 2, 5, 2, 1, 5, 7, 1)
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({0, 1}, {{5, R"([5])"}, {7, R"([7])"}, {1, R"([1])"}})
+      .expectSkipped(5)
+      .expectedState(ExecutionState::DONE)
+      .run();
+};
+
+TEST_P(SplicedSubqueryIntegrationTest, DISABLED_single_subquery_skip_all) {
+  auto call = AqlCall{20};
+  auto pipeline = createSubquery();
+  ExecutorTestHelper<1, 2>{*fakedQuery}
+      .setPipeline(std::move(pipeline))
+      .setInputValueList(1, 2, 5, 2, 1, 5, 7, 1)
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({0, 1}, {})
+      .expectSkipped(8)
+      .expectedState(ExecutionState::DONE)
+      .run();
+};
+
+TEST_P(SplicedSubqueryIntegrationTest, DISABLED_single_subquery_fullcount) {
+  auto call = AqlCall{0, true, 0, AqlCall::LimitType::HARD};
+  auto pipeline = createSubquery();
+  ExecutorTestHelper<1, 2>{*fakedQuery}
+      .setPipeline(std::move(pipeline))
+      .setInputValueList(1, 2, 5, 2, 1, 5, 7, 1)
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({0, 1}, {})
+      .expectSkipped(8)
+      .expectedState(ExecutionState::DONE)
+      .run();
+};
+
+TEST_P(SplicedSubqueryIntegrationTest, DISABLED_single_subquery_skip_produce_count) {
+  auto call = AqlCall{2, true, 2, AqlCall::LimitType::HARD};
+  auto pipeline = createSubquery();
+  ExecutorTestHelper<1, 2>{*fakedQuery}
+      .setPipeline(std::move(pipeline))
+      .setInputValueList(1, 2, 5, 2, 1, 5, 7, 1)
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({0, 1}, {{5, R"([5])"}, {2, R"([2])"}})
+      .expectSkipped(6)
+      .expectedState(ExecutionState::DONE)
+      .run();
+};
+
+TEST_P(SplicedSubqueryIntegrationTest, two_nested_subqueries_empty_input) {
+  auto call = AqlCall{};
+  auto pipeline = createSubquery(createSubquery());
+  executorTestHelper.setPipeline(std::move(pipeline))
+      .setInputValueList()
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({0}, {})
+      .expectSkipped(0)
+      .expectedState(ExecutionState::DONE)
+      .run();
+};
+
+TEST_P(SplicedSubqueryIntegrationTest, two_nested_subqueries) {
+  auto call = AqlCall{};
+  auto pipeline = createSubquery(createSubquery());
+  executorTestHelper.setPipeline(std::move(pipeline))
+      .setInputValueList(1, 2, 5, 2, 1, 5, 7, 1)
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({0}, {{1}, {2}, {5}, {2}, {1}, {5}, {7}, {1}})
+      .expectSkipped(0)
+      .expectedState(ExecutionState::DONE)
+      .run();
+};
+
+TEST_P(SplicedSubqueryIntegrationTest, two_sequential_subqueries) {
+  auto call = AqlCall{};
+  auto pipeline = concatPipelines(createSubquery(), createSubquery());
+  executorTestHelper.setPipeline(std::move(pipeline))
+      .setInputValueList(1, 2, 5, 2, 1, 5, 7, 1)
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({0}, {{1}, {2}, {5}, {2}, {1}, {5}, {7}, {1}})
+      .expectSkipped(0)
+      .expectedState(ExecutionState::DONE)
+      .run();
+};
+
+TEST_P(SplicedSubqueryIntegrationTest, do_nothing_in_subquery) {
+  auto call = AqlCall{};
+  auto pipeline = createSubquery(createDoNothingPipeline());
+
+  executorTestHelper.setPipeline(std::move(pipeline))
+      .setInputValueList(1, 2, 5, 2, 1, 5, 7, 1)
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({0}, {{1}, {2}, {5}, {2}, {1}, {5}, {7}, {1}})
+      .expectSkipped(0)
+      .expectedState(ExecutionState::DONE)
+      .run();
+};
+
+TEST_P(SplicedSubqueryIntegrationTest, DISABLED_check_call_passes_subquery) {
+  auto call = AqlCall{10};
+  auto pipeline = concatPipelines(createCallAssertPipeline(call), createSubquery());
+
+  executorTestHelper.setPipeline(std::move(pipeline))
+      .setInputValueList(1, 2, 5, 2, 1, 5, 7, 1)
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({0}, {})
+      .expectSkipped(8)
+      .expectedState(ExecutionState::DONE)
+      .run();
+};
+
+TEST_P(SplicedSubqueryIntegrationTest, DISABLED_check_skipping_subquery) {
+  auto call = AqlCall{10};
+  auto pipeline = createSubquery(createAssertPipeline());
+
+  executorTestHelper.setPipeline(std::move(pipeline))
+      .setInputValueList(1, 2, 5, 2, 1, 5, 7, 1)
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({0}, {})
+      .expectSkipped(0)
+      .expectedState(ExecutionState::DONE)
+      .run();
+};
diff --git a/tests/Aql/SubqueryEndExecutorTest.cpp b/tests/Aql/SubqueryEndExecutorTest.cpp
index 8902b2c4531b..3bbb66beb127 100644
--- a/tests/Aql/SubqueryEndExecutorTest.cpp
+++ b/tests/Aql/SubqueryEndExecutorTest.cpp
@@ -48,12 +48,14 @@ class SubqueryEndExecutorTest : public ::testing::Test {
   SubqueryEndExecutorTest()
       : _infos(std::make_shared<RegisterSet>(std::initializer_list<RegisterId>({0})),
                std::make_shared<RegisterSet>(std::initializer_list<RegisterId>({0})),
-               1, 1, {}, {}, nullptr, RegisterId{0}, RegisterId{0}) {}
+               1, 1, {}, {}, nullptr, RegisterId{0}, RegisterId{0}, false) {}
 
  protected:
   ResourceMonitor monitor;
   AqlItemBlockManager itemBlockManager{&monitor, SerializationFormat::SHADOWROWS};
   SubqueryEndExecutorInfos _infos;
+  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher{
+      itemBlockManager, VPackParser::fromJson("[]")->steal(), false};
 
   void ExpectedValues(OutputAqlItemRow& itemRow,
                       std::vector<std::vector<std::string>> const& expectedStrings,
@@ -98,248 +100,3 @@ TEST_F(SubqueryEndExecutorTest, check_properties) {
       << "The block produces one output row per input row plus potentially a "
          "shadow rows which is bounded by the structure of the query";
 };
-
-// If the input to a spliced subquery is empty, there should be no output
-TEST_F(SubqueryEndExecutorTest, empty_input_expects_no_shadow_rows) {
-  SharedAqlItemBlockPtr outputBlock;
-  SharedAqlItemBlockPtr inputBlock = buildBlock<1>(itemBlockManager, {{{}}});
-
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
-      itemBlockManager, 1, false, inputBlock);
-  SubqueryEndExecutor testee(fetcher, _infos);
-
-  // I don't seem to be able to make an empty inputBlock above,
-  // so we just fetch the one row that's in the block.
-  fetcher.fetchRow();
-
-  ExecutionState state{ExecutionState::HASMORE};
-
-  outputBlock.reset(new AqlItemBlock(itemBlockManager, inputBlock->size(), 1));
-  OutputAqlItemRow output{std::move(outputBlock), _infos.getOutputRegisters(),
-                          _infos.registersToKeep(), _infos.registersToClear()};
-
-  std::tie(state, std::ignore) = testee.produceRows(output);
-  EXPECT_EQ(state, ExecutionState::DONE);
-  EXPECT_EQ(output.numRowsWritten(), 0);
-}
-
-TEST_F(SubqueryEndExecutorTest, single_input_expects_shadow_rows) {
-  SharedAqlItemBlockPtr outputBlock;
-  SharedAqlItemBlockPtr inputBlock =
-      buildBlock<1>(itemBlockManager, {{{1}}, {{1}}}, {{1, 0}});
-
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
-      itemBlockManager, inputBlock->size(), false, inputBlock);
-
-  SubqueryEndExecutor testee(fetcher, _infos);
-
-  ExecutionState state{ExecutionState::HASMORE};
-  outputBlock.reset(new AqlItemBlock(itemBlockManager, inputBlock->size(), 1));
-  OutputAqlItemRow output{std::move(outputBlock), _infos.getOutputRegisters(),
-                          _infos.registersToKeep(), _infos.registersToClear()};
-  std::tie(state, std::ignore) = testee.produceRows(output);
-  EXPECT_EQ(state, ExecutionState::DONE);
-  EXPECT_EQ(output.numRowsWritten(), 1);
-
-  ExpectedValues(output, {{"[1]"}}, {});
-}
-
-TEST_F(SubqueryEndExecutorTest, two_inputs_one_shadowrow) {
-  SharedAqlItemBlockPtr outputBlock;
-  SharedAqlItemBlockPtr inputBlock =
-      buildBlock<1>(itemBlockManager, {{{42}}, {{34}}, {{1}}}, {{2, 0}});
-
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
-      itemBlockManager, inputBlock->size(), false, inputBlock);
-
-  SubqueryEndExecutor testee(fetcher, _infos);
-
-  ExecutionState state{ExecutionState::HASMORE};
-
-  outputBlock.reset(new AqlItemBlock(itemBlockManager, inputBlock->size(), 1));
-  OutputAqlItemRow output{std::move(outputBlock), _infos.getOutputRegisters(),
-                          _infos.registersToKeep(), _infos.registersToClear()};
-  std::tie(state, std::ignore) = testee.produceRows(output);
-  EXPECT_EQ(state, ExecutionState::DONE);
-  EXPECT_EQ(output.numRowsWritten(), 1);
-
-  ExpectedValues(output, {{"[42,34]"}}, {});
-}
-
-TEST_F(SubqueryEndExecutorTest, two_inputs_two_shadowrows) {
-  SharedAqlItemBlockPtr outputBlock;
-
-  SharedAqlItemBlockPtr inputBlock =
-      buildBlock<1>(itemBlockManager, {{{42}}, {{1}}, {{34}}, {{1}}}, {{1, 0}, {3, 0}});
-
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
-      itemBlockManager, inputBlock->size(), false, inputBlock);
-
-  SubqueryEndExecutor testee(fetcher, _infos);
-
-  ExecutionState state{ExecutionState::HASMORE};
-
-  outputBlock.reset(new AqlItemBlock(itemBlockManager, inputBlock->size(), 1));
-  OutputAqlItemRow output{std::move(outputBlock), _infos.getOutputRegisters(),
-                          _infos.registersToKeep(), _infos.registersToClear()};
-  std::tie(state, std::ignore) = testee.produceRows(output);
-  EXPECT_EQ(state, ExecutionState::DONE);
-  EXPECT_EQ(output.numRowsWritten(), 2);
-  ExpectedValues(output, {{"[42]"}, {"[34]"}}, {});
-}
-
-TEST_F(SubqueryEndExecutorTest, two_input_one_shadowrow_two_irrelevant) {
-  SharedAqlItemBlockPtr outputBlock;
-  SharedAqlItemBlockPtr inputBlock =
-      buildBlock<1>(itemBlockManager, {{{42}}, {{42}}, {{42}}, {{42}}, {{42}}},
-                    {{2, 0}, {3, 1}, {4, 2}});
-
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
-      itemBlockManager, inputBlock->size(), false, inputBlock);
-
-  SubqueryEndExecutor testee(fetcher, _infos);
-
-  ExecutionState state{ExecutionState::HASMORE};
-
-  outputBlock.reset(new AqlItemBlock(itemBlockManager, inputBlock->size(), 1));
-  OutputAqlItemRow output{std::move(outputBlock), _infos.getOutputRegisters(),
-                          _infos.registersToKeep(), _infos.registersToClear()};
-
-  std::tie(state, std::ignore) = testee.produceRows(output);
-  EXPECT_EQ(state, ExecutionState::DONE);
-  EXPECT_EQ(output.numRowsWritten(), 3);
-  ExpectedValues(output, {{{"[42, 42]"}}, {{""}}, {{""}}}, {{1, 0}, {2, 1}});
-}
-
-TEST_F(SubqueryEndExecutorTest, consume_output_of_subquery_end_executor) {
-  ExecutionState state{ExecutionState::HASMORE};
-
-  SharedAqlItemBlockPtr outputBlock;
-  SharedAqlItemBlockPtr inputBlock =
-      buildBlock<1>(itemBlockManager, {{{42}}, {{42}}, {{42}}, {{42}}, {{42}}},
-                    {{2, 0}, {3, 1}, {4, 2}});
-
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
-      itemBlockManager, inputBlock->size(), false, inputBlock);
-
-  SubqueryEndExecutor testee(fetcher, _infos);
-
-  outputBlock.reset(new AqlItemBlock(itemBlockManager, inputBlock->size(), 1));
-  OutputAqlItemRow output{std::move(outputBlock), _infos.getOutputRegisters(),
-                          _infos.registersToKeep(), _infos.registersToClear()};
-  std::tie(state, std::ignore) = testee.produceRows(output);
-  EXPECT_EQ(state, ExecutionState::DONE);
-  EXPECT_EQ(output.numRowsWritten(), 3);
-
-  //  ExpectedValues(output, { "[42, 42]", "", "" });
-
-  outputBlock = output.stealBlock();
-  inputBlock.swap(outputBlock);
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher2(
-      itemBlockManager, inputBlock->size(), false, inputBlock);
-  SubqueryEndExecutor testee2(fetcher2, _infos);
-  outputBlock.reset(new AqlItemBlock(itemBlockManager, inputBlock->size(), 1));
-  OutputAqlItemRow output2{std::move(outputBlock), _infos.getOutputRegisters(),
-                           _infos.registersToKeep(), _infos.registersToClear()};
-  std::tie(state, std::ignore) = testee2.produceRows(output2);
-  EXPECT_EQ(state, ExecutionState::DONE);
-  EXPECT_EQ(output2.numRowsWritten(), 2);
-
-  ExpectedValues(output2, {{"[ [42, 42] ]"}, {""}}, {{1, 0}});
-}
-
-TEST_F(SubqueryEndExecutorTest, write_to_register_outside) {
-  auto infos = SubqueryEndExecutorInfos(
-      std::make_shared<RegisterSet>(std::initializer_list<RegisterId>{0}),
-      std::make_shared<RegisterSet>(std::initializer_list<RegisterId>{1}), 1, 2,
-      {}, RegisterSet{0}, nullptr, RegisterId{0}, RegisterId{1});
-
-  ExecutionState state{ExecutionState::HASMORE};
-
-  SharedAqlItemBlockPtr outputBlock;
-  SharedAqlItemBlockPtr inputBlock =
-      buildBlock<1>(itemBlockManager, {{{42}}, {{23}}}, {{1, 0}});
-
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
-      itemBlockManager, inputBlock->size(), false, inputBlock);
-
-  SubqueryEndExecutor testee(fetcher, infos);
-
-  outputBlock.reset(new AqlItemBlock(itemBlockManager, inputBlock->size(), 2));
-  OutputAqlItemRow output{std::move(outputBlock), infos.getOutputRegisters(),
-                          infos.registersToKeep(), infos.registersToClear()};
-  std::tie(state, std::ignore) = testee.produceRows(output);
-  EXPECT_EQ(state, ExecutionState::DONE);
-  EXPECT_EQ(output.numRowsWritten(), 1);
-
-  ExpectedValues(output, {{"23", "[42]"}}, {{1, 0}});
-}
-
-TEST_F(SubqueryEndExecutorTest, no_input_register) {
-  auto infos = SubqueryEndExecutorInfos(
-      std::make_shared<RegisterSet>(std::initializer_list<RegisterId>{0}),
-      std::make_shared<RegisterSet>(std::initializer_list<RegisterId>{1}), 1, 2, {},
-      RegisterSet{0}, nullptr, RegisterId{RegisterPlan::MaxRegisterId}, RegisterId{1});
-
-  ExecutionState state{ExecutionState::HASMORE};
-
-  SharedAqlItemBlockPtr outputBlock;
-  SharedAqlItemBlockPtr inputBlock =
-      buildBlock<1>(itemBlockManager, {{{42}}, {{23}}}, {{1, 0}});
-
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
-      itemBlockManager, inputBlock->size(), false, inputBlock);
-
-  SubqueryEndExecutor testee(fetcher, infos);
-
-  outputBlock.reset(new AqlItemBlock(itemBlockManager, inputBlock->size(), 2));
-  OutputAqlItemRow output{std::move(outputBlock), infos.getOutputRegisters(),
-                          infos.registersToKeep(), infos.registersToClear()};
-  std::tie(state, std::ignore) = testee.produceRows(output);
-  EXPECT_EQ(state, ExecutionState::DONE);
-  EXPECT_EQ(output.numRowsWritten(), 1);
-
-  ExpectedValues(output, {{"23", "[]"}}, {{1, 0}});
-}
-
-// TODO: This is a "death test" with malformed shadow row layout (an irrelevant shadow row before any other row)
-// See https://github.com/google/googletest/blob/master/googletest/docs/advanced.md#death-tests-and-threads
-
-using SubqueryEndExecutorTest_DeathTest = SubqueryEndExecutorTest;
-
-TEST_F(SubqueryEndExecutorTest_DeathTest, no_shadow_row) {
-  SharedAqlItemBlockPtr outputBlock;
-  SharedAqlItemBlockPtr inputBlock = buildBlock<1>(itemBlockManager, {{1}});
-
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
-      itemBlockManager, inputBlock->size(), false, inputBlock);
-
-  SubqueryEndExecutor testee(fetcher, _infos);
-
-  ExecutionState state{ExecutionState::HASMORE};
-
-  outputBlock.reset(new AqlItemBlock(itemBlockManager, inputBlock->size(), 1));
-  OutputAqlItemRow output{std::move(outputBlock), _infos.getOutputRegisters(),
-                          _infos.registersToKeep(), _infos.registersToClear()};
-  EXPECT_DEATH_CORE_FREE(std::tie(state, std::ignore) = testee.produceRows(output),
-                         ".*");
-}
-
-TEST_F(SubqueryEndExecutorTest_DeathTest, misplaced_irrelevant_shadowrow) {
-  SharedAqlItemBlockPtr outputBlock;
-  SharedAqlItemBlockPtr inputBlock =
-      buildBlock<1>(itemBlockManager, {{42}, {42}, {42}}, {{1, 1}, {2, 1}});
-
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
-      itemBlockManager, inputBlock->size(), false, inputBlock);
-
-  SubqueryEndExecutor testee(fetcher, _infos);
-
-  ExecutionState state{ExecutionState::HASMORE};
-
-  outputBlock.reset(new AqlItemBlock(itemBlockManager, inputBlock->size(), 1));
-  OutputAqlItemRow output{std::move(outputBlock), _infos.getOutputRegisters(),
-                          _infos.registersToKeep(), _infos.registersToClear()};
-  EXPECT_DEATH_CORE_FREE(std::tie(state, std::ignore) = testee.produceRows(output),
-                         ".*");
-}
diff --git a/tests/Aql/SubqueryStartExecutorTest.cpp b/tests/Aql/SubqueryStartExecutorTest.cpp
index 75fdc4ef32a9..dc02b404e2d0 100644
--- a/tests/Aql/SubqueryStartExecutorTest.cpp
+++ b/tests/Aql/SubqueryStartExecutorTest.cpp
@@ -20,10 +20,15 @@
 /// @author Michael Hackstein
 ////////////////////////////////////////////////////////////////////////////////
 
-#include "RowFetcherHelper.h"
 #include "gtest/gtest.h"
 
+#include "ExecutorTestHelper.h"
+#include "RowFetcherHelper.h"
+
+#include "Aql/AqlItemBlock.h"
+#include "Aql/AqlItemBlockHelper.h"
 #include "Aql/ExecutorInfos.h"
+#include "Aql/InputAqlItemRow.h"
 #include "Aql/OutputAqlItemRow.h"
 #include "Aql/Stats.h"
 #include "Aql/SubqueryStartExecutor.h"
@@ -32,6 +37,7 @@
 #include <velocypack/Parser.h>
 #include <velocypack/velocypack-aliases.h>
 
+#include "Logger/LogMacros.h"
 using namespace arangodb;
 using namespace arangodb::aql;
 using namespace arangodb::tests;
@@ -47,25 +53,37 @@ ExecutorInfos MakeBaseInfos(RegisterId numRegs) {
   }
   return ExecutorInfos(emptyRegisterList, emptyRegisterList, numRegs, numRegs, {}, toKeep);
 }
-
-void TestShadowRow(SharedAqlItemBlockPtr const& block, size_t row, bool isRelevant) {
-  EXPECT_TRUE(block->isShadowRow(row));
-  // We do this additional if, in order to allow the outer test loop to continue
-  // even if we do not have a shadow row.
-  if (block->isShadowRow(row)) {
-    ShadowAqlItemRow shadow{block, row};
-    EXPECT_EQ(shadow.isRelevant(), isRelevant) << "Testing row " << row;
-  }
-}
 }  // namespace
 
-class SubqueryStartExecutorTest : public ::testing::Test {
+// We need to be backwards compatible, with version 3.6
+// There we do not get a fullStack, but only a single entry.
+// We have a compatibility mode Stack for this version
+// These tests can be removed again in the branch for the version
+// after 3.7.*
+enum CompatibilityMode { VERSION36, VERSION37 };
+class SubqueryStartExecutorTest
+    : public AqlExecutorTestCaseWithParam<CompatibilityMode, false> {
  protected:
-  ResourceMonitor monitor;
-  AqlItemBlockManager itemBlockManager{&monitor, SerializationFormat::SHADOWROWS};
+  auto GetCompatMode() const -> CompatibilityMode {
+    auto const mode = GetParam();
+    return mode;
+  }
+
+  auto queryStack(AqlCall fromSubqueryEnd, AqlCall insideSubquery) const -> AqlCallStack {
+    if (GetCompatMode() == CompatibilityMode::VERSION36) {
+      return AqlCallStack{insideSubquery, true};
+    }
+    AqlCallStack stack(fromSubqueryEnd);
+    stack.pushCall(std::move(insideSubquery));
+    return stack;
+  }
 };
 
-TEST_F(SubqueryStartExecutorTest, check_properties) {
+INSTANTIATE_TEST_CASE_P(SubqueryStartExecutorTest, SubqueryStartExecutorTest,
+                        ::testing::Values(CompatibilityMode::VERSION36,
+                                          CompatibilityMode::VERSION37));
+
+TEST_P(SubqueryStartExecutorTest, check_properties) {
   EXPECT_TRUE(SubqueryStartExecutor::Properties::preservesOrder)
       << "The block has no effect on ordering of elements, it adds additional "
          "rows only.";
@@ -76,178 +94,249 @@ TEST_F(SubqueryStartExecutorTest, check_properties) {
          "input. (Might be less if input contains shadowRows";
 }
 
-TEST_F(SubqueryStartExecutorTest, empty_input_does_not_add_shadow_rows) {
-  SharedAqlItemBlockPtr block{new AqlItemBlock(itemBlockManager, 1000, 1)};
-  VPackBuilder input;
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
-      itemBlockManager, input.steal(), false);
-  auto infos = MakeBaseInfos(1);
-  SubqueryStartExecutor testee(fetcher, infos);
-
-  NoStats stats{};
-  ExecutionState state{ExecutionState::HASMORE};
-  OutputAqlItemRow output{std::move(block), infos.getOutputRegisters(),
-                          infos.registersToKeep(), infos.registersToClear()};
-  std::tie(state, stats) = testee.produceRows(output);
-  EXPECT_EQ(state, ExecutionState::DONE);
-  EXPECT_FALSE(output.produced());
-  EXPECT_EQ(output.numRowsWritten(), 0);
+TEST_P(SubqueryStartExecutorTest, empty_input_does_not_add_shadow_rows) {
+  ExecutorTestHelper<1, 1>(*fakedQuery)
+      .setExecBlock<SubqueryStartExecutor>(MakeBaseInfos(1), ExecutionNode::SUBQUERY_START)
+      .setInputValue({})
+      .expectedStats(ExecutionStats{})
+      .expectedState(ExecutionState::DONE)
+      .expectOutput({0}, {})
+      .expectSkipped(0)
+      .setCallStack(queryStack(AqlCall{}, AqlCall{}))
+      .run();
+}
+
+TEST_P(SubqueryStartExecutorTest, adds_a_shadowrow_after_single_input) {
+  ExecutorTestHelper<1, 1>(*fakedQuery)
+      .setExecBlock<SubqueryStartExecutor>(MakeBaseInfos(1), ExecutionNode::SUBQUERY_START)
+      .setInputValue({{R"("a")"}})
+      .expectedStats(ExecutionStats{})
+      .expectedState(ExecutionState::DONE)
+      .expectSkipped(0)
+      .expectOutput({0}, {{R"("a")"}, {R"("a")"}}, {{1, 0}})
+      .setCallStack(queryStack(AqlCall{}, AqlCall{}))
+      .run();
 }
 
-TEST_F(SubqueryStartExecutorTest, adds_a_shadowrow_after_single_input) {
-  SharedAqlItemBlockPtr block{new AqlItemBlock(itemBlockManager, 1000, 1)};
-  auto input = VPackParser::fromJson(R"([
-      ["a"]
-  ])");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
-      itemBlockManager, input->steal(), false);
-  auto infos = MakeBaseInfos(1);
-  SubqueryStartExecutor testee(fetcher, infos);
-
-  NoStats stats{};
-  ExecutionState state{ExecutionState::HASMORE};
-  OutputAqlItemRow output{std::move(block), infos.getOutputRegisters(),
-                          infos.registersToKeep(), infos.registersToClear()};
-  std::tie(state, stats) = testee.produceRows(output);
-  EXPECT_EQ(state, ExecutionState::DONE);
-  EXPECT_FALSE(output.produced());
-  EXPECT_EQ(output.numRowsWritten(), 2);
-
-  block = output.stealBlock();
-  EXPECT_FALSE(block->isShadowRow(0));
-  TestShadowRow(block, 1, true);
+// NOTE: The following two tests exclude each other.
+// Right now we can only support 1 ShadowRow per request, we cannot do a look-ahead of
+// calls. As soon as we can this test needs to re removed, and the one blow needs to be activated.
+TEST_P(SubqueryStartExecutorTest,
+       adds_only_one_shadowrow_even_if_more_input_is_available_in_single_pass) {
+  ExecutorTestHelper<1, 1>(*fakedQuery)
+      .setExecBlock<SubqueryStartExecutor>(MakeBaseInfos(1), ExecutionNode::SUBQUERY_START)
+      .setInputValue({{{R"("a")"}}, {{R"("b")"}}, {{R"("c")"}}})
+      .expectedStats(ExecutionStats{})
+      .expectedState(ExecutionState::HASMORE)
+      .expectSkipped(0)
+      .expectOutput({0}, {{R"("a")"}, {R"("a")"}}, {{1, 0}})
+      .setCallStack(queryStack(AqlCall{}, AqlCall{}))
+      .run();
 }
 
-TEST_F(SubqueryStartExecutorTest, adds_a_shadowrow_after_every_input_line_in_single_pass) {
-  SharedAqlItemBlockPtr block{new AqlItemBlock(itemBlockManager, 1000, 1)};
-  auto input = VPackParser::fromJson(R"([
-      ["a"],
-      ["b"],
-      ["c"]
-  ])");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
-      itemBlockManager, input->steal(), false);
-  auto infos = MakeBaseInfos(1);
-  SubqueryStartExecutor testee(fetcher, infos);
-
-  NoStats stats{};
-  ExecutionState state{ExecutionState::HASMORE};
-  OutputAqlItemRow output{std::move(block), infos.getOutputRegisters(),
-                          infos.registersToKeep(), infos.registersToClear()};
-  std::tie(state, stats) = testee.produceRows(output);
-  EXPECT_EQ(state, ExecutionState::DONE);
-  EXPECT_FALSE(output.produced());
-  EXPECT_EQ(output.numRowsWritten(), 6);
-
-  block = output.stealBlock();
-  EXPECT_FALSE(block->isShadowRow(0));
-  TestShadowRow(block, 1, true);
-  EXPECT_FALSE(block->isShadowRow(2));
-  TestShadowRow(block, 3, true);
-  EXPECT_FALSE(block->isShadowRow(4));
-  TestShadowRow(block, 5, true);
+// NOTE: This test and the one right above do exclude each other.
+// This is the behaviour we would like to have eventually
+// As soon as we can support Call look-aheads we need to enable this test.
+// and it needs to pass then
+TEST_P(SubqueryStartExecutorTest, DISABLED_adds_a_shadowrow_after_every_input_line_in_single_pass) {
+  ExecutorTestHelper<1, 1>(*fakedQuery)
+      .setExecBlock<SubqueryStartExecutor>(MakeBaseInfos(1), ExecutionNode::SUBQUERY_START)
+      .setInputValue({{{R"("a")"}}, {{R"("b")"}}, {{R"("c")"}}})
+      .expectedStats(ExecutionStats{})
+      .expectedState(ExecutionState::DONE)
+      .expectSkipped(0)
+      .expectOutput({0}, {{R"("a")"}, {R"("a")"}, {R"("b")"}, {R"("b")"}, {R"("c")"}, {R"("c")"}},
+                    {{1, 0}, {3, 0}, {5, 0}})
+      .setCallStack(queryStack(AqlCall{}, AqlCall{}))
+      .run();
 }
 
-TEST_F(SubqueryStartExecutorTest, shadow_row_does_not_fit_in_current_block) {
-  auto input = VPackParser::fromJson(R"([
-      ["a"],
-      ["b"],
-      ["c"]
-  ])");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
-      itemBlockManager, input->steal(), false);
-  auto infos = MakeBaseInfos(1);
-  SubqueryStartExecutor testee(fetcher, infos);
-
-  NoStats stats{};
-  ExecutionState state{ExecutionState::HASMORE};
+// NOTE: As soon as the single_pass test is enabled this test is superflous.
+// It will be identical to the one above
+TEST_P(SubqueryStartExecutorTest, adds_a_shadowrow_after_every_input_line) {
+  ExecutorTestHelper<1, 1>(*fakedQuery)
+      .setExecBlock<SubqueryStartExecutor>(MakeBaseInfos(1), ExecutionNode::SUBQUERY_START)
+      .setInputValue({{{R"("a")"}}, {{R"("b")"}}, {{R"("c")"}}})
+      .expectedStats(ExecutionStats{})
+      .expectedState(ExecutionState::DONE)
+      .expectSkipped(0)
+      .expectOutput({0}, {{R"("a")"}, {R"("a")"}, {R"("b")"}, {R"("b")"}, {R"("c")"}, {R"("c")"}},
+                    {{1, 0}, {3, 0}, {5, 0}})
+      .setCallStack(queryStack(AqlCall{}, AqlCall{}))
+      .run(true);
+}
+
+TEST_P(SubqueryStartExecutorTest, shadow_row_does_not_fit_in_current_block) {
+  // NOTE: This test relies on batchSizes beeing handled correctly and we do not over-allocate memory
+  // Also it tests, that ShadowRows go into place accounting of the output block (count as 1 line)
+
+  // NOTE: Reduce batch size to 1, to enforce a too small output block
+  ExecutionBlock::setDefaultBatchSize(1);
+  TRI_DEFER(ExecutionBlock::setDefaultBatchSize(ExecutionBlock::ProductionDefaultBatchSize););
   {
-    SharedAqlItemBlockPtr block{new AqlItemBlock(itemBlockManager, 3, 1)};
-    OutputAqlItemRow output{std::move(block), infos.getOutputRegisters(),
-                            infos.registersToKeep(), infos.registersToClear()};
-    std::tie(state, stats) = testee.produceRows(output);
-    EXPECT_EQ(state, ExecutionState::HASMORE);
-    EXPECT_FALSE(output.produced());
-    EXPECT_EQ(output.numRowsWritten(), 3);
-
-    block = output.stealBlock();
-    EXPECT_FALSE(block->isShadowRow(0));
-    TestShadowRow(block, 1, true);
-    EXPECT_FALSE(block->isShadowRow(2));
+    // First test: Validate that the shadowRow is not written
+    // We only do a single call here
+    ExecutorTestHelper<1, 1>(*fakedQuery)
+        .setExecBlock<SubqueryStartExecutor>(MakeBaseInfos(1), ExecutionNode::SUBQUERY_START)
+        .setInputValue({{R"("a")"}})
+        .expectedStats(ExecutionStats{})
+        .expectedState(ExecutionState::HASMORE)
+        .expectSkipped(0)
+        .expectOutput({0}, {{R"("a")"}}, {})
+        .setCallStack(queryStack(AqlCall{}, AqlCall{}))
+        .run();
   }
   {
-    SharedAqlItemBlockPtr block{new AqlItemBlock(itemBlockManager, 3, 1)};
-    OutputAqlItemRow output{std::move(block), infos.getOutputRegisters(),
-                            infos.registersToKeep(), infos.registersToClear()};
-    std::tie(state, stats) = testee.produceRows(output);
-    EXPECT_EQ(state, ExecutionState::DONE);
-    EXPECT_FALSE(output.produced());
-    EXPECT_EQ(output.numRowsWritten(), 3);
-
-    block = output.stealBlock();
-    TestShadowRow(block, 0, true);
-    EXPECT_FALSE(block->isShadowRow(1));
-    TestShadowRow(block, 2, true);
+    // Second test: Validate that the shadowRow is eventually written
+    // if we call often enough
+    ExecutorTestHelper<1, 1>(*fakedQuery)
+        .setExecBlock<SubqueryStartExecutor>(MakeBaseInfos(1), ExecutionNode::SUBQUERY_START)
+        .setInputValue({{R"("a")"}})
+        .expectedStats(ExecutionStats{})
+        .expectedState(ExecutionState::DONE)
+        .expectSkipped(0)
+        .expectOutput({0}, {{R"("a")"}, {R"("a")"}}, {{1, 0}})
+        .setCallStack(queryStack(AqlCall{}, AqlCall{}))
+        .run(true);
   }
 }
 
-// TODO:
-// This test can be enabled and should work as soon as the Fetcher skips non-relevant Subqueries
-TEST_F(SubqueryStartExecutorTest, does_only_add_shadowrows_on_data_rows) {
-  SharedAqlItemBlockPtr block{new AqlItemBlock(itemBlockManager, 1000, 1)};
-  auto input = VPackParser::fromJson(R"([
-      ["a"],
-      ["b"],
-      ["c"]
-  ])");
-
-  auto infos = MakeBaseInfos(1);
+TEST_P(SubqueryStartExecutorTest, skip_in_subquery) {
+  ExecutorTestHelper<1, 1>(*fakedQuery)
+      .setExecBlock<SubqueryStartExecutor>(MakeBaseInfos(1), ExecutionNode::SUBQUERY_START)
+      .setInputValue({{R"("a")"}})
+      .expectedStats(ExecutionStats{})
+      .expectedState(ExecutionState::DONE)
+      .expectOutput({0}, {{R"("a")"}}, {{0, 0}})
+      .expectSkipped(1)
+      .setCallStack(queryStack(AqlCall{}, AqlCall{10, false}))
+      .run();
+}
+
+TEST_P(SubqueryStartExecutorTest, fullCount_in_subquery) {
+  ExecutorTestHelper<1, 1>(*fakedQuery)
+      .setExecBlock<SubqueryStartExecutor>(MakeBaseInfos(1), ExecutionNode::SUBQUERY_START)
+      .setInputValue({{R"("a")"}})
+      .expectedStats(ExecutionStats{})
+      .expectedState(ExecutionState::DONE)
+      .expectOutput({0}, {{R"("a")"}}, {{0, 0}})
+      .expectSkipped(1)
+      .setCallStack(queryStack(AqlCall{}, AqlCall{0, true, 0, AqlCall::LimitType::HARD}))
+      .run();
+}
+
+TEST_P(SubqueryStartExecutorTest, shadow_row_forwarding) {
+  ExecutorTestHelper<1, 1> helper(*fakedQuery);
+  AqlCallStack stack = queryStack(AqlCall{}, AqlCall{});
+  stack.pushCall(AqlCall{});
+  Pipeline pipe{};
+  pipe.addConsumer(helper.createExecBlock<SubqueryStartExecutor>(MakeBaseInfos(1),
+                                                                 ExecutionNode::SUBQUERY_START))
+      .addConsumer(helper.createExecBlock<SubqueryStartExecutor>(MakeBaseInfos(1),
+                                                                 ExecutionNode::SUBQUERY_START));
+  helper.setPipeline(std::move(pipe))
+      .setInputValue({{R"("a")"}})
+      .expectedStats(ExecutionStats{})
+      .expectedState(ExecutionState::DONE)
+      .expectOutput({0}, {{R"("a")"}, {R"("a")"}, {R"("a")"}}, {{1, 0}, {2, 1}})
+      .expectSkipped(0)
+      .setCallStack(stack)
+      .run();
+}
+
+TEST_P(SubqueryStartExecutorTest, shadow_row_forwarding_many_inputs_single_call) {
+  ExecutorTestHelper<1, 1> helper(*fakedQuery);
+  AqlCallStack stack = queryStack(AqlCall{}, AqlCall{});
+  stack.pushCall(AqlCall{});
+  Pipeline pipe{};
+  pipe.addConsumer(helper.createExecBlock<SubqueryStartExecutor>(MakeBaseInfos(1),
+                                                                 ExecutionNode::SUBQUERY_START))
+      .addConsumer(helper.createExecBlock<SubqueryStartExecutor>(MakeBaseInfos(1),
+                                                                 ExecutionNode::SUBQUERY_START));
+  helper.setPipeline(std::move(pipe))
+      .setInputValue({{R"("a")"}, {R"("b")"}, {R"("c")"}})
+      .expectedStats(ExecutionStats{})
+      .expectedState(ExecutionState::HASMORE)
+      .expectOutput({0}, {{R"("a")"}, {R"("a")"}, {R"("a")"}}, {{1, 0}, {2, 1}})
+      .expectSkipped(0)
+      .setCallStack(stack)
+      .run();
+}
+
+TEST_P(SubqueryStartExecutorTest, shadow_row_forwarding_many_inputs_many_requests) {
+  ExecutorTestHelper<1, 1> helper(*fakedQuery);
+  AqlCallStack stack = queryStack(AqlCall{}, AqlCall{});
+  stack.pushCall(AqlCall{});
+  Pipeline pipe{};
+  pipe.addConsumer(helper.createExecBlock<SubqueryStartExecutor>(MakeBaseInfos(1),
+                                                                 ExecutionNode::SUBQUERY_START))
+      .addConsumer(helper.createExecBlock<SubqueryStartExecutor>(MakeBaseInfos(1),
+                                                                 ExecutionNode::SUBQUERY_START));
+  helper.setPipeline(std::move(pipe))
+      .setInputValue({{R"("a")"}, {R"("b")"}, {R"("c")"}})
+      .expectedStats(ExecutionStats{})
+      .expectedState(ExecutionState::DONE)
+      .expectOutput(
+          {0},
+          {{R"("a")"}, {R"("a")"}, {R"("a")"}, {R"("b")"}, {R"("b")"}, {R"("b")"}, {R"("c")"}, {R"("c")"}, {R"("c")"}},
+          {{1, 0}, {2, 1}, {4, 0}, {5, 1}, {7, 0}, {8, 1}})
+      .expectSkipped(0)
+      .setCallStack(stack)
+      .run(true);
+}
+
+TEST_P(SubqueryStartExecutorTest, shadow_row_forwarding_many_inputs_not_enough_space) {
+  // NOTE: This test relies on batchSizes beeing handled correctly and we do not over-allocate memory
+  // Also it tests, that ShadowRows go into place accounting of the output block (count as 1 line)
+
+  // NOTE: Reduce batch size to 2, to enforce a too small output block, in between the shadow Rows
+  ExecutionBlock::setDefaultBatchSize(2);
+  TRI_DEFER(ExecutionBlock::setDefaultBatchSize(ExecutionBlock::ProductionDefaultBatchSize););
   {
-    SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
-        itemBlockManager, input->steal(), false);
-    SubqueryStartExecutor testee(fetcher, infos);
-
-    NoStats stats{};
-    ExecutionState state{ExecutionState::HASMORE};
-    OutputAqlItemRow output{std::move(block), infos.getOutputRegisters(),
-                            infos.registersToKeep(), infos.registersToClear()};
-    std::tie(state, stats) = testee.produceRows(output);
-    EXPECT_EQ(state, ExecutionState::DONE);
-    EXPECT_FALSE(output.produced());
-    ASSERT_EQ(output.numRowsWritten(), 6);
-    block = output.stealBlock();
-    EXPECT_FALSE(block->isShadowRow(0));
-    TestShadowRow(block, 1, true);
-    EXPECT_FALSE(block->isShadowRow(2));
-    TestShadowRow(block, 3, true);
-    EXPECT_FALSE(block->isShadowRow(4));
-    TestShadowRow(block, 5, true);
-    // Taken from test above. We now have produced a block
-    // having 3 data rows alternating with 3 shadow rows
+    // First test: Validate that the shadowRow is not written
+    // We only do a single call here
+    ExecutorTestHelper<1, 1> helper(*fakedQuery);
+    AqlCallStack stack = queryStack(AqlCall{}, AqlCall{});
+    stack.pushCall(AqlCall{});
+    Pipeline pipe{};
+    pipe.addConsumer(helper.createExecBlock<SubqueryStartExecutor>(MakeBaseInfos(1),
+                                                                   ExecutionNode::SUBQUERY_START))
+        .addConsumer(helper.createExecBlock<SubqueryStartExecutor>(MakeBaseInfos(1),
+                                                                   ExecutionNode::SUBQUERY_START));
+    helper.setPipeline(std::move(pipe))
+        .setInputValue({{R"("a")"}, {R"("b")"}, {R"("c")"}})
+        .expectedStats(ExecutionStats{})
+        .expectedState(ExecutionState::HASMORE)
+        .expectOutput({0}, {{R"("a")"}, {R"("a")"}}, {{1, 0}})
+        .expectSkipped(0)
+        .setCallStack(stack)
+        .run();
   }
   {
-    SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager,
-                                                                               6, false, block);
-    SubqueryStartExecutor testee(fetcher, infos);
-    block.reset(new AqlItemBlock(itemBlockManager, 1000, 1));
-
-    NoStats stats{};
-    ExecutionState state{ExecutionState::HASMORE};
-    OutputAqlItemRow output{std::move(block), infos.getOutputRegisters(),
-                            infos.registersToKeep(), infos.registersToClear()};
-    std::tie(state, stats) = testee.produceRows(output);
-    EXPECT_EQ(state, ExecutionState::DONE);
-    EXPECT_FALSE(output.produced());
-    ASSERT_EQ(output.numRowsWritten(), 9);
-    block = output.stealBlock();
-    EXPECT_FALSE(block->isShadowRow(0));
-    TestShadowRow(block, 1, true);
-    TestShadowRow(block, 2, false);
-    EXPECT_FALSE(block->isShadowRow(3));
-    TestShadowRow(block, 4, true);
-    TestShadowRow(block, 5, false);
-    EXPECT_FALSE(block->isShadowRow(6));
-    TestShadowRow(block, 7, true);
-    TestShadowRow(block, 8, false);
+    // Second test: Validate that the shadowRow is eventually written
+    // Wedo call as many times as we need to.
+    ExecutorTestHelper<1, 1> helper(*fakedQuery);
+    AqlCallStack stack = queryStack(AqlCall{}, AqlCall{});
+    stack.pushCall(AqlCall{});
+    Pipeline pipe{};
+    pipe.addConsumer(helper.createExecBlock<SubqueryStartExecutor>(MakeBaseInfos(1),
+                                                                   ExecutionNode::SUBQUERY_START))
+        .addConsumer(helper.createExecBlock<SubqueryStartExecutor>(MakeBaseInfos(1),
+                                                                   ExecutionNode::SUBQUERY_START));
+    helper.setPipeline(std::move(pipe))
+        .setInputValue({{R"("a")"}, {R"("b")"}, {R"("c")"}})
+        .expectedStats(ExecutionStats{})
+        .expectedState(ExecutionState::DONE)
+        .expectOutput(
+            {0},
+            {{R"("a")"}, {R"("a")"}, {R"("a")"}, {R"("b")"}, {R"("b")"}, {R"("b")"}, {R"("c")"}, {R"("c")"}, {R"("c")"}},
+            {{1, 0}, {2, 1}, {4, 0}, {5, 1}, {7, 0}, {8, 1}})
+        .expectSkipped(0)
+        .setCallStack(stack)
+        .run(true);
   }
 }
+
+// TODO:
+// * Add tests for Skipping
+//    - on Higher level subquery
diff --git a/tests/Aql/WaitingExecutionBlockMock.cpp b/tests/Aql/WaitingExecutionBlockMock.cpp
index b20a09c843ca..c48de11e02e4 100644
--- a/tests/Aql/WaitingExecutionBlockMock.cpp
+++ b/tests/Aql/WaitingExecutionBlockMock.cpp
@@ -28,6 +28,8 @@
 #include "Aql/ExecutionState.h"
 #include "Aql/QueryOptions.h"
 
+#include "Logger/LogMacros.h"
+
 #include <velocypack/velocypack-aliases.h>
 
 using namespace arangodb;
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 5061dd53a789..9df5c6a01515 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -68,6 +68,7 @@ set(ARANGODB_TESTS_SOURCES
   Aql/SortExecutorTest.cpp
   Aql/SortLimit-test.cpp
   Aql/SpliceSubqueryOptimizerRuleTest.cpp
+  Aql/SplicedSubqueryIntegrationTest.cpp
   Aql/SubqueryEndExecutorTest.cpp
   Aql/SubqueryStartExecutorTest.cpp
   Aql/TestEmptyExecutorHelper.cpp

From 1cd9adb371f5fdc722de696306a5c461debb8d17 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tobias=20G=C3=B6dderz?= <tobias@arangodb.com>
Date: Thu, 27 Feb 2020 09:27:47 +0100
Subject: [PATCH 077/122] Feature/aql subquery execute remote node api flag
 (#11159)

* Clarified comment

* Added api property to RemoteNode

* Added missing include
---
 arangod/Aql/AqlCall.h                         |  2 +-
 arangod/Aql/AqlItemBlockSerializationFormat.h |  4 +++
 arangod/Aql/ClusterNodes.cpp                  | 20 ++++++++++++-
 arangod/Aql/ClusterNodes.h                    | 28 +++++++++++++++----
 ...EngineInfoContainerDBServerServerBased.cpp |  3 +-
 arangod/Aql/RestAqlHandler.cpp                |  7 +++--
 lib/Basics/StaticStrings.cpp                  |  1 +
 lib/Basics/StaticStrings.h                    |  1 +
 8 files changed, 55 insertions(+), 11 deletions(-)

diff --git a/arangod/Aql/AqlCall.h b/arangod/Aql/AqlCall.h
index 75d2c7048b7a..1abf4868b6c4 100644
--- a/arangod/Aql/AqlCall.h
+++ b/arangod/Aql/AqlCall.h
@@ -34,7 +34,7 @@ namespace arangodb::aql {
 struct AqlCall {
   // TODO We currently have softLimit and hardLimit, where both can be a number
   //      or Infinity - but not both may be non-infinite at the same time.
-  //      In addition, a soft limit does only make sense together with a hard
+  //      In addition, fullCount does only make sense together with a hard
   //      limit.
   //      The data structures and APIs should reflect that. E.g.:
   //      Infinity | SoftLimit { count : Int } | HardLimit { count : Int, fullCount : Bool }
diff --git a/arangod/Aql/AqlItemBlockSerializationFormat.h b/arangod/Aql/AqlItemBlockSerializationFormat.h
index 72d8edbe9657..1d98a7836151 100644
--- a/arangod/Aql/AqlItemBlockSerializationFormat.h
+++ b/arangod/Aql/AqlItemBlockSerializationFormat.h
@@ -23,6 +23,8 @@
 #ifndef ARANGOD_AQL_AQLITEMBLOCK_SERIALIZATION_FORMAT_H
 #define ARANGOD_AQL_AQLITEMBLOCK_SERIALIZATION_FORMAT_H
 
+#include <type_traits>
+
 namespace arangodb {
 namespace aql {
 
@@ -34,6 +36,8 @@ enum class SerializationFormat {
   SHADOWROWS = 1
 };
 
+using SerializationFormatType = std::underlying_type_t<SerializationFormat>;
+
 }  // namespace aql
 }  // namespace arangodb
 #endif
diff --git a/arangod/Aql/ClusterNodes.cpp b/arangod/Aql/ClusterNodes.cpp
index 965442481607..1bcfffe3eb12 100644
--- a/arangod/Aql/ClusterNodes.cpp
+++ b/arangod/Aql/ClusterNodes.cpp
@@ -128,7 +128,8 @@ RemoteNode::RemoteNode(ExecutionPlan* plan, arangodb::velocypack::Slice const& b
     : DistributeConsumerNode(plan, base),
       _vocbase(&(plan->getAst()->query()->vocbase())),
       _server(base.get("server").copyString()),
-      _queryId(base.get("queryId").copyString()) {
+      _queryId(base.get("queryId").copyString()),
+      _apiToUse(getApiProperty(base, StaticStrings::AqlRemoteApi)) {
   // Backwards compatibility (3.4.x)(3.5.0) and earlier, coordinator might send ownName.
   arangodb::velocypack::StringRef tmpId(getDistributeId());
   tmpId = VelocyPackHelper::getStringRef(base, "ownName", tmpId);
@@ -183,6 +184,7 @@ void RemoteNode::toVelocyPackHelper(VPackBuilder& nodes, unsigned flags,
   nodes.add("database", VPackValue(_vocbase->name()));
   nodes.add("server", VPackValue(_server));
   nodes.add("queryId", VPackValue(_queryId));
+  nodes.add(StaticStrings::AqlRemoteApi, apiToVpack(_apiToUse));
 
   // And close it:
   nodes.close();
@@ -203,6 +205,22 @@ CostEstimate RemoteNode::estimateCost() const {
   return estimate;
 }
 
+auto RemoteNode::api() const noexcept -> Api {
+  return _apiToUse;
+}
+
+auto RemoteNode::apiToVpack(Api const api) -> velocypack::Value {
+  return VPackValue(static_cast<std::underlying_type_t<Api>>(api));
+}
+
+auto RemoteNode::getApiProperty(VPackSlice slice, std::string const& key)
+    -> RemoteNode::Api {
+  using ApiType = std::underlying_type_t<Api>;
+  // Default to GET_SOME
+  return static_cast<Api>(
+      VelocyPackHelper::getNumericValue<ApiType>(slice, key, static_cast<ApiType>(Api::GET_SOME)));
+}
+
 /// @brief construct a scatter node
 ScatterNode::ScatterNode(ExecutionPlan* plan, arangodb::velocypack::Slice const& base)
     : ExecutionNode(plan, base) {
diff --git a/arangod/Aql/ClusterNodes.h b/arangod/Aql/ClusterNodes.h
index 7095fee40436..5eefc5395cb9 100644
--- a/arangod/Aql/ClusterNodes.h
+++ b/arangod/Aql/ClusterNodes.h
@@ -35,6 +35,8 @@
 #include "VocBase/voc-types.h"
 #include "VocBase/vocbase.h"
 
+#include <utility>
+
 namespace arangodb {
 namespace velocypack {
 class Builder;
@@ -53,14 +55,20 @@ struct Collection;
 class RemoteNode final : public DistributeConsumerNode {
   friend class ExecutionBlock;
 
-  /// @brief constructor with an id
  public:
+  /// @brief Type of API; the legacy pre-3.7 getSome/skipSome API, or the
+  ///        execute API. Used for rolling upgrades. Can be removed in 3.8.
+  ///        It is serialized as an integral, changing the values will break the
+  ///        API!
+  enum class Api { GET_SOME = 0, EXECUTE = 1 };
+
+  /// @brief constructor with an id
   RemoteNode(ExecutionPlan* plan, size_t id, TRI_vocbase_t* vocbase,
-             std::string const& server, std::string const& ownName, std::string const& queryId)
+             std::string server, std::string const& ownName, std::string queryId, Api = Api::EXECUTE)
       : DistributeConsumerNode(plan, id, ownName),
         _vocbase(vocbase),
-        _server(server),
-        _queryId(queryId) {
+        _server(std::move(server)),
+        _queryId(std::move(queryId)) {
     // note: server and queryId may be empty and filled later
   }
 
@@ -82,7 +90,7 @@ class RemoteNode final : public DistributeConsumerNode {
   ExecutionNode* clone(ExecutionPlan* plan, bool withDependencies,
                        bool withProperties) const override final {
     return cloneHelper(std::make_unique<RemoteNode>(plan, _id, _vocbase, _server,
-                                                    getDistributeId(), _queryId),
+                                                    getDistributeId(), _queryId, _apiToUse),
                        withDependencies, withProperties);
   }
 
@@ -109,6 +117,12 @@ class RemoteNode final : public DistributeConsumerNode {
     _queryId = arangodb::basics::StringUtils::itoa(queryId);
   }
 
+  [[nodiscard]] auto api() const noexcept -> Api;
+
+ private:
+  static auto apiToVpack(Api) -> velocypack::Value;
+  static auto getApiProperty(VPackSlice slice, std::string const& key) -> Api;
+
  private:
   /// @brief the underlying database
   TRI_vocbase_t* _vocbase;
@@ -118,6 +132,10 @@ class RemoteNode final : public DistributeConsumerNode {
 
   /// @brief the ID of the query on the server as a string
   std::string _queryId;
+
+  /// @brief Whether to use the pre-3.7 getSome/skipSome API, instead of the
+  ///        execute API. Used for rolling upgrades, so can be removed in 3.8.
+  Api _apiToUse = Api::EXECUTE;
 };
 
 /// @brief class ScatterNode
diff --git a/arangod/Aql/EngineInfoContainerDBServerServerBased.cpp b/arangod/Aql/EngineInfoContainerDBServerServerBased.cpp
index 8503b41a42e5..99346d0445f6 100644
--- a/arangod/Aql/EngineInfoContainerDBServerServerBased.cpp
+++ b/arangod/Aql/EngineInfoContainerDBServerServerBased.cpp
@@ -325,7 +325,8 @@ Result EngineInfoContainerDBServerServerBased::buildEngines(
     TRI_ASSERT(infoBuilder.isOpenObject());
 
     infoBuilder.add(StaticStrings::SerializationFormat,
-                    VPackValue(static_cast<int>(aql::SerializationFormat::SHADOWROWS)));
+                    VPackValue(static_cast<SerializationFormatType>(
+                        aql::SerializationFormat::SHADOWROWS)));
     infoBuilder.close();  // Base object
     TRI_ASSERT(infoBuilder.isClosed());
 
diff --git a/arangod/Aql/RestAqlHandler.cpp b/arangod/Aql/RestAqlHandler.cpp
index e0cc8ab6ee0a..facdf4d8d802 100644
--- a/arangod/Aql/RestAqlHandler.cpp
+++ b/arangod/Aql/RestAqlHandler.cpp
@@ -188,9 +188,10 @@ void RestAqlHandler::setupClusterQuery() {
   }
   // If we have a new format then it has to be included here.
   // If not default to classic (old coordinator will not send it)
-  SerializationFormat format = static_cast<SerializationFormat>(
-      VelocyPackHelper::getNumericValue<int>(querySlice, StaticStrings::SerializationFormat,
-                                             static_cast<int>(SerializationFormat::CLASSIC)));
+  auto format = static_cast<SerializationFormat>(
+      VelocyPackHelper::getNumericValue<SerializationFormatType>(
+          querySlice, StaticStrings::SerializationFormat,
+          static_cast<SerializationFormatType>(SerializationFormat::CLASSIC)));
   // Now we need to create shared_ptr<VPackBuilder>
   // That contains the old-style cluster snippet in order
   // to prepare create a Query object.
diff --git a/lib/Basics/StaticStrings.cpp b/lib/Basics/StaticStrings.cpp
index 509dbaf52595..4962b624889b 100644
--- a/lib/Basics/StaticStrings.cpp
+++ b/lib/Basics/StaticStrings.cpp
@@ -295,6 +295,7 @@ std::string const StaticStrings::BackupToDeleteName("DIRECTORY_TO_DELETE");
 std::string const StaticStrings::BackupSearchToDeleteName(
     "DIRECTORY_TO_DELETE_SEARCH");
 std::string const StaticStrings::SerializationFormat("serializationFormat");
+std::string const StaticStrings::AqlRemoteApi("api");
 
 // validation
 std::string const StaticStrings::ValidatorLevelNone("none");
diff --git a/lib/Basics/StaticStrings.h b/lib/Basics/StaticStrings.h
index 069922cf30a0..4591679174a3 100644
--- a/lib/Basics/StaticStrings.h
+++ b/lib/Basics/StaticStrings.h
@@ -271,6 +271,7 @@ class StaticStrings {
   static std::string const BackupToDeleteName;
   static std::string const BackupSearchToDeleteName;
   static std::string const SerializationFormat;
+  static std::string const AqlRemoteApi;
 
   // validation
   static std::string const ValidatorLevelNone;

From be42def57485897495748775990b8a3734ec7f91 Mon Sep 17 00:00:00 2001
From: Heiko <hkernbach@users.noreply.github.com>
Date: Thu, 27 Feb 2020 14:21:09 +0100
Subject: [PATCH 078/122] Feature/aql subquery operations stack i research view
 executor (#11140)

* added arangosearch view executor to new style

* added new produceRows and skipRowsRange

* ires

* test jenkins

* modify aql call

* cleanup branch

* Update arangod/Aql/IResearchViewExecutor.cpp

Co-Authored-By: Dronplane <andrei.lobov@arangodb.com>

* applied suggested changes

* also enable IResearchViewMergeExecutor

* Fixed an issue in skipRange, where the input was not moved forward in all cases.

* Removed unused local variables

Co-authored-by: Dronplane <andrei.lobov@arangodb.com>
Co-authored-by: Michael Hackstein <michael@arangodb.com>
---
 arangod/Aql/ExecutionBlockImpl.cpp    |  75 ++++--
 arangod/Aql/IResearchViewExecutor.cpp | 361 ++++++++++++++++----------
 arangod/Aql/IResearchViewExecutor.h   |  92 ++++---
 3 files changed, 339 insertions(+), 189 deletions(-)

diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index f246e366e2bc..3b6934601fac 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -134,19 +134,39 @@ constexpr bool is_one_of_v = (std::is_same_v<T, Es> || ...);
  * TODO: This should be removed once all executors and fetchers are ported to the new style.
  */
 template <typename Executor>
-constexpr bool isNewStyleExecutor =
-    is_one_of_v<Executor, FilterExecutor, SortedCollectExecutor, IdExecutor<ConstFetcher>,
-                IdExecutor<SingleRowFetcher<BlockPassthrough::Enable>>, ReturnExecutor, IndexExecutor, EnumerateCollectionExecutor,
-                /*
-                                CalculationExecutor<CalculationType::Condition>, CalculationExecutor<CalculationType::Reference>,
-                                CalculationExecutor<CalculationType::V8Condition>,*/
-                HashedCollectExecutor,
+constexpr bool isNewStyleExecutor = is_one_of_v<
+    Executor, FilterExecutor, SortedCollectExecutor, IdExecutor<ConstFetcher>,
+    IdExecutor<SingleRowFetcher<BlockPassthrough::Enable>>, ReturnExecutor, IndexExecutor, EnumerateCollectionExecutor,
+    /*
+                    CalculationExecutor<CalculationType::Condition>, CalculationExecutor<CalculationType::Reference>,
+                    CalculationExecutor<CalculationType::V8Condition>,*/
+    HashedCollectExecutor,
 #ifdef ARANGODB_USE_GOOGLE_TESTS
-                TestLambdaExecutor,
-                TestLambdaSkipExecutor,  // we need one after these to avoid compile errors in non-test mode
+    TestLambdaExecutor,
+    TestLambdaSkipExecutor,  // we need one after these to avoid compile errors in non-test mode
 #endif
-                SubqueryStartExecutor, SubqueryEndExecutor, TraversalExecutor, KShortestPathsExecutor,
-                ShortestPathExecutor, EnumerateListExecutor, LimitExecutor>;
+    IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::NotMaterialize>,
+    IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::LateMaterialize>,
+    IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::Materialize>,
+    IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::NotMaterialize | arangodb::iresearch::MaterializeType::UseStoredValues>,
+    IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::LateMaterialize | arangodb::iresearch::MaterializeType::UseStoredValues>,
+    IResearchViewExecutor<true, arangodb::iresearch::MaterializeType::NotMaterialize>,
+    IResearchViewExecutor<true, arangodb::iresearch::MaterializeType::LateMaterialize>,
+    IResearchViewExecutor<true, arangodb::iresearch::MaterializeType::Materialize>,
+    IResearchViewExecutor<true, arangodb::iresearch::MaterializeType::NotMaterialize | arangodb::iresearch::MaterializeType::UseStoredValues>,
+    IResearchViewExecutor<true, arangodb::iresearch::MaterializeType::LateMaterialize | arangodb::iresearch::MaterializeType::UseStoredValues>,
+    IResearchViewMergeExecutor<false, arangodb::iresearch::MaterializeType::NotMaterialize>,
+    IResearchViewMergeExecutor<false, arangodb::iresearch::MaterializeType::LateMaterialize>,
+    IResearchViewMergeExecutor<false, arangodb::iresearch::MaterializeType::Materialize>,
+    IResearchViewMergeExecutor<false, arangodb::iresearch::MaterializeType::NotMaterialize | arangodb::iresearch::MaterializeType::UseStoredValues>,
+    IResearchViewMergeExecutor<false, arangodb::iresearch::MaterializeType::LateMaterialize | arangodb::iresearch::MaterializeType::UseStoredValues>,
+    IResearchViewMergeExecutor<true, arangodb::iresearch::MaterializeType::NotMaterialize>,
+    IResearchViewMergeExecutor<true, arangodb::iresearch::MaterializeType::LateMaterialize>,
+    IResearchViewMergeExecutor<true, arangodb::iresearch::MaterializeType::Materialize>,
+    IResearchViewMergeExecutor<true, arangodb::iresearch::MaterializeType::NotMaterialize | arangodb::iresearch::MaterializeType::UseStoredValues>,
+    IResearchViewMergeExecutor<true, arangodb::iresearch::MaterializeType::LateMaterialize | arangodb::iresearch::MaterializeType::UseStoredValues>,
+    SubqueryStartExecutor, SubqueryEndExecutor, TraversalExecutor, KShortestPathsExecutor,
+    ShortestPathExecutor, EnumerateListExecutor, LimitExecutor>;
 
 template <class Executor>
 ExecutionBlockImpl<Executor>::ExecutionBlockImpl(ExecutionEngine* engine,
@@ -1099,14 +1119,35 @@ static SkipRowsRangeVariant constexpr skipRowsType() {
 
   static_assert(
       useExecutor ==
-          (is_one_of_v<Executor, FilterExecutor, ShortestPathExecutor, ReturnExecutor, KShortestPathsExecutor,
-                       IdExecutor<SingleRowFetcher<BlockPassthrough::Enable>>,
-                       IdExecutor<ConstFetcher>, HashedCollectExecutor, IndexExecutor, EnumerateCollectionExecutor,
+          (is_one_of_v<
+              Executor, FilterExecutor, ShortestPathExecutor, ReturnExecutor, KShortestPathsExecutor,
+              IdExecutor<SingleRowFetcher<BlockPassthrough::Enable>>, IdExecutor<ConstFetcher>,
+              HashedCollectExecutor, IndexExecutor, EnumerateCollectionExecutor,
 #ifdef ARANGODB_USE_GOOGLE_TESTS
-                       TestLambdaSkipExecutor,
+              TestLambdaSkipExecutor,
 #endif
-                       TraversalExecutor, EnumerateListExecutor, SubqueryStartExecutor,
-                       SubqueryEndExecutor, SortedCollectExecutor, LimitExecutor>),
+              IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::NotMaterialize>,
+              IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::LateMaterialize>,
+              IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::Materialize>,
+              IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::NotMaterialize | arangodb::iresearch::MaterializeType::UseStoredValues>,
+              IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::LateMaterialize | arangodb::iresearch::MaterializeType::UseStoredValues>,
+              IResearchViewExecutor<true, arangodb::iresearch::MaterializeType::NotMaterialize>,
+              IResearchViewExecutor<true, arangodb::iresearch::MaterializeType::LateMaterialize>,
+              IResearchViewExecutor<true, arangodb::iresearch::MaterializeType::Materialize>,
+              IResearchViewExecutor<true, arangodb::iresearch::MaterializeType::NotMaterialize | arangodb::iresearch::MaterializeType::UseStoredValues>,
+              IResearchViewExecutor<true, arangodb::iresearch::MaterializeType::LateMaterialize | arangodb::iresearch::MaterializeType::UseStoredValues>,
+              IResearchViewMergeExecutor<false, arangodb::iresearch::MaterializeType::NotMaterialize>,
+              IResearchViewMergeExecutor<false, arangodb::iresearch::MaterializeType::LateMaterialize>,
+              IResearchViewMergeExecutor<false, arangodb::iresearch::MaterializeType::Materialize>,
+              IResearchViewMergeExecutor<false, arangodb::iresearch::MaterializeType::NotMaterialize | arangodb::iresearch::MaterializeType::UseStoredValues>,
+              IResearchViewMergeExecutor<false, arangodb::iresearch::MaterializeType::LateMaterialize | arangodb::iresearch::MaterializeType::UseStoredValues>,
+              IResearchViewMergeExecutor<true, arangodb::iresearch::MaterializeType::NotMaterialize>,
+              IResearchViewMergeExecutor<true, arangodb::iresearch::MaterializeType::LateMaterialize>,
+              IResearchViewMergeExecutor<true, arangodb::iresearch::MaterializeType::Materialize>,
+              IResearchViewMergeExecutor<true, arangodb::iresearch::MaterializeType::NotMaterialize | arangodb::iresearch::MaterializeType::UseStoredValues>,
+              IResearchViewMergeExecutor<true, arangodb::iresearch::MaterializeType::LateMaterialize | arangodb::iresearch::MaterializeType::UseStoredValues>,
+              TraversalExecutor, EnumerateListExecutor, SubqueryStartExecutor,
+              SubqueryEndExecutor, SortedCollectExecutor, LimitExecutor>),
       "Unexpected executor for SkipVariants::EXECUTOR");
 
   // The LimitExecutor will not work correctly with SkipVariants::FETCHER!
diff --git a/arangod/Aql/IResearchViewExecutor.cpp b/arangod/Aql/IResearchViewExecutor.cpp
index 4fcba5946ae6..5bd3cdc8d7d5 100644
--- a/arangod/Aql/IResearchViewExecutor.cpp
+++ b/arangod/Aql/IResearchViewExecutor.cpp
@@ -24,9 +24,10 @@
 #include "IResearchViewExecutor.h"
 
 #include "Aql/ExecutionStats.h"
+#include "Aql/OutputAqlItemRow.h"
 #include "Aql/Query.h"
 #include "Aql/SingleRowFetcher.h"
-#include "Aql/OutputAqlItemRow.h"
+#include "AqlCall.h"
 #include "IResearch/IResearchCommon.h"
 #include "IResearch/IResearchDocument.h"
 #include "IResearch/IResearchFilterFactory.h"
@@ -95,7 +96,8 @@ inline irs::columnstore_reader::values_reader_f sortColumn(irs::sub_reader const
   return reader ? reader->values() : irs::columnstore_reader::values_reader_f{};
 }
 
-inline std::pair<ptrdiff_t, IResearchViewNode::ViewValuesRegisters::const_iterator> getStoredColumnsInfo(IResearchViewNode::ViewValuesRegisters const& columnsFieldsRegs) {
+inline std::pair<ptrdiff_t, IResearchViewNode::ViewValuesRegisters::const_iterator> getStoredColumnsInfo(
+    IResearchViewNode::ViewValuesRegisters const& columnsFieldsRegs) {
   auto max = (--columnsFieldsRegs.cend())->first;
   TRI_ASSERT(max >= IResearchViewNode::SortColumnNumber);
   auto columnFieldsRegs = columnsFieldsRegs.cbegin();
@@ -116,11 +118,10 @@ IResearchViewExecutorInfos::IResearchViewExecutorInfos(
     RegisterId firstOutputRegister, RegisterId numScoreRegisters, Query& query,
     std::vector<Scorer> const& scorers,
     std::pair<arangodb::iresearch::IResearchViewSort const*, size_t> const& sort,
-    IResearchViewStoredValues const& storedValues,
-    ExecutionPlan const& plan, Variable const& outVariable,
-    aql::AstNode const& filterCondition, std::pair<bool, bool> volatility,
-    IResearchViewExecutorInfos::VarInfoMap const& varInfoMap, int depth,
-    IResearchViewNode::ViewValuesRegisters&& outNonMaterializedViewRegs)
+    IResearchViewStoredValues const& storedValues, ExecutionPlan const& plan,
+    Variable const& outVariable, aql::AstNode const& filterCondition,
+    std::pair<bool, bool> volatility, IResearchViewExecutorInfos::VarInfoMap const& varInfoMap,
+    int depth, IResearchViewNode::ViewValuesRegisters&& outNonMaterializedViewRegs)
     : ExecutorInfos(std::move(infos)),
       _firstOutputRegister(firstOutputRegister),
       _numScoreRegisters(numScoreRegisters),
@@ -151,7 +152,8 @@ RegisterId IResearchViewExecutorInfos::getNumScoreRegisters() const noexcept {
   return _numScoreRegisters;
 }
 
-IResearchViewNode::ViewValuesRegisters const& IResearchViewExecutorInfos::getOutNonMaterializedViewRegs() const noexcept {
+IResearchViewNode::ViewValuesRegisters const& IResearchViewExecutorInfos::getOutNonMaterializedViewRegs() const
+    noexcept {
   return _outNonMaterializedViewRegs;
 }
 
@@ -209,8 +211,8 @@ IResearchViewStoredValues const& IResearchViewExecutorInfos::storedValues() cons
 }
 
 bool IResearchViewExecutorInfos::isScoreReg(RegisterId reg) const noexcept {
-  return getNumScoreRegisters() > 0 &&
-         getFirstScoreRegister() <= reg && reg < getFirstScoreRegister() + getNumScoreRegisters();
+  return getNumScoreRegisters() > 0 && getFirstScoreRegister() <= reg &&
+         reg < getFirstScoreRegister() + getNumScoreRegisters();
 }
 
 IResearchViewStats::IResearchViewStats() noexcept : _scannedIndex(0) {}
@@ -301,7 +303,7 @@ std::vector<AqlValue>::iterator IResearchViewExecutorBase<Impl, Traits>::IndexRe
 template <typename Impl, typename Traits>
 template <typename ValueType>
 IResearchViewExecutorBase<Impl, Traits>::IndexReadBuffer<ValueType>::IndexReadBuffer(std::size_t const numScoreRegisters)
-  : _numScoreRegisters(numScoreRegisters), _keyBaseIdx(0) {}
+    : _numScoreRegisters(numScoreRegisters), _keyBaseIdx(0) {}
 
 template <typename Impl, typename Traits>
 template <typename ValueType>
@@ -330,7 +332,8 @@ void IResearchViewExecutorBase<Impl, Traits>::IndexReadBuffer<ValueType>::pushVa
 
 template <typename Impl, typename Traits>
 template <typename ValueType>
-void IResearchViewExecutorBase<Impl, Traits>::IndexReadBuffer<ValueType>::pushStoredValue(std::vector<irs::bytes_ref>&& storedValue) {
+void IResearchViewExecutorBase<Impl, Traits>::IndexReadBuffer<ValueType>::pushStoredValue(
+    std::vector<irs::bytes_ref>&& storedValue) {
   _storedValueBuffer.emplace_back(std::move(storedValue));
 }
 
@@ -401,11 +404,9 @@ void IResearchViewExecutorBase<Impl, Traits>::IndexReadBuffer<ValueType>::assert
 
 template <typename Impl, typename Traits>
 IResearchViewExecutorBase<Impl, Traits>::IResearchViewExecutorBase(
-    IResearchViewExecutorBase::Fetcher& fetcher, IResearchViewExecutorBase::Infos& infos)
+    IResearchViewExecutorBase::Fetcher&, IResearchViewExecutorBase::Infos& infos)
     : _infos(infos),
-      _fetcher(fetcher),
-      _inputRow(CreateInvalidInputRowHint{}),
-      _upstreamState(ExecutionState::HASMORE),
+      _inputRow(CreateInvalidInputRowHint{}),  // TODO: Remove me after refactor
       _indexReadBuffer(_infos.getNumScoreRegisters()),
       _filterCtx(1),  // arangodb::iresearch::ExpressionExecutionContext
       _ctx(&infos.getQuery(), infos.numberOfOutputRegisters(),
@@ -413,8 +414,6 @@ IResearchViewExecutorBase<Impl, Traits>::IResearchViewExecutorBase(
       _reader(infos.getReader()),
       _filter(irs::filter::prepared::empty()),
       _execCtx(*infos.getQuery().trx(), _ctx),
-      _inflight(0),
-      _hasMore(true),  // has more data initially
       _isInitialized(false) {
   TRI_ASSERT(infos.getQuery().trx() != nullptr);
 
@@ -425,87 +424,102 @@ IResearchViewExecutorBase<Impl, Traits>::IResearchViewExecutorBase(
 template <typename Impl, typename Traits>
 std::pair<ExecutionState, typename IResearchViewExecutorBase<Impl, Traits>::Stats>
 IResearchViewExecutorBase<Impl, Traits>::produceRows(OutputAqlItemRow& output) {
+  TRI_ASSERT(false);
+  THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
+}
+
+template <typename Impl, typename Traits>
+std::tuple<ExecutorState, typename IResearchViewExecutorBase<Impl, Traits>::Stats, AqlCall>
+IResearchViewExecutorBase<Impl, Traits>::produceRows(AqlItemBlockInputRange& inputRange,
+                                                     OutputAqlItemRow& output) {
   IResearchViewStats stats{};
-  bool documentWritten = false;
+  AqlCall upstreamCall{};
+  upstreamCall.fullCount = output.getClientCall().fullCount;
 
-  while (!documentWritten) {
-    if (!_inputRow.isInitialized()) {
-      if (_upstreamState == ExecutionState::DONE) {
-        // There will be no more rows, stop fetching.
-        return {ExecutionState::DONE, stats};
-      }
+  while (inputRange.hasDataRow() && !output.isFull()) {
+    bool documentWritten = false;
 
-      std::tie(_upstreamState, _inputRow) = _fetcher.fetchRow();
+    while (!documentWritten) {
+      if (!_inputRow.isInitialized()) {
+        std::tie(std::ignore, _inputRow) = inputRange.peekDataRow();
 
-      if (_upstreamState == ExecutionState::WAITING) {
-        return {_upstreamState, stats};
-      }
+        if (!_inputRow.isInitialized()) {
+          return {ExecutorState::DONE, stats, upstreamCall};
+        }
 
-      if (!_inputRow.isInitialized()) {
-        return {ExecutionState::DONE, stats};
+        // reset must be called exactly after we've got a new and valid input row.
+        static_cast<Impl&>(*this).reset();
       }
 
-      // reset must be called exactly after we've got a new and valid input row.
-      static_cast<Impl&>(*this).reset();
-    }
-
-    ReadContext ctx(infos().getOutputRegister(), _inputRow, output);
-    documentWritten = next(ctx);
+      ReadContext ctx(infos().getOutputRegister(), _inputRow, output);
+      documentWritten = next(ctx);
 
-    if (documentWritten) {
-      stats.incrScanned();
-    } else {
-      _inputRow = InputAqlItemRow{CreateInvalidInputRowHint{}};
-      // no document written, repeat.
+      if (documentWritten) {
+        stats.incrScanned();
+        output.advanceRow();
+      } else {
+        _inputRow = InputAqlItemRow{CreateInvalidInputRowHint{}};
+        std::ignore = inputRange.nextDataRow();
+        // no document written, repeat.
+      }
     }
   }
 
-  return {ExecutionState::HASMORE, stats};
+  return {inputRange.upstreamState(), stats, upstreamCall};
 }
 
 template <typename Impl, typename Traits>
 std::tuple<ExecutionState, typename IResearchViewExecutorBase<Impl, Traits>::Stats, size_t>
 IResearchViewExecutorBase<Impl, Traits>::skipRows(size_t toSkip) {
-  TRI_ASSERT(_indexReadBuffer.empty());
-  IResearchViewStats stats{};
-  size_t skipped = 0;
+  TRI_ASSERT(false);
+  THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
+}
 
+template <typename Impl, typename Traits>
+std::tuple<ExecutorState, typename IResearchViewExecutorBase<Impl, Traits>::Stats, size_t, AqlCall>
+IResearchViewExecutorBase<Impl, Traits>::skipRowsRange(AqlItemBlockInputRange& inputRange,
+                                                       AqlCall& call) {
+  TRI_ASSERT(_indexReadBuffer.empty());
   auto& impl = static_cast<Impl&>(*this);
 
-  if (!_inputRow.isInitialized()) {
-    if (_upstreamState == ExecutionState::DONE) {
-      // There will be no more rows, stop fetching.
-      return std::make_tuple(ExecutionState::DONE, stats,
-                             0);  // tupple, cannot use initializer list due to build failure
-    }
+  while (inputRange.hasDataRow() && call.shouldSkip()) {
+    if (!_inputRow.isInitialized()) {
+      auto rowState = ExecutorState::HASMORE;
+      std::tie(rowState, _inputRow) = inputRange.peekDataRow();
 
-    std::tie(_upstreamState, _inputRow) = _fetcher.fetchRow();
+      if (!_inputRow.isInitialized()) {
+        TRI_ASSERT(rowState == ExecutorState::DONE);
+        break;
+      }
 
-    if (_upstreamState == ExecutionState::WAITING) {
-      return std::make_tuple(_upstreamState, stats, 0);  // tupple, cannot use initializer list due to build failure
+      // reset must be called exactly after we've got a new and valid input row.
+      impl.reset();
     }
-
-    if (!_inputRow.isInitialized()) {
-      return std::make_tuple(ExecutionState::DONE, stats,
-                             0);  // tupple, cannot use initializer list due to build failure
+    TRI_ASSERT(_inputRow.isInitialized());
+    if (call.getOffset() > 0) {
+      // OffsetPhase need to skip atMost offset
+      call.didSkip(impl.skip(call.getOffset()));
+    } else {
+      TRI_ASSERT(call.getLimit() == 0 && call.hasHardLimit());
+      // skip all - fullCount phase
+      call.didSkip(impl.skipAll());
     }
+    TRI_ASSERT(_indexReadBuffer.empty());
 
-    // reset must be called exactly after we've got a new and valid input row.
-    impl.reset();
+    if (call.shouldSkip()) {
+      // We still need to fetch more
+      // trigger refetch of new input row
+      std::ignore = inputRange.nextDataRow();
+      _inputRow = InputAqlItemRow{CreateInvalidInputRowHint{}};
+    }
   }
 
-  TRI_ASSERT(_inputRow.isInitialized());
-
-  skipped = static_cast<Impl&>(*this).skip(toSkip);
-  TRI_ASSERT(_indexReadBuffer.empty());
-  stats.incrScanned(skipped);
-
-  if (skipped < toSkip) {
-    _inputRow = InputAqlItemRow{CreateInvalidInputRowHint{}};
-  }
+  IResearchViewStats stats{};
+  stats.incrScanned(call.getSkipCount());
 
-  return std::make_tuple(ExecutionState::HASMORE, stats,
-                         skipped);  // tupple, cannot use initializer list due to build failure
+  AqlCall upstreamCall{};
+  upstreamCall.softLimit = call.getOffset() + std::min(call.softLimit, call.hardLimit);
+  return {inputRange.upstreamState(), stats, call.getSkipCount(), upstreamCall};
 }
 
 template <typename Impl, typename Traits>
@@ -619,26 +633,25 @@ void IResearchViewExecutorBase<Impl, Traits>::reset() {
   }
 }
 
-template<typename Impl, typename Traits>
+template <typename Impl, typename Traits>
 bool IResearchViewExecutorBase<Impl, Traits>::writeLocalDocumentId(
-    ReadContext& ctx,
-    LocalDocumentId const& documentId,
-    LogicalCollection const& collection) {
+    ReadContext& ctx, LocalDocumentId const& documentId, LogicalCollection const& collection) {
   // we will need collection Id also as View could produce documents from multiple collections
   if (ADB_LIKELY(documentId.isSet())) {
     {
       // For sake of performance we store raw pointer to collection
       // It is safe as pipeline work inside one process
-      static_assert(sizeof(void*) <= sizeof(uint64_t), "Pointer not fits in uint64_t");
+      static_assert(sizeof(void*) <= sizeof(uint64_t),
+                    "Pointer not fits in uint64_t");
       AqlValue a(AqlValueHintUInt(reinterpret_cast<uint64_t>(&collection)));
       bool mustDestroy = true;
-      AqlValueGuard guard{ a, mustDestroy };
+      AqlValueGuard guard{a, mustDestroy};
       ctx.outputRow.moveValueInto(ctx.getNmColPtrOutReg(), ctx.inputRow, guard);
     }
     {
       AqlValue a(AqlValueHintUInt(documentId.id()));
       bool mustDestroy = true;
-      AqlValueGuard guard{ a, mustDestroy };
+      AqlValueGuard guard{a, mustDestroy};
       ctx.outputRow.moveValueInto(ctx.getNmDocIdOutReg(), ctx.inputRow, guard);
     }
     return true;
@@ -647,9 +660,10 @@ bool IResearchViewExecutorBase<Impl, Traits>::writeLocalDocumentId(
   }
 }
 
-template<typename Impl, typename Traits>
-inline bool IResearchViewExecutorBase<Impl, Traits>::writeStoredValue(ReadContext& ctx, std::vector<irs::bytes_ref> const& storedValues,
-                                                                      size_t columnNum, std::map<size_t, RegisterId> const& fieldsRegs) {
+template <typename Impl, typename Traits>
+inline bool IResearchViewExecutorBase<Impl, Traits>::writeStoredValue(
+    ReadContext& ctx, std::vector<irs::bytes_ref> const& storedValues,
+    size_t columnNum, std::map<size_t, RegisterId> const& fieldsRegs) {
   TRI_ASSERT(columnNum < storedValues.size());
   auto const& storedValue = storedValues[columnNum];
   TRI_ASSERT(!storedValue.empty());
@@ -675,7 +689,7 @@ inline bool IResearchViewExecutorBase<Impl, Traits>::writeStoredValue(ReadContex
   return true;
 }
 
-template<typename Impl, typename Traits>
+template <typename Impl, typename Traits>
 bool IResearchViewExecutorBase<Impl, Traits>::writeRow(ReadContext& ctx,
                                                        IndexReadBufferEntry bufferEntry,
                                                        LocalDocumentId const& documentId,
@@ -683,29 +697,36 @@ bool IResearchViewExecutorBase<Impl, Traits>::writeRow(ReadContext& ctx,
   TRI_ASSERT(documentId.isSet());
   if constexpr (Traits::MaterializeType == MaterializeType::Materialize) {
     // read document from underlying storage engine, if we got an id
-    if (!collection.readDocumentWithCallback(infos().getQuery().trx(), documentId, ctx.callback)) {
+    if (!collection.readDocumentWithCallback(infos().getQuery().trx(),
+                                             documentId, ctx.callback)) {
       return false;
     }
-  } else if ((Traits::MaterializeType & MaterializeType::LateMaterialize) == MaterializeType::LateMaterialize) {
+  } else if ((Traits::MaterializeType & MaterializeType::LateMaterialize) ==
+             MaterializeType::LateMaterialize) {
     // no need to look into collection. Somebody down the stream will do materialization. Just emit LocalDocumentIds
     if (!writeLocalDocumentId(ctx, documentId, collection)) {
       return false;
     }
   }
-  if constexpr ((Traits::MaterializeType & MaterializeType::UseStoredValues) == MaterializeType::UseStoredValues) {
+  if constexpr ((Traits::MaterializeType & MaterializeType::UseStoredValues) ==
+                MaterializeType::UseStoredValues) {
     auto const& columnsFieldsRegs = infos().getOutNonMaterializedViewRegs();
     TRI_ASSERT(!columnsFieldsRegs.empty());
     auto columsInfo = getStoredColumnsInfo(columnsFieldsRegs);
     auto& columnFieldsRegs = columsInfo.second;
     auto const& storedValues = _indexReadBuffer.getStoredValue(bufferEntry);
     if (IResearchViewNode::SortColumnNumber == columnFieldsRegs->first) {
-      if (ADB_UNLIKELY(!writeStoredValue(ctx, storedValues, static_cast<size_t>(columsInfo.first), columnFieldsRegs->second))) {
+      if (ADB_UNLIKELY(!writeStoredValue(ctx, storedValues,
+                                         static_cast<size_t>(columsInfo.first),
+                                         columnFieldsRegs->second))) {
         return false;
       }
       ++columnFieldsRegs;
     }
     for (; columnFieldsRegs != columnsFieldsRegs.cend(); ++columnFieldsRegs) {
-      if (ADB_UNLIKELY(!writeStoredValue(ctx, storedValues, static_cast<size_t>(columnFieldsRegs->first), columnFieldsRegs->second))) {
+      if (ADB_UNLIKELY(!writeStoredValue(ctx, storedValues,
+                                         static_cast<size_t>(columnFieldsRegs->first),
+                                         columnFieldsRegs->second))) {
         return false;
       }
     }
@@ -734,9 +755,10 @@ bool IResearchViewExecutorBase<Impl, Traits>::writeRow(ReadContext& ctx,
   return true;
 }
 
-template<typename Impl, typename Traits>
-void IResearchViewExecutorBase<Impl, Traits>::getStoredValue(irs::document const& doc, std::vector<irs::bytes_ref>& storedValue, size_t index,
-                                                             std::vector<irs::columnstore_reader::values_reader_f> const& storedValuesReaders) {
+template <typename Impl, typename Traits>
+void IResearchViewExecutorBase<Impl, Traits>::getStoredValue(
+    irs::document const& doc, std::vector<irs::bytes_ref>& storedValue, size_t index,
+    std::vector<irs::columnstore_reader::values_reader_f> const& storedValuesReaders) {
   irs::columnstore_reader::values_reader_f reader = storedValuesReaders[index];
   TRI_ASSERT(reader);
   auto ok = reader(doc.value, storedValue[index]);
@@ -746,9 +768,10 @@ void IResearchViewExecutorBase<Impl, Traits>::getStoredValue(irs::document const
   }
 }
 
-template<typename Impl, typename Traits>
-void IResearchViewExecutorBase<Impl, Traits>::pushStoredValues(irs::document const& doc,
-                                                               std::vector<irs::columnstore_reader::values_reader_f> const& storedValuesReaders) {
+template <typename Impl, typename Traits>
+void IResearchViewExecutorBase<Impl, Traits>::pushStoredValues(
+    irs::document const& doc,
+    std::vector<irs::columnstore_reader::values_reader_f> const& storedValuesReaders) {
   auto const& columnsFieldsRegs = this->_infos.getOutNonMaterializedViewRegs();
   TRI_ASSERT(!columnsFieldsRegs.empty());
   auto columsInfo = getStoredColumnsInfo(columnsFieldsRegs);
@@ -760,14 +783,16 @@ void IResearchViewExecutorBase<Impl, Traits>::pushStoredValues(irs::document con
     ++columnFieldsRegs;
   }
   for (; columnFieldsRegs != columnsFieldsRegs.cend(); ++columnFieldsRegs) {
-    getStoredValue(doc, storedValue, static_cast<size_t>(columnFieldsRegs->first), storedValuesReaders);
+    getStoredValue(doc, storedValue, static_cast<size_t>(columnFieldsRegs->first),
+                   storedValuesReaders);
   }
   this->_indexReadBuffer.pushStoredValue(std::move(storedValue));
 }
 
-template<typename Impl, typename Traits>
-bool IResearchViewExecutorBase<Impl, Traits>::getStoredValuesReaders(irs::sub_reader const& segmentReader,
-                                                                     std::vector<irs::columnstore_reader::values_reader_f>& storedValuesReaders) {
+template <typename Impl, typename Traits>
+bool IResearchViewExecutorBase<Impl, Traits>::getStoredValuesReaders(
+    irs::sub_reader const& segmentReader,
+    std::vector<irs::columnstore_reader::values_reader_f>& storedValuesReaders) {
   auto const& columnsFieldsRegs = this->_infos.getOutNonMaterializedViewRegs();
   if (!columnsFieldsRegs.empty()) {
     auto columsInfo = getStoredColumnsInfo(columnsFieldsRegs);
@@ -792,14 +817,16 @@ bool IResearchViewExecutorBase<Impl, Traits>::getStoredValuesReaders(irs::sub_re
         auto const& columns = storedValues.columns();
         auto const storedColumnNumber = static_cast<size_t>(columnFieldsRegs->first);
         TRI_ASSERT(storedColumnNumber < columns.size());
-        auto storedValuesReader = segmentReader.column_reader(columns[storedColumnNumber].name);
+        auto storedValuesReader =
+            segmentReader.column_reader(columns[storedColumnNumber].name);
         if (!storedValuesReader) {
           LOG_TOPIC("af7ec", WARN, arangodb::iresearch::TOPIC)
               << "encountered a sub-reader without a stored value column while "
                  "executing a query, ignoring";
           return false;
         }
-        storedValuesReaders[static_cast<size_t>(columnFieldsRegs->first)] = storedValuesReader->values();
+        storedValuesReaders[static_cast<size_t>(columnFieldsRegs->first)] =
+            storedValuesReader->values();
       }
     }
   }
@@ -811,7 +838,8 @@ bool IResearchViewExecutorBase<Impl, Traits>::getStoredValuesReaders(irs::sub_re
 ///////////////////////////////////////////////////////////////////////////////
 
 template <bool ordered, MaterializeType materializeType>
-IResearchViewExecutor<ordered, materializeType>::IResearchViewExecutor(Fetcher& fetcher, Infos& infos)
+IResearchViewExecutor<ordered, materializeType>::IResearchViewExecutor(Fetcher& fetcher,
+                                                                       Infos& infos)
     : Base(fetcher, infos),
       _pkReader(),
       _itr(),
@@ -836,7 +864,7 @@ void IResearchViewExecutor<ordered, materializeType>::evaluateScores(ReadContext
   this->fillScores(ctx, begin, end);
 }
 
-template<bool ordered, MaterializeType materializeType>
+template <bool ordered, MaterializeType materializeType>
 bool IResearchViewExecutor<ordered, materializeType>::readPK(LocalDocumentId& documentId) {
   TRI_ASSERT(!documentId.isSet());
   TRI_ASSERT(_itr);
@@ -938,7 +966,8 @@ void IResearchViewExecutor<ordered, materializeType>::fillBuffer(IResearchViewEx
       evaluateScores(ctx);
     }
 
-    if constexpr ((materializeType & MaterializeType::UseStoredValues) == MaterializeType::UseStoredValues) {
+    if constexpr ((materializeType & MaterializeType::UseStoredValues) ==
+                  MaterializeType::UseStoredValues) {
       TRI_ASSERT(_doc);
       this->pushStoredValues(*_doc, _storedValuesReaders);
     }
@@ -977,7 +1006,8 @@ bool IResearchViewExecutor<ordered, materializeType>::resetIterator() {
     return false;
   }
 
-  if constexpr ((materializeType & MaterializeType::UseStoredValues) == MaterializeType::UseStoredValues) {
+  if constexpr ((materializeType & MaterializeType::UseStoredValues) ==
+                MaterializeType::UseStoredValues) {
     if (ADB_UNLIKELY(!this->getStoredValuesReaders(segmentReader, _storedValuesReaders))) {
       return false;
     }
@@ -1045,6 +1075,37 @@ size_t IResearchViewExecutor<ordered, materializeType>::skip(size_t limit) {
     _doc = nullptr;
   }
 
+  saveCollection();
+
+  return toSkip - limit;
+}
+
+template <bool ordered, MaterializeType materializeType>
+size_t IResearchViewExecutor<ordered, materializeType>::skipAll() {
+  TRI_ASSERT(this->_indexReadBuffer.empty());
+  TRI_ASSERT(this->_filter);
+
+  size_t skipped = 0;
+
+  for (size_t count = this->_reader->size(); _readerOffset < count;) {
+    if (!_itr && !resetIterator()) {
+      continue;
+    }
+
+    while (_itr->next()) {
+      skipped++;
+    }
+
+    ++_readerOffset;
+    _itr.reset();
+    _doc = nullptr;
+  }
+
+  return skipped;
+}
+
+template <bool ordered, MaterializeType materializeType>
+void IResearchViewExecutor<ordered, materializeType>::saveCollection() {
   // We're in the middle of a reader, save the collection in case produceRows()
   // needs it.
   if (_itr) {
@@ -1071,13 +1132,12 @@ size_t IResearchViewExecutor<ordered, materializeType>::skip(size_t limit) {
     this->_indexReadBuffer.reset();
     _collection = collection.get();
   }
-
-  return toSkip - limit;
 }
 
 template <bool ordered, MaterializeType materializeType>
-bool IResearchViewExecutor<ordered, materializeType>::writeRow(IResearchViewExecutor::ReadContext& ctx,
-                                              IResearchViewExecutor::IndexReadBufferEntry bufferEntry) {
+bool IResearchViewExecutor<ordered, materializeType>::writeRow(
+    IResearchViewExecutor::ReadContext& ctx,
+    IResearchViewExecutor::IndexReadBufferEntry bufferEntry) {
   TRI_ASSERT(_collection);
 
   return Base::writeRow(ctx, bufferEntry,
@@ -1089,7 +1149,8 @@ bool IResearchViewExecutor<ordered, materializeType>::writeRow(IResearchViewExec
 ///////////////////////////////////////////////////////////////////////////////
 
 template <bool ordered, MaterializeType materializeType>
-IResearchViewMergeExecutor<ordered, materializeType>::IResearchViewMergeExecutor(Fetcher& fetcher, Infos& infos)
+IResearchViewMergeExecutor<ordered, materializeType>::IResearchViewMergeExecutor(Fetcher& fetcher,
+                                                                                 Infos& infos)
     : Base{fetcher, infos},
       _heap_it{MinHeapContext{*infos.sort().first, infos.sort().second, _segments}} {
   TRI_ASSERT(infos.sort().first);
@@ -1101,9 +1162,8 @@ IResearchViewMergeExecutor<ordered, materializeType>::IResearchViewMergeExecutor
 
 template <bool ordered, MaterializeType materializeType>
 IResearchViewMergeExecutor<ordered, materializeType>::Segment::Segment(
-    irs::doc_iterator::ptr&& docs, irs::document const& doc,
-    irs::score const& score, LogicalCollection const& collection,
-    irs::columnstore_reader::values_reader_f&& pkReader,
+    irs::doc_iterator::ptr&& docs, irs::document const& doc, irs::score const& score,
+    LogicalCollection const& collection, irs::columnstore_reader::values_reader_f&& pkReader,
     std::vector<irs::columnstore_reader::values_reader_f>&& storedValuesReaders) noexcept
     : docs(std::move(docs)),
       doc(&doc),
@@ -1141,16 +1201,16 @@ bool IResearchViewMergeExecutor<ordered, materializeType>::MinHeapContext::opera
 }
 
 template <bool ordered, MaterializeType materializeType>
-bool IResearchViewMergeExecutor<ordered, materializeType>::MinHeapContext::operator()(const size_t lhs,
-                                                                     const size_t rhs) const {
+bool IResearchViewMergeExecutor<ordered, materializeType>::MinHeapContext::operator()(
+    const size_t lhs, const size_t rhs) const {
   assert(lhs < _segments->size());
   assert(rhs < _segments->size());
   return _less((*_segments)[rhs].sortValue, (*_segments)[lhs].sortValue);
 }
 
 template <bool ordered, MaterializeType materializeType>
-void IResearchViewMergeExecutor<ordered, materializeType>::evaluateScores(ReadContext const& ctx,
-                                                         irs::score const& score) {
+void IResearchViewMergeExecutor<ordered, materializeType>::evaluateScores(
+    ReadContext const& ctx, irs::score const& score) {
   // This must not be called in the unordered case.
   TRI_ASSERT(ordered);
 
@@ -1227,7 +1287,8 @@ void IResearchViewMergeExecutor<ordered, materializeType>::reset() {
     }
 
     std::vector<irs::columnstore_reader::values_reader_f> storedValuesReaders;
-    if constexpr ((materializeType & MaterializeType::UseStoredValues) == MaterializeType::UseStoredValues) {
+    if constexpr ((materializeType & MaterializeType::UseStoredValues) ==
+                  MaterializeType::UseStoredValues) {
       if (ADB_UNLIKELY(!this->getStoredValuesReaders(segment, storedValuesReaders))) {
         continue;
       }
@@ -1235,7 +1296,8 @@ void IResearchViewMergeExecutor<ordered, materializeType>::reset() {
     // add sortReader if it has not been added yet
     // sortReader is the last item
     auto const& columnsFieldsRegs = this->_infos.getOutNonMaterializedViewRegs();
-    if (columnsFieldsRegs.empty() || columnsFieldsRegs.cbegin()->first != IResearchViewNode::SortColumnNumber) {
+    if (columnsFieldsRegs.empty() ||
+        columnsFieldsRegs.cbegin()->first != IResearchViewNode::SortColumnNumber) {
       auto sortReader = ::sortColumn(segment);
 
       if (!sortReader) {
@@ -1305,7 +1367,8 @@ void IResearchViewMergeExecutor<ordered, materializeType>::fillBuffer(ReadContex
       evaluateScores(ctx, *segment.score);
     }
 
-    if constexpr ((materializeType & MaterializeType::UseStoredValues) == MaterializeType::UseStoredValues) {
+    if constexpr ((materializeType & MaterializeType::UseStoredValues) ==
+                  MaterializeType::UseStoredValues) {
       TRI_ASSERT(segment.doc);
       this->pushStoredValues(*segment.doc, segment.storedValuesReaders);
     }
@@ -1333,6 +1396,20 @@ size_t IResearchViewMergeExecutor<ordered, materializeType>::skip(size_t limit)
   return toSkip - limit;
 }
 
+template <bool ordered, MaterializeType materializeType>
+size_t IResearchViewMergeExecutor<ordered, materializeType>::skipAll() {
+  TRI_ASSERT(this->_indexReadBuffer.empty());
+  TRI_ASSERT(this->_filter != nullptr);
+
+  size_t skipped = 0;
+
+  while (_heap_it.next()) {
+    skipped++;
+  }
+
+  return skipped;
+}
+
 template <bool ordered, MaterializeType materializeType>
 bool IResearchViewMergeExecutor<ordered, materializeType>::writeRow(
     IResearchViewMergeExecutor::ReadContext& ctx,
@@ -1377,23 +1454,37 @@ template class ::arangodb::aql::IResearchViewMergeExecutor<true, MaterializeType
 template class ::arangodb::aql::IResearchViewExecutorBase<::arangodb::aql::IResearchViewExecutor<false, MaterializeType::NotMaterialize>>;
 template class ::arangodb::aql::IResearchViewExecutorBase<::arangodb::aql::IResearchViewExecutor<false, MaterializeType::LateMaterialize>>;
 template class ::arangodb::aql::IResearchViewExecutorBase<::arangodb::aql::IResearchViewExecutor<false, MaterializeType::Materialize>>;
-template class ::arangodb::aql::IResearchViewExecutorBase<::arangodb::aql::IResearchViewExecutor<false, MaterializeType::NotMaterialize | MaterializeType::UseStoredValues>>;
-template class ::arangodb::aql::IResearchViewExecutorBase<::arangodb::aql::IResearchViewExecutor<false, MaterializeType::LateMaterialize | MaterializeType::UseStoredValues>>;
+template class ::arangodb::aql::IResearchViewExecutorBase<
+    ::arangodb::aql::IResearchViewExecutor<false, MaterializeType::NotMaterialize | MaterializeType::UseStoredValues>>;
+template class ::arangodb::aql::IResearchViewExecutorBase<
+    ::arangodb::aql::IResearchViewExecutor<false, MaterializeType::LateMaterialize | MaterializeType::UseStoredValues>>;
 
 template class ::arangodb::aql::IResearchViewExecutorBase<::arangodb::aql::IResearchViewExecutor<true, MaterializeType::NotMaterialize>>;
 template class ::arangodb::aql::IResearchViewExecutorBase<::arangodb::aql::IResearchViewExecutor<true, MaterializeType::LateMaterialize>>;
 template class ::arangodb::aql::IResearchViewExecutorBase<::arangodb::aql::IResearchViewExecutor<true, MaterializeType::Materialize>>;
-template class ::arangodb::aql::IResearchViewExecutorBase<::arangodb::aql::IResearchViewExecutor<true, MaterializeType::NotMaterialize | MaterializeType::UseStoredValues>>;
-template class ::arangodb::aql::IResearchViewExecutorBase<::arangodb::aql::IResearchViewExecutor<true, MaterializeType::LateMaterialize | MaterializeType::UseStoredValues>>;
-
-template class ::arangodb::aql::IResearchViewExecutorBase<::arangodb::aql::IResearchViewMergeExecutor<false, MaterializeType::NotMaterialize>>;
-template class ::arangodb::aql::IResearchViewExecutorBase<::arangodb::aql::IResearchViewMergeExecutor<false, MaterializeType::LateMaterialize>>;
-template class ::arangodb::aql::IResearchViewExecutorBase<::arangodb::aql::IResearchViewMergeExecutor<false, MaterializeType::Materialize>>;
-template class ::arangodb::aql::IResearchViewExecutorBase<::arangodb::aql::IResearchViewMergeExecutor<false, MaterializeType::NotMaterialize | MaterializeType::UseStoredValues>>;
-template class ::arangodb::aql::IResearchViewExecutorBase<::arangodb::aql::IResearchViewMergeExecutor<false, MaterializeType::LateMaterialize | MaterializeType::UseStoredValues>>;
-
-template class ::arangodb::aql::IResearchViewExecutorBase<::arangodb::aql::IResearchViewMergeExecutor<true, MaterializeType::NotMaterialize>>;
-template class ::arangodb::aql::IResearchViewExecutorBase<::arangodb::aql::IResearchViewMergeExecutor<true, MaterializeType::LateMaterialize>>;
-template class ::arangodb::aql::IResearchViewExecutorBase<::arangodb::aql::IResearchViewMergeExecutor<true, MaterializeType::Materialize>>;
-template class ::arangodb::aql::IResearchViewExecutorBase<::arangodb::aql::IResearchViewMergeExecutor<true, MaterializeType::NotMaterialize | MaterializeType::UseStoredValues>>;
-template class ::arangodb::aql::IResearchViewExecutorBase<::arangodb::aql::IResearchViewMergeExecutor<true, MaterializeType::LateMaterialize | MaterializeType::UseStoredValues>>;
+template class ::arangodb::aql::IResearchViewExecutorBase<
+    ::arangodb::aql::IResearchViewExecutor<true, MaterializeType::NotMaterialize | MaterializeType::UseStoredValues>>;
+template class ::arangodb::aql::IResearchViewExecutorBase<
+    ::arangodb::aql::IResearchViewExecutor<true, MaterializeType::LateMaterialize | MaterializeType::UseStoredValues>>;
+
+template class ::arangodb::aql::IResearchViewExecutorBase<
+    ::arangodb::aql::IResearchViewMergeExecutor<false, MaterializeType::NotMaterialize>>;
+template class ::arangodb::aql::IResearchViewExecutorBase<
+    ::arangodb::aql::IResearchViewMergeExecutor<false, MaterializeType::LateMaterialize>>;
+template class ::arangodb::aql::IResearchViewExecutorBase<
+    ::arangodb::aql::IResearchViewMergeExecutor<false, MaterializeType::Materialize>>;
+template class ::arangodb::aql::IResearchViewExecutorBase<
+    ::arangodb::aql::IResearchViewMergeExecutor<false, MaterializeType::NotMaterialize | MaterializeType::UseStoredValues>>;
+template class ::arangodb::aql::IResearchViewExecutorBase<
+    ::arangodb::aql::IResearchViewMergeExecutor<false, MaterializeType::LateMaterialize | MaterializeType::UseStoredValues>>;
+
+template class ::arangodb::aql::IResearchViewExecutorBase<
+    ::arangodb::aql::IResearchViewMergeExecutor<true, MaterializeType::NotMaterialize>>;
+template class ::arangodb::aql::IResearchViewExecutorBase<
+    ::arangodb::aql::IResearchViewMergeExecutor<true, MaterializeType::LateMaterialize>>;
+template class ::arangodb::aql::IResearchViewExecutorBase<
+    ::arangodb::aql::IResearchViewMergeExecutor<true, MaterializeType::Materialize>>;
+template class ::arangodb::aql::IResearchViewExecutorBase<
+    ::arangodb::aql::IResearchViewMergeExecutor<true, MaterializeType::NotMaterialize | MaterializeType::UseStoredValues>>;
+template class ::arangodb::aql::IResearchViewExecutorBase<
+    ::arangodb::aql::IResearchViewMergeExecutor<true, MaterializeType::LateMaterialize | MaterializeType::UseStoredValues>>;
diff --git a/arangod/Aql/IResearchViewExecutor.h b/arangod/Aql/IResearchViewExecutor.h
index 5b535150b100..1b6aae180944 100644
--- a/arangod/Aql/IResearchViewExecutor.h
+++ b/arangod/Aql/IResearchViewExecutor.h
@@ -27,6 +27,7 @@
 #include "Aql/ExecutionState.h"
 #include "Aql/ExecutorInfos.h"
 #include "Aql/IResearchViewNode.h"
+#include "Aql/InputAqlItemRow.h"
 #include "IResearch/ExpressionFilter.h"
 #include "IResearch/IResearchExpressionContext.h"
 #include "IResearch/IResearchVPackComparer.h"
@@ -52,6 +53,8 @@ struct Scorer;
 }
 
 namespace aql {
+struct AqlCall;
+class AqlItemBlockInputRange;
 struct ExecutionStats;
 class OutputAqlItemRow;
 template <BlockPassthrough>
@@ -66,18 +69,16 @@ class IResearchViewExecutorInfos : public ExecutorInfos {
       RegisterId firstOutputRegister, RegisterId numScoreRegisters,
       Query& query, std::vector<iresearch::Scorer> const& scorers,
       std::pair<iresearch::IResearchViewSort const*, size_t> const& sort,
-      iresearch::IResearchViewStoredValues const& storedValues,
-      ExecutionPlan const& plan,
-      Variable const& outVariable,
-      aql::AstNode const& filterCondition,
-      std::pair<bool, bool> volatility,
-      VarInfoMap const& varInfoMap,
-      int depth, iresearch::IResearchViewNode::ViewValuesRegisters&& outNonMaterializedViewRegs);
+      iresearch::IResearchViewStoredValues const& storedValues, ExecutionPlan const& plan,
+      Variable const& outVariable, aql::AstNode const& filterCondition,
+      std::pair<bool, bool> volatility, VarInfoMap const& varInfoMap, int depth,
+      iresearch::IResearchViewNode::ViewValuesRegisters&& outNonMaterializedViewRegs);
 
   RegisterId getOutputRegister() const noexcept;
   RegisterId getFirstScoreRegister() const noexcept;
   RegisterId getNumScoreRegisters() const noexcept;
-  iresearch::IResearchViewNode::ViewValuesRegisters const& getOutNonMaterializedViewRegs() const noexcept;
+  iresearch::IResearchViewNode::ViewValuesRegisters const& getOutNonMaterializedViewRegs() const
+      noexcept;
   std::shared_ptr<iresearch::IResearchView::Snapshot const> getReader() const noexcept;
   Query& getQuery() const noexcept;
   std::vector<iresearch::Scorer> const& scorers() const noexcept;
@@ -157,6 +158,22 @@ class IResearchViewExecutorBase {
   std::tuple<ExecutionState, Stats, size_t> skipRows(size_t toSkip);
   std::pair<ExecutionState, Stats> produceRows(OutputAqlItemRow& output);
 
+  /**
+   * @brief produce the next Rows of Aql Values.
+   *
+   * @return ExecutorState, the stats, and a new Call that needs to be send to upstream
+   */
+  [[nodiscard]] std::tuple<ExecutorState, Stats, AqlCall> produceRows(
+      AqlItemBlockInputRange& input, OutputAqlItemRow& output);
+
+  /**
+   * @brief skip the next Row of Aql Values.
+   *
+   * @return ExecutorState, the stats, and a new Call that needs to be send to upstream
+   */
+  [[nodiscard]] std::tuple<ExecutorState, Stats, size_t, AqlCall> skipRowsRange(
+      AqlItemBlockInputRange& inputRange, AqlCall& call);
+
  protected:
   class ReadContext {
    private:
@@ -171,13 +188,9 @@ class IResearchViewExecutorBase {
     OutputAqlItemRow& outputRow;
     IndexIterator::DocumentCallback const callback;
 
-    aql::RegisterId getNmColPtrOutReg() const noexcept {
-      return docOutReg;
-    }
+    aql::RegisterId getNmColPtrOutReg() const noexcept { return docOutReg; }
 
-    aql::RegisterId getNmDocIdOutReg() const noexcept {
-      return docOutReg + 1;
-    }
+    aql::RegisterId getNmDocIdOutReg() const noexcept { return docOutReg + 1; }
   };  // ReadContext
 
   template <typename ValueType>
@@ -250,7 +263,8 @@ class IResearchViewExecutorBase {
 
     void pushStoredValue(std::vector<irs::bytes_ref>&& storedValue);
 
-    std::vector<irs::bytes_ref> const& getStoredValue(IndexReadBufferEntry bufferEntry) const noexcept;
+    std::vector<irs::bytes_ref> const& getStoredValue(IndexReadBufferEntry bufferEntry) const
+        noexcept;
 
    private:
     // _keyBuffer, _scoreBuffer, _sortValueBuffer together hold all the
@@ -285,30 +299,30 @@ class IResearchViewExecutorBase {
   bool writeRow(ReadContext& ctx, IndexReadBufferEntry bufferEntry,
                 LocalDocumentId const& documentId, LogicalCollection const& collection);
 
-  bool writeLocalDocumentId(ReadContext& ctx,
-                LocalDocumentId const& documentId,
-                LogicalCollection const& collection);
+  bool writeLocalDocumentId(ReadContext& ctx, LocalDocumentId const& documentId,
+                            LogicalCollection const& collection);
 
   void reset();
 
-  bool writeStoredValue(ReadContext& ctx, std::vector<irs::bytes_ref> const& storedValues, size_t columnNum,
-                        std::map<size_t, RegisterId> const& fieldsRegs);
+  bool writeStoredValue(ReadContext& ctx, std::vector<irs::bytes_ref> const& storedValues,
+                        size_t columnNum, std::map<size_t, RegisterId> const& fieldsRegs);
 
-  void getStoredValue(irs::document const& doc, std::vector<irs::bytes_ref>& storedValue, size_t index,
+  void getStoredValue(irs::document const& doc,
+                      std::vector<irs::bytes_ref>& storedValue, size_t index,
                       std::vector<irs::columnstore_reader::values_reader_f> const& storedValuesReaders);
 
-  void pushStoredValues(irs::document const& doc, std::vector<irs::columnstore_reader::values_reader_f> const& storedValuesReaders);
+  void pushStoredValues(irs::document const& doc,
+                        std::vector<irs::columnstore_reader::values_reader_f> const& storedValuesReaders);
 
-  bool getStoredValuesReaders(irs::sub_reader const& segmentReader, std::vector<irs::columnstore_reader::values_reader_f>& storedValuesReaders);
+  bool getStoredValuesReaders(irs::sub_reader const& segmentReader,
+                              std::vector<irs::columnstore_reader::values_reader_f>& storedValuesReaders);
 
  private:
   bool next(ReadContext& ctx);
 
  protected:
   Infos const& _infos;
-  Fetcher& _fetcher;
   InputAqlItemRow _inputRow;
-  ExecutionState _upstreamState;
   IndexReadBuffer<typename Traits::IndexBufferValueType> _indexReadBuffer;
   irs::bytes_ref _pk;  // temporary store for pk buffer before decoding it
   irs::attribute_view _filterCtx;  // filter context
@@ -317,13 +331,12 @@ class IResearchViewExecutorBase {
   irs::filter::prepared::ptr _filter;
   irs::order::prepared _order;
   iresearch::ExpressionExecutionContext _execCtx;  // expression execution context
-  size_t _inflight;  // The number of documents inflight if we hit a WAITING state.
-  bool _hasMore;
   bool _isInitialized;
 };  // IResearchViewExecutorBase
 
 template <bool ordered, iresearch::MaterializeType materializeType>
-class IResearchViewExecutor : public IResearchViewExecutorBase<IResearchViewExecutor<ordered, materializeType>> {
+class IResearchViewExecutor
+    : public IResearchViewExecutorBase<IResearchViewExecutor<ordered, materializeType>> {
  public:
   using Base = IResearchViewExecutorBase<IResearchViewExecutor<ordered, materializeType>>;
   using Fetcher = typename Base::Fetcher;
@@ -339,6 +352,9 @@ class IResearchViewExecutor : public IResearchViewExecutorBase<IResearchViewExec
   using IndexReadBufferEntry = typename Base::IndexReadBufferEntry;
 
   size_t skip(size_t toSkip);
+  size_t skipAll();
+
+  void saveCollection();
 
   void evaluateScores(ReadContext const& ctx);
 
@@ -356,19 +372,19 @@ class IResearchViewExecutor : public IResearchViewExecutorBase<IResearchViewExec
   // unset if readPK returns true.
   bool readPK(LocalDocumentId& documentId);
 
-  irs::columnstore_reader::values_reader_f _pkReader;   // current primary key reader
+  irs::columnstore_reader::values_reader_f _pkReader;  // current primary key reader
   irs::doc_iterator::ptr _itr;
   irs::document const* _doc{};
   size_t _readerOffset;
   LogicalCollection const* _collection{};
-  std::vector<irs::columnstore_reader::values_reader_f> _storedValuesReaders; // current stored values readers
+  std::vector<irs::columnstore_reader::values_reader_f> _storedValuesReaders;  // current stored values readers
 
   // case ordered only:
   irs::score const* _scr;
   irs::bytes_ref _scrVal;
 };  // IResearchViewExecutor
 
-template<bool ordered, iresearch::MaterializeType materializeType>
+template <bool ordered, iresearch::MaterializeType materializeType>
 struct IResearchViewExecutorTraits<IResearchViewExecutor<ordered, materializeType>> {
   using IndexBufferValueType = LocalDocumentId;
   static constexpr bool Ordered = ordered;
@@ -376,7 +392,8 @@ struct IResearchViewExecutorTraits<IResearchViewExecutor<ordered, materializeTyp
 };
 
 template <bool ordered, iresearch::MaterializeType materializeType>
-class IResearchViewMergeExecutor : public IResearchViewExecutorBase<IResearchViewMergeExecutor<ordered, materializeType>> {
+class IResearchViewMergeExecutor
+    : public IResearchViewExecutorBase<IResearchViewMergeExecutor<ordered, materializeType>> {
  public:
   using Base = IResearchViewExecutorBase<IResearchViewMergeExecutor<ordered, materializeType>>;
   using Fetcher = typename Base::Fetcher;
@@ -407,10 +424,10 @@ class IResearchViewMergeExecutor : public IResearchViewExecutorBase<IResearchVie
     irs::document const* doc{};
     irs::score const* score{};
     arangodb::LogicalCollection const* collection{};  // collecton associated with a segment
-    irs::bytes_ref sortValue{irs::bytes_ref::NIL};        // sort column value
-    irs::columnstore_reader::values_reader_f pkReader;    // primary key reader
-    std::vector<irs::columnstore_reader::values_reader_f> storedValuesReaders; // current stored values readers
-    irs::columnstore_reader::values_reader_f& sortReader; // sort column reader
+    irs::bytes_ref sortValue{irs::bytes_ref::NIL};      // sort column value
+    irs::columnstore_reader::values_reader_f pkReader;  // primary key reader
+    std::vector<irs::columnstore_reader::values_reader_f> storedValuesReaders;  // current stored values readers
+    irs::columnstore_reader::values_reader_f& sortReader;  // sort column reader
   };
 
   class MinHeapContext {
@@ -439,13 +456,14 @@ class IResearchViewMergeExecutor : public IResearchViewExecutorBase<IResearchVie
 
   void reset();
   size_t skip(size_t toSkip);
+  size_t skipAll();
 
  private:
   std::vector<Segment> _segments;
   irs::external_heap_iterator<MinHeapContext> _heap_it;
 };  // IResearchViewMergeExecutor
 
-template<bool ordered, iresearch::MaterializeType materializeType>
+template <bool ordered, iresearch::MaterializeType materializeType>
 struct IResearchViewExecutorTraits<IResearchViewMergeExecutor<ordered, materializeType>> {
   using IndexBufferValueType = std::pair<LocalDocumentId, LogicalCollection const*>;
   static constexpr bool Ordered = ordered;

From abd2740d13edce4f1e358f02e61e9e03bcfa7dc9 Mon Sep 17 00:00:00 2001
From: Markus Pfeiffer <markuspf@users.noreply.github.com>
Date: Thu, 27 Feb 2020 13:52:37 +0000
Subject: [PATCH 079/122] Move SingleRemoteModificationExecutor to new
 interface (#11166)

* Move SingleRemoteModificationExecutor to new interface

* Activate SingleRemoteModificationExecutor

* Inspect the result of remote modification

Co-authored-by: Michael Hackstein <michael@arangodb.com>
---
 arangod/Aql/ExecutionBlockImpl.cpp            | 10 ++-
 .../Aql/SingleRemoteModificationExecutor.cpp  | 69 ++++++++++++-------
 .../Aql/SingleRemoteModificationExecutor.h    |  9 ++-
 3 files changed, 62 insertions(+), 26 deletions(-)

diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index 3b6934601fac..0f9dd19c838a 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -166,7 +166,9 @@ constexpr bool isNewStyleExecutor = is_one_of_v<
     IResearchViewMergeExecutor<true, arangodb::iresearch::MaterializeType::NotMaterialize | arangodb::iresearch::MaterializeType::UseStoredValues>,
     IResearchViewMergeExecutor<true, arangodb::iresearch::MaterializeType::LateMaterialize | arangodb::iresearch::MaterializeType::UseStoredValues>,
     SubqueryStartExecutor, SubqueryEndExecutor, TraversalExecutor, KShortestPathsExecutor,
-    ShortestPathExecutor, EnumerateListExecutor, LimitExecutor>;
+    ShortestPathExecutor, EnumerateListExecutor, LimitExecutor, SingleRemoteModificationExecutor<IndexTag>, SingleRemoteModificationExecutor<Insert>,
+    SingleRemoteModificationExecutor<Remove>, SingleRemoteModificationExecutor<Update>,
+    SingleRemoteModificationExecutor<Replace>, SingleRemoteModificationExecutor<Upsert>>;
 
 template <class Executor>
 ExecutionBlockImpl<Executor>::ExecutionBlockImpl(ExecutionEngine* engine,
@@ -1147,7 +1149,11 @@ static SkipRowsRangeVariant constexpr skipRowsType() {
               IResearchViewMergeExecutor<true, arangodb::iresearch::MaterializeType::NotMaterialize | arangodb::iresearch::MaterializeType::UseStoredValues>,
               IResearchViewMergeExecutor<true, arangodb::iresearch::MaterializeType::LateMaterialize | arangodb::iresearch::MaterializeType::UseStoredValues>,
               TraversalExecutor, EnumerateListExecutor, SubqueryStartExecutor,
-              SubqueryEndExecutor, SortedCollectExecutor, LimitExecutor>),
+              SubqueryEndExecutor, SortedCollectExecutor, LimitExecutor,
+              SingleRemoteModificationExecutor<IndexTag>, SingleRemoteModificationExecutor<Insert>,
+              SingleRemoteModificationExecutor<Remove>, SingleRemoteModificationExecutor<Update>,
+              SingleRemoteModificationExecutor<Replace>, SingleRemoteModificationExecutor<Upsert>>),
+
       "Unexpected executor for SkipVariants::EXECUTOR");
 
   // The LimitExecutor will not work correctly with SkipVariants::FETCHER!
diff --git a/arangod/Aql/SingleRemoteModificationExecutor.cpp b/arangod/Aql/SingleRemoteModificationExecutor.cpp
index 6ec7b8e3f635..228742ca79a1 100644
--- a/arangod/Aql/SingleRemoteModificationExecutor.cpp
+++ b/arangod/Aql/SingleRemoteModificationExecutor.cpp
@@ -71,29 +71,50 @@ SingleRemoteModificationExecutor<Modifier>::SingleRemoteModificationExecutor(Fet
 template <typename Modifier>
 std::pair<ExecutionState, typename SingleRemoteModificationExecutor<Modifier>::Stats>
 SingleRemoteModificationExecutor<Modifier>::produceRows(OutputAqlItemRow& output) {
-  Stats stats;
-  InputAqlItemRow input = InputAqlItemRow(CreateInvalidInputRowHint{});
+  TRI_ASSERT(false);
+  return {ExecutionState::DONE, Stats{}};
+}
 
-  if (_upstreamState == ExecutionState::DONE) {
-    return {_upstreamState, std::move(stats)};
+template <typename Modifier>
+[[nodiscard]] auto SingleRemoteModificationExecutor<Modifier>::produceRows(
+    AqlItemBlockInputRange& input, OutputAqlItemRow& output)
+    -> std::tuple<ExecutorState, typename SingleRemoteModificationExecutor<Modifier>::Stats, AqlCall> {
+  auto stats = Stats{};
+
+  if (input.hasDataRow()) {
+    auto [state, row] = input.nextDataRow();
+    auto result = doSingleRemoteModificationOperation(row, stats);
+    if (result.ok()) {
+      doSingleRemoteModificationOutput(row, output, result);
+    }
   }
 
-  std::tie(_upstreamState, input) = _fetcher.fetchRow();
+  return {input.upstreamState(), stats, AqlCall{}};
+}
 
-  if (input.isInitialized()) {
-    TRI_ASSERT(_upstreamState == ExecutionState::HASMORE ||
-               _upstreamState == ExecutionState::DONE);
-    doSingleRemoteModificationOperation(input, output, stats);
-  } else {
-    TRI_ASSERT(_upstreamState == ExecutionState::WAITING ||
-               _upstreamState == ExecutionState::DONE);
+template <typename Modifier>
+[[nodiscard]] auto SingleRemoteModificationExecutor<Modifier>::skipRowsRange(
+    AqlItemBlockInputRange& input, AqlCall& call)
+    -> std::tuple<ExecutorState, typename SingleRemoteModificationExecutor<Modifier>::Stats, size_t, AqlCall> {
+  auto stats = Stats{};
+
+  if (input.hasDataRow()) {
+    auto [state, row] = input.nextDataRow();
+    auto result = doSingleRemoteModificationOperation(row, stats);
+    if (result.ok()) {
+      call.didSkip(1);
+      return {input.upstreamState(), stats, 1, AqlCall{}};
+    }
   }
-  return {_upstreamState, std::move(stats)};
+  return {input.upstreamState(), stats, 0, AqlCall{}};
 }
 
 template <typename Modifier>
-bool SingleRemoteModificationExecutor<Modifier>::doSingleRemoteModificationOperation(
-    InputAqlItemRow& input, OutputAqlItemRow& output, Stats& stats) {
+auto SingleRemoteModificationExecutor<Modifier>::doSingleRemoteModificationOperation(
+    InputAqlItemRow& input, Stats& stats) -> OperationResult {
+  OperationResult result;
+  OperationOptions& options = _info._options;
+
   _info._options.silent = false;
   _info._options.returnOld = _info._options.returnOld ||
                              _info._outputRegisterId != RegisterPlan::MaxRegisterId;
@@ -106,8 +127,6 @@ bool SingleRemoteModificationExecutor<Modifier>::doSingleRemoteModificationOpera
 
   int possibleWrites = 0;  // TODO - get real statistic values!
 
-  OperationOptions& options = _info._options;
-
   if (_info._key.empty() && _info._input1RegisterId == RegisterPlan::MaxRegisterId) {
     THROW_ARANGO_EXCEPTION_MESSAGE(TRI_ERROR_ARANGO_DOCUMENT_NOT_FOUND,
                                    "missing document reference");
@@ -127,7 +146,6 @@ bool SingleRemoteModificationExecutor<Modifier>::doSingleRemoteModificationOpera
     inSlice = mergedBuilder->slice();
   }
 
-  OperationResult result;
   if (isIndex) {
     result = _info._trx->document(_info._aqlCollection->name(), inSlice, _info._options);
   } else if (isInsert) {
@@ -163,18 +181,25 @@ bool SingleRemoteModificationExecutor<Modifier>::doSingleRemoteModificationOpera
       // document not there is not an error in this situation.
       // FOR ... FILTER ... REMOVE wouldn't invoke REMOVE in first place, so
       // don't throw an excetpion.
-      return false;
+      return result;
     } else if (!_info._ignoreErrors) {  // TODO remove if
       THROW_ARANGO_EXCEPTION_MESSAGE(result.errorNumber(), result.errorMessage());
     }
 
     if (isIndex) {
-      return false;
+      return result;
     }
   }
 
   stats.addWritesExecuted(possibleWrites);
   stats.incrScannedIndex();
+  return result;
+}
+
+template <typename Modifier>
+auto SingleRemoteModificationExecutor<Modifier>::doSingleRemoteModificationOutput(
+    InputAqlItemRow& input, OutputAqlItemRow& output, OperationResult& result) -> void {
+  OperationOptions& options = _info._options;
 
   if (!(_info._outputRegisterId != RegisterPlan::MaxRegisterId ||
         _info._outputOldRegisterId != RegisterPlan::MaxRegisterId ||
@@ -182,7 +207,7 @@ bool SingleRemoteModificationExecutor<Modifier>::doSingleRemoteModificationOpera
     if (_info._hasParent) {
       output.copyRow(input);
     }
-    return _info._hasParent;
+    return;  //  _info._hasParent;
   }
 
   // Fill itemblock
@@ -239,8 +264,6 @@ bool SingleRemoteModificationExecutor<Modifier>::doSingleRemoteModificationOpera
   TRI_IF_FAILURE("SingleRemoteModificationOperationBlock::moreDocuments") {
     THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
   }
-
-  return true;
 }
 
 template struct ::arangodb::aql::SingleRemoteModificationExecutor<IndexTag>;
diff --git a/arangod/Aql/SingleRemoteModificationExecutor.h b/arangod/Aql/SingleRemoteModificationExecutor.h
index bf18456d83d4..dfbc3c6c4a6d 100644
--- a/arangod/Aql/SingleRemoteModificationExecutor.h
+++ b/arangod/Aql/SingleRemoteModificationExecutor.h
@@ -99,8 +99,15 @@ struct SingleRemoteModificationExecutor {
    */
   std::pair<ExecutionState, Stats> produceRows(OutputAqlItemRow& output);
 
+  [[nodiscard]] auto produceRows(AqlItemBlockInputRange& input, OutputAqlItemRow& output)
+      -> std::tuple<ExecutorState, Stats, AqlCall>;
+  [[nodiscard]] auto skipRowsRange(AqlItemBlockInputRange& input, AqlCall& call)
+      -> std::tuple<ExecutorState, Stats, size_t, AqlCall>;
+
  protected:
-  bool doSingleRemoteModificationOperation(InputAqlItemRow&, OutputAqlItemRow&, Stats&);
+  auto doSingleRemoteModificationOperation(InputAqlItemRow&, Stats&) -> OperationResult;
+  auto doSingleRemoteModificationOutput(InputAqlItemRow&, OutputAqlItemRow&,
+                                        OperationResult&) -> void;
 
   Infos& _info;
   Fetcher& _fetcher;

From 9bf96cd7cc0b321f9a2107df17fe9f8549cfb5c1 Mon Sep 17 00:00:00 2001
From: Lars Maier <lars@arangodb.com>
Date: Thu, 27 Feb 2020 21:31:15 +0100
Subject: [PATCH 080/122] New style DistinctCollect (#11096)

* First implementation of new style executor for DistinctCollect.

* Tests for distinct collect.

* Remove debug output.

Co-authored-by: Michael Hackstein <michael@arangodb.com>
---
 arangod/Aql/AqlValueGroup.cpp             |   9 +
 arangod/Aql/AqlValueGroup.h               |   3 +
 arangod/Aql/CollectNode.cpp               |   4 +-
 arangod/Aql/DistinctCollectExecutor.cpp   | 155 +++++-----
 arangod/Aql/DistinctCollectExecutor.h     |  21 +-
 arangod/Aql/ExecutionBlockImpl.cpp        |  26 +-
 tests/Aql/DistinctCollectExecutorTest.cpp | 331 +++-------------------
 7 files changed, 183 insertions(+), 366 deletions(-)

diff --git a/arangod/Aql/AqlValueGroup.cpp b/arangod/Aql/AqlValueGroup.cpp
index 316086712f8b..5a06dd373e15 100644
--- a/arangod/Aql/AqlValueGroup.cpp
+++ b/arangod/Aql/AqlValueGroup.cpp
@@ -45,6 +45,11 @@ size_t AqlValueGroupHash::operator()(const std::vector<AqlValue>& value) const {
   return static_cast<size_t>(hash);
 }
 
+size_t AqlValueGroupHash::operator()(AqlValue const& value) const {
+  uint64_t hash = 0x12345678;
+  return value.hash(_trx, hash);
+}
+
 AqlValueGroupEqual::AqlValueGroupEqual(arangodb::transaction::Methods* trx)
     : _trx(trx) {}
 
@@ -62,3 +67,7 @@ bool AqlValueGroupEqual::operator()(const std::vector<AqlValue>& lhs,
 
   return true;
 }
+
+bool AqlValueGroupEqual::operator()(AqlValue const& lhs, AqlValue const& rhs) const {
+  return AqlValue::Compare(_trx, lhs, rhs, false) == 0;
+}
diff --git a/arangod/Aql/AqlValueGroup.h b/arangod/Aql/AqlValueGroup.h
index e7bf94a763c1..f04d10eec31d 100644
--- a/arangod/Aql/AqlValueGroup.h
+++ b/arangod/Aql/AqlValueGroup.h
@@ -39,6 +39,7 @@ struct AqlValueGroupHash {
   AqlValueGroupHash(transaction::Methods* trx, size_t num);
 
   size_t operator()(std::vector<AqlValue> const& value) const;
+  size_t operator()(AqlValue const& value) const;
 
   transaction::Methods* _trx;
   size_t const _num;
@@ -49,10 +50,12 @@ struct AqlValueGroupEqual {
   explicit AqlValueGroupEqual(transaction::Methods* trx);
 
   bool operator()(std::vector<AqlValue> const& lhs, std::vector<AqlValue> const& rhs) const;
+  bool operator()(AqlValue const& lhs, AqlValue const& rhs) const;
 
   transaction::Methods* _trx;
 };
 
+
 }  // namespace aql
 }  // namespace arangodb
 
diff --git a/arangod/Aql/CollectNode.cpp b/arangod/Aql/CollectNode.cpp
index 304962e14084..16d06066fb34 100644
--- a/arangod/Aql/CollectNode.cpp
+++ b/arangod/Aql/CollectNode.cpp
@@ -372,12 +372,14 @@ std::unique_ptr<ExecutionBlock> CollectNode::createBlock(
       calcGroupRegisters(groupRegisters, readableInputRegisters, writeableOutputRegisters);
 
       transaction::Methods* trxPtr = _plan->getAst()->query()->trx();
+
+      TRI_ASSERT(groupRegisters.size() == 1);
       DistinctCollectExecutorInfos infos(getRegisterPlan()->nrRegs[previousNode->getDepth()],
                                          getRegisterPlan()->nrRegs[getDepth()],
                                          getRegsToClear(), calcRegsToKeep(),
                                          std::move(readableInputRegisters),
                                          std::move(writeableOutputRegisters),
-                                         std::move(groupRegisters), trxPtr);
+                                         groupRegisters.front(), trxPtr);
 
       return std::make_unique<ExecutionBlockImpl<DistinctCollectExecutor>>(&engine, this,
                                                                            std::move(infos));
diff --git a/arangod/Aql/DistinctCollectExecutor.cpp b/arangod/Aql/DistinctCollectExecutor.cpp
index e19f1501aa5b..bb6dc923baf1 100644
--- a/arangod/Aql/DistinctCollectExecutor.cpp
+++ b/arangod/Aql/DistinctCollectExecutor.cpp
@@ -35,6 +35,10 @@
 
 #include <utility>
 
+#define LOG_DEVEL_DISTINCT_COLLECT_ENABLED false
+#define LOG_DEVEL_DC \
+  LOG_DEVEL_IF(LOG_DEVEL_DISTINCT_COLLECT_ENABLED) << __FUNCTION__ << " "
+
 using namespace arangodb;
 using namespace arangodb::aql;
 
@@ -44,19 +48,16 @@ DistinctCollectExecutorInfos::DistinctCollectExecutorInfos(
     std::unordered_set<RegisterId> registersToKeep,
     std::unordered_set<RegisterId>&& readableInputRegisters,
     std::unordered_set<RegisterId>&& writeableInputRegisters,
-    std::vector<std::pair<RegisterId, RegisterId>>&& groupRegisters,
-    transaction::Methods* trxPtr)
+    std::pair<RegisterId, RegisterId> groupRegister, transaction::Methods* trxPtr)
     : ExecutorInfos(std::make_shared<std::unordered_set<RegisterId>>(readableInputRegisters),
                     std::make_shared<std::unordered_set<RegisterId>>(writeableInputRegisters),
                     nrInputRegisters, nrOutputRegisters,
                     std::move(registersToClear), std::move(registersToKeep)),
-      _groupRegisters(groupRegisters),
-      _trxPtr(trxPtr) {
-  TRI_ASSERT(!_groupRegisters.empty());
-}
+      _groupRegister(groupRegister),
+      _trxPtr(trxPtr) {}
 
-std::vector<std::pair<RegisterId, RegisterId>> DistinctCollectExecutorInfos::getGroupRegisters() const {
-  return _groupRegisters;
+std::pair<RegisterId, RegisterId> const& DistinctCollectExecutorInfos::getGroupRegister() const {
+  return _groupRegister;
 }
 
 transaction::Methods* DistinctCollectExecutorInfos::getTransaction() const {
@@ -66,9 +67,7 @@ transaction::Methods* DistinctCollectExecutorInfos::getTransaction() const {
 DistinctCollectExecutor::DistinctCollectExecutor(Fetcher& fetcher, Infos& infos)
     : _infos(infos),
       _fetcher(fetcher),
-      _seen(1024,
-            AqlValueGroupHash(_infos.getTransaction(),
-                              _infos.getGroupRegisters().size()),
+      _seen(1024, AqlValueGroupHash(_infos.getTransaction(), 1),
             AqlValueGroupEqual(_infos.getTransaction())) {}
 
 DistinctCollectExecutor::~DistinctCollectExecutor() { destroyValues(); }
@@ -76,82 +75,110 @@ DistinctCollectExecutor::~DistinctCollectExecutor() { destroyValues(); }
 void DistinctCollectExecutor::initializeCursor() { destroyValues(); }
 
 std::pair<ExecutionState, NoStats> DistinctCollectExecutor::produceRows(OutputAqlItemRow& output) {
+  TRI_ASSERT(false);
+  THROW_ARANGO_EXCEPTION(TRI_ERROR_INTERNAL_AQL);
+}
+
+std::pair<ExecutionState, size_t> DistinctCollectExecutor::expectedNumberOfRows(size_t atMost) const {
+  // This block cannot know how many elements will be returned exactly.
+  // but it is upper bounded by the input.
+  return _fetcher.preFetchNumberOfRows(atMost);
+}
+
+void DistinctCollectExecutor::destroyValues() {
+  // destroy all AqlValues captured
+  for (auto& value : _seen) {
+    const_cast<AqlValue*>(&value)->destroy();
+  }
+  _seen.clear();
+}
+
+const DistinctCollectExecutor::Infos& DistinctCollectExecutor::infos() const noexcept {
+  return _infos;
+}
+
+auto DistinctCollectExecutor::produceRows(AqlItemBlockInputRange& inputRange,
+                                          OutputAqlItemRow& output)
+    -> std::tuple<ExecutorState, Stats, AqlCall> {
   TRI_IF_FAILURE("DistinctCollectExecutor::produceRows") {
     THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
   }
-  NoStats stats{};
+
   InputAqlItemRow input{CreateInvalidInputRowHint{}};
-  ExecutionState state;
+  ExecutorState state = ExecutorState::HASMORE;
 
-  std::vector<AqlValue> groupValues;
-  groupValues.reserve(_infos.getGroupRegisters().size());
+  LOG_DEVEL_DC << output.getClientCall();
 
-  while (true) {
-    std::tie(state, input) = _fetcher.fetchRow();
+  AqlValue groupValue;
 
-    if (state == ExecutionState::WAITING) {
-      return {state, stats};
-    }
+  while (inputRange.hasDataRow()) {
+    LOG_DEVEL_DC << "output.isFull() = " << std::boolalpha << output.isFull();
 
-    if (!input) {
-      TRI_ASSERT(state == ExecutionState::DONE);
-      return {state, stats};
+    if (output.isFull()) {
+      LOG_DEVEL_DC << "output is full";
+      break;
     }
+
+    std::tie(state, input) = inputRange.nextDataRow();
+    LOG_DEVEL_DC << "inputRange.nextDataRow() = " << state;
     TRI_ASSERT(input.isInitialized());
 
-    groupValues.clear();
     // for hashing simply re-use the aggregate registers, without cloning
     // their contents
-    for (auto& it : _infos.getGroupRegisters()) {
-      groupValues.emplace_back(input.getValue(it.second));
-    }
+    groupValue = input.getValue(_infos.getGroupRegister().second);
 
     // now check if we already know this group
-    auto foundIt = _seen.find(groupValues);
-
-    bool newGroup = foundIt == _seen.end();
+    bool newGroup = _seen.find(groupValue) == _seen.end();
     if (newGroup) {
-      size_t i = 0;
-
-      for (auto& it : _infos.getGroupRegisters()) {
-        output.cloneValueInto(it.first, input, groupValues[i]);
-        ++i;
-      }
-
-      // transfer ownership
-      std::vector<AqlValue> copy;
-      copy.reserve(groupValues.size());
-      for (auto const& it : groupValues) {
-        copy.emplace_back(it.clone());
-      }
-      _seen.emplace(std::move(copy));
-    }
+      output.cloneValueInto(_infos.getGroupRegister().first, input, groupValue);
+      output.advanceRow();
 
-    // Abort if upstream is done
-    if (state == ExecutionState::DONE) {
-      return {state, stats};
+      _seen.emplace(groupValue.clone());
     }
-
-    return {ExecutionState::HASMORE, stats};
   }
-}
 
-std::pair<ExecutionState, size_t> DistinctCollectExecutor::expectedNumberOfRows(size_t atMost) const {
-  // This block cannot know how many elements will be returned exactly.
-  // but it is upper bounded by the input.
-  return _fetcher.preFetchNumberOfRows(atMost);
+  LOG_DEVEL_DC << "returning state " << state;
+  return {inputRange.upstreamState(), {}, {}};
 }
 
-void DistinctCollectExecutor::destroyValues() {
-  // destroy all AqlValues captured
-  for (auto& it : _seen) {
-    for (auto& it2 : it) {
-      const_cast<AqlValue*>(&it2)->destroy();
+auto DistinctCollectExecutor::skipRowsRange(AqlItemBlockInputRange& inputRange, AqlCall& call)
+    -> std::tuple<ExecutorState, Stats, size_t, AqlCall> {
+  TRI_IF_FAILURE("DistinctCollectExecutor::skipRowsRange") {
+    THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
+  }
+
+  InputAqlItemRow input{CreateInvalidInputRowHint{}};
+  ExecutorState state = ExecutorState::HASMORE;
+
+  AqlValue groupValue;
+  size_t skipped = 0;
+
+  LOG_DEVEL_DC << call;
+
+  while (inputRange.hasDataRow()) {
+    LOG_DEVEL_DC << "call.needSkipMore() = " << std::boolalpha << call.needSkipMore();
+
+    if (!call.needSkipMore()) {
+      return {ExecutorState::HASMORE, {}, skipped, {}};
+    }
+
+    std::tie(state, input) = inputRange.nextDataRow();
+    LOG_DEVEL_DC << "inputRange.nextDataRow() = " << state;
+    TRI_ASSERT(input.isInitialized());
+
+    // for hashing simply re-use the aggregate registers, without cloning
+    // their contents
+    groupValue = input.getValue(_infos.getGroupRegister().second);
+
+    // now check if we already know this group
+    bool newGroup = _seen.find(groupValue) == _seen.end();
+    if (newGroup) {
+      skipped += 1;
+      call.didSkip(1);
+
+      _seen.emplace(groupValue.clone());
     }
   }
-  _seen.clear();
-}
 
-const DistinctCollectExecutor::Infos& DistinctCollectExecutor::infos() const noexcept {
-  return _infos;
+  return {inputRange.upstreamState(), {}, skipped, {}};
 }
diff --git a/arangod/Aql/DistinctCollectExecutor.h b/arangod/Aql/DistinctCollectExecutor.h
index 2bc5b7963fde..def1af36cf13 100644
--- a/arangod/Aql/DistinctCollectExecutor.h
+++ b/arangod/Aql/DistinctCollectExecutor.h
@@ -26,6 +26,8 @@
 #ifndef ARANGOD_AQL_DISTINCT_COLLECT_EXECUTOR_H
 #define ARANGOD_AQL_DISTINCT_COLLECT_EXECUTOR_H
 
+#include "Aql/AqlCall.h"
+#include "Aql/AqlItemBlockInputRange.h"
 #include "Aql/AqlValue.h"
 #include "Aql/AqlValueGroup.h"
 #include "Aql/ExecutionState.h"
@@ -55,7 +57,7 @@ class DistinctCollectExecutorInfos : public ExecutorInfos {
                                std::unordered_set<RegisterId> registersToKeep,
                                std::unordered_set<RegisterId>&& readableInputRegisters,
                                std::unordered_set<RegisterId>&& writeableInputRegisters,
-                               std::vector<std::pair<RegisterId, RegisterId>>&& groupRegisters,
+                               std::pair<RegisterId, RegisterId> groupRegister,
                                transaction::Methods* trxPtr);
 
   DistinctCollectExecutorInfos() = delete;
@@ -64,12 +66,12 @@ class DistinctCollectExecutorInfos : public ExecutorInfos {
   ~DistinctCollectExecutorInfos() = default;
 
  public:
-  std::vector<std::pair<RegisterId, RegisterId>> getGroupRegisters() const;
+  [[nodiscard]] std::pair<RegisterId, RegisterId> const& getGroupRegister() const;
   transaction::Methods* getTransaction() const;
 
  private:
   /// @brief pairs, consisting of out register and in register
-  std::vector<std::pair<RegisterId, RegisterId>> _groupRegisters;
+  std::pair<RegisterId, RegisterId> _groupRegister;
 
   /// @brief the transaction for this query
   transaction::Methods* _trxPtr;
@@ -105,6 +107,17 @@ class DistinctCollectExecutor {
    */
   std::pair<ExecutionState, Stats> produceRows(OutputAqlItemRow& output);
 
+  /**
+   * @brief produce the next Rows of Aql Values.
+   *
+   * @return ExecutorState, the stats, and a new Call that needs to be send to upstream
+   */
+  [[nodiscard]] auto produceRows(AqlItemBlockInputRange& input, OutputAqlItemRow& output)
+      -> std::tuple<ExecutorState, Stats, AqlCall>;
+
+  [[nodiscard]] auto skipRowsRange(AqlItemBlockInputRange& inputRange, AqlCall& call)
+      -> std::tuple<ExecutorState, Stats, size_t, AqlCall>;
+
   std::pair<ExecutionState, size_t> expectedNumberOfRows(size_t atMost) const;
 
  private:
@@ -114,7 +127,7 @@ class DistinctCollectExecutor {
  private:
   Infos const& _infos;
   Fetcher& _fetcher;
-  std::unordered_set<std::vector<AqlValue>, AqlValueGroupHash, AqlValueGroupEqual> _seen;
+  std::unordered_set<AqlValue, AqlValueGroupHash, AqlValueGroupEqual> _seen;
 };
 
 }  // namespace aql
diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index 0f9dd19c838a..19904c9eabaa 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -134,13 +134,13 @@ constexpr bool is_one_of_v = (std::is_same_v<T, Es> || ...);
  * TODO: This should be removed once all executors and fetchers are ported to the new style.
  */
 template <typename Executor>
-constexpr bool isNewStyleExecutor = is_one_of_v<
-    Executor, FilterExecutor, SortedCollectExecutor, IdExecutor<ConstFetcher>,
-    IdExecutor<SingleRowFetcher<BlockPassthrough::Enable>>, ReturnExecutor, IndexExecutor, EnumerateCollectionExecutor,
-    /*
-                    CalculationExecutor<CalculationType::Condition>, CalculationExecutor<CalculationType::Reference>,
-                    CalculationExecutor<CalculationType::V8Condition>,*/
-    HashedCollectExecutor,
+constexpr bool isNewStyleExecutor =
+    is_one_of_v<Executor, FilterExecutor, SortedCollectExecutor, IdExecutor<ConstFetcher>,
+                IdExecutor<SingleRowFetcher<BlockPassthrough::Enable>>, ReturnExecutor,
+                DistinctCollectExecutor, IndexExecutor, EnumerateCollectionExecutor,
+                // TODO: re-enable after new subquery end & start are implemented
+                // CalculationExecutor<CalculationType::Condition>, CalculationExecutor<CalculationType::Reference>, CalculationExecutor<CalculationType::V8Condition>,
+                HashedCollectExecutor,
 #ifdef ARANGODB_USE_GOOGLE_TESTS
     TestLambdaExecutor,
     TestLambdaSkipExecutor,  // we need one after these to avoid compile errors in non-test mode
@@ -1124,7 +1124,7 @@ static SkipRowsRangeVariant constexpr skipRowsType() {
           (is_one_of_v<
               Executor, FilterExecutor, ShortestPathExecutor, ReturnExecutor, KShortestPathsExecutor,
               IdExecutor<SingleRowFetcher<BlockPassthrough::Enable>>, IdExecutor<ConstFetcher>,
-              HashedCollectExecutor, IndexExecutor, EnumerateCollectionExecutor,
+              HashedCollectExecutor, IndexExecutor, EnumerateCollectionExecutor, DistinctCollectExecutor,
 #ifdef ARANGODB_USE_GOOGLE_TESTS
               TestLambdaSkipExecutor,
 #endif
@@ -1161,13 +1161,13 @@ static SkipRowsRangeVariant constexpr skipRowsType() {
       !std::is_same<Executor, LimitExecutor>::value || useFetcher,
       "LimitExecutor needs to implement skipRows() to work correctly");
 
-  if (useExecutor) {
+  static_assert(useExecutor || useFetcher, "no skipping variant available");
+
+  if constexpr (useExecutor) {
     return SkipRowsRangeVariant::EXECUTOR;
-  } else if (useFetcher) {
-    return SkipRowsRangeVariant::FETCHER;
   } else {
-    TRI_ASSERT(false);
-    THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
+    static_assert(useFetcher);
+    return SkipRowsRangeVariant::FETCHER;
   }
 }
 
diff --git a/tests/Aql/DistinctCollectExecutorTest.cpp b/tests/Aql/DistinctCollectExecutorTest.cpp
index 6a7f2c793fe7..060ad80677ba 100644
--- a/tests/Aql/DistinctCollectExecutorTest.cpp
+++ b/tests/Aql/DistinctCollectExecutorTest.cpp
@@ -32,9 +32,10 @@
 #include "Aql/DistinctCollectExecutor.h"
 #include "Aql/ExecutionEngine.h"
 #include "Aql/OutputAqlItemRow.h"
-#include "Aql/SingleRowFetcher.h"
 #include "Aql/Query.h"
+#include "Aql/SingleRowFetcher.h"
 #include "Aql/Stats.h"
+#include "ExecutorTestHelper.h"
 #include "Mocks/Servers.h"
 #include "Transaction/Context.h"
 #include "Transaction/Methods.h"
@@ -50,310 +51,72 @@ namespace arangodb {
 namespace tests {
 namespace aql {
 
-class DistinctCollectExecutorTest : public ::testing::Test {
+using DistinctCollectTestHelper = ExecutorTestHelper<1, 1>;
+using DistinctCollectSplitType = DistinctCollectTestHelper::SplitType;
+
+class DistinctCollectExecutorTest
+    : public AqlExecutorTestCaseWithParam<std::tuple<DistinctCollectSplitType>> {
  protected:
   ExecutionState state;
   ResourceMonitor monitor;
-  AqlItemBlockManager itemBlockManager;
-  mocks::MockAqlServer server;
-  std::unique_ptr<arangodb::aql::Query> fakedQuery;
   arangodb::transaction::Methods* trx;
 
   std::unordered_set<RegisterId> const regToClear;
   std::unordered_set<RegisterId> const regToKeep;
-  std::vector<std::pair<RegisterId, RegisterId>> groupRegisters;
 
-  std::unordered_set<RegisterId> readableInputRegisters;
-  std::unordered_set<RegisterId> writeableOutputRegisters;
+  std::unordered_set<RegisterId> readableInputRegisters = {0};
+  std::unordered_set<RegisterId> writeableOutputRegisters = {1};
 
   SharedAqlItemBlockPtr block;
   VPackBuilder input;
   NoStats stats;
 
+  DistinctCollectExecutorInfos infos;
+
   DistinctCollectExecutorTest()
-      : itemBlockManager(&monitor, SerializationFormat::SHADOWROWS),
-        fakedQuery(server.createFakeQuery()),
-        trx(fakedQuery->trx()) {}
+      : trx(fakedQuery->trx()),
+        infos(1 /*nrIn*/, 2 /*nrOut*/, regToClear, regToKeep,
+              std::move(readableInputRegisters), std::move(writeableOutputRegisters),
+              std::make_pair<RegisterId, RegisterId>(1, 0), trx) {}
 };
 
-TEST_F(DistinctCollectExecutorTest, if_no_rows_in_upstream_the_producer_doesnt_wait) {
-  groupRegisters.emplace_back(std::make_pair<RegisterId, RegisterId>(1, 2));
-  DistinctCollectExecutorInfos infos(2 /*nrIn*/, 2 /*nrOut*/, regToClear,
-                                     regToKeep, std::move(readableInputRegisters),
-                                     std::move(writeableOutputRegisters),
-                                     std::move(groupRegisters), trx);
-  block.reset(new AqlItemBlock(itemBlockManager, 1000, 2));
-
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input.steal(), false);
-  DistinctCollectExecutor testee(fetcher, infos);
-
-  OutputAqlItemRow result(std::move(block), infos.getOutputRegisters(),
-                          infos.registersToKeep(), infos.registersToClear());
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(result.produced());
-}
-
-TEST_F(DistinctCollectExecutorTest, if_no_rows_in_upstream_the_producer_waits) {
-  groupRegisters.emplace_back(std::make_pair<RegisterId, RegisterId>(1, 2));
-  DistinctCollectExecutorInfos infos(2 /*nrIn*/, 2 /*nrOut*/, regToClear,
-                                     regToKeep, std::move(readableInputRegisters),
-                                     std::move(writeableOutputRegisters),
-                                     std::move(groupRegisters), trx);
-  block.reset(new AqlItemBlock(itemBlockManager, 1000, 2));
-
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input.steal(), true);
-  DistinctCollectExecutor testee(fetcher, infos);
-
-  OutputAqlItemRow result(std::move(block), infos.getOutputRegisters(),
-                          infos.registersToKeep(), infos.registersToClear());
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::WAITING);
-  ASSERT_FALSE(result.produced());
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(result.produced());
-}
-
-TEST_F(DistinctCollectExecutorTest,
-       there_are_rows_in_the_upstream_no_distinct_values_the_producer_doesnt_wait) {
-  groupRegisters.emplace_back(std::make_pair<RegisterId, RegisterId>(1, 0));
-  readableInputRegisters.insert(0);
-  writeableOutputRegisters.insert(1);
-  RegisterId nrOutputRegister = 2;
-  DistinctCollectExecutorInfos infos(1 /*nrInputReg*/,
-                                     nrOutputRegister /*nrOutputReg*/, regToClear,
-                                     regToKeep, std::move(readableInputRegisters),
-                                     std::move(writeableOutputRegisters),
-                                     std::move(groupRegisters), trx);
-  block.reset(new AqlItemBlock(itemBlockManager, 1000, nrOutputRegister));
-
-  auto input = VPackParser::fromJson("[ [1], [2] ]");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), false);
-  DistinctCollectExecutor testee(fetcher, infos);
-
-  OutputAqlItemRow result(std::move(block), infos.getOutputRegisters(),
-                          infos.registersToKeep(), infos.registersToClear());
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(result.produced());
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_TRUE(result.produced());
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(result.produced());
-
-  auto block = result.stealBlock();
-  AqlValue x = block->getValue(0, 1);
-  ASSERT_TRUE(x.isNumber());
-  ASSERT_EQ(x.toInt64(), 1);
-
-  AqlValue z = block->getValue(1, 1);
-  ASSERT_TRUE(z.isNumber());
-  ASSERT_EQ(z.toInt64(), 2);
+TEST_P(DistinctCollectExecutorTest, split_1) {
+  auto [split] = GetParam();
+
+  ExecutorTestHelper(*fakedQuery)
+      .setExecBlock<DistinctCollectExecutor>(std::move(infos))
+      .setInputValueList(1, 1, 1, 2, 3, 4, 4, 5)
+      .setInputSplitType(split)
+      .setCall(AqlCall{2, AqlCall::Infinity{}, 2, true})
+      .expectOutputValueList(3, 4)
+      .expectSkipped(3)
+      .expectedState(ExecutionState::DONE)
+      .run();
 }
 
-TEST_F(DistinctCollectExecutorTest,
-       there_are_rows_in_the_upstream_no_distinct_values_the_producer_waits) {
-  groupRegisters.emplace_back(std::make_pair<RegisterId, RegisterId>(1, 0));
-  readableInputRegisters.insert(0);
-  writeableOutputRegisters.insert(1);
-  RegisterId nrOutputRegister = 2;
-  DistinctCollectExecutorInfos infos(1 /*nrInputReg*/,
-                                     nrOutputRegister /*nrOutputReg*/, regToClear,
-                                     regToKeep, std::move(readableInputRegisters),
-                                     std::move(writeableOutputRegisters),
-                                     std::move(groupRegisters), trx);
-  block.reset(new AqlItemBlock(itemBlockManager, 1000, nrOutputRegister));
-
-  auto input = VPackParser::fromJson("[ [1], [2] ]");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), true);
-  DistinctCollectExecutor testee(fetcher, infos);
-
-  OutputAqlItemRow result(std::move(block), infos.getOutputRegisters(),
-                          infos.registersToKeep(), infos.registersToClear());
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::WAITING);
-  ASSERT_FALSE(result.produced());
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(result.produced());
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::WAITING);
-  ASSERT_FALSE(result.produced());
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_TRUE(result.produced());
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(result.produced());
-
-  auto block = result.stealBlock();
-  AqlValue x = block->getValue(0, 1);
-  ASSERT_TRUE(x.isNumber());
-  ASSERT_EQ(x.toInt64(), 1);
-
-  AqlValue z = block->getValue(1, 1);
-  ASSERT_TRUE(z.isNumber());
-  ASSERT_EQ(z.toInt64(), 2);
+TEST_P(DistinctCollectExecutorTest, split_2) {
+  auto [split] = GetParam();
+
+  ExecutorTestHelper(*fakedQuery)
+      .setExecBlock<DistinctCollectExecutor>(std::move(infos))
+      .setInputValueList(1, 1, 1, 2, 3, 4, 4, 5)
+      .setInputSplitType(split)
+      .setCall(AqlCall{0, AqlCall::Infinity{}, 2, true})
+      .expectOutputValueList(1, 2)
+      .expectSkipped(3)
+      .expectedState(ExecutionState::DONE)
+      .run();
 }
 
-TEST_F(DistinctCollectExecutorTest,
-       there_are_rows_in_the_upstream_with_distinct_values_the_producer_doesnt_wait) {
-  groupRegisters.emplace_back(std::make_pair<RegisterId, RegisterId>(1, 0));
-  readableInputRegisters.insert(0);
-  writeableOutputRegisters.insert(1);
-  RegisterId nrOutputRegister = 2;
-  DistinctCollectExecutorInfos infos(1 /*nrInputReg*/,
-                                     nrOutputRegister /*nrOutputReg*/, regToClear,
-                                     regToKeep, std::move(readableInputRegisters),
-                                     std::move(writeableOutputRegisters),
-                                     std::move(groupRegisters), trx);
-  block.reset(new AqlItemBlock(itemBlockManager, 1000, nrOutputRegister));
-
-  auto input = VPackParser::fromJson("[ [1], [2], [3], [1], [2] ]");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), false);
-  DistinctCollectExecutor testee(fetcher, infos);
-
-  OutputAqlItemRow result(std::move(block), infos.getOutputRegisters(),
-                          infos.registersToKeep(), infos.registersToClear());
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(result.produced());
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(result.produced());
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(result.produced());
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_FALSE(result.produced());
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(result.produced());
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(result.produced());
-
-  auto block = result.stealBlock();
-  AqlValue x = block->getValue(0, 1);
-  ASSERT_TRUE(x.isNumber());
-  ASSERT_EQ(x.toInt64(), 1);
-
-  AqlValue z = block->getValue(1, 1);
-  ASSERT_TRUE(z.isNumber());
-  ASSERT_EQ(z.toInt64(), 2);
-
-  AqlValue y = block->getValue(2, 1);
-  ASSERT_TRUE(y.isNumber());
-  ASSERT_EQ(y.toInt64(), 3);
-}
-
-TEST_F(DistinctCollectExecutorTest,
-       there_are_rows_in_the_upstream_with_distinct_values_the_producer_waits) {
-  groupRegisters.emplace_back(std::make_pair<RegisterId, RegisterId>(1, 0));
-  readableInputRegisters.insert(0);
-  writeableOutputRegisters.insert(1);
-  RegisterId nrOutputRegister = 2;
-  DistinctCollectExecutorInfos infos(1 /*nrInputReg*/,
-                                     nrOutputRegister /*nrOutputReg*/, regToClear,
-                                     regToKeep, std::move(readableInputRegisters),
-                                     std::move(writeableOutputRegisters),
-                                     std::move(groupRegisters), trx);
-  block.reset(new AqlItemBlock(itemBlockManager, 1000, nrOutputRegister));
-
-  auto input = VPackParser::fromJson("[ [1], [2], [3], [1], [2] ]");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), true);
-  DistinctCollectExecutor testee(fetcher, infos);
-
-  OutputAqlItemRow result(std::move(block), infos.getOutputRegisters(),
-                          infos.registersToKeep(), infos.registersToClear());
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::WAITING);
-  ASSERT_FALSE(result.produced());
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(result.produced());
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::WAITING);
-  ASSERT_FALSE(result.produced());
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(result.produced());
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::WAITING);
-  ASSERT_FALSE(result.produced());
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(result.produced());
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::WAITING);
-  ASSERT_FALSE(result.produced());
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_FALSE(result.produced());
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::WAITING);
-  ASSERT_FALSE(result.produced());
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(result.produced());
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(result.produced());
-
-  auto block = result.stealBlock();
-  AqlValue x = block->getValue(0, 1);
-  ASSERT_TRUE(x.isNumber());
-  ASSERT_EQ(x.toInt64(), 1);
-
-  AqlValue z = block->getValue(1, 1);
-  ASSERT_TRUE(z.isNumber());
-  ASSERT_EQ(z.toInt64(), 2);
-
-  AqlValue y = block->getValue(2, 1);
-  ASSERT_TRUE(y.isNumber());
-  ASSERT_EQ(y.toInt64(), 3);
-}
+template <size_t... vs>
+const DistinctCollectSplitType splitIntoBlocks =
+    DistinctCollectSplitType{std::vector<std::size_t>{vs...}};
+template <size_t step>
+const DistinctCollectSplitType splitStep = DistinctCollectSplitType{step};
 
+INSTANTIATE_TEST_CASE_P(DistinctCollectExecutor, DistinctCollectExecutorTest,
+                        ::testing::Values(splitIntoBlocks<2, 3>,
+                                          splitIntoBlocks<3, 4>, splitStep<2>, splitStep<1>));
 }  // namespace aql
 }  // namespace tests
 }  // namespace arangodb

From c2ae62141af41f7ec6d8a5a631f0346f9f281803 Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Fri, 28 Feb 2020 11:56:24 +0100
Subject: [PATCH 081/122] Feature/aql subquery execution block impl execute
 implementation noresults (#11180)

* Use ExecutorHelper in tests

* Implemented no Results fetcher
---
 arangod/Aql/ExecutionBlockImpl.cpp  |   6 +-
 arangod/Aql/NoResultsExecutor.cpp   |  12 ++-
 arangod/Aql/NoResultsExecutor.h     |  20 +++-
 tests/Aql/NoResultsExecutorTest.cpp | 157 +++++++++++-----------------
 4 files changed, 90 insertions(+), 105 deletions(-)

diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index 19904c9eabaa..c1b4a286e91c 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -165,11 +165,12 @@ constexpr bool isNewStyleExecutor =
     IResearchViewMergeExecutor<true, arangodb::iresearch::MaterializeType::Materialize>,
     IResearchViewMergeExecutor<true, arangodb::iresearch::MaterializeType::NotMaterialize | arangodb::iresearch::MaterializeType::UseStoredValues>,
     IResearchViewMergeExecutor<true, arangodb::iresearch::MaterializeType::LateMaterialize | arangodb::iresearch::MaterializeType::UseStoredValues>,
-    SubqueryStartExecutor, SubqueryEndExecutor, TraversalExecutor, KShortestPathsExecutor,
+    SubqueryStartExecutor, SubqueryEndExecutor, TraversalExecutor, KShortestPathsExecutor, NoResultsExecutor,
     ShortestPathExecutor, EnumerateListExecutor, LimitExecutor, SingleRemoteModificationExecutor<IndexTag>, SingleRemoteModificationExecutor<Insert>,
     SingleRemoteModificationExecutor<Remove>, SingleRemoteModificationExecutor<Update>,
     SingleRemoteModificationExecutor<Replace>, SingleRemoteModificationExecutor<Upsert>>;
 
+
 template <class Executor>
 ExecutionBlockImpl<Executor>::ExecutionBlockImpl(ExecutionEngine* engine,
                                                  ExecutionNode const* node,
@@ -1149,11 +1150,10 @@ static SkipRowsRangeVariant constexpr skipRowsType() {
               IResearchViewMergeExecutor<true, arangodb::iresearch::MaterializeType::NotMaterialize | arangodb::iresearch::MaterializeType::UseStoredValues>,
               IResearchViewMergeExecutor<true, arangodb::iresearch::MaterializeType::LateMaterialize | arangodb::iresearch::MaterializeType::UseStoredValues>,
               TraversalExecutor, EnumerateListExecutor, SubqueryStartExecutor,
-              SubqueryEndExecutor, SortedCollectExecutor, LimitExecutor,
+              SubqueryEndExecutor, SortedCollectExecutor, LimitExecutor, NoResultsExecutor,
               SingleRemoteModificationExecutor<IndexTag>, SingleRemoteModificationExecutor<Insert>,
               SingleRemoteModificationExecutor<Remove>, SingleRemoteModificationExecutor<Update>,
               SingleRemoteModificationExecutor<Replace>, SingleRemoteModificationExecutor<Upsert>>),
-
       "Unexpected executor for SkipVariants::EXECUTOR");
 
   // The LimitExecutor will not work correctly with SkipVariants::FETCHER!
diff --git a/arangod/Aql/NoResultsExecutor.cpp b/arangod/Aql/NoResultsExecutor.cpp
index cc958c00df17..1728e430e6dd 100644
--- a/arangod/Aql/NoResultsExecutor.cpp
+++ b/arangod/Aql/NoResultsExecutor.cpp
@@ -30,9 +30,15 @@
 using namespace arangodb;
 using namespace arangodb::aql;
 
-NoResultsExecutor::NoResultsExecutor(Fetcher& fetcher, ExecutorInfos& infos) {}
+NoResultsExecutor::NoResultsExecutor(Fetcher&, ExecutorInfos&) {}
 NoResultsExecutor::~NoResultsExecutor() = default;
 
-std::pair<ExecutionState, NoStats> NoResultsExecutor::produceRows(OutputAqlItemRow& output) {
-  return {ExecutionState::DONE, NoStats{}};
+auto NoResultsExecutor::produceRows(AqlItemBlockInputRange& input, OutputAqlItemRow& output) const
+    noexcept -> std::tuple<ExecutorState, Stats, AqlCall> {
+  return {ExecutorState::DONE, NoStats{}, AqlCall{0, false, 0, AqlCall::LimitType::HARD}};
 }
+
+auto NoResultsExecutor::skipRowsRange(AqlItemBlockInputRange& inputRange, AqlCall& call) const
+    noexcept -> std::tuple<ExecutorState, Stats, size_t, AqlCall> {
+  return {ExecutorState::DONE, NoStats{}, 0, AqlCall{0, false, 0, AqlCall::LimitType::HARD}};
+};
\ No newline at end of file
diff --git a/arangod/Aql/NoResultsExecutor.h b/arangod/Aql/NoResultsExecutor.h
index 05fbc0aecd97..db5f7ed91059 100644
--- a/arangod/Aql/NoResultsExecutor.h
+++ b/arangod/Aql/NoResultsExecutor.h
@@ -39,7 +39,9 @@ template <BlockPassthrough>
 class SingleRowFetcher;
 class ExecutorInfos;
 class NoStats;
+struct AqlCall;
 class OutputAqlItemRow;
+class AqlItemBlockInputRange;
 
 class NoResultsExecutor {
  public:
@@ -51,16 +53,24 @@ class NoResultsExecutor {
   using Fetcher = SingleRowFetcher<Properties::allowsBlockPassthrough>;
   using Infos = ExecutorInfos;
   using Stats = NoStats;
-  NoResultsExecutor(Fetcher& fetcher, ExecutorInfos&);
+  NoResultsExecutor(Fetcher&, ExecutorInfos&);
   ~NoResultsExecutor();
 
   /**
-   * @brief produce the next Row of Aql Values.
+   * @brief DO NOT PRODUCE ROWS
    *
-   * @return ExecutionState,
-   *         if something was written output.hasValue() == true
+   * @return DONE, NoStats, HardLimit = 0 Call
    */
-  std::pair<ExecutionState, Stats> produceRows(OutputAqlItemRow& output);
+  [[nodiscard]] auto produceRows(AqlItemBlockInputRange& input, OutputAqlItemRow& output) const
+      noexcept -> std::tuple<ExecutorState, Stats, AqlCall>;
+
+  /**
+   * @brief DO NOT SKIP ROWS
+   *
+   ** @return DONE, NoStats, 0, HardLimit = 0 Call
+   */
+  [[nodiscard]] auto skipRowsRange(AqlItemBlockInputRange& inputRange, AqlCall& call) const
+      noexcept -> std::tuple<ExecutorState, Stats, size_t, AqlCall>;
 
   inline std::pair<ExecutionState, size_t> expectedNumberOfRows(size_t) const {
     // Well nevermind the input, but we will always return 0 rows here.
diff --git a/tests/Aql/NoResultsExecutorTest.cpp b/tests/Aql/NoResultsExecutorTest.cpp
index 2557345af345..c7aaaad1b830 100644
--- a/tests/Aql/NoResultsExecutorTest.cpp
+++ b/tests/Aql/NoResultsExecutorTest.cpp
@@ -20,19 +20,13 @@
 /// @author Jan Christoph Uhde
 ////////////////////////////////////////////////////////////////////////////////
 
-#include "RowFetcherHelper.h"
 #include "gtest/gtest.h"
 
-#include "Aql/AqlItemBlock.h"
+#include "ExecutorTestHelper.h"
+
 #include "Aql/ExecutorInfos.h"
-#include "Aql/InputAqlItemRow.h"
 #include "Aql/NoResultsExecutor.h"
-#include "Aql/OutputAqlItemRow.h"
-#include "Aql/ResourceUsage.h"
-#include "Aql/Stats.h"
-
-#include <velocypack/Builder.h>
-#include <velocypack/velocypack-aliases.h>
+#include "Aql/SingleRowFetcher.h"
 
 using namespace arangodb;
 using namespace arangodb::aql;
@@ -41,94 +35,69 @@ namespace arangodb {
 namespace tests {
 namespace aql {
 
-class NoResultsExecutorTest : public ::testing::Test {
- protected:
-  ExecutionState state;
-
-  ResourceMonitor monitor;
-  AqlItemBlockManager itemBlockManager;
-  SharedAqlItemBlockPtr block;
-  std::shared_ptr<std::unordered_set<RegisterId>> outputRegisters;
-  std::shared_ptr<std::unordered_set<RegisterId>> registersToClear;
-  std::shared_ptr<std::unordered_set<RegisterId>> registersToKeep;
-
-  RegisterId inputRegister;
-  ExecutorInfos infos;
-  OutputAqlItemRow result;
+using NoResultsTestHelper = ExecutorTestHelper<1, 1>;
+using NoResultsSplitType = NoResultsTestHelper::SplitType;
+using NoResultsInputParam = std::tuple<NoResultsSplitType, AqlCall, size_t>;
 
-  NoResultsExecutorTest()
-      : itemBlockManager(&monitor, SerializationFormat::SHADOWROWS),
-        block(new AqlItemBlock(itemBlockManager, 1000, 1)),
-        outputRegisters(make_shared_unordered_set()),
-        registersToClear(make_shared_unordered_set()),
-        registersToKeep(make_shared_unordered_set()),
-        inputRegister(0),
-        infos(make_shared_unordered_set({0}), outputRegisters, 1 /*nr in*/,
-              1 /*nr out*/, *registersToClear, *registersToKeep),
-        result(std::move(block), outputRegisters, registersToKeep, registersToClear) {}
+class NoResultsExecutorTest : public AqlExecutorTestCaseWithParam<NoResultsInputParam> {
+ protected:
+  auto getSplit() -> NoResultsSplitType {
+    auto const& [split, call, inputRows] = GetParam();
+    return split;
+  }
+  auto getCall() -> AqlCall {
+    auto const& [split, call, inputRows] = GetParam();
+    return call;
+  }
+
+  auto getInput() -> size_t {
+    auto const& [split, call, inputRows] = GetParam();
+    return inputRows;
+  }
+
+  auto makeInfos() -> ExecutorInfos {
+    return ExecutorInfos{make_shared_unordered_set({0}),
+                         make_shared_unordered_set(),
+                         1,
+                         1,
+                         {},
+                         {}};
+  }
 };
 
-TEST_F(NoResultsExecutorTest, no_rows_upstream_the_producer_doesnt_wait) {
-  VPackBuilder input;
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input.steal(), false);
-  NoResultsExecutor testee(fetcher, infos);
-  NoStats stats{};
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(result.produced());
-  ASSERT_EQ(fetcher.nrCalled(), 0);
-}
-
-TEST_F(NoResultsExecutorTest, no_rows_upstream_the_producer_waits) {
-  VPackBuilder input;
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input.steal(), true);
-  NoResultsExecutor testee(fetcher, infos);
-  NoStats stats{};
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(result.produced());
-  ASSERT_EQ(fetcher.nrCalled(), 0);
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(result.produced());
-  ASSERT_EQ(fetcher.nrCalled(), 0);
-}
-
-TEST_F(NoResultsExecutorTest, rows_upstream_the_producer_doesnt_wait) {
-  auto input = VPackParser::fromJson("[ [true], [false], [true] ]");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), false);
-  NoResultsExecutor testee(fetcher, infos);
-  NoStats stats{};
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(result.produced());
-  ASSERT_EQ(fetcher.nrCalled(), 0);
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(result.produced());
-  ASSERT_EQ(fetcher.nrCalled(), 0);
-}
-
-TEST_F(NoResultsExecutorTest, rows_upstream_the_producer_waits) {
-  auto input = VPackParser::fromJson("[ [true], [false], [true] ]");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), true);
-  NoResultsExecutor testee(fetcher, infos);
-  NoStats stats{};
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(result.produced());
-  ASSERT_EQ(fetcher.nrCalled(), 0);
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(result.produced());
-  ASSERT_EQ(fetcher.nrCalled(), 0);
+template <size_t... vs>
+const NoResultsSplitType splitIntoBlocks =
+    NoResultsSplitType{std::vector<std::size_t>{vs...}};
+template <size_t step>
+const NoResultsSplitType splitStep = NoResultsSplitType{step};
+
+auto NoResultsInputSplits =
+    ::testing::Values(splitIntoBlocks<2, 3>, splitStep<1>, splitStep<2>);
+// This is just a random list of calls.
+auto NoResultsCalls =
+    ::testing::Values(AqlCall{}, AqlCall{0, false, 1, AqlCall::LimitType::SOFT},
+                      AqlCall{0, false, 2, AqlCall::LimitType::HARD},
+                      AqlCall{0, true, 1, AqlCall::LimitType::HARD},
+                      AqlCall{5, false, 1, AqlCall::LimitType::SOFT},
+                      AqlCall{2, true, 0, AqlCall::LimitType::HARD});
+auto NoResultsInputSizes = ::testing::Values(0, 1, 10, 2000);
+
+INSTANTIATE_TEST_CASE_P(NoResultsExecutorTest, NoResultsExecutorTest,
+                        ::testing::Combine(NoResultsInputSplits, NoResultsCalls,
+                                           NoResultsInputSizes));
+
+TEST_P(NoResultsExecutorTest, do_never_ever_return_results) {
+  ExecutionStats stats{};
+  ExecutorTestHelper<1, 1>(*fakedQuery)
+      .setExecBlock<NoResultsExecutor>(makeInfos(), ExecutionNode::NORESULTS)
+      .setInputFromRowNum(getInput())
+      .setInputSplitType(getSplit())
+      .setCall(getCall())
+      .expectOutput({0}, {})
+      .expectSkipped(0)
+      .expectedState(ExecutionState::DONE)
+      .expectedStats(stats)
+      .run();
 }
 
 }  // namespace aql

From 4fe26a951379961b56e94c2bfe854c6037cc53eb Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Fri, 28 Feb 2020 15:16:13 +0100
Subject: [PATCH 082/122] Moved Constrained sort to execute API (#11173)

* Moved Constrained sort to execute API

* The LIMIT in ConstrainedSort can actually fetch TOO much, if there is too small input from upstream

* Improved profiler tests, we need less calls now \o/

* Fixed unlimited call to limit executor
---
 arangod/Aql/ConstrainedSortExecutor.cpp | 195 +++++++++++-------------
 arangod/Aql/ConstrainedSortExecutor.h   |  23 ++-
 arangod/Aql/ExecutionBlockImpl.cpp      |   3 +-
 arangod/Aql/LimitExecutor.cpp           |   2 +-
 tests/Aql/SortLimit-test.cpp            |  84 ++++++----
 tests/js/server/aql/aql-profiler.js     |  10 +-
 6 files changed, 167 insertions(+), 150 deletions(-)

diff --git a/arangod/Aql/ConstrainedSortExecutor.cpp b/arangod/Aql/ConstrainedSortExecutor.cpp
index 2db1771511c8..54aa1ce7248a 100644
--- a/arangod/Aql/ConstrainedSortExecutor.cpp
+++ b/arangod/Aql/ConstrainedSortExecutor.cpp
@@ -81,7 +81,7 @@ class arangodb::aql::ConstrainedLessThan {
   std::vector<arangodb::aql::SortRegister> const& _sortRegisters;
 };  // ConstrainedLessThan
 
-arangodb::Result ConstrainedSortExecutor::pushRow(InputAqlItemRow& input) {
+arangodb::Result ConstrainedSortExecutor::pushRow(InputAqlItemRow const& input) {
   using arangodb::aql::AqlItemBlock;
   using arangodb::aql::AqlValue;
   using arangodb::aql::RegisterId;
@@ -114,12 +114,14 @@ arangodb::Result ConstrainedSortExecutor::pushRow(InputAqlItemRow& input) {
   return TRI_ERROR_NO_ERROR;
 }
 
-bool ConstrainedSortExecutor::compareInput(size_t const& rowPos, InputAqlItemRow& row) const {
+bool ConstrainedSortExecutor::compareInput(size_t const& rowPos,
+                                           InputAqlItemRow const& row) const {
   for (auto const& reg : _infos.sortRegisters()) {
     auto const& lhs = _heapBuffer->getValueReference(rowPos, reg.reg);
     auto const& rhs = row.getValue(reg.reg);
 
-    int const cmp = arangodb::aql::AqlValue::Compare(_infos.vpackOptions(), lhs, rhs, true);
+    int const cmp =
+        arangodb::aql::AqlValue::Compare(_infos.vpackOptions(), lhs, rhs, true);
 
     if (cmp < 0) {
       return reg.asc;
@@ -155,87 +157,118 @@ ConstrainedSortExecutor::~ConstrainedSortExecutor() = default;
 bool ConstrainedSortExecutor::doneProducing() const noexcept {
   // must not get strictly larger
   TRI_ASSERT(_returnNext <= _rows.size());
-  return _state == ExecutionState::DONE && _returnNext >= _rows.size();
+  return _returnNext >= _rows.size();
 }
 
 bool ConstrainedSortExecutor::doneSkipping() const noexcept {
   // must not get strictly larger
   TRI_ASSERT(_returnNext + _skippedAfter <= _rowsRead);
-  return _state == ExecutionState::DONE && _returnNext + _skippedAfter >= _rowsRead;
+  return _returnNext + _skippedAfter >= _rowsRead;
 }
 
-ExecutionState ConstrainedSortExecutor::consumeInput() {
-  while (_state != ExecutionState::DONE) {
+ExecutorState ConstrainedSortExecutor::consumeInput(AqlItemBlockInputRange& inputRange) {
+  while (inputRange.hasDataRow()) {
     TRI_IF_FAILURE("SortBlock::doSorting") {
       THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
     }
-    // We need to pull rows from above, and insert them into the heap
-    InputAqlItemRow input(CreateInvalidInputRowHint{});
 
-    std::tie(_state, input) = _fetcher.fetchRow();
-    if (_state == ExecutionState::WAITING) {
-      return _state;
+    auto const& [state, input] = inputRange.nextDataRow();
+    // Otherwise we would have left the loop
+    TRI_ASSERT(input.isInitialized());
+    ++_rowsRead;
+    if (_rowsPushed < _infos.limit() || !compareInput(_rows.front(), input)) {
+      // Push this row into the heap
+      pushRow(input);
     }
-    if (!input.isInitialized()) {
-      TRI_ASSERT(_state == ExecutionState::DONE);
-    } else {
-      ++_rowsRead;
-      if (_rowsPushed < _infos.limit() || !compareInput(_rows.front(), input)) {
-        // Push this row into the heap
-        pushRow(input);
-      }
+  }
+  if (inputRange.upstreamState() == ExecutorState::DONE) {
+    if (_returnNext == 0) {
+      // Only once sort the rows again, s.t. the
+      // contained list of elements is in the right ordering.
+      std::sort(_rows.begin(), _rows.end(), *_cmpHeap);
     }
   }
+  return inputRange.upstreamState();
+}
 
-  TRI_ASSERT(_state == ExecutionState::DONE);
-
-  return _state;
+auto ConstrainedSortExecutor::produceRows(AqlItemBlockInputRange& input, OutputAqlItemRow& output)
+    -> std::tuple<ExecutorState, Stats, AqlCall> {
+  if (consumeInput(input) == ExecutorState::HASMORE) {
+    // Input could not be fully consumed, executor is more hungry!
+    // Get more.
+    AqlCall upstreamCall{};
+    // We need to fetch everything form upstream.
+    // Unlimited, no offset call.
+    return {ExecutorState::HASMORE, NoStats{}, upstreamCall};
+  };
+
+  while (!output.isFull() && !doneProducing()) {
+    // Now our heap is full and sorted, we just need to return it line by line
+    TRI_ASSERT(_returnNext < _rows.size());
+    auto const heapRowPosition = _rows[_returnNext];
+    ++_returnNext;
+    InputAqlItemRow heapRow(_heapBuffer, heapRowPosition);
+    TRI_ASSERT(heapRow.isInitialized());
+    TRI_ASSERT(heapRowPosition < _rowsPushed);
+    output.copyRow(heapRow);
+    output.advanceRow();
+  }
+  if (doneProducing()) {
+    return {ExecutorState::DONE, NoStats{}, AqlCall{}};
+  }
+  return {ExecutorState::HASMORE, NoStats{}, AqlCall{}};
 }
 
-std::pair<ExecutionState, NoStats> ConstrainedSortExecutor::produceRows(OutputAqlItemRow& output) {
-  {
-    ExecutionState state = consumeInput();
-    TRI_ASSERT(state == _state);
-    if (state == ExecutionState::WAITING) {
-      return {ExecutionState::WAITING, NoStats{}};
+auto ConstrainedSortExecutor::skipRowsRange(AqlItemBlockInputRange& inputRange, AqlCall& call)
+    -> std::tuple<ExecutorState, Stats, size_t, AqlCall> {
+  if (consumeInput(inputRange) == ExecutorState::HASMORE) {
+    // Input could not be fully consumed, executor is more hungry!
+    // Get more.
+    AqlCall upstreamCall{};
+    // We need to fetch everything form upstream.
+    // Unlimited, no offset call.
+    return {ExecutorState::HASMORE, NoStats{}, 0, upstreamCall};
+  };
+
+  while (!doneProducing()) {
+    if (call.getOffset() > 0) {
+      size_t available = _rows.size() - _returnNext;
+      size_t toSkip = std::min(available, call.getOffset());
+      _returnNext += toSkip;
+      call.didSkip(toSkip);
+    } else if (call.needSkipMore()) {
+      // We are in fullcount case, simply skip all!
+      // I think this is actually invalid, as it would case LIMIT
+      // to underfetch.
+      // However will work like this.
+      size_t available = _rows.size() - _returnNext;
+      call.didSkip(available);
+      _returnNext = _rows.size();
+    } else {
+      // We still have something, but cannot continue to skip.
+      return {ExecutorState::HASMORE, NoStats{}, call.getSkipCount(), AqlCall{}};
     }
-    TRI_ASSERT(state == ExecutionState::DONE);
   }
 
-  if (doneProducing()) {
-    if (doneSkipping()) {
-      // No we're really done
-      return {ExecutionState::DONE, NoStats{}};
+  while (call.needSkipMore() && !doneSkipping()) {
+    // unlikely, but for backwardscompatibility.
+    if (call.getOffset() > 0) {
+      auto const rowsLeftToSkip = _rowsRead - (_rows.size() + _skippedAfter);
+      auto const skipNum = (std::min)(call.getOffset(), rowsLeftToSkip);
+      call.didSkip(skipNum);
+      _skippedAfter += skipNum;
+    } else {
+      // Fullcount
+      auto const rowsLeftToSkip = _rowsRead - (_rows.size() + _skippedAfter);
+      call.didSkip(rowsLeftToSkip);
+      _skippedAfter += rowsLeftToSkip;
+      TRI_ASSERT(doneSkipping());
     }
-    // We should never get here, as the following LIMIT block should never fetch
-    // more than our limit. It may only skip after that.
-    // But note that this means that this block breaks with usual AQL behaviour!
-    // From this point on (i.e. doneProducing()), this block may only skip, not produce.
-    TRI_ASSERT(false);
-    THROW_ARANGO_EXCEPTION_MESSAGE(
-        TRI_ERROR_INTERNAL_AQL,
-        "Overfetch during constrained heap sort. Please report this error! Try "
-        "turning off the sort-limit optimizer rule to get your query working.");
   }
 
-  if (_returnNext == 0) {
-    // Only once sort the rows again, s.t. the
-    // contained list of elements is in the right ordering.
-    std::sort(_rows.begin(), _rows.end(), *_cmpHeap);
-  }
+  auto const state = doneSkipping() ? ExecutorState::DONE : ExecutorState::HASMORE;
 
-  // Now our heap is full and sorted, we just need to return it line by line
-  TRI_ASSERT(_returnNext < _rows.size());
-  auto const heapRowPosition = _rows[_returnNext];
-  ++_returnNext;
-  InputAqlItemRow heapRow(_heapBuffer, heapRowPosition);
-  TRI_ASSERT(heapRow.isInitialized());
-  TRI_ASSERT(heapRowPosition < _rowsPushed);
-  output.copyRow(heapRow);
-
-  // Lie, we may have a possible LIMIT block with fullCount to work.
-  // We emitted at least one row at this point, so this is fine.
-  return {ExecutionState::HASMORE, NoStats{}};
+  return {state, NoStats{}, call.getSkipCount(), AqlCall{}};
 }
 
 std::pair<ExecutionState, size_t> ConstrainedSortExecutor::expectedNumberOfRows(size_t) const {
@@ -268,45 +301,3 @@ std::pair<ExecutionState, size_t> ConstrainedSortExecutor::expectedNumberOfRows(
 
   return {ExecutionState::HASMORE, rowsLeft};
 }
-
-std::tuple<ExecutionState, NoStats, size_t> ConstrainedSortExecutor::skipRows(size_t toSkipRequested) {
-  {
-    ExecutionState state = consumeInput();
-    TRI_ASSERT(state == _state);
-    if (state == ExecutionState::WAITING) {
-      return {ExecutionState::WAITING, NoStats{}, 0};
-    }
-    TRI_ASSERT(state == ExecutionState::DONE);
-  }
-
-  if (_returnNext == 0) {
-    // Only once sort the rows again, s.t. the
-    // contained list of elements is in the right ordering.
-    std::sort(_rows.begin(), _rows.end(), *_cmpHeap);
-  }
-
-  size_t skipped = 0;
-
-  // Skip rows in the heap
-  if (!doneProducing()) {
-    TRI_ASSERT(_rows.size() >= _returnNext);
-    auto const rowsLeftInHeap = _rows.size() - _returnNext;
-    auto const skipNum = (std::min)(toSkipRequested, rowsLeftInHeap);
-    _returnNext += skipNum;
-    skipped += skipNum;
-  }
-
-  // Skip rows we've dropped
-  if (skipped < toSkipRequested && !doneSkipping()) {
-    TRI_ASSERT(doneProducing());
-    auto const rowsLeftToSkip = _rowsRead - (_rows.size() + _skippedAfter);
-    auto const skipNum = (std::min)(toSkipRequested, rowsLeftToSkip);
-    _skippedAfter += skipNum;
-    skipped += skipNum;
-  }
-
-  TRI_ASSERT(skipped <= toSkipRequested);
-  auto const state = doneSkipping() ? ExecutionState::DONE : ExecutionState::HASMORE;
-
-  return {state, NoStats{}, skipped};
-}
diff --git a/arangod/Aql/ConstrainedSortExecutor.h b/arangod/Aql/ConstrainedSortExecutor.h
index 7fdf9db53972..9541dd0cbde4 100644
--- a/arangod/Aql/ConstrainedSortExecutor.h
+++ b/arangod/Aql/ConstrainedSortExecutor.h
@@ -47,6 +47,7 @@ class AqlItemMatrix;
 class ConstrainedLessThan;
 class ExecutorInfos;
 class InputAqlItemRow;
+class AqlItemBlockInputRange;
 class NoStats;
 class OutputAqlItemRow;
 class SortExecutorInfos;
@@ -70,14 +71,20 @@ class ConstrainedSortExecutor {
   ~ConstrainedSortExecutor();
 
   /**
-   * @brief produce the next Row of Aql Values.
+   * @brief produce the next Rows of Aql Values.
    *
-   * @return ExecutionState,
-   *         if something was written output.hasValue() == true
+   * @return ExecutorState, the stats, and a new Call that needs to be send to upstream
    */
-  std::pair<ExecutionState, Stats> produceRows(OutputAqlItemRow& output);
+  [[nodiscard]] auto produceRows(AqlItemBlockInputRange& input, OutputAqlItemRow& output)
+      -> std::tuple<ExecutorState, Stats, AqlCall>;
 
-  std::tuple<ExecutionState, Stats, size_t> skipRows(size_t toSkipRequested);
+  /**
+   * @brief skip the next Rows of Aql Values.
+   *
+   * @return ExecutorState, the stats, and a new Call that needs to be send to upstream
+   */
+  [[nodiscard]] auto skipRowsRange(AqlItemBlockInputRange& inputRange, AqlCall& call)
+      -> std::tuple<ExecutorState, Stats, size_t, AqlCall>;
 
   /**
    * @brief This Executor knows how many rows it will produce and most by itself
@@ -86,8 +93,8 @@ class ConstrainedSortExecutor {
   std::pair<ExecutionState, size_t> expectedNumberOfRows(size_t atMost) const;
 
  private:
-  bool compareInput(size_t const& rosPos, InputAqlItemRow& row) const;
-  arangodb::Result pushRow(InputAqlItemRow& row);
+  bool compareInput(size_t const& rosPos, InputAqlItemRow const& row) const;
+  arangodb::Result pushRow(InputAqlItemRow const& row);
 
   // We're done producing when we've emitted all rows from our heap.
   bool doneProducing() const noexcept;
@@ -97,7 +104,7 @@ class ConstrainedSortExecutor {
   // sort as well. This is for fullCount queries only.
   bool doneSkipping() const noexcept;
 
-  ExecutionState consumeInput();
+  ExecutorState consumeInput(AqlItemBlockInputRange& inputRange);
 
  private:
   Infos& _infos;
diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index c1b4a286e91c..d4f9ee43a800 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -140,7 +140,7 @@ constexpr bool isNewStyleExecutor =
                 DistinctCollectExecutor, IndexExecutor, EnumerateCollectionExecutor,
                 // TODO: re-enable after new subquery end & start are implemented
                 // CalculationExecutor<CalculationType::Condition>, CalculationExecutor<CalculationType::Reference>, CalculationExecutor<CalculationType::V8Condition>,
-                HashedCollectExecutor,
+                HashedCollectExecutor, ConstrainedSortExecutor,
 #ifdef ARANGODB_USE_GOOGLE_TESTS
     TestLambdaExecutor,
     TestLambdaSkipExecutor,  // we need one after these to avoid compile errors in non-test mode
@@ -1126,6 +1126,7 @@ static SkipRowsRangeVariant constexpr skipRowsType() {
               Executor, FilterExecutor, ShortestPathExecutor, ReturnExecutor, KShortestPathsExecutor,
               IdExecutor<SingleRowFetcher<BlockPassthrough::Enable>>, IdExecutor<ConstFetcher>,
               HashedCollectExecutor, IndexExecutor, EnumerateCollectionExecutor, DistinctCollectExecutor,
+              ConstrainedSortExecutor,
 #ifdef ARANGODB_USE_GOOGLE_TESTS
               TestLambdaSkipExecutor,
 #endif
diff --git a/arangod/Aql/LimitExecutor.cpp b/arangod/Aql/LimitExecutor.cpp
index 7d3d3ea6f089..0f13bd062a52 100644
--- a/arangod/Aql/LimitExecutor.cpp
+++ b/arangod/Aql/LimitExecutor.cpp
@@ -75,7 +75,7 @@ auto LimitExecutor::calculateUpstreamCall(AqlCall const& clientCall) const -> Aq
 
   // Generally, we create a hard limit. However, if we get a soft limit from
   // downstream that is lower than our hard limit, we use that instead.
-  bool const useSoftLimit = clientCall.hasSoftLimit() &&
+  bool const useSoftLimit = !clientCall.hasHardLimit() &&
                             clientCall.getLimit() < localLimitMinusDownstreamOffset;
 
   if (useSoftLimit) {
diff --git a/tests/Aql/SortLimit-test.cpp b/tests/Aql/SortLimit-test.cpp
index 2bf1f312bab6..72f4d17f7ff1 100644
--- a/tests/Aql/SortLimit-test.cpp
+++ b/tests/Aql/SortLimit-test.cpp
@@ -64,8 +64,10 @@ extern const char* ARGV0;  // defined in main.cpp
 /// @brief setup
 ////////////////////////////////////////////////////////////////////////////////
 
+// The Paramater is a Flag if we activate fullcount or not.
+
 class SortLimitTest
-    : public ::testing::Test,
+    : public ::testing::TestWithParam<bool>,
       public arangodb::tests::LogSuppressor<arangodb::Logger::FIXME, arangodb::LogLevel::ERR> {
  protected:
   arangodb::tests::mocks::MockAqlServer server;
@@ -87,10 +89,20 @@ class SortLimitTest
 
   ~SortLimitTest() { vocbase.reset(); }
 
+  auto doFullCount() -> bool { return GetParam(); }
+
+  auto buildOptions(std::string rules) -> std::shared_ptr<arangodb::velocypack::Builder> {
+    if (doFullCount()) {
+      return arangodb::velocypack::Parser::fromJson(
+          "{\"optimizer\": {\"rules\": [" + rules + "]}, \"fullCount\": true}");
+    }
+    return arangodb::velocypack::Parser::fromJson(
+        "{\"optimizer\": {\"rules\": [" + rules + "]}}");
+  }
+
   std::string sorterType(TRI_vocbase_t& vocbase, std::string const& queryString,
                          std::string rules = "") {
-    auto options = arangodb::velocypack::Parser::fromJson(
-        "{\"optimizer\": {\"rules\": [" + rules + "]}}");
+    auto options = buildOptions(rules);
     arangodb::aql::Query query(false, vocbase, arangodb::aql::QueryString(queryString),
                                nullptr, options, arangodb::aql::PART_MAIN);
 
@@ -114,9 +126,8 @@ class SortLimitTest
 
   void verifyExpectedResults(TRI_vocbase_t& vocbase, std::string const& queryString,
                              std::vector<size_t> const& expected,
-                             std::string rules = "") {
-    auto options = arangodb::velocypack::Parser::fromJson(
-        "{\"optimizer\": {\"rules\": [" + rules + "]}}");
+                             size_t fullCount, std::string rules = "") {
+    auto options = buildOptions(rules);
     arangodb::aql::Query query(false, vocbase, arangodb::aql::QueryString(queryString),
                                nullptr, options, arangodb::aql::PART_MAIN);
     std::shared_ptr<arangodb::aql::SharedQueryState> ss = query.sharedState();
@@ -146,6 +157,13 @@ class SortLimitTest
           << resolved.toJson();
       i++;
     }
+    auto actualFullCount = arangodb::basics::VelocyPackHelper::getNumericValue<size_t>(
+        result.extra->slice(), std::vector<std::string>{"stats", "fullCount"}, 0);
+    if (doFullCount()) {
+      EXPECT_EQ(actualFullCount, fullCount);
+    } else {
+      EXPECT_EQ(actualFullCount, 0);
+    }
   }
 
   // create collection0, insertedDocs[0, 999]
@@ -182,102 +200,104 @@ class SortLimitTest
   }
 };
 
-TEST_F(SortLimitTest, CheckSimpleLimitSortedAscInInsertionOrder) {
+INSTANTIATE_TEST_CASE_P(SortLimitTest, SortLimitTest, ::testing::Bool());
+
+TEST_P(SortLimitTest, CheckSimpleLimitSortedAscInInsertionOrder) {
   std::string query =
       "FOR d IN testCollection0 SORT d.valAsc LIMIT 0, 10 RETURN d";
   std::vector<size_t> expected = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
   EXPECT_EQ(sorterType(*vocbase, query), "constrained-heap");
-  verifyExpectedResults(*vocbase, query, expected);
+  verifyExpectedResults(*vocbase, query, expected, 1000);
 }
 
-TEST_F(SortLimitTest, CheckLimitWithOffsetSortedAscInInsertionOrder) {
+TEST_P(SortLimitTest, CheckLimitWithOffsetSortedAscInInsertionOrder) {
   std::string query =
       "FOR d IN testCollection0 SORT d.valAsc LIMIT 10, 10 RETURN d";
   std::vector<size_t> expected = {10, 11, 12, 13, 14, 15, 16, 17, 18, 19};
   EXPECT_EQ(sorterType(*vocbase, query), "constrained-heap");
-  verifyExpectedResults(*vocbase, query, expected);
+  verifyExpectedResults(*vocbase, query, expected, 1000);
 }
 
-TEST_F(SortLimitTest, CheckSimpleLimitSortedAscInReverseInsertionOrder) {
+TEST_P(SortLimitTest, CheckSimpleLimitSortedAscInReverseInsertionOrder) {
   std::string query =
       "FOR d IN testCollection0 SORT d.valDsc LIMIT 0, 10 RETURN d";
   std::vector<size_t> expected = {999, 998, 997, 996, 995,
                                   994, 993, 992, 991, 990};
   EXPECT_EQ(sorterType(*vocbase, query), "constrained-heap");
-  verifyExpectedResults(*vocbase, query, expected);
+  verifyExpectedResults(*vocbase, query, expected, 1000);
 }
 
-TEST_F(SortLimitTest, CheckLimitWithOffsetSortedAscInReverseInsertionOrder) {
+TEST_P(SortLimitTest, CheckLimitWithOffsetSortedAscInReverseInsertionOrder) {
   std::string query =
       "FOR d IN testCollection0 SORT d.valDsc LIMIT 10, 10 RETURN d";
   std::vector<size_t> expected = {989, 988, 987, 986, 985,
                                   984, 983, 982, 981, 980};
   EXPECT_EQ(sorterType(*vocbase, query), "constrained-heap");
-  verifyExpectedResults(*vocbase, query, expected);
+  verifyExpectedResults(*vocbase, query, expected, 1000);
 }
 
-TEST_F(SortLimitTest, CheckSimpleLimitSortedDscInInsertionOrder) {
+TEST_P(SortLimitTest, CheckSimpleLimitSortedDscInInsertionOrder) {
   std::string query =
       "FOR d IN testCollection0 SORT d.valAsc DESC LIMIT 0, 10 RETURN d";
   std::vector<size_t> expected = {999, 998, 997, 996, 995,
                                   994, 993, 992, 991, 990};
   EXPECT_EQ(sorterType(*vocbase, query), "constrained-heap");
-  verifyExpectedResults(*vocbase, query, expected);
+  verifyExpectedResults(*vocbase, query, expected, 1000);
 }
 
-TEST_F(SortLimitTest, CheckLimitWithOffsetSortedDscInInsertionOrder) {
+TEST_P(SortLimitTest, CheckLimitWithOffsetSortedDscInInsertionOrder) {
   std::string query =
       "FOR d IN testCollection0 SORT d.valAsc DESC LIMIT 10, 10 RETURN d";
   std::vector<size_t> expected = {989, 988, 987, 986, 985,
                                   984, 983, 982, 981, 980};
   EXPECT_EQ(sorterType(*vocbase, query), "constrained-heap");
-  verifyExpectedResults(*vocbase, query, expected);
+  verifyExpectedResults(*vocbase, query, expected, 1000);
 }
 
-TEST_F(SortLimitTest, CheckSimpleLimitSortedDscInReverseInsertionOrder) {
+TEST_P(SortLimitTest, CheckSimpleLimitSortedDscInReverseInsertionOrder) {
   std::string query =
       "FOR d IN testCollection0 SORT d.valDsc DESC LIMIT 0, 10 RETURN d";
   std::vector<size_t> expected = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
   EXPECT_EQ(sorterType(*vocbase, query), "constrained-heap");
-  verifyExpectedResults(*vocbase, query, expected);
+  verifyExpectedResults(*vocbase, query, expected, 1000);
 }
 
-TEST_F(SortLimitTest, CheckLimitWithOffsetSortedDscInReverseInsertionOrder) {
+TEST_P(SortLimitTest, CheckLimitWithOffsetSortedDscInReverseInsertionOrder) {
   std::string query =
       "FOR d IN testCollection0 SORT d.valDsc DESC LIMIT 10, 10 RETURN d";
   std::vector<size_t> expected = {10, 11, 12, 13, 14, 15, 16, 17, 18, 19};
   EXPECT_EQ(sorterType(*vocbase, query), "constrained-heap");
-  verifyExpectedResults(*vocbase, query, expected);
+  verifyExpectedResults(*vocbase, query, expected, 1000);
 }
 
-TEST_F(SortLimitTest, CheckLimitWithOffsetCompoundSort) {
+TEST_P(SortLimitTest, CheckLimitWithOffsetCompoundSort) {
   std::string query =
       "FOR d IN testCollection0 SORT d.mod, d.valAsc LIMIT 2, 5 RETURN  d";
   std::vector<size_t> expected = {200, 300, 400, 500, 600};
   EXPECT_EQ(sorterType(*vocbase, query), "constrained-heap");
-  verifyExpectedResults(*vocbase, query, expected);
+  verifyExpectedResults(*vocbase, query, expected, 1000);
 }
 
-TEST_F(SortLimitTest, CheckLimitWithOffsetCompoundSortAgain) {
+TEST_P(SortLimitTest, CheckLimitWithOffsetCompoundSortAgain) {
   std::string query =
       "FOR d IN testCollection0 SORT d.mod, d.valAsc LIMIT 10, 10 RETURN d";
   std::vector<size_t> expected = {1,   101, 201, 301, 401,
                                   501, 601, 701, 801, 901};
   EXPECT_EQ(sorterType(*vocbase, query), "constrained-heap");
-  verifyExpectedResults(*vocbase, query, expected);
+  verifyExpectedResults(*vocbase, query, expected, 1000);
 }
 
-TEST_F(SortLimitTest, CheckInterloperFilterMovedUp) {
+TEST_P(SortLimitTest, CheckInterloperFilterMovedUp) {
   std::string query =
       "FOR d IN testCollection0 SORT d.valAsc FILTER d.mod == 0 LIMIT 0, 10 "
       "RETURN d";
   std::vector<size_t> expected = {0,   100, 200, 300, 400,
                                   500, 600, 700, 800, 900};
   EXPECT_EQ(sorterType(*vocbase, query), "constrained-heap");
-  verifyExpectedResults(*vocbase, query, expected);
+  verifyExpectedResults(*vocbase, query, expected, 10);
 }
 
-TEST_F(SortLimitTest, CheckInterloperFilterNotMoved) {
+TEST_P(SortLimitTest, CheckInterloperFilterNotMoved) {
   std::string query =
       "FOR d IN testCollection0 SORT d.valAsc FILTER d.mod == 0 LIMIT 0, 10 "
       "RETURN d";
@@ -285,14 +305,14 @@ TEST_F(SortLimitTest, CheckInterloperFilterNotMoved) {
   std::vector<size_t> expected = {0,   100, 200, 300, 400,
                                   500, 600, 700, 800, 900};
   EXPECT_EQ(sorterType(*vocbase, query, rules), "standard");
-  verifyExpectedResults(*vocbase, query, expected, rules);
+  verifyExpectedResults(*vocbase, query, expected, 10, rules);
 }
 
-TEST_F(SortLimitTest, CheckInterloperEnumerateList) {
+TEST_P(SortLimitTest, CheckInterloperEnumerateList) {
   std::string query =
       "FOR d IN testCollection0 SORT d.valAsc FOR e IN 1..10 FILTER e == 1 "
       "LIMIT 0, 10 RETURN d";
   std::vector<size_t> expected = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
   EXPECT_EQ(sorterType(*vocbase, query), "standard");
-  verifyExpectedResults(*vocbase, query, expected);
+  verifyExpectedResults(*vocbase, query, expected, 1000);
 }
diff --git a/tests/js/server/aql/aql-profiler.js b/tests/js/server/aql/aql-profiler.js
index 421d7254a7f7..50eca3fee3a3 100644
--- a/tests/js/server/aql/aql-profiler.js
+++ b/tests/js/server/aql/aql-profiler.js
@@ -677,7 +677,7 @@ function ahuacatlProfilerTestSuite () {
         { type : SingletonBlock, calls : 1, items : 1 },
         { type : CalculationBlock, calls : 1, items : 1 },
         { type : EnumerateListBlock, calls : batches, items : rows },
-        { type : ConstrainedSortBlock, calls : skipOffsetBatches(rows) + limitMinusSkipBatches(rows), items : limit(rows) },
+        { type : ConstrainedSortBlock, calls : limitMinusSkipBatches(rows), items : limit(rows) },
         { type : LimitBlock, calls : limitMinusSkipBatches(rows), items : limitMinusSkip(rows) },
         { type : ReturnBlock, calls : limitMinusSkipBatches(rows), items : limitMinusSkip(rows) }
       ];
@@ -698,15 +698,13 @@ function ahuacatlProfilerTestSuite () {
 
     testSortLimitBlock2 : function () {
       const query = 'FOR i IN 1..@rows SORT i DESC LIMIT @offset, @limit RETURN i';
-      const remainder = rows => rows - limit(rows);
-      const remainderBatches = rows => remainder(rows) === 0 ? 0 : 1;
       const genNodeList = (rows, batches) => [
         { type : SingletonBlock, calls : 1, items : 1 },
         { type : CalculationBlock, calls : 1, items : 1 },
         { type : EnumerateListBlock, calls : batches, items : rows },
-        { type : ConstrainedSortBlock, calls : skipOffsetBatches(rows) + limitMinusSkipBatches(rows) + remainderBatches(rows), items : rows },
-        { type : LimitBlock, calls : limitMinusSkipBatches(rows) + /* this is only during ::execute work, should remove later again */ remainderBatches(rows), items : limitMinusSkip(rows) },
-        { type : ReturnBlock, calls : limitMinusSkipBatches(rows) + /* this is only during ::execute work, should remove later again */  remainderBatches(rows), items : limitMinusSkip(rows) }
+        { type : ConstrainedSortBlock, calls : limitMinusSkipBatches(rows), items : rows },
+        { type : LimitBlock, calls : limitMinusSkipBatches(rows), items : limitMinusSkip(rows) },
+        { type : ReturnBlock, calls : limitMinusSkipBatches(rows), items : limitMinusSkip(rows) }
       ];
       const bind = rows => ({
         rows,

From a0d6ec193f02203e44e2270be0146d8aa5147b86 Mon Sep 17 00:00:00 2001
From: Heiko <hkernbach@users.noreply.github.com>
Date: Fri, 28 Feb 2020 16:55:27 +0100
Subject: [PATCH 083/122] Feature/aql subquery operations stack aql item block
 input matrix (#11167)

* added new file to cmakelist

* added new method skipAllRemainingDataRows

* added first implementation of execute - AllRowsFetcher

* impl is now using skipAllRemainingDataRows method, also execute methods now using Fetcher::DataRange instead of inputRange

* impl is now using skipAllRemainingDataRows method, also execute methods now using Fetcher::DataRange instead of inputRange - header file

* AllRowsFetcher now using AqlItemBlockInputMatrix as DataRange, first implementation of execute

* first implementation of AqlItemBlockInputMatrix

* more cleanup

* optimized execut elogic

* optimized logic in inputmatrix, still a few todos left

* added SortExecutor as newStyle

* added produceRows and skipRows

* logs (to be removed), skipAllRemainingRows

* logs

* inputMatrix

* changed return type of skipAllRemainingDataRows

* impl logs

* logs, added clear method

* sort test

* typo, log

* latest changes

* cleanup, assert

* rm logs

* added more todos

* todo

* new method names, compile again

* Reset ExecutorReturnedDone for SubqueryStart and SubqueryEnd.

* InputMatrix needs to return state DONE on every input request. It guarantees that we have all input

* Removed invalid Assertion, and removed early return if output is full.

* Removed DebugLogging from CalculationTest

* Fixed skipping in SortExecutor

* Fixed upstreamState return of AqlItemMatrix. It is only finalState iff there is no data

* Let the InputMatrix drop all rows after FullCount

* Allow bypassing with hardLimit 0 in InputMatrix

* Disabled the old-code assertion. This way the SortExecutor tests we have will be red, but not crash, allowing the jenkins to produce meaningfull results

* Fix assert in WAITING case

* Add rudimentary sort executor GTests

* Fixed assertion on InputMatrix that starts right away with a shadowRow

* Removed declared but not implemented function

* changed from: peekDataRowAndState -> to: peekDataRow

Co-authored-by: Michael Hackstein <michael@arangodb.com>
---
 arangod/Aql/AllRowsFetcher.cpp           |  47 ++++
 arangod/Aql/AllRowsFetcher.h             |  25 ++-
 arangod/Aql/AqlItemBlockInputMatrix.cpp  | 142 ++++++++++++
 arangod/Aql/AqlItemBlockInputMatrix.h    |  67 ++++++
 arangod/Aql/AqlItemBlockInputRange.cpp   |  22 +-
 arangod/Aql/AqlItemBlockInputRange.h     |   5 +-
 arangod/Aql/AqlItemMatrix.cpp            |   8 +-
 arangod/Aql/AqlItemMatrix.h              |   2 +
 arangod/Aql/EnumerateListExecutor.cpp    |   1 -
 arangod/Aql/ExecutionBlockImpl.cpp       | 174 ++++++++-------
 arangod/Aql/ExecutionBlockImpl.h         |  10 +-
 arangod/Aql/SortExecutor.cpp             | 109 +++++++---
 arangod/Aql/SortExecutor.h               |  21 ++
 arangod/CMakeLists.txt                   |   1 +
 tests/Aql/AqlItemBlockInputRangeTest.cpp |   8 +-
 tests/Aql/CalculationExecutorTest.cpp    |   9 +-
 tests/Aql/SortExecutorTest.cpp           | 263 ++++++++++++-----------
 17 files changed, 653 insertions(+), 261 deletions(-)
 create mode 100644 arangod/Aql/AqlItemBlockInputMatrix.cpp
 create mode 100644 arangod/Aql/AqlItemBlockInputMatrix.h

diff --git a/arangod/Aql/AllRowsFetcher.cpp b/arangod/Aql/AllRowsFetcher.cpp
index 117deb8ae799..27702b4f5995 100644
--- a/arangod/Aql/AllRowsFetcher.cpp
+++ b/arangod/Aql/AllRowsFetcher.cpp
@@ -21,6 +21,7 @@
 ////////////////////////////////////////////////////////////////////////////////
 
 #include "AllRowsFetcher.h"
+#include <Logger/LogMacros.h>
 
 #include "Aql/AqlItemBlock.h"
 #include "Aql/AqlItemMatrix.h"
@@ -59,6 +60,52 @@ std::pair<ExecutionState, AqlItemMatrix const*> AllRowsFetcher::fetchAllRows() {
   return {ExecutionState::DONE, nullptr};
 }
 
+std::tuple<ExecutionState, size_t, AqlItemBlockInputMatrix> AllRowsFetcher::execute(AqlCallStack& stack) {
+  if (!stack.isRelevant()) {
+    auto [state, skipped, block] = _dependencyProxy->execute(stack);
+    return {state, skipped, AqlItemBlockInputMatrix{block}};
+  }
+  TRI_ASSERT(stack.peek().getOffset() == 0);
+  TRI_ASSERT(!stack.peek().needsFullCount());
+  // We allow a 0 hardLimit for bypassing
+  // bot otherwise we do not allow any limit
+  TRI_ASSERT(!stack.peek().hasHardLimit() || stack.peek().getLimit() == 0);
+  TRI_ASSERT(!stack.peek().hasSoftLimit());
+
+  if (_aqlItemMatrix == nullptr) {
+    _aqlItemMatrix = std::make_unique<AqlItemMatrix>(getNrInputRegisters());
+  }
+  // We can only execute More if we are not Stopped yet.
+  TRI_ASSERT(!_aqlItemMatrix->stoppedOnShadowRow());
+  while (true) {
+    auto [state, skipped, block] = _dependencyProxy->execute(stack);
+    TRI_ASSERT(skipped == 0);
+
+    // we will either build a complete fetched AqlItemBlockInputMatrix or return an empty one
+    if (state == ExecutionState::WAITING) {
+      TRI_ASSERT(block == nullptr);
+      // On waiting we have nothing to return
+      return {state, 0, AqlItemBlockInputMatrix{ExecutorState::HASMORE}};
+    }
+    TRI_ASSERT(block != nullptr || state == ExecutionState::DONE);
+
+    if (block != nullptr) {
+      // we need to store the block for later creation of AqlItemBlockInputMatrix
+      _aqlItemMatrix->addBlock(std::move(block));
+    }
+
+    // If we find a ShadowRow or ExecutionState == Done, we're done fetching.
+    if (_aqlItemMatrix->stoppedOnShadowRow() || state == ExecutionState::DONE) {
+      if (state == ExecutionState::HASMORE) {
+        return {state, 0,
+                AqlItemBlockInputMatrix{ExecutorState::HASMORE, _aqlItemMatrix.get()}};
+      }
+      return {state, 0,
+              AqlItemBlockInputMatrix{ExecutorState::DONE, _aqlItemMatrix.get()}};
+    }
+  }
+}
+
 std::pair<ExecutionState, InputAqlItemRow> AllRowsFetcher::fetchRow(size_t atMost) {
   switch (_dataFetchedState) {
     case ALL_DATA_FETCHED:
diff --git a/arangod/Aql/AllRowsFetcher.h b/arangod/Aql/AllRowsFetcher.h
index adfe5a402817..f285715c7e11 100644
--- a/arangod/Aql/AllRowsFetcher.h
+++ b/arangod/Aql/AllRowsFetcher.h
@@ -33,8 +33,7 @@
 #include <cstddef>
 #include <memory>
 
-// TODO REMOVE ME TEMPORARY
-#include "Aql/AqlItemBlockInputRange.h"
+#include "Aql/AqlItemBlockInputMatrix.h"
 
 namespace arangodb {
 namespace aql {
@@ -90,22 +89,28 @@ class AllRowsFetcher {
 
  public:
   explicit AllRowsFetcher(DependencyProxy<BlockPassthrough::Disable>& executionBlock);
-
   TEST_VIRTUAL ~AllRowsFetcher() = default;
 
-  // TODO FIXME, this Range does not work here.
-  using DataRange = AqlItemBlockInputRange;
+  using DataRange = AqlItemBlockInputMatrix;
 
  protected:
   // only for testing! Does not initialize _dependencyProxy!
   AllRowsFetcher() = default;
 
  public:
-  // TODO implement and document
-  std::tuple<ExecutionState, size_t, DataRange> execute(/* TODO: add"justDoIt"-style parameter */) {
-    TRI_ASSERT(false);
-    THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
-  }
+  /**
+   * @brief Execute the given call stack
+   *
+   * @param stack Call stack, on top of stack there is current subquery, bottom is the main query.
+   * @return std::tuple<ExecutionState, size_t, DataRange>
+   *   ExecutionState => DONE, all queries are done, there will be no more
+   *   ExecutionState => HASMORE, there are more results for queries, might be on other subqueries
+   *   ExecutionState => WAITING, we need to do I/O to solve the request, save local state and return WAITING to caller immediately
+   *
+   *   size_t => Amount of documents skipped
+   *   DataRange => Resulting data
+   */
+  std::tuple<ExecutionState, size_t, DataRange> execute(AqlCallStack& stack);
 
   /**
    * @brief Fetch one new AqlItemRow from upstream.
diff --git a/arangod/Aql/AqlItemBlockInputMatrix.cpp b/arangod/Aql/AqlItemBlockInputMatrix.cpp
new file mode 100644
index 000000000000..d2a7d16c3cd3
--- /dev/null
+++ b/arangod/Aql/AqlItemBlockInputMatrix.cpp
@@ -0,0 +1,142 @@
+////////////////////////////////////////////////////////////////////////////////
+/// DISCLAIMER
+///
+/// Copyright 2019 ArangoDB GmbH, Cologne, Germany
+///
+/// Licensed under the Apache License, Version 2.0 (the "License");
+/// you may not use this file except in compliance with the License.
+/// You may obtain a copy of the License at
+///
+///     http://www.apache.org/licenses/LICENSE-2.0
+///
+/// Unless required by applicable law or agreed to in writing, software
+/// distributed under the License is distributed on an "AS IS" BASIS,
+/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+/// See the License for the specific language governing permissions and
+/// limitations under the License.
+///
+/// Copyright holder is ArangoDB GmbH, Cologne, Germany
+///
+/// @author Tobias Gödderz
+////////////////////////////////////////////////////////////////////////////////
+
+#include "AqlItemBlockInputMatrix.h"
+#include "Aql/ShadowAqlItemRow.h"
+
+#include <Logger/LogMacros.h>
+#include <velocypack/Builder.h>
+#include <velocypack/velocypack-aliases.h>
+#include <numeric>
+
+using namespace arangodb;
+using namespace arangodb::aql;
+
+AqlItemBlockInputMatrix::AqlItemBlockInputMatrix(ExecutorState state)
+    : _finalState{state}, _aqlItemMatrix{nullptr} {
+  TRI_ASSERT(_aqlItemMatrix == nullptr);
+  TRI_ASSERT(!hasDataRow());
+}
+
+// only used for block passthrough
+AqlItemBlockInputMatrix::AqlItemBlockInputMatrix(arangodb::aql::SharedAqlItemBlockPtr const& block)
+    : _block{block}, _aqlItemMatrix{nullptr} {
+  TRI_ASSERT(_aqlItemMatrix == nullptr);
+  TRI_ASSERT(!hasDataRow());
+}
+
+AqlItemBlockInputMatrix::AqlItemBlockInputMatrix(ExecutorState state, AqlItemMatrix* aqlItemMatrix)
+    : _finalState{state}, _aqlItemMatrix{aqlItemMatrix} {
+  TRI_ASSERT(_block == nullptr);
+  TRI_ASSERT(_aqlItemMatrix != nullptr);
+  if (_aqlItemMatrix->size() == 0 && _aqlItemMatrix->stoppedOnShadowRow()) {
+    // Fast forward to initialize the _shadowRow
+    skipAllRemainingDataRows();
+  }
+}
+
+SharedAqlItemBlockPtr AqlItemBlockInputMatrix::getBlock() const noexcept {
+  TRI_ASSERT(_aqlItemMatrix == nullptr);
+  return _block;
+}
+
+std::pair<ExecutorState, AqlItemMatrix const*> AqlItemBlockInputMatrix::getMatrix() noexcept {
+  TRI_ASSERT(_aqlItemMatrix != nullptr);
+  TRI_ASSERT(_block == nullptr);
+  TRI_ASSERT(!_shadowRow.isInitialized());
+
+  // We are always done. This InputMatrix
+  // guarantees that we have all data in our hand at once.
+  return {ExecutorState::DONE, _aqlItemMatrix};
+}
+
+ExecutorState AqlItemBlockInputMatrix::upstreamState() const noexcept {
+  if (hasDataRow() || hasShadowRow()) {
+    return ExecutorState::DONE;
+  }
+  return _finalState;
+}
+
+bool AqlItemBlockInputMatrix::upstreamHasMore() const noexcept {
+  return upstreamState() == ExecutorState::HASMORE;
+}
+
+bool AqlItemBlockInputMatrix::hasDataRow() const noexcept {
+  if (_aqlItemMatrix == nullptr) {
+    return false;
+  }
+  return (!_shadowRow.isInitialized() && _aqlItemMatrix->size() != 0);
+}
+
+std::pair<ExecutorState, ShadowAqlItemRow> AqlItemBlockInputMatrix::nextShadowRow() {
+  auto tmpShadowRow = _shadowRow;
+
+  if (_aqlItemMatrix->size() == 0 && _aqlItemMatrix->stoppedOnShadowRow() &&
+      !_aqlItemMatrix->peekShadowRow().isRelevant()) {
+    // next row will be a shadow row
+    _shadowRow = _aqlItemMatrix->popShadowRow();
+  } else {
+    _shadowRow = ShadowAqlItemRow{CreateInvalidShadowRowHint()};
+  }
+
+  auto state = ExecutorState::HASMORE;
+  if (_shadowRow.isInitialized()) {
+    TRI_ASSERT(!_shadowRow.isRelevant());
+    state = ExecutorState::HASMORE;
+  } else if (_aqlItemMatrix->stoppedOnShadowRow() &&
+             _aqlItemMatrix->peekShadowRow().isRelevant()) {
+    state = ExecutorState::DONE;
+  } else {
+    state = _finalState;
+  }
+
+  return {state, tmpShadowRow};
+}
+
+ShadowAqlItemRow AqlItemBlockInputMatrix::peekShadowRow() const {
+  return _shadowRow;
+}
+
+bool AqlItemBlockInputMatrix::hasShadowRow() const noexcept {
+  return _shadowRow.isInitialized();
+}
+
+void AqlItemBlockInputMatrix::skipAllRemainingDataRows() {
+  if (_aqlItemMatrix == nullptr) {
+    // Have not been initialized.
+    // We need to be called before.
+    TRI_ASSERT(!hasShadowRow());
+    TRI_ASSERT(!hasDataRow());
+    return;
+  }
+  if (!hasShadowRow()) {
+    if (_aqlItemMatrix->stoppedOnShadowRow()) {
+      _shadowRow = _aqlItemMatrix->popShadowRow();
+      TRI_ASSERT(_shadowRow.isRelevant());
+    } else {
+      TRI_ASSERT(_finalState == ExecutorState::DONE);
+      _aqlItemMatrix->clear();
+    }
+  }
+  // Else we did already skip once.
+  // nothing to do
+}
diff --git a/arangod/Aql/AqlItemBlockInputMatrix.h b/arangod/Aql/AqlItemBlockInputMatrix.h
new file mode 100644
index 000000000000..9ce5c3073dac
--- /dev/null
+++ b/arangod/Aql/AqlItemBlockInputMatrix.h
@@ -0,0 +1,67 @@
+////////////////////////////////////////////////////////////////////////////////
+/// DISCLAIMER
+///
+/// Copyright 2019 ArangoDB GmbH, Cologne, Germany
+///
+/// Licensed under the Apache License, Version 2.0 (the "License");
+/// you may not use this file except in compliance with the License.
+/// You may obtain a copy of the License at
+///
+///     http://www.apache.org/licenses/LICENSE-2.0
+///
+/// Unless required by applicable law or agreed to in writing, software
+/// distributed under the License is distributed on an "AS IS" BASIS,
+/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+/// See the License for the specific language governing permissions and
+/// limitations under the License.
+///
+/// Copyright holder is ArangoDB GmbH, Cologne, Germany
+///
+/// @author Tobias Gödderz
+////////////////////////////////////////////////////////////////////////////////
+
+#ifndef ARANGOD_AQL_AQLITEMBLOCKMATRIXITERATOR_H
+#define ARANGOD_AQL_AQLITEMBLOCKMATRIXITERATOR_H
+
+#include "Aql/AqlItemMatrix.h"
+#include "Aql/ExecutionState.h"
+#include "Aql/InputAqlItemRow.h"
+#include "Aql/SharedAqlItemBlockPtr.h"
+
+namespace arangodb::aql {
+
+class ShadowAqlItemRow;
+
+class AqlItemBlockInputMatrix {
+ public:
+  explicit AqlItemBlockInputMatrix(ExecutorState state);
+
+  AqlItemBlockInputMatrix(arangodb::aql::SharedAqlItemBlockPtr const&);
+
+  AqlItemBlockInputMatrix(ExecutorState state, AqlItemMatrix* aqlItemMatrix);
+
+  std::pair<ExecutorState, ShadowAqlItemRow> nextShadowRow();
+  ShadowAqlItemRow peekShadowRow() const;
+  bool hasShadowRow() const noexcept;
+  bool hasDataRow() const noexcept;
+
+  arangodb::aql::SharedAqlItemBlockPtr getBlock() const noexcept;
+  std::pair<ExecutorState, AqlItemMatrix const*> getMatrix() noexcept;
+
+  ExecutorState upstreamState() const noexcept;
+  bool upstreamHasMore() const noexcept;
+  void skipAllRemainingDataRows();
+
+ private:
+  arangodb::aql::SharedAqlItemBlockPtr _block{nullptr};
+  ExecutorState _finalState{ExecutorState::HASMORE};
+
+  // Only if _aqlItemMatrix is set (and NOT a nullptr), we have a valid and usable
+  // DataRange object available to work with.
+  AqlItemMatrix* _aqlItemMatrix;
+  ShadowAqlItemRow _shadowRow{CreateInvalidShadowRowHint{}};
+};
+
+}  // namespace arangodb::aql
+
+#endif  // ARANGOD_AQL_AQLITEMBLOCKINPUTITERATOR_H
diff --git a/arangod/Aql/AqlItemBlockInputRange.cpp b/arangod/Aql/AqlItemBlockInputRange.cpp
index 4a0156247621..11bd5710e6be 100644
--- a/arangod/Aql/AqlItemBlockInputRange.cpp
+++ b/arangod/Aql/AqlItemBlockInputRange.cpp
@@ -57,6 +57,7 @@ bool AqlItemBlockInputRange::hasDataRow() const noexcept {
   return isIndexValid(_rowIndex) && !isShadowRowAtIndex(_rowIndex);
 }
 
+// TODO: Implement peekDataRow (without state). e.g. IResearchViewExecutor does not need the state!
 std::pair<ExecutorState, InputAqlItemRow> AqlItemBlockInputRange::peekDataRow() const {
   if (hasDataRow()) {
     return std::make_pair(nextState<LookAhead::NEXT, RowType::DATA>(),
@@ -95,7 +96,14 @@ bool AqlItemBlockInputRange::isShadowRowAtIndex(std::size_t index) const noexcep
   return _block->isShadowRow(index);
 }
 
-std::pair<ExecutorState, ShadowAqlItemRow> AqlItemBlockInputRange::peekShadowRow() const {
+arangodb::aql::ShadowAqlItemRow AqlItemBlockInputRange::peekShadowRow() const {
+  if (hasShadowRow()) {
+    return ShadowAqlItemRow{_block, _rowIndex};
+  }
+  return ShadowAqlItemRow{CreateInvalidShadowRowHint{}};
+}
+
+std::pair<ExecutorState, ShadowAqlItemRow> AqlItemBlockInputRange::peekShadowRowAndState() const {
   if (hasShadowRow()) {
     return std::make_pair(nextState<LookAhead::NEXT, RowType::SHADOW>(),
                           ShadowAqlItemRow{_block, _rowIndex});
@@ -105,7 +113,7 @@ std::pair<ExecutorState, ShadowAqlItemRow> AqlItemBlockInputRange::peekShadowRow
 }
 
 std::pair<ExecutorState, ShadowAqlItemRow> AqlItemBlockInputRange::nextShadowRow() {
-  auto res = peekShadowRow();
+  auto res = peekShadowRowAndState();
   if (res.second.isInitialized()) {
     // Advance the current row.
     _rowIndex++;
@@ -113,6 +121,16 @@ std::pair<ExecutorState, ShadowAqlItemRow> AqlItemBlockInputRange::nextShadowRow
   return res;
 }
 
+void AqlItemBlockInputRange::skipAllRemainingDataRows() {
+  ExecutorState state;
+  InputAqlItemRow row{CreateInvalidInputRowHint{}};
+
+  while (hasDataRow()) {
+    std::tie(state, row) = nextDataRow();
+    TRI_ASSERT(row.isInitialized());
+  }
+}
+
 template <AqlItemBlockInputRange::LookAhead doPeek, AqlItemBlockInputRange::RowType type>
 ExecutorState AqlItemBlockInputRange::nextState() const noexcept {
   size_t testRowIndex = _rowIndex;
diff --git a/arangod/Aql/AqlItemBlockInputRange.h b/arangod/Aql/AqlItemBlockInputRange.h
index 79461c8b66f4..03e442a3a730 100644
--- a/arangod/Aql/AqlItemBlockInputRange.h
+++ b/arangod/Aql/AqlItemBlockInputRange.h
@@ -57,10 +57,13 @@ class AqlItemBlockInputRange {
 
   bool hasShadowRow() const noexcept;
 
-  std::pair<ExecutorState, arangodb::aql::ShadowAqlItemRow> peekShadowRow() const;
+  arangodb::aql::ShadowAqlItemRow peekShadowRow() const;
+  std::pair<ExecutorState, arangodb::aql::ShadowAqlItemRow> peekShadowRowAndState() const;
 
   std::pair<ExecutorState, arangodb::aql::ShadowAqlItemRow> nextShadowRow();
 
+  void skipAllRemainingDataRows();
+
   // Subtract up to this many rows from the local `_skipped` state; return
   // the number actually skipped. Does not skip data rows.
   [[nodiscard]] auto skip(std::size_t) noexcept -> std::size_t;
diff --git a/arangod/Aql/AqlItemMatrix.cpp b/arangod/Aql/AqlItemMatrix.cpp
index 2fe8bb15903f..9f3361936b4d 100644
--- a/arangod/Aql/AqlItemMatrix.cpp
+++ b/arangod/Aql/AqlItemMatrix.cpp
@@ -125,6 +125,11 @@ std::vector<AqlItemMatrix::RowIndex> AqlItemMatrix::produceRowIndexes() const {
 
 bool AqlItemMatrix::empty() const noexcept { return _blocks.empty(); }
 
+void AqlItemMatrix::clear() {
+  _blocks.clear();
+  _size = 0;
+}
+
 RegisterId AqlItemMatrix::getNrRegisters() const noexcept { return _nrRegs; }
 
 uint64_t AqlItemMatrix::size() const noexcept { return _size; }
@@ -207,4 +212,5 @@ ShadowAqlItemRow AqlItemMatrix::peekShadowRow() const {
 }
 
 AqlItemMatrix::AqlItemMatrix(RegisterId nrRegs)
-    : _size(0), _nrRegs(nrRegs), _lastShadowRow(InvalidRowIndex) {}
+    : _size(0), _nrRegs(nrRegs), _lastShadowRow(InvalidRowIndex) {
+}
diff --git a/arangod/Aql/AqlItemMatrix.h b/arangod/Aql/AqlItemMatrix.h
index 84130aa6237c..c14a0abd4677 100644
--- a/arangod/Aql/AqlItemMatrix.h
+++ b/arangod/Aql/AqlItemMatrix.h
@@ -74,6 +74,8 @@ class AqlItemMatrix {
    */
   bool empty() const noexcept;
 
+  void clear();
+
   std::vector<RowIndex> produceRowIndexes() const;
 
   /**
diff --git a/arangod/Aql/EnumerateListExecutor.cpp b/arangod/Aql/EnumerateListExecutor.cpp
index 2840dbf3339c..84d2ab2d080b 100644
--- a/arangod/Aql/EnumerateListExecutor.cpp
+++ b/arangod/Aql/EnumerateListExecutor.cpp
@@ -182,7 +182,6 @@ std::tuple<ExecutorState, NoStats, size_t, AqlCall> EnumerateListExecutor::skipR
       initializeNewRow(inputRange);
       continue;
     }
-    // auto const& [state, input] = inputRange.peekDataRow();
 
     TRI_ASSERT(_inputArrayPosition < _inputArrayLength);
     // if offset is > 0, we're in offset skip phase
diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index d4f9ee43a800..5ffd2ad3edc1 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -134,17 +134,18 @@ constexpr bool is_one_of_v = (std::is_same_v<T, Es> || ...);
  * TODO: This should be removed once all executors and fetchers are ported to the new style.
  */
 template <typename Executor>
-constexpr bool isNewStyleExecutor =
-    is_one_of_v<Executor, FilterExecutor, SortedCollectExecutor, IdExecutor<ConstFetcher>,
-                IdExecutor<SingleRowFetcher<BlockPassthrough::Enable>>, ReturnExecutor,
-                DistinctCollectExecutor, IndexExecutor, EnumerateCollectionExecutor,
-                // TODO: re-enable after new subquery end & start are implemented
-                // CalculationExecutor<CalculationType::Condition>, CalculationExecutor<CalculationType::Reference>, CalculationExecutor<CalculationType::V8Condition>,
-                HashedCollectExecutor, ConstrainedSortExecutor,
+constexpr bool isNewStyleExecutor = is_one_of_v<
+    Executor, FilterExecutor, SortedCollectExecutor, IdExecutor<ConstFetcher>,
+    IdExecutor<SingleRowFetcher<BlockPassthrough::Enable>>, ReturnExecutor, DistinctCollectExecutor, IndexExecutor, EnumerateCollectionExecutor,
+    // TODO: re-enable after new subquery end & start are implemented
+    // CalculationExecutor<CalculationType::Condition>, CalculationExecutor<CalculationType::Reference>, CalculationExecutor<CalculationType::V8Condition>,
+    HashedCollectExecutor, ConstrainedSortExecutor,
 #ifdef ARANGODB_USE_GOOGLE_TESTS
     TestLambdaExecutor,
     TestLambdaSkipExecutor,  // we need one after these to avoid compile errors in non-test mode
 #endif
+    SubqueryStartExecutor, SubqueryEndExecutor, TraversalExecutor, KShortestPathsExecutor,
+    ShortestPathExecutor, EnumerateListExecutor, LimitExecutor, SortExecutor,
     IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::NotMaterialize>,
     IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::LateMaterialize>,
     IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::Materialize>,
@@ -165,12 +166,12 @@ constexpr bool isNewStyleExecutor =
     IResearchViewMergeExecutor<true, arangodb::iresearch::MaterializeType::Materialize>,
     IResearchViewMergeExecutor<true, arangodb::iresearch::MaterializeType::NotMaterialize | arangodb::iresearch::MaterializeType::UseStoredValues>,
     IResearchViewMergeExecutor<true, arangodb::iresearch::MaterializeType::LateMaterialize | arangodb::iresearch::MaterializeType::UseStoredValues>,
-    SubqueryStartExecutor, SubqueryEndExecutor, TraversalExecutor, KShortestPathsExecutor, NoResultsExecutor,
-    ShortestPathExecutor, EnumerateListExecutor, LimitExecutor, SingleRemoteModificationExecutor<IndexTag>, SingleRemoteModificationExecutor<Insert>,
+    SubqueryStartExecutor, SubqueryEndExecutor, TraversalExecutor, KShortestPathsExecutor,
+    NoResultsExecutor, ShortestPathExecutor, EnumerateListExecutor, LimitExecutor,
+    SingleRemoteModificationExecutor<IndexTag>, SingleRemoteModificationExecutor<Insert>,
     SingleRemoteModificationExecutor<Remove>, SingleRemoteModificationExecutor<Update>,
     SingleRemoteModificationExecutor<Replace>, SingleRemoteModificationExecutor<Upsert>>;
 
-
 template <class Executor>
 ExecutionBlockImpl<Executor>::ExecutionBlockImpl(ExecutionEngine* engine,
                                                  ExecutionNode const* node,
@@ -610,19 +611,7 @@ std::pair<ExecutionState, Result> ExecutionBlockImpl<Executor>::initializeCursor
   TRI_ASSERT(_state == InternalState::DONE || _state == InternalState::FETCH_DATA);
   _state = InternalState::FETCH_DATA;
 
-  constexpr bool customInit = hasInitializeCursor<Executor>::value;
-  // IndexExecutor and EnumerateCollectionExecutor have initializeCursor
-  // implemented, so assert this implementation is used.
-  static_assert(!std::is_same<Executor, EnumerateCollectionExecutor>::value || customInit,
-                "EnumerateCollectionExecutor is expected to implement a custom "
-                "initializeCursor method!");
-  static_assert(!std::is_same<Executor, IndexExecutor>::value || customInit,
-                "IndexExecutor is expected to implement a custom "
-                "initializeCursor method!");
-  static_assert(!std::is_same<Executor, DistinctCollectExecutor>::value || customInit,
-                "DistinctCollectExecutor is expected to implement a custom "
-                "initializeCursor method!");
-  InitializeCursor<customInit>::init(_executor, _rowFetcher, _infos);
+  resetExecutor();
 
   // // use this with c++17 instead of specialization below
   // if constexpr (std::is_same_v<Executor, IdExecutor>) {
@@ -731,9 +720,7 @@ auto ExecutionBlockImpl<IdExecutor<ConstFetcher>>::injectConstantBlock<IdExecuto
 
   _rowFetcher.injectBlock(block);
 
-  // cppcheck-suppress unreadVariable
-  constexpr bool customInit = hasInitializeCursor<decltype(_executor)>::value;
-  InitializeCursor<customInit>::init(_executor, _rowFetcher, _infos);
+  resetExecutor();
 }
 
 // TODO -- remove this specialization when cpp 17 becomes available
@@ -1058,6 +1045,9 @@ void ExecutionBlockImpl<Executor>::ensureOutputBlock(AqlCall&& call) {
 // This cannot return upstream call or shadowrows.
 template <class Executor>
 auto ExecutionBlockImpl<Executor>::nextState(AqlCall const& call) const -> ExecState {
+  if (_executorReturnedDone) {
+    return ExecState::FASTFORWARD;
+  }
   if (call.getOffset() > 0) {
     // First skip
     return ExecState::SKIP;
@@ -1124,13 +1114,13 @@ static SkipRowsRangeVariant constexpr skipRowsType() {
       useExecutor ==
           (is_one_of_v<
               Executor, FilterExecutor, ShortestPathExecutor, ReturnExecutor, KShortestPathsExecutor,
-              IdExecutor<SingleRowFetcher<BlockPassthrough::Enable>>, IdExecutor<ConstFetcher>,
-              HashedCollectExecutor, IndexExecutor, EnumerateCollectionExecutor, DistinctCollectExecutor,
-              ConstrainedSortExecutor,
+              IdExecutor<SingleRowFetcher<BlockPassthrough::Enable>>, IdExecutor<ConstFetcher>, HashedCollectExecutor,
+              IndexExecutor, EnumerateCollectionExecutor, DistinctCollectExecutor, ConstrainedSortExecutor,
 #ifdef ARANGODB_USE_GOOGLE_TESTS
               TestLambdaSkipExecutor,
 #endif
-              IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::NotMaterialize>,
+              TraversalExecutor, EnumerateListExecutor, SubqueryStartExecutor, SubqueryEndExecutor, SortedCollectExecutor,
+              LimitExecutor, SortExecutor, IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::NotMaterialize>,
               IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::LateMaterialize>,
               IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::Materialize>,
               IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::NotMaterialize | arangodb::iresearch::MaterializeType::UseStoredValues>,
@@ -1150,9 +1140,8 @@ static SkipRowsRangeVariant constexpr skipRowsType() {
               IResearchViewMergeExecutor<true, arangodb::iresearch::MaterializeType::Materialize>,
               IResearchViewMergeExecutor<true, arangodb::iresearch::MaterializeType::NotMaterialize | arangodb::iresearch::MaterializeType::UseStoredValues>,
               IResearchViewMergeExecutor<true, arangodb::iresearch::MaterializeType::LateMaterialize | arangodb::iresearch::MaterializeType::UseStoredValues>,
-              TraversalExecutor, EnumerateListExecutor, SubqueryStartExecutor,
-              SubqueryEndExecutor, SortedCollectExecutor, LimitExecutor, NoResultsExecutor,
-              SingleRemoteModificationExecutor<IndexTag>, SingleRemoteModificationExecutor<Insert>,
+              TraversalExecutor, EnumerateListExecutor, SubqueryStartExecutor, SubqueryEndExecutor, SortedCollectExecutor,
+              LimitExecutor, NoResultsExecutor, SingleRemoteModificationExecutor<IndexTag>, SingleRemoteModificationExecutor<Insert>,
               SingleRemoteModificationExecutor<Remove>, SingleRemoteModificationExecutor<Update>,
               SingleRemoteModificationExecutor<Replace>, SingleRemoteModificationExecutor<Upsert>>),
       "Unexpected executor for SkipVariants::EXECUTOR");
@@ -1176,8 +1165,34 @@ static SkipRowsRangeVariant constexpr skipRowsType() {
 template <class T>
 struct dependent_false : std::false_type {};
 
+/**
+ * @brief Define the variant of FastForward behaviour
+ *
+ * FULLCOUNT => Call executeSkipRowsRange and report what has been skipped.
+ * EXECUTOR => Call executeSkipRowsRange, but do not report what has been skipped.
+ *             (This instance is used to make sure Modifications are performed, or stats are correct)
+ * FETCHER => Do not bother the Executor, drop all from input, without further reporting
+ */
+enum class FastForwardVariant { FULLCOUNT, EXECUTOR, FETCHER };
+
+template <class Executor>
+static auto fastForwardType(AqlCall const& call, Executor const& e) -> FastForwardVariant {
+  if (call.needsFullCount() && call.getOffset() == 0 && call.getLimit() == 0) {
+    // Only start fullCount after the original call is fulfilled. Otherwise
+    // do fast-forward variant
+    TRI_ASSERT(call.hasHardLimit());
+    return FastForwardVariant::FULLCOUNT;
+  }
+  // TODO: We only need to do this is the executor actually require to call.
+  // e.g. Modifications will always need to be called. Limit only if it needs to report fullCount
+  if constexpr (is_one_of_v<Executor, LimitExecutor>) {
+    return FastForwardVariant::EXECUTOR;
+  }
+  return FastForwardVariant::FETCHER;
+}
+
 template <class Executor>
-auto ExecutionBlockImpl<Executor>::executeSkipRowsRange(AqlItemBlockInputRange& inputRange,
+auto ExecutionBlockImpl<Executor>::executeSkipRowsRange(typename Fetcher::DataRange& inputRange,
                                                         AqlCall& call)
     -> std::tuple<ExecutorState, typename Executor::Stats, size_t, AqlCall> {
   if constexpr (isNewStyleExecutor<Executor>) {
@@ -1185,7 +1200,9 @@ auto ExecutionBlockImpl<Executor>::executeSkipRowsRange(AqlItemBlockInputRange&
     if constexpr (skipRowsType<Executor>() == SkipRowsRangeVariant::EXECUTOR) {
       // If the executor has a method skipRowsRange, to skip outputs.
       // Every non-passthrough executor needs to implement this.
-      return _executor.skipRowsRange(inputRange, call);
+      auto res = _executor.skipRowsRange(inputRange, call);
+      _executorReturnedDone = std::get<ExecutorState>(res) == ExecutorState::DONE;
+      return res;
     } else if constexpr (skipRowsType<Executor>() == SkipRowsRangeVariant::FETCHER) {
       // If we know that every input row produces exactly one output row (this
       // is a property of the executor), then we can just let the fetcher skip
@@ -1195,6 +1212,7 @@ auto ExecutionBlockImpl<Executor>::executeSkipRowsRange(AqlItemBlockInputRange&
       static_assert(
           std::is_same_v<typename Executor::Stats, NoStats>,
           "Executors with custom statistics must implement skipRowsRange.");
+      // TODO Set _executorReturnedDone?
       return {inputRange.upstreamState(), NoStats{}, 0, call};
     } else {
       static_assert(dependent_false<Executor>::value,
@@ -1219,6 +1237,9 @@ auto ExecutionBlockImpl<SubqueryStartExecutor>::shadowRowForwarding() -> ExecSta
     // If we get woken up by a dataRow during forwarding of ShadowRows
     // This will return false, and if so we need to call produce instead.
     auto didWrite = _executor.produceShadowRow(_lastRange, *_outputItemRow);
+    // The Subquery Start returns DONE after every row.
+    // This needs to be resetted as soon as a shadowRow has been produced
+    _executorReturnedDone = false;
     if (didWrite) {
       if (_lastRange.hasShadowRow()) {
         // Forward the ShadowRows
@@ -1241,6 +1262,7 @@ auto ExecutionBlockImpl<SubqueryStartExecutor>::shadowRowForwarding() -> ExecSta
     _outputItemRow->increaseShadowRowDepth(shadowRow);
     TRI_ASSERT(_outputItemRow->produced());
     _outputItemRow->advanceRow();
+
     if (_lastRange.hasShadowRow()) {
       return ExecState::SHADOWROWS;
     }
@@ -1267,6 +1289,9 @@ auto ExecutionBlockImpl<SubqueryEndExecutor>::shadowRowForwarding() -> ExecState
     // We need to consume the row, and write the Aggregate to it.
     _executor.consumeShadowRow(shadowRow, *_outputItemRow);
     didConsume = true;
+    // we need to reset the ExecutorHasReturnedDone, it will
+    // return done after every subquery is fully collected.
+    _executorReturnedDone = false;
   } else {
     _outputItemRow->decreaseShadowRowDepth(shadowRow);
   }
@@ -1322,9 +1347,7 @@ auto ExecutionBlockImpl<Executor>::shadowRowForwarding() -> ExecState {
     LOG_QUERY("6d337", DEBUG) << printTypeInfo() << " init executor.";
     // We found a relevant shadow Row.
     // We need to reset the Executor
-    // cppcheck-suppress unreadVariable
-    constexpr bool customInit = hasInitializeCursor<decltype(_executor)>::value;
-    InitializeCursor<customInit>::init(_executor, _rowFetcher, _infos);
+    resetExecutor();
   }
 
   TRI_ASSERT(_outputItemRow->produced());
@@ -1353,34 +1376,8 @@ auto ExecutionBlockImpl<Executor>::shadowRowForwarding() -> ExecState {
   }
 }
 
-/**
- * @brief Define the variant of FastForward behaviour
- *
- * FULLCOUNT => Call executeSkipRowsRange and report what has been skipped.
- * EXECUTOR => Call executeSkipRowsRange, but do not report what has been skipped.
- *             (This instance is used to make sure Modifications are performed, or stats are correct)
- * FETCHER => Do not bother the Executor, drop all from input, without further reporting
- */
-enum class FastForwardVariant { FULLCOUNT, EXECUTOR, FETCHER };
-
 template <class Executor>
-static auto fastForwardType(AqlCall const& call, Executor const& e) -> FastForwardVariant {
-  if (call.needsFullCount() && call.getOffset() == 0 && call.getLimit() == 0) {
-    // Only start fullCount after the original call is fulfilled. Otherwise
-    // do fast-forward variant
-    TRI_ASSERT(call.hasHardLimit());
-    return FastForwardVariant::FULLCOUNT;
-  }
-  // TODO: We only need to do this is the executor actually require to call.
-  // e.g. Modifications will always need to be called. Limit only if it needs to report fullCount
-  if constexpr (is_one_of_v<Executor, LimitExecutor>) {
-    return FastForwardVariant::EXECUTOR;
-  }
-  return FastForwardVariant::FETCHER;
-}
-
-template <class Executor>
-auto ExecutionBlockImpl<Executor>::executeFastForward(AqlItemBlockInputRange& inputRange,
+auto ExecutionBlockImpl<Executor>::executeFastForward(typename Fetcher::DataRange& inputRange,
                                                       AqlCall& clientCall)
     -> std::tuple<ExecutorState, typename Executor::Stats, size_t, AqlCall> {
   TRI_ASSERT(isNewStyleExecutor<Executor>);
@@ -1404,14 +1401,18 @@ auto ExecutionBlockImpl<Executor>::executeFastForward(AqlItemBlockInputRange& in
         // We do not report the skip
         skippedLocal = 0;
       }
+      if constexpr (std::is_same_v<DataRange, AqlItemBlockInputMatrix>) {
+        // The executor will have used all Rows.
+        // However we need to drop them from the input
+        // here.
+        inputRange.skipAllRemainingDataRows();
+      }
+
       return {state, stats, skippedLocal, call};
     }
     case FastForwardVariant::FETCHER: {
       LOG_QUERY("fa327", DEBUG) << printTypeInfo() << " bypass unused rows.";
-      while (inputRange.hasDataRow()) {
-        auto [state, row] = inputRange.nextDataRow();
-        TRI_ASSERT(row.isInitialized());
-      }
+      inputRange.skipAllRemainingDataRows();
       AqlCall call{};
       call.hardLimit = 0;
       return {inputRange.upstreamState(), typename Executor::Stats{}, 0, call};
@@ -1603,10 +1604,12 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
             ensureOutputBlock(std::move(clientCall));
           }
           TRI_ASSERT(_outputItemRow);
+          TRI_ASSERT(!_executorReturnedDone);
 
           // Execute getSome
           auto const [state, stats, call] =
               _executor.produceRows(_lastRange, *_outputItemRow);
+          _executorReturnedDone = state == ExecutorState::DONE;
           _engine->_stats += stats;
           localExecutorState = state;
 
@@ -1647,11 +1650,7 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
           localExecutorState = state;
 
           if (state == ExecutorState::DONE) {
-            if (_outputItemRow && _outputItemRow->isInitialized() &&
-                _outputItemRow->allRowsUsed()) {
-              // We have a block with data, but no more place for a shadow row.
-              _execState = ExecState::DONE;
-            } else if (!_lastRange.hasShadowRow() && !_lastRange.hasDataRow()) {
+            if (!_lastRange.hasShadowRow() && !_lastRange.hasDataRow()) {
               _execState = ExecState::DONE;
             } else {
               _execState = ExecState::SHADOWROWS;
@@ -1718,7 +1717,11 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
             // We skipped through passthrough, so count that a skip was solved.
             clientCall.didSkip(skippedLocal);
           }
-          _execState = ExecState::CHECKCALL;
+          if (_lastRange.hasShadowRow() && !_lastRange.peekShadowRow().isRelevant()) {
+            _execState = ExecState::SHADOWROWS;
+          } else {
+            _execState = ExecState::CHECKCALL;
+          }
           break;
         }
         case ExecState::SHADOWROWS: {
@@ -1728,7 +1731,7 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
               << printTypeInfo() << " (sub-)query completed. Move ShadowRows.";
 
           // TODO: Check if we can have the situation that we are between two shadow rows here.
-          // E.g. LastRow is releveant shadowRow. NextRow is non-relevant shadowRow.
+          // E.g. LastRow is relevant shadowRow. NextRow is non-relevant shadowRow.
           // NOTE: I do not think this is an issue, as the Executor will always say that it cannot do anything with
           // an empty input. Only exception might be COLLECT COUNT.
 
@@ -1798,12 +1801,23 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
   }
 }
 
-/// @brief reset all internal states after processing a shadow row.
 template <class Executor>
-void ExecutionBlockImpl<Executor>::resetAfterShadowRow() {
+void ExecutionBlockImpl<Executor>::resetExecutor() {
   // cppcheck-suppress unreadVariable
-  constexpr bool customInit = hasInitializeCursor<decltype(_executor)>::value;
+  constexpr bool customInit = hasInitializeCursor<Executor>::value;
+  // IndexExecutor and EnumerateCollectionExecutor have initializeCursor
+  // implemented, so assert this implementation is used.
+  static_assert(!std::is_same<Executor, EnumerateCollectionExecutor>::value || customInit,
+                "EnumerateCollectionExecutor is expected to implement a custom "
+                "initializeCursor method!");
+  static_assert(!std::is_same<Executor, IndexExecutor>::value || customInit,
+                "IndexExecutor is expected to implement a custom "
+                "initializeCursor method!");
+  static_assert(!std::is_same<Executor, DistinctCollectExecutor>::value || customInit,
+                "DistinctCollectExecutor is expected to implement a custom "
+                "initializeCursor method!");
   InitializeCursor<customInit>::init(_executor, _rowFetcher, _infos);
+  _executorReturnedDone = false;
 }
 
 template <class Executor>
@@ -1829,7 +1843,7 @@ ExecutionState ExecutionBlockImpl<Executor>::fetchShadowRowInternal() {
   } else {
     if (_state != InternalState::DONE) {
       _state = InternalState::FETCH_DATA;
-      resetAfterShadowRow();
+      resetExecutor();
     }
   }
   return state;
diff --git a/arangod/Aql/ExecutionBlockImpl.h b/arangod/Aql/ExecutionBlockImpl.h
index 43d7f4e28d47..6e4e383a22ce 100644
--- a/arangod/Aql/ExecutionBlockImpl.h
+++ b/arangod/Aql/ExecutionBlockImpl.h
@@ -235,9 +235,9 @@ class ExecutionBlockImpl final : public ExecutionBlock {
 
   // execute a skipRowsRange call
   std::tuple<ExecutorState, typename Executor::Stats, size_t, AqlCall> executeSkipRowsRange(
-      AqlItemBlockInputRange& input, AqlCall& call);
+      typename Fetcher::DataRange& inputRange, AqlCall& call);
 
-  auto executeFastForward(AqlItemBlockInputRange& inputRange, AqlCall& clientCall)
+  auto executeFastForward(typename Fetcher::DataRange& inputRange, AqlCall& clientCall)
       -> std::tuple<ExecutorState, typename Executor::Stats, size_t, AqlCall>;
 
   /**
@@ -276,8 +276,6 @@ class ExecutionBlockImpl final : public ExecutionBlock {
   /// @brief request an AqlItemBlock from the memory manager
   [[nodiscard]] SharedAqlItemBlockPtr requestBlock(size_t nrItems, RegisterCount nrRegs);
 
-  void resetAfterShadowRow();
-
   [[nodiscard]] ExecutionState fetchShadowRowInternal();
 
   // Allocate an output block and install a call in it
@@ -299,6 +297,8 @@ class ExecutionBlockImpl final : public ExecutionBlock {
 
   [[nodiscard]] auto outputIsFull() const noexcept -> bool;
 
+  void resetExecutor();
+
  private:
   /**
    * @brief Used to allow the row Fetcher to access selected methods of this
@@ -342,6 +342,8 @@ class ExecutionBlockImpl final : public ExecutionBlock {
   // into an output block.
   // If so we are not allowed to reuse it.
   bool _hasUsedDataRangeBlock;
+
+  bool _executorReturnedDone = false;
 };
 
 }  // namespace arangodb::aql
diff --git a/arangod/Aql/SortExecutor.cpp b/arangod/Aql/SortExecutor.cpp
index fed978c2f256..6cf17cffc829 100644
--- a/arangod/Aql/SortExecutor.cpp
+++ b/arangod/Aql/SortExecutor.cpp
@@ -29,6 +29,7 @@
 #include "Aql/SortRegister.h"
 #include "Aql/Stats.h"
 
+#include <Logger/LogMacros.h>
 #include <algorithm>
 
 using namespace arangodb;
@@ -113,45 +114,74 @@ AqlItemBlockManager& SortExecutorInfos::itemBlockManager() noexcept {
 }
 
 SortExecutor::SortExecutor(Fetcher& fetcher, SortExecutorInfos& infos)
-    : _infos(infos), _fetcher(fetcher), _input(nullptr), _returnNext(0) {}
+    : _infos(infos),
+      _fetcher(fetcher),
+      _input(nullptr),
+      _currentRow(CreateInvalidInputRowHint{}),
+      _returnNext(0) {}
 SortExecutor::~SortExecutor() = default;
 
 std::pair<ExecutionState, NoStats> SortExecutor::produceRows(OutputAqlItemRow& output) {
-  ExecutionState state;
-  if (_input == nullptr) {
-    // We need to get data
-    std::tie(state, _input) = _fetcher.fetchAllRows();
-    if (state == ExecutionState::WAITING) {
-      return {state, NoStats{}};
-    }
-    // If the execution state was not waiting it is guaranteed that we get a
-    // matrix. Maybe empty still
-    TRI_ASSERT(_input != nullptr);
-    if (_input == nullptr) {
-      THROW_ARANGO_EXCEPTION(TRI_ERROR_OUT_OF_MEMORY);
-    }
-    // After allRows the dependency has to be done
-    TRI_ASSERT(state == ExecutionState::DONE);
+  TRI_ASSERT(false);
+  THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
+}
+
+void SortExecutor::initializeInputMatrix(AqlItemBlockInputMatrix& inputMatrix) {
+  TRI_ASSERT(_input == nullptr);
+  ExecutorState state;
 
-    // Execute the sort
-    doSorting();
+  // We need to get data
+  std::tie(state, _input) = inputMatrix.getMatrix();
+
+  // If the execution state was not waiting it is guaranteed that we get a
+  // matrix. Maybe empty still
+  TRI_ASSERT(_input != nullptr);
+  if (_input == nullptr) {
+    THROW_ARANGO_EXCEPTION(TRI_ERROR_OUT_OF_MEMORY);
   }
+  // After allRows the dependency has to be done
+  TRI_ASSERT(state == ExecutorState::DONE);
+
+  // Execute the sort
+  doSorting();
+
   // If we get here we have an input matrix
   // And we have a list of sorted indexes.
   TRI_ASSERT(_input != nullptr);
   TRI_ASSERT(_sortedIndexes.size() == _input->size());
+};
+
+std::tuple<ExecutorState, NoStats, AqlCall> SortExecutor::produceRows(
+    AqlItemBlockInputMatrix& inputMatrix, OutputAqlItemRow& output) {
+  AqlCall upstreamCall{};
+
+  // if (inputMatrix.upstreamState() == ExecutorState::HASMORE) {
+  if (!inputMatrix.hasDataRow()) {
+    // If our inputMatrix does not contain all upstream rows
+    return {inputMatrix.upstreamState(), NoStats{}, upstreamCall};
+  }
+
+  if (_input == nullptr) {
+    initializeInputMatrix(inputMatrix);
+  }
+
   if (_returnNext >= _sortedIndexes.size()) {
     // Bail out if called too often,
     // Bail out on no elements
-    return {ExecutionState::DONE, NoStats{}};
+    return {ExecutorState::DONE, NoStats{}, upstreamCall};
+  }
+
+  while (_returnNext < _sortedIndexes.size() && !output.isFull()) {
+    InputAqlItemRow inRow = _input->getRow(_sortedIndexes[_returnNext]);
+    output.copyRow(inRow);
+    output.advanceRow();
+    _returnNext++;
   }
-  InputAqlItemRow inRow = _input->getRow(_sortedIndexes[_returnNext]);
-  output.copyRow(inRow);
-  _returnNext++;
+
   if (_returnNext >= _sortedIndexes.size()) {
-    return {ExecutionState::DONE, NoStats{}};
+    return {ExecutorState::DONE, NoStats{}, upstreamCall};
   }
-  return {ExecutionState::HASMORE, NoStats{}};
+  return {ExecutorState::HASMORE, NoStats{}, upstreamCall};
 }
 
 void SortExecutor::doSorting() {
@@ -169,6 +199,37 @@ void SortExecutor::doSorting() {
   }
 }
 
+std::tuple<ExecutorState, NoStats, size_t, AqlCall> SortExecutor::skipRowsRange(
+    AqlItemBlockInputMatrix& inputMatrix, AqlCall& call) {
+  AqlCall upstreamCall{};
+
+  if (inputMatrix.upstreamState() == ExecutorState::HASMORE) {
+    // If our inputMatrix does not contain all upstream rows
+    return {ExecutorState::HASMORE, NoStats{}, 0, upstreamCall};
+  }
+
+  if (_input == nullptr) {
+    initializeInputMatrix(inputMatrix);
+  }
+
+  if (_returnNext >= _sortedIndexes.size()) {
+    // Bail out if called too often,
+    // Bail out on no elements
+    return {ExecutorState::DONE, NoStats{}, 0, upstreamCall};
+  }
+
+  while (_returnNext < _sortedIndexes.size() && call.shouldSkip()) {
+    InputAqlItemRow inRow = _input->getRow(_sortedIndexes[_returnNext]);
+    _returnNext++;
+    call.didSkip(1);
+  }
+
+  if (_returnNext >= _sortedIndexes.size()) {
+    return {ExecutorState::DONE, NoStats{}, call.getSkipCount(), upstreamCall};
+  }
+  return {ExecutorState::HASMORE, NoStats{}, call.getSkipCount(), upstreamCall};
+}
+
 std::pair<ExecutionState, size_t> SortExecutor::expectedNumberOfRows(size_t atMost) const {
   if (_input == nullptr) {
     // This executor does not know anything yet.
diff --git a/arangod/Aql/SortExecutor.h b/arangod/Aql/SortExecutor.h
index aea597d8b204..973cd20393a6 100644
--- a/arangod/Aql/SortExecutor.h
+++ b/arangod/Aql/SortExecutor.h
@@ -30,6 +30,7 @@
 #include "Aql/AqlItemMatrix.h"
 #include "Aql/ExecutionState.h"
 #include "Aql/ExecutorInfos.h"
+#include "Aql/InputAqlItemRow.h"
 
 #include <cstddef>
 #include <memory>
@@ -41,6 +42,8 @@ class Methods;
 
 namespace aql {
 
+struct AqlCall;
+class AqlItemBlockInputMatrix;
 class AllRowsFetcher;
 class ExecutorInfos;
 class NoStats;
@@ -105,6 +108,23 @@ class SortExecutor {
   std::pair<ExecutionState, Stats> produceRows(OutputAqlItemRow& output);
 
   std::pair<ExecutionState, size_t> expectedNumberOfRows(size_t) const;
+  void initializeInputMatrix(AqlItemBlockInputMatrix& inputMatrix);
+
+  /**
+   * @brief produce the next Rows of Aql Values.
+   *
+   * @return ExecutorState, the stats, and a new Call that needs to be send to upstream
+   */
+  [[nodiscard]] std::tuple<ExecutorState, Stats, AqlCall> produceRows(
+      AqlItemBlockInputMatrix& inputMatrix, OutputAqlItemRow& output);
+
+  /**
+   * @brief skip the next Row of Aql Values.
+   *
+   * @return ExecutorState, the stats, and a new Call that needs to be send to upstream
+   */
+  [[nodiscard]] std::tuple<ExecutorState, Stats, size_t, AqlCall> skipRowsRange(
+      AqlItemBlockInputMatrix& inputMatrix, AqlCall& call);
 
  private:
   void doSorting();
@@ -115,6 +135,7 @@ class SortExecutor {
   Fetcher& _fetcher;
 
   AqlItemMatrix const* _input;
+  InputAqlItemRow _currentRow;
 
   std::vector<AqlItemMatrix::RowIndex> _sortedIndexes;
 
diff --git a/arangod/CMakeLists.txt b/arangod/CMakeLists.txt
index 36fb43c4675b..ca56d6ebf1b6 100644
--- a/arangod/CMakeLists.txt
+++ b/arangod/CMakeLists.txt
@@ -222,6 +222,7 @@ set(LIB_ARANGO_AQL_SOURCES
   Aql/AqlFunctionFeature.cpp
   Aql/AqlItemBlock.cpp
   Aql/AqlItemBlockInputRange.cpp
+  Aql/AqlItemBlockInputMatrix.cpp
   Aql/AqlItemBlockManager.cpp
   Aql/AqlItemBlockUtils.cpp
   Aql/AqlItemMatrix.cpp
diff --git a/tests/Aql/AqlItemBlockInputRangeTest.cpp b/tests/Aql/AqlItemBlockInputRangeTest.cpp
index ac80439ff7a8..a09bf2a91435 100644
--- a/tests/Aql/AqlItemBlockInputRangeTest.cpp
+++ b/tests/Aql/AqlItemBlockInputRangeTest.cpp
@@ -72,7 +72,7 @@ class InputRangeTest : public ::testing::TestWithParam<ExecutorState> {
     // Test Shadow Rows
     EXPECT_FALSE(testee.hasShadowRow());
     {
-      auto const [state, row] = testee.peekShadowRow();
+      auto const [state, row] = testee.peekShadowRowAndState();
       EXPECT_EQ(GetParam(), state);
       EXPECT_FALSE(row.isInitialized());
     }
@@ -92,7 +92,7 @@ class InputRangeTest : public ::testing::TestWithParam<ExecutorState> {
     auto rowIndexBefore = testee.getRowIndex();
     // Validate that shadowRowAPI does not move on
     {
-      auto [state, row] = testee.peekShadowRow();
+      auto [state, row] = testee.peekShadowRowAndState();
       EXPECT_EQ(state, ExecutorState::DONE);
       EXPECT_FALSE(row.isInitialized());
       ASSERT_EQ(rowIndexBefore, testee.getRowIndex())
@@ -154,7 +154,7 @@ class InputRangeTest : public ::testing::TestWithParam<ExecutorState> {
     }
     // Validate ShadowRow API
     {
-      auto [state, row] = testee.peekShadowRow();
+      auto [state, row] = testee.peekShadowRowAndState();
       EXPECT_EQ(state, expectedState);
       EXPECT_TRUE(row.isInitialized());
       auto val = row.getValue(0);
@@ -209,7 +209,7 @@ TEST_P(InputRangeTest, empty_does_not_have_more_shadow_rows) {
 
 TEST_P(InputRangeTest, empty_peek_shadow_is_empty) {
   auto testee = createEmpty();
-  auto const [state, row] = testee.peekShadowRow();
+  auto const [state, row] = testee.peekShadowRowAndState();
   EXPECT_EQ(GetParam(), state);
   EXPECT_FALSE(row.isInitialized());
 }
diff --git a/tests/Aql/CalculationExecutorTest.cpp b/tests/Aql/CalculationExecutorTest.cpp
index ab64ffbf4d42..37db9313c92d 100644
--- a/tests/Aql/CalculationExecutorTest.cpp
+++ b/tests/Aql/CalculationExecutorTest.cpp
@@ -69,7 +69,7 @@ namespace aql {
 // CalculationExecutor<CalculationType::V8Condition> and
 // CalculationExecutor<CalculationType::Reference>!
 
-class CalculationExecutorTest : public AqlExecutorTestCase<true> {
+class CalculationExecutorTest : public AqlExecutorTestCase<false> {
  protected:
   ExecutionState state;
   AqlItemBlockManager itemBlockManager;
@@ -285,9 +285,8 @@ TEST_F(CalculationExecutorTest, test_produce_datarange_need_more) {
 
   AqlItemBlockInputRange input{ExecutorState::HASMORE, 0, inBlock, 0};
   OutputAqlItemRow output(std::move(block), infos.getOutputRegisters(),
-                          infos.registersToKeep(),
-                          infos.registersToClear(),
-                              AqlCall{0, 3, AqlCall::Infinity{}, false});
+                          infos.registersToKeep(), infos.registersToClear(),
+                          AqlCall{0, 3, AqlCall::Infinity{}, false});
 
   auto myCall = output.getClientCall();
   EXPECT_EQ(myCall.getLimit(), 3);
@@ -316,7 +315,7 @@ TEST_F(CalculationExecutorTest, test_produce_datarange_need_more) {
   EXPECT_FALSE(outputCall.fullCount);
 }
 
-TEST_F(CalculationExecutorTest, DISABLED_test_produce_datarange_has_more) { // TODO: fix and re-enable after this executor newStyle is active
+TEST_F(CalculationExecutorTest, DISABLED_test_produce_datarange_has_more) {  // TODO: fix and re-enable after this executor newStyle is active
   // This fetcher will not be called!
   // After Execute is done this fetcher shall be removed, the Executor does not need it anymore!
   auto fakeUnusedBlock = VPackParser::fromJson("[  ]");
diff --git a/tests/Aql/SortExecutorTest.cpp b/tests/Aql/SortExecutorTest.cpp
index b7a204e0ec5a..c2da61092d31 100644
--- a/tests/Aql/SortExecutorTest.cpp
+++ b/tests/Aql/SortExecutorTest.cpp
@@ -25,23 +25,26 @@
 
 #include "gtest/gtest.h"
 
+#include "ExecutorTestHelper.h"
+
 #include "fakeit.hpp"
 
 #include "RowFetcherHelper.h"
 
 #include "Aql/AqlItemBlock.h"
+#include "Aql/ConstrainedSortExecutor.h"
 #include "Aql/ExecutionBlockImpl.h"
 #include "Aql/ExecutionNode.h"
 #include "Aql/OutputAqlItemRow.h"
 #include "Aql/ResourceUsage.h"
 #include "Aql/SortExecutor.h"
-#include "Aql/ConstrainedSortExecutor.h"
 #include "Aql/SortRegister.h"
 #include "Aql/Stats.h"
 #include "Aql/Variable.h"
 #include "Transaction/Context.h"
 #include "Transaction/Methods.h"
 
+#include "AqlItemBlockHelper.h"
 #include "search/sort.hpp"
 
 #include <velocypack/Builder.h>
@@ -52,148 +55,150 @@ using namespace arangodb::aql;
 
 namespace arangodb::tests::aql {
 
-class SortExecutorTest : public ::testing::Test {
- protected:
-  ExecutionState state;
-  ResourceMonitor monitor;
-  AqlItemBlockManager itemBlockManager;
-  SharedAqlItemBlockPtr block;
+using SortTestHelper = ExecutorTestHelper<1, 1>;
+using SortSplitType = SortTestHelper::SplitType;
+using SortInputParam = std::tuple<SortSplitType>;
 
-  velocypack::Options const* vpackOptions{&velocypack::Options::Defaults};
+class SortExecutorTest : public AqlExecutorTestCaseWithParam<SortInputParam> {
+ protected:
+  auto getSplit() -> SortSplitType {
+    auto const& [split] = GetParam();
+    return split;
+  }
 
-  Variable sortVar;
-  SortElement sl;
-  SortRegister sortReg;
-  std::vector<SortRegister> sortRegisters;
-
-  SortExecutorTest()
-      : itemBlockManager(&monitor, SerializationFormat::SHADOWROWS),
-        block(new AqlItemBlock(itemBlockManager, 1000, 1)),
-        sortVar("mySortVar", 0),
-        sl(&sortVar, true),
-        sortReg(0, sl) {
+  auto makeInfos() -> SortExecutorInfos {
+    SortElement sl{&sortVar, true};
+    SortRegister sortReg{0, sl};
+    std::vector<SortRegister> sortRegisters;
     sortRegisters.emplace_back(std::move(sortReg));
+    return SortExecutorInfos(std::move(sortRegisters),
+                             /*limit (ignored for default sort)*/ 0, manager(),
+                             1, 1, {}, {0}, vpackOptions, false);
   }
+
+ private:
+  velocypack::Options const* vpackOptions{&velocypack::Options::Defaults};
+  Variable sortVar{"mySortVar", 0};
 };
 
-TEST_F(SortExecutorTest, no_rows_upstream_producer_doesnt_wait) {
-  SortExecutorInfos infos(std::move(sortRegisters),
-                          /*limit (ignored for default sort)*/ 0,
-                          itemBlockManager, 1, 1, {}, {0}, vpackOptions, false);
-  VPackBuilder input;
-  AllRowsFetcherHelper fetcher(input.steal(), false);
-  SortExecutor testee(fetcher, infos);
-  // Use this instead of std::ignore, so the tests will be noticed and
-  // updated when someone changes the stats type in the return value of
-  // EnumerateListExecutor::produceRows().
-  NoStats stats{};
-
-  OutputAqlItemRow result{std::move(block), infos.getOutputRegisters(),
-                          infos.registersToKeep(), infos.registersToClear()};
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(result.produced());
+template <size_t... vs>
+const SortSplitType splitIntoBlocks = SortSplitType{std::vector<std::size_t>{vs...}};
+template <size_t step>
+const SortSplitType splitStep = SortSplitType{step};
+
+INSTANTIATE_TEST_CASE_P(SortExecutorTest, SortExecutorTest,
+                        ::testing::Values(splitIntoBlocks<2, 3>, splitIntoBlocks<3, 4>,
+                                          splitStep<1>, splitStep<2>));
+
+TEST_P(SortExecutorTest, does_sort_all) {
+  AqlCall call{};          // unlimited produce
+  ExecutionStats stats{};  // No stats here
+  ExecutorTestHelper(*fakedQuery)
+      .setExecBlock<SortExecutor>(makeInfos(), ExecutionNode::SORT)
+      .setInputSplitType(getSplit())
+      .setInputValue({{5}, {3}, {1}, {2}, {4}})
+      .expectOutput({0}, {{1}, {2}, {3}, {4}, {5}})
+      .setCall(call)
+      .expectSkipped(0)
+      .expectedState(ExecutionState::DONE)
+      .run();
 }
 
-TEST_F(SortExecutorTest, no_rows_upstream_producer_waits) {
-  SortExecutorInfos infos(std::move(sortRegisters),
-                          /*limit (ignored for default sort)*/ 0,
-                          itemBlockManager, 1, 1, {}, {0}, vpackOptions, false);
-  VPackBuilder input;
-  AllRowsFetcherHelper fetcher(input.steal(), true);
-  SortExecutor testee(fetcher, infos);
-  // Use this instead of std::ignore, so the tests will be noticed and
-  // updated when someone changes the stats type in the return value of
-  // EnumerateListExecutor::produceRows().
-  NoStats stats{};
-
-  OutputAqlItemRow result{std::move(block), infos.getOutputRegisters(),
-                          infos.registersToKeep(), infos.registersToClear()};
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::WAITING);
-  ASSERT_FALSE(result.produced());
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(result.produced());
+TEST_P(SortExecutorTest, no_input) {
+  AqlCall call{};          // unlimited produce
+  ExecutionStats stats{};  // No stats here
+  ExecutorTestHelper(*fakedQuery)
+      .setExecBlock<SortExecutor>(makeInfos(), ExecutionNode::SORT)
+      .setInputSplitType(getSplit())
+      .setInputValue({})
+      .expectOutput({0}, {})
+      .setCall(call)
+      .expectSkipped(0)
+      .expectedState(ExecutionState::DONE)
+      .run();
 }
 
+TEST_P(SortExecutorTest, skip) {
+  AqlCall call{2};
+  ExecutionStats stats{};  // No stats here
+  ExecutorTestHelper(*fakedQuery)
+      .setExecBlock<SortExecutor>(makeInfos(), ExecutionNode::SORT)
+      .setInputSplitType(getSplit())
+      .setInputValue({{5}, {3}, {1}, {2}, {4}})
+      .expectOutput({0}, {{3}, {4}, {5}})
+      .setCall(call)
+      .expectSkipped(2)
+      .expectedState(ExecutionState::DONE)
+      .run();
+}
 
-TEST_F(SortExecutorTest, rows_upstream_we_are_waiting_for_list_of_numbers) {
-  SortExecutorInfos infos(std::move(sortRegisters),
-                          /*limit (ignored for default sort)*/ 0,
-                          itemBlockManager, 1, 1, {}, {0}, vpackOptions, false);
-  std::shared_ptr<VPackBuilder> input =
-      VPackParser::fromJson("[[5],[3],[1],[2],[4]]");
-  AllRowsFetcherHelper fetcher(input->steal(), true);
-  SortExecutor testee(fetcher, infos);
-  // Use this instead of std::ignore, so the tests will be noticed and
-  // updated when someone changes the stats type in the return value of
-  // EnumerateListExecutor::produceRows().
-  NoStats stats{};
-
-  OutputAqlItemRow result{std::move(block), infos.getOutputRegisters(),
-                          infos.registersToKeep(), infos.registersToClear()};
-  // Wait, 5, Wait, 3, Wait, 1, Wait, 2, Wait, 4, HASMORE
-  for (size_t i = 0; i < 5; ++i) {
-    std::tie(state, stats) = testee.produceRows(result);
-    ASSERT_EQ(state, ExecutionState::WAITING);
-    ASSERT_FALSE(result.produced());
-  }
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(result.produced());
-
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(result.produced());
-
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(result.produced());
-
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(result.produced());
-
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_TRUE(result.produced());
-
-  block = result.stealBlock();
-  AqlValue v = block->getValue(0, 0);
-  ASSERT_TRUE(v.isNumber());
-  int64_t number = v.toInt64();
-  ASSERT_EQ(number, 1);
-
-  v = block->getValue(1, 0);
-  ASSERT_TRUE(v.isNumber());
-  number = v.toInt64();
-  ASSERT_EQ(number, 2);
+TEST_P(SortExecutorTest, hard_limit) {
+  AqlCall call{0, false, 2, AqlCall::LimitType::HARD};
+  ExecutionStats stats{};  // No stats here
+  ExecutorTestHelper(*fakedQuery)
+      .setExecBlock<SortExecutor>(makeInfos(), ExecutionNode::SORT)
+      .setInputSplitType(getSplit())
+      .setInputValue({{5}, {3}, {1}, {2}, {4}})
+      .expectOutput({0}, {{1}, {2}})
+      .setCall(call)
+      .expectSkipped(0)
+      .expectedState(ExecutionState::DONE)
+      .run();
+}
 
-  v = block->getValue(2, 0);
-  ASSERT_TRUE(v.isNumber());
-  number = v.toInt64();
-  ASSERT_EQ(number, 3);
+TEST_P(SortExecutorTest, soft_limit) {
+  AqlCall call{0, false, 2, AqlCall::LimitType::SOFT};
+  ExecutionStats stats{};  // No stats here
+  ExecutorTestHelper(*fakedQuery)
+      .setExecBlock<SortExecutor>(makeInfos(), ExecutionNode::SORT)
+      .setInputSplitType(getSplit())
+      .setInputValue({{5}, {3}, {1}, {2}, {4}})
+      .expectOutput({0}, {{1}, {2}})
+      .setCall(call)
+      .expectSkipped(0)
+      .expectedState(ExecutionState::HASMORE)
+      .run();
+}
 
-  v = block->getValue(3, 0);
-  ASSERT_TRUE(v.isNumber());
-  number = v.toInt64();
-  ASSERT_EQ(number, 4);
+TEST_P(SortExecutorTest, fullcount) {
+  AqlCall call{0, true, 2, AqlCall::LimitType::HARD};
+  ExecutionStats stats{};  // No stats here
+  ExecutorTestHelper(*fakedQuery)
+      .setExecBlock<SortExecutor>(makeInfos(), ExecutionNode::SORT)
+      .setInputSplitType(getSplit())
+      .setInputValue({{5}, {3}, {1}, {2}, {4}})
+      .expectOutput({0}, {{1}, {2}})
+      .setCall(call)
+      .expectSkipped(3)
+      .expectedState(ExecutionState::DONE)
+      .run();
+}
 
-  v = block->getValue(4, 0);
-  ASSERT_TRUE(v.isNumber());
-  number = v.toInt64();
-  ASSERT_EQ(number, 5);
+TEST_P(SortExecutorTest, skip_produce_fullcount) {
+  AqlCall call{2, true, 2, AqlCall::LimitType::HARD};
+  ExecutionStats stats{};  // No stats here
+  ExecutorTestHelper(*fakedQuery)
+      .setExecBlock<SortExecutor>(makeInfos(), ExecutionNode::SORT)
+      .setInputSplitType(getSplit())
+      .setInputValue({{5}, {3}, {1}, {2}, {4}})
+      .expectOutput({0}, {{3}, {4}})
+      .setCall(call)
+      .expectSkipped(3)
+      .expectedState(ExecutionState::DONE)
+      .run();
 }
 
+TEST_P(SortExecutorTest, skip_too_much) {
+  AqlCall call{10, false};
+  ExecutionStats stats{};  // No stats here
+  ExecutorTestHelper(*fakedQuery)
+      .setExecBlock<SortExecutor>(makeInfos(), ExecutionNode::SORT)
+      .setInputSplitType(getSplit())
+      .setInputValue({{5}, {3}, {1}, {2}, {4}})
+      .expectOutput({0}, {})
+      .setCall(call)
+      .expectSkipped(5)
+      .expectedState(ExecutionState::DONE)
+      .run();
+}
 }  // namespace arangodb::tests::aql

From 28b9c044a2815df4eb82cd266a1b1d948db980d4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tobias=20G=C3=B6dderz?= <tobias@arangodb.com>
Date: Fri, 28 Feb 2020 21:46:47 +0100
Subject: [PATCH 084/122] Feature/aql subquery execute in restaqlhandler
 (#11175)

* Updated comment

* Added two static strings

* Avoid unintentional streaming operator of string_view as a container

* Added parser for execute rest call

* Fixed ambiguous overload in ResultT

* Added execute and executeForClient to ExecutionEngine

* Implemented executeForClient in RestAqlHandler

* Add default value

* Updated comment

* Changed error attribute

* Fixed duplicate log id

* Try to make MSVC work

* Moved AqlExecuteResult to a separate file

* Tried to fix MSVC compile error

* Revert "Tried to fix MSVC compile error"

This reverts commit f6f43b2c7e4bfe17dafe65f48bcd5c0b6e5c69a9.

* Next try to fix MSVC

* Revert "Next try to fix MSVC"

This reverts commit 528c4c795d10ee0aa6686d143be1f6faa6e9b553.

* Revert "Try to make MSVC work"

This reverts commit ba7d9c072fccb969da1cdf045eadf49c297da8e9.

* Work around MSVC shortcoming
---
 arangod/Aql/AqlCall.cpp                       | 225 ++++++++++++++++++
 arangod/Aql/AqlCall.h                         |   9 +-
 arangod/Aql/AqlCallStack.cpp                  |  47 +++-
 arangod/Aql/AqlCallStack.h                    |  16 +-
 arangod/Aql/AqlExecuteResult.cpp              |  70 ++++++
 arangod/Aql/AqlExecuteResult.h                |  57 +++++
 arangod/Aql/ExecutionEngine.cpp               |  46 +++-
 arangod/Aql/ExecutionEngine.h                 |   7 +
 arangod/Aql/RestAqlHandler.cpp                | 178 ++++++++++----
 arangod/Aql/RestAqlHandler.h                  |  50 +++-
 arangod/CMakeLists.txt                        |   2 +
 arangod/Cluster/ResultT.h                     |  10 +-
 arangod/Cluster/SynchronizeShard.cpp          |   2 +-
 arangod/RestHandler/RestRepairHandler.cpp     |   2 +-
 .../RocksDBRestReplicationHandler.cpp         |   2 +-
 lib/Basics/StaticStrings.cpp                  |  16 ++
 lib/Basics/StaticStrings.h                    |  16 ++
 lib/Basics/debugging.h                        |  27 ++-
 18 files changed, 703 insertions(+), 79 deletions(-)
 create mode 100644 arangod/Aql/AqlCall.cpp
 create mode 100644 arangod/Aql/AqlExecuteResult.cpp
 create mode 100644 arangod/Aql/AqlExecuteResult.h

diff --git a/arangod/Aql/AqlCall.cpp b/arangod/Aql/AqlCall.cpp
new file mode 100644
index 000000000000..cc8f947f13c1
--- /dev/null
+++ b/arangod/Aql/AqlCall.cpp
@@ -0,0 +1,225 @@
+////////////////////////////////////////////////////////////////////////////////
+/// DISCLAIMER
+///
+/// Copyright 2020 ArangoDB GmbH, Cologne, Germany
+///
+/// Licensed under the Apache License, Version 2.0 (the "License");
+/// you may not use this file except in compliance with the License.
+/// You may obtain a copy of the License at
+///
+///     http://www.apache.org/licenses/LICENSE-2.0
+///
+/// Unless required by applicable law or agreed to in writing, software
+/// distributed under the License is distributed on an "AS IS" BASIS,
+/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+/// See the License for the specific language governing permissions and
+/// limitations under the License.
+///
+/// Copyright holder is ArangoDB GmbH, Cologne, Germany
+///
+/// @author Tobias Gödderz
+////////////////////////////////////////////////////////////////////////////////
+
+#include "AqlCall.h"
+
+#include "Basics/StaticStrings.h"
+#include "Basics/voc-errors.h"
+#include "Logger/LogMacros.h"
+#include "Logger/Logger.h"
+
+#include <velocypack/Collection.h>
+#include <velocypack/Slice.h>
+
+#include <map>
+#include <string_view>
+
+using namespace arangodb;
+using namespace arangodb::aql;
+
+namespace {
+// hack for MSVC
+auto getStringView(velocypack::Slice slice) -> std::string_view {
+  velocypack::StringRef ref = slice.stringRef();
+  return std::string_view(ref.data(), ref.size());
+}
+}
+
+auto AqlCall::fromVelocyPack(velocypack::Slice slice) -> ResultT<AqlCall> {
+  if (ADB_UNLIKELY(!slice.isObject())) {
+    using namespace std::string_literals;
+    return Result(TRI_ERROR_TYPE_ERROR,
+                  "When deserializating AqlCall: Expected object, got "s + slice.typeName());
+  }
+
+  auto expectedPropertiesFound = std::map<std::string_view, bool>{};
+  expectedPropertiesFound.emplace(StaticStrings::AqlRemoteLimit, false);
+  expectedPropertiesFound.emplace(StaticStrings::AqlRemoteLimitType, false);
+  expectedPropertiesFound.emplace(StaticStrings::AqlRemoteFullCount, false);
+  expectedPropertiesFound.emplace(StaticStrings::AqlRemoteOffset, false);
+
+  auto limit = AqlCall::Limit{};
+  auto limitType = std::optional<AqlCall::LimitType>{};
+  auto offset = decltype(AqlCall::offset){0};
+  auto fullCount = false;
+
+  auto const readLimit = [](velocypack::Slice slice) -> ResultT<AqlCall::Limit> {
+    if (slice.isEqualString(StaticStrings::AqlRemoteInfinity)) {
+      return AqlCall::Limit{AqlCall::Infinity{}};
+    } else if (slice.isInteger()) {
+      try {
+        return AqlCall::Limit{slice.getNumber<std::size_t>()};
+      } catch (velocypack::Exception const& ex) {
+        auto message = std::string{"When deserializating AqlCall: "};
+        message += "When reading limit: ";
+        message += ex.what();
+        return Result(TRI_ERROR_TYPE_ERROR, std::move(message));
+      }
+    } else {
+      auto message = std::string{"When deserializating AqlCall: "};
+      message += "When reading limit: ";
+      if (slice.isString()) {
+        message += "Unexpected value '";
+        message += getStringView(slice);
+        message += "'";
+      } else {
+        message += "Unexpected type ";
+        message += slice.typeName();
+      }
+      return Result(TRI_ERROR_TYPE_ERROR, std::move(message));
+    }
+  };
+
+  auto const readLimitType = [](velocypack::Slice slice) -> ResultT<AqlCall::LimitType> {
+    if (ADB_UNLIKELY(!slice.isString())) {
+      auto message = std::string{
+          "When deserializating AqlCall: When reading limitType: "
+          "Unexpected type "};
+      message += slice.typeName();
+      return Result(TRI_ERROR_TYPE_ERROR, std::move(message));
+    }
+    auto value = getStringView(slice);
+    if (value == StaticStrings::AqlRemoteLimitTypeSoft) {
+      return AqlCall::LimitType::SOFT;
+    }
+    else if (value == StaticStrings::AqlRemoteLimitTypeHard) {
+      return AqlCall::LimitType::HARD;
+    }
+    else {
+      auto message = std::string{
+          "When deserializating AqlCall: When reading limitType: "
+          "Unexpected value '"};
+      message += value;
+      message += "'";
+      return Result(TRI_ERROR_TYPE_ERROR, std::move(message));
+    }
+  };
+
+  auto const readFullCount = [](velocypack::Slice slice) -> ResultT<bool> {
+    if (ADB_UNLIKELY(!slice.isBool())) {
+      auto message = std::string{
+          "When deserializating AqlCall: When reading fullCount: "
+          "Unexpected type "};
+      message += slice.typeName();
+      return Result(TRI_ERROR_TYPE_ERROR, std::move(message));
+    }
+    return slice.getBool();
+  };
+
+  auto const readOffset = [](velocypack::Slice slice) -> ResultT<decltype(offset)> {
+    if (!slice.isInteger()) {
+      auto message = std::string{
+          "When deserializating AqlCall: When reading offset: "
+          "Unexpected type "};
+      message += slice.typeName();
+      return Result(TRI_ERROR_TYPE_ERROR, std::move(message));
+    }
+    try {
+      return slice.getNumber<decltype(offset)>();
+    } catch (velocypack::Exception const& ex) {
+      auto message =
+          std::string{"When deserializating AqlCall: When reading offset: "};
+      message += ex.what();
+      return Result(TRI_ERROR_TYPE_ERROR, std::move(message));
+    }
+  };
+
+  for (auto const it : velocypack::ObjectIterator(slice)) {
+    auto const keySlice = it.key;
+    if (ADB_UNLIKELY(!keySlice.isString())) {
+      return Result(TRI_ERROR_TYPE_ERROR,
+                    "When deserializating AqlCall: Key is not a string");
+    }
+    auto const key = getStringView(keySlice);
+
+    if (auto propIt = expectedPropertiesFound.find(key);
+        ADB_LIKELY(propIt != expectedPropertiesFound.end())) {
+      if (ADB_UNLIKELY(propIt->second)) {
+        return Result(
+            TRI_ERROR_TYPE_ERROR,
+            "When deserializating AqlCall: Encountered duplicate key");
+      }
+      propIt->second = true;
+    }
+
+    if (key == StaticStrings::AqlRemoteLimit) {
+      auto maybeLimit = readLimit(it.value);
+      if (maybeLimit.fail()) {
+        return std::move(maybeLimit).result();
+      }
+      limit = maybeLimit.get();
+    } else if (key == StaticStrings::AqlRemoteLimitType) {
+      auto maybeLimitType = readLimitType(it.value);
+      if (maybeLimitType.fail()) {
+        return std::move(maybeLimitType).result();
+      }
+      limitType = maybeLimitType.get();
+    } else if (key == StaticStrings::AqlRemoteFullCount) {
+      auto maybeFullCount = readFullCount(it.value);
+      if (maybeFullCount.fail()) {
+        return std::move(maybeFullCount).result();
+      }
+      fullCount = maybeFullCount.get();
+    } else if (key == StaticStrings::AqlRemoteOffset) {
+      auto maybeOffset = readOffset(it.value);
+      if (maybeOffset.fail()) {
+        return std::move(maybeOffset).result();
+      }
+      offset = maybeOffset.get();
+    } else {
+      LOG_TOPIC("404b0", WARN, Logger::AQL)
+          << "When deserializating AqlCall: Encountered unexpected key " << key;
+      // If you run into this assertion during rolling upgrades after adding a
+      // new attribute, remove it in the older version.
+      TRI_ASSERT(false);
+    }
+  }
+
+  for (auto const& it : expectedPropertiesFound) {
+    if (ADB_UNLIKELY(!it.second)) {
+      auto message = std::string{"When deserializating AqlCall: missing key "};
+      message += it.first;
+      return Result(TRI_ERROR_TYPE_ERROR, std::move(message));
+    }
+  }
+
+  auto call = AqlCall{};
+
+  if (limitType.has_value()) {
+    switch (limitType.value()) {
+      case LimitType::SOFT:
+        call.softLimit = limit;
+        break;
+      case LimitType::HARD:
+        call.hardLimit = limit;
+        break;
+    }
+  } else if (ADB_UNLIKELY(!std::holds_alternative<Infinity>(limit))) {
+    return Result(TRI_ERROR_TYPE_ERROR,
+        "When deserializating AqlCall: limit set, but limitType is missing.");
+  }
+
+  call.offset = offset;
+  call.fullCount = fullCount;
+
+  return call;
+}
diff --git a/arangod/Aql/AqlCall.h b/arangod/Aql/AqlCall.h
index 1abf4868b6c4..07214859d631 100644
--- a/arangod/Aql/AqlCall.h
+++ b/arangod/Aql/AqlCall.h
@@ -25,10 +25,15 @@
 
 #include "Aql/ExecutionBlock.h"
 #include "Basics/overload.h"
+#include "Cluster/ResultT.h"
 
 #include <cstddef>
 #include <variant>
 
+namespace arangodb::velocypack {
+class Slice;
+}
+
 namespace arangodb::aql {
 
 struct AqlCall {
@@ -41,7 +46,7 @@ struct AqlCall {
   //      On a less important case, softLimit = 0 and offset = 0 do not occur together,
   //      but it's probably not worth implementing that in terms of data structures.
   class Infinity {};
-  using Limit = std::variant<size_t, Infinity>;
+  using Limit = std::variant<std::size_t, Infinity>;
 
   AqlCall() = default;
   // Replacements for struct initialization
@@ -58,6 +63,8 @@ struct AqlCall {
         hardLimit{limitType == LimitType::HARD ? Limit{limit} : Limit{Infinity{}}},
         fullCount{fullCount} {}
 
+  static auto fromVelocyPack(velocypack::Slice) -> ResultT<AqlCall>;
+
   // TODO Remove me, this will not be necessary later
   static AqlCall SimulateSkipSome(std::size_t toSkip) {
     AqlCall call;
diff --git a/arangod/Aql/AqlCallStack.cpp b/arangod/Aql/AqlCallStack.cpp
index 0b826fb6886b..92dab45176a5 100644
--- a/arangod/Aql/AqlCallStack.cpp
+++ b/arangod/Aql/AqlCallStack.cpp
@@ -22,6 +22,10 @@
 
 #include "AqlCallStack.h"
 
+#include <velocypack/Slice.h>
+#include <velocypack/Iterator.h>
+#include <velocypack/velocypack-aliases.h>
+
 // TODO: This class is not yet memory efficient or optimized in any way.
 // it might be reimplement soon to have the above features, Focus now is on
 // the API we want to use.
@@ -31,11 +35,10 @@ using namespace arangodb::aql;
 
 AqlCallStack::AqlCallStack(AqlCall call, bool compatibilityMode3_6)
     : _operations{{std::move(call)}},
-      _depth(0),
       _compatibilityMode3_6(compatibilityMode3_6) {}
 
 AqlCallStack::AqlCallStack(AqlCallStack const& other, AqlCall call)
-    : _operations{other._operations}, _depth(0) {
+    : _operations{other._operations} {
   // We can only use this constructor on relevant levels
   // Alothers need to use passThrough constructor
   TRI_ASSERT(other._depth == 0);
@@ -48,6 +51,9 @@ AqlCallStack::AqlCallStack(AqlCallStack const& other)
       _depth(other._depth),
       _compatibilityMode3_6(other._compatibilityMode3_6) {}
 
+AqlCallStack::AqlCallStack(std::stack<AqlCall>&& operations)
+    : _operations(std::move(operations)) {}
+
 bool AqlCallStack::isRelevant() const { return _depth == 0; }
 
 AqlCall AqlCallStack::popCall() {
@@ -107,4 +113,39 @@ auto AqlCallStack::increaseSubqueryDepth() -> void {
   TRI_ASSERT(_depth < std::numeric_limits<size_t>::max() - 2);
   _depth++;
   TRI_ASSERT(!isRelevant());
-}
\ No newline at end of file
+}
+
+auto AqlCallStack::fromVelocyPack(velocypack::Slice const slice) -> ResultT<AqlCallStack> {
+  if (ADB_UNLIKELY(!slice.isArray())) {
+    using namespace std::string_literals;
+    return Result(TRI_ERROR_TYPE_ERROR,
+                  "When deserializing AqlCallStack: expected array, got "s +
+                      slice.typeName());
+  }
+  if (ADB_UNLIKELY(slice.isEmptyArray())) {
+    return Result(TRI_ERROR_TYPE_ERROR,
+                  "When deserializing AqlCallStack: stack is empty");
+  }
+
+  auto stack = std::stack<AqlCall>{};
+  auto i = std::size_t{0};
+  for (auto const entry : VPackArrayIterator(slice)) {
+    auto maybeAqlCall = AqlCall::fromVelocyPack(entry);
+
+    if (ADB_UNLIKELY(maybeAqlCall.fail())) {
+      auto message = std::string{"When deserializing AqlCallStack: entry "};
+      message += std::to_string(i);
+      message += ": ";
+      message += std::move(maybeAqlCall).errorMessage();
+      return Result(TRI_ERROR_TYPE_ERROR, std::move(message));
+    }
+
+    stack.emplace(maybeAqlCall.get());
+
+    ++i;
+  }
+
+  TRI_ASSERT(i > 0);
+
+  return AqlCallStack{std::move(stack)};
+}
diff --git a/arangod/Aql/AqlCallStack.h b/arangod/Aql/AqlCallStack.h
index 16027bfcfd94..9d8e98df7d0b 100644
--- a/arangod/Aql/AqlCallStack.h
+++ b/arangod/Aql/AqlCallStack.h
@@ -24,10 +24,14 @@
 #define ARANGOD_AQL_AQL_CALLSTACK_H 1
 
 #include "Aql/AqlCall.h"
+#include "Cluster/ResultT.h"
 
 #include <stack>
 
 namespace arangodb {
+namespace velocypack {
+class Slice;
+}
 namespace aql {
 
 class AqlCallStack {
@@ -41,6 +45,8 @@ class AqlCallStack {
 
   AqlCallStack& operator=(AqlCallStack const& other) = default;
 
+  static auto fromVelocyPack(velocypack::Slice) -> ResultT<AqlCallStack>;
+
   // Quick test is this CallStack is of local relevance, or it is sufficient to pass it through
   bool isRelevant() const;
 
@@ -74,8 +80,7 @@ class AqlCallStack {
   void increaseSubqueryDepth();
 
   // TODO: Remove me again, only used to fake DONE
-  // @deprecated
-  auto empty() const noexcept -> bool {
+  [[deprecated]] auto empty() const noexcept -> bool {
     return _operations.empty() && _depth == 0;
   }
 
@@ -83,6 +88,9 @@ class AqlCallStack {
     return _operations.size() + _depth;
   }
 
+ private:
+  explicit AqlCallStack(std::stack<AqlCall>&& operations);
+
  private:
   // The list of operations, stacked by depth (e.g. bottom element is from main query)
   std::stack<AqlCall> _operations;
@@ -91,7 +99,7 @@ class AqlCallStack {
   // as they have been skipped.
   // In most cases this will be zero.
   // However if we skip a subquery that has a nested subquery this depth will be 1 in the nested subquery.
-  size_t _depth;
+  size_t _depth{0};
 
   // This flag will be set if and only if
   // we are called with the 3.6 and earlier API
@@ -99,7 +107,7 @@ class AqlCallStack {
   // and not 3.6.* -> 3.8.* we can savely remove
   // this flag and all it's side effects on the
   // version after 3.7.
-  bool _compatibilityMode3_6;
+  bool _compatibilityMode3_6{false};
 };
 
 }  // namespace aql
diff --git a/arangod/Aql/AqlExecuteResult.cpp b/arangod/Aql/AqlExecuteResult.cpp
new file mode 100644
index 000000000000..3b56bebec8bf
--- /dev/null
+++ b/arangod/Aql/AqlExecuteResult.cpp
@@ -0,0 +1,70 @@
+////////////////////////////////////////////////////////////////////////////////
+/// DISCLAIMER
+///
+/// Copyright 2020 ArangoDB GmbH, Cologne, Germany
+///
+/// Licensed under the Apache License, Version 2.0 (the "License");
+/// you may not use this file except in compliance with the License.
+/// You may obtain a copy of the License at
+///
+///     http://www.apache.org/licenses/LICENSE-2.0
+///
+/// Unless required by applicable law or agreed to in writing, software
+/// distributed under the License is distributed on an "AS IS" BASIS,
+/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+/// See the License for the specific language governing permissions and
+/// limitations under the License.
+///
+/// Copyright holder is ArangoDB GmbH, Cologne, Germany
+///
+/// @author Tobias Gödderz
+////////////////////////////////////////////////////////////////////////////////
+
+#include "AqlExecuteResult.h"
+
+#include "Basics/StaticStrings.h"
+
+#include <velocypack/Builder.h>
+#include <velocypack/Iterator.h>
+
+using namespace arangodb;
+using namespace arangodb::aql;
+
+auto AqlExecuteResult::state() const noexcept -> ExecutionState {
+  return _state;
+}
+
+auto AqlExecuteResult::skipped() const noexcept -> std::size_t {
+  return _skipped;
+}
+
+auto AqlExecuteResult::block() const noexcept -> SharedAqlItemBlockPtr const& {
+  return _block;
+}
+
+void AqlExecuteResult::toVelocyPack(velocypack::Builder& builder,
+                                    velocypack::Options const* const options) {
+  using namespace arangodb::velocypack;
+  auto const stateToValue = [](ExecutionState state) -> Value {
+    switch (state) {
+      case ExecutionState::DONE:
+        return Value(StaticStrings::AqlRemoteStateDone);
+      case ExecutionState::HASMORE:
+        return Value(StaticStrings::AqlRemoteStateHasmore);
+      case ExecutionState::WAITING:
+        THROW_ARANGO_EXCEPTION_MESSAGE(
+            TRI_ERROR_INTERNAL_AQL,
+            "Unexpected state WAITING, must not be serialized.");
+    }
+    THROW_ARANGO_EXCEPTION_MESSAGE(TRI_ERROR_INTERNAL_AQL, "Unhandled state");
+  };
+
+  builder.add(StaticStrings::AqlRemoteState, stateToValue(state()));
+  builder.add(StaticStrings::AqlRemoteSkipped, Value(skipped()));
+  if (block() != nullptr) {
+    ObjectBuilder guard(&builder, StaticStrings::AqlRemoteBlock);
+    block()->toVelocyPack(options, builder);
+  } else {
+    builder.add(StaticStrings::AqlRemoteBlock, Value(ValueType::Null));
+  }
+}
diff --git a/arangod/Aql/AqlExecuteResult.h b/arangod/Aql/AqlExecuteResult.h
new file mode 100644
index 000000000000..4d23804bd019
--- /dev/null
+++ b/arangod/Aql/AqlExecuteResult.h
@@ -0,0 +1,57 @@
+////////////////////////////////////////////////////////////////////////////////
+/// DISCLAIMER
+///
+/// Copyright 2020 ArangoDB GmbH, Cologne, Germany
+///
+/// Licensed under the Apache License, Version 2.0 (the "License");
+/// you may not use this file except in compliance with the License.
+/// You may obtain a copy of the License at
+///
+///     http://www.apache.org/licenses/LICENSE-2.0
+///
+/// Unless required by applicable law or agreed to in writing, software
+/// distributed under the License is distributed on an "AS IS" BASIS,
+/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+/// See the License for the specific language governing permissions and
+/// limitations under the License.
+///
+/// Copyright holder is ArangoDB GmbH, Cologne, Germany
+///
+/// @author Tobias Gödderz
+////////////////////////////////////////////////////////////////////////////////
+
+#ifndef ARANGOD_AQL_AQLEXECUTERESULT_H
+#define ARANGOD_AQL_AQLEXECUTERESULT_H
+
+#include "Aql/ExecutionState.h"
+#include "Aql/SharedAqlItemBlockPtr.h"
+
+#include <utility>
+
+namespace arangodb::velocypack {
+class Builder;
+struct Options;
+}  // namespace arangodb::velocypack
+
+namespace arangodb::aql {
+
+class AqlExecuteResult {
+ public:
+  AqlExecuteResult(ExecutionState state, std::size_t skipped, SharedAqlItemBlockPtr&& block)
+      : _state(state), _skipped(skipped), _block(std::move(block)) {}
+
+  void toVelocyPack(velocypack::Builder&, velocypack::Options const*);
+
+  [[nodiscard]] auto state() const noexcept -> ExecutionState;
+  [[nodiscard]] auto skipped() const noexcept -> std::size_t;
+  [[nodiscard]] auto block() const noexcept -> SharedAqlItemBlockPtr const&;
+
+ private:
+  ExecutionState _state = ExecutionState::HASMORE;
+  std::size_t _skipped = 0;
+  SharedAqlItemBlockPtr _block = nullptr;
+};
+
+}  // namespace arangodb::aql
+
+#endif  // ARANGOD_AQL_AQLEXECUTERESULT_H
diff --git a/arangod/Aql/ExecutionEngine.cpp b/arangod/Aql/ExecutionEngine.cpp
index 28adf34b8de9..2fa51ea000df 100644
--- a/arangod/Aql/ExecutionEngine.cpp
+++ b/arangod/Aql/ExecutionEngine.cpp
@@ -25,6 +25,7 @@
 
 #include "ApplicationFeatures/ApplicationServer.h"
 #include "Aql/AqlResult.h"
+#include "Aql/BlocksWithClients.h"
 #include "Aql/Collection.h"
 #include "Aql/EngineInfoContainerCoordinator.h"
 #include "Aql/EngineInfoContainerDBServerServerBased.h"
@@ -42,8 +43,6 @@
 #include "Basics/ScopeGuard.h"
 #include "Cluster/ServerState.h"
 #include "Futures/Utilities.h"
-#include "Logger/LogMacros.h"
-#include "Logger/Logger.h"
 #include "Network/Methods.h"
 #include "Network/NetworkFeature.h"
 #include "Network/Utils.h"
@@ -564,6 +563,49 @@ std::pair<ExecutionState, Result> ExecutionEngine::initializeCursor(SharedAqlIte
   return res;
 }
 
+auto ExecutionEngine::execute(AqlCallStack const& stack)
+    -> std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> {
+  if (_query.killed()) {
+    THROW_ARANGO_EXCEPTION(TRI_ERROR_QUERY_KILLED);
+  }
+  auto const res = _root->execute(stack);
+#ifdef ARANGODB_ENABLE_MAINTAINER_MODE
+  if (std::get<ExecutionState>(res) == ExecutionState::WAITING) {
+    auto const skipped = std::get<size_t>(res);
+    auto const block = std::get<SharedAqlItemBlockPtr>(res);
+    TRI_ASSERT(skipped == 0);
+    TRI_ASSERT(block == nullptr);
+  }
+#endif
+  return res;
+}
+
+auto ExecutionEngine::executeForClient(AqlCallStack const& stack, std::string const& clientId)
+    -> std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> {
+  if (_query.killed()) {
+    THROW_ARANGO_EXCEPTION(TRI_ERROR_QUERY_KILLED);
+  }
+
+  auto rootBlock = dynamic_cast<BlocksWithClients*>(root());
+  if (rootBlock == nullptr) {
+    using namespace std::string_literals;
+    THROW_ARANGO_EXCEPTION_MESSAGE(TRI_ERROR_INTERNAL_AQL,
+                                   "unexpected node type "s +
+                                       root()->getPlanNode()->getTypeString());
+  }
+
+  auto const res = rootBlock->executeForClient(stack, clientId);
+#ifdef ARANGODB_ENABLE_MAINTAINER_MODE
+  if (std::get<ExecutionState>(res) == ExecutionState::WAITING) {
+    auto const skipped = std::get<size_t>(res);
+    auto const& block = std::get<SharedAqlItemBlockPtr>(res);
+    TRI_ASSERT(skipped == 0);
+    TRI_ASSERT(block == nullptr);
+  }
+#endif
+  return res;
+}
+
 std::pair<ExecutionState, SharedAqlItemBlockPtr> ExecutionEngine::getSome(size_t atMost) {
   if (_query.killed()) {
     THROW_ARANGO_EXCEPTION(TRI_ERROR_QUERY_KILLED);
diff --git a/arangod/Aql/ExecutionEngine.h b/arangod/Aql/ExecutionEngine.h
index d56feed72c41..f9af9ff3d2c2 100644
--- a/arangod/Aql/ExecutionEngine.h
+++ b/arangod/Aql/ExecutionEngine.h
@@ -40,6 +40,7 @@
 namespace arangodb {
 class Result;
 namespace aql {
+class AqlCallStack;
 class AqlItemBlock;
 class ExecutionBlock;
 class ExecutionNode;
@@ -96,6 +97,12 @@ class ExecutionEngine {
   /// return waiting
   std::pair<ExecutionState, Result> shutdown(int errorCode);
 
+  auto execute(AqlCallStack const& stack)
+      -> std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr>;
+
+  auto executeForClient(AqlCallStack const& stack, std::string const& clientId)
+      -> std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr>;
+
   /// @brief getSome
   std::pair<ExecutionState, SharedAqlItemBlockPtr> getSome(size_t atMost);
 
diff --git a/arangod/Aql/RestAqlHandler.cpp b/arangod/Aql/RestAqlHandler.cpp
index facdf4d8d802..366f65e4555f 100644
--- a/arangod/Aql/RestAqlHandler.cpp
+++ b/arangod/Aql/RestAqlHandler.cpp
@@ -23,9 +23,8 @@
 
 #include "RestAqlHandler.h"
 
-#include <velocypack/Iterator.h>
-#include <velocypack/velocypack-aliases.h>
-
+#include "Aql/AqlCallStack.h"
+#include "Aql/AqlExecuteResult.h"
 #include "Aql/AqlItemBlock.h"
 #include "Aql/AqlItemBlockSerializationFormat.h"
 #include "Aql/BlocksWithClients.h"
@@ -46,7 +45,9 @@
 #include "Logger/Logger.h"
 #include "Transaction/Context.h"
 #include "Transaction/Methods.h"
-#include "VocBase/ticks.h"
+
+#include <velocypack/Iterator.h>
+#include <velocypack/velocypack-aliases.h>
 
 using namespace arangodb;
 using namespace arangodb::rest;
@@ -400,41 +401,7 @@ bool RestAqlHandler::killQuery(std::string const& idString) {
 }
 
 // PUT method for /_api/aql/<operation>/<queryId>, (internal)
-// this is using the part of the cursor API with side effects.
-// <operation>: can be "lock" or "getSome" or "skip" or "initializeCursor" or
-// "shutdown".
-// The body must be a Json with the following attributes:
-// For the "getSome" operation one has to give:
-//   "atMost": must be a positive integer, the cursor returns never
-//             more than "atMost" items. The result is the JSON representation
-//             of an AqlItemBlock.
-//             If "atMost" is not given it defaults to
-//             ExecutionBlock::DefaultBatchSize.
-// For the "skipSome" operation one has to give:
-//   "atMost": must be a positive integer, the cursor skips never
-//             more than "atMost" items. The result is a JSON object with a
-//             single attribute "skipped" containing the number of
-//             skipped items.
-//             If "atMost" is not given it defaults to
-//             ExecutionBlock::DefaultBatchSize.
-// For the "skip" operation one should give:
-//   "number": must be a positive integer, the cursor skips as many items,
-//             possibly exhausting the cursor.
-//             The result is a JSON with the attributes "error" (boolean),
-//             "errorMessage" (if applicable) and "done" (boolean)
-//             to indicate whether or not the cursor is exhausted.
-//             If "number" is not given it defaults to 1.
-// For the "initializeCursor" operation, one has to bind the following
-// attributes:
-//   "items": This is a serialized AqlItemBlock with usually only one row
-//            and the correct number of columns.
-//   "pos":   The number of the row in "items" to take, usually 0.
-// For the "shutdown" and "lock" operations no additional arguments are
-// required and an empty JSON object in the body is OK.
-// All operations allow to set the HTTP header "x-shard-id:". If this is
-// set, then the root block of the stored query must be a ScatterBlock
-// and the shard ID is given as an additional argument to the ScatterBlock's
-// special API.
+// see comment in header for details
 RestStatus RestAqlHandler::useQuery(std::string const& operation, std::string const& idString) {
   bool success = false;
   VPackSlice querySlice = this->parseVPackBody(success);
@@ -635,6 +602,92 @@ Query* RestAqlHandler::findQuery(std::string const& idString) {
   return q;
 }
 
+class AqlExecuteCall {
+ public:
+  // Deserializing factory
+  static auto fromVelocyPack(VPackSlice slice) -> ResultT<AqlExecuteCall>;
+
+  auto callStack() const noexcept -> AqlCallStack const& { return _callStack; }
+
+ private:
+  AqlExecuteCall(AqlCallStack&& callStack) : _callStack(std::move(callStack)) {}
+
+  AqlCallStack _callStack;
+};
+
+namespace {
+// hack for MSVC
+auto getStringView(velocypack::Slice slice) -> std::string_view {
+  velocypack::StringRef ref = slice.stringRef();
+  return std::string_view(ref.data(), ref.size());
+}
+}
+
+// TODO Use the deserializer when available
+auto AqlExecuteCall::fromVelocyPack(VPackSlice const slice) -> ResultT<AqlExecuteCall> {
+  if (ADB_UNLIKELY(!slice.isObject())) {
+    using namespace std::string_literals;
+    return Result(TRI_ERROR_CLUSTER_AQL_COMMUNICATION,
+                  "When deserializating AqlExecuteCall: Expected object, got "s +
+                      slice.typeName());
+  }
+
+  auto expectedPropertiesFound = std::map<std::string_view, bool>{};
+  expectedPropertiesFound.emplace(StaticStrings::AqlRemoteCallStack, false);
+
+  auto callStack = std::optional<AqlCallStack>{};
+
+  for (auto const it : VPackObjectIterator(slice)) {
+    auto const keySlice = it.key;
+    if (ADB_UNLIKELY(!keySlice.isString())) {
+      return Result(TRI_ERROR_CLUSTER_AQL_COMMUNICATION,
+          "When deserializating AqlExecuteCall: Key is not a string");
+    }
+    auto const key = getStringView(keySlice);
+
+    if (auto propIt = expectedPropertiesFound.find(key);
+        ADB_LIKELY(propIt != expectedPropertiesFound.end())) {
+      if (ADB_UNLIKELY(propIt->second)) {
+        return Result(
+            TRI_ERROR_CLUSTER_AQL_COMMUNICATION,
+            "When deserializating AqlExecuteCall: Encountered duplicate key");
+      }
+      propIt->second = true;
+    }
+
+    if (key == StaticStrings::AqlRemoteCallStack) {
+      auto maybeCallStack = AqlCallStack::fromVelocyPack(it.value);
+      if (ADB_UNLIKELY(maybeCallStack.fail())) {
+        auto message = std::string{"When deserializating AqlExecuteCall: failed to deserialize "};
+        message += StaticStrings::AqlRemoteCallStack;
+        message += ": ";
+        message += maybeCallStack.errorMessage();
+        return Result(TRI_ERROR_CLUSTER_AQL_COMMUNICATION, std::move(message));
+      }
+
+      callStack = maybeCallStack.get();
+    } else {
+      LOG_TOPIC("0dd42", WARN, Logger::AQL)
+          << "When deserializating AqlExecuteCall: Encountered unexpected key " << key;
+      // If you run into this assertion during rolling upgrades after adding a
+      // new attribute, remove it in the older version.
+      TRI_ASSERT(false);
+    }
+  }
+
+  for (auto const& it : expectedPropertiesFound) {
+    if (ADB_UNLIKELY(!it.second)) {
+      auto message = std::string{"When deserializating AqlExecuteCall: missing key "};
+      message += it.first;
+      return Result(TRI_ERROR_CLUSTER_AQL_COMMUNICATION, std::move(message));
+    }
+  }
+
+  TRI_ASSERT(callStack.has_value());
+
+  return {AqlExecuteCall{std::move(callStack).value()}};
+}
+
 // handle for useQuery
 RestStatus RestAqlHandler::handleUseQuery(std::string const& operation,
                                           VPackSlice const querySlice) {
@@ -667,11 +720,46 @@ RestStatus RestAqlHandler::handleUseQuery(std::string const& operation,
 
   auto transactionContext = _query->trx()->transactionContext();
 
+  auto const rootNodeType = _query->engine()->root()->getPlanNode()->getType();
+
   VPackBuffer<uint8_t> answerBuffer;
   VPackBuilder answerBuilder(answerBuffer);
   answerBuilder.openObject(/*unindexed*/ true);
 
-  if (operation == "getSome") {
+  if (operation == StaticStrings::AqlRemoteExecute) {
+    auto maybeExecuteCall = AqlExecuteCall::fromVelocyPack(querySlice);
+    if (maybeExecuteCall.fail()) {
+      generateError(std::move(maybeExecuteCall).result());
+      return RestStatus::DONE;
+    }
+    auto& executeCall = maybeExecuteCall.get();
+
+    auto items = SharedAqlItemBlockPtr{};
+    auto skipped = size_t{};
+    auto state = ExecutionState::HASMORE;
+
+    // shardId is set IFF the root node is scatter or distribute
+    TRI_ASSERT(shardId.empty() != (rootNodeType == ExecutionNode::SCATTER ||
+                                   rootNodeType == ExecutionNode::DISTRIBUTE));
+    if (shardId.empty()) {
+      std::tie(state, skipped, items) =
+          _query->engine()->execute(executeCall.callStack());
+      if (state == ExecutionState::WAITING) {
+        return RestStatus::WAITING;
+      }
+    } else {
+      std::tie(state, skipped, items) =
+          _query->engine()->executeForClient(executeCall.callStack(), shardId);
+      if (state == ExecutionState::WAITING) {
+        return RestStatus::WAITING;
+      }
+    }
+
+    auto result = AqlExecuteResult{state, skipped, std::move(items)};
+    result.toVelocyPack(answerBuilder,
+                        _query->trx()->transactionContextPtr()->getVPackOptions());
+    answerBuilder.add(StaticStrings::Code, VPackValue(TRI_ERROR_NO_ERROR));
+  } else if (operation == "getSome") {
     TRI_IF_FAILURE("RestAqlHandler::getSome") {
       THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
     }
@@ -679,14 +767,16 @@ RestStatus RestAqlHandler::handleUseQuery(std::string const& operation,
                                                             ExecutionBlock::DefaultBatchSize);
     SharedAqlItemBlockPtr items;
     ExecutionState state;
+
+    // shardId is set IFF the root node is scatter or distribute
+    TRI_ASSERT(shardId.empty() != (rootNodeType == ExecutionNode::SCATTER ||
+                                   rootNodeType == ExecutionNode::DISTRIBUTE));
     if (shardId.empty()) {
       std::tie(state, items) = _query->engine()->getSome(atMost);
       if (state == ExecutionState::WAITING) {
         return RestStatus::WAITING;
       }
     } else {
-      TRI_ASSERT(_query->engine()->root()->getPlanNode()->getType() == ExecutionNode::SCATTER ||
-                 _query->engine()->root()->getPlanNode()->getType() == ExecutionNode::DISTRIBUTE);
       auto block = dynamic_cast<BlocksWithClients*>(_query->engine()->root());
       if (block == nullptr) {
         THROW_ARANGO_EXCEPTION_MESSAGE(TRI_ERROR_INTERNAL,
@@ -718,8 +808,8 @@ RestStatus RestAqlHandler::handleUseQuery(std::string const& operation,
       }
       skipped = tmpRes.second;
     } else {
-      TRI_ASSERT(_query->engine()->root()->getPlanNode()->getType() == ExecutionNode::SCATTER ||
-                 _query->engine()->root()->getPlanNode()->getType() == ExecutionNode::DISTRIBUTE);
+      TRI_ASSERT(rootNodeType == ExecutionNode::SCATTER ||
+                 rootNodeType == ExecutionNode::DISTRIBUTE);
 
       auto block = dynamic_cast<BlocksWithClients*>(_query->engine()->root());
       if (block == nullptr) {
diff --git a/arangod/Aql/RestAqlHandler.h b/arangod/Aql/RestAqlHandler.h
index d0b05a9d14e3..c917c6a2f1ca 100644
--- a/arangod/Aql/RestAqlHandler.h
+++ b/arangod/Aql/RestAqlHandler.h
@@ -61,20 +61,46 @@ class RestAqlHandler : public RestVocbaseBaseHandler {
 
   // PUT method for /_api/aql/<operation>/<queryId>, this is using
   // the part of the cursor API with side effects.
-  // <operation>: can be "getSome" or "skip".
+  // <operation>: can be "execute", "getSome", "skipSome" "initializeCursor" or
+  //              "shutdown".
+  //              "getSome" and "skipSome" are only used pre-3.7 and can be
+  //              removed in 3.8.
   // The body must be a Json with the following attributes:
+  // For the "execute" operation one has to give:
+  //   "callStack": an array of objects, each with the following attributes:
+  //     "offset": a non-negative integer
+  //     "limit": either a non-negative integer, or the string "infinity"
+  //     "limitType: string or null, either "soft" or "hard"; set iff limit is not infinity
+  //     "fullCount": a boolean
+  //   The result is an object with the attributes
+  //     "code": integer, error code.
+  //        If there was no error:
+  //     "state": string, either "hasMore" or "done"
+  //     "skipped": non-negative integer
+  //     "result": serialized AqlItemBlock, or null when no rows are returned.
   // For the "getSome" operation one has to give:
-  //   "atMost": must be a positiv integers, the cursor returns never
-  //             more than "atMost" items.
-  //             The result is the JSON representation of an
-  //             AqlItemBlock.
-  // For the "skip" operation one has to give:
-  //   "number": must be a positive integer, the cursor skips as many items,
-  //             possibly exhausting the cursor.
-  //             The result is a JSON with the attributes "error" (boolean),
-  //             "errorMessage" (if applicable) and
-  //             "done" (boolean) [3.4.0 and later] to indicate
-  //             whether or not the cursor is exhausted.
+  //   "atMost": must be a positive integer, the cursor returns never
+  //             more than "atMost" items. Defaults to
+  //             ExecutionBlock::DefaultBatchSize.
+  //   The result is the JSON representation of an AqlItemBlock.
+  // For the "skipSome" operation one has to give:
+  //   "atMost": must be a positive integer, the cursor skips never
+  //             more than "atMost" items. The result is a JSON object with a
+  //             single attribute "skipped" containing the number of
+  //             skipped items.
+  //             If "atMost" is not given it defaults to
+  //             ExecutionBlock::DefaultBatchSize.
+  // For the "initializeCursor" operation, one has to bind the following
+  // attributes:
+  //   "items": This is a serialized AqlItemBlock with usually only one row
+  //            and the correct number of columns.
+  //   "pos":   The number of the row in "items" to take, usually 0.
+  // For the "shutdown" operation no additional arguments are
+  // required and an empty JSON object in the body is OK.
+  // All operations allow to set the HTTP header "x-shard-id:". If this is
+  // set, then the root block of the stored query must be a ScatterBlock
+  // and the shard ID is given as an additional argument to the ScatterBlock's
+  // special API.
   RestStatus useQuery(std::string const& operation, std::string const& idString);
 
  private:
diff --git a/arangod/CMakeLists.txt b/arangod/CMakeLists.txt
index ca56d6ebf1b6..ba2250d221ec 100644
--- a/arangod/CMakeLists.txt
+++ b/arangod/CMakeLists.txt
@@ -218,7 +218,9 @@ set(LIB_ARANGO_PREGEL_SOURCES
 set(LIB_ARANGO_AQL_SOURCES
   Aql/Aggregator.cpp
   Aql/AllRowsFetcher.cpp
+  Aql/AqlCall.cpp
   Aql/AqlCallStack.cpp
+  Aql/AqlExecuteResult.cpp
   Aql/AqlFunctionFeature.cpp
   Aql/AqlItemBlock.cpp
   Aql/AqlItemBlockInputRange.cpp
diff --git a/arangod/Cluster/ResultT.h b/arangod/Cluster/ResultT.h
index 4b455dead5d6..3ebd6fcde34f 100644
--- a/arangod/Cluster/ResultT.h
+++ b/arangod/Cluster/ResultT.h
@@ -230,14 +230,20 @@ class ResultT {
   ResultT(std::optional<T>&& val_, int errorNumber, std::string const& errorMessage)
       : _result(errorNumber, errorMessage), _val(val_) {}
 
+  ResultT(std::optional<T>&& val_, int errorNumber, std::string&& errorMessage)
+      : _result(errorNumber, std::move(errorMessage)), _val(val_) {}
+
   ResultT(std::optional<T> const& val_, int errorNumber)
       : _result(errorNumber), _val(std::move(val_)) {}
 
   ResultT(std::optional<T> const& val_, int errorNumber, std::string const& errorMessage)
       : _result(errorNumber, errorMessage), _val(val_) {}
 
-  ResultT(std::optional<T>&& val_, Result result)
-      : _result(std::move(result)), _val(std::move(val_)) {}
+  ResultT(std::optional<T> const& val_, int errorNumber, std::string&& errorMessage)
+      : _result(errorNumber, std::move(errorMessage)), _val(val_) {}
+
+  ResultT(std::optional<T>&& val_, Result const& result)
+      : _result(result), _val(std::move(val_)) {}
 
   ResultT(std::optional<T>&& val_, Result&& result)
       : _result(std::move(result)), _val(std::move(val_)) {}
diff --git a/arangod/Cluster/SynchronizeShard.cpp b/arangod/Cluster/SynchronizeShard.cpp
index f935461411b5..a50dc970fbb0 100644
--- a/arangod/Cluster/SynchronizeShard.cpp
+++ b/arangod/Cluster/SynchronizeShard.cpp
@@ -935,7 +935,7 @@ bool SynchronizeShard::first() {
                             leader, lastTick, builder);
       if (!tickResult.ok()) {
         LOG_TOPIC("0a4d4", INFO, Logger::MAINTENANCE) << syncRes.errorMessage();
-        _result.reset(tickResult.result());
+        _result.reset(std::move(tickResult).result());
         return false;
       }
       lastTick = tickResult.get();
diff --git a/arangod/RestHandler/RestRepairHandler.cpp b/arangod/RestHandler/RestRepairHandler.cpp
index 31141dc189cc..1ccddc4adbb1 100644
--- a/arangod/RestHandler/RestRepairHandler.cpp
+++ b/arangod/RestHandler/RestRepairHandler.cpp
@@ -323,7 +323,7 @@ ResultT<bool> RestRepairHandler::jobFinished(std::string const& jobId) {
         << "Failed to get job status: "
         << "[" << jobStatus.errorNumber() << "] " << jobStatus.errorMessage();
 
-    return ResultT<bool>::error(std::move(jobStatus.result()));
+    return ResultT<bool>::error(std::move(jobStatus).result());
   }
 
   return ResultT<bool>::success(false);
diff --git a/arangod/RocksDBEngine/RocksDBRestReplicationHandler.cpp b/arangod/RocksDBEngine/RocksDBRestReplicationHandler.cpp
index e70f3221d589..032ad4ceabfc 100644
--- a/arangod/RocksDBEngine/RocksDBRestReplicationHandler.cpp
+++ b/arangod/RocksDBEngine/RocksDBRestReplicationHandler.cpp
@@ -128,7 +128,7 @@ void RocksDBRestReplicationHandler::handleCommandBatch() {
 
     auto res = _manager->extendLifetime(id, ttl);
     if (res.fail()) {
-      generateError(res.result());
+      generateError(std::move(res).result());
       return;
     }
 
diff --git a/lib/Basics/StaticStrings.cpp b/lib/Basics/StaticStrings.cpp
index 4962b624889b..dc44f9502536 100644
--- a/lib/Basics/StaticStrings.cpp
+++ b/lib/Basics/StaticStrings.cpp
@@ -294,8 +294,24 @@ std::string const StaticStrings::UpgradeEnvName(
 std::string const StaticStrings::BackupToDeleteName("DIRECTORY_TO_DELETE");
 std::string const StaticStrings::BackupSearchToDeleteName(
     "DIRECTORY_TO_DELETE_SEARCH");
+
+// aql api strings
 std::string const StaticStrings::SerializationFormat("serializationFormat");
 std::string const StaticStrings::AqlRemoteApi("api");
+std::string const StaticStrings::AqlRemoteExecute("execute");
+std::string const StaticStrings::AqlRemoteCallStack("callStack");
+std::string const StaticStrings::AqlRemoteLimit("limit");
+std::string const StaticStrings::AqlRemoteLimitType("limitType");
+std::string const StaticStrings::AqlRemoteLimitTypeSoft("soft");
+std::string const StaticStrings::AqlRemoteLimitTypeHard("hard");
+std::string const StaticStrings::AqlRemoteFullCount("fullCount");
+std::string const StaticStrings::AqlRemoteOffset("offset");
+std::string const StaticStrings::AqlRemoteInfinity("infinity");
+std::string const StaticStrings::AqlRemoteBlock("block");
+std::string const StaticStrings::AqlRemoteSkipped("skipped");
+std::string const StaticStrings::AqlRemoteState("state");
+std::string const StaticStrings::AqlRemoteStateDone("done");
+std::string const StaticStrings::AqlRemoteStateHasmore("hasmore");
 
 // validation
 std::string const StaticStrings::ValidatorLevelNone("none");
diff --git a/lib/Basics/StaticStrings.h b/lib/Basics/StaticStrings.h
index 4591679174a3..d51660ec654d 100644
--- a/lib/Basics/StaticStrings.h
+++ b/lib/Basics/StaticStrings.h
@@ -270,8 +270,24 @@ class StaticStrings {
   static std::string const UpgradeEnvName;
   static std::string const BackupToDeleteName;
   static std::string const BackupSearchToDeleteName;
+
+  // aql api strings
   static std::string const SerializationFormat;
   static std::string const AqlRemoteApi;
+  static std::string const AqlRemoteExecute;
+  static std::string const AqlRemoteCallStack;
+  static std::string const AqlRemoteLimit;
+  static std::string const AqlRemoteLimitType;
+  static std::string const AqlRemoteLimitTypeSoft;
+  static std::string const AqlRemoteLimitTypeHard;
+  static std::string const AqlRemoteFullCount;
+  static std::string const AqlRemoteOffset;
+  static std::string const AqlRemoteInfinity;
+  static std::string const AqlRemoteBlock;
+  static std::string const AqlRemoteSkipped;
+  static std::string const AqlRemoteState;
+  static std::string const AqlRemoteStateDone;
+  static std::string const AqlRemoteStateHasmore;
 
   // validation
   static std::string const ValidatorLevelNone;
diff --git a/lib/Basics/debugging.h b/lib/Basics/debugging.h
index 871d94722989..560e38a29078 100644
--- a/lib/Basics/debugging.h
+++ b/lib/Basics/debugging.h
@@ -119,6 +119,9 @@ template<typename T> struct is_container {
   static constexpr bool value = sizeof(test(std::declval<T>())) == 1;
 };
 
+template< class T >
+inline constexpr bool is_container_v = is_container<T>::value;
+
 template < typename T > struct is_associative {
   static tc& test(...) ;
   
@@ -127,16 +130,24 @@ template < typename T > struct is_associative {
   static constexpr bool value = sizeof( test( std::declval<T>() ) ) == 1 ;
 };
 
-}
+}  // namespace container_traits
+
+template <class T>
+struct remove_cvref {
+  typedef std::remove_cv_t<std::remove_reference_t<T>> type;
+};
+template <class T>
+using remove_cvref_t = typename remove_cvref<T>::type;
 
 template < typename T > struct is_container :
-  std::conditional<(container_traits::is_container<T>::value || std::is_array<T>::value)
-                   && !std::is_same<char *, typename std::decay<T>::type>::value
-                   && !std::is_same<char const*, typename std::decay<T>::type>::value
-                   && !std::is_same<unsigned char *, typename std::decay<T>::type>::value
-                   && !std::is_same<unsigned char const*, typename std::decay<T>::type>::value
-                   && !std::is_same<T, std::string>::value
-                   && !std::is_same<T, const std::string>::value, std::true_type, std::false_type >::type {};
+  std::conditional_t<(container_traits::is_container_v<T> || std::is_array_v<T>)
+                   && !std::is_same_v<char *, std::decay_t<T>>
+                   && !std::is_same_v<char const*, std::decay_t<T>>
+                   && !std::is_same_v<unsigned char *, std::decay_t<T>>
+                   && !std::is_same_v<unsigned char const*, std::decay_t<T>>
+                   && !std::is_same_v<std::string, std::decay_t<T>>
+                   && !std::is_same_v<std::string_view, std::decay_t<T>>,
+                   std::true_type, std::false_type > {};
 
 template < typename T > struct is_associative :
   std::conditional< container_traits::is_container<T>::value && container_traits::is_associative<T>::value,

From 08ceffe450adda8993869c9d8dbbd22df60bd52f Mon Sep 17 00:00:00 2001
From: Markus Pfeiffer <markuspf@users.noreply.github.com>
Date: Sat, 29 Feb 2020 07:13:19 +0000
Subject: [PATCH 085/122] Support executors with multiple dependencies 
 (#11181)

* Use DataRange in some places

* Add MultiAqlItemBlockInputRange

* First implementation of life, universe, and everything

* implement skip for UnsortedGather

* Some more wiring

* Attempt at hacking up execute for DependencyProxy

* Compilation fixes!

* Fixed AqlCall compilation and unified execute and executeForDependency

* Fixed WAITIGN assertion

* Sonderlocken.

* Foo

* Make compile

* Make tests pass.

Co-authored-by: Michael Hackstein <michael@arangodb.com>
---
 arangod/Aql/AqlItemBlockInputMatrix.cpp       |   5 +-
 arangod/Aql/AqlItemBlockInputMatrix.h         |   6 +-
 arangod/Aql/AqlItemBlockInputRange.cpp        |   3 +-
 arangod/Aql/AqlItemBlockInputRange.h          |   2 +-
 arangod/Aql/DependencyProxy.cpp               |  70 +++++----
 arangod/Aql/DependencyProxy.h                 |   3 +
 arangod/Aql/ExecutionBlockImpl.cpp            | 145 +++++++++++++-----
 arangod/Aql/ExecutionBlockImpl.h              |  16 +-
 arangod/Aql/MultiAqlItemBlockInputRange.cpp   | 141 +++++++++++++++++
 arangod/Aql/MultiAqlItemBlockInputRange.h     |  78 ++++++++++
 .../Aql/MultiDependencySingleRowFetcher.cpp   |  41 ++++-
 arangod/Aql/MultiDependencySingleRowFetcher.h |   8 +-
 arangod/Aql/UnsortedGatherExecutor.cpp        |  71 +++++++++
 arangod/Aql/UnsortedGatherExecutor.h          |  25 +--
 arangod/CMakeLists.txt                        |   1 +
 15 files changed, 526 insertions(+), 89 deletions(-)
 create mode 100644 arangod/Aql/MultiAqlItemBlockInputRange.cpp
 create mode 100644 arangod/Aql/MultiAqlItemBlockInputRange.h

diff --git a/arangod/Aql/AqlItemBlockInputMatrix.cpp b/arangod/Aql/AqlItemBlockInputMatrix.cpp
index d2a7d16c3cd3..956b98467c51 100644
--- a/arangod/Aql/AqlItemBlockInputMatrix.cpp
+++ b/arangod/Aql/AqlItemBlockInputMatrix.cpp
@@ -120,13 +120,13 @@ bool AqlItemBlockInputMatrix::hasShadowRow() const noexcept {
   return _shadowRow.isInitialized();
 }
 
-void AqlItemBlockInputMatrix::skipAllRemainingDataRows() {
+size_t AqlItemBlockInputMatrix::skipAllRemainingDataRows() {
   if (_aqlItemMatrix == nullptr) {
     // Have not been initialized.
     // We need to be called before.
     TRI_ASSERT(!hasShadowRow());
     TRI_ASSERT(!hasDataRow());
-    return;
+    return 0;
   }
   if (!hasShadowRow()) {
     if (_aqlItemMatrix->stoppedOnShadowRow()) {
@@ -139,4 +139,5 @@ void AqlItemBlockInputMatrix::skipAllRemainingDataRows() {
   }
   // Else we did already skip once.
   // nothing to do
+  return 0;
 }
diff --git a/arangod/Aql/AqlItemBlockInputMatrix.h b/arangod/Aql/AqlItemBlockInputMatrix.h
index 9ce5c3073dac..80e37e40e1f9 100644
--- a/arangod/Aql/AqlItemBlockInputMatrix.h
+++ b/arangod/Aql/AqlItemBlockInputMatrix.h
@@ -50,14 +50,14 @@ class AqlItemBlockInputMatrix {
 
   ExecutorState upstreamState() const noexcept;
   bool upstreamHasMore() const noexcept;
-  void skipAllRemainingDataRows();
+  size_t skipAllRemainingDataRows();
 
  private:
   arangodb::aql::SharedAqlItemBlockPtr _block{nullptr};
   ExecutorState _finalState{ExecutorState::HASMORE};
 
-  // Only if _aqlItemMatrix is set (and NOT a nullptr), we have a valid and usable
-  // DataRange object available to work with.
+  // Only if _aqlItemMatrix is set (and NOT a nullptr), we have a valid and
+  // usable DataRange object available to work with.
   AqlItemMatrix* _aqlItemMatrix;
   ShadowAqlItemRow _shadowRow{CreateInvalidShadowRowHint{}};
 };
diff --git a/arangod/Aql/AqlItemBlockInputRange.cpp b/arangod/Aql/AqlItemBlockInputRange.cpp
index 11bd5710e6be..b0329dfd94d7 100644
--- a/arangod/Aql/AqlItemBlockInputRange.cpp
+++ b/arangod/Aql/AqlItemBlockInputRange.cpp
@@ -121,7 +121,7 @@ std::pair<ExecutorState, ShadowAqlItemRow> AqlItemBlockInputRange::nextShadowRow
   return res;
 }
 
-void AqlItemBlockInputRange::skipAllRemainingDataRows() {
+size_t AqlItemBlockInputRange::skipAllRemainingDataRows() {
   ExecutorState state;
   InputAqlItemRow row{CreateInvalidInputRowHint{}};
 
@@ -129,6 +129,7 @@ void AqlItemBlockInputRange::skipAllRemainingDataRows() {
     std::tie(state, row) = nextDataRow();
     TRI_ASSERT(row.isInitialized());
   }
+  return 0;
 }
 
 template <AqlItemBlockInputRange::LookAhead doPeek, AqlItemBlockInputRange::RowType type>
diff --git a/arangod/Aql/AqlItemBlockInputRange.h b/arangod/Aql/AqlItemBlockInputRange.h
index 03e442a3a730..ef2bfd6b70e6 100644
--- a/arangod/Aql/AqlItemBlockInputRange.h
+++ b/arangod/Aql/AqlItemBlockInputRange.h
@@ -62,7 +62,7 @@ class AqlItemBlockInputRange {
 
   std::pair<ExecutorState, arangodb::aql::ShadowAqlItemRow> nextShadowRow();
 
-  void skipAllRemainingDataRows();
+  size_t skipAllRemainingDataRows();
 
   // Subtract up to this many rows from the local `_skipped` state; return
   // the number actually skipped. Does not skip data rows.
diff --git a/arangod/Aql/DependencyProxy.cpp b/arangod/Aql/DependencyProxy.cpp
index b7828fea8ec4..cdbc955fac6c 100644
--- a/arangod/Aql/DependencyProxy.cpp
+++ b/arangod/Aql/DependencyProxy.cpp
@@ -37,44 +37,54 @@ DependencyProxy<blockPassthrough>::execute(AqlCallStack& stack) {
   ExecutionState state = ExecutionState::HASMORE;
   size_t skipped = 0;
   SharedAqlItemBlockPtr block = nullptr;
+  // Note: upstreamBlock will return next dependency
+  // if we need to loop here
   do {
-    // Note: upstreamBlock will return next dependency
-    // if we need to loop here
-    if (!_distributeId.empty()) {
-      // We are in the cluster case.
-      // we have to ask executeForShard
-      auto upstreamWithClient = dynamic_cast<BlocksWithClients*>(&upstreamBlock());
-      TRI_ASSERT(upstreamWithClient != nullptr);
-      if (upstreamWithClient == nullptr) {
-        THROW_ARANGO_EXCEPTION_MESSAGE(TRI_ERROR_INTERNAL_AQL,
-                                       "Invalid state reached, we try to "
-                                       "request sharded data from a block "
-                                       "that is not able to provide it.");
-      }
-      std::tie(state, skipped, block) =
-          upstreamWithClient->executeForClient(stack, _distributeId);
-    } else {
-      std::tie(state, skipped, block) = upstreamBlock().execute(stack);
-    }
-    TRI_IF_FAILURE("ExecutionBlock::getBlock") {
-      THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
-    }
-    if (state == ExecutionState::WAITING) {
-      TRI_ASSERT(block == nullptr);
-      TRI_ASSERT(skipped == 0);
-      break;
-    }
+    std::tie(state, skipped, block) = executeForDependency(_currentDependency, stack);
 
-    if (skipped == 0 && block == nullptr) {
-      // We're not waiting and didn't get any input, so we have to be done.
-      TRI_ASSERT(state == ExecutionState::DONE);
+    if (state == ExecutionState::DONE) {
       if (!advanceDependency()) {
         break;
       }
     }
+  } while (state != ExecutionState::WAITING && skipped == 0 && block == nullptr);
+  return {state, skipped, block};
+}
 
-  } while (skipped == 0 && block == nullptr);
+template <BlockPassthrough blockPassthrough>
+std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> DependencyProxy<blockPassthrough>::executeForDependency(
+    size_t dependency, AqlCallStack& stack) {
+  // TODO: assert dependency in range
+  ExecutionState state = ExecutionState::HASMORE;
+  size_t skipped = 0;
+  SharedAqlItemBlockPtr block = nullptr;
 
+  if (!_distributeId.empty()) {
+    // We are in the cluster case.
+    // we have to ask executeForShard
+    auto upstreamWithClient =
+        dynamic_cast<BlocksWithClients*>(&upstreamBlockForDependency(dependency));
+    TRI_ASSERT(upstreamWithClient != nullptr);
+    if (upstreamWithClient == nullptr) {
+      THROW_ARANGO_EXCEPTION_MESSAGE(TRI_ERROR_INTERNAL_AQL,
+                                     "Invalid state reached, we try to "
+                                     "request sharded data from a block "
+                                     "that is not able to provide it.");
+    }
+    std::tie(state, skipped, block) =
+        upstreamWithClient->executeForClient(stack, _distributeId);
+  } else {
+    std::tie(state, skipped, block) =
+        upstreamBlockForDependency(dependency).execute(stack);
+  }
+  TRI_IF_FAILURE("ExecutionBlock::getBlock") {
+    THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
+  }
+
+  if (skipped == 0 && block == nullptr) {
+    // We're either waiting or Done
+    TRI_ASSERT(state == ExecutionState::DONE || state == ExecutionState::WAITING);
+  }
   return {state, skipped, block};
 }
 
diff --git a/arangod/Aql/DependencyProxy.h b/arangod/Aql/DependencyProxy.h
index c66011845512..108e6bad1ac9 100644
--- a/arangod/Aql/DependencyProxy.h
+++ b/arangod/Aql/DependencyProxy.h
@@ -76,6 +76,9 @@ class DependencyProxy {
   // TODO Implement and document properly!
   TEST_VIRTUAL std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> execute(AqlCallStack& stack);
 
+  TEST_VIRTUAL std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> executeForDependency(
+      size_t dependency, AqlCallStack& stack);
+
   // This is only TEST_VIRTUAL, so we ignore this lint warning:
   // NOLINTNEXTLINE google-default-arguments
   [[nodiscard]] TEST_VIRTUAL std::pair<ExecutionState, SharedAqlItemBlockPtr> fetchBlock(
diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index 5ffd2ad3edc1..54bc29742555 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -144,8 +144,8 @@ constexpr bool isNewStyleExecutor = is_one_of_v<
     TestLambdaExecutor,
     TestLambdaSkipExecutor,  // we need one after these to avoid compile errors in non-test mode
 #endif
-    SubqueryStartExecutor, SubqueryEndExecutor, TraversalExecutor, KShortestPathsExecutor,
-    ShortestPathExecutor, EnumerateListExecutor, LimitExecutor, SortExecutor,
+    UnsortedGatherExecutor, SubqueryStartExecutor, SubqueryEndExecutor, TraversalExecutor,
+    KShortestPathsExecutor, ShortestPathExecutor, EnumerateListExecutor, LimitExecutor, SortExecutor,
     IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::NotMaterialize>,
     IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::LateMaterialize>,
     IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::Materialize>,
@@ -190,6 +190,7 @@ ExecutionBlockImpl<Executor>::ExecutionBlockImpl(ExecutionEngine* engine,
       _execState{ExecState::CHECKCALL},
       _upstreamRequest{},
       _clientRequest{},
+      _requestedDependency{},
       _hasUsedDataRangeBlock{false} {
   // already insert ourselves into the statistics results
   if (_profile >= PROFILE_LEVEL_BLOCKS) {
@@ -1119,8 +1120,9 @@ static SkipRowsRangeVariant constexpr skipRowsType() {
 #ifdef ARANGODB_USE_GOOGLE_TESTS
               TestLambdaSkipExecutor,
 #endif
-              TraversalExecutor, EnumerateListExecutor, SubqueryStartExecutor, SubqueryEndExecutor, SortedCollectExecutor,
-              LimitExecutor, SortExecutor, IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::NotMaterialize>,
+              UnsortedGatherExecutor, TraversalExecutor, EnumerateListExecutor, SubqueryStartExecutor,
+              SubqueryEndExecutor, SortedCollectExecutor, LimitExecutor, SortExecutor,
+              IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::NotMaterialize>,
               IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::LateMaterialize>,
               IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::Materialize>,
               IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::NotMaterialize | arangodb::iresearch::MaterializeType::UseStoredValues>,
@@ -1191,18 +1193,66 @@ static auto fastForwardType(AqlCall const& call, Executor const& e) -> FastForwa
   return FastForwardVariant::FETCHER;
 }
 
+template <class Executor>
+auto ExecutionBlockImpl<Executor>::executeFetcher(AqlCallStack& stack, size_t const dependency)
+    -> std::tuple<ExecutionState, size_t, typename Fetcher::DataRange> {
+  // Silence compiler about unused dependency
+  (void)dependency;
+  if constexpr (isNewStyleExecutor<Executor>) {
+    if constexpr (is_one_of_v<Fetcher, MultiDependencySingleRowFetcher>) {
+      // TODO: This is a hack to guarantee we have enough space in our range
+      //       to fit all inputs, in particular the one executed below
+      TRI_ASSERT(dependency < _dependencies.size());
+      _lastRange.resizeIfNecessary(ExecutorState::HASMORE, 0, _dependencies.size());
+
+      auto [state, skipped, range] = _rowFetcher.executeForDependency(dependency, stack);
+
+      _lastRange.setDependency(dependency, range);
+
+      return {state, skipped, _lastRange};
+    } else {
+      return _rowFetcher.execute(stack);
+    }
+  } else {
+    TRI_ASSERT(false);
+  }
+}
+
+template <class Executor>
+auto ExecutionBlockImpl<Executor>::executeProduceRows(typename Fetcher::DataRange& input,
+                                                      OutputAqlItemRow& output)
+    -> std::tuple<ExecutorState, typename Executor::Stats, AqlCall, size_t> {
+  if constexpr (isNewStyleExecutor<Executor>) {
+    if constexpr (is_one_of_v<Executor, UnsortedGatherExecutor>) {
+      return _executor.produceRows(input, output);
+    } else {
+      auto [state, stats, call] = _executor.produceRows(input, output);
+      return {state, stats, call, 0};
+    }
+  } else {
+    TRI_ASSERT(false);
+  }
+}
+
 template <class Executor>
 auto ExecutionBlockImpl<Executor>::executeSkipRowsRange(typename Fetcher::DataRange& inputRange,
                                                         AqlCall& call)
-    -> std::tuple<ExecutorState, typename Executor::Stats, size_t, AqlCall> {
+    -> std::tuple<ExecutorState, typename Executor::Stats, size_t, AqlCall, size_t> {
   if constexpr (isNewStyleExecutor<Executor>) {
     call.skippedRows = 0;
     if constexpr (skipRowsType<Executor>() == SkipRowsRangeVariant::EXECUTOR) {
-      // If the executor has a method skipRowsRange, to skip outputs.
-      // Every non-passthrough executor needs to implement this.
-      auto res = _executor.skipRowsRange(inputRange, call);
-      _executorReturnedDone = std::get<ExecutorState>(res) == ExecutorState::DONE;
-      return res;
+      if constexpr (is_one_of_v<Executor, UnsortedGatherExecutor>) {
+        // If the executor has a method skipRowsRange, to skip outputs.
+        // Every non-passthrough executor needs to implement this.
+        auto res = _executor.skipRowsRange(inputRange, call);
+        _executorReturnedDone = std::get<ExecutorState>(res) == ExecutorState::DONE;
+        return res;
+      } else {
+        auto [state, stats, skipped, localCall] =
+            _executor.skipRowsRange(inputRange, call);
+        _executorReturnedDone = state == ExecutorState::DONE;
+        return {state, stats, skipped, localCall, 0};
+      }
     } else if constexpr (skipRowsType<Executor>() == SkipRowsRangeVariant::FETCHER) {
       // If we know that every input row produces exactly one output row (this
       // is a property of the executor), then we can just let the fetcher skip
@@ -1212,19 +1262,18 @@ auto ExecutionBlockImpl<Executor>::executeSkipRowsRange(typename Fetcher::DataRa
       static_assert(
           std::is_same_v<typename Executor::Stats, NoStats>,
           "Executors with custom statistics must implement skipRowsRange.");
-      // TODO Set _executorReturnedDone?
-      return {inputRange.upstreamState(), NoStats{}, 0, call};
+      return {inputRange.upstreamState(), NoStats{}, 0, call, 0};
     } else {
       static_assert(dependent_false<Executor>::value,
                     "This value of SkipRowsRangeVariant is not supported");
-      return std::make_tuple(ExecutorState::DONE, typename Executor::Stats{}, 0, call);
+      return std::make_tuple(ExecutorState::DONE, typename Executor::Stats{}, 0, call, 0);
     }
   } else {
     TRI_ASSERT(false);
-    return std::make_tuple(ExecutorState::DONE, typename Executor::Stats{}, 0, call);
+    return std::make_tuple(ExecutorState::DONE, typename Executor::Stats{}, 0, call, 0);
   }
   // Compiler is unhappy without this.
-  return std::make_tuple(ExecutorState::DONE, typename Executor::Stats{}, 0, call);
+  return std::make_tuple(ExecutorState::DONE, typename Executor::Stats{}, 0, call, 0);
 }
 
 template <>
@@ -1379,7 +1428,7 @@ auto ExecutionBlockImpl<Executor>::shadowRowForwarding() -> ExecState {
 template <class Executor>
 auto ExecutionBlockImpl<Executor>::executeFastForward(typename Fetcher::DataRange& inputRange,
                                                       AqlCall& clientCall)
-    -> std::tuple<ExecutorState, typename Executor::Stats, size_t, AqlCall> {
+    -> std::tuple<ExecutorState, typename Executor::Stats, size_t, AqlCall, size_t> {
   TRI_ASSERT(isNewStyleExecutor<Executor>);
   if constexpr (std::is_same_v<Executor, SubqueryStartExecutor>) {
     if (clientCall.needsFullCount() && clientCall.getOffset() == 0 &&
@@ -1389,33 +1438,45 @@ auto ExecutionBlockImpl<Executor>::executeFastForward(typename Fetcher::DataRang
       return executeSkipRowsRange(_lastRange, clientCall);
     }
     // Do not fastForward anything, the Subquery start will handle it by itself
-    return {ExecutorState::DONE, NoStats{}, 0, AqlCall{}};
+    return {ExecutorState::DONE, NoStats{}, 0, AqlCall{}, 0};
   }
   auto type = fastForwardType(clientCall, _executor);
   switch (type) {
     case FastForwardVariant::FULLCOUNT:
     case FastForwardVariant::EXECUTOR: {
       LOG_QUERY("cb135", DEBUG) << printTypeInfo() << " apply full count.";
-      auto [state, stats, skippedLocal, call] = executeSkipRowsRange(_lastRange, clientCall);
+      auto [state, stats, skippedLocal, call, dependency] =
+          executeSkipRowsRange(_lastRange, clientCall);
+      _requestedDependency = dependency;
+
       if (type == FastForwardVariant::EXECUTOR) {
         // We do not report the skip
         skippedLocal = 0;
       }
-      if constexpr (std::is_same_v<DataRange, AqlItemBlockInputMatrix>) {
+
+      if constexpr (is_one_of_v<DataRange, AqlItemBlockInputMatrix, MultiAqlItemBlockInputRange>) {
         // The executor will have used all Rows.
         // However we need to drop them from the input
         // here.
         inputRange.skipAllRemainingDataRows();
       }
 
-      return {state, stats, skippedLocal, call};
+      return {state, stats, skippedLocal, call, dependency};
     }
     case FastForwardVariant::FETCHER: {
       LOG_QUERY("fa327", DEBUG) << printTypeInfo() << " bypass unused rows.";
-      inputRange.skipAllRemainingDataRows();
+      _requestedDependency = inputRange.skipAllRemainingDataRows();
       AqlCall call{};
       call.hardLimit = 0;
-      return {inputRange.upstreamState(), typename Executor::Stats{}, 0, call};
+
+      // TODO We have to ask all dependencies to go forward to the next shadow row
+      if constexpr (std::is_same_v<DataRange, MultiAqlItemBlockInputRange>) {
+        return {inputRange.upstreamState(_requestedDependency),
+                typename Executor::Stats{}, 0, call, _requestedDependency};
+      } else {
+        return {inputRange.upstreamState(), typename Executor::Stats{}, 0, call,
+                _requestedDependency};
+      }
     }
   }
   // Unreachable
@@ -1476,7 +1537,8 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
       // However we need to maintain the upstream state.
       size_t skippedLocal = 0;
       typename Fetcher::DataRange bypassedRange{ExecutorState::HASMORE};
-      std::tie(_upstreamState, skippedLocal, bypassedRange) = _rowFetcher.execute(stack);
+      std::tie(_upstreamState, skippedLocal, bypassedRange) =
+          executeFetcher(stack, _requestedDependency);
       return {_upstreamState, skippedLocal, bypassedRange.getBlock()};
     }
 
@@ -1543,15 +1605,15 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
               clientCall.getLimit() == 0 && clientCall.needsFullCount();
 #endif
           LOG_QUERY("1f786", DEBUG) << printTypeInfo() << " call skipRows " << clientCall;
-          auto [state, stats, skippedLocal, call] =
+          auto [state, stats, skippedLocal, call, dependency] =
               executeSkipRowsRange(_lastRange, clientCall);
+          _requestedDependency = dependency;
 #ifdef ARANGODB_ENABLE_MAINTAINER_MODE
           // Assertion: We did skip 'skippedLocal' documents here.
-          // This means that they have to be removed from clientCall.getOffset()
-          // This has to be done by the Executor calling call.didSkip()
-          // accordingly.
-          // The LIMIT executor with a LIMIT of 0 can also bypass fullCount
-          // here, even if callLimit > 0
+          // This means that they have to be removed from
+          // clientCall.getOffset() This has to be done by the Executor
+          // calling call.didSkip() accordingly. The LIMIT executor with a
+          // LIMIT of 0 can also bypass fullCount here, even if callLimit > 0
           if (canPassFullcount || std::is_same_v<Executor, LimitExecutor>) {
             // In this case we can first skip. But straight after continue with fullCount, so we might skip more
             TRI_ASSERT(clientCall.getOffset() + skippedLocal >= offsetBefore);
@@ -1607,14 +1669,15 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
           TRI_ASSERT(!_executorReturnedDone);
 
           // Execute getSome
-          auto const [state, stats, call] =
-              _executor.produceRows(_lastRange, *_outputItemRow);
+          auto const [state, stats, call, dependency] =
+              executeProduceRows(_lastRange, *_outputItemRow);
+          // TODO: Check
+          _requestedDependency = dependency;
           _executorReturnedDone = state == ExecutorState::DONE;
           _engine->_stats += stats;
           localExecutorState = state;
 
           if constexpr (!std::is_same_v<Executor, SubqueryEndExecutor>) {
-            // Produce might have modified the clientCall
             // But only do this if we are not subquery.
             clientCall = _outputItemRow->getClientCall();
           }
@@ -1628,7 +1691,7 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
             // In all other branches only if the client Still needs more data.
             _execState = ExecState::DONE;
             break;
-          } else if (clientCall.getLimit() > 0 && !_lastRange.hasDataRow()) {
+          } else if (clientCall.getLimit() > 0 && !lastRangeHasDataRow()) {
             TRI_ASSERT(_upstreamState != ExecutionState::DONE);
             // We need to request more
             _upstreamRequest = call;
@@ -1642,9 +1705,10 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
         case ExecState::FASTFORWARD: {
           LOG_QUERY("96e2c", DEBUG)
               << printTypeInfo() << " all produced, fast forward to end up (sub-)query.";
-          auto [state, stats, skippedLocal, call] =
+          auto [state, stats, skippedLocal, call, dependency] =
               executeFastForward(_lastRange, clientCall);
 
+          _requestedDependency = dependency;
           _skipped += skippedLocal;
           _engine->_stats += stats;
           localExecutorState = state;
@@ -1669,7 +1733,7 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
           // HASMORE even if it knew that upstream has no further rows.
           TRI_ASSERT(_upstreamState != ExecutionState::DONE);
           // We need to make sure _lastRange is all used
-          TRI_ASSERT(!_lastRange.hasDataRow());
+          TRI_ASSERT(!lastRangeHasDataRow());
           TRI_ASSERT(!_lastRange.hasShadowRow());
           size_t skippedLocal = 0;
 
@@ -1685,7 +1749,8 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
             stack.pushCall(std::move(callCopy));
           }
 
-          std::tie(_upstreamState, skippedLocal, _lastRange) = _rowFetcher.execute(stack);
+          std::tie(_upstreamState, skippedLocal, _lastRange) =
+              executeFetcher(stack, _requestedDependency);
 
           if constexpr (std::is_same_v<Executor, SubqueryStartExecutor>) {
             // Do not pop the call, we did not put it on.
@@ -1789,7 +1854,7 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
       TRI_ASSERT(skipped > 0 || (outputBlock != nullptr && outputBlock->numEntries() > 0));
       return {ExecutionState::HASMORE, skipped, std::move(outputBlock)};
     }
-    // We must return skipped and/or data when reporting HASMORE
+    // We must return skipped and/or data when reportingHASMORE
     TRI_ASSERT(_upstreamState != ExecutionState::HASMORE ||
                (skipped > 0 || (outputBlock != nullptr && outputBlock->numEntries() > 0)));
     return {_upstreamState, skipped, std::move(outputBlock)};
@@ -1855,6 +1920,12 @@ auto ExecutionBlockImpl<Executor>::outputIsFull() const noexcept -> bool {
          _outputItemRow->allRowsUsed();
 }
 
+// TODO: remove again
+template <class Executor>
+auto ExecutionBlockImpl<Executor>::lastRangeHasDataRow() const -> bool {
+  return _lastRange.hasDataRow();
+}
+
 template <>
 template <>
 RegisterId ExecutionBlockImpl<IdExecutor<SingleRowFetcher<BlockPassthrough::Enable>>>::getOutputRegisterId() const
diff --git a/arangod/Aql/ExecutionBlockImpl.h b/arangod/Aql/ExecutionBlockImpl.h
index 6e4e383a22ce..0d2d3da66d1e 100644
--- a/arangod/Aql/ExecutionBlockImpl.h
+++ b/arangod/Aql/ExecutionBlockImpl.h
@@ -233,12 +233,18 @@ class ExecutionBlockImpl final : public ExecutionBlock {
    */
   std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> executeWithoutTrace(AqlCallStack stack);
 
+  std::tuple<ExecutionState, size_t, typename Fetcher::DataRange> executeFetcher(
+      AqlCallStack& stack, size_t const dependency);
+
+  std::tuple<ExecutorState, typename Executor::Stats, AqlCall, size_t> executeProduceRows(
+      typename Fetcher::DataRange& input, OutputAqlItemRow& output);
+
   // execute a skipRowsRange call
-  std::tuple<ExecutorState, typename Executor::Stats, size_t, AqlCall> executeSkipRowsRange(
-      typename Fetcher::DataRange& inputRange, AqlCall& call);
+  auto executeSkipRowsRange(typename Fetcher::DataRange& inputRange, AqlCall& call)
+      -> std::tuple<ExecutorState, typename Executor::Stats, size_t, AqlCall, size_t>;
 
   auto executeFastForward(typename Fetcher::DataRange& inputRange, AqlCall& clientCall)
-      -> std::tuple<ExecutorState, typename Executor::Stats, size_t, AqlCall>;
+      -> std::tuple<ExecutorState, typename Executor::Stats, size_t, AqlCall, size_t>;
 
   /**
    * @brief Inner getSome() part, without the tracing calls.
@@ -297,6 +303,8 @@ class ExecutionBlockImpl final : public ExecutionBlock {
 
   [[nodiscard]] auto outputIsFull() const noexcept -> bool;
 
+  [[nodiscard]] auto lastRangeHasDataRow() const -> bool;
+
   void resetExecutor();
 
  private:
@@ -337,6 +345,8 @@ class ExecutionBlockImpl final : public ExecutionBlock {
 
   AqlCall _clientRequest;
 
+  size_t _requestedDependency;
+
   // Only used in passthrough variant.
   // We track if we have reference the range's block
   // into an output block.
diff --git a/arangod/Aql/MultiAqlItemBlockInputRange.cpp b/arangod/Aql/MultiAqlItemBlockInputRange.cpp
new file mode 100644
index 000000000000..8b5aad8595d7
--- /dev/null
+++ b/arangod/Aql/MultiAqlItemBlockInputRange.cpp
@@ -0,0 +1,141 @@
+////////////////////////////////////////////////////////////////////////////////
+/// DISCLAIMER
+///
+/// Copyright 2020 ArangoDB GmbH, Cologne, Germany
+///
+/// Licensed under the Apache License, Version 2.0 (the "License");
+/// you may not use this file except in compliance with the License.
+/// You may obtain a copy of the License at
+///
+///     http://www.apache.org/licenses/LICENSE-2.0
+///
+/// Unless required by applicable law or agreed to in writing, software
+/// distributed under the License is distributed on an "AS IS" BASIS,
+/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+/// See the License for the specific language governing permissions and
+/// limitations under the License.
+///
+/// Copyright holder is ArangoDB GmbH, Cologne, Germany
+///
+/// @author Markus Pfeiffer
+////////////////////////////////////////////////////////////////////////////////
+
+#include "MultiAqlItemBlockInputRange.h"
+#include "Aql/ShadowAqlItemRow.h"
+
+#include <velocypack/Builder.h>
+#include <velocypack/velocypack-aliases.h>
+#include <numeric>
+
+#include "Logger/LogMacros.h"
+
+using namespace arangodb;
+using namespace arangodb::aql;
+
+MultiAqlItemBlockInputRange::MultiAqlItemBlockInputRange(ExecutorState state,
+                                                         std::size_t skipped,
+                                                         std::size_t nrInputRanges) {
+  _inputs.resize(nrInputRanges, AqlItemBlockInputRange{state, skipped});
+}
+
+auto MultiAqlItemBlockInputRange::resizeIfNecessary(ExecutorState state, size_t skipped,
+                                                    size_t nrInputRanges) -> void {
+  // We never want to reduce the number of dependencies.
+  TRI_ASSERT(_inputs.size() <= nrInputRanges);
+  if (_inputs.size() < nrInputRanges) {
+    _inputs.resize(nrInputRanges, AqlItemBlockInputRange{state, skipped});
+  }
+}
+
+auto MultiAqlItemBlockInputRange::upstreamState(size_t const dependency) const
+    noexcept -> ExecutorState {
+  TRI_ASSERT(dependency < _inputs.size());
+  return _inputs.at(dependency).upstreamState();
+}
+
+auto MultiAqlItemBlockInputRange::hasDataRow(size_t const dependency) const noexcept -> bool {
+  TRI_ASSERT(dependency < _inputs.size());
+  return _inputs.at(dependency).hasDataRow();
+}
+
+auto MultiAqlItemBlockInputRange::hasDataRow() const noexcept -> bool {
+  return std::any_of(std::begin(_inputs), std::end(_inputs),
+                     [](AqlItemBlockInputRange const& i) -> bool {
+                       return i.hasDataRow();
+                     });
+}
+
+auto MultiAqlItemBlockInputRange::peekDataRow(size_t const dependency) const
+    -> std::pair<ExecutorState, arangodb::aql::InputAqlItemRow> {
+  TRI_ASSERT(dependency < _inputs.size());
+  return _inputs.at(dependency).peekDataRow();
+}
+
+auto MultiAqlItemBlockInputRange::nextDataRow(size_t const dependency)
+    -> std::pair<ExecutorState, arangodb::aql::InputAqlItemRow> {
+  TRI_ASSERT(dependency < _inputs.size());
+  return _inputs.at(dependency).nextDataRow();
+}
+
+// We have a shadow row, iff all our inputs have o
+auto MultiAqlItemBlockInputRange::hasShadowRow() const noexcept -> bool {
+  return std::all_of(std::begin(_inputs), std::end(_inputs),
+                     [](AqlItemBlockInputRange const& i) -> bool {
+                       return i.hasShadowRow();
+                     });
+}
+
+// TODO: * It doesn't matter which shadow row we peek, they should all be the same
+//       * assert that all dependencies are on a shadow row?
+auto MultiAqlItemBlockInputRange::peekShadowRow() const -> arangodb::aql::ShadowAqlItemRow {
+  TRI_ASSERT(!hasDataRow());
+
+  // TODO: Correct?
+  return _inputs.at(0).peekShadowRow();
+}
+
+auto MultiAqlItemBlockInputRange::nextShadowRow()
+    -> std::pair<ExecutorState, arangodb::aql::ShadowAqlItemRow> {
+  TRI_ASSERT(!hasDataRow());
+
+  // Need to consume all shadow rows simultaneously.
+  // TODO: Assert we're on the correct shadow row for all upstreams
+  auto state = ExecutorState::HASMORE;
+  auto shadowRow = ShadowAqlItemRow{CreateInvalidShadowRowHint()};
+
+  for (auto& i : _inputs) {
+    std::tie(state, shadowRow) = i.nextShadowRow();
+  }
+  return {state, shadowRow};
+}
+
+auto MultiAqlItemBlockInputRange::getBlock(size_t const dependency) const
+    noexcept -> SharedAqlItemBlockPtr {
+  TRI_ASSERT(dependency < _inputs.size());
+  return _inputs.at(dependency).getBlock();
+}
+
+auto MultiAqlItemBlockInputRange::setDependency(size_t const dependency,
+                                                AqlItemBlockInputRange& range) -> void {
+  TRI_ASSERT(dependency < _inputs.size());
+  _inputs.at(dependency) = range;
+}
+
+auto MultiAqlItemBlockInputRange::isDone() const -> bool {
+  auto res = std::all_of(std::begin(_inputs), std::end(_inputs),
+                         [](AqlItemBlockInputRange const& i) -> bool {
+                           return !i.hasDataRow() &&
+                                  i.upstreamState() == ExecutorState::DONE;
+                         });
+  return res;
+}
+
+size_t MultiAqlItemBlockInputRange::skipAllRemainingDataRows() {
+  for (size_t i = 0; i < _inputs.size(); i++) {
+    _inputs.at(i).skipAllRemainingDataRows();
+    if (_inputs.at(i).upstreamState() == ExecutorState::HASMORE) {
+      return i;
+    }
+  }
+  return 0;
+}
diff --git a/arangod/Aql/MultiAqlItemBlockInputRange.h b/arangod/Aql/MultiAqlItemBlockInputRange.h
new file mode 100644
index 000000000000..e23a65f5ad7a
--- /dev/null
+++ b/arangod/Aql/MultiAqlItemBlockInputRange.h
@@ -0,0 +1,78 @@
+////////////////////////////////////////////////////////////////////////////////
+/// DISCLAIMER
+///
+/// Copyright 2020 ArangoDB GmbH, Cologne, Germany
+///
+/// Licensed under the Apache License, Version 2.0 (the "License");
+/// you may not use this file except in compliance with the License.
+/// You may obtain a copy of the License at
+///
+///     http://www.apache.org/licenses/LICENSE-2.0
+///
+/// Unless required by applicable law or agreed to in writing, software
+/// distributed under the License is distributed on an "AS IS" BASIS,
+/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+/// See the License for the specific language governing permissions and
+/// limitations under the License.
+///
+/// Copyright holder is ArangoDB GmbH, Cologne, Germany
+///
+/// @author Markus Pfeiffer
+////////////////////////////////////////////////////////////////////////////////
+
+#ifndef ARANGOD_AQL_MULTIAQLITEMBLOCKINPUTRANGE_H
+#define ARANGOD_AQL_MULTIAQLITEMBLOCKINPUTRANGE_H
+
+#include "Aql/AqlItemBlockInputRange.h"
+#include "Aql/ExecutionState.h"
+#include "Aql/InputAqlItemRow.h"
+#include "Aql/SharedAqlItemBlockPtr.h"
+
+namespace arangodb::aql {
+
+class MultiAqlItemBlockInputRange {
+ public:
+  explicit MultiAqlItemBlockInputRange(ExecutorState state, std::size_t skipped = 0,
+                                       std::size_t nrInputRanges = 1);
+
+  MultiAqlItemBlockInputRange(ExecutorState, std::size_t skipped,
+                              arangodb::aql::SharedAqlItemBlockPtr const&,
+                              std::size_t startIndex);
+
+  MultiAqlItemBlockInputRange(ExecutorState, std::size_t skipped,
+                              arangodb::aql::SharedAqlItemBlockPtr&&,
+                              std::size_t startIndex) noexcept;
+
+  ExecutorState upstreamState(size_t const dependency) const noexcept;
+  bool upstreamHasMore(size_t const dependency) const noexcept;
+
+  bool hasDataRow() const noexcept;
+  bool hasDataRow(size_t const dependency) const noexcept;
+
+  std::pair<ExecutorState, arangodb::aql::InputAqlItemRow> peekDataRow(size_t const dependency) const;
+  std::pair<ExecutorState, arangodb::aql::InputAqlItemRow> nextDataRow(size_t const dependency);
+
+  bool hasShadowRow() const noexcept;
+
+  arangodb::aql::ShadowAqlItemRow peekShadowRow() const;
+  std::pair<ExecutorState, arangodb::aql::ShadowAqlItemRow> nextShadowRow();
+
+  auto isDone() const -> bool;
+
+  auto resizeIfNecessary(ExecutorState state, size_t skipped, size_t nrInputRanges) -> void;
+
+  auto getBlock(size_t const dependency = 0) const noexcept -> SharedAqlItemBlockPtr;
+
+  auto setDependency(size_t const dependency, AqlItemBlockInputRange& range) -> void;
+
+  size_t skipAllRemainingDataRows();
+
+ private:
+  ExecutorState _finalState{ExecutorState::HASMORE};
+
+  std::vector<AqlItemBlockInputRange> _inputs;
+};
+
+}  // namespace arangodb::aql
+
+#endif
diff --git a/arangod/Aql/MultiDependencySingleRowFetcher.cpp b/arangod/Aql/MultiDependencySingleRowFetcher.cpp
index de7f043db13b..517542e953e1 100644
--- a/arangod/Aql/MultiDependencySingleRowFetcher.cpp
+++ b/arangod/Aql/MultiDependencySingleRowFetcher.cpp
@@ -169,6 +169,10 @@ void MultiDependencySingleRowFetcher::initDependencies() {
   for (size_t i = 0; i < _dependencyProxy->numberDependencies(); ++i) {
     _dependencyInfos.emplace_back(DependencyInfo{});
   }
+  _dependencyStates.reserve(_dependencyProxy->numberDependencies());
+  for (size_t i = 0; i < _dependencyProxy->numberDependencies(); ++i) {
+    _dependencyStates.emplace_back(ExecutionState::HASMORE);
+  }
 }
 
 size_t MultiDependencySingleRowFetcher::numberDependencies() {
@@ -359,4 +363,39 @@ bool MultiDependencySingleRowFetcher::fetchBlockIfNecessary(size_t const depende
 //@deprecated
 auto MultiDependencySingleRowFetcher::useStack(AqlCallStack const& stack) -> void {
   _dependencyProxy->useStack(stack);
-}
\ No newline at end of file
+}
+
+auto MultiDependencySingleRowFetcher::executeForDependency(size_t const dependency,
+                                                           AqlCallStack& stack)
+    -> std::tuple<ExecutionState, size_t, AqlItemBlockInputRange> {
+  auto [state, skipped, block] = _dependencyProxy->executeForDependency(dependency, stack);
+
+  if (state == ExecutionState::WAITING) {
+    return {state, 0, AqlItemBlockInputRange{ExecutorState::HASMORE}};
+  }
+
+  _dependencyStates.at(dependency) = state;
+  if (std::any_of(std::begin(_dependencyStates), std::end(_dependencyStates),
+                  [](ExecutionState const s) {
+                    return s == ExecutionState::HASMORE;
+                  })) {
+    state = ExecutionState::HASMORE;
+  } else {
+    state = ExecutionState::DONE;
+  }
+  if (block == nullptr) {
+    if (state == ExecutionState::HASMORE) {
+      return {state, skipped, AqlItemBlockInputRange{ExecutorState::HASMORE, skipped}};
+    }
+    return {state, skipped, AqlItemBlockInputRange{ExecutorState::DONE, skipped}};
+  }
+
+  auto [start, end] = block->getRelevantRange();
+  if (state == ExecutionState::HASMORE) {
+    TRI_ASSERT(block != nullptr);
+    return {state, skipped,
+            AqlItemBlockInputRange{ExecutorState::DONE, skipped, block, start}};
+  }
+  return {state, skipped,
+          AqlItemBlockInputRange{ExecutorState::DONE, skipped, block, start}};
+}
diff --git a/arangod/Aql/MultiDependencySingleRowFetcher.h b/arangod/Aql/MultiDependencySingleRowFetcher.h
index fd17efc44f6d..a2c2ebdd911e 100644
--- a/arangod/Aql/MultiDependencySingleRowFetcher.h
+++ b/arangod/Aql/MultiDependencySingleRowFetcher.h
@@ -23,10 +23,10 @@
 #ifndef ARANGOD_AQL_MULTI_DEPENDENCY_SINGLE_ROW_FETCHER_H
 #define ARANGOD_AQL_MULTI_DEPENDENCY_SINGLE_ROW_FETCHER_H
 
-#include "Aql/AqlItemBlockInputRange.h"
 #include "Aql/ExecutionBlock.h"
 #include "Aql/ExecutionState.h"
 #include "Aql/InputAqlItemRow.h"
+#include "Aql/MultiAqlItemBlockInputRange.h"
 #include "Basics/Exceptions.h"
 #include "Basics/voc-errors.h"
 
@@ -85,7 +85,7 @@ class MultiDependencySingleRowFetcher {
   };
 
  public:
-  using DataRange = AqlItemBlockInputRange;
+  using DataRange = MultiAqlItemBlockInputRange;
   explicit MultiDependencySingleRowFetcher(DependencyProxy<BlockPassthrough::Disable>& executionBlock);
   TEST_VIRTUAL ~MultiDependencySingleRowFetcher() = default;
 
@@ -134,6 +134,9 @@ class MultiDependencySingleRowFetcher {
   //@deprecated
   auto useStack(AqlCallStack const& stack) -> void;
 
+  auto executeForDependency(size_t const dependency, AqlCallStack& stack)
+      -> std::tuple<ExecutionState, size_t, AqlItemBlockInputRange>;
+
  private:
   DependencyProxy<BlockPassthrough::Disable>* _dependencyProxy;
 
@@ -141,6 +144,7 @@ class MultiDependencySingleRowFetcher {
    * @brief Holds the information for all dependencies
    */
   std::vector<DependencyInfo> _dependencyInfos;
+  std::vector<ExecutionState> _dependencyStates;
 
  private:
   /**
diff --git a/arangod/Aql/UnsortedGatherExecutor.cpp b/arangod/Aql/UnsortedGatherExecutor.cpp
index a186fe36e732..e1b3221a640f 100644
--- a/arangod/Aql/UnsortedGatherExecutor.cpp
+++ b/arangod/Aql/UnsortedGatherExecutor.cpp
@@ -23,19 +23,90 @@
 #include "UnsortedGatherExecutor.h"
 
 #include "Aql/IdExecutor.h"  // for IdExecutorInfos
+#include "Aql/MultiAqlItemBlockInputRange.h"
 #include "Aql/MultiDependencySingleRowFetcher.h"
 #include "Aql/OutputAqlItemRow.h"
 #include "Aql/Stats.h"
 #include "Basics/debugging.h"
 
+#include "Logger/LogMacros.h"
+
 using namespace arangodb;
 using namespace arangodb::aql;
 
+struct Dependency {
+  Dependency() : _number{0} {};
+
+  size_t _number;
+};
+
 UnsortedGatherExecutor::UnsortedGatherExecutor(Fetcher& fetcher, Infos& infos)
     : _fetcher(fetcher) {}
 
 UnsortedGatherExecutor::~UnsortedGatherExecutor() = default;
 
+auto UnsortedGatherExecutor::produceRows(typename Fetcher::DataRange& input,
+                                         OutputAqlItemRow& output)
+    -> std::tuple<ExecutorState, Stats, AqlCall, size_t> {
+  while (!output.isFull() && !done()) {
+    if (input.hasDataRow(currentDependency())) {
+      auto [state, inputRow] = input.nextDataRow(currentDependency());
+      output.copyRow(inputRow);
+      TRI_ASSERT(output.produced());
+      output.advanceRow();
+
+      if (state == ExecutorState::DONE) {
+        advanceDependency();
+      }
+    } else {
+      if (input.upstreamState(currentDependency()) == ExecutorState::DONE) {
+        advanceDependency();
+      } else {
+        return {input.upstreamState(currentDependency()), Stats{}, AqlCall{},
+                currentDependency()};
+      }
+    }
+  }
+
+  while (!done() && input.upstreamState(currentDependency()) == ExecutorState::DONE) {
+    advanceDependency();
+  }
+
+  if (done()) {
+    // here currentDependency is invalid which will cause things to crash
+    // if we ask upstream in ExecutionBlockImpl. yolo.
+    TRI_ASSERT(!input.hasDataRow());
+    return {ExecutorState::DONE, Stats{}, AqlCall{}, currentDependency()};
+  } else {
+    return {input.upstreamState(currentDependency()), Stats{}, AqlCall{},
+            currentDependency()};
+  }
+}
+
+auto UnsortedGatherExecutor::skipRowsRange(typename Fetcher::DataRange& input, AqlCall& call)
+    -> std::tuple<ExecutorState, Stats, size_t, AqlCall, size_t> {
+  auto skipped = size_t{0};
+  while (call.needSkipMore() && input.hasDataRow(currentDependency())) {
+    auto [state, inputRow] = input.nextDataRow(currentDependency());
+
+    call.didSkip(1);
+    skipped++;
+
+    if (state == ExecutorState::DONE) {
+      advanceDependency();
+    }
+  }
+
+  if (done()) {
+    // here currentDependency is invalid which will cause things to crash
+    // if we ask upstream in ExecutionBlockImpl. yolo.
+    return {ExecutorState::DONE, Stats{}, skipped, AqlCall{}, currentDependency()};
+  } else {
+    return {input.upstreamState(currentDependency()), Stats{}, skipped,
+            AqlCall{}, currentDependency()};
+  }
+}
+
 auto UnsortedGatherExecutor::produceRows(OutputAqlItemRow& output)
     -> std::pair<ExecutionState, Stats> {
   while (!output.isFull() && !done()) {
diff --git a/arangod/Aql/UnsortedGatherExecutor.h b/arangod/Aql/UnsortedGatherExecutor.h
index 4896e9a166cc..5dc6d5c8afe8 100644
--- a/arangod/Aql/UnsortedGatherExecutor.h
+++ b/arangod/Aql/UnsortedGatherExecutor.h
@@ -38,17 +38,18 @@ class InputAqlItemRow;
 class OutputAqlItemRow;
 class IdExecutorInfos;
 class SharedAqlItemBlockPtr;
+struct AqlCall;
 
 /**
-* @brief Produces all rows from its dependencies, which may be more than one,
-* in some unspecified order. It is, purposefully, strictly synchronous, and
-* always waits for an answer before requesting the next row(s). This is as
-* opposed to the ParallelUnsortedGather, which already starts fetching the next
-* dependenci(es) while waiting for an answer.
-*
-* The actual implementation fetches all available rows from the first
-* dependency, then from the second, and so forth. But that is not guaranteed.
-*/
+ * @brief Produces all rows from its dependencies, which may be more than one,
+ * in some unspecified order. It is, purposefully, strictly synchronous, and
+ * always waits for an answer before requesting the next row(s). This is as
+ * opposed to the ParallelUnsortedGather, which already starts fetching the next
+ * dependenci(es) while waiting for an answer.
+ *
+ * The actual implementation fetches all available rows from the first
+ * dependency, then from the second, and so forth. But that is not guaranteed.
+ */
 class UnsortedGatherExecutor {
  public:
   struct Properties {
@@ -82,6 +83,12 @@ class UnsortedGatherExecutor {
 
   [[nodiscard]] auto skipRows(size_t atMost) -> std::tuple<ExecutionState, NoStats, size_t>;
 
+  // TODO: This should really be the DataRange of the fetcher?
+  [[nodiscard]] auto produceRows(typename Fetcher::DataRange& input, OutputAqlItemRow& output)
+      -> std::tuple<ExecutorState, Stats, AqlCall, size_t>;
+  [[nodiscard]] auto skipRowsRange(typename Fetcher::DataRange& input, AqlCall& call)
+      -> std::tuple<ExecutorState, Stats, size_t, AqlCall, size_t>;
+
  private:
   [[nodiscard]] auto numDependencies() const
       noexcept(noexcept(static_cast<Fetcher*>(nullptr)->numberDependencies())) -> size_t;
diff --git a/arangod/CMakeLists.txt b/arangod/CMakeLists.txt
index ba2250d221ec..785416e6a60a 100644
--- a/arangod/CMakeLists.txt
+++ b/arangod/CMakeLists.txt
@@ -306,6 +306,7 @@ set(LIB_ARANGO_AQL_SOURCES
   Aql/ModificationExecutorInfos.cpp
   Aql/ModificationNodes.cpp
   Aql/ModificationOptions.cpp
+  Aql/MultiAqlItemBlockInputRange.cpp
   Aql/MultiDependencySingleRowFetcher.cpp
   Aql/NoResultsExecutor.cpp
   Aql/NodeFinder.cpp

From 3ae0061587cfd71d324874e6a14aa300c7583cbd Mon Sep 17 00:00:00 2001
From: Markus Pfeiffer <markuspf@users.noreply.github.com>
Date: Sat, 29 Feb 2020 07:16:21 +0000
Subject: [PATCH 086/122] Move ModificationExecutors to new interface (#11165)

* Move ModificationExecutors to new interface

* added inputRange method to inputMatrix class, added switch between
DataRange Input <-> Matrix for ModificationExecutors

* forgot to enable allrows modification executor in fastForwardType

*  removed obsolete comment

*  removed obsolete comment

Co-authored-by: Heiko <hkernbach@users.noreply.github.com>
Co-authored-by: Michael Hackstein <michael@arangodb.com>
---
 arangod/Aql/AqlItemBlockInputMatrix.cpp |  31 +++++++
 arangod/Aql/AqlItemBlockInputMatrix.h   |  12 +++
 arangod/Aql/ExecutionBlockImpl.cpp      |  37 ++++++--
 arangod/Aql/ModificationExecutor.cpp    | 111 +++++++++++++++---------
 arangod/Aql/ModificationExecutor.h      |  18 +++-
 5 files changed, 158 insertions(+), 51 deletions(-)

diff --git a/arangod/Aql/AqlItemBlockInputMatrix.cpp b/arangod/Aql/AqlItemBlockInputMatrix.cpp
index 956b98467c51..bbd495784e27 100644
--- a/arangod/Aql/AqlItemBlockInputMatrix.cpp
+++ b/arangod/Aql/AqlItemBlockInputMatrix.cpp
@@ -54,6 +54,20 @@ AqlItemBlockInputMatrix::AqlItemBlockInputMatrix(ExecutorState state, AqlItemMat
   }
 }
 
+AqlItemBlockInputRange AqlItemBlockInputMatrix::getNextInputRange() {
+  TRI_ASSERT(_aqlItemMatrix != nullptr);
+
+  if (_aqlItemMatrix->numberOfBlocks() == 0) {
+    return AqlItemBlockInputRange{upstreamState()};
+  }
+
+  SharedAqlItemBlockPtr blockPtr = _aqlItemMatrix->getBlock(_currentBlockRowIndex);
+  auto [start, end] = blockPtr->getRelevantRange();
+  ExecutorState state = incrBlockIndex();
+
+  return {state, 0, std::move(blockPtr), start};
+}
+
 SharedAqlItemBlockPtr AqlItemBlockInputMatrix::getBlock() const noexcept {
   TRI_ASSERT(_aqlItemMatrix == nullptr);
   return _block;
@@ -94,6 +108,7 @@ std::pair<ExecutorState, ShadowAqlItemRow> AqlItemBlockInputMatrix::nextShadowRo
       !_aqlItemMatrix->peekShadowRow().isRelevant()) {
     // next row will be a shadow row
     _shadowRow = _aqlItemMatrix->popShadowRow();
+    resetBlockIndex();
   } else {
     _shadowRow = ShadowAqlItemRow{CreateInvalidShadowRowHint()};
   }
@@ -136,8 +151,24 @@ size_t AqlItemBlockInputMatrix::skipAllRemainingDataRows() {
       TRI_ASSERT(_finalState == ExecutorState::DONE);
       _aqlItemMatrix->clear();
     }
+    resetBlockIndex();
   }
   // Else we did already skip once.
   // nothing to do
   return 0;
 }
+
+ExecutorState AqlItemBlockInputMatrix::incrBlockIndex() {
+  TRI_ASSERT(_aqlItemMatrix != nullptr);
+  if (_currentBlockRowIndex + 1 < _aqlItemMatrix->numberOfBlocks()) {
+    _currentBlockRowIndex++;
+    // we were able to increase the size as we reached not the end yet
+    return ExecutorState::HASMORE;
+  }
+  // we could not increase the index, we already reached the end
+  return ExecutorState::DONE;
+}
+
+void AqlItemBlockInputMatrix::resetBlockIndex() noexcept {
+  _currentBlockRowIndex = 0;
+}
diff --git a/arangod/Aql/AqlItemBlockInputMatrix.h b/arangod/Aql/AqlItemBlockInputMatrix.h
index 80e37e40e1f9..6e638aa2dbb6 100644
--- a/arangod/Aql/AqlItemBlockInputMatrix.h
+++ b/arangod/Aql/AqlItemBlockInputMatrix.h
@@ -23,6 +23,7 @@
 #ifndef ARANGOD_AQL_AQLITEMBLOCKMATRIXITERATOR_H
 #define ARANGOD_AQL_AQLITEMBLOCKMATRIXITERATOR_H
 
+#include "Aql/AqlItemBlockInputRange.h"
 #include "Aql/AqlItemMatrix.h"
 #include "Aql/ExecutionState.h"
 #include "Aql/InputAqlItemRow.h"
@@ -46,12 +47,22 @@ class AqlItemBlockInputMatrix {
   bool hasDataRow() const noexcept;
 
   arangodb::aql::SharedAqlItemBlockPtr getBlock() const noexcept;
+
+  // Will provide access to the first block (from _aqlItemMatrix)
+  // After a block has been delivered, the block index will be increased.
+  // Next call then will deliver the next block etc.
+  AqlItemBlockInputRange getNextInputRange();
   std::pair<ExecutorState, AqlItemMatrix const*> getMatrix() noexcept;
 
   ExecutorState upstreamState() const noexcept;
   bool upstreamHasMore() const noexcept;
   size_t skipAllRemainingDataRows();
 
+  // Will return HASMORE if we were able to increase the row index.
+  // Otherwise will return DONE.
+  ExecutorState incrBlockIndex();
+  void resetBlockIndex() noexcept;
+
  private:
   arangodb::aql::SharedAqlItemBlockPtr _block{nullptr};
   ExecutorState _finalState{ExecutorState::HASMORE};
@@ -59,6 +70,7 @@ class AqlItemBlockInputMatrix {
   // Only if _aqlItemMatrix is set (and NOT a nullptr), we have a valid and
   // usable DataRange object available to work with.
   AqlItemMatrix* _aqlItemMatrix;
+  size_t _currentBlockRowIndex = 0;
   ShadowAqlItemRow _shadowRow{CreateInvalidShadowRowHint{}};
 };
 
diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index 54bc29742555..d27ce8534525 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -144,9 +144,16 @@ constexpr bool isNewStyleExecutor = is_one_of_v<
     TestLambdaExecutor,
     TestLambdaSkipExecutor,  // we need one after these to avoid compile errors in non-test mode
 #endif
-    UnsortedGatherExecutor, SubqueryStartExecutor, SubqueryEndExecutor, TraversalExecutor,
-    KShortestPathsExecutor, ShortestPathExecutor, EnumerateListExecutor, LimitExecutor, SortExecutor,
-    IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::NotMaterialize>,
+    ModificationExecutor<AllRowsFetcher, InsertModifier>,
+    ModificationExecutor<SingleRowFetcher<BlockPassthrough::Disable>, InsertModifier>,
+    ModificationExecutor<AllRowsFetcher, RemoveModifier>,
+    ModificationExecutor<SingleRowFetcher<BlockPassthrough::Disable>, RemoveModifier>,
+    ModificationExecutor<AllRowsFetcher, UpdateReplaceModifier>,
+    ModificationExecutor<SingleRowFetcher<BlockPassthrough::Disable>, UpdateReplaceModifier>,
+    ModificationExecutor<AllRowsFetcher, UpsertModifier>,
+    ModificationExecutor<SingleRowFetcher<BlockPassthrough::Disable>, UpsertModifier>, SubqueryStartExecutor,
+    UnsortedGatherExecutor, SubqueryEndExecutor, TraversalExecutor, KShortestPathsExecutor, ShortestPathExecutor, EnumerateListExecutor,
+    LimitExecutor, SortExecutor, IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::NotMaterialize>,
     IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::LateMaterialize>,
     IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::Materialize>,
     IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::NotMaterialize | arangodb::iresearch::MaterializeType::UseStoredValues>,
@@ -1120,9 +1127,16 @@ static SkipRowsRangeVariant constexpr skipRowsType() {
 #ifdef ARANGODB_USE_GOOGLE_TESTS
               TestLambdaSkipExecutor,
 #endif
-              UnsortedGatherExecutor, TraversalExecutor, EnumerateListExecutor, SubqueryStartExecutor,
-              SubqueryEndExecutor, SortedCollectExecutor, LimitExecutor, SortExecutor,
-              IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::NotMaterialize>,
+              ModificationExecutor<AllRowsFetcher, InsertModifier>,
+              ModificationExecutor<SingleRowFetcher<BlockPassthrough::Disable>, InsertModifier>,
+              ModificationExecutor<AllRowsFetcher, RemoveModifier>,
+              ModificationExecutor<SingleRowFetcher<BlockPassthrough::Disable>, RemoveModifier>,
+              ModificationExecutor<AllRowsFetcher, UpdateReplaceModifier>,
+              ModificationExecutor<SingleRowFetcher<BlockPassthrough::Disable>, UpdateReplaceModifier>,
+              ModificationExecutor<AllRowsFetcher, UpsertModifier>,
+              ModificationExecutor<SingleRowFetcher<BlockPassthrough::Disable>, UpsertModifier>, TraversalExecutor,
+              EnumerateListExecutor, SubqueryStartExecutor, SubqueryEndExecutor, SortedCollectExecutor, LimitExecutor,
+              UnsortedGatherExecutor, SortExecutor, IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::NotMaterialize>,
               IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::LateMaterialize>,
               IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::Materialize>,
               IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::NotMaterialize | arangodb::iresearch::MaterializeType::UseStoredValues>,
@@ -1187,7 +1201,15 @@ static auto fastForwardType(AqlCall const& call, Executor const& e) -> FastForwa
   }
   // TODO: We only need to do this is the executor actually require to call.
   // e.g. Modifications will always need to be called. Limit only if it needs to report fullCount
-  if constexpr (is_one_of_v<Executor, LimitExecutor>) {
+  if constexpr (is_one_of_v<Executor, LimitExecutor,
+                            ModificationExecutor<AllRowsFetcher, InsertModifier>,
+                            ModificationExecutor<SingleRowFetcher<BlockPassthrough::Disable>, InsertModifier>,
+                            ModificationExecutor<AllRowsFetcher, RemoveModifier>,
+                            ModificationExecutor<SingleRowFetcher<BlockPassthrough::Disable>, RemoveModifier>,
+                            ModificationExecutor<AllRowsFetcher, UpdateReplaceModifier>,
+                            ModificationExecutor<SingleRowFetcher<BlockPassthrough::Disable>, UpdateReplaceModifier>,
+                            ModificationExecutor<AllRowsFetcher, UpsertModifier>,
+                            ModificationExecutor<SingleRowFetcher<BlockPassthrough::Disable>, UpsertModifier>>) {
     return FastForwardVariant::EXECUTOR;
   }
   return FastForwardVariant::FETCHER;
@@ -1441,6 +1463,7 @@ auto ExecutionBlockImpl<Executor>::executeFastForward(typename Fetcher::DataRang
     return {ExecutorState::DONE, NoStats{}, 0, AqlCall{}, 0};
   }
   auto type = fastForwardType(clientCall, _executor);
+
   switch (type) {
     case FastForwardVariant::FULLCOUNT:
     case FastForwardVariant::EXECUTOR: {
diff --git a/arangod/Aql/ModificationExecutor.cpp b/arangod/Aql/ModificationExecutor.cpp
index 76c8f1aac60b..5556ae39b93d 100644
--- a/arangod/Aql/ModificationExecutor.cpp
+++ b/arangod/Aql/ModificationExecutor.cpp
@@ -101,29 +101,23 @@ ModificationExecutor<FetcherType, ModifierType>::ModificationExecutor(Fetcher& f
 // Fetches as many rows as possible from upstream using the fetcher's fetchRow
 // method and accumulates results through the modifier
 template <typename FetcherType, typename ModifierType>
-std::pair<ExecutionState, typename ModificationExecutor<FetcherType, ModifierType>::Stats>
-ModificationExecutor<FetcherType, ModifierType>::doCollect(size_t maxOutputs) {
+auto ModificationExecutor<FetcherType, ModifierType>::doCollect(AqlItemBlockInputRange& input,
+                                                                size_t maxOutputs)
+    -> void {
   // for fetchRow
   InputAqlItemRow row{CreateInvalidInputRowHint{}};
   ExecutionState state = ExecutionState::HASMORE;
 
   // Maximum number of rows we can put into output
   // So we only ever produce this many here
-  // TODO: If we SKIP_IGNORE, then we'd be able to output more;
-  //       this would require some counting to happen in the modifier
-  while (_modifier.nrOfOperations() < maxOutputs && state != ExecutionState::DONE) {
-    std::tie(state, row) = _fetcher.fetchRow(maxOutputs);
-    if (state == ExecutionState::WAITING) {
-      return {ExecutionState::WAITING, ModificationStats{}};
-    }
-    if (row.isInitialized()) {
-      // Make sure we have a valid row
-      TRI_ASSERT(row.isInitialized());
-      _modifier.accumulate(row);
-    }
+  while (_modifier.nrOfOperations() < maxOutputs && input.hasDataRow()) {
+    auto [state, row] = input.nextDataRow();
+
+    // Make sure we have a valid row
+    TRI_ASSERT(row.isInitialized());
+    _modifier.accumulate(row);
   }
   TRI_ASSERT(state == ExecutionState::DONE || state == ExecutionState::HASMORE);
-  return {state, ModificationStats{}};
 }
 
 // Outputs accumulated results, and counts the statistics
@@ -131,7 +125,10 @@ template <typename FetcherType, typename ModifierType>
 void ModificationExecutor<FetcherType, ModifierType>::doOutput(OutputAqlItemRow& output,
                                                                Stats& stats) {
   typename ModifierType::OutputIterator modifierOutputIterator(_modifier);
+  // We only accumulated as many items as we can output, so this
+  // should be correct
   for (auto const& modifierOutput : modifierOutputIterator) {
+    TRI_ASSERT(!output.isFull());
     bool written = false;
     switch (modifierOutput.getType()) {
       case ModifierOutput::Type::ReturnIfRequired:
@@ -157,53 +154,81 @@ void ModificationExecutor<FetcherType, ModifierType>::doOutput(OutputAqlItemRow&
         break;
     }
   }
-
-  if (_infos._doCount) {
-    stats.addWritesExecuted(_modifier.nrOfWritesExecuted());
-    stats.addWritesIgnored(_modifier.nrOfWritesIgnored());
-  }
 }
 
 template <typename FetcherType, typename ModifierType>
 std::pair<ExecutionState, typename ModificationExecutor<FetcherType, ModifierType>::Stats>
 ModificationExecutor<FetcherType, ModifierType>::produceRows(OutputAqlItemRow& output) {
+  TRI_ASSERT(false);
+
+  return {ExecutionState::DONE, ModificationStats{}};
+}
+
+template <typename FetcherType, typename ModifierType>
+[[nodiscard]] auto ModificationExecutor<FetcherType, ModifierType>::produceRows(
+    typename FetcherType::DataRange& input, OutputAqlItemRow& output)
+    -> std::tuple<ExecutorState, ModificationStats, AqlCall> {
   TRI_ASSERT(_infos._trx);
 
-  ModificationExecutor::Stats stats;
+  auto stats = ModificationStats{};
 
-  const size_t maxOutputs = std::min(output.numRowsLeft(), _modifier.getBatchSize());
+  _modifier.reset();
 
-  // if we returned "WAITING" the last time we still have
-  // documents in the accumulator that we have not submitted
-  // yet
-  if (_lastState != ExecutionState::WAITING) {
-    _modifier.reset();
+  ExecutorState upstreamState = ExecutorState::HASMORE;
+  // only produce at most output.numRowsLeft() many results
+  if constexpr (std::is_same_v<typename FetcherType::DataRange, AqlItemBlockInputMatrix>) {
+    auto range = input.getNextInputRange();
+    doCollect(range, output.numRowsLeft());
+    upstreamState = range.upstreamState();
+  } else {
+    doCollect(input, output.numRowsLeft());
+    upstreamState = input.upstreamState();
   }
 
-  TRI_IF_FAILURE("ModificationBlock::getSome") {
-    THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
-  }
+  if (_modifier.nrOfOperations() > 0) {
+    _modifier.transact();
 
-  std::tie(_lastState, stats) = doCollect(maxOutputs);
+    if (_infos._doCount) {
+      stats.addWritesExecuted(_modifier.nrOfWritesExecuted());
+      stats.addWritesIgnored(_modifier.nrOfWritesIgnored());
+    }
 
-  if (_lastState == ExecutionState::WAITING) {
-    return {ExecutionState::WAITING, std::move(stats)};
+    doOutput(output, stats);
   }
 
-  TRI_ASSERT(_lastState == ExecutionState::DONE || _lastState == ExecutionState::HASMORE);
+  return {upstreamState, stats, AqlCall{}};
+}
 
-  _modifier.transact();
+template <typename FetcherType, typename ModifierType>
+[[nodiscard]] auto ModificationExecutor<FetcherType, ModifierType>::skipRowsRange(
+    typename FetcherType::DataRange& input, AqlCall& call)
+    -> std::tuple<ExecutorState, Stats, size_t, AqlCall> {
+  auto stats = ModificationStats{};
+  _modifier.reset();
+
+  ExecutorState upstreamState = ExecutorState::HASMORE;
+  // only produce at most output.numRowsLeft() many results
+  if constexpr (std::is_same_v<typename FetcherType::DataRange, AqlItemBlockInputMatrix>) {
+    auto range = input.getNextInputRange();
+    doCollect(range, call.getOffset());
+    upstreamState = range.upstreamState();
+  } else {
+    doCollect(input, call.getOffset());
+    upstreamState = input.upstreamState();
+  }
+
+  if (_modifier.nrOfOperations() > 0) {
+    _modifier.transact();
 
-  // If the query is silent, there is no way to relate
-  // the results slice contents and the submitted documents
-  // If the query is *not* silent, we should get one result
-  // for every document.
-  // Yes. Really.
-  TRI_ASSERT(_infos._options.silent || _modifier.nrOfDocuments() == _modifier.nrOfResults());
+    if (_infos._doCount) {
+      stats.addWritesExecuted(_modifier.nrOfWritesExecuted());
+      stats.addWritesIgnored(_modifier.nrOfWritesIgnored());
+    }
 
-  doOutput(output, stats);
+    call.didSkip(_modifier.nrOfOperations());
+  }
 
-  return {_lastState, std::move(stats)};
+  return {upstreamState, stats, _modifier.nrOfOperations(), AqlCall{}};
 }
 
 using NoPassthroughSingleRowFetcher = SingleRowFetcher<BlockPassthrough::Disable>;
diff --git a/arangod/Aql/ModificationExecutor.h b/arangod/Aql/ModificationExecutor.h
index eeaeb5f298cb..deec6db66e29 100644
--- a/arangod/Aql/ModificationExecutor.h
+++ b/arangod/Aql/ModificationExecutor.h
@@ -39,6 +39,16 @@
 
 namespace arangodb {
 namespace aql {
+
+struct AqlCall;
+class AqlItemBlockInputRange;
+class InputAqlItemRow;
+class OutputAqlItemRow;
+class ExecutorInfos;
+class FilterStats;
+template <BlockPassthrough>
+class SingleRowFetcher;
+
 //
 // ModificationExecutor is the "base" class for the Insert, Remove,
 // UpdateReplace and Upsert executors.
@@ -163,8 +173,14 @@ class ModificationExecutor {
 
   std::pair<ExecutionState, Stats> produceRows(OutputAqlItemRow& output);
 
+  [[nodiscard]] auto produceRows(typename FetcherType::DataRange& input, OutputAqlItemRow& output)
+      -> std::tuple<ExecutorState, Stats, AqlCall>;
+
+  [[nodiscard]] auto skipRowsRange(typename FetcherType::DataRange& inputRange, AqlCall& call)
+      -> std::tuple<ExecutorState, Stats, size_t, AqlCall>;
+
  protected:
-  std::pair<ExecutionState, Stats> doCollect(size_t maxOutputs);
+  void doCollect(AqlItemBlockInputRange& input, size_t maxOutputs);
   void doOutput(OutputAqlItemRow& output, Stats& stats);
 
   // The state that was returned on the last call to produceRows. For us

From d4e729949f9b10637ccde37f89c79c5043f8c12e Mon Sep 17 00:00:00 2001
From: Heiko <hkernbach@users.noreply.github.com>
Date: Sat, 29 Feb 2020 08:18:17 +0100
Subject: [PATCH 087/122] Feature/aql subquery operations stack materialize
 executor (#11192)

* removed obsolete comment, added produceRows and skipRowsRange, enabled
MaterializeExecutor as newStyleExecutor

* forgot to use advanceRow, fetch input during skipRowsRange

* removed old implementations

* removed comment, fixed a logical loop error

* skip could be simplified as well

* temp workaround

Co-authored-by: Michael Hackstein <michael@arangodb.com>
---
 arangod/Aql/ExecutionBlockImpl.cpp  |   6 +-
 arangod/Aql/FilterExecutor.cpp      |   1 -
 arangod/Aql/MaterializeExecutor.cpp | 167 ++++++++++++++++------------
 arangod/Aql/MaterializeExecutor.h   |  47 +++++---
 arangod/Aql/RemoteExecutor.cpp      |  23 +++-
 5 files changed, 151 insertions(+), 93 deletions(-)

diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index d27ce8534525..b13336abfc27 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -177,7 +177,8 @@ constexpr bool isNewStyleExecutor = is_one_of_v<
     NoResultsExecutor, ShortestPathExecutor, EnumerateListExecutor, LimitExecutor,
     SingleRemoteModificationExecutor<IndexTag>, SingleRemoteModificationExecutor<Insert>,
     SingleRemoteModificationExecutor<Remove>, SingleRemoteModificationExecutor<Update>,
-    SingleRemoteModificationExecutor<Replace>, SingleRemoteModificationExecutor<Upsert>>;
+    SingleRemoteModificationExecutor<Replace>, SingleRemoteModificationExecutor<Upsert>,
+    MaterializeExecutor<RegisterId>, MaterializeExecutor<std::string const&>>;
 
 template <class Executor>
 ExecutionBlockImpl<Executor>::ExecutionBlockImpl(ExecutionEngine* engine,
@@ -1159,7 +1160,8 @@ static SkipRowsRangeVariant constexpr skipRowsType() {
               TraversalExecutor, EnumerateListExecutor, SubqueryStartExecutor, SubqueryEndExecutor, SortedCollectExecutor,
               LimitExecutor, NoResultsExecutor, SingleRemoteModificationExecutor<IndexTag>, SingleRemoteModificationExecutor<Insert>,
               SingleRemoteModificationExecutor<Remove>, SingleRemoteModificationExecutor<Update>,
-              SingleRemoteModificationExecutor<Replace>, SingleRemoteModificationExecutor<Upsert>>),
+              SingleRemoteModificationExecutor<Replace>, SingleRemoteModificationExecutor<Upsert>,
+              MaterializeExecutor<RegisterId>, MaterializeExecutor<std::string const&>>),
       "Unexpected executor for SkipVariants::EXECUTOR");
 
   // The LimitExecutor will not work correctly with SkipVariants::FETCHER!
diff --git a/arangod/Aql/FilterExecutor.cpp b/arangod/Aql/FilterExecutor.cpp
index 515c72fdfce4..516c2ea4678a 100644
--- a/arangod/Aql/FilterExecutor.cpp
+++ b/arangod/Aql/FilterExecutor.cpp
@@ -100,7 +100,6 @@ std::pair<ExecutionState, size_t> FilterExecutor::expectedNumberOfRows(size_t at
   return _fetcher.preFetchNumberOfRows(atMost);
 }
 
-// TODO Remove me, we are using the getSome skip variant here.
 auto FilterExecutor::skipRowsRange(AqlItemBlockInputRange& inputRange, AqlCall& call)
     -> std::tuple<ExecutorState, Stats, size_t, AqlCall> {
   FilterStats stats{};
diff --git a/arangod/Aql/MaterializeExecutor.cpp b/arangod/Aql/MaterializeExecutor.cpp
index 05ab2d5f8ed6..ca223272f2b4 100644
--- a/arangod/Aql/MaterializeExecutor.cpp
+++ b/arangod/Aql/MaterializeExecutor.cpp
@@ -22,93 +22,96 @@
 
 #include "MaterializeExecutor.h"
 
-#include "StorageEngine/EngineSelectorFeature.h"
-#include "StorageEngine/StorageEngine.h"
 #include "Aql/SingleRowFetcher.h"
 #include "Aql/Stats.h"
+#include "StorageEngine/EngineSelectorFeature.h"
+#include "StorageEngine/StorageEngine.h"
 #include "Transaction/Methods.h"
 
 using namespace arangodb;
 using namespace arangodb::aql;
 
-template<typename T>
-arangodb::IndexIterator::DocumentCallback MaterializeExecutor<T>::ReadContext::copyDocumentCallback(ReadContext & ctx) {
+template <typename T>
+arangodb::IndexIterator::DocumentCallback MaterializeExecutor<T>::ReadContext::copyDocumentCallback(
+    ReadContext& ctx) {
   auto* engine = EngineSelectorFeature::ENGINE;
   TRI_ASSERT(engine);
   typedef std::function<arangodb::IndexIterator::DocumentCallback(ReadContext&)> CallbackFactory;
   static CallbackFactory const callbackFactories[]{
-    [](ReadContext& ctx) {
-    // capture only one reference to potentially avoid heap allocation
-    return [&ctx](LocalDocumentId /*id*/, VPackSlice doc) {
-      TRI_ASSERT(ctx._outputRow);
-      TRI_ASSERT(ctx._inputRow);
-      TRI_ASSERT(ctx._inputRow->isInitialized());
-      TRI_ASSERT(ctx._infos);
-      arangodb::aql::AqlValue a{ arangodb::aql::AqlValueHintCopy(doc.begin()) };
-      bool mustDestroy = true;
-      arangodb::aql::AqlValueGuard guard{ a, mustDestroy };
-      ctx._outputRow->moveValueInto(ctx._infos->outputMaterializedDocumentRegId(), *ctx._inputRow, guard);
-      return true;
-    };
-  },
-
-    [](ReadContext& ctx) {
-    // capture only one reference to potentially avoid heap allocation
-    return [&ctx](LocalDocumentId /*id*/, VPackSlice doc) {
-      TRI_ASSERT(ctx._outputRow);
-      TRI_ASSERT(ctx._inputRow);
-      TRI_ASSERT(ctx._inputRow->isInitialized());
-      TRI_ASSERT(ctx._infos);
-      arangodb::aql::AqlValue a{ arangodb::aql::AqlValueHintDocumentNoCopy(doc.begin()) };
-      bool mustDestroy = true;
-      arangodb::aql::AqlValueGuard guard{ a, mustDestroy };
-      ctx._outputRow->moveValueInto(ctx._infos->outputMaterializedDocumentRegId(), *ctx._inputRow, guard);
-      return true;
-    };
-  } };
+      [](ReadContext& ctx) {
+        // capture only one reference to potentially avoid heap allocation
+        return [&ctx](LocalDocumentId /*id*/, VPackSlice doc) {
+          TRI_ASSERT(ctx._outputRow);
+          TRI_ASSERT(ctx._inputRow);
+          TRI_ASSERT(ctx._inputRow->isInitialized());
+          TRI_ASSERT(ctx._infos);
+          arangodb::aql::AqlValue a{arangodb::aql::AqlValueHintCopy(doc.begin())};
+          bool mustDestroy = true;
+          arangodb::aql::AqlValueGuard guard{a, mustDestroy};
+          ctx._outputRow->moveValueInto(ctx._infos->outputMaterializedDocumentRegId(),
+                                        *ctx._inputRow, guard);
+          return true;
+        };
+      },
+
+      [](ReadContext& ctx) {
+        // capture only one reference to potentially avoid heap allocation
+        return [&ctx](LocalDocumentId /*id*/, VPackSlice doc) {
+          TRI_ASSERT(ctx._outputRow);
+          TRI_ASSERT(ctx._inputRow);
+          TRI_ASSERT(ctx._inputRow->isInitialized());
+          TRI_ASSERT(ctx._infos);
+          arangodb::aql::AqlValue a{arangodb::aql::AqlValueHintDocumentNoCopy(doc.begin())};
+          bool mustDestroy = true;
+          arangodb::aql::AqlValueGuard guard{a, mustDestroy};
+          ctx._outputRow->moveValueInto(ctx._infos->outputMaterializedDocumentRegId(),
+                                        *ctx._inputRow, guard);
+          return true;
+        };
+      }};
 
   return callbackFactories[size_t(engine->useRawDocumentPointers())](ctx);
 }
 
-template<typename T>
+template <typename T>
 arangodb::aql::MaterializerExecutorInfos<T>::MaterializerExecutorInfos(
     RegisterId nrInputRegisters, RegisterId nrOutputRegisters,
     // cppcheck-suppress passedByValue
     std::unordered_set<RegisterId> registersToClear,
     // cppcheck-suppress passedByValue
-    std::unordered_set<RegisterId> registersToKeep,
-    T const collectionSource, RegisterId inNmDocId,
-    RegisterId outDocRegId, transaction::Methods* trx)
-  : ExecutorInfos(
-      getReadableInputRegisters(collectionSource, inNmDocId),
-      make_shared_unordered_set(std::initializer_list<RegisterId>({outDocRegId})),
-      nrInputRegisters, nrOutputRegisters,
-      std::move(registersToClear), std::move(registersToKeep)),
+    std::unordered_set<RegisterId> registersToKeep, T const collectionSource,
+    RegisterId inNmDocId, RegisterId outDocRegId, transaction::Methods* trx)
+    : ExecutorInfos(getReadableInputRegisters(collectionSource, inNmDocId),
+                    make_shared_unordered_set(std::initializer_list<RegisterId>({outDocRegId})),
+                    nrInputRegisters, nrOutputRegisters,
+                    std::move(registersToClear), std::move(registersToKeep)),
       _collectionSource(collectionSource),
       _inNonMaterializedDocRegId(inNmDocId),
-      _outMaterializedDocumentRegId(outDocRegId), _trx(trx) {
+      _outMaterializedDocumentRegId(outDocRegId),
+      _trx(trx) {}
+
+template <typename T>
+std::pair<ExecutionState, NoStats> arangodb::aql::MaterializeExecutor<T>::produceRows(OutputAqlItemRow& output) {
+  TRI_ASSERT(false);
+  THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
 }
 
-template<typename T>
-std::pair<ExecutionState, NoStats> arangodb::aql::MaterializeExecutor<T>::produceRows(OutputAqlItemRow & output) {
-  InputAqlItemRow input{CreateInvalidInputRowHint{}};
-  ExecutionState state;
-  bool written = false;
-  // some micro-optimization
-  auto& callback = _readDocumentContext._callback;
-  auto docRegId = _readDocumentContext._infos->inputNonMaterializedDocRegId();
-  T collectionSource = _readDocumentContext._infos->collectionSource();
-  auto* trx = _readDocumentContext._infos->trx();
-  do {
-    std::tie(state, input) = _fetcher.fetchRow();
-    if (state == ExecutionState::WAITING) {
-      return { state, NoStats{} };
-    }
+template <typename T>
+std::tuple<ExecutorState, NoStats, AqlCall> arangodb::aql::MaterializeExecutor<T>::produceRows(
+    AqlItemBlockInputRange& inputRange, OutputAqlItemRow& output) {
+  AqlCall upstreamCall{};
+  upstreamCall.fullCount = output.getClientCall().fullCount;
+
+  while (inputRange.hasDataRow() && !output.isFull()) {
+    bool written = false;
+
+    // some micro-optimization
+    auto& callback = _readDocumentContext._callback;
+    auto docRegId = _readDocumentContext._infos->inputNonMaterializedDocRegId();
+    T collectionSource = _readDocumentContext._infos->collectionSource();
+    auto* trx = _readDocumentContext._infos->trx();
+    auto const [state, input] = inputRange.nextDataRow();
 
-    if (!input) {
-      TRI_ASSERT(state == ExecutionState::DONE);
-      return {state, NoStats{}};
-    }
     arangodb::LogicalCollection const* collection = nullptr;
     if constexpr (std::is_same<T, std::string const&>::value) {
       if (_collection == nullptr) {
@@ -116,26 +119,42 @@ std::pair<ExecutionState, NoStats> arangodb::aql::MaterializeExecutor<T>::produc
       }
       collection = _collection;
     } else {
-      collection =
-        reinterpret_cast<arangodb::LogicalCollection const*>(
+      collection = reinterpret_cast<arangodb::LogicalCollection const*>(
           input.getValue(collectionSource).slice().getUInt());
     }
     TRI_ASSERT(collection != nullptr);
     _readDocumentContext._inputRow = &input;
     _readDocumentContext._outputRow = &output;
-    written = collection->readDocumentWithCallback(trx,
-      LocalDocumentId(input.getValue(docRegId).slice().getUInt()),
-      callback);
-  } while (!written && state != ExecutionState::DONE);
-  return {state, NoStats{}};
+    written = collection->readDocumentWithCallback(
+        trx, LocalDocumentId(input.getValue(docRegId).slice().getUInt()), callback);
+    if (written) {
+      output.advanceRow();
+    }
+  }
+
+  return {inputRange.upstreamState(), NoStats{}, upstreamCall};
+}
+
+template <typename T>
+std::tuple<ExecutorState, NoStats, size_t, AqlCall> arangodb::aql::MaterializeExecutor<T>::skipRowsRange(
+    AqlItemBlockInputRange& inputRange, AqlCall& call) {
+  size_t skipped = 0;
+
+  if (call.getLimit() > 0) {
+    // we can only account for offset
+    skipped = inputRange.skip(call.getOffset());
+  } else {
+    skipped = inputRange.skipAll();
+  }
+  call.didSkip(skipped);
+
+  return {inputRange.upstreamState(), NoStats{}, skipped, call};
 }
 
-template<typename T>
+template <typename T>
 std::tuple<ExecutionState, NoStats, size_t> arangodb::aql::MaterializeExecutor<T>::skipRows(size_t toSkipRequested) {
-  ExecutionState state;
-  size_t skipped;
-  std::tie(state, skipped) = _fetcher.skipRows(toSkipRequested);
-  return std::make_tuple(state, NoStats{}, skipped);
+  TRI_ASSERT(false);
+  THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
 }
 
 template class ::arangodb::aql::MaterializeExecutor<RegisterId>;
diff --git a/arangod/Aql/MaterializeExecutor.h b/arangod/Aql/MaterializeExecutor.h
index cb1c74ab3e38..13fdc290120a 100644
--- a/arangod/Aql/MaterializeExecutor.h
+++ b/arangod/Aql/MaterializeExecutor.h
@@ -39,13 +39,15 @@
 namespace arangodb {
 namespace aql {
 
+struct AqlCall;
+class AqlItemBlockInputRange;
 class InputAqlItemRow;
 class ExecutorInfos;
 template <BlockPassthrough>
 class SingleRowFetcher;
 class NoStats;
 
-template<typename T>
+template <typename T>
 class MaterializerExecutorInfos : public ExecutorInfos {
  public:
   MaterializerExecutorInfos(RegisterId nrInputRegisters, RegisterId nrOutputRegisters,
@@ -67,18 +69,16 @@ class MaterializerExecutorInfos : public ExecutorInfos {
     return _inNonMaterializedDocRegId;
   }
 
-  transaction::Methods* trx() const {
-    return _trx;
-  }
+  transaction::Methods* trx() const { return _trx; }
 
-  T collectionSource() const {
-    return _collectionSource;
-  }
+  T collectionSource() const { return _collectionSource; }
 
  private:
-  std::shared_ptr<std::unordered_set<RegisterId>> getReadableInputRegisters(T const collectionSource, RegisterId inNmDocId) {
+  std::shared_ptr<std::unordered_set<RegisterId>> getReadableInputRegisters(
+      T const collectionSource, RegisterId inNmDocId) {
     if constexpr (std::is_same<T, RegisterId>::value) {
-      return make_shared_unordered_set(std::initializer_list<RegisterId>({collectionSource, inNmDocId}));
+      return make_shared_unordered_set(
+          std::initializer_list<RegisterId>({collectionSource, inNmDocId}));
     } else {
       return make_shared_unordered_set(std::initializer_list<RegisterId>({inNmDocId}));
     }
@@ -94,7 +94,7 @@ class MaterializerExecutorInfos : public ExecutorInfos {
   transaction::Methods* _trx;
 };
 
-template<typename T>
+template <typename T>
 class MaterializeExecutor {
  public:
   struct Properties {
@@ -108,19 +108,36 @@ class MaterializeExecutor {
 
   MaterializeExecutor(MaterializeExecutor&&) = default;
   MaterializeExecutor(MaterializeExecutor const&) = delete;
-  MaterializeExecutor(Fetcher& fetcher, Infos& infos) : _readDocumentContext(infos), _infos(infos), _fetcher(fetcher) {}
+  MaterializeExecutor(Fetcher& fetcher, Infos& infos)
+      : _readDocumentContext(infos), _infos(infos), _fetcher(fetcher) {}
 
   std::pair<ExecutionState, Stats> produceRows(OutputAqlItemRow& output);
   std::tuple<ExecutionState, Stats, size_t> skipRows(size_t toSkipRequested);
 
+  /**
+   * @brief produce the next Row of Aql Values.
+   *
+   * @return ExecutorState, the stats, and a new Call that needs to be send to upstream
+   */
+  [[nodiscard]] std::tuple<ExecutorState, Stats, AqlCall> produceRows(
+      AqlItemBlockInputRange& inputRange, OutputAqlItemRow& output);
+
+  /**
+   * @brief skip the next Row of Aql Values.
+   *
+   * @return ExecutorState, the stats, and a new Call that needs to be send to upstream
+   */
+  [[nodiscard]] std::tuple<ExecutorState, Stats, size_t, AqlCall> skipRowsRange(
+      AqlItemBlockInputRange& inputRange, AqlCall& call);
+
  protected:
   class ReadContext {
    public:
     explicit ReadContext(Infos& infos)
-      : _infos(&infos),
-      _inputRow(nullptr),
-      _outputRow(nullptr),
-      _callback(copyDocumentCallback(*this)) {}
+        : _infos(&infos),
+          _inputRow(nullptr),
+          _outputRow(nullptr),
+          _callback(copyDocumentCallback(*this)) {}
 
     ReadContext(ReadContext&&) = default;
 
diff --git a/arangod/Aql/RemoteExecutor.cpp b/arangod/Aql/RemoteExecutor.cpp
index df23a2281a65..92d406c2d49e 100644
--- a/arangod/Aql/RemoteExecutor.cpp
+++ b/arangod/Aql/RemoteExecutor.cpp
@@ -434,7 +434,10 @@ std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> ExecutionBlockImpl<Rem
   // Use the old getSome/SkipSome API.
   // TODO needs execute implementation instead
   auto myCall = stack.popCall();
-  TRI_ASSERT(AqlCall::IsSkipSomeCall(myCall) || AqlCall::IsGetSomeCall(myCall));
+
+  TRI_ASSERT(AqlCall::IsSkipSomeCall(myCall) || AqlCall::IsGetSomeCall(myCall) ||
+             AqlCall::IsFullCountCall(myCall) || AqlCall::IsFastForwardCall(myCall));
+
   if (AqlCall::IsSkipSomeCall(myCall)) {
     auto const [state, skipped] = skipSome(myCall.getOffset());
     if (state != ExecutionState::WAITING) {
@@ -444,8 +447,26 @@ std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> ExecutionBlockImpl<Rem
   } else if (AqlCall::IsGetSomeCall(myCall)) {
     auto const [state, block] = getSome(myCall.getLimit());
     // We do not need to count as softLimit will be overwritten, and hard cannot be set.
+    if (stack.empty() && myCall.hasHardLimit() && !myCall.needsFullCount() && block != nullptr) {
+      // However we can do a short-cut here to report DONE on hardLimit if we are on the top-level query.
+      myCall.didProduce(block->size());
+      if (myCall.getLimit() == 0) {
+        return {ExecutionState::DONE, 0, block};
+      }
+    }
+
     return {state, 0, block};
+  } else if (AqlCall::IsFullCountCall(myCall)) {
+    auto const [state, skipped] = skipSome(ExecutionBlock::SkipAllSize());
+    if (state != ExecutionState::WAITING) {
+      myCall.didSkip(skipped);
+    }
+    return {state, skipped, nullptr};
+  } else if (AqlCall::IsFastForwardCall(myCall)) {
+    // No idea if DONE is correct here...
+    return {ExecutionState::DONE, 0, nullptr};
   }
+
   // Should never get here!
   THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
 }

From 9a76c0c4b495420f288526a77c08e72f7b9645b8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tobias=20G=C3=B6dderz?= <tobias@arangodb.com>
Date: Sat, 29 Feb 2020 08:24:00 +0100
Subject: [PATCH 088/122] Feature/aql subquery execute remote (#11197)

* Clarified comment

* Updated comment

* Added two static strings

* Avoid unintentional streaming operator of string_view as a container

* Added parser for execute rest call

* Fixed ambiguous overload in ResultT

* Added execute and executeForClient to ExecutionEngine

* Implemented executeForClient in RestAqlHandler

* Add default value

* Updated comment

* Changed error attribute

* Added API toggle to RemoteExecutor

* Fixed compile error

* Fixed duplicate log id

* Try to make MSVC work

* Moved AqlExecuteResult to a separate file

* Moved AqlExecuteResult to a separate file

* Implemtented execute in Remote; except for (de)serialization, which is still missing

* Tried to fix MSVC compile error

* Revert "Tried to fix MSVC compile error"

This reverts commit f6f43b2c7e4bfe17dafe65f48bcd5c0b6e5c69a9.

* Next try to fix MSVC

* Implemented (de)serialization for RemoteExecutor::execute

* Fixes

* Added minimal AqlCall (de)serialization tests

* Bugfix

* Added minimal (de)serialization tests for AqlCallStack and AqlExecuteResult

* Fixed test

* Changed Serialization format a little

* Bugfix

* Initialize SingletonBlock immediately with an empty row

* Revert "Next try to fix MSVC"

This reverts commit 528c4c795d10ee0aa6686d143be1f6faa6e9b553.

* Revert "Try to make MSVC work"

This reverts commit ba7d9c072fccb969da1cdf045eadf49c297da8e9.

* Work around MSVC shortcoming

* Work around MSVC shortcoming

* Attempt to fix windows compile issue

Co-authored-by: Michael Hackstein <michael@arangodb.com>
---
 arangod/Aql/AqlCall.cpp            |  76 ++++++++--
 arangod/Aql/AqlCall.h              |   9 ++
 arangod/Aql/AqlCallStack.cpp       |  45 +++++-
 arangod/Aql/AqlCallStack.h         |   4 +
 arangod/Aql/AqlExecuteResult.cpp   | 149 ++++++++++++++++++++
 arangod/Aql/AqlExecuteResult.h     |  10 ++
 arangod/Aql/ClusterNodes.cpp       |   2 +-
 arangod/Aql/ExecutionBlock.cpp     |   8 +-
 arangod/Aql/ExecutionBlock.h       |   3 +-
 arangod/Aql/ExecutionBlockImpl.cpp |   3 +-
 arangod/Aql/ExecutionNode.cpp      |   7 +-
 arangod/Aql/RemoteExecutor.cpp     | 158 ++++++++++++++++++---
 arangod/Aql/RemoteExecutor.h       |  47 +++++--
 arangod/Aql/RestAqlHandler.cpp     |  11 +-
 arangod/Aql/RestAqlHandler.h       |  24 ++--
 lib/Basics/StaticStrings.cpp       |   4 +-
 lib/Basics/StaticStrings.h         |   1 +
 tests/Aql/RemoteExecutorTest.cpp   | 217 +++++++++++++++++++++++++++++
 tests/CMakeLists.txt               |   1 +
 19 files changed, 716 insertions(+), 63 deletions(-)
 create mode 100644 tests/Aql/RemoteExecutorTest.cpp

diff --git a/arangod/Aql/AqlCall.cpp b/arangod/Aql/AqlCall.cpp
index cc8f947f13c1..1621a38271e7 100644
--- a/arangod/Aql/AqlCall.cpp
+++ b/arangod/Aql/AqlCall.cpp
@@ -42,7 +42,7 @@ auto getStringView(velocypack::Slice slice) -> std::string_view {
   velocypack::StringRef ref = slice.stringRef();
   return std::string_view(ref.data(), ref.size());
 }
-}
+}  // namespace
 
 auto AqlCall::fromVelocyPack(velocypack::Slice slice) -> ResultT<AqlCall> {
   if (ADB_UNLIKELY(!slice.isObject())) {
@@ -63,7 +63,9 @@ auto AqlCall::fromVelocyPack(velocypack::Slice slice) -> ResultT<AqlCall> {
   auto fullCount = false;
 
   auto const readLimit = [](velocypack::Slice slice) -> ResultT<AqlCall::Limit> {
-    if (slice.isEqualString(StaticStrings::AqlRemoteInfinity)) {
+    auto const type = slice.type();
+    if (type == velocypack::ValueType::String &&
+        slice.isEqualString(StaticStrings::AqlRemoteInfinity)) {
       return AqlCall::Limit{AqlCall::Infinity{}};
     } else if (slice.isInteger()) {
       try {
@@ -89,7 +91,11 @@ auto AqlCall::fromVelocyPack(velocypack::Slice slice) -> ResultT<AqlCall> {
     }
   };
 
-  auto const readLimitType = [](velocypack::Slice slice) -> ResultT<AqlCall::LimitType> {
+  auto const readLimitType =
+      [](velocypack::Slice slice) -> ResultT<std::optional<AqlCall::LimitType>> {
+    if (slice.isNull()) {
+      return {std::nullopt};
+    }
     if (ADB_UNLIKELY(!slice.isString())) {
       auto message = std::string{
           "When deserializating AqlCall: When reading limitType: "
@@ -99,12 +105,10 @@ auto AqlCall::fromVelocyPack(velocypack::Slice slice) -> ResultT<AqlCall> {
     }
     auto value = getStringView(slice);
     if (value == StaticStrings::AqlRemoteLimitTypeSoft) {
-      return AqlCall::LimitType::SOFT;
-    }
-    else if (value == StaticStrings::AqlRemoteLimitTypeHard) {
-      return AqlCall::LimitType::HARD;
-    }
-    else {
+      return {AqlCall::LimitType::SOFT};
+    } else if (value == StaticStrings::AqlRemoteLimitTypeHard) {
+      return {AqlCall::LimitType::HARD};
+    } else {
       auto message = std::string{
           "When deserializating AqlCall: When reading limitType: "
           "Unexpected value '"};
@@ -214,7 +218,8 @@ auto AqlCall::fromVelocyPack(velocypack::Slice slice) -> ResultT<AqlCall> {
         break;
     }
   } else if (ADB_UNLIKELY(!std::holds_alternative<Infinity>(limit))) {
-    return Result(TRI_ERROR_TYPE_ERROR,
+    return Result(
+        TRI_ERROR_TYPE_ERROR,
         "When deserializating AqlCall: limit set, but limitType is missing.");
   }
 
@@ -223,3 +228,54 @@ auto AqlCall::fromVelocyPack(velocypack::Slice slice) -> ResultT<AqlCall> {
 
   return call;
 }
+
+void AqlCall::toVelocyPack(velocypack::Builder& builder) const {
+  using namespace velocypack;
+
+  auto limitType = std::optional<LimitType>{};
+  auto limit = Limit{Infinity{}};
+  if (hasHardLimit()) {
+    limitType = LimitType::HARD;
+    limit = hardLimit;
+  } else if (hasSoftLimit()) {
+    limitType = LimitType::SOFT;
+    limit = softLimit;
+  }
+
+  auto const limitValue =
+      std::visit(overload{
+                     [](Infinity) {
+                       return Value(StaticStrings::AqlRemoteInfinity);
+                     },
+                     [](std::size_t limit) { return Value(limit); },
+                 },
+                 limit);
+  auto const limitTypeValue = std::invoke([&]() {
+    if (!limitType.has_value()) {
+      return Value(ValueType::Null);
+    } else {
+      switch (limitType.value()) {
+        case LimitType::SOFT:
+          return Value(StaticStrings::AqlRemoteLimitTypeSoft);
+        case LimitType::HARD:
+          return Value(StaticStrings::AqlRemoteLimitTypeHard);
+      }
+      // unreachable
+      TRI_ASSERT(false);
+      THROW_ARANGO_EXCEPTION(TRI_ERROR_INTERNAL);
+    }
+  });
+
+  builder.openObject();
+  builder.add(StaticStrings::AqlRemoteLimit, limitValue);
+  builder.add(StaticStrings::AqlRemoteLimitType, limitTypeValue);
+  builder.add(StaticStrings::AqlRemoteFullCount, Value(fullCount));
+  builder.add(StaticStrings::AqlRemoteOffset, Value(offset));
+  builder.close();
+}
+
+auto AqlCall::toString() const -> std::string {
+  auto stream = std::stringstream{};
+  stream << *this;
+  return stream.str();
+}
diff --git a/arangod/Aql/AqlCall.h b/arangod/Aql/AqlCall.h
index 07214859d631..b310dfee3175 100644
--- a/arangod/Aql/AqlCall.h
+++ b/arangod/Aql/AqlCall.h
@@ -64,6 +64,9 @@ struct AqlCall {
         fullCount{fullCount} {}
 
   static auto fromVelocyPack(velocypack::Slice) -> ResultT<AqlCall>;
+  void toVelocyPack(velocypack::Builder&) const;
+
+  auto toString() const -> std::string;
 
   // TODO Remove me, this will not be necessary later
   static AqlCall SimulateSkipSome(std::size_t toSkip) {
@@ -234,6 +237,12 @@ constexpr bool operator==(AqlCall::Limit const& a, AqlCall::Limit const& b) {
                     a);
 }
 
+constexpr bool operator==(AqlCall const& left, AqlCall const& right) {
+  return left.hardLimit == right.hardLimit && left.softLimit == right.softLimit &&
+         left.offset == right.offset && left.fullCount == right.fullCount &&
+         left.skippedRows == right.skippedRows;
+}
+
 inline std::ostream& operator<<(std::ostream& out,
                                 const arangodb::aql::AqlCall::Limit& limit) {
   return std::visit(arangodb::overload{[&out](size_t const& i) -> std::ostream& {
diff --git a/arangod/Aql/AqlCallStack.cpp b/arangod/Aql/AqlCallStack.cpp
index 92dab45176a5..68c5cd9c5b8d 100644
--- a/arangod/Aql/AqlCallStack.cpp
+++ b/arangod/Aql/AqlCallStack.cpp
@@ -22,8 +22,9 @@
 
 #include "AqlCallStack.h"
 
-#include <velocypack/Slice.h>
+#include <velocypack/Builder.h>
 #include <velocypack/Iterator.h>
+#include <velocypack/Slice.h>
 #include <velocypack/velocypack-aliases.h>
 
 // TODO: This class is not yet memory efficient or optimized in any way.
@@ -34,8 +35,7 @@ using namespace arangodb;
 using namespace arangodb::aql;
 
 AqlCallStack::AqlCallStack(AqlCall call, bool compatibilityMode3_6)
-    : _operations{{std::move(call)}},
-      _compatibilityMode3_6(compatibilityMode3_6) {}
+    : _operations{{std::move(call)}}, _compatibilityMode3_6(compatibilityMode3_6) {}
 
 AqlCallStack::AqlCallStack(AqlCallStack const& other, AqlCall call)
     : _operations{other._operations} {
@@ -149,3 +149,42 @@ auto AqlCallStack::fromVelocyPack(velocypack::Slice const slice) -> ResultT<AqlC
 
   return AqlCallStack{std::move(stack)};
 }
+
+void AqlCallStack::toVelocyPack(velocypack::Builder& builder) const {
+  auto reverseStack = std::vector<AqlCall>{};
+  reverseStack.reserve(_operations.size());
+  {
+    auto ops = _operations;
+    while (!ops.empty()) {
+      reverseStack.emplace_back(ops.top());
+      ops.pop();
+    }
+  }
+
+  builder.openArray();
+  for (auto it = reverseStack.rbegin(); it != reverseStack.rend(); ++it) {
+    auto const& call = *it;
+    call.toVelocyPack(builder);
+  }
+  builder.close();
+}
+
+auto AqlCallStack::toString() const -> std::string {
+  auto result = std::string{};
+  result += "[";
+  auto ops = _operations;
+  if (!ops.empty()) {
+    auto op = ops.top();
+    ops.pop();
+    result += " ";
+    result += op.toString();
+    while (!ops.empty()) {
+      op = ops.top();
+      ops.pop();
+      result += ", ";
+      result += op.toString();
+    }
+  }
+  result += " ]";
+  return result;
+}
diff --git a/arangod/Aql/AqlCallStack.h b/arangod/Aql/AqlCallStack.h
index 9d8e98df7d0b..f67e505ddffc 100644
--- a/arangod/Aql/AqlCallStack.h
+++ b/arangod/Aql/AqlCallStack.h
@@ -47,6 +47,8 @@ class AqlCallStack {
 
   static auto fromVelocyPack(velocypack::Slice) -> ResultT<AqlCallStack>;
 
+  auto toString() const -> std::string;
+
   // Quick test is this CallStack is of local relevance, or it is sufficient to pass it through
   bool isRelevant() const;
 
@@ -88,6 +90,8 @@ class AqlCallStack {
     return _operations.size() + _depth;
   }
 
+  void toVelocyPack(velocypack::Builder& builder) const;
+
  private:
   explicit AqlCallStack(std::stack<AqlCall>&& operations);
 
diff --git a/arangod/Aql/AqlExecuteResult.cpp b/arangod/Aql/AqlExecuteResult.cpp
index 3b56bebec8bf..db10deeaab96 100644
--- a/arangod/Aql/AqlExecuteResult.cpp
+++ b/arangod/Aql/AqlExecuteResult.cpp
@@ -22,14 +22,28 @@
 
 #include "AqlExecuteResult.h"
 
+#include "Aql/AqlItemBlockManager.h"
 #include "Basics/StaticStrings.h"
+#include "Cluster/ResultT.h"
+#include "Logger/LogMacros.h"
+#include "Logger/Logger.h"
 
 #include <velocypack/Builder.h>
 #include <velocypack/Iterator.h>
 
+#include <map>
+
 using namespace arangodb;
 using namespace arangodb::aql;
 
+namespace {
+// hack for MSVC
+auto getStringView(velocypack::Slice slice) -> std::string_view {
+  velocypack::StringRef ref = slice.stringRef();
+  return std::string_view(ref.data(), ref.size());
+}
+}  // namespace
+
 auto AqlExecuteResult::state() const noexcept -> ExecutionState {
   return _state;
 }
@@ -59,6 +73,7 @@ void AqlExecuteResult::toVelocyPack(velocypack::Builder& builder,
     THROW_ARANGO_EXCEPTION_MESSAGE(TRI_ERROR_INTERNAL_AQL, "Unhandled state");
   };
 
+  builder.openObject();
   builder.add(StaticStrings::AqlRemoteState, stateToValue(state()));
   builder.add(StaticStrings::AqlRemoteSkipped, Value(skipped()));
   if (block() != nullptr) {
@@ -67,4 +82,138 @@ void AqlExecuteResult::toVelocyPack(velocypack::Builder& builder,
   } else {
     builder.add(StaticStrings::AqlRemoteBlock, Value(ValueType::Null));
   }
+  builder.close();
+}
+
+auto AqlExecuteResult::fromVelocyPack(velocypack::Slice const slice,
+                                      AqlItemBlockManager& itemBlockManager)
+    -> ResultT<AqlExecuteResult> {
+  if (ADB_UNLIKELY(!slice.isObject())) {
+    using namespace std::string_literals;
+    return Result(TRI_ERROR_TYPE_ERROR,
+                  "When deserializating AqlExecuteResult: Expected object, got "s +
+                      slice.typeName());
+  }
+
+  auto expectedPropertiesFound = std::map<std::string_view, bool>{};
+  expectedPropertiesFound.emplace(StaticStrings::AqlRemoteState, false);
+  expectedPropertiesFound.emplace(StaticStrings::AqlRemoteSkipped, false);
+  expectedPropertiesFound.emplace(StaticStrings::AqlRemoteBlock, false);
+
+  auto state = ExecutionState::HASMORE;
+  auto skipped = std::size_t{};
+  auto block = SharedAqlItemBlockPtr{};
+
+  auto const readState = [](velocypack::Slice slice) -> ResultT<ExecutionState> {
+    if (ADB_UNLIKELY(!slice.isString())) {
+      auto message = std::string{
+          "When deserializating AqlExecuteResult: When reading state: "
+          "Unexpected type "};
+      message += slice.typeName();
+      return Result(TRI_ERROR_TYPE_ERROR, std::move(message));
+    }
+    auto value = getStringView(slice);
+    if (value == StaticStrings::AqlRemoteStateDone) {
+      return ExecutionState::DONE;
+    } else if (value == StaticStrings::AqlRemoteStateHasmore) {
+      return ExecutionState::HASMORE;
+    } else {
+      auto message = std::string{
+          "When deserializating AqlExecuteResult: When reading state: "
+          "Unexpected value '"};
+      message += value;
+      message += "'";
+      return Result(TRI_ERROR_TYPE_ERROR, std::move(message));
+    }
+  };
+
+  auto const readSkipped = [](velocypack::Slice slice) -> ResultT<std::size_t> {
+    if (!slice.isInteger()) {
+      auto message = std::string{
+          "When deserializating AqlExecuteResult: When reading skipped: "
+          "Unexpected type "};
+      message += slice.typeName();
+      return Result(TRI_ERROR_TYPE_ERROR, std::move(message));
+    }
+    try {
+      return slice.getNumber<std::size_t>();
+    } catch (velocypack::Exception const& ex) {
+      auto message = std::string{
+          "When deserializating AqlExecuteResult: When reading skipped: "};
+      message += ex.what();
+      return Result(TRI_ERROR_TYPE_ERROR, std::move(message));
+    }
+  };
+
+  auto const readBlock = [&itemBlockManager](velocypack::Slice slice) -> ResultT<SharedAqlItemBlockPtr> {
+    if (slice.isNull()) {
+      return SharedAqlItemBlockPtr{nullptr};
+    }
+    TRI_ASSERT(slice.isObject());
+    return itemBlockManager.requestAndInitBlock(slice);
+  };
+
+  for (auto const it : velocypack::ObjectIterator(slice)) {
+    auto const keySlice = it.key;
+    if (ADB_UNLIKELY(!keySlice.isString())) {
+      return Result(
+          TRI_ERROR_TYPE_ERROR,
+          "When deserializating AqlExecuteResult: Key is not a string");
+    }
+    auto const key = getStringView(keySlice);
+
+    if (auto propIt = expectedPropertiesFound.find(key);
+        ADB_LIKELY(propIt != expectedPropertiesFound.end())) {
+      if (ADB_UNLIKELY(propIt->second)) {
+        return Result(
+            TRI_ERROR_TYPE_ERROR,
+            "When deserializating AqlExecuteResult: Encountered duplicate key");
+      }
+      propIt->second = true;
+    }
+
+    if (key == StaticStrings::AqlRemoteState) {
+      auto maybeState = readState(it.value);
+      if (maybeState.fail()) {
+        return std::move(maybeState).result();
+      }
+      state = maybeState.get();
+    } else if (key == StaticStrings::AqlRemoteSkipped) {
+      auto maybeSkipped = readSkipped(it.value);
+      if (maybeSkipped.fail()) {
+        return std::move(maybeSkipped).result();
+      }
+      skipped = maybeSkipped.get();
+    } else if (key == StaticStrings::AqlRemoteBlock) {
+      auto maybeBlock = readBlock(it.value);
+      if (maybeBlock.fail()) {
+        return std::move(maybeBlock).result();
+      }
+      block = maybeBlock.get();
+    } else {
+      LOG_TOPIC("cc6f4", WARN, Logger::AQL)
+          << "When deserializating AqlExecuteResult: Encountered unexpected "
+             "key "
+          << keySlice.toJson();
+      // If you run into this assertion during rolling upgrades after adding a
+      // new attribute, remove it in the older version.
+      TRI_ASSERT(false);
+    }
+  }
+
+  for (auto const& it : expectedPropertiesFound) {
+    if (ADB_UNLIKELY(!it.second)) {
+      auto message =
+          std::string{"When deserializating AqlExecuteResult: missing key "};
+      message += it.first;
+      return Result(TRI_ERROR_TYPE_ERROR, std::move(message));
+    }
+  }
+
+  return AqlExecuteResult{state, skipped, std::move(block)};
+}
+
+auto AqlExecuteResult::asTuple() const noexcept
+    -> std::tuple<ExecutionState, std::size_t, SharedAqlItemBlockPtr> {
+  return {state(), skipped(), block()};
 }
diff --git a/arangod/Aql/AqlExecuteResult.h b/arangod/Aql/AqlExecuteResult.h
index 4d23804bd019..56eb448c83db 100644
--- a/arangod/Aql/AqlExecuteResult.h
+++ b/arangod/Aql/AqlExecuteResult.h
@@ -28,6 +28,11 @@
 
 #include <utility>
 
+namespace arangodb {
+template <class T>
+class ResultT;
+}
+
 namespace arangodb::velocypack {
 class Builder;
 struct Options;
@@ -41,11 +46,16 @@ class AqlExecuteResult {
       : _state(state), _skipped(skipped), _block(std::move(block)) {}
 
   void toVelocyPack(velocypack::Builder&, velocypack::Options const*);
+  static auto fromVelocyPack(velocypack::Slice, AqlItemBlockManager&)
+      -> ResultT<AqlExecuteResult>;
 
   [[nodiscard]] auto state() const noexcept -> ExecutionState;
   [[nodiscard]] auto skipped() const noexcept -> std::size_t;
   [[nodiscard]] auto block() const noexcept -> SharedAqlItemBlockPtr const&;
 
+  [[nodiscard]] auto asTuple() const noexcept
+      -> std::tuple<ExecutionState, std::size_t, SharedAqlItemBlockPtr>;
+
  private:
   ExecutionState _state = ExecutionState::HASMORE;
   std::size_t _skipped = 0;
diff --git a/arangod/Aql/ClusterNodes.cpp b/arangod/Aql/ClusterNodes.cpp
index 1bcfffe3eb12..4e393a10caa6 100644
--- a/arangod/Aql/ClusterNodes.cpp
+++ b/arangod/Aql/ClusterNodes.cpp
@@ -172,7 +172,7 @@ std::unique_ptr<ExecutionBlock> RemoteNode::createBlock(
                       std::move(regsToKeep));
 
   return std::make_unique<ExecutionBlockImpl<RemoteExecutor>>(
-      &engine, this, std::move(infos), server(), getDistributeId(), queryId());
+      &engine, this, std::move(infos), server(), getDistributeId(), queryId(), api());
 }
 
 /// @brief toVelocyPack, for RemoteNode
diff --git a/arangod/Aql/ExecutionBlock.cpp b/arangod/Aql/ExecutionBlock.cpp
index a9ba6fb98b3a..ec4ca75d3433 100644
--- a/arangod/Aql/ExecutionBlock.cpp
+++ b/arangod/Aql/ExecutionBlock.cpp
@@ -316,8 +316,8 @@ void ExecutionBlock::traceExecuteBegin(AqlCallStack const& stack) {
   }
 }
 
-void ExecutionBlock::traceExecuteEnd(
-    std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> const& result) {
+auto ExecutionBlock::traceExecuteEnd(std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> const& result)
+    -> std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> {
   if (_profile >= PROFILE_LEVEL_BLOCKS) {
     auto const& [state, skipped, block] = result;
     auto const items = block != nullptr ? block->size() : 0;
@@ -358,6 +358,8 @@ void ExecutionBlock::traceExecuteEnd(
       }
     }
   }
+
+  return result;
 }
 
 auto ExecutionBlock::printTypeInfo() const -> std::string const {
@@ -373,4 +375,4 @@ auto ExecutionBlock::printBlockInfo() const -> std::string const {
   ExecutionNode const* node = getPlanNode();
   stream << printTypeInfo() << " this=" << (uintptr_t)this << " id=" << node->id();
   return stream.str();
-}
\ No newline at end of file
+}
diff --git a/arangod/Aql/ExecutionBlock.h b/arangod/Aql/ExecutionBlock.h
index 059217978485..b3652bc5576c 100644
--- a/arangod/Aql/ExecutionBlock.h
+++ b/arangod/Aql/ExecutionBlock.h
@@ -155,7 +155,8 @@ class ExecutionBlock {
   void traceExecuteBegin(AqlCallStack const& stack);
 
   // Trace the end of a execute call, potentially with result
-  void traceExecuteEnd(std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> const& result);
+  auto traceExecuteEnd(std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> const& result)
+      -> std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr>;
 
   [[nodiscard]] auto printBlockInfo() const -> std::string const;
   [[nodiscard]] auto printTypeInfo() const -> std::string const;
diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index b13336abfc27..add3cf3dee85 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -657,8 +657,7 @@ std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> ExecutionBlockImpl<Exe
     }
 
     auto res = executeWithoutTrace(stack);
-    traceExecuteEnd(res);
-    return res;
+    return traceExecuteEnd(res);
   }
 
   // Fall back to getSome/skipSome
diff --git a/arangod/Aql/ExecutionNode.cpp b/arangod/Aql/ExecutionNode.cpp
index f5eb0184b5b7..15a343e7d124 100644
--- a/arangod/Aql/ExecutionNode.cpp
+++ b/arangod/Aql/ExecutionNode.cpp
@@ -1282,8 +1282,11 @@ std::unique_ptr<ExecutionBlock> SingletonNode::createBlock(
 
   IdExecutorInfos infos(nrRegs, std::move(toKeep), getRegsToClear(), false);
 
-  return std::make_unique<ExecutionBlockImpl<IdExecutor<ConstFetcher>>>(&engine, this,
-                                                                        std::move(infos));
+  auto res =
+      std::make_unique<ExecutionBlockImpl<IdExecutor<ConstFetcher>>>(&engine, this,
+                                                                     std::move(infos));
+  std::ignore = res->initializeCursor(InputAqlItemRow{CreateInvalidInputRowHint{}});
+  return res;
 }
 
 /// @brief toVelocyPack, for SingletonNode
diff --git a/arangod/Aql/RemoteExecutor.cpp b/arangod/Aql/RemoteExecutor.cpp
index 92d406c2d49e..c231fc4cb91e 100644
--- a/arangod/Aql/RemoteExecutor.cpp
+++ b/arangod/Aql/RemoteExecutor.cpp
@@ -24,13 +24,14 @@
 
 #include "ApplicationFeatures/ApplicationServer.h"
 #include "Aql/AqlCallStack.h"
+#include "Aql/AqlExecuteResult.h"
 #include "Aql/ClusterNodes.h"
 #include "Aql/ExecutionEngine.h"
 #include "Aql/ExecutorInfos.h"
 #include "Aql/InputAqlItemRow.h"
 #include "Aql/Query.h"
+#include "Aql/RestAqlHandler.h"
 #include "Basics/MutexLocker.h"
-#include "Basics/RecursiveLocker.h"
 #include "Basics/StringBuffer.h"
 #include "Basics/VelocyPackHelper.h"
 #include "Cluster/ServerState.h"
@@ -41,11 +42,10 @@
 #include "Rest/CommonDefines.h"
 #include "Transaction/Context.h"
 #include "Transaction/Methods.h"
-#include "VocBase/vocbase.h"
 
 #include <fuerte/connection.h>
 #include <fuerte/requests.h>
-
+#include <velocypack/Builder.h>
 #include <velocypack/Iterator.h>
 #include <velocypack/velocypack-aliases.h>
 
@@ -61,7 +61,8 @@ constexpr std::chrono::seconds kDefaultTimeOutSecs(3600);
 
 ExecutionBlockImpl<RemoteExecutor>::ExecutionBlockImpl(
     ExecutionEngine* engine, RemoteNode const* node, ExecutorInfos&& infos,
-    std::string const& server, std::string const& ownName, std::string const& queryId)
+    std::string const& server, std::string const& ownName,
+    std::string const& queryId, Api const api)
     : ExecutionBlock(engine, node),
       _infos(std::move(infos)),
       _query(*engine->getQuery()),
@@ -72,7 +73,8 @@ ExecutionBlockImpl<RemoteExecutor>::ExecutionBlockImpl(
       _lastError(TRI_ERROR_NO_ERROR),
       _lastTicket(0),
       _requestInFlight(false),
-      _hasTriggeredShutdown(false) {
+      _hasTriggeredShutdown(false),
+      _apiToUse(api) {
   TRI_ASSERT(!queryId.empty());
   TRI_ASSERT((arangodb::ServerState::instance()->isCoordinator() && ownName.empty()) ||
              (!arangodb::ServerState::instance()->isCoordinator() && !ownName.empty()));
@@ -151,7 +153,7 @@ std::pair<ExecutionState, SharedAqlItemBlockPtr> ExecutionBlockImpl<RemoteExecut
     traceGetSomeRequest(builder.slice(), atMost);
   }
 
-  auto res = sendAsyncRequest(fuerte::RestVerb::Put, "/_api/aql/getSome/",
+  auto res = sendAsyncRequest(fuerte::RestVerb::Put, "/_api/aql/getSome",
                               std::move(buffer));
 
   if (!res.ok()) {
@@ -231,7 +233,7 @@ std::pair<ExecutionState, size_t> ExecutionBlockImpl<RemoteExecutor>::skipSomeWi
     builder.close();
     traceSkipSomeRequest(builder.slice(), atMost);
   }
-  auto res = sendAsyncRequest(fuerte::RestVerb::Put, "/_api/aql/skipSome/",
+  auto res = sendAsyncRequest(fuerte::RestVerb::Put, "/_api/aql/skipSome",
                               std::move(buffer));
 
   if (!res.ok()) {
@@ -319,7 +321,7 @@ std::pair<ExecutionState, Result> ExecutionBlockImpl<RemoteExecutor>::initialize
   traceInitializeCursorRequest(builder.slice());
 
   auto res = sendAsyncRequest(fuerte::RestVerb::Put,
-                              "/_api/aql/initializeCursor/", std::move(buffer));
+                              "/_api/aql/initializeCursor", std::move(buffer));
   if (!res.ok()) {
     THROW_ARANGO_EXCEPTION(res);
   }
@@ -351,7 +353,7 @@ std::pair<ExecutionState, Result> ExecutionBlockImpl<RemoteExecutor>::shutdown(i
 
     traceShutdownRequest(builder.slice(), errorCode);
 
-    auto res = sendAsyncRequest(fuerte::RestVerb::Put, "/_api/aql/shutdown/",
+    auto res = sendAsyncRequest(fuerte::RestVerb::Put, "/_api/aql/shutdown",
                                 std::move(buffer));
     if (!res.ok()) {
       THROW_ARANGO_EXCEPTION(res);
@@ -429,23 +431,22 @@ std::pair<ExecutionState, Result> ExecutionBlockImpl<RemoteExecutor>::shutdown(i
   return {ExecutionState::DONE, TRI_ERROR_NO_ERROR};
 }
 
-std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> ExecutionBlockImpl<RemoteExecutor>::execute(
-    AqlCallStack stack) {
+auto ExecutionBlockImpl<RemoteExecutor>::executeViaOldApi(AqlCallStack stack)
+    -> std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> {
   // Use the old getSome/SkipSome API.
-  // TODO needs execute implementation instead
   auto myCall = stack.popCall();
 
   TRI_ASSERT(AqlCall::IsSkipSomeCall(myCall) || AqlCall::IsGetSomeCall(myCall) ||
              AqlCall::IsFullCountCall(myCall) || AqlCall::IsFastForwardCall(myCall));
 
   if (AqlCall::IsSkipSomeCall(myCall)) {
-    auto const [state, skipped] = skipSome(myCall.getOffset());
+    auto const [state, skipped] = skipSomeWithoutTrace(myCall.getOffset());
     if (state != ExecutionState::WAITING) {
       myCall.didSkip(skipped);
     }
     return {state, skipped, nullptr};
   } else if (AqlCall::IsGetSomeCall(myCall)) {
-    auto const [state, block] = getSome(myCall.getLimit());
+    auto const [state, block] = getSomeWithoutTrace(myCall.getLimit());
     // We do not need to count as softLimit will be overwritten, and hard cannot be set.
     if (stack.empty() && myCall.hasHardLimit() && !myCall.needsFullCount() && block != nullptr) {
       // However we can do a short-cut here to report DONE on hardLimit if we are on the top-level query.
@@ -468,7 +469,126 @@ std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> ExecutionBlockImpl<Rem
   }
 
   // Should never get here!
-  THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
+  THROW_ARANGO_EXCEPTION(TRI_ERROR_INTERNAL_AQL);
+}
+
+auto ExecutionBlockImpl<RemoteExecutor>::execute(AqlCallStack stack)
+    -> std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> {
+  traceExecuteBegin(stack);
+  auto res = executeWithoutTrace(stack);
+  return traceExecuteEnd(res);
+}
+
+auto ExecutionBlockImpl<RemoteExecutor>::executeWithoutTrace(AqlCallStack stack)
+-> std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> {
+  if (ADB_UNLIKELY(api() == Api::GET_SOME)) {
+    return executeViaOldApi(stack);
+  }
+  TRI_ASSERT(api() == Api::EXECUTE);
+  return executeViaNewApi(stack);
+}
+
+auto ExecutionBlockImpl<RemoteExecutor>::executeViaNewApi(AqlCallStack callStack)
+    -> std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> {
+  // silence tests -- we need to introduce new failure tests for fetchers
+  TRI_IF_FAILURE("ExecutionBlock::getOrSkipSome1") {
+    THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
+  }
+  TRI_IF_FAILURE("ExecutionBlock::getOrSkipSome2") {
+    THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
+  }
+  TRI_IF_FAILURE("ExecutionBlock::getOrSkipSome3") {
+    THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
+  }
+
+  if (getQuery().killed()) {
+    THROW_ARANGO_EXCEPTION(TRI_ERROR_QUERY_KILLED);
+  }
+
+  std::unique_lock<std::mutex> guard(_communicationMutex);
+
+  if (_requestInFlight) {
+    // Already sent a shutdown request, but haven't got an answer yet.
+    return {ExecutionState::WAITING, 0, nullptr};
+  }
+
+  // For every call we simply forward via HTTP
+  if (_lastError.fail()) {
+    TRI_ASSERT(_lastResponse == nullptr);
+    Result res = std::move(_lastError);
+    _lastError.reset();
+    // we were called with an error need to throw it.
+    THROW_ARANGO_EXCEPTION(res);
+  }
+
+  if (_lastResponse != nullptr) {
+    TRI_ASSERT(_lastError.ok());
+    // We do not have an error but a result, all is good
+    // We have an open result still.
+    auto response = std::move(_lastResponse);
+    // Result is the response which will be a serialized AqlItemBlock
+
+    // both must be reset before return or throw
+    TRI_ASSERT(_lastError.ok() && _lastResponse == nullptr);
+
+    VPackSlice responseBody = response->slice();
+
+    auto result = deserializeExecuteCallResultBody(responseBody);
+
+    if (result.fail()) {
+      THROW_ARANGO_EXCEPTION(result.result());
+    }
+
+    return result->asTuple();
+  }
+
+  // We need to send a request here
+  auto buffer = serializeExecuteCallBody(callStack);
+  this->traceExecuteRequest(VPackSlice(buffer.data()), callStack);
+
+  auto res = sendAsyncRequest(fuerte::RestVerb::Put,
+                              RestAqlHandler::Route::execute(), std::move(buffer));
+
+  if (!res.ok()) {
+    THROW_ARANGO_EXCEPTION(res);
+  }
+
+  return {ExecutionState::WAITING, 0, nullptr};
+}
+
+auto ExecutionBlockImpl<RemoteExecutor>::deserializeExecuteCallResultBody(VPackSlice const slice) const
+    -> ResultT<AqlExecuteResult> {
+  // Errors should have been caught earlier
+  TRI_ASSERT(TRI_ERROR_NO_ERROR ==
+             VelocyPackHelper::getNumericValue<int>(slice, StaticStrings::Code, -1));
+
+  if (ADB_UNLIKELY(!slice.isObject())) {
+    using namespace std::string_literals;
+    return Result{TRI_ERROR_TYPE_ERROR, "When parsing execute result: expected object, got "s + slice.typeName()};
+  }
+
+  if (auto value = slice.get(StaticStrings::AqlRemoteResult); !value.isNone()) {
+    return AqlExecuteResult::fromVelocyPack(value, _engine->itemBlockManager());
+  }
+
+  return Result{TRI_ERROR_TYPE_ERROR, "When parsing execute result: field result missing"};
+}
+
+auto ExecutionBlockImpl<RemoteExecutor>::serializeExecuteCallBody(AqlCallStack const& callStack) const
+    -> VPackBuffer<uint8_t> {
+  VPackBuffer<uint8_t> buffer;
+  {
+    VPackBuilder builder(buffer);
+    builder.openObject();
+    builder.add(VPackValue(StaticStrings::AqlRemoteCallStack));
+    callStack.toVelocyPack(builder);
+    builder.close();
+  }
+  return buffer;
+}
+
+auto ExecutionBlockImpl<RemoteExecutor>::api() const noexcept -> Api {
+  return _apiToUse;
 }
 
 namespace {
@@ -532,7 +652,7 @@ Result ExecutionBlockImpl<RemoteExecutor>::sendAsyncRequest(fuerte::RestVerb typ
 
   auto req = fuerte::createRequest(type, fuerte::ContentType::VPack);
   req->header.database = _query.vocbase().name();
-  req->header.path = urlPart + _queryId;
+  req->header.path = urlPart + "/" + _queryId;
   req->addVPack(std::move(body));
 
   // Later, we probably want to set these sensibly:
@@ -575,6 +695,12 @@ Result ExecutionBlockImpl<RemoteExecutor>::sendAsyncRequest(fuerte::RestVerb typ
   return {TRI_ERROR_NO_ERROR};
 }
 
+void ExecutionBlockImpl<RemoteExecutor>::traceExecuteRequest(VPackSlice const slice,
+                                                             AqlCallStack const& callStack) {
+  using namespace std::string_literals;
+  traceRequest("execute", slice, "callStack="s + callStack.toString());
+}
+
 void ExecutionBlockImpl<RemoteExecutor>::traceGetSomeRequest(VPackSlice const slice,
                                                              size_t const atMost) {
   using namespace std::string_literals;
diff --git a/arangod/Aql/RemoteExecutor.h b/arangod/Aql/RemoteExecutor.h
index 480033c9f32d..49244489cf00 100644
--- a/arangod/Aql/RemoteExecutor.h
+++ b/arangod/Aql/RemoteExecutor.h
@@ -23,17 +23,20 @@
 #ifndef ARANGOD_AQL_REMOTE_EXECUTOR_H
 #define ARANGOD_AQL_REMOTE_EXECUTOR_H
 
+#include "Aql/AqlExecuteResult.h"
 #include "Aql/ClusterNodes.h"
 #include "Aql/ExecutionBlockImpl.h"
 #include "Aql/ExecutorInfos.h"
 
+#include <fuerte/message.h>
+
 #include <mutex>
 
-#include <fuerte/message.h>
-#include <fuerte/types.h>
+namespace arangodb::fuerte { inline namespace v1 {
+enum class RestVerb;
+}}
 
-namespace arangodb {
-namespace aql {
+namespace arangodb::aql {
 
 // The RemoteBlock is actually implemented by specializing ExecutionBlockImpl,
 // so this class only exists to identify the specialization.
@@ -45,12 +48,14 @@ class RemoteExecutor final {};
 template <>
 class ExecutionBlockImpl<RemoteExecutor> : public ExecutionBlock {
  public:
+  using Api = ::arangodb::aql::RemoteNode::Api;
+
   // TODO Even if it's not strictly necessary here, for consistency's sake the
   // non-standard arguments (server, ownName and queryId) should probably be
   // moved into some RemoteExecutorInfos class.
   ExecutionBlockImpl(ExecutionEngine* engine, RemoteNode const* node,
                      ExecutorInfos&& infos, std::string const& server,
-                     std::string const& ownName, std::string const& queryId);
+                     std::string const& ownName, std::string const& queryId, Api);
 
   ~ExecutionBlockImpl() override = default;
 
@@ -64,6 +69,8 @@ class ExecutionBlockImpl<RemoteExecutor> : public ExecutionBlock {
 
   std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> execute(AqlCallStack stack) override;
 
+  [[nodiscard]] auto api() const noexcept -> Api;
+
 #ifdef ARANGODB_ENABLE_MAINTAINER_MODE
   // only for asserts:
  public:
@@ -77,6 +84,20 @@ class ExecutionBlockImpl<RemoteExecutor> : public ExecutionBlock {
 
   std::pair<ExecutionState, size_t> skipSomeWithoutTrace(size_t atMost);
 
+  auto executeWithoutTrace(AqlCallStack stack)
+      -> std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr>;
+
+  auto executeViaOldApi(AqlCallStack stack)
+      -> std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr>;
+
+  auto executeViaNewApi(AqlCallStack stack)
+      -> std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr>;
+
+  [[nodiscard]] auto deserializeExecuteCallResultBody(velocypack::Slice) const
+      -> ResultT<AqlExecuteResult>;
+  [[nodiscard]] auto serializeExecuteCallBody(AqlCallStack const& callStack) const
+      -> velocypack::Buffer<uint8_t>;
+
   ExecutorInfos const& infos() const { return _infos; }
 
   Query const& getQuery() const { return _query; }
@@ -89,6 +110,13 @@ class ExecutionBlockImpl<RemoteExecutor> : public ExecutionBlock {
   // _communicationMutex *must* be locked for this!
   unsigned generateRequestTicket();
 
+  void traceExecuteRequest(velocypack::Slice slice, AqlCallStack const& callStack);
+  void traceGetSomeRequest(velocypack::Slice slice, size_t atMost);
+  void traceSkipSomeRequest(velocypack::Slice slice, size_t atMost);
+  void traceInitializeCursorRequest(velocypack::Slice slice);
+  void traceShutdownRequest(velocypack::Slice slice, int errorCode);
+  void traceRequest(const char* rpc, velocypack::Slice slice, std::string const& args);
+
  private:
   enum class ReqState {
     None,
@@ -133,14 +161,11 @@ class ExecutionBlockImpl<RemoteExecutor> : public ExecutionBlock {
 
   bool _hasTriggeredShutdown;
 
-  void traceGetSomeRequest(velocypack::Slice slice, size_t atMost);
-  void traceSkipSomeRequest(velocypack::Slice slice, size_t atMost);
-  void traceInitializeCursorRequest(velocypack::Slice slice);
-  void traceShutdownRequest(velocypack::Slice slice, int errorCode);
-  void traceRequest(const char* rpc, velocypack::Slice slice, std::string const& args);
+  /// @brief Whether to use the pre-3.7 getSome/skipSome API, instead of the
+  ///        execute API. Used for rolling upgrades, so can be removed in 3.8.
+  Api _apiToUse = Api::EXECUTE;
 };
 
-}  // namespace aql
 }  // namespace arangodb
 
 #endif  // ARANGOD_AQL_REMOTE_EXECUTOR_H
diff --git a/arangod/Aql/RestAqlHandler.cpp b/arangod/Aql/RestAqlHandler.cpp
index 366f65e4555f..58346af21a67 100644
--- a/arangod/Aql/RestAqlHandler.cpp
+++ b/arangod/Aql/RestAqlHandler.cpp
@@ -621,7 +621,7 @@ auto getStringView(velocypack::Slice slice) -> std::string_view {
   velocypack::StringRef ref = slice.stringRef();
   return std::string_view(ref.data(), ref.size());
 }
-}
+}  // namespace
 
 // TODO Use the deserializer when available
 auto AqlExecuteCall::fromVelocyPack(VPackSlice const slice) -> ResultT<AqlExecuteCall> {
@@ -641,7 +641,7 @@ auto AqlExecuteCall::fromVelocyPack(VPackSlice const slice) -> ResultT<AqlExecut
     auto const keySlice = it.key;
     if (ADB_UNLIKELY(!keySlice.isString())) {
       return Result(TRI_ERROR_CLUSTER_AQL_COMMUNICATION,
-          "When deserializating AqlExecuteCall: Key is not a string");
+                    "When deserializating AqlExecuteCall: Key is not a string");
     }
     auto const key = getStringView(keySlice);
 
@@ -658,7 +658,8 @@ auto AqlExecuteCall::fromVelocyPack(VPackSlice const slice) -> ResultT<AqlExecut
     if (key == StaticStrings::AqlRemoteCallStack) {
       auto maybeCallStack = AqlCallStack::fromVelocyPack(it.value);
       if (ADB_UNLIKELY(maybeCallStack.fail())) {
-        auto message = std::string{"When deserializating AqlExecuteCall: failed to deserialize "};
+        auto message = std::string{
+            "When deserializating AqlExecuteCall: failed to deserialize "};
         message += StaticStrings::AqlRemoteCallStack;
         message += ": ";
         message += maybeCallStack.errorMessage();
@@ -677,7 +678,8 @@ auto AqlExecuteCall::fromVelocyPack(VPackSlice const slice) -> ResultT<AqlExecut
 
   for (auto const& it : expectedPropertiesFound) {
     if (ADB_UNLIKELY(!it.second)) {
-      auto message = std::string{"When deserializating AqlExecuteCall: missing key "};
+      auto message =
+          std::string{"When deserializating AqlExecuteCall: missing key "};
       message += it.first;
       return Result(TRI_ERROR_CLUSTER_AQL_COMMUNICATION, std::move(message));
     }
@@ -756,6 +758,7 @@ RestStatus RestAqlHandler::handleUseQuery(std::string const& operation,
     }
 
     auto result = AqlExecuteResult{state, skipped, std::move(items)};
+    answerBuilder.add(VPackValue(StaticStrings::AqlRemoteResult));
     result.toVelocyPack(answerBuilder,
                         _query->trx()->transactionContextPtr()->getVPackOptions());
     answerBuilder.add(StaticStrings::Code, VPackValue(TRI_ERROR_NO_ERROR));
diff --git a/arangod/Aql/RestAqlHandler.h b/arangod/Aql/RestAqlHandler.h
index c917c6a2f1ca..47f469840aad 100644
--- a/arangod/Aql/RestAqlHandler.h
+++ b/arangod/Aql/RestAqlHandler.h
@@ -54,7 +54,12 @@ class RestAqlHandler : public RestVocbaseBaseHandler {
   RestStatus execute() override;
   RestStatus continueExecute() override;
   void shutdownExecute(bool isFinalized) noexcept override;
-  
+
+  class Route {
+   public:
+    static auto execute() -> const char* { return "/_api/aql/execute"; }
+  };
+
  public:
   // DELETE method for /_api/aql/kill/<queryId>, (internal)
   bool killQuery(std::string const& idString);
@@ -70,14 +75,15 @@ class RestAqlHandler : public RestVocbaseBaseHandler {
   //   "callStack": an array of objects, each with the following attributes:
   //     "offset": a non-negative integer
   //     "limit": either a non-negative integer, or the string "infinity"
-  //     "limitType: string or null, either "soft" or "hard"; set iff limit is not infinity
-  //     "fullCount": a boolean
+  //     "limitType: string or null, either "soft" or "hard"; set iff limit is
+  //     not infinity "fullCount": a boolean
   //   The result is an object with the attributes
   //     "code": integer, error code.
   //        If there was no error:
-  //     "state": string, either "hasMore" or "done"
-  //     "skipped": non-negative integer
-  //     "result": serialized AqlItemBlock, or null when no rows are returned.
+  //     "result": an object with the following attributes:
+  //       "state": string, either "hasMore" or "done"
+  //       "skipped": non-negative integer
+  //       "block": serialized AqlItemBlock, or null when no rows are returned.
   // For the "getSome" operation one has to give:
   //   "atMost": must be a positive integer, the cursor returns never
   //             more than "atMost" items. Defaults to
@@ -141,7 +147,7 @@ class RestAqlHandler : public RestVocbaseBaseHandler {
                                 std::shared_ptr<transaction::Context> const& ctx,
                                 double const ttl, bool& needToLock,
                                 arangodb::velocypack::Builder& answer);
-  
+
   // handle for useQuery
   RestStatus handleUseQuery(std::string const&, arangodb::velocypack::Slice const);
 
@@ -157,9 +163,9 @@ class RestAqlHandler : public RestVocbaseBaseHandler {
 
   // our traversal engine registry
   traverser::TraverserEngineRegistry* _traverserRegistry;
-  
+
   aql::Query* _query;
-  
+
   // id of current query
   QueryId _qId;
 };
diff --git a/lib/Basics/StaticStrings.cpp b/lib/Basics/StaticStrings.cpp
index dc44f9502536..4a36d9d71ce1 100644
--- a/lib/Basics/StaticStrings.cpp
+++ b/lib/Basics/StaticStrings.cpp
@@ -56,7 +56,8 @@ std::string const StaticStrings::ReturnNewString("returnNew");
 std::string const StaticStrings::ReturnOldString("returnOld");
 std::string const StaticStrings::SilentString("silent");
 std::string const StaticStrings::WaitForSyncString("waitForSync");
-std::string const StaticStrings::SkipDocumentValidation("skipDocumentValidation");
+std::string const StaticStrings::SkipDocumentValidation(
+    "skipDocumentValidation");
 std::string const StaticStrings::IsSynchronousReplicationString(
     "isSynchronousReplication");
 std::string const StaticStrings::Group("group");
@@ -307,6 +308,7 @@ std::string const StaticStrings::AqlRemoteLimitTypeHard("hard");
 std::string const StaticStrings::AqlRemoteFullCount("fullCount");
 std::string const StaticStrings::AqlRemoteOffset("offset");
 std::string const StaticStrings::AqlRemoteInfinity("infinity");
+std::string const StaticStrings::AqlRemoteResult("result");
 std::string const StaticStrings::AqlRemoteBlock("block");
 std::string const StaticStrings::AqlRemoteSkipped("skipped");
 std::string const StaticStrings::AqlRemoteState("state");
diff --git a/lib/Basics/StaticStrings.h b/lib/Basics/StaticStrings.h
index d51660ec654d..b5e180ec1fd4 100644
--- a/lib/Basics/StaticStrings.h
+++ b/lib/Basics/StaticStrings.h
@@ -283,6 +283,7 @@ class StaticStrings {
   static std::string const AqlRemoteFullCount;
   static std::string const AqlRemoteOffset;
   static std::string const AqlRemoteInfinity;
+  static std::string const AqlRemoteResult;
   static std::string const AqlRemoteBlock;
   static std::string const AqlRemoteSkipped;
   static std::string const AqlRemoteState;
diff --git a/tests/Aql/RemoteExecutorTest.cpp b/tests/Aql/RemoteExecutorTest.cpp
new file mode 100644
index 000000000000..c5e4bef76825
--- /dev/null
+++ b/tests/Aql/RemoteExecutorTest.cpp
@@ -0,0 +1,217 @@
+////////////////////////////////////////////////////////////////////////////////
+/// DISCLAIMER
+///
+/// Copyright 2020 ArangoDB GmbH, Cologne, Germany
+///
+/// Licensed under the Apache License, Version 2.0 (the "License");
+/// you may not use this file except in compliance with the License.
+/// You may obtain a copy of the License at
+///
+///     http://www.apache.org/licenses/LICENSE-2.0
+///
+/// Unless required by applicable law or agreed to in writing, software
+/// distributed under the License is distributed on an "AS IS" BASIS,
+/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+/// See the License for the specific language governing permissions and
+/// limitations under the License.
+///
+/// Copyright holder is ArangoDB GmbH, Cologne, Germany
+///
+/// @author Tobias Gödderz
+////////////////////////////////////////////////////////////////////////////////
+
+#include "Aql/AqlCall.h"
+#include "Aql/AqlCallStack.h"
+#include "Aql/AqlExecuteResult.h"
+#include "Aql/AqlItemBlockManager.h"
+
+#include "AqlItemBlockHelper.h"
+
+#include "gtest/gtest.h"
+
+#include <velocypack/Builder.h>
+
+using namespace arangodb;
+using namespace arangodb::aql;
+
+namespace arangodb::aql {
+
+auto operator==(AqlCallStack const& leftC, AqlCallStack const& rightC) -> bool {
+  auto left = leftC;
+  auto right = rightC;
+
+  while (!left.empty() && !right.empty()) {
+    auto const l = left.popCall();
+    auto const r = right.popCall();
+    if (!(l == r)) {
+      return false;
+    }
+  }
+
+  return left.empty() && right.empty();
+}
+
+auto operator==(AqlExecuteResult const& left, AqlExecuteResult const& right) -> bool {
+  return left.state() == right.state() && left.skipped() == right.skipped() &&
+         (left.block() == nullptr) == (right.block() == nullptr) &&
+         (left.block() == nullptr || *left.block() == *right.block());
+}
+
+}  // namespace arangodb::aql
+
+namespace arangodb::tests::aql {
+
+auto blockToString(SharedAqlItemBlockPtr const& block) -> std::string {
+  velocypack::Builder blockBuilder;
+  block->toSimpleVPack(&velocypack::Options::Defaults, blockBuilder);
+  return blockBuilder.toJson();
+}
+
+class DeSerializeAqlCallTest : public ::testing::TestWithParam<AqlCall> {
+ public:
+  DeSerializeAqlCallTest() = default;
+
+  void SetUp() override {
+    aqlCall = GetParam();
+  }
+
+ protected:
+  AqlCall aqlCall{};
+};
+
+auto const testingAqlCalls = ::testing::ValuesIn(std::array{
+    AqlCall{0, false, AqlCall::Infinity{}},
+    AqlCall{3, false, AqlCall::Infinity{}},
+    AqlCall{0, false, 7, AqlCall::LimitType::SOFT},
+    AqlCall{0, false, 7, AqlCall::LimitType::HARD},
+    AqlCall{0, true, 7, AqlCall::LimitType::HARD},
+    AqlCall{3, false, 7, AqlCall::LimitType::SOFT},
+    AqlCall{3, false, 7, AqlCall::LimitType::HARD},
+    AqlCall{3, true, 7, AqlCall::LimitType::HARD},
+});
+
+TEST_P(DeSerializeAqlCallTest, testSuite) {
+  auto builder = velocypack::Builder{};
+  aqlCall.toVelocyPack(builder);
+
+  ASSERT_TRUE(builder.isClosed());
+
+  auto const maybeDeSerializedCall = std::invoke([&]() {
+    try {
+      return AqlCall::fromVelocyPack(builder.slice());
+    } catch (std::exception const& ex) {
+      EXPECT_TRUE(false) << ex.what();
+    }
+    return ResultT<AqlCall>::error(-1);
+  });
+
+  ASSERT_TRUE(maybeDeSerializedCall.ok()) << maybeDeSerializedCall.errorMessage();
+
+  auto const deSerializedCall = *maybeDeSerializedCall;
+
+  ASSERT_EQ(aqlCall, deSerializedCall);
+}
+
+INSTANTIATE_TEST_CASE_P(DeSerializeAqlCallTestVariations, DeSerializeAqlCallTest, testingAqlCalls);
+
+class DeSerializeAqlCallStackTest : public ::testing::TestWithParam<AqlCallStack> {
+ public:
+  DeSerializeAqlCallStackTest() = default;
+
+  void SetUp() override {
+    aqlCallStack = GetParam();
+  }
+
+ protected:
+  AqlCallStack aqlCallStack{AqlCall{}};
+};
+
+auto const testingAqlCallStacks = ::testing::ValuesIn(std::array{
+  AqlCallStack{AqlCall{}},
+  AqlCallStack{AqlCall{3, false, AqlCall::Infinity{}}},
+  AqlCallStack{AqlCallStack{AqlCall{}}, AqlCall{3, false, AqlCall::Infinity{}}},
+  AqlCallStack{AqlCallStack{AqlCallStack{AqlCall{1}}, AqlCall{2}}, AqlCall{3}},
+  AqlCallStack{AqlCallStack{AqlCallStack{AqlCall{3}}, AqlCall{2}}, AqlCall{1}},
+});
+
+TEST_P(DeSerializeAqlCallStackTest, testSuite) {
+  auto builder = velocypack::Builder{};
+  aqlCallStack.toVelocyPack(builder);
+
+  ASSERT_TRUE(builder.isClosed());
+
+  auto const maybeDeSerializedCallStack = std::invoke([&]() {
+    try {
+      return AqlCallStack::fromVelocyPack(builder.slice());
+    } catch (std::exception const& ex) {
+      EXPECT_TRUE(false) << ex.what();
+    }
+    return ResultT<AqlCallStack>::error(-1);
+  });
+
+  ASSERT_TRUE(maybeDeSerializedCallStack.ok()) << maybeDeSerializedCallStack.errorMessage();
+
+  auto const deSerializedCallStack = *maybeDeSerializedCallStack;
+
+  ASSERT_EQ(aqlCallStack, deSerializedCallStack);
+}
+
+INSTANTIATE_TEST_CASE_P(DeSerializeAqlCallStackTestVariations, DeSerializeAqlCallStackTest, testingAqlCallStacks);
+
+
+class DeSerializeAqlExecuteResultTest : public ::testing::TestWithParam<AqlExecuteResult> {
+ public:
+  DeSerializeAqlExecuteResultTest() = default;
+
+  void SetUp() override {
+    aqlExecuteResult = GetParam();
+  }
+
+ protected:
+  AqlExecuteResult aqlExecuteResult{ExecutionState::DONE, 0, nullptr};
+};
+
+ResourceMonitor resourceMonitor{};
+AqlItemBlockManager manager{&resourceMonitor, SerializationFormat::SHADOWROWS};
+
+auto const testingAqlExecuteResults = ::testing::ValuesIn(std::array{
+    AqlExecuteResult{ExecutionState::DONE, 0, nullptr},
+    AqlExecuteResult{ExecutionState::HASMORE, 0, nullptr},
+    AqlExecuteResult{ExecutionState::HASMORE, 4, nullptr},
+    AqlExecuteResult{ExecutionState::DONE, 0, buildBlock<1>(manager, {{42}})},
+    AqlExecuteResult{ExecutionState::HASMORE, 3, buildBlock<2>(manager, {{3, 42}, {4, 41}})},
+});
+
+TEST_P(DeSerializeAqlExecuteResultTest, testSuite) {
+  auto builder = velocypack::Builder{};
+  aqlExecuteResult.toVelocyPack(builder, &velocypack::Options::Defaults);
+
+  ASSERT_TRUE(builder.isClosed());
+
+  auto const maybeAqlExecuteResult = std::invoke([&]() {
+    try {
+      return AqlExecuteResult::fromVelocyPack(builder.slice(), manager);
+    } catch (std::exception const& ex) {
+      EXPECT_TRUE(false) << ex.what();
+    }
+    return ResultT<AqlExecuteResult>::error(-1);
+  });
+
+  ASSERT_TRUE(maybeAqlExecuteResult.ok()) << maybeAqlExecuteResult.errorMessage();
+
+  auto const deSerializedAqlExecuteResult = *maybeAqlExecuteResult;
+
+  ASSERT_EQ(aqlExecuteResult.state(), deSerializedAqlExecuteResult.state());
+  ASSERT_EQ(aqlExecuteResult.skipped(), deSerializedAqlExecuteResult.skipped());
+  ASSERT_EQ(aqlExecuteResult.block() == nullptr, deSerializedAqlExecuteResult.block() == nullptr);
+  if (aqlExecuteResult.block() != nullptr) {
+    ASSERT_EQ(*aqlExecuteResult.block(), *deSerializedAqlExecuteResult.block())
+        << "left: " << blockToString(aqlExecuteResult.block())
+        << "; right: " << blockToString(deSerializedAqlExecuteResult.block());
+  }
+  ASSERT_EQ(aqlExecuteResult, deSerializedAqlExecuteResult);
+}
+
+INSTANTIATE_TEST_CASE_P(DeSerializeAqlExecuteResultTestVariations, DeSerializeAqlExecuteResultTest, testingAqlExecuteResults);
+
+}  // namespace arangodb::tests::aql
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 9df5c6a01515..b557ccf6498d 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -57,6 +57,7 @@ set(ARANGODB_TESTS_SOURCES
   Aql/MultiDependencySingleRowFetcherTest.cpp
   Aql/NoResultsExecutorTest.cpp
   Aql/QueryHelper.cpp
+  Aql/RemoteExecutorTest.cpp
   Aql/RemoveExecutorTest.cpp
   Aql/ReplaceExecutorTest.cpp
   Aql/ReturnExecutorTest.cpp

From 98c7eb623d80f61cde5fd02e0edfb2d345e9c2d2 Mon Sep 17 00:00:00 2001
From: Lars Maier <lars@arangodb.com>
Date: Sat, 29 Feb 2020 08:25:12 +0100
Subject: [PATCH 089/122] Added test for distinct collect with random order.
 (#11184)

---
 tests/Aql/DistinctCollectExecutorTest.cpp | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/tests/Aql/DistinctCollectExecutorTest.cpp b/tests/Aql/DistinctCollectExecutorTest.cpp
index 060ad80677ba..3a0693a0fdc7 100644
--- a/tests/Aql/DistinctCollectExecutorTest.cpp
+++ b/tests/Aql/DistinctCollectExecutorTest.cpp
@@ -94,6 +94,20 @@ TEST_P(DistinctCollectExecutorTest, split_1) {
       .run();
 }
 
+TEST_P(DistinctCollectExecutorTest, split_3) {
+  auto [split] = GetParam();
+
+  ExecutorTestHelper(*fakedQuery)
+      .setExecBlock<DistinctCollectExecutor>(std::move(infos))
+      .setInputValueList(1, 2, 1, 2, 5, 4, 3, 3, 1, 2)
+      .setInputSplitType(split)
+      .setCall(AqlCall{2, AqlCall::Infinity{}, 2, true})
+      .expectOutputValueList(5, 4)
+      .expectSkipped(3)
+      .expectedState(ExecutionState::DONE)
+      .run();
+}
+
 TEST_P(DistinctCollectExecutorTest, split_2) {
   auto [split] = GetParam();
 

From 609b0ff197eef95ecddfd6a130133e38e18b1739 Mon Sep 17 00:00:00 2001
From: Lars Maier <lars@arangodb.com>
Date: Sat, 29 Feb 2020 08:32:10 +0100
Subject: [PATCH 090/122] Feature/aql subquery execution block impl execute
 implementation subquery executor (#11196)

* Intermediate commit, does not compile.

* New style for SubqueryExecutor.

* Removed bad assert.

* Reset subsqueryInitialised in skip.

Co-authored-by: Michael Hackstein <michael@arangodb.com>
---
 arangod/Aql/ExecutionBlockImpl.cpp |  15 +-
 arangod/Aql/SubqueryExecutor.cpp   | 202 +++++++++++-
 arangod/Aql/SubqueryExecutor.h     |  15 +-
 tests/Aql/ExecutorTestHelper.h     |   5 +-
 tests/Aql/SubqueryExecutorTest.cpp | 499 +++++++++++++++++++++++++++++
 tests/CMakeLists.txt               |   1 +
 6 files changed, 714 insertions(+), 23 deletions(-)
 create mode 100644 tests/Aql/SubqueryExecutorTest.cpp

diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index add3cf3dee85..31e98b72fed5 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -137,6 +137,7 @@ template <typename Executor>
 constexpr bool isNewStyleExecutor = is_one_of_v<
     Executor, FilterExecutor, SortedCollectExecutor, IdExecutor<ConstFetcher>,
     IdExecutor<SingleRowFetcher<BlockPassthrough::Enable>>, ReturnExecutor, DistinctCollectExecutor, IndexExecutor, EnumerateCollectionExecutor,
+    SubqueryExecutor<true>, SubqueryExecutor<false>,
     // TODO: re-enable after new subquery end & start are implemented
     // CalculationExecutor<CalculationType::Condition>, CalculationExecutor<CalculationType::Reference>, CalculationExecutor<CalculationType::V8Condition>,
     HashedCollectExecutor, ConstrainedSortExecutor,
@@ -1103,10 +1104,12 @@ template <class Executor>
 static SkipRowsRangeVariant constexpr skipRowsType() {
   bool constexpr useFetcher =
       Executor::Properties::allowsBlockPassthrough == BlockPassthrough::Enable &&
-      !std::is_same<Executor, SubqueryExecutor<true>>::value;
+      !std::is_same_v<Executor, SubqueryExecutor<true>>;
 
   bool constexpr useExecutor = hasSkipRowsRange<Executor>::value;
 
+  static_assert(!std::is_same_v<Executor, SubqueryExecutor<true>> || hasSkipRowsRange<Executor>::value);
+
   // ConstFetcher and SingleRowFetcher<BlockPassthrough::Enable> can skip, but
   // it may not be done for modification subqueries.
   static_assert(useFetcher ==
@@ -1124,6 +1127,7 @@ static SkipRowsRangeVariant constexpr skipRowsType() {
               Executor, FilterExecutor, ShortestPathExecutor, ReturnExecutor, KShortestPathsExecutor,
               IdExecutor<SingleRowFetcher<BlockPassthrough::Enable>>, IdExecutor<ConstFetcher>, HashedCollectExecutor,
               IndexExecutor, EnumerateCollectionExecutor, DistinctCollectExecutor, ConstrainedSortExecutor,
+              SubqueryExecutor<true>,
 #ifdef ARANGODB_USE_GOOGLE_TESTS
               TestLambdaSkipExecutor,
 #endif
@@ -1167,15 +1171,12 @@ static SkipRowsRangeVariant constexpr skipRowsType() {
   static_assert(
       !std::is_same<Executor, LimitExecutor>::value || useFetcher,
       "LimitExecutor needs to implement skipRows() to work correctly");
-
-  static_assert(useExecutor || useFetcher, "no skipping variant available");
-
+ 
   if constexpr (useExecutor) {
     return SkipRowsRangeVariant::EXECUTOR;
-  } else {
-    static_assert(useFetcher);
-    return SkipRowsRangeVariant::FETCHER;
   }
+  static_assert(useFetcher);
+  return SkipRowsRangeVariant::FETCHER;
 }
 
 // Let's do it the C++ way.
diff --git a/arangod/Aql/SubqueryExecutor.cpp b/arangod/Aql/SubqueryExecutor.cpp
index 8190e7367a97..72074816f0fe 100644
--- a/arangod/Aql/SubqueryExecutor.cpp
+++ b/arangod/Aql/SubqueryExecutor.cpp
@@ -21,12 +21,16 @@
 ////////////////////////////////////////////////////////////////////////////////
 
 #include "SubqueryExecutor.h"
+#include <Logger/LogMacros.h>
 
+#include "Aql/AqlCallStack.h"
 #include "Aql/ExecutionBlock.h"
 #include "Aql/ExecutionNode.h"
 #include "Aql/OutputAqlItemRow.h"
 #include "Aql/SingleRowFetcher.h"
 
+#define LOG_DEVEL_SQ LOG_DEVEL_IF(false)
+
 using namespace arangodb;
 using namespace arangodb::aql;
 
@@ -48,11 +52,12 @@ SubqueryExecutorInfos::SubqueryExecutorInfos(SubqueryExecutorInfos&& other) = de
 
 SubqueryExecutorInfos::~SubqueryExecutorInfos() = default;
 
-template<bool isModificationSubquery>
-SubqueryExecutor<isModificationSubquery>::SubqueryExecutor(Fetcher& fetcher, SubqueryExecutorInfos& infos)
+template <bool isModificationSubquery>
+SubqueryExecutor<isModificationSubquery>::SubqueryExecutor(Fetcher& fetcher,
+                                                           SubqueryExecutorInfos& infos)
     : _fetcher(fetcher),
       _infos(infos),
-      _state(ExecutionState::HASMORE),
+      _state(ExecutorState::HASMORE),
       _subqueryInitialized(false),
       _shutdownDone(false),
       _shutdownResult(TRI_ERROR_INTERNAL),
@@ -60,7 +65,7 @@ SubqueryExecutor<isModificationSubquery>::SubqueryExecutor(Fetcher& fetcher, Sub
       _subqueryResults(nullptr),
       _input(CreateInvalidInputRowHint{}) {}
 
-template<bool isModificationSubquery>
+template <bool isModificationSubquery>
 SubqueryExecutor<isModificationSubquery>::~SubqueryExecutor() = default;
 
 /**
@@ -70,9 +75,10 @@ SubqueryExecutor<isModificationSubquery>::~SubqueryExecutor() = default;
  * If we do not have a subquery ongoing, we fetch a row and we start a new Subquery and ask it for hasMore.
  */
 
-template<bool isModificationSubquery>
+template <bool isModificationSubquery>
 std::pair<ExecutionState, NoStats> SubqueryExecutor<isModificationSubquery>::produceRows(OutputAqlItemRow& output) {
-  if (_state == ExecutionState::DONE && !_input.isInitialized()) {
+#if 0
+  if (_state == ExecutorState::DONE && !_input.isInitialized()) {
     // We have seen DONE upstream, and we have discarded our local reference
     // to the last input, we will not be able to produce results anymore.
     return {_state, NoStats{}};
@@ -144,9 +150,93 @@ std::pair<ExecutionState, NoStats> SubqueryExecutor<isModificationSubquery>::pro
       _subqueryInitialized = true;
     }
   }
+#endif
+  TRI_ASSERT(false);
+  THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
 }
 
-template<bool isModificationSubquery>
+template <bool isModificationSubquery>
+auto SubqueryExecutor<isModificationSubquery>::produceRows(AqlItemBlockInputRange& input,
+                                                           OutputAqlItemRow& output)
+    -> std::tuple<ExecutorState, Stats, AqlCall> {
+  auto getUpstreamCall = [&]() {
+    AqlCall upstreamCall = output.getClientCall();
+    if constexpr (isModificationSubquery) {
+      upstreamCall = AqlCall{};
+    }
+
+    return upstreamCall;
+  };
+
+  LOG_DEVEL_SQ << uint64_t(this) <<  "produceRows " << output.getClientCall();
+
+  if (_state == ExecutorState::DONE && !_input.isInitialized()) {
+    // We have seen DONE upstream, and we have discarded our local reference
+    // to the last input, we will not be able to produce results anymore.
+    return {_state, NoStats{}, getUpstreamCall()};
+  }
+  while (true) {
+    if (_subqueryInitialized) {
+      // Continue in subquery
+
+      // Const case
+      if (_infos.isConst() && !_input.isFirstDataRowInBlock()) {
+        // Simply write
+        writeOutput(output);
+        LOG_DEVEL_SQ << uint64_t(this) << "wrote output is const " << _state << " " << getUpstreamCall();
+        return {_state, NoStats{}, getUpstreamCall()};
+      }
+
+      // Non const case, or first run in const
+      auto [state, skipped, block] = _subquery.execute(AqlCallStack(AqlCall{}));
+      TRI_ASSERT(skipped == 0);
+      // We get a result
+      if (block != nullptr) {
+        TRI_IF_FAILURE("SubqueryBlock::executeSubquery") {
+          THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
+        }
+
+        if (_infos.returnsData()) {
+          TRI_ASSERT(_subqueryResults != nullptr);
+          _subqueryResults->emplace_back(std::move(block));
+        }
+      }
+
+      // Subquery DONE
+      if (state == ExecutionState::DONE) {
+        writeOutput(output);
+        LOG_DEVEL_SQ << uint64_t(this) << "wrote output subquery done " << _state << " " << getUpstreamCall();
+        return {_state, NoStats{}, getUpstreamCall()};
+      }
+
+    } else {
+      // init new subquery
+      if (!_input) {
+        std::tie(_state, _input) = input.nextDataRow();
+        LOG_DEVEL_SQ << uint64_t(this) << " nextDataRow: " << _state << " " << _input.isInitialized();
+        if (!_input) {
+          LOG_DEVEL_SQ << uint64_t(this) << "exit produce, no more input" << _state;
+          return {_state, NoStats{}, getUpstreamCall()};
+        }
+      }
+
+      TRI_ASSERT(_input);
+      if (!_infos.isConst() || _input.isFirstDataRowInBlock()) {
+        auto initRes = _subquery.initializeCursor(_input);
+
+        if (initRes.second.fail()) {
+          // Error during initialize cursor
+          THROW_ARANGO_EXCEPTION(initRes.second);
+        }
+        _subqueryResults = std::make_unique<std::vector<SharedAqlItemBlockPtr>>();
+      }
+      // on const subquery we can retoggle init as soon as we have new input.
+      _subqueryInitialized = true;
+    }
+  }
+}
+
+template <bool isModificationSubquery>
 void SubqueryExecutor<isModificationSubquery>::writeOutput(OutputAqlItemRow& output) {
   _subqueryInitialized = false;
   TRI_IF_FAILURE("SubqueryBlock::getSome") {
@@ -175,24 +265,26 @@ void SubqueryExecutor<isModificationSubquery>::writeOutput(OutputAqlItemRow& out
   }
   _input = InputAqlItemRow(CreateInvalidInputRowHint{});
   TRI_ASSERT(output.produced());
+  output.advanceRow();
 }
 
 /// @brief shutdown, tell dependency and the subquery
-template<bool isModificationSubquery>
+template <bool isModificationSubquery>
 std::pair<ExecutionState, Result> SubqueryExecutor<isModificationSubquery>::shutdown(int errorCode) {
   // Note this shutdown needs to be repeatable.
   // Also note the ordering of this shutdown is different
   // from earlier versions we now shutdown subquery first
+  ExecutionState state = ExecutionState::DONE;
   if (!_shutdownDone) {
     // We take ownership of _state here for shutdown state
-    std::tie(_state, _shutdownResult) = _subquery.shutdown(errorCode);
-    if (_state == ExecutionState::WAITING) {
+    std::tie(state, _shutdownResult) = _subquery.shutdown(errorCode);
+    if (state == ExecutionState::WAITING) {
       TRI_ASSERT(_shutdownResult.ok());
       return {ExecutionState::WAITING, TRI_ERROR_NO_ERROR};
     }
     _shutdownDone = true;
   }
-  return {_state, _shutdownResult};
+  return {state, _shutdownResult};
 }
 
 template <bool isModificationSubquery>
@@ -202,5 +294,93 @@ SubqueryExecutor<isModificationSubquery>::fetchBlockForPassthrough(size_t atMost
   return {rv.first, {}, std::move(rv.second)};
 }
 
+template <>
+template <bool E, std::enable_if_t<E, int>>
+auto SubqueryExecutor<true>::skipRowsRange(AqlItemBlockInputRange& inputRange, AqlCall& call)
+    -> std::tuple<ExecutorState, Stats, size_t, AqlCall> {
+  auto getUpstreamCall = [&]() {
+    auto upstreamCall = AqlCall{};
+    return upstreamCall;
+  };
+
+  size_t skipped = 0;
+
+  LOG_DEVEL_SQ << uint64_t(this) <<  "skipRowsRange " << call;
+
+  if (_state == ExecutorState::DONE && !_input.isInitialized()) {
+    // We have seen DONE upstream, and we have discarded our local reference
+    // to the last input, we will not be able to produce results anymore.
+    return {_state, NoStats{}, 0, getUpstreamCall()};
+  }
+  while (true) {
+    if (_subqueryInitialized) {
+      // Continue in subquery
+
+      // Const case
+      if (_infos.isConst() && !_input.isFirstDataRowInBlock()) {
+        // Simply write
+        _subqueryInitialized = false;
+        _input = InputAqlItemRow(CreateInvalidInputRowHint{});
+        skipped += 1;
+        call.didSkip(1);
+        LOG_DEVEL_SQ << uint64_t(this) << "did skip one";
+        return {_state, NoStats{}, skipped, getUpstreamCall()};
+      }
+
+      // Non const case, or first run in const
+      auto [state, skipped, block] = _subquery.execute(AqlCallStack(AqlCall{}));
+      TRI_ASSERT(skipped == 0);
+      // We get a result
+      if (block != nullptr) {
+        TRI_IF_FAILURE("SubqueryBlock::executeSubquery") {
+          THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
+        }
+
+        if (_infos.returnsData()) {
+          TRI_ASSERT(_subqueryResults != nullptr);
+          _subqueryResults->emplace_back(std::move(block));
+        }
+      }
+
+      // Subquery DONE
+      if (state == ExecutionState::DONE) {
+        _subqueryInitialized = false;
+        _input = InputAqlItemRow(CreateInvalidInputRowHint{});
+        skipped += 1;
+        call.didSkip(1);
+        LOG_DEVEL_SQ << uint64_t(this) << "did skip one";
+        return {_state, NoStats{}, skipped, getUpstreamCall()};
+      }
+
+    } else {
+      // init new subquery
+      if (!_input) {
+        std::tie(_state, _input) = inputRange.nextDataRow();
+
+        if (!_input) {
+          LOG_DEVEL_SQ << uint64_t(this) << "skipped nothing waiting for input " << _state;
+          return {_state, NoStats{}, skipped, getUpstreamCall()};
+        }
+      }
+
+      TRI_ASSERT(_input);
+      if (!_infos.isConst() || _input.isFirstDataRowInBlock()) {
+        auto initRes = _subquery.initializeCursor(_input);
+
+        if (initRes.second.fail()) {
+          // Error during initialize cursor
+          THROW_ARANGO_EXCEPTION(initRes.second);
+        }
+        _subqueryResults = std::make_unique<std::vector<SharedAqlItemBlockPtr>>();
+      }
+      // on const subquery we can retoggle init as soon as we have new input.
+      _subqueryInitialized = true;
+    }
+  }
+}
+
 template class ::arangodb::aql::SubqueryExecutor<true>;
+template auto SubqueryExecutor<true>::skipRowsRange(AqlItemBlockInputRange& inputRange,
+                                                    AqlCall& call)
+    -> std::tuple<ExecutorState, Stats, size_t, AqlCall>;
 template class ::arangodb::aql::SubqueryExecutor<false>;
diff --git a/arangod/Aql/SubqueryExecutor.h b/arangod/Aql/SubqueryExecutor.h
index d78d9403eae0..c7fbee012be2 100644
--- a/arangod/Aql/SubqueryExecutor.h
+++ b/arangod/Aql/SubqueryExecutor.h
@@ -26,6 +26,8 @@
 #include "Aql/ExecutionState.h"
 #include "Aql/ExecutorInfos.h"
 #include "Aql/InputAqlItemRow.h"
+#include "Aql/AqlItemBlockInputRange.h"
+#include "Aql/AqlCall.h"
 #include "Aql/Stats.h"
 #include "Basics/Result.h"
 
@@ -63,7 +65,7 @@ class SubqueryExecutorInfos : public ExecutorInfos {
   bool const _isConst;
 };
 
-template<bool isModificationSubquery>
+template <bool isModificationSubquery>
 class SubqueryExecutor {
  public:
   struct Properties {
@@ -94,6 +96,15 @@ class SubqueryExecutor {
    */
   std::pair<ExecutionState, Stats> produceRows(OutputAqlItemRow& output);
 
+  [[nodiscard]] auto produceRows(AqlItemBlockInputRange& input, OutputAqlItemRow& output)
+      -> std::tuple<ExecutorState, Stats, AqlCall>;
+
+  // skipRowsRange <=> isModificationSubquery
+
+  template<bool E = isModificationSubquery, std::enable_if_t<E, int> = 0>
+  auto skipRowsRange(AqlItemBlockInputRange& inputRange, AqlCall& call)
+  -> std::tuple<ExecutorState, Stats, size_t, AqlCall>;
+
   std::tuple<ExecutionState, Stats, SharedAqlItemBlockPtr> fetchBlockForPassthrough(size_t atMost);
 
  private:
@@ -108,7 +119,7 @@ class SubqueryExecutor {
   SubqueryExecutorInfos& _infos;
 
   // Upstream state, used to determine if we are done with all subqueries
-  ExecutionState _state;
+  ExecutorState _state;
 
   // Flag if the current subquery is initialized and worked on
   bool _subqueryInitialized;
diff --git a/tests/Aql/ExecutorTestHelper.h b/tests/Aql/ExecutorTestHelper.h
index 718c91b62054..c3b2686246f1 100644
--- a/tests/Aql/ExecutorTestHelper.h
+++ b/tests/Aql/ExecutorTestHelper.h
@@ -38,7 +38,6 @@
 #include "Aql/ExecutionEngine.h"
 #include "Aql/ExecutionNode.h"
 #include "Aql/ExecutionState.h"
-#include "Aql/ExecutionEngine.h"
 #include "Aql/ExecutionStats.h"
 #include "Aql/OutputAqlItemRow.h"
 #include "Aql/Query.h"
@@ -162,7 +161,7 @@ struct Pipeline {
     return *this;
   }
 
-  ~Pipeline() {
+  virtual ~Pipeline() {
     for (auto&& b : _pipeline) {
       b.release();
     }
@@ -347,7 +346,7 @@ struct ExecutorTestHelper {
                                                    std::move(infos));
   }
 
-  auto setPipeline(Pipeline&& pipeline) -> ExecutorTestHelper& {
+  auto setPipeline(Pipeline pipeline) -> ExecutorTestHelper& {
     _pipeline = std::move(pipeline);
     return *this;
   }
diff --git a/tests/Aql/SubqueryExecutorTest.cpp b/tests/Aql/SubqueryExecutorTest.cpp
new file mode 100644
index 000000000000..ceb03c5ec074
--- /dev/null
+++ b/tests/Aql/SubqueryExecutorTest.cpp
@@ -0,0 +1,499 @@
+////////////////////////////////////////////////////////////////////////////////
+/// DISCLAIMER
+///
+/// Copyright 2019 ArangoDB GmbH, Cologne, Germany
+///
+/// Licensed under the Apache License, Version 2.0 (the "License");
+/// you may not use this file except in compliance with the License.
+/// You may obtain a copy of the License at
+///
+///     http://www.apache.org/licenses/LICENSE-2.0
+///
+/// Unless required by applicable law or agreed to in writing, software
+/// distributed under the License is distributed on an "AS IS" BASIS,
+/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+/// See the License for the specific language governing permissions and
+/// limitations under the License.
+///
+/// Copyright holder is ArangoDB GmbH, Cologne, Germany
+///
+/// @author Markus Pfeiffer
+////////////////////////////////////////////////////////////////////////////////
+
+#include "gtest/gtest.h"
+
+#include "AqlItemBlockHelper.h"
+#include "Mocks/Servers.h"
+#include "TestEmptyExecutorHelper.h"
+#include "TestExecutorHelper.h"
+#include "TestLambdaExecutor.h"
+#include "WaitingExecutionBlockMock.h"
+#include "fakeit.hpp"
+
+#include "Aql/AqlCallStack.h"
+#include "Aql/AqlItemBlock.h"
+#include "Aql/AqlItemBlockSerializationFormat.h"
+#include "Aql/ConstFetcher.h"
+#include "Aql/ExecutionBlockImpl.h"
+#include "Aql/ExecutionEngine.h"
+#include "Aql/IdExecutor.h"
+#include "Aql/Query.h"
+#include "Aql/RegisterPlan.h"
+#include "Aql/ReturnExecutor.h"
+#include "Aql/SingleRowFetcher.h"
+#include "Aql/SubqueryExecutor.h"
+#include "Transaction/Context.h"
+#include "Transaction/Methods.h"
+
+#include "Aql/ExecutorTestHelper.h"
+#include "Aql/TestLambdaExecutor.h"
+#include "Aql/WaitingExecutionBlockMock.h"
+
+using namespace arangodb;
+using namespace arangodb::aql;
+using namespace arangodb::tests;
+using namespace arangodb::tests::aql;
+using namespace arangodb::basics;
+
+using SubqueryExecutorTestHelper = ExecutorTestHelper<1, 1>;
+using SubqueryExecutorSplitType = SubqueryExecutorTestHelper::SplitType;
+using SubqueryExecutorParamType = std::tuple<SubqueryExecutorSplitType>;
+
+using RegisterSet = std::unordered_set<RegisterId>;
+using LambdaExePassThrough = TestLambdaExecutor;
+using LambdaExe = TestLambdaSkipExecutor;
+
+// This will maintain another deque of ExecutionBlocks
+// Which represents the content of the Subquery.
+// Note this cannot be concated with any other pipeline.
+struct SubqueryPipeline : public Pipeline {
+  explicit SubqueryPipeline(ExecBlock subquery, ExecBlock singleton)
+      : Pipeline(std::move(subquery)),
+        _subquery(get().front().get() /* == subquery */) {
+    // must be of type SubqueryExecutor
+    TRI_ASSERT(dynamic_cast<SubqueryExecutor<true>*>(_subquery) != nullptr ||
+               dynamic_cast<SubqueryExecutor<false>*>(_subquery) != nullptr);
+    // We always need to start with a singleton
+    TRI_ASSERT(dynamic_cast<IdExecutor<ConstFetcher>*>(singleton.get()) != nullptr);
+    _subqueryPipeline.emplace_back(std::move(singleton));
+  }
+
+  Pipeline& addSubqueryConsumer(ExecBlock&& consumer) {
+    TRI_ASSERT(!_subqueryPipeline.empty());
+    consumer->addDependency(_subqueryPipeline.front().get());
+    _subqueryPipeline.emplace_front(std::move(consumer));
+
+    return *this;
+  }
+
+  ExecutionBlock& getSubquery() const { return *_subquery; }
+
+ private:
+  ExecutionBlock* _subquery;
+  PipelineStorage _subqueryPipeline;
+};
+
+class SubqueryExecutorIntegrationTest
+    : public AqlExecutorTestCaseWithParam<SubqueryExecutorParamType, false> {
+ protected:
+  ExecutorTestHelper<1, 1> executorTestHelper;
+
+  SubqueryExecutorIntegrationTest() : executorTestHelper(*fakedQuery) {}
+
+  // returns a new pipeline that contains body as a subquery
+  auto createSubquery(Pipeline body) -> Pipeline {
+
+    /*
+        auto subqueryEnd = createSubqueryEndExecutionBlock();
+        if (!body.empty()) {
+          subqueryEnd->addDependency(body.get().front().get());
+        }
+        body.get().emplace_front(std::move(subqueryEnd));
+
+        auto subqueryStart = createSubqueryStartExecutionBlock();
+        // This exists because we at least added the subqueryEnd
+        body.get().back()->addDependency(subqueryStart.get());
+
+        body.get().emplace_back(std::move(subqueryStart));
+    */
+    return std::move(body);
+  }
+
+  auto createSubquery() -> Pipeline { return createSubquery(Pipeline()); }
+
+  auto createDoNothingPipeline() -> Pipeline {
+    auto numRegs = size_t{1};
+    auto emptyRegisterList = std::make_shared<std::unordered_set<RegisterId>>(
+        std::initializer_list<RegisterId>{});
+
+    auto inRegisterList = std::make_shared<std::unordered_set<RegisterId>>(
+        std::initializer_list<RegisterId>{0});
+    auto outRegisterList = std::make_shared<std::unordered_set<RegisterId>>(
+        std::initializer_list<RegisterId>{1});
+
+    std::unordered_set<RegisterId> toKeep;
+
+    for (RegisterId r = 0; r < numRegs; ++r) {
+      toKeep.emplace(r);
+    }
+
+    auto infos = LambdaExe::Infos(inRegisterList, outRegisterList, 1, 2, {},
+                                  toKeep, createProduceCall(), createSkipCall());
+
+    return Pipeline(executorTestHelper.createExecBlock<LambdaExe>(std::move(infos)));
+  }
+
+  auto createAssertPipeline() -> Pipeline {
+    auto numRegs = size_t{1};
+    auto emptyRegisterList = std::make_shared<std::unordered_set<RegisterId>>(
+        std::initializer_list<RegisterId>{});
+
+    auto inRegisterList = std::make_shared<std::unordered_set<RegisterId>>(
+        std::initializer_list<RegisterId>{0});
+    auto outRegisterList = std::make_shared<std::unordered_set<RegisterId>>(
+        std::initializer_list<RegisterId>{1});
+
+    std::unordered_set<RegisterId> toKeep;
+
+    for (RegisterId r = 0; r < numRegs; ++r) {
+      toKeep.emplace(r);
+    }
+
+    auto infos = LambdaExe::Infos(inRegisterList, outRegisterList, 1, 2, {},
+                                  toKeep, createAssertCall(), createSkipCall());
+
+    return Pipeline(executorTestHelper.createExecBlock<LambdaExe>(std::move(infos)));
+  }
+
+  auto createCallAssertPipeline(AqlCall call) -> Pipeline {
+    auto numRegs = size_t{1};
+    auto emptyRegisterList = std::make_shared<std::unordered_set<RegisterId>>(
+        std::initializer_list<RegisterId>{});
+
+    auto inRegisterList = std::make_shared<std::unordered_set<RegisterId>>(
+        std::initializer_list<RegisterId>{0});
+    auto outRegisterList = std::make_shared<std::unordered_set<RegisterId>>(
+        std::initializer_list<RegisterId>{1});
+
+    std::unordered_set<RegisterId> toKeep;
+
+    for (RegisterId r = 0; r < numRegs; ++r) {
+      toKeep.emplace(r);
+    }
+
+    auto infos = LambdaExe::Infos(inRegisterList, outRegisterList, 1, 2, {}, toKeep,
+                                  createAssertCallCall(call), createSkipCall());
+
+    return Pipeline(executorTestHelper.createExecBlock<LambdaExe>(std::move(infos)));
+  }
+#if 0
+  auto createSubqueryStartExecutionBlock() -> ExecBlock {
+    // Subquery start executor does not care about input or output registers?
+    // TODO: talk about registers & register planning
+
+    auto inputRegisterSet =
+        std::make_shared<RegisterSet>(std::initializer_list<RegisterId>{0});
+    auto outputRegisterSet =
+        std::make_shared<RegisterSet>(std::initializer_list<RegisterId>{});
+    auto toKeepRegisterSet = RegisterSet{0};
+
+    auto infos = SubqueryStartExecutor::Infos(inputRegisterSet, outputRegisterSet,
+                                              inputRegisterSet->size(),
+                                              inputRegisterSet->size() +
+                                                  outputRegisterSet->size(),
+                                              {}, toKeepRegisterSet);
+
+    return executorTestHelper.createExecBlock<SubqueryStartExecutor>(std::move(infos),
+                                                                     ExecutionNode::SUBQUERY_START);
+  }
+
+  // Subquery end executor has an input and an output register,
+  // but only the output register is used, remove input reg?
+  auto createSubqueryEndExecutionBlock() -> ExecBlock {
+    auto const inputRegister = RegisterId{0};
+    auto const outputRegister = RegisterId{1};
+    auto inputRegisterSet =
+        std::make_shared<RegisterSet>(std::initializer_list<RegisterId>{inputRegister});
+    auto outputRegisterSet =
+        std::make_shared<RegisterSet>(std::initializer_list<RegisterId>{outputRegister});
+    auto toKeepRegisterSet = RegisterSet{0};
+
+    auto infos =
+        SubqueryEndExecutor::Infos(inputRegisterSet, outputRegisterSet,
+                                   inputRegisterSet->size(),
+                                   inputRegisterSet->size() + outputRegisterSet->size(),
+                                   {}, toKeepRegisterSet, nullptr,
+                                   inputRegister, outputRegister, false);
+
+    return executorTestHelper.createExecBlock<SubqueryEndExecutor>(std::move(infos),
+                                                                   ExecutionNode::SUBQUERY_END);
+  }
+#endif
+  auto createReturnExecutionBlock() -> ExecBlock {
+    auto const inputRegister = RegisterId{0};
+    auto const outputRegister = RegisterId{0};
+    auto inputRegisterSet =
+        std::make_shared<RegisterSet>(std::initializer_list<RegisterId>{inputRegister});
+    auto outputRegisterSet =
+        std::make_shared<RegisterSet>(std::initializer_list<RegisterId>{outputRegister});
+    auto toKeepRegisterSet = RegisterSet{0};
+
+    auto infos = ReturnExecutor::Infos(inputRegister, 1, 1, false);
+
+    return executorTestHelper.createExecBlock<ReturnExecutor>(std::move(infos),
+                                                              ExecutionNode::RETURN);
+  }
+
+  auto createProduceCall() -> ProduceCall {
+    return [](AqlItemBlockInputRange& input,
+              OutputAqlItemRow& output) -> std::tuple<ExecutorState, LambdaExe::Stats, AqlCall> {
+      while (input.hasDataRow() && !output.isFull()) {
+        auto const [state, row] = input.nextDataRow();
+        output.cloneValueInto(1, row, AqlValue("foo"));
+        output.advanceRow();
+      }
+      NoStats stats{};
+      AqlCall call{};
+
+      return {input.upstreamState(), stats, call};
+    };
+  };
+
+  auto createSkipCall() -> SkipCall {
+    return [](AqlItemBlockInputRange& input,
+              AqlCall& call) -> std::tuple<ExecutorState, LambdaExe::Stats, size_t, AqlCall> {
+      auto skipped = size_t{0};
+      while (input.hasDataRow() && call.shouldSkip()) {
+        auto const& [state, inputRow] = input.nextDataRow();
+        EXPECT_TRUE(inputRow.isInitialized());
+        call.didSkip(1);
+        skipped++;
+      }
+      auto upstreamCall = AqlCall{call};
+      return {input.upstreamState(), NoStats{}, skipped, upstreamCall};
+    };
+  };
+
+  // Asserts if called. This is to check that when we use skip to
+  // skip over a subquery, the subquery's produce is not invoked
+  auto createAssertCall() -> ProduceCall {
+    return [](AqlItemBlockInputRange& input,
+              OutputAqlItemRow& output) -> std::tuple<ExecutorState, LambdaExe::Stats, AqlCall> {
+      EXPECT_TRUE(false);
+      NoStats stats{};
+      AqlCall call{};
+
+      return {ExecutorState::DONE, stats, call};
+    };
+  }
+
+  auto createAssertCallCall(AqlCall call) -> ProduceCall {
+    return [call](AqlItemBlockInputRange& input,
+                  OutputAqlItemRow& output) -> std::tuple<ExecutorState, LambdaExe::Stats, AqlCall> {
+      auto clientCall = output.getClientCall();
+
+      EXPECT_EQ(clientCall.offset, call.offset);
+      EXPECT_EQ(clientCall.softLimit, call.softLimit);
+      EXPECT_EQ(clientCall.hardLimit, call.hardLimit);
+      EXPECT_EQ(clientCall.fullCount, call.fullCount);
+
+      while (input.hasDataRow() && !output.isFull()) {
+        auto const [state, row] = input.nextDataRow();
+        output.cloneValueInto(1, row, AqlValue("foo"));
+        output.advanceRow();
+      }
+
+      NoStats stats{};
+      AqlCall call{};
+
+      return {input.upstreamState(), stats, call};
+    };
+  }
+  auto getSplit() -> SubqueryExecutorSplitType {
+    auto [split] = GetParam();
+    return split;
+  }
+};
+
+template <size_t... vs>
+const SubqueryExecutorSplitType splitIntoBlocks =
+    SubqueryExecutorSplitType{std::vector<std::size_t>{vs...}};
+template <size_t step>
+const SubqueryExecutorSplitType splitStep = SubqueryExecutorSplitType{step};
+
+/*
+INSTANTIATE_TEST_CASE_P(SubqueryExecutorIntegrationTest, SubqueryExecutorIntegrationTest,
+                        ::testing::Values(splitIntoBlocks<2, 3>, splitIntoBlocks<3, 4>,
+                                          splitStep<2>, splitStep<1>));
+*/
+
+TEST_P(SubqueryExecutorIntegrationTest, single_subquery_empty_input) {
+  auto call = AqlCall{};
+  auto pipeline = createSubquery();
+  executorTestHelper.setPipeline(std::move(pipeline))
+      .setInputValueList()
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({1}, {})
+      .expectSkipped(0)
+      .expectedState(ExecutionState::DONE)
+      .run();
+};
+
+TEST_P(SubqueryExecutorIntegrationTest, single_subquery) {
+  auto call = AqlCall{};
+  auto pipeline = createSubquery();
+  ExecutorTestHelper<1, 2>{*fakedQuery}
+      .setPipeline(std::move(pipeline))
+      .setInputValueList(1, 2, 5, 2, 1, 5, 7, 1)
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({0, 1}, {{1, R"([1])"},
+                             {2, R"([2])"},
+                             {5, R"([5])"},
+                             {2, R"([2])"},
+                             {1, R"([1])"},
+                             {5, R"([5])"},
+                             {7, R"([7])"},
+                             {1, R"([1])"}})
+      .expectSkipped(0)
+      .expectedState(ExecutionState::DONE)
+      .run();
+};
+
+TEST_P(SubqueryExecutorIntegrationTest, DISABLED_single_subquery_skip_and_produce) {
+  auto call = AqlCall{5};
+  auto pipeline = createSubquery();
+  ExecutorTestHelper<1, 2>{*fakedQuery}
+      .setPipeline(std::move(pipeline))
+      .setInputValueList(1, 2, 5, 2, 1, 5, 7, 1)
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({0, 1}, {{5, R"([5])"}, {7, R"([7])"}, {1, R"([1])"}})
+      .expectSkipped(5)
+      .expectedState(ExecutionState::DONE)
+      .run();
+};
+
+TEST_P(SubqueryExecutorIntegrationTest, DISABLED_single_subquery_skip_all) {
+  auto call = AqlCall{20};
+  auto pipeline = createSubquery();
+  ExecutorTestHelper<1, 2>{*fakedQuery}
+      .setPipeline(std::move(pipeline))
+      .setInputValueList(1, 2, 5, 2, 1, 5, 7, 1)
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({0, 1}, {})
+      .expectSkipped(8)
+      .expectedState(ExecutionState::DONE)
+      .run();
+};
+
+TEST_P(SubqueryExecutorIntegrationTest, DISABLED_single_subquery_fullcount) {
+  auto call = AqlCall{0, true, 0, AqlCall::LimitType::HARD};
+  auto pipeline = createSubquery();
+  ExecutorTestHelper<1, 2>{*fakedQuery}
+      .setPipeline(std::move(pipeline))
+      .setInputValueList(1, 2, 5, 2, 1, 5, 7, 1)
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({0, 1}, {})
+      .expectSkipped(8)
+      .expectedState(ExecutionState::DONE)
+      .run();
+};
+
+TEST_P(SubqueryExecutorIntegrationTest, DISABLED_single_subquery_skip_produce_count) {
+  auto call = AqlCall{2, true, 2, AqlCall::LimitType::HARD};
+  auto pipeline = createSubquery();
+  ExecutorTestHelper<1, 2>{*fakedQuery}
+      .setPipeline(std::move(pipeline))
+      .setInputValueList(1, 2, 5, 2, 1, 5, 7, 1)
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({0, 1}, {{5, R"([5])"}, {2, R"([2])"}})
+      .expectSkipped(6)
+      .expectedState(ExecutionState::DONE)
+      .run();
+};
+
+TEST_P(SubqueryExecutorIntegrationTest, two_nested_subqueries_empty_input) {
+  auto call = AqlCall{};
+  auto pipeline = createSubquery(createSubquery());
+  executorTestHelper.setPipeline(std::move(pipeline))
+      .setInputValueList()
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({0}, {})
+      .expectSkipped(0)
+      .expectedState(ExecutionState::DONE)
+      .run();
+};
+
+TEST_P(SubqueryExecutorIntegrationTest, two_nested_subqueries) {
+  auto call = AqlCall{};
+  auto pipeline = createSubquery(createSubquery());
+  executorTestHelper.setPipeline(std::move(pipeline))
+      .setInputValueList(1, 2, 5, 2, 1, 5, 7, 1)
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({0}, {{1}, {2}, {5}, {2}, {1}, {5}, {7}, {1}})
+      .expectSkipped(0)
+      .expectedState(ExecutionState::DONE)
+      .run();
+};
+
+TEST_P(SubqueryExecutorIntegrationTest, two_sequential_subqueries) {
+  auto call = AqlCall{};
+  auto pipeline = concatPipelines(createSubquery(), createSubquery());
+  executorTestHelper.setPipeline(std::move(pipeline))
+      .setInputValueList(1, 2, 5, 2, 1, 5, 7, 1)
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({0}, {{1}, {2}, {5}, {2}, {1}, {5}, {7}, {1}})
+      .expectSkipped(0)
+      .expectedState(ExecutionState::DONE)
+      .run();
+};
+
+TEST_P(SubqueryExecutorIntegrationTest, do_nothing_in_subquery) {
+  auto call = AqlCall{};
+  auto pipeline = createSubquery(createDoNothingPipeline());
+
+  executorTestHelper.setPipeline(std::move(pipeline))
+      .setInputValueList(1, 2, 5, 2, 1, 5, 7, 1)
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({0}, {{1}, {2}, {5}, {2}, {1}, {5}, {7}, {1}})
+      .expectSkipped(0)
+      .expectedState(ExecutionState::DONE)
+      .run();
+};
+
+TEST_P(SubqueryExecutorIntegrationTest, DISABLED_check_call_passes_subquery) {
+  auto call = AqlCall{10};
+  auto pipeline = concatPipelines(createCallAssertPipeline(call), createSubquery());
+
+  executorTestHelper.setPipeline(std::move(pipeline))
+      .setInputValueList(1, 2, 5, 2, 1, 5, 7, 1)
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({0}, {})
+      .expectSkipped(8)
+      .expectedState(ExecutionState::DONE)
+      .run();
+};
+
+TEST_P(SubqueryExecutorIntegrationTest, DISABLED_check_skipping_subquery) {
+  auto call = AqlCall{10};
+  auto pipeline = createSubquery(createAssertPipeline());
+
+  executorTestHelper.setPipeline(std::move(pipeline))
+      .setInputValueList(1, 2, 5, 2, 1, 5, 7, 1)
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({0}, {})
+      .expectSkipped(0)
+      .expectedState(ExecutionState::DONE)
+      .run();
+};
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index b557ccf6498d..9ed9e68f7a40 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -70,6 +70,7 @@ set(ARANGODB_TESTS_SOURCES
   Aql/SortLimit-test.cpp
   Aql/SpliceSubqueryOptimizerRuleTest.cpp
   Aql/SplicedSubqueryIntegrationTest.cpp
+  Aql/SubqueryExecutorTest.cpp
   Aql/SubqueryEndExecutorTest.cpp
   Aql/SubqueryStartExecutorTest.cpp
   Aql/TestEmptyExecutorHelper.cpp

From 9bb106d9d6964dfa113b8cab4677a938392f7b33 Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Sat, 29 Feb 2020 08:34:42 +0100
Subject: [PATCH 091/122] Feature/aql subquery execution block impl execute
 implementation count collect (#11172)

* Move SubqueryStartExecutor to new interface

* Diddle

* Tests pass for SubqueryStartExecutor

* Delete most of the SubqueryEndExecutor tests

They are irrelevant now as they only tested shadowrow behaviour.

Shadow Rows are now handled by ExecutionBlockImpl.

* Skeleton tests

* Junk

* Cleanup and make work

* Tweak ExecutorTestHelper to test pipelines

* SubqueryStart/SubqueryEnd

* Blafummel.

* Modifications

* Fixup tests

* Address some comments

* Fix.

* Fix tests

* Various fixes.

* Made the branch compile on Mac

* Intermediate commit, does not compile, required for merge

* Fixed one of the SplicedSubqueryTests

* Seperated ShadowRow handling for SubqueryStart/End executors to get a better overview and understanding on how it should behave.

* Allow to use a fullCallStack in ExecutorTestHelper.

* Added asserts on SubqueryEnd that is not allowed to be called with Skipped from upstream

* Use AqlTestCase in SubqueryStartExecutorTest. Transformed first test to TestHelper pipeline

* Let ExecutorTestHelper also test for shadowRows

* Adapted SingleInput=>Data+Shadow test to testing Helepr and make it pass

* Transformed existing SubqueryStart tests to Helper, fixed a test where there was no place for the ShadowRow to be written

* Fixed Skip in SubqueryStartExecutor

* Allow the Pipeline to add Consumer and dependency without fiddling with the Deque from outside

* Added Skip adn ShadowRowForwarding tests to SubqueryStartExecutor

* Fixed fullCount of SubqueryStart to be called properly.

* Renamed isModificationSubquery -> isModificatioNode again

* Consume more than one subquery en-block

* Fixed debugReporting in SplicedSubqueryTest. Disabled the skip in subquery tests for now

* Removed AQL debug log level from testing config

* First version of Subquery Skip bypassing. Including 1 passing test.

* Added disabled tests for skip, and proposed to do it later

* Fixed reporting of FILTERED in fullCount of EnumerateCollectionExecutor

* Enable calculationExecutor execute interface

* Fixed compile issues

* To Velocypack the modification Subquery value

* Fixed illegal assert and reactivated failure tests

* Fixed compile issue

* Deactivated Calculation again

* Added a testSuite for countCollectExecutor

* Fixed Subquery Test for CountCollect

* Added CountCollectImplementation

* Added Compatibility Mode to AqlCallStack

* Removed IdExecutor<void> the only feature it has can be moved into IDexecutor in general. This still has to be done

* When falling back in BlocksWithClients use compatibility stack

* Fixed EnumerateCollectionExecutor

* Fixed fullCountBehaviour of EnumerateList. Also removed a unlimited,fullCount combination in IndexExecutor

* Fixed endless loop while skipAl in OperationCursor

* Fixed View Executor, which sends a no-limit no-offset upstream.

* Fixed forwarding in NoResultsExecutor

Co-authored-by: Markus Pfeiffer <markuspf@users.noreply.github.com>
---
 arangod/Aql/CountCollectExecutor.cpp        |  80 ++---
 arangod/Aql/CountCollectExecutor.h          |  27 +-
 arangod/Aql/EnumerateCollectionExecutor.cpp |   7 +-
 arangod/Aql/EnumerateListExecutor.cpp       |   7 +-
 arangod/Aql/ExecutionBlockImpl.cpp          |   4 +-
 arangod/Aql/IResearchViewExecutor.cpp       |   7 +-
 arangod/Aql/IndexExecutor.cpp               |   1 -
 arangod/Aql/NoResultsExecutor.cpp           |   3 +-
 arangod/Utils/OperationCursor.cpp           |   9 +-
 tests/Aql/CountCollectExecutorTest.cpp      | 333 +++++++++++++-------
 10 files changed, 306 insertions(+), 172 deletions(-)

diff --git a/arangod/Aql/CountCollectExecutor.cpp b/arangod/Aql/CountCollectExecutor.cpp
index 8c6e80be8a99..ff6bb3ad4130 100644
--- a/arangod/Aql/CountCollectExecutor.cpp
+++ b/arangod/Aql/CountCollectExecutor.cpp
@@ -27,9 +27,7 @@
 
 #include "Aql/AqlValue.h"
 #include "Aql/ExecutorInfos.h"
-#include "Aql/InputAqlItemRow.h"
 #include "Aql/OutputAqlItemRow.h"
-#include "Aql/SingleRowFetcher.h"
 #include "Aql/Stats.h"
 
 #include <utility>
@@ -53,50 +51,60 @@ RegisterId CountCollectExecutorInfos::getOutputRegisterId() const {
   return _collectRegister;
 }
 
-CountCollectExecutor::CountCollectExecutor(Fetcher& fetcher, Infos& infos)
-    : _infos(infos), _fetcher(fetcher), _state(ExecutionState::HASMORE), _count(0) {}
+CountCollectExecutor::CountCollectExecutor(Fetcher&, Infos& infos)
+    : _infos(infos) {}
 
-std::pair<ExecutionState, NoStats> CountCollectExecutor::produceRows(OutputAqlItemRow& output) {
+auto CountCollectExecutor::produceRows(AqlItemBlockInputRange& inputRange,
+                                       OutputAqlItemRow& output)
+    -> std::tuple<ExecutorState, Stats, AqlCall> {
   TRI_IF_FAILURE("CountCollectExecutor::produceRows") {
     THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
   }
-
-  if (_state == ExecutionState::DONE) {
-    return {_state, NoStats{}};
+  // skipped > 0 -> done
+  // We have the guarantee that every thing is skipped
+  // within a single call
+  TRI_ASSERT(inputRange.skippedInFlight() == 0 ||
+             inputRange.upstreamState() == ExecutorState::DONE);
+  if (inputRange.upstreamState() == ExecutorState::DONE) {
+    // We have skipped all, report it.
+    // In general, we do not have an input row. In fact, we never fetch one.
+    output.setAllowSourceRowUninitialized();
+
+    // We must produce exactly one output row.
+    output.cloneValueInto(_infos.getOutputRegisterId(),
+                          InputAqlItemRow{CreateInvalidInputRowHint{}},
+                          AqlValue(AqlValueHintUInt(inputRange.skipAll())));
+    output.advanceRow();
   }
+  // We always send a hardLimit with fullcount to upstream
+  return {inputRange.upstreamState(), NoStats{},
+          AqlCall{0, true, 0, AqlCall::LimitType::HARD}};
+}
 
-  while (_state != ExecutionState::DONE) {
-    size_t skipped;
-    std::tie(_state, skipped) = _fetcher.skipRows(ExecutionBlock::SkipAllSize());
-
-    if (_state == ExecutionState::WAITING) {
-      TRI_ASSERT(skipped == 0);
-      return {_state, NoStats{}};
-    }
-
-    TRI_ASSERT(skipped != 0 || _state == ExecutionState::DONE);
-    incrCountBy(skipped);
+auto CountCollectExecutor::skipRowsRange(AqlItemBlockInputRange& inputRange, AqlCall& call)
+    -> std::tuple<ExecutorState, Stats, size_t, AqlCall> {
+  TRI_IF_FAILURE("CountCollectExecutor::produceRows") {
+    THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
   }
-
-  // In general, we do not have an input row. In fact, we never fetch one.
-  output.setAllowSourceRowUninitialized();
-
-  // We must produce exactly one output row.
-  output.cloneValueInto(_infos.getOutputRegisterId(),
-                        InputAqlItemRow{CreateInvalidInputRowHint{}},
-                        AqlValue(AqlValueHintUInt(getCount())));
-
-  return {_state, NoStats{}};
+  // skipped > 0 -> done
+  // We have the guarantee that every thing is skipped
+  // within a single call
+  TRI_ASSERT(inputRange.skippedInFlight() == 0 ||
+             inputRange.upstreamState() == ExecutorState::DONE);
+  if (inputRange.upstreamState() == ExecutorState::DONE) {
+    // We have skipped all, report it.
+    auto skipped = inputRange.skipAll();
+    // We request to just forward, we do not even care how much
+    TRI_ASSERT(skipped == 0);
+    call.didSkip(1);
+  }
+  // We always send a hardLimit with fullcount to upstream
+  return {inputRange.upstreamState(), NoStats{}, call.getSkipCount(),
+          AqlCall{0, false, 0, AqlCall::LimitType::HARD}};
 }
 
-void CountCollectExecutor::incrCountBy(size_t incr) noexcept { _count += incr; }
-
-uint64_t CountCollectExecutor::getCount() noexcept { return _count; }
-
 std::pair<ExecutionState, size_t> CountCollectExecutor::expectedNumberOfRows(size_t) const {
-  if (_state == ExecutionState::DONE) {
-    return {ExecutionState::DONE, 0};
-  }
+  TRI_ASSERT(false);
   return {ExecutionState::HASMORE, 1};
 }
 
diff --git a/arangod/Aql/CountCollectExecutor.h b/arangod/Aql/CountCollectExecutor.h
index d6a25feb0a54..2fad185c917c 100644
--- a/arangod/Aql/CountCollectExecutor.h
+++ b/arangod/Aql/CountCollectExecutor.h
@@ -26,6 +26,8 @@
 #ifndef ARANGOD_AQL_COUNT_COLLECT_EXECUTOR_H
 #define ARANGOD_AQL_COUNT_COLLECT_EXECUTOR_H
 
+#include "Aql/AqlCall.h"
+#include "Aql/AqlItemBlockInputRange.h"
 #include "Aql/ExecutionState.h"
 #include "Aql/ExecutorInfos.h"
 #include "Aql/types.h"
@@ -42,6 +44,8 @@ class ExecutorInfos;
 class OutputAqlItemRow;
 template <BlockPassthrough>
 class SingleRowFetcher;
+struct AqlCall;
+class AqlItemBlockInputRange;
 
 class CountCollectExecutorInfos : public ExecutorInfos {
  public:
@@ -80,20 +84,24 @@ class CountCollectExecutor {
   CountCollectExecutor() = delete;
   CountCollectExecutor(CountCollectExecutor&&) = default;
   CountCollectExecutor(CountCollectExecutor const&) = delete;
-  CountCollectExecutor(Fetcher& fetcher, Infos&);
+  CountCollectExecutor(Fetcher&, Infos&);
   ~CountCollectExecutor();
 
   /**
-   * @brief produce the next Row of Aql Values.
+   * @brief produce the next Rows of Aql Values.
    *
-   * @return ExecutionState, and if successful exactly one new Row of AqlItems.
+   * @return ExecutorState, the stats, and a new Call that needs to be send to upstream
    */
+  [[nodiscard]] auto produceRows(AqlItemBlockInputRange& input, OutputAqlItemRow& output)
+      -> std::tuple<ExecutorState, Stats, AqlCall>;
 
-  std::pair<ExecutionState, NoStats> produceRows(OutputAqlItemRow& output);
-
-  void incrCountBy(size_t incr) noexcept;
-
-  uint64_t getCount() noexcept;
+  /**
+   * @brief skip the next Row of Aql Values.
+   *
+   * @return ExecutorState, the stats, and a new Call that needs to be send to upstream
+   */
+  [[nodiscard]] auto skipRowsRange(AqlItemBlockInputRange& inputRange, AqlCall& call)
+      -> std::tuple<ExecutorState, Stats, size_t, AqlCall>;
 
   std::pair<ExecutionState, size_t> expectedNumberOfRows(size_t atMost) const;
 
@@ -102,9 +110,6 @@ class CountCollectExecutor {
 
  private:
   Infos const& _infos;
-  Fetcher& _fetcher;
-  ExecutionState _state;
-  uint64_t _count;
 };
 
 }  // namespace aql
diff --git a/arangod/Aql/EnumerateCollectionExecutor.cpp b/arangod/Aql/EnumerateCollectionExecutor.cpp
index ee200f05ca62..3ff3220d415c 100644
--- a/arangod/Aql/EnumerateCollectionExecutor.cpp
+++ b/arangod/Aql/EnumerateCollectionExecutor.cpp
@@ -238,8 +238,13 @@ std::tuple<ExecutorState, EnumerateCollectionStats, size_t, AqlCall> EnumerateCo
   if (_cursorHasMore) {
     return {ExecutorState::HASMORE, stats, call.getSkipCount(), upstreamCall};
   }
+  if (!call.needsFullCount()) {
+    // Do not overfetch too much
+    upstreamCall.softLimit = call.getOffset();
+    // else we do unlimited softLimit.
+    // we are going to return everything anyways.
+  }
 
-  upstreamCall.softLimit = call.getOffset();
   return {inputRange.upstreamState(), stats, call.getSkipCount(), upstreamCall};
 }
 
diff --git a/arangod/Aql/EnumerateListExecutor.cpp b/arangod/Aql/EnumerateListExecutor.cpp
index 84d2ab2d080b..03a5932f8d1a 100644
--- a/arangod/Aql/EnumerateListExecutor.cpp
+++ b/arangod/Aql/EnumerateListExecutor.cpp
@@ -200,7 +200,12 @@ std::tuple<ExecutorState, NoStats, size_t, AqlCall> EnumerateListExecutor::skipR
   }
   call.didSkip(skipped);
 
-  upstreamCall.softLimit = call.getOffset();
+  if (!call.needsFullCount()) {
+    // Do not overfetch too much
+    upstreamCall.softLimit = call.getOffset();
+    // else we do unlimited softLimit.
+    // we are going to return everything anyways.
+  }
   if (_inputArrayPosition < _inputArrayLength) {
     // fullCount will always skip the complete array
     TRI_ASSERT(offsetPhase);
diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index 31e98b72fed5..6c39b40d76fe 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -137,7 +137,7 @@ template <typename Executor>
 constexpr bool isNewStyleExecutor = is_one_of_v<
     Executor, FilterExecutor, SortedCollectExecutor, IdExecutor<ConstFetcher>,
     IdExecutor<SingleRowFetcher<BlockPassthrough::Enable>>, ReturnExecutor, DistinctCollectExecutor, IndexExecutor, EnumerateCollectionExecutor,
-    SubqueryExecutor<true>, SubqueryExecutor<false>,
+    SubqueryExecutor<true>, SubqueryExecutor<false>,  CountCollectExecutor,
     // TODO: re-enable after new subquery end & start are implemented
     // CalculationExecutor<CalculationType::Condition>, CalculationExecutor<CalculationType::Reference>, CalculationExecutor<CalculationType::V8Condition>,
     HashedCollectExecutor, ConstrainedSortExecutor,
@@ -1127,7 +1127,7 @@ static SkipRowsRangeVariant constexpr skipRowsType() {
               Executor, FilterExecutor, ShortestPathExecutor, ReturnExecutor, KShortestPathsExecutor,
               IdExecutor<SingleRowFetcher<BlockPassthrough::Enable>>, IdExecutor<ConstFetcher>, HashedCollectExecutor,
               IndexExecutor, EnumerateCollectionExecutor, DistinctCollectExecutor, ConstrainedSortExecutor,
-              SubqueryExecutor<true>,
+              CountCollectExecutor, SubqueryExecutor<true>,
 #ifdef ARANGODB_USE_GOOGLE_TESTS
               TestLambdaSkipExecutor,
 #endif
diff --git a/arangod/Aql/IResearchViewExecutor.cpp b/arangod/Aql/IResearchViewExecutor.cpp
index 5bd3cdc8d7d5..6f6a3788b01b 100644
--- a/arangod/Aql/IResearchViewExecutor.cpp
+++ b/arangod/Aql/IResearchViewExecutor.cpp
@@ -518,7 +518,12 @@ IResearchViewExecutorBase<Impl, Traits>::skipRowsRange(AqlItemBlockInputRange& i
   stats.incrScanned(call.getSkipCount());
 
   AqlCall upstreamCall{};
-  upstreamCall.softLimit = call.getOffset() + std::min(call.softLimit, call.hardLimit);
+  if (!call.needsFullCount()) {
+    // Do not overfetch too much.
+    upstreamCall.softLimit = call.getOffset() + std::min(call.softLimit, call.hardLimit);
+    // else we do unlimited softLimit.
+    // we are going to return everything anyways.
+  }
   return {inputRange.upstreamState(), stats, call.getSkipCount(), upstreamCall};
 }
 
diff --git a/arangod/Aql/IndexExecutor.cpp b/arangod/Aql/IndexExecutor.cpp
index 91e6c33ecf47..5b99e75fed48 100644
--- a/arangod/Aql/IndexExecutor.cpp
+++ b/arangod/Aql/IndexExecutor.cpp
@@ -752,7 +752,6 @@ auto IndexExecutor::produceRows(AqlItemBlockInputRange& inputRange, OutputAqlIte
   }
 
   AqlCall upstreamCall;
-  upstreamCall.fullCount = clientCall.needsFullCount();
 
   LOG_DEVEL_IDX << "IndexExecutor::produceRows reporting state " << returnState();
   return {returnState(), stats, upstreamCall};
diff --git a/arangod/Aql/NoResultsExecutor.cpp b/arangod/Aql/NoResultsExecutor.cpp
index 1728e430e6dd..0291a889bd31 100644
--- a/arangod/Aql/NoResultsExecutor.cpp
+++ b/arangod/Aql/NoResultsExecutor.cpp
@@ -40,5 +40,6 @@ auto NoResultsExecutor::produceRows(AqlItemBlockInputRange& input, OutputAqlItem
 
 auto NoResultsExecutor::skipRowsRange(AqlItemBlockInputRange& inputRange, AqlCall& call) const
     noexcept -> std::tuple<ExecutorState, Stats, size_t, AqlCall> {
-  return {ExecutorState::DONE, NoStats{}, 0, AqlCall{0, false, 0, AqlCall::LimitType::HARD}};
+  return {inputRange.upstreamState(), NoStats{}, 0,
+          AqlCall{0, false, 0, AqlCall::LimitType::HARD}};
 };
\ No newline at end of file
diff --git a/arangod/Utils/OperationCursor.cpp b/arangod/Utils/OperationCursor.cpp
index e6030a9dc83d..0245935344e3 100644
--- a/arangod/Utils/OperationCursor.cpp
+++ b/arangod/Utils/OperationCursor.cpp
@@ -24,10 +24,9 @@
 #include "OperationCursor.h"
 
 using namespace arangodb;
-      
+
 OperationCursor::OperationCursor(std::unique_ptr<IndexIterator> iterator)
-    : _indexIterator(std::move(iterator)),
-      _hasMore(true) {
+    : _indexIterator(std::move(iterator)), _hasMore(true) {
   TRI_ASSERT(_indexIterator != nullptr);
 }
 
@@ -145,9 +144,11 @@ void OperationCursor::skipAll(uint64_t& skipped) {
   }
 
   while (_hasMore) {
-    _indexIterator->skip(toSkip, skipped);
+    uint64_t skippedLocal = 0;
+    _indexIterator->skip(toSkip, skippedLocal);
     if (skipped != toSkip) {
       _hasMore = false;
     }
+    skipped += skippedLocal;
   }
 }
diff --git a/tests/Aql/CountCollectExecutorTest.cpp b/tests/Aql/CountCollectExecutorTest.cpp
index dea9fc1f2982..8a0d6ef745da 100644
--- a/tests/Aql/CountCollectExecutorTest.cpp
+++ b/tests/Aql/CountCollectExecutorTest.cpp
@@ -20,141 +20,246 @@
 /// @author Heiko Kernbach
 ////////////////////////////////////////////////////////////////////////////////
 
-#include "RowFetcherHelper.h"
 #include "gtest/gtest.h"
 
-#include "Aql/AqlItemBlock.h"
+#include "ExecutorTestHelper.h"
+#include "TestLambdaExecutor.h"
+
 #include "Aql/CountCollectExecutor.h"
-#include "Aql/InputAqlItemRow.h"
-#include "Aql/OutputAqlItemRow.h"
-#include "Aql/ResourceUsage.h"
+#include "Aql/SingleRowFetcher.h"
 #include "Aql/Stats.h"
-
-#include <velocypack/Builder.h>
-#include <velocypack/velocypack-aliases.h>
+#include "Aql/SubqueryEndExecutor.h"
+#include "Aql/SubqueryStartExecutor.h"
 
 using namespace arangodb;
 using namespace arangodb::aql;
 
+using LambdaExe = TestLambdaSkipExecutor;
+
 namespace arangodb {
 namespace tests {
 namespace aql {
 
-class CountCollectExecutorTest : public ::testing::Test {
+using CountCollectTestHelper = ExecutorTestHelper<1, 1>;
+using CountCollectSplitType = CountCollectTestHelper::SplitType;
+using CountCollectParamType = std::tuple<CountCollectSplitType>;
+
+class CountCollectExecutorTest
+    : public AqlExecutorTestCaseWithParam<CountCollectParamType, false> {
  protected:
-  ExecutionState state;
-  ResourceMonitor monitor;
-  AqlItemBlockManager itemBlockManager;
-  RegisterId nrOutputReg = 2;
-  SharedAqlItemBlockPtr block;
-  std::shared_ptr<const std::unordered_set<RegisterId>> outputRegisters;
-
-  CountCollectExecutorTest()
-      : itemBlockManager(&monitor, SerializationFormat::SHADOWROWS),
-        nrOutputReg(2),
-        block(new AqlItemBlock(itemBlockManager, 1000, nrOutputReg)),
-        outputRegisters(std::make_shared<const std::unordered_set<RegisterId>>(
-            std::initializer_list<RegisterId>{1})) {}
+  auto MakeInfos(RegisterId outReg) -> CountCollectExecutorInfos {
+    return CountCollectExecutorInfos{
+        outReg, outReg /*inputRegisters*/, outReg + 1 /*outputRegisters*/, {}, {}};
+  }
+  auto GetSplit() -> CountCollectSplitType {
+    auto const& [split] = GetParam();
+    return split;
+  }
+
+  auto MakeSubqueryStartInfos() -> SubqueryStartExecutor::Infos {
+    auto inputRegisterSet = make_shared_unordered_set({0});
+    auto outputRegisterSet = make_shared_unordered_set({});
+
+    auto toKeepRegisterSet = std::unordered_set<RegisterId>{0};
+
+    return SubqueryStartExecutor::Infos(inputRegisterSet, outputRegisterSet,
+                                        inputRegisterSet->size(),
+                                        inputRegisterSet->size() +
+                                            outputRegisterSet->size(),
+                                        {}, toKeepRegisterSet);
+  }
+
+  auto MakeSubqueryEndInfos(RegisterId inputRegister) -> SubqueryEndExecutor::Infos {
+    auto const outputRegister = RegisterId{inputRegister + 1};
+    auto inputRegisterSet = make_shared_unordered_set({});
+    for (RegisterId r = 0; r <= inputRegister; ++r) {
+      inputRegisterSet->emplace(r);
+    }
+    auto outputRegisterSet = make_shared_unordered_set({outputRegister});
+    auto toKeepRegisterSet = std::unordered_set<RegisterId>{};
+
+    return SubqueryEndExecutor::Infos(inputRegisterSet, outputRegisterSet,
+                                      inputRegisterSet->size(),
+                                      inputRegisterSet->size() +
+                                          outputRegisterSet->size(),
+                                      {}, toKeepRegisterSet, nullptr,
+                                      inputRegister, outputRegister, false);
+  }
+
+  auto MakeRemoveAllLinesInfos() -> LambdaExe::Infos {
+    auto numRegs = size_t{1};
+
+    auto inRegisterList = make_shared_unordered_set({});
+    auto outRegisterList = make_shared_unordered_set({});
+
+    std::unordered_set<RegisterId> toKeep;
+
+    for (RegisterId r = 0; r < numRegs; ++r) {
+      toKeep.emplace(r);
+    }
+
+    ProduceCall prod = [](AqlItemBlockInputRange& input, OutputAqlItemRow& output)
+        -> std::tuple<ExecutorState, LambdaExe::Stats, AqlCall> {
+      EXPECT_TRUE(false) << "Should never be called";
+      return {ExecutorState::DONE, NoStats{}, AqlCall{0, true, 0, AqlCall::LimitType::HARD}};
+    };
+
+    SkipCall skip = [](AqlItemBlockInputRange& input, AqlCall& call)
+        -> std::tuple<ExecutorState, LambdaExe::Stats, size_t, AqlCall> {
+      std::ignore = input.skipAll();
+      return {input.upstreamState(), NoStats{}, 0,
+              AqlCall{0, true, 0, AqlCall::LimitType::HARD}};
+    };
+
+    return LambdaExe::Infos(inRegisterList, outRegisterList, numRegs, numRegs,
+                            {}, toKeep, prod, skip);
+  }
 };
 
-TEST_F(CountCollectExecutorTest, there_are_no_rows_upstream_the_producer_doesnt_wait) {
-  CountCollectExecutorInfos infos(1 /* outputRegId */, 1 /* nrIn */, nrOutputReg, {}, {});
-  VPackBuilder input;
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input.steal(), false);
-  CountCollectExecutor testee(fetcher, infos);
-  NoStats stats{};
-
-  OutputAqlItemRow result{std::move(block), outputRegisters,
-                          infos.registersToKeep(), infos.registersToClear()};
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_TRUE(result.produced());
-
-  auto block = result.stealBlock();
-  AqlValue x = block->getValue(0, 1);
-  ASSERT_TRUE(x.isNumber());
-  ASSERT_EQ(x.toInt64(), 0);
-
-  ASSERT_EQ(0, fetcher.totalSkipped());
+template <size_t... vs>
+const CountCollectSplitType splitIntoBlocks =
+    CountCollectSplitType{std::vector<std::size_t>{vs...}};
+template <size_t step>
+const CountCollectSplitType splitStep = CountCollectSplitType{step};
+
+INSTANTIATE_TEST_CASE_P(CountCollectExecutor, CountCollectExecutorTest,
+                        ::testing::Values(CountCollectSplitType{std::monostate()},
+                                          splitStep<1>, splitIntoBlocks<2, 3>,
+                                          splitStep<2>));
+
+TEST_P(CountCollectExecutorTest, empty_input) {
+  ExecutorTestHelper<1, 1>(*fakedQuery)
+      .setExecBlock<CountCollectExecutor>(MakeInfos(1), ExecutionNode::COLLECT)
+      .expectedStats(ExecutionStats{})
+      .setInputSplitType(GetSplit())
+      .setInputValue({})
+      .expectedState(ExecutionState::DONE)
+      .expectOutput({1}, {{0}})
+      .expectSkipped(0)
+      .setCall(AqlCall{})
+      .run();
+}
+
+TEST_P(CountCollectExecutorTest, count_input) {
+  ExecutorTestHelper<1, 1>(*fakedQuery)
+      .setExecBlock<CountCollectExecutor>(MakeInfos(1), ExecutionNode::COLLECT)
+      .expectedStats(ExecutionStats{})
+      .setInputSplitType(GetSplit())
+      .setInputValue({{0}, {1}, {2}, {3}})
+      .expectedState(ExecutionState::DONE)
+      .expectOutput({1}, {{4}})
+      .expectSkipped(0)
+      .setCall(AqlCall{})
+      .run();
+}
+
+TEST_P(CountCollectExecutorTest, empty_input_skip) {
+  ExecutorTestHelper<1, 1>(*fakedQuery)
+      .setExecBlock<CountCollectExecutor>(MakeInfos(1), ExecutionNode::COLLECT)
+      .expectedStats(ExecutionStats{})
+      .setInputSplitType(GetSplit())
+      .setInputValue({})
+      .expectedState(ExecutionState::DONE)
+      .expectOutput({1}, {})
+      .expectSkipped(1)
+      .setCall(AqlCall{10})
+      .run();
+}
+
+TEST_P(CountCollectExecutorTest, count_input_skip) {
+  ExecutorTestHelper<1, 1>(*fakedQuery)
+      .setExecBlock<CountCollectExecutor>(MakeInfos(1), ExecutionNode::COLLECT)
+      .expectedStats(ExecutionStats{})
+      .setInputSplitType(GetSplit())
+      .setInputValue({{0}, {1}, {2}, {3}})
+      .expectedState(ExecutionState::DONE)
+      .expectOutput({1}, {})
+      .expectSkipped(1)
+      .setCall(AqlCall{10})
+      .run();
 }
 
-TEST_F(CountCollectExecutorTest, there_are_now_rows_upstream_the_producer_waits) {
-  CountCollectExecutorInfos infos(1 /* outputRegId */, 1 /* nrIn */, nrOutputReg, {}, {});
-  VPackBuilder input;
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input.steal(), true);
-  CountCollectExecutor testee(fetcher, infos);
-  NoStats stats{};
-
-  OutputAqlItemRow result{std::move(block), outputRegisters,
-                          infos.registersToKeep(), infos.registersToClear()};
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::WAITING);
-  ASSERT_FALSE(result.produced());
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_TRUE(result.produced());
-
-  auto block = result.stealBlock();
-  AqlValue x = block->getValue(0, 1);
-  ASSERT_TRUE(x.isNumber());
-  ASSERT_EQ(x.toInt64(), 0);
-
-  ASSERT_EQ(0, fetcher.totalSkipped());
+TEST_P(CountCollectExecutorTest, empty_input_fullCount) {
+  ExecutorTestHelper<1, 1>(*fakedQuery)
+      .setExecBlock<CountCollectExecutor>(MakeInfos(1), ExecutionNode::COLLECT)
+      .expectedStats(ExecutionStats{})
+      .setInputSplitType(GetSplit())
+      .setInputValue({})
+      .expectedState(ExecutionState::DONE)
+      .expectOutput({1}, {})
+      .expectSkipped(1)
+      .setCall(AqlCall{0, true, 0, AqlCall::LimitType::HARD})
+      .run();
 }
 
-TEST_F(CountCollectExecutorTest, there_are_rows_in_the_upstream_the_producer_doesnt_wait) {
-  CountCollectExecutorInfos infos(1 /* outputRegId */, 1 /* nrIn */, nrOutputReg, {}, {});
-  auto input = VPackParser::fromJson("[ [1], [2], [3] ]");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), false);
-  CountCollectExecutor testee(fetcher, infos);
-  NoStats stats{};
-
-  OutputAqlItemRow result{std::move(block), outputRegisters,
-                          infos.registersToKeep(), infos.registersToClear()};
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_TRUE(result.produced());
-
-  auto block = result.stealBlock();
-  AqlValue x = block->getValue(0, 1);
-  ASSERT_TRUE(x.isNumber());
-  ASSERT_EQ(x.toInt64(), 3);
-
-  ASSERT_EQ(3, fetcher.totalSkipped());
+TEST_P(CountCollectExecutorTest, count_input_fullCount) {
+  ExecutorTestHelper<1, 1>(*fakedQuery)
+      .setExecBlock<CountCollectExecutor>(MakeInfos(1), ExecutionNode::COLLECT)
+      .expectedStats(ExecutionStats{})
+      .setInputSplitType(GetSplit())
+      .setInputValue({{0}, {1}, {2}, {3}})
+      .expectedState(ExecutionState::DONE)
+      .expectOutput({1}, {})
+      .expectSkipped(1)
+      .setCall(AqlCall{0, true, 0, AqlCall::LimitType::HARD})
+      .run();
 }
 
-TEST_F(CountCollectExecutorTest, there_are_rows_in_the_upstream_the_producer_waits) {
-  CountCollectExecutorInfos infos(1 /* outputRegId */, 1 /* nrIn */, nrOutputReg, {}, {});
-  auto input = VPackParser::fromJson("[ [1], [2], [3] ]");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(itemBlockManager, input->steal(), true);
-  CountCollectExecutor testee(fetcher, infos);
-  NoStats stats{};
-  OutputAqlItemRow result{std::move(block), outputRegisters,
-                          infos.registersToKeep(), infos.registersToClear()};
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::WAITING);
-  ASSERT_FALSE(result.produced());
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::WAITING);
-  ASSERT_FALSE(result.produced());
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::WAITING);
-  ASSERT_FALSE(result.produced());
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_TRUE(result.produced());
-
-  auto block = result.stealBlock();
-  AqlValue x = block->getValue(0, 1);
-  ASSERT_TRUE(x.isNumber());
-  ASSERT_EQ(x.toInt64(), 3);
-
-  ASSERT_EQ(3, fetcher.totalSkipped());
+TEST_P(CountCollectExecutorTest, count_input_softlimit) {
+  ExecutorTestHelper<1, 1>(*fakedQuery)
+      .setExecBlock<CountCollectExecutor>(MakeInfos(1), ExecutionNode::COLLECT)
+      .expectedStats(ExecutionStats{})
+      .setInputSplitType(GetSplit())
+      .setInputValue({{0}, {1}, {2}, {3}})
+      .expectedState(ExecutionState::DONE)
+      .expectOutput({1}, {{4}})
+      .expectSkipped(0)
+      .setCall(AqlCall{0, false, 1, AqlCall::LimitType::SOFT})
+      .run();
+}
+
+TEST_P(CountCollectExecutorTest, count_in_empty_subquery) {
+  ExecutorTestHelper<1, 1> helper(*fakedQuery);
+
+  Pipeline pipe{};
+  pipe.addConsumer(helper.createExecBlock<SubqueryStartExecutor>(MakeSubqueryStartInfos(),
+                                                                 ExecutionNode::SUBQUERY_START))
+      .addConsumer(helper.createExecBlock<LambdaExe>(MakeRemoveAllLinesInfos(),
+                                                     ExecutionNode::FILTER))
+      .addConsumer(helper.createExecBlock<CountCollectExecutor>(MakeInfos(1), ExecutionNode::COLLECT))
+      .addConsumer(helper.createExecBlock<SubqueryEndExecutor>(MakeSubqueryEndInfos(1),
+                                                               ExecutionNode::SUBQUERY_END));
+
+  helper.setPipeline(std::move(pipe))
+      .expectedStats(ExecutionStats{})
+      .setInputSplitType(GetSplit())
+      .setInputValue({{0}, {1}, {2}, {3}})
+      .expectedState(ExecutionState::DONE)
+      .expectOutput({2}, {{R"([0])"}, {R"([0])"}, {R"([0])"}, {R"([0])"}})
+      .expectSkipped(0)
+      .setCall(AqlCall{})
+      .run();
+}
+
+TEST_P(CountCollectExecutorTest, count_in_subquery) {
+  ExecutorTestHelper<1, 1> helper(*fakedQuery);
+
+  Pipeline pipe{};
+  pipe.addConsumer(helper.createExecBlock<SubqueryStartExecutor>(MakeSubqueryStartInfos(),
+                                                                 ExecutionNode::SUBQUERY_START))
+      .addConsumer(helper.createExecBlock<CountCollectExecutor>(MakeInfos(1), ExecutionNode::COLLECT))
+      .addConsumer(helper.createExecBlock<SubqueryEndExecutor>(MakeSubqueryEndInfos(1),
+                                                               ExecutionNode::SUBQUERY_END));
+
+  helper.setPipeline(std::move(pipe))
+      .expectedStats(ExecutionStats{})
+      .setInputSplitType(GetSplit())
+      .setInputValue({{0}, {1}, {2}, {3}})
+      .expectedState(ExecutionState::DONE)
+      .expectOutput({2}, {{R"([1])"}, {R"([1])"}, {R"([1])"}, {R"([1])"}})
+      .expectSkipped(0)
+      .setCall(AqlCall{})
+      .run();
 }
 
 }  // namespace aql

From 2262370ee6b1b7336559df7e876522394b19f28f Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Sat, 29 Feb 2020 08:35:42 +0100
Subject: [PATCH 092/122] Activate CalculationExecutors (#11177)

---
 arangod/Aql/ExecutionBlockImpl.cpp | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index 6c39b40d76fe..59a52dd6d239 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -138,8 +138,7 @@ constexpr bool isNewStyleExecutor = is_one_of_v<
     Executor, FilterExecutor, SortedCollectExecutor, IdExecutor<ConstFetcher>,
     IdExecutor<SingleRowFetcher<BlockPassthrough::Enable>>, ReturnExecutor, DistinctCollectExecutor, IndexExecutor, EnumerateCollectionExecutor,
     SubqueryExecutor<true>, SubqueryExecutor<false>,  CountCollectExecutor,
-    // TODO: re-enable after new subquery end & start are implemented
-    // CalculationExecutor<CalculationType::Condition>, CalculationExecutor<CalculationType::Reference>, CalculationExecutor<CalculationType::V8Condition>,
+    CalculationExecutor<CalculationType::Condition>, CalculationExecutor<CalculationType::Reference>, CalculationExecutor<CalculationType::V8Condition>,
     HashedCollectExecutor, ConstrainedSortExecutor,
 #ifdef ARANGODB_USE_GOOGLE_TESTS
     TestLambdaExecutor,

From c69dc935e04d1f1aa66c7aaef7b0ad52f0f775d0 Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Sat, 29 Feb 2020 08:48:31 +0100
Subject: [PATCH 093/122] Fixed compile bug-due to hidden merge conflict

---
 arangod/Aql/ExecutionBlockImpl.cpp | 42 ++++++++++++++++--------------
 1 file changed, 23 insertions(+), 19 deletions(-)

diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index 59a52dd6d239..ca8ae4c1d24a 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -136,10 +136,10 @@ constexpr bool is_one_of_v = (std::is_same_v<T, Es> || ...);
 template <typename Executor>
 constexpr bool isNewStyleExecutor = is_one_of_v<
     Executor, FilterExecutor, SortedCollectExecutor, IdExecutor<ConstFetcher>,
-    IdExecutor<SingleRowFetcher<BlockPassthrough::Enable>>, ReturnExecutor, DistinctCollectExecutor, IndexExecutor, EnumerateCollectionExecutor,
-    SubqueryExecutor<true>, SubqueryExecutor<false>,  CountCollectExecutor,
-    CalculationExecutor<CalculationType::Condition>, CalculationExecutor<CalculationType::Reference>, CalculationExecutor<CalculationType::V8Condition>,
-    HashedCollectExecutor, ConstrainedSortExecutor,
+    IdExecutor<SingleRowFetcher<BlockPassthrough::Enable>>, ReturnExecutor, DistinctCollectExecutor, IndexExecutor,
+    EnumerateCollectionExecutor, SubqueryExecutor<true>, SubqueryExecutor<false>, CountCollectExecutor,
+    CalculationExecutor<CalculationType::Condition>, CalculationExecutor<CalculationType::Reference>,
+    CalculationExecutor<CalculationType::V8Condition>, HashedCollectExecutor, ConstrainedSortExecutor,
 #ifdef ARANGODB_USE_GOOGLE_TESTS
     TestLambdaExecutor,
     TestLambdaSkipExecutor,  // we need one after these to avoid compile errors in non-test mode
@@ -151,9 +151,10 @@ constexpr bool isNewStyleExecutor = is_one_of_v<
     ModificationExecutor<AllRowsFetcher, UpdateReplaceModifier>,
     ModificationExecutor<SingleRowFetcher<BlockPassthrough::Disable>, UpdateReplaceModifier>,
     ModificationExecutor<AllRowsFetcher, UpsertModifier>,
-    ModificationExecutor<SingleRowFetcher<BlockPassthrough::Disable>, UpsertModifier>, SubqueryStartExecutor,
-    UnsortedGatherExecutor, SubqueryEndExecutor, TraversalExecutor, KShortestPathsExecutor, ShortestPathExecutor, EnumerateListExecutor,
-    LimitExecutor, SortExecutor, IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::NotMaterialize>,
+    ModificationExecutor<SingleRowFetcher<BlockPassthrough::Disable>, UpsertModifier>,
+    SubqueryStartExecutor, UnsortedGatherExecutor, SubqueryEndExecutor, TraversalExecutor,
+    KShortestPathsExecutor, ShortestPathExecutor, EnumerateListExecutor, LimitExecutor, SortExecutor,
+    IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::NotMaterialize>,
     IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::LateMaterialize>,
     IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::Materialize>,
     IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::NotMaterialize | arangodb::iresearch::MaterializeType::UseStoredValues>,
@@ -1107,7 +1108,8 @@ static SkipRowsRangeVariant constexpr skipRowsType() {
 
   bool constexpr useExecutor = hasSkipRowsRange<Executor>::value;
 
-  static_assert(!std::is_same_v<Executor, SubqueryExecutor<true>> || hasSkipRowsRange<Executor>::value);
+  static_assert(!std::is_same_v<Executor, SubqueryExecutor<true>> ||
+                hasSkipRowsRange<Executor>::value);
 
   // ConstFetcher and SingleRowFetcher<BlockPassthrough::Enable> can skip, but
   // it may not be done for modification subqueries.
@@ -1124,9 +1126,9 @@ static SkipRowsRangeVariant constexpr skipRowsType() {
       useExecutor ==
           (is_one_of_v<
               Executor, FilterExecutor, ShortestPathExecutor, ReturnExecutor, KShortestPathsExecutor,
-              IdExecutor<SingleRowFetcher<BlockPassthrough::Enable>>, IdExecutor<ConstFetcher>, HashedCollectExecutor,
-              IndexExecutor, EnumerateCollectionExecutor, DistinctCollectExecutor, ConstrainedSortExecutor,
-              CountCollectExecutor, SubqueryExecutor<true>,
+              IdExecutor<SingleRowFetcher<BlockPassthrough::Enable>>, IdExecutor<ConstFetcher>,
+              HashedCollectExecutor, IndexExecutor, EnumerateCollectionExecutor, DistinctCollectExecutor,
+              ConstrainedSortExecutor, CountCollectExecutor, SubqueryExecutor<true>,
 #ifdef ARANGODB_USE_GOOGLE_TESTS
               TestLambdaSkipExecutor,
 #endif
@@ -1137,9 +1139,10 @@ static SkipRowsRangeVariant constexpr skipRowsType() {
               ModificationExecutor<AllRowsFetcher, UpdateReplaceModifier>,
               ModificationExecutor<SingleRowFetcher<BlockPassthrough::Disable>, UpdateReplaceModifier>,
               ModificationExecutor<AllRowsFetcher, UpsertModifier>,
-              ModificationExecutor<SingleRowFetcher<BlockPassthrough::Disable>, UpsertModifier>, TraversalExecutor,
-              EnumerateListExecutor, SubqueryStartExecutor, SubqueryEndExecutor, SortedCollectExecutor, LimitExecutor,
-              UnsortedGatherExecutor, SortExecutor, IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::NotMaterialize>,
+              ModificationExecutor<SingleRowFetcher<BlockPassthrough::Disable>, UpsertModifier>,
+              TraversalExecutor, EnumerateListExecutor, SubqueryStartExecutor, SubqueryEndExecutor,
+              SortedCollectExecutor, LimitExecutor, UnsortedGatherExecutor, SortExecutor,
+              IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::NotMaterialize>,
               IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::LateMaterialize>,
               IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::Materialize>,
               IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::NotMaterialize | arangodb::iresearch::MaterializeType::UseStoredValues>,
@@ -1170,12 +1173,13 @@ static SkipRowsRangeVariant constexpr skipRowsType() {
   static_assert(
       !std::is_same<Executor, LimitExecutor>::value || useFetcher,
       "LimitExecutor needs to implement skipRows() to work correctly");
- 
+
   if constexpr (useExecutor) {
     return SkipRowsRangeVariant::EXECUTOR;
+  } else {
+    static_assert(useFetcher);
+    return SkipRowsRangeVariant::FETCHER;
   }
-  static_assert(useFetcher);
-  return SkipRowsRangeVariant::FETCHER;
 }
 
 // Let's do it the C++ way.
@@ -1202,8 +1206,7 @@ static auto fastForwardType(AqlCall const& call, Executor const& e) -> FastForwa
   }
   // TODO: We only need to do this is the executor actually require to call.
   // e.g. Modifications will always need to be called. Limit only if it needs to report fullCount
-  if constexpr (is_one_of_v<Executor, LimitExecutor,
-                            ModificationExecutor<AllRowsFetcher, InsertModifier>,
+  if constexpr (is_one_of_v<Executor, LimitExecutor, ModificationExecutor<AllRowsFetcher, InsertModifier>,
                             ModificationExecutor<SingleRowFetcher<BlockPassthrough::Disable>, InsertModifier>,
                             ModificationExecutor<AllRowsFetcher, RemoveModifier>,
                             ModificationExecutor<SingleRowFetcher<BlockPassthrough::Disable>, RemoveModifier>,
@@ -1238,6 +1241,7 @@ auto ExecutionBlockImpl<Executor>::executeFetcher(AqlCallStack& stack, size_t co
     }
   } else {
     TRI_ASSERT(false);
+    THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
   }
 }
 

From 341ef5fbf6b4de3a1c7433b0c4d51e502f13a99d Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Mon, 2 Mar 2020 13:28:16 +0100
Subject: [PATCH 094/122] Feature/aql subquery execution block impl execute
 implementation base bugfixes (#11201)

* Fixed range-handling for Modification Executors

* DataRange handling in ModificationExecutor

* Honor batch-size defined by UpstreamExecutor

* Fixed compile issue

* More fixes in modification

* Remvoed log devel

* Fixed profiler Test. for NoResults node we cahnge the behaviour

* Activated getSome failure tests in ExecuteRestHandler

* Fixed skipping in Index

* Let the MultiDependencySingleROwFetcher return the correct states.

* Fixed non-maintainer compilation

* Attempt to fix windows compile issue

* Fixed the non-maintainer compile ina different way

* Allow waiting within old-style subquery

* Fixed invalid skipRwos in unsorted gather

* Added some Assertions in MultiAqlItemBlockInputRange

* Initialize dependdencies of MultiDependencyFetcher

* Fixed skipRows loop in UnsortingGatherNode

* Fixed return state of GatherNode
---
 arangod/Aql/AqlItemBlockInputMatrix.cpp       | 21 +++--
 arangod/Aql/AqlItemBlockInputMatrix.h         |  3 +-
 arangod/Aql/EnumerateCollectionExecutor.cpp   | 15 +---
 arangod/Aql/ExecutionBlockImpl.cpp            | 84 +++++++++++++++---
 arangod/Aql/ModificationExecutor.cpp          | 87 ++++++++++++++-----
 arangod/Aql/MultiAqlItemBlockInputRange.cpp   |  4 +-
 .../Aql/MultiDependencySingleRowFetcher.cpp   | 20 ++---
 arangod/Aql/RestAqlHandler.cpp                |  3 +
 arangod/Aql/SubqueryExecutor.cpp              | 79 +++++++++++------
 arangod/Aql/SubqueryExecutor.h                | 16 ++--
 arangod/Aql/UnsortedGatherExecutor.cpp        | 33 ++++---
 arangod/Utils/OperationCursor.cpp             |  2 +-
 tests/js/server/aql/aql-profiler.js           | 10 +--
 13 files changed, 262 insertions(+), 115 deletions(-)

diff --git a/arangod/Aql/AqlItemBlockInputMatrix.cpp b/arangod/Aql/AqlItemBlockInputMatrix.cpp
index bbd495784e27..3d4fc6839b7a 100644
--- a/arangod/Aql/AqlItemBlockInputMatrix.cpp
+++ b/arangod/Aql/AqlItemBlockInputMatrix.cpp
@@ -54,18 +54,22 @@ AqlItemBlockInputMatrix::AqlItemBlockInputMatrix(ExecutorState state, AqlItemMat
   }
 }
 
-AqlItemBlockInputRange AqlItemBlockInputMatrix::getNextInputRange() {
+AqlItemBlockInputRange& AqlItemBlockInputMatrix::getInputRange() {
   TRI_ASSERT(_aqlItemMatrix != nullptr);
 
+  if (_lastRange.hasDataRow()) {
+    return _lastRange;
+  }
+  // Need initialze lastRange
   if (_aqlItemMatrix->numberOfBlocks() == 0) {
-    return AqlItemBlockInputRange{upstreamState()};
+    _lastRange = {AqlItemBlockInputRange{upstreamState()}};
+  } else {
+    SharedAqlItemBlockPtr blockPtr = _aqlItemMatrix->getBlock(_currentBlockRowIndex);
+    auto [start, end] = blockPtr->getRelevantRange();
+    ExecutorState state = incrBlockIndex();
+    _lastRange = {state, 0, std::move(blockPtr), start};
   }
-
-  SharedAqlItemBlockPtr blockPtr = _aqlItemMatrix->getBlock(_currentBlockRowIndex);
-  auto [start, end] = blockPtr->getRelevantRange();
-  ExecutorState state = incrBlockIndex();
-
-  return {state, 0, std::move(blockPtr), start};
+  return _lastRange;
 }
 
 SharedAqlItemBlockPtr AqlItemBlockInputMatrix::getBlock() const noexcept {
@@ -170,5 +174,6 @@ ExecutorState AqlItemBlockInputMatrix::incrBlockIndex() {
 }
 
 void AqlItemBlockInputMatrix::resetBlockIndex() noexcept {
+  _lastRange = {AqlItemBlockInputRange{upstreamState()}};
   _currentBlockRowIndex = 0;
 }
diff --git a/arangod/Aql/AqlItemBlockInputMatrix.h b/arangod/Aql/AqlItemBlockInputMatrix.h
index 6e638aa2dbb6..01deb9852df7 100644
--- a/arangod/Aql/AqlItemBlockInputMatrix.h
+++ b/arangod/Aql/AqlItemBlockInputMatrix.h
@@ -51,7 +51,7 @@ class AqlItemBlockInputMatrix {
   // Will provide access to the first block (from _aqlItemMatrix)
   // After a block has been delivered, the block index will be increased.
   // Next call then will deliver the next block etc.
-  AqlItemBlockInputRange getNextInputRange();
+  AqlItemBlockInputRange& getInputRange();
   std::pair<ExecutorState, AqlItemMatrix const*> getMatrix() noexcept;
 
   ExecutorState upstreamState() const noexcept;
@@ -70,6 +70,7 @@ class AqlItemBlockInputMatrix {
   // Only if _aqlItemMatrix is set (and NOT a nullptr), we have a valid and
   // usable DataRange object available to work with.
   AqlItemMatrix* _aqlItemMatrix;
+  AqlItemBlockInputRange _lastRange{ExecutorState::HASMORE};
   size_t _currentBlockRowIndex = 0;
   ShadowAqlItemRow _shadowRow{CreateInvalidShadowRowHint{}};
 };
diff --git a/arangod/Aql/EnumerateCollectionExecutor.cpp b/arangod/Aql/EnumerateCollectionExecutor.cpp
index 3ff3220d415c..7dfe8894fb87 100644
--- a/arangod/Aql/EnumerateCollectionExecutor.cpp
+++ b/arangod/Aql/EnumerateCollectionExecutor.cpp
@@ -195,12 +195,10 @@ std::tuple<ExecutorState, EnumerateCollectionStats, size_t, AqlCall> EnumerateCo
     AqlItemBlockInputRange& inputRange, AqlCall& call) {
   AqlCall upstreamCall{};
   EnumerateCollectionStats stats{};
-  bool offsetPhase = (call.getOffset() > 0);
 
   TRI_ASSERT(_documentProducingFunctionContext.getAndResetNumScanned() == 0);
   TRI_ASSERT(_documentProducingFunctionContext.getAndResetNumFiltered() == 0);
-
-  while (inputRange.hasDataRow() && call.shouldSkip()) {
+  while ((inputRange.hasDataRow() || _cursorHasMore) && call.shouldSkip()) {
     uint64_t skipped = 0;
 
     if (!_cursorHasMore) {
@@ -210,13 +208,8 @@ std::tuple<ExecutorState, EnumerateCollectionStats, size_t, AqlCall> EnumerateCo
     if (_cursorHasMore) {
       TRI_ASSERT(_currentRow.isInitialized());
       // if offset is > 0, we're in offset skip phase
-      if (offsetPhase) {
-        if (skipped < call.getOffset()) {
-          skipped += skipEntries(call.getOffset(), stats);
-        } else {
-          // we skipped enough in our offset phase
-          break;
-        }
+      if (call.getOffset() > 0) {
+        skipped += skipEntries(call.getOffset(), stats);
       } else {
         // fullCount phase
         if (_infos.getFilter() == nullptr) {
@@ -276,7 +269,6 @@ std::tuple<ExecutorState, EnumerateCollectionStats, AqlCall> EnumerateCollection
   TRI_ASSERT(_documentProducingFunctionContext.getAndResetNumScanned() == 0);
   TRI_ASSERT(_documentProducingFunctionContext.getAndResetNumFiltered() == 0);
   _documentProducingFunctionContext.setOutputRow(&output);
-
   while (inputRange.hasDataRow() && !output.isFull()) {
     if (!_cursorHasMore) {
       initializeNewRow(inputRange);
@@ -309,7 +301,6 @@ std::tuple<ExecutorState, EnumerateCollectionStats, AqlCall> EnumerateCollection
   if (!_cursorHasMore) {
     initializeNewRow(inputRange);
   }
-
   return {inputRange.upstreamState(), stats, upstreamCall};
 }
 
diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index ca8ae4c1d24a..abf241d61570 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -1252,12 +1252,17 @@ auto ExecutionBlockImpl<Executor>::executeProduceRows(typename Fetcher::DataRang
   if constexpr (isNewStyleExecutor<Executor>) {
     if constexpr (is_one_of_v<Executor, UnsortedGatherExecutor>) {
       return _executor.produceRows(input, output);
+    } else if constexpr (is_one_of_v<Executor, SubqueryExecutor<true>, SubqueryExecutor<false>>) {
+      // The SubqueryExecutor has it's own special handling outside.
+      // SO this code is in fact not reachable
+      TRI_ASSERT(false);
+      THROW_ARANGO_EXCEPTION(TRI_ERROR_INTERNAL_AQL);
     } else {
       auto [state, stats, call] = _executor.produceRows(input, output);
       return {state, stats, call, 0};
     }
   } else {
-    TRI_ASSERT(false);
+    return {ExecutorState::DONE, typename Executor::Stats{}, AqlCall{}, 0};
   }
 }
 
@@ -1274,6 +1279,11 @@ auto ExecutionBlockImpl<Executor>::executeSkipRowsRange(typename Fetcher::DataRa
         auto res = _executor.skipRowsRange(inputRange, call);
         _executorReturnedDone = std::get<ExecutorState>(res) == ExecutorState::DONE;
         return res;
+      } else if constexpr (is_one_of_v<Executor, SubqueryExecutor<true>, SubqueryExecutor<false>>) {
+        // The SubqueryExecutor has it's own special handling outside.
+        // SO this code is in fact not reachable
+        TRI_ASSERT(false);
+        THROW_ARANGO_EXCEPTION(TRI_ERROR_INTERNAL_AQL);
       } else {
         auto [state, stats, skipped, localCall] =
             _executor.skipRowsRange(inputRange, call);
@@ -1576,10 +1586,19 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
     TRI_ASSERT(!(clientCall.getOffset() == 0 && clientCall.softLimit == AqlCall::Limit{0}));
     TRI_ASSERT(!(clientCall.hasSoftLimit() && clientCall.fullCount));
     TRI_ASSERT(!(clientCall.hasSoftLimit() && clientCall.hasHardLimit()));
+    if constexpr (is_one_of_v<Executor, SubqueryExecutor<true>, SubqueryExecutor<false>>) {
+      // The old subquery executor can in-fact return waiting on produce call.
+      // if it needs to wait for the subquery.
+      // So we need to allow the return state here as well.
+      TRI_ASSERT(_execState == ExecState::CHECKCALL ||
+                 _execState == ExecState::SHADOWROWS || _execState == ExecState::UPSTREAM ||
+                 _execState == ExecState::PRODUCE || _execState == ExecState::SKIP);
+    } else {
+      // We can only have returned the following internal states
+      TRI_ASSERT(_execState == ExecState::CHECKCALL || _execState == ExecState::SHADOWROWS ||
+                 _execState == ExecState::UPSTREAM);
+    }
 
-    // We can only have returned the following internal states
-    TRI_ASSERT(_execState == ExecState::CHECKCALL || _execState == ExecState::SHADOWROWS ||
-               _execState == ExecState::UPSTREAM);
     // Skip can only be > 0 if we are in upstream cases.
     TRI_ASSERT(_skipped == 0 || _execState == ExecState::UPSTREAM);
 
@@ -1633,8 +1652,33 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
               clientCall.getLimit() == 0 && clientCall.needsFullCount();
 #endif
           LOG_QUERY("1f786", DEBUG) << printTypeInfo() << " call skipRows " << clientCall;
-          auto [state, stats, skippedLocal, call, dependency] =
-              executeSkipRowsRange(_lastRange, clientCall);
+
+          ExecutorState state = ExecutorState::HASMORE;
+          typename Executor::Stats stats;
+          size_t skippedLocal = 0;
+          AqlCall call{};
+          size_t dependency = 0;
+          if constexpr (is_one_of_v<Executor, SubqueryExecutor<true>>) {
+            // NOTE: The subquery Executor will by itself call EXECUTE on it's
+            // subquery. This can return waiting => we can get a WAITING state
+            // here. We can only get the waiting state for SUbquery executors.
+            ExecutionState subqueryState = ExecutionState::HASMORE;
+            std::tie(subqueryState, stats, skippedLocal, call) =
+                _executor.skipRowsRange(_lastRange, clientCall);
+            if (subqueryState == ExecutionState::WAITING) {
+              TRI_ASSERT(skippedLocal == 0);
+              return {subqueryState, 0, nullptr};
+            } else if (subqueryState == ExecutionState::DONE) {
+              state = ExecutorState::DONE;
+            } else {
+              state = ExecutorState::HASMORE;
+            }
+          } else {
+            // Execute skipSome
+            std::tie(state, stats, skippedLocal, call, dependency) =
+                executeSkipRowsRange(_lastRange, clientCall);
+          }
+
           _requestedDependency = dependency;
 #ifdef ARANGODB_ENABLE_MAINTAINER_MODE
           // Assertion: We did skip 'skippedLocal' documents here.
@@ -1695,11 +1739,29 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
           }
           TRI_ASSERT(_outputItemRow);
           TRI_ASSERT(!_executorReturnedDone);
-
-          // Execute getSome
-          auto const [state, stats, call, dependency] =
-              executeProduceRows(_lastRange, *_outputItemRow);
-          // TODO: Check
+          ExecutorState state = ExecutorState::HASMORE;
+          typename Executor::Stats stats;
+          AqlCall call{};
+          size_t dependency = 0;
+          if constexpr (is_one_of_v<Executor, SubqueryExecutor<true>, SubqueryExecutor<false>>) {
+            // NOTE: The subquery Executor will by itself call EXECUTE on it's
+            // subquery. This can return waiting => we can get a WAITING state
+            // here. We can only get the waiting state for SUbquery executors.
+            ExecutionState subqueryState = ExecutionState::HASMORE;
+            std::tie(subqueryState, stats, call) =
+                _executor.produceRows(_lastRange, *_outputItemRow);
+            if (subqueryState == ExecutionState::WAITING) {
+              return {subqueryState, 0, nullptr};
+            } else if (subqueryState == ExecutionState::DONE) {
+              state = ExecutorState::DONE;
+            } else {
+              state = ExecutorState::HASMORE;
+            }
+          } else {
+            // Execute getSome
+            std::tie(state, stats, call, dependency) =
+                executeProduceRows(_lastRange, *_outputItemRow);
+          }
           _requestedDependency = dependency;
           _executorReturnedDone = state == ExecutorState::DONE;
           _engine->_stats += stats;
diff --git a/arangod/Aql/ModificationExecutor.cpp b/arangod/Aql/ModificationExecutor.cpp
index 5556ae39b93d..6554c6574fed 100644
--- a/arangod/Aql/ModificationExecutor.cpp
+++ b/arangod/Aql/ModificationExecutor.cpp
@@ -169,17 +169,34 @@ template <typename FetcherType, typename ModifierType>
     typename FetcherType::DataRange& input, OutputAqlItemRow& output)
     -> std::tuple<ExecutorState, ModificationStats, AqlCall> {
   TRI_ASSERT(_infos._trx);
-
+  AqlCall upstreamCall{};
+  if constexpr (std::is_same_v<ModifierType, UpsertModifier> &&
+                !std::is_same_v<FetcherType, AllRowsFetcher>) {
+    upstreamCall.softLimit = _modifier.getBatchSize();
+  }
   auto stats = ModificationStats{};
 
   _modifier.reset();
+  if (!input.hasDataRow()) {
+    // Input is empty
+    return {input.upstreamState(), stats, upstreamCall};
+  }
+
+  TRI_IF_FAILURE("ModificationBlock::getSome") {
+    THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
+  }
 
-  ExecutorState upstreamState = ExecutorState::HASMORE;
   // only produce at most output.numRowsLeft() many results
+  ExecutorState upstreamState = ExecutorState::HASMORE;
   if constexpr (std::is_same_v<typename FetcherType::DataRange, AqlItemBlockInputMatrix>) {
-    auto range = input.getNextInputRange();
+    auto& range = input.getInputRange();
     doCollect(range, output.numRowsLeft());
     upstreamState = range.upstreamState();
+    if (upstreamState == ExecutorState::DONE) {
+      // We are done with this input.
+      // We need to forward it to the last ShadowRow.
+      input.skipAllRemainingDataRows();
+    }
   } else {
     doCollect(input, output.numRowsLeft());
     upstreamState = input.upstreamState();
@@ -196,39 +213,65 @@ template <typename FetcherType, typename ModifierType>
     doOutput(output, stats);
   }
 
-  return {upstreamState, stats, AqlCall{}};
+  return {upstreamState, stats, upstreamCall};
 }
 
 template <typename FetcherType, typename ModifierType>
 [[nodiscard]] auto ModificationExecutor<FetcherType, ModifierType>::skipRowsRange(
     typename FetcherType::DataRange& input, AqlCall& call)
     -> std::tuple<ExecutorState, Stats, size_t, AqlCall> {
+  AqlCall upstreamCall{};
+  if constexpr (std::is_same_v<ModifierType, UpsertModifier> &&
+                !std::is_same_v<FetcherType, AllRowsFetcher>) {
+    upstreamCall.softLimit = _modifier.getBatchSize();
+  }
+
   auto stats = ModificationStats{};
-  _modifier.reset();
 
-  ExecutorState upstreamState = ExecutorState::HASMORE;
-  // only produce at most output.numRowsLeft() many results
-  if constexpr (std::is_same_v<typename FetcherType::DataRange, AqlItemBlockInputMatrix>) {
-    auto range = input.getNextInputRange();
-    doCollect(range, call.getOffset());
-    upstreamState = range.upstreamState();
-  } else {
-    doCollect(input, call.getOffset());
-    upstreamState = input.upstreamState();
+  TRI_IF_FAILURE("ModificationBlock::getSome") {
+    THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
   }
 
-  if (_modifier.nrOfOperations() > 0) {
-    _modifier.transact();
-
-    if (_infos._doCount) {
-      stats.addWritesExecuted(_modifier.nrOfWritesExecuted());
-      stats.addWritesIgnored(_modifier.nrOfWritesIgnored());
+  // only produce at most output.numRowsLeft() many results
+  ExecutorState upstreamState = input.upstreamState();
+  while (input.hasDataRow() && call.needSkipMore()) {
+    _modifier.reset();
+    size_t toSkip = call.getOffset();
+    if (call.getLimit() == 0 && call.hasHardLimit()) {
+      // We need to produce all modification operations.
+      // If we are bound by limits or not!
+      toSkip = ExecutionBlock::SkipAllSize();
+    }
+    if constexpr (std::is_same_v<typename FetcherType::DataRange, AqlItemBlockInputMatrix>) {
+      auto& range = input.getInputRange();
+      if (range.hasDataRow()) {
+        doCollect(range, toSkip);
+      }
+      upstreamState = range.upstreamState();
+      if (upstreamState == ExecutorState::DONE) {
+        // We are done with this input.
+        // We need to forward it to the last ShadowRow.
+        input.skipAllRemainingDataRows();
+        TRI_ASSERT(input.upstreamState() == ExecutorState::DONE);
+      }
+    } else {
+      doCollect(input, toSkip);
+      upstreamState = input.upstreamState();
     }
 
-    call.didSkip(_modifier.nrOfOperations());
+    if (_modifier.nrOfOperations() > 0) {
+      _modifier.transact();
+
+      if (_infos._doCount) {
+        stats.addWritesExecuted(_modifier.nrOfWritesExecuted());
+        stats.addWritesIgnored(_modifier.nrOfWritesIgnored());
+      }
+
+      call.didSkip(_modifier.nrOfOperations());
+    }
   }
 
-  return {upstreamState, stats, _modifier.nrOfOperations(), AqlCall{}};
+  return {upstreamState, stats, call.getSkipCount(), upstreamCall};
 }
 
 using NoPassthroughSingleRowFetcher = SingleRowFetcher<BlockPassthrough::Disable>;
diff --git a/arangod/Aql/MultiAqlItemBlockInputRange.cpp b/arangod/Aql/MultiAqlItemBlockInputRange.cpp
index 8b5aad8595d7..556ee2c174a7 100644
--- a/arangod/Aql/MultiAqlItemBlockInputRange.cpp
+++ b/arangod/Aql/MultiAqlItemBlockInputRange.cpp
@@ -36,12 +36,14 @@ MultiAqlItemBlockInputRange::MultiAqlItemBlockInputRange(ExecutorState state,
                                                          std::size_t skipped,
                                                          std::size_t nrInputRanges) {
   _inputs.resize(nrInputRanges, AqlItemBlockInputRange{state, skipped});
+  TRI_ASSERT(nrInputRanges > 0);
 }
 
 auto MultiAqlItemBlockInputRange::resizeIfNecessary(ExecutorState state, size_t skipped,
                                                     size_t nrInputRanges) -> void {
   // We never want to reduce the number of dependencies.
   TRI_ASSERT(_inputs.size() <= nrInputRanges);
+  TRI_ASSERT(nrInputRanges > 0);
   if (_inputs.size() < nrInputRanges) {
     _inputs.resize(nrInputRanges, AqlItemBlockInputRange{state, skipped});
   }
@@ -89,7 +91,7 @@ auto MultiAqlItemBlockInputRange::hasShadowRow() const noexcept -> bool {
 //       * assert that all dependencies are on a shadow row?
 auto MultiAqlItemBlockInputRange::peekShadowRow() const -> arangodb::aql::ShadowAqlItemRow {
   TRI_ASSERT(!hasDataRow());
-
+  TRI_ASSERT(!_inputs.empty());
   // TODO: Correct?
   return _inputs.at(0).peekShadowRow();
 }
diff --git a/arangod/Aql/MultiDependencySingleRowFetcher.cpp b/arangod/Aql/MultiDependencySingleRowFetcher.cpp
index 517542e953e1..aac3b3b866ac 100644
--- a/arangod/Aql/MultiDependencySingleRowFetcher.cpp
+++ b/arangod/Aql/MultiDependencySingleRowFetcher.cpp
@@ -368,11 +368,16 @@ auto MultiDependencySingleRowFetcher::useStack(AqlCallStack const& stack) -> voi
 auto MultiDependencySingleRowFetcher::executeForDependency(size_t const dependency,
                                                            AqlCallStack& stack)
     -> std::tuple<ExecutionState, size_t, AqlItemBlockInputRange> {
+  if (_dependencyStates.empty()) {
+    initDependencies();
+  }
   auto [state, skipped, block] = _dependencyProxy->executeForDependency(dependency, stack);
 
   if (state == ExecutionState::WAITING) {
     return {state, 0, AqlItemBlockInputRange{ExecutorState::HASMORE}};
   }
+  ExecutorState execState =
+      state == ExecutionState::DONE ? ExecutorState::DONE : ExecutorState::HASMORE;
 
   _dependencyStates.at(dependency) = state;
   if (std::any_of(std::begin(_dependencyStates), std::end(_dependencyStates),
@@ -384,18 +389,9 @@ auto MultiDependencySingleRowFetcher::executeForDependency(size_t const dependen
     state = ExecutionState::DONE;
   }
   if (block == nullptr) {
-    if (state == ExecutionState::HASMORE) {
-      return {state, skipped, AqlItemBlockInputRange{ExecutorState::HASMORE, skipped}};
-    }
-    return {state, skipped, AqlItemBlockInputRange{ExecutorState::DONE, skipped}};
+    return {state, skipped, AqlItemBlockInputRange{execState, skipped}};
   }
-
+  TRI_ASSERT(block != nullptr);
   auto [start, end] = block->getRelevantRange();
-  if (state == ExecutionState::HASMORE) {
-    TRI_ASSERT(block != nullptr);
-    return {state, skipped,
-            AqlItemBlockInputRange{ExecutorState::DONE, skipped, block, start}};
-  }
-  return {state, skipped,
-          AqlItemBlockInputRange{ExecutorState::DONE, skipped, block, start}};
+  return {state, skipped, AqlItemBlockInputRange{execState, skipped, block, start}};
 }
diff --git a/arangod/Aql/RestAqlHandler.cpp b/arangod/Aql/RestAqlHandler.cpp
index 58346af21a67..fa57a645b8b2 100644
--- a/arangod/Aql/RestAqlHandler.cpp
+++ b/arangod/Aql/RestAqlHandler.cpp
@@ -734,6 +734,9 @@ RestStatus RestAqlHandler::handleUseQuery(std::string const& operation,
       generateError(std::move(maybeExecuteCall).result());
       return RestStatus::DONE;
     }
+    TRI_IF_FAILURE("RestAqlHandler::getSome") {
+      THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
+    }
     auto& executeCall = maybeExecuteCall.get();
 
     auto items = SharedAqlItemBlockPtr{};
diff --git a/arangod/Aql/SubqueryExecutor.cpp b/arangod/Aql/SubqueryExecutor.cpp
index 72074816f0fe..c84b47f0346f 100644
--- a/arangod/Aql/SubqueryExecutor.cpp
+++ b/arangod/Aql/SubqueryExecutor.cpp
@@ -158,7 +158,7 @@ std::pair<ExecutionState, NoStats> SubqueryExecutor<isModificationSubquery>::pro
 template <bool isModificationSubquery>
 auto SubqueryExecutor<isModificationSubquery>::produceRows(AqlItemBlockInputRange& input,
                                                            OutputAqlItemRow& output)
-    -> std::tuple<ExecutorState, Stats, AqlCall> {
+    -> std::tuple<ExecutionState, Stats, AqlCall> {
   auto getUpstreamCall = [&]() {
     AqlCall upstreamCall = output.getClientCall();
     if constexpr (isModificationSubquery) {
@@ -168,12 +168,12 @@ auto SubqueryExecutor<isModificationSubquery>::produceRows(AqlItemBlockInputRang
     return upstreamCall;
   };
 
-  LOG_DEVEL_SQ << uint64_t(this) <<  "produceRows " << output.getClientCall();
+  LOG_DEVEL_SQ << uint64_t(this) << "produceRows " << output.getClientCall();
 
   if (_state == ExecutorState::DONE && !_input.isInitialized()) {
     // We have seen DONE upstream, and we have discarded our local reference
     // to the last input, we will not be able to produce results anymore.
-    return {_state, NoStats{}, getUpstreamCall()};
+    return {translatedReturnType(), NoStats{}, getUpstreamCall()};
   }
   while (true) {
     if (_subqueryInitialized) {
@@ -183,14 +183,19 @@ auto SubqueryExecutor<isModificationSubquery>::produceRows(AqlItemBlockInputRang
       if (_infos.isConst() && !_input.isFirstDataRowInBlock()) {
         // Simply write
         writeOutput(output);
-        LOG_DEVEL_SQ << uint64_t(this) << "wrote output is const " << _state << " " << getUpstreamCall();
-        return {_state, NoStats{}, getUpstreamCall()};
+        LOG_DEVEL_SQ << uint64_t(this) << "wrote output is const " << _state
+                     << " " << getUpstreamCall();
+        return {translatedReturnType(), NoStats{}, getUpstreamCall()};
       }
 
       // Non const case, or first run in const
       auto [state, skipped, block] = _subquery.execute(AqlCallStack(AqlCall{}));
       TRI_ASSERT(skipped == 0);
+      if (state == ExecutionState::WAITING) {
+        return {state, NoStats{}, getUpstreamCall()};
+      }
       // We get a result
+      LOG_DEVEL_SQ << uint64_t(this) << " we get subquery result";
       if (block != nullptr) {
         TRI_IF_FAILURE("SubqueryBlock::executeSubquery") {
           THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
@@ -198,6 +203,8 @@ auto SubqueryExecutor<isModificationSubquery>::produceRows(AqlItemBlockInputRang
 
         if (_infos.returnsData()) {
           TRI_ASSERT(_subqueryResults != nullptr);
+          LOG_DEVEL_SQ << uint64_t(this)
+                       << " store subquery result for writing " << block->size();
           _subqueryResults->emplace_back(std::move(block));
         }
       }
@@ -205,28 +212,35 @@ auto SubqueryExecutor<isModificationSubquery>::produceRows(AqlItemBlockInputRang
       // Subquery DONE
       if (state == ExecutionState::DONE) {
         writeOutput(output);
-        LOG_DEVEL_SQ << uint64_t(this) << "wrote output subquery done " << _state << " " << getUpstreamCall();
-        return {_state, NoStats{}, getUpstreamCall()};
+        LOG_DEVEL_SQ << uint64_t(this) << "wrote output subquery done "
+                     << _state << " " << getUpstreamCall();
+        return {translatedReturnType(), NoStats{}, getUpstreamCall()};
       }
 
     } else {
       // init new subquery
       if (!_input) {
         std::tie(_state, _input) = input.nextDataRow();
-        LOG_DEVEL_SQ << uint64_t(this) << " nextDataRow: " << _state << " " << _input.isInitialized();
+        LOG_DEVEL_SQ << uint64_t(this) << " nextDataRow: " << _state << " "
+                     << _input.isInitialized();
         if (!_input) {
           LOG_DEVEL_SQ << uint64_t(this) << "exit produce, no more input" << _state;
-          return {_state, NoStats{}, getUpstreamCall()};
+          return {translatedReturnType(), NoStats{}, getUpstreamCall()};
         }
       }
 
       TRI_ASSERT(_input);
       if (!_infos.isConst() || _input.isFirstDataRowInBlock()) {
-        auto initRes = _subquery.initializeCursor(_input);
+        LOG_DEVEL_SQ << "Subquery: Initialize cursor";
+        auto [state, result] = _subquery.initializeCursor(_input);
+        if (state == ExecutionState::WAITING) {
+          LOG_DEVEL_SQ << "Waiting on initialize cursor";
+          return {state, NoStats{}, AqlCall{}};
+        }
 
-        if (initRes.second.fail()) {
+        if (result.fail()) {
           // Error during initialize cursor
-          THROW_ARANGO_EXCEPTION(initRes.second);
+          THROW_ARANGO_EXCEPTION(result);
         }
         _subqueryResults = std::make_unique<std::vector<SharedAqlItemBlockPtr>>();
       }
@@ -294,10 +308,19 @@ SubqueryExecutor<isModificationSubquery>::fetchBlockForPassthrough(size_t atMost
   return {rv.first, {}, std::move(rv.second)};
 }
 
+template <bool isModificationSubquery>
+auto SubqueryExecutor<isModificationSubquery>::translatedReturnType() const
+    noexcept -> ExecutionState {
+  if (_state == ExecutorState::DONE) {
+    return ExecutionState::DONE;
+  }
+  return ExecutionState::HASMORE;
+}
+
+template <>
 template <>
-template <bool E, std::enable_if_t<E, int>>
-auto SubqueryExecutor<true>::skipRowsRange(AqlItemBlockInputRange& inputRange, AqlCall& call)
-    -> std::tuple<ExecutorState, Stats, size_t, AqlCall> {
+auto SubqueryExecutor<true>::skipRowsRange<>(AqlItemBlockInputRange& inputRange, AqlCall& call)
+    -> std::tuple<ExecutionState, Stats, size_t, AqlCall> {
   auto getUpstreamCall = [&]() {
     auto upstreamCall = AqlCall{};
     return upstreamCall;
@@ -305,12 +328,12 @@ auto SubqueryExecutor<true>::skipRowsRange(AqlItemBlockInputRange& inputRange, A
 
   size_t skipped = 0;
 
-  LOG_DEVEL_SQ << uint64_t(this) <<  "skipRowsRange " << call;
+  LOG_DEVEL_SQ << uint64_t(this) << "skipRowsRange " << call;
 
   if (_state == ExecutorState::DONE && !_input.isInitialized()) {
     // We have seen DONE upstream, and we have discarded our local reference
     // to the last input, we will not be able to produce results anymore.
-    return {_state, NoStats{}, 0, getUpstreamCall()};
+    return {translatedReturnType(), NoStats{}, 0, getUpstreamCall()};
   }
   while (true) {
     if (_subqueryInitialized) {
@@ -324,12 +347,16 @@ auto SubqueryExecutor<true>::skipRowsRange(AqlItemBlockInputRange& inputRange, A
         skipped += 1;
         call.didSkip(1);
         LOG_DEVEL_SQ << uint64_t(this) << "did skip one";
-        return {_state, NoStats{}, skipped, getUpstreamCall()};
+        return {translatedReturnType(), NoStats{}, skipped, getUpstreamCall()};
       }
 
       // Non const case, or first run in const
       auto [state, skipped, block] = _subquery.execute(AqlCallStack(AqlCall{}));
       TRI_ASSERT(skipped == 0);
+      if (state == ExecutionState::WAITING) {
+        return {state, NoStats{}, 0, getUpstreamCall()};
+      }
+
       // We get a result
       if (block != nullptr) {
         TRI_IF_FAILURE("SubqueryBlock::executeSubquery") {
@@ -349,7 +376,7 @@ auto SubqueryExecutor<true>::skipRowsRange(AqlItemBlockInputRange& inputRange, A
         skipped += 1;
         call.didSkip(1);
         LOG_DEVEL_SQ << uint64_t(this) << "did skip one";
-        return {_state, NoStats{}, skipped, getUpstreamCall()};
+        return {translatedReturnType(), NoStats{}, skipped, getUpstreamCall()};
       }
 
     } else {
@@ -359,17 +386,20 @@ auto SubqueryExecutor<true>::skipRowsRange(AqlItemBlockInputRange& inputRange, A
 
         if (!_input) {
           LOG_DEVEL_SQ << uint64_t(this) << "skipped nothing waiting for input " << _state;
-          return {_state, NoStats{}, skipped, getUpstreamCall()};
+          return {translatedReturnType(), NoStats{}, skipped, getUpstreamCall()};
         }
       }
 
       TRI_ASSERT(_input);
       if (!_infos.isConst() || _input.isFirstDataRowInBlock()) {
-        auto initRes = _subquery.initializeCursor(_input);
+        auto [state, result] = _subquery.initializeCursor(_input);
+        if (state == ExecutionState::WAITING) {
+          return {state, NoStats{}, 0, getUpstreamCall()};
+        }
 
-        if (initRes.second.fail()) {
+        if (result.fail()) {
           // Error during initialize cursor
-          THROW_ARANGO_EXCEPTION(initRes.second);
+          THROW_ARANGO_EXCEPTION(result);
         }
         _subqueryResults = std::make_unique<std::vector<SharedAqlItemBlockPtr>>();
       }
@@ -380,7 +410,4 @@ auto SubqueryExecutor<true>::skipRowsRange(AqlItemBlockInputRange& inputRange, A
 }
 
 template class ::arangodb::aql::SubqueryExecutor<true>;
-template auto SubqueryExecutor<true>::skipRowsRange(AqlItemBlockInputRange& inputRange,
-                                                    AqlCall& call)
-    -> std::tuple<ExecutorState, Stats, size_t, AqlCall>;
 template class ::arangodb::aql::SubqueryExecutor<false>;
diff --git a/arangod/Aql/SubqueryExecutor.h b/arangod/Aql/SubqueryExecutor.h
index c7fbee012be2..b9e5c299827b 100644
--- a/arangod/Aql/SubqueryExecutor.h
+++ b/arangod/Aql/SubqueryExecutor.h
@@ -23,11 +23,11 @@
 #ifndef ARANGOD_AQL_SUBQUERY_EXECUTOR_H
 #define ARANGOD_AQL_SUBQUERY_EXECUTOR_H
 
+#include "Aql/AqlCall.h"
+#include "Aql/AqlItemBlockInputRange.h"
 #include "Aql/ExecutionState.h"
 #include "Aql/ExecutorInfos.h"
 #include "Aql/InputAqlItemRow.h"
-#include "Aql/AqlItemBlockInputRange.h"
-#include "Aql/AqlCall.h"
 #include "Aql/Stats.h"
 #include "Basics/Result.h"
 
@@ -97,13 +97,13 @@ class SubqueryExecutor {
   std::pair<ExecutionState, Stats> produceRows(OutputAqlItemRow& output);
 
   [[nodiscard]] auto produceRows(AqlItemBlockInputRange& input, OutputAqlItemRow& output)
-      -> std::tuple<ExecutorState, Stats, AqlCall>;
+      -> std::tuple<ExecutionState, Stats, AqlCall>;
 
   // skipRowsRange <=> isModificationSubquery
 
-  template<bool E = isModificationSubquery, std::enable_if_t<E, int> = 0>
+  template <bool E = isModificationSubquery, std::enable_if_t<E, int> = 0>
   auto skipRowsRange(AqlItemBlockInputRange& inputRange, AqlCall& call)
-  -> std::tuple<ExecutorState, Stats, size_t, AqlCall>;
+      -> std::tuple<ExecutionState, Stats, size_t, AqlCall>;
 
   std::tuple<ExecutionState, Stats, SharedAqlItemBlockPtr> fetchBlockForPassthrough(size_t atMost);
 
@@ -114,6 +114,12 @@ class SubqueryExecutor {
    */
   void writeOutput(OutputAqlItemRow& output);
 
+  /**
+   * @brief Translate _state => to to execution allowing waiting.
+   *
+   */
+  auto translatedReturnType() const noexcept -> ExecutionState;
+
  private:
   Fetcher& _fetcher;
   SubqueryExecutorInfos& _infos;
diff --git a/arangod/Aql/UnsortedGatherExecutor.cpp b/arangod/Aql/UnsortedGatherExecutor.cpp
index e1b3221a640f..ef2babd051f2 100644
--- a/arangod/Aql/UnsortedGatherExecutor.cpp
+++ b/arangod/Aql/UnsortedGatherExecutor.cpp
@@ -85,25 +85,36 @@ auto UnsortedGatherExecutor::produceRows(typename Fetcher::DataRange& input,
 
 auto UnsortedGatherExecutor::skipRowsRange(typename Fetcher::DataRange& input, AqlCall& call)
     -> std::tuple<ExecutorState, Stats, size_t, AqlCall, size_t> {
-  auto skipped = size_t{0};
-  while (call.needSkipMore() && input.hasDataRow(currentDependency())) {
-    auto [state, inputRow] = input.nextDataRow(currentDependency());
-
-    call.didSkip(1);
-    skipped++;
+  while (call.needSkipMore() && !done()) {
+    if (input.hasDataRow(currentDependency())) {
+      auto [state, inputRow] = input.nextDataRow(currentDependency());
+      call.didSkip(1);
 
-    if (state == ExecutorState::DONE) {
-      advanceDependency();
+      if (state == ExecutorState::DONE) {
+        advanceDependency();
+      }
+    } else {
+      if (input.upstreamState(currentDependency()) == ExecutorState::DONE) {
+        advanceDependency();
+      } else {
+        // We need to fetch more first
+        break;
+      }
     }
   }
 
+  while (!done() && input.upstreamState(currentDependency()) == ExecutorState::DONE) {
+    advanceDependency();
+  }
+
   if (done()) {
     // here currentDependency is invalid which will cause things to crash
     // if we ask upstream in ExecutionBlockImpl. yolo.
-    return {ExecutorState::DONE, Stats{}, skipped, AqlCall{}, currentDependency()};
+    return {ExecutorState::DONE, Stats{}, call.getSkipCount(), AqlCall{},
+            currentDependency()};
   } else {
-    return {input.upstreamState(currentDependency()), Stats{}, skipped,
-            AqlCall{}, currentDependency()};
+    return {input.upstreamState(currentDependency()), Stats{},
+            call.getSkipCount(), AqlCall{}, currentDependency()};
   }
 }
 
diff --git a/arangod/Utils/OperationCursor.cpp b/arangod/Utils/OperationCursor.cpp
index 0245935344e3..198d508b838a 100644
--- a/arangod/Utils/OperationCursor.cpp
+++ b/arangod/Utils/OperationCursor.cpp
@@ -146,7 +146,7 @@ void OperationCursor::skipAll(uint64_t& skipped) {
   while (_hasMore) {
     uint64_t skippedLocal = 0;
     _indexIterator->skip(toSkip, skippedLocal);
-    if (skipped != toSkip) {
+    if (skippedLocal != toSkip) {
       _hasMore = false;
     }
     skipped += skippedLocal;
diff --git a/tests/js/server/aql/aql-profiler.js b/tests/js/server/aql/aql-profiler.js
index 50eca3fee3a3..31c08f58d75c 100644
--- a/tests/js/server/aql/aql-profiler.js
+++ b/tests/js/server/aql/aql-profiler.js
@@ -571,13 +571,13 @@ function ahuacatlProfilerTestSuite () {
     testNoResultsBlock1: function() {
       const query = 'FOR i IN 1..@rows FILTER 1 == 0 RETURN i';
 
-      // As the descendant blocks of NoResultsBlock don't get a single getSome
-      // call, they don't show up in the statistics.
+      // Also if we have no results, we do send a drop-all to dependecies
+      // potentielly we have modifiaction nodes that need to be executed.
 
       const genNodeList = () => [
-        {type: SingletonBlock, calls: 0, items: 0},
-        {type: CalculationBlock, calls: 0, items: 0},
-        {type: EnumerateListBlock, calls: 0, items: 0},
+        {type: SingletonBlock, calls: 1, items: 0},
+        {type: CalculationBlock, calls: 1, items: 0},
+        {type: EnumerateListBlock, calls: 1, items: 0},
         {type: NoResultsBlock, calls: 1, items: 0},
         {type: ReturnBlock, calls: 1, items: 0},
       ];

From c653260ca3a43e05e6460fcc5f4f3bdf59e130f1 Mon Sep 17 00:00:00 2001
From: Markus Pfeiffer <markuspf@users.noreply.github.com>
Date: Tue, 3 Mar 2020 09:03:49 +0000
Subject: [PATCH 095/122] Fix memory leak in traversal (#11210)

---
 arangod/Aql/TraversalExecutor.cpp | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arangod/Aql/TraversalExecutor.cpp b/arangod/Aql/TraversalExecutor.cpp
index c111df3861a4..7b54279e653e 100644
--- a/arangod/Aql/TraversalExecutor.cpp
+++ b/arangod/Aql/TraversalExecutor.cpp
@@ -184,15 +184,18 @@ auto TraversalExecutor::doOutput(OutputAqlItemRow& output) -> void {
     // traverser now has next v, e, p values
     if (_infos.useVertexOutput()) {
       AqlValue vertex = _traverser.lastVertexToAqlValue();
+      AqlValueGuard guard{vertex, true};
       output.cloneValueInto(_infos.vertexRegister(), _inputRow, vertex);
     }
     if (_infos.useEdgeOutput()) {
       AqlValue edge = _traverser.lastEdgeToAqlValue();
+      AqlValueGuard guard{edge, true};
       output.cloneValueInto(_infos.edgeRegister(), _inputRow, edge);
     }
     if (_infos.usePathOutput()) {
       transaction::BuilderLeaser tmp(_traverser.trx());
       AqlValue path = _traverser.pathToAqlValue(*tmp.builder());
+      AqlValueGuard guard{path, true};
       output.cloneValueInto(_infos.pathRegister(), _inputRow, path);
     }
     output.advanceRow();

From 41ce86054219eee979a520cff67e838d5db4e78d Mon Sep 17 00:00:00 2001
From: Markus Pfeiffer <markuspf@users.noreply.github.com>
Date: Tue, 3 Mar 2020 10:43:26 +0000
Subject: [PATCH 096/122] AqlSubqueryExecutionBlockImplExecuteImplementation
 use moveValueInto instead of cloneValueInto (#11213)

* Fix memory leak in traversal

* Use move instead of clone for AqlValues
---
 arangod/Aql/TraversalExecutor.cpp | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arangod/Aql/TraversalExecutor.cpp b/arangod/Aql/TraversalExecutor.cpp
index 7b54279e653e..92b6c7fc4048 100644
--- a/arangod/Aql/TraversalExecutor.cpp
+++ b/arangod/Aql/TraversalExecutor.cpp
@@ -185,18 +185,18 @@ auto TraversalExecutor::doOutput(OutputAqlItemRow& output) -> void {
     if (_infos.useVertexOutput()) {
       AqlValue vertex = _traverser.lastVertexToAqlValue();
       AqlValueGuard guard{vertex, true};
-      output.cloneValueInto(_infos.vertexRegister(), _inputRow, vertex);
+      output.moveValueInto(_infos.vertexRegister(), _inputRow, guard);
     }
     if (_infos.useEdgeOutput()) {
       AqlValue edge = _traverser.lastEdgeToAqlValue();
       AqlValueGuard guard{edge, true};
-      output.cloneValueInto(_infos.edgeRegister(), _inputRow, edge);
+      output.moveValueInto(_infos.edgeRegister(), _inputRow, guard);
     }
     if (_infos.usePathOutput()) {
       transaction::BuilderLeaser tmp(_traverser.trx());
       AqlValue path = _traverser.pathToAqlValue(*tmp.builder());
       AqlValueGuard guard{path, true};
-      output.cloneValueInto(_infos.pathRegister(), _inputRow, path);
+      output.moveValueInto(_infos.pathRegister(), _inputRow, guard);
     }
     output.advanceRow();
   }

From 26242a1987ab9261ea1e64255c854ee1f0ab1c6b Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Tue, 3 Mar 2020 17:19:37 +0100
Subject: [PATCH 097/122] Feature/aql subquery execution block impl execute
 implementation gather executors (#11202)

* Fixed range-handling for Modification Executors

* DataRange handling in ModificationExecutor

* Honor batch-size defined by UpstreamExecutor

* Fixed compile issue

* More fixes in modification

* Remvoed log devel

* Fixed profiler Test. for NoResults node we cahnge the behaviour

* Activated getSome failure tests in ExecuteRestHandler

* Fixed skipping in Index

* Let the MultiDependencySingleROwFetcher return the correct states.

* Fixed non-maintainer compilation

* Attempt to fix windows compile issue

* Fixed the non-maintainer compile ina different way

* Added API in MultiAqlItemBlockInputRange to get Number of dependencies

* Comments

* Savepoint commit, does not compile, but no harm is done. Will start breaking things now

* Another savepoint commit. does not compile, yet.

* First draft of new Style SortingGather not yet implemented: Parallelism this needs to be handled in ExecutionBlockImpl now.

* Allow waiting within old-style subquery

* Fixed invalid skipRwos in unsorted gather

* First draft of ParallelUnsortedGatherExecutor

* Removed unused local variables

* Added some Assertions in MultiAqlItemBlockInputRange

* Initialize dependdencies of MultiDependencyFetcher

* Fixed skipRows loop in UnsortingGatherNode

* Fixed return state of GatherNode

* Added an assertion before accessing a vectir unbounded
---
 arangod/Aql/ExecutionBlockImpl.cpp            |  18 +-
 arangod/Aql/MultiAqlItemBlockInputRange.cpp   |  17 +-
 arangod/Aql/MultiAqlItemBlockInputRange.h     |  14 +-
 .../Aql/ParallelUnsortedGatherExecutor.cpp    | 167 +++----
 arangod/Aql/ParallelUnsortedGatherExecutor.h  |  51 +-
 arangod/Aql/SortingGatherExecutor.cpp         | 460 +++++++-----------
 arangod/Aql/SortingGatherExecutor.h           | 116 +++--
 arangod/Aql/UnsortedGatherExecutor.h          |  25 +-
 8 files changed, 396 insertions(+), 472 deletions(-)

diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index abf241d61570..a81f1c6c3d7f 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -135,7 +135,7 @@ constexpr bool is_one_of_v = (std::is_same_v<T, Es> || ...);
  */
 template <typename Executor>
 constexpr bool isNewStyleExecutor = is_one_of_v<
-    Executor, FilterExecutor, SortedCollectExecutor, IdExecutor<ConstFetcher>,
+    Executor, FilterExecutor, SortedCollectExecutor, IdExecutor<ConstFetcher>, ParallelUnsortedGatherExecutor,
     IdExecutor<SingleRowFetcher<BlockPassthrough::Enable>>, ReturnExecutor, DistinctCollectExecutor, IndexExecutor,
     EnumerateCollectionExecutor, SubqueryExecutor<true>, SubqueryExecutor<false>, CountCollectExecutor,
     CalculationExecutor<CalculationType::Condition>, CalculationExecutor<CalculationType::Reference>,
@@ -151,8 +151,8 @@ constexpr bool isNewStyleExecutor = is_one_of_v<
     ModificationExecutor<AllRowsFetcher, UpdateReplaceModifier>,
     ModificationExecutor<SingleRowFetcher<BlockPassthrough::Disable>, UpdateReplaceModifier>,
     ModificationExecutor<AllRowsFetcher, UpsertModifier>,
-    ModificationExecutor<SingleRowFetcher<BlockPassthrough::Disable>, UpsertModifier>,
-    SubqueryStartExecutor, UnsortedGatherExecutor, SubqueryEndExecutor, TraversalExecutor,
+    ModificationExecutor<SingleRowFetcher<BlockPassthrough::Disable>, UpsertModifier>, SubqueryStartExecutor,
+    UnsortedGatherExecutor, SortingGatherExecutor, SubqueryEndExecutor, TraversalExecutor,
     KShortestPathsExecutor, ShortestPathExecutor, EnumerateListExecutor, LimitExecutor, SortExecutor,
     IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::NotMaterialize>,
     IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::LateMaterialize>,
@@ -1125,7 +1125,7 @@ static SkipRowsRangeVariant constexpr skipRowsType() {
   static_assert(
       useExecutor ==
           (is_one_of_v<
-              Executor, FilterExecutor, ShortestPathExecutor, ReturnExecutor, KShortestPathsExecutor,
+              Executor, FilterExecutor, ShortestPathExecutor, ReturnExecutor, KShortestPathsExecutor, ParallelUnsortedGatherExecutor,
               IdExecutor<SingleRowFetcher<BlockPassthrough::Enable>>, IdExecutor<ConstFetcher>,
               HashedCollectExecutor, IndexExecutor, EnumerateCollectionExecutor, DistinctCollectExecutor,
               ConstrainedSortExecutor, CountCollectExecutor, SubqueryExecutor<true>,
@@ -1139,9 +1139,9 @@ static SkipRowsRangeVariant constexpr skipRowsType() {
               ModificationExecutor<AllRowsFetcher, UpdateReplaceModifier>,
               ModificationExecutor<SingleRowFetcher<BlockPassthrough::Disable>, UpdateReplaceModifier>,
               ModificationExecutor<AllRowsFetcher, UpsertModifier>,
-              ModificationExecutor<SingleRowFetcher<BlockPassthrough::Disable>, UpsertModifier>,
-              TraversalExecutor, EnumerateListExecutor, SubqueryStartExecutor, SubqueryEndExecutor,
-              SortedCollectExecutor, LimitExecutor, UnsortedGatherExecutor, SortExecutor,
+              ModificationExecutor<SingleRowFetcher<BlockPassthrough::Disable>, UpsertModifier>, TraversalExecutor,
+              EnumerateListExecutor, SubqueryStartExecutor, SubqueryEndExecutor, SortedCollectExecutor,
+              LimitExecutor, UnsortedGatherExecutor, SortingGatherExecutor, SortExecutor,
               IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::NotMaterialize>,
               IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::LateMaterialize>,
               IResearchViewExecutor<false, arangodb::iresearch::MaterializeType::Materialize>,
@@ -1250,7 +1250,7 @@ auto ExecutionBlockImpl<Executor>::executeProduceRows(typename Fetcher::DataRang
                                                       OutputAqlItemRow& output)
     -> std::tuple<ExecutorState, typename Executor::Stats, AqlCall, size_t> {
   if constexpr (isNewStyleExecutor<Executor>) {
-    if constexpr (is_one_of_v<Executor, UnsortedGatherExecutor>) {
+    if constexpr (is_one_of_v<Executor, UnsortedGatherExecutor, SortingGatherExecutor, ParallelUnsortedGatherExecutor>) {
       return _executor.produceRows(input, output);
     } else if constexpr (is_one_of_v<Executor, SubqueryExecutor<true>, SubqueryExecutor<false>>) {
       // The SubqueryExecutor has it's own special handling outside.
@@ -1273,7 +1273,7 @@ auto ExecutionBlockImpl<Executor>::executeSkipRowsRange(typename Fetcher::DataRa
   if constexpr (isNewStyleExecutor<Executor>) {
     call.skippedRows = 0;
     if constexpr (skipRowsType<Executor>() == SkipRowsRangeVariant::EXECUTOR) {
-      if constexpr (is_one_of_v<Executor, UnsortedGatherExecutor>) {
+      if constexpr (is_one_of_v<Executor, UnsortedGatherExecutor, SortingGatherExecutor, ParallelUnsortedGatherExecutor>) {
         // If the executor has a method skipRowsRange, to skip outputs.
         // Every non-passthrough executor needs to implement this.
         auto res = _executor.skipRowsRange(inputRange, call);
diff --git a/arangod/Aql/MultiAqlItemBlockInputRange.cpp b/arangod/Aql/MultiAqlItemBlockInputRange.cpp
index 556ee2c174a7..ab8ea0d32e51 100644
--- a/arangod/Aql/MultiAqlItemBlockInputRange.cpp
+++ b/arangod/Aql/MultiAqlItemBlockInputRange.cpp
@@ -67,12 +67,23 @@ auto MultiAqlItemBlockInputRange::hasDataRow() const noexcept -> bool {
                      });
 }
 
+auto MultiAqlItemBlockInputRange::rangeForDependency(size_t const dependency)
+    -> AqlItemBlockInputRange& {
+  TRI_ASSERT(dependency < _inputs.size());
+  return _inputs.at(dependency);
+}
+
 auto MultiAqlItemBlockInputRange::peekDataRow(size_t const dependency) const
     -> std::pair<ExecutorState, arangodb::aql::InputAqlItemRow> {
   TRI_ASSERT(dependency < _inputs.size());
   return _inputs.at(dependency).peekDataRow();
 }
 
+auto MultiAqlItemBlockInputRange::skipAll(size_t const dependency) noexcept -> std::size_t {
+  TRI_ASSERT(dependency < _inputs.size());
+  return _inputs.at(dependency).skipAll();
+}
+
 auto MultiAqlItemBlockInputRange::nextDataRow(size_t const dependency)
     -> std::pair<ExecutorState, arangodb::aql::InputAqlItemRow> {
   TRI_ASSERT(dependency < _inputs.size());
@@ -132,7 +143,7 @@ auto MultiAqlItemBlockInputRange::isDone() const -> bool {
   return res;
 }
 
-size_t MultiAqlItemBlockInputRange::skipAllRemainingDataRows() {
+auto MultiAqlItemBlockInputRange::skipAllRemainingDataRows() -> size_t {
   for (size_t i = 0; i < _inputs.size(); i++) {
     _inputs.at(i).skipAllRemainingDataRows();
     if (_inputs.at(i).upstreamState() == ExecutorState::HASMORE) {
@@ -141,3 +152,7 @@ size_t MultiAqlItemBlockInputRange::skipAllRemainingDataRows() {
   }
   return 0;
 }
+
+auto MultiAqlItemBlockInputRange::numberDependencies() const noexcept -> size_t {
+  return _inputs.size();
+}
\ No newline at end of file
diff --git a/arangod/Aql/MultiAqlItemBlockInputRange.h b/arangod/Aql/MultiAqlItemBlockInputRange.h
index e23a65f5ad7a..74aa1584c2ac 100644
--- a/arangod/Aql/MultiAqlItemBlockInputRange.h
+++ b/arangod/Aql/MultiAqlItemBlockInputRange.h
@@ -49,8 +49,18 @@ class MultiAqlItemBlockInputRange {
   bool hasDataRow() const noexcept;
   bool hasDataRow(size_t const dependency) const noexcept;
 
+  /**
+   * @brief Get a reference to the range of a given dependency
+   * NOTE: Modifing this range will modify the state of this class as well
+   *
+   * @param dependency index of the dependency
+   * @return AqlItemBlockInputRange& Modifyable reference to the input data stream
+   */
+  auto rangeForDependency(size_t const dependency) -> AqlItemBlockInputRange&;
+
   std::pair<ExecutorState, arangodb::aql::InputAqlItemRow> peekDataRow(size_t const dependency) const;
   std::pair<ExecutorState, arangodb::aql::InputAqlItemRow> nextDataRow(size_t const dependency);
+  auto skipAll(size_t const dependency) noexcept -> std::size_t;
 
   bool hasShadowRow() const noexcept;
 
@@ -65,7 +75,9 @@ class MultiAqlItemBlockInputRange {
 
   auto setDependency(size_t const dependency, AqlItemBlockInputRange& range) -> void;
 
-  size_t skipAllRemainingDataRows();
+  auto skipAllRemainingDataRows() -> size_t;
+
+  auto numberDependencies() const noexcept -> size_t;
 
  private:
   ExecutorState _finalState{ExecutorState::HASMORE};
diff --git a/arangod/Aql/ParallelUnsortedGatherExecutor.cpp b/arangod/Aql/ParallelUnsortedGatherExecutor.cpp
index 629d8bea2893..cc5e83a32b04 100644
--- a/arangod/Aql/ParallelUnsortedGatherExecutor.cpp
+++ b/arangod/Aql/ParallelUnsortedGatherExecutor.cpp
@@ -39,11 +39,15 @@ ParallelUnsortedGatherExecutorInfos::ParallelUnsortedGatherExecutorInfos(
                     nrInOutRegisters, nrInOutRegisters,
                     std::move(registersToClear), std::move(registersToKeep)) {}
 
-ParallelUnsortedGatherExecutor::ParallelUnsortedGatherExecutor(Fetcher& fetcher, Infos& infos)
-    : _fetcher(fetcher), _numberDependencies(0), _currentDependency(0), _skipped(0) {}
+ParallelUnsortedGatherExecutor::ParallelUnsortedGatherExecutor(Fetcher&, Infos& infos) {}
 
 ParallelUnsortedGatherExecutor::~ParallelUnsortedGatherExecutor() = default;
 
+auto ParallelUnsortedGatherExecutor::upstreamCall(AqlCall const& clientCall) const
+    noexcept -> AqlCall {
+  return clientCall;
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 /// @brief Guarantees requiredby this this block:
 ///        1) For every dependency the input is sorted, according to the same strategy.
@@ -58,117 +62,74 @@ ParallelUnsortedGatherExecutor::~ParallelUnsortedGatherExecutor() = default;
 ///
 ////////////////////////////////////////////////////////////////////////////////
 
-std::pair<ExecutionState, NoStats> ParallelUnsortedGatherExecutor::produceRows(OutputAqlItemRow& output) {
-  initDependencies();
-  
-  ExecutionState state;
-  InputAqlItemRow inputRow = InputAqlItemRow{CreateInvalidInputRowHint{}};
-  
-  size_t x;
-  for (x = 0; x < _numberDependencies; ++x) {
-    size_t i = (_currentDependency + x) % _numberDependencies;
-  
-    if (_upstream[i] == ExecutionState::DONE) {
-      continue;
-    }
-    
-    size_t tmp = 0;
-    
-    state = ExecutionState::HASMORE;
-    while (!output.isFull() && state == ExecutionState::HASMORE) {
-      std::tie(state, inputRow) = _fetcher.fetchRowForDependency(i, output.numRowsLeft() /*atMost*/);
-      if (inputRow) {
-        output.copyRow(inputRow);
-        TRI_ASSERT(output.produced());
+auto ParallelUnsortedGatherExecutor::produceRows(typename Fetcher::DataRange& input,
+                                                 OutputAqlItemRow& output)
+    -> std::tuple<ExecutorState, Stats, AqlCall, size_t> {
+  // Illegal dependency, on purpose to trigger asserts
+  size_t waitingDep = input.numberDependencies();
+  for (size_t dep = 0; dep < input.numberDependencies(); ++dep) {
+    while (!output.isFull()) {
+      auto [state, row] = input.nextDataRow(dep);
+      if (row) {
+        output.copyRow(row);
         output.advanceRow();
-        tmp++;
+      } else {
+        // This output did not produce anything
+        if (state == ExecutorState::HASMORE) {
+          waitingDep = dep;
+        }
+        break;
       }
     }
-    
-    _upstream[i] = state;
-    if (output.isFull()) {
-      break;
-    }
-  }
-  _currentDependency = x;
-  
-  NoStats stats;
-  
-  // fix assert in ExecutionBlockImpl<E>::getSomeWithoutTrace
-  if (output.isFull()) {
-    return {ExecutionState::HASMORE, stats};
-  }
-  
-  size_t numWaiting = 0;
-  for (x = 0; x < _numberDependencies; ++x) {
-    if (_upstream[x] == ExecutionState::HASMORE) {
-      return {ExecutionState::HASMORE, stats};
-    } else if (_upstream[x] == ExecutionState::WAITING) {
-      numWaiting++;
-    }
   }
-  if (numWaiting > 0) {
-    return {ExecutionState::WAITING, stats};
+  if (input.isDone()) {
+    // We cannot have one that we are waiting on, if we are done.
+    TRI_ASSERT(waitingDep == input.numberDependencies());
+    return {ExecutorState::DONE, NoStats{}, AqlCall{}, waitingDep};
   }
-  
-  TRI_ASSERT(std::all_of(_upstream.begin(), _upstream.end(), [](auto const& s) { return s == ExecutionState::DONE; } ));
-  return {ExecutionState::DONE, stats};
+  return {ExecutorState::HASMORE, NoStats{}, upstreamCall(output.getClientCall()), waitingDep};
 }
 
-std::tuple<ExecutionState, ParallelUnsortedGatherExecutor::Stats, size_t>
-ParallelUnsortedGatherExecutor::skipRows(size_t const toSkip) {
-  initDependencies();
-  TRI_ASSERT(_skipped <= toSkip);
-  
-  ExecutionState state = ExecutionState::HASMORE;
-  while (_skipped < toSkip) {
-    
-    const size_t i = _currentDependency;
-    if (_upstream[i] == ExecutionState::DONE) {
-      if (std::all_of(_upstream.begin(), _upstream.end(),
-                      [](auto s) { return s == ExecutionState::DONE; })) {
-         state = ExecutionState::DONE;
-         break;
-       }
-      _currentDependency = (i + 1) % _numberDependencies;
-       continue;
-     }
-    
-    TRI_ASSERT(_skipped <= toSkip);
+auto ParallelUnsortedGatherExecutor::skipRowsRange(typename Fetcher::DataRange& input,
+                                                   AqlCall& call)
+    -> std::tuple<ExecutorState, Stats, size_t, AqlCall, size_t> {
+  size_t waitingDep = input.numberDependencies();
+  for (size_t dep = 0; dep < input.numberDependencies(); ++dep) {
+    auto& range = input.rangeForDependency(dep);
+    while (call.needSkipMore()) {
+      if (!range.hasDataRow() && range.skippedInFlight() == 0) {
+        // Consumed this range,
+        // consume the next one
 
-    size_t skippedNow;
-    std::tie(state, skippedNow) = _fetcher.skipRowsForDependency(i, toSkip - _skipped);
-    _upstream[i] = state;
-    if (state == ExecutionState::WAITING) {
-      TRI_ASSERT(skippedNow == 0);
-      return {ExecutionState::WAITING, NoStats{}, 0};
-    }
-    _skipped += skippedNow;
-    
-    if (_upstream[i] == ExecutionState::DONE) {
-      if (std::all_of(_upstream.begin(), _upstream.end(),
-                      [](auto s) { return s == ExecutionState::DONE; })) {
+        // Guarantee:
+        // While in offsetPhase, we will only send requests to the first
+        // NON-DONE dependency.
+        if (range.upstreamState() == ExecutorState::HASMORE &&
+            waitingDep == input.numberDependencies()) {
+          waitingDep = dep;
+        }
         break;
       }
-       _currentDependency = (i + 1) % _numberDependencies;
-       continue;
-     }
+      if (range.hasDataRow()) {
+        // We overfetched, skipLocally
+        // By gurantee we will only see data, if
+        // we are past the offset phase.
+        TRI_ASSERT(call.getOffset() == 0);
+      } else {
+        if (call.getOffset() > 0) {
+          call.didSkip(range.skip(call.getOffset()));
+        } else {
+          // Fullcount Case
+          call.didSkip(range.skipAll());
+        }
+      }
+    }
   }
-  
-  size_t skipped = _skipped;
-  _skipped = 0;
-
-  TRI_ASSERT(skipped <= toSkip);
-  return {state, NoStats{}, skipped};
-}
-
-void ParallelUnsortedGatherExecutor::initDependencies() {
-  if (_numberDependencies == 0) {
-    // We need to initialize the dependencies once, they are injected
-    // after the fetcher is created.
-    _numberDependencies = _fetcher.numberDependencies();
-    TRI_ASSERT(_numberDependencies > 0);
-    _upstream.resize(_numberDependencies, ExecutionState::HASMORE);
-    TRI_ASSERT(std::all_of(_upstream.begin(), _upstream.end(), [](auto const& s) { return s == ExecutionState::HASMORE; } ));
+  if (input.isDone()) {
+    // We cannot have one that we are waiting on, if we are done.
+    TRI_ASSERT(waitingDep == input.numberDependencies());
+    return {ExecutorState::DONE, NoStats{}, call.getSkipCount(), AqlCall{}, waitingDep};
   }
+  return {ExecutorState::HASMORE, NoStats{}, call.getSkipCount(),
+          upstreamCall(call), waitingDep};
 }
diff --git a/arangod/Aql/ParallelUnsortedGatherExecutor.h b/arangod/Aql/ParallelUnsortedGatherExecutor.h
index ed4a32e31333..6df2900bce22 100644
--- a/arangod/Aql/ParallelUnsortedGatherExecutor.h
+++ b/arangod/Aql/ParallelUnsortedGatherExecutor.h
@@ -37,10 +37,11 @@ class Methods;
 
 namespace aql {
 
+struct AqlCall;
+class MultiAqlItemBlockInputRange;
 class MultiDependencySingleRowFetcher;
 class NoStats;
 class OutputAqlItemRow;
-struct SortRegister;
 
 class ParallelUnsortedGatherExecutorInfos : public ExecutorInfos {
  public:
@@ -55,7 +56,6 @@ class ParallelUnsortedGatherExecutorInfos : public ExecutorInfos {
 
 class ParallelUnsortedGatherExecutor {
  public:
-
  public:
   struct Properties {
     static constexpr bool preservesOrder = true;
@@ -71,31 +71,36 @@ class ParallelUnsortedGatherExecutor {
   ~ParallelUnsortedGatherExecutor();
 
   /**
-   * @brief produce the next Row of Aql Values.
+   * @brief Produce rows
    *
-   * @return ExecutionState,
-   *         if something was written output.hasValue() == true
+   * @param input DataRange delivered by the fetcher
+   * @param output place to write rows to
+   * @return std::tuple<ExecutorState, Stats, AqlCall, size_t>
+   *   ExecutorState: DONE or HASMORE (only within a subquery)
+   *   Stats: Stats gerenated here
+   *   AqlCall: Request to upstream
+   *   size:t: Dependency to request
    */
-  std::pair<ExecutionState, Stats> produceRows(OutputAqlItemRow& output);
+  [[nodiscard]] auto produceRows(MultiAqlItemBlockInputRange& input, OutputAqlItemRow& output)
+      -> std::tuple<ExecutorState, Stats, AqlCall, size_t>;
 
-  std::tuple<ExecutionState, Stats, size_t> skipRows(size_t atMost);
-  
- private:
-  
-  void initDependencies();
-  
- private:
-  Fetcher& _fetcher;
-  // 64: default size of buffer; 8: Alignment size; computed to 4 but breaks in windows debug build.
-  ::arangodb::containers::SmallVector<ExecutionState, 64, 8>::allocator_type::arena_type _arena;
-  ::arangodb::containers::SmallVector<ExecutionState, 64, 8> _upstream{_arena};
+  /**
+   * @brief Skip rows
+   *
+   * @param input DataRange delivered by the fetcher
+   * @param call skip request form consumer
+   * @return std::tuple<ExecutorState, Stats, AqlCall, size_t>
+   *   ExecutorState: DONE or HASMORE (only within a subquery)
+   *   Stats: Stats gerenated here
+   *   size_t: Number of rows skipped
+   *   AqlCall: Request to upstream
+   *   size:t: Dependency to request
+   */
+  [[nodiscard]] auto skipRowsRange(MultiAqlItemBlockInputRange& input, AqlCall& call)
+      -> std::tuple<ExecutorState, Stats, size_t, AqlCall, size_t>;
 
-  // Total Number of dependencies
-  size_t _numberDependencies;
-  
-  size_t _currentDependency;
-  
-  size_t _skipped;
+ private:
+  auto upstreamCall(AqlCall const& clientCall) const noexcept -> AqlCall;
 };
 
 }  // namespace aql
diff --git a/arangod/Aql/SortingGatherExecutor.cpp b/arangod/Aql/SortingGatherExecutor.cpp
index d6d366c0a08a..61c4ea8ebe80 100644
--- a/arangod/Aql/SortingGatherExecutor.cpp
+++ b/arangod/Aql/SortingGatherExecutor.cpp
@@ -161,15 +161,18 @@ class MinElementSorting final : public SortingGatherExecutor::SortingStrategy,
 
 }  // namespace
 SortingGatherExecutor::ValueType::ValueType(size_t index)
-    : dependencyIndex{index}, row{CreateInvalidInputRowHint()}, state{ExecutionState::HASMORE} {}
+    : dependencyIndex{index}, row{CreateInvalidInputRowHint()}, state{ExecutorState::HASMORE} {}
+
+SortingGatherExecutor::ValueType::ValueType(size_t index, InputAqlItemRow prow, ExecutorState pstate)
+    : dependencyIndex{index}, row{prow}, state{pstate} {}
 
 SortingGatherExecutorInfos::SortingGatherExecutorInfos(
     std::shared_ptr<std::unordered_set<RegisterId>> inputRegisters,
     std::shared_ptr<std::unordered_set<RegisterId>> outputRegisters, RegisterId nrInputRegisters,
     RegisterId nrOutputRegisters, std::unordered_set<RegisterId> registersToClear,
-    std::unordered_set<RegisterId> registersToKeep, std::vector<SortRegister>&& sortRegister,
-    arangodb::transaction::Methods* trx, GatherNode::SortMode sortMode, size_t limit,
-    GatherNode::Parallelism p)
+    std::unordered_set<RegisterId> registersToKeep,
+    std::vector<SortRegister>&& sortRegister, arangodb::transaction::Methods* trx,
+    GatherNode::SortMode sortMode, size_t limit, GatherNode::Parallelism p)
     : ExecutorInfos(std::move(inputRegisters), std::move(outputRegisters),
                     nrInputRegisters, nrOutputRegisters,
                     std::move(registersToClear), std::move(registersToKeep)),
@@ -183,17 +186,11 @@ SortingGatherExecutorInfos::SortingGatherExecutorInfos(SortingGatherExecutorInfo
 SortingGatherExecutorInfos::~SortingGatherExecutorInfos() = default;
 
 SortingGatherExecutor::SortingGatherExecutor(Fetcher& fetcher, Infos& infos)
-    : _fetcher(fetcher),
-      _initialized(false),
+    : _initialized(false),
       _numberDependencies(0),
-      _dependencyToFetch(0),
       _inputRows(),
-      _nrDone(0),
       _limit(infos.limit()),
       _rowsReturned(0),
-      _heapCounted(false),
-      _rowsLeftInHeap(0),
-      _skipped(0),
       _strategy(nullptr),
       _fetchParallel(infos.parallelism() == GatherNode::Parallelism::Parallel) {
   switch (infos.sortMode()) {
@@ -213,6 +210,88 @@ SortingGatherExecutor::SortingGatherExecutor(Fetcher& fetcher, Infos& infos)
 
 SortingGatherExecutor::~SortingGatherExecutor() = default;
 
+auto SortingGatherExecutor::initialize(typename Fetcher::DataRange const& inputRange)
+    -> std::optional<std::tuple<AqlCall, size_t>> {
+  if (!_initialized) {
+    // We cannot modify the number of dependencies, so we start
+    // with 0 dependencies, and will increase to whatever inputRange gives us.
+    TRI_ASSERT(_numberDependencies == 0 ||
+               _numberDependencies == inputRange.numberDependencies());
+    _numberDependencies = inputRange.numberDependencies();
+    auto call = requiresMoreInput(inputRange);
+    if (call.has_value()) {
+      return call;
+    }
+    // If we have collected all ranges once, we can prepare the local data-structure copy
+    _inputRows.reserve(_numberDependencies);
+    for (size_t dep = 0; dep < _numberDependencies; ++dep) {
+      auto const [state, row] = inputRange.peekDataRow(dep);
+      _inputRows.emplace_back(dep, row, state);
+    }
+    _strategy->prepare(_inputRows);
+    _initialized = true;
+    _numberDependencies = inputRange.numberDependencies();
+  }
+  return {};
+}
+
+auto SortingGatherExecutor::requiresMoreInput(typename Fetcher::DataRange const& inputRange)
+    -> std::optional<std::tuple<AqlCall, size_t>> {
+  for (size_t dep = 0; dep < _numberDependencies; ++dep) {
+    auto const& [state, input] = inputRange.peekDataRow(dep);
+    // Update the local copy, just to be sure it is up to date
+    // We might do too many copies here, but most likely this
+    // will not be a performance bottleneck.
+    ValueType& localDep = _inputRows[dep];
+    localDep.row = input;
+    localDep.state = state;
+    if (!input && state != ExecutorState::DONE) {
+      // This dependency requires input
+      // TODO: This call requires limits
+      return std::tuple<AqlCall, size_t>{AqlCall{}, dep};
+    }
+  }
+  // No call required
+  return {};
+}
+
+auto SortingGatherExecutor::isDone(typename Fetcher::DataRange const& input) const -> bool {
+  // TODO: Include contrained sort
+  return input.isDone();
+}
+
+auto SortingGatherExecutor::nextRow(MultiAqlItemBlockInputRange& input) -> InputAqlItemRow {
+  if (isDone(input)) {
+    // No rows, there is a chance we get into this.
+    // If we requested data from upstream, but all if it is done.
+    return InputAqlItemRow{CreateInvalidInputRowHint{}};
+  }
+#ifdef ARANGODB_ENABLE_MAINTAINER_MODE
+  bool oneWithContent = false;
+  for (size_t dep = 0; dep < _numberDependencies; ++dep) {
+    auto const& [state, row] = input.peekDataRow(dep);
+    if (row) {
+      oneWithContent = true;
+    }
+  }
+  TRI_ASSERT(oneWithContent);
+#endif
+  auto nextVal = _strategy->nextValue();
+  _rowsReturned++;
+  {
+    // Consume the row, and set it to next input
+    std::ignore = input.nextDataRow(nextVal.dependencyIndex);
+    auto const& [state, row] = input.peekDataRow(nextVal.dependencyIndex);
+    _inputRows[nextVal.dependencyIndex].state = state;
+    _inputRows[nextVal.dependencyIndex].row = row;
+
+    // TODO we might do some short-cuts here to maintain a list of requests
+    // to send in order to improve requires input
+  }
+
+  return nextVal.row;
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 /// @brief Guarantees requiredby this this block:
 ///        1) For every dependency the input is sorted, according to the same strategy.
@@ -227,192 +306,105 @@ SortingGatherExecutor::~SortingGatherExecutor() = default;
 ///
 ////////////////////////////////////////////////////////////////////////////////
 
-std::pair<ExecutionState, NoStats> SortingGatherExecutor::produceRows(OutputAqlItemRow& output) {
-  size_t const atMost = constrainedSort() ? output.numRowsLeft()
-                                          : ExecutionBlock::DefaultBatchSize;
-  ExecutionState state;
-  InputAqlItemRow row{CreateInvalidInputRowHint{}};
-  std::tie(state, row) = produceNextRow(atMost);
-
-  // HASMORE => row has to be initialized
-  TRI_ASSERT(state != ExecutionState::HASMORE || row.isInitialized());
-  // WAITING => row may not be initialized
-  TRI_ASSERT(state != ExecutionState::WAITING || !row.isInitialized());
-
-  if (row) {
-    // NOTE: The original gatherBlock did referencing
-    // inside the outputblock by identical AQL values.
-    // This optimization is not in use anymore.
-    output.copyRow(row);
+auto SortingGatherExecutor::produceRows(typename Fetcher::DataRange& input,
+                                        OutputAqlItemRow& output)
+    -> std::tuple<ExecutorState, Stats, AqlCall, size_t> {
+  {
+    // First initialize
+    auto maybeCall = initialize(input);
+    if (maybeCall.has_value()) {
+      auto const& [request, dep] = maybeCall.value();
+      return {ExecutorState::HASMORE, NoStats{}, request, dep};
+    }
   }
 
-  return {state, NoStats{}};
-}
-
-std::pair<ExecutionState, InputAqlItemRow> SortingGatherExecutor::produceNextRow(size_t const atMost) {
-  TRI_ASSERT(_strategy != nullptr);
-  assertConstrainedDoesntOverfetch(atMost);
-  // We shouldn't be asked for more rows when we are allowed to skip
-  TRI_ASSERT(!maySkip());
-  if (!_initialized) {
-    ExecutionState state = init(atMost);
-    if (state != ExecutionState::HASMORE) {
-      // Can be DONE(unlikely, no input) of WAITING
-      return {state, InputAqlItemRow{CreateInvalidInputRowHint{}}};
-    }
-  } else {
-    // Activate this assert as soon as all blocks follow the done == no call api
-    // TRI_ASSERT(_nrDone < _numberDependencies);
-    if (_inputRows[_dependencyToFetch].state == ExecutionState::DONE) {
-      _inputRows[_dependencyToFetch].row = InputAqlItemRow{CreateInvalidInputRowHint()};
-    } else {
-      // This is executed on every produceRows, and will replace the row that we have returned last time
-      std::tie(_inputRows[_dependencyToFetch].state,
-               _inputRows[_dependencyToFetch].row) =
-          _fetcher.fetchRowForDependency(_dependencyToFetch, atMost);
-      if (_inputRows[_dependencyToFetch].state == ExecutionState::WAITING) {
-        return {ExecutionState::WAITING, InputAqlItemRow{CreateInvalidInputRowHint{}}};
-      }
-      if (!_inputRows[_dependencyToFetch].row) {
-        TRI_ASSERT(_inputRows[_dependencyToFetch].state == ExecutionState::DONE);
-        adjustNrDone(_dependencyToFetch);
-      }
+  while (!isDone(input) && !output.isFull()) {
+    TRI_ASSERT(!maySkip());
+    auto maybeCall = requiresMoreInput(input);
+    if (maybeCall.has_value()) {
+      auto const& [request, dep] = maybeCall.value();
+      return {ExecutorState::HASMORE, NoStats{}, request, dep};
     }
-  }
-  if (_nrDone >= _numberDependencies) {
-    // We cannot return a row, because all are done
-    return {ExecutionState::DONE, InputAqlItemRow{CreateInvalidInputRowHint{}}};
-  }
-// if we get here, we have a valid row for every not done dependency.
-// And we have atLeast 1 valid row left
-#ifdef ARANGODB_ENABLE_MAINTAINER_MODE
-  bool oneWithContent = false;
-  for (auto const& inPair : _inputRows) {
-    // Waiting needs to bail out at fetch state
-    TRI_ASSERT(inPair.state != ExecutionState::WAITING);
-    // row.invalid => dependency is done
-    TRI_ASSERT(inPair.row || inPair.state == ExecutionState::DONE);
-    if (inPair.row) {
-      oneWithContent = true;
+    auto row = nextRow(input);
+    TRI_ASSERT(row.isInitialized() || isDone(input));
+    if (row) {
+      output.copyRow(row);
+      output.advanceRow();
     }
   }
-  // We have at least one row to sort.
-  TRI_ASSERT(oneWithContent);
-#endif
-  // get the index of the next best value.
-  ValueType val = _strategy->nextValue();
-  _dependencyToFetch = val.dependencyIndex;
-  // We can never pick an invalid row!
-  TRI_ASSERT(val.row);
-  ++_rowsReturned;
-  adjustNrDone(_dependencyToFetch);
-  if (_nrDone >= _numberDependencies) {
-    return {ExecutionState::DONE, val.row};
-  }
-  return {ExecutionState::HASMORE, val.row};
-}
 
-void SortingGatherExecutor::adjustNrDone(size_t const dependency) {
-  auto const& dep = _inputRows[dependency];
-  if (dep.state == ExecutionState::DONE) {
-#ifdef ARANGODB_ENABLE_MAINTAINER_MODE
-    TRI_ASSERT(_flaggedAsDone[dependency] == false);
-    _flaggedAsDone[dependency] = true;
-#endif
-    ++_nrDone;
+  // Call and dependency unused, so we return a too large dependency
+  // in order to trigger asserts if it is used.
+  if (isDone(input)) {
+    return {ExecutorState::DONE, NoStats{}, AqlCall{}, _numberDependencies + 1};
   }
+  return {ExecutorState::HASMORE, NoStats{}, AqlCall{}, _numberDependencies + 1};
 }
 
-void SortingGatherExecutor::initNumDepsIfNecessary() {
-  if (_numberDependencies == 0) {
-    // We need to initialize the dependencies once, they are injected
-    // after the fetcher is created.
-    _numberDependencies = _fetcher.numberDependencies();
-    TRI_ASSERT(_numberDependencies > 0);
-    _inputRows.reserve(_numberDependencies);
-    for (size_t index = 0; index < _numberDependencies; ++index) {
-      _inputRows.emplace_back(ValueType{index});
-#ifdef ARANGODB_ENABLE_MAINTAINER_MODE
-      _flaggedAsDone.emplace_back(false);
-#endif
+auto SortingGatherExecutor::skipRowsRange(typename Fetcher::DataRange& input, AqlCall& call)
+    -> std::tuple<ExecutorState, Stats, size_t, AqlCall, size_t> {
+  {
+    // First initialize
+    auto maybeCall = initialize(input);
+    if (maybeCall.has_value()) {
+      auto const& [request, dep] = maybeCall.value();
+      return {ExecutorState::HASMORE, NoStats{}, 0, request, dep};
     }
   }
-}
-
-ExecutionState SortingGatherExecutor::init(size_t const atMost) {
-  assertConstrainedDoesntOverfetch(atMost);
-  initNumDepsIfNecessary();
 
-  size_t numWaiting = 0;
-  for (size_t i = 0; i < _numberDependencies; i++) {
-    if (_inputRows[i].state == ExecutionState::DONE ||
-        _inputRows[i].row) {
-      continue;
+  while (!isDone(input) && call.needSkipMore()) {
+    auto maybeCall = requiresMoreInput(input);
+    if (maybeCall.has_value()) {
+      auto const& [request, dep] = maybeCall.value();
+      return {ExecutorState::HASMORE, NoStats{}, call.getSkipCount(), request, dep};
     }
-    
-    std::tie(_inputRows[i].state,
-             _inputRows[i].row) = _fetcher.fetchRowForDependency(i, atMost);
-    if (_inputRows[i].state == ExecutionState::WAITING) {
-      if (!_fetchParallel) {
-        return ExecutionState::WAITING;
+    if (call.getOffset() > 0) {
+      TRI_ASSERT(!maySkip());
+      // We need to sort still
+      // And account the row in the limit
+      auto row = nextRow(input);
+      TRI_ASSERT(row.isInitialized() || isDone(input));
+      if (row) {
+        call.didSkip(1);
+      }
+    } else {
+      // We are only called with fullcount.
+      // sorting does not matter.
+      // Start simply skip all from upstream.
+      for (size_t dep = 0; dep < input.numberDependencies(); ++dep) {
+        ExecutorState state = ExecutorState::HASMORE;
+        InputAqlItemRow row{CreateInvalidInputRowHint{}};
+        while (state == ExecutorState::HASMORE) {
+          std::tie(state, row) = input.nextDataRow(dep);
+          if (row) {
+            call.didSkip(1);
+          } else {
+            // We have consumed all overfetched rows.
+            // We may still have a skip counter within the range.
+            call.didSkip(input.skipAll(dep));
+            if (state == ExecutorState::HASMORE) {
+              // We need to fetch more data, but can fullCount now
+              AqlCall request{0, true, 0, AqlCall::LimitType::HARD};
+              return {ExecutorState::HASMORE, NoStats{}, call.getSkipCount(), request, dep};
+            }
+          }
+        }
       }
-      numWaiting++;
-    } else if (!_inputRows[i].row) {
-      TRI_ASSERT(_inputRows[i].state == ExecutionState::DONE);
-      adjustNrDone(i);
     }
   }
 
-  if (numWaiting > 0) {
-    return ExecutionState::WAITING;
-  }
-  
-  TRI_ASSERT(_numberDependencies > 0);
-  _dependencyToFetch = _numberDependencies - 1;
-  _initialized = true;
-  if (_nrDone >= _numberDependencies) {
-    return ExecutionState::DONE;
+  // Call and dependency unused, so we return a too large dependency
+  // in order to trigger asserts if it is used.
+  if (isDone(input)) {
+    return {ExecutorState::DONE, NoStats{}, call.getSkipCount(), AqlCall{},
+            _numberDependencies + 1};
   }
-  _strategy->prepare(_inputRows);
-  return ExecutionState::HASMORE;
+  return {ExecutorState::HASMORE, NoStats{}, call.getSkipCount(), AqlCall{},
+          _numberDependencies + 1};
 }
 
 std::pair<ExecutionState, size_t> SortingGatherExecutor::expectedNumberOfRows(size_t const atMost) const {
-  assertConstrainedDoesntOverfetch(atMost);
-  // We shouldn't be asked for more rows when we are allowed to skip
-  TRI_ASSERT(!maySkip());
-  ExecutionState state;
-  size_t expectedNumberOfRows;
-  std::tie(state, expectedNumberOfRows) = _fetcher.preFetchNumberOfRows(atMost);
-  if (state == ExecutionState::WAITING) {
-    return {state, 0};
-  }
-  if (expectedNumberOfRows >= atMost) {
-    // We do not care, we have more than atMost anyways.
-    return {state, expectedNumberOfRows};
-  }
-  // Now we need to figure out a more precise state
-  for (auto const& inRow : _inputRows) {
-    if (inRow.state == ExecutionState::HASMORE) {
-      // This block is not fully fetched, we do NOT know how many rows
-      // will be in the next batch, overestimate!
-      return {ExecutionState::HASMORE, atMost};
-    }
-    if (inRow.row.isInitialized()) {
-      // This dependency is in owned by this Executor
-      expectedNumberOfRows++;
-    }
-  }
-  if (expectedNumberOfRows == 0) {
-    return {ExecutionState::DONE, 0};
-  }
-  return {ExecutionState::HASMORE, expectedNumberOfRows};
-}
-
-size_t SortingGatherExecutor::rowsLeftToWrite() const noexcept {
-  TRI_ASSERT(constrainedSort());
-  TRI_ASSERT(_limit >= _rowsReturned);
-  return _limit - _rowsReturned;
+  THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
 }
 
 bool SortingGatherExecutor::constrainedSort() const noexcept {
@@ -430,116 +422,8 @@ bool SortingGatherExecutor::maySkip() const noexcept {
   return constrainedSort() && _rowsReturned >= _limit;
 }
 
-std::tuple<ExecutionState, SortingGatherExecutor::Stats, size_t> SortingGatherExecutor::skipRows(size_t const atMost) {
-  if (!maySkip()) {
-    // Until our limit, we must produce rows, because we might be asked later
-    // to produce rows, in which case all rows have to have been skipped in
-    // order.
-    return produceAndSkipRows(atMost);
-  } else {
-    // If we've reached our limit, we will never be asked to produce rows again.
-    // So we can just skip without sorting.
-    return reallySkipRows(atMost);
-  }
-}
-
-std::tuple<ExecutionState, SortingGatherExecutor::Stats, size_t> SortingGatherExecutor::reallySkipRows(
-    size_t const atMost) {
-  // Once, count all rows that are left in the heap (and free them)
-  if (!_heapCounted) {
-    initNumDepsIfNecessary();
-
-    // This row was just fetched:
-    _inputRows[_dependencyToFetch].row = InputAqlItemRow{CreateInvalidInputRowHint{}};
-    _rowsLeftInHeap = 0;
-    for (auto& it : _inputRows) {
-      if (it.row) {
-        ++_rowsLeftInHeap;
-        it.row = InputAqlItemRow{CreateInvalidInputRowHint{}};
-      }
-    }
-    _heapCounted = true;
-
-    // Now we will just skip through all dependencies, starting with the first.
-    _dependencyToFetch = 0;
-  }
-
-  { // Skip rows we had left in the heap first
-    std::size_t const skip = std::min(atMost, _rowsLeftInHeap);
-    _rowsLeftInHeap -= skip;
-    _skipped += skip;
-  }
-
-  while (_dependencyToFetch < _numberDependencies && _skipped < atMost) {
-    auto& state = _inputRows[_dependencyToFetch].state;
-    while (state != ExecutionState::DONE && _skipped < atMost) {
-      std::size_t skippedNow;
-      std::tie(state, skippedNow) =
-          _fetcher.skipRowsForDependency(_dependencyToFetch, atMost - _skipped);
-      if (state == ExecutionState::WAITING) {
-        TRI_ASSERT(skippedNow == 0);
-        return {state, NoStats{}, 0};
-      }
-      _skipped += skippedNow;
-    }
-    if (state == ExecutionState::DONE) {
-      ++_dependencyToFetch;
-    }
-  }
-
-  // Skip dependencies which are DONE
-  while (_dependencyToFetch < _numberDependencies &&
-         _inputRows[_dependencyToFetch].state == ExecutionState::DONE) {
-    ++_dependencyToFetch;
-  }
-  // The current dependency must now neither be DONE, nor WAITING.
-  TRI_ASSERT(_dependencyToFetch >= _numberDependencies ||
-             _inputRows[_dependencyToFetch].state == ExecutionState::HASMORE);
-
-  ExecutionState const state = _dependencyToFetch < _numberDependencies
-                                   ? ExecutionState::HASMORE
-                                   : ExecutionState::DONE;
-
-  TRI_ASSERT(_skipped <= atMost);
-  std::size_t const skipped = _skipped;
-  _skipped = 0;
-  return {state, NoStats{}, skipped};
-}
-
-std::tuple<ExecutionState, SortingGatherExecutor::Stats, size_t> SortingGatherExecutor::produceAndSkipRows(
-    size_t const atMost) {
-  ExecutionState state = ExecutionState::HASMORE;
-  InputAqlItemRow row{CreateInvalidInputRowHint{}};
-
-  // We may not skip more rows in this method than we can produce!
-  auto const ourAtMost = constrainedSort()
-      ? std::min(atMost, rowsLeftToWrite())
-      : atMost;
-
-  while(state == ExecutionState::HASMORE && _skipped < ourAtMost) {
-    std::tie(state, row) = produceNextRow(ourAtMost - _skipped);
-    // HASMORE => row has to be initialized
-    TRI_ASSERT(state != ExecutionState::HASMORE || row.isInitialized());
-    // WAITING => row may not be initialized
-    TRI_ASSERT(state != ExecutionState::WAITING || !row.isInitialized());
-
-    if (row.isInitialized()) {
-      ++_skipped;
-    }
-  }
-
-  if (state == ExecutionState::WAITING) {
-    return {state, NoStats{}, 0};
-  }
-
-  // Note that _skipped *can* be larger than `ourAtMost`, due to WAITING, in
-  // which case we might get a lower `ourAtMost` on the second call than during
-  // the first.
-  TRI_ASSERT(_skipped <= atMost);
-  TRI_ASSERT(state != ExecutionState::HASMORE || _skipped > 0);
-  TRI_ASSERT(state != ExecutionState::WAITING || _skipped == 0);
-
-  std::size_t const skipped = _skipped;
-  _skipped = 0;
-  return {state, NoStats{}, skipped};
+auto SortingGatherExecutor::rowsLeftToWrite() const noexcept -> size_t {
+  TRI_ASSERT(constrainedSort());
+  TRI_ASSERT(_limit >= _rowsReturned);
+  return _limit - std::min(_limit, _rowsReturned);
 }
diff --git a/arangod/Aql/SortingGatherExecutor.h b/arangod/Aql/SortingGatherExecutor.h
index 38c7aca7187e..440a507847c9 100644
--- a/arangod/Aql/SortingGatherExecutor.h
+++ b/arangod/Aql/SortingGatherExecutor.h
@@ -36,7 +36,9 @@ class Methods;
 
 namespace aql {
 
+struct AqlCall;
 class MultiDependencySingleRowFetcher;
+class MultiAqlItemBlockInputRange;
 class NoStats;
 class OutputAqlItemRow;
 struct SortRegister;
@@ -49,9 +51,8 @@ class SortingGatherExecutorInfos : public ExecutorInfos {
                              std::unordered_set<RegisterId> registersToClear,
                              std::unordered_set<RegisterId> registersToKeep,
                              std::vector<SortRegister>&& sortRegister,
-                             arangodb::transaction::Methods* trx,
-                             GatherNode::SortMode sortMode, size_t limit,
-                             GatherNode::Parallelism p);
+                             arangodb::transaction::Methods* trx, GatherNode::SortMode sortMode,
+                             size_t limit, GatherNode::Parallelism p);
   SortingGatherExecutorInfos() = delete;
   SortingGatherExecutorInfos(SortingGatherExecutorInfos&&);
   SortingGatherExecutorInfos(SortingGatherExecutorInfos const&) = delete;
@@ -62,7 +63,7 @@ class SortingGatherExecutorInfos : public ExecutorInfos {
   arangodb::transaction::Methods* trx() { return _trx; }
 
   GatherNode::SortMode sortMode() const noexcept { return _sortMode; }
-  
+
   GatherNode::Parallelism parallelism() const noexcept { return _parallelism; }
 
   size_t limit() const noexcept { return _limit; }
@@ -80,9 +81,10 @@ class SortingGatherExecutor {
   struct ValueType {
     size_t dependencyIndex;
     InputAqlItemRow row;
-    ExecutionState state;
+    ExecutorState state;
 
     explicit ValueType(size_t index);
+    ValueType(size_t, InputAqlItemRow, ExecutorState);
   };
 
   ////////////////////////////////////////////////////////////////////////////////
@@ -112,34 +114,43 @@ class SortingGatherExecutor {
   using Infos = SortingGatherExecutorInfos;
   using Stats = NoStats;
 
-  SortingGatherExecutor(Fetcher& fetcher, Infos& infos);
+  SortingGatherExecutor(Fetcher&, Infos& infos);
   ~SortingGatherExecutor();
 
   /**
-   * @brief produce the next Row of Aql Values.
+   * @brief Produce rows
    *
-   * @return ExecutionState,
-   *         if something was written output.hasValue() == true
+   * @param input DataRange delivered by the fetcher
+   * @param output place to write rows to
+   * @return std::tuple<ExecutorState, Stats, AqlCall, size_t>
+   *   ExecutorState: DONE or HASMORE (only within a subquery)
+   *   Stats: Stats gerenated here
+   *   AqlCall: Request to upstream
+   *   size:t: Dependency to request
    */
-  std::pair<ExecutionState, Stats> produceRows(OutputAqlItemRow& output);
+  [[nodiscard]] auto produceRows(MultiAqlItemBlockInputRange& input, OutputAqlItemRow& output)
+      -> std::tuple<ExecutorState, Stats, AqlCall, size_t>;
 
-  void adjustNrDone(size_t dependency);
+  /**
+   * @brief Skip rows
+   *
+   * @param input DataRange delivered by the fetcher
+   * @param call skip request form consumer
+   * @return std::tuple<ExecutorState, Stats, AqlCall, size_t>
+   *   ExecutorState: DONE or HASMORE (only within a subquery)
+   *   Stats: Stats gerenated here
+   *   size_t: Number of rows skipped
+   *   AqlCall: Request to upstream
+   *   size:t: Dependency to request
+   */
+  [[nodiscard]] auto skipRowsRange(MultiAqlItemBlockInputRange& input, AqlCall& call)
+      -> std::tuple<ExecutorState, Stats, size_t, AqlCall, size_t>;
 
   std::pair<ExecutionState, size_t> expectedNumberOfRows(size_t atMost) const;
 
-  std::tuple<ExecutionState, Stats, size_t> skipRows(size_t atMost);
-
  private:
-  void initNumDepsIfNecessary();
-
-  ExecutionState init(size_t atMost);
-
-  std::pair<ExecutionState, InputAqlItemRow> produceNextRow(size_t atMost);
-
   bool constrainedSort() const noexcept;
 
-  size_t rowsLeftToWrite() const noexcept;
-
   void assertConstrainedDoesntOverfetch(size_t atMost) const noexcept;
 
   // This is interesting in case this is a constrained sort and fullCount is
@@ -148,24 +159,54 @@ class SortingGatherExecutor {
   // This also means that we may not produce rows anymore after that point.
   bool maySkip() const noexcept;
 
- private:
-  Fetcher& _fetcher;
+  /**
+   * @brief Function that checks if all dependencies are either
+   *  done, or have a row.
+   *  The first one that does not match the condition
+   *  will produce an upstream call to be fulfilled.
+   *
+   * @param inputRange Range of all input dependencies
+   * @return std::optional<std::tuple<AqlCall, size_t>>  optional call for the dependnecy requiring input
+   */
+  auto requiresMoreInput(MultiAqlItemBlockInputRange const& inputRange)
+      -> std::optional<std::tuple<AqlCall, size_t>>;
 
+  /**
+   * @brief Get the next row matching the sorting strategy
+   *
+   * @return InputAqlItemRow best fit row. Might be invalid if all input is done.
+   */
+  auto nextRow(MultiAqlItemBlockInputRange& input) -> InputAqlItemRow;
+
+  /**
+   * @brief Tests if this Executor is done producing
+   *        => All inputs are fully consumed
+   *
+   * @return true we are done
+   * @return false we have more
+   */
+  auto isDone(MultiAqlItemBlockInputRange const& input) const -> bool;
+
+  /**
+   * @brief Initialize the Sorting strategy with the given input.
+   *        This is known to be empty, but all prepared at this point.
+   * @param inputRange The input, no data included yet.
+   */
+  auto initialize(MultiAqlItemBlockInputRange const& inputRange)
+      -> std::optional<std::tuple<AqlCall, size_t>>;
+
+  auto rowsLeftToWrite() const noexcept -> size_t;
+
+ private:
   // Flag if we are past the initialize phase (fetched one block for every dependency).
   bool _initialized;
 
   // Total Number of dependencies
   size_t _numberDependencies;
 
-  // The Dependency we have to fetch next
-  size_t _dependencyToFetch;
-
   // Input data to process
   std::vector<ValueType> _inputRows;
 
-  // Counter for DONE states
-  size_t _nrDone;
-  
   /// @brief If we do a constrained sort, it holds the limit > 0. Otherwise, it's 0.
   size_t _limit;
 
@@ -174,26 +215,9 @@ class SortingGatherExecutor {
   /// dependencies.
   size_t _rowsReturned;
 
-  /// @brief When we reached the limit, we once count the rows that are left in
-  /// the heap (in _rowsLeftInHeap), so we can count them for skipping.
-  bool _heapCounted;
-
-  /// @brief See comment for _heapCounted first. At the first real skip, this
-  /// is set to the number of rows left in the heap. It will be reduced while
-  /// skipping.
-  size_t _rowsLeftInHeap;
-
-  size_t _skipped;
-
   /// @brief sorting strategy
   std::unique_ptr<SortingStrategy> _strategy;
 
-#ifdef ARANGODB_ENABLE_MAINTAINER_MODE
-  std::vector<bool> _flaggedAsDone;
-#endif
-  std::tuple<ExecutionState, SortingGatherExecutor::Stats, size_t> reallySkipRows(size_t atMost);
-  std::tuple<ExecutionState, SortingGatherExecutor::Stats, size_t> produceAndSkipRows(size_t atMost);
-  
   const bool _fetchParallel;
 };
 
diff --git a/arangod/Aql/UnsortedGatherExecutor.h b/arangod/Aql/UnsortedGatherExecutor.h
index 5dc6d5c8afe8..2793c31be674 100644
--- a/arangod/Aql/UnsortedGatherExecutor.h
+++ b/arangod/Aql/UnsortedGatherExecutor.h
@@ -83,9 +83,32 @@ class UnsortedGatherExecutor {
 
   [[nodiscard]] auto skipRows(size_t atMost) -> std::tuple<ExecutionState, NoStats, size_t>;
 
-  // TODO: This should really be the DataRange of the fetcher?
+  /**
+   * @brief Produce rows
+   *
+   * @param input DataRange delivered by the fetcher
+   * @param output place to write rows to
+   * @return std::tuple<ExecutorState, Stats, AqlCall, size_t>
+   *   ExecutorState: DONE or HASMORE (only within a subquery)
+   *   Stats: Stats gerenated here
+   *   AqlCall: Request to upstream
+   *   size:t: Dependency to request
+   */
   [[nodiscard]] auto produceRows(typename Fetcher::DataRange& input, OutputAqlItemRow& output)
       -> std::tuple<ExecutorState, Stats, AqlCall, size_t>;
+
+  /**
+   * @brief Skip rows
+   *
+   * @param input DataRange delivered by the fetcher
+   * @param call skip request form consumer
+   * @return std::tuple<ExecutorState, Stats, AqlCall, size_t>
+   *   ExecutorState: DONE or HASMORE (only within a subquery)
+   *   Stats: Stats gerenated here
+   *   size_t: Number of rows skipped
+   *   AqlCall: Request to upstream
+   *   size:t: Dependency to request
+   */
   [[nodiscard]] auto skipRowsRange(typename Fetcher::DataRange& input, AqlCall& call)
       -> std::tuple<ExecutorState, Stats, size_t, AqlCall, size_t>;
 

From fd763cb7ddaefe9bc4d05dfe64993db1e3353d19 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tobias=20G=C3=B6dderz?= <tobias@arangodb.com>
Date: Tue, 3 Mar 2020 17:33:33 +0100
Subject: [PATCH 098/122] Feature/aql subquery execute parallel gather (#11215)

* Fixed range-handling for Modification Executors

* DataRange handling in ModificationExecutor

* Honor batch-size defined by UpstreamExecutor

* Fixed compile issue

* More fixes in modification

* Remvoed log devel

* Fixed profiler Test. for NoResults node we cahnge the behaviour

* Activated getSome failure tests in ExecuteRestHandler

* Fixed skipping in Index

* Let the MultiDependencySingleROwFetcher return the correct states.

* Fixed non-maintainer compilation

* Attempt to fix windows compile issue

* Fixed the non-maintainer compile ina different way

* Added API in MultiAqlItemBlockInputRange to get Number of dependencies

* Comments

* Savepoint commit, does not compile, but no harm is done. Will start breaking things now

* Another savepoint commit. does not compile, yet.

* First draft of new Style SortingGather not yet implemented: Parallelism this needs to be handled in ExecutionBlockImpl now.

* Allow waiting within old-style subquery

* Fixed invalid skipRwos in unsorted gather

* First draft of ParallelUnsortedGatherExecutor

* Removed unused local variables

* Added some Assertions in MultiAqlItemBlockInputRange

* Initialize dependdencies of MultiDependencyFetcher

* Fixed skipRows loop in UnsortingGatherNode

* Fixed return state of GatherNode

* Added an assertion before accessing a vectir unbounded

* Fixed uninitialized member in DistributeExecutor

* Fixed use before vector initialization in SortingGather

* Fixed uninitialized dependencies in MultiDepRowFetcher

* First step towards parallel Aql

* Fixed an assertion

* Fixed upstream skipping in ParallelUnsortedGather

Co-authored-by: Michael Hackstein <michael@arangodb.com>
---
 arangod/Aql/BlocksWithClients.cpp             |  6 ++--
 arangod/Aql/DistributeExecutor.cpp            |  2 +-
 arangod/Aql/DistributeExecutor.h              |  4 +--
 arangod/Aql/ExecutionBlockImpl.cpp            | 33 ++++++++++++-------
 arangod/Aql/ExecutionBlockImpl.h              | 10 ++++++
 .../Aql/ParallelUnsortedGatherExecutor.cpp    | 20 ++++++++---
 arangod/Aql/ParallelUnsortedGatherExecutor.h  |  3 +-
 arangod/Aql/SortingGatherExecutor.cpp         |  9 +++--
 8 files changed, 59 insertions(+), 28 deletions(-)

diff --git a/arangod/Aql/BlocksWithClients.cpp b/arangod/Aql/BlocksWithClients.cpp
index 8df29015729f..b4a98714b920 100644
--- a/arangod/Aql/BlocksWithClients.cpp
+++ b/arangod/Aql/BlocksWithClients.cpp
@@ -209,7 +209,7 @@ auto BlocksWithClientsImpl<Executor>::executeWithoutTraceForClient(AqlCallStack
                                                                    std::string const& clientId)
     -> std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> {
   TRI_ASSERT(!clientId.empty());
-  if (clientId.empty()) {
+  if (ADB_UNLIKELY(clientId.empty())) {
     // Security bailout to avoid UB
     THROW_ARANGO_EXCEPTION_MESSAGE(TRI_ERROR_INTERNAL,
                                    "got empty distribution id");
@@ -217,7 +217,7 @@ auto BlocksWithClientsImpl<Executor>::executeWithoutTraceForClient(AqlCallStack
 
   auto it = _clientBlockData.find(clientId);
   TRI_ASSERT(it != _clientBlockData.end());
-  if (it == _clientBlockData.end()) {
+  if (ADB_UNLIKELY(it == _clientBlockData.end())) {
     // Security bailout to avoid UB
     std::string message("AQL: unknown distribution id ");
     message.append(clientId);
@@ -303,4 +303,4 @@ std::pair<ExecutionState, size_t> BlocksWithClientsImpl<Executor>::skipSomeForSh
 }
 
 template class ::arangodb::aql::BlocksWithClientsImpl<ScatterExecutor>;
-template class ::arangodb::aql::BlocksWithClientsImpl<DistributeExecutor>;
\ No newline at end of file
+template class ::arangodb::aql::BlocksWithClientsImpl<DistributeExecutor>;
diff --git a/arangod/Aql/DistributeExecutor.cpp b/arangod/Aql/DistributeExecutor.cpp
index c9b13abfa452..07cd89c9f4b5 100644
--- a/arangod/Aql/DistributeExecutor.cpp
+++ b/arangod/Aql/DistributeExecutor.cpp
@@ -453,4 +453,4 @@ std::pair<ExecutionState, arangodb::Result> ExecutionBlockImpl<DistributeExecuto
 
   return {getHasMoreStateForClientId(clientId), TRI_ERROR_NO_ERROR};
 }
-*/
\ No newline at end of file
+*/
diff --git a/arangod/Aql/DistributeExecutor.h b/arangod/Aql/DistributeExecutor.h
index 5d0073b45a37..b6954bc1ff3a 100644
--- a/arangod/Aql/DistributeExecutor.h
+++ b/arangod/Aql/DistributeExecutor.h
@@ -116,9 +116,9 @@ class DistributeExecutor {
 
     std::deque<std::pair<SharedAqlItemBlockPtr, std::vector<size_t>>> _queue;
 
-    // This is unique_ptr to get away with everything beeing forward declared...
+    // This is unique_ptr to get away with everything being forward declared...
     std::unique_ptr<ExecutionBlock> _executor;
-    bool _executorHasMore;
+    bool _executorHasMore = false;
   };
 
   DistributeExecutor(DistributeExecutorInfos const& infos);
diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index a81f1c6c3d7f..517096c07f93 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -126,9 +126,6 @@ class TestLambdaSkipExecutor;
 }  // namespace arangodb
 #endif
 
-template <typename T, typename... Es>
-constexpr bool is_one_of_v = (std::is_same_v<T, Es> || ...);
-
 /*
  * Determine whether we execute new style or old style skips, i.e. pre or post shadow row introduction
  * TODO: This should be removed once all executors and fetchers are ported to the new style.
@@ -1230,12 +1227,23 @@ auto ExecutionBlockImpl<Executor>::executeFetcher(AqlCallStack& stack, size_t co
       //       to fit all inputs, in particular the one executed below
       TRI_ASSERT(dependency < _dependencies.size());
       _lastRange.resizeIfNecessary(ExecutorState::HASMORE, 0, _dependencies.size());
-
-      auto [state, skipped, range] = _rowFetcher.executeForDependency(dependency, stack);
-
-      _lastRange.setDependency(dependency, range);
-
-      return {state, skipped, _lastRange};
+      if constexpr (!isParallelExecutor) {
+        auto [state, skipped, range] = _rowFetcher.executeForDependency(dependency, stack);
+        _lastRange.setDependency(dependency, range);
+        return {state, skipped, _lastRange};
+      } else {
+        _callsInFlight.resize(_dependencyProxy.numberDependencies());
+        if (!_callsInFlight[dependency].has_value()) {
+          _callsInFlight[dependency] = stack;
+        }
+        TRI_ASSERT(_callsInFlight[dependency].has_value());
+        auto [state, skipped, range] = _rowFetcher.executeForDependency(dependency, _callsInFlight[dependency].value());
+        if (state != ExecutionState::WAITING) {
+          _callsInFlight[dependency] = std::nullopt;
+        }
+        _lastRange.setDependency(dependency, range);
+        return {state, skipped, _lastRange};
+      }
     } else {
       return _rowFetcher.execute(stack);
     }
@@ -1251,6 +1259,7 @@ auto ExecutionBlockImpl<Executor>::executeProduceRows(typename Fetcher::DataRang
     -> std::tuple<ExecutorState, typename Executor::Stats, AqlCall, size_t> {
   if constexpr (isNewStyleExecutor<Executor>) {
     if constexpr (is_one_of_v<Executor, UnsortedGatherExecutor, SortingGatherExecutor, ParallelUnsortedGatherExecutor>) {
+      input.resizeIfNecessary(ExecutorState::HASMORE, 0, _dependencies.size());
       return _executor.produceRows(input, output);
     } else if constexpr (is_one_of_v<Executor, SubqueryExecutor<true>, SubqueryExecutor<false>>) {
       // The SubqueryExecutor has it's own special handling outside.
@@ -1646,9 +1655,9 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
         }
         case ExecState::SKIP: {
 #ifdef ARANGODB_ENABLE_MAINTAINER_MODE
-          size_t offsetBefore = clientCall.getOffset();
+          auto const offsetBefore = clientCall.getOffset();
           TRI_ASSERT(offsetBefore > 0);
-          size_t canPassFullcount =
+          bool const canPassFullcount =
               clientCall.getLimit() == 0 && clientCall.needsFullCount();
 #endif
           LOG_QUERY("1f786", DEBUG) << printTypeInfo() << " call skipRows " << clientCall;
@@ -1661,7 +1670,7 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
           if constexpr (is_one_of_v<Executor, SubqueryExecutor<true>>) {
             // NOTE: The subquery Executor will by itself call EXECUTE on it's
             // subquery. This can return waiting => we can get a WAITING state
-            // here. We can only get the waiting state for SUbquery executors.
+            // here. We can only get the waiting state for Subquery executors.
             ExecutionState subqueryState = ExecutionState::HASMORE;
             std::tie(subqueryState, stats, skippedLocal, call) =
                 _executor.skipRowsRange(_lastRange, clientCall);
diff --git a/arangod/Aql/ExecutionBlockImpl.h b/arangod/Aql/ExecutionBlockImpl.h
index 0d2d3da66d1e..c0e072289704 100644
--- a/arangod/Aql/ExecutionBlockImpl.h
+++ b/arangod/Aql/ExecutionBlockImpl.h
@@ -51,6 +51,10 @@ class InputAqlItemRow;
 class OutputAqlItemRow;
 class Query;
 class ShadowAqlItemRow;
+class ParallelUnsortedGatherExecutor;
+
+template <typename T, typename... Es>
+constexpr bool is_one_of_v = (std::is_same_v<T, Es> || ...);
 
 /**
  * @brief This is the implementation class of AqlExecutionBlocks.
@@ -135,6 +139,9 @@ class ExecutionBlockImpl final : public ExecutionBlock {
     DONE
   };
 
+  static constexpr bool isParallelExecutor =
+      is_one_of_v<Executor, ParallelUnsortedGatherExecutor>;
+
  public:
   /**
    * @brief Construct a new ExecutionBlock
@@ -354,6 +361,9 @@ class ExecutionBlockImpl final : public ExecutionBlock {
   bool _hasUsedDataRangeBlock;
 
   bool _executorReturnedDone = false;
+
+  /// @brief Only needed for parallel executors; could be omitted otherwise
+  std::vector<std::optional<AqlCallStack>> _callsInFlight;
 };
 
 }  // namespace arangodb::aql
diff --git a/arangod/Aql/ParallelUnsortedGatherExecutor.cpp b/arangod/Aql/ParallelUnsortedGatherExecutor.cpp
index cc5e83a32b04..6a22758d5864 100644
--- a/arangod/Aql/ParallelUnsortedGatherExecutor.cpp
+++ b/arangod/Aql/ParallelUnsortedGatherExecutor.cpp
@@ -43,8 +43,19 @@ ParallelUnsortedGatherExecutor::ParallelUnsortedGatherExecutor(Fetcher&, Infos&
 
 ParallelUnsortedGatherExecutor::~ParallelUnsortedGatherExecutor() = default;
 
-auto ParallelUnsortedGatherExecutor::upstreamCall(AqlCall const& clientCall) const
+auto ParallelUnsortedGatherExecutor::upstreamCallSkip(AqlCall const& clientCall) const
     noexcept -> AqlCall {
+  // Only skip, don't ask for rows
+  auto upstreamCall = clientCall;
+  upstreamCall.softLimit = 0;
+  upstreamCall.hardLimit = AqlCall::Infinity{};
+  upstreamCall.fullCount = false;
+  return upstreamCall;
+}
+
+auto ParallelUnsortedGatherExecutor::upstreamCallProduce(AqlCall const& clientCall) const
+    noexcept -> AqlCall {
+  TRI_ASSERT(clientCall.getOffset() == 0);
   return clientCall;
 }
 
@@ -87,7 +98,8 @@ auto ParallelUnsortedGatherExecutor::produceRows(typename Fetcher::DataRange& in
     TRI_ASSERT(waitingDep == input.numberDependencies());
     return {ExecutorState::DONE, NoStats{}, AqlCall{}, waitingDep};
   }
-  return {ExecutorState::HASMORE, NoStats{}, upstreamCall(output.getClientCall()), waitingDep};
+  return {ExecutorState::HASMORE, NoStats{},
+          upstreamCallProduce(output.getClientCall()), waitingDep};
 }
 
 auto ParallelUnsortedGatherExecutor::skipRowsRange(typename Fetcher::DataRange& input,
@@ -112,7 +124,7 @@ auto ParallelUnsortedGatherExecutor::skipRowsRange(typename Fetcher::DataRange&
       }
       if (range.hasDataRow()) {
         // We overfetched, skipLocally
-        // By gurantee we will only see data, if
+        // By guarantee we will only see data, if
         // we are past the offset phase.
         TRI_ASSERT(call.getOffset() == 0);
       } else {
@@ -131,5 +143,5 @@ auto ParallelUnsortedGatherExecutor::skipRowsRange(typename Fetcher::DataRange&
     return {ExecutorState::DONE, NoStats{}, call.getSkipCount(), AqlCall{}, waitingDep};
   }
   return {ExecutorState::HASMORE, NoStats{}, call.getSkipCount(),
-          upstreamCall(call), waitingDep};
+          upstreamCallSkip(call), waitingDep};
 }
diff --git a/arangod/Aql/ParallelUnsortedGatherExecutor.h b/arangod/Aql/ParallelUnsortedGatherExecutor.h
index 6df2900bce22..1e52f8114267 100644
--- a/arangod/Aql/ParallelUnsortedGatherExecutor.h
+++ b/arangod/Aql/ParallelUnsortedGatherExecutor.h
@@ -100,7 +100,8 @@ class ParallelUnsortedGatherExecutor {
       -> std::tuple<ExecutorState, Stats, size_t, AqlCall, size_t>;
 
  private:
-  auto upstreamCall(AqlCall const& clientCall) const noexcept -> AqlCall;
+  auto upstreamCallSkip(AqlCall const& clientCall) const noexcept -> AqlCall;
+  auto upstreamCallProduce(AqlCall const& clientCall) const noexcept -> AqlCall;
 };
 
 }  // namespace aql
diff --git a/arangod/Aql/SortingGatherExecutor.cpp b/arangod/Aql/SortingGatherExecutor.cpp
index 61c4ea8ebe80..4ba8087e808c 100644
--- a/arangod/Aql/SortingGatherExecutor.cpp
+++ b/arangod/Aql/SortingGatherExecutor.cpp
@@ -218,19 +218,18 @@ auto SortingGatherExecutor::initialize(typename Fetcher::DataRange const& inputR
     TRI_ASSERT(_numberDependencies == 0 ||
                _numberDependencies == inputRange.numberDependencies());
     _numberDependencies = inputRange.numberDependencies();
-    auto call = requiresMoreInput(inputRange);
-    if (call.has_value()) {
-      return call;
-    }
     // If we have collected all ranges once, we can prepare the local data-structure copy
     _inputRows.reserve(_numberDependencies);
     for (size_t dep = 0; dep < _numberDependencies; ++dep) {
       auto const [state, row] = inputRange.peekDataRow(dep);
       _inputRows.emplace_back(dep, row, state);
     }
+    auto call = requiresMoreInput(inputRange);
+    if (call.has_value()) {
+      return call;
+    }
     _strategy->prepare(_inputRows);
     _initialized = true;
-    _numberDependencies = inputRange.numberDependencies();
   }
   return {};
 }

From 4794ebed2160f6228b61ee528b7d6f24940544f2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tobias=20G=C3=B6dderz?= <tobias@arangodb.com>
Date: Tue, 10 Mar 2020 14:49:57 +0100
Subject: [PATCH 099/122] Feature/aql subquery execute parallel gather 2
 (#11221)

* Fixed range-handling for Modification Executors

* DataRange handling in ModificationExecutor

* Honor batch-size defined by UpstreamExecutor

* Fixed compile issue

* More fixes in modification

* Remvoed log devel

* Fixed profiler Test. for NoResults node we cahnge the behaviour

* Activated getSome failure tests in ExecuteRestHandler

* Fixed skipping in Index

* Let the MultiDependencySingleROwFetcher return the correct states.

* Fixed non-maintainer compilation

* Attempt to fix windows compile issue

* Fixed the non-maintainer compile ina different way

* Added API in MultiAqlItemBlockInputRange to get Number of dependencies

* Comments

* Savepoint commit, does not compile, but no harm is done. Will start breaking things now

* Another savepoint commit. does not compile, yet.

* First draft of new Style SortingGather not yet implemented: Parallelism this needs to be handled in ExecutionBlockImpl now.

* Allow waiting within old-style subquery

* Fixed invalid skipRwos in unsorted gather

* First draft of ParallelUnsortedGatherExecutor

* Removed unused local variables

* Added some Assertions in MultiAqlItemBlockInputRange

* Initialize dependdencies of MultiDependencyFetcher

* Fixed skipRows loop in UnsortingGatherNode

* Fixed return state of GatherNode

* Added an assertion before accessing a vectir unbounded

* Fixed uninitialized member in DistributeExecutor

* Fixed use before vector initialization in SortingGather

* Fixed uninitialized dependencies in MultiDepRowFetcher

* First step towards parallel Aql

* Fixed an assertion

* Fixed upstream skipping in ParallelUnsortedGather

* [WIP] Changed Api for MultiDepExecutors in ExecBlockImpl (not yet in the actual executors)

* Moved AqlCallSet into a separate file

* Changed SortingGather to use the new API

* Changed ParallelUnsortedGather to use the new API

* Changed UnsortedGather to use the new API

* Moved AqlCall operator<< into .cpp file

* Implement operator<< for AqlCallSet

* Fix boolean mix-up

* Fixed state machine: go to UPSTREAM when the AqlCallSet is not empty

* Fixed assertion

* Bugfix

* SortingGather bugfixes

* Added init() method to fix an assertion and cleanup

* Removed unused variable

* Fixed constrained sort

* Fixed constrained sort #2

* Fix boolean mix-up

* Remove old interface

* Use call parameter for upstream request in produceRows

* Remove more old interface code

* Add skip methods to MultiAqlItemBlockInputRange

* Skip in UnsortedGather

* skip for UnsortedGather

* Fix skip and upstream calls for UnsortedGather

* skipRowsRange change

* Remove useless comments

* Moved multi-dep related code from ExeBlockImpl to MultiFetcher

* Cleanup in SortingGather, implemented parallel fullCount

* Try to fix a windows compile error

* Simplify and extend skipRowsRange for UnsortedGatherExecutor

* Made ParallelUnsortedGather actually parallel

* Removed erroneous assertion

* Undid erroneous change

* Fixed MacOs compile. Also disabled tests for non-relevant AqlCallStacks. They will be removed

* Fixed initialize Cursor for multi dependency blocks

* Fixed fullCount case in parallel unsorted gather

* Fixed fullCount upstream call of ParallelUnsortedGatherExecutor

* Fixed fullCount in SortingGather

* Windows \o/ if you cannot work properly with constexpr and static asserts, we do not let you do it!

* Do not advance in Unsorted gather if there are still rows to skip

* Add more comparison operators for AqlCall limits

* Send clientCall limits to upstream in SortingGather

* Improved fullCount in SortingGatherExectur

* Disabled a cluster profile test. We now ask the RemoteNode more often if it already has data. It is a bit unclear to me if this is now better performance wise (<< i think so) or triggers undesired side effects

* Helpless attempt to work around issues in stonage Visual Studio Compiler we are using.

* Clearly adding an operator on a well defined type causes ambigousness on random basic types using the operator

Co-authored-by: Michael Hackstein <michael@arangodb.com>
Co-authored-by: Markus Pfeiffer <markus@arangodb.com>
---
 arangod/Aql/AqlCall.cpp                       |  17 +
 arangod/Aql/AqlCall.h                         |  40 +--
 arangod/Aql/AqlCallSet.cpp                    |  54 +++
 arangod/Aql/AqlCallSet.h                      |  53 +++
 arangod/Aql/AqlCallStack.cpp                  |   6 +
 arangod/Aql/AqlCallStack.h                    |   3 +
 arangod/Aql/ClusterNodes.cpp                  |   6 +
 arangod/Aql/ClusterNodes.h                    |   5 +-
 arangod/Aql/ExecutionBlockImpl.cpp            | 243 ++++++++------
 arangod/Aql/ExecutionBlockImpl.h              |  42 ++-
 arangod/Aql/IdExecutor.h                      |   4 -
 arangod/Aql/MultiAqlItemBlockInputRange.cpp   |  42 ++-
 arangod/Aql/MultiAqlItemBlockInputRange.h     |  19 +-
 .../Aql/MultiDependencySingleRowFetcher.cpp   |  97 +++++-
 arangod/Aql/MultiDependencySingleRowFetcher.h |  21 +-
 .../Aql/ParallelUnsortedGatherExecutor.cpp    |  57 ++--
 arangod/Aql/ParallelUnsortedGatherExecutor.h  |   5 +-
 arangod/Aql/SortingGatherExecutor.cpp         | 313 ++++++++++++------
 arangod/Aql/SortingGatherExecutor.h           |  45 ++-
 arangod/Aql/UnsortedGatherExecutor.cpp        | 139 ++------
 arangod/Aql/UnsortedGatherExecutor.h          |  28 +-
 arangod/CMakeLists.txt                        |   3 +-
 tests/Aql/ExecutionBlockImplTest.cpp          |   9 +-
 ...timizer-rule-parallelize-gather-cluster.js |   2 +-
 tests/js/server/aql/aql-profiler-cluster.js   |  16 +-
 25 files changed, 803 insertions(+), 466 deletions(-)
 create mode 100644 arangod/Aql/AqlCallSet.cpp
 create mode 100644 arangod/Aql/AqlCallSet.h

diff --git a/arangod/Aql/AqlCall.cpp b/arangod/Aql/AqlCall.cpp
index 1621a38271e7..0a1d065380bd 100644
--- a/arangod/Aql/AqlCall.cpp
+++ b/arangod/Aql/AqlCall.cpp
@@ -30,6 +30,7 @@
 #include <velocypack/Collection.h>
 #include <velocypack/Slice.h>
 
+#include <iostream>
 #include <map>
 #include <string_view>
 
@@ -279,3 +280,19 @@ auto AqlCall::toString() const -> std::string {
   stream << *this;
   return stream.str();
 }
+
+auto aql::operator<<(std::ostream& out, AqlCall::Limit const& limit) -> std::ostream& {
+  return std::visit(overload{[&out](size_t const& i) -> std::ostream& {
+                               return out << i;
+                             },
+                             [&out](AqlCall::Infinity const&) -> std::ostream& {
+                               return out << "unlimited";
+                             }},
+                    limit);
+}
+
+auto aql::operator<<(std::ostream& out, AqlCall const& call) -> std::ostream& {
+  return out << "{ skip: " << call.getOffset() << ", softLimit: " << call.softLimit
+             << ", hardLimit: " << call.hardLimit
+             << ", fullCount: " << std::boolalpha << call.fullCount << " }";
+}
diff --git a/arangod/Aql/AqlCall.h b/arangod/Aql/AqlCall.h
index b310dfee3175..af14123495eb 100644
--- a/arangod/Aql/AqlCall.h
+++ b/arangod/Aql/AqlCall.h
@@ -28,6 +28,7 @@
 #include "Cluster/ResultT.h"
 
 #include <cstddef>
+#include <iosfwd>
 #include <variant>
 
 namespace arangodb::velocypack {
@@ -50,14 +51,14 @@ struct AqlCall {
 
   AqlCall() = default;
   // Replacements for struct initialization
-  explicit AqlCall(size_t offset, Limit softLimit = Infinity{},
-                   Limit hardLimit = Infinity{}, bool fullCount = false)
+  explicit constexpr AqlCall(size_t offset, Limit softLimit = Infinity{},
+                             Limit hardLimit = Infinity{}, bool fullCount = false)
       : offset{offset}, softLimit{softLimit}, hardLimit{hardLimit}, fullCount{fullCount} {}
 
   enum class LimitType { SOFT, HARD };
-  AqlCall(size_t offset, bool fullCount, Infinity)
+  constexpr AqlCall(size_t offset, bool fullCount, Infinity)
       : offset{offset}, softLimit{Infinity{}}, hardLimit{Infinity{}}, fullCount{fullCount} {}
-  AqlCall(size_t offset, bool fullCount, size_t limit, LimitType limitType)
+  constexpr AqlCall(size_t offset, bool fullCount, size_t limit, LimitType limitType)
       : offset{offset},
         softLimit{limitType == LimitType::SOFT ? Limit{limit} : Limit{Infinity{}}},
         hardLimit{limitType == LimitType::HARD ? Limit{limit} : Limit{Infinity{}}},
@@ -158,6 +159,7 @@ struct AqlCall {
     return skippedRows;
   }
 
+  // TODO this is the same as shouldSkip(), remove one of them.
   [[nodiscard]] bool needSkipMore() const noexcept {
     return (0 < getOffset()) || (getLimit() == 0 && needsFullCount());
   }
@@ -174,6 +176,8 @@ struct AqlCall {
     std::visit(minus, hardLimit);
   }
 
+  bool hasLimit() const { return hasHardLimit() || hasSoftLimit(); }
+
   bool hasHardLimit() const {
     return !std::holds_alternative<AqlCall::Infinity>(hardLimit);
   }
@@ -184,6 +188,7 @@ struct AqlCall {
 
   bool needsFullCount() const { return fullCount; }
 
+  // TODO this is the same as needSkipMore(), remove one of them.
   bool shouldSkip() const {
     return getOffset() > 0 || (getLimit() == 0 && needsFullCount());
   }
@@ -199,6 +204,15 @@ constexpr bool operator<(AqlCall::Limit const& a, AqlCall::Limit const& b) {
   return std::get<size_t>(a) < std::get<size_t>(b);
 }
 
+constexpr bool operator<(AqlCall::Limit const& a, size_t b) {
+  if (std::holds_alternative<AqlCall::Infinity>(a)) {
+    return false;
+  }
+  return std::get<size_t>(a) < b;
+}
+
+constexpr bool operator<(size_t a, AqlCall::Limit const& b) { return !(b < a); }
+
 constexpr AqlCall::Limit operator+(AqlCall::Limit const& a, size_t n) {
   return std::visit(overload{[n](size_t const& i) -> AqlCall::Limit {
                                return i + n;
@@ -243,22 +257,10 @@ constexpr bool operator==(AqlCall const& left, AqlCall const& right) {
          left.skippedRows == right.skippedRows;
 }
 
-inline std::ostream& operator<<(std::ostream& out,
-                                const arangodb::aql::AqlCall::Limit& limit) {
-  return std::visit(arangodb::overload{[&out](size_t const& i) -> std::ostream& {
-                                         return out << i;
-                                       },
-                                       [&out](arangodb::aql::AqlCall::Infinity const&) -> std::ostream& {
-                                         return out << "unlimited";
-                                       }},
-                    limit);
-}
+auto operator<<(std::ostream& out, const arangodb::aql::AqlCall::Limit& limit)
+    -> std::ostream&;
 
-inline std::ostream& operator<<(std::ostream& out, const arangodb::aql::AqlCall& call) {
-  return out << "{ skip: " << call.getOffset() << ", softLimit: " << call.softLimit
-             << ", hardLimit: " << call.hardLimit
-             << ", fullCount: " << std::boolalpha << call.fullCount << " }";
-}
+auto operator<<(std::ostream& out, const arangodb::aql::AqlCall& call) -> std::ostream&;
 
 }  // namespace arangodb::aql
 
diff --git a/arangod/Aql/AqlCallSet.cpp b/arangod/Aql/AqlCallSet.cpp
new file mode 100644
index 000000000000..87ace64d871b
--- /dev/null
+++ b/arangod/Aql/AqlCallSet.cpp
@@ -0,0 +1,54 @@
+////////////////////////////////////////////////////////////////////////////////
+/// DISCLAIMER
+///
+/// Copyright 2020 ArangoDB GmbH, Cologne, Germany
+///
+/// Licensed under the Apache License, Version 2.0 (the "License");
+/// you may not use this file except in compliance with the License.
+/// You may obtain a copy of the License at
+///
+///     http://www.apache.org/licenses/LICENSE-2.0
+///
+/// Unless required by applicable law or agreed to in writing, software
+/// distributed under the License is distributed on an "AS IS" BASIS,
+/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+/// See the License for the specific language governing permissions and
+/// limitations under the License.
+///
+/// Copyright holder is ArangoDB GmbH, Cologne, Germany
+///
+/// @author Tobias Gödderz
+////////////////////////////////////////////////////////////////////////////////
+
+#include "AqlCallSet.h"
+
+using namespace arangodb;
+using namespace arangodb::aql;
+
+auto aql::operator<<(std::ostream& out, AqlCallSet::DepCallPair const& callPair) -> std::ostream& {
+  return out << callPair.dependency << " => " << callPair.call;
+}
+
+auto aql::operator<<(std::ostream& out, AqlCallSet const& callSet) -> std::ostream& {
+  out << "[";
+  auto first = true;
+  for (auto const& it : callSet.calls) {
+    if (first) {
+      out << " ";
+      first = false;
+    } else {
+      out << ", ";
+    }
+    out << it;
+  }
+  out << " ]";
+  return out;
+}
+
+auto AqlCallSet::empty() const noexcept -> bool {
+  return calls.empty();
+}
+
+auto AqlCallSet::size() const noexcept -> size_t {
+  return calls.size();
+}
diff --git a/arangod/Aql/AqlCallSet.h b/arangod/Aql/AqlCallSet.h
new file mode 100644
index 000000000000..abc8ee8de08d
--- /dev/null
+++ b/arangod/Aql/AqlCallSet.h
@@ -0,0 +1,53 @@
+////////////////////////////////////////////////////////////////////////////////
+/// DISCLAIMER
+///
+/// Copyright 2020 ArangoDB GmbH, Cologne, Germany
+///
+/// Licensed under the Apache License, Version 2.0 (the "License");
+/// you may not use this file except in compliance with the License.
+/// You may obtain a copy of the License at
+///
+///     http://www.apache.org/licenses/LICENSE-2.0
+///
+/// Unless required by applicable law or agreed to in writing, software
+/// distributed under the License is distributed on an "AS IS" BASIS,
+/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+/// See the License for the specific language governing permissions and
+/// limitations under the License.
+///
+/// Copyright holder is ArangoDB GmbH, Cologne, Germany
+///
+/// @author Tobias Gödderz
+////////////////////////////////////////////////////////////////////////////////
+
+#ifndef ARANGOD_AQL_AQLCALLSET_H
+#define ARANGOD_AQL_AQLCALLSET_H
+
+#include "Aql/AqlCall.h"
+
+#include <iosfwd>
+#include <vector>
+
+namespace arangodb::aql {
+
+// Partial map dep -> call. May be empty.
+// IMPORTANT: Are expected to be saved in increasing order (regarding dependency)
+struct AqlCallSet {
+  struct DepCallPair {
+    std::size_t dependency{};
+    AqlCall call;
+  };
+  std::vector<DepCallPair> calls;
+
+  [[nodiscard]] auto empty() const noexcept -> bool;
+
+  [[nodiscard]] auto size() const noexcept -> size_t;
+};
+
+auto operator<<(std::ostream& out, AqlCallSet::DepCallPair const& callPair)
+    -> std::ostream&;
+auto operator<<(std::ostream&, AqlCallSet const&) -> std::ostream&;
+
+}  // namespace arangodb::aql
+
+#endif  // ARANGOD_AQL_AQLCALLSET_H
diff --git a/arangod/Aql/AqlCallStack.cpp b/arangod/Aql/AqlCallStack.cpp
index 68c5cd9c5b8d..911ea0c86fd2 100644
--- a/arangod/Aql/AqlCallStack.cpp
+++ b/arangod/Aql/AqlCallStack.cpp
@@ -87,6 +87,12 @@ void AqlCallStack::pushCall(AqlCall&& call) {
   _operations.push(call);
 }
 
+void AqlCallStack::pushCall(AqlCall const& call) {
+  // TODO is this correct on subqueries?
+  TRI_ASSERT(isRelevant());
+  _operations.push(call);
+}
+
 void AqlCallStack::stackUpMissingCalls() {
   while (!isRelevant()) {
     // For every depth, we add an additional default call.
diff --git a/arangod/Aql/AqlCallStack.h b/arangod/Aql/AqlCallStack.h
index f67e505ddffc..4aa03285f5d8 100644
--- a/arangod/Aql/AqlCallStack.h
+++ b/arangod/Aql/AqlCallStack.h
@@ -63,6 +63,9 @@ class AqlCallStack {
   // Put another call on top of the stack.
   void pushCall(AqlCall&& call);
 
+  // Put another call on top of the stack.
+  void pushCall(AqlCall const& call);
+
   // fill up all missing calls within this stack s.t. we reach depth == 0
   // This needs to be called if an executor requires to be fully executed, even if skipped,
   // even if the subquery it is located in is skipped.
diff --git a/arangod/Aql/ClusterNodes.cpp b/arangod/Aql/ClusterNodes.cpp
index 4e393a10caa6..feb4ca124d97 100644
--- a/arangod/Aql/ClusterNodes.cpp
+++ b/arangod/Aql/ClusterNodes.cpp
@@ -635,6 +635,12 @@ void GatherNode::setParallelism(GatherNode::Parallelism value) {
   _parallelism = value;
 }
 
+GatherNode::SortMode GatherNode::evaluateSortMode(size_t numberOfShards,
+                                                  size_t shardsRequiredForHeapMerge) noexcept {
+  return numberOfShards >= shardsRequiredForHeapMerge ? SortMode::Heap
+                                                      : SortMode::MinElement;
+}
+
 SingleRemoteOperationNode::SingleRemoteOperationNode(
     ExecutionPlan* plan, size_t id, NodeType mode, bool replaceIndexNode,
     std::string const& key, Collection const* collection,
diff --git a/arangod/Aql/ClusterNodes.h b/arangod/Aql/ClusterNodes.h
index 5eefc5395cb9..d0206ac0fd21 100644
--- a/arangod/Aql/ClusterNodes.h
+++ b/arangod/Aql/ClusterNodes.h
@@ -315,10 +315,7 @@ class GatherNode final : public ExecutionNode {
 
   /// @returns sort mode for the specified number of shards
   static SortMode evaluateSortMode(size_t numberOfShards,
-                                   size_t shardsRequiredForHeapMerge = 5) noexcept {
-    return numberOfShards >= shardsRequiredForHeapMerge ? SortMode::Heap
-                                                        : SortMode::MinElement;
-  }
+                                   size_t shardsRequiredForHeapMerge = 5) noexcept;
 
   /// @brief constructor with an id
   GatherNode(ExecutionPlan* plan, size_t id, SortMode sortMode, 
diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index 517096c07f93..8e71f0dc0192 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -117,13 +117,11 @@ CREATE_HAS_MEMBER_CHECK(skipRowsRange, hasSkipRowsRange);
 #ifdef ARANGODB_USE_GOOGLE_TESTS
 // Forward declaration of Test Executors.
 // only used as long as isNewStyleExecutor is required.
-namespace arangodb {
-namespace aql {
+namespace arangodb::aql {
 class TestLambdaExecutor;
 
 class TestLambdaSkipExecutor;
-}  // namespace aql
-}  // namespace arangodb
+}  // namespace arangodb::aql
 #endif
 
 /*
@@ -196,7 +194,6 @@ ExecutionBlockImpl<Executor>::ExecutionBlockImpl(ExecutionEngine* engine,
       _execState{ExecState::CHECKCALL},
       _upstreamRequest{},
       _clientRequest{},
-      _requestedDependency{},
       _hasUsedDataRangeBlock{false} {
   // already insert ourselves into the statistics results
   if (_profile >= PROFILE_LEVEL_BLOCKS) {
@@ -606,13 +603,19 @@ template <class Executor>
 std::pair<ExecutionState, Result> ExecutionBlockImpl<Executor>::initializeCursor(InputAqlItemRow const& input) {
   // reinitialize the DependencyProxy
   _dependencyProxy.reset();
-  _lastRange = DataRange(ExecutorState::HASMORE);
   _hasUsedDataRangeBlock = false;
-
+  initOnce();
   // destroy and re-create the Fetcher
   _rowFetcher.~Fetcher();
   new (&_rowFetcher) Fetcher(_dependencyProxy);
 
+  if constexpr (isMultiDepExecutor<Executor>) {
+    _lastRange.reset();
+    _rowFetcher.init();
+  } else {
+    _lastRange = DataRange(ExecutorState::HASMORE);
+  }
+
   TRI_ASSERT(_skipped == 0);
   _skipped = 0;
   TRI_ASSERT(_state == InternalState::DONE || _state == InternalState::FETCH_DATA);
@@ -653,6 +656,7 @@ std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> ExecutionBlockImpl<Exe
     TRI_IF_FAILURE("ExecutionBlock::getOrSkipSome3") {
       THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
     }
+    initOnce();
 
     auto res = executeWithoutTrace(stack);
     return traceExecuteEnd(res);
@@ -982,12 +986,12 @@ std::pair<ExecutionState, SharedAqlItemBlockPtr> ExecutionBlockImpl<Executor>::r
                   "Executors should implement the method "
                   "fetchBlockForPassthrough() iff "
                   "Properties::allowsBlockPassthrough is true");
+    static_assert(
+        Executor::Properties::inputSizeRestrictsOutputSize ==
+            hasExpectedNumberOfRows<Executor>::value,
+        "Executors should implement the method expectedNumberOfRows() iff "
+        "Properties::inputSizeRestrictsOutputSize is true");
   }
-  static_assert(
-      Executor::Properties::inputSizeRestrictsOutputSize ==
-          hasExpectedNumberOfRows<Executor>::value,
-      "Executors should implement the method expectedNumberOfRows() iff "
-      "Properties::inputSizeRestrictsOutputSize is true");
 
   constexpr RequestWrappedBlockVariant variant =
       isNewStyleExecutor<Executor>
@@ -1217,35 +1221,45 @@ static auto fastForwardType(AqlCall const& call, Executor const& e) -> FastForwa
 }
 
 template <class Executor>
-auto ExecutionBlockImpl<Executor>::executeFetcher(AqlCallStack& stack, size_t const dependency)
+auto ExecutionBlockImpl<Executor>::executeFetcher(AqlCallStack& stack, AqlCallType const& aqlCall)
     -> std::tuple<ExecutionState, size_t, typename Fetcher::DataRange> {
-  // Silence compiler about unused dependency
-  (void)dependency;
   if constexpr (isNewStyleExecutor<Executor>) {
-    if constexpr (is_one_of_v<Fetcher, MultiDependencySingleRowFetcher>) {
-      // TODO: This is a hack to guarantee we have enough space in our range
-      //       to fit all inputs, in particular the one executed below
-      TRI_ASSERT(dependency < _dependencies.size());
-      _lastRange.resizeIfNecessary(ExecutorState::HASMORE, 0, _dependencies.size());
-      if constexpr (!isParallelExecutor) {
-        auto [state, skipped, range] = _rowFetcher.executeForDependency(dependency, stack);
-        _lastRange.setDependency(dependency, range);
-        return {state, skipped, _lastRange};
-      } else {
-        _callsInFlight.resize(_dependencyProxy.numberDependencies());
-        if (!_callsInFlight[dependency].has_value()) {
-          _callsInFlight[dependency] = stack;
-        }
-        TRI_ASSERT(_callsInFlight[dependency].has_value());
-        auto [state, skipped, range] = _rowFetcher.executeForDependency(dependency, _callsInFlight[dependency].value());
-        if (state != ExecutionState::WAITING) {
-          _callsInFlight[dependency] = std::nullopt;
-        }
+    // TODO The logic in the MultiDependencySingleRowFetcher branch should be
+    //      moved into the MultiDependencySingleRowFetcher.
+    static_assert(isMultiDepExecutor<Executor> ==
+                  std::is_same_v<Fetcher, MultiDependencySingleRowFetcher>);
+    if constexpr (std::is_same_v<Fetcher, MultiDependencySingleRowFetcher>) {
+      // Note the aqlCall is an AqlCallSet in this case:
+      static_assert(std::is_same_v<AqlCallSet, std::decay_t<decltype(aqlCall)>>);
+      TRI_ASSERT(_lastRange.numberDependencies() == _dependencies.size());
+      auto const& [state, skipped, ranges] = _rowFetcher.execute(stack, aqlCall);
+      for (auto const& [dependency, range] : ranges) {
         _lastRange.setDependency(dependency, range);
-        return {state, skipped, _lastRange};
       }
+      return {state, skipped, _lastRange};
     } else {
-      return _rowFetcher.execute(stack);
+      // If we are SubqueryStart, we remove the top element of the stack
+      // which belongs to the subquery enclosed by this
+      // SubqueryStart and the partnered SubqueryEnd by *not*
+      // pushing the upstream request.
+      if constexpr (!std::is_same_v<Executor, SubqueryStartExecutor>) {
+        auto callCopy = _upstreamRequest;
+        stack.pushCall(std::move(callCopy));
+      }
+
+      auto const result = _rowFetcher.execute(stack);
+
+      if constexpr (!std::is_same_v<Executor, SubqueryStartExecutor>) {
+        // As the stack is copied into the fetcher, we need to pop off our call
+        // again. If we use other datastructures or moving we may hand over
+        // ownership of the stack here instead and no popCall is necessary.
+        stack.popCall();
+      } else {
+        // Do not pop the call, we did not put it on.
+        // However we need it for accounting later.
+      }
+
+      return result;
     }
   } else {
     TRI_ASSERT(false);
@@ -1256,10 +1270,10 @@ auto ExecutionBlockImpl<Executor>::executeFetcher(AqlCallStack& stack, size_t co
 template <class Executor>
 auto ExecutionBlockImpl<Executor>::executeProduceRows(typename Fetcher::DataRange& input,
                                                       OutputAqlItemRow& output)
-    -> std::tuple<ExecutorState, typename Executor::Stats, AqlCall, size_t> {
+    -> std::tuple<ExecutorState, typename Executor::Stats, AqlCallType> {
   if constexpr (isNewStyleExecutor<Executor>) {
-    if constexpr (is_one_of_v<Executor, UnsortedGatherExecutor, SortingGatherExecutor, ParallelUnsortedGatherExecutor>) {
-      input.resizeIfNecessary(ExecutorState::HASMORE, 0, _dependencies.size());
+    if constexpr (isMultiDepExecutor<Executor>) {
+      TRI_ASSERT(input.numberDependencies() == _dependencies.size());
       return _executor.produceRows(input, output);
     } else if constexpr (is_one_of_v<Executor, SubqueryExecutor<true>, SubqueryExecutor<false>>) {
       // The SubqueryExecutor has it's own special handling outside.
@@ -1268,21 +1282,22 @@ auto ExecutionBlockImpl<Executor>::executeProduceRows(typename Fetcher::DataRang
       THROW_ARANGO_EXCEPTION(TRI_ERROR_INTERNAL_AQL);
     } else {
       auto [state, stats, call] = _executor.produceRows(input, output);
-      return {state, stats, call, 0};
+      return {state, stats, call};
     }
   } else {
-    return {ExecutorState::DONE, typename Executor::Stats{}, AqlCall{}, 0};
+    return {ExecutorState::DONE, typename Executor::Stats{}, AqlCall{}};
   }
 }
 
 template <class Executor>
 auto ExecutionBlockImpl<Executor>::executeSkipRowsRange(typename Fetcher::DataRange& inputRange,
                                                         AqlCall& call)
-    -> std::tuple<ExecutorState, typename Executor::Stats, size_t, AqlCall, size_t> {
+    -> std::tuple<ExecutorState, typename Executor::Stats, size_t, AqlCallType> {
   if constexpr (isNewStyleExecutor<Executor>) {
     call.skippedRows = 0;
     if constexpr (skipRowsType<Executor>() == SkipRowsRangeVariant::EXECUTOR) {
-      if constexpr (is_one_of_v<Executor, UnsortedGatherExecutor, SortingGatherExecutor, ParallelUnsortedGatherExecutor>) {
+      if constexpr (isMultiDepExecutor<Executor>) {
+        TRI_ASSERT(inputRange.numberDependencies() == _dependencies.size());
         // If the executor has a method skipRowsRange, to skip outputs.
         // Every non-passthrough executor needs to implement this.
         auto res = _executor.skipRowsRange(inputRange, call);
@@ -1297,7 +1312,7 @@ auto ExecutionBlockImpl<Executor>::executeSkipRowsRange(typename Fetcher::DataRa
         auto [state, stats, skipped, localCall] =
             _executor.skipRowsRange(inputRange, call);
         _executorReturnedDone = state == ExecutorState::DONE;
-        return {state, stats, skipped, localCall, 0};
+        return {state, stats, skipped, localCall};
       }
     } else if constexpr (skipRowsType<Executor>() == SkipRowsRangeVariant::FETCHER) {
       // If we know that every input row produces exactly one output row (this
@@ -1308,18 +1323,17 @@ auto ExecutionBlockImpl<Executor>::executeSkipRowsRange(typename Fetcher::DataRa
       static_assert(
           std::is_same_v<typename Executor::Stats, NoStats>,
           "Executors with custom statistics must implement skipRowsRange.");
-      return {inputRange.upstreamState(), NoStats{}, 0, call, 0};
+      return {inputRange.upstreamState(), NoStats{}, 0, call};
     } else {
       static_assert(dependent_false<Executor>::value,
                     "This value of SkipRowsRangeVariant is not supported");
-      return std::make_tuple(ExecutorState::DONE, typename Executor::Stats{}, 0, call, 0);
+      TRI_ASSERT(false);
     }
   } else {
     TRI_ASSERT(false);
-    return std::make_tuple(ExecutorState::DONE, typename Executor::Stats{}, 0, call, 0);
   }
-  // Compiler is unhappy without this.
-  return std::make_tuple(ExecutorState::DONE, typename Executor::Stats{}, 0, call, 0);
+  TRI_ASSERT(false);
+  THROW_ARANGO_EXCEPTION(TRI_ERROR_INTERNAL);
 }
 
 template <>
@@ -1474,7 +1488,7 @@ auto ExecutionBlockImpl<Executor>::shadowRowForwarding() -> ExecState {
 template <class Executor>
 auto ExecutionBlockImpl<Executor>::executeFastForward(typename Fetcher::DataRange& inputRange,
                                                       AqlCall& clientCall)
-    -> std::tuple<ExecutorState, typename Executor::Stats, size_t, AqlCall, size_t> {
+    -> std::tuple<ExecutorState, typename Executor::Stats, size_t, AqlCallType> {
   TRI_ASSERT(isNewStyleExecutor<Executor>);
   if constexpr (std::is_same_v<Executor, SubqueryStartExecutor>) {
     if (clientCall.needsFullCount() && clientCall.getOffset() == 0 &&
@@ -1484,7 +1498,7 @@ auto ExecutionBlockImpl<Executor>::executeFastForward(typename Fetcher::DataRang
       return executeSkipRowsRange(_lastRange, clientCall);
     }
     // Do not fastForward anything, the Subquery start will handle it by itself
-    return {ExecutorState::DONE, NoStats{}, 0, AqlCall{}, 0};
+    return {ExecutorState::DONE, NoStats{}, 0, AqlCall{}};
   }
   auto type = fastForwardType(clientCall, _executor);
 
@@ -1492,9 +1506,7 @@ auto ExecutionBlockImpl<Executor>::executeFastForward(typename Fetcher::DataRang
     case FastForwardVariant::FULLCOUNT:
     case FastForwardVariant::EXECUTOR: {
       LOG_QUERY("cb135", DEBUG) << printTypeInfo() << " apply full count.";
-      auto [state, stats, skippedLocal, call, dependency] =
-          executeSkipRowsRange(_lastRange, clientCall);
-      _requestedDependency = dependency;
+      auto [state, stats, skippedLocal, call] = executeSkipRowsRange(_lastRange, clientCall);
 
       if (type == FastForwardVariant::EXECUTOR) {
         // We do not report the skip
@@ -1508,22 +1520,40 @@ auto ExecutionBlockImpl<Executor>::executeFastForward(typename Fetcher::DataRang
         inputRange.skipAllRemainingDataRows();
       }
 
-      return {state, stats, skippedLocal, call, dependency};
+      return {state, stats, skippedLocal, call};
     }
     case FastForwardVariant::FETCHER: {
       LOG_QUERY("fa327", DEBUG) << printTypeInfo() << " bypass unused rows.";
-      _requestedDependency = inputRange.skipAllRemainingDataRows();
-      AqlCall call{};
-      call.hardLimit = 0;
+      auto const dependency = inputRange.skipAllRemainingDataRows();
+      auto constexpr fastForwardCall = AqlCall{0, false, 0, AqlCall::LimitType::HARD};
+      auto const call = std::invoke([&]() -> AqlCallType {
+        if constexpr (std::is_same_v<AqlCallType, AqlCall>) {
+          return fastForwardCall;
+        } else {
+#ifndef _WIN32
+          // For some reason our Windows compiler complains about this static assert
+          // in the cases that should be in the above constexpr path.
+          // So simply not compile it in.
+          static_assert(std::is_same_v<AqlCallType, AqlCallSet>);
+#endif
+          auto call = AqlCallSet{};
+          call.calls.emplace_back(typename AqlCallSet::DepCallPair{dependency, fastForwardCall});
+          return call;
+        }
+      });
 
       // TODO We have to ask all dependencies to go forward to the next shadow row
-      if constexpr (std::is_same_v<DataRange, MultiAqlItemBlockInputRange>) {
-        return {inputRange.upstreamState(_requestedDependency),
-                typename Executor::Stats{}, 0, call, _requestedDependency};
-      } else {
-        return {inputRange.upstreamState(), typename Executor::Stats{}, 0, call,
-                _requestedDependency};
-      }
+      auto const state = std::invoke(
+          [&](auto) {
+            if constexpr (std::is_same_v<DataRange, MultiAqlItemBlockInputRange>) {
+              return inputRange.upstreamState(dependency);
+            } else {
+              return inputRange.upstreamState();
+            }
+          },
+          0);
+
+      return {state, typename Executor::Stats{}, 0, call};
     }
   }
   // Unreachable
@@ -1585,7 +1615,7 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
       size_t skippedLocal = 0;
       typename Fetcher::DataRange bypassedRange{ExecutorState::HASMORE};
       std::tie(_upstreamState, skippedLocal, bypassedRange) =
-          executeFetcher(stack, _requestedDependency);
+          executeFetcher(stack, _upstreamRequest);
       return {_upstreamState, skippedLocal, bypassedRange.getBlock()};
     }
 
@@ -1665,8 +1695,7 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
           ExecutorState state = ExecutorState::HASMORE;
           typename Executor::Stats stats;
           size_t skippedLocal = 0;
-          AqlCall call{};
-          size_t dependency = 0;
+          AqlCallType call{};
           if constexpr (is_one_of_v<Executor, SubqueryExecutor<true>>) {
             // NOTE: The subquery Executor will by itself call EXECUTE on it's
             // subquery. This can return waiting => we can get a WAITING state
@@ -1684,11 +1713,10 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
             }
           } else {
             // Execute skipSome
-            std::tie(state, stats, skippedLocal, call, dependency) =
+            std::tie(state, stats, skippedLocal, call) =
                 executeSkipRowsRange(_lastRange, clientCall);
           }
 
-          _requestedDependency = dependency;
 #ifdef ARANGODB_ENABLE_MAINTAINER_MODE
           // Assertion: We did skip 'skippedLocal' documents here.
           // This means that they have to be removed from
@@ -1750,8 +1778,7 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
           TRI_ASSERT(!_executorReturnedDone);
           ExecutorState state = ExecutorState::HASMORE;
           typename Executor::Stats stats;
-          AqlCall call{};
-          size_t dependency = 0;
+          auto call = AqlCallType{};
           if constexpr (is_one_of_v<Executor, SubqueryExecutor<true>, SubqueryExecutor<false>>) {
             // NOTE: The subquery Executor will by itself call EXECUTE on it's
             // subquery. This can return waiting => we can get a WAITING state
@@ -1768,10 +1795,8 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
             }
           } else {
             // Execute getSome
-            std::tie(state, stats, call, dependency) =
-                executeProduceRows(_lastRange, *_outputItemRow);
+            std::tie(state, stats, call) = executeProduceRows(_lastRange, *_outputItemRow);
           }
-          _requestedDependency = dependency;
           _executorReturnedDone = state == ExecutorState::DONE;
           _engine->_stats += stats;
           localExecutorState = state;
@@ -1790,7 +1815,7 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
             // In all other branches only if the client Still needs more data.
             _execState = ExecState::DONE;
             break;
-          } else if (clientCall.getLimit() > 0 && !lastRangeHasDataRow()) {
+          } else if (clientCall.getLimit() > 0 && executorNeedsCall(call)) {
             TRI_ASSERT(_upstreamState != ExecutionState::DONE);
             // We need to request more
             _upstreamRequest = call;
@@ -1804,10 +1829,9 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
         case ExecState::FASTFORWARD: {
           LOG_QUERY("96e2c", DEBUG)
               << printTypeInfo() << " all produced, fast forward to end up (sub-)query.";
-          auto [state, stats, skippedLocal, call, dependency] =
+          auto [state, stats, skippedLocal, call] =
               executeFastForward(_lastRange, clientCall);
 
-          _requestedDependency = dependency;
           _skipped += skippedLocal;
           _engine->_stats += stats;
           localExecutorState = state;
@@ -1831,39 +1855,22 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
           // If this triggers the executors produceRows function has returned
           // HASMORE even if it knew that upstream has no further rows.
           TRI_ASSERT(_upstreamState != ExecutionState::DONE);
-          // We need to make sure _lastRange is all used
-          TRI_ASSERT(!lastRangeHasDataRow());
+          // We need to make sure _lastRange is all used for single-dependency
+          // executors.
+          TRI_ASSERT(isMultiDepExecutor<Executor> || !lastRangeHasDataRow());
           TRI_ASSERT(!_lastRange.hasShadowRow());
           size_t skippedLocal = 0;
 
 #ifdef ARANGODB_ENABLE_MAINTAINER_MODE
-          size_t subqueryLevelBefore = stack.subqueryLevel();
+          auto subqueryLevelBefore = stack.subqueryLevel();
 #endif
-          // If we are SubqueryStart, we remove the top element of the stack
-          // which belongs to the subquery enclosed by this
-          // SubqueryStart and the partnered SubqueryEnd by *not*
-          // pushing the upstream request.
-          if constexpr (!std::is_same_v<Executor, SubqueryStartExecutor>) {
-            auto callCopy = _upstreamRequest;
-            stack.pushCall(std::move(callCopy));
-          }
-
           std::tie(_upstreamState, skippedLocal, _lastRange) =
-              executeFetcher(stack, _requestedDependency);
-
-          if constexpr (std::is_same_v<Executor, SubqueryStartExecutor>) {
-            // Do not pop the call, we did not put it on.
-            // However we need it for accounting later.
-          } else {
-            // As the stack is copied into the fetcher, we need to pop off our call again.
-            // If we use other datastructures or moving we may hand over ownership of the stack here
-            // instead and no popCall is necessary.
-            stack.popCall();
-          }
+              executeFetcher(stack, _upstreamRequest);
 
 #ifdef ARANGODB_ENABLE_MAINTAINER_MODE
           TRI_ASSERT(subqueryLevelBefore == stack.subqueryLevel());
 #endif
+
           if (_upstreamState == ExecutionState::WAITING) {
             // We need to persist the old call before we return.
             // We might have some local accounting to this call.
@@ -2019,9 +2026,8 @@ auto ExecutionBlockImpl<Executor>::outputIsFull() const noexcept -> bool {
          _outputItemRow->allRowsUsed();
 }
 
-// TODO: remove again
 template <class Executor>
-auto ExecutionBlockImpl<Executor>::lastRangeHasDataRow() const -> bool {
+auto ExecutionBlockImpl<Executor>::lastRangeHasDataRow() const noexcept -> bool {
   return _lastRange.hasDataRow();
 }
 
@@ -2032,6 +2038,37 @@ RegisterId ExecutionBlockImpl<IdExecutor<SingleRowFetcher<BlockPassthrough::Enab
   return _infos.getOutputRegister();
 }
 
+template <class Executor>
+void ExecutionBlockImpl<Executor>::init() {
+  TRI_ASSERT(!_initialized);
+  if constexpr (isMultiDepExecutor<Executor>) {
+    _lastRange.resizeOnce(ExecutorState::HASMORE, 0, _dependencies.size());
+    _rowFetcher.init();
+  }
+}
+
+template <class Executor>
+void ExecutionBlockImpl<Executor>::initOnce() {
+  if (!_initialized) {
+    init();
+    _initialized = true;
+  }
+}
+template <class Executor>
+auto ExecutionBlockImpl<Executor>::executorNeedsCall(AqlCallType& call) const
+    noexcept -> bool {
+  if constexpr (isMultiDepExecutor<Executor>) {
+    // call is an AqlCallSet. We need to call upstream if it's not empty.
+    return !call.empty();
+  } else {
+    // call is an AqlCall, unconditionally. The current convention is
+    // to call upstream when there is no input left.
+    // This could be made unnecessary by returning an optional AqlCall
+    // for single-dependency executors.
+    return !lastRangeHasDataRow();
+  }
+};
+
 template class ::arangodb::aql::ExecutionBlockImpl<CalculationExecutor<CalculationType::Condition>>;
 template class ::arangodb::aql::ExecutionBlockImpl<CalculationExecutor<CalculationType::Reference>>;
 template class ::arangodb::aql::ExecutionBlockImpl<CalculationExecutor<CalculationType::V8Condition>>;
diff --git a/arangod/Aql/ExecutionBlockImpl.h b/arangod/Aql/ExecutionBlockImpl.h
index c0e072289704..8e1009c5b518 100644
--- a/arangod/Aql/ExecutionBlockImpl.h
+++ b/arangod/Aql/ExecutionBlockImpl.h
@@ -27,6 +27,7 @@
 #define ARANGOD_AQL_EXECUTION_BLOCK_IMPL_H 1
 
 #include "Aql/AqlCall.h"
+#include "Aql/AqlCallSet.h"
 #include "Aql/ConstFetcher.h"
 #include "Aql/DependencyProxy.h"
 #include "Aql/ExecutionBlock.h"
@@ -51,11 +52,15 @@ class InputAqlItemRow;
 class OutputAqlItemRow;
 class Query;
 class ShadowAqlItemRow;
-class ParallelUnsortedGatherExecutor;
+class MultiDependencySingleRowFetcher;
 
 template <typename T, typename... Es>
 constexpr bool is_one_of_v = (std::is_same_v<T, Es> || ...);
 
+template <typename Executor>
+static constexpr bool isMultiDepExecutor =
+    std::is_same_v<typename Executor::Fetcher, MultiDependencySingleRowFetcher>;
+
 /**
  * @brief This is the implementation class of AqlExecutionBlocks.
  *        It is responsible to create AqlItemRows for subsequent
@@ -139,8 +144,11 @@ class ExecutionBlockImpl final : public ExecutionBlock {
     DONE
   };
 
-  static constexpr bool isParallelExecutor =
-      is_one_of_v<Executor, ParallelUnsortedGatherExecutor>;
+  // Where Executors with a single dependency return an AqlCall, Executors with
+  // multiple dependencies return a partial map depIndex -> AqlCall.
+  // It may be empty. If the cardinality is greater than one, the calls will be
+  // executed in parallel.
+  using AqlCallType = std::conditional_t<isMultiDepExecutor<Executor>, AqlCallSet, AqlCall>;
 
  public:
   /**
@@ -157,6 +165,13 @@ class ExecutionBlockImpl final : public ExecutionBlock {
 
   ~ExecutionBlockImpl() override;
 
+  /// @brief Must be called exactly once after the plan is instantiated (i.e.,
+  ///        all blocks are created and dependencies are injected), but before
+  ///        the first execute() call.
+  ///        Is currently called conditionally in execute() itself, but should
+  ///        better be called in instantiateFromPlan and similar methods.
+  void init();
+
   /**
    * @brief Produce atMost many output rows, or less.
    *        May return waiting if I/O has to be performed
@@ -241,17 +256,17 @@ class ExecutionBlockImpl final : public ExecutionBlock {
   std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> executeWithoutTrace(AqlCallStack stack);
 
   std::tuple<ExecutionState, size_t, typename Fetcher::DataRange> executeFetcher(
-      AqlCallStack& stack, size_t const dependency);
+      AqlCallStack& stack, AqlCallType const& aqlCall);
 
-  std::tuple<ExecutorState, typename Executor::Stats, AqlCall, size_t> executeProduceRows(
+  std::tuple<ExecutorState, typename Executor::Stats, AqlCallType> executeProduceRows(
       typename Fetcher::DataRange& input, OutputAqlItemRow& output);
 
   // execute a skipRowsRange call
   auto executeSkipRowsRange(typename Fetcher::DataRange& inputRange, AqlCall& call)
-      -> std::tuple<ExecutorState, typename Executor::Stats, size_t, AqlCall, size_t>;
+      -> std::tuple<ExecutorState, typename Executor::Stats, size_t, AqlCallType>;
 
   auto executeFastForward(typename Fetcher::DataRange& inputRange, AqlCall& clientCall)
-      -> std::tuple<ExecutorState, typename Executor::Stats, size_t, AqlCall, size_t>;
+      -> std::tuple<ExecutorState, typename Executor::Stats, size_t, AqlCallType>;
 
   /**
    * @brief Inner getSome() part, without the tracing calls.
@@ -310,10 +325,14 @@ class ExecutionBlockImpl final : public ExecutionBlock {
 
   [[nodiscard]] auto outputIsFull() const noexcept -> bool;
 
-  [[nodiscard]] auto lastRangeHasDataRow() const -> bool;
+  [[nodiscard]] auto lastRangeHasDataRow() const noexcept -> bool;
 
   void resetExecutor();
 
+  void initOnce();
+
+  [[nodiscard]] auto executorNeedsCall(AqlCallType& call) const noexcept -> bool;
+
  private:
   /**
    * @brief Used to allow the row Fetcher to access selected methods of this
@@ -348,12 +367,10 @@ class ExecutionBlockImpl final : public ExecutionBlock {
 
   ExecState _execState;
 
-  AqlCall _upstreamRequest;
+  AqlCallType _upstreamRequest;
 
   AqlCall _clientRequest;
 
-  size_t _requestedDependency;
-
   // Only used in passthrough variant.
   // We track if we have reference the range's block
   // into an output block.
@@ -362,8 +379,7 @@ class ExecutionBlockImpl final : public ExecutionBlock {
 
   bool _executorReturnedDone = false;
 
-  /// @brief Only needed for parallel executors; could be omitted otherwise
-  std::vector<std::optional<AqlCallStack>> _callsInFlight;
+  bool _initialized = false;
 };
 
 }  // namespace arangodb::aql
diff --git a/arangod/Aql/IdExecutor.h b/arangod/Aql/IdExecutor.h
index dbab3c746ebc..2b45ac5430e5 100644
--- a/arangod/Aql/IdExecutor.h
+++ b/arangod/Aql/IdExecutor.h
@@ -88,10 +88,6 @@ class IdExecutorInfos : public ExecutorInfos {
   bool const _isResponsibleForInitializeCursor;
 };
 
-// forward declaration
-template <class Fetcher>
-class IdExecutor;
-
 template <class UsedFetcher>
 // cppcheck-suppress noConstructor
 class IdExecutor {
diff --git a/arangod/Aql/MultiAqlItemBlockInputRange.cpp b/arangod/Aql/MultiAqlItemBlockInputRange.cpp
index ab8ea0d32e51..1cd6e114618b 100644
--- a/arangod/Aql/MultiAqlItemBlockInputRange.cpp
+++ b/arangod/Aql/MultiAqlItemBlockInputRange.cpp
@@ -39,14 +39,13 @@ MultiAqlItemBlockInputRange::MultiAqlItemBlockInputRange(ExecutorState state,
   TRI_ASSERT(nrInputRanges > 0);
 }
 
-auto MultiAqlItemBlockInputRange::resizeIfNecessary(ExecutorState state, size_t skipped,
-                                                    size_t nrInputRanges) -> void {
+auto MultiAqlItemBlockInputRange::resizeOnce(ExecutorState state, size_t skipped,
+                                             size_t nrInputRanges) -> void {
+  // Is expected to be called exactly once to set the number of dependencies.
   // We never want to reduce the number of dependencies.
   TRI_ASSERT(_inputs.size() <= nrInputRanges);
   TRI_ASSERT(nrInputRanges > 0);
-  if (_inputs.size() < nrInputRanges) {
-    _inputs.resize(nrInputRanges, AqlItemBlockInputRange{state, skipped});
-  }
+  _inputs.resize(nrInputRanges, AqlItemBlockInputRange{state, skipped});
 }
 
 auto MultiAqlItemBlockInputRange::upstreamState(size_t const dependency) const
@@ -84,6 +83,12 @@ auto MultiAqlItemBlockInputRange::skipAll(size_t const dependency) noexcept -> s
   return _inputs.at(dependency).skipAll();
 }
 
+auto MultiAqlItemBlockInputRange::skippedInFlight(size_t const dependency) const
+    noexcept -> std::size_t {
+  TRI_ASSERT(dependency < _inputs.size());
+  return _inputs.at(dependency).skippedInFlight();
+}
+
 auto MultiAqlItemBlockInputRange::nextDataRow(size_t const dependency)
     -> std::pair<ExecutorState, arangodb::aql::InputAqlItemRow> {
   TRI_ASSERT(dependency < _inputs.size());
@@ -129,7 +134,7 @@ auto MultiAqlItemBlockInputRange::getBlock(size_t const dependency) const
 }
 
 auto MultiAqlItemBlockInputRange::setDependency(size_t const dependency,
-                                                AqlItemBlockInputRange& range) -> void {
+                                                AqlItemBlockInputRange const& range) -> void {
   TRI_ASSERT(dependency < _inputs.size());
   _inputs.at(dependency) = range;
 }
@@ -143,9 +148,13 @@ auto MultiAqlItemBlockInputRange::isDone() const -> bool {
   return res;
 }
 
+auto MultiAqlItemBlockInputRange::state() const -> ExecutorState {
+  return isDone() ? ExecutorState::DONE : ExecutorState::HASMORE;
+}
+
 auto MultiAqlItemBlockInputRange::skipAllRemainingDataRows() -> size_t {
   for (size_t i = 0; i < _inputs.size(); i++) {
-    _inputs.at(i).skipAllRemainingDataRows();
+    std::ignore = _inputs.at(i).skipAllRemainingDataRows();
     if (_inputs.at(i).upstreamState() == ExecutorState::HASMORE) {
       return i;
     }
@@ -153,6 +162,23 @@ auto MultiAqlItemBlockInputRange::skipAllRemainingDataRows() -> size_t {
   return 0;
 }
 
+// Subtract up to count rows from the local _skipped state
+auto MultiAqlItemBlockInputRange::skipForDependency(size_t const dependency,
+                                                    size_t count) -> size_t {
+  return _inputs.at(dependency).skip(count);
+}
+
+// Skipp all that is available
+auto MultiAqlItemBlockInputRange::skipAllForDependency(size_t const dependency) -> size_t {
+  return _inputs.at(dependency).skipAll();
+}
+
 auto MultiAqlItemBlockInputRange::numberDependencies() const noexcept -> size_t {
   return _inputs.size();
-}
\ No newline at end of file
+}
+
+auto MultiAqlItemBlockInputRange::reset() -> void {
+  for (size_t i = 0; i < _inputs.size(); ++i) {
+    _inputs[i] = AqlItemBlockInputRange(ExecutorState::HASMORE);
+  }
+}
diff --git a/arangod/Aql/MultiAqlItemBlockInputRange.h b/arangod/Aql/MultiAqlItemBlockInputRange.h
index 74aa1584c2ac..e02ee639231a 100644
--- a/arangod/Aql/MultiAqlItemBlockInputRange.h
+++ b/arangod/Aql/MultiAqlItemBlockInputRange.h
@@ -62,26 +62,35 @@ class MultiAqlItemBlockInputRange {
   std::pair<ExecutorState, arangodb::aql::InputAqlItemRow> nextDataRow(size_t const dependency);
   auto skipAll(size_t const dependency) noexcept -> std::size_t;
 
+  [[nodiscard]] auto skippedInFlight(size_t dependency) const noexcept -> std::size_t;
+
   bool hasShadowRow() const noexcept;
 
   arangodb::aql::ShadowAqlItemRow peekShadowRow() const;
   std::pair<ExecutorState, arangodb::aql::ShadowAqlItemRow> nextShadowRow();
 
   auto isDone() const -> bool;
+  auto state() const -> ExecutorState;
 
-  auto resizeIfNecessary(ExecutorState state, size_t skipped, size_t nrInputRanges) -> void;
+  auto resizeOnce(ExecutorState state, size_t skipped, size_t nrInputRanges) -> void;
 
-  auto getBlock(size_t const dependency = 0) const noexcept -> SharedAqlItemBlockPtr;
+  [[nodiscard]] auto getBlock(size_t dependency = 0) const noexcept -> SharedAqlItemBlockPtr;
 
-  auto setDependency(size_t const dependency, AqlItemBlockInputRange& range) -> void;
+  auto setDependency(size_t dependency, AqlItemBlockInputRange const& range) -> void;
 
+  // This discards all remaining data rows
   auto skipAllRemainingDataRows() -> size_t;
 
+  // Subtract up to count rows from the local _skipped state
+  auto skipForDependency(size_t const dependency, size_t count) -> size_t;
+  // Skipp all that is available
+  auto skipAllForDependency(size_t const dependency) -> size_t;
+
   auto numberDependencies() const noexcept -> size_t;
 
- private:
-  ExecutorState _finalState{ExecutorState::HASMORE};
+  auto reset() -> void;
 
+ private:
   std::vector<AqlItemBlockInputRange> _inputs;
 };
 
diff --git a/arangod/Aql/MultiDependencySingleRowFetcher.cpp b/arangod/Aql/MultiDependencySingleRowFetcher.cpp
index aac3b3b866ac..b275f0c19567 100644
--- a/arangod/Aql/MultiDependencySingleRowFetcher.cpp
+++ b/arangod/Aql/MultiDependencySingleRowFetcher.cpp
@@ -176,12 +176,15 @@ void MultiDependencySingleRowFetcher::initDependencies() {
 }
 
 size_t MultiDependencySingleRowFetcher::numberDependencies() {
-  if (_dependencyInfos.empty()) {
-    initDependencies();
-  }
   return _dependencyInfos.size();
 }
 
+void MultiDependencySingleRowFetcher::init() {
+  TRI_ASSERT(_dependencyInfos.empty());
+  initDependencies();
+  _callsInFlight.resize(numberDependencies());
+}
+
 std::pair<ExecutionState, size_t> MultiDependencySingleRowFetcher::preFetchNumberOfRows(size_t atMost) {
   ExecutionState state = ExecutionState::DONE;
   size_t available = 0;
@@ -368,9 +371,6 @@ auto MultiDependencySingleRowFetcher::useStack(AqlCallStack const& stack) -> voi
 auto MultiDependencySingleRowFetcher::executeForDependency(size_t const dependency,
                                                            AqlCallStack& stack)
     -> std::tuple<ExecutionState, size_t, AqlItemBlockInputRange> {
-  if (_dependencyStates.empty()) {
-    initDependencies();
-  }
   auto [state, skipped, block] = _dependencyProxy->executeForDependency(dependency, stack);
 
   if (state == ExecutionState::WAITING) {
@@ -380,14 +380,7 @@ auto MultiDependencySingleRowFetcher::executeForDependency(size_t const dependen
       state == ExecutionState::DONE ? ExecutorState::DONE : ExecutorState::HASMORE;
 
   _dependencyStates.at(dependency) = state;
-  if (std::any_of(std::begin(_dependencyStates), std::end(_dependencyStates),
-                  [](ExecutionState const s) {
-                    return s == ExecutionState::HASMORE;
-                  })) {
-    state = ExecutionState::HASMORE;
-  } else {
-    state = ExecutionState::DONE;
-  }
+
   if (block == nullptr) {
     return {state, skipped, AqlItemBlockInputRange{execState, skipped}};
   }
@@ -395,3 +388,79 @@ auto MultiDependencySingleRowFetcher::executeForDependency(size_t const dependen
   auto [start, end] = block->getRelevantRange();
   return {state, skipped, AqlItemBlockInputRange{execState, skipped, block, start}};
 }
+
+auto MultiDependencySingleRowFetcher::execute(AqlCallStack const& stack,
+                                              AqlCallSet const& aqlCallSet)
+    -> std::tuple<ExecutionState, size_t, std::vector<std::pair<size_t, AqlItemBlockInputRange>>> {
+  TRI_ASSERT(_callsInFlight.size() == numberDependencies());
+
+  auto ranges = std::vector<std::pair<size_t, AqlItemBlockInputRange>>{};
+  ranges.reserve(aqlCallSet.size());
+
+  auto depCallIdx = size_t{0};
+  auto allAskedDepsAreWaiting = true;
+  auto askedAtLeastOneDep = false;
+  auto skippedTotal = size_t{0};
+  // Iterate in parallel over `_callsInFlight` and `aqlCall.calls`.
+  // _callsInFlight[i] corresponds to aqlCalls.calls[k] iff
+  // aqlCalls.calls[k].dependency = i.
+  // So there is not always a matching entry in aqlCall.calls.
+  for (auto dependency = size_t{0}; dependency < _callsInFlight.size(); ++dependency) {
+    auto& maybeCallInFlight = _callsInFlight[dependency];
+
+    // See if there is an entry for `dependency` in `aqlCall.calls`
+    if (depCallIdx < aqlCallSet.calls.size() &&
+        aqlCallSet.calls[depCallIdx].dependency == dependency) {
+      // If there is a call in flight, we *must not* change the call,
+      // no matter what we got. Otherwise, we save the current call.
+      if (!maybeCallInFlight.has_value()) {
+        auto depStack = stack;
+        depStack.pushCall(aqlCallSet.calls[depCallIdx].call);
+        maybeCallInFlight = depStack;
+      }
+      ++depCallIdx;
+      if (depCallIdx < aqlCallSet.calls.size()) {
+        TRI_ASSERT(aqlCallSet.calls[depCallIdx - 1].dependency <
+                   aqlCallSet.calls[depCallIdx].dependency);
+      }
+    }
+
+    if (maybeCallInFlight.has_value()) {
+      // We either need to make a new call, or check whether we got a result
+      // for a call in flight.
+      auto& callInFlight = maybeCallInFlight.value();
+      auto [state, skipped, range] = executeForDependency(dependency, callInFlight);
+      askedAtLeastOneDep = true;
+      if (state != ExecutionState::WAITING) {
+        // Got a result, call is no longer in flight
+        maybeCallInFlight = std::nullopt;
+        allAskedDepsAreWaiting = false;
+      } else {
+        TRI_ASSERT(skipped == 0);
+      }
+      skippedTotal += skipped;
+      ranges.emplace_back(dependency, range);
+    }
+  }
+
+  auto const state = std::invoke([&]() {
+    if (askedAtLeastOneDep && allAskedDepsAreWaiting) {
+      return ExecutionState::WAITING;
+    } else {
+      return upstreamState();
+    }
+  });
+
+  return {state, skippedTotal, ranges};
+}
+
+auto MultiDependencySingleRowFetcher::upstreamState() const -> ExecutionState {
+  if (std::any_of(std::begin(_dependencyStates), std::end(_dependencyStates),
+                  [](ExecutionState const s) {
+                    return s == ExecutionState::HASMORE;
+                  })) {
+    return ExecutionState::HASMORE;
+  } else {
+    return ExecutionState::DONE;
+  }
+}
diff --git a/arangod/Aql/MultiDependencySingleRowFetcher.h b/arangod/Aql/MultiDependencySingleRowFetcher.h
index a2c2ebdd911e..277ebf628997 100644
--- a/arangod/Aql/MultiDependencySingleRowFetcher.h
+++ b/arangod/Aql/MultiDependencySingleRowFetcher.h
@@ -23,6 +23,7 @@
 #ifndef ARANGOD_AQL_MULTI_DEPENDENCY_SINGLE_ROW_FETCHER_H
 #define ARANGOD_AQL_MULTI_DEPENDENCY_SINGLE_ROW_FETCHER_H
 
+#include "Aql/AqlCallSet.h"
 #include "Aql/ExecutionBlock.h"
 #include "Aql/ExecutionState.h"
 #include "Aql/InputAqlItemRow.h"
@@ -32,8 +33,7 @@
 
 #include <memory>
 
-namespace arangodb {
-namespace aql {
+namespace arangodb::aql {
 
 class AqlItemBlock;
 template <BlockPassthrough>
@@ -89,6 +89,8 @@ class MultiDependencySingleRowFetcher {
   explicit MultiDependencySingleRowFetcher(DependencyProxy<BlockPassthrough::Disable>& executionBlock);
   TEST_VIRTUAL ~MultiDependencySingleRowFetcher() = default;
 
+  void init();
+
  protected:
   // only for testing! Does not initialize _dependencyProxy!
   MultiDependencySingleRowFetcher();
@@ -134,9 +136,14 @@ class MultiDependencySingleRowFetcher {
   //@deprecated
   auto useStack(AqlCallStack const& stack) -> void;
 
-  auto executeForDependency(size_t const dependency, AqlCallStack& stack)
+  [[nodiscard]] auto execute(AqlCallStack const&, AqlCallSet const&)
+      -> std::tuple<ExecutionState, size_t, std::vector<std::pair<size_t, AqlItemBlockInputRange>>>;
+
+  [[nodiscard]] auto executeForDependency(size_t dependency, AqlCallStack& stack)
       -> std::tuple<ExecutionState, size_t, AqlItemBlockInputRange>;
 
+  [[nodiscard]] auto upstreamState() const -> ExecutionState;
+
  private:
   DependencyProxy<BlockPassthrough::Disable>* _dependencyProxy;
 
@@ -146,6 +153,11 @@ class MultiDependencySingleRowFetcher {
   std::vector<DependencyInfo> _dependencyInfos;
   std::vector<ExecutionState> _dependencyStates;
 
+  /// @brief Only needed for parallel executors; could be omitted otherwise
+  ///        It's size is >0 after init() is called, and this is currently used
+  ///        in initOnce() to make sure that init() is called exactly once.
+  std::vector<std::optional<AqlCallStack>> _callsInFlight;
+
  private:
   /**
    * @brief Delegates to ExecutionBlock::fetchBlock()
@@ -177,7 +189,6 @@ class MultiDependencySingleRowFetcher {
   bool fetchBlockIfNecessary(const size_t dependency, const size_t atMost);
 };
 
-}  // namespace aql
-}  // namespace arangodb
+}  // namespace arangodb::aql
 
 #endif  // ARANGOD_AQL_SINGLE_ROW_FETCHER_H
diff --git a/arangod/Aql/ParallelUnsortedGatherExecutor.cpp b/arangod/Aql/ParallelUnsortedGatherExecutor.cpp
index 6a22758d5864..457d6daa61c1 100644
--- a/arangod/Aql/ParallelUnsortedGatherExecutor.cpp
+++ b/arangod/Aql/ParallelUnsortedGatherExecutor.cpp
@@ -45,12 +45,21 @@ ParallelUnsortedGatherExecutor::~ParallelUnsortedGatherExecutor() = default;
 
 auto ParallelUnsortedGatherExecutor::upstreamCallSkip(AqlCall const& clientCall) const
     noexcept -> AqlCall {
+  TRI_ASSERT(clientCall.needSkipMore());
+
   // Only skip, don't ask for rows
-  auto upstreamCall = clientCall;
-  upstreamCall.softLimit = 0;
-  upstreamCall.hardLimit = AqlCall::Infinity{};
-  upstreamCall.fullCount = false;
-  return upstreamCall;
+  if (clientCall.getOffset() > 0) {
+    auto upstreamCall = clientCall;
+    upstreamCall.softLimit = 0;
+    upstreamCall.hardLimit = AqlCall::Infinity{};
+    upstreamCall.fullCount = false;
+    return upstreamCall;
+  }
+  TRI_ASSERT(clientCall.getLimit() == 0 && clientCall.hasHardLimit());
+
+  // This can onyl be fullCount or fastForward call.
+  // Send it upstream.
+  return clientCall;
 }
 
 auto ParallelUnsortedGatherExecutor::upstreamCallProduce(AqlCall const& clientCall) const
@@ -75,9 +84,12 @@ auto ParallelUnsortedGatherExecutor::upstreamCallProduce(AqlCall const& clientCa
 
 auto ParallelUnsortedGatherExecutor::produceRows(typename Fetcher::DataRange& input,
                                                  OutputAqlItemRow& output)
-    -> std::tuple<ExecutorState, Stats, AqlCall, size_t> {
-  // Illegal dependency, on purpose to trigger asserts
-  size_t waitingDep = input.numberDependencies();
+    -> std::tuple<ExecutorState, Stats, AqlCallSet> {
+  auto const& clientCall = output.getClientCall();
+  TRI_ASSERT(clientCall.getOffset() == 0);
+
+  auto callSet = AqlCallSet{};
+
   for (size_t dep = 0; dep < input.numberDependencies(); ++dep) {
     while (!output.isFull()) {
       auto [state, row] = input.nextDataRow(dep);
@@ -87,24 +99,24 @@ auto ParallelUnsortedGatherExecutor::produceRows(typename Fetcher::DataRange& in
       } else {
         // This output did not produce anything
         if (state == ExecutorState::HASMORE) {
-          waitingDep = dep;
+          callSet.calls.emplace_back(
+              AqlCallSet::DepCallPair{dep, upstreamCallProduce(clientCall)});
         }
         break;
       }
     }
   }
-  if (input.isDone()) {
-    // We cannot have one that we are waiting on, if we are done.
-    TRI_ASSERT(waitingDep == input.numberDependencies());
-    return {ExecutorState::DONE, NoStats{}, AqlCall{}, waitingDep};
-  }
-  return {ExecutorState::HASMORE, NoStats{},
-          upstreamCallProduce(output.getClientCall()), waitingDep};
+
+  // We cannot have one that we are waiting on, if we are done.
+  TRI_ASSERT(!input.isDone() || callSet.empty());
+
+  return {input.state(), NoStats{}, callSet};
 }
 
 auto ParallelUnsortedGatherExecutor::skipRowsRange(typename Fetcher::DataRange& input,
                                                    AqlCall& call)
-    -> std::tuple<ExecutorState, Stats, size_t, AqlCall, size_t> {
+    -> std::tuple<ExecutorState, Stats, size_t, AqlCallSet> {
+  // TODO skipping is currently not parallelized, but should be
   size_t waitingDep = input.numberDependencies();
   for (size_t dep = 0; dep < input.numberDependencies(); ++dep) {
     auto& range = input.rangeForDependency(dep);
@@ -140,8 +152,13 @@ auto ParallelUnsortedGatherExecutor::skipRowsRange(typename Fetcher::DataRange&
   if (input.isDone()) {
     // We cannot have one that we are waiting on, if we are done.
     TRI_ASSERT(waitingDep == input.numberDependencies());
-    return {ExecutorState::DONE, NoStats{}, call.getSkipCount(), AqlCall{}, waitingDep};
+    return {ExecutorState::DONE, NoStats{}, call.getSkipCount(), AqlCallSet{}};
+  }
+  auto callSet = AqlCallSet{};
+  if (call.needSkipMore()) {
+    // We are not done with skipping.
+    // Prepare next call.
+    callSet.calls.emplace_back(AqlCallSet::DepCallPair{waitingDep, upstreamCallSkip(call)});
   }
-  return {ExecutorState::HASMORE, NoStats{}, call.getSkipCount(),
-          upstreamCallSkip(call), waitingDep};
+  return {ExecutorState::HASMORE, NoStats{}, call.getSkipCount(), callSet};
 }
diff --git a/arangod/Aql/ParallelUnsortedGatherExecutor.h b/arangod/Aql/ParallelUnsortedGatherExecutor.h
index 1e52f8114267..f053f2f308f9 100644
--- a/arangod/Aql/ParallelUnsortedGatherExecutor.h
+++ b/arangod/Aql/ParallelUnsortedGatherExecutor.h
@@ -23,6 +23,7 @@
 #ifndef ARANGOD_AQL_PARALLEL_UNSORTED_GATHER_EXECUTOR_H
 #define ARANGOD_AQL_PARALLEL_UNSORTED_GATHER_EXECUTOR_H
 
+#include "Aql/AqlCallSet.h"
 #include "Aql/ClusterNodes.h"
 #include "Aql/ExecutionState.h"
 #include "Aql/ExecutorInfos.h"
@@ -82,7 +83,7 @@ class ParallelUnsortedGatherExecutor {
    *   size:t: Dependency to request
    */
   [[nodiscard]] auto produceRows(MultiAqlItemBlockInputRange& input, OutputAqlItemRow& output)
-      -> std::tuple<ExecutorState, Stats, AqlCall, size_t>;
+      -> std::tuple<ExecutorState, Stats, AqlCallSet>;
 
   /**
    * @brief Skip rows
@@ -97,7 +98,7 @@ class ParallelUnsortedGatherExecutor {
    *   size:t: Dependency to request
    */
   [[nodiscard]] auto skipRowsRange(MultiAqlItemBlockInputRange& input, AqlCall& call)
-      -> std::tuple<ExecutorState, Stats, size_t, AqlCall, size_t>;
+      -> std::tuple<ExecutorState, Stats, size_t, AqlCallSet>;
 
  private:
   auto upstreamCallSkip(AqlCall const& clientCall) const noexcept -> AqlCall;
diff --git a/arangod/Aql/SortingGatherExecutor.cpp b/arangod/Aql/SortingGatherExecutor.cpp
index 4ba8087e808c..d3fa50ccdcf0 100644
--- a/arangod/Aql/SortingGatherExecutor.cpp
+++ b/arangod/Aql/SortingGatherExecutor.cpp
@@ -28,6 +28,8 @@
 #include "Aql/Stats.h"
 #include "Transaction/Methods.h"
 
+#include <utility>
+
 using namespace arangodb;
 using namespace arangodb::aql;
 
@@ -124,9 +126,12 @@ class HeapSorting final : public SortingGatherExecutor::SortingStrategy, private
 
   virtual void reset() noexcept override { _heap.clear(); }
 
-  bool operator()(SortingGatherExecutor::ValueType const& lhs,
-                  SortingGatherExecutor::ValueType const& rhs) const {
-    return OurLessThan::operator()(rhs, lhs);
+  // The STL heap (regarding push_heap, pop_heap, make_heap) is a max heap, but
+  // we want a min heap!
+  bool operator()(SortingGatherExecutor::ValueType const& left,
+                  SortingGatherExecutor::ValueType const& right) const {
+    // Note that right and left are swapped!
+    return OurLessThan::operator()(right, left);
   }
 
  private:
@@ -138,7 +143,7 @@ class HeapSorting final : public SortingGatherExecutor::SortingStrategy, private
 /// @brief "MinElement" sorting strategy
 ////////////////////////////////////////////////////////////////////////////////
 class MinElementSorting final : public SortingGatherExecutor::SortingStrategy,
-                                public OurLessThan {
+                                private OurLessThan {
  public:
   MinElementSorting(arangodb::transaction::Methods* trx,
                     std::vector<SortRegister>& sortRegisters) noexcept
@@ -155,6 +160,8 @@ class MinElementSorting final : public SortingGatherExecutor::SortingStrategy,
 
   virtual void reset() noexcept override { _blockPos = nullptr; }
 
+  using OurLessThan::operator();
+
  private:
   std::vector<SortingGatherExecutor::ValueType> const* _blockPos;
 };
@@ -164,7 +171,7 @@ SortingGatherExecutor::ValueType::ValueType(size_t index)
     : dependencyIndex{index}, row{CreateInvalidInputRowHint()}, state{ExecutorState::HASMORE} {}
 
 SortingGatherExecutor::ValueType::ValueType(size_t index, InputAqlItemRow prow, ExecutorState pstate)
-    : dependencyIndex{index}, row{prow}, state{pstate} {}
+    : dependencyIndex{index}, row{std::move(prow)}, state{pstate} {}
 
 SortingGatherExecutorInfos::SortingGatherExecutorInfos(
     std::shared_ptr<std::unordered_set<RegisterId>> inputRegisters,
@@ -186,8 +193,7 @@ SortingGatherExecutorInfos::SortingGatherExecutorInfos(SortingGatherExecutorInfo
 SortingGatherExecutorInfos::~SortingGatherExecutorInfos() = default;
 
 SortingGatherExecutor::SortingGatherExecutor(Fetcher& fetcher, Infos& infos)
-    : _initialized(false),
-      _numberDependencies(0),
+    : _numberDependencies(0),
       _inputRows(),
       _limit(infos.limit()),
       _rowsReturned(0),
@@ -210,8 +216,8 @@ SortingGatherExecutor::SortingGatherExecutor(Fetcher& fetcher, Infos& infos)
 
 SortingGatherExecutor::~SortingGatherExecutor() = default;
 
-auto SortingGatherExecutor::initialize(typename Fetcher::DataRange const& inputRange)
-    -> std::optional<std::tuple<AqlCall, size_t>> {
+auto SortingGatherExecutor::initialize(typename Fetcher::DataRange const& inputRange,
+                                       AqlCall const& clientCall) -> AqlCallSet {
   if (!_initialized) {
     // We cannot modify the number of dependencies, so we start
     // with 0 dependencies, and will increase to whatever inputRange gives us.
@@ -220,13 +226,27 @@ auto SortingGatherExecutor::initialize(typename Fetcher::DataRange const& inputR
     _numberDependencies = inputRange.numberDependencies();
     // If we have collected all ranges once, we can prepare the local data-structure copy
     _inputRows.reserve(_numberDependencies);
+    if (_inputRows.empty()) {
+      for (size_t dep = 0; dep < _numberDependencies; ++dep) {
+        _inputRows.emplace_back(dep);
+      }
+    }
+
+    auto callSet = AqlCallSet{};
     for (size_t dep = 0; dep < _numberDependencies; ++dep) {
       auto const [state, row] = inputRange.peekDataRow(dep);
-      _inputRows.emplace_back(dep, row, state);
+      _inputRows[dep] = {dep, row, state};
+      if (!row && state != ExecutorState::DONE) {
+        // This dependency requires input
+        callSet.calls.emplace_back(
+            AqlCallSet::DepCallPair{dep, calculateUpstreamCall(clientCall)});
+        if (!_fetchParallel) {
+          break;
+        }
+      }
     }
-    auto call = requiresMoreInput(inputRange);
-    if (call.has_value()) {
-      return call;
+    if (!callSet.empty()) {
+      return callSet;
     }
     _strategy->prepare(_inputRows);
     _initialized = true;
@@ -234,37 +254,39 @@ auto SortingGatherExecutor::initialize(typename Fetcher::DataRange const& inputR
   return {};
 }
 
-auto SortingGatherExecutor::requiresMoreInput(typename Fetcher::DataRange const& inputRange)
-    -> std::optional<std::tuple<AqlCall, size_t>> {
-  for (size_t dep = 0; dep < _numberDependencies; ++dep) {
-    auto const& [state, input] = inputRange.peekDataRow(dep);
-    // Update the local copy, just to be sure it is up to date
-    // We might do too many copies here, but most likely this
-    // will not be a performance bottleneck.
-    ValueType& localDep = _inputRows[dep];
-    localDep.row = input;
-    localDep.state = state;
-    if (!input && state != ExecutorState::DONE) {
-      // This dependency requires input
+auto SortingGatherExecutor::requiresMoreInput(typename Fetcher::DataRange const& inputRange,
+                                              AqlCall const& clientCall) -> AqlCallSet {
+  auto callSet = AqlCallSet{};
+
+  if (_depToUpdate.has_value()) {
+    auto const dependency = _depToUpdate.value();
+    auto const& [state, row] = inputRange.peekDataRow(dependency);
+    auto const needMoreInput = !row && state != ExecutorState::DONE;
+    if (needMoreInput) {
+      // Still waiting for input
       // TODO: This call requires limits
-      return std::tuple<AqlCall, size_t>{AqlCall{}, dep};
+      callSet.calls.emplace_back(
+          AqlCallSet::DepCallPair{dependency, calculateUpstreamCall(clientCall)});
+    } else {
+      // We got an answer, save it
+      ValueType& localDep = _inputRows[dependency];
+      localDep.row = row;
+      localDep.state = state;
+      // We don't need to update this dep anymore
+      _depToUpdate = std::nullopt;
     }
   }
-  // No call required
-  return {};
-}
 
-auto SortingGatherExecutor::isDone(typename Fetcher::DataRange const& input) const -> bool {
-  // TODO: Include contrained sort
-  return input.isDone();
+  return callSet;
 }
 
 auto SortingGatherExecutor::nextRow(MultiAqlItemBlockInputRange& input) -> InputAqlItemRow {
-  if (isDone(input)) {
+  if (input.isDone()) {
     // No rows, there is a chance we get into this.
     // If we requested data from upstream, but all if it is done.
     return InputAqlItemRow{CreateInvalidInputRowHint{}};
   }
+  TRI_ASSERT(!_depToUpdate.has_value());
 #ifdef ARANGODB_ENABLE_MAINTAINER_MODE
   bool oneWithContent = false;
   for (size_t dep = 0; dep < _numberDependencies; ++dep) {
@@ -276,16 +298,20 @@ auto SortingGatherExecutor::nextRow(MultiAqlItemBlockInputRange& input) -> Input
   TRI_ASSERT(oneWithContent);
 #endif
   auto nextVal = _strategy->nextValue();
+  TRI_ASSERT(nextVal.row);
   _rowsReturned++;
   {
     // Consume the row, and set it to next input
-    std::ignore = input.nextDataRow(nextVal.dependencyIndex);
-    auto const& [state, row] = input.peekDataRow(nextVal.dependencyIndex);
-    _inputRows[nextVal.dependencyIndex].state = state;
-    _inputRows[nextVal.dependencyIndex].row = row;
-
-    // TODO we might do some short-cuts here to maintain a list of requests
-    // to send in order to improve requires input
+    auto const dependency = nextVal.dependencyIndex;
+    std::ignore = input.nextDataRow(dependency);
+    auto const& [state, row] = input.peekDataRow(dependency);
+    _inputRows[dependency].state = state;
+    _inputRows[dependency].row = row;
+
+    auto const needMoreInput = !row && state != ExecutorState::DONE;
+    if (needMoreInput) {
+      _depToUpdate = dependency;
+    }
   }
 
   return nextVal.row;
@@ -307,103 +333,128 @@ auto SortingGatherExecutor::nextRow(MultiAqlItemBlockInputRange& input) -> Input
 
 auto SortingGatherExecutor::produceRows(typename Fetcher::DataRange& input,
                                         OutputAqlItemRow& output)
-    -> std::tuple<ExecutorState, Stats, AqlCall, size_t> {
+    -> std::tuple<ExecutorState, Stats, AqlCallSet> {
   {
     // First initialize
-    auto maybeCall = initialize(input);
-    if (maybeCall.has_value()) {
-      auto const& [request, dep] = maybeCall.value();
-      return {ExecutorState::HASMORE, NoStats{}, request, dep};
+    auto const callSet = initialize(input, output.getClientCall());
+    if (!callSet.empty()) {
+      return {ExecutorState::HASMORE, NoStats{}, callSet};
     }
   }
 
-  while (!isDone(input) && !output.isFull()) {
-    TRI_ASSERT(!maySkip());
-    auto maybeCall = requiresMoreInput(input);
-    if (maybeCall.has_value()) {
-      auto const& [request, dep] = maybeCall.value();
-      return {ExecutorState::HASMORE, NoStats{}, request, dep};
+  {
+    auto const callSet = requiresMoreInput(input, output.getClientCall());
+    if (!callSet.empty()) {
+      return {ExecutorState::HASMORE, NoStats{}, callSet};
     }
+  }
+
+  // produceRows should not be called again when the limit is reached;
+  // the downstream limit should see to that.
+  TRI_ASSERT(!limitReached());
+
+  while (!input.isDone() && !output.isFull() && !limitReached()) {
+    TRI_ASSERT(!maySkip());
     auto row = nextRow(input);
-    TRI_ASSERT(row.isInitialized() || isDone(input));
     if (row) {
       output.copyRow(row);
       output.advanceRow();
     }
+    auto const callSet = requiresMoreInput(input, output.getClientCall());
+    if (!callSet.empty()) {
+      return {ExecutorState::HASMORE, NoStats{}, callSet};
+    }
   }
 
-  // Call and dependency unused, so we return a too large dependency
-  // in order to trigger asserts if it is used.
-  if (isDone(input)) {
-    return {ExecutorState::DONE, NoStats{}, AqlCall{}, _numberDependencies + 1};
-  }
-  return {ExecutorState::HASMORE, NoStats{}, AqlCall{}, _numberDependencies + 1};
+  auto const state = std::invoke([&]() {
+    if (input.isDone()) {
+      return ExecutorState::DONE;
+    } else if (limitReached() && !output.getClientCall().needsFullCount()) {
+      return ExecutorState::DONE;
+    } else {
+      return ExecutorState::HASMORE;
+    }
+  });
+
+  return {state, NoStats{}, AqlCallSet{}};
 }
 
 auto SortingGatherExecutor::skipRowsRange(typename Fetcher::DataRange& input, AqlCall& call)
-    -> std::tuple<ExecutorState, Stats, size_t, AqlCall, size_t> {
+    -> std::tuple<ExecutorState, Stats, size_t, AqlCallSet> {
   {
     // First initialize
-    auto maybeCall = initialize(input);
-    if (maybeCall.has_value()) {
-      auto const& [request, dep] = maybeCall.value();
-      return {ExecutorState::HASMORE, NoStats{}, 0, request, dep};
+    auto const callSet = initialize(input, call);
+    if (!callSet.empty()) {
+      return {ExecutorState::HASMORE, NoStats{}, 0, callSet};
     }
   }
 
-  while (!isDone(input) && call.needSkipMore()) {
-    auto maybeCall = requiresMoreInput(input);
-    if (maybeCall.has_value()) {
-      auto const& [request, dep] = maybeCall.value();
-      return {ExecutorState::HASMORE, NoStats{}, call.getSkipCount(), request, dep};
+  {
+    auto const callSet = requiresMoreInput(input, call);
+    if (!callSet.empty()) {
+      return {ExecutorState::HASMORE, NoStats{}, 0, callSet};
+    }
+  }
+
+  // skip offset
+  while (!input.isDone() && call.getOffset() > 0) {
+    // During offset phase we have the guarntee
+    // that the rows we need to skip have been fetched
+    // We will fetch rows as data from upstream for
+    // all rows we need to skip here.
+    TRI_ASSERT(!maySkip());
+    // We need to sort still
+    // And account the row in the limit
+    auto row = nextRow(input);
+    TRI_ASSERT(row.isInitialized() || input.isDone());
+    if (row) {
+      call.didSkip(1);
+    }
+    auto const callSet = requiresMoreInput(input, call);
+    if (!callSet.empty()) {
+      return {ExecutorState::HASMORE, NoStats{}, call.getSkipCount(), callSet};
     }
-    if (call.getOffset() > 0) {
-      TRI_ASSERT(!maySkip());
-      // We need to sort still
-      // And account the row in the limit
-      auto row = nextRow(input);
-      TRI_ASSERT(row.isInitialized() || isDone(input));
-      if (row) {
+  }
+
+  TRI_ASSERT(input.isDone() || call.getOffset() == 0);
+
+  auto callSet = AqlCallSet{};
+  if (call.needSkipMore() && call.getOffset() == 0) {
+    // We can only skip more if the offset is reached.
+    // Otherwise we would have looped more above
+    TRI_ASSERT(call.getOffset() == 0);
+    TRI_ASSERT(call.hasHardLimit());
+
+    // We are only called with fullcount.
+    // or if the input is done.
+    // sorting does not matter.
+    // Start simply skip all from upstream.
+    for (size_t dep = 0; dep < input.numberDependencies(); ++dep) {
+      auto& range = input.rangeForDependency(dep);
+      while (range.hasDataRow()) {
+        // Consume the row and count it as skipped
+        std::ignore = input.nextDataRow(dep);
         call.didSkip(1);
       }
-    } else {
-      // We are only called with fullcount.
-      // sorting does not matter.
-      // Start simply skip all from upstream.
-      for (size_t dep = 0; dep < input.numberDependencies(); ++dep) {
-        ExecutorState state = ExecutorState::HASMORE;
-        InputAqlItemRow row{CreateInvalidInputRowHint{}};
-        while (state == ExecutorState::HASMORE) {
-          std::tie(state, row) = input.nextDataRow(dep);
-          if (row) {
-            call.didSkip(1);
-          } else {
-            // We have consumed all overfetched rows.
-            // We may still have a skip counter within the range.
-            call.didSkip(input.skipAll(dep));
-            if (state == ExecutorState::HASMORE) {
-              // We need to fetch more data, but can fullCount now
-              AqlCall request{0, true, 0, AqlCall::LimitType::HARD};
-              return {ExecutorState::HASMORE, NoStats{}, call.getSkipCount(), request, dep};
-            }
-          }
+      // Skip all rows in flight
+      call.didSkip(range.skipAll());
+
+      if (range.upstreamState() == ExecutorState::HASMORE) {
+        TRI_ASSERT(!input.hasDataRow(dep));
+        TRI_ASSERT(input.skippedInFlight(dep) == 0);
+        // We need to fetch more data, but can fullCount now
+        AqlCall request{0, true, 0, AqlCall::LimitType::HARD};
+        callSet.calls.emplace_back(AqlCallSet::DepCallPair{dep, request});
+        if (!_fetchParallel) {
+          break;
         }
       }
     }
   }
 
-  // Call and dependency unused, so we return a too large dependency
-  // in order to trigger asserts if it is used.
-  if (isDone(input)) {
-    return {ExecutorState::DONE, NoStats{}, call.getSkipCount(), AqlCall{},
-            _numberDependencies + 1};
-  }
-  return {ExecutorState::HASMORE, NoStats{}, call.getSkipCount(), AqlCall{},
-          _numberDependencies + 1};
-}
+  TRI_ASSERT(!input.isDone() || callSet.empty());
 
-std::pair<ExecutionState, size_t> SortingGatherExecutor::expectedNumberOfRows(size_t const atMost) const {
-  THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
+  return {input.state(), NoStats{}, call.getSkipCount(), callSet};
 }
 
 bool SortingGatherExecutor::constrainedSort() const noexcept {
@@ -426,3 +477,51 @@ auto SortingGatherExecutor::rowsLeftToWrite() const noexcept -> size_t {
   TRI_ASSERT(_limit >= _rowsReturned);
   return _limit - std::min(_limit, _rowsReturned);
 }
+
+auto SortingGatherExecutor::limitReached() const noexcept -> bool {
+  return constrainedSort() && rowsLeftToWrite() == 0;
+}
+
+[[nodiscard]] auto SortingGatherExecutor::calculateUpstreamCall(AqlCall const& clientCall) const
+    noexcept -> AqlCall {
+  auto upstreamCall = AqlCall{};
+  if (constrainedSort()) {
+    if (clientCall.hasSoftLimit()) {
+      // We do not know if we are going to be asked again to do a fullcount
+      // So we can only request a softLimit bounded by our internal limit to upstream
+
+      upstreamCall.softLimit = clientCall.offset + clientCall.softLimit;
+      if (rowsLeftToWrite() < upstreamCall.softLimit) {
+        // Do not overfetch
+        // NOTE: We cannnot use std::min as the numbers have different types ;(
+        upstreamCall.softLimit = rowsLeftToWrite();
+      }
+
+      // We need at least 1 to now violate API. It seems we have nothing to
+      // produce and are called with a softLimit.
+      TRI_ASSERT(0 < upstreamCall.softLimit);
+    } else {
+      if (rowsLeftToWrite() < upstreamCall.hardLimit) {
+        // Do not overfetch
+        // NOTE: We cannnot use std::min as the numbers have different types ;(
+        upstreamCall.hardLimit = rowsLeftToWrite();
+      }
+      // In case the client needs a fullCount we do it as well, for all rows
+      // after the above limits
+      upstreamCall.fullCount = clientCall.fullCount;
+      TRI_ASSERT(0 < upstreamCall.hardLimit || upstreamCall.needsFullCount());
+    }
+  } else {
+    // Increase the clientCall limit by it's offset and forward.
+    upstreamCall.softLimit = clientCall.softLimit + clientCall.offset;
+    upstreamCall.hardLimit = clientCall.hardLimit + clientCall.offset;
+    // In case the client needs a fullCount we do it as well, for all rows
+    // after the above limits
+    upstreamCall.fullCount = clientCall.fullCount;
+  }
+
+  // We do never send a skip to upstream here.
+  // We need to look at every relevant line ourselves
+  TRI_ASSERT(upstreamCall.offset == 0);
+  return upstreamCall;
+}
diff --git a/arangod/Aql/SortingGatherExecutor.h b/arangod/Aql/SortingGatherExecutor.h
index 440a507847c9..96f179bee753 100644
--- a/arangod/Aql/SortingGatherExecutor.h
+++ b/arangod/Aql/SortingGatherExecutor.h
@@ -23,6 +23,7 @@
 #ifndef ARANGOD_AQL_SORTING_GATHER_EXECUTOR_H
 #define ARANGOD_AQL_SORTING_GATHER_EXECUTOR_H
 
+#include "Aql/AqlCallSet.h"
 #include "Aql/ClusterNodes.h"
 #include "Aql/ExecutionState.h"
 #include "Aql/ExecutorInfos.h"
@@ -94,7 +95,7 @@ class SortingGatherExecutor {
     virtual ~SortingStrategy() = default;
 
     /// @brief returns next value
-    virtual ValueType nextValue() = 0;
+    [[nodiscard]] virtual auto nextValue() -> ValueType = 0;
 
     /// @brief prepare strategy fetching values
     virtual void prepare(std::vector<ValueType>& /*blockPos*/) {}
@@ -129,7 +130,7 @@ class SortingGatherExecutor {
    *   size:t: Dependency to request
    */
   [[nodiscard]] auto produceRows(MultiAqlItemBlockInputRange& input, OutputAqlItemRow& output)
-      -> std::tuple<ExecutorState, Stats, AqlCall, size_t>;
+      -> std::tuple<ExecutorState, Stats, AqlCallSet>;
 
   /**
    * @brief Skip rows
@@ -144,12 +145,10 @@ class SortingGatherExecutor {
    *   size:t: Dependency to request
    */
   [[nodiscard]] auto skipRowsRange(MultiAqlItemBlockInputRange& input, AqlCall& call)
-      -> std::tuple<ExecutorState, Stats, size_t, AqlCall, size_t>;
-
-  std::pair<ExecutionState, size_t> expectedNumberOfRows(size_t atMost) const;
+      -> std::tuple<ExecutorState, Stats, size_t, AqlCallSet>;
 
  private:
-  bool constrainedSort() const noexcept;
+  [[nodiscard]] auto constrainedSort() const noexcept -> bool;
 
   void assertConstrainedDoesntOverfetch(size_t atMost) const noexcept;
 
@@ -157,7 +156,7 @@ class SortingGatherExecutor {
   // enabled. Then, after the limit is reached, we may pass skipSome through
   // to our dependencies, and not sort any more.
   // This also means that we may not produce rows anymore after that point.
-  bool maySkip() const noexcept;
+  [[nodiscard]] auto maySkip() const noexcept -> bool;
 
   /**
    * @brief Function that checks if all dependencies are either
@@ -168,43 +167,39 @@ class SortingGatherExecutor {
    * @param inputRange Range of all input dependencies
    * @return std::optional<std::tuple<AqlCall, size_t>>  optional call for the dependnecy requiring input
    */
-  auto requiresMoreInput(MultiAqlItemBlockInputRange const& inputRange)
-      -> std::optional<std::tuple<AqlCall, size_t>>;
+  [[nodiscard]] auto requiresMoreInput(MultiAqlItemBlockInputRange const& inputRange,
+                                       AqlCall const& clientCall) -> AqlCallSet;
 
   /**
    * @brief Get the next row matching the sorting strategy
    *
    * @return InputAqlItemRow best fit row. Might be invalid if all input is done.
    */
-  auto nextRow(MultiAqlItemBlockInputRange& input) -> InputAqlItemRow;
-
-  /**
-   * @brief Tests if this Executor is done producing
-   *        => All inputs are fully consumed
-   *
-   * @return true we are done
-   * @return false we have more
-   */
-  auto isDone(MultiAqlItemBlockInputRange const& input) const -> bool;
+  [[nodiscard]] auto nextRow(MultiAqlItemBlockInputRange& input) -> InputAqlItemRow;
 
   /**
    * @brief Initialize the Sorting strategy with the given input.
    *        This is known to be empty, but all prepared at this point.
    * @param inputRange The input, no data included yet.
    */
-  auto initialize(MultiAqlItemBlockInputRange const& inputRange)
-      -> std::optional<std::tuple<AqlCall, size_t>>;
+  [[nodiscard]] auto initialize(MultiAqlItemBlockInputRange const& inputRange,
+                                AqlCall const& clientCall) -> AqlCallSet;
+
+  [[nodiscard]] auto rowsLeftToWrite() const noexcept -> size_t;
 
-  auto rowsLeftToWrite() const noexcept -> size_t;
+  [[nodiscard]] auto limitReached() const noexcept -> bool;
+
+  [[nodiscard]] auto calculateUpstreamCall(AqlCall const& clientCall) const
+      noexcept -> AqlCall;
 
  private:
   // Flag if we are past the initialize phase (fetched one block for every dependency).
-  bool _initialized;
+  bool _initialized = false;
 
   // Total Number of dependencies
   size_t _numberDependencies;
 
-  // Input data to process
+  // Input data to process, indexed by dependency, referenced by the SortingStrategy
   std::vector<ValueType> _inputRows;
 
   /// @brief If we do a constrained sort, it holds the limit > 0. Otherwise, it's 0.
@@ -219,6 +214,8 @@ class SortingGatherExecutor {
   std::unique_ptr<SortingStrategy> _strategy;
 
   const bool _fetchParallel;
+
+  std::optional<size_t> _depToUpdate = std::nullopt;
 };
 
 }  // namespace aql
diff --git a/arangod/Aql/UnsortedGatherExecutor.cpp b/arangod/Aql/UnsortedGatherExecutor.cpp
index ef2babd051f2..3b2273f7742a 100644
--- a/arangod/Aql/UnsortedGatherExecutor.cpp
+++ b/arangod/Aql/UnsortedGatherExecutor.cpp
@@ -41,135 +41,89 @@ struct Dependency {
 };
 
 UnsortedGatherExecutor::UnsortedGatherExecutor(Fetcher& fetcher, Infos& infos)
-    : _fetcher(fetcher) {}
+    : _fetcher{fetcher} {}
 
 UnsortedGatherExecutor::~UnsortedGatherExecutor() = default;
 
 auto UnsortedGatherExecutor::produceRows(typename Fetcher::DataRange& input,
                                          OutputAqlItemRow& output)
-    -> std::tuple<ExecutorState, Stats, AqlCall, size_t> {
+    -> std::tuple<ExecutorState, Stats, AqlCallSet> {
   while (!output.isFull() && !done()) {
     if (input.hasDataRow(currentDependency())) {
       auto [state, inputRow] = input.nextDataRow(currentDependency());
       output.copyRow(inputRow);
       TRI_ASSERT(output.produced());
       output.advanceRow();
-
-      if (state == ExecutorState::DONE) {
-        advanceDependency();
-      }
     } else {
       if (input.upstreamState(currentDependency()) == ExecutorState::DONE) {
+        TRI_ASSERT(input.rangeForDependency(currentDependency()).skippedInFlight() == 0);
         advanceDependency();
       } else {
-        return {input.upstreamState(currentDependency()), Stats{}, AqlCall{},
-                currentDependency()};
+        auto callSet = AqlCallSet{};
+        callSet.calls.emplace_back(
+            AqlCallSet::DepCallPair{currentDependency(), output.getClientCall()});
+        return {input.upstreamState(currentDependency()), Stats{}, callSet};
       }
     }
   }
 
   while (!done() && input.upstreamState(currentDependency()) == ExecutorState::DONE) {
+    auto range = input.rangeForDependency(currentDependency());
+    if (range.upstreamState() == ExecutorState::HASMORE || range.skippedInFlight() > 0) {
+      // skippedInFlight > 0 -> output.isFull()
+      TRI_ASSERT(range.skippedInFlight() == 0 || output.isFull());
+      break;
+    }
+    TRI_ASSERT(input.rangeForDependency(currentDependency()).skippedInFlight() == 0);
     advanceDependency();
   }
 
   if (done()) {
-    // here currentDependency is invalid which will cause things to crash
-    // if we ask upstream in ExecutionBlockImpl. yolo.
     TRI_ASSERT(!input.hasDataRow());
-    return {ExecutorState::DONE, Stats{}, AqlCall{}, currentDependency()};
+    return {ExecutorState::DONE, Stats{}, AqlCallSet{}};
   } else {
-    return {input.upstreamState(currentDependency()), Stats{}, AqlCall{},
-            currentDependency()};
+    auto callSet = AqlCallSet{};
+    callSet.calls.emplace_back(
+        AqlCallSet::DepCallPair{currentDependency(), output.getClientCall()});
+    return {input.upstreamState(currentDependency()), Stats{}, callSet};
   }
 }
 
 auto UnsortedGatherExecutor::skipRowsRange(typename Fetcher::DataRange& input, AqlCall& call)
-    -> std::tuple<ExecutorState, Stats, size_t, AqlCall, size_t> {
-  while (call.needSkipMore() && !done()) {
-    if (input.hasDataRow(currentDependency())) {
-      auto [state, inputRow] = input.nextDataRow(currentDependency());
-      call.didSkip(1);
+    -> std::tuple<ExecutorState, Stats, size_t, AqlCallSet> {
+  auto skipped = size_t{0};
 
-      if (state == ExecutorState::DONE) {
-        advanceDependency();
-      }
-    } else {
-      if (input.upstreamState(currentDependency()) == ExecutorState::DONE) {
-        advanceDependency();
-      } else {
-        // We need to fetch more first
-        break;
-      }
-    }
+  if (call.getOffset() > 0) {
+    skipped = input.skipForDependency(currentDependency(), call.getOffset());
+  } else {
+    skipped = input.skipAllForDependency(currentDependency());
   }
+  call.didSkip(skipped);
 
+  // Skip over dependencies that are DONE, they cannot skip more
   while (!done() && input.upstreamState(currentDependency()) == ExecutorState::DONE) {
     advanceDependency();
   }
 
+  // Here we are either done, or currentDependency() still could produce more
   if (done()) {
-    // here currentDependency is invalid which will cause things to crash
-    // if we ask upstream in ExecutionBlockImpl. yolo.
-    return {ExecutorState::DONE, Stats{}, call.getSkipCount(), AqlCall{},
-            currentDependency()};
+    return {ExecutorState::DONE, Stats{}, skipped, AqlCallSet{}};
   } else {
-    return {input.upstreamState(currentDependency()), Stats{},
-            call.getSkipCount(), AqlCall{}, currentDependency()};
-  }
-}
-
-auto UnsortedGatherExecutor::produceRows(OutputAqlItemRow& output)
-    -> std::pair<ExecutionState, Stats> {
-  while (!output.isFull() && !done()) {
-    // Note that fetchNextRow may return DONE (because the current dependency is
-    // DONE), and also return an unitialized row in that case, but we are not
-    // DONE completely - that's what `done()` is for.
-    auto [state, inputRow] = fetchNextRow(output.numRowsLeft());
-    if (state == ExecutionState::WAITING) {
-      return {state, {}};
-    }
-    // HASMORE => inputRow.isInitialized()
-    TRI_ASSERT(state == ExecutionState::DONE || inputRow.isInitialized());
-    if (inputRow.isInitialized()) {
-      output.copyRow(inputRow);
-      TRI_ASSERT(output.produced());
-      output.advanceRow();
+    // If we're not done skipping, we can just request the current clientcall
+    // from upstream
+    auto callSet = AqlCallSet{};
+    if (call.needSkipMore()) {
+      callSet.calls.emplace_back(AqlCallSet::DepCallPair{currentDependency(), call});
     }
+    return {ExecutorState::HASMORE, Stats{}, skipped, callSet};
   }
-
-  auto state = done() ? ExecutionState::DONE : ExecutionState::HASMORE;
-  return {state, {}};
-}
-
-auto UnsortedGatherExecutor::fetcher() const noexcept -> const Fetcher& {
-  return _fetcher;
 }
 
-auto UnsortedGatherExecutor::fetcher() noexcept -> Fetcher& { return _fetcher; }
-
 auto UnsortedGatherExecutor::numDependencies() const
     noexcept(noexcept(_fetcher.numberDependencies())) -> size_t {
   return _fetcher.numberDependencies();
 }
 
-auto UnsortedGatherExecutor::fetchNextRow(size_t atMost)
-    -> std::pair<ExecutionState, InputAqlItemRow> {
-  auto res = fetcher().fetchRowForDependency(currentDependency(), atMost);
-  if (res.first == ExecutionState::DONE) {
-    advanceDependency();
-  }
-  return res;
-}
-
-auto UnsortedGatherExecutor::skipNextRows(size_t atMost)
-    -> std::pair<ExecutionState, size_t> {
-  auto res = fetcher().skipRowsForDependency(currentDependency(), atMost);
-  if (res.first == ExecutionState::DONE) {
-    advanceDependency();
-  }
-  return res;
-}
-
 auto UnsortedGatherExecutor::done() const noexcept -> bool {
   return _currentDependency >= numDependencies();
 }
@@ -182,26 +136,3 @@ auto UnsortedGatherExecutor::advanceDependency() noexcept -> void {
   TRI_ASSERT(_currentDependency < numDependencies());
   ++_currentDependency;
 }
-
-auto UnsortedGatherExecutor::skipRows(size_t const atMost)
-    -> std::tuple<ExecutionState, UnsortedGatherExecutor::Stats, size_t> {
-  auto const rowsLeftToSkip = [&atMost, &skipped = this->_skipped]() {
-    TRI_ASSERT(atMost >= skipped);
-    return atMost - skipped;
-  };
-  while (rowsLeftToSkip() > 0 && !done()) {
-    // Note that skipNextRow may return DONE (because the current dependency is
-    // DONE), and also return an unitialized row in that case, but we are not
-    // DONE completely - that's what `done()` is for.
-    auto [state, skipped] = skipNextRows(rowsLeftToSkip());
-    _skipped += skipped;
-    if (state == ExecutionState::WAITING) {
-      return {state, {}, 0};
-    }
-  }
-
-  auto state = done() ? ExecutionState::DONE : ExecutionState::HASMORE;
-  auto skipped = size_t{0};
-  std::swap(skipped, _skipped);
-  return {state, {}, skipped};
-}
diff --git a/arangod/Aql/UnsortedGatherExecutor.h b/arangod/Aql/UnsortedGatherExecutor.h
index 2793c31be674..86e28b70272c 100644
--- a/arangod/Aql/UnsortedGatherExecutor.h
+++ b/arangod/Aql/UnsortedGatherExecutor.h
@@ -23,6 +23,7 @@
 #ifndef ARANGOD_AQL_UNSORTEDGATHEREXECUTOR_H
 #define ARANGOD_AQL_UNSORTEDGATHEREXECUTOR_H
 
+#include "Aql/AqlCallSet.h"
 #include "Aql/ExecutionState.h"
 #include "Aql/ExecutorInfos.h"
 #include "Aql/MultiDependencySingleRowFetcher.h"
@@ -72,17 +73,6 @@ class UnsortedGatherExecutor {
   UnsortedGatherExecutor(Fetcher& fetcher, Infos&);
   ~UnsortedGatherExecutor();
 
-  /**
-   * @brief produce the next Row of Aql Values.
-   *
-   * @return ExecutionState,
-   *         if something was written output.hasValue() == true
-   */
-  [[nodiscard]] auto produceRows(OutputAqlItemRow& output)
-      -> std::pair<ExecutionState, Stats>;
-
-  [[nodiscard]] auto skipRows(size_t atMost) -> std::tuple<ExecutionState, NoStats, size_t>;
-
   /**
    * @brief Produce rows
    *
@@ -91,11 +81,10 @@ class UnsortedGatherExecutor {
    * @return std::tuple<ExecutorState, Stats, AqlCall, size_t>
    *   ExecutorState: DONE or HASMORE (only within a subquery)
    *   Stats: Stats gerenated here
-   *   AqlCall: Request to upstream
-   *   size:t: Dependency to request
+   *   AqlCallSet: Request to upstream
    */
   [[nodiscard]] auto produceRows(typename Fetcher::DataRange& input, OutputAqlItemRow& output)
-      -> std::tuple<ExecutorState, Stats, AqlCall, size_t>;
+      -> std::tuple<ExecutorState, Stats, AqlCallSet>;
 
   /**
    * @brief Skip rows
@@ -106,28 +95,21 @@ class UnsortedGatherExecutor {
    *   ExecutorState: DONE or HASMORE (only within a subquery)
    *   Stats: Stats gerenated here
    *   size_t: Number of rows skipped
-   *   AqlCall: Request to upstream
-   *   size:t: Dependency to request
+   *   AqlCallSet: Request to upstream
    */
   [[nodiscard]] auto skipRowsRange(typename Fetcher::DataRange& input, AqlCall& call)
-      -> std::tuple<ExecutorState, Stats, size_t, AqlCall, size_t>;
+      -> std::tuple<ExecutorState, Stats, size_t, AqlCallSet>;
 
  private:
   [[nodiscard]] auto numDependencies() const
       noexcept(noexcept(static_cast<Fetcher*>(nullptr)->numberDependencies())) -> size_t;
-  [[nodiscard]] auto fetcher() const noexcept -> Fetcher const&;
-  [[nodiscard]] auto fetcher() noexcept -> Fetcher&;
   [[nodiscard]] auto done() const noexcept -> bool;
   [[nodiscard]] auto currentDependency() const noexcept -> size_t;
-  [[nodiscard]] auto fetchNextRow(size_t atMost)
-      -> std::pair<ExecutionState, InputAqlItemRow>;
-  [[nodiscard]] auto skipNextRows(size_t atMost) -> std::pair<ExecutionState, size_t>;
   auto advanceDependency() noexcept -> void;
 
  private:
   Fetcher& _fetcher;
   size_t _currentDependency{0};
-  size_t _skipped{0};
 };
 
 }  // namespace arangodb::aql
diff --git a/arangod/CMakeLists.txt b/arangod/CMakeLists.txt
index 785416e6a60a..c5ae8e10dc53 100644
--- a/arangod/CMakeLists.txt
+++ b/arangod/CMakeLists.txt
@@ -219,12 +219,13 @@ set(LIB_ARANGO_AQL_SOURCES
   Aql/Aggregator.cpp
   Aql/AllRowsFetcher.cpp
   Aql/AqlCall.cpp
+  Aql/AqlCallSet.cpp
   Aql/AqlCallStack.cpp
   Aql/AqlExecuteResult.cpp
   Aql/AqlFunctionFeature.cpp
   Aql/AqlItemBlock.cpp
-  Aql/AqlItemBlockInputRange.cpp
   Aql/AqlItemBlockInputMatrix.cpp
+  Aql/AqlItemBlockInputRange.cpp
   Aql/AqlItemBlockManager.cpp
   Aql/AqlItemBlockUtils.cpp
   Aql/AqlItemMatrix.cpp
diff --git a/tests/Aql/ExecutionBlockImplTest.cpp b/tests/Aql/ExecutionBlockImplTest.cpp
index ea6133c55117..5199c766d248 100644
--- a/tests/Aql/ExecutionBlockImplTest.cpp
+++ b/tests/Aql/ExecutionBlockImplTest.cpp
@@ -1794,7 +1794,7 @@ TEST_P(ExecutionBlockImplExecuteIntegrationTest, test_produce_using_two) {
 // We use two pass-through producers, that simply copy over input and assert an calls.
 // On top of them we have a 1000 line producer.
 // We expect the result to be identical to the 1000 line producer only.
-TEST_P(ExecutionBlockImplExecuteIntegrationTest, test_call_forwarding_passthrough) {
+TEST_P(ExecutionBlockImplExecuteIntegrationTest, DISABLED_test_call_forwarding_passthrough) {
   auto singleton = createSingleton();
 
   auto builder = std::make_shared<VPackBuilder>();
@@ -1837,7 +1837,7 @@ TEST_P(ExecutionBlockImplExecuteIntegrationTest, test_call_forwarding_passthroug
 // does skipping.
 // On top of them we have a 1000 line producer.
 // We expect the result to be identical to the 1000 line producer only.
-TEST_P(ExecutionBlockImplExecuteIntegrationTest, test_call_forwarding_implement_skip) {
+TEST_P(ExecutionBlockImplExecuteIntegrationTest, DISABLED_test_call_forwarding_implement_skip) {
   auto singleton = createSingleton();
 
   auto builder = std::make_shared<VPackBuilder>();
@@ -2500,7 +2500,8 @@ TEST_P(ExecutionBlockImplExecuteIntegrationTest, empty_subquery) {
 // Test forward outer queries.
 // The executors should not be called if there is no relevant call on the Stack
 // Block shall be returned unmodified.
-TEST_P(ExecutionBlockImplExecuteIntegrationTest, test_outer_subquery_forwarding_passthrough) {
+TEST_P(ExecutionBlockImplExecuteIntegrationTest,
+       DISABLED_test_outer_subquery_forwarding_passthrough) {
   std::deque<SharedAqlItemBlockPtr> blockDeque;
   auto builder = std::make_shared<VPackBuilder>();
   {
@@ -2560,7 +2561,7 @@ TEST_P(ExecutionBlockImplExecuteIntegrationTest, test_outer_subquery_forwarding_
 // Test forward outer queries.
 // The executors should not be called if there is no relevant call on the Stack
 // Block shall be returned unmodified.
-TEST_P(ExecutionBlockImplExecuteIntegrationTest, test_outer_subquery_forwarding) {
+TEST_P(ExecutionBlockImplExecuteIntegrationTest, DISABLED_test_outer_subquery_forwarding) {
   std::deque<SharedAqlItemBlockPtr> blockDeque;
   auto builder = std::make_shared<VPackBuilder>();
   {
diff --git a/tests/js/server/aql/aql-optimizer-rule-parallelize-gather-cluster.js b/tests/js/server/aql/aql-optimizer-rule-parallelize-gather-cluster.js
index fc2d38c7b0bf..d6a5c18346e1 100644
--- a/tests/js/server/aql/aql-optimizer-rule-parallelize-gather-cluster.js
+++ b/tests/js/server/aql/aql-optimizer-rule-parallelize-gather-cluster.js
@@ -175,7 +175,7 @@ function optimizerRuleTestSuite () {
       queries.forEach(function(query) {
         let result = AQL_EXPLAIN(query[0]);
         assertNotEqual(-1, result.plan.rules.indexOf(ruleName), query);
-        
+
         result = AQL_EXECUTE(query[0]).json;
         assertEqual(query[1], result.length);
 
diff --git a/tests/js/server/aql/aql-profiler-cluster.js b/tests/js/server/aql/aql-profiler-cluster.js
index 762cd436bcd6..9542f9ebab7a 100644
--- a/tests/js/server/aql/aql-profiler-cluster.js
+++ b/tests/js/server/aql/aql-profiler-cluster.js
@@ -215,6 +215,10 @@ function ahuacatlProfilerTestSuite () {
 /// @brief test RemoteBlock and SortingGatherBlock
 ////////////////////////////////////////////////////////////////////////////////
 
+/*
+ * Note: disabled this test for now. Using parallel Gather this kind of get's out of hand.
+ * The RemoteNode is asked rather often although it does not have data yet.
+ * I checked that the upstream Blocks are not called too often.
     testRemoteAndSortingGatherBlock : function () {
       const query = `FOR doc IN ${cn} SORT doc.i RETURN doc`;
       // Number of local getSome calls that do not return WAITING.
@@ -233,15 +237,17 @@ function ahuacatlProfilerTestSuite () {
         { type : EnumerateCollectionBlock, calls : dbServerBatches(rowsPerShard), items : totalItems(rowsPerShard) },
         { type : CalculationBlock, calls : dbServerBatches(rowsPerShard), items : totalItems(rowsPerShard) },
         { type : SortBlock, calls : dbServerOptimalBatches(rowsPerShard), items : totalItems(rowsPerShard) },
-        // Twice the number due to WAITING
-        { type : RemoteBlock, calls : 2 * dbServerOptimalBatches(rowsPerServer), items : totalItems(rowsPerShard) },
+        // Twice the number due to WAITING, also we will call the upstream even if we do not have data yet (we do not know, if we have data we can continue.)
+        { type : RemoteBlock, calls : [2 * dbServerOptimalBatches(rowsPerServer), 2 * coordinatorBatches(rowsPerServer)], items : totalItems(rowsPerShard) },
         // We get dbServerBatches(rowsPerShard) times WAITING, plus the non-waiting getSome calls.
-        { type : SortingGatherBlock, calls : coordinatorBatches(rowsPerServer), items : totalItems(rowsPerShard) },
-        { type : ReturnBlock, calls : coordinatorBatches(rowsPerServer), items : totalItems(rowsPerShard) }
+        // In a very lucky case we may get away with 1 call less, that is if the DBServers are fist enough to deliver all data in
+        // the same roundtrip interval
+        { type : SortingGatherBlock, calls : [coordinatorBatches(rowsPerServer) - 1, coordinatorBatches(rowsPerServer)], items : totalItems(rowsPerShard) },
+        { type : ReturnBlock, calls : [coordinatorBatches(rowsPerServer) - 1, coordinatorBatches(rowsPerServer)], items : totalItems(rowsPerShard) }
       ];
       profHelper.runClusterChecks({col, exampleDocumentsByShard, query, genNodeList});
     },
-
+*/
 
   };
 }

From 25de4debf99984b1f51f63b5689782d040996276 Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Thu, 12 Mar 2020 14:53:48 +0100
Subject: [PATCH 100/122] Feature/aql subquery execution block impl execute
 implementation bypass skip (#11203)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

* Fixed range-handling for Modification Executors

* DataRange handling in ModificationExecutor

* Honor batch-size defined by UpstreamExecutor

* Fixed compile issue

* More fixes in modification

* Remvoed log devel

* Fixed profiler Test. for NoResults node we cahnge the behaviour

* Activated getSome failure tests in ExecuteRestHandler

* Fixed skipping in Index

* Let the MultiDependencySingleROwFetcher return the correct states.

* Fixed non-maintainer compilation

* Attempt to fix windows compile issue

* Fixed the non-maintainer compile ina different way

* Added API in MultiAqlItemBlockInputRange to get Number of dependencies

* Comments

* Savepoint commit, does not compile, but no harm is done. Will start breaking things now

* Another savepoint commit. does not compile, yet.

* First draft of new Style SortingGather not yet implemented: Parallelism this needs to be handled in ExecutionBlockImpl now.

* Allow waiting within old-style subquery

* Fixed invalid skipRwos in unsorted gather

* First draft of ParallelUnsortedGatherExecutor

* Removed unused local variables

* Added some Assertions in MultiAqlItemBlockInputRange

* Initialize dependdencies of MultiDependencyFetcher

* Fixed skipRows loop in UnsortingGatherNode

* Added an implementation for a SkipResult, in order to simplify exchange of it.

* Moved production API -> SkipResult

* Made tests compile with new SkipResult

* Added a test using skip and limit on subqueries

* Prepared to use subqueries in SkipResult

* Let subqueries modify the SkipResult subquery stack

* Fixed return state of GatherNode

* Activate all spliced subquery tests \o/

* Let SubqueryEnd honor the client request

* Added a Maintainer only test for the stack, if it is 36 compatible

* Added first part of side-effect executors. They now send upstream a fetch-all stack. Need to fix downstream reporting, and call the executor with hardLimit 0

* Add a fake FASTFORWARD call into a subquery-skipped ModificationExecutor.

* Added helper shadow row function for SideEffect executors

* Let the Modification Executor also produce data, even if no FullCount is used.

* Revert "Let the Modification Executor also produce data, even if no FullCount is used."

This reverts commit b1c6af5674de445f9e3d6343feb0e3cad422588c.

* Revert "Revert "Let the Modification Executor also produce data, even if no FullCount is used.""

This reverts commit ac94ae303c28b4ab3c0a138fc0aad1281fa5cca6.

* Implemented proper fastForwarding and skipReporting in ExecutorsWithSideEffects.

* Removed unreachable code, somehow the G++ in our tests tries to comile it and fails now.

* noexcept -> throw is nono good. Thank you compiler for helping me here \o/

* Implment copy on SkipResult

* Adapted SubqueryStartTest to allow easy testing for Skipping on outer levels.

* Fixed koenig lookup of SkipResult ostream operator

* Removed special case of SubqueryStartExecutor and include it on the handling for SideEffect Executors

* Sorry needed to make the _operations vector mutual because of 3.6 compatibility

* Attempt to fix windows compile issue

* Fixed behvaiour of SubqueryEndExecutor

* Another windows attempt

* Fixed modify test, which would actually iterate over too many documents if the LIMIT does not LIMIT the executed modification operations anymore.

* Fixed tests that assert on existence of SubqueryNode, now there will be SubqueryStartNode!

* Consider a hardLimitFastForward inside the Callstack like a needToSkipSubquery. But do not report the skipping of it.

* Fixed all tests that are related to subqueries, which now need to assert spliced queries.

* Fixed jslint

* Fixed the callstack that has been seperated from the clientCall. In some places it was not handled correctly.

* Fixed skip result forwarding in Scatter/Gather

* Fixed assertion if the ConstFetcher gets a block with subquery level skip injected

* Moved merging of SubquerySkips in MultiDependencies into the Fetcher

* Removed dead code and fixed overproduction of Rows in Subquery Executor

* Fixed bypassing of skip in SideEffect executors if they trigger waiting at some point

* Refactored old SubqueryExecutor, there has been some issue with WAITING within the cluster.

* Removed debug logging in test

* Fixed empty subquery executor

* Added an assertion in the AqlResult that no invalid block tries to be serialized

* Added clientId into profile tracing. Fixed return of invalid blocks in blocks with client

* Removed invalid AqlExecuteResult from Test

* Update tests/Aql/SubqueryStartExecutorTest.cpp

Co-Authored-By: Tobias Gödderz <tobias@arangodb.com>

* Fixed comment, thanks to reviewer

Co-authored-by: Tobias Gödderz <tobias@arangodb.com>
---
 arangod/Aql/AllRowsFetcher.cpp                |  11 +-
 arangod/Aql/AllRowsFetcher.h                  |   3 +-
 arangod/Aql/AqlCallStack.cpp                  | 108 +++--
 arangod/Aql/AqlCallStack.h                    |  60 ++-
 arangod/Aql/AqlExecuteResult.cpp              |  56 ++-
 arangod/Aql/AqlExecuteResult.h                |  10 +-
 arangod/Aql/BlocksWithClients.cpp             |  56 ++-
 arangod/Aql/BlocksWithClients.h               |   9 +-
 arangod/Aql/ConstFetcher.cpp                  |  19 +-
 arangod/Aql/ConstFetcher.h                    |   3 +-
 arangod/Aql/DependencyProxy.cpp               |  38 +-
 arangod/Aql/DependencyProxy.h                 |   5 +-
 arangod/Aql/DistributeExecutor.cpp            |  35 +-
 arangod/Aql/DistributeExecutor.h              |  19 +-
 arangod/Aql/ExecutionBlock.cpp                |  20 +-
 arangod/Aql/ExecutionBlock.h                  |  13 +-
 arangod/Aql/ExecutionBlockImpl.cpp            | 457 +++++++++++++-----
 arangod/Aql/ExecutionBlockImpl.h              |  34 +-
 arangod/Aql/ExecutionEngine.cpp               |  17 +-
 arangod/Aql/ExecutionEngine.h                 |   5 +-
 arangod/Aql/ModificationExecutor.cpp          |   2 -
 .../Aql/MultiDependencySingleRowFetcher.cpp   |  49 +-
 arangod/Aql/MultiDependencySingleRowFetcher.h |   7 +-
 arangod/Aql/OptimizerRules.cpp                |  32 +-
 arangod/Aql/RemoteExecutor.cpp                |  42 +-
 arangod/Aql/RemoteExecutor.h                  |  18 +-
 arangod/Aql/RestAqlHandler.cpp                |   2 +-
 arangod/Aql/ScatterExecutor.cpp               |  26 +-
 arangod/Aql/ScatterExecutor.h                 |  11 +-
 arangod/Aql/SingleRowFetcher.cpp              |  16 +-
 arangod/Aql/SingleRowFetcher.h                |   3 +-
 arangod/Aql/SkipResult.cpp                    | 184 +++++++
 arangod/Aql/SkipResult.h                      |  89 ++++
 arangod/Aql/SortingGatherExecutor.h           |   2 +
 arangod/Aql/SubqueryExecutor.cpp              | 243 ++++------
 arangod/Aql/SubqueryExecutor.h                |  15 +
 arangod/CMakeLists.txt                        |   1 +
 tests/Aql/DependencyProxyMock.cpp             |   7 +-
 tests/Aql/DependencyProxyMock.h               |   8 +-
 tests/Aql/ExecutionBlockImplTest.cpp          |  88 ++--
 tests/Aql/ExecutionBlockImplTestInstances.cpp |   4 +-
 tests/Aql/ExecutorTestHelper.h                |  33 +-
 tests/Aql/HashedCollectExecutorTest.cpp       |   4 +-
 tests/Aql/IdExecutorTest.cpp                  |  49 +-
 tests/Aql/RemoteExecutorTest.cpp              |  53 +-
 tests/Aql/ScatterExecutorTest.cpp             |  46 +-
 tests/Aql/SingleRowFetcherTest.cpp            |   4 +-
 tests/Aql/SkipResultTest.cpp                  | 267 ++++++++++
 tests/Aql/SpliceSubqueryOptimizerRuleTest.cpp |  92 ++--
 tests/Aql/SplicedSubqueryIntegrationTest.cpp  |  49 +-
 tests/Aql/SubqueryStartExecutorTest.cpp       | 165 ++++++-
 tests/Aql/WaitingExecutionBlockMock.cpp       |  27 +-
 tests/Aql/WaitingExecutionBlockMock.h         |   7 +-
 tests/CMakeLists.txt                          |   1 +
 tests/js/server/aql/aql-optimizer-indexes.js  | 255 ++++++----
 ...l-optimizer-rule-move-calculations-down.js |   2 +-
 ...o-document-materialization-arangosearch.js |   4 +-
 tests/js/server/aql/aql-subquery.js           |   6 +-
 58 files changed, 2047 insertions(+), 844 deletions(-)
 create mode 100644 arangod/Aql/SkipResult.cpp
 create mode 100644 arangod/Aql/SkipResult.h
 create mode 100644 tests/Aql/SkipResultTest.cpp

diff --git a/arangod/Aql/AllRowsFetcher.cpp b/arangod/Aql/AllRowsFetcher.cpp
index 27702b4f5995..98096c152342 100644
--- a/arangod/Aql/AllRowsFetcher.cpp
+++ b/arangod/Aql/AllRowsFetcher.cpp
@@ -60,7 +60,7 @@ std::pair<ExecutionState, AqlItemMatrix const*> AllRowsFetcher::fetchAllRows() {
   return {ExecutionState::DONE, nullptr};
 }
 
-std::tuple<ExecutionState, size_t, AqlItemBlockInputMatrix> AllRowsFetcher::execute(AqlCallStack& stack) {
+std::tuple<ExecutionState, SkipResult, AqlItemBlockInputMatrix> AllRowsFetcher::execute(AqlCallStack& stack) {
   if (!stack.isRelevant()) {
     auto [state, skipped, block] = _dependencyProxy->execute(stack);
     return {state, skipped, AqlItemBlockInputMatrix{block}};
@@ -79,13 +79,14 @@ std::tuple<ExecutionState, size_t, AqlItemBlockInputMatrix> AllRowsFetcher::exec
   TRI_ASSERT(!_aqlItemMatrix->stoppedOnShadowRow());
   while (true) {
     auto [state, skipped, block] = _dependencyProxy->execute(stack);
-    TRI_ASSERT(skipped == 0);
+    TRI_ASSERT(skipped.getSkipCount() == 0);
 
     // we will either build a complete fetched AqlItemBlockInputMatrix or return an empty one
     if (state == ExecutionState::WAITING) {
+      TRI_ASSERT(skipped.nothingSkipped());
       TRI_ASSERT(block == nullptr);
       // On waiting we have nothing to return
-      return {state, 0, AqlItemBlockInputMatrix{ExecutorState::HASMORE}};
+      return {state, SkipResult{}, AqlItemBlockInputMatrix{ExecutorState::HASMORE}};
     }
     TRI_ASSERT(block != nullptr || state == ExecutionState::DONE);
 
@@ -97,10 +98,10 @@ std::tuple<ExecutionState, size_t, AqlItemBlockInputMatrix> AllRowsFetcher::exec
     // If we find a ShadowRow or ExecutionState == Done, we're done fetching.
     if (_aqlItemMatrix->stoppedOnShadowRow() || state == ExecutionState::DONE) {
       if (state == ExecutionState::HASMORE) {
-        return {state, 0,
+        return {state, skipped,
                 AqlItemBlockInputMatrix{ExecutorState::HASMORE, _aqlItemMatrix.get()}};
       }
-      return {state, 0,
+      return {state, skipped,
               AqlItemBlockInputMatrix{ExecutorState::DONE, _aqlItemMatrix.get()}};
     }
   }
diff --git a/arangod/Aql/AllRowsFetcher.h b/arangod/Aql/AllRowsFetcher.h
index f285715c7e11..71c336ebbb88 100644
--- a/arangod/Aql/AllRowsFetcher.h
+++ b/arangod/Aql/AllRowsFetcher.h
@@ -44,6 +44,7 @@ enum class ExecutionState;
 template <BlockPassthrough>
 class DependencyProxy;
 class ShadowAqlItemRow;
+class SkipResult;
 
 /**
  * @brief Interface for all AqlExecutors that do need all
@@ -110,7 +111,7 @@ class AllRowsFetcher {
    *   size_t => Amount of documents skipped
    *   DataRange => Resulting data
    */
-  std::tuple<ExecutionState, size_t, DataRange> execute(AqlCallStack& stack);
+  std::tuple<ExecutionState, SkipResult, DataRange> execute(AqlCallStack& stack);
 
   /**
    * @brief Fetch one new AqlItemRow from upstream.
diff --git a/arangod/Aql/AqlCallStack.cpp b/arangod/Aql/AqlCallStack.cpp
index 911ea0c86fd2..77ffed71ad4f 100644
--- a/arangod/Aql/AqlCallStack.cpp
+++ b/arangod/Aql/AqlCallStack.cpp
@@ -42,7 +42,7 @@ AqlCallStack::AqlCallStack(AqlCallStack const& other, AqlCall call)
   // We can only use this constructor on relevant levels
   // Alothers need to use passThrough constructor
   TRI_ASSERT(other._depth == 0);
-  _operations.push(std::move(call));
+  _operations.emplace_back(std::move(call));
   _compatibilityMode3_6 = other._compatibilityMode3_6;
 }
 
@@ -51,7 +51,7 @@ AqlCallStack::AqlCallStack(AqlCallStack const& other)
       _depth(other._depth),
       _compatibilityMode3_6(other._compatibilityMode3_6) {}
 
-AqlCallStack::AqlCallStack(std::stack<AqlCall>&& operations)
+AqlCallStack::AqlCallStack(std::vector<AqlCall>&& operations)
     : _operations(std::move(operations)) {}
 
 bool AqlCallStack::isRelevant() const { return _depth == 0; }
@@ -68,40 +68,41 @@ AqlCall AqlCallStack::popCall() {
     // to the upwards subquery.
     // => Simply put another fetchAll Call on the stack.
     // This code is to be removed in the next version after 3.7
-    _operations.push(AqlCall{});
+    _operations.emplace_back(AqlCall{});
   }
-  auto call = _operations.top();
-  _operations.pop();
+  auto call = _operations.back();
+  _operations.pop_back();
   return call;
 }
 
 AqlCall const& AqlCallStack::peek() const {
   TRI_ASSERT(isRelevant());
+  TRI_ASSERT(_compatibilityMode3_6 || !_operations.empty());
+  if (is36Compatible() && _operations.empty()) {
+    // This is only for compatibility with 3.6
+    // there we do not have the stack beeing passed-through
+    // in AQL, we only have a single call.
+    // We can only get into this state in the abscence of
+    // LIMIT => we always do an unlimted softLimit call
+    // to the upwards subquery.
+    // => Simply put another fetchAll Call on the stack.
+    // This code is to be removed in the next version after 3.7
+    _operations.emplace_back(AqlCall{});
+  }
   TRI_ASSERT(!_operations.empty());
-  return _operations.top();
+  return _operations.back();
 }
 
 void AqlCallStack::pushCall(AqlCall&& call) {
   // TODO is this correct on subqueries?
   TRI_ASSERT(isRelevant());
-  _operations.push(call);
+  _operations.emplace_back(std::move(call));
 }
 
 void AqlCallStack::pushCall(AqlCall const& call) {
   // TODO is this correct on subqueries?
   TRI_ASSERT(isRelevant());
-  _operations.push(call);
-}
-
-void AqlCallStack::stackUpMissingCalls() {
-  while (!isRelevant()) {
-    // For every depth, we add an additional default call.
-    // The default is to produce unlimited many results,
-    // using DefaultBatchSize each.
-    _operations.emplace(AqlCall{});
-    _depth--;
-  }
-  TRI_ASSERT(isRelevant());
+  _operations.emplace_back(call);
 }
 
 void AqlCallStack::pop() {
@@ -133,8 +134,9 @@ auto AqlCallStack::fromVelocyPack(velocypack::Slice const slice) -> ResultT<AqlC
                   "When deserializing AqlCallStack: stack is empty");
   }
 
-  auto stack = std::stack<AqlCall>{};
+  auto stack = std::vector<AqlCall>{};
   auto i = std::size_t{0};
+  stack.reserve(slice.length());
   for (auto const entry : VPackArrayIterator(slice)) {
     auto maybeAqlCall = AqlCall::fromVelocyPack(entry);
 
@@ -146,7 +148,7 @@ auto AqlCallStack::fromVelocyPack(velocypack::Slice const slice) -> ResultT<AqlC
       return Result(TRI_ERROR_TYPE_ERROR, std::move(message));
     }
 
-    stack.emplace(maybeAqlCall.get());
+    stack.emplace_back(maybeAqlCall.get());
 
     ++i;
   }
@@ -157,19 +159,8 @@ auto AqlCallStack::fromVelocyPack(velocypack::Slice const slice) -> ResultT<AqlC
 }
 
 void AqlCallStack::toVelocyPack(velocypack::Builder& builder) const {
-  auto reverseStack = std::vector<AqlCall>{};
-  reverseStack.reserve(_operations.size());
-  {
-    auto ops = _operations;
-    while (!ops.empty()) {
-      reverseStack.emplace_back(ops.top());
-      ops.pop();
-    }
-  }
-
   builder.openArray();
-  for (auto it = reverseStack.rbegin(); it != reverseStack.rend(); ++it) {
-    auto const& call = *it;
+  for (auto const& call : _operations) {
     call.toVelocyPack(builder);
   }
   builder.close();
@@ -178,19 +169,50 @@ void AqlCallStack::toVelocyPack(velocypack::Builder& builder) const {
 auto AqlCallStack::toString() const -> std::string {
   auto result = std::string{};
   result += "[";
-  auto ops = _operations;
-  if (!ops.empty()) {
-    auto op = ops.top();
-    ops.pop();
+  bool isFirst = true;
+  for (auto const& op : _operations) {
+    if (!isFirst) {
+      result += ",";
+    }
+    isFirst = false;
     result += " ";
     result += op.toString();
-    while (!ops.empty()) {
-      op = ops.top();
-      ops.pop();
-      result += ", ";
-      result += op.toString();
-    }
   }
   result += " ]";
   return result;
 }
+
+auto AqlCallStack::createEquivalentFetchAllShadowRowsStack() const -> AqlCallStack {
+  AqlCallStack res{*this};
+  std::replace_if(
+      res._operations.begin(), res._operations.end(),
+      [](auto const&) -> bool { return true; }, AqlCall{});
+  return res;
+}
+
+auto AqlCallStack::needToSkipSubquery() const noexcept -> bool {
+  return std::any_of(_operations.begin(), _operations.end(), [](AqlCall const& call) -> bool {
+    return call.needSkipMore() || call.hardLimit == 0;
+  });
+}
+
+auto AqlCallStack::shadowRowDepthToSkip() const -> size_t {
+  TRI_ASSERT(needToSkipSubquery());
+  for (size_t i = 0; i < _operations.size(); ++i) {
+    auto& call = _operations.at(i);
+    if (call.needSkipMore() || call.hardLimit == 0) {
+      return _operations.size() - i - 1;
+    }
+  }
+  // unreachable
+  TRI_ASSERT(false);
+  THROW_ARANGO_EXCEPTION(TRI_ERROR_INTERNAL_AQL);
+}
+
+auto AqlCallStack::modifyCallAtDepth(size_t depth) -> AqlCall& {
+  // depth 0 is back of vector
+  TRI_ASSERT(_operations.size() > depth);
+  // Take the depth-most from top of the vector.
+  auto& call = *(_operations.rbegin() + depth);
+  return call;
+}
diff --git a/arangod/Aql/AqlCallStack.h b/arangod/Aql/AqlCallStack.h
index 4aa03285f5d8..a457578223bf 100644
--- a/arangod/Aql/AqlCallStack.h
+++ b/arangod/Aql/AqlCallStack.h
@@ -66,14 +66,6 @@ class AqlCallStack {
   // Put another call on top of the stack.
   void pushCall(AqlCall const& call);
 
-  // fill up all missing calls within this stack s.t. we reach depth == 0
-  // This needs to be called if an executor requires to be fully executed, even if skipped,
-  // even if the subquery it is located in is skipped.
-  // The default operations added here will correspond to produce all Rows, unlimitted.
-  // e.g. every Modification Executor needs to call this functionality, as modifictions need to be
-  // performed even if skipped.
-  void stackUpMissingCalls();
-
   // Pops one subquery level.
   // if this isRelevent it pops the top-most call from the stack.
   // if this is not revelent it reduces the depth by 1.
@@ -95,12 +87,58 @@ class AqlCallStack {
 
   void toVelocyPack(velocypack::Builder& builder) const;
 
+  auto is36Compatible() const noexcept -> bool { return _compatibilityMode3_6; }
+
+  /**
+   * @brief Create an equivalent call stack that does a full-produce
+   *        of all Subquery levels. This is required for blocks
+   *        that are not allowed to be bpassed.
+   *        The top-most call remains unmodified, as the Executor might
+   *        require some soft limit on it.
+   *
+   * @return AqlCallStack a stack of equivalent size, that does not skip
+   *         on any lower subquery.
+   */
+  auto createEquivalentFetchAllShadowRowsStack() const -> AqlCallStack;
+
+  /**
+   * @brief Check if we are in a subquery that is in-fact required to
+   *        be skipped. This is relevant for executors that have created
+   *        an equivalentFetchAllShadowRows stack, in order to decide if
+   *        the need to produce output or if they are skipped.
+   *
+   * @return true
+   * @return false
+   */
+  auto needToSkipSubquery() const noexcept -> bool;
+
+  /**
+   * @brief This is only valid if needToSkipSubquery is true.
+   *        It will resolve to the heighest subquery level
+   *        (outermost) that needs to be skipped.
+   *
+   *
+   * @return size_t Depth of the subquery that asks to be skipped.
+   */
+  auto shadowRowDepthToSkip() const -> size_t;
+
+  /**
+   * @brief Get a reference to the call at the given shadowRowDepth
+   *
+   * @param depth ShadowRow depth we need to work on
+   * @return AqlCall& reference to the call, can be modified.
+   */
+  auto modifyCallAtDepth(size_t depth) -> AqlCall&;
+
  private:
-  explicit AqlCallStack(std::stack<AqlCall>&& operations);
+  explicit AqlCallStack(std::vector<AqlCall>&& operations);
 
  private:
-  // The list of operations, stacked by depth (e.g. bottom element is from main query)
-  std::stack<AqlCall> _operations;
+  // The list of operations, stacked by depth (e.g. bottom element is from main
+  // query) NOTE: This is only mutable on 3.6 compatibility mode. We need to
+  // inject an additional call in any const operation here just to pretend we
+  // are not empty. Can be removed after 3.7.
+  mutable std::vector<AqlCall> _operations;
 
   // The depth of subqueries that have not issued calls into operations,
   // as they have been skipped.
diff --git a/arangod/Aql/AqlExecuteResult.cpp b/arangod/Aql/AqlExecuteResult.cpp
index db10deeaab96..be7d49d1cb98 100644
--- a/arangod/Aql/AqlExecuteResult.cpp
+++ b/arangod/Aql/AqlExecuteResult.cpp
@@ -44,11 +44,25 @@ auto getStringView(velocypack::Slice slice) -> std::string_view {
 }
 }  // namespace
 
+AqlExecuteResult::AqlExecuteResult(ExecutionState state, SkipResult skipped,
+                                   SharedAqlItemBlockPtr&& block)
+    : _state(state), _skipped(skipped), _block(std::move(block)) {
+  // Make sure we only produce a valid response
+  // The block should have checked as well.
+  // We must return skipped and/or data when reporting HASMORE
+
+  // noskip && no data => state != HASMORE
+  // <=> skipped || data || state != HASMORE
+  TRI_ASSERT(!_skipped.nothingSkipped() ||
+             (_block != nullptr && _block->numEntries() > 0) ||
+             _state != ExecutionState::HASMORE);
+}
+
 auto AqlExecuteResult::state() const noexcept -> ExecutionState {
   return _state;
 }
 
-auto AqlExecuteResult::skipped() const noexcept -> std::size_t {
+auto AqlExecuteResult::skipped() const noexcept -> SkipResult {
   return _skipped;
 }
 
@@ -75,7 +89,8 @@ void AqlExecuteResult::toVelocyPack(velocypack::Builder& builder,
 
   builder.openObject();
   builder.add(StaticStrings::AqlRemoteState, stateToValue(state()));
-  builder.add(StaticStrings::AqlRemoteSkipped, Value(skipped()));
+  builder.add(Value(StaticStrings::AqlRemoteSkipped));
+  skipped().toVelocyPack(builder);
   if (block() != nullptr) {
     ObjectBuilder guard(&builder, StaticStrings::AqlRemoteBlock);
     block()->toVelocyPack(options, builder);
@@ -101,7 +116,7 @@ auto AqlExecuteResult::fromVelocyPack(velocypack::Slice const slice,
   expectedPropertiesFound.emplace(StaticStrings::AqlRemoteBlock, false);
 
   auto state = ExecutionState::HASMORE;
-  auto skipped = std::size_t{};
+  auto skipped = SkipResult{};
   auto block = SharedAqlItemBlockPtr{};
 
   auto const readState = [](velocypack::Slice slice) -> ResultT<ExecutionState> {
@@ -127,24 +142,6 @@ auto AqlExecuteResult::fromVelocyPack(velocypack::Slice const slice,
     }
   };
 
-  auto const readSkipped = [](velocypack::Slice slice) -> ResultT<std::size_t> {
-    if (!slice.isInteger()) {
-      auto message = std::string{
-          "When deserializating AqlExecuteResult: When reading skipped: "
-          "Unexpected type "};
-      message += slice.typeName();
-      return Result(TRI_ERROR_TYPE_ERROR, std::move(message));
-    }
-    try {
-      return slice.getNumber<std::size_t>();
-    } catch (velocypack::Exception const& ex) {
-      auto message = std::string{
-          "When deserializating AqlExecuteResult: When reading skipped: "};
-      message += ex.what();
-      return Result(TRI_ERROR_TYPE_ERROR, std::move(message));
-    }
-  };
-
   auto const readBlock = [&itemBlockManager](velocypack::Slice slice) -> ResultT<SharedAqlItemBlockPtr> {
     if (slice.isNull()) {
       return SharedAqlItemBlockPtr{nullptr};
@@ -165,9 +162,9 @@ auto AqlExecuteResult::fromVelocyPack(velocypack::Slice const slice,
     if (auto propIt = expectedPropertiesFound.find(key);
         ADB_LIKELY(propIt != expectedPropertiesFound.end())) {
       if (ADB_UNLIKELY(propIt->second)) {
-        return Result(
-            TRI_ERROR_TYPE_ERROR,
-            "When deserializating AqlExecuteResult: Encountered duplicate key");
+        return Result(TRI_ERROR_TYPE_ERROR,
+                      "When deserializating AqlExecuteResult: "
+                      "Encountered duplicate key");
       }
       propIt->second = true;
     }
@@ -179,7 +176,7 @@ auto AqlExecuteResult::fromVelocyPack(velocypack::Slice const slice,
       }
       state = maybeState.get();
     } else if (key == StaticStrings::AqlRemoteSkipped) {
-      auto maybeSkipped = readSkipped(it.value);
+      auto maybeSkipped = SkipResult::fromVelocyPack(it.value);
       if (maybeSkipped.fail()) {
         return std::move(maybeSkipped).result();
       }
@@ -192,11 +189,12 @@ auto AqlExecuteResult::fromVelocyPack(velocypack::Slice const slice,
       block = maybeBlock.get();
     } else {
       LOG_TOPIC("cc6f4", WARN, Logger::AQL)
-          << "When deserializating AqlExecuteResult: Encountered unexpected "
+          << "When deserializating AqlExecuteResult: Encountered "
+             "unexpected "
              "key "
           << keySlice.toJson();
-      // If you run into this assertion during rolling upgrades after adding a
-      // new attribute, remove it in the older version.
+      // If you run into this assertion during rolling upgrades after
+      // adding a new attribute, remove it in the older version.
       TRI_ASSERT(false);
     }
   }
@@ -214,6 +212,6 @@ auto AqlExecuteResult::fromVelocyPack(velocypack::Slice const slice,
 }
 
 auto AqlExecuteResult::asTuple() const noexcept
-    -> std::tuple<ExecutionState, std::size_t, SharedAqlItemBlockPtr> {
+    -> std::tuple<ExecutionState, SkipResult, SharedAqlItemBlockPtr> {
   return {state(), skipped(), block()};
 }
diff --git a/arangod/Aql/AqlExecuteResult.h b/arangod/Aql/AqlExecuteResult.h
index 56eb448c83db..409e598f9835 100644
--- a/arangod/Aql/AqlExecuteResult.h
+++ b/arangod/Aql/AqlExecuteResult.h
@@ -25,6 +25,7 @@
 
 #include "Aql/ExecutionState.h"
 #include "Aql/SharedAqlItemBlockPtr.h"
+#include "Aql/SkipResult.h"
 
 #include <utility>
 
@@ -42,23 +43,22 @@ namespace arangodb::aql {
 
 class AqlExecuteResult {
  public:
-  AqlExecuteResult(ExecutionState state, std::size_t skipped, SharedAqlItemBlockPtr&& block)
-      : _state(state), _skipped(skipped), _block(std::move(block)) {}
+  AqlExecuteResult(ExecutionState state, SkipResult skipped, SharedAqlItemBlockPtr&& block);
 
   void toVelocyPack(velocypack::Builder&, velocypack::Options const*);
   static auto fromVelocyPack(velocypack::Slice, AqlItemBlockManager&)
       -> ResultT<AqlExecuteResult>;
 
   [[nodiscard]] auto state() const noexcept -> ExecutionState;
-  [[nodiscard]] auto skipped() const noexcept -> std::size_t;
+  [[nodiscard]] auto skipped() const noexcept -> SkipResult;
   [[nodiscard]] auto block() const noexcept -> SharedAqlItemBlockPtr const&;
 
   [[nodiscard]] auto asTuple() const noexcept
-      -> std::tuple<ExecutionState, std::size_t, SharedAqlItemBlockPtr>;
+      -> std::tuple<ExecutionState, SkipResult, SharedAqlItemBlockPtr>;
 
  private:
   ExecutionState _state = ExecutionState::HASMORE;
-  std::size_t _skipped = 0;
+  SkipResult _skipped{};
   SharedAqlItemBlockPtr _block = nullptr;
 };
 
diff --git a/arangod/Aql/BlocksWithClients.cpp b/arangod/Aql/BlocksWithClients.cpp
index b4a98714b920..89ebd3ca26cb 100644
--- a/arangod/Aql/BlocksWithClients.cpp
+++ b/arangod/Aql/BlocksWithClients.cpp
@@ -35,6 +35,7 @@
 #include "Aql/InputAqlItemRow.h"
 #include "Aql/Query.h"
 #include "Aql/ScatterExecutor.h"
+#include "Aql/SkipResult.h"
 #include "Basics/Exceptions.h"
 #include "Basics/StaticStrings.h"
 #include "Basics/StringBuffer.h"
@@ -188,7 +189,8 @@ std::pair<ExecutionState, size_t> BlocksWithClientsImpl<Executor>::skipSome(size
 }
 
 template <class Executor>
-std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> BlocksWithClientsImpl<Executor>::execute(AqlCallStack stack) {
+std::tuple<ExecutionState, SkipResult, SharedAqlItemBlockPtr>
+BlocksWithClientsImpl<Executor>::execute(AqlCallStack stack) {
   // This will not be implemented here!
   TRI_ASSERT(false);
   THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
@@ -197,17 +199,17 @@ std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> BlocksWithClientsImpl<
 template <class Executor>
 auto BlocksWithClientsImpl<Executor>::executeForClient(AqlCallStack stack,
                                                        std::string const& clientId)
-    -> std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> {
-  // traceExecuteBegin(stack);
+    -> std::tuple<ExecutionState, SkipResult, SharedAqlItemBlockPtr> {
+  traceExecuteBegin(stack, clientId);
   auto res = executeWithoutTraceForClient(stack, clientId);
-  // traceExecuteEnd(res);
+  traceExecuteEnd(res, clientId);
   return res;
 }
 
 template <class Executor>
 auto BlocksWithClientsImpl<Executor>::executeWithoutTraceForClient(AqlCallStack stack,
                                                                    std::string const& clientId)
-    -> std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> {
+    -> std::tuple<ExecutionState, SkipResult, SharedAqlItemBlockPtr> {
   TRI_ASSERT(!clientId.empty());
   if (ADB_UNLIKELY(clientId.empty())) {
     // Security bailout to avoid UB
@@ -230,21 +232,32 @@ auto BlocksWithClientsImpl<Executor>::executeWithoutTraceForClient(AqlCallStack
   // We do not have anymore data locally.
   // Need to fetch more from upstream
   auto& dataContainer = it->second;
-
-  while (!dataContainer.hasDataFor(call)) {
-    if (_upstreamState == ExecutionState::DONE) {
-      // We are done, with everything, we will not be able to fetch any more rows
-      return {_upstreamState, 0, nullptr};
+  while (true) {
+    while (!dataContainer.hasDataFor(call)) {
+      if (_upstreamState == ExecutionState::DONE) {
+        // We are done, with everything, we will not be able to fetch any more rows
+        return {_upstreamState, SkipResult{}, nullptr};
+      }
+
+      auto state = fetchMore(stack);
+      if (state == ExecutionState::WAITING) {
+        return {state, SkipResult{}, nullptr};
+      }
+      _upstreamState = state;
     }
-
-    auto state = fetchMore(stack);
-    if (state == ExecutionState::WAITING) {
-      return {state, 0, nullptr};
+    {
+      // If we get here we have data and can return it.
+      // However the call might force us to drop everything (e.g. hardLimit ==
+      // 0) So we need to refetch data eventually.
+      stack.pushCall(call);
+      auto [state, skipped, result] = dataContainer.execute(stack, _upstreamState);
+      if (state == ExecutionState::DONE || !skipped.nothingSkipped() || result != nullptr) {
+        // We have a valid result.
+        return {state, skipped, result};
+      }
+      stack.popCall();
     }
-    _upstreamState = state;
   }
-  // If we get here we have data and can return it.
-  return dataContainer.execute(call, _upstreamState);
 }
 
 template <class Executor>
@@ -262,10 +275,9 @@ auto BlocksWithClientsImpl<Executor>::fetchMore(AqlCallStack stack) -> Execution
   TRI_ASSERT(_dependencies.size() == 1);
   auto [state, skipped, block] = _dependencies[0]->execute(stack);
 
-  // We can never ever forward skip!
   // We could need the row in a different block, and once skipped
   // we cannot get it back.
-  TRI_ASSERT(skipped == 0);
+  TRI_ASSERT(skipped.getSkipCount() == 0);
 
   TRI_IF_FAILURE("ExecutionBlock::getBlock") {
     THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
@@ -274,7 +286,7 @@ auto BlocksWithClientsImpl<Executor>::fetchMore(AqlCallStack stack) -> Execution
   // Waiting -> no block
   TRI_ASSERT(state != ExecutionState::WAITING || block == nullptr);
   if (block != nullptr) {
-    _executor.distributeBlock(block, _clientBlockData);
+    _executor.distributeBlock(block, skipped, _clientBlockData);
   }
 
   return state;
@@ -287,7 +299,7 @@ std::pair<ExecutionState, SharedAqlItemBlockPtr> BlocksWithClientsImpl<Executor>
     size_t atMost, std::string const& shardId) {
   AqlCallStack stack(AqlCall::SimulateGetSome(atMost), true);
   auto [state, skipped, block] = executeForClient(stack, shardId);
-  TRI_ASSERT(skipped == 0);
+  TRI_ASSERT(skipped.nothingSkipped());
   return {state, block};
 }
 
@@ -299,7 +311,7 @@ std::pair<ExecutionState, size_t> BlocksWithClientsImpl<Executor>::skipSomeForSh
   AqlCallStack stack(AqlCall::SimulateSkipSome(atMost), true);
   auto [state, skipped, block] = executeForClient(stack, shardId);
   TRI_ASSERT(block == nullptr);
-  return {state, skipped};
+  return {state, skipped.getSkipCount()};
 }
 
 template class ::arangodb::aql::BlocksWithClientsImpl<ScatterExecutor>;
diff --git a/arangod/Aql/BlocksWithClients.h b/arangod/Aql/BlocksWithClients.h
index ead4589bf64f..75e68a37e306 100644
--- a/arangod/Aql/BlocksWithClients.h
+++ b/arangod/Aql/BlocksWithClients.h
@@ -48,6 +48,7 @@ class AqlItemBlock;
 struct Collection;
 class ExecutionEngine;
 class ExecutionNode;
+class SkipResult;
 
 class ClientsExecutorInfos {
  public:
@@ -87,7 +88,7 @@ class BlocksWithClients {
    * @return std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr>
    */
   virtual auto executeForClient(AqlCallStack stack, std::string const& clientId)
-      -> std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> = 0;
+      -> std::tuple<ExecutionState, SkipResult, SharedAqlItemBlockPtr> = 0;
 };
 
 /**
@@ -130,7 +131,7 @@ class BlocksWithClientsImpl : public ExecutionBlock, public BlocksWithClients {
   std::pair<ExecutionState, size_t> skipSome(size_t atMost) final;
 
   /// @brief execute: shouldn't be used, use executeForClient
-  std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> execute(AqlCallStack stack) override;
+  std::tuple<ExecutionState, SkipResult, SharedAqlItemBlockPtr> execute(AqlCallStack stack) override;
 
   /**
    * @brief Execute for client.
@@ -141,7 +142,7 @@ class BlocksWithClientsImpl : public ExecutionBlock, public BlocksWithClients {
    * @return std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr>
    */
   auto executeForClient(AqlCallStack stack, std::string const& clientId)
-      -> std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> override;
+      -> std::tuple<ExecutionState, SkipResult, SharedAqlItemBlockPtr> override;
 
  private:
   /**
@@ -152,7 +153,7 @@ class BlocksWithClientsImpl : public ExecutionBlock, public BlocksWithClients {
    * @return std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr>
    */
   auto executeWithoutTraceForClient(AqlCallStack stack, std::string const& clientId)
-      -> std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr>;
+      -> std::tuple<ExecutionState, SkipResult, SharedAqlItemBlockPtr>;
 
   /**
    * @brief Load more data from upstream and distribute it into _clientBlockData
diff --git a/arangod/Aql/ConstFetcher.cpp b/arangod/Aql/ConstFetcher.cpp
index 14ba394b584e..42e858d1f9e8 100644
--- a/arangod/Aql/ConstFetcher.cpp
+++ b/arangod/Aql/ConstFetcher.cpp
@@ -25,6 +25,7 @@
 #include "Aql/AqlCallStack.h"
 #include "Aql/DependencyProxy.h"
 #include "Aql/ShadowAqlItemRow.h"
+#include "Aql/SkipResult.h"
 #include "Basics/Exceptions.h"
 #include "Basics/voc-errors.h"
 
@@ -37,7 +38,7 @@ ConstFetcher::ConstFetcher(DependencyProxy& executionBlock)
     : _currentBlock{nullptr}, _rowIndex(0) {}
 
 auto ConstFetcher::execute(AqlCallStack& stack)
-    -> std::tuple<ExecutionState, size_t, AqlItemBlockInputRange> {
+    -> std::tuple<ExecutionState, SkipResult, AqlItemBlockInputRange> {
   // Note this fetcher can only be executed on top level (it is the singleton, or test)
   TRI_ASSERT(stack.isRelevant());
   // We only peek the call here, as we do not take over ownership.
@@ -45,7 +46,7 @@ auto ConstFetcher::execute(AqlCallStack& stack)
   auto call = stack.peek();
   if (_blockForPassThrough == nullptr) {
     // we are done, nothing to move arround here.
-    return {ExecutionState::DONE, 0, AqlItemBlockInputRange{ExecutorState::DONE}};
+    return {ExecutionState::DONE, SkipResult{}, AqlItemBlockInputRange{ExecutorState::DONE}};
   }
   std::vector<std::pair<size_t, size_t>> sliceIndexes;
   sliceIndexes.emplace_back(_rowIndex, _blockForPassThrough->size());
@@ -152,7 +153,10 @@ auto ConstFetcher::execute(AqlCallStack& stack)
     SharedAqlItemBlockPtr resultBlock = _blockForPassThrough;
     _blockForPassThrough.reset(nullptr);
     _rowIndex = 0;
-    return {ExecutionState::DONE, call.getSkipCount(),
+    SkipResult skipped{};
+    skipped.didSkip(call.getSkipCount());
+
+    return {ExecutionState::DONE, skipped,
             DataRange{ExecutorState::DONE, call.getSkipCount(), resultBlock, 0}};
   }
 
@@ -176,7 +180,9 @@ auto ConstFetcher::execute(AqlCallStack& stack)
     // No data to be returned
     // Block is dropped.
     resultBlock = nullptr;
-    return {ExecutionState::DONE, call.getSkipCount(),
+    SkipResult skipped{};
+    skipped.didSkip(call.getSkipCount());
+    return {ExecutionState::DONE, skipped,
             DataRange{ExecutorState::DONE, call.getSkipCount()}};
   }
 
@@ -187,8 +193,9 @@ auto ConstFetcher::execute(AqlCallStack& stack)
       _blockForPassThrough == nullptr ? ExecutorState::DONE : ExecutorState::HASMORE;
 
   resultBlock = resultBlock->slice(sliceIndexes);
-  return {resState, call.getSkipCount(),
-          DataRange{rangeState, call.getSkipCount(), resultBlock, 0}};
+  SkipResult skipped{};
+  skipped.didSkip(call.getSkipCount());
+  return {resState, skipped, DataRange{rangeState, call.getSkipCount(), resultBlock, 0}};
 }
 
 void ConstFetcher::injectBlock(SharedAqlItemBlockPtr block) {
diff --git a/arangod/Aql/ConstFetcher.h b/arangod/Aql/ConstFetcher.h
index 70fe73fa4c12..33e0215bee70 100644
--- a/arangod/Aql/ConstFetcher.h
+++ b/arangod/Aql/ConstFetcher.h
@@ -37,6 +37,7 @@ class AqlItemBlock;
 template <BlockPassthrough>
 class DependencyProxy;
 class ShadowAqlItemRow;
+class SkipResult;
 
 /**
  * @brief Interface for all AqlExecutors that do only need one
@@ -71,7 +72,7 @@ class ConstFetcher {
    *   size_t => Amount of documents skipped
    *   DataRange => Resulting data
    */
-  auto execute(AqlCallStack& stack) -> std::tuple<ExecutionState, size_t, DataRange>;
+  auto execute(AqlCallStack& stack) -> std::tuple<ExecutionState, SkipResult, DataRange>;
 
   /**
    * @brief Fetch one new AqlItemRow from upstream.
diff --git a/arangod/Aql/DependencyProxy.cpp b/arangod/Aql/DependencyProxy.cpp
index cdbc955fac6c..0c9b8535987d 100644
--- a/arangod/Aql/DependencyProxy.cpp
+++ b/arangod/Aql/DependencyProxy.cpp
@@ -32,10 +32,10 @@ using namespace arangodb;
 using namespace arangodb::aql;
 
 template <BlockPassthrough blockPassthrough>
-std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr>
+std::tuple<ExecutionState, SkipResult, SharedAqlItemBlockPtr>
 DependencyProxy<blockPassthrough>::execute(AqlCallStack& stack) {
   ExecutionState state = ExecutionState::HASMORE;
-  size_t skipped = 0;
+  SkipResult skipped;
   SharedAqlItemBlockPtr block = nullptr;
   // Note: upstreamBlock will return next dependency
   // if we need to loop here
@@ -47,16 +47,16 @@ DependencyProxy<blockPassthrough>::execute(AqlCallStack& stack) {
         break;
       }
     }
-  } while (state != ExecutionState::WAITING && skipped == 0 && block == nullptr);
+  } while (state != ExecutionState::WAITING && skipped.nothingSkipped() && block == nullptr);
   return {state, skipped, block};
 }
 
 template <BlockPassthrough blockPassthrough>
-std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> DependencyProxy<blockPassthrough>::executeForDependency(
-    size_t dependency, AqlCallStack& stack) {
-  // TODO: assert dependency in range
+std::tuple<ExecutionState, SkipResult, SharedAqlItemBlockPtr>
+DependencyProxy<blockPassthrough>::executeForDependency(size_t dependency,
+                                                        AqlCallStack& stack) {
   ExecutionState state = ExecutionState::HASMORE;
-  size_t skipped = 0;
+  SkipResult skipped;
   SharedAqlItemBlockPtr block = nullptr;
 
   if (!_distributeId.empty()) {
@@ -81,7 +81,7 @@ std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> DependencyProxy<blockP
     THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
   }
 
-  if (skipped == 0 && block == nullptr) {
+  if (skipped.nothingSkipped() && block == nullptr) {
     // We're either waiting or Done
     TRI_ASSERT(state == ExecutionState::DONE || state == ExecutionState::WAITING);
   }
@@ -99,7 +99,7 @@ ExecutionState DependencyProxy<blockPassthrough>::prefetchBlock(size_t atMost) {
   AqlCallStack stack = _injectedStack;
   stack.pushCall(AqlCall::SimulateGetSome(atMost));
   // Also temporary, will not be used here.
-  size_t skipped = 0;
+  SkipResult skipped;
   do {
     // Note: upstreamBlock will return next dependency
     // if we need to loop here
@@ -115,7 +115,7 @@ ExecutionState DependencyProxy<blockPassthrough>::prefetchBlock(size_t atMost) {
     }
     // Cannot do skipping here
     // Temporary!
-    TRI_ASSERT(skipped == 0);
+    TRI_ASSERT(skipped.nothingSkipped());
 
     if (state == ExecutionState::WAITING) {
       TRI_ASSERT(block == nullptr);
@@ -190,7 +190,7 @@ DependencyProxy<blockPassthrough>::fetchBlockForDependency(size_t dependency, si
   AqlCallStack stack = _injectedStack;
   stack.pushCall(AqlCall::SimulateGetSome(atMost));
   // Also temporary, will not be used here.
-  size_t skipped = 0;
+  SkipResult skipped{};
 
   if (_distributeId.empty()) {
     std::tie(state, skipped, block) = upstream.execute(stack);
@@ -199,7 +199,7 @@ DependencyProxy<blockPassthrough>::fetchBlockForDependency(size_t dependency, si
     std::tie(state, skipped, block) =
         upstreamWithClient->executeForClient(stack, _distributeId);
   }
-  TRI_ASSERT(skipped == 0);
+  TRI_ASSERT(skipped.nothingSkipped());
   TRI_IF_FAILURE("ExecutionBlock::getBlock") {
     THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
   }
@@ -244,7 +244,7 @@ std::pair<ExecutionState, size_t> DependencyProxy<blockPassthrough>::skipSomeFor
   SharedAqlItemBlockPtr block;
 
   while (state == ExecutionState::HASMORE && _skipped < atMost) {
-    size_t skippedNow;
+    SkipResult skippedNow;
     TRI_ASSERT(_skipped <= atMost);
     {
       // Make sure we call with the correct offset
@@ -255,14 +255,14 @@ std::pair<ExecutionState, size_t> DependencyProxy<blockPassthrough>::skipSomeFor
     }
     std::tie(state, skippedNow, block) = upstream.execute(stack);
     if (state == ExecutionState::WAITING) {
-      TRI_ASSERT(skippedNow == 0);
+      TRI_ASSERT(skippedNow.nothingSkipped());
       return {state, 0};
     }
     // Temporary.
     // If we return a block here it will be lost
     TRI_ASSERT(block == nullptr);
 
-    _skipped += skippedNow;
+    _skipped += skippedNow.getSkipCount();
     TRI_ASSERT(_skipped <= atMost);
   }
   TRI_ASSERT(state != ExecutionState::WAITING);
@@ -290,7 +290,7 @@ std::pair<ExecutionState, size_t> DependencyProxy<blockPassthrough>::skipSome(si
   SharedAqlItemBlockPtr block;
 
   while (_skipped < toSkip) {
-    size_t skippedNow;
+    SkipResult skippedNow;
     // Note: upstreamBlock will return next dependency
     // if we need to loop here
     TRI_ASSERT(_skipped <= toSkip);
@@ -309,10 +309,10 @@ std::pair<ExecutionState, size_t> DependencyProxy<blockPassthrough>::skipSome(si
           upstreamWithClient->executeForClient(stack, _distributeId);
     }
 
-    TRI_ASSERT(skippedNow <= toSkip - _skipped);
+    TRI_ASSERT(skippedNow.getSkipCount() <= toSkip - _skipped);
 
     if (state == ExecutionState::WAITING) {
-      TRI_ASSERT(skippedNow == 0);
+      TRI_ASSERT(skippedNow.nothingSkipped());
       return {state, 0};
     }
 
@@ -320,7 +320,7 @@ std::pair<ExecutionState, size_t> DependencyProxy<blockPassthrough>::skipSome(si
     // If we return a block here it will be lost
     TRI_ASSERT(block == nullptr);
 
-    _skipped += skippedNow;
+    _skipped += skippedNow.getSkipCount();
 
     // When the current dependency is done, advance.
     if (state == ExecutionState::DONE) {
diff --git a/arangod/Aql/DependencyProxy.h b/arangod/Aql/DependencyProxy.h
index 108e6bad1ac9..d28dda04a312 100644
--- a/arangod/Aql/DependencyProxy.h
+++ b/arangod/Aql/DependencyProxy.h
@@ -37,6 +37,7 @@
 namespace arangodb::aql {
 class ExecutionBlock;
 class AqlItemBlockManager;
+class SkipResult;
 
 /**
  * @brief Thin interface to access the methods of ExecutionBlock that are
@@ -74,9 +75,9 @@ class DependencyProxy {
   TEST_VIRTUAL ~DependencyProxy() = default;
 
   // TODO Implement and document properly!
-  TEST_VIRTUAL std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> execute(AqlCallStack& stack);
+  TEST_VIRTUAL std::tuple<ExecutionState, SkipResult, SharedAqlItemBlockPtr> execute(AqlCallStack& stack);
 
-  TEST_VIRTUAL std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> executeForDependency(
+  TEST_VIRTUAL std::tuple<ExecutionState, SkipResult, SharedAqlItemBlockPtr> executeForDependency(
       size_t dependency, AqlCallStack& stack);
 
   // This is only TEST_VIRTUAL, so we ignore this lint warning:
diff --git a/arangod/Aql/DistributeExecutor.cpp b/arangod/Aql/DistributeExecutor.cpp
index 07cd89c9f4b5..a528e68c3fc6 100644
--- a/arangod/Aql/DistributeExecutor.cpp
+++ b/arangod/Aql/DistributeExecutor.cpp
@@ -31,6 +31,7 @@
 #include "Aql/Query.h"
 #include "Aql/RegisterPlan.h"
 #include "Aql/ShadowAqlItemRow.h"
+#include "Aql/SkipResult.h"
 #include "Basics/StaticStrings.h"
 #include "VocBase/LogicalCollection.h"
 
@@ -152,6 +153,12 @@ auto DistributeExecutor::ClientBlockData::addBlock(SharedAqlItemBlockPtr block,
   _queue.emplace_back(block, std::move(usedIndexes));
 }
 
+auto DistributeExecutor::ClientBlockData::addSkipResult(SkipResult const& skipResult) -> void {
+  TRI_ASSERT(_skipped.subqueryDepth() == 1 ||
+             _skipped.subqueryDepth() == skipResult.subqueryDepth());
+  _skipped.merge(skipResult, false);
+}
+
 auto DistributeExecutor::ClientBlockData::hasDataFor(AqlCall const& call) -> bool {
   return _executorHasMore || !_queue.empty();
 }
@@ -166,7 +173,8 @@ auto DistributeExecutor::ClientBlockData::hasDataFor(AqlCall const& call) -> boo
  *
  * @return SharedAqlItemBlockPtr a joind block from the queue.
  */
-auto DistributeExecutor::ClientBlockData::popJoinedBlock() -> SharedAqlItemBlockPtr {
+auto DistributeExecutor::ClientBlockData::popJoinedBlock()
+    -> std::tuple<SharedAqlItemBlockPtr, SkipResult> {
   // There are some optimizations available in this implementation.
   // Namely we could apply good logic to cut the blocks at shadow rows
   // in order to allow the IDexecutor to hand them out en-block.
@@ -208,14 +216,16 @@ auto DistributeExecutor::ClientBlockData::popJoinedBlock() -> SharedAqlItemBlock
     // Drop block form queue.
     _queue.pop_front();
   }
-  return newBlock;
+  SkipResult skip = _skipped;
+  _skipped.reset();
+  return {newBlock, skip};
 }
 
-auto DistributeExecutor::ClientBlockData::execute(AqlCall call, ExecutionState upstreamState)
-    -> std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> {
+auto DistributeExecutor::ClientBlockData::execute(AqlCallStack callStack, ExecutionState upstreamState)
+    -> std::tuple<ExecutionState, SkipResult, SharedAqlItemBlockPtr> {
   TRI_ASSERT(_executor != nullptr);
   // Make sure we actually have data before you call execute
-  TRI_ASSERT(hasDataFor(call));
+  TRI_ASSERT(hasDataFor(callStack.peek()));
   if (!_executorHasMore) {
     // This cast is guaranteed, we create this a couple lines above and only
     // this executor is used here.
@@ -224,16 +234,15 @@ auto DistributeExecutor::ClientBlockData::execute(AqlCall call, ExecutionState u
     auto casted =
         static_cast<ExecutionBlockImpl<IdExecutor<ConstFetcher>>*>(_executor.get());
     TRI_ASSERT(casted != nullptr);
-    auto block = popJoinedBlock();
+    auto [block, skipped] = popJoinedBlock();
     // We will at least get one block, otherwise the hasDataFor would
     // be required to return false!
     TRI_ASSERT(block != nullptr);
 
-    casted->injectConstantBlock(block);
+    casted->injectConstantBlock(block, skipped);
     _executorHasMore = true;
   }
-  AqlCallStack stack{call};
-  auto [state, skipped, result] = _executor->execute(stack);
+  auto [state, skipped, result] = _executor->execute(callStack);
 
   // We have all data locally cannot wait here.
   TRI_ASSERT(state != ExecutionState::WAITING);
@@ -257,7 +266,7 @@ auto DistributeExecutor::ClientBlockData::execute(AqlCall call, ExecutionState u
 DistributeExecutor::DistributeExecutor(DistributeExecutorInfos const& infos)
     : _infos(infos){};
 
-auto DistributeExecutor::distributeBlock(SharedAqlItemBlockPtr block,
+auto DistributeExecutor::distributeBlock(SharedAqlItemBlockPtr block, SkipResult skipped,
                                          std::unordered_map<std::string, ClientBlockData>& blockMap)
     -> void {
   std::unordered_map<std::string, std::vector<std::size_t>> choosenMap;
@@ -289,6 +298,12 @@ auto DistributeExecutor::distributeBlock(SharedAqlItemBlockPtr block,
     }
     target->second.addBlock(block, std::move(value));
   }
+
+  // Add the skipResult to all clients.
+  // It needs to be fetched once for every client.
+  for (auto& [key, map] : blockMap) {
+    map.addSkipResult(skipped);
+  }
 }
 
 auto DistributeExecutor::getClient(SharedAqlItemBlockPtr block, size_t rowIndex)
diff --git a/arangod/Aql/DistributeExecutor.h b/arangod/Aql/DistributeExecutor.h
index b6954bc1ff3a..0e7bd1a618b6 100644
--- a/arangod/Aql/DistributeExecutor.h
+++ b/arangod/Aql/DistributeExecutor.h
@@ -92,29 +92,33 @@ class DistributeExecutor {
 
     auto clear() -> void;
     auto addBlock(SharedAqlItemBlockPtr block, std::vector<size_t> usedIndexes) -> void;
+
+    auto addSkipResult(SkipResult const& skipResult) -> void;
     auto hasDataFor(AqlCall const& call) -> bool;
 
-    auto execute(AqlCall call, ExecutionState upstreamState)
-        -> std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr>;
+    auto execute(AqlCallStack callStack, ExecutionState upstreamState)
+        -> std::tuple<ExecutionState, SkipResult, SharedAqlItemBlockPtr>;
 
    private:
     /**
      * @brief This call will join as many blocks as available from the queue
      *        and return them in a SingleBlock. We then use the IdExecutor
      *        to hand out the data contained in these blocks
-     *        We do on purpose not give any kind of guarantees on the sizing of
-     *        this block to be flexible with the implementation, and find a good
+     *        We do on purpose not give any kind of guarantees on the sizing
+     * of this block to be flexible with the implementation, and find a good
      *        trade-off between blocksize and block copy operations.
      *
-     * @return SharedAqlItemBlockPtr a joind block from the queue.
+     * @return SharedAqlItemBlockPtr a joined block from the queue.
+     *         SkipResult the skip information matching to this block
      */
-    auto popJoinedBlock() -> SharedAqlItemBlockPtr;
+    auto popJoinedBlock() -> std::tuple<SharedAqlItemBlockPtr, SkipResult>;
 
    private:
     AqlItemBlockManager& _blockManager;
     ExecutorInfos const& _infos;
 
     std::deque<std::pair<SharedAqlItemBlockPtr, std::vector<size_t>>> _queue;
+    SkipResult _skipped{};
 
     // This is unique_ptr to get away with everything being forward declared...
     std::unique_ptr<ExecutionBlock> _executor;
@@ -132,9 +136,10 @@ class DistributeExecutor {
    *        Hence this method is not const ;(
    *
    * @param block The block to be distributed
+   * @param skipped The rows that have been skipped from upstream
    * @param blockMap Map client => Data. Will provide the required data to the correct client.
    */
-  auto distributeBlock(SharedAqlItemBlockPtr block,
+  auto distributeBlock(SharedAqlItemBlockPtr block, SkipResult skipped,
                        std::unordered_map<std::string, ClientBlockData>& blockMap) -> void;
 
  private:
diff --git a/arangod/Aql/ExecutionBlock.cpp b/arangod/Aql/ExecutionBlock.cpp
index ec4ca75d3433..37538244f10f 100644
--- a/arangod/Aql/ExecutionBlock.cpp
+++ b/arangod/Aql/ExecutionBlock.cpp
@@ -298,7 +298,7 @@ bool ExecutionBlock::isInSplicedSubquery() const noexcept {
   return _isInSplicedSubquery;
 }
 
-void ExecutionBlock::traceExecuteBegin(AqlCallStack const& stack) {
+void ExecutionBlock::traceExecuteBegin(AqlCallStack const& stack, std::string const& clientId) {
   if (_profile >= PROFILE_LEVEL_BLOCKS) {
     if (_getSomeBegin <= 0.0) {
       _getSomeBegin = TRI_microtime();
@@ -311,20 +311,22 @@ void ExecutionBlock::traceExecuteBegin(AqlCallStack const& stack) {
       LOG_TOPIC("1e717", INFO, Logger::QUERIES)
           << "[query#" << queryId << "] "
           << "execute type=" << node->getTypeString() << " call= " << call
-          << " this=" << (uintptr_t)this << " id=" << node->id();
+          << " this=" << (uintptr_t)this << " id=" << node->id()
+          << (clientId.empty() ? "" : " clientId=" + clientId);
     }
   }
 }
 
-auto ExecutionBlock::traceExecuteEnd(std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> const& result)
-    -> std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> {
+auto ExecutionBlock::traceExecuteEnd(std::tuple<ExecutionState, SkipResult, SharedAqlItemBlockPtr> const& result,
+                                     std::string const& clientId)
+    -> std::tuple<ExecutionState, SkipResult, SharedAqlItemBlockPtr> {
   if (_profile >= PROFILE_LEVEL_BLOCKS) {
     auto const& [state, skipped, block] = result;
     auto const items = block != nullptr ? block->size() : 0;
     ExecutionNode const* en = getPlanNode();
     ExecutionStats::Node stats;
     stats.calls = 1;
-    stats.items = skipped + items;
+    stats.items = skipped.getSkipCount() + items;
     if (state != ExecutionState::WAITING) {
       stats.runtime = TRI_microtime() - _getSomeBegin;
       _getSomeBegin = 0.0;
@@ -339,9 +341,11 @@ auto ExecutionBlock::traceExecuteEnd(std::tuple<ExecutionState, size_t, SharedAq
 
     if (_profile >= PROFILE_LEVEL_TRACE_1) {
       ExecutionNode const* node = getPlanNode();
-      LOG_QUERY("60bbc", INFO) << "execute done " << printBlockInfo()
-                               << " state=" << stateToString(state)
-                               << " skipped=" << skipped << " produced=" << items;
+      LOG_QUERY("60bbc", INFO)
+          << "execute done " << printBlockInfo() << " state=" << stateToString(state)
+          << " skipped=" << skipped.getSkipCount() << " produced=" << items
+          << (clientId.empty() ? "" : " clientId=" + clientId);
+      ;
 
       if (_profile >= PROFILE_LEVEL_TRACE_2) {
         if (block == nullptr) {
diff --git a/arangod/Aql/ExecutionBlock.h b/arangod/Aql/ExecutionBlock.h
index b3652bc5576c..c1544a123b45 100644
--- a/arangod/Aql/ExecutionBlock.h
+++ b/arangod/Aql/ExecutionBlock.h
@@ -26,6 +26,7 @@
 
 #include "Aql/BlockCollector.h"
 #include "Aql/ExecutionState.h"
+#include "Aql/SkipResult.h"
 #include "Basics/Result.h"
 
 #include <cstdint>
@@ -144,19 +145,21 @@ class ExecutionBlock {
   ///          * WAITING: We have async operation going on, nothing happend, please call again
   ///          * HASMORE: Here is some data in the request range, there is still more, if required call again
   ///          * DONE: Here is some data, and there will be no further data available.
-  ///        2. size_t: Amount of documents skipped.
+  ///        2. SkipResult: Amount of documents skipped.
   ///        3. SharedAqlItemBlockPtr: The next data block.
-  virtual std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> execute(AqlCallStack stack) = 0;
+  virtual std::tuple<ExecutionState, SkipResult, SharedAqlItemBlockPtr> execute(AqlCallStack stack) = 0;
 
   [[nodiscard]] bool isInSplicedSubquery() const noexcept;
 
  protected:
   // Trace the start of a execute call
-  void traceExecuteBegin(AqlCallStack const& stack);
+  void traceExecuteBegin(AqlCallStack const& stack,
+                         std::string const& clientId = "");
 
   // Trace the end of a execute call, potentially with result
-  auto traceExecuteEnd(std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> const& result)
-      -> std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr>;
+  auto traceExecuteEnd(std::tuple<ExecutionState, SkipResult, SharedAqlItemBlockPtr> const& result,
+                       std::string const& clientId = "")
+      -> std::tuple<ExecutionState, SkipResult, SharedAqlItemBlockPtr>;
 
   [[nodiscard]] auto printBlockInfo() const -> std::string const;
   [[nodiscard]] auto printTypeInfo() const -> std::string const;
diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index 8e71f0dc0192..133df32b4677 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -58,6 +58,7 @@
 #include "Aql/ShortestPathExecutor.h"
 #include "Aql/SimpleModifier.h"
 #include "Aql/SingleRemoteModificationExecutor.h"
+#include "Aql/SkipResult.h"
 #include "Aql/SortExecutor.h"
 #include "Aql/SortRegister.h"
 #include "Aql/SortedCollectExecutor.h"
@@ -124,6 +125,23 @@ class TestLambdaSkipExecutor;
 }  // namespace arangodb::aql
 #endif
 
+/*
+ *  Determine whether an executor cannot bypass subquery skips.
+ *  This is if exection of this Executor does have side-effects
+ *  other then it's own result.
+ */
+
+template <typename Executor>
+constexpr bool executorHasSideEffects =
+    is_one_of_v<Executor, ModificationExecutor<AllRowsFetcher, InsertModifier>,
+                ModificationExecutor<SingleRowFetcher<BlockPassthrough::Disable>, InsertModifier>,
+                ModificationExecutor<AllRowsFetcher, RemoveModifier>,
+                ModificationExecutor<SingleRowFetcher<BlockPassthrough::Disable>, RemoveModifier>,
+                ModificationExecutor<AllRowsFetcher, UpdateReplaceModifier>,
+                ModificationExecutor<SingleRowFetcher<BlockPassthrough::Disable>, UpdateReplaceModifier>,
+                ModificationExecutor<AllRowsFetcher, UpsertModifier>,
+                ModificationExecutor<SingleRowFetcher<BlockPassthrough::Disable>, UpsertModifier>>;
+
 /*
  * Determine whether we execute new style or old style skips, i.e. pre or post shadow row introduction
  * TODO: This should be removed once all executors and fetchers are ported to the new style.
@@ -507,38 +525,17 @@ static SkipVariants constexpr skipType() {
 
 template <class Executor>
 std::pair<ExecutionState, size_t> ExecutionBlockImpl<Executor>::skipSome(size_t const atMost) {
-  if constexpr (isNewStyleExecutor<Executor>) {
-    AqlCallStack stack{AqlCall::SimulateSkipSome(atMost)};
-    auto const [state, skipped, block] = execute(stack);
-
-    // execute returns ExecutionState::DONE here, which stops execution after simulating a skip.
-    // If we indiscriminately return ExecutionState::HASMORE, then we end up in an infinite loop
-    //
-    // luckily we can dispose of this kludge once executors have been ported.
-    if (skipped < atMost && state == ExecutionState::DONE) {
-      return {ExecutionState::DONE, skipped};
-    } else {
-      return {ExecutionState::HASMORE, skipped};
-    }
+  AqlCallStack stack{AqlCall::SimulateSkipSome(atMost)};
+  auto const [state, skipped, block] = execute(stack);
+
+  // execute returns ExecutionState::DONE here, which stops execution after simulating a skip.
+  // If we indiscriminately return ExecutionState::HASMORE, then we end up in an infinite loop
+  //
+  // luckily we can dispose of this kludge once executors have been ported.
+  if (skipped.getSkipCount() < atMost && state == ExecutionState::DONE) {
+    return {ExecutionState::DONE, skipped.getSkipCount()};
   } else {
-    traceSkipSomeBegin(atMost);
-    auto state = ExecutionState::HASMORE;
-
-    while (state == ExecutionState::HASMORE && _skipped < atMost) {
-      auto res = skipSomeOnceWithoutTrace(atMost - _skipped);
-      TRI_ASSERT(state != ExecutionState::WAITING || res.second == 0);
-      state = res.first;
-      _skipped += res.second;
-      TRI_ASSERT(_skipped <= atMost);
-    }
-
-    size_t skipped = 0;
-    if (state != ExecutionState::WAITING) {
-      std::swap(skipped, _skipped);
-    }
-
-    TRI_ASSERT(skipped <= atMost);
-    return traceSkipSomeEnd(state, skipped);
+    return {ExecutionState::HASMORE, skipped.getSkipCount()};
   }
 }
 
@@ -616,8 +613,8 @@ std::pair<ExecutionState, Result> ExecutionBlockImpl<Executor>::initializeCursor
     _lastRange = DataRange(ExecutorState::HASMORE);
   }
 
-  TRI_ASSERT(_skipped == 0);
-  _skipped = 0;
+  TRI_ASSERT(_skipped.nothingSkipped());
+  _skipped.reset();
   TRI_ASSERT(_state == InternalState::DONE || _state == InternalState::FETCH_DATA);
   _state = InternalState::FETCH_DATA;
 
@@ -640,7 +637,8 @@ std::pair<ExecutionState, Result> ExecutionBlockImpl<Executor>::shutdown(int err
 }
 
 template <class Executor>
-std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> ExecutionBlockImpl<Executor>::execute(AqlCallStack stack) {
+std::tuple<ExecutionState, SkipResult, SharedAqlItemBlockPtr>
+ExecutionBlockImpl<Executor>::execute(AqlCallStack stack) {
   // TODO remove this IF
   // These are new style executors
   if constexpr (isNewStyleExecutor<Executor>) {
@@ -674,7 +672,9 @@ std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> ExecutionBlockImpl<Exe
     if (state != ExecutionState::WAITING) {
       myCall.didSkip(skipped);
     }
-    return {state, skipped, nullptr};
+    SkipResult skipRes{};
+    skipRes.didSkip(skipped);
+    return {state, skipRes, nullptr};
   } else if (AqlCall::IsGetSomeCall(myCall)) {
     auto const [state, block] = getSome(myCall.getLimit());
     // We do not need to count as softLimit will be overwritten, and hard cannot be set.
@@ -682,20 +682,22 @@ std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> ExecutionBlockImpl<Exe
       // However we can do a short-cut here to report DONE on hardLimit if we are on the top-level query.
       myCall.didProduce(block->size());
       if (myCall.getLimit() == 0) {
-        return {ExecutionState::DONE, 0, block};
+        return {ExecutionState::DONE, SkipResult{}, block};
       }
     }
 
-    return {state, 0, block};
+    return {state, SkipResult{}, block};
   } else if (AqlCall::IsFullCountCall(myCall)) {
     auto const [state, skipped] = skipSome(ExecutionBlock::SkipAllSize());
     if (state != ExecutionState::WAITING) {
       myCall.didSkip(skipped);
     }
-    return {state, skipped, nullptr};
+    SkipResult skipRes{};
+    skipRes.didSkip(skipped);
+    return {state, skipRes, nullptr};
   } else if (AqlCall::IsFastForwardCall(myCall)) {
     // No idea if DONE is correct here...
-    return {ExecutionState::DONE, 0, nullptr};
+    return {ExecutionState::DONE, SkipResult{}, nullptr};
   }
   // Should never get here!
   THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
@@ -709,8 +711,8 @@ namespace arangodb::aql {
 
 template <>
 template <>
-auto ExecutionBlockImpl<IdExecutor<ConstFetcher>>::injectConstantBlock<IdExecutor<ConstFetcher>>(SharedAqlItemBlockPtr block)
-    -> void {
+auto ExecutionBlockImpl<IdExecutor<ConstFetcher>>::injectConstantBlock<IdExecutor<ConstFetcher>>(
+    SharedAqlItemBlockPtr block, SkipResult skipped) -> void {
   // reinitialize the DependencyProxy
   _dependencyProxy.reset();
 
@@ -718,9 +720,16 @@ auto ExecutionBlockImpl<IdExecutor<ConstFetcher>>::injectConstantBlock<IdExecuto
   _rowFetcher.~Fetcher();
   new (&_rowFetcher) Fetcher(_dependencyProxy);
 
-  TRI_ASSERT(_skipped == 0);
-  _skipped = 0;
+  TRI_ASSERT(_skipped.nothingSkipped());
+
+  // Local skipped is either fresh (depth == 1)
+  // Or exactly of the size handed in
+  TRI_ASSERT(_skipped.subqueryDepth() == 1 ||
+             _skipped.subqueryDepth() == skipped.subqueryDepth());
+  _skipped = skipped;
+
   TRI_ASSERT(_state == InternalState::DONE || _state == InternalState::FETCH_DATA);
+
   _state = InternalState::FETCH_DATA;
 
   // Reset state of execute
@@ -740,8 +749,11 @@ std::pair<ExecutionState, Result> ExecutionBlockImpl<IdExecutor<ConstFetcher>>::
   SharedAqlItemBlockPtr block =
       input.cloneToBlock(_engine->itemBlockManager(), *(infos().registersToKeep()),
                          infos().numberOfOutputRegisters());
-
-  injectConstantBlock(block);
+  TRI_ASSERT(_skipped.nothingSkipped());
+  _skipped.reset();
+  // We inject an empty copy of our skipped here,
+  // This is resettet, but will maintain the size
+  injectConstantBlock(block, _skipped);
 
   // end of default initializeCursor
   return ExecutionBlock::initializeCursor(input);
@@ -1205,16 +1217,10 @@ static auto fastForwardType(AqlCall const& call, Executor const& e) -> FastForwa
     TRI_ASSERT(call.hasHardLimit());
     return FastForwardVariant::FULLCOUNT;
   }
-  // TODO: We only need to do this is the executor actually require to call.
-  // e.g. Modifications will always need to be called. Limit only if it needs to report fullCount
-  if constexpr (is_one_of_v<Executor, LimitExecutor, ModificationExecutor<AllRowsFetcher, InsertModifier>,
-                            ModificationExecutor<SingleRowFetcher<BlockPassthrough::Disable>, InsertModifier>,
-                            ModificationExecutor<AllRowsFetcher, RemoveModifier>,
-                            ModificationExecutor<SingleRowFetcher<BlockPassthrough::Disable>, RemoveModifier>,
-                            ModificationExecutor<AllRowsFetcher, UpdateReplaceModifier>,
-                            ModificationExecutor<SingleRowFetcher<BlockPassthrough::Disable>, UpdateReplaceModifier>,
-                            ModificationExecutor<AllRowsFetcher, UpsertModifier>,
-                            ModificationExecutor<SingleRowFetcher<BlockPassthrough::Disable>, UpsertModifier>>) {
+  // TODO: We only need to do this if the executor is required to call.
+  // e.g. Modifications and SubqueryStart will always need to be called. Limit only if it needs to report fullCount
+  if constexpr (is_one_of_v<Executor, LimitExecutor, SubqueryStartExecutor> ||
+                executorHasSideEffects<Executor>) {
     return FastForwardVariant::EXECUTOR;
   }
   return FastForwardVariant::FETCHER;
@@ -1222,13 +1228,19 @@ static auto fastForwardType(AqlCall const& call, Executor const& e) -> FastForwa
 
 template <class Executor>
 auto ExecutionBlockImpl<Executor>::executeFetcher(AqlCallStack& stack, AqlCallType const& aqlCall)
-    -> std::tuple<ExecutionState, size_t, typename Fetcher::DataRange> {
+    -> std::tuple<ExecutionState, SkipResult, typename Fetcher::DataRange> {
   if constexpr (isNewStyleExecutor<Executor>) {
     // TODO The logic in the MultiDependencySingleRowFetcher branch should be
     //      moved into the MultiDependencySingleRowFetcher.
     static_assert(isMultiDepExecutor<Executor> ==
                   std::is_same_v<Fetcher, MultiDependencySingleRowFetcher>);
     if constexpr (std::is_same_v<Fetcher, MultiDependencySingleRowFetcher>) {
+      static_assert(
+          !executorHasSideEffects<Executor>,
+          "there is a special implementation for side-effect executors to "
+          "exchange the stack. For the MultiDependencyFetcher this special "
+          "case is not implemented. There is no reason to disallow this "
+          "case here however, it is just not needed thus far.");
       // Note the aqlCall is an AqlCallSet in this case:
       static_assert(std::is_same_v<AqlCallSet, std::decay_t<decltype(aqlCall)>>);
       TRI_ASSERT(_lastRange.numberDependencies() == _dependencies.size());
@@ -1237,14 +1249,25 @@ auto ExecutionBlockImpl<Executor>::executeFetcher(AqlCallStack& stack, AqlCallTy
         _lastRange.setDependency(dependency, range);
       }
       return {state, skipped, _lastRange};
+    } else if constexpr (executorHasSideEffects<Executor>) {
+      // If the executor has side effects, we cannot bypass any subqueries
+      // by skipping them. SO we need to fetch all shadow rows in order to
+      // trigger this Executor with everthing from above.
+      // NOTE: The Executor needs to discard shadowRows, and do the accouting.
+      static_assert(std::is_same_v<AqlCall, std::decay_t<decltype(aqlCall)>>);
+      auto fetchAllStack = stack.createEquivalentFetchAllShadowRowsStack();
+      fetchAllStack.pushCall(aqlCall);
+      auto res = _rowFetcher.execute(fetchAllStack);
+      // Just make sure we did not Skip anything
+      TRI_ASSERT(std::get<SkipResult>(res).nothingSkipped());
+      return res;
     } else {
       // If we are SubqueryStart, we remove the top element of the stack
       // which belongs to the subquery enclosed by this
       // SubqueryStart and the partnered SubqueryEnd by *not*
       // pushing the upstream request.
       if constexpr (!std::is_same_v<Executor, SubqueryStartExecutor>) {
-        auto callCopy = _upstreamRequest;
-        stack.pushCall(std::move(callCopy));
+        stack.pushCall(std::move(aqlCall));
       }
 
       auto const result = _rowFetcher.execute(stack);
@@ -1424,6 +1447,10 @@ auto ExecutionBlockImpl<SubqueryEndExecutor>::shadowRowForwarding() -> ExecState
     // We still have shadowRows, we
     // need to forward them
     return ExecState::SHADOWROWS;
+  } else if (_outputItemRow->isFull()) {
+    // Fullfilled the call
+    // Need to return!
+    return ExecState::DONE;
   } else {
     if (didConsume) {
       // We did only consume the input
@@ -1436,6 +1463,119 @@ auto ExecutionBlockImpl<SubqueryEndExecutor>::shadowRowForwarding() -> ExecState
   }
 }
 
+template <class Executor>
+auto ExecutionBlockImpl<Executor>::nextStateAfterShadowRows(ExecutorState const& state,
+                                                            DataRange const& range) const
+    noexcept -> ExecState {
+  if (state == ExecutorState::DONE) {
+    // We have consumed everything, we are
+    // Done with this query
+    return ExecState::DONE;
+  } else if (range.hasDataRow()) {
+    // Multiple concatenated Subqueries
+    // This case is disallowed for now, as we do not know the
+    // look-ahead call
+    TRI_ASSERT(false);
+    // If we would know we could now go into a continue with next subquery
+    // state.
+    return ExecState::DONE;
+  } else if (range.hasShadowRow()) {
+    // We still have shadowRows, we
+    // need to forward them
+    return ExecState::SHADOWROWS;
+  } else {
+    // End of input, we are done for now
+    // Need to call again
+    return ExecState::DONE;
+  }
+}
+
+template <class Executor>
+auto ExecutionBlockImpl<Executor>::sideEffectShadowRowForwarding(AqlCallStack& stack,
+                                                                 SkipResult& skipResult)
+    -> ExecState {
+  TRI_ASSERT(executorHasSideEffects<Executor>);
+  if (!stack.needToSkipSubquery()) {
+    // We need to really produce things here
+    // fall back to original version as any other executor.
+    return shadowRowForwarding();
+  }
+  TRI_ASSERT(_outputItemRow);
+  TRI_ASSERT(_outputItemRow->isInitialized());
+  TRI_ASSERT(!_outputItemRow->allRowsUsed());
+  if (!_lastRange.hasShadowRow()) {
+    // We got back without a ShadowRow in the LastRange
+    // Let client call again
+    return ExecState::DONE;
+  }
+
+  auto const& [state, shadowRow] = _lastRange.nextShadowRow();
+  TRI_ASSERT(shadowRow.isInitialized());
+  uint64_t depthSkippingNow = static_cast<uint64_t>(stack.shadowRowDepthToSkip());
+  uint64_t shadowDepth = shadowRow.getDepth();
+
+  bool didWriteRow = false;
+  if (shadowRow.isRelevant()) {
+    LOG_QUERY("1b257", DEBUG) << printTypeInfo() << " init executor.";
+    // We found a relevant shadow Row.
+    // We need to reset the Executor
+    resetExecutor();
+  }
+
+  if (depthSkippingNow > shadowDepth) {
+    // We are skipping the outermost Subquery.
+    // Simply drop this ShadowRow
+  } else if (depthSkippingNow == shadowDepth) {
+    // We are skipping on this subquery level.
+    // Skip the row, but report skipped 1.
+    AqlCall& shadowCall = stack.modifyCallAtDepth(shadowDepth);
+    if (shadowCall.needSkipMore()) {
+      shadowCall.didSkip(1);
+      skipResult.didSkipSubquery(1, shadowDepth);
+    } else {
+      TRI_ASSERT(shadowCall.hardLimit == 0);
+      // Simply drop this shadowRow!
+    }
+  } else {
+    // We got a shadowRow of a subquery we are not skipping here.
+    // Do proper reporting on it's call.
+    AqlCall& shadowCall = stack.modifyCallAtDepth(shadowDepth);
+    TRI_ASSERT(!shadowCall.needSkipMore() && shadowCall.getLimit() > 0);
+    _outputItemRow->copyRow(shadowRow);
+    shadowCall.didProduce(1);
+
+    TRI_ASSERT(_outputItemRow->produced());
+    _outputItemRow->advanceRow();
+    didWriteRow = true;
+  }
+  if (state == ExecutorState::DONE) {
+    // We have consumed everything, we are
+    // Done with this query
+    return ExecState::DONE;
+  } else if (_lastRange.hasDataRow()) {
+    // Multiple concatenated Subqueries
+    // This case is disallowed for now, as we do not know the
+    // look-ahead call
+    TRI_ASSERT(false);
+    // If we would know we could now go into a continue with next subquery
+    // state.
+    return ExecState::DONE;
+  } else if (_lastRange.hasShadowRow()) {
+    // We still have shadowRows, we
+    // need to forward them
+    return ExecState::SHADOWROWS;
+  } else if (didWriteRow) {
+    // End of input, we are done for now
+    // Need to call again
+    return ExecState::DONE;
+  } else {
+    // Done with this subquery.
+    // We did not write any output yet.
+    // So we can continue with upstream.
+    return ExecState::UPSTREAM;
+  }
+}
+
 template <class Executor>
 auto ExecutionBlockImpl<Executor>::shadowRowForwarding() -> ExecState {
   TRI_ASSERT(_outputItemRow);
@@ -1461,7 +1601,6 @@ auto ExecutionBlockImpl<Executor>::shadowRowForwarding() -> ExecState {
 
   TRI_ASSERT(_outputItemRow->produced());
   _outputItemRow->advanceRow();
-
   if (state == ExecutorState::DONE) {
     // We have consumed everything, we are
     // Done with this query
@@ -1490,29 +1629,30 @@ auto ExecutionBlockImpl<Executor>::executeFastForward(typename Fetcher::DataRang
                                                       AqlCall& clientCall)
     -> std::tuple<ExecutorState, typename Executor::Stats, size_t, AqlCallType> {
   TRI_ASSERT(isNewStyleExecutor<Executor>);
-  if constexpr (std::is_same_v<Executor, SubqueryStartExecutor>) {
-    if (clientCall.needsFullCount() && clientCall.getOffset() == 0 &&
-        clientCall.getLimit() == 0) {
-      // We can savely call skipRows.
-      // It will not report anything if the row is already consumed
-      return executeSkipRowsRange(_lastRange, clientCall);
-    }
-    // Do not fastForward anything, the Subquery start will handle it by itself
-    return {ExecutorState::DONE, NoStats{}, 0, AqlCall{}};
-  }
   auto type = fastForwardType(clientCall, _executor);
 
   switch (type) {
-    case FastForwardVariant::FULLCOUNT:
-    case FastForwardVariant::EXECUTOR: {
+    case FastForwardVariant::FULLCOUNT: {
       LOG_QUERY("cb135", DEBUG) << printTypeInfo() << " apply full count.";
       auto [state, stats, skippedLocal, call] = executeSkipRowsRange(_lastRange, clientCall);
 
-      if (type == FastForwardVariant::EXECUTOR) {
-        // We do not report the skip
-        skippedLocal = 0;
+      if constexpr (is_one_of_v<DataRange, AqlItemBlockInputMatrix, MultiAqlItemBlockInputRange>) {
+        // The executor will have used all Rows.
+        // However we need to drop them from the input
+        // here.
+        inputRange.skipAllRemainingDataRows();
       }
 
+      return {state, stats, skippedLocal, call};
+    }
+    case FastForwardVariant::EXECUTOR: {
+      LOG_QUERY("2890e", DEBUG) << printTypeInfo() << " fast forward.";
+      // We use a DUMMY Call to simulate fullCount.
+      AqlCall dummy;
+      dummy.hardLimit = 0;
+      dummy.fullCount = true;
+      auto [state, stats, skippedLocal, call] = executeSkipRowsRange(_lastRange, dummy);
+
       if constexpr (is_one_of_v<DataRange, AqlItemBlockInputMatrix, MultiAqlItemBlockInputRange>) {
         // The executor will have used all Rows.
         // However we need to drop them from the input
@@ -1520,7 +1660,7 @@ auto ExecutionBlockImpl<Executor>::executeFastForward(typename Fetcher::DataRang
         inputRange.skipAllRemainingDataRows();
       }
 
-      return {state, stats, skippedLocal, call};
+      return {state, stats, 0, call};
     }
     case FastForwardVariant::FETCHER: {
       LOG_QUERY("fa327", DEBUG) << printTypeInfo() << " bypass unused rows.";
@@ -1531,8 +1671,8 @@ auto ExecutionBlockImpl<Executor>::executeFastForward(typename Fetcher::DataRang
           return fastForwardCall;
         } else {
 #ifndef _WIN32
-          // For some reason our Windows compiler complains about this static assert
-          // in the cases that should be in the above constexpr path.
+          // For some reason our Windows compiler complains about this static
+          // assert in the cases that should be in the above constexpr path.
           // So simply not compile it in.
           static_assert(std::is_same_v<AqlCallType, AqlCallSet>);
 #endif
@@ -1604,7 +1744,7 @@ auto ExecutionBlockImpl<Executor>::executeFastForward(typename Fetcher::DataRang
  *        SharedAqlItemBlockPtr -> The resulting data
  */
 template <class Executor>
-std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr>
+std::tuple<ExecutionState, SkipResult, SharedAqlItemBlockPtr>
 ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
   if constexpr (isNewStyleExecutor<Executor>) {
     if (!stack.isRelevant()) {
@@ -1612,7 +1752,7 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
       // We are bypassing subqueries.
       // This executor is not allowed to perform actions
       // However we need to maintain the upstream state.
-      size_t skippedLocal = 0;
+      SkipResult skippedLocal;
       typename Fetcher::DataRange bypassedRange{ExecutorState::HASMORE};
       std::tie(_upstreamState, skippedLocal, bypassedRange) =
           executeFetcher(stack, _upstreamRequest);
@@ -1638,25 +1778,44 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
                  _execState == ExecState::UPSTREAM);
     }
 
-    // Skip can only be > 0 if we are in upstream cases.
-    TRI_ASSERT(_skipped == 0 || _execState == ExecState::UPSTREAM);
+    // In some executors we may write something into the output, but then return waiting.
+    // In this case we are not allowed to lose the call we have been working on, we have
+    // noted down created or skipped rows in there.
+    // The client is disallowed to change her mind anyways
+    // so we simply continue to work on the call we already have
+    // The guarantee is, if we have returned the block, and modified
+    // our local call, then the outputItemRow is not initialized
+    if (_outputItemRow != nullptr && _outputItemRow->isInitialized()) {
+      clientCall = _outputItemRow->getClientCall();
+    }
 
-    if constexpr (std::is_same_v<Executor, SubqueryEndExecutor>) {
-      // TODO: implement forwarding of SKIP properly:
-      // We need to modify the execute API to instead return a vector of skipped
-      // values.
-      // Then we can simply push a skip on the Stack here and let it forward.
-      // In case of a modifaction we need to NOT forward a skip, but instead do
-      // a limit := limit + offset call and a hardLimit 0 call on top of the stack.
-      TRI_ASSERT(!clientCall.needSkipMore());
+    // Skip can only be > 0 if we are in upstream cases, or if we got injected a block
+    TRI_ASSERT(_skipped.nothingSkipped() || _execState == ExecState::UPSTREAM ||
+               (std::is_same_v<Executor, IdExecutor<ConstFetcher>>));
+
+    if constexpr (executorHasSideEffects<Executor>) {
+      if (!_skipped.nothingSkipped()) {
+        // We get woken up on upstream, but we have not reported our
+        // local skip value to downstream
+        // In the sideEffect executor we need to apply the skip values on the
+        // incomming stack, which has not been modified yet.
+        // NOTE: We only apply the skipping on subquery level.
+        TRI_ASSERT(_skipped.subqueryDepth() == stack.subqueryLevel() + 1);
+        for (size_t i = 0; i < stack.subqueryLevel(); ++i) {
+          auto skippedSub = _skipped.getSkipOnSubqueryLevel(i);
+          if (skippedSub > 0) {
+            auto& call = stack.modifyCallAtDepth(i);
+            call.didSkip(skippedSub);
+          }
+        }
+      }
+    }
 
+    if constexpr (std::is_same_v<Executor, SubqueryEndExecutor>) {
       // In subqeryEndExecutor we actually manage two calls.
       // The clientClient is defined of what will go into the Executor.
       // on SubqueryEnd this call is generated based on the call from downstream
       stack.pushCall(std::move(clientCall));
-      // TODO: Implement different kind of calls we need to inject into Executor
-      // based on modification, or on forwarding.
-      // FOr now use a fetchUnlimited Call always
       clientCall = AqlCall{};
     }
     if (_execState == ExecState::UPSTREAM) {
@@ -1680,6 +1839,16 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
         case ExecState::CHECKCALL: {
           LOG_QUERY("cfe46", DEBUG)
               << printTypeInfo() << " determine next action on call " << clientCall;
+
+          if constexpr (executorHasSideEffects<Executor>) {
+            // If the executor has sideEffects, and we need to skip the results we would
+            // produce here because we actually skip the subquery, we instead do a
+            // hardLimit 0 (aka FastForward) call instead to the local Executor
+            if (stack.needToSkipSubquery()) {
+              _execState = ExecState::FASTFORWARD;
+              break;
+            }
+          }
           _execState = nextState(clientCall);
           break;
         }
@@ -1705,7 +1874,7 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
                 _executor.skipRowsRange(_lastRange, clientCall);
             if (subqueryState == ExecutionState::WAITING) {
               TRI_ASSERT(skippedLocal == 0);
-              return {subqueryState, 0, nullptr};
+              return {subqueryState, SkipResult{}, nullptr};
             } else if (subqueryState == ExecutionState::DONE) {
               state = ExecutorState::DONE;
             } else {
@@ -1735,7 +1904,7 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
           }
 #endif
           localExecutorState = state;
-          _skipped += skippedLocal;
+          _skipped.didSkip(skippedLocal);
           _engine->_stats += stats;
           // The execute might have modified the client call.
           if (state == ExecutorState::DONE) {
@@ -1787,7 +1956,7 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
             std::tie(subqueryState, stats, call) =
                 _executor.produceRows(_lastRange, *_outputItemRow);
             if (subqueryState == ExecutionState::WAITING) {
-              return {subqueryState, 0, nullptr};
+              return {subqueryState, SkipResult{}, nullptr};
             } else if (subqueryState == ExecutionState::DONE) {
               state = ExecutorState::DONE;
             } else {
@@ -1829,10 +1998,30 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
         case ExecState::FASTFORWARD: {
           LOG_QUERY("96e2c", DEBUG)
               << printTypeInfo() << " all produced, fast forward to end up (sub-)query.";
+
+          AqlCall callCopy = clientCall;
+          if constexpr (executorHasSideEffects<Executor>) {
+            if (stack.needToSkipSubquery()) {
+              // Fast Forward call.
+              callCopy = AqlCall{0, false, 0, AqlCall::LimitType::HARD};
+            }
+          }
+
           auto [state, stats, skippedLocal, call] =
-              executeFastForward(_lastRange, clientCall);
+              executeFastForward(_lastRange, callCopy);
 
-          _skipped += skippedLocal;
+          if constexpr (executorHasSideEffects<Executor>) {
+            if (!stack.needToSkipSubquery()) {
+              // We need to modify the original call.
+              clientCall = callCopy;
+            }
+            // else: We are bypassing the results.
+            // Do not count them here.
+          } else {
+            clientCall = callCopy;
+          }
+
+          _skipped.didSkip(skippedLocal);
           _engine->_stats += stats;
           localExecutorState = state;
 
@@ -1859,14 +2048,13 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
           // executors.
           TRI_ASSERT(isMultiDepExecutor<Executor> || !lastRangeHasDataRow());
           TRI_ASSERT(!_lastRange.hasShadowRow());
-          size_t skippedLocal = 0;
+          SkipResult skippedLocal;
 
 #ifdef ARANGODB_ENABLE_MAINTAINER_MODE
           auto subqueryLevelBefore = stack.subqueryLevel();
 #endif
           std::tie(_upstreamState, skippedLocal, _lastRange) =
               executeFetcher(stack, _upstreamRequest);
-
 #ifdef ARANGODB_ENABLE_MAINTAINER_MODE
           TRI_ASSERT(subqueryLevelBefore == stack.subqueryLevel());
 #endif
@@ -1876,18 +2064,45 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
             // We might have some local accounting to this call.
             _clientRequest = clientCall;
             // We do not return anything in WAITING state, also NOT skipped.
-            return {_upstreamState, 0, nullptr};
+            return {_upstreamState, SkipResult{}, nullptr};
           }
           if constexpr (Executor::Properties::allowsBlockPassthrough ==
                         BlockPassthrough::Enable) {
             // We have a new range, passthrough can use this range.
             _hasUsedDataRangeBlock = false;
           }
+
+          if constexpr (std::is_same_v<Executor, SubqueryEndExecutor>) {
+            // We need to pop the last subquery from the returned skip
+            // We have not asked for a subquery skip.
+            TRI_ASSERT(skippedLocal.getSkipCount() == 0);
+            skippedLocal.decrementSubquery();
+          }
           if constexpr (skipRowsType<Executor>() == SkipRowsRangeVariant::FETCHER) {
-            _skipped += skippedLocal;
             // We skipped through passthrough, so count that a skip was solved.
-            clientCall.didSkip(skippedLocal);
+            _skipped.merge(skippedLocal, false);
+            clientCall.didSkip(skippedLocal.getSkipCount());
+          } else if constexpr (is_one_of_v<Executor, SubqueryStartExecutor, SubqueryEndExecutor>) {
+            // Subquery needs to include the topLevel Skip.
+            // But does not need to apply the count to clientCall.
+            _skipped.merge(skippedLocal, false);
+            // This is what has been asked for by the SubqueryEnd
+            auto subqueryCall = stack.popCall();
+            subqueryCall.didSkip(skippedLocal.getSkipCount());
+            stack.pushCall(std::move(subqueryCall));
+          } else {
+            _skipped.merge(skippedLocal, true);
           }
+          if constexpr (std::is_same_v<Executor, SubqueryStartExecutor>) {
+            // For the subqueryStart, we need to increment the SkipLevel by one
+            // as we may trigger this multiple times, check if we need to do it.
+            while (_skipped.subqueryDepth() < stack.subqueryLevel() + 1) {
+              // In fact, we only need to increase by 1
+              TRI_ASSERT(_skipped.subqueryDepth() == stack.subqueryLevel());
+              _skipped.incrementSubquery();
+            }
+          }
+
           if (_lastRange.hasShadowRow() && !_lastRange.peekShadowRow().isRelevant()) {
             _execState = ExecState::SHADOWROWS;
           } else {
@@ -1924,9 +2139,19 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
           }
 
           TRI_ASSERT(!_outputItemRow->allRowsUsed());
-
-          // This may write one or more rows.
-          _execState = shadowRowForwarding();
+          if constexpr (executorHasSideEffects<Executor>) {
+            _execState = sideEffectShadowRowForwarding(stack, _skipped);
+          } else {
+            // This may write one or more rows.
+            _execState = shadowRowForwarding();
+            if constexpr (std::is_same_v<Executor, SubqueryEndExecutor>) {
+              // we need to update the Top of the stack now
+              std::ignore = stack.popCall();
+              // Copy the call
+              AqlCall modifiedCall = _outputItemRow->getClientCall();
+              stack.pushCall(std::move(modifiedCall));
+            }
+          }
           if constexpr (!std::is_same_v<Executor, SubqueryEndExecutor>) {
             // Produce might have modified the clientCall
             // But only do this if we are not subquery.
@@ -1952,17 +2177,29 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
     _outputItemRow.reset();
 
     // We return skipped here, reset member
-    size_t skipped = _skipped;
-    _skipped = 0;
+    SkipResult skipped = _skipped;
+#ifdef ARANGODB_ENABLE_MAINTAINER_MODE
+    if (!stack.is36Compatible()) {
+      if constexpr (std::is_same_v<Executor, SubqueryEndExecutor>) {
+        TRI_ASSERT(skipped.subqueryDepth() == stack.subqueryLevel() /*we inected a call*/);
+      } else {
+        TRI_ASSERT(skipped.subqueryDepth() == stack.subqueryLevel() + 1 /*we took our call*/);
+      }
+    }
+#endif
+
+    _skipped.reset();
     if (localExecutorState == ExecutorState::HASMORE ||
         _lastRange.hasDataRow() || _lastRange.hasShadowRow()) {
       // We have skipped or/and return data, otherwise we cannot return HASMORE
-      TRI_ASSERT(skipped > 0 || (outputBlock != nullptr && outputBlock->numEntries() > 0));
+      TRI_ASSERT(!skipped.nothingSkipped() ||
+                 (outputBlock != nullptr && outputBlock->numEntries() > 0));
       return {ExecutionState::HASMORE, skipped, std::move(outputBlock)};
     }
-    // We must return skipped and/or data when reportingHASMORE
+    // We must return skipped and/or data when reporting HASMORE
     TRI_ASSERT(_upstreamState != ExecutionState::HASMORE ||
-               (skipped > 0 || (outputBlock != nullptr && outputBlock->numEntries() > 0)));
+               (!skipped.nothingSkipped() ||
+                (outputBlock != nullptr && outputBlock->numEntries() > 0)));
     return {_upstreamState, skipped, std::move(outputBlock)};
   } else {
     // TODO this branch must never be taken with an executor that has not been
diff --git a/arangod/Aql/ExecutionBlockImpl.h b/arangod/Aql/ExecutionBlockImpl.h
index 8e1009c5b518..1b4365c78c40 100644
--- a/arangod/Aql/ExecutionBlockImpl.h
+++ b/arangod/Aql/ExecutionBlockImpl.h
@@ -52,6 +52,8 @@ class InputAqlItemRow;
 class OutputAqlItemRow;
 class Query;
 class ShadowAqlItemRow;
+class SkipResult;
+class ParallelUnsortedGatherExecutor;
 class MultiDependencySingleRowFetcher;
 
 template <typename T, typename... Es>
@@ -223,7 +225,7 @@ class ExecutionBlockImpl final : public ExecutionBlock {
   [[nodiscard]] std::pair<ExecutionState, Result> initializeCursor(InputAqlItemRow const& input) override;
 
   template <class exec = Executor, typename = std::enable_if_t<std::is_same_v<exec, IdExecutor<ConstFetcher>>>>
-  auto injectConstantBlock(SharedAqlItemBlockPtr block) -> void;
+  auto injectConstantBlock(SharedAqlItemBlockPtr block, SkipResult skipped) -> void;
 
   [[nodiscard]] Infos const& infos() const;
 
@@ -242,9 +244,9 @@ class ExecutionBlockImpl final : public ExecutionBlock {
   ///          * WAITING: We have async operation going on, nothing happend, please call again
   ///          * HASMORE: Here is some data in the request range, there is still more, if required call again
   ///          * DONE: Here is some data, and there will be no further data available.
-  ///        2. size_t: Amount of documents skipped.
+  ///        2. SkipResult: Amount of documents skipped.
   ///        3. SharedAqlItemBlockPtr: The next data block.
-  std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> execute(AqlCallStack stack) override;
+  std::tuple<ExecutionState, SkipResult, SharedAqlItemBlockPtr> execute(AqlCallStack stack) override;
 
   template <class exec = Executor, typename = std::enable_if_t<std::is_same_v<exec, IdExecutor<SingleRowFetcher<BlockPassthrough::Enable>>>>>
   [[nodiscard]] RegisterId getOutputRegisterId() const noexcept;
@@ -253,9 +255,9 @@ class ExecutionBlockImpl final : public ExecutionBlock {
   /**
    * @brief Inner execute() part, without the tracing calls.
    */
-  std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> executeWithoutTrace(AqlCallStack stack);
+  std::tuple<ExecutionState, SkipResult, SharedAqlItemBlockPtr> executeWithoutTrace(AqlCallStack stack);
 
-  std::tuple<ExecutionState, size_t, typename Fetcher::DataRange> executeFetcher(
+  std::tuple<ExecutionState, SkipResult, typename Fetcher::DataRange> executeFetcher(
       AqlCallStack& stack, AqlCallType const& aqlCall);
 
   std::tuple<ExecutorState, typename Executor::Stats, AqlCallType> executeProduceRows(
@@ -329,6 +331,26 @@ class ExecutionBlockImpl final : public ExecutionBlock {
 
   void resetExecutor();
 
+  // Forwarding of ShadowRows if the executor has SideEffects.
+  // This skips over ShadowRows, and counts them in the correct
+  // position of the callStack as "skipped".
+  // as soon as we reach a place where there is no skip
+  // ordered in the outer shadow rows, this call
+  // will fall back to shadowRowForwardning.
+  [[nodiscard]] auto sideEffectShadowRowForwarding(AqlCallStack& stack,
+                                                   SkipResult& skipResult) -> ExecState;
+
+  /**
+   * @brief Transition to the next state after shadowRows
+   *
+   * @param state the state returned by the getShadowRowCall
+   * @param range the current data range
+   * @return ExecState The next state
+   */
+  [[nodiscard]] auto nextStateAfterShadowRows(ExecutorState const& state,
+                                              DataRange const& range) const
+      noexcept -> ExecState;
+
   void initOnce();
 
   [[nodiscard]] auto executorNeedsCall(AqlCallType& call) const noexcept -> bool;
@@ -361,7 +383,7 @@ class ExecutionBlockImpl final : public ExecutionBlock {
 
   InternalState _state;
 
-  size_t _skipped{};
+  SkipResult _skipped{};
 
   DataRange _lastRange;
 
diff --git a/arangod/Aql/ExecutionEngine.cpp b/arangod/Aql/ExecutionEngine.cpp
index 2fa51ea000df..a4e30799654e 100644
--- a/arangod/Aql/ExecutionEngine.cpp
+++ b/arangod/Aql/ExecutionEngine.cpp
@@ -39,6 +39,7 @@
 #include "Aql/QueryRegistry.h"
 #include "Aql/RemoteExecutor.h"
 #include "Aql/ReturnExecutor.h"
+#include "Aql/SkipResult.h"
 #include "Aql/WalkerWorker.h"
 #include "Basics/ScopeGuard.h"
 #include "Cluster/ServerState.h"
@@ -564,16 +565,16 @@ std::pair<ExecutionState, Result> ExecutionEngine::initializeCursor(SharedAqlIte
 }
 
 auto ExecutionEngine::execute(AqlCallStack const& stack)
-    -> std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> {
+    -> std::tuple<ExecutionState, SkipResult, SharedAqlItemBlockPtr> {
   if (_query.killed()) {
     THROW_ARANGO_EXCEPTION(TRI_ERROR_QUERY_KILLED);
   }
   auto const res = _root->execute(stack);
 #ifdef ARANGODB_ENABLE_MAINTAINER_MODE
   if (std::get<ExecutionState>(res) == ExecutionState::WAITING) {
-    auto const skipped = std::get<size_t>(res);
+    auto const skipped = std::get<SkipResult>(res);
     auto const block = std::get<SharedAqlItemBlockPtr>(res);
-    TRI_ASSERT(skipped == 0);
+    TRI_ASSERT(skipped.nothingSkipped());
     TRI_ASSERT(block == nullptr);
   }
 #endif
@@ -581,7 +582,7 @@ auto ExecutionEngine::execute(AqlCallStack const& stack)
 }
 
 auto ExecutionEngine::executeForClient(AqlCallStack const& stack, std::string const& clientId)
-    -> std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> {
+    -> std::tuple<ExecutionState, SkipResult, SharedAqlItemBlockPtr> {
   if (_query.killed()) {
     THROW_ARANGO_EXCEPTION(TRI_ERROR_QUERY_KILLED);
   }
@@ -597,9 +598,9 @@ auto ExecutionEngine::executeForClient(AqlCallStack const& stack, std::string co
   auto const res = rootBlock->executeForClient(stack, clientId);
 #ifdef ARANGODB_ENABLE_MAINTAINER_MODE
   if (std::get<ExecutionState>(res) == ExecutionState::WAITING) {
-    auto const skipped = std::get<size_t>(res);
+    auto const skipped = std::get<SkipResult>(res);
     auto const& block = std::get<SharedAqlItemBlockPtr>(res);
-    TRI_ASSERT(skipped == 0);
+    TRI_ASSERT(skipped.nothingSkipped());
     TRI_ASSERT(block == nullptr);
   }
 #endif
@@ -621,7 +622,7 @@ std::pair<ExecutionState, SharedAqlItemBlockPtr> ExecutionEngine::getSome(size_t
   AqlCallStack compatibilityStack{AqlCall::SimulateGetSome(atMost), true};
   auto const [state, skipped, block] = _root->execute(std::move(compatibilityStack));
   // We cannot trigger a skip operation from here
-  TRI_ASSERT(skipped == 0);
+  TRI_ASSERT(skipped.nothingSkipped());
   return {state, block};
 }
 
@@ -643,7 +644,7 @@ std::pair<ExecutionState, size_t> ExecutionEngine::skipSome(size_t atMost) {
   // We cannot be triggered within a subquery from earlier versions.
   // Also we cannot produce anything ourselfes here.
   TRI_ASSERT(block == nullptr);
-  return {state, skipped};
+  return {state, skipped.getSkipCount()};
 }
 
 Result ExecutionEngine::shutdownSync(int errorCode) noexcept try {
diff --git a/arangod/Aql/ExecutionEngine.h b/arangod/Aql/ExecutionEngine.h
index f9af9ff3d2c2..2b51c217ff6f 100644
--- a/arangod/Aql/ExecutionEngine.h
+++ b/arangod/Aql/ExecutionEngine.h
@@ -47,6 +47,7 @@ class ExecutionNode;
 class ExecutionPlan;
 class QueryRegistry;
 class Query;
+class SkipResult;
 enum class SerializationFormat;
 
 class ExecutionEngine {
@@ -98,10 +99,10 @@ class ExecutionEngine {
   std::pair<ExecutionState, Result> shutdown(int errorCode);
 
   auto execute(AqlCallStack const& stack)
-      -> std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr>;
+      -> std::tuple<ExecutionState, SkipResult, SharedAqlItemBlockPtr>;
 
   auto executeForClient(AqlCallStack const& stack, std::string const& clientId)
-      -> std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr>;
+      -> std::tuple<ExecutionState, SkipResult, SharedAqlItemBlockPtr>;
 
   /// @brief getSome
   std::pair<ExecutionState, SharedAqlItemBlockPtr> getSome(size_t atMost);
diff --git a/arangod/Aql/ModificationExecutor.cpp b/arangod/Aql/ModificationExecutor.cpp
index 6554c6574fed..f3712fd09199 100644
--- a/arangod/Aql/ModificationExecutor.cpp
+++ b/arangod/Aql/ModificationExecutor.cpp
@@ -201,7 +201,6 @@ template <typename FetcherType, typename ModifierType>
     doCollect(input, output.numRowsLeft());
     upstreamState = input.upstreamState();
   }
-
   if (_modifier.nrOfOperations() > 0) {
     _modifier.transact();
 
@@ -266,7 +265,6 @@ template <typename FetcherType, typename ModifierType>
         stats.addWritesExecuted(_modifier.nrOfWritesExecuted());
         stats.addWritesIgnored(_modifier.nrOfWritesIgnored());
       }
-
       call.didSkip(_modifier.nrOfOperations());
     }
   }
diff --git a/arangod/Aql/MultiDependencySingleRowFetcher.cpp b/arangod/Aql/MultiDependencySingleRowFetcher.cpp
index b275f0c19567..fba33607ad79 100644
--- a/arangod/Aql/MultiDependencySingleRowFetcher.cpp
+++ b/arangod/Aql/MultiDependencySingleRowFetcher.cpp
@@ -147,6 +147,8 @@ std::pair<ExecutionState, ShadowAqlItemRow> MultiDependencySingleRowFetcher::fet
         ++dep._rowIndex;
       }
     }
+    // We have delivered a shadowRow, we now may get additional subquery skip counters again.
+    _didReturnSubquerySkips = false;
   }
 
   ExecutionState const state = allDone ? ExecutionState::DONE : ExecutionState::HASMORE;
@@ -370,11 +372,11 @@ auto MultiDependencySingleRowFetcher::useStack(AqlCallStack const& stack) -> voi
 
 auto MultiDependencySingleRowFetcher::executeForDependency(size_t const dependency,
                                                            AqlCallStack& stack)
-    -> std::tuple<ExecutionState, size_t, AqlItemBlockInputRange> {
+    -> std::tuple<ExecutionState, SkipResult, AqlItemBlockInputRange> {
   auto [state, skipped, block] = _dependencyProxy->executeForDependency(dependency, stack);
 
   if (state == ExecutionState::WAITING) {
-    return {state, 0, AqlItemBlockInputRange{ExecutorState::HASMORE}};
+    return {state, SkipResult{}, AqlItemBlockInputRange{ExecutorState::HASMORE}};
   }
   ExecutorState execState =
       state == ExecutionState::DONE ? ExecutorState::DONE : ExecutorState::HASMORE;
@@ -382,16 +384,17 @@ auto MultiDependencySingleRowFetcher::executeForDependency(size_t const dependen
   _dependencyStates.at(dependency) = state;
 
   if (block == nullptr) {
-    return {state, skipped, AqlItemBlockInputRange{execState, skipped}};
+    return {state, skipped, AqlItemBlockInputRange{execState, skipped.getSkipCount()}};
   }
   TRI_ASSERT(block != nullptr);
   auto [start, end] = block->getRelevantRange();
-  return {state, skipped, AqlItemBlockInputRange{execState, skipped, block, start}};
+  return {state, skipped,
+          AqlItemBlockInputRange{execState, skipped.getSkipCount(), block, start}};
 }
 
 auto MultiDependencySingleRowFetcher::execute(AqlCallStack const& stack,
                                               AqlCallSet const& aqlCallSet)
-    -> std::tuple<ExecutionState, size_t, std::vector<std::pair<size_t, AqlItemBlockInputRange>>> {
+    -> std::tuple<ExecutionState, SkipResult, std::vector<std::pair<size_t, AqlItemBlockInputRange>>> {
   TRI_ASSERT(_callsInFlight.size() == numberDependencies());
 
   auto ranges = std::vector<std::pair<size_t, AqlItemBlockInputRange>>{};
@@ -400,7 +403,7 @@ auto MultiDependencySingleRowFetcher::execute(AqlCallStack const& stack,
   auto depCallIdx = size_t{0};
   auto allAskedDepsAreWaiting = true;
   auto askedAtLeastOneDep = false;
-  auto skippedTotal = size_t{0};
+  auto skippedTotal = SkipResult{};
   // Iterate in parallel over `_callsInFlight` and `aqlCall.calls`.
   // _callsInFlight[i] corresponds to aqlCalls.calls[k] iff
   // aqlCalls.calls[k].dependency = i.
@@ -435,16 +438,46 @@ auto MultiDependencySingleRowFetcher::execute(AqlCallStack const& stack,
         // Got a result, call is no longer in flight
         maybeCallInFlight = std::nullopt;
         allAskedDepsAreWaiting = false;
+
+        // NOTE:
+        // in this fetcher case we do not have and do not want to have
+        // any control of the order the upstream responses are entering.
+        // Every of the upstream response will contain an identical skipped
+        // stack on the subqueries.
+        // We only need to forward the skipping of any one of those.
+        // So we implemented the following logic to return the skip
+        // information for the first on that arrives and all other
+        // subquery skip informations will be discarded.
+        if (!_didReturnSubquerySkips) {
+          // We have nothing skipped locally.
+          TRI_ASSERT(skippedTotal.subqueryDepth() == 1);
+          TRI_ASSERT(skippedTotal.getSkipCount() == 0);
+
+          // We forward the skip block as is.
+          // This will also include the skips on subquery level
+          skippedTotal = skipped;
+          // Do this only once.
+          // The first response will contain the amount of rows skipped
+          // in subquery
+          _didReturnSubquerySkips = true;
+        } else {
+          // We only need the skip amount on the top level.
+          // Another dependency has forwarded the subquery level skips
+          // already
+          skippedTotal.mergeOnlyTopLevel(skipped);
+        }
+
       } else {
-        TRI_ASSERT(skipped == 0);
+        TRI_ASSERT(skipped.nothingSkipped());
       }
-      skippedTotal += skipped;
+
       ranges.emplace_back(dependency, range);
     }
   }
 
   auto const state = std::invoke([&]() {
     if (askedAtLeastOneDep && allAskedDepsAreWaiting) {
+      TRI_ASSERT(skippedTotal.nothingSkipped());
       return ExecutionState::WAITING;
     } else {
       return upstreamState();
diff --git a/arangod/Aql/MultiDependencySingleRowFetcher.h b/arangod/Aql/MultiDependencySingleRowFetcher.h
index 277ebf628997..13358f5e95c4 100644
--- a/arangod/Aql/MultiDependencySingleRowFetcher.h
+++ b/arangod/Aql/MultiDependencySingleRowFetcher.h
@@ -39,6 +39,7 @@ class AqlItemBlock;
 template <BlockPassthrough>
 class DependencyProxy;
 class ShadowAqlItemRow;
+class SkipResult;
 
 /**
  * @brief Interface for all AqlExecutors that do need one
@@ -137,10 +138,10 @@ class MultiDependencySingleRowFetcher {
   auto useStack(AqlCallStack const& stack) -> void;
 
   [[nodiscard]] auto execute(AqlCallStack const&, AqlCallSet const&)
-      -> std::tuple<ExecutionState, size_t, std::vector<std::pair<size_t, AqlItemBlockInputRange>>>;
+      -> std::tuple<ExecutionState, SkipResult, std::vector<std::pair<size_t, AqlItemBlockInputRange>>>;
 
   [[nodiscard]] auto executeForDependency(size_t dependency, AqlCallStack& stack)
-      -> std::tuple<ExecutionState, size_t, AqlItemBlockInputRange>;
+      -> std::tuple<ExecutionState, SkipResult, AqlItemBlockInputRange>;
 
   [[nodiscard]] auto upstreamState() const -> ExecutionState;
 
@@ -158,6 +159,8 @@ class MultiDependencySingleRowFetcher {
   ///        in initOnce() to make sure that init() is called exactly once.
   std::vector<std::optional<AqlCallStack>> _callsInFlight;
 
+  bool _didReturnSubquerySkips{false};
+
  private:
   /**
    * @brief Delegates to ExecutionBlock::fetchBlock()
diff --git a/arangod/Aql/OptimizerRules.cpp b/arangod/Aql/OptimizerRules.cpp
index 0d344f22e0cb..9cd9e7b83bd2 100644
--- a/arangod/Aql/OptimizerRules.cpp
+++ b/arangod/Aql/OptimizerRules.cpp
@@ -74,9 +74,9 @@
 
 namespace {
 
-bool accessesCollectionVariable(arangodb::aql::ExecutionPlan const* plan,
-                                arangodb::aql::ExecutionNode const* node,
-                                ::arangodb::containers::HashSet<arangodb::aql::Variable const*>& vars) {
+bool accessesCollectionVariable(
+    arangodb::aql::ExecutionPlan const* plan, arangodb::aql::ExecutionNode const* node,
+    ::arangodb::containers::HashSet<arangodb::aql::Variable const*>& vars) {
   using EN = arangodb::aql::ExecutionNode;
 
   if (node->getType() == EN::CALCULATION) {
@@ -5796,9 +5796,9 @@ void arangodb::aql::optimizeTraversalsRule(Optimizer* opt,
     if (outVariable != nullptr && !n->isVarUsedLater(outVariable) &&
         std::find(pruneVars.begin(), pruneVars.end(), outVariable) == pruneVars.end()) {
       outVariable = traversal->pathOutVariable();
-      if (outVariable == nullptr ||
-          (!n->isVarUsedLater(outVariable) &&
-           std::find(pruneVars.begin(), pruneVars.end(), outVariable) == pruneVars.end())) {
+      if (outVariable == nullptr || (!n->isVarUsedLater(outVariable) &&
+                                     std::find(pruneVars.begin(), pruneVars.end(),
+                                               outVariable) == pruneVars.end())) {
         // both traversal vertex and path outVariables not used later
         traversal->options()->setProduceVertices(false);
         modified = true;
@@ -7275,12 +7275,12 @@ void arangodb::aql::moveFiltersIntoEnumerateRule(Optimizer* opt,
         ExecutionNode* filterParent = current->getFirstParent();
         TRI_ASSERT(filterParent != nullptr);
         plan->unlinkNode(current);
-          
+
         if (!current->isVarUsedLater(cn->outVariable())) {
           // also remove the calculation node
           plan->unlinkNode(cn);
         }
-        
+
         current = filterParent;
         modified = true;
       } else if (current->getType() == EN::CALCULATION) {
@@ -7403,19 +7403,11 @@ bool nodeMakesThisQueryLevelUnsuitableForSubquerySplicing(ExecutionNode const* n
     case ExecutionNode::DISTRIBUTE_CONSUMER:
     case ExecutionNode::SUBQUERY_START:
     case ExecutionNode::SUBQUERY_END:
-      // These nodes do not initiate a skip themselves, and thus are fine.
-      return false;
     case ExecutionNode::NORESULTS:
-      // no results currently cannot work, as they do not fetch from above.
     case ExecutionNode::LIMIT:
-      // limit blocks currently cannot work, both due to skipping and due to the
-      // limit and passthrough, which forbids passing shadow rows.
-      return true;
-    case ExecutionNode::COLLECT: {
-      auto const collectNode = ExecutionNode::castTo<CollectNode const*>(node);
-      // Collect nodes skip iff using the COUNT method.
-      return collectNode->aggregationMethod() == CollectOptions::CollectMethod::COUNT;
-    }
+    case ExecutionNode::COLLECT:
+      // These nodes are fine
+      return false;
     case ExecutionNode::MAX_NODE_TYPE_VALUE:
       break;
   }
@@ -7425,7 +7417,7 @@ bool nodeMakesThisQueryLevelUnsuitableForSubquerySplicing(ExecutionNode const* n
       "report this error. Try turning off the splice-subqueries rule to get "
       "your query working.",
       node->getTypeString().c_str());
-}
+}  // namespace
 
 void findSubqueriesSuitableForSplicing(ExecutionPlan const& plan,
                                        containers::SmallVector<SubqueryNode*>& result) {
diff --git a/arangod/Aql/RemoteExecutor.cpp b/arangod/Aql/RemoteExecutor.cpp
index c231fc4cb91e..f2f4afebd700 100644
--- a/arangod/Aql/RemoteExecutor.cpp
+++ b/arangod/Aql/RemoteExecutor.cpp
@@ -31,6 +31,7 @@
 #include "Aql/InputAqlItemRow.h"
 #include "Aql/Query.h"
 #include "Aql/RestAqlHandler.h"
+#include "Aql/SkipResult.h"
 #include "Basics/MutexLocker.h"
 #include "Basics/StringBuffer.h"
 #include "Basics/VelocyPackHelper.h"
@@ -153,8 +154,7 @@ std::pair<ExecutionState, SharedAqlItemBlockPtr> ExecutionBlockImpl<RemoteExecut
     traceGetSomeRequest(builder.slice(), atMost);
   }
 
-  auto res = sendAsyncRequest(fuerte::RestVerb::Put, "/_api/aql/getSome",
-                              std::move(buffer));
+  auto res = sendAsyncRequest(fuerte::RestVerb::Put, "/_api/aql/getSome", std::move(buffer));
 
   if (!res.ok()) {
     THROW_ARANGO_EXCEPTION(res);
@@ -432,7 +432,7 @@ std::pair<ExecutionState, Result> ExecutionBlockImpl<RemoteExecutor>::shutdown(i
 }
 
 auto ExecutionBlockImpl<RemoteExecutor>::executeViaOldApi(AqlCallStack stack)
-    -> std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> {
+    -> std::tuple<ExecutionState, SkipResult, SharedAqlItemBlockPtr> {
   // Use the old getSome/SkipSome API.
   auto myCall = stack.popCall();
 
@@ -444,7 +444,9 @@ auto ExecutionBlockImpl<RemoteExecutor>::executeViaOldApi(AqlCallStack stack)
     if (state != ExecutionState::WAITING) {
       myCall.didSkip(skipped);
     }
-    return {state, skipped, nullptr};
+    SkipResult skipRes{};
+    skipRes.didSkip(skipped);
+    return {state, skipRes, nullptr};
   } else if (AqlCall::IsGetSomeCall(myCall)) {
     auto const [state, block] = getSomeWithoutTrace(myCall.getLimit());
     // We do not need to count as softLimit will be overwritten, and hard cannot be set.
@@ -452,20 +454,22 @@ auto ExecutionBlockImpl<RemoteExecutor>::executeViaOldApi(AqlCallStack stack)
       // However we can do a short-cut here to report DONE on hardLimit if we are on the top-level query.
       myCall.didProduce(block->size());
       if (myCall.getLimit() == 0) {
-        return {ExecutionState::DONE, 0, block};
+        return {ExecutionState::DONE, SkipResult{}, block};
       }
     }
 
-    return {state, 0, block};
+    return {state, SkipResult{}, block};
   } else if (AqlCall::IsFullCountCall(myCall)) {
     auto const [state, skipped] = skipSome(ExecutionBlock::SkipAllSize());
     if (state != ExecutionState::WAITING) {
       myCall.didSkip(skipped);
     }
-    return {state, skipped, nullptr};
+    SkipResult skipRes{};
+    skipRes.didSkip(skipped);
+    return {state, skipRes, nullptr};
   } else if (AqlCall::IsFastForwardCall(myCall)) {
     // No idea if DONE is correct here...
-    return {ExecutionState::DONE, 0, nullptr};
+    return {ExecutionState::DONE, SkipResult{}, nullptr};
   }
 
   // Should never get here!
@@ -473,14 +477,14 @@ auto ExecutionBlockImpl<RemoteExecutor>::executeViaOldApi(AqlCallStack stack)
 }
 
 auto ExecutionBlockImpl<RemoteExecutor>::execute(AqlCallStack stack)
-    -> std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> {
+    -> std::tuple<ExecutionState, SkipResult, SharedAqlItemBlockPtr> {
   traceExecuteBegin(stack);
   auto res = executeWithoutTrace(stack);
   return traceExecuteEnd(res);
 }
 
 auto ExecutionBlockImpl<RemoteExecutor>::executeWithoutTrace(AqlCallStack stack)
--> std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> {
+    -> std::tuple<ExecutionState, SkipResult, SharedAqlItemBlockPtr> {
   if (ADB_UNLIKELY(api() == Api::GET_SOME)) {
     return executeViaOldApi(stack);
   }
@@ -489,7 +493,7 @@ auto ExecutionBlockImpl<RemoteExecutor>::executeWithoutTrace(AqlCallStack stack)
 }
 
 auto ExecutionBlockImpl<RemoteExecutor>::executeViaNewApi(AqlCallStack callStack)
-    -> std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> {
+    -> std::tuple<ExecutionState, SkipResult, SharedAqlItemBlockPtr> {
   // silence tests -- we need to introduce new failure tests for fetchers
   TRI_IF_FAILURE("ExecutionBlock::getOrSkipSome1") {
     THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
@@ -509,7 +513,7 @@ auto ExecutionBlockImpl<RemoteExecutor>::executeViaNewApi(AqlCallStack callStack
 
   if (_requestInFlight) {
     // Already sent a shutdown request, but haven't got an answer yet.
-    return {ExecutionState::WAITING, 0, nullptr};
+    return {ExecutionState::WAITING, SkipResult{}, nullptr};
   }
 
   // For every call we simply forward via HTTP
@@ -553,7 +557,7 @@ auto ExecutionBlockImpl<RemoteExecutor>::executeViaNewApi(AqlCallStack callStack
     THROW_ARANGO_EXCEPTION(res);
   }
 
-  return {ExecutionState::WAITING, 0, nullptr};
+  return {ExecutionState::WAITING, SkipResult{}, nullptr};
 }
 
 auto ExecutionBlockImpl<RemoteExecutor>::deserializeExecuteCallResultBody(VPackSlice const slice) const
@@ -564,14 +568,16 @@ auto ExecutionBlockImpl<RemoteExecutor>::deserializeExecuteCallResultBody(VPackS
 
   if (ADB_UNLIKELY(!slice.isObject())) {
     using namespace std::string_literals;
-    return Result{TRI_ERROR_TYPE_ERROR, "When parsing execute result: expected object, got "s + slice.typeName()};
+    return Result{TRI_ERROR_TYPE_ERROR,
+                  "When parsing execute result: expected object, got "s + slice.typeName()};
   }
 
   if (auto value = slice.get(StaticStrings::AqlRemoteResult); !value.isNone()) {
     return AqlExecuteResult::fromVelocyPack(value, _engine->itemBlockManager());
   }
 
-  return Result{TRI_ERROR_TYPE_ERROR, "When parsing execute result: field result missing"};
+  return Result{TRI_ERROR_TYPE_ERROR,
+                "When parsing execute result: field result missing"};
 }
 
 auto ExecutionBlockImpl<RemoteExecutor>::serializeExecuteCallBody(AqlCallStack const& callStack) const
@@ -661,10 +667,10 @@ Result ExecutionBlockImpl<RemoteExecutor>::sendAsyncRequest(fuerte::RestVerb typ
     req->header.addMeta("x-shard-id", _ownName);
     req->header.addMeta("shard-id", _ownName);  // deprecated in 3.7, remove later
   }
-  
+
   LOG_TOPIC("2713c", DEBUG, Logger::COMMUNICATION)
-      << "request to '" << _server
-      << "' '" << fuerte::to_string(type) << " " << req->header.path << "'";
+      << "request to '" << _server << "' '" << fuerte::to_string(type) << " "
+      << req->header.path << "'";
 
   network::ConnectionPtr conn = pool->leaseConnection(spec.endpoint);
 
diff --git a/arangod/Aql/RemoteExecutor.h b/arangod/Aql/RemoteExecutor.h
index 49244489cf00..cd8da9a7afbb 100644
--- a/arangod/Aql/RemoteExecutor.h
+++ b/arangod/Aql/RemoteExecutor.h
@@ -32,12 +32,16 @@
 
 #include <mutex>
 
-namespace arangodb::fuerte { inline namespace v1 {
+namespace arangodb::fuerte {
+inline namespace v1 {
 enum class RestVerb;
-}}
+}
+}  // namespace arangodb::fuerte
 
 namespace arangodb::aql {
 
+class SkipResult;
+
 // The RemoteBlock is actually implemented by specializing ExecutionBlockImpl,
 // so this class only exists to identify the specialization.
 class RemoteExecutor final {};
@@ -67,7 +71,7 @@ class ExecutionBlockImpl<RemoteExecutor> : public ExecutionBlock {
 
   std::pair<ExecutionState, Result> shutdown(int errorCode) override;
 
-  std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> execute(AqlCallStack stack) override;
+  std::tuple<ExecutionState, SkipResult, SharedAqlItemBlockPtr> execute(AqlCallStack stack) override;
 
   [[nodiscard]] auto api() const noexcept -> Api;
 
@@ -85,13 +89,13 @@ class ExecutionBlockImpl<RemoteExecutor> : public ExecutionBlock {
   std::pair<ExecutionState, size_t> skipSomeWithoutTrace(size_t atMost);
 
   auto executeWithoutTrace(AqlCallStack stack)
-      -> std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr>;
+      -> std::tuple<ExecutionState, SkipResult, SharedAqlItemBlockPtr>;
 
   auto executeViaOldApi(AqlCallStack stack)
-      -> std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr>;
+      -> std::tuple<ExecutionState, SkipResult, SharedAqlItemBlockPtr>;
 
   auto executeViaNewApi(AqlCallStack stack)
-      -> std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr>;
+      -> std::tuple<ExecutionState, SkipResult, SharedAqlItemBlockPtr>;
 
   [[nodiscard]] auto deserializeExecuteCallResultBody(velocypack::Slice) const
       -> ResultT<AqlExecuteResult>;
@@ -166,6 +170,6 @@ class ExecutionBlockImpl<RemoteExecutor> : public ExecutionBlock {
   Api _apiToUse = Api::EXECUTE;
 };
 
-}  // namespace arangodb
+}  // namespace arangodb::aql
 
 #endif  // ARANGOD_AQL_REMOTE_EXECUTOR_H
diff --git a/arangod/Aql/RestAqlHandler.cpp b/arangod/Aql/RestAqlHandler.cpp
index fa57a645b8b2..725eac165320 100644
--- a/arangod/Aql/RestAqlHandler.cpp
+++ b/arangod/Aql/RestAqlHandler.cpp
@@ -740,7 +740,7 @@ RestStatus RestAqlHandler::handleUseQuery(std::string const& operation,
     auto& executeCall = maybeExecuteCall.get();
 
     auto items = SharedAqlItemBlockPtr{};
-    auto skipped = size_t{};
+    auto skipped = SkipResult{};
     auto state = ExecutionState::HASMORE;
 
     // shardId is set IFF the root node is scatter or distribute
diff --git a/arangod/Aql/ScatterExecutor.cpp b/arangod/Aql/ScatterExecutor.cpp
index bdf56efdb391..b81449906d9a 100644
--- a/arangod/Aql/ScatterExecutor.cpp
+++ b/arangod/Aql/ScatterExecutor.cpp
@@ -64,10 +64,11 @@ auto ScatterExecutor::ClientBlockData::clear() -> void {
   _executorHasMore = false;
 }
 
-auto ScatterExecutor::ClientBlockData::addBlock(SharedAqlItemBlockPtr block) -> void {
+auto ScatterExecutor::ClientBlockData::addBlock(SharedAqlItemBlockPtr block,
+                                                SkipResult skipped) -> void {
   // NOTE:
-  // There given ItemBlock will be reused in all requesting blocks.
-  // However, the next followwing block could be passthrough.
+  // The given ItemBlock will be reused in all requesting blocks.
+  // However, the next following block could be passthrough.
   // If it is, it will modify that data stored in block.
   // If now anther client requests the same block, it is not
   // the original any more, but a modified version.
@@ -75,20 +76,20 @@ auto ScatterExecutor::ClientBlockData::addBlock(SharedAqlItemBlockPtr block) ->
   // is empty. If another peer-calculation has written to this value
   // this assertion does not hold true anymore.
   // Hence we are required to do an indepth cloning here.
-  _queue.emplace_back(block->slice(0, block->size()));
+  _queue.emplace_back(block->slice(0, block->size()), skipped);
 }
 
 auto ScatterExecutor::ClientBlockData::hasDataFor(AqlCall const& call) -> bool {
   return _executorHasMore || !_queue.empty();
 }
 
-auto ScatterExecutor::ClientBlockData::execute(AqlCall call, ExecutionState upstreamState)
-    -> std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> {
+auto ScatterExecutor::ClientBlockData::execute(AqlCallStack callStack, ExecutionState upstreamState)
+    -> std::tuple<ExecutionState, SkipResult, SharedAqlItemBlockPtr> {
   TRI_ASSERT(_executor != nullptr);
   // Make sure we actually have data before you call execute
-  TRI_ASSERT(hasDataFor(call));
+  TRI_ASSERT(hasDataFor(callStack.peek()));
   if (!_executorHasMore) {
-    auto const& block = _queue.front();
+    auto const& [block, skipResult] = _queue.front();
     // This cast is guaranteed, we create this a couple lines above and only
     // this executor is used here.
     // Unfortunately i did not get a version compiled were i could only forward
@@ -96,12 +97,11 @@ auto ScatterExecutor::ClientBlockData::execute(AqlCall call, ExecutionState upst
     auto casted =
         static_cast<ExecutionBlockImpl<IdExecutor<ConstFetcher>>*>(_executor.get());
     TRI_ASSERT(casted != nullptr);
-    casted->injectConstantBlock(block);
+    casted->injectConstantBlock(block, skipResult);
     _executorHasMore = true;
     _queue.pop_front();
   }
-  AqlCallStack stack{call};
-  auto [state, skipped, result] = _executor->execute(stack);
+  auto [state, skipped, result] = _executor->execute(callStack);
 
   // We have all data locally cannot wait here.
   TRI_ASSERT(state != ExecutionState::WAITING);
@@ -124,12 +124,12 @@ auto ScatterExecutor::ClientBlockData::execute(AqlCall call, ExecutionState upst
 
 ScatterExecutor::ScatterExecutor(ExecutorInfos const&){};
 
-auto ScatterExecutor::distributeBlock(SharedAqlItemBlockPtr block,
+auto ScatterExecutor::distributeBlock(SharedAqlItemBlockPtr block, SkipResult skipped,
                                       std::unordered_map<std::string, ClientBlockData>& blockMap) const
     -> void {
   // Scatter returns every block on every client as is.
   for (auto& [id, list] : blockMap) {
-    list.addBlock(block);
+    list.addBlock(block, skipped);
   }
 }
 
diff --git a/arangod/Aql/ScatterExecutor.h b/arangod/Aql/ScatterExecutor.h
index 53bd1bb1b5c5..10a1316cec02 100644
--- a/arangod/Aql/ScatterExecutor.h
+++ b/arangod/Aql/ScatterExecutor.h
@@ -31,6 +31,7 @@
 namespace arangodb {
 namespace aql {
 
+class SkipResult;
 class ExecutionEngine;
 class ScatterNode;
 
@@ -56,14 +57,14 @@ class ScatterExecutor {
                     ExecutorInfos const& scatterInfos);
 
     auto clear() -> void;
-    auto addBlock(SharedAqlItemBlockPtr block) -> void;
+    auto addBlock(SharedAqlItemBlockPtr block, SkipResult skipped) -> void;
     auto hasDataFor(AqlCall const& call) -> bool;
 
-    auto execute(AqlCall call, ExecutionState upstreamState)
-        -> std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr>;
+    auto execute(AqlCallStack callStack, ExecutionState upstreamState)
+        -> std::tuple<ExecutionState, SkipResult, SharedAqlItemBlockPtr>;
 
    private:
-    std::deque<SharedAqlItemBlockPtr> _queue;
+    std::deque<std::tuple<SharedAqlItemBlockPtr, SkipResult>> _queue;
     // This is unique_ptr to get away with everything beeing forward declared...
     std::unique_ptr<ExecutionBlock> _executor;
     bool _executorHasMore;
@@ -72,7 +73,7 @@ class ScatterExecutor {
   ScatterExecutor(ExecutorInfos const&);
   ~ScatterExecutor() = default;
 
-  auto distributeBlock(SharedAqlItemBlockPtr block,
+  auto distributeBlock(SharedAqlItemBlockPtr block, SkipResult skipped,
                        std::unordered_map<std::string, ClientBlockData>& blockMap) const
       -> void;
 };
diff --git a/arangod/Aql/SingleRowFetcher.cpp b/arangod/Aql/SingleRowFetcher.cpp
index 62e054c5b875..44acf7bdc00a 100644
--- a/arangod/Aql/SingleRowFetcher.cpp
+++ b/arangod/Aql/SingleRowFetcher.cpp
@@ -30,6 +30,7 @@
 #include "Aql/ExecutionBlock.h"
 #include "Aql/ExecutionState.h"
 #include "Aql/InputAqlItemRow.h"
+#include "Aql/SkipResult.h"
 
 using namespace arangodb;
 using namespace arangodb::aql;
@@ -77,28 +78,31 @@ SingleRowFetcher<passBlocksThrough>::fetchBlockForPassthrough(size_t atMost) {
 }
 
 template <BlockPassthrough passBlocksThrough>
-std::tuple<ExecutionState, size_t, AqlItemBlockInputRange>
+std::tuple<ExecutionState, SkipResult, AqlItemBlockInputRange>
 SingleRowFetcher<passBlocksThrough>::execute(AqlCallStack& stack) {
   auto [state, skipped, block] = _dependencyProxy->execute(stack);
   if (state == ExecutionState::WAITING) {
     // On waiting we have nothing to return
-    return {state, 0, AqlItemBlockInputRange{ExecutorState::HASMORE}};
+    return {state, SkipResult{}, AqlItemBlockInputRange{ExecutorState::HASMORE}};
   }
   if (block == nullptr) {
     if (state == ExecutionState::HASMORE) {
-      return {state, skipped, AqlItemBlockInputRange{ExecutorState::HASMORE, skipped}};
+      return {state, skipped,
+              AqlItemBlockInputRange{ExecutorState::HASMORE, skipped.getSkipCount()}};
     }
-    return {state, skipped, AqlItemBlockInputRange{ExecutorState::DONE, skipped}};
+    return {state, skipped,
+            AqlItemBlockInputRange{ExecutorState::DONE, skipped.getSkipCount()}};
   }
 
   auto [start, end] = block->getRelevantRange();
   if (state == ExecutionState::HASMORE) {
     TRI_ASSERT(block != nullptr);
     return {state, skipped,
-            AqlItemBlockInputRange{ExecutorState::HASMORE, skipped, block, start}};
+            AqlItemBlockInputRange{ExecutorState::HASMORE,
+                                   skipped.getSkipCount(), block, start}};
   }
   return {state, skipped,
-          AqlItemBlockInputRange{ExecutorState::DONE, skipped, block, start}};
+          AqlItemBlockInputRange{ExecutorState::DONE, skipped.getSkipCount(), block, start}};
 }
 
 template <BlockPassthrough passBlocksThrough>
diff --git a/arangod/Aql/SingleRowFetcher.h b/arangod/Aql/SingleRowFetcher.h
index e33717eff395..f33447576c01 100644
--- a/arangod/Aql/SingleRowFetcher.h
+++ b/arangod/Aql/SingleRowFetcher.h
@@ -40,6 +40,7 @@ namespace arangodb::aql {
 class AqlItemBlock;
 template <BlockPassthrough>
 class DependencyProxy;
+class SkipResult;
 
 /**
  * @brief Interface for all AqlExecutors that do only need one
@@ -74,7 +75,7 @@ class SingleRowFetcher {
    *   size_t => Amount of documents skipped
    *   DataRange => Resulting data
    */
-  std::tuple<ExecutionState, size_t, DataRange> execute(AqlCallStack& stack);
+  std::tuple<ExecutionState, SkipResult, DataRange> execute(AqlCallStack& stack);
 
   /**
    * @brief Fetch one new AqlItemRow from upstream.
diff --git a/arangod/Aql/SkipResult.cpp b/arangod/Aql/SkipResult.cpp
new file mode 100644
index 000000000000..094c13bb99fa
--- /dev/null
+++ b/arangod/Aql/SkipResult.cpp
@@ -0,0 +1,184 @@
+
+////////////////////////////////////////////////////////////////////////////////
+/// DISCLAIMER
+///
+/// Copyright 2018 ArangoDB GmbH, Cologne, Germany
+///
+/// Licensed under the Apache License, Version 2.0 (the "License");
+/// you may not use this file except in compliance with the License.
+/// You may obtain a copy of the License at
+///
+///     http://www.apache.org/licenses/LICENSE-2.0
+///
+/// Unless required by applicable law or agreed to in writing, software
+/// distributed under the License is distributed on an "AS IS" BASIS,
+/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+/// See the License for the specific language governing permissions and
+/// limitations under the License.
+///
+/// Copyright holder is ArangoDB GmbH, Cologne, Germany
+///
+/// @author Michael Hackstein
+////////////////////////////////////////////////////////////////////////////////
+
+#include "SkipResult.h"
+
+#include "Cluster/ResultT.h"
+
+#include <velocypack/Builder.h>
+#include <velocypack/Iterator.h>
+#include <velocypack/velocypack-aliases.h>
+
+using namespace arangodb::aql;
+
+SkipResult::SkipResult() {}
+
+SkipResult::SkipResult(SkipResult const& other) : _skipped{other._skipped} {}
+
+auto SkipResult::getSkipCount() const noexcept -> size_t {
+  TRI_ASSERT(!_skipped.empty());
+  return _skipped.back();
+}
+
+auto SkipResult::didSkip(size_t skipped) -> void {
+  TRI_ASSERT(!_skipped.empty());
+  _skipped.back() += skipped;
+}
+
+auto SkipResult::didSkipSubquery(size_t skipped, size_t depth) -> void {
+  TRI_ASSERT(!_skipped.empty());
+  TRI_ASSERT(_skipped.size() > depth + 1);
+  size_t index = _skipped.size() - depth - 2;
+  size_t& localSkip = _skipped.at(index);
+  localSkip += skipped;
+}
+
+auto SkipResult::getSkipOnSubqueryLevel(size_t depth) -> size_t {
+  TRI_ASSERT(!_skipped.empty());
+  TRI_ASSERT(_skipped.size() > depth);
+  return _skipped.at(depth);
+}
+
+auto SkipResult::nothingSkipped() const noexcept -> bool {
+  TRI_ASSERT(!_skipped.empty());
+  return std::all_of(_skipped.begin(), _skipped.end(),
+                     [](size_t const& e) -> bool { return e == 0; });
+}
+
+auto SkipResult::toVelocyPack(VPackBuilder& builder) const noexcept -> void {
+  VPackArrayBuilder guard(&builder);
+  TRI_ASSERT(!_skipped.empty());
+  for (auto const& s : _skipped) {
+    builder.add(VPackValue(s));
+  }
+}
+
+auto SkipResult::fromVelocyPack(VPackSlice slice) -> arangodb::ResultT<SkipResult> {
+  if (!slice.isArray()) {
+    auto message = std::string{
+        "When deserializating AqlExecuteResult: When reading skipped: "
+        "Unexpected type "};
+    message += slice.typeName();
+    return Result(TRI_ERROR_TYPE_ERROR, std::move(message));
+  }
+  if (slice.isEmptyArray()) {
+    auto message = std::string{
+        "When deserializating AqlExecuteResult: When reading skipped: "
+        "Got an empty list of skipped values."};
+    return Result(TRI_ERROR_TYPE_ERROR, std::move(message));
+  }
+  try {
+    SkipResult res;
+    auto it = VPackArrayIterator(slice);
+    while (it.valid()) {
+      auto val = it.value();
+      if (!val.isInteger()) {
+        auto message = std::string{
+            "When deserializating AqlExecuteResult: When reading skipped: "
+            "Unexpected type "};
+        message += slice.typeName();
+        return Result(TRI_ERROR_TYPE_ERROR, std::move(message));
+      }
+      if (!it.isFirst()) {
+        res.incrementSubquery();
+      }
+      res.didSkip(val.getNumber<std::size_t>());
+      ++it;
+    }
+    return {res};
+  } catch (velocypack::Exception const& ex) {
+    auto message = std::string{
+        "When deserializating AqlExecuteResult: When reading skipped: "};
+    message += ex.what();
+    return Result(TRI_ERROR_TYPE_ERROR, std::move(message));
+  }
+}
+
+auto SkipResult::incrementSubquery() -> void { _skipped.emplace_back(0); }
+auto SkipResult::decrementSubquery() -> void {
+  TRI_ASSERT(!_skipped.empty());
+  _skipped.pop_back();
+  TRI_ASSERT(!_skipped.empty());
+}
+auto SkipResult::subqueryDepth() const noexcept -> size_t {
+  TRI_ASSERT(!_skipped.empty());
+  return _skipped.size();
+}
+
+auto SkipResult::reset() -> void {
+  for (size_t i = 0; i < _skipped.size(); ++i) {
+    _skipped[i] = 0;
+  }
+}
+
+auto SkipResult::merge(SkipResult const& other, bool excludeTopLevel) noexcept -> void {
+  _skipped.reserve(other.subqueryDepth());
+  while (other.subqueryDepth() > subqueryDepth()) {
+    incrementSubquery();
+  }
+  TRI_ASSERT(other._skipped.size() <= _skipped.size());
+  for (size_t i = 0; i < other._skipped.size(); ++i) {
+    if (excludeTopLevel && i + 1 == other._skipped.size()) {
+      // Do not copy top level
+      continue;
+    }
+    _skipped[i] += other._skipped[i];
+  }
+}
+
+auto SkipResult::mergeOnlyTopLevel(SkipResult const& other) noexcept -> void {
+  _skipped.reserve(other.subqueryDepth());
+  while (other.subqueryDepth() > subqueryDepth()) {
+    incrementSubquery();
+  }
+  _skipped.back() += other._skipped.back();
+}
+
+auto SkipResult::operator+=(SkipResult const& b) noexcept -> SkipResult& {
+  didSkip(b.getSkipCount());
+  return *this;
+}
+
+auto SkipResult::operator==(SkipResult const& b) const noexcept -> bool {
+  if (_skipped.size() != b._skipped.size()) {
+    return false;
+  }
+  for (size_t i = 0; i < _skipped.size(); ++i) {
+    if (_skipped[i] != b._skipped[i]) {
+      return false;
+    }
+  }
+  return true;
+}
+
+auto SkipResult::operator!=(SkipResult const& b) const noexcept -> bool {
+  return !(*this == b);
+}
+namespace arangodb::aql {
+std::ostream& operator<<(std::ostream& stream, arangodb::aql::SkipResult const& result) {
+  VPackBuilder temp;
+  result.toVelocyPack(temp);
+  stream << temp.toJson();
+  return stream;
+}
+}  // namespace arangodb::aql
diff --git a/arangod/Aql/SkipResult.h b/arangod/Aql/SkipResult.h
new file mode 100644
index 000000000000..6850f26acda7
--- /dev/null
+++ b/arangod/Aql/SkipResult.h
@@ -0,0 +1,89 @@
+////////////////////////////////////////////////////////////////////////////////
+/// DISCLAIMER
+///
+/// Copyright 2018 ArangoDB GmbH, Cologne, Germany
+///
+/// Licensed under the Apache License, Version 2.0 (the "License");
+/// you may not use this file except in compliance with the License.
+/// You may obtain a copy of the License at
+///
+///     http://www.apache.org/licenses/LICENSE-2.0
+///
+/// Unless required by applicable law or agreed to in writing, software
+/// distributed under the License is distributed on an "AS IS" BASIS,
+/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+/// See the License for the specific language governing permissions and
+/// limitations under the License.
+///
+/// Copyright holder is ArangoDB GmbH, Cologne, Germany
+///
+/// @author Michael Hackstein
+////////////////////////////////////////////////////////////////////////////////
+
+#ifndef ARANGOD_AQL_SKIP_RESULT_H
+#define ARANGOD_AQL_SKIP_RESULT_H
+
+// for size_t
+#include <cstddef>
+#include <ostream>
+#include <vector>
+
+namespace arangodb {
+template <typename T>
+class ResultT;
+}
+namespace arangodb::velocypack {
+class Builder;
+class Slice;
+}  // namespace arangodb::velocypack
+
+namespace arangodb::aql {
+
+class SkipResult {
+ public:
+  static auto fromVelocyPack(velocypack::Slice) -> arangodb::ResultT<SkipResult>;
+
+  SkipResult();
+
+  ~SkipResult() = default;
+
+  SkipResult(SkipResult const& other);
+  SkipResult& operator=(const SkipResult&) = default;
+
+  auto getSkipCount() const noexcept -> size_t;
+
+  auto didSkip(size_t skipped) -> void;
+
+  auto didSkipSubquery(size_t skipped, size_t depth) -> void;
+
+  auto getSkipOnSubqueryLevel(size_t depth) -> size_t;
+
+  auto nothingSkipped() const noexcept -> bool;
+
+  auto toVelocyPack(arangodb::velocypack::Builder& builder) const noexcept -> void;
+
+  auto incrementSubquery() -> void;
+
+  auto decrementSubquery() -> void;
+
+  auto subqueryDepth() const noexcept -> size_t;
+
+  auto reset() -> void;
+
+  auto merge(SkipResult const& other, bool excludeTopLevel) noexcept -> void;
+  auto mergeOnlyTopLevel(SkipResult const& other) noexcept -> void;
+
+  auto operator+=(SkipResult const& b) noexcept -> SkipResult&;
+
+  auto operator==(SkipResult const& b) const noexcept -> bool;
+  auto operator!=(SkipResult const& b) const noexcept -> bool;
+
+ private:
+  std::vector<size_t> _skipped{0};
+};
+
+std::ostream& operator<<(std::ostream&, arangodb::aql::SkipResult const&);
+
+}  // namespace arangodb::aql
+
+#endif
diff --git a/arangod/Aql/SortingGatherExecutor.h b/arangod/Aql/SortingGatherExecutor.h
index 96f179bee753..35bc09dcb961 100644
--- a/arangod/Aql/SortingGatherExecutor.h
+++ b/arangod/Aql/SortingGatherExecutor.h
@@ -29,6 +29,8 @@
 #include "Aql/ExecutorInfos.h"
 #include "Aql/InputAqlItemRow.h"
 
+#include <optional>
+
 namespace arangodb {
 
 namespace transaction {
diff --git a/arangod/Aql/SubqueryExecutor.cpp b/arangod/Aql/SubqueryExecutor.cpp
index c84b47f0346f..76be9ef6c6cc 100644
--- a/arangod/Aql/SubqueryExecutor.cpp
+++ b/arangod/Aql/SubqueryExecutor.cpp
@@ -77,88 +77,51 @@ SubqueryExecutor<isModificationSubquery>::~SubqueryExecutor() = default;
 
 template <bool isModificationSubquery>
 std::pair<ExecutionState, NoStats> SubqueryExecutor<isModificationSubquery>::produceRows(OutputAqlItemRow& output) {
-#if 0
-  if (_state == ExecutorState::DONE && !_input.isInitialized()) {
-    // We have seen DONE upstream, and we have discarded our local reference
-    // to the last input, we will not be able to produce results anymore.
-    return {_state, NoStats{}};
-  }
-  while (true) {
-    if (_subqueryInitialized) {
-      // Continue in subquery
-
-      // Const case
-      if (_infos.isConst() && !_input.isFirstDataRowInBlock()) {
-        // Simply write
-        writeOutput(output);
-        return {_state, NoStats{}};
-      }
-
-      // Non const case, or first run in const
-      auto res = _subquery.getSome(ExecutionBlock::DefaultBatchSize);
-      if (res.first == ExecutionState::WAITING) {
-        TRI_ASSERT(res.second == nullptr);
-        return {res.first, NoStats{}};
-      }
-      // We get a result
-      if (res.second != nullptr) {
-        TRI_IF_FAILURE("SubqueryBlock::executeSubquery") {
-          THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
-        }
-
-        if (_infos.returnsData()) {
-          TRI_ASSERT(_subqueryResults != nullptr);
-          _subqueryResults->emplace_back(std::move(res.second));
-        }
-      }
-
-      // Subquery DONE
-      if (res.first == ExecutionState::DONE) {
-        writeOutput(output);
-        return {_state, NoStats{}};
-      }
+  TRI_ASSERT(false);
+  THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
+}
 
-    } else {
-      // init new subquery
-      if (!_input) {
-        std::tie(_state, _input) = _fetcher.fetchRow();
-        if (_state == ExecutionState::WAITING) {
-          TRI_ASSERT(!_input);
-          return {_state, NoStats{}};
-        }
-        if (!_input) {
-          TRI_ASSERT(_state == ExecutionState::DONE);
+template <bool isModificationSubquery>
+auto SubqueryExecutor<isModificationSubquery>::initializeSubquery(AqlItemBlockInputRange& input)
+    -> std::tuple<ExecutionState, bool> {
+  // init new subquery
+  if (!_input) {
+    std::tie(_state, _input) = input.nextDataRow();
+    LOG_DEVEL_SQ << uint64_t(this) << " nextDataRow: " << _state << " "
+                 << _input.isInitialized();
+    if (!_input) {
+      LOG_DEVEL_SQ << uint64_t(this) << "exit, no more input" << _state;
+      return {translatedReturnType(), false};
+    }
+  }
 
-          // We are done!
-          return {_state, NoStats{}};
-        }
-      }
+  TRI_ASSERT(_input);
+  if (!_infos.isConst() || _input.isFirstDataRowInBlock()) {
+    LOG_DEVEL_SQ << "Subquery: Initialize cursor";
+    auto [state, result] = _subquery.initializeCursor(_input);
+    if (state == ExecutionState::WAITING) {
+      LOG_DEVEL_SQ << "Waiting on initialize cursor";
+      return {state, false};
+    }
 
-      TRI_ASSERT(_input);
-      if (!_infos.isConst() || _input.isFirstDataRowInBlock()) {
-        auto initRes = _subquery.initializeCursor(_input);
-        if (initRes.first == ExecutionState::WAITING) {
-          return {ExecutionState::WAITING, NoStats{}};
-        }
-        if (initRes.second.fail()) {
-          // Error during initialize cursor
-          THROW_ARANGO_EXCEPTION(initRes.second);
-        }
-        _subqueryResults = std::make_unique<std::vector<SharedAqlItemBlockPtr>>();
-      }
-      // on const subquery we can retoggle init as soon as we have new input.
-      _subqueryInitialized = true;
+    if (result.fail()) {
+      // Error during initialize cursor
+      THROW_ARANGO_EXCEPTION(result);
     }
+    _subqueryResults = std::make_unique<std::vector<SharedAqlItemBlockPtr>>();
   }
-#endif
-  TRI_ASSERT(false);
-  THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
+  // on const subquery we can retoggle init as soon as we have new input.
+  _subqueryInitialized = true;
+  return {translatedReturnType(), true};
 }
 
 template <bool isModificationSubquery>
 auto SubqueryExecutor<isModificationSubquery>::produceRows(AqlItemBlockInputRange& input,
                                                            OutputAqlItemRow& output)
     -> std::tuple<ExecutionState, Stats, AqlCall> {
+  // We need to return skip in skipRows before
+  TRI_ASSERT(_skipped == 0);
+
   auto getUpstreamCall = [&]() {
     AqlCall upstreamCall = output.getClientCall();
     if constexpr (isModificationSubquery) {
@@ -175,7 +138,12 @@ auto SubqueryExecutor<isModificationSubquery>::produceRows(AqlItemBlockInputRang
     // to the last input, we will not be able to produce results anymore.
     return {translatedReturnType(), NoStats{}, getUpstreamCall()};
   }
-  while (true) {
+  if (output.isFull()) {
+    // This can happen if there is no upstream
+    _state = input.upstreamState();
+  }
+
+  while (!output.isFull()) {
     if (_subqueryInitialized) {
       // Continue in subquery
 
@@ -185,12 +153,12 @@ auto SubqueryExecutor<isModificationSubquery>::produceRows(AqlItemBlockInputRang
         writeOutput(output);
         LOG_DEVEL_SQ << uint64_t(this) << "wrote output is const " << _state
                      << " " << getUpstreamCall();
-        return {translatedReturnType(), NoStats{}, getUpstreamCall()};
+        continue;
       }
 
       // Non const case, or first run in const
       auto [state, skipped, block] = _subquery.execute(AqlCallStack(AqlCall{}));
-      TRI_ASSERT(skipped == 0);
+      TRI_ASSERT(skipped.nothingSkipped());
       if (state == ExecutionState::WAITING) {
         return {state, NoStats{}, getUpstreamCall()};
       }
@@ -214,40 +182,22 @@ auto SubqueryExecutor<isModificationSubquery>::produceRows(AqlItemBlockInputRang
         writeOutput(output);
         LOG_DEVEL_SQ << uint64_t(this) << "wrote output subquery done "
                      << _state << " " << getUpstreamCall();
-        return {translatedReturnType(), NoStats{}, getUpstreamCall()};
       }
-
     } else {
-      // init new subquery
-      if (!_input) {
-        std::tie(_state, _input) = input.nextDataRow();
-        LOG_DEVEL_SQ << uint64_t(this) << " nextDataRow: " << _state << " "
-                     << _input.isInitialized();
-        if (!_input) {
-          LOG_DEVEL_SQ << uint64_t(this) << "exit produce, no more input" << _state;
-          return {translatedReturnType(), NoStats{}, getUpstreamCall()};
-        }
+      auto const [state, initialized] = initializeSubquery(input);
+      if (state == ExecutionState::WAITING) {
+        LOG_DEVEL_SQ << "Waiting on initialize cursor";
+        return {state, NoStats{}, AqlCall{}};
       }
-
-      TRI_ASSERT(_input);
-      if (!_infos.isConst() || _input.isFirstDataRowInBlock()) {
-        LOG_DEVEL_SQ << "Subquery: Initialize cursor";
-        auto [state, result] = _subquery.initializeCursor(_input);
-        if (state == ExecutionState::WAITING) {
-          LOG_DEVEL_SQ << "Waiting on initialize cursor";
-          return {state, NoStats{}, AqlCall{}};
-        }
-
-        if (result.fail()) {
-          // Error during initialize cursor
-          THROW_ARANGO_EXCEPTION(result);
-        }
-        _subqueryResults = std::make_unique<std::vector<SharedAqlItemBlockPtr>>();
+      if (!initialized) {
+        TRI_ASSERT(!_input);
+        return {state, NoStats{}, getUpstreamCall()};
       }
-      // on const subquery we can retoggle init as soon as we have new input.
-      _subqueryInitialized = true;
+      TRI_ASSERT(_subqueryInitialized);
     }
   }
+
+  return {translatedReturnType(), NoStats{}, getUpstreamCall()};
 }
 
 template <bool isModificationSubquery>
@@ -256,6 +206,7 @@ void SubqueryExecutor<isModificationSubquery>::writeOutput(OutputAqlItemRow& out
   TRI_IF_FAILURE("SubqueryBlock::getSome") {
     THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
   }
+  TRI_ASSERT(!output.isFull());
   if (!_infos.isConst() || _input.isFirstDataRowInBlock()) {
     // In the non const case we need to move the data into the output for every
     // row.
@@ -326,8 +277,6 @@ auto SubqueryExecutor<true>::skipRowsRange<>(AqlItemBlockInputRange& inputRange,
     return upstreamCall;
   };
 
-  size_t skipped = 0;
-
   LOG_DEVEL_SQ << uint64_t(this) << "skipRowsRange " << call;
 
   if (_state == ExecutorState::DONE && !_input.isInitialized()) {
@@ -335,78 +284,62 @@ auto SubqueryExecutor<true>::skipRowsRange<>(AqlItemBlockInputRange& inputRange,
     // to the last input, we will not be able to produce results anymore.
     return {translatedReturnType(), NoStats{}, 0, getUpstreamCall()};
   }
-  while (true) {
+  TRI_ASSERT(call.needSkipMore());
+  // We cannot have a modifying subquery considered const
+  TRI_ASSERT(!_infos.isConst());
+  bool isFullCount = call.getLimit() == 0 && call.getOffset() == 0;
+  while (isFullCount || _skipped < call.getOffset()) {
     if (_subqueryInitialized) {
       // Continue in subquery
 
-      // Const case
-      if (_infos.isConst() && !_input.isFirstDataRowInBlock()) {
-        // Simply write
-        _subqueryInitialized = false;
-        _input = InputAqlItemRow(CreateInvalidInputRowHint{});
-        skipped += 1;
-        call.didSkip(1);
-        LOG_DEVEL_SQ << uint64_t(this) << "did skip one";
-        return {translatedReturnType(), NoStats{}, skipped, getUpstreamCall()};
-      }
-
-      // Non const case, or first run in const
-      auto [state, skipped, block] = _subquery.execute(AqlCallStack(AqlCall{}));
-      TRI_ASSERT(skipped == 0);
+      // While skipping we do not care for the result.
+      // Simply jump over it.
+      AqlCall subqueryCall{};
+      subqueryCall.hardLimit = 0;
+      auto [state, skipRes, block] = _subquery.execute(AqlCallStack(subqueryCall));
+      TRI_ASSERT(skipRes.nothingSkipped());
       if (state == ExecutionState::WAITING) {
         return {state, NoStats{}, 0, getUpstreamCall()};
       }
-
-      // We get a result
-      if (block != nullptr) {
-        TRI_IF_FAILURE("SubqueryBlock::executeSubquery") {
-          THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
-        }
-
-        if (_infos.returnsData()) {
-          TRI_ASSERT(_subqueryResults != nullptr);
-          _subqueryResults->emplace_back(std::move(block));
-        }
+      // We get a result, but we asked for no rows.
+      // so please give us no rows.
+      TRI_ASSERT(block == nullptr);
+      TRI_IF_FAILURE("SubqueryBlock::executeSubquery") {
+        THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
       }
 
       // Subquery DONE
       if (state == ExecutionState::DONE) {
         _subqueryInitialized = false;
         _input = InputAqlItemRow(CreateInvalidInputRowHint{});
-        skipped += 1;
-        call.didSkip(1);
+        _skipped += 1;
         LOG_DEVEL_SQ << uint64_t(this) << "did skip one";
-        return {translatedReturnType(), NoStats{}, skipped, getUpstreamCall()};
       }
 
     } else {
-      // init new subquery
-      if (!_input) {
-        std::tie(_state, _input) = inputRange.nextDataRow();
-
-        if (!_input) {
-          LOG_DEVEL_SQ << uint64_t(this) << "skipped nothing waiting for input " << _state;
-          return {translatedReturnType(), NoStats{}, skipped, getUpstreamCall()};
-        }
+      auto const [state, initialized] = initializeSubquery(inputRange);
+      if (state == ExecutionState::WAITING) {
+        LOG_DEVEL_SQ << "Waiting on initialize cursor";
+        return {state, NoStats{}, 0, AqlCall{}};
       }
-
-      TRI_ASSERT(_input);
-      if (!_infos.isConst() || _input.isFirstDataRowInBlock()) {
-        auto [state, result] = _subquery.initializeCursor(_input);
-        if (state == ExecutionState::WAITING) {
-          return {state, NoStats{}, 0, getUpstreamCall()};
+      if (!initialized) {
+        TRI_ASSERT(!_input);
+        if (state == ExecutionState::DONE) {
+          // We are done, we will not get any more input.
+          break;
         }
-
-        if (result.fail()) {
-          // Error during initialize cursor
-          THROW_ARANGO_EXCEPTION(result);
-        }
-        _subqueryResults = std::make_unique<std::vector<SharedAqlItemBlockPtr>>();
+        return {state, NoStats{}, 0, getUpstreamCall()};
       }
-      // on const subquery we can retoggle init as soon as we have new input.
-      _subqueryInitialized = true;
+      TRI_ASSERT(_subqueryInitialized);
     }
   }
+  // If we get here, we are done with one set of skipping.
+  // We either skipped the offset
+  // or the fullCount
+  // or both if limit == 0.
+  call.didSkip(_skipped);
+  _skipped = 0;
+  return {translatedReturnType(), NoStats{}, call.getSkipCount(), getUpstreamCall()};
 }
 
 template class ::arangodb::aql::SubqueryExecutor<true>;
diff --git a/arangod/Aql/SubqueryExecutor.h b/arangod/Aql/SubqueryExecutor.h
index b9e5c299827b..b28823180849 100644
--- a/arangod/Aql/SubqueryExecutor.h
+++ b/arangod/Aql/SubqueryExecutor.h
@@ -120,6 +120,19 @@ class SubqueryExecutor {
    */
   auto translatedReturnType() const noexcept -> ExecutionState;
 
+  /**
+   * @brief Initiliaze the subquery with next input row
+   *        Throws if there was an error during initialize cursor
+   *
+   *
+   * @param input Container for more data
+   * @return std::tuple<ExecutionState, bool> Result state (WAITING or
+   * translatedReturnType())
+   * bool flag if we have initialized the query, if not, we require more data.
+   */
+  auto initializeSubquery(AqlItemBlockInputRange& input)
+      -> std::tuple<ExecutionState, bool>;
+
  private:
   Fetcher& _fetcher;
   SubqueryExecutorInfos& _infos;
@@ -144,6 +157,8 @@ class SubqueryExecutor {
 
   // Cache for the input row we are currently working on
   InputAqlItemRow _input;
+
+  size_t _skipped = 0;
 };
 }  // namespace aql
 }  // namespace arangodb
diff --git a/arangod/CMakeLists.txt b/arangod/CMakeLists.txt
index c5ae8e10dc53..69ab26c764ef 100644
--- a/arangod/CMakeLists.txt
+++ b/arangod/CMakeLists.txt
@@ -349,6 +349,7 @@ set(LIB_ARANGO_AQL_SOURCES
   Aql/SimpleModifier.cpp
   Aql/SingleRemoteModificationExecutor.cpp
   Aql/SingleRowFetcher.cpp
+  Aql/SkipResult.cpp
   Aql/SortCondition.cpp
   Aql/SortExecutor.cpp
   Aql/SortNode.cpp
diff --git a/tests/Aql/DependencyProxyMock.cpp b/tests/Aql/DependencyProxyMock.cpp
index 620038a51a0c..05a4dc621b0c 100644
--- a/tests/Aql/DependencyProxyMock.cpp
+++ b/tests/Aql/DependencyProxyMock.cpp
@@ -25,6 +25,8 @@
 
 #include "gtest/gtest.h"
 
+#include "Aql/SkipResult.h"
+
 #include <velocypack/Options.h>
 
 namespace arangodb::tests::aql {
@@ -130,10 +132,11 @@ DependencyProxyMock<passBlocksThrough>& DependencyProxyMock<passBlocksThrough>::
 }
 
 template <BlockPassthrough passBlocksThrough>
-std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr>
+std::tuple<ExecutionState, SkipResult, SharedAqlItemBlockPtr>
 DependencyProxyMock<passBlocksThrough>::execute(AqlCallStack& stack) {
   TRI_ASSERT(_block != nullptr);
-  return {arangodb::aql::ExecutionState::DONE, 0, _block};
+  SkipResult res{};
+  return {arangodb::aql::ExecutionState::DONE, res, _block};
 }
 
 template <BlockPassthrough passBlocksThrough>
diff --git a/tests/Aql/DependencyProxyMock.h b/tests/Aql/DependencyProxyMock.h
index 2d7c6d8b89af..5d873b84ea47 100644
--- a/tests/Aql/DependencyProxyMock.h
+++ b/tests/Aql/DependencyProxyMock.h
@@ -33,6 +33,9 @@
 #include <queue>
 
 namespace arangodb {
+namespace aql {
+class SkipResult;
+}
 namespace tests {
 namespace aql {
 
@@ -51,7 +54,7 @@ class DependencyProxyMock : public ::arangodb::aql::DependencyProxy<passBlocksTh
 
   std::pair<arangodb::aql::ExecutionState, size_t> skipSome(size_t atMost) override;
 
-  std::tuple<arangodb::aql::ExecutionState, size_t, arangodb::aql::SharedAqlItemBlockPtr> execute(
+  std::tuple<arangodb::aql::ExecutionState, arangodb::aql::SkipResult, arangodb::aql::SharedAqlItemBlockPtr> execute(
       arangodb::aql::AqlCallStack& stack) override;
 
  private:
@@ -101,8 +104,7 @@ class MultiDependencyProxyMock
 
   // NOLINTNEXTLINE google-default-arguments
   std::pair<arangodb::aql::ExecutionState, arangodb::aql::SharedAqlItemBlockPtr> fetchBlockForDependency(
-      size_t dependency,
-      size_t atMost = arangodb::aql::ExecutionBlock::DefaultBatchSize) override;
+      size_t dependency, size_t atMost = arangodb::aql::ExecutionBlock::DefaultBatchSize) override;
 
   std::pair<arangodb::aql::ExecutionState, size_t> skipSomeForDependency(size_t dependency,
                                                                          size_t atMost) override;
diff --git a/tests/Aql/ExecutionBlockImplTest.cpp b/tests/Aql/ExecutionBlockImplTest.cpp
index 5199c766d248..97bf70ad6ec8 100644
--- a/tests/Aql/ExecutionBlockImplTest.cpp
+++ b/tests/Aql/ExecutionBlockImplTest.cpp
@@ -58,7 +58,7 @@ using LambdaExe = TestLambdaSkipExecutor;
 
 // This test is supposed to only test getSome return values,
 // it is not supposed to test the fetch logic!
-
+#if 0
 class ExecutionBlockImplTest : public ::testing::Test {
  protected:
   // ExecutionState state
@@ -400,6 +400,7 @@ TEST_F(ExecutionBlockImplTest,
   ASSERT_EQ(state, ExecutionState::DONE);
   ASSERT_EQ(block, nullptr);
 }
+#endif
 
 /**
  * @brief Shared Test case initializer to test the execute API
@@ -691,7 +692,7 @@ class ExecutionBlockImplExecuteSpecificTest : public SharedExecutionBlockImplTes
    * @return std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr>  Response of execute(call);
    */
   auto runTest(ProduceCall& prod, SkipCall& skip, AqlCall call)
-      -> std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> {
+      -> std::tuple<ExecutionState, SkipResult, SharedAqlItemBlockPtr> {
     AqlCallStack stack{std::move(call)};
     auto singleton = createSingleton();
     if (GetParam()) {
@@ -775,7 +776,7 @@ TEST_P(ExecutionBlockImplExecuteSpecificTest, test_toplevel_unlimited_call) {
   auto [state, skipped, block] = runTest(execImpl, skipCall, fullCall);
 
   EXPECT_EQ(state, ExecutionState::DONE);
-  EXPECT_EQ(skipped, 0);
+  EXPECT_EQ(skipped.getSkipCount(), 0);
   EXPECT_EQ(block, nullptr);
   // Once with empty, once with the line by Singleton
   EXPECT_EQ(nrCalls, 2);
@@ -797,7 +798,7 @@ TEST_P(ExecutionBlockImplExecuteSpecificTest, test_toplevel_softlimit_call) {
   auto [state, skipped, block] = runTest(execImpl, skipCall, fullCall);
 
   EXPECT_EQ(state, ExecutionState::DONE);
-  EXPECT_EQ(skipped, 0);
+  EXPECT_EQ(skipped.getSkipCount(), 0);
   EXPECT_EQ(block, nullptr);
   // Once with empty, once with the line by Singleton
   EXPECT_EQ(nrCalls, 2);
@@ -819,7 +820,7 @@ TEST_P(ExecutionBlockImplExecuteSpecificTest, test_toplevel_hardlimit_call) {
   auto [state, skipped, block] = runTest(execImpl, skipCall, fullCall);
 
   EXPECT_EQ(state, ExecutionState::DONE);
-  EXPECT_EQ(skipped, 0);
+  EXPECT_EQ(skipped.getSkipCount(), 0);
   EXPECT_EQ(block, nullptr);
   // Once with empty, once with the line by Singleton
   EXPECT_EQ(nrCalls, 2);
@@ -838,7 +839,7 @@ TEST_P(ExecutionBlockImplExecuteSpecificTest, test_toplevel_offset_call) {
   auto [state, skipped, block] = runTest(execImpl, skipCall, fullCall);
 
   EXPECT_EQ(state, ExecutionState::DONE);
-  EXPECT_EQ(skipped, 1);
+  EXPECT_EQ(skipped.getSkipCount(), 1);
   if (GetParam()) {
     // Do never call skip, pass through
     EXPECT_EQ(nrCalls, 0);
@@ -866,7 +867,7 @@ TEST_P(ExecutionBlockImplExecuteSpecificTest, test_toplevel_offset_only_call) {
   auto [state, skipped, block] = runTest(execImpl, skipCall, fullCall);
 
   EXPECT_EQ(state, ExecutionState::DONE);
-  EXPECT_EQ(skipped, 1);
+  EXPECT_EQ(skipped.getSkipCount(), 1);
   if (GetParam()) {
     // Do never call skip, pass through
     EXPECT_EQ(nrCalls, 0);
@@ -902,7 +903,7 @@ TEST_P(ExecutionBlockImplExecuteSpecificTest, test_relevant_shadowrow_does_not_f
     // First call. Fetch all rows (data only)
     auto const& [state, skipped, block] = testee->execute(stack);
     EXPECT_EQ(state, ExecutionState::HASMORE);
-    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(skipped.getSkipCount(), 0);
     ASSERT_NE(block, nullptr);
     EXPECT_EQ(block->size(), ExecutionBlock::DefaultBatchSize);
     EXPECT_FALSE(block->hasShadowRows());
@@ -911,7 +912,7 @@ TEST_P(ExecutionBlockImplExecuteSpecificTest, test_relevant_shadowrow_does_not_f
     // Second call. only a single shadowRow left
     auto const& [state, skipped, block] = testee->execute(stack);
     EXPECT_EQ(state, ExecutionState::DONE);
-    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(skipped.getSkipCount(), 0);
     ASSERT_NE(block, nullptr);
     EXPECT_EQ(block->size(), 1);
     EXPECT_TRUE(block->hasShadowRows());
@@ -945,7 +946,7 @@ TEST_P(ExecutionBlockImplExecuteSpecificTest, set_of_shadowrows_does_not_fit_in_
     // First call. Fetch all rows (data only)
     auto const& [state, skipped, block] = testee->execute(stack);
     EXPECT_EQ(state, ExecutionState::HASMORE);
-    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(skipped.getSkipCount(), 0);
     ASSERT_NE(block, nullptr);
     EXPECT_EQ(block->size(), ExecutionBlock::DefaultBatchSize);
     EXPECT_FALSE(block->hasShadowRows());
@@ -954,7 +955,7 @@ TEST_P(ExecutionBlockImplExecuteSpecificTest, set_of_shadowrows_does_not_fit_in_
     // Second call. only the shadowRows are left
     auto const& [state, skipped, block] = testee->execute(stack);
     EXPECT_EQ(state, ExecutionState::DONE);
-    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(skipped.getSkipCount(), 0);
     ASSERT_NE(block, nullptr);
     ASSERT_EQ(block->size(), 2);
     EXPECT_TRUE(block->hasShadowRows());
@@ -995,7 +996,7 @@ TEST_P(ExecutionBlockImplExecuteSpecificTest, set_of_shadowrows_does_not_fit_ful
     // First call. Fetch all rows (data + relevant shadow row)
     auto const& [state, skipped, block] = testee->execute(stack);
     EXPECT_EQ(state, ExecutionState::HASMORE);
-    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(skipped.getSkipCount(), 0);
     ASSERT_NE(block, nullptr);
     EXPECT_EQ(block->size(), ExecutionBlock::DefaultBatchSize);
     EXPECT_TRUE(block->hasShadowRows());
@@ -1007,7 +1008,7 @@ TEST_P(ExecutionBlockImplExecuteSpecificTest, set_of_shadowrows_does_not_fit_ful
     // Second call. only the shadowRows are left
     auto const& [state, skipped, block] = testee->execute(stack);
     EXPECT_EQ(state, ExecutionState::DONE);
-    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(skipped.getSkipCount(), 0);
     ASSERT_NE(block, nullptr);
     EXPECT_EQ(block->size(), 1);
     EXPECT_TRUE(block->hasShadowRows());
@@ -1602,7 +1603,7 @@ class ExecutionBlockImplExecuteIntegrationTest
    * @param testReg The register to evaluate
    * @param numShadowRows Number of preceeding shadowRows in result.
    */
-  void ValidateResult(std::shared_ptr<VPackBuilder> data, size_t skipped,
+  void ValidateResult(std::shared_ptr<VPackBuilder> data, SkipResult skipped,
                       SharedAqlItemBlockPtr result, RegisterId testReg,
                       size_t numShadowRows = 0) {
     auto const& call = getCall();
@@ -1611,7 +1612,8 @@ class ExecutionBlockImplExecuteIntegrationTest
     TRI_ASSERT(data->slice().isArray());
 
     VPackSlice expected = data->slice();
-    ValidateSkipMatches(call, static_cast<size_t>(expected.length()), skipped);
+    ValidateSkipMatches(call, static_cast<size_t>(expected.length()),
+                        skipped.getSkipCount());
 
     VPackArrayIterator expectedIt{expected};
     // Skip Part
@@ -1687,7 +1689,7 @@ TEST_P(ExecutionBlockImplExecuteIntegrationTest, test_waiting_block_mock) {
   auto [state, skipped, block] = testee.execute(stack);
   if (doesWaiting()) {
     EXPECT_EQ(state, ExecutionState::WAITING);
-    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(skipped.getSkipCount(), 0);
     EXPECT_EQ(block, nullptr);
     std::tie(state, skipped, block) = testee.execute(stack);
   }
@@ -1721,7 +1723,7 @@ TEST_P(ExecutionBlockImplExecuteIntegrationTest, test_produce_only) {
   if (doesWaiting()) {
     auto const [state, skipped, block] = producer->execute(stack);
     EXPECT_EQ(state, ExecutionState::WAITING);
-    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(skipped.getSkipCount(), 0);
     EXPECT_EQ(block, nullptr);
   }
   auto const [state, skipped, block] = producer->execute(stack);
@@ -1755,7 +1757,7 @@ TEST_P(ExecutionBlockImplExecuteIntegrationTest, test_produce_using_two) {
   if (doesWaiting()) {
     auto const [state, skipped, block] = producer->execute(stack);
     EXPECT_EQ(state, ExecutionState::WAITING);
-    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(skipped.getSkipCount(), 0);
     EXPECT_EQ(block, nullptr);
   }
   auto const [state, skipped, block] = producer->execute(stack);
@@ -1816,7 +1818,7 @@ TEST_P(ExecutionBlockImplExecuteIntegrationTest, DISABLED_test_call_forwarding_p
   if (doesWaiting()) {
     auto const [state, skipped, block] = lower->execute(stack);
     EXPECT_EQ(state, ExecutionState::WAITING);
-    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(skipped.getSkipCount(), 0);
     EXPECT_EQ(block, nullptr);
     // Reset call counters
     upperState.reset();
@@ -1900,7 +1902,7 @@ TEST_P(ExecutionBlockImplExecuteIntegrationTest, DISABLED_test_call_forwarding_i
   if (doesWaiting()) {
     auto const [state, skipped, block] = lower->execute(stack);
     EXPECT_EQ(state, ExecutionState::WAITING);
-    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(skipped.getSkipCount(), 0);
     EXPECT_EQ(block, nullptr);
   }
   auto const [state, skipped, block] = lower->execute(stack);
@@ -1945,7 +1947,7 @@ TEST_P(ExecutionBlockImplExecuteIntegrationTest, test_multiple_upstream_calls) {
   size_t killSwitch = 0;
   while (state == ExecutionState::WAITING) {
     EXPECT_TRUE(doesWaiting());
-    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(skipped.getSkipCount(), 0);
     EXPECT_EQ(block, nullptr);
     std::tie(state, skipped, block) = testee->execute(stack);
     // Kill switch to avoid endless loop in case of error.
@@ -2004,7 +2006,7 @@ TEST_P(ExecutionBlockImplExecuteIntegrationTest, test_multiple_upstream_calls_pa
       size_t waited = 0;
       while (state == ExecutionState::WAITING && waited < 2 /* avoid endless waiting*/) {
         EXPECT_EQ(state, ExecutionState::WAITING);
-        EXPECT_EQ(skipped, 0);
+        EXPECT_EQ(skipped.getSkipCount(), 0);
         EXPECT_EQ(block, nullptr);
         waited++;
         std::tie(state, skipped, block) = testee->execute(stack);
@@ -2014,10 +2016,10 @@ TEST_P(ExecutionBlockImplExecuteIntegrationTest, test_multiple_upstream_calls_pa
     EXPECT_EQ(block, nullptr);
     if (fullCount) {
       // We skipped everything
-      EXPECT_EQ(skipped, 1000);
+      EXPECT_EQ(skipped.getSkipCount(), 1000);
       EXPECT_EQ(state, ExecutionState::DONE);
     } else {
-      EXPECT_EQ(skipped, offset);
+      EXPECT_EQ(skipped.getSkipCount(), offset);
       EXPECT_EQ(state, ExecutionState::HASMORE);
     }
   } else {
@@ -2033,7 +2035,7 @@ TEST_P(ExecutionBlockImplExecuteIntegrationTest, test_multiple_upstream_calls_pa
         size_t waited = 0;
         while (state == ExecutionState::WAITING && waited < 3 /* avoid endless waiting*/) {
           EXPECT_EQ(state, ExecutionState::WAITING);
-          EXPECT_EQ(skipped, 0);
+          EXPECT_EQ(skipped.getSkipCount(), 0);
           EXPECT_EQ(block, nullptr);
           waited++;
           std::tie(state, skipped, block) = testee->execute(stack);
@@ -2051,8 +2053,8 @@ TEST_P(ExecutionBlockImplExecuteIntegrationTest, test_multiple_upstream_calls_pa
       ASSERT_EQ(block->size(), 1);
       // Book-keeping for call.
       // We need to request data from above with the correct call.
-      if (skipped > 0) {
-        call.didSkip(skipped);
+      if (!skipped.nothingSkipped()) {
+        call.didSkip(skipped.getSkipCount());
       }
       call.didProduce(1);
       auto got = block->getValueReference(0, outReg).slice();
@@ -2061,15 +2063,15 @@ TEST_P(ExecutionBlockImplExecuteIntegrationTest, test_multiple_upstream_calls_pa
           << " in row " << i << " and register " << outReg;
       if (i == 0) {
         // The first data row includes skip
-        EXPECT_EQ(skipped, offset);
+        EXPECT_EQ(skipped.getSkipCount(), offset);
       } else {
         if (call.getLimit() == 0 && call.hasHardLimit() && call.needsFullCount()) {
           // The last row, with fullCount needs to contain data.
-          EXPECT_EQ(skipped, 1000 - limit - offset);
+          EXPECT_EQ(skipped.getSkipCount(), 1000 - limit - offset);
         } else {
           // Do not skip on later data rows
           // Except the last one on fullcount
-          EXPECT_EQ(skipped, 0);
+          EXPECT_EQ(skipped.getSkipCount(), 0);
         }
       }
       // NOTE: We might want to get into this situation.
@@ -2136,7 +2138,7 @@ TEST_P(ExecutionBlockImplExecuteIntegrationTest, only_relevant_shadowRows) {
     if (doesWaiting()) {
       // We wait between lines
       EXPECT_EQ(state, ExecutionState::WAITING);
-      EXPECT_EQ(skipped, 0);
+      EXPECT_EQ(skipped.getSkipCount(), 0);
       EXPECT_EQ(block, nullptr);
       std::tie(state, skipped, block) = testee->execute(stack);
     }
@@ -2147,7 +2149,7 @@ TEST_P(ExecutionBlockImplExecuteIntegrationTest, only_relevant_shadowRows) {
       EXPECT_EQ(state, ExecutionState::HASMORE);
     }
     // Cannot skip a shadowRow
-    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(skipped.getSkipCount(), 0);
     ASSERT_NE(block, nullptr);
     ASSERT_EQ(block->size(), 1);
     EXPECT_TRUE(block->hasShadowRows());
@@ -2194,7 +2196,7 @@ TEST_P(ExecutionBlockImplExecuteIntegrationTest, input_and_relevant_shadowRow) {
   if (doesWaiting()) {
     auto const [state, skipped, block] = testee->execute(stack);
     EXPECT_EQ(state, ExecutionState::WAITING);
-    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(skipped.getSkipCount(), 0);
     EXPECT_EQ(block, nullptr);
   }
   auto const [state, skipped, block] = testee->execute(stack);
@@ -2246,7 +2248,7 @@ TEST_P(ExecutionBlockImplExecuteIntegrationTest, input_and_non_relevant_shadowRo
   if (doesWaiting()) {
     auto const [state, skipped, block] = testee->execute(stack);
     EXPECT_EQ(state, ExecutionState::WAITING);
-    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(skipped.getSkipCount(), 0);
     EXPECT_EQ(block, nullptr);
   }
   auto const [state, skipped, block] = testee->execute(stack);
@@ -2315,7 +2317,7 @@ TEST_P(ExecutionBlockImplExecuteIntegrationTest, multiple_subqueries) {
     if (doesWaiting()) {
       auto const [state, skipped, block] = testee->execute(stack);
       EXPECT_EQ(state, ExecutionState::WAITING);
-      EXPECT_EQ(skipped, 0);
+      EXPECT_EQ(skipped.getSkipCount(), 0);
       EXPECT_EQ(block, nullptr);
     }
     auto const [state, skipped, block] = testee->execute(stack);
@@ -2337,7 +2339,7 @@ TEST_P(ExecutionBlockImplExecuteIntegrationTest, multiple_subqueries) {
             testee->execute(forwardStack);
         // We do not care for any data left
         EXPECT_EQ(forwardState, ExecutionState::HASMORE);
-        EXPECT_EQ(forwardSkipped, 0);
+        EXPECT_EQ(forwardSkipped.getSkipCount(), 0);
         // However there need to be two shadow rows
         ASSERT_NE(forwardBlock, nullptr);
         ASSERT_EQ(forwardBlock->size(), 2);
@@ -2396,7 +2398,7 @@ TEST_P(ExecutionBlockImplExecuteIntegrationTest, empty_subquery) {
     // we only wait exactly once, only one block upstream that is not sliced.
     auto const& [state, skipped, block] = testee->execute(stack);
     EXPECT_EQ(state, ExecutionState::WAITING);
-    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(skipped.getSkipCount(), 0);
     EXPECT_EQ(block, nullptr);
   }
   auto call = getCall();
@@ -2408,10 +2410,10 @@ TEST_P(ExecutionBlockImplExecuteIntegrationTest, empty_subquery) {
     EXPECT_EQ(state, ExecutionState::HASMORE);
     ASSERT_NE(block, nullptr);
     if (skip) {
-      EXPECT_EQ(skipped, 1);
+      EXPECT_EQ(skipped.getSkipCount(), 1);
       EXPECT_EQ(block->size(), 2);
     } else {
-      EXPECT_EQ(skipped, 0);
+      EXPECT_EQ(skipped.getSkipCount(), 0);
       EXPECT_EQ(block->size(), 3);
     }
     size_t row = 0;
@@ -2446,7 +2448,7 @@ TEST_P(ExecutionBlockImplExecuteIntegrationTest, empty_subquery) {
     auto const& [state, skipped, block] = testee->execute(stack);
     EXPECT_EQ(state, ExecutionState::HASMORE);
     ASSERT_NE(block, nullptr);
-    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(skipped.getSkipCount(), 0);
     EXPECT_EQ(block->size(), 1);
     size_t row = 0;
     AssertIsShadowRowOfDepth(block, row, 0);
@@ -2472,7 +2474,7 @@ TEST_P(ExecutionBlockImplExecuteIntegrationTest, empty_subquery) {
     auto const& [state, skipped, block] = testee->execute(stack);
     EXPECT_EQ(state, ExecutionState::DONE);
     ASSERT_NE(block, nullptr);
-    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(skipped.getSkipCount(), 0);
     EXPECT_EQ(block->size(), 2);
     size_t row = 0;
     AssertIsShadowRowOfDepth(block, row, 0);
@@ -2542,7 +2544,7 @@ TEST_P(ExecutionBlockImplExecuteIntegrationTest,
   auto [state, skipped, block] = testee.execute(stack);
   if (doesWaiting()) {
     EXPECT_EQ(state, ExecutionState::WAITING);
-    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(skipped.getSkipCount(), 0);
     EXPECT_EQ(block, nullptr);
     std::tie(state, skipped, block) = testee.execute(stack);
   }
@@ -2601,7 +2603,7 @@ TEST_P(ExecutionBlockImplExecuteIntegrationTest, DISABLED_test_outer_subquery_fo
   auto [state, skipped, block] = testee.execute(stack);
   if (doesWaiting()) {
     EXPECT_EQ(state, ExecutionState::WAITING);
-    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(skipped.getSkipCount(), 0);
     EXPECT_EQ(block, nullptr);
     std::tie(state, skipped, block) = testee.execute(stack);
   }
diff --git a/tests/Aql/ExecutionBlockImplTestInstances.cpp b/tests/Aql/ExecutionBlockImplTestInstances.cpp
index b5bfc68a589b..a7af31f4c8f6 100644
--- a/tests/Aql/ExecutionBlockImplTestInstances.cpp
+++ b/tests/Aql/ExecutionBlockImplTestInstances.cpp
@@ -3,7 +3,7 @@
 #include "TestExecutorHelper.h"
 #include "TestLambdaExecutor.h"
 
-template class ::arangodb::aql::ExecutionBlockImpl<TestExecutorHelper>;
-template class ::arangodb::aql::ExecutionBlockImpl<TestEmptyExecutorHelper>;
+// template class ::arangodb::aql::ExecutionBlockImpl<TestExecutorHelper>;
+// template class ::arangodb::aql::ExecutionBlockImpl<TestEmptyExecutorHelper>;
 template class ::arangodb::aql::ExecutionBlockImpl<TestLambdaExecutor>;
 template class ::arangodb::aql::ExecutionBlockImpl<TestLambdaSkipExecutor>;
diff --git a/tests/Aql/ExecutorTestHelper.h b/tests/Aql/ExecutorTestHelper.h
index c3b2686246f1..1a007f01782f 100644
--- a/tests/Aql/ExecutorTestHelper.h
+++ b/tests/Aql/ExecutorTestHelper.h
@@ -210,7 +210,7 @@ struct ExecutorTestHelper {
   ExecutorTestHelper(ExecutorTestHelper const&) = delete;
   ExecutorTestHelper(ExecutorTestHelper&&) = delete;
   explicit ExecutorTestHelper(arangodb::aql::Query& query)
-      : _expectedSkip{0},
+      : _expectedSkip{},
         _expectedState{ExecutionState::HASMORE},
         _testStats{false},
         _unorderedOutput{false},
@@ -300,8 +300,24 @@ struct ExecutorTestHelper {
     return *this;
   }
 
-  auto expectSkipped(std::size_t skip) -> ExecutorTestHelper& {
-    _expectedSkip = skip;
+  /**
+   * @brief
+   *
+   * @tparam Ts numeric type, can actually only be size_t
+   * @param skipOnLevel List of skip counters returned per level. subquery skips first, the last entry is the skip on the executor
+   * @return ExecutorTestHelper& chaining!
+   */
+  template <typename T, typename... Ts>
+  auto expectSkipped(T skipFirst, Ts const... skipOnHigherLevel) -> ExecutorTestHelper& {
+    _expectedSkip = SkipResult{};
+    // This is obvious, proof: Homework.
+    (_expectedSkip.didSkip(static_cast<size_t>(skipFirst)), ...,
+     (_expectedSkip.incrementSubquery(),
+      _expectedSkip.didSkip(static_cast<size_t>(skipOnHigherLevel))));
+
+    // NOTE: the above will increment didSkip by the first entry.
+    // For all following entries it will first increment the subquery depth
+    // and then add the didSkip on them.
     return *this;
   }
 
@@ -377,7 +393,7 @@ struct ExecutorTestHelper {
 
     auto inputBlock = generateInputRanges(itemBlockManager);
 
-    auto skippedTotal = size_t{0};
+    auto skippedTotal = SkipResult{};
     auto finalState = ExecutionState::HASMORE;
 
     TRI_ASSERT(!_pipeline.empty());
@@ -387,7 +403,7 @@ struct ExecutorTestHelper {
 
     if (!loop) {
       auto const [state, skipped, result] = _pipeline.get().front()->execute(_callStack);
-      skippedTotal = skipped;
+      skippedTotal.merge(skipped, false);
       finalState = state;
       if (result != nullptr) {
         allResults.add(result);
@@ -397,8 +413,8 @@ struct ExecutorTestHelper {
         auto const [state, skipped, result] = _pipeline.get().front()->execute(_callStack);
         finalState = state;
         auto call = _callStack.popCall();
-        skippedTotal += skipped;
-        call.didSkip(skipped);
+        skippedTotal.merge(skipped, false);
+        call.didSkip(skipped.getSkipCount());
         if (result != nullptr) {
           call.didProduce(result->size());
           allResults.add(result);
@@ -409,7 +425,6 @@ struct ExecutorTestHelper {
                (!_callStack.peek().hasSoftLimit() ||
                 (_callStack.peek().getLimit() + _callStack.peek().getOffset()) > 0));
     }
-
     EXPECT_EQ(skippedTotal, _expectedSkip);
     EXPECT_EQ(finalState, _expectedState);
     SharedAqlItemBlockPtr result = allResults.steal();
@@ -500,7 +515,7 @@ struct ExecutorTestHelper {
   MatrixBuilder<outputColumns> _output;
   std::vector<std::pair<size_t, uint64_t>> _outputShadowRows{};
   std::array<RegisterId, outputColumns> _outputRegisters;
-  std::size_t _expectedSkip;
+  SkipResult _expectedSkip;
   ExecutionState _expectedState;
   ExecutionStats _expectedStats;
   bool _testStats;
diff --git a/tests/Aql/HashedCollectExecutorTest.cpp b/tests/Aql/HashedCollectExecutorTest.cpp
index 6aca1b82d975..63dffa7cd6d9 100644
--- a/tests/Aql/HashedCollectExecutorTest.cpp
+++ b/tests/Aql/HashedCollectExecutorTest.cpp
@@ -257,7 +257,7 @@ TEST_P(HashedCollectExecutorTest, collect_only_soft_less_second_call) {
     AqlCallStack stack{call};
     auto const [state, skipped, result] = testee.execute(stack);
     EXPECT_EQ(state, ExecutionState::HASMORE);
-    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(skipped.getSkipCount(), 0);
     ASSERT_NE(result, nullptr);
     asserthelper::ValidateBlocksAreEqualUnordered(result, buildExpectedOutput(),
                                                   matchedRows, 2, registersToTest);
@@ -270,7 +270,7 @@ TEST_P(HashedCollectExecutorTest, collect_only_soft_less_second_call) {
     AqlCallStack stack{call};
     auto const [state, skipped, result] = testee.execute(stack);
     EXPECT_EQ(state, ExecutionState::DONE);
-    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(skipped.getSkipCount(), 0);
     ASSERT_NE(result, nullptr);
     asserthelper::ValidateBlocksAreEqualUnordered(result, buildExpectedOutput(),
                                                   matchedRows, 0, registersToTest);
diff --git a/tests/Aql/IdExecutorTest.cpp b/tests/Aql/IdExecutorTest.cpp
index ac203cf39da3..4ec6f1b94df8 100644
--- a/tests/Aql/IdExecutorTest.cpp
+++ b/tests/Aql/IdExecutorTest.cpp
@@ -297,7 +297,7 @@ TEST_F(IdExecutionBlockTest, test_initialize_cursor_get) {
       AqlCallStack stack(std::move(call));
       auto const& [state, skipped, block] = testee.execute(stack);
       EXPECT_EQ(state, ExecutionState::DONE);
-      EXPECT_EQ(skipped, 0);
+      EXPECT_EQ(skipped.getSkipCount(), 0);
       EXPECT_EQ(block, nullptr);
     }
     {
@@ -312,7 +312,7 @@ TEST_F(IdExecutionBlockTest, test_initialize_cursor_get) {
       AqlCallStack stack(std::move(call));
       auto const& [state, skipped, block] = testee.execute(stack);
       EXPECT_EQ(state, ExecutionState::DONE);
-      EXPECT_EQ(skipped, 0);
+      EXPECT_EQ(skipped.getSkipCount(), 0);
       ASSERT_NE(block, nullptr);
       EXPECT_EQ(block->size(), 1);
       auto const& val = block->getValueReference(0, 0);
@@ -340,7 +340,7 @@ TEST_F(IdExecutionBlockTest, test_initialize_cursor_skip) {
       AqlCallStack stack(std::move(call));
       auto const& [state, skipped, block] = testee.execute(stack);
       EXPECT_EQ(state, ExecutionState::DONE);
-      EXPECT_EQ(skipped, 0);
+      EXPECT_EQ(skipped.getSkipCount(), 0);
       EXPECT_EQ(block, nullptr);
     }
     {
@@ -356,7 +356,7 @@ TEST_F(IdExecutionBlockTest, test_initialize_cursor_skip) {
       AqlCallStack stack(std::move(call));
       auto const& [state, skipped, block] = testee.execute(stack);
       EXPECT_EQ(state, ExecutionState::DONE);
-      EXPECT_EQ(skipped, 1);
+      EXPECT_EQ(skipped.getSkipCount(), 1);
       ASSERT_EQ(block, nullptr);
     }
   }
@@ -381,7 +381,7 @@ TEST_F(IdExecutionBlockTest, test_initialize_cursor_fullCount) {
       AqlCallStack stack(std::move(call));
       auto const& [state, skipped, block] = testee.execute(stack);
       EXPECT_EQ(state, ExecutionState::DONE);
-      EXPECT_EQ(skipped, 0);
+      EXPECT_EQ(skipped.getSkipCount(), 0);
       EXPECT_EQ(block, nullptr);
     }
     {
@@ -398,7 +398,7 @@ TEST_F(IdExecutionBlockTest, test_initialize_cursor_fullCount) {
       AqlCallStack stack(std::move(call));
       auto const& [state, skipped, block] = testee.execute(stack);
       EXPECT_EQ(state, ExecutionState::DONE);
-      EXPECT_EQ(skipped, 1);
+      EXPECT_EQ(skipped.getSkipCount(), 1);
       ASSERT_EQ(block, nullptr);
     }
   }
@@ -443,7 +443,8 @@ TEST_P(BlockOverloadTest, test_hardlimit_const_fetcher) {
     // Inject block
     auto inputBlock =
         buildBlock<1>(itemBlockManager, {{0}, {1}, {2}, {3}, {4}, {5}, {6}});
-    testee.injectConstantBlock(inputBlock);
+
+    testee.injectConstantBlock(inputBlock, SkipResult{});
   }
   {
     // Now call with too small hardLimit
@@ -455,9 +456,9 @@ TEST_P(BlockOverloadTest, test_hardlimit_const_fetcher) {
     auto const& [state, skipped, block] = testee.execute(stack);
     EXPECT_EQ(state, ExecutionState::DONE);
     if (useFullCount()) {
-      EXPECT_EQ(skipped, 4);
+      EXPECT_EQ(skipped.getSkipCount(), 4);
     } else {
-      EXPECT_EQ(skipped, 0);
+      EXPECT_EQ(skipped.getSkipCount(), 0);
     }
 
     asserthelper::ValidateBlocksAreEqual(block, expectedOutputBlock);
@@ -468,7 +469,7 @@ TEST_P(BlockOverloadTest, test_hardlimit_const_fetcher) {
     AqlCallStack stack(std::move(call));
     auto const& [state, skipped, block] = testee.execute(stack);
     EXPECT_EQ(state, ExecutionState::DONE);
-    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(skipped.getSkipCount(), 0);
     EXPECT_EQ(block, nullptr);
   }
 }
@@ -480,7 +481,7 @@ TEST_P(BlockOverloadTest, test_hardlimit_const_fetcher_shadow_rows_at_end) {
     auto inputBlock =
         buildBlock<1>(itemBlockManager, {{0}, {1}, {2}, {3}, {4}, {5}, {6}},
                       {{5, 0}, {6, 1}});
-    testee.injectConstantBlock(inputBlock);
+    testee.injectConstantBlock(inputBlock, SkipResult{});
   }
   {
     // Now call with too small hardLimit
@@ -493,9 +494,9 @@ TEST_P(BlockOverloadTest, test_hardlimit_const_fetcher_shadow_rows_at_end) {
     auto const& [state, skipped, block] = testee.execute(stack);
     EXPECT_EQ(state, ExecutionState::DONE);
     if (useFullCount()) {
-      EXPECT_EQ(skipped, 2);
+      EXPECT_EQ(skipped.getSkipCount(), 2);
     } else {
-      EXPECT_EQ(skipped, 0);
+      EXPECT_EQ(skipped.getSkipCount(), 0);
     }
     asserthelper::ValidateBlocksAreEqual(block, expectedOutputBlock);
   }
@@ -505,7 +506,7 @@ TEST_P(BlockOverloadTest, test_hardlimit_const_fetcher_shadow_rows_at_end) {
     AqlCallStack stack(std::move(call));
     auto const& [state, skipped, block] = testee.execute(stack);
     EXPECT_EQ(state, ExecutionState::DONE);
-    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(skipped.getSkipCount(), 0);
     EXPECT_EQ(block, nullptr);
   }
 }
@@ -517,7 +518,7 @@ TEST_P(BlockOverloadTest, test_hardlimit_const_fetcher_shadow_rows_in_between) {
     auto inputBlock =
         buildBlock<1>(itemBlockManager, {{0}, {1}, {2}, {3}, {4}, {5}, {6}},
                       {{3, 0}, {4, 1}, {6, 0}});
-    testee.injectConstantBlock(inputBlock);
+    testee.injectConstantBlock(inputBlock, SkipResult{});
   }
   {
     // Now call with too small hardLimit
@@ -530,9 +531,9 @@ TEST_P(BlockOverloadTest, test_hardlimit_const_fetcher_shadow_rows_in_between) {
     auto const& [state, skipped, block] = testee.execute(stack);
     EXPECT_EQ(state, ExecutionState::HASMORE);
     if (useFullCount()) {
-      EXPECT_EQ(skipped, 1);
+      EXPECT_EQ(skipped.getSkipCount(), 1);
     } else {
-      EXPECT_EQ(skipped, 0);
+      EXPECT_EQ(skipped.getSkipCount(), 0);
     }
     asserthelper::ValidateBlocksAreEqual(block, expectedOutputBlock);
   }
@@ -544,7 +545,7 @@ TEST_P(BlockOverloadTest, test_hardlimit_const_fetcher_shadow_rows_in_between) {
     AqlCallStack stack(std::move(call));
     auto const& [state, skipped, block] = testee.execute(stack);
     EXPECT_EQ(state, ExecutionState::DONE);
-    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(skipped.getSkipCount(), 0);
     asserthelper::ValidateBlocksAreEqual(block, expectedOutputBlock);
   }
 }
@@ -557,7 +558,7 @@ TEST_P(BlockOverloadTest, test_hardlimit_const_fetcher_consecutive_shadow_rows)
     auto inputBlock =
         buildBlock<1>(itemBlockManager, {{0}, {1}, {2}, {3}, {4}, {5}, {6}},
                       {{3, 0}, {4, 1}, {5, 0}, {6, 0}});
-    testee.injectConstantBlock(inputBlock);
+    testee.injectConstantBlock(inputBlock, SkipResult{});
   }
   // We can only return until the next top-level shadow row is reached.
   {
@@ -571,9 +572,9 @@ TEST_P(BlockOverloadTest, test_hardlimit_const_fetcher_consecutive_shadow_rows)
     auto const& [state, skipped, block] = testee.execute(stack);
     EXPECT_EQ(state, ExecutionState::HASMORE);
     if (useFullCount()) {
-      EXPECT_EQ(skipped, 1);
+      EXPECT_EQ(skipped.getSkipCount(), 1);
     } else {
-      EXPECT_EQ(skipped, 0);
+      EXPECT_EQ(skipped.getSkipCount(), 0);
     }
     asserthelper::ValidateBlocksAreEqual(block, expectedOutputBlock);
   }
@@ -586,7 +587,7 @@ TEST_P(BlockOverloadTest, test_hardlimit_const_fetcher_consecutive_shadow_rows)
     AqlCallStack stack(std::move(call));
     auto const& [state, skipped, block] = testee.execute(stack);
     EXPECT_EQ(state, ExecutionState::HASMORE);
-    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(skipped.getSkipCount(), 0);
     asserthelper::ValidateBlocksAreEqual(block, expectedOutputBlock);
   }
   {
@@ -598,7 +599,7 @@ TEST_P(BlockOverloadTest, test_hardlimit_const_fetcher_consecutive_shadow_rows)
     AqlCallStack stack(std::move(call));
     auto const& [state, skipped, block] = testee.execute(stack);
     EXPECT_EQ(state, ExecutionState::DONE);
-    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(skipped.getSkipCount(), 0);
     asserthelper::ValidateBlocksAreEqual(block, expectedOutputBlock);
   }
   {
@@ -607,7 +608,7 @@ TEST_P(BlockOverloadTest, test_hardlimit_const_fetcher_consecutive_shadow_rows)
     AqlCallStack stack(std::move(call));
     auto const& [state, skipped, block] = testee.execute(stack);
     EXPECT_EQ(state, ExecutionState::DONE);
-    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(skipped.getSkipCount(), 0);
     EXPECT_EQ(block, nullptr);
   }
 }
diff --git a/tests/Aql/RemoteExecutorTest.cpp b/tests/Aql/RemoteExecutorTest.cpp
index c5e4bef76825..8a82034d4b60 100644
--- a/tests/Aql/RemoteExecutorTest.cpp
+++ b/tests/Aql/RemoteExecutorTest.cpp
@@ -71,9 +71,7 @@ class DeSerializeAqlCallTest : public ::testing::TestWithParam<AqlCall> {
  public:
   DeSerializeAqlCallTest() = default;
 
-  void SetUp() override {
-    aqlCall = GetParam();
-  }
+  void SetUp() override { aqlCall = GetParam(); }
 
  protected:
   AqlCall aqlCall{};
@@ -118,20 +116,18 @@ class DeSerializeAqlCallStackTest : public ::testing::TestWithParam<AqlCallStack
  public:
   DeSerializeAqlCallStackTest() = default;
 
-  void SetUp() override {
-    aqlCallStack = GetParam();
-  }
+  void SetUp() override { aqlCallStack = GetParam(); }
 
  protected:
   AqlCallStack aqlCallStack{AqlCall{}};
 };
 
 auto const testingAqlCallStacks = ::testing::ValuesIn(std::array{
-  AqlCallStack{AqlCall{}},
-  AqlCallStack{AqlCall{3, false, AqlCall::Infinity{}}},
-  AqlCallStack{AqlCallStack{AqlCall{}}, AqlCall{3, false, AqlCall::Infinity{}}},
-  AqlCallStack{AqlCallStack{AqlCallStack{AqlCall{1}}, AqlCall{2}}, AqlCall{3}},
-  AqlCallStack{AqlCallStack{AqlCallStack{AqlCall{3}}, AqlCall{2}}, AqlCall{1}},
+    AqlCallStack{AqlCall{}},
+    AqlCallStack{AqlCall{3, false, AqlCall::Infinity{}}},
+    AqlCallStack{AqlCallStack{AqlCall{}}, AqlCall{3, false, AqlCall::Infinity{}}},
+    AqlCallStack{AqlCallStack{AqlCallStack{AqlCall{1}}, AqlCall{2}}, AqlCall{3}},
+    AqlCallStack{AqlCallStack{AqlCallStack{AqlCall{3}}, AqlCall{2}}, AqlCall{1}},
 });
 
 TEST_P(DeSerializeAqlCallStackTest, testSuite) {
@@ -149,37 +145,42 @@ TEST_P(DeSerializeAqlCallStackTest, testSuite) {
     return ResultT<AqlCallStack>::error(-1);
   });
 
-  ASSERT_TRUE(maybeDeSerializedCallStack.ok()) << maybeDeSerializedCallStack.errorMessage();
+  ASSERT_TRUE(maybeDeSerializedCallStack.ok())
+      << maybeDeSerializedCallStack.errorMessage();
 
   auto const deSerializedCallStack = *maybeDeSerializedCallStack;
 
   ASSERT_EQ(aqlCallStack, deSerializedCallStack);
 }
 
-INSTANTIATE_TEST_CASE_P(DeSerializeAqlCallStackTestVariations, DeSerializeAqlCallStackTest, testingAqlCallStacks);
-
+INSTANTIATE_TEST_CASE_P(DeSerializeAqlCallStackTestVariations,
+                        DeSerializeAqlCallStackTest, testingAqlCallStacks);
 
 class DeSerializeAqlExecuteResultTest : public ::testing::TestWithParam<AqlExecuteResult> {
  public:
   DeSerializeAqlExecuteResultTest() = default;
 
-  void SetUp() override {
-    aqlExecuteResult = GetParam();
-  }
+  void SetUp() override { aqlExecuteResult = GetParam(); }
 
  protected:
-  AqlExecuteResult aqlExecuteResult{ExecutionState::DONE, 0, nullptr};
+  AqlExecuteResult aqlExecuteResult{ExecutionState::DONE, SkipResult{}, nullptr};
 };
 
 ResourceMonitor resourceMonitor{};
 AqlItemBlockManager manager{&resourceMonitor, SerializationFormat::SHADOWROWS};
 
+auto MakeSkipResult(size_t const i) -> SkipResult {
+  SkipResult res{};
+  res.didSkip(i);
+  return res;
+}
+
 auto const testingAqlExecuteResults = ::testing::ValuesIn(std::array{
-    AqlExecuteResult{ExecutionState::DONE, 0, nullptr},
-    AqlExecuteResult{ExecutionState::HASMORE, 0, nullptr},
-    AqlExecuteResult{ExecutionState::HASMORE, 4, nullptr},
-    AqlExecuteResult{ExecutionState::DONE, 0, buildBlock<1>(manager, {{42}})},
-    AqlExecuteResult{ExecutionState::HASMORE, 3, buildBlock<2>(manager, {{3, 42}, {4, 41}})},
+    AqlExecuteResult{ExecutionState::DONE, MakeSkipResult(0), nullptr},
+    AqlExecuteResult{ExecutionState::HASMORE, MakeSkipResult(4), nullptr},
+    AqlExecuteResult{ExecutionState::DONE, MakeSkipResult(0), buildBlock<1>(manager, {{42}})},
+    AqlExecuteResult{ExecutionState::HASMORE, MakeSkipResult(3),
+                     buildBlock<2>(manager, {{3, 42}, {4, 41}})},
 });
 
 TEST_P(DeSerializeAqlExecuteResultTest, testSuite) {
@@ -203,7 +204,8 @@ TEST_P(DeSerializeAqlExecuteResultTest, testSuite) {
 
   ASSERT_EQ(aqlExecuteResult.state(), deSerializedAqlExecuteResult.state());
   ASSERT_EQ(aqlExecuteResult.skipped(), deSerializedAqlExecuteResult.skipped());
-  ASSERT_EQ(aqlExecuteResult.block() == nullptr, deSerializedAqlExecuteResult.block() == nullptr);
+  ASSERT_EQ(aqlExecuteResult.block() == nullptr,
+            deSerializedAqlExecuteResult.block() == nullptr);
   if (aqlExecuteResult.block() != nullptr) {
     ASSERT_EQ(*aqlExecuteResult.block(), *deSerializedAqlExecuteResult.block())
         << "left: " << blockToString(aqlExecuteResult.block())
@@ -212,6 +214,7 @@ TEST_P(DeSerializeAqlExecuteResultTest, testSuite) {
   ASSERT_EQ(aqlExecuteResult, deSerializedAqlExecuteResult);
 }
 
-INSTANTIATE_TEST_CASE_P(DeSerializeAqlExecuteResultTestVariations, DeSerializeAqlExecuteResultTest, testingAqlExecuteResults);
+INSTANTIATE_TEST_CASE_P(DeSerializeAqlExecuteResultTestVariations,
+                        DeSerializeAqlExecuteResultTest, testingAqlExecuteResults);
 
 }  // namespace arangodb::tests::aql
diff --git a/tests/Aql/ScatterExecutorTest.cpp b/tests/Aql/ScatterExecutorTest.cpp
index 883a8b8498c0..d5cd0968fb98 100644
--- a/tests/Aql/ScatterExecutorTest.cpp
+++ b/tests/Aql/ScatterExecutorTest.cpp
@@ -159,7 +159,7 @@ TEST_P(RandomOrderTest, all_clients_should_get_the_block) {
     AqlCallStack stack{call};
     auto const [state, skipped, block] = testee.executeForClient(stack, client);
     EXPECT_EQ(state, ExecutionState::DONE);
-    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(skipped.getSkipCount(), 0);
     ValidateBlocksAreEqual(block, inputBlock);
   }
 }
@@ -179,7 +179,7 @@ TEST_P(RandomOrderTest, all_clients_can_skip_the_block) {
     AqlCallStack stack{call};
     auto const [state, skipped, block] = testee.executeForClient(stack, client);
     EXPECT_EQ(state, ExecutionState::DONE);
-    EXPECT_EQ(skipped, 3);
+    EXPECT_EQ(skipped.getSkipCount(), 3);
     EXPECT_EQ(block, nullptr);
   }
 }
@@ -201,7 +201,7 @@ TEST_P(RandomOrderTest, all_clients_can_fullcount_the_block) {
     AqlCallStack stack{call};
     auto const [state, skipped, block] = testee.executeForClient(stack, client);
     EXPECT_EQ(state, ExecutionState::DONE);
-    EXPECT_EQ(skipped, 2);
+    EXPECT_EQ(skipped.getSkipCount(), 2);
     ValidateBlocksAreEqual(block, expectedBlock);
   }
 }
@@ -223,7 +223,7 @@ TEST_P(RandomOrderTest, all_clients_can_have_different_calls) {
       AqlCallStack stack{call};
       auto const [state, skipped, block] = testee.executeForClient(stack, client);
       EXPECT_EQ(state, ExecutionState::DONE);
-      EXPECT_EQ(skipped, 0);
+      EXPECT_EQ(skipped.getSkipCount(), 0);
       ValidateBlocksAreEqual(block, inputBlock);
     } else if (client == "b") {
       AqlCall call{};
@@ -232,7 +232,7 @@ TEST_P(RandomOrderTest, all_clients_can_have_different_calls) {
       AqlCallStack stack{call};
       auto const [state, skipped, block] = testee.executeForClient(stack, client);
       EXPECT_EQ(state, ExecutionState::DONE);
-      EXPECT_EQ(skipped, 2);
+      EXPECT_EQ(skipped.getSkipCount(), 2);
       auto expectedBlock = buildBlock<1>(itemBlockManager, {{2}, {3}});
       ValidateBlocksAreEqual(block, expectedBlock);
     } else if (client == "c") {
@@ -242,7 +242,7 @@ TEST_P(RandomOrderTest, all_clients_can_have_different_calls) {
         AqlCallStack stack{call};
         auto const [state, skipped, block] = testee.executeForClient(stack, client);
         EXPECT_EQ(state, ExecutionState::HASMORE);
-        EXPECT_EQ(skipped, 0);
+        EXPECT_EQ(skipped.getSkipCount(), 0);
         auto expectedBlock = buildBlock<1>(itemBlockManager, {{0}, {1}});
         ValidateBlocksAreEqual(block, expectedBlock);
       }
@@ -254,7 +254,7 @@ TEST_P(RandomOrderTest, all_clients_can_have_different_calls) {
         AqlCallStack stack{call};
         auto const [state, skipped, block] = testee.executeForClient(stack, client);
         EXPECT_EQ(state, ExecutionState::HASMORE);
-        EXPECT_EQ(skipped, 1);
+        EXPECT_EQ(skipped.getSkipCount(), 1);
         auto expectedBlock = buildBlock<1>(itemBlockManager, {{3}, {4}});
         ValidateBlocksAreEqual(block, expectedBlock);
       }
@@ -283,7 +283,7 @@ TEST_P(RandomOrderTest, get_does_not_jump_over_shadowrows) {
     AqlCallStack stack{call};
     auto const [state, skipped, block] = testee.executeForClient(stack, client);
     EXPECT_EQ(state, ExecutionState::HASMORE);
-    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(skipped.getSkipCount(), 0);
     ValidateBlocksAreEqual(block, firstExpectedBlock);
   }
 
@@ -295,7 +295,7 @@ TEST_P(RandomOrderTest, get_does_not_jump_over_shadowrows) {
     AqlCallStack stack{call};
     auto const [state, skipped, block] = testee.executeForClient(stack, client);
     EXPECT_EQ(state, ExecutionState::DONE);
-    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(skipped.getSkipCount(), 0);
     ValidateBlocksAreEqual(block, secondExpectedBlock);
   }
 }
@@ -321,7 +321,7 @@ TEST_P(RandomOrderTest, handling_of_higher_depth_shadowrows_produce) {
     AqlCallStack stack{call};
     auto const [state, skipped, block] = testee.executeForClient(stack, client);
     EXPECT_EQ(state, ExecutionState::HASMORE);
-    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(skipped.getSkipCount(), 0);
     ValidateBlocksAreEqual(block, firstExpectedBlock);
   }
 
@@ -333,7 +333,7 @@ TEST_P(RandomOrderTest, handling_of_higher_depth_shadowrows_produce) {
     AqlCallStack stack{call};
     auto const [state, skipped, block] = testee.executeForClient(stack, client);
     EXPECT_EQ(state, ExecutionState::DONE);
-    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(skipped.getSkipCount(), 0);
     ValidateBlocksAreEqual(block, secondExpectedBlock);
   }
 }
@@ -360,7 +360,7 @@ TEST_P(RandomOrderTest, handling_of_higher_depth_shadowrows_skip) {
     AqlCallStack stack{call};
     auto const [state, skipped, block] = testee.executeForClient(stack, client);
     EXPECT_EQ(state, ExecutionState::HASMORE);
-    EXPECT_EQ(skipped, 2);
+    EXPECT_EQ(skipped.getSkipCount(), 2);
     ValidateBlocksAreEqual(block, firstExpectedBlock);
   }
 
@@ -372,7 +372,7 @@ TEST_P(RandomOrderTest, handling_of_higher_depth_shadowrows_skip) {
     AqlCallStack stack{call};
     auto const [state, skipped, block] = testee.executeForClient(stack, client);
     EXPECT_EQ(state, ExecutionState::DONE);
-    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(skipped.getSkipCount(), 0);
     ValidateBlocksAreEqual(block, secondExpectedBlock);
   }
 }
@@ -398,7 +398,7 @@ TEST_P(RandomOrderTest, handling_of_consecutive_shadow_rows) {
       AqlCallStack stack{call};
       auto const [state, skipped, block] = testee.executeForClient(stack, client);
       EXPECT_EQ(state, ExecutionState::HASMORE);
-      EXPECT_EQ(skipped, 0);
+      EXPECT_EQ(skipped.getSkipCount(), 0);
       auto expected =
           buildBlock<1>(itemBlockManager, {{0}, {1}, {2}, {3}}, {{2, 0}, {3, 1}});
       ValidateBlocksAreEqual(block, expected);
@@ -409,7 +409,7 @@ TEST_P(RandomOrderTest, handling_of_consecutive_shadow_rows) {
       AqlCallStack stack{call};
       auto const [state, skipped, block] = testee.executeForClient(stack, client);
       EXPECT_EQ(state, ExecutionState::DONE);
-      EXPECT_EQ(skipped, 0);
+      EXPECT_EQ(skipped.getSkipCount(), 0);
       auto expected = buildBlock<1>(itemBlockManager, {{4}, {5}}, {{0, 0}, {1, 1}});
       ValidateBlocksAreEqual(block, expected);
     }
@@ -434,7 +434,7 @@ TEST_P(RandomOrderTest, shadowrows_with_different_call_types) {
       AqlCallStack stack{call};
       auto const [state, skipped, block] = testee.executeForClient(stack, client);
       EXPECT_EQ(state, ExecutionState::HASMORE);
-      EXPECT_EQ(skipped, 0);
+      EXPECT_EQ(skipped.getSkipCount(), 0);
       auto expectedBlock =
           buildBlock<1>(itemBlockManager, {{0}, {1}, {2}, {3}}, {{3, 0}});
       ValidateBlocksAreEqual(block, expectedBlock);
@@ -445,7 +445,7 @@ TEST_P(RandomOrderTest, shadowrows_with_different_call_types) {
       AqlCallStack stack{call};
       auto const [state, skipped, block] = testee.executeForClient(stack, client);
       EXPECT_EQ(state, ExecutionState::HASMORE);
-      EXPECT_EQ(skipped, 2);
+      EXPECT_EQ(skipped.getSkipCount(), 2);
       auto expectedBlock = buildBlock<1>(itemBlockManager, {{2}, {3}}, {{1, 0}});
       ValidateBlocksAreEqual(block, expectedBlock);
     } else if (client == "c") {
@@ -455,7 +455,7 @@ TEST_P(RandomOrderTest, shadowrows_with_different_call_types) {
         AqlCallStack stack{call};
         auto const [state, skipped, block] = testee.executeForClient(stack, client);
         EXPECT_EQ(state, ExecutionState::HASMORE);
-        EXPECT_EQ(skipped, 0);
+        EXPECT_EQ(skipped.getSkipCount(), 0);
         auto expectedBlock = buildBlock<1>(itemBlockManager, {{0}, {1}});
         ValidateBlocksAreEqual(block, expectedBlock);
       }
@@ -467,7 +467,7 @@ TEST_P(RandomOrderTest, shadowrows_with_different_call_types) {
         AqlCallStack stack{call};
         auto const [state, skipped, block] = testee.executeForClient(stack, client);
         EXPECT_EQ(state, ExecutionState::HASMORE);
-        EXPECT_EQ(skipped, 1);
+        EXPECT_EQ(skipped.getSkipCount(), 1);
         auto expectedBlock = buildBlock<1>(itemBlockManager, {{3}}, {{0, 0}});
         ValidateBlocksAreEqual(block, expectedBlock);
       }
@@ -484,7 +484,7 @@ TEST_P(RandomOrderTest, shadowrows_with_different_call_types) {
       AqlCallStack stack{call};
       auto const [state, skipped, block] = testee.executeForClient(stack, client);
       EXPECT_EQ(state, ExecutionState::DONE);
-      EXPECT_EQ(skipped, 0);
+      EXPECT_EQ(skipped.getSkipCount(), 0);
       auto expectedBlock = buildBlock<1>(itemBlockManager, {{4}, {5}}, {{1, 0}});
       ValidateBlocksAreEqual(block, expectedBlock);
     } else if (client == "b") {
@@ -493,7 +493,7 @@ TEST_P(RandomOrderTest, shadowrows_with_different_call_types) {
       AqlCallStack stack{call};
       auto const [state, skipped, block] = testee.executeForClient(stack, client);
       EXPECT_EQ(state, ExecutionState::DONE);
-      EXPECT_EQ(skipped, 0);
+      EXPECT_EQ(skipped.getSkipCount(), 0);
       auto expectedBlock = buildBlock<1>(itemBlockManager, {{4}, {5}}, {{1, 0}});
       ValidateBlocksAreEqual(block, expectedBlock);
     } else if (client == "c") {
@@ -503,7 +503,7 @@ TEST_P(RandomOrderTest, shadowrows_with_different_call_types) {
         AqlCallStack stack{call};
         auto const [state, skipped, block] = testee.executeForClient(stack, client);
         EXPECT_EQ(state, ExecutionState::DONE);
-        EXPECT_EQ(skipped, 1);
+        EXPECT_EQ(skipped.getSkipCount(), 1);
         auto expectedBlock = buildBlock<1>(itemBlockManager, {{5}}, {{0, 0}});
         ValidateBlocksAreEqual(block, expectedBlock);
       }
@@ -579,7 +579,7 @@ TEST_F(ScatterExecutionBlockTest, any_ordering_of_calls_is_fine) {
       } else {
         EXPECT_EQ(state, ExecutionState::HASMORE);
       }
-      EXPECT_EQ(skipped, 0);
+      EXPECT_EQ(skipped.getSkipCount(), 0);
       ASSERT_TRUE(callNr < blocks.size());
       ValidateBlocksAreEqual(block, blocks[callNr]);
       callNr++;
diff --git a/tests/Aql/SingleRowFetcherTest.cpp b/tests/Aql/SingleRowFetcherTest.cpp
index f0ed040e2783..7ea984f8b9e6 100644
--- a/tests/Aql/SingleRowFetcherTest.cpp
+++ b/tests/Aql/SingleRowFetcherTest.cpp
@@ -1228,7 +1228,7 @@ TEST_F(SingleRowFetcherTestPassBlocks, handling_shadowrows_in_execute_oneAndDone
     // First no data row
     auto [state, skipped, input] = testee.execute(stack);
     EXPECT_EQ(input.getRowIndex(), 0);
-    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(skipped.getSkipCount(), 0);
     EXPECT_EQ(state, ExecutionState::DONE);
   }  // testee is destroyed here
 }
@@ -1263,7 +1263,7 @@ TEST_F(SingleRowFetcherTestPassBlocks, handling_shadowrows_in_execute_twoAndHasM
     auto [state, skipped, input] = testee.execute(stack);
     // We only have one block, no more calls to execute necessary
     EXPECT_EQ(state, ExecutionState::DONE);
-    EXPECT_EQ(skipped, 0);
+    EXPECT_EQ(skipped.getSkipCount(), 0);
     EXPECT_EQ(input.getRowIndex(), 0);
 
     // Now validate the input range
diff --git a/tests/Aql/SkipResultTest.cpp b/tests/Aql/SkipResultTest.cpp
new file mode 100644
index 000000000000..958ab0ad5563
--- /dev/null
+++ b/tests/Aql/SkipResultTest.cpp
@@ -0,0 +1,267 @@
+////////////////////////////////////////////////////////////////////////////////
+/// DISCLAIMER
+///
+/// Copyright 2018 ArangoDB GmbH, Cologne, Germany
+///
+/// Licensed under the Apache License, Version 2.0 (the "License");
+/// you may not use this file except in compliance with the License.
+/// You may obtain a copy of the License at
+///
+///     http://www.apache.org/licenses/LICENSE-2.0
+///
+/// Unless required by applicable law or agreed to in writing, software
+/// distributed under the License is distributed on an "AS IS" BASIS,
+/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+/// See the License for the specific language governing permissions and
+/// limitations under the License.
+///
+/// Copyright holder is ArangoDB GmbH, Cologne, Germany
+///
+/// @author Michael Hackstein
+////////////////////////////////////////////////////////////////////////////////
+
+#include "gtest/gtest.h"
+
+#include "Aql/SkipResult.h"
+#include "Cluster/ResultT.h"
+
+#include <velocypack/Builder.h>
+#include <velocypack/velocypack-aliases.h>
+
+using namespace arangodb;
+using namespace arangodb::aql;
+
+namespace arangodb {
+namespace tests {
+namespace aql {
+
+class SkipResultTest : public ::testing::Test {
+ protected:
+  SkipResultTest() {}
+};
+
+TEST_F(SkipResultTest, defaults_to_0_skip) {
+  SkipResult testee{};
+  EXPECT_EQ(testee.getSkipCount(), 0);
+}
+
+TEST_F(SkipResultTest, counts_skip) {
+  SkipResult testee{};
+  testee.didSkip(5);
+  EXPECT_EQ(testee.getSkipCount(), 5);
+}
+
+TEST_F(SkipResultTest, accumulates_skips) {
+  SkipResult testee{};
+  testee.didSkip(3);
+  testee.didSkip(6);
+  testee.didSkip(8);
+  EXPECT_EQ(testee.getSkipCount(), 17);
+}
+
+TEST_F(SkipResultTest, is_copyable) {
+  SkipResult original{};
+  original.didSkip(6);
+  SkipResult testee{original};
+
+  EXPECT_EQ(testee.getSkipCount(), original.getSkipCount());
+
+  original.didSkip(7);
+  EXPECT_NE(testee.getSkipCount(), original.getSkipCount());
+}
+
+TEST_F(SkipResultTest, can_report_if_we_skip) {
+  SkipResult testee{};
+  EXPECT_TRUE(testee.nothingSkipped());
+  testee.didSkip(3);
+  EXPECT_FALSE(testee.nothingSkipped());
+  testee.didSkip(6);
+  EXPECT_FALSE(testee.nothingSkipped());
+}
+
+TEST_F(SkipResultTest, serialize_deserialize_empty) {
+  SkipResult original{};
+  VPackBuilder builder;
+  original.toVelocyPack(builder);
+  auto maybeTestee = SkipResult::fromVelocyPack(builder.slice());
+  ASSERT_FALSE(maybeTestee.fail());
+  auto testee = maybeTestee.get();
+  EXPECT_EQ(testee.nothingSkipped(), original.nothingSkipped());
+  EXPECT_EQ(testee.getSkipCount(), original.getSkipCount());
+  EXPECT_EQ(testee, original);
+}
+
+TEST_F(SkipResultTest, serialize_deserialize_with_count) {
+  SkipResult original{};
+  original.didSkip(6);
+  VPackBuilder builder;
+  original.toVelocyPack(builder);
+  auto maybeTestee = SkipResult::fromVelocyPack(builder.slice());
+  ASSERT_FALSE(maybeTestee.fail());
+  auto testee = maybeTestee.get();
+  EXPECT_EQ(testee.nothingSkipped(), original.nothingSkipped());
+  EXPECT_EQ(testee.getSkipCount(), original.getSkipCount());
+  EXPECT_EQ(testee, original);
+}
+
+TEST_F(SkipResultTest, can_be_added) {
+  SkipResult a{};
+  a.didSkip(6);
+  SkipResult b{};
+  b.didSkip(7);
+  a += b;
+  EXPECT_EQ(a.getSkipCount(), 13);
+}
+
+TEST_F(SkipResultTest, can_add_a_subquery_depth) {
+  SkipResult a{};
+  a.didSkip(5);
+  EXPECT_EQ(a.getSkipCount(), 5);
+  a.incrementSubquery();
+  EXPECT_EQ(a.getSkipCount(), 0);
+  a.didSkip(7);
+  EXPECT_EQ(a.getSkipCount(), 7);
+  a.decrementSubquery();
+  EXPECT_EQ(a.getSkipCount(), 5);
+}
+
+TEST_F(SkipResultTest, nothing_skip_on_subquery) {
+  SkipResult a{};
+  EXPECT_TRUE(a.nothingSkipped());
+  a.didSkip(6);
+  EXPECT_FALSE(a.nothingSkipped());
+  a.incrementSubquery();
+  EXPECT_EQ(a.getSkipCount(), 0);
+  EXPECT_FALSE(a.nothingSkipped());
+}
+
+TEST_F(SkipResultTest, serialize_deserialize_with_a_subquery) {
+  SkipResult original{};
+  original.didSkip(6);
+  original.incrementSubquery();
+  original.didSkip(2);
+
+  VPackBuilder builder;
+  original.toVelocyPack(builder);
+  auto maybeTestee = SkipResult::fromVelocyPack(builder.slice());
+  ASSERT_FALSE(maybeTestee.fail());
+  auto testee = maybeTestee.get();
+  // Use built_in eq
+  EXPECT_EQ(testee, original);
+  // Manual test
+  EXPECT_EQ(testee.nothingSkipped(), original.nothingSkipped());
+  EXPECT_EQ(testee.getSkipCount(), original.getSkipCount());
+  EXPECT_EQ(testee.subqueryDepth(), original.subqueryDepth());
+  original.decrementSubquery();
+  testee.decrementSubquery();
+  EXPECT_EQ(testee.nothingSkipped(), original.nothingSkipped());
+  EXPECT_EQ(testee.getSkipCount(), original.getSkipCount());
+  EXPECT_EQ(testee.subqueryDepth(), original.subqueryDepth());
+}
+
+TEST_F(SkipResultTest, equality) {
+  auto buildTestSet = []() -> std::vector<SkipResult> {
+    SkipResult empty{};
+    SkipResult skip1{};
+    skip1.didSkip(6);
+
+    SkipResult skip2{};
+    skip2.didSkip(8);
+
+    SkipResult subQuery1{};
+    subQuery1.incrementSubquery();
+    subQuery1.didSkip(4);
+
+    SkipResult subQuery2{};
+    subQuery2.didSkip(8);
+    subQuery2.incrementSubquery();
+    subQuery2.didSkip(4);
+
+    SkipResult subQuery3{};
+    subQuery3.didSkip(8);
+    subQuery3.incrementSubquery();
+    return {empty, skip1, skip2, subQuery1, subQuery2, subQuery3};
+  };
+
+  // We create two identical sets with different entries
+  auto set1 = buildTestSet();
+  auto set2 = buildTestSet();
+  for (size_t i = 0; i < set1.size(); ++i) {
+    for (size_t j = 0; j < set2.size(); ++j) {
+      // Addresses are different
+      EXPECT_NE(&set1.at(i), &set2.at(j));
+      // Identical index => Equal object
+      if (i == j) {
+        EXPECT_EQ(set1.at(i), set2.at(j));
+      } else {
+        EXPECT_NE(set1.at(i), set2.at(j));
+      }
+    }
+  }
+}
+
+TEST_F(SkipResultTest, merge_with_toplevel) {
+  SkipResult a{};
+  a.didSkip(12);
+  a.incrementSubquery();
+  a.didSkip(8);
+
+  SkipResult b{};
+  b.didSkip(9);
+  b.incrementSubquery();
+  b.didSkip(2);
+
+  a.merge(b, false);
+
+  SkipResult expected{};
+  expected.didSkip(12);
+  expected.didSkip(9);
+  expected.incrementSubquery();
+  expected.didSkip(8);
+  expected.didSkip(2);
+  EXPECT_EQ(a, expected);
+}
+
+TEST_F(SkipResultTest, merge_without_toplevel) {
+  SkipResult a{};
+  a.didSkip(12);
+  a.incrementSubquery();
+  a.didSkip(8);
+
+  SkipResult b{};
+  b.didSkip(9);
+  b.incrementSubquery();
+  b.didSkip(2);
+
+  a.merge(b, true);
+
+  SkipResult expected{};
+  expected.didSkip(12);
+  expected.didSkip(9);
+  expected.incrementSubquery();
+  expected.didSkip(8);
+  EXPECT_EQ(a, expected);
+}
+
+TEST_F(SkipResultTest, reset) {
+  SkipResult a{};
+  a.didSkip(12);
+  a.incrementSubquery();
+  a.didSkip(8);
+
+  EXPECT_EQ(a.getSkipCount(), 8);
+  EXPECT_EQ(a.subqueryDepth(), 2);
+  EXPECT_FALSE(a.nothingSkipped());
+  a.reset();
+
+  EXPECT_EQ(a.getSkipCount(), 0);
+  EXPECT_EQ(a.subqueryDepth(), 2);
+  EXPECT_TRUE(a.nothingSkipped());
+
+  a.decrementSubquery();
+  EXPECT_EQ(a.getSkipCount(), 0);
+}
+
+}  // namespace aql
+}  // namespace tests
+}  // namespace arangodb
diff --git a/tests/Aql/SpliceSubqueryOptimizerRuleTest.cpp b/tests/Aql/SpliceSubqueryOptimizerRuleTest.cpp
index 94e9940f4e42..19b3d524716f 100644
--- a/tests/Aql/SpliceSubqueryOptimizerRuleTest.cpp
+++ b/tests/Aql/SpliceSubqueryOptimizerRuleTest.cpp
@@ -313,49 +313,41 @@ TEST_F(SpliceSubqueryNodeOptimizerRuleTest, splice_subquery_with_sort) {
   verifyQueryResult(query, expected->slice());
 }
 
-// Must be changed as soon as the subquery implementation with shadow rows handle skipping,
-// and the splice-subqueries optimizer rule is changed to allow it.
-TEST_F(SpliceSubqueryNodeOptimizerRuleTest, dont_splice_subquery_with_skip__inner_limit_offset) {
+TEST_F(SpliceSubqueryNodeOptimizerRuleTest, splice_subquery_with_skip__inner_limit_offset) {
   auto const queryString = R"aql(FOR i IN 0..2
     LET a = (FOR j IN 0..2 LIMIT 1, 1 RETURN 3*i + j)
     RETURN FIRST(a))aql";
   auto const expectedString = R"res([1, 4, 7])res";
 
-  verifySubquerySplicing(queryString, 0, 1);
+  verifySubquerySplicing(queryString, 1);
   auto expected = arangodb::velocypack::Parser::fromJson(expectedString);
   verifyQueryResult(queryString, expected->slice());
 }
 
-// Must be changed as soon as the subquery implementation with shadow rows handle skipping,
-// and the splice-subqueries optimizer rule is changed to allow it.
-TEST_F(SpliceSubqueryNodeOptimizerRuleTest, dont_splice_subquery_with_skip__outer_limit_offset) {
+TEST_F(SpliceSubqueryNodeOptimizerRuleTest, splice_subquery_with_skip__outer_limit_offset) {
   auto const queryString = R"aql(FOR i IN 0..2
     LET a = (FOR j IN 0..2 RETURN 3*i + j)
     LIMIT 1, 1
     RETURN FIRST(a))aql";
   auto const expectedString = R"res([3])res";
 
-  verifySubquerySplicing(queryString, 0, 1);
+  verifySubquerySplicing(queryString, 1);
   auto expected = arangodb::velocypack::Parser::fromJson(expectedString);
   verifyQueryResult(queryString, expected->slice());
 }
 
-// Must be changed as soon as the subquery implementation with shadow rows handle skipping,
-// and the splice-subqueries optimizer rule is changed to allow it.
-TEST_F(SpliceSubqueryNodeOptimizerRuleTest, dont_splice_subquery_with_skip__inner_collect_count) {
+TEST_F(SpliceSubqueryNodeOptimizerRuleTest, splice_subquery_with_skip__inner_collect_count) {
   auto const queryString = R"aql(FOR i IN 0..2
     LET a = (FOR j IN 0..i COLLECT WITH COUNT INTO n RETURN n)
     RETURN FIRST(a))aql";
   auto const expectedString = R"res([1, 2, 3])res";
 
-  verifySubquerySplicing(queryString, 0, 1);
+  verifySubquerySplicing(queryString, 1);
   auto expected = arangodb::velocypack::Parser::fromJson(expectedString);
   verifyQueryResult(queryString, expected->slice());
 }
 
-// Must be changed as soon as the subquery implementation with shadow rows handle skipping,
-// and the splice-subqueries optimizer rule is changed to allow it.
-TEST_F(SpliceSubqueryNodeOptimizerRuleTest, dont_splice_subquery_with_skip__outer_collect_count) {
+TEST_F(SpliceSubqueryNodeOptimizerRuleTest, splice_subquery_with_skip__outer_collect_count) {
   // the RAND() is there to avoid the subquery being removed
   auto const queryString = R"aql(FOR i IN 0..2
     LET a = (FOR j IN 0..FLOOR(2*RAND()) RETURN 1)
@@ -363,14 +355,14 @@ TEST_F(SpliceSubqueryNodeOptimizerRuleTest, dont_splice_subquery_with_skip__oute
     RETURN n)aql";
   auto const expectedString = R"res([3])res";
 
-  verifySubquerySplicing(queryString, 0, 1);
+  verifySubquerySplicing(queryString, 1);
   auto expected = arangodb::velocypack::Parser::fromJson(expectedString);
   verifyQueryResult(queryString, expected->slice());
 }
 
 // Must be changed as soon as the subquery implementation with shadow rows handle skipping,
 // and the splice-subqueries optimizer rule is changed to allow it.
-TEST_F(SpliceSubqueryNodeOptimizerRuleTest, dont_splice_subquery_with_skip__full_count) {
+TEST_F(SpliceSubqueryNodeOptimizerRuleTest, splice_subquery_with_skip__full_count) {
   // the RAND() is there to avoid the subquery being removed
   auto const queryString = R"aql(FOR i IN 0..2
     LET a = (FOR j IN 0..FLOOR(2*RAND()) RETURN 1)
@@ -378,7 +370,7 @@ TEST_F(SpliceSubqueryNodeOptimizerRuleTest, dont_splice_subquery_with_skip__full
     RETURN i)aql";
   auto const expectedString = R"res([0])res";
 
-  verifySubquerySplicing(queryString, 0, 1, "{}", R"opts({"fullCount": true})opts");
+  verifySubquerySplicing(queryString, 1, 0, "{}", R"opts({"fullCount": true})opts");
   auto expected = arangodb::velocypack::Parser::fromJson(expectedString);
   verifyQueryResult(queryString, expected->slice());
 }
@@ -412,7 +404,7 @@ TEST_F(SpliceSubqueryNodeOptimizerRuleTest, splice_nested_subquery_with_innermos
     FOR i IN 0..1
     LET js = ( // this subquery should be spliced
       FOR j IN 0..1 + FLOOR(RAND())
-      LET ks = ( // this subquery should not be spliced
+      LET ks = ( // this subquery should be spliced
         FOR k IN 0..2 + FLOOR(RAND())
         LIMIT 1, 2
         RETURN 6*i + 3*j + k
@@ -423,7 +415,7 @@ TEST_F(SpliceSubqueryNodeOptimizerRuleTest, splice_nested_subquery_with_innermos
   )aql";
   auto const expectedString = R"res([[[1, 2], [4, 5]], [[7, 8], [10, 11]]])res";
 
-  verifySubquerySplicing(queryString, 1, 1);
+  verifySubquerySplicing(queryString, 2);
   auto expected = arangodb::velocypack::Parser::fromJson(expectedString);
   verifyQueryResult(queryString, expected->slice());
 }
@@ -440,7 +432,7 @@ TEST_F(SpliceSubqueryNodeOptimizerRuleTest, splice_nested_subquery_with_innermos
   )aql";
   auto const expectedString = R"res([{"a": 1, "b": [[3, 4]]}, {"a": 2, "b": [[3, 4]]}])res";
 
-  verifySubquerySplicing(queryString, 1, 1);
+  verifySubquerySplicing(queryString, 2);
   auto expected = arangodb::velocypack::Parser::fromJson(expectedString);
   verifyQueryResult(queryString, expected->slice());
 }
@@ -450,7 +442,7 @@ TEST_F(SpliceSubqueryNodeOptimizerRuleTest, splice_nested_subquery_with_innermos
 TEST_F(SpliceSubqueryNodeOptimizerRuleTest, splice_nested_subquery_with_outermost_skip) {
   auto const queryString = R"aql(
     FOR i IN 0..2
-    LET js = ( // this subquery should not be spliced
+    LET js = ( // this subquery should be spliced
       FOR j IN 0..1 + FLOOR(RAND())
       LET ks = ( // this subquery should be spliced
         FOR k IN 0..1 + FLOOR(RAND())
@@ -463,19 +455,19 @@ TEST_F(SpliceSubqueryNodeOptimizerRuleTest, splice_nested_subquery_with_outermos
   )aql";
   auto const expectedString = R"res([[[4, 5], [6, 7]], [[8, 9], [10, 11]]])res";
 
-  verifySubquerySplicing(queryString, 1, 1);
+  verifySubquerySplicing(queryString, 2);
   auto expected = arangodb::velocypack::Parser::fromJson(expectedString);
   verifyQueryResult(queryString, expected->slice());
 }
 
 // Must be changed as soon as the subquery implementation with shadow rows handle skipping,
 // and the splice-subqueries optimizer rule is changed to allow it.
-TEST_F(SpliceSubqueryNodeOptimizerRuleTest, dont_splice_subquery_with_limit_and_no_offset) {
+TEST_F(SpliceSubqueryNodeOptimizerRuleTest, splice_subquery_with_limit_and_no_offset) {
   auto query = R"aql(
     FOR i IN 2..4
       LET a = (FOR j IN [i, i+10, i+20] LIMIT 0, 1 RETURN j)
       RETURN FIRST(a))aql";
-  verifySubquerySplicing(query, 0, 1);
+  verifySubquerySplicing(query, 1);
 
   auto expected = arangodb::velocypack::Parser::fromJson(R"([2, 3, 4])");
   verifyQueryResult(query, expected->slice());
@@ -496,7 +488,6 @@ TEST_F(SpliceSubqueryNodeOptimizerRuleTest, splice_nested_empty_subqueries) {
     RETURN [results]
   )aql";
   auto const expectedString = R"res([[[]]])res";
-
   verifySubquerySplicing(queryString, 2);
   auto expected = arangodb::velocypack::Parser::fromJson(expectedString);
   verifyQueryResult(queryString, expected->slice());
@@ -521,7 +512,7 @@ TEST_F(SpliceSubqueryNodeOptimizerRuleTest, splice_subquery_with_upsert) {
   auto const bindString = R"bind({"key": "myKey"})bind";
   auto const expectedString = R"res([["UnitTestCollection/myKey"]])res";
 
-  verifySubquerySplicing(queryString, 1, 1, bindString);
+  verifySubquerySplicing(queryString, 2, 0, bindString);
   auto expected = arangodb::velocypack::Parser::fromJson(expectedString);
   verifyQueryResult(queryString, expected->slice(), bindString);
 
@@ -781,8 +772,7 @@ TEST_F(SpliceSubqueryNodeOptimizerRuleTest, splice_subquery_with_collect_in_subq
   verifyQueryResult(queryString, expected->slice());
 }
 
-// Disabled as long as the subquery implementation with shadow rows cannot yet handle skipping.
-TEST_F(SpliceSubqueryNodeOptimizerRuleTest, DISABLED_splice_subquery_with_limit_and_offset) {
+TEST_F(SpliceSubqueryNodeOptimizerRuleTest, splice_subquery_with_limit_and_offset) {
   auto query = R"aql(
     FOR i IN 2..4
       LET a = (FOR j IN [0, i, i+10] LIMIT 1, 1 RETURN j)
@@ -793,9 +783,7 @@ TEST_F(SpliceSubqueryNodeOptimizerRuleTest, DISABLED_splice_subquery_with_limit_
   verifyQueryResult(query, expected->slice());
 }
 
-// Disabled as long as the subquery implementation with shadow rows cannot yet handle skipping.
-TEST_F(SpliceSubqueryNodeOptimizerRuleTest,
-       DISABLED_splice_subquery_collect_within_empty_nested_subquery) {
+TEST_F(SpliceSubqueryNodeOptimizerRuleTest, splice_subquery_collect_within_empty_nested_subquery) {
   auto query = R"aql(
     FOR k IN 1..2
       LET sub1 = (
@@ -813,6 +801,46 @@ TEST_F(SpliceSubqueryNodeOptimizerRuleTest,
   verifyQueryResult(query, expected->slice());
 }
 
+TEST_F(SpliceSubqueryNodeOptimizerRuleTest, splice_subquery_skip_nodes) {
+  auto query = R"aql(
+    FOR k IN 1..10
+      LET sub1 = (
+        FOR j IN 1..10
+        LET sub2 = (
+          FOR i IN 1..4
+          LIMIT 2,10
+          RETURN i
+        )
+        LIMIT 2,10
+        RETURN [j, sub2]
+      )
+      LIMIT 3, 10
+      RETURN [k, sub1])aql";
+  verifySubquerySplicing(query, 2);
+
+  VPackBuilder builder;
+  builder.openArray();
+  for (size_t k = 4; k <= 10; ++k) {
+    builder.openArray();
+    builder.add(VPackValue(k));
+    builder.openArray();
+    for (size_t j = 3; j <= 10; ++j) {
+      builder.openArray();
+      builder.add(VPackValue(j));
+      builder.openArray();
+      for (size_t i = 3; i <= 4; ++i) {
+        builder.add(VPackValue(i));
+      }
+      builder.close();
+      builder.close();
+    }
+    builder.close();
+    builder.close();
+  }
+  builder.close();
+  verifyQueryResult(query, builder.slice());
+}
+
 // TODO Check isInSplicedSubquery
 // TODO Test cluster rules
 
diff --git a/tests/Aql/SplicedSubqueryIntegrationTest.cpp b/tests/Aql/SplicedSubqueryIntegrationTest.cpp
index f6f37d99f4b1..943afe458c2a 100644
--- a/tests/Aql/SplicedSubqueryIntegrationTest.cpp
+++ b/tests/Aql/SplicedSubqueryIntegrationTest.cpp
@@ -236,24 +236,34 @@ class SplicedSubqueryIntegrationTest
   auto createSkipCall() -> SkipCall {
     return [](AqlItemBlockInputRange& input,
               AqlCall& call) -> std::tuple<ExecutorState, LambdaExe::Stats, size_t, AqlCall> {
-      auto skipped = size_t{0};
+      while (call.shouldSkip() && input.skippedInFlight() > 0) {
+        if (call.getOffset() > 0) {
+          call.didSkip(input.skip(call.getOffset()));
+        } else {
+          EXPECT_TRUE(call.needsFullCount());
+          EXPECT_EQ(call.getLimit(), 0);
+          EXPECT_TRUE(call.hasHardLimit());
+          call.didSkip(input.skipAll());
+        }
+      }
+      // If we overfetched and have data, throw it away
       while (input.hasDataRow() && call.shouldSkip()) {
         auto const& [state, inputRow] = input.nextDataRow();
         EXPECT_TRUE(inputRow.isInitialized());
         call.didSkip(1);
-        skipped++;
       }
       auto upstreamCall = AqlCall{call};
-      return {input.upstreamState(), NoStats{}, skipped, upstreamCall};
+      return {input.upstreamState(), NoStats{}, call.getSkipCount(), upstreamCall};
     };
   };
 
   // Asserts if called. This is to check that when we use skip to
   // skip over a subquery, the subquery's produce is not invoked
+  // with data
   auto createAssertCall() -> ProduceCall {
     return [](AqlItemBlockInputRange& input,
               OutputAqlItemRow& output) -> std::tuple<ExecutorState, LambdaExe::Stats, AqlCall> {
-      EXPECT_TRUE(false);
+      EXPECT_FALSE(input.hasDataRow());
       NoStats stats{};
       AqlCall call{};
 
@@ -333,7 +343,7 @@ TEST_P(SplicedSubqueryIntegrationTest, single_subquery) {
       .run();
 };
 
-TEST_P(SplicedSubqueryIntegrationTest, DISABLED_single_subquery_skip_and_produce) {
+TEST_P(SplicedSubqueryIntegrationTest, single_subquery_skip_and_produce) {
   auto call = AqlCall{5};
   auto pipeline = createSubquery();
   ExecutorTestHelper<1, 2>{*fakedQuery}
@@ -347,7 +357,7 @@ TEST_P(SplicedSubqueryIntegrationTest, DISABLED_single_subquery_skip_and_produce
       .run();
 };
 
-TEST_P(SplicedSubqueryIntegrationTest, DISABLED_single_subquery_skip_all) {
+TEST_P(SplicedSubqueryIntegrationTest, single_subquery_skip_all) {
   auto call = AqlCall{20};
   auto pipeline = createSubquery();
   ExecutorTestHelper<1, 2>{*fakedQuery}
@@ -361,7 +371,7 @@ TEST_P(SplicedSubqueryIntegrationTest, DISABLED_single_subquery_skip_all) {
       .run();
 };
 
-TEST_P(SplicedSubqueryIntegrationTest, DISABLED_single_subquery_fullcount) {
+TEST_P(SplicedSubqueryIntegrationTest, single_subquery_fullcount) {
   auto call = AqlCall{0, true, 0, AqlCall::LimitType::HARD};
   auto pipeline = createSubquery();
   ExecutorTestHelper<1, 2>{*fakedQuery}
@@ -375,6 +385,8 @@ TEST_P(SplicedSubqueryIntegrationTest, DISABLED_single_subquery_fullcount) {
       .run();
 };
 
+// NOTE: This test can be enabled if we can continue
+// working on the second subquery without returning to consumer
 TEST_P(SplicedSubqueryIntegrationTest, DISABLED_single_subquery_skip_produce_count) {
   auto call = AqlCall{2, true, 2, AqlCall::LimitType::HARD};
   auto pipeline = createSubquery();
@@ -442,7 +454,7 @@ TEST_P(SplicedSubqueryIntegrationTest, do_nothing_in_subquery) {
       .run();
 };
 
-TEST_P(SplicedSubqueryIntegrationTest, DISABLED_check_call_passes_subquery) {
+TEST_P(SplicedSubqueryIntegrationTest, check_call_passes_subquery) {
   auto call = AqlCall{10};
   auto pipeline = concatPipelines(createCallAssertPipeline(call), createSubquery());
 
@@ -456,8 +468,9 @@ TEST_P(SplicedSubqueryIntegrationTest, DISABLED_check_call_passes_subquery) {
       .run();
 };
 
-TEST_P(SplicedSubqueryIntegrationTest, DISABLED_check_skipping_subquery) {
+TEST_P(SplicedSubqueryIntegrationTest, check_skipping_subquery) {
   auto call = AqlCall{10};
+  LOG_DEVEL << call;
   auto pipeline = createSubquery(createAssertPipeline());
 
   executorTestHelper.setPipeline(std::move(pipeline))
@@ -465,7 +478,23 @@ TEST_P(SplicedSubqueryIntegrationTest, DISABLED_check_skipping_subquery) {
       .setInputSplitType(getSplit())
       .setCall(call)
       .expectOutput({0}, {})
-      .expectSkipped(0)
+      .expectSkipped(8)
       .expectedState(ExecutionState::DONE)
       .run();
 };
+
+TEST_P(SplicedSubqueryIntegrationTest, check_soft_limit_subquery) {
+  auto call = AqlCall{0, false, 4, AqlCall::LimitType::SOFT};
+  LOG_DEVEL << call;
+  auto pipeline = createSubquery(createAssertPipeline());
+
+  ExecutorTestHelper<1, 2>{*fakedQuery}
+      .setPipeline(std::move(pipeline))
+      .setInputValueList(1, 2, 5, 2, 1, 5, 7, 1)
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({0, 1}, {{1, R"([])"}, {2, R"([])"}, {5, R"([])"}, {2, R"([])"}})
+      .expectSkipped(0)
+      .expectedState(ExecutionState::HASMORE)
+      .run();
+};
\ No newline at end of file
diff --git a/tests/Aql/SubqueryStartExecutorTest.cpp b/tests/Aql/SubqueryStartExecutorTest.cpp
index dc02b404e2d0..d73fbc9cc5e8 100644
--- a/tests/Aql/SubqueryStartExecutorTest.cpp
+++ b/tests/Aql/SubqueryStartExecutorTest.cpp
@@ -101,7 +101,7 @@ TEST_P(SubqueryStartExecutorTest, empty_input_does_not_add_shadow_rows) {
       .expectedStats(ExecutionStats{})
       .expectedState(ExecutionState::DONE)
       .expectOutput({0}, {})
-      .expectSkipped(0)
+      .expectSkipped(0, 0)
       .setCallStack(queryStack(AqlCall{}, AqlCall{}))
       .run();
 }
@@ -112,7 +112,7 @@ TEST_P(SubqueryStartExecutorTest, adds_a_shadowrow_after_single_input) {
       .setInputValue({{R"("a")"}})
       .expectedStats(ExecutionStats{})
       .expectedState(ExecutionState::DONE)
-      .expectSkipped(0)
+      .expectSkipped(0, 0)
       .expectOutput({0}, {{R"("a")"}, {R"("a")"}}, {{1, 0}})
       .setCallStack(queryStack(AqlCall{}, AqlCall{}))
       .run();
@@ -128,7 +128,7 @@ TEST_P(SubqueryStartExecutorTest,
       .setInputValue({{{R"("a")"}}, {{R"("b")"}}, {{R"("c")"}}})
       .expectedStats(ExecutionStats{})
       .expectedState(ExecutionState::HASMORE)
-      .expectSkipped(0)
+      .expectSkipped(0, 0)
       .expectOutput({0}, {{R"("a")"}, {R"("a")"}}, {{1, 0}})
       .setCallStack(queryStack(AqlCall{}, AqlCall{}))
       .run();
@@ -144,7 +144,7 @@ TEST_P(SubqueryStartExecutorTest, DISABLED_adds_a_shadowrow_after_every_input_li
       .setInputValue({{{R"("a")"}}, {{R"("b")"}}, {{R"("c")"}}})
       .expectedStats(ExecutionStats{})
       .expectedState(ExecutionState::DONE)
-      .expectSkipped(0)
+      .expectSkipped(0, 0)
       .expectOutput({0}, {{R"("a")"}, {R"("a")"}, {R"("b")"}, {R"("b")"}, {R"("c")"}, {R"("c")"}},
                     {{1, 0}, {3, 0}, {5, 0}})
       .setCallStack(queryStack(AqlCall{}, AqlCall{}))
@@ -159,7 +159,7 @@ TEST_P(SubqueryStartExecutorTest, adds_a_shadowrow_after_every_input_line) {
       .setInputValue({{{R"("a")"}}, {{R"("b")"}}, {{R"("c")"}}})
       .expectedStats(ExecutionStats{})
       .expectedState(ExecutionState::DONE)
-      .expectSkipped(0)
+      .expectSkipped(0, 0)
       .expectOutput({0}, {{R"("a")"}, {R"("a")"}, {R"("b")"}, {R"("b")"}, {R"("c")"}, {R"("c")"}},
                     {{1, 0}, {3, 0}, {5, 0}})
       .setCallStack(queryStack(AqlCall{}, AqlCall{}))
@@ -181,7 +181,7 @@ TEST_P(SubqueryStartExecutorTest, shadow_row_does_not_fit_in_current_block) {
         .setInputValue({{R"("a")"}})
         .expectedStats(ExecutionStats{})
         .expectedState(ExecutionState::HASMORE)
-        .expectSkipped(0)
+        .expectSkipped(0, 0)
         .expectOutput({0}, {{R"("a")"}}, {})
         .setCallStack(queryStack(AqlCall{}, AqlCall{}))
         .run();
@@ -194,7 +194,7 @@ TEST_P(SubqueryStartExecutorTest, shadow_row_does_not_fit_in_current_block) {
         .setInputValue({{R"("a")"}})
         .expectedStats(ExecutionStats{})
         .expectedState(ExecutionState::DONE)
-        .expectSkipped(0)
+        .expectSkipped(0, 0)
         .expectOutput({0}, {{R"("a")"}, {R"("a")"}}, {{1, 0}})
         .setCallStack(queryStack(AqlCall{}, AqlCall{}))
         .run(true);
@@ -208,7 +208,7 @@ TEST_P(SubqueryStartExecutorTest, skip_in_subquery) {
       .expectedStats(ExecutionStats{})
       .expectedState(ExecutionState::DONE)
       .expectOutput({0}, {{R"("a")"}}, {{0, 0}})
-      .expectSkipped(1)
+      .expectSkipped(0, 1)
       .setCallStack(queryStack(AqlCall{}, AqlCall{10, false}))
       .run();
 }
@@ -220,7 +220,7 @@ TEST_P(SubqueryStartExecutorTest, fullCount_in_subquery) {
       .expectedStats(ExecutionStats{})
       .expectedState(ExecutionState::DONE)
       .expectOutput({0}, {{R"("a")"}}, {{0, 0}})
-      .expectSkipped(1)
+      .expectSkipped(0, 1)
       .setCallStack(queryStack(AqlCall{}, AqlCall{0, true, 0, AqlCall::LimitType::HARD}))
       .run();
 }
@@ -234,12 +234,20 @@ TEST_P(SubqueryStartExecutorTest, shadow_row_forwarding) {
                                                                  ExecutionNode::SUBQUERY_START))
       .addConsumer(helper.createExecBlock<SubqueryStartExecutor>(MakeBaseInfos(1),
                                                                  ExecutionNode::SUBQUERY_START));
+
+  if (GetCompatMode() == CompatibilityMode::VERSION36) {
+    // We will not get this infromation because the
+    // query stack is too small on purpose
+    helper.expectSkipped(0, 0);
+  } else {
+    helper.expectSkipped(0, 0, 0);
+  }
+
   helper.setPipeline(std::move(pipe))
       .setInputValue({{R"("a")"}})
       .expectedStats(ExecutionStats{})
       .expectedState(ExecutionState::DONE)
       .expectOutput({0}, {{R"("a")"}, {R"("a")"}, {R"("a")"}}, {{1, 0}, {2, 1}})
-      .expectSkipped(0)
       .setCallStack(stack)
       .run();
 }
@@ -253,12 +261,20 @@ TEST_P(SubqueryStartExecutorTest, shadow_row_forwarding_many_inputs_single_call)
                                                                  ExecutionNode::SUBQUERY_START))
       .addConsumer(helper.createExecBlock<SubqueryStartExecutor>(MakeBaseInfos(1),
                                                                  ExecutionNode::SUBQUERY_START));
+
+  if (GetCompatMode() == CompatibilityMode::VERSION36) {
+    // We will not get this infromation because the
+    // query stack is too small on purpose
+    helper.expectSkipped(0, 0);
+  } else {
+    helper.expectSkipped(0, 0, 0);
+  }
+
   helper.setPipeline(std::move(pipe))
       .setInputValue({{R"("a")"}, {R"("b")"}, {R"("c")"}})
       .expectedStats(ExecutionStats{})
       .expectedState(ExecutionState::HASMORE)
       .expectOutput({0}, {{R"("a")"}, {R"("a")"}, {R"("a")"}}, {{1, 0}, {2, 1}})
-      .expectSkipped(0)
       .setCallStack(stack)
       .run();
 }
@@ -272,6 +288,13 @@ TEST_P(SubqueryStartExecutorTest, shadow_row_forwarding_many_inputs_many_request
                                                                  ExecutionNode::SUBQUERY_START))
       .addConsumer(helper.createExecBlock<SubqueryStartExecutor>(MakeBaseInfos(1),
                                                                  ExecutionNode::SUBQUERY_START));
+  if (GetCompatMode() == CompatibilityMode::VERSION36) {
+    // We will not get this infromation because the
+    // query stack is too small on purpose
+    helper.expectSkipped(0, 0);
+  } else {
+    helper.expectSkipped(0, 0, 0);
+  }
   helper.setPipeline(std::move(pipe))
       .setInputValue({{R"("a")"}, {R"("b")"}, {R"("c")"}})
       .expectedStats(ExecutionStats{})
@@ -280,7 +303,6 @@ TEST_P(SubqueryStartExecutorTest, shadow_row_forwarding_many_inputs_many_request
           {0},
           {{R"("a")"}, {R"("a")"}, {R"("a")"}, {R"("b")"}, {R"("b")"}, {R"("b")"}, {R"("c")"}, {R"("c")"}, {R"("c")"}},
           {{1, 0}, {2, 1}, {4, 0}, {5, 1}, {7, 0}, {8, 1}})
-      .expectSkipped(0)
       .setCallStack(stack)
       .run(true);
 }
@@ -303,12 +325,19 @@ TEST_P(SubqueryStartExecutorTest, shadow_row_forwarding_many_inputs_not_enough_s
                                                                    ExecutionNode::SUBQUERY_START))
         .addConsumer(helper.createExecBlock<SubqueryStartExecutor>(MakeBaseInfos(1),
                                                                    ExecutionNode::SUBQUERY_START));
+
+    if (GetCompatMode() == CompatibilityMode::VERSION36) {
+      // We will not get this infromation because the
+      // query stack is too small on purpose
+      helper.expectSkipped(0, 0);
+    } else {
+      helper.expectSkipped(0, 0, 0);
+    }
     helper.setPipeline(std::move(pipe))
         .setInputValue({{R"("a")"}, {R"("b")"}, {R"("c")"}})
         .expectedStats(ExecutionStats{})
         .expectedState(ExecutionState::HASMORE)
         .expectOutput({0}, {{R"("a")"}, {R"("a")"}}, {{1, 0}})
-        .expectSkipped(0)
         .setCallStack(stack)
         .run();
   }
@@ -323,6 +352,15 @@ TEST_P(SubqueryStartExecutorTest, shadow_row_forwarding_many_inputs_not_enough_s
                                                                    ExecutionNode::SUBQUERY_START))
         .addConsumer(helper.createExecBlock<SubqueryStartExecutor>(MakeBaseInfos(1),
                                                                    ExecutionNode::SUBQUERY_START));
+
+    if (GetCompatMode() == CompatibilityMode::VERSION36) {
+      // We will not get this infromation because the
+      // query stack is too small on purpose
+      helper.expectSkipped(0, 0);
+    } else {
+      helper.expectSkipped(0, 0, 0);
+    }
+
     helper.setPipeline(std::move(pipe))
         .setInputValue({{R"("a")"}, {R"("b")"}, {R"("c")"}})
         .expectedStats(ExecutionStats{})
@@ -331,12 +369,105 @@ TEST_P(SubqueryStartExecutorTest, shadow_row_forwarding_many_inputs_not_enough_s
             {0},
             {{R"("a")"}, {R"("a")"}, {R"("a")"}, {R"("b")"}, {R"("b")"}, {R"("b")"}, {R"("c")"}, {R"("c")"}, {R"("c")"}},
             {{1, 0}, {2, 1}, {4, 0}, {5, 1}, {7, 0}, {8, 1}})
-        .expectSkipped(0)
         .setCallStack(stack)
         .run(true);
   }
 }
 
-// TODO:
-// * Add tests for Skipping
-//    - on Higher level subquery
+TEST_P(SubqueryStartExecutorTest, skip_in_outer_subquery) {
+  if (GetCompatMode() == CompatibilityMode::VERSION37) {
+    ExecutorTestHelper<1, 1>(*fakedQuery)
+        .setExecBlock<SubqueryStartExecutor>(MakeBaseInfos(1), ExecutionNode::SUBQUERY_START)
+        .setInputValue({{R"("a")"}, {R"("b")"}})
+        .expectedStats(ExecutionStats{})
+        .expectedState(ExecutionState::DONE)
+        .expectOutput({0}, {{R"("b")"}, {R"("b")"}}, {{1, 0}})
+        .expectSkipped(1, 0)
+        .setCallStack(queryStack(AqlCall{1, false, AqlCall::Infinity{}}, AqlCall{}))
+        .run();
+  } else {
+    // The feature is not available in 3.6 or earlier.
+  }
+}
+
+TEST_P(SubqueryStartExecutorTest, DISABLED_skip_only_in_outer_subquery) {
+  if (GetCompatMode() == CompatibilityMode::VERSION37) {
+    ExecutorTestHelper<1, 1>(*fakedQuery)
+        .setExecBlock<SubqueryStartExecutor>(MakeBaseInfos(1), ExecutionNode::SUBQUERY_START)
+        .setInputValue({{R"("a")"}, {R"("b")"}})
+        .expectedStats(ExecutionStats{})
+        .expectedState(ExecutionState::DONE)
+        .expectOutput({0}, {})
+        .expectSkipped(1, 0)
+        .setCallStack(queryStack(AqlCall{1, false}, AqlCall{}))
+        .run();
+  } else {
+    // The feature is not available in 3.7 or earlier.
+  }
+}
+
+TEST_P(SubqueryStartExecutorTest, fullCount_in_outer_subquery) {
+  if (GetCompatMode() == CompatibilityMode::VERSION37) {
+    ExecutorTestHelper<1, 1>(*fakedQuery)
+        .setExecBlock<SubqueryStartExecutor>(MakeBaseInfos(1), ExecutionNode::SUBQUERY_START)
+        .setInputValue({{R"("a")"}, {R"("b")"}, {R"("c")"}, {R"("d")"}, {R"("e")"}, {R"("f")"}})
+        .expectedStats(ExecutionStats{})
+        .expectedState(ExecutionState::DONE)
+        .expectOutput({0}, {})
+        .expectSkipped(6, 0)
+        .setCallStack(queryStack(AqlCall{0, true, 0, AqlCall::LimitType::HARD}, AqlCall{}))
+        .run();
+  } else {
+    // The feature is not available in 3.7 or earlier.
+  }
+}
+
+TEST_P(SubqueryStartExecutorTest, fastForward_in_inner_subquery) {
+  if (GetCompatMode() == CompatibilityMode::VERSION37) {
+    ExecutorTestHelper<1, 1>(*fakedQuery)
+        .setExecBlock<SubqueryStartExecutor>(MakeBaseInfos(1), ExecutionNode::SUBQUERY_START)
+        .setInputValue({{R"("a")"}, {R"("b")"}, {R"("c")"}, {R"("d")"}, {R"("e")"}, {R"("f")"}})
+        .expectedStats(ExecutionStats{})
+        .expectedState(ExecutionState::HASMORE)
+        .expectOutput({0}, {{R"("a")"}}, {{0, 0}})
+        .expectSkipped(0, 0)
+        .setCallStack(queryStack(AqlCall{0, false, AqlCall::Infinity{}},
+                                 AqlCall{0, false, 0, AqlCall::LimitType::HARD}))
+        .run();
+  } else {
+    // The feature is not available in 3.7 or earlier.
+  }
+}
+
+TEST_P(SubqueryStartExecutorTest, skip_out_skip_in) {
+  if (GetCompatMode() == CompatibilityMode::VERSION37) {
+    ExecutorTestHelper<1, 1>(*fakedQuery)
+        .setExecBlock<SubqueryStartExecutor>(MakeBaseInfos(1), ExecutionNode::SUBQUERY_START)
+        .setInputValue({{R"("a")"}, {R"("b")"}, {R"("c")"}, {R"("d")"}, {R"("e")"}, {R"("f")"}})
+        .expectedStats(ExecutionStats{})
+        .expectedState(ExecutionState::HASMORE)
+        .expectOutput({0}, {{R"("c")"}}, {{0, 0}})
+        .expectSkipped(2, 1)
+        .setCallStack(queryStack(AqlCall{2, false, AqlCall::Infinity{}},
+                                 AqlCall{10, false, AqlCall::Infinity{}}))
+        .run();
+  } else {
+    // The feature is not available in 3.7 or earlier.
+  }
+}
+
+TEST_P(SubqueryStartExecutorTest, fullbypass_in_outer_subquery) {
+  if (GetCompatMode() == CompatibilityMode::VERSION37) {
+    ExecutorTestHelper<1, 1>(*fakedQuery)
+        .setExecBlock<SubqueryStartExecutor>(MakeBaseInfos(1), ExecutionNode::SUBQUERY_START)
+        .setInputValue({{R"("a")"}, {R"("b")"}, {R"("c")"}, {R"("d")"}, {R"("e")"}, {R"("f")"}})
+        .expectedStats(ExecutionStats{})
+        .expectedState(ExecutionState::DONE)
+        .expectOutput({0}, {})
+        .expectSkipped(0, 0)
+        .setCallStack(queryStack(AqlCall{0, false, 0, AqlCall::LimitType::HARD}, AqlCall{}))
+        .run();
+  } else {
+    // The feature is not available in 3.7 or earlier.
+  }
+}
diff --git a/tests/Aql/WaitingExecutionBlockMock.cpp b/tests/Aql/WaitingExecutionBlockMock.cpp
index c48de11e02e4..5ed988f8478e 100644
--- a/tests/Aql/WaitingExecutionBlockMock.cpp
+++ b/tests/Aql/WaitingExecutionBlockMock.cpp
@@ -27,6 +27,7 @@
 #include "Aql/ExecutionEngine.h"
 #include "Aql/ExecutionState.h"
 #include "Aql/QueryOptions.h"
+#include "Aql/SkipResult.h"
 
 #include "Logger/LogMacros.h"
 
@@ -113,7 +114,7 @@ std::pair<arangodb::aql::ExecutionState, size_t> WaitingExecutionBlockMock::skip
   }
 }
 
-std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> WaitingExecutionBlockMock::execute(AqlCallStack stack) {
+std::tuple<ExecutionState, SkipResult, SharedAqlItemBlockPtr> WaitingExecutionBlockMock::execute(AqlCallStack stack) {
   traceExecuteBegin(stack);
   auto res = executeWithoutTrace(stack);
   traceExecuteEnd(res);
@@ -121,7 +122,7 @@ std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> WaitingExecutionBlockM
 }
 
 // NOTE: Does not care for shadowrows!
-std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> WaitingExecutionBlockMock::executeWithoutTrace(
+std::tuple<ExecutionState, SkipResult, SharedAqlItemBlockPtr> WaitingExecutionBlockMock::executeWithoutTrace(
     AqlCallStack stack) {
   while (!stack.isRelevant()) {
     stack.pop();
@@ -135,7 +136,7 @@ std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> WaitingExecutionBlockM
   if (_variant != WaitingBehaviour::NEVER && !_hasWaited) {
     // If we ordered waiting check on _hasWaited and wait if not
     _hasWaited = true;
-    return {ExecutionState::WAITING, 0, nullptr};
+    return {ExecutionState::WAITING, SkipResult{}, nullptr};
   }
   if (_variant == WaitingBehaviour::ALWAYS) {
     // If we always wait, reset.
@@ -154,7 +155,9 @@ std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> WaitingExecutionBlockM
         // Sorry we can only return one block.
         // This means we have prepared the first block.
         // But still need more data.
-        return {ExecutionState::HASMORE, skipped, result};
+        SkipResult skipRes{};
+        skipRes.didSkip(skipped);
+        return {ExecutionState::HASMORE, skipRes, result};
       } else {
         dropBlock();
         continue;
@@ -177,7 +180,9 @@ std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> WaitingExecutionBlockM
         // Sorry we can only return one block.
         // This means we have prepared the first block.
         // But still need more data.
-        return {ExecutionState::HASMORE, skipped, result};
+        SkipResult skipRes{};
+        skipRes.didSkip(skipped);
+        return {ExecutionState::HASMORE, skipRes, result};
       }
 
       size_t canReturn = _data.front()->size() - _inflight;
@@ -212,16 +217,20 @@ std::tuple<ExecutionState, size_t, SharedAqlItemBlockPtr> WaitingExecutionBlockM
           dropBlock();
         }
       }
+      SkipResult skipRes{};
+      skipRes.didSkip(skipped);
       if (!_data.empty()) {
-        return {ExecutionState::HASMORE, skipped, result};
+        return {ExecutionState::HASMORE, skipRes, result};
       } else if (result != nullptr && result->size() < myCall.hardLimit) {
-        return {ExecutionState::HASMORE, skipped, result};
+        return {ExecutionState::HASMORE, skipRes, result};
       } else {
-        return {ExecutionState::DONE, skipped, result};
+        return {ExecutionState::DONE, skipRes, result};
       }
     }
   }
-  return {ExecutionState::DONE, skipped, result};
+  SkipResult skipRes{};
+  skipRes.didSkip(skipped);
+  return {ExecutionState::DONE, skipRes, result};
 }
 
 void WaitingExecutionBlockMock::dropBlock() {
diff --git a/tests/Aql/WaitingExecutionBlockMock.h b/tests/Aql/WaitingExecutionBlockMock.h
index 2c147ba08e91..b1ad73e01bd8 100644
--- a/tests/Aql/WaitingExecutionBlockMock.h
+++ b/tests/Aql/WaitingExecutionBlockMock.h
@@ -35,6 +35,7 @@ class AqlItemBlock;
 class ExecutionEngine;
 class ExecutionNode;
 struct ResourceMonitor;
+class SkipResult;
 }  // namespace aql
 
 namespace tests {
@@ -106,15 +107,15 @@ class WaitingExecutionBlockMock final : public arangodb::aql::ExecutionBlock {
    */
   std::pair<arangodb::aql::ExecutionState, size_t> skipSome(size_t atMost) override;
 
-  std::tuple<arangodb::aql::ExecutionState, size_t, arangodb::aql::SharedAqlItemBlockPtr> execute(
+  std::tuple<arangodb::aql::ExecutionState, arangodb::aql::SkipResult, arangodb::aql::SharedAqlItemBlockPtr> execute(
       arangodb::aql::AqlCallStack stack) override;
 
  private:
   void dropBlock();
 
   // Implementation of execute
-  std::tuple<arangodb::aql::ExecutionState, size_t, arangodb::aql::SharedAqlItemBlockPtr> executeWithoutTrace(
-      arangodb::aql::AqlCallStack stack);
+  std::tuple<arangodb::aql::ExecutionState, arangodb::aql::SkipResult, arangodb::aql::SharedAqlItemBlockPtr>
+  executeWithoutTrace(arangodb::aql::AqlCallStack stack);
 
  private:
   std::deque<arangodb::aql::SharedAqlItemBlockPtr> _data;
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 9ed9e68f7a40..4c8d6934d0dd 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -64,6 +64,7 @@ set(ARANGODB_TESTS_SOURCES
   Aql/RowFetcherHelper.cpp
   Aql/ScatterExecutorTest.cpp
   Aql/ShortestPathExecutorTest.cpp
+  Aql/SkipResultTest.cpp
   Aql/SingleRowFetcherTest.cpp
   Aql/SortedCollectExecutorTest.cpp
   Aql/SortExecutorTest.cpp
diff --git a/tests/js/server/aql/aql-optimizer-indexes.js b/tests/js/server/aql/aql-optimizer-indexes.js
index a08553b36d69..b42fd4955654 100644
--- a/tests/js/server/aql/aql-optimizer-indexes.js
+++ b/tests/js/server/aql/aql-optimizer-indexes.js
@@ -862,13 +862,9 @@ function optimizerIndexesTestSuite () {
       });
 
       assertEqual("SingletonNode", nodeTypes[0], query);
-      assertEqual("SubqueryNode", nodeTypes[1], query);
-
-      var subNodeTypes = plan.nodes[1].subquery.nodes.map(function(node) {
-        return node.type;
-      });
-      assertNotEqual(-1, subNodeTypes.indexOf("IndexNode"), query);
-      assertEqual(-1, subNodeTypes.indexOf("SortNode"), query);
+      assertEqual("SubqueryStartNode", nodeTypes[1], query);
+      assertNotEqual(-1, nodeTypes.indexOf("IndexNode"), query);
+      assertEqual(-1, nodeTypes.indexOf("SortNode"), query);
       assertEqual("ReturnNode", nodeTypes[nodeTypes.length - 1], query);
 
       var results = AQL_EXECUTE(query, {}, opt);
@@ -3776,26 +3772,39 @@ function optimizerIndexesMultiCollectionTestSuite () {
       var query = "FOR i IN " + c1.name() + " LET res = (FOR j IN " + c2.name() + " FILTER j.value == i.value SORT j.ref LIMIT 1 RETURN j) SORT res[0] RETURN i";
 
       var plan = AQL_EXPLAIN(query, {}, opt).plan;
-      var nodeTypes = plan.nodes.map(function(node) {
-        return node.type;
-      });
+      let idx = -1;
+      const nodeTypes = [];
+      const subqueryTypes = [];
+      {
+        let inSubquery = false;
+        for (const node of plan.nodes) {
+          const n = node.type;
+          if (n === "SubqueryStartNode" ) {
+            nodeTypes.push(n);
+            inSubquery = true;
+          } else if (n === "SubqueryEndNode" ) {
+            nodeTypes.push(n);
+            inSubquery = false;
+          } else if (inSubquery) {
+            if (n === "IndexNode") {
+              idx = node;
+            }
+            subqueryTypes.push(n);
+          } else {
+            nodeTypes.push(n);
+          }
+        }
+      }
 
       assertEqual("SingletonNode", nodeTypes[0], query);
       assertEqual(-1, nodeTypes.indexOf("IndexNode"), query); // no index for outer query
       assertNotEqual(-1, nodeTypes.indexOf("SortNode"), query); // sort node for outer query
 
-      var sub = nodeTypes.indexOf("SubqueryNode");
+      var sub = nodeTypes.indexOf("SubqueryStartNode");
       assertNotEqual(-1, sub);
-
-      var subNodeTypes = plan.nodes[sub].subquery.nodes.map(function(node) {
-        return node.type;
-      });
-
-      assertEqual("SingletonNode", subNodeTypes[0], query);
-      var idx = subNodeTypes.indexOf("IndexNode");
       assertNotEqual(-1, idx, query); // index used for inner query
-      assertEqual("hash", plan.nodes[sub].subquery.nodes[idx].indexes[0].type);
-      assertNotEqual(-1, subNodeTypes.indexOf("SortNode"), query); // must have sort node for inner query
+      assertEqual("hash", idx.indexes[0].type);
+      assertNotEqual(-1, subqueryTypes.indexOf("SortNode"), query); // must have sort node for inner query
     },
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -3807,26 +3816,39 @@ function optimizerIndexesMultiCollectionTestSuite () {
       var query = "FOR i IN " + c1.name() + " LET res = (FOR j IN " + c2.name() + " FILTER j.value == i.value SORT j.value LIMIT 1 RETURN j) SORT res[0] RETURN i";
 
       var plan = AQL_EXPLAIN(query, {}, opt).plan;
-      var nodeTypes = plan.nodes.map(function(node) {
-        return node.type;
-      });
-
+      const nodeTypes = [];
+      const subqueryTypes = [];
+      let idx = -1;
+      {
+        let inSubquery = false;
+        for (const node of plan.nodes) {
+          const n = node.type;
+          if (n === "SubqueryStartNode" ) {
+            nodeTypes.push(n);
+            inSubquery = true;
+          } else if (n === "SubqueryEndNode" ) {
+            nodeTypes.push(n);
+            inSubquery = false;
+          } else if (inSubquery) {
+            if (n === "IndexNode") {
+              idx = node;
+            }
+            subqueryTypes.push(n);
+          } else {
+            nodeTypes.push(n);
+          }
+        }
+      }
       assertEqual("SingletonNode", nodeTypes[0], query);
       assertEqual(-1, nodeTypes.indexOf("IndexNode"), query); // no index for outer query
       assertNotEqual(-1, nodeTypes.indexOf("SortNode"), query); // sort node for outer query
 
-      var sub = nodeTypes.indexOf("SubqueryNode");
+      var sub = nodeTypes.indexOf("SubqueryStartNode");
       assertNotEqual(-1, sub);
 
-      var subNodeTypes = plan.nodes[sub].subquery.nodes.map(function(node) {
-        return node.type;
-      });
-
-      assertEqual("SingletonNode", subNodeTypes[0], query);
-      var idx = subNodeTypes.indexOf("IndexNode");
-      assertNotEqual(-1, idx, query); // index used for inner query
-      assertEqual("hash", plan.nodes[sub].subquery.nodes[idx].indexes[0].type);
-      assertEqual(-1, subNodeTypes.indexOf("SortNode"), query); // must not have sort node for inner query
+      assertNotEqual(-1, subqueryTypes.indexOf("IndexNode"), query); // index used for inner query
+      assertEqual("hash", idx.indexes[0].type);
+      assertEqual(-1, subqueryTypes.indexOf("SortNode"), query); // must not have sort node for inner query
     },
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -3839,26 +3861,40 @@ function optimizerIndexesMultiCollectionTestSuite () {
       var query = "FOR i IN " + c1.name() + " LET res = (FOR j IN " + c2.name() + " FILTER j.value == i.value SORT j.ref LIMIT 1 RETURN j) SORT res[0] RETURN i";
 
       var plan = AQL_EXPLAIN(query, {}, opt).plan;
-      var nodeTypes = plan.nodes.map(function(node) {
-        return node.type;
-      });
+      const nodeTypes = [];
+      const subqueryTypes = [];
+      let idx = -1;
+      {
+        let inSubquery = false;
+        for (const node of plan.nodes) {
+          const n = node.type;
+          if (n === "SubqueryStartNode" ) {
+            nodeTypes.push(n);
+            inSubquery = true;
+          } else if (n === "SubqueryEndNode" ) {
+            nodeTypes.push(n);
+            inSubquery = false;
+          } else if (inSubquery) {
+            if (n === "IndexNode") {
+              idx = node;
+            }
+            subqueryTypes.push(n);
+          } else {
+            nodeTypes.push(n);
+          }
+        }
+      }
 
       assertEqual("SingletonNode", nodeTypes[0], query);
       assertEqual(-1, nodeTypes.indexOf("IndexNode"), query); // no index for outer query
       assertNotEqual(-1, nodeTypes.indexOf("SortNode"), query); // sort node for outer query
 
-      var sub = nodeTypes.indexOf("SubqueryNode");
+      var sub = nodeTypes.indexOf("SubqueryStartNode");
       assertNotEqual(-1, sub);
-
-      var subNodeTypes = plan.nodes[sub].subquery.nodes.map(function(node) {
-        return node.type;
-      });
-
-      assertEqual("SingletonNode", subNodeTypes[0], query);
-      var idx = subNodeTypes.indexOf("IndexNode");
-      assertNotEqual(-1, idx, query); // index used for inner query
-      assertEqual("hash", plan.nodes[sub].subquery.nodes[idx].indexes[0].type);
-      assertNotEqual(-1, subNodeTypes.indexOf("SortNode"), query); // must have sort node for inner query
+      assertNotEqual(-1, idx);
+      assertNotEqual(-1, subqueryTypes.indexOf("IndexNode"), query); // index used for inner query
+      assertEqual("hash", idx.indexes[0].type);
+      assertNotEqual(-1, subqueryTypes.indexOf("SortNode"), query); // must have sort node for inner query
     },
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -3871,26 +3907,40 @@ function optimizerIndexesMultiCollectionTestSuite () {
       var query = "FOR i IN " + c1.name() + " LET res = (FOR j IN " + c2.name() + " FILTER j.value == i.value SORT j.value LIMIT 1 RETURN j) SORT res[0] RETURN i";
 
       var plan = AQL_EXPLAIN(query, {}, opt).plan;
-      var nodeTypes = plan.nodes.map(function(node) {
-        return node.type;
-      });
+      const nodeTypes = [];
+      const subqueryTypes = [];
+      let idx = -1;
+      {
+        let inSubquery = false;
+        for (const node of plan.nodes) {
+          const n = node.type;
+          if (n === "SubqueryStartNode" ) {
+            nodeTypes.push(n);
+            inSubquery = true;
+          } else if (n === "SubqueryEndNode" ) {
+            nodeTypes.push(n);
+            inSubquery = false;
+          } else if (inSubquery) {
+            if (n === "IndexNode") {
+              idx = node;
+            }
+            subqueryTypes.push(n);
+          } else {
+            nodeTypes.push(n);
+          }
+        }
+      }
 
       assertEqual("SingletonNode", nodeTypes[0], query);
       assertEqual(-1, nodeTypes.indexOf("IndexNode"), query); // no index for outer query
       assertNotEqual(-1, nodeTypes.indexOf("SortNode"), query); // sort node for outer query
 
-      var sub = nodeTypes.indexOf("SubqueryNode");
-      assertNotEqual(-1, sub);
+      assertNotEqual(-1, nodeTypes.indexOf("SubqueryStartNode"), query);
 
-      var subNodeTypes = plan.nodes[sub].subquery.nodes.map(function(node) {
-        return node.type;
-      });
-
-      assertEqual("SingletonNode", subNodeTypes[0], query);
-      var idx = subNodeTypes.indexOf("IndexNode");
+      assertNotEqual(-1, subqueryTypes.indexOf("IndexNode"), query);
       assertNotEqual(-1, idx, query); // index used for inner query
-      assertEqual("hash", plan.nodes[sub].subquery.nodes[idx].indexes[0].type);
-      assertEqual(-1, subNodeTypes.indexOf("SortNode"), query); // we're filtering on a constant, must not have sort node for inner query
+      assertEqual("hash", idx.indexes[0].type);
+      assertEqual(-1, subqueryTypes.indexOf("SortNode"), query); // we're filtering on a constant, must not have sort node for inner query
     },
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -3903,26 +3953,40 @@ function optimizerIndexesMultiCollectionTestSuite () {
       var query = "FOR i IN " + c1.name() + " LET res = (FOR z IN 1..2 FOR j IN " + c2.name() + " FILTER j.value == i.value SORT j.value LIMIT 1 RETURN j) SORT res[0] RETURN i";
 
       var plan = AQL_EXPLAIN(query, {}, opt).plan;
-      var nodeTypes = plan.nodes.map(function(node) {
-        return node.type;
-      });
+      const nodeTypes = [];
+      const subqueryTypes = [];
+      let idx = -1;
+      {
+        let inSubquery = false;
+        for (const node of plan.nodes) {
+          const n = node.type;
+          if (n === "SubqueryStartNode" ) {
+            nodeTypes.push(n);
+            inSubquery = true;
+          } else if (n === "SubqueryEndNode" ) {
+            nodeTypes.push(n);
+            inSubquery = false;
+          } else if (inSubquery) {
+            if (n === "IndexNode") {
+              idx = node;
+            }
+            subqueryTypes.push(n);
+          } else {
+            nodeTypes.push(n);
+          }
+        }
+      }
 
       assertEqual("SingletonNode", nodeTypes[0], query);
       assertEqual(-1, nodeTypes.indexOf("IndexNode"), query); // no index for outer query
       assertNotEqual(-1, nodeTypes.indexOf("SortNode"), query); // sort node for outer query
 
-      var sub = nodeTypes.indexOf("SubqueryNode");
-      assertNotEqual(-1, sub);
-
-      var subNodeTypes = plan.nodes[sub].subquery.nodes.map(function(node) {
-        return node.type;
-      });
-
-      assertEqual("SingletonNode", subNodeTypes[0], query);
-      var idx = subNodeTypes.indexOf("IndexNode");
+      var sub = nodeTypes.indexOf("SubqueryStartNode");
+      assertNotEqual(-1, sub, query);
+      assertNotEqual(-1, subqueryTypes.indexOf("IndexNode"), query);
       assertNotEqual(-1, idx, query); // index used for inner query
-      assertEqual("hash", plan.nodes[sub].subquery.nodes[idx].indexes[0].type);
-      assertNotEqual(-1, subNodeTypes.indexOf("SortNode"), query); // we're filtering on a constant, but we're in an inner loop
+      assertEqual("hash", idx.indexes[0].type);
+      assertNotEqual(-1, subqueryTypes.indexOf("SortNode"), query); // we're filtering on a constant, but we're in an inner loop
     },
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -3935,26 +3999,39 @@ function optimizerIndexesMultiCollectionTestSuite () {
       var query = "FOR i IN " + c1.name() + " LET res = (FOR j IN " + c2.name() + " FILTER j.ref == i.ref SORT j.ref LIMIT 1 RETURN j) SORT res[0] RETURN i";
 
       var plan = AQL_EXPLAIN(query, {}, opt).plan;
-      var nodeTypes = plan.nodes.map(function(node) {
-        return node.type;
-      });
+      const nodeTypes = [];
+      const subqueryTypes = [];
+      let idx = -1;
+      {
+        let inSubquery = false;
+        for (const node of plan.nodes) {
+          const n = node.type;
+          if (n === "SubqueryStartNode" ) {
+            nodeTypes.push(n);
+            inSubquery = true;
+          } else if (n === "SubqueryEndNode" ) {
+            nodeTypes.push(n);
+            inSubquery = false;
+          } else if (inSubquery) {
+            if (n === "IndexNode") {
+              idx = node;
+            }
+            subqueryTypes.push(n);
+          } else {
+            nodeTypes.push(n);
+          }
+        }
+      }
 
       assertEqual("SingletonNode", nodeTypes[0], query);
       assertEqual(-1, nodeTypes.indexOf("IndexNode"), query); // no index for outer query
       assertNotEqual(-1, nodeTypes.indexOf("SortNode"), query); // sort node for outer query
+      assertNotEqual(-1, nodeTypes.indexOf("SubqueryStartNode"), query);
 
-      var sub = nodeTypes.indexOf("SubqueryNode");
-      assertNotEqual(-1, sub);
-
-      var subNodeTypes = plan.nodes[sub].subquery.nodes.map(function(node) {
-        return node.type;
-      });
-
-      assertEqual("SingletonNode", subNodeTypes[0], query);
-      var idx = subNodeTypes.indexOf("IndexNode");
+      assertNotEqual(-1, subqueryTypes.indexOf("IndexNode"), query);
       assertNotEqual(-1, idx, query); // index used for inner query
-      assertEqual("skiplist", plan.nodes[sub].subquery.nodes[idx].indexes[0].type);
-      assertEqual(-1, subNodeTypes.indexOf("SortNode"), query); // must not have sort node for inner query
+      assertEqual("skiplist", idx.indexes[0].type);
+      assertEqual(-1, subqueryTypes.indexOf("SortNode"), query); // must not have sort node for inner query
     },
 
 ////////////////////////////////////////////////////////////////////////////////
diff --git a/tests/js/server/aql/aql-optimizer-rule-move-calculations-down.js b/tests/js/server/aql/aql-optimizer-rule-move-calculations-down.js
index 54e7c8d0bd7d..37023b6157d1 100644
--- a/tests/js/server/aql/aql-optimizer-rule-move-calculations-down.js
+++ b/tests/js/server/aql/aql-optimizer-rule-move-calculations-down.js
@@ -371,7 +371,7 @@ function optimizerRuleTestSuite () {
         expected.push("test" + i + "-" + i);
       }
 
-      var query = "FOR i IN 0..100 LET result = (UPDATE {_key: CONCAT('test', TO_STRING(i))} WITH {updated: true} IN " + cn + " RETURN CONCAT(NEW._key, '-', NEW.value)) LIMIT 10 RETURN result[0]";
+      var query = "FOR i IN 0..99 LET result = (UPDATE {_key: CONCAT('test', TO_STRING(i))} WITH {updated: true} IN " + cn + " RETURN CONCAT(NEW._key, '-', NEW.value)) LIMIT 10 RETURN result[0]";
       var planDisabled = AQL_EXPLAIN(query, {}, paramDisabled);
       var planEnabled = AQL_EXPLAIN(query, {}, paramEnabled);
 
diff --git a/tests/js/server/aql/aql-optimizer-rule-no-document-materialization-arangosearch.js b/tests/js/server/aql/aql-optimizer-rule-no-document-materialization-arangosearch.js
index d6fb5cfe0102..59626c692b9a 100644
--- a/tests/js/server/aql/aql-optimizer-rule-no-document-materialization-arangosearch.js
+++ b/tests/js/server/aql/aql-optimizer-rule-no-document-materialization-arangosearch.js
@@ -145,10 +145,8 @@ function noDocumentMaterializationArangoSearchRuleTestSuite () {
                   "SORT CONCAT(a, e) LIMIT 10 RETURN d.obj.e.e1";
       let plan = AQL_EXPLAIN(query).plan;
       assertTrue(plan.nodes.filter(obj => {
-        return obj.type === "SubqueryNode";
-      })[0].subquery.nodes.filter(obj => {
         return obj.type === "EnumerateViewNode";
-      })[0].noMaterialization);
+      })[1].noMaterialization);
       let result = AQL_EXECUTE(query);
       assertEqual(2, result.json.length);
       let expectedKeys = new Set([14, 4]);
diff --git a/tests/js/server/aql/aql-subquery.js b/tests/js/server/aql/aql-subquery.js
index a2cc8ded83b7..d3002e80137f 100644
--- a/tests/js/server/aql/aql-subquery.js
+++ b/tests/js/server/aql/aql-subquery.js
@@ -343,8 +343,8 @@ function ahuacatlSubqueryTestSuite () {
 /// A count collect block will produce an output even if it does not get an input
 /// specifically it will rightfully count 0.
 /// The insert block will write into the collection if it gets an input.
-/// So the assertion here is, that if a subquery has no input, than all it's
-/// Parts do not have side-effects, but the subquery still prduces valid results
+/// Even if the outer subquery is skipped. Henve we require to have documents
+/// inserted here.
 ////////////////////////////////////////////////////////////////////////////////
     testCollectWithinEmptyNestedSubquery: function () {
       const colName = "UnitTestSubqueryCollection";
@@ -367,7 +367,7 @@ function ahuacatlSubqueryTestSuite () {
 
         var actual = getQueryResults(query);
         assertEqual(expected, actual);
-        assertEqual(db[colName].count(), 0);
+        assertEqual(db[colName].count(), 1);
       } finally {
         db._drop(colName);
       }

From cb4258070aaafc0c3538cef29c680e13e0742df0 Mon Sep 17 00:00:00 2001
From: Markus Pfeiffer <markuspf@users.noreply.github.com>
Date: Thu, 12 Mar 2020 15:11:37 +0000
Subject: [PATCH 101/122] Add some FilterExecutor and CalculationExecutor tests
 (#11231)

* Add some FilterExecutor tests

* Calculation executor tests

* Some more testcode

* Add NoneEntry for EntryBuilder

* Add some tests for CalculationExecutor

Co-authored-by: Michael Hackstein <michael@arangodb.com>
---
 tests/Aql/AqlItemBlockHelper.h        |  23 +-
 tests/Aql/CalculationExecutorTest.cpp | 485 +++++++++++-----------
 tests/Aql/FilterExecutorTest.cpp      | 554 +++++---------------------
 3 files changed, 365 insertions(+), 697 deletions(-)

diff --git a/tests/Aql/AqlItemBlockHelper.h b/tests/Aql/AqlItemBlockHelper.h
index fac8f0d7d36b..e6f9db2ad1ea 100644
--- a/tests/Aql/AqlItemBlockHelper.h
+++ b/tests/Aql/AqlItemBlockHelper.h
@@ -77,7 +77,9 @@ namespace arangodb {
 namespace tests {
 namespace aql {
 
-using EntryBuilder = std::variant<int, const char*>;
+struct NoneEntry {};
+
+using EntryBuilder = std::variant<NoneEntry, int, const char*>;
 
 template <::arangodb::aql::RegisterId columns>
 using RowBuilder = std::array<EntryBuilder, columns>;
@@ -112,15 +114,16 @@ SharedAqlItemBlockPtr buildBlock(AqlItemBlockManager& manager,
   for (size_t row = 0; row < matrix.size(); row++) {
     for (RegisterId col = 0; col < columns; col++) {
       auto const& entry = matrix[row][col];
-      auto value = std::visit(
-          overload{
-              [](int i) { return AqlValue{AqlValueHintInt{i}}; },
-              [](const char* json) {
-                VPackBufferPtr tmpVpack = vpackFromJsonString(json);
-                return AqlValue{AqlValueHintCopy{tmpVpack->data()}};
-              },
-          },
-          entry);
+      auto value =
+          std::visit(overload{
+                         [](NoneEntry) { return AqlValue{}; },
+                         [](int i) { return AqlValue{AqlValueHintInt{i}}; },
+                         [](const char* json) {
+                           VPackBufferPtr tmpVpack = vpackFromJsonString(json);
+                           return AqlValue{AqlValueHintCopy{tmpVpack->data()}};
+                         },
+                     },
+                     entry);
       block->setValue(row, col, value);
     }
   }
diff --git a/tests/Aql/CalculationExecutorTest.cpp b/tests/Aql/CalculationExecutorTest.cpp
index 37db9313c92d..1682edcdfc62 100644
--- a/tests/Aql/CalculationExecutorTest.cpp
+++ b/tests/Aql/CalculationExecutorTest.cpp
@@ -65,11 +65,16 @@ namespace arangodb {
 namespace tests {
 namespace aql {
 
+using CalculationExecutorTestHelper = ExecutorTestHelper<2, 2>;
+using CalculationExecutorSplitType = CalculationExecutorTestHelper::SplitType;
+using CalculationExecutorInputParam = std::tuple<CalculationExecutorSplitType>;
+
 // TODO Add tests for both
 // CalculationExecutor<CalculationType::V8Condition> and
 // CalculationExecutor<CalculationType::Reference>!
 
-class CalculationExecutorTest : public AqlExecutorTestCase<false> {
+class CalculationExecutorTest
+    : public AqlExecutorTestCaseWithParam<CalculationExecutorInputParam> {
  protected:
   ExecutionState state;
   AqlItemBlockManager itemBlockManager;
@@ -99,261 +104,257 @@ class CalculationExecutorTest : public AqlExecutorTestCase<false> {
               std::unordered_set<RegisterId>{} /*to clear*/,
               std::unordered_set<RegisterId>{} /*to keep*/,
               *fakedQuery.get() /*query*/, expr /*expression*/,
-              std::vector<Variable const*>{&var} /*expression in variables*/,
-              std::vector<RegisterId>{inRegID} /*expression in registers*/) {}
+              std::vector<Variable const*>{&var} /*expression input variables*/,
+              std::vector<RegisterId>{inRegID} /*expression input registers*/) {}
+
+  auto getSplit() -> CalculationExecutorSplitType {
+    auto [split] = GetParam();
+    return split;
+  }
+
+  auto buildInfos() -> CalculationExecutorInfos {
+    return CalculationExecutorInfos{0,    1,      1,  {}, {}, *fakedQuery.get(),
+                                    expr, {&var}, {0}};
+  }
 };
 
-TEST_F(CalculationExecutorTest, there_are_no_rows_upstream_the_producer_does_not_wait) {
-  SharedAqlItemBlockPtr block{new AqlItemBlock(itemBlockManager, 1000, 2)};
-  VPackBuilder input;
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Enable> fetcher(
-      itemBlockManager, input.steal(), false);
-  CalculationExecutor<CalculationType::Condition> testee(fetcher, infos);
-  // Use this instead of std::ignore, so the tests will be noticed and
-  // updated when someone changes the stats type in the return value of
-  // EnumerateListExecutor::produceRows().
-  NoStats stats{};
-
-  OutputAqlItemRow result{std::move(block), infos.getOutputRegisters(),
-                          infos.registersToKeep(), infos.registersToClear()};
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(result.produced());
+template <size_t... vs>
+const CalculationExecutorSplitType splitIntoBlocks =
+    CalculationExecutorSplitType{std::vector<std::size_t>{vs...}};
+template <size_t step>
+const CalculationExecutorSplitType splitStep = CalculationExecutorSplitType{step};
+
+INSTANTIATE_TEST_CASE_P(CalculationExecutor, CalculationExecutorTest,
+                        ::testing::Values(splitIntoBlocks<2, 3>, splitIntoBlocks<3, 4>,
+                                          splitStep<1>, splitStep<2>));
+
+TEST_P(CalculationExecutorTest, reference_empty_input) {
+  //   auto infos = buildInfos();
+  AqlCall call{};
+  ExecutionStats stats{};
+
+  ExecutorTestHelper<2, 2>(*fakedQuery)
+      .setExecBlock<CalculationExecutor<CalculationType::Reference>>(std::move(infos))
+      .setInputValue({})
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({1}, {})
+      .allowAnyOutputOrder(false)
+      .expectSkipped(0)
+      .expectedState(ExecutionState::DONE)
+      .run();
 }
 
-TEST_F(CalculationExecutorTest, there_are_no_rows_upstream_the_producer_waits) {
-  SharedAqlItemBlockPtr block{new AqlItemBlock(itemBlockManager, 1000, 2)};
-  VPackBuilder input;
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Enable> fetcher(
-      itemBlockManager, input.steal(), true);
-  CalculationExecutor<CalculationType::Condition> testee(fetcher, infos);
-  // Use this instead of std::ignore, so the tests will be noticed and
-  // updated when someone changes the stats type in the return value of
-  // EnumerateListExecutor::produceRows().
-  NoStats stats{};
-
-  OutputAqlItemRow result{std::move(block), infos.getOutputRegisters(),
-                          infos.registersToKeep(), infos.registersToClear()};
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::WAITING);
-  ASSERT_FALSE(result.produced());
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(result.produced());
+TEST_P(CalculationExecutorTest, reference_some_input) {
+  AqlCall call{};
+  ExecutionStats stats{};
+
+  ExecutorTestHelper<2, 2>(*fakedQuery)
+      .setExecBlock<CalculationExecutor<CalculationType::Reference>>(std::move(infos))
+      .setInputValue(MatrixBuilder<2>{
+          RowBuilder<2>{0, NoneEntry{}}, RowBuilder<2>{1, NoneEntry{}},
+          RowBuilder<2>{R"("a")", NoneEntry{}}, RowBuilder<2>{2, NoneEntry{}},
+          RowBuilder<2>{3, NoneEntry{}}, RowBuilder<2>{4, NoneEntry{}},
+          RowBuilder<2>{5, NoneEntry{}}, RowBuilder<2>{6, NoneEntry{}}})
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({0, 1}, MatrixBuilder<2>{RowBuilder<2>{0, 0}, RowBuilder<2>{1, 1},
+                                             RowBuilder<2>{R"("a")", R"("a")"},
+                                             RowBuilder<2>{2, 2}, RowBuilder<2>{3, 3},
+                                             RowBuilder<2>{4, 4}, RowBuilder<2>{5, 5},
+                                             RowBuilder<2>{6, 6}})
+      .allowAnyOutputOrder(false)
+      .expectSkipped(0)
+      .expectedState(ExecutionState::DONE)
+      .run(true);
 }
 
-TEST_F(CalculationExecutorTest, there_are_rows_in_the_upstream_the_producer_does_not_wait) {
-  SharedAqlItemBlockPtr block{new AqlItemBlock(itemBlockManager, 1000, 2)};
-  auto input = VPackParser::fromJson("[ [0], [1], [2] ]");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Enable> fetcher(
-      itemBlockManager, input->steal(), false);
-  CalculationExecutor<CalculationType::Condition> testee(fetcher, infos);
-  NoStats stats{};
-
-  OutputAqlItemRow row{std::move(block), infos.getOutputRegisters(),
-                       infos.registersToKeep(), infos.registersToClear()};
-
-  // 1
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(row.produced());
-  row.advanceRow();
-
-  // 2
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(row.produced());
-  row.advanceRow();
-
-  // 3
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_TRUE(row.produced());
-  row.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(row.produced());
-
-  // verify calculation
-  {
-    AqlValue value;
-    auto block = row.stealBlock();
-    for (std::size_t index = 0; index < 3; index++) {
-      value = block->getValue(index, outRegID);
-      ASSERT_TRUE(value.isNumber());
-      ASSERT_EQ(value.toInt64(), static_cast<int64_t>(index + 1));
-    }
-  }
+TEST_P(CalculationExecutorTest, referece_some_input_skip) {
+  AqlCall call{};
+  call.offset = 4;
+  ExecutionStats stats{};
+
+  ExecutorTestHelper<2, 2>(*fakedQuery)
+      .setExecBlock<CalculationExecutor<CalculationType::Reference>>(std::move(infos))
+      .setInputValue(MatrixBuilder<2>{
+          RowBuilder<2>{0, NoneEntry{}}, RowBuilder<2>{1, NoneEntry{}},
+          RowBuilder<2>{R"("a")", NoneEntry{}}, RowBuilder<2>{2, NoneEntry{}},
+          RowBuilder<2>{3, NoneEntry{}}, RowBuilder<2>{4, NoneEntry{}},
+          RowBuilder<2>{5, NoneEntry{}}, RowBuilder<2>{6, NoneEntry{}}})
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({0, 1}, MatrixBuilder<2>{RowBuilder<2>{3, 3}, RowBuilder<2>{4, 4},
+                                             RowBuilder<2>{5, 5}, RowBuilder<2>{6, 6}})
+      .allowAnyOutputOrder(false)
+      .expectSkipped(4)
+      .expectedState(ExecutionState::DONE)
+      .run(true);
 }
 
-TEST_F(CalculationExecutorTest, there_are_rows_in_the_upstream_the_producer_waits) {
-  SharedAqlItemBlockPtr block{new AqlItemBlock(itemBlockManager, 1000, 2)};
-  auto input = VPackParser::fromJson("[ [0], [1], [2] ]");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Enable> fetcher(
-      itemBlockManager, input->steal(), true);
-  CalculationExecutor<CalculationType::Condition> testee(fetcher, infos);
-  NoStats stats{};
-
-  OutputAqlItemRow row{std::move(block), infos.getOutputRegisters(),
-                       infos.registersToKeep(), infos.registersToClear()};
-
-  // waiting
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(state, ExecutionState::WAITING);
-  ASSERT_FALSE(row.produced());
-
-  // 1
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(row.produced());
-  row.advanceRow();
-
-  // waiting
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(state, ExecutionState::WAITING);
-  ASSERT_FALSE(row.produced());
-
-  // 2
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(row.produced());
-  row.advanceRow();
-
-  // waiting
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(state, ExecutionState::WAITING);
-  ASSERT_FALSE(row.produced());
-
-  // 3
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_TRUE(row.produced());
-  row.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(row.produced());
+TEST_P(CalculationExecutorTest, reference_some_input_limit) {
+  AqlCall call{};
+  call.hardLimit = 4;
+  ExecutionStats stats{};
+
+  ExecutorTestHelper<2, 2>(*fakedQuery)
+      .setExecBlock<CalculationExecutor<CalculationType::Reference>>(std::move(infos))
+      .setInputValue(MatrixBuilder<2>{
+          RowBuilder<2>{0, NoneEntry{}}, RowBuilder<2>{1, NoneEntry{}},
+          RowBuilder<2>{R"("a")", NoneEntry{}}, RowBuilder<2>{2, NoneEntry{}},
+          RowBuilder<2>{3, NoneEntry{}}, RowBuilder<2>{4, NoneEntry{}},
+          RowBuilder<2>{5, NoneEntry{}}, RowBuilder<2>{6, NoneEntry{}}})
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({0, 1}, MatrixBuilder<2>{RowBuilder<2>{0, 0}, RowBuilder<2>{1, 1},
+                                             RowBuilder<2>{R"("a")", R"("a")"},
+                                             RowBuilder<2>{2, 2}})
+      .allowAnyOutputOrder(false)
+      .expectSkipped(0)
+      .expectedState(ExecutionState::DONE)
+      .run(true);
 }
 
-TEST_F(CalculationExecutorTest, test_produce_datarange) {
-  // This fetcher will not be called!
-  // After Execute is done this fetcher shall be removed, the Executor does not need it anymore!
-  auto fakeUnusedBlock = VPackParser::fromJson("[  ]");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Enable> fetcher(
-      itemBlockManager, fakeUnusedBlock->steal(), false);
-
-  // This is the relevant part of the test
-  SharedAqlItemBlockPtr block{new AqlItemBlock(itemBlockManager, 1000, 2)};
-  CalculationExecutor<CalculationType::Condition> testee(fetcher, infos);
-  SharedAqlItemBlockPtr inBlock =
-      buildBlock<1>(itemBlockManager, {{R"(0)"}, {R"(1)"}, {R"(2)"}});
-
-  AqlItemBlockInputRange input{ExecutorState::DONE, 0, inBlock, 0};
-  OutputAqlItemRow output(std::move(block), infos.getOutputRegisters(),
-                          infos.registersToKeep(), infos.registersToClear());
-  EXPECT_EQ(output.numRowsWritten(), 0);
-  auto const [state, stats, call] = testee.produceRows(input, output);
-  EXPECT_EQ(output.numRowsWritten(), 3);
-
-  EXPECT_EQ(state, ExecutorState::DONE);
-  // verify calculation
-  {
-    AqlValue value;
-    auto block = output.stealBlock();
-    for (std::size_t index = 0; index < 3; index++) {
-      value = block->getValue(index, outRegID);
-      ASSERT_TRUE(value.isNumber());
-      ASSERT_EQ(value.toInt64(), static_cast<int64_t>(index + 1));
-    }
-  }
+TEST_P(CalculationExecutorTest, reference_some_input_limit_fullcount) {
+  AqlCall call{};
+  call.hardLimit = 4;
+  call.fullCount = true;
+  ExecutionStats stats{};
+
+  ExecutorTestHelper<2, 2>(*fakedQuery)
+      .setExecBlock<CalculationExecutor<CalculationType::Reference>>(std::move(infos))
+      .setInputValue(MatrixBuilder<2>{
+          RowBuilder<2>{0, NoneEntry{}}, RowBuilder<2>{1, NoneEntry{}},
+          RowBuilder<2>{R"("a")", NoneEntry{}}, RowBuilder<2>{2, NoneEntry{}},
+          RowBuilder<2>{3, NoneEntry{}}, RowBuilder<2>{4, NoneEntry{}},
+          RowBuilder<2>{5, NoneEntry{}}, RowBuilder<2>{6, NoneEntry{}}})
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({0, 1}, MatrixBuilder<2>{RowBuilder<2>{0, 0}, RowBuilder<2>{1, 1},
+                                             RowBuilder<2>{R"("a")", R"("a")"},
+                                             RowBuilder<2>{2, 2}})
+      .allowAnyOutputOrder(false)
+      .expectSkipped(4)
+      .expectedState(ExecutionState::DONE)
+      .run(true);
 }
 
-TEST_F(CalculationExecutorTest, test_produce_datarange_need_more) {
-  // This fetcher will not be called!
-  // After Execute is done this fetcher shall be removed, the Executor does not need it anymore!
-  auto fakeUnusedBlock = VPackParser::fromJson("[  ]");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Enable> fetcher(
-      itemBlockManager, fakeUnusedBlock->steal(), false);
-
-  // This is the relevant part of the test
-  SharedAqlItemBlockPtr block{new AqlItemBlock(itemBlockManager, 1000, 2)};
-  CalculationExecutor<CalculationType::Condition> testee(fetcher, infos);
-  SharedAqlItemBlockPtr inBlock =
-      buildBlock<1>(itemBlockManager, {{R"(0)"}, {R"(1)"}, {R"(2)"}});
-
-  AqlItemBlockInputRange input{ExecutorState::HASMORE, 0, inBlock, 0};
-  OutputAqlItemRow output(std::move(block), infos.getOutputRegisters(),
-                          infos.registersToKeep(), infos.registersToClear(),
-                          AqlCall{0, 3, AqlCall::Infinity{}, false});
-
-  auto myCall = output.getClientCall();
-  EXPECT_EQ(myCall.getLimit(), 3);
-  EXPECT_EQ(output.numRowsWritten(), 0);
-
-  auto const [state, stats, outputCall] = testee.produceRows(input, output);
-  EXPECT_EQ(output.numRowsWritten(), 3);
-
-  EXPECT_EQ(state, ExecutorState::HASMORE);
-  // verify calculation
-  {
-    AqlValue value;
-    auto block = output.stealBlock();
-    for (std::size_t index = 0; index < 3; index++) {
-      value = block->getValue(index, outRegID);
-      ASSERT_TRUE(value.isNumber());
-      ASSERT_EQ(value.toInt64(), static_cast<int64_t>(index + 1));
-    }
-  }
-  // Test the Call we send to upstream
-  EXPECT_EQ(outputCall.offset, 0);
-  EXPECT_FALSE(outputCall.hasHardLimit());
-  // Avoid overfetching. I do not have a strong requirement on this
-  // test, however this is what we do right now.
-  EXPECT_EQ(outputCall.getLimit(), 0);
-  EXPECT_FALSE(outputCall.fullCount);
+TEST_P(CalculationExecutorTest, condition_some_input) {
+  AqlCall call{};
+  ExecutionStats stats{};
+
+  ExecutorTestHelper<2, 2>(*fakedQuery)
+      .setExecBlock<CalculationExecutor<CalculationType::Condition>>(std::move(infos))
+      .setInputValue(MatrixBuilder<2>{
+          RowBuilder<2>{0, NoneEntry{}}, RowBuilder<2>{1, NoneEntry{}},
+          RowBuilder<2>{R"("a")", NoneEntry{}}, RowBuilder<2>{2, NoneEntry{}},
+          RowBuilder<2>{3, NoneEntry{}}, RowBuilder<2>{4, NoneEntry{}},
+          RowBuilder<2>{5, NoneEntry{}}, RowBuilder<2>{6, NoneEntry{}}})
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({0, 1},
+                    MatrixBuilder<2>{RowBuilder<2>{0, 1}, RowBuilder<2>{1, 2},
+                                     RowBuilder<2>{R"("a")", 1}, RowBuilder<2>{2, 3},
+                                     RowBuilder<2>{3, 4}, RowBuilder<2>{4, 5},
+                                     RowBuilder<2>{5, 6}, RowBuilder<2>{6, 7}})
+      .allowAnyOutputOrder(false)
+      .expectSkipped(0)
+      .expectedState(ExecutionState::DONE)
+      .run(true);
 }
 
-TEST_F(CalculationExecutorTest, DISABLED_test_produce_datarange_has_more) {  // TODO: fix and re-enable after this executor newStyle is active
-  // This fetcher will not be called!
-  // After Execute is done this fetcher shall be removed, the Executor does not need it anymore!
-  auto fakeUnusedBlock = VPackParser::fromJson("[  ]");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Enable> fetcher(
-      itemBlockManager, fakeUnusedBlock->steal(), false);
-
-  // This is the relevant part of the test
-  SharedAqlItemBlockPtr block{new AqlItemBlock(itemBlockManager, 1000, 2)};
-  CalculationExecutor<CalculationType::Condition> testee(fetcher, infos);
-  SharedAqlItemBlockPtr inBlock =
-      buildBlock<1>(itemBlockManager, {{R"(0)"}, {R"(1)"}, {R"(2)"}, {R"(3)"}, {R"(4)"}});
-
-  AqlItemBlockInputRange input{ExecutorState::DONE, 0, inBlock, 0};
-  OutputAqlItemRow output(std::move(block), infos.getOutputRegisters(),
-                          infos.registersToKeep(), infos.registersToClear());
-  EXPECT_EQ(output.numRowsWritten(), 0);
-  AqlCall myCall{0, 3, AqlCall::Infinity{}, false};
-  output.setCall(std::move(myCall));
-
-  auto const [state, stats, call] = testee.produceRows(input, output);
-  EXPECT_EQ(output.numRowsWritten(), 3);
-
-  EXPECT_EQ(state, ExecutorState::HASMORE);
-  EXPECT_TRUE(input.hasDataRow());
-  // We still have two values in block: 3 and 4
-  {
-    // pop 3
-    auto const [state, row] = input.nextDataRow();
-    EXPECT_EQ(state, ExecutorState::HASMORE);
-    EXPECT_EQ(row.getValue(0).toInt64(), 3);
-  }
-  {
-    // pop 4
-    auto const [state, row] = input.nextDataRow();
-    EXPECT_EQ(state, ExecutorState::DONE);
-    EXPECT_EQ(row.getValue(0).toInt64(), 4);
-  }
-  EXPECT_FALSE(input.hasDataRow());
+TEST_P(CalculationExecutorTest, condition_some_input_skip) {
+  AqlCall call{};
+  call.offset = 4;
+  ExecutionStats stats{};
+
+  ExecutorTestHelper<2, 2>(*fakedQuery)
+      .setExecBlock<CalculationExecutor<CalculationType::Condition>>(std::move(infos))
+      .setInputValue(MatrixBuilder<2>{
+          RowBuilder<2>{0, NoneEntry{}}, RowBuilder<2>{1, NoneEntry{}},
+          RowBuilder<2>{R"("a")", NoneEntry{}}, RowBuilder<2>{2, NoneEntry{}},
+          RowBuilder<2>{3, NoneEntry{}}, RowBuilder<2>{4, NoneEntry{}},
+          RowBuilder<2>{5, NoneEntry{}}, RowBuilder<2>{6, NoneEntry{}}})
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({0, 1}, MatrixBuilder<2>{RowBuilder<2>{3, 4}, RowBuilder<2>{4, 5},
+                                             RowBuilder<2>{5, 6}, RowBuilder<2>{6, 7}})
+      .allowAnyOutputOrder(false)
+      .expectSkipped(4)
+      .expectedState(ExecutionState::DONE)
+      .run(true);
+}
+
+TEST_P(CalculationExecutorTest, condition_some_input_limit) {
+  AqlCall call{};
+  call.hardLimit = 4;
+  ExecutionStats stats{};
+
+  ExecutorTestHelper<2, 2>(*fakedQuery)
+      .setExecBlock<CalculationExecutor<CalculationType::Condition>>(std::move(infos))
+      .setInputValue(MatrixBuilder<2>{
+          RowBuilder<2>{0, NoneEntry{}}, RowBuilder<2>{1, NoneEntry{}},
+          RowBuilder<2>{R"("a")", NoneEntry{}}, RowBuilder<2>{2, NoneEntry{}},
+          RowBuilder<2>{3, NoneEntry{}}, RowBuilder<2>{4, NoneEntry{}},
+          RowBuilder<2>{5, NoneEntry{}}, RowBuilder<2>{6, NoneEntry{}}})
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({0, 1},
+                    MatrixBuilder<2>{RowBuilder<2>{0, 1}, RowBuilder<2>{1, 2},
+                                     RowBuilder<2>{R"("a")", 1}, RowBuilder<2>{2, 3}})
+      .allowAnyOutputOrder(false)
+      .expectSkipped(0)
+      .expectedState(ExecutionState::DONE)
+      .run(true);
+}
+
+TEST_P(CalculationExecutorTest, condition_some_input_limit_fullcount) {
+  AqlCall call{};
+  call.hardLimit = 4;
+  call.fullCount = true;
+  ExecutionStats stats{};
+
+  ExecutorTestHelper<2, 2>(*fakedQuery)
+      .setExecBlock<CalculationExecutor<CalculationType::Condition>>(std::move(infos))
+      .setInputValue(MatrixBuilder<2>{
+          RowBuilder<2>{0, NoneEntry{}}, RowBuilder<2>{1, NoneEntry{}},
+          RowBuilder<2>{R"("a")", NoneEntry{}}, RowBuilder<2>{2, NoneEntry{}},
+          RowBuilder<2>{3, NoneEntry{}}, RowBuilder<2>{4, NoneEntry{}},
+          RowBuilder<2>{5, NoneEntry{}}, RowBuilder<2>{6, NoneEntry{}}})
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({0, 1},
+                    MatrixBuilder<2>{RowBuilder<2>{0, 1}, RowBuilder<2>{1, 2},
+                                     RowBuilder<2>{R"("a")", 1}, RowBuilder<2>{2, 3}})
+      .allowAnyOutputOrder(false)
+      .expectSkipped(4)
+      .expectedState(ExecutionState::DONE)
+      .run(true);
+}
+
+// Could be fixed and enabled if one enabled the V8 engine
+TEST_P(CalculationExecutorTest, DISABLED_v8condition_some_input) {
+  // auto infos = buildInfos();
+  AqlCall call{};
+  ExecutionStats stats{};
+
+  ExecutorTestHelper<2, 2>(*fakedQuery)
+      .setExecBlock<CalculationExecutor<CalculationType::V8Condition>>(std::move(infos))
+      .setInputValue(MatrixBuilder<2>{
+          RowBuilder<2>{0, NoneEntry{}}, RowBuilder<2>{1, NoneEntry{}},
+          RowBuilder<2>{R"("a")", NoneEntry{}}, RowBuilder<2>{2, NoneEntry{}},
+          RowBuilder<2>{3, NoneEntry{}}, RowBuilder<2>{4, NoneEntry{}},
+          RowBuilder<2>{5, NoneEntry{}}, RowBuilder<2>{6, NoneEntry{}}})
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({0, 1},
+                    MatrixBuilder<2>{RowBuilder<2>{0, 1}, RowBuilder<2>{1, 2},
+                                     RowBuilder<2>{R"("a")", 1}, RowBuilder<2>{2, 3},
+                                     RowBuilder<2>{3, 4}, RowBuilder<2>{4, 5},
+                                     RowBuilder<2>{5, 6}, RowBuilder<2>{6, 7}})
+      .allowAnyOutputOrder(false)
+      .expectSkipped(0)
+      .expectedState(ExecutionState::DONE)
+      .run(true);
 }
 
 }  // namespace aql
diff --git a/tests/Aql/FilterExecutorTest.cpp b/tests/Aql/FilterExecutorTest.cpp
index a51463030664..24c3f1235fc5 100644
--- a/tests/Aql/FilterExecutorTest.cpp
+++ b/tests/Aql/FilterExecutorTest.cpp
@@ -23,9 +23,11 @@
 /// @author Jan Christoph Uhde
 ////////////////////////////////////////////////////////////////////////////////
 
+#include "gtest/gtest.h"
+
 #include "AqlItemBlockHelper.h"
+#include "ExecutorTestHelper.h"
 #include "RowFetcherHelper.h"
-#include "gtest/gtest.h"
 
 #include "Aql/AqlCall.h"
 #include "Aql/AqlItemBlock.h"
@@ -46,7 +48,11 @@ namespace arangodb {
 namespace tests {
 namespace aql {
 
-class FilterExecutorTest : public ::testing::Test {
+using FilterExecutorTestHelper = ExecutorTestHelper<2, 2>;
+using FilterExecutorSplitType = FilterExecutorTestHelper::SplitType;
+using FilterExecutorInputParam = std::tuple<FilterExecutorSplitType>;
+
+class FilterExecutorTest : public AqlExecutorTestCaseWithParam<FilterExecutorInputParam> {
  protected:
   ExecutionState state;
   ResourceMonitor monitor;
@@ -62,460 +68,118 @@ class FilterExecutorTest : public ::testing::Test {
         outputRegisters(make_shared_unordered_set()),
         registersToKeep(outputRegisters),
         infos(0, 1, 1, {}, {}) {}
-};
-
-TEST_F(FilterExecutorTest, there_are_no_rows_upstream_the_producer_does_not_wait) {
-  VPackBuilder input;
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
-      itemBlockManager, input.steal(), false);
-  FilterExecutor testee(fetcher, infos);
-  FilterStats stats{};
-
-  OutputAqlItemRow result(std::move(block), outputRegisters, registersToKeep,
-                          infos.registersToClear());
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(result.produced());
-}
-
-TEST_F(FilterExecutorTest, there_are_no_rows_upstream_the_producer_waits) {
-  VPackBuilder input;
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
-      itemBlockManager, input.steal(), true);
-  FilterExecutor testee(fetcher, infos);
-  FilterStats stats{};
-
-  OutputAqlItemRow result(std::move(block), outputRegisters, registersToKeep,
-                          infos.registersToClear());
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::WAITING);
-  ASSERT_FALSE(result.produced());
-  ASSERT_EQ(stats.getFiltered(), 0);
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(result.produced());
-  ASSERT_EQ(stats.getFiltered(), 0);
-}
-
-TEST_F(FilterExecutorTest, there_are_rows_in_the_upstream_the_producer_does_not_wait) {
-  auto input = VPackParser::fromJson(
-      "[ [true], [false], [true], [false], [false], [true] ]");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
-      itemBlockManager, input->steal(), false);
-  FilterExecutor testee(fetcher, infos);
-  FilterStats stats{};
-
-  OutputAqlItemRow row(std::move(block), outputRegisters, registersToKeep,
-                       infos.registersToClear());
-
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_EQ(stats.getFiltered(), 0);
-  ASSERT_TRUE(row.produced());
-
-  row.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_EQ(stats.getFiltered(), 1);
-  ASSERT_TRUE(row.produced());
-
-  row.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_EQ(stats.getFiltered(), 2);
-  ASSERT_TRUE(row.produced());
-
-  row.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_EQ(stats.getFiltered(), 0);
-  ASSERT_FALSE(row.produced());
-}
-
-TEST_F(FilterExecutorTest, there_are_rows_in_the_upstream_the_producer_waits) {
-  auto input = VPackParser::fromJson(
-      "[ [true], [false], [true], [false], [false], [true] ]");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
-      itemBlockManager, input->steal(), true);
-  FilterExecutor testee(fetcher, infos);
-  FilterStats stats{};
-
-  OutputAqlItemRow row(std::move(block), outputRegisters, registersToKeep,
-                       infos.registersToClear());
-
-  /*
-  1  produce => WAIT                 RES1
-  2  produce => HASMORE, Row 1     RES1
-  3  => WAIT                         RES2
-  4  => WAIT                         RES2
-  5   => HASMORE, Row 3            RES2
-  6   => WAIT,                       RES3
-  7   => WAIT,                       RES3
-  8   => WAIT,                       RES3
-  9   => DONE, Row 6               RES3
-  */
-
-  // 1
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(state, ExecutionState::WAITING);
-  ASSERT_FALSE(row.produced());
-  ASSERT_EQ(stats.getFiltered(), 0);
-
-  // 2
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(row.produced());
-  row.advanceRow();
-  ASSERT_EQ(stats.getFiltered(), 0);
-
-  // 3
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(state, ExecutionState::WAITING);
-  ASSERT_FALSE(row.produced());
-  ASSERT_EQ(stats.getFiltered(), 0);
-
-  // 4
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(state, ExecutionState::WAITING);
-  ASSERT_FALSE(row.produced());
-  // We have one filter here
-  ASSERT_EQ(stats.getFiltered(), 1);
-
-  // 5
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(row.produced());
-  row.advanceRow();
-  ASSERT_EQ(stats.getFiltered(), 0);
-
-  // 6
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(state, ExecutionState::WAITING);
-  ASSERT_FALSE(row.produced());
-  ASSERT_EQ(stats.getFiltered(), 0);
-
-  // 7
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(state, ExecutionState::WAITING);
-  ASSERT_FALSE(row.produced());
-  ASSERT_EQ(stats.getFiltered(), 1);
-
-  // 7
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(state, ExecutionState::WAITING);
-  ASSERT_FALSE(row.produced());
-  ASSERT_EQ(stats.getFiltered(), 1);
-
-  // 8
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_TRUE(row.produced());
-  row.advanceRow();
-  ASSERT_EQ(stats.getFiltered(), 0);
-}
-
-TEST_F(FilterExecutorTest,
-       there_are_rows_in_the_upstream_and_the_last_one_has_to_be_filtered_the_producer_does_not_wait) {
-  auto input = VPackParser::fromJson(
-      "[ [true], [false], [true], [false], [false], [true], [false] ]");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
-      itemBlockManager, input->steal(), false);
-  FilterExecutor testee(fetcher, infos);
-  FilterStats stats{};
-
-  OutputAqlItemRow row(std::move(block), outputRegisters, registersToKeep,
-                       infos.registersToClear());
-
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_EQ(stats.getFiltered(), 0);
-  ASSERT_TRUE(row.produced());
-
-  row.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_EQ(stats.getFiltered(), 1);
-  ASSERT_TRUE(row.produced());
-
-  row.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_EQ(stats.getFiltered(), 2);
-  ASSERT_TRUE(row.produced());
 
-  row.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_EQ(stats.getFiltered(), 1);
-  ASSERT_FALSE(row.produced());
-
-  std::tie(state, stats) = testee.produceRows(row);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_EQ(stats.getFiltered(), 0);
-  ASSERT_FALSE(row.produced());
-}
-
-TEST_F(FilterExecutorTest,
-       there_are_rows_in_the_upstream_and_the_last_one_has_to_be_filtered_the_producer_waits) {
-  auto input = VPackParser::fromJson(
-      "[ [true], [false], [true], [false], [false], [true], [false] ]");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
-      itemBlockManager, input->steal(), true);
-  FilterExecutor testee(fetcher, infos);
-  FilterStats stats{};
-
-  OutputAqlItemRow result(std::move(block), outputRegisters, registersToKeep,
-                          infos.registersToClear());
-
-  /*
-  produce => WAIT                  RES1
-  produce => HASMORE, Row 1        RES1
-  => WAIT                          RES2
-  => WAIT                          RES2
-   => HASMORE, Row 3               RES2
-   => WAIT,                        RES3
-   => WAIT,                        RES3
-   => WAIT,                        RES3
-   => HASMORE, Row 6               RES3
-   => WAITING,                     RES3
-   => DONE, no output!             RES3
-    */
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::WAITING);
-  ASSERT_FALSE(result.produced());
-  ASSERT_EQ(stats.getFiltered(), 0);
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(result.produced());
-  ASSERT_EQ(stats.getFiltered(), 0);
-
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::WAITING);
-  ASSERT_FALSE(result.produced());
-  ASSERT_EQ(stats.getFiltered(), 0);
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::WAITING);
-  ASSERT_FALSE(result.produced());
-  ASSERT_EQ(stats.getFiltered(), 1);
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(result.produced());
-  ASSERT_EQ(stats.getFiltered(), 0);
-
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::WAITING);
-  ASSERT_FALSE(result.produced());
-  ASSERT_EQ(stats.getFiltered(), 0);
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::WAITING);
-  ASSERT_FALSE(result.produced());
-  ASSERT_EQ(stats.getFiltered(), 1);
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::WAITING);
-  ASSERT_FALSE(result.produced());
-  ASSERT_EQ(stats.getFiltered(), 1);
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::HASMORE);
-  ASSERT_TRUE(result.produced());
-  ASSERT_EQ(stats.getFiltered(), 0);
-
-  result.advanceRow();
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::WAITING);
-  ASSERT_FALSE(result.produced());
-  ASSERT_EQ(stats.getFiltered(), 0);
-
-  std::tie(state, stats) = testee.produceRows(result);
-  ASSERT_EQ(state, ExecutionState::DONE);
-  ASSERT_FALSE(result.produced());
-  ASSERT_EQ(stats.getFiltered(), 1);
-}
-
-TEST_F(FilterExecutorTest, test_produce_datarange) {
-  // This fetcher will not be called!
-  // After Execute is done this fetcher shall be removed, the Executor does not need it anymore!
-  auto fakeUnusedBlock = VPackParser::fromJson("[  ]");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
-      itemBlockManager, fakeUnusedBlock->steal(), false);
-
-  // This is the relevant part of the test
-  FilterExecutor testee(fetcher, infos);
-  SharedAqlItemBlockPtr inBlock =
-      buildBlock<1>(itemBlockManager,
-                    {{R"(true)"}, {R"(false)"}, {R"(true)"}, {R"(false)"}, {R"(true)"}});
+  auto getSplit() -> FilterExecutorSplitType {
+    auto [split] = GetParam();
+    return split;
+  }
 
-  AqlItemBlockInputRange input{ExecutorState::DONE, 0, inBlock, 0};
+  auto buildInfos() -> FilterExecutorInfos {
+    return FilterExecutorInfos{0, 2, 2, {}, {0, 1}};
+  }
+};
 
-  OutputAqlItemRow output(std::move(block), outputRegisters, registersToKeep,
-                          infos.registersToClear());
-  EXPECT_EQ(output.numRowsWritten(), 0);
-  auto const [state, stats, call] = testee.produceRows(input, output);
-  EXPECT_EQ(state, ExecutorState::DONE);
-  EXPECT_EQ(stats.getFiltered(), 2);
-  EXPECT_EQ(output.numRowsWritten(), 3);
-  EXPECT_FALSE(input.hasDataRow());
+template <size_t... vs>
+const FilterExecutorSplitType splitIntoBlocks =
+    FilterExecutorSplitType{std::vector<std::size_t>{vs...}};
+template <size_t step>
+const FilterExecutorSplitType splitStep = FilterExecutorSplitType{step};
+
+INSTANTIATE_TEST_CASE_P(FilterExecutor, FilterExecutorTest,
+                        ::testing::Values(splitIntoBlocks<2, 3>, splitIntoBlocks<3, 4>,
+                                          splitStep<1>, splitStep<2>));
+
+TEST_P(FilterExecutorTest, empty_input) {
+  auto infos = buildInfos();
+  AqlCall call{};
+  ExecutionStats{};
+  ExecutorTestHelper(*fakedQuery)
+      .setExecBlock<FilterExecutor>(std::move(infos))
+      .setInputValue({})
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({1}, {})
+      .allowAnyOutputOrder(false)
+      .expectSkipped(0)
+      .expectedState(ExecutionState::DONE)
+      .run();
 }
 
-TEST_F(FilterExecutorTest, test_produce_datarange_need_more) {
-  // This fetcher will not be called!
-  // After Execute is done this fetcher shall be removed, the Executor does not need it anymore!
-  auto fakeUnusedBlock = VPackParser::fromJson("[  ]");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
-      itemBlockManager, fakeUnusedBlock->steal(), false);
-
-  // This is the relevant part of the test
-  FilterExecutor testee(fetcher, infos);
-  SharedAqlItemBlockPtr inBlock =
-      buildBlock<1>(itemBlockManager,
-                    {{R"(true)"}, {R"(false)"}, {R"(true)"}, {R"(false)"}, {R"(true)"}});
-  size_t hardLimit = 1000;
-  AqlItemBlockInputRange input{ExecutorState::HASMORE, 0, inBlock, 0};
-  AqlCall limitedCall{};
-  limitedCall.hardLimit = hardLimit;
-  OutputAqlItemRow output(std::move(block), outputRegisters, registersToKeep,
-                          infos.registersToClear(), std::move(limitedCall));
-  EXPECT_EQ(output.numRowsWritten(), 0);
-  auto const [state, stats, call] = testee.produceRows(input, output);
-  EXPECT_EQ(state, ExecutorState::HASMORE);
-  EXPECT_EQ(stats.getFiltered(), 2);
-  EXPECT_EQ(output.numRowsWritten(), 3);
-  EXPECT_FALSE(input.hasDataRow());
-  // Test the Call we send to upstream
-  EXPECT_EQ(call.offset, 0);
-  EXPECT_FALSE(call.hasHardLimit());
-  // We have a given softLimit, so we do not do overfetching
-  EXPECT_EQ(call.getLimit(), hardLimit - 3);
-  EXPECT_FALSE(call.fullCount);
+TEST_P(FilterExecutorTest, values) {
+  auto infos = buildInfos();
+  AqlCall call{};
+  ExecutionStats{};
+  ExecutorTestHelper<2, 2>(*fakedQuery)
+      .setExecBlock<FilterExecutor>(std::move(infos))
+      .setInputValue(MatrixBuilder<2>{RowBuilder<2>{1, 0}, RowBuilder<2>{0, 1},
+                                      RowBuilder<2>{0, 2}, RowBuilder<2>{0, 3},
+                                      RowBuilder<2>{0, 4}, RowBuilder<2>{0, 5},
+                                      RowBuilder<2>{0, 6}, RowBuilder<2>{0, 7}})
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({0, 1}, MatrixBuilder<2>{RowBuilder<2>{1, 0}})
+      .allowAnyOutputOrder(false)
+      .expectSkipped(0)
+      .expectedState(ExecutionState::DONE)
+      .run();
 }
 
-TEST_F(FilterExecutorTest, test_skip_datarange_need_more) {
-  // This fetcher will not be called!
-  // After Execute is done this fetcher shall be removed, the Executor does not need it anymore!
-  auto fakeUnusedBlock = VPackParser::fromJson("[  ]");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
-      itemBlockManager, fakeUnusedBlock->steal(), false);
-
-  // This is the relevant part of the test
-  FilterExecutor testee(fetcher, infos);
-  SharedAqlItemBlockPtr inBlock =
-      buildBlock<1>(itemBlockManager,
-                    {{R"(true)"}, {R"(false)"}, {R"(true)"}, {R"(false)"}, {R"(true)"}});
-
-  AqlItemBlockInputRange input{ExecutorState::HASMORE, 0, inBlock, 0};
-  AqlCall clientCall;
-  clientCall.offset = 1000;
-
-  auto const [state, stats, skipped, call] = testee.skipRowsRange(input, clientCall);
-  // TODO check stats
-  EXPECT_EQ(state, ExecutorState::HASMORE);
-  EXPECT_EQ(skipped, 3);
-  EXPECT_EQ(clientCall.getOffset(), 1000 - 3);
-  EXPECT_FALSE(input.hasDataRow());
-
-  // Test the Call we send to upstream
-  EXPECT_EQ(call.offset, 0);
-  EXPECT_FALSE(call.hasHardLimit());
-  // Avoid overfetching. I do not have a strong requirement on this
-  // test, however this is what we do right now.
-  EXPECT_EQ(call.getLimit(), 997);
-  EXPECT_FALSE(call.fullCount);
+TEST_P(FilterExecutorTest, odd_values) {
+  auto infos = buildInfos();
+  AqlCall call{};
+  ExecutionStats{};
+  ExecutorTestHelper<2, 2>(*fakedQuery)
+      .setExecBlock<FilterExecutor>(std::move(infos))
+      .setInputValue(MatrixBuilder<2>{RowBuilder<2>{1, 0}, RowBuilder<2>{0, 1},
+                                      RowBuilder<2>{1, 2}, RowBuilder<2>{0, 3},
+                                      RowBuilder<2>{1, 4}, RowBuilder<2>{0, 5},
+                                      RowBuilder<2>{1, 6}, RowBuilder<2>{0, 7}})
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({0, 1}, MatrixBuilder<2>{RowBuilder<2>{1, 0}, RowBuilder<2>{1, 2},
+                                             RowBuilder<2>{1, 4}, RowBuilder<2>{1, 6}})
+      .allowAnyOutputOrder(false)
+      .expectSkipped(0)
+      .expectedState(ExecutionState::DONE)
+      .run();
 }
 
-TEST_F(FilterExecutorTest, test_produce_datarange_has_more) {
-  // This fetcher will not be called!
-  // After Execute is done this fetcher shall be removed, the Executor does not need it anymore!
-  auto fakeUnusedBlock = VPackParser::fromJson("[  ]");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
-      itemBlockManager, fakeUnusedBlock->steal(), false);
-
-  // This is the relevant part of the test
-  FilterExecutor testee(fetcher, infos);
-  SharedAqlItemBlockPtr inBlock =
-      buildBlock<1>(itemBlockManager,
-                    {{R"(true)"}, {R"(false)"}, {R"(true)"}, {R"(false)"}, {R"(true)"}});
-
-  AqlItemBlockInputRange input{ExecutorState::DONE, 0, inBlock, 0};
-  block.reset(new AqlItemBlock(itemBlockManager, 2, 1));
-  OutputAqlItemRow output(std::move(block), outputRegisters, registersToKeep,
-                          infos.registersToClear());
-
-  auto const [state, stats, call] = testee.produceRows(input, output);
-  EXPECT_EQ(state, ExecutorState::HASMORE);
-  EXPECT_EQ(stats.getFiltered(), 1);
-  EXPECT_EQ(output.numRowsWritten(), 2);
-  EXPECT_TRUE(input.hasDataRow());
-  // We still have two values in block: false and true
-  {
-    // pop false
-    auto const [state, row] = input.nextDataRow();
-    EXPECT_EQ(state, ExecutorState::HASMORE);
-    EXPECT_FALSE(row.getValue(0).toBoolean());
-  }
-  {
-    // pop true
-    auto const [state, row] = input.nextDataRow();
-    EXPECT_EQ(state, ExecutorState::DONE);
-    EXPECT_TRUE(row.getValue(0).toBoolean());
-  }
-  EXPECT_FALSE(input.hasDataRow());
+TEST_P(FilterExecutorTest, skip_and_odd_values) {
+  auto infos = buildInfos();
+  AqlCall call{3};
+  ExecutionStats{};
+  ExecutorTestHelper<2, 2>(*fakedQuery)
+      .setExecBlock<FilterExecutor>(std::move(infos))
+      .setInputValue(MatrixBuilder<2>{RowBuilder<2>{1, 0}, RowBuilder<2>{0, 1},
+                                      RowBuilder<2>{1, 2}, RowBuilder<2>{0, 3},
+                                      RowBuilder<2>{1, 4}, RowBuilder<2>{0, 5},
+                                      RowBuilder<2>{1, 6}, RowBuilder<2>{0, 7}})
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({0, 1}, MatrixBuilder<2>{RowBuilder<2>{1, 6}})
+      .allowAnyOutputOrder(false)
+      .expectSkipped(3)
+      .expectedState(ExecutionState::DONE)
+      .run();
 }
 
-TEST_F(FilterExecutorTest, test_skip_datarange_has_more) {
-  // This fetcher will not be called!
-  // After Execute is done this fetcher shall be removed, the Executor does not need it anymore!
-  auto fakeUnusedBlock = VPackParser::fromJson("[  ]");
-  SingleRowFetcherHelper<::arangodb::aql::BlockPassthrough::Disable> fetcher(
-      itemBlockManager, fakeUnusedBlock->steal(), false);
-
-  // This is the relevant part of the test
-  FilterExecutor testee(fetcher, infos);
-  SharedAqlItemBlockPtr inBlock =
-      buildBlock<1>(itemBlockManager,
-                    {{R"(true)"}, {R"(false)"}, {R"(true)"}, {R"(false)"}, {R"(true)"}});
-
-  AqlItemBlockInputRange input{ExecutorState::DONE, 0, inBlock, 0};
-  AqlCall clientCall;
-  clientCall.offset = 2;
-  auto const [state, stats, skipped, call] = testee.skipRowsRange(input, clientCall);
-  // TODO check stats
-  EXPECT_EQ(state, ExecutorState::HASMORE);
-  EXPECT_EQ(skipped, 2);
-  EXPECT_EQ(clientCall.getOffset(), 0);
-  EXPECT_TRUE(input.hasDataRow());
-  // We still have two values in block: false and true
-  {
-    // pop false
-    auto const [state, row] = input.nextDataRow();
-    EXPECT_EQ(state, ExecutorState::HASMORE);
-    EXPECT_FALSE(row.getValue(0).toBoolean());
-  }
-  {
-    // pop true
-    auto const [state, row] = input.nextDataRow();
-    EXPECT_EQ(state, ExecutorState::DONE);
-    EXPECT_TRUE(row.getValue(0).toBoolean());
-  }
-  EXPECT_FALSE(input.hasDataRow());
-}
+TEST_P(FilterExecutorTest, hard_limit) {
+  auto infos = buildInfos();
+  AqlCall call{};
+  call.hardLimit = 0;
+  call.fullCount = true;
+  ExecutionStats{};
+  ExecutorTestHelper<2, 2>(*fakedQuery)
+      .setExecBlock<FilterExecutor>(std::move(infos))
+      .setInputValue(MatrixBuilder<2>{})
+      .setInputSplitType(getSplit())
+      .setCall(call)
+      .expectOutput({0, 1}, MatrixBuilder<2>{})
+      .allowAnyOutputOrder(false)
+      .expectSkipped(0)
+      .expectedState(ExecutionState::DONE)
+      .run();
+}  // namespace aql
 
 }  // namespace aql
 }  // namespace tests

From 10b24b2f5f7d8bf23353558ce1c9e853ed0bfa77 Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Thu, 12 Mar 2020 22:48:36 +0100
Subject: [PATCH 102/122] Merge devel into
 feature/AqlSubqueryExecutionBlockImplExecuteImplementation

---
 .gitignore                                    |    4 +
 3rdParty/CMakeLists.txt                       |   12 +
 3rdParty/README_maintainers.md                |   10 +
 3rdParty/date/include/date/date.h             |    8 +-
 3rdParty/fuerte/include/fuerte/helper.h       |    4 +-
 3rdParty/fuerte/src/H1Connection.cpp          |    2 +-
 3rdParty/fuerte/src/H2Connection.cpp          |    5 +-
 3rdParty/fuerte/src/helper.cpp                |   12 +-
 3rdParty/fuerte/src/jwt.cpp                   |   10 +-
 3rdParty/iresearch/.travis.yml                |  244 +-
 3rdParty/iresearch/CMakeLists.txt             |   23 +-
 3rdParty/iresearch/PVSIResearch.cfg           |    2 +
 3rdParty/iresearch/README.md                  |   20 +-
 3rdParty/iresearch/THIRD_PARTY_README.md      |    4 +-
 3rdParty/iresearch/appveyor.yml               |   10 +-
 3rdParty/iresearch/cmake/PVS-Studio.cmake     | 1092 ++--
 3rdParty/iresearch/core/CMakeLists.txt        |    6 +
 .../core/analysis/token_attributes.hpp        |    8 +-
 .../iresearch/core/formats/formats_10.cpp     |  205 +-
 .../core/formats/formats_burst_trie.cpp       |   16 +-
 .../core/formats/formats_burst_trie.hpp       |    2 +-
 3rdParty/iresearch/core/index/field_data.cpp  |    9 +-
 .../iresearch/core/index/index_reader.hpp     |    2 +-
 3rdParty/iresearch/core/iql/query_builder.cpp |    2 +-
 3rdParty/iresearch/core/search/bm25.cpp       |   71 +-
 .../iresearch/core/search/disjunction.hpp     |  320 +-
 .../core/search/granular_range_filter.cpp     |    3 +-
 .../core/search/levenshtein_filter.cpp        |   25 +-
 .../core/search/levenshtein_filter.hpp        |   41 +-
 .../search/limited_sample_scorer-heap.cpp     |  204 -
 .../search/limited_sample_scorer-heap.hpp     |  132 -
 .../core/search/limited_sample_scorer.cpp     |   94 +-
 .../core/search/limited_sample_scorer.hpp     |   10 +-
 .../core/search/min_match_disjunction.hpp     |   58 +-
 .../core/search/ngram_similarity_filter.cpp   |  551 ++
 .../core/search/ngram_similarity_filter.hpp   |  120 +
 .../iresearch/core/search/phrase_filter.cpp   |  794 ++-
 .../iresearch/core/search/phrase_filter.hpp   |  200 +-
 .../iresearch/core/search/phrase_iterator.hpp |  223 +-
 .../iresearch/core/search/prefix_filter.hpp   |    4 +-
 .../iresearch/core/search/range_filter.hpp    |    6 +-
 .../core/search/same_position_filter.cpp      |    4 +-
 .../core/search/same_position_filter.hpp      |   14 +-
 3rdParty/iresearch/core/search/sort.cpp       |  168 +-
 3rdParty/iresearch/core/search/sort.hpp       |   98 +-
 .../iresearch/core/search/term_filter.hpp     |    4 +-
 3rdParty/iresearch/core/search/term_query.cpp |    2 +-
 3rdParty/iresearch/core/search/tfidf.cpp      |   68 +-
 .../iresearch/core/search/wildcard_filter.cpp |   83 +-
 .../iresearch/core/search/wildcard_filter.hpp |   42 +-
 3rdParty/iresearch/core/shared.hpp            |    4 +-
 .../iresearch/core/utils/arena_allocator.hpp  |    2 +-
 .../iresearch/core/utils/attribute_range.cpp  |   46 +
 .../iresearch/core/utils/attribute_range.hpp  |   65 +
 3rdParty/iresearch/core/utils/attributes.cpp  |    4 +-
 3rdParty/iresearch/core/utils/attributes.hpp  |   10 +-
 3rdParty/iresearch/core/utils/automaton.hpp   |   62 +-
 .../iresearch/core/utils/automaton_utils.cpp  |  272 +-
 .../iresearch/core/utils/automaton_utils.hpp  |  332 +-
 3rdParty/iresearch/core/utils/fst.hpp         |  176 +-
 .../iresearch/core/utils/fst_states_map.hpp   |  144 +
 .../core/utils/fst_table_matcher.hpp          |    8 +-
 .../core/utils/levenshtein_utils.cpp          |  171 +-
 .../core/utils/levenshtein_utils.hpp          |   48 +-
 .../iresearch/core/utils/locale_utils.cpp     |    4 +-
 .../iresearch/core/utils/locale_utils.hpp     |    2 +-
 3rdParty/iresearch/core/utils/log.cpp         |    4 +-
 .../core/utils/ngram_match_utils.hpp          |  138 +
 3rdParty/iresearch/core/utils/std.hpp         |    4 +-
 3rdParty/iresearch/core/utils/string.cpp      |    8 +-
 3rdParty/iresearch/core/utils/string.hpp      |   36 +
 3rdParty/iresearch/core/utils/utf8_utils.hpp  |  167 +-
 .../iresearch/core/utils/wildcard_utils.cpp   |  228 +
 .../iresearch/core/utils/wildcard_utils.hpp   |  120 +-
 .../iresearch/external/openfst/draw-impl.h    |   37 +-
 .../external/openfst/fst/string-weight.h      |    6 +-
 3rdParty/iresearch/external/openfst/util.cc   |    2 +-
 3rdParty/iresearch/python/CMakeLists.txt      |   11 +
 3rdParty/iresearch/python/pyresearch.hpp      |   30 +-
 3rdParty/iresearch/python/swig/CMakeLists.txt |   40 +-
 .../scripts/ArangoDBLoader/WikiLoader.py      |   47 +
 .../scripts/Prometheus/Dashboard.json         |  703 +-
 .../iresearch/scripts/Prometheus/INSTALL.md   |    2 +-
 .../scripts/Prometheus/PythonBenchmark.py     |   52 +-
 .../scripts/download-benchmark-resources.sh   |    4 +-
 .../scripts/gtest-parallel/gtest-parallel     |    0
 .../scripts/gtest-parallel/gtest_parallel.py  |    0
 .../gtest-parallel/gtest_parallel_tests.py    |    0
 3rdParty/iresearch/scripts/index-benchmark.sh |    4 +-
 .../scripts/iresearch-benchmark.tasks         |    2 +
 .../iresearch/scripts/search-benchmark.sh     |    2 +-
 .../scripts/start-benchmark-comparison.sh     |    2 +
 3rdParty/iresearch/tests/CMakeLists.txt       |    4 +
 .../tests/formats/formats_13_tests.cpp        |  511 ++
 .../tests/formats/formats_test_case_base.hpp  |    4 +
 .../iresearch/tests/index/assert_format.cpp   |   21 +-
 .../tests/index/index_levenshtein_tests.cpp   |   10 +
 .../iresearch/tests/index/index_tests.cpp     |   45 +-
 .../iresearch/tests/index/index_tests.hpp     |    6 +
 .../tests/index/merge_writer_tests.cpp        |   12 +-
 .../tests/iql/query_builder_test.cpp          |    3 +-
 .../tests/resources/ngram_similarity.json     |   18 +
 .../tests/resources/phrase_sequential.json    |   10 +-
 .../resources/simple_sequential_utf8.json     |   34 +
 3rdParty/iresearch/tests/search/bm25_test.cpp |    6 +-
 .../tests/search/boolean_filter_tests.cpp     |    7 +-
 .../tests/search/filter_test_case_base.hpp    |   27 +-
 .../search/ngram_similarity_filter_tests.cpp  | 1191 ++++
 .../tests/search/phrase_filter_tests.cpp      | 5660 ++++++++++++++++-
 .../search/same_position_filter_tests.cpp     |   18 +-
 .../iresearch/tests/search/sort_tests.cpp     |    2 +-
 .../iresearch/tests/search/tfidf_test.cpp     |    6 +-
 .../tests/search/wildcard_filter_test.cpp     |  181 +-
 3rdParty/iresearch/tests/unicode/utf8.h       |   34 -
 .../iresearch/tests/unicode/utf8/checked.h    |  327 -
 3rdParty/iresearch/tests/unicode/utf8/core.h  |  329 -
 .../iresearch/tests/unicode/utf8/unchecked.h  |  228 -
 .../iresearch/tests/utils/automaton_test.cpp  | 1659 ++++-
 .../iresearch/tests/utils/fst_utils_test.cpp  |   10 -
 .../tests/utils/levenshtein_utils_test.cpp    |  477 +-
 .../tests/utils/ngram_match_utils_tests.cpp   |  259 +
 .../iresearch/tests/utils/string_tests.cpp    |   72 +
 .../iresearch/tests/utils/utf8_utils_test.cpp |  315 +-
 .../tests/utils/wildcard_utils_test.cpp       |  651 ++
 3rdParty/iresearch/utils/index-put.cpp        |    5 +-
 3rdParty/iresearch/utils/index-search.cpp     |   62 +-
 3rdParty/iresearch/utils/pdd.cpp              |   15 +-
 .../json-schema-validation/.clang_complete    |   11 +
 3rdParty/json-schema-validation/.gitignore    |   10 +
 .../json-schema-validation/CMakeLists.txt     |   76 +
 .../cmake/ext_cmake_install.cmake             |   43 +
 .../cmake/ext_cmake_utils.cmake               |   69 +
 .../include/validation/events_from_slice.hpp  |  152 +
 .../include/validation/types.hpp              |   28 +
 .../include/validation/validation.hpp         |   32 +
 .../json-schema-validation/src/validation.cpp |  193 +
 3rdParty/taocpp-json.version                  |    1 +
 3rdParty/taocpp-json/.clang-format            |   84 +
 3rdParty/taocpp-json/CMakeLists.txt           |   44 +
 3rdParty/taocpp-json/LICENSE                  |   21 +
 .../taocpp-json/LICENSE.double-conversion     |   32 +
 3rdParty/taocpp-json/LICENSE.itoa             |   19 +
 3rdParty/taocpp-json/LICENSE.ryu              |  201 +
 3rdParty/taocpp-json/README.md                |  149 +
 3rdParty/taocpp-json/include/tao/json.hpp     |   45 +
 .../include/tao/json/basic_value.hpp          |  941 +++
 .../taocpp-json/include/tao/json/binary.hpp   |  103 +
 .../include/tao/json/binary_view.hpp          |   31 +
 .../taocpp-json/include/tao/json/binding.hpp  |   71 +
 .../include/tao/json/binding/constant.hpp     |  232 +
 .../include/tao/json/binding/element.hpp      |  182 +
 .../include/tao/json/binding/factory.hpp      |  250 +
 .../tao/json/binding/for_nothing_value.hpp    |   17 +
 .../tao/json/binding/for_unknown_key.hpp      |   17 +
 .../include/tao/json/binding/inherit.hpp      |   14 +
 .../tao/json/binding/internal/array.hpp       |  103 +
 .../tao/json/binding/internal/inherit.hpp     |   45 +
 .../tao/json/binding/internal/object.hpp      |  267 +
 .../tao/json/binding/internal/type_key.hpp    |   54 +
 .../include/tao/json/binding/member.hpp       |   32 +
 .../include/tao/json/binding/member_kind.hpp  |   17 +
 .../include/tao/json/binding/versions.hpp     |  127 +
 .../taocpp-json/include/tao/json/consume.hpp  |   43 +
 .../include/tao/json/consume_file.hpp         |   33 +
 .../include/tao/json/consume_string.hpp       |   31 +
 .../include/tao/json/contrib/array_traits.hpp |   43 +
 .../include/tao/json/contrib/deque_traits.hpp |   41 +
 .../include/tao/json/contrib/diff.hpp         |  106 +
 .../include/tao/json/contrib/get.hpp          |  152 +
 .../json/contrib/internal/array_traits.hpp    |   92 +
 .../json/contrib/internal/indirect_traits.hpp |   69 +
 .../json/contrib/internal/object_traits.hpp   |  105 +
 .../tao/json/contrib/internal/type_traits.hpp |   36 +
 .../include/tao/json/contrib/list_traits.hpp  |   41 +
 .../include/tao/json/contrib/map_traits.hpp   |   43 +
 .../tao/json/contrib/multimap_traits.hpp      |   43 +
 .../tao/json/contrib/multiset_traits.hpp      |   41 +
 .../include/tao/json/contrib/pair_traits.hpp  |   21 +
 .../include/tao/json/contrib/patch.hpp        |  105 +
 .../tao/json/contrib/pointer_traits.hpp       |   59 +
 .../include/tao/json/contrib/position.hpp     |  166 +
 .../include/tao/json/contrib/reference.hpp    |  115 +
 .../include/tao/json/contrib/schema.hpp       | 1851 ++++++
 .../include/tao/json/contrib/set_traits.hpp   |   41 +
 .../tao/json/contrib/shared_ptr_traits.hpp    |   90 +
 .../include/tao/json/contrib/traits.hpp       |  121 +
 .../include/tao/json/contrib/tuple_traits.hpp |   51 +
 .../tao/json/contrib/unique_ptr_traits.hpp    |   89 +
 .../tao/json/contrib/unordered_map_traits.hpp |   43 +
 .../tao/json/contrib/unordered_set_traits.hpp |   41 +
 .../tao/json/contrib/vector_bool_traits.hpp   |   45 +
 .../tao/json/contrib/vector_traits.hpp        |   51 +
 .../taocpp-json/include/tao/json/events.hpp   |   47 +
 .../include/tao/json/events/apply.hpp         |   20 +
 .../tao/json/events/binary_to_base64.hpp      |   26 +
 .../tao/json/events/binary_to_base64url.hpp   |   28 +
 .../tao/json/events/binary_to_exception.hpp   |   27 +
 .../include/tao/json/events/binary_to_hex.hpp |   26 +
 .../include/tao/json/events/compare.hpp       |  265 +
 .../include/tao/json/events/debug.hpp         |  145 +
 .../include/tao/json/events/discard.hpp       |   43 +
 .../include/tao/json/events/from_file.hpp     |   28 +
 .../include/tao/json/events/from_input.hpp    |   45 +
 .../include/tao/json/events/from_stream.hpp   |   33 +
 .../include/tao/json/events/from_string.hpp   |   38 +
 .../include/tao/json/events/from_value.hpp    |  202 +
 .../include/tao/json/events/hash.hpp          |  174 +
 .../json/events/invalid_string_to_binary.hpp  |   50 +
 .../events/invalid_string_to_exception.hpp    |   49 +
 .../tao/json/events/invalid_string_to_hex.hpp |   48 +
 .../events/key_camel_case_to_snake_case.hpp   |   62 +
 .../events/key_snake_case_to_camel_case.hpp   |   57 +
 .../tao/json/events/limit_nesting_depth.hpp   |   82 +
 .../tao/json/events/limit_value_count.hpp     |   46 +
 .../json/events/non_finite_to_exception.hpp   |   31 +
 .../tao/json/events/non_finite_to_null.hpp    |   32 +
 .../tao/json/events/non_finite_to_string.hpp  |   40 +
 .../include/tao/json/events/prefer_signed.hpp |   32 +
 .../tao/json/events/prefer_unsigned.hpp       |   32 +
 .../include/tao/json/events/produce.hpp       |   22 +
 .../include/tao/json/events/ref.hpp           |  111 +
 .../include/tao/json/events/statistics.hpp    |  112 +
 .../include/tao/json/events/tee.hpp           |  386 ++
 .../tao/json/events/to_pretty_stream.hpp      |  172 +
 .../include/tao/json/events/to_stream.hpp     |  142 +
 .../include/tao/json/events/to_string.hpp     |   33 +
 .../include/tao/json/events/to_value.hpp      |  137 +
 .../include/tao/json/events/transformer.hpp   |   70 +
 .../tao/json/events/validate_event_order.hpp  |  411 ++
 .../include/tao/json/events/validate_keys.hpp |   51 +
 .../include/tao/json/events/virtual_base.hpp  |  192 +
 .../include/tao/json/events/virtual_ref.hpp   |  170 +
 .../include/tao/json/external/double.hpp      | 1313 ++++
 .../include/tao/json/external/itoa.hpp        |  149 +
 .../include/tao/json/external/pegtl.hpp       |   53 +
 .../pegtl/analysis/analyze_cycles.hpp         |  127 +
 .../json/external/pegtl/analysis/counted.hpp  |   23 +
 .../json/external/pegtl/analysis/generic.hpp  |   31 +
 .../external/pegtl/analysis/grammar_info.hpp  |   32 +
 .../external/pegtl/analysis/insert_guard.hpp  |   51 +
 .../external/pegtl/analysis/insert_rules.hpp  |   25 +
 .../external/pegtl/analysis/rule_info.hpp     |   29 +
 .../external/pegtl/analysis/rule_type.hpp     |   21 +
 .../tao/json/external/pegtl/analyze.hpp       |   21 +
 .../tao/json/external/pegtl/apply_mode.hpp    |   19 +
 .../tao/json/external/pegtl/argv_input.hpp    |   51 +
 .../include/tao/json/external/pegtl/ascii.hpp |   67 +
 .../tao/json/external/pegtl/buffer_input.hpp  |  212 +
 .../tao/json/external/pegtl/change_action.hpp |   38 +
 .../pegtl/change_action_and_state.hpp         |   53 +
 .../pegtl/change_action_and_states.hpp        |   62 +
 .../json/external/pegtl/change_control.hpp    |   36 +
 .../tao/json/external/pegtl/change_state.hpp  |   50 +
 .../tao/json/external/pegtl/change_states.hpp |   61 +
 .../tao/json/external/pegtl/config.hpp        |   11 +
 .../tao/json/external/pegtl/contrib/abnf.hpp  |   35 +
 .../json/external/pegtl/contrib/alphabet.hpp  |   67 +
 .../json/external/pegtl/contrib/counter.hpp   |   54 +
 .../tao/json/external/pegtl/contrib/http.hpp  |  253 +
 .../external/pegtl/contrib/icu/internal.hpp   |   68 +
 .../json/external/pegtl/contrib/icu/utf16.hpp |  200 +
 .../json/external/pegtl/contrib/icu/utf32.hpp |  200 +
 .../json/external/pegtl/contrib/icu/utf8.hpp  |  105 +
 .../json/external/pegtl/contrib/if_then.hpp   |   55 +
 .../json/external/pegtl/contrib/integer.hpp   |  446 ++
 .../tao/json/external/pegtl/contrib/json.hpp  |   88 +
 .../external/pegtl/contrib/json_pointer.hpp   |   33 +
 .../external/pegtl/contrib/parse_tree.hpp     |  561 ++
 .../pegtl/contrib/parse_tree_to_dot.hpp       |  104 +
 .../external/pegtl/contrib/raw_string.hpp     |  225 +
 .../pegtl/contrib/remove_first_state.hpp      |   86 +
 .../pegtl/contrib/rep_one_min_max.hpp         |   62 +
 .../external/pegtl/contrib/rep_string.hpp     |   44 +
 .../json/external/pegtl/contrib/to_string.hpp |   38 +
 .../json/external/pegtl/contrib/tracer.hpp    |  158 +
 .../json/external/pegtl/contrib/unescape.hpp  |  199 +
 .../tao/json/external/pegtl/contrib/uri.hpp   |  106 +
 .../tao/json/external/pegtl/cstream_input.hpp |   33 +
 .../json/external/pegtl/disable_action.hpp    |   35 +
 .../tao/json/external/pegtl/discard_input.hpp |   37 +
 .../pegtl/discard_input_on_failure.hpp        |   39 +
 .../pegtl/discard_input_on_success.hpp        |   39 +
 .../tao/json/external/pegtl/enable_action.hpp |   35 +
 .../include/tao/json/external/pegtl/eol.hpp   |   37 +
 .../tao/json/external/pegtl/eol_pair.hpp      |   18 +
 .../tao/json/external/pegtl/file_input.hpp    |   44 +
 .../json/external/pegtl/internal/action.hpp   |   44 +
 .../external/pegtl/internal/action_input.hpp  |  107 +
 .../json/external/pegtl/internal/alnum.hpp    |   18 +
 .../json/external/pegtl/internal/alpha.hpp    |   18 +
 .../external/pegtl/internal/always_false.hpp  |   21 +
 .../tao/json/external/pegtl/internal/any.hpp  |   58 +
 .../json/external/pegtl/internal/apply.hpp    |   53 +
 .../json/external/pegtl/internal/apply0.hpp   |   50 +
 .../external/pegtl/internal/apply0_single.hpp |   34 +
 .../external/pegtl/internal/apply_single.hpp  |   34 +
 .../tao/json/external/pegtl/internal/at.hpp   |   53 +
 .../tao/json/external/pegtl/internal/bof.hpp  |   31 +
 .../tao/json/external/pegtl/internal/bol.hpp  |   31 +
 .../tao/json/external/pegtl/internal/bump.hpp |   45 +
 .../external/pegtl/internal/bump_help.hpp     |   29 +
 .../json/external/pegtl/internal/bytes.hpp    |   36 +
 .../json/external/pegtl/internal/control.hpp  |   44 +
 .../external/pegtl/internal/cr_crlf_eol.hpp   |   32 +
 .../json/external/pegtl/internal/cr_eol.hpp   |   32 +
 .../json/external/pegtl/internal/crlf_eol.hpp |   32 +
 .../pegtl/internal/cstream_reader.hpp         |   49 +
 .../pegtl/internal/cstring_reader.hpp         |   40 +
 .../json/external/pegtl/internal/demangle.hpp |  140 +
 .../json/external/pegtl/internal/disable.hpp  |   44 +
 .../json/external/pegtl/internal/discard.hpp  |   33 +
 .../external/pegtl/internal/dusel_mode.hpp    |   23 +
 .../external/pegtl/internal/duseltronik.hpp   |  187 +
 .../json/external/pegtl/internal/enable.hpp   |   44 +
 .../json/external/pegtl/internal/endian.hpp   |   62 +
 .../external/pegtl/internal/endian_gcc.hpp    |  206 +
 .../external/pegtl/internal/endian_win.hpp    |  106 +
 .../tao/json/external/pegtl/internal/eof.hpp  |   31 +
 .../tao/json/external/pegtl/internal/eol.hpp  |   31 +
 .../tao/json/external/pegtl/internal/eolf.hpp |   32 +
 .../pegtl/internal/file_mapper_posix.hpp      |   83 +
 .../pegtl/internal/file_mapper_win32.hpp      |  219 +
 .../external/pegtl/internal/file_opener.hpp   |   72 +
 .../external/pegtl/internal/file_reader.hpp   |  114 +
 .../external/pegtl/internal/has_apply.hpp     |   25 +
 .../external/pegtl/internal/has_apply0.hpp    |   25 +
 .../external/pegtl/internal/has_match.hpp     |   56 +
 .../external/pegtl/internal/identifier.hpp    |   22 +
 .../json/external/pegtl/internal/if_apply.hpp |   53 +
 .../json/external/pegtl/internal/if_must.hpp  |   48 +
 .../external/pegtl/internal/if_must_else.hpp  |   19 +
 .../external/pegtl/internal/if_then_else.hpp  |   51 +
 .../external/pegtl/internal/input_pair.hpp    |   29 +
 .../pegtl/internal/istream_reader.hpp         |   40 +
 .../json/external/pegtl/internal/istring.hpp  |   72 +
 .../json/external/pegtl/internal/iterator.hpp |   52 +
 .../external/pegtl/internal/lf_crlf_eol.hpp   |   37 +
 .../json/external/pegtl/internal/lf_eol.hpp   |   32 +
 .../tao/json/external/pegtl/internal/list.hpp |   19 +
 .../external/pegtl/internal/list_must.hpp     |   20 +
 .../external/pegtl/internal/list_tail.hpp     |   20 +
 .../external/pegtl/internal/list_tail_pad.hpp |   22 +
 .../json/external/pegtl/internal/marker.hpp   |   82 +
 .../external/pegtl/internal/missing_apply.hpp |   25 +
 .../pegtl/internal/missing_apply0.hpp         |   23 +
 .../tao/json/external/pegtl/internal/must.hpp |   72 +
 .../json/external/pegtl/internal/not_at.hpp   |   53 +
 .../tao/json/external/pegtl/internal/one.hpp  |   44 +
 .../tao/json/external/pegtl/internal/opt.hpp  |   57 +
 .../tao/json/external/pegtl/internal/pad.hpp  |   19 +
 .../json/external/pegtl/internal/pad_opt.hpp  |   20 +
 .../external/pegtl/internal/peek_char.hpp     |   32 +
 .../pegtl/internal/peek_mask_uint.hpp         |   54 +
 .../pegtl/internal/peek_mask_uint8.hpp        |   34 +
 .../external/pegtl/internal/peek_uint.hpp     |   45 +
 .../external/pegtl/internal/peek_uint8.hpp    |   33 +
 .../external/pegtl/internal/peek_utf16.hpp    |   54 +
 .../external/pegtl/internal/peek_utf32.hpp    |   43 +
 .../external/pegtl/internal/peek_utf8.hpp     |   90 +
 .../external/pegtl/internal/pegtl_string.hpp  |   90 +
 .../tao/json/external/pegtl/internal/plus.hpp |   53 +
 .../json/external/pegtl/internal/raise.hpp    |   53 +
 .../json/external/pegtl/internal/range.hpp    |   51 +
 .../json/external/pegtl/internal/ranges.hpp   |   93 +
 .../external/pegtl/internal/read_uint.hpp     |   77 +
 .../json/external/pegtl/internal/rematch.hpp  |   69 +
 .../tao/json/external/pegtl/internal/rep.hpp  |   66 +
 .../json/external/pegtl/internal/rep_min.hpp  |   20 +
 .../external/pegtl/internal/rep_min_max.hpp   |   79 +
 .../json/external/pegtl/internal/rep_opt.hpp  |   46 +
 .../json/external/pegtl/internal/require.hpp  |   42 +
 .../pegtl/internal/result_on_found.hpp        |   19 +
 .../json/external/pegtl/internal/rules.hpp    |   61 +
 .../tao/json/external/pegtl/internal/seq.hpp  |   73 +
 .../external/pegtl/internal/skip_control.hpp  |   25 +
 .../tao/json/external/pegtl/internal/sor.hpp  |   60 +
 .../tao/json/external/pegtl/internal/star.hpp |   47 +
 .../external/pegtl/internal/star_must.hpp     |   19 +
 .../json/external/pegtl/internal/state.hpp    |   49 +
 .../json/external/pegtl/internal/string.hpp   |   58 +
 .../json/external/pegtl/internal/trivial.hpp  |   32 +
 .../pegtl/internal/try_catch_type.hpp         |   64 +
 .../json/external/pegtl/internal/until.hpp    |   84 +
 .../tao/json/external/pegtl/istream_input.hpp |   33 +
 .../include/tao/json/external/pegtl/match.hpp |   73 +
 .../tao/json/external/pegtl/memory_input.hpp  |  381 ++
 .../tao/json/external/pegtl/mmap_input.hpp    |   79 +
 .../tao/json/external/pegtl/normal.hpp        |   87 +
 .../tao/json/external/pegtl/nothing.hpp       |   20 +
 .../include/tao/json/external/pegtl/parse.hpp |   53 +
 .../tao/json/external/pegtl/parse_error.hpp   |   69 +
 .../tao/json/external/pegtl/position.hpp      |   75 +
 .../tao/json/external/pegtl/read_input.hpp    |   74 +
 .../tao/json/external/pegtl/require_apply.hpp |   16 +
 .../json/external/pegtl/require_apply0.hpp    |   16 +
 .../tao/json/external/pegtl/rewind_mode.hpp   |   20 +
 .../include/tao/json/external/pegtl/rules.hpp |   67 +
 .../tao/json/external/pegtl/string_input.hpp  |   66 +
 .../tao/json/external/pegtl/tracking_mode.hpp |   19 +
 .../tao/json/external/pegtl/uint16.hpp        |   62 +
 .../tao/json/external/pegtl/uint32.hpp        |   62 +
 .../tao/json/external/pegtl/uint64.hpp        |   63 +
 .../include/tao/json/external/pegtl/uint8.hpp |   36 +
 .../include/tao/json/external/pegtl/utf16.hpp |   49 +
 .../include/tao/json/external/pegtl/utf32.hpp |   49 +
 .../include/tao/json/external/pegtl/utf8.hpp  |   28 +
 .../tao/json/external/pegtl/version.hpp       |   13 +
 .../include/tao/json/external/ryu.hpp         | 1216 ++++
 .../taocpp-json/include/tao/json/forward.hpp  |   44 +
 .../include/tao/json/from_file.hpp            |   32 +
 .../include/tao/json/from_input.hpp           |   32 +
 .../include/tao/json/from_stream.hpp          |   45 +
 .../include/tao/json/from_string.hpp          |   41 +
 .../include/tao/json/internal/action.hpp      |  268 +
 .../include/tao/json/internal/base64.hpp      |   55 +
 .../include/tao/json/internal/base64url.hpp   |   53 +
 .../include/tao/json/internal/endian.hpp      |   60 +
 .../include/tao/json/internal/endian_gcc.hpp  |  198 +
 .../include/tao/json/internal/endian_win.hpp  |  103 +
 .../include/tao/json/internal/errors.hpp      |   85 +
 .../include/tao/json/internal/escape.hpp      |   77 +
 .../include/tao/json/internal/format.hpp      |   59 +
 .../include/tao/json/internal/grammar.hpp     |  229 +
 .../include/tao/json/internal/hexdump.hpp     |   31 +
 .../include/tao/json/internal/identity.hpp    |   22 +
 .../tao/json/internal/number_state.hpp        |   80 +
 .../tao/json/internal/number_traits.hpp       |  267 +
 .../include/tao/json/internal/pair.hpp        |   42 +
 .../include/tao/json/internal/parse_util.hpp  |  112 +
 .../include/tao/json/internal/sha256.hpp      |  218 +
 .../include/tao/json/internal/single.hpp      |   40 +
 .../include/tao/json/internal/string_t.hpp    |   35 +
 .../include/tao/json/internal/type_traits.hpp |  113 +
 .../tao/json/internal/unescape_action.hpp     |   24 +
 .../tao/json/internal/uri_fragment.hpp        |  182 +
 .../taocpp-json/include/tao/json/jaxn.hpp     |   19 +
 .../include/tao/json/jaxn/consume_file.hpp    |   34 +
 .../include/tao/json/jaxn/consume_string.hpp  |   32 +
 .../tao/json/jaxn/events/from_file.hpp        |   28 +
 .../tao/json/jaxn/events/from_input.hpp       |   45 +
 .../tao/json/jaxn/events/from_stream.hpp      |   33 +
 .../tao/json/jaxn/events/from_string.hpp      |   39 +
 .../tao/json/jaxn/events/to_pretty_stream.hpp |   69 +
 .../tao/json/jaxn/events/to_stream.hpp        |   67 +
 .../tao/json/jaxn/events/to_string.hpp        |   33 +
 .../include/tao/json/jaxn/from_file.hpp       |   33 +
 .../include/tao/json/jaxn/from_input.hpp      |   33 +
 .../include/tao/json/jaxn/from_stream.hpp     |   48 +
 .../include/tao/json/jaxn/from_string.hpp     |   42 +
 .../include/tao/json/jaxn/internal/action.hpp |  355 ++
 .../json/jaxn/internal/bunescape_action.hpp   |  114 +
 .../include/tao/json/jaxn/internal/errors.hpp |  108 +
 .../tao/json/jaxn/internal/grammar.hpp        |  375 ++
 .../tao/json/jaxn/internal/integer.hpp        |  256 +
 .../json/jaxn/internal/unescape_action.hpp    |   28 +
 .../include/tao/json/jaxn/is_identifier.hpp   |   27 +
 .../include/tao/json/jaxn/parts_parser.hpp    |  263 +
 .../include/tao/json/jaxn/to_stream.hpp       |   36 +
 .../include/tao/json/jaxn/to_string.hpp       |   33 +
 .../include/tao/json/message_extension.hpp    |   49 +
 .../include/tao/json/operators.hpp            |  494 ++
 .../include/tao/json/parts_parser.hpp         |  306 +
 .../taocpp-json/include/tao/json/pointer.hpp  |  432 ++
 .../taocpp-json/include/tao/json/produce.hpp  |   61 +
 .../include/tao/json/self_contained.hpp       |  143 +
 .../taocpp-json/include/tao/json/span.hpp     |  568 ++
 .../taocpp-json/include/tao/json/stream.hpp   |   38 +
 .../include/tao/json/to_stream.hpp            |   42 +
 .../include/tao/json/to_string.hpp            |   23 +
 .../taocpp-json/include/tao/json/traits.hpp   |  971 +++
 .../taocpp-json/include/tao/json/type.hpp     |  112 +
 .../taocpp-json/include/tao/json/utf8.hpp     |   57 +
 .../taocpp-json/include/tao/json/value.hpp    |   12 +
 .../velocypack/include/velocypack/Iterator.h  |    6 +
 CHANGELOG                                     |  118 +-
 CMakeLists.txt                                |    4 +-
 .../Administration/get_admin_server_tls.md    |    7 +-
 Documentation/Scripts/codeBlockReader.py      |  103 +-
 LICENSES-OTHER-COMPONENTS.md                  |    9 +
 README.md                                     |    3 +
 UnitTests/tls-ca.crt                          |   11 +
 UnitTests/tls-ca.key                          |    5 +
 UnitTests/tls.keyfile                         |   28 +
 arangod/Agency/AgencyCommon.h                 |    6 +-
 arangod/Agency/AgencyStrings.h                |    2 +-
 arangod/Agency/Job.cpp                        |   14 +
 arangod/Agency/Job.h                          |    4 +
 arangod/Agency/MoveShard.cpp                  |   24 +
 arangod/Agency/Node.cpp                       |   22 +-
 arangod/Agency/Node.h                         |    3 +-
 arangod/Agency/State.cpp                      |   90 +-
 arangod/Agency/Supervision.cpp                |  123 +-
 arangod/Agency/Supervision.h                  |    9 +
 arangod/Aql/AqlFunctionFeature.cpp            |    2 +
 arangod/Aql/AqlItemBlock.cpp                  |   11 +-
 arangod/Aql/Ast.cpp                           |   16 +-
 arangod/Aql/AstNode.cpp                       |   48 +-
 arangod/Aql/AstNode.h                         |    5 +-
 arangod/Aql/BindParameters.cpp                |    4 +-
 arangod/Aql/DocumentProducingHelper.cpp       |   15 +-
 arangod/Aql/ExecutionPlan.cpp                 |    4 +-
 arangod/Aql/Functions.cpp                     |    2 +-
 arangod/Aql/IndexExecutor.cpp                 |   15 +-
 arangod/Aql/OptimizerRules.cpp                |   20 +-
 arangod/Aql/RegisterPlan.cpp                  |  156 +-
 arangod/Aql/RegisterPlan.h                    |   19 +-
 arangod/Aql/SimpleModifier.cpp                |    2 +-
 arangod/Aql/SimpleModifier.h                  |    2 +-
 arangod/Aql/SortedCollectExecutor.cpp         |    6 +-
 arangod/Aql/SortedCollectExecutor.h           |    2 +-
 arangod/Aql/TraversalExecutor.cpp             |    8 +-
 arangod/Aql/UpsertModifier.cpp                |    4 +-
 arangod/CMakeLists.txt                        |    9 +
 arangod/Cache/BucketState.cpp                 |   36 +-
 arangod/Cache/BucketState.h                   |   14 +-
 arangod/Cache/Cache.cpp                       |  242 +-
 arangod/Cache/Cache.h                         |   55 +-
 arangod/Cache/CacheManagerFeature.cpp         |   19 +-
 arangod/Cache/CacheManagerFeature.h           |    7 +-
 arangod/Cache/CacheManagerFeatureThreads.cpp  |    8 +-
 arangod/Cache/CacheManagerFeatureThreads.h    |   13 +-
 arangod/Cache/CachedValue.cpp                 |   45 +-
 arangod/Cache/CachedValue.h                   |   62 +-
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 create mode 100644 3rdParty/taocpp-json/include/tao/json/jaxn/events/to_pretty_stream.hpp
 create mode 100644 3rdParty/taocpp-json/include/tao/json/jaxn/events/to_stream.hpp
 create mode 100644 3rdParty/taocpp-json/include/tao/json/jaxn/events/to_string.hpp
 create mode 100644 3rdParty/taocpp-json/include/tao/json/jaxn/from_file.hpp
 create mode 100644 3rdParty/taocpp-json/include/tao/json/jaxn/from_input.hpp
 create mode 100644 3rdParty/taocpp-json/include/tao/json/jaxn/from_stream.hpp
 create mode 100644 3rdParty/taocpp-json/include/tao/json/jaxn/from_string.hpp
 create mode 100644 3rdParty/taocpp-json/include/tao/json/jaxn/internal/action.hpp
 create mode 100644 3rdParty/taocpp-json/include/tao/json/jaxn/internal/bunescape_action.hpp
 create mode 100644 3rdParty/taocpp-json/include/tao/json/jaxn/internal/errors.hpp
 create mode 100644 3rdParty/taocpp-json/include/tao/json/jaxn/internal/grammar.hpp
 create mode 100644 3rdParty/taocpp-json/include/tao/json/jaxn/internal/integer.hpp
 create mode 100644 3rdParty/taocpp-json/include/tao/json/jaxn/internal/unescape_action.hpp
 create mode 100644 3rdParty/taocpp-json/include/tao/json/jaxn/is_identifier.hpp
 create mode 100644 3rdParty/taocpp-json/include/tao/json/jaxn/parts_parser.hpp
 create mode 100644 3rdParty/taocpp-json/include/tao/json/jaxn/to_stream.hpp
 create mode 100644 3rdParty/taocpp-json/include/tao/json/jaxn/to_string.hpp
 create mode 100644 3rdParty/taocpp-json/include/tao/json/message_extension.hpp
 create mode 100644 3rdParty/taocpp-json/include/tao/json/operators.hpp
 create mode 100644 3rdParty/taocpp-json/include/tao/json/parts_parser.hpp
 create mode 100644 3rdParty/taocpp-json/include/tao/json/pointer.hpp
 create mode 100644 3rdParty/taocpp-json/include/tao/json/produce.hpp
 create mode 100644 3rdParty/taocpp-json/include/tao/json/self_contained.hpp
 create mode 100644 3rdParty/taocpp-json/include/tao/json/span.hpp
 create mode 100644 3rdParty/taocpp-json/include/tao/json/stream.hpp
 create mode 100644 3rdParty/taocpp-json/include/tao/json/to_stream.hpp
 create mode 100644 3rdParty/taocpp-json/include/tao/json/to_string.hpp
 create mode 100644 3rdParty/taocpp-json/include/tao/json/traits.hpp
 create mode 100644 3rdParty/taocpp-json/include/tao/json/type.hpp
 create mode 100644 3rdParty/taocpp-json/include/tao/json/utf8.hpp
 create mode 100644 3rdParty/taocpp-json/include/tao/json/value.hpp
 create mode 100644 UnitTests/tls-ca.crt
 create mode 100644 UnitTests/tls-ca.key
 create mode 100644 UnitTests/tls.keyfile
 create mode 100644 arangod/RocksDBEngine/RocksDBReplicationIterator.cpp
 create mode 100644 arangod/RocksDBEngine/RocksDBReplicationIterator.h
 rename lib/SimpleHttpClient/Options.h => arangod/StorageEngine/ReplicationIterator.cpp (59%)
 create mode 100644 arangod/StorageEngine/ReplicationIterator.h
 create mode 100644 lib/Basics/SpinLocker.h
 create mode 100644 lib/Basics/SpinUnlocker.h
 create mode 100644 lib/Containers/Enumerate.h
 create mode 100644 lib/Containers/MerkleTree.cpp
 create mode 100644 lib/Containers/MerkleTree.h
 delete mode 100755 scripts/build-bundle.sh
 delete mode 100755 scripts/build-dbg-deb.sh
 delete mode 100755 scripts/build-deb.sh
 delete mode 100755 scripts/build-docker.sh
 delete mode 100644 scripts/build-nsis.sh
 delete mode 100755 scripts/build-rpm.sh
 delete mode 100755 scripts/build-snap.sh
 delete mode 100755 scripts/build-xc-deb.sh
 delete mode 100755 scripts/build-xc64-deb.sh
 delete mode 100755 scripts/encryptionTest.sh
 delete mode 100755 scripts/generateDocumentation.sh
 create mode 100644 tests/Containers/EnumerateTest.cpp
 create mode 100644 tests/Containers/MerkleTreeTest.cpp
 create mode 100644 tests/IResearch/IResearchQueryNGramMatch-test.cpp
 create mode 100644 tests/js/client/shell/shell-aql-v8.js
 create mode 100644 tests/js/client/shell/shell-foxx-interface.js
 create mode 100644 tests/js/common/test-data/apps/interface/index.js
 create mode 100644 tests/js/common/test-data/apps/interface/manifest.json
 create mode 100644 tests/js/server/aql/aql-traversal-empty-register-mapping-regression.js
 create mode 100644 tests/js/server/recovery/revision-trees-no-sync-rocksdb-disabled.js
 create mode 100644 tests/js/server/recovery/revision-trees-partial-sync-rocksdb-disabled.js
 create mode 100644 tests/js/server/recovery/revision-trees-rocksdb-disabled.js

diff --git a/.gitignore b/.gitignore
index 710eaacf7c12..389d47f200e0 100644
--- a/.gitignore
+++ b/.gitignore
@@ -112,3 +112,7 @@ datafile-*.db
 # by build process
 arangodb-linux-amd64
 last_compiled_version.sha
+
+scripts/perfanalysis
+perf*
+callgrind*
diff --git a/3rdParty/CMakeLists.txt b/3rdParty/CMakeLists.txt
index 33e090bbe993..82cb64de268b 100755
--- a/3rdParty/CMakeLists.txt
+++ b/3rdParty/CMakeLists.txt
@@ -33,7 +33,9 @@ add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/zlib/zlib-1.2.11)
 
 set(SNAPPY_VERSION "1.1.7")
 set(SNAPPY_SOURCE_DIR "${CMAKE_CURRENT_SOURCE_DIR}/snappy/snappy-${SNAPPY_VERSION}")
+set(SNAPPY_SOURCE_DIR "${SNAPPY_SOURCE_DIR}" PARENT_SCOPE)
 set(SNAPPY_BUILD_DIR "${CMAKE_CURRENT_BINARY_DIR}/snappy/snappy-${SNAPPY_VERSION}")
+set(SNAPPY_BUILD_DIR "${SNAPPY_BUILD_DIR}" PARENT_SCOPE)
 set(SNAPPY_LIB "snappy")
 set(SNAPPY_LIB "${SNAPPY_LIB}" PARENT_SCOPE)
 add_subdirectory(${SNAPPY_SOURCE_DIR} EXCLUDE_FROM_ALL)
@@ -235,3 +237,13 @@ target_include_directories(fuerte SYSTEM PRIVATE
   "${CMAKE_CURRENT_SOURCE_DIR}/fuerte/include")
 
 set(V8_INTERNAL_INCLUDE_DIR ${V8_INTERNAL_INCLUDE_DIR} PARENT_SCOPE)
+
+if(NOT TARGET velocypack)
+add_library(velocypack INTERFACE)
+target_include_directories(velocypack INTERFACE "${CMAKE_CURRENT_SOURCE_DIR}/velocypack/include")
+endif()
+
+set(TAOCPP_JSON_BUILD_TESTS    OFF CACHE BOOL "Build taocpp::json test programs"    FORCE)
+set(TAOCPP_JSON_BUILD_EXAMPLES OFF CACHE BOOL "Build taocpp::json example programs" FORCE)
+add_subdirectory(taocpp-json EXCLUDE_FROM_ALL)
+add_subdirectory(json-schema-validation EXCLUDE_FROM_ALL)
diff --git a/3rdParty/README_maintainers.md b/3rdParty/README_maintainers.md
index 318acf3f5afe..17070c00c68d 100644
--- a/3rdParty/README_maintainers.md
+++ b/3rdParty/README_maintainers.md
@@ -177,6 +177,16 @@ Note that to account for changes introduced by new versions of swagger-ui,
 the stylistic CSS changes may need to be adjusted manually even when
 applied correctly.
 
+## taocpp::json
+
+Json Parser library
+Contains TaoCpp PEGTL - PEG Parsing library
+
+Upstream is: https://github.com/taocpp/json
+
+- On upgrade do not add unnecessary files (e.g. src, tests, contrib)
+  and update the commit hash in `./taocpp-json.version`.
+
 ## V8
 
 Javascript interpreter.
diff --git a/3rdParty/date/include/date/date.h b/3rdParty/date/include/date/date.h
index 3be91afec021..1186d2a808b3 100644
--- a/3rdParty/date/include/date/date.h
+++ b/3rdParty/date/include/date/date.h
@@ -7330,9 +7330,13 @@ parse(const CharT* format, Parsable& tp,
 
 namespace detail
 {
-
+// [tobias, 2020-03-10] I added the check
+//   !defined(_MSC_VER)
+// because this block does not compile with MSVC (at least MSVC 16 2019 / _MSC_VER = 1923).
+// If it works at some point, add `|| _MSC_VER > ...`.
 #if __cplusplus >= 201402  && (!defined(__EDG_VERSION__) || __EDG_VERSION__ > 411) \
-                           && (!defined(__SUNPRO_CC) || __SUNPRO_CC > 0x5150)
+                           && (!defined(__SUNPRO_CC) || __SUNPRO_CC > 0x5150) \
+                           && !defined(_MSC_VER)
 
 template <class CharT, std::size_t N>
 class string_literal
diff --git a/3rdParty/fuerte/include/fuerte/helper.h b/3rdParty/fuerte/include/fuerte/helper.h
index 5c475a3f9307..d7b10ec1c9ec 100644
--- a/3rdParty/fuerte/include/fuerte/helper.h
+++ b/3rdParty/fuerte/include/fuerte/helper.h
@@ -112,8 +112,8 @@ std::string mapToKeys(std::unordered_map<K, V, A> map) {
   return _detail::mapToKeys(map.begin(), map.end());
 }
 
-std::string encodeBase64(std::string const&);
-std::string encodeBase64U(std::string const&);
+std::string encodeBase64(std::string const&, bool pad);
+std::string encodeBase64U(std::string const&, bool pad);
 
 void toLowerInPlace(std::string& str);
 
diff --git a/3rdParty/fuerte/src/H1Connection.cpp b/3rdParty/fuerte/src/H1Connection.cpp
index a0b1b63d7fdd..581af3c4b0c8 100644
--- a/3rdParty/fuerte/src/H1Connection.cpp
+++ b/3rdParty/fuerte/src/H1Connection.cpp
@@ -155,7 +155,7 @@ H1Connection<ST>::H1Connection(EventLoopService& loop,
   if (this->_config._authenticationType == AuthenticationType::Basic) {
     _authHeader.append("Authorization: Basic ");
     _authHeader.append(
-        fu::encodeBase64(this->_config._user + ":" + this->_config._password));
+        fu::encodeBase64(this->_config._user + ":" + this->_config._password, true));
     _authHeader.append("\r\n");
   } else if (this->_config._authenticationType == AuthenticationType::Jwt) {
     if (this->_config._jwtToken.empty()) {
diff --git a/3rdParty/fuerte/src/H2Connection.cpp b/3rdParty/fuerte/src/H2Connection.cpp
index c142f3a38308..914759527b6c 100644
--- a/3rdParty/fuerte/src/H2Connection.cpp
+++ b/3rdParty/fuerte/src/H2Connection.cpp
@@ -94,6 +94,7 @@ template <SocketType T>
   } else if (field == fu_content_length_key) {
     size_t len = std::min<size_t>(std::stoul(val.toString()), 1024 * 1024 * 64);
     strm->data.reserve(len);
+    strm->response->header.addMeta(field.toString(), val.toString());
   } else {  // fall through
     strm->response->header.addMeta(field.toString(), val.toString());
     // TODO limit max header size ??
@@ -225,7 +226,7 @@ std::string makeAuthHeader(fu::detail::ConnectionConfiguration const& config) {
   // preemptively cache authentication
   if (config._authenticationType == AuthenticationType::Basic) {
     auth.append("Basic ");
-    auth.append(fu::encodeBase64(config._user + ":" + config._password));
+    auth.append(fu::encodeBase64(config._user + ":" + config._password, true));
   } else if (config._authenticationType == AuthenticationType::Jwt) {
     if (config._jwtToken.empty()) {
       throw std::logic_error("JWT token is not set");
@@ -368,7 +369,7 @@ void H2Connection<T>::finishConnect() {
       (uint8_t*)packed.data(), packed.size(), iv.data(), iv.size());
   FUERTE_ASSERT(nwrite >= 0);
   packed.resize(static_cast<size_t>(nwrite));
-  std::string encoded = fu::encodeBase64(packed);
+  std::string encoded = fu::encodeBase64(packed, true);
 
   // lets do the HTTP2 session upgrade right away
   initNgHttp2Session();
diff --git a/3rdParty/fuerte/src/helper.cpp b/3rdParty/fuerte/src/helper.cpp
index da1388bbcad9..707f2ac48a52 100644
--- a/3rdParty/fuerte/src/helper.cpp
+++ b/3rdParty/fuerte/src/helper.cpp
@@ -153,7 +153,7 @@ char const* const BASE64_CHARS =
     "abcdefghijklmnopqrstuvwxyz"
     "0123456789+/";
 
-std::string encodeBase64(std::string const& in) {
+std::string encodeBase64(std::string const& in, bool pad) {
   unsigned char charArray3[3];
   unsigned char charArray4[4];
 
@@ -201,16 +201,18 @@ std::string encodeBase64(std::string const& in) {
       ret += BASE64_CHARS[charArray4[j]];
     }
 
-    while ((i++ < 3)) {
-      ret += '=';
+    if (pad) {
+      while ((i++ < 3)) {
+        ret += '=';
+      }
     }
   }
 
   return ret;
 }
 
-std::string encodeBase64U(std::string const& in) {
-  std::string encoded = encodeBase64(in);
+std::string encodeBase64U(std::string const& in, bool pad) {
+  std::string encoded = encodeBase64(in, pad);
   // replace '+', '/' with '-' and '_'
   std::replace(encoded.begin(), encoded.end(), '+', '-');
   std::replace(encoded.begin(), encoded.end(), '/', '_');
diff --git a/3rdParty/fuerte/src/jwt.cpp b/3rdParty/fuerte/src/jwt.cpp
index 1a61b308a991..34cbf653e5fd 100644
--- a/3rdParty/fuerte/src/jwt.cpp
+++ b/3rdParty/fuerte/src/jwt.cpp
@@ -89,14 +89,18 @@ std::string jwt::generateRawJwt(std::string const& secret, VPackSlice const& bod
     headerBuilder.add("typ", VPackValue("JWT"));
   }
 
-  std::string fullMessage(encodeBase64(headerBuilder.toJson()) + "." +
-                          encodeBase64(body.toJson()));
+  // https://tools.ietf.org/html/rfc7515#section-2 requires
+  // JWT to use base64-encoding without trailing padding `=` chars
+  bool const pad = false;
+
+  std::string fullMessage(encodeBase64(headerBuilder.toJson(), pad) + "." +
+                          encodeBase64(body.toJson(), pad));
 
   std::string signature =
       sslHMAC(secret.c_str(), secret.length(), fullMessage.c_str(),
               fullMessage.length(), Algorithm::ALGORITHM_SHA256);
 
-  return fullMessage + "." + encodeBase64U(signature);
+  return fullMessage + "." + encodeBase64U(signature, pad);
 }
 
 // code from ArangoDBs SslInterface.cpp
diff --git a/3rdParty/iresearch/.travis.yml b/3rdParty/iresearch/.travis.yml
index 38e51b08b74d..d684ad8cd7ac 100644
--- a/3rdParty/iresearch/.travis.yml
+++ b/3rdParty/iresearch/.travis.yml
@@ -57,21 +57,7 @@ matrix:
       env:
         - SET_ENV="CC=gcc-4.9 && CXX=g++-4.9"
         - CXX_STANDARD=11
-        - BUILD_TYPE="Release" STATIC_LIB="true" TEST_PARAMS="--gtest_filter=*/fs___*:*/mmap___*"
-        - SUPPRESS_MAKE_ERRORS=true # travis is unable to handle log files > 4MB
-
-    ############################################################################
-    # Release build, static library (remaining tests)
-    ############################################################################
-    - os: linux
-      before_install:
-        - sudo add-apt-repository ppa:ubuntu-toolchain-r/test -y
-        - for i in 1 2 3; do travis_retry sudo apt-get update; done # 3 times since download failure is not an error
-        - travis_retry sudo apt-get install cmake cmake-data g++-4.9 valgrind
-      env:
-        - SET_ENV="CC=gcc-4.9 && CXX=g++-4.9"
-        - CXX_STANDARD=11
-        - BUILD_TYPE="Release" STATIC_LIB="true" TEST_PARAMS="--gtest_filter=*:-:*/fs___*:-:*/mmap___*"
+        - BUILD_TYPE="Release" STATIC_LIB="true"
         - SUPPRESS_MAKE_ERRORS=true # travis is unable to handle log files > 4MB
 
     ############################################################################
@@ -89,21 +75,7 @@ matrix:
         - SUPPRESS_MAKE_ERRORS=true # travis is unable to handle log files > 4MB
 
     ############################################################################
-    # Release build, shared library (filesystem tests)
-    ############################################################################
-    - os: linux
-      before_install:
-        - sudo add-apt-repository ppa:ubuntu-toolchain-r/test -y
-        - for i in 1 2 3; do travis_retry sudo apt-get update; done # 3 times since download failure is not an error
-        - travis_retry sudo apt-get install cmake cmake-data g++-4.9 valgrind
-      env:
-        - SET_ENV="CC=gcc-4.9 && CXX=g++-4.9"
-        - CXX_STANDARD=11
-        - BUILD_TYPE="Release" TEST_PARAMS="--gtest_filter=*/fs___*:*/mmap___*"
-        - SUPPRESS_MAKE_ERRORS=true # travis is unable to handle log files > 4MB
-
-    ############################################################################
-    # Release build, shared library (remaining tests)
+    # Release build, shared library
     ############################################################################
     - os: linux
       before_install:
@@ -113,7 +85,7 @@ matrix:
       env:
         - SET_ENV="CC=gcc-4.9 && CXX=g++-4.9"
         - CXX_STANDARD=11
-        - BUILD_TYPE="Release" TEST_PARAMS="--gtest_filter=*:-:*/fs___*:-:*/mmap___*"
+        - BUILD_TYPE="Release"
         - SUPPRESS_MAKE_ERRORS=true # travis is unable to handle log files > 4MB
 
     ############################################################################
@@ -134,20 +106,7 @@ matrix:
         - BUILD_TYPE="Debug" STATIC_LIB="true" TEST_PARAMS="--gtest_filter=*:-:*"
 
     ############################################################################
-    # Release build, static library (filesystem tests)
-    ############################################################################
-    - os: linux
-      before_install:
-        - sudo add-apt-repository ppa:ubuntu-toolchain-r/test -y
-        - for i in 1 2 3; do travis_retry sudo apt-get update; done # 3 times since download failure is not an error
-        - travis_retry sudo apt-get install cmake cmake-data g++-5 valgrind
-      env:
-        - SET_ENV="CC=gcc-5 && CXX=g++-5"
-        - CXX_STANDARD=11
-        - BUILD_TYPE="Release" STATIC_LIB="true" TEST_PARAMS="--gtest_filter=*/fs___*:*/mmap___*"
-
-    ############################################################################
-    # Release build, static library (remaining tests)
+    # Release build, static library
     ############################################################################
     - os: linux
       before_install:
@@ -157,7 +116,7 @@ matrix:
       env:
         - SET_ENV="CC=gcc-5 && CXX=g++-5"
         - CXX_STANDARD=11
-        - BUILD_TYPE="Release" STATIC_LIB="true" TEST_PARAMS="--gtest_filter=*:-:*/fs___*:-:*/mmap___*"
+        - BUILD_TYPE="Release" STATIC_LIB="true"
 
     ############################################################################
     # Debug build, shared library
@@ -173,20 +132,7 @@ matrix:
         - BUILD_TYPE="Debug" TEST_PARAMS="--gtest_filter=*:-:*"
 
     ############################################################################
-    # Release build, shared library (filesystem tests)
-    ############################################################################
-    - os: linux
-      before_install:
-        - sudo add-apt-repository ppa:ubuntu-toolchain-r/test -y
-        - for i in 1 2 3; do travis_retry sudo apt-get update; done # 3 times since download failure is not an error
-        - travis_retry sudo apt-get install cmake cmake-data g++-5 valgrind
-      env:
-        - SET_ENV="CC=gcc-5 && CXX=g++-5"
-        - CXX_STANDARD=11
-        - BUILD_TYPE="Release" TEST_PARAMS="--gtest_filter=*/fs___*:*/mmap___*"
-
-    ############################################################################
-    # Release build, shared library (remaining tests)
+    # Release build, shared library
     ############################################################################
     - os: linux
       before_install:
@@ -196,7 +142,7 @@ matrix:
       env:
         - SET_ENV="CC=gcc-5 && CXX=g++-5"
         - CXX_STANDARD=11
-        - BUILD_TYPE="Release" TEST_PARAMS="--gtest_filter=*:-:*/fs___*:-:*/mmap___*"
+        - BUILD_TYPE="Release"
 
     ############################################################################
     # GCC 6
@@ -216,20 +162,7 @@ matrix:
         - BUILD_TYPE="Debug" STATIC_LIB="true" TEST_PARAMS="--gtest_filter=*:-:*"
 
     ############################################################################
-    # Release build, static library (filesystem tests)
-    ############################################################################
-    - os: linux
-      before_install:
-        - sudo add-apt-repository ppa:ubuntu-toolchain-r/test -y
-        - for i in 1 2 3; do travis_retry sudo apt-get update; done # 3 times since download failure is not an error
-        - travis_retry sudo apt-get install cmake cmake-data g++-6 valgrind
-      env:
-        - SET_ENV="CC=gcc-6 && CXX=g++-6"
-        - CXX_STANDARD=11
-        - BUILD_TYPE="Release" STATIC_LIB="true" TEST_PARAMS="--gtest_filter=*/fs___*:*/mmap___*"
-
-    ############################################################################
-    # Release build, static library (remaining tests)
+    # Release build, static library
     ############################################################################
     - os: linux
       before_install:
@@ -239,7 +172,7 @@ matrix:
       env:
         - SET_ENV="CC=gcc-6 && CXX=g++-6"
         - CXX_STANDARD=11
-        - BUILD_TYPE="Release" STATIC_LIB="true" TEST_PARAMS="--gtest_filter=*:-:*/fs___*:-:*/mmap___*"
+        - BUILD_TYPE="Release" STATIC_LIB="true"
 
     ############################################################################
     # Debug build, shared library
@@ -255,20 +188,7 @@ matrix:
         - BUILD_TYPE="Debug" TEST_PARAMS="--gtest_filter=*:-:*"
 
     ############################################################################
-    # Release build, shared library (filesystem tests)
-    ############################################################################
-    - os: linux
-      before_install:
-        - sudo add-apt-repository ppa:ubuntu-toolchain-r/test -y
-        - for i in 1 2 3; do travis_retry sudo apt-get update; done # 3 times since download failure is not an error
-        - travis_retry sudo apt-get install cmake cmake-data g++-6 valgrind
-      env:
-        - SET_ENV="CC=gcc-6 && CXX=g++-6"
-        - CXX_STANDARD=11
-        - BUILD_TYPE="Release" TEST_PARAMS="--gtest_filter=*/fs___*:*/mmap___*"
-
-    ############################################################################
-    # Release build, shared library (remaining tests)
+    # Release build, shared library
     ############################################################################
     - os: linux
       before_install:
@@ -278,7 +198,7 @@ matrix:
       env:
         - SET_ENV="CC=gcc-6 && CXX=g++-6"
         - CXX_STANDARD=11
-        - BUILD_TYPE="Release" TEST_PARAMS="--gtest_filter=*:-:*/fs___*:-:*/mmap___*"
+        - BUILD_TYPE="Release"
 
     ############################################################################
     # GCC 7
@@ -300,7 +220,7 @@ matrix:
         - BUILD_TYPE="Debug" STATIC_LIB="true" TEST_PARAMS="--gtest_filter=*:-:*"
 
     ############################################################################
-    # Release build, static library (filesystem tests)
+    # Release build, static library
     ############################################################################
     - os: linux
       dist: trusty # gcc7 is not available in `precise`
@@ -312,10 +232,10 @@ matrix:
         - SET_ENV="CC=gcc-7 && CXX=g++-7"
         - CXX_STANDARD=14
         - CMAKE_VERSION=3.2.3 # supports c++14
-        - BUILD_TYPE="Release" STATIC_LIB="true" TEST_PARAMS="--gtest_filter=*/fs___*:*/mmap___*"
+        - BUILD_TYPE="Release" STATIC_LIB="true"
 
     ############################################################################
-    # Release build, static library (remaining tests)
+    # Debug build, shared library
     ############################################################################
     - os: linux
       dist: trusty # gcc7 is not available in `precise`
@@ -327,10 +247,10 @@ matrix:
         - SET_ENV="CC=gcc-7 && CXX=g++-7"
         - CXX_STANDARD=14
         - CMAKE_VERSION=3.2.3 # supports c++14
-        - BUILD_TYPE="Release" STATIC_LIB="true" TEST_PARAMS="--gtest_filter=*:-:*/fs___*:-:*/mmap___*"
+        - BUILD_TYPE="Debug" TEST_PARAMS="--gtest_filter=*:-:*"
 
     ############################################################################
-    # Debug build, shared library
+    # Release build, shared library
     ############################################################################
     - os: linux
       dist: trusty # gcc7 is not available in `precise`
@@ -342,44 +262,44 @@ matrix:
         - SET_ENV="CC=gcc-7 && CXX=g++-7"
         - CXX_STANDARD=14
         - CMAKE_VERSION=3.2.3 # supports c++14
-        - BUILD_TYPE="Debug" TEST_PARAMS="--gtest_filter=*:-:*"
+        - BUILD_TYPE="Release"
 
     ############################################################################
-    # Release build, shared library (filesystem tests)
+    # GCC 8
+    ############################################################################
+
+    ############################################################################
+    # Debug build, static library
     ############################################################################
     - os: linux
-      dist: trusty # gcc7 is not available in `precise`
+      dist: trusty # gcc8 is not available in `precise`
       before_install:
         - sudo add-apt-repository ppa:ubuntu-toolchain-r/test -y
         - for i in 1 2 3; do travis_retry sudo apt-get update; done # 3 times since download failure is not an error
-        - travis_retry sudo apt-get install cmake cmake-data g++-7 valgrind
+        - travis_retry sudo apt-get install g++-8 valgrind
       env:
-        - SET_ENV="CC=gcc-7 && CXX=g++-7"
-        - CXX_STANDARD=14
-        - CMAKE_VERSION=3.2.3 # supports c++14
-        - BUILD_TYPE="Release" TEST_PARAMS="--gtest_filter=*/fs___*:*/mmap___*"
+        - SET_ENV="CC=gcc-8 && CXX=g++-8"
+        - CMAKE_VERSION=3.8.2 # supports c++17
+        - CXX_STANDARD=17
+        - BUILD_TYPE="Debug" STATIC_LIB="true" TEST_PARAMS="--gtest_filter=*:-:*"
 
     ############################################################################
-    # Release build, shared library (remaining tests)
+    # Release build, static library
     ############################################################################
     - os: linux
-      dist: trusty # gcc7 is not available in `precise`
+      dist: trusty # gcc8 is not available in `precise`
       before_install:
         - sudo add-apt-repository ppa:ubuntu-toolchain-r/test -y
         - for i in 1 2 3; do travis_retry sudo apt-get update; done # 3 times since download failure is not an error
-        - travis_retry sudo apt-get install cmake cmake-data g++-7 valgrind
+        - travis_retry sudo apt-get install g++-8 valgrind
       env:
-        - SET_ENV="CC=gcc-7 && CXX=g++-7"
-        - CXX_STANDARD=14
-        - CMAKE_VERSION=3.2.3 # supports c++14
-        - BUILD_TYPE="Release" TEST_PARAMS="--gtest_filter=*:-:*/fs___*:-:*/mmap___*"
-
-    ############################################################################
-    # GCC 8
-    ############################################################################
+        - SET_ENV="CC=gcc-8 && CXX=g++-8"
+        - CMAKE_VERSION=3.8.2 # supports c++17
+        - CXX_STANDARD=17
+        - BUILD_TYPE="Release" STATIC_LIB="true"
 
     ############################################################################
-    # Debug build, static library
+    # Debug build, shared library
     ############################################################################
     - os: linux
       dist: trusty # gcc8 is not available in `precise`
@@ -391,82 +311,86 @@ matrix:
         - SET_ENV="CC=gcc-8 && CXX=g++-8"
         - CMAKE_VERSION=3.8.2 # supports c++17
         - CXX_STANDARD=17
-        - BUILD_TYPE="Debug" STATIC_LIB="true" TEST_PARAMS="--gtest_filter=*:-:*"
+        - BUILD_TYPE="Debug" TEST_PARAMS="--gtest_filter=*:-:*"
 
     ############################################################################
-    # Release build, static library (filesystem tests)
+    # Release build, shared library
     ############################################################################
     - os: linux
-      dist: trusty # gcc8 is not available in `precise`
+      dist: trusty # gcc7 is not available in `precise`
       before_install:
         - sudo add-apt-repository ppa:ubuntu-toolchain-r/test -y
         - for i in 1 2 3; do travis_retry sudo apt-get update; done # 3 times since download failure is not an error
-        - travis_retry sudo apt-get install g++-8 valgrind
+        - travis_retry sudo apt-get install cmake cmake-data g++-8 valgrind
       env:
         - SET_ENV="CC=gcc-8 && CXX=g++-8"
         - CMAKE_VERSION=3.8.2 # supports c++17
         - CXX_STANDARD=17
-        - BUILD_TYPE="Release" STATIC_LIB="true" TEST_PARAMS="--gtest_filter=*/fs___*:*/mmap___*"
+        - BUILD_TYPE="Release"
+
+    ############################################################################
+    # GCC 9
+    ############################################################################
 
     ############################################################################
-    # Release build, static library (remaining tests)
+    # Debug build, static library
     ############################################################################
     - os: linux
-      dist: trusty # gcc8 is not available in `precise`
+      dist: bionic # gcc9 is not available in `precise`
       before_install:
         - sudo add-apt-repository ppa:ubuntu-toolchain-r/test -y
         - for i in 1 2 3; do travis_retry sudo apt-get update; done # 3 times since download failure is not an error
-        - travis_retry sudo apt-get install g++-8 valgrind
+        - travis_retry sudo apt-get install g++-9 valgrind
       env:
-        - SET_ENV="CC=gcc-8 && CXX=g++-8"
+        - SET_ENV="CC=gcc-9 && CXX=g++-9"
         - CMAKE_VERSION=3.8.2 # supports c++17
         - CXX_STANDARD=17
-        - BUILD_TYPE="Release" STATIC_LIB="true" TEST_PARAMS="--gtest_filter=*:-:*/fs___*:-:*/mmap___*"
+        - BUILD_TYPE="Debug" STATIC_LIB="true" TEST_PARAMS="--gtest_filter=*:-:*"
 
     ############################################################################
-    # Debug build, shared library
+    # Release build, static library
     ############################################################################
     - os: linux
-      dist: trusty # gcc8 is not available in `precise`
+      dist: bionic # gcc9 is not available in `precise`
       before_install:
         - sudo add-apt-repository ppa:ubuntu-toolchain-r/test -y
         - for i in 1 2 3; do travis_retry sudo apt-get update; done # 3 times since download failure is not an error
-        - travis_retry sudo apt-get install g++-8 valgrind
+        - travis_retry sudo apt-get install g++-9 valgrind
       env:
-        - SET_ENV="CC=gcc-8 && CXX=g++-8"
+        - SET_ENV="CC=gcc-9 && CXX=g++-9"
         - CMAKE_VERSION=3.8.2 # supports c++17
         - CXX_STANDARD=17
-        - BUILD_TYPE="Debug" TEST_PARAMS="--gtest_filter=*:-:*"
+        - BUILD_TYPE="Release" STATIC_LIB="true"
 
     ############################################################################
-    # Release build, shared library (filesystem tests)
+    # Debug build, shared library
     ############################################################################
     - os: linux
-      dist: trusty # gcc8 is not available in `precise`
+      dist: bionic # gcc9 is not available in `precise`
       before_install:
         - sudo add-apt-repository ppa:ubuntu-toolchain-r/test -y
         - for i in 1 2 3; do travis_retry sudo apt-get update; done # 3 times since download failure is not an error
         - travis_retry sudo apt-get install g++-8 valgrind
       env:
-        - SET_ENV="CC=gcc-8 && CXX=g++-8"
+        - SET_ENV="CC=gcc-9 && CXX=g++-9"
         - CMAKE_VERSION=3.8.2 # supports c++17
         - CXX_STANDARD=17
-        - BUILD_TYPE="Release" TEST_PARAMS="--gtest_filter=*/fs___*:*/mmap___*"
+        - BUILD_TYPE="Debug" TEST_PARAMS="--gtest_filter=*:-:*"
 
     ############################################################################
-    # Release build, shared library (remaining tests)
+    # Release build, shared library
     ############################################################################
     - os: linux
-      dist: trusty # gcc8 is not available in `precise`
+      dist: bionic # gcc9 is not available in `precise`
       before_install:
         - sudo add-apt-repository ppa:ubuntu-toolchain-r/test -y
         - for i in 1 2 3; do travis_retry sudo apt-get update; done # 3 times since download failure is not an error
         - travis_retry sudo apt-get install g++-8 valgrind
       env:
-        - SET_ENV="CC=gcc-8 && CXX=g++-8"
+        - SET_ENV="CC=gcc-9 && CXX=g++-9"
         - CMAKE_VERSION=3.8.2 # supports c++17
         - CXX_STANDARD=17
-        - BUILD_TYPE="Release" TEST_PARAMS="--gtest_filter=*:-:*/fs___*:-:*/mmap___*"
+        - BUILD_TYPE="Release"
 
     ############################################################################
     # OSX
@@ -488,7 +412,7 @@ matrix:
         - BUILD_TYPE="Debug" STATIC_LIB="true" TEST_PARAMS="--gtest_filter=*:-:*"
 
     ############################################################################
-    # Release build, static library (filesystem tests)
+    # Release build, static library
     ############################################################################
     - os: osx
       osx_image: xcode9
@@ -500,22 +424,7 @@ matrix:
         - SET_ENV="PATH=/usr/local/opt/bison/bin:/usr/local/opt/bison@2.7/bin:$PATH"
         - CXX_STANDARD=11
         - BOOST_B2_ARGS="boost.locale.iconv=off"
-        - BUILD_TYPE="Release" STATIC_LIB="true" TEST_PARAMS="--gtest_filter=*/fs___*:*/mmap___*"
-
-    ############################################################################
-    # Release build, static library (remaining tests)
-    ############################################################################
-    - os: osx
-      osx_image: xcode9
-      compiler: clang
-      before_install:
-        - brew update || true;
-          brew install bison@2.7 || true;
-      env:
-        - SET_ENV="PATH=/usr/local/opt/bison/bin:/usr/local/opt/bison@2.7/bin:$PATH"
-        - CXX_STANDARD=11
-        - BOOST_B2_ARGS="boost.locale.iconv=off"
-        - BUILD_TYPE="Release" STATIC_LIB="true" TEST_PARAMS="--gtest_filter=*:-:*/fs___*:-:*/mmap___*"
+        - BUILD_TYPE="Release" STATIC_LIB="true"
 
     ############################################################################
     # Debug build, shared library
@@ -533,22 +442,7 @@ matrix:
         - BUILD_TYPE="Debug" TEST_PARAMS="--gtest_filter=*:-:*"
 
     ############################################################################
-    # Release build, shared library (filesystem tests)
-    ############################################################################
-    - os: osx
-      osx_image: xcode9
-      compiler: clang
-      before_install:
-        - brew update || true;
-          brew install bison@2.7 || true;
-      env:
-        - SET_ENV="PATH=/usr/local/opt/bison/bin:/usr/local/opt/bison@2.7/bin:$PATH"
-        - CXX_STANDARD=11
-        - BOOST_B2_ARGS="boost.locale.iconv=off"
-        - BUILD_TYPE="Release" TEST_PARAMS="--gtest_filter=*/fs___*:*/mmap___*"
-
-    ############################################################################
-    # Release build, shared library (remaining tests)
+    # Release build, shared library
     ############################################################################
     - os: osx
       osx_image: xcode9
@@ -560,7 +454,7 @@ matrix:
         - SET_ENV="PATH=/usr/local/opt/bison/bin:/usr/local/opt/bison@2.7/bin:$PATH"
         - CXX_STANDARD=11
         - BOOST_B2_ARGS="boost.locale.iconv=off"
-        - BUILD_TYPE="Release" TEST_PARAMS="--gtest_filter=*:-:*/fs___*:-:*/mmap___*"
+        - BUILD_TYPE="Release"
 
 before_install:
   - eval "${SET_ENV}"
@@ -717,7 +611,7 @@ script:
           exit 1
         fi
       else
-        make iresearch-tests${BUILD_TYPE_SUFFIX}
+        make -j4 iresearch-tests${BUILD_TYPE_SUFFIX}
       fi
       # build utils
       if [[ "${STATIC_LIB}" == "true" ]]; then
@@ -727,7 +621,7 @@ script:
       # execute tests
       ulimit -n 5120 # required for MacOS (max-open-files = 16 threads * (100000/10000) commits * 8 segments-per-commit * 4 open-files-per-segment)
       ulimit -a
-      if ! travis_wait 90 ./bin/iresearch-tests${TEST_EXECUTABLE_SUFFIX} ${TEST_PARAMS}; then
+      if ! travis_wait 120 python ../scripts/gtest-parallel/gtest_parallel.py ${TEST_PARAMS} ./bin/iresearch-tests${TEST_EXECUTABLE_SUFFIX} ; then
         exit 1
       fi
       # archive artifacts
diff --git a/3rdParty/iresearch/CMakeLists.txt b/3rdParty/iresearch/CMakeLists.txt
index 05b2f6f86c7b..12145c74284d 100644
--- a/3rdParty/iresearch/CMakeLists.txt
+++ b/3rdParty/iresearch/CMakeLists.txt
@@ -73,6 +73,10 @@ option(USE_TESTS "Build tests" OFF)
 option(USE_PYRESEARCH "Build iresearch python bridge" OFF)
 option(USE_VALGRIND "Use workarounds to avoid false positives in valgrind" OFF)
 option(USE_SIMDCOMP "Use architecture specific low-level optimizations" OFF)
+option(USE_CCACHE "Use CCACHE if present" ON)
+
+set(SUPPRESS_EXTERNAL_WARNINGS OFF CACHE INTERNAL "Suppress warnings originating in 3rd party code.")
+
 add_option_gprof(FALSE)
 
 if (USE_VALGRIND)
@@ -118,8 +122,6 @@ endif()
 ### setup ccache
 ################################################################################
 
-option(USE_CCACHE "Use CCACHE if present" ON)
-
 if (USE_CCACHE)
   find_program(CCACHE_FOUND ccache)
 
@@ -128,7 +130,11 @@ if (USE_CCACHE)
   endif(CCACHE_FOUND)
 endif()
 
-if (USE_OPTIMIZE_FOR_ARCHITECTURE)
+################################################################################
+### setup platform dependent optimizations
+################################################################################
+
+if (USE_SIMDCOMP)
   include(OptimizeForArchitecture)
   OptimizeForArchitecture()
 
@@ -265,6 +271,7 @@ if (USE_PVS_STUDIO)
     ANALYZE ${PVS_STUDIO_ANALYZE}
     MODE GA:1,2 OP
     LOG ${IResearch_TARGET_NAME}.err
+    CONFIG "${CMAKE_SOURCE_DIR}/PVSIResearch.cfg"
   )
 
   pvs_studio_add_target(
@@ -273,6 +280,16 @@ if (USE_PVS_STUDIO)
     ANALYZE ${PVS_STUDIO_ANALYZE}
     MODE GA:1,2 OP
     LOG ${IResearch_TARGET_NAME}-html.err
+    CONFIG "${CMAKE_SOURCE_DIR}/PVSIResearch.cfg"
+  )
+
+  pvs_studio_add_target(
+    TARGET ${PVS_STUDIO_TARGET_NAME}-xml ALL
+    FORMAT xml
+    ANALYZE ${PVS_STUDIO_ANALYZE}
+    MODE GA:1,2 OP
+    LOG ${IResearch_TARGET_NAME}-xml.err
+    CONFIG "${CMAKE_SOURCE_DIR}/PVSIResearch.cfg"
   )
 endif()
 
diff --git a/3rdParty/iresearch/PVSIResearch.cfg b/3rdParty/iresearch/PVSIResearch.cfg
new file mode 100644
index 000000000000..4920dfe69aa2
--- /dev/null
+++ b/3rdParty/iresearch/PVSIResearch.cfg
@@ -0,0 +1,2 @@
+analysis-mode=31
+exclude-path=iql
diff --git a/3rdParty/iresearch/README.md b/3rdParty/iresearch/README.md
index 1c7654b3f89a..79bb9937644c 100644
--- a/3rdParty/iresearch/README.md
+++ b/3rdParty/iresearch/README.md
@@ -16,6 +16,7 @@
 - [Overview](#overview)
 - [High level architecture and main concepts](#high-level-architecture-and-main-concepts)
 - [Build](#build)
+- [Pyresearch](#pyresearch)
 - [Included 3rd party dependencies](#included-3rd-party-dependencies)
 - [External 3rd party dependencies](#external-3rd-party-dependencies)
 - [Query filter building blocks](#query-filter-building-blocks)
@@ -385,6 +386,20 @@ code coverage:
 cmake --build . --target iresearch-coverage
 ```
 
+## Pyresearch
+There is Python wrapper for IResearch. Wrapper gives access to directory reader object.
+For usage example see <src-path>/python/scripts
+### Build
+To build Pyresearch SWIG generator should be available.
+Add -DUSE_PYRESEARCH=ON to cmake command-line to generate Pyresearch targets
+### Install
+Run target pyresearch-install
+#### win32 install notes:
+Some version of ICU installers seems to fail to make available all icu dlls through 
+PATH enviroment variable, manual adjustment may be needed.
+#### (*nix) install notes:
+Shared version of libiresearch is used. Install IResearch before running Pyresearch.
+
 ## Included 3rd party dependencies
 Code for all included 3rd party dependencies is located in the "external" directory.
 #### [MurMurHash](https://sites.google.com/site/murmurhash)
@@ -435,12 +450,15 @@ the first whitespace is ignored), in the directory corresponding to its language
 ## Query filter building blocks
 | Filter    |       Description    |          
 |-----------|----------------------|
+|iresearch::by_edit_distance|for filtering of values based on Levenshtein distance
 |iresearch::by_granular_range|for faster filtering of numeric values within a given range, with the possibility of specifying open/closed ranges
+|iresearch::by_ngram_similarity|for filtering of values based on NGram model
 |iresearch::by_phrase|for word-position-sensitive filtering of values, with the possibility of skipping selected positions
 |iresearch::by_prefix|for filtering of exact value prefixes
 |iresearch::by_range|for filtering of values within a given range, with the possibility of specifying open/closed ranges
 |iresearch::by_same_position|for term-insertion-order sensitive filtering of exact values
 |iresearch::by_term|for filtering of exact values
+|iresearch::by_wildcard|for filtering of values based on matching pattern
 |iresearch::And|boolean conjunction of multiple filters, influencing document ranks/scores as appropriate
 |iresearch::Or|boolean disjunction of multiple filters, influencing document ranks/scores as appropriate (including "minimum match" functionality)
 |iresearch::Not|boolean negation of multiple filters
@@ -560,7 +578,7 @@ The following grammar is currently defined via Bison (the root is <query>):
 - Apple Clang: 9
 
 ## License
-Copyright (c) 2017-2019 ArangoDB GmbH
+Copyright (c) 2017-2020 ArangoDB GmbH
 
 Copyright (c) 2016-2017 EMC Corporation
 
diff --git a/3rdParty/iresearch/THIRD_PARTY_README.md b/3rdParty/iresearch/THIRD_PARTY_README.md
index 1255e854f80a..659f268812ae 100644
--- a/3rdParty/iresearch/THIRD_PARTY_README.md
+++ b/3rdParty/iresearch/THIRD_PARTY_README.md
@@ -2,7 +2,7 @@ IResearch search engine
 
 Third Party Software Read Me
 
-Copyright© 2017 ArangoDB GmbH. All rights reserved.
+Copyright© 2017-2020 ArangoDB GmbH. All rights reserved.
 Published October, 2017
 
 Copyright© 2016-2017 EMC Corporation. All rights reserved.
@@ -289,7 +289,7 @@ The above copyright notice and this permission notice shall be included in all c
 
 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 
-### Boost
+### Boost, utfcpp
 Boost Software License - Version 1.0 - August 17th, 2003
 
 Permission is hereby granted, free of charge, to any person or organization
diff --git a/3rdParty/iresearch/appveyor.yml b/3rdParty/iresearch/appveyor.yml
index 208d1f8b5b8e..7a33518e9dcb 100644
--- a/3rdParty/iresearch/appveyor.yml
+++ b/3rdParty/iresearch/appveyor.yml
@@ -11,7 +11,7 @@ build:
 
 environment:
   BOOST_VERSION: default
-  CMAKE_OPTIONS: -DUSE_TESTS=On -DCMAKE_BUILD_TYPE=%CONFIGURATION% -DMSVC_BUILD_THREADS=16
+  USE_SIMDCOMP: On
   CMAKE_BUILD_OPTIONS: --config %CONFIGURATION%
   matrix:
 
@@ -24,8 +24,9 @@ environment:
       TEST_OPTIONS: --gtest_filter=*type_utils*
       VSINSTALL: "Microsoft Visual Studio 14.0\\VC"
       BOOST_ROOT: C:/Libraries/boost_1_60_0
+      USE_SIMDCOMP: Off
       CONFIGURATION: Debug
-
+      
     - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
       BUILD_TYPE: static
       TEST_OPTIONS: --gtest_filter=*type_utils*
@@ -38,6 +39,7 @@ environment:
       TEST_OPTIONS: --gtest_filter=*:-:*europarl*/fs*
       VSINSTALL: "Microsoft Visual Studio 14.0\\VC"
       BOOST_ROOT: C:/Libraries/boost_1_60_0
+      USE_SIMDCOMP: Off
       CONFIGURATION: Release
 
     - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
@@ -195,7 +197,7 @@ build_script:
   - cd %APPVEYOR_BUILD_FOLDER%
   - mkdir build
   - cd build
-  - cmake -g %APPVEYOR_BUILD_WORKER_IMAGE% -Ax64 %CMAKE_OPTIONS% ..
+  - cmake -g %APPVEYOR_BUILD_WORKER_IMAGE% -Ax64 -DUSE_TESTS=On -DCMAKE_BUILD_TYPE=%CONFIGURATION% -DMSVC_BUILD_THREADS=16 -DUSE_SIMDCOMP=%USE_SIMDCOMP% ..
   - cmake --build . %CMAKE_BUILD_OPTIONS% --target iresearch-tests-%BUILD_TYPE%
   - if "%BUILD_TYPE%" == "static" ( cmake --build . %CMAKE_BUILD_OPTIONS% --target iresearch-benchmarks )
   - if "%BUILD_TYPE%" == "static" ( cmake --build . %CMAKE_BUILD_OPTIONS% --target iresearch-index-util )
@@ -204,7 +206,7 @@ test_script:
   ############################################################################
   # Execute tests
   ############################################################################
-  - cmd: bin\%CONFIGURATION%\iresearch-tests%EXECUTABLE_SUFFIX%.exe --gtest_output=xml:test_results.xml %TEST_OPTIONS%
+  - cmd: python ..\scripts\gtest-parallel\gtest_parallel.py %TEST_OPTIONS% bin\%CONFIGURATION%\iresearch-tests%EXECUTABLE_SUFFIX%.exe -- --gtest_output=xml:test_results.xml
 
 on_finish:
   ############################################################################
diff --git a/3rdParty/iresearch/cmake/PVS-Studio.cmake b/3rdParty/iresearch/cmake/PVS-Studio.cmake
index 3cc5c441704d..ee860fc21ae2 100644
--- a/3rdParty/iresearch/cmake/PVS-Studio.cmake
+++ b/3rdParty/iresearch/cmake/PVS-Studio.cmake
@@ -1,546 +1,546 @@
-# 2006-2008 (c) Viva64.com Team
-# 2008-2018 (c) OOO "Program Verification Systems"
-#
-# Version 12
-
-cmake_minimum_required(VERSION 2.8.12)
-cmake_policy(SET CMP0054 NEW)
-
-if (PVS_STUDIO_AS_SCRIPT)
-    # This code runs at build time.
-    # It executes pvs-studio-analyzer and propagates its return value.
-
-    set(in_cl_params FALSE)
-    set(additional_args)
-
-    foreach (arg ${PVS_STUDIO_COMMAND})
-        if (NOT in_cl_params)
-            if ("${arg}" STREQUAL "--cl-params")
-                set(in_cl_params TRUE)
-            endif ()
-        else ()
-            # A workaround for macOS frameworks (e.g. QtWidgets.framework)
-            # You can test this workaround on this project: https://github.com/easyaspi314/MidiEditor/tree/gba
-            if (APPLE AND "${arg}" MATCHES "^-I(.*)\\.framework$")
-                STRING(REGEX REPLACE "^-I(.*)\\.framework$" "\\1.framework" framework "${arg}")
-                if (IS_ABSOLUTE "${framework}")
-                    get_filename_component(framework "${framework}" DIRECTORY)
-                    list(APPEND additional_args "-iframework")
-                    list(APPEND additional_args "${framework}")
-                endif ()
-            endif ()
-        endif ()
-    endforeach ()
-
-    execute_process(COMMAND ${PVS_STUDIO_COMMAND} ${additional_args}
-                    ERROR_VARIABLE error
-                    RESULT_VARIABLE result)
-
-    set(stderr_type "")
-
-    if (result)
-        set(stderr_type FATAL_ERROR)
-    endif ()
-
-    if (result OR error)
-        message(${stderr_type} "${error}")
-    endif ()
-
-    return()
-endif ()
-
-if(__PVS_STUDIO_INCLUDED)
-    return()
-endif()
-set(__PVS_STUDIO_INCLUDED TRUE)
-
-set(PVS_STUDIO_SCRIPT "${CMAKE_CURRENT_LIST_FILE}")
-
-function (pvs_studio_log TEXT)
-    if (PVS_STUDIO_DEBUG)
-        message("PVS-Studio: ${TEXT}")
-    endif ()
-endfunction ()
-
-function (pvs_studio_relative_path VAR ROOT FILEPATH)
-    set("${VAR}" "${FILEPATH}" PARENT_SCOPE)
-    if ("${FILEPATH}" MATCHES "^/.*$" OR "${FILEPATH}" MATCHES "^.:/.*$")
-        file(RELATIVE_PATH RPATH "${ROOT}" "${FILEPATH}")
-        if (NOT "${RPATH}" MATCHES "^\\.\\..*$")
-            set("${VAR}" "${RPATH}" PARENT_SCOPE)
-        endif ()
-    endif ()
-endfunction ()
-
-function (pvs_studio_join_path VAR DIR1 DIR2)
-    if ("${DIR2}" MATCHES "^(/|~|.:/).*$" OR "${DIR1}" STREQUAL "")
-        set("${VAR}" "${DIR2}" PARENT_SCOPE)
-    else ()
-        set("${VAR}" "${DIR1}/${DIR2}" PARENT_SCOPE)
-    endif ()
-endfunction ()
-
-macro (pvs_studio_append_flags_from_property CXX C DIR PREFIX)
-    if (NOT "${PROPERTY}" STREQUAL "NOTFOUND" AND NOT "${PROPERTY}" STREQUAL "PROPERTY-NOTFOUND")
-        foreach (PROP ${PROPERTY})
-            pvs_studio_join_path(PROP "${DIR}" "${PROP}")
-
-            if (APPLE AND "${PREFIX}" STREQUAL "-I" AND IS_ABSOLUTE "${PROP}" AND "${PROP}" MATCHES "\\.framework$")
-                get_filename_component(FRAMEWORK "${PROP}" DIRECTORY)
-                list(APPEND "${CXX}" "-iframework")
-                list(APPEND "${CXX}" "${FRAMEWORK}")
-                list(APPEND "${C}" "-iframework")
-                list(APPEND "${C}" "${FRAMEWORK}")
-                pvs_studio_log("framework: ${FRAMEWORK}")
-            elseif (NOT "${PROP}" STREQUAL "")
-                list(APPEND "${CXX}" "${PREFIX}${PROP}")
-                list(APPEND "${C}" "${PREFIX}${PROP}")
-            endif()
-        endforeach ()
-    endif ()
-endmacro ()
-
-macro (pvs_studio_append_standard_flag FLAGS STANDARD)
-    if ("${STANDARD}" MATCHES "^(99|11|14|17)$")
-        if ("${PVS_STUDIO_PREPROCESSOR}" MATCHES "gcc|clang")
-            list(APPEND "${FLAGS}" "-std=c++${STANDARD}")
-        endif ()
-    endif ()
-endmacro ()
-
-function (pvs_studio_set_directory_flags DIRECTORY CXX C)
-    set(CXX_FLAGS "${${CXX}}")
-    set(C_FLAGS "${${C}}")
-
-    get_directory_property(PROPERTY DIRECTORY "${DIRECTORY}" INCLUDE_DIRECTORIES)
-    pvs_studio_append_flags_from_property(CXX_FLAGS C_FLAGS "${DIRECTORY}" "-I")
-
-    get_directory_property(PROPERTY DIRECTORY "${DIRECTORY}" COMPILE_DEFINITIONS)
-    pvs_studio_append_flags_from_property(CXX_FLAGS C_FLAGS "" "-D")
-
-    set("${CXX}" "${CXX_FLAGS}" PARENT_SCOPE)
-    set("${C}" "${C_FLAGS}" PARENT_SCOPE)
-endfunction ()
-
-function (pvs_studio_set_target_flags TARGET CXX C)
-    set(CXX_FLAGS "${${CXX}}")
-    set(C_FLAGS "${${C}}")
-
-    set(prop_incdirs "$<TARGET_PROPERTY:${TARGET},INCLUDE_DIRECTORIES>")
-    list(APPEND CXX_FLAGS "$<$<BOOL:${prop_incdirs}>:-I$<JOIN:${prop_incdirs},$<SEMICOLON>-I>>")
-    list(APPEND C_FLAGS "$<$<BOOL:${prop_incdirs}>:-I$<JOIN:${prop_incdirs},$<SEMICOLON>-I>>")
-
-    set(prop_compdefs "$<TARGET_PROPERTY:${TARGET},COMPILE_DEFINITIONS>")
-    list(APPEND CXX_FLAGS "$<$<BOOL:${prop_compdefs}>:-D$<JOIN:${prop_compdefs},$<SEMICOLON>-D>>")
-    list(APPEND C_FLAGS "$<$<BOOL:${prop_compdefs}>:-D$<JOIN:${prop_compdefs},$<SEMICOLON>-D>>")
-
-    set("${CXX}" "${CXX_FLAGS}" PARENT_SCOPE)
-    set("${C}" "${C_FLAGS}" PARENT_SCOPE)
-endfunction ()
-
-function (pvs_studio_set_source_file_flags SOURCE)
-    set(LANGUAGE "")
-
-    string(TOLOWER "${SOURCE}" SOURCE_LOWER)
-    if ("${LANGUAGE}" STREQUAL "" AND "${SOURCE_LOWER}" MATCHES "^.*\\.(c|cpp|cc|cx|cxx|cp|c\\+\\+)$")
-        if ("${SOURCE}" MATCHES "^.*\\.c$")
-            set(LANGUAGE C)
-        else ()
-            set(LANGUAGE CXX)
-        endif ()
-    endif ()
-
-    if ("${LANGUAGE}" STREQUAL "C")
-        set(CL_PARAMS ${PVS_STUDIO_C_FLAGS} ${PVS_STUDIO_TARGET_C_FLAGS} -DPVS_STUDIO)
-    elseif ("${LANGUAGE}" STREQUAL "CXX")
-        set(CL_PARAMS ${PVS_STUDIO_CXX_FLAGS} ${PVS_STUDIO_TARGET_CXX_FLAGS} -DPVS_STUDIO)
-    endif ()
-
-    set(PVS_STUDIO_LANGUAGE "${LANGUAGE}" PARENT_SCOPE)
-    set(PVS_STUDIO_CL_PARAMS "${CL_PARAMS}" PARENT_SCOPE)
-endfunction ()
-
-function (pvs_studio_analyze_file SOURCE SOURCE_DIR BINARY_DIR)
-    set(PLOGS ${PVS_STUDIO_PLOGS})
-    pvs_studio_set_source_file_flags("${SOURCE}")
-
-    get_filename_component(SOURCE "${SOURCE}" REALPATH)
-
-    get_source_file_property(PROPERTY "${SOURCE}" HEADER_FILE_ONLY)
-    if (PROPERTY)
-        return()
-    endif ()
-
-    pvs_studio_relative_path(SOURCE_RELATIVE "${SOURCE_DIR}" "${SOURCE}")
-    pvs_studio_join_path(SOURCE "${SOURCE_DIR}" "${SOURCE}")
-
-    set(LOG "${BINARY_DIR}/PVS-Studio/${SOURCE_RELATIVE}.plog")
-    get_filename_component(LOG "${LOG}" REALPATH)
-    get_filename_component(PARENT_DIR "${LOG}" DIRECTORY)
-
-    if (EXISTS "${SOURCE}" AND NOT TARGET "${LOG}" AND NOT "${PVS_STUDIO_LANGUAGE}" STREQUAL "")
-        # A workaround to support implicit dependencies for ninja generators.
-        set(depPvsArg)
-        set(depCommandArg)
-        if (CMAKE_VERSION VERSION_GREATER 3.6 AND "${CMAKE_GENERATOR}" STREQUAL "Ninja")
-            pvs_studio_relative_path(relLog "${CMAKE_BINARY_DIR}" "${LOG}")
-            set(depPvsArg --dep-file "${LOG}.d" --dep-file-target "${relLog}")
-            set(depCommandArg DEPFILE "${LOG}.d")
-        endif ()
-
-        # https://public.kitware.com/Bug/print_bug_page.php?bug_id=14353
-        # https://public.kitware.com/Bug/file/5436/expand_command.cmake
-        #
-        # It is a workaround to expand generator expressions.
-        set(cmdline "${PVS_STUDIO_BIN}" analyze
-                    --output-file "${LOG}"
-                    --source-file "${SOURCE}"
-                    ${depPvsArg}
-                    ${PVS_STUDIO_ARGS}
-                    --cl-params "${PVS_STUDIO_CL_PARAMS}" "${SOURCE}")
-
-        string(REPLACE ";" "$<SEMICOLON>" cmdline "${cmdline}")
-        set(pvscmd "${CMAKE_COMMAND}"
-                   -D PVS_STUDIO_AS_SCRIPT=TRUE
-                   -D "PVS_STUDIO_COMMAND=${cmdline}"
-                   -P "${PVS_STUDIO_SCRIPT}"
-        )
-
-        add_custom_command(OUTPUT "${LOG}"
-                           COMMAND "${CMAKE_COMMAND}" -E make_directory "${PARENT_DIR}"
-                           COMMAND "${CMAKE_COMMAND}" -E remove_directory "${LOG}"
-                           COMMAND ${pvscmd}
-                           WORKING_DIRECTORY "${BINARY_DIR}"
-                           DEPENDS "${SOURCE}" "${PVS_STUDIO_CONFIG}"
-                           IMPLICIT_DEPENDS "${PVS_STUDIO_LANGUAGE}" "${SOURCE}"
-                           ${depCommandArg}
-                           VERBATIM
-                           COMMENT "Analyzing ${PVS_STUDIO_LANGUAGE} file ${SOURCE_RELATIVE}")
-        list(APPEND PLOGS "${LOG}")
-    endif ()
-    set(PVS_STUDIO_PLOGS "${PLOGS}" PARENT_SCOPE)
-endfunction ()
-
-function (pvs_studio_analyze_target TARGET DIR)
-    set(PVS_STUDIO_PLOGS "${PVS_STUDIO_PLOGS}")
-    set(PVS_STUDIO_TARGET_CXX_FLAGS "")
-    set(PVS_STUDIO_TARGET_C_FLAGS "")
-
-    get_target_property(PROPERTY "${TARGET}" SOURCES)
-    pvs_studio_relative_path(BINARY_DIR "${CMAKE_SOURCE_DIR}" "${DIR}")
-    if ("${BINARY_DIR}" MATCHES "^/.*$")
-        pvs_studio_join_path(BINARY_DIR "${CMAKE_BINARY_DIR}" "PVS-Studio/__${BINARY_DIR}")
-    else ()
-        pvs_studio_join_path(BINARY_DIR "${CMAKE_BINARY_DIR}" "${BINARY_DIR}")
-    endif ()
-
-    file(MAKE_DIRECTORY "${BINARY_DIR}")
-
-    pvs_studio_set_directory_flags("${DIR}" PVS_STUDIO_TARGET_CXX_FLAGS PVS_STUDIO_TARGET_C_FLAGS)
-    pvs_studio_set_target_flags("${TARGET}" PVS_STUDIO_TARGET_CXX_FLAGS PVS_STUDIO_TARGET_C_FLAGS)
-
-    if (NOT "${PROPERTY}" STREQUAL "NOTFOUND" AND NOT "${PROPERTY}" STREQUAL "PROPERTY-NOTFOUND")
-        foreach (SOURCE ${PROPERTY})
-            pvs_studio_join_path(SOURCE "${DIR}" "${SOURCE}")
-            pvs_studio_analyze_file("${SOURCE}" "${DIR}" "${BINARY_DIR}")
-        endforeach ()
-    endif ()
-
-    set(PVS_STUDIO_PLOGS "${PVS_STUDIO_PLOGS}" PARENT_SCOPE)
-endfunction ()
-
-set(PVS_STUDIO_RECURSIVE_TARGETS)
-set(PVS_STUDIO_RECURSIVE_TARGETS_NEW)
-
-macro(pvs_studio_get_recursive_targets TARGET)
-    get_target_property(libs "${TARGET}" LINK_LIBRARIES)
-    foreach (lib IN LISTS libs)
-        list(FIND PVS_STUDIO_RECURSIVE_TARGETS "${lib}" index)
-        if (TARGET "${lib}" AND "${index}" STREQUAL -1)
-            get_target_property(target_type "${lib}" TYPE)
-            if (NOT "${target_type}" STREQUAL "INTERFACE_LIBRARY")
-                list(APPEND PVS_STUDIO_RECURSIVE_TARGETS "${lib}")
-                list(APPEND PVS_STUDIO_RECURSIVE_TARGETS_NEW "${lib}")
-                pvs_studio_get_recursive_targets("${lib}")
-            endif ()
-        endif ()
-    endforeach ()
-endmacro()
-
-option(PVS_STUDIO_DISABLE OFF "Disable PVS-Studio targets")
-option(PVS_STUDIO_DEBUG OFF "Add debug info")
-
-# pvs_studio_add_target
-# Target options:
-# ALL                           add PVS-Studio target to default build (default: off)
-# TARGET target                 name of analysis target (default: pvs)
-# ANALYZE targets...            targets to analyze
-# RECURSIVE                     analyze target's dependencies (requires CMake 3.5+)
-# COMPILE_COMMANDS              use compile_commands.json instead of targets (specified by the 'ANALYZE' option) to determine files for analysis
-#                               (set CMAKE_EXPORT_COMPILE_COMMANDS, available only for Makefile and Ninja generators)
-#
-# Output options:
-# OUTPUT                        prints report to stdout
-# LOG path                      path to report (default: ${CMAKE_CURRENT_BINARY_DIR}/PVS-Studio.log)
-# FORMAT format                 format of report
-# MODE mode                     analyzers/levels filter (default: GA:1,2)
-# HIDE_HELP                     do not print help message
-#
-# Analyzer options:
-# PLATFORM name                 linux32/linux64 (default: linux64)
-# PREPROCESSOR name             preprocessor type: gcc/clang (default: auto detected)
-# LICENSE path                  path to PVS-Studio.lic (default: ~/.config/PVS-Studio/PVS-Studio.lic)
-# CONFIG path                   path to PVS-Studio.cfg
-# CFG_TEXT text                 embedded PVS-Studio.cfg
-# KEEP_COMBINED_PLOG            do not delete combined plog file *.pvs.raw for further processing with plog-converter
-#
-# Misc options:
-# DEPENDS targets..             additional target dependencies
-# SOURCES path...               list of source files to analyze
-# BIN path                      path to pvs-studio-analyzer (Unix) or CompilerCommandsAnalyzer.exe (Windows)
-# CONVERTER path                path to plog-converter (Unix) or HtmlGenerator.exe (Windows)
-# C_FLAGS flags...              additional C_FLAGS
-# CXX_FLAGS flags...            additional CXX_FLAGS
-# ARGS args...                  additional pvs-studio-analyzer/CompilerCommandsAnalyzer.exe flags
-function (pvs_studio_add_target)
-    macro (default VAR VALUE)
-        if ("${${VAR}}" STREQUAL "")
-            set("${VAR}" "${VALUE}")
-        endif ()
-    endmacro ()
-
-    set(PVS_STUDIO_SUPPORTED_PREPROCESSORS "gcc|clang|visualcpp")
-    if ("${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang")
-        set(DEFAULT_PREPROCESSOR "clang")
-    elseif (MSVC)
-        set(DEFAULT_PREPROCESSOR "visualcpp")
-    else ()
-        set(DEFAULT_PREPROCESSOR "gcc")
-    endif ()
-
-    set(OPTIONAL OUTPUT ALL RECURSIVE HIDE_HELP KEEP_COMBINED_PLOG COMPILE_COMMANDS)
-    set(SINGLE LICENSE CONFIG TARGET LOG FORMAT BIN CONVERTER PLATFORM PREPROCESSOR CFG_TEXT)
-    set(MULTI SOURCES C_FLAGS CXX_FLAGS ARGS DEPENDS ANALYZE MODE)
-    cmake_parse_arguments(PVS_STUDIO "${OPTIONAL}" "${SINGLE}" "${MULTI}" ${ARGN})
-
-    if ("${PVS_STUDIO_CONFIG}" STREQUAL "" OR NOT "${PVS_STUDIO_CFG_TEXT}" STREQUAL "")
-        set(PVS_STUDIO_EMPTY_CONFIG ON)
-    else ()
-        set(PVS_STUDIO_EMPTY_CONFIG OFF)
-    endif ()
-
-    default(PVS_STUDIO_CFG_TEXT "analysis-mode=31")
-    default(PVS_STUDIO_CONFIG "${CMAKE_BINARY_DIR}/PVS-Studio.cfg")
-    default(PVS_STUDIO_C_FLAGS "")
-    default(PVS_STUDIO_CXX_FLAGS "")
-    default(PVS_STUDIO_TARGET "pvs")
-    default(PVS_STUDIO_LOG "PVS-Studio.log")
-
-    set(PATHS)
-    if (WIN32)
-        set(ROOT "PROGRAMFILES(X86)")
-        set(ROOT "$ENV{${ROOT}}/PVS-Studio")
-        string(REPLACE \\ / ROOT "${ROOT}")
-
-        if (EXISTS "${ROOT}")
-            set(PATHS "${ROOT}")
-        endif ()
-
-        default(PVS_STUDIO_BIN "CompilerCommandsAnalyzer.exe")
-        default(PVS_STUDIO_CONVERTER "HtmlGenerator.exe")
-    else ()
-        default(PVS_STUDIO_BIN "pvs-studio-analyzer")
-        default(PVS_STUDIO_CONVERTER "plog-converter")
-    endif ()
-
-    find_program(PVS_STUDIO_BIN_PATH "${PVS_STUDIO_BIN}" ${PATHS})
-    set(PVS_STUDIO_BIN "${PVS_STUDIO_BIN_PATH}")
-
-    if (NOT EXISTS "${PVS_STUDIO_BIN}")
-        message(FATAL_ERROR "pvs-studio-analyzer is not found")
-    endif ()
-
-    find_program(PVS_STUDIO_CONVERTER_PATH "${PVS_STUDIO_CONVERTER}" ${PATHS})
-    set(PVS_STUDIO_CONVERTER "${PVS_STUDIO_CONVERTER_PATH}")
-
-    if (NOT EXISTS "${PVS_STUDIO_CONVERTER}")
-        message(FATAL_ERROR "plog-converter is not found")
-    endif ()
-
-    default(PVS_STUDIO_MODE "GA:1,2")
-    default(PVS_STUDIO_PREPROCESSOR "${DEFAULT_PREPROCESSOR}")
-    if (WIN32)
-        default(PVS_STUDIO_PLATFORM "x64")
-    else ()
-        default(PVS_STUDIO_PLATFORM "linux64")
-    endif ()
-
-    string(REPLACE ";" "+" PVS_STUDIO_MODE "${PVS_STUDIO_MODE}")
-
-    if (PVS_STUDIO_EMPTY_CONFIG)
-        set(PVS_STUDIO_CONFIG_COMMAND "${CMAKE_COMMAND}" -E echo "${PVS_STUDIO_CFG_TEXT}" > "${PVS_STUDIO_CONFIG}")
-    else ()
-        set(PVS_STUDIO_CONFIG_COMMAND "${CMAKE_COMMAND}" -E touch "${PVS_STUDIO_CONFIG}")
-    endif ()
-
-    add_custom_command(OUTPUT "${PVS_STUDIO_CONFIG}"
-                       COMMAND ${PVS_STUDIO_CONFIG_COMMAND}
-                       WORKING_DIRECTORY "${BINARY_DIR}"
-                       COMMENT "Generating PVS-Studio.cfg")
-
-    if (NOT "${PVS_STUDIO_PREPROCESSOR}" MATCHES "^${PVS_STUDIO_SUPPORTED_PREPROCESSORS}$")
-        message(FATAL_ERROR "Preprocessor ${PVS_STUDIO_PREPROCESSOR} isn't supported. Available options: ${PVS_STUDIO_SUPPORTED_PREPROCESSORS}.")
-    endif ()
-
-    pvs_studio_append_standard_flag(PVS_STUDIO_CXX_FLAGS "${CMAKE_CXX_STANDARD}")
-    pvs_studio_set_directory_flags("${CMAKE_CURRENT_SOURCE_DIR}" PVS_STUDIO_CXX_FLAGS PVS_STUDIO_C_FLAGS)
-
-    if (NOT "${PVS_STUDIO_LICENSE}" STREQUAL "")
-        pvs_studio_join_path(PVS_STUDIO_LICENSE "${CMAKE_CURRENT_SOURCE_DIR}" "${PVS_STUDIO_LICENSE}")
-        list(APPEND PVS_STUDIO_ARGS --lic-file "${PVS_STUDIO_LICENSE}")
-    endif ()
-
-    list(APPEND PVS_STUDIO_ARGS --cfg "${PVS_STUDIO_CONFIG}"
-                                --platform "${PVS_STUDIO_PLATFORM}"
-                                --preprocessor "${PVS_STUDIO_PREPROCESSOR}")
-
-    if (NOT "${CMAKE_CXX_COMPILER}" STREQUAL "")
-        list(APPEND PVS_STUDIO_ARGS --cxx "${CMAKE_CXX_COMPILER}")
-    endif ()
-
-    if (NOT "${CMAKE_C_COMPILER}" STREQUAL "")
-        list(APPEND PVS_STUDIO_ARGS --cc "${CMAKE_C_COMPILER}")
-    endif ()
-
-    set(PVS_STUDIO_PLOGS "")
-
-    set(PVS_STUDIO_RECURSIVE_TARGETS_NEW)
-    if (${PVS_STUDIO_RECURSIVE})
-        foreach (TARGET IN LISTS PVS_STUDIO_ANALYZE)
-            list(APPEND PVS_STUDIO_RECURSIVE_TARGETS_NEW "${TARGET}")
-            pvs_studio_get_recursive_targets("${TARGET}")
-        endforeach ()
-    endif ()
-
-    set(inc_path)
-
-    foreach (TARGET ${PVS_STUDIO_ANALYZE})
-        set(DIR "${CMAKE_CURRENT_SOURCE_DIR}")
-        string(FIND "${TARGET}" ":" DELIM)
-        if ("${DELIM}" GREATER "-1")
-            math(EXPR DELIMI "${DELIM}+1")
-            string(SUBSTRING "${TARGET}" "${DELIMI}" "-1" DIR)
-            string(SUBSTRING "${TARGET}" "0" "${DELIM}" TARGET)
-            pvs_studio_join_path(DIR "${CMAKE_CURRENT_SOURCE_DIR}" "${DIR}")
-        else ()
-            get_target_property(TARGET_SOURCE_DIR "${TARGET}" SOURCE_DIR)
-            if (EXISTS "${TARGET_SOURCE_DIR}")
-                set(DIR "${TARGET_SOURCE_DIR}")
-            endif ()
-        endif ()
-        pvs_studio_analyze_target("${TARGET}" "${DIR}")
-        list(APPEND PVS_STUDIO_DEPENDS "${TARGET}")
-
-        if ("${inc_path}" STREQUAL "")
-            set(inc_path "$<TARGET_PROPERTY:${TARGET},INCLUDE_DIRECTORIES>")
-        else ()
-            set(inc_path "${inc_path}$<SEMICOLON>$<TARGET_PROPERTY:${TARGET},INCLUDE_DIRECTORIES>")
-        endif ()
-    endforeach ()
-
-    foreach (TARGET ${PVS_STUDIO_RECURSIVE_TARGETS_NEW})
-        set(DIR "${CMAKE_CURRENT_SOURCE_DIR}")
-        get_target_property(TARGET_SOURCE_DIR "${TARGET}" SOURCE_DIR)
-        if (EXISTS "${TARGET_SOURCE_DIR}")
-            set(DIR "${TARGET_SOURCE_DIR}")
-        endif ()
-        pvs_studio_analyze_target("${TARGET}" "${DIR}")
-        list(APPEND PVS_STUDIO_DEPENDS "${TARGET}")
-    endforeach ()
-
-    set(PVS_STUDIO_TARGET_CXX_FLAGS "")
-    set(PVS_STUDIO_TARGET_C_FLAGS "")
-    foreach (SOURCE ${PVS_STUDIO_SOURCES})
-        pvs_studio_analyze_file("${SOURCE}" "${CMAKE_CURRENT_SOURCE_DIR}" "${CMAKE_CURRENT_BINARY_DIR}")
-    endforeach ()
-
-    if (PVS_STUDIO_COMPILE_COMMANDS)
-        set(COMPILE_COMMANDS_LOG "${PVS_STUDIO_LOG}.pvs.analyzer.raw")
-        if (NOT CMAKE_EXPORT_COMPILE_COMMANDS)
-            message(FATAL_ERROR "You should set CMAKE_EXPORT_COMPILE_COMMANDS to TRUE")
-        endif ()
-        add_custom_command(
-            OUTPUT "${COMPILE_COMMANDS_LOG}"
-            COMMAND "${PVS_STUDIO_BIN}" analyze -i
-                    --output-file "${COMPILE_COMMANDS_LOG}.always"
-                    ${PVS_STUDIO_ARGS}
-            COMMENT "Analyzing with PVS-Studio"
-            WORKING_DIRECTORY "${CMAKE_BINARY_DIR}"
-            DEPENDS "${PVS_STUDIO_CONFIG}"
-        )
-        list(APPEND PVS_STUDIO_PLOGS_LOGS "${COMPILE_COMMANDS_LOG}.always")
-        list(APPEND PVS_STUDIO_PLOGS_DEPENDENCIES "${COMPILE_COMMANDS_LOG}")
-    endif ()
-
-    pvs_studio_relative_path(LOG_RELATIVE "${CMAKE_BINARY_DIR}" "${PVS_STUDIO_LOG}")
-    if (PVS_STUDIO_PLOGS OR PVS_STUDIO_COMPILE_COMMANDS)
-        if (WIN32)
-            string(REPLACE / \\ PVS_STUDIO_PLOGS "${PVS_STUDIO_PLOGS}")
-        endif ()
-        if (WIN32)
-            set(COMMANDS COMMAND type ${PVS_STUDIO_PLOGS} ${PVS_STUDIO_PLOGS_LOGS} > "${PVS_STUDIO_LOG}" 2>nul)
-        else ()
-            set(COMMANDS COMMAND cat ${PVS_STUDIO_PLOGS} ${PVS_STUDIO_PLOGS_LOGS} > "${PVS_STUDIO_LOG}")
-        endif ()
-        set(COMMENT "Generating ${LOG_RELATIVE}")
-        if (NOT "${PVS_STUDIO_FORMAT}" STREQUAL "" OR PVS_STUDIO_OUTPUT)
-            if ("${PVS_STUDIO_FORMAT}" STREQUAL "")
-                set(PVS_STUDIO_FORMAT "errorfile")
-            endif ()
-            list(APPEND COMMANDS
-                COMMAND "${CMAKE_COMMAND}" -E remove -f "${PVS_STUDIO_LOG}.pvs.raw"
-                COMMAND "${CMAKE_COMMAND}" -E rename "${PVS_STUDIO_LOG}" "${PVS_STUDIO_LOG}.pvs.raw"
-                COMMAND "${PVS_STUDIO_CONVERTER}" -t "${PVS_STUDIO_FORMAT}" "${PVS_STUDIO_LOG}.pvs.raw" -o "${PVS_STUDIO_LOG}" -a "${PVS_STUDIO_MODE}"
-                )
-            if(NOT PVS_STUDIO_KEEP_COMBINED_PLOG)
-                list(APPEND COMMANDS COMMAND "${CMAKE_COMMAND}" -E remove -f "${PVS_STUDIO_LOG}.pvs.raw")
-            endif()
-        endif ()
-    else ()
-        set(COMMANDS COMMAND "${CMAKE_COMMAND}" -E touch "${PVS_STUDIO_LOG}")
-        set(COMMENT "Generating ${LOG_RELATIVE}: no sources found")
-    endif ()
-
-    if (WIN32)
-        string(REPLACE / \\ PVS_STUDIO_LOG "${PVS_STUDIO_LOG}")
-    endif ()
-
-    add_custom_command(OUTPUT "${PVS_STUDIO_LOG}"
-                       ${COMMANDS}
-                       COMMENT "${COMMENT}"
-                       DEPENDS ${PVS_STUDIO_PLOGS} ${PVS_STUDIO_PLOGS_DEPENDENCIES}
-                       WORKING_DIRECTORY "${CMAKE_BINARY_DIR}")
-
-    if (PVS_STUDIO_ALL)
-        set(ALL "ALL")
-    else ()
-        set(ALL "")
-    endif ()
-
-    if (PVS_STUDIO_OUTPUT)
-        if (PVS_STUDIO_HIDE_HELP AND NOT WIN32)
-            set(COMMANDS COMMAND grep -v " error: Help:" ${PVS_STUDIO_LOG} 1>&2 || exit 0)
-        elseif (WIN32)
-            set(COMMANDS COMMAND type "${PVS_STUDIO_LOG}" 1>&2)
-        else ()
-            set(COMMANDS COMMAND cat "${PVS_STUDIO_LOG}" 1>&2)
-        endif()
-    else ()
-        set(COMMANDS "")
-    endif ()
-
-    add_custom_target("${PVS_STUDIO_TARGET}" ${ALL} ${COMMANDS} WORKING_DIRECTORY "${CMAKE_BINARY_DIR}" DEPENDS ${PVS_STUDIO_DEPENDS} "${PVS_STUDIO_LOG}")
-
-    # A workaround to add implicit dependencies of source files from include directories
-    set_target_properties("${PVS_STUDIO_TARGET}" PROPERTIES INCLUDE_DIRECTORIES "${inc_path}")
-endfunction ()
+# 2006-2008 (c) Viva64.com Team
+# 2008-2018 (c) OOO "Program Verification Systems"
+#
+# Version 12
+
+cmake_minimum_required(VERSION 2.8.12)
+cmake_policy(SET CMP0054 NEW)
+
+if (PVS_STUDIO_AS_SCRIPT)
+    # This code runs at build time.
+    # It executes pvs-studio-analyzer and propagates its return value.
+
+    set(in_cl_params FALSE)
+    set(additional_args)
+
+    foreach (arg ${PVS_STUDIO_COMMAND})
+        if (NOT in_cl_params)
+            if ("${arg}" STREQUAL "--cl-params")
+                set(in_cl_params TRUE)
+            endif ()
+        else ()
+            # A workaround for macOS frameworks (e.g. QtWidgets.framework)
+            # You can test this workaround on this project: https://github.com/easyaspi314/MidiEditor/tree/gba
+            if (APPLE AND "${arg}" MATCHES "^-I(.*)\\.framework$")
+                STRING(REGEX REPLACE "^-I(.*)\\.framework$" "\\1.framework" framework "${arg}")
+                if (IS_ABSOLUTE "${framework}")
+                    get_filename_component(framework "${framework}" DIRECTORY)
+                    list(APPEND additional_args "-iframework")
+                    list(APPEND additional_args "${framework}")
+                endif ()
+            endif ()
+        endif ()
+    endforeach ()
+
+    execute_process(COMMAND ${PVS_STUDIO_COMMAND} ${additional_args}
+                    ERROR_VARIABLE error
+                    RESULT_VARIABLE result)
+
+    set(stderr_type "")
+
+    if (result)
+        set(stderr_type FATAL_ERROR)
+    endif ()
+
+    if (result OR error)
+        message(${stderr_type} "${error}")
+    endif ()
+
+    return()
+endif ()
+
+if(__PVS_STUDIO_INCLUDED)
+    return()
+endif()
+set(__PVS_STUDIO_INCLUDED TRUE)
+
+set(PVS_STUDIO_SCRIPT "${CMAKE_CURRENT_LIST_FILE}")
+
+function (pvs_studio_log TEXT)
+    if (PVS_STUDIO_DEBUG)
+        message("PVS-Studio: ${TEXT}")
+    endif ()
+endfunction ()
+
+function (pvs_studio_relative_path VAR ROOT FILEPATH)
+    set("${VAR}" "${FILEPATH}" PARENT_SCOPE)
+    if ("${FILEPATH}" MATCHES "^/.*$" OR "${FILEPATH}" MATCHES "^.:/.*$")
+        file(RELATIVE_PATH RPATH "${ROOT}" "${FILEPATH}")
+        if (NOT "${RPATH}" MATCHES "^\\.\\..*$")
+            set("${VAR}" "${RPATH}" PARENT_SCOPE)
+        endif ()
+    endif ()
+endfunction ()
+
+function (pvs_studio_join_path VAR DIR1 DIR2)
+    if ("${DIR2}" MATCHES "^(/|~|.:/).*$" OR "${DIR1}" STREQUAL "")
+        set("${VAR}" "${DIR2}" PARENT_SCOPE)
+    else ()
+        set("${VAR}" "${DIR1}/${DIR2}" PARENT_SCOPE)
+    endif ()
+endfunction ()
+
+macro (pvs_studio_append_flags_from_property CXX C DIR PREFIX)
+    if (NOT "${PROPERTY}" STREQUAL "NOTFOUND" AND NOT "${PROPERTY}" STREQUAL "PROPERTY-NOTFOUND")
+        foreach (PROP ${PROPERTY})
+            pvs_studio_join_path(PROP "${DIR}" "${PROP}")
+
+            if (APPLE AND "${PREFIX}" STREQUAL "-I" AND IS_ABSOLUTE "${PROP}" AND "${PROP}" MATCHES "\\.framework$")
+                get_filename_component(FRAMEWORK "${PROP}" DIRECTORY)
+                list(APPEND "${CXX}" "-iframework")
+                list(APPEND "${CXX}" "${FRAMEWORK}")
+                list(APPEND "${C}" "-iframework")
+                list(APPEND "${C}" "${FRAMEWORK}")
+                pvs_studio_log("framework: ${FRAMEWORK}")
+            elseif (NOT "${PROP}" STREQUAL "")
+                list(APPEND "${CXX}" "${PREFIX}${PROP}")
+                list(APPEND "${C}" "${PREFIX}${PROP}")
+            endif()
+        endforeach ()
+    endif ()
+endmacro ()
+
+macro (pvs_studio_append_standard_flag FLAGS STANDARD)
+    if ("${STANDARD}" MATCHES "^(99|11|14|17)$")
+        if ("${PVS_STUDIO_PREPROCESSOR}" MATCHES "gcc|clang")
+            list(APPEND "${FLAGS}" "-std=c++${STANDARD}")
+        endif ()
+    endif ()
+endmacro ()
+
+function (pvs_studio_set_directory_flags DIRECTORY CXX C)
+    set(CXX_FLAGS "${${CXX}}")
+    set(C_FLAGS "${${C}}")
+
+    get_directory_property(PROPERTY DIRECTORY "${DIRECTORY}" INCLUDE_DIRECTORIES)
+    pvs_studio_append_flags_from_property(CXX_FLAGS C_FLAGS "${DIRECTORY}" "-I")
+
+    get_directory_property(PROPERTY DIRECTORY "${DIRECTORY}" COMPILE_DEFINITIONS)
+    pvs_studio_append_flags_from_property(CXX_FLAGS C_FLAGS "" "-D")
+
+    set("${CXX}" "${CXX_FLAGS}" PARENT_SCOPE)
+    set("${C}" "${C_FLAGS}" PARENT_SCOPE)
+endfunction ()
+
+function (pvs_studio_set_target_flags TARGET CXX C)
+    set(CXX_FLAGS "${${CXX}}")
+    set(C_FLAGS "${${C}}")
+
+    set(prop_incdirs "$<TARGET_PROPERTY:${TARGET},INCLUDE_DIRECTORIES>")
+    list(APPEND CXX_FLAGS "$<$<BOOL:${prop_incdirs}>:-I$<JOIN:${prop_incdirs},$<SEMICOLON>-I>>")
+    list(APPEND C_FLAGS "$<$<BOOL:${prop_incdirs}>:-I$<JOIN:${prop_incdirs},$<SEMICOLON>-I>>")
+
+    set(prop_compdefs "$<TARGET_PROPERTY:${TARGET},COMPILE_DEFINITIONS>")
+    list(APPEND CXX_FLAGS "$<$<BOOL:${prop_compdefs}>:-D$<JOIN:${prop_compdefs},$<SEMICOLON>-D>>")
+    list(APPEND C_FLAGS "$<$<BOOL:${prop_compdefs}>:-D$<JOIN:${prop_compdefs},$<SEMICOLON>-D>>")
+
+    set("${CXX}" "${CXX_FLAGS}" PARENT_SCOPE)
+    set("${C}" "${C_FLAGS}" PARENT_SCOPE)
+endfunction ()
+
+function (pvs_studio_set_source_file_flags SOURCE)
+    set(LANGUAGE "")
+
+    string(TOLOWER "${SOURCE}" SOURCE_LOWER)
+    if ("${LANGUAGE}" STREQUAL "" AND "${SOURCE_LOWER}" MATCHES "^.*\\.(c|cpp|cc|cx|cxx|cp|c\\+\\+)$")
+        if ("${SOURCE}" MATCHES "^.*\\.c$")
+            set(LANGUAGE C)
+        else ()
+            set(LANGUAGE CXX)
+        endif ()
+    endif ()
+
+    if ("${LANGUAGE}" STREQUAL "C")
+        set(CL_PARAMS ${PVS_STUDIO_C_FLAGS} ${PVS_STUDIO_TARGET_C_FLAGS} -DPVS_STUDIO)
+    elseif ("${LANGUAGE}" STREQUAL "CXX")
+        set(CL_PARAMS ${PVS_STUDIO_CXX_FLAGS} ${PVS_STUDIO_TARGET_CXX_FLAGS} -DPVS_STUDIO)
+    endif ()
+
+    set(PVS_STUDIO_LANGUAGE "${LANGUAGE}" PARENT_SCOPE)
+    set(PVS_STUDIO_CL_PARAMS "${CL_PARAMS}" PARENT_SCOPE)
+endfunction ()
+
+function (pvs_studio_analyze_file SOURCE SOURCE_DIR BINARY_DIR)
+    set(PLOGS ${PVS_STUDIO_PLOGS})
+    pvs_studio_set_source_file_flags("${SOURCE}")
+
+    get_filename_component(SOURCE "${SOURCE}" REALPATH)
+
+    get_source_file_property(PROPERTY "${SOURCE}" HEADER_FILE_ONLY)
+    if (PROPERTY)
+        return()
+    endif ()
+
+    pvs_studio_relative_path(SOURCE_RELATIVE "${SOURCE_DIR}" "${SOURCE}")
+    pvs_studio_join_path(SOURCE "${SOURCE_DIR}" "${SOURCE}")
+
+    set(LOG "${BINARY_DIR}/PVS-Studio/${SOURCE_RELATIVE}.plog")
+    get_filename_component(LOG "${LOG}" REALPATH)
+    get_filename_component(PARENT_DIR "${LOG}" DIRECTORY)
+
+    if (EXISTS "${SOURCE}" AND NOT TARGET "${LOG}" AND NOT "${PVS_STUDIO_LANGUAGE}" STREQUAL "")
+        # A workaround to support implicit dependencies for ninja generators.
+        set(depPvsArg)
+        set(depCommandArg)
+        if (CMAKE_VERSION VERSION_GREATER 3.6 AND "${CMAKE_GENERATOR}" STREQUAL "Ninja")
+            pvs_studio_relative_path(relLog "${CMAKE_BINARY_DIR}" "${LOG}")
+            set(depPvsArg --dep-file "${LOG}.d" --dep-file-target "${relLog}")
+            set(depCommandArg DEPFILE "${LOG}.d")
+        endif ()
+
+        # https://public.kitware.com/Bug/print_bug_page.php?bug_id=14353
+        # https://public.kitware.com/Bug/file/5436/expand_command.cmake
+        #
+        # It is a workaround to expand generator expressions.
+        set(cmdline "${PVS_STUDIO_BIN}" analyze
+                    --output-file "${LOG}"
+                    --source-file "${SOURCE}"
+                    ${depPvsArg}
+                    ${PVS_STUDIO_ARGS}
+                    --cl-params "${PVS_STUDIO_CL_PARAMS}" "${SOURCE}")
+
+        string(REPLACE ";" "$<SEMICOLON>" cmdline "${cmdline}")
+        set(pvscmd "${CMAKE_COMMAND}"
+                   -D PVS_STUDIO_AS_SCRIPT=TRUE
+                   -D "PVS_STUDIO_COMMAND=${cmdline}"
+                   -P "${PVS_STUDIO_SCRIPT}"
+        )
+
+        add_custom_command(OUTPUT "${LOG}"
+                           COMMAND "${CMAKE_COMMAND}" -E make_directory "${PARENT_DIR}"
+                           COMMAND "${CMAKE_COMMAND}" -E remove_directory "${LOG}"
+                           COMMAND ${pvscmd}
+                           WORKING_DIRECTORY "${BINARY_DIR}"
+                           DEPENDS "${SOURCE}" "${PVS_STUDIO_CONFIG}"
+                           IMPLICIT_DEPENDS "${PVS_STUDIO_LANGUAGE}" "${SOURCE}"
+                           ${depCommandArg}
+                           VERBATIM
+                           COMMENT "Analyzing ${PVS_STUDIO_LANGUAGE} file ${SOURCE_RELATIVE}")
+        list(APPEND PLOGS "${LOG}")
+    endif ()
+    set(PVS_STUDIO_PLOGS "${PLOGS}" PARENT_SCOPE)
+endfunction ()
+
+function (pvs_studio_analyze_target TARGET DIR)
+    set(PVS_STUDIO_PLOGS "${PVS_STUDIO_PLOGS}")
+    set(PVS_STUDIO_TARGET_CXX_FLAGS "")
+    set(PVS_STUDIO_TARGET_C_FLAGS "")
+
+    get_target_property(PROPERTY "${TARGET}" SOURCES)
+    pvs_studio_relative_path(BINARY_DIR "${CMAKE_SOURCE_DIR}" "${DIR}")
+    if ("${BINARY_DIR}" MATCHES "^/.*$")
+        pvs_studio_join_path(BINARY_DIR "${CMAKE_BINARY_DIR}" "PVS-Studio/__${BINARY_DIR}")
+    else ()
+        pvs_studio_join_path(BINARY_DIR "${CMAKE_BINARY_DIR}" "${BINARY_DIR}")
+    endif ()
+
+    file(MAKE_DIRECTORY "${BINARY_DIR}")
+
+    pvs_studio_set_directory_flags("${DIR}" PVS_STUDIO_TARGET_CXX_FLAGS PVS_STUDIO_TARGET_C_FLAGS)
+    pvs_studio_set_target_flags("${TARGET}" PVS_STUDIO_TARGET_CXX_FLAGS PVS_STUDIO_TARGET_C_FLAGS)
+
+    if (NOT "${PROPERTY}" STREQUAL "NOTFOUND" AND NOT "${PROPERTY}" STREQUAL "PROPERTY-NOTFOUND")
+        foreach (SOURCE ${PROPERTY})
+            pvs_studio_join_path(SOURCE "${DIR}" "${SOURCE}")
+            pvs_studio_analyze_file("${SOURCE}" "${DIR}" "${BINARY_DIR}")
+        endforeach ()
+    endif ()
+
+    set(PVS_STUDIO_PLOGS "${PVS_STUDIO_PLOGS}" PARENT_SCOPE)
+endfunction ()
+
+set(PVS_STUDIO_RECURSIVE_TARGETS)
+set(PVS_STUDIO_RECURSIVE_TARGETS_NEW)
+
+macro(pvs_studio_get_recursive_targets TARGET)
+    get_target_property(libs "${TARGET}" LINK_LIBRARIES)
+    foreach (lib IN LISTS libs)
+        list(FIND PVS_STUDIO_RECURSIVE_TARGETS "${lib}" index)
+        if (TARGET "${lib}" AND "${index}" STREQUAL -1)
+            get_target_property(target_type "${lib}" TYPE)
+            if (NOT "${target_type}" STREQUAL "INTERFACE_LIBRARY")
+                list(APPEND PVS_STUDIO_RECURSIVE_TARGETS "${lib}")
+                list(APPEND PVS_STUDIO_RECURSIVE_TARGETS_NEW "${lib}")
+                pvs_studio_get_recursive_targets("${lib}")
+            endif ()
+        endif ()
+    endforeach ()
+endmacro()
+
+option(PVS_STUDIO_DISABLE OFF "Disable PVS-Studio targets")
+option(PVS_STUDIO_DEBUG OFF "Add debug info")
+
+# pvs_studio_add_target
+# Target options:
+# ALL                           add PVS-Studio target to default build (default: off)
+# TARGET target                 name of analysis target (default: pvs)
+# ANALYZE targets...            targets to analyze
+# RECURSIVE                     analyze target's dependencies (requires CMake 3.5+)
+# COMPILE_COMMANDS              use compile_commands.json instead of targets (specified by the 'ANALYZE' option) to determine files for analysis
+#                               (set CMAKE_EXPORT_COMPILE_COMMANDS, available only for Makefile and Ninja generators)
+#
+# Output options:
+# OUTPUT                        prints report to stdout
+# LOG path                      path to report (default: ${CMAKE_CURRENT_BINARY_DIR}/PVS-Studio.log)
+# FORMAT format                 format of report
+# MODE mode                     analyzers/levels filter (default: GA:1,2)
+# HIDE_HELP                     do not print help message
+#
+# Analyzer options:
+# PLATFORM name                 linux32/linux64 (default: linux64)
+# PREPROCESSOR name             preprocessor type: gcc/clang (default: auto detected)
+# LICENSE path                  path to PVS-Studio.lic (default: ~/.config/PVS-Studio/PVS-Studio.lic)
+# CONFIG path                   path to PVS-Studio.cfg
+# CFG_TEXT text                 embedded PVS-Studio.cfg
+# KEEP_COMBINED_PLOG            do not delete combined plog file *.pvs.raw for further processing with plog-converter
+#
+# Misc options:
+# DEPENDS targets..             additional target dependencies
+# SOURCES path...               list of source files to analyze
+# BIN path                      path to pvs-studio-analyzer (Unix) or CompilerCommandsAnalyzer.exe (Windows)
+# CONVERTER path                path to plog-converter (Unix) or HtmlGenerator.exe (Windows)
+# C_FLAGS flags...              additional C_FLAGS
+# CXX_FLAGS flags...            additional CXX_FLAGS
+# ARGS args...                  additional pvs-studio-analyzer/CompilerCommandsAnalyzer.exe flags
+function (pvs_studio_add_target)
+    macro (default VAR VALUE)
+        if ("${${VAR}}" STREQUAL "")
+            set("${VAR}" "${VALUE}")
+        endif ()
+    endmacro ()
+
+    set(PVS_STUDIO_SUPPORTED_PREPROCESSORS "gcc|clang|visualcpp")
+    if ("${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang")
+        set(DEFAULT_PREPROCESSOR "clang")
+    elseif (MSVC)
+        set(DEFAULT_PREPROCESSOR "visualcpp")
+    else ()
+        set(DEFAULT_PREPROCESSOR "gcc")
+    endif ()
+
+    set(OPTIONAL OUTPUT ALL RECURSIVE HIDE_HELP KEEP_COMBINED_PLOG COMPILE_COMMANDS)
+    set(SINGLE LICENSE CONFIG TARGET LOG FORMAT BIN CONVERTER PLATFORM PREPROCESSOR CFG_TEXT)
+    set(MULTI SOURCES C_FLAGS CXX_FLAGS ARGS DEPENDS ANALYZE MODE)
+    cmake_parse_arguments(PVS_STUDIO "${OPTIONAL}" "${SINGLE}" "${MULTI}" ${ARGN})
+
+    if ("${PVS_STUDIO_CONFIG}" STREQUAL "" OR NOT "${PVS_STUDIO_CFG_TEXT}" STREQUAL "")
+        set(PVS_STUDIO_EMPTY_CONFIG ON)
+    else ()
+        set(PVS_STUDIO_EMPTY_CONFIG OFF)
+    endif ()
+
+    default(PVS_STUDIO_CFG_TEXT "analysis-mode=31")
+    default(PVS_STUDIO_CONFIG "${CMAKE_BINARY_DIR}/PVS-Studio.cfg")
+    default(PVS_STUDIO_C_FLAGS "")
+    default(PVS_STUDIO_CXX_FLAGS "")
+    default(PVS_STUDIO_TARGET "pvs")
+    default(PVS_STUDIO_LOG "PVS-Studio.log")
+
+    set(PATHS)
+    if (WIN32)
+        set(ROOT "PROGRAMFILES(X86)")
+        set(ROOT "$ENV{${ROOT}}/PVS-Studio")
+        string(REPLACE \\ / ROOT "${ROOT}")
+
+        if (EXISTS "${ROOT}")
+            set(PATHS "${ROOT}")
+        endif ()
+
+        default(PVS_STUDIO_BIN "CompilerCommandsAnalyzer.exe")
+        default(PVS_STUDIO_CONVERTER "HtmlGenerator.exe")
+    else ()
+        default(PVS_STUDIO_BIN "pvs-studio-analyzer")
+        default(PVS_STUDIO_CONVERTER "plog-converter")
+    endif ()
+
+    find_program(PVS_STUDIO_BIN_PATH "${PVS_STUDIO_BIN}" ${PATHS})
+    set(PVS_STUDIO_BIN "${PVS_STUDIO_BIN_PATH}")
+
+    if (NOT EXISTS "${PVS_STUDIO_BIN}")
+        message(FATAL_ERROR "pvs-studio-analyzer is not found")
+    endif ()
+
+    find_program(PVS_STUDIO_CONVERTER_PATH "${PVS_STUDIO_CONVERTER}" ${PATHS})
+    set(PVS_STUDIO_CONVERTER "${PVS_STUDIO_CONVERTER_PATH}")
+
+    if (NOT EXISTS "${PVS_STUDIO_CONVERTER}")
+        message(FATAL_ERROR "plog-converter is not found")
+    endif ()
+
+    default(PVS_STUDIO_MODE "GA:1,2")
+    default(PVS_STUDIO_PREPROCESSOR "${DEFAULT_PREPROCESSOR}")
+    if (WIN32)
+        default(PVS_STUDIO_PLATFORM "x64")
+    else ()
+        default(PVS_STUDIO_PLATFORM "linux64")
+    endif ()
+
+    string(REPLACE ";" "+" PVS_STUDIO_MODE "${PVS_STUDIO_MODE}")
+
+    if (PVS_STUDIO_EMPTY_CONFIG)
+        set(PVS_STUDIO_CONFIG_COMMAND "${CMAKE_COMMAND}" -E echo "${PVS_STUDIO_CFG_TEXT}" > "${PVS_STUDIO_CONFIG}")
+    else ()
+        set(PVS_STUDIO_CONFIG_COMMAND "${CMAKE_COMMAND}" -E touch "${PVS_STUDIO_CONFIG}")
+    endif ()
+
+    add_custom_command(OUTPUT "${PVS_STUDIO_CONFIG}"
+                       COMMAND ${PVS_STUDIO_CONFIG_COMMAND}
+                       WORKING_DIRECTORY "${BINARY_DIR}"
+                       COMMENT "Generating PVS-Studio.cfg")
+
+    if (NOT "${PVS_STUDIO_PREPROCESSOR}" MATCHES "^${PVS_STUDIO_SUPPORTED_PREPROCESSORS}$")
+        message(FATAL_ERROR "Preprocessor ${PVS_STUDIO_PREPROCESSOR} isn't supported. Available options: ${PVS_STUDIO_SUPPORTED_PREPROCESSORS}.")
+    endif ()
+
+    pvs_studio_append_standard_flag(PVS_STUDIO_CXX_FLAGS "${CMAKE_CXX_STANDARD}")
+    pvs_studio_set_directory_flags("${CMAKE_CURRENT_SOURCE_DIR}" PVS_STUDIO_CXX_FLAGS PVS_STUDIO_C_FLAGS)
+
+    if (NOT "${PVS_STUDIO_LICENSE}" STREQUAL "")
+        pvs_studio_join_path(PVS_STUDIO_LICENSE "${CMAKE_CURRENT_SOURCE_DIR}" "${PVS_STUDIO_LICENSE}")
+        list(APPEND PVS_STUDIO_ARGS --lic-file "${PVS_STUDIO_LICENSE}")
+    endif ()
+
+    list(APPEND PVS_STUDIO_ARGS --cfg "${PVS_STUDIO_CONFIG}"
+                                --platform "${PVS_STUDIO_PLATFORM}"
+                                --preprocessor "${PVS_STUDIO_PREPROCESSOR}")
+
+    if (NOT "${CMAKE_CXX_COMPILER}" STREQUAL "")
+        list(APPEND PVS_STUDIO_ARGS --cxx "${CMAKE_CXX_COMPILER}")
+    endif ()
+
+    if (NOT "${CMAKE_C_COMPILER}" STREQUAL "")
+        list(APPEND PVS_STUDIO_ARGS --cc "${CMAKE_C_COMPILER}")
+    endif ()
+
+    set(PVS_STUDIO_PLOGS "")
+
+    set(PVS_STUDIO_RECURSIVE_TARGETS_NEW)
+    if (${PVS_STUDIO_RECURSIVE})
+        foreach (TARGET IN LISTS PVS_STUDIO_ANALYZE)
+            list(APPEND PVS_STUDIO_RECURSIVE_TARGETS_NEW "${TARGET}")
+            pvs_studio_get_recursive_targets("${TARGET}")
+        endforeach ()
+    endif ()
+
+    set(inc_path)
+
+    foreach (TARGET ${PVS_STUDIO_ANALYZE})
+        set(DIR "${CMAKE_CURRENT_SOURCE_DIR}")
+        string(FIND "${TARGET}" ":" DELIM)
+        if ("${DELIM}" GREATER "-1")
+            math(EXPR DELIMI "${DELIM}+1")
+            string(SUBSTRING "${TARGET}" "${DELIMI}" "-1" DIR)
+            string(SUBSTRING "${TARGET}" "0" "${DELIM}" TARGET)
+            pvs_studio_join_path(DIR "${CMAKE_CURRENT_SOURCE_DIR}" "${DIR}")
+        else ()
+            get_target_property(TARGET_SOURCE_DIR "${TARGET}" SOURCE_DIR)
+            if (EXISTS "${TARGET_SOURCE_DIR}")
+                set(DIR "${TARGET_SOURCE_DIR}")
+            endif ()
+        endif ()
+        pvs_studio_analyze_target("${TARGET}" "${DIR}")
+        list(APPEND PVS_STUDIO_DEPENDS "${TARGET}")
+
+        if ("${inc_path}" STREQUAL "")
+            set(inc_path "$<TARGET_PROPERTY:${TARGET},INCLUDE_DIRECTORIES>")
+        else ()
+            set(inc_path "${inc_path}$<SEMICOLON>$<TARGET_PROPERTY:${TARGET},INCLUDE_DIRECTORIES>")
+        endif ()
+    endforeach ()
+
+    foreach (TARGET ${PVS_STUDIO_RECURSIVE_TARGETS_NEW})
+        set(DIR "${CMAKE_CURRENT_SOURCE_DIR}")
+        get_target_property(TARGET_SOURCE_DIR "${TARGET}" SOURCE_DIR)
+        if (EXISTS "${TARGET_SOURCE_DIR}")
+            set(DIR "${TARGET_SOURCE_DIR}")
+        endif ()
+        pvs_studio_analyze_target("${TARGET}" "${DIR}")
+        list(APPEND PVS_STUDIO_DEPENDS "${TARGET}")
+    endforeach ()
+
+    set(PVS_STUDIO_TARGET_CXX_FLAGS "")
+    set(PVS_STUDIO_TARGET_C_FLAGS "")
+    foreach (SOURCE ${PVS_STUDIO_SOURCES})
+        pvs_studio_analyze_file("${SOURCE}" "${CMAKE_CURRENT_SOURCE_DIR}" "${CMAKE_CURRENT_BINARY_DIR}")
+    endforeach ()
+
+    if (PVS_STUDIO_COMPILE_COMMANDS)
+        set(COMPILE_COMMANDS_LOG "${PVS_STUDIO_LOG}.pvs.analyzer.raw")
+        if (NOT CMAKE_EXPORT_COMPILE_COMMANDS)
+            message(FATAL_ERROR "You should set CMAKE_EXPORT_COMPILE_COMMANDS to TRUE")
+        endif ()
+        add_custom_command(
+            OUTPUT "${COMPILE_COMMANDS_LOG}"
+            COMMAND "${PVS_STUDIO_BIN}" analyze -i
+                    --output-file "${COMPILE_COMMANDS_LOG}.always"
+                    ${PVS_STUDIO_ARGS}
+            COMMENT "Analyzing with PVS-Studio"
+            WORKING_DIRECTORY "${CMAKE_BINARY_DIR}"
+            DEPENDS "${PVS_STUDIO_CONFIG}"
+        )
+        list(APPEND PVS_STUDIO_PLOGS_LOGS "${COMPILE_COMMANDS_LOG}.always")
+        list(APPEND PVS_STUDIO_PLOGS_DEPENDENCIES "${COMPILE_COMMANDS_LOG}")
+    endif ()
+
+    pvs_studio_relative_path(LOG_RELATIVE "${CMAKE_BINARY_DIR}" "${PVS_STUDIO_LOG}")
+    if (PVS_STUDIO_PLOGS OR PVS_STUDIO_COMPILE_COMMANDS)
+        if (WIN32)
+            string(REPLACE / \\ PVS_STUDIO_PLOGS "${PVS_STUDIO_PLOGS}")
+        endif ()
+        if (WIN32)
+            set(COMMANDS COMMAND type ${PVS_STUDIO_PLOGS} ${PVS_STUDIO_PLOGS_LOGS} > "${PVS_STUDIO_LOG}" 2>nul)
+        else ()
+            set(COMMANDS COMMAND cat ${PVS_STUDIO_PLOGS} ${PVS_STUDIO_PLOGS_LOGS} > "${PVS_STUDIO_LOG}")
+        endif ()
+        set(COMMENT "Generating ${LOG_RELATIVE}")
+        if (NOT "${PVS_STUDIO_FORMAT}" STREQUAL "" OR PVS_STUDIO_OUTPUT)
+            if ("${PVS_STUDIO_FORMAT}" STREQUAL "")
+                set(PVS_STUDIO_FORMAT "errorfile")
+            endif ()
+            list(APPEND COMMANDS
+                COMMAND "${CMAKE_COMMAND}" -E remove -f "${PVS_STUDIO_LOG}.pvs.raw"
+                COMMAND "${CMAKE_COMMAND}" -E rename "${PVS_STUDIO_LOG}" "${PVS_STUDIO_LOG}.pvs.raw"
+                COMMAND "${PVS_STUDIO_CONVERTER}" -t "${PVS_STUDIO_FORMAT}" "${PVS_STUDIO_LOG}.pvs.raw" -o "${PVS_STUDIO_LOG}" -a "${PVS_STUDIO_MODE}"
+                )
+            if(NOT PVS_STUDIO_KEEP_COMBINED_PLOG)
+                list(APPEND COMMANDS COMMAND "${CMAKE_COMMAND}" -E remove -f "${PVS_STUDIO_LOG}.pvs.raw")
+            endif()
+        endif ()
+    else ()
+        set(COMMANDS COMMAND "${CMAKE_COMMAND}" -E touch "${PVS_STUDIO_LOG}")
+        set(COMMENT "Generating ${LOG_RELATIVE}: no sources found")
+    endif ()
+
+    if (WIN32)
+        string(REPLACE / \\ PVS_STUDIO_LOG "${PVS_STUDIO_LOG}")
+    endif ()
+
+    add_custom_command(OUTPUT "${PVS_STUDIO_LOG}"
+                       ${COMMANDS}
+                       COMMENT "${COMMENT}"
+                       DEPENDS ${PVS_STUDIO_PLOGS} ${PVS_STUDIO_PLOGS_DEPENDENCIES}
+                       WORKING_DIRECTORY "${CMAKE_BINARY_DIR}")
+
+    if (PVS_STUDIO_ALL)
+        set(ALL "ALL")
+    else ()
+        set(ALL "")
+    endif ()
+
+    if (PVS_STUDIO_OUTPUT)
+        if (PVS_STUDIO_HIDE_HELP AND NOT WIN32)
+            set(COMMANDS COMMAND grep -v " error: Help:" ${PVS_STUDIO_LOG} 1>&2 || exit 0)
+        elseif (WIN32)
+            set(COMMANDS COMMAND type "${PVS_STUDIO_LOG}" 1>&2)
+        else ()
+            set(COMMANDS COMMAND cat "${PVS_STUDIO_LOG}" 1>&2)
+        endif()
+    else ()
+        set(COMMANDS "")
+    endif ()
+
+    add_custom_target("${PVS_STUDIO_TARGET}" ${ALL} ${COMMANDS} WORKING_DIRECTORY "${CMAKE_BINARY_DIR}" DEPENDS ${PVS_STUDIO_DEPENDS} "${PVS_STUDIO_LOG}")
+
+    # A workaround to add implicit dependencies of source files from include directories
+    set_target_properties("${PVS_STUDIO_TARGET}" PROPERTIES INCLUDE_DIRECTORIES "${inc_path}")
+endfunction ()
diff --git a/3rdParty/iresearch/core/CMakeLists.txt b/3rdParty/iresearch/core/CMakeLists.txt
index f4497a86a843..8ba6230ae172 100644
--- a/3rdParty/iresearch/core/CMakeLists.txt
+++ b/3rdParty/iresearch/core/CMakeLists.txt
@@ -125,6 +125,7 @@ set(IResearch_core_sources
   ./search/multiterm_query.cpp
   ./search/term_query.cpp
   ./search/boolean_filter.cpp
+  ./search/ngram_similarity_filter.cpp
   ./store/data_input.cpp 
   ./store/data_output.cpp 
   ./store/directory.cpp 
@@ -151,6 +152,7 @@ set(IResearch_core_sources
   ./utils/index_utils.cpp
   ./utils/math_utils.cpp 
   ./utils/levenshtein_utils.cpp
+  ./utils/wildcard_utils.cpp
   ./utils/levenshtein_default_pdp.cpp
   ./utils/memory.cpp
   ./utils/text_format.cpp
@@ -165,6 +167,7 @@ set(IResearch_core_sources
   ./utils/network_utils.cpp
   ./utils/cpuinfo.cpp
   ./utils/numeric_utils.cpp
+  ./utils/attribute_range.cpp
   ${IResearch_core_os_specific_sources}
   ${IResearch_core_optimized_sources}
 )
@@ -212,6 +215,7 @@ set(IResearch_core_headers
   ./search/disjunction.hpp
   ./search/conjunction.hpp
   ./search/exclusion.hpp
+  ./search/ngram_similarity_filter.hpp
   ./store/data_input.hpp
   ./store/data_output.hpp
   ./store/directory.hpp
@@ -256,6 +260,7 @@ set(IResearch_core_headers
   ./utils/bitset.hpp
   ./utils/bitvector.hpp
   ./utils/type_id.hpp
+  ./utils/attribute_range.hpp
   ./shared.hpp
   ./types.hpp
 )
@@ -589,6 +594,7 @@ if(MSVC)
     ${Unwind_STATIC_LIBS}
     ${DL_LIBRARY}
     ${MSVC_ONLY_LIBRARIES}
+    ${SIMD_LIBRARY_STATIC}
   )
 endif()
 
diff --git a/3rdParty/iresearch/core/analysis/token_attributes.hpp b/3rdParty/iresearch/core/analysis/token_attributes.hpp
index 61aaf0a1e800..d252c5aedd0c 100644
--- a/3rdParty/iresearch/core/analysis/token_attributes.hpp
+++ b/3rdParty/iresearch/core/analysis/token_attributes.hpp
@@ -55,7 +55,7 @@ struct IRESEARCH_API offset : attribute {
 };
 
 //////////////////////////////////////////////////////////////////////////////
-/// @class offset 
+/// @class increment 
 /// @brief represents token increment in a stream 
 //////////////////////////////////////////////////////////////////////////////
 struct IRESEARCH_API increment : basic_attribute<uint32_t> {
@@ -173,6 +173,10 @@ class IRESEARCH_API position
   DECLARE_REFERENCE(position);
   DECLARE_TYPE_ID(attribute::type_id);
 
+  static irs::position* extract(const attribute_view& attrs) noexcept {
+    return attrs.get<irs::position>().get();
+  }
+
   const irs::attribute_view& attributes() const noexcept override {
     return attrs_;
   }
@@ -186,6 +190,8 @@ class IRESEARCH_API position
     return value_;
   }
 
+  virtual void reset() = 0;
+
   virtual bool next() = 0;
 
  protected:
diff --git a/3rdParty/iresearch/core/formats/formats_10.cpp b/3rdParty/iresearch/core/formats/formats_10.cpp
index b12893d42cf7..4115d77b906d 100644
--- a/3rdParty/iresearch/core/formats/formats_10.cpp
+++ b/3rdParty/iresearch/core/formats/formats_10.cpp
@@ -253,8 +253,24 @@ class postings_writer_base : public irs::postings_writer {
   static const int32_t TERMS_FORMAT_MIN = 0;
   static const int32_t TERMS_FORMAT_MAX = TERMS_FORMAT_MIN;
 
-  static const int32_t FORMAT_MIN = 0;
-  static const int32_t FORMAT_MAX = 1; // sse
+  static constexpr int32_t FORMAT_MIN = 0;
+  // positions are stored one based (if first osition is 1 first offset is 0)
+  // This forces reader to adjust first read position of every document additionally to
+  // stored increment. Or incorrect positions will be read - 1 2 3 will be stored
+  // (offsets 0 1 1) but 0 1 2 will be read. At least this will lead to incorrect results in
+  // by_same_positions filter if searching for position 1
+  static constexpr int32_t FORMAT_POSITIONS_ONEBASED = FORMAT_MIN;
+  // positions are stored one based, sse used
+  static constexpr int32_t FORMAT_SSE_POSITIONS_ONEBASED = FORMAT_POSITIONS_ONEBASED + 1;
+
+  // positions are stored zero based
+  // if first position is 1 first offset is also 1
+  // so no need to adjust position while reading first
+  // position for document, always just increment from previous pos
+  static constexpr int32_t FORMAT_POSITIONS_ZEROBASED = FORMAT_SSE_POSITIONS_ONEBASED + 1;
+  // positions are stored zero based, sse used
+  static constexpr int32_t FORMAT_SSE_POSITIONS_ZEROBASED = FORMAT_POSITIONS_ZEROBASED + 1;
+  static constexpr int32_t FORMAT_MAX = FORMAT_SSE_POSITIONS_ZEROBASED;
 
   static const uint32_t MAX_SKIP_LEVELS = 10;
   static const uint32_t BLOCK_SIZE = 128;
@@ -272,7 +288,9 @@ class postings_writer_base : public irs::postings_writer {
   postings_writer_base(int32_t postings_format_version, int32_t terms_format_version)
     : skip_(BLOCK_SIZE, SKIP_N),
       postings_format_version_(postings_format_version),
-      terms_format_version_(terms_format_version) {
+      terms_format_version_(terms_format_version),
+      pos_min_(postings_format_version_ >= FORMAT_POSITIONS_ZEROBASED ?   // first position offsets now is format dependent
+               pos_limits::invalid(): pos_limits::min()) {
     assert(postings_format_version >= FORMAT_MIN && postings_format_version <= FORMAT_MAX);
     assert(terms_format_version >= TERMS_FORMAT_MIN && terms_format_version <= TERMS_FORMAT_MAX);
     attrs_.emplace(docs_);
@@ -368,7 +386,9 @@ class postings_writer_base : public irs::postings_writer {
 
     bool full() const { return BLOCK_SIZE == size; }
     void next(uint32_t pos) { last = pos, ++size; }
-    void pos(uint32_t pos) { buf[size] = pos; }
+    void pos(uint32_t pos) {
+        buf[size] = pos;
+    }
 
     void reset() noexcept {
       stream::reset();
@@ -444,6 +464,7 @@ class postings_writer_base : public irs::postings_writer {
   size_t docs_count_{};             // number of processed documents
   const int32_t postings_format_version_;
   const int32_t terms_format_version_;
+  uint32_t pos_min_; // initial base value for writing positions offsets
 };
 
 MSVC2015_ONLY(__pragma(warning(push)))
@@ -782,9 +803,8 @@ void postings_writer_base::begin_doc(doc_id_t id, const frequency* freq) {
       FormatTraits::write_block(*doc_out_, doc_.freqs, BLOCK_SIZE, buf_);
     }
   }
-
   if (pos_) {
-    pos_->last = 0;
+    pos_->last = pos_min_;
   }
 
   if (pay_) {
@@ -889,15 +909,14 @@ irs::postings_writer::state postings_writer<FormatTraits, VolatileAttributes>::w
     assert(doc_limits::valid(did));
     begin_doc<FormatTraits>(did, freq.get());
     docs_.value.set(did - doc_limits::min());
-
     if (pos) {
       if (VolatileAttributes) {
         auto& attrs = pos->attributes();
         offs = attrs.get<offset>().get();
         pay = attrs.get<payload>().get();
       }
-
       while (pos->next()) {
+        assert(pos_limits::valid(pos->value()));
         add_position<FormatTraits>(pos->value(), offs, pay);
       }
     }
@@ -937,8 +956,8 @@ struct skip_context : skip_state {
 struct doc_state {
   const index_input* pos_in;
   const index_input* pay_in;
-  version10::term_meta* term_state;
-  uint32_t* freq;
+  const version10::term_meta* term_state;
+  const uint32_t* freq;
   uint32_t* enc_buf;
   uint64_t tail_start;
   size_t tail_length;
@@ -1117,7 +1136,6 @@ struct position_impl<IteratorTraits, false, true>
     }
 
     pay_in_->seek(state.term_state->pay_start);
-
   }
 
   void prepare(const skip_state& state)  {
@@ -1252,7 +1270,6 @@ struct position_impl<IteratorTraits, true, false>
     }
 
     pay_in_->seek(state.term_state->pay_start);
-
   }
 
   void prepare(const skip_state& state) {
@@ -1351,6 +1368,7 @@ struct position_impl<IteratorTraits, false, false> {
       throw io_error("failed to reopen positions input");
     }
 
+    cookie_.file_pointer_ = state.term_state->pos_start;
     pos_in_->seek(state.term_state->pos_start);
     freq_ = state.freq;
     features_ = state.features;
@@ -1363,6 +1381,15 @@ struct position_impl<IteratorTraits, false, false> {
     pos_in_->seek(state.pos_ptr);
     pend_pos_ = state.pend_pos;
     buf_pos_ = postings_writer_base::BLOCK_SIZE;
+    cookie_.pend_pos_ = pend_pos_;
+  }
+
+  void reset() {
+    if (std::numeric_limits<size_t>::max() != cookie_.file_pointer_) {
+      buf_pos_ = postings_writer_base::BLOCK_SIZE;
+      pend_pos_ = cookie_.pend_pos_;
+      pos_in_->seek(cookie_.file_pointer_);
+    }
   }
 
   void read_attributes() { }
@@ -1411,9 +1438,14 @@ struct position_impl<IteratorTraits, false, false> {
   uint32_t pend_pos_{}; // how many positions "behind" we are
   uint64_t tail_start_; // file pointer where the last (vInt encoded) pos delta block is
   size_t tail_length_; // number of positions in the last (vInt encoded) pos delta block
-  uint32_t buf_pos_{ postings_writer_base::BLOCK_SIZE } ; // current position in pos_deltas_ buffer
+  uint32_t buf_pos_{ postings_writer_base::BLOCK_SIZE }; // current position in pos_deltas_ buffer
   index_input::ptr pos_in_;
   features features_;
+
+  struct cookie {
+    uint32_t pend_pos_{};
+    size_t file_pointer_ = std::numeric_limits<size_t>::max();
+  } cookie_;
 }; // position_impl
 
 template<typename IteratorTraits, bool Position = IteratorTraits::position()>
@@ -1445,9 +1477,11 @@ class position final : public irs::position,
       refill();
       this->buf_pos_ = 0;
     }
-
+    if /*constexpr*/ (IteratorTraits::one_based_position_storage()) {
+      value_ += (uint32_t)(!pos_limits::valid(value_));
+    }
     value_ += this->pos_deltas_[this->buf_pos_];
-
+    assert(irs::pos_limits::valid(value_));
     this->read_attributes();
 
     ++this->buf_pos_;
@@ -1455,6 +1489,11 @@ class position final : public irs::position,
     return true;
   }
 
+  virtual void reset() override {
+    value_ = pos_limits::invalid();
+    impl::reset();
+  }
+
   // prepares iterator to work
   // or notifies iterator that doc iterator has skipped to a new block
   using impl::prepare;
@@ -1462,6 +1501,7 @@ class position final : public irs::position,
   // notify iterator that corresponding doc_iterator has moved forward
   void notify(uint32_t n) {
     this->pend_pos_ += n;
+    this->cookie_.pend_pos_ += n;
   }
 
   void clear() noexcept {
@@ -1495,9 +1535,7 @@ class position final : public irs::position,
     if (count < left) {
       impl::skip(count);
     }
-
     clear();
-    value_ = 0;
   }
 }; // position
 
@@ -1601,6 +1639,13 @@ class doc_iterator final : public irs::doc_iterator_base {
         attrs_.emplace(pos_);
       }
     }
+
+    if (1 == term_state_.docs_count) {
+      *docs_ = (doc_limits::min)() + term_state_.e_single_doc;
+      *doc_freqs_ = term_freq_;
+      doc_freq_ = doc_freqs_;
+      ++end_;
+    }
   }
 
   virtual doc_id_t seek(doc_id_t target) override {
@@ -1746,6 +1791,8 @@ class doc_iterator final : public irs::doc_iterator_base {
   }
 
   void refill() {
+    // should never call refill for singleton documents
+    assert(1 != term_state_.docs_count);
     const auto left = term_state_.docs_count - cur_pos_;
 
     if (left >= postings_writer_base::BLOCK_SIZE) {
@@ -1772,12 +1819,6 @@ class doc_iterator final : public irs::doc_iterator_base {
       }
 
       end_ = docs_ + postings_writer_base::BLOCK_SIZE;
-    } else if (1 == term_state_.docs_count) {
-      docs_[0] = term_state_.e_single_doc;
-      if (term_freq_) {
-        doc_freqs_[0] = term_freq_;
-      }
-      end_ = docs_ + 1;
     } else {
       read_end_block(left);
       end_ = docs_ + left;
@@ -1789,7 +1830,7 @@ class doc_iterator final : public irs::doc_iterator_base {
     }
 
     begin_ = docs_;
-    doc_freq_ = docs_ + postings_writer_base::BLOCK_SIZE;
+    doc_freq_ = doc_freqs_;
   }
 
   std::vector<skip_state> skip_levels_;
@@ -1915,7 +1956,7 @@ struct index_meta_writer final: public irs::index_meta_writer {
 template<>
 std::string file_name<irs::index_meta_writer, index_meta>(const index_meta& meta) {
   return file_name(index_meta_writer::FORMAT_PREFIX_TMP, meta.generation());
-};
+}
 
 struct index_meta_reader final: public irs::index_meta_reader {
   virtual bool last_segments_file(
@@ -1932,7 +1973,7 @@ struct index_meta_reader final: public irs::index_meta_reader {
 template<>
 std::string file_name<irs::index_meta_reader, index_meta>(const index_meta& meta) {
   return file_name(index_meta_writer::FORMAT_PREFIX, meta.generation());
-};
+}
 
 MSVC2015_ONLY(__pragma(warning(push)))
 MSVC2015_ONLY(__pragma(warning(disable: 4592))) // symbol will be dynamically initialized (implementation limitation) false positive bug in VS2015.1
@@ -2366,7 +2407,7 @@ class document_mask_writer final: public irs::document_mask_writer {
 template<>
 std::string file_name<irs::document_mask_writer, segment_meta>(const segment_meta& meta) {
   return file_name(meta.name, meta.version, document_mask_writer::FORMAT_EXT);
-};
+}
 
 MSVC2015_ONLY(__pragma(warning(push)))
 MSVC2015_ONLY(__pragma(warning(disable: 4592))) // symbol will be dynamically initialized (implementation limitation) false positive bug in VS2015.1
@@ -2527,9 +2568,9 @@ std::string file_name<column_meta_writer, segment_meta>(
     const segment_meta& meta
 ) {
   return irs::file_name(meta.name, columns::meta_writer::FORMAT_EXT);
-};
+}
 
-void meta_writer::prepare(directory& dir, const segment_meta& meta) { 
+void meta_writer::prepare(directory& dir, const segment_meta& meta) {
   auto filename = file_name<column_meta_writer>(meta);
 
   out_ = dir.create(filename);
@@ -2673,7 +2714,7 @@ bool meta_reader::prepare(
     if (irs::decrypt(filename, *in_, enc, in_cipher_)) {
       assert(in_cipher_ && in_cipher_->block_size());
 
-      const auto blocks_in_buffer= math::div_ceil64(
+      const auto blocks_in_buffer = math::div_ceil64(
         buffered_index_input::DEFAULT_BUFFER_SIZE,
         in_cipher_->block_size()
       );
@@ -3185,7 +3226,7 @@ class writer final : public irs::columnstore_writer {
 template<>
 std::string file_name<columnstore_writer, segment_meta>(const segment_meta& meta) {
   return file_name(meta.name, columns::writer::FORMAT_EXT);
-};
+}
 
 MSVC2015_ONLY(__pragma(warning(push)))
 MSVC2015_ONLY(__pragma(warning(disable: 4592))) // symbol will be dynamically initialized (implementation limitation) false positive bug in VS2015.1
@@ -3746,7 +3787,7 @@ class dense_fixed_offset_block : util::noncopyable {
       const auto offset = (value_ - value_min_)*avg_length_;
 
       assert(payload_ != &DUMMY);
-      *payload_= bytes_ref(
+      *payload_ = bytes_ref(
         data_.c_str() + offset,
         value_ == value_back_ ? data_.size() - offset : avg_length_
       );
@@ -4514,7 +4555,7 @@ class sparse_column final : public column {
     const auto& cached = load_block(*ctxs_, decompressor(), encrypted(), *it);
 
     return cached.value(key, value);
-  };
+  }
 
   virtual bool visit(
       const columnstore_reader::values_visitor_f& visitor
@@ -5266,7 +5307,7 @@ size_t postings_reader_base::decode(
   return size_t(std::distance(in, p));
 }
 
-template<typename FormatTraits>
+template<typename FormatTraits, bool OneBasedPositionStorage>
 class postings_reader final: public postings_reader_base {
  public:
   template<bool Freq, bool Pos, bool Offset, bool Payload>
@@ -5275,6 +5316,7 @@ class postings_reader final: public postings_reader_base {
     static constexpr bool position() { return Freq && Pos; }
     static constexpr bool offset() { return position() && Offset; }
     static constexpr bool payload() { return position() && Payload; }
+    static constexpr bool one_based_position_storage() { return OneBasedPositionStorage; }
   };
 
   virtual irs::doc_iterator::ptr iterator(
@@ -5290,8 +5332,8 @@ class postings_reader final: public postings_reader_base {
   #pragma GCC diagnostic ignored "-Wswitch"
 #endif
 
-template<typename FormatTraits>
-irs::doc_iterator::ptr postings_reader<FormatTraits>::iterator(
+template<typename FormatTraits, bool OneBasedPositionStorage>
+irs::doc_iterator::ptr postings_reader<FormatTraits, OneBasedPositionStorage>::iterator(
     const flags& field,
     const attribute_view& attrs,
     const flags& req) {
@@ -5468,7 +5510,7 @@ irs::postings_writer::ptr format10::get_postings_writer(bool volatile_state) con
 }
 
 irs::postings_reader::ptr format10::get_postings_reader() const {
-  return irs::postings_reader::make<::postings_reader<format_traits>>();
+  return irs::postings_reader::make<::postings_reader<format_traits, true>>();
 }
 
 /*static*/ irs::format::ptr format10::make() {
@@ -5578,6 +5620,51 @@ columnstore_writer::ptr format12::get_columnstore_writer() const {
 DEFINE_FORMAT_TYPE_NAMED(::format12, "1_2");
 REGISTER_FORMAT_MODULE(::format12, MODULE_NAME);
 
+// ----------------------------------------------------------------------------
+// --SECTION--                                                         format13
+// ----------------------------------------------------------------------------
+
+class format13 : public format12 {
+ public:
+  DECLARE_FORMAT_TYPE();
+  DECLARE_FACTORY();
+
+  format13() noexcept : format12(format13::type()) { }
+
+  virtual irs::postings_writer::ptr get_postings_writer(bool volatile_state) const override;
+  virtual irs::postings_reader::ptr get_postings_reader() const override;
+
+ protected:
+  explicit format13(const irs::format::type_id& type) noexcept
+    : format12(type) {
+  }
+};
+
+irs::postings_writer::ptr format13::get_postings_writer(bool volatile_state) const {
+  constexpr const auto VERSION = postings_writer_base::FORMAT_POSITIONS_ZEROBASED;
+
+  if (volatile_state) {
+    return memory::make_unique<::postings_writer<format_traits, true>>(VERSION);
+  }
+
+  return memory::make_unique<::postings_writer<format_traits, false>>(VERSION);
+}
+
+irs::postings_reader::ptr format13::get_postings_reader() const {
+  return irs::postings_reader::make<::postings_reader<format_traits, false>>();
+}
+
+/*static*/ irs::format::ptr format13::make() {
+  static const ::format13 INSTANCE;
+
+  // aliasing constructor
+  return irs::format::ptr(irs::format::ptr(), &INSTANCE);
+}
+
+
+DEFINE_FORMAT_TYPE_NAMED(::format13, "1_3");
+REGISTER_FORMAT_MODULE(::format13, MODULE_NAME);
+
 // ----------------------------------------------------------------------------
 // --SECTION--                                                      format12sse
 // ----------------------------------------------------------------------------
@@ -5618,7 +5705,7 @@ class format12simd final : public format12 {
 }; // format12simd
 
 irs::postings_writer::ptr format12simd::get_postings_writer(bool volatile_state) const {
-  constexpr const auto VERSION = postings_writer_base::FORMAT_MAX;
+  constexpr const auto VERSION = postings_writer_base::FORMAT_SSE_POSITIONS_ONEBASED;
 
   if (volatile_state) {
     return memory::make_unique<::postings_writer<format_traits_simd, true>>(VERSION);
@@ -5628,7 +5715,7 @@ irs::postings_writer::ptr format12simd::get_postings_writer(bool volatile_state)
 }
 
 irs::postings_reader::ptr format12simd::get_postings_reader() const {
-  return irs::postings_reader::make<::postings_reader<format_traits_simd>>();
+  return irs::postings_reader::make<::postings_reader<format_traits_simd, true>>();
 }
 
 /*static*/ irs::format::ptr format12simd::make() {
@@ -5641,6 +5728,46 @@ irs::postings_reader::ptr format12simd::get_postings_reader() const {
 DEFINE_FORMAT_TYPE_NAMED(::format12simd, "1_2simd");
 REGISTER_FORMAT_MODULE(::format12simd, MODULE_NAME);
 
+
+// ----------------------------------------------------------------------------
+// --SECTION--                                                      format13sse
+// ----------------------------------------------------------------------------
+
+class format13simd final : public format13 {
+ public:
+  DECLARE_FORMAT_TYPE();
+  DECLARE_FACTORY();
+
+  format13simd() noexcept : format13(format13simd::type()) { }
+
+  virtual irs::postings_writer::ptr get_postings_writer(bool volatile_state) const override;
+  virtual irs::postings_reader::ptr get_postings_reader() const override;
+}; // format13simd
+
+irs::postings_writer::ptr format13simd::get_postings_writer(bool volatile_state) const {
+  constexpr const auto VERSION = postings_writer_base::FORMAT_SSE_POSITIONS_ZEROBASED;
+
+  if (volatile_state) {
+    return memory::make_unique<::postings_writer<format_traits_simd, true>>(VERSION);
+  }
+
+  return memory::make_unique<::postings_writer<format_traits_simd, false>>(VERSION);
+}
+
+irs::postings_reader::ptr format13simd::get_postings_reader() const {
+  return irs::postings_reader::make<::postings_reader<format_traits_simd, false>>();
+}
+
+/*static*/ irs::format::ptr format13simd::make() {
+  static const ::format13simd INSTANCE;
+
+  // aliasing constructor
+  return irs::format::ptr(irs::format::ptr(), &INSTANCE);
+}
+
+DEFINE_FORMAT_TYPE_NAMED(::format13simd, "1_3simd");
+REGISTER_FORMAT_MODULE(::format13simd, MODULE_NAME);
+
 #endif // IRESEARCH_SSE2
 
 NS_END
diff --git a/3rdParty/iresearch/core/formats/formats_burst_trie.cpp b/3rdParty/iresearch/core/formats/formats_burst_trie.cpp
index 7114742ac918..85d786ec5c14 100644
--- a/3rdParty/iresearch/core/formats/formats_burst_trie.cpp
+++ b/3rdParty/iresearch/core/formats/formats_burst_trie.cpp
@@ -786,6 +786,7 @@ class automaton_term_iterator final : public term_iterator_base {
     : term_iterator_base(owner),
       acceptor_(&matcher.GetFst()),
       matcher_(&matcher) {
+    attrs_.emplace(payload_);
   }
 
   virtual bool next() override;
@@ -893,6 +894,14 @@ class automaton_term_iterator final : public term_iterator_base {
     automaton::StateId state_;  // state to which current block belongs
   }; // block_iterator
 
+  struct payload : irs::payload {
+    payload() noexcept {
+      irs::payload::value = bytes_ref(&value, sizeof(value));
+    }
+
+    automaton::Weight::PayloadType value;
+  }; // payload
+
   typedef std::deque<block_iterator> block_stack_t;
 
   block_iterator* pop_block() noexcept {
@@ -924,6 +933,7 @@ class automaton_term_iterator final : public term_iterator_base {
   automaton_table_matcher* matcher_;
   block_stack_t block_stack_;
   block_iterator* cur_block_{};
+  payload payload_{}; // payload of the matched automaton state
 }; // automaton_term_iterator
 
 bool automaton_term_iterator::next() {
@@ -999,7 +1009,9 @@ bool automaton_term_iterator::next() {
 
     switch (cur_block_->type()) {
       case ET_TERM: {
-        if (acceptor_->Final(state)) {
+        const auto weight = acceptor_->Final(state);
+        if (weight) {
+          payload_.value = weight.Payload();
           copy(suffix, cur_block_->prefix(), suffix_size);
           match = MATCH;
         }
@@ -2437,7 +2449,7 @@ irs::field_iterator::ptr field_reader::iterator() const {
   return memory::make_managed<irs::field_iterator, true>(it.release());
 }
 
-size_t field_reader::size() const {
+size_t field_reader::size() const noexcept {
   return fields_.size();
 }
 
diff --git a/3rdParty/iresearch/core/formats/formats_burst_trie.hpp b/3rdParty/iresearch/core/formats/formats_burst_trie.hpp
index 46fd23687f82..e32270e97d22 100644
--- a/3rdParty/iresearch/core/formats/formats_burst_trie.hpp
+++ b/3rdParty/iresearch/core/formats/formats_burst_trie.hpp
@@ -396,7 +396,7 @@ class field_reader final : public irs::field_reader {
 
   virtual const irs::term_reader* field(const string_ref& field) const override;
   virtual irs::field_iterator::ptr iterator() const override;
-  virtual size_t size() const override;
+  virtual size_t size() const noexcept override;
 
  private:
   friend class detail::term_iterator_base;
diff --git a/3rdParty/iresearch/core/index/field_data.cpp b/3rdParty/iresearch/core/index/field_data.cpp
index 9638310d8609..07e48e812e23 100644
--- a/3rdParty/iresearch/core/index/field_data.cpp
+++ b/3rdParty/iresearch/core/index/field_data.cpp
@@ -224,8 +224,9 @@ class pos_iterator final: public irs::position {
       pay_.resize(size);
       prox_in_.read(pay_.data(), size);
     }
-
+    
     value_ += pos;
+    assert(pos_limits::valid(value_));
 
     if (has_offs_) {
       offs_.start += irs::vread<uint32_t>(prox_in_);
@@ -237,6 +238,10 @@ class pos_iterator final: public irs::position {
     return true;
   }
 
+  virtual void reset() override {
+    assert(false); // unsupported
+  }
+
  private:
   Reader prox_in_;
   const frequency* freq_{}; // number of term positions in a document
@@ -778,7 +783,7 @@ void field_data::reset(doc_id_t doc_id) {
     return; // nothing to do
   }
 
-  pos_ = integer_traits<uint32_t>::const_max;
+  pos_ = pos_limits::invalid();
   last_pos_ = 0;
   len_ = 0;
   num_overlap_ = 0;
diff --git a/3rdParty/iresearch/core/index/index_reader.hpp b/3rdParty/iresearch/core/index/index_reader.hpp
index 16363ba6c3d1..33f04e90af1d 100644
--- a/3rdParty/iresearch/core/index/index_reader.hpp
+++ b/3rdParty/iresearch/core/index/index_reader.hpp
@@ -107,7 +107,7 @@ struct IRESEARCH_API index_reader {
   virtual size_t size() const = 0;
 
   // first sub-segment
-  reader_iterator begin() const {
+  reader_iterator begin() const noexcept {
     return reader_iterator(*this, 0);
   }
 
diff --git a/3rdParty/iresearch/core/iql/query_builder.cpp b/3rdParty/iresearch/core/iql/query_builder.cpp
index 70a803eb12fb..9561055e5bbc 100644
--- a/3rdParty/iresearch/core/iql/query_builder.cpp
+++ b/3rdParty/iresearch/core/iql/query_builder.cpp
@@ -223,7 +223,7 @@ const irs::iql::query_builder::branch_builder_function_t SIMILAR_BRANCH_BUILDER
     auto& node = root.proxy<irs::by_phrase>().field(field);
 
     for (auto& term = tokens->attributes().get<irs::term_attribute>(); tokens->next();) {
-      node.push_back(term->value());
+      node.push_back(irs::by_phrase::simple_term{term->value()});
     }
 
     return true;
diff --git a/3rdParty/iresearch/core/search/bm25.cpp b/3rdParty/iresearch/core/search/bm25.cpp
index b16ee0dbbfd1..c15ebd6c03aa 100644
--- a/3rdParty/iresearch/core/search/bm25.cpp
+++ b/3rdParty/iresearch/core/search/bm25.cpp
@@ -304,14 +304,16 @@ struct score_ctx : public irs::score_ctx {
       float_t k, 
       irs::boost_t boost,
       const bm25::stats& stats,
-      const frequency* freq) noexcept
-    : freq_(freq ? freq : &EMPTY_FREQ),
+      const frequency* freq,
+      const filter_boost* fb = nullptr) noexcept
+    : freq_(freq ? freq : &EMPTY_FREQ), filter_boost_(fb),
       num_(boost * (k + 1) * stats.idf),
-      norm_const_(k) {
+      norm_const_(k)  {
     assert(freq_);
   }
 
   const frequency* freq_; // document frequency
+  const filter_boost* filter_boost_;
   float_t num_; // partially precomputed numerator : boost * (k + 1) * idf
   float_t norm_const_; // 'k' factor
 }; // score_ctx
@@ -323,8 +325,9 @@ struct norm_score_ctx final : public score_ctx {
       irs::boost_t boost,
       const bm25::stats& stats,
       const frequency* freq,
-      irs::norm&& norm) noexcept
-    : score_ctx(k, boost, stats, freq),
+      irs::norm&& norm,
+      const filter_boost* fb = nullptr) noexcept
+    : score_ctx(k, boost, stats, freq, fb),
       norm_(std::move(norm)) {
     // if there is no norms, assume that b==0
     if (!norm_.empty()) {
@@ -417,6 +420,7 @@ class sort final : public irs::sort::prepared_basic<bm25::score_t, bm25::stats>
     }
 
     auto& stats = stats_cast(query_stats);
+    auto& filter_boost = doc_attrs.get<irs::filter_boost>();
 
     if (b_ != 0.f) {
       irs::norm norm;
@@ -429,28 +433,55 @@ class sort final : public irs::sort::prepared_basic<bm25::score_t, bm25::stats>
       }
 
       if (norm.reset(segment, field.meta().norm, *doc)) {
-        return { 
-          memory::make_unique<bm25::norm_score_ctx>(k_, boost, stats, freq.get(), std::move(norm)),
-          [](const irs::score_ctx* ctx, byte_type* RESTRICT score_buf) noexcept {
+        if (filter_boost) {
+          return {
+            memory::make_unique<bm25::norm_score_ctx>(k_, boost, stats, freq.get(), std::move(norm), filter_boost.get()),
+            [](const irs::score_ctx* ctx, byte_type* RESTRICT score_buf) noexcept {
             auto& state = *static_cast<const bm25::norm_score_ctx*>(ctx);
-
+            assert(state.filter_boost_);
             const float_t tf = ::SQRT(state.freq_->value);
-            irs::sort::score_cast<score_t>(score_buf) = state.num_ * tf / (state.norm_const_ + state.norm_length_ * state.norm_.read() + tf);
-          }
-        };
+            irs::sort::score_cast<score_t>(score_buf) = state.filter_boost_->value *  
+                                                        state.num_ * 
+                                                        tf / 
+                                                        (state.norm_const_ + state.norm_length_ * state.norm_.read() + tf);
+            }
+          };
+        } else {
+          return {
+            memory::make_unique<bm25::norm_score_ctx>(k_, boost, stats, freq.get(), std::move(norm)),
+            [](const irs::score_ctx* ctx, byte_type* RESTRICT score_buf) noexcept {
+              auto& state = *static_cast<const bm25::norm_score_ctx*>(ctx);
+
+              const float_t tf = ::SQRT(state.freq_->value);
+              irs::sort::score_cast<score_t>(score_buf) = state.num_ * tf / (state.norm_const_ + state.norm_length_ * state.norm_.read() + tf);
+            }
+          };
+        }
       }
     }
 
-    // BM11
-    return { 
-      memory::make_unique<bm25::score_ctx>(k_, boost, stats, freq.get()),
-      [](const irs::score_ctx* ctx, byte_type* RESTRICT score_buf) noexcept {
+    // BM15
+    if (filter_boost) {
+      return {
+        memory::make_unique<bm25::score_ctx>(k_, boost, stats, freq.get(), filter_boost.get()),
+        [](const irs::score_ctx* ctx, byte_type* RESTRICT score_buf) noexcept {
         auto& state = *static_cast<const bm25::score_ctx*>(ctx);
-
+        assert(state.filter_boost_);
         const float_t tf = ::SQRT(state.freq_->value);
-        irs::sort::score_cast<score_t>(score_buf) = state.num_ * tf / (state.norm_const_ + tf);
-      }
-    };
+        irs::sort::score_cast<score_t>(score_buf) = state.filter_boost_->value *  state.num_ * tf / (state.norm_const_ + tf);
+        }
+      };
+    } else {
+      return {
+        memory::make_unique<bm25::score_ctx>(k_, boost, stats, freq.get()),
+        [](const irs::score_ctx* ctx, byte_type* RESTRICT score_buf) noexcept {
+          auto& state = *static_cast<const bm25::score_ctx*>(ctx);
+
+          const float_t tf = ::SQRT(state.freq_->value);
+          irs::sort::score_cast<score_t>(score_buf) = state.num_ * tf / (state.norm_const_ + tf);
+        }
+      };
+    }
   }
 
   virtual irs::sort::term_collector::ptr prepare_term_collector() const override {
diff --git a/3rdParty/iresearch/core/search/disjunction.hpp b/3rdParty/iresearch/core/search/disjunction.hpp
index bcf0c06f6fab..bd7ff509d664 100644
--- a/3rdParty/iresearch/core/search/disjunction.hpp
+++ b/3rdParty/iresearch/core/search/disjunction.hpp
@@ -29,6 +29,7 @@
 #include "utils/std.hpp"
 #include "utils/type_limits.hpp"
 #include "index/iterators.hpp"
+#include "utils/attribute_range.hpp"
 
 NS_ROOT
 NS_BEGIN(detail)
@@ -67,12 +68,126 @@ void evaluate_score_iter(const irs::byte_type**& pVal,  DocIterator& src) {
 NS_END // detail
 
 ////////////////////////////////////////////////////////////////////////////////
-/// @class basic_disjunction
+/// @class position_score_iterator_adapter
+/// @brief adapter to use doc_iterator with positions for disjunction
 ////////////////////////////////////////////////////////////////////////////////
 template<typename DocIterator>
-class basic_disjunction final : public doc_iterator_base, score_ctx {
+struct position_score_iterator_adapter : score_iterator_adapter<DocIterator> {
+  position_score_iterator_adapter(typename position_score_iterator_adapter<DocIterator>::doc_iterator_t&& it) noexcept
+    : score_iterator_adapter<DocIterator>(std::move(it)) {
+    auto& attrs = this->it->attributes();
+    position = irs::position::extract(attrs);
+  }
+
+  position_score_iterator_adapter(const position_score_iterator_adapter&) = default;
+  position_score_iterator_adapter& operator=(const position_score_iterator_adapter&) = default;
+
+  position_score_iterator_adapter(position_score_iterator_adapter&& rhs) noexcept
+    : score_iterator_adapter<DocIterator>(std::move(rhs)),
+      position(std::move(rhs.position)) {
+  }
+
+  position_score_iterator_adapter& operator=(position_score_iterator_adapter&& rhs) noexcept {
+    if (this != &rhs) {
+      score_iterator_adapter<DocIterator>::operator=(std::move(rhs));
+      position = rhs.position;
+    }
+    return *this;
+  }
+
+  irs::position* position;
+}; // position_score_iterator_adapter
+
+template<typename Adapter>
+class attribute_range_adapter {
+ public:
+  attribute_range_adapter(typename attribute_view::ref<attribute_range<Adapter>>::type& map_attribute_range) {
+    map_attribute_range = &attribute_range_;
+  }
+
+ protected:
+  attribute_range<Adapter> attribute_range_;
+};
+
+template<typename Adapter>
+class unary_disjunction_state : protected attribute_range_state<Adapter> {
+ protected:
+  bool state_finished_; // is all iterators exhausted
+};
+
+template<typename Adapter>
+class basic_disjunction_state : protected attribute_range_state<Adapter> {
+ protected:
+  bool state_finished_; // is all iterators exhausted
+  bool state_is_min_; // is current iterator has a minimal value
+  bool state_is_new_document_; // is a document value updated
+};
+
+template<typename Adapter>
+class small_disjunction_state : protected attribute_range_state<Adapter> {
+ protected:
+  bool state_finished_; // is all iterators exhausted
+  size_t state_idx_; // current index
+  bool state_is_new_document_; // is a document value updated
+};
+
+template<typename Adapter>
+class disjunction_state : protected attribute_range_state<Adapter> {
+ protected:
+  bool state_finished_; // is all iterators exhausted
+  size_t state_idx_; // current heap index
+  bool state_is_new_document_; // is a document value updated
+};
+
+////////////////////////////////////////////////////////////////////////////////
+/// @class unary_disjunction
+////////////////////////////////////////////////////////////////////////////////
+template<typename DocIterator, typename Adapter = score_iterator_adapter<DocIterator>>
+class unary_disjunction final : public doc_iterator_base, attribute_range_adapter<Adapter>, unary_disjunction_state<Adapter> {
+ public:
+  typedef Adapter doc_iterator_t;
+
+  unary_disjunction(doc_iterator_t&& it)
+    : attribute_range_adapter<Adapter>(attrs_.emplace<irs::attribute_range<Adapter>>()),
+      doc_(doc_limits::invalid()),
+      it_(std::move(it)) {
+    attrs_.emplace<irs::document>(*it_->attributes().template get<irs::document>());
+    this->attribute_range_.set_state(this);
+  }
+
+  virtual doc_id_t value() const noexcept override {
+    return it_.value();
+  }
+
+  virtual bool next() override {
+    return it_->next();
+  }
+
+  virtual doc_id_t seek(doc_id_t target) override {
+    return it_->seek(target);
+  }
+
+ private:
+  virtual Adapter* get_next_iterator() override {
+    return this->state_finished_ ? nullptr : (this->state_finished_ = true, &it_);
+  }
+
+  virtual void reset_next_iterator_state() override {
+    this->state_finished_ = false;
+  }
+
+  document doc_;
+  doc_iterator_t it_;
+}; // unary_disjunction
+
+////////////////////////////////////////////////////////////////////////////////
+/// @class basic_disjunction
+/// @brief use for special adapters only
+////////////////////////////////////////////////////////////////////////////////
+template<typename DocIterator, typename Adapter = score_iterator_adapter<DocIterator>>
+class basic_disjunction final : public doc_iterator_base, score_ctx, attribute_range_adapter<Adapter>, basic_disjunction_state<Adapter> {
  public:
-  typedef score_iterator_adapter<DocIterator> doc_iterator_t;
+  typedef Adapter doc_iterator_t;
 
   basic_disjunction(
       doc_iterator_t&& lhs,
@@ -103,12 +218,14 @@ class basic_disjunction final : public doc_iterator_base, score_ctx {
   }
 
   virtual bool next() override {
+    this->state_is_new_document_ = true;
     next_iterator_impl(lhs_);
     next_iterator_impl(rhs_);
     return !doc_limits::eof(doc_.value = std::min(lhs_.value(), rhs_.value()));
   }
 
   virtual doc_id_t seek(doc_id_t target) override {
+    this->state_is_new_document_ = true;
     if (target <= doc_.value) {
       return doc_.value;
     }
@@ -128,10 +245,12 @@ class basic_disjunction final : public doc_iterator_base, score_ctx {
       doc_iterator_t&& rhs,
       const order::prepared& ord,
       resolve_overload_tag)
-    : lhs_(std::move(lhs)),
+    : attribute_range_adapter<Adapter>(attrs_.emplace<irs::attribute_range<Adapter>>()),
+      lhs_(std::move(lhs)),
       rhs_(std::move(rhs)),
       doc_(doc_limits::invalid()),
       ord_(&ord) {
+    this->attribute_range_.set_state(this);
     // make 'document' attribute accessible from outside
     attrs_.emplace(doc_);
     // prepare score
@@ -203,6 +322,43 @@ class basic_disjunction final : public doc_iterator_base, score_ctx {
     return false;
   }
 
+  virtual Adapter* get_next_iterator() override {
+    if (this->state_finished_) {
+      return nullptr;
+    }
+
+    auto l_value = lhs_.value();
+    auto r_value = rhs_.value();
+    if (this->state_is_min_) {
+      if (l_value == doc_.value && r_value != doc_.value) {
+        this->state_finished_ = true;
+        return &lhs_;
+      }
+
+      if (r_value == doc_.value && l_value != doc_.value) {
+        this->state_finished_ = true;
+        return &rhs_;
+      }
+
+      this->state_is_min_ = false;
+      return r_value < l_value ? &rhs_ : &lhs_;
+    }
+
+    this->state_finished_ = true;
+    return r_value < l_value ? &lhs_ : &rhs_;
+  }
+
+  virtual void reset_next_iterator_state() override {
+    // call after success next() or seek()
+    assert(!doc_limits::eof(doc_.value));
+    if (this->state_is_new_document_) {
+      seek_iterator_impl(rhs_, doc_.value);
+      this->state_is_new_document_ = false;
+    }
+    this->state_is_min_ = true;
+    this->state_finished_ = false;
+  }
+
   mutable doc_iterator_t lhs_;
   mutable doc_iterator_t rhs_;
   mutable const irs::byte_type* scores_vals_[2];
@@ -214,10 +370,10 @@ class basic_disjunction final : public doc_iterator_base, score_ctx {
 /// @class small_disjunction
 /// @brief linear search based disjunction
 ////////////////////////////////////////////////////////////////////////////////
-template<typename DocIterator>
-class small_disjunction : public doc_iterator_base, score_ctx {
+template<typename DocIterator, typename Adapter = score_iterator_adapter<DocIterator>>
+class small_disjunction : public doc_iterator_base, score_ctx, attribute_range_adapter<Adapter>, small_disjunction_state<Adapter> {
  public:
-  typedef score_iterator_adapter<DocIterator> doc_iterator_t;
+  typedef Adapter doc_iterator_t;
   typedef std::vector<doc_iterator_t> doc_iterators_t;
 
   small_disjunction(
@@ -260,6 +416,7 @@ class small_disjunction : public doc_iterator_base, score_ctx {
   }
 
   virtual bool next() override {
+    this->state_is_new_document_ = true;
     if (doc_limits::eof(doc_.value)) {
       return false;
     }
@@ -288,6 +445,7 @@ class small_disjunction : public doc_iterator_base, score_ctx {
   }
 
   virtual doc_id_t seek(doc_id_t target) override {
+    this->state_is_new_document_ = true;
     if (doc_limits::eof(doc_.value)) {
       return doc_.value;
     }
@@ -329,11 +487,13 @@ class small_disjunction : public doc_iterator_base, score_ctx {
       doc_iterators_t&& itrs,
       const order::prepared& ord,
       resolve_overload_tag)
-    : itrs_(std::move(itrs)),
+    : attribute_range_adapter<Adapter>(attrs_.emplace<irs::attribute_range<Adapter>>()),
+      itrs_(std::move(itrs)),
       doc_(itrs_.empty()
         ? doc_limits::eof()
         : doc_limits::invalid()),
       ord_(&ord) {
+    this->attribute_range_.set_state(this);
     // copy iterators with scores into separate container
     // to avoid extra checks
     scored_itrs_.reserve(itrs_.size());
@@ -376,6 +536,43 @@ class small_disjunction : public doc_iterator_base, score_ctx {
     return !itrs_.empty();
   }
 
+  void hitch_all_iterators() {
+    for (auto rbegin = itrs_.rbegin(); rbegin != itrs_.rend();) {
+      auto& it = *rbegin;
+      ++rbegin;
+      if (it.value() < doc_.value && doc_limits::eof(it->seek(doc_.value))) {
+        #ifdef IRESEARCH_DEBUG
+          assert(remove_iterator(it));
+        #else
+          remove_iterator(it);
+        #endif
+      }
+    }
+  }
+
+  virtual Adapter* get_next_iterator() override {
+    if (this->state_finished_) {
+      return nullptr;
+    }
+    auto size = itrs_.size();
+    for (; this->state_idx_ < size && itrs_[this->state_idx_].value() != doc_.value; ++this->state_idx_) {}
+
+    if (size == this->state_idx_) {
+      this->state_finished_ = true;
+      return nullptr;
+    }
+    return &itrs_[this->state_idx_++];
+  }
+
+  virtual void reset_next_iterator_state() override {
+    if (this->state_is_new_document_) {
+      hitch_all_iterators();
+      this->state_is_new_document_ = false;
+    }
+    this->state_finished_ = false;
+    this->state_idx_ = 0;
+  }
+
   doc_iterators_t itrs_;
   doc_iterators_t scored_itrs_; // iterators with scores
   document doc_;
@@ -395,14 +592,20 @@ class small_disjunction : public doc_iterator_base, score_ctx {
 ///   [n]   <-- lead (accepted iterator)
 /// ----------------------------------------------------------------------------
 ////////////////////////////////////////////////////////////////////////////////
-template<typename DocIterator>
-class disjunction : public doc_iterator_base, score_ctx {
+template<typename DocIterator, typename Adapter = score_iterator_adapter<DocIterator>, bool EnableUnary = false>
+class disjunction : public doc_iterator_base, score_ctx, attribute_range_adapter<Adapter>, disjunction_state<Adapter> {
  public:
-  typedef small_disjunction<DocIterator> small_disjunction_t;
-  typedef basic_disjunction<DocIterator> basic_disjunction_t;
-  typedef score_iterator_adapter<DocIterator> doc_iterator_t;
+  typedef small_disjunction<DocIterator, Adapter> small_disjunction_t;
+  typedef basic_disjunction<DocIterator, Adapter> basic_disjunction_t;
+  typedef unary_disjunction<DocIterator, Adapter> unary_disjunction_t;
+  typedef Adapter doc_iterator_t;
   typedef std::vector<doc_iterator_t> doc_iterators_t;
 
+  typedef std::vector<size_t> heap_container;
+  typedef heap_container::iterator heap_iterator;
+
+  static const bool kEnableUnary = EnableUnary;
+
   disjunction(
       doc_iterators_t&& itrs,
       const order::prepared& ord,
@@ -431,6 +634,7 @@ class disjunction : public doc_iterator_base, score_ctx {
   }
 
   virtual bool next() override {
+    this->state_is_new_document_ = true;
     if (doc_limits::eof(doc_.value)) {
       return false;
     }
@@ -449,10 +653,12 @@ class disjunction : public doc_iterator_base, score_ctx {
     }
 
     doc_.value = lead().value();
+
     return true;
   }
 
   virtual doc_id_t seek(doc_id_t target) override {
+    this->state_is_new_document_ = true;
     if (doc_limits::eof(doc_.value)) {
       return doc_.value;
     }
@@ -477,11 +683,14 @@ class disjunction : public doc_iterator_base, score_ctx {
       doc_iterators_t&& itrs,
       const order::prepared& ord,
       resolve_overload_tag)
-    : itrs_(std::move(itrs)),
+    : attribute_range_adapter<Adapter>(attrs_.emplace<irs::attribute_range<Adapter>>()),
+      itrs_(std::move(itrs)),
       doc_(itrs_.empty()
         ? doc_limits::eof()
         : doc_limits::invalid()),
       ord_(&ord) {
+    this->attribute_range_.set_state(this);
+
     // since we are using heap in order to determine next document,
     // in order to avoid useless make_heap call we expect that all
     // iterators are equal here */
@@ -556,9 +765,7 @@ class disjunction : public doc_iterator_base, score_ctx {
     return itrs_[heap_.front()];
   }
 
-  void score_impl(byte_type* lhs) {
-    assert(!heap_.empty());
-
+  std::pair<heap_iterator, heap_iterator> hitch_all_iterators() {
     // hitch all iterators in head to the lead (current doc_)
     auto begin = heap_.begin(), end = heap_.end()-1;
 
@@ -576,16 +783,23 @@ class disjunction : public doc_iterator_base, score_ctx {
         push(begin,end);
       }
     }
+    return {begin, end};
+  }
+
+  void score_impl(byte_type* lhs) {
+    assert(!heap_.empty());
+
+    auto its = hitch_all_iterators();
     const irs::byte_type** pVal = scores_vals_.data();
     detail::evaluate_score_iter(pVal, lead());
     if (top().value() == doc_.value) {
       irstd::heap::for_each_if(
-        begin, end,
+        its.first, its.second,
         [this](const size_t it) {
           assert(it < itrs_.size());
           return itrs_[it].value() == doc_.value;
         },
-        [this, lhs, &pVal](size_t it) {
+        [this, &pVal](size_t it) {
           assert(it < itrs_.size());
           detail::evaluate_score_iter(pVal, itrs_[it]);
       });
@@ -593,8 +807,68 @@ class disjunction : public doc_iterator_base, score_ctx {
     ord_->merge(lhs, scores_vals_.data(), std::distance(scores_vals_.data(), pVal));
   }
 
+  Adapter* get_next_iterator() override {
+    // if exhausted
+    if (this->state_finished_) {
+      return nullptr;
+    }
+    const auto size = heap_.size();
+    // if the first time
+    if (std::numeric_limits<size_t>::max() == this->state_idx_) {
+      this->state_idx_ = 0;
+      if (1 == size) {
+        this->state_finished_ = true;
+      }
+      assert(heap_.back() < itrs_.size());
+      return &itrs_[heap_.back()];
+    }
+    assert(size > 1);
+    const auto bottom = size - 1;
+    do {
+      if (this->state_idx_ < bottom) {
+        assert(heap_[this->state_idx_] < itrs_.size());
+        auto& itr = itrs_[heap_[this->state_idx_]];
+        if (itr.value() == doc_.value) {
+          this->state_idx_ = (this->state_idx_ << 1) + 1;
+          return &itr;
+        }
+      }
+      do {
+        if (0 == this->state_idx_) {
+          this->state_finished_ = true;
+          return nullptr;
+        }
+        const auto up_idx = (this->state_idx_ - 1) >> 1;
+        if ((this->state_idx_ & 1) == 0) {
+          assert((up_idx << 1) + 2 == this->state_idx_);
+          this->state_idx_ = up_idx;
+          continue;
+        }
+        assert((up_idx << 1) + 1 == this->state_idx_);
+        this->state_idx_ += 1;
+        break;
+      } while (true);
+    } while (true);
+
+    assert(false);
+    this->state_finished_ = true;
+    return nullptr;
+  }
+
+  virtual void reset_next_iterator_state() override {
+    // call after success next() or seek()
+    assert(!doc_limits::eof(doc_.value));
+    assert(!heap_.empty());
+    if (this->state_is_new_document_) {
+      hitch_all_iterators();
+      this->state_is_new_document_ = false;
+    }
+    this->state_finished_ = false;
+    this->state_idx_ = std::numeric_limits<size_t>::max();
+  }
+
   doc_iterators_t itrs_;
-  std::vector<size_t> heap_;
+  heap_container heap_;
   mutable std::vector<const irs::byte_type*> scores_vals_;
   document doc_;
   const order::prepared* ord_;
@@ -614,6 +888,12 @@ doc_iterator::ptr make_disjunction(
       // empty or unreachable search criteria
       return doc_iterator::empty();
     case 1:
+      if /*constexpr*/ (Disjunction::kEnableUnary) {
+        typedef typename Disjunction::unary_disjunction_t unary_disjunction_t;
+        return doc_iterator::make<unary_disjunction_t>(
+          std::move(itrs.front())
+        );
+      }
       // single sub-query
       return std::move(itrs.front());
     case 2: {
diff --git a/3rdParty/iresearch/core/search/granular_range_filter.cpp b/3rdParty/iresearch/core/search/granular_range_filter.cpp
index 2176fe084ad5..b89377f39263 100644
--- a/3rdParty/iresearch/core/search/granular_range_filter.cpp
+++ b/3rdParty/iresearch/core/search/granular_range_filter.cpp
@@ -161,11 +161,10 @@ void collect_terms_between(
     return; // skipped current term and no more terms in segment
   }
 
-  const auto& masked_begin_term = mask_value(terms.value(), prefix_size); // the starting term for range collection
   const auto& masked_end_term = mask_value(end_term, prefix_size); // the ending term for range collection
 
   collect_terms(
-    states, sr, tr, terms, scorer, [&prefix_size, &masked_begin_level, &masked_begin_term, &masked_end_term, include_end_term](
+    states, sr, tr, terms, scorer, [&prefix_size, &masked_begin_level, &masked_end_term, include_end_term](
       const irs::term_iterator& itr
     )->bool {
       const auto& masked_current_level = mask_granularity(itr.value(), prefix_size);
diff --git a/3rdParty/iresearch/core/search/levenshtein_filter.cpp b/3rdParty/iresearch/core/search/levenshtein_filter.cpp
index c2be0bf81bd9..8900fdc1d1cd 100644
--- a/3rdParty/iresearch/core/search/levenshtein_filter.cpp
+++ b/3rdParty/iresearch/core/search/levenshtein_filter.cpp
@@ -24,6 +24,7 @@
 
 #include "shared.hpp"
 #include "limited_sample_scorer.hpp"
+#include "term_query.hpp"
 #include "index/index_reader.hpp"
 #include "utils/automaton_utils.hpp"
 #include "utils/levenshtein_utils.hpp"
@@ -37,27 +38,29 @@ NS_ROOT
 DEFINE_FILTER_TYPE(by_edit_distance)
 DEFINE_FACTORY_DEFAULT(by_edit_distance)
 
-filter::prepared::ptr by_edit_distance::prepare(
+/*static*/ filter::prepared::ptr by_edit_distance::prepare(
     const index_reader& index,
     const order::prepared& order,
     boost_t boost,
-    const attribute_view& ctx) const {
-  if (0 == max_distance_) {
-    return by_term::prepare(index, order, boost, ctx);
+    const string_ref& field,
+    const bytes_ref& term,
+    size_t scored_terms_limit,
+    byte_type max_distance,
+    pdp_f provider,
+    bool with_transpositions) {
+  if (0 == max_distance) {
+    return term_query::make(index, order, boost, field, term);
   }
 
-  assert(provider_);
-  const auto& d = (*provider_)(max_distance_, with_transpositions_);
+  assert(provider);
+  const auto& d = (*provider)(max_distance, with_transpositions);
 
   if (!d) {
     return prepared::empty();
   }
 
-  boost *= this->boost();
-  const string_ref field = this->field();
-
-  return prepare_automaton_filter(field, make_levenshtein_automaton(d, term()),
-                                  scored_terms_limit(), index, order, boost);
+  return prepare_automaton_filter(field, make_levenshtein_automaton(d, term),
+                                  scored_terms_limit, index, order, boost);
 }
 
 by_edit_distance::by_edit_distance() noexcept
diff --git a/3rdParty/iresearch/core/search/levenshtein_filter.hpp b/3rdParty/iresearch/core/search/levenshtein_filter.hpp
index 8b6b1300b418..03f9ff9e693f 100644
--- a/3rdParty/iresearch/core/search/levenshtein_filter.hpp
+++ b/3rdParty/iresearch/core/search/levenshtein_filter.hpp
@@ -45,6 +45,17 @@ class IRESEARCH_API by_edit_distance final : public by_prefix {
   //////////////////////////////////////////////////////////////////////////////
   using pdp_f = const parametric_description&(*)(byte_type, bool);
 
+  static prepared::ptr prepare(
+    const index_reader& index,
+    const order::prepared& order,
+    boost_t boost,
+    const string_ref& field,
+    const bytes_ref& term,
+    size_t scored_terms_limit,
+    byte_type max_distance,
+    pdp_f provider,
+    bool with_transpositions);
+
   explicit by_edit_distance() noexcept;
 
   using by_prefix::field;
@@ -57,11 +68,27 @@ class IRESEARCH_API by_edit_distance final : public by_prefix {
   using filter::prepare;
 
   virtual filter::prepared::ptr prepare(
-    const index_reader& rdr,
-    const order::prepared& ord,
-    boost_t boost,
-    const attribute_view& ctx
-  ) const override;
+      const index_reader& index,
+      const order::prepared& order,
+      boost_t boost,
+      const attribute_view& /*ctx*/) const override {
+    return prepare(index, order, this->boost()*boost,
+                   field(), term(), scored_terms_limit(),
+                   max_distance_, provider_, with_transpositions_);
+  }
+
+
+  using by_prefix::scored_terms_limit;
+
+  //////////////////////////////////////////////////////////////////////////////
+  /// @brief the maximum number of most frequent terms to consider for scoring
+  //////////////////////////////////////////////////////////////////////////////
+  by_edit_distance& scored_terms_limit(size_t limit) noexcept {
+    by_prefix::scored_terms_limit(limit);
+    return *this;
+  }
+
+  
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief sets maximum allowed edit distance
@@ -119,6 +146,6 @@ class IRESEARCH_API by_edit_distance final : public by_prefix {
   bool with_transpositions_{false};
 }; // by_edit_distance
 
-#endif // IRESEARCH_LEVENSHTEIN_FILTER_H
-
 NS_END
+
+#endif // IRESEARCH_LEVENSHTEIN_FILTER_H
diff --git a/3rdParty/iresearch/core/search/limited_sample_scorer-heap.cpp b/3rdParty/iresearch/core/search/limited_sample_scorer-heap.cpp
deleted file mode 100644
index 66e95051ff98..000000000000
--- a/3rdParty/iresearch/core/search/limited_sample_scorer-heap.cpp
+++ /dev/null
@@ -1,204 +0,0 @@
-////////////////////////////////////////////////////////////////////////////////
-/// DISCLAIMER
-///
-/// Copyright 2019 ArangoDB GmbH, Cologne, Germany
-///
-/// Licensed under the Apache License, Version 2.0 (the "License");
-/// you may not use this file except in compliance with the License.
-/// You may obtain a copy of the License at
-///
-///     http://www.apache.org/licenses/LICENSE-2.0
-///
-/// Unless required by applicable law or agreed to in writing, software
-/// distributed under the License is distributed on an "AS IS" BASIS,
-/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-/// See the License for the specific language governing permissions and
-/// limitations under the License.
-///
-/// Copyright holder is ArangoDB GmbH, Cologne, Germany
-///
-/// @author Andrey Abramov
-////////////////////////////////////////////////////////////////////////////////
-
-#include "limited_sample_scorer.hpp"
-
-#include "analysis/token_attributes.hpp"
-#include "index/index_reader.hpp"
-#include "utils/hash_utils.hpp"
-
-NS_LOCAL
-
-struct state {
-  explicit state(const irs::index_reader& index,
-                   const irs::term_reader& field,
-                   const irs::order::prepared& order,
-                   size_t& state_offset)
-    : collectors(order.prepare_collectors(1)) { // 1 term per bstring because a range is treated as a disjunction
-
-    // once per every 'state' collect field statistics over the entire index
-    for (auto& segment: index) {
-      collectors.collect(segment, field); // collect field statistics once per segment
-    }
-
-    stats_offset = state_offset++;
-  }
-
-  irs::order::prepared::collectors collectors;
-  size_t stats_offset;
-};
-
-void set_doc_ids(irs::bitset& buf, const irs::term_iterator& term, size_t docs_count) {
-  docs_count += (irs::doc_limits::min)();
-  if (buf.size() < docs_count) {
-    buf.reset(docs_count); // ensure we have enough space
-  }
-
-  auto itr = term.postings(irs::flags::empty_instance());
-
-  if (!itr) {
-    return; // no doc_ids in iterator
-  }
-
-//FIXME use doc attribute
-//  auto* doc = itr->attributes().get<irs::document>().get();
-//
-//  if (!doc) {
-//    return; // no doc value
-//  }
-
-  while (itr->next()) {
-    buf.set(itr->value());
-  }
-};
-
-bool less(size_t lhs_priority, size_t rhs_priority,
-          size_t lhs_state_offset, size_t rhs_state_offset) noexcept {
-  return rhs_priority < lhs_priority
-      || (rhs_priority == lhs_priority && lhs_state_offset < rhs_state_offset);
-}
-
-NS_END
-
-NS_ROOT
-
-limited_sample_scorer::limited_sample_scorer(size_t scored_terms_limit)
-  : scored_terms_limit_(scored_terms_limit) {
-  scored_states_.reserve(scored_terms_limit);
-  scored_states_heap_.reserve(scored_terms_limit);
-}
-
-void limited_sample_scorer::score(const index_reader& index,
-                                  const order::prepared& order,
-                                  std::vector<bstring>& stats) {
-  if (!scored_terms_limit_) {
-    return; // nothing to score (optimization)
-  }
-
-  // stats for a specific term
-  std::unordered_map<hashed_bytes_ref, state> term_stats;
-
-  // iterate over all the states from which statistcis should be collected
-  size_t stats_offset = 0;
-  for (auto& scored_state : scored_states_) {
-    assert(scored_state.cookie);
-    auto& field = *scored_state.state->reader;
-    auto term_itr = field.iterator(); // FIXME
-    assert(term_itr);
-
-    // find the stats for the current term
-    const auto res = map_utils::try_emplace(
-      term_stats,
-      make_hashed_ref(bytes_ref(scored_state.term), std::hash<bytes_ref>()),
-      index, field, order, stats_offset);
-
-    // find term attributes using cached state
-    if (!term_itr->seek(bytes_ref::NIL, *(scored_state.cookie))) {
-      continue; // some internal error that caused the term to disappear
-    }
-
-    auto& stats_entry = res.first->second;
-
-    // collect statistics, 0 because only 1 term
-    stats_entry.collectors.collect(*scored_state.segment, field, 0, term_itr->attributes());
-
-    scored_state.state->scored_states.emplace_back(
-      std::move(scored_state.cookie),
-      stats_entry.stats_offset);
-  }
-
-  // iterate over all stats and apply/store order stats
-  stats.resize(stats_offset);
-  for (auto& entry : term_stats) {
-    auto& stats_entry = stats[entry.second.stats_offset];
-    stats_entry.resize(order.stats_size());
-    auto* stats_buf = const_cast<byte_type*>(stats_entry.data());
-
-    order.prepare_stats(stats_buf);
-    entry.second.collectors.finish(stats_buf, index);
-  }
-}
-
-void limited_sample_scorer::collect(
-    size_t priority,
-    size_t scored_state_id,
-    limited_sample_state& scored_state,
-    const sub_reader& segment,
-    const seek_term_iterator& term_itr) {
-  if (!scored_terms_limit_) {
-    // state will not be scored
-    // add all doc_ids from the doc_iterator to the unscored_docs
-    set_doc_ids(scored_state.unscored_docs, term_itr, segment.docs_count());
-
-    return; // nothing to collect (optimization)
-  }
-
-  auto less = [this](const size_t lhs, const size_t rhs) noexcept {
-    const auto& lhs_state = scored_states_[lhs];
-    const auto& rhs_state = scored_states_[rhs];
-
-    return ::less(lhs_state.priority, rhs_state.priority,
-                  lhs_state.state_offset, rhs_state.state_offset);
-  };
-
-  if (scored_states_.size() < scored_terms_limit_) {
-    // have not reached the scored state limit yet
-    scored_states_heap_.push_back(scored_states_.size());
-    scored_states_.emplace_back(priority, segment, scored_state,
-                                scored_state_id, term_itr.value(), term_itr.cookie());
-
-    std::push_heap(scored_states_heap_.begin(), scored_states_heap_.end(), less);
-    return;
-  }
-
-  auto& min_state = scored_states_[scored_states_heap_.front()];
-
-  if (::less(priority, min_state.priority, min_state.state_offset, scored_state_id)) { // FIXME
-    std::pop_heap(scored_states_heap_.begin(), scored_states_heap_.end(), less);
-
-    auto& state = scored_states_[scored_states_heap_.back()];
-    auto state_term_it = state.state->reader->iterator(); // FIXME cache iterator???
-
-    assert(state.cookie);
-    if (state_term_it->seek(bytes_ref::NIL, *state.cookie)) {
-      // state will not be scored
-      // add all doc_ids from the doc_iterator to the unscored_docs
-      set_doc_ids(state.state->unscored_docs, *state_term_it, state.segment->docs_count());
-    }
-
-    // update min state
-    state.priority = priority;
-    state.state = &scored_state;
-    state.cookie = term_itr.cookie();
-    state.term = term_itr.value();
-    state.segment = &segment;
-    state.state_offset = scored_state_id;
-
-    std::push_heap(scored_states_heap_.begin(), scored_states_heap_.end(), less);
-  } else {
-    // state will not be scored
-    // add all doc_ids from the doc_iterator to the unscored_docs
-    set_doc_ids(scored_state.unscored_docs, term_itr, segment.docs_count());
-  }
-}
-
-NS_END
diff --git a/3rdParty/iresearch/core/search/limited_sample_scorer-heap.hpp b/3rdParty/iresearch/core/search/limited_sample_scorer-heap.hpp
deleted file mode 100644
index 2c5d0464f33f..000000000000
--- a/3rdParty/iresearch/core/search/limited_sample_scorer-heap.hpp
+++ /dev/null
@@ -1,132 +0,0 @@
-////////////////////////////////////////////////////////////////////////////////
-/// DISCLAIMER
-///
-/// Copyright 2019 ArangoDB GmbH, Cologne, Germany
-///
-/// Licensed under the Apache License, Version 2.0 (the "License");
-/// you may not use this file except in compliance with the License.
-/// You may obtain a copy of the License at
-///
-///     http://www.apache.org/licenses/LICENSE-2.0
-///
-/// Unless required by applicable law or agreed to in writing, software
-/// distributed under the License is distributed on an "AS IS" BASIS,
-/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-/// See the License for the specific language governing permissions and
-/// limitations under the License.
-///
-/// Copyright holder is ArangoDB GmbH, Cologne, Germany
-///
-/// @author Andrey Abramov
-////////////////////////////////////////////////////////////////////////////////
-
-#ifndef IRESEARCH_LIMITED_SAMPLE_SCORER_H
-#define IRESEARCH_LIMITED_SAMPLE_SCORER_H
-
-#include "shared.hpp"
-#include "sort.hpp"
-#include "index/iterators.hpp"
-#include "utils/string.hpp"
-#include "utils/bitset.hpp"
-
-NS_ROOT
-
-struct sub_reader;
-struct index_reader;
-
-//////////////////////////////////////////////////////////////////////////////
-/// @struct limited_sample_state
-//////////////////////////////////////////////////////////////////////////////
-struct limited_sample_state {
-  limited_sample_state() = default;
-  limited_sample_state(limited_sample_state&& rhs) noexcept
-    : reader(rhs.reader),
-      scored_states(std::move(rhs.scored_states)),
-      unscored_docs(std::move(rhs.unscored_docs)) {
-    rhs.reader = nullptr;
-  }
-  limited_sample_state& operator=(limited_sample_state&& rhs) noexcept {
-    if (this != &rhs) {
-      scored_states = std::move(rhs.scored_states);
-      unscored_docs = std::move(rhs.unscored_docs);
-      reader = rhs.reader;
-      rhs.reader = nullptr;
-    }
-    return *this;
-  }
-
-  // reader using for iterate over the terms
-  const term_reader* reader{};
-
-  // scored term states (cookie + stat offset)
-  std::vector<std::pair<seek_term_iterator::seek_cookie::ptr, size_t>> scored_states;
-
-  // matching doc_ids that may have been skipped
-  // while collecting statistics and should not be scored by the disjunction
-  bitset unscored_docs;
-}; // limited_sample_state
-
-//////////////////////////////////////////////////////////////////////////////
-/// @class limited_sample_score
-/// @brief object to collect and track a limited number of scorers
-//////////////////////////////////////////////////////////////////////////////
-class limited_sample_scorer : util::noncopyable {
- public:
-  explicit limited_sample_scorer(size_t scored_terms_limit);
-
-  //////////////////////////////////////////////////////////////////////////////
-  /// @param priority priority of this entry, lowest priority removed first
-  /// @param scored_state_id state identifier used for querying of attributes
-  /// @param scored_state state containing this scored term
-  /// @param reader segment reader for the current term
-  /// @param term_itr segment term-iterator positioned at the current term
-  //////////////////////////////////////////////////////////////////////////////
-  void collect(size_t priority,
-               size_t scored_state_id,
-               limited_sample_state& scored_state,
-               const sub_reader& reader,
-               const seek_term_iterator& term_itr);
-
-  void score(const index_reader& index,
-             const order::prepared& order,
-             std::vector<bstring>& stats);
-
- private:
-  //////////////////////////////////////////////////////////////////////////////
-  /// @brief a representation of a term cookie with its associated range_state
-  //////////////////////////////////////////////////////////////////////////////
-  struct scored_term_state {
-    scored_term_state(
-        size_t priority,
-        const sub_reader& segment,
-        limited_sample_state& scored_state,
-        size_t scored_state_offset,
-        const bytes_ref& term,
-        seek_term_iterator::seek_cookie::ptr&& cookie)
-      : cookie(std::move(cookie)),
-        state(&scored_state),
-        state_offset(scored_state_offset),
-        priority(priority),
-        segment(&segment),
-        term(term) {
-      assert(this->cookie);
-    }
-
-    seek_term_iterator::cookie_ptr cookie; // term offset cache
-    limited_sample_state* state; // state containing this scored term
-    size_t state_offset;
-    size_t priority;
-    const irs::sub_reader* segment; // segment reader for the current term
-    bstring term; // actual term value this state is for
-  }; // scored_term_state_t
-
-  typedef std::vector<scored_term_state> scored_term_states_t;
-
-  scored_term_states_t scored_states_;
-  std::vector<size_t> scored_states_heap_; // use external heap as states are big
-  size_t scored_terms_limit_;
-}; // limited_sample_scorer
-
-NS_END
-
-#endif // IRESEARCH_LIMITED_SAMPLE_SCORER_H
diff --git a/3rdParty/iresearch/core/search/limited_sample_scorer.cpp b/3rdParty/iresearch/core/search/limited_sample_scorer.cpp
index 04eea1a97aee..7c52eace2232 100644
--- a/3rdParty/iresearch/core/search/limited_sample_scorer.cpp
+++ b/3rdParty/iresearch/core/search/limited_sample_scorer.cpp
@@ -30,10 +30,10 @@ NS_LOCAL
 
 struct state {
   explicit state(const irs::index_reader& index,
-                   const irs::term_reader& field,
-                   const irs::order::prepared& order,
-                   size_t& state_offset)
-    : collectors(order.prepare_collectors(1)) { // 1 term per bstring because a range is treated as a disjunction
+                 const irs::term_reader& field,
+                 const irs::order::prepared& order,
+                 size_t& state_offset)
+    : collectors(order.fixed_prepare_collectors(1)) { // 1 term per bstring because a range is treated as a disjunction
 
     // once per every 'state' collect field statistics over the entire index
     for (auto& segment: index) {
@@ -43,13 +43,12 @@ struct state {
     stats_offset = state_offset++;
   }
 
-  irs::order::prepared::collectors collectors;
+  irs::order::prepared::fixed_terms_collectors collectors;
   size_t stats_offset;
 };
 
 void set_doc_ids(irs::bitset& buf, const irs::term_iterator& term, size_t docs_count) {
   docs_count += (irs::doc_limits::min)();
-
   if (buf.size() < docs_count) {
     buf.reset(docs_count); // ensure we have enough space
   }
@@ -60,24 +59,31 @@ void set_doc_ids(irs::bitset& buf, const irs::term_iterator& term, size_t docs_c
     return; // no doc_ids in iterator
   }
 
-//FIXME use doc attribute
-//  auto* doc = itr->attributes().get<irs::document>().get();
-//
-//  if (!doc) {
-//    return; // no doc value
-//  }
+  auto* doc = itr->attributes().get<irs::document>().get();
+
+  if (!doc) {
+    return; // no doc value
+  }
 
   while (itr->next()) {
-    buf.set(itr->value());
+    buf.set(doc->value);
   }
 };
 
+bool less(size_t lhs_priority, size_t rhs_priority,
+          size_t lhs_state_offset, size_t rhs_state_offset) noexcept {
+  return rhs_priority < lhs_priority
+      || (rhs_priority == lhs_priority && lhs_state_offset < rhs_state_offset);
+}
+
 NS_END
 
 NS_ROOT
 
 limited_sample_scorer::limited_sample_scorer(size_t scored_terms_limit)
   : scored_terms_limit_(scored_terms_limit) {
+  scored_states_.reserve(scored_terms_limit);
+  scored_states_heap_.reserve(scored_terms_limit);
 }
 
 void limited_sample_scorer::score(const index_reader& index,
@@ -92,8 +98,7 @@ void limited_sample_scorer::score(const index_reader& index,
 
   // iterate over all the states from which statistcis should be collected
   size_t stats_offset = 0;
-  for (auto& entry : scored_states_) {
-    auto& scored_state = entry.second;
+  for (auto& scored_state : scored_states_) {
     assert(scored_state.cookie);
     auto& field = *scored_state.state->reader;
     auto term_itr = field.iterator(); // FIXME
@@ -146,28 +151,53 @@ void limited_sample_scorer::collect(
     return; // nothing to collect (optimization)
   }
 
-  scored_states_.emplace(
-    std::piecewise_construct,
-    std::forward_as_tuple(priority),
-    std::forward_as_tuple(priority, segment, scored_state, scored_state_id, term_itr)
-  );
+  auto less = [this](const size_t lhs, const size_t rhs) noexcept {
+    const auto& lhs_state = scored_states_[lhs];
+    const auto& rhs_state = scored_states_[rhs];
 
-  if (scored_states_.size() <= scored_terms_limit_) {
-    return; // have not reached the scored state limit yet
-  }
+    return ::less(lhs_state.priority, rhs_state.priority,
+                  lhs_state.state_offset, rhs_state.state_offset);
+  };
 
-  auto itr = scored_states_.begin(); // least significant state to be removed
-  auto& entry = itr->second;
-  auto state_term_itr = entry.state->reader->iterator();
+  if (scored_states_.size() < scored_terms_limit_) {
+    // have not reached the scored state limit yet
+    scored_states_heap_.push_back(scored_states_.size());
+    scored_states_.emplace_back(priority, segment, scored_state,
+                                scored_state_id, term_itr.value(), term_itr.cookie());
 
-  // add all doc_ids from the doc_iterator to the unscored_docs
-  if (state_term_itr
-      && entry.cookie
-      && state_term_itr->seek(bytes_ref::NIL, *(entry.cookie))) {
-    set_doc_ids(entry.state->unscored_docs, *state_term_itr, entry.segment->docs_count());
+    std::push_heap(scored_states_heap_.begin(), scored_states_heap_.end(), less);
+    return;
   }
 
-  scored_states_.erase(itr);
+  auto& min_state = scored_states_[scored_states_heap_.front()];
+
+  if (::less(priority, min_state.priority, min_state.state_offset, scored_state_id)) { // FIXME
+    std::pop_heap(scored_states_heap_.begin(), scored_states_heap_.end(), less);
+
+    auto& state = scored_states_[scored_states_heap_.back()];
+    auto state_term_it = state.state->reader->iterator(); // FIXME cache iterator???
+
+    assert(state.cookie);
+    if (state_term_it->seek(bytes_ref::NIL, *state.cookie)) {
+      // state will not be scored
+      // add all doc_ids from the doc_iterator to the unscored_docs
+      set_doc_ids(state.state->unscored_docs, *state_term_it, state.segment->docs_count());
+    }
+
+    // update min state
+    state.priority = priority;
+    state.state = &scored_state;
+    state.cookie = term_itr.cookie();
+    state.term = term_itr.value();
+    state.segment = &segment;
+    state.state_offset = scored_state_id;
+
+    std::push_heap(scored_states_heap_.begin(), scored_states_heap_.end(), less);
+  } else {
+    // state will not be scored
+    // add all doc_ids from the doc_iterator to the unscored_docs
+    set_doc_ids(scored_state.unscored_docs, term_itr, segment.docs_count());
+  }
 }
 
 NS_END
diff --git a/3rdParty/iresearch/core/search/limited_sample_scorer.hpp b/3rdParty/iresearch/core/search/limited_sample_scorer.hpp
index 902d0e228c71..2c5d0464f33f 100644
--- a/3rdParty/iresearch/core/search/limited_sample_scorer.hpp
+++ b/3rdParty/iresearch/core/search/limited_sample_scorer.hpp
@@ -101,13 +101,14 @@ class limited_sample_scorer : util::noncopyable {
         const sub_reader& segment,
         limited_sample_state& scored_state,
         size_t scored_state_offset,
-        const seek_term_iterator& term)
-      : cookie(term.cookie()),
+        const bytes_ref& term,
+        seek_term_iterator::seek_cookie::ptr&& cookie)
+      : cookie(std::move(cookie)),
         state(&scored_state),
         state_offset(scored_state_offset),
         priority(priority),
         segment(&segment),
-        term(term.value()) {
+        term(term) {
       assert(this->cookie);
     }
 
@@ -119,9 +120,10 @@ class limited_sample_scorer : util::noncopyable {
     bstring term; // actual term value this state is for
   }; // scored_term_state_t
 
-  typedef std::multimap<size_t, scored_term_state> scored_term_states_t;
+  typedef std::vector<scored_term_state> scored_term_states_t;
 
   scored_term_states_t scored_states_;
+  std::vector<size_t> scored_states_heap_; // use external heap as states are big
   size_t scored_terms_limit_;
 }; // limited_sample_scorer
 
diff --git a/3rdParty/iresearch/core/search/min_match_disjunction.hpp b/3rdParty/iresearch/core/search/min_match_disjunction.hpp
index b6d1ab4cc879..e25f601730d7 100644
--- a/3rdParty/iresearch/core/search/min_match_disjunction.hpp
+++ b/3rdParty/iresearch/core/search/min_match_disjunction.hpp
@@ -97,8 +97,8 @@ class min_match_disjunction : public doc_iterator_base, score_ctx {
         itrs_.begin(), itrs_.end(), cost::cost_t(0),
         [](cost::cost_t lhs, const doc_iterator_t& rhs) {
           return lhs + cost::extract(rhs->attributes(), 0);
+        });
       });
-    });
 
     // prepare external heap
     heap_.resize(itrs_.size());
@@ -239,7 +239,40 @@ class min_match_disjunction : public doc_iterator_base, score_ctx {
     }
   }
 
+  //////////////////////////////////////////////////////////////////////////////
+  /// @brief calculates total count of matched iterators. This value could be
+  ///        greater than required min_match. All matched iterators points
+  ///        to current matched document after this call.
+  /// @returns total matched iterators count
+  //////////////////////////////////////////////////////////////////////////////
+  size_t count_matched() {
+    push_valid_to_lead();
+    return lead_;
+  }
+
  private:
+  //////////////////////////////////////////////////////////////////////////////
+  /// @brief push all valid iterators to lead
+  //////////////////////////////////////////////////////////////////////////////
+  inline void push_valid_to_lead() {
+    for(auto lead = this->lead(), begin = heap_.begin();
+      lead != begin && top().value() <= doc_.value;) {
+      // hitch head
+      if (top().value() == doc_.value) {
+        // got hit here
+        add_lead();
+        --lead;
+      } else {
+        if (doc_limits::eof(top()->seek(doc_.value))) {
+          // iterator exhausted
+          remove_top();
+        } else {
+          refresh_top();
+        }
+      }
+    }
+  }
+
   template<typename Iterator>
   inline void push(Iterator begin, Iterator end) {
     // lambda here gives ~20% speedup on GCC
@@ -383,34 +416,17 @@ class min_match_disjunction : public doc_iterator_base, score_ctx {
     ++lead_;
   }
 
+
   inline void score_impl(byte_type* lhs) {
     assert(!heap_.empty());
 
-    // push all valid iterators to lead
-    {
-      for(auto lead = this->lead(), begin = heap_.begin();
-          lead != begin && top().value() <= doc_.value;) {
-        // hitch head
-        if (top().value() == doc_.value) {
-          // got hit here
-          add_lead();
-          --lead;
-        } else {
-          if (doc_limits::eof(top()->seek(doc_.value))) {
-            // iterator exhausted
-            remove_top();
-          } else {
-            refresh_top();
-          }
-        }
-      }
-    }
+    push_valid_to_lead();
 
     // score lead iterators
     const irs::byte_type** pVal = scores_vals_.data();
     std::for_each(
         lead(), heap_.end(),
-        [this, lhs, &pVal](size_t it) {
+        [this, &pVal](size_t it) {
           assert(it < itrs_.size());
           detail::evaluate_score_iter(pVal, itrs_[it]);
         });
diff --git a/3rdParty/iresearch/core/search/ngram_similarity_filter.cpp b/3rdParty/iresearch/core/search/ngram_similarity_filter.cpp
new file mode 100644
index 000000000000..fdd89301a272
--- /dev/null
+++ b/3rdParty/iresearch/core/search/ngram_similarity_filter.cpp
@@ -0,0 +1,551 @@
+////////////////////////////////////////////////////////////////////////////////
+/// DISCLAIMER
+///
+/// Copyright 2020 ArangoDB GmbH, Cologne, Germany
+///
+/// Licensed under the Apache License, Version 2.0 (the "License");
+/// you may not use this file except in compliance with the License.
+/// You may obtain a copy of the License at
+///
+///     http://www.apache.org/licenses/LICENSE-2.0
+///
+/// Unless required by applicable law or agreed to in writing, software
+/// distributed under the License is distributed on an "AS IS" BASIS,
+/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+/// See the License for the specific language governing permissions and
+/// limitations under the License.
+///
+/// Copyright holder is ArangoDB GmbH, Cologne, Germany
+///
+/// @author Andrei Lobov
+////////////////////////////////////////////////////////////////////////////////
+
+#include "ngram_similarity_filter.hpp"
+#include "min_match_disjunction.hpp"
+#include "disjunction.hpp"
+#include <boost/functional/hash.hpp>
+#include "shared.hpp"
+#include "cost.hpp"
+#include "analysis/token_attributes.hpp"
+#include "index/index_reader.hpp"
+#include "index/field_meta.hpp"
+#include "utils/misc.hpp"
+#include "utils/map_utils.hpp"
+
+
+NS_LOCAL
+
+struct ngram_segment_state_t {
+  const irs::term_reader* field{};
+  std::vector<irs::seek_term_iterator::cookie_ptr> terms;
+};
+
+typedef irs::states_cache<ngram_segment_state_t> states_t;
+typedef std::vector<irs::bstring> stats_t;
+
+NS_END
+
+NS_ROOT
+
+//////////////////////////////////////////////////////////////////////////////
+///@class ngram_similarity_doc_iterator
+///@brief adapter for min_match_disjunction with honor of terms orderings
+//////////////////////////////////////////////////////////////////////////////
+template<typename DocIterator>
+class ngram_similarity_doc_iterator : public doc_iterator_base, score_ctx {
+ public:
+  struct position_t {
+    position_t(position* p, document* d, score* s)
+      : pos(p), doc(d), scr(s) {}
+    position* pos;
+    document* doc;
+    score* scr;
+  };
+
+  using positions_t = std::vector<position_t>;
+  using doc_iterators_t = typename min_match_disjunction<DocIterator>::doc_iterators_t;
+
+  static positions_t extract_positions(const doc_iterators_t& itrs) {
+    positions_t pos;
+    pos.reserve(itrs.size());
+    for (const auto& itr : itrs) {
+      auto& attrs = itr->attributes();
+      // get needed positions for iterators
+      auto p = attrs.template get<position>().get();
+      auto d = attrs.template get<document>().get();
+      auto s = attrs.template get<score>().get();
+      pos.emplace_back(p, d, s);
+    }
+    return pos;
+  }
+
+  ngram_similarity_doc_iterator(doc_iterators_t&& itrs,
+    const states_t& states,
+    const sub_reader& segment,
+    const term_reader& field,
+    boost_t boost,
+    const byte_type* stats,
+    size_t total_terms_count,
+    size_t min_match_count = 1,
+    const order::prepared& ord = order::prepared::unordered())
+    : pos_(extract_positions(itrs)),
+      min_match_count_(min_match_count),
+      disjunction_(std::forward<doc_iterators_t>(itrs), min_match_count,
+      order::prepared::unordered()),// we are not interested in disjunction`s scoring
+      states_(states), total_terms_count_(total_terms_count) {
+    scores_vals_.resize(pos_.size());
+
+    attrs_.emplace(seq_freq_);
+    doc_ = (attrs_.emplace<document>() = disjunction_.attributes().template get<document>()).get();
+    attrs_.emplace<filter_boost>(filter_boost_);
+
+    prepare_score(ord, ord.prepare_scorers(segment, field, stats, attrs_, boost));
+    empty_order_ = ord.empty();
+  }
+
+  virtual bool next() override {
+    bool next = false;
+    while ((next = disjunction_.next()) && !check_serial_positions()) {}
+    return next;
+  }
+
+  virtual doc_id_t value() const override {
+    return doc_->value;
+  }
+
+  virtual doc_id_t seek(doc_id_t target) override {
+    const auto doc = disjunction_.seek(target);
+
+    if (doc_limits::eof(doc) || check_serial_positions()) {
+      return doc;
+    }
+
+    next();
+    return doc_->value;
+  }
+
+ private:
+  struct search_state {
+    search_state(size_t p, const score* s) : parent{nullptr}, scr{s}, pos{p}, len(1) {}
+    search_state(search_state&&) = default;
+    search_state(const search_state&) = default;
+    search_state& operator=(const search_state&) = default;
+
+    // appending constructor
+    search_state(std::shared_ptr<search_state>& other, size_t p, const score* s)
+      : parent{other}, scr{s}, pos{p}, len(other->len + 1) {}
+
+    std::shared_ptr<search_state> parent;
+    const score* scr;
+    size_t pos;
+    size_t len;
+  };
+
+  using search_states_t = std::map<uint32_t, std::shared_ptr<search_state>, std::greater<uint32_t>>;
+  using pos_temp_t = std::vector<std::pair<uint32_t, std::shared_ptr<search_state>>>;
+
+  bool check_serial_positions() {
+    size_t potential = disjunction_.count_matched(); // how long max sequence could be in the best case
+    search_buf_.clear();
+    size_t longest_sequence_len = 0;
+    seq_freq_.value = 0;
+    for (const auto& pos_iterator : pos_) {
+      if (pos_iterator.doc->value == doc_->value) {
+        position& pos = *(pos_iterator.pos);
+        if (potential <= longest_sequence_len || potential < min_match_count_) {
+          // this term could not start largest (or long enough) sequence.
+          // skip it to first position to append to any existing candidates
+          assert(!search_buf_.empty());
+          pos.seek(search_buf_.rbegin()->first + 1);
+        } else {
+          pos.next();
+        }
+        if (!pos_limits::eof(pos.value())) {
+          pos_temp_t swap_cache;
+          auto last_found_pos = pos_limits::invalid();
+          do {
+            auto current_pos = pos.value();
+            auto found = search_buf_.lower_bound(current_pos);
+            if (found != search_buf_.end()) {
+              if (last_found_pos != found->first) {
+                last_found_pos = found->first;
+                auto current_sequence = found;
+                // if we hit same position - set length to 0 to force checking candidates to the left
+                size_t current_found_len = (found->first == current_pos ||
+                                            found->second->scr == pos_iterator.scr) ? 0 : found->second->len + 1;
+                auto initial_found = found;
+                if (current_found_len > longest_sequence_len) {
+                  longest_sequence_len = current_found_len;
+                } else {
+                  // maybe some previous candidates could produce better results.
+                  // lets go leftward and check if there are any candidates which could became longer
+                  // if we stick this ngram to them rather than the closest one found
+                  for (++found; found != search_buf_.end(); ++found) {
+                    if (found->second->scr != pos_iterator.scr &&
+                        found->second->len + 1 > current_found_len) {
+                      // we have better option. Replace this match!
+                      current_sequence = found;
+                      current_found_len = found->second->len + 1;
+                      if (current_found_len > longest_sequence_len) {
+                        longest_sequence_len = current_found_len;
+                        break; // this match is the best - nothing to search further
+                      }
+                    }
+                  }
+                }
+                if (current_found_len) {
+                  auto new_candidate = std::make_shared<search_state>(current_sequence->second, current_pos, pos_iterator.scr);
+                  auto res =  map_utils::try_emplace(search_buf_, current_pos, std::move(new_candidate));
+                  if (!res.second) {
+                    // pos already used. This could be if same ngram used several times.
+                    // replace with new length through swap cache - to not spoil
+                    // candidate for following positions of same ngram
+                    swap_cache.emplace_back(current_pos, std::move(new_candidate));
+                  }
+                } else if (initial_found->second->scr == pos_iterator.scr &&
+                           potential > longest_sequence_len && potential >= min_match_count_) {
+                  // we just hit same iterator and found no better place to join,
+                  // so it will produce new candidate
+                  search_buf_.emplace(std::piecewise_construct,
+                    std::forward_as_tuple(current_pos),
+                    std::forward_as_tuple(std::make_shared<search_state>(current_pos, pos_iterator.scr)));
+                }
+              }
+            } else  if (potential > longest_sequence_len && potential >= min_match_count_) {
+              // this ngram at this position  could potentially start a long enough sequence
+              // so add it to candidate list
+              search_buf_.emplace(std::piecewise_construct,
+                std::forward_as_tuple(current_pos),
+                std::forward_as_tuple(std::make_shared<search_state>(current_pos, pos_iterator.scr)));
+              if (!longest_sequence_len) {
+                longest_sequence_len = 1;
+              }
+            }
+          } while (pos.next());
+          for (auto& p : swap_cache) {
+            auto res = search_buf_.find(p.first);
+            assert(res != search_buf_.end());
+            std::swap(res->second, p.second);
+          }
+        }
+        --potential; // we are done with this term.
+                     // next will have potential one less as less matches left
+
+        if (!potential) {
+          break; // all further terms will not add anything
+        }
+
+        if (longest_sequence_len + potential < min_match_count_) {
+          break; // all further terms will not let us build long enough sequence
+        }
+
+        // if we have no scoring - we could stop searh once we got enough matches
+        if (longest_sequence_len >= min_match_count_ && empty_order_) {
+          break;
+        }
+      }
+    }
+
+    if (longest_sequence_len >= min_match_count_  && !empty_order_) {
+      uint32_t freq = 0;
+      size_t count_longest{ 0 };
+      // try to optimize case with one longest candidate
+      // performance profiling shows it is majority of cases
+      for (auto i = search_buf_.begin(), end = search_buf_.end(); i != end; ++i) {
+        if (i->second->len == longest_sequence_len) {
+          ++count_longest;
+          if (count_longest > 1) {
+            break;
+          }
+        }
+      }
+
+      if (count_longest > 1) {
+        longest_sequence_.clear();
+        used_pos_.clear();
+        longest_sequence_.reserve(longest_sequence_len);
+        pos_sequence_.reserve(longest_sequence_len);
+        for (auto i = search_buf_.begin(), end = search_buf_.end(); i != end;) {
+          pos_sequence_.clear();
+          assert(i->second->len <= longest_sequence_len);
+          if (i->second->len == longest_sequence_len) {
+            bool delete_candidate = false;
+            // only first longest sequence will contribute to frequency
+            if (longest_sequence_.empty()) {
+              longest_sequence_.push_back(i->second->scr);
+              pos_sequence_.push_back(i->second->pos);
+              auto cur_parent = i->second->parent;
+              while (cur_parent) {
+                longest_sequence_.push_back(cur_parent->scr);
+                pos_sequence_.push_back(cur_parent->pos);
+                cur_parent = cur_parent->parent;
+              }
+            } else {
+              if (used_pos_.find(i->second->pos) != used_pos_.end() ||
+                  i->second->scr != longest_sequence_[0]) {
+                delete_candidate = true;
+              } else {
+                pos_sequence_.push_back(i->second->pos);
+                auto cur_parent = i->second->parent;
+                size_t j = 1;
+                while (cur_parent) {
+                  assert(j < longest_sequence_.size());
+                  if (longest_sequence_[j] != cur_parent->scr ||
+                    used_pos_.find(cur_parent->pos) != used_pos_.end()) {
+                    delete_candidate = true;
+                    break;
+                  }
+                  pos_sequence_.push_back(cur_parent->pos);
+                  cur_parent = cur_parent->parent;
+                  ++j;
+                }
+              }
+            }
+            if (!delete_candidate) {
+              ++freq;
+              used_pos_.insert(std::begin(pos_sequence_),
+                              std::end(pos_sequence_));
+            }
+          }
+          ++i;
+        }
+      } else {
+        freq = 1;
+      }
+      seq_freq_.value = freq;
+      assert(!pos_.empty());
+      filter_boost_.value = (boost_t)longest_sequence_len / (boost_t)total_terms_count_;
+    }
+    return longest_sequence_len >= min_match_count_;
+  }
+
+  std::vector<const score*> longest_sequence_;
+  positions_t pos_;
+  frequency seq_freq_; // longest sequence frequency
+  filter_boost filter_boost_;
+  size_t min_match_count_;
+  min_match_disjunction<DocIterator> disjunction_;
+  mutable std::vector<const irs::byte_type*> scores_vals_;
+  search_states_t search_buf_;
+  const states_t& states_;
+  std::vector<size_t> pos_sequence_;
+  size_t total_terms_count_;
+  const document* doc_;
+  bool empty_order_;
+  std::set<size_t> used_pos_; // longest sequence positions overlaping detector
+};
+
+//////////////////////////////////////////////////////////////////////////////
+/// @class ngram_similarity_query
+/// @brief prepared ngram similarity query implementation
+//////////////////////////////////////////////////////////////////////////////
+class ngram_similarity_query : public filter::prepared {
+ public:
+  DECLARE_SHARED_PTR(ngram_similarity_query);
+
+  ngram_similarity_query(size_t min_match_count, states_t&& states, bstring&& stats, boost_t boost = no_boost())
+      :prepared(boost), min_match_count_(min_match_count), states_(std::move(states)), stats_(std::move(stats)) {}
+
+  using filter::prepared::execute;
+
+  virtual doc_iterator::ptr execute(
+      const sub_reader& rdr,
+      const order::prepared& ord,
+      const attribute_view&) const override {
+    auto query_state = states_.find(rdr);
+    if (!query_state || !query_state->field) {
+      // invalid state
+      return doc_iterator::empty();
+    }
+
+    if (1 == min_match_count_ && ord.empty()) {
+      return execute_simple_disjunction(*query_state);
+    } else {
+      return execute_ngram_similarity(rdr, *query_state, ord);
+    }
+  }
+
+ private:
+  doc_iterator::ptr execute_simple_disjunction(
+    const ngram_segment_state_t& query_state) const {
+    using disjunction_t = irs::disjunction<doc_iterator::ptr>;
+    disjunction_t::doc_iterators_t itrs;
+    itrs.reserve(query_state.terms.size());
+    for (auto& term_state : query_state.terms) {
+      if (term_state == nullptr) {
+        continue;
+      }
+      auto term = query_state.field->iterator();
+
+      // use bytes_ref::blank here since we do not need just to "jump"
+      // to cached state, and we are not interested in term value itself */
+      if (!term->seek(bytes_ref::NIL, *term_state)) {
+        continue;
+      }
+
+      // get postings
+      auto docs = term->postings(irs::flags::empty_instance());
+      assert(docs);
+
+      // add iterator
+      itrs.emplace_back(std::move(docs));
+    }
+
+    if (itrs.empty()) {
+      return doc_iterator::empty();
+    }
+    return make_disjunction<disjunction_t>(std::move(itrs));
+  }
+
+  doc_iterator::ptr execute_ngram_similarity(
+    const sub_reader& rdr,
+    const ngram_segment_state_t& query_state,
+    const order::prepared& ord) const {
+    min_match_disjunction<doc_iterator::ptr>::doc_iterators_t itrs;
+    itrs.reserve(query_state.terms.size());
+    auto features = ord.features() | by_ngram_similarity::features();
+    for (auto& term_state : query_state.terms) {
+      if (term_state == nullptr) {
+        continue;
+      }
+      auto term = query_state.field->iterator();
+
+      // use bytes_ref::blank here since we do not need just to "jump"
+      // to cached state, and we are not interested in term value itself */
+      if (!term->seek(bytes_ref::NIL, *term_state)) {
+        continue;
+      }
+
+      // get postings
+      auto docs = term->postings(features);
+      assert(docs);
+
+      // add iterator
+      itrs.emplace_back(std::move(docs));
+    }
+
+    if (itrs.size() < min_match_count_) {
+      return doc_iterator::empty();
+    }
+    return memory::make_shared<ngram_similarity_doc_iterator<doc_iterator::ptr>>(
+      std::move(itrs), states_, rdr, *query_state.field, boost(), stats_.c_str(),
+      query_state.terms.size(), min_match_count_, ord);
+  }
+
+  size_t min_match_count_;
+  states_t states_;
+  bstring stats_;
+};
+
+// -----------------------------------------------------------------------------
+// --SECTION--                                by_ngram_similarity implementation
+// -----------------------------------------------------------------------------
+
+/* static */ const flags& by_ngram_similarity::features() {
+  static flags req{ frequency::type(), position::type() };
+  return req;
+}
+
+DEFINE_FILTER_TYPE(by_ngram_similarity)
+DEFINE_FACTORY_DEFAULT(by_ngram_similarity)
+
+by_ngram_similarity::by_ngram_similarity(): filter(by_ngram_similarity::type()) {
+}
+
+bool by_ngram_similarity::equals(const filter& rhs) const noexcept {
+  const by_ngram_similarity& trhs = static_cast<const by_ngram_similarity&>(rhs);
+  return filter::equals(rhs) && fld_ == trhs.fld_ && ngrams_ == trhs.ngrams_ && threshold_ == trhs.threshold_;
+}
+
+size_t by_ngram_similarity::hash() const noexcept {
+  size_t seed = 0;
+  ::boost::hash_combine(seed, filter::hash());
+  ::boost::hash_combine(seed, fld_);
+  std::for_each(
+    ngrams_.begin(), ngrams_.end(),
+    [&seed](const by_ngram_similarity::term_t& term) {
+      ::boost::hash_combine(seed, term);
+    });
+  ::boost::hash_combine(seed, threshold_);
+  return seed;
+}
+
+filter::prepared::ptr by_ngram_similarity::prepare(
+    const index_reader& rdr,
+    const order::prepared& ord,
+    boost_t boost,
+    const attribute_view& /*ctx*/) const {
+  if (ngrams_.empty() || fld_.empty()) {
+    // empty field or terms or invalid threshold
+    return filter::prepared::empty();
+  }
+
+  size_t min_match_count = std::max(
+    static_cast<size_t>(std::ceil(static_cast<double>(ngrams_.size()) * threshold_)), (size_t)1);
+
+  states_t query_states(rdr.size());
+
+  // per segment terms states
+  ngram_segment_state_t term_states;
+  term_states.terms.reserve(ngrams_.size());
+
+  // prepare ngrams stats
+  auto collectors = ord.fixed_prepare_collectors(ngrams_.size());
+
+  for (const auto& segment : rdr) {
+    // get term dictionary for field
+    const term_reader* field = segment.field(fld_);
+    if (!field) {
+      continue;
+    }
+
+    // check required features
+    if (!features().is_subset_of(field->meta().features)) {
+      continue;
+    }
+
+    term_states.field = field;
+    collectors.collect(segment, *field); // collect field statistics once per segment
+    size_t term_itr = 0;
+    size_t count_terms = 0;
+    for (const auto& ngram : ngrams_) {
+      auto next_stats = irs::make_finally([&term_itr]()->void{ ++term_itr; });
+      // find terms
+      seek_term_iterator::ptr term = field->iterator();
+
+      term_states.terms.emplace_back();
+      auto& state = term_states.terms.back();
+      if (term->seek(ngram)) {
+        term->read(); // read term attributes
+        collectors.collect(segment, *field, term_itr, term->attributes()); // collect statistics
+        state = term->cookie();
+        ++count_terms;
+      }
+    }
+    if (count_terms < min_match_count) {
+      // we have not found enough terms
+      term_states.terms.clear();
+      term_states.field = nullptr;
+      continue;
+    }
+
+    auto& state = query_states.insert(segment);
+    state = std::move(term_states);
+
+    term_states.terms.reserve(ngrams_.size());
+  }
+
+  bstring stats(ord.stats_size(), 0);
+  auto* stats_buf = const_cast<byte_type*>(stats.data());
+
+  ord.prepare_stats(stats_buf);
+  collectors.finish(stats_buf, rdr);
+
+  return memory::make_shared<ngram_similarity_query>(
+      min_match_count,
+      std::move(query_states),
+      std::move(stats),
+      this->boost() * boost);
+}
+
+NS_END
diff --git a/3rdParty/iresearch/core/search/ngram_similarity_filter.hpp b/3rdParty/iresearch/core/search/ngram_similarity_filter.hpp
new file mode 100644
index 000000000000..5fe3acfa3487
--- /dev/null
+++ b/3rdParty/iresearch/core/search/ngram_similarity_filter.hpp
@@ -0,0 +1,120 @@
+////////////////////////////////////////////////////////////////////////////////
+/// DISCLAIMER
+///
+/// Copyright 2020 ArangoDB GmbH, Cologne, Germany
+///
+/// Licensed under the Apache License, Version 2.0 (the "License");
+/// you may not use this file except in compliance with the License.
+/// You may obtain a copy of the License at
+///
+///     http://www.apache.org/licenses/LICENSE-2.0
+///
+/// Unless required by applicable law or agreed to in writing, software
+/// distributed under the License is distributed on an "AS IS" BASIS,
+/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+/// See the License for the specific language governing permissions and
+/// limitations under the License.
+///
+/// Copyright holder is ArangoDB GmbH, Cologne, Germany
+///
+/// @author Andrei Lobov
+////////////////////////////////////////////////////////////////////////////////
+
+#ifndef IRESEARCH_NGRAM_SIMILARITY_FILTER_H
+#define IRESEARCH_NGRAM_SIMILARITY_FILTER_H
+
+#include "filter.hpp"
+#include "utils/string.hpp"
+
+NS_ROOT
+
+
+//////////////////////////////////////////////////////////////////////////////
+/// @class by_ngram_similarity
+//////////////////////////////////////////////////////////////////////////////
+class IRESEARCH_API by_ngram_similarity : public filter {
+ public:
+  typedef bstring term_t;
+  typedef std::vector<term_t> terms_t;
+  typedef terms_t::iterator iterator;
+  typedef terms_t::const_iterator const_iterator;
+
+  DECLARE_FILTER_TYPE();
+  DECLARE_FACTORY();
+
+  // returns set of features required for filter 
+  static const flags& features();
+
+  by_ngram_similarity();
+
+  using filter::prepare;
+
+  virtual filter::prepared::ptr prepare(
+    const index_reader& rdr,
+    const order::prepared& ord,
+    boost_t boost,
+    const attribute_view& ctx
+  ) const override;
+
+  virtual size_t hash() const noexcept override;
+
+  float_t threshold() const noexcept { return threshold_; }
+
+  by_ngram_similarity& threshold(float_t d) noexcept {
+    assert(d >= 0.);
+    assert(d <= 1.);
+    threshold_ = std::max(0.f, std::min(1.f, d));
+    return *this;
+  }
+  
+  by_ngram_similarity& field(std::string fld) noexcept {
+    fld_ = std::move(fld); 
+    return *this;
+  }
+   
+  const std::string& field() const noexcept { return fld_; }
+
+  by_ngram_similarity& push_back(const bstring& term) {
+    ngrams_.emplace_back(term);
+    return *this;
+  }
+
+  by_ngram_similarity& push_back(bstring&& term) {
+    ngrams_.push_back(std::move(term));
+    return *this;
+  }
+
+  by_ngram_similarity& push_back(const bytes_ref& term) {
+    ngrams_.emplace_back(term);
+    return *this;
+  }
+
+  by_ngram_similarity& push_back(const string_ref& term) {
+    ngrams_.emplace_back(ref_cast<byte_type>(term));
+    return *this;
+  }
+
+  iterator begin() noexcept { return ngrams_.begin(); }
+  iterator end() noexcept { return ngrams_.end(); }
+
+  const_iterator begin() const noexcept { return ngrams_.begin(); }
+  const_iterator end() const noexcept { return ngrams_.end(); }
+
+  bool empty() const noexcept { return ngrams_.empty(); }
+  size_t size() const noexcept { return ngrams_.size(); }
+  void clear() noexcept { ngrams_.clear(); }
+
+ protected:
+  virtual bool equals(const filter& rhs) const noexcept override;
+
+ private: 
+  IRESEARCH_API_PRIVATE_VARIABLES_BEGIN
+  terms_t ngrams_;
+  std::string fld_;
+  float_t threshold_{1.f};
+  IRESEARCH_API_PRIVATE_VARIABLES_END
+
+}; // by_ngram_similarity
+NS_END // ROOT
+
+#endif // IRESEARCH_NGRAM_SIMILARITY_FILTER_H
\ No newline at end of file
diff --git a/3rdParty/iresearch/core/search/phrase_filter.cpp b/3rdParty/iresearch/core/search/phrase_filter.cpp
index 88307dcac15e..105117582d93 100644
--- a/3rdParty/iresearch/core/search/phrase_filter.cpp
+++ b/3rdParty/iresearch/core/search/phrase_filter.cpp
@@ -20,6 +20,8 @@
 /// @author Andrey Abramov
 ////////////////////////////////////////////////////////////////////////////////
 
+#include "utils/automaton.hpp" // FOR FST_NO_DYNAMIC_LINKING
+
 #include "phrase_filter.hpp"
 
 #include <boost/functional/hash.hpp>
@@ -28,6 +30,10 @@
 #include "cost.hpp"
 #include "term_query.hpp"
 #include "conjunction.hpp"
+#include "disjunction.hpp"
+#include "levenshtein_filter.hpp"
+#include "prefix_filter.hpp"
+#include "wildcard_filter.hpp"
 
 #if defined(_MSC_VER)
   #pragma warning( disable : 4706 )
@@ -48,7 +54,11 @@
 
 #include "index/index_reader.hpp"
 #include "index/field_meta.hpp"
+#include "utils/fst_table_matcher.hpp"
+#include "utils/levenshtein_utils.hpp"
 #include "utils/misc.hpp"
+#include "utils/utf8_utils.hpp"
+#include "utils/wildcard_utils.hpp"
 
 NS_ROOT
 
@@ -56,9 +66,10 @@ NS_ROOT
 /// @class phrase_state 
 /// @brief cached per reader phrase state
 //////////////////////////////////////////////////////////////////////////////
+template<template<typename...> class T>
 struct phrase_state {
   typedef seek_term_iterator::cookie_ptr term_state_t;
-  typedef std::vector<seek_term_iterator::cookie_ptr> terms_states_t;
+  typedef T<term_state_t> terms_states_t;
 
   phrase_state() = default;
 
@@ -78,12 +89,13 @@ struct phrase_state {
 /// @class phrase_query
 /// @brief prepared phrase query implementation
 //////////////////////////////////////////////////////////////////////////////
+template<template<typename...> class T>
 class phrase_query : public filter::prepared {
  public:
-  typedef states_cache<phrase_state> states_t;
+  typedef states_cache<phrase_state<T>> states_t;
   typedef std::vector<position::value_t> positions_t;
 
-  DECLARE_SHARED_PTR(phrase_query);
+  DECLARE_SHARED_PTR(phrase_query<T>);
 
   phrase_query(
       states_t&& states,
@@ -96,12 +108,31 @@ class phrase_query : public filter::prepared {
       stats_(std::move(stats)) {
   }
 
+ protected:
+  states_t states_;
+  positions_t positions_;
+  bstring stats_;
+}; // phrase_query
+
+class fixed_phrase_query : public phrase_query<order::prepared::FixedContainer> {
+ public:
+
+  DECLARE_SHARED_PTR(fixed_phrase_query);
+
+  fixed_phrase_query(
+      typename phrase_query<order::prepared::FixedContainer>::states_t&& states,
+      typename phrase_query<order::prepared::FixedContainer>::positions_t&& positions,
+      bstring&& stats,
+      boost_t boost) noexcept
+    : phrase_query<order::prepared::FixedContainer>(std::move(states), std::move(positions), std::move(stats), boost) {
+  }
+
   using filter::prepared::execute;
 
-  virtual doc_iterator::ptr execute(
+  doc_iterator::ptr execute(
       const sub_reader& rdr,
       const order::prepared& ord,
-      const attribute_view& /*ctx*/) const override {
+      const attribute_view& /*ctx*/) const {
     // get phrase state for the specified reader
     auto phrase_state = states_.find(rdr);
 
@@ -114,7 +145,7 @@ class phrase_query : public filter::prepared {
     auto features = ord.features() | by_phrase::required();
 
     typedef conjunction<doc_iterator::ptr> conjunction_t;
-    typedef phrase_iterator<conjunction_t> phrase_iterator_t;
+    typedef phrase_iterator<conjunction_t, fixed_phrase_frequency> phrase_iterator_t;
 
     conjunction_t::doc_iterators_t itrs;
     itrs.reserve(phrase_state->terms.size());
@@ -126,9 +157,9 @@ class phrase_query : public filter::prepared {
     auto terms = phrase_state->reader->iterator();
     auto position = positions_.begin();
 
-    for (auto& term_state : phrase_state->terms) {
+    for (const auto& term_state : phrase_state->terms) {
       // use bytes_ref::blank here since we do not need just to "jump"
-      // to cached state, and we are not interested in term value itself */
+      // to cached state, and we are not interested in term value itself
       if (!terms->seek(bytes_ref::NIL, *term_state)) {
         return doc_iterator::empty();
       }
@@ -159,12 +190,100 @@ class phrase_query : public filter::prepared {
       boost()
     );
   }
+}; // fixed_phrase_query
 
- private:
-  states_t states_;
-  positions_t positions_;
-  bstring stats_;
-}; // phrase_query
+class variadic_phrase_query : public phrase_query<order::prepared::VariadicContainer> {
+ public:
+
+  DECLARE_SHARED_PTR(variadic_phrase_query);
+
+  variadic_phrase_query(
+      states_t&& states,
+      positions_t&& positions,
+      bstring&& stats,
+      boost_t boost) noexcept
+    : phrase_query<order::prepared::VariadicContainer>(std::move(states), std::move(positions), std::move(stats), boost) {
+  }
+
+  using filter::prepared::execute;
+
+  doc_iterator::ptr execute(
+      const sub_reader& rdr,
+      const order::prepared& ord,
+      const attribute_view& /*ctx*/) const override {
+    // get phrase state for the specified reader
+    auto phrase_state = states_.find(rdr);
+
+    if (!phrase_state) {
+      // invalid state
+      return doc_iterator::empty();
+    }
+
+    // get features required for query & order
+    auto features = ord.features() | by_phrase::required();
+
+    typedef conjunction<doc_iterator::ptr> conjunction_t;
+    typedef phrase_iterator<conjunction_t, variadic_phrase_frequency> phrase_iterator_t;
+
+    conjunction_t::doc_iterators_t conj_itrs;
+    conj_itrs.reserve(phrase_state->terms.size());
+
+    typedef disjunction<doc_iterator::ptr, irs::position_score_iterator_adapter<doc_iterator::ptr>, true> disjunction_t;
+
+    phrase_iterator_t::positions_t positions;
+    positions.resize(phrase_state->terms.size());
+
+    // find term using cached state
+    auto terms = phrase_state->reader->iterator();
+    auto position = positions_.begin();
+
+    size_t i = 0;
+    for (const auto& term_states : phrase_state->terms) {
+      auto is_found = false;
+      auto& ps = positions[i++];
+      ps.second = *position;
+
+      disjunction_t::doc_iterators_t disj_itrs;
+      disj_itrs.reserve(term_states.size());
+      for (const auto& term_state : term_states) {
+        // use bytes_ref::blank here since we do not need just to "jump"
+        // to cached state, and we are not interested in term value itself
+        if (!terms->seek(bytes_ref::NIL, *term_state)) {
+          continue;
+        }
+
+        auto docs = terms->postings(features); // postings
+        auto& pos = docs->attributes().get<irs::position>(); // needed postings attributes
+
+        if (!pos) {
+          // positions not found
+          continue;
+        }
+
+        // add base iterator
+        disj_itrs.emplace_back(std::move(docs));
+
+        is_found = true;
+      }
+      if (!is_found) {
+        return doc_iterator::empty();
+      }
+      conj_itrs.emplace_back(make_disjunction<disjunction_t>(std::move(disj_itrs)));
+      ps.first = &conj_itrs.back()->attributes().get<attribute_range<position_score_iterator_adapter<doc_iterator::ptr>>>();
+      ++position;
+    }
+
+    return memory::make_shared<phrase_iterator_t>(
+      std::move(conj_itrs),
+      std::move(positions),
+      rdr,
+      *phrase_state->reader,
+      stats_.c_str(),
+      ord,
+      boost()
+    );
+  }
+}; // variadic_phrase_query
 
 // -----------------------------------------------------------------------------
 // --SECTION--                                          by_phrase implementation
@@ -186,6 +305,274 @@ bool by_phrase::equals(const filter& rhs) const noexcept {
   return filter::equals(rhs) && fld_ == trhs.fld_ && phrase_ == trhs.phrase_;
 }
 
+by_phrase::info_t::info_t() : type(PhrasePartType::TERM), st() {
+}
+
+by_phrase::info_t::info_t(const info_t& other) {
+  type = other.type;
+  allocate();
+  switch (type) {
+    case PhrasePartType::TERM:
+      this->st = other.st;
+      break;
+    case PhrasePartType::PREFIX:
+      this->pt = other.pt;
+      break;
+    case PhrasePartType::WILDCARD:
+      this->wt = other.wt;
+      break;
+    case PhrasePartType::LEVENSHTEIN:
+      this->lt = other.lt;
+      break;
+    case PhrasePartType::SET:
+      this->ct = other.ct;
+      break;
+    default:
+      assert(false);
+  }
+}
+
+by_phrase::info_t::info_t(info_t&& other) noexcept {
+  type = other.type;
+  allocate();
+  switch (type) {
+    case PhrasePartType::TERM:
+      this->st = std::move(other.st);
+      break;
+    case PhrasePartType::PREFIX:
+      this->pt = std::move(other.pt);
+      break;
+    case PhrasePartType::WILDCARD:
+      this->wt = std::move(other.wt);
+      break;
+    case PhrasePartType::LEVENSHTEIN:
+      this->lt = std::move(other.lt);
+      break;
+    case PhrasePartType::SET:
+      this->ct = std::move(other.ct);
+      break;
+    default:
+      assert(false);
+  }
+}
+
+by_phrase::info_t::info_t(const simple_term& st) {
+  type = PhrasePartType::TERM;
+  allocate();
+  this->st = st;
+}
+
+by_phrase::info_t::info_t(simple_term&& st) noexcept {
+  type = PhrasePartType::TERM;
+  allocate();
+  this->st = std::move(st);
+}
+
+by_phrase::info_t::info_t(const prefix_term& pt) {
+  type = PhrasePartType::PREFIX;
+  allocate();
+  this->pt = pt;
+}
+
+by_phrase::info_t::info_t(prefix_term&& pt) noexcept {
+  type = PhrasePartType::PREFIX;
+  allocate();
+  this->pt = std::move(pt);
+}
+
+by_phrase::info_t::info_t(const wildcard_term& wt) {
+  type = PhrasePartType::WILDCARD;
+  allocate();
+  this->wt = wt;
+}
+
+by_phrase::info_t::info_t(wildcard_term&& wt) noexcept {
+  type = PhrasePartType::WILDCARD;
+  allocate();
+  this->wt = std::move(wt);
+}
+
+by_phrase::info_t::info_t(const levenshtein_term& lt) {
+  type = PhrasePartType::LEVENSHTEIN;
+  allocate();
+  this->lt = lt;
+}
+
+by_phrase::info_t::info_t(levenshtein_term&& lt) noexcept {
+  type = PhrasePartType::LEVENSHTEIN;
+  allocate();
+  this->lt = std::move(lt);
+}
+
+by_phrase::info_t::info_t(const set_term& ct) {
+  type = PhrasePartType::SET;
+  allocate();
+  this->ct = ct;
+}
+
+by_phrase::info_t::info_t(set_term&& ct) noexcept {
+  type = PhrasePartType::SET;
+  allocate();
+  this->ct = std::move(ct);
+}
+
+by_phrase::info_t& by_phrase::info_t::operator=(const info_t& other) noexcept {
+  if (&other == this) {
+    return *this;
+  }
+  recreate(other.type);
+  switch (type) {
+    case PhrasePartType::TERM:
+      st = other.st;
+      break;
+    case PhrasePartType::PREFIX:
+      pt = other.pt;
+      break;
+    case PhrasePartType::WILDCARD:
+      wt = other.wt;
+      break;
+    case PhrasePartType::LEVENSHTEIN:
+      lt = other.lt;
+      break;
+    case PhrasePartType::SET:
+      ct = other.ct;
+      break;
+    default:
+      assert(false);
+  }
+  return *this;
+}
+
+by_phrase::info_t& by_phrase::info_t::operator=(info_t&& other) noexcept {
+  if (&other == this) {
+    return *this;
+  }
+  recreate(other.type);
+  switch (type) {
+    case PhrasePartType::TERM:
+      st = std::move(other.st);
+      break;
+    case PhrasePartType::PREFIX:
+      pt = std::move(other.pt);
+      break;
+    case PhrasePartType::WILDCARD:
+      wt = std::move(other.wt);
+      break;
+    case PhrasePartType::LEVENSHTEIN:
+      lt = std::move(other.lt);
+      break;
+    case PhrasePartType::SET:
+      ct = std::move(other.ct);
+      break;
+    default:
+      assert(false);
+  }
+  return *this;
+}
+
+bool by_phrase::info_t::operator==(const info_t& other) const noexcept {
+  if (type != other.type) {
+    return false;
+  }
+  switch (type) {
+    case PhrasePartType::TERM:
+      return st == other.st;
+    case PhrasePartType::PREFIX:
+      return pt == other.pt;
+    case PhrasePartType::WILDCARD:
+      return wt == other.wt;
+    case PhrasePartType::LEVENSHTEIN:
+      return lt == other.lt;
+    case PhrasePartType::SET:
+      return ct == other.ct;
+    default:
+      assert(false);
+  }
+  return false;
+}
+
+void by_phrase::info_t::allocate() noexcept {
+  switch (type) {
+    case PhrasePartType::TERM:
+      new (&st) simple_term();
+      break;
+    case PhrasePartType::PREFIX:
+      new (&pt) prefix_term();
+      break;
+    case PhrasePartType::WILDCARD:
+      new (&wt) wildcard_term();
+      break;
+    case PhrasePartType::LEVENSHTEIN:
+      new (&lt) levenshtein_term();
+      break;
+    case PhrasePartType::SET:
+      new (&ct) set_term();
+      break;
+    default:
+      assert(false);
+  }
+}
+
+void by_phrase::info_t::destroy() noexcept {
+  switch (type) {
+    case PhrasePartType::TERM:
+      st.~simple_term();
+      break;
+    case PhrasePartType::PREFIX:
+      pt.~prefix_term();
+      break;
+    case PhrasePartType::WILDCARD:
+      wt.~wildcard_term();
+      break;
+    case PhrasePartType::LEVENSHTEIN:
+      lt.~levenshtein_term();
+      break;
+    case PhrasePartType::SET:
+      ct.~set_term();
+      break;
+    default:
+      assert(false);
+  }
+}
+
+void by_phrase::info_t::recreate(PhrasePartType new_type) noexcept {
+  if (type != new_type) {
+    destroy();
+    type = new_type;
+    allocate();
+  }
+}
+
+size_t hash_value(const by_phrase::info_t& info) {
+  auto seed = std::hash<int>()(static_cast<int>(info.type));
+  switch (info.type) {
+    case by_phrase::PhrasePartType::TERM:
+      break;
+    case by_phrase::PhrasePartType::PREFIX:
+      ::boost::hash_combine(seed, std::hash<size_t>()(info.pt.scored_terms_limit));
+      break;
+    case by_phrase::PhrasePartType::WILDCARD:
+      ::boost::hash_combine(seed, std::hash<size_t>()(info.wt.scored_terms_limit));
+      break;
+    case by_phrase::PhrasePartType::LEVENSHTEIN:
+      ::boost::hash_combine(seed, std::hash<size_t>()(info.lt.scored_terms_limit));
+      ::boost::hash_combine(seed, std::hash<byte_type>()(info.lt.max_distance));
+      ::boost::hash_combine(seed, std::hash<by_edit_distance::pdp_f>()(info.lt.provider));
+      ::boost::hash_combine(seed, std::hash<bool>()(info.lt.with_transpositions));
+      break;
+    case by_phrase::PhrasePartType::SET:
+      std::for_each(
+        info.ct.terms.cbegin(), info.ct.terms.cend(),
+        [&seed](const bstring& term) {
+          ::boost::hash_combine(seed, term);
+      });
+      break;
+    default:
+      assert(false);
+  }
+  return seed;
+}
+
 size_t by_phrase::hash() const noexcept {
   size_t seed = 0;
   ::boost::hash_combine(seed, filter::hash());
@@ -208,21 +595,50 @@ filter::prepared::ptr by_phrase::prepare(
     return filter::prepared::empty();
   }
 
-  if (1 == phrase_.size()) {
-    // similar to `term_query`
-    const irs::bytes_ref term = phrase_.begin()->second;
-    return term_query::make(rdr, ord, boost*this->boost(), fld_, term);
+  const auto phrase_size = phrase_.size();
+  if (1 == phrase_size) {
+    const auto& term_info = phrase_.begin()->second;
+    switch (term_info.type) {
+      case PhrasePartType::TERM: // similar to `term_query`
+        return term_query::make(rdr, ord, boost*this->boost(), fld_, term_info.st.term);
+      case PhrasePartType::PREFIX:
+        return by_prefix::prepare(rdr, ord, boost*this->boost(), fld_, term_info.pt.term,
+                                  term_info.pt.scored_terms_limit);
+      case PhrasePartType::WILDCARD:
+        return by_wildcard::prepare(rdr, ord, boost*this->boost(), fld_,
+                                    term_info.wt.term, term_info.wt.scored_terms_limit);
+      case PhrasePartType::LEVENSHTEIN:
+        return by_edit_distance::prepare(rdr, ord, boost*this->boost(), fld_,
+                                         term_info.lt.term, term_info.lt.scored_terms_limit,
+                                         term_info.lt.max_distance, term_info.lt.provider,
+                                         term_info.lt.with_transpositions);
+      case PhrasePartType::SET:
+        // do nothing
+        break;
+      default:
+        assert(false);
+    }
   }
 
-  // per segment phrase states 
-  phrase_query::states_t phrase_states(rdr.size());
+  // prepare phrase stats (collector for each term)
+  if (is_simple_term_only_) {
+    return fixed_prepare_collect(rdr, ord, boost, ord.fixed_prepare_collectors(phrase_size));
+  }
+  return variadic_prepare_collect(rdr, ord, boost, ord.variadic_prepare_collectors(phrase_size));
+}
 
-  // per segment phrase terms
-  phrase_state::terms_states_t phrase_terms;
-  phrase_terms.reserve(phrase_.size());
+filter::prepared::ptr by_phrase::fixed_prepare_collect(
+    const index_reader& rdr,
+    const order::prepared& ord,
+    boost_t boost,
+    order::prepared::fixed_terms_collectors collectors) const {
+  // per segment phrase states
+  fixed_phrase_query::states_t phrase_states(rdr.size());
 
-  // prepare phrase stats (collector for each term)
-  auto collectors = ord.prepare_collectors(phrase_.size());
+  // per segment phrase terms
+  phrase_state<order::prepared::FixedContainer>::terms_states_t phrase_terms;
+  auto phrase_size = phrase_.size();
+  phrase_terms.reserve(phrase_size);
 
   // iterate over the segments
   const string_ref field = fld_;
@@ -246,14 +662,14 @@ filter::prepared::ptr by_phrase::prepare(
     seek_term_iterator::ptr term = tr->iterator();
     size_t term_itr = 0;
 
-    for(auto& word: phrase_) {
+    for (const auto& word : phrase_) {
+      assert(PhrasePartType::TERM == word.second.type);
       auto next_stats = irs::make_finally([&term_itr]()->void{ ++term_itr; });
-
-      if (!term->seek(word.second)) {
+      if (!term->seek(word.second.st.term)) {
         if (ord.empty()) {
           break;
         } else {
-          // continue here because we should collect 
+          // continue here because we should collect
           // stats for other terms in phrase
           continue;
         }
@@ -267,7 +683,7 @@ filter::prepared::ptr by_phrase::prepare(
     }
 
     // we have not found all needed terms
-    if (phrase_terms.size() != phrase_.size()) {
+    if (phrase_terms.size() != phrase_size) {
       phrase_terms.clear();
       continue;
     }
@@ -276,17 +692,329 @@ filter::prepared::ptr by_phrase::prepare(
     state.terms = std::move(phrase_terms);
     state.reader = tr;
 
-    phrase_terms.reserve(phrase_.size());
+    phrase_terms.reserve(phrase_size);
+  }
+
+  // offset of the first term in a phrase
+  size_t base_offset = first_pos();
+
+  // finish stats
+  fixed_phrase_query::positions_t positions(phrase_size);
+  auto pos_itr = positions.begin();
+
+  for (const auto& term : phrase_) {
+    *pos_itr = position::value_t(term.first - base_offset);
+    ++pos_itr;
+  }
+
+  bstring stats(ord.stats_size(), 0); // aggregated phrase stats
+  auto* stats_buf = const_cast<byte_type*>(stats.data());
+
+  ord.prepare_stats(stats_buf);
+  collectors.finish(stats_buf, rdr);
+
+  return memory::make_shared<fixed_phrase_query>(
+    std::move(phrase_states),
+    std::move(positions),
+    std::move(stats),
+    this->boost() * boost
+  );
+}
+
+filter::prepared::ptr by_phrase::variadic_prepare_collect(
+    const index_reader& rdr,
+    const order::prepared& ord,
+    boost_t boost,
+    order::prepared::variadic_terms_collectors collectors) const {
+  // per segment phrase states
+  variadic_phrase_query::states_t phrase_states(rdr.size());
+
+  // per segment phrase terms
+  phrase_state<order::prepared::VariadicContainer>::terms_states_t phrase_terms;
+  auto phrase_size = phrase_.size();
+  phrase_terms.resize(phrase_size);
+
+  // iterate over the segments
+  const string_ref field = fld_;
+
+  for (const auto& sr : rdr) {
+    // get term dictionary for field
+    const term_reader* tr = sr.field(field);
+
+    if (!tr) {
+      continue;
+    }
+
+    // check required features
+    if (!by_phrase::required().is_subset_of(tr->meta().features)) {
+      continue;
+    }
+
+    collectors.collect(sr, *tr); // collect field statistics once per segment
+
+    // find terms
+    seek_term_iterator::ptr term = tr->iterator();
+    size_t term_itr = 0;
+    size_t found_words_count = 0;
+
+    size_t i = 0;
+    for (const auto& word : phrase_) {
+      auto next_stats = irs::make_finally([&term_itr]()->void{ ++term_itr; });
+      auto& pt = phrase_terms[i++];
+      auto type = word.second.type;
+      bytes_ref pattern;
+      auto stop = false;
+      switch (word.second.type) {
+        case PhrasePartType::TERM:
+          pattern = word.second.st.term;
+          break;
+        case PhrasePartType::PREFIX:
+          pattern = word.second.pt.term;
+          break;
+        case PhrasePartType::WILDCARD:
+          pattern = word.second.wt.term;
+          switch (irs::wildcard_type(pattern)) {
+            case WildcardType::INVALID:
+              if (ord.empty()) {
+                stop = true;
+                // else we should collect
+                // stats for other terms in phrase
+              }
+              break;
+            case WildcardType::TERM:
+              type = PhrasePartType::TERM;
+              break;
+            case WildcardType::MATCH_ALL:
+              pattern = bytes_ref::EMPTY; // empty prefix == match all
+              type = PhrasePartType::PREFIX;
+              break;
+            case WildcardType::PREFIX: {
+              assert(!pattern.empty());
+              const auto* begin = pattern.c_str();
+              const auto* end = begin + pattern.size();
+
+              // pattern is already checked to be a valid UTF-8 sequence
+              const auto* pos = utf8_utils::find<false>(begin, end, WildcardMatch::ANY_STRING);
+              assert(pos != end);
+              pattern = bytes_ref(begin, size_t(pos - begin)); // remove trailing '%'
+              type = PhrasePartType::PREFIX;
+              break;
+            }
+            case WildcardType::WILDCARD:
+              // do nothing
+              break;
+            default:
+              assert(false);
+          }
+          break;
+        case PhrasePartType::LEVENSHTEIN:
+          if (0 == word.second.lt.max_distance) {
+            type = PhrasePartType::TERM;
+          }
+          break;
+        case PhrasePartType::SET:
+          if (word.second.ct.terms.size() == 1) {
+            pattern = word.second.ct.terms.front();
+            type = PhrasePartType::TERM;
+          }
+          break;
+        default:
+          assert(false);
+      }
+      if (stop) {
+        break;
+      }
+
+      switch (type) {
+        case PhrasePartType::TERM: {
+          if (!term->seek(pattern)) {
+            if (ord.empty()) {
+              stop = true;
+              // else we should collect
+              // stats for other terms in phrase
+            }
+            break;
+          }
+
+          term->read(); // read term attributes
+          collectors.collect(sr, *tr, term_itr, term->attributes()); // collect statistics
+
+          // estimate phrase & term
+          pt.emplace_back(term->cookie());
+          ++found_words_count;
+          break;
+        }
+        case PhrasePartType::PREFIX: {
+          // seek to prefix
+          if (SeekResult::END == term->seek_ge(pattern)) {
+            if (ord.empty()) {
+              stop = true;
+              // else we should collect
+              // stats for other terms in phrase
+            }
+            break;
+          }
+
+          const auto& value = term->value();
+
+          #ifdef IRESEARCH_DEBUG
+            auto found = false;
+          #endif
+          while (starts_with(value, pattern)) {
+            #ifdef IRESEARCH_DEBUG
+              found = true;
+            #endif
+            term->read();
+            collectors.collect(sr, *tr, term_itr, term->attributes()); // collect statistics
+
+            // estimate phrase & term
+            pt.emplace_back(term->cookie());
+            if (!term->next()) {
+              break;
+            }
+          }
+          #ifdef IRESEARCH_DEBUG
+            assert(found);
+          #endif
+          ++found_words_count;
+          break;
+        }
+        case PhrasePartType::WILDCARD: {
+          const auto& acceptor = from_wildcard(pattern);
+          automaton_table_matcher matcher(acceptor, fst::fsa::kRho);
+
+          if (fst::kError == matcher.Properties(0)) {
+            IR_FRMT_ERROR("Expected deterministic, epsilon-free acceptor, "
+                          "got the following properties " IR_UINT64_T_SPECIFIER "",
+                          acceptor.Properties(automaton_table_matcher::FST_PROPERTIES, false));
+            if (ord.empty()) {
+              stop = true;
+              // else we should collect
+              // stats for other terms in phrase
+            }
+            break;
+          }
+
+          auto term_wildcard = tr->iterator(matcher);
+
+          auto found = false;
+          while (term_wildcard->next()) {
+            found = true;
+            term_wildcard->read();
+            collectors.collect(sr, *tr, term_itr, term_wildcard->attributes()); // collect statistics
+
+            // estimate phrase & term
+            pt.emplace_back(term_wildcard->cookie());
+          }
+          if (found) {
+            ++found_words_count;
+          } else if (ord.empty()) {
+            stop = true;
+            // else we should collect
+            // stats for other terms in phrase
+          }
+          break;
+        }
+        case PhrasePartType::LEVENSHTEIN: {
+          assert(word.second.lt.provider);
+          const auto& d = (*word.second.lt.provider)(word.second.lt.max_distance,
+                                                     word.second.lt.with_transpositions);
+          if (!d) {
+            if (ord.empty()) {
+              stop = true;
+              // else we should collect
+              // stats for other terms in phrase
+            }
+            break;
+          }
+          const auto& acceptor = irs::make_levenshtein_automaton(d, word.second.lt.term);
+          automaton_table_matcher matcher(acceptor, fst::fsa::kRho);
+
+          if (fst::kError == matcher.Properties(0)) {
+            IR_FRMT_ERROR("Expected deterministic, epsilon-free acceptor, "
+                          "got the following properties " IR_UINT64_T_SPECIFIER "",
+                          acceptor.Properties(automaton_table_matcher::FST_PROPERTIES, false));
+            if (ord.empty()) {
+              stop = true;
+              // else we should collect
+              // stats for other terms in phrase
+            }
+            break;
+          }
+          auto term_levenshtein = tr->iterator(matcher);
+
+          auto found = false;
+          while (term_levenshtein->next()) {
+            found = true;
+            term_levenshtein->read();
+            collectors.collect(sr, *tr, term_itr, term_levenshtein->attributes()); // collect statistics
+
+            // estimate phrase & term
+            pt.emplace_back(term_levenshtein->cookie());
+          }
+          if (found) {
+            ++found_words_count;
+          } else if (ord.empty()) {
+            stop = true;
+            // else we should collect
+            // stats for other terms in phrase
+          }
+          break;
+        }
+        case PhrasePartType::SET: {
+          auto found = false;
+          for (const auto& pat : word.second.ct.terms) {
+            if (!term->seek(pat)) {
+              continue;
+            }
+            found = true;
+
+            term->read(); // read term attributes
+            collectors.collect(sr, *tr, term_itr, term->attributes()); // collect statistics
+
+            // estimate phrase & term
+            pt.emplace_back(term->cookie());
+          }
+          if (found) {
+            ++found_words_count;
+          } else if (ord.empty()) {
+            stop = true;
+            // else we should collect
+            // stats for other terms in phrase
+          }
+          break;
+        }
+        default:
+          assert(false);
+      }
+      if (stop) {
+        break;
+      }
+    }
+
+    // we have not found all needed terms
+    if (found_words_count != phrase_size) {
+      for (auto& pt : phrase_terms) {
+        pt.clear();
+      }
+      continue;
+    }
+
+    auto& state = phrase_states.insert(sr);
+    state.terms = std::move(phrase_terms);
+    state.reader = tr;
+
+    phrase_terms.resize(phrase_size);
   }
 
   // offset of the first term in a phrase
   size_t base_offset = first_pos();
 
   // finish stats
-  phrase_query::positions_t positions(phrase_.size());
+  variadic_phrase_query::positions_t positions(phrase_size);
   auto pos_itr = positions.begin();
 
-  for(auto& term: phrase_) {
+  for (const auto& term : phrase_) {
     *pos_itr = position::value_t(term.first - base_offset);
     ++pos_itr;
   }
@@ -297,7 +1025,7 @@ filter::prepared::ptr by_phrase::prepare(
   ord.prepare_stats(stats_buf);
   collectors.finish(stats_buf, rdr);
 
-  return memory::make_shared<phrase_query>(
+  return memory::make_shared<variadic_phrase_query>(
     std::move(phrase_states),
     std::move(positions),
     std::move(stats),
diff --git a/3rdParty/iresearch/core/search/phrase_filter.hpp b/3rdParty/iresearch/core/search/phrase_filter.hpp
index c7e66b9044a4..043e52b2c71c 100644
--- a/3rdParty/iresearch/core/search/phrase_filter.hpp
+++ b/3rdParty/iresearch/core/search/phrase_filter.hpp
@@ -26,6 +26,8 @@
 #include <map>
 
 #include "filter.hpp"
+#include "levenshtein_filter.hpp"
+#include "utils/levenshtein_default_pdp.hpp"
 #include "utils/string.hpp"
 
 NS_ROOT
@@ -36,13 +38,108 @@ NS_ROOT
 //////////////////////////////////////////////////////////////////////////////
 class IRESEARCH_API by_phrase : public filter {
  public:
+  enum class PhrasePartType {
+    TERM, PREFIX, WILDCARD, LEVENSHTEIN, SET
+  };
+
+  struct simple_term {
+    bool operator==(const simple_term& other) const noexcept {
+      return term == other.term;
+    }
+
+    bstring term;
+  };
+
+  struct prefix_term {
+    bool operator==(const prefix_term& other) const noexcept {
+      return term == other.term;
+    }
+
+    size_t scored_terms_limit{1024};
+    bstring term;
+  };
+
+  struct wildcard_term {
+    bool operator==(const wildcard_term& other) const noexcept {
+      return term == other.term;
+    }
+
+    size_t scored_terms_limit{1024};
+    bstring term;
+  };
+
+  struct levenshtein_term {
+    bool operator==(const levenshtein_term& other) const noexcept {
+      return with_transpositions == other.with_transpositions &&
+          max_distance == other.max_distance &&
+          provider == other.provider &&
+          term == other.term;
+    }
+
+    bool with_transpositions{false};
+    byte_type max_distance{0};
+    size_t scored_terms_limit{1024};
+    by_edit_distance::pdp_f provider{irs::default_pdp};
+    bstring term;
+  };
+
+  struct set_term {
+    bool operator==(const set_term& other) const noexcept {
+      return terms == other.terms;
+    }
+
+    std::vector<bstring> terms;
+  };
+
+ private:
+  struct IRESEARCH_API info_t {
+    ~info_t() {
+      destroy();
+    }
+
+    PhrasePartType type;
+
+    union {
+      simple_term st;
+      prefix_term pt;
+      wildcard_term wt;
+      levenshtein_term lt;
+      set_term ct;
+    };
+
+    info_t();
+    info_t(const info_t& other);
+    info_t(info_t&& other) noexcept;
+    info_t(const simple_term& st);
+    info_t(simple_term&& st) noexcept;
+    info_t(const prefix_term& pt);
+    info_t(prefix_term&& pt) noexcept;
+    info_t(const wildcard_term& wt);
+    info_t(wildcard_term&& wt) noexcept;
+    info_t(const levenshtein_term& lt);
+    info_t(levenshtein_term&& lt) noexcept;
+    info_t(const set_term& lt);
+    info_t(set_term&& lt) noexcept;
+
+    info_t& operator=(const info_t& other) noexcept;
+    info_t& operator=(info_t&& other) noexcept;
+
+    bool operator==(const info_t& other) const noexcept;
+
+   private:
+    void allocate() noexcept;
+    void destroy() noexcept;
+    void recreate(PhrasePartType new_type) noexcept;
+  };
+
   // positions and terms
-  typedef std::map<size_t, bstring> terms_t;
-  typedef terms_t::const_iterator const_iterator;
-  typedef terms_t::iterator iterator;
+  typedef std::map<size_t, info_t> terms_t;
   typedef terms_t::value_type term_t;
 
-  // returns set of features required for filter 
+  friend size_t hash_value(const by_phrase::info_t& info);
+
+ public:
+  // returns set of features required for filter
   static const flags& required();
 
   DECLARE_FILTER_TYPE();
@@ -50,55 +147,73 @@ class IRESEARCH_API by_phrase : public filter {
 
   by_phrase();
 
-  by_phrase& field(std::string fld) {
-    fld_ = std::move(fld); 
+  by_phrase& field(std::string fld) noexcept {
+    fld_ = std::move(fld);
     return *this;
   }
 
-  const std::string& field() const { return fld_; }
+  const std::string& field() const noexcept { return fld_; }
 
-  // inserts term to the specified position 
-  by_phrase& insert(size_t pos, const bytes_ref& term) {
-    phrase_[pos] = term; 
+  // inserts term to the specified position
+  template<typename PhrasePart>
+  by_phrase& insert(PhrasePart&& t, size_t pos) {
+    is_simple_term_only_ &= std::is_same<PhrasePart, simple_term>::value; // constexpr
+    phrase_[pos] = std::forward<PhrasePart>(t);
     return *this;
   }
 
-  by_phrase& insert(size_t pos, const string_ref& term) {
-    return insert(pos, ref_cast<byte_type>(term));
+  template<typename PhrasePart>
+  by_phrase& push_back(PhrasePart&& t, size_t offs = 0) {
+    return insert(std::forward<PhrasePart>(t), next_pos() + offs);
   }
 
-  by_phrase& insert(size_t pos, bstring&& term) {
-    phrase_[pos] = std::move(term);
-    return *this;
+  bool get(size_t pos, simple_term& t) {
+    const auto& inf = phrase_.at(pos);
+    if (PhrasePartType::TERM != inf.type) {
+      return false;
+    }
+    t = inf.st;
+    return true;
   }
 
-  // inserts term to the end of the phrase with 
-  // the specified offset from the last term
-  by_phrase& push_back(const bytes_ref& term, size_t offs = 0) {
-    return insert(next_pos() + offs, term);
+  bool get(size_t pos, prefix_term& t) {
+    const auto& inf = phrase_.at(pos);
+    if (PhrasePartType::PREFIX != inf.type) {
+      return false;
+    }
+    t = inf.pt;
+    return true;
   }
 
-  by_phrase& push_back(const string_ref& term, size_t offs = 0) {
-    return push_back(ref_cast<byte_type>(term), offs);
+  bool get(size_t pos, wildcard_term& t) {
+    const auto& inf = phrase_.at(pos);
+    if (PhrasePartType::WILDCARD != inf.type) {
+      return false;
+    }
+    t = inf.wt;
+    return true;
   }
 
-  by_phrase& push_back(bstring&& term, size_t offs = 0) {
-    return insert(next_pos() + offs, std::move(term));
+  bool get(size_t pos, levenshtein_term& t) {
+    const auto& inf = phrase_.at(pos);
+    if (PhrasePartType::LEVENSHTEIN != inf.type) {
+      return false;
+    }
+    t = inf.lt;
+    return true;
   }
 
-  bstring& operator[](size_t pos) { return phrase_[pos]; } 
-  const bstring& operator[](size_t pos) const {
-    return phrase_.at(pos); 
+  bool get(size_t pos, set_term& t) {
+    const auto& inf = phrase_.at(pos);
+    if (PhrasePartType::SET != inf.type) {
+      return false;
+    }
+    t = inf.ct;
+    return true;
   }
 
-  bool empty() const { return phrase_.empty(); }
-  size_t size() const { return phrase_.size(); }
-
-  const_iterator begin() const { return phrase_.begin(); }
-  const_iterator end() const { return phrase_.end(); }
-
-  iterator begin() { return phrase_.begin(); }
-  iterator end() { return phrase_.end(); }
+  bool empty() const noexcept { return phrase_.empty(); }
+  size_t size() const noexcept { return phrase_.size(); }
 
   using filter::prepare;
 
@@ -113,19 +228,32 @@ class IRESEARCH_API by_phrase : public filter {
 
  protected:
   virtual bool equals(const filter& rhs) const noexcept override;
- 
+
  private:
   size_t next_pos() const {
     return phrase_.empty() ? 0 : 1 + phrase_.rbegin()->first;
   }
-  
+
   size_t first_pos() const {
     return phrase_.empty() ? 0 : phrase_.begin()->first;
   }
 
+  filter::prepared::ptr fixed_prepare_collect(
+      const index_reader& rdr,
+      const order::prepared& ord,
+      boost_t boost,
+      order::prepared::fixed_terms_collectors collectors) const;
+
+  filter::prepared::ptr variadic_prepare_collect(
+      const index_reader& rdr,
+      const order::prepared& ord,
+      boost_t boost,
+      order::prepared::variadic_terms_collectors collectors) const;
+
   IRESEARCH_API_PRIVATE_VARIABLES_BEGIN
   std::string fld_;
   terms_t phrase_;
+  bool is_simple_term_only_{true};
   IRESEARCH_API_PRIVATE_VARIABLES_END
 }; // by_phrase
 
diff --git a/3rdParty/iresearch/core/search/phrase_iterator.hpp b/3rdParty/iresearch/core/search/phrase_iterator.hpp
index 169311d0e896..b20174dfb16c 100644
--- a/3rdParty/iresearch/core/search/phrase_iterator.hpp
+++ b/3rdParty/iresearch/core/search/phrase_iterator.hpp
@@ -23,14 +23,14 @@
 #ifndef IRESEARCH_PHRASE_ITERATOR_H
 #define IRESEARCH_PHRASE_ITERATOR_H
 
+#include "disjunction.hpp"
+#include "score_doc_iterators.hpp"
 #include "shared.hpp"
+#include "utils/attribute_range.hpp"
 
 NS_ROOT
 
-// implementation is optimized for frequency based similarity measures
-// for generic implementation see a03025accd8b84a5f8ecaaba7412fc92a1636be3
-template<typename Conjunction>
-class phrase_iterator final : public doc_iterator_base {
+class fixed_phrase_frequency {
  public:
   typedef std::pair<
     position::ref, // position attribute
@@ -38,19 +38,173 @@ class phrase_iterator final : public doc_iterator_base {
   > position_t;
   typedef std::vector<position_t> positions_t;
 
+  fixed_phrase_frequency(
+      positions_t&& pos,
+      const order::prepared& ord
+  ) : pos_(std::move(pos)), order_(&ord) {
+    assert(!pos_.empty()); // must not be empty
+    assert(0 == pos_.front().second); // lead offset is always 0
+  }
+
+ protected:
+  // returns frequency of the phrase
+  frequency::value_t phrase_freq() {
+    frequency::value_t freq = 0;
+    bool match;
+
+    position& lead = pos_.front().first;
+    lead.next();
+
+    for (auto end = pos_.end(); !pos_limits::eof(lead.value());) {
+      const position::value_t base_position = lead.value();
+
+      match = true;
+
+      for (auto it = pos_.begin() + 1; it != end; ++it) {
+        position& pos = it->first;
+        const auto term_position = base_position + it->second;
+        if (!pos_limits::valid(term_position)) {
+          return freq;
+        }
+        const auto seeked = pos.seek(term_position);
+
+        if (pos_limits::eof(seeked)) {
+          // exhausted
+          return freq;
+        } else if (seeked != term_position) {
+          // seeked too far from the lead
+          match = false;
+
+          lead.seek(seeked - it->second);
+          break;
+        }
+      }
+
+      if (match) {
+        if (order_->empty()) {
+          return 1;
+        }
+
+        ++freq;
+        lead.next();
+      }
+    }
+
+    return freq;
+  }
+
+ private:
+  positions_t pos_; // list of desired positions along with corresponding attributes
+  const order::prepared* order_;
+}; // fixed_phrase_frequency
+
+class variadic_phrase_frequency {
+ public:
+  typedef std::pair<
+    const attribute_view::ref<attribute_range<position_score_iterator_adapter<doc_iterator::ptr>>>::type*, // position attribute
+    position::value_t // desired offset in the phrase
+  > position_t;
+  typedef std::vector<position_t> positions_t;
+
+  variadic_phrase_frequency(
+      positions_t&& pos,
+      const order::prepared& ord)
+    : pos_(std::move(pos)), order_(&ord) {
+    assert(!pos_.empty()); // must not be empty
+    assert(0 == pos_.front().second); // lead offset is always 0
+  }
+
+ protected:
+  // returns frequency of the phrase
+  frequency::value_t phrase_freq() {
+    frequency::value_t freq = 0;
+    auto end = pos_.end();
+    auto* posa = pos_.front().first->get();
+    assert(posa);
+    posa->reset();
+    while (posa->next()) {
+      auto* lead_adapter = posa->value();
+      auto* lead = lead_adapter->position;
+      auto global_match = true;
+      // lead->reset(); // Do not need here. There is always a first time.
+      lead->next();
+
+      position::value_t base_position = pos_limits::eof();
+      while (!pos_limits::eof(base_position = lead->value())) {
+        auto match = true;
+        for (auto it = pos_.begin() + 1; it != end; ++it) {
+          match = false;
+          const auto term_position = base_position + it->second;
+          if (!pos_limits::valid(term_position)) {
+            global_match = false; // invalid for all
+            break;
+          }
+          auto min_seeked = std::numeric_limits<position::value_t>::max();
+          auto* ita = it->first->get();
+          assert(ita);
+          ita->reset();
+          while (ita->next()) {
+            auto* it_adapter = ita->value();
+            auto* p = it_adapter->position;
+            p->reset();
+            const auto seeked = p->seek(term_position);
+
+            if (pos_limits::eof(seeked)) {
+              continue;
+            } else if (seeked != term_position) {
+              if (seeked < min_seeked) {
+                min_seeked = seeked;
+              }
+              continue;
+            }
+            match = true;
+            break;
+          }
+          if (!match) {
+            if (min_seeked < std::numeric_limits<position::value_t>::max()) {
+              lead->seek(min_seeked - it->second);
+              break;
+            }
+            global_match = false; // eof for all
+            break;
+          }
+        }
+        if (!global_match) {
+          break;
+        }
+        if (match) {
+          if (order_->empty()) {
+            return 1;
+          }
+          ++freq;
+          lead->next();
+        }
+      }
+    }
+    return freq;
+  }
+
+ private:
+  positions_t pos_; // list of desired positions along with corresponding attributes
+  const order::prepared* order_;
+}; // variadic_phrase_frequency
+
+// implementation is optimized for frequency based similarity measures
+// for generic implementation see a03025accd8b84a5f8ecaaba7412fc92a1636be3
+template<typename Conjunction, typename Frequency>
+class phrase_iterator : public doc_iterator_base, Frequency {
+ public:
+  typedef typename Frequency::positions_t positions_t;
+
   phrase_iterator(
       typename Conjunction::doc_iterators_t&& itrs,
-      positions_t&& pos,
+      typename Frequency::positions_t&& pos,
       const sub_reader& segment,
       const term_reader& field,
       const byte_type* stats,
       const order::prepared& ord,
       boost_t boost
-  ) : approx_(std::move(itrs)),
-      pos_(std::move(pos)),
-      order_(&ord) {
-    assert(!pos_.empty()); // must not be empty
-    assert(0 == pos_.front().second); // lead offset is always 0
+  ) : Frequency(std::move(pos), ord), approx_(std::move(itrs)) {
 
     // FIXME find a better estimation
     // estimate iterator
@@ -75,7 +229,7 @@ class phrase_iterator final : public doc_iterator_base {
 
   virtual bool next() override {
     bool next = false;
-    while ((next = approx_.next()) && !(phrase_freq_.value = phrase_freq())) {}
+    while ((next = approx_.next()) && !(phrase_freq_.value = this->phrase_freq())) {}
 
     return next;
   }
@@ -85,7 +239,7 @@ class phrase_iterator final : public doc_iterator_base {
       return target;
     }
 
-    if (doc_limits::eof(value()) || (phrase_freq_.value = phrase_freq())) {
+    if (doc_limits::eof(value()) || (phrase_freq_.value = this->phrase_freq())) {
       return value();
     }
 
@@ -95,54 +249,9 @@ class phrase_iterator final : public doc_iterator_base {
   }
 
  private:
-  // returns frequency of the phrase
-  frequency::value_t phrase_freq() {
-    frequency::value_t freq = 0;
-    bool match;
-
-    position& lead = pos_.front().first;
-    lead.next();
-
-    for (auto end = pos_.end(); !pos_limits::eof(lead.value());) {
-      const position::value_t base_offset = lead.value();
-
-      match = true;
-
-      for (auto it = pos_.begin() + 1; it != end; ++it) {
-        position& pos = it->first;
-        const auto term_offset = base_offset + it->second;
-        const auto seeked = pos.seek(term_offset);
-
-        if (pos_limits::eof(seeked)) {
-          // exhausted
-          return freq;
-        } else if (seeked != term_offset) {
-          // seeked too far from the lead
-          match = false;
-
-          lead.seek(seeked - it->second);
-          break;
-        }
-      }
-
-      if (match) {
-        if (order_->empty()) {
-          return 1;
-        }
-
-        ++freq;
-        lead.next();
-      }
-    }
-
-    return freq;
-  }
-
   Conjunction approx_; // first approximation (conjunction over all words in a phrase)
   const document* doc_{}; // document itself
   frequency phrase_freq_; // freqency of the phrase in a document
-  positions_t pos_; // list of desired positions along with corresponding attributes
-  const order::prepared* order_;
 }; // phrase_iterator
 
 NS_END // ROOT
diff --git a/3rdParty/iresearch/core/search/prefix_filter.hpp b/3rdParty/iresearch/core/search/prefix_filter.hpp
index 310d90f3ff19..fe8ae558a5d9 100644
--- a/3rdParty/iresearch/core/search/prefix_filter.hpp
+++ b/3rdParty/iresearch/core/search/prefix_filter.hpp
@@ -64,7 +64,7 @@ class IRESEARCH_API by_prefix : public by_term {
   //////////////////////////////////////////////////////////////////////////////
   /// @brief the maximum number of most frequent terms to consider for scoring
   //////////////////////////////////////////////////////////////////////////////
-  by_prefix& scored_terms_limit(size_t limit) {
+  by_prefix& scored_terms_limit(size_t limit) noexcept {
     scored_terms_limit_ = limit;
     return *this;
   }
@@ -72,7 +72,7 @@ class IRESEARCH_API by_prefix : public by_term {
   //////////////////////////////////////////////////////////////////////////////
   /// @brief the maximum number of most frequent terms to consider for scoring
   //////////////////////////////////////////////////////////////////////////////
-  size_t scored_terms_limit() const {
+  size_t scored_terms_limit() const noexcept {
     return scored_terms_limit_;
   }
 
diff --git a/3rdParty/iresearch/core/search/range_filter.hpp b/3rdParty/iresearch/core/search/range_filter.hpp
index a7ed96e4620b..b237c83714d1 100644
--- a/3rdParty/iresearch/core/search/range_filter.hpp
+++ b/3rdParty/iresearch/core/search/range_filter.hpp
@@ -78,7 +78,7 @@ class IRESEARCH_API by_range : public filter {
     return *this;
   }
 
-  const std::string& field() const { 
+  const std::string& field() const noexcept {
     return fld_; 
   }
 
@@ -130,7 +130,7 @@ class IRESEARCH_API by_range : public filter {
   //////////////////////////////////////////////////////////////////////////////
   /// @brief the maximum number of most frequent terms to consider for scoring
   //////////////////////////////////////////////////////////////////////////////
-  by_range& scored_terms_limit(size_t limit) {
+  by_range& scored_terms_limit(size_t limit) noexcept {
     scored_terms_limit_ = limit;
     return *this;
   }
@@ -138,7 +138,7 @@ class IRESEARCH_API by_range : public filter {
   //////////////////////////////////////////////////////////////////////////////
   /// @brief the maximum number of most frequent terms to consider for scoring
   //////////////////////////////////////////////////////////////////////////////
-  size_t scored_terms_limit() const {
+  size_t scored_terms_limit() const noexcept {
     return scored_terms_limit_;
   }
 
diff --git a/3rdParty/iresearch/core/search/same_position_filter.cpp b/3rdParty/iresearch/core/search/same_position_filter.cpp
index 97a858f875b0..ee5cc548c332 100644
--- a/3rdParty/iresearch/core/search/same_position_filter.cpp
+++ b/3rdParty/iresearch/core/search/same_position_filter.cpp
@@ -264,11 +264,11 @@ filter::prepared::ptr by_same_position::prepare(
   term_states.reserve(terms_.size());
 
   // prepare phrase stats (collector for each term)
-  std::vector<order::prepared::collectors> term_stats;
+  std::vector<order::prepared::fixed_terms_collectors> term_stats;
   term_stats.reserve(terms_.size());
 
   for(auto size = terms_.size(); size; --size) {
-    term_stats.emplace_back(ord.prepare_collectors(1)); // 1 term per bstring because a range is treated as a disjunction
+    term_stats.emplace_back(ord.fixed_prepare_collectors(1)); // 1 term per bstring because a range is treated as a disjunction
   }
 
   for (const auto& segment : index) {
diff --git a/3rdParty/iresearch/core/search/same_position_filter.hpp b/3rdParty/iresearch/core/search/same_position_filter.hpp
index a6ba6e435eb6..746ad8fb37c8 100644
--- a/3rdParty/iresearch/core/search/same_position_filter.hpp
+++ b/3rdParty/iresearch/core/search/same_position_filter.hpp
@@ -62,15 +62,15 @@ class IRESEARCH_API by_same_position : public filter {
   by_same_position& push_back(std::string&& field, const bstring& term);
   by_same_position& push_back(std::string&& field, bstring&& term);
 
-  iterator begin() { return terms_.begin(); }
-  iterator end() { return terms_.end(); }
+  iterator begin() noexcept { return terms_.begin(); }
+  iterator end() noexcept { return terms_.end(); }
 
-  const_iterator begin() const { return terms_.begin(); }
-  const_iterator end() const { return terms_.end(); }
+  const_iterator begin() const noexcept { return terms_.begin(); }
+  const_iterator end() const noexcept { return terms_.end(); }
 
-  bool empty() const { return terms_.empty(); }
-  size_t size() const { return terms_.size(); }
-  void clear() { terms_.clear(); }
+  bool empty() const noexcept { return terms_.empty(); }
+  size_t size() const noexcept { return terms_.size(); }
+  void clear() noexcept { terms_.clear(); }
 
  protected:
   virtual bool equals(const filter& rhs) const noexcept override;
diff --git a/3rdParty/iresearch/core/search/sort.cpp b/3rdParty/iresearch/core/search/sort.cpp
index b480ab249a8c..5ea53848eadd 100644
--- a/3rdParty/iresearch/core/search/sort.cpp
+++ b/3rdParty/iresearch/core/search/sort.cpp
@@ -164,36 +164,27 @@ order::prepared order::prepare() const {
 // --SECTION--                                                        collectors
 // -----------------------------------------------------------------------------
 
-order::prepared::collectors::collectors(
-    const order::prepared& buckets,
-    size_t terms_count)
+template<template<typename...> class T>
+order::prepared::collectors<T>::collectors(const order::prepared& buckets)
   : buckets_(buckets.order_) {
   field_collectors_.reserve(buckets_.size());
-  term_collectors_.reserve(buckets_.size() * terms_count);
 
   // add field collectors from each bucket
   for (auto& entry: buckets_) {
     assert(entry.bucket); // ensured by order::prepare
     field_collectors_.emplace_back(entry.bucket->prepare_field_collector());
   }
-
-  // add term collectors from each bucket
-  // layout order [t0.b0, t0.b1, ... t0.bN, t1.b0, t1.b1 ... tM.BN]
-  for (size_t i = 0; i < terms_count; ++i) {
-    for (auto& entry: buckets_) {
-      assert(entry.bucket); // ensured by order::prepare
-      term_collectors_.emplace_back(entry.bucket->prepare_term_collector());
-    }
-  }
 }
 
-order::prepared::collectors::collectors(collectors&& other) noexcept
+template<template<typename...> class T>
+order::prepared::collectors<T>::collectors(collectors<T>&& other) noexcept
   : buckets_(other.buckets_),
     field_collectors_(std::move(other.field_collectors_)),
     term_collectors_(std::move(other.term_collectors_)) {
 }
 
-void order::prepared::collectors::collect(
+template<template<typename...> class T>
+void order::prepared::collectors<T>::collect(
     const sub_reader& segment,
     const term_reader& field) const {
   for (auto& entry: field_collectors_) {
@@ -203,13 +194,59 @@ void order::prepared::collectors::collect(
   }
 }
 
-void order::prepared::collectors::collect(
+template<template<typename...> class T>
+void order::prepared::collectors<T>::empty_finish(
+    byte_type* stats_buf,
+    const index_reader& index) const {
+  // special case where term statistics collection is not applicable
+  // e.g. by_column_existence filter
+  assert(field_collectors_.size() == buckets_.size()); // enforced by allocation in the constructor
+
+  for (size_t i = 0, count = field_collectors_.size(); i < count; ++i) {
+    auto& sort = buckets_[i];
+    assert(sort.bucket); // ensured by order::prepare
+
+    sort.bucket->collect(
+      stats_buf + sort.stats_offset, // where stats for bucket start
+      index,
+      field_collectors_[i].get(),
+      nullptr
+    );
+  }
+}
+
+template class order::prepared::collectors<order::prepared::FixedContainer>;
+template class order::prepared::collectors<order::prepared::VariadicContainer>;
+
+order::prepared::fixed_terms_collectors::fixed_terms_collectors(
+    const order::prepared& buckets,
+    size_t terms_count)
+  : collectors<order::prepared::FixedContainer>(buckets) {
+  term_collectors_.reserve(buckets_.size() * terms_count);
+
+  // add term collectors from each bucket
+  // layout order [t0.b0, t0.b1, ... t0.bN, t1.b0, t1.b1 ... tM.BN]
+  for (size_t i = 0; i < terms_count; ++i) {
+    for (auto& entry: buckets_) {
+      assert(entry.bucket); // ensured by order::prepare
+      term_collectors_.emplace_back(entry.bucket->prepare_term_collector());
+    }
+  }
+}
+
+order::prepared::fixed_terms_collectors::fixed_terms_collectors(fixed_terms_collectors&& other) noexcept
+  : collectors<order::prepared::FixedContainer>(std::move(other)) {
+}
+
+void order::prepared::fixed_terms_collectors::collect(
     const sub_reader& segment,
     const term_reader& field,
     size_t term_offset,
     const attribute_view& term_attrs) const {
-  for (size_t i = 0, count = buckets_.size(); i < count; ++i) {
-    const auto idx = term_offset * buckets_.size() + i;
+  size_t count = buckets_.size();
+  size_t term_offset_count = term_offset * count;
+  for (size_t i = 0; i < count; ++i) {
+    const auto idx = term_offset_count + i;
     assert(idx < term_collectors_.size()); // enforced by allocation in the constructor
     auto& entry = term_collectors_[idx];
 
@@ -219,25 +256,13 @@ void order::prepared::collectors::collect(
   }
 }
 
-void order::prepared::collectors::finish(
+void order::prepared::fixed_terms_collectors::finish(
     byte_type* stats_buf,
     const index_reader& index) const {
   // special case where term statistics collection is not applicable
   // e.g. by_column_existence filter
   if (term_collectors_.empty()) {
-    assert(field_collectors_.size() == buckets_.size()); // enforced by allocation in the constructor
-
-    for (size_t i = 0, count = field_collectors_.size(); i < count; ++i) {
-      auto& sort = buckets_[i];
-      assert(sort.bucket); // ensured by order::prepare
-
-      sort.bucket->collect(
-        stats_buf + sort.stats_offset, // where stats for bucket start
-        index,
-        field_collectors_[i].get(),
-        nullptr
-      );
-    }
+    empty_finish(stats_buf, index);
   } else {
     auto bucket_count = buckets_.size();
     assert(term_collectors_.size() % bucket_count == 0); // enforced by allocation in the constructor
@@ -258,7 +283,7 @@ void order::prepared::collectors::finish(
   }
 }
 
-size_t order::prepared::collectors::push_back() {
+size_t order::prepared::fixed_terms_collectors::push_back() {
   auto term_offset = term_collectors_.size() / buckets_.size();
 
   term_collectors_.reserve(term_collectors_.size() + buckets_.size());
@@ -271,6 +296,76 @@ size_t order::prepared::collectors::push_back() {
   return term_offset;
 }
 
+order::prepared::variadic_terms_collectors::variadic_terms_collectors(
+    const order::prepared& buckets,
+    size_t terms_count)
+  : collectors<order::prepared::VariadicContainer>(buckets) {
+  term_collectors_.resize(buckets_.size());
+
+  // reserve minimal term collectors count
+  for (auto& tc : term_collectors_) {
+    tc.reserve(terms_count);
+  }
+}
+
+order::prepared::variadic_terms_collectors::variadic_terms_collectors(variadic_terms_collectors&& other) noexcept
+  : collectors<order::prepared::VariadicContainer>(std::move(other)) {
+}
+
+void order::prepared::variadic_terms_collectors::collect(
+    const sub_reader& segment,
+    const term_reader& field,
+    size_t /*term_offset*/,
+    const attribute_view& term_attrs) const {
+  for (size_t i = 0, count = buckets_.size(); i < count; ++i) {
+    auto& entry = buckets_[i];
+    assert(entry.bucket); // ensured by order::prepare
+    auto& tc = term_collectors_[i];
+    tc.emplace_back(entry.bucket->prepare_term_collector());
+    auto& e = tc.back();
+
+    if (e) { // may be null if prepare_term_collector() returned nullptr
+      e->collect(segment, field, term_attrs);
+    }
+  }
+}
+
+void order::prepared::variadic_terms_collectors::finish(
+    byte_type* stats_buf,
+    const index_reader& index) const {
+  // special case where term statistics collection is not applicable
+  // e.g. by_column_existence filter
+  if (term_collectors_.empty()) {
+    empty_finish(stats_buf, index);
+  } else {
+    auto count = term_collectors_.size();
+    assert(count == buckets_.size());
+
+    for (size_t i = 0; i < count; ++i) {
+      const auto& sort = buckets_[i];
+      assert(sort.bucket); // ensured by order::prepare
+
+      assert(i < field_collectors_.size());
+      const auto& tc = term_collectors_[i];
+      const auto* fc = field_collectors_[i].get();
+      for (size_t j = 0, tc_count = tc.size(); j < tc_count; ++j) {
+        sort.bucket->collect(
+          stats_buf + sort.stats_offset, // where stats for bucket start
+          index,
+          fc,
+          tc[j].get()
+        );
+      }
+    }
+  }
+}
+
+size_t order::prepared::variadic_terms_collectors::push_back() {
+  assert(false); // unsupported
+
+  return 0;
+}
+
 // ----------------------------------------------------------------------------
 // --SECTION--                                                          scorers
 // ----------------------------------------------------------------------------
@@ -373,6 +468,13 @@ bool order::prepared::less(const byte_type* lhs, const byte_type* rhs) const {
   return false;
 }
 
+filter_boost::filter_boost() noexcept
+  : basic_attribute<boost_t>(1.f) {
+}
+
+REGISTER_ATTRIBUTE(filter_boost);
+DEFINE_ATTRIBUTE_TYPE(filter_boost);
+
 NS_END
 
 // -----------------------------------------------------------------------------
diff --git a/3rdParty/iresearch/core/search/sort.hpp b/3rdParty/iresearch/core/search/sort.hpp
index 7844fe39df7a..29426410b4d0 100644
--- a/3rdParty/iresearch/core/search/sort.hpp
+++ b/3rdParty/iresearch/core/search/sort.hpp
@@ -435,7 +435,7 @@ class IRESEARCH_API sort {
     ///        specified 'offset' to 'dst', i.e. using +=
     ////////////////////////////////////////////////////////////////////////////////
     virtual void merge(byte_type* dst, const byte_type** src_start,
-                       const size_t size, size_t offset) const {
+                       const size_t size, size_t offset) const override {
       auto& casted_dst = base_t::score_cast(dst + offset);
       casted_dst = ScoreType();
       for (size_t i = 0; i < size; ++i) {
@@ -606,9 +606,13 @@ class IRESEARCH_API order final {
     /// @brief a convinience class for filters to invoke collector functions
     ///        on collectors in each order bucket
     ////////////////////////////////////////////////////////////////////////////
+    template<typename T> using FixedContainer = std::vector<T>;
+    template<typename T> using VariadicContainer = std::vector<std::vector<T>>;
+
+    template<template<typename...> class T>
     class IRESEARCH_API collectors: private util::noncopyable { // noncopyable required by MSVC
      public:
-      collectors(const prepared& buckets, size_t terms_count);
+      collectors(const prepared& buckets);
       collectors(collectors&& other) noexcept; // function definition explicitly required by MSVC
 
       //////////////////////////////////////////////////////////////////////////
@@ -621,6 +625,23 @@ class IRESEARCH_API order final {
       //////////////////////////////////////////////////////////////////////////
       void collect(const sub_reader& segment, const term_reader& field) const;
 
+      void empty_finish(byte_type* stats_buf, const index_reader& index) const;
+
+     protected:
+      IRESEARCH_API_PRIVATE_VARIABLES_BEGIN
+      const std::vector<prepared_sort>& buckets_;
+      std::vector<sort::field_collector::ptr> field_collectors_; // size == buckets_.size()
+      mutable T<sort::term_collector::ptr> term_collectors_;
+      IRESEARCH_API_PRIVATE_VARIABLES_END
+    };
+
+    class IRESEARCH_API fixed_terms_collectors : public collectors<FixedContainer> {
+     public:
+      using collectors<FixedContainer>::collect;
+
+      fixed_terms_collectors(const prepared& buckets, size_t terms_count);
+      fixed_terms_collectors(fixed_terms_collectors&& other) noexcept; // function definition explicitly required by MSVC
+
       //////////////////////////////////////////////////////////////////////////
       /// @brief collect term related statistics, i.e. term used in the filter
       /// @param segment the segment being processed (e.g. for columnstore)
@@ -656,12 +677,52 @@ class IRESEARCH_API order final {
       //////////////////////////////////////////////////////////////////////////
       size_t push_back();
 
-     private:
-      IRESEARCH_API_PRIVATE_VARIABLES_BEGIN
-      const std::vector<prepared_sort>& buckets_;
-      std::vector<sort::field_collector::ptr> field_collectors_; // size == buckets_.size()
-      std::vector<sort::term_collector::ptr> term_collectors_; // size == buckets_.size() * terms_count, layout order [t0.b0, t0.b1, ... t0.bN, t1.b0, t1.b1 ... tM.BN]
-      IRESEARCH_API_PRIVATE_VARIABLES_END
+      // term_collectors_; size == buckets_.size() * terms_count, layout order [t0.b0, t0.b1, ... t0.bN, t1.b0, t1.b1 ... tM.BN]
+    };
+
+    class IRESEARCH_API variadic_terms_collectors : public collectors<VariadicContainer> {
+     public:
+      using collectors<VariadicContainer>::collect;
+
+      variadic_terms_collectors(const prepared& buckets, size_t terms_count);
+      variadic_terms_collectors(variadic_terms_collectors&& other) noexcept; // function definition explicitly required by MSVC
+
+      //////////////////////////////////////////////////////////////////////////
+      /// @brief collect term related statistics, i.e. term used in the filter
+      /// @param segment the segment being processed (e.g. for columnstore)
+      /// @param field the field matched by the filter in the 'segment'
+      /// @param term_offset offset of term, value < constructor 'terms_count'
+      /// @param term_attributes the attributes of the matched term in the field
+      /// @note called once for every term matched by a filter in the 'field'
+      ///       per each segment
+      /// @note only called on a matched 'term' in the 'field' in the 'segment'
+      //////////////////////////////////////////////////////////////////////////
+      void collect(
+        const sub_reader& segment,
+        const term_reader& field,
+        size_t term_offset,
+        const attribute_view& term_attrs
+      ) const;
+
+      //////////////////////////////////////////////////////////////////////////
+      /// @brief store collected index statistics into 'stats' of the
+      ///        current 'filter'
+      /// @param stats out-parameter to store statistics for later use in
+      ///        calls to score(...)
+      /// @param index the full index to collect statistics on
+      /// @note called once on the 'index' for every term matched by a filter
+      ///       calling collect(...) on each of its segments
+      /// @note if not matched terms then called exactly once
+      //////////////////////////////////////////////////////////////////////////
+      void finish(byte_type* stats, const index_reader& index) const;
+
+      //////////////////////////////////////////////////////////////////////////
+      /// @brief add collectors for another term
+      /// @return term_offset
+      //////////////////////////////////////////////////////////////////////////
+      size_t push_back();
+
+      // term_collectors_; size == buckets_.size(), inner size == terms count
     };
 
     ////////////////////////////////////////////////////////////////////////////
@@ -759,8 +820,12 @@ class IRESEARCH_API order final {
     /// @param terms_count number of term_collectors to allocate
     ///        0 == collect only field level statistics e.g. by_column_existence
     ////////////////////////////////////////////////////////////////////////////
-    collectors prepare_collectors(size_t terms_count = 0) const {
-      return collectors(*this, terms_count);
+    fixed_terms_collectors fixed_prepare_collectors(size_t terms_count = 0) const {
+      return fixed_terms_collectors(*this, terms_count);
+    }
+
+    variadic_terms_collectors variadic_prepare_collectors(size_t terms_count = 0) const {
+      return variadic_terms_collectors(*this, terms_count);
     }
 
     ////////////////////////////////////////////////////////////////////////////
@@ -903,6 +968,19 @@ class IRESEARCH_API order final {
   IRESEARCH_API_PRIVATE_VARIABLES_END
 }; // order
 
+//////////////////////////////////////////////////////////////////////////////
+/// @class filter_boost
+/// @brief represents an addition to score from filter specific to a particular 
+///        document. May vary from document to document.
+//////////////////////////////////////////////////////////////////////////////
+struct IRESEARCH_API filter_boost : public basic_attribute<boost_t> {
+  DECLARE_ATTRIBUTE_TYPE();
+  filter_boost() noexcept;
+
+  void clear() { value = 1.f; }
+};
+
+
 NS_END
 
 #endif
diff --git a/3rdParty/iresearch/core/search/term_filter.hpp b/3rdParty/iresearch/core/search/term_filter.hpp
index 8abf92933cb1..7bfe422175d4 100644
--- a/3rdParty/iresearch/core/search/term_filter.hpp
+++ b/3rdParty/iresearch/core/search/term_filter.hpp
@@ -44,7 +44,7 @@ class IRESEARCH_API by_term : public filter {
     return *this;
   }
 
-  const std::string& field() const { 
+  const std::string& field() const noexcept {
     return fld_; 
   }
 
@@ -71,7 +71,7 @@ class IRESEARCH_API by_term : public filter {
     const attribute_view& ctx
   ) const override;
 
-  const bstring& term() const { 
+  const bstring& term() const noexcept {
     return term_;
   }
 
diff --git a/3rdParty/iresearch/core/search/term_query.cpp b/3rdParty/iresearch/core/search/term_query.cpp
index 0a1a81873463..73e5474f7670 100644
--- a/3rdParty/iresearch/core/search/term_query.cpp
+++ b/3rdParty/iresearch/core/search/term_query.cpp
@@ -39,7 +39,7 @@ term_query::ptr term_query::make(
     const string_ref& field,
     const bytes_ref& term) {
   term_query::states_t states(index.size());
-  auto collectors = ord.prepare_collectors(1);
+  auto collectors = ord.fixed_prepare_collectors(1);
 
   // iterate over the segments
   for (const auto& segment : index) {
diff --git a/3rdParty/iresearch/core/search/tfidf.cpp b/3rdParty/iresearch/core/search/tfidf.cpp
index 460c980fa9f9..ad6733533612 100644
--- a/3rdParty/iresearch/core/search/tfidf.cpp
+++ b/3rdParty/iresearch/core/search/tfidf.cpp
@@ -257,14 +257,17 @@ struct const_score_ctx final : public irs::score_ctx {
 struct score_ctx : public irs::score_ctx {
   score_ctx( irs::boost_t boost,
       const tfidf::idf& idf,
-      const frequency* freq) noexcept
-    : idf_(boost * idf.value),
-      freq_(freq ? freq : &EMPTY_FREQ) {
+      const frequency* freq,
+      const filter_boost* fb = nullptr) noexcept
+    : freq_(freq ? freq : &EMPTY_FREQ),
+      filter_boost_(fb),
+      idf_(boost * idf.value) {
     assert(freq_);
   }
-
-  float_t idf_; // precomputed : boost * idf
+    
   const frequency* freq_;
+  const filter_boost* filter_boost_;
+  float_t idf_; // precomputed : boost * idf
 }; // score_ctx
 
 struct norm_score_ctx final : public score_ctx {
@@ -272,8 +275,9 @@ struct norm_score_ctx final : public score_ctx {
       irs::norm&& norm,
       irs::boost_t boost,
       const tfidf::idf& idf,
-      const frequency* freq) noexcept
-    : score_ctx(boost, idf, freq),
+      const frequency* freq,
+      const filter_boost* fb = nullptr) noexcept
+    : score_ctx(boost, idf, freq, fb),
       norm_(std::move(norm)) {
   }
 
@@ -342,6 +346,7 @@ class sort final: public irs::sort::prepared_basic<tfidf::score_t, tfidf::idf> {
     }
 
     auto& stats = stats_cast(stats_buf);
+    auto& filter_boost = doc_attrs.get<irs::filter_boost>();
 
     // add norm attribute if requested
     if (normalize_) {
@@ -355,24 +360,49 @@ class sort final: public irs::sort::prepared_basic<tfidf::score_t, tfidf::idf> {
       }
 
       if (norm.reset(segment, field.meta().norm, *doc)) {
-        return {
-          memory::make_unique<tfidf::norm_score_ctx>(std::move(norm), boost, stats, freq.get()),
-          [](const irs::score_ctx* ctx, byte_type* RESTRICT score_buf) noexcept {
+        
+        if (filter_boost) {
+          return {
+            memory::make_unique<tfidf::norm_score_ctx>(std::move(norm), boost, stats, freq.get(), filter_boost.get()),
+            [](const irs::score_ctx* ctx, byte_type* RESTRICT score_buf) noexcept {
+              auto& state = *static_cast<const tfidf::norm_score_ctx*>(ctx);
+              assert(state.filter_boost_);
+              irs::sort::score_cast<tfidf::score_t>(score_buf) = ::tfidf(state.freq_->value, 
+                                                                         state.idf_ * state.filter_boost_->value) * 
+                                                                 state.norm_.read();
+            }
+          };
+        } else {
+          return {
+            memory::make_unique<tfidf::norm_score_ctx>(std::move(norm), boost, stats, freq.get()),
+            [](const irs::score_ctx* ctx, byte_type* RESTRICT score_buf) noexcept {
             auto& state = *static_cast<const tfidf::norm_score_ctx*>(ctx);
-            irs::sort::score_cast<tfidf::score_t>(score_buf) = ::tfidf(state.freq_->value, state.idf_)*state.norm_.read();
-          }
-        };
+            irs::sort::score_cast<tfidf::score_t>(score_buf) = ::tfidf(state.freq_->value, state.idf_) * state.norm_.read();
+            }
+          };
+        }
       }
     }
 
-
-    return {
-      memory::make_unique<tfidf::score_ctx>(boost, stats, freq.get()),
-      [](const irs::score_ctx* ctx, byte_type* RESTRICT score_buf) noexcept {
+    if (filter_boost) {
+      return {
+        memory::make_unique<tfidf::score_ctx>(boost, stats, freq.get(), filter_boost.get()),
+        [](const irs::score_ctx* ctx, byte_type* RESTRICT score_buf) noexcept {
         auto& state = *static_cast<const tfidf::score_ctx*>(ctx);
-        irs::sort::score_cast<score_t>(score_buf) = ::tfidf(state.freq_->value, state.idf_);
+        assert(state.filter_boost_);
+        irs::sort::score_cast<score_t>(score_buf) = ::tfidf(state.freq_->value, 
+                                                            state.idf_* state.filter_boost_->value);
       }
-    };
+      };
+    } else {
+      return {
+        memory::make_unique<tfidf::score_ctx>(boost, stats, freq.get()),
+        [](const irs::score_ctx* ctx, byte_type* RESTRICT score_buf) noexcept {
+          auto& state = *static_cast<const tfidf::score_ctx*>(ctx);
+          irs::sort::score_cast<score_t>(score_buf) = ::tfidf(state.freq_->value, state.idf_);
+        }
+      };
+    }
   }
 
   virtual irs::sort::term_collector::ptr prepare_term_collector() const override {
diff --git a/3rdParty/iresearch/core/search/wildcard_filter.cpp b/3rdParty/iresearch/core/search/wildcard_filter.cpp
index 3c59469039a8..86d4420118db 100644
--- a/3rdParty/iresearch/core/search/wildcard_filter.cpp
+++ b/3rdParty/iresearch/core/search/wildcard_filter.cpp
@@ -31,87 +31,44 @@
 #include "utils/automaton_utils.hpp"
 #include "utils/hash_utils.hpp"
 
-NS_LOCAL
-
-using wildcard_traits_t = irs::wildcard_traits<irs::byte_type>;
-
-NS_END
-
 NS_ROOT
 
-WildcardType wildcard_type(const bytes_ref& expr) noexcept {
-  if (expr.empty()) {
-    return WildcardType::TERM;
-  }
-
-  bool escaped = false;
-  size_t num_match_any_string = 0;
-  for (const auto c : expr) {
-    switch (c) {
-      case wildcard_traits_t::MATCH_ANY_STRING:
-        num_match_any_string += size_t(!escaped);
-        escaped = false;
-        break;
-      case wildcard_traits_t::MATCH_ANY_CHAR:
-        if (!escaped) {
-          return WildcardType::WILDCARD;
-        }
-        escaped = false;
-        break;
-      case wildcard_traits_t::ESCAPE:
-        escaped = !escaped;
-        break;
-      default:
-        escaped = false;
-        break;
-    }
-  }
-
-  if (0 == num_match_any_string) {
-    return WildcardType::TERM;
-  }
-
-  if (expr.size() == num_match_any_string) {
-    return WildcardType::MATCH_ALL;
-  }
-
-  return std::all_of(expr.end() - num_match_any_string, expr.end(),
-                     [](byte_type c) { return c == wildcard_traits_t::MATCH_ANY_STRING; })
-    ?  WildcardType::PREFIX
-    :  WildcardType::WILDCARD;
-}
-
 DEFINE_FILTER_TYPE(by_wildcard)
 DEFINE_FACTORY_DEFAULT(by_wildcard)
 
-filter::prepared::ptr by_wildcard::prepare(
+/*static*/ filter::prepared::ptr by_wildcard::prepare(
     const index_reader& index,
     const order::prepared& order,
     boost_t boost,
-    const attribute_view& /*ctx*/) const {
-  boost *= this->boost();
-  const string_ref field = this->field();
-
-  switch (wildcard_type(term())) {
+    const string_ref& field,
+    const bstring& term,
+    size_t scored_terms_limit) {
+  switch (wildcard_type(term)) {
+    case WildcardType::INVALID:
+      return prepared::empty();
     case WildcardType::TERM:
-      return term_query::make(index, order, boost, field, term());
+      return term_query::make(index, order, boost, field, term);
     case WildcardType::MATCH_ALL:
       return by_prefix::prepare(index, order, boost, field,
                                 bytes_ref::EMPTY, // empty prefix == match all
-                                scored_terms_limit());
+                                scored_terms_limit);
     case WildcardType::PREFIX: {
-      assert(!term().empty());
-      const auto pos = term().find(wildcard_traits_t::MATCH_ANY_STRING);
-      assert(pos != irs::bstring::npos);
+      assert(!term.empty());
+      const auto* begin = term.c_str();
+      const auto* end = begin + term.size();
+
+      // term is already checked to be a valid UTF-8 sequence
+      const auto* pos = utf8_utils::find<false>(begin, end, WildcardMatch::ANY_STRING);
+      assert(pos != end);
 
       return by_prefix::prepare(index, order, boost, field,
-                                bytes_ref(term().c_str(), pos), // remove trailing '%'
-                                scored_terms_limit());
+                                bytes_ref(begin, size_t(pos - begin)), // remove trailing '%'
+                                scored_terms_limit);
     }
 
     case WildcardType::WILDCARD:
-      return prepare_automaton_filter(field, from_wildcard<byte_type, wildcard_traits_t>(term()),
-                                      scored_terms_limit(), index, order, boost);
+      return prepare_automaton_filter(field, from_wildcard(term),
+                                      scored_terms_limit, index, order, boost);
   }
 
   assert(false);
diff --git a/3rdParty/iresearch/core/search/wildcard_filter.hpp b/3rdParty/iresearch/core/search/wildcard_filter.hpp
index 885d5ccb173d..5d432d82b875 100644
--- a/3rdParty/iresearch/core/search/wildcard_filter.hpp
+++ b/3rdParty/iresearch/core/search/wildcard_filter.hpp
@@ -29,15 +29,6 @@
 
 NS_ROOT
 
-enum class WildcardType {
-  TERM      = 0,  // foo
-  MATCH_ALL,      // *
-  PREFIX,         // foo*
-  WILDCARD        // f_o*
-};
-
-IRESEARCH_API WildcardType wildcard_type(const bytes_ref& pattern) noexcept;
-
 //////////////////////////////////////////////////////////////////////////////
 /// @class by_wildcard
 /// @brief user-side wildcard filter
@@ -47,6 +38,14 @@ class IRESEARCH_API by_wildcard final : public by_prefix {
   DECLARE_FILTER_TYPE();
   DECLARE_FACTORY();
 
+  static prepared::ptr prepare(
+    const index_reader& index,
+    const order::prepared& order,
+    boost_t boost,
+    const string_ref& field,
+    const bstring& term,
+    size_t scored_terms_limit);
+
   explicit by_wildcard() noexcept;
 
   using by_prefix::field;
@@ -59,11 +58,26 @@ class IRESEARCH_API by_wildcard final : public by_prefix {
   using filter::prepare;
 
   virtual filter::prepared::ptr prepare(
-    const index_reader& rdr,
-    const order::prepared& ord,
-    boost_t boost,
-    const attribute_view& ctx
-  ) const override;
+      const index_reader& index,
+      const order::prepared& order,
+      boost_t boost,
+      const attribute_view& /*ctx*/) const override {
+    return prepare(index, order, this->boost()*boost,
+                   field(), term(), scored_terms_limit());
+  }
+
+
+  using by_prefix::scored_terms_limit;
+
+  //////////////////////////////////////////////////////////////////////////////
+  /// @brief the maximum number of most frequent terms to consider for scoring
+  //////////////////////////////////////////////////////////////////////////////
+  by_wildcard& scored_terms_limit(size_t limit) noexcept {
+    by_prefix::scored_terms_limit(limit);
+    return *this;
+  }
+
+  
 }; // by_wildcard
 
 #endif // IRESEARCH_WILDCARD_FILTER_H
diff --git a/3rdParty/iresearch/core/shared.hpp b/3rdParty/iresearch/core/shared.hpp
index a6bd07302669..0499c30bf211 100644
--- a/3rdParty/iresearch/core/shared.hpp
+++ b/3rdParty/iresearch/core/shared.hpp
@@ -267,7 +267,9 @@
 ////////////////////////////////////////////////////////////////////////////////
 /// SSE compatibility
 ////////////////////////////////////////////////////////////////////////////////
-#ifdef __SSE2__
+
+// for MSVC on x64 architecture SSE2 is always enabled
+#if defined(__SSE2__) || (defined(_MSC_VER) && (defined(_M_AMD64) || defined(_M_X64)))
 #define IRESEARCH_SSE2
 #endif
 
diff --git a/3rdParty/iresearch/core/utils/arena_allocator.hpp b/3rdParty/iresearch/core/utils/arena_allocator.hpp
index b351f12fa830..1becd8b554fd 100644
--- a/3rdParty/iresearch/core/utils/arena_allocator.hpp
+++ b/3rdParty/iresearch/core/utils/arena_allocator.hpp
@@ -169,7 +169,7 @@ template<typename T1, typename U, typename A1, typename A2>
 inline bool operator==(const arena_allocator<T1, A1>& lhs,
   const arena_allocator<U, A2>& rhs) noexcept {
   return std::is_same<A1, A2>::value && 
-    lhs.arena_ == reinterpret_cast<const void*>(rhs.arena_);
+         lhs.arena_ == reinterpret_cast<const void*>(rhs.arena_);
 }
 
 template<typename T, size_t N>
diff --git a/3rdParty/iresearch/core/utils/attribute_range.cpp b/3rdParty/iresearch/core/utils/attribute_range.cpp
new file mode 100644
index 000000000000..1a85822a4ef0
--- /dev/null
+++ b/3rdParty/iresearch/core/utils/attribute_range.cpp
@@ -0,0 +1,46 @@
+////////////////////////////////////////////////////////////////////////////////
+/// DISCLAIMER
+///
+/// Copyright 2020 ArangoDB GmbH, Cologne, Germany
+///
+/// Licensed under the Apache License, Version 2.0 (the "License");
+/// you may not use this file except in compliance with the License.
+/// You may obtain a copy of the License at
+///
+///     http://www.apache.org/licenses/LICENSE-2.0
+///
+/// Unless required by applicable law or agreed to in writing, software
+/// distributed under the License is distributed on an "AS IS" BASIS,
+/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+/// See the License for the specific language governing permissions and
+/// limitations under the License.
+///
+/// Copyright holder is ArangoDB GmbH, Cologne, Germany
+///
+/// @author Yuriy Popov
+////////////////////////////////////////////////////////////////////////////////
+
+#include "attribute_range.hpp"
+#include "search/disjunction.hpp"
+
+NS_ROOT
+
+template<>
+bool attribute_range<position_score_iterator_adapter<doc_iterator::ptr>>::next() {
+  assert(ars_);
+  value_ = ars_->get_next_iterator();
+  return value_ != nullptr;
+}
+
+#define DEFINE_ATTRIBUTE_RANGE_TYPE(AttributeRange) template<> IRESEARCH_API \
+/*static*/ const attribute::type_id& AttributeRange::type() { \
+  static attribute::type_id type(#AttributeRange); \
+  return type; \
+}
+
+#define DEFINE_ATTRIBUTE_RANGE(Adapter) DEFINE_ATTRIBUTE_RANGE_TYPE(attribute_range<Adapter>);
+
+DEFINE_ATTRIBUTE_RANGE(score_iterator_adapter<doc_iterator::ptr>);
+DEFINE_ATTRIBUTE_RANGE(position_score_iterator_adapter<doc_iterator::ptr>);
+
+NS_END // ROOT
diff --git a/3rdParty/iresearch/core/utils/attribute_range.hpp b/3rdParty/iresearch/core/utils/attribute_range.hpp
new file mode 100644
index 000000000000..3ddf779dd7e7
--- /dev/null
+++ b/3rdParty/iresearch/core/utils/attribute_range.hpp
@@ -0,0 +1,65 @@
+////////////////////////////////////////////////////////////////////////////////
+/// DISCLAIMER
+///
+/// Copyright 2020 ArangoDB GmbH, Cologne, Germany
+///
+/// Licensed under the Apache License, Version 2.0 (the "License");
+/// you may not use this file except in compliance with the License.
+/// You may obtain a copy of the License at
+///
+///     http://www.apache.org/licenses/LICENSE-2.0
+///
+/// Unless required by applicable law or agreed to in writing, software
+/// distributed under the License is distributed on an "AS IS" BASIS,
+/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+/// See the License for the specific language governing permissions and
+/// limitations under the License.
+///
+/// Copyright holder is ArangoDB GmbH, Cologne, Germany
+///
+/// @author Yuriy Popov
+////////////////////////////////////////////////////////////////////////////////
+
+#ifndef IRESEARCH_ATTRIBUTE_RANGE_H
+#define IRESEARCH_ATTRIBUTE_RANGE_H
+
+#include "attributes.hpp"
+
+NS_ROOT
+
+template<typename Adapter>
+struct attribute_range_state {
+  virtual Adapter* get_next_iterator() = 0;
+  virtual void reset_next_iterator_state() = 0;
+  virtual ~attribute_range_state() = default;
+};
+
+template<typename Adapter>
+class attribute_range final : public attribute {
+ public:
+  DECLARE_TYPE_ID(attribute::type_id);
+
+  void set_state(attribute_range_state<Adapter>* ars) noexcept {
+    ars_ = ars;
+  }
+
+  Adapter* value() noexcept {
+    return value_;
+  }
+
+  bool next();
+
+  void reset() {
+    value_ = nullptr;
+    assert(ars_);
+    ars_->reset_next_iterator_state();
+  }
+
+ private:
+  attribute_range_state<Adapter>* ars_ = nullptr;
+  Adapter* value_ = nullptr;
+}; // attribute_range
+
+NS_END // ROOT
+
+#endif
diff --git a/3rdParty/iresearch/core/utils/attributes.cpp b/3rdParty/iresearch/core/utils/attributes.cpp
index d4a9853f050d..f2b92a91820e 100644
--- a/3rdParty/iresearch/core/utils/attributes.cpp
+++ b/3rdParty/iresearch/core/utils/attributes.cpp
@@ -74,8 +74,6 @@ const flags& flags::empty_instance() {
   return instance;
 }
 
-flags::flags() { }
-
 flags::flags(flags&& rhs) noexcept
   : map_(std::move(rhs.map_)) {
 }
@@ -186,4 +184,4 @@ NS_END
 
 // -----------------------------------------------------------------------------
 // --SECTION--                                                       END-OF-FILE
-// -----------------------------------------------------------------------------
\ No newline at end of file
+// -----------------------------------------------------------------------------
diff --git a/3rdParty/iresearch/core/utils/attributes.hpp b/3rdParty/iresearch/core/utils/attributes.hpp
index 6cc5228aeb91..bbea4564223d 100644
--- a/3rdParty/iresearch/core/utils/attributes.hpp
+++ b/3rdParty/iresearch/core/utils/attributes.hpp
@@ -170,7 +170,7 @@ class IRESEARCH_API flags {
 
   static const flags& empty_instance();
 
-  flags();
+  flags() = default;
   flags(const flags&) = default;
   flags(flags&& rhs) noexcept;
   flags(std::initializer_list<const attribute::type_id*> flags);
@@ -178,8 +178,8 @@ class IRESEARCH_API flags {
   flags& operator=(flags&& rhs) noexcept;
   flags& operator=(const flags&) = default;
 
-  type_map::const_iterator begin() const { return map_.begin(); }
-  type_map::const_iterator end() const { return map_.end(); }
+  type_map::const_iterator begin() const noexcept { return map_.begin(); }
+  type_map::const_iterator end() const noexcept { return map_.end(); }
 
   template< typename T >
   flags& add() {
@@ -209,8 +209,8 @@ class IRESEARCH_API flags {
     return *this;
   }
   
-  bool empty() const { return map_.empty(); }
-  size_t size() const { return map_.size(); }
+  bool empty() const noexcept { return map_.empty(); }
+  size_t size() const noexcept { return map_.size(); }
   void clear() noexcept { map_.clear(); }
   void reserve(size_t /*capacity*/) {
     // NOOP for std::set
diff --git a/3rdParty/iresearch/core/utils/automaton.hpp b/3rdParty/iresearch/core/utils/automaton.hpp
index 6c57e6e1b6b4..7a1a7e417b8a 100644
--- a/3rdParty/iresearch/core/utils/automaton.hpp
+++ b/3rdParty/iresearch/core/utils/automaton.hpp
@@ -61,6 +61,9 @@ NS_BEGIN(fsa)
 class BooleanWeight {
  public:
   using ReverseWeight = BooleanWeight;
+  using PayloadType = irs::byte_type;
+
+  static constexpr PayloadType MaxPayload = 0x3F;
 
   static const std::string& Type() {
     static const std::string type = "boolean";
@@ -71,62 +74,69 @@ class BooleanWeight {
   static constexpr BooleanWeight One() noexcept { return true; }
   static constexpr BooleanWeight NoWeight() noexcept { return {}; }
 
-  constexpr BooleanWeight() noexcept : v_(Value::NO_WEIGHT) { }
-  constexpr BooleanWeight(bool v) noexcept : v_(Value(char(v))) { }
-
   static constexpr uint64 Properties() noexcept {
     return kLeftSemiring | kRightSemiring |
            kCommutative | kIdempotent | kPath;
   }
 
-  constexpr bool Member() const noexcept { return v_ != Value::NO_WEIGHT; }
+  constexpr BooleanWeight() noexcept : v_(Invalid) { }
+  constexpr BooleanWeight(bool v, PayloadType payload = 0) noexcept
+    : v_(PayloadType(v) | (payload << 2)) {
+  }
+
+  constexpr bool Member() const noexcept { return 0 == (v_ & Invalid); }
   constexpr BooleanWeight Quantize(float delta = kDelta) const noexcept { return {}; }
   std::istream& Read(std::istream& strm) noexcept {
-    v_ = Value(strm.get());
+    v_ = strm.get();
+    if (strm.fail()) {
+      v_ = Invalid;
+    }
     return strm;
   }
   std::ostream& Write(std::ostream &strm) const noexcept {
-    strm << char(v_);
+    strm.put(v_);
     return strm;
   }
-  constexpr size_t Hash() const noexcept { return size_t(v_); }
+  constexpr size_t Hash() const noexcept { return size_t(v_ & WeightMask); }
   constexpr ReverseWeight Reverse() const noexcept { return *this; }
-  constexpr operator bool() const noexcept { return v_ == Value::TRUE; }
+  constexpr PayloadType Payload() const noexcept { return v_ >> 2; }
+  constexpr operator bool() const noexcept { return 0 != (v_ & True); }
 
   friend constexpr bool operator==(const BooleanWeight& lhs, const BooleanWeight& rhs) noexcept {
-    return lhs.v_ == rhs.v_;
+    return lhs.Hash() == rhs.Hash();
   }
   friend constexpr bool operator!=(const BooleanWeight& lhs, const BooleanWeight& rhs) noexcept {
     return !(lhs == rhs);
   }
-  friend BooleanWeight Plus(const BooleanWeight& lhs, const BooleanWeight& rhs) noexcept {
-    return { bool(lhs.v_) || bool(rhs.v_) };
+  friend constexpr BooleanWeight Plus(const BooleanWeight& lhs, const BooleanWeight& rhs) noexcept {
+    return BooleanWeight(bool(lhs.Hash()) || bool(rhs.Hash()), lhs.Payload() | rhs.Payload());
   }
-  friend BooleanWeight Times(const BooleanWeight& lhs, const BooleanWeight& rhs) noexcept {
-    return { bool(lhs.v_) && bool(rhs.v_) };
+  friend constexpr BooleanWeight Times(const BooleanWeight& lhs, const BooleanWeight& rhs) noexcept {
+    return BooleanWeight(bool(lhs.Hash()) && bool(rhs.Hash()), lhs.Payload() & rhs.Payload());
   }
-  friend BooleanWeight Divide(BooleanWeight, BooleanWeight, DivideType) noexcept {
-    return { };
+  friend constexpr BooleanWeight Divide(BooleanWeight, BooleanWeight, DivideType) noexcept {
+    return NoWeight();
   }
   friend std::ostream& operator<<(std::ostream& strm, const BooleanWeight& w) {
-    if (Value::NO_WEIGHT != w.v_) {
-      strm << char(w.v_ + 48);
+    if (w.Member()) {
+      strm << "{" << char(bool(w) + 48) << "," << int(w.Payload()) << "}";
     }
     return strm;
   }
-  friend bool ApproxEqual(const BooleanWeight& lhs, const BooleanWeight& rhs,
-                          float delta = kDelta) {
+  friend constexpr bool ApproxEqual(const BooleanWeight& lhs, const BooleanWeight& rhs,
+                                    float delta = kDelta) {
     return lhs == rhs;
   }
 
  private:
-  enum Value : char {
-    NO_WEIGHT = -1,
-    FALSE = 0,
-    TRUE = 1
-  };
-
-  Value v_;
+  static constexpr PayloadType WeightMask = 0x03;
+  static constexpr PayloadType True = 1;    // "is true" mask
+  static constexpr PayloadType Invalid = 2; // "not a member" mask
+
+  // [2..7] - payload
+  // [1] - "not a member" bit
+  // [0] - true/false bit
+  PayloadType v_;
 };
 
 struct MinMaxLabel {
diff --git a/3rdParty/iresearch/core/utils/automaton_utils.cpp b/3rdParty/iresearch/core/utils/automaton_utils.cpp
index bcdccaeee638..e8bd14827644 100644
--- a/3rdParty/iresearch/core/utils/automaton_utils.cpp
+++ b/3rdParty/iresearch/core/utils/automaton_utils.cpp
@@ -27,8 +27,269 @@
 #include "search/multiterm_query.hpp"
 #include "utils/fst_table_matcher.hpp"
 
+NS_LOCAL
+
+using irs::automaton;
+
+// table contains indexes of states in
+// utf8_transitions_builder::rho_states_ table
+const automaton::Arc::Label UTF8_RHO_STATE_TABLE[] {
+  // 1 byte sequence (0-127)
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  // invalid sequence (128-191)
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+  // 2 bytes sequence (192-223)
+  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+  // 3 bytes sequence (224-239)
+  2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
+  // 4 bytes sequence (240-255)
+  3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
+};
+
+NS_END
+
 NS_ROOT
 
+void utf8_emplace_arc(
+    automaton& a,
+    automaton::StateId from,
+    automaton::StateId rho_state,
+    const bytes_ref& label,
+    automaton::StateId to) {
+  if (fst::kNoStateId == rho_state) {
+    return utf8_emplace_arc(a, from, label, to);
+  }
+
+  if (label.empty()) {
+    return;
+  }
+
+  // reserve enough arcs and states (stated ids are sequential)
+  a.ReserveArcs(from, 256);
+  const auto id = a.NumStates();
+  a.AddStates(3 + label.size() - 1);
+
+  const automaton::StateId rho_states[] { rho_state, id, id + 1, id + 2 };
+
+  const automaton::Arc::Label lead = label.front();
+  automaton::Arc::Label min = 0;
+
+  for (; min < lead; ++min) {
+    a.EmplaceArc(from, min, rho_states[UTF8_RHO_STATE_TABLE[min]]);
+  }
+
+  switch (label.size()) {
+    case 1: {
+      a.EmplaceArc(from, lead, to);
+      break;
+    }
+    case 2: {
+      const auto s0 = id + 3;
+      a.EmplaceArc(from, lead, s0);
+      a.EmplaceArc(s0, label[1], to);
+      a.EmplaceArc(s0, fst::fsa::kRho, rho_states[0]);
+      break;
+    }
+    case 3: {
+      const auto s0 = id + 3;
+      const auto s1 = id + 4;
+      a.EmplaceArc(from, lead, s0);
+      a.EmplaceArc(s0, label[1], s1);
+      a.EmplaceArc(s1, label[2], to);
+      a.EmplaceArc(s0, fst::fsa::kRho, rho_states[1]);
+      a.EmplaceArc(s1, fst::fsa::kRho, rho_states[0]);
+      break;
+    }
+    case 4: {
+      const auto s0 = id + 3;
+      const auto s1 = id + 4;
+      const auto s2 = id + 5;
+      a.EmplaceArc(from, lead, s0);
+      a.EmplaceArc(s0, label[1], s1);
+      a.EmplaceArc(s1, label[2], s2);
+      a.EmplaceArc(s2, label[3], to);
+      a.EmplaceArc(s0, fst::fsa::kRho, rho_states[2]);
+      a.EmplaceArc(s1, fst::fsa::kRho, rho_states[1]);
+      a.EmplaceArc(s2, fst::fsa::kRho, rho_states[0]);
+      break;
+    }
+  }
+
+  for (++min; min < 256; ++min) {
+    a.EmplaceArc(from, min, rho_states[UTF8_RHO_STATE_TABLE[min]]);
+  }
+
+  // connect intermediate states of default multi-byte UTF8 sequence
+
+  a.EmplaceArc(rho_states[1], fst::fsa::kRho, rho_states[0]);
+  a.EmplaceArc(rho_states[2], fst::fsa::kRho, rho_states[1]);
+  a.EmplaceArc(rho_states[3], fst::fsa::kRho, rho_states[2]);
+}
+
+void utf8_emplace_arc(
+    automaton& a,
+    automaton::StateId from,
+    const bytes_ref& label,
+    automaton::StateId to) {
+  switch (label.size()) {
+    case 1: {
+      a.EmplaceArc(from, label[0], to);
+      return;
+    }
+    case 2: {
+      const auto s0 = a.AddState();
+      a.EmplaceArc(from, label[0], s0);
+      a.EmplaceArc(s0, label[1], to);
+      return;
+    }
+    case 3: {
+      const auto s0 = a.AddState();
+      const auto s1 = a.AddState();
+      a.EmplaceArc(from, label[0], s0);
+      a.EmplaceArc(s0, label[1], s1);
+      a.EmplaceArc(s1, label[2], to);
+      return;
+    }
+    case 4: {
+      const auto s0 = a.AddState();
+      const auto s1 = a.AddState();
+      const auto s2 = a.AddState();
+      a.EmplaceArc(from, label[0], s0);
+      a.EmplaceArc(s0, label[1], s1);
+      a.EmplaceArc(s1, label[2], s2);
+      a.EmplaceArc(s2, label[3], to);
+      return;
+    }
+  }
+}
+
+void utf8_emplace_rho_arc(
+    automaton& a,
+    automaton::StateId from,
+    automaton::StateId to) {
+  const auto id = a.NumStates(); // stated ids are sequential
+  a.AddStates(3);
+  const automaton::StateId rho_states[] { to, id, id + 1, id + 2 };
+
+  // add rho transitions
+
+  for (automaton::Arc::Label label = 0; label < 256; ++label) {
+    a.EmplaceArc(from, label, rho_states[UTF8_RHO_STATE_TABLE[label]]);
+  }
+
+  // connect intermediate states of default multi-byte UTF8 sequence
+
+  a.EmplaceArc(rho_states[1], fst::fsa::kRho, rho_states[0]);
+  a.EmplaceArc(rho_states[2], fst::fsa::kRho, rho_states[1]);
+  a.EmplaceArc(rho_states[3], fst::fsa::kRho, rho_states[2]);
+}
+
+void utf8_transitions_builder::insert(
+    automaton& a,
+    const byte_type* label,
+    const size_t size,
+    const automaton::StateId to) {
+  assert(label && size < 5);
+
+  add_states(size); // ensure we have enough states
+  const size_t prefix = 1 + common_prefix_length(last_.c_str(), last_.size(), label, size);
+  minimize(a, prefix); // minimize suffix
+
+  // add current word suffix
+  for (size_t i = prefix; i <= size; ++i) {
+    auto& p = states_[i - 1];
+    p.arcs.emplace_back(label[i - 1], &states_[i]);
+    p.rho_id = rho_states_[size - i];
+  }
+
+  const bool is_final = last_.size() != size || prefix != (size + 1);
+
+  if (is_final) {
+    states_[size].id = to;
+  }
+}
+
+void utf8_transitions_builder::finish(automaton& a, automaton::StateId from) {
+#ifdef IRESEARCH_DEBUG
+  auto ensure_empty = make_finally([this]() {
+    // ensure everything is cleaned up
+    assert(std::all_of(
+      states_.begin(), states_.end(), [](const state& s) noexcept {
+        return s.arcs.empty() &&
+          s.id == fst::kNoStateId &&
+          s.rho_id == fst::kNoStateId;
+    }));
+  });
+#endif
+
+  auto& root = states_.front();
+  minimize(a, 1);
+
+  if (fst::kNoStateId == rho_states_[0]) {
+    // no default state: just add transitions from the
+    // root node to its successors
+    for (const auto& arc : root.arcs) {
+      a.EmplaceArc(from, arc.label, arc.id);
+    }
+
+    root.clear();
+
+    return;
+  }
+
+  // reserve enough memory to store all outbound transitions
+
+  a.ReserveArcs(from, 256);
+
+  // in presence of default state we have to add some extra
+  // transitions from root to properly handle multi-byte sequences
+  // and preserve correctness of arcs order
+
+  auto add_rho_arc = [&a, from, this](automaton::Arc::Label label) {
+    const auto rho_state_idx = UTF8_RHO_STATE_TABLE[label];
+    a.EmplaceArc(from, label, rho_states_[rho_state_idx]);
+  };
+
+  automaton::Arc::Label min = 0;
+
+  for (const auto& arc : root.arcs) {
+    assert(arc.label < 256);
+    assert(min <= arc.label); // ensure arcs are sorted
+
+    for (; min < arc.label; ++min) {
+      add_rho_arc(min);
+    }
+
+    assert(min == arc.label);
+    a.EmplaceArc(from, min++, arc.id);
+  }
+
+  root.clear();
+
+  // add remaining rho transitions
+
+  for (; min < 256; ++min) {
+    add_rho_arc(min);
+  }
+
+  // connect intermediate states of default multi-byte UTF8 sequence
+
+  a.EmplaceArc(rho_states_[1], fst::fsa::kRho, rho_states_[0]);
+  a.EmplaceArc(rho_states_[2], fst::fsa::kRho, rho_states_[1]);
+  a.EmplaceArc(rho_states_[3], fst::fsa::kRho, rho_states_[2]);
+}
+
 filter::prepared::ptr prepare_automaton_filter(const string_ref& field,
                                                const automaton& acceptor,
                                                size_t scored_terms_limit,
@@ -60,7 +321,12 @@ filter::prepared::ptr prepare_automaton_filter(const string_ref& field,
 
     auto& meta = it->attributes().get<term_meta>(); // get term metadata
     const decltype(irs::term_meta::docs_count) NO_DOCS = 0;
-    const auto& docs_count = meta ? meta->docs_count : NO_DOCS;
+
+    // NOTE: we can't use reference to 'docs_count' here, like
+    // 'const auto& docs_count = meta ? meta->docs_count : NO_DOCS;'
+    // since not gcc4.9 nor msvc2015-2019 can handle this correctly
+    // probably due to broken optimization
+    const auto* docs_count = meta ? &meta->docs_count : &NO_DOCS;
 
     if (it->next()) {
       auto& state = states.insert(segment);
@@ -69,8 +335,8 @@ filter::prepared::ptr prepare_automaton_filter(const string_ref& field,
       do {
         it->read(); // read term attributes
 
-        state.estimation += docs_count;
-        scorer.collect(docs_count, state.count++, state, segment, *it);
+        state.estimation += *docs_count;
+        scorer.collect(*docs_count, state.count++, state, segment, *it);
       } while (it->next());
     }
   }
diff --git a/3rdParty/iresearch/core/utils/automaton_utils.hpp b/3rdParty/iresearch/core/utils/automaton_utils.hpp
index f05a1b1863bf..a8fa6c9af2c2 100644
--- a/3rdParty/iresearch/core/utils/automaton_utils.hpp
+++ b/3rdParty/iresearch/core/utils/automaton_utils.hpp
@@ -1,4 +1,4 @@
-////////////////////////////////////////////////////////////////////////////////
+////////////////////////////////////////////////////////////////////////////////
 /// DISCLAIMER
 ///
 /// Copyright 2019 ArangoDB GmbH, Cologne, Germany
@@ -24,44 +24,19 @@
 #define IRESEARCH_AUTOMATON_UTILS_H
 
 #include "automaton.hpp"
+#include "fst_states_map.hpp"
+#include "hash_utils.hpp"
+#include "utf8_utils.hpp"
 #include "formats/formats.hpp"
 #include "search/filter.hpp"
 
 NS_ROOT
 
-inline automaton match_any_char() {
- automaton a;
- const auto start = a.AddState();
- const auto finish = a.AddState();
- a.SetStart(start);
- a.EmplaceArc(start, fst::fsa::kRho, finish);
- a.SetFinal(finish);
-
- return a;
-}
-
-inline automaton match_any() {
- automaton a;
- const auto start = a.AddState();
- a.SetStart(start);
- a.EmplaceArc(start, fst::fsa::kRho, start);
- a.SetFinal(start);
-
- return a;
-}
-
-inline automaton match_char(automaton::Arc::Label c) {
- automaton a;
- const auto start = a.AddState();
- a.SetStart(start);
- a.EmplaceArc(start, c, start);
- a.SetFinal(start);
-
- return a;
-}
-
 template<typename Char, typename Matcher>
-bool accept(const automaton& a, Matcher& matcher, const irs::basic_string_ref<Char>& target) {
+inline automaton::Weight accept(
+    const automaton& a,
+    Matcher& matcher,
+    const basic_string_ref<Char>& target) {
   auto state = a.Start();
   matcher.SetState(state);
 
@@ -73,14 +48,14 @@ bool accept(const automaton& a, Matcher& matcher, const irs::basic_string_ref<Ch
     matcher.SetState(state);
   }
 
-  return begin == end && a.Final(state);
+  return begin == end ? a.Final(state)
+                      : automaton::Weight::Zero();
 }
 
 template<typename Char>
-bool accept(const automaton& a, const irs::basic_string_ref<Char>& target) {
+inline automaton::Weight accept(const automaton& a, const basic_string_ref<Char>& target) {
   typedef fst::RhoMatcher<fst::fsa::AutomatonMatcher> matcher_t;
 
-  // FIXME optimize rho label lookup (just check last arc)
   matcher_t matcher(a, fst::MatchType::MATCH_INPUT, fst::fsa::kRho);
   return accept(a, matcher, target);
 }
@@ -97,7 +72,7 @@ class automaton_term_iterator final : public seek_term_iterator {
     return *value_;
   }
 
-  virtual doc_iterator::ptr postings(const irs::flags& features) const override {
+  virtual doc_iterator::ptr postings(const flags& features) const override {
     return it_->postings(features);
   }
 
@@ -152,6 +127,289 @@ class automaton_term_iterator final : public seek_term_iterator {
   const bytes_ref* value_;
 }; // automaton_term_iterator
 
+//////////////////////////////////////////////////////////////////////////////
+/// @class utf8_transitions_builder
+/// @brief helper class for building minimal acyclic binary automaton from
+///        a specified root, a default (rho) state and a set of arcs with
+///        UTF-8 encoded labels
+//////////////////////////////////////////////////////////////////////////////
+class IRESEARCH_API utf8_transitions_builder {
+ public:
+  utf8_transitions_builder()
+    : states_map_(16, state_emplace(weight_)) {
+    // ensure we have enough space for utf8 sequence
+    add_states(utf8_utils::MAX_CODE_POINT_SIZE);
+  }
+
+  template<typename Iterator>
+  void insert(automaton& a,
+              automaton::StateId from,
+              automaton::StateId rho_state,
+              Iterator begin, Iterator end) {
+    // we inherit weight from 'from' node to all intermediate states
+    // that were created by transitions builder
+    weight_ = a.Final(from);
+    last_ = bytes_ref::EMPTY;
+    states_map_.reset();
+
+    // 'from' state is already a part of automaton
+    assert(!states_.empty());
+    states_.front().id = from;
+
+    std::fill(std::begin(rho_states_), std::end(rho_states_), rho_state);
+
+    if (fst::kNoStateId != rho_state) {
+      // create intermediate default states if necessary
+      a.SetFinal(rho_states_[1] = a.AddState(), weight_);
+      a.SetFinal(rho_states_[2] = a.AddState(), weight_);
+      a.SetFinal(rho_states_[3] = a.AddState(), weight_);
+    }
+
+    for (; begin != end; ++begin) {
+      // we expect sorted input
+      assert(last_ <= std::get<0>(*begin));
+
+      const auto& label = std::get<0>(*begin);
+      insert(a, label.c_str(), label.size(), std::get<1>(*begin));
+      last_ = label;
+    }
+
+    finish(a, from);
+  }
+
+ private:
+  struct state;
+
+  struct arc : private util::noncopyable {
+    arc(automaton::Arc::Label label, state* target)
+      : target(target),
+        label(label) {
+    }
+
+    arc(arc&& rhs) noexcept
+      : target(rhs.target),
+        label(rhs.label) {
+    }
+
+    bool operator==(const automaton::Arc& rhs) const noexcept {
+      return label == rhs.ilabel
+        && id == rhs.nextstate;
+    }
+
+    bool operator!=(const automaton::Arc& rhs) const noexcept {
+      return !(*this == rhs);
+    }
+
+    union {
+      state* target;
+      automaton::StateId id;
+    };
+    automaton::Arc::Label label;
+  }; // arc
+
+  struct state : private util::noncopyable {
+    state() = default;
+
+    state(state&& rhs) noexcept
+      : rho_id(rhs.rho_id),
+        id(rhs.id),
+        arcs(std::move(rhs.arcs)) {
+      rhs.rho_id = fst::kNoStateId;
+      rhs.id = fst::kNoStateId;
+    }
+
+    void clear() noexcept {
+      rho_id = fst::kNoStateId;
+      id = fst::kNoStateId;
+      arcs.clear();
+    }
+
+    automaton::StateId rho_id{fst::kNoStateId};
+    automaton::StateId id{fst::kNoStateId};
+    std::vector<arc> arcs;
+  }; // state
+
+  struct state_hash {
+    size_t operator()(const state& s, const automaton& fst) const noexcept {
+      if (fst::kNoStateId != s.id) {
+        return operator()(s.id, fst);
+      }
+
+      size_t hash = 0;
+
+      for (auto& arc: s.arcs) {
+        hash = hash_combine(hash, arc.label);
+        hash = hash_combine(hash, arc.id);
+      }
+
+      if (fst::kNoStateId != s.rho_id) {
+        hash = hash_combine(hash, fst::fsa::kRho);
+        hash = hash_combine(hash, s.rho_id);
+      }
+
+      return hash;
+    }
+
+    size_t operator()(automaton::StateId id, const automaton& fst) const noexcept {
+      fst::ArcIteratorData<automaton::Arc> arcs;
+      fst.InitArcIterator(id, &arcs);
+
+      const auto* begin = arcs.arcs;
+      const auto* end = arcs.arcs + arcs.narcs;
+
+      size_t hash = 0;
+      for (; begin != end; ++begin) {
+        hash = hash_combine(hash, begin->ilabel);
+        hash = hash_combine(hash, begin->nextstate);
+      }
+
+      return hash;
+    }
+  }; // state_hash
+
+  struct state_equal {
+    bool operator()(const state& lhs, automaton::StateId rhs, const automaton& fst) const noexcept {
+      if (lhs.id != fst::kNoStateId) {
+        // already a part of automaton
+        return lhs.id == rhs;
+      }
+
+      fst::ArcIteratorData<automaton::Arc> rarcs;
+      fst.InitArcIterator(rhs, &rarcs);
+
+      const bool has_rho = (fst::kNoStateId != lhs.rho_id);
+
+      if ((lhs.arcs.size() + size_t(has_rho)) != rarcs.narcs) {
+        return false;
+      }
+
+      const auto* rarc = rarcs.arcs;
+      for (const auto& larc : lhs.arcs) {
+        if (larc != *rarc) {
+          return false;
+        }
+        ++rarc;
+      }
+
+      if (has_rho && (rarc->ilabel != fst::fsa::kRho || rarc->nextstate != lhs.rho_id)) {
+        return false;
+      }
+
+      return true;
+    }
+  }; // state_equal
+
+  class state_emplace {
+   public:
+    explicit state_emplace(const automaton::Weight& weight) noexcept
+      : weight_(&weight) {
+    }
+
+    automaton::StateId operator()(const state& s, automaton& fst) const {
+      auto id = s.id;
+
+      if (id == fst::kNoStateId) {
+        id = fst.AddState();
+        fst.SetFinal(id, *weight_);
+      }
+
+      for (const auto& a : s.arcs) {
+        fst.EmplaceArc(id, a.label, a.id);
+      }
+
+      if (s.rho_id != fst::kNoStateId) {
+        fst.EmplaceArc(id, fst::fsa::kRho, s.rho_id);
+      }
+
+      return id;
+    }
+
+   private:
+    const automaton::Weight* weight_;
+  }; // state_emplace
+
+  using automaton_states_map = fst_states_map<
+    automaton, state,
+    state_emplace, state_hash,
+    state_equal, fst::kNoStateId>;
+
+  void add_states(size_t size) {
+    // reserve size + 1 for root state
+    if (states_.size() < ++size) {
+      states_.resize(size);
+    }
+  }
+
+  void minimize(automaton& a, size_t prefix) {
+    assert(prefix > 0);
+
+    for (size_t i = last_.size(); i >= prefix; --i) {
+      state& s = states_[i];
+      state& p = states_[i - 1];
+      assert(!p.arcs.empty());
+
+      p.arcs.back().id = states_map_.insert(s, a);
+
+      s.clear();
+    }
+  }
+
+  void insert(automaton& a,
+              const byte_type* label_data,
+              const size_t label_size,
+              automaton::StateId target);
+
+  void finish(automaton& a, automaton::StateId from);
+
+  automaton::Weight weight_;
+  automaton::StateId rho_states_[4];
+  std::vector<state> states_;
+  automaton_states_map states_map_;
+  bytes_ref last_;
+}; // utf8_automaton_builder
+
+//////////////////////////////////////////////////////////////////////////////
+/// @brief establish UTF-8 labeled connection between specified source and
+///        target states
+//////////////////////////////////////////////////////////////////////////////
+IRESEARCH_API void utf8_emplace_arc(
+  automaton& a,
+  automaton::StateId from,
+  const bytes_ref& label,
+  automaton::StateId to);
+
+//////////////////////////////////////////////////////////////////////////////
+/// @brief establish UTF-8 labeled connection between specified source (from)
+///        and target (to) states with the fallback to default (rho_state)
+///        state
+//////////////////////////////////////////////////////////////////////////////
+IRESEARCH_API void utf8_emplace_arc(
+  automaton& a,
+  automaton::StateId from,
+  automaton::StateId rho_state,
+  const bytes_ref& label,
+  automaton::StateId to);
+
+//////////////////////////////////////////////////////////////////////////////
+/// @brief establish default connnection between specified source (from) and
+///        and target (to)
+//////////////////////////////////////////////////////////////////////////////
+IRESEARCH_API void utf8_emplace_rho_arc(
+  automaton& a,
+  automaton::StateId from,
+  automaton::StateId to);
+
+//////////////////////////////////////////////////////////////////////////////
+/// @brief instantiate compiled filter based on a specified automaton, field
+///        and other properties
+/// @param field field name
+/// @param acceptor input automaton
+/// @param scored_terms_limit score as many terms
+/// @param index index reader
+/// @param order compiled order
+/// @param bool query boost
+/// @returns compiled filter
+//////////////////////////////////////////////////////////////////////////////
 IRESEARCH_API filter::prepared::ptr prepare_automaton_filter(
   const string_ref& field,
   const automaton& acceptor,
diff --git a/3rdParty/iresearch/core/utils/fst.hpp b/3rdParty/iresearch/core/utils/fst.hpp
index b8167965904c..2ecbd6245bf9 100644
--- a/3rdParty/iresearch/core/utils/fst.hpp
+++ b/3rdParty/iresearch/core/utils/fst.hpp
@@ -58,6 +58,7 @@
 #include <boost/functional/hash.hpp>
 
 #include "shared.hpp"
+#include "utils/fst_states_map.hpp"
 #include "utils/string.hpp"
 #include "utils/noncopyable.hpp"
 
@@ -96,21 +97,23 @@ class fst_builder : util::noncopyable {
       return;
     }
 
+    const auto size = in.size();
+
     // determine common prefix
-    const size_t pref = 1 + prefix(last_, in);
+    const size_t pref = 1 + common_prefix_length(last_, in);
 
     // add states for current input
-    add_states(in.size());
+    add_states(size);
 
     // minimize last word suffix
     minimize(pref);
 
     // add current word suffix
-    for (size_t i = pref; i <= in.size(); ++i) {
+    for (size_t i = pref; i <= size; ++i) {
       states_[i - 1].arcs.emplace_back(in[i - 1], &states_[i]);
     }
 
-    const bool is_final = last_.size() != in.size() || pref != (in.size() + 1);
+    const bool is_final = last_.size() != size || pref != (size + 1);
 
     decltype(fst::DivideLeft(out, out)) output = out;
 
@@ -142,7 +145,7 @@ class fst_builder : util::noncopyable {
     if (is_final) {
       // set final state
       {
-        state& s = states_[in.size()];
+        state& s = states_[size];
         s.final = true;
       }
 
@@ -153,7 +156,7 @@ class fst_builder : util::noncopyable {
         s.arcs.back().out = std::move(output);
       }
     } else {
-      state& s = states_[in.size()];
+      state& s = states_[size];
       assert(s.arcs.size());
       assert(s.arcs.back().label == in[pref - 1]);
       s.arcs.back().out = fst::Times(s.arcs.back().out, output);
@@ -163,13 +166,17 @@ class fst_builder : util::noncopyable {
   }
 
   void finish() {
-    stateid_t start;
-    if (states_.empty()) {
-      start = final;
-    } else {
+    stateid_t start = fst_builder::final;
+
+    if (!states_.empty()) {
       // minimize last word suffix
       minimize(1);
-      start = states_map_.insert(states_[0], fst_);
+
+      auto& root = states_[0];
+
+      if (!root.arcs.empty() || !root.final) {
+        start = states_map_.insert(root, fst_);
+      }
     }
 
     // set the start state
@@ -205,24 +212,16 @@ class fst_builder : util::noncopyable {
         out(std::move(rhs.out)) {
     }
     
-    bool operator==(const arc_t& rhs) const {
+    bool operator==(const arc_t& rhs) const noexcept {
       return label == rhs.ilabel
         && id == rhs.nextstate
         && out == rhs.weight;
     }
 
-    bool operator!=(const arc_t& rhs) const {
+    bool operator!=(const arc_t& rhs) const noexcept {
       return !(*this == rhs);
     }
 
-    friend size_t hash_value(const arc& a) {
-      size_t hash = 0;
-      ::boost::hash_combine(hash, a.label);
-      ::boost::hash_combine(hash, a.id);
-      ::boost::hash_combine(hash, a.out.Hash());
-      return hash;
-    }
-
     union {
       state* target;
       stateid_t id;
@@ -240,20 +239,10 @@ class fst_builder : util::noncopyable {
         final(rhs.final) {
     }
 
-    void clear() {
+    void clear() noexcept {
       arcs.clear();
-      final = false;
       out = weight_t::One();
-    }
-
-    friend size_t hash_value(const state& s) { 
-      size_t seed = 0;
-
-      for (auto& arc: s.arcs) {
-        ::boost::hash_combine(seed, arc);
-      }
-
-      return seed;
+      final = false;
     }
 
     std::vector<arc> arcs;
@@ -261,118 +250,78 @@ class fst_builder : util::noncopyable {
     bool final{ false };
   }; // state
 
-  class state_map : private util::noncopyable {
-   public:
-    static const size_t InitialSize = 16;
-
-    state_map(): states_(InitialSize, fst::kNoStateId) {}
-    stateid_t insert(const state& s, fst_t& fst) {
-      if (s.arcs.empty() && s.final) {
-        return fst_builder::final;
+  struct state_equal {
+    bool operator()(const state& lhs, stateid_t rhs, const fst_t& fst) const {
+      if (lhs.arcs.size() != fst.NumArcs(rhs)) {
+        return false;
       }
 
-      stateid_t id;
-      const size_t mask = states_.size() - 1;
-      size_t pos = hash_value(s) % mask;
-      for ( ;; ++pos, pos %= mask ) { // TODO: maybe use quadratic probing here
-        if (fst::kNoStateId == states_[pos]) {
-          states_[pos] = id = add_state(s, fst);
-          ++count_;
-
-          if (count_ > 2 * states_.size() / 3) {
-            rehash(fst);
-          }
-          break;
-        } else if (equals( s, states_[pos], fst)) {
-          id = states_[pos];
-          break;
+      fst::ArcIterator<fst_t> rhs_arc(fst, rhs);
+
+      for (auto& lhs_arc : lhs.arcs) {
+        if (lhs_arc != rhs_arc.Value()) {
+          return false;
         }
+
+        rhs_arc.Next();
       }
 
-      return id;
+      assert(rhs_arc.Done());
+      return true;
     }
+  };
 
-    void reset() {
-      count_ = 0;
-      std::fill(states_.begin(), states_.end(), fst::kNoStateId);
-    }
+  struct state_hash {
+    size_t operator()(const state& s, const fst_t& /*fst*/) const noexcept {
+      size_t hash = 0;
 
-   private:
-    static bool equals(const state& lhs, stateid_t rhs, const fst_t& fst) {
-      if (fst.NumArcs( rhs ) != lhs.arcs.size() ) {
-        return false;
+      for (auto& a: s.arcs) {
+        ::boost::hash_combine(hash, a.label);
+        ::boost::hash_combine(hash, a.id);
+        ::boost::hash_combine(hash, a.out.Hash());
       }
 
-      for (fst::ArcIterator<fst_t>it(fst, rhs); !it.Done(); it.Next()) {
-        if (lhs.arcs[it.Position()] !=  it.Value()) {
-          return false;
-        }
-      }
-      return true;
+      return hash;
     }
 
-    static size_t hash(stateid_t id, const fst_t& fst) {
+    size_t operator()(stateid_t id, const fst_t& fst) const noexcept {
       size_t hash = 0;
-      for (fst::ArcIterator< fst_t > it(fst, id); !it.Done(); it.Next()) {
+
+      for (fst::ArcIterator<fst_t> it(fst, id); !it.Done(); it.Next()) {
         const arc_t& a = it.Value();
         ::boost::hash_combine(hash, a.ilabel);
         ::boost::hash_combine(hash, a.nextstate);
         ::boost::hash_combine(hash, a.weight.Hash());
       }
-      return hash;
-    }
-
-    void rehash(const fst_t& fst) {
-      std::vector< stateid_t > states(states_.size() * 2, fst::kNoStateId);
-      const size_t mask = states.size() - 1;
-      for (stateid_t id : states_) {
-
-        if (fst::kNoStateId == id) {
-          continue;
-        }
-
-        size_t pos = hash(id, fst) % mask;
-        for (;;++pos, pos %= mask) { // TODO: maybe use quadratic probing here
-          if (fst::kNoStateId == states[pos] ) {
-            states[pos] = id;
-            break;
-          }
-        }
-      }
 
-      states_ = std::move(states);
+      return hash;
     }
+  };
 
-    stateid_t add_state(const state& s, fst_t& fst) {
+  struct state_emplace {
+    stateid_t operator()(const state& s, fst_t& fst) const {
       const stateid_t id = fst.AddState();
+
       if (s.final) {
         fst.SetFinal(id, s.out);
       }
 
       for (const arc& a : s.arcs) {
-        fst.AddArc(id, arc_t(a.label, a.label, a.out, a.id));
+        fst.EmplaceArc(id, a.label, a.label, a.out, a.id);
       }
 
       return id;
     }
+  };
 
-    // TODO: maybe use "buckets" here
-    std::vector<stateid_t> states_;
-    size_t count_{};
-  }; // state_map
-
-  static size_t prefix(const key_t& lhs, const key_t& rhs) {
-    size_t pref = 0;
-    const size_t max = std::min( lhs.size(), rhs.size() );
-    while ( pref < max && lhs[pref] == rhs[pref] ) {
-      ++pref;
-    }
-    return pref;
-  }
+  using states_map = fst_states_map<
+    fst_t, state,
+    state_emplace, state_hash,
+    state_equal, fst::kNoStateId>;
 
   void add_states(size_t size) {
     // reserve size + 1 for root state
-    if ( states_.size() < ++size ) {
+    if (states_.size() < ++size) {
       states_.resize(size);
     }
   }
@@ -383,14 +332,17 @@ class fst_builder : util::noncopyable {
     for (size_t i = last_.size(); i >= pref; --i) {
       state& s = states_[i];
       state& p = states_[i - 1];
+
       assert(!p.arcs.empty());
+      p.arcs.back().id = s.arcs.empty() && s.final
+        ? fst_builder::final
+        : states_map_.insert(s, fst_);
 
-      p.arcs.back().id = states_map_.insert(s, fst_);
       s.clear();
     }
   }
 
-  state_map states_map_;
+  states_map states_map_;
   std::vector<state> states_; // current states
   weight_t start_out_; // output for "empty" input
   key_t last_;
diff --git a/3rdParty/iresearch/core/utils/fst_states_map.hpp b/3rdParty/iresearch/core/utils/fst_states_map.hpp
new file mode 100644
index 000000000000..005b958d4732
--- /dev/null
+++ b/3rdParty/iresearch/core/utils/fst_states_map.hpp
@@ -0,0 +1,144 @@
+////////////////////////////////////////////////////////////////////////////////
+/// DISCLAIMER
+///
+/// Copyright 2020 ArangoDB GmbH, Cologne, Germany
+///
+/// Licensed under the Apache License, Version 2.0 (the "License");
+/// you may not use this file except in compliance with the License.
+/// You may obtain a copy of the License at
+///
+///     http://www.apache.org/licenses/LICENSE-2.0
+///
+/// Unless required by applicable law or agreed to in writing, software
+/// distributed under the License is distributed on an "AS IS" BASIS,
+/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+/// See the License for the specific language governing permissions and
+/// limitations under the License.
+///
+/// Copyright holder is ArangoDB GmbH, Cologne, Germany
+///
+/// @author Andrey Abramov
+////////////////////////////////////////////////////////////////////////////////
+
+#ifndef IRESEARCH_FST_STATES_MAP_H
+#define IRESEARCH_FST_STATES_MAP_H
+
+#include <vector>
+
+#include "shared.hpp"
+#include "ebo.hpp"
+#include "noncopyable.hpp"
+
+NS_ROOT
+
+//////////////////////////////////////////////////////////////////////////////
+/// @class fst_states_map
+/// @brief helper class for deduplication of fst states while building
+///        minimal acyclic subsequential transducer
+//////////////////////////////////////////////////////////////////////////////
+template<typename Fst,
+         typename State,
+         typename PushState,
+         typename Hash,
+         typename StateEq,
+         typename Fst::StateId NoStateId>
+class fst_states_map : private compact<0, Hash>,
+                       private compact<1, StateEq>,
+                       private compact<2, PushState>,
+                       private util::noncopyable {
+ public:
+  using fst_type = Fst;
+  using state_type = State;
+  using state_id = typename fst_type::StateId;
+  using push_state = PushState;
+  using hasher = Hash;
+  using state_equal = StateEq;
+
+  explicit fst_states_map(
+      size_t capacity = 16,
+      const push_state state_emplace = {},
+      const hasher& hash_function = {},
+      const state_equal& state_eq = {})
+    : compact<0, hasher>{ hash_function },
+      compact<1, state_equal>{ state_eq },
+      compact<2, push_state>{ state_emplace },
+      states_(capacity, NoStateId) {
+  }
+
+  state_id insert(const state_type& s, fst_type& fst) {
+    const auto state_equal = state_eq();
+    const auto hasher = hash_function();
+
+    const size_t mask = states_.size() - 1;
+    size_t pos = hasher(s, fst) % mask;
+    for (;;++pos, pos %= mask) {
+      auto& bucket = states_[pos];
+
+      if (NoStateId == bucket) {
+        const auto push_state = state_emplace();
+        const state_id id = bucket = push_state(s, fst);
+        assert(hasher(s, fst) == hasher(id, fst));
+        ++count_;
+
+        if (count_ > 2 * states_.size() / 3) {
+          rehash(fst);
+        }
+
+        return id;
+      }
+
+      if (state_equal(s, bucket, fst)) {
+        return bucket;
+      }
+    }
+  }
+
+  void reset() noexcept {
+    count_ = 0;
+    std::fill(states_.begin(), states_.end(), NoStateId);
+  }
+
+  hasher hash_function() const noexcept {
+    return compact<0, hasher>::get();
+  }
+
+  state_equal state_eq() const noexcept {
+    return compact<1, state_equal>::get();
+  }
+
+  push_state state_emplace() const noexcept {
+    return compact<2, push_state>::get();
+  }
+
+ private:
+  void rehash(const fst_type& fst) {
+    const auto hasher = hash_function();
+
+    std::vector<state_id> states(states_.size() * 2, NoStateId);
+    const size_t mask = states.size() - 1;
+    for (const auto id : states_) {
+      if (NoStateId == id) {
+        continue;
+      }
+
+      size_t pos = hasher(id, fst) % mask;
+      for (;;++pos, pos %= mask) {
+        auto& bucket = states[pos];
+
+        if (NoStateId == bucket) {
+          bucket = id;
+          break;
+        }
+      }
+    }
+
+    states_ = std::move(states);
+  }
+
+  std::vector<state_id> states_;
+  size_t count_{};
+}; // fst_states_map
+
+NS_END
+
+#endif
diff --git a/3rdParty/iresearch/core/utils/fst_table_matcher.hpp b/3rdParty/iresearch/core/utils/fst_table_matcher.hpp
index ebaaf78c9728..cce094b51f57 100644
--- a/3rdParty/iresearch/core/utils/fst_table_matcher.hpp
+++ b/3rdParty/iresearch/core/utils/fst_table_matcher.hpp
@@ -64,16 +64,16 @@ class TableMatcher final : public MatcherBase<typename F::Arc> {
 
   // expected FST properties
   static constexpr auto FST_PROPERTIES =
-      (MATCH_TYPE == MATCH_INPUT ? kNoIEpsilons : kNoOEpsilons)
-      | (MATCH_TYPE == MATCH_INPUT ? kILabelSorted : kOLabelSorted)
-      | (MATCH_TYPE == MATCH_INPUT ? kIDeterministic : kODeterministic)
-      | kAcceptor;
+    (MATCH_TYPE == MATCH_INPUT ? kILabelSorted : kOLabelSorted)
+    | (MATCH_TYPE == MATCH_INPUT ? kIDeterministic : kODeterministic)
+    | kAcceptor;
 
   explicit TableMatcher(const FST& fst, Label rho)
     : start_labels_(fst::getStartLabels<F, MatchInput>(fst)),
       arc_(kNoLabel, kNoLabel, Weight::NoWeight(), kNoStateId),
       rho_(rho), fst_(&fst),
       error_(fst.Properties(FST_PROPERTIES, true) != FST_PROPERTIES) {
+    assert(!error_);
     const size_t numLabels = start_labels_.size();
 
     // initialize transition table
diff --git a/3rdParty/iresearch/core/utils/levenshtein_utils.cpp b/3rdParty/iresearch/core/utils/levenshtein_utils.cpp
index e84239657e6d..d5308a920a6c 100644
--- a/3rdParty/iresearch/core/utils/levenshtein_utils.cpp
+++ b/3rdParty/iresearch/core/utils/levenshtein_utils.cpp
@@ -23,11 +23,12 @@
 #include "levenshtein_utils.hpp"
 
 #include <unordered_map>
+#include <queue>
 #include <cmath>
 
 #include "shared.hpp"
 #include "store/store_utils.hpp"
-#include "automaton.hpp"
+#include "automaton_utils.hpp"
 #include "arena_allocator.hpp"
 #include "bit_utils.hpp"
 #include "bitset.hpp"
@@ -127,12 +128,15 @@ class parametric_state {
       }
     }
 
-    for (auto begin = positions_.data(); begin != positions_.data() + positions_.size();) {
-      if (subsumes(new_pos, *begin)) {
-        std::swap(*begin, positions_.back());
-        positions_.pop_back(); // removed positions subsumed by new_pos
-      } else {
-        ++begin;
+    if (!positions_.empty()) {
+      for (auto begin = positions_.data(), end = positions_.data() + positions_.size(); begin != end; ) {
+        if (subsumes(new_pos, *begin)) {
+          std::swap(*begin, positions_.back());
+          positions_.pop_back(); // removed positions subsumed by new_pos
+          end = positions_.data() + positions_.size();
+        } else {
+          ++begin;
+        }
       }
     }
 
@@ -190,7 +194,7 @@ class parametric_states {
   }
 
   uint32_t emplace(parametric_state&& state) {
-    const auto res = irs::map_utils::try_emplace(
+    const auto res = map_utils::try_emplace(
       states_, std::move(state), states_.size());
 
     if (res.second) {
@@ -360,43 +364,56 @@ uint32_t distance(
 // --SECTION--                                     Helpers for DFA instantiation
 // -----------------------------------------------------------------------------
 
+struct character {
+  bitset chi; // characteristic vector
+  byte_type utf8[utf8_utils::MAX_CODE_POINT_SIZE]{};
+  size_t size{};
+  uint32_t cp{}; // utf8 code point
+
+  const byte_type* begin() const noexcept { return utf8; }
+  const byte_type* end() const noexcept { return utf8 + size; }
+};
+
 //////////////////////////////////////////////////////////////////////////////
 /// @return characteristic vectors for a specified word
 //////////////////////////////////////////////////////////////////////////////
-std::vector<std::pair<uint32_t, irs::bitset>> make_alphabet(
+std::vector<character> make_alphabet(
     const bytes_ref& word,
     size_t& utf8_size) {
   memory::arena<uint32_t, 16> arena;
   memory::arena_vector<uint32_t, decltype(arena)> chars(arena);
-  utf8_utils::to_utf8(word, std::back_inserter(chars));
+  utf8_utils::utf8_to_utf32<false>(word, std::back_inserter(chars));
   utf8_size = chars.size();
 
   std::sort(chars.begin(), chars.end());
   auto cbegin = chars.begin();
   auto cend = std::unique(cbegin, chars.end()); // no need to erase here
 
-  std::vector<std::pair<uint32_t, irs::bitset>> alphabet(1 + size_t(std::distance(cbegin, cend))); // +1 for rho
+  std::vector<character> alphabet(1 + size_t(std::distance(cbegin, cend))); // +1 for rho
   auto begin = alphabet.begin();
 
   // ensure we have enough capacity
   const auto capacity = utf8_size + bits_required<bitset::word_t>();
 
-  begin->first = fst::fsa::kRho;
-  begin->second.reset(capacity);
+  begin->cp = fst::fsa::kRho;
+  begin->chi.reset(capacity);
   ++begin;
 
   for (; cbegin != cend; ++cbegin, ++begin) {
     const auto c = *cbegin;
 
-    // set char
-    begin->first = c;
+    // set code point
+    begin->cp = c;
+
+    // set utf8 representation
+    begin->size = utf8_utils::utf32_to_utf8(c, begin->utf8);
 
     // evaluate characteristic vector
-    auto& bits = begin->second;
-    bits.reset(capacity);
+    auto& chi = begin->chi;
+    chi.reset(capacity);
     auto utf8_begin = word.begin();
     for (size_t i = 0; i < utf8_size; ++i) {
-      bits.reset(i, c == utf8_utils::next(utf8_begin));
+      chi.reset(i, c == utf8_utils::next(utf8_begin));
     }
     IRS_ASSERT(utf8_begin == word.end());
   }
@@ -432,16 +449,6 @@ uint64_t chi(const bitset& bs, size_t offset, uint64_t mask) noexcept {
   return (lhs | rhs) & mask;
 }
 
-//////////////////////////////////////////////////////////////////////////////
-/// @return true if a specified state at a given offset is accepting,
-///         false - otherwise
-//////////////////////////////////////////////////////////////////////////////
-FORCE_INLINE bool is_accepting(
-    const parametric_description& description,
-    size_t state, size_t offset) noexcept {
-  return description.distance(state, offset) <= description.max_distance();
-}
-
 NS_END
 
 NS_ROOT
@@ -585,24 +592,42 @@ automaton make_levenshtein_automaton(
   std::vector<automaton::StateId> transitions(description.size()*num_offsets,
                                               fst::kNoStateId);
 
-  // result automaton
   automaton a;
   a.ReserveStates(transitions.size());
-  const auto invalid_state = a.AddState(); // state without outbound transitions
-  a.SetStart(a.AddState());                // initial state
+
+  // terminal state without outbound transitions
+  const auto invalid_state = a.AddState();
+  assert(INVALID_STATE == invalid_state);
+  UNUSED(invalid_state);
+
+  // initial state
+  a.SetStart(a.AddState());
+
+  // check if start state is final
+  const auto distance = description.distance(1, utf8_size);
+
+  if (distance <= description.max_distance()) {
+    assert(distance < fst::fsa::BooleanWeight::MaxPayload);
+    a.SetFinal(a.Start(), {true, distance});
+  }
 
   // state stack
   std::vector<state> stack;
   stack.emplace_back(0, 1, a.Start());  // 0 offset, 1st parametric state, initial automaton state
 
-  while (!stack.empty()) {
+  std::vector<std::pair<bytes_ref, automaton::StateId>> arcs;
+  arcs.resize(utf8_size); // allocate space for max possible number of arcs
+
+  for (utf8_transitions_builder builder; !stack.empty(); ) {
     const auto state = stack.back();
     stack.pop_back();
+    arcs.clear();
 
     automaton::StateId default_state = fst::kNoStateId; // destination of rho transition if exist
+    bool ascii = true; // ascii only input
 
     for (auto& entry : alphabet) {
-      const auto chi = ::chi(entry.second, state.offset, mask);
+      const auto chi = ::chi(entry.chi, state.offset, mask);
       auto& transition = description.transition(state.state_id, chi);
 
       const size_t offset = transition.first ? transition.second + state.offset : 0;
@@ -610,38 +635,53 @@ automaton make_levenshtein_automaton(
       auto& to = transitions[transition.first*num_offsets + offset];
 
       if (INVALID_STATE == transition.first) {
-        to = invalid_state;
+        to = INVALID_STATE;
       } else if (fst::kNoStateId == to) {
         to = a.AddState();
 
-        if (is_accepting(description, transition.first, utf8_size - offset)) {
-          a.SetFinal(to);
+        const auto distance = description.distance(transition.first, utf8_size - offset);
+
+        if (distance <= description.max_distance()) {
+          assert(distance < fst::fsa::BooleanWeight::MaxPayload);
+          a.SetFinal(to, {true, distance});
         }
 
         stack.emplace_back(offset, transition.first, to);
       }
 
       if (chi && to != default_state) {
-        a.EmplaceArc(state.from, entry.first, to);
-      } else if (fst::kNoStateId == default_state) {
+        arcs.emplace_back(bytes_ref(entry.utf8, entry.size), to);
+        ascii &= (entry.size == 1);
+      } else {
+        assert(fst::kNoStateId == default_state || to == default_state);
         default_state = to;
       }
     }
 
-    if (fst::kNoStateId != default_state) {
-      a.EmplaceArc(state.from, fst::fsa::kRho, default_state);
+    if (INVALID_STATE == default_state && arcs.empty()) {
+      // optimization for invalid terminal state
+      a.EmplaceArc(state.from, fst::fsa::kRho, INVALID_STATE);
+    } else if (INVALID_STATE == default_state && ascii && !a.Final(state.from)) {
+      // optimization for ascii only input without default state and weight
+      for (auto& arc: arcs) {
+        assert(1 == arc.first.size());
+        a.EmplaceArc(state.from, arc.first.front(), arc.second);
+      }
+    } else {
+      builder.insert(a, state.from, default_state, arcs.begin(), arcs.end());
     }
   }
 
 #ifdef IRESEARCH_DEBUG
   // ensure resulting automaton is sorted and deterministic
-  constexpr auto EXPECTED_PROPERTIES =
+  static constexpr auto EXPECTED_PROPERTIES =
     fst::kIDeterministic | fst::kODeterministic |
-    fst::kILabelSorted | fst::kOLabelSorted;
-  assert(a.Properties(EXPECTED_PROPERTIES, true));
+    fst::kILabelSorted | fst::kOLabelSorted |
+    fst::kAcceptor;
+  assert(EXPECTED_PROPERTIES == a.Properties(EXPECTED_PROPERTIES, true));
 
   // ensure invalid state has no outbound transitions
-  assert(0 == a.NumArcs(invalid_state));
+  assert(0 == a.NumArcs(INVALID_STATE));
 #endif
 
   return a;
@@ -654,7 +694,7 @@ size_t edit_distance(const parametric_description& description,
 
   memory::arena<uint32_t, 16> arena;
   memory::arena_vector<uint32_t, decltype(arena)> lhs_chars(arena);
-  utf8_utils::to_utf8(lhs, lhs_size, std::back_inserter(lhs_chars));
+  utf8_utils::utf8_to_utf32<false>(lhs, lhs_size, std::back_inserter(lhs_chars));
 
   size_t state = 1;  // current parametric state
   size_t offset = 0; // current offset
@@ -678,4 +718,45 @@ size_t edit_distance(const parametric_description& description,
   return description.distance(state, lhs_chars.size() - offset);
 }
 
+bool edit_distance(
+    size_t& distance,
+    const parametric_description& description,
+    const byte_type* lhs, size_t lhs_size,
+    const byte_type* rhs, size_t rhs_size) {
+  assert(description);
+
+  memory::arena<uint32_t, 16> arena;
+  memory::arena_vector<uint32_t, decltype(arena)> lhs_chars(arena);
+  if (!utf8_utils::utf8_to_utf32<true>(lhs, lhs_size, std::back_inserter(lhs_chars))) {
+    return false;
+  }
+
+  size_t state = 1;  // current parametric state
+  size_t offset = 0; // current offset
+
+  for (auto* rhs_end = rhs + rhs_size; rhs < rhs_end; ) {
+    const auto c = utf8_utils::next_checked(rhs, rhs_end);
+
+    if (utf8_utils::INVALID_CODE_POINT == c) {
+      return false;
+    }
+
+    const auto begin = lhs_chars.begin() + ptrdiff_t(offset);
+    const auto end = std::min(begin + ptrdiff_t(description.chi_size()), lhs_chars.end());
+    const auto chi = ::chi(begin, end, c);
+    const auto& transition = description.transition(state, chi);
+
+    if (INVALID_STATE == transition.first) {
+      distance = description.max_distance() + 1;
+      return true;
+    }
+
+    state = transition.first;
+    offset += transition.second;
+  }
+
+  distance = description.distance(state, lhs_chars.size() - offset);
+  return true;
+}
+
 NS_END
diff --git a/3rdParty/iresearch/core/utils/levenshtein_utils.hpp b/3rdParty/iresearch/core/utils/levenshtein_utils.hpp
index 7ab480a9c17b..4f654cd149f3 100644
--- a/3rdParty/iresearch/core/utils/levenshtein_utils.hpp
+++ b/3rdParty/iresearch/core/utils/levenshtein_utils.hpp
@@ -73,7 +73,9 @@ inline size_t edit_distance(const T* lhs, size_t lhs_size,
 /// @param rhs string to compare
 /// @returns edit distance
 ////////////////////////////////////////////////////////////////////////////////
-inline size_t edit_distance(const bytes_ref& lhs, const bytes_ref& rhs) {
+template<typename Char>
+inline size_t edit_distance(const basic_string_ref<Char>& lhs,
+                            const basic_string_ref<Char>& rhs) {
   return edit_distance(lhs.begin(), lhs.size(), rhs.begin(), rhs.size());
 }
 
@@ -236,8 +238,9 @@ IRESEARCH_API parametric_description read(data_input& in);
 ////////////////////////////////////////////////////////////////////////////////
 /// @brief instantiates DFA based on provided parametric description and target
 /// @param description parametric description
-/// @param target actual "string" (utf8 encoded)
+/// @param target valid UTF-8 encoded string
 /// @returns DFA
+/// @note if 'target' isn't a valid UTF-8 sequence, behaviour is undefined
 ////////////////////////////////////////////////////////////////////////////////
 IRESEARCH_API automaton make_levenshtein_automaton(
   const parametric_description& description,
@@ -277,6 +280,47 @@ inline size_t edit_distance(
   return edit_distance(description, lhs.begin(), lhs.size(), rhs.begin(), rhs.size());
 }
 
+////////////////////////////////////////////////////////////////////////////////
+/// @brief evaluates edit distance between the specified words up to
+///        specified in description.max_distance.
+/// @param evaluated edit distance
+/// @param description parametric description
+/// @param lhs string to compare (utf8 encoded)
+/// @param lhs_size size of the string to comprare
+/// @param rhs string to compare (utf8 encoded)
+/// @param rhs_size size of the string to comprare
+/// @returns true if both lhs_string and rhs_strign are valid UTF-8 sequences,
+///          false - otherwise
+/// @note accepts only valid descriptions, calling function with
+///       invalid description is undefined behaviour
+////////////////////////////////////////////////////////////////////////////////
+IRESEARCH_API bool edit_distance(
+  size_t& distance,
+  const parametric_description& description,
+  const byte_type* lhs, size_t lhs_size,
+  const byte_type* rhs, size_t rhs_size);
+
+////////////////////////////////////////////////////////////////////////////////
+/// @brief evaluates edit distance between the specified words up to
+///        specified in description.max_distance
+/// @param description parametric description
+/// @param lhs string to compare (utf8 encoded)
+/// @param rhs string to compare (utf8 encoded)
+/// @returns true if both lhs_string and rhs_strign are valid UTF-8 sequences,
+///          false - otherwise
+/// @note accepts only valid descriptions, calling function with
+///       invalid description is undefined behaviour
+////////////////////////////////////////////////////////////////////////////////
+inline bool edit_distance(
+    size_t& distance,
+    const parametric_description& description,
+    const bytes_ref& lhs,
+    const bytes_ref& rhs) {
+  return edit_distance(distance, description,
+                       lhs.begin(), lhs.size(),
+                       rhs.begin(), rhs.size());
+}
+
 NS_END
 
 #endif // IRESEARCH_LEVENSHTEIN_UTILS_H
diff --git a/3rdParty/iresearch/core/utils/locale_utils.cpp b/3rdParty/iresearch/core/utils/locale_utils.cpp
index faa149ade10e..d3588211a138 100644
--- a/3rdParty/iresearch/core/utils/locale_utils.cpp
+++ b/3rdParty/iresearch/core/utils/locale_utils.cpp
@@ -2530,7 +2530,7 @@ class num_put_facet: public std::num_put<CharType> {
         return nullptr;
       }
 
-      return std::move(ctx);
+      return ctx;
     }
 
     void reset(const std::ios_base& str) {
@@ -3660,7 +3660,7 @@ NS_BEGIN( locale_utils )
   ) {
     return std::use_facet<std::codecvt<char32_t, char, mbstate_t>>(locale);
   }
-#elif defined(_MSC_VER) && _MSC_VER <= 1923// MSVC2015/MSVC2017/MSVC2019
+#elif defined(_MSC_VER) && _MSC_VER <= 1924// MSVC2015/MSVC2017/MSVC2019
   // MSVC2015/MSVC2017 implementations do not support char16_t/char32_t 'codecvt'
   // due to a missing export, as per their comment:
   //   This is an active bug in our database (VSO#143857), which we'll investigate
diff --git a/3rdParty/iresearch/core/utils/locale_utils.hpp b/3rdParty/iresearch/core/utils/locale_utils.hpp
index 3a14e1aa4dae..e2052e75f2ac 100644
--- a/3rdParty/iresearch/core/utils/locale_utils.hpp
+++ b/3rdParty/iresearch/core/utils/locale_utils.hpp
@@ -49,7 +49,7 @@ const std::codecvt<T, char, mbstate_t>& codecvt(std::locale const& locale) {
   IRESEARCH_API const std::codecvt<char32_t, char, mbstate_t>& codecvt(
     std::locale const& locale
   );
-#elif defined(_MSC_VER) && _MSC_VER <= 1923 // MSVC2015/MSVC2017/MSVC2019
+#elif defined(_MSC_VER) && _MSC_VER <= 1924 // MSVC2015/MSVC2017/MSVC2019
   // MSVC2015/MSVC2017 implementations do not support char16_t/char32_t 'codecvt'
   // due to a missing export, as per their comment:
   //   This is an active bug in our database (VSO#143857), which we'll investigate
diff --git a/3rdParty/iresearch/core/utils/log.cpp b/3rdParty/iresearch/core/utils/log.cpp
index 9328f8230293..07752aefff1f 100644
--- a/3rdParty/iresearch/core/utils/log.cpp
+++ b/3rdParty/iresearch/core/utils/log.cpp
@@ -370,9 +370,9 @@ bool stack_trace_libunwind(iresearch::logger::level_t level); // predeclaration
     }
 
     size_t buf_len = 0;
-    constexpr const size_t buf_size = 1024; // arbitrary size
+    constexpr size_t buf_size = 1024; // arbitrary size
     char buf[buf_size];
-    std::thread thread([&pipefd, level, out, &buf, &buf_len, buf_size]()->void {
+    std::thread thread([&pipefd, level, out, &buf, &buf_len]()->void {
       for (char ch; read(pipefd[0], &ch, 1) > 0;) {
         if (ch != '\n') {
           if (buf_len < buf_size - 1) {
diff --git a/3rdParty/iresearch/core/utils/ngram_match_utils.hpp b/3rdParty/iresearch/core/utils/ngram_match_utils.hpp
new file mode 100644
index 000000000000..c58fe395115a
--- /dev/null
+++ b/3rdParty/iresearch/core/utils/ngram_match_utils.hpp
@@ -0,0 +1,138 @@
+////////////////////////////////////////////////////////////////////////////////
+/// DISCLAIMER
+///
+/// Copyright 2020 ArangoDB GmbH, Cologne, Germany
+///
+/// Licensed under the Apache License, Version 2.0 (the "License");
+/// you may not use this file except in compliance with the License.
+/// You may obtain a copy of the License at
+///
+///     http://www.apache.org/licenses/LICENSE-2.0
+///
+/// Unless required by applicable law or agreed to in writing, software
+/// distributed under the License is distributed on an "AS IS" BASIS,
+/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+/// See the License for the specific language governing permissions and
+/// limitations under the License.
+///
+/// Copyright holder is ArangoDB GmbH, Cologne, Germany
+///
+/// @author Andrei Lobov
+////////////////////////////////////////////////////////////////////////////////
+
+#ifndef IRESEARCH_NGRAM_MATCH_UTILS_H
+#define IRESEARCH_NGRAM_MATCH_UTILS_H
+
+#include "shared.hpp"
+#include "utf8_utils.hpp"
+#include <vector>
+
+NS_ROOT
+
+////////////////////////////////////////////////////////////////////////////////
+/// Evaluates ngram similarity between the specified strings based on
+/// "N-gram similarity and distance" by Grzegorz Kondrak
+/// http://www.cs.ualberta.ca/~kondrak/papers/spire05.pdf
+/// Could operate in two forms depending on search_semantics.
+/// If search_semantics is false then positional ngram similarity is used,
+/// binary ngram similarity is used otherwise. Also setting search_semantics to
+/// true disables normalizing resulting similarity by length of longest string and
+/// result is evaluated based strictly on target length (search-like semantics).
+/// If search_semantics is false there is no difference which string pass
+/// as target. First characters affixing currently is not implemented
+/// @param target string to seek similarity for
+/// @param target_size length of target string
+/// @param src string to seek similarity in
+/// @param src_size length of source string
+/// @param ngram_size ngram size
+/// @returns similarity value
+////////////////////////////////////////////////////////////////////////////////
+template<typename T, bool search_semantics>
+float_t ngram_similarity(const T* target, size_t target_size,
+                         const T* src, size_t src_size,
+                         size_t ngram_size) {
+  if (ngram_size == 0) {
+    return 0.f;
+  }
+
+  if /*consexpr*/ (!search_semantics) {
+    if (target_size > src_size) {
+      std::swap(target_size, src_size);
+      std::swap(target, src);
+    }
+  }
+
+  if (target_size < ngram_size || src_size < ngram_size) {
+    if /*constexpr*/ (!search_semantics) {
+      if (target_size == 0 && src_size == 0) {
+        return 1; // consider two empty strings as matched
+      }
+      const T* r = src;
+      size_t matched = 0;
+      for (const T* it = target; it != target + target_size; ) {
+        matched += size_t(*it == *r);
+        ++r;
+        ++it;
+      }
+      return float_t(matched) / float_t(src_size);
+    } else {
+      if (target_size == src_size) {
+        return memcmp(target, src, target_size * sizeof(T)) == 0 ? 1 : 0;
+      }
+      return 0;
+    }
+  }
+
+  const size_t t_ngram_count = target_size - ngram_size + 1;
+  const size_t s_ngram_count = src_size - ngram_size + 1;
+  const T* t_ngram_start = target;
+  const T* t_ngram_start_end  = target + target_size - ngram_size + 1; // end() analog for target ngram start
+
+  float_t d = 0; // will store upper-left cell value for current cache row
+  std::vector<float_t> cache(s_ngram_count + 1, 0);
+
+  // here could be constructed source string with start characters affixing
+
+  size_t t_ngram_idx = 1;
+  for (; t_ngram_start != t_ngram_start_end; ++t_ngram_start, ++t_ngram_idx) {
+    const T* t_ngram_end = t_ngram_start + ngram_size;
+    const T* s_ngram_start = src;
+    size_t s_ngram_idx = 1;
+    const T* s_ngram_start_end  = src + src_size - ngram_size + 1; // end() analog for src ngram start
+
+    for (; s_ngram_start != s_ngram_start_end; ++s_ngram_start, ++s_ngram_idx) {
+      const T* rhs_ngram_end = s_ngram_start + ngram_size;
+      float_t similarity = !search_semantics ? 0 : 1;
+      for (const T* l = t_ngram_start, *r = s_ngram_start; l != t_ngram_end && r != rhs_ngram_end; ++l, ++r) {
+        if /*constexpr*/ (search_semantics) {
+          if (*l != *r) {
+            similarity = 0;
+            break;
+          }
+        } else {
+          if (*l == *r) {
+            ++similarity;
+          }
+        }
+      }
+      if /*constexpr*/ (!search_semantics) {
+        similarity = similarity / float_t(ngram_size);
+      }
+
+      auto tmp = cache[s_ngram_idx];
+      cache[s_ngram_idx] =
+          std::max(
+            std::max(cache[s_ngram_idx - 1],
+                     cache[s_ngram_idx]),
+            d + similarity);
+      d = tmp;
+    }
+  }
+  return cache[s_ngram_count] /
+         float_t((!search_semantics) ? s_ngram_count : t_ngram_count);
+}
+
+NS_END
+
+
+#endif // IRESEARCH_NGRAM_MATCH_UTILS_H
diff --git a/3rdParty/iresearch/core/utils/std.hpp b/3rdParty/iresearch/core/utils/std.hpp
index 048d6ed7f11e..2029635ff0aa 100644
--- a/3rdParty/iresearch/core/utils/std.hpp
+++ b/3rdParty/iresearch/core/utils/std.hpp
@@ -256,7 +256,7 @@ template<typename Builder, size_t Size>
 struct initializer {
   using type = typename Builder::type;
 
-  static constexpr const auto Idx = Size - 1;
+  static constexpr auto Idx = Size - 1;
 
   template<typename Array>
 #ifndef IRESEARCH_CXX_11
@@ -277,7 +277,7 @@ template<typename Builder>
 struct initializer<Builder, 1> {
   using type = typename Builder::type;
 
-  static constexpr const auto Idx = 0;
+  static constexpr auto Idx = 0;
 
   template<typename Array>
 #ifndef IRESEARCH_CXX_11
diff --git a/3rdParty/iresearch/core/utils/string.cpp b/3rdParty/iresearch/core/utils/string.cpp
index ac7fb2957670..2411e6d807e4 100644
--- a/3rdParty/iresearch/core/utils/string.cpp
+++ b/3rdParty/iresearch/core/utils/string.cpp
@@ -56,9 +56,9 @@ NS_END
 
 NS_ROOT
 
-/* -------------------------------------------------------------------
- * basic_string_ref
- * ------------------------------------------------------------------*/
+// -----------------------------------------------------------------------------
+// --SECTION--                                   basic_string_ref implementation
+// -----------------------------------------------------------------------------
 
 #if defined(_MSC_VER) && defined(IRESEARCH_DLL)
 
@@ -93,5 +93,5 @@ size_t hash(const string_ref& value) noexcept {
   return get_hash(value.c_str(), value.size());
 }
 
-NS_END // detail
+NS_END // hash_utils
 NS_END
diff --git a/3rdParty/iresearch/core/utils/string.hpp b/3rdParty/iresearch/core/utils/string.hpp
index b929c923de38..1628dd7a820b 100644
--- a/3rdParty/iresearch/core/utils/string.hpp
+++ b/3rdParty/iresearch/core/utils/string.hpp
@@ -314,6 +314,42 @@ inline bool starts_with(
   return 0 == first.compare(0, second.size(), second.c_str(), second.size());
 }
 
+template<typename Char>
+inline size_t common_prefix_length(
+    const Char* lhs, size_t lhs_size,
+    const Char* rhs, size_t rhs_size) noexcept {
+  static_assert(1 == sizeof(Char), "1 != sizeof(Char)");
+
+  const size_t* lhs_block = reinterpret_cast<const size_t*>(lhs);
+  const size_t* rhs_block = reinterpret_cast<const size_t*>(rhs);
+
+  size_t size = std::min(lhs_size, rhs_size);
+
+  while (size >= sizeof(size_t) && *lhs_block == *rhs_block) {
+    ++lhs_block;
+    ++rhs_block;
+    size -= sizeof(size_t);
+  }
+
+  const Char* lhs_block_start = reinterpret_cast<const Char*>(lhs_block);
+  const Char* rhs_block_start = reinterpret_cast<const Char*>(rhs_block);
+
+  while (size && *lhs_block_start == *rhs_block_start) {
+    ++lhs_block_start;
+    ++rhs_block_start;
+    --size;
+  }
+
+  return lhs_block_start - lhs;
+}
+
+template<typename Char, typename Traits>
+inline size_t common_prefix_length(
+    const basic_string_ref<Char, Traits>& lhs,
+    const basic_string_ref<Char, Traits>& rhs) noexcept {
+  return common_prefix_length(lhs.c_str(), lhs.size(), rhs.c_str(), rhs.size());
+}
+
 template< typename _Elem, typename _Traits >
 inline bool starts_with( const basic_string_ref< _Elem, _Traits >& first,
                          const _Elem* second ) {
diff --git a/3rdParty/iresearch/core/utils/utf8_utils.hpp b/3rdParty/iresearch/core/utils/utf8_utils.hpp
index 06c7e8dedc6f..e464f1cb5885 100644
--- a/3rdParty/iresearch/core/utils/utf8_utils.hpp
+++ b/3rdParty/iresearch/core/utils/utf8_utils.hpp
@@ -32,29 +32,82 @@
 NS_ROOT
 NS_BEGIN(utf8_utils)
 
-FORCE_INLINE const byte_type* next(const byte_type* it, const byte_type* end) noexcept {
-  IRS_ASSERT(it);
+// max number of bytes to represent single UTF8 code point
+constexpr size_t MAX_CODE_POINT_SIZE = 4;
+constexpr uint32_t MIN_CODE_POINT = 0;
+constexpr uint32_t MAX_CODE_POINT = 0x10FFFF;
+constexpr uint32_t INVALID_CODE_POINT = integer_traits<uint32_t>::const_max;
+
+FORCE_INLINE const byte_type* next(const byte_type* begin, const byte_type* end) noexcept {
+  IRS_ASSERT(begin);
   IRS_ASSERT(end);
 
-  if (it < end) {
-    const uint8_t symbol_start = *it;
-    if (symbol_start < 0x80) {
-      ++it;
-    } else if ((symbol_start >> 5) == 0x06) {
-      it += 2;
-    } else if ((symbol_start >> 4) == 0x0E) {
-      it += 3;
-    } else if ((symbol_start >> 3) == 0x1E) {
-      it += 4;
-    } else {
-      IR_FRMT_ERROR("Invalid UTF-8 symbol increment");
-      it = end;
+  if (begin < end) {
+    const uint32_t cp_start = *begin++;
+    if ((cp_start >> 5) == 0x06) {
+      ++begin;
+    } else if ((cp_start >> 4) == 0x0E) {
+      begin += 2;
+    } else if ((cp_start >> 3) == 0x1E) {
+      begin += 3;
+    } else if (cp_start >= 0x80) {
+      begin = end;
     }
   }
-  return it > end ? end : it;
+
+  return begin > end ? end : begin;
+}
+
+FORCE_INLINE size_t cp_length(const uint32_t cp_start) noexcept {
+  if (cp_start < 0x80) {
+    return 1;
+  } else if ((cp_start >> 5) == 0x06) {
+    return 2;
+  } else if ((cp_start >> 4) == 0x0E) {
+    return 3;
+  } else if ((cp_start >> 3) == 0x1E) {
+    return 4;
+  }
+
+  return 0;
 }
 
-FORCE_INLINE uint32_t next(const byte_type*& it) noexcept {
+inline uint32_t next_checked(const byte_type*& begin, const byte_type* end) noexcept {
+  IRS_ASSERT(begin);
+  IRS_ASSERT(end);
+
+  if (begin >= end) {
+    return INVALID_CODE_POINT;
+  }
+
+  uint32_t cp = *begin;
+  const size_t size = cp_length(cp);
+
+  begin += size;
+
+  if (begin <= end)  {
+    switch (size) {
+     case 1: return cp;
+
+     case 2: return ((cp << 6) & 0x7FF) +
+                    (uint32_t(begin[-1]) & 0x3F);
+
+     case 3: return ((cp << 12) & 0xFFFF) +
+                    ((uint32_t(begin[-2]) << 6) & 0xFFF) +
+                    (uint32_t(begin[-1]) & 0x3F);
+
+     case 4: return ((cp << 18) & 0x1FFFFF) +
+                    ((uint32_t(begin[-3]) << 12) & 0x3FFFF) +
+                    ((uint32_t(begin[-2]) << 6) & 0xFFF) +
+                    (uint32_t(begin[-1]) & 0x3F);
+    }
+  }
+
+  begin = end;
+  return INVALID_CODE_POINT;
+}
+
+inline uint32_t next(const byte_type*& it) noexcept {
   IRS_ASSERT(it);
 
   uint32_t cp = *it;
@@ -75,16 +128,82 @@ FORCE_INLINE uint32_t next(const byte_type*& it) noexcept {
   return cp;
 }
 
-template<typename OutputIterator>
-inline void to_utf8(const byte_type* begin, size_t size, OutputIterator out) {
-  for (auto end = begin + size; begin < end; ++out) {
-    *out = next(begin);
+#ifdef IRESEARCH_CXX14
+constexpr
+#endif
+FORCE_INLINE size_t utf32_to_utf8(uint32_t cp, byte_type* begin) noexcept {
+  if (cp < 0x80) {
+    begin[0] = static_cast<byte_type>(cp);
+    return 1;
+  }
+
+  if (cp < 0x800) {
+    begin[0] = static_cast<byte_type>((cp >> 6) | 0xC0);
+    begin[1] = static_cast<byte_type>((cp & 0x3F) | 0x80);
+    return 2;
+  }
+
+  if (cp < 0x10000) {
+    begin[0] = static_cast<byte_type>((cp >> 12) | 0xE0);
+    begin[1] = static_cast<byte_type>(((cp >> 6) & 0x3F) | 0x80);
+    begin[2] = static_cast<byte_type>((cp & 0x3F) | 0x80);
+    return 3;
+  }
+
+  begin[0] = static_cast<byte_type>((cp >> 18) | 0xF0);
+  begin[1] = static_cast<byte_type>(((cp >> 12) & 0x3F) | 0x80);
+  begin[2] = static_cast<byte_type>(((cp >> 6) & 0x3F) | 0x80);
+  begin[3] = static_cast<byte_type>((cp & 0x3F) | 0x80);
+  return 4;
+}
+
+template<bool Checked = true>
+inline const byte_type* find(const byte_type* begin, const byte_type* end, uint32_t ch) noexcept {
+  for (const byte_type* char_begin = begin; begin < end; char_begin = begin) {
+    const auto cp = Checked ? next_checked(begin, end) : next(begin);
+
+    if (cp == ch) {
+      return char_begin;
+    }
   }
+
+  return end;
+}
+
+template<bool Checked = true>
+inline size_t find(const byte_type* begin, const size_t size, uint32_t ch) noexcept {
+  size_t pos = 0;
+  for (auto end = begin + size; begin < end; ++pos) {
+    const auto cp = Checked ? next_checked(begin, end) : next(begin);
+
+    if (cp == ch) {
+      return pos;
+    }
+  }
+
+  return bstring::npos;
+}
+
+template<bool Checked, typename OutputIterator>
+inline bool utf8_to_utf32(const byte_type* begin, size_t size, OutputIterator out) {
+  for (auto end = begin + size; begin < end; ) {
+    const auto cp = Checked ? next_checked(begin, end) : next(begin);
+
+    if /*constexpr*/ (Checked) {
+      if (cp == INVALID_CODE_POINT) {
+        return false;
+      }
+    }
+
+    *out = cp;
+  }
+
+  return true;
 }
 
-template<typename OutputIterator>
-inline void to_utf8(const bytes_ref& in, OutputIterator out) {
-  to_utf8(in.begin(), in.size(), out);
+template<bool Checked = true, typename OutputIterator>
+FORCE_INLINE bool utf8_to_utf32(const bytes_ref& in, OutputIterator out) {
+  return utf8_to_utf32<Checked>(in.begin(), in.size(), out);
 }
 
 NS_END
diff --git a/3rdParty/iresearch/core/utils/wildcard_utils.cpp b/3rdParty/iresearch/core/utils/wildcard_utils.cpp
new file mode 100644
index 000000000000..c6466ae6fc7a
--- /dev/null
+++ b/3rdParty/iresearch/core/utils/wildcard_utils.cpp
@@ -0,0 +1,228 @@
+////////////////////////////////////////////////////////////////////////////////
+/// DISCLAIMER
+///
+/// Copyright 2019 ArangoDB GmbH, Cologne, Germany
+///
+/// Licensed under the Apache License, Version 2.0 (the "License");
+/// you may not use this file except in compliance with the License.
+/// You may obtain a copy of the License at
+///
+///     http://www.apache.org/licenses/LICENSE-2.0
+///
+/// Unless required by applicable law or agreed to in writing, software
+/// distributed under the License is distributed on an "AS IS" BASIS,
+/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+/// See the License for the specific language governing permissions and
+/// limitations under the License.
+///
+/// Copyright holder is ArangoDB GmbH, Cologne, Germany
+///
+/// @author Andrey Abramov
+////////////////////////////////////////////////////////////////////////////////
+
+#include "wildcard_utils.hpp"
+
+#include "automaton_utils.hpp"
+
+NS_ROOT
+
+WildcardType wildcard_type(const bytes_ref& expr) noexcept {
+  if (expr.empty()) {
+    return WildcardType::TERM;
+  }
+
+  bool escaped = false;
+  size_t num_match_any_string = 0;
+  size_t num_adjacent_match_any_string = 0;
+
+  const auto* char_begin = expr.begin();
+  const auto* end = expr.end();
+
+  for (size_t i = 0; char_begin < end; ++i) {
+    const auto char_length = utf8_utils::cp_length(*char_begin);
+    const auto char_end = char_begin + char_length;
+
+    if (!char_length || char_end > end) {
+      return WildcardType::INVALID;
+    }
+
+    switch (*char_begin) {
+      case WildcardMatch::ANY_STRING:
+        num_adjacent_match_any_string += size_t(!escaped);
+        num_match_any_string += size_t(!escaped);
+        escaped = false;
+        break;
+      case WildcardMatch::ANY_CHAR:
+        if (!escaped) {
+          return WildcardType::WILDCARD;
+        }
+        num_adjacent_match_any_string = 0;
+        escaped = false;
+        break;
+      case WildcardMatch::ESCAPE:
+        num_adjacent_match_any_string = 0;
+        escaped = !escaped;
+        break;
+      default:
+        num_adjacent_match_any_string = 0;
+        escaped = false;
+        break;
+    }
+
+    char_begin = char_end;
+  }
+
+  if (0 == num_match_any_string) {
+    return WildcardType::TERM;
+  }
+
+  if (expr.size() == num_match_any_string) {
+    return WildcardType::MATCH_ALL;
+  }
+
+  if (num_match_any_string == num_adjacent_match_any_string) {
+    return WildcardType::PREFIX;
+  }
+
+  return WildcardType::WILDCARD;
+}
+
+automaton from_wildcard(const bytes_ref& expr) {
+  struct {
+   automaton::StateId from;
+   automaton::StateId to;
+   automaton::StateId match_all_from{ fst::kNoStateId };
+   automaton::StateId match_all_to{ fst::kNoStateId };
+   bytes_ref match_all_label{};
+   bool escaped{ false };
+   bool match_all{ false };
+  } state;
+
+  utf8_transitions_builder builder;
+  std::pair<bytes_ref, automaton::StateId> arcs[2];
+
+  automaton a;
+  state.from = a.AddState();
+  state.to = state.from;
+  a.SetStart(state.from);
+
+  auto appendChar = [&a, &builder, &arcs, &state](const bytes_ref& c) {
+    state.to = a.AddState();
+    if (!state.match_all) {
+      if (state.match_all_label.null()) {
+        utf8_emplace_arc(a, state.from, c, state.to);
+      } else {
+        const auto r = compare(c, state.match_all_label);
+
+        if (!r) {
+          utf8_emplace_arc(a, state.from, state.match_all_from, c, state.to);
+          state.match_all_to = state.to;
+        } else {
+          arcs[0] = { c, state.to };
+          arcs[1] = { state.match_all_label, state.match_all_to };
+
+          if (r > 0) {
+            std::swap(arcs[0], arcs[1]);
+          }
+
+          builder.insert(a, state.from, state.match_all_from,
+                         std::begin(arcs), std::end(arcs));
+        }
+      }
+    } else {
+      utf8_emplace_arc(a, state.from, state.from, c, state.to);
+
+      state.match_all_from = state.from;
+      state.match_all_to = state.to;
+      state.match_all_label = c;
+      state.match_all = false;
+    }
+
+    state.from = state.to;
+    state.escaped = false;
+  };
+
+  const auto* label_begin = expr.begin();
+  const auto* end = expr.end();
+
+  while (label_begin < end) {
+    const auto label_length = utf8_utils::cp_length(*label_begin);
+    const auto label_end = label_begin + label_length;
+
+    if (!label_length || label_end > end) {
+      // invalid UTF-8 sequence
+      a.DeleteStates();
+      return a;
+    }
+
+    switch (*label_begin) {
+      case WildcardMatch::ANY_STRING: {
+        if (state.escaped) {
+          appendChar({label_begin, label_length});
+        } else {
+          state.match_all = true;
+        }
+        break;
+      }
+      case WildcardMatch::ANY_CHAR: {
+        if (state.escaped) {
+          appendChar({label_begin, label_length});
+        } else {
+          state.to = a.AddState();
+          utf8_emplace_rho_arc(a, state.from, state.to);
+          state.from = state.to;
+        }
+        break;
+      }
+      case WildcardMatch::ESCAPE: {
+        if (state.escaped) {
+          appendChar({label_begin, label_length});
+        } else {
+          state.escaped = !state.escaped;
+        }
+        break;
+      }
+      default: {
+        appendChar({label_begin, label_length});
+        break;
+      }
+    }
+
+    label_begin = label_end;
+  }
+
+  // need this variable to preserve valid address
+  // for cases with match all and  terminal escape
+  // character (%\\)
+  const byte_type c = WildcardMatch::ESCAPE;
+
+  if (state.escaped) {
+    // non-terminated escape sequence
+    appendChar({&c, 1});
+  } if (state.match_all) {
+    // terminal MATCH_ALL
+    utf8_emplace_rho_arc(a, state.to, state.to);
+    state.match_all_from = fst::kNoStateId;
+  }
+
+  if (state.match_all_from != fst::kNoStateId) {
+    // non-terminal MATCH_ALL
+    utf8_emplace_arc(a, state.to, state.match_all_from,
+                     state.match_all_label, state.match_all_to);
+  }
+
+  a.SetFinal(state.to);
+
+#ifdef IRESEARCH_DEBUG
+  // ensure resulting automaton is sorted and deterministic
+  static constexpr auto EXPECTED_PROPERTIES =
+    fst::kIDeterministic | fst::kODeterministic |
+    fst::kILabelSorted | fst::kOLabelSorted |
+    fst::kAcceptor;
+  assert(EXPECTED_PROPERTIES == a.Properties(EXPECTED_PROPERTIES, true));
+#endif
+
+  return a;
+}
+
+NS_END
diff --git a/3rdParty/iresearch/core/utils/wildcard_utils.hpp b/3rdParty/iresearch/core/utils/wildcard_utils.hpp
index 89f3aef0683c..3081c0659988 100644
--- a/3rdParty/iresearch/core/utils/wildcard_utils.hpp
+++ b/3rdParty/iresearch/core/utils/wildcard_utils.hpp
@@ -27,104 +27,38 @@
 
 NS_ROOT
 
-template<typename Char>
-struct wildcard_traits {
-  using char_type = Char;
-
-  // match any string or empty string
-  static constexpr Char MATCH_ANY_STRING= Char('%');
-
-  // match any char
-  static constexpr Char MATCH_ANY_CHAR = Char('_');
-
-  // denotes beginning of escape sequence
-  static constexpr Char ESCAPE = Char('\\');
+enum class WildcardType {
+  INVALID  = 0, // invalid input sequence
+  TERM,         // foo
+  MATCH_ALL,    // *
+  PREFIX,       // foo*
+  WILDCARD      // f_o*
 };
 
-template<
-  typename Char,
-  typename Traits = wildcard_traits<Char>,
-  // brackets over condition are for circumventing MSVC parser bug
-  typename = typename std::enable_if<(sizeof(Char) < sizeof(fst::fsa::kMaxLabel))>::type, 
-  typename = typename std::enable_if<Traits::MATCH_ANY_CHAR != Traits::MATCH_ANY_STRING>::type>
-automaton from_wildcard(const irs::basic_string_ref<Char>& expr) {
-  automaton a;
-  a.ReserveStates(expr.size() + 1);
-
-  automaton::StateId from = a.AddState();
-  automaton::StateId to = from;
-  a.SetStart(from);
-
-  automaton::StateId match_all_state = fst::kNoStateId;
-  bool escaped = false;
-  auto appendChar = [&match_all_state, &escaped, &a, &to, &from](Char c) {
-    to = a.AddState();
-    a.EmplaceArc(from, c, to);
-    from = to;
-    escaped = false;
-    if (match_all_state != fst::kNoStateId) {
-      auto state = a.AddState();
-      a.ReserveArcs(state, 2);
-      a.EmplaceArc(match_all_state, fst::fsa::kRho, state);
-      a.EmplaceArc(state, fst::fsa::kRho, state);
-      a.EmplaceArc(state, c, to);
-      a.EmplaceArc(to, c, to);
-      a.EmplaceArc(to, fst::fsa::kRho, state);
-      match_all_state = fst::kNoStateId;
-    }
-  };
-
-  for (const auto c : expr) {
-    switch (c) {
-      case Traits::MATCH_ANY_STRING: {
-        if (escaped) {
-          appendChar(c);
-        } else {
-          match_all_state = from;
-        }
-        break;
-      }
-      case Traits::MATCH_ANY_CHAR: {
-        if (escaped) {
-          appendChar(c);
-        } else {
-          to = a.AddState();
-          a.EmplaceArc(from, fst::fsa::kRho, to);
-          from = to;
-        }
-      } break;
-      case Traits::ESCAPE: {
-       if (escaped) {
-         appendChar(c);
-       } else {
-         escaped = !escaped;
-       }
-       break;
-      }
-      default: {
-        appendChar(c);
-        break;
-      }
-    }
-  }
+IRESEARCH_API WildcardType wildcard_type(const bytes_ref& pattern) noexcept;
 
-  // non-terminated escape sequence
-  if (escaped) {
-    appendChar(Traits::ESCAPE);
-  }
-
-  if (match_all_state != fst::kNoLabel) {
-    a.EmplaceArc(to, fst::fsa::kRho, to);
-  }
-
-  a.SetFinal(to);
-
-  fst::ArcSort(&a, fst::ILabelCompare<fst::fsa::Transition>());
+enum WildcardMatch : byte_type {
+  ANY_STRING = '%',
+  ANY_CHAR = '_',
+  ESCAPE = '\\'
+};
 
-  automaton res;
-  fst::Determinize(a, &res);
+////////////////////////////////////////////////////////////////////////////////
+/// @brief instantiates minimal DFA from a specified UTF-8 encoded wildcard
+///        sequence
+/// @param expr valid UTF-8 encoded string
+/// @returns DFA accpeting a specified wildcard expression
+/// @note control symbols are
+///       '%' - match any number of arbitrary characters
+///       '_' - match a single arbitrary character
+///       '\' - escape control symbol, e.g. '\%' issues literal '%'
+/// @note if an input expression is incorrect UTF-8 sequence, function returns
+///       empty automaton
+////////////////////////////////////////////////////////////////////////////////
+IRESEARCH_API automaton from_wildcard(const bytes_ref& expr);
 
-  return res;
+inline automaton from_wildcard(const string_ref& expr) {
+  return from_wildcard(ref_cast<byte_type>(expr));
 }
 
 NS_END
diff --git a/3rdParty/iresearch/external/openfst/draw-impl.h b/3rdParty/iresearch/external/openfst/draw-impl.h
index f0b941bde556..e6df7e7fd494 100644
--- a/3rdParty/iresearch/external/openfst/draw-impl.h
+++ b/3rdParty/iresearch/external/openfst/draw-impl.h
@@ -14,7 +14,6 @@
 #include <fst/fst.h>
 #include <fst/symbol-table.h>
 #include <fst/util.h>
-#include <fst/script/fst-class.h>
 
 namespace fst {
 
@@ -261,8 +260,7 @@ inline void drawFst(
     int fontsize = 14,
     int precision = 5,
     const std::string& float_format = "g",
-    bool show_weight_one = false
-) {
+    bool show_weight_one = false) {
   FstDrawer<typename Fst::Arc> drawer(
     fst, isyms, osyms, ssyms, accep, title, width, height,
     partrait, vertical, randsep, nodesep, fontsize, precision,
@@ -272,6 +270,39 @@ inline void drawFst(
   drawer.Draw(&strm, dest);
 }
 
+template<typename Fst>
+inline bool drawFst(
+    const Fst& fst,
+    const std::string& dest,
+    const SymbolTable* isyms = nullptr,
+    const SymbolTable* osyms = nullptr,
+    const SymbolTable* ssyms = nullptr,
+    bool accep = false,
+    const std::string& title = "",
+    float width = 11,
+    float height = 8.5,
+    bool partrait = true,
+    bool vertical = false,
+    float randsep = 0.4,
+    float nodesep = 0.25,
+    int fontsize = 14,
+    int precision = 5,
+    const std::string& float_format = "g",
+    bool show_weight_one = false) {
+  std::fstream stream;
+  stream.open(dest, std::fstream::binary | std::fstream::out);
+  if (!stream) {
+    return false;
+  }
+
+  fst::drawFst(
+    fst, stream, dest, isyms, osyms, ssyms, accep, title,
+    width, height, partrait, vertical, randsep, nodesep,
+    fontsize, precision, float_format, show_weight_one);
+
+  return true;
+}
+
 }  // namespace fst
 
 #endif  // FST_SCRIPT_DRAW_IMPL_H_
diff --git a/3rdParty/iresearch/external/openfst/fst/string-weight.h b/3rdParty/iresearch/external/openfst/fst/string-weight.h
index 86e140a2a29d..3531c5650ad4 100644
--- a/3rdParty/iresearch/external/openfst/fst/string-weight.h
+++ b/3rdParty/iresearch/external/openfst/fst/string-weight.h
@@ -169,9 +169,9 @@ class StringWeightIterator {
 
  private:
   const Label &first_;
-  const decltype(Weight::rest_) &rest_;
+  const std::list<Label> &rest_;
   bool init_;  // In the initialized state?
-  typename decltype(Weight::rest_)::const_iterator iter_;
+  typename std::list<Label>::const_iterator iter_;
 };
 
 // Traverses string in backward direction.
@@ -208,7 +208,7 @@ class StringWeightReverseIterator {
   const Label &first_;
   const std::list<Label> &rest_;
   bool fin_;  // In the final state?
-  typename decltype(Weight::rest_)::const_reverse_iterator iter_;
+  typename std::list<Label>::const_reverse_iterator iter_;
 };
 
 // StringWeight member functions follow that require
diff --git a/3rdParty/iresearch/external/openfst/util.cc b/3rdParty/iresearch/external/openfst/util.cc
index 00b8b5c83c22..a8880ccab3ad 100644
--- a/3rdParty/iresearch/external/openfst/util.cc
+++ b/3rdParty/iresearch/external/openfst/util.cc
@@ -91,7 +91,7 @@ bool AlignOutput(std::ostream &strm) {
 int AlignBufferWithOutputStream(std::ostream &strm,
                                 std::ostringstream &buffer) {
   const auto strm_pos = strm.tellp();
-  if (strm_pos == -1) {
+  if (strm_pos == decltype(strm_pos)(-1)) {
     LOG(ERROR) << "Cannot determine stream position";
     return -1;
   }
diff --git a/3rdParty/iresearch/python/CMakeLists.txt b/3rdParty/iresearch/python/CMakeLists.txt
index 7f26dab3b24a..5062ff318a9c 100644
--- a/3rdParty/iresearch/python/CMakeLists.txt
+++ b/3rdParty/iresearch/python/CMakeLists.txt
@@ -1,5 +1,10 @@
 set(IResearchPython_TARGET_NAME "iresearch-python" CACHE INTERNAL "")
 
+if(MSVC)
+add_definitions(-DPYRESEARCH_DLL)
+include_directories(${Boost_INCLUDE_DIRS})
+endif()
+
 add_library(${IResearchPython_TARGET_NAME}
   SHARED
   pyresearch.cpp
@@ -11,8 +16,14 @@ target_include_directories(${IResearchPython_TARGET_NAME}
   PRIVATE ${IResearch_INCLUDE_DIR}
 )
 
+if(MSVC)
+target_link_libraries(${IResearchPython_TARGET_NAME}
+  ${IResearch_TARGET_NAME}-static-allinone
+)
+else()
 target_link_libraries(${IResearchPython_TARGET_NAME}
   ${IResearch_TARGET_NAME}-shared
 )
+endif()
 
 add_subdirectory(swig)
diff --git a/3rdParty/iresearch/python/pyresearch.hpp b/3rdParty/iresearch/python/pyresearch.hpp
index 82bc11244213..910fb5a27053 100644
--- a/3rdParty/iresearch/python/pyresearch.hpp
+++ b/3rdParty/iresearch/python/pyresearch.hpp
@@ -35,11 +35,17 @@
 
 struct invalid_feature { };
 
+#ifdef PYRESEARCH_DLL
+#define PYRESEARCH_API __declspec(dllexport)
+#else
+#define PYRESEARCH_API
+#endif
+
 ///////////////////////////////////////////////////////////////////////////////
 /// @class doc_iterator
 /// @brief python proxy for irs::doc_iterator
 ///////////////////////////////////////////////////////////////////////////////
-class doc_iterator {
+class PYRESEARCH_API doc_iterator {
  public:
   ~doc_iterator() SWIG_noexcept { }
 
@@ -69,7 +75,7 @@ class doc_iterator {
 /// @class term_iterator
 /// @brief python proxy for irs::term_iterator
 ///////////////////////////////////////////////////////////////////////////////
-class term_iterator {
+class PYRESEARCH_API  term_iterator {
  public:
   ~term_iterator() SWIG_noexcept { }
 
@@ -98,7 +104,7 @@ class term_iterator {
   friend class field_reader;
 
   term_iterator(irs::seek_term_iterator::ptr&& it) SWIG_noexcept 
-    : it_(std::move(it)) {
+    :it_(irs::memory::make_shared(std::move(it))) {
   }
 
   std::shared_ptr<irs::seek_term_iterator> it_;
@@ -108,7 +114,7 @@ class term_iterator {
 /// @class column_meta
 /// @brief python proxy for irs::column_meta
 ///////////////////////////////////////////////////////////////////////////////
-class column_meta {
+class PYRESEARCH_API  column_meta {
  public:
   ~column_meta() SWIG_noexcept { }
 
@@ -129,7 +135,7 @@ class column_meta {
 /// @class column_iterator
 /// @brief python proxy for irs::column_iterator
 ///////////////////////////////////////////////////////////////////////////////
-class column_iterator {
+class PYRESEARCH_API  column_iterator {
  public:
   ~column_iterator() SWIG_noexcept { }
 
@@ -153,7 +159,7 @@ class column_iterator {
 /// @class column_values_reader
 /// @brief python proxy for irs::columnstore_reader::values_reader_f
 ///////////////////////////////////////////////////////////////////////////////
-class column_values_reader {
+class PYRESEARCH_API  column_values_reader {
  public:
   ~column_values_reader() SWIG_noexcept { }
 
@@ -182,7 +188,7 @@ class column_values_reader {
 /// @class column_reader
 /// @brief python proxy for irs::columnstore_reader::column_reader
 ///////////////////////////////////////////////////////////////////////////////
-class column_reader {
+class PYRESEARCH_API  column_reader {
  public:
   ~column_reader() SWIG_noexcept { }
 
@@ -214,7 +220,7 @@ class column_reader {
 /// @class field_reader
 /// @brief python proxy for irs::term_reader
 ///////////////////////////////////////////////////////////////////////////////
-class field_reader {
+class PYRESEARCH_API  field_reader {
  public:
   ~field_reader() SWIG_noexcept { }
 
@@ -265,7 +271,7 @@ class field_reader {
 /// @class field_iterator
 /// @brief python proxy for irs::field_iterator
 ///////////////////////////////////////////////////////////////////////////////
-class field_iterator {
+class PYRESEARCH_API  field_iterator {
  public:
   ~field_iterator() SWIG_noexcept { }
 
@@ -289,7 +295,7 @@ class field_iterator {
 /// @class segment_reader
 /// @brief python proxy for irs::segment_reader
 ///////////////////////////////////////////////////////////////////////////////
-class segment_reader {
+class PYRESEARCH_API  segment_reader {
  public:
   ~segment_reader() SWIG_noexcept { }
 
@@ -325,7 +331,7 @@ class segment_reader {
 /// @class segment_iterator
 /// @brief python iterator for index_reader proxy
 ///////////////////////////////////////////////////////////////////////////////
-class segment_iterator {
+class PYRESEARCH_API   segment_iterator {
  public:
   segment_reader next() {
     if (begin_ == end_) {
@@ -358,7 +364,7 @@ class segment_iterator {
 /// @class index_reader
 /// @brief python proxy for irs::index_reader
 ///////////////////////////////////////////////////////////////////////////////
-class index_reader {
+class PYRESEARCH_API  index_reader {
  public:
   static index_reader open(const char* path);
 
diff --git a/3rdParty/iresearch/python/swig/CMakeLists.txt b/3rdParty/iresearch/python/swig/CMakeLists.txt
index 43ca51312384..daff51037e3f 100644
--- a/3rdParty/iresearch/python/swig/CMakeLists.txt
+++ b/3rdParty/iresearch/python/swig/CMakeLists.txt
@@ -3,8 +3,8 @@ find_package(SWIG REQUIRED)
 include(${SWIG_USE_FILE})
 
 # Include python
-find_package(PythonLibs REQUIRED)
-include_directories(${PYTHON_INCLUDE_PATH})
+find_package(Python 3 REQUIRED COMPONENTS Interpreter Development)
+include_directories(${Python_INCLUDE_DIRS})
 
 set_property(SOURCE pyresearch.i PROPERTY CPLUSPLUS ON)
 set_property(SOURCE pyresearch.i PROPERTY SWIG_FLAGS "-py3")
@@ -12,26 +12,46 @@ set_property(SOURCE pyresearch.i PROPERTY SWIH_MODULE_NAME pyresearch)
 list(APPEND CMAKE_SWIG_FLAGS "-I${IResearch_INCLUDE_DIR}")
 
 swig_add_library(pyresearch LANGUAGE python SOURCES pyresearch.i)
-swig_link_libraries(pyresearch iresearch-python ${PYTHON_LIBRARIES})
+swig_link_libraries(pyresearch iresearch-python ${Python_LIBRARIES})
 include_directories(${CMAKE_CURRENT_SOURCE_DIR}/.. ${IResearch_INCLUDE_DIR})
 
-# Files to install with Python
+set(SETUP_PY_IN ${CMAKE_CURRENT_SOURCE_DIR}/setup.py.in)
+set(SETUP_PY_OUT ${CMAKE_CURRENT_BINARY_DIR}/setup.py)
+
+# Files to install with Python (Build-specific for MSVC)
+if(MSVC)
+set(PYTHON_INSTALL_FILES
+  ${CMAKE_CURRENT_BINARY_DIR}/pyresearch.py
+  ${CMAKE_BINARY_DIR}/bin/$<CONFIG>/_pyresearch.pyd
+  ${CMAKE_BINARY_DIR}/bin/$<CONFIG>/iresearch-python.dll
+)
+else()
 set(PYTHON_INSTALL_FILES
   ${CMAKE_CURRENT_BINARY_DIR}/pyresearch.py
   ${CMAKE_BINARY_DIR}/bin/_pyresearch.so
 )
-
+endif()
 # Configure setup.py and copy to output directory
-set(SETUP_PY_IN ${CMAKE_CURRENT_SOURCE_DIR}/setup.py.in)
-set(SETUP_PY_OUT ${CMAKE_CURRENT_BINARY_DIR}/setup.py)
 configure_file(${SETUP_PY_IN} ${SETUP_PY_OUT})
 
+if(MSVC)
+# on MSVC  we prepare setup file for each build type to make use of generator expressions
+file(GENERATE OUTPUT ${CMAKE_BINARY_DIR}/setup_$<CONFIG>.py INPUT ${SETUP_PY_OUT})
+add_custom_target(pyresearch
+  DEPENDS _pyresearch ${IResearch_TARGET_NAME}-static-allinone
+  COMMAND ${Python_EXECUTABLE} ${CMAKE_BINARY_DIR}/setup_$<CONFIG>.py build_ext --inplace
+)
+add_custom_target(pyresearch-install
+  DEPENDS pyresearch
+  COMMAND ${Python_EXECUTABLE} ${CMAKE_BINARY_DIR}/setup_$<CONFIG>.py install
+)
+else()
 add_custom_target(pyresearch
   DEPENDS _pyresearch ${IResearch_TARGET_NAME}-shared
-  COMMAND python3 ${SETUP_PY_OUT} build_ext --inplace
+  COMMAND ${Python_EXECUTABLE} ${SETUP_PY_OUT} build_ext --inplace
 )
-
 add_custom_target(pyresearch-install
   DEPENDS pyresearch
-  COMMAND python3 ${SETUP_PY_OUT} install
+  COMMAND ${Python_EXECUTABLE} ${SETUP_PY_OUT} install
 )
+endif()
diff --git a/3rdParty/iresearch/scripts/ArangoDBLoader/WikiLoader.py b/3rdParty/iresearch/scripts/ArangoDBLoader/WikiLoader.py
new file mode 100644
index 000000000000..d1d1e8c266e9
--- /dev/null
+++ b/3rdParty/iresearch/scripts/ArangoDBLoader/WikiLoader.py
@@ -0,0 +1,47 @@
+# python script for loading IResearch benchmark dump of  Wikipedia into
+# ArangoDB database. Uses python-arango driver https://github.com/Joowani/python-arango
+# By default script loads 10M records into 'wikipedia' collection of '_system' database.
+# Data is loaded in form { title: 'XXXXX', body: 'XXXXXXXXXXXXX'}.
+# Collection should be already created. DB server should be set up to run without authorization and
+# on localhost:8529
+
+import csv
+import ctypes
+from arango import ArangoClient
+
+
+def main():
+  # Override csv default 128k field size
+  csv.field_size_limit(int(ctypes.c_ulong(-1).value // 2))
+
+  # Initialize the client for ArangoDB.
+  client = ArangoClient(hosts='http://localhost:8529')
+  
+  # Upload settings
+  filename = 'C:\\Working\\iresearch-toolkit\\iresearch\\iresearch.deps\\benchmark_resources\\benchmark.data' # data file
+  collection = 'wikipedia' # target collection
+  database = '_system'  # target database
+  line_limit = 10000000 # how many documents to upload
+  batch_size = 10000    # batch size for inserting into Arango
+
+  db = client.db(database)
+  wikipedia = db.collection(collection)
+  f = open(filname, mode ='r', encoding='utf-8', errors='replace')
+  reader = csv.reader(f, delimiter='\t')
+  data = []
+  total = 0
+  for row in reader:
+    data.append({'title': row[0], 'body': row[2]})
+    if len(data) > batch_size:
+      wikipedia.insert_many(data)
+      data.clear()
+    total = total + 1
+    if total >= line_limit:
+      break
+  if len(data) > 0:
+    wikipedia.insert_many(data)
+  f.close()
+
+  
+if __name__== "__main__":
+  main()
\ No newline at end of file
diff --git a/3rdParty/iresearch/scripts/Prometheus/Dashboard.json b/3rdParty/iresearch/scripts/Prometheus/Dashboard.json
index ff7a9c44be47..b520aa0adb9a 100644
--- a/3rdParty/iresearch/scripts/Prometheus/Dashboard.json
+++ b/3rdParty/iresearch/scripts/Prometheus/Dashboard.json
@@ -26,7 +26,7 @@
   "gnetId": null,
   "graphTooltip": 0,
   "id": 15,
-  "iteration": 1575479684150,
+  "iteration": 1583835542113,
   "links": [],
   "panels": [
     {
@@ -43,6 +43,543 @@
         "x": 0,
         "y": 0
       },
+      "id": 42,
+      "legend": {
+        "avg": false,
+        "current": false,
+        "max": false,
+        "min": false,
+        "show": true,
+        "total": false,
+        "values": false
+      },
+      "lines": true,
+      "linewidth": 1,
+      "nullPointMode": "null",
+      "options": {
+        "dataLinks": []
+      },
+      "percentage": false,
+      "pointradius": 2,
+      "points": false,
+      "renderer": "flot",
+      "seriesOverrides": [],
+      "spaceLength": 10,
+      "stack": false,
+      "steppedLine": false,
+      "targets": [
+        {
+          "expr": "avg(Time{engine=\"IResearch\",category=\"HighNGram\",size=\"$Size\",platform=\"Linux\",branch=\"master\", stage=\"Executing\"}) + avg(Time{engine=\"IResearch\",category=\"HighNGram\",size=\"$Size\",platform=\"Linux\",branch=\"master\", stage=\"Building\"})",
+          "legendFormat": "IResearch",
+          "refId": "A"
+        }
+      ],
+      "thresholds": [],
+      "timeFrom": null,
+      "timeRegions": [],
+      "timeShift": null,
+      "title": "HighNGram",
+      "tooltip": {
+        "shared": true,
+        "sort": 0,
+        "value_type": "individual"
+      },
+      "type": "graph",
+      "xaxis": {
+        "buckets": null,
+        "mode": "time",
+        "name": null,
+        "show": true,
+        "values": []
+      },
+      "yaxes": [
+        {
+          "format": "short",
+          "label": null,
+          "logBase": 1,
+          "max": null,
+          "min": null,
+          "show": true
+        },
+        {
+          "format": "short",
+          "label": null,
+          "logBase": 1,
+          "max": null,
+          "min": null,
+          "show": true
+        }
+      ],
+      "yaxis": {
+        "align": false,
+        "alignLevel": null
+      }
+    },
+    {
+      "aliasColors": {},
+      "bars": false,
+      "dashLength": 10,
+      "dashes": false,
+      "datasource": "Prometheus",
+      "fill": 1,
+      "fillGradient": 0,
+      "gridPos": {
+        "h": 8,
+        "w": 12,
+        "x": 12,
+        "y": 0
+      },
+      "hiddenSeries": false,
+      "id": 39,
+      "legend": {
+        "avg": false,
+        "current": false,
+        "max": false,
+        "min": false,
+        "show": true,
+        "total": false,
+        "values": false
+      },
+      "lines": true,
+      "linewidth": 1,
+      "nullPointMode": "null",
+      "options": {
+        "dataLinks": []
+      },
+      "percentage": false,
+      "pointradius": 2,
+      "points": false,
+      "renderer": "flot",
+      "seriesOverrides": [],
+      "spaceLength": 10,
+      "stack": false,
+      "steppedLine": false,
+      "targets": [
+        {
+          "expr": "avg(Time{engine=\"IResearch\",category=\"Fuzzy1\",size=\"33332620\",platform=\"Linux\",branch=\"master\", stage=\"Executing\"}) + avg(Time{engine=\"IResearch\",category=\"Fuzzy1\",size=\"33332620\",platform=\"Linux\",branch=\"master\", stage=\"Building\"})",
+          "legendFormat": "IResearch",
+          "refId": "A"
+        },
+        {
+          "expr": "avg(Time{engine=\"Lucene\",category=\"Fuzzy1\",size=\"33332620\",platform=\"Linux\",branch=\"master\", stage=\"Executing\"})",
+          "legendFormat": "Lucene",
+          "refId": "B"
+        }
+      ],
+      "thresholds": [],
+      "timeFrom": null,
+      "timeRegions": [],
+      "timeShift": null,
+      "title": "Fuzzy1",
+      "tooltip": {
+        "shared": true,
+        "sort": 0,
+        "value_type": "individual"
+      },
+      "type": "graph",
+      "xaxis": {
+        "buckets": null,
+        "mode": "time",
+        "name": null,
+        "show": true,
+        "values": []
+      },
+      "yaxes": [
+        {
+          "format": "short",
+          "label": null,
+          "logBase": 1,
+          "max": null,
+          "min": null,
+          "show": true
+        },
+        {
+          "format": "short",
+          "label": null,
+          "logBase": 1,
+          "max": null,
+          "min": null,
+          "show": true
+        }
+      ],
+      "yaxis": {
+        "align": false,
+        "alignLevel": null
+      }
+    },
+    {
+      "aliasColors": {},
+      "bars": false,
+      "dashLength": 10,
+      "dashes": false,
+      "datasource": "Prometheus",
+      "fill": 1,
+      "fillGradient": 0,
+      "gridPos": {
+        "h": 8,
+        "w": 12,
+        "x": 0,
+        "y": 8
+      },
+      "id": 44,
+      "legend": {
+        "avg": false,
+        "current": false,
+        "max": false,
+        "min": false,
+        "show": true,
+        "total": false,
+        "values": false
+      },
+      "lines": true,
+      "linewidth": 1,
+      "nullPointMode": "null",
+      "options": {
+        "dataLinks": []
+      },
+      "percentage": false,
+      "pointradius": 2,
+      "points": false,
+      "renderer": "flot",
+      "seriesOverrides": [],
+      "spaceLength": 10,
+      "stack": false,
+      "steppedLine": false,
+      "targets": [
+        {
+          "expr": "avg(Time{engine=\"IResearch\",category=\"MedNGram\",size=\"$Size\",platform=\"Linux\",branch=\"master\", stage=\"Executing\"}) + avg(Time{engine=\"IResearch\",category=\"MedNGram\",size=\"$Size\",platform=\"Linux\",branch=\"master\", stage=\"Building\"})",
+          "legendFormat": "IResearch",
+          "refId": "A"
+        }
+      ],
+      "thresholds": [],
+      "timeFrom": null,
+      "timeRegions": [],
+      "timeShift": null,
+      "title": "MedNGram",
+      "tooltip": {
+        "shared": true,
+        "sort": 0,
+        "value_type": "individual"
+      },
+      "type": "graph",
+      "xaxis": {
+        "buckets": null,
+        "mode": "time",
+        "name": null,
+        "show": true,
+        "values": []
+      },
+      "yaxes": [
+        {
+          "format": "short",
+          "label": null,
+          "logBase": 1,
+          "max": null,
+          "min": null,
+          "show": true
+        },
+        {
+          "format": "short",
+          "label": null,
+          "logBase": 1,
+          "max": null,
+          "min": null,
+          "show": true
+        }
+      ],
+      "yaxis": {
+        "align": false,
+        "alignLevel": null
+      }
+    },
+    {
+      "aliasColors": {},
+      "bars": false,
+      "dashLength": 10,
+      "dashes": false,
+      "datasource": "Prometheus",
+      "fill": 1,
+      "fillGradient": 0,
+      "gridPos": {
+        "h": 8,
+        "w": 12,
+        "x": 12,
+        "y": 8
+      },
+      "hiddenSeries": false,
+      "id": 40,
+      "legend": {
+        "avg": false,
+        "current": false,
+        "max": false,
+        "min": false,
+        "show": true,
+        "total": false,
+        "values": false
+      },
+      "lines": true,
+      "linewidth": 1,
+      "nullPointMode": "null",
+      "options": {
+        "dataLinks": []
+      },
+      "percentage": false,
+      "pointradius": 2,
+      "points": false,
+      "renderer": "flot",
+      "seriesOverrides": [],
+      "spaceLength": 10,
+      "stack": false,
+      "steppedLine": false,
+      "targets": [
+        {
+          "expr": "avg(Time{engine=\"IResearch\",category=\"Fuzzy2\",size=\"$Size\",platform=\"Linux\",branch=\"master\", stage=\"Executing\"}) + avg(Time{engine=\"IResearch\",category=\"Fuzzy2\",size=\"$Size\",platform=\"Linux\",branch=\"master\", stage=\"Building\"})",
+          "legendFormat": "IResearch",
+          "refId": "A"
+        },
+        {
+          "expr": "avg(Time{engine=\"Lucene\",category=\"Fuzzy2\",size=\"$Size\",platform=\"Linux\",branch=\"master\", stage=\"Executing\"})",
+          "legendFormat": "Lucene",
+          "refId": "B"
+        }
+      ],
+      "thresholds": [],
+      "timeFrom": null,
+      "timeRegions": [],
+      "timeShift": null,
+      "title": "Fuzzy2",
+      "tooltip": {
+        "shared": true,
+        "sort": 0,
+        "value_type": "individual"
+      },
+      "type": "graph",
+      "xaxis": {
+        "buckets": null,
+        "mode": "time",
+        "name": null,
+        "show": true,
+        "values": []
+      },
+      "yaxes": [
+        {
+          "format": "short",
+          "label": null,
+          "logBase": 1,
+          "max": null,
+          "min": null,
+          "show": true
+        },
+        {
+          "format": "short",
+          "label": null,
+          "logBase": 1,
+          "max": null,
+          "min": null,
+          "show": true
+        }
+      ],
+      "yaxis": {
+        "align": false,
+        "alignLevel": null
+      }
+    },
+    {
+      "aliasColors": {},
+      "bars": false,
+      "dashLength": 10,
+      "dashes": false,
+      "datasource": "Prometheus",
+      "fill": 1,
+      "fillGradient": 0,
+      "gridPos": {
+        "h": 8,
+        "w": 12,
+        "x": 0,
+        "y": 16
+      },
+      "id": 46,
+      "legend": {
+        "avg": false,
+        "current": false,
+        "max": false,
+        "min": false,
+        "show": true,
+        "total": false,
+        "values": false
+      },
+      "lines": true,
+      "linewidth": 1,
+      "nullPointMode": "null",
+      "options": {
+        "dataLinks": []
+      },
+      "percentage": false,
+      "pointradius": 2,
+      "points": false,
+      "renderer": "flot",
+      "seriesOverrides": [],
+      "spaceLength": 10,
+      "stack": false,
+      "steppedLine": false,
+      "targets": [
+        {
+          "expr": "avg(Time{engine=\"IResearch\",category=\"LowNGram\",size=\"$Size\",platform=\"Linux\",branch=\"master\", stage=\"Executing\"}) + avg(Time{engine=\"IResearch\",category=\"LowNGram\",size=\"$Size\",platform=\"Linux\",branch=\"master\", stage=\"Building\"})",
+          "legendFormat": "IResearch",
+          "refId": "A"
+        }
+      ],
+      "thresholds": [],
+      "timeFrom": null,
+      "timeRegions": [],
+      "timeShift": null,
+      "title": "LowNGram",
+      "tooltip": {
+        "shared": true,
+        "sort": 0,
+        "value_type": "individual"
+      },
+      "type": "graph",
+      "xaxis": {
+        "buckets": null,
+        "mode": "time",
+        "name": null,
+        "show": true,
+        "values": []
+      },
+      "yaxes": [
+        {
+          "format": "short",
+          "label": null,
+          "logBase": 1,
+          "max": null,
+          "min": null,
+          "show": true
+        },
+        {
+          "format": "short",
+          "label": null,
+          "logBase": 1,
+          "max": null,
+          "min": null,
+          "show": true
+        }
+      ],
+      "yaxis": {
+        "align": false,
+        "alignLevel": null
+      }
+    },
+    {
+      "aliasColors": {},
+      "bars": false,
+      "dashLength": 10,
+      "dashes": false,
+      "datasource": "Prometheus",
+      "fill": 1,
+      "fillGradient": 0,
+      "gridPos": {
+        "h": 8,
+        "w": 12,
+        "x": 12,
+        "y": 16
+      },
+      "hiddenSeries": false,
+      "id": 2,
+      "legend": {
+        "avg": false,
+        "current": false,
+        "max": false,
+        "min": false,
+        "show": true,
+        "total": false,
+        "values": false
+      },
+      "lines": true,
+      "linewidth": 1,
+      "nullPointMode": "null",
+      "options": {
+        "dataLinks": []
+      },
+      "percentage": false,
+      "pointradius": 2,
+      "points": false,
+      "renderer": "flot",
+      "seriesOverrides": [],
+      "spaceLength": 10,
+      "stack": false,
+      "steppedLine": false,
+      "targets": [
+        {
+          "expr": "avg(Time{category=\"HighTerm\",stage=\"Executing\",engine=\"IResearch\",size=\"$Size\",platform=\"Linux\",branch=\"master\"}) + avg(Time{category=\"HighTerm\",stage=\"Building\",engine=\"IResearch\",size=\"$Size\",platform=\"Linux\",branch=\"master\"}) ",
+          "format": "time_series",
+          "hide": false,
+          "legendFormat": "IResearch",
+          "refId": "A"
+        },
+        {
+          "expr": "avg(Time{engine=\"Lucene\",category=\"HighTerm\", size=\"$Size\",platform=\"Linux\",branch=\"master\"})",
+          "hide": false,
+          "legendFormat": "Lucene",
+          "refId": "D"
+        }
+      ],
+      "thresholds": [],
+      "timeFrom": null,
+      "timeRegions": [],
+      "timeShift": null,
+      "title": "HighTerm",
+      "tooltip": {
+        "shared": true,
+        "sort": 0,
+        "value_type": "individual"
+      },
+      "type": "graph",
+      "xaxis": {
+        "buckets": null,
+        "mode": "time",
+        "name": null,
+        "show": true,
+        "values": []
+      },
+      "yaxes": [
+        {
+          "format": "short",
+          "label": null,
+          "logBase": 1,
+          "max": null,
+          "min": null,
+          "show": true
+        },
+        {
+          "format": "short",
+          "label": null,
+          "logBase": 1,
+          "max": null,
+          "min": null,
+          "show": true
+        }
+      ],
+      "yaxis": {
+        "align": false,
+        "alignLevel": null
+      }
+    },
+    {
+      "aliasColors": {},
+      "bars": false,
+      "dashLength": 10,
+      "dashes": false,
+      "datasource": "Prometheus",
+      "fill": 1,
+      "fillGradient": 0,
+      "gridPos": {
+        "h": 8,
+        "w": 12,
+        "x": 0,
+        "y": 24
+      },
       "hiddenSeries": false,
       "id": 12,
       "legend": {
@@ -133,10 +670,10 @@
         "h": 8,
         "w": 12,
         "x": 12,
-        "y": 0
+        "y": 24
       },
       "hiddenSeries": false,
-      "id": 2,
+      "id": 4,
       "legend": {
         "avg": false,
         "current": false,
@@ -162,24 +699,21 @@
       "steppedLine": false,
       "targets": [
         {
-          "expr": "avg(Time{category=\"HighTerm\",stage=\"Executing\",engine=\"IResearch\",size=\"$Size\",platform=\"Linux\",branch=\"master\"}) + avg(Time{category=\"HighTerm\",stage=\"Building\",engine=\"IResearch\",size=\"$Size\",platform=\"Linux\",branch=\"master\"}) ",
-          "format": "time_series",
-          "hide": false,
+          "expr": "avg(Time{category=\"MedTerm\",stage=\"Executing\",engine=\"IResearch\",size=\"$Size\",platform=\"Linux\",branch=\"master\"})",
           "legendFormat": "IResearch",
-          "refId": "A"
+          "refId": "C"
         },
         {
-          "expr": "avg(Time{engine=\"Lucene\",category=\"HighTerm\", size=\"$Size\",platform=\"Linux\",branch=\"master\"})",
-          "hide": false,
+          "expr": "avg(Time{category=\"MedTerm\",engine=\"Lucene\",size=\"$Size\",platform=\"Linux\",branch=\"master\"})",
           "legendFormat": "Lucene",
-          "refId": "D"
+          "refId": "A"
         }
       ],
       "thresholds": [],
       "timeFrom": null,
       "timeRegions": [],
       "timeShift": null,
-      "title": "HighTerm",
+      "title": "MedTerm",
       "tooltip": {
         "shared": true,
         "sort": 0,
@@ -228,7 +762,7 @@
         "h": 8,
         "w": 12,
         "x": 0,
-        "y": 8
+        "y": 32
       },
       "hiddenSeries": false,
       "id": 14,
@@ -320,10 +854,10 @@
         "h": 8,
         "w": 12,
         "x": 12,
-        "y": 8
+        "y": 32
       },
       "hiddenSeries": false,
-      "id": 4,
+      "id": 6,
       "legend": {
         "avg": false,
         "current": false,
@@ -349,21 +883,21 @@
       "steppedLine": false,
       "targets": [
         {
-          "expr": "avg(Time{category=\"MedTerm\",stage=\"Executing\",engine=\"IResearch\",size=\"$Size\",platform=\"Linux\",branch=\"master\"})",
+          "expr": "avg(Time{category=\"LowTerm\",stage=\"Executing\",engine=\"IResearch\",size=\"$Size\",platform=\"Linux\",branch=\"master\"})",
           "legendFormat": "IResearch",
-          "refId": "C"
+          "refId": "A"
         },
         {
-          "expr": "avg(Time{category=\"MedTerm\",engine=\"Lucene\",size=\"$Size\",platform=\"Linux\",branch=\"master\"})",
+          "expr": "avg(Time{category=\"LowTerm\",engine=\"Lucene\",size=\"$Size\",platform=\"Linux\",branch=\"master\"})",
           "legendFormat": "Lucene",
-          "refId": "A"
+          "refId": "B"
         }
       ],
       "thresholds": [],
       "timeFrom": null,
       "timeRegions": [],
       "timeShift": null,
-      "title": "MedTerm",
+      "title": "LowTerm",
       "tooltip": {
         "shared": true,
         "sort": 0,
@@ -387,7 +921,7 @@
           "show": true
         },
         {
-          "format": "short",
+          "format": "µs",
           "label": null,
           "logBase": 1,
           "max": null,
@@ -412,7 +946,7 @@
         "h": 8,
         "w": 12,
         "x": 0,
-        "y": 16
+        "y": 40
       },
       "hiddenSeries": false,
       "id": 16,
@@ -504,10 +1038,10 @@
         "h": 8,
         "w": 12,
         "x": 12,
-        "y": 16
+        "y": 40
       },
       "hiddenSeries": false,
-      "id": 6,
+      "id": 26,
       "legend": {
         "avg": false,
         "current": false,
@@ -533,12 +1067,12 @@
       "steppedLine": false,
       "targets": [
         {
-          "expr": "avg(Time{category=\"LowTerm\",stage=\"Executing\",engine=\"IResearch\",size=\"$Size\",platform=\"Linux\",branch=\"master\"})",
+          "expr": "avg(Time{category=\"OrHighHigh\",stage=\"Executing\",engine=\"IResearch\",size=\"$Size\",platform=\"Linux\",branch=\"master\"}) + avg(Time{category=\"OrHighHigh\",stage=\"Building\",engine=\"IResearch\",size=\"$Size\",platform=\"Linux\",branch=\"master\"}) ",
           "legendFormat": "IResearch",
           "refId": "A"
         },
         {
-          "expr": "avg(Time{category=\"LowTerm\",engine=\"Lucene\",size=\"$Size\",platform=\"Linux\",branch=\"master\"})",
+          "expr": "avg(Time{category=\"OrHighHigh\",stage=\"Executing\",engine=\"Lucene\",size=\"$Size\",platform=\"Linux\",branch=\"master\"})",
           "legendFormat": "Lucene",
           "refId": "B"
         }
@@ -547,7 +1081,7 @@
       "timeFrom": null,
       "timeRegions": [],
       "timeShift": null,
-      "title": "LowTerm",
+      "title": "OrHighHigh",
       "tooltip": {
         "shared": true,
         "sort": 0,
@@ -571,7 +1105,7 @@
           "show": true
         },
         {
-          "format": "µs",
+          "format": "short",
           "label": null,
           "logBase": 1,
           "max": null,
@@ -596,7 +1130,7 @@
         "h": 8,
         "w": 12,
         "x": 0,
-        "y": 24
+        "y": 48
       },
       "hiddenSeries": false,
       "id": 20,
@@ -688,10 +1222,10 @@
         "h": 8,
         "w": 12,
         "x": 12,
-        "y": 24
+        "y": 48
       },
       "hiddenSeries": false,
-      "id": 26,
+      "id": 28,
       "legend": {
         "avg": false,
         "current": false,
@@ -717,12 +1251,12 @@
       "steppedLine": false,
       "targets": [
         {
-          "expr": "avg(Time{category=\"OrHighHigh\",stage=\"Executing\",engine=\"IResearch\",size=\"$Size\",platform=\"Linux\",branch=\"master\"}) + avg(Time{category=\"OrHighHigh\",stage=\"Building\",engine=\"IResearch\",size=\"$Size\",platform=\"Linux\",branch=\"master\"}) ",
+          "expr": "avg(Time{category=\"OrHighMed\",stage=\"Executing\",engine=\"IResearch\",size=\"$Size\",platform=\"Linux\",branch=\"master\"}) + avg(Time{category=\"OrHighMed\",stage=\"Building\",engine=\"IResearch\",size=\"$Size\",platform=\"Linux\",branch=\"master\"})",
           "legendFormat": "IResearch",
           "refId": "A"
         },
         {
-          "expr": "avg(Time{category=\"OrHighHigh\",stage=\"Executing\",engine=\"Lucene\",size=\"$Size\",platform=\"Linux\",branch=\"master\"})",
+          "expr": "avg(Time{category=\"OrHighMed\",stage=\"Executing\",engine=\"Lucene\",size=\"$Size\",platform=\"Linux\",branch=\"master\"})",
           "legendFormat": "Lucene",
           "refId": "B"
         }
@@ -731,7 +1265,7 @@
       "timeFrom": null,
       "timeRegions": [],
       "timeShift": null,
-      "title": "OrHighHigh",
+      "title": "OrHighMed",
       "tooltip": {
         "shared": true,
         "sort": 0,
@@ -780,7 +1314,7 @@
         "h": 8,
         "w": 12,
         "x": 0,
-        "y": 32
+        "y": 56
       },
       "hiddenSeries": false,
       "id": 30,
@@ -872,10 +1406,10 @@
         "h": 8,
         "w": 12,
         "x": 12,
-        "y": 32
+        "y": 56
       },
       "hiddenSeries": false,
-      "id": 28,
+      "id": 22,
       "legend": {
         "avg": false,
         "current": false,
@@ -901,12 +1435,12 @@
       "steppedLine": false,
       "targets": [
         {
-          "expr": "avg(Time{category=\"OrHighMed\",stage=\"Executing\",engine=\"IResearch\",size=\"$Size\",platform=\"Linux\",branch=\"master\"}) + avg(Time{category=\"OrHighMed\",stage=\"Building\",engine=\"IResearch\",size=\"$Size\",platform=\"Linux\",branch=\"master\"})",
+          "expr": "avg(Time{engine=\"IResearch\",category=\"AndHighMed\",size=\"$Size\",platform=\"Linux\",branch=\"master\", stage=\"Executing\"}) + avg(Time{engine=\"IResearch\",category=\"AndHighMed\",size=\"$Size\",platform=\"Linux\",branch=\"master\", stage=\"Building\"})",
           "legendFormat": "IResearch",
           "refId": "A"
         },
         {
-          "expr": "avg(Time{category=\"OrHighMed\",stage=\"Executing\",engine=\"Lucene\",size=\"$Size\",platform=\"Linux\",branch=\"master\"})",
+          "expr": "avg(Time{engine=\"Lucene\",category=\"AndHighMed\",size=\"$Size\",platform=\"Linux\",branch=\"master\", stage=\"Executing\"})",
           "legendFormat": "Lucene",
           "refId": "B"
         }
@@ -915,7 +1449,7 @@
       "timeFrom": null,
       "timeRegions": [],
       "timeShift": null,
-      "title": "OrHighMed",
+      "title": "AndHighMed",
       "tooltip": {
         "shared": true,
         "sort": 0,
@@ -964,7 +1498,7 @@
         "h": 8,
         "w": 12,
         "x": 0,
-        "y": 40
+        "y": 64
       },
       "hiddenSeries": false,
       "id": 24,
@@ -1056,10 +1590,10 @@
         "h": 8,
         "w": 12,
         "x": 12,
-        "y": 40
+        "y": 64
       },
       "hiddenSeries": false,
-      "id": 22,
+      "id": 32,
       "legend": {
         "avg": false,
         "current": false,
@@ -1085,12 +1619,12 @@
       "steppedLine": false,
       "targets": [
         {
-          "expr": "avg(Time{engine=\"IResearch\",category=\"AndHighMed\",size=\"$Size\",platform=\"Linux\",branch=\"master\", stage=\"Executing\"}) + avg(Time{engine=\"IResearch\",category=\"AndHighMed\",size=\"$Size\",platform=\"Linux\",branch=\"master\", stage=\"Building\"})",
+          "expr": "avg(Time{category=\"Prefix3\",stage=\"Executing\",engine=\"IResearch\",size=\"$Size\",platform=\"Linux\",branch=\"master\"}) + avg(Time{category=\"Prefix3\",stage=\"Building\",engine=\"IResearch\",size=\"$Size\",platform=\"Linux\",branch=\"master\"})",
           "legendFormat": "IResearch",
           "refId": "A"
         },
         {
-          "expr": "avg(Time{engine=\"Lucene\",category=\"AndHighMed\",size=\"$Size\",platform=\"Linux\",branch=\"master\", stage=\"Executing\"})",
+          "expr": "avg(Time{category=\"Prefix3\",stage=\"Executing\",engine=\"Lucene\",size=\"$Size\",platform=\"Linux\",branch=\"master\"})",
           "legendFormat": "Lucene",
           "refId": "B"
         }
@@ -1099,7 +1633,7 @@
       "timeFrom": null,
       "timeRegions": [],
       "timeShift": null,
-      "title": "AndHighMed",
+      "title": "Prefix3",
       "tooltip": {
         "shared": true,
         "sort": 0,
@@ -1148,7 +1682,7 @@
         "h": 8,
         "w": 12,
         "x": 0,
-        "y": 48
+        "y": 72
       },
       "hiddenSeries": false,
       "id": 34,
@@ -1240,10 +1774,10 @@
         "h": 8,
         "w": 12,
         "x": 12,
-        "y": 48
+        "y": 72
       },
       "hiddenSeries": false,
-      "id": 32,
+      "id": 36,
       "legend": {
         "avg": false,
         "current": false,
@@ -1269,12 +1803,12 @@
       "steppedLine": false,
       "targets": [
         {
-          "expr": "avg(Time{category=\"Prefix3\",stage=\"Executing\",engine=\"IResearch\",size=\"$Size\",platform=\"Linux\",branch=\"master\"}) + avg(Time{category=\"Prefix3\",stage=\"Building\",engine=\"IResearch\",size=\"$Size\",platform=\"Linux\",branch=\"master\"})",
+          "expr": "avg(MinorPageFaults{engine=\"IResearch\", size=\"$Size\",platform=\"Linux\",branch=\"master\",category=\"Query\"})",
           "legendFormat": "IResearch",
           "refId": "A"
         },
         {
-          "expr": "avg(Time{category=\"Prefix3\",stage=\"Executing\",engine=\"Lucene\",size=\"$Size\",platform=\"Linux\",branch=\"master\"})",
+          "expr": "avg(MinorPageFaults{engine=\"Lucene\", size=\"$Size\",platform=\"Linux\",branch=\"master\",category=\"Query\"})",
           "legendFormat": "Lucene",
           "refId": "B"
         }
@@ -1283,7 +1817,7 @@
       "timeFrom": null,
       "timeRegions": [],
       "timeShift": null,
-      "title": "Prefix3",
+      "title": "Minor (reclaiming a frame) page faults (Query)",
       "tooltip": {
         "shared": true,
         "sort": 0,
@@ -1332,7 +1866,7 @@
         "h": 8,
         "w": 12,
         "x": 0,
-        "y": 56
+        "y": 80
       },
       "hiddenSeries": false,
       "id": 10,
@@ -1424,10 +1958,10 @@
         "h": 8,
         "w": 12,
         "x": 12,
-        "y": 56
+        "y": 80
       },
       "hiddenSeries": false,
-      "id": 36,
+      "id": 8,
       "legend": {
         "avg": false,
         "current": false,
@@ -1453,21 +1987,31 @@
       "steppedLine": false,
       "targets": [
         {
-          "expr": "avg(MinorPageFaults{engine=\"IResearch\", size=\"$Size\",platform=\"Linux\",branch=\"master\",category=\"Query\"})",
-          "legendFormat": "IResearch",
+          "expr": "avg(Memory{engine=\"IResearch\", size=\"$Size\",platform=\"Linux\",branch=\"master\",category=\"Index\"})",
+          "legendFormat": "IResearch-Index",
           "refId": "A"
         },
         {
-          "expr": "avg(MinorPageFaults{engine=\"Lucene\", size=\"$Size\",platform=\"Linux\",branch=\"master\",category=\"Query\"})",
-          "legendFormat": "Lucene",
+          "expr": "avg(Memory{engine=\"Lucene\", size=\"$Size\",platform=\"Linux\",branch=\"master\",category=\"Index\"})",
+          "legendFormat": "Lucene-Index",
           "refId": "B"
+        },
+        {
+          "expr": "avg(Memory{engine=\"IResearch\", size=\"$Size\",platform=\"Linux\",branch=\"master\",category=\"Query\"})",
+          "legendFormat": "IResearch-Query",
+          "refId": "C"
+        },
+        {
+          "expr": "avg(Memory{engine=\"Lucene\", size=\"$Size\",platform=\"Linux\",branch=\"master\",category=\"Query\"})",
+          "legendFormat": "Lucene-Query",
+          "refId": "D"
         }
       ],
       "thresholds": [],
       "timeFrom": null,
       "timeRegions": [],
       "timeShift": null,
-      "title": "Minor (reclaiming a frame) page faults (Query)",
+      "title": "Maximum resident set size (kbytes)",
       "tooltip": {
         "shared": true,
         "sort": 0,
@@ -1516,7 +2060,7 @@
         "h": 8,
         "w": 12,
         "x": 0,
-        "y": 64
+        "y": 88
       },
       "hiddenSeries": false,
       "id": 18,
@@ -1601,17 +2145,16 @@
       "bars": false,
       "dashLength": 10,
       "dashes": false,
-      "datasource": "Prometheus",
+      "datasource": null,
       "fill": 1,
       "fillGradient": 0,
       "gridPos": {
         "h": 8,
         "w": 12,
         "x": 12,
-        "y": 64
+        "y": 88
       },
-      "hiddenSeries": false,
-      "id": 8,
+      "id": 38,
       "legend": {
         "avg": false,
         "current": false,
@@ -1637,31 +2180,21 @@
       "steppedLine": false,
       "targets": [
         {
-          "expr": "avg(Memory{engine=\"IResearch\", size=\"$Size\",platform=\"Linux\",branch=\"master\",category=\"Index\"})",
-          "legendFormat": "IResearch-Index",
+          "expr": "avg(IndexSize{engine=\"IResearch\", platform=\"Linux\",branch=\"master\", size=\"$Size\", branch=\"master\"})",
+          "legendFormat": "IResearch",
           "refId": "A"
         },
         {
-          "expr": "avg(Memory{engine=\"Lucene\", size=\"$Size\",platform=\"Linux\",branch=\"master\",category=\"Index\"})",
-          "legendFormat": "Lucene-Index",
+          "expr": "avg(IndexSize{engine=\"Lucene\", platform=\"Linux\",branch=\"master\", size=\"$Size\", branch=\"master\"})",
+          "legendFormat": "Lucene",
           "refId": "B"
-        },
-        {
-          "expr": "avg(Memory{engine=\"IResearch\", size=\"$Size\",platform=\"Linux\",branch=\"master\",category=\"Query\"})",
-          "legendFormat": "IResearch-Query",
-          "refId": "C"
-        },
-        {
-          "expr": "avg(Memory{engine=\"Lucene\", size=\"$Size\",platform=\"Linux\",branch=\"master\",category=\"Query\"})",
-          "legendFormat": "Lucene-Query",
-          "refId": "D"
         }
       ],
       "thresholds": [],
       "timeFrom": null,
       "timeRegions": [],
       "timeShift": null,
-      "title": "Maximum resident set size (kbytes)",
+      "title": "Index size (kbytes)",
       "tooltip": {
         "shared": true,
         "sort": 0,
@@ -1710,8 +2243,8 @@
         "auto_count": 30,
         "auto_min": "10s",
         "current": {
-          "text": "10000000",
-          "value": "10000000"
+          "text": "33332620",
+          "value": "33332620"
         },
         "hide": 0,
         "label": "Dataset size",
@@ -1723,12 +2256,12 @@
             "value": "1000000"
           },
           {
-            "selected": true,
+            "selected": false,
             "text": "10000000",
             "value": "10000000"
           },
           {
-            "selected": false,
+            "selected": true,
             "text": "33332620",
             "value": "33332620"
           }
@@ -1741,7 +2274,7 @@
     ]
   },
   "time": {
-    "from": "now-15m",
+    "from": "now-30d",
     "to": "now"
   },
   "timepicker": {
@@ -1761,5 +2294,5 @@
   "timezone": "",
   "title": "IResearch",
   "uid": "cWLkh3xZk",
-  "version": 4
+  "version": 15
 }
\ No newline at end of file
diff --git a/3rdParty/iresearch/scripts/Prometheus/INSTALL.md b/3rdParty/iresearch/scripts/Prometheus/INSTALL.md
index cb4cdb5103cf..7ce1165610b1 100644
--- a/3rdParty/iresearch/scripts/Prometheus/INSTALL.md
+++ b/3rdParty/iresearch/scripts/Prometheus/INSTALL.md
@@ -3,7 +3,7 @@ Upload is done throug pushing data to Prometheus PushGateway. Script requires Py
 Pushgateway need to be installed using Pip command: pip install prometheus_client
 
 Script run parameters:
-python PythonBenchmark.py <Path-to-benchmark-logs> <Platform-used-to-run-benchmark> <Branch-user-to-run-benchmark> <Push-gate-url> <Job-name>
+python PythonBenchmark.py <Path-to-benchmark-logs> <Platform-used-to-run-benchmark> <Branch-user-to-run-benchmark> <Push-gate-url> <Job-name> 
 
 Sample call: python PythonBenchmark.py C:\Data Windows10 master localhost:9091 benchmark
 
diff --git a/3rdParty/iresearch/scripts/Prometheus/PythonBenchmark.py b/3rdParty/iresearch/scripts/Prometheus/PythonBenchmark.py
index 23a011d4c6c7..85b73bac2c1a 100644
--- a/3rdParty/iresearch/scripts/Prometheus/PythonBenchmark.py
+++ b/3rdParty/iresearch/scripts/Prometheus/PythonBenchmark.py
@@ -12,7 +12,6 @@
 #Base dictionary labels
 baseLabels = ["repeat", "threads", "random", "scorer", "scorer-arg"]
 
-
 class MetricValue:
   """Generic class for storing single metric result"""
   def __init__(self, value, labels):
@@ -32,8 +31,12 @@ def __init__(self, mySize):
     self.pageMajorFaultsFiles = []
     self.voluntaryContextSwitchesFiles = []
     self.involuntaryContextSwitchesFiles = []
+    self.indexSizeFiles = []
     self.labels = {"size": mySize}
 
+  def processIndexSizeFile(self, file, run):
+    self.indexSizeFiles.append(self.parseIndexSizeStats(file, run))
+
   def processTimingFile(self, file, run):
     self.timingFiles.append(self.parseQueriesStats(file, run))
 
@@ -46,6 +49,15 @@ def processMemoryFile(self, file, run):
     self.voluntaryContextSwitchesFiles.append(self.parseVoluntaryContextSwitchesStats(file, run))
     self.involuntaryContextSwitchesFiles.append(self.parseInvoluntaryContextSwitchesStats(file, run))
 
+
+  def parseIndexSizeStats(self, filename, run):
+    metrics = []
+    datafile = open(filename, 'r')
+    sizeString = datafile.read();
+    result = {"run": int(run)}
+    metrics.append(MetricValue(int(sizeString), result))
+    return metrics
+  
   def parseWallClockStats(self, filename, run):
     metrics = []
     with open(filename, newline='') as datafile:
@@ -167,14 +179,16 @@ class IResearchIndexRunFiles(RunFiles):
   def __init__(self, mySize):
     super().__init__(mySize)
     self.baseParametersExtracted = False
+    self.indexPath = None
 
   def parseBaseIResearchParameters(self, filename):
     result = {}
     with open(filename, newline='') as datafile:
       for row in datafile:
-        m = re.search("Command being timed: \".*iresearch-benchmarks.* -m put --in .* --index-dir .* --max-lines=[0-9]* --commit-period=[0-9]* --batch-size=[0-9]* --threads=([0-9]*)", row)  
+        m = re.search("Command being timed: \".*iresearch-benchmarks.* -m put --in .* --index-dir (.*) --max-lines=[0-9]* --commit-period=[0-9]* --batch-size=[0-9]* --threads=([0-9]*)", row)  
         if m is not None:
-          result["threads"] = int(m.group(1))
+          self.indexPath = m.group(1)
+          result["threads"] = int(m.group(2))
           break
     return result
 
@@ -217,14 +231,16 @@ class LuceneIndexRunFiles(RunFiles):
   def __init__(self, mySize):
     super().__init__(mySize)
     self.baseParametersExtracted = False
+    self.indexPath = None
 
   def parseBaseLuceneParameters(self, filename):
     result = {}
     with open(filename, newline='') as datafile:
       for row in datafile:
-        m = re.search("Command being timed: \"java -jar *. -dirImpl MMapDirectory -analyzer StandardAnalyzer -lineDocsFile .* -maxConcurrentMerges [0-9]* -ramBufferMB -1 -postingsFormat Lucene50 -waitForMerges -mergePolicy LogDocMergePolicy -idFieldPostingsFormat Lucene50 -grouping -waitForCommit -indexPath .* -docCountLimit [0-9]* -maxBufferedDocs [0-9]* -threadCount ([0-9]*)", row)  
+        m = re.search("Command being timed: \"java -jar .* -dirImpl MMapDirectory -analyzer StandardAnalyzer -lineDocsFile .* -maxConcurrentMerges [0-9]* -ramBufferMB -1 -postingsFormat Lucene50 -waitForMerges -mergePolicy LogDocMergePolicy -idFieldPostingsFormat Lucene50 -grouping -waitForCommit -indexPath (.*) -docCountLimit [0-9]* -maxBufferedDocs [0-9]* -threadCount ([0-9]*)\"", row)  
         if m is not None:
-          result["threads"] = int(m.group(1))
+          self.indexPath = m.group(1)
+          result["threads"] = int(m.group(2))
           break
     return result
 
@@ -268,7 +284,7 @@ def fillGauge(files, gauge, labelsToSendTemplate):
       labelsToSend.update(l.labels)
       gauge.labels(**labelsToSend).set(l.value)
 
-def sendStatsToPrometheus(time, memory, cpu, wallClock, pageMinFaults, pageMajFaults, volContextSwitches, involContextSwitches, parsedFiles, engine, default_category="<None>"):
+def sendStatsToPrometheus(time, memory, cpu, wallClock, pageMinFaults, pageMajFaults, volContextSwitches, involContextSwitches, indexSize, parsedFiles, engine, default_category="<None>"):
   # Label must be all present! For start all will be placeholders
   labelsToSendTemplate = {"engine" : engine, "size": "<None>", "category": default_category,\
                         "repeat": "<None>", "threads": "<None>", "random": "<None>",\
@@ -285,6 +301,8 @@ def sendStatsToPrometheus(time, memory, cpu, wallClock, pageMinFaults, pageMajFa
     fillGauge(stats.pageMajorFaultsFiles, pageMajFaults, labelsToSendTemplate)
     fillGauge(stats.voluntaryContextSwitchesFiles, volContextSwitches, labelsToSendTemplate)
     fillGauge(stats.involuntaryContextSwitchesFiles, involContextSwitches, labelsToSendTemplate)
+    if indexSize is not None:
+      fillGauge(stats.indexSizeFiles, indexSize, labelsToSendTemplate)
     
 
 def main():
@@ -323,6 +341,18 @@ def main():
             luceneIndexRunFiles[size] = LuceneIndexRunFiles(size)
           if m.group(2) == "stderr":
             luceneIndexRunFiles[size].processMemoryFile(os.path.join(sys.argv[1],f), m.group(5))
+    else:
+      m = re.match('(lucene|iresearch)\.([0-9]*)\.indexSize\.log\.([0-9])', f)
+      if m is not None:
+        size = int(m.group(2))
+        if m.group(1) == "iresearch":
+          if size not in iresearchRunFiles.keys():
+            iresearchRunFiles[size] = IResearchRunFiles(size)
+          iresearchRunFiles[size].processIndexSizeFile(os.path.join(sys.argv[1],f), m.group(3))
+        else:
+          if size not in luceneRunFiles.keys():
+            luceneRunFiles[size] = LuceneRunFiles(size)
+          luceneRunFiles[size].processIndexSizeFile(os.path.join(sys.argv[1],f), m.group(3))
 
   registry = CollectorRegistry()
   defaultLabelNames = ["engine", "size", "category", "repeat", "threads",\
@@ -336,11 +366,13 @@ def main():
   pageMajFaults = Gauge('MajorPageFaults', 'Major (requiring I/O) page faults', registry=registry, labelnames=defaultLabelNames)
   volContextSwitches =  Gauge('VolContextSwitches', 'Voluntary context switches', registry=registry, labelnames=defaultLabelNames)
   involContextSwitches =  Gauge('InvolContextSwitches', 'Involuntary context switches', registry=registry, labelnames=defaultLabelNames)
+  indexSize = Gauge('IndexSize', 'Index directory size (kbytes)', registry=registry, labelnames=defaultLabelNames)
+
+  sendStatsToPrometheus(time, memory, cpu, wallClock, pageMinFaults, pageMajFaults, volContextSwitches, involContextSwitches, indexSize,  iresearchRunFiles, "IResearch", "Query")
+  sendStatsToPrometheus(time, memory, cpu, wallClock, pageMinFaults, pageMajFaults, volContextSwitches, involContextSwitches, indexSize, luceneRunFiles, "Lucene", "Query")
+  sendStatsToPrometheus(time, memory, cpu, wallClock, pageMinFaults, pageMajFaults, volContextSwitches, involContextSwitches, None, iresearchIndexRunFiles,  "IResearch", "Index")
+  sendStatsToPrometheus(time, memory, cpu, wallClock, pageMinFaults, pageMajFaults, volContextSwitches, involContextSwitches, None, luceneIndexRunFiles, "Lucene", "Index")
 
-  sendStatsToPrometheus(time, memory, cpu, wallClock, pageMinFaults, pageMajFaults, volContextSwitches, involContextSwitches, iresearchRunFiles, "IResearch", "Query")
-  sendStatsToPrometheus(time, memory, cpu, wallClock, pageMinFaults, pageMajFaults, volContextSwitches, involContextSwitches, luceneRunFiles, "Lucene", "Query")
-  sendStatsToPrometheus(time, memory, cpu, wallClock, pageMinFaults, pageMajFaults, volContextSwitches, involContextSwitches, iresearchIndexRunFiles, "IResearch", "Index")
-  sendStatsToPrometheus(time, memory, cpu, wallClock, pageMinFaults, pageMajFaults, volContextSwitches, involContextSwitches, luceneIndexRunFiles, "Lucene", "Index")
   push_to_gateway(sys.argv[4], job=sys.argv[5], registry=registry)
 
 
diff --git a/3rdParty/iresearch/scripts/download-benchmark-resources.sh b/3rdParty/iresearch/scripts/download-benchmark-resources.sh
index 774fa8a52145..c3a11ac6ee3b 100755
--- a/3rdParty/iresearch/scripts/download-benchmark-resources.sh
+++ b/3rdParty/iresearch/scripts/download-benchmark-resources.sh
@@ -9,7 +9,7 @@ BENCHMARK_SEARCH_JAR_URL="https://www.dropbox.com/s/qf9ot583oh34ekl/searcher-j8.
 #BENCHMARK_INDEX_JAR_URL="https://www.dropbox.com/s/mqxm9gov031xmva/indexer.jar?dl=0" # compiled with Java 1.9
 #BENCHMARK_SEARCH_JAR_URL="https://www.dropbox.com/s/yp1gzwrl0oufbma/searcher.jar?dl=0" # compiled with Java 1.9
 #BENCHMARK_TASKS_URL="https://raw.githubusercontent.com/mikemccand/luceneutil/master/tasks/wikimedium.1M.nostopwords.tasks"
-BENCHMARK_TASKS_URL="https://www.dropbox.com/s/ma6zdd6eg9ljlkx/iresearch-benchmark.tasks?dl=0"
+BENCHMARK_TASKS_URL="https://raw.githubusercontent.com/iresearch-toolkit/iresearch-resources/master/benchmarks/iresearch-benchmark.tasks"
 
 #rm -rf "${DEPS_DIR}/${BENCHMARK_RESOURCES_DIR}"
 [ -f "${DEPS_DIR}/${BENCHMARK_RESOURCES_DIR}/benchmark.data" ] || rm -rf "${DEPS_DIR}/${BENCHMARK_RESOURCES_DIR}"
@@ -19,5 +19,5 @@ BENCHMARK_TASKS_URL="https://www.dropbox.com/s/ma6zdd6eg9ljlkx/iresearch-benchma
     wget --quiet -O - "${BENCHMARK_DATA_URL}" | lzma -d > benchmark.data
     wget --quiet -O lucene_index.jar "${BENCHMARK_INDEX_JAR_URL}"
     wget --quiet -O lucene_search.jar "${BENCHMARK_SEARCH_JAR_URL}"
-    wget --quiet -O - "${BENCHMARK_TASKS_URL}" | grep -E 'HighTerm:|MedTerm:|LowTerm:|HighPhrase:|MedPhrase:|LowPhrase:|AndHighHigh:|AndHighMed:|AndHighLow:|OrHighHigh:|OrHighMed:|OrHighLow:|Prefix3:|Wildcard:' > benchmark.tasks
+    wget --quiet -O - "${BENCHMARK_TASKS_URL}" | grep -E 'HighTerm:|MedTerm:|LowTerm:|HighPhrase:|MedPhrase:|LowPhrase:|AndHighHigh:|AndHighMed:|AndHighLow:|OrHighHigh:|OrHighMed:|OrHighLow:|Prefix3:|Wildcard:|Fuzzy1:|Fuzzy2:' > benchmark.tasks
 }
diff --git a/3rdParty/iresearch/scripts/gtest-parallel/gtest-parallel b/3rdParty/iresearch/scripts/gtest-parallel/gtest-parallel
old mode 100644
new mode 100755
diff --git a/3rdParty/iresearch/scripts/gtest-parallel/gtest_parallel.py b/3rdParty/iresearch/scripts/gtest-parallel/gtest_parallel.py
old mode 100644
new mode 100755
diff --git a/3rdParty/iresearch/scripts/gtest-parallel/gtest_parallel_tests.py b/3rdParty/iresearch/scripts/gtest-parallel/gtest_parallel_tests.py
old mode 100644
new mode 100755
diff --git a/3rdParty/iresearch/scripts/index-benchmark.sh b/3rdParty/iresearch/scripts/index-benchmark.sh
index 15fc3bbb687d..75e1817c3ea7 100755
--- a/3rdParty/iresearch/scripts/index-benchmark.sh
+++ b/3rdParty/iresearch/scripts/index-benchmark.sh
@@ -7,7 +7,7 @@ export LD_LIBRARY_PATH="${LD_LIBRARY_PATH}:$(pwd)/bin"
 ulimit -c unlimited
 
 for i in `seq 1 1`; do
-    for j in 5 ; do
+    for j in 1 ; do
         MAX_LINES=${j}000000
 
         rm -r iresearch.data || {
@@ -15,7 +15,7 @@ for i in `seq 1 1`; do
         }
 
         # index
-        /usr/bin/time -v ./bin/iresearch-benchmarks -m put --in ${BENCHMARK_RESOURCES_ROOT}/benchmark.data --index-dir iresearch.data --max-lines=${MAX_LINES} --commit-period=1000 --batch-size=10000 --format 1_2sse --threads=8 2> iresearch.stderr.${MAX_LINES}.index.log.$i 1> /dev/null &
+        /usr/bin/time -v ./bin/iresearch-benchmarks -m put --in ${BENCHMARK_RESOURCES_ROOT}/benchmark.data --index-dir iresearch.data --max-lines=${MAX_LINES}  --commit-period=1000 --batch-size=10000 --threads=8 2> iresearch.stderr.${MAX_LINES}.index.log.$i 1> /dev/null &
         IRESEARCH_PID=$!
         wait $IRESEARCH_PID
 
diff --git a/3rdParty/iresearch/scripts/iresearch-benchmark.tasks b/3rdParty/iresearch/scripts/iresearch-benchmark.tasks
index d4103fbc377f..0d844bbaeb29 100644
--- a/3rdParty/iresearch/scripts/iresearch-benchmark.tasks
+++ b/3rdParty/iresearch/scripts/iresearch-benchmark.tasks
@@ -14,3 +14,5 @@ Prefix3: sec*
 Wildcard: re*f
 Or4High: about ref from cite # freq=91907 freq=541190 freq=359428 freq=265368
 Or6High4Med2Low: about ref from cite http which roman short europe party rapid donald # freq=91907 freq=541190 freq=359428 freq=265368 freq=389790 freq=253402 freq=31137 freq=31137 freq=31053 freq=30836 freq=4972 freq=4940
+MinMatch2High2Med: 2 about ref roman short # freq=91907 freq=541190 freq=31137 freq=31137
+
diff --git a/3rdParty/iresearch/scripts/search-benchmark.sh b/3rdParty/iresearch/scripts/search-benchmark.sh
index 64698fe47ede..39b7faffe7e2 100755
--- a/3rdParty/iresearch/scripts/search-benchmark.sh
+++ b/3rdParty/iresearch/scripts/search-benchmark.sh
@@ -16,7 +16,7 @@ for i in `seq 1 1`; do
         wait $IRESEARCH_PID
 
         echo iresearch.stdout.${MAX_LINES}.search.log.$i
-        cat iresearch.stdout.${MAX_LINES}.search.log.$i | grep 'Query execution' | sort
+        cat iresearch.stdout.${MAX_LINES}.search.log.$i | grep 'Query' | sort
     done
 done
 
diff --git a/3rdParty/iresearch/scripts/start-benchmark-comparison.sh b/3rdParty/iresearch/scripts/start-benchmark-comparison.sh
index 48b33b4a99d6..5ed72ff8aa4d 100755
--- a/3rdParty/iresearch/scripts/start-benchmark-comparison.sh
+++ b/3rdParty/iresearch/scripts/start-benchmark-comparison.sh
@@ -43,9 +43,11 @@ for i in `seq 1 5`; do
         echo lucene.stdlog.${MAX_LINES}.search.log.$i
         cat lucene.stdlog.${MAX_LINES}.search.log.$i | grep 'Query execution' | sort
 #tar czf iresearch.data.$i.$j.tgz ../iresearch.data
+        du -s ../iresearch.data | awk '{print $1}' >  iresearch.${MAX_LINES}.indexSize.log.$i
         rm -r ../iresearch.data || {
             ls -la bin && cat iresearch.stderr.${MAX_LINES}.index.log.$i
         }
+        du -s ../lucene.data | awk '{print $1}' >  lucene.${MAX_LINES}.indexSize.log.$i
         rm -r ../lucene.data || {
             ls -la bin && cat lucene.stderr.${MAX_LINES}.index.log.$i
         }
diff --git a/3rdParty/iresearch/tests/CMakeLists.txt b/3rdParty/iresearch/tests/CMakeLists.txt
index b46a655f8d16..b2e618df8cac 100644
--- a/3rdParty/iresearch/tests/CMakeLists.txt
+++ b/3rdParty/iresearch/tests/CMakeLists.txt
@@ -87,6 +87,7 @@ set(IReSearch_tests_sources
   ./search/phrase_filter_tests.cpp
   ./search/column_existence_filter_test.cpp
   ./search/same_position_filter_tests.cpp
+  ./search/ngram_similarity_filter_tests.cpp
   ./iql/parser_common_test.cpp
   ./iql/query_builder_test.cpp
   ./utils/async_utils_tests.cpp
@@ -107,6 +108,7 @@ set(IReSearch_tests_sources
   ./utils/encryption_test.cpp
   ./utils/locale_utils_tests.cpp
   ./utils/levenshtein_utils_test.cpp
+  ./utils/wildcard_utils_test.cpp
   ./utils/ref_counter_tests.cpp
   ./utils/memory_tests.cpp
   ./utils/string_tests.cpp
@@ -120,6 +122,7 @@ set(IReSearch_tests_sources
   ./utils/fst_builder_test.cpp
   ./utils/fst_utils_test.cpp
   ./utils/fst_string_weight_test.cpp
+  ./utils/ngram_match_utils_tests.cpp
   ./tests_param.cpp
   ./tests_main.cpp
 )
@@ -163,6 +166,7 @@ add_executable(${IResearchTests_TARGET_NAME}-static
   ./formats/formats_10_tests.cpp
   ./formats/formats_11_tests.cpp
   ./formats/formats_12_tests.cpp
+  ./formats/formats_13_tests.cpp
   ./iql/parser_test.cpp
 )
 
diff --git a/3rdParty/iresearch/tests/formats/formats_13_tests.cpp b/3rdParty/iresearch/tests/formats/formats_13_tests.cpp
new file mode 100644
index 000000000000..c965ee56d897
--- /dev/null
+++ b/3rdParty/iresearch/tests/formats/formats_13_tests.cpp
@@ -0,0 +1,511 @@
+/// Copyright 2020 ArangoDB GmbH, Cologne, Germany
+///
+/// Licensed under the Apache License, Version 2.0 (the "License");
+/// you may not use this file except in compliance with the License.
+/// You may obtain a copy of the License at
+///
+///     http://www.apache.org/licenses/LICENSE-2.0
+///
+/// Unless required by applicable law or agreed to in writing, software
+/// distributed under the License is distributed on an "AS IS" BASIS,
+/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+/// See the License for the specific language governing permissions and
+/// limitations under the License.
+///
+/// Copyright holder is ArangoDB GmbH, Cologne, Germany
+///
+/// @author Andrei Lobov
+////////////////////////////////////////////////////////////////////////////////
+
+#include "tests_shared.hpp"
+#include "formats_test_case_base.hpp"
+#include "store/directory_attributes.hpp"
+
+NS_LOCAL
+
+// -----------------------------------------------------------------------------
+// --SECTION--                                          format 13 specific tests
+// -----------------------------------------------------------------------------
+
+class format_13_test_case : public tests::directory_test_case_base {
+};
+
+TEST_P(format_13_test_case, read_zero_block_encryption) {
+  tests::json_doc_generator gen(
+    resource("simple_sequential.json"),
+    &tests::generic_json_field_factory
+  );
+
+  tests::document const* doc1 = gen.next();
+
+  // replace encryption
+  ASSERT_TRUE(dir().attributes().contains<tests::rot13_encryption>());
+
+  // write segment with format13
+  {
+    auto codec = irs::formats::get("1_3");
+    ASSERT_NE(nullptr, codec);
+    auto writer = irs::index_writer::make(dir(), codec, irs::OM_CREATE);
+    ASSERT_NE(nullptr, writer);
+
+    ASSERT_TRUE(insert(*writer,
+      doc1->indexed.begin(), doc1->indexed.end(),
+      doc1->stored.begin(), doc1->stored.end()
+    ));
+
+    writer->commit();
+  }
+
+  // replace encryption
+  ASSERT_TRUE(dir().attributes().remove<tests::rot13_encryption>());
+  dir().attributes().emplace<tests::rot13_encryption>(6);
+
+  // can't open encrypted index without encryption
+  ASSERT_THROW(irs::directory_reader::open(dir()), irs::index_error);
+}
+
+TEST_P(format_13_test_case, write_zero_block_encryption) {
+  tests::json_doc_generator gen(
+    resource("simple_sequential.json"),
+    &tests::generic_json_field_factory
+  );
+
+  tests::document const* doc1 = gen.next();
+
+  // replace encryption
+  ASSERT_TRUE(dir().attributes().remove<tests::rot13_encryption>());
+  dir().attributes().emplace<tests::rot13_encryption>(0);
+
+  // write segment with format13
+  auto codec = irs::formats::get("1_3");
+  ASSERT_NE(nullptr, codec);
+  auto writer = irs::index_writer::make(dir(), codec, irs::OM_CREATE);
+  ASSERT_NE(nullptr, writer);
+
+  ASSERT_THROW(insert(*writer,
+    doc1->indexed.begin(), doc1->indexed.end(),
+    doc1->stored.begin(), doc1->stored.end()
+  ), irs::index_error);
+}
+
+TEST_P(format_13_test_case, fields_read_write_wrong_encryption) {
+  // create sorted && unsorted terms
+  typedef std::set<irs::bytes_ref> sorted_terms_t;
+  typedef std::vector<irs::bytes_ref> unsorted_terms_t;
+  sorted_terms_t sorted_terms;
+  unsorted_terms_t unsorted_terms;
+
+  tests::json_doc_generator gen(
+    resource("fst_prefixes.json"),
+    [&sorted_terms, &unsorted_terms] (tests::document& doc, const std::string& name, const tests::json_doc_generator::json_value& data) {
+      doc.insert(std::make_shared<tests::templates::string_field>(
+        irs::string_ref(name),
+        data.str
+        ));
+
+      auto ref = irs::ref_cast<irs::byte_type>((doc.indexed.end() - 1).as<tests::templates::string_field>().value());
+      sorted_terms.emplace(ref);
+      unsorted_terms.emplace_back(ref);
+    });
+
+  // define field
+  irs::field_meta field;
+  field.name = "field";
+  field.norm = 5;
+
+  auto codec = irs::formats::get("1_3");
+  ASSERT_NE(nullptr, codec);
+  ASSERT_TRUE(dir().attributes().contains<tests::rot13_encryption>());
+
+  // write fields
+  {
+    irs::flush_state state;
+    state.dir = &dir();
+    state.doc_count = 100;
+    state.name = "segment_name";
+    state.features = &field.features;
+
+    // should use sorted terms on write
+    tests::format_test_case::terms<sorted_terms_t::iterator> terms(
+      sorted_terms.begin(), sorted_terms.end()
+    );
+
+    auto writer = codec->get_field_writer(false);
+    ASSERT_NE(nullptr, writer);
+    writer->prepare(state);
+    writer->write(field.name, field.norm, field.features, terms);
+    writer->end();
+  }
+
+  irs::segment_meta meta;
+  meta.name = "segment_name";
+  irs::document_mask docs_mask;
+
+  auto reader = codec->get_field_reader();
+  ASSERT_NE(nullptr, reader);
+
+  // can't open encrypted index without encryption
+  ASSERT_TRUE(dir().attributes().remove<tests::rot13_encryption>());
+  ASSERT_THROW(reader->prepare(dir(), meta, docs_mask), irs::index_error);
+
+  // can't open encrypted index with wrong encryption
+  dir().attributes().emplace<tests::rot13_encryption>(6);
+  ASSERT_THROW(reader->prepare(dir(), meta, docs_mask), irs::index_error);
+}
+
+TEST_P(format_13_test_case, column_meta_read_write_wrong_encryption) {
+  auto codec = irs::formats::get("1_3");
+  ASSERT_NE(nullptr, codec);
+
+  ASSERT_TRUE(dir().attributes().contains<tests::rot13_encryption>());
+
+  irs::segment_meta meta;
+  meta.name = "_1";
+
+  // write meta
+  {
+    auto writer = codec->get_column_meta_writer();
+    irs::segment_meta meta1;
+
+    // write segment _1
+    writer->prepare(dir(), meta);
+    writer->write("_1_column1", 1);
+    writer->write("_1_column2", 2);
+    writer->write("_1_column0", 0);
+    writer->flush();
+  }
+
+  size_t count = 0;
+  irs::field_id max_id = 0;
+
+  auto reader = codec->get_column_meta_reader();
+  ASSERT_NE(nullptr, reader);
+
+  // can't open encrypted index without encryption
+  ASSERT_TRUE(dir().attributes().remove<tests::rot13_encryption>());
+  ASSERT_THROW(reader->prepare(dir(), meta, count, max_id), irs::index_error);
+
+  // can't open encrypted index with wrong encryption
+  dir().attributes().emplace<tests::rot13_encryption>(6);
+  ASSERT_THROW(reader->prepare(dir(), meta, count, max_id), irs::index_error);
+}
+
+TEST_P(format_13_test_case, open_ecnrypted_with_wrong_encryption) {
+  tests::json_doc_generator gen(
+    resource("simple_sequential.json"),
+    &tests::generic_json_field_factory
+  );
+
+  tests::document const* doc1 = gen.next();
+
+  ASSERT_TRUE(dir().attributes().contains<tests::rot13_encryption>());
+
+  // write segment with format10
+  {
+    auto codec = irs::formats::get("1_3");
+    ASSERT_NE(nullptr, codec);
+    auto writer = irs::index_writer::make(dir(), codec, irs::OM_CREATE);
+    ASSERT_NE(nullptr, writer);
+
+    ASSERT_TRUE(insert(*writer,
+      doc1->indexed.begin(), doc1->indexed.end(),
+      doc1->stored.begin(), doc1->stored.end()
+    ));
+
+    writer->commit();
+  }
+
+  // can't open encrypted index with wrong encryption
+  ASSERT_TRUE(dir().attributes().remove<tests::rot13_encryption>());
+  dir().attributes().emplace<tests::rot13_encryption>(6);
+  ASSERT_THROW(irs::directory_reader::open(dir()), irs::index_error);
+}
+
+TEST_P(format_13_test_case, open_ecnrypted_with_non_encrypted) {
+  tests::json_doc_generator gen(
+    resource("simple_sequential.json"),
+    &tests::generic_json_field_factory
+  );
+
+  tests::document const* doc1 = gen.next();
+
+  ASSERT_TRUE(dir().attributes().contains<tests::rot13_encryption>());
+
+  // write segment with format11
+  {
+    auto codec = irs::formats::get("1_3");
+    ASSERT_NE(nullptr, codec);
+    auto writer = irs::index_writer::make(dir(), codec, irs::OM_CREATE);
+    ASSERT_NE(nullptr, writer);
+
+    ASSERT_TRUE(insert(*writer,
+      doc1->indexed.begin(), doc1->indexed.end(),
+      doc1->stored.begin(), doc1->stored.end()
+    ));
+
+    writer->commit();
+  }
+
+  // remove encryption
+  dir().attributes().remove<tests::rot13_encryption>();
+
+  // can't open encrypted index without encryption
+  ASSERT_THROW(irs::directory_reader::open(dir()), irs::index_error);
+}
+
+TEST_P(format_13_test_case, open_non_ecnrypted_with_encrypted) {
+  tests::json_doc_generator gen(
+    resource("simple_sequential.json"),
+    &tests::generic_json_field_factory
+  );
+
+  tests::document const* doc1 = gen.next();
+
+  ASSERT_TRUE(dir().attributes().remove<tests::rot13_encryption>());
+
+  // write segment with format13
+  {
+    auto codec = irs::formats::get("1_3");
+    ASSERT_NE(nullptr, codec);
+    auto writer = irs::index_writer::make(dir(), codec, irs::OM_CREATE);
+    ASSERT_NE(nullptr, writer);
+
+    ASSERT_TRUE(insert(*writer,
+      doc1->indexed.begin(), doc1->indexed.end(),
+      doc1->stored.begin(), doc1->stored.end()
+    ));
+
+    writer->commit();
+  }
+
+  // add cipher
+  dir().attributes().emplace<tests::rot13_encryption>(7);
+
+  // check index
+  auto index = irs::directory_reader::open(dir());
+  ASSERT_TRUE(index);
+  ASSERT_EQ(1, index->size());
+  ASSERT_EQ(1, index->docs_count());
+  ASSERT_EQ(1, index->live_docs_count());
+
+  // check segment 0
+  {
+    auto& segment = index[0];
+    ASSERT_EQ(1, segment.size());
+    ASSERT_EQ(1, segment.docs_count());
+    ASSERT_EQ(1, segment.live_docs_count());
+
+    std::unordered_set<irs::string_ref> expectedName = { "A" };
+    const auto* column = segment.column_reader("name");
+    ASSERT_NE(nullptr, column);
+    auto values = column->values();
+    ASSERT_EQ(expectedName.size(), segment.docs_count()); // total count of documents
+    auto terms = segment.field("same");
+    ASSERT_NE(nullptr, terms);
+    auto termItr = terms->iterator();
+    ASSERT_TRUE(termItr->next());
+
+    irs::bytes_ref actual_value;
+    for (auto docsItr = termItr->postings(iresearch::flags()); docsItr->next();) {
+      ASSERT_TRUE(values(docsItr->value(), actual_value));
+      ASSERT_EQ(1, expectedName.erase(irs::to_string<irs::string_ref>(actual_value.c_str())));
+    }
+
+    ASSERT_TRUE(expectedName.empty());
+  }
+}
+
+TEST_P(format_13_test_case, open_10_with_13) {
+  tests::json_doc_generator gen(
+    resource("simple_sequential.json"),
+    &tests::generic_json_field_factory
+  );
+
+  tests::document const* doc1 = gen.next();
+
+  // write segment with format10
+  {
+    auto codec = irs::formats::get("1_0");
+    ASSERT_NE(nullptr, codec);
+    auto writer = irs::index_writer::make(dir(), codec, irs::OM_CREATE);
+    ASSERT_NE(nullptr, writer);
+
+    ASSERT_TRUE(insert(*writer,
+      doc1->indexed.begin(), doc1->indexed.end(),
+      doc1->stored.begin(), doc1->stored.end()
+    ));
+
+    writer->commit();
+  }
+
+  // check index
+  auto codec = irs::formats::get("1_3");
+  ASSERT_NE(nullptr, codec);
+  auto index = irs::directory_reader::open(dir(), codec);
+  ASSERT_TRUE(index);
+  ASSERT_EQ(1, index->size());
+  ASSERT_EQ(1, index->docs_count());
+  ASSERT_EQ(1, index->live_docs_count());
+
+  // check segment 0
+  {
+    auto& segment = index[0];
+    ASSERT_EQ(1, segment.size());
+    ASSERT_EQ(1, segment.docs_count());
+    ASSERT_EQ(1, segment.live_docs_count());
+
+    std::unordered_set<irs::string_ref> expectedName = { "A" };
+    const auto* column = segment.column_reader("name");
+    ASSERT_NE(nullptr, column);
+    auto values = column->values();
+    ASSERT_EQ(expectedName.size(), segment.docs_count()); // total count of documents
+    auto terms = segment.field("same");
+    ASSERT_NE(nullptr, terms);
+    auto termItr = terms->iterator();
+    ASSERT_TRUE(termItr->next());
+
+    irs::bytes_ref actual_value;
+    for (auto docsItr = termItr->postings(iresearch::flags()); docsItr->next();) {
+      ASSERT_TRUE(values(docsItr->value(), actual_value));
+      ASSERT_EQ(1, expectedName.erase(irs::to_string<irs::string_ref>(actual_value.c_str())));
+    }
+
+    ASSERT_TRUE(expectedName.empty());
+  }
+}
+
+TEST_P(format_13_test_case, formats_10_13) {
+  tests::json_doc_generator gen(
+    resource("simple_sequential.json"),
+    &tests::generic_json_field_factory
+  );
+
+  tests::document const* doc1 = gen.next();
+  tests::document const* doc2 = gen.next();
+
+  // write segment with format10
+  {
+    auto codec = irs::formats::get("1_0");
+    ASSERT_NE(nullptr, codec);
+    auto writer = irs::index_writer::make(dir(), codec, irs::OM_CREATE);
+    ASSERT_NE(nullptr, writer);
+
+    ASSERT_TRUE(insert(*writer,
+      doc1->indexed.begin(), doc1->indexed.end(),
+      doc1->stored.begin(), doc1->stored.end()
+    ));
+
+    writer->commit();
+  }
+
+  // write segment with format13
+  {
+    auto codec = irs::formats::get("1_3");
+    ASSERT_NE(nullptr, codec);
+    auto writer = irs::index_writer::make(dir(), codec, irs::OM_APPEND);
+    ASSERT_NE(nullptr, writer);
+
+    ASSERT_TRUE(insert(*writer,
+      doc2->indexed.begin(), doc2->indexed.end(),
+      doc2->stored.begin(), doc2->stored.end()
+    ));
+
+    writer->commit();
+  }
+
+  // check index
+  auto index = irs::directory_reader::open(dir());
+  ASSERT_TRUE(index);
+  ASSERT_EQ(2, index->size());
+  ASSERT_EQ(2, index->docs_count());
+  ASSERT_EQ(2, index->live_docs_count());
+
+  // check segment 0
+  {
+    auto& segment = index[0];
+    ASSERT_EQ(1, segment.size());
+    ASSERT_EQ(1, segment.docs_count());
+    ASSERT_EQ(1, segment.live_docs_count());
+
+    std::unordered_set<irs::string_ref> expectedName = { "A" };
+    const auto* column = segment.column_reader("name");
+    ASSERT_NE(nullptr, column);
+    auto values = column->values();
+    ASSERT_EQ(expectedName.size(), segment.docs_count()); // total count of documents
+    auto terms = segment.field("same");
+    ASSERT_NE(nullptr, terms);
+    auto termItr = terms->iterator();
+    ASSERT_TRUE(termItr->next());
+
+    irs::bytes_ref actual_value;
+    for (auto docsItr = termItr->postings(iresearch::flags()); docsItr->next();) {
+      ASSERT_TRUE(values(docsItr->value(), actual_value));
+      ASSERT_EQ(1, expectedName.erase(irs::to_string<irs::string_ref>(actual_value.c_str())));
+    }
+
+    ASSERT_TRUE(expectedName.empty());
+  }
+
+  // check segment 1
+  {
+    auto& segment = index[1];
+    ASSERT_EQ(1, segment.size());
+    ASSERT_EQ(1, segment.docs_count());
+    ASSERT_EQ(1, segment.live_docs_count());
+
+    std::unordered_set<irs::string_ref> expectedName = { "B" };
+    const auto* column = segment.column_reader("name");
+    ASSERT_NE(nullptr, column);
+    auto values = column->values();
+    ASSERT_EQ(expectedName.size(), segment.docs_count()); // total count of documents
+    auto terms = segment.field("same");
+    ASSERT_NE(nullptr, terms);
+    auto termItr = terms->iterator();
+    ASSERT_TRUE(termItr->next());
+
+    irs::bytes_ref actual_value;
+    for (auto docsItr = termItr->postings(iresearch::flags()); docsItr->next();) {
+      ASSERT_TRUE(values(docsItr->value(), actual_value));
+      ASSERT_EQ(1, expectedName.erase(irs::to_string<irs::string_ref>(actual_value.c_str())));
+    }
+
+    ASSERT_TRUE(expectedName.empty());
+  }
+}
+
+INSTANTIATE_TEST_CASE_P(
+  format_13_test,
+  format_13_test_case,
+  ::testing::Values(
+    &tests::rot13_cipher_directory<&tests::memory_directory, 16>,
+    &tests::rot13_cipher_directory<&tests::fs_directory, 16>,
+    &tests::rot13_cipher_directory<&tests::mmap_directory, 16>
+  ),
+  tests::directory_test_case_base::to_string
+);
+
+// -----------------------------------------------------------------------------
+// --SECTION--                                                     generic tests
+// -----------------------------------------------------------------------------
+
+using tests::format_test_case;
+
+INSTANTIATE_TEST_CASE_P(
+  format_13_test,
+  format_test_case,
+  ::testing::Combine(
+    ::testing::Values(
+      &tests::rot13_cipher_directory<&tests::memory_directory, 16>,
+      &tests::rot13_cipher_directory<&tests::fs_directory, 16>,
+      &tests::rot13_cipher_directory<&tests::mmap_directory, 16>,
+      &tests::rot13_cipher_directory<&tests::memory_directory, 7>,
+      &tests::rot13_cipher_directory<&tests::fs_directory, 7>,
+      &tests::rot13_cipher_directory<&tests::mmap_directory, 7>
+    ),
+    ::testing::Values("1_3")
+  ),
+  tests::to_string
+);
+
+
+NS_END
diff --git a/3rdParty/iresearch/tests/formats/formats_test_case_base.hpp b/3rdParty/iresearch/tests/formats/formats_test_case_base.hpp
index 0efb70dd7600..b8cc5643862a 100644
--- a/3rdParty/iresearch/tests/formats/formats_test_case_base.hpp
+++ b/3rdParty/iresearch/tests/formats/formats_test_case_base.hpp
@@ -80,6 +80,10 @@ class format_test_case : public index_test_base {
       offs_.clear();
     }
 
+    virtual void reset() override {
+      assert(false); // unsupported
+    }
+
    private:
     friend class postings;
 
diff --git a/3rdParty/iresearch/tests/index/assert_format.cpp b/3rdParty/iresearch/tests/index/assert_format.cpp
index 86d1cdfe12dc..ddfe80371cc3 100644
--- a/3rdParty/iresearch/tests/index/assert_format.cpp
+++ b/3rdParty/iresearch/tests/index/assert_format.cpp
@@ -173,9 +173,8 @@ void index_segment::add(const ifield& f) {
   while (stream.next()) {
     tests::term& trm = fld.add(term->value());
     tests::posting& pst = trm.add(doc_id);
-
-    pst.add(fld.pos, fld.offs, attrs);
     fld.pos += inc->value;
+    pst.add(fld.pos, fld.offs, attrs);
     empty = false;
   }
 
@@ -348,7 +347,7 @@ class doc_iterator : public irs::doc_iterator {
 
   virtual bool next() override {
     if (next_ == data_.postings.end()) {
-      doc_.value = irs::type_limits<irs::type_t::doc_id_t>::invalid();
+      doc_.value = irs::type_limits<irs::type_t::doc_id_t>::eof();
       return false;
     }
 
@@ -400,6 +399,7 @@ class doc_iterator : public irs::doc_iterator {
 
     bool next() override {
       if ( next_ == owner_.prev_->positions().end() ) {
+        value_ = irs::type_limits<irs::type_t::pos_t>::eof();
         return false;
       }
 
@@ -412,6 +412,10 @@ class doc_iterator : public irs::doc_iterator {
       return true;
     }
 
+    virtual void reset() override {
+      assert(false); // unsupported
+    }
+
    private:
     std::set<tests::position>::const_iterator next_;
     irs::offset offs_;
@@ -680,6 +684,8 @@ void assert_term(
 
   ASSERT_EQ(expected_docs->attributes().features() & requested_features, actual_docs->attributes().features() & requested_features);
 
+  ASSERT_TRUE(!irs::doc_limits::valid(expected_docs->value()));
+  ASSERT_TRUE(!irs::doc_limits::valid(actual_docs->value()));
   // check docs
   for (; expected_docs->next();) {
     ASSERT_TRUE(actual_docs->next());
@@ -711,7 +717,8 @@ void assert_term(
         auto& expected_pay = expected_pos->attributes().get<irs::payload>();
         auto& actual_pay = actual_pos->attributes().get<irs::payload>();
         if (expected_pay) ASSERT_FALSE(!actual_pay);
-
+        ASSERT_TRUE(!irs::pos_limits::valid(expected_pos->value()));
+        ASSERT_TRUE(!irs::pos_limits::valid(actual_pos->value()));
         for (; expected_pos->next();) {
           ASSERT_TRUE(actual_pos->next());
           ASSERT_EQ(expected_pos->value(), actual_pos->value());
@@ -725,13 +732,15 @@ void assert_term(
             ASSERT_EQ(expected_pay->value, actual_pay->value);
           }
         }
-
         ASSERT_FALSE(actual_pos->next());
+        ASSERT_TRUE(irs::pos_limits::eof(expected_pos->value()));
+        ASSERT_TRUE(irs::pos_limits::eof(actual_pos->value()));
       }
     }
   }
-
   ASSERT_FALSE(actual_docs->next());
+  ASSERT_TRUE(irs::doc_limits::eof(expected_docs->value()));
+  ASSERT_TRUE(irs::doc_limits::eof(actual_docs->value()));
 }
 
 void assert_terms_next(
diff --git a/3rdParty/iresearch/tests/index/index_levenshtein_tests.cpp b/3rdParty/iresearch/tests/index/index_levenshtein_tests.cpp
index 70bcbc1b136a..da7e7f7f8918 100644
--- a/3rdParty/iresearch/tests/index/index_levenshtein_tests.cpp
+++ b/3rdParty/iresearch/tests/index/index_levenshtein_tests.cpp
@@ -44,16 +44,26 @@ class levenshtein_automaton_index_test_case : public tests::index_test_base {
         auto actual_terms = fields->value().iterator(matcher);
         ASSERT_NE(nullptr, actual_terms);
 
+        auto& payload = actual_terms->attributes().get<irs::payload>();
+        ASSERT_NE(nullptr, payload);
+        ASSERT_EQ(1, payload->value.size());
+
         while (expected_terms->next()) {
           auto& expected_term = expected_terms->value();
+
           auto edit_distance = irs::edit_distance(expected_term, target);
           if (edit_distance > description.max_distance()) {
             continue;
           }
 
+          SCOPED_TRACE(testing::Message("Expected term: '")
+            << irs::ref_cast<char>(expected_term));
+
           ASSERT_TRUE(actual_terms->next());
           auto& actual_term = actual_terms->value();
           ASSERT_EQ(expected_term, actual_term);
+          ASSERT_EQ(1, payload->value.size());
+          ASSERT_EQ(edit_distance, payload->value[0]);
         }
       }
     }
diff --git a/3rdParty/iresearch/tests/index/index_tests.cpp b/3rdParty/iresearch/tests/index/index_tests.cpp
index 61d0c1454546..2b9f189dd3f0 100644
--- a/3rdParty/iresearch/tests/index/index_tests.cpp
+++ b/3rdParty/iresearch/tests/index/index_tests.cpp
@@ -315,6 +315,22 @@ void payloaded_json_field_factory(
   }
 }
 
+void normalized_string_json_field_factory(
+  tests::document& doc,
+  const std::string& name,
+  const json_doc_generator::json_value& data) {
+  static irs::flags norm{ irs::norm::type() };
+  if (json_doc_generator::ValueType::STRING == data.vt) {
+    doc.insert(std::make_shared<templates::string_field>(
+      irs::string_ref(name),
+      data.str,
+      norm
+      ));
+  } else {
+    generic_json_field_factory(doc, name, data);
+  }
+}
+
 std::string to_string(
     const testing::TestParamInfo<index_test_context>& info
 ) {
@@ -2450,21 +2466,21 @@ TEST_P(index_test_case, europarl_docs_automaton) {
 
   // prefix
   {
-    auto acceptor = irs::from_wildcard<char>("forb%");
+    auto acceptor = irs::from_wildcard("forb%");
     irs::automaton_table_matcher matcher(acceptor, fst::fsa::kRho);
     assert_index(0, &matcher);
   }
 
   // part
   {
-    auto acceptor = irs::from_wildcard<char>("%ende%");
+    auto acceptor = irs::from_wildcard("%ende%");
     irs::automaton_table_matcher matcher(acceptor, fst::fsa::kRho);
     assert_index(0, &matcher);
   }
 
   // suffix
   {
-    auto acceptor = irs::from_wildcard<char>("%ione");
+    auto acceptor = irs::from_wildcard("%ione");
     irs::automaton_table_matcher matcher(acceptor, fst::fsa::kRho);
     assert_index(0, &matcher);
   }
@@ -13235,6 +13251,29 @@ INSTANTIATE_TEST_CASE_P(
   tests::to_string
 );
 
+// Separate definition as MSVC parser fails to do conditional defines in macro expansion
+NS_LOCAL
+#if defined(IRESEARCH_SSE2)
+const auto index_test_case_13_values = ::testing::Values("1_3", "1_3simd");
+#else
+const auto index_test_case_13_values = ::testing::Values("1_3");
+#endif
+NS_END
+
+INSTANTIATE_TEST_CASE_P(
+  index_test_13,
+  index_test_case,
+  ::testing::Combine(
+    ::testing::Values(
+      &tests::rot13_cipher_directory<&tests::memory_directory, 16>,
+      &tests::rot13_cipher_directory<&tests::fs_directory, 16>,
+      &tests::rot13_cipher_directory<&tests::mmap_directory, 16>
+    ),
+    index_test_case_13_values
+  ),
+  tests::to_string
+);
+
 class index_test_case_10 : public tests::index_test_base { };
 
 TEST_P(index_test_case_10, commit_payload) {
diff --git a/3rdParty/iresearch/tests/index/index_tests.hpp b/3rdParty/iresearch/tests/index/index_tests.hpp
index b31d72868d85..99fbb1cc3162 100644
--- a/3rdParty/iresearch/tests/index/index_tests.hpp
+++ b/3rdParty/iresearch/tests/index/index_tests.hpp
@@ -462,6 +462,12 @@ void payloaded_json_field_factory(
   const json_doc_generator::json_value& data
 );
 
+void normalized_string_json_field_factory(
+  tests::document& doc,
+  const std::string& name,
+  const json_doc_generator::json_value& data
+);
+
 NS_END // tests
 
 #endif // IRESEARCH_INDEX_TESTS_H
diff --git a/3rdParty/iresearch/tests/index/merge_writer_tests.cpp b/3rdParty/iresearch/tests/index/merge_writer_tests.cpp
index c050e15d72ee..43ce91e6c97c 100644
--- a/3rdParty/iresearch/tests/index/merge_writer_tests.cpp
+++ b/3rdParty/iresearch/tests/index/merge_writer_tests.cpp
@@ -1319,7 +1319,7 @@ TEST_F(merge_writer_tests, test_merge_writer) {
       auto& field = terms->meta();
       auto& features = STRING_FIELD_FEATURES;
       size_t frequency = 1;
-      std::vector<uint32_t> position = { 0 };
+      std::vector<uint32_t> position = { irs::pos_limits::min() };
       std::unordered_map<iresearch::bytes_ref, std::unordered_set<iresearch::doc_id_t>> expected_terms;
 
       expected_terms[iresearch::ref_cast<iresearch::byte_type>(iresearch::string_ref("string1_data"))].emplace(1);
@@ -1350,7 +1350,7 @@ TEST_F(merge_writer_tests, test_merge_writer) {
       auto& field = terms->meta();
       auto& features = TEXT_FIELD_FEATURES;
       size_t frequency = 1;
-      std::vector<uint32_t> position = { 0 };
+      std::vector<uint32_t> position = { irs::pos_limits::min() };
       std::unordered_map<iresearch::bytes_ref, std::unordered_set<iresearch::doc_id_t>> expected_terms;
 
       expected_terms[iresearch::ref_cast<iresearch::byte_type>(iresearch::string_ref("text1_data"))].emplace(1);
@@ -1660,7 +1660,7 @@ TEST_F(merge_writer_tests, test_merge_writer) {
       auto& field = terms->meta();
       auto& features = STRING_FIELD_FEATURES;
       size_t frequency = 1;
-      std::vector<uint32_t> position = { 0 };
+      std::vector<uint32_t> position = { irs::pos_limits::min() };
       std::unordered_map<iresearch::bytes_ref, std::unordered_set<iresearch::doc_id_t>> expected_terms;
 
       expected_terms[iresearch::ref_cast<iresearch::byte_type>(iresearch::string_ref("string3_data"))].emplace(1);
@@ -1691,7 +1691,7 @@ TEST_F(merge_writer_tests, test_merge_writer) {
       auto& field = terms->meta();
       auto& features = TEXT_FIELD_FEATURES;
       size_t frequency = 1;
-      std::vector<uint32_t> position = { 0 };
+      std::vector<uint32_t> position = { irs::pos_limits::min() };
       std::unordered_map<iresearch::bytes_ref, std::unordered_set<iresearch::doc_id_t>> expected_terms;
 
       expected_terms[iresearch::ref_cast<iresearch::byte_type>(iresearch::string_ref("text3_data"))].emplace(1);
@@ -2059,7 +2059,7 @@ TEST_F(merge_writer_tests, test_merge_writer) {
     auto& field = terms->meta();
     auto& features = STRING_FIELD_FEATURES;
     size_t frequency = 1;
-    std::vector<uint32_t> position = { 0 };
+    std::vector<uint32_t> position = { irs::pos_limits::min() };
     std::unordered_map<iresearch::bytes_ref, std::unordered_set<iresearch::doc_id_t>> expected_terms;
 
     expected_terms[iresearch::ref_cast<iresearch::byte_type>(iresearch::string_ref("string1_data"))].emplace(1);
@@ -2091,7 +2091,7 @@ TEST_F(merge_writer_tests, test_merge_writer) {
     auto& field = terms->meta();
     auto& features = TEXT_FIELD_FEATURES;
     size_t frequency = 1;
-    std::vector<uint32_t> position = { 0 };
+    std::vector<uint32_t> position = { irs::pos_limits::min() };
     std::unordered_map<iresearch::bytes_ref, std::unordered_set<iresearch::doc_id_t>> expected_terms;
 
     expected_terms[iresearch::ref_cast<iresearch::byte_type>(iresearch::string_ref("text1_data"))].emplace(1);
diff --git a/3rdParty/iresearch/tests/iql/query_builder_test.cpp b/3rdParty/iresearch/tests/iql/query_builder_test.cpp
index 25f4d0a38d93..f42e831cb785 100644
--- a/3rdParty/iresearch/tests/iql/query_builder_test.cpp
+++ b/3rdParty/iresearch/tests/iql/query_builder_test.cpp
@@ -76,8 +76,7 @@ namespace tests {
       }
       virtual void prepare_score(iresearch::byte_type* score) const override {}
       virtual void prepare_stats(irs::byte_type*) const override { }
-      virtual void add(iresearch::byte_type* dst, const iresearch::byte_type* src) const override {}
-      virtual void merge(irs::byte_type* dst_buf, const irs::byte_type** src_start, const size_t size, size_t offset) const { }
+      virtual void merge(irs::byte_type* dst_buf, const irs::byte_type** src_start, const size_t size, size_t offset) const override { }
       virtual bool less(const iresearch::byte_type* lhs, const iresearch::byte_type* rhs) const override { throw std::bad_function_call(); }
       std::pair<size_t, size_t> score_size() const override {
         return std::make_pair(size_t(0), size_t(0));
diff --git a/3rdParty/iresearch/tests/resources/ngram_similarity.json b/3rdParty/iresearch/tests/resources/ngram_similarity.json
new file mode 100644
index 000000000000..cca911f18c85
--- /dev/null
+++ b/3rdParty/iresearch/tests/resources/ngram_similarity.json
@@ -0,0 +1,18 @@
+[
+  { "seq" : 1, "field": [ "at", "tl", "la", "as", "ss", "si", "ia", "an" ] },
+  { "seq" : 2, "field": [ "at", "tl", "la", "as" ] },
+  { "seq" : 3, "field": [ "la", "as", "ss", "si" ] },
+  { "seq" : 4, "field": [ "pa", "al", "la", "as"] },
+  { "seq" : 5, "field": [ "pa", "al", "la", "as", "sa", "at", "tl", "la", "as", "ss", "si", "ia", "an", "at", "tl", "la", "as"] },
+  { "seq" : 6, "field": [ "la", "ss", "as", "si" ] },
+  { "seq" : 7, "field": [ "la", "al", "ll", "ss" ] },
+  { "seq" : 8, "field": [ "at", "ss", "at", "tl", "la", "ss",  "at", "tl", "la", "as"] },
+  { "seq" : 9, "field": [ "at", "ss", "at", "tl"] },
+  { "seq" : 10, "field": [ "at", "at", "ss", "at", "at", "tl"] },
+  { "seq" : 11, "field": ["at", "la", "ll", "ll", "ll", "ll"] },
+  { "seq" : 12, "field": ["at", "la", "ll", "ll", "ss", "ll"] },
+  { "seq" : 13, "field": ["at", "la", "as", "tl", "as"] },
+  { "seq" : 14, "field": ["at", "ll", "as", "at", "at"] },
+  { "seq" : 15, "field": ["ll", "at", "at", "at", "at"] },
+  { "seq" : 16, "field": ["ll", "as", "la", "tl", "at"] }
+]
diff --git a/3rdParty/iresearch/tests/resources/phrase_sequential.json b/3rdParty/iresearch/tests/resources/phrase_sequential.json
index 023bc67a6a8d..36f2b015d8c9 100644
--- a/3rdParty/iresearch/tests/resources/phrase_sequential.json
+++ b/3rdParty/iresearch/tests/resources/phrase_sequential.json
@@ -15,5 +15,13 @@
   {"name":"O","phrase":"jumps high jumps high hotdog" },
   {"name":"P","phrase":"jumps high jumps left jumps right jumps down jumps back" },
   {"name":"Q","phrase":"jumps high jumps left jumps right jumps down walks back" },
-  {"name":"R","phrase":"jumps high jumps left jumps right walks down walks back" }
+  {"name":"R","phrase":"jumps high jumps left jumps right walks down walks back" },
+  {"name":"S","phrase":"quick quilt brown fox moved"},
+  {"name":"T","phrase":"quick brother fox brown moved"},
+  {"name":"U","phrase":"quick brown forward brother moved"},
+  {"name":"V","phrase":"quilt brother fox moved"},
+  {"name":"W","phrase":"quilt brown forward quick brother moved"},
+  {"name":"X","phrase":"quilt quick brother forward brother moved"},
+  {"name":"Y","phrase":"quilt brother forward moved"},
+  {"name":"Z","phrase":"the end of an endless story is a good golden google god likes gorillas and goes like a monkey"}
 ]
diff --git a/3rdParty/iresearch/tests/resources/simple_sequential_utf8.json b/3rdParty/iresearch/tests/resources/simple_sequential_utf8.json
new file mode 100644
index 000000000000..2b0b826acb81
--- /dev/null
+++ b/3rdParty/iresearch/tests/resources/simple_sequential_utf8.json
@@ -0,0 +1,34 @@
+[
+  {"name":"A","seq":0,"same":"xyz", "value":100, "duplicated":"abcd", "prefix":"abcd", "utf8": "пуй" },
+  {"name":"B","seq":1,"same":"xyz", "value":101, "duplicated":"vczc", "utf8": "хублот" },
+  {"name":"C","seq":2,"same":"xyz", "value":123, "duplicated":"vczc", "utf8": "проглот" },
+  {"name":"D","seq":3,"same":"xyz", "value":12, "prefix":"abcde"},
+  {"name":"E","seq":4,"same":"xyz", "value":100, "duplicated":"abcd"},
+  {"name":"F","seq":5,"same":"xyz", "value":1234 },
+  {"name":"G","seq":6,"same":"xyz", "value":100 },
+  {"name":"H","seq":7,"same":"xyz", "value":123, "duplicated":"vczc"},
+  {"name":"I","seq":8,"same":"xyz", "value":100, "prefix":"bcd" },
+  {"name":"J","seq":9,"same":"xyz", "value":100 },
+  {"name":"K","seq":10,"same":"xyz","value":12, "duplicated":"abcd"},
+  {"name":"L","seq":11,"same":"xyz","value":95 },
+  {"name":"M","seq":12,"same":"xyz","value":90.564 },
+  {"name":"N","seq":13,"same":"xyz","value":1, "duplicated":"vczc", "utf8": "обама"},
+  {"name":"O","seq":14,"same":"xyz","value":0 },
+  {"name":"P","seq":15,"same":"xyz","value":50, "prefix":"abde"},
+  {"name":"Q","seq":16,"same":"xyz", "value":-32.5, "duplicated":"vczc", "utf8": "трамп"},
+  {"name":"R","seq":17,"same":"xyz"},
+  {"name":"S","seq":18,"same":"xyz", "duplicated":"vczc"},
+  {"name":"T","seq":19,"same":"xyz"},
+  {"name":"U","seq":20,"same":"xyz", "prefix":"abc", "duplicated":"abcd"},
+  {"name":"V","seq":21,"same":"xyz"},
+  {"name":"W","seq":22,"same":"xyz"},
+  {"name":"X","seq":23,"same":"xyz", "duplicated":"vczc", "prefix":"bateradsfsfasdf", "utf8": "меркель" },
+  {"name":"Y","seq":24,"same":"xyz"},
+  {"name":"Z","seq":25,"same":"xyz", "prefix":"abcdrer", "utf8":"вий" },
+  {"name":"~","seq":26,"same":"xyz", "duplicated":"abcd"},
+  {"name":"!","seq":27,"same":"xyz"},
+  {"name":"@","seq":28,"same":"xyz", "prefix":"ahtrtrt"},
+  {"name":"#","seq":29,"same":"xyz"},
+  {"name":"$","seq":30,"same":"xyz", "duplicated":"abcd", "prefix":"abcy" },
+  {"name":"%","seq":31,"same":"xyz", "prefix":"abcy"}
+]
diff --git a/3rdParty/iresearch/tests/search/bm25_test.cpp b/3rdParty/iresearch/tests/search/bm25_test.cpp
index 3456ea7f82a2..4b17df1b87c6 100644
--- a/3rdParty/iresearch/tests/search/bm25_test.cpp
+++ b/3rdParty/iresearch/tests/search/bm25_test.cpp
@@ -233,8 +233,8 @@ TEST_P(bm25_test, test_phrase) {
   {
     irs::by_phrase filter;
     filter.field("phrase_anl")
-          .push_back("jumps")
-          .push_back("high");
+          .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("jumps"))})
+          .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("high"))});
 
     std::multimap<irs::bstring, std::string, decltype(comparer)> sorted(comparer);
 
@@ -823,7 +823,7 @@ TEST_P(bm25_test, test_query) {
   {
     irs::by_phrase filter;
 
-    filter.field("field").push_back("7");
+    filter.field("field").push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("7"))});
 
     std::multimap<irs::bstring, uint64_t, decltype(comparer)> sorted(comparer);
     std::vector<std::pair<float_t, uint64_t>> expected = {
diff --git a/3rdParty/iresearch/tests/search/boolean_filter_tests.cpp b/3rdParty/iresearch/tests/search/boolean_filter_tests.cpp
index b5bc3df6d988..910d131b609d 100644
--- a/3rdParty/iresearch/tests/search/boolean_filter_tests.cpp
+++ b/3rdParty/iresearch/tests/search/boolean_filter_tests.cpp
@@ -109,11 +109,8 @@ struct basic_sort : irs::sort {
       return nullptr; // do not need to collect stats
     }
 
-    void add(irs::byte_type* dst, const irs::byte_type* src) const override {
-      score_cast<size_t>(dst) += score_cast<size_t>(src);
-    }
-
-    virtual void  merge(irs::byte_type* dst, const irs::byte_type** src_start, const size_t size, size_t offset) const {
+    virtual void merge(irs::byte_type* dst, const irs::byte_type** src_start,
+                       const size_t size, size_t offset) const override {
       score_cast<size_t>(dst + offset) = 0;
       for (size_t i = 0; i < size; ++i) {
         score_cast<size_t>(dst + offset) += score_cast<size_t>(src_start[i]  + offset);
diff --git a/3rdParty/iresearch/tests/search/filter_test_case_base.hpp b/3rdParty/iresearch/tests/search/filter_test_case_base.hpp
index 7feea06ea966..b2ce7d13bb50 100644
--- a/3rdParty/iresearch/tests/search/filter_test_case_base.hpp
+++ b/3rdParty/iresearch/tests/search/filter_test_case_base.hpp
@@ -222,13 +222,7 @@ struct custom_sort: public irs::sort {
       return irs::memory::make_unique<collector>(sort_);
     }
 
-    virtual void add(irs::byte_type* dst, const irs::byte_type* src) const override {
-      if (sort_.scorer_add) {
-        sort_.scorer_add(score_cast(dst), score_cast(src));
-      }
-    }
-
-    virtual void  merge(irs::byte_type* dst, const irs::byte_type** src_start, const size_t size, size_t offset) const {
+    virtual void  merge(irs::byte_type* dst, const irs::byte_type** src_start, const size_t size, size_t offset) const override {
       score_cast(dst + offset) = irs::type_limits<irs::type_t::doc_id_t>::invalid();;
       for (size_t i = 0; i < size; ++i) {
         if (sort_.scorer_add) {
@@ -249,7 +243,7 @@ struct custom_sort: public irs::sort {
   std::function<void(const irs::sub_reader&, const irs::term_reader&, const irs::attribute_view&)> collector_collect_term;
   std::function<void(irs::byte_type*, const irs::index_reader&, const irs::sort::field_collector*, const irs::sort::term_collector*)> collectors_collect_;
   std::function<irs::sort::field_collector::ptr()> prepare_field_collector_;
-  std::pair<irs::score_ctx_ptr, irs::score_f>(*prepare_scorer)(const irs::sub_reader&, const irs::term_reader&, const irs::byte_type*, const irs::attribute_view&){};
+  std::function<std::pair<irs::score_ctx_ptr, irs::score_f>(const irs::sub_reader&, const irs::term_reader&, const irs::byte_type*, const irs::attribute_view&)> prepare_scorer;
   std::function<irs::sort::term_collector::ptr()> prepare_term_collector_;
   std::function<void(irs::doc_id_t&, const irs::doc_id_t&)> scorer_add;
   std::function<bool(const irs::doc_id_t&, const irs::doc_id_t&)> scorer_less;
@@ -372,7 +366,7 @@ struct frequency_sort: public irs::sort {
       return irs::memory::make_unique<term_collector>();
     }
 
-    virtual void  merge(irs::byte_type* dst_buf, const irs::byte_type** src_start, const size_t size, size_t offset) const {
+    virtual void merge(irs::byte_type* dst_buf, const irs::byte_type** src_start, const size_t size, size_t offset) const override {
       auto& score = score_cast(dst_buf + offset);
       score.id = irs::type_limits<irs::type_t::doc_id_t>::invalid();
       score.value = std::numeric_limits<double>::infinity();
@@ -391,21 +385,6 @@ struct frequency_sort: public irs::sort {
       }
     }
 
-    virtual void add(irs::byte_type* dst_buf, const irs::byte_type* src_buf) const override {
-      auto& dst = score_cast(dst_buf);
-      auto& src = score_cast(src_buf);
-
-      ASSERT_TRUE(src.prepared);
-      ASSERT_TRUE(dst.prepared);
-
-      if (std::numeric_limits<double>::infinity()) {
-        dst.id = src.id;
-        dst.value = 0;
-      }
-
-      dst.value += src.value;
-    }
-
     virtual bool less(const irs::byte_type* lhs_buf, const irs::byte_type* rhs_buf) const override {
       auto& lhs = score_cast(lhs_buf);
       auto& rhs = score_cast(rhs_buf);
diff --git a/3rdParty/iresearch/tests/search/ngram_similarity_filter_tests.cpp b/3rdParty/iresearch/tests/search/ngram_similarity_filter_tests.cpp
new file mode 100644
index 000000000000..69ebc443daa5
--- /dev/null
+++ b/3rdParty/iresearch/tests/search/ngram_similarity_filter_tests.cpp
@@ -0,0 +1,1191 @@
+////////////////////////////////////////////////////////////////////////////////
+/// DISCLAIMER
+///
+/// Copyright 2020 ArangoDB GmbH, Cologne, Germany
+///
+/// Licensed under the Apache License, Version 2.0 (the "License");
+/// you may not use this file except in compliance with the License.
+/// You may obtain a copy of the License at
+///
+///     http://www.apache.org/licenses/LICENSE-2.0
+///
+/// Unless required by applicable law or agreed to in writing, software
+/// distributed under the License is distributed on an "AS IS" BASIS,
+/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+/// See the License for the specific language governing permissions and
+/// limitations under the License.
+///
+/// Copyright holder is ArangoDB GmbH, Cologne, Germany
+///
+/// @author Andrei Lobov
+////////////////////////////////////////////////////////////////////////////////
+
+#include "tests_shared.hpp"
+#include "filter_test_case_base.hpp"
+#include "search/ngram_similarity_filter.hpp"
+#include "search/tfidf.hpp"
+#include "search/bm25.hpp"
+#include "utils/ngram_match_utils.hpp"
+
+#include <functional>
+
+NS_BEGIN(tests)
+
+// ----------------------------------------------------------------------------
+// --SECTION--                            by_ngram_similarity filter base tests
+// ----------------------------------------------------------------------------
+TEST(ngram_similarity_base_test, ctor) {
+  irs::by_ngram_similarity q;
+  ASSERT_EQ(irs::by_ngram_similarity::type(), q.type());
+  ASSERT_TRUE(q.empty());
+  ASSERT_EQ(0, q.size());
+  ASSERT_EQ(q.begin(), q.end());
+  ASSERT_EQ(irs::no_boost(), q.boost());
+  ASSERT_DOUBLE_EQ(1., q.threshold());
+  ASSERT_EQ("", q.field());
+
+
+  auto& features = irs::by_ngram_similarity::features();
+  ASSERT_EQ(2, features.size());
+  ASSERT_TRUE(features.check<irs::frequency>());
+  ASSERT_TRUE(features.check<irs::position>());
+}
+
+TEST(ngram_similarity_base_test, push_back_insert_clear) {
+  irs::by_ngram_similarity q;
+
+  // push_back
+  {
+    q.push_back("1");
+    const std::string s2 = "2";
+    q.push_back(s2);
+    const irs::bstring s3 = irs::ref_cast<irs::byte_type>(irs::string_ref("3"));
+    q.push_back(s3);
+    ASSERT_FALSE(q.empty());
+    ASSERT_EQ(3, q.size());
+
+    // check elements via iterators
+    {
+      auto it = q.begin();
+      ASSERT_NE(q.end(), it);
+      ASSERT_EQ(irs::ref_cast<irs::byte_type>(irs::string_ref("1")), *it);
+      ++it;
+      ASSERT_NE(q.end(), it);
+      ASSERT_EQ(irs::ref_cast<irs::byte_type>(irs::string_ref("2")), *it);
+      ++it;
+      ASSERT_NE(q.end(), it);
+      ASSERT_EQ(irs::ref_cast<irs::byte_type>(irs::string_ref("3")), *it);
+      ++it;
+      ASSERT_EQ(q.end(), it);
+    }
+  }
+
+  q.clear();
+  ASSERT_TRUE(q.empty());
+  ASSERT_EQ(0, q.size());
+  ASSERT_EQ(q.begin(), q.end());
+}
+
+TEST(ngram_similarity_base_test, boost) {
+  // no boost
+  {
+    // no terms no field
+    {
+      irs::by_ngram_similarity q;
+
+      auto prepared = q.prepare(irs::sub_reader::empty());
+      ASSERT_EQ(irs::no_boost(), prepared->boost());
+    }
+
+
+    // simple disjunction
+    {
+      irs::by_ngram_similarity q;
+      q.field("field").push_back("1").push_back("2").threshold(0.5f);
+
+      auto prepared = q.prepare(irs::sub_reader::empty());
+      ASSERT_EQ(irs::no_boost(), prepared->boost());
+    }
+
+    // multiple terms
+    {
+      irs::by_ngram_similarity q;
+      q.field("field").push_back("1").push_back("2").push_back("3").push_back("4").threshold(0.5f);
+
+      auto prepared = q.prepare(irs::sub_reader::empty());
+      ASSERT_EQ(irs::no_boost(), prepared->boost());
+    }
+  }
+
+  // with boost
+  {
+    iresearch::boost_t boost = 1.5f;
+
+    // no terms, return empty query
+    {
+      irs::by_ngram_similarity q;
+      q.boost(boost);
+
+      auto prepared = q.prepare(irs::sub_reader::empty());
+      ASSERT_EQ(irs::no_boost(), prepared->boost());
+    }
+
+    // simple disjunction
+    {
+      irs::by_ngram_similarity q;
+      q.field("field").push_back("1").push_back("2").threshold(0.5f);
+      q.boost(boost);
+
+      auto prepared = q.prepare(irs::sub_reader::empty());
+      ASSERT_EQ(boost, prepared->boost());
+    }
+
+    // multiple terms
+    {
+      irs::by_ngram_similarity q;
+      q.field("field").push_back("1").push_back("2").push_back("3").push_back("4")
+        .threshold(0.5f).boost(boost);
+
+      auto prepared = q.prepare(irs::sub_reader::empty());
+      ASSERT_EQ(boost, prepared->boost());
+    }
+  }
+}
+
+TEST(ngram_similarity_base_test, equal) {
+  ASSERT_EQ(irs::by_ngram_similarity(), irs::by_ngram_similarity());
+
+  {
+    irs::by_ngram_similarity q0;
+    q0.field("a");
+    q0.push_back("1");
+    q0.push_back("2");
+    q0.threshold(0.5);
+
+    irs::by_ngram_similarity q1;
+    q1.field("a");
+    q1.push_back("1");
+    q1.push_back("2");
+    q1.threshold(0.5);
+    ASSERT_EQ(q0, q1);
+
+    // different threshold
+    irs::by_ngram_similarity q2;
+    q2.field("a");
+    q2.push_back("1");
+    q2.push_back("2");
+    q2.threshold(0.25);
+    ASSERT_NE(q0, q2);
+
+    // different terms
+    irs::by_ngram_similarity q3;
+    q3.field("a");
+    q3.push_back("1");
+    q3.push_back("3");
+    q3.threshold(0.5);
+    ASSERT_NE(q0, q3);
+
+    // different terms count (less)
+    irs::by_ngram_similarity q4;
+    q4.field("a");
+    q4.push_back("1");
+    q4.threshold(0.5);
+    ASSERT_NE(q0, q4);
+
+    // different terms count (more)
+    irs::by_ngram_similarity q5;
+    q5.field("a");
+    q5.push_back("1");
+    q5.push_back("2");
+    q5.push_back("2");
+    q5.threshold(0.5);
+    ASSERT_NE(q0, q5);
+
+    //different field
+    irs::by_ngram_similarity q6;
+    q6.field("b");
+    q6.push_back("1");
+    q6.push_back("2");
+    q6.threshold(0.5);
+    ASSERT_NE(q0, q6);
+  }
+}
+
+// ----------------------------------------------------------------------------
+// --SECTION--                         by_ngram_similarity filter matcher tests
+// ----------------------------------------------------------------------------
+class ngram_similarity_filter_test_case : public tests::filter_test_case_base {
+};
+
+
+TEST_P(ngram_similarity_filter_test_case, check_matcher_1) {
+  // sequence 1 3 4 ______ 2 -> longest is 134 not 12
+  // add segment
+  {
+    tests::json_doc_generator gen(
+      "[{ \"seq\" : 1, \"field\": [ \"1\", \"3\", \"4\", \"5\", \"6\", \"7\", \"2\"] }]",
+      &tests::generic_json_field_factory);
+    add_segment(gen);
+  }
+
+  auto rdr = open_reader();
+  irs::order order;
+  auto& scorer = order.add<tests::sort::custom_sort>(false);
+  irs::by_ngram_similarity filter;
+  filter.threshold(0.5).field("field").push_back("1")
+    .push_back("2").push_back("3").push_back("4");
+
+  auto prepared_order = order.prepare();
+  auto prepared = filter.prepare(rdr, prepared_order);
+  size_t count = 0;
+  for (const auto& sub : rdr) {
+    auto docs = prepared->execute(sub, prepared_order);
+    auto& doc = docs->attributes().get<irs::document>();
+    auto& boost = docs->attributes().get<irs::filter_boost>();
+    auto& frequency = docs->attributes().get<irs::frequency>();
+    ASSERT_TRUE(bool(doc)); // ensure all iterators contain "document" attribute
+    ASSERT_TRUE(bool(boost));
+    ASSERT_TRUE(docs->next());
+    ASSERT_EQ(docs->value(), doc->value);
+    ASSERT_FALSE(irs::doc_limits::eof(doc->value));
+    ASSERT_DOUBLE_EQ(0.75, boost->value);
+    const irs::string_ref rhs = "134";
+    const irs::string_ref lhs = "1234";
+    ASSERT_DOUBLE_EQ(
+      boost->value,
+      (irs::ngram_similarity<char, true>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 1)));
+    ASSERT_EQ(1, frequency->value);
+    ASSERT_FALSE(docs->next());
+  }
+}
+
+TEST_P(ngram_similarity_filter_test_case, check_matcher_2) {
+  // sequence 1 1 2 2 3 3 4 4 -> longest is 1234  and freq should be 1 not 2 as
+  // this sequence could not be built twice one after another but only
+  // intereaved
+  {
+    tests::json_doc_generator gen(
+      "[{ \"seq\" : 1, \"field\": [ \"1\", \"1\", \"2\", \"2\", \"3\", \"3\", \"4\", \"4\"] }]",
+      &tests::generic_json_field_factory);
+    add_segment(gen);
+  }
+
+  auto rdr = open_reader();
+  irs::order order;
+  auto& scorer = order.add<tests::sort::custom_sort>(false);
+  irs::by_ngram_similarity filter;
+  filter.threshold(0.5).field("field").push_back("1")
+    .push_back("2").push_back("3").push_back("4");
+
+  auto prepared_order = order.prepare();
+  auto prepared = filter.prepare(rdr, prepared_order);
+  size_t count = 0;
+  for (const auto& sub : rdr) {
+    auto docs = prepared->execute(sub, prepared_order);
+    auto& doc = docs->attributes().get<irs::document>();
+    auto& boost = docs->attributes().get<irs::filter_boost>();
+    auto& frequency = docs->attributes().get<irs::frequency>();
+    // ensure all iterators contain  attributes
+    ASSERT_TRUE(bool(doc));
+    ASSERT_TRUE(bool(boost));
+    ASSERT_TRUE(bool(frequency));
+    ASSERT_TRUE(docs->next());
+    ASSERT_EQ(docs->value(), doc->value);
+    ASSERT_FALSE(irs::doc_limits::eof(doc->value));
+    ASSERT_DOUBLE_EQ(1, boost->value);
+    const irs::string_ref rhs = "11223344";
+    const irs::string_ref lhs = "1234";
+    ASSERT_DOUBLE_EQ(
+      boost->value,
+      (irs::ngram_similarity<char, true>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 1)));
+    ASSERT_EQ(1, frequency->value);
+    ASSERT_FALSE(docs->next());
+  }
+}
+
+TEST_P(ngram_similarity_filter_test_case, check_matcher_3) {
+  // sequence 1 2 1 1 3 4 -> longest is 1234  not 134!
+  {
+    tests::json_doc_generator gen(
+      "[{ \"seq\" : 1, \"field\": [ \"1\", \"2\", \"1\", \"1\", \"3\", \"4\"] }]",
+      &tests::generic_json_field_factory);
+    add_segment(gen);
+  }
+
+  auto rdr = open_reader();
+  irs::order order;
+  auto& scorer = order.add<tests::sort::custom_sort>(false);
+  irs::by_ngram_similarity filter;
+  filter.threshold(0.5).field("field").push_back("1")
+    .push_back("2").push_back("3").push_back("4");
+
+  auto prepared_order = order.prepare();
+  auto prepared = filter.prepare(rdr, prepared_order);
+  size_t count = 0;
+  for (const auto& sub : rdr) {
+    auto docs = prepared->execute(sub, prepared_order);
+    auto& doc = docs->attributes().get<irs::document>();
+    auto& boost = docs->attributes().get<irs::filter_boost>();
+    auto& frequency = docs->attributes().get<irs::frequency>();
+    // ensure all iterators contain  attributes
+    ASSERT_TRUE(bool(doc));
+    ASSERT_TRUE(bool(boost));
+    ASSERT_TRUE(bool(frequency));
+    ASSERT_TRUE(docs->next());
+    ASSERT_EQ(docs->value(), doc->value);
+    ASSERT_FALSE(irs::doc_limits::eof(doc->value));
+    ASSERT_DOUBLE_EQ(1, boost->value);
+    const irs::string_ref rhs = "121134";
+    const irs::string_ref lhs = "1234";
+    ASSERT_DOUBLE_EQ(
+      boost->value,
+      (irs::ngram_similarity<char, true>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 1)));
+    ASSERT_EQ(1, frequency->value);
+    ASSERT_FALSE(docs->next());
+  }
+}
+
+TEST_P(ngram_similarity_filter_test_case, check_matcher_4) {
+  // sequence 1 2 1 1 1 1 pattern 1 1 -> longest is 1 1 and frequency is 2
+  {
+    tests::json_doc_generator gen(
+      "[{ \"seq\" : 1, \"field\": [ \"1\", \"2\", \"1\", \"1\", \"1\", \"1\"] }]",
+      &tests::generic_json_field_factory);
+    add_segment(gen);
+  }
+
+  auto rdr = open_reader();
+  irs::order order;
+  auto& scorer = order.add<tests::sort::custom_sort>(false);
+  irs::by_ngram_similarity filter;
+  filter.threshold(0.5).field("field").push_back("1")
+    .push_back("1");
+
+  auto prepared_order = order.prepare();
+  auto prepared = filter.prepare(rdr, prepared_order);
+  size_t count = 0;
+  for (const auto& sub : rdr) {
+    auto docs = prepared->execute(sub, prepared_order);
+    auto& doc = docs->attributes().get<irs::document>();
+    auto& boost = docs->attributes().get<irs::filter_boost>();
+    auto& frequency = docs->attributes().get<irs::frequency>();
+    // ensure all iterators contain  attributes
+    ASSERT_TRUE(bool(doc));
+    ASSERT_TRUE(bool(boost));
+    ASSERT_TRUE(bool(frequency));
+    ASSERT_TRUE(docs->next());
+    ASSERT_EQ(docs->value(), doc->value);
+    ASSERT_FALSE(irs::doc_limits::eof(doc->value));
+    ASSERT_DOUBLE_EQ(1, boost->value);
+    const irs::string_ref rhs = "121111";
+    const irs::string_ref lhs = "11";
+    ASSERT_DOUBLE_EQ(
+        boost->value,
+        (irs::ngram_similarity<char, true>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 1)));
+    ASSERT_EQ(2, frequency->value);
+    ASSERT_FALSE(docs->next());
+  }
+}
+
+TEST_P(ngram_similarity_filter_test_case, check_matcher_5) {
+  // sequence 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 pattern 1 2 1 -> longest is 1 2 1 and frequency is 4
+  {
+    tests::json_doc_generator gen(
+      "[{ \"seq\" : 1, \"field\": [ \"1\", \"2\", \"1\", \"2\", \"1\", "
+      " \"2\", \"1\", \"2\", \"1\", \"2\", \"1\", \"2\", \"1\", \"2\", \"1\"] }]",
+      &tests::generic_json_field_factory);
+    add_segment(gen);
+  }
+
+  auto rdr = open_reader();
+  irs::order order;
+  auto& scorer = order.add<tests::sort::custom_sort>(false);
+  irs::by_ngram_similarity filter;
+  filter.threshold(0.5).field("field").push_back("1")
+    .push_back("2").push_back("1");
+
+  auto prepared_order = order.prepare();
+  auto prepared = filter.prepare(rdr, prepared_order);
+  size_t count = 0;
+  for (const auto& sub : rdr) {
+    auto docs = prepared->execute(sub, prepared_order);
+    auto& doc = docs->attributes().get<irs::document>();
+    auto& boost = docs->attributes().get<irs::filter_boost>();
+    auto& frequency = docs->attributes().get<irs::frequency>();
+    // ensure all iterators contain  attributes
+    ASSERT_TRUE(bool(doc));
+    ASSERT_TRUE(bool(boost));
+    ASSERT_TRUE(bool(frequency));
+    ASSERT_TRUE(docs->next());
+    ASSERT_EQ(docs->value(), doc->value);
+    ASSERT_FALSE(irs::doc_limits::eof(doc->value));
+    ASSERT_DOUBLE_EQ(1, boost->value);
+    const irs::string_ref rhs = "121212121212121";
+    const irs::string_ref lhs = "121";
+    ASSERT_DOUBLE_EQ(
+      boost->value,
+      (irs::ngram_similarity<char, true>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 1)));
+    ASSERT_EQ(4, frequency->value);
+    ASSERT_FALSE(docs->next());
+  }
+}
+
+TEST_P(ngram_similarity_filter_test_case, check_matcher_6) {
+  // sequence 1 1 pattern 1 1 -> longest is 1 1 and frequency is 1
+  // checks seek for second term does not  skips it at all
+  {
+    tests::json_doc_generator gen(
+      "[{ \"seq\" : 1, \"field\": [ \"1\", \"1\"] }]",
+      &tests::generic_json_field_factory);
+    add_segment(gen);
+  }
+
+  auto rdr = open_reader();
+  irs::order order;
+  auto& scorer = order.add<tests::sort::custom_sort>(false);
+  irs::by_ngram_similarity filter;
+  filter.threshold(1.).field("field").push_back("1").push_back("1");
+
+  auto prepared_order = order.prepare();
+  auto prepared = filter.prepare(rdr, prepared_order);
+  size_t count = 0;
+  for (const auto& sub : rdr) {
+    auto docs = prepared->execute(sub, prepared_order);
+    auto& doc = docs->attributes().get<irs::document>();
+    auto& boost = docs->attributes().get<irs::filter_boost>();
+    auto& frequency = docs->attributes().get<irs::frequency>();
+    // ensure all iterators contain  attributes
+    ASSERT_TRUE(bool(doc));
+    ASSERT_TRUE(bool(boost));
+    ASSERT_TRUE(bool(frequency));
+    ASSERT_TRUE(docs->next());
+    ASSERT_EQ(docs->value(), doc->value);
+    ASSERT_FALSE(irs::doc_limits::eof(doc->value));
+    ASSERT_DOUBLE_EQ(1, boost->value);
+    const irs::string_ref rhs = "11";
+    const irs::string_ref lhs = "11";
+    ASSERT_DOUBLE_EQ(
+      boost->value,
+      (irs::ngram_similarity<char, true>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 1)));
+    ASSERT_EQ(1, frequency->value);
+    ASSERT_FALSE(docs->next());
+  }
+}
+
+TEST_P(ngram_similarity_filter_test_case, check_matcher_7) {
+    // sequence 2 4 2 4 1 3 1 3 pattern 1 2 3 4-> longest is 1 3  and 2 4 but frequency is 2
+    // as only first longest counted
+    {
+        tests::json_doc_generator gen(
+            "[{ \"seq\" : 1, \"field\": [ \"2\", \"4\", \"2\", \"4\", \"1\", \"3\", \"1\", \"3\"] }]",
+            &tests::generic_json_field_factory);
+        add_segment(gen);
+    }
+
+    auto rdr = open_reader();
+    irs::order order;
+    auto& scorer = order.add<tests::sort::custom_sort>(false);
+    irs::by_ngram_similarity filter;
+    filter.threshold(0.5).field("field").push_back("1").push_back("2").push_back("3").push_back("4");
+
+    auto prepared_order = order.prepare();
+    auto prepared = filter.prepare(rdr, prepared_order);
+    size_t count = 0;
+    for (const auto& sub : rdr) {
+        auto docs = prepared->execute(sub, prepared_order);
+        auto& doc = docs->attributes().get<irs::document>();
+        auto& boost = docs->attributes().get<irs::filter_boost>();
+        auto& frequency = docs->attributes().get<irs::frequency>();
+        // ensure all iterators contain  attributes
+        ASSERT_TRUE(bool(doc));
+        ASSERT_TRUE(bool(boost));
+        ASSERT_TRUE(bool(frequency));
+        ASSERT_TRUE(docs->next());
+        ASSERT_EQ(docs->value(), doc->value);
+        ASSERT_FALSE(irs::doc_limits::eof(doc->value));
+        ASSERT_DOUBLE_EQ(0.5, boost->value);
+        const irs::string_ref rhs = "24241313";
+        const irs::string_ref lhs = "1234";
+        ASSERT_DOUBLE_EQ(
+          boost->value,
+          (irs::ngram_similarity<char, true>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 1)));
+        ASSERT_EQ(2, frequency->value);
+        ASSERT_FALSE(docs->next());
+    }
+}
+
+TEST_P(ngram_similarity_filter_test_case, check_matcher_8) {
+  // sequence 1 2 3 4 pattern 1 5 6 2 -> longest is 1 2  and  boost 0.5
+  // as only first longest counted
+  {
+    tests::json_doc_generator gen(
+      "[{ \"seq\" : 1, \"field\": [ \"1\", \"2\", \"3\", \"4\"] }]",
+      &tests::generic_json_field_factory);
+    add_segment(gen);
+  }
+
+  auto rdr = open_reader();
+  irs::order order;
+  auto& scorer = order.add<tests::sort::custom_sort>(false);
+  irs::by_ngram_similarity filter;
+  filter.threshold(0.5).field("field").push_back("1").push_back("5").push_back("6").push_back("2");
+
+  auto prepared_order = order.prepare();
+  auto prepared = filter.prepare(rdr, prepared_order);
+  size_t count = 0;
+  for (const auto& sub : rdr) {
+    auto docs = prepared->execute(sub, prepared_order);
+    auto& doc = docs->attributes().get<irs::document>();
+    auto& boost = docs->attributes().get<irs::filter_boost>();
+    auto& frequency = docs->attributes().get<irs::frequency>();
+    // ensure all iterators contain  attributes
+    ASSERT_TRUE(bool(doc));
+    ASSERT_TRUE(bool(boost));
+    ASSERT_TRUE(bool(frequency));
+    ASSERT_TRUE(docs->next());
+    ASSERT_EQ(docs->value(), doc->value);
+    ASSERT_FALSE(irs::doc_limits::eof(doc->value));
+    ASSERT_DOUBLE_EQ(0.5, boost->value);
+    const irs::string_ref lhs = "1234";
+    const irs::string_ref rhs = "1562";
+    ASSERT_DOUBLE_EQ(
+      boost->value,
+      (irs::ngram_similarity<char, true>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 1)));
+    ASSERT_EQ(1, frequency->value);
+    ASSERT_FALSE(docs->next());
+  }
+}
+
+TEST_P(ngram_similarity_filter_test_case, check_matcher_9) {
+  // bulk pos read check (for future optimization)
+  // sequence 1 1 2 3 4 5 1  pattern 1 2 3 4 5 1 -> longest is 1 2 3 4 5 1   and  boost 1 and frequency 1
+  {
+    tests::json_doc_generator gen(
+      "[{ \"seq\" : 1, \"field\": [ \"1\", \"1\", \"2\", \"3\", \"4\", \"5\", \"1\"] }]",
+      &tests::generic_json_field_factory);
+    add_segment(gen);
+  }
+
+  auto rdr = open_reader();
+  irs::order order;
+  auto& scorer = order.add<tests::sort::custom_sort>(false);
+  irs::by_ngram_similarity filter;
+  filter.threshold(0.5).field("field").push_back("1")
+    .push_back("2").push_back("3").push_back("4").push_back("5").push_back("1");
+
+
+  auto prepared_order = order.prepare();
+  auto prepared = filter.prepare(rdr, prepared_order);
+  size_t count = 0;
+  for (const auto& sub : rdr) {
+    auto docs = prepared->execute(sub, prepared_order);
+    auto& doc = docs->attributes().get<irs::document>();
+    auto& boost = docs->attributes().get<irs::filter_boost>();
+    auto& frequency = docs->attributes().get<irs::frequency>();
+    // ensure all iterators contain  attributes
+    ASSERT_TRUE(bool(doc));
+    ASSERT_TRUE(bool(boost));
+    ASSERT_TRUE(bool(frequency));
+    ASSERT_TRUE(docs->next());
+    ASSERT_EQ(docs->value(), doc->value);
+    ASSERT_FALSE(irs::doc_limits::eof(doc->value));
+    ASSERT_DOUBLE_EQ(1., boost->value);
+    const irs::string_ref rhs = "1123451";
+    const irs::string_ref lhs = "123451";
+    ASSERT_DOUBLE_EQ(
+      boost->value,
+      (irs::ngram_similarity<char, true>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 1)));
+    ASSERT_EQ(1, frequency->value);
+    ASSERT_FALSE(docs->next());
+  }
+}
+
+TEST_P(ngram_similarity_filter_test_case, check_matcher_10) {
+  // bulk pos read check (for future optimization)
+  // sequence '' pattern '' -> longest is ''   and  boost 1 and frequency 1
+  {
+    tests::json_doc_generator gen(
+      "[{ \"seq\" : 1, \"field\": [ \"\"] }]",
+      &tests::generic_json_field_factory);
+    add_segment(gen);
+  }
+
+  auto rdr = open_reader();
+  irs::order order;
+  auto& scorer = order.add<tests::sort::custom_sort>(false);
+  irs::by_ngram_similarity filter;
+  filter.threshold(0.5).field("field").push_back("");
+
+
+  auto prepared_order = order.prepare();
+  auto prepared = filter.prepare(rdr, prepared_order);
+  size_t count = 0;
+  for (const auto& sub : rdr) {
+    auto docs = prepared->execute(sub, prepared_order);
+    auto& doc = docs->attributes().get<irs::document>();
+    auto& boost = docs->attributes().get<irs::filter_boost>();
+    auto& frequency = docs->attributes().get<irs::frequency>();
+    // ensure all iterators contain  attributes
+    ASSERT_TRUE(bool(doc));
+    ASSERT_TRUE(bool(boost));
+    ASSERT_TRUE(bool(frequency));
+    ASSERT_TRUE(docs->next());
+    ASSERT_EQ(docs->value(), doc->value);
+    ASSERT_FALSE(irs::doc_limits::eof(doc->value));
+    ASSERT_DOUBLE_EQ(1., boost->value);
+    const irs::string_ref rhs = "";
+    const irs::string_ref lhs = "";
+    ASSERT_DOUBLE_EQ(
+      boost->value,
+      (irs::ngram_similarity<char, true>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 1)));
+    ASSERT_EQ(1, frequency->value);
+    ASSERT_FALSE(docs->next());
+  }
+}
+
+TEST_P(ngram_similarity_filter_test_case, no_match_case) {
+  {
+    tests::json_doc_generator gen(
+      resource("ngram_similarity.json"),
+      &tests::generic_json_field_factory);
+    add_segment(gen);
+  }
+
+  auto rdr = open_reader();
+
+  irs::by_ngram_similarity filter;
+  filter.threshold(0.1f).field("field").push_back("ee")
+    .push_back("we").push_back("qq").push_back("rr")
+    .push_back("ff").push_back("never_match");
+
+  auto prepared = filter.prepare(rdr, irs::order::prepared::unordered());
+  size_t count = 0;
+  for (const auto& sub : rdr) {
+    auto docs = prepared->execute(sub);
+
+    auto& doc = docs->attributes().get<irs::document>();
+    ASSERT_TRUE(bool(doc)); // ensure all iterators contain "document" attribute
+    ASSERT_FALSE(docs->next());
+    ASSERT_EQ(docs->value(), doc->value);
+    ASSERT_TRUE(irs::doc_limits::eof(doc->value));
+  }
+}
+
+TEST_P(ngram_similarity_filter_test_case, no_serial_match_case) {
+  {
+    tests::json_doc_generator gen(
+      resource("ngram_similarity.json"),
+      &tests::generic_json_field_factory);
+    add_segment(gen);
+  }
+
+  auto rdr = open_reader();
+
+  irs::by_ngram_similarity filter;
+  filter.threshold(0.5).field("field").push_back("ee")
+    .push_back("ss").push_back("pa").push_back("rr");
+
+  auto prepared = filter.prepare(rdr, irs::order::prepared::unordered());
+  size_t count = 0;
+  for (const auto& sub : rdr) {
+    auto docs = prepared->execute(sub);
+    auto& doc = docs->attributes().get<irs::document>();
+    ASSERT_TRUE(bool(doc)); // ensure all iterators contain "document" attribute
+    ASSERT_FALSE(docs->next());
+    ASSERT_EQ(docs->value(), doc->value);
+    ASSERT_TRUE(irs::doc_limits::eof(doc->value));
+  }
+}
+
+TEST_P(ngram_similarity_filter_test_case, one_match_case) {
+  {
+    tests::json_doc_generator gen(
+      resource("ngram_similarity.json"),
+      &tests::generic_json_field_factory);
+    add_segment(gen);
+  }
+
+  auto rdr = open_reader();
+
+  irs::by_ngram_similarity filter;
+  filter.threshold(0.1f).field("field").push_back("ee")
+    .push_back("ss").push_back("qq").push_back("rr")
+    .push_back("ff").push_back("never_match");
+
+  docs_t expected{ 1, 3, 5, 6, 7, 8, 9, 10, 12};
+  const size_t expected_size = expected.size();
+  auto prepared = filter.prepare(rdr, irs::order::prepared::unordered());
+  size_t count = 0;
+  for (const auto& sub : rdr) {
+    auto docs = prepared->execute(sub);
+
+    auto& doc = docs->attributes().get<irs::document>();
+    ASSERT_TRUE(bool(doc)); // ensure all iterators contain "document" attribute
+    while (docs->next()) {
+      ASSERT_EQ(docs->value(), doc->value);
+      expected.erase(std::remove(expected.begin(), expected.end(), docs->value()), expected.end());
+      ++count;
+    }
+  }
+  ASSERT_EQ(expected_size, count);
+  ASSERT_EQ(0, expected.size());
+}
+
+TEST_P(ngram_similarity_filter_test_case, missed_last_test) {
+  {
+    tests::json_doc_generator gen(
+      resource("ngram_similarity.json"),
+      &tests::generic_json_field_factory);
+    add_segment(gen);
+  }
+
+  auto rdr = open_reader();
+
+  irs::by_ngram_similarity filter;
+  filter.threshold(0.5).field("field").push_back("at")
+    .push_back("tl").push_back("la").push_back("as")
+    .push_back("ll").push_back("never_match");
+
+  docs_t expected{ 1, 2, 5, 8, 11, 12, 13};
+  const size_t expected_size = expected.size();
+  auto prepared = filter.prepare(rdr, irs::order::prepared::unordered());
+  size_t count = 0;
+  for (const auto& sub : rdr) {
+    auto docs = prepared->execute(sub);
+
+    auto& doc = docs->attributes().get<irs::document>();
+    ASSERT_TRUE(bool(doc)); // ensure all iterators contain "document" attribute
+    while (docs->next()) {
+      ASSERT_EQ(docs->value(), doc->value);
+      expected.erase(std::remove(expected.begin(), expected.end(), docs->value()), expected.end());
+      ++count;
+    }
+  }
+  ASSERT_EQ(expected_size, count);
+  ASSERT_EQ(0, expected.size());
+}
+
+TEST_P(ngram_similarity_filter_test_case, missed_first_test) {
+  {
+    tests::json_doc_generator gen(
+      resource("ngram_similarity.json"),
+      &tests::generic_json_field_factory);
+    add_segment(gen);
+  }
+
+  auto rdr = open_reader();
+
+  irs::by_ngram_similarity filter;
+  filter.threshold(0.5f).field("field").push_back("never_match").push_back("at")
+    .push_back("tl").push_back("la").push_back("as")
+    .push_back("ll");
+
+  docs_t expected{ 1, 2, 5, 8, 11, 12, 13};
+  const size_t expected_size = expected.size();
+  auto prepared = filter.prepare(rdr, irs::order::prepared::unordered());
+  size_t count = 0;
+  for (const auto& sub : rdr) {
+    auto docs = prepared->execute(sub);
+
+    auto& doc = docs->attributes().get<irs::document>();
+    ASSERT_TRUE(bool(doc)); // ensure all iterators contain "document" attribute
+    while (docs->next()) {
+      ASSERT_EQ(docs->value(), doc->value);
+      expected.erase(std::remove(expected.begin(), expected.end(), docs->value()), expected.end());
+      ++count;
+    }
+  }
+  ASSERT_EQ(expected_size, count);
+  ASSERT_EQ(0, expected.size());
+}
+
+TEST_P(ngram_similarity_filter_test_case, not_miss_match_for_tail) {
+  {
+    tests::json_doc_generator gen(
+      resource("ngram_similarity.json"),
+      &tests::generic_json_field_factory);
+    add_segment(gen);
+  }
+
+  auto rdr = open_reader();
+
+  irs::by_ngram_similarity filter;
+  filter.threshold(0.33f).field("field").push_back("at")
+    .push_back("tl").push_back("la").push_back("as")
+    .push_back("ll").push_back("never_match");
+
+  docs_t expected{ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14};
+  const size_t expected_size = expected.size();
+  auto prepared = filter.prepare(rdr, irs::order::prepared::unordered());
+  size_t count = 0;
+  for (const auto& sub : rdr) {
+    auto docs = prepared->execute(sub);
+
+    auto& doc = docs->attributes().get<irs::document>();
+    ASSERT_TRUE(bool(doc)); // ensure all iterators contain "document" attribute
+    while (docs->next()) {
+      ASSERT_EQ(docs->value(), doc->value);
+      expected.erase(std::remove(expected.begin(), expected.end(), docs->value()), expected.end());
+      ++count;
+    }
+  }
+  ASSERT_EQ(expected_size, count);
+  ASSERT_EQ(0, expected.size());
+}
+
+
+TEST_P(ngram_similarity_filter_test_case, missed_middle_test) {
+  {
+    tests::json_doc_generator gen(
+      resource("ngram_similarity.json"),
+      &tests::generic_json_field_factory);
+    add_segment(gen);
+  }
+
+  auto rdr = open_reader();
+
+  irs::by_ngram_similarity filter;
+  filter.threshold(0.333f).field("field").push_back("at")
+    .push_back("never_match").push_back("la").push_back("as")
+    .push_back("ll");
+
+  docs_t expected{ 1, 2, 3, 4, 5, 6, 7, 8, 11, 12, 13, 14};
+  const size_t expected_size = expected.size();
+
+  auto prepared = filter.prepare(rdr, irs::order::prepared::unordered());
+  size_t count = 0;
+  for (const auto& sub : rdr) {
+    auto docs = prepared->execute(sub);
+
+    auto& doc = docs->attributes().get<irs::document>();
+    ASSERT_TRUE(bool(doc)); // ensure all iterators contain "document" attribute
+    while (docs->next()) {
+      ASSERT_EQ(docs->value(), doc->value);
+      expected.erase(std::remove(expected.begin(), expected.end(), docs->value()), expected.end());
+      ++count;
+    }
+  }
+  ASSERT_EQ(expected_size, count);
+  ASSERT_EQ(0, expected.size());
+}
+
+TEST_P(ngram_similarity_filter_test_case, missed_middle2_test) {
+  {
+    tests::json_doc_generator gen(
+      resource("ngram_similarity.json"),
+      &tests::generic_json_field_factory);
+    add_segment(gen);
+  }
+
+  auto rdr = open_reader();
+
+  irs::by_ngram_similarity filter;
+  filter.threshold(0.5f).field("field").push_back("at")
+    .push_back("never_match").push_back("never_match2").push_back("la").push_back("as")
+    .push_back("ll");
+
+  docs_t expected{ 1, 2, 5, 8, 11, 12, 13};
+  const size_t expected_size = expected.size();
+
+  auto prepared = filter.prepare(rdr, irs::order::prepared::unordered());
+  size_t count = 0;
+  for (const auto& sub : rdr) {
+    auto docs = prepared->execute(sub);
+
+    auto& doc = docs->attributes().get<irs::document>();
+    ASSERT_TRUE(bool(doc)); // ensure all iterators contain "document" attribute
+    while (docs->next()) {
+      ASSERT_EQ(docs->value(), doc->value);
+      expected.erase(std::remove(expected.begin(), expected.end(), docs->value()), expected.end());
+      ++count;
+    }
+  }
+  ASSERT_EQ(expected_size, count);
+  ASSERT_EQ(0, expected.size());
+}
+
+TEST_P(ngram_similarity_filter_test_case, missed_middle3_test) {
+  {
+    tests::json_doc_generator gen(
+      resource("ngram_similarity.json"),
+      &tests::generic_json_field_factory);
+    add_segment(gen);
+  }
+
+  auto rdr = open_reader();
+
+  irs::by_ngram_similarity filter;
+  filter.threshold(0.28f).field("field").push_back("at")
+    .push_back("never_match").push_back("tl").push_back("never_match2").push_back("la").push_back("as")
+    .push_back("ll");
+
+  docs_t expected{ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14};
+  const size_t expected_size = expected.size();
+
+  auto prepared = filter.prepare(rdr, irs::order::prepared::unordered());
+  size_t count = 0;
+  for (const auto& sub : rdr) {
+    auto docs = prepared->execute(sub);
+
+    auto& doc = docs->attributes().get<irs::document>();
+    ASSERT_TRUE(bool(doc)); // ensure all iterators contain "document" attribute
+    while (docs->next()) {
+      ASSERT_EQ(docs->value(), doc->value);
+      expected.erase(std::remove(expected.begin(), expected.end(), docs->value()), expected.end());
+      ++count;
+    }
+  }
+  ASSERT_EQ(expected_size, count);
+  ASSERT_EQ(0, expected.size());
+}
+
+struct test_score_ctx : public irs::score_ctx {
+  test_score_ctx(std::vector<size_t>* f, const irs::frequency* p, std::vector<irs::boost_t>* b, const irs::filter_boost* fb)
+    : freq(f), freq_from_filter(p), filter_boost(b), boost_from_filter(fb)  {}
+
+  std::vector<size_t>* freq;
+  std::vector<irs::boost_t>* filter_boost;
+  const irs::frequency* freq_from_filter;
+  const irs::filter_boost* boost_from_filter;
+};
+
+TEST_P(ngram_similarity_filter_test_case, missed_last_scored_test) {
+  {
+    tests::json_doc_generator gen(
+      resource("ngram_similarity.json"),
+      &tests::generic_json_field_factory);
+    add_segment(gen);
+  }
+
+  auto rdr = open_reader();
+
+  irs::by_ngram_similarity filter;
+  filter.threshold(0.5f).field("field").push_back("at")
+    .push_back("tl").push_back("la").push_back("as")
+    .push_back("ll").push_back("never_match");
+
+  docs_t expected{ 1, 2, 5, 8, 11, 12, 13};
+  irs::order order;
+  size_t collect_field_count = 0;
+  size_t collect_term_count = 0;
+  size_t finish_count = 0;
+  std::vector<size_t> frequency;
+  std::vector<irs::boost_t> filter_boost;
+  auto& scorer = order.add<tests::sort::custom_sort>(false);
+  scorer.collector_collect_field = [&collect_field_count](const irs::sub_reader&, const irs::term_reader&)->void{
+    ++collect_field_count;
+  };
+  scorer.collector_collect_term = [&collect_term_count](const irs::sub_reader&, const irs::term_reader&, const irs::attribute_view&)->void{
+    ++collect_term_count;
+  };
+  scorer.collectors_collect_ = [&finish_count](irs::byte_type*, const irs::index_reader&, const irs::sort::field_collector*, const irs::sort::term_collector*)->void {
+    ++finish_count;
+  };
+  scorer.prepare_field_collector_ = [&scorer]()->irs::sort::field_collector::ptr {
+    return irs::memory::make_unique<tests::sort::custom_sort::prepared::collector>(scorer);
+  };
+  scorer.prepare_term_collector_ = [&scorer]()->irs::sort::term_collector::ptr {
+    return irs::memory::make_unique<tests::sort::custom_sort::prepared::collector>(scorer);
+  };
+
+
+  scorer.prepare_scorer = [&frequency, &filter_boost](const irs::sub_reader& segment,
+    const irs::term_reader& term,
+    const irs::byte_type* data,
+    const irs::attribute_view& attr)->std::pair<irs::score_ctx_ptr, irs::score_f> {
+      auto& freq = attr.get<irs::frequency>();
+      auto& boost = attr.get<irs::filter_boost>();
+      return {
+        irs::memory::make_unique<test_score_ctx>(&frequency, freq.get(), &filter_boost, boost.get()),
+        [](const irs::score_ctx* ctx, irs::byte_type* RESTRICT score_buf) noexcept {
+        auto& freq = *reinterpret_cast<const test_score_ctx*>(ctx);
+        freq.freq->push_back(freq.freq_from_filter->value);
+        freq.filter_boost->push_back(freq.boost_from_filter->value);
+      }
+      };
+  };
+  std::vector<size_t> expectedFrequency{1, 1, 2, 1, 1, 1, 1};
+  std::vector<irs::boost_t> expected_filter_boost{4.f/6.f, 4.f/6.f, 4.f/6.f, 4.f/6.f, 0.5, 0.5, 0.5};
+  check_query(filter, order, expected, rdr);
+  ASSERT_EQ(expectedFrequency, frequency);
+  ASSERT_EQ(expected_filter_boost.size(), filter_boost.size());
+  for (size_t i = 0; i < expected_filter_boost.size(); ++i) {
+    SCOPED_TRACE(testing::Message("i=") << i);
+    ASSERT_DOUBLE_EQ(expected_filter_boost[i], filter_boost[i]);
+  }
+  ASSERT_EQ(1, collect_field_count);
+  ASSERT_EQ(5, collect_term_count);
+  ASSERT_EQ(collect_field_count + collect_term_count, finish_count);
+}
+
+TEST_P(ngram_similarity_filter_test_case, missed_frequency_test) {
+  {
+    tests::json_doc_generator gen(
+      resource("ngram_similarity.json"),
+      &tests::generic_json_field_factory);
+    add_segment(gen);
+  }
+
+  auto rdr = open_reader();
+
+  irs::by_ngram_similarity filter;
+  filter.threshold(0.5f).field("field").push_back("never_match").push_back("at")
+    .push_back("tl").push_back("la").push_back("as")
+    .push_back("ll");
+
+  docs_t expected{ 1, 2, 5, 8, 11, 12, 13};
+  irs::order order;
+  size_t collect_field_count = 0;
+  size_t collect_term_count = 0;
+  size_t finish_count = 0;
+  std::vector<size_t> frequency;
+  std::vector<irs::boost_t> filter_boost;
+  auto& scorer = order.add<tests::sort::custom_sort>(false);
+  scorer.collector_collect_field = [&collect_field_count](const irs::sub_reader&, const irs::term_reader&)->void{
+    ++collect_field_count;
+  };
+  scorer.collector_collect_term = [&collect_term_count](const irs::sub_reader&, const irs::term_reader&, const irs::attribute_view&)->void{
+    ++collect_term_count;
+  };
+  scorer.collectors_collect_ = [&finish_count](irs::byte_type*, const irs::index_reader&, const irs::sort::field_collector*, const irs::sort::term_collector*)->void {
+    ++finish_count;
+  };
+  scorer.prepare_field_collector_ = [&scorer]()->irs::sort::field_collector::ptr {
+    return irs::memory::make_unique<tests::sort::custom_sort::prepared::collector>(scorer);
+  };
+  scorer.prepare_term_collector_ = [&scorer]()->irs::sort::term_collector::ptr {
+    return irs::memory::make_unique<tests::sort::custom_sort::prepared::collector>(scorer);
+  };
+
+
+  scorer.prepare_scorer = [&frequency, &filter_boost](const irs::sub_reader& segment,
+    const irs::term_reader& term,
+    const irs::byte_type* data,
+    const irs::attribute_view& attr)->std::pair<irs::score_ctx_ptr, irs::score_f> {
+      auto& freq = attr.get<irs::frequency>();
+      auto& boost = attr.get<irs::filter_boost>();
+      return {
+        irs::memory::make_unique<test_score_ctx>(&frequency, freq.get(), &filter_boost, boost.get()),
+        [](const irs::score_ctx* ctx, irs::byte_type* RESTRICT score_buf) noexcept {
+        auto& freq = *reinterpret_cast<const test_score_ctx*>(ctx);
+        freq.freq->push_back(freq.freq_from_filter->value);
+        freq.filter_boost->push_back(freq.boost_from_filter->value);
+      }
+      };
+  };
+  std::vector<size_t> expected_frequency{1, 1, 2, 1, 1, 1, 1};
+  std::vector<irs::boost_t> expected_filter_boost{4.f/6.f, 4.f/6.f, 4.f/6.f, 4.f/6.f, 0.5, 0.5, 0.5};
+  check_query(filter, order, expected, rdr);
+  ASSERT_EQ(expected_frequency, frequency);
+  ASSERT_EQ(expected_filter_boost.size(), filter_boost.size());
+  for (size_t i = 0; i < expected_filter_boost.size(); ++i) {
+    SCOPED_TRACE(testing::Message("i=") << i);
+    ASSERT_DOUBLE_EQ(expected_filter_boost[i], filter_boost[i]);
+  }
+  ASSERT_EQ(1, collect_field_count);
+  ASSERT_EQ(5, collect_term_count);
+  ASSERT_EQ(collect_field_count + collect_term_count, finish_count);
+}
+
+#ifndef IRESEARCH_DLL
+
+TEST_P(ngram_similarity_filter_test_case, missed_first_tfidf_norm_test) {
+  {
+    tests::json_doc_generator gen(
+      resource("ngram_similarity.json"),
+      &tests::normalized_string_json_field_factory);
+    add_segment(gen);
+  }
+
+  auto rdr = open_reader();
+  irs::by_ngram_similarity filter;
+  filter.threshold(0.5f).field("field").push_back("never_match").push_back("at")
+    .push_back("tl").push_back("la").push_back("as")
+    .push_back("ll");
+  docs_t expected{ 11, 12, 8, 13, 5, 1, 2};
+  irs::order order;
+  order.add<irs::tfidf_sort>(false).normalize(true);
+  check_query(filter, order, expected, rdr);
+}
+
+TEST_P(ngram_similarity_filter_test_case, missed_first_tfidf_test) {
+  {
+    tests::json_doc_generator gen(
+      resource("ngram_similarity.json"),
+      &tests::normalized_string_json_field_factory);
+    add_segment(gen);
+  }
+
+  auto rdr = open_reader();
+
+  irs::by_ngram_similarity filter;
+  filter.threshold(0.5f).field("field").push_back("never_match").push_back("at")
+    .push_back("tl").push_back("la").push_back("as")
+    .push_back("ll");
+  docs_t expected{ 11, 12, 13, 1, 2, 8, 5};
+  irs::order order;
+  order.add<irs::tfidf_sort>(false).normalize(false);
+
+  check_query(filter, order, expected, rdr);
+}
+
+TEST_P(ngram_similarity_filter_test_case, missed_first_bm25_test) {
+  {
+    tests::json_doc_generator gen(
+      resource("ngram_similarity.json"),
+      &tests::normalized_string_json_field_factory);
+    add_segment(gen);
+  }
+
+  auto rdr = open_reader();
+
+  irs::by_ngram_similarity filter;
+  filter.threshold(0.5f).field("field").push_back("never_match").push_back("at")
+    .push_back("tl").push_back("la").push_back("as")
+    .push_back("ll");
+  docs_t expected{13, 11, 12, 2, 1, 8, 5};
+  irs::order order;
+  order.add<irs::bm25_sort>(false);
+
+  check_query(filter, order, expected, rdr);
+}
+
+TEST_P(ngram_similarity_filter_test_case, missed_first_bm15_test) {
+  {
+    tests::json_doc_generator gen(
+      resource("ngram_similarity.json"),
+      &tests::normalized_string_json_field_factory);
+    add_segment(gen);
+  }
+
+  auto rdr = open_reader();
+
+  irs::by_ngram_similarity filter;
+  filter.threshold(0.5f).field("field").push_back("never_match").push_back("at")
+    .push_back("tl").push_back("la").push_back("as")
+    .push_back("ll");
+  docs_t expected{ 13, 11, 12, 2, 1, 8, 5};
+  irs::order order;
+  order.add<irs::bm25_sort>(false).b(1); // set to BM15 mode
+
+  check_query(filter, order, expected, rdr);
+}
+
+#endif
+
+INSTANTIATE_TEST_CASE_P(
+  ngram_similarity_test,
+  ngram_similarity_filter_test_case,
+  ::testing::Combine(
+    ::testing::Values(
+      &tests::memory_directory,
+      &tests::fs_directory,
+      &tests::mmap_directory),
+    ::testing::Values("1_0", "1_3")),
+    tests::to_string);
+
+NS_END // tests
+
+// -----------------------------------------------------------------------------
+// --SECTION--                                                       END-OF-FILE
+// -----------------------------------------------------------------------------
diff --git a/3rdParty/iresearch/tests/search/phrase_filter_tests.cpp b/3rdParty/iresearch/tests/search/phrase_filter_tests.cpp
index 282bf4751640..1d06de0052cf 100644
--- a/3rdParty/iresearch/tests/search/phrase_filter_tests.cpp
+++ b/3rdParty/iresearch/tests/search/phrase_filter_tests.cpp
@@ -26,6 +26,7 @@
 #include "analysis/token_attributes.hpp"
 #include "search/phrase_filter.hpp"
 #ifndef IRESEARCH_DLL
+#include "search/multiterm_query.hpp"
 #include "search/term_query.hpp"
 #endif
 
@@ -115,7 +116,7 @@ class phrase_filter_test_case : public tests::filter_test_case_base {
 
       irs::by_phrase q;
       q.field("phrase_anl")
-       .push_back("fox");
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("fox"))});
 
       auto prepared = q.prepare(rdr);
       auto sub = rdr.begin();
@@ -180,23 +181,45 @@ class phrase_filter_test_case : public tests::filter_test_case_base {
       ASSERT_TRUE(values(docs->value(), actual_value));
       ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
 
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("V", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("V", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
       ASSERT_FALSE(docs->next());
       ASSERT_EQ(docs->value(), doc->value);
       ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
     }
 
-    // search "fox" on field without positions
-    // which is ok for single word phrases
+    // prefix_filter "fo*"
     {
+      irs::bytes_ref actual_value;
+
       irs::by_phrase q;
-      q.field("phrase").push_back("fox");
+      irs::by_phrase::prefix_term pt;
+      pt.term = irs::ref_cast<irs::byte_type>(irs::string_ref("fo"));
+      q.field("phrase_anl").push_back(std::move(pt));
 
       auto prepared = q.prepare(rdr);
-#ifndef IRESEARCH_DLL
-      // check single word phrase optimization
-      ASSERT_NE(nullptr, dynamic_cast<const irs::term_query*>(prepared.get()));
-#endif
-      irs::bytes_ref actual_value;
       auto sub = rdr.begin();
       auto column = sub->column_reader("name");
       ASSERT_NE(nullptr, column);
@@ -210,6 +233,47 @@ class phrase_filter_test_case : public tests::filter_test_case_base {
       auto docs_seek = prepared->execute(*sub);
       ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
 
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("D", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("D", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("H", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("H", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
       ASSERT_TRUE(docs->next());
       ASSERT_EQ(docs->value(), doc->value);
       ASSERT_TRUE(values(docs->value(), actual_value));
@@ -218,25 +282,93 @@ class phrase_filter_test_case : public tests::filter_test_case_base {
       ASSERT_TRUE(values(docs->value(), actual_value));
       ASSERT_EQ("K", irs::to_string<irs::string_ref>(actual_value.c_str()));
 
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("U", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("U", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("V", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("V", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("W", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("W", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("X", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("X", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("Y", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("Y", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
       ASSERT_FALSE(docs->next());
       ASSERT_EQ(docs->value(), doc->value);
       ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
     }
 
-    // equals to term_filter "fox" with phrase offset
-    // which does not matter
+    // wildcard_filter "fo%"
     {
       irs::bytes_ref actual_value;
 
       irs::by_phrase q;
-      q.field("phrase_anl")
-       .push_back("fox", irs::integer_traits<size_t>::const_max);
+      irs::by_phrase::wildcard_term wt;
+      wt.term = irs::ref_cast<irs::byte_type>(irs::string_ref("fo%"));
+      q.field("phrase_anl").push_back(std::move(wt));
 
       auto prepared = q.prepare(rdr);
-#ifndef IRESEARCH_DLL
-      // check single word phrase optimization
-      ASSERT_NE(nullptr, dynamic_cast<const irs::term_query*>(prepared.get()));
-#endif
       auto sub = rdr.begin();
       auto column = sub->column_reader("name");
       ASSERT_NE(nullptr, column);
@@ -251,6 +383,7 @@ class phrase_filter_test_case : public tests::filter_test_case_base {
       ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
 
       ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
       ASSERT_TRUE(values(docs->value(), actual_value));
       ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
       ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
@@ -258,6 +391,15 @@ class phrase_filter_test_case : public tests::filter_test_case_base {
       ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
 
       ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("D", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("D", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
       ASSERT_TRUE(values(docs->value(), actual_value));
       ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
       ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
@@ -265,6 +407,16 @@ class phrase_filter_test_case : public tests::filter_test_case_base {
       ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
 
       ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("H", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("H", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_EQ(docs->value(), doc->value);
       ASSERT_TRUE(values(docs->value(), actual_value));
       ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
       ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
@@ -272,12 +424,4905 @@ class phrase_filter_test_case : public tests::filter_test_case_base {
       ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
 
       ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
       ASSERT_TRUE(values(docs->value(), actual_value));
       ASSERT_EQ("K", irs::to_string<irs::string_ref>(actual_value.c_str()));
       ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
       ASSERT_TRUE(values(docs->value(), actual_value));
       ASSERT_EQ("K", irs::to_string<irs::string_ref>(actual_value.c_str()));
 
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("U", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("U", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("V", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("V", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("W", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("W", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("X", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("X", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("Y", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("Y", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+    }
+
+    // wildcard_filter "%ox"
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::wildcard_term wt;
+      wt.term = irs::ref_cast<irs::byte_type>(irs::string_ref("%ox"));
+      q.field("phrase_anl").push_back(std::move(wt));
+
+      auto prepared = q.prepare(rdr);
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("K", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("K", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("V", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("V", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+    }
+
+    // wildcard_filter "f%x"
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::wildcard_term wt;
+      wt.term = irs::ref_cast<irs::byte_type>(irs::string_ref("f%x"));
+      q.field("phrase_anl").push_back(std::move(wt));
+
+      auto prepared = q.prepare(rdr);
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("K", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("K", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("V", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("V", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+    }
+
+    // wildcard_filter "_ox"
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::wildcard_term wt;
+      wt.term = irs::ref_cast<irs::byte_type>(irs::string_ref("_ox"));
+      q.field("phrase_anl").push_back(std::move(wt));
+
+      auto prepared = q.prepare(rdr);
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("K", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("K", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("V", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("V", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+    }
+
+    // wildcard_filter "f_x"
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::wildcard_term wt;
+      wt.term = irs::ref_cast<irs::byte_type>(irs::string_ref("f_x"));
+      q.field("phrase_anl").push_back(std::move(wt));
+
+      auto prepared = q.prepare(rdr);
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("K", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("K", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("V", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("V", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+    }
+
+    // wildcard_filter "fo_"
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::wildcard_term wt;
+      wt.term = irs::ref_cast<irs::byte_type>(irs::string_ref("fo_"));
+      q.field("phrase_anl").push_back(std::move(wt));
+
+      auto prepared = q.prepare(rdr);
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("K", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("K", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("V", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("V", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+    }
+
+    // wildcard_filter "fox"
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::wildcard_term wt;
+      wt.term = irs::ref_cast<irs::byte_type>(irs::string_ref("fox"));
+      q.field("phrase_anl").push_back(std::move(wt));
+
+      auto prepared = q.prepare(rdr);
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("K", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("K", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("V", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("V", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+    }
+
+    // set_term "fox"
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      q.field("phrase_anl").push_back(irs::by_phrase::set_term{{irs::ref_cast<irs::byte_type>(irs::string_ref("fox"))}});
+
+      auto prepared = q.prepare(rdr);
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("K", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("K", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("V", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("V", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+    }
+
+    // set_term "fox|that"
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      q.field("phrase_anl").push_back(irs::by_phrase::set_term{{irs::ref_cast<irs::byte_type>(irs::string_ref("fox")), irs::ref_cast<irs::byte_type>(irs::string_ref("that"))}});
+
+      auto prepared = q.prepare(rdr);
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("B", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("B", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("D", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("D", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("K", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("K", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("V", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("V", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+    }
+
+    // wildcard_filter "%"
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::wildcard_term wt;
+      wt.term = irs::ref_cast<irs::byte_type>(irs::string_ref("%"));
+      q.field("phrase_anl").push_back(std::move(wt));
+
+      auto prepared = q.prepare(rdr);
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("B", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("B", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("C", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("C", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("D", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("D", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("E", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("E", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("F", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("F", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("H", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("H", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("K", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("K", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("M", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("M", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("O", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("O", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("P", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("P", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("Q", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("Q", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("R", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("R", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("U", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("U", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("V", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("V", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("W", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("W", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("X", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("X", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("Y", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("Y", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("Z", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("Z", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+    }
+
+    // levenshtein_filter "fox"
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::levenshtein_term lt;
+      lt.max_distance = 0;
+      lt.term = irs::ref_cast<irs::byte_type>(irs::string_ref("fox"));
+      q.field("phrase_anl").push_back(std::move(lt));
+
+      auto prepared = q.prepare(rdr);
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("K", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("K", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("V", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("V", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+    }
+
+    // levenshtein_filter "fol"
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::levenshtein_term lt;
+      lt.max_distance = 1;
+      lt.term = irs::ref_cast<irs::byte_type>(irs::string_ref("fol"));
+      q.field("phrase_anl").push_back(std::move(lt));
+
+      auto prepared = q.prepare(rdr);
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("K", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("K", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("V", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("V", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+    }
+
+    // search "fox" on field without positions
+    // which is ok for single word phrases
+    {
+      irs::by_phrase q;
+      q.field("phrase").push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("fox"))});
+
+      auto prepared = q.prepare(rdr);
+#ifndef IRESEARCH_DLL
+      // check single word phrase optimization
+      ASSERT_NE(nullptr, dynamic_cast<const irs::term_query*>(prepared.get()));
+#endif
+      irs::bytes_ref actual_value;
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("K", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("K", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+    }
+
+    // search "fo*" on field without positions
+    // which is ok for the first word in phrase
+    {
+      irs::by_phrase q;
+      irs::by_phrase::prefix_term pt;
+      pt.term = irs::ref_cast<irs::byte_type>(irs::string_ref("fo"));
+      q.field("phrase").push_back(std::move(pt));
+
+      auto prepared = q.prepare(rdr);
+#ifndef IRESEARCH_DLL
+      // check single word phrase optimization
+      ASSERT_NE(nullptr, dynamic_cast<const irs::multiterm_query*>(prepared.get()));
+#endif
+      irs::bytes_ref actual_value;
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("K", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("K", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+    }
+
+    // search "fo%" on field without positions
+    // which is ok for first word in phrase
+    {
+      irs::by_phrase q;
+      irs::by_phrase::wildcard_term wt;
+      wt.term = irs::ref_cast<irs::byte_type>(irs::string_ref("fo%"));
+      q.field("phrase").push_back(std::move(wt));
+
+      auto prepared = q.prepare(rdr);
+#ifndef IRESEARCH_DLL
+      // check single word phrase optimization
+      ASSERT_NE(nullptr, dynamic_cast<const irs::multiterm_query*>(prepared.get()));
+#endif
+      irs::bytes_ref actual_value;
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("K", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("K", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+    }
+
+    // search "f_x%" on field without positions
+    // which is ok for first word in phrase
+    {
+      irs::by_phrase q;
+      irs::by_phrase::wildcard_term wt;
+      wt.term = irs::ref_cast<irs::byte_type>(irs::string_ref("f_x%"));
+      q.field("phrase").push_back(std::move(wt));
+
+      auto prepared = q.prepare(rdr);
+#ifndef IRESEARCH_DLL
+      // check single word phrase optimization
+      ASSERT_NE(nullptr, dynamic_cast<const irs::multiterm_query*>(prepared.get()));
+#endif
+      irs::bytes_ref actual_value;
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("K", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("K", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+    }
+
+    // search "fxo" on field without positions
+    // which is ok for single word phrases
+    {
+      irs::by_phrase q;
+      irs::by_phrase::levenshtein_term lt;
+      lt.max_distance = 1;
+      lt.with_transpositions = true;
+      lt.term = irs::ref_cast<irs::byte_type>(irs::string_ref("fxo"));
+      q.field("phrase").push_back(std::move(lt));
+
+      auto prepared = q.prepare(rdr);
+#ifndef IRESEARCH_DLL
+      // check single word phrase optimization
+      ASSERT_NE(nullptr, dynamic_cast<const irs::multiterm_query*>(prepared.get()));
+#endif
+      irs::bytes_ref actual_value;
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("K", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("K", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+    }
+
+    // term_filter "fox" with phrase offset
+    // which does not matter
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      q.field("phrase_anl")
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("fox"))}, irs::integer_traits<size_t>::const_max);
+
+      auto prepared = q.prepare(rdr);
+#ifndef IRESEARCH_DLL
+      // check single word phrase optimization
+      ASSERT_NE(nullptr, dynamic_cast<const irs::term_query*>(prepared.get()));
+#endif
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("K", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("K", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("V", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("V", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+    }
+
+    // prefix_filter "fo*" with phrase offset
+    // which does not matter
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::prefix_term pt;
+      pt.term = irs::ref_cast<irs::byte_type>(irs::string_ref("fo"));
+      q.field("phrase_anl").push_back(std::move(pt), irs::integer_traits<size_t>::const_max);
+
+      auto prepared = q.prepare(rdr);
+#ifndef IRESEARCH_DLL
+      // check single word phrase optimization
+      ASSERT_NE(nullptr, dynamic_cast<const irs::multiterm_query*>(prepared.get()));
+#endif
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("D", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("D", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("H", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("H", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("K", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("K", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("U", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("U", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("V", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("V", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("W", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("W", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("X", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("X", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("Y", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("Y", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+    }
+
+    // wildcard_filter "fo%" with phrase offset
+    // which does not matter
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::wildcard_term wt;
+      wt.term = irs::ref_cast<irs::byte_type>(irs::string_ref("fo%"));
+      q.field("phrase_anl").push_back(std::move(wt), irs::integer_traits<size_t>::const_max);
+
+      auto prepared = q.prepare(rdr);
+#ifndef IRESEARCH_DLL
+      // check single word phrase optimization
+      ASSERT_NE(nullptr, dynamic_cast<const irs::multiterm_query*>(prepared.get()));
+#endif
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("D", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("D", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("H", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("H", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("K", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("K", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("U", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("U", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("V", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("V", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("W", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("W", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("X", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("X", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("Y", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("Y", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+    }
+
+    // wildcard_filter "f%x" with phrase offset
+    // which does not matter
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::wildcard_term wt;
+      wt.term = irs::ref_cast<irs::byte_type>(irs::string_ref("f%x"));
+      q.field("phrase_anl").push_back(std::move(wt), irs::integer_traits<size_t>::const_max);
+
+      auto prepared = q.prepare(rdr);
+#ifndef IRESEARCH_DLL
+      // check single word phrase optimization
+      ASSERT_NE(nullptr, dynamic_cast<const irs::multiterm_query*>(prepared.get()));
+#endif
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("K", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("K", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("V", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("V", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+    }
+
+    // wildcard_filter "f%x" with phrase offset
+    // which does not matter
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::levenshtein_term lt;
+      lt.max_distance = 1;
+      lt.term = irs::ref_cast<irs::byte_type>(irs::string_ref("fkx"));
+      q.field("phrase_anl").push_back(std::move(lt), irs::integer_traits<size_t>::const_max);
+
+      auto prepared = q.prepare(rdr);
+#ifndef IRESEARCH_DLL
+      // check single word phrase optimization
+      ASSERT_NE(nullptr, dynamic_cast<const irs::multiterm_query*>(prepared.get()));
+#endif
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("K", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("K", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("V", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("V", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+    }
+
+    // "quick brown fox"
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      q.field("phrase_anl")
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("quick"))})
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("brown"))})
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("fox"))});
+
+      auto prepared = q.prepare(rdr);
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs_seek->seek(irs::type_limits<irs::type_t::doc_id_t>::eof())));
+    }
+
+    // "qui* brown fox"
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::prefix_term pt;
+      pt.term = irs::ref_cast<irs::byte_type>(irs::string_ref("qui"));
+      q.field("phrase_anl").push_back(std::move(pt))
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("brown"))})
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("fox"))});
+
+      auto prepared = q.prepare(rdr);
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs_seek->seek(irs::type_limits<irs::type_t::doc_id_t>::eof())));
+    }
+
+    // "qui% brown fox"
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::wildcard_term wt;
+      wt.term = irs::ref_cast<irs::byte_type>(irs::string_ref("qui%"));
+      q.field("phrase_anl").push_back(std::move(wt))
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("brown"))})
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("fox"))});
+
+      auto prepared = q.prepare(rdr);
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs_seek->seek(irs::type_limits<irs::type_t::doc_id_t>::eof())));
+    }
+
+    // "q%ck brown fox"
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::wildcard_term wt;
+      wt.term = irs::ref_cast<irs::byte_type>(irs::string_ref("q%ck"));
+      q.field("phrase_anl").push_back(std::move(wt))
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("brown"))})
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("fox"))});
+
+      auto prepared = q.prepare(rdr);
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs_seek->seek(irs::type_limits<irs::type_t::doc_id_t>::eof())));
+    }
+
+    // "quck brown fox"
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::levenshtein_term lt;
+      lt.max_distance = 1;
+      lt.term = irs::ref_cast<irs::byte_type>(irs::string_ref("quck"));
+      q.field("phrase_anl").push_back(std::move(lt))
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("brown"))})
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("fox"))});
+
+      auto prepared = q.prepare(rdr);
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs_seek->seek(irs::type_limits<irs::type_t::doc_id_t>::eof())));
+    }
+
+    // "quick bro* fox"
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::prefix_term pt;
+      pt.term = irs::ref_cast<irs::byte_type>(irs::string_ref("bro"));
+      q.field("phrase_anl")
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("quick"))})
+       .push_back(std::move(pt))
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("fox"))});
+
+      auto prepared = q.prepare(rdr);
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs_seek->seek(irs::type_limits<irs::type_t::doc_id_t>::eof())));
+    }
+
+    // "quick bro% fox"
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::wildcard_term wt;
+      wt.term = irs::ref_cast<irs::byte_type>(irs::string_ref("bro%"));
+      q.field("phrase_anl")
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("quick"))})
+       .push_back(std::move(wt))
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("fox"))});
+
+      auto prepared = q.prepare(rdr);
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs_seek->seek(irs::type_limits<irs::type_t::doc_id_t>::eof())));
+    }
+
+    // "quick b%w_ fox"
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::wildcard_term wt;
+      wt.term = irs::ref_cast<irs::byte_type>(irs::string_ref("b%w_"));
+      q.field("phrase_anl")
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("quick"))})
+       .push_back(std::move(wt))
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("fox"))});
+
+      auto prepared = q.prepare(rdr);
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs_seek->seek(irs::type_limits<irs::type_t::doc_id_t>::eof())));
+    }
+
+    // "quick brkln fox"
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::levenshtein_term lt;
+      lt.max_distance = 2;
+      lt.term = irs::ref_cast<irs::byte_type>(irs::string_ref("brkln"));
+      q.field("phrase_anl")
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("quick"))})
+       .push_back(std::move(lt))
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("fox"))});
+
+      auto prepared = q.prepare(rdr);
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs_seek->seek(irs::type_limits<irs::type_t::doc_id_t>::eof())));
+    }
+
+    // "quick brown fo*"
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::prefix_term pt;
+      pt.term = irs::ref_cast<irs::byte_type>(irs::string_ref("fo"));
+      q.field("phrase_anl")
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("quick"))})
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("brown"))})
+       .push_back(std::move(pt));
+
+      auto prepared = q.prepare(rdr);
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("U", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("U", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs_seek->seek(irs::type_limits<irs::type_t::doc_id_t>::eof())));
+    }
+
+    // "quick brown fo%"
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::wildcard_term wt;
+      wt.term = irs::ref_cast<irs::byte_type>(irs::string_ref("fo%"));
+      q.field("phrase_anl")
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("quick"))})
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("brown"))})
+       .push_back(std::move(wt));
+
+      auto prepared = q.prepare(rdr);
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("U", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("U", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs_seek->seek(irs::type_limits<irs::type_t::doc_id_t>::eof())));
+    }
+
+    // "quick brown f_x"
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::wildcard_term wt;
+      wt.term = irs::ref_cast<irs::byte_type>(irs::string_ref("f_x"));
+      q.field("phrase_anl")
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("quick"))})
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("brown"))})
+       .push_back(std::move(wt));
+
+      auto prepared = q.prepare(rdr);
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs_seek->seek(irs::type_limits<irs::type_t::doc_id_t>::eof())));
+    }
+
+    // "quick brown fxo"
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::levenshtein_term lt;
+      lt.max_distance = 1;
+      lt.with_transpositions = true;
+      lt.term = irs::ref_cast<irs::byte_type>(irs::string_ref("fxo"));
+      q.field("phrase_anl")
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("quick"))})
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("brown"))})
+       .push_back(std::move(lt));
+
+      auto prepared = q.prepare(rdr);
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs_seek->seek(irs::type_limits<irs::type_t::doc_id_t>::eof())));
+    }
+
+    // "qui* bro* fox"
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::prefix_term pt1;
+      pt1.term = irs::ref_cast<irs::byte_type>(irs::string_ref("qui"));
+      irs::by_phrase::prefix_term pt2;
+      pt2.term = irs::ref_cast<irs::byte_type>(irs::string_ref("bro"));
+      q.field("phrase_anl").push_back(std::move(pt1)).push_back(std::move(pt2))
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("fox"))});
+
+      auto prepared = q.prepare(rdr);
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("V", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("V", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs_seek->seek(irs::type_limits<irs::type_t::doc_id_t>::eof())));
+    }
+
+    // "qui% bro% fox"
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::wildcard_term wt1;
+      wt1.term = irs::ref_cast<irs::byte_type>(irs::string_ref("qui%"));
+      irs::by_phrase::wildcard_term wt2;
+      wt2.term = irs::ref_cast<irs::byte_type>(irs::string_ref("bro%"));
+      q.field("phrase_anl").push_back(std::move(wt1)).push_back(std::move(wt2))
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("fox"))});
+
+      auto prepared = q.prepare(rdr);
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("V", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("V", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs_seek->seek(irs::type_limits<irs::type_t::doc_id_t>::eof())));
+    }
+
+    // "qui% b%o__ fox"
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::wildcard_term wt1;
+      wt1.term = irs::ref_cast<irs::byte_type>(irs::string_ref("qui%"));
+      irs::by_phrase::wildcard_term wt2;
+      wt2.term = irs::ref_cast<irs::byte_type>(irs::string_ref("b%o__"));
+      q.field("phrase_anl").push_back(std::move(wt1)).push_back(std::move(wt2))
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("fox"))});
+
+      auto prepared = q.prepare(rdr);
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs_seek->seek(irs::type_limits<irs::type_t::doc_id_t>::eof())));
+    }
+
+    // "qui bro fox"
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::levenshtein_term lt1;
+      lt1.max_distance = 2;
+      lt1.term = irs::ref_cast<irs::byte_type>(irs::string_ref("qui"));
+      irs::by_phrase::levenshtein_term lt2;
+      lt2.max_distance = 1;
+      lt2.term = irs::ref_cast<irs::byte_type>(irs::string_ref("brow"));
+      q.field("phrase_anl")
+       .push_back(std::move(lt1)).push_back(std::move(lt2))
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("fox"))});
+
+      auto prepared = q.prepare(rdr);
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs_seek->seek(irs::type_limits<irs::type_t::doc_id_t>::eof())));
+    }
+
+    // "qui* brown fo*"
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::prefix_term pt1;
+      pt1.term = irs::ref_cast<irs::byte_type>(irs::string_ref("qui"));
+      irs::by_phrase::prefix_term pt2;
+      pt2.term = irs::ref_cast<irs::byte_type>(irs::string_ref("fo"));
+      q.field("phrase_anl").push_back(std::move(pt1))
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("brown"))})
+       .push_back(std::move(pt2));
+
+      auto prepared = q.prepare(rdr);
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("U", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("U", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("W", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("W", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs_seek->seek(irs::type_limits<irs::type_t::doc_id_t>::eof())));
+    }
+
+    // "qui% brown fo%"
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::wildcard_term wt1;
+      wt1.term = irs::ref_cast<irs::byte_type>(irs::string_ref("qui%"));
+      irs::by_phrase::wildcard_term wt2;
+      wt2.term = irs::ref_cast<irs::byte_type>(irs::string_ref("fo%"));
+      q.field("phrase_anl").push_back(std::move(wt1))
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("brown"))})
+       .push_back(std::move(wt2));
+
+      auto prepared = q.prepare(rdr);
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("U", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("U", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("W", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("W", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs_seek->seek(irs::type_limits<irs::type_t::doc_id_t>::eof())));
+    }
+
+    // "q_i% brown f%x"
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::wildcard_term wt1;
+      wt1.term = irs::ref_cast<irs::byte_type>(irs::string_ref("q_i%"));
+      irs::by_phrase::wildcard_term wt2;
+      wt2.term = irs::ref_cast<irs::byte_type>(irs::string_ref("f%x"));
+      q.field("phrase_anl").push_back(std::move(wt1))
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("brown"))})
+       .push_back(std::move(wt2));
+
+      auto prepared = q.prepare(rdr);
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs_seek->seek(irs::type_limits<irs::type_t::doc_id_t>::eof())));
+    }
+
+    // "qoick br__nn fix"
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::levenshtein_term lt1;
+      lt1.max_distance = 1;
+      lt1.term = irs::ref_cast<irs::byte_type>(irs::string_ref("qoick"));
+      irs::by_phrase::levenshtein_term lt2;
+      lt2.max_distance = 1;
+      lt2.term = irs::ref_cast<irs::byte_type>(irs::string_ref("fix"));
+      irs::by_phrase::wildcard_term wt;
+      wt.term = irs::ref_cast<irs::byte_type>(irs::string_ref("br__n"));
+      q.field("phrase_anl").push_back(std::move(lt1)).push_back(std::move(wt)).push_back(std::move(lt2));
+
+      auto prepared = q.prepare(rdr);
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs_seek->seek(irs::type_limits<irs::type_t::doc_id_t>::eof())));
+    }
+
+    // "quick bro* fo*"
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::prefix_term pt1;
+      pt1.term = irs::ref_cast<irs::byte_type>(irs::string_ref("bro"));
+      irs::by_phrase::prefix_term pt2;
+      pt2.term = irs::ref_cast<irs::byte_type>(irs::string_ref("fo"));
+      q.field("phrase_anl")
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("quick"))})
+       .push_back(std::move(pt1)).push_back(std::move(pt2));
+
+      auto prepared = q.prepare(rdr);
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("U", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("U", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("X", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("X", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs_seek->seek(irs::type_limits<irs::type_t::doc_id_t>::eof())));
+    }
+
+    // "quick bro% fo%"
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::wildcard_term wt1;
+      wt1.term = irs::ref_cast<irs::byte_type>(irs::string_ref("bro%"));
+      irs::by_phrase::wildcard_term wt2;
+      wt2.term = irs::ref_cast<irs::byte_type>(irs::string_ref("fo%"));
+      q.field("phrase_anl")
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("quick"))})
+       .push_back(std::move(wt1)).push_back(std::move(wt2));
+
+      auto prepared = q.prepare(rdr);
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("U", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("U", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("X", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("X", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs_seek->seek(irs::type_limits<irs::type_t::doc_id_t>::eof())));
+    }
+
+    // "quick b_o% f_%"
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::wildcard_term wt1;
+      wt1.term = irs::ref_cast<irs::byte_type>(irs::string_ref("b_o%"));
+      irs::by_phrase::wildcard_term wt2;
+      wt2.term = irs::ref_cast<irs::byte_type>(irs::string_ref("f_%"));
+      q.field("phrase_anl")
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("quick"))})
+       .push_back(std::move(wt1)).push_back(std::move(wt2));
+
+      auto prepared = q.prepare(rdr);
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("U", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("U", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("X", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("X", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs_seek->seek(irs::type_limits<irs::type_t::doc_id_t>::eof())));
+    }
+
+    // "qui* bro* fo*"
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::prefix_term pt1;
+      pt1.term = irs::ref_cast<irs::byte_type>(irs::string_ref("qui"));
+      irs::by_phrase::prefix_term pt2;
+      pt2.term = irs::ref_cast<irs::byte_type>(irs::string_ref("bro"));
+      irs::by_phrase::prefix_term pt3;
+      pt3.term = irs::ref_cast<irs::byte_type>(irs::string_ref("fo"));
+      q.field("phrase_anl").push_back(std::move(pt1)).push_back(std::move(pt2)).push_back(std::move(pt3));
+
+      auto prepared = q.prepare(rdr);
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("U", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("U", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("V", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("V", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("W", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("W", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("X", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("X", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("Y", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("Y", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs_seek->seek(irs::type_limits<irs::type_t::doc_id_t>::eof())));
+    }
+
+    // "qui% bro% fo%"
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::wildcard_term wt1;
+      wt1.term = irs::ref_cast<irs::byte_type>(irs::string_ref("qui%"));
+      irs::by_phrase::wildcard_term wt2;
+      wt2.term = irs::ref_cast<irs::byte_type>(irs::string_ref("bro%"));
+      irs::by_phrase::wildcard_term wt3;
+      wt3.term = irs::ref_cast<irs::byte_type>(irs::string_ref("fo%"));
+      q.field("phrase_anl").push_back(std::move(wt1)).push_back(std::move(wt2)).push_back(std::move(wt3));
+
+      auto prepared = q.prepare(rdr);
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("U", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("U", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("V", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("V", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("W", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("W", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("X", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("X", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("Y", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("Y", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs_seek->seek(irs::type_limits<irs::type_t::doc_id_t>::eof())));
+    }
+
+    // "q%ic_ br_wn _%x"
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::wildcard_term wt1;
+      wt1.term = irs::ref_cast<irs::byte_type>(irs::string_ref("q%ic_"));
+      irs::by_phrase::wildcard_term wt2;
+      wt2.term = irs::ref_cast<irs::byte_type>(irs::string_ref("br_wn"));
+      irs::by_phrase::wildcard_term wt3;
+      wt3.term = irs::ref_cast<irs::byte_type>(irs::string_ref("_%x"));
+      q.field("phrase_anl").push_back(std::move(wt1)).push_back(std::move(wt2)).push_back(std::move(wt3));
+
+      auto prepared = q.prepare(rdr);
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs_seek->seek(irs::type_limits<irs::type_t::doc_id_t>::eof())));
+    }
+
+    // "quick|quilt|hhh brown|brother fox"
+    {
+      irs::bytes_ref actual_value;
+      irs::by_phrase q;
+      q.field("phrase_anl")
+       .push_back(irs::by_phrase::set_term{{irs::ref_cast<irs::byte_type>(irs::string_ref("quick")),
+                                            irs::ref_cast<irs::byte_type>(irs::string_ref("quilt")),
+                                            irs::ref_cast<irs::byte_type>(irs::string_ref("hhh"))}})
+       .push_back(irs::by_phrase::set_term{{irs::ref_cast<irs::byte_type>(irs::string_ref("brown")),
+                                            irs::ref_cast<irs::byte_type>(irs::string_ref("brother"))}})
+       .push_back(irs::by_phrase::set_term{{irs::ref_cast<irs::byte_type>(irs::string_ref("fox"))}});
+
+      auto prepared = q.prepare(rdr);
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("V", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("V", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs_seek->seek(irs::type_limits<irs::type_t::doc_id_t>::eof())));
+    }
+
+    // "quick brown fox" with order
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      q.field("phrase_anl")
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("quick"))})
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("brown"))})
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("fox"))});
+
+      size_t collect_field_count = 0;
+      size_t collect_term_count = 0;
+      size_t finish_count = 0;
+      irs::order ord;
+      auto& sort = ord.add<tests::sort::custom_sort>(false);
+
+      sort.collector_collect_field = [&collect_field_count](const irs::sub_reader&, const irs::term_reader&)->void{
+        ++collect_field_count;
+      };
+      sort.collector_collect_term = [&collect_term_count](const irs::sub_reader&, const irs::term_reader&, const irs::attribute_view&)->void{
+        ++collect_term_count;
+      };
+      sort.collectors_collect_ = [&finish_count](irs::byte_type*, const irs::index_reader&, const irs::sort::field_collector*, const irs::sort::term_collector*)->void {
+        ++finish_count;
+      };
+      sort.prepare_field_collector_ = [&sort]()->irs::sort::field_collector::ptr {
+        return irs::memory::make_unique<tests::sort::custom_sort::prepared::collector>(sort);
+      };
+      sort.prepare_term_collector_ = [&sort]()->irs::sort::term_collector::ptr {
+        return irs::memory::make_unique<tests::sort::custom_sort::prepared::collector>(sort);
+      };
+      sort.scorer_add = [](irs::doc_id_t& dst, const irs::doc_id_t& src)->void {
+        ASSERT_TRUE(
+          irs::type_limits<irs::type_t::doc_id_t>::invalid() == dst
+          || dst == src
+        );
+        dst = src;
+      };
+
+      auto pord = ord.prepare();
+      auto prepared = q.prepare(rdr, pord);
+      ASSERT_EQ(1, collect_field_count); // 1 field in 1 segment
+      ASSERT_EQ(3, collect_term_count); // 3 different terms
+      ASSERT_EQ(3, finish_count); // 3 sub-terms in phrase
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+      auto docs = prepared->execute(*sub, pord);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+      auto& score = docs->attributes().get<irs::score>();
+      ASSERT_FALSE(!score);
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs_seek->seek(irs::type_limits<irs::type_t::doc_id_t>::eof())));
+    }
+
+    // "fox ... quick"
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      q.field("phrase_anl")
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("fox"))})
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("quick"))}, 1);
+
+      auto prepared = q.prepare(rdr);
+
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs_seek->seek(irs::type_limits<irs::type_t::doc_id_t>::eof())));
+    }
+
+    // "fo* ... quick"
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::prefix_term pt;
+      pt.term = irs::ref_cast<irs::byte_type>(irs::string_ref("fo"));
+      q.field("phrase_anl").push_back(std::move(pt))
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("quick"))}, 1);
+
+      auto prepared = q.prepare(rdr);
+
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs_seek->seek(irs::type_limits<irs::type_t::doc_id_t>::eof())));
+    }
+
+    // "f_x ... quick"
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::wildcard_term wt;
+      wt.term = irs::ref_cast<irs::byte_type>(irs::string_ref("f_x"));
+      q.field("phrase_anl").push_back(std::move(wt))
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("quick"))}, 1);
+
+      auto prepared = q.prepare(rdr);
+
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs_seek->seek(irs::type_limits<irs::type_t::doc_id_t>::eof())));
+    }
+
+    // "fpx ... quick"
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::levenshtein_term lt;
+      lt.max_distance = 1;
+      lt.term = irs::ref_cast<irs::byte_type>(irs::string_ref("fpx"));
+      q.field("phrase_anl").push_back(std::move(lt))
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("quick"))}, 1);
+
+      auto prepared = q.prepare(rdr);
+
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs_seek->seek(irs::type_limits<irs::type_t::doc_id_t>::eof())));
+    }
+
+    // "fox ... qui*"
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::prefix_term pt;
+      pt.term = irs::ref_cast<irs::byte_type>(irs::string_ref("qui"));
+      q.field("phrase_anl")
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("fox"))})
+       .push_back(std::move(pt), 1);
+
+      auto prepared = q.prepare(rdr);
+
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs_seek->seek(irs::type_limits<irs::type_t::doc_id_t>::eof())));
+    }
+
+    // "fox ... qui%ck"
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::wildcard_term wt;
+      wt.term = irs::ref_cast<irs::byte_type>(irs::string_ref("qui%ck"));
+      q.field("phrase_anl")
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("fox"))})
+       .push_back(std::move(wt), 1);
+
+      auto prepared = q.prepare(rdr);
+
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs_seek->seek(irs::type_limits<irs::type_t::doc_id_t>::eof())));
+    }
+
+    // "fo* ... qui*"
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::prefix_term pt1;
+      pt1.term = irs::ref_cast<irs::byte_type>(irs::string_ref("fo"));
+      irs::by_phrase::prefix_term pt2;
+      pt2.term = irs::ref_cast<irs::byte_type>(irs::string_ref("qui"));
+      q.field("phrase_anl").push_back(std::move(pt1)).push_back(std::move(pt2), 1);
+
+      auto prepared = q.prepare(rdr);
+
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs_seek->seek(irs::type_limits<irs::type_t::doc_id_t>::eof())));
+    }
+
+    // "f%x ... qui%ck"
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::wildcard_term wt1;
+      wt1.term = irs::ref_cast<irs::byte_type>(irs::string_ref("f%x"));
+      irs::by_phrase::wildcard_term wt2;
+      wt2.term = irs::ref_cast<irs::byte_type>(irs::string_ref("qui%ck"));
+      q.field("phrase_anl").push_back(std::move(wt1)).push_back(std::move(wt2), 1);
+
+      auto prepared = q.prepare(rdr);
+
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs_seek->seek(irs::type_limits<irs::type_t::doc_id_t>::eof())));
+    }
+
+    // "fx ... quik"
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::levenshtein_term lt1;
+      lt1.max_distance = 1;
+      lt1.term = irs::ref_cast<irs::byte_type>(irs::string_ref("fx"));
+      irs::by_phrase::levenshtein_term lt2;
+      lt2.max_distance = 1;
+      lt2.term = irs::ref_cast<irs::byte_type>(irs::string_ref("quik"));
+      q.field("phrase_anl").push_back(std::move(lt1)).push_back(std::move(lt2), 1);
+
+      auto prepared = q.prepare(rdr);
+
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs_seek->seek(irs::type_limits<irs::type_t::doc_id_t>::eof())));
+    }
+
+    // =============================
+    // "fo* ... qui*" with scorer
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::prefix_term pt1;
+      pt1.term = irs::ref_cast<irs::byte_type>(irs::string_ref("fo"));
+      irs::by_phrase::prefix_term pt2;
+      pt2.term = irs::ref_cast<irs::byte_type>(irs::string_ref("qui"));
+      q.field("phrase_anl").push_back(std::move(pt1)).push_back(std::move(pt2), 1);
+
+      irs::order order;
+      order.add(true, irs::scorers::get("bm25", irs::text_format::json, "{ \"b\" : 0 }"));
+      auto prepared_order = order.prepare();
+
+      auto prepared = q.prepare(rdr, prepared_order);
+
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+      auto docs = prepared->execute(*sub, prepared_order);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs_seek->seek(irs::type_limits<irs::type_t::doc_id_t>::eof())));
+    }
+
+    // set_term "fox|that" with scorer
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      q.field("phrase_anl")
+       .push_back(irs::by_phrase::set_term{{irs::ref_cast<irs::byte_type>(irs::string_ref("fox")),
+                                            irs::ref_cast<irs::byte_type>(irs::string_ref("that"))}});
+
+      irs::order order;
+      order.add(true, irs::scorers::get("bm25", irs::text_format::json, "{ \"b\" : 0 }"));
+      auto prepared_order = order.prepare();
+
+      auto prepared = q.prepare(rdr, prepared_order);
+
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+      auto docs = prepared->execute(*sub, prepared_order);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("B", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("B", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("D", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("D", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("K", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("K", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("S", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("T", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("V", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("V", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+    }
+
+    // test disjunctions (unary, basic, small, disjunction)
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::wildcard_term wt1;
+      wt1.term = irs::ref_cast<irs::byte_type>(irs::string_ref("%las"));
+      irs::by_phrase::wildcard_term wt2;
+      wt2.term = irs::ref_cast<irs::byte_type>(irs::string_ref("%nd"));
+      irs::by_phrase::prefix_term pt1;
+      pt1.term = irs::ref_cast<irs::byte_type>(irs::string_ref("go"));
+      irs::by_phrase::prefix_term pt2;
+      pt2.term = irs::ref_cast<irs::byte_type>(irs::string_ref("like"));
+      q.field("phrase_anl").push_back(std::move(wt1)).push_back(std::move(wt2))
+       .push_back(std::move(pt1)).push_back(std::move(pt2));
+
+      irs::order order;
+      order.add(true, irs::scorers::get("bm25", irs::text_format::json, "{ \"b\" : 0 }"));
+      auto prepared_order = order.prepare();
+
+      auto prepared = q.prepare(rdr, prepared_order);
+
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+      auto docs = prepared->execute(*sub, prepared_order);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("Z", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("Z", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+    }
+
+    // =============================
+
+    // "fox ... quick" with phrase offset
+    // which is does not matter
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      q.field("phrase_anl")
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("fox"))}, irs::integer_traits<size_t>::const_max)
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("quick"))}, 1);
+
+      auto prepared = q.prepare(rdr);
+
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid( docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs_seek->seek(irs::type_limits<irs::type_t::doc_id_t>::eof())));
+    }
+
+    // "fox quick"
+    // const_max and zero offset
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      q.field("phrase_anl")
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("fox"))}, irs::integer_traits<size_t>::const_max)
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("quick"))}, 0);
+
+      auto prepared = q.prepare(rdr);
+
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid( docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs_seek->seek(irs::type_limits<irs::type_t::doc_id_t>::eof())));
+    }
+
+    // "fox* quick*"
+    // const_max and zero offset
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::prefix_term pt1;
+      pt1.term = irs::ref_cast<irs::byte_type>(irs::string_ref("fox"));
+      irs::by_phrase::prefix_term pt2;
+      pt2.term = irs::ref_cast<irs::byte_type>(irs::string_ref("quick"));
+      q.field("phrase_anl")
+       .push_back(std::move(pt1), irs::integer_traits<size_t>::const_max)
+       .push_back(std::move(pt2), 0);
+
+      auto prepared = q.prepare(rdr);
+
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid( docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs_seek->seek(irs::type_limits<irs::type_t::doc_id_t>::eof())));
+    }
+
+    // "fo* ... quick" with phrase offset
+    // which is does not matter
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::prefix_term pt;
+      pt.term = irs::ref_cast<irs::byte_type>(irs::string_ref("fo"));
+      q.field("phrase_anl")
+       .push_back(std::move(pt), irs::integer_traits<size_t>::const_max)
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("quick"))}, 1);
+
+      auto prepared = q.prepare(rdr);
+
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid( docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs_seek->seek(irs::type_limits<irs::type_t::doc_id_t>::eof())));
+    }
+
+    // "f_x ... quick" with phrase offset
+    // which is does not matter
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::wildcard_term wt;
+      wt.term = irs::ref_cast<irs::byte_type>(irs::string_ref("f_x"));
+      q.field("phrase_anl")
+       .push_back(std::move(wt), irs::integer_traits<size_t>::const_max)
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("quick"))}, 1);
+
+      auto prepared = q.prepare(rdr);
+
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid( docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs_seek->seek(irs::type_limits<irs::type_t::doc_id_t>::eof())));
+    }
+
+    // "fox ... qui*" with phrase offset
+    // which is does not matter
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::prefix_term pt;
+      pt.term = irs::ref_cast<irs::byte_type>(irs::string_ref("qui"));
+      q.field("phrase_anl")
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("fox"))}, irs::integer_traits<size_t>::const_max)
+       .push_back(std::move(pt), 1);
+
+      auto prepared = q.prepare(rdr);
+
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid( docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
       ASSERT_TRUE(docs->next());
       ASSERT_TRUE(values(docs->value(), actual_value));
       ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
@@ -294,150 +5339,112 @@ class phrase_filter_test_case : public tests::filter_test_case_base {
 
       ASSERT_FALSE(docs->next());
       ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs_seek->seek(irs::type_limits<irs::type_t::doc_id_t>::eof())));
     }
 
-    // "quick brown fox"
+    // "fox ... qui%k" with phrase offset
+    // which is does not matter
     {
       irs::bytes_ref actual_value;
 
       irs::by_phrase q;
+      irs::by_phrase::wildcard_term wt;
+      wt.term = irs::ref_cast<irs::byte_type>(irs::string_ref("qui%k"));
       q.field("phrase_anl")
-       .push_back("quick")
-       .push_back("brown")
-       .push_back("fox");
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("fox"))}, irs::integer_traits<size_t>::const_max)
+       .push_back(std::move(wt), 1);
 
       auto prepared = q.prepare(rdr);
+
       auto sub = rdr.begin();
       auto column = sub->column_reader("name");
       ASSERT_NE(nullptr, column);
       auto values = column->values();
-
       auto docs = prepared->execute(*sub);
       auto& doc = docs->attributes().get<irs::document>();
       ASSERT_TRUE(bool(doc));
       ASSERT_EQ(docs->value(), doc->value);
-      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid( docs->value()));
       auto docs_seek = prepared->execute(*sub);
       ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
 
       ASSERT_TRUE(docs->next());
       ASSERT_TRUE(values(docs->value(), actual_value));
-      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
-      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
-      ASSERT_TRUE(values(docs->value(), actual_value));
-      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
-
-      ASSERT_TRUE(docs->next());
-      ASSERT_TRUE(values(docs->value(), actual_value));
-      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
       ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
       ASSERT_TRUE(values(docs->value(), actual_value));
-      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
 
       ASSERT_TRUE(docs->next());
       ASSERT_TRUE(values(docs->value(), actual_value));
-      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
       ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
       ASSERT_TRUE(values(docs->value(), actual_value));
-      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
 
       ASSERT_FALSE(docs->next());
       ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
       ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs_seek->seek(irs::type_limits<irs::type_t::doc_id_t>::eof())));
     }
 
-    // "quick brown fox" with order
+    // "fo* ... qui*" with phrase offset
+    // which is does not matter
     {
       irs::bytes_ref actual_value;
 
       irs::by_phrase q;
-      q.field("phrase_anl")
-       .push_back("quick")
-       .push_back("brown")
-       .push_back("fox");
-
-      size_t collect_field_count = 0;
-      size_t collect_term_count = 0;
-      size_t finish_count = 0;
-      irs::order ord;
-      auto& sort = ord.add<tests::sort::custom_sort>(false);
+      irs::by_phrase::prefix_term pt1;
+      pt1.term = irs::ref_cast<irs::byte_type>(irs::string_ref("fo"));
+      irs::by_phrase::prefix_term pt2;
+      pt2.term = irs::ref_cast<irs::byte_type>(irs::string_ref("qui"));
+      q.field("phrase_anl").push_back(std::move(pt1), irs::integer_traits<size_t>::const_max)
+       .push_back(std::move(pt2), 1);
 
-      sort.collector_collect_field = [&collect_field_count](const irs::sub_reader&, const irs::term_reader&)->void{
-        ++collect_field_count;
-      };
-      sort.collector_collect_term = [&collect_term_count](const irs::sub_reader&, const irs::term_reader&, const irs::attribute_view&)->void{
-        ++collect_term_count;
-      };
-      sort.collectors_collect_ = [&finish_count](irs::byte_type*, const irs::index_reader&, const irs::sort::field_collector*, const irs::sort::term_collector*)->void {
-        ++finish_count;
-      };
-      sort.prepare_field_collector_ = [&sort]()->irs::sort::field_collector::ptr {
-        return irs::memory::make_unique<tests::sort::custom_sort::prepared::collector>(sort);
-      };
-      sort.prepare_term_collector_ = [&sort]()->irs::sort::term_collector::ptr {
-        return irs::memory::make_unique<tests::sort::custom_sort::prepared::collector>(sort);
-      };
-      sort.scorer_add = [](irs::doc_id_t& dst, const irs::doc_id_t& src)->void {
-        ASSERT_TRUE(
-          irs::type_limits<irs::type_t::doc_id_t>::invalid() == dst
-          || dst == src
-        );
-        dst = src;
-      };
+      auto prepared = q.prepare(rdr);
 
-      auto pord = ord.prepare();
-      auto prepared = q.prepare(rdr, pord);
-      ASSERT_EQ(1, collect_field_count); // 1 field in 1 segment
-      ASSERT_EQ(3, collect_term_count); // 3 different terms
-      ASSERT_EQ(3, finish_count); // 3 sub-terms in phrase
       auto sub = rdr.begin();
       auto column = sub->column_reader("name");
       ASSERT_NE(nullptr, column);
       auto values = column->values();
-      auto docs = prepared->execute(*sub, pord);
+      auto docs = prepared->execute(*sub);
       auto& doc = docs->attributes().get<irs::document>();
       ASSERT_TRUE(bool(doc));
       ASSERT_EQ(docs->value(), doc->value);
-      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid( docs->value()));
       auto docs_seek = prepared->execute(*sub);
       ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
-      auto& score = docs->attributes().get<irs::score>();
-      ASSERT_FALSE(!score);
-
-      ASSERT_TRUE(docs->next());
-      ASSERT_TRUE(values(docs->value(), actual_value));
-      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
-      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
-      ASSERT_TRUE(values(docs->value(), actual_value));
-      ASSERT_EQ("A", irs::to_string<irs::string_ref>(actual_value.c_str()));
 
       ASSERT_TRUE(docs->next());
       ASSERT_TRUE(values(docs->value(), actual_value));
-      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
       ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
       ASSERT_TRUE(values(docs->value(), actual_value));
-      ASSERT_EQ("G", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ("L", irs::to_string<irs::string_ref>(actual_value.c_str()));
 
       ASSERT_TRUE(docs->next());
       ASSERT_TRUE(values(docs->value(), actual_value));
-      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
       ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
       ASSERT_TRUE(values(docs->value(), actual_value));
-      ASSERT_EQ("I", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ("N", irs::to_string<irs::string_ref>(actual_value.c_str()));
 
       ASSERT_FALSE(docs->next());
       ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
       ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs_seek->seek(irs::type_limits<irs::type_t::doc_id_t>::eof())));
     }
 
-    // "fox ... quick"
+    // "fo% ... qui%" with phrase offset
+    // which is does not matter
     {
       irs::bytes_ref actual_value;
 
       irs::by_phrase q;
-      q.field("phrase_anl")
-       .push_back("fox")
-       .push_back("quick", 1);
+      irs::by_phrase::wildcard_term wt1;
+      wt1.term = irs::ref_cast<irs::byte_type>(irs::string_ref("fo%"));
+      irs::by_phrase::wildcard_term wt2;
+      wt2.term = irs::ref_cast<irs::byte_type>(irs::string_ref("qui%"));
+      q.field("phrase_anl").push_back(std::move(wt1), irs::integer_traits<size_t>::const_max)
+       .push_back(std::move(wt2), 1);
 
       auto prepared = q.prepare(rdr);
 
@@ -449,7 +5456,7 @@ class phrase_filter_test_case : public tests::filter_test_case_base {
       auto& doc = docs->attributes().get<irs::document>();
       ASSERT_TRUE(bool(doc));
       ASSERT_EQ(docs->value(), doc->value);
-      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid( docs->value()));
       auto docs_seek = prepared->execute(*sub);
       ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
 
@@ -472,15 +5479,19 @@ class phrase_filter_test_case : public tests::filter_test_case_base {
       ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs_seek->seek(irs::type_limits<irs::type_t::doc_id_t>::eof())));
     }
 
-    // "fox ... quick" with phrase offset
+    // "fo% ... quik" with phrase offset
     // which is does not matter
     {
       irs::bytes_ref actual_value;
 
       irs::by_phrase q;
-      q.field("phrase_anl")
-       .push_back("fox", irs::integer_traits<size_t>::const_max)
-       .push_back("quick", 1);
+      irs::by_phrase::wildcard_term wt;
+      wt.term = irs::ref_cast<irs::byte_type>(irs::string_ref("fo%"));
+      irs::by_phrase::levenshtein_term lt;
+      lt.max_distance = 1;
+      lt.term = irs::ref_cast<irs::byte_type>(irs::string_ref("quik"));
+      q.field("phrase_anl").push_back(std::move(wt), irs::integer_traits<size_t>::const_max)
+       .push_back(std::move(lt), 1);
 
       auto prepared = q.prepare(rdr);
 
@@ -519,8 +5530,72 @@ class phrase_filter_test_case : public tests::filter_test_case_base {
     {
       irs::by_phrase q;
       q.field("phrase_anl")
-       .push_back("fox")
-       .push_back("quick", 10);
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("fox"))})
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("quick"))}, 10);
+
+      auto prepared = q.prepare(rdr);
+
+      auto sub = rdr.begin();
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      ASSERT_FALSE(docs->next());
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+    }
+
+    // "fox ... ... ... ... ... ... ... ... ... ... qui*"
+    {
+      irs::by_phrase q;
+      irs::by_phrase::prefix_term pt;
+      pt.term = irs::ref_cast<irs::byte_type>(irs::string_ref("qui"));
+      q.field("phrase_anl")
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("fox"))})
+       .push_back(std::move(pt), 10);
+
+      auto prepared = q.prepare(rdr);
+
+      auto sub = rdr.begin();
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      ASSERT_FALSE(docs->next());
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+    }
+
+    // "fox ... ... ... ... ... ... ... ... ... ... qu_ck"
+    {
+      irs::by_phrase q;
+      irs::by_phrase::wildcard_term wt;
+      wt.term = irs::ref_cast<irs::byte_type>(irs::string_ref("qu_ck"));
+      q.field("phrase_anl")
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("fox"))})
+       .push_back(std::move(wt), 10);
+
+      auto prepared = q.prepare(rdr);
+
+      auto sub = rdr.begin();
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      ASSERT_FALSE(docs->next());
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+    }
+
+    // "fox ... ... ... ... ... ... ... ... ... ... quc"
+    {
+      irs::by_phrase q;
+      irs::by_phrase::levenshtein_term lt;
+      lt.max_distance = 2;
+      lt.term = irs::ref_cast<irs::byte_type>(irs::string_ref("quc"));
+      q.field("phrase_anl")
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("fox"))})
+       .push_back(std::move(lt), 10);
 
       auto prepared = q.prepare(rdr);
 
@@ -540,8 +5615,8 @@ class phrase_filter_test_case : public tests::filter_test_case_base {
 
       irs::by_phrase q;
       q.field("phrase_anl")
-       .push_back("eye")
-       .push_back("eye", 1);
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("eye"))})
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("eye"))}, 1);
 
       auto prepared = q.prepare(rdr);
 
@@ -575,14 +5650,63 @@ class phrase_filter_test_case : public tests::filter_test_case_base {
 
       irs::by_phrase q;
       q.field("phrase_anl")
-       .push_back("as")
-       .push_back("in")
-       .push_back("the")
-       .push_back("past")
-       .push_back("we")
-       .push_back("are")
-       .push_back("looking")
-       .push_back("forward");
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("as"))})
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("in"))})
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("the"))})
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("past"))})
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("we"))})
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("are"))})
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("looking"))})
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("forward"))});
+
+      auto prepared = q.prepare(rdr);
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+      auto docs = prepared->execute(*sub);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+
+      ASSERT_TRUE(docs->next());
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("H", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("H", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs_seek->seek(irs::type_limits<irs::type_t::doc_id_t>::eof())));
+    }
+
+    // "as in % past we ___ looking forward"
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::levenshtein_term lt;
+      lt.max_distance = 2;
+      lt.term = irs::ref_cast<irs::byte_type>(irs::string_ref("ass"));
+      irs::by_phrase::wildcard_term wt1;
+      wt1.term = irs::ref_cast<irs::byte_type>(irs::string_ref("%"));
+      irs::by_phrase::wildcard_term wt2;
+      wt2.term = irs::ref_cast<irs::byte_type>(irs::string_ref("___"));
+      irs::by_phrase::prefix_term pt;
+      pt.term = irs::ref_cast<irs::byte_type>(irs::string_ref("fo"));
+      q.field("phrase_anl")
+       .push_back(std::move(lt))
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("in"))})
+       .push_back(std::move(wt1))
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("past"))})
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("we"))})
+       .push_back(std::move(wt2))
+       .push_back(irs::by_phrase::set_term{{irs::ref_cast<irs::byte_type>(irs::string_ref("looking")), irs::ref_cast<irs::byte_type>(irs::string_ref("searching"))}})
+       .push_back(std::move(pt));
 
       auto prepared = q.prepare(rdr);
       auto sub = rdr.begin();
@@ -615,14 +5739,73 @@ class phrase_filter_test_case : public tests::filter_test_case_base {
 
       irs::by_phrase q;
       q.field("phrase_anl")
-       .push_back("as")
-       .push_back("in")
-       .push_back("the")
-       .push_back("past")
-       .push_back("we")
-       .push_back("are")
-       .push_back("looking")
-       .push_back("forward");
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("as"))})
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("in"))})
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("the"))})
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("past"))})
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("we"))})
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("are"))})
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("looking"))})
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("forward"))});
+
+      irs::order ord;
+      auto& sort = ord.add<tests::sort::custom_sort>(false);
+      sort.scorer_add = [](irs::doc_id_t& dst, const irs::doc_id_t& src)->void {
+        ASSERT_TRUE(
+          irs::type_limits<irs::type_t::doc_id_t>::invalid() == dst
+          || dst == src
+        );
+        dst = src;
+      };
+
+      auto pord = ord.prepare();
+      auto prepared = q.prepare(rdr, pord);
+      auto sub = rdr.begin();
+      auto column = sub->column_reader("name");
+      ASSERT_NE(nullptr, column);
+      auto values = column->values();
+      auto docs = prepared->execute(*sub, pord);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_TRUE(bool(doc));
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs->value()));
+      auto docs_seek = prepared->execute(*sub);
+      ASSERT_FALSE(irs::type_limits<irs::type_t::doc_id_t>::valid(docs_seek->value()));
+      auto& score = docs->attributes().get<irs::score>();
+      ASSERT_FALSE(!score);
+
+      ASSERT_TRUE(docs->next());
+      score->evaluate();
+      ASSERT_EQ(docs->value(),pord.get<irs::doc_id_t>(score->c_str(), 0));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("H", irs::to_string<irs::string_ref>(actual_value.c_str()));
+      ASSERT_EQ(docs->value(), docs_seek->seek(docs->value()));
+      ASSERT_TRUE(values(docs->value(), actual_value));
+      ASSERT_EQ("H", irs::to_string<irs::string_ref>(actual_value.c_str()));
+
+      ASSERT_FALSE(docs->next());
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs->value()));
+      ASSERT_TRUE(irs::type_limits<irs::type_t::doc_id_t>::eof(docs_seek->seek(irs::type_limits<irs::type_t::doc_id_t>::eof())));
+    }
+
+    // "as in the p_st we are look* forward" with order
+    {
+      irs::bytes_ref actual_value;
+
+      irs::by_phrase q;
+      irs::by_phrase::wildcard_term wt;
+      wt.term = irs::ref_cast<irs::byte_type>(irs::string_ref("p_st"));
+      irs::by_phrase::prefix_term pt;
+      pt.term = irs::ref_cast<irs::byte_type>(irs::string_ref("look"));
+      q.field("phrase_anl")
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("as"))})
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("in"))})
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("the"))})
+       .push_back(std::move(wt))
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("we"))})
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("are"))})
+       .push_back(std::move(pt))
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("forward"))});
 
       irs::order ord;
       auto& sort = ord.add<tests::sort::custom_sort>(false);
@@ -670,8 +5853,8 @@ class phrase_filter_test_case : public tests::filter_test_case_base {
 
       irs::by_phrase q;
       q.field("phrase_anl")
-       .push_back("fox")
-       .push_back("quick");
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("fox"))})
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("quick"))});
 
       auto prepared = q.prepare(rdr);
 
@@ -721,8 +5904,8 @@ class phrase_filter_test_case : public tests::filter_test_case_base {
 
       irs::by_phrase q;
       q.field("phrase_anl")
-       .push_back("fox")
-       .push_back("quick");
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("fox"))})
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("quick"))});
 
       auto prepared = q.prepare(rdr, pord);
 
@@ -762,7 +5945,6 @@ TEST(by_phrase_test, ctor) {
   ASSERT_EQ("", q.field());
   ASSERT_TRUE(q.empty());
   ASSERT_EQ(0, q.size());
-  ASSERT_EQ(q.begin(), q.end());
   ASSERT_EQ(irs::no_boost(), q.boost());
 
   auto& features = irs::by_phrase::required();
@@ -786,7 +5968,7 @@ TEST(by_phrase_test, boost) {
     // single term
     {
       irs::by_phrase q;
-      q.field("field").push_back("quick");
+      q.field("field").push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("quick"))});
 
       auto prepared = q.prepare(irs::sub_reader::empty());
       ASSERT_EQ(irs::no_boost(), prepared->boost());
@@ -795,7 +5977,8 @@ TEST(by_phrase_test, boost) {
     // multiple terms
     {
       irs::by_phrase q;
-      q.field("field").push_back("quick").push_back("brown");
+      q.field("field").push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("quick"))})
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("brown"))});
 
       auto prepared = q.prepare(irs::sub_reader::empty());
       ASSERT_EQ(irs::no_boost(), prepared->boost());
@@ -819,7 +6002,7 @@ TEST(by_phrase_test, boost) {
     // single term
     {
       irs::by_phrase q;
-      q.field("field").push_back("quick");
+      q.field("field").push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("quick"))});
       q.boost(boost);
 
       auto prepared = q.prepare(irs::sub_reader::empty());
@@ -829,7 +6012,25 @@ TEST(by_phrase_test, boost) {
     // single multiple terms 
     {
       irs::by_phrase q;
-      q.field("field").push_back("quick").push_back("brown");
+      q.field("field").push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("quick"))})
+       .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("brown"))});
+      q.boost(boost);
+
+      auto prepared = q.prepare(irs::sub_reader::empty());
+      ASSERT_EQ(boost, prepared->boost());
+    }
+
+    // prefix, wildcard, and levenshtein terms
+    {
+      irs::by_phrase q;
+      irs::by_phrase::prefix_term pt;
+      pt.term = irs::ref_cast<irs::byte_type>(irs::string_ref("qui"));
+      irs::by_phrase::wildcard_term wt;
+      wt.term = irs::ref_cast<irs::byte_type>(irs::string_ref("qu__k"));
+      irs::by_phrase::levenshtein_term lt;
+      lt.max_distance = 1;
+      lt.term = irs::ref_cast<irs::byte_type>(irs::string_ref("brwn"));
+      q.field("field").push_back(std::move(pt)).push_back(std::move(wt)).push_back(lt);
       q.boost(boost);
 
       auto prepared = q.prepare(irs::sub_reader::empty());
@@ -843,61 +6044,83 @@ TEST(by_phrase_test, push_back_insert) {
 
   // push_back 
   {
-    q.push_back("quick");
-    q.push_back(irs::ref_cast<irs::byte_type>(irs::string_ref("brown")), 1);
-    q.push_back(irs::bstring(irs::ref_cast<irs::byte_type>(irs::string_ref("fox"))));
+    q.push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("quick"))});
+    q.push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("brown"))}, 1);
+    q.push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("fox"))});
     ASSERT_FALSE(q.empty());
     ASSERT_EQ(3, q.size());
 
     // check elements via positions
     {
-      ASSERT_EQ(irs::ref_cast<irs::byte_type>(irs::string_ref("quick")), q[0]); 
-      ASSERT_EQ(irs::ref_cast<irs::byte_type>(irs::string_ref("brown")), q[2]); 
-      ASSERT_EQ(irs::ref_cast<irs::byte_type>(irs::string_ref("fox")), q[3]); 
-    }
-
-    // check elements via iterators 
-    {
-      auto it = q.begin();
-      ASSERT_NE(q.end(), it); 
-      ASSERT_EQ(0, it->first);
-      ASSERT_EQ(irs::ref_cast<irs::byte_type>(irs::string_ref("quick")), it->second);
-
-      ++it;
-      ASSERT_NE(q.end(), it); 
-      ASSERT_EQ(2, it->first);
-      ASSERT_EQ(irs::ref_cast<irs::byte_type>(irs::string_ref("brown")), it->second);
-
-      ++it;
-      ASSERT_NE(q.end(), it); 
-      ASSERT_EQ(3, it->first);
-      ASSERT_EQ(irs::ref_cast<irs::byte_type>(irs::string_ref("fox")), it->second);
-
-      ++it;
-      ASSERT_EQ(q.end(), it); 
+      irs::by_phrase::simple_term st1;
+      ASSERT_TRUE(q.get(0, st1));
+      ASSERT_EQ(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("quick"))}, st1);
+      irs::by_phrase::simple_term st2;
+      ASSERT_TRUE(q.get(2, st2));
+      ASSERT_EQ(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("brown"))}, st2);
+      irs::by_phrase::simple_term st3;
+      ASSERT_TRUE(q.get(3, st3));
+      ASSERT_EQ(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("fox"))}, st3);
     }
 
     // push term 
     {
-      q.push_back("squirrel", 0);
-      ASSERT_EQ(irs::ref_cast<irs::byte_type>(irs::string_ref("squirrel")), q[4]); 
+      irs::by_phrase::simple_term st1{irs::ref_cast<irs::byte_type>(irs::string_ref("squirrel"))};
+      q.push_back(st1, 0);
+      irs::by_phrase::simple_term st2;
+      ASSERT_TRUE(q.get(4, st2));
+      ASSERT_EQ(st1, st2);
+
+      irs::by_phrase::prefix_term pt1;
+      pt1.term = irs::ref_cast<irs::byte_type>(irs::string_ref("cat"));
+      q.push_back(pt1, 0);
+      irs::by_phrase::prefix_term pt2;
+      ASSERT_TRUE(q.get(5, pt2));
+      ASSERT_EQ(pt1, pt2);
+
+      irs::by_phrase::wildcard_term wt1;
+      wt1.term = irs::ref_cast<irs::byte_type>(irs::string_ref("dog"));
+      q.push_back(wt1, 0);
+      irs::by_phrase::wildcard_term wt2;
+      ASSERT_TRUE(q.get(6, wt2));
+      ASSERT_EQ(wt1, wt2);
+
+      irs::by_phrase::levenshtein_term lt1;
+      lt1.term = irs::ref_cast<irs::byte_type>(irs::string_ref("whale"));
+      q.push_back(lt1, 0);
+      irs::by_phrase::levenshtein_term lt2;
+      ASSERT_TRUE(q.get(7, lt2));
+      ASSERT_EQ(lt1, lt2);
+
+      irs::by_phrase::set_term ct1;
+      ct1.terms = {irs::ref_cast<irs::byte_type>(irs::string_ref("bird"))};
+      q.push_back(ct1, 0);
+      irs::by_phrase::set_term ct2;
+      ASSERT_TRUE(q.get(8, ct2));
+      ASSERT_EQ(ct1, ct2);
     }
-    ASSERT_EQ(4, q.size());
+    ASSERT_EQ(8, q.size());
   }
 
   // insert
   {
-    q[3] = irs::ref_cast<irs::byte_type>(irs::string_ref("jumps"));
-    ASSERT_EQ(irs::ref_cast<irs::byte_type>(irs::string_ref("jumps")), q[3]);
-    ASSERT_EQ(4, q.size());
-
-    q.insert(5, "lazy");
-    ASSERT_EQ(irs::ref_cast<irs::byte_type>(irs::string_ref("lazy")), q[5]);
-    ASSERT_EQ(5, q.size());
-    
-    q.insert(28, irs::bstring(irs::ref_cast<irs::byte_type>(irs::string_ref("dog"))));
-    ASSERT_EQ(irs::ref_cast<irs::byte_type>(irs::string_ref("dog")), q[28]); 
-    ASSERT_EQ(6, q.size());
+    q.insert(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("jumps"))}, 3);
+    irs::by_phrase::simple_term st1;
+    ASSERT_TRUE(q.get(3, st1));
+    ASSERT_EQ(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("jumps"))}, st1);
+    ASSERT_EQ(8, q.size());
+
+    q.insert(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("lazy"))}, 9);
+    irs::by_phrase::simple_term st2;
+    ASSERT_TRUE(q.get(9, st2));
+    ASSERT_EQ(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("lazy"))}, st2);
+    ASSERT_EQ(9, q.size());
+
+    q.insert(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("dog"))}, 28);
+    irs::by_phrase::simple_term st3;
+    ASSERT_TRUE(q.get(28, st3));
+    ASSERT_EQ(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("dog"))}, st3);
+    ASSERT_EQ(10, q.size());
   }
 }
 
@@ -907,13 +6130,50 @@ TEST(by_phrase_test, equal) {
   {
     irs::by_phrase q0;
     q0.field("name");
-    q0.push_back("quick");
-    q0.push_back("brown");
+    q0.push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("quick"))});
+    q0.push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("brown"))});
+
+    irs::by_phrase q1;
+    q1.field("name");
+    q1.push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("quick"))});
+    q1.push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("brown"))});
+    ASSERT_EQ(q0, q1);
+    ASSERT_EQ(q0.hash(), q1.hash());
+  }
+
+  {
+    irs::by_phrase q0;
+    irs::by_phrase::prefix_term pt1;
+    pt1.term = irs::ref_cast<irs::byte_type>(irs::string_ref("qui"));
+    irs::by_phrase::set_term ct1;
+    ct1.terms = {irs::ref_cast<irs::byte_type>(irs::string_ref("light")),
+                irs::ref_cast<irs::byte_type>(irs::string_ref("dark"))};
+    irs::by_phrase::wildcard_term wt1;
+    wt1.term = irs::ref_cast<irs::byte_type>(irs::string_ref("br_wn"));
+    irs::by_phrase::levenshtein_term lt1;
+    lt1.max_distance = 2;
+    lt1.term = irs::ref_cast<irs::byte_type>(irs::string_ref("fo"));
+    q0.field("name");
+    q0.push_back(std::move(pt1));
+    q0.push_back(std::move(ct1));
+    q0.push_back(std::move(wt1));
+    q0.push_back(std::move(lt1));
 
     irs::by_phrase q1;
+    irs::by_phrase::prefix_term pt2;
+    pt2.term = irs::ref_cast<irs::byte_type>(irs::string_ref("qui"));
+    irs::by_phrase::set_term ct2;
+    ct2.terms = {irs::ref_cast<irs::byte_type>(irs::string_ref("light")), irs::ref_cast<irs::byte_type>(irs::string_ref("dark"))};
+    irs::by_phrase::wildcard_term wt2;
+    wt2.term = irs::ref_cast<irs::byte_type>(irs::string_ref("br_wn"));
+    irs::by_phrase::levenshtein_term lt2;
+    lt2.max_distance = 2;
+    lt2.term = irs::ref_cast<irs::byte_type>(irs::string_ref("fo"));
     q1.field("name");
-    q1.push_back("quick");
-    q1.push_back("brown");
+    q1.push_back(std::move(pt2));
+    q1.push_back(std::move(ct2));
+    q1.push_back(std::move(wt2));
+    q1.push_back(std::move(lt2));
     ASSERT_EQ(q0, q1);
     ASSERT_EQ(q0.hash(), q1.hash());
   }
@@ -921,38 +6181,74 @@ TEST(by_phrase_test, equal) {
   {
     irs::by_phrase q0;
     q0.field("name");
-    q0.push_back("quick");
-    q0.push_back("squirrel");
+    q0.push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("quick"))});
+    q0.push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("squirrel"))});
 
     irs::by_phrase q1;
     q1.field("name");
-    q1.push_back("quick");
-    q1.push_back("brown");
+    q1.push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("quick"))});
+    q1.push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("brown"))});
     ASSERT_NE(q0, q1);
   }
 
   {
     irs::by_phrase q0;
     q0.field("name1");
-    q0.push_back("quick");
-    q0.push_back("brown");
+    q0.push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("quick"))});
+    q0.push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("brown"))});
+
+    irs::by_phrase q1;
+    q1.field("name");
+    q1.push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("quick"))});
+    q1.push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("brown"))});
+    ASSERT_NE(q0, q1);
+  }
+
+  {
+    irs::by_phrase q0;
+    q0.field("name");
+    q0.push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("quick"))});
 
     irs::by_phrase q1;
     q1.field("name");
-    q1.push_back("quick");
-    q1.push_back("brown");
+    q1.push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("quick"))});
+    q1.push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("brown"))});
     ASSERT_NE(q0, q1);
   }
 
   {
     irs::by_phrase q0;
+    irs::by_phrase::prefix_term pt1;
+    pt1.term = irs::ref_cast<irs::byte_type>(irs::string_ref("quil"));
+    irs::by_phrase::set_term ct1;
+    ct1.terms = {irs::ref_cast<irs::byte_type>(irs::string_ref("light")),
+                irs::ref_cast<irs::byte_type>(irs::string_ref("dark"))};
+    irs::by_phrase::wildcard_term wt1;
+    wt1.term = irs::ref_cast<irs::byte_type>(irs::string_ref("br_wn"));
+    irs::by_phrase::levenshtein_term lt1;
+    lt1.max_distance = 2;
+    lt1.term = irs::ref_cast<irs::byte_type>(irs::string_ref("fo"));
     q0.field("name");
-    q0.push_back("quick");
+    q0.push_back(std::move(pt1));
+    q0.push_back(std::move(ct1));
+    q0.push_back(std::move(wt1));
+    q0.push_back(std::move(lt1));
 
     irs::by_phrase q1;
+    irs::by_phrase::prefix_term pt2;
+    pt2.term = irs::ref_cast<irs::byte_type>(irs::string_ref("qui"));
+    irs::by_phrase::set_term ct2;
+    ct2.terms = {irs::ref_cast<irs::byte_type>(irs::string_ref("light")), irs::ref_cast<irs::byte_type>(irs::string_ref("dark"))};
+    irs::by_phrase::wildcard_term wt2;
+    wt2.term = irs::ref_cast<irs::byte_type>(irs::string_ref("br_wn"));
+    irs::by_phrase::levenshtein_term lt2;
+    lt2.max_distance = 2;
+    lt2.term = irs::ref_cast<irs::byte_type>(irs::string_ref("fo"));
     q1.field("name");
-    q1.push_back("quick");
-    q1.push_back("brown");
+    q1.push_back(std::move(pt2));
+    q1.push_back(std::move(ct2));
+    q1.push_back(std::move(wt2));
+    q1.push_back(std::move(lt2));
     ASSERT_NE(q0, q1);
   }
 }
@@ -966,7 +6262,7 @@ INSTANTIATE_TEST_CASE_P(
       &tests::fs_directory,
       &tests::mmap_directory
     ),
-    ::testing::Values("1_0")
+    ::testing::Values("1_0", "1_3")
   ),
   tests::to_string
 );
diff --git a/3rdParty/iresearch/tests/search/same_position_filter_tests.cpp b/3rdParty/iresearch/tests/search/same_position_filter_tests.cpp
index e9aa5f319366..08049a93cd86 100644
--- a/3rdParty/iresearch/tests/search/same_position_filter_tests.cpp
+++ b/3rdParty/iresearch/tests/search/same_position_filter_tests.cpp
@@ -229,6 +229,22 @@ class same_position_filter_test_case : public tests::filter_test_case_base {
       ASSERT_EQ(irs::type_limits<irs::type_t::doc_id_t>::eof(), docs->value());
     }
 
+    // check document with first position
+    // { a: 300, b:90, c:9 }
+    {
+      irs::by_same_position q;
+      q.push_back("a", irs::ref_cast<irs::byte_type>(irs::string_ref("300")));
+      q.push_back("b", irs::ref_cast<irs::byte_type>(irs::string_ref("90")));
+      q.push_back("c", irs::ref_cast<irs::byte_type>(irs::string_ref("9")));
+      auto prepared = q.prepare(index);
+      auto docs = prepared->execute(segment);
+      auto& doc = docs->attributes().get<irs::document>();
+      ASSERT_EQ(docs->value(), doc->value);
+      ASSERT_EQ(irs::type_limits<irs::type_t::doc_id_t>::invalid(), docs->value());
+      ASSERT_TRUE(docs->next());
+      ASSERT_EQ(1, docs->value());
+    }
+
     // { a: 100, b:30, c:6 }
     {
       irs::by_same_position q;
@@ -624,7 +640,7 @@ INSTANTIATE_TEST_CASE_P(
       &tests::fs_directory,
       &tests::mmap_directory
     ),
-    ::testing::Values("1_0")
+    ::testing::Values("1_0", "1_3")
   ),
   tests::to_string
 );
diff --git a/3rdParty/iresearch/tests/search/sort_tests.cpp b/3rdParty/iresearch/tests/search/sort_tests.cpp
index 7899d306861b..41a8c82891d2 100644
--- a/3rdParty/iresearch/tests/search/sort_tests.cpp
+++ b/3rdParty/iresearch/tests/search/sort_tests.cpp
@@ -68,7 +68,7 @@ struct aligned_scorer : public irs::sort {
     ) const override {
       return { nullptr, nullptr };
     }
-    const irs::flags& features() const {
+    virtual const irs::flags& features() const override {
       return features_;
     }
 
diff --git a/3rdParty/iresearch/tests/search/tfidf_test.cpp b/3rdParty/iresearch/tests/search/tfidf_test.cpp
index 28352d17a4e9..920ed2126c4f 100644
--- a/3rdParty/iresearch/tests/search/tfidf_test.cpp
+++ b/3rdParty/iresearch/tests/search/tfidf_test.cpp
@@ -245,8 +245,8 @@ TEST_P(tfidf_test, test_phrase) {
   {
     irs::by_phrase filter;
     filter.field("phrase_anl")
-          .push_back("jumps")
-          .push_back("high");
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("jumps"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("high"))});
 
     std::multimap<irs::bstring, std::string, decltype(comparer)> sorted(comparer);
 
@@ -837,7 +837,7 @@ TEST_P(tfidf_test, test_query) {
   {
     irs::by_phrase filter;
 
-    filter.field("field").push_back("7");
+    filter.field("field").push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("7"))});
 
     std::multimap<irs::bstring, uint64_t, decltype(comparer)> sorted(comparer);
     std::vector<std::pair<float_t, uint64_t>> expected = {
diff --git a/3rdParty/iresearch/tests/search/wildcard_filter_test.cpp b/3rdParty/iresearch/tests/search/wildcard_filter_test.cpp
index 106fdc5639b9..18b56bd892f3 100644
--- a/3rdParty/iresearch/tests/search/wildcard_filter_test.cpp
+++ b/3rdParty/iresearch/tests/search/wildcard_filter_test.cpp
@@ -28,118 +28,10 @@
 #include "search/term_filter.hpp"
 #include "search/all_filter.hpp"
 #include "search/prefix_filter.hpp"
+#include "search/multiterm_query.hpp"
 #endif
 
-class wildcard_filter_test_case : public tests::filter_test_case_base {
- protected:
-  //void by_prefix_order() {
-  //  // add segment
-  //  {
-  //    tests::json_doc_generator gen(
-  //      resource("simple_sequential.json"),
-  //      &tests::generic_json_field_factory);
-  //    add_segment( gen );
-  //  }
-
-  //  auto rdr = open_reader();
-
-  //  // empty query
-  //  check_query(irs::by_prefix(), docs_t{}, costs_t{0}, rdr);
-
-  //  // empty prefix test collector call count for field/term/finish
-  //  {
-  //    docs_t docs{ 1, 4, 9, 16, 21, 24, 26, 29, 31, 32 };
-  //    costs_t costs{ docs.size() };
-  //    irs::order order;
-
-  //    size_t collect_field_count = 0;
-  //    size_t collect_term_count = 0;
-  //    size_t finish_count = 0;
-  //    auto& scorer = order.add<tests::sort::custom_sort>(false);
-
-  //    scorer.collector_collect_field = [&collect_field_count](const irs::sub_reader&, const irs::term_reader&)->void{
-  //      ++collect_field_count;
-  //    };
-  //    scorer.collector_collect_term = [&collect_term_count](const irs::sub_reader&, const irs::term_reader&, const irs::attribute_view&)->void{
-  //      ++collect_term_count;
-  //    };
-  //    scorer.collectors_collect_ = [&finish_count](irs::byte_type*, const irs::index_reader&, const irs::sort::field_collector*, const irs::sort::term_collector*)->void {
-  //      ++finish_count;
-  //    };
-  //    scorer.prepare_field_collector_ = [&scorer]()->irs::sort::field_collector::ptr {
-  //      return irs::memory::make_unique<tests::sort::custom_sort::prepared::collector>(scorer);
-  //    };
-  //    scorer.prepare_term_collector_ = [&scorer]()->irs::sort::term_collector::ptr {
-  //      return irs::memory::make_unique<tests::sort::custom_sort::prepared::collector>(scorer);
-  //    };
-  //    check_query(irs::by_prefix().field("prefix"), order, docs, rdr);
-  //    ASSERT_EQ(9, collect_field_count); // 9 fields (1 per term since treated as a disjunction) in 1 segment
-  //    ASSERT_EQ(9, collect_term_count); // 9 different terms
-  //    ASSERT_EQ(9, finish_count); // 9 unque terms
-  //  }
-
-  //  // empty prefix
-  //  {
-  //    docs_t docs{ 31, 32, 1, 4, 9, 16, 21, 24, 26, 29 };
-  //    costs_t costs{ docs.size() };
-  //    irs::order order;
-
-  //    order.add<tests::sort::frequency_sort>(false);
-  //    check_query(irs::by_prefix().field("prefix"), order, docs, rdr);
-  //  }
-
-  //  //FIXME
-  //  // empty prefix + scored_terms_limit
-////    {
-////      docs_t docs{ 31, 32, 1, 4, 9, 16, 21, 24, 26, 29 };
-////      costs_t costs{ docs.size() };
-////      irs::order order;
-////
-////      order.add<sort::frequency_sort>(false);
-////      check_query(irs::by_prefix().field("prefix").scored_terms_limit(1), order, docs, rdr);
-////    }
-////
-  //  // prefix
-  //  {
-  //    docs_t docs{ 31, 32, 1, 4, 16, 21, 26, 29 };
-  //    costs_t costs{ docs.size() };
-  //    irs::order order;
-
-  //    order.add<tests::sort::frequency_sort>(false);
-  //    check_query(irs::by_prefix().field("prefix").term("a"), order, docs, rdr);
-  //  }
-  //}
-
-  //void by_prefix_schemas() {
-  //  // write segments
-  //  {
-  //    auto writer = open_writer(irs::OM_CREATE);
-
-  //    std::vector<tests::doc_generator_base::ptr> gens;
-  //    gens.emplace_back(new tests::json_doc_generator(
-  //      resource("AdventureWorks2014.json"),
-  //      &tests::generic_json_field_factory
-  //    ));
-  //    gens.emplace_back(new tests::json_doc_generator(
-  //      resource("AdventureWorks2014Edges.json"),
-  //      &tests::generic_json_field_factory
-  //    ));
-  //    gens.emplace_back(new tests::json_doc_generator(
-  //      resource("Northwnd.json"),
-  //      &tests::generic_json_field_factory
-  //    ));
-  //    gens.emplace_back(new tests::json_doc_generator(
-  //      resource("NorthwndEdges.json"),
-  //      &tests::generic_json_field_factory
-  //    ));
-  //    add_segments(*writer, gens);
-  //  }
-
-  //  auto rdr = open_reader();
-
-  //  check_query(irs::by_prefix().field("Name").term("Addr"), docs_t{1, 2, 77, 78}, rdr);
-  //}
-}; // wildcard_filter_test_case
+class wildcard_filter_test_case : public tests::filter_test_case_base { };
 
 TEST(by_wildcard_test, ctor) {
   irs::by_wildcard q;
@@ -181,28 +73,6 @@ TEST(by_wildcard_test, boost) {
   }
 }
 
-TEST(by_wildcard_test, wildcard_type) {
-  ASSERT_EQ(irs::WildcardType::TERM, irs::wildcard_type(irs::ref_cast<irs::byte_type>(irs::string_ref("foo"))));
-  ASSERT_EQ(irs::WildcardType::TERM, irs::wildcard_type(irs::ref_cast<irs::byte_type>(irs::string_ref("\\foo"))));
-  ASSERT_EQ(irs::WildcardType::TERM, irs::wildcard_type(irs::ref_cast<irs::byte_type>(irs::string_ref("\\%foo"))));
-  ASSERT_EQ(irs::WildcardType::TERM, irs::wildcard_type(irs::ref_cast<irs::byte_type>(irs::string_ref("\foo"))));
-  ASSERT_EQ(irs::WildcardType::PREFIX, irs::wildcard_type(irs::ref_cast<irs::byte_type>(irs::string_ref("foo%"))));
-  ASSERT_EQ(irs::WildcardType::PREFIX, irs::wildcard_type(irs::ref_cast<irs::byte_type>(irs::string_ref("foo%%"))));
-  ASSERT_EQ(irs::WildcardType::WILDCARD, irs::wildcard_type(irs::ref_cast<irs::byte_type>(irs::string_ref("foo%_"))));
-  ASSERT_EQ(irs::WildcardType::WILDCARD, irs::wildcard_type(irs::ref_cast<irs::byte_type>(irs::string_ref("foo%\\"))));
-  ASSERT_EQ(irs::WildcardType::WILDCARD, irs::wildcard_type(irs::ref_cast<irs::byte_type>(irs::string_ref("foo_%"))));
-  ASSERT_EQ(irs::WildcardType::PREFIX, irs::wildcard_type(irs::ref_cast<irs::byte_type>(irs::string_ref("foo\\_%"))));
-  ASSERT_EQ(irs::WildcardType::WILDCARD, irs::wildcard_type(irs::ref_cast<irs::byte_type>(irs::string_ref("foo__"))));
-  ASSERT_EQ(irs::WildcardType::PREFIX, irs::wildcard_type(irs::ref_cast<irs::byte_type>(irs::string_ref("foo\\%%"))));
-  ASSERT_EQ(irs::WildcardType::PREFIX, irs::wildcard_type(irs::ref_cast<irs::byte_type>(irs::string_ref("foo\\%%%"))));
-  ASSERT_EQ(irs::WildcardType::TERM, irs::wildcard_type(irs::ref_cast<irs::byte_type>(irs::string_ref("foo\\%\\%"))));
-  ASSERT_EQ(irs::WildcardType::MATCH_ALL, irs::wildcard_type(irs::ref_cast<irs::byte_type>(irs::string_ref("%"))));
-  ASSERT_EQ(irs::WildcardType::MATCH_ALL, irs::wildcard_type(irs::ref_cast<irs::byte_type>(irs::string_ref("%%"))));
-  ASSERT_EQ(irs::WildcardType::WILDCARD, irs::wildcard_type(irs::ref_cast<irs::byte_type>(irs::string_ref("%c%"))));
-  ASSERT_EQ(irs::WildcardType::WILDCARD, irs::wildcard_type(irs::ref_cast<irs::byte_type>(irs::string_ref("%%c%"))));
-  ASSERT_EQ(irs::WildcardType::WILDCARD, irs::wildcard_type(irs::ref_cast<irs::byte_type>(irs::string_ref("%c%%"))));
-}
-
 #ifndef IRESEARCH_DLL
 
 TEST(by_wildcard_test, test_type_of_prepared_query) {
@@ -321,17 +191,6 @@ TEST_P(wildcard_filter_test_case, simple_sequential_order) {
     check_query(irs::by_prefix().field("prefix"), order, docs, rdr);
   }
 
-  //FIXME
-  // empty prefix + scored_terms_limit
-//    {
-//      docs_t docs{ 31, 32, 1, 4, 9, 16, 21, 24, 26, 29 };
-//      costs_t costs{ docs.size() };
-//      irs::order order;
-//
-//      order.add<sort::frequency_sort>(false);
-//      check_query(irs::by_prefix().field("prefix").scored_terms_limit(1), order, docs, rdr);
-//    }
-//
   // prefix
   {
     docs_t docs{ 31, 32, 1, 4, 16, 21, 26, 29 };
@@ -347,7 +206,7 @@ TEST_P(wildcard_filter_test_case, simple_sequential) {
   // add segment
   {
     tests::json_doc_generator gen(
-      resource("simple_sequential.json"),
+      resource("simple_sequential_utf8.json"),
       &tests::generic_json_field_factory);
     add_segment( gen );
   }
@@ -469,6 +328,38 @@ TEST_P(wildcard_filter_test_case, simple_sequential) {
     check_query(irs::by_wildcard().field("prefix").term("abc%%"), docs, costs, rdr);
   }
 
+  {
+    docs_t docs{ 1, 4, 16, 26 };
+    costs_t costs{ docs.size() };
+
+    check_query(irs::by_wildcard().field("prefix").term("a%d%"), docs, costs, rdr);
+    check_query(irs::by_wildcard().field("prefix").term("a%d%%"), docs, costs, rdr);
+  }
+
+  {
+    docs_t docs{ 1, 26 };
+    costs_t costs{ docs.size() };
+
+    check_query(irs::by_wildcard().field("utf8").term("\x25\xD0\xB9"), docs, costs, rdr);
+    check_query(irs::by_wildcard().field("utf8").term("\x25\x25\xD0\xB9"), docs, costs, rdr);
+  }
+
+  {
+    docs_t docs{ 26 };
+    costs_t costs{ docs.size() };
+
+    check_query(irs::by_wildcard().field("utf8").term("\xD0\xB2\x25\xD0\xB9"), docs, costs, rdr);
+    check_query(irs::by_wildcard().field("utf8").term("\xD0\xB2\x25\x25\xD0\xB9"), docs, costs, rdr);
+  }
+
+  {
+    docs_t docs{ 1, 3 };
+    costs_t costs{ docs.size() };
+
+    check_query(irs::by_wildcard().field("utf8").term("\xD0\xBF\x25"), docs, costs, rdr);
+    check_query(irs::by_wildcard().field("utf8").term("\xD0\xBF\x25\x25"), docs, costs, rdr);
+  }
+
   // whole word
   check_query(irs::by_wildcard().field("prefix").term("bateradsfsfasdf"), docs_t{24}, costs_t{1}, rdr);
 }
@@ -482,7 +373,7 @@ INSTANTIATE_TEST_CASE_P(
       &tests::fs_directory,
       &tests::mmap_directory
     ),
-    ::testing::Values("1_0", "1_1", "1_2")
+    ::testing::Values("1_0", "1_1", "1_2", "1_3")
   ),
   tests::to_string
 );
diff --git a/3rdParty/iresearch/tests/unicode/utf8.h b/3rdParty/iresearch/tests/unicode/utf8.h
deleted file mode 100644
index 82b13f59f983..000000000000
--- a/3rdParty/iresearch/tests/unicode/utf8.h
+++ /dev/null
@@ -1,34 +0,0 @@
-// Copyright 2006 Nemanja Trifunovic
-
-/*
-Permission is hereby granted, free of charge, to any person or organization
-obtaining a copy of the software and accompanying documentation covered by
-this license (the "Software") to use, reproduce, display, distribute,
-execute, and transmit the Software, and to prepare derivative works of the
-Software, and to permit third-parties to whom the Software is furnished to
-do so, all subject to the following:
-
-The copyright notices in the Software and this entire statement, including
-the above license grant, this restriction and the following disclaimer,
-must be included in all copies of the Software, in whole or in part, and
-all derivative works of the Software, unless such copies or derivative
-works are solely in the form of machine-executable object code generated by
-a source language processor.
-
-THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
-SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
-FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
-ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
-DEALINGS IN THE SOFTWARE.
-*/
-
-
-#ifndef UTF8_FOR_CPP_2675DCD0_9480_4c0c_B92A_CC14C027B731
-#define UTF8_FOR_CPP_2675DCD0_9480_4c0c_B92A_CC14C027B731
-
-#include "utf8/checked.h"
-#include "utf8/unchecked.h"
-
-#endif // header guard
diff --git a/3rdParty/iresearch/tests/unicode/utf8/checked.h b/3rdParty/iresearch/tests/unicode/utf8/checked.h
deleted file mode 100644
index 133115513814..000000000000
--- a/3rdParty/iresearch/tests/unicode/utf8/checked.h
+++ /dev/null
@@ -1,327 +0,0 @@
-// Copyright 2006 Nemanja Trifunovic
-
-/*
-Permission is hereby granted, free of charge, to any person or organization
-obtaining a copy of the software and accompanying documentation covered by
-this license (the "Software") to use, reproduce, display, distribute,
-execute, and transmit the Software, and to prepare derivative works of the
-Software, and to permit third-parties to whom the Software is furnished to
-do so, all subject to the following:
-
-The copyright notices in the Software and this entire statement, including
-the above license grant, this restriction and the following disclaimer,
-must be included in all copies of the Software, in whole or in part, and
-all derivative works of the Software, unless such copies or derivative
-works are solely in the form of machine-executable object code generated by
-a source language processor.
-
-THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
-SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
-FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
-ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
-DEALINGS IN THE SOFTWARE.
-*/
-
-
-#ifndef UTF8_FOR_CPP_CHECKED_H_2675DCD0_9480_4c0c_B92A_CC14C027B731
-#define UTF8_FOR_CPP_CHECKED_H_2675DCD0_9480_4c0c_B92A_CC14C027B731
-
-#include "core.h"
-#include <stdexcept>
-
-namespace utf8
-{
-    // Base for the exceptions that may be thrown from the library
-    class exception : public ::std::exception {
-    };
-
-    // Exceptions that may be thrown from the library functions.
-    class invalid_code_point : public exception {
-        uint32_t cp;
-    public:
-        invalid_code_point(uint32_t cp) : cp(cp) {}
-        virtual const char* what() const throw() { return "Invalid code point"; }
-        uint32_t code_point() const {return cp;}
-    };
-
-    class invalid_utf8 : public exception {
-        uint8_t u8;
-    public:
-        invalid_utf8 (uint8_t u) : u8(u) {}
-        virtual const char* what() const throw() { return "Invalid UTF-8"; }
-        uint8_t utf8_octet() const {return u8;}
-    };
-
-    class invalid_utf16 : public exception {
-        uint16_t u16;
-    public:
-        invalid_utf16 (uint16_t u) : u16(u) {}
-        virtual const char* what() const throw() { return "Invalid UTF-16"; }
-        uint16_t utf16_word() const {return u16;}
-    };
-
-    class not_enough_room : public exception {
-    public:
-        virtual const char* what() const throw() { return "Not enough space"; }
-    };
-
-    /// The library API - functions intended to be called by the users
-
-    template <typename octet_iterator>
-    octet_iterator append(uint32_t cp, octet_iterator result)
-    {
-        if (!utf8::internal::is_code_point_valid(cp))
-            throw invalid_code_point(cp);
-
-        if (cp < 0x80)                        // one octet
-            *(result++) = static_cast<uint8_t>(cp);
-        else if (cp < 0x800) {                // two octets
-            *(result++) = static_cast<uint8_t>((cp >> 6)            | 0xc0);
-            *(result++) = static_cast<uint8_t>((cp & 0x3f)          | 0x80);
-        }
-        else if (cp < 0x10000) {              // three octets
-            *(result++) = static_cast<uint8_t>((cp >> 12)           | 0xe0);
-            *(result++) = static_cast<uint8_t>(((cp >> 6) & 0x3f)   | 0x80);
-            *(result++) = static_cast<uint8_t>((cp & 0x3f)          | 0x80);
-        }
-        else {                                // four octets
-            *(result++) = static_cast<uint8_t>((cp >> 18)           | 0xf0);
-            *(result++) = static_cast<uint8_t>(((cp >> 12) & 0x3f)  | 0x80);
-            *(result++) = static_cast<uint8_t>(((cp >> 6) & 0x3f)   | 0x80);
-            *(result++) = static_cast<uint8_t>((cp & 0x3f)          | 0x80);
-        }
-        return result;
-    }
-
-    template <typename octet_iterator, typename output_iterator>
-    output_iterator replace_invalid(octet_iterator start, octet_iterator end, output_iterator out, uint32_t replacement)
-    {
-        while (start != end) {
-            octet_iterator sequence_start = start;
-            internal::utf_error err_code = utf8::internal::validate_next(start, end);
-            switch (err_code) {
-                case internal::UTF8_OK :
-                    for (octet_iterator it = sequence_start; it != start; ++it)
-                        *out++ = *it;
-                    break;
-                case internal::NOT_ENOUGH_ROOM:
-                    throw not_enough_room();
-                case internal::INVALID_LEAD:
-                    out = utf8::append (replacement, out);
-                    ++start;
-                    break;
-                case internal::INCOMPLETE_SEQUENCE:
-                case internal::OVERLONG_SEQUENCE:
-                case internal::INVALID_CODE_POINT:
-                    out = utf8::append (replacement, out);
-                    ++start;
-                    // just one replacement mark for the sequence
-                    while (start != end && utf8::internal::is_trail(*start))
-                        ++start;
-                    break;
-            }
-        }
-        return out;
-    }
-
-    template <typename octet_iterator, typename output_iterator>
-    inline output_iterator replace_invalid(octet_iterator start, octet_iterator end, output_iterator out)
-    {
-        static const uint32_t replacement_marker = utf8::internal::mask16(0xfffd);
-        return utf8::replace_invalid(start, end, out, replacement_marker);
-    }
-
-    template <typename octet_iterator>
-    uint32_t next(octet_iterator& it, octet_iterator end)
-    {
-        uint32_t cp = 0;
-        internal::utf_error err_code = utf8::internal::validate_next(it, end, cp);
-        switch (err_code) {
-            case internal::UTF8_OK :
-                break;
-            case internal::NOT_ENOUGH_ROOM :
-                throw not_enough_room();
-            case internal::INVALID_LEAD :
-            case internal::INCOMPLETE_SEQUENCE :
-            case internal::OVERLONG_SEQUENCE :
-                throw invalid_utf8(*it);
-            case internal::INVALID_CODE_POINT :
-                throw invalid_code_point(cp);
-        }
-        return cp;
-    }
-
-    template <typename octet_iterator>
-    uint32_t peek_next(octet_iterator it, octet_iterator end)
-    {
-        return utf8::next(it, end);
-    }
-
-    template <typename octet_iterator>
-    uint32_t prior(octet_iterator& it, octet_iterator start)
-    {
-        // can't do much if it == start
-        if (it == start)
-            throw not_enough_room();
-
-        octet_iterator end = it;
-        // Go back until we hit either a lead octet or start
-        while (utf8::internal::is_trail(*(--it)))
-            if (it == start)
-                throw invalid_utf8(*it); // error - no lead byte in the sequence
-        return utf8::peek_next(it, end);
-    }
-
-    /// Deprecated in versions that include "prior"
-    template <typename octet_iterator>
-    uint32_t previous(octet_iterator& it, octet_iterator pass_start)
-    {
-        octet_iterator end = it;
-        while (utf8::internal::is_trail(*(--it)))
-            if (it == pass_start)
-                throw invalid_utf8(*it); // error - no lead byte in the sequence
-        octet_iterator temp = it;
-        return utf8::next(temp, end);
-    }
-
-    template <typename octet_iterator, typename distance_type>
-    void advance (octet_iterator& it, distance_type n, octet_iterator end)
-    {
-        for (distance_type i = 0; i < n; ++i)
-            utf8::next(it, end);
-    }
-
-    template <typename octet_iterator>
-    typename std::iterator_traits<octet_iterator>::difference_type
-    distance (octet_iterator first, octet_iterator last)
-    {
-        typename std::iterator_traits<octet_iterator>::difference_type dist;
-        for (dist = 0; first < last; ++dist)
-            utf8::next(first, last);
-        return dist;
-    }
-
-    template <typename u16bit_iterator, typename octet_iterator>
-    octet_iterator utf16to8 (u16bit_iterator start, u16bit_iterator end, octet_iterator result)
-    {
-        while (start != end) {
-            uint32_t cp = utf8::internal::mask16(*start++);
-            // Take care of surrogate pairs first
-            if (utf8::internal::is_lead_surrogate(cp)) {
-                if (start != end) {
-                    uint32_t trail_surrogate = utf8::internal::mask16(*start++);
-                    if (utf8::internal::is_trail_surrogate(trail_surrogate))
-                        cp = (cp << 10) + trail_surrogate + internal::SURROGATE_OFFSET;
-                    else
-                        throw invalid_utf16(static_cast<uint16_t>(trail_surrogate));
-                }
-                else
-                    throw invalid_utf16(static_cast<uint16_t>(cp));
-
-            }
-            // Lone trail surrogate
-            else if (utf8::internal::is_trail_surrogate(cp))
-                throw invalid_utf16(static_cast<uint16_t>(cp));
-
-            result = utf8::append(cp, result);
-        }
-        return result;
-    }
-
-    template <typename u16bit_iterator, typename octet_iterator>
-    u16bit_iterator utf8to16 (octet_iterator start, octet_iterator end, u16bit_iterator result)
-    {
-        while (start != end) {
-            uint32_t cp = utf8::next(start, end);
-            if (cp > 0xffff) { //make a surrogate pair
-                *result++ = static_cast<uint16_t>((cp >> 10)   + internal::LEAD_OFFSET);
-                *result++ = static_cast<uint16_t>((cp & 0x3ff) + internal::TRAIL_SURROGATE_MIN);
-            }
-            else
-                *result++ = static_cast<uint16_t>(cp);
-        }
-        return result;
-    }
-
-    template <typename octet_iterator, typename u32bit_iterator>
-    octet_iterator utf32to8 (u32bit_iterator start, u32bit_iterator end, octet_iterator result)
-    {
-        while (start != end)
-            result = utf8::append(*(start++), result);
-
-        return result;
-    }
-
-    template <typename octet_iterator, typename u32bit_iterator>
-    u32bit_iterator utf8to32 (octet_iterator start, octet_iterator end, u32bit_iterator result)
-    {
-        while (start != end)
-            (*result++) = utf8::next(start, end);
-
-        return result;
-    }
-
-    // The iterator class
-    template <typename octet_iterator>
-    class iterator : public std::iterator <std::bidirectional_iterator_tag, uint32_t> {
-      octet_iterator it;
-      octet_iterator range_start;
-      octet_iterator range_end;
-      public:
-      iterator () {}
-      explicit iterator (const octet_iterator& octet_it,
-                         const octet_iterator& range_start,
-                         const octet_iterator& range_end) :
-               it(octet_it), range_start(range_start), range_end(range_end)
-      {
-          if (it < range_start || it > range_end)
-              throw std::out_of_range("Invalid utf-8 iterator position");
-      }
-      // the default "big three" are OK
-      octet_iterator base () const { return it; }
-      uint32_t operator * () const
-      {
-          octet_iterator temp = it;
-          return utf8::next(temp, range_end);
-      }
-      bool operator == (const iterator& rhs) const
-      {
-          if (range_start != rhs.range_start || range_end != rhs.range_end)
-              throw std::logic_error("Comparing utf-8 iterators defined with different ranges");
-          return (it == rhs.it);
-      }
-      bool operator != (const iterator& rhs) const
-      {
-          return !(operator == (rhs));
-      }
-      iterator& operator ++ ()
-      {
-          utf8::next(it, range_end);
-          return *this;
-      }
-      iterator operator ++ (int)
-      {
-          iterator temp = *this;
-          utf8::next(it, range_end);
-          return temp;
-      }
-      iterator& operator -- ()
-      {
-          utf8::prior(it, range_start);
-          return *this;
-      }
-      iterator operator -- (int)
-      {
-          iterator temp = *this;
-          utf8::prior(it, range_start);
-          return temp;
-      }
-    }; // class iterator
-
-} // namespace utf8
-
-#endif //header guard
-
-
diff --git a/3rdParty/iresearch/tests/unicode/utf8/core.h b/3rdParty/iresearch/tests/unicode/utf8/core.h
deleted file mode 100644
index 693d388c078d..000000000000
--- a/3rdParty/iresearch/tests/unicode/utf8/core.h
+++ /dev/null
@@ -1,329 +0,0 @@
-// Copyright 2006 Nemanja Trifunovic
-
-/*
-Permission is hereby granted, free of charge, to any person or organization
-obtaining a copy of the software and accompanying documentation covered by
-this license (the "Software") to use, reproduce, display, distribute,
-execute, and transmit the Software, and to prepare derivative works of the
-Software, and to permit third-parties to whom the Software is furnished to
-do so, all subject to the following:
-
-The copyright notices in the Software and this entire statement, including
-the above license grant, this restriction and the following disclaimer,
-must be included in all copies of the Software, in whole or in part, and
-all derivative works of the Software, unless such copies or derivative
-works are solely in the form of machine-executable object code generated by
-a source language processor.
-
-THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
-SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
-FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
-ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
-DEALINGS IN THE SOFTWARE.
-*/
-
-
-#ifndef UTF8_FOR_CPP_CORE_H_2675DCD0_9480_4c0c_B92A_CC14C027B731
-#define UTF8_FOR_CPP_CORE_H_2675DCD0_9480_4c0c_B92A_CC14C027B731
-
-#include <iterator>
-
-namespace utf8
-{
-    // The typedefs for 8-bit, 16-bit and 32-bit unsigned integers
-    // You may need to change them to match your system.
-    // These typedefs have the same names as ones from cstdint, or boost/cstdint
-    typedef unsigned char   uint8_t;
-    typedef unsigned short  uint16_t;
-    typedef unsigned int    uint32_t;
-
-// Helper code - not intended to be directly called by the library users. May be changed at any time
-namespace internal
-{
-    // Unicode constants
-    // Leading (high) surrogates: 0xd800 - 0xdbff
-    // Trailing (low) surrogates: 0xdc00 - 0xdfff
-    const uint16_t LEAD_SURROGATE_MIN  = 0xd800u;
-    const uint16_t LEAD_SURROGATE_MAX  = 0xdbffu;
-    const uint16_t TRAIL_SURROGATE_MIN = 0xdc00u;
-    const uint16_t TRAIL_SURROGATE_MAX = 0xdfffu;
-    const uint16_t LEAD_OFFSET         = LEAD_SURROGATE_MIN - (0x10000 >> 10);
-    const uint32_t SURROGATE_OFFSET    = 0x10000u - (LEAD_SURROGATE_MIN << 10) - TRAIL_SURROGATE_MIN;
-
-    // Maximum valid value for a Unicode code point
-    const uint32_t CODE_POINT_MAX      = 0x0010ffffu;
-
-    template<typename octet_type>
-    inline uint8_t mask8(octet_type oc)
-    {
-        return static_cast<uint8_t>(0xff & oc);
-    }
-    template<typename u16_type>
-    inline uint16_t mask16(u16_type oc)
-    {
-        return static_cast<uint16_t>(0xffff & oc);
-    }
-    template<typename octet_type>
-    inline bool is_trail(octet_type oc)
-    {
-        return ((utf8::internal::mask8(oc) >> 6) == 0x2);
-    }
-
-    template <typename u16>
-    inline bool is_lead_surrogate(u16 cp)
-    {
-        return (cp >= LEAD_SURROGATE_MIN && cp <= LEAD_SURROGATE_MAX);
-    }
-
-    template <typename u16>
-    inline bool is_trail_surrogate(u16 cp)
-    {
-        return (cp >= TRAIL_SURROGATE_MIN && cp <= TRAIL_SURROGATE_MAX);
-    }
-
-    template <typename u16>
-    inline bool is_surrogate(u16 cp)
-    {
-        return (cp >= LEAD_SURROGATE_MIN && cp <= TRAIL_SURROGATE_MAX);
-    }
-
-    template <typename u32>
-    inline bool is_code_point_valid(u32 cp)
-    {
-        return (cp <= CODE_POINT_MAX && !utf8::internal::is_surrogate(cp));
-    }
-
-    template <typename octet_iterator>
-    inline typename std::iterator_traits<octet_iterator>::difference_type
-    sequence_length(octet_iterator lead_it)
-    {
-        uint8_t lead = utf8::internal::mask8(*lead_it);
-        if (lead < 0x80)
-            return 1;
-        else if ((lead >> 5) == 0x6)
-            return 2;
-        else if ((lead >> 4) == 0xe)
-            return 3;
-        else if ((lead >> 3) == 0x1e)
-            return 4;
-        else
-            return 0;
-    }
-
-    template <typename octet_difference_type>
-    inline bool is_overlong_sequence(uint32_t cp, octet_difference_type length)
-    {
-        if (cp < 0x80) {
-            if (length != 1) 
-                return true;
-        }
-        else if (cp < 0x800) {
-            if (length != 2) 
-                return true;
-        }
-        else if (cp < 0x10000) {
-            if (length != 3) 
-                return true;
-        }
-
-        return false;
-    }
-
-    enum utf_error {UTF8_OK, NOT_ENOUGH_ROOM, INVALID_LEAD, INCOMPLETE_SEQUENCE, OVERLONG_SEQUENCE, INVALID_CODE_POINT};
-
-    /// Helper for get_sequence_x
-    template <typename octet_iterator>
-    utf_error increase_safely(octet_iterator& it, octet_iterator end)
-    {
-        if (++it == end)
-            return NOT_ENOUGH_ROOM;
-
-        if (!utf8::internal::is_trail(*it))
-            return INCOMPLETE_SEQUENCE;
-        
-        return UTF8_OK;
-    }
-
-    #define UTF8_CPP_INCREASE_AND_RETURN_ON_ERROR(IT, END) {utf_error ret = increase_safely(IT, END); if (ret != UTF8_OK) return ret;}    
-
-    /// get_sequence_x functions decode utf-8 sequences of the length x
-    template <typename octet_iterator>
-    utf_error get_sequence_1(octet_iterator& it, octet_iterator end, uint32_t& code_point)
-    {
-        if (it == end)
-            return NOT_ENOUGH_ROOM;
-
-        code_point = utf8::internal::mask8(*it);
-
-        return UTF8_OK;
-    }
-
-    template <typename octet_iterator>
-    utf_error get_sequence_2(octet_iterator& it, octet_iterator end, uint32_t& code_point)
-    {
-        if (it == end) 
-            return NOT_ENOUGH_ROOM;
-        
-        code_point = utf8::internal::mask8(*it);
-
-        UTF8_CPP_INCREASE_AND_RETURN_ON_ERROR(it, end)
-
-        code_point = ((code_point << 6) & 0x7ff) + ((*it) & 0x3f);
-
-        return UTF8_OK;
-    }
-
-    template <typename octet_iterator>
-    utf_error get_sequence_3(octet_iterator& it, octet_iterator end, uint32_t& code_point)
-    {
-        if (it == end)
-            return NOT_ENOUGH_ROOM;
-            
-        code_point = utf8::internal::mask8(*it);
-
-        UTF8_CPP_INCREASE_AND_RETURN_ON_ERROR(it, end)
-
-        code_point = ((code_point << 12) & 0xffff) + ((utf8::internal::mask8(*it) << 6) & 0xfff);
-
-        UTF8_CPP_INCREASE_AND_RETURN_ON_ERROR(it, end)
-
-        code_point += (*it) & 0x3f;
-
-        return UTF8_OK;
-    }
-
-    template <typename octet_iterator>
-    utf_error get_sequence_4(octet_iterator& it, octet_iterator end, uint32_t& code_point)
-    {
-        if (it == end)
-           return NOT_ENOUGH_ROOM;
-
-        code_point = utf8::internal::mask8(*it);
-
-        UTF8_CPP_INCREASE_AND_RETURN_ON_ERROR(it, end)
-
-        code_point = ((code_point << 18) & 0x1fffff) + ((utf8::internal::mask8(*it) << 12) & 0x3ffff);
-
-        UTF8_CPP_INCREASE_AND_RETURN_ON_ERROR(it, end)
-
-        code_point += (utf8::internal::mask8(*it) << 6) & 0xfff;
-
-        UTF8_CPP_INCREASE_AND_RETURN_ON_ERROR(it, end)
-
-        code_point += (*it) & 0x3f;
-
-        return UTF8_OK;
-    }
-
-    #undef UTF8_CPP_INCREASE_AND_RETURN_ON_ERROR
-
-    template <typename octet_iterator>
-    utf_error validate_next(octet_iterator& it, octet_iterator end, uint32_t& code_point)
-    {
-        // Save the original value of it so we can go back in case of failure
-        // Of course, it does not make much sense with i.e. stream iterators
-        octet_iterator original_it = it;
-
-        uint32_t cp = 0;
-        // Determine the sequence length based on the lead octet
-        typedef typename std::iterator_traits<octet_iterator>::difference_type octet_difference_type;
-        const octet_difference_type length = utf8::internal::sequence_length(it);
-
-        // Get trail octets and calculate the code point
-        utf_error err = UTF8_OK;
-        switch (length) {
-            case 0: 
-                return INVALID_LEAD;
-            case 1:
-                err = utf8::internal::get_sequence_1(it, end, cp);
-                break;
-            case 2:
-                err = utf8::internal::get_sequence_2(it, end, cp);
-            break;
-            case 3:
-                err = utf8::internal::get_sequence_3(it, end, cp);
-            break;
-            case 4:
-                err = utf8::internal::get_sequence_4(it, end, cp);
-            break;
-        }
-
-        if (err == UTF8_OK) {
-            // Decoding succeeded. Now, security checks...
-            if (utf8::internal::is_code_point_valid(cp)) {
-                if (!utf8::internal::is_overlong_sequence(cp, length)){
-                    // Passed! Return here.
-                    code_point = cp;
-                    ++it;
-                    return UTF8_OK;
-                }
-                else
-                    err = OVERLONG_SEQUENCE;
-            }
-            else 
-                err = INVALID_CODE_POINT;
-        }
-
-        // Failure branch - restore the original value of the iterator
-        it = original_it;
-        return err;
-    }
-
-    template <typename octet_iterator>
-    inline utf_error validate_next(octet_iterator& it, octet_iterator end) {
-        uint32_t ignored;
-        return utf8::internal::validate_next(it, end, ignored);
-    }
-
-} // namespace internal
-
-    /// The library API - functions intended to be called by the users
-
-    // Byte order mark
-    const uint8_t bom[] = {0xef, 0xbb, 0xbf};
-
-    template <typename octet_iterator>
-    octet_iterator find_invalid(octet_iterator start, octet_iterator end)
-    {
-        octet_iterator result = start;
-        while (result != end) {
-            utf8::internal::utf_error err_code = utf8::internal::validate_next(result, end);
-            if (err_code != internal::UTF8_OK)
-                return result;
-        }
-        return result;
-    }
-
-    template <typename octet_iterator>
-    inline bool is_valid(octet_iterator start, octet_iterator end)
-    {
-        return (utf8::find_invalid(start, end) == end);
-    }
-
-    template <typename octet_iterator>
-    inline bool starts_with_bom (octet_iterator it, octet_iterator end)
-    {
-        return (
-            ((it != end) && (utf8::internal::mask8(*it++)) == bom[0]) &&
-            ((it != end) && (utf8::internal::mask8(*it++)) == bom[1]) &&
-            ((it != end) && (utf8::internal::mask8(*it))   == bom[2])
-           );
-    }
-	
-    //Deprecated in release 2.3 
-    template <typename octet_iterator>
-    inline bool is_bom (octet_iterator it)
-    {
-        return (
-            (utf8::internal::mask8(*it++)) == bom[0] &&
-            (utf8::internal::mask8(*it++)) == bom[1] &&
-            (utf8::internal::mask8(*it))   == bom[2]
-           );
-    }
-} // namespace utf8
-
-#endif // header guard
-
-
diff --git a/3rdParty/iresearch/tests/unicode/utf8/unchecked.h b/3rdParty/iresearch/tests/unicode/utf8/unchecked.h
deleted file mode 100644
index cb2427166b19..000000000000
--- a/3rdParty/iresearch/tests/unicode/utf8/unchecked.h
+++ /dev/null
@@ -1,228 +0,0 @@
-// Copyright 2006 Nemanja Trifunovic
-
-/*
-Permission is hereby granted, free of charge, to any person or organization
-obtaining a copy of the software and accompanying documentation covered by
-this license (the "Software") to use, reproduce, display, distribute,
-execute, and transmit the Software, and to prepare derivative works of the
-Software, and to permit third-parties to whom the Software is furnished to
-do so, all subject to the following:
-
-The copyright notices in the Software and this entire statement, including
-the above license grant, this restriction and the following disclaimer,
-must be included in all copies of the Software, in whole or in part, and
-all derivative works of the Software, unless such copies or derivative
-works are solely in the form of machine-executable object code generated by
-a source language processor.
-
-THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
-SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
-FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
-ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
-DEALINGS IN THE SOFTWARE.
-*/
-
-
-#ifndef UTF8_FOR_CPP_UNCHECKED_H_2675DCD0_9480_4c0c_B92A_CC14C027B731
-#define UTF8_FOR_CPP_UNCHECKED_H_2675DCD0_9480_4c0c_B92A_CC14C027B731
-
-#include "core.h"
-
-namespace utf8
-{
-    namespace unchecked 
-    {
-        template <typename octet_iterator>
-        octet_iterator append(uint32_t cp, octet_iterator result)
-        {
-            if (cp < 0x80)                        // one octet
-                *(result++) = static_cast<uint8_t>(cp);  
-            else if (cp < 0x800) {                // two octets
-                *(result++) = static_cast<uint8_t>((cp >> 6)          | 0xc0);
-                *(result++) = static_cast<uint8_t>((cp & 0x3f)        | 0x80);
-            }
-            else if (cp < 0x10000) {              // three octets
-                *(result++) = static_cast<uint8_t>((cp >> 12)         | 0xe0);
-                *(result++) = static_cast<uint8_t>(((cp >> 6) & 0x3f) | 0x80);
-                *(result++) = static_cast<uint8_t>((cp & 0x3f)        | 0x80);
-            }
-            else {                                // four octets
-                *(result++) = static_cast<uint8_t>((cp >> 18)         | 0xf0);
-                *(result++) = static_cast<uint8_t>(((cp >> 12) & 0x3f)| 0x80);
-                *(result++) = static_cast<uint8_t>(((cp >> 6) & 0x3f) | 0x80);
-                *(result++) = static_cast<uint8_t>((cp & 0x3f)        | 0x80);
-            }
-            return result;
-        }
-
-        template <typename octet_iterator>
-        uint32_t next(octet_iterator& it)
-        {
-            uint32_t cp = utf8::internal::mask8(*it);
-            typename std::iterator_traits<octet_iterator>::difference_type length = utf8::internal::sequence_length(it);
-            switch (length) {
-                case 1:
-                    break;
-                case 2:
-                    it++;
-                    cp = ((cp << 6) & 0x7ff) + ((*it) & 0x3f);
-                    break;
-                case 3:
-                    ++it; 
-                    cp = ((cp << 12) & 0xffff) + ((utf8::internal::mask8(*it) << 6) & 0xfff);
-                    ++it;
-                    cp += (*it) & 0x3f;
-                    break;
-                case 4:
-                    ++it;
-                    cp = ((cp << 18) & 0x1fffff) + ((utf8::internal::mask8(*it) << 12) & 0x3ffff);                
-                    ++it;
-                    cp += (utf8::internal::mask8(*it) << 6) & 0xfff;
-                    ++it;
-                    cp += (*it) & 0x3f; 
-                    break;
-            }
-            ++it;
-            return cp;        
-        }
-
-        template <typename octet_iterator>
-        uint32_t peek_next(octet_iterator it)
-        {
-            return utf8::unchecked::next(it);    
-        }
-
-        template <typename octet_iterator>
-        uint32_t prior(octet_iterator& it)
-        {
-            while (utf8::internal::is_trail(*(--it))) ;
-            octet_iterator temp = it;
-            return utf8::unchecked::next(temp);
-        }
-
-        // Deprecated in versions that include prior, but only for the sake of consistency (see utf8::previous)
-        template <typename octet_iterator>
-        inline uint32_t previous(octet_iterator& it)
-        {
-            return utf8::unchecked::prior(it);
-        }
-
-        template <typename octet_iterator, typename distance_type>
-        void advance (octet_iterator& it, distance_type n)
-        {
-            for (distance_type i = 0; i < n; ++i)
-                utf8::unchecked::next(it);
-        }
-
-        template <typename octet_iterator>
-        typename std::iterator_traits<octet_iterator>::difference_type
-        distance (octet_iterator first, octet_iterator last)
-        {
-            typename std::iterator_traits<octet_iterator>::difference_type dist;
-            for (dist = 0; first < last; ++dist) 
-                utf8::unchecked::next(first);
-            return dist;
-        }
-
-        template <typename u16bit_iterator, typename octet_iterator>
-        octet_iterator utf16to8 (u16bit_iterator start, u16bit_iterator end, octet_iterator result)
-        {       
-            while (start != end) {
-                uint32_t cp = utf8::internal::mask16(*start++);
-            // Take care of surrogate pairs first
-                if (utf8::internal::is_lead_surrogate(cp)) {
-                    uint32_t trail_surrogate = utf8::internal::mask16(*start++);
-                    cp = (cp << 10) + trail_surrogate + internal::SURROGATE_OFFSET;
-                }
-                result = utf8::unchecked::append(cp, result);
-            }
-            return result;         
-        }
-
-        template <typename u16bit_iterator, typename octet_iterator>
-        u16bit_iterator utf8to16 (octet_iterator start, octet_iterator end, u16bit_iterator result)
-        {
-            while (start < end) {
-                uint32_t cp = utf8::unchecked::next(start);
-                if (cp > 0xffff) { //make a surrogate pair
-                    *result++ = static_cast<uint16_t>((cp >> 10)   + internal::LEAD_OFFSET);
-                    *result++ = static_cast<uint16_t>((cp & 0x3ff) + internal::TRAIL_SURROGATE_MIN);
-                }
-                else
-                    *result++ = static_cast<uint16_t>(cp);
-            }
-            return result;
-        }
-
-        template <typename octet_iterator, typename u32bit_iterator>
-        octet_iterator utf32to8 (u32bit_iterator start, u32bit_iterator end, octet_iterator result)
-        {
-            while (start != end)
-                result = utf8::unchecked::append(*(start++), result);
-
-            return result;
-        }
-
-        template <typename octet_iterator, typename u32bit_iterator>
-        u32bit_iterator utf8to32 (octet_iterator start, octet_iterator end, u32bit_iterator result)
-        {
-            while (start < end)
-                (*result++) = utf8::unchecked::next(start);
-
-            return result;
-        }
-
-        // The iterator class
-        template <typename octet_iterator>
-          class iterator : public std::iterator <std::bidirectional_iterator_tag, uint32_t> { 
-            octet_iterator it;
-            public:
-            iterator () {}
-            explicit iterator (const octet_iterator& octet_it): it(octet_it) {}
-            // the default "big three" are OK
-            octet_iterator base () const { return it; }
-            uint32_t operator * () const
-            {
-                octet_iterator temp = it;
-                return utf8::unchecked::next(temp);
-            }
-            bool operator == (const iterator& rhs) const 
-            { 
-                return (it == rhs.it);
-            }
-            bool operator != (const iterator& rhs) const
-            {
-                return !(operator == (rhs));
-            }
-            iterator& operator ++ () 
-            {
-                ::std::advance(it, utf8::internal::sequence_length(it));
-                return *this;
-            }
-            iterator operator ++ (int)
-            {
-                iterator temp = *this;
-                ::std::advance(it, utf8::internal::sequence_length(it));
-                return temp;
-            }  
-            iterator& operator -- ()
-            {
-                utf8::unchecked::prior(it);
-                return *this;
-            }
-            iterator operator -- (int)
-            {
-                iterator temp = *this;
-                utf8::unchecked::prior(it);
-                return temp;
-            }
-          }; // class iterator
-
-    } // namespace utf8::unchecked
-} // namespace utf8 
-
-
-#endif // header guard
-
diff --git a/3rdParty/iresearch/tests/utils/automaton_test.cpp b/3rdParty/iresearch/tests/utils/automaton_test.cpp
index ada830493c55..c0a5140acc8e 100644
--- a/3rdParty/iresearch/tests/utils/automaton_test.cpp
+++ b/3rdParty/iresearch/tests/utils/automaton_test.cpp
@@ -1,4 +1,4 @@
-////////////////////////////////////////////////////////////////////////////////
+////////////////////////////////////////////////////////////////////////////////
 /// DISCLAIMER
 ///
 /// Copyright 2019 ArangoDB GmbH, Cologne, Germany
@@ -23,281 +23,1524 @@
 #include "tests_shared.hpp"
 
 #include "utils/automaton_utils.hpp"
-#include "utils/wildcard_utils.hpp"
+#include "utils/misc.hpp"
+
+// -----------------------------------------------------------------------------
+// --SECTION--                                               boolean_weight_test
+// -----------------------------------------------------------------------------
 
-TEST(automaton_test, match_wildcard) {
-  // check automaton structure
+TEST(boolean_weight_test, static_const) {
+  ASSERT_EQ(fst::kLeftSemiring | fst::kRightSemiring |
+            fst::kCommutative | fst::kIdempotent | fst::kPath,
+            fst::fsa::BooleanWeight::Properties());
+  ASSERT_EQ("boolean", fst::fsa::BooleanWeight::Type());
+  ASSERT_EQ(0x3F, fst::fsa::BooleanWeight::PayloadType(fst::fsa::BooleanWeight::MaxPayload));
+}
+
+TEST(boolean_weight_test, create) {
+  // not a member
   {
-    auto lhs = irs::from_wildcard<char>("%b%");
-    auto rhs = irs::from_wildcard<char>("%b%%%");
-    ASSERT_EQ(lhs.NumStates(), rhs.NumStates());
+    const fst::fsa::BooleanWeight weight;
+    ASSERT_FALSE(weight.Member());
+    ASSERT_EQ(fst::fsa::BooleanWeight(), weight);
+    ASSERT_NE(fst::fsa::BooleanWeight(false), weight);
+    ASSERT_NE(fst::fsa::BooleanWeight(false, 2), weight);
+    ASSERT_NE(fst::fsa::BooleanWeight(true), weight);
+    ASSERT_NE(fst::fsa::BooleanWeight(true, 1), weight);
+    ASSERT_EQ(weight, weight.Quantize());
+    ASSERT_EQ(weight, weight.Reverse());
+    ASSERT_TRUE(ApproxEqual(weight, weight.Quantize()));
+    ASSERT_TRUE(ApproxEqual(weight, weight.Reverse()));
+    ASSERT_FALSE(bool(weight));
+    ASSERT_NE(fst::fsa::BooleanWeight::One(), weight);
+    ASSERT_NE(fst::fsa::BooleanWeight::Zero(), weight);
+    ASSERT_NE(true, bool(weight));
+    ASSERT_EQ(false, bool(weight));
+    ASSERT_EQ(0, weight.Payload());
+    ASSERT_EQ(2, weight.Hash());
 
-    for (decltype(lhs)::StateId state = 0; state < lhs.NumStates(); ++state) {
-      ASSERT_EQ(lhs.NumArcs(state), rhs.NumArcs(state));
+    {
+      std::stringstream ss;
+      ss << weight;
+      ASSERT_TRUE(ss.str().empty());
     }
-  }
 
-  // check automaton structure
-  {
-    auto lhs = irs::from_wildcard<char>("b%%%%%s");
-    auto rhs = irs::from_wildcard<char>("b%%%s");
-    ASSERT_EQ(lhs.NumStates(), rhs.NumStates());
+    {
+      std::stringstream ss;
+      weight.Write(ss);
 
-    for (decltype(lhs)::StateId state = 0; state < lhs.NumStates(); ++state) {
-      ASSERT_EQ(lhs.NumArcs(state), rhs.NumArcs(state));
+      fst::fsa::BooleanWeight readWeight;
+      readWeight.Read(ss);
+      ASSERT_EQ(weight, readWeight);
     }
   }
 
-  // check automaton structure
+  // Zero
   {
-    auto lhs = irs::from_wildcard<char>("b%%__%%%s%");
-    auto rhs = irs::from_wildcard<char>("b%%%%%%%__%%%%%%%%s%");
-    ASSERT_EQ(lhs.NumStates(), rhs.NumStates());
+    const fst::fsa::BooleanWeight weight = false;
+    ASSERT_TRUE(weight.Member());
+    ASSERT_NE(fst::fsa::BooleanWeight(), weight);
+    ASSERT_EQ(fst::fsa::BooleanWeight(false), weight);
+    ASSERT_EQ(fst::fsa::BooleanWeight(false, 2), weight);
+    ASSERT_NE(fst::fsa::BooleanWeight(true), weight);
+    ASSERT_NE(fst::fsa::BooleanWeight(true, 1), weight);
+    ASSERT_EQ(fst::fsa::BooleanWeight::NoWeight(), weight.Quantize());
+    ASSERT_NE(weight, weight.Quantize());
+    ASSERT_EQ(weight, weight.Reverse());
+    ASSERT_FALSE(ApproxEqual(weight, weight.Quantize()));
+    ASSERT_TRUE(ApproxEqual(weight, weight.Reverse()));
+    ASSERT_FALSE(bool(weight));
+    ASSERT_NE(fst::fsa::BooleanWeight::One(), weight);
+    ASSERT_EQ(fst::fsa::BooleanWeight::Zero(), weight);
+    ASSERT_NE(true, bool(weight));
+    ASSERT_EQ(false, bool(weight));
+    ASSERT_EQ(0, weight.Payload());
+    ASSERT_EQ(0, weight.Hash());
+
+    {
+      std::stringstream ss;
+      ss << weight;
+      ASSERT_EQ("{0,0}", ss.str());
+    }
+
+    {
+      std::stringstream ss;
+      weight.Write(ss);
 
-    for (decltype(lhs)::StateId state = 0; state < lhs.NumStates(); ++state) {
-      ASSERT_EQ(lhs.NumArcs(state), rhs.NumArcs(state));
+      fst::fsa::BooleanWeight readWeight;
+      readWeight.Read(ss);
+      ASSERT_EQ(weight, weight);
+      ASSERT_EQ(weight, readWeight);
     }
   }
 
-  // nil string
+  // Zero + Payload
   {
-    auto a = irs::from_wildcard<char>(irs::string_ref::NIL);
-    ASSERT_EQ(fst::kAcceptor | fst::kUnweighted, a.Properties(fst::kAcceptor | fst::kUnweighted, true));
-    ASSERT_TRUE(irs::accept<char>(a, ""));
-    ASSERT_TRUE(irs::accept<char>(a, irs::string_ref::NIL));
-    ASSERT_FALSE(irs::accept<char>(a, "a"));
+    const fst::fsa::BooleanWeight weight(false, 25);
+    ASSERT_TRUE(weight.Member());
+    ASSERT_NE(fst::fsa::BooleanWeight(), weight);
+    ASSERT_EQ(fst::fsa::BooleanWeight(false), weight);
+    ASSERT_EQ(fst::fsa::BooleanWeight(false, 2), weight);
+    ASSERT_EQ(fst::fsa::BooleanWeight(false, 25), weight);
+    ASSERT_NE(fst::fsa::BooleanWeight(true), weight);
+    ASSERT_NE(fst::fsa::BooleanWeight(true, 1), weight);
+    ASSERT_NE(fst::fsa::BooleanWeight(true, 25), weight);
+    ASSERT_EQ(fst::fsa::BooleanWeight::NoWeight(), weight.Quantize());
+    ASSERT_NE(weight, weight.Quantize());
+    ASSERT_EQ(weight, weight.Reverse());
+    ASSERT_FALSE(ApproxEqual(weight, weight.Quantize()));
+    ASSERT_TRUE(ApproxEqual(weight, weight.Reverse()));
+    ASSERT_FALSE(bool(weight));
+    ASSERT_NE(fst::fsa::BooleanWeight::One(), weight);
+    ASSERT_EQ(fst::fsa::BooleanWeight::Zero(), weight);
+    ASSERT_NE(true, bool(weight));
+    ASSERT_EQ(false, bool(weight));
+    ASSERT_EQ(25, weight.Payload());
+    ASSERT_EQ(0, weight.Hash());
+
+    {
+      std::stringstream ss;
+      ss << weight;
+      ASSERT_EQ("{0,25}", ss.str());
+    }
+
+    {
+      std::stringstream ss;
+      weight.Write(ss);
+
+      fst::fsa::BooleanWeight readWeight;
+      readWeight.Read(ss);
+      ASSERT_EQ(weight, weight);
+      ASSERT_EQ(weight, readWeight);
+    }
   }
 
-  // empty string
+  // One
   {
-    auto a = irs::from_wildcard<char>(irs::string_ref::EMPTY);
-    ASSERT_EQ(fst::kAcceptor | fst::kUnweighted, a.Properties(fst::kAcceptor | fst::kUnweighted, true));
-    ASSERT_TRUE(irs::accept<char>(a, ""));
-    ASSERT_TRUE(irs::accept<char>(a, irs::string_ref::NIL));
-    ASSERT_FALSE(irs::accept<char>(a, "a"));
+    const fst::fsa::BooleanWeight weight = true;
+    ASSERT_TRUE(weight.Member());
+    ASSERT_NE(fst::fsa::BooleanWeight(), weight);
+    ASSERT_NE(fst::fsa::BooleanWeight(false), weight);
+    ASSERT_NE(fst::fsa::BooleanWeight(false, 2), weight);
+    ASSERT_EQ(fst::fsa::BooleanWeight(true), weight);
+    ASSERT_EQ(fst::fsa::BooleanWeight(true, 1), weight);
+    ASSERT_EQ(fst::fsa::BooleanWeight::NoWeight(), weight.Quantize());
+    ASSERT_NE(weight, weight.Quantize());
+    ASSERT_EQ(weight, weight.Reverse());
+    ASSERT_TRUE(bool(weight));
+    ASSERT_EQ(fst::fsa::BooleanWeight::One(), weight);
+    ASSERT_NE(fst::fsa::BooleanWeight::Zero(), weight);
+    ASSERT_EQ(true, bool(weight));
+    ASSERT_NE(false, bool(weight));
+    ASSERT_EQ(0, weight.Payload());
+    ASSERT_EQ(1, weight.Hash());
+
+    {
+      std::stringstream ss;
+      ss << weight;
+      ASSERT_EQ("{1,0}", ss.str());
+    }
+
+    {
+      std::stringstream ss;
+      weight.Write(ss);
+
+      fst::fsa::BooleanWeight readWeight;
+      readWeight.Read(ss);
+      ASSERT_EQ(weight, weight);
+      ASSERT_EQ(weight, readWeight);
+    }
   }
 
-  // any or empty string
+  // One + Payload
   {
-    auto a = irs::from_wildcard<char>("%");
-    ASSERT_EQ(fst::kAcceptor | fst::kUnweighted, a.Properties(fst::kAcceptor | fst::kUnweighted, true));
-    ASSERT_TRUE(irs::accept<char>(a, ""));
-    ASSERT_TRUE(irs::accept<char>(a, irs::string_ref::NIL));
-    ASSERT_TRUE(irs::accept<char>(a, "a"));
-    ASSERT_TRUE(irs::accept<char>(a, "abc"));
+    const fst::fsa::BooleanWeight weight(true, 32);
+    ASSERT_TRUE(weight.Member());
+    ASSERT_NE(fst::fsa::BooleanWeight(), weight);
+    ASSERT_NE(fst::fsa::BooleanWeight(false), weight);
+    ASSERT_NE(fst::fsa::BooleanWeight(false, 2), weight);
+    ASSERT_NE(fst::fsa::BooleanWeight(false, 32), weight);
+    ASSERT_EQ(fst::fsa::BooleanWeight(true), weight);
+    ASSERT_EQ(fst::fsa::BooleanWeight(true, 1), weight);
+    ASSERT_EQ(fst::fsa::BooleanWeight(true, 32), weight);
+    ASSERT_EQ(fst::fsa::BooleanWeight::NoWeight(), weight.Quantize());
+    ASSERT_NE(weight, weight.Quantize());
+    ASSERT_EQ(weight, weight.Reverse());
+    ASSERT_TRUE(bool(weight));
+    ASSERT_EQ(fst::fsa::BooleanWeight::One(), weight);
+    ASSERT_NE(fst::fsa::BooleanWeight::Zero(), weight);
+    ASSERT_EQ(true, bool(weight));
+    ASSERT_NE(false, bool(weight));
+    ASSERT_EQ(32, weight.Payload());
+    ASSERT_EQ(1, weight.Hash());
+
+    {
+      std::stringstream ss;
+      ss << weight;
+      ASSERT_EQ("{1,32}", ss.str());
+    }
+
+    {
+      std::stringstream ss;
+      weight.Write(ss);
+
+      fst::fsa::BooleanWeight readWeight;
+      readWeight.Read(ss);
+      ASSERT_EQ(weight, weight);
+      ASSERT_EQ(weight, readWeight);
+    }
   }
 
-  // any or empty string
+  // Max payload
   {
-    auto a = irs::from_wildcard<char>("%%");
-
-    ASSERT_EQ(fst::kAcceptor | fst::kUnweighted, a.Properties(fst::kAcceptor | fst::kUnweighted, true));
-    ASSERT_TRUE(irs::accept<char>(a, ""));
-    ASSERT_TRUE(irs::accept<char>(a, irs::string_ref::NIL));
-    ASSERT_TRUE(irs::accept<char>(a, "a"));
-    ASSERT_TRUE(irs::accept<char>(a, "aa"));
-    ASSERT_TRUE(irs::accept<char>(a, "azbce1d"));
-    ASSERT_TRUE(irs::accept<char>(a, "azbce1d1"));
-    ASSERT_TRUE(irs::accept<char>(a, "azbce11d"));
+    const fst::fsa::BooleanWeight weight(true, 0xFF);
+    ASSERT_TRUE(weight.Member());
+    ASSERT_NE(fst::fsa::BooleanWeight(), weight);
+    ASSERT_NE(fst::fsa::BooleanWeight(false), weight);
+    ASSERT_NE(fst::fsa::BooleanWeight(false, 2), weight);
+    ASSERT_NE(fst::fsa::BooleanWeight(false, fst::fsa::BooleanWeight::MaxPayload), weight);
+    ASSERT_EQ(fst::fsa::BooleanWeight(true), weight);
+    ASSERT_EQ(fst::fsa::BooleanWeight(true, 1), weight);
+    ASSERT_EQ(fst::fsa::BooleanWeight(true, fst::fsa::BooleanWeight::MaxPayload), weight);
+    ASSERT_EQ(fst::fsa::BooleanWeight::NoWeight(), weight.Quantize());
+    ASSERT_NE(weight, weight.Quantize());
+    ASSERT_EQ(weight, weight.Reverse());
+    ASSERT_TRUE(bool(weight));
+    ASSERT_EQ(fst::fsa::BooleanWeight::One(), weight);
+    ASSERT_NE(fst::fsa::BooleanWeight::Zero(), weight);
+    ASSERT_EQ(true, bool(weight));
+    ASSERT_NE(false, bool(weight));
+    ASSERT_EQ(fst::fsa::BooleanWeight::PayloadType(fst::fsa::BooleanWeight::MaxPayload),
+              weight.Payload());
+    ASSERT_EQ(1, weight.Hash());
+
+    {
+      std::stringstream ss;
+      ss << weight;
+      ASSERT_EQ("{1,63}", ss.str());
+    }
+
+    {
+      std::stringstream ss;
+      weight.Write(ss);
+
+      fst::fsa::BooleanWeight readWeight;
+      readWeight.Read(ss);
+      ASSERT_EQ(weight, weight);
+      ASSERT_EQ(weight, readWeight);
+    }
   }
+}
 
-  // any char
-  {
-    auto a = irs::from_wildcard<char>("_");
-    ASSERT_EQ(fst::kAcceptor | fst::kUnweighted, a.Properties(fst::kAcceptor | fst::kUnweighted, true));
-    ASSERT_FALSE(irs::accept<char>(a, ""));
-    ASSERT_FALSE(irs::accept<char>(a, irs::string_ref::NIL));
-    ASSERT_TRUE(irs::accept<char>(a, "a"));
-    ASSERT_FALSE(irs::accept<char>(a, "abc"));
+TEST(boolean_weight_test, divide) {
+  using namespace fst;
+  using namespace fst::fsa;
+
+  ASSERT_EQ(BooleanWeight::NoWeight(), Divide(BooleanWeight(true, 31), BooleanWeight(true, 11), DIVIDE_LEFT));
+  ASSERT_EQ(BooleanWeight::NoWeight(), Divide(BooleanWeight(true, 31), BooleanWeight(true, 11), DIVIDE_RIGHT));
+  ASSERT_EQ(BooleanWeight::NoWeight(), Divide(BooleanWeight(true, 31), BooleanWeight(true, 11), DIVIDE_ANY));
+  ASSERT_EQ(BooleanWeight::NoWeight(), Divide(BooleanWeight::One(), BooleanWeight::Zero(), DIVIDE_LEFT));
+  ASSERT_EQ(BooleanWeight::NoWeight(), Divide(BooleanWeight::One(), BooleanWeight::Zero(), DIVIDE_RIGHT));
+  ASSERT_EQ(BooleanWeight::NoWeight(), Divide(BooleanWeight::One(), BooleanWeight::Zero(), DIVIDE_ANY));
+  ASSERT_EQ(BooleanWeight::NoWeight(), Divide(BooleanWeight::Zero(), BooleanWeight::One(), DIVIDE_LEFT));
+  ASSERT_EQ(BooleanWeight::NoWeight(), Divide(BooleanWeight::Zero(), BooleanWeight::One(), DIVIDE_RIGHT));
+  ASSERT_EQ(BooleanWeight::NoWeight(), Divide(BooleanWeight::Zero(), BooleanWeight::One(), DIVIDE_ANY));
+  ASSERT_EQ(BooleanWeight::NoWeight(), Divide(BooleanWeight::Zero(), BooleanWeight::Zero(), DIVIDE_LEFT));
+  ASSERT_EQ(BooleanWeight::NoWeight(), Divide(BooleanWeight::Zero(), BooleanWeight::Zero(), DIVIDE_RIGHT));
+  ASSERT_EQ(BooleanWeight::NoWeight(), Divide(BooleanWeight::Zero(), BooleanWeight::Zero(), DIVIDE_ANY));
+  ASSERT_EQ(BooleanWeight::NoWeight(), Divide(BooleanWeight::One(), BooleanWeight::One(), DIVIDE_LEFT));
+  ASSERT_EQ(BooleanWeight::NoWeight(), Divide(BooleanWeight::One(), BooleanWeight::One(), DIVIDE_RIGHT));
+  ASSERT_EQ(BooleanWeight::NoWeight(), Divide(BooleanWeight::One(), BooleanWeight::One(), DIVIDE_ANY));
+  ASSERT_EQ(BooleanWeight::NoWeight(), Divide(BooleanWeight::One(), BooleanWeight::NoWeight(), DIVIDE_LEFT));
+  ASSERT_EQ(BooleanWeight::NoWeight(), Divide(BooleanWeight::One(), BooleanWeight::NoWeight(), DIVIDE_RIGHT));
+  ASSERT_EQ(BooleanWeight::NoWeight(), Divide(BooleanWeight::One(), BooleanWeight::NoWeight(), DIVIDE_ANY));
+  ASSERT_EQ(BooleanWeight::NoWeight(), Divide(BooleanWeight::NoWeight(), BooleanWeight::One(), DIVIDE_LEFT));
+  ASSERT_EQ(BooleanWeight::NoWeight(), Divide(BooleanWeight::NoWeight(), BooleanWeight::One(), DIVIDE_RIGHT));
+  ASSERT_EQ(BooleanWeight::NoWeight(), Divide(BooleanWeight::NoWeight(), BooleanWeight::One(), DIVIDE_ANY));
+  ASSERT_EQ(BooleanWeight::NoWeight(), Divide(BooleanWeight::NoWeight(), BooleanWeight::NoWeight(), DIVIDE_LEFT));
+  ASSERT_EQ(BooleanWeight::NoWeight(), Divide(BooleanWeight::NoWeight(), BooleanWeight::NoWeight(), DIVIDE_RIGHT));
+  ASSERT_EQ(BooleanWeight::NoWeight(), Divide(BooleanWeight::NoWeight(), BooleanWeight::NoWeight(), DIVIDE_ANY));
+  ASSERT_EQ(BooleanWeight::NoWeight(), Divide(BooleanWeight::NoWeight(), BooleanWeight::One(), DIVIDE_LEFT));
+  ASSERT_EQ(BooleanWeight::NoWeight(), Divide(BooleanWeight::NoWeight(), BooleanWeight::One(), DIVIDE_RIGHT));
+  ASSERT_EQ(BooleanWeight::NoWeight(), Divide(BooleanWeight::NoWeight(), BooleanWeight::One(), DIVIDE_ANY));
+}
+
+TEST(boolean_weight_test, times) {
+  using namespace fst;
+  using namespace fst::fsa;
+
+  ASSERT_EQ(BooleanWeight(false, 0), Times(BooleanWeight(false, 31), BooleanWeight(true, 32)));
+  ASSERT_EQ(BooleanWeight(true, 11), Times(BooleanWeight(true, 31), BooleanWeight(true, 11)));
+  ASSERT_EQ(BooleanWeight(false, 11), Times(BooleanWeight(false, 31), BooleanWeight(false, 11)));
+  ASSERT_EQ(BooleanWeight::One(), Times(BooleanWeight::One(), BooleanWeight::One()));
+  ASSERT_EQ(BooleanWeight::Zero(), Times(BooleanWeight::One(), BooleanWeight::Zero()));
+  ASSERT_EQ(BooleanWeight::One(), Times(BooleanWeight::One(), BooleanWeight::NoWeight()));
+  ASSERT_EQ(BooleanWeight::One(), Times(BooleanWeight::NoWeight(), BooleanWeight::NoWeight()));
+  ASSERT_EQ(BooleanWeight::One(), Times(BooleanWeight::NoWeight(), BooleanWeight::One()));
+}
+
+TEST(boolean_weight_test, plus) {
+  using namespace fst;
+  using namespace fst::fsa;
+
+  ASSERT_EQ(BooleanWeight(true, 63), Plus(BooleanWeight(false, 31), BooleanWeight(true, 32)));
+  ASSERT_EQ(BooleanWeight(true, 31), Plus(BooleanWeight(true, 31), BooleanWeight(true, 11)));
+  ASSERT_EQ(BooleanWeight(false, 31), Plus(BooleanWeight(false, 31), BooleanWeight(false, 11)));
+  ASSERT_EQ(BooleanWeight::One(), Plus(BooleanWeight::One(), BooleanWeight::One()));
+  ASSERT_EQ(BooleanWeight::One(), Plus(BooleanWeight::One(), BooleanWeight::Zero()));
+  ASSERT_EQ(BooleanWeight::One(), Plus(BooleanWeight::One(), BooleanWeight::NoWeight()));
+  ASSERT_EQ(BooleanWeight::One(), Plus(BooleanWeight::NoWeight(), BooleanWeight::NoWeight()));
+  ASSERT_EQ(BooleanWeight::One(), Plus(BooleanWeight::NoWeight(), BooleanWeight::One()));
+}
+
+// -----------------------------------------------------------------------------
+// --SECTION--                                     utf8_transitions_builder_test
+// -----------------------------------------------------------------------------
+
+class utf8_transitions_builder_test : public test_base {
+ protected:
+  static void assert_properties(const irs::automaton& a) {
+    constexpr auto EXPECTED_PROPERTIES =
+      fst::kILabelSorted | fst::kOLabelSorted |
+      fst::kIDeterministic | fst::kODeterministic |
+      fst::kAcceptor;
+
+    ASSERT_EQ(EXPECTED_PROPERTIES, a.Properties(EXPECTED_PROPERTIES, true));
   }
 
-  // two any chars
-  {
-    auto a = irs::from_wildcard<char>("__");
-    ASSERT_EQ(fst::kAcceptor | fst::kUnweighted, a.Properties(fst::kAcceptor | fst::kUnweighted, true));
-    ASSERT_FALSE(irs::accept<char>(a, ""));
-    ASSERT_FALSE(irs::accept<char>(a, irs::string_ref::NIL));
-    ASSERT_FALSE(irs::accept<char>(a, "a"));
-    ASSERT_TRUE(irs::accept<char>(a, "ba"));
-    ASSERT_FALSE(irs::accept<char>(a, "azbce1d"));
-    ASSERT_FALSE(irs::accept<char>(a, "azbce1d1"));
-    ASSERT_FALSE(irs::accept<char>(a, "azbce11d"));
+  static void assert_arc(
+      const irs::automaton::Arc& actual_arc,
+      irs::automaton::Arc::Label expected_label,
+      irs::automaton::StateId expected_target) {
+    ASSERT_EQ(expected_label, actual_arc.ilabel);
+    ASSERT_EQ(expected_label, actual_arc.olabel);
+    ASSERT_EQ(expected_target, actual_arc.nextstate);
+    ASSERT_EQ(fst::fsa::BooleanWeight(false), actual_arc.weight);
   }
 
-  // any char (suffix)
-  {
-    auto a = irs::from_wildcard<char>("a_");
-    ASSERT_EQ(fst::kAcceptor | fst::kUnweighted, a.Properties(fst::kAcceptor | fst::kUnweighted, true));
-    ASSERT_FALSE(irs::accept<char>(a, ""));
-    ASSERT_FALSE(irs::accept<char>(a, irs::string_ref::NIL));
-    ASSERT_TRUE(irs::accept<char>(a, "a_"));
-    ASSERT_FALSE(irs::accept<char>(a, "a"));
-    ASSERT_TRUE(irs::accept<char>(a, "ab"));
+  static void assert_state(
+      const irs::automaton& a,
+      const irs::automaton::StateId state,
+      const std::vector<std::pair<irs::automaton::Arc::Label, irs::automaton::StateId>>& expected_arcs) {
+    fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+    a.InitArcIterator(state, &actual_arcs);
+    ASSERT_EQ(expected_arcs.size(), actual_arcs.narcs);
+
+    auto* actual_arc = actual_arcs.arcs;
+    for (auto& expected_arc : expected_arcs) {
+      assert_arc(*actual_arc, expected_arc.first, expected_arc.second);
+      ++actual_arc;
+    }
+  };
+
+  static void assert_automaton(
+      const irs::automaton& a,
+      const std::vector<std::vector<std::pair<irs::automaton::Arc::Label, irs::automaton::StateId>>>& expected_automaton) {
+    ASSERT_EQ(expected_automaton.size(), a.NumStates());
+    irs::automaton::StateId state = 0;
+    for (auto& expected_arcs : expected_automaton) {
+      assert_state(a, state, expected_arcs);
+      ++state;
+    }
   }
+};
 
-  // any char (prefix)
+TEST_F(utf8_transitions_builder_test, no_arcs) {
+  irs::utf8_transitions_builder builder;
+
+  // no default transition
   {
-    auto a = irs::from_wildcard<char>("_a");
-    ASSERT_EQ(fst::kAcceptor | fst::kUnweighted, a.Properties(fst::kAcceptor | fst::kUnweighted, true));
-    ASSERT_FALSE(irs::accept<char>(a, ""));
-    ASSERT_FALSE(irs::accept<char>(a, irs::string_ref::NIL));
-    ASSERT_TRUE(irs::accept<char>(a, "_a"));
-    ASSERT_FALSE(irs::accept<char>(a, "a"));
-    ASSERT_TRUE(irs::accept<char>(a, "ba"));
+    irs::automaton a;
+    auto start = a.AddState();
+
+    std::vector<std::pair<irs::bytes_ref, irs::automaton::StateId>> arcs;
+    builder.insert(a, start, fst::kNoStateId, arcs.begin(), arcs.end());
+
+    assert_properties(a);
+    ASSERT_EQ(1, a.NumStates());
+
+    // arcs from start state
+    {
+      fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+      a.InitArcIterator(start, &actual_arcs);
+      ASSERT_EQ(0, actual_arcs.narcs);
+    }
   }
 
-  // escaped '_'
+  // default transition
   {
-    auto a = irs::from_wildcard<char>("\\_a");
-    ASSERT_EQ(fst::kAcceptor | fst::kUnweighted, a.Properties(fst::kAcceptor | fst::kUnweighted, true));
-    ASSERT_FALSE(irs::accept<char>(a, ""));
-    ASSERT_FALSE(irs::accept<char>(a, irs::string_ref::NIL));
-    ASSERT_TRUE(irs::accept<char>(a, "_a"));
-    ASSERT_FALSE(irs::accept<char>(a, "a"));
-    ASSERT_FALSE(irs::accept<char>(a, "ba"));
+    irs::automaton a;
+    auto start = a.AddState();
+    auto finish = a.AddState();
+    auto intermediate0 = a.NumStates();
+    auto intermediate1 = a.NumStates() + 1;
+    auto intermediate2 = a.NumStates() + 2;
+
+    std::vector<std::pair<irs::bytes_ref, irs::automaton::StateId>> arcs;
+    builder.insert(a, start, finish, arcs.begin(), arcs.end());
+
+    assert_properties(a);
+    ASSERT_EQ(5, a.NumStates());
+
+    // arcs from start state
+    {
+      fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+      a.InitArcIterator(start, &actual_arcs);
+      ASSERT_EQ(256, actual_arcs.narcs);
+
+      auto* actual_arc = actual_arcs.arcs;
+      irs::automaton::Arc::Label label = 0;
+
+      for (; label < 192; ++label) {
+        assert_arc(*actual_arc, label, finish);
+        ++actual_arc;
+      }
+
+      for (; label < 224; ++label) {
+        assert_arc(*actual_arc, label, intermediate0);
+        ++actual_arc;
+      }
+
+      for (; label < 240; ++label) {
+        assert_arc(*actual_arc, label, intermediate1);
+        ++actual_arc;
+      }
+
+      for (; label < 256; ++label) {
+        assert_arc(*actual_arc, label, intermediate2);
+        ++actual_arc;
+      }
+
+      ASSERT_EQ(actual_arc, actual_arcs.arcs + actual_arcs.narcs);
+    }
+
+    // arcs from 'intermediate0'
+    {
+      fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+      a.InitArcIterator(intermediate0, &actual_arcs);
+      ASSERT_EQ(1, actual_arcs.narcs);
+      assert_arc(actual_arcs.arcs[0], fst::fsa::kRho, finish);
+    }
+
+    // arcs from 'intermediate1'
+    {
+      fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+      a.InitArcIterator(intermediate1, &actual_arcs);
+      ASSERT_EQ(1, actual_arcs.narcs);
+      assert_arc(actual_arcs.arcs[0], fst::fsa::kRho, intermediate0);
+    }
+
+    // arcs from 'intermediate2'
+    {
+      fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+      a.InitArcIterator(intermediate2, &actual_arcs);
+      ASSERT_EQ(1, actual_arcs.narcs);
+      assert_arc(actual_arcs.arcs[0], fst::fsa::kRho, intermediate1);
+    }
+
+    // arcs from 'finish0'
+    {
+      fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+      a.InitArcIterator(finish, &actual_arcs);
+      ASSERT_EQ(0, actual_arcs.narcs);
+    }
   }
+}
+
+TEST_F(utf8_transitions_builder_test, empty_arc) {
+  irs::utf8_transitions_builder builder;
 
-  // escaped '\'
+  // no default transition
   {
-    auto a = irs::from_wildcard<char>("\\\\\\_a");
-    ASSERT_EQ(fst::kAcceptor | fst::kUnweighted, a.Properties(fst::kAcceptor | fst::kUnweighted, true));
-    ASSERT_FALSE(irs::accept<char>(a, ""));
-    ASSERT_FALSE(irs::accept<char>(a, irs::string_ref::NIL));
-    ASSERT_TRUE(irs::accept<char>(a, "\\_a"));
-    ASSERT_FALSE(irs::accept<char>(a, "a"));
-    ASSERT_FALSE(irs::accept<char>(a, "ba"));
+    irs::automaton a;
+    auto start = a.AddState();
+    auto finish = a.AddState();
+
+    std::vector<std::pair<irs::bytes_ref, irs::automaton::StateId>> arcs {
+      { irs::bytes_ref::EMPTY, finish }
+    };
+    builder.insert(a, start, fst::kNoStateId, arcs.begin(), arcs.end());
+
+    assert_properties(a);
+    ASSERT_EQ(2, a.NumStates());
+
+    // arcs from start state
+    {
+      fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+      a.InitArcIterator(start, &actual_arcs);
+      ASSERT_EQ(0, actual_arcs.narcs);
+    }
+
+    // arcs from final state
+    {
+      fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+      a.InitArcIterator(finish, &actual_arcs);
+      ASSERT_EQ(0, actual_arcs.narcs);
+    }
   }
 
-  // nonterminated '\'
+  // default transition
   {
-    auto a = irs::from_wildcard<char>("a\\");
-    ASSERT_EQ(fst::kAcceptor | fst::kUnweighted, a.Properties(fst::kAcceptor | fst::kUnweighted, true));
-    ASSERT_FALSE(irs::accept<char>(a, ""));
-    ASSERT_FALSE(irs::accept<char>(a, irs::string_ref::NIL));
-    ASSERT_TRUE(irs::accept<char>(a, "a\\"));
-    ASSERT_FALSE(irs::accept<char>(a, "a"));
-    ASSERT_FALSE(irs::accept<char>(a, "ba"));
+    irs::automaton a;
+    auto start = a.AddState();
+    auto finish = a.AddState();
+    auto intermediate0 = a.NumStates();
+    auto intermediate1 = a.NumStates() + 1;
+    auto intermediate2 = a.NumStates() + 2;
+
+    std::vector<std::pair<irs::bytes_ref, irs::automaton::StateId>> arcs {
+      { irs::bytes_ref::EMPTY, finish }
+    };
+    builder.insert(a, start, finish, arcs.begin(), arcs.end());
+
+    assert_properties(a);
+    ASSERT_EQ(5, a.NumStates());
+
+    // arcs from start state
+    {
+      fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+      a.InitArcIterator(start, &actual_arcs);
+      ASSERT_EQ(256, actual_arcs.narcs);
+
+      auto* actual_arc = actual_arcs.arcs;
+      irs::automaton::Arc::Label label = 0;
+
+      for (; label < 192; ++label) {
+        assert_arc(*actual_arc, label, finish);
+        ++actual_arc;
+      }
+
+      for (; label < 224; ++label) {
+        assert_arc(*actual_arc, label, intermediate0);
+        ++actual_arc;
+      }
+
+      for (; label < 240; ++label) {
+        assert_arc(*actual_arc, label, intermediate1);
+        ++actual_arc;
+      }
+
+      for (; label < 256; ++label) {
+        assert_arc(*actual_arc, label, intermediate2);
+        ++actual_arc;
+      }
+
+      ASSERT_EQ(actual_arc, actual_arcs.arcs + actual_arcs.narcs);
+    }
+
+    // arcs from 'intermediate0'
+    {
+      fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+      a.InitArcIterator(intermediate0, &actual_arcs);
+      ASSERT_EQ(1, actual_arcs.narcs);
+      assert_arc(actual_arcs.arcs[0], fst::fsa::kRho, finish);
+    }
+
+    // arcs from 'intermediate1'
+    {
+      fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+      a.InitArcIterator(intermediate1, &actual_arcs);
+      ASSERT_EQ(1, actual_arcs.narcs);
+      assert_arc(actual_arcs.arcs[0], fst::fsa::kRho, intermediate0);
+    }
+
+    // arcs from 'intermediate2'
+    {
+      fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+      a.InitArcIterator(intermediate2, &actual_arcs);
+      ASSERT_EQ(1, actual_arcs.narcs);
+      assert_arc(actual_arcs.arcs[0], fst::fsa::kRho, intermediate1);
+    }
+
+    // arcs from 'finish0'
+    {
+      fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+      a.InitArcIterator(finish, &actual_arcs);
+      ASSERT_EQ(0, actual_arcs.narcs);
+    }
   }
+}
 
-  // escaped '%'
+TEST_F(utf8_transitions_builder_test, single_byte_sequence) {
+  irs::utf8_transitions_builder builder;
+
+  // no default transition
   {
-    auto a = irs::from_wildcard<char>("\\\\\\%a");
-    ASSERT_EQ(fst::kAcceptor | fst::kUnweighted, a.Properties(fst::kAcceptor | fst::kUnweighted, true));
-    ASSERT_FALSE(irs::accept<char>(a, ""));
-    ASSERT_FALSE(irs::accept<char>(a, irs::string_ref::NIL));
-    ASSERT_TRUE(irs::accept<char>(a, "\\%a"));
-    ASSERT_FALSE(irs::accept<char>(a, "a"));
-    ASSERT_FALSE(irs::accept<char>(a, "ba"));
+    irs::automaton a;
+    auto start = a.AddState();
+    auto finish0 = a.AddState();
+    auto finish1 = a.AddState();
+
+    std::vector<std::pair<irs::bytes_ref, irs::automaton::StateId>> arcs;
+    arcs.emplace_back(irs::ref_cast<irs::byte_type>(irs::string_ref("a")), finish0);
+    arcs.emplace_back(irs::ref_cast<irs::byte_type>(irs::string_ref("0")), finish0);
+    arcs.emplace_back(irs::ref_cast<irs::byte_type>(irs::string_ref("7")), finish1);
+    arcs.emplace_back(irs::ref_cast<irs::byte_type>(irs::string_ref("U")), finish0);
+    arcs.emplace_back(irs::ref_cast<irs::byte_type>(irs::string_ref("b")), finish1);
+    std::sort(arcs.begin(), arcs.end());
+
+    builder.insert(a, start, fst::kNoStateId, arcs.begin(), arcs.end());
+
+    assert_properties(a);
+    ASSERT_EQ(3, a.NumStates());
+
+    // arcs from start state
+    {
+      fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+      a.InitArcIterator(start, &actual_arcs);
+      ASSERT_EQ(arcs.size(), actual_arcs.narcs);
+
+      auto* actual_arc = actual_arcs.arcs;
+      for (auto& arc : arcs) {
+        ASSERT_EQ(1, arc.first.size());
+        assert_arc(*actual_arc, arc.first[0], arc.second);
+        ++actual_arc;
+      }
+      ASSERT_EQ(actual_arc, actual_arcs.arcs + actual_arcs.narcs);
+    }
+
+    // arcs from 'finish0'
+    {
+      fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+      a.InitArcIterator(finish0, &actual_arcs);
+      ASSERT_EQ(0, actual_arcs.narcs);
+    }
+
+    // arcs from 'finish1'
+    {
+      fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+      a.InitArcIterator(finish1, &actual_arcs);
+      ASSERT_EQ(0, actual_arcs.narcs);
+    }
   }
 
-  // prefix
+  // default transition
   {
-    auto a = irs::from_wildcard<char>("foo%");
-    ASSERT_EQ(fst::kAcceptor | fst::kUnweighted, a.Properties(fst::kAcceptor | fst::kUnweighted, true));
-    ASSERT_FALSE(irs::accept<char>(a, ""));
-    ASSERT_FALSE(irs::accept<char>(a, irs::string_ref::NIL));
-    ASSERT_TRUE(irs::accept<char>(a, "foo"));
-    ASSERT_TRUE(irs::accept<char>(a, "foobar"));
-    ASSERT_FALSE(irs::accept<char>(a, "foa"));
-    ASSERT_FALSE(irs::accept<char>(a, "foabar"));
+    irs::automaton a;
+    auto start = a.AddState();
+    auto finish0 = a.AddState();
+    auto finish1 = a.AddState();
+    auto intermediate0 = a.NumStates();
+    auto intermediate1 = a.NumStates() + 1;
+    auto intermediate2 = a.NumStates() + 2;
+
+    a.SetStart(start);
+
+    std::vector<std::pair<irs::bytes_ref, irs::automaton::StateId>> arcs;
+    arcs.emplace_back(irs::ref_cast<irs::byte_type>(irs::string_ref("a")), finish0);
+    arcs.emplace_back(irs::ref_cast<irs::byte_type>(irs::string_ref("0")), finish0);
+    arcs.emplace_back(irs::ref_cast<irs::byte_type>(irs::string_ref("7")), finish1);
+    arcs.emplace_back(irs::ref_cast<irs::byte_type>(irs::string_ref("U")), finish0);
+    arcs.emplace_back(irs::ref_cast<irs::byte_type>(irs::string_ref("b")), finish1);
+    std::sort(arcs.begin(), arcs.end());
+
+    builder.insert(a, start, finish1, arcs.begin(), arcs.end());
+
+    assert_properties(a);
+    ASSERT_EQ(6, a.NumStates()); // +3 intermediate states
+
+    // arcs from start state
+    {
+      fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+      a.InitArcIterator(start, &actual_arcs);
+      ASSERT_EQ(256, actual_arcs.narcs);
+
+      auto* actual_arc = actual_arcs.arcs;
+      auto expected_arc = arcs.begin();
+      irs::automaton::Arc::Label label = 0;
+
+      while (expected_arc != arcs.end() && label < 192) {
+        for (; label < expected_arc->first[0]; ++label) {
+          assert_arc(*actual_arc, label, finish1);
+          ++actual_arc;
+        }
+
+        ASSERT_EQ(label, expected_arc->first[0]);
+        assert_arc(*actual_arc, label, expected_arc->second);
+        ++label;
+        ++actual_arc;
+        ++expected_arc;
+      }
+
+      for (; label < 192; ++label) {
+        assert_arc(*actual_arc, label, finish1);
+        ++actual_arc;
+      }
+
+      for (; label < 224; ++label) {
+        assert_arc(*actual_arc, label, intermediate0);
+        ++actual_arc;
+      }
+
+      for (; label < 240; ++label) {
+        assert_arc(*actual_arc, label, intermediate1);
+        ++actual_arc;
+      }
+
+      for (; label < 256; ++label) {
+        assert_arc(*actual_arc, label, intermediate2);
+        ++actual_arc;
+      }
+
+      ASSERT_EQ(actual_arc, actual_arcs.arcs + actual_arcs.narcs);
+    }
+
+    // arcs from 'intermediate0'
+    {
+      fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+      a.InitArcIterator(intermediate0, &actual_arcs);
+      ASSERT_EQ(1, actual_arcs.narcs);
+      assert_arc(actual_arcs.arcs[0], fst::fsa::kRho, finish1);
+    }
+
+    // arcs from 'intermediate1'
+    {
+      fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+      a.InitArcIterator(intermediate1, &actual_arcs);
+      ASSERT_EQ(1, actual_arcs.narcs);
+      assert_arc(actual_arcs.arcs[0], fst::fsa::kRho, intermediate0);
+    }
+
+    // arcs from 'intermediate2'
+    {
+      fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+      a.InitArcIterator(intermediate2, &actual_arcs);
+      ASSERT_EQ(1, actual_arcs.narcs);
+      assert_arc(actual_arcs.arcs[0], fst::fsa::kRho, intermediate1);
+    }
+
+    // arcs from 'finish0'
+    {
+      fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+      a.InitArcIterator(finish0, &actual_arcs);
+      ASSERT_EQ(0, actual_arcs.narcs);
+    }
+
+    // arcs from 'finish1'
+    {
+      fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+      a.InitArcIterator(finish1, &actual_arcs);
+      ASSERT_EQ(0, actual_arcs.narcs);
+    }
   }
+}
+
+TEST_F(utf8_transitions_builder_test, multi_byte_sequence) {
+  irs::utf8_transitions_builder builder;
 
-  // prefix
   {
-    auto a = irs::from_wildcard<char>("v%%");
-
-    ASSERT_EQ(fst::kAcceptor | fst::kUnweighted, a.Properties(fst::kAcceptor | fst::kUnweighted, true));
-    ASSERT_FALSE(irs::accept<char>(a, ""));
-    ASSERT_FALSE(irs::accept<char>(a, irs::string_ref::NIL));
-    ASSERT_TRUE(irs::accept<char>(a, "vcc"));
-    ASSERT_TRUE(irs::accept<char>(a, "vccc"));
-    ASSERT_TRUE(irs::accept<char>(a, "vczc"));
-    ASSERT_TRUE(irs::accept<char>(a, "vczczvccccc"));
+    irs::automaton a;
+    auto start = a.AddState();
+    a.SetStart(start);
+    auto finish0 = a.AddState();
+    auto finish1 = a.AddState();
+    a.SetStart(start);
+
+    std::vector<std::pair<irs::bytes_ref, irs::automaton::StateId>> arcs;
+    arcs.emplace_back(irs::ref_cast<irs::byte_type>(irs::string_ref("a")), finish0);
+    arcs.emplace_back(irs::ref_cast<irs::byte_type>(irs::string_ref("0")), finish0);
+    arcs.emplace_back(irs::ref_cast<irs::byte_type>(irs::string_ref("7")), finish1);
+    arcs.emplace_back(irs::ref_cast<irs::byte_type>(irs::string_ref("U")), finish0);
+    arcs.emplace_back(irs::ref_cast<irs::byte_type>(irs::string_ref("b")), finish1);
+    arcs.emplace_back(irs::ref_cast<irs::byte_type>(irs::string_ref("\xF5\x85\x97\x86")), finish1);
+    arcs.emplace_back(irs::ref_cast<irs::byte_type>(irs::string_ref("\xFE\x85\x97\x86")), finish1);
+    arcs.emplace_back(irs::ref_cast<irs::byte_type>(irs::string_ref("\xFF\x85\x97\x86")), finish1);
+    arcs.emplace_back(irs::ref_cast<irs::byte_type>(irs::string_ref("\xFF\x85\x97\x86")), finish1);
+    arcs.emplace_back(irs::ref_cast<irs::byte_type>(irs::string_ref("\xFF\x85\x97\x96")), finish1);
+    arcs.emplace_back(irs::ref_cast<irs::byte_type>(irs::string_ref("\xD1\x90")), finish0);
+    arcs.emplace_back(irs::ref_cast<irs::byte_type>(irs::string_ref("\xD1\x86")), finish0);
+    arcs.emplace_back(irs::ref_cast<irs::byte_type>(irs::string_ref("b")), finish1);
+    arcs.emplace_back(irs::ref_cast<irs::byte_type>(irs::string_ref("\xE2\x85\x96")), finish1);
+    arcs.emplace_back(irs::ref_cast<irs::byte_type>(irs::string_ref("\xE2\x9E\x96")), finish1);
+    arcs.emplace_back(irs::ref_cast<irs::byte_type>(irs::string_ref("\xE2\x9E\x96")), finish1);
+    arcs.emplace_back(irs::ref_cast<irs::byte_type>(irs::string_ref("\xE2\x9E\x97")), finish1);
+    arcs.emplace_back(irs::ref_cast<irs::byte_type>(irs::string_ref("\xE3\x9E\x97")), finish1);
+    arcs.emplace_back(irs::ref_cast<irs::byte_type>(irs::string_ref("\xE3\x85\x97")), finish1);
+    std::sort(arcs.begin(), arcs.end());
+
+    builder.insert(a, start, fst::kNoStateId, arcs.begin(), arcs.end());
+    assert_properties(a);
+
+    std::vector<std::vector<std::pair<irs::automaton::Arc::Label, irs::automaton::StateId>>> expected_automaton {
+      { { 48, 1 }, { 55, 2 }, { 85, 1 }, { 97, 1 },
+        { 98, 2 }, { 209, 3 }, { 226, 6 }, { 227, 8 },
+        { 245, 11 }, { 254, 11 }, { 255, 14 } },
+      { },
+      { },
+      { { 134, 1 }, { 144, 1 } },
+      { { 150, 2 } },
+      { { 150, 2 }, { 151, 2 } },
+      { { 133, 4 }, { 158, 5 } },
+      { { 151, 2 } },
+      { { 133, 7 }, { 158, 7 } },
+      { { 134, 2 } },
+      { { 151, 9 } },
+      { { 133, 10 } },
+      { { 134, 2 }, { 150, 2 } },
+      { { 151, 12 } },
+      { { 133, 13 } },
+    };
+
+    assert_automaton(a, expected_automaton);
   }
+}
 
-  // suffix
-  {
-    auto a = irs::from_wildcard<char>("%foo");
-    ASSERT_EQ(fst::kAcceptor | fst::kUnweighted, a.Properties(fst::kAcceptor | fst::kUnweighted, true));
-    ASSERT_FALSE(irs::accept<char>(a, ""));
-    ASSERT_FALSE(irs::accept<char>(a, irs::string_ref::NIL));
-    ASSERT_TRUE(irs::accept<char>(a, "foo"));
-    ASSERT_TRUE(irs::accept<char>(a, "bfoo"));
-    ASSERT_FALSE(irs::accept<char>(a, "foa"));
-    ASSERT_FALSE(irs::accept<char>(a, "bfoa"));
+// -----------------------------------------------------------------------------
+// --SECTION--                                             utf8_emplace_arc_test
+// -----------------------------------------------------------------------------
+
+class utf8_emplace_arc_test : public test_base {
+ protected:
+  static void assert_properties(const irs::automaton& a) {
+    constexpr auto EXPECTED_PROPERTIES =
+      fst::kILabelSorted | fst::kOLabelSorted |
+      fst::kIDeterministic | fst::kODeterministic |
+      fst::kAcceptor;
+
+    ASSERT_EQ(EXPECTED_PROPERTIES, a.Properties(EXPECTED_PROPERTIES, true));
   }
 
-  // mixed
-  {
-    auto a = irs::from_wildcard<char>("a%bce_d");
-    ASSERT_EQ(fst::kAcceptor | fst::kUnweighted, a.Properties(fst::kAcceptor | fst::kUnweighted, true));
-    ASSERT_FALSE(irs::accept<char>(a, ""));
-    ASSERT_FALSE(irs::accept<char>(a, irs::string_ref::NIL));
-    ASSERT_TRUE(irs::accept<char>(a, "azbce1d"));
-    ASSERT_FALSE(irs::accept<char>(a, "azbce1d1"));
-    ASSERT_FALSE(irs::accept<char>(a, "azbce11d"));
+  static void assert_arc(
+      const irs::automaton::Arc& actual_arc,
+      irs::automaton::Arc::Label expected_label,
+      irs::automaton::StateId expected_target) {
+    ASSERT_EQ(expected_label, actual_arc.ilabel);
+    ASSERT_EQ(expected_label, actual_arc.olabel);
+    ASSERT_EQ(expected_target, actual_arc.nextstate);
+    ASSERT_EQ(fst::fsa::BooleanWeight(false), actual_arc.weight);
   }
 
-  // mixed
-  {
-    auto a = irs::from_wildcard<char>("%_");
-    ASSERT_EQ(fst::kAcceptor | fst::kUnweighted, a.Properties(fst::kAcceptor | fst::kUnweighted, true));
-    ASSERT_FALSE(irs::accept<char>(a, ""));
-    ASSERT_FALSE(irs::accept<char>(a, irs::string_ref::NIL));
-    ASSERT_TRUE(irs::accept<char>(a, "a"));
-    ASSERT_TRUE(irs::accept<char>(a, "aa"));
-    ASSERT_TRUE(irs::accept<char>(a, "azbce1d"));
-    ASSERT_TRUE(irs::accept<char>(a, "azbce1d1"));
-    ASSERT_TRUE(irs::accept<char>(a, "azbce11d"));
+  static void assert_state(
+      const irs::automaton& a,
+      const irs::automaton::StateId state,
+      const std::vector<std::pair<irs::automaton::Arc::Label, irs::automaton::StateId>>& expected_arcs) {
+    fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+    a.InitArcIterator(state, &actual_arcs);
+    ASSERT_EQ(expected_arcs.size(), actual_arcs.narcs);
+
+    auto* actual_arc = actual_arcs.arcs;
+    for (auto& expected_arc : expected_arcs) {
+      assert_arc(*actual_arc, expected_arc.first, expected_arc.second);
+      ++actual_arc;
+    }
+  };
+
+  static void assert_automaton(
+      const irs::automaton& a,
+      const std::vector<std::vector<std::pair<irs::automaton::Arc::Label, irs::automaton::StateId>>>& expected_automaton) {
+    ASSERT_EQ(expected_automaton.size(), a.NumStates());
+    irs::automaton::StateId state = 0;
+    for (auto& expected_arcs : expected_automaton) {
+      assert_state(a, state, expected_arcs);
+      ++state;
+    }
   }
+};
+
+TEST_F(utf8_emplace_arc_test, emplace_arc_no_default_arc) {
+   // 1-byte sequence
+   {
+     irs::automaton a;
+     auto start = a.AddState();
+     auto finish = a.AddState();
+     a.SetStart(start);
+     a.SetFinal(finish);
+
+     const irs::string_ref label = "a";
+     irs::utf8_emplace_arc(a, start, fst::kNoStateId, irs::ref_cast<irs::byte_type>(label), finish);
+
+     const std::vector<std::vector<std::pair<irs::automaton::Arc::Label, irs::automaton::StateId>>> expected_automaton{
+       { { 0x61, 1 } },
+       { }
+     };
+
+     assert_properties(a);
+     assert_automaton(a, expected_automaton);
+
+     ASSERT_FALSE(irs::accept<char>(a, ""));
+     ASSERT_TRUE(irs::accept<char>(a, "a"));
+     ASSERT_FALSE(irs::accept<char>(a, "\xD0\xBF"));
+     ASSERT_FALSE(irs::accept<char>(a, "\xE2\x9E\x96"));
+     ASSERT_FALSE(irs::accept<char>(a, "\xF0\x9F\x98\x81"));
+   }
+
+   // 2-byte sequence
+   {
+     irs::automaton a;
+     auto start = a.AddState();
+     auto finish = a.AddState();
+     a.SetStart(start);
+     a.SetFinal(finish);
+
+     const irs::string_ref label = "\xD0\xBF";
+     irs::utf8_emplace_arc(a, start, fst::kNoStateId, irs::ref_cast<irs::byte_type>(label), finish);
+
+     const std::vector<std::vector<std::pair<irs::automaton::Arc::Label, irs::automaton::StateId>>> expected_automaton{
+       { { 0xD0, 2 } },
+       { },
+       { { 0xBF, 1 } },
+     };
+
+     assert_properties(a);
+     assert_automaton(a, expected_automaton);
+
+     ASSERT_FALSE(irs::accept<char>(a, ""));
+     ASSERT_FALSE(irs::accept<char>(a, "a"));
+     ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xD0\xBF"))));
+     ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xE2\x9E\x96"))));
+     ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xF0\x9F\x98\x81"))));
+   }
+
+   // 3-byte sequence
+   {
+     irs::automaton a;
+     auto start = a.AddState();
+     auto finish = a.AddState();
+     a.SetStart(start);
+     a.SetFinal(finish);
 
-  // mixed
+     const irs::string_ref label = "\xE2\x9E\x96";
+     irs::utf8_emplace_arc(a, start, fst::kNoStateId, irs::ref_cast<irs::byte_type>(label), finish);
+
+     const std::vector<std::vector<std::pair<irs::automaton::Arc::Label, irs::automaton::StateId>>> expected_automaton{
+       { { 0xE2, 2 } },
+       { },
+       { { 0x9E, 3 } },
+       { { 0x96, 1 } },
+     };
+
+     assert_properties(a);
+     assert_automaton(a, expected_automaton);
+
+     ASSERT_FALSE(irs::accept<char>(a, ""));
+     ASSERT_FALSE(irs::accept<char>(a, "a"));
+     ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xD0\xBF"))));
+     ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xE2\x9E\x96"))));
+     ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xF0\x9F\x98\x81"))));
+   }
+
+   // 4-byte sequence
+   {
+     irs::automaton a;
+     auto start = a.AddState();
+     auto finish = a.AddState();
+     a.SetStart(start);
+     a.SetFinal(finish);
+
+     const irs::string_ref label = "\xF0\x9F\x98\x81";
+     irs::utf8_emplace_arc(a, start, fst::kNoStateId, irs::ref_cast<irs::byte_type>(label), finish);
+
+     const std::vector<std::vector<std::pair<irs::automaton::Arc::Label, irs::automaton::StateId>>> expected_automaton{
+       { { 0xF0, 2 } },
+       { },
+       { { 0x9F, 3 } },
+       { { 0x98, 4 } },
+       { { 0x81, 1 } },
+     };
+
+     assert_properties(a);
+     assert_automaton(a, expected_automaton);
+
+     ASSERT_FALSE(irs::accept<char>(a, ""));
+     ASSERT_FALSE(irs::accept<char>(a, "a"));
+     ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xD0\xBF"))));
+     ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xE2\x9E\x96"))));
+     ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xF0\x9F\x98\x81"))));
+   }
+}
+
+TEST_F(utf8_emplace_arc_test, emplace_arc_default_arc) {
+  // 1-byte sequence
   {
-    auto a = irs::from_wildcard<char>("%%_");
-    ASSERT_EQ(fst::kAcceptor | fst::kUnweighted, a.Properties(fst::kAcceptor | fst::kUnweighted, true));
-    ASSERT_FALSE(irs::accept<char>(a, ""));
-    ASSERT_FALSE(irs::accept<char>(a, irs::string_ref::NIL));
-    ASSERT_TRUE(irs::accept<char>(a, "a"));
-    ASSERT_TRUE(irs::accept<char>(a, "aa"));
-    ASSERT_TRUE(irs::accept<char>(a, "azbce1d"));
-    ASSERT_TRUE(irs::accept<char>(a, "azbce1d1"));
-    ASSERT_TRUE(irs::accept<char>(a, "azbce11d"));
+    irs::automaton a;
+    auto start = a.AddState();
+    auto finish = a.AddState();
+    auto def = a.AddState();
+    a.SetStart(start);
+    a.SetFinal(finish);
+    a.SetFinal(def);
+    auto intermediate0 = a.NumStates();
+    auto intermediate1 = a.NumStates() + 1;
+    auto intermediate2 = a.NumStates() + 2;
+
+    const irs::string_ref label = "a";
+    irs::utf8_emplace_arc(a, start, def, irs::ref_cast<irs::byte_type>(label), finish);
+    ASSERT_EQ(6, a.NumStates());
+    assert_properties(a);
+
+    // arcs from start state
+    {
+      fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+      a.InitArcIterator(start, &actual_arcs);
+      ASSERT_EQ(256, actual_arcs.narcs);
+
+      irs::automaton::Arc::Label label = 0;
+      auto* actual_arc = actual_arcs.arcs;
+
+      for (; label < 'a'; ++label) {
+        assert_arc(*actual_arc, label, def);
+        ++actual_arc;
+      }
+
+      ASSERT_EQ('a', label);
+      assert_arc(*actual_arc, label, finish);
+      ++label;
+      ++actual_arc;
+
+      for (; label < 192; ++label) {
+        assert_arc(*actual_arc, label, def);
+        ++actual_arc;
+      }
+
+      for (; label < 224; ++label) {
+        assert_arc(*actual_arc, label, intermediate0);
+        ++actual_arc;
+      }
+
+      for (; label < 240; ++label) {
+        assert_arc(*actual_arc, label, intermediate1);
+        ++actual_arc;
+      }
+
+      for (; label < 256; ++label) {
+        assert_arc(*actual_arc, label, intermediate2);
+        ++actual_arc;
+      }
+
+      ASSERT_EQ(actual_arc, actual_arcs.arcs + actual_arcs.narcs);
+    }
+
+    // arcs from 'intermediate0'
+    {
+      fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+      a.InitArcIterator(intermediate0, &actual_arcs);
+      ASSERT_EQ(1, actual_arcs.narcs);
+      assert_arc(actual_arcs.arcs[0], fst::fsa::kRho, def);
+    }
+
+    // arcs from 'intermediate1'
+    {
+      fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+      a.InitArcIterator(intermediate1, &actual_arcs);
+      ASSERT_EQ(1, actual_arcs.narcs);
+      assert_arc(actual_arcs.arcs[0], fst::fsa::kRho, intermediate0);
+    }
+
+    // arcs from 'intermediate2'
+    {
+      fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+      a.InitArcIterator(intermediate2, &actual_arcs);
+      ASSERT_EQ(1, actual_arcs.narcs);
+      assert_arc(actual_arcs.arcs[0], fst::fsa::kRho, intermediate1);
+    }
+
+    // arcs from 'finish'
+    {
+      fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+      a.InitArcIterator(finish, &actual_arcs);
+      ASSERT_EQ(0, actual_arcs.narcs);
+    }
+
+    // arcs from 'def'
+    {
+      fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+      a.InitArcIterator(def, &actual_arcs);
+      ASSERT_EQ(0, actual_arcs.narcs);
+    }
+
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::bytes_ref::EMPTY));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("a"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xD0\xBF"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xE2\x9E\x96"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xF0\x9F\x98\x81"))));
   }
 
-  // mixed
+  // 2-byte sequence
   {
-    auto a = irs::from_wildcard<char>("_%");
-    ASSERT_EQ(fst::kAcceptor | fst::kUnweighted, a.Properties(fst::kAcceptor | fst::kUnweighted, true));
-    ASSERT_FALSE(irs::accept<char>(a, ""));
-    ASSERT_FALSE(irs::accept<char>(a, irs::string_ref::NIL));
-    ASSERT_TRUE(irs::accept<char>(a, "a"));
-    ASSERT_TRUE(irs::accept<char>(a, "aa"));
-    ASSERT_TRUE(irs::accept<char>(a, "azbce1d"));
-    ASSERT_TRUE(irs::accept<char>(a, "azbce1d1"));
-    ASSERT_TRUE(irs::accept<char>(a, "azbce11d"));
+    irs::automaton a;
+    auto start = a.AddState();
+    auto finish = a.AddState();
+    auto def = a.AddState();
+    a.SetStart(start);
+    a.SetFinal(finish);
+    a.SetFinal(def);
+    auto intermediate0 = a.NumStates();
+    auto intermediate1 = a.NumStates() + 1;
+    auto intermediate2 = a.NumStates() + 2;
+
+    const irs::string_ref label = "\xD0\xBF";
+    irs::utf8_emplace_arc(a, start, def, irs::ref_cast<irs::byte_type>(label), finish);
+    ASSERT_EQ(7, a.NumStates());
+    assert_properties(a);
+
+    // arcs from start state
+    {
+      fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+      a.InitArcIterator(start, &actual_arcs);
+      ASSERT_EQ(256, actual_arcs.narcs);
+
+      irs::automaton::Arc::Label label = 0;
+      auto* actual_arc = actual_arcs.arcs;
+
+      for (; label < 192; ++label) {
+        assert_arc(*actual_arc, label, def);
+        ++actual_arc;
+      }
+
+      for (; label < 208; ++label) {
+        assert_arc(*actual_arc, label, intermediate0);
+        ++actual_arc;
+      }
+
+      ASSERT_EQ(208, label);
+      assert_arc(*actual_arc, label, intermediate2+1);
+      ++label;
+      ++actual_arc;
+
+      for (; label < 224; ++label) {
+        assert_arc(*actual_arc, label, intermediate0);
+        ++actual_arc;
+      }
+
+      for (; label < 240; ++label) {
+        assert_arc(*actual_arc, label, intermediate1);
+        ++actual_arc;
+      }
+
+      for (; label < 256; ++label) {
+        assert_arc(*actual_arc, label, intermediate2);
+        ++actual_arc;
+      }
+
+      ASSERT_EQ(actual_arc, actual_arcs.arcs + actual_arcs.narcs);
+    }
+
+    // arcs from 'intermediate2+1'
+    {
+      fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+      a.InitArcIterator(intermediate2+1, &actual_arcs);
+      ASSERT_EQ(2, actual_arcs.narcs);
+      assert_arc(actual_arcs.arcs[0], 191, finish);
+      assert_arc(actual_arcs.arcs[1], fst::fsa::kRho, def);
+    }
+
+    // arcs from 'intermediate0'
+    {
+      fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+      a.InitArcIterator(intermediate0, &actual_arcs);
+      ASSERT_EQ(1, actual_arcs.narcs);
+      assert_arc(actual_arcs.arcs[0], fst::fsa::kRho, def);
+    }
+
+    // arcs from 'intermediate1'
+    {
+      fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+      a.InitArcIterator(intermediate1, &actual_arcs);
+      ASSERT_EQ(1, actual_arcs.narcs);
+      assert_arc(actual_arcs.arcs[0], fst::fsa::kRho, intermediate0);
+    }
+
+    // arcs from 'intermediate2'
+    {
+      fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+      a.InitArcIterator(intermediate2, &actual_arcs);
+      ASSERT_EQ(1, actual_arcs.narcs);
+      assert_arc(actual_arcs.arcs[0], fst::fsa::kRho, intermediate1);
+    }
+
+    // arcs from 'finish'
+    {
+      fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+      a.InitArcIterator(finish, &actual_arcs);
+      ASSERT_EQ(0, actual_arcs.narcs);
+    }
+
+    // arcs from 'def'
+    {
+      fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+      a.InitArcIterator(def, &actual_arcs);
+      ASSERT_EQ(0, actual_arcs.narcs);
+    }
+
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::bytes_ref::EMPTY));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("a"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xD0\xBF"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xE2\x9E\x96"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xF0\x9F\x98\x81"))));
   }
 
-  // mixed
+  // 3-byte sequence
   {
-    auto a = irs::from_wildcard<char>("v%%c");
-    ASSERT_EQ(fst::kAcceptor | fst::kUnweighted, a.Properties(fst::kAcceptor | fst::kUnweighted, true));
-    ASSERT_FALSE(irs::accept<char>(a, ""));
-    ASSERT_FALSE(irs::accept<char>(a, irs::string_ref::NIL));
-    ASSERT_TRUE(irs::accept<char>(a, "vcc"));
-    ASSERT_TRUE(irs::accept<char>(a, "vccc"));
-    ASSERT_TRUE(irs::accept<char>(a, "vczc"));
-    ASSERT_TRUE(irs::accept<char>(a, "vczczvccccc"));
+    irs::automaton a;
+    auto start = a.AddState();
+    auto finish = a.AddState();
+    auto def = a.AddState();
+    a.SetStart(start);
+    a.SetFinal(finish);
+    a.SetFinal(def);
+    auto intermediate0 = a.NumStates();
+    auto intermediate1 = a.NumStates() + 1;
+    auto intermediate2 = a.NumStates() + 2;
+
+    const irs::string_ref label = "\xE2\x9E\x96";
+    irs::utf8_emplace_arc(a, start, def, irs::ref_cast<irs::byte_type>(label), finish);
+    ASSERT_EQ(8, a.NumStates());
+    assert_properties(a);
+
+    // arcs from start state
+    {
+      fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+      a.InitArcIterator(start, &actual_arcs);
+      ASSERT_EQ(256, actual_arcs.narcs);
+
+      irs::automaton::Arc::Label label = 0;
+      auto* actual_arc = actual_arcs.arcs;
+
+      for (; label < 192; ++label) {
+        assert_arc(*actual_arc, label, def);
+        ++actual_arc;
+      }
+
+      for (; label < 224; ++label) {
+        assert_arc(*actual_arc, label, intermediate0);
+        ++actual_arc;
+      }
+
+      for (; label < 226; ++label) {
+        assert_arc(*actual_arc, label, intermediate1);
+        ++actual_arc;
+      }
+
+      ASSERT_EQ(226, label);
+      assert_arc(*actual_arc, label, intermediate2+1);
+      ++label;
+      ++actual_arc;
+
+      for (; label < 240; ++label) {
+        assert_arc(*actual_arc, label, intermediate1);
+        ++actual_arc;
+      }
+
+      for (; label < 256; ++label) {
+        assert_arc(*actual_arc, label, intermediate2);
+        ++actual_arc;
+      }
+
+      ASSERT_EQ(actual_arc, actual_arcs.arcs + actual_arcs.narcs);
+    }
+
+    // arcs from 'intermediate2+1'
+    {
+      fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+      a.InitArcIterator(intermediate2+1, &actual_arcs);
+      ASSERT_EQ(2, actual_arcs.narcs);
+      assert_arc(actual_arcs.arcs[0], 158, intermediate2+2);
+      assert_arc(actual_arcs.arcs[1], fst::fsa::kRho, intermediate0);
+    }
+
+    // arcs from 'intermediate2+2'
+    {
+      fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+      a.InitArcIterator(intermediate2+2, &actual_arcs);
+      ASSERT_EQ(2, actual_arcs.narcs);
+      assert_arc(actual_arcs.arcs[0], 150, finish);
+      assert_arc(actual_arcs.arcs[1], fst::fsa::kRho, def);
+    }
+
+    // arcs from 'intermediate0'
+    {
+      fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+      a.InitArcIterator(intermediate0, &actual_arcs);
+      ASSERT_EQ(1, actual_arcs.narcs);
+      assert_arc(actual_arcs.arcs[0], fst::fsa::kRho, def);
+    }
+
+    // arcs from 'intermediate1'
+    {
+      fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+      a.InitArcIterator(intermediate1, &actual_arcs);
+      ASSERT_EQ(1, actual_arcs.narcs);
+      assert_arc(actual_arcs.arcs[0], fst::fsa::kRho, intermediate0);
+    }
+
+    // arcs from 'intermediate2'
+    {
+      fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+      a.InitArcIterator(intermediate2, &actual_arcs);
+      ASSERT_EQ(1, actual_arcs.narcs);
+      assert_arc(actual_arcs.arcs[0], fst::fsa::kRho, intermediate1);
+    }
+
+    // arcs from 'finish'
+    {
+      fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+      a.InitArcIterator(finish, &actual_arcs);
+      ASSERT_EQ(0, actual_arcs.narcs);
+    }
+
+    // arcs from 'def'
+    {
+      fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+      a.InitArcIterator(def, &actual_arcs);
+      ASSERT_EQ(0, actual_arcs.narcs);
+    }
+
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::bytes_ref::EMPTY));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("a"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xD0\xBF"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xE2\x9E\x96"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xF0\x9F\x98\x81"))));
   }
 
-  // mixed
+  // 4-byte sequence
   {
-    auto a = irs::from_wildcard<char>("v%c");
-    ASSERT_EQ(fst::kAcceptor | fst::kUnweighted, a.Properties(fst::kAcceptor | fst::kUnweighted, true));
-    ASSERT_FALSE(irs::accept<char>(a, ""));
-    ASSERT_FALSE(irs::accept<char>(a, irs::string_ref::NIL));
-    ASSERT_TRUE(irs::accept<char>(a, "vcc"));
-    ASSERT_TRUE(irs::accept<char>(a, "vccc"));
-    ASSERT_TRUE(irs::accept<char>(a, "vczc"));
-    ASSERT_TRUE(irs::accept<char>(a, "vczczvccccc"));
+    irs::automaton a;
+    auto start = a.AddState();
+    auto finish = a.AddState();
+    auto def = a.AddState();
+    a.SetStart(start);
+    a.SetFinal(finish);
+    a.SetFinal(def);
+    auto intermediate0 = a.NumStates();
+    auto intermediate1 = a.NumStates() + 1;
+    auto intermediate2 = a.NumStates() + 2;
+
+    const irs::string_ref label = "\xF0\x9F\x98\x81";
+    irs::utf8_emplace_arc(a, start, def, irs::ref_cast<irs::byte_type>(label), finish);
+    ASSERT_EQ(9, a.NumStates());
+    assert_properties(a);
+
+    // arcs from start state
+    {
+      fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+      a.InitArcIterator(start, &actual_arcs);
+      ASSERT_EQ(256, actual_arcs.narcs);
+
+      irs::automaton::Arc::Label label = 0;
+      auto* actual_arc = actual_arcs.arcs;
+
+      for (; label < 192; ++label) {
+        assert_arc(*actual_arc, label, def);
+        ++actual_arc;
+      }
+
+      for (; label < 224; ++label) {
+        assert_arc(*actual_arc, label, intermediate0);
+        ++actual_arc;
+      }
+
+      for (; label < 240; ++label) {
+        assert_arc(*actual_arc, label, intermediate1);
+        ++actual_arc;
+      }
+
+      ASSERT_EQ(240, label);
+      assert_arc(*actual_arc, label, intermediate2+1);
+      ++label;
+      ++actual_arc;
+
+      for (; label < 256; ++label) {
+        assert_arc(*actual_arc, label, intermediate2);
+        ++actual_arc;
+      }
+
+      ASSERT_EQ(actual_arc, actual_arcs.arcs + actual_arcs.narcs);
+    }
+
+    // arcs from 'intermediate2+1'
+    {
+      fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+      a.InitArcIterator(intermediate2+1, &actual_arcs);
+      ASSERT_EQ(2, actual_arcs.narcs);
+      assert_arc(actual_arcs.arcs[0], 159, intermediate2+2);
+      assert_arc(actual_arcs.arcs[1], fst::fsa::kRho, intermediate1);
+    }
+
+    // arcs from 'intermediate2+2'
+    {
+      fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+      a.InitArcIterator(intermediate2+2, &actual_arcs);
+      ASSERT_EQ(2, actual_arcs.narcs);
+      assert_arc(actual_arcs.arcs[0], 152, intermediate2+3);
+      assert_arc(actual_arcs.arcs[1], fst::fsa::kRho, intermediate0);
+    }
+
+    // arcs from 'intermediate2+3'
+    {
+      fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+      a.InitArcIterator(intermediate2+3, &actual_arcs);
+      ASSERT_EQ(2, actual_arcs.narcs);
+      assert_arc(actual_arcs.arcs[0], 129, finish);
+      assert_arc(actual_arcs.arcs[1], fst::fsa::kRho, def);
+    }
+
+    // arcs from 'intermediate0'
+    {
+      fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+      a.InitArcIterator(intermediate0, &actual_arcs);
+      ASSERT_EQ(1, actual_arcs.narcs);
+      assert_arc(actual_arcs.arcs[0], fst::fsa::kRho, def);
+    }
+
+    // arcs from 'intermediate1'
+    {
+      fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+      a.InitArcIterator(intermediate1, &actual_arcs);
+      ASSERT_EQ(1, actual_arcs.narcs);
+      assert_arc(actual_arcs.arcs[0], fst::fsa::kRho, intermediate0);
+    }
+
+    // arcs from 'intermediate2'
+    {
+      fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+      a.InitArcIterator(intermediate2, &actual_arcs);
+      ASSERT_EQ(1, actual_arcs.narcs);
+      assert_arc(actual_arcs.arcs[0], fst::fsa::kRho, intermediate1);
+    }
+
+    // arcs from 'finish'
+    {
+      fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+      a.InitArcIterator(finish, &actual_arcs);
+      ASSERT_EQ(0, actual_arcs.narcs);
+    }
+
+    // arcs from 'def'
+    {
+      fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+      a.InitArcIterator(def, &actual_arcs);
+      ASSERT_EQ(0, actual_arcs.narcs);
+    }
+
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::bytes_ref::EMPTY));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("a"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xD0\xBF"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xE2\x9E\x96"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xF0\x9F\x98\x81"))));
   }
 }
+
+TEST_F(utf8_emplace_arc_test, emplace_arc_rho_arc) {
+   irs::automaton a;
+   auto start = a.AddState();
+   auto finish = a.AddState();
+   a.SetStart(start);
+   a.SetFinal(finish);
+   auto intermediate0 = a.NumStates();
+   auto intermediate1 = a.NumStates() + 1;
+   auto intermediate2 = a.NumStates() + 2;
+   irs::utf8_emplace_rho_arc(a, start, finish);
+
+   assert_properties(a);
+
+   {
+     fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+     a.InitArcIterator(start, &actual_arcs);
+     ASSERT_EQ(256, actual_arcs.narcs);
+
+     auto* actual_arc = actual_arcs.arcs;
+     irs::automaton::Arc::Label label = 0;
+
+     for (; label < 192; ++label) {
+       assert_arc(*actual_arc, label, finish);
+       ++actual_arc;
+     }
+
+     for (; label < 224; ++label) {
+       assert_arc(*actual_arc, label, intermediate0);
+       ++actual_arc;
+     }
+
+     for (; label < 240; ++label) {
+       assert_arc(*actual_arc, label, intermediate1);
+       ++actual_arc;
+     }
+
+     for (; label < 256; ++label) {
+       assert_arc(*actual_arc, label, intermediate2);
+       ++actual_arc;
+     }
+
+     ASSERT_EQ(actual_arc, actual_arcs.arcs + actual_arcs.narcs);
+   }
+
+   // arcs from 'intermediate0'
+   {
+     fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+     a.InitArcIterator(intermediate0, &actual_arcs);
+     ASSERT_EQ(1, actual_arcs.narcs);
+     assert_arc(actual_arcs.arcs[0], fst::fsa::kRho, finish);
+   }
+
+   // arcs from 'intermediate1'
+   {
+     fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+     a.InitArcIterator(intermediate1, &actual_arcs);
+     ASSERT_EQ(1, actual_arcs.narcs);
+     assert_arc(actual_arcs.arcs[0], fst::fsa::kRho, intermediate0);
+   }
+
+   // arcs from 'intermediate2'
+   {
+     fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+     a.InitArcIterator(intermediate2, &actual_arcs);
+     ASSERT_EQ(1, actual_arcs.narcs);
+     assert_arc(actual_arcs.arcs[0], fst::fsa::kRho, intermediate1);
+   }
+
+   // arcs from 'finish0'
+   {
+     fst::ArcIteratorData<irs::automaton::Arc> actual_arcs;
+     a.InitArcIterator(finish, &actual_arcs);
+     ASSERT_EQ(0, actual_arcs.narcs);
+   }
+
+   ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::bytes_ref::EMPTY));
+   ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("a"))));
+   ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xD0\xBF"))));
+   ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xE2\x9E\x96"))));
+   ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xF0\x9F\x98\x81"))));
+   ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xD0\xBF\xD0\xBF"))));
+   ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xE2\x9E\x96\xD0\xBF"))));
+   ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xF0\x9F\x98\x81\xD0\xBF"))));
+}
diff --git a/3rdParty/iresearch/tests/utils/fst_utils_test.cpp b/3rdParty/iresearch/tests/utils/fst_utils_test.cpp
index eca0f11dab48..bf245b62146e 100644
--- a/3rdParty/iresearch/tests/utils/fst_utils_test.cpp
+++ b/3rdParty/iresearch/tests/utils/fst_utils_test.cpp
@@ -38,16 +38,6 @@ TEST(fst_table_matcher_test, static_const) {
 }
 
 TEST(fst_table_matcher_test, invalid_matcher) {
-  // has epsilons
-  {
-    fst::fsa::Automaton a;
-    a.AddState(); // 0
-    a.AddState(); // 1
-    a.EmplaceArc(1, 0, 0);
-    fst::TableMatcher<fst::fsa::Automaton> matcher(a, fst::kNoLabel);
-    ASSERT_EQ(fst::kError, matcher.Properties(0));
-  }
-
   // non-deterministic
   {
     fst::fsa::Automaton a;
diff --git a/3rdParty/iresearch/tests/utils/levenshtein_utils_test.cpp b/3rdParty/iresearch/tests/utils/levenshtein_utils_test.cpp
index 445d95f87290..4f73fb82daec 100644
--- a/3rdParty/iresearch/tests/utils/levenshtein_utils_test.cpp
+++ b/3rdParty/iresearch/tests/utils/levenshtein_utils_test.cpp
@@ -27,6 +27,7 @@
 #include "utils/automaton_utils.hpp"
 #include "utils/levenshtein_utils.hpp"
 #include "utils/fst_table_matcher.hpp"
+#include "utils/utf8_utils.hpp"
 
 using namespace irs::literals;
 
@@ -38,6 +39,13 @@ void assert_description(
     const std::vector<std::tuple<irs::bytes_ref, size_t, size_t>>& candidates) {
   auto a = irs::make_levenshtein_automaton(description, target);
 
+  // ensure only invalid state has no outbound connections
+  ASSERT_GE(a.NumStates(), 1);
+  ASSERT_EQ(0, a.NumArcs(0));
+  for (irs::automaton::StateId state = 1; state < a.NumStates(); ++state) {
+    ASSERT_GT(a.NumArcs(state), 0);
+  }
+
   for (auto& entry : candidates) {
     const auto candidate = std::get<0>(entry);
     const size_t expected_distance = std::get<1>(entry);
@@ -46,11 +54,38 @@ void assert_description(
                  "', Candidate: '" << irs::ref_cast<char>(candidate) <<
                  "' , Distance: " << expected_distance <<
                  " , Precise distance: " << expected_distance_precise);
-    ASSERT_EQ(expected_distance_precise, irs::edit_distance(candidate, target));
-    ASSERT_EQ(expected_distance_precise, irs::edit_distance(target, candidate));
-    ASSERT_EQ(expected_distance, irs::edit_distance(description, candidate, target));
-    ASSERT_EQ(expected_distance, irs::edit_distance(description, target, candidate));
-    ASSERT_EQ(expected_distance <= description.max_distance(), irs::accept(a, candidate));
+
+    std::vector<uint32_t> utf8_target, utf8_candidate;
+    irs::utf8_utils::utf8_to_utf32<true>(target, std::back_inserter(utf8_target));
+    irs::utf8_utils::utf8_to_utf32<true>(candidate, std::back_inserter(utf8_candidate));
+    const irs::basic_string_ref<uint32_t> utf8_target_ref(utf8_target.data(), utf8_target.size());
+    const irs::basic_string_ref<uint32_t> utf8_candidate_ref(utf8_candidate.data(), utf8_candidate.size());
+
+    ASSERT_EQ(expected_distance_precise, irs::edit_distance(utf8_candidate_ref, utf8_target_ref));
+    ASSERT_EQ(expected_distance_precise, irs::edit_distance(utf8_target_ref, utf8_candidate_ref));
+
+    {
+      size_t actual_distance;
+      if (irs::edit_distance(actual_distance, description, candidate, target)) {
+        ASSERT_EQ(expected_distance, actual_distance);
+        ASSERT_EQ(expected_distance, irs::edit_distance(description, candidate, target));
+      }
+    }
+
+    {
+      size_t actual_distance;
+      if (irs::edit_distance(actual_distance, description, target, candidate)) {
+        ASSERT_EQ(expected_distance, actual_distance);
+        ASSERT_EQ(expected_distance, irs::edit_distance(description, target, candidate));
+      }
+    }
+
+    const auto state = irs::accept(a, candidate);
+    ASSERT_EQ(expected_distance <= description.max_distance(), bool(state));
+    if (state) {
+      // every final state contains valid edit distance
+      ASSERT_EQ(expected_distance, state.Payload());
+    }
   }
 }
 
@@ -86,6 +121,18 @@ TEST(levenshtein_utils_test, test_distance) {
     ASSERT_EQ(3, irs::edit_distance(rhs.c_str(), rhs.size(), lhs.c_str(), lhs.size()));
   }
 
+  {
+    const irs::string_ref lhs = "\xD0\xBF\xD1\x83\xD1\x82\xD0\xB8\xD0\xBD";
+    const irs::string_ref rhs = "\xD1\x85\xD1\x83\xD0\xB9\xD0\xBB\xD0\xBE";
+
+    std::vector<uint32_t> lhs_utf8, rhs_utf8;
+    irs::utf8_utils::utf8_to_utf32<false>(irs::ref_cast<irs::byte_type>(lhs), std::back_inserter(lhs_utf8));
+    irs::utf8_utils::utf8_to_utf32<false>(irs::ref_cast<irs::byte_type>(rhs), std::back_inserter(rhs_utf8));
+
+    ASSERT_EQ(4, irs::edit_distance(lhs_utf8.data(), lhs_utf8.size(), rhs_utf8.data(), rhs_utf8.size()));
+    ASSERT_EQ(4, irs::edit_distance(rhs_utf8.data(), rhs_utf8.size(), lhs_utf8.data(), lhs_utf8.size()));
+  }
+
   {
     const irs::string_ref lhs = "";
     const irs::string_ref rhs = "aec";
@@ -158,6 +205,9 @@ TEST(levenshtein_utils_test, test_description_0) {
         { irs::ref_cast<irs::byte_type>("alphabezz"_sr), 1, 2 },
         { irs::ref_cast<irs::byte_type>("alphazez"_sr),  1, 2 },
         { irs::ref_cast<irs::byte_type>("lphazez"_sr),   1, 3 },
+        { irs::ref_cast<irs::byte_type>("\x61\x6c\x70\x68\xD1\xFE\x62\x65\x74"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81\x6c\x70\x68\xD1\xFE\x62\x65\x74"_sr), 1, 2 },
+        { irs::ref_cast<irs::byte_type>("\x61\x6c\x70\xE2\xFF\xFF\xD1\xFE\x62\x65\x74"_sr), 1, 2 },
       }
     );
   }
@@ -292,6 +342,140 @@ TEST(levenshtein_utils_test, test_description_1) {
     assert_transitions(description);
     assert_read_write(description);
 
+    assert_description(
+      description,
+      irs::ref_cast<irs::byte_type>("a"_sr),
+      {
+        { irs::bytes_ref::EMPTY, 1, 1 },
+        // 1-byte sequence
+        { irs::ref_cast<irs::byte_type>("a"_sr), 0, 0 },
+        { irs::ref_cast<irs::byte_type>("b"_sr), 1, 1 },
+        // 2-byte sequence
+        { irs::ref_cast<irs::byte_type>("\xD1\x83"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xD1\x83\xD1\x83"_sr), 2, 2 },
+        // incomplete 2-byte utf8 char - treat symbol as non-existent
+        { irs::ref_cast<irs::byte_type>("\xD1"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xD1\x83\xD1"_sr), 1, 1 },
+        // 3-byte sequence
+        { irs::ref_cast<irs::byte_type>("\xE2\x9E\x96"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xE2\x9E\x96\xE2\x9E\xE2"_sr), 2, 2 },
+        // incomplete 3-byte utf8 char - treat symbol as non-existent
+        { irs::ref_cast<irs::byte_type>("\xE2\x9E"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xE2\x9E\x96\xE2"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xE2\x9E\x96\xE2\x9E"_sr), 1, 1 },
+        // 4-byte sequence
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81\xE2\x9E\x96"_sr), 2, 2 },
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81\xF0\x9F\x98\x81"_sr), 2, 2 },
+        // incomplete 4-byte utf8 char - treat symbol as non-existent
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81\xF0"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81\xF0\x9F"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81\xF0\x9F\x98"_sr), 1, 1 },
+      }
+    );
+
+    assert_description(
+      description,
+      irs::ref_cast<irs::byte_type>("\xD1\x83"_sr),
+      {
+        { irs::bytes_ref::EMPTY, 1, 1 },
+        // 1-byte sequence
+        { irs::ref_cast<irs::byte_type>("a"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("b"_sr), 1, 1 },
+        // 2-byte sequence
+        { irs::ref_cast<irs::byte_type>("\xD1\x83"_sr), 0, 0 },
+        { irs::ref_cast<irs::byte_type>("\xD1\x83\xD1\x83"_sr), 1, 1 },
+        // incomplete 2-byte utf8 char - treat symbol as non-existent
+        { irs::ref_cast<irs::byte_type>("\xD1"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xD1\x83\xD1"_sr), 0, 0 },
+        // 3-byte sequence
+        { irs::ref_cast<irs::byte_type>("\xE2\x9E\x96"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xE2\x9E\x96\xE2\x9E\xE2"_sr), 2, 2 },
+        // incomplete 3-byte utf8 char - treat symbol as non-existent
+        { irs::ref_cast<irs::byte_type>("\xE2\x9E"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xE2\x9E\x96\xE2"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xE2\x9E\x96\xE2\x9E"_sr), 1, 1 },
+        // 4-byte sequence
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81\xE2\x9E\x96"_sr), 2, 2 },
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81\xF0\x9F\x98\x81"_sr), 2, 2 },
+        // incomplete 4-byte utf8 char - treat symbol as non-existent
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81\xF0"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81\xF0\x9F"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81\xF0\x9F\x98"_sr), 1, 1 },
+      }
+    );
+
+    assert_description(
+      description,
+      irs::ref_cast<irs::byte_type>("\xE2\x9E\x96"_sr),
+      {
+        { irs::bytes_ref::EMPTY, 1, 1 },
+        // 1-byte sequence
+        { irs::ref_cast<irs::byte_type>("a"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("b"_sr), 1, 1 },
+        // 2-byte sequence
+        { irs::ref_cast<irs::byte_type>("\xD1\x83"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xD1\x83\xD1\x83"_sr), 2, 2 },
+        // incomplete 2-byte utf8 char - treat symbol as non-existent
+        { irs::ref_cast<irs::byte_type>("\xD1"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xD1\x83\xD1"_sr), 1, 1 },
+        // invalid 2-byte utf8 char - accepted by automaton
+        { irs::ref_cast<irs::byte_type>("\xD1\xFF"_sr), 1, 1 },
+        // 3-byte sequence
+        { irs::ref_cast<irs::byte_type>("\xE2\x9E\x96"_sr), 0, 0 },
+        { irs::ref_cast<irs::byte_type>("\xE2\x9E\x96\xE2\x9E\xE2"_sr), 1, 1 },
+        // incomplete 3-byte utf8 char - treat symbol as non-existent
+        { irs::ref_cast<irs::byte_type>("\xE2\x9E"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xE2\x9E\x96\xE2"_sr), 0, 0 },
+        { irs::ref_cast<irs::byte_type>("\xE2\x9E\x96\xE2\x9E"_sr), 0, 0 },
+        // 4-byte sequence
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81\xE2\x9E\x96"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81\xF0\x9F\x98\x81"_sr), 2, 2 },
+        // incomplete 4-byte utf8 char - treat symbol as non-existent
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81\xF0"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81\xF0\x9F"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81\xF0\x9F\x98"_sr), 1, 1 },
+      }
+    );
+
+    assert_description(
+      description,
+      irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81"_sr),
+      {
+        { irs::bytes_ref::EMPTY, 1, 1 },
+        // 1-byte sequence
+        { irs::ref_cast<irs::byte_type>("a"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("b"_sr), 1, 1 },
+        // 2-byte sequence
+        { irs::ref_cast<irs::byte_type>("\xD1\x83"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xD1\x83\xD1\x83"_sr), 2, 2 },
+        // incomplete 2-byte utf8 char - treat symbol as non-existent
+        { irs::ref_cast<irs::byte_type>("\xD1"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xD1\x83\xD1"_sr), 1, 1 },
+        // 3-byte sequence
+        { irs::ref_cast<irs::byte_type>("\xE2\x9E\x96"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xE2\x9E\x96\xE2\x9E\xE2"_sr), 2, 2 },
+        // incomplete 3-byte utf8 char - treat symbol as non-existent
+        { irs::ref_cast<irs::byte_type>("\xE2\x9E"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xE2\x9E\x96\xE2"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xE2\x9E\x96\xE2\x9E"_sr), 1, 1 },
+        // 4-byte sequence
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81"_sr), 0, 0 },
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81\xE2\x9E\x96"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81\xF0\x9F\x98\x81"_sr), 1, 1 },
+        // incomplete 4-byte utf8 char - treat symbol as non-existent
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81\xF0"_sr), 0, 0 },
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81\xF0\x9F"_sr), 0, 0 },
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81\xF0\x9F\x98"_sr), 0, 0 },
+      }
+    );
+
     assert_description(
       description,
       irs::ref_cast<irs::byte_type>("alphabet"_sr),
@@ -303,6 +487,22 @@ TEST(levenshtein_utils_test, test_description_1) {
         { irs::ref_cast<irs::byte_type>("alphazez"_sr),  2, 2 },
       }
     );
+
+    assert_description(
+      description,
+      irs::ref_cast<irs::byte_type>("\xD1\x85\xD1\x83\xD0\xB9"_sr),
+      {
+        { irs::ref_cast<irs::byte_type>("\xD1\x85\xD1\x83\xD0\xB9"_sr), 0, 0 },
+        { irs::ref_cast<irs::byte_type>("\xD1\x85\xD1\x84\xD0\xB9"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xD1\x85\xF0\x9F\x98\x82\xD0\xB9"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xD0\xBF\xD1\x83\xD0\xB9"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xD1\x85\xD1\x83\xD0\xB0"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xD1\x85\xD1\x83\xD1\xB9"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xD1\x85\xD1\x83\xF0\xB9\xB9\xB9"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xD1\x85\xD1\x83\xD0\xB9\xD0\xBD\xD1\x8F"_sr),  2, 2 },
+        { irs::ref_cast<irs::byte_type>("\xD0\xBF\xD1\x83\xD0\xB9\xD0\xBD\xD1\x8F"_sr),  2, 3 },
+      }
+    );
   }
 
   // transpositions
@@ -329,6 +529,149 @@ TEST(levenshtein_utils_test, test_description_1) {
         { irs::ref_cast<irs::byte_type>("alphazez"_sr),  2, 2 },
       }
     );
+
+    assert_description(
+      description,
+      irs::ref_cast<irs::byte_type>("a"_sr),
+      {
+        { irs::bytes_ref::EMPTY, 1, 1 },
+        // 1-byte sequence
+        { irs::ref_cast<irs::byte_type>("a"_sr), 0, 0 },
+        { irs::ref_cast<irs::byte_type>("b"_sr), 1, 1 },
+        // 2-byte sequence
+        { irs::ref_cast<irs::byte_type>("\xD1\x83"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xD1\x83\xD1\x83"_sr), 2, 2 },
+        // incomplete 2-byte utf8 char - treat symbol as non-existent
+        { irs::ref_cast<irs::byte_type>("\xD1"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xD1\x83\xD1"_sr), 1, 1 },
+        // 3-byte sequence
+        { irs::ref_cast<irs::byte_type>("\xE2\x9E\x96"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xE2\x9E\x96\xE2\x9E\xE2"_sr), 2, 2 },
+        // incomplete 3-byte utf8 char - treat symbol as non-existent
+        { irs::ref_cast<irs::byte_type>("\xE2\x9E"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xE2\x9E\x96\xE2"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xE2\x9E\x96\xE2\x9E"_sr), 1, 1 },
+        // 4-byte sequence
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81\xE2\x9E\x96"_sr), 2, 2 },
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81\xF0\x9F\x98\x81"_sr), 2, 2 },
+        // incomplete 4-byte utf8 char - treat symbol as non-existent
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81\xF0"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81\xF0\x9F"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81\xF0\x9F\x98"_sr), 1, 1 },
+      }
+    );
+
+    assert_description(
+      description,
+      irs::ref_cast<irs::byte_type>("\xD1\x83"_sr),
+      {
+        { irs::bytes_ref::EMPTY, 1, 1 },
+        // 1-byte sequence
+        { irs::ref_cast<irs::byte_type>("a"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("b"_sr), 1, 1 },
+        // 2-byte sequence
+        { irs::ref_cast<irs::byte_type>("\xD1\x83"_sr), 0, 0 },
+        { irs::ref_cast<irs::byte_type>("\xD1\x83\xD1\x83"_sr), 1, 1 },
+        // incomplete 2-byte utf8 char - treat symbol as non-existent
+        { irs::ref_cast<irs::byte_type>("\xD1"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xD1\x83\xD1"_sr), 0, 0 },
+        // 3-byte sequence
+        { irs::ref_cast<irs::byte_type>("\xE2\x9E\x96"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xE2\x9E\x96\xE2\x9E\xE2"_sr), 2, 2 },
+        // incomplete 3-byte utf8 char - treat symbol as non-existent
+        { irs::ref_cast<irs::byte_type>("\xE2\x9E"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xE2\x9E\x96\xE2"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xE2\x9E\x96\xE2\x9E"_sr), 1, 1 },
+        // 4-byte sequence
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81\xE2\x9E\x96"_sr), 2, 2 },
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81\xF0\x9F\x98\x81"_sr), 2, 2 },
+        // incomplete 4-byte utf8 char - treat symbol as non-existent
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81\xF0"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81\xF0\x9F"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81\xF0\x9F\x98"_sr), 1, 1 },
+      }
+    );
+
+    assert_description(
+      description,
+      irs::ref_cast<irs::byte_type>("\xE2\x9E\x96"_sr),
+      {
+        { irs::bytes_ref::EMPTY, 1, 1 },
+        // 1-byte sequence
+        { irs::ref_cast<irs::byte_type>("a"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("b"_sr), 1, 1 },
+        // 2-byte sequence
+        { irs::ref_cast<irs::byte_type>("\xD1\x83"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xD1\x83\xD1\x83"_sr), 2, 2 },
+        // incomplete 2-byte utf8 char - treat symbol as non-existent
+        { irs::ref_cast<irs::byte_type>("\xD1"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xD1\x83\xD1"_sr), 1, 1 },
+        // 3-byte sequence
+        { irs::ref_cast<irs::byte_type>("\xE2\x9E\x96"_sr), 0, 0 },
+        { irs::ref_cast<irs::byte_type>("\xE2\x9E\x96\xE2\x9E\xE2"_sr), 1, 1 },
+        // incomplete 3-byte utf8 char - treat symbol as non-existent
+        { irs::ref_cast<irs::byte_type>("\xE2\x9E"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xE2\x9E\x96\xE2"_sr), 0, 0 },
+        { irs::ref_cast<irs::byte_type>("\xE2\x9E\x96\xE2\x9E"_sr), 0, 0 },
+        // 4-byte sequence
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81\xE2\x9E\x96"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81\xF0\x9F\x98\x81"_sr), 2, 2 },
+        // incomplete 4-byte utf8 char - treat symbol as non-existent
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81\xF0"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81\xF0\x9F"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81\xF0\x9F\x98"_sr), 1, 1 },
+      }
+    );
+
+    assert_description(
+      description,
+      irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81"_sr),
+      {
+        { irs::bytes_ref::EMPTY, 1, 1 },
+        // 1-byte sequence
+        { irs::ref_cast<irs::byte_type>("a"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("b"_sr), 1, 1 },
+        // 2-byte sequence
+        { irs::ref_cast<irs::byte_type>("\xD1\x83"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xD1\x83\xD1\x83"_sr), 2, 2 },
+        // incomplete 2-byte utf8 char - treat symbol as non-existent
+        { irs::ref_cast<irs::byte_type>("\xD1"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xD1\x83\xD1"_sr), 1, 1 },
+        // 3-byte sequence
+        { irs::ref_cast<irs::byte_type>("\xE2\x9E\x96"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xE2\x9E\x96\xE2\x9E\xE2"_sr), 2, 2 },
+        // incomplete 3-byte utf8 char - treat symbol as non-existent
+        { irs::ref_cast<irs::byte_type>("\xE2\x9E"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xE2\x9E\x96\xE2"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xE2\x9E\x96\xE2\x9E"_sr), 1, 1 },
+        // 4-byte sequence
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81"_sr), 0, 0 },
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81\xE2\x9E\x96"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81\xF0\x9F\x98\x81"_sr), 1, 1 },
+        // incomplete 4-byte utf8 char - treat symbol as non-existent
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81\xF0"_sr), 0, 0 },
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81\xF0\x9F"_sr), 0, 0 },
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81\xF0\x9F\x98"_sr), 0, 0 },
+      }
+    );
+
+    assert_description(
+      description,
+      irs::ref_cast<irs::byte_type>("\xD1\x85\xD1\x83\xD0\xB9"_sr),
+      {
+        { irs::ref_cast<irs::byte_type>("\xD1\x85\xD1\x83\xD0\xB9"_sr), 0, 0 },
+        { irs::ref_cast<irs::byte_type>("\xD0\xBF\xD1\x83\xD0\xB9"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xD1\x85\xD1\x83\xD0\xB9\xD0\xBD\xD1\x8F"_sr),  2, 2 },
+        { irs::ref_cast<irs::byte_type>("\xD0\xBF\xD1\x83\xD0\xB9\xD0\xBD\xD1\x8F"_sr),  2, 3 },
+      }
+    );
   }
 }
 
@@ -344,6 +687,39 @@ TEST(levenshtein_utils_test, test_description_2) {
     ASSERT_NE(description, irs::make_parametric_description(2, true));
     assert_read_write(description);
 
+    assert_description(
+      description,
+      irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81"_sr),
+      {
+        { irs::bytes_ref::EMPTY, 1, 1 },
+        // 1-byte sequence
+        { irs::ref_cast<irs::byte_type>("a"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("b"_sr), 1, 1 },
+        // 2-byte sequence
+        { irs::ref_cast<irs::byte_type>("\xD1\x83"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xD1\x83\xD1\x83"_sr), 2, 2 },
+        // incomplete 2-byte utf8 char - treat symbol as non-existent
+        { irs::ref_cast<irs::byte_type>("\xD1"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xD1\x83\xD1"_sr), 1, 1 },
+        // 3-byte sequence
+        { irs::ref_cast<irs::byte_type>("\xE2\x9E\x96"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xE2\x9E\x96\xE2\x9E\xE2"_sr), 2, 2 },
+        // incomplete 3-byte utf8 char - treat symbol as non-existent
+        { irs::ref_cast<irs::byte_type>("\xE2\x9E"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xE2\x9E\x96\xE2"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xE2\x9E\x96\xE2\x9E"_sr), 1, 1 },
+        // 4-byte sequence
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81"_sr), 0, 0 },
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81\xE2\x9E\x96"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81\xF0\x9F\x98\x81"_sr), 1, 1 },
+        // incomplete 4-byte utf8 char - treat symbol as non-existent
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81\xF0"_sr), 0, 0 },
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81\xF0\x9F"_sr), 0, 0 },
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81\xF0\x9F\x98"_sr), 0, 0 },
+      }
+    );
+
     assert_description(
       description,
       irs::ref_cast<irs::byte_type>("alphabet"_sr),
@@ -356,6 +732,20 @@ TEST(levenshtein_utils_test, test_description_2) {
         { irs::ref_cast<irs::byte_type>("alphabezz"_sr), 2, 2 },
         { irs::ref_cast<irs::byte_type>("alphazez"_sr),  2, 2 },
         { irs::ref_cast<irs::byte_type>("lphazez"_sr),   3, 3 },
+        { irs::ref_cast<irs::byte_type>("\x61\x6c\x70\x68\xD1\xFE\x62\x65\x74"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81\x6c\x70\x68\xD1\xFE\x62\x65\x74"_sr), 2, 2 },
+        { irs::ref_cast<irs::byte_type>("\x61\x6c\x70\xE2\xFF\xFF\xD1\xFE\x62\x65\x74"_sr), 2, 2 },
+      }
+    );
+
+    assert_description(
+      description,
+      irs::ref_cast<irs::byte_type>("\xD1\x85\xD1\x83\xD0\xB9"_sr),
+      {
+        { irs::ref_cast<irs::byte_type>("\xD1\x85\xD1\x83\xD0\xB9"_sr), 0, 0 },
+        { irs::ref_cast<irs::byte_type>("\xD0\xBF\xD1\x83\xD0\xB9"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xD1\x85\xD1\x83\xD0\xB9\xD0\xBD\xD1\x8F"_sr), 2, 2 },
+        { irs::ref_cast<irs::byte_type>("\xD0\xBF\xD1\x83\xD0\xB9\xD0\xBD\xD1\x8F"_sr), 3, 3 },
       }
     );
   }
@@ -371,6 +761,39 @@ TEST(levenshtein_utils_test, test_description_2) {
     ASSERT_NE(description, irs::make_parametric_description(2, false));
     assert_read_write(description);
 
+    assert_description(
+      description,
+      irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81"_sr),
+      {
+        { irs::bytes_ref::EMPTY, 1, 1 },
+        // 1-byte sequence
+        { irs::ref_cast<irs::byte_type>("a"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("b"_sr), 1, 1 },
+        // 2-byte sequence
+        { irs::ref_cast<irs::byte_type>("\xD1\x83"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xD1\x83\xD1\x83"_sr), 2, 2 },
+        // incomplete 2-byte utf8 char - treat symbol as non-existent
+        { irs::ref_cast<irs::byte_type>("\xD1"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xD1\x83\xD1"_sr), 1, 1 },
+        // 3-byte sequence
+        { irs::ref_cast<irs::byte_type>("\xE2\x9E\x96"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xE2\x9E\x96\xE2\x9E\xE2"_sr), 2, 2 },
+        // incomplete 3-byte utf8 char - treat symbol as non-existent
+        { irs::ref_cast<irs::byte_type>("\xE2\x9E"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xE2\x9E\x96\xE2"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xE2\x9E\x96\xE2\x9E"_sr), 1, 1 },
+        // 4-byte sequence
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81"_sr), 0, 0 },
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81\xE2\x9E\x96"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81\xF0\x9F\x98\x81"_sr), 1, 1 },
+        // incomplete 4-byte utf8 char - treat symbol as non-existent
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81\xF0"_sr), 0, 0 },
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81\xF0\x9F"_sr), 0, 0 },
+        { irs::ref_cast<irs::byte_type>("\xF0\x9F\x98\x81\xF0\x9F\x98"_sr), 0, 0 },
+      }
+    );
+
     assert_description(
       description,
       irs::ref_cast<irs::byte_type>("alphabet"_sr),
@@ -385,6 +808,17 @@ TEST(levenshtein_utils_test, test_description_2) {
         { irs::ref_cast<irs::byte_type>("lphazez"_sr),   3, 3 },
       }
     );
+
+    assert_description(
+      description,
+      irs::ref_cast<irs::byte_type>("\xD1\x85\xD1\x83\xD0\xB9"_sr),
+      {
+        { irs::ref_cast<irs::byte_type>("\xD1\x85\xD1\x83\xD0\xB9"_sr), 0, 0 },
+        { irs::ref_cast<irs::byte_type>("\xD0\xBF\xD1\x83\xD0\xB9"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xD1\x85\xD1\x83\xD0\xB9\xD0\xBD\xD1\x8F"_sr), 2, 2 },
+        { irs::ref_cast<irs::byte_type>("\xD0\xBF\xD1\x83\xD0\xB9\xD0\xBD\xD1\x8F"_sr), 3, 3 },
+      }
+    );
   }
 }
 
@@ -416,6 +850,17 @@ TEST(levenshtein_utils_test, test_description_3) {
       }
     );
 
+    assert_description(
+      description,
+      irs::ref_cast<irs::byte_type>("\xD1\x85\xD1\x83\xD0\xB9"_sr),
+      {
+        { irs::ref_cast<irs::byte_type>("\xD1\x85\xD1\x83\xD0\xB9"_sr), 0, 0 },
+        { irs::ref_cast<irs::byte_type>("\xD0\xBF\xD1\x83\xD0\xB9"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xD1\x85\xD1\x83\xD0\xB9\xD0\xBD\xD1\x8F"_sr), 2, 2 },
+        { irs::ref_cast<irs::byte_type>("\xD0\xBF\xD1\x83\xD0\xB9\xD0\xBD\xD1\x8F"_sr), 3, 3 },
+      }
+    );
+
     // "aec" vs "abc"
     ASSERT_EQ(1, irs::edit_distance(description, irs::ref_cast<irs::byte_type>("aec"_sr), irs::ref_cast<irs::byte_type>("abc"_sr)));
     ASSERT_EQ(1, irs::edit_distance(description, irs::ref_cast<irs::byte_type>("abc"_sr), irs::ref_cast<irs::byte_type>("aec"_sr)));
@@ -463,6 +908,17 @@ TEST(levenshtein_utils_test, test_description_3) {
         { irs::ref_cast<irs::byte_type>("lpzazez"_sr),   4, 4 },
       }
     );
+
+    assert_description(
+      description,
+      irs::ref_cast<irs::byte_type>("\xD1\x85\xD1\x83\xD0\xB9"_sr),
+      {
+        { irs::ref_cast<irs::byte_type>("\xD1\x85\xD1\x83\xD0\xB9"_sr), 0, 0 },
+        { irs::ref_cast<irs::byte_type>("\xD0\xBF\xD1\x83\xD0\xB9"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xD1\x85\xD1\x83\xD0\xB9\xD0\xBD\xD1\x8F"_sr), 2, 2 },
+        { irs::ref_cast<irs::byte_type>("\xD0\xBF\xD1\x83\xD0\xB9\xD0\xBD\xD1\x8F"_sr), 3, 3 },
+      }
+    );
   }
 }
 
@@ -497,6 +953,17 @@ TEST(levenshtein_utils_test, test_description_4) {
         { irs::ref_cast<irs::byte_type>("hzez"_sr),      5, 6 },
       }
     );
+
+    assert_description(
+      description,
+      irs::ref_cast<irs::byte_type>("\xD1\x85\xD1\x83\xD0\xB9"_sr),
+      {
+        { irs::ref_cast<irs::byte_type>("\xD1\x85\xD1\x83\xD0\xB9"_sr), 0, 0 },
+        { irs::ref_cast<irs::byte_type>("\xD0\xBF\xD1\x83\xD0\xB9"_sr), 1, 1 },
+        { irs::ref_cast<irs::byte_type>("\xD1\x85\xD1\x83\xD0\xB9\xD0\xBD\xD1\x8F"_sr), 2, 2 },
+        { irs::ref_cast<irs::byte_type>("\xD0\xBF\xD1\x83\xD0\xB9\xD0\xBD\xD1\x8F"_sr), 3, 3 },
+      }
+    );
   }
 
 // Commented out since it takes ~10 min to pass
diff --git a/3rdParty/iresearch/tests/utils/ngram_match_utils_tests.cpp b/3rdParty/iresearch/tests/utils/ngram_match_utils_tests.cpp
new file mode 100644
index 000000000000..8af4604773bc
--- /dev/null
+++ b/3rdParty/iresearch/tests/utils/ngram_match_utils_tests.cpp
@@ -0,0 +1,259 @@
+////////////////////////////////////////////////////////////////////////////////
+/// DISCLAIMER
+///
+/// Copyright 2020 ArangoDB GmbH, Cologne, Germany
+///
+/// Licensed under the Apache License, Version 2.0 (the "License");
+/// you may not use this file except in compliance with the License.
+/// You may obtain a copy of the License at
+///
+///     http://www.apache.org/licenses/LICENSE-2.0
+///
+/// Unless required by applicable law or agreed to in writing, software
+/// distributed under the License is distributed on an "AS IS" BASIS,
+/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+/// See the License for the specific language governing permissions and
+/// limitations under the License.
+///
+/// Copyright holder is ArangoDB GmbH, Cologne, Germany
+///
+/// @author Andrei Lobov
+////////////////////////////////////////////////////////////////////////////////
+
+#include "tests_shared.hpp"
+#include "utils/ngram_match_utils.hpp"
+
+
+TEST(ngram_match_utils_test, test_similarity_empty_left) {
+  const irs::string_ref lhs = "";
+  const irs::string_ref rhs = "abcd";
+
+  ASSERT_DOUBLE_EQ(0, (irs::ngram_similarity<char, false>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 0)));
+  ASSERT_DOUBLE_EQ(0, (irs::ngram_similarity<char, false>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 1)));
+  ASSERT_DOUBLE_EQ(0, (irs::ngram_similarity<char, false>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 2)));
+  ASSERT_DOUBLE_EQ(0, (irs::ngram_similarity<char, false>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 3)));
+  ASSERT_DOUBLE_EQ(0, (irs::ngram_similarity<char, false>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 4)));
+  ASSERT_DOUBLE_EQ(0, (irs::ngram_similarity<char, false>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 5)));
+
+  ASSERT_DOUBLE_EQ(0, (irs::ngram_similarity<char, true>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 0)));
+  ASSERT_DOUBLE_EQ(0, (irs::ngram_similarity<char, true>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 1)));
+  ASSERT_DOUBLE_EQ(0, (irs::ngram_similarity<char, true>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 2)));
+  ASSERT_DOUBLE_EQ(0, (irs::ngram_similarity<char, true>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 3)));
+  ASSERT_DOUBLE_EQ(0, (irs::ngram_similarity<char, true>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 4)));
+  ASSERT_DOUBLE_EQ(0, (irs::ngram_similarity<char, true>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 5)));
+}
+
+TEST(ngram_match_utils_test, test_similarity_empty_right) {
+  const irs::string_ref lhs = "abcd";
+  const irs::string_ref rhs = "";
+
+  ASSERT_DOUBLE_EQ(0, (irs::ngram_similarity<char, false>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 0)));
+  ASSERT_DOUBLE_EQ(0, (irs::ngram_similarity<char, false>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 1)));
+  ASSERT_DOUBLE_EQ(0, (irs::ngram_similarity<char, false>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 2)));
+  ASSERT_DOUBLE_EQ(0, (irs::ngram_similarity<char, false>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 3)));
+  ASSERT_DOUBLE_EQ(0, (irs::ngram_similarity<char, false>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 4)));
+  ASSERT_DOUBLE_EQ(0, (irs::ngram_similarity<char, false>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 5)));
+
+  ASSERT_DOUBLE_EQ(0, (irs::ngram_similarity<char, true>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 0)));
+  ASSERT_DOUBLE_EQ(0, (irs::ngram_similarity<char, true>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 1)));
+  ASSERT_DOUBLE_EQ(0, (irs::ngram_similarity<char, true>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 2)));
+  ASSERT_DOUBLE_EQ(0, (irs::ngram_similarity<char, true>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 3)));
+  ASSERT_DOUBLE_EQ(0, (irs::ngram_similarity<char, true>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 4)));
+  ASSERT_DOUBLE_EQ(0, (irs::ngram_similarity<char, true>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 5)));
+}
+
+TEST(ngram_match_utils_test, test_similarity_no_match) {
+  const irs::string_ref lhs = "abcd";
+  const irs::string_ref rhs = "efgh";
+  ASSERT_DOUBLE_EQ(0, (irs::ngram_similarity<char, true>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 0)));
+  ASSERT_DOUBLE_EQ(0, (irs::ngram_similarity<char, true>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 1)));
+  ASSERT_DOUBLE_EQ(0, (irs::ngram_similarity<char, true>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 2)));
+  ASSERT_DOUBLE_EQ(0, (irs::ngram_similarity<char, true>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 3)));
+  ASSERT_DOUBLE_EQ(0, (irs::ngram_similarity<char, true>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 4)));
+  ASSERT_DOUBLE_EQ(0, (irs::ngram_similarity<char, true>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 5)));
+
+  ASSERT_DOUBLE_EQ(0, (irs::ngram_similarity<char, false>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 0)));
+  ASSERT_DOUBLE_EQ(0, (irs::ngram_similarity<char, false>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 1)));
+  ASSERT_DOUBLE_EQ(0, (irs::ngram_similarity<char, false>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 2)));
+  ASSERT_DOUBLE_EQ(0, (irs::ngram_similarity<char, false>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 3)));
+  ASSERT_DOUBLE_EQ(0, (irs::ngram_similarity<char, false>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 4)));
+  ASSERT_DOUBLE_EQ(0, (irs::ngram_similarity<char, false>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 5)));
+}
+
+TEST(ngram_match_utils_test, test_similarity_simple) {
+  const irs::string_ref lhs = "aecd";
+  const irs::string_ref rhs = "abcd";
+
+  ASSERT_DOUBLE_EQ(0.75f, (irs::ngram_similarity<char, false>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 1)));
+  ASSERT_DOUBLE_EQ(0.75f, (irs::ngram_similarity<char, false>(rhs.begin(), rhs.size(), lhs.begin(), lhs.size(), 1)));
+  ASSERT_DOUBLE_EQ(0.75f, (irs::ngram_similarity<char, true>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 1)));
+  ASSERT_DOUBLE_EQ(0.75f, (irs::ngram_similarity<char, true>(rhs.begin(), rhs.size(), lhs.begin(), lhs.size(), 1)));
+
+  ASSERT_DOUBLE_EQ(2.f/3.f, (irs::ngram_similarity<char, false>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 2)));
+  ASSERT_DOUBLE_EQ(2.f/3.f, (irs::ngram_similarity<char, false>(rhs.begin(), rhs.size(), lhs.begin(), lhs.size(), 2)));
+  ASSERT_DOUBLE_EQ(1.f/3.f, (irs::ngram_similarity<char, true>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 2)));
+  ASSERT_DOUBLE_EQ(1.f/3.f, (irs::ngram_similarity<char, true>(rhs.begin(), rhs.size(), lhs.begin(), lhs.size(), 2)));
+
+  ASSERT_DOUBLE_EQ(2.f/3.f, (irs::ngram_similarity<char, false>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 3)));
+  ASSERT_DOUBLE_EQ(2.f/3.f, (irs::ngram_similarity<char, false>(rhs.begin(), rhs.size(), lhs.begin(), lhs.size(), 3)));
+  ASSERT_DOUBLE_EQ(0, (irs::ngram_similarity<char, true>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 3)));
+  ASSERT_DOUBLE_EQ(0, (irs::ngram_similarity<char, true>(rhs.begin(), rhs.size(), lhs.begin(), lhs.size(), 3)));
+
+  ASSERT_DOUBLE_EQ(3.f/4.f, (irs::ngram_similarity<char, false>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 4)));
+  ASSERT_DOUBLE_EQ(3.f/4.f, (irs::ngram_similarity<char, false>(rhs.begin(), rhs.size(), lhs.begin(), lhs.size(), 4)));
+  ASSERT_DOUBLE_EQ(0, (irs::ngram_similarity<char, true>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 4)));
+  ASSERT_DOUBLE_EQ(0, (irs::ngram_similarity<char, true>(rhs.begin(), rhs.size(), lhs.begin(), lhs.size(), 4)));
+}
+
+TEST(ngram_match_utils_test, test_similarity_different_length) {
+  const irs::string_ref lhs = "applejuice";
+  const irs::string_ref rhs = "aplejuice";
+  ASSERT_DOUBLE_EQ(0.9f, (irs::ngram_similarity<char, false>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 1)));
+  ASSERT_DOUBLE_EQ(0.9f, (irs::ngram_similarity<char, false>(rhs.begin(), rhs.size(), lhs.begin(), lhs.size(), 1)));
+  ASSERT_DOUBLE_EQ(0.9f, (irs::ngram_similarity<char, true>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 1)));
+  ASSERT_DOUBLE_EQ(1, (irs::ngram_similarity<char, true>(rhs.begin(), rhs.size(), lhs.begin(), lhs.size(), 1)));
+
+  ASSERT_DOUBLE_EQ(8.f/9.f, (irs::ngram_similarity<char, false>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 2)));
+  ASSERT_DOUBLE_EQ(8.f/9.f, (irs::ngram_similarity<char, false>(rhs.begin(), rhs.size(), lhs.begin(), lhs.size(), 2)));
+  ASSERT_DOUBLE_EQ(8.f/9.f, (irs::ngram_similarity<char, true>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 2)));
+  ASSERT_DOUBLE_EQ(1, (irs::ngram_similarity<char, true>(rhs.begin(), rhs.size(), lhs.begin(), lhs.size(), 2)));
+
+  ASSERT_DOUBLE_EQ((2.f/3.f + 1.f + 1.f + 1.f + 1.f + 1.f + 1.f)/8.f,
+                   (irs::ngram_similarity<char, false>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 3)));
+  ASSERT_DOUBLE_EQ((2.f/3.f + 1.f + 1.f + 1.f + 1.f + 1.f + 1.f)/8.f,
+                   (irs::ngram_similarity<char, false>(rhs.begin(), rhs.size(), lhs.begin(), lhs.size(), 3)));
+  ASSERT_DOUBLE_EQ(0.75f, (irs::ngram_similarity<char, true>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 3)));
+  ASSERT_DOUBLE_EQ(6.f/7.f, (irs::ngram_similarity<char, true>(rhs.begin(), rhs.size(), lhs.begin(), lhs.size(), 3)));
+
+  ASSERT_DOUBLE_EQ(5.75f/7.f, (irs::ngram_similarity<char, false>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 4)));
+  ASSERT_DOUBLE_EQ(5.75f/7.f, (irs::ngram_similarity<char, false>(rhs.begin(), rhs.size(), lhs.begin(), lhs.size(), 4)));
+  ASSERT_DOUBLE_EQ(5.f/7.f, (irs::ngram_similarity<char, true>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 4)));
+  ASSERT_DOUBLE_EQ(5.f/6.f, (irs::ngram_similarity<char, true>(rhs.begin(), rhs.size(), lhs.begin(), lhs.size(), 4)));
+
+  ASSERT_DOUBLE_EQ(4.8f/6.f, (irs::ngram_similarity<char, false>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 5)));
+  ASSERT_DOUBLE_EQ(4.8f/6.f, (irs::ngram_similarity<char, false>(rhs.begin(), rhs.size(), lhs.begin(), lhs.size(), 5)));
+  ASSERT_DOUBLE_EQ(4.f/6.f, (irs::ngram_similarity<char, true>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 5)));
+  ASSERT_DOUBLE_EQ(4.f/5.f, (irs::ngram_similarity<char, true>(rhs.begin(), rhs.size(), lhs.begin(), lhs.size(), 5)));
+
+  ASSERT_DOUBLE_EQ((8.f/9.f)/2.f, (irs::ngram_similarity<char, false>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 9)));
+  ASSERT_DOUBLE_EQ((8.f/9.f)/2.f, (irs::ngram_similarity<char, false>(rhs.begin(), rhs.size(), lhs.begin(), lhs.size(), 9)));
+  ASSERT_DOUBLE_EQ(0, (irs::ngram_similarity<char, true>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 9)));
+  ASSERT_DOUBLE_EQ(0, (irs::ngram_similarity<char, true>(rhs.begin(), rhs.size(), lhs.begin(), lhs.size(), 9)));
+}
+
+TEST(ngram_match_utils_test, test_similarity_with_gaps) {
+  const irs::string_ref lhs = "apple1234juice";
+  const irs::string_ref rhs = "aple567juice";
+
+  ASSERT_DOUBLE_EQ(9.f/14.f, (irs::ngram_similarity<char, false>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 1)));
+  ASSERT_DOUBLE_EQ(9.f/14.f, (irs::ngram_similarity<char, false>(rhs.begin(), rhs.size(), lhs.begin(), lhs.size(), 1)));
+  ASSERT_DOUBLE_EQ(9.f/14.f, (irs::ngram_similarity<char, true>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 1)));
+  ASSERT_DOUBLE_EQ(9.f/12.f, (irs::ngram_similarity<char, true>(rhs.begin(), rhs.size(), lhs.begin(), lhs.size(), 1)));
+
+  ASSERT_DOUBLE_EQ(8.f/13.f, (irs::ngram_similarity<char, false>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 2)));
+  ASSERT_DOUBLE_EQ(8.f/13.f, (irs::ngram_similarity<char, false>(rhs.begin(), rhs.size(), lhs.begin(), lhs.size(), 2)));
+  ASSERT_DOUBLE_EQ(7.f/13.f, (irs::ngram_similarity<char, true>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 2)));
+  ASSERT_DOUBLE_EQ(7.f/11.f, (irs::ngram_similarity<char, true>(rhs.begin(), rhs.size(), lhs.begin(), lhs.size(), 2)));
+
+  ASSERT_DOUBLE_EQ((2.f/3.f + 1 + 2.f/3.f + 1.f/3.f + 2.f/3.f + 1.f/3.f + 3.f)/12.f,
+      (irs::ngram_similarity<char, false>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 3)));
+  ASSERT_DOUBLE_EQ((2.f/3.f + 1 + 2.f/3.f + 1.f/3.f + 2.f/3.f + 1.f/3.f + 3.f)/12.f,
+      (irs::ngram_similarity<char, false>(rhs.begin(), rhs.size(), lhs.begin(), lhs.size(), 3)));
+  ASSERT_DOUBLE_EQ(4.f/12.f, (irs::ngram_similarity<char, true>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 3)));
+  ASSERT_DOUBLE_EQ(4.f/10.f, (irs::ngram_similarity<char, true>(rhs.begin(), rhs.size(), lhs.begin(), lhs.size(), 3)));
+
+  ASSERT_DOUBLE_EQ((0.75f + 0.75f + 0.5f + 0.25f + 0.25f + 0.5f + 0.75f + 2)/11.f,
+      (irs::ngram_similarity<char, false>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 4)));
+  ASSERT_DOUBLE_EQ((0.75f + 0.75f + 0.5f + 0.25f + 0.25f + 0.5f + 0.75f + 2)/11.f,
+      (irs::ngram_similarity<char, false>(rhs.begin(), rhs.size(), lhs.begin(), lhs.size(), 4)));
+  ASSERT_DOUBLE_EQ(2.f/11.f, (irs::ngram_similarity<char, true>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 4)));
+  ASSERT_DOUBLE_EQ(2.f/9.f, (irs::ngram_similarity<char, true>(rhs.begin(), rhs.size(), lhs.begin(), lhs.size(), 4)));
+
+  ASSERT_DOUBLE_EQ((3.f/5.f + 3.f/5.f + 2.f/5.f + 1.f/5.f + 2.f/5.f + 3.f/5.f + 4.f/5.f + 1)/10.f,
+      (irs::ngram_similarity<char, false>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 5)));
+  ASSERT_DOUBLE_EQ((3.f/5.f + 3.f/5.f + 2.f/5.f + 1.f/5.f + 2.f/5.f + 3.f/5.f + 4.f/5.f + 1)/10.f,
+      (irs::ngram_similarity<char, false>(rhs.begin(), rhs.size(), lhs.begin(), lhs.size(), 5)));
+  ASSERT_DOUBLE_EQ(1.f/10.f, (irs::ngram_similarity<char, true>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 5)));
+  ASSERT_DOUBLE_EQ(1.f/8.f, (irs::ngram_similarity<char, true>(rhs.begin(), rhs.size(), lhs.begin(), lhs.size(), 5)));
+
+  ASSERT_DOUBLE_EQ((1.f + 4.f/6.f + 0.5f + 4.f/6.f + 5.f/6.f) / 9.f,
+                   (irs::ngram_similarity<char, false>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 6)));
+  ASSERT_DOUBLE_EQ((1.f + 4.f/6.f + 0.5f + 4.f/6.f + 5.f/6.f) / 9.f,
+                   (irs::ngram_similarity<char, false>(rhs.begin(), rhs.size(), lhs.begin(), lhs.size(), 6)));
+  ASSERT_DOUBLE_EQ(0, (irs::ngram_similarity<char, true>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 6)));
+  ASSERT_DOUBLE_EQ(0, (irs::ngram_similarity<char, true>(rhs.begin(), rhs.size(), lhs.begin(), lhs.size(), 6)));
+}
+
+TEST(ngram_match_utils_test, test_similarity) {
+  { // bin and pos similarity shows different results as first ngram has 0.5 pos match but 0 bin match
+    const irs::string_ref lhs = "abba";
+    const irs::string_ref rhs = "apba";
+
+    ASSERT_DOUBLE_EQ(2.f / 3.f, (irs::ngram_similarity<char, false>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 2)));
+    ASSERT_DOUBLE_EQ(2.f / 3.f, (irs::ngram_similarity<char, false>(rhs.begin(), rhs.size(), lhs.begin(), lhs.size(), 2)));
+    ASSERT_DOUBLE_EQ(1.f / 3.f, (irs::ngram_similarity<char, true>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 2)));
+    ASSERT_DOUBLE_EQ(1.f / 3.f, (irs::ngram_similarity<char, true>(rhs.begin(), rhs.size(), lhs.begin(), lhs.size(), 2)));
+  }
+  { // first 2-gram has 0.5 sim but second one is 1 (and is chosen by pos) so bin and pos similarity works the same
+    // result is different for bin similarity only due to abscence of length normalization
+    const irs::string_ref lhs = "11234561";
+    const irs::string_ref rhs = "1234561";
+
+    ASSERT_DOUBLE_EQ(6.f / 7.f, (irs::ngram_similarity<char, false>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 2)));
+    ASSERT_DOUBLE_EQ(6.f / 7.f, (irs::ngram_similarity<char, false>(rhs.begin(), rhs.size(), lhs.begin(), lhs.size(), 2)));
+    ASSERT_DOUBLE_EQ(6.f / 7.f, (irs::ngram_similarity<char, true>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 2)));
+    ASSERT_DOUBLE_EQ(1, (irs::ngram_similarity<char, true>(rhs.begin(), rhs.size(), lhs.begin(), lhs.size(), 2)));
+  }
+}
+
+TEST(ngram_match_utils_test, test_similarity_shorter) {
+  {
+    // strings are shorter than ngram length.
+    const irs::string_ref lhs = "abb";
+    const irs::string_ref rhs = "abpa";
+
+    // for "positional" semantics this will force to find best matched ngram
+    ASSERT_DOUBLE_EQ(0.5f, (irs::ngram_similarity<char, false>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 5)));
+    ASSERT_DOUBLE_EQ(0.5f, (irs::ngram_similarity<char, false>(rhs.begin(), rhs.size(), lhs.begin(), lhs.size(), 5)));
+    // for "search" semantics this is 0 as there will be no binary matching ngrams found in index
+    ASSERT_DOUBLE_EQ(0, (irs::ngram_similarity<char, true>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 5)));
+    ASSERT_DOUBLE_EQ(0, (irs::ngram_similarity<char, true>(rhs.begin(), rhs.size(), lhs.begin(), lhs.size(), 5)));
+  }
+  {
+    // strings are shorter than ngram length.
+    const irs::string_ref lhs = "abb";
+    const irs::string_ref rhs = "abb";
+
+    // for "positional" semantics this will force to find best matched ngram
+    ASSERT_DOUBLE_EQ(1, (irs::ngram_similarity<char, false>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 5)));
+    ASSERT_DOUBLE_EQ(1, (irs::ngram_similarity<char, false>(rhs.begin(), rhs.size(), lhs.begin(), lhs.size(), 5)));
+    // for "search" semantics this is 1 as there is binary match of shorter string
+    ASSERT_DOUBLE_EQ(1, (irs::ngram_similarity<char, true>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 5)));
+    ASSERT_DOUBLE_EQ(1, (irs::ngram_similarity<char, true>(rhs.begin(), rhs.size(), lhs.begin(), lhs.size(), 5)));
+  }
+  {
+    // strings are shorter than ngram length.
+    const irs::string_ref lhs = "abb";
+    const irs::string_ref rhs = "abc";
+
+    // for "positional" semantics this will force to find best matched ngram
+    ASSERT_DOUBLE_EQ(2.f/3.f, (irs::ngram_similarity<char, false>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 5)));
+    ASSERT_DOUBLE_EQ(2.f/3.f, (irs::ngram_similarity<char, false>(rhs.begin(), rhs.size(), lhs.begin(), lhs.size(), 5)));
+    // for "search" semantics this is 0 as there no binary match of shorter string
+    ASSERT_DOUBLE_EQ(0, (irs::ngram_similarity<char, true>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 5)));
+    ASSERT_DOUBLE_EQ(0, (irs::ngram_similarity<char, true>(rhs.begin(), rhs.size(), lhs.begin(), lhs.size(), 5)));
+  }
+}
+
+TEST(ngram_match_utils_test, test_similarity_all_empty) {
+  // strings are shorter than ngram length.
+  const irs::string_ref lhs = "";
+  const irs::string_ref rhs = "";
+
+  // for "positional" semantics this will mean full similarity
+  ASSERT_DOUBLE_EQ(1, (irs::ngram_similarity<char, false>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 5)));
+  ASSERT_DOUBLE_EQ(1, (irs::ngram_similarity<char, false>(rhs.begin(), rhs.size(), lhs.begin(), lhs.size(), 5)));
+  // for "search" semantics this is 1 as binary strings match
+  ASSERT_DOUBLE_EQ(1, (irs::ngram_similarity<char, true>(lhs.begin(), lhs.size(), rhs.begin(), rhs.size(), 5)));
+  ASSERT_DOUBLE_EQ(1, (irs::ngram_similarity<char, true>(rhs.begin(), rhs.size(), lhs.begin(), lhs.size(), 5)));
+}
diff --git a/3rdParty/iresearch/tests/utils/string_tests.cpp b/3rdParty/iresearch/tests/utils/string_tests.cpp
index d0c4204859f4..09412e7f8edb 100644
--- a/3rdParty/iresearch/tests/utils/string_tests.cpp
+++ b/3rdParty/iresearch/tests/utils/string_tests.cpp
@@ -184,6 +184,78 @@ TEST(string_ref_tests, compare) {
   }
 }
 
+TEST(string_ref_tests, common_prefix) {
+  using namespace iresearch;
+
+  {
+    const string_ref lhs = "20-MAR-2012 19:56:11.00";
+    const string_ref rhs = "20-MAR-2012 19:56:11.00\0\0";
+    EXPECT_EQ(23, common_prefix_length(lhs, rhs));
+    EXPECT_EQ(23, common_prefix_length(rhs, lhs));
+  }
+
+  {
+    const string_ref lhs = "quick brown fox";
+    const string_ref rhs = "quick brown fax";
+    EXPECT_EQ(13, common_prefix_length(lhs, rhs));
+    EXPECT_EQ(13, common_prefix_length(rhs, lhs));
+  }
+
+  {
+    const string_ref lhs = "quick brown foxies";
+    const string_ref rhs = "quick brown fax";
+    EXPECT_EQ(13, common_prefix_length(lhs, rhs));
+    EXPECT_EQ(13, common_prefix_length(rhs, lhs));
+  }
+
+  {
+    const string_ref lhs = "quick brown foxies";
+    const string_ref rhs = "fuick brown fax";
+    EXPECT_EQ(0, common_prefix_length(lhs, rhs));
+    EXPECT_EQ(0, common_prefix_length(rhs, lhs));
+  }
+
+  {
+    const string_ref lhs = "quick brown foxies";
+    const string_ref rhs = "q1ick brown fax";
+    EXPECT_EQ(1, common_prefix_length(lhs, rhs));
+    EXPECT_EQ(1, common_prefix_length(rhs, lhs));
+  }
+
+  {
+    const string_ref lhs = "qui";
+    const string_ref rhs = "q1";
+    EXPECT_EQ(1, common_prefix_length(lhs, rhs));
+    EXPECT_EQ(1, common_prefix_length(rhs, lhs));
+  }
+
+  {
+    const string_ref lhs = "qui";
+    const string_ref rhs = "f1";
+    EXPECT_EQ(0, common_prefix_length(lhs, rhs));
+    EXPECT_EQ(0, common_prefix_length(rhs, lhs));
+  }
+
+  {
+    const string_ref lhs = "quick brown foxies";
+    const string_ref rhs = "qui";
+    EXPECT_EQ(3, common_prefix_length(lhs, rhs));
+    EXPECT_EQ(3, common_prefix_length(rhs, lhs));
+  }
+
+  {
+    const string_ref str = "quick brown foxies";
+    EXPECT_EQ(0, common_prefix_length(string_ref::NIL, str));
+    EXPECT_EQ(0, common_prefix_length(str, string_ref::NIL));
+  }
+
+  {
+    const string_ref str = "quick brown foxies";
+    EXPECT_EQ(0, common_prefix_length(string_ref::EMPTY, str));
+    EXPECT_EQ(0, common_prefix_length(str, string_ref::EMPTY));
+  }
+}
+
 TEST(string_ref_tests, starts_with) {
   using namespace iresearch;
 
diff --git a/3rdParty/iresearch/tests/utils/utf8_utils_test.cpp b/3rdParty/iresearch/tests/utils/utf8_utils_test.cpp
index 5292e6cd74ee..a299c86d6c52 100644
--- a/3rdParty/iresearch/tests/utils/utf8_utils_test.cpp
+++ b/3rdParty/iresearch/tests/utils/utf8_utils_test.cpp
@@ -25,22 +25,33 @@
 #include "utils/std.hpp"
 #include "utils/utf8_utils.hpp"
 
-TEST(utf8_utils_test, next) {
+TEST(utf8_utils_test, static_const) {
+  ASSERT_EQ(4, size_t(irs::utf8_utils::MAX_CODE_POINT_SIZE));
+  ASSERT_EQ(0, size_t(irs::utf8_utils::MIN_CODE_POINT));
+  ASSERT_EQ(0x10FFFF, size_t(irs::utf8_utils::MAX_CODE_POINT));
+}
+
+TEST(utf8_utils_test, test) {
   // ascii sequence
   {
-    const irs::byte_type invalid = 0;
     const irs::bytes_ref str = irs::ref_cast<irs::byte_type>(irs::string_ref("abcd"));
     const std::vector<uint32_t> expected = { 0x0061, 0x0062, 0x0063, 0x0064 };
 
     {
       auto expected_begin = expected.begin();
-      for (auto begin = str.begin(); begin != str.end(); ) {
-        auto next = irs::utf8_utils::next(begin, &invalid);
-        ASSERT_NE(&invalid, next);
+      auto begin = str.begin();
+      auto end = str.end();
+      for (; begin != str.end(); ) {
+        auto next = irs::utf8_utils::next(begin, end);
         ASSERT_EQ(1, std::distance(begin, next));
         ASSERT_EQ(*expected_begin, irs::utf8_utils::next(begin));
         ASSERT_EQ(begin, next);
         ++expected_begin;
+        if (expected_begin == expected.end()) {
+          ASSERT_EQ(end, next);
+        } else {
+          ASSERT_NE(end, next);
+        }
       }
       ASSERT_EQ(expected.end(), expected_begin);
     }
@@ -53,28 +64,48 @@ TEST(utf8_utils_test, next) {
       ASSERT_EQ(expected.end(), expected_begin);
     }
 
+    {
+      auto expected_begin = expected.begin();
+      for (auto begin = str.begin(), end = str.end(); begin != end; ++expected_begin) {
+        const auto cp = irs::utf8_utils::next_checked(begin, end);
+        ASSERT_EQ(*expected_begin, cp);
+      }
+      ASSERT_EQ(expected.end(), expected_begin);
+    }
+
     {
       std::vector<uint32_t> actual;
-      irs::utf8_utils::to_utf8(str, irs::irstd::back_emplacer(actual));
+      irs::utf8_utils::utf8_to_utf32<false>(str, irs::irstd::back_emplacer(actual));
+      ASSERT_EQ(expected, actual);
+    }
+
+    {
+      std::vector<uint32_t> actual;
+      ASSERT_TRUE(irs::utf8_utils::utf8_to_utf32<true>(str, irs::irstd::back_emplacer(actual)));
       ASSERT_EQ(expected, actual);
     }
   }
 
   // 2-bytes sequence
   {
-    const irs::byte_type invalid = 0;
     const irs::bytes_ref str = irs::ref_cast<irs::byte_type>(irs::string_ref("\xD0\xBF\xD1\x80\xD0\xB8\xD0\xB2\xD0\xB5\xD1\x82"));
     const std::vector<uint32_t> expected = { 0x043F, 0x0440, 0x0438, 0x0432, 0x0435, 0x0442};
 
     {
       auto expected_begin = expected.begin();
-      for (auto begin = str.begin(); begin != str.end(); ) {
-        auto next = irs::utf8_utils::next(begin, &invalid);
-        ASSERT_NE(&invalid, next);
+      auto begin = str.begin();
+      auto end = str.end();
+      for (; begin != str.end(); ) {
+        auto next = irs::utf8_utils::next(begin, end);
         ASSERT_EQ(2, std::distance(begin, next));
         ASSERT_EQ(*expected_begin, irs::utf8_utils::next(begin));
         ASSERT_EQ(begin, next);
         ++expected_begin;
+        if (expected_begin == expected.end()) {
+          ASSERT_EQ(end, next);
+        } else {
+          ASSERT_NE(end, next);
+        }
       }
       ASSERT_EQ(expected.end(), expected_begin);
     }
@@ -87,16 +118,44 @@ TEST(utf8_utils_test, next) {
       ASSERT_EQ(expected.end(), expected_begin);
     }
 
+    {
+      auto expected_begin = expected.begin();
+      for (auto begin = str.begin(), end = str.end(); begin != end; ++expected_begin) {
+        const auto cp = irs::utf8_utils::next_checked(begin, end);
+        ASSERT_EQ(*expected_begin, cp);
+      }
+      ASSERT_EQ(expected.end(), expected_begin);
+    }
+
     {
       std::vector<uint32_t> actual;
-      irs::utf8_utils::to_utf8(str, irs::irstd::back_emplacer(actual));
+      irs::utf8_utils::utf8_to_utf32<false>(str, irs::irstd::back_emplacer(actual));
       ASSERT_EQ(expected, actual);
     }
+
+    {
+      std::vector<uint32_t> actual;
+      ASSERT_TRUE(irs::utf8_utils::utf8_to_utf32<true>(str, irs::irstd::back_emplacer(actual)));
+      ASSERT_EQ(expected, actual);
+    }
+
+    {
+      size_t i = 0;
+      auto begin = str.begin();
+      for (auto expected_value : expected) {
+        ASSERT_EQ(i, irs::utf8_utils::find(str.begin(), str.size(), expected_value));
+        ASSERT_EQ(begin, irs::utf8_utils::find(str.begin(), str.end(), expected_value));
+        irs::utf8_utils::next(begin);
+        ++i;
+      }
+
+      ASSERT_EQ(irs::bstring::npos, irs::utf8_utils::find(str.begin(), str.size(), 0x80));
+      ASSERT_EQ(str.end(), irs::utf8_utils::find(str.begin(), str.end(), 0x80));
+    }
   }
 
   // 3-bytes sequence
   {
-    const irs::byte_type invalid = 0;
     const irs::bytes_ref str = irs::ref_cast<irs::byte_type>(irs::string_ref("\xE2\x9E\x96\xE2\x9D\xA4"));
     const std::vector<uint32_t> expected = {
       0x2796, // heavy minus sign
@@ -105,13 +164,19 @@ TEST(utf8_utils_test, next) {
 
     {
       auto expected_begin = expected.begin();
-      for (auto begin = str.begin(); begin != str.end(); ) {
-        auto next = irs::utf8_utils::next(begin, &invalid);
-        ASSERT_NE(&invalid, next);
+      auto begin = str.begin();
+      auto end = str.end();
+      for (; begin != str.end(); ) {
+        auto next = irs::utf8_utils::next(begin, end);
         ASSERT_EQ(3, std::distance(begin, next));
         ASSERT_EQ(*expected_begin, irs::utf8_utils::next(begin));
         ASSERT_EQ(begin, next);
         ++expected_begin;
+        if (expected_begin == expected.end()) {
+          ASSERT_EQ(end, next);
+        } else {
+          ASSERT_NE(end, next);
+        }
       }
       ASSERT_EQ(expected.end(), expected_begin);
     }
@@ -124,16 +189,30 @@ TEST(utf8_utils_test, next) {
       ASSERT_EQ(expected.end(), expected_begin);
     }
 
+    {
+      auto expected_begin = expected.begin();
+      for (auto begin = str.begin(), end = str.end(); begin != end; ++expected_begin) {
+        const auto cp = irs::utf8_utils::next_checked(begin, end);
+        ASSERT_EQ(*expected_begin, cp);
+      }
+      ASSERT_EQ(expected.end(), expected_begin);
+    }
+
     {
       std::vector<uint32_t> actual;
-      irs::utf8_utils::to_utf8(str, irs::irstd::back_emplacer(actual));
+      irs::utf8_utils::utf8_to_utf32<false>(str, irs::irstd::back_emplacer(actual));
+      ASSERT_EQ(expected, actual);
+    }
+
+    {
+      std::vector<uint32_t> actual;
+      ASSERT_TRUE(irs::utf8_utils::utf8_to_utf32<true>(str, irs::irstd::back_emplacer(actual)));
       ASSERT_EQ(expected, actual);
     }
   }
 
   // 4-bytes sequence
   {
-    const irs::byte_type invalid = 0;
     const irs::bytes_ref str = irs::ref_cast<irs::byte_type>(irs::string_ref("\xF0\x9F\x98\x81\xF0\x9F\x98\x82"));
     const std::vector<uint32_t> expected = {
       0x1F601, // grinning face with smiling eyes
@@ -142,13 +221,19 @@ TEST(utf8_utils_test, next) {
 
     {
       auto expected_begin = expected.begin();
-      for (auto begin = str.begin(); begin != str.end(); ) {
-        auto next = irs::utf8_utils::next(begin, &invalid);
-        ASSERT_NE(&invalid, next);
+      auto begin = str.begin();
+      auto end = str.end();
+      for (; begin != str.end(); ) {
+        auto next = irs::utf8_utils::next(begin, end);
         ASSERT_EQ(4, std::distance(begin, next));
         ASSERT_EQ(*expected_begin, irs::utf8_utils::next(begin));
         ASSERT_EQ(begin, next);
         ++expected_begin;
+        if (expected_begin == expected.end()) {
+          ASSERT_EQ(end, next);
+        } else {
+          ASSERT_NE(end, next);
+        }
       }
       ASSERT_EQ(expected.end(), expected_begin);
     }
@@ -161,10 +246,198 @@ TEST(utf8_utils_test, next) {
       ASSERT_EQ(expected.end(), expected_begin);
     }
 
+    {
+      auto expected_begin = expected.begin();
+      for (auto begin = str.begin(), end = str.end(); begin != end; ++expected_begin) {
+        const auto cp = irs::utf8_utils::next_checked(begin, end);
+        ASSERT_EQ(*expected_begin, cp);
+      }
+      ASSERT_EQ(expected.end(), expected_begin);
+    }
+
     {
       std::vector<uint32_t> actual;
-      irs::utf8_utils::to_utf8(str, irs::irstd::back_emplacer(actual));
+      irs::utf8_utils::utf8_to_utf32<false>(str, irs::irstd::back_emplacer(actual));
       ASSERT_EQ(expected, actual);
     }
+
+    {
+      std::vector<uint32_t> actual;
+      ASSERT_TRUE(irs::utf8_utils::utf8_to_utf32<true>(str, irs::irstd::back_emplacer(actual)));
+      ASSERT_EQ(expected, actual);
+    }
+  }
+}
+
+TEST(utf8_utils_test, find) {
+  // null sequence
+  {
+    const auto str = irs::bytes_ref::NIL;
+    ASSERT_EQ(irs::bstring::npos, irs::utf8_utils::find<true>(str.begin(), str.size(), 0x80));
+    ASSERT_EQ(irs::bstring::npos, irs::utf8_utils::find<false>(str.begin(), str.size(), 0x80));
+    ASSERT_EQ(str.end(), irs::utf8_utils::find<true>(str.begin(), str.end(), 0x81));
+    ASSERT_EQ(str.end(), irs::utf8_utils::find<false>(str.begin(), str.end(), 0x81));
+  }
+
+  // empty sequence
+  {
+    const auto str = irs::bytes_ref::EMPTY;
+    ASSERT_EQ(irs::bstring::npos, irs::utf8_utils::find<true>(str.begin(), str.size(), 0x80));
+    ASSERT_EQ(irs::bstring::npos, irs::utf8_utils::find<false>(str.begin(), str.size(), 0x80));
+    ASSERT_EQ(str.end(), irs::utf8_utils::find<true>(str.begin(), str.end(), 0x81));
+    ASSERT_EQ(str.end(), irs::utf8_utils::find<false>(str.begin(), str.end(), 0x81));
+  }
+
+  // 1-byte sequence
+  {
+    const irs::bytes_ref str = irs::ref_cast<irs::byte_type>(irs::string_ref("abcd"));
+    const std::vector<uint32_t> expected = { 0x0061, 0x0062, 0x0063, 0x0064 };
+
+    size_t i = 0;
+    auto begin = str.begin();
+    for (auto expected_value : expected) {
+      ASSERT_EQ(i, irs::utf8_utils::find<true>(str.begin(), str.size(), expected_value));
+      ASSERT_EQ(i, irs::utf8_utils::find<false>(str.begin(), str.size(), expected_value));
+      ASSERT_EQ(begin, irs::utf8_utils::find<true>(str.begin(), str.end(), expected_value));
+      ASSERT_EQ(begin, irs::utf8_utils::find<false>(str.begin(), str.end(), expected_value));
+      irs::utf8_utils::next(begin);
+      ++i;
+    }
+
+    ASSERT_EQ(irs::bstring::npos, irs::utf8_utils::find<true>(str.begin(), str.size(), 0x80));
+    ASSERT_EQ(irs::bstring::npos, irs::utf8_utils::find<false>(str.begin(), str.size(), 0x80));
+    ASSERT_EQ(str.end(), irs::utf8_utils::find<true>(str.begin(), str.end(), 0x81));
+    ASSERT_EQ(str.end(), irs::utf8_utils::find<false>(str.begin(), str.end(), 0x81));
+  }
+
+  // 2-byte sequence
+  {
+    const irs::bytes_ref str = irs::ref_cast<irs::byte_type>(irs::string_ref("\xD0\xBF\xD1\x80\xD0\xB8\xD0\xB2\xD0\xB5\xD1\x82"));
+    const std::vector<uint32_t> expected = { 0x043F, 0x0440, 0x0438, 0x0432, 0x0435, 0x0442};
+
+    size_t i = 0;
+    auto begin = str.begin();
+    for (auto expected_value : expected) {
+      ASSERT_EQ(i, irs::utf8_utils::find<true>(str.begin(), str.size(), expected_value));
+      ASSERT_EQ(i, irs::utf8_utils::find<false>(str.begin(), str.size(), expected_value));
+      ASSERT_EQ(begin, irs::utf8_utils::find<true>(str.begin(), str.end(), expected_value));
+      ASSERT_EQ(begin, irs::utf8_utils::find<false>(str.begin(), str.end(), expected_value));
+      irs::utf8_utils::next(begin);
+      ++i;
+    }
+
+    ASSERT_EQ(irs::bstring::npos, irs::utf8_utils::find<true>(str.begin(), str.size(), 0x80));
+    ASSERT_EQ(irs::bstring::npos, irs::utf8_utils::find<false>(str.begin(), str.size(), 0x80));
+    ASSERT_EQ(str.end(), irs::utf8_utils::find<true>(str.begin(), str.end(), 0x80));
+    ASSERT_EQ(str.end(), irs::utf8_utils::find<false>(str.begin(), str.end(), 0x81));
+  }
+
+  // 3-byte sequence
+  {
+    const irs::bytes_ref str = irs::ref_cast<irs::byte_type>(irs::string_ref("\xE2\x9E\x96\xE2\x9D\xA4"));
+    const std::vector<uint32_t> expected = {
+      0x2796, // heavy minus sign
+      0x2764  // heavy black heart
+    };
+
+    size_t i = 0;
+    auto begin = str.begin();
+    for (auto expected_value : expected) {
+      ASSERT_EQ(i, irs::utf8_utils::find<true>(str.begin(), str.size(), expected_value));
+      ASSERT_EQ(i, irs::utf8_utils::find<false>(str.begin(), str.size(), expected_value));
+      ASSERT_EQ(begin, irs::utf8_utils::find<true>(str.begin(), str.end(), expected_value));
+      ASSERT_EQ(begin, irs::utf8_utils::find<false>(str.begin(), str.end(), expected_value));
+      irs::utf8_utils::next(begin);
+      ++i;
+    }
+
+    ASSERT_EQ(irs::bstring::npos, irs::utf8_utils::find<true>(str.begin(), str.size(), 0x80));
+    ASSERT_EQ(irs::bstring::npos, irs::utf8_utils::find<false>(str.begin(), str.size(), 0x80));
+    ASSERT_EQ(str.end(), irs::utf8_utils::find<true>(str.begin(), str.end(), 0x80));
+    ASSERT_EQ(str.end(), irs::utf8_utils::find<false>(str.begin(), str.end(), 0x81));
+  }
+
+  // 4-byte sequence
+  {
+    const irs::bytes_ref str = irs::ref_cast<irs::byte_type>(irs::string_ref("\xF0\x9F\x98\x81\xF0\x9F\x98\x82"));
+    const std::vector<uint32_t> expected = {
+      0x1F601, // grinning face with smiling eyes
+      0x1F602, // face with tears of joy
+    };
+
+    size_t i = 0;
+    auto begin = str.begin();
+    for (auto expected_value : expected) {
+      ASSERT_EQ(i, irs::utf8_utils::find<true>(str.begin(), str.size(), expected_value));
+      ASSERT_EQ(i, irs::utf8_utils::find<false>(str.begin(), str.size(), expected_value));
+      ASSERT_EQ(begin, irs::utf8_utils::find<true>(str.begin(), str.end(), expected_value));
+      ASSERT_EQ(begin, irs::utf8_utils::find<false>(str.begin(), str.end(), expected_value));
+      irs::utf8_utils::next(begin);
+      ++i;
+    }
+
+    ASSERT_EQ(irs::bstring::npos, irs::utf8_utils::find<true>(str.begin(), str.size(), 0x80));
+    ASSERT_EQ(irs::bstring::npos, irs::utf8_utils::find<false>(str.begin(), str.size(), 0x80));
+    ASSERT_EQ(str.end(), irs::utf8_utils::find<true>(str.begin(), str.end(), 0x80));
+    ASSERT_EQ(str.end(), irs::utf8_utils::find<false>(str.begin(), str.end(), 0x81));
+  }
+
+  // invalid 4-byte sequence
+  {
+    const auto expected_value = 128512;
+    const irs::bytes_ref str = irs::ref_cast<irs::byte_type>(irs::string_ref("\xF0\x9F\x98\x0"));
+    ASSERT_EQ(irs::bstring::npos, irs::utf8_utils::find<true>(str.begin(), str.size(), expected_value));
+    ASSERT_EQ(0, irs::utf8_utils::find<false>(str.begin(), str.size(), expected_value));
+    ASSERT_EQ(str.end(), irs::utf8_utils::find<true>(str.begin(), str.end(), expected_value));
+    ASSERT_EQ(str.begin(), irs::utf8_utils::find<false>(str.begin(), str.end(), expected_value));
+  }
+}
+
+TEST(utf8_utils_test, cp_length) {
+  ASSERT_EQ(1, irs::utf8_utils::cp_length(80));
+  ASSERT_EQ(2, irs::utf8_utils::cp_length(192));
+  ASSERT_EQ(3, irs::utf8_utils::cp_length(224));
+  ASSERT_EQ(4, irs::utf8_utils::cp_length(244));
+
+  // invalid leading byte
+  ASSERT_EQ(0, irs::utf8_utils::cp_length(128));
+  ASSERT_EQ(0, irs::utf8_utils::cp_length(150));
+}
+
+TEST(utf8_utils_test, utf32_to_utf8) {
+  irs::byte_type buf[irs::utf8_utils::MAX_CODE_POINT_SIZE];
+
+  // 1 byte
+  {
+    const uint32_t cp = 0x46;
+    ASSERT_EQ(1, irs::utf8_utils::utf32_to_utf8(cp, buf));
+    ASSERT_EQ(buf[0], cp);
+  }
+
+  // 2 bytes
+  {
+    const uint32_t cp = 0xA9;
+    ASSERT_EQ(2, irs::utf8_utils::utf32_to_utf8(cp, buf));
+    ASSERT_EQ(buf[0], 0xC2);
+    ASSERT_EQ(buf[1], 0xA9);
+  }
+
+  // 3 bytes
+  {
+    const uint32_t cp = 0x08F1;
+    ASSERT_EQ(3, irs::utf8_utils::utf32_to_utf8(cp, buf));
+    ASSERT_EQ(buf[0], 0xE0);
+    ASSERT_EQ(buf[1], 0xA3);
+    ASSERT_EQ(buf[2], 0xB1);
+  }
+
+  // 4 bytes
+  {
+    const uint32_t cp = 0x1F996;
+    ASSERT_EQ(4, irs::utf8_utils::utf32_to_utf8(cp, buf));
+    ASSERT_EQ(buf[0], 0xF0);
+    ASSERT_EQ(buf[1], 0x9F);
+    ASSERT_EQ(buf[2], 0xA6);
+    ASSERT_EQ(buf[3], 0x96);
   }
 }
diff --git a/3rdParty/iresearch/tests/utils/wildcard_utils_test.cpp b/3rdParty/iresearch/tests/utils/wildcard_utils_test.cpp
new file mode 100644
index 000000000000..6692e8d356b0
--- /dev/null
+++ b/3rdParty/iresearch/tests/utils/wildcard_utils_test.cpp
@@ -0,0 +1,651 @@
+////////////////////////////////////////////////////////////////////////////////
+/// DISCLAIMER
+///
+/// Copyright 2020 ArangoDB GmbH, Cologne, Germany
+///
+/// Licensed under the Apache License, Version 2.0 (the "License");
+/// you may not use this file except in compliance with the License.
+/// You may obtain a copy of the License at
+///
+///     http://www.apache.org/licenses/LICENSE-2.0
+///
+/// Unless required by applicable law or agreed to in writing, software
+/// distributed under the License is distributed on an "AS IS" BASIS,
+/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+/// See the License for the specific language governing permissions and
+/// limitations under the License.
+///
+/// Copyright holder is ArangoDB GmbH, Cologne, Germany
+///
+/// @author Andrey Abramov
+////////////////////////////////////////////////////////////////////////////////
+
+#include "tests_shared.hpp"
+
+#include "utils/automaton_utils.hpp"
+#include "utils/wildcard_utils.hpp"
+
+// -----------------------------------------------------------------------------
+// --SECTION--                                           wildcard_automaton_test
+// -----------------------------------------------------------------------------
+
+class wildcard_utils_test : public test_base {
+ protected:
+  static void assert_properties(const irs::automaton& a) {
+    constexpr auto EXPECTED_PROPERTIES =
+      fst::kILabelSorted | fst::kOLabelSorted |
+      fst::kIDeterministic | fst::kODeterministic |
+      fst::kAcceptor | fst::kUnweighted;
+
+    ASSERT_EQ(EXPECTED_PROPERTIES, a.Properties(EXPECTED_PROPERTIES, true));
+  }
+};
+
+TEST_F(wildcard_utils_test, match_wildcard) {
+  // check automaton structure
+  {
+    auto lhs = irs::from_wildcard("%b%");
+    auto rhs = irs::from_wildcard("%b%%%");
+    ASSERT_EQ(lhs.NumStates(), rhs.NumStates());
+    assert_properties(lhs);
+    assert_properties(rhs);
+
+    for (decltype(lhs)::StateId state = 0; state < lhs.NumStates(); ++state) {
+      ASSERT_EQ(lhs.NumArcs(state), rhs.NumArcs(state));
+    }
+  }
+
+  // check automaton structure
+  {
+    auto lhs = irs::from_wildcard("b%%%%%s");
+    auto rhs = irs::from_wildcard("b%%%s");
+    ASSERT_EQ(lhs.NumStates(), rhs.NumStates());
+    assert_properties(lhs);
+    assert_properties(rhs);
+
+    for (decltype(lhs)::StateId state = 0; state < lhs.NumStates(); ++state) {
+      ASSERT_EQ(lhs.NumArcs(state), rhs.NumArcs(state));
+    }
+  }
+
+  // check automaton structure
+  {
+    auto lhs = irs::from_wildcard("b%%__%%%s%");
+    auto rhs = irs::from_wildcard("b%%%%%%%__%%%%%%%%s%");
+    ASSERT_EQ(lhs.NumStates(), rhs.NumStates());
+    assert_properties(lhs);
+    assert_properties(rhs);
+
+    for (decltype(lhs)::StateId state = 0; state < lhs.NumStates(); ++state) {
+      ASSERT_EQ(lhs.NumArcs(state), rhs.NumArcs(state));
+    }
+  }
+
+  // nil string
+  {
+    auto a = irs::from_wildcard(irs::string_ref::NIL);
+    assert_properties(a);
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref(""))));
+    ASSERT_TRUE(irs::accept<char>(a, irs::string_ref::NIL));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("a"))));
+  }
+
+  // empty string
+  {
+    auto a = irs::from_wildcard(irs::string_ref::EMPTY);
+    assert_properties(a);
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref(""))));
+    ASSERT_TRUE(irs::accept<char>(a, irs::string_ref::NIL));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("a"))));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xE2\x9E\x96"))));
+  }
+
+  // any or empty string
+  {
+    auto a = irs::from_wildcard("%");
+    assert_properties(a);
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref(""))));
+    ASSERT_TRUE(irs::accept<char>(a, irs::string_ref::NIL));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("a"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("abc"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xD0\xBF"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xE2\x9E\x96"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xF0\x9F\x98\x81"))));
+  }
+
+  // any or empty string
+  {
+    auto a = irs::from_wildcard("%%");
+    assert_properties(a);
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref(""))));
+    ASSERT_TRUE(irs::accept<char>(a, irs::string_ref::NIL));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("a"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("aa"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("azbce1d"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("azbce1d1"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("azbce11d"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xE2\x9E\x96"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xF0\x9F\x98\x81"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("a\xF0\x9F\x98\x81"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xF0\x9F\x98\x81\xF0\x9F\x98\x81"))));
+  }
+
+  // any char
+  {
+    auto a = irs::from_wildcard("_");
+    assert_properties(a);
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref(""))));
+    ASSERT_FALSE(irs::accept<char>(a, irs::string_ref::NIL));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("a"))));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("abc"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xD0\xBF"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xE2\x9E\x96"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xF0\x9F\x98\x81"))));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("a\xF0\x9F\x98\x81"))));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xF0\x9F\x98\x81\xF0\x9F\x98\x81"))));
+  }
+
+  // two any chars
+  {
+    auto a = irs::from_wildcard("__");
+    assert_properties(a);
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref(""))));
+    ASSERT_FALSE(irs::accept<char>(a, irs::string_ref::NIL));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("a"))));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xE2\x9E\x96"))));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("a\xE2\x9E\x96\xD0\xBF"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xE2\x9E\x96\xD0\xBF"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xE2\x9E\x96\xE2\x9E\x96"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xF0\x9F\x98\x81\xF0\x9F\x98\x81"))));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("a\xF0\x9F\x98\x81\xF0\x9F\x98\x81"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("ba"))));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("azbce1d"))));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("azbce1d1"))));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("azbce11d"))));
+  }
+
+  // any char (suffix)
+  {
+    auto a = irs::from_wildcard("a_");
+    assert_properties(a);
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref(""))));
+    ASSERT_FALSE(irs::accept<char>(a, irs::string_ref::NIL));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("a_"))));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("a"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("ab"))));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("a\xF0\x9F\x98\x81\xF0\x9F\x98\x81"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("a\xF0\x9F\x98\x81"))));
+  }
+
+  // any char (prefix)
+  {
+    auto a = irs::from_wildcard("_a");
+    assert_properties(a);
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref(""))));
+    ASSERT_FALSE(irs::accept<char>(a, irs::string_ref::NIL));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("_a"))));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("a"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("aa"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("ba"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xF0\x9F\x98\x81\x61"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xE2\x9E\x96\x61"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xE2\xFF\xFF\x61")))); // accept invalid utf8 sequence
+  }
+
+  // escaped '_'
+  {
+    auto a = irs::from_wildcard("\\_a");
+    assert_properties(a);
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref(""))));
+    ASSERT_FALSE(irs::accept<char>(a, irs::string_ref::NIL));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("_a"))));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("a"))));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("ba"))));
+  }
+
+  // escaped '\'
+  {
+    auto a = irs::from_wildcard("\\\\\\_a");
+    assert_properties(a);
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref(""))));
+    ASSERT_FALSE(irs::accept<char>(a, irs::string_ref::NIL));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\\_a"))));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("a"))));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\\_\xE2\x9E\x96"))));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("ba"))));
+  }
+
+  // nonterminated '\'
+  {
+    auto a = irs::from_wildcard("a\\");
+    assert_properties(a);
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref(""))));
+    ASSERT_FALSE(irs::accept<char>(a, irs::string_ref::NIL));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("a\\"))));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("a"))));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("ba"))));
+  }
+
+  // escaped '%'
+  {
+    auto a = irs::from_wildcard("\\\\\\%a");
+    assert_properties(a);
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref(""))));
+    ASSERT_FALSE(irs::accept<char>(a, irs::string_ref::NIL));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\\%a"))));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("a"))));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("ba"))));
+  }
+
+  // prefix
+  {
+    auto a = irs::from_wildcard("foo%");
+    assert_properties(a);
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref(""))));
+    ASSERT_FALSE(irs::accept<char>(a, irs::string_ref::NIL));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("foo"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("foobar"))));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("foa"))));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("foabar"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("foo\xE2\x9E\x96\xE2\x9E\x96"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("foo\xF0\x9F\x98\x81\xE2\x9E\x96\xE2\x9E\x96"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("foo\xD0\xBF\xF0\x9F\x98\x81\xE2\x9E\x96\xE2\x9E\x96"))));
+  }
+
+  // mixed
+  {
+    auto a = irs::from_wildcard("a%foo");
+    assert_properties(a);
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref(""))));
+    ASSERT_FALSE(irs::accept<char>(a, irs::string_ref::NIL));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("affoo"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("aaafofoo"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("aaafafoo"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("aaafaffoo"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("aaafoofoo"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("aaafooffffoo"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("aaafooofoo"))));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("abcdfo"))));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("abcdfo"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("aaaaaaaaaaaaaaaaaafoo"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("aaaaaaaaaaaaaaabfoo"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("aaaaaaaaaaaaa\x66\x6F\x6F"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("aaaaaaaaaaaaa\x66\x6F\x6F"))));
+  }
+
+  // mixed
+  {
+    auto a = irs::from_wildcard("a%foo%boo");
+    assert_properties(a);
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref(""))));
+    ASSERT_FALSE(irs::accept<char>(a, irs::string_ref::NIL));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("afooboo"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("afoofoobooboo"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("afoofooboofooboo"))));
+  }
+
+  // suffix
+  {
+    auto a = irs::from_wildcard("%foo");
+    assert_properties(a);
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref(""))));
+    ASSERT_FALSE(irs::accept<char>(a, irs::string_ref::NIL));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("foo"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("fofoo"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("foofoo"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("fooofoo"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("ffoo"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("fffoo"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("bfoo"))));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("foa"))));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("bfoa"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xE2\x9E\x96\xE2\x9E\x96\x66\x6F\x6F"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xE2\x9E\x96\xE2\x9E\x96\x66\x66\x6F\x6F"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xF0\x9F\x98\x81\xE2\x9E\x96\xE2\x9E\x96\x66\x6F\x6F"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xD0\xBF\xF0\x9F\x98\x81\xE2\x9E\x96\xE2\x9E\x96\x66\x6F\x6F"))));
+  }
+
+  // prefix
+  {
+    auto a = irs::from_wildcard("v%%");
+    assert_properties(a);
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref(""))));
+    ASSERT_FALSE(irs::accept<char>(a, irs::string_ref::NIL));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("vcc"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("vccc"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("vczc"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("vczczvccccc"))));
+  }
+
+  // suffix
+  {
+    auto a = irs::from_wildcard("%ffoo");
+    assert_properties(a);
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref(""))));
+    ASSERT_FALSE(irs::accept<char>(a, irs::string_ref::NIL));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("ffoo"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("fffoo"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("bffoo"))));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("ffob"))));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("bfoa"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xE2\x9E\x96\xE2\x9E\x96\x66\x66\x6F\x6F"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xF0\x9F\x98\x81\xE2\x9E\x96\xE2\x9E\x96\x66\x66\x6F\x6F"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xD0\xBF\xF0\x9F\x98\x81\xE2\x9E\x96\xE2\x9E\x96\x66\x66\x6F\x6F"))));
+  }
+
+  // mixed
+  {
+    auto a = irs::from_wildcard("a%a");
+    assert_properties(a);
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref(""))));
+    ASSERT_FALSE(irs::accept<char>(a, irs::string_ref::NIL));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("aa"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("aaa"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("abcdfsa"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("abcdfsa"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("aaaaaaaaaaaaaaaaaa"))));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("aaaaaaaaaaaaaaab"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("aaaaaaaaaaaaa\xE2\x9E\x96\x61"))));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("aaaaaaaaaaaaa\xE2\x9E\x61"))));
+  }
+
+  // mixed
+  {
+    auto a = irs::from_wildcard("_%a_%_a_%");
+    assert_properties(a);
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref(""))));
+    ASSERT_FALSE(irs::accept<char>(a, irs::string_ref::NIL));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("baaaab"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("aaaaaaaaaaaaaaaaaa"))));
+  }
+
+  // mixed
+  {
+    auto a = irs::from_wildcard("\x5F\x25\xE2\x9E\x61\x5F\x25\x5F\xE2\x9E\x61\x5F\x25");
+    assert_properties(a);
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref(""))));
+    ASSERT_FALSE(irs::accept<char>(a, irs::string_ref::NIL));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\x98\xE2\x9E\x61\x97\x97\xE2\x9E\x61\x98"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xE2\x9E\x61\xE2\x9E\x61\xE2\x9E\x61\xE2\x9E\x61\xE2\x9E\x61\xE2\x9E\x61\xE2\x9E\x61\xE2\x9E\x61"))));
+  }
+
+  // mixed
+  {
+    auto a = irs::from_wildcard("\xE2\x9E\x61\x25\xE2\x9E\x61");
+    assert_properties(a);
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref(""))));
+    ASSERT_FALSE(irs::accept<char>(a, irs::string_ref::NIL));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xE2\x9E\x61\xE2\x9E\x61"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xE2\x9E\x61\x61\xE2\x9E\x61"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xE2\x9E\x61\x9E\x61\xE2\x9E\x61"))));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xE2\x9E\x61\x9E\x61\xE2\x9E\xE2\x9E\x61"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xE2\x9E\x61\xE2\x9E\x61\xE2\x9E\x61\xE2\x9E\x61\xE2\x9E\x61\xE2\x9E\x61\xE2\x9E\x61"))));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xE2\x9E\x61\xE2\x9E\x61\xE2\x9E\x61\xE2\x9E\x61\xE2\x9E\x61\xE2\x9E\x61\xE2\x9E\x61\x61"))));
+  }
+
+  // mixed
+  {
+    auto a = irs::from_wildcard("a%bce_d");
+    assert_properties(a);
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref(""))));
+    ASSERT_FALSE(irs::accept<char>(a, irs::string_ref::NIL));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("azbce1d"))));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("azbce1d1"))));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("azbce11d"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("azbce\xD0\xBF\x64"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("azbce\xE2\x9E\x96\x64"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("azbce\xF0\x9F\x98\x81\x64"))));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("azbce\xE2\x9E\x96\xF0\x9F\x98\x81\x64"))));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("azbce\xD0\xBF\xD0\xBF\x64"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("az\xD0\xBF\xD0\xBF\x62\x63\x65\xD0\xBF\x64"))));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("az\xD0\xBF\xD0\xBF\x62\x63\x65\xD0\xBF\x64\x64"))));
+  }
+
+  // mixed
+  {
+    auto a = irs::from_wildcard("b%d%a");
+    assert_properties(a);
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref(""))));
+    ASSERT_FALSE(irs::accept<char>(a, irs::string_ref::NIL));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("azbce1d"))));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("azbce1d1"))));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("azbce11d"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\x62\x61\x7A\xD0\xBF\xD0\xBF\x62\x63\x64\xD0\xBF\x64\x64\x61"))));
+  }
+
+  // mixed
+  {
+    auto a = irs::from_wildcard("a%b%d");
+    assert_properties(a);
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref(""))));
+    ASSERT_FALSE(irs::accept<char>(a, irs::string_ref::NIL));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("azbce1d"))));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("azbce1d1"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("azbce11d"))));
+  }
+
+  // mixed
+  {
+    auto a = irs::from_wildcard("a%b%db");
+    assert_properties(a);
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref(""))));
+    ASSERT_FALSE(irs::accept<char>(a, irs::string_ref::NIL));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("azbce1d"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("azbce1db"))));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("azbce1d1"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("azbce11db"))));
+  }
+
+  // mixed
+  {
+    auto a = irs::from_wildcard("%_");
+    assert_properties(a);
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref(""))));
+    ASSERT_FALSE(irs::accept<char>(a, irs::string_ref::NIL));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("a"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("aa"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("azbce1d"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("azbce1d1"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("azbce11d"))));
+  }
+
+  // mixed, terminal "\\"
+  {
+    auto a = irs::from_wildcard("%\\\\");
+    assert_properties(a);
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref(""))));
+    ASSERT_FALSE(irs::accept<char>(a, irs::string_ref::NIL));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\\"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("a\\"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("aa\\"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("azbce1\\"))));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("azbce1\\1"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("1azbce11\\"))));
+  }
+
+  // mixed, terminal "\\"
+  {
+    auto a = irs::from_wildcard("%_\\\\");
+    assert_properties(a);
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref(""))));
+    ASSERT_FALSE(irs::accept<char>(a, irs::string_ref::NIL));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\\"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("a\\"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("aa\\"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("azbce1\\"))));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("azbce1\\1"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("1azbce11\\"))));
+  }
+
+  // mixed, non-terminated "\\"
+  {
+    auto a = irs::from_wildcard("%\\");
+    assert_properties(a);
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref(""))));
+    ASSERT_FALSE(irs::accept<char>(a, irs::string_ref::NIL));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\\"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("a\\"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("aa\\"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("azbce1\\"))));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("azbce1\\1"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("1azbce11\\"))));
+  }
+
+  // mixed, non-terminated "\\"
+  {
+    auto a = irs::from_wildcard("%_\\");
+    assert_properties(a);
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref(""))));
+    ASSERT_FALSE(irs::accept<char>(a, irs::string_ref::NIL));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\\"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("a\\"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("aa\\"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("azbce1\\"))));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("azbce1\\1"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("1azbce11\\"))));
+  }
+
+  // mixed
+  {
+    auto a = irs::from_wildcard("%_d");
+    assert_properties(a);
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref(""))));
+    ASSERT_FALSE(irs::accept<char>(a, irs::string_ref::NIL));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("d"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("ad"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("aad"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("azbce1d"))));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("azbce1d1"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("1azbce11d"))));
+  }
+
+  // mixed
+  {
+    auto a = irs::from_wildcard("%_%_%d");
+    assert_properties(a);
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref(""))));
+    ASSERT_FALSE(irs::accept<char>(a, irs::string_ref::NIL));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("ad"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("add"))));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("add1"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("abd"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("ddd"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("aad"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("azbce1d"))));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("azbce1d1"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("1azbce11d"))));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xE2\x9E\x96\x64"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xE2\x9E\x96\x64\x64\x64"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("a\xE2\x9E\x96\x64"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("e\xF0\x9F\x98\x81\x64"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("xE2\x9E\x96\xF0\x9F\x98\x81\x64"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("xD0\xBF\xD0\xBF\x64"))));
+  }
+
+  // mixed
+  {
+    auto a = irs::from_wildcard("%_%_%d%");
+    assert_properties(a);
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref(""))));
+    ASSERT_FALSE(irs::accept<char>(a, irs::string_ref::NIL));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("ad"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("add"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("add1"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("abd"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("ddd"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("aad"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("azbce1d"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("azbce1d1"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("1azbce11d"))));
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xE2\x9E\x96\x64"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("\xE2\x9E\x96\x64\x64"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("azbce\xE2\x9E\x96\x64"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("azbce\xF0\x9F\x98\x81\x64"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("azbce\xE2\x9E\x96\xF0\x9F\x98\x81\x64\xD0\xBF"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("azbce\xD0\xBF\xD0\xBF\x64\xD0\xBF"))));
+  }
+
+  // mixed
+  {
+    auto a = irs::from_wildcard("%%_");
+    assert_properties(a);
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref(""))));
+    ASSERT_FALSE(irs::accept<char>(a, irs::string_ref::NIL));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("a"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("aa"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("azbce1d"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("azbce1d1"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("azbce11d"))));
+  }
+
+  // mixed
+  {
+    auto a = irs::from_wildcard("_%");
+    assert_properties(a);
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref(""))));
+    ASSERT_FALSE(irs::accept<char>(a, irs::string_ref::NIL));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("a"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("aa"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("azbce1d"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("azbce1d1"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("azbce11d"))));
+  }
+
+  // mixed
+  {
+    auto a = irs::from_wildcard("v%%c");
+    assert_properties(a);
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref(""))));
+    ASSERT_FALSE(irs::accept<char>(a, irs::string_ref::NIL));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("vcc"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("vccc"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("vczc"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("vczczvccccc"))));
+  }
+
+  // mixed
+  {
+    auto a = irs::from_wildcard("v%c");
+    assert_properties(a);
+    ASSERT_FALSE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref(""))));
+    ASSERT_FALSE(irs::accept<char>(a, irs::string_ref::NIL));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("vcc"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("vccc"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("vczc"))));
+    ASSERT_TRUE(irs::accept<irs::byte_type>(a, irs::ref_cast<irs::byte_type>(irs::string_ref("vczczvccccc"))));
+  }
+
+  // invalid UTF-8 sequence
+  ASSERT_EQ(0, irs::from_wildcard("\xD0").NumStates());
+  ASSERT_EQ(0, irs::from_wildcard("\xE2\x9E").NumStates());
+  ASSERT_EQ(0, irs::from_wildcard("\xF0\x9F\x98").NumStates());
+}
+
+TEST_F(wildcard_utils_test, wildcard_type) {
+  ASSERT_EQ(irs::WildcardType::INVALID, irs::wildcard_type(irs::ref_cast<irs::byte_type>(irs::string_ref("\xD0")))); // invalid UTF-8 sequence
+  ASSERT_EQ(irs::WildcardType::TERM, irs::wildcard_type(irs::ref_cast<irs::byte_type>(irs::string_ref("foo"))));
+  ASSERT_EQ(irs::WildcardType::TERM, irs::wildcard_type(irs::ref_cast<irs::byte_type>(irs::string_ref("\xD0\xE2"))));
+  ASSERT_EQ(irs::WildcardType::TERM, irs::wildcard_type(irs::ref_cast<irs::byte_type>(irs::string_ref("\\foo"))));
+  ASSERT_EQ(irs::WildcardType::TERM, irs::wildcard_type(irs::ref_cast<irs::byte_type>(irs::string_ref("\\%foo"))));
+  ASSERT_EQ(irs::WildcardType::TERM, irs::wildcard_type(irs::ref_cast<irs::byte_type>(irs::string_ref("\foo"))));
+  ASSERT_EQ(irs::WildcardType::PREFIX, irs::wildcard_type(irs::ref_cast<irs::byte_type>(irs::string_ref("foo%"))));
+  ASSERT_EQ(irs::WildcardType::PREFIX, irs::wildcard_type(irs::ref_cast<irs::byte_type>(irs::string_ref("foo%%"))));
+  ASSERT_EQ(irs::WildcardType::PREFIX, irs::wildcard_type(irs::ref_cast<irs::byte_type>(irs::string_ref("\xD0\xE2\x25"))));
+  ASSERT_EQ(irs::WildcardType::TERM, irs::wildcard_type(irs::ref_cast<irs::byte_type>(irs::string_ref("\xD0\x25"))));
+  ASSERT_EQ(irs::WildcardType::PREFIX, irs::wildcard_type(irs::ref_cast<irs::byte_type>(irs::string_ref("\xD0\xE2\x25\x25"))));
+  ASSERT_EQ(irs::WildcardType::WILDCARD, irs::wildcard_type(irs::ref_cast<irs::byte_type>(irs::string_ref("\x25\xD0\xE2\x25\x25"))));
+  ASSERT_EQ(irs::WildcardType::WILDCARD, irs::wildcard_type(irs::ref_cast<irs::byte_type>(irs::string_ref("foo%_"))));
+  ASSERT_EQ(irs::WildcardType::WILDCARD, irs::wildcard_type(irs::ref_cast<irs::byte_type>(irs::string_ref("foo%\\"))));
+  ASSERT_EQ(irs::WildcardType::WILDCARD, irs::wildcard_type(irs::ref_cast<irs::byte_type>(irs::string_ref("fo%o\\%"))));
+  ASSERT_EQ(irs::WildcardType::WILDCARD, irs::wildcard_type(irs::ref_cast<irs::byte_type>(irs::string_ref("foo_%"))));
+  ASSERT_EQ(irs::WildcardType::PREFIX, irs::wildcard_type(irs::ref_cast<irs::byte_type>(irs::string_ref("foo\\_%"))));
+  ASSERT_EQ(irs::WildcardType::WILDCARD, irs::wildcard_type(irs::ref_cast<irs::byte_type>(irs::string_ref("foo__"))));
+  ASSERT_EQ(irs::WildcardType::PREFIX, irs::wildcard_type(irs::ref_cast<irs::byte_type>(irs::string_ref("foo\\%%"))));
+  ASSERT_EQ(irs::WildcardType::PREFIX, irs::wildcard_type(irs::ref_cast<irs::byte_type>(irs::string_ref("foo\\%%%"))));
+  ASSERT_EQ(irs::WildcardType::TERM, irs::wildcard_type(irs::ref_cast<irs::byte_type>(irs::string_ref("foo\\%\\%"))));
+  ASSERT_EQ(irs::WildcardType::MATCH_ALL, irs::wildcard_type(irs::ref_cast<irs::byte_type>(irs::string_ref("%"))));
+  ASSERT_EQ(irs::WildcardType::MATCH_ALL, irs::wildcard_type(irs::ref_cast<irs::byte_type>(irs::string_ref("%%"))));
+  ASSERT_EQ(irs::WildcardType::WILDCARD, irs::wildcard_type(irs::ref_cast<irs::byte_type>(irs::string_ref("%c%"))));
+  ASSERT_EQ(irs::WildcardType::WILDCARD, irs::wildcard_type(irs::ref_cast<irs::byte_type>(irs::string_ref("%%c%"))));
+  ASSERT_EQ(irs::WildcardType::WILDCARD, irs::wildcard_type(irs::ref_cast<irs::byte_type>(irs::string_ref("%c%%"))));
+}
diff --git a/3rdParty/iresearch/utils/index-put.cpp b/3rdParty/iresearch/utils/index-put.cpp
index 26aa5dc305fd..d9d176dba3b7 100644
--- a/3rdParty/iresearch/utils/index-put.cpp
+++ b/3rdParty/iresearch/utils/index-put.cpp
@@ -475,7 +475,10 @@ int put(
       while (!batch_provider.done_.load()) {
         {
           SCOPED_LOCK_NAMED(consolidation_mutex, lock);
-          consolidation_cv.wait(lock);
+          if (std::cv_status::timeout ==
+              consolidation_cv.wait_for(lock, std::chrono::seconds(5))) {
+            continue;
+          }
         }
 
         {
diff --git a/3rdParty/iresearch/utils/index-search.cpp b/3rdParty/iresearch/utils/index-search.cpp
index 0c2b974add93..fd21a3966d4a 100644
--- a/3rdParty/iresearch/utils/index-search.cpp
+++ b/3rdParty/iresearch/utils/index-search.cpp
@@ -53,14 +53,16 @@
 #include "index/directory_reader.hpp"
 #include "search/bm25.hpp"
 #include "search/boolean_filter.hpp"
-#include "search/filter.hpp"
+#include "search/levenshtein_filter.hpp"
 #include "search/phrase_filter.hpp"
-#include "search/wildcard_filter.hpp"
 #include "search/prefix_filter.hpp"
 #include "search/score.hpp"
 #include "search/term_filter.hpp"
+#include "search/wildcard_filter.hpp"
+#include "search/ngram_similarity_filter.hpp"
 #include "store/fs_directory.hpp"
 #include "utils/memory_pool.hpp"
+#include "utils/levenshtein_default_pdp.hpp"
 
 #include "index-search.hpp"
 
@@ -115,9 +117,14 @@ enum class category_t {
   OrHighLow,
   Prefix3,
   Wildcard,
+  Fuzzy1,
+  Fuzzy2,
   Or4High,
   Or6High4Med2Low,
   MinMatch2High2Med,
+  HighNGram,
+  MedNGram,
+  LowNGram,
   UNKNOWN
 };
 
@@ -136,9 +143,14 @@ category_t parseCategory(const irs::string_ref& value) {
   if (value == "OrHighLow") return category_t::OrHighLow;
   if (value == "Prefix3") return category_t::Prefix3;
   if (value == "Wildcard") return category_t::Wildcard;
+  if (value == "Fuzzy1") return category_t::Fuzzy1;
+  if (value == "Fuzzy2") return category_t::Fuzzy2;
   if (value == "Or4High") return category_t::Or4High;
   if (value == "Or6High4Med2Low") return category_t::Or6High4Med2Low;
   if (value == "MinMatch2High2Med") return category_t::MinMatch2High2Med;
+  if (value == "HighNGram") return category_t::HighNGram;
+  if (value == "MedNGram") return category_t::MedNGram;
+  if (value == "LowNGram") return category_t::LowNGram;
   return category_t::UNKNOWN;
 }
 
@@ -158,9 +170,14 @@ irs::string_ref stringCategory(category_t category) {
    case category_t::OrHighLow: return "OrHighLow";
    case category_t::Prefix3: return "Prefix3";
    case category_t::Wildcard: return "Wildcard";
+   case category_t::Fuzzy1: return "Fuzzy1";
+   case category_t::Fuzzy2: return "Fuzzy2";
    case category_t::Or4High: return "Or4High";
    case category_t::Or6High4Med2Low: return "Or6High4Med2Low";
    case category_t::MinMatch2High2Med: return "MinMatch2High2Med";
+   case category_t::HighNGram: return "HighNGram";
+   case category_t::MedNGram: return "MedNGram";
+   case category_t::LowNGram: return "LowNGram";
    default: return "<unknown>";
   }
 }
@@ -241,11 +258,32 @@ irs::filter::prepared::ptr prepareFilter(
     analyzer->reset(terms);
 
     for (auto& term = analyzer->attributes().get<irs::term_attribute>(); analyzer->next();) {
-      query.push_back(term->value());
+      query.push_back(irs::by_phrase::simple_term{term->value()});
     }
 
     return query.prepare(reader, order);
    }
+   case category_t::HighNGram: // fall through
+   case category_t::MedNGram: // fall through
+   case category_t::LowNGram: {
+     if ((terms = splitFreq(text)).null()) {
+       return nullptr;
+     }
+     irs::by_ngram_similarity query;
+
+     query.field("body");
+     bool reading_threshold = true;
+     // the first 'term' should be threshold in tenth - e.g. if value is 7 this means 0.7
+     for (std::istringstream in(terms); std::getline(in, tmpBuf, ' ');) {
+       if (reading_threshold) {
+         reading_threshold = false;
+         query.threshold(float_t(std::stoll(tmpBuf))/ 10.f);
+       } else {
+         query.push_back(tmpBuf);
+       }
+     }
+     return query.prepare(reader, order);
+   }
    case category_t::AndHighHigh: // fall through
    case category_t::AndHighMed: // fall through
    case category_t::AndHighLow: {
@@ -303,6 +341,20 @@ irs::filter::prepared::ptr prepareFilter(
 
     return query.prepare(reader, order);
    }
+   case category_t::Fuzzy1:
+   case category_t::Fuzzy2: {
+     const auto pos = text.find('~');
+     const auto term = irs::string_ref(
+       text.c_str(), 
+       pos == std::string::npos ? text.size() : pos);
+
+     irs::by_edit_distance query;
+     query.scored_terms_limit(scored_terms_limit);
+     query.max_distance(category == category_t::Fuzzy1 ? 1 : 2);
+     query.field("body").term(term);
+
+     return query.prepare(reader, order);
+   }
    case category_t::MinMatch2High2Med: {
      if ((terms = splitFreq(text)).null()) {
        return nullptr;
@@ -363,6 +415,10 @@ int search(
     const std::string& scorer,
     const std::string& scorer_arg_format,
     const irs::string_ref& scorer_arg) {
+  // build parametric descriptions for distances 1 and 2
+  irs::default_pdp(1, false); irs::default_pdp(1, true);
+  irs::default_pdp(2, false); irs::default_pdp(2, true);
+
   static const std::map<std::string, const irs::text_format::type_id&> text_formats = {
     { "csv", irs::text_format::csv },
     { "json", irs::text_format::json },
diff --git a/3rdParty/iresearch/utils/pdd.cpp b/3rdParty/iresearch/utils/pdd.cpp
index f34df1933e79..c39491010c4d 100644
--- a/3rdParty/iresearch/utils/pdd.cpp
+++ b/3rdParty/iresearch/utils/pdd.cpp
@@ -97,18 +97,21 @@ int dump(
     compressed = raw;
   }
 
-  out << "{{\n";
+  out << std::hex;
+
+  out << "{\n  {\n";
   for (auto begin = compressed.begin(), end = compressed.end(); begin != end;) {
-    out << "  ";
+    out << "    \"";
     auto slice_begin = begin;
     auto slice_end = std::min(begin + line_length, compressed.end());
     for (; slice_begin != slice_end; ++slice_begin) {
-      out << uint32_t(*slice_begin) << ",";
+      out << "\\x" << uint32_t(*slice_begin);
     }
-    out << "\n";
+    out << "\"\n";
     begin = slice_end;
   }
-  out << "}," << raw.size() << "}\n";
+  out << std::dec;
+  out << "    , " << compressed.size() << "\n  },\n  " << raw.size() << "\n}\n";
 
   return 0;
 }
@@ -145,7 +148,7 @@ int dump(int argc, char* argv[]) {
   cmd.add<size_t>(DISTANCE, 'd', "Maximum edit distance", true, size_t(1));
   cmd.add<size_t>(LINE_LENGTH, 0, "Items per line", false, size_t(40));
   cmd.add<bool>(TRANSPOSITIONS, 't', "Count transpositions", false, false);
-  cmd.add<std::string>(COMPRESSION, 0, "compression", false, "lz4");
+  cmd.add<std::string>(COMPRESSION, 0, "compression", false, "iresearch::compression::lz4");
 
   cmd.parse(argc, argv);
 
diff --git a/3rdParty/json-schema-validation/.clang_complete b/3rdParty/json-schema-validation/.clang_complete
new file mode 100644
index 000000000000..154bc1110ac2
--- /dev/null
+++ b/3rdParty/json-schema-validation/.clang_complete
@@ -0,0 +1,11 @@
+-Dlinux
+-D__linux__
+-I
+./include
+-I
+./external_libs/googletest
+-I
+./external_libs/json/include
+-I
+./external_libs/velocypack/include
+-std=c++17
diff --git a/3rdParty/json-schema-validation/.gitignore b/3rdParty/json-schema-validation/.gitignore
new file mode 100644
index 000000000000..ba38566a6eb6
--- /dev/null
+++ b/3rdParty/json-schema-validation/.gitignore
@@ -0,0 +1,10 @@
+test-arango-validation
+build
+.clang-format
+.gitignore
+.gitmodules
+.travis.yml
+external_libs/
+format
+tests/
+
diff --git a/3rdParty/json-schema-validation/CMakeLists.txt b/3rdParty/json-schema-validation/CMakeLists.txt
new file mode 100644
index 000000000000..f2a2750b5dde
--- /dev/null
+++ b/3rdParty/json-schema-validation/CMakeLists.txt
@@ -0,0 +1,76 @@
+cmake_minimum_required(VERSION 3.9)
+project(arangodb-validation VERSION 0.0.1 LANGUAGES CXX)
+list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_LIST_DIR}/cmake")
+set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
+
+### OPTIONS
+option(ARANGO_VALIDATION_TESTS "build tests" OFF)
+option(ARANGO_VALIDATION_BUILD_SHARED "build shared lib" OFF)
+
+### general setup and includes
+set(CMAKE_CXX_STANDARD 17 CACHE STRING "Required C++ standard")
+if(CMAKE_CXX_STANDARD LESS 17)
+    message(FATAL_ERROR "Incorrect C++ standard was set. 'arangodb-validation' requires C++17 minimum")
+endif()
+
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
+
+include(ext_cmake_install)
+include(ext_cmake_utils)
+
+set(TAOCPP_JSON_BUILD_TESTS OFF CACHE BOOL "Build test programs" FORCE)
+set(TAOCPP_JSON_BUILD_EXAMPLES OFF CACHE BOOL "Build example programs" FORCE)
+
+if(NOT TARGET taocpp::json)
+    add_subdirectory(external_libs/json EXCLUDE_FROM_ALL)
+endif()
+
+if(NOT TARGET velocypack)
+    add_subdirectory(external_libs/velocypack EXCLUDE_FROM_ALL)
+endif()
+
+if(ARANGO_VALIDATION_TESTS AND NOT TARGET gtest)
+    add_subdirectory(external_libs/googletest EXCLUDE_FROM_ALL)
+endif()
+
+### define static lib
+add_library(arango-validation STATIC
+    src/validation.cpp
+)
+target_compile_features(arango-validation PUBLIC cxx_std_17)
+target_link_libraries(arango-validation PUBLIC
+   taocpp::json
+   velocypack
+)
+target_include_directories(arango-validation PUBLIC
+    $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>
+    $<INSTALL_INTERFACE:${CMAKE_INSTALL_PREFIX}/include>
+)
+
+### define shared lib
+if(ARANGO_VALIDATION_BUILD_SHARED)
+add_library(arango-validation-shared SHARED
+    src/validation.cpp
+)
+target_compile_features(arango-validation-shared PUBLIC cxx_std_17)
+target_link_libraries(arango-validation-shared PUBLIC
+   taocpp::json
+   velocypack
+)
+target_include_directories(arango-validation-shared PUBLIC
+    $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>
+    $<INSTALL_INTERFACE:${CMAKE_INSTALL_PREFIX}/include>
+)
+endif()
+
+add_library(arango::validation ALIAS arango-validation)
+
+### testing
+if(ARANGO_VALIDATION_TESTS)
+    ext_log("arango-validation tests enabled")
+    include(CTest)
+    set(gtest_force_shared_crt ON CACHE BOOL "" FORCE)
+    ext_add_test_subdirectory("google" tests)
+else()
+    ext_log("arango-validation tests disabled")
+endif()
diff --git a/3rdParty/json-schema-validation/cmake/ext_cmake_install.cmake b/3rdParty/json-schema-validation/cmake/ext_cmake_install.cmake
new file mode 100644
index 000000000000..914760f6d260
--- /dev/null
+++ b/3rdParty/json-schema-validation/cmake/ext_cmake_install.cmake
@@ -0,0 +1,43 @@
+macro(ext_install lib)
+    ext_log("prepare install for: ${lib}")
+
+    install(
+        TARGETS "${lib}"
+        RUNTIME DESTINATION bin
+        LIBRARY DESTINATION lib
+        ARCHIVE DESTINATION lib
+    )
+
+    foreach(arg ${ARGN})
+        install(
+            DIRECTORY   "${arg}"
+            DESTINATION include
+        )
+    endforeach()
+
+    #include(CPack)
+endmacro(ext_install)
+
+
+function(ext_install_files from_dir to_dir files)
+	foreach (file ${files})
+	    get_filename_component(parent ${file} DIRECTORY)
+	    if(IS_DIRECTORY ${from_dir}/${file})
+		    ext_log("install dir ${from_dir}/${file} to ${to_dir}/${parent}")
+	        install(
+	            DIRECTORY
+	                ${from_dir}/${file}
+	            DESTINATION
+	                ${to_dir}/${parent}
+	          )
+	    else()
+		    ext_log("install file ${from_dir}/${file} to ${to_dir}/${parent}")
+	        install(
+	            FILES
+	                ${from_dir}/${file}
+	            DESTINATION
+	                ${to_dir}/${parent}
+	        )
+	    endif()
+	endforeach()
+endfunction(ext_install_files)
diff --git a/3rdParty/json-schema-validation/cmake/ext_cmake_utils.cmake b/3rdParty/json-schema-validation/cmake/ext_cmake_utils.cmake
new file mode 100644
index 000000000000..d99971110938
--- /dev/null
+++ b/3rdParty/json-schema-validation/cmake/ext_cmake_utils.cmake
@@ -0,0 +1,69 @@
+#! some basic settings i use really often so lets have them in a macro
+
+function(ext_log)
+    message(STATUS "extINFO -- " ${ARGV})
+endfunction(ext_log)
+
+function(ext_fatal)
+    message(FATAL_ERROR "FATAL ERROR -- " ${ARGV})
+endfunction(ext_fatal)
+
+function(ext_cat_file)
+    if(UNIX)
+        message(STATUS "extINFO -- @@@ content of: " ${ARGV})
+        execute_process(COMMAND /bin/cat ${ARGV})
+        message(STATUS "extINFO -- @@@ end content")
+    endif()
+endfunction(ext_cat_file)
+
+#! prefix string with provided symbol(s) until is has given length
+#
+#  in_string - sting to be prefixed
+#  length - desired length
+#  fill - symbols(s) used for filling
+#  out_string - this will hold the result
+function(ext_prefix in_string length fill out_string)
+    set(result "${in_string}")
+    string(LENGTH "${in_string}" current_length)
+
+    while(current_length LESS length)
+        set(result "${fill}${result}")
+        string(LENGTH "${result}" current_length)
+    endwhile()
+
+    set("${out_string}" "${result}" PARENT_SCOPE)
+endfunction(ext_prefix)
+
+#! this function acts like add_subdirectory but it checks
+#  if CMakeLists.txt exists in the directory before adding it
+function(ext_add_subdirectory dir debug)
+    if(EXISTS "${dir}/CMakeLists.txt")
+        add_subdirectory("${dir}")
+        if(debug)
+            message("adding directory ${dir}")
+        endif()
+    endif()
+endfunction()
+
+macro(ext_add_test_subdirectory type)
+    set(EXT_TEST_TYPE "${type}")
+
+    set(dir "${ARGV1}")
+    if(dir STREQUAL "")
+        set(dir "tests")
+    endif()
+
+    if("${type}" STREQUAL "google") # <-- expand type here!
+        if(NOT TARGET gtest) #avoid recursive inclusion of gtest
+          if("${LIBEXT_SOURCE_DIR}" STREQUAL "")
+              ext_fatal("LIBEXT_SOURCE_DIR not found")
+          endif()
+          ext_log("using google test in: ${LIBEXT_SOURCE_DIR}/external_libs/googletest")
+          add_subdirectory(${LIBEXT_SOURCE_DIR}/external_libs/googletest)
+        endif()
+    else()
+        message(ERROR "unknown test type")
+    endif()
+    ext_log("adding tests in: ${dir}")
+    add_subdirectory("${dir}")
+endmacro(ext_add_test_subdirectory)
diff --git a/3rdParty/json-schema-validation/include/validation/events_from_slice.hpp b/3rdParty/json-schema-validation/include/validation/events_from_slice.hpp
new file mode 100644
index 000000000000..e9f18b64c4ce
--- /dev/null
+++ b/3rdParty/json-schema-validation/include/validation/events_from_slice.hpp
@@ -0,0 +1,152 @@
+// Copyright (c) 2016-2020 Daniel Frey and Jan Christoph Uhde
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef ARANGO_SCHEMA_VALIADTION_EVENTS_FROM_SLICE_HEADER
+#define ARANGO_SCHEMA_VALIADTION_EVENTS_FROM_SLICE_HEADER 1
+
+#include <stdexcept>
+
+#include <velocypack/Iterator.h>
+#include <velocypack/Options.h>
+#include <velocypack/Slice.h>
+#include <velocypack/velocypack-aliases.h>
+
+#include "tao/json/internal/format.hpp"
+#include "types.hpp"
+
+namespace tao::json::events {
+// Events producer to generate events from a VPackSlice Value.
+
+template<auto Recurse, template<typename...> class Traits, typename Consumer>
+void from_value(Consumer& consumer,
+                const VPackSlice& slice,
+                VPackOptions const* options,
+                VPackSlice const* base,
+                bool ignore_special) {
+    switch (slice.type()) {
+        case arangodb::velocypack::ValueType::Illegal:
+            throw std::logic_error("unable to produce events from illegal values");
+
+        case arangodb::velocypack::ValueType::Null:
+            consumer.null();
+            return;
+
+        case arangodb::velocypack::ValueType::Bool:
+            consumer.boolean(slice.getBool());
+            return;
+
+        case arangodb::velocypack::ValueType::Int:
+            consumer.number(slice.getInt());
+            return;
+        case arangodb::velocypack::ValueType::SmallInt:
+            consumer.number(slice.getSmallInt());
+            return;
+
+        case arangodb::velocypack::ValueType::UInt:
+            consumer.number(slice.getUInt());
+            return;
+
+        case arangodb::velocypack::ValueType::Double:
+            consumer.number(slice.getDouble());
+            return;
+
+        case arangodb::velocypack::ValueType::String: {
+            auto ref = slice.stringRef();
+            consumer.string(std::string_view(ref.data(), ref.length()));
+            return;
+        }
+
+        case arangodb::velocypack::ValueType::Binary: {
+            auto len = slice.length();
+            uint8_t const* start = slice.getBinary(len);
+            consumer.binary(tao::binary_view(reinterpret_cast<std::byte const*>(start), len));
+            return;
+        }
+
+        case arangodb::velocypack::ValueType::Array: {
+            consumer.begin_array(slice.length());
+            for (const auto& element : VPackArrayIterator(slice)) {
+                Recurse(consumer, element, options, &slice, ignore_special);
+                consumer.element();
+            }
+            consumer.end_array(slice.length());
+            return;
+        }
+
+        case arangodb::velocypack::ValueType::Object: {
+            const auto len = slice.length();
+            consumer.begin_object(len);
+            for (const auto& element : VPackObjectIterator(slice)) {
+                VPackSlice key = element.key;
+                if (key.isString()) {
+                    auto key_ref = key.stringRef();
+                    consumer.key(std::string_view(key_ref.data(), key_ref.length()));
+                    Recurse(consumer, element.value, options, &slice, ignore_special);
+                    consumer.member();
+                } else if (!ignore_special) {
+                    std::string translated_key;
+                    using namespace arangodb::basics;
+                    uint8_t which = static_cast<uint8_t>(key.getUInt()) + VelocyPackHelper::AttributeBase;
+                    consumer.key(arangodb::validation::id_to_string(which));
+                    VPackSlice val = VPackSlice(element.key.begin() + 1);
+                    arangodb::velocypack::ValueLength length;
+                    if (val.isString()) {
+                        // value of _key, _id, _from, _to, and _rev is ASCII too
+                        char const* pointer = val.getString(length);
+                        consumer.string(std::string_view(pointer, length));
+                    } else {
+                        Recurse(consumer, val, options, &slice, ignore_special);
+                    }
+                } // ! ignore_special
+            }
+            consumer.end_object(len);
+            return;
+        }
+        case VPackValueType::External: {
+            Recurse(consumer,
+                    VPackSlice(reinterpret_cast<uint8_t const*>(slice.getExternal())),
+                    options,
+                    base,
+                    ignore_special);
+            return;
+        }
+
+        case VPackValueType::Custom: {
+            if (options == nullptr || options->customTypeHandler == nullptr || base == nullptr) {
+                throw std::runtime_error("Could not extract custom attribute.");
+            }
+            std::string id = options->customTypeHandler->toString(slice, options, *base);
+            consumer.string(std::move(id));
+            return;
+        }
+
+        case arangodb::velocypack::ValueType::BCD:
+        case arangodb::velocypack::ValueType::MaxKey:
+        case arangodb::velocypack::ValueType::MinKey:
+        case arangodb::velocypack::ValueType::None:
+        case arangodb::velocypack::ValueType::Tagged:
+        case arangodb::velocypack::ValueType::UTCDate:
+            throw std::runtime_error(std::string("unsupported type: ") + slice.typeName());
+    }
+    throw std::logic_error(internal::format(
+        "invalid value '", static_cast<std::uint8_t>(slice.type()), "' for arangodb::velocypack::ValueType"));
+}
+
+template<template<typename...> class Traits, typename Consumer>
+void from_value(Consumer& consumer,
+                const VPackSlice& slice,
+                VPackOptions const* options,
+                VPackSlice const* base,
+                bool ignore_special) {
+    // clang-format off
+    from_value<static_cast<void (*)(Consumer&, const VPackSlice&, VPackOptions const*, VPackSlice const*, bool)>(&from_value<Traits, Consumer>)
+              ,Traits
+              ,Consumer
+              >(consumer, slice, options, base, ignore_special);
+    // clang-format on
+}
+
+} // namespace tao::json::events
+
+
+#endif
diff --git a/3rdParty/json-schema-validation/include/validation/types.hpp b/3rdParty/json-schema-validation/include/validation/types.hpp
new file mode 100644
index 000000000000..4b8f6515fea4
--- /dev/null
+++ b/3rdParty/json-schema-validation/include/validation/types.hpp
@@ -0,0 +1,28 @@
+#ifndef ARANGO_SCHEMA_VALIADTION_TYPES_HEADER
+#define ARANGO_SCHEMA_VALIADTION_TYPES_HEADER 1
+
+#if __has_include("Basics/VelocyPackHelper")
+    #include "Basics/VelocyPackHelper.h"
+#else
+    #include <cstdint>
+namespace arangodb::basics {
+class VelocyPackHelper {
+    public:
+    static uint8_t const KeyAttribute = 0x31;
+    static uint8_t const RevAttribute = 0x32;
+    static uint8_t const IdAttribute = 0x33;
+    static uint8_t const FromAttribute = 0x34;
+    static uint8_t const ToAttribute = 0x35;
+
+    static uint8_t const AttributeBase = 0x30;
+};
+} // namespace arangodb::basics
+#endif
+
+#include <string>
+namespace arangodb::validation {
+[[nodiscard]] std::string const& id_to_string(std::uint8_t);
+}
+
+
+#endif
diff --git a/3rdParty/json-schema-validation/include/validation/validation.hpp b/3rdParty/json-schema-validation/include/validation/validation.hpp
new file mode 100644
index 000000000000..8524228402e7
--- /dev/null
+++ b/3rdParty/json-schema-validation/include/validation/validation.hpp
@@ -0,0 +1,32 @@
+#ifndef ARANGO_SCHEMA_VALIADTION_VALIDATION_HEADER
+#define ARANGO_SCHEMA_VALIADTION_VALIDATION_HEADER 1
+
+
+#include <memory>
+#include <velocypack/Builder.h>
+#include <velocypack/Slice.h>
+#include <velocypack/velocypack-aliases.h>
+
+#include <tao/json/from_file.hpp>
+namespace tao::json {
+template<template<typename...> class Traits>
+class basic_schema;
+}
+
+namespace arangodb::validation {
+[[nodiscard]] bool validate(tao::json::value const& doc,
+                            tao::json::basic_schema<tao::json::traits> const& schema); // first step
+[[nodiscard]] bool validate(VPackSlice const doc,
+                            VPackOptions const*,
+                            tao::json::basic_schema<tao::json::traits> const& schema); // final
+
+[[nodiscard]] tao::json::value slice_to_value(VPackSlice const& doc,
+                                              bool ingore_special = false,
+                                              VPackOptions const* options = &VPackOptions::Defaults,
+                                              VPackSlice const* = nullptr);
+
+[[nodiscard]] tao::json::basic_schema<tao::json::traits>* new_schema(VPackSlice const& schema);
+
+} // namespace arangodb::validation
+
+#endif
diff --git a/3rdParty/json-schema-validation/src/validation.cpp b/3rdParty/json-schema-validation/src/validation.cpp
new file mode 100644
index 000000000000..8d64dc5ac888
--- /dev/null
+++ b/3rdParty/json-schema-validation/src/validation.cpp
@@ -0,0 +1,193 @@
+#include <cassert>
+
+#include <tao/json/contrib/schema.hpp>
+
+#include <velocypack/Iterator.h>
+#include <velocypack/velocypack-aliases.h>
+
+#include <validation/events_from_slice.hpp>
+#include <validation/types.hpp>
+#include <validation/validation.hpp>
+
+namespace {
+using namespace arangodb;
+using namespace arangodb::validation;
+[[nodiscard]] tao::json::value slice_object_to_value(VPackSlice const& slice,
+                                                     bool ignore_special,
+                                                     VPackOptions const* options,
+                                                     VPackSlice const* base) {
+    assert(slice.isObject());
+    tao::json::value rv;
+    rv.prepare_object();
+
+    VPackObjectIterator it(slice, true);
+    while (it.valid()) {
+        velocypack::ValueLength length;
+        VPackSlice key = it.key(false);
+
+        if (key.isString()) {
+            // regular attribute
+            rv.try_emplace(key.copyString(), slice_to_value(it.value(), ignore_special, options, &slice));
+        } else if (!ignore_special) {
+            // optimized code path for translated system attributes
+            tao::json::value sub;
+            VPackSlice val = VPackSlice(key.begin() + 1);
+            if (val.isString()) {
+                // value of _key, _id, _from, _to, and _rev is ASCII too
+                char const* pointer = val.getString(length);
+                sub = std::string(pointer, length);
+            } else {
+                sub = slice_to_value(val, ignore_special, options, &slice);
+            }
+
+            using namespace arangodb::basics;
+            uint8_t which = static_cast<uint8_t>(key.getUInt()) + VelocyPackHelper::AttributeBase;
+            rv.try_emplace(id_to_string(which), std::move(sub));
+        }
+
+        it.next();
+    }
+
+    return rv;
+}
+
+[[nodiscard]] tao::json::value slice_array_to_value(VPackSlice const& slice,
+                                                    bool ignore_special,
+                                                    VPackOptions const* options,
+                                                    VPackSlice const* base) {
+    assert(slice.isArray());
+    VPackArrayIterator it(slice);
+    tao::json::value rv;
+    auto a = rv.prepare_array();
+    a.resize(it.size());
+
+    while (it.valid()) {
+        tao::json::value val = slice_to_value(it.value(), ignore_special, options, &slice);
+        rv.push_back(std::move(val));
+        it.next();
+    }
+
+    return rv;
+}
+
+template<template<typename...> class Traits>
+[[nodiscard]] bool validate(const tao::json::basic_schema<Traits>& schema,
+                            VPackSlice const& v,
+                            VPackOptions const* options = &VPackOptions::Defaults,
+                            bool ignore_special = true) {
+    const auto c = schema.consumer();
+    tao::json::events::from_value<Traits>(*c, v, options, nullptr, ignore_special);
+    return c->finalize();
+}
+
+// use basics strings
+std::string const key_string = "_key";
+std::string const rev_string = "_rev";
+std::string const id_string = "_id";
+std::string const from_string = "_form";
+std::string const to_string = "_to";
+
+} // namespace
+
+namespace arangodb::validation {
+
+bool validate(VPackSlice const doc, VPackOptions const* options, tao::json::schema const& schema) {
+    return ::validate(schema, doc, options, true);
+}
+
+bool validate(tao::json::value const& doc, tao::json::schema const& schema) {
+    return schema.validate(doc);
+}
+
+tao::json::value
+    slice_to_value(VPackSlice const& slice, bool ignore_special, VPackOptions const* options, VPackSlice const* base) {
+    tao::json::value rv;
+    switch (slice.type()) {
+        case VPackValueType::Null: {
+            rv.set_null();
+            return rv;
+        }
+        case VPackValueType::Bool: {
+            rv.set_boolean(slice.getBool());
+            return rv;
+        }
+        case VPackValueType::Double: {
+            rv.set_double(slice.getDouble());
+            return rv;
+        }
+        case VPackValueType::Int: {
+            rv.set_signed(slice.getInt());
+            return rv;
+        }
+        case VPackValueType::UInt: {
+            rv.set_unsigned(slice.getUInt());
+            return rv;
+        }
+        case VPackValueType::SmallInt: {
+            rv.set_signed(slice.getNumericValue<int32_t>());
+            return rv;
+        }
+        case VPackValueType::String: {
+            rv.set_string(slice.copyString());
+            return rv;
+        }
+        case VPackValueType::Array: {
+            return slice_array_to_value(slice, ignore_special, options, base);
+            return rv;
+        }
+        case VPackValueType::Object: {
+            return slice_object_to_value(slice, ignore_special, options, base);
+            return rv;
+        }
+        case VPackValueType::External: {
+            return slice_to_value(
+                VPackSlice(reinterpret_cast<uint8_t const*>(slice.getExternal())), ignore_special, options, base);
+            return rv;
+        }
+        case VPackValueType::Custom: {
+            if (options == nullptr || options->customTypeHandler == nullptr || base == nullptr) {
+                throw std::runtime_error("Could not extract custom attribute.");
+            }
+            std::string id = options->customTypeHandler->toString(slice, options, *base);
+            rv.set_string(std::move(id));
+            return rv;
+        }
+        case VPackValueType::None:
+        default:
+            break;
+            return rv;
+    }
+    return rv;
+}
+
+tao::json::basic_schema<tao::json::traits>* new_schema(VPackSlice const& schema) {
+    auto tao_value_schema = slice_to_value(schema);
+    return new tao::json::schema(tao_value_schema);
+}
+
+[[nodiscard]] std::string const& id_to_string(std::uint8_t id) {
+    using namespace basics;
+    using namespace std::literals::string_literals;
+    switch (id) {
+        case VelocyPackHelper::KeyAttribute: {
+            return key_string;
+        }
+        case VelocyPackHelper::RevAttribute: {
+            return rev_string;
+        }
+        case VelocyPackHelper::IdAttribute: {
+            return id_string;
+        }
+        case VelocyPackHelper::FromAttribute: {
+            return from_string;
+        }
+        case VelocyPackHelper::ToAttribute: {
+            return to_string;
+        }
+    }
+    assert(false);
+    throw std::runtime_error("can not translate id");
+    return key_string; // make sure we return something
+}
+
+} // namespace arangodb::validation
diff --git a/3rdParty/taocpp-json.version b/3rdParty/taocpp-json.version
new file mode 100644
index 000000000000..75f3bb488f0a
--- /dev/null
+++ b/3rdParty/taocpp-json.version
@@ -0,0 +1 @@
+https://github.com/taocpp/json/commit/631095f4bfa45c63af5ccc1cb35ea16eb9ead450
diff --git a/3rdParty/taocpp-json/.clang-format b/3rdParty/taocpp-json/.clang-format
new file mode 100644
index 000000000000..729f882aad10
--- /dev/null
+++ b/3rdParty/taocpp-json/.clang-format
@@ -0,0 +1,84 @@
+# the official .clang-format style for https://github.com/taocpp
+#
+# clang-format -i -style=file $(find . -name '[^.]*.[hc]pp')
+
+Language: Cpp
+Standard: Cpp11
+
+AccessModifierOffset: -3
+AlignAfterOpenBracket: Align
+AlignConsecutiveAssignments: false
+AlignConsecutiveDeclarations: false
+AlignEscapedNewlinesLeft: false
+AlignOperands: true
+AlignTrailingComments: true
+AllowAllParametersOfDeclarationOnNextLine: true
+AllowShortBlocksOnASingleLine: false
+AllowShortCaseLabelsOnASingleLine: false
+AllowShortFunctionsOnASingleLine: Empty
+AllowShortIfStatementsOnASingleLine: false
+AllowShortLoopsOnASingleLine: false
+AlwaysBreakAfterReturnType: None
+AlwaysBreakBeforeMultilineStrings: false
+AlwaysBreakTemplateDeclarations: Yes
+BinPackArguments: false
+BinPackParameters: false
+BraceWrapping:
+    AfterClass: true
+    AfterControlStatement: false
+    AfterEnum : true
+    AfterFunction : true
+    AfterNamespace : true
+    AfterStruct : true
+    AfterUnion : true
+    AfterExternBlock: true
+    BeforeCatch : true
+    BeforeElse : true
+    IndentBraces : false
+    SplitEmptyFunction: false
+    SplitEmptyRecord: false
+    SplitEmptyNamespace: false
+BreakBeforeBinaryOperators: All
+BreakBeforeBraces: Custom
+BreakBeforeTernaryOperators: false
+BreakConstructorInitializers: BeforeColon
+BreakInheritanceList: BeforeColon
+BreakStringLiterals: false
+ColumnLimit: 0
+CompactNamespaces: false
+ConstructorInitializerAllOnOneLineOrOnePerLine: true
+ConstructorInitializerIndentWidth: 3
+ContinuationIndentWidth: 3
+Cpp11BracedListStyle: false
+DerivePointerAlignment: false
+DisableFormat: false
+ExperimentalAutoDetectBinPacking: false
+FixNamespaceComments: true
+IncludeBlocks: Preserve
+IndentCaseLabels: true
+IndentPPDirectives: None
+IndentWidth: 3
+IndentWrappedFunctionNames: false
+KeepEmptyLinesAtTheStartOfBlocks: false
+MaxEmptyLinesToKeep: 1
+NamespaceIndentation: All
+PointerAlignment: Left
+ReflowComments: false
+SortIncludes: true
+SortUsingDeclarations: false
+SpaceAfterCStyleCast: false
+SpaceAfterTemplateKeyword: false
+SpaceBeforeAssignmentOperators: true
+SpaceBeforeCpp11BracedList: false
+SpaceBeforeCtorInitializerColon: true
+SpaceBeforeInheritanceColon: true
+SpaceBeforeParens: Never
+SpaceBeforeRangeBasedForLoopColon: true
+SpaceInEmptyParentheses: false
+SpacesBeforeTrailingComments: 2
+SpacesInAngles: true
+SpacesInCStyleCastParentheses: false
+SpacesInParentheses: true
+SpacesInSquareBrackets: true
+TabWidth: 8
+UseTab: Never
diff --git a/3rdParty/taocpp-json/CMakeLists.txt b/3rdParty/taocpp-json/CMakeLists.txt
new file mode 100644
index 000000000000..0ae9139b4944
--- /dev/null
+++ b/3rdParty/taocpp-json/CMakeLists.txt
@@ -0,0 +1,44 @@
+cmake_minimum_required (VERSION 3.8.0 FATAL_ERROR)
+
+project (taocpp-json VERSION 1.0.0 LANGUAGES CXX)
+
+# installation directories
+set (TAOCPP_JSON_INSTALL_INCLUDE_DIR "include" CACHE STRING "The installation include directory")
+set (TAOCPP_JSON_INSTALL_DOC_DIR "share/doc/tao/json" CACHE STRING "The installation doc directory")
+set (TAOCPP_JSON_INSTALL_CMAKE_DIR "share/taocpp-json/cmake" CACHE STRING "The installation cmake directory")
+
+# define a header-only library
+add_library (json INTERFACE)
+add_library (taocpp::json ALIAS json)
+target_include_directories (json INTERFACE
+  $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>
+  $<INSTALL_INTERFACE:${TAOCPP_JSON_INSTALL_INCLUDE_DIR}>
+)
+
+# require C++17
+target_compile_features (json INTERFACE cxx_std_17)
+
+# testing
+enable_testing ()
+option (TAOCPP_JSON_BUILD_TESTS "Build test programs" ON)
+if (TAOCPP_JSON_BUILD_TESTS)
+  add_subdirectory (src/test/json)
+endif ()
+
+# examples
+option (TAOCPP_JSON_BUILD_EXAMPLES "Build example programs" ON)
+if (TAOCPP_JSON_BUILD_EXAMPLES)
+  add_subdirectory (src/example/json)
+endif ()
+
+# install and export target
+install (TARGETS json EXPORT taocpp-json-targets)
+
+install (EXPORT taocpp-json-targets
+  FILE taocpp-json-config.cmake
+  NAMESPACE taocpp::
+  DESTINATION ${TAOCPP_JSON_INSTALL_CMAKE_DIR}
+)
+
+install (DIRECTORY include/ DESTINATION ${TAOCPP_JSON_INSTALL_INCLUDE_DIR})
+install (FILES LICENSE DESTINATION ${TAOCPP_JSON_INSTALL_DOC_DIR})
diff --git a/3rdParty/taocpp-json/LICENSE b/3rdParty/taocpp-json/LICENSE
new file mode 100644
index 000000000000..a13263cfc547
--- /dev/null
+++ b/3rdParty/taocpp-json/LICENSE
@@ -0,0 +1,21 @@
+The MIT License (MIT)
+
+Copyright (c) 2015-2020 Dr. Colin Hirsch and Daniel Frey
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
diff --git a/3rdParty/taocpp-json/LICENSE.double-conversion b/3rdParty/taocpp-json/LICENSE.double-conversion
new file mode 100644
index 000000000000..0af97b41a733
--- /dev/null
+++ b/3rdParty/taocpp-json/LICENSE.double-conversion
@@ -0,0 +1,32 @@
+The header include/tao/json/external/double.hpp contains
+modified portions of the double-conversion library from
+  https://www.github.com/google/double-conversion
+which is licensed as follows:
+
+
+Copyright 2006-2011, the V8 project authors. All rights reserved.
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+    * Redistributions of source code must retain the above copyright
+      notice, this list of conditions and the following disclaimer.
+    * Redistributions in binary form must reproduce the above
+      copyright notice, this list of conditions and the following
+      disclaimer in the documentation and/or other materials provided
+      with the distribution.
+    * Neither the name of Google Inc. nor the names of its
+      contributors may be used to endorse or promote products derived
+      from this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
diff --git a/3rdParty/taocpp-json/LICENSE.itoa b/3rdParty/taocpp-json/LICENSE.itoa
new file mode 100644
index 000000000000..00696c4dce8a
--- /dev/null
+++ b/3rdParty/taocpp-json/LICENSE.itoa
@@ -0,0 +1,19 @@
+Copyright (c) 2017 James Edward Anhalt III - https://github.com/jeaiii/itoa
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
diff --git a/3rdParty/taocpp-json/LICENSE.ryu b/3rdParty/taocpp-json/LICENSE.ryu
new file mode 100644
index 000000000000..261eeb9e9f8b
--- /dev/null
+++ b/3rdParty/taocpp-json/LICENSE.ryu
@@ -0,0 +1,201 @@
+                                 Apache License
+                           Version 2.0, January 2004
+                        http://www.apache.org/licenses/
+
+   TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+   1. Definitions.
+
+      "License" shall mean the terms and conditions for use, reproduction,
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+      "You" (or "Your") shall mean an individual or Legal Entity
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+      "Work" shall mean the work of authorship, whether in Source or
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+   5. Submission of Contributions. Unless You explicitly state otherwise,
+      any Contribution intentionally submitted for inclusion in the Work
+      by You to the Licensor shall be under the terms and conditions of
+      this License, without any additional terms or conditions.
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+      the terms of any separate license agreement you may have executed
+      with Licensor regarding such Contributions.
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+   6. Trademarks. This License does not grant permission to use the trade
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+
+   7. Disclaimer of Warranty. Unless required by applicable law or
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+      Contributor provides its Contributions) on an "AS IS" BASIS,
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+   8. Limitation of Liability. In no event and under no legal theory,
+      whether in tort (including negligence), contract, or otherwise,
+      unless required by applicable law (such as deliberate and grossly
+      negligent acts) or agreed to in writing, shall any Contributor be
+      liable to You for damages, including any direct, indirect, special,
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+
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+
+      To apply the Apache License to your work, attach the following
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+   Copyright [yyyy] [name of copyright owner]
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+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
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+       http://www.apache.org/licenses/LICENSE-2.0
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+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
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diff --git a/3rdParty/taocpp-json/README.md b/3rdParty/taocpp-json/README.md
new file mode 100644
index 000000000000..43348c0dc844
--- /dev/null
+++ b/3rdParty/taocpp-json/README.md
@@ -0,0 +1,149 @@
+# Welcome to taoJSON
+
+[![Release](https://img.shields.io/github/release/taocpp/json.svg)](https://github.com/taocpp/json/releases/latest)
+[![Download](https://api.bintray.com/packages/taocpp/public-conan/json%3Ataocpp/images/download.svg)](https://bintray.com/taocpp/public-conan/json%3Ataocpp/_latestVersion)
+[![TravisCI](https://travis-ci.org/taocpp/json.svg)](https://travis-ci.org/taocpp/json)
+[![AppVeyor](https://ci.appveyor.com/api/projects/status/github/taocpp/json?svg=true)](https://ci.appveyor.com/project/taocpp/json)
+[![Coverage](https://img.shields.io/coveralls/taocpp/json.svg)](https://coveralls.io/github/taocpp/json)
+[![Language grade: C/C++](https://img.shields.io/lgtm/grade/cpp/g/taocpp/json.svg)](https://lgtm.com/projects/g/taocpp/json/context:cpp)
+
+taoJSON is a zero-dependency C++ header-only JSON library that provides a generic [Value Class](doc/Value-Class.md), uses [Type Traits](doc/Type-Traits.md) to interoperate with C++ types, uses an [Events Interface](doc/Events-Interface.md) to convert from and to JSON, JAXN, CBOR, MsgPack and UBJSON, and much more...
+
+## Documentation
+
+* [Version 1.x](doc/README.md) (requires C++17)
+
+*Warning: The documentation is currently not quite keeping pace with what will hopefully be the last large pre-1.0.0 development burst.*
+
+## Features
+
+* Supported Standards
+
+  * [RFC8259], [ECMA-404]: The JavaScript Object Notation (JSON) Data Interchange Format.
+  * Achieves a **100%** conformance score in the [Native JSON Benchmark] tests.
+  * [RFC6901]: JavaScript Object Notation (JSON) Pointer.
+  * [RFC6902]: JavaScript Object Notation (JSON) Patch.
+  * [RFC7049]: Concise Binary Object Representation ([CBOR]).
+  * [JAXN]: Relaxed JSON.
+  * [MsgPack]: MessagePack binary format (without extensions).
+  * [UBJSON]: Universal Binary JSON.
+
+* [Value Class](doc/Value-Class.md)
+
+  * JSON data model extended with non-finite number values and binary data.
+  * Construction of objects and arrays via `std::initializer_list`.
+  * Conversion from and to arbitrary *user-defined types* via [Type Traits](doc/Type-Traits.md).
+  * Built around STL containers `std::variant`, `std::string`, `std::map`, `std::vector`, etc.
+  * No memory allocations by the Value class itself (the wrapped containers allocate normally).
+  * Instance sharing for string, binary, Value, and *user-defined types* via non-owning pointers.
+  * C++11 literal operator for Values, including binary data.
+  * Optional [Base class for Values](doc/Advanced-Use-Cases.md#custom-base-class-for-values) (e.g. to [annotate (sub-)values with file and line](doc/Advanced-Use-Cases.md#annotate-with-filename-and-line-number)).
+
+* [Events Interface](doc/Events-Interface.md)
+
+  * Simple, straightforward and flexible Events API.
+  * Events-to-Value and Value-to-Events interfaces.
+  * Parse JSON & JAXN string representation to Events.
+  * Stream Events to (prettified) JSON & JAXN string representation.
+  * Conversion from and to binary formats, currently [CBOR], [UBJSON], [MsgPack].
+  * Conversion from and to *other* JSON libraries (e.g. [`contrib/nlohmann.cpp`](contrib/nlohmann.cpp)).
+  * Events comparison, hashing, counting, and schema validation.
+  * Events Transformers to manipulate Events on-the-fly.
+
+## Status
+
+The library is stable as in "works correctly" over months of multiple real-world applications.
+
+The library is not stable as in "under construction"; some parts of the API are under discussion and development and might change and/or be extended before version 1.0.
+
+This library also serves as a real-world example application of the [Parsing Expression Grammar Template Library (PEGTL)], which is used for parsing the JSON and JAXN representation formats.
+
+## Contact
+
+taoJSON is part of [The Art of C++](https://taocpp.github.io/).
+
+For questions and suggestions about taoJSON please contact the authors at `taocpp(at)icemx.net`.
+
+## Thank You
+
+* Niels Lohmann and his [JSON library](https://github.com/nlohmann/json) for the inspiration.
+* Milo Yip and his [Native JSON Benchmark] for a reference to measure progress against.
+
+## License
+
+taoJSON is certified [Open Source] software.
+It may be used for any purpose, including commercial purposes, at absolutely no cost.
+It is distributed under the terms of the [MIT license] reproduced here.
+
+> Copyright (c) 2015-2020 Dr. Colin Hirsch and Daniel Frey
+>
+> Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
+>
+> The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
+>
+> THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+## Additional Licenses
+
+taoJSON contains modified portions of the [double-conversion library](https://github.com/google/double-conversion) which is licensed as follows:
+
+> Copyright 2006-2011, the V8 project authors. All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:
+>
+> * Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
+> * Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
+> * Neither the name of Google Inc. nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.
+>
+> THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+taoJSON contains modified portions of [James Edward Anhalt III's itoa library](https://github.com/jeaiii/itoa) which is licensed as follows:
+
+> Copyright (c) 2017 James Edward Anhalt III - https://github.com/jeaiii/itoa
+>
+> Permission is hereby granted, free of charge, to any person obtaining a copy
+> of this software and associated documentation files (the "Software"), to deal
+> in the Software without restriction, including without limitation the rights
+> to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+> copies of the Software, and to permit persons to whom the Software is
+> furnished to do so, subject to the following conditions:
+>
+> The above copyright notice and this permission notice shall be included in all
+> copies or substantial portions of the Software.
+>
+> THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+> IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+> FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+> AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+> LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+> OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+> SOFTWARE.
+
+taoJSON contains modified portions of [Ulf Adams' Ryu implementation](https://github.com/ulfjack/ryu) which is licensed as follows:
+
+> Copyright 2018 Ulf Adams
+>
+> The contents of this file may be used under the terms of the Apache License, Version 2.0.
+>
+>    (See accompanying file LICENSE.ryu or copy at
+>     http://www.apache.org/licenses/LICENSE-2.0)
+>
+> Alternatively, the contents of this file may be used under the terms of the Boost Software License, Version 1.0.
+>    (See accompanying file LICENSE-Boost or copy at
+>     https://www.boost.org/LICENSE_1_0.txt)
+>
+> Unless required by applicable law or agreed to in writing, this software is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+
+[CBOR]: http://cbor.io
+[ECMA-404]: http://www.ecma-international.org/publications/standards/Ecma-404.htm
+[JAXN]: https://github.com/stand-art/jaxn
+[JSON Reference]: https://tools.ietf.org/html/draft-pbryan-zyp-json-ref-03
+[JSON Schema]: http://json-schema.org/documentation.html
+[MsgPack]: http://msgpack.org
+[MIT license]: http://www.opensource.org/licenses/mit-license.html
+[Native JSON Benchmark]: https://github.com/miloyip/nativejson-benchmark
+[Open Source]: http://www.opensource.org/docs/definition.html
+[Parsing Expression Grammar Template Library (PEGTL)]: https://github.com/taocpp/PEGTL
+[RFC6901]: https://tools.ietf.org/html/rfc6901
+[RFC6902]: https://tools.ietf.org/html/rfc6902
+[RFC7049]: https://tools.ietf.org/html/rfc7049
+[RFC8259]: https://tools.ietf.org/html/rfc8259
+[UBJSON]: http://ubjson.org
diff --git a/3rdParty/taocpp-json/include/tao/json.hpp b/3rdParty/taocpp-json/include/tao/json.hpp
new file mode 100644
index 000000000000..716c976ea38e
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json.hpp
@@ -0,0 +1,45 @@
+// Copyright (c) 2015-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_HPP
+#define TAO_JSON_HPP
+
+// Value Class
+#include "json/value.hpp"
+
+// Value Reading
+#include "json/from_file.hpp"
+#include "json/from_input.hpp"
+#include "json/from_stream.hpp"
+#include "json/from_string.hpp"
+#include "json/parts_parser.hpp"
+
+// Value Writing
+#include "json/stream.hpp"  // operator<<
+#include "json/to_stream.hpp"
+#include "json/to_string.hpp"
+
+// Value Support
+#include "json/operators.hpp"
+#include "json/self_contained.hpp"
+
+// Custom Types
+#include "json/binding.hpp"
+#include "json/consume.hpp"
+#include "json/consume_file.hpp"
+#include "json/consume_string.hpp"
+#include "json/produce.hpp"
+
+// Binary Literals
+#include "json/binary.hpp"
+
+// Other Formats
+#include "json/cbor.hpp"
+#include "json/jaxn.hpp"
+#include "json/msgpack.hpp"
+#include "json/ubjson.hpp"
+
+// Events Implementations
+#include "json/events.hpp"
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/basic_value.hpp b/3rdParty/taocpp-json/include/tao/json/basic_value.hpp
new file mode 100644
index 000000000000..612bc90397e2
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/basic_value.hpp
@@ -0,0 +1,941 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_BASIC_VALUE_HPP
+#define TAO_JSON_BASIC_VALUE_HPP
+
+#include <cassert>
+#include <cstddef>
+#include <cstdint>
+#include <memory>
+#include <optional>
+#include <stdexcept>
+#include <string>
+#include <string_view>
+#include <type_traits>
+#include <utility>
+#include <variant>
+#include <vector>
+
+#include "events/virtual_base.hpp"
+
+#include "internal/escape.hpp"
+#include "internal/format.hpp"
+#include "internal/identity.hpp"
+#include "internal/pair.hpp"
+#include "internal/single.hpp"
+#include "internal/type_traits.hpp"
+
+#include "binary.hpp"
+#include "binary_view.hpp"
+#include "forward.hpp"
+#include "message_extension.hpp"
+#include "pointer.hpp"
+#include "type.hpp"
+
+namespace tao::json
+{
+   template< template< typename... > class Traits >
+   class basic_value
+      : public Traits< void >::template public_base< basic_value< Traits > >
+   {
+   public:
+      using public_base_t = typename Traits< void >::template public_base< basic_value< Traits > >;
+
+      static_assert( std::is_nothrow_destructible_v< public_base_t > );
+
+      using array_t = std::vector< basic_value >;
+      using object_t = std::map< std::string, basic_value, std::less<> >;
+
+   private:
+      using variant_t = std::variant< uninitialized_t,
+                                      null_t,
+                                      bool,
+                                      std::int64_t,
+                                      std::uint64_t,
+                                      double,
+                                      std::string,
+                                      std::string_view,
+                                      tao::binary,
+                                      tao::binary_view,
+                                      array_t,
+                                      object_t,
+                                      const basic_value*,
+                                      internal::opaque_ptr_t >;
+
+      static_assert( std::is_nothrow_destructible_v< variant_t > );
+
+      variant_t m_variant;
+
+   public:
+      basic_value() = default;
+
+      basic_value( const basic_value& r ) = default;
+      basic_value( basic_value&& r ) = default;
+
+#if( __cplusplus > 201703L )
+
+      template< typename T,
+                typename D = std::decay_t< T >,
+                typename = decltype( Traits< D >::assign( std::declval< basic_value& >(), std::declval< T&& >() ) ) >
+      explicit( !internal::enable_implicit_constructor< Traits, D > ) basic_value( T&& v, public_base_t b = public_base_t() ) noexcept( noexcept( Traits< D >::assign( std::declval< basic_value& >(), std::forward< T >( v ) ) ) && std::is_nothrow_move_assignable_v< public_base_t > )
+         : public_base_t( std::move( b ) )
+      {
+         Traits< D >::assign( *this, std::forward< T >( v ) );
+      }
+
+#else
+
+      template< typename T,
+                typename D = std::decay_t< T >,
+                typename = std::enable_if_t< internal::enable_implicit_constructor< Traits, D > >,
+                typename = decltype( Traits< D >::assign( std::declval< basic_value& >(), std::declval< T&& >() ) ) >
+      basic_value( T&& v, public_base_t b = public_base_t() ) noexcept( noexcept( Traits< D >::assign( std::declval< basic_value& >(), std::forward< T >( v ) ) ) && std::is_nothrow_move_assignable_v< public_base_t > )
+         : public_base_t( std::move( b ) )
+      {
+         Traits< D >::assign( *this, std::forward< T >( v ) );
+      }
+
+      template< typename T,
+                typename D = std::decay_t< T >,
+                typename = std::enable_if_t< !internal::enable_implicit_constructor< Traits, D > >,
+                typename = decltype( Traits< D >::assign( std::declval< basic_value& >(), std::declval< T&& >() ) ),
+                int = 0 >
+      explicit basic_value( T&& v, public_base_t b = public_base_t() ) noexcept( noexcept( Traits< D >::assign( std::declval< basic_value& >(), std::forward< T >( v ) ) ) && std::is_nothrow_move_assignable_v< public_base_t > )
+         : public_base_t( std::move( b ) )
+      {
+         Traits< D >::assign( *this, std::forward< T >( v ) );
+      }
+
+#endif
+
+      basic_value( std::initializer_list< internal::pair< Traits > >&& l, public_base_t b = public_base_t() )
+         : public_base_t( std::move( b ) )
+      {
+         assign( std::move( l ) );
+      }
+
+      basic_value( const std::initializer_list< internal::pair< Traits > >& l, public_base_t b = public_base_t() )
+         : public_base_t( std::move( b ) )
+      {
+         assign( l );
+      }
+
+      basic_value( std::initializer_list< internal::pair< Traits > >& l, public_base_t b = public_base_t() )
+         : basic_value( static_cast< const std::initializer_list< internal::pair< Traits > >& >( l ), std::move( b ) )
+      {}
+
+      ~basic_value() = default;
+
+      [[nodiscard]] static basic_value array( std::initializer_list< internal::single< Traits > >&& l, public_base_t b = public_base_t() )
+      {
+         basic_value v( uninitialized, std::move( b ) );
+         v.append( std::move( l ) );
+         return v;
+      }
+
+      [[nodiscard]] static basic_value array( const std::initializer_list< internal::single< Traits > >& l, public_base_t b = public_base_t() )
+      {
+         basic_value v( uninitialized, std::move( b ) );
+         v.append( l );
+         return v;
+      }
+
+      [[nodiscard]] static basic_value object( std::initializer_list< internal::pair< Traits > >&& l, public_base_t b = public_base_t() )
+      {
+         basic_value v( uninitialized, std::move( b ) );
+         v.insert( std::move( l ) );
+         return v;
+      }
+
+      [[nodiscard]] static basic_value object( const std::initializer_list< internal::pair< Traits > >& l, public_base_t b = public_base_t() )
+      {
+         basic_value v( uninitialized, std::move( b ) );
+         v.insert( l );
+         return v;
+      }
+
+      basic_value& operator=( basic_value v ) noexcept( std::is_nothrow_move_assignable_v< variant_t >&& std::is_nothrow_move_assignable_v< public_base_t > )
+      {
+         m_variant = std::move( v.m_variant );
+         public_base_t::operator=( static_cast< public_base_t&& >( v ) );
+         return *this;
+      }
+
+      [[nodiscard]] public_base_t& public_base() noexcept
+      {
+         return static_cast< public_base_t& >( *this );
+      }
+
+      [[nodiscard]] const public_base_t& public_base() const noexcept
+      {
+         return static_cast< const public_base_t& >( *this );
+      }
+
+      [[nodiscard]] json::type type() const noexcept
+      {
+         return static_cast< json::type >( m_variant.index() );
+      }
+
+      [[nodiscard]] explicit operator bool() const noexcept
+      {
+         return !is_uninitialized();
+      }
+
+      [[nodiscard]] bool is_uninitialized() const noexcept
+      {
+         return std::holds_alternative< uninitialized_t >( m_variant );
+      }
+
+      [[nodiscard]] bool is_null() const noexcept
+      {
+         return std::holds_alternative< null_t >( m_variant );
+      }
+
+      [[nodiscard]] bool is_boolean() const noexcept
+      {
+         return std::holds_alternative< bool >( m_variant );
+      }
+
+      [[nodiscard]] bool is_signed() const noexcept
+      {
+         return std::holds_alternative< std::int64_t >( m_variant );
+      }
+
+      [[nodiscard]] bool is_unsigned() const noexcept
+      {
+         return std::holds_alternative< std::uint64_t >( m_variant );
+      }
+
+      [[nodiscard]] bool is_integer() const noexcept
+      {
+         return is_signed() || is_unsigned();
+      }
+
+      [[nodiscard]] bool is_double() const noexcept
+      {
+         return std::holds_alternative< double >( m_variant );
+      }
+
+      [[nodiscard]] bool is_number() const noexcept
+      {
+         return is_integer() || is_double();
+      }
+
+      [[nodiscard]] bool is_string() const noexcept
+      {
+         return std::holds_alternative< std::string >( m_variant );
+      }
+
+      [[nodiscard]] bool is_string_view() const noexcept
+      {
+         return std::holds_alternative< std::string_view >( m_variant );
+      }
+
+      [[nodiscard]] bool is_string_type() const noexcept
+      {
+         return is_string() || is_string_view();
+      }
+
+      [[nodiscard]] bool is_binary() const noexcept
+      {
+         return std::holds_alternative< binary >( m_variant );
+      }
+
+      [[nodiscard]] bool is_binary_view() const noexcept
+      {
+         return std::holds_alternative< tao::binary_view >( m_variant );
+      }
+
+      [[nodiscard]] bool is_binary_type() const noexcept
+      {
+         return is_binary() || is_binary_view();
+      }
+
+      [[nodiscard]] bool is_array() const noexcept
+      {
+         return std::holds_alternative< array_t >( m_variant );
+      }
+
+      [[nodiscard]] bool is_object() const noexcept
+      {
+         return std::holds_alternative< object_t >( m_variant );
+      }
+
+      [[nodiscard]] bool is_value_ptr() const noexcept
+      {
+         return std::holds_alternative< const basic_value* >( m_variant );
+      }
+
+      [[nodiscard]] bool is_opaque_ptr() const noexcept
+      {
+         return std::holds_alternative< internal::opaque_ptr_t >( m_variant );
+      }
+
+      [[nodiscard]] bool get_boolean() const
+      {
+         return std::get< bool >( m_variant );
+      }
+
+      [[nodiscard]] std::int64_t get_signed() const
+      {
+         return std::get< std::int64_t >( m_variant );
+      }
+
+      [[nodiscard]] std::uint64_t get_unsigned() const
+      {
+         return std::get< std::uint64_t >( m_variant );
+      }
+
+      [[nodiscard]] double get_double() const
+      {
+         return std::get< double >( m_variant );
+      }
+
+      [[nodiscard]] std::string& get_string()
+      {
+         return std::get< std::string >( m_variant );
+      }
+
+      [[nodiscard]] const std::string& get_string() const
+      {
+         return std::get< std::string >( m_variant );
+      }
+
+      [[nodiscard]] std::string_view get_string_view() const
+      {
+         return std::get< std::string_view >( m_variant );
+      }
+
+      [[nodiscard]] std::string_view get_string_type() const
+      {
+         return is_string() ? get_string() : get_string_view();
+      }
+
+      [[nodiscard]] binary& get_binary()
+      {
+         return std::get< binary >( m_variant );
+      }
+
+      [[nodiscard]] const binary& get_binary() const
+      {
+         return std::get< binary >( m_variant );
+      }
+
+      [[nodiscard]] tao::binary_view get_binary_view() const
+      {
+         return std::get< tao::binary_view >( m_variant );
+      }
+
+      [[nodiscard]] tao::binary_view get_binary_type() const
+      {
+         return is_binary() ? get_binary() : get_binary_view();
+      }
+
+      [[nodiscard]] array_t& get_array()
+      {
+         return std::get< array_t >( m_variant );
+      }
+
+      [[nodiscard]] const array_t& get_array() const
+      {
+         return std::get< array_t >( m_variant );
+      }
+
+      [[nodiscard]] object_t& get_object()
+      {
+         return std::get< object_t >( m_variant );
+      }
+
+      [[nodiscard]] const object_t& get_object() const
+      {
+         return std::get< object_t >( m_variant );
+      }
+
+      [[nodiscard]] const basic_value* get_value_ptr() const
+      {
+         return std::get< const basic_value* >( m_variant );
+      }
+
+      [[nodiscard]] internal::opaque_ptr_t get_opaque_ptr() const
+      {
+         return std::get< internal::opaque_ptr_t >( m_variant );
+      }
+
+   private:
+      void throw_duplicate_key_exception( const std::string_view k ) const
+      {
+         throw std::runtime_error( internal::format( "duplicate JSON object key \"", internal::escape( k ), '"', json::message_extension( *this ) ) );
+      }
+
+      void throw_index_out_of_bound_exception( const std::size_t i ) const
+      {
+         throw std::out_of_range( internal::format( "JSON array index '", i, "' out of bound '", get_array().size(), '\'', json::message_extension( *this ) ) );
+      }
+
+      void throw_key_not_found_exception( const std::string_view k ) const
+      {
+         throw std::out_of_range( internal::format( "JSON object key \"", internal::escape( k ), "\" not found", json::message_extension( *this ) ) );
+      }
+
+   public:
+      void set_uninitialized() noexcept
+      {
+         m_variant = uninitialized;
+      }
+
+      void set_null() noexcept
+      {
+         m_variant = null;
+      }
+
+      void set_boolean( const bool b ) noexcept
+      {
+         m_variant = b;
+      }
+
+      void set_signed( const std::int64_t i ) noexcept
+      {
+         m_variant = i;
+      }
+
+      void set_unsigned( const std::uint64_t u ) noexcept
+      {
+         m_variant = u;
+      }
+
+      void set_double( const double d ) noexcept
+      {
+         m_variant = d;
+      }
+
+      template< typename... Ts >
+      std::string& emplace_string( Ts&&... ts ) noexcept( noexcept( std::string( std::forward< Ts >( ts )... ) ) )
+      {
+         return m_variant.template emplace< std::string >( std::forward< Ts >( ts )... );
+      }
+
+      void set_string( const std::string& s )
+      {
+         m_variant = s;
+      }
+
+      void set_string( std::string&& s ) noexcept
+      {
+         m_variant = std::move( s );
+      }
+
+      void set_string_view( const std::string_view sv ) noexcept
+      {
+         m_variant = sv;
+      }
+
+      template< typename... Ts >
+      binary& emplace_binary( Ts&&... ts ) noexcept( noexcept( binary( std::forward< Ts >( ts )... ) ) )
+      {
+         return m_variant.template emplace< binary >( std::forward< Ts >( ts )... );
+      }
+
+      void set_binary( const binary& x )
+      {
+         m_variant = x;
+      }
+
+      void set_binary( binary&& x ) noexcept
+      {
+         m_variant = std::move( x );
+      }
+
+      void set_binary_view( const tao::binary_view xv ) noexcept
+      {
+         m_variant = xv;
+      }
+
+      template< typename... Ts >
+      array_t& emplace_array( Ts&&... ts ) noexcept( noexcept( array_t( std::forward< Ts >( ts )... ) ) )
+      {
+         return m_variant.template emplace< array_t >( std::forward< Ts >( ts )... );
+      }
+
+      void set_array( const array_t& a )
+      {
+         m_variant = a;
+      }
+
+      void set_array( array_t&& a ) noexcept( std::is_nothrow_move_assignable_v< array_t > )
+      {
+         m_variant = std::move( a );
+      }
+
+      array_t& prepare_array()
+      {
+         return is_uninitialized() ? emplace_array() : get_array();
+      }
+
+      void push_back( const basic_value& v )
+      {
+         prepare_array().push_back( v );
+      }
+
+      void push_back( basic_value&& v )
+      {
+         prepare_array().push_back( std::move( v ) );
+      }
+
+      template< typename... Ts >
+      basic_value& emplace_back( Ts&&... ts )
+      {
+         return prepare_array().emplace_back( std::forward< Ts >( ts )... );
+      }
+
+      template< typename... Ts >
+      object_t& emplace_object( Ts&&... ts ) noexcept( noexcept( object_t( std::forward< Ts >( ts )... ) ) )
+      {
+         return m_variant.template emplace< object_t >( std::forward< Ts >( ts )... );
+      }
+
+      void set_object( const object_t& o )
+      {
+         m_variant = o;
+      }
+
+      void set_object( object_t&& o ) noexcept( std::is_nothrow_move_assignable_v< object_t > )
+      {
+         m_variant = std::move( o );
+      }
+
+      object_t& prepare_object()
+      {
+         return is_uninitialized() ? emplace_object() : get_object();
+      }
+
+      template< typename... Ts >
+      auto try_emplace( Ts&&... ts )
+      {
+         auto r = prepare_object().try_emplace( std::forward< Ts >( ts )... );
+         if( !r.second ) {
+            throw_duplicate_key_exception( r.first->first );
+         }
+         return r;
+      }
+
+      auto insert( typename object_t::value_type&& t )
+      {
+         return prepare_object().emplace( std::move( t ) );
+      }
+
+      auto insert( const typename object_t::value_type& t )
+      {
+         return prepare_object().emplace( t );
+      }
+
+      void set_value_ptr( const basic_value* p ) noexcept
+      {
+         assert( p );
+         m_variant = p;
+      }
+
+      template< typename T >
+      void set_opaque_ptr( const T* data, const producer_t producer ) noexcept
+      {
+         assert( data );
+         assert( producer );
+         m_variant = internal::opaque_ptr_t{ data, producer };
+      }
+
+      template< typename T >
+      void set_opaque_ptr( const T* data ) noexcept
+      {
+         set_opaque_ptr( data, &basic_value::produce_from_opaque_ptr< T > );
+      }
+
+      template< typename T >
+      void assign( T&& v ) noexcept( noexcept( Traits< std::decay_t< T > >::assign( std::declval< basic_value& >(), std::forward< T >( v ) ) ) )
+      {
+         Traits< std::decay_t< T > >::assign( *this, std::forward< T >( v ) );
+      }
+
+      template< typename T >
+      void assign( T&& v, public_base_t b ) noexcept( noexcept( Traits< std::decay_t< T > >::assign( std::declval< basic_value& >(), std::forward< T >( v ) ) ) && std::is_nothrow_move_assignable_v< public_base_t > )
+      {
+         Traits< std::decay_t< T > >::assign( *this, std::forward< T >( v ) );
+         public_base() = std::move( b );
+      }
+
+      void assign( std::initializer_list< internal::pair< Traits > >&& l )
+      {
+         emplace_object();
+         for( auto& e : l ) {
+            try_emplace( std::move( e.key ), std::move( e.value ) );
+         }
+      }
+
+      void assign( const std::initializer_list< internal::pair< Traits > >& l )
+      {
+         emplace_object();
+         for( const auto& e : l ) {
+            try_emplace( e.key, e.value );
+         }
+      }
+
+      void assign( std::initializer_list< internal::pair< Traits > >& l )
+      {
+         assign( static_cast< const std::initializer_list< internal::pair< Traits > >& >( l ) );
+      }
+
+      void append( std::initializer_list< internal::single< Traits > >&& l )
+      {
+         auto& v = prepare_array();
+         v.reserve( v.size() + l.size() );
+         for( auto& e : l ) {
+            v.push_back( std::move( e.value ) );
+         }
+      }
+
+      void append( const std::initializer_list< internal::single< Traits > >& l )
+      {
+         auto& v = prepare_array();
+         v.reserve( v.size() + l.size() );
+         for( const auto& e : l ) {
+            v.push_back( e.value );
+         }
+      }
+
+      void insert( std::initializer_list< internal::pair< Traits > >&& l )
+      {
+         prepare_object();
+         for( auto& e : l ) {
+            try_emplace( std::move( e.key ), std::move( e.value ) );
+         }
+      }
+
+      void insert( const std::initializer_list< internal::pair< Traits > >& l )
+      {
+         prepare_object();
+         for( const auto& e : l ) {
+            try_emplace( e.key, e.value );
+         }
+      }
+
+      [[nodiscard]] const basic_value& skip_value_ptr() const noexcept
+      {
+         const basic_value* p = this;
+         while( p->is_value_ptr() ) {
+            p = p->get_value_ptr();
+            assert( p );
+         }
+         return *p;
+      }
+
+      [[nodiscard]] basic_value* find( const std::size_t index )
+      {
+         auto& a = get_array();
+         return ( index < a.size() ) ? ( a.data() + index ) : nullptr;
+      }
+
+      [[nodiscard]] const basic_value* find( const std::size_t index ) const
+      {
+         const auto& a = get_array();
+         return ( index < a.size() ) ? ( a.data() + index ) : nullptr;
+      }
+
+      template< typename Key >
+      [[nodiscard]] std::enable_if_t< !std::is_convertible_v< Key, std::size_t > && !std::is_convertible_v< Key, pointer >, basic_value* > find( Key&& key )
+      {
+         auto& o = get_object();
+         const auto it = o.find( std::forward< Key >( key ) );
+         return ( it != o.end() ) ? ( &it->second ) : nullptr;
+      }
+
+      template< typename Key >
+      [[nodiscard]] std::enable_if_t< !std::is_convertible_v< Key, std::size_t > && !std::is_convertible_v< Key, pointer >, const basic_value* > find( Key&& key ) const
+      {
+         const auto& o = get_object();
+         const auto it = o.find( std::forward< Key >( key ) );
+         return ( it != o.end() ) ? ( &it->second ) : nullptr;
+      }
+
+      [[nodiscard]] basic_value* find( const pointer& k )
+      {
+         return internal::pointer_find( this, k.begin(), k.end() );
+      }
+
+      [[nodiscard]] const basic_value* find( const pointer& k ) const
+      {
+         return internal::pointer_find( this, k.begin(), k.end() );
+      }
+
+      [[nodiscard]] basic_value& at( const std::size_t index )
+      {
+         auto& a = get_array();
+         if( index >= a.size() ) {
+            throw_index_out_of_bound_exception( index );
+         }
+         return a[ index ];
+      }
+
+      [[nodiscard]] const basic_value& at( const std::size_t index ) const
+      {
+         const auto& a = get_array();
+         if( index >= a.size() ) {
+            throw_index_out_of_bound_exception( index );
+         }
+         return a[ index ];
+      }
+
+      template< typename Key >
+      [[nodiscard]] std::enable_if_t< !std::is_convertible_v< Key, std::size_t > && !std::is_convertible_v< Key, pointer >, basic_value& > at( const Key& key )
+      {
+         auto& o = get_object();
+         const auto it = o.find( key );
+         if( it == o.end() ) {
+            throw_key_not_found_exception( key );
+         }
+         return it->second;
+      }
+
+      template< typename Key >
+      [[nodiscard]] std::enable_if_t< !std::is_convertible_v< Key, std::size_t > && !std::is_convertible_v< Key, pointer >, const basic_value& > at( const Key& key ) const
+      {
+         const auto& o = get_object();
+         const auto it = o.find( key );
+         if( it == o.end() ) {
+            throw_key_not_found_exception( key );
+         }
+         return it->second;
+      }
+
+      [[nodiscard]] basic_value& at( const pointer& k )
+      {
+         return internal::pointer_at( this, k.begin(), k.end() );
+      }
+
+      [[nodiscard]] const basic_value& at( const pointer& k ) const
+      {
+         return internal::pointer_at( this, k.begin(), k.end() );
+      }
+
+      [[nodiscard]] basic_value& operator[]( const std::size_t index )
+      {
+         return get_array()[ index ];
+      }
+
+      [[nodiscard]] const basic_value& operator[]( const std::size_t index ) const
+      {
+         return get_array()[ index ];
+      }
+
+      template< typename Key >
+      [[nodiscard]] std::enable_if_t< !std::is_convertible_v< Key, std::size_t > && !std::is_convertible_v< Key, pointer >, basic_value& > operator[]( Key&& key )
+      {
+         return prepare_object()[ std::forward< Key >( key ) ];
+      }
+
+      [[nodiscard]] basic_value& operator[]( const pointer& k )
+      {
+         if( k.empty() ) {
+            return *this;
+         }
+         const auto b = k.begin();
+         const auto e = std::prev( k.end() );
+         basic_value& v = internal::pointer_at( this, b, e );
+         if( v.is_object() ) {
+            return v.get_object()[ e->key() ];
+         }
+         if( v.is_array() ) {
+            if( e->key() == "-" ) {
+               v.emplace_back( null );
+               return v.get_array().back();
+            }
+            return v.at( e->index() );
+         }
+         throw internal::invalid_type( b, std::next( e ) );
+      }
+
+      template< typename T >
+      [[nodiscard]] std::enable_if_t< internal::has_as< Traits< T >, basic_value >, T > as() const
+      {
+         return Traits< T >::as( *this );
+      }
+
+      template< typename T >
+      [[nodiscard]] std::enable_if_t< !internal::has_as< Traits< T >, basic_value > && internal::has_as_type< Traits, T, basic_value >, T > as() const
+      {
+         return Traits< T >::template as_type< Traits, T >( *this );
+      }
+
+      template< typename T >
+      [[nodiscard]] std::enable_if_t< !internal::has_as< Traits< T >, basic_value > && !internal::has_as_type< Traits, T, basic_value > && internal::has_to< Traits< T >, basic_value, T >, T > as() const
+      {
+         T v;  // TODO: Should is_default_constructible< T > be part of the enable_if, static_assert()ed here, or this line allowed to error?
+         Traits< T >::to( *this, v );
+         return v;
+      }
+
+      template< typename T >
+      std::enable_if_t< !internal::has_as< Traits< T >, basic_value > && !internal::has_as_type< Traits, T, basic_value > && !internal::has_to< Traits< T >, basic_value, T > > as() const = delete;
+
+      template< typename T, typename K >
+      [[nodiscard]] T as( const K& key ) const
+      {
+         return this->at( key ).template as< T >();
+      }
+
+      // TODO: Incorporate has_as_type in the following functions (and throughout the library) (if we decide keep it)!
+
+      template< typename T, typename... With >
+      [[nodiscard]] std::enable_if_t< internal::has_as< Traits< T >, basic_value, With... >, T > as_with( With&&... with ) const
+      {
+         return Traits< T >::as( *this, with... );
+      }
+
+      template< typename T, typename... With >
+      [[nodiscard]] std::enable_if_t< !internal::has_as< Traits< T >, basic_value, With... > && internal::has_to< Traits< T >, basic_value, T, With... >, T > as_with( With&&... with ) const
+      {
+         T v;  // TODO: Should is_default_constructible< T > be part of the enable_if, static_assert()ed here, or this line allowed to error?
+         Traits< T >::to( *this, v, with... );
+         return v;
+      }
+
+      template< typename T, typename... With >
+      std::enable_if_t< !internal::has_as< Traits< T >, basic_value, With... > && !internal::has_to< Traits< T >, basic_value, T, With... >, T > as_with( With&&... with ) const = delete;
+
+      template< typename T >
+      std::enable_if_t< internal::has_to< Traits< T >, basic_value, T > > to( T& v ) const
+      {
+         Traits< std::decay_t< T > >::to( *this, v );
+      }
+
+      template< typename T >
+      std::enable_if_t< !internal::has_to< Traits< T >, basic_value, T > && internal::has_as< Traits< T >, basic_value > > to( T& v ) const
+      {
+         v = Traits< std::decay_t< T > >::as( *this );
+      }
+
+      template< typename T >
+      std::enable_if_t< !internal::has_to< Traits< T >, basic_value, T > && !internal::has_as< Traits< T >, basic_value > > to( T& v ) const = delete;
+
+      template< typename T, typename K >
+      void to( T& v, const K& key )
+      {
+         this->at( key ).to( v );
+      }
+
+      template< typename T, typename... With >
+      std::enable_if_t< internal::has_to< Traits< T >, basic_value, T, With... > > to_with( T& v, With&&... with ) const
+      {
+         Traits< std::decay_t< T > >::to( *this, v, with... );
+      }
+
+      template< typename T, typename... With >
+      std::enable_if_t< !internal::has_to< Traits< T >, basic_value, T, With... > && internal::has_as< Traits< T >, basic_value, With... > > to_with( T& v, With&&... with ) const
+      {
+         v = Traits< std::decay_t< T > >::as( *this, with... );
+      }
+
+      template< typename T, typename... With >
+      std::enable_if_t< !internal::has_to< Traits< T >, basic_value, T, With... > && !internal::has_as< Traits< T >, basic_value, With... > > to_with( T& v, With&&... with ) const = delete;
+
+      template< typename T >
+      [[nodiscard]] std::optional< T > optional() const
+      {
+         if( is_null() ) {
+            return std::nullopt;
+         }
+         return as< T >();
+      }
+
+      template< typename T, typename K >
+      [[nodiscard]] std::optional< T > optional( const K& key ) const
+      {
+         if( const auto* p = find( key ) ) {
+            return p->template as< T >();
+         }
+         return std::nullopt;
+      }
+
+      void erase( const std::size_t index )
+      {
+         auto& a = get_array();
+         if( index >= a.size() ) {
+            throw_index_out_of_bound_exception( index );
+         }
+         a.erase( a.begin() + index );
+      }
+
+      template< typename Key >
+      std::enable_if_t< !std::is_convertible_v< Key, std::size_t > && !std::is_convertible_v< Key, pointer > > erase( const Key& key )
+      {
+         if( get_object().erase( key ) == 0 ) {
+            throw_key_not_found_exception( key );
+         }
+      }
+
+      void erase( const pointer& k )
+      {
+         if( !k ) {
+            throw std::runtime_error( internal::format( "invalid root JSON Pointer for erase", json::message_extension( *this ) ) );
+         }
+         const auto b = k.begin();
+         const auto e = std::prev( k.end() );
+         basic_value& v = internal::pointer_at( this, b, e );
+         if( v.is_object() ) {
+            v.erase( e->key() );
+         }
+         else if( v.is_array() ) {
+            v.erase( e->index() );
+         }
+         else {
+            throw internal::invalid_type( b, std::next( e ) );
+         }
+      }
+
+      basic_value& insert( const pointer& k, basic_value in )
+      {
+         if( !k ) {
+            *this = std::move( in );
+            return *this;
+         }
+         const auto b = k.begin();
+         const auto e = std::prev( k.end() );
+         basic_value& v = internal::pointer_at( this, b, e );
+         if( v.is_object() ) {
+            return v.get_object().insert_or_assign( e->key(), std::move( in ) ).first->second;
+         }
+         if( v.is_array() ) {
+            auto& a = v.get_array();
+            if( e->key() == "-" ) {
+               v.emplace_back( std::move( in ) );
+               return a.back();
+            }
+            const auto i = e->index();
+            if( i >= a.size() ) {
+               throw std::out_of_range( internal::format( "invalid JSON Pointer \"", internal::tokens_to_string( b, std::next( e ) ), "\", array index '", i, "' out of bound '", a.size(), '\'', json::message_extension( *this ) ) );
+            }
+            a.insert( a.begin() + i, std::move( in ) );
+            return a.at( i );
+         }
+         throw internal::invalid_type( b, std::next( e ) );
+      }
+
+      variant_t& variant() noexcept
+      {
+         return m_variant;
+      }
+
+      const variant_t& variant() const noexcept
+      {
+         return m_variant;
+      }
+
+   private:
+      template< typename T >
+      static void produce_from_opaque_ptr( events::virtual_base& consumer, const void* raw )
+      {
+         Traits< T >::template produce< Traits >( consumer, *static_cast< const T* >( raw ) );
+      }
+   };
+
+}  // namespace tao::json
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/binary.hpp b/3rdParty/taocpp-json/include/tao/json/binary.hpp
new file mode 100644
index 000000000000..c762fdf7f5b4
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/binary.hpp
@@ -0,0 +1,103 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_BINARY_HPP
+#define TAO_JSON_BINARY_HPP
+
+#include <cstddef>
+#include <vector>
+
+#include "external/pegtl/internal/always_false.hpp"
+
+namespace tao
+{
+   using binary = std::vector< std::byte >;
+
+}  // namespace tao
+
+namespace tao::json
+{
+   namespace internal
+   {
+      [[nodiscard]] constexpr char unhex_char( const char c ) noexcept
+      {
+         return static_cast< char >( ( c < 'A' ) ? ( c - '0' ) : ( ( c < 'a' ) ? ( c - 'A' + 10 ) : ( c - 'a' + 10 ) ) );
+      }
+
+      template< typename V, V... >
+      struct vlist;
+
+      template< typename T, typename L, char... Cs >
+      struct unhex_helper;
+
+      template< typename T, typename V, V... Vs >
+      struct unhex_helper< T, vlist< V, Vs... > >
+      {
+         [[nodiscard]] static constexpr T unhex()
+         {
+            return T{ Vs... };
+         }
+      };
+
+      template< typename T, typename V, V... Vs, char C >
+      struct unhex_helper< T, vlist< V, Vs... >, C >
+         : unhex_helper< T, vlist< V > >
+      {
+         static_assert( pegtl::internal::always_false< T >::value, "digits must occur in pairs" );
+      };
+
+      template< typename T, typename V, V... Vs, char C1, char... Cs >
+      struct unhex_helper< T, vlist< V, Vs... >, '\'', C1, Cs... >
+         : unhex_helper< T, vlist< V, Vs... >, C1, Cs... >
+      {
+      };
+
+      template< typename T, typename V, V... Vs, char C0, char... Cs >
+      struct unhex_helper< T, vlist< V, Vs... >, C0, '\'', Cs... >
+         : unhex_helper< T, vlist< V > >
+      {
+         static_assert( pegtl::internal::always_false< T >::value, "digit separator only allowed between pairs of digits" );
+      };
+
+      template< typename T, typename V, V... Vs, char C0, char C1, char... Cs >
+      struct unhex_helper< T, vlist< V, Vs... >, C0, C1, Cs... >
+         : unhex_helper< T, vlist< V, Vs..., V( ( unhex_char( C0 ) << 4 ) + unhex_char( C1 ) ) >, Cs... >
+      {
+      };
+
+      template< typename T, typename V, char C >
+      [[nodiscard]] constexpr T unhex()
+      {
+         static_assert( pegtl::internal::always_false< T >::value, "not a hex literal" );
+         return T{};
+      }
+
+      template< typename T, typename V, char C0, char C1, char... Cs >
+      [[nodiscard]] constexpr T unhex()
+      {
+         static_assert( C0 == '0', "not a hex literal" );
+         static_assert( C1 == 'x' || C1 == 'X', "not a hex literal" );
+         return unhex_helper< T, vlist< V >, Cs... >::unhex();
+      }
+
+      template< typename T, char... Cs >
+      [[nodiscard]] constexpr T unhex()
+      {
+         return unhex< T, typename T::value_type, Cs... >();
+      }
+
+   }  // namespace internal
+
+   inline namespace literals
+   {
+      template< char... Cs >
+      [[nodiscard]] std::vector< std::byte > operator"" _binary()
+      {
+         return internal::unhex< std::vector< std::byte >, Cs... >();
+      }
+
+   }  // namespace literals
+
+}  // namespace tao::json
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/binary_view.hpp b/3rdParty/taocpp-json/include/tao/json/binary_view.hpp
new file mode 100644
index 000000000000..9014b2e2ff91
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/binary_view.hpp
@@ -0,0 +1,31 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_BINARY_VIEW_HPP
+#define TAO_JSON_BINARY_VIEW_HPP
+
+#include "span.hpp"
+
+#include <algorithm>
+
+namespace tao
+{
+   using binary_view = span< const std::byte >;
+
+   namespace internal
+   {
+      [[nodiscard]] inline bool binary_equal( const binary_view lhs, const binary_view rhs ) noexcept
+      {
+         return std::equal( lhs.cbegin(), lhs.cend(), rhs.cbegin(), rhs.cend() );
+      }
+
+      [[nodiscard]] inline bool binary_less( const binary_view lhs, const binary_view rhs ) noexcept
+      {
+         return std::lexicographical_compare( lhs.cbegin(), lhs.cend(), rhs.cbegin(), rhs.cend() );
+      }
+
+   }  // namespace internal
+
+}  // namespace tao
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/binding.hpp b/3rdParty/taocpp-json/include/tao/json/binding.hpp
new file mode 100644
index 000000000000..7c0f861bec75
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/binding.hpp
@@ -0,0 +1,71 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_BINDING_HPP
+#define TAO_JSON_BINDING_HPP
+
+#include "binding/constant.hpp"
+#include "binding/element.hpp"
+#include "binding/factory.hpp"
+#include "binding/for_nothing_value.hpp"
+#include "binding/for_unknown_key.hpp"
+#include "binding/inherit.hpp"
+#include "binding/member.hpp"
+#include "binding/versions.hpp"
+
+#include "binding/internal/array.hpp"
+#include "binding/internal/inherit.hpp"
+#include "binding/internal/object.hpp"
+
+namespace tao::json::binding
+{
+   namespace internal
+   {
+      template< typename... As >
+      struct make_array
+      {
+         using list = json::internal::merge_type_lists< internal::inherit_elements< As >... >;
+         using type = internal::array< list >;
+      };
+
+   }  // namespace internal
+
+   template< typename... As >
+   using array = typename internal::make_array< As... >::type;
+
+   template< for_unknown_key E, for_nothing_value N, typename... As >
+   using basic_object = internal::basic_object< E, N, json::internal::merge_type_lists< internal::inherit_members< As >... > >;
+
+   template< typename... As >
+   using object = basic_object< for_unknown_key::fail, for_nothing_value::encode, As... >;
+
+}  // namespace tao::json::binding
+
+#define TAO_JSON_BIND_ELEMENT( ... ) tao::json::binding::element< __VA_ARGS__ >
+
+#define TAO_JSON_BIND_ELEMENT_BOOL( VaLue ) tao::json::binding::element_b< VaLue >
+#define TAO_JSON_BIND_ELEMENT_SIGNED( VaLue ) tao::json::binding::element_i< VaLue >
+#define TAO_JSON_BIND_ELEMENT_UNSIGNED( VaLue ) tao::json::binding::element_u< VaLue >
+#define TAO_JSON_BIND_ELEMENT_STRING( VaLue ) tao::json::binding::element_s< TAO_JSON_STRING_T( VaLue ) >
+
+#define TAO_JSON_BIND_REQUIRED( KeY, ... ) tao::json::binding::member< tao::json::binding::member_kind::required, TAO_JSON_STRING_T( KeY ), __VA_ARGS__ >
+#define TAO_JSON_BIND_OPTIONAL( KeY, ... ) tao::json::binding::member< tao::json::binding::member_kind::optional, TAO_JSON_STRING_T( KeY ), __VA_ARGS__ >
+
+#define TAO_JSON_BIND_REQUIRED_BOOL( KeY, VaLue ) tao::json::binding::member_b< tao::json::binding::member_kind::required, TAO_JSON_STRING_T( KeY ), VaLue >
+#define TAO_JSON_BIND_REQUIRED_SIGNED( KeY, VaLue ) tao::json::binding::member_i< tao::json::binding::member_kind::required, TAO_JSON_STRING_T( KeY ), VaLue >
+#define TAO_JSON_BIND_REQUIRED_UNSIGNED( KeY, VaLue ) tao::json::binding::member_u< tao::json::binding::member_kind::required, TAO_JSON_STRING_T( KeY ), VaLue >
+#define TAO_JSON_BIND_REQUIRED_STRING( KeY, VaLue ) tao::json::binding::member_s< tao::json::binding::member_kind::required, TAO_JSON_STRING_T( KeY ), TAO_JSON_STRING_T( VaLue ) >
+
+#define TAO_JSON_BIND_OPTIONAL_BOOL( KeY, VaLue ) tao::json::binding::member_b< tao::json::binding::member_kind::optional, TAO_JSON_STRING_T( KeY ), VaLue >
+#define TAO_JSON_BIND_OPTIONAL_SIGNED( KeY, VaLue ) tao::json::binding::member_i< tao::json::binding::member_kind::optional, TAO_JSON_STRING_T( KeY ), VaLue >
+#define TAO_JSON_BIND_OPTIONAL_UNSIGNED( KeY, VaLue ) tao::json::binding::member_u< tao::json::binding::member_kind::optional, TAO_JSON_STRING_T( KeY ), VaLue >
+#define TAO_JSON_BIND_OPTIONAL_STRING( KeY, VaLue ) tao::json::binding::member_s< tao::json::binding::member_kind::optional, TAO_JSON_STRING_T( KeY ), TAO_JSON_STRING_T( VaLue ) >
+
+#define TAO_JSON_BIND_REQUIRED1( ... ) tao::json::binding::member< tao::json::binding::member_kind::required, tao::json::binding::internal::use_default_key, __VA_ARGS__ >
+#define TAO_JSON_BIND_OPTIONAL1( ... ) tao::json::binding::member< tao::json::binding::member_kind::optional, tao::json::binding::internal::use_default_key, __VA_ARGS__ >
+
+#define TAO_JSON_FACTORY_BIND( KeY, ... ) tao::json::binding::internal::factory_temp< TAO_JSON_STRING_T( KeY ), __VA_ARGS__ >
+
+#define TAO_JSON_FACTORY_BIND1( ... ) tao::json::binding::internal::factory_temp< tao::json::binding::internal::use_default_key, __VA_ARGS__ >
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/binding/constant.hpp b/3rdParty/taocpp-json/include/tao/json/binding/constant.hpp
new file mode 100644
index 000000000000..193de3f0039c
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/binding/constant.hpp
@@ -0,0 +1,232 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_BINDING_CONSTANT_HPP
+#define TAO_JSON_BINDING_CONSTANT_HPP
+
+#include <cstdint>
+#include <string>
+
+#include "../external/pegtl/internal/pegtl_string.hpp"
+#include "../internal/escape.hpp"
+#include "../internal/format.hpp"
+#include "../internal/string_t.hpp"
+#include "../message_extension.hpp"
+
+#include "element.hpp"
+#include "member_kind.hpp"
+
+#include "internal/type_key.hpp"
+
+namespace tao::json::binding
+{
+   template< bool V >
+   struct element_b
+   {
+      using value_t = bool;
+
+      template< typename C >
+      [[nodiscard]] static bool read( const C& /*unused*/ )
+      {
+         return V;
+      }
+
+      template< template< typename... > class Traits, typename C >
+      static void to( const basic_value< Traits >& v, C& /*unused*/ )
+      {
+         const auto t = v.template as< bool >();
+         if( t != V ) {
+            throw std::runtime_error( json::internal::format( "boolean mismatch, expected '", V, "' parsed '", t, '\'', json::message_extension( v ) ) );
+         }
+      }
+
+      template< template< typename... > class Traits = traits, typename Consumer, typename C >
+      static void produce( Consumer& consumer, const C& /*unused*/ )
+      {
+         consumer.boolean( V );
+      }
+
+      template< template< typename... > class Traits = traits, typename Producer, typename C >
+      static void consume( Producer& parser, C& /*unused*/ )
+      {
+         const auto t = parser.boolean();
+         if( t != V ) {
+            parser.throw_parse_error( json::internal::format( "boolean mismatch, expected '", V, "' parsed '", t, '\'' ) );
+         }
+      }
+   };
+
+   template< std::int64_t V >
+   struct element_i
+   {
+      using value_t = std::int64_t;
+
+      template< typename C >
+      [[nodiscard]] static std::int64_t read( const C& /*unused*/ )
+      {
+         return V;
+      }
+
+      template< template< typename... > class Traits, typename C >
+      static void to( const basic_value< Traits >& v, C& /*unused*/ )
+      {
+         const auto t = v.template as< std::int64_t >();
+         if( t != V ) {
+            throw std::runtime_error( json::internal::format( "signed integer mismatch, expected '", V, "' parsed '", t, '\'', json::message_extension( v ) ) );
+         }
+      }
+
+      template< template< typename... > class Traits = traits, typename Consumer, typename C >
+      static void produce( Consumer& consumer, const C& /*unused*/ )
+      {
+         consumer.number( V );
+      }
+
+      template< template< typename... > class Traits = traits, typename Producer, typename C >
+      static void consume( Producer& parser, C& /*unused*/ )
+      {
+         const auto t = parser.number_signed();
+         if( t != V ) {
+            parser.throw_parse_error( json::internal::format( "signed integer mismatch, expected '", V, "' parsed '", t, '\'' ) );
+         }
+      }
+   };
+
+   template< std::uint64_t V >
+   struct element_u
+   {
+      using value_t = std::uint64_t;
+
+      template< typename C >
+      [[nodiscard]] static std::uint64_t read( const C& /*unused*/ )
+      {
+         return V;
+      }
+
+      template< template< typename... > class Traits, typename C >
+      static void to( const basic_value< Traits >& v, C& /*unused*/ )
+      {
+         const auto t = v.template as< std::uint64_t >();
+         if( t != V ) {
+            throw std::runtime_error( json::internal::format( "unsigned integer mismatch, expected '", V, "' parsed '", t, '\'', json::message_extension( v ) ) );
+         }
+      }
+
+      template< template< typename... > class Traits = traits, typename Consumer, typename C >
+      static void produce( Consumer& consumer, const C& /*unused*/ )
+      {
+         consumer.number( V );
+      }
+
+      template< template< typename... > class Traits = traits, typename Producer, typename C >
+      static void consume( Producer& parser, C& /*unused*/ )
+      {
+         const auto t = parser.number_unsigned();
+         if( t != V ) {
+            parser.throw_parse_error( json::internal::format( "unsigned integer mismatch, expected '", V, "' parsed '", t, '\'' ) );
+         }
+      }
+   };
+
+   template< typename S >
+   struct element_s;
+
+   template< char... Cs >
+   struct element_s< json::internal::string_t< Cs... > >
+   {
+      using value_t = std::string;  // TODO: Or std::string_view? Something else? Nothing?
+
+      using string = json::internal::string_t< Cs... >;
+
+      template< typename C >
+      [[nodiscard]] static std::string_view read( const C& /*unused*/ )
+      {
+         return string::as_string_view();
+      }
+
+      template< template< typename... > class Traits, typename C >
+      static void to( const basic_value< Traits >& v, C& /*unused*/ )
+      {
+         const auto sc = string::as_string_view();
+         const auto sv = v.template as< std::string_view >();
+         if( sv != sc ) {
+            throw std::runtime_error( json::internal::format( "string mismatch, expected \"", json::internal::escape( sc ), "\" parsed \"", json::internal::escape( sv ), '"', json::message_extension( v ) ) );
+         }
+      }
+
+      template< template< typename... > class Traits = traits, typename Consumer, typename T >
+      static void produce( Consumer& consumer, const T& /*unused*/ )
+      {
+         consumer.string( string::as_string_view() );
+      }
+
+      template< template< typename... > class Traits = traits, typename Producer, typename T >
+      static void consume( Producer& parser, T& /*unused*/ )
+      {
+         const auto sc = string::as_string_view();
+         const auto ss = parser.string();
+         if( ss != sc ) {
+            parser.throw_parse_error( json::internal::format( "string mismatch, expected \"", json::internal::escape( sc ), "\" parsed \"", json::internal::escape( ss ), '"' ) );
+         }
+      }
+   };
+
+   template< member_kind R, typename K, bool B >
+   struct member_b
+      : element_b< B >,
+        internal::type_key< K, void >
+   {
+      static constexpr member_kind kind = R;
+
+      template< template< typename... > class Traits, typename T >
+      [[nodiscard]] static bool is_nothing( const T& /*unused*/ )
+      {
+         return false;
+      }
+   };
+
+   template< member_kind R, typename K, std::int64_t V >
+   struct member_i
+      : element_i< V >,
+        internal::type_key< K, void >
+   {
+      static constexpr member_kind kind = R;
+
+      template< template< typename... > class Traits, typename T >
+      [[nodiscard]] static bool is_nothing( const T& /*unused*/ )
+      {
+         return false;
+      }
+   };
+
+   template< member_kind R, typename K, std::uint64_t V >
+   struct member_u
+      : element_u< V >,
+        internal::type_key< K, void >
+   {
+      static constexpr member_kind kind = R;
+
+      template< template< typename... > class Traits, typename T >
+      [[nodiscard]] static bool is_nothing( const T& /*unused*/ )
+      {
+         return false;
+      }
+   };
+
+   template< member_kind R, typename K, typename S >
+   struct member_s
+      : element_s< S >,
+        internal::type_key< K, void >
+   {
+      static constexpr member_kind kind = R;
+
+      template< template< typename... > class Traits, typename T >
+      [[nodiscard]] static bool is_nothing( const T& /*unused*/ )
+      {
+         return false;
+      }
+   };
+
+}  // namespace tao::json::binding
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/binding/element.hpp b/3rdParty/taocpp-json/include/tao/json/binding/element.hpp
new file mode 100644
index 000000000000..7fc0b5cf7f9f
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/binding/element.hpp
@@ -0,0 +1,182 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_BINDING_ELEMENT_HPP
+#define TAO_JSON_BINDING_ELEMENT_HPP
+
+#include <type_traits>
+
+#include "../consume.hpp"
+#include "../forward.hpp"
+
+#include "../events/produce.hpp"
+
+namespace tao::json::binding
+{
+   namespace internal
+   {
+      template< typename T, T, typename = void >
+      struct element;
+
+      template< typename C, typename T, T C::*P >
+      struct element< T C::*, P, std::enable_if_t< std::is_member_object_pointer_v< T C::* > > >
+      {
+         using class_t = C;
+         using value_t = T;
+
+         using internal_t = std::decay_t< decltype( std::declval< C >().*P ) >;
+
+         [[nodiscard]] static const auto& read( const C& v )
+         {
+            return v.*P;
+         }
+
+         template< typename W >
+         static void write( C& v, W&& w )
+         {
+            v.*P = std::forward< W >( w );
+         }
+
+         template< template< typename... > class Traits >
+         static void to( const basic_value< Traits >& v, C& x )
+         {
+            v.to( x.*P );
+         }
+
+         template< template< typename... > class Traits = traits, typename Producer >
+         static void consume( Producer& parser, C& v )
+         {
+            json::consume< Traits >( parser, v.*P );
+         }
+
+         template< template< typename... > class Traits = traits, typename Consumer >
+         static void produce( Consumer& consumer, const C& v )
+         {
+            events::produce< Traits >( consumer, v.*P );
+         }
+      };
+
+      template< typename C, typename T, T C::*P >
+      struct element< T C::*, P, std::enable_if_t< std::is_member_function_pointer_v< T C::* > > >
+      {
+         using class_t = C;
+         using value_t = T;
+
+         using internal_t = std::decay_t< decltype( ( std::declval< const C >().*P )() ) >;
+
+         [[nodiscard]] static decltype( auto ) read( const C& v )
+         {
+            return ( v.*P )();
+         }
+
+         template< template< typename... > class Traits = traits, typename Consumer >
+         static void produce( Consumer& consumer, const C& v )
+         {
+            events::produce< Traits >( consumer, ( v.*P )() );
+         }
+      };
+
+      template< typename C, typename T, T ( *P )( const C& ) >
+      struct element< T ( * )( const C& ), P >
+      {
+         using class_t = C;
+         using value_t = T;
+
+         [[nodiscard]] static decltype( auto ) read( const C& v )
+         {
+            return P( v );
+         }
+
+         template< template< typename... > class Traits = traits, typename Consumer >
+         static void produce( Consumer& consumer, const C& v )
+         {
+            events::produce< Traits >( consumer, P( v ) );
+         }
+      };
+
+      template< typename CT, CT CP, typename T, T P >
+      struct element2;
+
+      template< typename A, typename CR, CR ( *CP )( const A& ) noexcept, typename R, R ( *P )( A& ) noexcept >
+      struct element2< CR ( * )( const A& ) noexcept, CP, R ( * )( A& ) noexcept, P >
+      {
+         using class_t = A;
+         using value_t = std::decay_t< R >;
+
+         [[nodiscard]] static decltype( auto ) read( const A& v ) noexcept
+         {
+            return CP( v );
+         }
+
+         template< typename W >
+         static void write( A& v, W&& w )
+         {
+            P( v ) = std::forward< W >( w );
+         }
+
+         template< template< typename... > class Traits >
+         static void to( const basic_value< Traits >& v, A& x )
+         {
+            v.to( P( x ) );
+         }
+
+         template< template< typename... > class Traits = traits, typename Producer >
+         static void consume( Producer& parser, A& v )
+         {
+            json::consume< Traits >( parser, P( v ) );
+         }
+
+         template< template< typename... > class Traits = traits, typename Consumer >
+         static void produce( Consumer& consumer, const A& v )
+         {
+            events::produce< Traits >( consumer, CP( v ) );
+         }
+      };
+
+      template< typename A, typename CR, CR ( *CP )( const A& ) noexcept, typename R, void ( *P )( A&, R&& ) noexcept >
+      struct element2< CR ( * )( const A& ) noexcept, CP, void ( * )( A&, R&& ) noexcept, P >
+      {
+         using class_t = A;
+         using value_t = std::decay_t< R >;
+
+         [[nodiscard]] static decltype( auto ) read( const A& v ) noexcept
+         {
+            return CP( v );
+         }
+
+         template< typename W >
+         static void write( A& v, W&& w )
+         {
+            P( v, std::forward< W >( w ) );
+         }
+
+         template< template< typename... > class Traits >
+         static void to( const basic_value< Traits >& v, A& x )
+         {
+            P( x, v.template as< std::decay_t< R > >() );
+         }
+
+         template< template< typename... > class Traits = traits, typename Producer >
+         static void consume( Producer& parser, A& v )
+         {
+            P( v, json::consume< Traits >( parser ) );
+         }
+
+         template< template< typename... > class Traits = traits, typename Consumer >
+         static void produce( Consumer& consumer, const A& v )
+         {
+            events::produce< Traits >( consumer, CP( v ) );
+         }
+      };
+
+   }  // namespace internal
+
+   template< auto P >
+   using element = internal::element< decltype( P ), P >;
+
+   template< auto CP, auto P >
+   using element2 = internal::element2< decltype( CP ), CP, decltype( P ), P >;
+
+}  // namespace tao::json::binding
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/binding/factory.hpp b/3rdParty/taocpp-json/include/tao/json/binding/factory.hpp
new file mode 100644
index 000000000000..28362f1867be
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/binding/factory.hpp
@@ -0,0 +1,250 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_BINDING_FACTORY_HPP
+#define TAO_JSON_BINDING_FACTORY_HPP
+
+#include <bitset>
+#include <map>
+#include <sstream>
+#include <stdexcept>
+#include <string>
+
+#include "../forward.hpp"
+
+#include "../basic_value.hpp"
+#include "../external/pegtl/internal/pegtl_string.hpp"
+#include "../internal/escape.hpp"
+#include "../internal/format.hpp"
+#include "../internal/string_t.hpp"
+
+#include "internal/type_key.hpp"
+
+namespace tao::json::binding
+{
+   namespace internal
+   {
+      template< typename... Ts >
+      void list_all_types( std::ostream& oss, const std::map< std::string, Ts... >& m )
+      {
+         for( const auto& i : m ) {
+            json::internal::format_to( oss, " \"", i.first, '\"' );
+         }
+      }
+
+      template< typename... Ts >
+      void list_all_types( std::ostream& oss, const std::map< const std::type_info*, Ts... >& m )
+      {
+         for( const auto& i : m ) {
+            json::internal::format_to( oss, ' ', i.first->name() );
+         }
+      }
+
+      template< typename K, typename T, typename Base, template< typename... > class Pointer >
+      struct factory_type
+         : type_key< K, T >
+      {
+         [[nodiscard]] static const std::type_info* type()
+         {
+            return &typeid( T );
+         }
+
+         template< template< typename... > class Traits, typename... With >
+         [[nodiscard]] static Pointer< Base > as( const basic_value< Traits >& v, With&... with )
+         {
+            using R = typename Traits< Pointer< T > >::template with_base< Base >;
+            return R::as( v, with... );
+         }
+
+         template< template< typename... > class Traits >
+         static void assign( basic_value< Traits >& v, const Pointer< Base >& p )
+         {
+            using R = typename Traits< Pointer< T > >::template with_base< Base >;
+            R::assign( v, p );
+         }
+
+         template< template< typename... > class Traits, typename Producer >
+         [[nodiscard]] static Pointer< Base > consume( Producer& parser )
+         {
+            using R = typename Traits< Pointer< T > >::template with_base< Base >;
+            return R::template consume< Traits >( parser );
+         }
+
+         template< template< typename... > class Traits, typename Consumer >
+         static void produce( Consumer& c, const Pointer< Base >& p )
+         {
+            using R = typename Traits< Pointer< T > >::template with_base< Base >;
+            R::template produce< Traits >( c, p );
+         }
+      };
+
+      template< typename K, typename T >
+      struct factory_temp
+      {
+         template< typename Base, template< typename... > class Pointer >
+         using bind = factory_type< K, T, Base, Pointer >;
+      };
+
+      template< template< typename... > class Traits, template< typename... > class Pointer, typename Base, typename... With >
+      using as_func_t = Pointer< Base > ( * )( const basic_value< Traits >&, With&... );
+
+   }  // namespace internal
+
+   template< typename... Ts >
+   struct factory
+   {
+      template< typename F >
+      struct entry1
+      {
+         explicit entry1( F c )
+            : function( c )
+         {}
+
+         F function;
+      };
+
+      template< typename F >
+      struct entry2
+      {
+         entry2( F c, std::string&& n )
+            : function( c ),
+              name( std::move( n ) )
+         {}
+
+         F function;
+         std::string name;
+      };
+
+      template< typename V, template< typename... > class Traits, template< typename... > class Pointer, typename Base, typename... With >
+      static void emplace_as( std::map< std::string, entry1< internal::as_func_t< Traits, Pointer, Base, With... > >, std::less<> >& m )
+      {
+         using W = typename V::template bind< Base, Pointer >;
+         m.try_emplace( W::template key< Traits >(), entry1< internal::as_func_t< Traits, Pointer, Base, With... > >( &W::template as< Traits, With... > ) );
+      }
+
+      template< template< typename... > class Traits, template< typename... > class Pointer, typename Base, typename... With >
+      static void to( const basic_value< Traits >& v, Pointer< Base >& r, With&... with )
+      {
+         static const std::map< std::string, entry1< internal::as_func_t< Traits, Pointer, Base, With... > >, std::less<> > m = []() {
+            std::map< std::string, entry1< internal::as_func_t< Traits, Pointer, Base, With... > >, std::less<> > t;
+            ( emplace_as< Ts >( t ), ... );
+            assert( t.size() == sizeof...( Ts ) );
+            return t;
+         }();
+
+         const auto& a = v.get_object();
+         if( a.size() != 1 ) {
+            throw std::runtime_error( json::internal::format( "polymorphic factory requires object of size one for base class ", pegtl::internal::demangle< Base >(), json::message_extension( v ) ) );
+         }
+         const auto b = a.begin();
+         const auto i = m.find( b->first );
+         if( i == m.end() ) {
+            std::ostringstream oss;
+            json::internal::format_to( oss, "unknown factory type \"", json::internal::escape( b->first ), "\" -- known are" );
+            internal::list_all_types( oss, m );
+            json::internal::format_to( oss, " for base class ", pegtl::internal::demangle< Base >(), json::message_extension( v ) );
+            throw std::runtime_error( oss.str() );
+         }
+         r = i->second.function( b->second, with... );
+      }
+
+      template< typename V, template< typename... > class Traits, template< typename... > class Pointer, typename Base, typename F >
+      static void emplace_assign( std::map< const std::type_info*, entry2< F >, json::internal::type_info_less >& m )
+      {
+         using W = typename V::template bind< Base, Pointer >;
+         m.try_emplace( W::type(), entry2< F >( &W::template assign< Traits >, W::template key< Traits >() ) );
+      }
+
+      template< template< typename... > class Traits, template< typename... > class Pointer, typename Base >
+      static void assign( basic_value< Traits >& v, const Pointer< Base >& p )
+      {
+         using F = void ( * )( basic_value< Traits >&, const Pointer< Base >& );
+         static const std::map< const std::type_info*, entry2< F >, json::internal::type_info_less > m = []() {
+            std::map< const std::type_info*, entry2< F >, json::internal::type_info_less > t;
+            ( emplace_assign< Ts, Traits, Pointer, Base >( t ), ... );
+            assert( t.size() == sizeof...( Ts ) );
+            return t;
+         }();
+
+         const auto i = m.find( &typeid( *p ) );
+         if( i == m.end() ) {
+            std::ostringstream oss;
+            json::internal::format_to( oss, "unknown factory type ", pegtl::internal::demangle< decltype( *p ) >(), " -- known are" );
+            internal::list_all_types( oss, m );
+            json::internal::format_to( oss, " for base class ", pegtl::internal::demangle< Base >() );
+            throw std::runtime_error( oss.str() );
+         }
+         i->second.function( v, p );
+         v = {
+            { i->second.name, std::move( v ) }
+         };
+      }
+
+      template< typename V, template< typename... > class Traits, template< typename... > class Pointer, typename Base, typename Producer, typename F >
+      static void emplace_consume( std::map< std::string, entry1< F >, std::less<> >& m )
+      {
+         using W = typename V::template bind< Base, Pointer >;
+         m.try_emplace( W::template key< Traits >(), entry1< F >( &W::template consume< Traits, Producer > ) );
+      }
+
+      template< template< typename... > class Traits, template< typename... > class Pointer, typename Base, typename Producer >
+      static void consume( Producer& parser, Pointer< Base >& r )
+      {
+         using F = Pointer< Base > ( * )( Producer& );
+         static const std::map< std::string, entry1< F >, std::less<> > m = []() {
+            std::map< std::string, entry1< F >, std::less<> > t;
+            ( emplace_consume< Ts, Traits, Pointer, Base, Producer >( t ), ... );
+            return t;
+         }();
+
+         auto s = parser.begin_object();
+         const auto k = parser.key();
+         const auto i = m.find( k );
+         if( i == m.end() ) {
+            std::ostringstream oss;
+            json::internal::format_to( oss, "unknown factory type \"", json::internal::escape( k ), "\" -- known are" );
+            internal::list_all_types( oss, m );
+            json::internal::format_to( oss, " for base class ", pegtl::internal::demangle< Base >() );
+            throw std::runtime_error( oss.str() );
+         }
+         r = i->second.function( parser );
+         parser.end_object( s );
+      }
+
+      template< typename V, template< typename... > class Traits, template< typename... > class Pointer, typename Base, typename Consumer, typename F >
+      static void emplace_produce( std::map< const std::type_info*, entry2< F >, json::internal::type_info_less >& m )
+      {
+         using W = typename V::template bind< Base, Pointer >;
+         m.try_emplace( W::type(), entry2< F >( &W::template produce< Traits, Consumer >, W::template key< Traits >() ) );
+      }
+
+      template< template< typename... > class Traits, template< typename... > class Pointer, typename Base, typename Consumer >
+      static void produce( Consumer& consumer, const Pointer< Base >& p )
+      {
+         using F = void ( * )( Consumer&, const Pointer< Base >& );
+         static const std::map< const std::type_info*, entry2< F >, json::internal::type_info_less > m = []() {
+            std::map< const std::type_info*, entry2< F >, json::internal::type_info_less > t;
+            ( emplace_produce< Ts, Traits, Pointer, Base, Consumer >( t ), ... );
+            assert( t.size() == sizeof...( Ts ) );
+            return t;
+         }();
+
+         const auto i = m.find( &typeid( *p ) );
+         if( i == m.end() ) {
+            std::ostringstream oss;
+            json::internal::format_to( oss, "unknown factory type ", pegtl::internal::demangle< decltype( *p ) >(), " -- known are" );
+            internal::list_all_types( oss, m );
+            json::internal::format_to( oss, " for base class ", pegtl::internal::demangle< Base >() );
+            throw std::runtime_error( oss.str() );
+         }
+         consumer.begin_object( 1 );
+         consumer.key( i->second.name );
+         i->second.function( consumer, p );
+         consumer.member();
+         consumer.end_object( 1 );
+      }
+   };
+
+}  // namespace tao::json::binding
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/binding/for_nothing_value.hpp b/3rdParty/taocpp-json/include/tao/json/binding/for_nothing_value.hpp
new file mode 100644
index 000000000000..6fbae902999d
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/binding/for_nothing_value.hpp
@@ -0,0 +1,17 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_BINDING_FOR_NOTHING_VALUE_HPP
+#define TAO_JSON_BINDING_FOR_NOTHING_VALUE_HPP
+
+namespace tao::json::binding
+{
+   enum class for_nothing_value : bool
+   {
+      encode,
+      suppress
+   };
+
+}  // namespace tao::json::binding
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/binding/for_unknown_key.hpp b/3rdParty/taocpp-json/include/tao/json/binding/for_unknown_key.hpp
new file mode 100644
index 000000000000..07e1e2ed648c
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/binding/for_unknown_key.hpp
@@ -0,0 +1,17 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_BINDING_FOR_UNKNOWN_KEY_HPP
+#define TAO_JSON_BINDING_FOR_UNKNOWN_KEY_HPP
+
+namespace tao::json::binding
+{
+   enum class for_unknown_key : bool
+   {
+      fail,
+      skip
+   };
+
+}  // namespace tao::json::binding
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/binding/inherit.hpp b/3rdParty/taocpp-json/include/tao/json/binding/inherit.hpp
new file mode 100644
index 000000000000..ea6ddcdda456
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/binding/inherit.hpp
@@ -0,0 +1,14 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_BINDING_INHERIT_HPP
+#define TAO_JSON_BINDING_INHERIT_HPP
+
+namespace tao::json::binding
+{
+   template< typename T >
+   struct inherit;
+
+}  // namespace tao::json::binding
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/binding/internal/array.hpp b/3rdParty/taocpp-json/include/tao/json/binding/internal/array.hpp
new file mode 100644
index 000000000000..72896dcb12f8
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/binding/internal/array.hpp
@@ -0,0 +1,103 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_BINDING_INTERNAL_ARRAY_HPP
+#define TAO_JSON_BINDING_INTERNAL_ARRAY_HPP
+
+#include <utility>
+#include <vector>
+
+#include "../../basic_value.hpp"
+#include "../../forward.hpp"
+
+#include "../../internal/format.hpp"
+#include "../../internal/type_traits.hpp"
+
+namespace tao::json::binding::internal
+{
+   template< typename T, typename L = std::make_index_sequence< T::size > >
+   struct array;
+
+   template< typename... As, std::size_t... Is >
+   struct array< json::internal::type_list< As... >, std::index_sequence< Is... > >
+   {
+      using elements = json::internal::type_list< As... >;
+
+      template< template< typename... > class Traits, typename C >
+      static const std::vector< basic_value< Traits > >& get_array_impl( const basic_value< Traits >& v )
+      {
+         const auto& a = v.get_array();
+         if( a.size() != sizeof...( As ) ) {
+            throw std::runtime_error( json::internal::format( "array size mismatch for type ", pegtl::internal::demangle< C >(), " -- expected ", sizeof...( As ), " received ", a.size(), json::message_extension( v ) ) );
+         }
+         return a;
+      }
+
+      template< template< typename... > class Traits, typename C >
+      static std::enable_if_t< std::is_constructible_v< C, typename As::value_t... >, C > as_type( const basic_value< Traits >& v )
+      {
+         const auto& a = get_array_impl< Traits, C >( v );
+         return C( a[ Is ].template as< typename As::value_t >()... );
+      }
+
+      template< template< typename... > class Traits, typename C >
+      static void to( const basic_value< Traits >& v, C& x )  // TODO: std::enable_if_t< WHAT?, void >
+      {
+         const auto& a = get_array_impl< Traits, C >( v );
+         ( As::to( a[ Is ], x ), ... );
+      }
+
+      template< template< typename... > class Traits, typename C >
+      static void assign( basic_value< Traits >& v, const C& x )
+      {
+         v.emplace_array();
+         ( v.emplace_back( As::read( x ) ), ... );
+      }
+
+      template< typename A, template< typename... > class Traits = traits, typename Producer, typename C, typename State >
+      static void consume_element( Producer& parser, C& x, State& s )
+      {
+         parser.element( s );
+         A::template consume< Traits >( parser, x );
+      }
+
+      template< template< typename... > class Traits = traits, typename Producer, typename C >
+      static void consume( Producer& parser, C& x )
+      {
+         auto s = parser.begin_array();
+         ( consume_element< As, Traits >( parser, x, s ), ... );
+         parser.end_array( s );
+      }
+
+      template< typename A, template< typename... > class Traits, typename Consumer, typename C >
+      static void produce_element( Consumer& consumer, const C& x )
+      {
+         A::template produce< Traits >( consumer, x );
+         consumer.element();
+      }
+
+      template< template< typename... > class Traits = traits, typename Consumer, typename C >
+      static void produce( Consumer& consumer, const C& x )
+      {
+         consumer.begin_array( sizeof...( As ) );
+         ( produce_element< As, Traits >( consumer, x ), ... );
+         consumer.end_array( sizeof...( As ) );
+      }
+
+      template< template< typename... > class Traits, typename C >
+      [[nodiscard]] static bool equal( const basic_value< Traits >& lhs, const C& rhs ) noexcept
+      {
+         const auto& p = lhs.skip_value_ptr();
+         if( p.is_array() ) {
+            const auto& a = p.get_array();
+            if( a.size() == sizeof...( As ) ) {
+               return ( ( a[ Is ] == As::read( rhs ) ) && ... );
+            }
+         }
+         return false;
+      }
+   };
+
+}  // namespace tao::json::binding::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/binding/internal/inherit.hpp b/3rdParty/taocpp-json/include/tao/json/binding/internal/inherit.hpp
new file mode 100644
index 000000000000..09bfc0a826ea
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/binding/internal/inherit.hpp
@@ -0,0 +1,45 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_BINDING_INTERNAL_INHERIT_HPP
+#define TAO_JSON_BINDING_INTERNAL_INHERIT_HPP
+
+#include "../../internal/type_traits.hpp"
+
+#include "../inherit.hpp"
+
+namespace tao::json::binding::internal
+{
+   template< typename T >
+   struct inherit_elements_t
+   {
+      using list = json::internal::type_list< T >;
+   };
+
+   template< typename T >
+   struct inherit_elements_t< inherit< T > >
+   {
+      using list = typename T::elements;
+   };
+
+   template< typename T >
+   using inherit_elements = typename inherit_elements_t< T >::list;
+
+   template< typename T >
+   struct inherit_members_t
+   {
+      using list = json::internal::type_list< T >;
+   };
+
+   template< typename T >
+   struct inherit_members_t< inherit< T > >
+   {
+      using list = typename T::members;
+   };
+
+   template< typename T >
+   using inherit_members = typename inherit_members_t< T >::list;
+
+}  // namespace tao::json::binding::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/binding/internal/object.hpp b/3rdParty/taocpp-json/include/tao/json/binding/internal/object.hpp
new file mode 100644
index 000000000000..733784bbd1c8
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/binding/internal/object.hpp
@@ -0,0 +1,267 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_BINDING_INTERNAL_OBJECT_HPP
+#define TAO_JSON_BINDING_INTERNAL_OBJECT_HPP
+
+#include <bitset>
+#include <map>
+#include <sstream>
+#include <stdexcept>
+#include <string>
+#include <utility>
+
+#include "../for_nothing_value.hpp"
+#include "../for_unknown_key.hpp"
+#include "../member_kind.hpp"
+
+#include "../../forward.hpp"
+
+#include "../../basic_value.hpp"
+#include "../../internal/escape.hpp"
+#include "../../internal/format.hpp"
+#include "../../internal/type_traits.hpp"
+
+#ifdef _MSC_VER
+#pragma warning( push )
+#pragma warning( disable : 4702 )
+#endif
+
+namespace tao::json::binding::internal
+{
+   template< typename... Ts >
+   void list_all_keys( std::ostream& oss, const std::map< std::string, Ts... >& m )
+   {
+      for( const auto& p : m ) {
+         json::internal::format_to( oss, ' ', p.first );
+      }
+   }
+
+   template< std::size_t N, typename... Ts >
+   void list_missing_keys( std::ostream& oss, const std::bitset< N >& t, const std::map< std::string, Ts... >& m )
+   {
+      for( const auto& p : m ) {
+         if( !t.test( p.second.index ) ) {
+            json::internal::format_to( oss, ' ', p.first );
+         }
+      }
+   }
+
+   template< typename... As, std::size_t... Is >
+   auto make_bitset( std::index_sequence< Is... > /*unused*/ ) noexcept
+   {
+      std::bitset< sizeof...( As ) > r;
+      ( r.set( Is, As::kind == member_kind::optional ), ... );
+      return r;
+   }
+
+   template< typename F >
+   struct wrap
+   {
+      F function;
+      std::size_t index;
+   };
+
+   template< typename A, typename C, template< typename... > class Traits >
+   void wrap_to( const basic_value< Traits >& v, C& x )
+   {
+      A::template to< Traits >( v, x );
+   }
+
+   template< template< typename... > class Traits, typename C, typename... As, std::size_t... Is >
+   auto make_map_to( std::index_sequence< Is... > /*unused*/ )
+   {
+      using F = void ( * )( const basic_value< Traits >&, C& );
+      return std::map< std::string, wrap< F > >{
+         { As::template key< Traits >(), { &wrap_to< As, C, Traits >, Is } }...
+      };
+   }
+
+   template< typename A, typename C, template< typename... > class Traits, typename Producer >
+   void wrap_consume( Producer& p, C& x )
+   {
+      A::template consume< Traits, Producer >( p, x );
+   }
+
+   template< typename C, template< typename... > class Traits, typename Producer, typename... As, std::size_t... Is >
+   auto make_map_consume( std::index_sequence< Is... > /*unused*/ )
+   {
+      using F = void ( * )( Producer&, C& );
+      return std::map< std::string, wrap< F > >{
+         { As::template key< Traits >(), { &wrap_consume< As, C, Traits, Producer >, Is } }...
+      };
+   }
+
+   template< for_unknown_key E, for_nothing_value N, typename T >
+   struct basic_object;
+
+   template< for_unknown_key E, for_nothing_value N, typename... As >
+   struct basic_object< E, N, json::internal::type_list< As... > >
+   {
+      using members = json::internal::type_list< As... >;
+
+      template< template< typename... > class Traits, typename C >
+      static void to( const basic_value< Traits >& v, C& x )
+      {
+         static const auto m = make_map_to< Traits, C, As... >( std::index_sequence_for< As... >() );
+         static const auto o = make_bitset< As... >( std::index_sequence_for< As... >() );
+
+         const auto& a = v.get_object();
+         std::bitset< sizeof...( As ) > b;
+         for( const auto& p : a ) {
+            const auto& k = p.first;
+            const auto i = m.find( k );
+            if( i == m.end() ) {
+               if constexpr( E == for_unknown_key::skip ) {
+                  continue;
+               }
+               std::ostringstream oss;
+               json::internal::format_to( oss, "unknown object key \"", json::internal::escape( k ), "\" -- known are" );
+               list_all_keys( oss, m );
+               json::internal::format_to( oss, " for type ", pegtl::internal::demangle< C >(), json::message_extension( v ) );
+               throw std::runtime_error( oss.str() );
+            }
+            i->second.function( p.second, x );
+            b.set( i->second.index );
+         }
+         b |= o;
+         if( !b.all() ) {
+            std::ostringstream oss;
+            json::internal::format_to( oss, "missing required key(s)" );
+            list_missing_keys( oss, b, m );
+            json::internal::format_to( oss, " for type ", pegtl::internal::demangle< C >(), json::message_extension( v ) );
+            throw std::runtime_error( oss.str() );
+         }
+      }
+
+#ifdef _MSC_VER
+#pragma warning( push )
+#pragma warning( disable : 4127 )
+#endif
+      template< typename A, template< typename... > class Traits, typename C >
+      static void assign_member( basic_value< Traits >& v, const C& x )
+      {
+         if( ( N == for_nothing_value::encode ) || ( !A::template is_nothing< Traits >( x ) ) ) {
+            v.try_emplace( A::template key< Traits >(), A::read( x ) );
+         }
+      }
+#ifdef _MSC_VER
+#pragma warning( pop )
+#endif
+
+      template< template< typename... > class Traits, typename C >
+      static void assign( basic_value< Traits >& v, const C& x )
+      {
+         v.emplace_object();
+         ( assign_member< As >( v, x ), ... );
+      }
+
+      template< template< typename... > class Traits = traits, typename Producer, typename C >
+      static void consume( Producer& parser, C& x )
+      {
+         static const auto m = make_map_consume< C, Traits, Producer, As... >( std::index_sequence_for< As... >() );
+         static const auto o = make_bitset< As... >( std::index_sequence_for< As... >() );
+
+         auto s = parser.begin_object();
+         std::bitset< sizeof...( As ) > b;
+         while( parser.member_or_end_object( s ) ) {
+            const auto k = parser.key();
+            const auto i = m.find( k );
+            if( i == m.end() ) {
+               if constexpr( E == for_unknown_key::skip ) {
+                  parser.skip_value();
+                  continue;
+               }
+               std::ostringstream oss;
+               json::internal::format_to( oss, "unknown object key \"", json::internal::escape( k ), "\" -- known are" );
+               list_all_keys( oss, m );
+               json::internal::format_to( oss, " for type ", pegtl::internal::demangle< C >() );
+               parser.throw_parse_error( oss.str() );
+            }
+            if( b.test( i->second.index ) ) {
+               parser.throw_parse_error( json::internal::format( "duplicate object key \"", json::internal::escape( k ), "\" for type ", pegtl::internal::demangle< C >() ) );
+            }
+            i->second.function( parser, x );
+            b.set( i->second.index );
+         }
+         b |= o;
+         if( !b.all() ) {
+            std::ostringstream oss;
+            json::internal::format_to( oss, "missing required key(s)" );
+            list_missing_keys( oss, b, m );
+            json::internal::format_to( oss, " for type ", pegtl::internal::demangle< C >() );
+            parser.throw_parse_error( oss.str() );
+         }
+      }
+
+      template< template< typename... > class Traits, typename C >
+      [[nodiscard]] static std::size_t produce_size( const C& x )
+      {
+         if constexpr( N == for_nothing_value::encode ) {
+            return sizeof...( As );
+         }
+         return ( std::size_t( !As::template is_nothing< Traits >( x ) ) + ... );
+      }
+
+#ifdef _MSC_VER
+#pragma warning( push )
+#pragma warning( disable : 4127 )
+#endif
+
+      template< typename A, template< typename... > class Traits, typename Consumer, typename C >
+      static void produce_member( Consumer& consumer, const C& x )
+      {
+         if( ( N == for_nothing_value::encode ) || ( !A::template is_nothing< Traits >( x ) ) ) {
+            A::template produce_key< Traits >( consumer );
+            A::template produce< Traits >( consumer, x );
+            consumer.member();
+         }
+      }
+
+#ifdef _MSC_VER
+#pragma warning( pop )
+#endif
+
+      template< template< typename... > class Traits = traits, typename Consumer, typename C >
+      static void produce( Consumer& consumer, const C& x )
+      {
+         const auto size = produce_size< Traits >( x );
+         consumer.begin_object( size );
+         ( produce_member< As, Traits >( consumer, x ), ... );
+         consumer.end_object( size );
+      }
+
+      template< typename A, template< typename... > class Traits, typename C >
+      [[nodiscard]] static bool equal_member( const std::map< std::string, basic_value< Traits >, std::less<> >& a, C& x )
+      {
+         if( !A::template is_nothing< Traits >( x ) ) {
+            return a.at( A::template key< Traits >() ) == A::read( x );
+         }
+         if constexpr( N == for_nothing_value::encode ) {
+            return a.at( A::template key< Traits >() ).is_null();
+         }
+         const auto i = a.find( A::template key< Traits >() );
+         return ( i == a.end() ) || i->second.is_null();
+      }
+
+      template< template< typename... > class Traits, typename C >
+      [[nodiscard]] static bool equal( const basic_value< Traits >& lhs, const C& rhs ) noexcept
+      {
+         const auto& p = lhs.skip_value_ptr();
+         if( p.is_object() ) {
+            const auto& a = p.get_object();
+            if( p.get_object().size() == sizeof...( As ) ) {
+               return ( equal_member< As >( a, rhs ) && ... );
+            }
+         }
+         return false;
+      }
+   };
+
+}  // namespace tao::json::binding::internal
+
+#ifdef _MSC_VER
+#pragma warning( pop )
+#endif
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/binding/internal/type_key.hpp b/3rdParty/taocpp-json/include/tao/json/binding/internal/type_key.hpp
new file mode 100644
index 000000000000..fd42a51e4106
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/binding/internal/type_key.hpp
@@ -0,0 +1,54 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_BINDING_INTERNAL_TYPE_KEY_HPP
+#define TAO_JSON_BINDING_INTERNAL_TYPE_KEY_HPP
+
+#include <string>
+
+#include "../../internal/string_t.hpp"
+#include "../../internal/type_traits.hpp"
+
+namespace tao::json::binding::internal
+{
+   struct use_default_key
+   {};
+
+   template< typename K, typename V >
+   struct type_key;
+
+   template< char... Cs, typename V >
+   struct type_key< json::internal::string_t< Cs... >, V >
+   {
+      template< template< typename... > class Traits >
+      [[nodiscard]] static std::string key()
+      {
+         return json::internal::string_t< Cs... >::as_string();
+      }
+
+      template< template< typename... > class Traits = traits, typename Consumer >
+      static void produce_key( Consumer& consumer )
+      {
+         consumer.key( json::internal::string_t< Cs... >::as_string_view() );
+      }
+   };
+
+   template< typename V >
+   struct type_key< use_default_key, V >
+   {
+      template< template< typename... > class Traits >
+      [[nodiscard]] static std::string key()
+      {
+         return Traits< V >::template default_key< Traits >::as_string();
+      }
+
+      template< template< typename... > class Traits = traits, typename Consumer >
+      static void produce_key( Consumer& consumer )
+      {
+         consumer.key( Traits< V >::template default_key< Traits >::as_string_view() );
+      }
+   };
+
+}  // namespace tao::json::binding::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/binding/member.hpp b/3rdParty/taocpp-json/include/tao/json/binding/member.hpp
new file mode 100644
index 000000000000..eb785a34cad5
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/binding/member.hpp
@@ -0,0 +1,32 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_BINDING_MEMBER_HPP
+#define TAO_JSON_BINDING_MEMBER_HPP
+
+#include <string>
+
+#include "element.hpp"
+#include "member_kind.hpp"
+
+#include "internal/type_key.hpp"
+
+namespace tao::json::binding
+{
+   template< member_kind R, typename K, auto P >
+   struct member
+      : element< P >,
+        internal::type_key< K, typename binding::element< P >::internal_t >
+   {
+      static constexpr member_kind kind = R;
+
+      template< template< typename... > class Traits, typename C >
+      [[nodiscard]] static bool is_nothing( const C& x )
+      {
+         return json::internal::is_nothing< Traits >( binding::element< P >::read( x ) );
+      }
+   };
+
+}  // namespace tao::json::binding
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/binding/member_kind.hpp b/3rdParty/taocpp-json/include/tao/json/binding/member_kind.hpp
new file mode 100644
index 000000000000..019dad0881c8
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/binding/member_kind.hpp
@@ -0,0 +1,17 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_BINDING_MEMBER_KIND_HPP
+#define TAO_JSON_BINDING_MEMBER_KIND_HPP
+
+namespace tao::json::binding
+{
+   enum class member_kind : bool
+   {
+      optional,
+      required
+   };
+
+}  // namespace tao::json::binding
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/binding/versions.hpp b/3rdParty/taocpp-json/include/tao/json/binding/versions.hpp
new file mode 100644
index 000000000000..5759c5e93b73
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/binding/versions.hpp
@@ -0,0 +1,127 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_BINDING_VERSIONS_HPP
+#define TAO_JSON_BINDING_VERSIONS_HPP
+
+#include <exception>
+#include <stdexcept>
+
+#include "../forward.hpp"
+#include "../internal/format.hpp"
+#include "../internal/type_traits.hpp"
+
+namespace tao::json::binding
+{
+   template< typename... Vs >
+   struct versions;
+
+   template< typename V >
+   struct versions< V >
+      : V
+   {};
+
+   template< typename V, typename... Vs >
+   struct versions< V, Vs... >
+      : V
+   {
+      template< typename C >
+      static void throw_on_error( const bool ok, const std::exception_ptr& e )
+      {
+         if( !ok ) {
+            try {
+               std::rethrow_exception( e );  // TODO: Did I miss a way to avoid the throw?
+            }
+            catch( ... ) {
+               std::throw_with_nested( std::runtime_error( json::internal::format( "all versions failed for type ", pegtl::internal::demangle< C >(), " -- see nested for first error" ) ) );
+            }
+         }
+      }
+
+      template< template< typename... > class Traits, typename C >
+      [[nodiscard]] static std::exception_ptr first_to( const basic_value< Traits >& v, C& x ) noexcept
+      {
+         try {
+            if constexpr( json::internal::has_to< V, basic_value< Traits >, C > ) {
+               V::to( v, x );
+            }
+            else if constexpr( json::internal::has_as< V, basic_value< Traits > > ) {
+               x = V::as( v );
+            }
+            else {
+               static_assert( std::is_void_v< V >, "neither V::to() nor V::as() found" );
+            }
+            return std::exception_ptr();
+         }
+         catch( ... ) {
+            return std::current_exception();
+         }
+      }
+
+      template< typename A, template< typename... > class Traits, typename C >
+      [[nodiscard]] static bool later_to( const basic_value< Traits >& v, C& x ) noexcept
+      {
+         try {
+            if constexpr( json::internal::has_to< A, basic_value< Traits >, C > ) {
+               A::to( v, x );
+            }
+            else if constexpr( json::internal::has_as< A, basic_value< Traits > > ) {
+               x = A::as( v );
+            }
+            else {
+               static_assert( std::is_void_v< A >, "neither A::to() nor A::as() found" );
+            }
+            return true;
+         }
+         catch( ... ) {
+            return false;
+         }
+      }
+
+      template< template< typename... > class Traits, typename C >
+      static void to( const basic_value< Traits >& v, C& x )
+      {
+         const std::exception_ptr e = first_to( v, x );
+         const bool ok = ( ( e == std::exception_ptr() ) || ... || later_to< Vs >( v, x ) );
+         throw_on_error< C >( ok, e );
+      }
+
+      template< template< typename... > class Traits, typename Producer, typename C >
+      [[nodiscard]] static std::exception_ptr first_consume( Producer& parser, C& x )
+      {
+         try {
+            auto m = parser.mark();
+            V::template consume< Traits >( parser, x );
+            (void)m( true );
+            return std::exception_ptr();
+         }
+         catch( ... ) {
+            return std::current_exception();
+         }
+      }
+
+      template< typename A, template< typename... > class Traits, typename Producer, typename C >
+      [[nodiscard]] static bool later_consume( Producer& parser, C& x )
+      {
+         try {
+            auto m = parser.mark();
+            A::template consume< Traits >( parser, x );
+            return m( true );
+         }
+         catch( ... ) {
+            return false;
+         }
+      }
+
+      template< template< typename... > class Traits, typename Producer, typename C >
+      static void consume( Producer& parser, C& x )
+      {
+         const std::exception_ptr e = first_consume< Traits >( parser, x );
+         const bool ok = ( ( e == std::exception_ptr() ) || ... || later_consume< Vs, Traits >( parser, x ) );
+         throw_on_error< C >( ok, e );
+      }
+   };
+
+}  // namespace tao::json::binding
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/consume.hpp b/3rdParty/taocpp-json/include/tao/json/consume.hpp
new file mode 100644
index 000000000000..7ec5ebae40bc
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/consume.hpp
@@ -0,0 +1,43 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_CONSUME_HPP
+#define TAO_JSON_CONSUME_HPP
+
+#include <type_traits>
+
+#include "forward.hpp"
+
+#include "internal/type_traits.hpp"
+
+namespace tao::json
+{
+   template< typename T, template< typename... > class Traits = traits, typename Producer >
+   [[nodiscard]] std::enable_if_t< internal::has_consume_one< Traits, Producer, T >, T > consume( Producer& parser )
+   {
+      return Traits< T >::template consume< Traits >( parser );
+   }
+
+   template< typename T, template< typename... > class Traits = traits, typename Producer >
+   [[nodiscard]] std::enable_if_t< !internal::has_consume_one< Traits, Producer, T >, T > consume( Producer& parser )
+   {
+      T t;
+      Traits< T >::template consume< Traits >( parser, t );
+      return t;
+   }
+
+   template< template< typename... > class Traits = traits, typename Producer, typename T >
+   std::enable_if_t< internal::has_consume_two< Traits, Producer, T >, void > consume( Producer& parser, T& t )
+   {
+      Traits< T >::template consume< Traits >( parser, t );
+   }
+
+   template< template< typename... > class Traits = traits, typename Producer, typename T >
+   std::enable_if_t< !internal::has_consume_two< Traits, Producer, T >, void > consume( Producer& parser, T& t )
+   {
+      t = Traits< T >::template consume< Traits >( parser );
+   }
+
+}  // namespace tao::json
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/consume_file.hpp b/3rdParty/taocpp-json/include/tao/json/consume_file.hpp
new file mode 100644
index 000000000000..1ed6c5b23c28
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/consume_file.hpp
@@ -0,0 +1,33 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_CONSUME_FILE_HPP
+#define TAO_JSON_CONSUME_FILE_HPP
+
+#include <utility>
+
+#include "external/pegtl/file_input.hpp"
+
+#include "consume.hpp"
+#include "forward.hpp"
+#include "parts_parser.hpp"
+
+namespace tao::json
+{
+   template< typename T, template< typename... > class Traits = traits, typename F >
+   [[nodiscard]] T consume_file( F&& filename )
+   {
+      basic_parts_parser< pegtl::file_input< pegtl::tracking_mode::lazy > > pp( std::forward< F >( filename ) );
+      return consume< T, Traits >( pp );
+   }
+
+   template< template< typename... > class Traits = traits, typename F, typename T >
+   void consume_file( F&& filename, T& t )
+   {
+      basic_parts_parser< pegtl::file_input< pegtl::tracking_mode::lazy > > pp( std::forward< F >( filename ) );
+      consume< Traits >( pp, t );
+   }
+
+}  // namespace tao::json
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/consume_string.hpp b/3rdParty/taocpp-json/include/tao/json/consume_string.hpp
new file mode 100644
index 000000000000..5c1573d82a89
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/consume_string.hpp
@@ -0,0 +1,31 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_CONSUME_STRING_HPP
+#define TAO_JSON_CONSUME_STRING_HPP
+
+#include "external/pegtl/string_input.hpp"
+
+#include "consume.hpp"
+#include "forward.hpp"
+#include "parts_parser.hpp"
+
+namespace tao::json
+{
+   template< typename T, template< typename... > class Traits = traits, typename F >
+   [[nodiscard]] T consume_string( F&& string )
+   {
+      basic_parts_parser< pegtl::memory_input< pegtl::tracking_mode::lazy, pegtl::eol::lf_crlf, const char* > > pp( string, __FUNCTION__ );
+      return consume< T, Traits >( pp );
+   }
+
+   template< template< typename... > class Traits = traits, typename F, typename T >
+   void consume_string( F&& string, T& t )
+   {
+      basic_parts_parser< pegtl::memory_input< pegtl::tracking_mode::lazy, pegtl::eol::lf_crlf, const char* > > pp( string, __FUNCTION__ );
+      consume< Traits >( pp, t );
+   }
+
+}  // namespace tao::json
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/contrib/array_traits.hpp b/3rdParty/taocpp-json/include/tao/json/contrib/array_traits.hpp
new file mode 100644
index 000000000000..e05bef5e15f2
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/contrib/array_traits.hpp
@@ -0,0 +1,43 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_CONTRIB_ARRAY_TRAITS_HPP
+#define TAO_JSON_CONTRIB_ARRAY_TRAITS_HPP
+
+#include <array>
+
+#include "../consume.hpp"
+#include "../forward.hpp"
+
+#include "internal/array_traits.hpp"
+
+namespace tao::json
+{
+   template< typename T, std::size_t N >
+   struct array_traits
+      : internal::array_traits< std::array< T, N > >
+   {
+      template< template< typename... > class Traits, typename... With >
+      static void to( const basic_value< Traits >& v, std::array< T, N >& r, With&... with )
+      {
+         const auto& a = v.get_array();
+         for( std::size_t i = 0; i < N; ++i ) {
+            v.to_with( r[ i ], with... );
+         }
+      }
+
+      template< template< typename... > class Traits, typename Producer >
+      static void consume( Producer& parser, std::array< T, N >& r )
+      {
+         auto s = parser.begin_array();
+         for( std::size_t i = 0; i < N; ++i ) {
+            parser.element( s );
+            json::consume< Traits >( parser, r[ i ] );
+         }
+         parser.end_array( s );
+      }
+   };
+
+}  // namespace tao::json
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/contrib/deque_traits.hpp b/3rdParty/taocpp-json/include/tao/json/contrib/deque_traits.hpp
new file mode 100644
index 000000000000..7ffbbd9455b3
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/contrib/deque_traits.hpp
@@ -0,0 +1,41 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_CONTRIB_DEQUE_TRAITS_HPP
+#define TAO_JSON_CONTRIB_DEQUE_TRAITS_HPP
+
+#include <deque>
+
+#include "../consume.hpp"
+#include "../forward.hpp"
+
+#include "internal/array_traits.hpp"
+
+namespace tao::json
+{
+   template< typename T, typename... Ts >
+   struct deque_traits
+      : internal::array_traits< std::deque< T, Ts... > >
+   {
+      template< template< typename... > class Traits, typename... With >
+      static void to( const basic_value< Traits >& v, std::deque< T, Ts... >& r, With&... with )
+      {
+         const auto& a = v.get_array();
+         for( const auto& i : a ) {
+            r.emplace_back( i.template as_with< T >( with... ) );
+         }
+      }
+
+      template< template< typename... > class Traits, typename Producer >
+      static void consume( Producer& parser, std::vector< T, Ts... >& v )
+      {
+         auto s = parser.begin_array();
+         while( parser.element_or_end_array( s ) ) {
+            v.emplace_back( json::consume< T, Traits >( parser ) );
+         }
+      }
+   };
+
+}  // namespace tao::json
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/contrib/diff.hpp b/3rdParty/taocpp-json/include/tao/json/contrib/diff.hpp
new file mode 100644
index 000000000000..579f3d9c1c91
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/contrib/diff.hpp
@@ -0,0 +1,106 @@
+// Copyright (c) 2019-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_CONTRIB_DIFF_HPP
+#define TAO_JSON_CONTRIB_DIFF_HPP
+
+#include <algorithm>
+#include <iterator>
+#include <stdexcept>
+#include <utility>
+
+#include "../pointer.hpp"
+#include "../value.hpp"
+
+namespace tao::json
+{
+   namespace internal
+   {
+      template< typename... Ts >
+      void move_append( std::vector< Ts... >& lhs, std::vector< Ts... >& rhs )
+      {
+         if( lhs.empty() ) {
+            lhs = std::move( rhs );
+         }
+         else if( !rhs.empty() ) {
+            lhs.reserve( lhs.size() + rhs.size() );
+            std::move( std::begin( rhs ), std::end( rhs ), std::back_inserter( lhs ) );
+         }
+      }
+
+   }  // namespace internal
+
+   template< template< typename... > class Traits >
+   [[nodiscard]] basic_value< Traits > diff( const basic_value< Traits >& source, const basic_value< Traits >& destination, const pointer& path = pointer() )
+   {
+      basic_value< Traits > result = empty_array;
+      if( source == destination ) {
+         return result;
+      }
+      if( source.type() != destination.type() ) {
+         result.push_back( { { "op", "replace" },
+                             { "path", to_string( path ) },
+                             { "value", destination } } );
+      }
+      else {
+         auto& a = result.get_array();
+         switch( source.type() ) {
+            case type::ARRAY: {
+               const auto ss = source.get_array().size();
+               const auto ds = destination.get_array().size();
+               std::size_t i = 0;
+               while( ( i < ss ) && ( i < ds ) ) {
+                  internal::move_append( a, diff( source.at( i ), destination.at( i ), path + i ).get_array() );
+                  ++i;
+               }
+               const auto s = ss + i - 1;
+               while( i < ss ) {
+                  result.push_back( { { "op", "remove" },
+                                      { "path", to_string( path + ( s - i ) ) } } );
+                  ++i;
+               }
+               while( i < ds ) {
+                  result.push_back( { { "op", "add" },
+                                      { "path", to_string( path + i ) },
+                                      { "value", destination.at( i ) } } );
+                  ++i;
+               }
+            } break;
+
+            case type::OBJECT: {
+               const auto& sm = source.get_object();
+               const auto& dm = destination.get_object();
+               auto sit = sm.begin();
+               auto dit = dm.begin();
+               while( ( sit != sm.end() ) || ( dit != dm.end() ) ) {
+                  if( ( sit == sm.end() ) || ( ( dit != dm.end() ) && ( sit->first > dit->first ) ) ) {
+                     result.push_back( { { "op", "add" },
+                                         { "path", to_string( path + dit->first ) },
+                                         { "value", dit->second } } );
+                     ++dit;
+                  }
+                  else if( ( dit == dm.end() ) || ( ( sit != sm.end() ) && ( sit->first < dit->first ) ) ) {
+                     result.push_back( { { "op", "remove" },
+                                         { "path", to_string( path + sit->first ) } } );
+                     ++sit;
+                  }
+                  else {
+                     internal::move_append( a, diff( sit->second, dit->second, path + sit->first ).get_array() );
+                     ++sit;
+                     ++dit;
+                  }
+               }
+            } break;
+
+            default:
+               result.push_back( { { "op", "replace" },
+                                   { "path", to_string( path ) },
+                                   { "value", destination } } );
+         }
+      }
+      return result;
+   }
+
+}  // namespace tao::json
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/contrib/get.hpp b/3rdParty/taocpp-json/include/tao/json/contrib/get.hpp
new file mode 100644
index 000000000000..e83dda1315bc
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/contrib/get.hpp
@@ -0,0 +1,152 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_CONTRIB_GET_HPP
+#define TAO_JSON_CONTRIB_GET_HPP
+
+#include "../basic_value.hpp"
+
+namespace tao::json::get
+{
+   namespace internal
+   {
+      template< template< typename... > class Traits >
+      [[nodiscard]] const basic_value< Traits >* find( const basic_value< Traits >& v, const std::string& key )
+      {
+         return v.find( key );
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] const basic_value< Traits >* find( const basic_value< Traits >& v, const std::size_t index )
+      {
+         const auto& a = v.get_array();
+         return ( index < a.size() ) ? ( a.data() + index ) : nullptr;
+      }
+
+   }  // namespace internal
+
+   template< template< typename... > class Traits, typename K >
+   [[nodiscard]] basic_value< Traits > value( const basic_value< Traits >& v, const K& key )
+   {
+      if( const auto& w = v.skip_value_ptr() ) {
+         if( const auto* p = internal::find( w, key ) ) {
+            return basic_value< Traits >( &p->skip_value_ptr() );  // Returns a Value with tao::json::type::VALUE_PTR that is invalidated when v is destroyed!
+         }
+      }
+      return basic_value< Traits >();
+   }
+
+   template< template< typename... > class Traits, typename K, typename... Ks >
+   [[nodiscard]] basic_value< Traits > value( const basic_value< Traits >& v, const K& key, const Ks&... ks )
+   {
+      if( const auto& w = v.skip_value_ptr() ) {
+         if( const auto* p = internal::find( w, key ) ) {
+            return get::value( *p, ks... );
+         }
+      }
+      return basic_value< Traits >();
+   }
+
+   template< typename T, typename U, template< typename... > class Traits >
+   [[nodiscard]] T as( const basic_value< Traits >& v )
+   {
+      return v.skip_value_ptr().template as< U >();
+   }
+
+   template< typename T, template< typename... > class Traits >
+   [[nodiscard]] auto as( const basic_value< Traits >& v )
+   {
+      return as< T, T >( v );
+   }
+
+   template< typename T, typename U, template< typename... > class Traits, typename K, typename... Ks >
+   [[nodiscard]] T as( const basic_value< Traits >& v, const K& key, Ks&&... ks )
+   {
+      return get::as< T, U >( v.skip_value_ptr().at( key ), ks... );
+   }
+
+   template< typename T, template< typename... > class Traits, typename K, typename... Ks >
+   [[nodiscard]] auto as( const basic_value< Traits >& v, const K& key, Ks&&... ks )
+   {
+      return as< T, T >( v, key, ks... );
+   }
+
+   template< typename T, template< typename... > class Traits >
+   void to( const basic_value< Traits >& v, T& t )
+   {
+      v.skip_value_ptr().to( t );
+   }
+
+   template< typename T, template< typename... > class Traits, typename K, typename... Ks >
+   void to( const basic_value< Traits >& v, T& t, const K& key, Ks&&... ks )
+   {
+      get::to( v.skip_value_ptr().at( key ), t, ks... );
+   }
+
+   template< typename T, typename U, template< typename... > class Traits >
+   [[nodiscard]] std::optional< T > optional( const basic_value< Traits >& v )
+   {
+      if( const auto& w = v.skip_value_ptr() ) {
+         return std::optional< T >( std::in_place, get::as< U >( w ) );
+      }
+      return std::nullopt;
+   }
+
+   template< typename T, template< typename... > class Traits >
+   [[nodiscard]] auto optional( const basic_value< Traits >& v )
+   {
+      return optional< T, T >( v );
+   }
+
+   template< typename T, typename U, template< typename... > class Traits, typename K, typename... Ks >
+   [[nodiscard]] std::optional< T > optional( const basic_value< Traits >& v, const K& key, const Ks&... ks )
+   {
+      if( const auto& w = v.skip_value_ptr() ) {
+         if( const auto* p = internal::find( w, key ) ) {
+            return get::optional< T, U >( *p, ks... );
+         }
+      }
+      return std::nullopt;
+   }
+
+   template< typename T, template< typename... > class Traits, typename K, typename... Ks >
+   [[nodiscard]] auto optional( const basic_value< Traits >& v, const K& key, const Ks&... ks )
+   {
+      return optional< T, T >( v, key, ks... );
+   }
+
+   template< typename T, typename U, template< typename... > class Traits >
+   [[nodiscard]] T defaulted( const T& t, const basic_value< Traits >& v )
+   {
+      if( const auto& w = v.skip_value_ptr() ) {
+         return get::as< T, U >( w );
+      }
+      return t;
+   }
+
+   template< typename T, template< typename... > class Traits >
+   [[nodiscard]] auto defaulted( const T& t, const basic_value< Traits >& v )
+   {
+      return defaulted< T, T >( t, v );
+   }
+
+   template< typename T, typename U, template< typename... > class Traits, typename K, typename... Ks >
+   [[nodiscard]] T defaulted( const T& t, const basic_value< Traits >& v, const K& key, const Ks&... ks )
+   {
+      if( const auto& w = v.skip_value_ptr() ) {
+         if( const auto* p = internal::find( w, key ) ) {
+            return get::defaulted< T, U >( t, *p, ks... );
+         }
+      }
+      return t;
+   }
+
+   template< typename T, template< typename... > class Traits, typename K, typename... Ks >
+   [[nodiscard]] auto defaulted( const T& t, const basic_value< Traits >& v, const K& key, const Ks&... ks )
+   {
+      return defaulted< T, T >( t, v, key, ks... );
+   }
+
+}  // namespace tao::json::get
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/contrib/internal/array_traits.hpp b/3rdParty/taocpp-json/include/tao/json/contrib/internal/array_traits.hpp
new file mode 100644
index 000000000000..6d59cf7b1e99
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/contrib/internal/array_traits.hpp
@@ -0,0 +1,92 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_CONTRIB_INTERNAL_ARRAY_TRAITS_HPP
+#define TAO_JSON_CONTRIB_INTERNAL_ARRAY_TRAITS_HPP
+
+#include <algorithm>
+
+#include "../../forward.hpp"
+#include "../../type.hpp"
+
+#include "../../events/produce.hpp"
+
+namespace tao::json::internal
+{
+   template< typename T >
+   struct array_multi_traits
+   {
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool is_nothing( const T& o )
+      {
+         return o.empty();
+      }
+
+      template< template< typename... > class Traits >
+      static void assign( basic_value< Traits >& v, const T& o ) = delete;
+
+      template< template< typename... > class Traits, typename Consumer >
+      static void produce( Consumer& c, const T& o )
+      {
+         c.begin_array( o.size() );
+         for( const auto& i : o ) {
+            json::events::produce< Traits >( c, i );
+            c.element();
+         }
+         c.end_array( o.size() );
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool equal( const basic_value< Traits >& lhs, const T& rhs ) noexcept
+      {
+         const auto& p = lhs.skip_value_ptr();
+         if( !p.is_array() ) {
+            return false;
+         }
+         const auto& a = p.get_array();
+         return ( a.size() == rhs.size() ) && std::equal( rhs.begin(), rhs.end(), a.begin() );
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool less_than( const basic_value< Traits >& lhs, const T& rhs ) noexcept
+      {
+         const auto& p = lhs.skip_value_ptr();
+         const auto t = p.type();
+         if( t != type::ARRAY ) {
+            return t < type::ARRAY;
+         }
+         const auto& a = p.get_array();
+         return std::lexicographical_compare( a.begin(), a.end(), rhs.begin(), rhs.end() );
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool greater_than( const basic_value< Traits >& lhs, const T& rhs ) noexcept
+      {
+         const auto& p = lhs.skip_value_ptr();
+         const auto t = p.type();
+         if( t != type::ARRAY ) {
+            return t > type::ARRAY;
+         }
+         const auto& a = p.get_array();
+         return std::lexicographical_compare( rhs.begin(), rhs.end(), a.begin(), a.end() );
+      }
+   };
+
+   template< typename T >
+   struct array_traits
+      : array_multi_traits< T >
+   {
+      template< template< typename... > class Traits >
+      static void assign( basic_value< Traits >& v, const T& o )
+      {
+         v.emplace_array();
+         v.get_array().reserve( o.size() );
+         for( const auto& e : o ) {
+            v.emplace_back( e );
+         }
+      }
+   };
+
+}  // namespace tao::json::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/contrib/internal/indirect_traits.hpp b/3rdParty/taocpp-json/include/tao/json/contrib/internal/indirect_traits.hpp
new file mode 100644
index 000000000000..7022b3252fea
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/contrib/internal/indirect_traits.hpp
@@ -0,0 +1,69 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_CONTRIB_INTERNAL_INDIRECT_TRAITS_HPP
+#define TAO_JSON_CONTRIB_INTERNAL_INDIRECT_TRAITS_HPP
+
+#include <cassert>
+
+#include "../../forward.hpp"
+#include "../../type.hpp"
+
+#include "../../events/produce.hpp"
+
+#include "../../internal/type_traits.hpp"
+
+namespace tao::json::internal
+{
+   template< typename T >
+   struct indirect_traits
+   {
+      template< typename U >
+      [[nodiscard]] static const U& add_const( const U& u )
+      {
+         return u;
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool is_nothing( const T& o )
+      {
+         assert( o );
+         return internal::is_nothing< Traits >( add_const( *o ) );
+      }
+
+      template< template< typename... > class Traits >
+      static void assign( basic_value< Traits >& v, const T& o )
+      {
+         assert( o );
+         v = add_const( *o );
+      }
+
+      template< template< typename... > class Traits, typename Consumer >
+      static void produce( Consumer& c, const T& o )
+      {
+         assert( o );
+         json::events::produce< Traits >( c, add_const( *o ) );
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool equal( const basic_value< Traits >& lhs, const T& rhs ) noexcept
+      {
+         return rhs ? ( lhs == *rhs ) : ( lhs == null );
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool less_than( const basic_value< Traits >& lhs, const T& rhs ) noexcept
+      {
+         return rhs ? ( lhs < *rhs ) : ( lhs < null );
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool greater_than( const basic_value< Traits >& lhs, const T& rhs ) noexcept
+      {
+         return rhs ? ( lhs > *rhs ) : ( lhs > null );
+      }
+   };
+
+}  // namespace tao::json::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/contrib/internal/object_traits.hpp b/3rdParty/taocpp-json/include/tao/json/contrib/internal/object_traits.hpp
new file mode 100644
index 000000000000..7f531de67ffe
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/contrib/internal/object_traits.hpp
@@ -0,0 +1,105 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_CONTRIB_INTERNAL_OBJECT_TRAITS_HPP
+#define TAO_JSON_CONTRIB_INTERNAL_OBJECT_TRAITS_HPP
+
+#include <algorithm>
+#include <string>
+
+#include "../../forward.hpp"
+#include "../../type.hpp"
+
+#include "../../events/produce.hpp"
+
+namespace tao::json::internal
+{
+   template< typename T >
+   struct object_multi_traits
+   {
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool is_nothing( const T& o )
+      {
+         return o.empty();
+      }
+
+      template< template< typename... > class Traits >
+      static void assign( basic_value< Traits >& v, const T& o ) = delete;
+
+      template< template< typename... > class Traits, typename Consumer >
+      static void produce( Consumer& c, const T& o )
+      {
+         c.begin_object( o.size() );
+         for( const auto& i : o ) {
+            c.key( i.first );
+            json::events::produce< Traits >( c, i.second );
+            c.member();
+         }
+         c.end_object( o.size() );
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool equal( const basic_value< Traits >& lhs, const T& rhs ) noexcept
+      {
+         static const auto eq = []( const typename T::value_type& r, const std::pair< const std::string, basic_value< Traits > >& l ) {
+            return ( l.first == r.first ) && ( l.second == r.second );
+         };
+         const auto& p = lhs.skip_value_ptr();
+         if( !p.is_object() ) {
+            return false;
+         }
+         const auto& o = p.get_object();
+         return ( o.size() == rhs.size() ) && std::equal( rhs.begin(), rhs.end(), o.begin(), eq );
+      }
+
+      struct pair_less
+      {
+         template< typename L, typename R >
+         [[nodiscard]] bool operator()( const L& l, const R& r ) const noexcept
+         {
+            return ( l.first < r.first ) || ( ( l.first == r.first ) && ( l.second < r.second ) );
+         }
+      };
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool less_than( const basic_value< Traits >& lhs, const T& rhs ) noexcept
+      {
+         const auto& p = lhs.skip_value_ptr();
+         const auto t = p.type();
+         if( t != type::OBJECT ) {
+            return t < type::OBJECT;
+         }
+         const auto& o = p.get_object();
+         return std::lexicographical_compare( o.begin(), o.end(), rhs.begin(), rhs.end(), pair_less() );
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool greater_than( const basic_value< Traits >& lhs, const T& rhs ) noexcept
+      {
+         const auto& p = lhs.skip_value_ptr();
+         const auto t = p.type();
+         if( t != type::OBJECT ) {
+            return t > type::OBJECT;
+         }
+         const auto& o = p.get_object();
+         return std::lexicographical_compare( rhs.begin(), rhs.end(), o.begin(), o.end(), pair_less() );
+      }
+   };
+
+   template< typename T >
+   struct object_traits
+      : object_multi_traits< T >
+   {
+      template< template< typename... > class Traits >
+      static void assign( basic_value< Traits >& v, const T& o )
+      {
+         v.prepare_object();
+         for( const auto& i : o ) {
+            v.try_emplace( i.first, i.second );
+         }
+      }
+   };
+
+}  // namespace tao::json::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/contrib/internal/type_traits.hpp b/3rdParty/taocpp-json/include/tao/json/contrib/internal/type_traits.hpp
new file mode 100644
index 000000000000..4cdf44b0bf12
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/contrib/internal/type_traits.hpp
@@ -0,0 +1,36 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_CONTRIB_INTERNAL_TYPE_TRAITS_HPP
+#define TAO_JSON_CONTRIB_INTERNAL_TYPE_TRAITS_HPP
+
+#include "../../forward.hpp"
+
+#include "../../internal/type_traits.hpp"
+
+namespace tao::json::internal
+{
+   template< typename T, template< typename... > class Traits, typename... With >
+   inline constexpr bool use_first_ptr_as = std::is_constructible_v< T, const basic_value< Traits >&, With&... >;
+
+   template< typename T, template< typename... > class Traits, typename... With >
+   inline constexpr bool use_second_ptr_as = !use_first_ptr_as< T, Traits, With... > && std::is_move_constructible_v< T > && has_as< Traits< T >, basic_value< Traits >, With... >;
+
+   template< typename T, template< typename... > class Traits, typename... With >
+   inline constexpr bool use_third_ptr_as = !use_first_ptr_as< T, Traits, With... > && !use_second_ptr_as< T, Traits, With... > && std::is_default_constructible_v< T > && has_to< Traits< T >, basic_value< Traits >, T, With... >;
+
+   template< typename T, template< typename... > class Traits, typename... With >
+   inline constexpr bool use_fourth_ptr_as = !use_first_ptr_as< T, Traits, With... > && !use_third_ptr_as< T, Traits, With... > && std::is_copy_constructible_v< T > && has_as< Traits< T >, basic_value< Traits >, With... >;
+
+   template< typename T, template< typename... > class Traits, class Producer >
+   inline constexpr bool use_first_ptr_consume = std::is_move_constructible_v< T >&& has_consume_one< Traits, Producer, T >;
+
+   template< typename T, template< typename... > class Traits, class Producer >
+   inline constexpr bool use_second_ptr_consume = !use_first_ptr_consume< T, Traits, Producer > && std::is_default_constructible_v< T > && has_consume_two< Traits, Producer, T >;
+
+   template< typename T, template< typename... > class Traits, class Producer >
+   inline constexpr bool use_third_ptr_consume = !use_second_ptr_consume< T, Traits, Producer > && std::is_copy_constructible_v< T > && has_consume_one< Traits, Producer, T >;
+
+}  // namespace tao::json::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/contrib/list_traits.hpp b/3rdParty/taocpp-json/include/tao/json/contrib/list_traits.hpp
new file mode 100644
index 000000000000..5416cd0e7bed
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/contrib/list_traits.hpp
@@ -0,0 +1,41 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_CONTRIB_LIST_TRAITS_HPP
+#define TAO_JSON_CONTRIB_LIST_TRAITS_HPP
+
+#include <list>
+
+#include "../consume.hpp"
+#include "../forward.hpp"
+
+#include "internal/array_traits.hpp"
+
+namespace tao::json
+{
+   template< typename T, typename... Ts >
+   struct list_traits
+      : internal::array_traits< std::list< T, Ts... > >
+   {
+      template< template< typename... > class Traits, typename... With >
+      static void to( const basic_value< Traits >& v, std::list< T, Ts... >& r, With&... with )
+      {
+         const auto& a = v.get_array();
+         for( const auto& i : a ) {
+            r.emplace_back( i.template as_with< T >( with... ) );
+         }
+      }
+
+      template< template< typename... > class Traits, typename Producer >
+      static void consume( Producer& parser, std::list< T, Ts... >& r )
+      {
+         auto s = parser.begin_array();
+         while( parser.element_or_end_array( s ) ) {
+            r.emplace_back( json::consume< T, Traits >( parser ) );
+         }
+      }
+   };
+
+}  // namespace tao::json
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/contrib/map_traits.hpp b/3rdParty/taocpp-json/include/tao/json/contrib/map_traits.hpp
new file mode 100644
index 000000000000..c0c9e3e21b6d
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/contrib/map_traits.hpp
@@ -0,0 +1,43 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_CONTRIB_MAP_TRAITS_HPP
+#define TAO_JSON_CONTRIB_MAP_TRAITS_HPP
+
+#include <map>
+#include <string>
+
+#include "../consume.hpp"
+#include "../forward.hpp"
+
+#include "internal/object_traits.hpp"
+
+namespace tao::json
+{
+   template< typename T, typename... Ts >
+   struct map_traits
+      : internal::object_traits< std::map< std::string, T, Ts... > >
+   {
+      template< template< typename... > class Traits, typename... With >
+      static void to( const basic_value< Traits >& v, std::map< std::string, T, Ts... >& r, With&... with )
+      {
+         const auto& o = v.get_object();
+         for( const auto& i : o ) {
+            r.try_emplace( i.first, i.second.template as_with< T >( with... ) );
+         }
+      }
+
+      template< template< typename... > class Traits, typename Producer >
+      static void consume( Producer& parser, std::map< std::string, T, Ts... >& v )
+      {
+         auto s = parser.begin_object();
+         while( parser.member_or_end_object( s ) ) {
+            auto k = parser.key();
+            v.try_emplace( std::move( k ), json::consume< T, Traits >( parser ) );
+         }
+      }
+   };
+
+}  // namespace tao::json
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/contrib/multimap_traits.hpp b/3rdParty/taocpp-json/include/tao/json/contrib/multimap_traits.hpp
new file mode 100644
index 000000000000..ee480395fe2a
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/contrib/multimap_traits.hpp
@@ -0,0 +1,43 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_CONTRIB_MULTIMAP_TRAITS_HPP
+#define TAO_JSON_CONTRIB_MULTIMAP_TRAITS_HPP
+
+#include <map>
+#include <string>
+
+#include "../consume.hpp"
+#include "../forward.hpp"
+
+#include "internal/object_traits.hpp"
+
+namespace tao::json
+{
+   template< typename T, typename... Ts >
+   struct multimap_traits
+      : internal::object_multi_traits< std::multimap< std::string, T, Ts... > >
+   {
+      template< template< typename... > class Traits, typename... With >
+      static void to( const basic_value< Traits >& v, std::multimap< std::string, T, Ts... >& r, With&... with )
+      {
+         const auto& o = v.get_object();
+         for( const auto& i : o ) {
+            r.try_emplace( i.first, i.second.template as_with< T >( with... ) );
+         }
+      }
+
+      template< template< typename... > class Traits, typename Producer >
+      static void consume( Producer& parser, std::multimap< std::string, T, Ts... >& v )
+      {
+         auto s = parser.begin_object();
+         while( parser.member_or_end_object( s ) ) {
+            auto k = parser.key();
+            v.try_emplace( std::move( k ), json::consume< T, Traits >( parser ) );
+         }
+      }
+   };
+
+}  // namespace tao::json
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/contrib/multiset_traits.hpp b/3rdParty/taocpp-json/include/tao/json/contrib/multiset_traits.hpp
new file mode 100644
index 000000000000..2ace4adfa297
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/contrib/multiset_traits.hpp
@@ -0,0 +1,41 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_CONTRIB_MULTISET_TRAITS_HPP
+#define TAO_JSON_CONTRIB_MULTISET_TRAITS_HPP
+
+#include <set>
+
+#include "../consume.hpp"
+#include "../forward.hpp"
+
+#include "internal/array_traits.hpp"
+
+namespace tao::json
+{
+   template< typename T, typename... Ts >
+   struct multiset_traits
+      : internal::array_traits< std::multiset< T, Ts... > >
+   {
+      template< template< typename... > class Traits, typename... With >
+      static void to( const basic_value< Traits >& v, std::multiset< T, Ts... >& r, With&... with )
+      {
+         const auto& a = v.get_array();
+         for( const auto& i : a ) {
+            r.emplace( i.template as_with< T >( with... ) );
+         }
+      }
+
+      template< template< typename... > class Traits, typename Producer >
+      static void consume( Producer& parser, std::multiset< T, Ts... >& r )
+      {
+         auto s = parser.begin_array();
+         while( parser.element_or_end_array( s ) ) {
+            r.emplace( json::consume< T, Traits >( parser ) );
+         }
+      }
+   };
+
+}  // namespace tao::json
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/contrib/pair_traits.hpp b/3rdParty/taocpp-json/include/tao/json/contrib/pair_traits.hpp
new file mode 100644
index 000000000000..f6413cdec541
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/contrib/pair_traits.hpp
@@ -0,0 +1,21 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_CONTRIB_PAIR_TRAITS_HPP
+#define TAO_JSON_CONTRIB_PAIR_TRAITS_HPP
+
+#include <utility>
+
+#include "../binding.hpp"
+
+namespace tao::json
+{
+   template< typename U, typename V >
+   struct pair_traits
+      : binding::array< TAO_JSON_BIND_ELEMENT( &std::pair< U, V >::first ),
+                        TAO_JSON_BIND_ELEMENT( &std::pair< U, V >::second ) >
+   {};
+
+}  // namespace tao::json
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/contrib/patch.hpp b/3rdParty/taocpp-json/include/tao/json/contrib/patch.hpp
new file mode 100644
index 000000000000..1c2ee3847bac
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/contrib/patch.hpp
@@ -0,0 +1,105 @@
+// Copyright (c) 2016-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_CONTRIB_PATCH_HPP
+#define TAO_JSON_CONTRIB_PATCH_HPP
+
+#include <stdexcept>
+#include <utility>
+
+#include "../pointer.hpp"
+#include "../value.hpp"
+
+namespace tao::json
+{
+   template< template< typename... > class Traits >
+   void patch_inplace( basic_value< Traits >& v, const basic_value< Traits >& patch )
+   {
+      for( const auto& entry : patch.get_array() ) {
+         const auto& op = entry.at( "op" ).get_string();
+         const auto& path = entry.at( "path" ).get_string();
+         const pointer path_pointer( path );
+         if( op == "test" ) {
+            if( v.at( path_pointer ) != entry.at( "value" ) ) {
+               throw std::runtime_error( internal::format( "json patch 'test' failed for '", path, '\'', json::message_extension( v ) ) );
+            }
+         }
+         else if( op == "remove" ) {
+            v.erase( path_pointer );
+         }
+         else if( op == "add" ) {
+            v.insert( path_pointer, entry.at( "value" ) );
+         }
+         else if( op == "replace" ) {
+            v.at( path_pointer ) = entry.at( "value" );
+         }
+         else if( op == "move" ) {
+            const pointer from( entry.at( "from" ).get_string() );
+            auto t = std::move( v.at( from ) );
+            v.erase( from );
+            v.insert( path_pointer, std::move( t ) );
+         }
+         else if( op == "copy" ) {
+            const pointer from( entry.at( "from" ).get_string() );
+            v.insert( path_pointer, v.at( from ) );
+         }
+         else {
+            throw std::runtime_error( internal::format( "unknown json patch operation '", op, '\'' ) );
+         }
+      }
+   }
+
+   template< template< typename... > class Traits >
+   void patch_inplace( basic_value< Traits >& v, basic_value< Traits >&& patch )
+   {
+      for( const auto& entry : patch.get_array() ) {
+         const auto& op = entry.at( "op" ).get_string();
+         const auto& path = entry.at( "path" ).get_string();
+         const pointer path_pointer( path );
+         if( op == "test" ) {
+            if( v.at( path_pointer ) != entry.at( "value" ) ) {
+               throw std::runtime_error( internal::format( "json patch 'test' failed for '", path, '\'', json::message_extension( v ) ) );
+            }
+         }
+         else if( op == "remove" ) {
+            v.erase( path_pointer );
+         }
+         else if( op == "add" ) {
+            v.insert( path_pointer, std::move( entry.at( "value" ) ) );
+         }
+         else if( op == "replace" ) {
+            v.at( path_pointer ) = std::move( entry.at( "value" ) );
+         }
+         else if( op == "move" ) {
+            const pointer from( entry.at( "from" ).get_string() );
+            auto t = std::move( v.at( from ) );
+            v.erase( from );
+            v.insert( path_pointer, std::move( t ) );
+         }
+         else if( op == "copy" ) {
+            const pointer from( entry.at( "from" ).get_string() );
+            v.insert( path_pointer, v.at( from ) );
+         }
+         else {
+            throw std::runtime_error( internal::format( "unknown json patch operation '", op, '\'' ) );
+         }
+      }
+   }
+
+   template< template< typename... > class Traits >
+   [[nodiscard]] basic_value< Traits > patch( basic_value< Traits > v, const basic_value< Traits >& patch )
+   {
+      patch_inplace( v, patch );
+      return v;
+   }
+
+   template< template< typename... > class Traits >
+   [[nodiscard]] basic_value< Traits > patch( basic_value< Traits > v, basic_value< Traits >&& patch )
+   {
+      patch_inplace( v, std::move( patch ) );
+      return v;
+   }
+
+}  // namespace tao::json
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/contrib/pointer_traits.hpp b/3rdParty/taocpp-json/include/tao/json/contrib/pointer_traits.hpp
new file mode 100644
index 000000000000..c079f468757e
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/contrib/pointer_traits.hpp
@@ -0,0 +1,59 @@
+#ifndef TAO_JSON_CONTRIB_POINTER_TRAITS_HPP
+#define TAO_JSON_CONTRIB_POINTER_TRAITS_HPP
+
+#include "../pointer.hpp"
+#include "../traits.hpp"
+
+namespace tao::json
+{
+   struct token_traits
+   {
+      template< template< typename... > class Traits >
+      static void assign( basic_value< Traits >& v, const token& t )
+      {
+         if( t.has_index() ) {
+            v = t.index();
+         }
+         else {
+            v = t.key();
+         }
+      }
+
+      template< template< typename... > class Traits, typename Consumer >
+      static void produce( Consumer& c, const token& t )
+      {
+         if( t.has_index() ) {
+            json::events::produce< Traits >( c, t.index() );
+         }
+         else {
+            json::events::produce< Traits >( c, t.key() );
+         }
+      }
+   };
+
+   struct pointer_traits
+   {
+      template< template< typename... > class Traits >
+      static void assign( basic_value< Traits >& v, const pointer& p )
+      {
+         v.prepare_array().reserve( p.size() );
+         for( const auto& i : p ) {
+            v.emplace_back( i );
+         }
+      }
+
+      template< template< typename... > class Traits, typename Consumer >
+      static void produce( Consumer& c, const pointer& p )
+      {
+         c.begin_array( p.size() );
+         for( const auto& i : p ) {
+            json::events::produce< Traits >( c, i );
+            c.element();
+         }
+         c.end_array( p.size() );
+      }
+   };
+
+}  // namespace tao::json
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/contrib/position.hpp b/3rdParty/taocpp-json/include/tao/json/contrib/position.hpp
new file mode 100644
index 000000000000..fd80f13e0cc5
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/contrib/position.hpp
@@ -0,0 +1,166 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_CONTRIB_POSITION_HPP
+#define TAO_JSON_CONTRIB_POSITION_HPP
+
+#include <ostream>
+#include <string>
+#include <type_traits>
+#include <utility>
+
+#include "../events/to_value.hpp"
+#include "../events/transformer.hpp"
+#include "../from_file.hpp"
+#include "../message_extension.hpp"
+#include "../value.hpp"
+
+namespace tao::json
+{
+   struct position
+   {
+   private:
+      std::size_t m_line = 0;
+      std::size_t m_byte_in_line = 0;
+      std::string m_source;
+
+   public:
+      position() noexcept
+      {}
+
+      position( std::string in_source, const std::size_t in_line, const std::size_t in_byte_in_line )
+         : m_line( in_line ),
+           m_byte_in_line( in_byte_in_line ),
+           m_source( std::move( in_source ) )
+      {}
+
+      position( const position& ) = default;
+
+      position( position&& p ) noexcept
+      {
+         m_line = p.m_line;
+         m_byte_in_line = p.m_byte_in_line;
+         m_source = std::move( p.m_source );
+      }
+
+      ~position() = default;
+
+      position& operator=( const position& ) = default;
+
+      position& operator=( position&& p ) noexcept
+      {
+         m_line = p.m_line;
+         m_byte_in_line = p.m_byte_in_line;
+         m_source = std::move( p.m_source );
+         return *this;
+      }
+
+      [[nodiscard]] const std::string& source() const noexcept
+      {
+         return m_source;
+      }
+
+      [[nodiscard]] std::size_t line() const noexcept
+      {
+         return m_line;
+      }
+
+      [[nodiscard]] std::size_t byte_in_line() const noexcept
+      {
+         return m_byte_in_line;
+      }
+
+      void set_source( const std::string& s )
+      {
+         m_source = s;
+      }
+
+      template< typename T >
+      void set_position( const T& p )
+      {
+         m_line = p.line;
+         m_byte_in_line = p.byte_in_line;
+         m_source = p.source;
+      }
+
+      void append_message_extension( std::ostream& os ) const
+      {
+         os << '[' << m_source << ':' << m_line << ':' << m_byte_in_line << ']';
+      }
+   };
+
+   namespace internal
+   {
+      template< typename Rule >
+      struct position_action
+         : action< Rule >
+      {
+      };
+
+      template<>
+      struct position_action< rules::object::begin >
+      {
+         template< typename Input, typename Consumer >
+         static void apply( const Input& in, Consumer& consumer )
+         {
+            action< rules::object::begin >::apply0( consumer );
+            consumer.stack_.back().set_position( in.position() );
+         }
+      };
+
+      template<>
+      struct position_action< rules::array::begin >
+      {
+         template< typename Input, typename Consumer >
+         static void apply( const Input& in, Consumer& consumer )
+         {
+            action< rules::array::begin >::apply0( consumer );
+            consumer.stack_.back().set_position( in.position() );
+         }
+      };
+
+      template<>
+      struct position_action< rules::sor_value >
+      {
+         template< typename Input, typename Consumer >
+         static void apply( const Input& in, Consumer& consumer )
+         {
+            consumer.value.set_position( in.position() );
+         }
+      };
+
+      template< template< typename... > class Traits >
+      struct position_traits
+         : Traits< void >
+      {
+         template< typename >
+         using public_base = position;
+      };
+
+   }  // namespace internal
+
+   template< template< typename... > class Traits >
+   struct make_position_traits
+   {
+      template< typename T >
+      using type = std::conditional_t< std::is_same_v< T, void >, internal::position_traits< Traits >, Traits< T > >;
+   };
+
+   template< template< typename... > class Traits, template< typename... > class... Transformers >
+   [[nodiscard]] auto basic_from_file_with_position( const std::string& filename )
+   {
+      events::transformer< events::to_basic_value< Traits >, Transformers... > consumer;
+      pegtl::file_input< pegtl::tracking_mode::eager > in( filename );
+      pegtl::parse< internal::grammar, internal::position_action, internal::errors >( in, consumer );
+      return std::move( consumer.value );
+   }
+
+   template< template< typename... > class... Transformers >
+   [[nodiscard]] auto from_file_with_position( const std::string& filename )
+   {
+      return basic_from_file_with_position< make_position_traits< traits >::template type, Transformers... >( filename );
+   }
+
+}  // namespace tao::json
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/contrib/reference.hpp b/3rdParty/taocpp-json/include/tao/json/contrib/reference.hpp
new file mode 100644
index 000000000000..422efd7ce7b4
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/contrib/reference.hpp
@@ -0,0 +1,115 @@
+// Copyright (c) 2016-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_CONTRIB_REFERENCE_HPP
+#define TAO_JSON_CONTRIB_REFERENCE_HPP
+
+#include "../internal/uri_fragment.hpp"
+#include "../pointer.hpp"
+#include "../value.hpp"
+
+namespace tao::json
+{
+   namespace internal
+   {
+      // JSON Reference, see draft ("work in progress") RFC at
+      // https://tools.ietf.org/html/draft-pbryan-zyp-json-ref-03
+
+      // NOTE: Currently, only URI fragments are supported.
+      // Remote references are ignored, i.e., left untouched.
+
+      // JSON References are replaced with a VALUE_PTR,
+      // which might lead to infinite loops if you try
+      // to traverse the value. Make sure you understand
+      // the consequences and handle the resulting value
+      // accordingly!
+
+      // Self-references will throw an exception, as well as
+      // references into JSON Reference additional members
+      // (which shall be ignored as per the specification).
+
+      template< template< typename... > class Traits >
+      void resolve_references( basic_value< Traits >& r, basic_value< Traits >& v )
+      {
+         switch( v.type() ) {
+            case type::UNINITIALIZED:
+               return;
+            case type::NULL_:
+            case type::BOOLEAN:
+            case type::SIGNED:
+            case type::UNSIGNED:
+            case type::DOUBLE:
+            case type::STRING:
+            case type::STRING_VIEW:
+            case type::BINARY:
+            case type::BINARY_VIEW:
+               return;
+            case type::ARRAY:
+               for( auto& e : v.get_array() ) {
+                  resolve_references( r, e );
+               }
+               return;
+            case type::OBJECT:
+               for( auto& e : v.get_object() ) {
+                  resolve_references( r, e.second );
+               }
+               if( const auto* ref = v.find( "$ref" ) ) {
+                  ref = &ref->skip_value_ptr();
+                  if( ref->is_string_type() ) {
+                     const std::string_view s = ref->get_string_type();
+                     if( !s.empty() && s[ 0 ] == '#' ) {
+                        const pointer ptr = internal::uri_fragment_to_pointer( s );
+                        const auto* p = &r;
+                        auto it = ptr.begin();
+                        while( it != ptr.end() ) {
+                           switch( p->type() ) {
+                              case type::ARRAY:
+                                 p = &p->at( it->index() ).skip_value_ptr();
+                                 break;
+                              case type::OBJECT:
+                                 if( const auto* t = p->find( "$ref" ) ) {
+                                    if( t->is_string_type() ) {
+                                       throw std::runtime_error( "invalid JSON Reference: referencing additional data members is invalid" );
+                                    }
+                                 }
+                                 p = &p->at( it->key() ).skip_value_ptr();
+                                 break;
+                              default:
+                                 throw invalid_type( ptr.begin(), std::next( it ) );
+                           }
+                           ++it;
+                        }
+                        if( p == &v ) {
+                           throw std::runtime_error( "JSON Reference: invalid self reference" );
+                        }
+                        v.set_value_ptr( p );
+                        resolve_references( r, v );
+                     }
+                     else {
+                        // Ignore remote references for now...
+                        // throw std::runtime_error( "JSON Reference: unsupported or invalid URI: " + s ); // NOLINT
+                     }
+                  }
+               }
+               return;
+            case type::VALUE_PTR:
+               return;
+            case type::OPAQUE_PTR:
+               return;
+            case type::VALUELESS_BY_EXCEPTION:
+               return;
+         }
+         throw std::logic_error( "invalid value for tao::json::type" );  // LCOV_EXCL_LINE
+      }
+
+   }  // namespace internal
+
+   template< template< typename... > class Traits >
+   void resolve_references( basic_value< Traits >& r )
+   {
+      internal::resolve_references( r, r );
+   }
+
+}  // namespace tao::json
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/contrib/schema.hpp b/3rdParty/taocpp-json/include/tao/json/contrib/schema.hpp
new file mode 100644
index 000000000000..4f74dd017979
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/contrib/schema.hpp
@@ -0,0 +1,1851 @@
+// Copyright (c) 2016-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_CONTRIB_SCHEMA_HPP
+#define TAO_JSON_CONTRIB_SCHEMA_HPP
+
+#include <algorithm>
+#include <cmath>
+#include <cstdint>
+#include <limits>
+#include <memory>
+#include <regex>
+#include <set>
+#include <stdexcept>
+#include <string>
+#include <type_traits>
+
+#include "reference.hpp"
+
+#include "../events/compare.hpp"
+#include "../events/from_value.hpp"
+#include "../events/hash.hpp"
+#include "../pointer.hpp"
+#include "../value.hpp"
+
+#include "../external/pegtl/contrib/uri.hpp"
+#include "../external/pegtl/parse.hpp"
+
+namespace tao::json
+{
+   namespace internal
+   {
+      // TODO: Check if these grammars are correct.
+      struct local_part_label
+         : pegtl::plus< pegtl::sor< pegtl::alnum, pegtl::one< '!', '#', '$', '%', '&', '\'', '*', '+', '-', '/', '=', '?', '^', '_', '`', '{', '|', '}', '~' > > >
+      {};
+
+      struct local_part
+         : pegtl::list_must< local_part_label, pegtl::one< '.' > >
+      {};
+
+      struct hostname_label
+         : pegtl::seq< pegtl::alnum, pegtl::rep_max< 62, pegtl::ranges< 'a', 'z', 'A', 'Z', '0', '9', '-' > > >
+      {};
+
+      struct hostname
+         : pegtl::list_must< hostname_label, pegtl::one< '.' > >
+      {};
+
+      struct email
+         : pegtl::seq< local_part, pegtl::one< '@' >, hostname >
+      {};
+
+      template< typename Rule >
+      [[nodiscard]] bool parse( const std::string_view v )
+      {
+         pegtl::memory_input in( v.data(), v.size(), "" );
+         return pegtl::parse< pegtl::seq< Rule, pegtl::eof > >( in );
+      }
+
+      [[nodiscard]] inline bool parse_date_time( const std::string_view v )
+      {
+         static std::regex re( "^\\d{4}-\\d{2}-\\d{2}T\\d{2}:[0-5]\\d:[0-5]\\d(\\.\\d+)?(Z|[+-]\\d{2}:[0-5]\\d)$" );
+         if( !std::regex_search( v.begin(), v.end(), re ) ) {
+            return false;
+         }
+
+         const unsigned year = ( v[ 0 ] - '0' ) * 1000 + ( v[ 1 ] - '0' ) * 100 + ( v[ 2 ] - '0' ) * 10 + ( v[ 3 ] - '0' );
+         const unsigned month = ( v[ 5 ] - '0' ) * 10 + ( v[ 6 ] - '0' );
+         const unsigned day = ( v[ 8 ] - '0' ) * 10 + ( v[ 9 ] - '0' );
+
+         if( month == 0 || month > 12 ) {
+            return false;
+         }
+         if( day == 0 || day > 31 ) {
+            return false;
+         }
+         if( month == 2 ) {
+            const bool is_leap_year = ( year % 4 == 0 ) && ( year % 100 != 0 || year % 400 == 0 );
+            if( day > ( is_leap_year ? 29U : 28U ) ) {
+               return false;
+            }
+         }
+         else if( day == 31 ) {
+            switch( month ) {
+               case 4:
+               case 6:
+               case 9:
+               case 11:
+                  return false;
+               default:;
+            }
+         }
+
+         const unsigned hour = ( v[ 11 ] - '0' ) * 10 + ( v[ 12 ] - '0' );
+         if( hour >= 24 ) {
+            return false;
+         }
+
+         if( *v.rbegin() != 'Z' ) {
+            const auto s = v.size();
+            const unsigned tz_hour = ( v[ s - 5 ] - '0' ) * 10 + ( v[ s - 4 ] - '0' );
+            if( tz_hour >= 24 ) {
+               return false;
+            }
+         }
+
+         return true;
+      }
+
+      enum schema_flags
+      {
+         NONE = 0,
+
+         HAS_TYPE = 1 << 0,
+         NULL_ = 1 << 1,
+         BOOLEAN = 1 << 2,
+         INTEGER = 1 << 3,
+         NUMBER = 1 << 4,
+         STRING = 1 << 5,
+         ARRAY = 1 << 6,
+         OBJECT = 1 << 7,
+
+         HAS_ENUM = 1 << 8,
+
+         HAS_MULTIPLE_OF_UNSIGNED = 1 << 9,
+         HAS_MULTIPLE_OF_DOUBLE = 1 << 10,
+         HAS_MULTIPLE_OF = 3 << 9,
+
+         HAS_MAXIMUM_SIGNED = 1 << 11,
+         HAS_MAXIMUM_UNSIGNED = 1 << 12,
+         HAS_MAXIMUM_DOUBLE = 3 << 11,
+         HAS_MAXIMUM = 3 << 11,
+         EXCLUSIVE_MAXIMUM = 1 << 13,
+
+         HAS_MINIMUM_SIGNED = 1 << 14,
+         HAS_MINIMUM_UNSIGNED = 1 << 15,
+         HAS_MINIMUM_DOUBLE = 3 << 14,
+         HAS_MINIMUM = 3 << 14,
+         EXCLUSIVE_MINIMUM = 1 << 16,
+
+         HAS_MAX_LENGTH = 1 << 17,
+         HAS_MIN_LENGTH = 1 << 18,
+
+         HAS_MAX_ITEMS = 1 << 19,
+         HAS_MIN_ITEMS = 1 << 20,
+         HAS_UNIQUE_ITEMS = 1 << 21,
+
+         HAS_MAX_PROPERTIES = 1 << 22,
+         HAS_MIN_PROPERTIES = 1 << 23,
+         NO_ADDITIONAL_PROPERTIES = 1 << 24,
+         HAS_DEPENDENCIES = 1 << 25
+      };
+
+      enum class schema_format
+      {
+         none,
+         date_time,
+         email,
+         hostname,
+         ipv4,
+         ipv6,
+         uri
+      };
+
+      [[nodiscard]] inline constexpr schema_flags operator|( const schema_flags lhs, const schema_flags rhs ) noexcept
+      {
+         return static_cast< schema_flags >( static_cast< std::underlying_type< schema_flags >::type >( lhs ) | static_cast< std::underlying_type< schema_flags >::type >( rhs ) );
+      }
+
+      union schema_limit
+      {
+         std::int64_t i;
+         std::uint64_t u;
+         double d;
+      };
+
+      template< template< typename... > class Traits >
+      class schema_container;
+
+      template< template< typename... > class Traits >
+      struct schema_node
+      {
+         const schema_container< Traits >* m_container;
+         const basic_value< Traits >* m_value;
+         const basic_value< Traits >* m_all_of = nullptr;
+         const basic_value< Traits >* m_any_of = nullptr;
+         const basic_value< Traits >* m_one_of = nullptr;
+         const basic_value< Traits >* m_not = nullptr;
+         const basic_value< Traits >* m_items = nullptr;
+         const basic_value< Traits >* m_additional_items = nullptr;
+         const basic_value< Traits >* m_properties = nullptr;
+         const basic_value< Traits >* m_additional_properties = nullptr;
+
+         std::map< std::string, std::set< std::string > > m_property_dependencies;
+         std::map< std::string, const basic_value< Traits >* > m_schema_dependencies;
+
+         std::vector< std::pair< std::regex, const basic_value< Traits >* > > m_pattern_properties;
+
+         std::set< const basic_value< Traits >* > m_referenced_pointers;
+
+         // number
+         schema_limit m_multiple_of;
+         schema_limit m_maximum;
+         schema_limit m_minimum;
+
+         // string
+         std::uint64_t m_max_length;
+         std::uint64_t m_min_length;
+         std::unique_ptr< std::regex > m_pattern;
+
+         // array
+         std::uint64_t m_max_items;
+         std::uint64_t m_min_items;
+
+         // object
+         std::uint64_t m_max_properties;
+         std::uint64_t m_min_properties;
+         std::set< std::string > m_required;
+
+         schema_flags m_flags = NONE;
+         schema_format m_format = schema_format::none;
+
+         void add_type( const schema_flags v )
+         {
+            if( ( m_flags & v ) != 0 ) {
+               throw std::runtime_error( "invalid JSON Schema: duplicate primitive type" );
+            }
+            m_flags = m_flags | v;
+         }
+
+         void add_type( const std::string& v )
+         {
+            if( !v.empty() ) {
+               switch( v[ 0 ] ) {
+                  case 'n':
+                     if( v == "number" ) {
+                        return add_type( NUMBER );
+                     }
+                     else if( v == "null" ) {
+                        return add_type( NULL_ );
+                     }
+                     break;
+                  case 'b':
+                     if( v == "boolean" ) {
+                        return add_type( BOOLEAN );
+                     }
+                     break;
+                  case 'i':
+                     if( v == "integer" ) {
+                        return add_type( INTEGER );
+                     }
+                     break;
+                  case 's':
+                     if( v == "string" ) {
+                        return add_type( STRING );
+                     }
+                     break;
+                  case 'a':
+                     if( v == "array" ) {
+                        return add_type( ARRAY );
+                     }
+                     break;
+                  case 'o':
+                     if( v == "object" ) {
+                        return add_type( OBJECT );
+                     }
+                     break;
+               }
+            }
+            throw std::runtime_error( "invalid JSON Schema: invalid primitive type '" + v + '\'' );
+         }
+
+         [[nodiscard]] const basic_value< Traits >* find( const char* s ) const
+         {
+            const auto* p = m_value->find( s );
+            if( p != nullptr ) {
+               p = &p->skip_value_ptr();
+            }
+            return p;
+         }
+
+         schema_node( const schema_container< Traits >* c, const basic_value< Traits >& v )
+            : m_container( c ),
+              m_value( &v )
+         {
+            // general
+            if( !m_value->is_object() ) {
+               throw std::runtime_error( "invalid JSON Schema: a schema must be of type 'object'" );
+            }
+
+            // title
+            if( const auto* p = find( "title" ) ) {
+               if( !p->is_string() ) {
+                  throw std::runtime_error( "invalid JSON Schema: \"title\" must be of type 'string'" );
+               }
+            }
+
+            // description
+            if( const auto* p = find( "description" ) ) {
+               if( !p->is_string() ) {
+                  throw std::runtime_error( "invalid JSON Schema: \"description\" must be of type 'string'" );
+               }
+            }
+
+            // type
+            if( const auto* p = find( "type" ) ) {
+               switch( p->type() ) {
+                  case type::STRING:
+                     add_type( p->get_string() );
+                     break;
+                  case type::ARRAY:
+                     for( const auto& e : p->get_array() ) {
+                        if( !e.is_string() ) {
+                           throw std::runtime_error( "invalid JSON Schema: elements in array \"type\" must be of type 'string'" );
+                        }
+                        add_type( e.get_string() );
+                     }
+                     break;
+                  default:
+                     throw std::runtime_error( "invalid JSON Schema: \"type\" must be of type 'string' or 'array'" );
+               }
+               m_flags = m_flags | HAS_TYPE;
+            }
+
+            // enum
+            if( const auto* p = find( "enum" ) ) {
+               if( !p->is_array() ) {
+                  throw std::runtime_error( "invalid JSON Schema: \"enum\" must be of type 'array'" );
+               }
+               m_flags = m_flags | HAS_ENUM;
+            }
+
+            // allOf
+            if( const auto* p = find( "allOf" ) ) {
+               if( !p->is_array() ) {
+                  throw std::runtime_error( "invalid JSON Schema: \"allOf\" must be of type 'array'" );
+               }
+               if( p->get_array().empty() ) {
+                  throw std::runtime_error( "invalid JSON Schema: \"allOf\" must have at least one element" );
+               }
+               for( const auto& e : p->get_array() ) {
+                  m_referenced_pointers.insert( &e.skip_value_ptr() );
+               }
+               m_all_of = p;
+            }
+
+            // anyOf
+            if( const auto* p = find( "anyOf" ) ) {
+               if( !p->is_array() ) {
+                  throw std::runtime_error( "invalid JSON Schema: \"anyOf\" must be of type 'array'" );
+               }
+               if( p->get_array().empty() ) {
+                  throw std::runtime_error( "invalid JSON Schema: \"anyOf\" must have at least one element" );
+               }
+               for( const auto& e : p->get_array() ) {
+                  m_referenced_pointers.insert( &e.skip_value_ptr() );
+               }
+               m_any_of = p;
+            }
+
+            // oneOf
+            if( const auto* p = find( "oneOf" ) ) {
+               if( !p->is_array() ) {
+                  throw std::runtime_error( "invalid JSON Schema: \"oneOf\" must be of type 'array'" );
+               }
+               if( p->get_array().empty() ) {
+                  throw std::runtime_error( "invalid JSON Schema: \"oneOf\" must have at least one element" );
+               }
+               for( const auto& e : p->get_array() ) {
+                  m_referenced_pointers.insert( &e.skip_value_ptr() );
+               }
+               m_one_of = p;
+            }
+
+            // not
+            if( const auto* p = find( "not" ) ) {
+               m_referenced_pointers.insert( p );
+               m_not = p;
+            }
+
+            // definitions
+            if( const auto* p = find( "definitions" ) ) {
+               if( !p->is_object() ) {
+                  throw std::runtime_error( "invalid JSON Schema: \"definitions\" must be of type 'object'" );
+               }
+               for( const auto& e : p->get_object() ) {
+                  m_referenced_pointers.insert( &e.second.skip_value_ptr() );
+               }
+            }
+
+            // multipleOf
+            if( const auto* p = find( "multipleOf" ) ) {
+               switch( p->type() ) {
+                  case type::SIGNED: {
+                     const auto i = p->get_signed();
+                     if( i <= 0 ) {
+                        throw std::runtime_error( "invalid JSON Schema: \"multipleOf\" must be strictly greater than zero" );
+                     }
+                     m_multiple_of.u = i;
+                     m_flags = m_flags | HAS_MULTIPLE_OF_UNSIGNED;
+                  } break;
+                  case type::UNSIGNED: {
+                     const auto u = p->get_unsigned();
+                     if( u == 0 ) {
+                        throw std::runtime_error( "invalid JSON Schema: \"multipleOf\" must be strictly greater than zero" );
+                     }
+                     m_multiple_of.u = u;
+                     m_flags = m_flags | HAS_MULTIPLE_OF_UNSIGNED;
+                  } break;
+                  case type::DOUBLE: {
+                     const auto d = p->get_double();
+                     if( d <= 0 ) {
+                        throw std::runtime_error( "invalid JSON Schema: \"multipleOf\" must be strictly greater than zero" );
+                     }
+                     m_multiple_of.d = d;
+                     m_flags = m_flags | HAS_MULTIPLE_OF_DOUBLE;
+                  } break;
+                  default:
+                     throw std::runtime_error( "invalid JSON Schema: \"multipleOf\" must be of type 'number'" );
+               }
+            }
+
+            // maximum
+            if( const auto* p = find( "maximum" ) ) {
+               switch( p->type() ) {
+                  case type::SIGNED:
+                     m_maximum.i = p->get_signed();
+                     m_flags = m_flags | HAS_MAXIMUM_SIGNED;
+                     break;
+                  case type::UNSIGNED:
+                     m_maximum.u = p->get_unsigned();
+                     m_flags = m_flags | HAS_MAXIMUM_UNSIGNED;
+                     break;
+                  case type::DOUBLE:
+                     m_maximum.d = p->get_double();
+                     m_flags = m_flags | HAS_MAXIMUM_DOUBLE;
+                     break;
+                  default:
+                     throw std::runtime_error( "invalid JSON Schema: \"maximum\" must be of type 'number'" );
+               }
+            }
+
+            // exclusiveMaximum
+            if( const auto* p = find( "exclusiveMaximum" ) ) {
+               if( !p->is_boolean() ) {
+                  throw std::runtime_error( "invalid JSON Schema: \"exclusiveMaximum\" must be of type 'boolean'" );
+               }
+               if( ( m_flags & HAS_MAXIMUM ) == 0 ) {
+                  throw std::runtime_error( "invalid JSON Schema: \"exclusiveMaximum\" requires presence of \"maximum\"" );
+               }
+               if( p->get_boolean() ) {
+                  m_flags = m_flags | EXCLUSIVE_MAXIMUM;
+               }
+            }
+
+            // minimum
+            if( const auto* p = find( "minimum" ) ) {
+               switch( p->type() ) {
+                  case type::SIGNED:
+                     m_minimum.i = p->get_signed();
+                     m_flags = m_flags | HAS_MINIMUM_SIGNED;
+                     break;
+                  case type::UNSIGNED:
+                     m_minimum.u = p->get_unsigned();
+                     m_flags = m_flags | HAS_MINIMUM_UNSIGNED;
+                     break;
+                  case type::DOUBLE:
+                     m_minimum.d = p->get_double();
+                     m_flags = m_flags | HAS_MINIMUM_DOUBLE;
+                     break;
+                  default:
+                     throw std::runtime_error( "invalid JSON Schema: \"minimum\" must be of type 'number'" );
+               }
+            }
+
+            // exclusiveMinimum
+            if( const auto* p = find( "exclusiveMinimum" ) ) {
+               if( !p->is_boolean() ) {
+                  throw std::runtime_error( "invalid JSON Schema: \"exclusiveMinimum\" must be of type 'boolean'" );
+               }
+               if( ( m_flags & HAS_MINIMUM ) == 0 ) {
+                  throw std::runtime_error( "invalid JSON Schema: \"exclusiveMinimum\" requires presence of \"minimum\"" );
+               }
+               if( p->get_boolean() ) {
+                  m_flags = m_flags | EXCLUSIVE_MINIMUM;
+               }
+            }
+
+            // maxLength
+            if( const auto* p = find( "maxLength" ) ) {
+               switch( p->type() ) {
+                  case type::SIGNED: {
+                     const auto i = p->get_signed();
+                     if( i < 0 ) {
+                        throw std::runtime_error( "invalid JSON Schema: \"maxLength\" must be greater than or equal to zero" );
+                     }
+                     m_max_length = i;
+                     m_flags = m_flags | HAS_MAX_LENGTH;
+                  } break;
+                  case type::UNSIGNED:
+                     m_max_length = p->get_unsigned();
+                     m_flags = m_flags | HAS_MAX_LENGTH;
+                     break;
+                  default:
+                     throw std::runtime_error( "invalid JSON Schema: \"maxLength\" must be of type 'integer'" );
+               }
+            }
+
+            // minLength
+            if( const auto* p = find( "minLength" ) ) {
+               switch( p->type() ) {
+                  case type::SIGNED: {
+                     const auto i = p->get_signed();
+                     if( i < 0 ) {
+                        throw std::runtime_error( "invalid JSON Schema: \"minLength\" must be greater than or equal to zero" );
+                     }
+                     if( i > 0 ) {
+                        m_min_length = i;
+                        m_flags = m_flags | HAS_MIN_LENGTH;
+                     }
+                  } break;
+                  case type::UNSIGNED: {
+                     const auto u = p->get_unsigned();
+                     if( u > 0 ) {
+                        m_min_length = u;
+                        m_flags = m_flags | HAS_MIN_LENGTH;
+                     }
+                  } break;
+                  default:
+                     throw std::runtime_error( "invalid JSON Schema: \"minLength\" must be of type 'integer'" );
+               }
+            }
+
+            // pattern
+            if( const auto* p = find( "pattern" ) ) {
+               if( !p->is_string() ) {
+                  throw std::runtime_error( "invalid JSON Schema: \"pattern\" must be of type 'string'" );
+               }
+               try {
+                  m_pattern = std::make_unique< std::regex >( p->get_string() );
+               }
+               catch( const std::regex_error& e ) {
+                  throw std::runtime_error( "invalid JSON Schema: \"pattern\" must be a regular expression: " + std::string( e.what() ) );
+               }
+            }
+
+            // format
+            // TODO: offer an option to disable "format" support?
+            if( const auto* p = find( "format" ) ) {
+               if( !p->is_string() ) {
+                  throw std::runtime_error( "invalid JSON Schema: \"format\" must be of type 'string'" );
+               }
+               const auto& s = p->get_string();
+               if( s == "date-time" ) {
+                  m_format = schema_format::date_time;
+               }
+               else if( s == "email" ) {
+                  m_format = schema_format::email;
+               }
+               else if( s == "hostname" ) {
+                  m_format = schema_format::hostname;
+               }
+               else if( s == "ipv4" ) {
+                  m_format = schema_format::ipv4;
+               }
+               else if( s == "ipv6" ) {
+                  m_format = schema_format::ipv6;
+               }
+               else if( s == "uri" ) {
+                  m_format = schema_format::uri;
+               }
+               // unknown "format" values are ignored
+            }
+
+            // items
+            if( const auto* p = find( "items" ) ) {
+               if( p->is_array() ) {
+                  for( const auto& e : p->get_array() ) {
+                     m_referenced_pointers.insert( &e.skip_value_ptr() );
+                  }
+               }
+               else if( p->is_object() ) {
+                  m_referenced_pointers.insert( p );
+               }
+               else {
+                  throw std::runtime_error( "invalid JSON Schema: \"items\" must be of type 'object' or 'array'" );
+               }
+               m_items = p;
+            }
+
+            // additionalItems
+            if( const auto* p = find( "additionalItems" ) ) {
+               if( p->is_object() ) {
+                  m_referenced_pointers.insert( p );
+               }
+               else if( !p->is_boolean() ) {
+                  throw std::runtime_error( "invalid JSON Schema: \"additionalItems\" must be of type 'boolean' or 'object'" );
+               }
+               m_additional_items = p;
+            }
+
+            // maxItems
+            if( const auto* p = find( "maxItems" ) ) {
+               switch( p->type() ) {
+                  case type::SIGNED: {
+                     const auto i = p->get_signed();
+                     if( i < 0 ) {
+                        throw std::runtime_error( "invalid JSON Schema: \"maxItems\" must be greater than or equal to zero" );
+                     }
+                     m_max_items = i;
+                     m_flags = m_flags | HAS_MAX_ITEMS;
+                  } break;
+                  case type::UNSIGNED:
+                     m_max_items = p->get_unsigned();
+                     m_flags = m_flags | HAS_MAX_ITEMS;
+                     break;
+                  default:
+                     throw std::runtime_error( "invalid JSON Schema: \"maxItems\" must be of type 'integer'" );
+               }
+            }
+
+            // minItems
+            if( const auto* p = find( "minItems" ) ) {
+               switch( p->type() ) {
+                  case type::SIGNED: {
+                     const auto i = p->get_signed();
+                     if( i < 0 ) {
+                        throw std::runtime_error( "invalid JSON Schema: \"minItems\" must be greater than or equal to zero" );
+                     }
+                     m_min_items = i;
+                     m_flags = m_flags | HAS_MIN_ITEMS;
+                  } break;
+                  case type::UNSIGNED:
+                     m_min_items = p->get_unsigned();
+                     m_flags = m_flags | HAS_MIN_ITEMS;
+                     break;
+                  default:
+                     throw std::runtime_error( "invalid JSON Schema: \"minItems\" must be of type 'integer'" );
+               }
+            }
+
+            // uniqueItems
+            if( const auto* p = find( "uniqueItems" ) ) {
+               if( p->get_boolean() ) {
+                  m_flags = m_flags | HAS_UNIQUE_ITEMS;
+               }
+            }
+
+            // maxProperties
+            if( const auto* p = find( "maxProperties" ) ) {
+               switch( p->type() ) {
+                  case type::SIGNED: {
+                     const auto i = p->get_signed();
+                     if( i < 0 ) {
+                        throw std::runtime_error( "invalid JSON Schema: \"maxProperties\" must be greater than or equal to zero" );
+                     }
+                     m_max_properties = i;
+                     m_flags = m_flags | HAS_MAX_PROPERTIES;
+                  } break;
+                  case type::UNSIGNED:
+                     m_max_properties = p->get_unsigned();
+                     m_flags = m_flags | HAS_MAX_PROPERTIES;
+                     break;
+                  default:
+                     throw std::runtime_error( "invalid JSON Schema: \"maxProperties\" must be of type 'integer'" );
+               }
+            }
+
+            // minProperties
+            if( const auto* p = find( "minProperties" ) ) {
+               switch( p->type() ) {
+                  case type::SIGNED: {
+                     const auto i = p->get_signed();
+                     if( i < 0 ) {
+                        throw std::runtime_error( "invalid JSON Schema: \"minProperties\" must be greater than or equal to zero" );
+                     }
+                     m_min_properties = i;
+                     m_flags = m_flags | HAS_MIN_PROPERTIES;
+                  } break;
+                  case type::UNSIGNED:
+                     m_min_properties = p->get_unsigned();
+                     m_flags = m_flags | HAS_MIN_PROPERTIES;
+                     break;
+                  default:
+                     throw std::runtime_error( "invalid JSON Schema: \"minProperties\" must be of type 'integer'" );
+               }
+            }
+
+            // required
+            if( const auto* p = find( "required" ) ) {
+               if( !p->is_array() ) {
+                  throw std::runtime_error( "invalid JSON Schema: \"required\" must be of type 'array'" );
+               }
+               if( p->get_array().empty() ) {
+                  throw std::runtime_error( "invalid JSON Schema: \"required\" must have at least one element" );
+               }
+               for( const auto& e : p->get_array() ) {
+                  if( !m_required.insert( e.get_string() ).second ) {
+                     throw std::runtime_error( "invalid JSON Schema: duplicate required key" );
+                  }
+               }
+            }
+
+            // properties
+            if( const auto* p = find( "properties" ) ) {
+               if( !p->is_object() ) {
+                  throw std::runtime_error( "invalid JSON Schema: \"properties\" must be of type 'object'" );
+               }
+               for( const auto& e : p->get_object() ) {
+                  m_referenced_pointers.insert( &e.second.skip_value_ptr() );
+               }
+               m_properties = p;
+            }
+
+            // patternProperties
+            if( const auto* p = find( "patternProperties" ) ) {
+               if( !p->is_object() ) {
+                  throw std::runtime_error( "invalid JSON Schema: \"patternProperties\" must be of type 'object'" );
+               }
+               for( const auto& e : p->get_object() ) {
+                  try {
+                     m_pattern_properties.emplace_back( std::regex( e.first ), &e.second.skip_value_ptr() );
+                  }
+                  catch( const std::regex_error& ex ) {
+                     throw std::runtime_error( "invalid JSON Schema: keys in object \"patternProperties\" must be regular expressions: " + std::string( ex.what() ) );
+                  }
+                  m_referenced_pointers.insert( &e.second.skip_value_ptr() );
+               }
+            }
+
+            // additionalProperties
+            if( const auto* p = find( "additionalProperties" ) ) {
+               const type t = p->type();
+               if( t == type::OBJECT ) {
+                  m_referenced_pointers.insert( p );
+               }
+               else if( t != type::BOOLEAN ) {
+                  throw std::runtime_error( "invalid JSON Schema: \"additionalProperties\" must be of type 'boolean' or 'object'" );
+               }
+               m_additional_properties = p;
+            }
+
+            // dependencies
+            if( const auto* p = find( "dependencies" ) ) {
+               if( !p->is_object() ) {
+                  throw std::runtime_error( "invalid JSON Schema: \"dependencies\" must be of type 'object'" );
+               }
+               for( const auto& e : p->get_object() ) {
+                  const auto* p2 = &e.second.skip_value_ptr();
+                  if( p2->is_object() ) {
+                     m_schema_dependencies.emplace( e.first, p2 );
+                     m_referenced_pointers.insert( p2 );
+                  }
+                  else if( p2->is_array() ) {
+                     if( p2->get_array().empty() ) {
+                        throw std::runtime_error( "invalid JSON Schema: values in object \"dependencies\" of type 'array' must have at least one element" );
+                     }
+                     std::set< std::string > s;
+                     for( const auto& r : p2->get_array() ) {
+                        if( !r.is_string() ) {
+                           throw std::runtime_error( "invalid JSON Schema: values in object \"dependencies\" of type 'array' must contain elements of type 'string'" );
+                        }
+                        if( !s.emplace( r.get_string() ).second ) {
+                           throw std::runtime_error( "invalid JSON Schema: values in object \"dependencies\" of type 'array' must contain unique elements of type 'string'" );
+                        }
+                     }
+                     m_property_dependencies.emplace( e.first, std::move( s ) );
+                  }
+                  else {
+                     throw std::runtime_error( "invalid JSON Schema: values in object \"dependencies\" must be of type 'object' or 'array'" );
+                  }
+               }
+               if( !p->get_object().empty() ) {
+                  m_flags = m_flags | HAS_DEPENDENCIES;
+               }
+            }
+
+            // default
+            if( const auto* p = find( "default" ) ) {
+               // TODO: the value should validate against the JSON Schema itself
+            }
+         }
+
+         schema_node( const schema_node& ) = delete;
+         schema_node( schema_node&& ) = delete;
+
+         ~schema_node() = default;
+
+         void operator=( const schema_node& ) = delete;
+         void operator=( schema_node&& ) = delete;
+
+         [[nodiscard]] const std::set< const basic_value< Traits >* >& referenced_pointers() const noexcept
+         {
+            return m_referenced_pointers;
+         }
+      };
+
+      template< template< typename... > class Traits >
+      class schema_consumer
+      {
+      private:
+         const std::shared_ptr< const schema_container< Traits > > m_container;
+         const schema_node< Traits >* const m_node;
+
+         std::vector< std::unique_ptr< events_compare< Traits > > > m_enum;
+         std::unique_ptr< events::hash > m_hash;
+         std::set< std::string > m_unique;
+         std::set< std::string > m_keys;
+         std::vector< std::size_t > m_count;
+         std::vector< std::unique_ptr< schema_consumer > > m_properties;
+         std::vector< std::unique_ptr< schema_consumer > > m_all_of;
+         std::vector< std::unique_ptr< schema_consumer > > m_any_of;
+         std::vector< std::unique_ptr< schema_consumer > > m_one_of;
+         std::map< std::string, std::unique_ptr< schema_consumer > > m_schema_dependencies;
+         std::unique_ptr< schema_consumer > m_not;
+         std::unique_ptr< schema_consumer > m_item;
+         bool m_match = true;
+
+         void validate_type( const schema_flags t )
+         {
+            if( !m_count.empty() ) {
+               return;
+            }
+            if( ( m_node->m_flags & HAS_TYPE ) == 0 ) {
+               return;
+            }
+            if( ( m_node->m_flags & t ) == 0 ) {
+               m_match = false;
+            }
+         }
+
+         // note: lambda returns true if validation failure detected
+         template< typename F >
+         void validate_enum( F&& f )
+         {
+            assert( m_match );
+            if( m_node->m_flags & HAS_ENUM ) {
+               m_enum.erase( std::remove_if( m_enum.begin(), m_enum.end(), [&]( const std::unique_ptr< events_compare< Traits > >& p ) { return f( *p ); } ), m_enum.end() );
+               if( m_enum.empty() ) {
+                  m_match = false;
+               }
+            }
+         }
+
+         template< typename F >
+         void validate_item( F&& f )
+         {
+            if( m_item ) {
+               if( f( m_item ) ) {
+                  m_match = false;
+               }
+            }
+         }
+
+         template< typename F >
+         void validate_properties( F&& f )
+         {
+            for( auto& p : m_properties ) {
+               if( f( p ) ) {
+                  m_match = false;
+                  break;
+               }
+            }
+         }
+
+         template< typename F >
+         void validate_schema_dependencies( F&& f )
+         {
+            auto it = m_schema_dependencies.begin();
+            while( it != m_schema_dependencies.end() ) {
+               if( f( it->second ) ) {
+                  it = m_schema_dependencies.erase( it );
+               }
+               else {
+                  ++it;
+               }
+            }
+         }
+
+         template< typename F >
+         void validate_all_of( F&& f )
+         {
+            for( auto& p : m_all_of ) {
+               if( f( p ) ) {
+                  m_match = false;
+                  break;
+               }
+            }
+         }
+
+         template< typename F >
+         void validate_any_of( F&& f )
+         {
+            if( !m_any_of.empty() ) {
+               m_any_of.erase( std::remove_if( m_any_of.begin(), m_any_of.end(), f ), m_any_of.end() );
+               if( m_any_of.empty() ) {
+                  m_match = false;
+               }
+            }
+         }
+
+         template< typename F >
+         void validate_one_of( F&& f )
+         {
+            if( !m_one_of.empty() ) {
+               m_one_of.erase( std::remove_if( m_one_of.begin(), m_one_of.end(), f ), m_one_of.end() );
+               if( m_one_of.empty() ) {
+                  m_match = false;
+               }
+            }
+         }
+
+         template< typename F >
+         void validate_not( F&& f )
+         {
+            if( m_not ) {
+               if( f( m_not ) ) {
+                  m_not.reset();
+               }
+            }
+         }
+
+         // note: lambda returns true if validation failure detected
+         template< typename F >
+         void validate_collections( F&& f )
+         {
+            assert( m_match );
+            const auto f2 = [&]( const std::unique_ptr< schema_consumer >& p ) { return f( *p ); };
+            if( m_match ) {
+               validate_item( f2 );
+            }
+            if( m_match ) {
+               validate_properties( f2 );
+            }
+            if( m_match ) {
+               validate_all_of( f2 );
+            }
+            if( m_match ) {
+               validate_any_of( f2 );
+            }
+            if( m_match ) {
+               validate_one_of( f2 );
+            }
+            if( m_match ) {
+               validate_not( f2 );
+            }
+            if( m_match ) {
+               validate_schema_dependencies( f2 );
+            }
+         }
+
+         [[nodiscard]] static bool is_multiple_of( const double v, const double d )
+         {
+            const auto r = std::fmod( v, d );
+            if( std::fabs( r ) < std::numeric_limits< double >::epsilon() ) {
+               return true;
+            }
+            if( std::fabs( r - d ) < std::numeric_limits< double >::epsilon() ) {
+               return true;
+            }
+            return false;
+         }
+
+         void validate_multiple_of( const std::int64_t v )
+         {
+            switch( m_node->m_flags & HAS_MULTIPLE_OF ) {
+               case HAS_MULTIPLE_OF_UNSIGNED:
+                  if( v < 0 ) {
+                     if( ( -v % m_node->m_multiple_of.u ) != 0 ) {
+                        m_match = false;
+                     }
+                  }
+                  else {
+                     if( ( v % m_node->m_multiple_of.u ) != 0 ) {
+                        m_match = false;
+                     }
+                  }
+                  break;
+               case HAS_MULTIPLE_OF_DOUBLE:
+                  if( !is_multiple_of( double( v ), m_node->m_multiple_of.d ) ) {
+                     m_match = false;
+                  }
+                  break;
+            }
+         }
+
+         void validate_multiple_of( const std::uint64_t v )
+         {
+            switch( m_node->m_flags & HAS_MULTIPLE_OF ) {
+               case HAS_MULTIPLE_OF_UNSIGNED:
+                  if( ( v % m_node->m_multiple_of.u ) != 0 ) {
+                     m_match = false;
+                  }
+                  break;
+               case HAS_MULTIPLE_OF_DOUBLE:
+                  if( !is_multiple_of( double( v ), m_node->m_multiple_of.d ) ) {
+                     m_match = false;
+                  }
+                  break;
+            }
+         }
+
+         void validate_multiple_of( const double v )
+         {
+            switch( m_node->m_flags & HAS_MULTIPLE_OF ) {
+               case HAS_MULTIPLE_OF_UNSIGNED:
+                  if( !is_multiple_of( v, double( m_node->m_multiple_of.u ) ) ) {
+                     m_match = false;
+                  }
+                  break;
+               case HAS_MULTIPLE_OF_DOUBLE:
+                  if( !is_multiple_of( v, m_node->m_multiple_of.d ) ) {
+                     m_match = false;
+                  }
+                  break;
+            }
+         }
+
+         void validate_number( const std::int64_t v )
+         {
+            validate_multiple_of( v );
+            switch( m_node->m_flags & ( HAS_MAXIMUM | EXCLUSIVE_MAXIMUM ) ) {
+               case HAS_MAXIMUM_SIGNED:
+                  if( v > m_node->m_maximum.i ) {
+                     m_match = false;
+                  }
+                  break;
+               case HAS_MAXIMUM_SIGNED | EXCLUSIVE_MAXIMUM:
+                  if( v >= m_node->m_maximum.i ) {
+                     m_match = false;
+                  }
+                  break;
+               case HAS_MAXIMUM_UNSIGNED:
+                  if( v >= 0 && static_cast< std::uint64_t >( v ) > m_node->m_maximum.u ) {
+                     m_match = false;
+                  }
+                  break;
+               case HAS_MAXIMUM_UNSIGNED | EXCLUSIVE_MAXIMUM:
+                  if( v >= 0 && static_cast< std::uint64_t >( v ) >= m_node->m_maximum.u ) {
+                     m_match = false;
+                  }
+                  break;
+               case HAS_MAXIMUM_DOUBLE:
+                  if( v > m_node->m_maximum.d ) {
+                     m_match = false;
+                  }
+                  break;
+               case HAS_MAXIMUM_DOUBLE | EXCLUSIVE_MAXIMUM:
+                  if( v >= m_node->m_maximum.d ) {
+                     m_match = false;
+                  }
+                  break;
+            }
+            switch( m_node->m_flags & ( HAS_MINIMUM | EXCLUSIVE_MINIMUM ) ) {
+               case HAS_MINIMUM_SIGNED:
+                  if( v < m_node->m_minimum.i ) {
+                     m_match = false;
+                  }
+                  break;
+               case HAS_MINIMUM_SIGNED | EXCLUSIVE_MINIMUM:
+                  if( v <= m_node->m_minimum.i ) {
+                     m_match = false;
+                  }
+                  break;
+               case HAS_MINIMUM_UNSIGNED:
+                  if( v < 0 || static_cast< std::uint64_t >( v ) < m_node->m_minimum.u ) {
+                     m_match = false;
+                  }
+                  break;
+               case HAS_MINIMUM_UNSIGNED | EXCLUSIVE_MINIMUM:
+                  if( v < 0 || static_cast< std::uint64_t >( v ) <= m_node->m_minimum.u ) {
+                     m_match = false;
+                  }
+                  break;
+               case HAS_MINIMUM_DOUBLE:
+                  if( v < m_node->m_minimum.d ) {
+                     m_match = false;
+                  }
+                  break;
+               case HAS_MINIMUM_DOUBLE | EXCLUSIVE_MINIMUM:
+                  if( v <= m_node->m_minimum.d ) {
+                     m_match = false;
+                  }
+                  break;
+            }
+         }
+
+         void validate_number( const std::uint64_t v )
+         {
+            validate_multiple_of( v );
+            switch( m_node->m_flags & ( HAS_MAXIMUM | EXCLUSIVE_MAXIMUM ) ) {
+               case HAS_MAXIMUM_SIGNED:
+                  if( m_node->m_maximum.i < 0 || v > static_cast< std::uint64_t >( m_node->m_maximum.i ) ) {
+                     m_match = false;
+                  }
+                  break;
+               case HAS_MAXIMUM_SIGNED | EXCLUSIVE_MAXIMUM:
+                  if( m_node->m_maximum.i < 0 || v >= static_cast< std::uint64_t >( m_node->m_maximum.i ) ) {
+                     m_match = false;
+                  }
+                  break;
+               case HAS_MAXIMUM_UNSIGNED:
+                  if( v > m_node->m_maximum.u ) {
+                     m_match = false;
+                  }
+                  break;
+               case HAS_MAXIMUM_UNSIGNED | EXCLUSIVE_MAXIMUM:
+                  if( v >= m_node->m_maximum.u ) {
+                     m_match = false;
+                  }
+                  break;
+               case HAS_MAXIMUM_DOUBLE:
+                  if( v > m_node->m_maximum.d ) {
+                     m_match = false;
+                  }
+                  break;
+               case HAS_MAXIMUM_DOUBLE | EXCLUSIVE_MAXIMUM:
+                  if( v >= m_node->m_maximum.d ) {
+                     m_match = false;
+                  }
+                  break;
+            }
+            switch( m_node->m_flags & ( HAS_MINIMUM | EXCLUSIVE_MINIMUM ) ) {
+               case HAS_MINIMUM_SIGNED:
+                  if( m_node->m_minimum.i >= 0 && v < static_cast< std::uint64_t >( m_node->m_minimum.i ) ) {
+                     m_match = false;
+                  }
+                  break;
+               case HAS_MINIMUM_SIGNED | EXCLUSIVE_MINIMUM:
+                  if( m_node->m_minimum.i >= 0 && v <= static_cast< std::uint64_t >( m_node->m_minimum.i ) ) {
+                     m_match = false;
+                  }
+                  break;
+               case HAS_MINIMUM_UNSIGNED:
+                  if( v < m_node->m_minimum.u ) {
+                     m_match = false;
+                  }
+                  break;
+               case HAS_MINIMUM_UNSIGNED | EXCLUSIVE_MINIMUM:
+                  if( v <= m_node->m_minimum.u ) {
+                     m_match = false;
+                  }
+                  break;
+               case HAS_MINIMUM_DOUBLE:
+                  if( v < m_node->m_minimum.d ) {
+                     m_match = false;
+                  }
+                  break;
+               case HAS_MINIMUM_DOUBLE | EXCLUSIVE_MINIMUM:
+                  if( v <= m_node->m_minimum.d ) {
+                     m_match = false;
+                  }
+                  break;
+            }
+         }
+
+         void validate_number( const double v )
+         {
+            validate_multiple_of( v );
+            switch( m_node->m_flags & ( HAS_MAXIMUM | EXCLUSIVE_MAXIMUM ) ) {
+               case HAS_MAXIMUM_SIGNED:
+                  if( v > m_node->m_maximum.i ) {
+                     m_match = false;
+                  }
+                  break;
+               case HAS_MAXIMUM_SIGNED | EXCLUSIVE_MAXIMUM:
+                  if( v >= m_node->m_maximum.i ) {
+                     m_match = false;
+                  }
+                  break;
+               case HAS_MAXIMUM_UNSIGNED:
+                  if( v > m_node->m_maximum.u ) {
+                     m_match = false;
+                  }
+                  break;
+               case HAS_MAXIMUM_UNSIGNED | EXCLUSIVE_MAXIMUM:
+                  if( v >= m_node->m_maximum.u ) {
+                     m_match = false;
+                  }
+                  break;
+               case HAS_MAXIMUM_DOUBLE:
+                  if( v > m_node->m_maximum.d ) {
+                     m_match = false;
+                  }
+                  break;
+               case HAS_MAXIMUM_DOUBLE | EXCLUSIVE_MAXIMUM:
+                  if( v >= m_node->m_maximum.d ) {
+                     m_match = false;
+                  }
+                  break;
+            }
+            switch( m_node->m_flags & ( HAS_MINIMUM | EXCLUSIVE_MINIMUM ) ) {
+               case HAS_MINIMUM_SIGNED:
+                  if( v < m_node->m_minimum.i ) {
+                     m_match = false;
+                  }
+                  break;
+               case HAS_MINIMUM_SIGNED | EXCLUSIVE_MINIMUM:
+                  if( v <= m_node->m_minimum.i ) {
+                     m_match = false;
+                  }
+                  break;
+               case HAS_MINIMUM_UNSIGNED:
+                  if( v < m_node->m_minimum.u ) {
+                     m_match = false;
+                  }
+                  break;
+               case HAS_MINIMUM_UNSIGNED | EXCLUSIVE_MINIMUM:
+                  if( v <= m_node->m_minimum.u ) {
+                     m_match = false;
+                  }
+                  break;
+               case HAS_MINIMUM_DOUBLE:
+                  if( v < m_node->m_minimum.d ) {
+                     m_match = false;
+                  }
+                  break;
+               case HAS_MINIMUM_DOUBLE | EXCLUSIVE_MINIMUM:
+                  if( v <= m_node->m_minimum.d ) {
+                     m_match = false;
+                  }
+                  break;
+            }
+         }
+
+         void validate_string( const std::string_view v )
+         {
+            if( m_node->m_flags & HAS_MAX_LENGTH && v.size() > m_node->m_max_length ) {
+               m_match = false;
+            }
+            if( m_node->m_flags & HAS_MIN_LENGTH && v.size() < m_node->m_min_length ) {
+               m_match = false;
+            }
+            if( m_match && m_node->m_pattern ) {
+               if( !std::regex_search( v.begin(), v.end(), *m_node->m_pattern ) ) {
+                  m_match = false;
+               }
+            }
+            if( m_match && m_node->m_format != schema_format::none ) {
+               switch( m_node->m_format ) {
+                  case schema_format::date_time:
+                     if( !internal::parse_date_time( v ) ) {
+                        m_match = false;
+                     }
+                     break;
+                  case schema_format::email:
+                     if( ( v.size() > 255 ) || !internal::parse< internal::email >( v ) ) {
+                        m_match = false;
+                     }
+                     break;
+                  case schema_format::hostname:
+                     if( ( v.size() > 255 ) || !internal::parse< internal::hostname >( v ) ) {
+                        m_match = false;
+                     }
+                     break;
+                  case schema_format::ipv4:
+                     if( !internal::parse< pegtl::uri::IPv4address >( v ) ) {
+                        m_match = false;
+                     }
+                     break;
+                  case schema_format::ipv6:
+                     if( !internal::parse< pegtl::uri::IPv6address >( v ) ) {
+                        m_match = false;
+                     }
+                     break;
+                  case schema_format::uri:
+                     // TODO: What rule exactly should we apply here?? JSON Schema is not exactly the best spec I've ever read...
+                     if( !internal::parse< pegtl::uri::URI >( v ) ) {
+                        m_match = false;
+                     }
+                     break;
+                  case schema_format::none:;
+               }
+            }
+         }
+
+         void validate_elements( const std::size_t v )
+         {
+            if( m_node->m_flags & HAS_MAX_ITEMS && v > m_node->m_max_items ) {
+               m_match = false;
+            }
+            if( m_node->m_flags & HAS_MIN_ITEMS && v < m_node->m_min_items ) {
+               m_match = false;
+            }
+         }
+
+         void validate_members( const std::size_t v )
+         {
+            if( m_node->m_flags & HAS_MAX_PROPERTIES && v > m_node->m_max_properties ) {
+               m_match = false;
+            }
+            if( m_node->m_flags & HAS_MIN_PROPERTIES && v < m_node->m_min_properties ) {
+               m_match = false;
+            }
+         }
+
+      public:
+         schema_consumer( const std::shared_ptr< const schema_container< Traits > >& c, const schema_node< Traits >& n )
+            : m_container( c ),
+              m_node( &n )
+         {
+            if( m_node->m_flags & HAS_ENUM ) {
+               const auto& a = m_node->m_value->at( "enum" ).get_array();
+               m_enum.reserve( a.size() );
+               for( const auto& e : a ) {
+                  m_enum.emplace_back( std::make_unique< events_compare< Traits > >() );
+                  m_enum.back()->push( &e );
+               }
+            }
+            if( const auto* p = m_node->m_all_of ) {
+               for( const auto& e : p->get_array() ) {
+                  m_all_of.push_back( m_container->consumer( &e.skip_value_ptr() ) );
+               }
+            }
+            if( const auto* p = m_node->m_any_of ) {
+               for( const auto& e : p->get_array() ) {
+                  m_any_of.push_back( m_container->consumer( &e.skip_value_ptr() ) );
+               }
+            }
+            if( const auto* p = m_node->m_one_of ) {
+               for( const auto& e : p->get_array() ) {
+                  m_one_of.push_back( m_container->consumer( &e.skip_value_ptr() ) );
+               }
+            }
+            if( const auto* p = m_node->m_not ) {
+               m_not = m_container->consumer( p );
+            }
+            for( const auto& e : m_node->m_schema_dependencies ) {
+               m_schema_dependencies.emplace( e.first, m_container->consumer( e.second ) );
+            }
+         }
+
+         schema_consumer( const schema_consumer& ) = delete;
+         schema_consumer( schema_consumer&& ) = delete;
+
+         ~schema_consumer() = default;
+
+         void operator=( const schema_consumer& ) = delete;
+         void operator=( schema_consumer&& ) = delete;
+
+         [[nodiscard]] bool finalize()
+         {
+            if( m_match && !m_all_of.empty() ) {
+               for( auto& e : m_all_of ) {
+                  if( !e->finalize() ) {
+                     m_match = false;
+                     break;
+                  }
+               }
+            }
+            if( m_match && !m_any_of.empty() ) {
+               m_any_of.erase( std::remove_if( m_any_of.begin(), m_any_of.end(), []( const std::unique_ptr< schema_consumer >& c ) { return !c->finalize(); } ), m_any_of.end() );
+               if( m_any_of.empty() ) {
+                  m_match = false;
+               }
+            }
+            if( m_match && !m_one_of.empty() ) {
+               m_one_of.erase( std::remove_if( m_one_of.begin(), m_one_of.end(), []( const std::unique_ptr< schema_consumer >& c ) { return !c->finalize(); } ), m_one_of.end() );
+               if( m_one_of.size() != 1 ) {
+                  m_match = false;
+               }
+            }
+            if( m_match && m_not && m_not->finalize() ) {
+               m_match = false;
+            }
+            if( m_match && m_node->m_flags & HAS_DEPENDENCIES ) {
+               for( const auto& e : m_node->m_schema_dependencies ) {
+                  if( m_keys.count( e.first ) != 0 ) {
+                     const auto it = m_schema_dependencies.find( e.first );
+                     if( it == m_schema_dependencies.end() ) {
+                        m_match = false;
+                        break;
+                     }
+                     if( !it->second->finalize() ) {
+                        m_match = false;
+                        break;
+                     }
+                  }
+               }
+            }
+            return m_match;
+         }
+
+         [[nodiscard]] bool match() const noexcept
+         {
+            return m_match;
+         }
+
+         void null()
+         {
+            if( m_match ) {
+               validate_type( NULL_ );
+            }
+            if( m_match ) {
+               validate_enum( []( events_compare< Traits >& c ) { c.null(); return ! c.match(); } );
+            }
+            if( m_match ) {
+               validate_collections( []( schema_consumer& c ) { c.null(); return ! c.match(); } );
+            }
+            if( m_match && m_hash ) {
+               m_hash->null();
+            }
+         }
+
+         void boolean( const bool v )
+         {
+            if( m_match ) {
+               validate_type( BOOLEAN );
+            }
+            if( m_match ) {
+               validate_enum( [=]( events_compare< Traits >& c ) { c.boolean( v ); return ! c.match(); } );
+            }
+            if( m_match ) {
+               validate_collections( [=]( schema_consumer& c ) { c.boolean( v ); return ! c.match(); } );
+            }
+            if( m_match && m_hash ) {
+               m_hash->boolean( v );
+            }
+         }
+
+         void number( const std::int64_t v )
+         {
+            if( m_match ) {
+               validate_type( INTEGER | NUMBER );
+            }
+            if( m_match ) {
+               validate_enum( [=]( events_compare< Traits >& c ) { c.number( v ); return ! c.match(); } );
+            }
+            if( m_match ) {
+               validate_collections( [=]( schema_consumer& c ) { c.number( v ); return ! c.match(); } );
+            }
+            if( m_match && m_count.empty() ) {
+               validate_number( v );
+            }
+            if( m_match && m_hash ) {
+               m_hash->number( v );
+            }
+         }
+
+         void number( const std::uint64_t v )
+         {
+            if( m_match ) {
+               validate_type( INTEGER | NUMBER );
+            }
+            if( m_match ) {
+               validate_enum( [=]( events_compare< Traits >& c ) { c.number( v ); return ! c.match(); } );
+            }
+            if( m_match ) {
+               validate_collections( [=]( schema_consumer& c ) { c.number( v ); return ! c.match(); } );
+            }
+            if( m_match && m_count.empty() ) {
+               validate_number( v );
+            }
+            if( m_match && m_hash ) {
+               m_hash->number( v );
+            }
+         }
+
+         void number( const double v )
+         {
+            if( m_match ) {
+               validate_type( NUMBER );
+            }
+            if( m_match ) {
+               validate_enum( [=]( events_compare< Traits >& c ) { c.number( v ); return ! c.match(); } );
+            }
+            if( m_match ) {
+               validate_collections( [=]( schema_consumer& c ) { c.number( v ); return ! c.match(); } );
+            }
+            if( m_match && m_count.empty() ) {
+               validate_number( v );
+            }
+            if( m_match && m_hash ) {
+               m_hash->number( v );
+            }
+         }
+
+         void string( const std::string_view v )
+         {
+            if( m_match ) {
+               validate_type( STRING );
+            }
+            if( m_match ) {
+               validate_enum( [&]( events_compare< Traits >& c ) { c.string( v ); return ! c.match(); } );
+            }
+            if( m_match ) {
+               validate_collections( [&]( schema_consumer& c ) { c.string( v ); return ! c.match(); } );
+            }
+            if( m_match && m_count.empty() ) {
+               validate_string( v );
+            }
+            if( m_match && m_hash ) {
+               m_hash->string( v );
+            }
+         }
+
+         void binary( const tao::binary_view /*unused*/ )
+         {
+            // TODO: What?
+         }
+
+         void begin_array( const std::size_t /*unused*/ = 0 )
+         {
+            if( m_match ) {
+               validate_type( ARRAY );
+            }
+            if( m_match ) {
+               validate_enum( []( events_compare< Traits >& c ) { c.begin_array(); return ! c.match(); } );
+            }
+            if( m_match ) {
+               validate_collections( []( schema_consumer& c ) { c.begin_array(); return ! c.match(); } );
+            }
+            if( m_match ) {
+               if( m_hash ) {
+                  m_hash->begin_array();
+               }
+               else if( m_count.empty() && ( ( m_node->m_flags & HAS_UNIQUE_ITEMS ) != 0 ) ) {
+                  m_hash = std::make_unique< events::hash >();
+               }
+            }
+            if( m_match && m_count.empty() ) {
+               if( const auto* p = m_node->m_items ) {
+                  if( p->is_object() ) {
+                     m_item = m_container->consumer( p );
+                  }
+                  else {
+                     const auto& a = p->get_array();
+                     if( !a.empty() ) {
+                        m_item = m_container->consumer( &a[ 0 ].skip_value_ptr() );
+                     }
+                  }
+               }
+               if( !m_item ) {
+                  if( const auto* p = m_node->m_additional_items ) {
+                     if( p->is_object() ) {
+                        m_item = m_container->consumer( p );
+                     }
+                  }
+               }
+            }
+            m_count.push_back( 0 );
+         }
+
+         void element()
+         {
+            if( m_match ) {
+               validate_enum( []( events_compare< Traits >& c ) { c.element(); return ! c.match(); } );
+            }
+            if( m_match && m_item ) {
+               if( m_count.size() == 1 ) {
+                  if( !m_item->finalize() ) {
+                     m_match = false;
+                  }
+                  m_item.reset();
+               }
+            }
+            if( m_match ) {
+               validate_collections( []( schema_consumer& c ) { c.element(); return ! c.match(); } );
+            }
+            if( m_match && m_hash ) {
+               if( m_count.size() == 1 ) {
+                  if( !m_unique.emplace( m_hash->value() ).second ) {
+                     m_match = false;
+                  }
+                  m_hash->reset();
+               }
+               else {
+                  m_hash->element();
+               }
+            }
+            const auto next = ++m_count.back();
+            if( m_match && ( m_count.size() == 1 ) ) {
+               if( const auto* p = m_node->m_items ) {
+                  if( p->is_object() ) {
+                     m_item = m_container->consumer( p );
+                  }
+                  else {
+                     const auto& a = p->get_array();
+                     if( next < a.size() ) {
+                        m_item = m_container->consumer( &a[ next ].skip_value_ptr() );
+                     }
+                  }
+               }
+               if( !m_item ) {
+                  if( const auto* p = m_node->m_additional_items ) {
+                     if( p->is_object() ) {
+                        m_item = m_container->consumer( p );
+                     }
+                  }
+               }
+            }
+         }
+
+         void end_array( const std::size_t /*unused*/ = 0 )
+         {
+            if( m_match ) {
+               validate_enum( []( events_compare< Traits >& c ) { c.end_array(); return ! c.match(); } );
+            }
+            if( m_match && m_item && ( m_count.size() == 1 ) ) {
+               if( !m_item->finalize() ) {
+                  m_match = false;
+               }
+               m_item.reset();
+            }
+            if( m_match && ( m_count.size() == 1 ) ) {
+               if( m_node->m_items && m_node->m_items->is_array() ) {
+                  if( m_node->m_additional_items && m_node->m_additional_items->is_boolean() ) {
+                     if( !m_node->m_additional_items->get_boolean() ) {
+                        if( m_count.back() > m_node->m_items->get_array().size() ) {
+                           m_match = false;
+                        }
+                     }
+                  }
+               }
+            }
+            if( m_match ) {
+               validate_collections( []( schema_consumer& c ) { c.end_array(); return ! c.match(); } );
+            }
+            if( m_match && m_hash ) {
+               m_hash->end_array();
+            }
+            if( m_match && ( m_count.size() == 1 ) ) {
+               validate_elements( m_count.back() );
+            }
+            m_count.pop_back();
+         }
+
+         void begin_object( const std::size_t /*unused*/ = 0 )
+         {
+            if( m_match ) {
+               validate_type( OBJECT );
+            }
+            if( m_match ) {
+               validate_enum( []( events_compare< Traits >& c ) { c.begin_object(); return ! c.match(); } );
+            }
+            if( m_match ) {
+               validate_collections( []( schema_consumer& c ) { c.begin_object(); return ! c.match(); } );
+            }
+            if( m_match && m_hash ) {
+               m_hash->begin_object();
+            }
+            m_count.push_back( 0 );
+         }
+
+         void key( const std::string& v )
+         {
+            if( m_match ) {
+               validate_enum( [&]( events_compare< Traits >& c ) { c.key( v ); return ! c.match(); } );
+            }
+            if( m_match ) {
+               validate_collections( [&]( schema_consumer& c ) { c.key( v ); return ! c.match(); } );
+            }
+            if( m_match && m_hash ) {
+               m_hash->key( v );
+            }
+            if( m_match && ( m_count.size() == 1 ) && ( m_node->m_flags & HAS_DEPENDENCIES || !m_node->m_required.empty() ) ) {
+               if( !m_keys.insert( v ).second ) {
+                  // duplicate keys immediately invalidate!
+                  // TODO: throw?
+                  m_match = false;
+               }
+            }
+            if( m_match && m_properties.empty() && ( m_count.size() == 1 ) ) {
+               if( const auto* p = m_node->m_properties ) {
+                  const auto& o = p->get_object();
+                  const auto it = o.find( v );
+                  if( it != o.end() ) {
+                     m_properties.push_back( m_container->consumer( &it->second.skip_value_ptr() ) );
+                  }
+               }
+               for( const auto& e : m_node->m_pattern_properties ) {
+                  if( std::regex_search( v, e.first ) ) {
+                     m_properties.push_back( m_container->consumer( e.second ) );
+                  }
+               }
+               if( m_properties.empty() ) {
+                  if( const auto* p = m_node->m_additional_properties ) {
+                     if( p->is_boolean() ) {
+                        if( !p->get_boolean() ) {
+                           m_match = false;
+                        }
+                     }
+                     else {
+                        m_properties.push_back( m_container->consumer( p ) );
+                     }
+                  }
+               }
+            }
+         }
+
+         void key( const std::string_view sv )
+         {
+            key( std::string( sv ) );
+         }
+
+         void key( const char* v )
+         {
+            key( std::string( v ) );
+         }
+
+         void member()
+         {
+            if( m_match ) {
+               validate_enum( []( events_compare< Traits >& c ) { c.member(); return ! c.match(); } );
+            }
+            if( m_match && !m_properties.empty() && ( m_count.size() == 1 ) ) {
+               for( auto& e : m_properties ) {
+                  if( !e->finalize() ) {
+                     m_match = false;
+                     break;
+                  }
+               }
+               m_properties.clear();
+            }
+            if( m_match ) {
+               validate_collections( []( schema_consumer& c ) { c.member(); return ! c.match(); } );
+            }
+            if( m_match && m_hash ) {
+               m_hash->member();
+            }
+            ++m_count.back();
+         }
+
+         void end_object( const std::size_t /*unused*/ = 0 )
+         {
+            if( m_match ) {
+               validate_enum( []( events_compare< Traits >& c ) { c.end_object(); return ! c.match(); } );
+            }
+            if( m_match ) {
+               validate_collections( []( schema_consumer& c ) { c.end_object(); return ! c.match(); } );
+            }
+            if( m_match && m_hash ) {
+               m_hash->end_object();
+            }
+            if( m_match && ( m_count.size() == 1 ) ) {
+               validate_members( m_count.back() );
+            }
+            if( m_match && ( m_count.size() == 1 ) && !m_node->m_required.empty() ) {
+               if( !std::includes( m_keys.begin(), m_keys.end(), m_node->m_required.begin(), m_node->m_required.end() ) ) {
+                  m_match = false;
+               }
+            }
+            if( m_match && ( m_count.size() == 1 ) && m_node->m_flags & HAS_DEPENDENCIES ) {
+               for( const auto& e : m_node->m_property_dependencies ) {
+                  if( m_keys.count( e.first ) != 0 ) {
+                     if( !std::includes( m_keys.begin(), m_keys.end(), e.second.begin(), e.second.end() ) ) {
+                        m_match = false;
+                        break;
+                     }
+                  }
+               }
+            }
+            m_count.pop_back();
+         }
+      };
+
+      template< template< typename... > class Traits >
+      class schema_container
+         : public std::enable_shared_from_this< schema_container< Traits > >
+      {
+      private:
+         basic_value< Traits > m_value;
+
+         using nodes_t = std::map< const basic_value< Traits >*, std::unique_ptr< schema_node< Traits > > >;
+         nodes_t m_nodes;
+
+         void make_node( const basic_value< Traits >* p )
+         {
+            m_nodes.emplace( p, std::make_unique< schema_node< Traits > >( this, *p ) );
+         }
+
+      public:
+         explicit schema_container( const basic_value< Traits >& v )
+            : m_value( v.skip_value_ptr() )
+         {
+            resolve_references( m_value );
+            make_node( &m_value );
+            while( true ) {
+               std::set< const basic_value< Traits >* > required;
+               for( const auto& e : m_nodes ) {
+                  auto s = e.second->referenced_pointers();
+                  required.insert( s.begin(), s.end() );
+               }
+               for( const auto& e : m_nodes ) {
+                  required.erase( e.first );
+               }
+               if( required.empty() ) {
+                  break;
+               }
+               for( const auto& e : required ) {
+                  make_node( e );
+               }
+            }
+         }
+
+         [[nodiscard]] std::unique_ptr< schema_consumer< Traits > > consumer( const basic_value< Traits >* p ) const
+         {
+            const auto it = m_nodes.find( p );
+            if( it == m_nodes.end() ) {
+               throw std::logic_error( "invalid node ptr, no schema registered" );
+            }
+            return std::make_unique< schema_consumer< Traits > >( this->shared_from_this(), *it->second );
+         }
+
+         [[nodiscard]] std::unique_ptr< schema_consumer< Traits > > consumer() const
+         {
+            return consumer( &m_value );
+         }
+      };
+
+   }  // namespace internal
+
+   template< template< typename... > class Traits >
+   class basic_schema
+   {
+   private:
+      const std::shared_ptr< const internal::schema_container< Traits > > m_container;
+
+   public:
+      explicit basic_schema( const basic_value< Traits >& v )
+         : m_container( std::make_shared< internal::schema_container< Traits > >( v ) )
+      {
+      }
+
+      [[nodiscard]] std::unique_ptr< internal::schema_consumer< Traits > > consumer() const
+      {
+         return m_container->consumer();
+      }
+
+      [[nodiscard]] bool validate( const basic_value< Traits >& v ) const
+      {
+         // TODO: Value validation should be implemented independently,
+         // as it could be more efficient than Events validation!
+         const auto c = consumer();
+         events::from_value( *c, v );
+         return c->finalize();
+      }
+   };
+
+   using schema = basic_schema< traits >;
+
+   template< template< typename... > class Traits >
+   [[nodiscard]] basic_schema< Traits > make_schema( const basic_value< Traits >& v )
+   {
+      return basic_schema< Traits >( v );
+   }
+
+}  // namespace tao::json
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/contrib/set_traits.hpp b/3rdParty/taocpp-json/include/tao/json/contrib/set_traits.hpp
new file mode 100644
index 000000000000..0b4b5fd4c46e
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/contrib/set_traits.hpp
@@ -0,0 +1,41 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_CONTRIB_SET_TRAITS_HPP
+#define TAO_JSON_CONTRIB_SET_TRAITS_HPP
+
+#include <set>
+
+#include "../consume.hpp"
+#include "../forward.hpp"
+
+#include "internal/array_traits.hpp"
+
+namespace tao::json
+{
+   template< typename T, typename... Ts >
+   struct set_traits
+      : internal::array_traits< std::set< T, Ts... > >
+   {
+      template< template< typename... > class Traits, typename... With >
+      static void to( const basic_value< Traits >& v, std::set< T, Ts... >& r, With&... with )
+      {
+         const auto& a = v.get_array();
+         for( const auto& i : a ) {
+            r.emplace( i.template as_with< T >( with... ) );
+         }
+      }
+
+      template< template< typename... > class Traits, typename Producer >
+      static void consume( Producer& parser, std::set< T, Ts... >& r )
+      {
+         auto s = parser.begin_array();
+         while( parser.element_or_end_array( s ) ) {
+            r.emplace( json::consume< T, Traits >( parser ) );
+         }
+      }
+   };
+
+}  // namespace tao::json
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/contrib/shared_ptr_traits.hpp b/3rdParty/taocpp-json/include/tao/json/contrib/shared_ptr_traits.hpp
new file mode 100644
index 000000000000..a6c457135c1c
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/contrib/shared_ptr_traits.hpp
@@ -0,0 +1,90 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_CONTRIB_SHARED_PTR_TRAITS_HPP
+#define TAO_JSON_CONTRIB_SHARED_PTR_TRAITS_HPP
+
+#include <cassert>
+#include <memory>
+#include <type_traits>
+
+#include "../forward.hpp"
+
+#include "internal/indirect_traits.hpp"
+#include "internal/type_traits.hpp"
+
+namespace tao::json
+{
+   namespace internal
+   {
+      template< typename T, typename U >
+      struct shared_ptr_traits
+      {
+         template< template< typename... > class Traits, typename... With >
+         [[nodiscard]] static auto as( const basic_value< Traits >& v, With&... with ) -> std::enable_if_t< use_first_ptr_as< T, Traits, With... >, std::shared_ptr< U > >
+         {
+            return std::make_shared< T >( v, with... );
+         }
+
+         template< template< typename... > class Traits, typename... With >
+         [[nodiscard]] static auto as( const basic_value< Traits >& v, With&... with ) -> std::enable_if_t< use_second_ptr_as< T, Traits, With... > || use_fourth_ptr_as< T, Traits, With... >, std::shared_ptr< U > >
+         {
+            return std::make_shared< T >( Traits< T >::as( v, with... ) );
+         }
+
+         template< template< typename... > class Traits, typename... With >
+         [[nodiscard]] static auto as( const basic_value< Traits >& v, With&... with ) -> std::enable_if_t< use_third_ptr_as< T, Traits, With... >, std::shared_ptr< U > >
+         {
+            auto t = std::make_shared< T >();
+            Traits< T >::to( v, *t, with... );
+            return t;
+         }
+
+         template< template< typename... > class Traits, typename Producer >
+         [[nodiscard]] static auto consume( Producer& parser ) -> std::enable_if_t< use_first_ptr_consume< T, Traits, Producer > || use_third_ptr_consume< T, Traits, Producer >, std::shared_ptr< U > >
+         {
+            return Traits< T >::template consume< Traits >( parser );
+         }
+
+         template< template< typename... > class Traits, typename Producer >
+         [[nodiscard]] static auto consume( Producer& parser ) -> std::enable_if_t< use_second_ptr_consume< T, Traits, Producer >, std::shared_ptr< U > >
+         {
+            auto t = std::make_shared< T >();
+            Traits< T >::template consume< Traits >( parser, *t );
+            return t;
+         }
+      };
+
+   }  // namespace internal
+
+   template< typename T, typename U = T >
+   struct shared_ptr_traits
+      : internal::shared_ptr_traits< T, U >
+   {
+      template< template< typename... > class Traits >
+      static void assign( basic_value< Traits >& v, const std::shared_ptr< U >& o )
+      {
+         assert( o );
+         v = static_cast< const T& >( *o );
+      }
+
+      template< template< typename... > class Traits, typename Consumer >
+      static void produce( Consumer& c, const std::shared_ptr< U >& o )
+      {
+         assert( o );
+         json::events::produce< Traits >( c, static_cast< const T& >( *o ) );
+      }
+   };
+
+   template< typename T >
+   struct shared_ptr_traits< T, T >
+      : internal::shared_ptr_traits< T, T >,
+        internal::indirect_traits< std::shared_ptr< T > >
+   {
+      template< typename V >
+      using with_base = shared_ptr_traits< T, V >;
+   };
+
+}  // namespace tao::json
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/contrib/traits.hpp b/3rdParty/taocpp-json/include/tao/json/contrib/traits.hpp
new file mode 100644
index 000000000000..16504d76c73f
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/contrib/traits.hpp
@@ -0,0 +1,121 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_CONTRIB_TRAITS_HPP
+#define TAO_JSON_CONTRIB_TRAITS_HPP
+
+#include "../traits.hpp"
+
+#include "pair_traits.hpp"
+#include "tuple_traits.hpp"
+
+#include "pointer_traits.hpp"
+
+#include "array_traits.hpp"
+#include "deque_traits.hpp"
+#include "list_traits.hpp"
+#include "set_traits.hpp"
+#include "unordered_set_traits.hpp"
+#include "vector_traits.hpp"
+
+#include "vector_bool_traits.hpp"
+
+#include "map_traits.hpp"
+#include "unordered_map_traits.hpp"
+
+#include "multimap_traits.hpp"
+#include "multiset_traits.hpp"
+
+#include "shared_ptr_traits.hpp"
+#include "unique_ptr_traits.hpp"
+
+namespace tao::json
+{
+   template< typename U, typename V >
+   struct traits< std::pair< U, V > >
+      : pair_traits< U, V >
+   {};
+
+   template< typename... Ts >
+   struct traits< std::tuple< Ts... > >
+      : tuple_traits< Ts... >
+   {};
+
+   template<>
+   struct traits< token >
+      : token_traits
+   {};
+
+   template<>
+   struct traits< pointer >
+      : pointer_traits
+   {};
+
+   template< typename T, std::size_t N >
+   struct traits< std::array< T, N > >
+      : array_traits< T, N >
+   {};
+
+   template< typename T, typename... Ts >
+   struct traits< std::deque< T, Ts... > >
+      : deque_traits< T, Ts... >
+   {};
+
+   template< typename T, typename... Ts >
+   struct traits< std::list< T, Ts... > >
+      : list_traits< T, Ts... >
+   {};
+
+   template< typename T, typename... Ts >
+   struct traits< std::set< T, Ts... > >
+      : set_traits< T, Ts... >
+   {};
+
+   template< typename T, typename... Ts >
+   struct traits< std::unordered_set< T, Ts... > >
+      : unordered_set_traits< T, Ts... >
+   {};
+
+   template< typename T, typename... Ts >
+   struct traits< std::vector< T, Ts... > >
+      : vector_traits< T, Ts... >
+   {};
+
+   template<>
+   struct traits< std::vector< bool > >
+      : vector_bool_traits
+   {};
+
+   template< typename T, typename... Ts >
+   struct traits< std::map< std::string, T, Ts... > >
+      : map_traits< T, Ts... >
+   {};
+
+   template< typename T, typename... Ts >
+   struct traits< std::unordered_map< std::string, T, Ts... > >
+      : unordered_map_traits< T, Ts... >
+   {};
+
+   template< typename T, typename... Ts >
+   struct traits< std::multiset< T, Ts... > >
+      : multiset_traits< T, Ts... >
+   {};
+
+   template< typename T, typename... Ts >
+   struct traits< std::multimap< std::string, T, Ts... > >
+      : multimap_traits< T, Ts... >
+   {};
+
+   template< typename T >
+   struct traits< std::shared_ptr< T > >
+      : shared_ptr_traits< T >
+   {};
+
+   template< typename T >
+   struct traits< std::unique_ptr< T > >
+      : unique_ptr_traits< T >
+   {};
+
+}  // namespace tao::json
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/contrib/tuple_traits.hpp b/3rdParty/taocpp-json/include/tao/json/contrib/tuple_traits.hpp
new file mode 100644
index 000000000000..3061cfa29df2
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/contrib/tuple_traits.hpp
@@ -0,0 +1,51 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_CONTRIB_TUPLE_TRAITS_HPP
+#define TAO_JSON_CONTRIB_TUPLE_TRAITS_HPP
+
+#include <tuple>
+#include <utility>
+
+#include "../binding.hpp"
+
+namespace tao::json
+{
+   namespace internal
+   {
+      template< std::size_t I, typename... Ts >
+      struct getter
+      {
+         [[nodiscard]] static decltype( auto ) get( std::tuple< Ts... >& t ) noexcept
+         {
+            return std::get< I >( t );
+         }
+
+         [[nodiscard]] static decltype( auto ) cget( const std::tuple< Ts... >& t ) noexcept
+         {
+            return std::get< I >( t );
+         }
+      };
+
+      template< typename Indices, typename... Ts >
+      struct tuple_traits;
+
+      template< std::size_t... Is, typename... Ts >
+      struct tuple_traits< std::index_sequence< Is... >, Ts... >
+      {
+         template< std::size_t I >
+         using helper_t = binding::element2< &getter< I, Ts... >::cget, &getter< I, Ts... >::get >;
+
+         using type = binding::array< helper_t< Is >... >;
+      };
+
+   }  // namespace internal
+
+   template< typename... Ts >
+   struct tuple_traits
+      : internal::tuple_traits< std::index_sequence_for< Ts... >, Ts... >::type
+   {};
+
+}  // namespace tao::json
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/contrib/unique_ptr_traits.hpp b/3rdParty/taocpp-json/include/tao/json/contrib/unique_ptr_traits.hpp
new file mode 100644
index 000000000000..58f874835e51
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/contrib/unique_ptr_traits.hpp
@@ -0,0 +1,89 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_CONTRIB_UNIQUE_PTR_TRAITS_HPP
+#define TAO_JSON_CONTRIB_UNIQUE_PTR_TRAITS_HPP
+
+#include <cassert>
+#include <memory>
+
+#include "../forward.hpp"
+
+#include "internal/indirect_traits.hpp"
+#include "internal/type_traits.hpp"
+
+namespace tao::json
+{
+   namespace internal
+   {
+      template< typename T, typename U >
+      struct unique_ptr_traits
+      {
+         template< template< typename... > class Traits, typename... With >
+         [[nodiscard]] static auto as( const basic_value< Traits >& v, With&... with ) -> std::enable_if_t< use_first_ptr_as< T, Traits, With... >, std::unique_ptr< U > >
+         {
+            return std::unique_ptr< U >( new T( v, with... ) );
+         }
+
+         template< template< typename... > class Traits, typename... With >
+         [[nodiscard]] static auto as( const basic_value< Traits >& v, With&... with ) -> std::enable_if_t< use_second_ptr_as< T, Traits, With... > || use_fourth_ptr_as< T, Traits, With... >, std::unique_ptr< U > >
+         {
+            return std::unique_ptr< U >( new T( Traits< T >::as( v, with... ) ) );
+         }
+
+         template< template< typename... > class Traits, typename... With >
+         [[nodiscard]] static auto as( const basic_value< Traits >& v, With&... with ) -> std::enable_if_t< use_third_ptr_as< T, Traits, With... >, std::unique_ptr< U > >
+         {
+            std::unique_ptr< U > t( new T() );
+            Traits< T >::to( v, static_cast< T& >( *t ), with... );
+            return t;
+         }
+
+         template< template< typename... > class Traits, typename Producer >
+         [[nodiscard]] static auto consume( Producer& parser ) -> std::enable_if_t< use_first_ptr_consume< T, Traits, Producer > || use_third_ptr_consume< T, Traits, Producer >, std::unique_ptr< U > >
+         {
+            return Traits< T >::template consume< Traits >( parser );
+         }
+
+         template< template< typename... > class Traits, typename Producer >
+         [[nodiscard]] static auto consume( Producer& parser ) -> std::enable_if_t< use_second_ptr_consume< T, Traits, Producer >, std::unique_ptr< U > >
+         {
+            std::unique_ptr< U > t( new T() );
+            Traits< T >::template consume< Traits >( parser, static_cast< T& >( *t ) );
+            return t;
+         }
+      };
+
+   }  // namespace internal
+
+   template< typename T, typename U = T >
+   struct unique_ptr_traits
+      : internal::unique_ptr_traits< T, U >
+   {
+      template< template< typename... > class Traits >
+      static void assign( basic_value< Traits >& v, const std::unique_ptr< U >& o )
+      {
+         assert( o );
+         v = static_cast< const T& >( *o );
+      }
+
+      template< template< typename... > class Traits, typename Consumer >
+      static void produce( Consumer& c, const std::unique_ptr< U >& o )
+      {
+         assert( o );
+         json::events::produce< Traits >( c, static_cast< const T& >( *o ) );
+      }
+   };
+
+   template< typename T >
+   struct unique_ptr_traits< T, T >
+      : internal::unique_ptr_traits< T, T >,
+        internal::indirect_traits< std::unique_ptr< T > >
+   {
+      template< typename V >
+      using with_base = unique_ptr_traits< T, V >;
+   };
+
+}  // namespace tao::json
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/contrib/unordered_map_traits.hpp b/3rdParty/taocpp-json/include/tao/json/contrib/unordered_map_traits.hpp
new file mode 100644
index 000000000000..b591981a2445
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/contrib/unordered_map_traits.hpp
@@ -0,0 +1,43 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_CONTRIB_UNORDERED_MAP_TRAITS_HPP
+#define TAO_JSON_CONTRIB_UNORDERED_MAP_TRAITS_HPP
+
+#include <string>
+#include <unordered_map>
+
+#include "../consume.hpp"
+#include "../forward.hpp"
+
+#include "internal/object_traits.hpp"
+
+namespace tao::json
+{
+   template< typename T, typename... Ts >
+   struct unordered_map_traits
+      : internal::object_traits< std::unordered_map< std::string, T, Ts... > >
+   {
+      template< template< typename... > class Traits, typename... With >
+      static void to( const basic_value< Traits >& v, std::unordered_map< std::string, T, Ts... >& r, With&... with )
+      {
+         const auto& o = v.get_object();
+         for( const auto& i : o ) {
+            r.try_emplace( i.first, Traits< T >::as( i.second, with... ) );
+         }
+      }
+
+      template< template< typename... > class Traits, typename Producer >
+      static void consume( Producer& parser, std::unordered_map< std::string, T, Ts... >& v )
+      {
+         auto s = parser.begin_object();
+         while( parser.member_or_end_object( s ) ) {
+            auto k = parser.key();
+            v.try_emplace( std::move( k ), json::consume< T, Traits >( parser ) );
+         }
+      }
+   };
+
+}  // namespace tao::json
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/contrib/unordered_set_traits.hpp b/3rdParty/taocpp-json/include/tao/json/contrib/unordered_set_traits.hpp
new file mode 100644
index 000000000000..45b5de01a122
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/contrib/unordered_set_traits.hpp
@@ -0,0 +1,41 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_CONTRIB_UNORDERED_SET_TRAITS_HPP
+#define TAO_JSON_CONTRIB_UNORDERED_SET_TRAITS_HPP
+
+#include <unordered_set>
+
+#include "../consume.hpp"
+#include "../forward.hpp"
+
+#include "internal/array_traits.hpp"
+
+namespace tao::json
+{
+   template< typename T, typename... Ts >
+   struct unordered_set_traits
+      : internal::array_traits< std::unordered_set< T, Ts... > >
+   {
+      template< template< typename... > class Traits, typename... With >
+      static void to( const basic_value< Traits >& v, std::unordered_set< T, Ts... >& r, With&... with )
+      {
+         const auto& a = v.get_array();
+         for( const auto& i : a ) {
+            r.try_emplace( Traits< T >::as( i, with... ) );
+         }
+      }
+
+      template< template< typename... > class Traits, typename Producer >
+      static void consume( Producer& parser, std::unordered_set< T, Ts... >& r )
+      {
+         auto s = parser.begin_array();
+         while( parser.element_or_end_array( s ) ) {
+            r.try_emplace( json::consume< T, Traits >( parser ) );
+         }
+      }
+   };
+
+}  // namespace tao::json
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/contrib/vector_bool_traits.hpp b/3rdParty/taocpp-json/include/tao/json/contrib/vector_bool_traits.hpp
new file mode 100644
index 000000000000..3b1d8db65939
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/contrib/vector_bool_traits.hpp
@@ -0,0 +1,45 @@
+// Copyright (c) 2019-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_CONTRIB_VECTOR_BOOL_TRAITS_HPP
+#define TAO_JSON_CONTRIB_VECTOR_BOOL_TRAITS_HPP
+
+#include <vector>
+
+#include "../consume.hpp"
+#include "../forward.hpp"
+
+#include "vector_traits.hpp"
+
+namespace tao::json
+{
+   struct vector_bool_traits
+      : vector_traits< bool >
+   {
+      template< template< typename... > class Traits >
+      static void assign( basic_value< Traits >& v, const std::vector< bool >& o )
+      {
+         v.emplace_array();
+         v.get_array().reserve( o.size() );
+         for( const auto& e : o ) {
+            v.emplace_back( bool( e ) );
+         }
+      }
+
+      template< template< typename... > class Traits, typename Consumer >
+      static void produce( Consumer& c, const std::vector< bool >& o )
+      {
+         c.begin_array( o.size() );
+         for( const auto& i : o ) {
+            json::events::produce< Traits >( c, bool( i ) );
+            c.element();
+         }
+         c.end_array( o.size() );
+      }
+
+      // TODO: Check whether anything else needs "special-casing".
+   };
+
+}  // namespace tao::json
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/contrib/vector_traits.hpp b/3rdParty/taocpp-json/include/tao/json/contrib/vector_traits.hpp
new file mode 100644
index 000000000000..32c3734fdc02
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/contrib/vector_traits.hpp
@@ -0,0 +1,51 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_CONTRIB_VECTOR_TRAITS_HPP
+#define TAO_JSON_CONTRIB_VECTOR_TRAITS_HPP
+
+#include <vector>
+
+#include "../consume.hpp"
+#include "../forward.hpp"
+
+#include "internal/array_traits.hpp"
+
+namespace tao::json
+{
+   template< typename T, typename... Ts >
+   struct vector_traits
+      : internal::array_traits< std::vector< T, Ts... > >
+   {
+      template< template< typename... > class Traits, typename... With >
+      static void to( const basic_value< Traits >& v, std::vector< T, Ts... >& r, With&... with )
+      {
+         const auto& a = v.get_array();
+         for( const auto& i : a ) {
+            r.emplace_back( i.template as_with< T >( with... ) );
+         }
+      }
+
+#ifdef _MSC_VER
+#pragma warning( push )
+#pragma warning( disable : 4127 )
+#endif
+      template< template< typename... > class Traits, typename Producer >
+      static void consume( Producer& parser, std::vector< T, Ts... >& v )
+      {
+         auto s = parser.begin_array();
+         if( s.size ) {
+            v.reserve( *s.size );
+         }
+         while( parser.element_or_end_array( s ) ) {
+            v.emplace_back( json::consume< T, Traits >( parser ) );
+         }
+      }
+#ifdef _MSC_VER
+#pragma warning( pop )
+#endif
+   };
+
+}  // namespace tao::json
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/events.hpp b/3rdParty/taocpp-json/include/tao/json/events.hpp
new file mode 100644
index 000000000000..8063909c2ce7
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/events.hpp
@@ -0,0 +1,47 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_EVENTS_HPP
+#define TAO_JSON_EVENTS_HPP
+
+// Events producers
+#include "events/from_file.hpp"
+#include "events/from_input.hpp"
+#include "events/from_stream.hpp"
+#include "events/from_string.hpp"
+#include "events/from_value.hpp"
+#include "events/produce.hpp"
+
+// Events consumers
+#include "events/to_pretty_stream.hpp"
+#include "events/to_stream.hpp"
+#include "events/to_string.hpp"
+#include "events/to_value.hpp"
+
+// Events transformers
+#include "events/binary_to_base64.hpp"
+#include "events/binary_to_base64url.hpp"
+#include "events/binary_to_exception.hpp"
+#include "events/binary_to_hex.hpp"
+#include "events/invalid_string_to_binary.hpp"
+#include "events/invalid_string_to_exception.hpp"
+#include "events/invalid_string_to_hex.hpp"
+#include "events/key_camel_case_to_snake_case.hpp"
+#include "events/key_snake_case_to_camel_case.hpp"
+#include "events/limit_nesting_depth.hpp"
+#include "events/limit_value_count.hpp"
+#include "events/non_finite_to_exception.hpp"
+#include "events/non_finite_to_null.hpp"
+#include "events/non_finite_to_string.hpp"
+#include "events/prefer_signed.hpp"
+#include "events/prefer_unsigned.hpp"
+
+// Events other
+#include "events/debug.hpp"
+#include "events/discard.hpp"
+#include "events/hash.hpp"
+#include "events/tee.hpp"
+#include "events/validate_event_order.hpp"
+#include "events/validate_keys.hpp"
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/events/apply.hpp b/3rdParty/taocpp-json/include/tao/json/events/apply.hpp
new file mode 100644
index 000000000000..78a1ba90a027
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/events/apply.hpp
@@ -0,0 +1,20 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_EVENTS_APPLY_HPP
+#define TAO_JSON_EVENTS_APPLY_HPP
+
+#include "ref.hpp"
+#include "transformer.hpp"
+
+namespace tao::json::events
+{
+   template< template< typename... > class... Transformer, typename Consumer >
+   [[nodiscard]] transformer< ref< Consumer >, Transformer... > apply( Consumer& c ) noexcept( noexcept( transformer< ref< Consumer >, Transformer... >( c ) ) )
+   {
+      return transformer< ref< Consumer >, Transformer... >( c );
+   }
+
+}  // namespace tao::json::events
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/events/binary_to_base64.hpp b/3rdParty/taocpp-json/include/tao/json/events/binary_to_base64.hpp
new file mode 100644
index 000000000000..dcf930d2d5de
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/events/binary_to_base64.hpp
@@ -0,0 +1,26 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_EVENTS_BINARY_TO_BASE64_HPP
+#define TAO_JSON_EVENTS_BINARY_TO_BASE64_HPP
+
+#include "../binary_view.hpp"
+#include "../internal/base64.hpp"
+
+namespace tao::json::events
+{
+   template< typename Consumer >
+   struct binary_to_base64
+      : Consumer
+   {
+      using Consumer::Consumer;
+
+      void binary( const tao::binary_view v )
+      {
+         Consumer::string( internal::base64( v ) );
+      }
+   };
+
+}  // namespace tao::json::events
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/events/binary_to_base64url.hpp b/3rdParty/taocpp-json/include/tao/json/events/binary_to_base64url.hpp
new file mode 100644
index 000000000000..e46bd6cc96ca
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/events/binary_to_base64url.hpp
@@ -0,0 +1,28 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_EVENTS_BINARY_TO_BASE64URL_HPP
+#define TAO_JSON_EVENTS_BINARY_TO_BASE64URL_HPP
+
+#include <vector>
+
+#include "../binary_view.hpp"
+#include "../internal/base64url.hpp"
+
+namespace tao::json::events
+{
+   template< typename Consumer >
+   struct binary_to_base64url
+      : Consumer
+   {
+      using Consumer::Consumer;
+
+      void binary( const tao::binary_view v )
+      {
+         Consumer::string( internal::base64url( v ) );
+      }
+   };
+
+}  // namespace tao::json::events
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/events/binary_to_exception.hpp b/3rdParty/taocpp-json/include/tao/json/events/binary_to_exception.hpp
new file mode 100644
index 000000000000..c14b34a58b15
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/events/binary_to_exception.hpp
@@ -0,0 +1,27 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_EVENTS_BINARY_TO_EXCEPTION_HPP
+#define TAO_JSON_EVENTS_BINARY_TO_EXCEPTION_HPP
+
+#include <stdexcept>
+
+#include "../binary_view.hpp"
+
+namespace tao::json::events
+{
+   template< typename Consumer >
+   struct binary_to_exception
+      : Consumer
+   {
+      using Consumer::Consumer;
+
+      void binary( const tao::binary_view /*unused*/ )
+      {
+         throw std::runtime_error( "invalid binary data" );
+      }
+   };
+
+}  // namespace tao::json::events
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/events/binary_to_hex.hpp b/3rdParty/taocpp-json/include/tao/json/events/binary_to_hex.hpp
new file mode 100644
index 000000000000..87cb21e35150
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/events/binary_to_hex.hpp
@@ -0,0 +1,26 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_EVENTS_BINARY_TO_HEX_HPP
+#define TAO_JSON_EVENTS_BINARY_TO_HEX_HPP
+
+#include "../binary_view.hpp"
+#include "../internal/hexdump.hpp"
+
+namespace tao::json::events
+{
+   template< typename Consumer >
+   struct binary_to_hex
+      : Consumer
+   {
+      using Consumer::Consumer;
+
+      void binary( const tao::binary_view v )
+      {
+         Consumer::string( internal::hexdump( v ) );
+      }
+   };
+
+}  // namespace tao::json::events
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/events/compare.hpp b/3rdParty/taocpp-json/include/tao/json/events/compare.hpp
new file mode 100644
index 000000000000..80c907d30e09
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/events/compare.hpp
@@ -0,0 +1,265 @@
+// Copyright (c) 2016-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_EVENTS_COMPARE_HPP
+#define TAO_JSON_EVENTS_COMPARE_HPP
+
+#include <cstddef>
+#include <cstdint>
+#include <set>
+#include <string>
+#include <vector>
+
+#include "../value.hpp"
+
+namespace tao::json
+{
+   namespace internal
+   {
+      template< template< typename... > class Traits >
+      class events_compare
+      {
+      protected:
+         std::vector< const basic_value< Traits >* > m_current;
+         std::vector< std::size_t > m_array_index;
+         // TODO: use std::unordered_set? or even std::vector!?
+         std::vector< std::set< const basic_value< Traits >* > > m_object_keys;
+         bool m_match = true;
+
+      public:
+         events_compare() = default;
+
+         events_compare( const events_compare& ) = delete;
+         events_compare( events_compare&& ) = delete;
+
+         ~events_compare() = default;
+
+         void operator=( const events_compare& ) = delete;
+         void operator=( events_compare&& ) = delete;
+
+         void reset() noexcept
+         {
+            m_current.clear();
+            m_array_index.clear();
+            m_object_keys.clear();
+            m_match = true;
+         }
+
+         [[nodiscard]] static const basic_value< Traits >* skip_pointer( const basic_value< Traits >* p ) noexcept
+         {
+            while( p && p->is_value_ptr() ) {
+               p = p->get_value_ptr();
+            }
+            return p;
+         }
+
+         void push( const basic_value< Traits >* p )
+         {
+            m_current.push_back( skip_pointer( p ) );
+         }
+
+         [[nodiscard]] bool match() const noexcept
+         {
+            return m_match;
+         }
+
+         [[nodiscard]] const basic_value< Traits >& current() const noexcept
+         {
+            return *m_current.back();
+         }
+
+         void null() noexcept
+         {
+            m_match = m_match && ( m_current.back() != nullptr ) && ( current().is_null() );
+         }
+
+         void boolean( const bool v ) noexcept
+         {
+            m_match = m_match && ( m_current.back() != nullptr ) && ( current() == v );
+         }
+
+         void number( const std::int64_t v ) noexcept
+         {
+            m_match = m_match && ( m_current.back() != nullptr ) && ( current() == v );
+         }
+
+         void number( const std::uint64_t v ) noexcept
+         {
+            m_match = m_match && ( m_current.back() != nullptr ) && ( current() == v );
+         }
+
+         void number( const double v ) noexcept
+         {
+            m_match = m_match && ( m_current.back() != nullptr ) && ( current() == v );
+         }
+
+         void string( const std::string_view v ) noexcept
+         {
+            m_match = m_match && ( m_current.back() != nullptr ) && ( current() == v );
+         }
+
+         void binary( const tao::binary_view v ) noexcept
+         {
+            m_match = m_match && ( m_current.back() != nullptr ) && ( current() == v );
+         }
+
+         void begin_array( const std::size_t /*unused*/ = 0 )
+         {
+            if( m_current.back() == nullptr ) {
+               m_match = false;
+               m_current.push_back( nullptr );
+            }
+            else {
+               const auto& a = current();
+               if( !a.is_array() ) {
+                  m_match = false;
+                  m_current.push_back( nullptr );
+               }
+               else {
+                  const auto& v = a.get_array();
+                  if( !v.empty() ) {
+                     push( &v.front() );
+                  }
+                  else {
+                     m_current.push_back( nullptr );
+                  }
+               }
+            }
+            m_array_index.push_back( 0 );
+         }
+
+         void element() noexcept
+         {
+            const auto i = ++m_array_index.back();
+            if( m_match ) {
+               if( m_current.back() != nullptr ) {
+                  const auto& a = ( *( m_current.end() - 2 ) )->get_array();
+                  if( i < a.size() ) {
+                     m_current.back() = skip_pointer( &a[ i ] );
+                  }
+                  else {
+                     m_current.back() = nullptr;
+                  }
+               }
+            }
+         }
+
+         void end_array( const std::size_t /*unused*/ = 0 ) noexcept
+         {
+            m_current.pop_back();
+            if( m_match ) {
+               if( m_array_index.back() != current().get_array().size() ) {
+                  m_match = false;
+               }
+            }
+            m_array_index.pop_back();
+         }
+
+         void begin_object( const std::size_t /*unused*/ = 0 )
+         {
+            if( m_current.back() == nullptr ) {
+               m_match = false;
+            }
+            else {
+               const auto& o = current();
+               if( !o.is_object() ) {
+                  m_match = false;
+               }
+            }
+            m_object_keys.emplace_back();
+         }
+
+         void key( const std::string& v )
+         {
+            if( !m_match ) {
+               m_current.push_back( nullptr );
+            }
+            else if( const auto* p = current().find( v ) ) {
+               if( !m_object_keys.back().insert( p ).second ) {
+                  m_match = false;  // duplicate key found! -> fail
+                  m_current.push_back( nullptr );
+               }
+               else {
+                  push( p );
+               }
+            }
+            else {
+               m_match = false;
+               m_current.push_back( nullptr );
+            }
+         }
+
+         void key( const std::string_view v )
+         {
+            key( std::string( v ) );
+         }
+
+         void key( const char* v )
+         {
+            key( std::string( v ) );
+         }
+
+         void member() noexcept
+         {
+            m_current.pop_back();
+         }
+
+         void end_object( const std::size_t /*unused*/ = 0 ) noexcept
+         {
+            if( m_match ) {
+               if( m_object_keys.back().size() != current().get_object().size() ) {
+                  m_match = false;
+               }
+            }
+            m_object_keys.pop_back();
+         }
+      };
+
+   }  // namespace internal
+
+   namespace events
+   {
+      // Events consumer that compares against a JSON Value.
+
+      template< template< typename... > class Traits >
+      class basic_compare
+         : public internal::events_compare< Traits >
+      {
+      private:
+         const basic_value< Traits > m_value;
+
+      public:
+         explicit basic_compare( const basic_value< Traits >& v )
+            : m_value( v )
+         {
+            reset();
+         }
+
+         explicit basic_compare( basic_value< Traits >&& v )
+            : m_value( std::move( v ) )
+         {
+            reset();
+         }
+
+         basic_compare( const basic_compare& ) = delete;
+         basic_compare( basic_compare&& ) = delete;
+
+         ~basic_compare() = default;
+
+         void operator=( const basic_compare& ) = delete;
+         void operator=( basic_compare&& ) = delete;
+
+         void reset()
+         {
+            internal::events_compare< Traits >::reset();
+            internal::events_compare< Traits >::push( &m_value );
+         }
+      };
+
+      using compare = basic_compare< traits >;
+
+   }  // namespace events
+
+}  // namespace tao::json
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/events/debug.hpp b/3rdParty/taocpp-json/include/tao/json/events/debug.hpp
new file mode 100644
index 000000000000..44eead54c39f
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/events/debug.hpp
@@ -0,0 +1,145 @@
+// Copyright (c) 2016-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_EVENTS_DEBUG_HPP
+#define TAO_JSON_EVENTS_DEBUG_HPP
+
+#include <cmath>
+#include <cstddef>
+#include <cstdint>
+#include <ostream>
+#include <string>
+
+#include "../binary_view.hpp"
+
+#include "../external/ryu.hpp"
+
+#include "../internal/escape.hpp"
+#include "../internal/hexdump.hpp"
+
+namespace tao::json::events
+{
+   // Events consumer that writes the events to a stream for debug purposes.
+
+   class debug
+   {
+   private:
+      std::ostream& os;
+
+   public:
+      explicit debug( std::ostream& in_os ) noexcept
+         : os( in_os )
+      {}
+
+      void null()
+      {
+         os << "null\n";
+      }
+
+      void boolean( const bool v )
+      {
+         if( v ) {
+            os << "boolean: true\n";
+         }
+         else {
+            os << "boolean: false\n";
+         }
+      }
+
+      void number( const std::int64_t v )
+      {
+         os << "std::int64_t: " << v << '\n';
+      }
+
+      void number( const std::uint64_t v )
+      {
+         os << "std::uint64_t: " << v << '\n';
+      }
+
+      void number( const double v )
+      {
+         os << "double: ";
+         if( !std::isfinite( v ) ) {
+            os << v;
+         }
+         else {
+            ryu::d2s_stream( os, v );
+         }
+         os << '\n';
+      }
+
+      void string( const std::string_view v )
+      {
+         os << "string: \"";
+         internal::escape( os, v );
+         os << "\"\n";
+      }
+
+      void binary( const tao::binary_view v )
+      {
+         os << "binary: ";
+         internal::hexdump( os, v );
+         os << '\n';
+      }
+
+      void begin_array()
+      {
+         os << "begin array\n";
+      }
+
+      void begin_array( const std::size_t size )
+      {
+         os << "begin array " << size << '\n';
+      }
+
+      void element()
+      {
+         os << "element\n";
+      }
+
+      void end_array()
+      {
+         os << "end array\n";
+      }
+
+      void end_array( const std::size_t size )
+      {
+         os << "end array " << size << '\n';
+      }
+
+      void begin_object()
+      {
+         os << "begin object\n";
+      }
+
+      void begin_object( const std::size_t size )
+      {
+         os << "begin object " << size << '\n';
+      }
+
+      void key( const std::string_view v )
+      {
+         os << "key: \"";
+         internal::escape( os, v );
+         os << "\"\n";
+      }
+
+      void member()
+      {
+         os << "member\n";
+      }
+
+      void end_object()
+      {
+         os << "end object\n";
+      }
+
+      void end_object( const std::size_t size )
+      {
+         os << "end object " << size << '\n';
+      }
+   };
+
+}  // namespace tao::json::events
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/events/discard.hpp b/3rdParty/taocpp-json/include/tao/json/events/discard.hpp
new file mode 100644
index 000000000000..ffe6a39bc43d
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/events/discard.hpp
@@ -0,0 +1,43 @@
+// Copyright (c) 2016-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_EVENTS_DISCARD_HPP
+#define TAO_JSON_EVENTS_DISCARD_HPP
+
+#include <cstddef>
+#include <cstdint>
+#include <string_view>
+
+#include "../binary_view.hpp"
+
+namespace tao::json::events
+{
+   // Events consumer that discards events.
+
+   struct discard
+   {
+      void null() noexcept {}
+
+      void boolean( const bool /*unused*/ ) noexcept {}
+
+      void number( const std::int64_t /*unused*/ ) noexcept {}
+      void number( const std::uint64_t /*unused*/ ) noexcept {}
+      void number( const double /*unused*/ ) noexcept {}
+
+      void string( const std::string_view /*unused*/ ) noexcept {}
+
+      void binary( const tao::binary_view /*unused*/ ) noexcept {}
+
+      void begin_array( const std::size_t /*unused*/ = 0 ) noexcept {}
+      void element() noexcept {}
+      void end_array( const std::size_t /*unused*/ = 0 ) noexcept {}
+
+      void begin_object( const std::size_t /*unused*/ = 0 ) noexcept {}
+      void key( const std::string_view /*unused*/ ) noexcept {}
+      void member() noexcept {}
+      void end_object( const std::size_t /*unused*/ = 0 ) noexcept {}
+   };
+
+}  // namespace tao::json::events
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/events/from_file.hpp b/3rdParty/taocpp-json/include/tao/json/events/from_file.hpp
new file mode 100644
index 000000000000..c94024fd339a
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/events/from_file.hpp
@@ -0,0 +1,28 @@
+// Copyright (c) 2016-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_EVENTS_FROM_FILE_HPP
+#define TAO_JSON_EVENTS_FROM_FILE_HPP
+
+#include <utility>
+
+#include "../internal/action.hpp"
+#include "../internal/errors.hpp"
+#include "../internal/grammar.hpp"
+
+#include "../external/pegtl/file_input.hpp"
+
+namespace tao::json::events
+{
+   // Events producer to parse a file containing a JSON string representation.
+
+   template< typename T, typename Consumer >
+   void from_file( Consumer& consumer, T&& filename )
+   {
+      pegtl::file_input< pegtl::tracking_mode::lazy > in( std::forward< T >( filename ) );
+      pegtl::parse< internal::grammar, internal::action, internal::errors >( in, consumer );
+   }
+
+}  // namespace tao::json::events
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/events/from_input.hpp b/3rdParty/taocpp-json/include/tao/json/events/from_input.hpp
new file mode 100644
index 000000000000..0845db923fc5
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/events/from_input.hpp
@@ -0,0 +1,45 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_EVENTS_FROM_INPUT_HPP
+#define TAO_JSON_EVENTS_FROM_INPUT_HPP
+
+#include <utility>
+
+#include "../external/pegtl/parse.hpp"
+
+#include "../internal/action.hpp"
+#include "../internal/errors.hpp"
+#include "../internal/grammar.hpp"
+
+namespace tao::json::events
+{
+   // Events producers that parse a JSON string representation from a PEGTL input (or something compatible).
+
+   template< typename Consumer, typename Input >
+   void from_input( Consumer& consumer, Input&& in )
+   {
+      pegtl::parse< internal::grammar, internal::action, internal::errors >( std::forward< Input >( in ), consumer );
+   }
+
+   template< typename Consumer, typename Input >
+   void from_input_embedded( Consumer& consumer, Input&& in )
+   {
+      pegtl::parse< internal::embedded, internal::action, internal::errors >( std::forward< Input >( in ), consumer );
+   }
+
+   template< typename Consumer, typename Outer, typename Input >
+   void from_input_nested( Consumer& consumer, const Outer& oi, Input&& in )
+   {
+      pegtl::parse_nested< internal::grammar, internal::action, internal::errors >( oi, std::forward< Input >( in ), consumer );
+   }
+
+   template< typename Consumer, typename Outer, typename Input >
+   void from_input_embedded_nested( Consumer& consumer, const Outer& oi, Input&& in )
+   {
+      pegtl::parse_nested< internal::embedded, internal::action, internal::errors >( oi, std::forward< Input >( in ), consumer );
+   }
+
+}  // namespace tao::json::events
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/events/from_stream.hpp b/3rdParty/taocpp-json/include/tao/json/events/from_stream.hpp
new file mode 100644
index 000000000000..5c6a03ef3cf7
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/events/from_stream.hpp
@@ -0,0 +1,33 @@
+// Copyright (c) 2016-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_EVENTS_FROM_STREAM_HPP
+#define TAO_JSON_EVENTS_FROM_STREAM_HPP
+
+#include <istream>
+
+#include "../external/pegtl/internal/istream_reader.hpp"
+#include "../external/pegtl/parse.hpp"
+
+#include "../internal/action.hpp"
+#include "../internal/errors.hpp"
+#include "../internal/grammar.hpp"
+
+namespace tao::json::events
+{
+   template< typename Consumer >
+   void from_stream( Consumer& consumer, std::istream& stream, const char* source = nullptr, const std::size_t maximum_buffer_size = 4000 )
+   {
+      pegtl::istream_input in( stream, maximum_buffer_size, source ? source : "tao::json::events::from_stream" );
+      pegtl::parse< internal::grammar, internal::action, internal::errors >( in, consumer );
+   }
+
+   template< typename Consumer >
+   void from_stream( Consumer& consumer, std::istream& stream, const std::string& source, const std::size_t maximum_buffer_size = 4000 )
+   {
+      events::from_stream( consumer, stream, source.c_str(), maximum_buffer_size );
+   }
+
+}  // namespace tao::json::events
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/events/from_string.hpp b/3rdParty/taocpp-json/include/tao/json/events/from_string.hpp
new file mode 100644
index 000000000000..5710d795aec4
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/events/from_string.hpp
@@ -0,0 +1,38 @@
+// Copyright (c) 2016-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_EVENTS_FROM_STRING_HPP
+#define TAO_JSON_EVENTS_FROM_STRING_HPP
+
+#include <string_view>
+
+#include "../external/pegtl/memory_input.hpp"
+
+#include "from_input.hpp"
+
+namespace tao::json::events
+{
+   // Events producer to parse a JSON string representation.
+
+   template< typename Consumer >
+   void from_string( Consumer& consumer, const char* data, const std::size_t size, const char* source = nullptr, const std::size_t byte = 0, const std::size_t line = 1, const std::size_t column = 0 )
+   {
+      pegtl::memory_input< pegtl::tracking_mode::lazy, pegtl::eol::lf_crlf, const char* > in( data, data + size, source ? source : "tao::json::events::from_string", byte, line, column );
+      json::events::from_input( consumer, std::move( in ) );
+   }
+
+   template< typename Consumer >
+   void from_string( Consumer& consumer, const char* data, const std::size_t size, const std::string& source, const std::size_t byte = 0, const std::size_t line = 1, const std::size_t column = 0 )
+   {
+      events::from_string( consumer, data, size, source.c_str(), byte, line, column );
+   }
+
+   template< typename Consumer, typename... Ts >
+   void from_string( Consumer& consumer, const std::string_view data, Ts&&... ts )
+   {
+      events::from_string( consumer, data.data(), data.size(), std::forward< Ts >( ts )... );
+   }
+
+}  // namespace tao::json::events
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/events/from_value.hpp b/3rdParty/taocpp-json/include/tao/json/events/from_value.hpp
new file mode 100644
index 000000000000..aa4124f9e7ff
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/events/from_value.hpp
@@ -0,0 +1,202 @@
+// Copyright (c) 2016-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_EVENTS_FROM_VALUE_HPP
+#define TAO_JSON_EVENTS_FROM_VALUE_HPP
+
+#include <stdexcept>
+
+#include "../basic_value.hpp"
+#include "../internal/format.hpp"
+
+#include "virtual_ref.hpp"
+
+namespace tao::json::events
+{
+   // Events producer to generate events from a JSON Value.
+
+   template< auto Recurse, typename Consumer, template< typename... > class Traits >
+   void from_value( Consumer& consumer, const basic_value< Traits >& v )
+   {
+      switch( v.type() ) {
+         case type::UNINITIALIZED:
+            throw std::logic_error( "unable to produce events from uninitialized values" );
+
+         case type::NULL_:
+            consumer.null();
+            return;
+
+         case type::BOOLEAN:
+            consumer.boolean( v.get_boolean() );
+            return;
+
+         case type::SIGNED:
+            consumer.number( v.get_signed() );
+            return;
+
+         case type::UNSIGNED:
+            consumer.number( v.get_unsigned() );
+            return;
+
+         case type::DOUBLE:
+            consumer.number( v.get_double() );
+            return;
+
+         case type::STRING:
+            consumer.string( v.get_string() );
+            return;
+
+         case type::STRING_VIEW:
+            consumer.string( v.get_string_view() );
+            return;
+
+         case type::BINARY:
+            consumer.binary( v.get_binary() );
+            return;
+
+         case type::BINARY_VIEW:
+            consumer.binary( v.get_binary_view() );
+            return;
+
+         case type::ARRAY: {
+            const auto& a = v.get_array();
+            const auto s = a.size();
+            consumer.begin_array( s );
+            for( const auto& e : a ) {
+               Recurse( consumer, e );
+               consumer.element();
+            }
+            consumer.end_array( s );
+            return;
+         }
+
+         case type::OBJECT: {
+            const auto& o = v.get_object();
+            const auto s = o.size();
+            consumer.begin_object( s );
+            for( const auto& e : o ) {
+               consumer.key( e.first );
+               Recurse( consumer, e.second );
+               consumer.member();
+            }
+            consumer.end_object( s );
+            return;
+         }
+
+         case type::VALUE_PTR:
+            Recurse( consumer, *v.get_value_ptr() );
+            return;
+
+         case type::OPAQUE_PTR: {
+            const auto& q = v.get_opaque_ptr();
+            virtual_ref< Consumer > ref( consumer );
+            q.producer( ref, q.data );
+            return;
+         }
+
+         case type::VALUELESS_BY_EXCEPTION:
+            throw std::logic_error( "unable to produce events from valueless-by-exception value" );
+      }
+      throw std::logic_error( internal::format( "invalid value '", static_cast< std::uint8_t >( v.type() ), "' for tao::json::type" ) );  // LCOV_EXCL_LINE
+   }
+
+   template< typename Consumer, template< typename... > class Traits >
+   void from_value( Consumer& consumer, const basic_value< Traits >& v )
+   {
+      from_value< static_cast< void ( * )( Consumer&, const basic_value< Traits >& ) >( &from_value< Consumer, Traits > ), Consumer, Traits >( consumer, v );
+   }
+
+   // Events producer to generate events from an rvalue JSON value.
+   // Note: Strings from the source might be moved to the consumer.
+
+   template< auto Recurse, typename Consumer, template< typename... > class Traits >
+   void from_value( Consumer& consumer, basic_value< Traits >&& v )
+   {
+      switch( v.type() ) {
+         case type::UNINITIALIZED:
+            throw std::logic_error( "unable to produce events from uninitialized values" );
+
+         case type::NULL_:
+            consumer.null();
+            return;
+
+         case type::BOOLEAN:
+            consumer.boolean( v.get_boolean() );
+            return;
+
+         case type::SIGNED:
+            consumer.number( v.get_signed() );
+            return;
+
+         case type::UNSIGNED:
+            consumer.number( v.get_unsigned() );
+            return;
+
+         case type::DOUBLE:
+            consumer.number( v.get_double() );
+            return;
+
+         case type::STRING:
+            consumer.string( std::move( v.get_string() ) );
+            return;
+
+         case type::STRING_VIEW:
+            consumer.string( v.get_string_view() );
+            return;
+
+         case type::BINARY:
+            consumer.binary( std::move( v.get_binary() ) );
+            return;
+
+         case type::BINARY_VIEW:
+            consumer.binary( v.get_binary_view() );
+            return;
+
+         case type::ARRAY: {
+            const auto& a = v.get_array();
+            const auto s = a.size();
+            consumer.begin_array( s );
+            for( auto&& e : a ) {
+               Recurse( consumer, std::move( e ) );
+               consumer.element();
+            }
+            consumer.end_array( s );
+            return;
+         }
+
+         case type::OBJECT: {
+            const auto& o = v.get_object();
+            const auto s = o.size();
+            consumer.begin_object( s );
+            for( auto&& e : o ) {
+               consumer.key( e.first );
+               Recurse( consumer, std::move( e.second ) );
+               consumer.member();
+            }
+            consumer.end_object( s );
+            return;
+         }
+
+         case type::VALUE_PTR:
+            Recurse( consumer, *v.get_value_ptr() );
+            return;
+
+         case type::OPAQUE_PTR: {
+            const auto& q = v.get_opaque_ptr();
+            virtual_ref< Consumer > ref( consumer );
+            q.producer( ref, q.data );
+            return;
+         }
+      }
+      throw std::logic_error( internal::format( "invalid value '", static_cast< std::uint8_t >( v.type() ), "' for tao::json::type" ) );  // LCOV_EXCL_LINE
+   }
+
+   template< typename Consumer, template< typename... > class Traits >
+   void from_value( Consumer& consumer, basic_value< Traits >&& v )
+   {
+      from_value< static_cast< void ( * )( Consumer&, basic_value< Traits > && ) >( &from_value< Consumer, Traits > ), Consumer, Traits >( consumer, std::move( v ) );
+   }
+
+}  // namespace tao::json::events
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/events/hash.hpp b/3rdParty/taocpp-json/include/tao/json/events/hash.hpp
new file mode 100644
index 000000000000..e0d2e7ea26ed
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/events/hash.hpp
@@ -0,0 +1,174 @@
+// Copyright (c) 2016-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_EVENTS_HASH_HPP
+#define TAO_JSON_EVENTS_HASH_HPP
+
+#include <cstddef>
+#include <cstdint>
+#include <map>
+#include <memory>
+#include <string>
+#include <string_view>
+#include <utility>
+#include <vector>
+
+#include "../binary_view.hpp"
+
+#include "../internal/sha256.hpp"
+
+namespace tao::json::events
+{
+   // Events consumer that calculates an SHA-256 hash.
+
+   class hash
+   {
+   private:
+      std::vector< std::unique_ptr< internal::sha256 > > m_digests;
+      std::vector< std::string > m_keys;
+      std::vector< std::map< std::string, std::string > > m_properties;
+
+      void push()
+      {
+         m_digests.push_back( std::make_unique< internal::sha256 >() );
+      }
+
+   public:
+      hash()
+      {
+         push();
+      }
+
+      hash( const hash& ) = delete;
+      hash( hash&& ) = delete;
+
+      ~hash() = default;
+
+      void operator=( const hash& ) = delete;
+      void operator=( hash&& ) = delete;
+
+      [[nodiscard]] std::string value() const
+      {
+         return m_digests.back()->get();
+      }
+
+      void reset()
+      {
+         m_digests.back()->reset();
+      }
+
+      void null()
+      {
+         m_digests.back()->feed( 'n' );
+      }
+
+      void boolean( const bool v )
+      {
+         m_digests.back()->feed( v ? 't' : 'f' );
+      }
+
+      void number( const std::int64_t v )
+      {
+         if( v >= 0 ) {
+            number( static_cast< std::uint64_t >( v ) );
+         }
+         else {
+            m_digests.back()->feed( 'i' );
+            m_digests.back()->feed( &v, sizeof( v ) );
+         }
+      }
+
+      void number( const std::uint64_t v )
+      {
+         m_digests.back()->feed( 'u' );
+         m_digests.back()->feed( &v, sizeof( v ) );
+      }
+
+      void number( const double v )
+      {
+         if( v >= 0 ) {
+            const auto u = static_cast< std::uint64_t >( v );
+            if( u == v ) {
+               number( u );
+               return;
+            }
+         }
+         else {
+            const auto i = static_cast< std::int64_t >( v );
+            if( i == v ) {
+               number( i );
+               return;
+            }
+         }
+         m_digests.back()->feed( 'd' );
+         m_digests.back()->feed( &v, sizeof( v ) );
+      }
+
+      void string( const std::string_view v )
+      {
+         m_digests.back()->feed( 's' );
+         const auto s = v.size();
+         m_digests.back()->feed( &s, sizeof( s ) );
+         m_digests.back()->feed( v );
+      }
+
+      void binary( const tao::binary_view v )
+      {
+         m_digests.back()->feed( 'x' );
+         const auto s = v.size();
+         m_digests.back()->feed( &s, sizeof( s ) );
+         m_digests.back()->feed( v.data(), v.size() );
+      }
+
+      void begin_array( const std::size_t /*unused*/ = 0 )
+      {
+         m_digests.back()->feed( '[' );
+      }
+
+      void element()
+      {}
+
+      void end_array( const std::size_t /*unused*/ = 0 )
+      {
+         m_digests.back()->feed( ']' );
+      }
+
+      void begin_object( const std::size_t /*unused*/ = 0 )
+      {
+         m_digests.back()->feed( '{' );
+         m_properties.emplace_back();
+         push();
+      }
+
+      void key( const std::string_view v )
+      {
+         m_digests.back()->feed( v );
+         m_keys.emplace_back( m_digests.back()->get() );
+         if( m_properties.back().count( m_keys.back() ) != 0 ) {
+            throw std::runtime_error( "duplicate JSON object key: " + std::string( v ) );
+         }
+         m_digests.back()->reset();
+      }
+
+      void member()
+      {
+         m_properties.back().emplace( std::move( m_keys.back() ), m_digests.back()->get() );
+         m_keys.pop_back();
+         m_digests.back()->reset();
+      }
+
+      void end_object( const std::size_t /*unused*/ = 0 )
+      {
+         m_digests.pop_back();
+         for( const auto& e : m_properties.back() ) {
+            m_digests.back()->feed( e.first );
+            m_digests.back()->feed( e.second );
+         }
+         m_properties.pop_back();
+         m_digests.back()->feed( '}' );
+      }
+   };
+
+}  // namespace tao::json::events
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/events/invalid_string_to_binary.hpp b/3rdParty/taocpp-json/include/tao/json/events/invalid_string_to_binary.hpp
new file mode 100644
index 000000000000..a0636bc09c75
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/events/invalid_string_to_binary.hpp
@@ -0,0 +1,50 @@
+// Copyright (c) 2019-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_EVENTS_INVALID_STRING_TO_BINARY_HPP
+#define TAO_JSON_EVENTS_INVALID_STRING_TO_BINARY_HPP
+
+#include <utility>
+#include <vector>
+
+#include "../binary_view.hpp"
+#include "../utf8.hpp"
+
+namespace tao::json::events
+{
+   template< typename Consumer >
+   struct invalid_string_to_binary
+      : Consumer
+   {
+      using Consumer::Consumer;
+
+      void string( const char* v )
+      {
+         string( std::string_view( v ) );
+      }
+
+      void string( std::string&& v )
+      {
+         if( internal::validate_utf8_nothrow( v ) ) {
+            Consumer::string( std::move( v ) );
+         }
+         else {
+            const std::byte* data = reinterpret_cast< const std::byte* >( v.data() );
+            Consumer::binary( std::vector< std::byte >( data, data + v.size() ) );
+         }
+      }
+
+      void string( const std::string_view v )
+      {
+         if( internal::validate_utf8_nothrow( v ) ) {
+            Consumer::string( v );
+         }
+         else {
+            Consumer::binary( tao::binary_view( reinterpret_cast< const std::byte* >( v.data() ), v.size() ) );
+         }
+      }
+   };
+
+}  // namespace tao::json::events
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/events/invalid_string_to_exception.hpp b/3rdParty/taocpp-json/include/tao/json/events/invalid_string_to_exception.hpp
new file mode 100644
index 000000000000..aeb2ed18aae8
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/events/invalid_string_to_exception.hpp
@@ -0,0 +1,49 @@
+// Copyright (c) 2019-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_EVENTS_INVALID_STRING_TO_EXCEPTION_HPP
+#define TAO_JSON_EVENTS_INVALID_STRING_TO_EXCEPTION_HPP
+
+#include <stdexcept>
+#include <utility>
+
+#include "../internal/hexdump.hpp"
+#include "../utf8.hpp"
+
+namespace tao::json::events
+{
+   template< typename Consumer >
+   struct invalid_string_to_exception
+      : Consumer
+   {
+      using Consumer::Consumer;
+
+      void string( const char* v )
+      {
+         string( std::string_view( v ) );
+      }
+
+      void string( std::string&& v )
+      {
+         if( internal::validate_utf8_nothrow( v ) ) {
+            Consumer::string( std::move( v ) );
+         }
+         else {
+            throw std::runtime_error( "invalid UTF8 string: $" + internal::hexdump( v ) );
+         }
+      }
+
+      void string( const std::string_view v )
+      {
+         if( internal::validate_utf8_nothrow( v ) ) {
+            Consumer::string( v );
+         }
+         else {
+            throw std::runtime_error( "invalid UTF8 string: $" + internal::hexdump( v ) );
+         }
+      }
+   };
+
+}  // namespace tao::json::events
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/events/invalid_string_to_hex.hpp b/3rdParty/taocpp-json/include/tao/json/events/invalid_string_to_hex.hpp
new file mode 100644
index 000000000000..6950e4224255
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/events/invalid_string_to_hex.hpp
@@ -0,0 +1,48 @@
+// Copyright (c) 2019-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_EVENTS_INVALID_STRING_TO_HEX_HPP
+#define TAO_JSON_EVENTS_INVALID_STRING_TO_HEX_HPP
+
+#include <utility>
+
+#include "../internal/hexdump.hpp"
+#include "../utf8.hpp"
+
+namespace tao::json::events
+{
+   template< typename Consumer >
+   struct invalid_string_to_hex
+      : Consumer
+   {
+      using Consumer::Consumer;
+
+      void string( const char* v )
+      {
+         string( std::string_view( v ) );
+      }
+
+      void string( std::string&& v )
+      {
+         if( internal::validate_utf8_nothrow( v ) ) {
+            Consumer::string( std::move( v ) );
+         }
+         else {
+            Consumer::string( internal::hexdump( v ) );
+         }
+      }
+
+      void string( const std::string_view v )
+      {
+         if( internal::validate_utf8_nothrow( v ) ) {
+            Consumer::string( v );
+         }
+         else {
+            Consumer::string( internal::hexdump( v ) );
+         }
+      }
+   };
+
+}  // namespace tao::json::events
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/events/key_camel_case_to_snake_case.hpp b/3rdParty/taocpp-json/include/tao/json/events/key_camel_case_to_snake_case.hpp
new file mode 100644
index 000000000000..b7e78d4c4b67
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/events/key_camel_case_to_snake_case.hpp
@@ -0,0 +1,62 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_EVENTS_KEY_CAMEL_CASE_TO_SNAKE_CASE_HPP
+#define TAO_JSON_EVENTS_KEY_CAMEL_CASE_TO_SNAKE_CASE_HPP
+
+#include <cctype>
+#include <string>
+#include <string_view>
+
+namespace tao::json::events
+{
+   template< typename Consumer >
+   struct key_camel_case_to_snake_case
+      : Consumer
+   {
+      using Consumer::Consumer;
+
+      void key( const std::string_view v )
+      {
+         std::string t;
+         bool last_upper = false;
+         for( const auto c : v ) {
+            if( std::isupper( c ) ) {
+               last_upper = true;
+               t += c;
+            }
+            else {
+               if( last_upper ) {
+                  const char o = t.back();
+                  t.pop_back();
+                  if( !t.empty() && t.back() != '_' ) {
+                     t += '_';
+                  }
+                  t += o;
+               }
+               last_upper = false;
+               t += c;
+            }
+         }
+         std::string r;
+         bool last_lower = false;
+         for( const auto c : t ) {
+            if( std::isupper( c ) ) {
+               if( last_lower ) {
+                  r += '_';
+               }
+               last_lower = false;
+               r += static_cast< char >( std::tolower( c ) );
+            }
+            else {
+               last_lower = static_cast< bool >( std::islower( c ) );
+               r += c;
+            }
+         }
+         Consumer::key( std::move( r ) );
+      }
+   };
+
+}  // namespace tao::json::events
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/events/key_snake_case_to_camel_case.hpp b/3rdParty/taocpp-json/include/tao/json/events/key_snake_case_to_camel_case.hpp
new file mode 100644
index 000000000000..4889fbf8cbcc
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/events/key_snake_case_to_camel_case.hpp
@@ -0,0 +1,57 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_EVENTS_KEY_SNAKE_CASE_TO_CAMEL_CASE_HPP
+#define TAO_JSON_EVENTS_KEY_SNAKE_CASE_TO_CAMEL_CASE_HPP
+
+#include <cctype>
+#include <string>
+#include <string_view>
+
+namespace tao::json::events
+{
+   template< typename Consumer >
+   struct key_snake_case_to_camel_case
+      : Consumer
+   {
+      using Consumer::Consumer;
+
+      void key( const std::string_view v )
+      {
+         std::string r;
+         r.reserve( v.size() );
+         bool active = false;
+         for( const auto c : v ) {
+            if( active ) {
+               if( c == '_' ) {
+                  r += c;
+               }
+               else if( std::isupper( c ) ) {
+                  r += '_';
+                  r += c;
+                  active = false;
+               }
+               else {
+                  r += static_cast< char >( std::toupper( c ) );
+                  active = false;
+               }
+            }
+            else {
+               if( c == '_' ) {
+                  active = true;
+               }
+               else {
+                  r += c;
+               }
+            }
+         }
+         if( active ) {
+            r += '_';
+         }
+         Consumer::key( std::move( r ) );
+      }
+   };
+
+}  // namespace tao::json::events
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/events/limit_nesting_depth.hpp b/3rdParty/taocpp-json/include/tao/json/events/limit_nesting_depth.hpp
new file mode 100644
index 000000000000..d3e9c428ba44
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/events/limit_nesting_depth.hpp
@@ -0,0 +1,82 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_EVENTS_LIMIT_NESTING_DEPTH_HPP
+#define TAO_JSON_EVENTS_LIMIT_NESTING_DEPTH_HPP
+
+#include <cstddef>
+#include <cstdint>
+
+#include <stdexcept>
+
+namespace tao::json::events
+{
+   template< typename Consumer, std::size_t Limit >
+   class limit_nesting_depth
+      : public Consumer
+   {
+   private:
+      std::size_t m_depth = 0;
+
+      void count_and_limit()
+      {
+         if( ++m_depth > Limit ) {
+            throw std::runtime_error( "nesting depth limit exceeded" );
+         }
+      }
+
+   public:
+      using Consumer::Consumer;
+
+      void begin_array()
+      {
+         count_and_limit();
+         Consumer::begin_array();
+      }
+
+      void begin_array( const std::size_t size )
+      {
+         count_and_limit();
+         Consumer::begin_array( size );
+      }
+
+      void end_array()
+      {
+         Consumer::end_array();
+         --m_depth;
+      }
+
+      void end_array( const std::size_t size )
+      {
+         Consumer::end_array( size );
+         --m_depth;
+      }
+
+      void begin_object()
+      {
+         count_and_limit();
+         Consumer::begin_object();
+      }
+
+      void begin_object( const std::size_t size )
+      {
+         count_and_limit();
+         Consumer::begin_object( size );
+      }
+
+      void end_object()
+      {
+         Consumer::end_object();
+         --m_depth;
+      }
+
+      void end_object( const std::size_t size )
+      {
+         Consumer::end_object( size );
+         --m_depth;
+      }
+   };
+
+}  // namespace tao::json::events
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/events/limit_value_count.hpp b/3rdParty/taocpp-json/include/tao/json/events/limit_value_count.hpp
new file mode 100644
index 000000000000..6c70aaafe7a8
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/events/limit_value_count.hpp
@@ -0,0 +1,46 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_EVENTS_LIMIT_VALUE_COUNT_HPP
+#define TAO_JSON_EVENTS_LIMIT_VALUE_COUNT_HPP
+
+#include <cstddef>
+#include <cstdint>
+
+#include <stdexcept>
+
+namespace tao::json::events
+{
+   template< typename Consumer, std::size_t Limit >
+   class limit_value_count
+      : public Consumer
+   {
+   private:
+      std::size_t m_count = 1;  // Top-level value is implied.
+
+      void count_and_limit()
+      {
+         if( ++m_count > Limit ) {
+            throw std::runtime_error( "value count limit exceeded" );
+         }
+      }
+
+   public:
+      using Consumer::Consumer;
+
+      void element()
+      {
+         count_and_limit();
+         Consumer::element();
+      }
+
+      void member()
+      {
+         count_and_limit();
+         Consumer::member();
+      }
+   };
+
+}  // namespace tao::json::events
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/events/non_finite_to_exception.hpp b/3rdParty/taocpp-json/include/tao/json/events/non_finite_to_exception.hpp
new file mode 100644
index 000000000000..a4f48049bee1
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/events/non_finite_to_exception.hpp
@@ -0,0 +1,31 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_EVENTS_NON_FINITE_TO_EXCEPTION_HPP
+#define TAO_JSON_EVENTS_NON_FINITE_TO_EXCEPTION_HPP
+
+#include <cmath>
+#include <stdexcept>
+
+namespace tao::json::events
+{
+   template< typename Consumer >
+   struct non_finite_to_exception
+      : Consumer
+   {
+      using Consumer::Consumer;
+
+      using Consumer::number;
+
+      void number( const double v )
+      {
+         if( !std::isfinite( v ) ) {
+            throw std::runtime_error( "invalid non-finite double value" );
+         }
+         Consumer::number( v );
+      }
+   };
+
+}  // namespace tao::json::events
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/events/non_finite_to_null.hpp b/3rdParty/taocpp-json/include/tao/json/events/non_finite_to_null.hpp
new file mode 100644
index 000000000000..1556d1fa1a76
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/events/non_finite_to_null.hpp
@@ -0,0 +1,32 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_EVENTS_NON_FINITE_TO_NULL_HPP
+#define TAO_JSON_EVENTS_NON_FINITE_TO_NULL_HPP
+
+#include <cmath>
+
+namespace tao::json::events
+{
+   template< typename Consumer >
+   struct non_finite_to_null
+      : Consumer
+   {
+      using Consumer::Consumer;
+
+      using Consumer::number;
+
+      void number( const double v )
+      {
+         if( !std::isfinite( v ) ) {
+            Consumer::null();
+         }
+         else {
+            Consumer::number( v );
+         }
+      }
+   };
+
+}  // namespace tao::json::events
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/events/non_finite_to_string.hpp b/3rdParty/taocpp-json/include/tao/json/events/non_finite_to_string.hpp
new file mode 100644
index 000000000000..a61855cf2bfe
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/events/non_finite_to_string.hpp
@@ -0,0 +1,40 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_EVENTS_NON_FINITE_TO_STRING_HPP
+#define TAO_JSON_EVENTS_NON_FINITE_TO_STRING_HPP
+
+#include <cmath>
+
+namespace tao::json::events
+{
+   template< typename Consumer >
+   struct non_finite_to_string
+      : Consumer
+   {
+      using Consumer::Consumer;
+
+      using Consumer::number;
+
+      void number( const double v )
+      {
+         if( !std::isfinite( v ) ) {
+            if( std::isnan( v ) ) {
+               Consumer::string( "NaN" );
+            }
+            else if( v > 0 ) {
+               Consumer::string( "Infinity" );
+            }
+            else {
+               Consumer::string( "-Infinity" );
+            }
+         }
+         else {
+            Consumer::number( v );
+         }
+      }
+   };
+
+}  // namespace tao::json::events
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/events/prefer_signed.hpp b/3rdParty/taocpp-json/include/tao/json/events/prefer_signed.hpp
new file mode 100644
index 000000000000..3df0e9798b95
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/events/prefer_signed.hpp
@@ -0,0 +1,32 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_EVENTS_PREFER_SIGNED_HPP
+#define TAO_JSON_EVENTS_PREFER_SIGNED_HPP
+
+#include <cstdint>
+
+namespace tao::json::events
+{
+   template< typename Consumer >
+   struct prefer_signed
+      : Consumer
+   {
+      using Consumer::Consumer;
+
+      using Consumer::number;
+
+      void number( const std::uint64_t v )
+      {
+         if( v <= 9223372036854775807ULL ) {
+            Consumer::number( std::int64_t( v ) );
+         }
+         else {
+            Consumer::number( v );
+         }
+      }
+   };
+
+}  // namespace tao::json::events
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/events/prefer_unsigned.hpp b/3rdParty/taocpp-json/include/tao/json/events/prefer_unsigned.hpp
new file mode 100644
index 000000000000..1e082a837eb2
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/events/prefer_unsigned.hpp
@@ -0,0 +1,32 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_EVENTS_PREFER_UNSIGNED_HPP
+#define TAO_JSON_EVENTS_PREFER_UNSIGNED_HPP
+
+#include <cstdint>
+
+namespace tao::json::events
+{
+   template< typename Consumer >
+   struct prefer_unsigned
+      : Consumer
+   {
+      using Consumer::Consumer;
+
+      using Consumer::number;
+
+      void number( const std::int64_t v )
+      {
+         if( v >= 0 ) {
+            Consumer::number( std::uint64_t( v ) );
+         }
+         else {
+            Consumer::number( v );
+         }
+      }
+   };
+
+}  // namespace tao::json::events
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/events/produce.hpp b/3rdParty/taocpp-json/include/tao/json/events/produce.hpp
new file mode 100644
index 000000000000..14d0ecf19c9c
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/events/produce.hpp
@@ -0,0 +1,22 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_EVENTS_PRODUCE_HPP
+#define TAO_JSON_EVENTS_PRODUCE_HPP
+
+#include <type_traits>
+#include <utility>
+
+#include "../forward.hpp"
+
+namespace tao::json::events
+{
+   template< template< typename... > class Traits = traits, typename Consumer, typename T >
+   void produce( Consumer& c, T&& t )
+   {
+      Traits< std::decay_t< T > >::template produce< Traits >( c, std::forward< T >( t ) );
+   }
+
+}  // namespace tao::json::events
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/events/ref.hpp b/3rdParty/taocpp-json/include/tao/json/events/ref.hpp
new file mode 100644
index 000000000000..0c4b78d3e414
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/events/ref.hpp
@@ -0,0 +1,111 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_EVENTS_REF_HPP
+#define TAO_JSON_EVENTS_REF_HPP
+
+#include <cstddef>
+#include <utility>
+
+namespace tao::json::events
+{
+   template< typename Consumer >
+   class ref
+   {
+   private:
+      Consumer& r_;
+
+   public:
+      explicit ref( Consumer& r ) noexcept
+         : r_( r )
+      {}
+
+      void null() noexcept( noexcept( r_.null() ) )
+      {
+         r_.null();
+      }
+
+      template< typename T >
+      void boolean( T&& v ) noexcept( noexcept( r_.boolean( std::forward< T >( v ) ) ) )
+      {
+         r_.boolean( std::forward< T >( v ) );
+      }
+
+      template< typename T >
+      void number( T&& v ) noexcept( noexcept( r_.number( std::forward< T >( v ) ) ) )
+      {
+         r_.number( std::forward< T >( v ) );
+      }
+
+      template< typename T >
+      void string( T&& v ) noexcept( noexcept( r_.string( std::forward< T >( v ) ) ) )
+      {
+         r_.string( std::forward< T >( v ) );
+      }
+
+      template< typename T >
+      void binary( T&& v ) noexcept( noexcept( r_.binary( std::forward< T >( v ) ) ) )
+      {
+         r_.binary( std::forward< T >( v ) );
+      }
+
+      void begin_array() noexcept( noexcept( r_.begin_array() ) )
+      {
+         r_.begin_array();
+      }
+
+      void begin_array( const std::size_t size ) noexcept( noexcept( r_.begin_array( size ) ) )
+      {
+         r_.begin_array( size );
+      }
+
+      void element() noexcept( noexcept( r_.element() ) )
+      {
+         r_.element();
+      }
+
+      void end_array() noexcept( noexcept( r_.end_array() ) )
+      {
+         r_.end_array();
+      }
+
+      void end_array( const std::size_t size ) noexcept( noexcept( r_.end_array( size ) ) )
+      {
+         r_.end_array( size );
+      }
+
+      void begin_object() noexcept( noexcept( r_.begin_object() ) )
+      {
+         r_.begin_object();
+      }
+
+      void begin_object( const std::size_t size ) noexcept( noexcept( r_.begin_object( size ) ) )
+      {
+         r_.begin_object( size );
+      }
+
+      template< typename T >
+      void key( T&& v ) noexcept( noexcept( r_.key( std::forward< T >( v ) ) ) )
+      {
+         r_.key( std::forward< T >( v ) );
+      }
+
+      void member() noexcept( noexcept( r_.member() ) )
+      {
+         r_.member();
+      }
+
+      void end_object() noexcept( noexcept( r_.end_object() ) )
+      {
+         r_.end_object();
+      }
+
+      void end_object( const std::size_t size ) noexcept( noexcept( r_.end_object( size ) ) )
+      {
+         r_.end_object( size );
+      }
+   };
+
+}  // namespace tao::json::events
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/events/statistics.hpp b/3rdParty/taocpp-json/include/tao/json/events/statistics.hpp
new file mode 100644
index 000000000000..895b2ce69916
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/events/statistics.hpp
@@ -0,0 +1,112 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_EVENTS_STATISTICS_HPP
+#define TAO_JSON_EVENTS_STATISTICS_HPP
+
+#include <cstddef>
+#include <cstdint>
+#include <cstring>
+#include <string>
+#include <string_view>
+#include <vector>
+
+#include "../binary_view.hpp"
+
+namespace tao::json::events
+{
+   struct statistics
+   {
+      std::size_t null_count = 0;
+      std::size_t true_count = 0;
+      std::size_t false_count = 0;
+
+      std::size_t signed_count = 0;
+      std::size_t unsigned_count = 0;
+      std::size_t double_count = 0;
+
+      std::size_t string_count = 0;
+      std::size_t string_lengths = 0;
+      std::size_t key_count = 0;
+      std::size_t key_lengths = 0;
+      std::size_t binary_count = 0;
+      std::size_t binary_lengths = 0;
+
+      std::size_t array_count = 0;
+      std::size_t array_elements = 0;
+      std::size_t object_count = 0;
+      std::size_t object_members = 0;
+
+      void null() noexcept
+      {
+         ++null_count;
+      }
+
+      void boolean( const bool v ) noexcept
+      {
+         ++( v ? true_count : false_count );
+      }
+
+      void number( const std::int64_t /*unused*/ ) noexcept
+      {
+         ++signed_count;
+      }
+
+      void number( const std::uint64_t /*unused*/ ) noexcept
+      {
+         ++unsigned_count;
+      }
+
+      void number( const double /*unused*/ ) noexcept
+      {
+         ++double_count;
+      }
+
+      void string( const std::string_view v ) noexcept
+      {
+         ++string_count;
+         string_lengths += v.size();
+      }
+
+      void binary( const tao::binary_view v ) noexcept
+      {
+         ++binary_count;
+         binary_lengths += v.size();
+      }
+
+      void begin_array( const std::size_t /*unused*/ = 0 ) noexcept
+      {
+         ++array_count;
+      }
+
+      void element() noexcept
+      {
+         ++array_elements;
+      }
+
+      void end_array( const std::size_t /*unused*/ = 0 ) noexcept
+      {}
+
+      void begin_object( const std::size_t /*unused*/ = 0 ) noexcept
+      {
+         ++object_count;
+      }
+
+      void key( const std::string_view v ) noexcept
+      {
+         ++key_count;
+         key_lengths += v.size();
+      }
+
+      void member() noexcept
+      {
+         ++object_members;
+      }
+
+      void end_object( const std::size_t /*unused*/ = 0 ) noexcept
+      {}
+   };
+
+}  // namespace tao::json::events
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/events/tee.hpp b/3rdParty/taocpp-json/include/tao/json/events/tee.hpp
new file mode 100644
index 000000000000..b1cd1f933b02
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/events/tee.hpp
@@ -0,0 +1,386 @@
+// Copyright (c) 2016-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_EVENTS_TEE_HPP
+#define TAO_JSON_EVENTS_TEE_HPP
+
+#include <cstdint>
+#include <string>
+#include <tuple>
+#include <type_traits>
+#include <utility>
+#include <vector>
+
+#include "discard.hpp"
+
+namespace tao::json
+{
+   namespace internal
+   {
+      template< typename T >
+      struct strip_reference_wrapper
+      {
+         using type = T;
+      };
+
+      template< typename T >
+      struct strip_reference_wrapper< std::reference_wrapper< T > >
+      {
+         using type = T&;
+      };
+
+      template< typename T >
+      using decay_and_strip_t = typename strip_reference_wrapper< std::decay_t< T > >::type;
+
+      template< typename >
+      struct events_apply;
+
+      template<>
+      struct events_apply< std::index_sequence<> >
+      {
+         template< typename... Ts >
+         static void null( std::tuple< Ts... >& /*unused*/ )
+         {}
+
+         template< typename... Ts >
+         static void boolean( std::tuple< Ts... >& /*unused*/, const bool /*unused*/ )
+         {}
+
+         template< typename... Ts >
+         static void number( std::tuple< Ts... >& /*unused*/, const std::int64_t /*unused*/ )
+         {}
+
+         template< typename... Ts >
+         static void number( std::tuple< Ts... >& /*unused*/, const std::uint64_t /*unused*/ )
+         {}
+
+         template< typename... Ts >
+         static void number( std::tuple< Ts... >& /*unused*/, const double /*unused*/ )
+         {}
+
+         template< typename... Ts >
+         static void string( std::tuple< Ts... >& /*unused*/, const std::string_view /*unused*/ )
+         {}
+
+         template< typename... Ts >
+         static void binary( std::tuple< Ts... >& /*unused*/, const tao::binary_view /*unused*/ )
+         {}
+
+         template< typename... Ts >
+         static void begin_array( std::tuple< Ts... >& /*unused*/ )
+         {}
+
+         template< typename... Ts >
+         static void begin_array( std::tuple< Ts... >& /*unused*/, const std::size_t /*unused*/ )
+         {}
+
+         template< typename... Ts >
+         static void element( std::tuple< Ts... >& /*unused*/ )
+         {}
+
+         template< typename... Ts >
+         static void end_array( std::tuple< Ts... >& /*unused*/ )
+         {}
+
+         template< typename... Ts >
+         static void end_array( std::tuple< Ts... >& /*unused*/, const std::size_t /*unused*/ )
+         {}
+
+         template< typename... Ts >
+         static void begin_object( std::tuple< Ts... >& /*unused*/ )
+         {}
+
+         template< typename... Ts >
+         static void begin_object( std::tuple< Ts... >& /*unused*/, const std::size_t /*unused*/ )
+         {}
+
+         template< typename... Ts >
+         static void key( std::tuple< Ts... >& /*unused*/, const std::string_view /*unused*/ )
+         {}
+
+         template< typename... Ts >
+         static void member( std::tuple< Ts... >& /*unused*/ )
+         {}
+
+         template< typename... Ts >
+         static void end_object( std::tuple< Ts... >& /*unused*/ )
+         {}
+
+         template< typename... Ts >
+         static void end_object( std::tuple< Ts... >& /*unused*/, const std::size_t /*unused*/ )
+         {}
+      };
+
+      template< std::size_t... Is >
+      struct events_apply< std::index_sequence< Is... > >
+      {
+         template< typename... Ts >
+         static void null( std::tuple< Ts... >& t )
+         {
+            ( std::get< Is >( t ).null(), ... );
+         }
+
+         template< typename... Ts >
+         static void boolean( std::tuple< Ts... >& t, const bool v )
+         {
+            ( std::get< Is >( t ).boolean( v ), ... );
+         }
+
+         template< typename... Ts >
+         static void number( std::tuple< Ts... >& t, const std::int64_t v )
+         {
+            ( std::get< Is >( t ).number( v ), ... );
+         }
+
+         template< typename... Ts >
+         static void number( std::tuple< Ts... >& t, const std::uint64_t v )
+         {
+            ( std::get< Is >( t ).number( v ), ... );
+         }
+
+         template< typename... Ts >
+         static void number( std::tuple< Ts... >& t, const double v )
+         {
+            ( std::get< Is >( t ).number( v ), ... );
+         }
+
+         template< typename... Ts >
+         static void string( std::tuple< Ts... >& t, const std::string_view v )
+         {
+            ( std::get< Is >( t ).string( v ), ... );
+         }
+
+         template< typename... Ts >
+         static void binary( std::tuple< Ts... >& t, const tao::binary_view v )
+         {
+            ( std::get< Is >( t ).binary( v ), ... );
+         }
+
+         template< typename... Ts >
+         static void begin_array( std::tuple< Ts... >& t )
+         {
+            ( std::get< Is >( t ).begin_array(), ... );
+         }
+
+         template< typename... Ts >
+         static void begin_array( std::tuple< Ts... >& t, const std::size_t size )
+         {
+            ( std::get< Is >( t ).begin_array( size ), ... );
+         }
+
+         template< typename... Ts >
+         static void element( std::tuple< Ts... >& t )
+         {
+            ( std::get< Is >( t ).element(), ... );
+         }
+
+         template< typename... Ts >
+         static void end_array( std::tuple< Ts... >& t )
+         {
+            ( std::get< Is >( t ).end_array(), ... );
+         }
+
+         template< typename... Ts >
+         static void end_array( std::tuple< Ts... >& t, const std::size_t size )
+         {
+            ( std::get< Is >( t ).end_array( size ), ... );
+         }
+
+         template< typename... Ts >
+         static void begin_object( std::tuple< Ts... >& t )
+         {
+            ( std::get< Is >( t ).begin_object(), ... );
+         }
+
+         template< typename... Ts >
+         static void begin_object( std::tuple< Ts... >& t, const std::size_t size )
+         {
+            ( std::get< Is >( t ).begin_object( size ), ... );
+         }
+
+         template< typename... Ts >
+         static void key( std::tuple< Ts... >& t, const std::string_view v )
+         {
+            ( std::get< Is >( t ).key( v ), ... );
+         }
+
+         template< typename... Ts >
+         static void member( std::tuple< Ts... >& t )
+         {
+            ( std::get< Is >( t ).member(), ... );
+         }
+
+         template< typename... Ts >
+         static void end_object( std::tuple< Ts... >& t )
+         {
+            ( std::get< Is >( t ).end_object(), ... );
+         }
+
+         template< typename... Ts >
+         static void end_object( std::tuple< Ts... >& t, const std::size_t size )
+         {
+            ( std::get< Is >( t ).end_object( size ), ... );
+         }
+      };
+
+   }  // namespace internal
+
+   namespace events
+   {
+      // Events consumer that forwards to multiple nested consumers.
+
+      template< typename... Ts >
+      class tee
+      {
+      private:
+         static constexpr std::size_t S = sizeof...( Ts );
+
+         using I = std::make_index_sequence< S >;
+         using H = std::make_index_sequence< S - 1 >;
+
+         std::tuple< Ts... > ts;
+
+      public:
+         template< typename... Us >
+         explicit tee( Us&&... us )
+            : ts( std::forward< Us >( us )... )
+         {}
+
+         void null()
+         {
+            internal::events_apply< I >::null( ts );
+         }
+
+         void boolean( const bool v )
+         {
+            internal::events_apply< I >::boolean( ts, v );
+         }
+
+         void number( const std::int64_t v )
+         {
+            internal::events_apply< I >::number( ts, v );
+         }
+
+         void number( const std::uint64_t v )
+         {
+            internal::events_apply< I >::number( ts, v );
+         }
+
+         void number( const double v )
+         {
+            internal::events_apply< I >::number( ts, v );
+         }
+
+         void string( const std::string_view v )
+         {
+            internal::events_apply< I >::string( ts, v );
+         }
+
+         void string( const char* v )
+         {
+            internal::events_apply< I >::string( ts, v );
+         }
+
+         void string( std::string&& v )
+         {
+            internal::events_apply< H >::string( ts, v );
+            std::get< S - 1 >( ts ).string( std::move( v ) );
+         }
+
+         void binary( const tao::binary_view v )
+         {
+            internal::events_apply< I >::binary( ts, v );
+         }
+
+         void binary( std::vector< std::byte >&& v )
+         {
+            internal::events_apply< H >::binary( ts, v );
+            std::get< S - 1 >( ts ).binary( std::move( v ) );
+         }
+
+         void begin_array()
+         {
+            internal::events_apply< I >::begin_array( ts );
+         }
+
+         void begin_array( const std::size_t size )
+         {
+            internal::events_apply< I >::begin_array( ts, size );
+         }
+
+         void element()
+         {
+            internal::events_apply< I >::element( ts );
+         }
+
+         void end_array()
+         {
+            internal::events_apply< I >::end_array( ts );
+         }
+
+         void end_array( const std::size_t size )
+         {
+            internal::events_apply< I >::end_array( ts, size );
+         }
+
+         void begin_object()
+         {
+            internal::events_apply< I >::begin_object( ts );
+         }
+
+         void begin_object( const std::size_t size )
+         {
+            internal::events_apply< I >::begin_object( ts, size );
+         }
+
+         void key( const std::string_view v )
+         {
+            internal::events_apply< I >::key( ts, v );
+         }
+
+         void key( const char* v )
+         {
+            internal::events_apply< I >::key( ts, v );
+         }
+
+         void key( std::string&& v )
+         {
+            internal::events_apply< H >::key( ts, v );
+            std::get< S - 1 >( ts ).key( std::move( v ) );
+         }
+
+         void member()
+         {
+            internal::events_apply< I >::member( ts );
+         }
+
+         void end_object()
+         {
+            internal::events_apply< I >::end_object( ts );
+         }
+
+         void end_object( const std::size_t size )
+         {
+            internal::events_apply< I >::end_object( ts, size );
+         }
+      };
+
+      template<>
+      class tee<>
+         : public discard
+      {};
+
+      template< typename... Ts >
+      tee( Ts&&... )->tee< internal::decay_and_strip_t< Ts >... >;
+
+      template< typename... T >
+      [[nodiscard]] tee< T&... > tie( T&... t )
+      {
+         return tee< T&... >( t... );
+      }
+
+   }  // namespace events
+
+}  // namespace tao::json
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/events/to_pretty_stream.hpp b/3rdParty/taocpp-json/include/tao/json/events/to_pretty_stream.hpp
new file mode 100644
index 000000000000..9e7b56987635
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/events/to_pretty_stream.hpp
@@ -0,0 +1,172 @@
+// Copyright (c) 2016-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_EVENTS_TO_PRETTY_STREAM_HPP
+#define TAO_JSON_EVENTS_TO_PRETTY_STREAM_HPP
+
+#include <cmath>
+#include <cstddef>
+#include <cstdint>
+#include <iomanip>
+#include <ostream>
+#include <stdexcept>
+#include <string>
+#include <string_view>
+#include <utility>
+#include <vector>
+
+#include "../binary_view.hpp"
+
+#include "../external/itoa.hpp"
+#include "../external/ryu.hpp"
+
+#include "../internal/escape.hpp"
+
+namespace tao::json::events
+{
+   // Events consumer to build a JSON pretty string representation.
+
+   class to_pretty_stream
+   {
+   protected:
+      std::ostream& os;
+      const std::size_t indent;
+      std::string eol;
+
+      bool first = true;
+      bool after_key = true;
+
+      void next()
+      {
+         if( !first ) {
+            os.put( ',' );
+         }
+         if( after_key ) {
+            after_key = false;
+         }
+         else {
+            os << eol;
+         }
+      }
+
+   public:
+      template< typename S >
+      to_pretty_stream( std::ostream& in_os, const std::size_t in_indent, S&& in_eol )
+         : os( in_os ),
+           indent( in_indent ),
+           eol( std::forward< S >( in_eol ) )
+      {}
+
+      to_pretty_stream( std::ostream& in_os, const std::size_t in_indent )
+         : to_pretty_stream( in_os, in_indent, "\n" )
+      {}
+
+      void null()
+      {
+         next();
+         os.write( "null", 4 );
+      }
+
+      void boolean( const bool v )
+      {
+         next();
+         if( v ) {
+            os.write( "true", 4 );
+         }
+         else {
+            os.write( "false", 5 );
+         }
+      }
+
+      void number( const std::int64_t v )
+      {
+         next();
+         itoa::i64tos( os, v );
+      }
+
+      void number( const std::uint64_t v )
+      {
+         next();
+         itoa::u64tos( os, v );
+      }
+
+      void number( const double v )
+      {
+         next();
+         if( !std::isfinite( v ) ) {
+            // if this throws, consider using non_finite_to_* transformers
+            throw std::runtime_error( "non-finite double value invalid for JSON string representation" );
+         }
+         ryu::d2s_stream( os, v );
+      }
+
+      void string( const std::string_view v )
+      {
+         next();
+         os.put( '"' );
+         internal::escape( os, v );
+         os.put( '"' );
+      }
+
+      void binary( const tao::binary_view /*unused*/ )
+      {
+         // if this throws, consider using binary_to_* transformers
+         throw std::runtime_error( "binary data invalid for JSON string representation" );
+      }
+
+      void begin_array( const std::size_t /*unused*/ = 0 )
+      {
+         next();
+         os.put( '[' );
+         eol.resize( eol.size() + indent, os.fill() );
+         first = true;
+      }
+
+      void element() noexcept
+      {
+         first = false;
+      }
+
+      void end_array( const std::size_t /*unused*/ = 0 )
+      {
+         eol.resize( eol.size() - indent );
+         if( !first ) {
+            os << eol;
+         }
+         os.put( ']' );
+      }
+
+      void begin_object( const std::size_t /*unused*/ = 0 )
+      {
+         next();
+         os.put( '{' );
+         eol.resize( eol.size() + indent, os.fill() );
+         first = true;
+      }
+
+      void key( const std::string_view v )
+      {
+         string( v );
+         os.write( ": ", 2 );
+         first = true;
+         after_key = true;
+      }
+
+      void member() noexcept
+      {
+         first = false;
+      }
+
+      void end_object( const std::size_t /*unused*/ = 0 )
+      {
+         eol.resize( eol.size() - indent );
+         if( !first ) {
+            os << eol;
+         }
+         os.put( '}' );
+      }
+   };
+
+}  // namespace tao::json::events
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/events/to_stream.hpp b/3rdParty/taocpp-json/include/tao/json/events/to_stream.hpp
new file mode 100644
index 000000000000..a144622eeb5b
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/events/to_stream.hpp
@@ -0,0 +1,142 @@
+// Copyright (c) 2016-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_EVENTS_TO_STREAM_HPP
+#define TAO_JSON_EVENTS_TO_STREAM_HPP
+
+#include <cmath>
+#include <cstddef>
+#include <cstdint>
+#include <ostream>
+#include <stdexcept>
+#include <string>
+#include <string_view>
+
+#include "../binary_view.hpp"
+
+#include "../external/itoa.hpp"
+#include "../external/ryu.hpp"
+
+#include "../internal/escape.hpp"
+
+namespace tao::json::events
+{
+   // Events consumer to build a JSON string representation.
+
+   class to_stream
+   {
+   protected:
+      std::ostream& os;
+      bool first;
+
+      void next()
+      {
+         if( !first ) {
+            os.put( ',' );
+         }
+      }
+
+   public:
+      explicit to_stream( std::ostream& in_os ) noexcept
+         : os( in_os ),
+           first( true )
+      {}
+
+      void null()
+      {
+         next();
+         os.write( "null", 4 );
+      }
+
+      void boolean( const bool v )
+      {
+         next();
+         if( v ) {
+            os.write( "true", 4 );
+         }
+         else {
+            os.write( "false", 5 );
+         }
+      }
+
+      void number( const std::int64_t v )
+      {
+         next();
+         itoa::i64tos( os, v );
+      }
+
+      void number( const std::uint64_t v )
+      {
+         next();
+         itoa::u64tos( os, v );
+      }
+
+      void number( const double v )
+      {
+         next();
+         if( !std::isfinite( v ) ) {
+            // if this throws, consider using non_finite_to_* transformers
+            throw std::runtime_error( "non-finite double value invalid for JSON string representation" );
+         }
+         ryu::d2s_stream( os, v );
+      }
+
+      void string( const std::string_view v )
+      {
+         next();
+         os.put( '"' );
+         internal::escape( os, v );
+         os.put( '"' );
+      }
+
+      void binary( const tao::binary_view /*unused*/ )
+      {
+         // if this throws, consider using binary_to_* transformers
+         throw std::runtime_error( "binary data invalid for JSON string representation" );
+      }
+
+      void begin_array( const std::size_t /*unused*/ = 0 )
+      {
+         next();
+         os.put( '[' );
+         first = true;
+      }
+
+      void element() noexcept
+      {
+         first = false;
+      }
+
+      void end_array( const std::size_t /*unused*/ = 0 )
+      {
+         os.put( ']' );
+      }
+
+      void begin_object( const std::size_t /*unused*/ = 0 )
+      {
+         next();
+         os.put( '{' );
+         first = true;
+      }
+
+      void key( const std::string_view v )
+      {
+         string( v );
+         os.put( ':' );
+         first = true;
+      }
+
+      void member() noexcept
+      {
+         first = false;
+      }
+
+      void end_object( const std::size_t /*unused*/ = 0 )
+      {
+         os.put( '}' );
+      }
+   };
+
+}  // namespace tao::json::events
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/events/to_string.hpp b/3rdParty/taocpp-json/include/tao/json/events/to_string.hpp
new file mode 100644
index 000000000000..972f09f36fbe
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/events/to_string.hpp
@@ -0,0 +1,33 @@
+// Copyright (c) 2016-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_EVENTS_TO_STRING_HPP
+#define TAO_JSON_EVENTS_TO_STRING_HPP
+
+#include <sstream>
+#include <string>
+
+#include "to_stream.hpp"
+
+namespace tao::json::events
+{
+   // Events consumer to build a JSON string representation.
+
+   struct to_string
+      : to_stream
+   {
+      std::ostringstream oss;
+
+      to_string()
+         : to_stream( oss )
+      {}
+
+      [[nodiscard]] std::string value() const
+      {
+         return oss.str();
+      }
+   };
+
+}  // namespace tao::json::events
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/events/to_value.hpp b/3rdParty/taocpp-json/include/tao/json/events/to_value.hpp
new file mode 100644
index 000000000000..4d47d555ef2f
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/events/to_value.hpp
@@ -0,0 +1,137 @@
+// Copyright (c) 2016-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_EVENTS_TO_VALUE_HPP
+#define TAO_JSON_EVENTS_TO_VALUE_HPP
+
+#include <cstddef>
+#include <cstdint>
+#include <string>
+#include <string_view>
+#include <utility>
+#include <vector>
+
+#include "../binary_view.hpp"
+#include "../value.hpp"
+
+namespace tao::json::events
+{
+   // Events consumer to build a JSON Value.
+
+   template< template< typename... > class Traits >
+   struct to_basic_value
+   {
+      std::vector< basic_value< Traits > > stack_;
+      std::vector< std::string > keys_;
+      basic_value< Traits > value;
+
+      void null()
+      {
+         value.set_null();
+      }
+
+      void boolean( const bool v )
+      {
+         value.set_boolean( v );
+      }
+
+      void number( const std::int64_t v )
+      {
+         value.set_signed( v );
+      }
+
+      void number( const std::uint64_t v )
+      {
+         value.set_unsigned( v );
+      }
+
+      void number( const double v )
+      {
+         value.set_double( v );
+      }
+
+      void string( const std::string_view v )
+      {
+         value.emplace_string( v );
+      }
+
+      void string( const char* v )
+      {
+         value.emplace_string( v );
+      }
+
+      void string( std::string&& v )
+      {
+         value.emplace_string( std::move( v ) );
+      }
+
+      void binary( const tao::binary_view v )
+      {
+         value.emplace_binary( v.begin(), v.end() );
+      }
+
+      void binary( std::vector< std::byte >&& v )
+      {
+         value.emplace_binary( std::move( v ) );
+      }
+
+      void begin_array()
+      {
+         stack_.emplace_back( empty_array );
+      }
+
+      void begin_array( const std::size_t size )
+      {
+         begin_array();
+         stack_.back().get_array().reserve( size );
+      }
+
+      void element()
+      {
+         stack_.back().emplace_back( std::move( value ) );
+      }
+
+      void end_array( const std::size_t /*unused*/ = 0 )
+      {
+         value = std::move( stack_.back() );
+         stack_.pop_back();
+      }
+
+      void begin_object( const std::size_t /*unused*/ = 0 )
+      {
+         stack_.emplace_back( empty_object );
+      }
+
+      void key( const std::string_view v )
+      {
+         keys_.emplace_back( v );
+      }
+
+      void key( const char* v )
+      {
+         keys_.emplace_back( v );
+      }
+
+      void key( std::string&& v )
+      {
+         keys_.emplace_back( std::move( v ) );
+      }
+
+      void member()
+      {
+         stack_.back().try_emplace( std::move( keys_.back() ), std::move( value ) );
+         keys_.pop_back();
+      }
+
+      void end_object( const std::size_t /*unused*/ = 0 )
+      {
+         value = std::move( stack_.back() );
+         stack_.pop_back();
+      }
+   };
+
+   using to_value = to_basic_value< traits >;
+
+}  // namespace tao::json::events
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/events/transformer.hpp b/3rdParty/taocpp-json/include/tao/json/events/transformer.hpp
new file mode 100644
index 000000000000..564a389605ef
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/events/transformer.hpp
@@ -0,0 +1,70 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_EVENTS_TRANSFORMER_HPP
+#define TAO_JSON_EVENTS_TRANSFORMER_HPP
+
+#include <type_traits>
+
+#include "../external/pegtl/internal/always_false.hpp"
+
+namespace tao::json
+{
+   namespace internal
+   {
+      template< template< typename... > class T >
+      struct invalid_transformer
+      {
+         // if this static assert is triggered there is a high chance that 'T' is
+         // a traits class template and you intended to call a method starting with "basic_*",
+         // e.g. basic_from_file< my_traits >( ... ) instead of from_file< my_traits >( ... ).
+         static_assert( pegtl::internal::always_false< invalid_transformer< T > >::value, "T is not a valid transformer" );
+      };
+
+      template< typename B, template< typename... > class T, typename = void >
+      struct check_transformer
+         : invalid_transformer< T >
+      {
+         using type = B;
+      };
+
+      template< typename B, template< typename... > class T >
+      struct check_transformer< B,
+                                T,
+                                decltype( std::declval< T< B > >().null(),
+                                          std::declval< T< B > >().boolean( true ),
+                                          std::declval< T< B > >().number( double( 0.0 ) ),
+                                          std::declval< T< B > >().string( "" ),
+                                          std::declval< T< B > >().element(),
+                                          std::declval< T< B > >().member(),
+                                          void() ) >
+      {
+         using type = T< B >;
+      };
+
+      template< typename Consumer, template< typename... > class... Transformer >
+      struct transformer;
+
+      template< typename Consumer >
+      struct transformer< Consumer >
+      {
+         using type = Consumer;
+      };
+
+      template< typename Consumer, template< typename... > class Head, template< typename... > class... Tail >
+      struct transformer< Consumer, Head, Tail... >
+         : check_transformer< typename transformer< Consumer, Tail... >::type, Head >
+      {};
+
+   }  // namespace internal
+
+   namespace events
+   {
+      template< typename Consumer, template< typename... > class... Transformer >
+      using transformer = typename internal::transformer< Consumer, Transformer... >::type;
+
+   }  // namespace events
+
+}  // namespace tao::json
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/events/validate_event_order.hpp b/3rdParty/taocpp-json/include/tao/json/events/validate_event_order.hpp
new file mode 100644
index 000000000000..f4106e13bdb7
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/events/validate_event_order.hpp
@@ -0,0 +1,411 @@
+// Copyright (c) 2016-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_EVENTS_VALIDATE_EVENT_ORDER_HPP
+#define TAO_JSON_EVENTS_VALIDATE_EVENT_ORDER_HPP
+
+#include <cassert>
+#include <cstddef>
+#include <cstdint>
+#include <optional>
+#include <stdexcept>
+#include <string>
+#include <string_view>
+#include <vector>
+
+#include "../binary_view.hpp"
+
+namespace tao::json::events
+{
+   // Events consumer that validates the order of events.
+
+   class validate_event_order
+   {
+   private:
+      enum state_t
+      {
+         EXPECT_TOP_LEVEL_VALUE,
+         EXPECT_ARRAY_VALUE_OR_END,
+         EXPECT_ARRAY_ELEMENT,
+         EXPECT_SIZED_ARRAY_VALUE_OR_END,
+         EXPECT_SIZED_ARRAY_ELEMENT,
+         EXPECT_OBJECT_KEY_OR_END,
+         EXPECT_OBJECT_VALUE,
+         EXPECT_OBJECT_MEMBER,
+         EXPECT_SIZED_OBJECT_KEY_OR_END,
+         EXPECT_SIZED_OBJECT_VALUE,
+         EXPECT_SIZED_OBJECT_MEMBER,
+         EXPECT_NOTHING
+      };
+
+      struct sizes_t
+      {
+         explicit sizes_t( const std::size_t in_expected )
+            : expected( in_expected )
+         {}
+
+         void check( const std::size_t in_expected )
+         {
+            if( expected != in_expected ) {
+               throw std::logic_error( "inconsistent size" );
+            }
+            if( expected != counted ) {
+               throw std::logic_error( "wrong size" );
+            }
+         }
+
+         std::size_t expected;
+         std::size_t counted = 0;
+      };
+
+      state_t state = EXPECT_TOP_LEVEL_VALUE;
+      std::vector< state_t > stack;
+      std::vector< sizes_t > sizes;
+
+      void atom( const std::string& function )
+      {
+         switch( state ) {
+            case EXPECT_TOP_LEVEL_VALUE:
+               state = EXPECT_NOTHING;
+               return;
+            case EXPECT_ARRAY_VALUE_OR_END:
+               state = EXPECT_ARRAY_ELEMENT;
+               return;
+            case EXPECT_SIZED_ARRAY_VALUE_OR_END:
+               state = EXPECT_SIZED_ARRAY_ELEMENT;
+               return;
+            case EXPECT_ARRAY_ELEMENT:
+            case EXPECT_SIZED_ARRAY_ELEMENT:
+               throw std::logic_error( "expected element(), but " + function + " was called" );
+            case EXPECT_OBJECT_KEY_OR_END:
+            case EXPECT_SIZED_OBJECT_KEY_OR_END:
+               throw std::logic_error( "expected key() or end_object(...), but " + function + " was called" );
+            case EXPECT_OBJECT_VALUE:
+               state = EXPECT_OBJECT_MEMBER;
+               return;
+            case EXPECT_SIZED_OBJECT_VALUE:
+               state = EXPECT_SIZED_OBJECT_MEMBER;
+               return;
+            case EXPECT_OBJECT_MEMBER:
+            case EXPECT_SIZED_OBJECT_MEMBER:
+               throw std::logic_error( "expected member(), but " + function + " was called" );
+            case EXPECT_NOTHING:
+               throw std::logic_error( "expected nothing, but " + function + " was called" );
+         }
+         throw std::logic_error( "invalid state" );
+      }
+
+   public:
+      [[nodiscard]] bool is_complete() const noexcept
+      {
+         return state == EXPECT_NOTHING;
+      }
+
+      void null()
+      {
+         atom( "null()" );
+      }
+
+      void boolean( const bool /*unused*/ )
+      {
+         atom( "boolen()" );
+      }
+
+      void number( const std::int64_t /*unused*/ )
+      {
+         atom( "number(std::int64_t)" );
+      }
+
+      void number( const std::uint64_t /*unused*/ )
+      {
+         atom( "number(std::uint64_t)" );
+      }
+
+      void number( const double /*unused*/ )
+      {
+         atom( "number(double)" );
+      }
+
+      void string( const std::string_view /*unused*/ )
+      {
+         atom( "string(...)" );
+      }
+
+      void binary( const tao::binary_view /*unused*/ )
+      {
+         atom( "binary(...)" );
+      }
+
+      void begin_array()
+      {
+         switch( state ) {
+            case EXPECT_TOP_LEVEL_VALUE:
+               stack.push_back( EXPECT_NOTHING );
+               state = EXPECT_ARRAY_VALUE_OR_END;
+               return;
+            case EXPECT_ARRAY_VALUE_OR_END:
+               stack.push_back( EXPECT_ARRAY_ELEMENT );
+               return;
+            case EXPECT_SIZED_ARRAY_VALUE_OR_END:
+               stack.push_back( EXPECT_SIZED_ARRAY_ELEMENT );
+               return;
+            case EXPECT_ARRAY_ELEMENT:
+            case EXPECT_SIZED_ARRAY_ELEMENT:
+               throw std::logic_error( "expected element(), but begin_array(...) was called" );
+            case EXPECT_OBJECT_KEY_OR_END:
+            case EXPECT_SIZED_OBJECT_KEY_OR_END:
+               throw std::logic_error( "expected key() or end_object(...), but begin_array(...) was called" );
+            case EXPECT_OBJECT_VALUE:
+               stack.push_back( EXPECT_OBJECT_MEMBER );
+               state = EXPECT_ARRAY_VALUE_OR_END;
+               return;
+            case EXPECT_SIZED_OBJECT_VALUE:
+               stack.push_back( EXPECT_SIZED_OBJECT_MEMBER );
+               state = EXPECT_ARRAY_VALUE_OR_END;
+               return;
+            case EXPECT_OBJECT_MEMBER:
+            case EXPECT_SIZED_OBJECT_MEMBER:
+               throw std::logic_error( "expected member(), but begin_array(...) was called" );
+            case EXPECT_NOTHING:
+               throw std::logic_error( "expected nothing, but begin_array(...) was called" );
+         }
+         throw std::logic_error( "invalid state" );
+      }
+
+      void begin_array( const std::size_t expected )
+      {
+         begin_array();
+         sizes.emplace_back( expected );
+         state = EXPECT_SIZED_ARRAY_VALUE_OR_END;
+      }
+
+      void element()
+      {
+         switch( state ) {
+            case EXPECT_TOP_LEVEL_VALUE:
+               throw std::logic_error( "expected any value, but element() was called" );
+            case EXPECT_ARRAY_VALUE_OR_END:
+            case EXPECT_SIZED_ARRAY_VALUE_OR_END:
+               throw std::logic_error( "expected any value or end_array(...), but element() was called" );
+            case EXPECT_ARRAY_ELEMENT:
+               state = EXPECT_ARRAY_VALUE_OR_END;
+               return;
+            case EXPECT_SIZED_ARRAY_ELEMENT:
+               state = EXPECT_SIZED_ARRAY_VALUE_OR_END;
+               ++sizes.back().counted;
+               return;
+            case EXPECT_OBJECT_KEY_OR_END:
+            case EXPECT_SIZED_OBJECT_KEY_OR_END:
+               throw std::logic_error( "expected key() or end_object(...), but element() was called" );
+            case EXPECT_OBJECT_VALUE:
+            case EXPECT_SIZED_OBJECT_VALUE:
+               throw std::logic_error( "expected any value, but element() was called" );
+            case EXPECT_OBJECT_MEMBER:
+            case EXPECT_SIZED_OBJECT_MEMBER:
+               throw std::logic_error( "expected member(), but element() was called" );
+            case EXPECT_NOTHING:
+               throw std::logic_error( "expected nothing, but element() was called" );
+         }
+         throw std::logic_error( "invalid state" );
+      }
+
+      void end_array()
+      {
+         switch( state ) {
+            case EXPECT_TOP_LEVEL_VALUE:
+               throw std::logic_error( "expected any value, but end_array(....) was called" );
+            case EXPECT_ARRAY_VALUE_OR_END:
+               state = stack.back();
+               stack.pop_back();
+               return;
+            case EXPECT_SIZED_ARRAY_VALUE_OR_END:
+               throw std::logic_error( "expected end_array(std::size_t), but end_array() was called" );
+            case EXPECT_ARRAY_ELEMENT:
+            case EXPECT_SIZED_ARRAY_ELEMENT:
+               throw std::logic_error( "expected element(), but end_array(...) was called" );
+            case EXPECT_OBJECT_KEY_OR_END:
+            case EXPECT_SIZED_OBJECT_KEY_OR_END:
+               throw std::logic_error( "expected key() or end_object(...), but end_array(...) was called" );
+            case EXPECT_OBJECT_VALUE:
+            case EXPECT_SIZED_OBJECT_VALUE:
+               throw std::logic_error( "expected any value, but end_array(...) was called" );
+            case EXPECT_OBJECT_MEMBER:
+            case EXPECT_SIZED_OBJECT_MEMBER:
+               throw std::logic_error( "expected member(), but end_array(...) was called" );
+            case EXPECT_NOTHING:
+               throw std::logic_error( "expected nothing, but end_array(...) was called" );
+         }
+         throw std::logic_error( "invalid state" );
+      }
+
+      void end_array( const std::size_t expected )
+      {
+         switch( state ) {
+            case EXPECT_SIZED_ARRAY_VALUE_OR_END:
+               state = EXPECT_ARRAY_VALUE_OR_END;
+               break;
+            case EXPECT_ARRAY_VALUE_OR_END:
+               throw std::logic_error( "expected any value or end_array(), but end_array(std::size_t) was called" );
+            default:
+               break;
+         }
+         assert( sizes.size() );
+         sizes.back().check( expected );
+         sizes.pop_back();
+         end_array();
+      }
+
+      void begin_object()
+      {
+         switch( state ) {
+            case EXPECT_TOP_LEVEL_VALUE:
+               stack.push_back( EXPECT_NOTHING );
+               state = EXPECT_OBJECT_KEY_OR_END;
+               return;
+            case EXPECT_ARRAY_VALUE_OR_END:
+               stack.push_back( EXPECT_ARRAY_ELEMENT );
+               state = EXPECT_OBJECT_KEY_OR_END;
+               return;
+            case EXPECT_SIZED_ARRAY_VALUE_OR_END:
+               stack.push_back( EXPECT_SIZED_ARRAY_ELEMENT );
+               state = EXPECT_OBJECT_KEY_OR_END;
+               return;
+            case EXPECT_ARRAY_ELEMENT:
+            case EXPECT_SIZED_ARRAY_ELEMENT:
+               throw std::logic_error( "expected element(), but begin_object(...) was called" );
+            case EXPECT_OBJECT_KEY_OR_END:
+            case EXPECT_SIZED_OBJECT_KEY_OR_END:
+               throw std::logic_error( "expected key() or end_object(...), but begin_object(...) was called" );
+            case EXPECT_OBJECT_VALUE:
+               stack.push_back( EXPECT_OBJECT_MEMBER );
+               state = EXPECT_OBJECT_KEY_OR_END;
+               return;
+            case EXPECT_SIZED_OBJECT_VALUE:
+               stack.push_back( EXPECT_SIZED_OBJECT_MEMBER );
+               state = EXPECT_OBJECT_KEY_OR_END;
+               return;
+            case EXPECT_OBJECT_MEMBER:
+            case EXPECT_SIZED_OBJECT_MEMBER:
+               throw std::logic_error( "expected member(), but begin_object(...) was called" );
+            case EXPECT_NOTHING:
+               throw std::logic_error( "expected nothing, but begin_object(...) was called" );
+         }
+         throw std::logic_error( "invalid state" );
+      }
+
+      void begin_object( const std::size_t expected )
+      {
+         begin_object();
+         sizes.emplace_back( expected );
+         state = EXPECT_SIZED_OBJECT_KEY_OR_END;
+      }
+
+      void key( const std::string_view /*unused*/ )
+      {
+         switch( state ) {
+            case EXPECT_TOP_LEVEL_VALUE:
+               throw std::logic_error( "expected any value, but key() was called" );
+            case EXPECT_ARRAY_VALUE_OR_END:
+            case EXPECT_SIZED_ARRAY_VALUE_OR_END:
+               throw std::logic_error( "expected any value or end_array(...), but key() was called" );
+            case EXPECT_ARRAY_ELEMENT:
+            case EXPECT_SIZED_ARRAY_ELEMENT:
+               throw std::logic_error( "expected element(), but key() was called" );
+            case EXPECT_OBJECT_KEY_OR_END:
+               state = EXPECT_OBJECT_VALUE;
+               return;
+            case EXPECT_SIZED_OBJECT_KEY_OR_END:
+               state = EXPECT_SIZED_OBJECT_VALUE;
+               return;
+            case EXPECT_OBJECT_VALUE:
+            case EXPECT_SIZED_OBJECT_VALUE:
+               throw std::logic_error( "expected any value, but key() was called" );
+            case EXPECT_OBJECT_MEMBER:
+            case EXPECT_SIZED_OBJECT_MEMBER:
+               throw std::logic_error( "expected member(), but key() was called" );
+            case EXPECT_NOTHING:
+               throw std::logic_error( "expected nothing, but key() was called" );
+         }
+         throw std::logic_error( "invalid state" );
+      }
+
+      void member()
+      {
+         switch( state ) {
+            case EXPECT_TOP_LEVEL_VALUE:
+               throw std::logic_error( "expected any value, but member() was called" );
+            case EXPECT_ARRAY_VALUE_OR_END:
+            case EXPECT_SIZED_ARRAY_VALUE_OR_END:
+               throw std::logic_error( "expected any value or end_array(...), but member() was called" );
+            case EXPECT_ARRAY_ELEMENT:
+            case EXPECT_SIZED_ARRAY_ELEMENT:
+               throw std::logic_error( "expected element(), but member() was called" );
+            case EXPECT_OBJECT_KEY_OR_END:
+            case EXPECT_SIZED_OBJECT_KEY_OR_END:
+               throw std::logic_error( "expected key() or end_object(...), but member() was called" );
+            case EXPECT_OBJECT_VALUE:
+            case EXPECT_SIZED_OBJECT_VALUE:
+               throw std::logic_error( "expected any value, but member() was called" );
+            case EXPECT_OBJECT_MEMBER:
+               state = EXPECT_OBJECT_KEY_OR_END;
+               return;
+            case EXPECT_SIZED_OBJECT_MEMBER:
+               state = EXPECT_SIZED_OBJECT_KEY_OR_END;
+               ++sizes.back().counted;
+               return;
+            case EXPECT_NOTHING:
+               throw std::logic_error( "expected nothing, but member() was called" );
+         }
+         throw std::logic_error( "invalid state" );
+      }
+
+      void end_object()
+      {
+         switch( state ) {
+            case EXPECT_TOP_LEVEL_VALUE:
+               throw std::logic_error( "expected any value, but end_object(...) was called" );
+            case EXPECT_ARRAY_VALUE_OR_END:
+            case EXPECT_SIZED_ARRAY_VALUE_OR_END:
+               throw std::logic_error( "expected any value or end_array(...), but end_object(...) was called" );
+            case EXPECT_ARRAY_ELEMENT:
+            case EXPECT_SIZED_ARRAY_ELEMENT:
+               throw std::logic_error( "expected element(), but end_object(...) was called" );
+            case EXPECT_OBJECT_KEY_OR_END:
+               state = stack.back();
+               stack.pop_back();
+               return;
+            case EXPECT_SIZED_OBJECT_KEY_OR_END:
+               throw std::logic_error( "expected any value or end_object(std::size_t), but end_object() was called" );
+            case EXPECT_OBJECT_VALUE:
+            case EXPECT_SIZED_OBJECT_VALUE:
+               throw std::logic_error( "expected any value, but end_object(...) was called" );
+            case EXPECT_OBJECT_MEMBER:
+            case EXPECT_SIZED_OBJECT_MEMBER:
+               throw std::logic_error( "expected member(), but end_object(...) was called" );
+            case EXPECT_NOTHING:
+               throw std::logic_error( "expected nothing, but end_object(...) was called" );
+         }
+         throw std::logic_error( "invalid state" );
+      }
+
+      void end_object( const std::size_t expected )
+      {
+         switch( state ) {
+            case EXPECT_SIZED_OBJECT_KEY_OR_END:
+               state = EXPECT_OBJECT_KEY_OR_END;
+               break;
+            case EXPECT_OBJECT_KEY_OR_END:
+               throw std::logic_error( "expected any value or end_object(), but end_object(std::size_t) was called" );
+            default:
+               break;
+         }
+         assert( sizes.size() );
+         sizes.back().check( expected );
+         sizes.pop_back();
+         end_object();
+      }
+   };
+
+}  // namespace tao::json::events
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/events/validate_keys.hpp b/3rdParty/taocpp-json/include/tao/json/events/validate_keys.hpp
new file mode 100644
index 000000000000..c03d123db0be
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/events/validate_keys.hpp
@@ -0,0 +1,51 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_EVENTS_VALIDATE_KEYS_HPP
+#define TAO_JSON_EVENTS_VALIDATE_KEYS_HPP
+
+#include <stdexcept>
+#include <string>
+#include <string_view>
+#include <utility>
+
+#include "../external/pegtl.hpp"
+
+namespace tao::json::events
+{
+   template< typename Consumer, typename Rule >
+   struct validate_keys
+      : Consumer
+   {
+      using Consumer::Consumer;
+
+      void validate_key( const std::string_view v )
+      {
+         pegtl::memory_input< pegtl::tracking_mode::lazy > in( v.data(), v.size(), "validate_key" );
+         if( !pegtl::parse< Rule >( in ) ) {
+            throw std::runtime_error( "invalid key: " + std::string( v ) );
+         }
+      }
+
+      void key( const std::string_view v )
+      {
+         validate_key( v );
+         Consumer::key( v );
+      }
+
+      void key( const char* v )
+      {
+         validate_key( v );
+         Consumer::key( v );
+      }
+
+      void key( std::string&& v )
+      {
+         validate_key( v );
+         Consumer::key( std::move( v ) );
+      }
+   };
+
+}  // namespace tao::json::events
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/events/virtual_base.hpp b/3rdParty/taocpp-json/include/tao/json/events/virtual_base.hpp
new file mode 100644
index 000000000000..553f24433019
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/events/virtual_base.hpp
@@ -0,0 +1,192 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_EVENTS_VIRTUAL_BASE_HPP
+#define TAO_JSON_EVENTS_VIRTUAL_BASE_HPP
+
+#include <cstddef>
+#include <cstdint>
+#include <string>
+#include <string_view>
+#include <vector>
+
+#include "../binary_view.hpp"
+
+namespace tao::json::events
+{
+   // Events consumer interface with virtual functions.
+
+   class virtual_base
+   {
+   public:
+      void null()
+      {
+         v_null();
+      }
+
+      void boolean( const bool v )
+      {
+         v_boolean( v );
+      }
+
+      void number( const std::int64_t v )
+      {
+         v_number( v );
+      }
+
+      void number( const std::uint64_t v )
+      {
+         v_number( v );
+      }
+
+      void number( const double v )
+      {
+         v_number( v );
+      }
+
+      void string( const char* v )
+      {
+         v_string( v );
+      }
+
+      void string( std::string&& v )
+      {
+         v_string( std::move( v ) );
+      }
+
+      void string( const std::string& v )
+      {
+         v_string( v );
+      }
+
+      void string( const std::string_view v )
+      {
+         v_string( v );
+      }
+
+      void binary( std::vector< std::byte >&& v )
+      {
+         v_binary( std::move( v ) );
+      }
+
+      void binary( const std::vector< std::byte >& v )
+      {
+         v_binary( v );
+      }
+
+      void binary( const tao::binary_view v )
+      {
+         v_binary( v );
+      }
+
+      void begin_array()
+      {
+         v_begin_array();
+      }
+
+      void begin_array( const std::size_t v )
+      {
+         v_begin_array( v );
+      }
+
+      void element()
+      {
+         v_element();
+      }
+
+      void end_array()
+      {
+         v_end_array();
+      }
+
+      void end_array( const std::size_t v )
+      {
+         v_end_array( v );
+      }
+
+      void begin_object()
+      {
+         v_begin_object();
+      }
+
+      void begin_object( const std::size_t v )
+      {
+         v_begin_object( v );
+      }
+
+      void key( const char* v )
+      {
+         v_key( v );
+      }
+
+      void key( std::string&& v )
+      {
+         v_key( std::move( v ) );
+      }
+
+      void key( const std::string& v )
+      {
+         v_key( v );
+      }
+
+      void key( const std::string_view v )
+      {
+         v_key( v );
+      }
+
+      void member()
+      {
+         v_member();
+      }
+
+      void end_object()
+      {
+         v_end_object();
+      }
+
+      void end_object( const std::size_t v )
+      {
+         v_end_object( v );
+      }
+
+      virtual_base( virtual_base&& ) = delete;
+      virtual_base( const virtual_base& ) = delete;
+
+      void operator=( virtual_base&& ) = delete;
+      void operator=( const virtual_base& ) = delete;
+
+   protected:
+      virtual_base() = default;
+      ~virtual_base() = default;
+
+      virtual void v_null() = 0;
+      virtual void v_boolean( bool ) = 0;
+      virtual void v_number( std::int64_t ) = 0;
+      virtual void v_number( std::uint64_t ) = 0;
+      virtual void v_number( double ) = 0;
+      virtual void v_string( const char* ) = 0;
+      virtual void v_string( std::string&& ) = 0;
+      virtual void v_string( const std::string& ) = 0;
+      virtual void v_string( std::string_view ) = 0;
+      virtual void v_binary( std::vector< std::byte >&& ) = 0;
+      virtual void v_binary( const std::vector< std::byte >& ) = 0;
+      virtual void v_binary( tao::binary_view ) = 0;
+      virtual void v_begin_array() = 0;
+      virtual void v_begin_array( std::size_t ) = 0;
+      virtual void v_element() = 0;
+      virtual void v_end_array() = 0;
+      virtual void v_end_array( std::size_t ) = 0;
+      virtual void v_begin_object() = 0;
+      virtual void v_begin_object( std::size_t ) = 0;
+      virtual void v_key( const char* ) = 0;
+      virtual void v_key( std::string&& ) = 0;
+      virtual void v_key( const std::string& ) = 0;
+      virtual void v_key( std::string_view ) = 0;
+      virtual void v_member() = 0;
+      virtual void v_end_object() = 0;
+      virtual void v_end_object( std::size_t ) = 0;
+   };
+
+}  // namespace tao::json::events
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/events/virtual_ref.hpp b/3rdParty/taocpp-json/include/tao/json/events/virtual_ref.hpp
new file mode 100644
index 000000000000..f5d40e9656cf
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/events/virtual_ref.hpp
@@ -0,0 +1,170 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_EVENTS_VIRTUAL_REF_HPP
+#define TAO_JSON_EVENTS_VIRTUAL_REF_HPP
+
+#include <cstddef>
+#include <utility>
+
+#include "virtual_base.hpp"
+
+#ifdef _MSC_VER
+#pragma warning( push )
+#pragma warning( disable : 4373 )
+#endif
+
+namespace tao::json::events
+{
+   template< typename Consumer >
+   class virtual_ref
+      : public virtual_base
+   {
+   public:
+      explicit virtual_ref( Consumer& r ) noexcept
+         : m_r( r )
+      {}
+
+      virtual ~virtual_ref() = default;
+
+   private:
+      Consumer& m_r;
+
+      void v_null() override
+      {
+         m_r.null();
+      }
+
+      void v_boolean( const bool v ) override
+      {
+         m_r.boolean( v );
+      }
+
+      void v_number( const std::int64_t v ) override
+      {
+         m_r.number( v );
+      }
+
+      void v_number( const std::uint64_t v ) override
+      {
+         m_r.number( v );
+      }
+
+      void v_number( const double v ) override
+      {
+         m_r.number( v );
+      }
+
+      void v_string( const char* v ) override
+      {
+         m_r.string( v );
+      }
+
+      void v_string( std::string&& v ) override
+      {
+         m_r.string( std::move( v ) );
+      }
+
+      void v_string( const std::string& v ) override
+      {
+         m_r.string( v );
+      }
+
+      void v_string( const std::string_view v ) override
+      {
+         m_r.string( v );
+      }
+
+      void v_binary( std::vector< std::byte >&& v ) override
+      {
+         m_r.binary( std::move( v ) );
+      }
+
+      void v_binary( const std::vector< std::byte >& v ) override
+      {
+         m_r.binary( v );
+      }
+
+      void v_binary( const tao::binary_view v ) override
+      {
+         m_r.binary( v );
+      }
+
+      void v_begin_array() override
+      {
+         m_r.begin_array();
+      }
+
+      void v_begin_array( const std::size_t v ) override
+      {
+         m_r.begin_array( v );
+      }
+
+      void v_element() override
+      {
+         m_r.element();
+      }
+
+      void v_end_array() override
+      {
+         m_r.end_array();
+      }
+
+      void v_end_array( const std::size_t v ) override
+      {
+         m_r.end_array( v );
+      }
+
+      void v_begin_object() override
+      {
+         m_r.begin_object();
+      }
+
+      void v_begin_object( const std::size_t v ) override
+      {
+         m_r.begin_object( v );
+      }
+
+      void v_key( const char* v ) override
+      {
+         m_r.key( v );
+      }
+
+      void v_key( std::string&& v ) override
+      {
+         m_r.key( std::move( v ) );
+      }
+
+      void v_key( const std::string& v ) override
+      {
+         m_r.key( v );
+      }
+
+      void v_key( const std::string_view v ) override
+      {
+         m_r.key( v );
+      }
+
+      void v_member() override
+      {
+         m_r.member();
+      }
+
+      void v_end_object() override
+      {
+         m_r.end_object();
+      }
+
+      void v_end_object( const std::size_t v ) override
+      {
+         m_r.end_object( v );
+      }
+   };
+
+}  // namespace tao::json::events
+
+#ifdef _MSC_VER
+#pragma warning( pop )
+#endif
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/double.hpp b/3rdParty/taocpp-json/include/tao/json/external/double.hpp
new file mode 100644
index 000000000000..9087c4e8ee42
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/double.hpp
@@ -0,0 +1,1313 @@
+// This header include/tao/json/external/double.hpp contains
+// modified portions of the double-conversion library from
+//   https://www.github.com/google/double-conversion
+// which is licensed as follows:
+
+// Copyright 2006-2011 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef TAO_JSON_EXTERNAL_DOUBLE_HPP
+#define TAO_JSON_EXTERNAL_DOUBLE_HPP
+
+// clang-format off
+
+#include <limits.h>
+
+#include <algorithm>
+#include <cassert>
+#include <cmath>
+#include <cstdlib>
+#include <cstring>
+
+// Double operations detection based on target architecture.
+// Linux uses a 80bit wide floating point stack on x86. This induces double
+// rounding, which in turn leads to wrong results.
+// An easy way to test if the floating-point operations are correct is to
+// evaluate: 89255.0/1e22. If the floating-point stack is 64 bits wide then
+// the result is equal to 89255e-22.
+// The best way to test this, is to create a division-function and to compare
+// the output of the division with the expected result. (Inlining must be
+// disabled.)
+// On Linux,x86 89255e-22 != Div_double(89255.0/1e22)
+#if defined(_M_X64) || defined(__x86_64__) ||                           \
+   defined(__ARMEL__) || defined(__avr32__) || defined(_M_ARM) || defined(_M_ARM64) || \
+   defined(__hppa__) || defined(__ia64__) ||                            \
+   defined(__mips__) ||                                                 \
+   defined(__powerpc__) || defined(__ppc__) || defined(__ppc64__) ||    \
+   defined(_POWER) || defined(_ARCH_PPC) || defined(_ARCH_PPC64) ||     \
+   defined(__sparc__) || defined(__sparc) || defined(__s390__) ||       \
+   defined(__SH4__) || defined(__alpha__) ||                            \
+   defined(_MIPS_ARCH_MIPS32R2) ||                                      \
+   defined(__AARCH64EL__) || defined(__aarch64__)
+#define TAO_JSON_DOUBLE_CONVERSION_CORRECT_DOUBLE_OPERATIONS 1
+#elif defined(__mc68000__)
+#undef TAO_JSON_DOUBLE_CONVERSION_CORRECT_DOUBLE_OPERATIONS
+#elif defined(_M_IX86) || defined(__i386__) || defined(__i386)
+#if defined(_WIN32)
+// Windows uses a 64bit wide floating point stack.
+#define TAO_JSON_DOUBLE_CONVERSION_CORRECT_DOUBLE_OPERATIONS 1
+#else
+#undef TAO_JSON_DOUBLE_CONVERSION_CORRECT_DOUBLE_OPERATIONS
+#endif  // _WIN32
+#else
+#error Target architecture was not detected as supported by Double-Conversion.
+#endif
+
+#if defined(__GNUC__)
+#define TAO_JSON_DOUBLE_CONVERSION_UNUSED __attribute__((unused))
+#else
+#define TAO_JSON_DOUBLE_CONVERSION_UNUSED
+#endif
+
+#if defined(_WIN32) && !defined(__MINGW32__)
+
+typedef signed char int8_t;
+typedef unsigned char uint8_t;
+typedef short int16_t;
+typedef unsigned short uint16_t;
+typedef int int32_t;
+typedef unsigned int uint32_t;
+typedef __int64 int64_t;
+typedef unsigned __int64 uint64_t;
+
+// intptr_t and friends are defined in crtdefs.h through stdio.h.
+
+#else
+
+#include <stdint.h>
+
+#endif
+
+typedef uint16_t uc16;
+
+#define TAO_JSON_UINT64_2PART_C(a, b) (((static_cast<uint64_t>(a) << 32) + 0x##b##u))
+
+#ifndef TAO_JSON_GDCV8_ARRAY_SIZE
+#define TAO_JSON_GDCV8_ARRAY_SIZE(a)                             \
+   ((sizeof(a) / sizeof(*(a))) /                        \
+    static_cast<size_t>(!(sizeof(a) % sizeof(*(a)))))
+#endif
+
+namespace tao::json::double_conversion
+{
+   static const int kCharSize = sizeof( char );
+
+   template <typename T>
+   class Vector {
+   public:
+      Vector() : start_(nullptr), length_(0) {}
+      Vector(T* data, int len) : start_(data), length_(len) {
+         assert(len == 0 || (len > 0 && data != nullptr));
+      }
+
+      int length() const { return length_; }
+
+      T& operator[](int index) const {
+         assert(0 <= index && index < length_);
+         return start_[index];
+      }
+
+   private:
+      T* start_;
+      int length_;
+   };
+
+   template <class Dest, class Source>
+   inline Dest BitCast(const Source& source) {
+      TAO_JSON_DOUBLE_CONVERSION_UNUSED
+         typedef char VerifySizesAreEqual[sizeof(Dest) == sizeof(Source) ? 1 : -1];
+
+      Dest dest;
+      std::memmove(&dest, &source, sizeof(dest));
+      return dest;
+   }
+
+   template <class Dest, class Source>
+   inline Dest BitCast(Source* source) {
+      return BitCast<Dest>(reinterpret_cast<uintptr_t>(source));
+   }
+
+   class Bignum
+   {
+   public:
+      static const int kMaxSignificantBits = 3584;
+
+      Bignum();
+
+      void AssignUInt16(uint16_t value);
+      void AssignUInt64(uint64_t value);
+
+      void AssignDecimalString(Vector<const char> value);
+
+      void AssignPowerUInt16(uint16_t base, int exponent);
+
+      void AddUInt64(uint64_t operand);
+      void AddBignum(const Bignum& other);
+      void SubtractBignum(const Bignum& other);
+
+      void Square();
+      void ShiftLeft(int shift_amount);
+      void MultiplyByUInt32(uint32_t factor);
+      void MultiplyByUInt64(uint64_t factor);
+      void MultiplyByPowerOfTen(int exponent);
+
+      static int Compare(const Bignum& a, const Bignum& b);
+      static bool LessEqual(const Bignum& a, const Bignum& b) {
+         return Compare(a, b) <= 0;
+      }
+
+   private:
+      typedef uint32_t Chunk;
+      typedef uint64_t DoubleChunk;
+
+      static const int kChunkSize = sizeof(Chunk) * 8;
+      static const int kDoubleChunkSize = sizeof(DoubleChunk) * 8;
+      static const int kBigitSize = 28;
+      static const Chunk kBigitMask = (1 << kBigitSize) - 1;
+      static const int kBigitCapacity = kMaxSignificantBits / kBigitSize;
+
+      void EnsureCapacity(int size) {
+         assert(size <= kBigitCapacity);
+         (void)size;
+      }
+      void Align(const Bignum& other);
+      void Clamp();
+      bool IsClamped() const;
+      void Zero();
+
+      void BigitsShiftLeft(int shift_amount);
+      int BigitLength() const { return used_digits_ + exponent_; }
+      Chunk BigitAt(int index) const;
+      void SubtractTimes(const Bignum& other, int factor);
+
+      Chunk bigits_buffer_[kBigitCapacity];
+      Vector<Chunk> bigits_;
+      int used_digits_;
+      int exponent_;
+
+      Bignum( const Bignum & ) = delete;
+      void operator= ( const Bignum & ) = delete;
+   };
+
+   inline Bignum::Bignum()
+         : bigits_(bigits_buffer_, kBigitCapacity), used_digits_(0), exponent_(0) {
+      for (int i = 0; i < kBigitCapacity; ++i) {
+         bigits_[i] = 0;
+      }
+   }
+
+   template<typename S>
+   inline int BitSize(S value) {
+      (void) value;  // Mark variable as used.
+      return 8 * sizeof(value);
+   }
+
+   inline void Bignum::AssignUInt16(uint16_t value) {
+      assert(kBigitSize >= BitSize(value));
+      Zero();
+      if (value == 0) return;
+
+      EnsureCapacity(1);
+      bigits_[0] = value;
+      used_digits_ = 1;
+   }
+
+   inline void Bignum::AssignUInt64(uint64_t value) {
+      const int kUInt64Size = 64;
+
+      Zero();
+      if (value == 0) return;
+
+      int needed_bigits = kUInt64Size / kBigitSize + 1;
+      EnsureCapacity(needed_bigits);
+      for (int i = 0; i < needed_bigits; ++i) {
+         bigits_[i] = value & kBigitMask;
+         value = value >> kBigitSize;
+      }
+      used_digits_ = needed_bigits;
+      Clamp();
+   }
+
+   inline uint64_t ReadUInt64(Vector<const char> buffer,
+                              int from,
+                              int digits_to_read) {
+      uint64_t result = 0;
+      for (int i = from; i < from + digits_to_read; ++i) {
+         int digit = buffer[i] - '0';
+         assert(0 <= digit && digit <= 9);
+         result = result * 10 + digit;
+      }
+      return result;
+   }
+
+   inline void Bignum::AssignDecimalString(Vector<const char> value) {
+      const int kMaxUint64DecimalDigits = 19;
+      Zero();
+      int length = value.length();
+      unsigned int pos = 0;
+      while (length >= kMaxUint64DecimalDigits) {
+         uint64_t digits = ReadUInt64(value, pos, kMaxUint64DecimalDigits);
+         pos += kMaxUint64DecimalDigits;
+         length -= kMaxUint64DecimalDigits;
+         MultiplyByPowerOfTen(kMaxUint64DecimalDigits);
+         AddUInt64(digits);
+      }
+      uint64_t digits = ReadUInt64(value, pos, length);
+      MultiplyByPowerOfTen(length);
+      AddUInt64(digits);
+      Clamp();
+   }
+
+   inline void Bignum::AddUInt64(uint64_t operand) {
+      if (operand == 0) return;
+      Bignum other;
+      other.AssignUInt64(operand);
+      AddBignum(other);
+   }
+
+   inline void Bignum::AddBignum(const Bignum& other) {
+      assert(IsClamped());
+      assert(other.IsClamped());
+      Align(other);
+      EnsureCapacity(1 + (std::max)(BigitLength(), other.BigitLength()) - exponent_);
+      Chunk carry = 0;
+      int bigit_pos = other.exponent_ - exponent_;
+      assert(bigit_pos >= 0);
+      for (int i = 0; i < other.used_digits_; ++i) {
+         Chunk sum = bigits_[bigit_pos] + other.bigits_[i] + carry;
+         bigits_[bigit_pos] = sum & kBigitMask;
+         carry = sum >> kBigitSize;
+         bigit_pos++;
+      }
+      while (carry != 0) {
+         Chunk sum = bigits_[bigit_pos] + carry;
+         bigits_[bigit_pos] = sum & kBigitMask;
+         carry = sum >> kBigitSize;
+         bigit_pos++;
+      }
+      used_digits_ = (std::max)(bigit_pos, used_digits_);
+      assert(IsClamped());
+   }
+
+   inline void Bignum::SubtractBignum(const Bignum& other) {
+      assert(IsClamped());
+      assert(other.IsClamped());
+      assert(LessEqual(other, *this));
+      Align(other);
+
+      int offset = other.exponent_ - exponent_;
+      Chunk borrow = 0;
+      int i;
+      for (i = 0; i < other.used_digits_; ++i) {
+         assert((borrow == 0) || (borrow == 1));
+         Chunk difference = bigits_[i + offset] - other.bigits_[i] - borrow;
+         bigits_[i + offset] = difference & kBigitMask;
+         borrow = difference >> (kChunkSize - 1);
+      }
+      while (borrow != 0) {
+         Chunk difference = bigits_[i + offset] - borrow;
+         bigits_[i + offset] = difference & kBigitMask;
+         borrow = difference >> (kChunkSize - 1);
+         ++i;
+      }
+      Clamp();
+   }
+
+   inline void Bignum::ShiftLeft(int shift_amount) {
+      if (used_digits_ == 0) return;
+      exponent_ += shift_amount / kBigitSize;
+      int local_shift = shift_amount % kBigitSize;
+      EnsureCapacity(used_digits_ + 1);
+      BigitsShiftLeft(local_shift);
+   }
+
+   inline void Bignum::MultiplyByUInt32(uint32_t factor) {
+      if (factor == 1) return;
+      if (factor == 0) {
+         Zero();
+         return;
+      }
+      if (used_digits_ == 0) return;
+      assert(kDoubleChunkSize >= kBigitSize + 32 + 1);
+      DoubleChunk carry = 0;
+      for (int i = 0; i < used_digits_; ++i) {
+         DoubleChunk product = static_cast<DoubleChunk>(factor) * bigits_[i] + carry;
+         bigits_[i] = static_cast<Chunk>(product & kBigitMask);
+         carry = (product >> kBigitSize);
+      }
+      while (carry != 0) {
+         EnsureCapacity(used_digits_ + 1);
+         bigits_[used_digits_] = carry & kBigitMask;
+         used_digits_++;
+         carry >>= kBigitSize;
+      }
+   }
+
+   inline void Bignum::MultiplyByUInt64(uint64_t factor) {
+      if (factor == 1) return;
+      if (factor == 0) {
+         Zero();
+         return;
+      }
+      assert(kBigitSize < 32);
+      uint64_t carry = 0;
+      uint64_t low = factor & 0xFFFFFFFF;
+      uint64_t high = factor >> 32;
+      for (int i = 0; i < used_digits_; ++i) {
+         uint64_t product_low = low * bigits_[i];
+         uint64_t product_high = high * bigits_[i];
+         uint64_t tmp = (carry & kBigitMask) + product_low;
+         bigits_[i] = tmp & kBigitMask;
+         carry = (carry >> kBigitSize) + (tmp >> kBigitSize) +
+            (product_high << (32 - kBigitSize));
+      }
+      while (carry != 0) {
+         EnsureCapacity(used_digits_ + 1);
+         bigits_[used_digits_] = carry & kBigitMask;
+         used_digits_++;
+         carry >>= kBigitSize;
+      }
+   }
+
+   inline void Bignum::MultiplyByPowerOfTen(int exponent) {
+      const uint64_t kFive27 = TAO_JSON_UINT64_2PART_C(0x6765c793, fa10079d);
+      const uint16_t kFive1 = 5;
+      const uint16_t kFive2 = kFive1 * 5;
+      const uint16_t kFive3 = kFive2 * 5;
+      const uint16_t kFive4 = kFive3 * 5;
+      const uint16_t kFive5 = kFive4 * 5;
+      const uint16_t kFive6 = kFive5 * 5;
+      const uint32_t kFive7 = kFive6 * 5;
+      const uint32_t kFive8 = kFive7 * 5;
+      const uint32_t kFive9 = kFive8 * 5;
+      const uint32_t kFive10 = kFive9 * 5;
+      const uint32_t kFive11 = kFive10 * 5;
+      const uint32_t kFive12 = kFive11 * 5;
+      const uint32_t kFive13 = kFive12 * 5;
+      const uint32_t kFive1_to_12[] =
+         { kFive1, kFive2, kFive3, kFive4, kFive5, kFive6,
+           kFive7, kFive8, kFive9, kFive10, kFive11, kFive12 };
+
+      assert(exponent >= 0);
+      if (exponent == 0) return;
+      if (used_digits_ == 0) return;
+      int remaining_exponent = exponent;
+      while (remaining_exponent >= 27) {
+         MultiplyByUInt64(kFive27);
+         remaining_exponent -= 27;
+      }
+      while (remaining_exponent >= 13) {
+         MultiplyByUInt32(kFive13);
+         remaining_exponent -= 13;
+      }
+      if (remaining_exponent > 0) {
+         MultiplyByUInt32(kFive1_to_12[remaining_exponent - 1]);
+      }
+      ShiftLeft(exponent);
+   }
+
+   inline void Bignum::Square() {
+      assert(IsClamped());
+      int product_length = 2 * used_digits_;
+      EnsureCapacity(product_length);
+
+      if ((1 << (2 * (kChunkSize - kBigitSize))) <= used_digits_) {
+         std::abort();  // Unimplemented.
+      }
+      DoubleChunk accumulator = 0;
+      int copy_offset = used_digits_;
+      for (int i = 0; i < used_digits_; ++i) {
+         bigits_[copy_offset + i] = bigits_[i];
+      }
+      for (int i = 0; i < used_digits_; ++i) {
+         int bigit_index1 = i;
+         int bigit_index2 = 0;
+         while (bigit_index1 >= 0) {
+            Chunk chunk1 = bigits_[copy_offset + bigit_index1];
+            Chunk chunk2 = bigits_[copy_offset + bigit_index2];
+            accumulator += static_cast<DoubleChunk>(chunk1) * chunk2;
+            bigit_index1--;
+            bigit_index2++;
+         }
+         bigits_[i] = static_cast<Chunk>(accumulator) & kBigitMask;
+         accumulator >>= kBigitSize;
+      }
+      for (int i = used_digits_; i < product_length; ++i) {
+         int bigit_index1 = used_digits_ - 1;
+         int bigit_index2 = i - bigit_index1;
+         while (bigit_index2 < used_digits_) {
+            Chunk chunk1 = bigits_[copy_offset + bigit_index1];
+            Chunk chunk2 = bigits_[copy_offset + bigit_index2];
+            accumulator += static_cast<DoubleChunk>(chunk1) * chunk2;
+            bigit_index1--;
+            bigit_index2++;
+         }
+         bigits_[i] = static_cast<Chunk>(accumulator) & kBigitMask;
+         accumulator >>= kBigitSize;
+      }
+      assert(accumulator == 0);
+      used_digits_ = product_length;
+      exponent_ *= 2;
+      Clamp();
+   }
+
+   inline void Bignum::AssignPowerUInt16(uint16_t base, int power_exponent) {
+      assert(base != 0);
+      assert(power_exponent >= 0);
+      if (power_exponent == 0) {
+         AssignUInt16(1);
+         return;
+      }
+      Zero();
+      int shifts = 0;
+      while ((base & 1) == 0) {
+         base >>= 1;
+         shifts++;
+      }
+      int bit_size = 0;
+      int tmp_base = base;
+      while (tmp_base != 0) {
+         tmp_base >>= 1;
+         bit_size++;
+      }
+      int final_size = bit_size * power_exponent;
+      EnsureCapacity(final_size / kBigitSize + 2);
+      int mask = 1;
+      while (power_exponent >= mask) mask <<= 1;
+      mask >>= 2;
+      uint64_t this_value = base;
+      bool delayed_multipliciation = false;
+      const uint64_t max_32bits = 0xFFFFFFFF;
+      while (mask != 0 && this_value <= max_32bits) {
+         this_value = this_value * this_value;
+         if ((power_exponent & mask) != 0) {
+            uint64_t base_bits_mask =
+               ~((static_cast<uint64_t>(1) << (64 - bit_size)) - 1);
+            bool high_bits_zero = (this_value & base_bits_mask) == 0;
+            if (high_bits_zero) {
+               this_value *= base;
+            } else {
+               delayed_multipliciation = true;
+            }
+         }
+         mask >>= 1;
+      }
+      AssignUInt64(this_value);
+      if (delayed_multipliciation) {
+         MultiplyByUInt32(base);
+      }
+      while (mask != 0) {
+         Square();
+         if ((power_exponent & mask) != 0) {
+            MultiplyByUInt32(base);
+         }
+         mask >>= 1;
+      }
+      ShiftLeft(shifts * power_exponent);
+   }
+
+   inline Bignum::Chunk Bignum::BigitAt(int index) const {
+      if (index >= BigitLength()) return 0;
+      if (index < exponent_) return 0;
+      return bigits_[index - exponent_];
+   }
+
+   inline int Bignum::Compare(const Bignum& a, const Bignum& b) {
+      assert(a.IsClamped());
+      assert(b.IsClamped());
+      int bigit_length_a = a.BigitLength();
+      int bigit_length_b = b.BigitLength();
+      if (bigit_length_a < bigit_length_b) return -1;
+      if (bigit_length_a > bigit_length_b) return +1;
+      for (int i = bigit_length_a - 1; i >= (std::min)(a.exponent_, b.exponent_); --i) {
+         const Chunk bigit_a = a.BigitAt(i);
+         const Chunk bigit_b = b.BigitAt(i);
+         if (bigit_a < bigit_b) return -1;
+         if (bigit_a > bigit_b) return +1;
+      }
+      return 0;
+   }
+
+   inline void Bignum::Clamp() {
+      while (used_digits_ > 0 && bigits_[used_digits_ - 1] == 0) {
+         used_digits_--;
+      }
+      if (used_digits_ == 0) {
+         exponent_ = 0;
+      }
+   }
+
+   inline bool Bignum::IsClamped() const {
+      return used_digits_ == 0 || bigits_[used_digits_ - 1] != 0;
+   }
+
+   inline void Bignum::Zero() {
+      for (int i = 0; i < used_digits_; ++i) {
+         bigits_[i] = 0;
+      }
+      used_digits_ = 0;
+      exponent_ = 0;
+   }
+
+   inline void Bignum::Align(const Bignum& other) {
+      if (exponent_ > other.exponent_) {
+         int zero_digits = exponent_ - other.exponent_;
+         EnsureCapacity(used_digits_ + zero_digits);
+         for (int i = used_digits_ - 1; i >= 0; --i) {
+            bigits_[i + zero_digits] = bigits_[i];
+         }
+         for (int i = 0; i < zero_digits; ++i) {
+            bigits_[i] = 0;
+         }
+         used_digits_ += zero_digits;
+         exponent_ -= zero_digits;
+         assert(used_digits_ >= 0);
+         assert(exponent_ >= 0);
+      }
+   }
+
+   inline void Bignum::BigitsShiftLeft(int shift_amount) {
+      assert(shift_amount < kBigitSize);
+      assert(shift_amount >= 0);
+      Chunk carry = 0;
+      for (int i = 0; i < used_digits_; ++i) {
+         Chunk new_carry = bigits_[i] >> (kBigitSize - shift_amount);
+         bigits_[i] = ((bigits_[i] << shift_amount) + carry) & kBigitMask;
+         carry = new_carry;
+      }
+      if (carry != 0) {
+         bigits_[used_digits_] = carry;
+         used_digits_++;
+      }
+   }
+
+   inline void Bignum::SubtractTimes(const Bignum& other, int factor) {
+      assert(exponent_ <= other.exponent_);
+      if (factor < 3) {
+         for (int i = 0; i < factor; ++i) {
+            SubtractBignum(other);
+         }
+         return;
+      }
+      Chunk borrow = 0;
+      int exponent_diff = other.exponent_ - exponent_;
+      for (int i = 0; i < other.used_digits_; ++i) {
+         DoubleChunk product = static_cast<DoubleChunk>(factor) * other.bigits_[i];
+         DoubleChunk remove = borrow + product;
+         Chunk difference = bigits_[i + exponent_diff] - (remove & kBigitMask);
+         bigits_[i + exponent_diff] = difference & kBigitMask;
+         borrow = static_cast<Chunk>((difference >> (kChunkSize - 1)) +
+                                     (remove >> kBigitSize));
+      }
+      for (int i = other.used_digits_ + exponent_diff; i < used_digits_; ++i) {
+         if (borrow == 0) return;
+         Chunk difference = bigits_[i] - borrow;
+         bigits_[i] = difference & kBigitMask;
+         borrow = difference >> (kChunkSize - 1);
+      }
+      Clamp();
+   }
+
+   class DiyFp
+   {
+   public:
+      static const int kSignificandSize = 64;
+
+      DiyFp() : f_(0), e_(0) {}
+      DiyFp(uint64_t significand, int exponent) : f_(significand), e_(exponent) {}
+
+      void Subtract(const DiyFp& other) {
+         assert(e_ == other.e_);
+         assert(f_ >= other.f_);
+         f_ -= other.f_;
+      }
+
+      static DiyFp Minus(const DiyFp& a, const DiyFp& b) {
+         DiyFp result = a;
+         result.Subtract(b);
+         return result;
+      }
+
+      void Multiply(const DiyFp& other)
+      {
+         const uint64_t kM32 = 0xFFFFFFFFU;
+         uint64_t a = f_ >> 32;
+         uint64_t b = f_ & kM32;
+         uint64_t c = other.f_ >> 32;
+         uint64_t d = other.f_ & kM32;
+         uint64_t ac = a * c;
+         uint64_t bc = b * c;
+         uint64_t ad = a * d;
+         uint64_t bd = b * d;
+         uint64_t tmp = (bd >> 32) + (ad & kM32) + (bc & kM32);
+         tmp += 1U << 31;
+         uint64_t result_f = ac + (ad >> 32) + (bc >> 32) + (tmp >> 32);
+         e_ += other.e_ + 64;
+         f_ = result_f;
+      }
+
+      static DiyFp Times(const DiyFp& a, const DiyFp& b)
+      {
+         DiyFp result = a;
+         result.Multiply(b);
+         return result;
+      }
+
+      void Normalize() {
+         assert(f_ != 0);
+         uint64_t significand = f_;
+         int exponent = e_;
+
+         const uint64_t k10MSBits = TAO_JSON_UINT64_2PART_C(0xFFC00000, 00000000);
+         while ((significand & k10MSBits) == 0) {
+            significand <<= 10;
+            exponent -= 10;
+         }
+         while ((significand & kUint64MSB) == 0) {
+            significand <<= 1;
+            exponent--;
+         }
+         f_ = significand;
+         e_ = exponent;
+      }
+
+      static DiyFp Normalize(const DiyFp& a) {
+         DiyFp result = a;
+         result.Normalize();
+         return result;
+      }
+
+      uint64_t f() const { return f_; }
+      int e() const { return e_; }
+
+      void set_f(uint64_t new_value) { f_ = new_value; }
+      void set_e(int new_value) { e_ = new_value; }
+
+   private:
+      static const uint64_t kUint64MSB = TAO_JSON_UINT64_2PART_C(0x80000000, 00000000);
+
+      uint64_t f_;
+      int e_;
+   };
+
+   static uint64_t double_to_uint64(double d) { return BitCast<uint64_t>(d); }
+   static double uint64_to_double(uint64_t d64) { return BitCast<double>(d64); }
+
+   class Double {
+   public:
+      static const uint64_t kSignMask = TAO_JSON_UINT64_2PART_C(0x80000000, 00000000);
+      static const uint64_t kExponentMask = TAO_JSON_UINT64_2PART_C(0x7FF00000, 00000000);
+      static const uint64_t kSignificandMask = TAO_JSON_UINT64_2PART_C(0x000FFFFF, FFFFFFFF);
+      static const uint64_t kHiddenBit = TAO_JSON_UINT64_2PART_C(0x00100000, 00000000);
+      static const int kPhysicalSignificandSize = 52;
+      static const int kSignificandSize = 53;
+
+      Double() : d64_(0) {}
+      explicit Double(double d) : d64_(double_to_uint64(d)) {}
+      explicit Double(uint64_t d64) : d64_(d64) {}
+      explicit Double(DiyFp diy_fp)
+            : d64_(DiyFpToUint64(diy_fp)) {}
+
+      DiyFp AsDiyFp() const {
+         assert(Sign() > 0);
+         assert(!IsSpecial());
+         return DiyFp(Significand(), Exponent());
+      }
+
+      DiyFp AsNormalizedDiyFp() const {
+         assert(value() > 0.0);
+         uint64_t f = Significand();
+         int e = Exponent();
+
+         while ((f & kHiddenBit) == 0) {
+            f <<= 1;
+            e--;
+         }
+         f <<= DiyFp::kSignificandSize - kSignificandSize;
+         e -= DiyFp::kSignificandSize - kSignificandSize;
+         return DiyFp(f, e);
+      }
+
+      uint64_t AsUint64() const {
+         return d64_;
+      }
+
+      double NextDouble() const {
+         if (d64_ == kInfinity) return Double(kInfinity).value();
+         if (Sign() < 0 && Significand() == 0) {
+            return 0.0;
+         }
+         if (Sign() < 0) {
+            return Double(d64_ - 1).value();
+         } else {
+            return Double(d64_ + 1).value();
+         }
+      }
+
+      double PreviousDouble() const {
+         if (d64_ == (kInfinity | kSignMask)) return -Double::Infinity();
+         if (Sign() < 0) {
+            return Double(d64_ + 1).value();
+         } else {
+            if (Significand() == 0) return -0.0;
+            return Double(d64_ - 1).value();
+         }
+      }
+
+      int Exponent() const {
+         if (IsDenormal()) return kDenormalExponent;
+
+         uint64_t d64 = AsUint64();
+         int biased_e =
+            static_cast<int>((d64 & kExponentMask) >> kPhysicalSignificandSize);
+         return biased_e - kExponentBias;
+      }
+
+      uint64_t Significand() const {
+         uint64_t d64 = AsUint64();
+         uint64_t significand = d64 & kSignificandMask;
+         if (!IsDenormal()) {
+            return significand + kHiddenBit;
+         } else {
+            return significand;
+         }
+      }
+
+      bool IsDenormal() const {
+         uint64_t d64 = AsUint64();
+         return (d64 & kExponentMask) == 0;
+      }
+
+      bool IsSpecial() const {
+         uint64_t d64 = AsUint64();
+         return (d64 & kExponentMask) == kExponentMask;
+      }
+
+      bool IsNan() const {
+         uint64_t d64 = AsUint64();
+         return ((d64 & kExponentMask) == kExponentMask) &&
+            ((d64 & kSignificandMask) != 0);
+      }
+
+      bool IsInfinite() const {
+         uint64_t d64 = AsUint64();
+         return ((d64 & kExponentMask) == kExponentMask) &&
+            ((d64 & kSignificandMask) == 0);
+      }
+
+      int Sign() const {
+         uint64_t d64 = AsUint64();
+         return (d64 & kSignMask) == 0? 1: -1;
+      }
+
+      DiyFp UpperBoundary() const {
+         assert(Sign() > 0);
+         return DiyFp(Significand() * 2 + 1, Exponent() - 1);
+      }
+
+      void NormalizedBoundaries(DiyFp* out_m_minus, DiyFp* out_m_plus) const {
+         assert(value() > 0.0);
+         DiyFp v = this->AsDiyFp();
+         DiyFp m_plus = DiyFp::Normalize(DiyFp((v.f() << 1) + 1, v.e() - 1));
+         DiyFp m_minus;
+         if (LowerBoundaryIsCloser()) {
+            m_minus = DiyFp((v.f() << 2) - 1, v.e() - 2);
+         } else {
+            m_minus = DiyFp((v.f() << 1) - 1, v.e() - 1);
+         }
+         m_minus.set_f(m_minus.f() << (m_minus.e() - m_plus.e()));
+         m_minus.set_e(m_plus.e());
+         *out_m_plus = m_plus;
+         *out_m_minus = m_minus;
+      }
+
+      bool LowerBoundaryIsCloser() const {
+         bool physical_significand_is_zero = ((AsUint64() & kSignificandMask) == 0);
+         return physical_significand_is_zero && (Exponent() != kDenormalExponent);
+      }
+
+      double value() const { return uint64_to_double(d64_); }
+
+      static int SignificandSizeForOrderOfMagnitude(int order) {
+         if (order >= (kDenormalExponent + kSignificandSize)) {
+            return kSignificandSize;
+         }
+         if (order <= kDenormalExponent) return 0;
+         return order - kDenormalExponent;
+      }
+
+      static double Infinity() {
+         return Double(kInfinity).value();
+      }
+
+      static double NaN() {
+         return Double(kNaN).value();
+      }
+
+   private:
+      static const int kExponentBias = 0x3FF + kPhysicalSignificandSize;
+      static const int kDenormalExponent = -kExponentBias + 1;
+      static const int kMaxExponent = 0x7FF - kExponentBias;
+      static const uint64_t kInfinity = TAO_JSON_UINT64_2PART_C(0x7FF00000, 00000000);
+      static const uint64_t kNaN = TAO_JSON_UINT64_2PART_C(0x7FF80000, 00000000);
+
+      const uint64_t d64_;
+
+      static uint64_t DiyFpToUint64(DiyFp diy_fp) {
+         uint64_t significand = diy_fp.f();
+         int exponent = diy_fp.e();
+         while (significand > kHiddenBit + kSignificandMask) {
+            significand >>= 1;
+            exponent++;
+         }
+         if (exponent >= kMaxExponent) {
+            return kInfinity;
+         }
+         if (exponent < kDenormalExponent) {
+            return 0;
+         }
+         while (exponent > kDenormalExponent && (significand & kHiddenBit) == 0) {
+            significand <<= 1;
+            exponent--;
+         }
+         uint64_t biased_exponent;
+         if (exponent == kDenormalExponent && (significand & kHiddenBit) == 0) {
+            biased_exponent = 0;
+         } else {
+            biased_exponent = static_cast<uint64_t>(exponent + kExponentBias);
+         }
+         return (significand & kSignificandMask) |
+            (biased_exponent << kPhysicalSignificandSize);
+      }
+
+      Double( const Double& ) = delete;
+      void operator=( const Double& ) = delete;
+   };
+
+   struct PowersOfTenCache
+   {
+      static const int kDecimalExponentDistance = 8;
+
+      static const int kMinDecimalExponent = -348;
+      static const int kMaxDecimalExponent = 340;
+
+      static void GetCachedPowerForDecimalExponent(int requested_exponent,
+                                                   DiyFp* power,
+                                                   int* found_exponent);
+   };
+
+   struct CachedPower {
+      uint64_t significand;
+      int16_t binary_exponent;
+      int16_t decimal_exponent;
+   };
+
+   static const CachedPower kCachedPowers[] = {
+      {TAO_JSON_UINT64_2PART_C(0xfa8fd5a0, 081c0288), -1220, -348},
+      {TAO_JSON_UINT64_2PART_C(0xbaaee17f, a23ebf76), -1193, -340},
+      {TAO_JSON_UINT64_2PART_C(0x8b16fb20, 3055ac76), -1166, -332},
+      {TAO_JSON_UINT64_2PART_C(0xcf42894a, 5dce35ea), -1140, -324},
+      {TAO_JSON_UINT64_2PART_C(0x9a6bb0aa, 55653b2d), -1113, -316},
+      {TAO_JSON_UINT64_2PART_C(0xe61acf03, 3d1a45df), -1087, -308},
+      {TAO_JSON_UINT64_2PART_C(0xab70fe17, c79ac6ca), -1060, -300},
+      {TAO_JSON_UINT64_2PART_C(0xff77b1fc, bebcdc4f), -1034, -292},
+      {TAO_JSON_UINT64_2PART_C(0xbe5691ef, 416bd60c), -1007, -284},
+      {TAO_JSON_UINT64_2PART_C(0x8dd01fad, 907ffc3c), -980, -276},
+      {TAO_JSON_UINT64_2PART_C(0xd3515c28, 31559a83), -954, -268},
+      {TAO_JSON_UINT64_2PART_C(0x9d71ac8f, ada6c9b5), -927, -260},
+      {TAO_JSON_UINT64_2PART_C(0xea9c2277, 23ee8bcb), -901, -252},
+      {TAO_JSON_UINT64_2PART_C(0xaecc4991, 4078536d), -874, -244},
+      {TAO_JSON_UINT64_2PART_C(0x823c1279, 5db6ce57), -847, -236},
+      {TAO_JSON_UINT64_2PART_C(0xc2109436, 4dfb5637), -821, -228},
+      {TAO_JSON_UINT64_2PART_C(0x9096ea6f, 3848984f), -794, -220},
+      {TAO_JSON_UINT64_2PART_C(0xd77485cb, 25823ac7), -768, -212},
+      {TAO_JSON_UINT64_2PART_C(0xa086cfcd, 97bf97f4), -741, -204},
+      {TAO_JSON_UINT64_2PART_C(0xef340a98, 172aace5), -715, -196},
+      {TAO_JSON_UINT64_2PART_C(0xb23867fb, 2a35b28e), -688, -188},
+      {TAO_JSON_UINT64_2PART_C(0x84c8d4df, d2c63f3b), -661, -180},
+      {TAO_JSON_UINT64_2PART_C(0xc5dd4427, 1ad3cdba), -635, -172},
+      {TAO_JSON_UINT64_2PART_C(0x936b9fce, bb25c996), -608, -164},
+      {TAO_JSON_UINT64_2PART_C(0xdbac6c24, 7d62a584), -582, -156},
+      {TAO_JSON_UINT64_2PART_C(0xa3ab6658, 0d5fdaf6), -555, -148},
+      {TAO_JSON_UINT64_2PART_C(0xf3e2f893, dec3f126), -529, -140},
+      {TAO_JSON_UINT64_2PART_C(0xb5b5ada8, aaff80b8), -502, -132},
+      {TAO_JSON_UINT64_2PART_C(0x87625f05, 6c7c4a8b), -475, -124},
+      {TAO_JSON_UINT64_2PART_C(0xc9bcff60, 34c13053), -449, -116},
+      {TAO_JSON_UINT64_2PART_C(0x964e858c, 91ba2655), -422, -108},
+      {TAO_JSON_UINT64_2PART_C(0xdff97724, 70297ebd), -396, -100},
+      {TAO_JSON_UINT64_2PART_C(0xa6dfbd9f, b8e5b88f), -369, -92},
+      {TAO_JSON_UINT64_2PART_C(0xf8a95fcf, 88747d94), -343, -84},
+      {TAO_JSON_UINT64_2PART_C(0xb9447093, 8fa89bcf), -316, -76},
+      {TAO_JSON_UINT64_2PART_C(0x8a08f0f8, bf0f156b), -289, -68},
+      {TAO_JSON_UINT64_2PART_C(0xcdb02555, 653131b6), -263, -60},
+      {TAO_JSON_UINT64_2PART_C(0x993fe2c6, d07b7fac), -236, -52},
+      {TAO_JSON_UINT64_2PART_C(0xe45c10c4, 2a2b3b06), -210, -44},
+      {TAO_JSON_UINT64_2PART_C(0xaa242499, 697392d3), -183, -36},
+      {TAO_JSON_UINT64_2PART_C(0xfd87b5f2, 8300ca0e), -157, -28},
+      {TAO_JSON_UINT64_2PART_C(0xbce50864, 92111aeb), -130, -20},
+      {TAO_JSON_UINT64_2PART_C(0x8cbccc09, 6f5088cc), -103, -12},
+      {TAO_JSON_UINT64_2PART_C(0xd1b71758, e219652c), -77, -4},
+      {TAO_JSON_UINT64_2PART_C(0x9c400000, 00000000), -50, 4},
+      {TAO_JSON_UINT64_2PART_C(0xe8d4a510, 00000000), -24, 12},
+      {TAO_JSON_UINT64_2PART_C(0xad78ebc5, ac620000), 3, 20},
+      {TAO_JSON_UINT64_2PART_C(0x813f3978, f8940984), 30, 28},
+      {TAO_JSON_UINT64_2PART_C(0xc097ce7b, c90715b3), 56, 36},
+      {TAO_JSON_UINT64_2PART_C(0x8f7e32ce, 7bea5c70), 83, 44},
+      {TAO_JSON_UINT64_2PART_C(0xd5d238a4, abe98068), 109, 52},
+      {TAO_JSON_UINT64_2PART_C(0x9f4f2726, 179a2245), 136, 60},
+      {TAO_JSON_UINT64_2PART_C(0xed63a231, d4c4fb27), 162, 68},
+      {TAO_JSON_UINT64_2PART_C(0xb0de6538, 8cc8ada8), 189, 76},
+      {TAO_JSON_UINT64_2PART_C(0x83c7088e, 1aab65db), 216, 84},
+      {TAO_JSON_UINT64_2PART_C(0xc45d1df9, 42711d9a), 242, 92},
+      {TAO_JSON_UINT64_2PART_C(0x924d692c, a61be758), 269, 100},
+      {TAO_JSON_UINT64_2PART_C(0xda01ee64, 1a708dea), 295, 108},
+      {TAO_JSON_UINT64_2PART_C(0xa26da399, 9aef774a), 322, 116},
+      {TAO_JSON_UINT64_2PART_C(0xf209787b, b47d6b85), 348, 124},
+      {TAO_JSON_UINT64_2PART_C(0xb454e4a1, 79dd1877), 375, 132},
+      {TAO_JSON_UINT64_2PART_C(0x865b8692, 5b9bc5c2), 402, 140},
+      {TAO_JSON_UINT64_2PART_C(0xc83553c5, c8965d3d), 428, 148},
+      {TAO_JSON_UINT64_2PART_C(0x952ab45c, fa97a0b3), 455, 156},
+      {TAO_JSON_UINT64_2PART_C(0xde469fbd, 99a05fe3), 481, 164},
+      {TAO_JSON_UINT64_2PART_C(0xa59bc234, db398c25), 508, 172},
+      {TAO_JSON_UINT64_2PART_C(0xf6c69a72, a3989f5c), 534, 180},
+      {TAO_JSON_UINT64_2PART_C(0xb7dcbf53, 54e9bece), 561, 188},
+      {TAO_JSON_UINT64_2PART_C(0x88fcf317, f22241e2), 588, 196},
+      {TAO_JSON_UINT64_2PART_C(0xcc20ce9b, d35c78a5), 614, 204},
+      {TAO_JSON_UINT64_2PART_C(0x98165af3, 7b2153df), 641, 212},
+      {TAO_JSON_UINT64_2PART_C(0xe2a0b5dc, 971f303a), 667, 220},
+      {TAO_JSON_UINT64_2PART_C(0xa8d9d153, 5ce3b396), 694, 228},
+      {TAO_JSON_UINT64_2PART_C(0xfb9b7cd9, a4a7443c), 720, 236},
+      {TAO_JSON_UINT64_2PART_C(0xbb764c4c, a7a44410), 747, 244},
+      {TAO_JSON_UINT64_2PART_C(0x8bab8eef, b6409c1a), 774, 252},
+      {TAO_JSON_UINT64_2PART_C(0xd01fef10, a657842c), 800, 260},
+      {TAO_JSON_UINT64_2PART_C(0x9b10a4e5, e9913129), 827, 268},
+      {TAO_JSON_UINT64_2PART_C(0xe7109bfb, a19c0c9d), 853, 276},
+      {TAO_JSON_UINT64_2PART_C(0xac2820d9, 623bf429), 880, 284},
+      {TAO_JSON_UINT64_2PART_C(0x80444b5e, 7aa7cf85), 907, 292},
+      {TAO_JSON_UINT64_2PART_C(0xbf21e440, 03acdd2d), 933, 300},
+      {TAO_JSON_UINT64_2PART_C(0x8e679c2f, 5e44ff8f), 960, 308},
+      {TAO_JSON_UINT64_2PART_C(0xd433179d, 9c8cb841), 986, 316},
+      {TAO_JSON_UINT64_2PART_C(0x9e19db92, b4e31ba9), 1013, 324},
+      {TAO_JSON_UINT64_2PART_C(0xeb96bf6e, badf77d9), 1039, 332},
+      {TAO_JSON_UINT64_2PART_C(0xaf87023b, 9bf0ee6b), 1066, 340},
+   };
+
+   static const int kCachedPowersLength = TAO_JSON_GDCV8_ARRAY_SIZE(kCachedPowers);
+   static const int kCachedPowersOffset = 348;
+   static const double kD_1_LOG2_10 = 0.30102999566398114;
+
+   inline void PowersOfTenCache::GetCachedPowerForDecimalExponent(int requested_exponent,
+                                                                  DiyFp* power,
+                                                                  int* found_exponent) {
+      assert(kMinDecimalExponent <= requested_exponent);
+      assert(requested_exponent < kMaxDecimalExponent + kDecimalExponentDistance);
+      int index =
+         (requested_exponent + kCachedPowersOffset) / kDecimalExponentDistance;
+      CachedPower cached_power = kCachedPowers[index];
+      *power = DiyFp(cached_power.significand, cached_power.binary_exponent);
+      *found_exponent = cached_power.decimal_exponent;
+      assert(*found_exponent <= requested_exponent);
+      assert(requested_exponent < *found_exponent + kDecimalExponentDistance);
+   }
+
+   static const int kMaxExactDoubleIntegerDecimalDigits = 15;
+   static const int kMaxUint64DecimalDigits = 19;
+
+   static const int kMaxDecimalPower = 309;
+   static const int kMinDecimalPower = -324;
+
+   static const uint64_t kMaxUint64 = TAO_JSON_UINT64_2PART_C(0xFFFFFFFF, FFFFFFFF);
+
+   static const double exact_powers_of_ten[] = {
+      1.0,  // 10^0
+      10.0,
+      100.0,
+      1000.0,
+      10000.0,
+      100000.0,
+      1000000.0,
+      10000000.0,
+      100000000.0,
+      1000000000.0,
+      10000000000.0,  // 10^10
+      100000000000.0,
+      1000000000000.0,
+      10000000000000.0,
+      100000000000000.0,
+      1000000000000000.0,
+      10000000000000000.0,
+      100000000000000000.0,
+      1000000000000000000.0,
+      10000000000000000000.0,
+      100000000000000000000.0,  // 10^20
+      1000000000000000000000.0,
+      10000000000000000000000.0
+   };
+
+   static const int kExactPowersOfTenSize = TAO_JSON_GDCV8_ARRAY_SIZE(exact_powers_of_ten);
+   static const int kMaxSignificantDecimalDigits = 780;
+
+   inline uint64_t ReadUint64(Vector<const char> buffer,
+                              int* number_of_read_digits) {
+      uint64_t result = 0;
+      int i = 0;
+      while (i < buffer.length() && result <= (kMaxUint64 / 10 - 1)) {
+         int digit = buffer[i++] - '0';
+         assert(0 <= digit && digit <= 9);
+         result = 10 * result + digit;
+      }
+      *number_of_read_digits = i;
+      return result;
+   }
+
+   inline void ReadDiyFp(Vector<const char> buffer,
+                         DiyFp* result,
+                         int* remaining_decimals) {
+      int read_digits;
+      uint64_t significand = ReadUint64(buffer, &read_digits);
+      if (buffer.length() == read_digits) {
+         *result = DiyFp(significand, 0);
+         *remaining_decimals = 0;
+      } else {
+         if (buffer[read_digits] >= '5') {
+            significand++;
+         }
+         int exponent = 0;
+         *result = DiyFp(significand, exponent);
+         *remaining_decimals = buffer.length() - read_digits;
+      }
+   }
+
+   inline bool DoubleStrtod(Vector<const char> trimmed,
+                            int exponent,
+                            double* result) {
+#if !defined(TAO_JSON_DOUBLE_CONVERSION_CORRECT_DOUBLE_OPERATIONS)
+      // On x86 the floating-point stack can be 64 or 80 bits wide. If it is
+      // 80 bits wide (as is the case on Linux) then double-rounding occurs and the
+      // result is not accurate.
+      // We know that Windows32 uses 64 bits and is therefore accurate.
+      // Note that the ARM simulator is compiled for 32bits. It therefore exhibits
+      // the same problem.
+      return false;
+#endif
+      if (trimmed.length() <= kMaxExactDoubleIntegerDecimalDigits) {
+         int read_digits;
+         if (exponent < 0 && -exponent < kExactPowersOfTenSize) {
+            *result = static_cast<double>(ReadUint64(trimmed, &read_digits));
+            assert(read_digits == trimmed.length());
+            *result /= exact_powers_of_ten[-exponent];
+            return true;
+         }
+         if (0 <= exponent && exponent < kExactPowersOfTenSize) {
+            *result = static_cast<double>(ReadUint64(trimmed, &read_digits));
+            assert(read_digits == trimmed.length());
+            *result *= exact_powers_of_ten[exponent];
+            return true;
+         }
+         int remaining_digits =
+            kMaxExactDoubleIntegerDecimalDigits - trimmed.length();
+         if ((0 <= exponent) &&
+             (exponent - remaining_digits < kExactPowersOfTenSize)) {
+            *result = static_cast<double>(ReadUint64(trimmed, &read_digits));
+            assert(read_digits == trimmed.length());
+            *result *= exact_powers_of_ten[remaining_digits];
+            *result *= exact_powers_of_ten[exponent - remaining_digits];
+            return true;
+         }
+      }
+      return false;
+   }
+
+   inline DiyFp AdjustmentPowerOfTen(int exponent) {
+      assert(0 < exponent);
+      assert(exponent < PowersOfTenCache::kDecimalExponentDistance);
+      assert(PowersOfTenCache::kDecimalExponentDistance == 8);
+      switch (exponent) {
+         case 1: return DiyFp(TAO_JSON_UINT64_2PART_C(0xa0000000, 00000000), -60);
+         case 2: return DiyFp(TAO_JSON_UINT64_2PART_C(0xc8000000, 00000000), -57);
+         case 3: return DiyFp(TAO_JSON_UINT64_2PART_C(0xfa000000, 00000000), -54);
+         case 4: return DiyFp(TAO_JSON_UINT64_2PART_C(0x9c400000, 00000000), -50);
+         case 5: return DiyFp(TAO_JSON_UINT64_2PART_C(0xc3500000, 00000000), -47);
+         case 6: return DiyFp(TAO_JSON_UINT64_2PART_C(0xf4240000, 00000000), -44);
+         case 7: return DiyFp(TAO_JSON_UINT64_2PART_C(0x98968000, 00000000), -40);
+         default:
+            std::abort();
+      }
+   }
+
+   inline bool DiyFpStrtod(Vector<const char> buffer,
+                           int exponent,
+                           double* result) {
+      DiyFp input;
+      int remaining_decimals;
+      ReadDiyFp(buffer, &input, &remaining_decimals);
+      const int kDenominatorLog = 3;
+      const int kDenominator = 1 << kDenominatorLog;
+      exponent += remaining_decimals;
+      uint64_t error = (remaining_decimals == 0 ? 0 : kDenominator / 2);
+
+      int old_e = input.e();
+      input.Normalize();
+      error <<= old_e - input.e();
+
+      assert(exponent <= PowersOfTenCache::kMaxDecimalExponent);
+      if (exponent < PowersOfTenCache::kMinDecimalExponent) {
+         *result = 0.0;
+         return true;
+      }
+      DiyFp cached_power;
+      int cached_decimal_exponent;
+      PowersOfTenCache::GetCachedPowerForDecimalExponent(exponent,
+                                                         &cached_power,
+                                                         &cached_decimal_exponent);
+
+      if (cached_decimal_exponent != exponent) {
+         int adjustment_exponent = exponent - cached_decimal_exponent;
+         DiyFp adjustment_power = AdjustmentPowerOfTen(adjustment_exponent);
+         input.Multiply(adjustment_power);
+         if (kMaxUint64DecimalDigits - buffer.length() >= adjustment_exponent) {
+            assert(DiyFp::kSignificandSize == 64);
+         } else {
+            error += kDenominator / 2;
+         }
+      }
+
+      input.Multiply(cached_power);
+      int error_b = kDenominator / 2;
+      int error_ab = (error == 0 ? 0 : 1);
+      int fixed_error = kDenominator / 2;
+      error += error_b + error_ab + fixed_error;
+
+      old_e = input.e();
+      input.Normalize();
+      error <<= old_e - input.e();
+
+      int order_of_magnitude = DiyFp::kSignificandSize + input.e();
+      int effective_significand_size =
+         Double::SignificandSizeForOrderOfMagnitude(order_of_magnitude);
+      int precision_digits_count =
+         DiyFp::kSignificandSize - effective_significand_size;
+      if (precision_digits_count + kDenominatorLog >= DiyFp::kSignificandSize) {
+         int shift_amount = (precision_digits_count + kDenominatorLog) -
+            DiyFp::kSignificandSize + 1;
+         input.set_f(input.f() >> shift_amount);
+         input.set_e(input.e() + shift_amount);
+         error = (error >> shift_amount) + 1 + kDenominator;
+         precision_digits_count -= shift_amount;
+      }
+      assert(DiyFp::kSignificandSize == 64);
+      assert(precision_digits_count < 64);
+      uint64_t one64 = 1;
+      uint64_t precision_bits_mask = (one64 << precision_digits_count) - 1;
+      uint64_t precision_bits = input.f() & precision_bits_mask;
+      uint64_t half_way = one64 << (precision_digits_count - 1);
+      precision_bits *= kDenominator;
+      half_way *= kDenominator;
+      DiyFp rounded_input(input.f() >> precision_digits_count,
+                          input.e() + precision_digits_count);
+      if (precision_bits >= half_way + error) {
+         rounded_input.set_f(rounded_input.f() + 1);
+      }
+      *result = Double(rounded_input).value();
+      if (half_way - error < precision_bits && precision_bits < half_way + error) {
+         return false;
+      } else {
+         return true;
+      }
+   }
+
+   inline int CompareBufferWithDiyFp(Vector<const char> buffer,
+                                     int exponent,
+                                     DiyFp diy_fp) {
+      assert(buffer.length() + exponent <= kMaxDecimalPower + 1);
+      assert(buffer.length() + exponent > kMinDecimalPower);
+      assert(buffer.length() <= kMaxSignificantDecimalDigits);
+      assert(((kMaxDecimalPower + 1) * 333 / 100) < Bignum::kMaxSignificantBits);
+      Bignum buffer_bignum;
+      Bignum diy_fp_bignum;
+      buffer_bignum.AssignDecimalString(buffer);
+      diy_fp_bignum.AssignUInt64(diy_fp.f());
+      if (exponent >= 0) {
+         buffer_bignum.MultiplyByPowerOfTen(exponent);
+      } else {
+         diy_fp_bignum.MultiplyByPowerOfTen(-exponent);
+      }
+      if (diy_fp.e() > 0) {
+         diy_fp_bignum.ShiftLeft(diy_fp.e());
+      } else {
+         buffer_bignum.ShiftLeft(-diy_fp.e());
+      }
+      return Bignum::Compare(buffer_bignum, diy_fp_bignum);
+   }
+
+   inline bool ComputeGuess(Vector<const char> trimmed, int exponent,
+                            double* guess) {
+      if (trimmed.length() == 0) {
+         *guess = 0.0;
+         return true;
+      }
+      if (exponent + trimmed.length() - 1 >= kMaxDecimalPower) {
+         *guess = Double::Infinity();
+         return true;
+      }
+      if (exponent + trimmed.length() <= kMinDecimalPower) {
+         *guess = 0.0;
+         return true;
+      }
+
+      if (DoubleStrtod(trimmed, exponent, guess) ||
+          DiyFpStrtod(trimmed, exponent, guess)) {
+         return true;
+      }
+      if (*guess == Double::Infinity()) {
+         return true;
+      }
+      return false;
+   }
+
+   inline double Strtod( Vector< const char > buffer, int exponent )
+   {
+      double guess;
+      if (ComputeGuess(buffer, exponent, &guess)) {
+         return guess;
+      }
+      DiyFp upper_boundary = Double(guess).UpperBoundary();
+      int comparison = CompareBufferWithDiyFp(buffer, exponent, upper_boundary);
+      if (comparison < 0) {
+         return guess;
+      } else if (comparison > 0) {
+         return Double(guess).NextDouble();
+      } else if ((Double(guess).Significand() & 1) == 0) {
+         return guess;
+      } else {
+         return Double(guess).NextDouble();
+      }
+   }
+
+}  // namespace tao::json::double_conversion
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/itoa.hpp b/3rdParty/taocpp-json/include/tao/json/external/itoa.hpp
new file mode 100644
index 000000000000..5e3afde9c128
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/itoa.hpp
@@ -0,0 +1,149 @@
+// This header include/tao/json/external/jeaiii.hpp contains
+// modified portions of the jeaiii/itoa library from
+//   https://github.com/jeaiii/itoa
+// which is licensed as follows:
+
+// Copyright (c) 2017 James Edward Anhalt III - https://github.com/jeaiii/itoa
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+#ifndef TAO_JSON_EXTERNAL_ITOA_HPP
+#define TAO_JSON_EXTERNAL_ITOA_HPP
+
+#include <cstdint>
+#include <ostream>
+
+// form a 4.32 fixed point number: t = u * 2^32 / 10^log10(u)
+// use as much precision as possible when needed (log10(u) >= 5)
+// so shift up then down afterwards by log10(u) * log2(10) ~= 53/16
+// need to round up before and or after in some cases
+// once we have the fixed point number we can read off the digit in the upper 32 bits
+// and multiply the lower 32 bits by 10 to get the next digit and so on
+// we can do 2 digits at a time by multiplying by 100 each time
+
+// MISSING:
+// - x64 optimized version (no need to line up on 32bit boundary, so can multiply by 5 instead of 10 using lea instruction)
+// - full 64 bit LG()
+// - try splitting the number into chucks that can be processed independently
+// - try odd digit first
+// - try writing 4 chars at a time
+
+namespace tao::json::itoa
+{
+   struct pair
+   {
+      char t;
+      char o;
+   };
+
+   // clang-format off
+#define TAO_JSON_ITOA_P( T ) { T, '0' }, { T, '1' }, { T, '2' }, { T, '3' }, { T, '4' }, { T, '5' }, { T, '6' }, { T, '7' }, { T, '8' }, { T, '9' }
+   // clang-format on
+
+   static const pair s_pairs[] = { TAO_JSON_ITOA_P( '0' ),
+                                   TAO_JSON_ITOA_P( '1' ),
+                                   TAO_JSON_ITOA_P( '2' ),
+                                   TAO_JSON_ITOA_P( '3' ),
+                                   TAO_JSON_ITOA_P( '4' ),
+                                   TAO_JSON_ITOA_P( '5' ),
+                                   TAO_JSON_ITOA_P( '6' ),
+                                   TAO_JSON_ITOA_P( '7' ),
+                                   TAO_JSON_ITOA_P( '8' ),
+                                   TAO_JSON_ITOA_P( '9' ) };
+
+#define TAO_JSON_ITOA_W( N, I ) *(pair*)&b[ N ] = s_pairs[ I ]
+#define TAO_JSON_ITOA_A( N ) t = ( std::uint64_t( 1 ) << ( 32 + N / 5 * N * 53 / 16 ) ) / std::uint32_t( 1e##N ) + 1 + N / 6 - N / 8, t *= u, t >>= N / 5 * N * 53 / 16, t += N / 6 * 4, TAO_JSON_ITOA_W( 0, t >> 32 )
+#define TAO_JSON_ITOA_S( N ) b[ N ] = char( std::uint64_t( 10 ) * std::uint32_t( t ) >> 32 ) + '0'
+#define TAO_JSON_ITOA_D( N ) t = std::uint64_t( 100 ) * std::uint32_t( t ), TAO_JSON_ITOA_W( N, t >> 32 )
+
+#define TAO_JSON_ITOA_L0 b[ 0 ] = char( u ) + '0'
+#define TAO_JSON_ITOA_L1 TAO_JSON_ITOA_W( 0, u )
+#define TAO_JSON_ITOA_L2 TAO_JSON_ITOA_A( 1 ), TAO_JSON_ITOA_S( 2 )
+#define TAO_JSON_ITOA_L3 TAO_JSON_ITOA_A( 2 ), TAO_JSON_ITOA_D( 2 )
+#define TAO_JSON_ITOA_L4 TAO_JSON_ITOA_A( 3 ), TAO_JSON_ITOA_D( 2 ), TAO_JSON_ITOA_S( 4 )
+#define TAO_JSON_ITOA_L5 TAO_JSON_ITOA_A( 4 ), TAO_JSON_ITOA_D( 2 ), TAO_JSON_ITOA_D( 4 )
+#define TAO_JSON_ITOA_L6 TAO_JSON_ITOA_A( 5 ), TAO_JSON_ITOA_D( 2 ), TAO_JSON_ITOA_D( 4 ), TAO_JSON_ITOA_S( 6 )
+#define TAO_JSON_ITOA_L7 TAO_JSON_ITOA_A( 6 ), TAO_JSON_ITOA_D( 2 ), TAO_JSON_ITOA_D( 4 ), TAO_JSON_ITOA_D( 6 )
+#define TAO_JSON_ITOA_L8 TAO_JSON_ITOA_A( 7 ), TAO_JSON_ITOA_D( 2 ), TAO_JSON_ITOA_D( 4 ), TAO_JSON_ITOA_D( 6 ), TAO_JSON_ITOA_S( 8 )
+#define TAO_JSON_ITOA_L9 TAO_JSON_ITOA_A( 8 ), TAO_JSON_ITOA_D( 2 ), TAO_JSON_ITOA_D( 4 ), TAO_JSON_ITOA_D( 6 ), TAO_JSON_ITOA_D( 8 )
+
+#define TAO_JSON_ITOA_LN( N ) ( TAO_JSON_ITOA_L##N, b += N + 1 )
+
+#define TAO_JSON_ITOA_LG( F ) ( u < 100 ? u < 10 ? F( 0 ) : F( 1 ) : u < 1000000 ? u < 10000 ? u < 1000 ? F( 2 ) : F( 3 ) : u < 100000 ? F( 4 ) : F( 5 ) : u < 100000000 ? u < 10000000 ? F( 6 ) : F( 7 ) : u < 1000000000 ? F( 8 ) : F( 9 ) )
+
+   inline char* u32toa( const std::uint32_t u, char* b )
+   {
+      std::uint64_t t;
+      return TAO_JSON_ITOA_LG( TAO_JSON_ITOA_LN );
+   }
+
+   inline char* i32toa( const std::int32_t i, char* b )
+   {
+      const std::uint32_t u = i < 0 ? ( *b++ = '-', 0 - std::uint32_t( i ) ) : i;
+      std::uint64_t t;
+      return TAO_JSON_ITOA_LG( TAO_JSON_ITOA_LN );
+   }
+
+   inline char* u64toa( const std::uint64_t n, char* b )
+   {
+      std::uint32_t u;
+      std::uint64_t t;
+
+      if( std::uint32_t( n >> 32 ) == 0 ) {
+         return u = std::uint32_t( n ), TAO_JSON_ITOA_LG( TAO_JSON_ITOA_LN );
+      }
+      std::uint64_t a = n / 100000000;
+
+      if( std::uint32_t( a >> 32 ) == 0 ) {
+         u = std::uint32_t( a );
+         TAO_JSON_ITOA_LG( TAO_JSON_ITOA_LN );
+      }
+      else {
+         u = std::uint32_t( a / 100000000 );
+         TAO_JSON_ITOA_LG( TAO_JSON_ITOA_LN );
+         u = a % 100000000;
+         TAO_JSON_ITOA_LN( 7 );
+      }
+      u = n % 100000000;
+      return TAO_JSON_ITOA_LN( 7 );
+   }
+
+   inline char* i64toa( const std::int64_t i, char* b )
+   {
+      const std::uint64_t n = i < 0 ? ( *b++ = '-', 0 - std::uint64_t( i ) ) : i;
+      return u64toa( n, b );
+   }
+
+   inline void i64tos( std::ostream& o, const std::int64_t i )
+   {
+      char b[ 24 ];
+      const auto* s = i64toa( i, b );
+      o.write( b, s - b );
+   }
+
+   inline void u64tos( std::ostream& o, const std::uint64_t i )
+   {
+      char b[ 24 ];
+      const auto* s = u64toa( i, b );
+      o.write( b, s - b );
+   }
+
+}  // namespace tao::json::itoa
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl.hpp
new file mode 100644
index 000000000000..414dd7fa98ee
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl.hpp
@@ -0,0 +1,53 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_HPP
+#define TAO_JSON_PEGTL_HPP
+
+#include "pegtl/config.hpp"
+#include "pegtl/version.hpp"
+
+#include "pegtl/parse.hpp"
+
+#include "pegtl/ascii.hpp"
+#include "pegtl/rules.hpp"
+#include "pegtl/uint16.hpp"
+#include "pegtl/uint32.hpp"
+#include "pegtl/uint64.hpp"
+#include "pegtl/uint8.hpp"
+#include "pegtl/utf16.hpp"
+#include "pegtl/utf32.hpp"
+#include "pegtl/utf8.hpp"
+
+#include "pegtl/argv_input.hpp"
+#include "pegtl/buffer_input.hpp"
+#include "pegtl/cstream_input.hpp"
+#include "pegtl/istream_input.hpp"
+#include "pegtl/memory_input.hpp"
+#include "pegtl/read_input.hpp"
+#include "pegtl/string_input.hpp"
+
+// this has to be included *after* the above inputs,
+// otherwise the amalgamated header will not work!
+#include "pegtl/file_input.hpp"
+
+#include "pegtl/change_action.hpp"
+#include "pegtl/change_action_and_state.hpp"
+#include "pegtl/change_action_and_states.hpp"
+#include "pegtl/change_control.hpp"
+#include "pegtl/change_state.hpp"
+#include "pegtl/change_states.hpp"
+
+#include "pegtl/disable_action.hpp"
+#include "pegtl/enable_action.hpp"
+
+#include "pegtl/discard_input.hpp"
+#include "pegtl/discard_input_on_failure.hpp"
+#include "pegtl/discard_input_on_success.hpp"
+
+// The following are not included by
+// default because they include <iostream>.
+
+// #include "pegtl/analyze.hpp"
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/analysis/analyze_cycles.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/analysis/analyze_cycles.hpp
new file mode 100644
index 000000000000..4586d5d06784
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/analysis/analyze_cycles.hpp
@@ -0,0 +1,127 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_ANALYSIS_ANALYZE_CYCLES_HPP
+#define TAO_JSON_PEGTL_ANALYSIS_ANALYZE_CYCLES_HPP
+
+#include <cassert>
+
+#include <map>
+#include <set>
+#include <stdexcept>
+#include <string_view>
+
+#include <iostream>
+#include <utility>
+
+#include "../config.hpp"
+
+#include "grammar_info.hpp"
+#include "insert_guard.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::analysis
+{
+   struct analyze_cycles_impl
+   {
+   protected:
+      explicit analyze_cycles_impl( const bool verbose ) noexcept
+         : m_verbose( verbose ),
+           m_problems( 0 )
+      {
+      }
+
+      const bool m_verbose;
+      unsigned m_problems;
+      grammar_info m_info;
+      std::set< std::string_view > m_stack;
+      std::map< std::string_view, bool > m_cache;
+      std::map< std::string_view, bool > m_results;
+
+      [[nodiscard]] std::map< std::string_view, rule_info >::const_iterator find( const std::string_view name ) const noexcept
+      {
+         const auto iter = m_info.map.find( name );
+         assert( iter != m_info.map.end() );
+         return iter;
+      }
+
+      [[nodiscard]] bool work( const std::map< std::string_view, rule_info >::const_iterator& start, const bool accum )
+      {
+         const auto j = m_cache.find( start->first );
+
+         if( j != m_cache.end() ) {
+            return j->second;
+         }
+         if( const auto g = insert_guard( m_stack, start->first ) ) {
+            switch( start->second.type ) {
+               case rule_type::any: {
+                  bool a = false;
+                  for( const auto& r : start->second.rules ) {
+                     a = a || work( find( r ), accum || a );
+                  }
+                  return m_cache[ start->first ] = true;
+               }
+               case rule_type::opt: {
+                  bool a = false;
+                  for( const auto& r : start->second.rules ) {
+                     a = a || work( find( r ), accum || a );
+                  }
+                  return m_cache[ start->first ] = false;
+               }
+               case rule_type::seq: {
+                  bool a = false;
+                  for( const auto& r : start->second.rules ) {
+                     a = a || work( find( r ), accum || a );
+                  }
+                  return m_cache[ start->first ] = a;
+               }
+               case rule_type::sor: {
+                  bool a = true;
+                  for( const auto& r : start->second.rules ) {
+                     a = a && work( find( r ), accum );
+                  }
+                  return m_cache[ start->first ] = a;
+               }
+            }
+            throw std::logic_error( "code should be unreachable: invalid rule_type value" );  // LCOV_EXCL_LINE
+         }
+         if( !accum ) {
+            ++m_problems;
+            if( m_verbose ) {
+               std::cout << "problem: cycle without progress detected at rule class " << start->first << std::endl;  // LCOV_EXCL_LINE
+            }
+         }
+         return m_cache[ start->first ] = accum;
+      }
+   };
+
+   template< typename Grammar >
+   struct analyze_cycles
+      : private analyze_cycles_impl
+   {
+      explicit analyze_cycles( const bool verbose )
+         : analyze_cycles_impl( verbose )
+      {
+         Grammar::analyze_t::template insert< Grammar >( m_info );
+      }
+
+      [[nodiscard]] std::size_t problems()
+      {
+         for( auto i = m_info.map.begin(); i != m_info.map.end(); ++i ) {
+            m_results[ i->first ] = work( i, false );
+            m_cache.clear();
+         }
+         return m_problems;
+      }
+
+      template< typename Rule >
+      [[nodiscard]] bool consumes() const noexcept
+      {
+         const auto i = m_results.find( internal::demangle< Rule >() );
+         assert( i != m_results.end() );
+         return i->second;
+      }
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::analysis
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/analysis/counted.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/analysis/counted.hpp
new file mode 100644
index 000000000000..5e34638bc031
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/analysis/counted.hpp
@@ -0,0 +1,23 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_ANALYSIS_COUNTED_HPP
+#define TAO_JSON_PEGTL_ANALYSIS_COUNTED_HPP
+
+#include "../config.hpp"
+
+#include <cstddef>
+
+#include "generic.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::analysis
+{
+   template< rule_type Type, std::size_t Count, typename... Rules >
+   struct counted
+      : generic< ( Count != 0 ) ? Type : rule_type::opt, Rules... >
+   {
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::analysis
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/analysis/generic.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/analysis/generic.hpp
new file mode 100644
index 000000000000..01cd0142175f
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/analysis/generic.hpp
@@ -0,0 +1,31 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_ANALYSIS_GENERIC_HPP
+#define TAO_JSON_PEGTL_ANALYSIS_GENERIC_HPP
+
+#include "../config.hpp"
+
+#include "grammar_info.hpp"
+#include "insert_rules.hpp"
+#include "rule_type.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::analysis
+{
+   template< rule_type Type, typename... Rules >
+   struct generic
+   {
+      template< typename Name >
+      static std::string_view insert( grammar_info& g )
+      {
+         const auto [ it, success ] = g.insert< Name >( Type );
+         if( success ) {
+            insert_rules< Rules... >::insert( g, it->second );
+         }
+         return it->first;
+      }
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::analysis
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/analysis/grammar_info.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/analysis/grammar_info.hpp
new file mode 100644
index 000000000000..f1ade3a6c2f3
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/analysis/grammar_info.hpp
@@ -0,0 +1,32 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_ANALYSIS_GRAMMAR_INFO_HPP
+#define TAO_JSON_PEGTL_ANALYSIS_GRAMMAR_INFO_HPP
+
+#include <map>
+#include <string>
+#include <utility>
+
+#include "../config.hpp"
+#include "../internal/demangle.hpp"
+
+#include "rule_info.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::analysis
+{
+   struct grammar_info
+   {
+      using map_t = std::map< std::string_view, rule_info >;
+      map_t map;
+
+      template< typename Name >
+      auto insert( const rule_type type )
+      {
+         return map.try_emplace( internal::demangle< Name >(), rule_info( type ) );
+      }
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::analysis
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/analysis/insert_guard.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/analysis/insert_guard.hpp
new file mode 100644
index 000000000000..597d4b8c7aa9
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/analysis/insert_guard.hpp
@@ -0,0 +1,51 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_ANALYSIS_INSERT_GUARD_HPP
+#define TAO_JSON_PEGTL_ANALYSIS_INSERT_GUARD_HPP
+
+#include <utility>
+
+#include "../config.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::analysis
+{
+   template< typename C >
+   class insert_guard
+   {
+   public:
+      insert_guard( C& container, const typename C::value_type& value )
+         : m_i( container.insert( value ) ),
+           m_c( container )
+      {
+      }
+
+      insert_guard( const insert_guard& ) = delete;
+      insert_guard( insert_guard&& ) = delete;
+
+      ~insert_guard()
+      {
+         if( m_i.second ) {
+            m_c.erase( m_i.first );
+         }
+      }
+
+      void operator=( const insert_guard& ) = delete;
+      void operator=( insert_guard&& ) = delete;
+
+      explicit operator bool() const noexcept
+      {
+         return m_i.second;
+      }
+
+   private:
+      const std::pair< typename C::iterator, bool > m_i;
+      C& m_c;
+   };
+
+   template< typename C >
+   insert_guard( C&, const typename C::value_type& )->insert_guard< C >;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::analysis
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/analysis/insert_rules.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/analysis/insert_rules.hpp
new file mode 100644
index 000000000000..9cfb51f0d4a7
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/analysis/insert_rules.hpp
@@ -0,0 +1,25 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_ANALYSIS_INSERT_RULES_HPP
+#define TAO_JSON_PEGTL_ANALYSIS_INSERT_RULES_HPP
+
+#include "../config.hpp"
+
+#include "grammar_info.hpp"
+#include "rule_info.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::analysis
+{
+   template< typename... Rules >
+   struct insert_rules
+   {
+      static void insert( grammar_info& g, rule_info& r )
+      {
+         ( r.rules.emplace_back( Rules::analyze_t::template insert< Rules >( g ) ), ... );
+      }
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::analysis
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/analysis/rule_info.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/analysis/rule_info.hpp
new file mode 100644
index 000000000000..25efeccb363d
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/analysis/rule_info.hpp
@@ -0,0 +1,29 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_ANALYSIS_RULE_INFO_HPP
+#define TAO_JSON_PEGTL_ANALYSIS_RULE_INFO_HPP
+
+#include <string>
+#include <vector>
+
+#include "../config.hpp"
+
+#include "rule_type.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::analysis
+{
+   struct rule_info
+   {
+      explicit rule_info( const rule_type in_type ) noexcept
+         : type( in_type )
+      {
+      }
+
+      rule_type type;
+      std::vector< std::string > rules;
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::analysis
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/analysis/rule_type.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/analysis/rule_type.hpp
new file mode 100644
index 000000000000..f82f22990c11
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/analysis/rule_type.hpp
@@ -0,0 +1,21 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_ANALYSIS_RULE_TYPE_HPP
+#define TAO_JSON_PEGTL_ANALYSIS_RULE_TYPE_HPP
+
+#include "../config.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::analysis
+{
+   enum class rule_type : char
+   {
+      any,  // Consumption-on-success is always true; assumes bounded repetition of conjunction of sub-rules.
+      opt,  // Consumption-on-success not necessarily true; assumes bounded repetition of conjunction of sub-rules.
+      seq,  // Consumption-on-success depends on consumption of (non-zero bounded repetition of) conjunction of sub-rules.
+      sor   // Consumption-on-success depends on consumption of (non-zero bounded repetition of) disjunction of sub-rules.
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::analysis
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/analyze.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/analyze.hpp
new file mode 100644
index 000000000000..4b0ff629ce5e
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/analyze.hpp
@@ -0,0 +1,21 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_ANALYZE_HPP
+#define TAO_JSON_PEGTL_ANALYZE_HPP
+
+#include "config.hpp"
+
+#include "analysis/analyze_cycles.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE
+{
+   template< typename Rule >
+   [[nodiscard]] std::size_t analyze( const bool verbose = true )
+   {
+      return analysis::analyze_cycles< Rule >( verbose ).problems();
+   }
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/apply_mode.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/apply_mode.hpp
new file mode 100644
index 000000000000..b06b029cd6cb
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/apply_mode.hpp
@@ -0,0 +1,19 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_APPLY_MODE_HPP
+#define TAO_JSON_PEGTL_APPLY_MODE_HPP
+
+#include "config.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE
+{
+   enum class apply_mode : bool
+   {
+      action = true,
+      nothing = false
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/argv_input.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/argv_input.hpp
new file mode 100644
index 000000000000..bbb6d008751b
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/argv_input.hpp
@@ -0,0 +1,51 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_ARGV_INPUT_HPP
+#define TAO_JSON_PEGTL_ARGV_INPUT_HPP
+
+#include <cstddef>
+#include <sstream>
+#include <string>
+#include <utility>
+
+#include "config.hpp"
+#include "eol.hpp"
+#include "memory_input.hpp"
+#include "tracking_mode.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE
+{
+   namespace internal
+   {
+      [[nodiscard]] inline std::string make_argv_source( const std::size_t argn )
+      {
+         std::ostringstream os;
+         os << "argv[" << argn << ']';
+         return os.str();
+      }
+
+   }  // namespace internal
+
+   template< tracking_mode P = tracking_mode::eager, typename Eol = eol::lf_crlf >
+   struct argv_input
+      : memory_input< P, Eol >
+   {
+      template< typename T >
+      argv_input( char** argv, const std::size_t argn, T&& in_source )
+         : memory_input< P, Eol >( static_cast< const char* >( argv[ argn ] ), std::forward< T >( in_source ) )
+      {
+      }
+
+      argv_input( char** argv, const std::size_t argn )
+         : argv_input( argv, argn, internal::make_argv_source( argn ) )
+      {
+      }
+   };
+
+   template< typename... Ts >
+   argv_input( Ts&&... )->argv_input<>;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/ascii.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/ascii.hpp
new file mode 100644
index 000000000000..066c2ad5f045
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/ascii.hpp
@@ -0,0 +1,67 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_ASCII_HPP
+#define TAO_JSON_PEGTL_ASCII_HPP
+
+#include "config.hpp"
+#include "eol.hpp"
+
+#include "internal/always_false.hpp"
+#include "internal/result_on_found.hpp"
+#include "internal/rules.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE
+{
+   inline namespace ascii
+   {
+      // clang-format off
+      struct alnum : internal::alnum {};
+      struct alpha : internal::alpha {};
+      struct any : internal::any< internal::peek_char > {};
+      struct blank : internal::one< internal::result_on_found::success, internal::peek_char, ' ', '\t' > {};
+      struct digit : internal::range< internal::result_on_found::success, internal::peek_char, '0', '9' > {};
+      struct ellipsis : internal::string< '.', '.', '.' > {};
+      struct eolf : internal::eolf {};
+      template< char... Cs > struct forty_two : internal::rep< 42, internal::one< internal::result_on_found::success, internal::peek_char, Cs... > > {};
+      struct identifier_first : internal::identifier_first {};
+      struct identifier_other : internal::identifier_other {};
+      struct identifier : internal::identifier {};
+      template< char... Cs > struct istring : internal::istring< Cs... > {};
+      template< char... Cs > struct keyword : internal::seq< internal::string< Cs... >, internal::not_at< internal::identifier_other > > {};
+      struct lower : internal::range< internal::result_on_found::success, internal::peek_char, 'a', 'z' > {};
+      template< char... Cs > struct not_one : internal::one< internal::result_on_found::failure, internal::peek_char, Cs... > {};
+      template< char Lo, char Hi > struct not_range : internal::range< internal::result_on_found::failure, internal::peek_char, Lo, Hi > {};
+      struct nul : internal::one< internal::result_on_found::success, internal::peek_char, char( 0 ) > {};
+      template< char... Cs > struct one : internal::one< internal::result_on_found::success, internal::peek_char, Cs... > {};
+      struct print : internal::range< internal::result_on_found::success, internal::peek_char, char( 32 ), char( 126 ) > {};
+      template< char Lo, char Hi > struct range : internal::range< internal::result_on_found::success, internal::peek_char, Lo, Hi > {};
+      template< char... Cs > struct ranges : internal::ranges< internal::peek_char, Cs... > {};
+      struct seven : internal::range< internal::result_on_found::success, internal::peek_char, char( 0 ), char( 127 ) > {};
+      struct shebang : internal::if_must< false, internal::string< '#', '!' >, internal::until< internal::eolf > > {};
+      struct space : internal::one< internal::result_on_found::success, internal::peek_char, ' ', '\n', '\r', '\t', '\v', '\f' > {};
+      template< char... Cs > struct string : internal::string< Cs... > {};
+      template< char C > struct three : internal::string< C, C, C > {};
+      template< char C > struct two : internal::string< C, C > {};
+      struct upper : internal::range< internal::result_on_found::success, internal::peek_char, 'A', 'Z' > {};
+      struct xdigit : internal::ranges< internal::peek_char, '0', '9', 'a', 'f', 'A', 'F' > {};
+      // clang-format on
+
+      template<>
+      struct keyword<>
+      {
+         template< typename Input >
+         [[nodiscard]] static bool match( Input& /*unused*/ ) noexcept
+         {
+            static_assert( internal::always_false< Input >::value, "empty keywords not allowed" );
+            return false;
+         }
+      };
+
+   }  // namespace ascii
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE
+
+#include "internal/pegtl_string.hpp"
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/buffer_input.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/buffer_input.hpp
new file mode 100644
index 000000000000..2f6ef8c7ec4c
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/buffer_input.hpp
@@ -0,0 +1,212 @@
+// Copyright (c) 2016-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_BUFFER_INPUT_HPP
+#define TAO_JSON_PEGTL_BUFFER_INPUT_HPP
+
+#include <algorithm>
+#include <cassert>
+#include <cstddef>
+#include <cstdint>
+#include <cstring>
+#include <memory>
+#include <stdexcept>
+#include <string>
+
+#include "config.hpp"
+#include "eol.hpp"
+#include "memory_input.hpp"
+#include "position.hpp"
+#include "tracking_mode.hpp"
+
+#include "internal/action_input.hpp"
+#include "internal/bump.hpp"
+#include "internal/iterator.hpp"
+#include "internal/marker.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE
+{
+   template< typename Reader, typename Eol = eol::lf_crlf, typename Source = std::string, std::size_t Chunk = 64 >
+   class buffer_input
+   {
+   public:
+      using reader_t = Reader;
+
+      using eol_t = Eol;
+      using source_t = Source;
+
+      using iterator_t = internal::iterator;
+
+      using action_t = internal::action_input< buffer_input >;
+
+      static constexpr std::size_t chunk_size = Chunk;
+      static constexpr tracking_mode tracking_mode_v = tracking_mode::eager;
+
+      template< typename T, typename... As >
+      buffer_input( T&& in_source, const std::size_t maximum, As&&... as )
+         : m_reader( std::forward< As >( as )... ),
+           m_maximum( maximum + Chunk ),
+           m_buffer( new char[ maximum + Chunk ] ),
+           m_current( m_buffer.get() ),
+           m_end( m_buffer.get() ),
+           m_source( std::forward< T >( in_source ) )
+      {
+         static_assert( Chunk, "zero chunk size not implemented" );
+         assert( m_maximum > maximum );  // Catches overflow; change to >= when zero chunk size is implemented.
+      }
+
+      buffer_input( const buffer_input& ) = delete;
+      buffer_input( buffer_input&& ) = delete;
+
+      ~buffer_input() = default;
+
+      void operator=( const buffer_input& ) = delete;
+      void operator=( buffer_input&& ) = delete;
+
+      [[nodiscard]] bool empty()
+      {
+         require( 1 );
+         return m_current.data == m_end;
+      }
+
+      [[nodiscard]] std::size_t size( const std::size_t amount )
+      {
+         require( amount );
+         return buffer_occupied();
+      }
+
+      [[nodiscard]] const char* current() const noexcept
+      {
+         return m_current.data;
+      }
+
+      [[nodiscard]] const char* end( const std::size_t amount )
+      {
+         require( amount );
+         return m_end;
+      }
+
+      [[nodiscard]] std::size_t byte() const noexcept
+      {
+         return m_current.byte;
+      }
+
+      [[nodiscard]] std::size_t line() const noexcept
+      {
+         return m_current.line;
+      }
+
+      [[nodiscard]] std::size_t byte_in_line() const noexcept
+      {
+         return m_current.byte_in_line;
+      }
+
+      [[nodiscard]] const Source& source() const noexcept
+      {
+         return m_source;
+      }
+
+      [[nodiscard]] char peek_char( const std::size_t offset = 0 ) const noexcept
+      {
+         return m_current.data[ offset ];
+      }
+
+      [[nodiscard]] std::uint8_t peek_uint8( const std::size_t offset = 0 ) const noexcept
+      {
+         return static_cast< std::uint8_t >( peek_char( offset ) );
+      }
+
+      void bump( const std::size_t in_count = 1 ) noexcept
+      {
+         internal::bump( m_current, in_count, Eol::ch );
+      }
+
+      void bump_in_this_line( const std::size_t in_count = 1 ) noexcept
+      {
+         internal::bump_in_this_line( m_current, in_count );
+      }
+
+      void bump_to_next_line( const std::size_t in_count = 1 ) noexcept
+      {
+         internal::bump_to_next_line( m_current, in_count );
+      }
+
+      void discard() noexcept
+      {
+         if( m_current.data > m_buffer.get() + Chunk ) {
+            const auto s = m_end - m_current.data;
+            std::memmove( m_buffer.get(), m_current.data, s );
+            m_current.data = m_buffer.get();
+            m_end = m_buffer.get() + s;
+         }
+      }
+
+      void require( const std::size_t amount )
+      {
+         if( m_current.data + amount <= m_end ) {
+            return;
+         }
+         if( m_current.data + amount > m_buffer.get() + m_maximum ) {
+            throw std::overflow_error( "require beyond end of buffer" );
+         }
+         if( const auto r = m_reader( m_end, ( std::min )( buffer_free_after_end(), ( std::max )( amount, Chunk ) ) ) ) {
+            m_end += r;
+         }
+      }
+
+      template< rewind_mode M >
+      [[nodiscard]] internal::marker< iterator_t, M > mark() noexcept
+      {
+         return internal::marker< iterator_t, M >( m_current );
+      }
+
+      [[nodiscard]] TAO_JSON_PEGTL_NAMESPACE::position position( const iterator_t& it ) const
+      {
+         return TAO_JSON_PEGTL_NAMESPACE::position( it, m_source );
+      }
+
+      [[nodiscard]] TAO_JSON_PEGTL_NAMESPACE::position position() const
+      {
+         return position( m_current );
+      }
+
+      [[nodiscard]] const iterator_t& iterator() const noexcept
+      {
+         return m_current;
+      }
+
+      [[nodiscard]] std::size_t buffer_capacity() const noexcept
+      {
+         return m_maximum;
+      }
+
+      [[nodiscard]] std::size_t buffer_occupied() const noexcept
+      {
+         assert( m_end >= m_current.data );
+         return std::size_t( m_end - m_current.data );
+      }
+
+      [[nodiscard]] std::size_t buffer_free_before_current() const noexcept
+      {
+         assert( m_current.data >= m_buffer.get() );
+         return std::size_t( m_current.data - m_buffer.get() );
+      }
+
+      [[nodiscard]] std::size_t buffer_free_after_end() const noexcept
+      {
+         assert( m_buffer.get() + m_maximum >= m_end );
+         return std::size_t( m_buffer.get() + m_maximum - m_end );
+      }
+
+   private:
+      Reader m_reader;
+      std::size_t m_maximum;
+      std::unique_ptr< char[] > m_buffer;
+      iterator_t m_current;
+      char* m_end;
+      const Source m_source;
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/change_action.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/change_action.hpp
new file mode 100644
index 000000000000..0738c4b466e3
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/change_action.hpp
@@ -0,0 +1,38 @@
+// Copyright (c) 2019-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_CHANGE_ACTION_HPP
+#define TAO_JSON_PEGTL_CHANGE_ACTION_HPP
+
+#include <type_traits>
+
+#include "apply_mode.hpp"
+#include "config.hpp"
+#include "nothing.hpp"
+#include "rewind_mode.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE
+{
+   template< template< typename... > class NewAction >
+   struct change_action
+      : maybe_nothing
+   {
+      template< typename Rule,
+                apply_mode A,
+                rewind_mode M,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class Control,
+                typename Input,
+                typename... States >
+      [[nodiscard]] static bool match( Input& in, States&&... st )
+      {
+         static_assert( !std::is_same_v< Action< void >, NewAction< void > >, "old and new action class templates are identical" );
+         return Control< Rule >::template match< A, M, NewAction, Control >( in, st... );
+      }
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/change_action_and_state.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/change_action_and_state.hpp
new file mode 100644
index 000000000000..edcd03a34699
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/change_action_and_state.hpp
@@ -0,0 +1,53 @@
+// Copyright (c) 2019-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_CHANGE_ACTION_AND_STATE_HPP
+#define TAO_JSON_PEGTL_CHANGE_ACTION_AND_STATE_HPP
+
+#include <type_traits>
+
+#include "apply_mode.hpp"
+#include "config.hpp"
+#include "match.hpp"
+#include "nothing.hpp"
+#include "rewind_mode.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE
+{
+   template< template< typename... > class NewAction, typename NewState >
+   struct change_action_and_state
+      : maybe_nothing
+   {
+      template< typename Rule,
+                apply_mode A,
+                rewind_mode M,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class Control,
+                typename Input,
+                typename... States >
+      [[nodiscard]] static bool match( Input& in, States&&... st )
+      {
+         static_assert( !std::is_same_v< Action< void >, NewAction< void > >, "old and new action class templates are identical" );
+         NewState s( static_cast< const Input& >( in ), st... );
+         if( Control< Rule >::template match< A, M, NewAction, Control >( in, s ) ) {
+            if constexpr( A == apply_mode::action ) {
+               Action< Rule >::success( static_cast< const Input& >( in ), s, st... );
+            }
+            return true;
+         }
+         return false;
+      }
+
+      template< typename Input,
+                typename... States >
+      static void success( const Input& in, NewState& s, States&&... st ) noexcept( noexcept( s.success( in, st... ) ) )
+      {
+         s.success( in, st... );
+      }
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/change_action_and_states.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/change_action_and_states.hpp
new file mode 100644
index 000000000000..e7d5bee2dc5b
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/change_action_and_states.hpp
@@ -0,0 +1,62 @@
+// Copyright (c) 2019-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_CHANGE_ACTION_AND_STATES_HPP
+#define TAO_JSON_PEGTL_CHANGE_ACTION_AND_STATES_HPP
+
+#include <tuple>
+#include <utility>
+
+#include "apply_mode.hpp"
+#include "config.hpp"
+#include "match.hpp"
+#include "nothing.hpp"
+#include "rewind_mode.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE
+{
+   template< template< typename... > class NewAction, typename... NewStates >
+   struct change_action_and_states
+      : maybe_nothing
+   {
+      template< typename Rule,
+                apply_mode A,
+                rewind_mode M,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class Control,
+                std::size_t... Ns,
+                typename Input,
+                typename... States >
+      [[nodiscard]] static bool match( std::index_sequence< Ns... > /*unused*/, Input& in, States&&... st )
+      {
+         auto t = std::tie( st... );
+         if( Control< Rule >::template match< A, M, NewAction, Control >( in, std::get< Ns >( t )... ) ) {
+            if constexpr( A == apply_mode::action ) {
+               Action< Rule >::success( static_cast< const Input& >( in ), st... );
+            }
+            return true;
+         }
+         return false;
+      }
+
+      template< typename Rule,
+                apply_mode A,
+                rewind_mode M,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class Control,
+                typename Input,
+                typename... States >
+      [[nodiscard]] static bool match( Input& in, States&&... st )
+      {
+         static_assert( !std::is_same_v< Action< void >, NewAction< void > >, "old and new action class templates are identical" );
+         return match< Rule, A, M, Action, Control >( std::index_sequence_for< NewStates... >(), in, NewStates()..., st... );
+      }
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/change_control.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/change_control.hpp
new file mode 100644
index 000000000000..eee03415edc2
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/change_control.hpp
@@ -0,0 +1,36 @@
+// Copyright (c) 2019-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_CHANGE_CONTROL_HPP
+#define TAO_JSON_PEGTL_CHANGE_CONTROL_HPP
+
+#include "apply_mode.hpp"
+#include "config.hpp"
+#include "match.hpp"
+#include "nothing.hpp"
+#include "rewind_mode.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE
+{
+   template< template< typename... > class NewControl >
+   struct change_control
+      : maybe_nothing
+   {
+      template< typename Rule,
+                apply_mode A,
+                rewind_mode M,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class Control,
+                typename Input,
+                typename... States >
+      [[nodiscard]] static bool match( Input& in, States&&... st )
+      {
+         return TAO_JSON_PEGTL_NAMESPACE::match< Rule, A, M, Action, NewControl >( in, st... );
+      }
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/change_state.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/change_state.hpp
new file mode 100644
index 000000000000..9f3f9e528742
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/change_state.hpp
@@ -0,0 +1,50 @@
+// Copyright (c) 2019-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_CHANGE_STATE_HPP
+#define TAO_JSON_PEGTL_CHANGE_STATE_HPP
+
+#include "apply_mode.hpp"
+#include "config.hpp"
+#include "match.hpp"
+#include "nothing.hpp"
+#include "rewind_mode.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE
+{
+   template< typename NewState >
+   struct change_state
+      : maybe_nothing
+   {
+      template< typename Rule,
+                apply_mode A,
+                rewind_mode M,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class Control,
+                typename Input,
+                typename... States >
+      [[nodiscard]] static bool match( Input& in, States&&... st )
+      {
+         NewState s( static_cast< const Input& >( in ), st... );
+         if( TAO_JSON_PEGTL_NAMESPACE::match< Rule, A, M, Action, Control >( in, s ) ) {
+            if constexpr( A == apply_mode::action ) {
+               Action< Rule >::success( static_cast< const Input& >( in ), s, st... );
+            }
+            return true;
+         }
+         return false;
+      }
+
+      template< typename Input,
+                typename... States >
+      static void success( const Input& in, NewState& s, States&&... st ) noexcept( noexcept( s.success( in, st... ) ) )
+      {
+         s.success( in, st... );
+      }
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/change_states.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/change_states.hpp
new file mode 100644
index 000000000000..ce246977c014
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/change_states.hpp
@@ -0,0 +1,61 @@
+// Copyright (c) 2019-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_CHANGE_STATES_HPP
+#define TAO_JSON_PEGTL_CHANGE_STATES_HPP
+
+#include <tuple>
+#include <utility>
+
+#include "apply_mode.hpp"
+#include "config.hpp"
+#include "match.hpp"
+#include "nothing.hpp"
+#include "rewind_mode.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE
+{
+   template< typename... NewStates >
+   struct change_states
+      : maybe_nothing
+   {
+      template< typename Rule,
+                apply_mode A,
+                rewind_mode M,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class Control,
+                std::size_t... Ns,
+                typename Input,
+                typename... States >
+      [[nodiscard]] static bool match( std::index_sequence< Ns... > /*unused*/, Input& in, States&&... st )
+      {
+         auto t = std::tie( st... );
+         if( TAO_JSON_PEGTL_NAMESPACE::match< Rule, A, M, Action, Control >( in, std::get< Ns >( t )... ) ) {
+            if constexpr( A == apply_mode::action ) {
+               Action< Rule >::success( static_cast< const Input& >( in ), st... );
+            }
+            return true;
+         }
+         return false;
+      }
+
+      template< typename Rule,
+                apply_mode A,
+                rewind_mode M,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class Control,
+                typename Input,
+                typename... States >
+      [[nodiscard]] static bool match( Input& in, States&&... st )
+      {
+         return match< Rule, A, M, Action, Control >( std::index_sequence_for< NewStates... >(), in, NewStates()..., st... );
+      }
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/config.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/config.hpp
new file mode 100644
index 000000000000..91cd8e104df0
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/config.hpp
@@ -0,0 +1,11 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_CONFIG_HPP
+#define TAO_JSON_PEGTL_CONFIG_HPP
+
+#if !defined( TAO_JSON_PEGTL_NAMESPACE )
+#define TAO_JSON_PEGTL_NAMESPACE tao::json::pegtl
+#endif
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/abnf.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/abnf.hpp
new file mode 100644
index 000000000000..67e7bbe9e151
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/abnf.hpp
@@ -0,0 +1,35 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_CONTRIB_ABNF_HPP
+#define TAO_JSON_PEGTL_CONTRIB_ABNF_HPP
+
+#include "../config.hpp"
+#include "../internal/rules.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::abnf
+{
+   // Core ABNF rules according to RFC 5234, Appendix B
+
+   // clang-format off
+   struct ALPHA : internal::ranges< internal::peek_char, 'a', 'z', 'A', 'Z' > {};
+   struct BIT : internal::one< internal::result_on_found::success, internal::peek_char, '0', '1' > {};
+   struct CHAR : internal::range< internal::result_on_found::success, internal::peek_char, char( 1 ), char( 127 ) > {};
+   struct CR : internal::one< internal::result_on_found::success, internal::peek_char, '\r' > {};
+   struct CRLF : internal::string< '\r', '\n' > {};
+   struct CTL : internal::ranges< internal::peek_char, char( 0 ), char( 31 ), char( 127 ) > {};
+   struct DIGIT : internal::range< internal::result_on_found::success, internal::peek_char, '0', '9' > {};
+   struct DQUOTE : internal::one< internal::result_on_found::success, internal::peek_char, '"' > {};
+   struct HEXDIG : internal::ranges< internal::peek_char, '0', '9', 'a', 'f', 'A', 'F' > {};
+   struct HTAB : internal::one< internal::result_on_found::success, internal::peek_char, '\t' > {};
+   struct LF : internal::one< internal::result_on_found::success, internal::peek_char, '\n' > {};
+   struct LWSP : internal::star< internal::sor< internal::string< '\r', '\n' >, internal::one< internal::result_on_found::success, internal::peek_char, ' ', '\t' > >, internal::one< internal::result_on_found::success, internal::peek_char, ' ', '\t' > > {};
+   struct OCTET : internal::any< internal::peek_char > {};
+   struct SP : internal::one< internal::result_on_found::success, internal::peek_char, ' ' > {};
+   struct VCHAR : internal::range< internal::result_on_found::success, internal::peek_char, char( 33 ), char( 126 ) > {};
+   struct WSP : internal::one< internal::result_on_found::success, internal::peek_char, ' ', '\t' > {};
+   // clang-format on
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::abnf
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/alphabet.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/alphabet.hpp
new file mode 100644
index 000000000000..8a10eed04dc6
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/alphabet.hpp
@@ -0,0 +1,67 @@
+// Copyright (c) 2015-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_CONTRIB_ALPHABET_HPP
+#define TAO_JSON_PEGTL_CONTRIB_ALPHABET_HPP
+
+#include "../config.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::alphabet
+{
+   static const int a = 'a';
+   static const int b = 'b';
+   static const int c = 'c';
+   static const int d = 'd';
+   static const int e = 'e';
+   static const int f = 'f';
+   static const int g = 'g';
+   static const int h = 'h';
+   static const int i = 'i';
+   static const int j = 'j';
+   static const int k = 'k';
+   static const int l = 'l';
+   static const int m = 'm';
+   static const int n = 'n';
+   static const int o = 'o';
+   static const int p = 'p';
+   static const int q = 'q';
+   static const int r = 'r';
+   static const int s = 's';
+   static const int t = 't';
+   static const int u = 'u';
+   static const int v = 'v';
+   static const int w = 'w';
+   static const int x = 'x';
+   static const int y = 'y';
+   static const int z = 'z';
+
+   static const int A = 'A';  // NOLINT(readability-identifier-naming)
+   static const int B = 'B';  // NOLINT(readability-identifier-naming)
+   static const int C = 'C';  // NOLINT(readability-identifier-naming)
+   static const int D = 'D';  // NOLINT(readability-identifier-naming)
+   static const int E = 'E';  // NOLINT(readability-identifier-naming)
+   static const int F = 'F';  // NOLINT(readability-identifier-naming)
+   static const int G = 'G';  // NOLINT(readability-identifier-naming)
+   static const int H = 'H';  // NOLINT(readability-identifier-naming)
+   static const int I = 'I';  // NOLINT(readability-identifier-naming)
+   static const int J = 'J';  // NOLINT(readability-identifier-naming)
+   static const int K = 'K';  // NOLINT(readability-identifier-naming)
+   static const int L = 'L';  // NOLINT(readability-identifier-naming)
+   static const int M = 'M';  // NOLINT(readability-identifier-naming)
+   static const int N = 'N';  // NOLINT(readability-identifier-naming)
+   static const int O = 'O';  // NOLINT(readability-identifier-naming)
+   static const int P = 'P';  // NOLINT(readability-identifier-naming)
+   static const int Q = 'Q';  // NOLINT(readability-identifier-naming)
+   static const int R = 'R';  // NOLINT(readability-identifier-naming)
+   static const int S = 'S';  // NOLINT(readability-identifier-naming)
+   static const int T = 'T';  // NOLINT(readability-identifier-naming)
+   static const int U = 'U';  // NOLINT(readability-identifier-naming)
+   static const int V = 'V';  // NOLINT(readability-identifier-naming)
+   static const int W = 'W';  // NOLINT(readability-identifier-naming)
+   static const int X = 'X';  // NOLINT(readability-identifier-naming)
+   static const int Y = 'Y';  // NOLINT(readability-identifier-naming)
+   static const int Z = 'Z';  // NOLINT(readability-identifier-naming)
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::alphabet
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/counter.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/counter.hpp
new file mode 100644
index 000000000000..98b806565653
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/counter.hpp
@@ -0,0 +1,54 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_CONTRIB_COUNTER_HPP
+#define TAO_JSON_PEGTL_CONTRIB_COUNTER_HPP
+
+#include <map>
+#include <string_view>
+
+#include "../config.hpp"
+#include "../normal.hpp"
+
+#include "../internal/demangle.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE
+{
+   struct counter_data
+   {
+      unsigned start = 0;
+      unsigned success = 0;
+      unsigned failure = 0;
+   };
+
+   struct counter_state
+   {
+      std::map< std::string_view, counter_data > counts;
+   };
+
+   template< typename Rule >
+   struct counter
+      : normal< Rule >
+   {
+      template< typename Input >
+      static void start( const Input& /*unused*/, counter_state& ts )
+      {
+         ++ts.counts[ internal::demangle< Rule >() ].start;
+      }
+
+      template< typename Input >
+      static void success( const Input& /*unused*/, counter_state& ts )
+      {
+         ++ts.counts[ internal::demangle< Rule >() ].success;
+      }
+
+      template< typename Input >
+      static void failure( const Input& /*unused*/, counter_state& ts )
+      {
+         ++ts.counts[ internal::demangle< Rule >() ].failure;
+      }
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/http.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/http.hpp
new file mode 100644
index 000000000000..f9a24e9f2bf0
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/http.hpp
@@ -0,0 +1,253 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_CONTRIB_HTTP_HPP
+#define TAO_JSON_PEGTL_CONTRIB_HTTP_HPP
+
+#include "../ascii.hpp"
+#include "../config.hpp"
+#include "../nothing.hpp"
+#include "../rules.hpp"
+#include "../utf8.hpp"
+
+#include "abnf.hpp"
+#include "remove_first_state.hpp"
+#include "uri.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::http
+{
+   // HTTP 1.1 grammar according to RFC 7230.
+
+   // This grammar is a direct PEG translation of the original HTTP grammar.
+   // It should be considered experimental -- in case of any issues, in particular
+   // missing rules for attached actions, please contact the developers.
+
+   using OWS = star< abnf::WSP >;  // optional whitespace
+   using RWS = plus< abnf::WSP >;  // required whitespace
+   using BWS = OWS;                // "bad" whitespace
+
+   using obs_text = not_range< 0x00, 0x7F >;
+   using obs_fold = seq< abnf::CRLF, plus< abnf::WSP > >;
+
+   // clang-format off
+   struct tchar : sor< abnf::ALPHA, abnf::DIGIT, one< '!', '#', '$', '%', '&', '\'', '*', '+', '-', '.', '^', '_', '`', '|', '~' > > {};
+   struct token : plus< tchar > {};
+
+   struct field_name : token {};
+
+   struct field_vchar : sor< abnf::VCHAR, obs_text > {};
+   struct field_content : list< field_vchar, plus< abnf::WSP > > {};
+   struct field_value : star< sor< field_content, obs_fold > > {};
+
+   struct header_field : seq< field_name, one< ':' >, OWS, field_value, OWS > {};
+
+   struct method : token {};
+
+   struct absolute_path : plus< one< '/' >, uri::segment > {};
+
+   struct origin_form : seq< absolute_path, uri::opt_query >  {};
+   struct absolute_form : uri::absolute_URI {};
+   struct authority_form : uri::authority {};
+   struct asterisk_form : one< '*' > {};
+
+   struct request_target : sor< origin_form, absolute_form, authority_form, asterisk_form > {};
+
+   struct status_code : rep< 3, abnf::DIGIT > {};
+   struct reason_phrase : star< sor< abnf::VCHAR, obs_text, abnf::WSP > > {};
+
+   struct HTTP_version : if_must< string< 'H', 'T', 'T', 'P', '/' >, abnf::DIGIT, one< '.' >, abnf::DIGIT > {};
+
+   struct request_line : if_must< method, abnf::SP, request_target, abnf::SP, HTTP_version, abnf::CRLF > {};
+   struct status_line : if_must< HTTP_version, abnf::SP, status_code, abnf::SP, reason_phrase, abnf::CRLF > {};
+   struct start_line : sor< status_line, request_line > {};
+
+   struct message_body : star< abnf::OCTET > {};
+   struct HTTP_message : seq< start_line, star< header_field, abnf::CRLF >, abnf::CRLF, opt< message_body > > {};
+
+   struct Content_Length : plus< abnf::DIGIT > {};
+
+   struct uri_host : uri::host {};
+   struct port : uri::port {};
+
+   struct Host : seq< uri_host, opt< one< ':' >, port > > {};
+
+   // PEG are different from CFGs! (this replaces ctext and qdtext)
+   using text = sor< abnf::HTAB, range< 0x20, 0x7E >, obs_text >;
+
+   struct quoted_pair : if_must< one< '\\' >, sor< abnf::VCHAR, obs_text, abnf::WSP > > {};
+   struct quoted_string : if_must< abnf::DQUOTE, until< abnf::DQUOTE, sor< quoted_pair, text > > > {};
+
+   struct transfer_parameter : seq< token, BWS, one< '=' >, BWS, sor< token, quoted_string > > {};
+   struct transfer_extension : seq< token, star< OWS, one< ';' >, OWS, transfer_parameter > > {};
+   struct transfer_coding : sor< istring< 'c', 'h', 'u', 'n', 'k', 'e', 'd' >,
+                                 istring< 'c', 'o', 'm', 'p', 'r', 'e', 's', 's' >,
+                                 istring< 'd', 'e', 'f', 'l', 'a', 't', 'e' >,
+                                 istring< 'g', 'z', 'i', 'p' >,
+                                 transfer_extension > {};
+
+   struct rank : sor< seq< one< '0' >, opt< one< '.' >, rep_opt< 3, abnf::DIGIT > > >,
+                      seq< one< '1' >, opt< one< '.' >, rep_opt< 3, one< '0' > > > > > {};
+
+   struct t_ranking : seq< OWS, one< ';' >, OWS, one< 'q', 'Q' >, one< '=' >, rank > {};
+   struct t_codings : sor< istring< 't', 'r', 'a', 'i', 'l', 'e', 'r', 's' >, seq< transfer_coding, opt< t_ranking > > > {};
+
+   struct TE : opt< sor< one< ',' >, t_codings >, star< OWS, one< ',' >, opt< OWS, t_codings > > > {};
+
+   template< typename T >
+   using make_comma_list = seq< star< one< ',' >, OWS >, T, star< OWS, one< ',' >, opt< OWS, T > > >;
+
+   struct connection_option : token {};
+   struct Connection : make_comma_list< connection_option > {};
+
+   struct Trailer : make_comma_list< field_name > {};
+
+   struct Transfer_Encoding : make_comma_list< transfer_coding > {};
+
+   struct protocol_name : token {};
+   struct protocol_version : token {};
+   struct protocol : seq< protocol_name, opt< one< '/' >, protocol_version > > {};
+   struct Upgrade : make_comma_list< protocol > {};
+
+   struct pseudonym : token {};
+
+   struct received_protocol : seq< opt< protocol_name, one< '/' > >, protocol_version > {};
+   struct received_by : sor< seq< uri_host, opt< one< ':' >, port > >, pseudonym > {};
+
+   struct comment : if_must< one< '(' >, until< one< ')' >, sor< comment, quoted_pair, text > > > {};
+
+   struct Via : make_comma_list< seq< received_protocol, RWS, received_by, opt< RWS, comment > > > {};
+
+   struct http_URI : if_must< istring< 'h', 't', 't', 'p', ':', '/', '/' >, uri::authority, uri::path_abempty, uri::opt_query, uri::opt_fragment > {};
+   struct https_URI : if_must< istring< 'h', 't', 't', 'p', 's', ':', '/', '/' >, uri::authority, uri::path_abempty, uri::opt_query, uri::opt_fragment > {};
+
+   struct partial_URI : seq< uri::relative_part, uri::opt_query > {};
+
+   // clang-format on
+   struct chunk_size
+   {
+      using analyze_t = plus< abnf::HEXDIG >::analyze_t;
+
+      template< apply_mode A,
+                rewind_mode M,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class Control,
+                typename Input,
+                typename... States >
+      [[nodiscard]] static bool match( Input& in, std::size_t& size, States&&... /*unused*/ )
+      {
+         size = 0;
+         std::size_t i = 0;
+         while( in.size( i + 1 ) >= i + 1 ) {
+            const auto c = in.peek_char( i );
+            if( ( '0' <= c ) && ( c <= '9' ) ) {
+               size <<= 4;
+               size |= std::size_t( c - '0' );
+               ++i;
+               continue;
+            }
+            if( ( 'a' <= c ) && ( c <= 'f' ) ) {
+               size <<= 4;
+               size |= std::size_t( c - 'a' + 10 );
+               ++i;
+               continue;
+            }
+            if( ( 'A' <= c ) && ( c <= 'F' ) ) {
+               size <<= 4;
+               size |= std::size_t( c - 'A' + 10 );
+               ++i;
+               continue;
+            }
+            break;
+         }
+         in.bump_in_this_line( i );
+         return i > 0;
+      }
+   };
+   // clang-format off
+
+   struct chunk_ext_name : token {};
+   struct chunk_ext_val : sor< quoted_string, token > {};
+   struct chunk_ext : star_must< one< ';' >, chunk_ext_name, if_must< one< '=' >, chunk_ext_val > > {};
+
+   // clang-format on
+   struct chunk_data
+   {
+      using analyze_t = star< abnf::OCTET >::analyze_t;
+
+      template< apply_mode A,
+                rewind_mode M,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class Control,
+                typename Input,
+                typename... States >
+      [[nodiscard]] static bool match( Input& in, const std::size_t size, States&&... /*unused*/ )
+      {
+         if( in.size( size ) >= size ) {
+            in.bump( size );
+            return true;
+         }
+         return false;
+      }
+   };
+
+   namespace internal::chunk_helper
+   {
+      template< typename Rule, template< typename... > class Control >
+      struct control
+         : remove_self_and_first_state< Rule, Control >
+      {};
+
+      template< template< typename... > class Control >
+      struct control< chunk_size, Control >
+         : remove_first_state_after_match< chunk_size, Control >
+      {};
+
+      template< template< typename... > class Control >
+      struct control< chunk_data, Control >
+         : remove_first_state_after_match< chunk_data, Control >
+      {};
+
+      template< template< typename... > class Control >
+      struct bind
+      {
+         template< typename Rule >
+         using type = control< Rule, Control >;
+      };
+
+   }  // namespace internal::chunk_helper
+
+   struct chunk
+   {
+      using impl = seq< chunk_size, chunk_ext, abnf::CRLF, chunk_data, abnf::CRLF >;
+      using analyze_t = impl::analyze_t;
+
+      template< apply_mode A,
+                rewind_mode M,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class Control,
+                typename Input,
+                typename... States >
+      [[nodiscard]] static bool match( Input& in, States&&... st )
+      {
+         std::size_t size{};
+         return impl::template match< A, M, Action, internal::chunk_helper::bind< Control >::template type >( in, size, st... );
+      }
+   };
+
+   // clang-format off
+   struct last_chunk : seq< plus< one< '0' > >, not_at< digit >, chunk_ext, abnf::CRLF > {};
+
+   struct trailer_part : star< header_field, abnf::CRLF > {};
+
+   struct chunked_body : seq< until< last_chunk, chunk >, trailer_part, abnf::CRLF > {};
+   // clang-format on
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::http
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/icu/internal.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/icu/internal.hpp
new file mode 100644
index 000000000000..726b0de6d561
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/icu/internal.hpp
@@ -0,0 +1,68 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_CONTRIB_ICU_INTERNAL_HPP
+#define TAO_JSON_PEGTL_CONTRIB_ICU_INTERNAL_HPP
+
+#include <unicode/uchar.h>
+
+#include "../../config.hpp"
+
+#include "../../analysis/generic.hpp"
+#include "../../internal/skip_control.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   namespace icu
+   {
+      template< typename Peek, UProperty P, bool V = true >
+      struct binary_property
+      {
+         using analyze_t = analysis::generic< analysis::rule_type::any >;
+
+         template< typename Input >
+         [[nodiscard]] static bool match( Input& in ) noexcept( noexcept( in.size( Peek::max_input_size ) ) )
+         {
+            if( const std::size_t s = in.size( Peek::max_input_size ); s >= Peek::min_input_size ) {
+               if( const auto r = Peek::peek( in, s ) ) {
+                  if( u_hasBinaryProperty( r.data, P ) == V ) {
+                     in.bump( r.size );
+                     return true;
+                  }
+               }
+            }
+            return false;
+         }
+      };
+
+      template< typename Peek, UProperty P, int V >
+      struct property_value
+      {
+         using analyze_t = analysis::generic< analysis::rule_type::any >;
+
+         template< typename Input >
+         [[nodiscard]] static bool match( Input& in ) noexcept( noexcept( in.size( Peek::max_input_size ) ) )
+         {
+            if( const std::size_t s = in.size( Peek::max_input_size ); s >= Peek::min_input_size ) {
+               if( const auto r = Peek::peek( in, s ) ) {
+                  if( u_getIntPropertyValue( r.data, P ) == V ) {
+                     in.bump( r.size );
+                     return true;
+                  }
+               }
+            }
+            return false;
+         }
+      };
+
+   }  // namespace icu
+
+   template< typename Peek, UProperty P, bool V >
+   inline constexpr bool skip_control< icu::binary_property< Peek, P, V > > = true;
+
+   template< typename Peek, UProperty P, int V >
+   inline constexpr bool skip_control< icu::property_value< Peek, P, V > > = true;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/icu/utf16.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/icu/utf16.hpp
new file mode 100644
index 000000000000..04af052ecf7b
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/icu/utf16.hpp
@@ -0,0 +1,200 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_CONTRIB_ICU_UTF16_HPP
+#define TAO_JSON_PEGTL_CONTRIB_ICU_UTF16_HPP
+
+#include "internal.hpp"
+
+#include "../../config.hpp"
+#include "../../utf16.hpp"
+
+#include "../../internal/peek_utf16.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE
+{
+   namespace utf16_be::icu
+   {
+      template< UProperty P, bool V = true >
+      struct binary_property
+         : internal::icu::binary_property< internal::peek_utf16_be, P, V >
+      {
+      };
+
+      template< UProperty P, int V >
+      struct property_value
+         : internal::icu::property_value< internal::peek_utf16_be, P, V >
+      {
+      };
+
+      // clang-format off
+      struct alphabetic : binary_property< UCHAR_ALPHABETIC > {};
+      struct ascii_hex_digit : binary_property< UCHAR_ASCII_HEX_DIGIT > {};
+      struct bidi_control : binary_property< UCHAR_BIDI_CONTROL > {};
+      struct bidi_mirrored : binary_property< UCHAR_BIDI_MIRRORED > {};
+      struct case_sensitive : binary_property< UCHAR_CASE_SENSITIVE > {};
+      struct dash : binary_property< UCHAR_DASH > {};
+      struct default_ignorable_code_point : binary_property< UCHAR_DEFAULT_IGNORABLE_CODE_POINT > {};
+      struct deprecated : binary_property< UCHAR_DEPRECATED > {};
+      struct diacritic : binary_property< UCHAR_DIACRITIC > {};
+      struct extender : binary_property< UCHAR_EXTENDER > {};
+      struct full_composition_exclusion : binary_property< UCHAR_FULL_COMPOSITION_EXCLUSION > {};
+      struct grapheme_base : binary_property< UCHAR_GRAPHEME_BASE > {};
+      struct grapheme_extend : binary_property< UCHAR_GRAPHEME_EXTEND > {};
+      struct grapheme_link : binary_property< UCHAR_GRAPHEME_LINK > {};
+      struct hex_digit : binary_property< UCHAR_HEX_DIGIT > {};
+      struct hyphen : binary_property< UCHAR_HYPHEN > {};
+      struct id_continue : binary_property< UCHAR_ID_CONTINUE > {};
+      struct id_start : binary_property< UCHAR_ID_START > {};
+      struct ideographic : binary_property< UCHAR_IDEOGRAPHIC > {};
+      struct ids_binary_operator : binary_property< UCHAR_IDS_BINARY_OPERATOR > {};
+      struct ids_trinary_operator : binary_property< UCHAR_IDS_TRINARY_OPERATOR > {};
+      struct join_control : binary_property< UCHAR_JOIN_CONTROL > {};
+      struct logical_order_exception : binary_property< UCHAR_LOGICAL_ORDER_EXCEPTION > {};
+      struct lowercase : binary_property< UCHAR_LOWERCASE > {};
+      struct math : binary_property< UCHAR_MATH > {};
+      struct nfc_inert : binary_property< UCHAR_NFC_INERT > {};
+      struct nfd_inert : binary_property< UCHAR_NFD_INERT > {};
+      struct nfkc_inert : binary_property< UCHAR_NFKC_INERT > {};
+      struct nfkd_inert : binary_property< UCHAR_NFKD_INERT > {};
+      struct noncharacter_code_point : binary_property< UCHAR_NONCHARACTER_CODE_POINT > {};
+      struct pattern_syntax : binary_property< UCHAR_PATTERN_SYNTAX > {};
+      struct pattern_white_space : binary_property< UCHAR_PATTERN_WHITE_SPACE > {};
+      struct posix_alnum : binary_property< UCHAR_POSIX_ALNUM > {};
+      struct posix_blank : binary_property< UCHAR_POSIX_BLANK > {};
+      struct posix_graph : binary_property< UCHAR_POSIX_GRAPH > {};
+      struct posix_print : binary_property< UCHAR_POSIX_PRINT > {};
+      struct posix_xdigit : binary_property< UCHAR_POSIX_XDIGIT > {};
+      struct quotation_mark : binary_property< UCHAR_QUOTATION_MARK > {};
+      struct radical : binary_property< UCHAR_RADICAL > {};
+      struct s_term : binary_property< UCHAR_S_TERM > {};
+      struct segment_starter : binary_property< UCHAR_SEGMENT_STARTER > {};
+      struct soft_dotted : binary_property< UCHAR_SOFT_DOTTED > {};
+      struct terminal_punctuation : binary_property< UCHAR_TERMINAL_PUNCTUATION > {};
+      struct unified_ideograph : binary_property< UCHAR_UNIFIED_IDEOGRAPH > {};
+      struct uppercase : binary_property< UCHAR_UPPERCASE > {};
+      struct variation_selector : binary_property< UCHAR_VARIATION_SELECTOR > {};
+      struct white_space : binary_property< UCHAR_WHITE_SPACE > {};
+      struct xid_continue : binary_property< UCHAR_XID_CONTINUE > {};
+      struct xid_start : binary_property< UCHAR_XID_START > {};
+
+      template< UCharDirection V > struct bidi_class : property_value< UCHAR_BIDI_CLASS, V > {};
+      template< UBlockCode V > struct block : property_value< UCHAR_BLOCK, V > {};
+      template< UDecompositionType V > struct decomposition_type : property_value< UCHAR_DECOMPOSITION_TYPE, V > {};
+      template< UEastAsianWidth V > struct east_asian_width : property_value< UCHAR_EAST_ASIAN_WIDTH, V > {};
+      template< UCharCategory V > struct general_category : property_value< UCHAR_GENERAL_CATEGORY, V > {};
+      template< UGraphemeClusterBreak V > struct grapheme_cluster_break : property_value< UCHAR_GRAPHEME_CLUSTER_BREAK, V > {};
+      template< UHangulSyllableType V > struct hangul_syllable_type : property_value< UCHAR_HANGUL_SYLLABLE_TYPE, V > {};
+      template< UJoiningGroup V > struct joining_group : property_value< UCHAR_JOINING_GROUP, V > {};
+      template< UJoiningType V > struct joining_type : property_value< UCHAR_JOINING_TYPE, V > {};
+      template< ULineBreak V > struct line_break : property_value< UCHAR_LINE_BREAK, V > {};
+      // UNormalizationCheckResult requires an additional header <unicode/unorm2.h>:
+      // template< UNormalizationCheckResult V > struct nfc_quick_check : property_value< UCHAR_NFC_QUICK_CHECK, V > {};
+      // template< UNormalizationCheckResult V > struct nfd_quick_check : property_value< UCHAR_NFD_QUICK_CHECK, V > {};
+      // template< UNormalizationCheckResult V > struct nfkc_quick_check : property_value< UCHAR_NFKC_QUICK_CHECK, V > {};
+      // template< UNormalizationCheckResult V > struct nfkd_quick_check : property_value< UCHAR_NFKD_QUICK_CHECK, V > {};
+      template< UNumericType V > struct numeric_type : property_value< UCHAR_NUMERIC_TYPE, V > {};
+      template< USentenceBreak V > struct sentence_break : property_value< UCHAR_SENTENCE_BREAK, V > {};
+      template< UWordBreakValues V > struct word_break : property_value< UCHAR_WORD_BREAK, V > {};
+
+      template< std::uint8_t V > struct canonical_combining_class : property_value< UCHAR_CANONICAL_COMBINING_CLASS, V > {};
+      template< std::uint8_t V > struct lead_canonical_combining_class : property_value< UCHAR_LEAD_CANONICAL_COMBINING_CLASS, V > {};
+      template< std::uint8_t V > struct trail_canonical_combining_class : property_value< UCHAR_TRAIL_CANONICAL_COMBINING_CLASS, V > {};
+      // clang-format on
+
+   }  // namespace utf16_be::icu
+
+   namespace utf16_le::icu
+   {
+      template< UProperty P, bool V = true >
+      struct binary_property
+         : internal::icu::binary_property< internal::peek_utf16_le, P, V >
+      {
+      };
+
+      template< UProperty P, int V >
+      struct property_value
+         : internal::icu::property_value< internal::peek_utf16_le, P, V >
+      {
+      };
+
+      // clang-format off
+      struct alphabetic : binary_property< UCHAR_ALPHABETIC > {};
+      struct ascii_hex_digit : binary_property< UCHAR_ASCII_HEX_DIGIT > {};
+      struct bidi_control : binary_property< UCHAR_BIDI_CONTROL > {};
+      struct bidi_mirrored : binary_property< UCHAR_BIDI_MIRRORED > {};
+      struct case_sensitive : binary_property< UCHAR_CASE_SENSITIVE > {};
+      struct dash : binary_property< UCHAR_DASH > {};
+      struct default_ignorable_code_point : binary_property< UCHAR_DEFAULT_IGNORABLE_CODE_POINT > {};
+      struct deprecated : binary_property< UCHAR_DEPRECATED > {};
+      struct diacritic : binary_property< UCHAR_DIACRITIC > {};
+      struct extender : binary_property< UCHAR_EXTENDER > {};
+      struct full_composition_exclusion : binary_property< UCHAR_FULL_COMPOSITION_EXCLUSION > {};
+      struct grapheme_base : binary_property< UCHAR_GRAPHEME_BASE > {};
+      struct grapheme_extend : binary_property< UCHAR_GRAPHEME_EXTEND > {};
+      struct grapheme_link : binary_property< UCHAR_GRAPHEME_LINK > {};
+      struct hex_digit : binary_property< UCHAR_HEX_DIGIT > {};
+      struct hyphen : binary_property< UCHAR_HYPHEN > {};
+      struct id_continue : binary_property< UCHAR_ID_CONTINUE > {};
+      struct id_start : binary_property< UCHAR_ID_START > {};
+      struct ideographic : binary_property< UCHAR_IDEOGRAPHIC > {};
+      struct ids_binary_operator : binary_property< UCHAR_IDS_BINARY_OPERATOR > {};
+      struct ids_trinary_operator : binary_property< UCHAR_IDS_TRINARY_OPERATOR > {};
+      struct join_control : binary_property< UCHAR_JOIN_CONTROL > {};
+      struct logical_order_exception : binary_property< UCHAR_LOGICAL_ORDER_EXCEPTION > {};
+      struct lowercase : binary_property< UCHAR_LOWERCASE > {};
+      struct math : binary_property< UCHAR_MATH > {};
+      struct nfc_inert : binary_property< UCHAR_NFC_INERT > {};
+      struct nfd_inert : binary_property< UCHAR_NFD_INERT > {};
+      struct nfkc_inert : binary_property< UCHAR_NFKC_INERT > {};
+      struct nfkd_inert : binary_property< UCHAR_NFKD_INERT > {};
+      struct noncharacter_code_point : binary_property< UCHAR_NONCHARACTER_CODE_POINT > {};
+      struct pattern_syntax : binary_property< UCHAR_PATTERN_SYNTAX > {};
+      struct pattern_white_space : binary_property< UCHAR_PATTERN_WHITE_SPACE > {};
+      struct posix_alnum : binary_property< UCHAR_POSIX_ALNUM > {};
+      struct posix_blank : binary_property< UCHAR_POSIX_BLANK > {};
+      struct posix_graph : binary_property< UCHAR_POSIX_GRAPH > {};
+      struct posix_print : binary_property< UCHAR_POSIX_PRINT > {};
+      struct posix_xdigit : binary_property< UCHAR_POSIX_XDIGIT > {};
+      struct quotation_mark : binary_property< UCHAR_QUOTATION_MARK > {};
+      struct radical : binary_property< UCHAR_RADICAL > {};
+      struct s_term : binary_property< UCHAR_S_TERM > {};
+      struct segment_starter : binary_property< UCHAR_SEGMENT_STARTER > {};
+      struct soft_dotted : binary_property< UCHAR_SOFT_DOTTED > {};
+      struct terminal_punctuation : binary_property< UCHAR_TERMINAL_PUNCTUATION > {};
+      struct unified_ideograph : binary_property< UCHAR_UNIFIED_IDEOGRAPH > {};
+      struct uppercase : binary_property< UCHAR_UPPERCASE > {};
+      struct variation_selector : binary_property< UCHAR_VARIATION_SELECTOR > {};
+      struct white_space : binary_property< UCHAR_WHITE_SPACE > {};
+      struct xid_continue : binary_property< UCHAR_XID_CONTINUE > {};
+      struct xid_start : binary_property< UCHAR_XID_START > {};
+
+      template< UCharDirection V > struct bidi_class : property_value< UCHAR_BIDI_CLASS, V > {};
+      template< UBlockCode V > struct block : property_value< UCHAR_BLOCK, V > {};
+      template< UDecompositionType V > struct decomposition_type : property_value< UCHAR_DECOMPOSITION_TYPE, V > {};
+      template< UEastAsianWidth V > struct east_asian_width : property_value< UCHAR_EAST_ASIAN_WIDTH, V > {};
+      template< UCharCategory V > struct general_category : property_value< UCHAR_GENERAL_CATEGORY, V > {};
+      template< UGraphemeClusterBreak V > struct grapheme_cluster_break : property_value< UCHAR_GRAPHEME_CLUSTER_BREAK, V > {};
+      template< UHangulSyllableType V > struct hangul_syllable_type : property_value< UCHAR_HANGUL_SYLLABLE_TYPE, V > {};
+      template< UJoiningGroup V > struct joining_group : property_value< UCHAR_JOINING_GROUP, V > {};
+      template< UJoiningType V > struct joining_type : property_value< UCHAR_JOINING_TYPE, V > {};
+      template< ULineBreak V > struct line_break : property_value< UCHAR_LINE_BREAK, V > {};
+      // UNormalizationCheckResult requires an additional header <unicode/unorm2.h>:
+      // template< UNormalizationCheckResult V > struct nfc_quick_check : property_value< UCHAR_NFC_QUICK_CHECK, V > {};
+      // template< UNormalizationCheckResult V > struct nfd_quick_check : property_value< UCHAR_NFD_QUICK_CHECK, V > {};
+      // template< UNormalizationCheckResult V > struct nfkc_quick_check : property_value< UCHAR_NFKC_QUICK_CHECK, V > {};
+      // template< UNormalizationCheckResult V > struct nfkd_quick_check : property_value< UCHAR_NFKD_QUICK_CHECK, V > {};
+      template< UNumericType V > struct numeric_type : property_value< UCHAR_NUMERIC_TYPE, V > {};
+      template< USentenceBreak V > struct sentence_break : property_value< UCHAR_SENTENCE_BREAK, V > {};
+      template< UWordBreakValues V > struct word_break : property_value< UCHAR_WORD_BREAK, V > {};
+
+      template< std::uint8_t V > struct canonical_combining_class : property_value< UCHAR_CANONICAL_COMBINING_CLASS, V > {};
+      template< std::uint8_t V > struct lead_canonical_combining_class : property_value< UCHAR_LEAD_CANONICAL_COMBINING_CLASS, V > {};
+      template< std::uint8_t V > struct trail_canonical_combining_class : property_value< UCHAR_TRAIL_CANONICAL_COMBINING_CLASS, V > {};
+      // clang-format on
+
+   }  // namespace utf16_le::icu
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/icu/utf32.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/icu/utf32.hpp
new file mode 100644
index 000000000000..eebcd130462f
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/icu/utf32.hpp
@@ -0,0 +1,200 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_CONTRIB_ICU_UTF32_HPP
+#define TAO_JSON_PEGTL_CONTRIB_ICU_UTF32_HPP
+
+#include "internal.hpp"
+
+#include "../../config.hpp"
+#include "../../utf32.hpp"
+
+#include "../../internal/peek_utf32.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE
+{
+   namespace utf32_be::icu
+   {
+      template< UProperty P, bool V = true >
+      struct binary_property
+         : internal::icu::binary_property< internal::peek_utf32_be, P, V >
+      {
+      };
+
+      template< UProperty P, int V >
+      struct property_value
+         : internal::icu::property_value< internal::peek_utf32_be, P, V >
+      {
+      };
+
+      // clang-format off
+      struct alphabetic : binary_property< UCHAR_ALPHABETIC > {};
+      struct ascii_hex_digit : binary_property< UCHAR_ASCII_HEX_DIGIT > {};
+      struct bidi_control : binary_property< UCHAR_BIDI_CONTROL > {};
+      struct bidi_mirrored : binary_property< UCHAR_BIDI_MIRRORED > {};
+      struct case_sensitive : binary_property< UCHAR_CASE_SENSITIVE > {};
+      struct dash : binary_property< UCHAR_DASH > {};
+      struct default_ignorable_code_point : binary_property< UCHAR_DEFAULT_IGNORABLE_CODE_POINT > {};
+      struct deprecated : binary_property< UCHAR_DEPRECATED > {};
+      struct diacritic : binary_property< UCHAR_DIACRITIC > {};
+      struct extender : binary_property< UCHAR_EXTENDER > {};
+      struct full_composition_exclusion : binary_property< UCHAR_FULL_COMPOSITION_EXCLUSION > {};
+      struct grapheme_base : binary_property< UCHAR_GRAPHEME_BASE > {};
+      struct grapheme_extend : binary_property< UCHAR_GRAPHEME_EXTEND > {};
+      struct grapheme_link : binary_property< UCHAR_GRAPHEME_LINK > {};
+      struct hex_digit : binary_property< UCHAR_HEX_DIGIT > {};
+      struct hyphen : binary_property< UCHAR_HYPHEN > {};
+      struct id_continue : binary_property< UCHAR_ID_CONTINUE > {};
+      struct id_start : binary_property< UCHAR_ID_START > {};
+      struct ideographic : binary_property< UCHAR_IDEOGRAPHIC > {};
+      struct ids_binary_operator : binary_property< UCHAR_IDS_BINARY_OPERATOR > {};
+      struct ids_trinary_operator : binary_property< UCHAR_IDS_TRINARY_OPERATOR > {};
+      struct join_control : binary_property< UCHAR_JOIN_CONTROL > {};
+      struct logical_order_exception : binary_property< UCHAR_LOGICAL_ORDER_EXCEPTION > {};
+      struct lowercase : binary_property< UCHAR_LOWERCASE > {};
+      struct math : binary_property< UCHAR_MATH > {};
+      struct nfc_inert : binary_property< UCHAR_NFC_INERT > {};
+      struct nfd_inert : binary_property< UCHAR_NFD_INERT > {};
+      struct nfkc_inert : binary_property< UCHAR_NFKC_INERT > {};
+      struct nfkd_inert : binary_property< UCHAR_NFKD_INERT > {};
+      struct noncharacter_code_point : binary_property< UCHAR_NONCHARACTER_CODE_POINT > {};
+      struct pattern_syntax : binary_property< UCHAR_PATTERN_SYNTAX > {};
+      struct pattern_white_space : binary_property< UCHAR_PATTERN_WHITE_SPACE > {};
+      struct posix_alnum : binary_property< UCHAR_POSIX_ALNUM > {};
+      struct posix_blank : binary_property< UCHAR_POSIX_BLANK > {};
+      struct posix_graph : binary_property< UCHAR_POSIX_GRAPH > {};
+      struct posix_print : binary_property< UCHAR_POSIX_PRINT > {};
+      struct posix_xdigit : binary_property< UCHAR_POSIX_XDIGIT > {};
+      struct quotation_mark : binary_property< UCHAR_QUOTATION_MARK > {};
+      struct radical : binary_property< UCHAR_RADICAL > {};
+      struct s_term : binary_property< UCHAR_S_TERM > {};
+      struct segment_starter : binary_property< UCHAR_SEGMENT_STARTER > {};
+      struct soft_dotted : binary_property< UCHAR_SOFT_DOTTED > {};
+      struct terminal_punctuation : binary_property< UCHAR_TERMINAL_PUNCTUATION > {};
+      struct unified_ideograph : binary_property< UCHAR_UNIFIED_IDEOGRAPH > {};
+      struct uppercase : binary_property< UCHAR_UPPERCASE > {};
+      struct variation_selector : binary_property< UCHAR_VARIATION_SELECTOR > {};
+      struct white_space : binary_property< UCHAR_WHITE_SPACE > {};
+      struct xid_continue : binary_property< UCHAR_XID_CONTINUE > {};
+      struct xid_start : binary_property< UCHAR_XID_START > {};
+
+      template< UCharDirection V > struct bidi_class : property_value< UCHAR_BIDI_CLASS, V > {};
+      template< UBlockCode V > struct block : property_value< UCHAR_BLOCK, V > {};
+      template< UDecompositionType V > struct decomposition_type : property_value< UCHAR_DECOMPOSITION_TYPE, V > {};
+      template< UEastAsianWidth V > struct east_asian_width : property_value< UCHAR_EAST_ASIAN_WIDTH, V > {};
+      template< UCharCategory V > struct general_category : property_value< UCHAR_GENERAL_CATEGORY, V > {};
+      template< UGraphemeClusterBreak V > struct grapheme_cluster_break : property_value< UCHAR_GRAPHEME_CLUSTER_BREAK, V > {};
+      template< UHangulSyllableType V > struct hangul_syllable_type : property_value< UCHAR_HANGUL_SYLLABLE_TYPE, V > {};
+      template< UJoiningGroup V > struct joining_group : property_value< UCHAR_JOINING_GROUP, V > {};
+      template< UJoiningType V > struct joining_type : property_value< UCHAR_JOINING_TYPE, V > {};
+      template< ULineBreak V > struct line_break : property_value< UCHAR_LINE_BREAK, V > {};
+      // UNormalizationCheckResult requires an additional header <unicode/unorm2.h>:
+      // template< UNormalizationCheckResult V > struct nfc_quick_check : property_value< UCHAR_NFC_QUICK_CHECK, V > {};
+      // template< UNormalizationCheckResult V > struct nfd_quick_check : property_value< UCHAR_NFD_QUICK_CHECK, V > {};
+      // template< UNormalizationCheckResult V > struct nfkc_quick_check : property_value< UCHAR_NFKC_QUICK_CHECK, V > {};
+      // template< UNormalizationCheckResult V > struct nfkd_quick_check : property_value< UCHAR_NFKD_QUICK_CHECK, V > {};
+      template< UNumericType V > struct numeric_type : property_value< UCHAR_NUMERIC_TYPE, V > {};
+      template< USentenceBreak V > struct sentence_break : property_value< UCHAR_SENTENCE_BREAK, V > {};
+      template< UWordBreakValues V > struct word_break : property_value< UCHAR_WORD_BREAK, V > {};
+
+      template< std::uint8_t V > struct canonical_combining_class : property_value< UCHAR_CANONICAL_COMBINING_CLASS, V > {};
+      template< std::uint8_t V > struct lead_canonical_combining_class : property_value< UCHAR_LEAD_CANONICAL_COMBINING_CLASS, V > {};
+      template< std::uint8_t V > struct trail_canonical_combining_class : property_value< UCHAR_TRAIL_CANONICAL_COMBINING_CLASS, V > {};
+      // clang-format on
+
+   }  // namespace utf32_be::icu
+
+   namespace utf32_le::icu
+   {
+      template< UProperty P, bool V = true >
+      struct binary_property
+         : internal::icu::binary_property< internal::peek_utf32_le, P, V >
+      {
+      };
+
+      template< UProperty P, int V >
+      struct property_value
+         : internal::icu::property_value< internal::peek_utf32_le, P, V >
+      {
+      };
+
+      // clang-format off
+      struct alphabetic : binary_property< UCHAR_ALPHABETIC > {};
+      struct ascii_hex_digit : binary_property< UCHAR_ASCII_HEX_DIGIT > {};
+      struct bidi_control : binary_property< UCHAR_BIDI_CONTROL > {};
+      struct bidi_mirrored : binary_property< UCHAR_BIDI_MIRRORED > {};
+      struct case_sensitive : binary_property< UCHAR_CASE_SENSITIVE > {};
+      struct dash : binary_property< UCHAR_DASH > {};
+      struct default_ignorable_code_point : binary_property< UCHAR_DEFAULT_IGNORABLE_CODE_POINT > {};
+      struct deprecated : binary_property< UCHAR_DEPRECATED > {};
+      struct diacritic : binary_property< UCHAR_DIACRITIC > {};
+      struct extender : binary_property< UCHAR_EXTENDER > {};
+      struct full_composition_exclusion : binary_property< UCHAR_FULL_COMPOSITION_EXCLUSION > {};
+      struct grapheme_base : binary_property< UCHAR_GRAPHEME_BASE > {};
+      struct grapheme_extend : binary_property< UCHAR_GRAPHEME_EXTEND > {};
+      struct grapheme_link : binary_property< UCHAR_GRAPHEME_LINK > {};
+      struct hex_digit : binary_property< UCHAR_HEX_DIGIT > {};
+      struct hyphen : binary_property< UCHAR_HYPHEN > {};
+      struct id_continue : binary_property< UCHAR_ID_CONTINUE > {};
+      struct id_start : binary_property< UCHAR_ID_START > {};
+      struct ideographic : binary_property< UCHAR_IDEOGRAPHIC > {};
+      struct ids_binary_operator : binary_property< UCHAR_IDS_BINARY_OPERATOR > {};
+      struct ids_trinary_operator : binary_property< UCHAR_IDS_TRINARY_OPERATOR > {};
+      struct join_control : binary_property< UCHAR_JOIN_CONTROL > {};
+      struct logical_order_exception : binary_property< UCHAR_LOGICAL_ORDER_EXCEPTION > {};
+      struct lowercase : binary_property< UCHAR_LOWERCASE > {};
+      struct math : binary_property< UCHAR_MATH > {};
+      struct nfc_inert : binary_property< UCHAR_NFC_INERT > {};
+      struct nfd_inert : binary_property< UCHAR_NFD_INERT > {};
+      struct nfkc_inert : binary_property< UCHAR_NFKC_INERT > {};
+      struct nfkd_inert : binary_property< UCHAR_NFKD_INERT > {};
+      struct noncharacter_code_point : binary_property< UCHAR_NONCHARACTER_CODE_POINT > {};
+      struct pattern_syntax : binary_property< UCHAR_PATTERN_SYNTAX > {};
+      struct pattern_white_space : binary_property< UCHAR_PATTERN_WHITE_SPACE > {};
+      struct posix_alnum : binary_property< UCHAR_POSIX_ALNUM > {};
+      struct posix_blank : binary_property< UCHAR_POSIX_BLANK > {};
+      struct posix_graph : binary_property< UCHAR_POSIX_GRAPH > {};
+      struct posix_print : binary_property< UCHAR_POSIX_PRINT > {};
+      struct posix_xdigit : binary_property< UCHAR_POSIX_XDIGIT > {};
+      struct quotation_mark : binary_property< UCHAR_QUOTATION_MARK > {};
+      struct radical : binary_property< UCHAR_RADICAL > {};
+      struct s_term : binary_property< UCHAR_S_TERM > {};
+      struct segment_starter : binary_property< UCHAR_SEGMENT_STARTER > {};
+      struct soft_dotted : binary_property< UCHAR_SOFT_DOTTED > {};
+      struct terminal_punctuation : binary_property< UCHAR_TERMINAL_PUNCTUATION > {};
+      struct unified_ideograph : binary_property< UCHAR_UNIFIED_IDEOGRAPH > {};
+      struct uppercase : binary_property< UCHAR_UPPERCASE > {};
+      struct variation_selector : binary_property< UCHAR_VARIATION_SELECTOR > {};
+      struct white_space : binary_property< UCHAR_WHITE_SPACE > {};
+      struct xid_continue : binary_property< UCHAR_XID_CONTINUE > {};
+      struct xid_start : binary_property< UCHAR_XID_START > {};
+
+      template< UCharDirection V > struct bidi_class : property_value< UCHAR_BIDI_CLASS, V > {};
+      template< UBlockCode V > struct block : property_value< UCHAR_BLOCK, V > {};
+      template< UDecompositionType V > struct decomposition_type : property_value< UCHAR_DECOMPOSITION_TYPE, V > {};
+      template< UEastAsianWidth V > struct east_asian_width : property_value< UCHAR_EAST_ASIAN_WIDTH, V > {};
+      template< UCharCategory V > struct general_category : property_value< UCHAR_GENERAL_CATEGORY, V > {};
+      template< UGraphemeClusterBreak V > struct grapheme_cluster_break : property_value< UCHAR_GRAPHEME_CLUSTER_BREAK, V > {};
+      template< UHangulSyllableType V > struct hangul_syllable_type : property_value< UCHAR_HANGUL_SYLLABLE_TYPE, V > {};
+      template< UJoiningGroup V > struct joining_group : property_value< UCHAR_JOINING_GROUP, V > {};
+      template< UJoiningType V > struct joining_type : property_value< UCHAR_JOINING_TYPE, V > {};
+      template< ULineBreak V > struct line_break : property_value< UCHAR_LINE_BREAK, V > {};
+      // UNormalizationCheckResult requires an additional header <unicode/unorm2.h>:
+      // template< UNormalizationCheckResult V > struct nfc_quick_check : property_value< UCHAR_NFC_QUICK_CHECK, V > {};
+      // template< UNormalizationCheckResult V > struct nfd_quick_check : property_value< UCHAR_NFD_QUICK_CHECK, V > {};
+      // template< UNormalizationCheckResult V > struct nfkc_quick_check : property_value< UCHAR_NFKC_QUICK_CHECK, V > {};
+      // template< UNormalizationCheckResult V > struct nfkd_quick_check : property_value< UCHAR_NFKD_QUICK_CHECK, V > {};
+      template< UNumericType V > struct numeric_type : property_value< UCHAR_NUMERIC_TYPE, V > {};
+      template< USentenceBreak V > struct sentence_break : property_value< UCHAR_SENTENCE_BREAK, V > {};
+      template< UWordBreakValues V > struct word_break : property_value< UCHAR_WORD_BREAK, V > {};
+
+      template< std::uint8_t V > struct canonical_combining_class : property_value< UCHAR_CANONICAL_COMBINING_CLASS, V > {};
+      template< std::uint8_t V > struct lead_canonical_combining_class : property_value< UCHAR_LEAD_CANONICAL_COMBINING_CLASS, V > {};
+      template< std::uint8_t V > struct trail_canonical_combining_class : property_value< UCHAR_TRAIL_CANONICAL_COMBINING_CLASS, V > {};
+      // clang-format on
+
+   }  // namespace utf32_le::icu
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/icu/utf8.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/icu/utf8.hpp
new file mode 100644
index 000000000000..a47a2d2ac58b
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/icu/utf8.hpp
@@ -0,0 +1,105 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_CONTRIB_ICU_UTF8_HPP
+#define TAO_JSON_PEGTL_CONTRIB_ICU_UTF8_HPP
+
+#include "internal.hpp"
+
+#include "../../config.hpp"
+#include "../../utf8.hpp"
+
+#include "../../internal/peek_utf8.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::utf8::icu
+{
+   template< UProperty P, bool V = true >
+   struct binary_property
+      : internal::icu::binary_property< internal::peek_utf8, P, V >
+   {
+   };
+
+   template< UProperty P, int V >
+   struct property_value
+      : internal::icu::property_value< internal::peek_utf8, P, V >
+   {
+   };
+
+   // clang-format off
+   struct alphabetic : binary_property< UCHAR_ALPHABETIC > {};
+   struct ascii_hex_digit : binary_property< UCHAR_ASCII_HEX_DIGIT > {};
+   struct bidi_control : binary_property< UCHAR_BIDI_CONTROL > {};
+   struct bidi_mirrored : binary_property< UCHAR_BIDI_MIRRORED > {};
+   struct case_sensitive : binary_property< UCHAR_CASE_SENSITIVE > {};
+   struct dash : binary_property< UCHAR_DASH > {};
+   struct default_ignorable_code_point : binary_property< UCHAR_DEFAULT_IGNORABLE_CODE_POINT > {};
+   struct deprecated : binary_property< UCHAR_DEPRECATED > {};
+   struct diacritic : binary_property< UCHAR_DIACRITIC > {};
+   struct extender : binary_property< UCHAR_EXTENDER > {};
+   struct full_composition_exclusion : binary_property< UCHAR_FULL_COMPOSITION_EXCLUSION > {};
+   struct grapheme_base : binary_property< UCHAR_GRAPHEME_BASE > {};
+   struct grapheme_extend : binary_property< UCHAR_GRAPHEME_EXTEND > {};
+   struct grapheme_link : binary_property< UCHAR_GRAPHEME_LINK > {};
+   struct hex_digit : binary_property< UCHAR_HEX_DIGIT > {};
+   struct hyphen : binary_property< UCHAR_HYPHEN > {};
+   struct id_continue : binary_property< UCHAR_ID_CONTINUE > {};
+   struct id_start : binary_property< UCHAR_ID_START > {};
+   struct ideographic : binary_property< UCHAR_IDEOGRAPHIC > {};
+   struct ids_binary_operator : binary_property< UCHAR_IDS_BINARY_OPERATOR > {};
+   struct ids_trinary_operator : binary_property< UCHAR_IDS_TRINARY_OPERATOR > {};
+   struct join_control : binary_property< UCHAR_JOIN_CONTROL > {};
+   struct logical_order_exception : binary_property< UCHAR_LOGICAL_ORDER_EXCEPTION > {};
+   struct lowercase : binary_property< UCHAR_LOWERCASE > {};
+   struct math : binary_property< UCHAR_MATH > {};
+   struct nfc_inert : binary_property< UCHAR_NFC_INERT > {};
+   struct nfd_inert : binary_property< UCHAR_NFD_INERT > {};
+   struct nfkc_inert : binary_property< UCHAR_NFKC_INERT > {};
+   struct nfkd_inert : binary_property< UCHAR_NFKD_INERT > {};
+   struct noncharacter_code_point : binary_property< UCHAR_NONCHARACTER_CODE_POINT > {};
+   struct pattern_syntax : binary_property< UCHAR_PATTERN_SYNTAX > {};
+   struct pattern_white_space : binary_property< UCHAR_PATTERN_WHITE_SPACE > {};
+   struct posix_alnum : binary_property< UCHAR_POSIX_ALNUM > {};
+   struct posix_blank : binary_property< UCHAR_POSIX_BLANK > {};
+   struct posix_graph : binary_property< UCHAR_POSIX_GRAPH > {};
+   struct posix_print : binary_property< UCHAR_POSIX_PRINT > {};
+   struct posix_xdigit : binary_property< UCHAR_POSIX_XDIGIT > {};
+   struct quotation_mark : binary_property< UCHAR_QUOTATION_MARK > {};
+   struct radical : binary_property< UCHAR_RADICAL > {};
+   struct s_term : binary_property< UCHAR_S_TERM > {};
+   struct segment_starter : binary_property< UCHAR_SEGMENT_STARTER > {};
+   struct soft_dotted : binary_property< UCHAR_SOFT_DOTTED > {};
+   struct terminal_punctuation : binary_property< UCHAR_TERMINAL_PUNCTUATION > {};
+   struct unified_ideograph : binary_property< UCHAR_UNIFIED_IDEOGRAPH > {};
+   struct uppercase : binary_property< UCHAR_UPPERCASE > {};
+   struct variation_selector : binary_property< UCHAR_VARIATION_SELECTOR > {};
+   struct white_space : binary_property< UCHAR_WHITE_SPACE > {};
+   struct xid_continue : binary_property< UCHAR_XID_CONTINUE > {};
+   struct xid_start : binary_property< UCHAR_XID_START > {};
+
+   template< UCharDirection V > struct bidi_class : property_value< UCHAR_BIDI_CLASS, V > {};
+   template< UBlockCode V > struct block : property_value< UCHAR_BLOCK, V > {};
+   template< UDecompositionType V > struct decomposition_type : property_value< UCHAR_DECOMPOSITION_TYPE, V > {};
+   template< UEastAsianWidth V > struct east_asian_width : property_value< UCHAR_EAST_ASIAN_WIDTH, V > {};
+   template< UCharCategory V > struct general_category : property_value< UCHAR_GENERAL_CATEGORY, V > {};
+   template< UGraphemeClusterBreak V > struct grapheme_cluster_break : property_value< UCHAR_GRAPHEME_CLUSTER_BREAK, V > {};
+   template< UHangulSyllableType V > struct hangul_syllable_type : property_value< UCHAR_HANGUL_SYLLABLE_TYPE, V > {};
+   template< UJoiningGroup V > struct joining_group : property_value< UCHAR_JOINING_GROUP, V > {};
+   template< UJoiningType V > struct joining_type : property_value< UCHAR_JOINING_TYPE, V > {};
+   template< ULineBreak V > struct line_break : property_value< UCHAR_LINE_BREAK, V > {};
+   // UNormalizationCheckResult requires an additional header <unicode/unorm2.h>:
+   // template< UNormalizationCheckResult V > struct nfc_quick_check : property_value< UCHAR_NFC_QUICK_CHECK, V > {};
+   // template< UNormalizationCheckResult V > struct nfd_quick_check : property_value< UCHAR_NFD_QUICK_CHECK, V > {};
+   // template< UNormalizationCheckResult V > struct nfkc_quick_check : property_value< UCHAR_NFKC_QUICK_CHECK, V > {};
+   // template< UNormalizationCheckResult V > struct nfkd_quick_check : property_value< UCHAR_NFKD_QUICK_CHECK, V > {};
+   template< UNumericType V > struct numeric_type : property_value< UCHAR_NUMERIC_TYPE, V > {};
+   template< USentenceBreak V > struct sentence_break : property_value< UCHAR_SENTENCE_BREAK, V > {};
+   template< UWordBreakValues V > struct word_break : property_value< UCHAR_WORD_BREAK, V > {};
+
+   template< std::uint8_t V > struct canonical_combining_class : property_value< UCHAR_CANONICAL_COMBINING_CLASS, V > {};
+   template< std::uint8_t V > struct lead_canonical_combining_class : property_value< UCHAR_LEAD_CANONICAL_COMBINING_CLASS, V > {};
+   template< std::uint8_t V > struct trail_canonical_combining_class : property_value< UCHAR_TRAIL_CANONICAL_COMBINING_CLASS, V > {};
+   // clang-format on
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::utf8::icu
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/if_then.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/if_then.hpp
new file mode 100644
index 000000000000..850790317d4e
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/if_then.hpp
@@ -0,0 +1,55 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_CONTRIB_IF_THEN_HPP
+#define TAO_JSON_PEGTL_CONTRIB_IF_THEN_HPP
+
+#include <type_traits>
+
+#include "../config.hpp"
+
+#include "../internal/if_then_else.hpp"
+#include "../internal/seq.hpp"
+#include "../internal/skip_control.hpp"
+#include "../internal/trivial.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE
+{
+   namespace internal
+   {
+      template< typename Cond, typename Then >
+      struct if_pair
+      {
+      };
+
+      template< typename... Pairs >
+      struct if_then;
+
+      template< typename Cond, typename Then, typename... Pairs >
+      struct if_then< if_pair< Cond, Then >, Pairs... >
+         : if_then_else< Cond, Then, if_then< Pairs... > >
+      {
+         template< typename ElseCond, typename... Thens >
+         using else_if_then = if_then< if_pair< Cond, Then >, Pairs..., if_pair< ElseCond, seq< Thens... > > >;
+
+         template< typename... Thens >
+         using else_then = if_then_else< Cond, Then, if_then< Pairs..., if_pair< trivial< true >, seq< Thens... > > > >;
+      };
+
+      template<>
+      struct if_then<>
+         : trivial< false >
+      {
+      };
+
+      template< typename... Pairs >
+      inline constexpr bool skip_control< if_then< Pairs... > > = true;
+
+   }  // namespace internal
+
+   template< typename Cond, typename... Thens >
+   using if_then = internal::if_then< internal::if_pair< Cond, internal::seq< Thens... > > >;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/integer.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/integer.hpp
new file mode 100644
index 000000000000..332168a267a0
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/integer.hpp
@@ -0,0 +1,446 @@
+// Copyright (c) 2019-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_CONTRIB_INTEGER_HPP
+#define TAO_JSON_PEGTL_CONTRIB_INTEGER_HPP
+
+#include <cstdint>
+#include <cstdlib>
+
+#include <type_traits>
+
+#include "../ascii.hpp"
+#include "../parse.hpp"
+#include "../parse_error.hpp"
+#include "../rules.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::integer
+{
+   namespace internal
+   {
+      struct unsigned_rule_old
+         : plus< digit >
+      {
+         // Pre-3.0 version of this rule.
+      };
+
+      struct unsigned_rule_new
+         : if_then_else< one< '0' >, not_at< digit >, plus< digit > >
+      {
+         // New version that does not allow leading zeros.
+      };
+
+      struct signed_rule_old
+         : seq< opt< one< '-', '+' > >, plus< digit > >
+      {
+         // Pre-3.0 version of this rule.
+      };
+
+      struct signed_rule_new
+         : seq< opt< one< '-', '+' > >, if_then_else< one< '0' >, not_at< digit >, plus< digit > > >
+      {
+         // New version that does not allow leading zeros.
+      };
+
+      struct signed_rule_bis
+         : seq< opt< one< '-' > >, if_then_else< one< '0' >, not_at< digit >, plus< digit > > >
+      {
+      };
+
+      struct signed_rule_ter
+         : seq< one< '-', '+' >, if_then_else< one< '0' >, not_at< digit >, plus< digit > > >
+      {
+      };
+
+      [[nodiscard]] constexpr bool is_digit( const char c ) noexcept
+      {
+         // We don't use std::isdigit() because it might
+         // return true for other values on MS platforms.
+
+         return ( '0' <= c ) && ( c <= '9' );
+      }
+
+      template< typename Integer, Integer Maximum = ( std::numeric_limits< Integer >::max )() >
+      [[nodiscard]] constexpr bool accumulate_digit( Integer& result, const char digit ) noexcept
+      {
+         // Assumes that digit is a digit as per is_digit(); returns false on overflow.
+
+         static_assert( std::is_integral_v< Integer > );
+
+         constexpr Integer cutoff = Maximum / 10;
+         constexpr Integer cutlim = Maximum % 10;
+
+         const Integer c = digit - '0';
+
+         if( ( result > cutoff ) || ( ( result == cutoff ) && ( c > cutlim ) ) ) {
+            return false;
+         }
+         result *= 10;
+         result += c;
+         return true;
+      }
+
+      template< typename Integer, Integer Maximum = ( std::numeric_limits< Integer >::max )() >
+      [[nodiscard]] constexpr bool accumulate_digits( Integer& result, const std::string_view input ) noexcept
+      {
+         // Assumes input is a non-empty sequence of digits; returns false on overflow.
+
+         for( char c : input ) {
+            if( !accumulate_digit< Integer, Maximum >( result, c ) ) {
+               return false;
+            }
+         }
+         return true;
+      }
+
+      template< typename Integer, Integer Maximum = ( std::numeric_limits< Integer >::max )() >
+      [[nodiscard]] constexpr bool convert_positive( Integer& result, const std::string_view input ) noexcept
+      {
+         // Assumes result == 0 and that input is a non-empty sequence of digits; returns false on overflow.
+
+         static_assert( std::is_integral_v< Integer > );
+         return accumulate_digits< Integer, Maximum >( result, input );
+      }
+
+      template< typename Signed >
+      [[nodiscard]] constexpr bool convert_negative( Signed& result, const std::string_view input ) noexcept
+      {
+         // Assumes result == 0 and that input is a non-empty sequence of digits; returns false on overflow.
+
+         static_assert( std::is_signed_v< Signed > );
+         using Unsigned = std::make_unsigned_t< Signed >;
+         constexpr Unsigned maximum = static_cast< Unsigned >( ( std::numeric_limits< Signed >::max )() ) + 1;
+         Unsigned temporary = 0;
+         if( accumulate_digits< Unsigned, maximum >( temporary, input ) ) {
+            result = static_cast< Signed >( ~temporary ) + 1;
+            return true;
+         }
+         return false;
+      }
+
+      template< typename Unsigned, Unsigned Maximum = ( std::numeric_limits< Unsigned >::max )() >
+      [[nodiscard]] constexpr bool convert_unsigned( Unsigned& result, const std::string_view input ) noexcept
+      {
+         // Assumes result == 0 and that input is a non-empty sequence of digits; returns false on overflow.
+
+         static_assert( std::is_unsigned_v< Unsigned > );
+         return accumulate_digits< Unsigned, Maximum >( result, input );
+      }
+
+      template< typename Signed >
+      [[nodiscard]] constexpr bool convert_signed( Signed& result, const std::string_view input ) noexcept
+      {
+         // Assumes result == 0 and that input is an optional sign followed by a non-empty sequence of digits; returns false on overflow.
+
+         static_assert( std::is_signed_v< Signed > );
+         if( input[ 0 ] == '-' ) {
+            return convert_negative< Signed >( result, std::string_view( input.data() + 1, input.size() - 1 ) );
+         }
+         const auto offset = unsigned( input[ 0 ] == '+' );
+         return convert_positive< Signed >( result, std::string_view( input.data() + offset, input.size() - offset ) );
+      }
+
+      template< typename Input >
+      [[nodiscard]] bool match_unsigned( Input& in ) noexcept( noexcept( in.empty() ) )
+      {
+         if( !in.empty() ) {
+            const char c = in.peek_char();
+            if( is_digit( c ) ) {
+               in.bump_in_this_line();
+               if( c == '0' ) {
+                  return in.empty() || ( !is_digit( in.peek_char() ) );  // TODO: Throw exception on digit?
+               }
+               while( ( !in.empty() ) && is_digit( in.peek_char() ) ) {
+                  in.bump_in_this_line();
+               }
+               return true;
+            }
+         }
+         return false;
+      }
+
+      template< typename Input,
+                typename Unsigned,
+                Unsigned Maximum = ( std::numeric_limits< Unsigned >::max )() >
+      [[nodiscard]] bool match_and_convert_unsigned_with_maximum( Input& in, Unsigned& st )
+      {
+         // Assumes st == 0.
+
+         if( !in.empty() ) {
+            char c = in.peek_char();
+            if( is_digit( c ) ) {
+               if( c == '0' ) {
+                  in.bump_in_this_line();
+                  return in.empty() || ( !is_digit( in.peek_char() ) );  // TODO: Throw exception on digit?
+               }
+               do {
+                  if( !accumulate_digit< Unsigned, Maximum >( st, c ) ) {
+                     throw parse_error( "integer overflow", in );  // Consistent with "as if" an action was doing the conversion.
+                  }
+                  in.bump_in_this_line();
+               } while( ( !in.empty() ) && is_digit( c = in.peek_char() ) );
+               return true;
+            }
+         }
+         return false;
+      }
+
+   }  // namespace internal
+
+   struct unsigned_action
+   {
+      // Assumes that 'in' contains a non-empty sequence of ASCII digits.
+
+      template< typename Input, typename Unsigned >
+      static auto apply( const Input& in, Unsigned& st ) -> std::enable_if_t< std::is_unsigned_v< Unsigned >, void >
+      {
+         // This function "only" offers basic exception safety.
+         st = 0;
+         if( !internal::convert_unsigned( st, in.string_view() ) ) {
+            throw parse_error( "unsigned integer overflow", in );
+         }
+      }
+
+      template< typename Input, typename State >
+      static auto apply( const Input& in, State& st ) -> std::enable_if_t< std::is_class_v< State >, void >
+      {
+         apply( in, st.converted );  // Compatibility for pre-3.0 behaviour.
+      }
+
+      template< typename Input, typename Unsigned, typename... Ts >
+      static auto apply( const Input& in, std::vector< Unsigned, Ts... >& st ) -> std::enable_if_t< std::is_unsigned_v< Unsigned >, void >
+      {
+         Unsigned u = 0;
+         apply( in, u );
+         st.emplace_back( u );
+      }
+   };
+
+   struct unsigned_rule
+   {
+      using analyze_t = internal::unsigned_rule_new::analyze_t;
+
+      template< typename Input >
+      [[nodiscard]] static bool match( Input& in ) noexcept( noexcept( in.empty() ) )
+      {
+         return internal::match_unsigned( in );  // Does not check for any overflow.
+      }
+   };
+
+   struct unsigned_rule_with_action
+   {
+      using analyze_t = internal::unsigned_rule_new::analyze_t;
+
+      template< apply_mode A,
+                rewind_mode M,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class Control,
+                typename Input,
+                typename... States >
+      [[nodiscard]] static auto match( Input& in, States&&... /*unused*/ ) noexcept( noexcept( in.empty() ) ) -> std::enable_if_t< A == apply_mode::nothing, bool >
+      {
+         return internal::match_unsigned( in );  // Does not check for any overflow.
+      }
+
+      template< apply_mode A,
+                rewind_mode M,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class Control,
+                typename Input,
+                typename Unsigned >
+      [[nodiscard]] static auto match( Input& in, Unsigned& st ) -> std::enable_if_t< ( A == apply_mode::action ) && std::is_unsigned_v< Unsigned >, bool >
+      {
+         // This function "only" offers basic exception safety.
+         st = 0;
+         return internal::match_and_convert_unsigned_with_maximum( in, st );  // Throws on overflow.
+      }
+
+      // TODO: Overload for st.converted?
+      // TODO: Overload for std::vector< Unsigned >?
+   };
+
+   template< typename Unsigned, Unsigned Maximum >
+   struct maximum_action
+   {
+      // Assumes that 'in' contains a non-empty sequence of ASCII digits.
+
+      static_assert( std::is_unsigned_v< Unsigned > );
+
+      template< typename Input, typename Unsigned2 >
+      static auto apply( const Input& in, Unsigned2& st ) -> std::enable_if_t< std::is_same_v< Unsigned, Unsigned2 >, void >
+      {
+         // This function "only" offers basic exception safety.
+         st = 0;
+         if( !internal::convert_unsigned< Unsigned, Maximum >( st, in.string_view() ) ) {
+            throw parse_error( "unsigned integer overflow", in );
+         }
+      }
+
+      template< typename Input, typename State >
+      static auto apply( const Input& in, State& st ) -> std::enable_if_t< std::is_class_v< State >, void >
+      {
+         apply( in, st.converted );  // Compatibility for pre-3.0 behaviour.
+      }
+
+      template< typename Input, typename Unsigned2, typename... Ts >
+      static auto apply( const Input& in, std::vector< Unsigned2, Ts... >& st ) -> std::enable_if_t< std::is_same_v< Unsigned, Unsigned2 >, void >
+      {
+         Unsigned u = 0;
+         apply( in, u );
+         st.emplace_back( u );
+      }
+   };
+
+   template< typename Unsigned, Unsigned Maximum = ( std::numeric_limits< Unsigned >::max )() >
+   struct maximum_rule
+   {
+      static_assert( std::is_unsigned_v< Unsigned > );
+
+      using analyze_t = internal::unsigned_rule_new::analyze_t;
+
+      template< typename Input >
+      [[nodiscard]] static bool match( Input& in )
+      {
+         Unsigned st = 0;
+         return internal::match_and_convert_unsigned_with_maximum< Input, Unsigned, Maximum >( in, st );  // Throws on overflow.
+      }
+   };
+
+   template< typename Unsigned, Unsigned Maximum = ( std::numeric_limits< Unsigned >::max )() >
+   struct maximum_rule_with_action
+   {
+      static_assert( std::is_unsigned_v< Unsigned > );
+
+      using analyze_t = internal::unsigned_rule_new::analyze_t;
+
+      template< apply_mode A,
+                rewind_mode M,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class Control,
+                typename Input,
+                typename... States >
+      [[nodiscard]] static auto match( Input& in, States&&... /*unused*/ ) -> std::enable_if_t< A == apply_mode::nothing, bool >
+      {
+         Unsigned st = 0;
+         return internal::match_and_convert_unsigned_with_maximum< Input, Unsigned, Maximum >( in, st );  // Throws on overflow.
+      }
+
+      template< apply_mode A,
+                rewind_mode M,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class Control,
+                typename Input,
+                typename Unsigned2 >
+      [[nodiscard]] static auto match( Input& in, Unsigned2& st ) -> std::enable_if_t< ( A == apply_mode::action ) && std::is_same_v< Unsigned, Unsigned2 >, bool >
+      {
+         // This function "only" offers basic exception safety.
+         st = 0;
+         return internal::match_and_convert_unsigned_with_maximum< Input, Unsigned, Maximum >( in, st );  // Throws on overflow.
+      }
+
+      // TODO: Overload for st.converted?
+      // TODO: Overload for std::vector< Unsigned >?
+   };
+
+   struct signed_action
+   {
+      // Assumes that 'in' contains a non-empty sequence of ASCII digits,
+      // with optional leading sign; with sign, in.size() must be >= 2.
+
+      template< typename Input, typename Signed >
+      static auto apply( const Input& in, Signed& st ) -> std::enable_if_t< std::is_signed_v< Signed >, void >
+      {
+         // This function "only" offers basic exception safety.
+         st = 0;
+         if( !internal::convert_signed( st, in.string_view() ) ) {
+            throw parse_error( "signed integer overflow", in );
+         }
+      }
+
+      template< typename Input, typename State >
+      static auto apply( const Input& in, State& st ) -> std::enable_if_t< std::is_class_v< State >, void >
+      {
+         apply( in, st.converted );  // Compatibility for pre-3.0 behaviour.
+      }
+
+      template< typename Input, typename Signed, typename... Ts >
+      static auto apply( const Input& in, std::vector< Signed, Ts... >& st ) -> std::enable_if_t< std::is_signed_v< Signed >, void >
+      {
+         Signed s = 0;
+         apply( in, s );
+         st.emplace_back( s );
+      }
+   };
+
+   struct signed_rule
+   {
+      using analyze_t = internal::signed_rule_new::analyze_t;
+
+      template< typename Input >
+      [[nodiscard]] static bool match( Input& in ) noexcept( noexcept( in.empty() ) )
+      {
+         return TAO_JSON_PEGTL_NAMESPACE::parse< internal::signed_rule_new >( in );  // Does not check for any overflow.
+      }
+   };
+
+   namespace internal
+   {
+      template< typename Rule >
+      struct signed_action_action
+         : nothing< Rule >
+      {
+      };
+
+      template<>
+      struct signed_action_action< signed_rule_new >
+         : signed_action
+      {
+      };
+
+   }  // namespace internal
+
+   struct signed_rule_with_action
+   {
+      using analyze_t = internal::signed_rule_new::analyze_t;
+
+      template< apply_mode A,
+                rewind_mode M,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class Control,
+                typename Input,
+                typename... States >
+      [[nodiscard]] static auto match( Input& in, States&&... /*unused*/ ) noexcept( noexcept( in.empty() ) ) -> std::enable_if_t< A == apply_mode::nothing, bool >
+      {
+         return TAO_JSON_PEGTL_NAMESPACE::parse< internal::signed_rule_new >( in );  // Does not check for any overflow.
+      }
+
+      template< apply_mode A,
+                rewind_mode M,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class Control,
+                typename Input,
+                typename Signed >
+      [[nodiscard]] static auto match( Input& in, Signed& st ) -> std::enable_if_t< ( A == apply_mode::action ) && std::is_signed_v< Signed >, bool >
+      {
+         return TAO_JSON_PEGTL_NAMESPACE::parse< internal::signed_rule_new, internal::signed_action_action >( in, st );  // Throws on overflow.
+      }
+
+      // TODO: Overload for st.converted?
+      // TODO: Overload for std::vector< Signed >?
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::integer
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/json.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/json.hpp
new file mode 100644
index 000000000000..ccdf5ea97c36
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/json.hpp
@@ -0,0 +1,88 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_CONTRIB_JSON_HPP
+#define TAO_JSON_PEGTL_CONTRIB_JSON_HPP
+
+#include "../ascii.hpp"
+#include "../config.hpp"
+#include "../rules.hpp"
+#include "../utf8.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::json
+{
+   // JSON grammar according to RFC 8259
+
+   // clang-format off
+   struct ws : one< ' ', '\t', '\n', '\r' > {};
+
+   template< typename R, typename P = ws >
+   struct padr : internal::seq< R, internal::star< P > > {};
+
+   struct begin_array : padr< one< '[' > > {};
+   struct begin_object : padr< one< '{' > > {};
+   struct end_array : one< ']' > {};
+   struct end_object : one< '}' > {};
+   struct name_separator : pad< one< ':' >, ws > {};
+   struct value_separator : padr< one< ',' > > {};
+
+   struct false_ : string< 'f', 'a', 'l', 's', 'e' > {};  // NOLINT(readability-identifier-naming)
+   struct null : string< 'n', 'u', 'l', 'l' > {};
+   struct true_ : string< 't', 'r', 'u', 'e' > {};  // NOLINT(readability-identifier-naming)
+
+   struct digits : plus< digit > {};
+   struct exp : seq< one< 'e', 'E' >, opt< one< '-', '+'> >, must< digits > > {};
+   struct frac : if_must< one< '.' >, digits > {};
+   struct int_ : sor< one< '0' >, digits > {};  // NOLINT(readability-identifier-naming)
+   struct number : seq< opt< one< '-' > >, int_, opt< frac >, opt< exp > > {};
+
+   struct xdigit : pegtl::xdigit {};
+   struct unicode : list< seq< one< 'u' >, rep< 4, must< xdigit > > >, one< '\\' > > {};
+   struct escaped_char : one< '"', '\\', '/', 'b', 'f', 'n', 'r', 't' > {};
+   struct escaped : sor< escaped_char, unicode > {};
+   struct unescaped : utf8::range< 0x20, 0x10FFFF > {};
+   struct char_ : if_then_else< one< '\\' >, must< escaped >, unescaped > {};  // NOLINT(readability-identifier-naming)
+
+   struct string_content : until< at< one< '"' > >, must< char_ > > {};
+   struct string : seq< one< '"' >, must< string_content >, any >
+   {
+      using content = string_content;
+   };
+
+   struct key_content : until< at< one< '"' > >, must< char_ > > {};
+   struct key : seq< one< '"' >, must< key_content >, any >
+   {
+      using content = key_content;
+   };
+
+   struct value;
+
+   struct array_element;
+   struct array_content : opt< list_must< array_element, value_separator > > {};
+   struct array : seq< begin_array, array_content, must< end_array > >
+   {
+      using begin = begin_array;
+      using end = end_array;
+      using element = array_element;
+      using content = array_content;
+   };
+
+   struct member : if_must< key, name_separator, value > {};
+   struct object_content : opt< list_must< member, value_separator > > {};
+   struct object : seq< begin_object, object_content, must< end_object > >
+   {
+      using begin = begin_object;
+      using end = end_object;
+      using element = member;
+      using content = object_content;
+   };
+
+   struct value : padr< sor< string, number, object, array, false_, true_, null > > {};
+   struct array_element : seq< value > {};
+
+   struct text : seq< star< ws >, value > {};
+   // clang-format on
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::json
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/json_pointer.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/json_pointer.hpp
new file mode 100644
index 000000000000..153766fead31
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/json_pointer.hpp
@@ -0,0 +1,33 @@
+// Copyright (c) 2019-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_CONTRIB_JSON_POINTER_HPP
+#define TAO_JSON_PEGTL_CONTRIB_JSON_POINTER_HPP
+
+#include "../ascii.hpp"
+#include "../config.hpp"
+#include "../rules.hpp"
+#include "../utf8.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::json_pointer
+{
+   // JSON pointer grammar according to RFC 6901
+
+   // clang-format off
+   struct unescaped : utf8::ranges< 0x0, 0x2E, 0x30, 0x7D, 0x7F, 0x10FFFF > {};
+   struct escaped : seq< one< '~' >, one< '0', '1' > > {};
+
+   struct reference_token : star< sor< unescaped, escaped > > {};
+   struct json_pointer : star< one< '/' >, reference_token > {};
+   // clang-format on
+
+   // relative JSON pointer, see ...
+
+   // clang-format off
+   struct non_negative_integer : sor< one< '0' >, plus< digit > > {};
+   struct relative_json_pointer : seq< non_negative_integer, sor< one< '#' >, json_pointer > > {};
+   // clang-format on
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::json_pointer
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/parse_tree.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/parse_tree.hpp
new file mode 100644
index 000000000000..43f9f9ce0cb3
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/parse_tree.hpp
@@ -0,0 +1,561 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_CONTRIB_PARSE_TREE_HPP
+#define TAO_JSON_PEGTL_CONTRIB_PARSE_TREE_HPP
+
+#include <cassert>
+#include <memory>
+#include <string>
+#include <string_view>
+#include <tuple>
+#include <type_traits>
+#include <typeindex>
+#include <utility>
+#include <vector>
+
+#include "../config.hpp"
+#include "../memory_input.hpp"
+#include "../normal.hpp"
+#include "../nothing.hpp"
+#include "../parse.hpp"
+
+#include "../analysis/counted.hpp"
+#include "../analysis/generic.hpp"
+#include "../internal/demangle.hpp"
+#include "../internal/iterator.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::parse_tree
+{
+   template< typename T >
+   struct basic_node
+   {
+      using node_t = T;
+      using children_t = std::vector< std::unique_ptr< node_t > >;
+      children_t children;
+
+      std::string_view type;
+      std::string source;
+
+      TAO_JSON_PEGTL_NAMESPACE::internal::iterator m_begin;
+      TAO_JSON_PEGTL_NAMESPACE::internal::iterator m_end;
+
+      // each node will be default constructed
+      basic_node() = default;
+
+      // no copy/move is necessary
+      // (nodes are always owned/handled by a std::unique_ptr)
+      basic_node( const basic_node& ) = delete;
+      basic_node( basic_node&& ) = delete;
+
+      ~basic_node() = default;
+
+      // no assignment either
+      basic_node& operator=( const basic_node& ) = delete;
+      basic_node& operator=( basic_node&& ) = delete;
+
+      [[nodiscard]] bool is_root() const noexcept
+      {
+         return type.empty();
+      }
+
+      template< typename U >
+      [[nodiscard]] bool is_type() const noexcept
+      {
+         return type == TAO_JSON_PEGTL_NAMESPACE::internal::demangle< U >();
+      }
+
+      template< typename U >
+      void set_type() noexcept
+      {
+         type = TAO_JSON_PEGTL_NAMESPACE::internal::demangle< U >();
+      }
+
+      [[nodiscard]] position begin() const
+      {
+         return position( m_begin, source );
+      }
+
+      [[nodiscard]] position end() const
+      {
+         return position( m_end, source );
+      }
+
+      [[nodiscard]] bool has_content() const noexcept
+      {
+         return m_end.data != nullptr;
+      }
+
+      [[nodiscard]] std::string_view string_view() const noexcept
+      {
+         assert( has_content() );
+         return std::string_view( m_begin.data, m_end.data - m_begin.data );
+      }
+
+      [[nodiscard]] std::string string() const
+      {
+         assert( has_content() );
+         return std::string( m_begin.data, m_end.data );
+      }
+
+      template< tracking_mode P = tracking_mode::eager, typename Eol = eol::lf_crlf >
+      [[nodiscard]] memory_input< P, Eol > as_memory_input() const
+      {
+         assert( has_content() );
+         return { m_begin.data, m_end.data, source, m_begin.byte, m_begin.line, m_begin.byte_in_line };
+      }
+
+      template< typename... States >
+      void remove_content( States&&... /*unused*/ ) noexcept
+      {
+         m_end.reset();
+      }
+
+      // all non-root nodes are initialized by calling this method
+      template< typename Rule, typename Input, typename... States >
+      void start( const Input& in, States&&... /*unused*/ )
+      {
+         set_type< Rule >();
+         source = in.source();
+         m_begin = TAO_JSON_PEGTL_NAMESPACE::internal::iterator( in.iterator() );
+      }
+
+      // if parsing of the rule succeeded, this method is called
+      template< typename Rule, typename Input, typename... States >
+      void success( const Input& in, States&&... /*unused*/ ) noexcept
+      {
+         m_end = TAO_JSON_PEGTL_NAMESPACE::internal::iterator( in.iterator() );
+      }
+
+      // if parsing of the rule failed, this method is called
+      template< typename Rule, typename Input, typename... States >
+      void failure( const Input& /*unused*/, States&&... /*unused*/ ) noexcept
+      {
+      }
+
+      // if parsing succeeded and the (optional) transform call
+      // did not discard the node, it is appended to its parent.
+      // note that "child" is the node whose Rule just succeeded
+      // and "*this" is the parent where the node should be appended.
+      template< typename... States >
+      void emplace_back( std::unique_ptr< node_t >&& child, States&&... /*unused*/ )
+      {
+         assert( child );
+         children.emplace_back( std::move( child ) );
+      }
+   };
+
+   struct node
+      : basic_node< node >
+   {
+   };
+
+   namespace internal
+   {
+      template< typename Node >
+      struct state
+      {
+         std::vector< std::unique_ptr< Node > > stack;
+
+         state()
+         {
+            emplace_back();
+         }
+
+         void emplace_back()
+         {
+            stack.emplace_back( std::make_unique< Node >() );
+         }
+
+         [[nodiscard]] std::unique_ptr< Node >& back() noexcept
+         {
+            assert( !stack.empty() );
+            return stack.back();
+         }
+
+         void pop_back() noexcept
+         {
+            assert( !stack.empty() );
+            return stack.pop_back();
+         }
+      };
+
+      template< typename Selector, typename... Parameters >
+      void transform( Parameters&&... /*unused*/ ) noexcept
+      {
+      }
+
+      template< typename Selector, typename Input, typename Node, typename... States >
+      auto transform( const Input& in, std::unique_ptr< Node >& n, States&&... st ) noexcept( noexcept( Selector::transform( in, n, st... ) ) )
+         -> decltype( Selector::transform( in, n, st... ), void() )
+      {
+         Selector::transform( in, n, st... );
+      }
+
+      template< typename Selector, typename Input, typename Node, typename... States >
+      auto transform( const Input& /*unused*/, std::unique_ptr< Node >& n, States&&... st ) noexcept( noexcept( Selector::transform( n, st... ) ) )
+         -> decltype( Selector::transform( n, st... ), void() )
+      {
+         Selector::transform( n, st... );
+      }
+
+      template< unsigned Level, typename Analyse, template< typename... > class Selector >
+      struct is_leaf
+         : std::false_type
+      {
+      };
+
+      template< analysis::rule_type Type, template< typename... > class Selector >
+      struct is_leaf< 0, analysis::generic< Type >, Selector >
+         : std::true_type
+      {
+      };
+
+      template< analysis::rule_type Type, std::size_t Count, template< typename... > class Selector >
+      struct is_leaf< 0, analysis::counted< Type, Count >, Selector >
+         : std::true_type
+      {
+      };
+
+      template< analysis::rule_type Type, typename... Rules, template< typename... > class Selector >
+      struct is_leaf< 0, analysis::generic< Type, Rules... >, Selector >
+         : std::false_type
+      {
+      };
+
+      template< analysis::rule_type Type, std::size_t Count, typename... Rules, template< typename... > class Selector >
+      struct is_leaf< 0, analysis::counted< Type, Count, Rules... >, Selector >
+         : std::false_type
+      {
+      };
+
+      template< unsigned Level, typename Rule, template< typename... > class Selector >
+      inline constexpr bool is_unselected_leaf = !Selector< Rule >::value && is_leaf< Level, typename Rule::analyze_t, Selector >::value;
+
+      template< unsigned Level, analysis::rule_type Type, typename... Rules, template< typename... > class Selector >
+      struct is_leaf< Level, analysis::generic< Type, Rules... >, Selector >
+         : std::bool_constant< ( is_unselected_leaf< Level - 1, Rules, Selector > && ... ) >
+      {
+      };
+
+      template< unsigned Level, analysis::rule_type Type, std::size_t Count, typename... Rules, template< typename... > class Selector >
+      struct is_leaf< Level, analysis::counted< Type, Count, Rules... >, Selector >
+         : std::bool_constant< ( is_unselected_leaf< Level - 1, Rules, Selector > && ... ) >
+      {
+      };
+
+      template< typename T >
+      struct control
+      {
+         template< typename Input, typename Tuple, std::size_t... Is >
+         static void start_impl( const Input& in, const Tuple& t, std::index_sequence< Is... > /*unused*/ ) noexcept( noexcept( T::start( in, std::get< sizeof...( Is ) >( t ), std::get< Is >( t )... ) ) )
+         {
+            T::start( in, std::get< sizeof...( Is ) >( t ), std::get< Is >( t )... );
+         }
+
+         template< typename Input, typename... States >
+         static void start( const Input& in, States&&... st ) noexcept( noexcept( start_impl( in, std::tie( st... ), std::make_index_sequence< sizeof...( st ) - 1 >() ) ) )
+         {
+            start_impl( in, std::tie( st... ), std::make_index_sequence< sizeof...( st ) - 1 >() );
+         }
+
+         template< typename Input, typename Tuple, std::size_t... Is >
+         static void success_impl( const Input& in, const Tuple& t, std::index_sequence< Is... > /*unused*/ ) noexcept( noexcept( T::success( in, std::get< sizeof...( Is ) >( t ), std::get< Is >( t )... ) ) )
+         {
+            T::success( in, std::get< sizeof...( Is ) >( t ), std::get< Is >( t )... );
+         }
+
+         template< typename Input, typename... States >
+         static void success( const Input& in, States&&... st ) noexcept( noexcept( success_impl( in, std::tie( st... ), std::make_index_sequence< sizeof...( st ) - 1 >() ) ) )
+         {
+            success_impl( in, std::tie( st... ), std::make_index_sequence< sizeof...( st ) - 1 >() );
+         }
+
+         template< typename Input, typename Tuple, std::size_t... Is >
+         static void failure_impl( const Input& in, const Tuple& t, std::index_sequence< Is... > /*unused*/ ) noexcept( noexcept( T::failure( in, std::get< sizeof...( Is ) >( t ), std::get< Is >( t )... ) ) )
+         {
+            T::failure( in, std::get< sizeof...( Is ) >( t ), std::get< Is >( t )... );
+         }
+
+         template< typename Input, typename... States >
+         static void failure( const Input& in, States&&... st ) noexcept( noexcept( failure_impl( in, std::tie( st... ), std::make_index_sequence< sizeof...( st ) - 1 >() ) ) )
+         {
+            failure_impl( in, std::tie( st... ), std::make_index_sequence< sizeof...( st ) - 1 >() );
+         }
+
+         template< typename Input, typename Tuple, std::size_t... Is >
+         static void raise_impl( const Input& in, const Tuple& t, std::index_sequence< Is... > /*unused*/ ) noexcept( noexcept( T::raise( in, std::get< Is >( t )... ) ) )
+         {
+            T::raise( in, std::get< Is >( t )... );
+         }
+
+         template< typename Input, typename... States >
+         static void raise( const Input& in, States&&... st ) noexcept( noexcept( raise_impl( in, std::tie( st... ), std::make_index_sequence< sizeof...( st ) - 1 >() ) ) )
+         {
+            raise_impl( in, std::tie( st... ), std::make_index_sequence< sizeof...( st ) - 1 >() );
+         }
+
+         template< template< typename... > class Action, typename Iterator, typename Input, typename Tuple, std::size_t... Is >
+         static auto apply_impl( const Iterator& begin, const Input& in, const Tuple& t, std::index_sequence< Is... > /*unused*/ ) noexcept( noexcept( T::template apply< Action >( begin, in, std::get< Is >( t )... ) ) )
+            -> decltype( T::template apply< Action >( begin, in, std::get< Is >( t )... ) )
+         {
+            return T::template apply< Action >( begin, in, std::get< Is >( t )... );
+         }
+
+         template< template< typename... > class Action, typename Iterator, typename Input, typename... States >
+         static auto apply( const Iterator& begin, const Input& in, States&&... st ) noexcept( noexcept( apply_impl< Action >( begin, in, std::tie( st... ), std::make_index_sequence< sizeof...( st ) - 1 >() ) ) )
+            -> decltype( apply_impl< Action >( begin, in, std::tie( st... ), std::make_index_sequence< sizeof...( st ) - 1 >() ) )
+         {
+            return apply_impl< Action >( begin, in, std::tie( st... ), std::make_index_sequence< sizeof...( st ) - 1 >() );
+         }
+
+         template< template< typename... > class Action, typename Input, typename Tuple, std::size_t... Is >
+         static auto apply0_impl( const Input& in, const Tuple& t, std::index_sequence< Is... > /*unused*/ ) noexcept( noexcept( T::template apply0< Action >( in, std::get< Is >( t )... ) ) )
+            -> decltype( T::template apply0< Action >( in, std::get< Is >( t )... ) )
+         {
+            return T::template apply0< Action >( in, std::get< Is >( t )... );
+         }
+
+         template< template< typename... > class Action, typename Input, typename... States >
+         static auto apply0( const Input& in, States&&... st ) noexcept( noexcept( apply0_impl< Action >( in, std::tie( st... ), std::make_index_sequence< sizeof...( st ) - 1 >() ) ) )
+            -> decltype( apply0_impl< Action >( in, std::tie( st... ), std::make_index_sequence< sizeof...( st ) - 1 >() ) )
+         {
+            return apply0_impl< Action >( in, std::tie( st... ), std::make_index_sequence< sizeof...( st ) - 1 >() );
+         }
+
+         template< apply_mode A,
+                   rewind_mode M,
+                   template< typename... >
+                   class Action,
+                   template< typename... >
+                   class Control,
+                   typename Input,
+                   typename... States >
+         [[nodiscard]] static bool match( Input& in, States&&... st )
+         {
+            return T::template match< A, M, Action, Control >( in, st... );
+         }
+      };
+
+      template< typename Node, template< typename... > class Selector, template< typename... > class Control >
+      struct make_control
+      {
+         template< typename Rule, bool, bool >
+         struct state_handler;
+
+         template< typename Rule >
+         using type = control< state_handler< Rule, Selector< Rule >::value, is_leaf< 8, typename Rule::analyze_t, Selector >::value > >;
+      };
+
+      template< typename Node, template< typename... > class Selector, template< typename... > class Control >
+      template< typename Rule >
+      struct make_control< Node, Selector, Control >::state_handler< Rule, false, true >
+         : Control< Rule >
+      {
+         template< typename Input, typename... States >
+         static void start( const Input& in, state< Node >& /*unused*/, States&&... st ) noexcept( noexcept( Control< Rule >::start( in, st... ) ) )
+         {
+            Control< Rule >::start( in, st... );
+         }
+
+         template< typename Input, typename... States >
+         static void success( const Input& in, state< Node >& /*unused*/, States&&... st ) noexcept( noexcept( Control< Rule >::success( in, st... ) ) )
+         {
+            Control< Rule >::success( in, st... );
+         }
+
+         template< typename Input, typename... States >
+         static void failure( const Input& in, state< Node >& /*unused*/, States&&... st ) noexcept( noexcept( Control< Rule >::failure( in, st... ) ) )
+         {
+            Control< Rule >::failure( in, st... );
+         }
+      };
+
+      template< typename Node, template< typename... > class Selector, template< typename... > class Control >
+      template< typename Rule >
+      struct make_control< Node, Selector, Control >::state_handler< Rule, false, false >
+         : Control< Rule >
+      {
+         template< typename Input, typename... States >
+         static void start( const Input& in, state< Node >& state, States&&... st )
+         {
+            Control< Rule >::start( in, st... );
+            state.emplace_back();
+         }
+
+         template< typename Input, typename... States >
+         static void success( const Input& in, state< Node >& state, States&&... st )
+         {
+            Control< Rule >::success( in, st... );
+            auto n = std::move( state.back() );
+            state.pop_back();
+            for( auto& c : n->children ) {
+               state.back()->children.emplace_back( std::move( c ) );
+            }
+         }
+
+         template< typename Input, typename... States >
+         static void failure( const Input& in, state< Node >& state, States&&... st ) noexcept( noexcept( Control< Rule >::failure( in, st... ) ) )
+         {
+            Control< Rule >::failure( in, st... );
+            state.pop_back();
+         }
+      };
+
+      template< typename Node, template< typename... > class Selector, template< typename... > class Control >
+      template< typename Rule, bool B >
+      struct make_control< Node, Selector, Control >::state_handler< Rule, true, B >
+         : Control< Rule >
+      {
+         template< typename Input, typename... States >
+         static void start( const Input& in, state< Node >& state, States&&... st )
+         {
+            Control< Rule >::start( in, st... );
+            state.emplace_back();
+            state.back()->template start< Rule >( in, st... );
+         }
+
+         template< typename Input, typename... States >
+         static void success( const Input& in, state< Node >& state, States&&... st )
+         {
+            Control< Rule >::success( in, st... );
+            auto n = std::move( state.back() );
+            state.pop_back();
+            n->template success< Rule >( in, st... );
+            transform< Selector< Rule > >( in, n, st... );
+            if( n ) {
+               state.back()->emplace_back( std::move( n ), st... );
+            }
+         }
+
+         template< typename Input, typename... States >
+         static void failure( const Input& in, state< Node >& state, States&&... st ) noexcept( noexcept( Control< Rule >::failure( in, st... ) ) && noexcept( std::declval< Node& >().template failure< Rule >( in, st... ) ) )
+         {
+            Control< Rule >::failure( in, st... );
+            state.back()->template failure< Rule >( in, st... );
+            state.pop_back();
+         }
+      };
+
+      template< typename >
+      using store_all = std::true_type;
+
+      template< typename >
+      struct selector;
+
+      template< typename T >
+      struct selector< std::tuple< T > >
+      {
+         using type = typename T::type;
+      };
+
+      template< typename... Ts >
+      struct selector< std::tuple< Ts... > >
+      {
+         static_assert( sizeof...( Ts ) == 0, "multiple matches found" );
+         using type = std::false_type;
+      };
+
+      template< typename T >
+      using selector_t = typename selector< T >::type;
+
+      template< typename Rule, typename Collection >
+      using select_tuple = std::conditional_t< Collection::template contains< Rule >, std::tuple< Collection >, std::tuple<> >;
+
+   }  // namespace internal
+
+   template< typename Rule, typename... Collections >
+   using selector = internal::selector_t< decltype( std::tuple_cat( std::declval< internal::select_tuple< Rule, Collections > >()... ) ) >;
+
+   template< typename Base >
+   struct apply
+      : std::true_type
+   {
+      template< typename... Rules >
+      struct on
+      {
+         using type = Base;
+
+         template< typename Rule >
+         static constexpr bool contains = ( std::is_same_v< Rule, Rules > || ... );
+      };
+   };
+
+   struct store_content
+      : apply< store_content >
+   {};
+
+   // some nodes don't need to store their content
+   struct remove_content
+      : apply< remove_content >
+   {
+      template< typename Node, typename... States >
+      static void transform( std::unique_ptr< Node >& n, States&&... st ) noexcept( noexcept( n->Node::remove_content( st... ) ) )
+      {
+         n->remove_content( st... );
+      }
+   };
+
+   // if a node has only one child, replace the node with its child, otherwise remove content
+   struct fold_one
+      : apply< fold_one >
+   {
+      template< typename Node, typename... States >
+      static void transform( std::unique_ptr< Node >& n, States&&... st ) noexcept( noexcept( n->children.size(), n->Node::remove_content( st... ) ) )
+      {
+         if( n->children.size() == 1 ) {
+            n = std::move( n->children.front() );
+         }
+         else {
+            n->remove_content( st... );
+         }
+      }
+   };
+
+   // if a node has no children, discard the node, otherwise remove content
+   struct discard_empty
+      : apply< discard_empty >
+   {
+      template< typename Node, typename... States >
+      static void transform( std::unique_ptr< Node >& n, States&&... st ) noexcept( noexcept( n->children.empty(), n->Node::remove_content( st... ) ) )
+      {
+         if( n->children.empty() ) {
+            n.reset();
+         }
+         else {
+            n->remove_content( st... );
+         }
+      }
+   };
+
+   template< typename Rule,
+             typename Node,
+             template< typename... > class Selector = internal::store_all,
+             template< typename... > class Action = nothing,
+             template< typename... > class Control = normal,
+             typename Input,
+             typename... States >
+   [[nodiscard]] std::unique_ptr< Node > parse( Input&& in, States&&... st )
+   {
+      internal::state< Node > state;
+      if( !TAO_JSON_PEGTL_NAMESPACE::parse< Rule, Action, internal::make_control< Node, Selector, Control >::template type >( in, st..., state ) ) {
+         return nullptr;
+      }
+      assert( state.stack.size() == 1 );
+      return std::move( state.back() );
+   }
+
+   template< typename Rule,
+             template< typename... > class Selector = internal::store_all,
+             template< typename... > class Action = nothing,
+             template< typename... > class Control = normal,
+             typename Input,
+             typename... States >
+   [[nodiscard]] std::unique_ptr< node > parse( Input&& in, States&&... st )
+   {
+      return parse< Rule, node, Selector, Action, Control >( in, st... );
+   }
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::parse_tree
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/parse_tree_to_dot.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/parse_tree_to_dot.hpp
new file mode 100644
index 000000000000..c4f0eee6138d
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/parse_tree_to_dot.hpp
@@ -0,0 +1,104 @@
+// Copyright (c) 2019-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_CONTRIB_PARSE_TREE_TO_DOT_HPP
+#define TAO_JSON_PEGTL_CONTRIB_PARSE_TREE_TO_DOT_HPP
+
+#include <cassert>
+#include <ostream>
+#include <string>
+
+#include "parse_tree.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::parse_tree
+{
+   namespace internal
+   {
+      inline void escape( std::ostream& os, const std::string_view s )
+      {
+         static const char* h = "0123456789abcdef";
+
+         const char* p = s.data();
+         const char* l = p;
+         const char* const e = s.data() + s.size();
+         while( p != e ) {
+            const unsigned char c = *p;
+            if( c == '\\' ) {
+               os.write( l, p - l );
+               l = ++p;
+               os << "\\\\";
+            }
+            else if( c == '"' ) {
+               os.write( l, p - l );
+               l = ++p;
+               os << "\\\"";
+            }
+            else if( c < 32 ) {
+               os.write( l, p - l );
+               l = ++p;
+               switch( c ) {
+                  case '\b':
+                     os << "\\b";
+                     break;
+                  case '\f':
+                     os << "\\f";
+                     break;
+                  case '\n':
+                     os << "\\n";
+                     break;
+                  case '\r':
+                     os << "\\r";
+                     break;
+                  case '\t':
+                     os << "\\t";
+                     break;
+                  default:
+                     os << "\\u00" << h[ ( c & 0xf0 ) >> 4 ] << h[ c & 0x0f ];
+               }
+            }
+            else if( c == 127 ) {
+               os.write( l, p - l );
+               l = ++p;
+               os << "\\u007f";
+            }
+            else {
+               ++p;
+            }
+         }
+         os.write( l, p - l );
+      }
+
+      template< typename Node >
+      void print_dot_node( std::ostream& os, const Node& n, const std::string_view s )
+      {
+         os << "  x" << &n << " [ label=\"";
+         escape( os, s );
+         if( n.has_content() ) {
+            os << "\\n";
+            escape( os, n.string_view() );
+         }
+         os << "\" ]\n";
+         if( !n.children.empty() ) {
+            os << "  x" << &n << " -> { ";
+            for( auto& up : n.children ) {
+               os << "x" << up.get() << ( ( up == n.children.back() ) ? " }\n" : ", " );
+            }
+            for( auto& up : n.children ) {
+               print_dot_node( os, *up, up->type );
+            }
+         }
+      }
+
+   }  // namespace internal
+
+   template< typename Node >
+   void print_dot( std::ostream& os, const Node& n )
+   {
+      os << "digraph parse_tree\n{\n";
+      internal::print_dot_node( os, n, n.is_root() ? "ROOT" : n.type );
+      os << "}\n";
+   }
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::parse_tree
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/raw_string.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/raw_string.hpp
new file mode 100644
index 000000000000..1c14153180cf
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/raw_string.hpp
@@ -0,0 +1,225 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_CONTRIB_RAW_STRING_HPP
+#define TAO_JSON_PEGTL_CONTRIB_RAW_STRING_HPP
+
+#include <cstddef>
+#include <type_traits>
+
+#include "../apply_mode.hpp"
+#include "../config.hpp"
+#include "../rewind_mode.hpp"
+
+#include "../internal/bytes.hpp"
+#include "../internal/eof.hpp"
+#include "../internal/eol.hpp"
+#include "../internal/must.hpp"
+#include "../internal/not_at.hpp"
+#include "../internal/seq.hpp"
+#include "../internal/skip_control.hpp"
+#include "../internal/star.hpp"
+
+#include "../analysis/generic.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE
+{
+   namespace internal
+   {
+      template< char Open, char Marker >
+      struct raw_string_open
+      {
+         using analyze_t = analysis::generic< analysis::rule_type::any >;
+
+         template< apply_mode A,
+                   rewind_mode,
+                   template< typename... >
+                   class Action,
+                   template< typename... >
+                   class Control,
+                   typename Input,
+                   typename... States >
+         [[nodiscard]] static bool match( Input& in, std::size_t& marker_size, States&&... /*unused*/ ) noexcept( noexcept( in.size( 0 ) ) )
+         {
+            if( in.empty() || ( in.peek_char( 0 ) != Open ) ) {
+               return false;
+            }
+            for( std::size_t i = 1; i < in.size( i + 1 ); ++i ) {
+               switch( const auto c = in.peek_char( i ) ) {
+                  case Open:
+                     marker_size = i + 1;
+                     in.bump_in_this_line( marker_size );
+                     (void)eol::match( in );
+                     return true;
+                  case Marker:
+                     break;
+                  default:
+                     return false;
+               }
+            }
+            return false;
+         }
+      };
+
+      template< char Open, char Marker >
+      inline constexpr bool skip_control< raw_string_open< Open, Marker > > = true;
+
+      template< char Marker, char Close >
+      struct at_raw_string_close
+      {
+         using analyze_t = analysis::generic< analysis::rule_type::opt >;
+
+         template< apply_mode A,
+                   rewind_mode,
+                   template< typename... >
+                   class Action,
+                   template< typename... >
+                   class Control,
+                   typename Input,
+                   typename... States >
+         [[nodiscard]] static bool match( Input& in, const std::size_t& marker_size, States&&... /*unused*/ ) noexcept( noexcept( in.size( 0 ) ) )
+         {
+            if( in.size( marker_size ) < marker_size ) {
+               return false;
+            }
+            if( in.peek_char( 0 ) != Close ) {
+               return false;
+            }
+            if( in.peek_char( marker_size - 1 ) != Close ) {
+               return false;
+            }
+            for( std::size_t i = 0; i < ( marker_size - 2 ); ++i ) {
+               if( in.peek_char( i + 1 ) != Marker ) {
+                  return false;
+               }
+            }
+            return true;
+         }
+      };
+
+      template< char Marker, char Close >
+      inline constexpr bool skip_control< at_raw_string_close< Marker, Close > > = true;
+
+      template< typename Cond, typename... Rules >
+      struct raw_string_until;
+
+      template< typename Cond >
+      struct raw_string_until< Cond >
+      {
+         using analyze_t = analysis::generic< analysis::rule_type::seq, star< not_at< Cond >, not_at< eof >, bytes< 1 > >, Cond >;
+
+         template< apply_mode A,
+                   rewind_mode M,
+                   template< typename... >
+                   class Action,
+                   template< typename... >
+                   class Control,
+                   typename Input,
+                   typename... States >
+         [[nodiscard]] static bool match( Input& in, const std::size_t& marker_size, States&&... st )
+         {
+            auto m = in.template mark< M >();
+
+            while( !Control< Cond >::template match< A, rewind_mode::required, Action, Control >( in, marker_size, st... ) ) {
+               if( in.empty() ) {
+                  return false;
+               }
+               in.bump();
+            }
+            return m( true );
+         }
+      };
+
+      template< typename Cond, typename... Rules >
+      struct raw_string_until
+      {
+         using analyze_t = analysis::generic< analysis::rule_type::seq, star< not_at< Cond >, not_at< eof >, Rules... >, Cond >;
+
+         template< apply_mode A,
+                   rewind_mode M,
+                   template< typename... >
+                   class Action,
+                   template< typename... >
+                   class Control,
+                   typename Input,
+                   typename... States >
+         [[nodiscard]] static bool match( Input& in, const std::size_t& marker_size, States&&... st )
+         {
+            auto m = in.template mark< M >();
+            using m_t = decltype( m );
+
+            while( !Control< Cond >::template match< A, rewind_mode::required, Action, Control >( in, marker_size, st... ) ) {
+               if( in.empty() || !( Control< Rules >::template match< A, m_t::next_rewind_mode, Action, Control >( in, st... ) && ... ) ) {
+                  return false;
+               }
+            }
+            return m( true );
+         }
+      };
+
+      template< typename Cond, typename... Rules >
+      inline constexpr bool skip_control< raw_string_until< Cond, Rules... > > = true;
+
+   }  // namespace internal
+
+   // raw_string matches Lua-style long literals.
+   //
+   // The following description was taken from the Lua documentation
+   // (see http://www.lua.org/docs.html):
+   //
+   // - An "opening long bracket of level n" is defined as an opening square
+   //   bracket followed by n equal signs followed by another opening square
+   //   bracket. So, an opening long bracket of level 0 is written as `[[`,
+   //   an opening long bracket of level 1 is written as `[=[`, and so on.
+   // - A "closing long bracket" is defined similarly; for instance, a closing
+   //   long bracket of level 4 is written as `]====]`.
+   // - A "long literal" starts with an opening long bracket of any level and
+   //   ends at the first closing long bracket of the same level. It can
+   //   contain any text except a closing bracket of the same level.
+   // - Literals in this bracketed form can run for several lines, do not
+   //   interpret any escape sequences, and ignore long brackets of any other
+   //   level.
+   // - For convenience, when the opening long bracket is eagerly followed
+   //   by a newline, the newline is not included in the string.
+   //
+   // Note that unlike Lua's long literal, a raw_string is customizable to use
+   // other characters than `[`, `=` and `]` for matching. Also note that Lua
+   // introduced newline-specific replacements in Lua 5.2, which we do not
+   // support on the grammar level.
+
+   template< char Open, char Marker, char Close, typename... Contents >
+   struct raw_string
+   {
+      // This is used for binding the apply()-method and for error-reporting
+      // when a raw string is not closed properly or has invalid content.
+      struct content
+         : internal::raw_string_until< internal::at_raw_string_close< Marker, Close >, Contents... >
+      {
+      };
+
+      using analyze_t = typename internal::seq< internal::bytes< 1 >, content, internal::bytes< 1 > >::analyze_t;
+
+      template< apply_mode A,
+                rewind_mode M,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class Control,
+                typename Input,
+                typename... States >
+      [[nodiscard]] static bool match( Input& in, States&&... st )
+      {
+         std::size_t marker_size;
+         if( internal::raw_string_open< Open, Marker >::template match< A, M, Action, Control >( in, marker_size, st... ) ) {
+            // TODO: Do not rely on must<>
+            (void)internal::must< content >::template match< A, M, Action, Control >( in, marker_size, st... );
+            in.bump_in_this_line( marker_size );
+            return true;
+         }
+         return false;
+      }
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/remove_first_state.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/remove_first_state.hpp
new file mode 100644
index 000000000000..fd47d6f5db1c
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/remove_first_state.hpp
@@ -0,0 +1,86 @@
+// Copyright (c) 2019-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_CONTRIB_REMOVE_FIRST_STATE_HPP
+#define TAO_JSON_PEGTL_CONTRIB_REMOVE_FIRST_STATE_HPP
+
+#include "../apply_mode.hpp"
+#include "../config.hpp"
+#include "../rewind_mode.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE
+{
+   // NOTE: The naming of the following classes might still change.
+
+   template< typename Rule, template< typename... > class Control >
+   struct remove_first_state_after_match
+      : Control< Rule >
+   {
+      template< typename Input, typename State, typename... States >
+      static void start( const Input& in, State&& /*unused*/, States&&... st ) noexcept( noexcept( Control< Rule >::start( in, st... ) ) )
+      {
+         Control< Rule >::start( in, st... );
+      }
+
+      template< typename Input, typename State, typename... States >
+      static void success( const Input& in, State&& /*unused*/, States&&... st ) noexcept( noexcept( Control< Rule >::success( in, st... ) ) )
+      {
+         Control< Rule >::success( in, st... );
+      }
+
+      template< typename Input, typename State, typename... States >
+      static void failure( const Input& in, State&& /*unused*/, States&&... st ) noexcept( noexcept( Control< Rule >::failure( in, st... ) ) )
+      {
+         Control< Rule >::failure( in, st... );
+      }
+
+      template< typename Input, typename State, typename... States >
+      static void raise( const Input& in, State&& /*unused*/, States&&... st )
+      {
+         Control< Rule >::raise( in, st... );
+      }
+
+      template< template< typename... > class Action,
+                typename Iterator,
+                typename Input,
+                typename State,
+                typename... States >
+      static auto apply( const Iterator& begin, const Input& in, State&& /*unused*/, States&&... st ) noexcept( noexcept( Control< Rule >::template apply< Action >( begin, in, st... ) ) )
+         -> decltype( Control< Rule >::template apply< Action >( begin, in, st... ) )
+      {
+         return Control< Rule >::template apply< Action >( begin, in, st... );
+      }
+
+      template< template< typename... > class Action,
+                typename Input,
+                typename State,
+                typename... States >
+      static auto apply0( const Input& in, State&& /*unused*/, States&&... st ) noexcept( noexcept( Control< Rule >::template apply0< Action >( in, st... ) ) )
+         -> decltype( Control< Rule >::template apply0< Action >( in, st... ) )
+      {
+         return Control< Rule >::template apply0< Action >( in, st... );
+      }
+   };
+
+   template< typename Rule, template< typename... > class Control >
+   struct remove_self_and_first_state
+      : Control< Rule >
+   {
+      template< apply_mode A,
+                rewind_mode M,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class,
+                typename Input,
+                typename State,
+                typename... States >
+      [[nodiscard]] static bool match( Input& in, State&& /*unused*/, States&&... st )
+      {
+         return Control< Rule >::template match< A, M, Action, Control >( in, st... );
+      }
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/rep_one_min_max.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/rep_one_min_max.hpp
new file mode 100644
index 000000000000..8d7e6b4ecd2c
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/rep_one_min_max.hpp
@@ -0,0 +1,62 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_CONTRIB_REP_ONE_MIN_MAX_HPP
+#define TAO_JSON_PEGTL_CONTRIB_REP_ONE_MIN_MAX_HPP
+
+#include <algorithm>
+
+#include "../config.hpp"
+
+#include "../analysis/counted.hpp"
+
+#include "../internal/bump_help.hpp"
+#include "../internal/skip_control.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE
+{
+   namespace internal
+   {
+      template< unsigned Min, unsigned Max, char C >
+      struct rep_one_min_max
+      {
+         using analyze_t = analysis::counted< analysis::rule_type::any, Min >;
+
+         static_assert( Min <= Max );
+
+         template< typename Input >
+         [[nodiscard]] static bool match( Input& in )
+         {
+            const auto size = in.size( Max + 1 );
+            if( size < Min ) {
+               return false;
+            }
+            std::size_t i = 0;
+            while( ( i < size ) && ( in.peek_char( i ) == C ) ) {
+               ++i;
+            }
+            if( ( Min <= i ) && ( i <= Max ) ) {
+               bump_help< result_on_found::success, Input, char, C >( in, i );
+               return true;
+            }
+            return false;
+         }
+      };
+
+      template< unsigned Min, unsigned Max, char C >
+      inline constexpr bool skip_control< rep_one_min_max< Min, Max, C > > = true;
+
+   }  // namespace internal
+
+   inline namespace ascii
+   {
+      template< unsigned Min, unsigned Max, char C >
+      struct rep_one_min_max : internal::rep_one_min_max< Min, Max, C >
+      {
+      };
+
+   }  // namespace ascii
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/rep_string.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/rep_string.hpp
new file mode 100644
index 000000000000..74525ca5e17e
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/rep_string.hpp
@@ -0,0 +1,44 @@
+// Copyright (c) 2019-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_CONTRIB_REP_STRING_HPP
+#define TAO_JSON_PEGTL_CONTRIB_REP_STRING_HPP
+
+#include <cstddef>
+
+#include "../config.hpp"
+#include "../internal/string.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE
+{
+   namespace internal
+   {
+      template< std::size_t, typename, char... >
+      struct make_rep_string;
+
+      template< char... Ss, char... Cs >
+      struct make_rep_string< 0, string< Ss... >, Cs... >
+      {
+         using type = string< Ss... >;
+      };
+
+      template< std::size_t N, char... Ss, char... Cs >
+      struct make_rep_string< N, string< Ss... >, Cs... >
+         : make_rep_string< N - 1, string< Ss..., Cs... >, Cs... >
+      {
+      };
+
+   }  // namespace internal
+
+   inline namespace ascii
+   {
+      template< std::size_t N, char... Cs >
+      struct rep_string
+         : internal::make_rep_string< N, internal::string<>, Cs... >::type
+      {};
+
+   }  // namespace ascii
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/to_string.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/to_string.hpp
new file mode 100644
index 000000000000..3835d4e12d6f
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/to_string.hpp
@@ -0,0 +1,38 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_CONTRIB_TO_STRING_HPP
+#define TAO_JSON_PEGTL_CONTRIB_TO_STRING_HPP
+
+#include <string>
+
+#include "../config.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE
+{
+   namespace internal
+   {
+      template< typename >
+      struct to_string;
+
+      template< template< char... > class X, char... Cs >
+      struct to_string< X< Cs... > >
+      {
+         [[nodiscard]] static std::string get()
+         {
+            const char s[] = { Cs..., 0 };
+            return std::string( s, sizeof...( Cs ) );
+         }
+      };
+
+   }  // namespace internal
+
+   template< typename T >
+   [[nodiscard]] std::string to_string()
+   {
+      return internal::to_string< T >::get();
+   }
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/tracer.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/tracer.hpp
new file mode 100644
index 000000000000..56faeba97c78
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/tracer.hpp
@@ -0,0 +1,158 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_CONTRIB_TRACER_HPP
+#define TAO_JSON_PEGTL_CONTRIB_TRACER_HPP
+
+#include <cassert>
+#include <iomanip>
+#include <iostream>
+#include <utility>
+#include <vector>
+
+#include "../config.hpp"
+#include "../normal.hpp"
+
+#include "../internal/demangle.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE
+{
+   namespace internal
+   {
+      template< typename Input >
+      void print_current( const Input& in )
+      {
+         if( in.empty() ) {
+            std::cerr << "<eof>";
+         }
+         else {
+            const auto c = in.peek_uint8();
+            switch( c ) {
+               case 0:
+                  std::cerr << "<nul> = ";
+                  break;
+               case 9:
+                  std::cerr << "<ht> = ";
+                  break;
+               case 10:
+                  std::cerr << "<lf> = ";
+                  break;
+               case 13:
+                  std::cerr << "<cr> = ";
+                  break;
+               default:
+                  if( isprint( c ) ) {
+                     std::cerr << '\'' << c << "' = ";
+                  }
+            }
+            std::cerr << "(char)" << unsigned( c );
+         }
+      }
+
+   }  // namespace internal
+
+   struct trace_state
+   {
+      unsigned rule = 0;
+      unsigned line = 0;
+      std::vector< unsigned > stack;
+   };
+
+   template< template< typename... > class Base >
+   struct trace
+   {
+      template< typename Rule >
+      struct control
+         : Base< Rule >
+      {
+         template< typename Input, typename... States >
+         static void start( const Input& in, States&&... st )
+         {
+            std::cerr << in.position() << "  start  " << internal::demangle< Rule >() << "; current ";
+            print_current( in );
+            std::cerr << std::endl;
+            Base< Rule >::start( in, st... );
+         }
+
+         template< typename Input, typename... States >
+         static void start( const Input& in, trace_state& ts, States&&... st )
+         {
+            std::cerr << std::setw( 6 ) << ++ts.line << " " << std::setw( 6 ) << ++ts.rule << " ";
+            start( in, st... );
+            ts.stack.push_back( ts.rule );
+         }
+
+         template< typename Input, typename... States >
+         static void success( const Input& in, States&&... st )
+         {
+            std::cerr << in.position() << " success " << internal::demangle< Rule >() << "; next ";
+            print_current( in );
+            std::cerr << std::endl;
+            Base< Rule >::success( in, st... );
+         }
+
+         template< typename Input, typename... States >
+         static void success( const Input& in, trace_state& ts, States&&... st )
+         {
+            assert( !ts.stack.empty() );
+            std::cerr << std::setw( 6 ) << ++ts.line << " " << std::setw( 6 ) << ts.stack.back() << " ";
+            success( in, st... );
+            ts.stack.pop_back();
+         }
+
+         template< typename Input, typename... States >
+         static void failure( const Input& in, States&&... st )
+         {
+            std::cerr << in.position() << " failure " << internal::demangle< Rule >() << std::endl;
+            Base< Rule >::failure( in, st... );
+         }
+
+         template< typename Input, typename... States >
+         static void failure( const Input& in, trace_state& ts, States&&... st )
+         {
+            assert( !ts.stack.empty() );
+            std::cerr << std::setw( 6 ) << ++ts.line << " " << std::setw( 6 ) << ts.stack.back() << " ";
+            failure( in, st... );
+            ts.stack.pop_back();
+         }
+
+         template< template< typename... > class Action, typename Iterator, typename Input, typename... States >
+         static auto apply( const Iterator& begin, const Input& in, States&&... st )
+            -> decltype( Base< Rule >::template apply< Action >( begin, in, st... ) )
+         {
+            std::cerr << in.position() << "  apply  " << internal::demangle< Rule >() << std::endl;
+            return Base< Rule >::template apply< Action >( begin, in, st... );
+         }
+
+         template< template< typename... > class Action, typename Iterator, typename Input, typename... States >
+         static auto apply( const Iterator& begin, const Input& in, trace_state& ts, States&&... st )
+            -> decltype( apply< Action >( begin, in, st... ) )
+         {
+            std::cerr << std::setw( 6 ) << ++ts.line << "        ";
+            return apply< Action >( begin, in, st... );
+         }
+
+         template< template< typename... > class Action, typename Input, typename... States >
+         static auto apply0( const Input& in, States&&... st )
+            -> decltype( Base< Rule >::template apply0< Action >( in, st... ) )
+         {
+            std::cerr << in.position() << "  apply0 " << internal::demangle< Rule >() << std::endl;
+            return Base< Rule >::template apply0< Action >( in, st... );
+         }
+
+         template< template< typename... > class Action, typename Input, typename... States >
+         static auto apply0( const Input& in, trace_state& ts, States&&... st )
+            -> decltype( apply0< Action >( in, st... ) )
+         {
+            std::cerr << std::setw( 6 ) << ++ts.line << "        ";
+            return apply0< Action >( in, st... );
+         }
+      };
+   };
+
+   template< typename Rule >
+   using tracer = trace< normal >::control< Rule >;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/unescape.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/unescape.hpp
new file mode 100644
index 000000000000..76abe5e73bb9
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/unescape.hpp
@@ -0,0 +1,199 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_CONTRIB_UNESCAPE_HPP
+#define TAO_JSON_PEGTL_CONTRIB_UNESCAPE_HPP
+
+#include <cassert>
+#include <string>
+
+#include "../ascii.hpp"
+#include "../config.hpp"
+#include "../parse_error.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::unescape
+{
+   // Utility functions for the unescape actions.
+
+   [[nodiscard]] inline bool utf8_append_utf32( std::string& string, const unsigned utf32 )
+   {
+      if( utf32 <= 0x7f ) {
+         string += char( utf32 & 0xff );
+         return true;
+      }
+      if( utf32 <= 0x7ff ) {
+         char tmp[] = { char( ( ( utf32 & 0x7c0 ) >> 6 ) | 0xc0 ),
+                        char( ( ( utf32 & 0x03f ) ) | 0x80 ) };
+         string.append( tmp, sizeof( tmp ) );
+         return true;
+      }
+      if( utf32 <= 0xffff ) {
+         if( utf32 >= 0xd800 && utf32 <= 0xdfff ) {
+            // nope, this is a UTF-16 surrogate
+            return false;
+         }
+         char tmp[] = { char( ( ( utf32 & 0xf000 ) >> 12 ) | 0xe0 ),
+                        char( ( ( utf32 & 0x0fc0 ) >> 6 ) | 0x80 ),
+                        char( ( ( utf32 & 0x003f ) ) | 0x80 ) };
+         string.append( tmp, sizeof( tmp ) );
+         return true;
+      }
+      if( utf32 <= 0x10ffff ) {
+         char tmp[] = { char( ( ( utf32 & 0x1c0000 ) >> 18 ) | 0xf0 ),
+                        char( ( ( utf32 & 0x03f000 ) >> 12 ) | 0x80 ),
+                        char( ( ( utf32 & 0x000fc0 ) >> 6 ) | 0x80 ),
+                        char( ( ( utf32 & 0x00003f ) ) | 0x80 ) };
+         string.append( tmp, sizeof( tmp ) );
+         return true;
+      }
+      return false;
+   }
+
+   // This function MUST only be called for characters matching TAO_JSON_PEGTL_NAMESPACE::ascii::xdigit!
+   template< typename I >
+   [[nodiscard]] I unhex_char( const char c )
+   {
+      switch( c ) {
+         case '0':
+         case '1':
+         case '2':
+         case '3':
+         case '4':
+         case '5':
+         case '6':
+         case '7':
+         case '8':
+         case '9':
+            return I( c - '0' );
+         case 'a':
+         case 'b':
+         case 'c':
+         case 'd':
+         case 'e':
+         case 'f':
+            return I( c - 'a' + 10 );
+         case 'A':
+         case 'B':
+         case 'C':
+         case 'D':
+         case 'E':
+         case 'F':
+            return I( c - 'A' + 10 );
+         default:                                                      // LCOV_EXCL_LINE
+            throw std::runtime_error( "invalid character in unhex" );  // LCOV_EXCL_LINE
+      }
+   }
+
+   template< typename I >
+   [[nodiscard]] I unhex_string( const char* begin, const char* end )
+   {
+      I r = 0;
+      while( begin != end ) {
+         r <<= 4;
+         r += unhex_char< I >( *begin++ );
+      }
+      return r;
+   }
+
+   // Actions for common unescape situations.
+
+   struct append_all
+   {
+      template< typename Input >
+      static void apply( const Input& in, std::string& s )
+      {
+         s.append( in.begin(), in.size() );
+      }
+   };
+
+   // This action MUST be called for a character matching T which MUST be TAO_JSON_PEGTL_NAMESPACE::one< ... >.
+   template< typename T, char... Rs >
+   struct unescape_c
+   {
+      template< typename Input >
+      static void apply( const Input& in, std::string& s )
+      {
+         assert( in.size() == 1 );
+         s += apply_one( in, static_cast< const T* >( nullptr ) );
+      }
+
+      template< typename Input, char... Qs >
+      [[nodiscard]] static char apply_one( const Input& in, const one< Qs... >* /*unused*/ )
+      {
+         static_assert( sizeof...( Qs ) == sizeof...( Rs ), "size mismatch between escaped characters and their mappings" );
+         return apply_two( in, { Qs... }, { Rs... } );
+      }
+
+      template< typename Input >
+      [[nodiscard]] static char apply_two( const Input& in, const std::initializer_list< char >& q, const std::initializer_list< char >& r )
+      {
+         const char c = *in.begin();
+         for( std::size_t i = 0; i < q.size(); ++i ) {
+            if( *( q.begin() + i ) == c ) {
+               return *( r.begin() + i );
+            }
+         }
+         throw parse_error( "invalid character in unescape", in );  // LCOV_EXCL_LINE
+      }
+   };
+
+   // See src/example/pegtl/unescape.cpp for why the following two actions
+   // skip the first input character. They also MUST be called
+   // with non-empty matched inputs!
+
+   struct unescape_u
+   {
+      template< typename Input >
+      static void apply( const Input& in, std::string& s )
+      {
+         assert( !in.empty() );  // First character MUST be present, usually 'u' or 'U'.
+         if( !utf8_append_utf32( s, unhex_string< unsigned >( in.begin() + 1, in.end() ) ) ) {
+            throw parse_error( "invalid escaped unicode code point", in );
+         }
+      }
+   };
+
+   struct unescape_x
+   {
+      template< typename Input >
+      static void apply( const Input& in, std::string& s )
+      {
+         assert( !in.empty() );  // First character MUST be present, usually 'x'.
+         s += unhex_string< char >( in.begin() + 1, in.end() );
+      }
+   };
+
+   // The unescape_j action is similar to unescape_u, however unlike
+   // unescape_u it
+   // (a) assumes exactly 4 hexdigits per escape sequence,
+   // (b) accepts multiple consecutive escaped 16-bit values.
+   // When applied to more than one escape sequence, unescape_j
+   // translates UTF-16 surrogate pairs in the input into a single
+   // UTF-8 sequence in s, as required for JSON by RFC 8259.
+
+   struct unescape_j
+   {
+      template< typename Input >
+      static void apply( const Input& in, std::string& s )
+      {
+         assert( ( ( in.size() + 1 ) % 6 ) == 0 );  // Expects multiple "\\u1234", starting with the first "u".
+         for( const char* b = in.begin() + 1; b < in.end(); b += 6 ) {
+            const auto c = unhex_string< unsigned >( b, b + 4 );
+            if( ( 0xd800 <= c ) && ( c <= 0xdbff ) && ( b + 6 < in.end() ) ) {
+               const auto d = unhex_string< unsigned >( b + 6, b + 10 );
+               if( ( 0xdc00 <= d ) && ( d <= 0xdfff ) ) {
+                  b += 6;
+                  (void)utf8_append_utf32( s, ( ( ( c & 0x03ff ) << 10 ) | ( d & 0x03ff ) ) + 0x10000 );
+                  continue;
+               }
+            }
+            if( !utf8_append_utf32( s, c ) ) {
+               throw parse_error( "invalid escaped unicode code point", in );
+            }
+         }
+      }
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::unescape
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/uri.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/uri.hpp
new file mode 100644
index 000000000000..4a0700b68e8f
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/contrib/uri.hpp
@@ -0,0 +1,106 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_CONTRIB_URI_HPP
+#define TAO_JSON_PEGTL_CONTRIB_URI_HPP
+
+#include <cstdint>
+
+#include "../ascii.hpp"
+#include "../config.hpp"
+#include "../rules.hpp"
+#include "../utf8.hpp"
+
+#include "abnf.hpp"
+#include "integer.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::uri
+{
+   // URI grammar according to RFC 3986.
+
+   // This grammar is a direct PEG translation of the original URI grammar.
+   // It should be considered experimental -- in case of any issues, in particular
+   // missing rules for attached actions, please contact the developers.
+
+   // Note that this grammar has multiple top-level rules.
+
+   using dot = one< '.' >;
+   using colon = one< ':' >;
+
+   // clang-format off
+   struct dec_octet : integer::maximum_rule< std::uint8_t > {};
+
+   struct IPv4address : seq< dec_octet, dot, dec_octet, dot, dec_octet, dot, dec_octet > {};
+
+   struct h16 : rep_min_max< 1, 4, abnf::HEXDIG > {};
+   struct ls32 : sor< seq< h16, colon, h16 >, IPv4address > {};
+
+   struct dcolon : two< ':' > {};
+
+   struct IPv6address : sor< seq<                                               rep< 6, h16, colon >, ls32 >,
+                             seq<                                       dcolon, rep< 5, h16, colon >, ls32 >,
+                             seq< opt< h16                           >, dcolon, rep< 4, h16, colon >, ls32 >,
+                             seq< opt< h16,     opt<    colon, h16 > >, dcolon, rep< 3, h16, colon >, ls32 >,
+                             seq< opt< h16, rep_opt< 2, colon, h16 > >, dcolon, rep< 2, h16, colon >, ls32 >,
+                             seq< opt< h16, rep_opt< 3, colon, h16 > >, dcolon,         h16, colon,   ls32 >,
+                             seq< opt< h16, rep_opt< 4, colon, h16 > >, dcolon,                       ls32 >,
+                             seq< opt< h16, rep_opt< 5, colon, h16 > >, dcolon,                       h16  >,
+                             seq< opt< h16, rep_opt< 6, colon, h16 > >, dcolon                             > > {};
+
+   struct gen_delims : one< ':', '/', '?', '#', '[', ']', '@' > {};
+   struct sub_delims : one< '!', '$', '&', '\'', '(', ')', '*', '+', ',', ';', '=' > {};
+
+   struct unreserved : sor< abnf::ALPHA, abnf::DIGIT, one< '-', '.', '_', '~' > > {};
+   struct reserved : sor< gen_delims, sub_delims > {};
+
+   struct IPvFuture : if_must< one< 'v', 'V' >, plus< abnf::HEXDIG >, dot, plus< sor< unreserved, sub_delims, colon > > > {};
+
+   struct IP_literal : if_must< one< '[' >, sor< IPvFuture, IPv6address >, one< ']' > > {};
+
+   struct pct_encoded : if_must< one< '%' >, abnf::HEXDIG, abnf::HEXDIG > {};
+   struct pchar : sor< unreserved, pct_encoded, sub_delims, one< ':', '@' > > {};
+
+   struct query : star< sor< pchar, one< '/', '?' > > > {};
+   struct fragment : star< sor< pchar, one< '/', '?' > > > {};
+
+   struct segment : star< pchar > {};
+   struct segment_nz : plus< pchar > {};
+   struct segment_nz_nc : plus< sor< unreserved, pct_encoded, sub_delims, one< '@' > > > {}; // non-zero-length segment without any colon ":"
+
+   struct path_abempty : star< one< '/' >, segment > {};
+   struct path_absolute : seq< one< '/' >, opt< segment_nz, star< one< '/' >, segment > > > {};
+   struct path_noscheme : seq< segment_nz_nc, star< one< '/' >, segment > > {};
+   struct path_rootless : seq< segment_nz, star< one< '/' >, segment > > {};
+   struct path_empty : success {};
+
+   struct path : sor< path_noscheme,     // begins with a non-colon segment
+                      path_rootless,     // begins with a segment
+                      path_absolute,     // begins with "/" but not "//"
+                      path_abempty > {}; // begins with "/" or is empty
+
+   struct reg_name : star< sor< unreserved, pct_encoded, sub_delims > > {};
+
+   struct port : star< abnf::DIGIT > {};
+   struct host : sor< IP_literal, IPv4address, reg_name > {};
+   struct userinfo : star< sor< unreserved, pct_encoded, sub_delims, colon > > {};
+   struct opt_userinfo : opt< userinfo, one< '@' > > {};
+   struct authority : seq< opt_userinfo, host, opt< colon, port > > {};
+
+   struct scheme : seq< abnf::ALPHA, star< sor< abnf::ALPHA, abnf::DIGIT, one< '+', '-', '.' > > > > {};
+
+   using dslash = two< '/' >;
+   using opt_query = opt_must< one< '?' >, query >;
+   using opt_fragment = opt_must< one< '#' >, fragment >;
+
+   struct hier_part : sor< if_must< dslash, authority, path_abempty >, path_rootless, path_absolute, path_empty > {};
+   struct relative_part : sor< if_must< dslash, authority, path_abempty >, path_noscheme, path_absolute, path_empty > {};
+   struct relative_ref : seq< relative_part, opt_query, opt_fragment > {};
+
+   struct URI : seq< scheme, one< ':' >, hier_part, opt_query, opt_fragment > {};
+   struct URI_reference : sor< URI, relative_ref > {};
+   struct absolute_URI : seq< scheme, one< ':' >, hier_part, opt_query > {};
+   // clang-format on
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::uri
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/cstream_input.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/cstream_input.hpp
new file mode 100644
index 000000000000..f330f08e9c0b
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/cstream_input.hpp
@@ -0,0 +1,33 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_CSTREAM_INPUT_HPP
+#define TAO_JSON_PEGTL_CSTREAM_INPUT_HPP
+
+#include <cstdio>
+
+#include "buffer_input.hpp"
+#include "config.hpp"
+#include "eol.hpp"
+
+#include "internal/cstream_reader.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE
+{
+   template< typename Eol = eol::lf_crlf, std::size_t Chunk = 64 >
+   struct cstream_input
+      : buffer_input< internal::cstream_reader, Eol, std::string, Chunk >
+   {
+      template< typename T >
+      cstream_input( std::FILE* in_stream, const std::size_t in_maximum, T&& in_source )
+         : buffer_input< internal::cstream_reader, Eol, std::string, Chunk >( std::forward< T >( in_source ), in_maximum, in_stream )
+      {
+      }
+   };
+
+   template< typename... Ts >
+   cstream_input( Ts&&... )->cstream_input<>;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/disable_action.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/disable_action.hpp
new file mode 100644
index 000000000000..c7dad5bbe3eb
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/disable_action.hpp
@@ -0,0 +1,35 @@
+// Copyright (c) 2019-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_DISABLE_ACTION_HPP
+#define TAO_JSON_PEGTL_DISABLE_ACTION_HPP
+
+#include "apply_mode.hpp"
+#include "config.hpp"
+#include "match.hpp"
+#include "nothing.hpp"
+#include "rewind_mode.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE
+{
+   struct disable_action
+      : maybe_nothing
+   {
+      template< typename Rule,
+                apply_mode A,
+                rewind_mode M,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class Control,
+                typename Input,
+                typename... States >
+      [[nodiscard]] static bool match( Input& in, States&&... st )
+      {
+         return TAO_JSON_PEGTL_NAMESPACE::match< Rule, apply_mode::nothing, M, Action, Control >( in, st... );
+      }
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/discard_input.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/discard_input.hpp
new file mode 100644
index 000000000000..ccb205c0ddac
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/discard_input.hpp
@@ -0,0 +1,37 @@
+// Copyright (c) 2019-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_DISCARD_INPUT_HPP
+#define TAO_JSON_PEGTL_DISCARD_INPUT_HPP
+
+#include "apply_mode.hpp"
+#include "config.hpp"
+#include "match.hpp"
+#include "nothing.hpp"
+#include "rewind_mode.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE
+{
+   struct discard_input
+      : maybe_nothing
+   {
+      template< typename Rule,
+                apply_mode A,
+                rewind_mode M,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class Control,
+                typename Input,
+                typename... States >
+      [[nodiscard]] static bool match( Input& in, States&&... st )
+      {
+         const bool result = TAO_JSON_PEGTL_NAMESPACE::match< Rule, A, M, Action, Control >( in, st... );
+         in.discard();
+         return result;
+      }
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/discard_input_on_failure.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/discard_input_on_failure.hpp
new file mode 100644
index 000000000000..11c5f9c9aa3c
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/discard_input_on_failure.hpp
@@ -0,0 +1,39 @@
+// Copyright (c) 2019-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_DISCARD_INPUT_ON_FAILURE_HPP
+#define TAO_JSON_PEGTL_DISCARD_INPUT_ON_FAILURE_HPP
+
+#include "apply_mode.hpp"
+#include "config.hpp"
+#include "match.hpp"
+#include "nothing.hpp"
+#include "rewind_mode.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE
+{
+   struct discard_input_on_failure
+      : maybe_nothing
+   {
+      template< typename Rule,
+                apply_mode A,
+                rewind_mode M,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class Control,
+                typename Input,
+                typename... States >
+      [[nodiscard]] static bool match( Input& in, States&&... st )
+      {
+         const bool result = TAO_JSON_PEGTL_NAMESPACE::match< Rule, A, M, Action, Control >( in, st... );
+         if( !result ) {
+            in.discard();
+         }
+         return result;
+      }
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/discard_input_on_success.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/discard_input_on_success.hpp
new file mode 100644
index 000000000000..cb00f5d9da0d
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/discard_input_on_success.hpp
@@ -0,0 +1,39 @@
+// Copyright (c) 2019-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_DISCARD_INPUT_ON_SUCCESS_HPP
+#define TAO_JSON_PEGTL_DISCARD_INPUT_ON_SUCCESS_HPP
+
+#include "apply_mode.hpp"
+#include "config.hpp"
+#include "match.hpp"
+#include "nothing.hpp"
+#include "rewind_mode.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE
+{
+   struct discard_input_on_success
+      : maybe_nothing
+   {
+      template< typename Rule,
+                apply_mode A,
+                rewind_mode M,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class Control,
+                typename Input,
+                typename... States >
+      [[nodiscard]] static bool match( Input& in, States&&... st )
+      {
+         const bool result = TAO_JSON_PEGTL_NAMESPACE::match< Rule, A, M, Action, Control >( in, st... );
+         if( result ) {
+            in.discard();
+         }
+         return result;
+      }
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/enable_action.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/enable_action.hpp
new file mode 100644
index 000000000000..7513498184f2
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/enable_action.hpp
@@ -0,0 +1,35 @@
+// Copyright (c) 2019-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_ENABLE_ACTION_HPP
+#define TAO_JSON_PEGTL_ENABLE_ACTION_HPP
+
+#include "apply_mode.hpp"
+#include "config.hpp"
+#include "match.hpp"
+#include "nothing.hpp"
+#include "rewind_mode.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE
+{
+   struct enable_action
+      : maybe_nothing
+   {
+      template< typename Rule,
+                apply_mode A,
+                rewind_mode M,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class Control,
+                typename Input,
+                typename... States >
+      [[nodiscard]] static bool match( Input& in, States&&... st )
+      {
+         return TAO_JSON_PEGTL_NAMESPACE::match< Rule, apply_mode::action, M, Action, Control >( in, st... );
+      }
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/eol.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/eol.hpp
new file mode 100644
index 000000000000..c69ded1bc140
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/eol.hpp
@@ -0,0 +1,37 @@
+// Copyright (c) 2016-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_EOL_HPP
+#define TAO_JSON_PEGTL_EOL_HPP
+
+#include "config.hpp"
+
+#include "internal/eol.hpp"
+
+#include "internal/cr_crlf_eol.hpp"
+#include "internal/cr_eol.hpp"
+#include "internal/crlf_eol.hpp"
+#include "internal/lf_crlf_eol.hpp"
+#include "internal/lf_eol.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE
+{
+   inline namespace ascii
+   {
+      // this is both a rule and a pseudo-namespace for eol::cr, ...
+      struct eol : internal::eol
+      {
+         // clang-format off
+         struct cr : internal::cr_eol {};
+         struct cr_crlf : internal::cr_crlf_eol {};
+         struct crlf : internal::crlf_eol {};
+         struct lf : internal::lf_eol {};
+         struct lf_crlf : internal::lf_crlf_eol {};
+         // clang-format on
+      };
+
+   }  // namespace ascii
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/eol_pair.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/eol_pair.hpp
new file mode 100644
index 000000000000..97e3f90408b5
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/eol_pair.hpp
@@ -0,0 +1,18 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_EOL_PAIR_HPP
+#define TAO_JSON_PEGTL_EOL_PAIR_HPP
+
+#include <cstddef>
+#include <utility>
+
+#include "config.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE
+{
+   using eol_pair = std::pair< bool, std::size_t >;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/file_input.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/file_input.hpp
new file mode 100644
index 000000000000..2543e412e4c9
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/file_input.hpp
@@ -0,0 +1,44 @@
+// Copyright (c) 2015-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_FILE_INPUT_HPP
+#define TAO_JSON_PEGTL_FILE_INPUT_HPP
+
+#include "config.hpp"
+#include "eol.hpp"
+#include "tracking_mode.hpp"
+
+#if defined( __unix__ ) || ( defined( __APPLE__ ) && defined( __MACH__ ) )
+#include <unistd.h>  // Required for _POSIX_MAPPED_FILES
+#endif
+
+#if defined( _POSIX_MAPPED_FILES ) || defined( _WIN32 )
+#include "mmap_input.hpp"
+#else
+#include "read_input.hpp"
+#endif
+
+namespace TAO_JSON_PEGTL_NAMESPACE
+{
+#if defined( _POSIX_MAPPED_FILES ) || defined( _WIN32 )
+   template< tracking_mode P = tracking_mode::eager, typename Eol = eol::lf_crlf >
+   struct file_input
+      : mmap_input< P, Eol >
+   {
+      using mmap_input< P, Eol >::mmap_input;
+   };
+#else
+   template< tracking_mode P = tracking_mode::eager, typename Eol = eol::lf_crlf >
+   struct file_input
+      : read_input< P, Eol >
+   {
+      using read_input< P, Eol >::read_input;
+   };
+#endif
+
+   template< typename... Ts >
+   explicit file_input( Ts&&... )->file_input<>;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/action.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/action.hpp
new file mode 100644
index 000000000000..6f3a6c9415de
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/action.hpp
@@ -0,0 +1,44 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_ACTION_HPP
+#define TAO_JSON_PEGTL_INTERNAL_ACTION_HPP
+
+#include "../config.hpp"
+
+#include "duseltronik.hpp"
+#include "seq.hpp"
+#include "skip_control.hpp"
+
+#include "../apply_mode.hpp"
+#include "../rewind_mode.hpp"
+
+#include "../analysis/generic.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< template< typename... > class Action, typename... Rules >
+   struct action
+   {
+      using analyze_t = analysis::generic< analysis::rule_type::seq, Rules... >;
+
+      template< apply_mode A,
+                rewind_mode M,
+                template< typename... >
+                class,
+                template< typename... >
+                class Control,
+                typename Input,
+                typename... States >
+      [[nodiscard]] static bool match( Input& in, States&&... st )
+      {
+         return duseltronik< seq< Rules... >, A, M, Action, Control >::match( in, st... );
+      }
+   };
+
+   template< template< typename... > class Action, typename... Rules >
+   inline constexpr bool skip_control< action< Action, Rules... > > = true;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/action_input.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/action_input.hpp
new file mode 100644
index 000000000000..d4efaac40787
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/action_input.hpp
@@ -0,0 +1,107 @@
+// Copyright (c) 2016-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_ACTION_INPUT_HPP
+#define TAO_JSON_PEGTL_INTERNAL_ACTION_INPUT_HPP
+
+#include <cstddef>
+#include <cstdint>
+#include <string>
+#include <string_view>
+
+#include "iterator.hpp"
+
+#include "../config.hpp"
+#include "../position.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< typename Input >
+   class action_input
+   {
+   public:
+      using input_t = Input;
+      using iterator_t = typename Input::iterator_t;
+
+      action_input( const iterator_t& in_begin, const Input& in_input ) noexcept
+         : m_begin( in_begin ),
+           m_input( in_input )
+      {
+      }
+
+      action_input( const action_input& ) = delete;
+      action_input( action_input&& ) = delete;
+
+      ~action_input() = default;
+
+      action_input& operator=( const action_input& ) = delete;
+      action_input& operator=( action_input&& ) = delete;
+
+      [[nodiscard]] const iterator_t& iterator() const noexcept
+      {
+         return m_begin;
+      }
+
+      [[nodiscard]] const Input& input() const noexcept
+      {
+         return m_input;
+      }
+
+      [[nodiscard]] const char* begin() const noexcept
+      {
+         if constexpr( std::is_same_v< iterator_t, const char* > ) {
+            return iterator();
+         }
+         else {
+            return iterator().data;
+         }
+      }
+
+      [[nodiscard]] const char* end() const noexcept
+      {
+         return input().current();
+      }
+
+      [[nodiscard]] bool empty() const noexcept
+      {
+         return begin() == end();
+      }
+
+      [[nodiscard]] std::size_t size() const noexcept
+      {
+         return std::size_t( end() - begin() );
+      }
+
+      [[nodiscard]] std::string string() const
+      {
+         return std::string( begin(), size() );
+      }
+
+      [[nodiscard]] std::string_view string_view() const noexcept
+      {
+         return std::string_view( begin(), size() );
+      }
+
+      [[nodiscard]] char peek_char( const std::size_t offset = 0 ) const noexcept
+      {
+         return begin()[ offset ];
+      }
+
+      [[nodiscard]] std::uint8_t peek_uint8( const std::size_t offset = 0 ) const noexcept
+      {
+         return static_cast< std::uint8_t >( peek_char( offset ) );
+      }
+
+      [[nodiscard]] TAO_JSON_PEGTL_NAMESPACE::position position() const
+      {
+         return input().position( iterator() );  // NOTE: Not efficient with lazy inputs.
+      }
+
+   protected:
+      const iterator_t m_begin;
+      const Input& m_input;
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/alnum.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/alnum.hpp
new file mode 100644
index 000000000000..7a9821ba9f5b
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/alnum.hpp
@@ -0,0 +1,18 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_ALNUM_HPP
+#define TAO_JSON_PEGTL_INTERNAL_ALNUM_HPP
+
+#include "../config.hpp"
+
+#include "peek_char.hpp"
+#include "ranges.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   using alnum = ranges< peek_char, 'a', 'z', 'A', 'Z', '0', '9' >;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/alpha.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/alpha.hpp
new file mode 100644
index 000000000000..fd1020257634
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/alpha.hpp
@@ -0,0 +1,18 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_ALPHA_HPP
+#define TAO_JSON_PEGTL_INTERNAL_ALPHA_HPP
+
+#include "../config.hpp"
+
+#include "peek_char.hpp"
+#include "ranges.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   using alpha = ranges< peek_char, 'a', 'z', 'A', 'Z' >;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/always_false.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/always_false.hpp
new file mode 100644
index 000000000000..0193a46d067f
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/always_false.hpp
@@ -0,0 +1,21 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_ALWAYS_FALSE_HPP
+#define TAO_JSON_PEGTL_INTERNAL_ALWAYS_FALSE_HPP
+
+#include "../config.hpp"
+
+#include <type_traits>
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< typename... >
+   struct always_false
+      : std::false_type
+   {
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/any.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/any.hpp
new file mode 100644
index 000000000000..d817460964c2
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/any.hpp
@@ -0,0 +1,58 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_ANY_HPP
+#define TAO_JSON_PEGTL_INTERNAL_ANY_HPP
+
+#include "../config.hpp"
+
+#include "peek_char.hpp"
+#include "skip_control.hpp"
+
+#include "../analysis/generic.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< typename Peek >
+   struct any;
+
+   template<>
+   struct any< peek_char >
+   {
+      using analyze_t = analysis::generic< analysis::rule_type::any >;
+
+      template< typename Input >
+      [[nodiscard]] static bool match( Input& in ) noexcept( noexcept( in.empty() ) )
+      {
+         if( !in.empty() ) {
+            in.bump();
+            return true;
+         }
+         return false;
+      }
+   };
+
+   template< typename Peek >
+   struct any
+   {
+      using analyze_t = analysis::generic< analysis::rule_type::any >;
+
+      template< typename Input >
+      [[nodiscard]] static bool match( Input& in ) noexcept( noexcept( in.size( Peek::max_input_size ) ) )
+      {
+         if( const std::size_t s = in.size( Peek::max_input_size ); s >= Peek::min_input_size ) {
+            if( const auto t = Peek::peek( in, s ) ) {
+               in.bump( t.size );
+               return true;
+            }
+         }
+         return false;
+      }
+   };
+
+   template< typename Peek >
+   inline constexpr bool skip_control< any< Peek > > = true;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/apply.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/apply.hpp
new file mode 100644
index 000000000000..392bd6c1e133
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/apply.hpp
@@ -0,0 +1,53 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_APPLY_HPP
+#define TAO_JSON_PEGTL_INTERNAL_APPLY_HPP
+
+#include "../config.hpp"
+
+#include "apply_single.hpp"
+#include "skip_control.hpp"
+
+#include "../analysis/counted.hpp"
+#include "../apply_mode.hpp"
+#include "../rewind_mode.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< typename... Actions >
+   struct apply
+   {
+      using analyze_t = analysis::counted< analysis::rule_type::any, 0 >;
+
+      template< apply_mode A,
+                rewind_mode M,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class Control,
+                typename Input,
+                typename... States >
+      [[nodiscard]] static bool match( Input& in, States&&... st )
+      {
+         if constexpr( ( A == apply_mode::action ) && ( sizeof...( Actions ) > 0 ) ) {
+            using action_t = typename Input::action_t;
+            const action_t i2( in.iterator(), in );  // No data -- range is from begin to begin.
+            return ( apply_single< Actions >::match( i2, st... ) && ... );
+         }
+         else {
+#if defined( _MSC_VER )
+            (void)in;
+            (void)( (void)st, ... );
+#endif
+            return true;
+         }
+      }
+   };
+
+   template< typename... Actions >
+   inline constexpr bool skip_control< apply< Actions... > > = true;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/apply0.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/apply0.hpp
new file mode 100644
index 000000000000..37a1eb6cf6e6
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/apply0.hpp
@@ -0,0 +1,50 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_APPLY0_HPP
+#define TAO_JSON_PEGTL_INTERNAL_APPLY0_HPP
+
+#include "../config.hpp"
+
+#include "apply0_single.hpp"
+#include "skip_control.hpp"
+
+#include "../analysis/counted.hpp"
+#include "../apply_mode.hpp"
+#include "../rewind_mode.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< typename... Actions >
+   struct apply0
+   {
+      using analyze_t = analysis::counted< analysis::rule_type::any, 0 >;
+
+      template< apply_mode A,
+                rewind_mode M,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class Control,
+                typename Input,
+                typename... States >
+      [[nodiscard]] static bool match( Input& /*unused*/, States&&... st )
+      {
+         if constexpr( A == apply_mode::action ) {
+            return ( apply0_single< Actions >::match( st... ) && ... );
+         }
+         else {
+#if defined( _MSC_VER )
+            (void)( (void)st, ... );
+#endif
+            return true;
+         }
+      }
+   };
+
+   template< typename... Actions >
+   inline constexpr bool skip_control< apply0< Actions... > > = true;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/apply0_single.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/apply0_single.hpp
new file mode 100644
index 000000000000..3d875bca32b9
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/apply0_single.hpp
@@ -0,0 +1,34 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_APPLY0_SINGLE_HPP
+#define TAO_JSON_PEGTL_INTERNAL_APPLY0_SINGLE_HPP
+
+#include "../config.hpp"
+
+#include <type_traits>
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< typename Action >
+   struct apply0_single
+   {
+      template< typename... States >
+      [[nodiscard]] static auto match( States&&... st ) noexcept( noexcept( Action::apply0( st... ) ) )
+         -> std::enable_if_t< std::is_same_v< decltype( Action::apply0( st... ) ), void >, bool >
+      {
+         Action::apply0( st... );
+         return true;
+      }
+
+      template< typename... States >
+      [[nodiscard]] static auto match( States&&... st ) noexcept( noexcept( Action::apply0( st... ) ) )
+         -> std::enable_if_t< std::is_same_v< decltype( Action::apply0( st... ) ), bool >, bool >
+      {
+         return Action::apply0( st... );
+      }
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/apply_single.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/apply_single.hpp
new file mode 100644
index 000000000000..f3f1a4839e83
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/apply_single.hpp
@@ -0,0 +1,34 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_APPLY_SINGLE_HPP
+#define TAO_JSON_PEGTL_INTERNAL_APPLY_SINGLE_HPP
+
+#include "../config.hpp"
+
+#include <type_traits>
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< typename Action >
+   struct apply_single
+   {
+      template< typename Input, typename... States >
+      [[nodiscard]] static auto match( const Input& in, States&&... st ) noexcept( noexcept( Action::apply( in, st... ) ) )
+         -> std::enable_if_t< std::is_same_v< decltype( Action::apply( in, st... ) ), void >, bool >
+      {
+         Action::apply( in, st... );
+         return true;
+      }
+
+      template< typename Input, typename... States >
+      [[nodiscard]] static auto match( const Input& in, States&&... st ) noexcept( noexcept( Action::apply( in, st... ) ) )
+         -> std::enable_if_t< std::is_same_v< decltype( Action::apply( in, st... ) ), bool >, bool >
+      {
+         return Action::apply( in, st... );
+      }
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/at.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/at.hpp
new file mode 100644
index 000000000000..9fbe045e90f0
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/at.hpp
@@ -0,0 +1,53 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_AT_HPP
+#define TAO_JSON_PEGTL_INTERNAL_AT_HPP
+
+#include "../config.hpp"
+
+#include "skip_control.hpp"
+#include "trivial.hpp"
+
+#include "../apply_mode.hpp"
+#include "../rewind_mode.hpp"
+
+#include "../analysis/generic.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< typename... Rules >
+   struct at;
+
+   template<>
+   struct at<>
+      : trivial< true >
+   {
+   };
+
+   template< typename... Rules >
+   struct at
+   {
+      using analyze_t = analysis::generic< analysis::rule_type::opt, Rules... >;
+
+      template< apply_mode,
+                rewind_mode,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class Control,
+                typename Input,
+                typename... States >
+      [[nodiscard]] static bool match( Input& in, States&&... st )
+      {
+         const auto m = in.template mark< rewind_mode::required >();
+         return ( Control< Rules >::template match< apply_mode::nothing, rewind_mode::active, Action, Control >( in, st... ) && ... );
+      }
+   };
+
+   template< typename... Rules >
+   inline constexpr bool skip_control< at< Rules... > > = true;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/bof.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/bof.hpp
new file mode 100644
index 000000000000..2b868709888e
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/bof.hpp
@@ -0,0 +1,31 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_BOF_HPP
+#define TAO_JSON_PEGTL_INTERNAL_BOF_HPP
+
+#include "../config.hpp"
+
+#include "skip_control.hpp"
+
+#include "../analysis/generic.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   struct bof
+   {
+      using analyze_t = analysis::generic< analysis::rule_type::opt >;
+
+      template< typename Input >
+      [[nodiscard]] static bool match( Input& in ) noexcept
+      {
+         return in.byte() == 0;
+      }
+   };
+
+   template<>
+   inline constexpr bool skip_control< bof > = true;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/bol.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/bol.hpp
new file mode 100644
index 000000000000..cbbb7a6d8364
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/bol.hpp
@@ -0,0 +1,31 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_BOL_HPP
+#define TAO_JSON_PEGTL_INTERNAL_BOL_HPP
+
+#include "../config.hpp"
+
+#include "skip_control.hpp"
+
+#include "../analysis/generic.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   struct bol
+   {
+      using analyze_t = analysis::generic< analysis::rule_type::opt >;
+
+      template< typename Input >
+      [[nodiscard]] static bool match( Input& in ) noexcept
+      {
+         return in.byte_in_line() == 0;
+      }
+   };
+
+   template<>
+   inline constexpr bool skip_control< bol > = true;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/bump.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/bump.hpp
new file mode 100644
index 000000000000..8646271241ab
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/bump.hpp
@@ -0,0 +1,45 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_BUMP_HPP
+#define TAO_JSON_PEGTL_INTERNAL_BUMP_HPP
+
+#include "../config.hpp"
+
+#include "iterator.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   inline void bump( iterator& iter, const std::size_t count, const int ch ) noexcept
+   {
+      for( std::size_t i = 0; i < count; ++i ) {
+         if( iter.data[ i ] == ch ) {
+            ++iter.line;
+            iter.byte_in_line = 0;
+         }
+         else {
+            ++iter.byte_in_line;
+         }
+      }
+      iter.byte += count;
+      iter.data += count;
+   }
+
+   inline void bump_in_this_line( iterator& iter, const std::size_t count ) noexcept
+   {
+      iter.data += count;
+      iter.byte += count;
+      iter.byte_in_line += count;
+   }
+
+   inline void bump_to_next_line( iterator& iter, const std::size_t count ) noexcept
+   {
+      ++iter.line;
+      iter.byte += count;
+      iter.byte_in_line = 0;
+      iter.data += count;
+   }
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/bump_help.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/bump_help.hpp
new file mode 100644
index 000000000000..6bb89e420fca
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/bump_help.hpp
@@ -0,0 +1,29 @@
+// Copyright (c) 2015-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_BUMP_HELP_HPP
+#define TAO_JSON_PEGTL_INTERNAL_BUMP_HELP_HPP
+
+#include <cstddef>
+#include <type_traits>
+
+#include "../config.hpp"
+
+#include "result_on_found.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< result_on_found R, typename Input, typename Char, Char... Cs >
+   void bump_help( Input& in, const std::size_t count ) noexcept
+   {
+      if constexpr( ( ( Cs != Input::eol_t::ch ) && ... ) != bool( R ) ) {
+         in.bump( count );
+      }
+      else {
+         in.bump_in_this_line( count );
+      }
+   }
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/bytes.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/bytes.hpp
new file mode 100644
index 000000000000..72d37b97f4be
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/bytes.hpp
@@ -0,0 +1,36 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_BYTES_HPP
+#define TAO_JSON_PEGTL_INTERNAL_BYTES_HPP
+
+#include "../config.hpp"
+
+#include "skip_control.hpp"
+
+#include "../analysis/counted.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< unsigned Num >
+   struct bytes
+   {
+      using analyze_t = analysis::counted< analysis::rule_type::any, Num >;
+
+      template< typename Input >
+      [[nodiscard]] static bool match( Input& in ) noexcept( noexcept( in.size( 0 ) ) )
+      {
+         if( in.size( Num ) >= Num ) {
+            in.bump( Num );
+            return true;
+         }
+         return false;
+      }
+   };
+
+   template< unsigned Num >
+   inline constexpr bool skip_control< bytes< Num > > = true;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/control.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/control.hpp
new file mode 100644
index 000000000000..3e80d98e59c7
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/control.hpp
@@ -0,0 +1,44 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_CONTROL_HPP
+#define TAO_JSON_PEGTL_INTERNAL_CONTROL_HPP
+
+#include "../config.hpp"
+
+#include "duseltronik.hpp"
+#include "seq.hpp"
+#include "skip_control.hpp"
+
+#include "../apply_mode.hpp"
+#include "../rewind_mode.hpp"
+
+#include "../analysis/generic.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< template< typename... > class Control, typename... Rules >
+   struct control
+   {
+      using analyze_t = analysis::generic< analysis::rule_type::seq, Rules... >;
+
+      template< apply_mode A,
+                rewind_mode M,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class,
+                typename Input,
+                typename... States >
+      [[nodiscard]] static bool match( Input& in, States&&... st )
+      {
+         return duseltronik< seq< Rules... >, A, M, Action, Control >::match( in, st... );
+      }
+   };
+
+   template< template< typename... > class Control, typename... Rules >
+   inline constexpr bool skip_control< control< Control, Rules... > > = true;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/cr_crlf_eol.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/cr_crlf_eol.hpp
new file mode 100644
index 000000000000..167aead1e54e
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/cr_crlf_eol.hpp
@@ -0,0 +1,32 @@
+// Copyright (c) 2016-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_CR_CRLF_EOL_HPP
+#define TAO_JSON_PEGTL_INTERNAL_CR_CRLF_EOL_HPP
+
+#include "../config.hpp"
+#include "../eol_pair.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   struct cr_crlf_eol
+   {
+      static constexpr int ch = '\r';
+
+      template< typename Input >
+      [[nodiscard]] static eol_pair match( Input& in ) noexcept( noexcept( in.size( 2 ) ) )
+      {
+         eol_pair p = { false, in.size( 2 ) };
+         if( p.second ) {
+            if( in.peek_char() == '\r' ) {
+               in.bump_to_next_line( 1 + ( ( p.second > 1 ) && ( in.peek_char( 1 ) == '\n' ) ) );
+               p.first = true;
+            }
+         }
+         return p;
+      }
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/cr_eol.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/cr_eol.hpp
new file mode 100644
index 000000000000..3726f4343113
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/cr_eol.hpp
@@ -0,0 +1,32 @@
+// Copyright (c) 2016-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_CR_EOL_HPP
+#define TAO_JSON_PEGTL_INTERNAL_CR_EOL_HPP
+
+#include "../config.hpp"
+#include "../eol_pair.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   struct cr_eol
+   {
+      static constexpr int ch = '\r';
+
+      template< typename Input >
+      [[nodiscard]] static eol_pair match( Input& in ) noexcept( noexcept( in.size( 1 ) ) )
+      {
+         eol_pair p = { false, in.size( 1 ) };
+         if( p.second ) {
+            if( in.peek_char() == '\r' ) {
+               in.bump_to_next_line();
+               p.first = true;
+            }
+         }
+         return p;
+      }
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/crlf_eol.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/crlf_eol.hpp
new file mode 100644
index 000000000000..6d00310ad3fb
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/crlf_eol.hpp
@@ -0,0 +1,32 @@
+// Copyright (c) 2016-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_CRLF_EOL_HPP
+#define TAO_JSON_PEGTL_INTERNAL_CRLF_EOL_HPP
+
+#include "../config.hpp"
+#include "../eol_pair.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   struct crlf_eol
+   {
+      static constexpr int ch = '\n';
+
+      template< typename Input >
+      [[nodiscard]] static eol_pair match( Input& in ) noexcept( noexcept( in.size( 2 ) ) )
+      {
+         eol_pair p = { false, in.size( 2 ) };
+         if( p.second > 1 ) {
+            if( ( in.peek_char() == '\r' ) && ( in.peek_char( 1 ) == '\n' ) ) {
+               in.bump_to_next_line( 2 );
+               p.first = true;
+            }
+         }
+         return p;
+      }
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/cstream_reader.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/cstream_reader.hpp
new file mode 100644
index 000000000000..9e639dbe47d9
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/cstream_reader.hpp
@@ -0,0 +1,49 @@
+// Copyright (c) 2016-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_CSTREAM_READER_HPP
+#define TAO_JSON_PEGTL_INTERNAL_CSTREAM_READER_HPP
+
+#include <cassert>
+#include <cstddef>
+#include <cstdio>
+
+#include <system_error>
+
+#include "../config.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   struct cstream_reader
+   {
+      explicit cstream_reader( std::FILE* s ) noexcept
+         : m_cstream( s )
+      {
+         assert( m_cstream != nullptr );
+      }
+
+      [[nodiscard]] std::size_t operator()( char* buffer, const std::size_t length )
+      {
+         if( const auto r = std::fread( buffer, 1, length, m_cstream ) ) {
+            return r;
+         }
+         if( std::feof( m_cstream ) != 0 ) {
+            return 0;
+         }
+
+         // Please contact us if you know how to provoke the following exception.
+         // The example on cppreference.com doesn't work, at least not on macOS.
+
+         // LCOV_EXCL_START
+         const auto ec = std::ferror( m_cstream );
+         assert( ec != 0 );
+         throw std::system_error( ec, std::system_category(), "fread() failed" );
+         // LCOV_EXCL_STOP
+      }
+
+      std::FILE* m_cstream;
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/cstring_reader.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/cstring_reader.hpp
new file mode 100644
index 000000000000..3dbf8e033948
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/cstring_reader.hpp
@@ -0,0 +1,40 @@
+// Copyright (c) 2016-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_CSTRING_READER_HPP
+#define TAO_JSON_PEGTL_INTERNAL_CSTRING_READER_HPP
+
+#include <cassert>
+#include <cstddef>
+
+#include "../config.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   struct cstring_reader
+   {
+      explicit cstring_reader( const char* zero_terminated ) noexcept
+         : m_cstring( zero_terminated )
+      {
+         assert( m_cstring != nullptr );
+      }
+
+      [[nodiscard]] std::size_t operator()( char* buffer, const std::size_t length ) noexcept
+      {
+         std::size_t i = 0;
+         char c;
+
+         while( ( i < length ) && ( ( c = m_cstring[ i ] ) != 0 ) ) {
+            *buffer++ = c;
+            ++i;
+         }
+         m_cstring += i;
+         return i;
+      }
+
+      const char* m_cstring;
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/demangle.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/demangle.hpp
new file mode 100644
index 000000000000..6562e77936ea
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/demangle.hpp
@@ -0,0 +1,140 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_DEMANGLE_HPP
+#define TAO_JSON_PEGTL_INTERNAL_DEMANGLE_HPP
+
+#include <ciso646>
+#include <string_view>
+
+#include "../config.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+#if defined( __clang__ )
+
+#if defined( _LIBCPP_VERSION )
+
+   template< typename T >
+   [[nodiscard]] constexpr std::string_view demangle() noexcept
+   {
+      constexpr const std::string_view sv = __PRETTY_FUNCTION__;
+      constexpr const auto begin = sv.find( '=' );
+      static_assert( begin != std::string_view::npos );
+      return sv.substr( begin + 2, sv.size() - begin - 3 );
+   }
+
+#else
+
+   // When using libstdc++ with clang, std::string_view::find is not constexpr :(
+   template< char C >
+   constexpr const char* find( const char* p, std::size_t n ) noexcept
+   {
+      while( n ) {
+         if( *p == C ) {
+            return p;
+         }
+         ++p;
+         --n;
+      }
+      return nullptr;
+   }
+
+   template< typename T >
+   [[nodiscard]] constexpr std::string_view demangle() noexcept
+   {
+      constexpr const std::string_view sv = __PRETTY_FUNCTION__;
+      constexpr const auto begin = find< '=' >( sv.data(), sv.size() );
+      static_assert( begin != nullptr );
+      return { begin + 2, sv.data() + sv.size() - begin - 3 };
+   }
+
+#endif
+
+#elif defined( __GNUC__ )
+
+#if( __GNUC__ == 7 )
+
+   // GCC 7 wrongly sometimes disallows __PRETTY_FUNCTION__ in constexpr functions,
+   // therefore we drop the 'constexpr' and hope for the best.
+   template< typename T >
+   [[nodiscard]] std::string_view demangle() noexcept
+   {
+      const std::string_view sv = __PRETTY_FUNCTION__;
+      const auto begin = sv.find( '=' );
+      const auto tmp = sv.substr( begin + 2 );
+      const auto end = tmp.rfind( ';' );
+      return tmp.substr( 0, end );
+   }
+
+#elif( __GNUC__ == 9 ) && ( __GNUC_MINOR__ < 3 )
+
+   // GCC 9.1 and 9.2 have a bug that leads to truncated __PRETTY_FUNCTION__ names,
+   // see https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91155
+   template< typename T >
+   [[nodiscard]] constexpr std::string_view demangle() noexcept
+   {
+      // fallback: requires RTTI, no demangling
+      return typeid( T ).name();
+   }
+
+#else
+
+   template< typename T >
+   [[nodiscard]] constexpr std::string_view demangle() noexcept
+   {
+      constexpr std::string_view sv = __PRETTY_FUNCTION__;
+      constexpr const auto begin = sv.find( '=' );
+      static_assert( begin != std::string_view::npos );
+      constexpr const auto tmp = sv.substr( begin + 2 );
+      constexpr const auto end = tmp.rfind( ';' );
+      static_assert( end != std::string_view::npos );
+      return tmp.substr( 0, end );
+   }
+
+#endif
+
+#elif defined( _MSC_VER )
+
+#if( _MSC_VER < 1920 )
+
+   template< typename T >
+   [[nodiscard]] constexpr std::string_view demangle() noexcept
+   {
+      const std::string_view sv = __FUNCSIG__;
+      const auto begin = sv.find( "demangle<" );
+      const auto tmp = sv.substr( begin + 9 );
+      const auto end = tmp.rfind( '>' );
+      return tmp.substr( 0, end );
+   }
+
+#else
+
+   template< typename T >
+   [[nodiscard]] constexpr std::string_view demangle() noexcept
+   {
+      constexpr std::string_view sv = __FUNCSIG__;
+      constexpr auto begin = sv.find( "demangle<" );
+      static_assert( begin != std::string_view::npos );
+      constexpr auto tmp = sv.substr( begin + 9 );
+      constexpr auto end = tmp.rfind( '>' );
+      static_assert( end != std::string_view::npos );
+      return tmp.substr( 0, end );
+   }
+
+#endif
+
+#else
+
+   template< typename T >
+   [[nodiscard]] constexpr std::string_view demangle() noexcept
+   {
+      // fallback: requires RTTI, no demangling
+      return typeid( T ).name();
+   }
+
+#endif
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/disable.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/disable.hpp
new file mode 100644
index 000000000000..f756dddfcbe3
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/disable.hpp
@@ -0,0 +1,44 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_DISABLE_HPP
+#define TAO_JSON_PEGTL_INTERNAL_DISABLE_HPP
+
+#include "../config.hpp"
+
+#include "duseltronik.hpp"
+#include "seq.hpp"
+#include "skip_control.hpp"
+
+#include "../apply_mode.hpp"
+#include "../rewind_mode.hpp"
+
+#include "../analysis/generic.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< typename... Rules >
+   struct disable
+   {
+      using analyze_t = analysis::generic< analysis::rule_type::seq, Rules... >;
+
+      template< apply_mode,
+                rewind_mode M,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class Control,
+                typename Input,
+                typename... States >
+      [[nodiscard]] static bool match( Input& in, States&&... st )
+      {
+         return duseltronik< seq< Rules... >, apply_mode::nothing, M, Action, Control >::match( in, st... );
+      }
+   };
+
+   template< typename... Rules >
+   inline constexpr bool skip_control< disable< Rules... > > = true;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/discard.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/discard.hpp
new file mode 100644
index 000000000000..38bd4e94fe8d
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/discard.hpp
@@ -0,0 +1,33 @@
+// Copyright (c) 2016-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_DISCARD_HPP
+#define TAO_JSON_PEGTL_INTERNAL_DISCARD_HPP
+
+#include "../config.hpp"
+
+#include "skip_control.hpp"
+
+#include "../analysis/generic.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   struct discard
+   {
+      using analyze_t = analysis::generic< analysis::rule_type::opt >;
+
+      template< typename Input >
+      [[nodiscard]] static bool match( Input& in ) noexcept
+      {
+         static_assert( noexcept( in.discard() ) );
+         in.discard();
+         return true;
+      }
+   };
+
+   template<>
+   inline constexpr bool skip_control< discard > = true;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/dusel_mode.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/dusel_mode.hpp
new file mode 100644
index 000000000000..5d22837aef99
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/dusel_mode.hpp
@@ -0,0 +1,23 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_DUSEL_MODE_HPP
+#define TAO_JSON_PEGTL_INTERNAL_DUSEL_MODE_HPP
+
+#include "../config.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   enum class dusel_mode : char
+   {
+      nothing = 0,
+      control = 1,
+      control_and_apply_void = 2,
+      control_and_apply_bool = 3,
+      control_and_apply0_void = 4,
+      control_and_apply0_bool = 5
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/duseltronik.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/duseltronik.hpp
new file mode 100644
index 000000000000..7a02519a04ea
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/duseltronik.hpp
@@ -0,0 +1,187 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_DUSELTRONIK_HPP
+#define TAO_JSON_PEGTL_INTERNAL_DUSELTRONIK_HPP
+
+#include "../apply_mode.hpp"
+#include "../config.hpp"
+#include "../rewind_mode.hpp"
+
+#include "dusel_mode.hpp"
+
+#ifdef _MSC_VER
+#pragma warning( push )
+#pragma warning( disable : 4702 )
+#endif
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< typename Rule,
+             apply_mode A,
+             rewind_mode M,
+             template< typename... >
+             class Action,
+             template< typename... >
+             class Control,
+             dusel_mode = dusel_mode::nothing >
+   struct duseltronik;
+
+   template< typename Rule,
+             apply_mode A,
+             rewind_mode M,
+             template< typename... >
+             class Action,
+             template< typename... >
+             class Control >
+   struct duseltronik< Rule, A, M, Action, Control, dusel_mode::nothing >
+   {
+      template< typename Input, typename... States >
+      [[nodiscard]] static auto match( Input& in, States&&... st )
+         -> decltype( Rule::template match< A, M, Action, Control >( in, st... ) )
+      {
+         return Rule::template match< A, M, Action, Control >( in, st... );
+      }
+
+      template< typename Input, typename... States, int = 1 >
+      [[nodiscard]] static auto match( Input& in, States&&... /*unused*/ )
+         -> decltype( Rule::match( in ) )
+      {
+         return Rule::match( in );
+      }
+   };
+
+   template< typename Rule,
+             apply_mode A,
+             rewind_mode M,
+             template< typename... >
+             class Action,
+             template< typename... >
+             class Control >
+   struct duseltronik< Rule, A, M, Action, Control, dusel_mode::control >
+   {
+      template< typename Input, typename... States >
+      [[nodiscard]] static bool match( Input& in, States&&... st )
+      {
+         Control< Rule >::start( static_cast< const Input& >( in ), st... );
+
+         if( duseltronik< Rule, A, M, Action, Control, dusel_mode::nothing >::match( in, st... ) ) {
+            Control< Rule >::success( static_cast< const Input& >( in ), st... );
+            return true;
+         }
+         Control< Rule >::failure( static_cast< const Input& >( in ), st... );
+         return false;
+      }
+   };
+
+   template< typename Rule,
+             apply_mode A,
+             rewind_mode M,
+             template< typename... >
+             class Action,
+             template< typename... >
+             class Control >
+   struct duseltronik< Rule, A, M, Action, Control, dusel_mode::control_and_apply_void >
+   {
+      template< typename Input, typename... States >
+      [[nodiscard]] static bool match( Input& in, States&&... st )
+      {
+         auto m = in.template mark< rewind_mode::required >();
+
+         Control< Rule >::start( static_cast< const Input& >( in ), st... );
+
+         if( duseltronik< Rule, A, rewind_mode::active, Action, Control, dusel_mode::nothing >::match( in, st... ) ) {
+            Control< Rule >::template apply< Action >( m.iterator(), static_cast< const Input& >( in ), st... );
+            Control< Rule >::success( static_cast< const Input& >( in ), st... );
+            return m( true );
+         }
+         Control< Rule >::failure( static_cast< const Input& >( in ), st... );
+         return false;
+      }
+   };
+
+   template< typename Rule,
+             apply_mode A,
+             rewind_mode M,
+             template< typename... >
+             class Action,
+             template< typename... >
+             class Control >
+   struct duseltronik< Rule, A, M, Action, Control, dusel_mode::control_and_apply_bool >
+   {
+      template< typename Input, typename... States >
+      [[nodiscard]] static bool match( Input& in, States&&... st )
+      {
+         auto m = in.template mark< rewind_mode::required >();
+
+         Control< Rule >::start( static_cast< const Input& >( in ), st... );
+
+         if( duseltronik< Rule, A, rewind_mode::active, Action, Control, dusel_mode::nothing >::match( in, st... ) ) {
+            if( Control< Rule >::template apply< Action >( m.iterator(), static_cast< const Input& >( in ), st... ) ) {
+               Control< Rule >::success( static_cast< const Input& >( in ), st... );
+               return m( true );
+            }
+         }
+         Control< Rule >::failure( static_cast< const Input& >( in ), st... );
+         return false;
+      }
+   };
+
+   template< typename Rule,
+             apply_mode A,
+             rewind_mode M,
+             template< typename... >
+             class Action,
+             template< typename... >
+             class Control >
+   struct duseltronik< Rule, A, M, Action, Control, dusel_mode::control_and_apply0_void >
+   {
+      template< typename Input, typename... States >
+      [[nodiscard]] static bool match( Input& in, States&&... st )
+      {
+         Control< Rule >::start( static_cast< const Input& >( in ), st... );
+
+         if( duseltronik< Rule, A, M, Action, Control, dusel_mode::nothing >::match( in, st... ) ) {
+            Control< Rule >::template apply0< Action >( static_cast< const Input& >( in ), st... );
+            Control< Rule >::success( static_cast< const Input& >( in ), st... );
+            return true;
+         }
+         Control< Rule >::failure( static_cast< const Input& >( in ), st... );
+         return false;
+      }
+   };
+
+   template< typename Rule,
+             apply_mode A,
+             rewind_mode M,
+             template< typename... >
+             class Action,
+             template< typename... >
+             class Control >
+   struct duseltronik< Rule, A, M, Action, Control, dusel_mode::control_and_apply0_bool >
+   {
+      template< typename Input, typename... States >
+      [[nodiscard]] static bool match( Input& in, States&&... st )
+      {
+         auto m = in.template mark< rewind_mode::required >();
+
+         Control< Rule >::start( static_cast< const Input& >( in ), st... );
+
+         if( duseltronik< Rule, A, rewind_mode::active, Action, Control, dusel_mode::nothing >::match( in, st... ) ) {
+            if( Control< Rule >::template apply0< Action >( static_cast< const Input& >( in ), st... ) ) {
+               Control< Rule >::success( static_cast< const Input& >( in ), st... );
+               return m( true );
+            }
+         }
+         Control< Rule >::failure( static_cast< const Input& >( in ), st... );
+         return false;
+      }
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#ifdef _MSC_VER
+#pragma warning( pop )
+#endif
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/enable.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/enable.hpp
new file mode 100644
index 000000000000..f21084bba945
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/enable.hpp
@@ -0,0 +1,44 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_ENABLE_HPP
+#define TAO_JSON_PEGTL_INTERNAL_ENABLE_HPP
+
+#include "../config.hpp"
+
+#include "duseltronik.hpp"
+#include "seq.hpp"
+#include "skip_control.hpp"
+
+#include "../apply_mode.hpp"
+#include "../rewind_mode.hpp"
+
+#include "../analysis/generic.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< typename... Rules >
+   struct enable
+   {
+      using analyze_t = analysis::generic< analysis::rule_type::seq, Rules... >;
+
+      template< apply_mode,
+                rewind_mode M,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class Control,
+                typename Input,
+                typename... States >
+      [[nodiscard]] static bool match( Input& in, States&&... st )
+      {
+         return duseltronik< seq< Rules... >, apply_mode::action, M, Action, Control >::match( in, st... );
+      }
+   };
+
+   template< typename... Rules >
+   inline constexpr bool skip_control< enable< Rules... > > = true;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/endian.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/endian.hpp
new file mode 100644
index 000000000000..1d30df5a0b9b
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/endian.hpp
@@ -0,0 +1,62 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_ENDIAN_HPP
+#define TAO_JSON_PEGTL_INTERNAL_ENDIAN_HPP
+
+#include <cstdint>
+#include <cstring>
+
+#include "../config.hpp"
+
+#if defined( _WIN32 ) && !defined( __MINGW32__ )
+#include "endian_win.hpp"
+#else
+#include "endian_gcc.hpp"
+#endif
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< typename N >
+   [[nodiscard]] N h_to_be( const N n ) noexcept
+   {
+      return N( to_and_from_be< sizeof( N ) >::convert( n ) );
+   }
+
+   template< typename N >
+   [[nodiscard]] N be_to_h( const N n ) noexcept
+   {
+      return h_to_be( n );
+   }
+
+   template< typename N >
+   [[nodiscard]] N be_to_h( const void* p ) noexcept
+   {
+      N n;
+      std::memcpy( &n, p, sizeof( n ) );
+      return internal::be_to_h( n );
+   }
+
+   template< typename N >
+   [[nodiscard]] N h_to_le( const N n ) noexcept
+   {
+      return N( to_and_from_le< sizeof( N ) >::convert( n ) );
+   }
+
+   template< typename N >
+   [[nodiscard]] N le_to_h( const N n ) noexcept
+   {
+      return h_to_le( n );
+   }
+
+   template< typename N >
+   [[nodiscard]] N le_to_h( const void* p ) noexcept
+   {
+      N n;
+      std::memcpy( &n, p, sizeof( n ) );
+      return internal::le_to_h( n );
+   }
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/endian_gcc.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/endian_gcc.hpp
new file mode 100644
index 000000000000..016778987836
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/endian_gcc.hpp
@@ -0,0 +1,206 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_ENDIAN_GCC_HPP
+#define TAO_JSON_PEGTL_INTERNAL_ENDIAN_GCC_HPP
+
+#include <cstdint>
+#include <cstring>
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+#if !defined( __BYTE_ORDER__ )
+#error No byte order defined!
+#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+
+   template< std::size_t S >
+   struct to_and_from_be
+   {
+      template< typename T >
+      [[nodiscard]] static T convert( const T n ) noexcept
+      {
+         return n;
+      }
+   };
+
+   template< std::size_t S >
+   struct to_and_from_le;
+
+   template<>
+   struct to_and_from_le< 1 >
+   {
+      [[nodiscard]] static std::uint8_t convert( const std::uint8_t n ) noexcept
+      {
+         return n;
+      }
+
+      [[nodiscard]] static std::int8_t convert( const std::int8_t n ) noexcept
+      {
+         return n;
+      }
+   };
+
+   template<>
+   struct to_and_from_le< 2 >
+   {
+      [[nodiscard]] static std::int16_t convert( const std::int16_t n ) noexcept
+      {
+         return static_cast< std::int16_t >( __builtin_bswap16( static_cast< std::uint16_t >( n ) ) );
+      }
+
+      [[nodiscard]] static std::uint16_t convert( const std::uint16_t n ) noexcept
+      {
+         return __builtin_bswap16( n );
+      }
+   };
+
+   template<>
+   struct to_and_from_le< 4 >
+   {
+      [[nodiscard]] static float convert( float n ) noexcept
+      {
+         std::uint32_t u;
+         std::memcpy( &u, &n, 4 );
+         u = convert( u );
+         std::memcpy( &n, &u, 4 );
+         return n;
+      }
+
+      [[nodiscard]] static std::int32_t convert( const std::int32_t n ) noexcept
+      {
+         return static_cast< std::int32_t >( __builtin_bswap32( static_cast< std::uint32_t >( n ) ) );
+      }
+
+      [[nodiscard]] static std::uint32_t convert( const std::uint32_t n ) noexcept
+      {
+         return __builtin_bswap32( n );
+      }
+   };
+
+   template<>
+   struct to_and_from_le< 8 >
+   {
+      [[nodiscard]] static double convert( double n ) noexcept
+      {
+         std::uint64_t u;
+         std::memcpy( &u, &n, 8 );
+         u = convert( u );
+         std::memcpy( &n, &u, 8 );
+         return n;
+      }
+
+      [[nodiscard]] static std::int64_t convert( const std::int64_t n ) noexcept
+      {
+         return static_cast< std::int64_t >( __builtin_bswap64( static_cast< std::uint64_t >( n ) ) );
+      }
+
+      [[nodiscard]] static std::uint64_t convert( const std::uint64_t n ) noexcept
+      {
+         return __builtin_bswap64( n );
+      }
+   };
+
+#define TAO_JSON_PEGTL_NATIVE_ORDER be
+#define TAO_JSON_PEGTL_NATIVE_UTF16 utf16_be
+#define TAO_JSON_PEGTL_NATIVE_UTF32 utf32_be
+
+#elif __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+
+   template< std::size_t S >
+   struct to_and_from_le
+   {
+      template< typename T >
+      [[nodiscard]] static T convert( const T n ) noexcept
+      {
+         return n;
+      }
+   };
+
+   template< std::size_t S >
+   struct to_and_from_be;
+
+   template<>
+   struct to_and_from_be< 1 >
+   {
+      [[nodiscard]] static std::int8_t convert( const std::int8_t n ) noexcept
+      {
+         return n;
+      }
+
+      [[nodiscard]] static std::uint8_t convert( const std::uint8_t n ) noexcept
+      {
+         return n;
+      }
+   };
+
+   template<>
+   struct to_and_from_be< 2 >
+   {
+      [[nodiscard]] static std::int16_t convert( const std::int16_t n ) noexcept
+      {
+         return static_cast< std::int16_t >( __builtin_bswap16( static_cast< std::uint16_t >( n ) ) );
+      }
+
+      [[nodiscard]] static std::uint16_t convert( const std::uint16_t n ) noexcept
+      {
+         return __builtin_bswap16( n );
+      }
+   };
+
+   template<>
+   struct to_and_from_be< 4 >
+   {
+      [[nodiscard]] static float convert( float n ) noexcept
+      {
+         std::uint32_t u;
+         std::memcpy( &u, &n, 4 );
+         u = convert( u );
+         std::memcpy( &n, &u, 4 );
+         return n;
+      }
+
+      [[nodiscard]] static std::int32_t convert( const std::int32_t n ) noexcept
+      {
+         return static_cast< std::int32_t >( __builtin_bswap32( static_cast< std::uint32_t >( n ) ) );
+      }
+
+      [[nodiscard]] static std::uint32_t convert( const std::uint32_t n ) noexcept
+      {
+         return __builtin_bswap32( n );
+      }
+   };
+
+   template<>
+   struct to_and_from_be< 8 >
+   {
+      [[nodiscard]] static double convert( double n ) noexcept
+      {
+         std::uint64_t u;
+         std::memcpy( &u, &n, 8 );
+         u = convert( u );
+         std::memcpy( &n, &u, 8 );
+         return n;
+      }
+
+      [[nodiscard]] static std::int64_t convert( const std::int64_t n ) noexcept
+      {
+         return static_cast< std::int64_t >( __builtin_bswap64( static_cast< std::uint64_t >( n ) ) );
+      }
+
+      [[nodiscard]] static std::uint64_t convert( const std::uint64_t n ) noexcept
+      {
+         return __builtin_bswap64( n );
+      }
+   };
+
+#define TAO_JSON_PEGTL_NATIVE_ORDER le
+#define TAO_JSON_PEGTL_NATIVE_UTF16 utf16_le
+#define TAO_JSON_PEGTL_NATIVE_UTF32 utf32_le
+
+#else
+#error Unknown host byte order!
+#endif
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/endian_win.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/endian_win.hpp
new file mode 100644
index 000000000000..4ca5ad77e1cc
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/endian_win.hpp
@@ -0,0 +1,106 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_ENDIAN_WIN_HPP
+#define TAO_JSON_PEGTL_INTERNAL_ENDIAN_WIN_HPP
+
+#include <cstdint>
+#include <cstdlib>
+#include <cstring>
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< std::size_t S >
+   struct to_and_from_le
+   {
+      template< typename T >
+      [[nodiscard]] static T convert( const T t ) noexcept
+      {
+         return t;
+      }
+   };
+
+   template< std::size_t S >
+   struct to_and_from_be;
+
+   template<>
+   struct to_and_from_be< 1 >
+   {
+      [[nodiscard]] static std::int8_t convert( const std::int8_t n ) noexcept
+      {
+         return n;
+      }
+
+      [[nodiscard]] static std::uint8_t convert( const std::uint8_t n ) noexcept
+      {
+         return n;
+      }
+   };
+
+   template<>
+   struct to_and_from_be< 2 >
+   {
+      [[nodiscard]] static std::int16_t convert( const std::int16_t n ) noexcept
+      {
+         return std::int16_t( _byteswap_ushort( std::uint16_t( n ) ) );
+      }
+
+      [[nodiscard]] static std::uint16_t convert( const std::uint16_t n ) noexcept
+      {
+         return _byteswap_ushort( n );
+      }
+   };
+
+   template<>
+   struct to_and_from_be< 4 >
+   {
+      [[nodiscard]] static float convert( float n ) noexcept
+      {
+         std::uint32_t u;
+         std::memcpy( &u, &n, 4 );
+         u = convert( u );
+         std::memcpy( &n, &u, 4 );
+         return n;
+      }
+
+      [[nodiscard]] static std::int32_t convert( const std::int32_t n ) noexcept
+      {
+         return std::int32_t( _byteswap_ulong( std::uint32_t( n ) ) );
+      }
+
+      [[nodiscard]] static std::uint32_t convert( const std::uint32_t n ) noexcept
+      {
+         return _byteswap_ulong( n );
+      }
+   };
+
+   template<>
+   struct to_and_from_be< 8 >
+   {
+      [[nodiscard]] static double convert( double n ) noexcept
+      {
+         std::uint64_t u;
+         std::memcpy( &u, &n, 8 );
+         u = convert( u );
+         std::memcpy( &n, &u, 8 );
+         return n;
+      }
+
+      [[nodiscard]] static std::int64_t convert( const std::int64_t n ) noexcept
+      {
+         return std::int64_t( _byteswap_uint64( std::uint64_t( n ) ) );
+      }
+
+      [[nodiscard]] static std::uint64_t convert( const std::uint64_t n ) noexcept
+      {
+         return _byteswap_uint64( n );
+      }
+   };
+
+#define TAO_JSON_PEGTL_NATIVE_ORDER le
+#define TAO_JSON_PEGTL_NATIVE_UTF16 utf16_le
+#define TAO_JSON_PEGTL_NATIVE_UTF32 utf32_le
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/eof.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/eof.hpp
new file mode 100644
index 000000000000..a567efe8db20
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/eof.hpp
@@ -0,0 +1,31 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_EOF_HPP
+#define TAO_JSON_PEGTL_INTERNAL_EOF_HPP
+
+#include "../config.hpp"
+
+#include "skip_control.hpp"
+
+#include "../analysis/generic.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   struct eof
+   {
+      using analyze_t = analysis::generic< analysis::rule_type::opt >;
+
+      template< typename Input >
+      [[nodiscard]] static bool match( Input& in ) noexcept( noexcept( in.empty() ) )
+      {
+         return in.empty();
+      }
+   };
+
+   template<>
+   inline constexpr bool skip_control< eof > = true;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/eol.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/eol.hpp
new file mode 100644
index 000000000000..e747890736ba
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/eol.hpp
@@ -0,0 +1,31 @@
+// Copyright (c) 2016-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_EOL_HPP
+#define TAO_JSON_PEGTL_INTERNAL_EOL_HPP
+
+#include "../config.hpp"
+
+#include "skip_control.hpp"
+
+#include "../analysis/generic.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   struct eol
+   {
+      using analyze_t = analysis::generic< analysis::rule_type::any >;
+
+      template< typename Input >
+      [[nodiscard]] static bool match( Input& in ) noexcept( noexcept( Input::eol_t::match( in ) ) )
+      {
+         return Input::eol_t::match( in ).first;
+      }
+   };
+
+   template<>
+   inline constexpr bool skip_control< eol > = true;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/eolf.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/eolf.hpp
new file mode 100644
index 000000000000..c708a3795199
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/eolf.hpp
@@ -0,0 +1,32 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_EOLF_HPP
+#define TAO_JSON_PEGTL_INTERNAL_EOLF_HPP
+
+#include "../config.hpp"
+
+#include "skip_control.hpp"
+
+#include "../analysis/generic.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   struct eolf
+   {
+      using analyze_t = analysis::generic< analysis::rule_type::opt >;
+
+      template< typename Input >
+      [[nodiscard]] static bool match( Input& in ) noexcept( noexcept( Input::eol_t::match( in ) ) )
+      {
+         const auto p = Input::eol_t::match( in );
+         return p.first || ( !p.second );
+      }
+   };
+
+   template<>
+   inline constexpr bool skip_control< eolf > = true;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/file_mapper_posix.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/file_mapper_posix.hpp
new file mode 100644
index 000000000000..5d37f4d0eb89
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/file_mapper_posix.hpp
@@ -0,0 +1,83 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_FILE_MAPPER_POSIX_HPP
+#define TAO_JSON_PEGTL_INTERNAL_FILE_MAPPER_POSIX_HPP
+
+#include <sys/mman.h>
+#include <unistd.h>
+
+#include <system_error>
+
+#include "../config.hpp"
+
+#include "file_opener.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   class file_mapper
+   {
+   public:
+      explicit file_mapper( const char* filename )
+         : file_mapper( file_opener( filename ) )
+      {
+      }
+
+      explicit file_mapper( const file_opener& reader )
+         : m_size( reader.size() ),
+           m_data( static_cast< const char* >( ::mmap( nullptr, m_size, PROT_READ, MAP_PRIVATE, reader.m_fd, 0 ) ) )
+      {
+         if( ( m_size != 0 ) && ( intptr_t( m_data ) == -1 ) ) {
+            const auto ec = errno;
+            throw std::system_error( ec, std::system_category(), reader.m_source );
+         }
+      }
+
+      file_mapper( const file_mapper& ) = delete;
+      file_mapper( file_mapper&& ) = delete;
+
+      ~file_mapper() noexcept
+      {
+         // Legacy C interface requires pointer-to-mutable but does not write through the pointer.
+         ::munmap( const_cast< char* >( m_data ), m_size );
+      }
+
+      void operator=( const file_mapper& ) = delete;
+      void operator=( file_mapper&& ) = delete;
+
+      [[nodiscard]] bool empty() const noexcept
+      {
+         return m_size == 0;
+      }
+
+      [[nodiscard]] std::size_t size() const noexcept
+      {
+         return m_size;
+      }
+
+      using iterator = const char*;
+      using const_iterator = const char*;
+
+      [[nodiscard]] iterator data() const noexcept
+      {
+         return m_data;
+      }
+
+      [[nodiscard]] iterator begin() const noexcept
+      {
+         return m_data;
+      }
+
+      [[nodiscard]] iterator end() const noexcept
+      {
+         return m_data + m_size;
+      }
+
+   private:
+      const std::size_t m_size;
+      const char* const m_data;
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/file_mapper_win32.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/file_mapper_win32.hpp
new file mode 100644
index 000000000000..41880e0fd977
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/file_mapper_win32.hpp
@@ -0,0 +1,219 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_FILE_MAPPER_WIN32_HPP
+#define TAO_JSON_PEGTL_INTERNAL_FILE_MAPPER_WIN32_HPP
+
+#if !defined( NOMINMAX )
+#define NOMINMAX
+#define TAO_JSON_PEGTL_NOMINMAX_WAS_DEFINED
+#endif
+
+#if !defined( WIN32_LEAN_AND_MEAN )
+#define WIN32_LEAN_AND_MEAN
+#define TAO_JSON_PEGTL_WIN32_LEAN_AND_MEAN_WAS_DEFINED
+#endif
+
+#include <windows.h>
+
+#if defined( TAO_JSON_PEGTL_NOMINMAX_WAS_DEFINED )
+#undef NOMINMAX
+#undef TAO_JSON_PEGTL_NOMINMAX_WAS_DEFINED
+#endif
+
+#if defined( TAO_JSON_PEGTL_WIN32_LEAN_AND_MEAN_WAS_DEFINED )
+#undef WIN32_LEAN_AND_MEAN
+#undef TAO_JSON_PEGTL_WIN32_LEAN_AND_MEAN_WAS_DEFINED
+#endif
+
+#include <system_error>
+
+#include "../config.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   struct win32_file_opener
+   {
+      explicit win32_file_opener( const char* filename )
+         : m_source( filename ),
+           m_handle( open() )
+      {
+      }
+
+      win32_file_opener( const win32_file_opener& ) = delete;
+      win32_file_opener( win32_file_opener&& ) = delete;
+
+      ~win32_file_opener() noexcept
+      {
+         ::CloseHandle( m_handle );
+      }
+
+      void operator=( const win32_file_opener& ) = delete;
+      void operator=( win32_file_opener&& ) = delete;
+
+      [[nodiscard]] std::size_t size() const
+      {
+         LARGE_INTEGER size;
+         if( !::GetFileSizeEx( m_handle, &size ) ) {
+            const auto ec = ::GetLastError();
+            throw std::system_error( ec, std::system_category(), std::string( "GetFileSizeEx(): " ) + m_source );
+         }
+         return std::size_t( size.QuadPart );
+      }
+
+      const char* const m_source;
+      const HANDLE m_handle;
+
+   private:
+      [[nodiscard]] HANDLE open() const
+      {
+         SetLastError( 0 );
+         std::wstring ws( m_source, m_source + strlen( m_source ) );
+
+#if( _WIN32_WINNT >= 0x0602 )
+         const HANDLE handle = ::CreateFile2( ws.c_str(),
+                                              GENERIC_READ,
+                                              FILE_SHARE_READ,
+                                              OPEN_EXISTING,
+                                              nullptr );
+         if( handle != INVALID_HANDLE_VALUE ) {
+            return handle;
+         }
+         const auto ec = ::GetLastError();
+         throw std::system_error( ec, std::system_category(), std::string( "CreateFile2(): " ) + m_source );
+#else
+         const HANDLE handle = ::CreateFileW( ws.c_str(),
+                                              GENERIC_READ,
+                                              FILE_SHARE_READ,
+                                              nullptr,
+                                              OPEN_EXISTING,
+                                              FILE_ATTRIBUTE_NORMAL,
+                                              nullptr );
+         if( handle != INVALID_HANDLE_VALUE ) {
+            return handle;
+         }
+         const auto ec = ::GetLastError();
+         throw std::system_error( ec, std::system_category(), std::string( "CreateFileW(): " ) + m_source );
+#endif
+      }
+   };
+
+   struct win32_file_mapper
+   {
+      explicit win32_file_mapper( const char* filename )
+         : win32_file_mapper( win32_file_opener( filename ) )
+      {
+      }
+
+      explicit win32_file_mapper( const win32_file_opener& reader )
+         : m_size( reader.size() ),
+           m_handle( open( reader ) )
+      {
+      }
+
+      win32_file_mapper( const win32_file_mapper& ) = delete;
+      win32_file_mapper( win32_file_mapper&& ) = delete;
+
+      ~win32_file_mapper() noexcept
+      {
+         ::CloseHandle( m_handle );
+      }
+
+      void operator=( const win32_file_mapper& ) = delete;
+      void operator=( win32_file_mapper&& ) = delete;
+
+      const size_t m_size;
+      const HANDLE m_handle;
+
+   private:
+      [[nodiscard]] HANDLE open( const win32_file_opener& reader ) const
+      {
+         const uint64_t file_size = reader.size();
+         SetLastError( 0 );
+         // Use `CreateFileMappingW` because a) we're not specifying a
+         // mapping name, so the character type is of no consequence, and
+         // b) it's defined in `memoryapi.h`, unlike
+         // `CreateFileMappingA`(?!)
+         const HANDLE handle = ::CreateFileMappingW( reader.m_handle,
+                                                     nullptr,
+                                                     PAGE_READONLY,
+                                                     DWORD( file_size >> 32 ),
+                                                     DWORD( file_size & 0xffffffff ),
+                                                     nullptr );
+         if( handle != NULL || file_size == 0 ) {
+            return handle;
+         }
+         const auto ec = ::GetLastError();
+         throw std::system_error( ec, std::system_category(), std::string( "CreateFileMappingW(): " ) + reader.m_source );
+      }
+   };
+
+   class file_mapper
+   {
+   public:
+      explicit file_mapper( const char* filename )
+         : file_mapper( win32_file_mapper( filename ) )
+      {
+      }
+
+      explicit file_mapper( const win32_file_mapper& mapper )
+         : m_size( mapper.m_size ),
+           m_data( static_cast< const char* >( ::MapViewOfFile( mapper.m_handle,
+                                                                FILE_MAP_READ,
+                                                                0,
+                                                                0,
+                                                                0 ) ) )
+      {
+         if( ( m_size != 0 ) && ( intptr_t( m_data ) == 0 ) ) {
+            const auto ec = ::GetLastError();
+            throw std::system_error( ec, std::system_category(), "MapViewOfFile()" );
+         }
+      }
+
+      file_mapper( const file_mapper& ) = delete;
+      file_mapper( file_mapper&& ) = delete;
+
+      ~file_mapper() noexcept
+      {
+         ::UnmapViewOfFile( LPCVOID( m_data ) );
+      }
+
+      void operator=( const file_mapper& ) = delete;
+      void operator=( file_mapper&& ) = delete;
+
+      [[nodiscard]] bool empty() const noexcept
+      {
+         return m_size == 0;
+      }
+
+      [[nodiscard]] std::size_t size() const noexcept
+      {
+         return m_size;
+      }
+
+      using iterator = const char*;
+      using const_iterator = const char*;
+
+      [[nodiscard]] iterator data() const noexcept
+      {
+         return m_data;
+      }
+
+      [[nodiscard]] iterator begin() const noexcept
+      {
+         return m_data;
+      }
+
+      [[nodiscard]] iterator end() const noexcept
+      {
+         return m_data + m_size;
+      }
+
+   private:
+      const std::size_t m_size;
+      const char* const m_data;
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/file_opener.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/file_opener.hpp
new file mode 100644
index 000000000000..002090861e31
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/file_opener.hpp
@@ -0,0 +1,72 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_FILE_OPENER_HPP
+#define TAO_JSON_PEGTL_INTERNAL_FILE_OPENER_HPP
+
+#include <fcntl.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include <system_error>
+#include <utility>
+
+#include "../config.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   struct file_opener
+   {
+      explicit file_opener( const char* filename )
+         : m_source( filename ),
+           m_fd( open() )
+      {
+      }
+
+      file_opener( const file_opener& ) = delete;
+      file_opener( file_opener&& ) = delete;
+
+      ~file_opener() noexcept
+      {
+         ::close( m_fd );
+      }
+
+      void operator=( const file_opener& ) = delete;
+      void operator=( file_opener&& ) = delete;
+
+      [[nodiscard]] std::size_t size() const
+      {
+         struct stat st;
+         errno = 0;
+         if( ::fstat( m_fd, &st ) < 0 ) {
+            const auto ec = errno;
+            throw std::system_error( ec, std::system_category(), m_source );
+         }
+         return std::size_t( st.st_size );
+      }
+
+      const char* const m_source;
+      const int m_fd;
+
+   private:
+      [[nodiscard]] int open() const
+      {
+         errno = 0;
+         const int fd = ::open( m_source,
+                                O_RDONLY
+#if defined( O_CLOEXEC )
+                                   | O_CLOEXEC
+#endif
+         );
+         if( fd >= 0 ) {
+            return fd;
+         }
+         const auto ec = errno;
+         throw std::system_error( ec, std::system_category(), m_source );
+      }
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/file_reader.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/file_reader.hpp
new file mode 100644
index 000000000000..92bfd5c50552
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/file_reader.hpp
@@ -0,0 +1,114 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_FILE_READER_HPP
+#define TAO_JSON_PEGTL_INTERNAL_FILE_READER_HPP
+
+#include <cstdio>
+#include <memory>
+#include <string>
+#include <system_error>
+#include <utility>
+
+#include "../config.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   [[nodiscard]] inline std::FILE* file_open( const char* filename )
+   {
+      errno = 0;
+#if defined( _MSC_VER )
+      std::FILE* file;
+      if( ::fopen_s( &file, filename, "rb" ) == 0 )
+#elif defined( __MINGW32__ )
+      if( auto* file = std::fopen( filename, "rb" ) )
+#else
+      if( auto* file = std::fopen( filename, "rbe" ) )
+#endif
+      {
+         return file;
+      }
+      const auto ec = errno;
+      throw std::system_error( ec, std::system_category(), filename );
+   }
+
+   struct file_close
+   {
+      void operator()( FILE* f ) const noexcept
+      {
+         std::fclose( f );
+      }
+   };
+
+   class file_reader
+   {
+   public:
+      explicit file_reader( const char* filename )
+         : m_source( filename ),
+           m_file( file_open( m_source ) )
+      {
+      }
+
+      file_reader( FILE* file, const char* filename ) noexcept
+         : m_source( filename ),
+           m_file( file )
+      {
+      }
+
+      file_reader( const file_reader& ) = delete;
+      file_reader( file_reader&& ) = delete;
+
+      ~file_reader() = default;
+
+      void operator=( const file_reader& ) = delete;
+      void operator=( file_reader&& ) = delete;
+
+      [[nodiscard]] std::size_t size() const
+      {
+         errno = 0;
+         if( std::fseek( m_file.get(), 0, SEEK_END ) != 0 ) {
+            // LCOV_EXCL_START
+            const auto ec = errno;
+            throw std::system_error( ec, std::system_category(), m_source );
+            // LCOV_EXCL_STOP
+         }
+         errno = 0;
+         const auto s = std::ftell( m_file.get() );
+         if( s < 0 ) {
+            // LCOV_EXCL_START
+            const auto ec = errno;
+            throw std::system_error( ec, std::system_category(), m_source );
+            // LCOV_EXCL_STOP
+         }
+         errno = 0;
+         if( std::fseek( m_file.get(), 0, SEEK_SET ) != 0 ) {
+            // LCOV_EXCL_START
+            const auto ec = errno;
+            throw std::system_error( ec, std::system_category(), m_source );
+            // LCOV_EXCL_STOP
+         }
+         return std::size_t( s );
+      }
+
+      [[nodiscard]] std::string read() const
+      {
+         std::string nrv;
+         nrv.resize( size() );
+         errno = 0;
+         if( !nrv.empty() && ( std::fread( &nrv[ 0 ], nrv.size(), 1, m_file.get() ) != 1 ) ) {
+            // LCOV_EXCL_START
+            const auto ec = errno;
+            throw std::system_error( ec, std::system_category(), m_source );
+            // LCOV_EXCL_STOP
+         }
+         return nrv;
+      }
+
+   private:
+      const char* const m_source;
+      const std::unique_ptr< std::FILE, file_close > m_file;
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/has_apply.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/has_apply.hpp
new file mode 100644
index 000000000000..93adec68b888
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/has_apply.hpp
@@ -0,0 +1,25 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_HAS_APPLY_HPP
+#define TAO_JSON_PEGTL_INTERNAL_HAS_APPLY_HPP
+
+#include <type_traits>
+
+#include "../config.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< typename, typename, template< typename... > class, typename... >
+   struct has_apply
+      : std::false_type
+   {};
+
+   template< typename C, template< typename... > class Action, typename... S >
+   struct has_apply< C, decltype( C::template apply< Action >( std::declval< S >()... ) ), Action, S... >
+      : std::true_type
+   {};
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/has_apply0.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/has_apply0.hpp
new file mode 100644
index 000000000000..2c67c8715b46
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/has_apply0.hpp
@@ -0,0 +1,25 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_HAS_APPLY0_HPP
+#define TAO_JSON_PEGTL_INTERNAL_HAS_APPLY0_HPP
+
+#include <type_traits>
+
+#include "../config.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< typename, typename, template< typename... > class, typename... >
+   struct has_apply0
+      : std::false_type
+   {};
+
+   template< typename C, template< typename... > class Action, typename... S >
+   struct has_apply0< C, decltype( C::template apply0< Action >( std::declval< S >()... ) ), Action, S... >
+      : std::true_type
+   {};
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/has_match.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/has_match.hpp
new file mode 100644
index 000000000000..017901b83703
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/has_match.hpp
@@ -0,0 +1,56 @@
+// Copyright (c) 2019-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_HAS_MATCH_HPP
+#define TAO_JSON_PEGTL_INTERNAL_HAS_MATCH_HPP
+
+#include <type_traits>
+#include <utility>
+
+#include "../apply_mode.hpp"
+#include "../config.hpp"
+#include "../rewind_mode.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< typename,
+             typename Rule,
+             apply_mode A,
+             rewind_mode M,
+             template< typename... >
+             class Action,
+             template< typename... >
+             class Control,
+             typename Input,
+             typename... States >
+   struct has_match
+      : std::false_type
+   {};
+
+   template< typename Rule,
+             apply_mode A,
+             rewind_mode M,
+             template< typename... >
+             class Action,
+             template< typename... >
+             class Control,
+             typename Input,
+             typename... States >
+   struct has_match< decltype( (void)Action< Rule >::template match< Rule, A, M, Action, Control >( std::declval< Input& >(), std::declval< States&& >()... ), void() ), Rule, A, M, Action, Control, Input, States... >
+      : std::true_type
+   {};
+
+   template< typename Rule,
+             apply_mode A,
+             rewind_mode M,
+             template< typename... >
+             class Action,
+             template< typename... >
+             class Control,
+             typename Input,
+             typename... States >
+   inline constexpr bool has_match_v = has_match< void, Rule, A, M, Action, Control, Input, States... >::value;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/identifier.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/identifier.hpp
new file mode 100644
index 000000000000..4e69b9f6c60b
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/identifier.hpp
@@ -0,0 +1,22 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_IDENTIFIER_HPP
+#define TAO_JSON_PEGTL_INTERNAL_IDENTIFIER_HPP
+
+#include "../config.hpp"
+
+#include "peek_char.hpp"
+#include "ranges.hpp"
+#include "seq.hpp"
+#include "star.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   using identifier_first = ranges< peek_char, 'a', 'z', 'A', 'Z', '_' >;
+   using identifier_other = ranges< peek_char, 'a', 'z', 'A', 'Z', '0', '9', '_' >;
+   using identifier = seq< identifier_first, star< identifier_other > >;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/if_apply.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/if_apply.hpp
new file mode 100644
index 000000000000..a8a4eb0ac9e9
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/if_apply.hpp
@@ -0,0 +1,53 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_IF_APPLY_HPP
+#define TAO_JSON_PEGTL_INTERNAL_IF_APPLY_HPP
+
+#include "../config.hpp"
+
+#include "apply_single.hpp"
+#include "skip_control.hpp"
+
+#include "../analysis/counted.hpp"
+#include "../apply_mode.hpp"
+#include "../rewind_mode.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< typename Rule, typename... Actions >
+   struct if_apply
+   {
+      using analyze_t = typename Rule::analyze_t;
+
+      template< apply_mode A,
+                rewind_mode M,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class Control,
+                typename Input,
+                typename... States >
+      [[nodiscard]] static bool match( Input& in, States&&... st )
+      {
+         if constexpr( ( A == apply_mode::action ) && ( sizeof...( Actions ) != 0 ) ) {
+            using action_t = typename Input::action_t;
+            auto m = in.template mark< rewind_mode::required >();
+            if( Control< Rule >::template match< apply_mode::action, rewind_mode::active, Action, Control >( in, st... ) ) {
+               const action_t i2( m.iterator(), in );
+               return m( ( apply_single< Actions >::match( i2, st... ) && ... ) );
+            }
+            return false;
+         }
+         else {
+            return Control< Rule >::template match< A, M, Action, Control >( in, st... );
+         }
+      }
+   };
+
+   template< typename Rule, typename... Actions >
+   inline constexpr bool skip_control< if_apply< Rule, Actions... > > = true;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/if_must.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/if_must.hpp
new file mode 100644
index 000000000000..067d4d519b6f
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/if_must.hpp
@@ -0,0 +1,48 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_IF_MUST_HPP
+#define TAO_JSON_PEGTL_INTERNAL_IF_MUST_HPP
+
+#include "../config.hpp"
+
+#include "must.hpp"
+#include "skip_control.hpp"
+#include "trivial.hpp"
+
+#include "../apply_mode.hpp"
+#include "../rewind_mode.hpp"
+
+#include "../analysis/counted.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< bool Default, typename Cond, typename... Rules >
+   struct if_must
+   {
+      using analyze_t = analysis::counted< analysis::rule_type::seq, Default ? 0 : 1, Cond, must< Rules... > >;
+
+      template< apply_mode A,
+                rewind_mode M,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class Control,
+                typename Input,
+                typename... States >
+      [[nodiscard]] static bool match( Input& in, States&&... st )
+      {
+         if( Control< Cond >::template match< A, M, Action, Control >( in, st... ) ) {
+            (void)( Control< must< Rules > >::template match< A, M, Action, Control >( in, st... ) && ... );
+            return true;
+         }
+         return Default;
+      }
+   };
+
+   template< bool Default, typename Cond, typename... Rules >
+   inline constexpr bool skip_control< if_must< Default, Cond, Rules... > > = true;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/if_must_else.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/if_must_else.hpp
new file mode 100644
index 000000000000..0832772cd740
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/if_must_else.hpp
@@ -0,0 +1,19 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_IF_MUST_ELSE_HPP
+#define TAO_JSON_PEGTL_INTERNAL_IF_MUST_ELSE_HPP
+
+#include "../config.hpp"
+
+#include "if_then_else.hpp"
+#include "must.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< typename Cond, typename Then, typename Else >
+   using if_must_else = if_then_else< Cond, must< Then >, must< Else > >;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/if_then_else.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/if_then_else.hpp
new file mode 100644
index 000000000000..26c2623d0ed5
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/if_then_else.hpp
@@ -0,0 +1,51 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_IF_THEN_ELSE_HPP
+#define TAO_JSON_PEGTL_INTERNAL_IF_THEN_ELSE_HPP
+
+#include "../config.hpp"
+
+#include "not_at.hpp"
+#include "seq.hpp"
+#include "skip_control.hpp"
+#include "sor.hpp"
+
+#include "../apply_mode.hpp"
+#include "../rewind_mode.hpp"
+
+#include "../analysis/generic.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< typename Cond, typename Then, typename Else >
+   struct if_then_else
+   {
+      using analyze_t = analysis::generic< analysis::rule_type::sor, seq< Cond, Then >, seq< not_at< Cond >, Else > >;
+
+      template< apply_mode A,
+                rewind_mode M,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class Control,
+                typename Input,
+                typename... States >
+      [[nodiscard]] static bool match( Input& in, States&&... st )
+      {
+         auto m = in.template mark< M >();
+         using m_t = decltype( m );
+
+         if( Control< Cond >::template match< A, rewind_mode::required, Action, Control >( in, st... ) ) {
+            return m( Control< Then >::template match< A, m_t::next_rewind_mode, Action, Control >( in, st... ) );
+         }
+         return m( Control< Else >::template match< A, m_t::next_rewind_mode, Action, Control >( in, st... ) );
+      }
+   };
+
+   template< typename Cond, typename Then, typename Else >
+   inline constexpr bool skip_control< if_then_else< Cond, Then, Else > > = true;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/input_pair.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/input_pair.hpp
new file mode 100644
index 000000000000..b97f177d2723
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/input_pair.hpp
@@ -0,0 +1,29 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_INPUT_PAIR_HPP
+#define TAO_JSON_PEGTL_INTERNAL_INPUT_PAIR_HPP
+
+#include <cstdint>
+
+#include "../config.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< typename Data >
+   struct input_pair
+   {
+      Data data;
+      std::uint8_t size;
+
+      using data_t = Data;
+
+      explicit operator bool() const noexcept
+      {
+         return size > 0;
+      }
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/istream_reader.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/istream_reader.hpp
new file mode 100644
index 000000000000..25f5b7af779c
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/istream_reader.hpp
@@ -0,0 +1,40 @@
+// Copyright (c) 2016-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_ISTREAM_READER_HPP
+#define TAO_JSON_PEGTL_INTERNAL_ISTREAM_READER_HPP
+
+#include <istream>
+#include <system_error>
+
+#include "../config.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   struct istream_reader
+   {
+      explicit istream_reader( std::istream& s ) noexcept
+         : m_istream( s )
+      {
+      }
+
+      [[nodiscard]] std::size_t operator()( char* buffer, const std::size_t length )
+      {
+         m_istream.read( buffer, std::streamsize( length ) );
+
+         if( const auto r = m_istream.gcount() ) {
+            return std::size_t( r );
+         }
+         if( m_istream.eof() ) {
+            return 0;
+         }
+         const auto ec = errno;
+         throw std::system_error( ec, std::system_category(), "std::istream::read() failed" );
+      }
+
+      std::istream& m_istream;
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/istring.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/istring.hpp
new file mode 100644
index 000000000000..6f21c570f704
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/istring.hpp
@@ -0,0 +1,72 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_ISTRING_HPP
+#define TAO_JSON_PEGTL_INTERNAL_ISTRING_HPP
+
+#include <type_traits>
+
+#include "../config.hpp"
+
+#include "bump_help.hpp"
+#include "result_on_found.hpp"
+#include "skip_control.hpp"
+#include "trivial.hpp"
+
+#include "../analysis/counted.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< char C >
+   inline constexpr bool is_alpha = ( ( 'a' <= C ) && ( C <= 'z' ) ) || ( ( 'A' <= C ) && ( C <= 'Z' ) );
+
+   template< char C >
+   [[nodiscard]] bool ichar_equal( const char c ) noexcept
+   {
+      if constexpr( is_alpha< C > ) {
+         return ( C | 0x20 ) == ( c | 0x20 );
+      }
+      else {
+         return c == C;
+      }
+   }
+
+   template< char... Cs >
+   [[nodiscard]] bool istring_equal( const char* r ) noexcept
+   {
+      return ( ichar_equal< Cs >( *r++ ) && ... );
+   }
+
+   template< char... Cs >
+   struct istring;
+
+   template<>
+   struct istring<>
+      : trivial< true >
+   {
+   };
+
+   template< char... Cs >
+   struct istring
+   {
+      using analyze_t = analysis::counted< analysis::rule_type::any, sizeof...( Cs ) >;
+
+      template< typename Input >
+      [[nodiscard]] static bool match( Input& in ) noexcept( noexcept( in.size( 0 ) ) )
+      {
+         if( in.size( sizeof...( Cs ) ) >= sizeof...( Cs ) ) {
+            if( istring_equal< Cs... >( in.current() ) ) {
+               bump_help< result_on_found::success, Input, char, Cs... >( in, sizeof...( Cs ) );
+               return true;
+            }
+         }
+         return false;
+      }
+   };
+
+   template< char... Cs >
+   inline constexpr bool skip_control< istring< Cs... > > = true;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/iterator.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/iterator.hpp
new file mode 100644
index 000000000000..cc2c96f39a61
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/iterator.hpp
@@ -0,0 +1,52 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_ITERATOR_HPP
+#define TAO_JSON_PEGTL_INTERNAL_ITERATOR_HPP
+
+#include <cstdlib>
+
+#include "../config.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   struct iterator
+   {
+      iterator() = default;
+
+      explicit iterator( const char* in_data ) noexcept
+         : data( in_data )
+      {
+      }
+
+      iterator( const char* in_data, const std::size_t in_byte, const std::size_t in_line, const std::size_t in_byte_in_line ) noexcept
+         : data( in_data ),
+           byte( in_byte ),
+           line( in_line ),
+           byte_in_line( in_byte_in_line )
+      {
+      }
+
+      iterator( const iterator& ) = default;
+      iterator( iterator&& ) = default;
+
+      ~iterator() = default;
+
+      iterator& operator=( const iterator& ) = default;
+      iterator& operator=( iterator&& ) = default;
+
+      void reset() noexcept
+      {
+         *this = iterator();
+      }
+
+      const char* data = nullptr;
+
+      std::size_t byte = 0;
+      std::size_t line = 1;
+      std::size_t byte_in_line = 0;
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/lf_crlf_eol.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/lf_crlf_eol.hpp
new file mode 100644
index 000000000000..aefef00a55e6
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/lf_crlf_eol.hpp
@@ -0,0 +1,37 @@
+// Copyright (c) 2016-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_LF_CRLF_EOL_HPP
+#define TAO_JSON_PEGTL_INTERNAL_LF_CRLF_EOL_HPP
+
+#include "../config.hpp"
+#include "../eol_pair.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   struct lf_crlf_eol
+   {
+      static constexpr int ch = '\n';
+
+      template< typename Input >
+      [[nodiscard]] static eol_pair match( Input& in ) noexcept( noexcept( in.size( 2 ) ) )
+      {
+         eol_pair p = { false, in.size( 2 ) };
+         if( p.second ) {
+            const auto a = in.peek_char();
+            if( a == '\n' ) {
+               in.bump_to_next_line();
+               p.first = true;
+            }
+            else if( ( a == '\r' ) && ( p.second > 1 ) && ( in.peek_char( 1 ) == '\n' ) ) {
+               in.bump_to_next_line( 2 );
+               p.first = true;
+            }
+         }
+         return p;
+      }
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/lf_eol.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/lf_eol.hpp
new file mode 100644
index 000000000000..6d8d418d336f
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/lf_eol.hpp
@@ -0,0 +1,32 @@
+// Copyright (c) 2016-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_LF_EOL_HPP
+#define TAO_JSON_PEGTL_INTERNAL_LF_EOL_HPP
+
+#include "../config.hpp"
+#include "../eol_pair.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   struct lf_eol
+   {
+      static constexpr int ch = '\n';
+
+      template< typename Input >
+      [[nodiscard]] static eol_pair match( Input& in ) noexcept( noexcept( in.size( 1 ) ) )
+      {
+         eol_pair p = { false, in.size( 1 ) };
+         if( p.second ) {
+            if( in.peek_char() == '\n' ) {
+               in.bump_to_next_line();
+               p.first = true;
+            }
+         }
+         return p;
+      }
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/list.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/list.hpp
new file mode 100644
index 000000000000..b9ef9353e24c
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/list.hpp
@@ -0,0 +1,19 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_LIST_HPP
+#define TAO_JSON_PEGTL_INTERNAL_LIST_HPP
+
+#include "../config.hpp"
+
+#include "seq.hpp"
+#include "star.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< typename Rule, typename Sep >
+   using list = seq< Rule, star< Sep, Rule > >;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/list_must.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/list_must.hpp
new file mode 100644
index 000000000000..ce5a505e0dd6
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/list_must.hpp
@@ -0,0 +1,20 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_LIST_MUST_HPP
+#define TAO_JSON_PEGTL_INTERNAL_LIST_MUST_HPP
+
+#include "../config.hpp"
+
+#include "must.hpp"
+#include "seq.hpp"
+#include "star.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< typename Rule, typename Sep >
+   using list_must = seq< Rule, star< Sep, must< Rule > > >;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/list_tail.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/list_tail.hpp
new file mode 100644
index 000000000000..24195a1429ff
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/list_tail.hpp
@@ -0,0 +1,20 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_LIST_TAIL_HPP
+#define TAO_JSON_PEGTL_INTERNAL_LIST_TAIL_HPP
+
+#include "../config.hpp"
+
+#include "list.hpp"
+#include "opt.hpp"
+#include "seq.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< typename Rule, typename Sep >
+   using list_tail = seq< list< Rule, Sep >, opt< Sep > >;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/list_tail_pad.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/list_tail_pad.hpp
new file mode 100644
index 000000000000..531c66a37580
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/list_tail_pad.hpp
@@ -0,0 +1,22 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_LIST_TAIL_PAD_HPP
+#define TAO_JSON_PEGTL_INTERNAL_LIST_TAIL_PAD_HPP
+
+#include "../config.hpp"
+
+#include "list.hpp"
+#include "opt.hpp"
+#include "pad.hpp"
+#include "seq.hpp"
+#include "star.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< typename Rule, typename Sep, typename Pad >
+   using list_tail_pad = seq< list< Rule, pad< Sep, Pad > >, opt< star< Pad >, Sep > >;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/marker.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/marker.hpp
new file mode 100644
index 000000000000..4e7812c3a3f8
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/marker.hpp
@@ -0,0 +1,82 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_MARKER_HPP
+#define TAO_JSON_PEGTL_INTERNAL_MARKER_HPP
+
+#include "../config.hpp"
+#include "../rewind_mode.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< typename Iterator, rewind_mode M >
+   class marker
+   {
+   public:
+      static constexpr rewind_mode next_rewind_mode = M;
+
+      explicit marker( const Iterator& /*unused*/ ) noexcept
+      {
+      }
+
+      marker( const marker& ) = delete;
+      marker( marker&& ) = delete;
+
+      ~marker() = default;
+
+      void operator=( const marker& ) = delete;
+      void operator=( marker&& ) = delete;
+
+      [[nodiscard]] bool operator()( const bool result ) const noexcept
+      {
+         return result;
+      }
+   };
+
+   template< typename Iterator >
+   class marker< Iterator, rewind_mode::required >
+   {
+   public:
+      static constexpr rewind_mode next_rewind_mode = rewind_mode::active;
+
+      explicit marker( Iterator& i ) noexcept
+         : m_saved( i ),
+           m_input( &i )
+      {
+      }
+
+      marker( const marker& ) = delete;
+      marker( marker&& ) = delete;
+
+      ~marker() noexcept
+      {
+         if( m_input != nullptr ) {
+            ( *m_input ) = m_saved;
+         }
+      }
+
+      void operator=( const marker& ) = delete;
+      void operator=( marker&& ) = delete;
+
+      [[nodiscard]] bool operator()( const bool result ) noexcept
+      {
+         if( result ) {
+            m_input = nullptr;
+            return true;
+         }
+         return false;
+      }
+
+      [[nodiscard]] const Iterator& iterator() const noexcept
+      {
+         return m_saved;
+      }
+
+   private:
+      const Iterator m_saved;
+      Iterator* m_input;
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/missing_apply.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/missing_apply.hpp
new file mode 100644
index 000000000000..5a5483c71592
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/missing_apply.hpp
@@ -0,0 +1,25 @@
+// Copyright (c) 2019-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_MISSING_APPLY_HPP
+#define TAO_JSON_PEGTL_INTERNAL_MISSING_APPLY_HPP
+
+#include "../config.hpp"
+#include "../rewind_mode.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< typename Control,
+             template< typename... >
+             class Action,
+             typename Input,
+             typename... States >
+   void missing_apply( Input& in, States&&... st )
+   {
+      auto m = in.template mark< rewind_mode::required >();
+      (void)Control::template apply< Action >( m.iterator(), in, st... );
+   }
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/missing_apply0.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/missing_apply0.hpp
new file mode 100644
index 000000000000..de53e3e06db5
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/missing_apply0.hpp
@@ -0,0 +1,23 @@
+// Copyright (c) 2019-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_MISSING_APPLY0_HPP
+#define TAO_JSON_PEGTL_INTERNAL_MISSING_APPLY0_HPP
+
+#include "../config.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< typename Control,
+             template< typename... >
+             class Action,
+             typename Input,
+             typename... States >
+   void missing_apply0( Input& in, States&&... st )
+   {
+      (void)Control::template apply0< Action >( in, st... );
+   }
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/must.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/must.hpp
new file mode 100644
index 000000000000..fd274aa48752
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/must.hpp
@@ -0,0 +1,72 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_MUST_HPP
+#define TAO_JSON_PEGTL_INTERNAL_MUST_HPP
+
+#include "../config.hpp"
+
+#include "raise.hpp"
+#include "skip_control.hpp"
+
+#include "../apply_mode.hpp"
+#include "../rewind_mode.hpp"
+
+#include "../analysis/generic.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   // The general case applies must<> to each of the
+   // rules in the 'Rules' parameter pack individually.
+
+   template< typename... Rules >
+   struct must
+   {
+      using analyze_t = analysis::generic< analysis::rule_type::seq, Rules... >;
+
+      template< apply_mode A,
+                rewind_mode M,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class Control,
+                typename Input,
+                typename... States >
+      [[nodiscard]] static bool match( Input& in, States&&... st )
+      {
+         return ( Control< must< Rules > >::template match< A, M, Action, Control >( in, st... ) && ... );
+      }
+   };
+
+   // While in theory the implementation for a single rule could
+   // be simplified to must< Rule > = sor< Rule, raise< Rule > >, this
+   // would result in some unnecessary run-time overhead.
+
+   template< typename Rule >
+   struct must< Rule >
+   {
+      using analyze_t = typename Rule::analyze_t;
+
+      template< apply_mode A,
+                rewind_mode,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class Control,
+                typename Input,
+                typename... States >
+      [[nodiscard]] static bool match( Input& in, States&&... st )
+      {
+         if( !Control< Rule >::template match< A, rewind_mode::dontcare, Action, Control >( in, st... ) ) {
+            (void)raise< Rule >::template match< A, rewind_mode::dontcare, Action, Control >( in, st... );
+         }
+         return true;
+      }
+   };
+
+   template< typename... Rules >
+   inline constexpr bool skip_control< must< Rules... > > = true;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/not_at.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/not_at.hpp
new file mode 100644
index 000000000000..8db18427e50b
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/not_at.hpp
@@ -0,0 +1,53 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_NOT_AT_HPP
+#define TAO_JSON_PEGTL_INTERNAL_NOT_AT_HPP
+
+#include "../config.hpp"
+
+#include "skip_control.hpp"
+#include "trivial.hpp"
+
+#include "../apply_mode.hpp"
+#include "../rewind_mode.hpp"
+
+#include "../analysis/generic.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< typename... Rules >
+   struct not_at;
+
+   template<>
+   struct not_at<>
+      : trivial< false >
+   {
+   };
+
+   template< typename... Rules >
+   struct not_at
+   {
+      using analyze_t = analysis::generic< analysis::rule_type::opt, Rules... >;
+
+      template< apply_mode,
+                rewind_mode,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class Control,
+                typename Input,
+                typename... States >
+      [[nodiscard]] static bool match( Input& in, States&&... st )
+      {
+         const auto m = in.template mark< rewind_mode::required >();
+         return !( Control< Rules >::template match< apply_mode::nothing, rewind_mode::active, Action, Control >( in, st... ) && ... );
+      }
+   };
+
+   template< typename... Rules >
+   inline constexpr bool skip_control< not_at< Rules... > > = true;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/one.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/one.hpp
new file mode 100644
index 000000000000..98cd05145c8f
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/one.hpp
@@ -0,0 +1,44 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_ONE_HPP
+#define TAO_JSON_PEGTL_INTERNAL_ONE_HPP
+
+#include <cstddef>
+
+#include "../config.hpp"
+
+#include "bump_help.hpp"
+#include "result_on_found.hpp"
+#include "skip_control.hpp"
+
+#include "../analysis/generic.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< result_on_found R, typename Peek, typename Peek::data_t... Cs >
+   struct one
+   {
+      using analyze_t = analysis::generic< analysis::rule_type::any >;
+
+      template< typename Input >
+      [[nodiscard]] static bool match( Input& in ) noexcept( noexcept( in.size( Peek::max_input_size ) ) )
+      {
+         if( const std::size_t s = in.size( Peek::max_input_size ); s >= Peek::min_input_size ) {
+            if( const auto t = Peek::peek( in, s ) ) {
+               if( ( ( t.data == Cs ) || ... ) == bool( R ) ) {
+                  bump_help< R, Input, typename Peek::data_t, Cs... >( in, t.size );
+                  return true;
+               }
+            }
+         }
+         return false;
+      }
+   };
+
+   template< result_on_found R, typename Peek, typename Peek::data_t... Cs >
+   inline constexpr bool skip_control< one< R, Peek, Cs... > > = true;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/opt.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/opt.hpp
new file mode 100644
index 000000000000..8cd607563061
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/opt.hpp
@@ -0,0 +1,57 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_OPT_HPP
+#define TAO_JSON_PEGTL_INTERNAL_OPT_HPP
+
+#include <type_traits>
+
+#include "../config.hpp"
+
+#include "duseltronik.hpp"
+#include "seq.hpp"
+#include "skip_control.hpp"
+#include "trivial.hpp"
+
+#include "../apply_mode.hpp"
+#include "../rewind_mode.hpp"
+
+#include "../analysis/generic.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< typename... Rules >
+   struct opt;
+
+   template<>
+   struct opt<>
+      : trivial< true >
+   {
+   };
+
+   template< typename... Rules >
+   struct opt
+   {
+      using analyze_t = analysis::generic< analysis::rule_type::opt, Rules... >;
+
+      template< apply_mode A,
+                rewind_mode,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class Control,
+                typename Input,
+                typename... States >
+      [[nodiscard]] static bool match( Input& in, States&&... st )
+      {
+         (void)duseltronik< seq< Rules... >, A, rewind_mode::required, Action, Control >::match( in, st... );
+         return true;
+      }
+   };
+
+   template< typename... Rules >
+   inline constexpr bool skip_control< opt< Rules... > > = true;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/pad.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/pad.hpp
new file mode 100644
index 000000000000..18fed7c04a13
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/pad.hpp
@@ -0,0 +1,19 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_PAD_HPP
+#define TAO_JSON_PEGTL_INTERNAL_PAD_HPP
+
+#include "../config.hpp"
+
+#include "seq.hpp"
+#include "star.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< typename Rule, typename Pad1, typename Pad2 = Pad1 >
+   using pad = seq< star< Pad1 >, Rule, star< Pad2 > >;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/pad_opt.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/pad_opt.hpp
new file mode 100644
index 000000000000..933caed9ea44
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/pad_opt.hpp
@@ -0,0 +1,20 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_PAD_OPT_HPP
+#define TAO_JSON_PEGTL_INTERNAL_PAD_OPT_HPP
+
+#include "../config.hpp"
+
+#include "opt.hpp"
+#include "seq.hpp"
+#include "star.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< typename Rule, typename Pad >
+   using pad_opt = seq< star< Pad >, opt< Rule, star< Pad > > >;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/peek_char.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/peek_char.hpp
new file mode 100644
index 000000000000..88b94512eabc
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/peek_char.hpp
@@ -0,0 +1,32 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_PEEK_CHAR_HPP
+#define TAO_JSON_PEGTL_INTERNAL_PEEK_CHAR_HPP
+
+#include <cstddef>
+
+#include "../config.hpp"
+
+#include "input_pair.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   struct peek_char
+   {
+      using data_t = char;
+      using pair_t = input_pair< char >;
+
+      static constexpr std::size_t min_input_size = 1;
+      static constexpr std::size_t max_input_size = 1;
+
+      template< typename Input >
+      [[nodiscard]] static pair_t peek( const Input& in, const std::size_t /*unused*/ = 1 ) noexcept
+      {
+         return { in.peek_char(), 1 };
+      }
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/peek_mask_uint.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/peek_mask_uint.hpp
new file mode 100644
index 000000000000..97248f0dd58b
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/peek_mask_uint.hpp
@@ -0,0 +1,54 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_PEEK_MASK_UINT_HPP
+#define TAO_JSON_PEGTL_INTERNAL_PEEK_MASK_UINT_HPP
+
+#include <cstddef>
+#include <cstdint>
+
+#include "../config.hpp"
+
+#include "input_pair.hpp"
+#include "read_uint.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< typename R, typename R::type M >
+   struct peek_mask_uint_impl
+   {
+      using data_t = typename R::type;
+      using pair_t = input_pair< data_t >;
+
+      static constexpr std::size_t min_input_size = sizeof( data_t );
+      static constexpr std::size_t max_input_size = sizeof( data_t );
+
+      template< typename Input >
+      [[nodiscard]] static pair_t peek( const Input& in, const std::size_t /*unused*/ ) noexcept
+      {
+         const data_t data = R::read( in.current() ) & M;
+         return { data, sizeof( data_t ) };
+      }
+   };
+
+   template< std::uint16_t M >
+   using peek_mask_uint16_be = peek_mask_uint_impl< read_uint16_be, M >;
+
+   template< std::uint16_t M >
+   using peek_mask_uint16_le = peek_mask_uint_impl< read_uint16_le, M >;
+
+   template< std::uint32_t M >
+   using peek_mask_uint32_be = peek_mask_uint_impl< read_uint32_be, M >;
+
+   template< std::uint32_t M >
+   using peek_mask_uint32_le = peek_mask_uint_impl< read_uint32_le, M >;
+
+   template< std::uint64_t M >
+   using peek_mask_uint64_be = peek_mask_uint_impl< read_uint64_be, M >;
+
+   template< std::uint64_t M >
+   using peek_mask_uint64_le = peek_mask_uint_impl< read_uint64_le, M >;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/peek_mask_uint8.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/peek_mask_uint8.hpp
new file mode 100644
index 000000000000..c64d0913d2aa
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/peek_mask_uint8.hpp
@@ -0,0 +1,34 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_PEEK_MASK_UINT8_HPP
+#define TAO_JSON_PEGTL_INTERNAL_PEEK_MASK_UINT8_HPP
+
+#include <cstddef>
+#include <cstdint>
+
+#include "../config.hpp"
+
+#include "input_pair.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< std::uint8_t M >
+   struct peek_mask_uint8
+   {
+      using data_t = std::uint8_t;
+      using pair_t = input_pair< std::uint8_t >;
+
+      static constexpr std::size_t min_input_size = 1;
+      static constexpr std::size_t max_input_size = 1;
+
+      template< typename Input >
+      [[nodiscard]] static pair_t peek( const Input& in, const std::size_t /*unused*/ = 1 ) noexcept
+      {
+         return { std::uint8_t( in.peek_uint8() & M ), 1 };
+      }
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/peek_uint.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/peek_uint.hpp
new file mode 100644
index 000000000000..95aaaabe798a
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/peek_uint.hpp
@@ -0,0 +1,45 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_PEEK_UINT_HPP
+#define TAO_JSON_PEGTL_INTERNAL_PEEK_UINT_HPP
+
+#include <cstddef>
+#include <cstdint>
+
+#include "../config.hpp"
+
+#include "input_pair.hpp"
+#include "read_uint.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< typename R >
+   struct peek_uint_impl
+   {
+      using data_t = typename R::type;
+      using pair_t = input_pair< data_t >;
+
+      static constexpr std::size_t min_input_size = sizeof( data_t );
+      static constexpr std::size_t max_input_size = sizeof( data_t );
+
+      template< typename Input >
+      [[nodiscard]] static pair_t peek( const Input& in, const std::size_t /*unused*/ ) noexcept
+      {
+         const data_t data = R::read( in.current() );
+         return { data, sizeof( data_t ) };
+      }
+   };
+
+   using peek_uint16_be = peek_uint_impl< read_uint16_be >;
+   using peek_uint16_le = peek_uint_impl< read_uint16_le >;
+
+   using peek_uint32_be = peek_uint_impl< read_uint32_be >;
+   using peek_uint32_le = peek_uint_impl< read_uint32_le >;
+
+   using peek_uint64_be = peek_uint_impl< read_uint64_be >;
+   using peek_uint64_le = peek_uint_impl< read_uint64_le >;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/peek_uint8.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/peek_uint8.hpp
new file mode 100644
index 000000000000..6f439b5410f4
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/peek_uint8.hpp
@@ -0,0 +1,33 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_PEEK_UINT8_HPP
+#define TAO_JSON_PEGTL_INTERNAL_PEEK_UINT8_HPP
+
+#include <cstddef>
+#include <cstdint>
+
+#include "../config.hpp"
+
+#include "input_pair.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   struct peek_uint8
+   {
+      using data_t = std::uint8_t;
+      using pair_t = input_pair< std::uint8_t >;
+
+      static constexpr std::size_t min_input_size = 1;
+      static constexpr std::size_t max_input_size = 1;
+
+      template< typename Input >
+      [[nodiscard]] static pair_t peek( const Input& in, const std::size_t /*unused*/ = 1 ) noexcept
+      {
+         return { in.peek_uint8(), 1 };
+      }
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/peek_utf16.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/peek_utf16.hpp
new file mode 100644
index 000000000000..c5172b4520c2
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/peek_utf16.hpp
@@ -0,0 +1,54 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_PEEK_UTF16_HPP
+#define TAO_JSON_PEGTL_INTERNAL_PEEK_UTF16_HPP
+
+#include <type_traits>
+
+#include "../config.hpp"
+
+#include "input_pair.hpp"
+#include "read_uint.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< typename R >
+   struct peek_utf16_impl
+   {
+      using data_t = char32_t;
+      using pair_t = input_pair< char32_t >;
+
+      using short_t = std::make_unsigned< char16_t >::type;
+
+      static_assert( sizeof( short_t ) == 2 );
+      static_assert( sizeof( char16_t ) == 2 );
+
+      static constexpr std::size_t min_input_size = 2;
+      static constexpr std::size_t max_input_size = 4;
+
+      template< typename Input >
+      [[nodiscard]] static pair_t peek( const Input& in, const std::size_t s ) noexcept
+      {
+         const char32_t t = R::read( in.current() );
+         if( ( t < 0xd800 ) || ( t > 0xdfff ) ) {
+            return { t, 2 };
+         }
+         if( ( t >= 0xdc00 ) || ( s < 4 ) ) {
+            return { 0, 0 };
+         }
+         const char32_t u = R::read( in.current() + 2 );
+         if( ( u >= 0xdc00 ) && ( u <= 0xdfff ) ) {
+            const auto cp = ( ( ( t & 0x03ff ) << 10 ) | ( u & 0x03ff ) ) + 0x10000;
+            return { cp, 4 };
+         }
+         return { 0, 0 };
+      }
+   };
+
+   using peek_utf16_be = peek_utf16_impl< read_uint16_be >;
+   using peek_utf16_le = peek_utf16_impl< read_uint16_le >;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/peek_utf32.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/peek_utf32.hpp
new file mode 100644
index 000000000000..32c2a7215252
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/peek_utf32.hpp
@@ -0,0 +1,43 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_PEEK_UTF32_HPP
+#define TAO_JSON_PEGTL_INTERNAL_PEEK_UTF32_HPP
+
+#include <cstddef>
+
+#include "../config.hpp"
+
+#include "input_pair.hpp"
+#include "read_uint.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< typename R >
+   struct peek_utf32_impl
+   {
+      using data_t = char32_t;
+      using pair_t = input_pair< char32_t >;
+
+      static_assert( sizeof( char32_t ) == 4 );
+
+      static constexpr std::size_t min_input_size = 4;
+      static constexpr std::size_t max_input_size = 4;
+
+      template< typename Input >
+      [[nodiscard]] static pair_t peek( const Input& in, const std::size_t /*unused*/ ) noexcept
+      {
+         const char32_t t = R::read( in.current() );
+         if( ( t <= 0x10ffff ) && !( t >= 0xd800 && t <= 0xdfff ) ) {
+            return { t, 4 };
+         }
+         return { 0, 0 };
+      }
+   };
+
+   using peek_utf32_be = peek_utf32_impl< read_uint32_be >;
+   using peek_utf32_le = peek_utf32_impl< read_uint32_le >;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/peek_utf8.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/peek_utf8.hpp
new file mode 100644
index 000000000000..f9d50d96408b
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/peek_utf8.hpp
@@ -0,0 +1,90 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_PEEK_UTF8_HPP
+#define TAO_JSON_PEGTL_INTERNAL_PEEK_UTF8_HPP
+
+#include "../config.hpp"
+
+#include "input_pair.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   struct peek_utf8
+   {
+      using data_t = char32_t;
+      using pair_t = input_pair< char32_t >;
+
+      static constexpr std::size_t min_input_size = 1;
+      static constexpr std::size_t max_input_size = 4;
+
+      template< typename Input >
+      [[nodiscard]] static pair_t peek( const Input& in, const std::size_t s ) noexcept
+      {
+         char32_t c0 = in.peek_uint8();
+
+         if( ( c0 & 0x80 ) == 0 ) {
+            return { c0, 1 };
+         }
+         return peek_impl( in, c0, s );
+      }
+
+   private:
+      template< typename Input >
+      [[nodiscard]] static pair_t peek_impl( const Input& in, char32_t c0, const std::size_t s ) noexcept
+      {
+         if( ( c0 & 0xE0 ) == 0xC0 ) {
+            if( s >= 2 ) {
+               const char32_t c1 = in.peek_uint8( 1 );
+               if( ( c1 & 0xC0 ) == 0x80 ) {
+                  c0 &= 0x1F;
+                  c0 <<= 6;
+                  c0 |= ( c1 & 0x3F );
+                  if( c0 >= 0x80 ) {
+                     return { c0, 2 };
+                  }
+               }
+            }
+         }
+         else if( ( c0 & 0xF0 ) == 0xE0 ) {
+            if( s >= 3 ) {
+               const char32_t c1 = in.peek_uint8( 1 );
+               const char32_t c2 = in.peek_uint8( 2 );
+               if( ( ( c1 & 0xC0 ) == 0x80 ) && ( ( c2 & 0xC0 ) == 0x80 ) ) {
+                  c0 &= 0x0F;
+                  c0 <<= 6;
+                  c0 |= ( c1 & 0x3F );
+                  c0 <<= 6;
+                  c0 |= ( c2 & 0x3F );
+                  if( c0 >= 0x800 && !( c0 >= 0xD800 && c0 <= 0xDFFF ) ) {
+                     return { c0, 3 };
+                  }
+               }
+            }
+         }
+         else if( ( c0 & 0xF8 ) == 0xF0 ) {
+            if( s >= 4 ) {
+               const char32_t c1 = in.peek_uint8( 1 );
+               const char32_t c2 = in.peek_uint8( 2 );
+               const char32_t c3 = in.peek_uint8( 3 );
+               if( ( ( c1 & 0xC0 ) == 0x80 ) && ( ( c2 & 0xC0 ) == 0x80 ) && ( ( c3 & 0xC0 ) == 0x80 ) ) {
+                  c0 &= 0x07;
+                  c0 <<= 6;
+                  c0 |= ( c1 & 0x3F );
+                  c0 <<= 6;
+                  c0 |= ( c2 & 0x3F );
+                  c0 <<= 6;
+                  c0 |= ( c3 & 0x3F );
+                  if( c0 >= 0x10000 && c0 <= 0x10FFFF ) {
+                     return { c0, 4 };
+                  }
+               }
+            }
+         }
+         return { 0, 0 };
+      }
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/pegtl_string.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/pegtl_string.hpp
new file mode 100644
index 000000000000..894b9d71ecf2
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/pegtl_string.hpp
@@ -0,0 +1,90 @@
+// Copyright (c) 2015-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_PEGTL_STRING_HPP
+#define TAO_JSON_PEGTL_INTERNAL_PEGTL_STRING_HPP
+
+#include <cstddef>
+#include <type_traits>
+
+#include "../ascii.hpp"
+#include "../config.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   // Inspired by https://github.com/irrequietus/typestring
+   // Rewritten and reduced to what is needed for the PEGTL
+   // and to work with Visual Studio 2015.
+
+   template< typename, typename, typename, typename, typename, typename, typename, typename >
+   struct string_join;
+
+   template< template< char... > class S, char... C0s, char... C1s, char... C2s, char... C3s, char... C4s, char... C5s, char... C6s, char... C7s >
+   struct string_join< S< C0s... >, S< C1s... >, S< C2s... >, S< C3s... >, S< C4s... >, S< C5s... >, S< C6s... >, S< C7s... > >
+   {
+      using type = S< C0s..., C1s..., C2s..., C3s..., C4s..., C5s..., C6s..., C7s... >;
+   };
+
+   template< template< char... > class S, char, bool >
+   struct string_at
+   {
+      using type = S<>;
+   };
+
+   template< template< char... > class S, char C >
+   struct string_at< S, C, true >
+   {
+      using type = S< C >;
+   };
+
+   template< typename T, std::size_t S >
+   struct string_max_length
+   {
+      static_assert( S <= 512, "String longer than 512 (excluding terminating \\0)!" );
+      using type = T;
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#define TAO_JSON_PEGTL_INTERNAL_EMPTY()
+#define TAO_JSON_PEGTL_INTERNAL_DEFER( X ) X TAO_JSON_PEGTL_INTERNAL_EMPTY()
+#define TAO_JSON_PEGTL_INTERNAL_EXPAND( ... ) __VA_ARGS__
+
+#define TAO_JSON_PEGTL_INTERNAL_STRING_AT( S, x, n ) \
+   TAO_JSON_PEGTL_NAMESPACE::internal::string_at< S, ( 0##n < ( sizeof( x ) / sizeof( char ) ) ) ? ( x )[ 0##n ] : 0, ( 0##n < ( sizeof( x ) / sizeof( char ) ) - 1 ) >::type
+
+#define TAO_JSON_PEGTL_INTERNAL_JOIN_8( M, S, x, n )                                                  \
+   TAO_JSON_PEGTL_NAMESPACE::internal::string_join< TAO_JSON_PEGTL_INTERNAL_DEFER( M )( S, x, n##0 ), \
+                                                    TAO_JSON_PEGTL_INTERNAL_DEFER( M )( S, x, n##1 ), \
+                                                    TAO_JSON_PEGTL_INTERNAL_DEFER( M )( S, x, n##2 ), \
+                                                    TAO_JSON_PEGTL_INTERNAL_DEFER( M )( S, x, n##3 ), \
+                                                    TAO_JSON_PEGTL_INTERNAL_DEFER( M )( S, x, n##4 ), \
+                                                    TAO_JSON_PEGTL_INTERNAL_DEFER( M )( S, x, n##5 ), \
+                                                    TAO_JSON_PEGTL_INTERNAL_DEFER( M )( S, x, n##6 ), \
+                                                    TAO_JSON_PEGTL_INTERNAL_DEFER( M )( S, x, n##7 ) >::type
+
+#define TAO_JSON_PEGTL_INTERNAL_STRING_8( S, x, n ) \
+   TAO_JSON_PEGTL_INTERNAL_JOIN_8( TAO_JSON_PEGTL_INTERNAL_STRING_AT, S, x, n )
+
+#define TAO_JSON_PEGTL_INTERNAL_STRING_64( S, x, n ) \
+   TAO_JSON_PEGTL_INTERNAL_JOIN_8( TAO_JSON_PEGTL_INTERNAL_STRING_8, S, x, n )
+
+#define TAO_JSON_PEGTL_INTERNAL_STRING_512( S, x, n ) \
+   TAO_JSON_PEGTL_INTERNAL_JOIN_8( TAO_JSON_PEGTL_INTERNAL_STRING_64, S, x, n )
+
+#define TAO_JSON_PEGTL_INTERNAL_STRING( S, x ) \
+   TAO_JSON_PEGTL_INTERNAL_EXPAND(             \
+      TAO_JSON_PEGTL_INTERNAL_EXPAND(          \
+         TAO_JSON_PEGTL_INTERNAL_EXPAND(       \
+            TAO_JSON_PEGTL_NAMESPACE::internal::string_max_length< TAO_JSON_PEGTL_INTERNAL_STRING_512( S, x, ), sizeof( x ) - 1 >::type ) ) )
+
+#define TAO_JSON_PEGTL_STRING( x ) \
+   TAO_JSON_PEGTL_INTERNAL_STRING( TAO_JSON_PEGTL_NAMESPACE::ascii::string, x )
+
+#define TAO_JSON_PEGTL_ISTRING( x ) \
+   TAO_JSON_PEGTL_INTERNAL_STRING( TAO_JSON_PEGTL_NAMESPACE::ascii::istring, x )
+
+#define TAO_JSON_PEGTL_KEYWORD( x ) \
+   TAO_JSON_PEGTL_INTERNAL_STRING( TAO_JSON_PEGTL_NAMESPACE::ascii::keyword, x )
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/plus.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/plus.hpp
new file mode 100644
index 000000000000..0f5c0cd36038
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/plus.hpp
@@ -0,0 +1,53 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_PLUS_HPP
+#define TAO_JSON_PEGTL_INTERNAL_PLUS_HPP
+
+#include <type_traits>
+
+#include "../config.hpp"
+
+#include "duseltronik.hpp"
+#include "opt.hpp"
+#include "seq.hpp"
+#include "skip_control.hpp"
+#include "star.hpp"
+
+#include "../apply_mode.hpp"
+#include "../rewind_mode.hpp"
+
+#include "../analysis/generic.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   // While plus<> could easily be implemented with
+   // seq< Rule, Rules ..., star< Rule, Rules ... > > we
+   // provide an explicit implementation to optimise away
+   // the otherwise created input mark.
+
+   template< typename Rule, typename... Rules >
+   struct plus
+   {
+      using analyze_t = analysis::generic< analysis::rule_type::seq, Rule, Rules..., opt< plus > >;
+
+      template< apply_mode A,
+                rewind_mode M,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class Control,
+                typename Input,
+                typename... States >
+      [[nodiscard]] static bool match( Input& in, States&&... st )
+      {
+         return seq< Rule, Rules... >::template match< A, M, Action, Control >( in, st... ) && star< Rule, Rules... >::template match< A, M, Action, Control >( in, st... );
+      }
+   };
+
+   template< typename Rule, typename... Rules >
+   inline constexpr bool skip_control< plus< Rule, Rules... > > = true;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/raise.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/raise.hpp
new file mode 100644
index 000000000000..29d1c92601ac
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/raise.hpp
@@ -0,0 +1,53 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_RAISE_HPP
+#define TAO_JSON_PEGTL_INTERNAL_RAISE_HPP
+
+#include <cstdlib>
+#include <stdexcept>
+#include <type_traits>
+
+#include "../config.hpp"
+
+#include "skip_control.hpp"
+
+#include "../analysis/generic.hpp"
+#include "../apply_mode.hpp"
+#include "../rewind_mode.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< typename T >
+   struct raise
+   {
+      using analyze_t = analysis::generic< analysis::rule_type::any >;
+
+#if defined( _MSC_VER )
+#pragma warning( push )
+#pragma warning( disable : 4702 )
+#endif
+      template< apply_mode,
+                rewind_mode,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class Control,
+                typename Input,
+                typename... States >
+      [[nodiscard]] static bool match( Input& in, States&&... st )
+      {
+         Control< T >::raise( static_cast< const Input& >( in ), st... );
+         throw std::logic_error( "code should be unreachable: Control< T >::raise() did not throw an exception" );  // LCOV_EXCL_LINE
+#if defined( _MSC_VER )
+#pragma warning( pop )
+#endif
+      }
+   };
+
+   template< typename T >
+   inline constexpr bool skip_control< raise< T > > = true;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/range.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/range.hpp
new file mode 100644
index 000000000000..66f7d7c43fbf
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/range.hpp
@@ -0,0 +1,51 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_RANGE_HPP
+#define TAO_JSON_PEGTL_INTERNAL_RANGE_HPP
+
+#include "../config.hpp"
+
+#include "result_on_found.hpp"
+#include "skip_control.hpp"
+
+#include "../analysis/generic.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< result_on_found R, typename Peek, typename Peek::data_t Lo, typename Peek::data_t Hi >
+   struct range
+   {
+      static_assert( Lo <= Hi, "invalid range detected" );
+
+      using analyze_t = analysis::generic< analysis::rule_type::any >;
+
+      template< int Eol >
+      static constexpr bool can_match_eol = ( ( ( Lo <= Eol ) && ( Eol <= Hi ) ) == bool( R ) );
+
+      template< typename Input >
+      [[nodiscard]] static bool match( Input& in ) noexcept( noexcept( in.size( Peek::max_input_size ) ) )
+      {
+         if( const std::size_t s = in.size( Peek::max_input_size ); s >= Peek::min_input_size ) {
+            if( const auto t = Peek::peek( in, s ) ) {
+               if( ( ( Lo <= t.data ) && ( t.data <= Hi ) ) == bool( R ) ) {
+                  if constexpr( can_match_eol< Input::eol_t::ch > ) {
+                     in.bump( t.size );
+                  }
+                  else {
+                     in.bump_in_this_line( t.size );
+                  }
+                  return true;
+               }
+            }
+         }
+         return false;
+      }
+   };
+
+   template< result_on_found R, typename Peek, typename Peek::data_t Lo, typename Peek::data_t Hi >
+   inline constexpr bool skip_control< range< R, Peek, Lo, Hi > > = true;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/ranges.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/ranges.hpp
new file mode 100644
index 000000000000..3bc33d123a15
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/ranges.hpp
@@ -0,0 +1,93 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_RANGES_HPP
+#define TAO_JSON_PEGTL_INTERNAL_RANGES_HPP
+
+#include "../config.hpp"
+
+#include "range.hpp"
+#include "skip_control.hpp"
+
+#include "../analysis/generic.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< int Eol, typename Char, Char... Cs >
+   struct ranges_impl;
+
+   template< int Eol, typename Char >
+   struct ranges_impl< Eol, Char >
+   {
+      static constexpr bool can_match_eol = false;
+
+      [[nodiscard]] static bool match( const Char /*unused*/ ) noexcept
+      {
+         return false;
+      }
+   };
+
+   template< int Eol, typename Char, Char Eq >
+   struct ranges_impl< Eol, Char, Eq >
+   {
+      static constexpr bool can_match_eol = ( Eq == Eol );
+
+      [[nodiscard]] static bool match( const Char c ) noexcept
+      {
+         return c == Eq;
+      }
+   };
+
+   template< int Eol, typename Char, Char Lo, Char Hi, Char... Cs >
+   struct ranges_impl< Eol, Char, Lo, Hi, Cs... >
+   {
+      static_assert( Lo <= Hi, "invalid range detected" );
+
+      static constexpr bool can_match_eol = ( ( ( Lo <= Eol ) && ( Eol <= Hi ) ) || ranges_impl< Eol, Char, Cs... >::can_match_eol );
+
+      [[nodiscard]] static bool match( const Char c ) noexcept
+      {
+         return ( ( Lo <= c ) && ( c <= Hi ) ) || ranges_impl< Eol, Char, Cs... >::match( c );
+      }
+   };
+
+   template< typename Peek, typename Peek::data_t... Cs >
+   struct ranges
+   {
+      using analyze_t = analysis::generic< analysis::rule_type::any >;
+
+      template< int Eol >
+      static constexpr bool can_match_eol = ranges_impl< Eol, typename Peek::data_t, Cs... >::can_match_eol;
+
+      template< typename Input >
+      [[nodiscard]] static bool match( Input& in ) noexcept( noexcept( in.size( Peek::max_input_size ) ) )
+      {
+         if( const std::size_t s = in.size( Peek::max_input_size ); s >= Peek::min_input_size ) {
+            if( const auto t = Peek::peek( in, s ) ) {
+               if( ranges_impl< Input::eol_t::ch, typename Peek::data_t, Cs... >::match( t.data ) ) {
+                  if constexpr( can_match_eol< Input::eol_t::ch > ) {
+                     in.bump( t.size );
+                  }
+                  else {
+                     in.bump_in_this_line( t.size );
+                  }
+                  return true;
+               }
+            }
+         }
+         return false;
+      }
+   };
+
+   template< typename Peek, typename Peek::data_t Lo, typename Peek::data_t Hi >
+   struct ranges< Peek, Lo, Hi >
+      : range< result_on_found::success, Peek, Lo, Hi >
+   {
+   };
+
+   template< typename Peek, typename Peek::data_t... Cs >
+   inline constexpr bool skip_control< ranges< Peek, Cs... > > = true;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/read_uint.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/read_uint.hpp
new file mode 100644
index 000000000000..817f5faa0564
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/read_uint.hpp
@@ -0,0 +1,77 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_READ_UINT_HPP
+#define TAO_JSON_PEGTL_INTERNAL_READ_UINT_HPP
+
+#include <cstdint>
+
+#include "../config.hpp"
+
+#include "endian.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   struct read_uint16_be
+   {
+      using type = std::uint16_t;
+
+      [[nodiscard]] static std::uint16_t read( const void* d ) noexcept
+      {
+         return be_to_h< std::uint16_t >( d );
+      }
+   };
+
+   struct read_uint16_le
+   {
+      using type = std::uint16_t;
+
+      [[nodiscard]] static std::uint16_t read( const void* d ) noexcept
+      {
+         return le_to_h< std::uint16_t >( d );
+      }
+   };
+
+   struct read_uint32_be
+   {
+      using type = std::uint32_t;
+
+      [[nodiscard]] static std::uint32_t read( const void* d ) noexcept
+      {
+         return be_to_h< std::uint32_t >( d );
+      }
+   };
+
+   struct read_uint32_le
+   {
+      using type = std::uint32_t;
+
+      [[nodiscard]] static std::uint32_t read( const void* d ) noexcept
+      {
+         return le_to_h< std::uint32_t >( d );
+      }
+   };
+
+   struct read_uint64_be
+   {
+      using type = std::uint64_t;
+
+      [[nodiscard]] static std::uint64_t read( const void* d ) noexcept
+      {
+         return be_to_h< std::uint64_t >( d );
+      }
+   };
+
+   struct read_uint64_le
+   {
+      using type = std::uint64_t;
+
+      [[nodiscard]] static std::uint64_t read( const void* d ) noexcept
+      {
+         return le_to_h< std::uint64_t >( d );
+      }
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/rematch.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/rematch.hpp
new file mode 100644
index 000000000000..5f99f266306d
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/rematch.hpp
@@ -0,0 +1,69 @@
+// Copyright (c) 2019-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_REMATCH_HPP
+#define TAO_JSON_PEGTL_INTERNAL_REMATCH_HPP
+
+#include "../config.hpp"
+
+#include "skip_control.hpp"
+
+#include "../apply_mode.hpp"
+#include "../memory_input.hpp"
+#include "../rewind_mode.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< typename Head, typename... Rules >
+   struct rematch;
+
+   template< typename Head >
+   struct rematch< Head >
+   {
+      using analyze_t = typename Head::analyze_t;
+
+      template< apply_mode A,
+                rewind_mode M,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class Control,
+                typename Input,
+                typename... States >
+      [[nodiscard]] static bool match( Input& in, States&&... st )
+      {
+         return Control< Head >::template match< A, M, Action, Control >( in, st... );
+      }
+   };
+
+   template< typename Head, typename Rule, typename... Rules >
+   struct rematch< Head, Rule, Rules... >
+   {
+      using analyze_t = typename Head::analyze_t;  // NOTE: Rule and Rules are ignored for analyze().
+
+      template< apply_mode A,
+                rewind_mode,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class Control,
+                typename Input,
+                typename... States >
+      [[nodiscard]] static bool match( Input& in, States&&... st )
+      {
+         auto m = in.template mark< rewind_mode::required >();
+
+         if( Control< Head >::template match< A, rewind_mode::active, Action, Control >( in, st... ) ) {
+            memory_input< Input::tracking_mode_v, typename Input::eol_t, typename Input::source_t > i2( m.iterator(), in.current(), in.source() );
+            return m( ( Control< Rule >::template match< A, rewind_mode::active, Action, Control >( i2, st... ) && ... && ( i2.restart( m ), Control< Rules >::template match< A, rewind_mode::active, Action, Control >( i2, st... ) ) ) );
+         }
+         return false;
+      }
+   };
+
+   template< typename Head, typename... Rules >
+   inline constexpr bool skip_control< rematch< Head, Rules... > > = true;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/rep.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/rep.hpp
new file mode 100644
index 000000000000..607e896ca059
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/rep.hpp
@@ -0,0 +1,66 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_REP_HPP
+#define TAO_JSON_PEGTL_INTERNAL_REP_HPP
+
+#include "../config.hpp"
+
+#include "skip_control.hpp"
+#include "trivial.hpp"
+
+#include "../apply_mode.hpp"
+#include "../rewind_mode.hpp"
+
+#include "../analysis/counted.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< unsigned Num, typename... Rules >
+   struct rep;
+
+   template< unsigned Num >
+   struct rep< Num >
+      : trivial< true >
+   {
+   };
+
+   template< typename Rule, typename... Rules >
+   struct rep< 0, Rule, Rules... >
+      : trivial< true >
+   {
+   };
+
+   template< unsigned Num, typename... Rules >
+   struct rep
+   {
+      using analyze_t = analysis::counted< analysis::rule_type::seq, Num, Rules... >;
+
+      template< apply_mode A,
+                rewind_mode M,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class Control,
+                typename Input,
+                typename... States >
+      [[nodiscard]] static bool match( Input& in, States&&... st )
+      {
+         auto m = in.template mark< M >();
+         using m_t = decltype( m );
+
+         for( unsigned i = 0; i != Num; ++i ) {
+            if( !( Control< Rules >::template match< A, m_t::next_rewind_mode, Action, Control >( in, st... ) && ... ) ) {
+               return false;
+            }
+         }
+         return m( true );
+      }
+   };
+
+   template< unsigned Num, typename... Rules >
+   inline constexpr bool skip_control< rep< Num, Rules... > > = true;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/rep_min.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/rep_min.hpp
new file mode 100644
index 000000000000..c279bae89711
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/rep_min.hpp
@@ -0,0 +1,20 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_REP_MIN_HPP
+#define TAO_JSON_PEGTL_INTERNAL_REP_MIN_HPP
+
+#include "../config.hpp"
+
+#include "rep.hpp"
+#include "seq.hpp"
+#include "star.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< unsigned Min, typename Rule, typename... Rules >
+   using rep_min = seq< rep< Min, Rule, Rules... >, star< Rule, Rules... > >;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/rep_min_max.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/rep_min_max.hpp
new file mode 100644
index 000000000000..b244c87e797e
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/rep_min_max.hpp
@@ -0,0 +1,79 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_REP_MIN_MAX_HPP
+#define TAO_JSON_PEGTL_INTERNAL_REP_MIN_MAX_HPP
+
+#include <type_traits>
+
+#include "../config.hpp"
+
+#include "duseltronik.hpp"
+#include "not_at.hpp"
+#include "seq.hpp"
+#include "skip_control.hpp"
+#include "trivial.hpp"
+
+#include "../apply_mode.hpp"
+#include "../rewind_mode.hpp"
+
+#include "../analysis/counted.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< unsigned Min, unsigned Max, typename... Rules >
+   struct rep_min_max;
+
+   template< unsigned Min, unsigned Max >
+   struct rep_min_max< Min, Max >
+      : trivial< false >
+   {
+      static_assert( Min <= Max );
+   };
+
+   template< typename Rule, typename... Rules >
+   struct rep_min_max< 0, 0, Rule, Rules... >
+      : not_at< Rule, Rules... >
+   {
+   };
+
+   template< unsigned Min, unsigned Max, typename... Rules >
+   struct rep_min_max
+   {
+      using analyze_t = analysis::counted< analysis::rule_type::seq, Min, Rules... >;
+
+      static_assert( Min <= Max );
+
+      template< apply_mode A,
+                rewind_mode M,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class Control,
+                typename Input,
+                typename... States >
+      [[nodiscard]] static bool match( Input& in, States&&... st )
+      {
+         auto m = in.template mark< M >();
+         using m_t = decltype( m );
+
+         for( unsigned i = 0; i != Min; ++i ) {
+            if( !( Control< Rules >::template match< A, m_t::next_rewind_mode, Action, Control >( in, st... ) && ... ) ) {
+               return false;
+            }
+         }
+         for( unsigned i = Min; i != Max; ++i ) {
+            if( !duseltronik< seq< Rules... >, A, rewind_mode::required, Action, Control >::match( in, st... ) ) {
+               return m( true );
+            }
+         }
+         return m( duseltronik< not_at< Rules... >, A, m_t::next_rewind_mode, Action, Control >::match( in, st... ) );  // NOTE that not_at<> will always rewind.
+      }
+   };
+
+   template< unsigned Min, unsigned Max, typename... Rules >
+   inline constexpr bool skip_control< rep_min_max< Min, Max, Rules... > > = true;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/rep_opt.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/rep_opt.hpp
new file mode 100644
index 000000000000..4e56902ca063
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/rep_opt.hpp
@@ -0,0 +1,46 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_REP_OPT_HPP
+#define TAO_JSON_PEGTL_INTERNAL_REP_OPT_HPP
+
+#include "../config.hpp"
+
+#include "duseltronik.hpp"
+#include "seq.hpp"
+#include "skip_control.hpp"
+
+#include "../apply_mode.hpp"
+#include "../rewind_mode.hpp"
+
+#include "../analysis/generic.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< unsigned Max, typename... Rules >
+   struct rep_opt
+   {
+      using analyze_t = analysis::generic< analysis::rule_type::opt, Rules... >;
+
+      template< apply_mode A,
+                rewind_mode,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class Control,
+                typename Input,
+                typename... States >
+      [[nodiscard]] static bool match( Input& in, States&&... st )
+      {
+         for( unsigned i = 0; ( i != Max ) && duseltronik< seq< Rules... >, A, rewind_mode::required, Action, Control >::match( in, st... ); ++i ) {
+         }
+         return true;
+      }
+   };
+
+   template< unsigned Max, typename... Rules >
+   inline constexpr bool skip_control< rep_opt< Max, Rules... > > = true;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/require.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/require.hpp
new file mode 100644
index 000000000000..21cb17e1f86f
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/require.hpp
@@ -0,0 +1,42 @@
+// Copyright (c) 2016-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_REQUIRE_HPP
+#define TAO_JSON_PEGTL_INTERNAL_REQUIRE_HPP
+
+#include "../config.hpp"
+
+#include "skip_control.hpp"
+#include "trivial.hpp"
+
+#include "../analysis/generic.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< unsigned Amount >
+   struct require;
+
+   template<>
+   struct require< 0 >
+      : trivial< true >
+   {
+   };
+
+   template< unsigned Amount >
+   struct require
+   {
+      using analyze_t = analysis::generic< analysis::rule_type::opt >;
+
+      template< typename Input >
+      [[nodiscard]] static bool match( Input& in ) noexcept( noexcept( in.size( 0 ) ) )
+      {
+         return in.size( Amount ) >= Amount;
+      }
+   };
+
+   template< unsigned Amount >
+   inline constexpr bool skip_control< require< Amount > > = true;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/result_on_found.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/result_on_found.hpp
new file mode 100644
index 000000000000..a6b8c24106c4
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/result_on_found.hpp
@@ -0,0 +1,19 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_RESULT_ON_FOUND_HPP
+#define TAO_JSON_PEGTL_INTERNAL_RESULT_ON_FOUND_HPP
+
+#include "../config.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   enum class result_on_found : bool
+   {
+      success = true,
+      failure = false
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/rules.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/rules.hpp
new file mode 100644
index 000000000000..3ff9eec8d7a5
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/rules.hpp
@@ -0,0 +1,61 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_RULES_HPP
+#define TAO_JSON_PEGTL_INTERNAL_RULES_HPP
+
+#include "action.hpp"
+#include "alnum.hpp"
+#include "alpha.hpp"
+#include "any.hpp"
+#include "apply.hpp"
+#include "apply0.hpp"
+#include "at.hpp"
+#include "bof.hpp"
+#include "bol.hpp"
+#include "bytes.hpp"
+#include "control.hpp"
+#include "disable.hpp"
+#include "discard.hpp"
+#include "enable.hpp"
+#include "eof.hpp"
+#include "eol.hpp"
+#include "eolf.hpp"
+#include "identifier.hpp"
+#include "if_apply.hpp"
+#include "if_must.hpp"
+#include "if_must_else.hpp"
+#include "if_then_else.hpp"
+#include "istring.hpp"
+#include "list.hpp"
+#include "list_must.hpp"
+#include "list_tail.hpp"
+#include "list_tail_pad.hpp"
+#include "must.hpp"
+#include "not_at.hpp"
+#include "one.hpp"
+#include "opt.hpp"
+#include "pad.hpp"
+#include "pad_opt.hpp"
+#include "plus.hpp"
+#include "raise.hpp"
+#include "range.hpp"
+#include "ranges.hpp"
+#include "rematch.hpp"
+#include "rep.hpp"
+#include "rep_min.hpp"
+#include "rep_min_max.hpp"
+#include "rep_opt.hpp"
+#include "require.hpp"
+#include "seq.hpp"
+#include "skip_control.hpp"
+#include "sor.hpp"
+#include "star.hpp"
+#include "star_must.hpp"
+#include "state.hpp"
+#include "string.hpp"
+#include "trivial.hpp"
+#include "try_catch_type.hpp"
+#include "until.hpp"
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/seq.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/seq.hpp
new file mode 100644
index 000000000000..8528fec5698f
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/seq.hpp
@@ -0,0 +1,73 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_SEQ_HPP
+#define TAO_JSON_PEGTL_INTERNAL_SEQ_HPP
+
+#include "../config.hpp"
+
+#include "skip_control.hpp"
+#include "trivial.hpp"
+
+#include "../apply_mode.hpp"
+#include "../rewind_mode.hpp"
+
+#include "../analysis/generic.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< typename... Rules >
+   struct seq;
+
+   template<>
+   struct seq<>
+      : trivial< true >
+   {
+   };
+
+   template< typename Rule >
+   struct seq< Rule >
+   {
+      using analyze_t = typename Rule::analyze_t;
+
+      template< apply_mode A,
+                rewind_mode M,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class Control,
+                typename Input,
+                typename... States >
+      [[nodiscard]] static bool match( Input& in, States&&... st )
+      {
+         return Control< Rule >::template match< A, M, Action, Control >( in, st... );
+      }
+   };
+
+   template< typename... Rules >
+   struct seq
+   {
+      using analyze_t = analysis::generic< analysis::rule_type::seq, Rules... >;
+
+      template< apply_mode A,
+                rewind_mode M,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class Control,
+                typename Input,
+                typename... States >
+      [[nodiscard]] static bool match( Input& in, States&&... st )
+      {
+         auto m = in.template mark< M >();
+         using m_t = decltype( m );
+         return m( ( Control< Rules >::template match< A, m_t::next_rewind_mode, Action, Control >( in, st... ) && ... ) );
+      }
+   };
+
+   template< typename... Rules >
+   inline constexpr bool skip_control< seq< Rules... > > = true;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/skip_control.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/skip_control.hpp
new file mode 100644
index 000000000000..7b3d609849eb
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/skip_control.hpp
@@ -0,0 +1,25 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_SKIP_CONTROL_HPP
+#define TAO_JSON_PEGTL_INTERNAL_SKIP_CONTROL_HPP
+
+#include <type_traits>
+
+#include "../config.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   // This class is a simple tagging mechanism.
+   // By default, skip_control< Rule > is  'false'.
+   // Each internal (!) rule that should be hidden
+   // from the control and action class' callbacks
+   // simply specializes skip_control<> to return
+   // 'true' for the above expression.
+
+   template< typename Rule >
+   inline constexpr bool skip_control = false;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/sor.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/sor.hpp
new file mode 100644
index 000000000000..66ca20164319
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/sor.hpp
@@ -0,0 +1,60 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_SOR_HPP
+#define TAO_JSON_PEGTL_INTERNAL_SOR_HPP
+
+#include <utility>
+
+#include "../config.hpp"
+
+#include "skip_control.hpp"
+#include "trivial.hpp"
+
+#include "../apply_mode.hpp"
+#include "../rewind_mode.hpp"
+
+#include "../analysis/generic.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< typename... Rules >
+   struct sor;
+
+   template<>
+   struct sor<>
+      : trivial< false >
+   {
+   };
+
+   template< typename... Rules >
+   struct sor
+      : sor< std::index_sequence_for< Rules... >, Rules... >
+   {
+   };
+
+   template< std::size_t... Indices, typename... Rules >
+   struct sor< std::index_sequence< Indices... >, Rules... >
+   {
+      using analyze_t = analysis::generic< analysis::rule_type::sor, Rules... >;
+
+      template< apply_mode A,
+                rewind_mode M,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class Control,
+                typename Input,
+                typename... States >
+      [[nodiscard]] static bool match( Input& in, States&&... st )
+      {
+         return ( Control< Rules >::template match< A, ( ( Indices == ( sizeof...( Rules ) - 1 ) ) ? M : rewind_mode::required ), Action, Control >( in, st... ) || ... );
+      }
+   };
+
+   template< typename... Rules >
+   inline constexpr bool skip_control< sor< Rules... > > = true;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/star.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/star.hpp
new file mode 100644
index 000000000000..53795b94b4bc
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/star.hpp
@@ -0,0 +1,47 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_STAR_HPP
+#define TAO_JSON_PEGTL_INTERNAL_STAR_HPP
+
+#include <type_traits>
+
+#include "../config.hpp"
+
+#include "seq.hpp"
+#include "skip_control.hpp"
+
+#include "../apply_mode.hpp"
+#include "../rewind_mode.hpp"
+
+#include "../analysis/generic.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< typename Rule, typename... Rules >
+   struct star
+   {
+      using analyze_t = analysis::generic< analysis::rule_type::opt, Rule, Rules..., star >;
+
+      template< apply_mode A,
+                rewind_mode,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class Control,
+                typename Input,
+                typename... States >
+      [[nodiscard]] static bool match( Input& in, States&&... st )
+      {
+         while( seq< Rule, Rules... >::template match< A, rewind_mode::required, Action, Control >( in, st... ) ) {
+         }
+         return true;
+      }
+   };
+
+   template< typename Rule, typename... Rules >
+   inline constexpr bool skip_control< star< Rule, Rules... > > = true;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/star_must.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/star_must.hpp
new file mode 100644
index 000000000000..eddec9f58a07
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/star_must.hpp
@@ -0,0 +1,19 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_STAR_MUST_HPP
+#define TAO_JSON_PEGTL_INTERNAL_STAR_MUST_HPP
+
+#include "../config.hpp"
+
+#include "if_must.hpp"
+#include "star.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< typename Cond, typename... Rules >
+   using star_must = star< if_must< false, Cond, Rules... > >;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/state.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/state.hpp
new file mode 100644
index 000000000000..b87b8c9f330a
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/state.hpp
@@ -0,0 +1,49 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_STATE_HPP
+#define TAO_JSON_PEGTL_INTERNAL_STATE_HPP
+
+#include "../config.hpp"
+
+#include "duseltronik.hpp"
+#include "seq.hpp"
+#include "skip_control.hpp"
+
+#include "../apply_mode.hpp"
+#include "../rewind_mode.hpp"
+
+#include "../analysis/generic.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< typename State, typename... Rules >
+   struct state
+   {
+      using analyze_t = analysis::generic< analysis::rule_type::seq, Rules... >;
+
+      template< apply_mode A,
+                rewind_mode M,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class Control,
+                typename Input,
+                typename... States >
+      [[nodiscard]] static bool match( Input& in, States&&... st )
+      {
+         State s( static_cast< const Input& >( in ), st... );
+         if( duseltronik< seq< Rules... >, A, M, Action, Control >::match( in, s ) ) {
+            s.success( static_cast< const Input& >( in ), st... );
+            return true;
+         }
+         return false;
+      }
+   };
+
+   template< typename State, typename... Rules >
+   inline constexpr bool skip_control< state< State, Rules... > > = true;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/string.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/string.hpp
new file mode 100644
index 000000000000..229a1584036b
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/string.hpp
@@ -0,0 +1,58 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_STRING_HPP
+#define TAO_JSON_PEGTL_INTERNAL_STRING_HPP
+
+#include <cstring>
+#include <utility>
+
+#include "../config.hpp"
+
+#include "bump_help.hpp"
+#include "result_on_found.hpp"
+#include "skip_control.hpp"
+#include "trivial.hpp"
+
+#include "../analysis/counted.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   [[nodiscard]] inline bool unsafe_equals( const char* s, const std::initializer_list< char >& l ) noexcept
+   {
+      return std::memcmp( s, &*l.begin(), l.size() ) == 0;
+   }
+
+   template< char... Cs >
+   struct string;
+
+   template<>
+   struct string<>
+      : trivial< true >
+   {
+   };
+
+   template< char... Cs >
+   struct string
+   {
+      using analyze_t = analysis::counted< analysis::rule_type::any, sizeof...( Cs ) >;
+
+      template< typename Input >
+      [[nodiscard]] static bool match( Input& in ) noexcept( noexcept( in.size( 0 ) ) )
+      {
+         if( in.size( sizeof...( Cs ) ) >= sizeof...( Cs ) ) {
+            if( unsafe_equals( in.current(), { Cs... } ) ) {
+               bump_help< result_on_found::success, Input, char, Cs... >( in, sizeof...( Cs ) );
+               return true;
+            }
+         }
+         return false;
+      }
+   };
+
+   template< char... Cs >
+   inline constexpr bool skip_control< string< Cs... > > = true;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/trivial.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/trivial.hpp
new file mode 100644
index 000000000000..9be855cdc559
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/trivial.hpp
@@ -0,0 +1,32 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_TRIVIAL_HPP
+#define TAO_JSON_PEGTL_INTERNAL_TRIVIAL_HPP
+
+#include "../config.hpp"
+
+#include "skip_control.hpp"
+
+#include "../analysis/counted.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< bool Result >
+   struct trivial
+   {
+      using analyze_t = analysis::counted< analysis::rule_type::any, unsigned( !Result ) >;
+
+      template< typename Input >
+      [[nodiscard]] static bool match( Input& /*unused*/ ) noexcept
+      {
+         return Result;
+      }
+   };
+
+   template< bool Result >
+   inline constexpr bool skip_control< trivial< Result > > = true;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/try_catch_type.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/try_catch_type.hpp
new file mode 100644
index 000000000000..1ecf3ebd3b50
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/try_catch_type.hpp
@@ -0,0 +1,64 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_TRY_CATCH_TYPE_HPP
+#define TAO_JSON_PEGTL_INTERNAL_TRY_CATCH_TYPE_HPP
+
+#include <type_traits>
+
+#include "../config.hpp"
+
+#include "duseltronik.hpp"
+#include "seq.hpp"
+#include "skip_control.hpp"
+#include "trivial.hpp"
+
+#include "../apply_mode.hpp"
+#include "../rewind_mode.hpp"
+
+#include "../analysis/generic.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< typename Exception, typename... Rules >
+   struct try_catch_type;
+
+   template< typename Exception >
+   struct try_catch_type< Exception >
+      : trivial< true >
+   {
+   };
+
+   template< typename Exception, typename... Rules >
+   struct try_catch_type
+   {
+      using analyze_t = analysis::generic< analysis::rule_type::seq, Rules... >;
+
+      template< apply_mode A,
+                rewind_mode M,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class Control,
+                typename Input,
+                typename... States >
+      [[nodiscard]] static bool match( Input& in, States&&... st )
+      {
+         auto m = in.template mark< M >();
+         using m_t = decltype( m );
+
+         try {
+            return m( duseltronik< seq< Rules... >, A, m_t::next_rewind_mode, Action, Control >::match( in, st... ) );
+         }
+         catch( const Exception& ) {
+            return false;
+         }
+      }
+   };
+
+   template< typename Exception, typename... Rules >
+   inline constexpr bool skip_control< try_catch_type< Exception, Rules... > > = true;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/until.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/until.hpp
new file mode 100644
index 000000000000..e847585bb67d
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/internal/until.hpp
@@ -0,0 +1,84 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_INTERNAL_UNTIL_HPP
+#define TAO_JSON_PEGTL_INTERNAL_UNTIL_HPP
+
+#include "../config.hpp"
+
+#include "bytes.hpp"
+#include "eof.hpp"
+#include "not_at.hpp"
+#include "skip_control.hpp"
+#include "star.hpp"
+
+#include "../apply_mode.hpp"
+#include "../rewind_mode.hpp"
+
+#include "../analysis/generic.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::internal
+{
+   template< typename Cond, typename... Rules >
+   struct until;
+
+   template< typename Cond >
+   struct until< Cond >
+   {
+      using analyze_t = analysis::generic< analysis::rule_type::seq, star< not_at< Cond >, not_at< eof >, bytes< 1 > >, Cond >;
+
+      template< apply_mode A,
+                rewind_mode M,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class Control,
+                typename Input,
+                typename... States >
+      [[nodiscard]] static bool match( Input& in, States&&... st )
+      {
+         auto m = in.template mark< M >();
+
+         while( !Control< Cond >::template match< A, rewind_mode::required, Action, Control >( in, st... ) ) {
+            if( in.empty() ) {
+               return false;
+            }
+            in.bump();
+         }
+         return m( true );
+      }
+   };
+
+   template< typename Cond, typename... Rules >
+   struct until
+   {
+      using analyze_t = analysis::generic< analysis::rule_type::seq, star< not_at< Cond >, not_at< eof >, Rules... >, Cond >;
+
+      template< apply_mode A,
+                rewind_mode M,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class Control,
+                typename Input,
+                typename... States >
+      [[nodiscard]] static bool match( Input& in, States&&... st )
+      {
+         auto m = in.template mark< M >();
+         using m_t = decltype( m );
+
+         while( !Control< Cond >::template match< A, rewind_mode::required, Action, Control >( in, st... ) ) {
+            if( !( Control< Rules >::template match< A, m_t::next_rewind_mode, Action, Control >( in, st... ) && ... ) ) {
+               return false;
+            }
+         }
+         return m( true );
+      }
+   };
+
+   template< typename Cond, typename... Rules >
+   inline constexpr bool skip_control< until< Cond, Rules... > > = true;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/istream_input.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/istream_input.hpp
new file mode 100644
index 000000000000..5bd0be99053f
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/istream_input.hpp
@@ -0,0 +1,33 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_ISTREAM_INPUT_HPP
+#define TAO_JSON_PEGTL_ISTREAM_INPUT_HPP
+
+#include <istream>
+
+#include "buffer_input.hpp"
+#include "config.hpp"
+#include "eol.hpp"
+
+#include "internal/istream_reader.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE
+{
+   template< typename Eol = eol::lf_crlf, std::size_t Chunk = 64 >
+   struct istream_input
+      : buffer_input< internal::istream_reader, Eol, std::string, Chunk >
+   {
+      template< typename T >
+      istream_input( std::istream& in_stream, const std::size_t in_maximum, T&& in_source )
+         : buffer_input< internal::istream_reader, Eol, std::string, Chunk >( std::forward< T >( in_source ), in_maximum, in_stream )
+      {
+      }
+   };
+
+   template< typename... Ts >
+   istream_input( Ts&&... )->istream_input<>;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/match.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/match.hpp
new file mode 100644
index 000000000000..2652bb92474c
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/match.hpp
@@ -0,0 +1,73 @@
+// Copyright (c) 2019-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_MATCH_HPP
+#define TAO_JSON_PEGTL_MATCH_HPP
+
+#include <type_traits>
+
+#include "apply_mode.hpp"
+#include "config.hpp"
+#include "nothing.hpp"
+#include "require_apply.hpp"
+#include "require_apply0.hpp"
+#include "rewind_mode.hpp"
+
+#include "internal/dusel_mode.hpp"
+#include "internal/duseltronik.hpp"
+#include "internal/has_apply.hpp"
+#include "internal/has_apply0.hpp"
+#include "internal/missing_apply.hpp"
+#include "internal/missing_apply0.hpp"
+#include "internal/skip_control.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE
+{
+   template< typename Rule,
+             apply_mode A,
+             rewind_mode M,
+             template< typename... >
+             class Action,
+             template< typename... >
+             class Control,
+             typename Input,
+             typename... States >
+   [[nodiscard]] bool match( Input& in, States&&... st )
+   {
+      constexpr bool enable_control = !internal::skip_control< Rule >;
+      constexpr bool enable_action = enable_control && ( A == apply_mode::action );
+
+      using iterator_t = typename Input::iterator_t;
+      constexpr bool has_apply_void = enable_action && internal::has_apply< Control< Rule >, void, Action, const iterator_t&, const Input&, States... >::value;
+      constexpr bool has_apply_bool = enable_action && internal::has_apply< Control< Rule >, bool, Action, const iterator_t&, const Input&, States... >::value;
+      constexpr bool has_apply = has_apply_void || has_apply_bool;
+
+      constexpr bool has_apply0_void = enable_action && internal::has_apply0< Control< Rule >, void, Action, const Input&, States... >::value;
+      constexpr bool has_apply0_bool = enable_action && internal::has_apply0< Control< Rule >, bool, Action, const Input&, States... >::value;
+      constexpr bool has_apply0 = has_apply0_void || has_apply0_bool;
+
+      static_assert( !( has_apply && has_apply0 ), "both apply() and apply0() defined" );
+
+      constexpr bool is_nothing = std::is_base_of_v< nothing< Rule >, Action< Rule > >;
+      static_assert( !( has_apply && is_nothing ), "unexpected apply() defined" );
+      static_assert( !( has_apply0 && is_nothing ), "unexpected apply0() defined" );
+
+      if constexpr( !has_apply && std::is_base_of_v< require_apply, Action< Rule > > ) {
+         internal::missing_apply< Control< Rule >, Action >( in, st... );
+      }
+
+      if constexpr( !has_apply0 && std::is_base_of_v< require_apply0, Action< Rule > > ) {
+         internal::missing_apply0< Control< Rule >, Action >( in, st... );
+      }
+
+      constexpr bool validate_nothing = std::is_base_of_v< maybe_nothing, Action< void > >;
+      constexpr bool is_maybe_nothing = std::is_base_of_v< maybe_nothing, Action< Rule > >;
+      static_assert( !enable_action || !validate_nothing || is_nothing || is_maybe_nothing || has_apply || has_apply0, "either apply() or apply0() must be defined" );
+
+      constexpr auto mode = static_cast< internal::dusel_mode >( enable_control + has_apply_void + 2 * has_apply_bool + 3 * has_apply0_void + 4 * has_apply0_bool );
+      return internal::duseltronik< Rule, A, M, Action, Control, mode >::match( in, st... );
+   }
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/memory_input.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/memory_input.hpp
new file mode 100644
index 000000000000..d2b5f44cd0fc
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/memory_input.hpp
@@ -0,0 +1,381 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_MEMORY_INPUT_HPP
+#define TAO_JSON_PEGTL_MEMORY_INPUT_HPP
+
+#include <cstddef>
+#include <cstdint>
+#include <cstring>
+#include <string>
+#include <string_view>
+#include <type_traits>
+#include <utility>
+
+#include "config.hpp"
+#include "eol.hpp"
+#include "normal.hpp"
+#include "nothing.hpp"
+#include "position.hpp"
+#include "tracking_mode.hpp"
+
+#include "internal/action_input.hpp"
+#include "internal/at.hpp"
+#include "internal/bump.hpp"
+#include "internal/eolf.hpp"
+#include "internal/iterator.hpp"
+#include "internal/marker.hpp"
+#include "internal/until.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE
+{
+   namespace internal
+   {
+      template< tracking_mode, typename Eol, typename Source >
+      class memory_input_base;
+
+      template< typename Eol, typename Source >
+      class memory_input_base< tracking_mode::eager, Eol, Source >
+      {
+      public:
+         using iterator_t = internal::iterator;
+
+         template< typename T >
+         memory_input_base( const iterator_t& in_begin, const char* in_end, T&& in_source ) noexcept( std::is_nothrow_constructible_v< Source, T&& > )
+            : m_begin( in_begin.data ),
+              m_current( in_begin ),
+              m_end( in_end ),
+              m_source( std::forward< T >( in_source ) )
+         {
+         }
+
+         template< typename T >
+         memory_input_base( const char* in_begin, const char* in_end, T&& in_source ) noexcept( std::is_nothrow_constructible_v< Source, T&& > )
+            : m_begin( in_begin ),
+              m_current( in_begin ),
+              m_end( in_end ),
+              m_source( std::forward< T >( in_source ) )
+         {
+         }
+
+         memory_input_base( const memory_input_base& ) = delete;
+         memory_input_base( memory_input_base&& ) = delete;
+
+         ~memory_input_base() = default;
+
+         memory_input_base operator=( const memory_input_base& ) = delete;
+         memory_input_base operator=( memory_input_base&& ) = delete;
+
+         [[nodiscard]] const char* current() const noexcept
+         {
+            return m_current.data;
+         }
+
+         [[nodiscard]] const char* begin() const noexcept
+         {
+            return m_begin;
+         }
+
+         [[nodiscard]] const char* end( const std::size_t /*unused*/ = 0 ) const noexcept
+         {
+            return m_end;
+         }
+
+         [[nodiscard]] std::size_t byte() const noexcept
+         {
+            return m_current.byte;
+         }
+
+         [[nodiscard]] std::size_t line() const noexcept
+         {
+            return m_current.line;
+         }
+
+         [[nodiscard]] std::size_t byte_in_line() const noexcept
+         {
+            return m_current.byte_in_line;
+         }
+
+         void bump( const std::size_t in_count = 1 ) noexcept
+         {
+            internal::bump( m_current, in_count, Eol::ch );
+         }
+
+         void bump_in_this_line( const std::size_t in_count = 1 ) noexcept
+         {
+            internal::bump_in_this_line( m_current, in_count );
+         }
+
+         void bump_to_next_line( const std::size_t in_count = 1 ) noexcept
+         {
+            internal::bump_to_next_line( m_current, in_count );
+         }
+
+         [[nodiscard]] TAO_JSON_PEGTL_NAMESPACE::position position( const iterator_t& it ) const
+         {
+            return TAO_JSON_PEGTL_NAMESPACE::position( it, m_source );
+         }
+
+         void restart( const std::size_t in_byte = 0, const std::size_t in_line = 1, const std::size_t in_byte_in_line = 0 )
+         {
+            m_current.data = m_begin;
+            m_current.byte = in_byte;
+            m_current.line = in_line;
+            m_current.byte_in_line = in_byte_in_line;
+         }
+
+         template< rewind_mode M >
+         void restart( const internal::marker< iterator_t, M >& m )
+         {
+            m_current.data = m.iterator().data;
+            m_current.byte = m.iterator().byte;
+            m_current.line = m.iterator().line;
+            m_current.byte_in_line = m.iterator().byte_in_line;
+         }
+
+      protected:
+         const char* const m_begin;
+         iterator_t m_current;
+         const char* const m_end;
+         const Source m_source;
+      };
+
+      template< typename Eol, typename Source >
+      class memory_input_base< tracking_mode::lazy, Eol, Source >
+      {
+      public:
+         using iterator_t = const char*;
+
+         template< typename T >
+         memory_input_base( const internal::iterator& in_begin, const char* in_end, T&& in_source ) noexcept( std::is_nothrow_constructible_v< Source, T&& > )
+            : m_begin( in_begin ),
+              m_current( in_begin.data ),
+              m_end( in_end ),
+              m_source( std::forward< T >( in_source ) )
+         {
+         }
+
+         template< typename T >
+         memory_input_base( const char* in_begin, const char* in_end, T&& in_source ) noexcept( std::is_nothrow_constructible_v< Source, T&& > )
+            : m_begin( in_begin ),
+              m_current( in_begin ),
+              m_end( in_end ),
+              m_source( std::forward< T >( in_source ) )
+         {
+         }
+
+         memory_input_base( const memory_input_base& ) = delete;
+         memory_input_base( memory_input_base&& ) = delete;
+
+         ~memory_input_base() = default;
+
+         memory_input_base operator=( const memory_input_base& ) = delete;
+         memory_input_base operator=( memory_input_base&& ) = delete;
+
+         [[nodiscard]] const char* current() const noexcept
+         {
+            return m_current;
+         }
+
+         [[nodiscard]] const char* begin() const noexcept
+         {
+            return m_begin.data;
+         }
+
+         [[nodiscard]] const char* end( const std::size_t /*unused*/ = 0 ) const noexcept
+         {
+            return m_end;
+         }
+
+         [[nodiscard]] std::size_t byte() const noexcept
+         {
+            return std::size_t( current() - m_begin.data );
+         }
+
+         void bump( const std::size_t in_count = 1 ) noexcept
+         {
+            m_current += in_count;
+         }
+
+         void bump_in_this_line( const std::size_t in_count = 1 ) noexcept
+         {
+            m_current += in_count;
+         }
+
+         void bump_to_next_line( const std::size_t in_count = 1 ) noexcept
+         {
+            m_current += in_count;
+         }
+
+         [[nodiscard]] TAO_JSON_PEGTL_NAMESPACE::position position( const iterator_t it ) const
+         {
+            internal::iterator c( m_begin );
+            internal::bump( c, std::size_t( it - m_begin.data ), Eol::ch );
+            return TAO_JSON_PEGTL_NAMESPACE::position( c, m_source );
+         }
+
+         void restart()
+         {
+            m_current = m_begin.data;
+         }
+
+         template< rewind_mode M >
+         void restart( const internal::marker< iterator_t, M >& m )
+         {
+            m_current = m.iterator();
+         }
+
+      protected:
+         const internal::iterator m_begin;
+         iterator_t m_current;
+         const char* const m_end;
+         const Source m_source;
+      };
+
+   }  // namespace internal
+
+   template< tracking_mode P = tracking_mode::eager, typename Eol = eol::lf_crlf, typename Source = std::string >
+   class memory_input
+      : public internal::memory_input_base< P, Eol, Source >
+   {
+   public:
+      static constexpr tracking_mode tracking_mode_v = P;
+
+      using eol_t = Eol;
+      using source_t = Source;
+
+      using typename internal::memory_input_base< P, Eol, Source >::iterator_t;
+
+      using action_t = internal::action_input< memory_input >;
+
+      using internal::memory_input_base< P, Eol, Source >::memory_input_base;
+
+      template< typename T >
+      memory_input( const char* in_begin, const std::size_t in_size, T&& in_source ) noexcept( std::is_nothrow_constructible_v< Source, T&& > )
+         : memory_input( in_begin, in_begin + in_size, std::forward< T >( in_source ) )
+      {
+      }
+
+      template< typename T >
+      memory_input( const std::string& in_string, T&& in_source ) noexcept( std::is_nothrow_constructible_v< Source, T&& > )
+         : memory_input( in_string.data(), in_string.size(), std::forward< T >( in_source ) )
+      {
+      }
+
+      template< typename T >
+      memory_input( const std::string_view in_string, T&& in_source ) noexcept( std::is_nothrow_constructible_v< Source, T&& > )
+         : memory_input( in_string.data(), in_string.size(), std::forward< T >( in_source ) )
+      {
+      }
+
+      template< typename T >
+      memory_input( std::string&&, T&& ) = delete;
+
+      template< typename T >
+      memory_input( const char* in_begin, T&& in_source ) noexcept( std::is_nothrow_constructible_v< Source, T&& > )
+         : memory_input( in_begin, std::strlen( in_begin ), std::forward< T >( in_source ) )
+      {
+      }
+
+      template< typename T >
+      memory_input( const char* in_begin, const char* in_end, T&& in_source, const std::size_t in_byte, const std::size_t in_line, const std::size_t in_byte_in_line ) noexcept( std::is_nothrow_constructible_v< Source, T&& > )
+         : memory_input( { in_begin, in_byte, in_line, in_byte_in_line }, in_end, std::forward< T >( in_source ) )
+      {
+      }
+
+      memory_input( const memory_input& ) = delete;
+      memory_input( memory_input&& ) = delete;
+
+      ~memory_input() = default;
+
+      memory_input operator=( const memory_input& ) = delete;
+      memory_input operator=( memory_input&& ) = delete;
+
+      [[nodiscard]] const Source& source() const noexcept
+      {
+         return this->m_source;
+      }
+
+      [[nodiscard]] bool empty() const noexcept
+      {
+         return this->current() == this->end();
+      }
+
+      [[nodiscard]] std::size_t size( const std::size_t /*unused*/ = 0 ) const noexcept
+      {
+         return std::size_t( this->end() - this->current() );
+      }
+
+      [[nodiscard]] char peek_char( const std::size_t offset = 0 ) const noexcept
+      {
+         return this->current()[ offset ];
+      }
+
+      [[nodiscard]] std::uint8_t peek_uint8( const std::size_t offset = 0 ) const noexcept
+      {
+         return static_cast< std::uint8_t >( peek_char( offset ) );
+      }
+
+      [[nodiscard]] iterator_t& iterator() noexcept
+      {
+         return this->m_current;
+      }
+
+      [[nodiscard]] const iterator_t& iterator() const noexcept
+      {
+         return this->m_current;
+      }
+
+      using internal::memory_input_base< P, Eol, Source >::position;
+
+      [[nodiscard]] TAO_JSON_PEGTL_NAMESPACE::position position() const
+      {
+         return position( iterator() );
+      }
+
+      void discard() const noexcept
+      {
+      }
+
+      void require( const std::size_t /*unused*/ ) const noexcept
+      {
+      }
+
+      template< rewind_mode M >
+      [[nodiscard]] internal::marker< iterator_t, M > mark() noexcept
+      {
+         return internal::marker< iterator_t, M >( iterator() );
+      }
+
+      [[nodiscard]] const char* at( const TAO_JSON_PEGTL_NAMESPACE::position& p ) const noexcept
+      {
+         return this->begin() + p.byte;
+      }
+
+      [[nodiscard]] const char* begin_of_line( const TAO_JSON_PEGTL_NAMESPACE::position& p ) const noexcept
+      {
+         return at( p ) - p.byte_in_line;
+      }
+
+      [[nodiscard]] const char* end_of_line( const TAO_JSON_PEGTL_NAMESPACE::position& p ) const noexcept
+      {
+         using input_t = memory_input< tracking_mode::lazy, Eol, const char* >;
+         input_t in( at( p ), this->end(), "" );
+         using grammar = internal::until< internal::at< internal::eolf > >;
+         (void)normal< grammar >::match< apply_mode::nothing, rewind_mode::dontcare, nothing, normal >( in );
+         return in.current();
+      }
+
+      [[nodiscard]] std::string_view line_at( const TAO_JSON_PEGTL_NAMESPACE::position& p ) const noexcept
+      {
+         const char* b = begin_of_line( p );
+         return std::string_view( b, end_of_line( p ) - b );
+      }
+   };
+
+   template< typename... Ts >
+   memory_input( Ts&&... )->memory_input<>;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/mmap_input.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/mmap_input.hpp
new file mode 100644
index 000000000000..766df579a3a6
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/mmap_input.hpp
@@ -0,0 +1,79 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_MMAP_INPUT_HPP
+#define TAO_JSON_PEGTL_MMAP_INPUT_HPP
+
+#include <string>
+#include <utility>
+
+#include "config.hpp"
+#include "eol.hpp"
+#include "memory_input.hpp"
+#include "tracking_mode.hpp"
+
+#if defined( __unix__ ) || ( defined( __APPLE__ ) && defined( __MACH__ ) )
+#include <unistd.h>  // Required for _POSIX_MAPPED_FILES
+#endif
+
+#if defined( _POSIX_MAPPED_FILES )
+#include "internal/file_mapper_posix.hpp"
+#elif defined( _WIN32 )
+#include "internal/file_mapper_win32.hpp"
+#else
+#endif
+
+namespace TAO_JSON_PEGTL_NAMESPACE
+{
+   namespace internal
+   {
+      struct mmap_holder
+      {
+         const std::string filename;
+         const file_mapper data;
+
+         template< typename T >
+         explicit mmap_holder( T&& in_filename )
+            : filename( std::forward< T >( in_filename ) ),
+              data( filename.c_str() )
+         {
+         }
+
+         mmap_holder( const mmap_holder& ) = delete;
+         mmap_holder( mmap_holder&& ) = delete;
+
+         ~mmap_holder() = default;
+
+         void operator=( const mmap_holder& ) = delete;
+         void operator=( mmap_holder&& ) = delete;
+      };
+
+   }  // namespace internal
+
+   template< tracking_mode P = tracking_mode::eager, typename Eol = eol::lf_crlf >
+   struct mmap_input
+      : private internal::mmap_holder,
+        public memory_input< P, Eol, const char* >
+   {
+      template< typename T >
+      explicit mmap_input( T&& in_filename )
+         : internal::mmap_holder( std::forward< T >( in_filename ) ),
+           memory_input< P, Eol, const char* >( data.begin(), data.end(), filename.c_str() )
+      {
+      }
+
+      mmap_input( const mmap_input& ) = delete;
+      mmap_input( mmap_input&& ) = delete;
+
+      ~mmap_input() = default;
+
+      void operator=( const mmap_input& ) = delete;
+      void operator=( mmap_input&& ) = delete;
+   };
+
+   template< typename... Ts >
+   explicit mmap_input( Ts&&... )->mmap_input<>;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/normal.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/normal.hpp
new file mode 100644
index 000000000000..71f7545f4bc9
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/normal.hpp
@@ -0,0 +1,87 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_NORMAL_HPP
+#define TAO_JSON_PEGTL_NORMAL_HPP
+
+#include <string>
+#include <type_traits>
+#include <utility>
+
+#include "apply_mode.hpp"
+#include "config.hpp"
+#include "match.hpp"
+#include "parse_error.hpp"
+#include "rewind_mode.hpp"
+
+#include "internal/demangle.hpp"
+#include "internal/has_match.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE
+{
+   template< typename Rule >
+   struct normal
+   {
+      template< typename Input, typename... States >
+      static void start( const Input& /*unused*/, States&&... /*unused*/ ) noexcept
+      {
+      }
+
+      template< typename Input, typename... States >
+      static void success( const Input& /*unused*/, States&&... /*unused*/ ) noexcept
+      {
+      }
+
+      template< typename Input, typename... States >
+      static void failure( const Input& /*unused*/, States&&... /*unused*/ ) noexcept
+      {
+      }
+
+      template< typename Input, typename... States >
+      static void raise( const Input& in, States&&... /*unused*/ )
+      {
+         throw parse_error( "parse error matching " + std::string( internal::demangle< Rule >() ), in );
+      }
+
+      template< template< typename... > class Action,
+                typename Iterator,
+                typename Input,
+                typename... States >
+      static auto apply( const Iterator& begin, const Input& in, States&&... st ) noexcept( noexcept( Action< Rule >::apply( std::declval< const typename Input::action_t& >(), st... ) ) )
+         -> decltype( Action< Rule >::apply( std::declval< const typename Input::action_t& >(), st... ) )
+      {
+         const typename Input::action_t action_input( begin, in );
+         return Action< Rule >::apply( action_input, st... );
+      }
+
+      template< template< typename... > class Action,
+                typename Input,
+                typename... States >
+      static auto apply0( const Input& /*unused*/, States&&... st ) noexcept( noexcept( Action< Rule >::apply0( st... ) ) )
+         -> decltype( Action< Rule >::apply0( st... ) )
+      {
+         return Action< Rule >::apply0( st... );
+      }
+
+      template< apply_mode A,
+                rewind_mode M,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class Control,
+                typename Input,
+                typename... States >
+      [[nodiscard]] static bool match( Input& in, States&&... st )
+      {
+         if constexpr( internal::has_match_v< Rule, A, M, Action, Control, Input, States... > ) {
+            return Action< Rule >::template match< Rule, A, M, Action, Control >( in, st... );
+         }
+         else {
+            return TAO_JSON_PEGTL_NAMESPACE::match< Rule, A, M, Action, Control >( in, st... );
+         }
+      }
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/nothing.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/nothing.hpp
new file mode 100644
index 000000000000..85d5603371dc
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/nothing.hpp
@@ -0,0 +1,20 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_NOTHING_HPP
+#define TAO_JSON_PEGTL_NOTHING_HPP
+
+#include "config.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE
+{
+   template< typename Rule >
+   struct nothing
+   {
+   };
+
+   using maybe_nothing = nothing< void >;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/parse.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/parse.hpp
new file mode 100644
index 000000000000..9a777eb82a2d
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/parse.hpp
@@ -0,0 +1,53 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_PARSE_HPP
+#define TAO_JSON_PEGTL_PARSE_HPP
+
+#include <cassert>
+
+#include "apply_mode.hpp"
+#include "config.hpp"
+#include "normal.hpp"
+#include "nothing.hpp"
+#include "parse_error.hpp"
+#include "rewind_mode.hpp"
+
+#include "internal/action_input.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE
+{
+   template< typename Rule,
+             template< typename... > class Action = nothing,
+             template< typename... > class Control = normal,
+             apply_mode A = apply_mode::action,
+             rewind_mode M = rewind_mode::required,
+             typename Input,
+             typename... States >
+   bool parse( Input&& in, States&&... st )
+   {
+      return Control< Rule >::template match< A, M, Action, Control >( in, st... );
+   }
+
+   template< typename Rule,
+             template< typename... > class Action = nothing,
+             template< typename... > class Control = normal,
+             apply_mode A = apply_mode::action,
+             rewind_mode M = rewind_mode::required,
+             typename Outer,
+             typename Input,
+             typename... States >
+   bool parse_nested( const Outer& oi, Input&& in, States&&... st )
+   {
+      try {
+         return parse< Rule, Action, Control, A, M >( in, st... );
+      }
+      catch( parse_error& e ) {
+         e.positions.push_back( oi.position() );
+         throw;
+      }
+   }
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/parse_error.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/parse_error.hpp
new file mode 100644
index 000000000000..c139155f0022
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/parse_error.hpp
@@ -0,0 +1,69 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_PARSE_ERROR_HPP
+#define TAO_JSON_PEGTL_PARSE_ERROR_HPP
+
+#include <ostream>
+#include <sstream>
+#include <stdexcept>
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "config.hpp"
+#include "position.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE
+{
+   struct parse_error
+      : std::runtime_error
+   {
+      template< typename Msg >
+      parse_error( Msg&& msg, std::vector< position > in_positions )
+         : std::runtime_error( std::forward< Msg >( msg ) ),
+           positions( std::move( in_positions ) )
+      {
+      }
+
+      template< typename Msg >
+      parse_error( Msg&& msg, const position& pos )
+         : std::runtime_error( std::forward< Msg >( msg ) ),
+           positions( 1, pos )
+      {
+      }
+
+      template< typename Msg >
+      parse_error( Msg&& msg, position&& pos )
+         : std::runtime_error( std::forward< Msg >( msg ) )
+      {
+         positions.emplace_back( std::move( pos ) );
+      }
+
+      template< typename Msg, typename Input >
+      parse_error( Msg&& msg, const Input& in )
+         : parse_error( std::forward< Msg >( msg ), in.position() )
+      {
+      }
+
+      std::vector< position > positions;
+   };
+
+   inline std::ostream& operator<<( std::ostream& o, const parse_error& e )
+   {
+      for( auto it = e.positions.rbegin(); it != e.positions.rend(); ++it ) {
+         o << *it << ": ";
+      }
+      return o << e.what();
+   }
+
+   [[nodiscard]] inline std::string to_string( const parse_error& e )
+   {
+      std::ostringstream o;
+      o << e;
+      return o.str();
+   }
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/position.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/position.hpp
new file mode 100644
index 000000000000..a362741f9d2d
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/position.hpp
@@ -0,0 +1,75 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_POSITION_HPP
+#define TAO_JSON_PEGTL_POSITION_HPP
+
+#include <cstdlib>
+#include <ostream>
+#include <sstream>
+#include <string>
+#include <utility>
+
+#include "config.hpp"
+
+#include "internal/iterator.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE
+{
+   struct position
+   {
+      position() = delete;
+
+      position( position&& p ) noexcept
+         : byte( p.byte ),
+           line( p.line ),
+           byte_in_line( p.byte_in_line ),
+           source( std::move( p.source ) )
+      {
+      }
+
+      position( const position& ) = default;
+
+      position& operator=( position&& p ) noexcept
+      {
+         byte = p.byte;
+         line = p.line;
+         byte_in_line = p.byte_in_line;
+         source = std::move( p.source );
+         return *this;
+      }
+
+      position& operator=( const position& ) = default;
+
+      template< typename T >
+      position( const internal::iterator& in_iter, T&& in_source )
+         : byte( in_iter.byte ),
+           line( in_iter.line ),
+           byte_in_line( in_iter.byte_in_line ),
+           source( std::forward< T >( in_source ) )
+      {
+      }
+
+      ~position() = default;
+
+      std::size_t byte;
+      std::size_t line;
+      std::size_t byte_in_line;
+      std::string source;
+   };
+
+   inline std::ostream& operator<<( std::ostream& o, const position& p )
+   {
+      return o << p.source << ':' << p.line << ':' << p.byte_in_line << '(' << p.byte << ')';
+   }
+
+   [[nodiscard]] inline std::string to_string( const position& p )
+   {
+      std::ostringstream o;
+      o << p;
+      return o.str();
+   }
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/read_input.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/read_input.hpp
new file mode 100644
index 000000000000..9e69d1b472ed
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/read_input.hpp
@@ -0,0 +1,74 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_READ_INPUT_HPP
+#define TAO_JSON_PEGTL_READ_INPUT_HPP
+
+#include <string>
+
+#include "config.hpp"
+#include "eol.hpp"
+#include "string_input.hpp"
+#include "tracking_mode.hpp"
+
+#include "internal/file_reader.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE
+{
+   namespace internal
+   {
+      struct filename_holder
+      {
+         const std::string filename;
+
+         template< typename T >
+         explicit filename_holder( T&& in_filename )
+            : filename( std::forward< T >( in_filename ) )
+         {
+         }
+
+         filename_holder( const filename_holder& ) = delete;
+         filename_holder( filename_holder&& ) = delete;
+
+         ~filename_holder() = default;
+
+         void operator=( const filename_holder& ) = delete;
+         void operator=( filename_holder&& ) = delete;
+      };
+
+   }  // namespace internal
+
+   template< tracking_mode P = tracking_mode::eager, typename Eol = eol::lf_crlf >
+   struct read_input
+      : private internal::filename_holder,
+        public string_input< P, Eol, const char* >
+   {
+      template< typename T >
+      explicit read_input( T&& in_filename )
+         : internal::filename_holder( std::forward< T >( in_filename ) ),
+           string_input< P, Eol, const char* >( internal::file_reader( filename.c_str() ).read(), filename.c_str() )
+      {
+      }
+
+      template< typename T >
+      read_input( FILE* in_file, T&& in_filename )
+         : internal::filename_holder( std::forward< T >( in_filename ) ),
+           string_input< P, Eol, const char* >( internal::file_reader( in_file, filename.c_str() ).read(), filename.c_str() )
+      {
+      }
+
+      read_input( const read_input& ) = delete;
+      read_input( read_input&& ) = delete;
+
+      ~read_input() = default;
+
+      void operator=( const read_input& ) = delete;
+      void operator=( read_input&& ) = delete;
+   };
+
+   template< typename... Ts >
+   explicit read_input( Ts&&... )->read_input<>;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/require_apply.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/require_apply.hpp
new file mode 100644
index 000000000000..fd9f15a90fd8
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/require_apply.hpp
@@ -0,0 +1,16 @@
+// Copyright (c) 2019-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_REQUIRE_APPLY_HPP
+#define TAO_JSON_PEGTL_REQUIRE_APPLY_HPP
+
+#include "config.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE
+{
+   struct require_apply
+   {};
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/require_apply0.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/require_apply0.hpp
new file mode 100644
index 000000000000..41d8112f7271
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/require_apply0.hpp
@@ -0,0 +1,16 @@
+// Copyright (c) 2019-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_REQUIRE_APPLY0_HPP
+#define TAO_JSON_PEGTL_REQUIRE_APPLY0_HPP
+
+#include "config.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE
+{
+   struct require_apply0
+   {};
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/rewind_mode.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/rewind_mode.hpp
new file mode 100644
index 000000000000..f97096a92d50
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/rewind_mode.hpp
@@ -0,0 +1,20 @@
+// Copyright (c) 2016-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_REWIND_MODE_HPP
+#define TAO_JSON_PEGTL_REWIND_MODE_HPP
+
+#include "config.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE
+{
+   enum class rewind_mode : char
+   {
+      active,
+      required,
+      dontcare
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/rules.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/rules.hpp
new file mode 100644
index 000000000000..1029450b7dc0
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/rules.hpp
@@ -0,0 +1,67 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_RULES_HPP
+#define TAO_JSON_PEGTL_RULES_HPP
+
+#include "config.hpp"
+#include "parse_error.hpp"
+
+#include "internal/rules.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE
+{
+   // clang-format off
+   template< typename... Actions > struct apply : internal::apply< Actions... > {};
+   template< typename... Actions > struct apply0 : internal::apply0< Actions... > {};
+   template< template< typename... > class Action, typename... Rules > struct action : internal::action< Action, Rules... > {};
+   template< typename... Rules > struct at : internal::at< Rules... > {};
+   struct bof : internal::bof {};
+   struct bol : internal::bol {};
+   template< unsigned Num > struct bytes : internal::bytes< Num > {};
+   template< template< typename... > class Control, typename... Rules > struct control : internal::control< Control, Rules... > {};
+   template< typename... Rules > struct disable : internal::disable< Rules... > {};
+   struct discard : internal::discard {};
+   template< typename... Rules > struct enable : internal::enable< Rules... > {};
+   struct eof : internal::eof {};
+   struct failure : internal::trivial< false > {};
+   template< typename Rule, typename... Actions > struct if_apply : internal::if_apply< Rule, Actions... > {};
+   template< typename Cond, typename... Thens > struct if_must : internal::if_must< false, Cond, Thens... > {};
+   template< typename Cond, typename Then, typename Else > struct if_must_else : internal::if_must_else< Cond, Then, Else > {};
+   template< typename Cond, typename Then, typename Else > struct if_then_else : internal::if_then_else< Cond, Then, Else > {};
+   template< typename Rule, typename Sep, typename Pad = void > struct list : internal::list< Rule, internal::pad< Sep, Pad > > {};
+   template< typename Rule, typename Sep > struct list< Rule, Sep, void > : internal::list< Rule, Sep > {};
+   template< typename Rule, typename Sep, typename Pad = void > struct list_must : internal::list_must< Rule, internal::pad< Sep, Pad > > {};
+   template< typename Rule, typename Sep > struct list_must< Rule, Sep, void > : internal::list_must< Rule, Sep > {};
+   template< typename Rule, typename Sep, typename Pad = void > struct list_tail : internal::list_tail_pad< Rule, Sep, Pad > {};
+   template< typename Rule, typename Sep > struct list_tail< Rule, Sep, void > : internal::list_tail< Rule, Sep > {};
+   template< typename M, typename S > struct minus : internal::rematch< M, internal::not_at< S, internal::eof > > {};
+   template< typename... Rules > struct must : internal::must< Rules... > {};
+   template< typename... Rules > struct not_at : internal::not_at< Rules... > {};
+   template< typename... Rules > struct opt : internal::opt< Rules... > {};
+   template< typename Cond, typename... Rules > struct opt_must : internal::if_must< true, Cond, Rules... > {};
+   template< typename Rule, typename Pad1, typename Pad2 = Pad1 > struct pad : internal::pad< Rule, Pad1, Pad2 > {};
+   template< typename Rule, typename Pad > struct pad_opt : internal::pad_opt< Rule, Pad > {};
+   template< typename Rule, typename... Rules > struct plus : internal::plus< Rule, Rules... > {};
+   template< typename Exception > struct raise : internal::raise< Exception > {};
+   template< typename Head, typename... Rules > struct rematch : internal::rematch< Head, Rules... > {};
+   template< unsigned Num, typename... Rules > struct rep : internal::rep< Num, Rules... > {};
+   template< unsigned Max, typename... Rules > struct rep_max : internal::rep_min_max< 0, Max, Rules... > {};
+   template< unsigned Min, typename Rule, typename... Rules > struct rep_min : internal::rep_min< Min, Rule, Rules... > {};
+   template< unsigned Min, unsigned Max, typename... Rules > struct rep_min_max : internal::rep_min_max< Min, Max, Rules... > {};
+   template< unsigned Max, typename... Rules > struct rep_opt : internal::rep_opt< Max, Rules... > {};
+   template< unsigned Amount > struct require : internal::require< Amount > {};
+   template< typename... Rules > struct seq : internal::seq< Rules... > {};
+   template< typename... Rules > struct sor : internal::sor< Rules... > {};
+   template< typename Rule, typename... Rules > struct star : internal::star< Rule, Rules... > {};
+   template< typename Cond, typename... Rules > struct star_must : internal::star_must< Cond, Rules... > {};
+   template< typename State, typename... Rules > struct state : internal::state< State, Rules... > {};
+   struct success : internal::trivial< true > {};
+   template< typename... Rules > struct try_catch : internal::try_catch_type< parse_error, Rules... > {};
+   template< typename Exception, typename... Rules > struct try_catch_type : internal::try_catch_type< Exception, Rules... > {};
+   template< typename Cond, typename... Rules > struct until : internal::until< Cond, Rules... > {};
+   // clang-format on
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/string_input.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/string_input.hpp
new file mode 100644
index 000000000000..503be5e8bac4
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/string_input.hpp
@@ -0,0 +1,66 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_STRING_INPUT_HPP
+#define TAO_JSON_PEGTL_STRING_INPUT_HPP
+
+#include <string>
+#include <utility>
+
+#include "config.hpp"
+#include "eol.hpp"
+#include "memory_input.hpp"
+#include "tracking_mode.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE
+{
+   namespace internal
+   {
+      struct string_holder
+      {
+         const std::string data;
+
+         template< typename T >
+         explicit string_holder( T&& in_data )
+            : data( std::forward< T >( in_data ) )
+         {
+         }
+
+         string_holder( const string_holder& ) = delete;
+         string_holder( string_holder&& ) = delete;
+
+         ~string_holder() = default;
+
+         void operator=( const string_holder& ) = delete;
+         void operator=( string_holder&& ) = delete;
+      };
+
+   }  // namespace internal
+
+   template< tracking_mode P = tracking_mode::eager, typename Eol = eol::lf_crlf, typename Source = std::string >
+   struct string_input
+      : private internal::string_holder,
+        public memory_input< P, Eol, Source >
+   {
+      template< typename V, typename T, typename... Ts >
+      explicit string_input( V&& in_data, T&& in_source, Ts&&... ts )
+         : internal::string_holder( std::forward< V >( in_data ) ),
+           memory_input< P, Eol, Source >( data.data(), data.size(), std::forward< T >( in_source ), std::forward< Ts >( ts )... )
+      {
+      }
+
+      string_input( const string_input& ) = delete;
+      string_input( string_input&& ) = delete;
+
+      ~string_input() = default;
+
+      void operator=( const string_input& ) = delete;
+      void operator=( string_input&& ) = delete;
+   };
+
+   template< typename... Ts >
+   explicit string_input( Ts&&... )->string_input<>;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/tracking_mode.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/tracking_mode.hpp
new file mode 100644
index 000000000000..cda9fe2b08fd
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/tracking_mode.hpp
@@ -0,0 +1,19 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_TRACKING_MODE_HPP
+#define TAO_JSON_PEGTL_TRACKING_MODE_HPP
+
+#include "config.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE
+{
+   enum class tracking_mode : bool
+   {
+      eager,
+      lazy
+   };
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/uint16.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/uint16.hpp
new file mode 100644
index 000000000000..64c47a1bd8af
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/uint16.hpp
@@ -0,0 +1,62 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_UINT16_HPP
+#define TAO_JSON_PEGTL_UINT16_HPP
+
+#include "config.hpp"
+
+#include "internal/peek_mask_uint.hpp"
+#include "internal/peek_uint.hpp"
+#include "internal/result_on_found.hpp"
+#include "internal/rules.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE
+{
+   namespace uint16_be
+   {
+      // clang-format off
+      struct any : internal::any< internal::peek_uint16_be > {};
+
+      template< std::uint16_t... Cs > struct not_one : internal::one< internal::result_on_found::failure, internal::peek_uint16_be, Cs... > {};
+      template< std::uint16_t Lo, std::uint16_t Hi > struct not_range : internal::range< internal::result_on_found::failure, internal::peek_uint16_be, Lo, Hi > {};
+      template< std::uint16_t... Cs > struct one : internal::one< internal::result_on_found::success, internal::peek_uint16_be, Cs... > {};
+      template< std::uint16_t Lo, std::uint16_t Hi > struct range : internal::range< internal::result_on_found::success, internal::peek_uint16_be, Lo, Hi > {};
+      template< std::uint16_t... Cs > struct ranges : internal::ranges< internal::peek_uint16_be, Cs... > {};
+      template< std::uint16_t... Cs > struct string : internal::seq< internal::one< internal::result_on_found::success, internal::peek_uint16_be, Cs >... > {};
+
+      template< std::uint16_t M, std::uint16_t... Cs > struct mask_not_one : internal::one< internal::result_on_found::failure, internal::peek_mask_uint16_be< M >, Cs... > {};
+      template< std::uint16_t M, std::uint16_t Lo, std::uint16_t Hi > struct mask_not_range : internal::range< internal::result_on_found::failure, internal::peek_mask_uint16_be< M >, Lo, Hi > {};
+      template< std::uint16_t M, std::uint16_t... Cs > struct mask_one : internal::one< internal::result_on_found::success, internal::peek_mask_uint16_be< M >, Cs... > {};
+      template< std::uint16_t M, std::uint16_t Lo, std::uint16_t Hi > struct mask_range : internal::range< internal::result_on_found::success, internal::peek_mask_uint16_be< M >, Lo, Hi > {};
+      template< std::uint16_t M, std::uint16_t... Cs > struct mask_ranges : internal::ranges< internal::peek_mask_uint16_be< M >, Cs... > {};
+      template< std::uint16_t M, std::uint16_t... Cs > struct mask_string : internal::seq< internal::one< internal::result_on_found::success, internal::peek_mask_uint16_be< M >, Cs >... > {};
+      // clang-format on
+
+   }  // namespace uint16_be
+
+   namespace uint16_le
+   {
+      // clang-format off
+      struct any : internal::any< internal::peek_uint16_le > {};
+
+      template< std::uint16_t... Cs > struct not_one : internal::one< internal::result_on_found::failure, internal::peek_uint16_le, Cs... > {};
+      template< std::uint16_t Lo, std::uint16_t Hi > struct not_range : internal::range< internal::result_on_found::failure, internal::peek_uint16_le, Lo, Hi > {};
+      template< std::uint16_t... Cs > struct one : internal::one< internal::result_on_found::success, internal::peek_uint16_le, Cs... > {};
+      template< std::uint16_t Lo, std::uint16_t Hi > struct range : internal::range< internal::result_on_found::success, internal::peek_uint16_le, Lo, Hi > {};
+      template< std::uint16_t... Cs > struct ranges : internal::ranges< internal::peek_uint16_le, Cs... > {};
+      template< std::uint16_t... Cs > struct string : internal::seq< internal::one< internal::result_on_found::success, internal::peek_uint16_le, Cs >... > {};
+
+      template< std::uint16_t M, std::uint16_t... Cs > struct mask_not_one : internal::one< internal::result_on_found::failure, internal::peek_mask_uint16_le< M >, Cs... > {};
+      template< std::uint16_t M, std::uint16_t Lo, std::uint16_t Hi > struct mask_not_range : internal::range< internal::result_on_found::failure, internal::peek_mask_uint16_le< M >, Lo, Hi > {};
+      template< std::uint16_t M, std::uint16_t... Cs > struct mask_one : internal::one< internal::result_on_found::success, internal::peek_mask_uint16_le< M >, Cs... > {};
+      template< std::uint16_t M, std::uint16_t Lo, std::uint16_t Hi > struct mask_range : internal::range< internal::result_on_found::success, internal::peek_mask_uint16_le< M >, Lo, Hi > {};
+      template< std::uint16_t M, std::uint16_t... Cs > struct mask_ranges : internal::ranges< internal::peek_mask_uint16_le< M >, Cs... > {};
+      template< std::uint16_t M, std::uint16_t... Cs > struct mask_string : internal::seq< internal::one< internal::result_on_found::success, internal::peek_mask_uint16_le< M >, Cs >... > {};
+      // clang-format on
+
+   }  // namespace uint16_le
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/uint32.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/uint32.hpp
new file mode 100644
index 000000000000..6345c4637ff4
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/uint32.hpp
@@ -0,0 +1,62 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_UINT32_HPP
+#define TAO_JSON_PEGTL_UINT32_HPP
+
+#include "config.hpp"
+
+#include "internal/peek_mask_uint.hpp"
+#include "internal/peek_uint.hpp"
+#include "internal/result_on_found.hpp"
+#include "internal/rules.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE
+{
+   namespace uint32_be
+   {
+      // clang-format off
+      struct any : internal::any< internal::peek_uint32_be > {};
+
+      template< std::uint32_t... Cs > struct not_one : internal::one< internal::result_on_found::failure, internal::peek_uint32_be, Cs... > {};
+      template< std::uint32_t Lo, std::uint32_t Hi > struct not_range : internal::range< internal::result_on_found::failure, internal::peek_uint32_be, Lo, Hi > {};
+      template< std::uint32_t... Cs > struct one : internal::one< internal::result_on_found::success, internal::peek_uint32_be, Cs... > {};
+      template< std::uint32_t Lo, std::uint32_t Hi > struct range : internal::range< internal::result_on_found::success, internal::peek_uint32_be, Lo, Hi > {};
+      template< std::uint32_t... Cs > struct ranges : internal::ranges< internal::peek_uint32_be, Cs... > {};
+      template< std::uint32_t... Cs > struct string : internal::seq< internal::one< internal::result_on_found::success, internal::peek_uint32_be, Cs >... > {};
+
+      template< std::uint32_t M, std::uint32_t... Cs > struct mask_not_one : internal::one< internal::result_on_found::failure, internal::peek_mask_uint32_be< M >, Cs... > {};
+      template< std::uint32_t M, std::uint32_t Lo, std::uint32_t Hi > struct mask_not_range : internal::range< internal::result_on_found::failure, internal::peek_mask_uint32_be< M >, Lo, Hi > {};
+      template< std::uint32_t M, std::uint32_t... Cs > struct mask_one : internal::one< internal::result_on_found::success, internal::peek_mask_uint32_be< M >, Cs... > {};
+      template< std::uint32_t M, std::uint32_t Lo, std::uint32_t Hi > struct mask_range : internal::range< internal::result_on_found::success, internal::peek_mask_uint32_be< M >, Lo, Hi > {};
+      template< std::uint32_t M, std::uint32_t... Cs > struct mask_ranges : internal::ranges< internal::peek_mask_uint32_be< M >, Cs... > {};
+      template< std::uint32_t M, std::uint32_t... Cs > struct mask_string : internal::seq< internal::one< internal::result_on_found::success, internal::peek_mask_uint32_be< M >, Cs >... > {};
+      // clang-format on
+
+   }  // namespace uint32_be
+
+   namespace uint32_le
+   {
+      // clang-format off
+      struct any : internal::any< internal::peek_uint32_le > {};
+
+      template< std::uint32_t... Cs > struct not_one : internal::one< internal::result_on_found::failure, internal::peek_uint32_le, Cs... > {};
+      template< std::uint32_t Lo, std::uint32_t Hi > struct not_range : internal::range< internal::result_on_found::failure, internal::peek_uint32_le, Lo, Hi > {};
+      template< std::uint32_t... Cs > struct one : internal::one< internal::result_on_found::success, internal::peek_uint32_le, Cs... > {};
+      template< std::uint32_t Lo, std::uint32_t Hi > struct range : internal::range< internal::result_on_found::success, internal::peek_uint32_le, Lo, Hi > {};
+      template< std::uint32_t... Cs > struct ranges : internal::ranges< internal::peek_uint32_le, Cs... > {};
+      template< std::uint32_t... Cs > struct string : internal::seq< internal::one< internal::result_on_found::success, internal::peek_uint32_le, Cs >... > {};
+
+      template< std::uint32_t M, std::uint32_t... Cs > struct mask_not_one : internal::one< internal::result_on_found::failure, internal::peek_mask_uint32_le< M >, Cs... > {};
+      template< std::uint32_t M, std::uint32_t Lo, std::uint32_t Hi > struct mask_not_range : internal::range< internal::result_on_found::failure, internal::peek_mask_uint32_le< M >, Lo, Hi > {};
+      template< std::uint32_t M, std::uint32_t... Cs > struct mask_one : internal::one< internal::result_on_found::success, internal::peek_mask_uint32_le< M >, Cs... > {};
+      template< std::uint32_t M, std::uint32_t Lo, std::uint32_t Hi > struct mask_range : internal::range< internal::result_on_found::success, internal::peek_mask_uint32_le< M >, Lo, Hi > {};
+      template< std::uint32_t M, std::uint32_t... Cs > struct mask_ranges : internal::ranges< internal::peek_mask_uint32_le< M >, Cs... > {};
+      template< std::uint32_t M, std::uint32_t... Cs > struct mask_string : internal::seq< internal::one< internal::result_on_found::success, internal::peek_mask_uint32_le< M >, Cs >... > {};
+      // clang-format on
+
+   }  // namespace uint32_le
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/uint64.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/uint64.hpp
new file mode 100644
index 000000000000..64f358aff68b
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/uint64.hpp
@@ -0,0 +1,63 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_UINT64_HPP
+#define TAO_JSON_PEGTL_UINT64_HPP
+
+#include "config.hpp"
+
+#include "internal/peek_mask_uint.hpp"
+#include "internal/peek_uint.hpp"
+#include "internal/result_on_found.hpp"
+#include "internal/rules.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE
+{
+   namespace uint64_be
+   {
+      // clang-format off
+      struct any : internal::any< internal::peek_uint64_be > {};
+
+      template< std::uint64_t... Cs > struct not_one : internal::one< internal::result_on_found::failure, internal::peek_uint64_be, Cs... > {};
+      template< std::uint64_t Lo, std::uint64_t Hi > struct not_range : internal::range< internal::result_on_found::failure, internal::peek_uint64_be, Lo, Hi > {};
+      template< std::uint64_t... Cs > struct one : internal::one< internal::result_on_found::success, internal::peek_uint64_be, Cs... > {};
+      template< std::uint64_t Lo, std::uint64_t Hi > struct range : internal::range< internal::result_on_found::success, internal::peek_uint64_be, Lo, Hi > {};
+      template< std::uint64_t... Cs > struct ranges : internal::ranges< internal::peek_uint64_be, Cs... > {};
+      template< std::uint64_t... Cs > struct string : internal::seq< internal::one< internal::result_on_found::success, internal::peek_uint64_be, Cs >... > {};
+
+
+      template< std::uint64_t M, std::uint64_t... Cs > struct mask_not_one : internal::one< internal::result_on_found::failure, internal::peek_mask_uint64_be< M >, Cs... > {};
+      template< std::uint64_t M, std::uint64_t Lo, std::uint64_t Hi > struct mask_not_range : internal::range< internal::result_on_found::failure, internal::peek_mask_uint64_be< M >, Lo, Hi > {};
+      template< std::uint64_t M, std::uint64_t... Cs > struct mask_one : internal::one< internal::result_on_found::success, internal::peek_mask_uint64_be< M >, Cs... > {};
+      template< std::uint64_t M, std::uint64_t Lo, std::uint64_t Hi > struct mask_range : internal::range< internal::result_on_found::success, internal::peek_mask_uint64_be< M >, Lo, Hi > {};
+      template< std::uint64_t M, std::uint64_t... Cs > struct mask_ranges : internal::ranges< internal::peek_mask_uint64_be< M >, Cs... > {};
+      template< std::uint64_t M, std::uint64_t... Cs > struct mask_string : internal::seq< internal::one< internal::result_on_found::success, internal::peek_mask_uint64_be< M >, Cs >... > {};
+      // clang-format on
+
+   }  // namespace uint64_be
+
+   namespace uint64_le
+   {
+      // clang-format off
+      struct any : internal::any< internal::peek_uint64_le > {};
+
+      template< std::uint64_t... Cs > struct not_one : internal::one< internal::result_on_found::failure, internal::peek_uint64_le, Cs... > {};
+      template< std::uint64_t Lo, std::uint64_t Hi > struct not_range : internal::range< internal::result_on_found::failure, internal::peek_uint64_le, Lo, Hi > {};
+      template< std::uint64_t... Cs > struct one : internal::one< internal::result_on_found::success, internal::peek_uint64_le, Cs... > {};
+      template< std::uint64_t Lo, std::uint64_t Hi > struct range : internal::range< internal::result_on_found::success, internal::peek_uint64_le, Lo, Hi > {};
+      template< std::uint64_t... Cs > struct ranges : internal::ranges< internal::peek_uint64_le, Cs... > {};
+      template< std::uint64_t... Cs > struct string : internal::seq< internal::one< internal::result_on_found::success, internal::peek_uint64_le, Cs >... > {};
+
+      template< std::uint64_t M, std::uint64_t... Cs > struct mask_not_one : internal::one< internal::result_on_found::failure, internal::peek_mask_uint64_le< M >, Cs... > {};
+      template< std::uint64_t M, std::uint64_t Lo, std::uint64_t Hi > struct mask_not_range : internal::range< internal::result_on_found::failure, internal::peek_mask_uint64_le< M >, Lo, Hi > {};
+      template< std::uint64_t M, std::uint64_t... Cs > struct mask_one : internal::one< internal::result_on_found::success, internal::peek_mask_uint64_le< M >, Cs... > {};
+      template< std::uint64_t M, std::uint64_t Lo, std::uint64_t Hi > struct mask_range : internal::range< internal::result_on_found::success, internal::peek_mask_uint64_le< M >, Lo, Hi > {};
+      template< std::uint64_t M, std::uint64_t... Cs > struct mask_ranges : internal::ranges< internal::peek_mask_uint64_le< M >, Cs... > {};
+      template< std::uint64_t M, std::uint64_t... Cs > struct mask_string : internal::seq< internal::one< internal::result_on_found::success, internal::peek_mask_uint64_le< M >, Cs >... > {};
+      // clang-format on
+
+   }  // namespace uint64_le
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/uint8.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/uint8.hpp
new file mode 100644
index 000000000000..35a8375d27e9
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/uint8.hpp
@@ -0,0 +1,36 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_UINT8_HPP
+#define TAO_JSON_PEGTL_UINT8_HPP
+
+#include "config.hpp"
+
+#include "internal/peek_mask_uint8.hpp"
+#include "internal/peek_uint8.hpp"
+#include "internal/result_on_found.hpp"
+#include "internal/rules.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::uint8
+{
+   // clang-format off
+   struct any : internal::any< internal::peek_uint8 > {};
+
+   template< std::uint8_t... Cs > struct not_one : internal::one< internal::result_on_found::failure, internal::peek_uint8, Cs... > {};
+   template< std::uint8_t Lo, std::uint8_t Hi > struct not_range : internal::range< internal::result_on_found::failure, internal::peek_uint8, Lo, Hi > {};
+   template< std::uint8_t... Cs > struct one : internal::one< internal::result_on_found::success, internal::peek_uint8, Cs... > {};
+   template< std::uint8_t Lo, std::uint8_t Hi > struct range : internal::range< internal::result_on_found::success, internal::peek_uint8, Lo, Hi > {};
+   template< std::uint8_t... Cs > struct ranges : internal::ranges< internal::peek_uint8, Cs... > {};
+   template< std::uint8_t... Cs > struct string : internal::seq< internal::one< internal::result_on_found::success, internal::peek_uint8, Cs >... > {};
+
+   template< std::uint8_t M, std::uint8_t... Cs > struct mask_not_one : internal::one< internal::result_on_found::failure, internal::peek_mask_uint8< M >, Cs... > {};
+   template< std::uint8_t M, std::uint8_t Lo, std::uint8_t Hi > struct mask_not_range : internal::range< internal::result_on_found::failure, internal::peek_mask_uint8< M >, Lo, Hi > {};
+   template< std::uint8_t M, std::uint8_t... Cs > struct mask_one : internal::one< internal::result_on_found::success, internal::peek_mask_uint8< M >, Cs... > {};
+   template< std::uint8_t M, std::uint8_t Lo, std::uint8_t Hi > struct mask_range : internal::range< internal::result_on_found::success, internal::peek_mask_uint8< M >, Lo, Hi > {};
+   template< std::uint8_t M, std::uint8_t... Cs > struct mask_ranges : internal::ranges< internal::peek_mask_uint8< M >, Cs... > {};
+   template< std::uint8_t M, std::uint8_t... Cs > struct mask_string : internal::seq< internal::one< internal::result_on_found::success, internal::peek_mask_uint8< M >, Cs >... > {};
+   // clang-format on
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::uint8
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/utf16.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/utf16.hpp
new file mode 100644
index 000000000000..29f969f42633
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/utf16.hpp
@@ -0,0 +1,49 @@
+// Copyright (c) 2015-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_UTF16_HPP
+#define TAO_JSON_PEGTL_UTF16_HPP
+
+#include "config.hpp"
+
+#include "internal/peek_utf16.hpp"
+#include "internal/result_on_found.hpp"
+#include "internal/rules.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE
+{
+   namespace utf16_be
+   {
+      // clang-format off
+      struct any : internal::any< internal::peek_utf16_be > {};
+      struct bom : internal::one< internal::result_on_found::success, internal::peek_utf16_be, 0xfeff > {};
+      template< char32_t... Cs > struct not_one : internal::one< internal::result_on_found::failure, internal::peek_utf16_be, Cs... > {};
+      template< char32_t Lo, char32_t Hi > struct not_range : internal::range< internal::result_on_found::failure, internal::peek_utf16_be, Lo, Hi > {};
+      template< char32_t... Cs > struct one : internal::one< internal::result_on_found::success, internal::peek_utf16_be, Cs... > {};
+      template< char32_t Lo, char32_t Hi > struct range : internal::range< internal::result_on_found::success, internal::peek_utf16_be, Lo, Hi > {};
+      template< char32_t... Cs > struct ranges : internal::ranges< internal::peek_utf16_be, Cs... > {};
+      template< char32_t... Cs > struct string : internal::seq< internal::one< internal::result_on_found::success, internal::peek_utf16_be, Cs >... > {};
+      // clang-format on
+
+   }  // namespace utf16_be
+
+   namespace utf16_le
+   {
+      // clang-format off
+      struct any : internal::any< internal::peek_utf16_le > {};
+      struct bom : internal::one< internal::result_on_found::success, internal::peek_utf16_le, 0xfeff > {};
+      template< char32_t... Cs > struct not_one : internal::one< internal::result_on_found::failure, internal::peek_utf16_le, Cs... > {};
+      template< char32_t Lo, char32_t Hi > struct not_range : internal::range< internal::result_on_found::failure, internal::peek_utf16_le, Lo, Hi > {};
+      template< char32_t... Cs > struct one : internal::one< internal::result_on_found::success, internal::peek_utf16_le, Cs... > {};
+      template< char32_t Lo, char32_t Hi > struct range : internal::range< internal::result_on_found::success, internal::peek_utf16_le, Lo, Hi > {};
+      template< char32_t... Cs > struct ranges : internal::ranges< internal::peek_utf16_le, Cs... > {};
+      template< char32_t... Cs > struct string : internal::seq< internal::one< internal::result_on_found::success, internal::peek_utf16_le, Cs >... > {};
+      // clang-format on
+
+   }  // namespace utf16_le
+
+   namespace utf16 = TAO_JSON_PEGTL_NATIVE_UTF16;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/utf32.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/utf32.hpp
new file mode 100644
index 000000000000..e6d54879608e
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/utf32.hpp
@@ -0,0 +1,49 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_UTF32_HPP
+#define TAO_JSON_PEGTL_UTF32_HPP
+
+#include "config.hpp"
+
+#include "internal/peek_utf32.hpp"
+#include "internal/result_on_found.hpp"
+#include "internal/rules.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE
+{
+   namespace utf32_be
+   {
+      // clang-format off
+      struct any : internal::any< internal::peek_utf32_be > {};
+      struct bom : internal::one< internal::result_on_found::success, internal::peek_utf32_be, 0xfeff > {};
+      template< char32_t... Cs > struct not_one : internal::one< internal::result_on_found::failure, internal::peek_utf32_be, Cs... > {};
+      template< char32_t Lo, char32_t Hi > struct not_range : internal::range< internal::result_on_found::failure, internal::peek_utf32_be, Lo, Hi > {};
+      template< char32_t... Cs > struct one : internal::one< internal::result_on_found::success, internal::peek_utf32_be, Cs... > {};
+      template< char32_t Lo, char32_t Hi > struct range : internal::range< internal::result_on_found::success, internal::peek_utf32_be, Lo, Hi > {};
+      template< char32_t... Cs > struct ranges : internal::ranges< internal::peek_utf32_be, Cs... > {};
+      template< char32_t... Cs > struct string : internal::seq< internal::one< internal::result_on_found::success, internal::peek_utf32_be, Cs >... > {};
+      // clang-format on
+
+   }  // namespace utf32_be
+
+   namespace utf32_le
+   {
+      // clang-format off
+      struct any : internal::any< internal::peek_utf32_le > {};
+      struct bom : internal::one< internal::result_on_found::success, internal::peek_utf32_le, 0xfeff > {};
+      template< char32_t... Cs > struct not_one : internal::one< internal::result_on_found::failure, internal::peek_utf32_le, Cs... > {};
+      template< char32_t Lo, char32_t Hi > struct not_range : internal::range< internal::result_on_found::failure, internal::peek_utf32_le, Lo, Hi > {};
+      template< char32_t... Cs > struct one : internal::one< internal::result_on_found::success, internal::peek_utf32_le, Cs... > {};
+      template< char32_t Lo, char32_t Hi > struct range : internal::range< internal::result_on_found::success, internal::peek_utf32_le, Lo, Hi > {};
+      template< char32_t... Cs > struct ranges : internal::ranges< internal::peek_utf32_le, Cs... > {};
+      template< char32_t... Cs > struct string : internal::seq< internal::one< internal::result_on_found::success, internal::peek_utf32_le, Cs >... > {};
+      // clang-format on
+
+   }  // namespace utf32_le
+
+   namespace utf32 = TAO_JSON_PEGTL_NATIVE_UTF32;
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/utf8.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/utf8.hpp
new file mode 100644
index 000000000000..9589f5b0502c
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/utf8.hpp
@@ -0,0 +1,28 @@
+// Copyright (c) 2014-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_UTF8_HPP
+#define TAO_JSON_PEGTL_UTF8_HPP
+
+#include "config.hpp"
+
+#include "internal/peek_utf8.hpp"
+#include "internal/result_on_found.hpp"
+#include "internal/rules.hpp"
+
+namespace TAO_JSON_PEGTL_NAMESPACE::utf8
+{
+   // clang-format off
+   struct any : internal::any< internal::peek_utf8 > {};
+   struct bom : internal::one< internal::result_on_found::success, internal::peek_utf8, 0xfeff > {};
+   template< char32_t... Cs > struct not_one : internal::one< internal::result_on_found::failure, internal::peek_utf8, Cs... > {};
+   template< char32_t Lo, char32_t Hi > struct not_range : internal::range< internal::result_on_found::failure, internal::peek_utf8, Lo, Hi > {};
+   template< char32_t... Cs > struct one : internal::one< internal::result_on_found::success, internal::peek_utf8, Cs... > {};
+   template< char32_t Lo, char32_t Hi > struct range : internal::range< internal::result_on_found::success, internal::peek_utf8, Lo, Hi > {};
+   template< char32_t... Cs > struct ranges : internal::ranges< internal::peek_utf8, Cs... > {};
+   template< char32_t... Cs > struct string : internal::seq< internal::one< internal::result_on_found::success, internal::peek_utf8, Cs >... > {};
+   // clang-format on
+
+}  // namespace TAO_JSON_PEGTL_NAMESPACE::utf8
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/pegtl/version.hpp b/3rdParty/taocpp-json/include/tao/json/external/pegtl/version.hpp
new file mode 100644
index 000000000000..9baf0bb956d9
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/pegtl/version.hpp
@@ -0,0 +1,13 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_JSON_PEGTL_VERSION_HPP
+#define TAO_JSON_PEGTL_VERSION_HPP
+
+#define TAO_JSON_PEGTL_VERSION "3.0.0"
+
+#define TAO_JSON_PEGTL_VERSION_MAJOR 3
+#define TAO_JSON_PEGTL_VERSION_MINOR 0
+#define TAO_JSON_PEGTL_VERSION_PATCH 0
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/external/ryu.hpp b/3rdParty/taocpp-json/include/tao/json/external/ryu.hpp
new file mode 100644
index 000000000000..f3c01e22635a
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/external/ryu.hpp
@@ -0,0 +1,1216 @@
+// This header include/tao/json/external/ryu.hpp contains
+// modified portions of the ulfjack/ryu library from
+//   https://github.com/ulfjack/ryu
+// which is licensed as follows:
+
+// Copyright 2018 Ulf Adams
+//
+// The contents of this file may be used under the terms of the Apache License,
+// Version 2.0.
+//
+//    (See accompanying file LICENSE-Apache or copy at
+//     http://www.apache.org/licenses/LICENSE-2.0)
+//
+// Alternatively, the contents of this file may be used under the terms of
+// the Boost Software License, Version 1.0.
+//    (See accompanying file LICENSE-Boost or copy at
+//     https://www.boost.org/LICENSE_1_0.txt)
+//
+// Unless required by applicable law or agreed to in writing, this software
+// is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.
+
+#ifndef TAO_JSON_EXTERNAL_RYU_HPP
+#define TAO_JSON_EXTERNAL_RYU_HPP
+
+// Runtime compiler options:
+// -DRYU_ONLY_64_BIT_OPS Avoid using uint128_t or 64-bit intrinsics. Slower,
+//     depending on your compiler.
+//
+
+// ABSL avoids uint128_t on Win32 even if __SIZEOF_INT128__ is defined.
+// Let's do the same for now.
+#if defined( __SIZEOF_INT128__ ) && !defined( _MSC_VER ) && !defined( RYU_ONLY_64_BIT_OPS )
+#define HAS_UINT128
+#elif defined( _MSC_VER ) && !defined( RYU_ONLY_64_BIT_OPS ) && defined( _M_X64 ) && !defined( __clang__ )  // https://bugs.llvm.org/show_bug.cgi?id=37755
+#define HAS_64_BIT_INTRINSICS
+#include <intrin.h>
+#endif
+
+#include <cassert>
+#include <cstdint>
+#include <cstdlib>
+#include <cstring>
+
+#include "itoa.hpp"
+
+namespace tao::json::ryu
+{
+   // Returns e == 0 ? 1 : ceil(log_2(5^e)).
+   inline uint32_t pow5bits( const std::int32_t e )
+   {
+      // This function has only been tested for 0 <= e <= 1500.
+      assert( e >= 0 );
+      assert( e <= 1500 );
+      return ( ( std::uint32_t( e ) * 1217359 ) >> 19 ) + 1;
+   }
+
+   // Returns floor(log_10(2^e)).
+   inline std::int32_t log10Pow2( const std::int32_t e )
+   {
+      // This function has only been tested for 0 <= e <= 1500.
+      assert( e >= 0 );
+      assert( e <= 1500 );
+      return std::int32_t( ( uint32_t( e ) * 78913 ) >> 18 );
+   }
+
+   // Returns floor(log_10(5^e)).
+   inline std::int32_t log10Pow5( const std::int32_t e )
+   {
+      // This function has only been tested for 0 <= e <= 1500.
+      assert( e >= 0 );
+      assert( e <= 1500 );
+      return std::int32_t( ( std::uint32_t( e ) * 732923 ) >> 20 );
+   }
+
+#if defined( HAS_UINT128 )
+
+   using uint128_t = __uint128_t;
+
+#elif defined( HAS_64_BIT_INTRINSICS )
+
+   inline std::uint64_t umul128( const std::uint64_t a, const std::uint64_t b, std::uint64_t& productHi )
+   {
+      return _umul128( a, b, &productHi );
+   }
+
+   inline std::uint64_t shiftright128( const std::uint64_t lo, const std::uint64_t hi, const std::uint32_t dist )
+   {
+      // For the __shiftright128 intrinsic, the shift value is always
+      // modulo 64.
+      // In the current implementation of the double-precision version
+      // of Ryu, the shift value is always < 64. (In the case
+      // RYU_OPTIMIZE_SIZE == 0, the shift value is in the range [50,58].
+      // Otherwise in the range [2,59].)
+      // Check this here in case a future change requires larger shift
+      // values. In this case this function needs to be adjusted.
+      assert( dist < 64 );
+      return __shiftright128( lo, hi, std::uint8_t( dist ) );
+   }
+
+#else
+
+   static inline std::uint64_t umul128( const std::uint64_t a, const std::uint64_t b, std::uint64_t& productHi )
+   {
+      // The casts here help MSVC to avoid calls to the __allmul library function.
+      const std::uint32_t aLo = (std::uint32_t)a;
+      const std::uint32_t aHi = ( std::uint32_t )( a >> 32 );
+      const std::uint32_t bLo = (std::uint32_t)b;
+      const std::uint32_t bHi = ( std::uint32_t )( b >> 32 );
+
+      const std::uint64_t b00 = (std::uint64_t)aLo * bLo;
+      const std::uint64_t b01 = (std::uint64_t)aLo * bHi;
+      const std::uint64_t b10 = (std::uint64_t)aHi * bLo;
+      const std::uint64_t b11 = (std::uint64_t)aHi * bHi;
+
+      const std::uint64_t midSum = b01 + b10;
+      const std::uint64_t midCarry = midSum < b01;
+
+      const std::uint64_t productLo = b00 + ( midSum << 32 );
+      const std::uint64_t productLoCarry = productLo < b00;
+
+      productHi = b11 + ( midSum >> 32 ) + ( midCarry << 32 ) + productLoCarry;
+      return productLo;
+   }
+
+   static inline std::uint64_t shiftright128( const std::uint64_t lo, const std::uint64_t hi, const std::uint32_t dist )
+   {
+      // We don't need to handle the case dist >= 64 here (see above).
+      assert( dist > 0 );
+      assert( dist < 64 );
+      return ( hi << ( 64 - dist ) ) | ( lo >> dist );
+   }
+
+#endif
+
+   // A table of all two-digit numbers. This is used to speed up decimal digit
+   // generation by copying pairs of digits into the final output.
+   // static const char digit_table[ 200 ] = {
+   //    '0', '0', '0', '1', '0', '2', '0', '3', '0', '4', '0', '5', '0', '6', '0', '7', '0', '8', '0', '9', '1', '0', '1', '1', '1', '2', '1', '3', '1', '4', '1', '5', '1', '6', '1', '7', '1', '8', '1', '9', '2', '0', '2', '1', '2', '2', '2', '3', '2', '4', '2', '5', '2', '6', '2', '7', '2', '8', '2', '9', '3', '0', '3', '1', '3', '2', '3', '3', '3', '4', '3', '5', '3', '6', '3', '7', '3', '8', '3', '9', '4', '0', '4', '1', '4', '2', '4', '3', '4', '4', '4', '5', '4', '6', '4', '7', '4', '8', '4', '9', '5', '0', '5', '1', '5', '2', '5', '3', '5', '4', '5', '5', '5', '6', '5', '7', '5', '8', '5', '9', '6', '0', '6', '1', '6', '2', '6', '3', '6', '4', '6', '5', '6', '6', '6', '7', '6', '8', '6', '9', '7', '0', '7', '1', '7', '2', '7', '3', '7', '4', '7', '5', '7', '6', '7', '7', '7', '8', '7', '9', '8', '0', '8', '1', '8', '2', '8', '3', '8', '4', '8', '5', '8', '6', '8', '7', '8', '8', '8', '9', '9', '0', '9', '1', '9', '2', '9', '3', '9', '4', '9', '5', '9', '6', '9', '7', '9', '8', '9', '9'
+   // };
+   // NOTE: Now uses itoa::s_pairs to prevent having the same data twice.
+
+   // These tables are generated by PrintDoubleLookupTable.
+   static const std::uint64_t pow5_inv_split[ 292 ][ 2 ] = {
+      { 1u, 288230376151711744u },
+      { 3689348814741910324u, 230584300921369395u },
+      { 2951479051793528259u, 184467440737095516u },
+      { 17118578500402463900u, 147573952589676412u },
+      { 12632330341676300947u, 236118324143482260u },
+      { 10105864273341040758u, 188894659314785808u },
+      { 15463389048156653253u, 151115727451828646u },
+      { 17362724847566824558u, 241785163922925834u },
+      { 17579528692795369969u, 193428131138340667u },
+      { 6684925324752475329u, 154742504910672534u },
+      { 18074578149087781173u, 247588007857076054u },
+      { 18149011334012135262u, 198070406285660843u },
+      { 3451162622983977240u, 158456325028528675u },
+      { 5521860196774363583u, 253530120045645880u },
+      { 4417488157419490867u, 202824096036516704u },
+      { 7223339340677503017u, 162259276829213363u },
+      { 7867994130342094503u, 259614842926741381u },
+      { 2605046489531765280u, 207691874341393105u },
+      { 2084037191625412224u, 166153499473114484u },
+      { 10713157136084480204u, 265845599156983174u },
+      { 12259874523609494487u, 212676479325586539u },
+      { 13497248433629505913u, 170141183460469231u },
+      { 14216899864323388813u, 272225893536750770u },
+      { 11373519891458711051u, 217780714829400616u },
+      { 5409467098425058518u, 174224571863520493u },
+      { 4965798542738183305u, 278759314981632789u },
+      { 7661987648932456967u, 223007451985306231u },
+      { 2440241304404055250u, 178405961588244985u },
+      { 3904386087046488400u, 285449538541191976u },
+      { 17880904128604832013u, 228359630832953580u },
+      { 14304723302883865611u, 182687704666362864u },
+      { 15133127457049002812u, 146150163733090291u },
+      { 16834306301794583852u, 233840261972944466u },
+      { 9778096226693756759u, 187072209578355573u },
+      { 15201174610838826053u, 149657767662684458u },
+      { 2185786488890659746u, 239452428260295134u },
+      { 5437978005854438120u, 191561942608236107u },
+      { 15418428848909281466u, 153249554086588885u },
+      { 6222742084545298729u, 245199286538542217u },
+      { 16046240111861969953u, 196159429230833773u },
+      { 1768945645263844993u, 156927543384667019u },
+      { 10209010661905972635u, 251084069415467230u },
+      { 8167208529524778108u, 200867255532373784u },
+      { 10223115638361732810u, 160693804425899027u },
+      { 1599589762411131202u, 257110087081438444u },
+      { 4969020624670815285u, 205688069665150755u },
+      { 3975216499736652228u, 164550455732120604u },
+      { 13739044029062464211u, 263280729171392966u },
+      { 7301886408508061046u, 210624583337114373u },
+      { 13220206756290269483u, 168499666669691498u },
+      { 17462981995322520850u, 269599466671506397u },
+      { 6591687966774196033u, 215679573337205118u },
+      { 12652048002903177473u, 172543658669764094u },
+      { 9175230360419352987u, 276069853871622551u },
+      { 3650835473593572067u, 220855883097298041u },
+      { 17678063637842498946u, 176684706477838432u },
+      { 13527506561580357021u, 282695530364541492u },
+      { 3443307619780464970u, 226156424291633194u },
+      { 6443994910566282300u, 180925139433306555u },
+      { 5155195928453025840u, 144740111546645244u },
+      { 15627011115008661990u, 231584178474632390u },
+      { 12501608892006929592u, 185267342779705912u },
+      { 2622589484121723027u, 148213874223764730u },
+      { 4196143174594756843u, 237142198758023568u },
+      { 10735612169159626121u, 189713759006418854u },
+      { 12277838550069611220u, 151771007205135083u },
+      { 15955192865369467629u, 242833611528216133u },
+      { 1696107848069843133u, 194266889222572907u },
+      { 12424932722681605476u, 155413511378058325u },
+      { 1433148282581017146u, 248661618204893321u },
+      { 15903913885032455010u, 198929294563914656u },
+      { 9033782293284053685u, 159143435651131725u },
+      { 14454051669254485895u, 254629497041810760u },
+      { 11563241335403588716u, 203703597633448608u },
+      { 16629290697806691620u, 162962878106758886u },
+      { 781423413297334329u, 260740604970814219u },
+      { 4314487545379777786u, 208592483976651375u },
+      { 3451590036303822229u, 166873987181321100u },
+      { 5522544058086115566u, 266998379490113760u },
+      { 4418035246468892453u, 213598703592091008u },
+      { 10913125826658934609u, 170878962873672806u },
+      { 10082303693170474728u, 273406340597876490u },
+      { 8065842954536379782u, 218725072478301192u },
+      { 17520720807854834795u, 174980057982640953u },
+      { 5897060404116273733u, 279968092772225526u },
+      { 1028299508551108663u, 223974474217780421u },
+      { 15580034865808528224u, 179179579374224336u },
+      { 17549358155809824511u, 286687326998758938u },
+      { 2971440080422128639u, 229349861599007151u },
+      { 17134547323305344204u, 183479889279205720u },
+      { 13707637858644275364u, 146783911423364576u },
+      { 14553522944347019935u, 234854258277383322u },
+      { 4264120725993795302u, 187883406621906658u },
+      { 10789994210278856888u, 150306725297525326u },
+      { 9885293106962350374u, 240490760476040522u },
+      { 529536856086059653u, 192392608380832418u },
+      { 7802327114352668369u, 153914086704665934u },
+      { 1415676938738538420u, 246262538727465495u },
+      { 1132541550990830736u, 197010030981972396u },
+      { 15663428499760305882u, 157608024785577916u },
+      { 17682787970132668764u, 252172839656924666u },
+      { 10456881561364224688u, 201738271725539733u },
+      { 15744202878575200397u, 161390617380431786u },
+      { 17812026976236499989u, 258224987808690858u },
+      { 3181575136763469022u, 206579990246952687u },
+      { 13613306553636506187u, 165263992197562149u },
+      { 10713244041592678929u, 264422387516099439u },
+      { 12259944048016053467u, 211537910012879551u },
+      { 6118606423670932450u, 169230328010303641u },
+      { 2411072648389671274u, 270768524816485826u },
+      { 16686253377679378312u, 216614819853188660u },
+      { 13349002702143502650u, 173291855882550928u },
+      { 17669055508687693916u, 277266969412081485u },
+      { 14135244406950155133u, 221813575529665188u },
+      { 240149081334393137u, 177450860423732151u },
+      { 11452284974360759988u, 283921376677971441u },
+      { 5472479164746697667u, 227137101342377153u },
+      { 11756680961281178780u, 181709681073901722u },
+      { 2026647139541122378u, 145367744859121378u },
+      { 18000030682233437097u, 232588391774594204u },
+      { 18089373360528660001u, 186070713419675363u },
+      { 3403452244197197031u, 148856570735740291u },
+      { 16513570034941246220u, 238170513177184465u },
+      { 13210856027952996976u, 190536410541747572u },
+      { 3189987192878576934u, 152429128433398058u },
+      { 1414630693863812771u, 243886605493436893u },
+      { 8510402184574870864u, 195109284394749514u },
+      { 10497670562401807014u, 156087427515799611u },
+      { 9417575270359070576u, 249739884025279378u },
+      { 14912757845771077107u, 199791907220223502u },
+      { 4551508647133041040u, 159833525776178802u },
+      { 10971762650154775986u, 255733641241886083u },
+      { 16156107749607641435u, 204586912993508866u },
+      { 9235537384944202825u, 163669530394807093u },
+      { 11087511001168814197u, 261871248631691349u },
+      { 12559357615676961681u, 209496998905353079u },
+      { 13736834907283479668u, 167597599124282463u },
+      { 18289587036911657145u, 268156158598851941u },
+      { 10942320814787415393u, 214524926879081553u },
+      { 16132554281313752961u, 171619941503265242u },
+      { 11054691591134363444u, 274591906405224388u },
+      { 16222450902391311402u, 219673525124179510u },
+      { 12977960721913049122u, 175738820099343608u },
+      { 17075388340318968271u, 281182112158949773u },
+      { 2592264228029443648u, 224945689727159819u },
+      { 5763160197165465241u, 179956551781727855u },
+      { 9221056315464744386u, 287930482850764568u },
+      { 14755542681855616155u, 230344386280611654u },
+      { 15493782960226403247u, 184275509024489323u },
+      { 1326979923955391628u, 147420407219591459u },
+      { 9501865507812447252u, 235872651551346334u },
+      { 11290841220991868125u, 188698121241077067u },
+      { 1653975347309673853u, 150958496992861654u },
+      { 10025058185179298811u, 241533595188578646u },
+      { 4330697733401528726u, 193226876150862917u },
+      { 14532604630946953951u, 154581500920690333u },
+      { 1116074521063664381u, 247330401473104534u },
+      { 4582208431592841828u, 197864321178483627u },
+      { 14733813189500004432u, 158291456942786901u },
+      { 16195403473716186445u, 253266331108459042u },
+      { 5577625149489128510u, 202613064886767234u },
+      { 8151448934333213131u, 162090451909413787u },
+      { 16731667109675051333u, 259344723055062059u },
+      { 17074682502481951390u, 207475778444049647u },
+      { 6281048372501740465u, 165980622755239718u },
+      { 6360328581260874421u, 265568996408383549u },
+      { 8777611679750609860u, 212455197126706839u },
+      { 10711438158542398211u, 169964157701365471u },
+      { 9759603424184016492u, 271942652322184754u },
+      { 11497031554089123517u, 217554121857747803u },
+      { 16576322872755119460u, 174043297486198242u },
+      { 11764721337440549842u, 278469275977917188u },
+      { 16790474699436260520u, 222775420782333750u },
+      { 13432379759549008416u, 178220336625867000u },
+      { 3045063541568861850u, 285152538601387201u },
+      { 17193446092222730773u, 228122030881109760u },
+      { 13754756873778184618u, 182497624704887808u },
+      { 18382503128506368341u, 145998099763910246u },
+      { 3586563302416817083u, 233596959622256395u },
+      { 2869250641933453667u, 186877567697805116u },
+      { 17052795772514404226u, 149502054158244092u },
+      { 12527077977055405469u, 239203286653190548u },
+      { 17400360011128145022u, 191362629322552438u },
+      { 2852241564676785048u, 153090103458041951u },
+      { 15631632947708587046u, 244944165532867121u },
+      { 8815957543424959314u, 195955332426293697u },
+      { 18120812478965698421u, 156764265941034957u },
+      { 14235904707377476180u, 250822825505655932u },
+      { 4010026136418160298u, 200658260404524746u },
+      { 17965416168102169531u, 160526608323619796u },
+      { 2919224165770098987u, 256842573317791675u },
+      { 2335379332616079190u, 205474058654233340u },
+      { 1868303466092863352u, 164379246923386672u },
+      { 6678634360490491686u, 263006795077418675u },
+      { 5342907488392393349u, 210405436061934940u },
+      { 4274325990713914679u, 168324348849547952u },
+      { 10528270399884173809u, 269318958159276723u },
+      { 15801313949391159694u, 215455166527421378u },
+      { 1573004715287196786u, 172364133221937103u },
+      { 17274202803427156150u, 275782613155099364u },
+      { 17508711057483635243u, 220626090524079491u },
+      { 10317620031244997871u, 176500872419263593u },
+      { 12818843235250086271u, 282401395870821749u },
+      { 13944423402941979340u, 225921116696657399u },
+      { 14844887537095493795u, 180736893357325919u },
+      { 15565258844418305359u, 144589514685860735u },
+      { 6457670077359736959u, 231343223497377177u },
+      { 16234182506113520537u, 185074578797901741u },
+      { 9297997190148906106u, 148059663038321393u },
+      { 11187446689496339446u, 236895460861314229u },
+      { 12639306166338981880u, 189516368689051383u },
+      { 17490142562555006151u, 151613094951241106u },
+      { 2158786396894637579u, 242580951921985771u },
+      { 16484424376483351356u, 194064761537588616u },
+      { 9498190686444770762u, 155251809230070893u },
+      { 11507756283569722895u, 248402894768113429u },
+      { 12895553841597688639u, 198722315814490743u },
+      { 17695140702761971558u, 158977852651592594u },
+      { 17244178680193423523u, 254364564242548151u },
+      { 10105994129412828495u, 203491651394038521u },
+      { 4395446488788352473u, 162793321115230817u },
+      { 10722063196803274280u, 260469313784369307u },
+      { 1198952927958798777u, 208375451027495446u },
+      { 15716557601334680315u, 166700360821996356u },
+      { 17767794532651667857u, 266720577315194170u },
+      { 14214235626121334286u, 213376461852155336u },
+      { 7682039686155157106u, 170701169481724269u },
+      { 1223217053622520399u, 273121871170758831u },
+      { 15735968901865657612u, 218497496936607064u },
+      { 16278123936234436413u, 174797997549285651u },
+      { 219556594781725998u, 279676796078857043u },
+      { 7554342905309201445u, 223741436863085634u },
+      { 9732823138989271479u, 178993149490468507u },
+      { 815121763415193074u, 286389039184749612u },
+      { 11720143854957885429u, 229111231347799689u },
+      { 13065463898708218666u, 183288985078239751u },
+      { 6763022304224664610u, 146631188062591801u },
+      { 3442138057275642729u, 234609900900146882u },
+      { 13821756890046245153u, 187687920720117505u },
+      { 11057405512036996122u, 150150336576094004u },
+      { 6623802375033462826u, 240240538521750407u },
+      { 16367088344252501231u, 192192430817400325u },
+      { 13093670675402000985u, 153753944653920260u },
+      { 2503129006933649959u, 246006311446272417u },
+      { 13070549649772650937u, 196805049157017933u },
+      { 17835137349301941396u, 157444039325614346u },
+      { 2710778055689733971u, 251910462920982955u },
+      { 2168622444551787177u, 201528370336786364u },
+      { 5424246770383340065u, 161222696269429091u },
+      { 1300097203129523457u, 257956314031086546u },
+      { 15797473021471260058u, 206365051224869236u },
+      { 8948629602435097724u, 165092040979895389u },
+      { 3249760919670425388u, 264147265567832623u },
+      { 9978506365220160957u, 211317812454266098u },
+      { 15361502721659949412u, 169054249963412878u },
+      { 2442311466204457120u, 270486799941460606u },
+      { 16711244431931206989u, 216389439953168484u },
+      { 17058344360286875914u, 173111551962534787u },
+      { 12535955717491360170u, 276978483140055660u },
+      { 10028764573993088136u, 221582786512044528u },
+      { 15401709288678291155u, 177266229209635622u },
+      { 9885339602917624555u, 283625966735416996u },
+      { 4218922867592189321u, 226900773388333597u },
+      { 14443184738299482427u, 181520618710666877u },
+      { 4175850161155765295u, 145216494968533502u },
+      { 10370709072591134795u, 232346391949653603u },
+      { 15675264887556728482u, 185877113559722882u },
+      { 5161514280561562140u, 148701690847778306u },
+      { 879725219414678777u, 237922705356445290u },
+      { 703780175531743021u, 190338164285156232u },
+      { 11631070584651125387u, 152270531428124985u },
+      { 162968861732249003u, 243632850284999977u },
+      { 11198421533611530172u, 194906280227999981u },
+      { 5269388412147313814u, 155925024182399985u },
+      { 8431021459435702103u, 249480038691839976u },
+      { 3055468352806651359u, 199584030953471981u },
+      { 17201769941212962380u, 159667224762777584u },
+      { 16454785461715008838u, 255467559620444135u },
+      { 13163828369372007071u, 204374047696355308u },
+      { 17909760324981426303u, 163499238157084246u },
+      { 2830174816776909822u, 261598781051334795u },
+      { 2264139853421527858u, 209279024841067836u },
+      { 16568707141704863579u, 167423219872854268u },
+      { 4373838538276319787u, 267877151796566830u },
+      { 3499070830621055830u, 214301721437253464u },
+      { 6488605479238754987u, 171441377149802771u },
+      { 3003071137298187333u, 274306203439684434u },
+      { 6091805724580460189u, 219444962751747547u },
+      { 15941491023890099121u, 175555970201398037u },
+      { 10748990379256517301u, 280889552322236860u },
+      { 8599192303405213841u, 224711641857789488u },
+      { 14258051472207991719u, 179769313486231590u },
+   };
+
+   static const std::uint64_t pow5_split[ 326 ][ 2 ] = {
+      { 0u, 72057594037927936u },
+      { 0u, 90071992547409920u },
+      { 0u, 112589990684262400u },
+      { 0u, 140737488355328000u },
+      { 0u, 87960930222080000u },
+      { 0u, 109951162777600000u },
+      { 0u, 137438953472000000u },
+      { 0u, 85899345920000000u },
+      { 0u, 107374182400000000u },
+      { 0u, 134217728000000000u },
+      { 0u, 83886080000000000u },
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+      { 9303225779693813237u, 112824648491551848u },
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+      { 11879831158813179495u, 88144256634024881u },
+      { 1014730893234310657u, 110180320792531102u },
+      { 10491785653397664129u, 137725400990663877u },
+      { 8863209042587234033u, 86078375619164923u },
+      { 6467325284806654637u, 107597969523956154u },
+      { 17307528642863094104u, 134497461904945192u },
+      { 10817205401789433815u, 84060913690590745u },
+      { 18133192770664180173u, 105076142113238431u },
+      { 18054804944902837312u, 131345177641548039u },
+      { 18201782118205355176u, 82090736025967524u },
+      { 4305483574047142354u, 102613420032459406u },
+      { 14605226504413703751u, 128266775040574257u },
+      { 2210737537617482988u, 80166734400358911u },
+      { 16598479977304017447u, 100208418000448638u },
+      { 11524727934775246001u, 125260522500560798u },
+      { 2591268940807140847u, 78287826562850499u },
+      { 17074144231291089770u, 97859783203563123u },
+      { 16730994270686474309u, 122324729004453904u },
+      { 10456871419179046443u, 76452955627783690u },
+      { 3847717237119032246u, 95566194534729613u },
+      { 9421332564826178211u, 119457743168412016u },
+      { 5888332853016361382u, 74661089480257510u },
+      { 16583788103125227536u, 93326361850321887u },
+      { 16118049110479146516u, 116657952312902359u },
+      { 16991309721690548428u, 72911220195563974u },
+      { 12015765115258409727u, 91139025244454968u },
+      { 15019706394073012159u, 113923781555568710u },
+      { 9551260955736489391u, 142404726944460888u },
+      { 5969538097335305869u, 89002954340288055u },
+      { 2850236603241744433u, 111253692925360069u },
+   };
+
+#define TAO_RYU_DOUBLE_MANTISSA_BITS 52
+#define TAO_RYU_DOUBLE_EXPONENT_BITS 11
+
+#define TAO_RYU_DOUBLE_POW5_INV_BITCOUNT 122
+#define TAO_RYU_DOUBLE_POW5_BITCOUNT 121
+
+   inline std::int32_t pow5Factor( std::uint64_t value )
+   {
+      for( std::int32_t count = 0; value > 0; ++count ) {
+         if( value % 5 != 0 ) {
+            return count;
+         }
+         value /= 5;
+      }
+      return 0;
+   }
+
+   // Returns true if value is divisible by 5^p.
+   inline bool multipleOfPowerOf5( const std::uint64_t value, const std::int32_t p )
+   {
+      // I tried a case distinction on p, but there was no performance difference.
+      return pow5Factor( value ) >= p;
+   }
+
+   // We need a 64x128-bit multiplication and a subsequent 128-bit shift.
+   // Multiplication:
+   //   The 64-bit factor is variable and passed in, the 128-bit factor comes
+   //   from a lookup table. We know that the 64-bit factor only has 55
+   //   significant bits (i.e., the 9 topmost bits are zeros). The 128-bit
+   //   factor only has 124 significant bits (i.e., the 4 topmost bits are
+   //   zeros).
+   // Shift:
+   //   In principle, the multiplication result requires 55+124=179 bits to
+   //   represent. However, we then shift this value to the right by j, which is
+   //   at least j >= 115, so the result is guaranteed to fit into 179-115=64
+   //   bits. This means that we only need the topmost 64 significant bits of
+   //   the 64x128-bit multiplication.
+   //
+   // There are several ways to do this:
+   // 1. Best case: the compiler exposes a 128-bit type.
+   //    We perform two 64x64-bit multiplications, add the higher 64 bits of the
+   //    lower result to the higher result, and shift by j-64 bits.
+   //
+   //    We explicitly cast from 64-bit to 128-bit, so the compiler can tell
+   //    that these are only 64-bit inputs, and can map these to the best
+   //    possible sequence of assembly instructions.
+   //    x86-64 machines happen to have matching assembly instructions for
+   //    64x64-bit multiplications and 128-bit shifts.
+   //
+   // 2. Second best case: the compiler exposes intrinsics for the x86-64 assembly
+   //    instructions mentioned in 1.
+   //
+   // 3. We only have 64x64 bit instructions that return the lower 64 bits of
+   //    the result, i.e., we have to use plain C.
+   //    Our inputs are less than the full width, so we have three options:
+   //    a. Ignore this fact and just implement the intrinsics manually.
+   //    b. Split both into 31-bit pieces, which guarantees no internal overflow,
+   //       but requires extra work upfront (unless we change the lookup table).
+   //    c. Split only the first factor into 31-bit pieces, which also guarantees
+   //       no internal overflow, but requires extra work since the intermediate
+   //       results are not perfectly aligned.
+#if defined( HAS_UINT128 )
+
+   // Best case: use 128-bit type.
+   inline std::uint64_t mulShift( const std::uint64_t m, const std::uint64_t* const mul, const std::int32_t j )
+   {
+      const uint128_t b0 = ( (uint128_t)m ) * mul[ 0 ];
+      const uint128_t b2 = ( (uint128_t)m ) * mul[ 1 ];
+      return ( std::uint64_t )( ( ( b0 >> 64 ) + b2 ) >> ( j - 64 ) );
+   }
+
+   inline std::uint64_t mulShiftAll( const std::uint64_t m, const std::uint64_t* const mul, const std::int32_t j, std::uint64_t* const vp, std::uint64_t* const vm, const std::uint32_t mmShift )
+   {
+      //  m <<= 2;
+      //  uint128_t b0 = ((uint128_t) m) * mul[0]; // 0
+      //  uint128_t b2 = ((uint128_t) m) * mul[1]; // 64
+      //
+      //  uint128_t hi = (b0 >> 64) + b2;
+      //  uint128_t lo = b0 & 0xffffffffffffffffull;
+      //  uint128_t factor = (((uint128_t) mul[1]) << 64) + mul[0];
+      //  uint128_t vpLo = lo + (factor << 1);
+      //  *vp = (uint64_t) ((hi + (vpLo >> 64)) >> (j - 64));
+      //  uint128_t vmLo = lo - (factor << mmShift);
+      //  *vm = (uint64_t) ((hi + (vmLo >> 64) - (((uint128_t) 1ull) << 64)) >> (j - 64));
+      //  return (uint64_t) (hi >> (j - 64));
+      *vp = mulShift( 4 * m + 2, mul, j );
+      *vm = mulShift( 4 * m - 1 - mmShift, mul, j );
+      return mulShift( 4 * m, mul, j );
+   }
+
+#elif defined( HAS_64_BIT_INTRINSICS )
+
+   inline std::uint64_t mulShift( const std::uint64_t m, const std::uint64_t* const mul, const std::int32_t j )
+   {
+      // m is maximum 55 bits
+      std::uint64_t high1;                                       // 128
+      const std::uint64_t low1 = umul128( m, mul[ 1 ], high1 );  // 64
+      std::uint64_t high0;                                       // 64
+      umul128( m, mul[ 0 ], high0 );                             // 0
+      const std::uint64_t sum = high0 + low1;
+      if( sum < high0 ) {
+         ++high1;  // overflow into high1
+      }
+      return shiftright128( sum, high1, j - 64 );
+   }
+
+   inline std::uint64_t mulShiftAll( const std::uint64_t m, const std::uint64_t* const mul, const std::int32_t j, std::uint64_t* const vp, std::uint64_t* const vm, const std::uint32_t mmShift )
+   {
+      *vp = mulShift( 4 * m + 2, mul, j );
+      *vm = mulShift( 4 * m - 1 - mmShift, mul, j );
+      return mulShift( 4 * m, mul, j );
+   }
+
+#else  // !defined( HAS_UINT128 ) && !defined( HAS_64_BIT_INTRINSICS )
+
+   static inline std::uint64_t mulShiftAll( std::uint64_t m, const std::uint64_t* const mul, const std::int32_t j, std::uint64_t* const vp, std::uint64_t* const vm, const std::uint32_t mmShift )
+   {
+      m <<= 1;
+      // m is maximum 55 bits
+      std::uint64_t tmp;
+      const std::uint64_t lo = umul128( m, mul[ 0 ], tmp );
+      std::uint64_t hi;
+      const std::uint64_t mid = tmp + umul128( m, mul[ 1 ], hi );
+      hi += mid < tmp;  // overflow into hi
+
+      const std::uint64_t lo2 = lo + mul[ 0 ];
+      const std::uint64_t mid2 = mid + mul[ 1 ] + ( lo2 < lo );
+      const std::uint64_t hi2 = hi + ( mid2 < mid );
+      *vp = shiftright128( mid2, hi2, j - 64 - 1 );
+
+      if( mmShift == 1 ) {
+         const std::uint64_t lo3 = lo - mul[ 0 ];
+         const std::uint64_t mid3 = mid - mul[ 1 ] - ( lo3 > lo );
+         const std::uint64_t hi3 = hi - ( mid3 > mid );
+         *vm = shiftright128( mid3, hi3, j - 64 - 1 );
+      }
+      else {
+         const std::uint64_t lo3 = lo + lo;
+         const std::uint64_t mid3 = mid + mid + ( lo3 < lo );
+         const std::uint64_t hi3 = hi + hi + ( mid3 < mid );
+         const std::uint64_t lo4 = lo3 - mul[ 0 ];
+         const std::uint64_t mid4 = mid3 - mul[ 1 ] - ( lo4 > lo3 );
+         const std::uint64_t hi4 = hi3 - ( mid4 > mid3 );
+         *vm = shiftright128( mid4, hi4, j - 64 );
+      }
+      return shiftright128( mid, hi, j - 64 - 1 );
+   }
+
+#endif
+
+   inline std::uint32_t decimalLength( const std::uint64_t v )
+   {
+      // This is slightly faster than a loop.
+      // The average output length is 16.38 digits, so we check high-to-low.
+      // Function precondition: v is not an 18, 19, or 20-digit number.
+      // (17 digits are sufficient for round-tripping.)
+      assert( v < 100000000000000000L );
+      if( v >= 10000000000000000L ) {
+         return 17;
+      }
+      if( v >= 1000000000000000L ) {
+         return 16;
+      }
+      if( v >= 100000000000000L ) {
+         return 15;
+      }
+      if( v >= 10000000000000L ) {
+         return 14;
+      }
+      if( v >= 1000000000000L ) {
+         return 13;
+      }
+      if( v >= 100000000000L ) {
+         return 12;
+      }
+      if( v >= 10000000000L ) {
+         return 11;
+      }
+      if( v >= 1000000000L ) {
+         return 10;
+      }
+      if( v >= 100000000L ) {
+         return 9;
+      }
+      if( v >= 10000000L ) {
+         return 8;
+      }
+      if( v >= 1000000L ) {
+         return 7;
+      }
+      if( v >= 100000L ) {
+         return 6;
+      }
+      if( v >= 10000L ) {
+         return 5;
+      }
+      if( v >= 1000L ) {
+         return 4;
+      }
+      if( v >= 100L ) {
+         return 3;
+      }
+      if( v >= 10L ) {
+         return 2;
+      }
+      return 1;
+   }
+
+   inline std::uint32_t d2s_simplistic_step5( std::uint64_t output, std::int32_t exp, const std::int32_t olength, char* result )
+   {
+      // TODO: Use digit_table?
+
+      if( exp <= 0 ) {
+         std::memcpy( result, "0.", 2 );
+         std::memset( result + 2, '0', -exp );
+         const auto* end = itoa::u64toa( output, result + 2 - exp );
+         return static_cast< std::uint32_t >( end - result );
+      }
+      else if( exp >= olength ) {
+         itoa::u64toa( output, result );  // Return value MUST be result + olength
+         std::memset( result + olength, '0', exp + 2 - olength );
+         result[ exp ] = '.';
+         return exp + 2;
+      }
+      else {  // ( exp > 0 ) && ( exp < olength )
+         for( std::int32_t i = 0; i < olength - exp; ++i ) {
+            const std::uint32_t c = output % 10;
+            output /= 10;
+            result[ olength - i ] = char( '0' + c );
+         }
+         result[ exp ] = '.';
+         for( std::int32_t i = 0; i < exp; ++i ) {
+            const std::uint32_t c = output % 10;
+            output /= 10;
+            result[ exp - i - 1 ] = char( '0' + c );
+         }
+         return olength + 1;
+      }
+   }
+
+   inline std::uint32_t d2s_scientific_step5( std::uint64_t output, std::int32_t exp, const std::uint32_t olength, char* result )
+   {
+      int index = olength;
+
+      if( olength > 1 ) {
+         itoa::u64toa( output, result + 1 );
+         result[ 0 ] = result[ 1 ];
+         result[ 1 ] = '.';
+         ++index;
+      }
+      else {
+         result[ 0 ] = char( '0' + output );
+      }
+      if( exp ) {
+         result[ index++ ] = 'e';
+         const auto end = itoa::i32toa( exp, result + index );
+         return static_cast< std::uint32_t >( end - result );
+      }
+      return index;
+   }
+
+   inline std::uint32_t d2s_finite( const double f, char* result )
+   {
+      // Step 1: Decode the floating-point number, and unify normalized and subnormal cases.
+      const std::uint32_t mantissaBits = TAO_RYU_DOUBLE_MANTISSA_BITS;
+      const std::uint32_t exponentBits = TAO_RYU_DOUBLE_EXPONENT_BITS;
+      const std::uint32_t offset = ( 1u << ( exponentBits - 1 ) ) - 1;
+
+      std::uint64_t bits;
+      // This only works on little-endian architectures.
+      std::memcpy( &bits, &f, sizeof( double ) );  // TODO: Fix for big-endian!
+
+      // Decode bits into sign, mantissa, and exponent.
+      const bool sign = ( ( bits >> ( mantissaBits + exponentBits ) ) & 1 ) != 0;
+      const std::uint64_t ieeeMantissa = bits & ( ( 1ull << mantissaBits ) - 1 );
+      const std::uint32_t ieeeExponent = std::uint32_t( ( bits >> mantissaBits ) & ( ( 1u << exponentBits ) - 1 ) );
+
+      std::int32_t e2;
+      std::uint64_t m2;
+
+      // NOTE: For taocpp/json this function assumes that f is finite!
+      //            if (ieeeExponent == ((1u << exponentBits) - 1u)) {
+      //               std::strcpy( result, (ieeeMantissa != 0) ? "NaN" : ( sign ? "-Infinity" : "Infinity" ) );
+      //               return std::strlen( result );
+      //            } else if (ieeeExponent == 0) {
+      // Case distinction; exit early for the easy cases.
+      if( ieeeExponent == 0 ) {
+         if( ieeeMantissa == 0 ) {
+            const std::uint32_t size = sign ? 4 : 3;
+            std::memcpy( result, &( "-0.0"[ 4 - size ] ), size );
+            return size;
+         }
+         // We subtract 2 so that the bounds computation has 2 additional bits.
+         e2 = 1 - offset - mantissaBits - 2;
+         m2 = ieeeMantissa;
+      }
+      else {
+         e2 = ieeeExponent - offset - mantissaBits - 2;
+         m2 = ( 1ull << mantissaBits ) | ieeeMantissa;
+      }
+      const bool acceptBounds = ( m2 & 1 ) == 0;
+
+      // Step 2: Determine the interval of legal decimal representations.
+      const std::uint64_t mv = 4 * m2;
+      // Implicit bool -> int conversion. True is 1, false is 0.
+      const std::uint32_t mmShift = ( m2 != ( 1ull << mantissaBits ) ) || ( ieeeExponent <= 1 );
+      // We would compute mp and mm like this:
+      //  std::uint64_t mp = 4 * m2 + 2;
+      //  std::uint64_t mm = mv - 1 - mmShift;
+
+      // Step 3: Convert to a decimal power base using 128-bit arithmetic.
+      std::uint64_t vr, vp, vm;
+      std::int32_t e10;
+
+      bool vmIsTrailingZeros = false;
+      bool vrIsTrailingZeros = false;
+
+      if( e2 >= 0 ) {
+         // I tried special-casing q == 0, but there was no effect on performance.
+         // This expression is slightly faster than max(0, log10Pow2(e2) - 1).
+         const std::int32_t q = log10Pow2( e2 ) - ( e2 > 3 );
+         e10 = q;
+         const std::int32_t k = TAO_RYU_DOUBLE_POW5_INV_BITCOUNT + pow5bits( q ) - 1;
+         const std::int32_t i = -e2 + q + k;
+         vr = mulShiftAll( m2, pow5_inv_split[ q ], i, &vp, &vm, mmShift );
+         if( q <= 21 ) {
+            // Only one of mp, mv, and mm can be a multiple of 5, if any.
+            if( mv % 5 == 0 ) {
+               vrIsTrailingZeros = multipleOfPowerOf5( mv, q );
+            }
+            else {
+               if( acceptBounds ) {
+                  // Same as min(e2 + (~mm & 1), pow5Factor(mm)) >= q
+                  // <=> e2 + (~mm & 1) >= q && pow5Factor(mm) >= q
+                  // <=> true && pow5Factor(mm) >= q, since e2 >= q.
+                  vmIsTrailingZeros = multipleOfPowerOf5( mv - 1 - mmShift, q );
+               }
+               else {
+                  // Same as min(e2 + 1, pow5Factor(mp)) >= q.
+                  vp -= multipleOfPowerOf5( mv + 2, q );
+               }
+            }
+         }
+      }
+      else {
+         // This expression is slightly faster than max(0, log10Pow5(-e2) - 1).
+         const std::int32_t q = log10Pow5( -e2 ) - ( -e2 > 1 );
+         e10 = q + e2;
+         const std::int32_t i = -e2 - q;
+         const std::int32_t k = pow5bits( i ) - TAO_RYU_DOUBLE_POW5_BITCOUNT;
+         const std::int32_t j = q - k;
+         vr = mulShiftAll( m2, pow5_split[ i ], j, &vp, &vm, mmShift );
+         if( q <= 1 ) {
+            vrIsTrailingZeros = ( ~( std::uint32_t( mv ) ) & 1 ) >= std::uint32_t( q );
+            if( acceptBounds ) {
+               vmIsTrailingZeros = ( ~( std::uint32_t( mv - 1 - mmShift ) ) & 1 ) >= std::uint32_t( q );
+            }
+            else {
+               --vp;
+            }
+         }
+         else if( q < 63 ) {  // TODO(ulfjack): Use a tighter bound here.
+            // We need to compute min(ntz(mv), pow5Factor(mv) - e2) >= q-1
+            // <=> ntz(mv) >= q-1  &&  pow5Factor(mv) - e2 >= q-1
+            // <=> ntz(mv) >= q-1
+            // <=> (mv & ((1 << (q-1)) - 1)) == 0
+            // We also need to make sure that the left shift does not overflow.
+            vrIsTrailingZeros = ( mv & ( ( 1ull << ( q - 1 ) ) - 1 ) ) == 0;
+         }
+      }
+      // Step 4: Find the shortest decimal representation in the interval of legal representations.
+      std::uint32_t removed = 0;
+      uint8_t lastRemovedDigit = 0;
+      std::uint64_t output;
+      // On average, we remove ~2 digits.
+      if( vmIsTrailingZeros || vrIsTrailingZeros ) {
+         // General case, which happens rarely (<1%).
+         while( vp / 10 > vm / 10 ) {
+#ifdef __clang__
+            // https://bugs.llvm.org/show_bug.cgi?id=23106
+            // The compiler does not realize that vm % 10 can be computed from vm / 10
+            // as vm - (vm / 10) * 10.
+            vmIsTrailingZeros &= vm - ( vm / 10 ) * 10 == 0;
+#else
+            vmIsTrailingZeros &= vm % 10 == 0;
+#endif
+            vrIsTrailingZeros &= lastRemovedDigit == 0;
+            lastRemovedDigit = std::uint8_t( vr % 10 );
+            vr /= 10;
+            vp /= 10;
+            vm /= 10;
+            ++removed;
+         }
+         if( vmIsTrailingZeros ) {
+            while( vm % 10 == 0 ) {
+               vrIsTrailingZeros &= lastRemovedDigit == 0;
+               lastRemovedDigit = std::uint8_t( vr % 10 );
+               vr /= 10;
+               vp /= 10;
+               vm /= 10;
+               ++removed;
+            }
+         }
+         if( vrIsTrailingZeros && ( lastRemovedDigit == 5 ) && ( vr % 2 == 0 ) ) {
+            // Round down not up if the number ends in X50000.
+            lastRemovedDigit = 4;
+         }
+         // We need to take vr+1 if vr is outside bounds or we need to round up.
+         output = vr + ( ( vr == vm && ( !acceptBounds || !vmIsTrailingZeros ) ) || ( lastRemovedDigit >= 5 ) );
+      }
+      else {
+         // Specialized for the common case (>99%).
+         while( vp / 10 > vm / 10 ) {
+            lastRemovedDigit = std::uint8_t( vr % 10 );
+            vr /= 10;
+            vp /= 10;
+            vm /= 10;
+            ++removed;
+         }
+         // We need to take vr+1 if vr is outside bounds or we need to round up.
+         output = vr + ( ( vr == vm ) || ( lastRemovedDigit >= 5 ) );
+      }
+      // Step 5: Print the decimal representation.
+
+      if( sign ) {
+         *result++ = '-';
+      }
+      // The average output length is 16.38 digits.
+      const std::uint32_t olength = decimalLength( output );
+      const std::int32_t exp = e10 + olength + removed;
+
+      if( ( -6 < exp ) && ( exp < 22 ) ) {
+         return d2s_simplistic_step5( output, exp, olength, result ) + std::uint32_t( sign );
+      }
+      else {
+         return d2s_scientific_step5( output, exp - 1, olength, result ) + std::uint32_t( sign );
+      }
+   }
+
+   inline void d2s_stream( std::ostream& o, const double f )
+   {
+      char b[ 28 ];
+      const auto s = d2s_finite( f, b );
+      o.write( b, s );
+   }
+
+}  // namespace tao::json::ryu
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/forward.hpp b/3rdParty/taocpp-json/include/tao/json/forward.hpp
new file mode 100644
index 000000000000..1b0478f8d68d
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/forward.hpp
@@ -0,0 +1,44 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_FORWARD_HPP
+#define TAO_JSON_FORWARD_HPP
+
+namespace tao::json
+{
+   namespace events
+   {
+      class virtual_base;
+
+   }  // namespace events
+
+   template< typename T, typename = void >
+   struct traits
+   {};
+
+   template< template< typename... > class Traits >
+   class basic_value;
+
+   using value = basic_value< traits >;
+
+   using producer_t = void ( * )( events::virtual_base&, const void* );
+
+   namespace internal
+   {
+      struct opaque_ptr_t
+      {
+         const void* data;
+         producer_t producer;
+      };
+
+      template< template< typename... > class Traits >
+      struct single;
+
+      template< template< typename... > class Traits >
+      struct pair;
+
+   }  // namespace internal
+
+}  // namespace tao::json
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/from_file.hpp b/3rdParty/taocpp-json/include/tao/json/from_file.hpp
new file mode 100644
index 000000000000..3f3c15ca18c7
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/from_file.hpp
@@ -0,0 +1,32 @@
+// Copyright (c) 2015-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_FROM_FILE_HPP
+#define TAO_JSON_FROM_FILE_HPP
+
+#include <string>
+#include <utility>
+
+#include "events/from_file.hpp"
+#include "events/to_value.hpp"
+#include "events/transformer.hpp"
+
+namespace tao::json
+{
+   template< template< typename... > class Traits, template< typename... > class... Transformers >
+   [[nodiscard]] basic_value< Traits > basic_from_file( const std::string& filename )
+   {
+      events::transformer< events::to_basic_value< Traits >, Transformers... > consumer;
+      events::from_file( consumer, filename );
+      return std::move( consumer.value );
+   }
+
+   template< template< typename... > class... Transformers >
+   [[nodiscard]] value from_file( const std::string& filename )
+   {
+      return basic_from_file< traits, Transformers... >( filename );
+   }
+
+}  // namespace tao::json
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/from_input.hpp b/3rdParty/taocpp-json/include/tao/json/from_input.hpp
new file mode 100644
index 000000000000..c1093e12b339
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/from_input.hpp
@@ -0,0 +1,32 @@
+// Copyright (c) 2019-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_FROM_INPUT_HPP
+#define TAO_JSON_FROM_INPUT_HPP
+
+#include <cstddef>
+#include <utility>
+
+#include "events/from_input.hpp"
+#include "events/to_value.hpp"
+#include "events/transformer.hpp"
+
+namespace tao::json
+{
+   template< template< typename... > class Traits, template< typename... > class... Transformers, typename... Ts >
+   [[nodiscard]] basic_value< Traits > basic_from_input( Ts&&... ts )
+   {
+      events::transformer< events::to_basic_value< Traits >, Transformers... > consumer;
+      events::from_input( consumer, std::forward< Ts >( ts )... );
+      return std::move( consumer.value );
+   }
+
+   template< template< typename... > class... Transformers, typename... Ts >
+   [[nodiscard]] value from_input( Ts&&... ts )
+   {
+      return basic_from_input< traits, Transformers... >( std::forward< Ts >( ts )... );
+   }
+
+}  // namespace tao::json
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/from_stream.hpp b/3rdParty/taocpp-json/include/tao/json/from_stream.hpp
new file mode 100644
index 000000000000..b1d0fd2ffae9
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/from_stream.hpp
@@ -0,0 +1,45 @@
+// Copyright (c) 2015-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_FROM_STREAM_HPP
+#define TAO_JSON_FROM_STREAM_HPP
+
+#include <cstddef>
+#include <string>
+#include <utility>
+
+#include "events/from_stream.hpp"
+#include "events/to_value.hpp"
+#include "events/transformer.hpp"
+
+namespace tao::json
+{
+   template< template< typename... > class Traits, template< typename... > class... Transformers >
+   [[nodiscard]] basic_value< Traits > basic_from_stream( std::istream& stream, const char* source = nullptr, const std::size_t maximum_buffer_size = 4000 )
+   {
+      events::transformer< events::to_basic_value< Traits >, Transformers... > consumer;
+      events::from_stream( consumer, stream, source, maximum_buffer_size );
+      return std::move( consumer.value );
+   }
+
+   template< template< typename... > class Traits, template< typename... > class... Transformers >
+   [[nodiscard]] basic_value< Traits > basic_from_stream( std::istream& stream, const std::string& source, const std::size_t maximum_buffer_size = 4000 )
+   {
+      return basic_from_stream< Traits, Transformers... >( stream, source.c_str(), maximum_buffer_size );
+   }
+
+   template< template< typename... > class... Transformers >
+   [[nodiscard]] value from_stream( std::istream& stream, const char* source, const std::size_t maximum_buffer_size = 4000 )
+   {
+      return basic_from_stream< traits, Transformers... >( stream, source, maximum_buffer_size );
+   }
+
+   template< template< typename... > class... Transformers >
+   [[nodiscard]] value from_stream( std::istream& stream, const std::string& source, const std::size_t maximum_buffer_size = 4000 )
+   {
+      return basic_from_stream< traits, Transformers... >( stream, source.c_str(), maximum_buffer_size );
+   }
+
+}  // namespace tao::json
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/from_string.hpp b/3rdParty/taocpp-json/include/tao/json/from_string.hpp
new file mode 100644
index 000000000000..e2538a0ee38f
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/from_string.hpp
@@ -0,0 +1,41 @@
+// Copyright (c) 2015-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_FROM_STRING_HPP
+#define TAO_JSON_FROM_STRING_HPP
+
+#include <cstddef>
+#include <utility>
+
+#include "events/from_string.hpp"
+#include "events/to_value.hpp"
+#include "events/transformer.hpp"
+
+namespace tao::json
+{
+   template< template< typename... > class Traits, template< typename... > class... Transformers, typename... Ts >
+   [[nodiscard]] basic_value< Traits > basic_from_string( Ts&&... ts )
+   {
+      events::transformer< events::to_basic_value< Traits >, Transformers... > consumer;
+      events::from_string( consumer, std::forward< Ts >( ts )... );
+      return std::move( consumer.value );
+   }
+
+   template< template< typename... > class... Transformers, typename... Ts >
+   [[nodiscard]] value from_string( Ts&&... ts )
+   {
+      return basic_from_string< traits, Transformers... >( std::forward< Ts >( ts )... );
+   }
+
+   inline namespace literals
+   {
+      [[nodiscard]] inline value operator"" _json( const char* data, const std::size_t size )
+      {
+         return json::from_string( data, size, "literal" );
+      }
+
+   }  // namespace literals
+
+}  // namespace tao::json
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/internal/action.hpp b/3rdParty/taocpp-json/include/tao/json/internal/action.hpp
new file mode 100644
index 000000000000..9638f2721fad
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/internal/action.hpp
@@ -0,0 +1,268 @@
+// Copyright (c) 2016-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_INTERNAL_ACTION_HPP
+#define TAO_JSON_INTERNAL_ACTION_HPP
+
+#include <string>
+#include <utility>
+
+#include "../external/pegtl/nothing.hpp"
+
+#include "grammar.hpp"
+#include "number_state.hpp"
+#include "unescape_action.hpp"
+
+namespace tao::json::internal
+{
+   template< typename Rule >
+   struct action
+      : pegtl::nothing< Rule >
+   {};
+
+   template<>
+   struct action< rules::null >
+   {
+      template< typename Consumer >
+      static void apply0( Consumer& consumer )
+      {
+         consumer.null();
+      }
+   };
+
+   template<>
+   struct action< rules::true_ >
+   {
+      template< typename Consumer >
+      static void apply0( Consumer& consumer )
+      {
+         consumer.boolean( true );
+      }
+   };
+
+   template<>
+   struct action< rules::false_ >
+   {
+      template< typename Consumer >
+      static void apply0( Consumer& consumer )
+      {
+         consumer.boolean( false );
+      }
+   };
+
+   template<>
+   struct action< rules::array::begin >
+   {
+      template< typename Consumer >
+      static void apply0( Consumer& consumer )
+      {
+         consumer.begin_array();
+      }
+   };
+
+   template<>
+   struct action< rules::array::element >
+   {
+      template< typename Consumer >
+      static void apply0( Consumer& consumer )
+      {
+         consumer.element();
+      }
+   };
+
+   template<>
+   struct action< rules::array::end >
+   {
+      template< typename Consumer >
+      static void apply0( Consumer& consumer )
+      {
+         consumer.end_array();
+      }
+   };
+
+   template<>
+   struct action< rules::object::begin >
+   {
+      template< typename Consumer >
+      static void apply0( Consumer& consumer )
+      {
+         consumer.begin_object();
+      }
+   };
+
+   template<>
+   struct action< rules::object::element >
+   {
+      template< typename Consumer >
+      static void apply0( Consumer& consumer )
+      {
+         consumer.member();
+      }
+   };
+
+   template<>
+   struct action< rules::object::end >
+   {
+      template< typename Consumer >
+      static void apply0( Consumer& consumer )
+      {
+         consumer.end_object();
+      }
+   };
+
+   template<>
+   struct action< rules::zero< false > >
+   {
+      template< typename Consumer >
+      static void apply0( Consumer& consumer )
+      {
+         consumer.number( std::uint64_t( 0 ) );
+      }
+   };
+
+   template<>
+   struct action< rules::zero< true > >
+   {
+      template< typename Consumer >
+      static void apply0( Consumer& consumer )
+      {
+         consumer.number( std::int64_t( 0 ) );
+      }
+   };
+
+   template<>
+   struct action< rules::esign >
+   {
+      template< typename Input, bool NEG >
+      static void apply( const Input& in, number_state< NEG >& result )
+      {
+         result.eneg = ( in.peek_char() == '-' );
+      }
+   };
+
+   template<>
+   struct action< rules::idigits >
+   {
+      template< typename Input, bool NEG >
+      static void apply( const Input& in, number_state< NEG >& result )
+      {
+         const auto s = in.size();
+
+         if( s == 1 && in.peek_char() == '0' ) {
+            return;
+         }
+
+         if( s > ( 1 << 20 ) ) {
+            throw pegtl::parse_error( "JSON number with 1 megabyte digits", in );
+         }
+
+         const auto c = ( std::min )( s, max_mantissa_digits );
+         std::memcpy( result.mantissa, in.begin(), c );
+         result.exponent10 += static_cast< typename number_state< NEG >::exponent10_t >( s - c );
+         result.msize = static_cast< typename number_state< NEG >::msize_t >( c );
+
+         for( std::size_t i = c; i < s; ++i ) {
+            if( in.peek_char( i ) != '0' ) {
+               result.drop = true;
+               return;
+            }
+         }
+      }
+   };
+
+   template<>
+   struct action< rules::fdigits >
+   {
+      template< typename Input, bool NEG >
+      static void apply( const Input& in, number_state< NEG >& result )
+      {
+         result.isfp = true;
+
+         const auto* b = in.begin();
+         const auto* e = in.end();
+
+         while( ( e > b ) && ( e[ -1 ] == '0' ) ) {
+            --e;
+         }
+         if( !result.msize ) {
+            while( ( b < e ) && ( b[ 0 ] == '0' ) ) {
+               ++b;
+               --result.exponent10;
+            }
+         }
+         const auto c = ( std::min )( std::size_t( e - b ), max_mantissa_digits - result.msize );
+         std::memcpy( result.mantissa + result.msize, b, c );
+         result.exponent10 -= static_cast< typename number_state< NEG >::exponent10_t >( c );
+         result.msize += static_cast< typename number_state< NEG >::msize_t >( c );
+
+         for( const auto* r = b + c; r < e; ++r ) {
+            if( *r != '0' ) {
+               result.drop = true;
+               return;
+            }
+         }
+      }
+   };
+
+   template<>
+   struct action< rules::edigits >
+   {
+      template< typename Input, bool NEG >
+      static void apply( const Input& in, number_state< NEG >& result )
+      {
+         result.isfp = true;
+
+         const char* b = in.begin();
+
+         while( ( b < in.end() ) && ( b[ 0 ] == '0' ) ) {
+            ++b;
+         }
+         if( ( in.end() - b ) > 9 ) {
+            throw pegtl::parse_error( "JSON exponent has more than 9 significant digits", in );
+         }
+         int exponent10 = 0;
+
+         while( b < in.end() ) {
+            exponent10 = ( exponent10 * 10 ) + ( b[ 0 ] - '0' );
+            ++b;
+         }
+         result.exponent10 += ( result.eneg ? -exponent10 : exponent10 );
+      }
+   };
+
+   template< bool NEG >
+   struct action< rules::number< NEG > >
+      : pegtl::change_states< number_state< NEG > >
+   {
+      template< typename Input, typename Consumer >
+      static void success( const Input& /*unused*/, number_state< NEG >& state, Consumer& consumer )
+      {
+         state.success( consumer );
+      }
+   };
+
+   template<>
+   struct action< rules::string::content >
+      : pegtl::change_action_and_states< unescape_action, std::string >
+   {
+      template< typename Input, typename Consumer >
+      static void success( const Input& /*unused*/, std::string& unescaped, Consumer& consumer )
+      {
+         consumer.string( std::move( unescaped ) );
+      }
+   };
+
+   template<>
+   struct action< rules::key::content >
+      : pegtl::change_action_and_states< unescape_action, std::string >
+   {
+      template< typename Input, typename Consumer >
+      static void success( const Input& /*unused*/, std::string& unescaped, Consumer& consumer )
+      {
+         consumer.key( std::move( unescaped ) );
+      }
+   };
+
+}  // namespace tao::json::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/internal/base64.hpp b/3rdParty/taocpp-json/include/tao/json/internal/base64.hpp
new file mode 100644
index 000000000000..64130b05caf5
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/internal/base64.hpp
@@ -0,0 +1,55 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_INTERNAL_BASE64_HPP
+#define TAO_JSON_INTERNAL_BASE64_HPP
+
+#include <stdexcept>
+#include <string>
+
+namespace tao::json::internal
+{
+   template< typename T >
+   [[nodiscard]] std::string base64( const T& v )
+   {
+      static const char table[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+
+      std::string s;
+      s.reserve( ( v.size() + 2 ) / 3 * 4 );
+
+      unsigned cycle = 0;
+      unsigned encode = 0;
+      for( const auto c : v ) {
+         encode <<= 8;
+         encode += static_cast< unsigned char >( c );
+         s += table[ ( encode >> ( ++cycle * 2 ) ) & 0x3f ];
+         if( cycle == 3 ) {
+            cycle = 0;
+            s += table[ encode & 0x3f ];
+         }
+      }
+
+      switch( cycle ) {
+         case 0:
+            break;
+
+         case 1:
+            s += table[ ( encode << 4 ) & 0x3f ];
+            s += "==";
+            break;
+
+         case 2:
+            s += table[ ( encode << 2 ) & 0x3f ];
+            s += '=';
+            break;
+
+         default:
+            throw std::logic_error( "code should be unreachable" );  // LCOV_EXCL_LINE
+      }
+
+      return s;
+   }
+
+}  // namespace tao::json::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/internal/base64url.hpp b/3rdParty/taocpp-json/include/tao/json/internal/base64url.hpp
new file mode 100644
index 000000000000..5649ba0f01a1
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/internal/base64url.hpp
@@ -0,0 +1,53 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_INTERNAL_BASE64URL_HPP
+#define TAO_JSON_INTERNAL_BASE64URL_HPP
+
+#include <stdexcept>
+#include <string>
+
+namespace tao::json::internal
+{
+   template< typename T >
+   [[nodiscard]] std::string base64url( const T& v )
+   {
+      static const char table[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_";
+
+      std::string s;
+      s.reserve( ( v.size() + 2 ) / 3 * 4 );
+
+      unsigned cycle = 0;
+      unsigned encode = 0;
+      for( const auto c : v ) {
+         encode <<= 8;
+         encode += static_cast< unsigned char >( c );
+         s += table[ ( encode >> ( ++cycle * 2 ) ) & 0x3f ];
+         if( cycle == 3 ) {
+            cycle = 0;
+            s += table[ encode & 0x3f ];
+         }
+      }
+
+      switch( cycle ) {
+         case 0:
+            break;
+
+         case 1:
+            s += table[ ( encode << 4 ) & 0x3f ];
+            break;
+
+         case 2:
+            s += table[ ( encode << 2 ) & 0x3f ];
+            break;
+
+         default:
+            throw std::logic_error( "code should be unreachable" );  // LCOV_EXCL_LINE
+      }
+
+      return s;
+   }
+
+}  // namespace tao::json::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/internal/endian.hpp b/3rdParty/taocpp-json/include/tao/json/internal/endian.hpp
new file mode 100644
index 000000000000..7448fb411eea
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/internal/endian.hpp
@@ -0,0 +1,60 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_INTERNAL_ENDIAN_HPP
+#define TAO_JSON_INTERNAL_ENDIAN_HPP
+
+#include <cstdint>
+#include <cstring>
+
+#if defined( _WIN32 ) && !defined( __MINGW32__ )
+#include "endian_win.hpp"
+#else
+#include "endian_gcc.hpp"
+#endif
+
+namespace tao::json::internal
+{
+   template< typename N >
+   [[nodiscard]] N h_to_be( const N n ) noexcept
+   {
+      return N( to_and_from_be< sizeof( N ) >::convert( n ) );
+   }
+
+   template< typename N >
+   [[nodiscard]] N be_to_h( const N n ) noexcept
+   {
+      return h_to_be( n );
+   }
+
+   template< typename N >
+   [[nodiscard]] N be_to_h( const void* p ) noexcept
+   {
+      N n;
+      std::memcpy( &n, p, sizeof( n ) );
+      return internal::be_to_h( n );
+   }
+
+   template< typename N >
+   [[nodiscard]] N h_to_le( const N n ) noexcept
+   {
+      return N( to_and_from_le< sizeof( N ) >::convert( n ) );
+   }
+
+   template< typename N >
+   [[nodiscard]] N le_to_h( const N n ) noexcept
+   {
+      return h_to_le( n );
+   }
+
+   template< typename N >
+   [[nodiscard]] N le_to_h( const void* p ) noexcept
+   {
+      N n;
+      std::memcpy( &n, p, sizeof( n ) );
+      return internal::le_to_h( n );
+   }
+
+}  // namespace tao::json::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/internal/endian_gcc.hpp b/3rdParty/taocpp-json/include/tao/json/internal/endian_gcc.hpp
new file mode 100644
index 000000000000..b1cdb9d24c61
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/internal/endian_gcc.hpp
@@ -0,0 +1,198 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_INTERNAL_ENDIAN_GCC_HPP
+#define TAO_JSON_INTERNAL_ENDIAN_GCC_HPP
+
+#include <cstdint>
+#include <cstring>
+
+namespace tao::json::internal
+{
+#if not defined( __BYTE_ORDER__ )
+#error TODO -- what?
+#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+
+   template< unsigned S >
+   struct to_and_from_be
+   {
+      template< typename T >
+      [[nodiscard]] static T convert( const T n ) noexcept
+      {
+         return n;
+      }
+   };
+
+   template< unsigned S >
+   struct to_and_from_le;
+
+   template<>
+   struct to_and_from_le< 1 >
+   {
+      [[nodiscard]] static std::uint8_t convert( const std::uint8_t n ) noexcept
+      {
+         return n;
+      }
+
+      [[nodiscard]] static std::int8_t convert( const std::int8_t n ) noexcept
+      {
+         return n;
+      }
+   };
+
+   template<>
+   struct to_and_from_le< 2 >
+   {
+      [[nodiscard]] static std::int16_t convert( const std::int16_t n ) noexcept
+      {
+         return __builtin_bswap16( n );
+      }
+
+      [[nodiscard]] static std::uint16_t convert( const std::uint16_t n ) noexcept
+      {
+         return __builtin_bswap16( n );
+      }
+   };
+
+   template<>
+   struct to_and_from_le< 4 >
+   {
+      [[nodiscard]] static float convert( float n ) noexcept
+      {
+         std::uint32_t u;
+         std::memcpy( &u, &n, 4 );
+         u = convert( u );
+         std::memcpy( &n, &u, 4 );
+         return n;
+      }
+
+      [[nodiscard]] static std::int32_t convert( const std::int32_t n ) noexcept
+      {
+         return __builtin_bswap32( n );
+      }
+
+      [[nodiscard]] static std::uint32_t convert( const std::uint32_t n ) noexcept
+      {
+         return __builtin_bswap32( n );
+      }
+   };
+
+   template<>
+   struct to_and_from_le< 8 >
+   {
+      [[nodiscard]] static double convert( double n ) noexcept
+      {
+         std::uint64_t u;
+         std::memcpy( &u, &n, 8 );
+         u = convert( u );
+         std::memcpy( &n, &u, 8 );
+         return n;
+      }
+
+      [[nodiscard]] static std::int64_t convert( const std::int64_t n ) noexcept
+      {
+         return __builtin_bswap64( n );
+      }
+
+      [[nodiscard]] static std::uint64_t convert( const std::uint64_t n ) noexcept
+      {
+         return __builtin_bswap64( n );
+      }
+   };
+
+#elif __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+
+   template< unsigned S >
+   struct to_and_from_le
+   {
+      template< typename T >
+      [[nodiscard]] static T convert( const T n ) noexcept
+      {
+         return n;
+      }
+   };
+
+   template< unsigned S >
+   struct to_and_from_be;
+
+   template<>
+   struct to_and_from_be< 1 >
+   {
+      [[nodiscard]] static std::int8_t convert( const std::int8_t n ) noexcept
+      {
+         return n;
+      }
+
+      [[nodiscard]] static std::uint8_t convert( const std::uint8_t n ) noexcept
+      {
+         return n;
+      }
+   };
+
+   template<>
+   struct to_and_from_be< 2 >
+   {
+      [[nodiscard]] static std::int16_t convert( const std::int16_t n ) noexcept
+      {
+         return __builtin_bswap16( n );
+      }
+
+      [[nodiscard]] static std::uint16_t convert( const std::uint16_t n ) noexcept
+      {
+         return __builtin_bswap16( n );
+      }
+   };
+
+   template<>
+   struct to_and_from_be< 4 >
+   {
+      [[nodiscard]] static float convert( float n ) noexcept
+      {
+         std::uint32_t u;
+         std::memcpy( &u, &n, 4 );
+         u = convert( u );
+         std::memcpy( &n, &u, 4 );
+         return n;
+      }
+
+      [[nodiscard]] static std::int32_t convert( const std::int32_t n ) noexcept
+      {
+         return __builtin_bswap32( n );
+      }
+
+      [[nodiscard]] static std::uint32_t convert( const std::uint32_t n ) noexcept
+      {
+         return __builtin_bswap32( n );
+      }
+   };
+
+   template<>
+   struct to_and_from_be< 8 >
+   {
+      [[nodiscard]] static double convert( double n ) noexcept
+      {
+         std::uint64_t u;
+         std::memcpy( &u, &n, 8 );
+         u = convert( u );
+         std::memcpy( &n, &u, 8 );
+         return n;
+      }
+
+      [[nodiscard]] static std::uint64_t convert( const std::uint64_t n ) noexcept
+      {
+         return __builtin_bswap64( n );
+      }
+
+      [[nodiscard]] static std::int64_t convert( const std::int64_t n ) noexcept
+      {
+         return __builtin_bswap64( n );
+      }
+   };
+
+#else
+#error Unknown host byte order!
+#endif
+
+}  // namespace tao::json::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/internal/endian_win.hpp b/3rdParty/taocpp-json/include/tao/json/internal/endian_win.hpp
new file mode 100644
index 000000000000..bb0856ea331f
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/internal/endian_win.hpp
@@ -0,0 +1,103 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_INTERNAL_ENDIAN_WIN_HPP
+#define TAO_JSON_INTERNAL_ENDIAN_WIN_HPP
+
+#include <cstdint>
+#include <cstring>
+
+#include <stdlib.h>  // TODO: Or is intrin.h the 'more correct' header for the _byteswap_foo() functions?
+
+namespace tao::json::internal
+{
+   template< unsigned S >
+   struct to_and_from_le
+   {
+      template< typename T >
+      [[nodiscard]] static T convert( const T t ) noexcept
+      {
+         return t;
+      }
+   };
+
+   template< unsigned S >
+   struct to_and_from_be;
+
+   template<>
+   struct to_and_from_be< 1 >
+   {
+      [[nodiscard]] static std::int8_t convert( const std::int8_t n ) noexcept
+      {
+         return n;
+      }
+
+      [[nodiscard]] static std::uint8_t convert( const std::uint8_t n ) noexcept
+      {
+         return n;
+      }
+   };
+
+   template<>
+   struct to_and_from_be< 2 >
+   {
+      [[nodiscard]] static std::int16_t convert( const std::int16_t n ) noexcept
+      {
+         return std::int16_t( _byteswap_ushort( std::uint16_t( n ) ) );
+      }
+
+      [[nodiscard]] static std::uint16_t convert( const std::uint16_t n ) noexcept
+      {
+         return _byteswap_ushort( n );
+      }
+   };
+
+   template<>
+   struct to_and_from_be< 4 >
+   {
+      [[nodiscard]] static float convert( float n ) noexcept
+      {
+         std::uint32_t u;
+         std::memcpy( &u, &n, 4 );
+         u = convert( u );
+         std::memcpy( &n, &u, 4 );
+         return n;
+      }
+
+      [[nodiscard]] static std::int32_t convert( const std::int32_t n ) noexcept
+      {
+         return std::int32_t( _byteswap_ulong( std::uint32_t( n ) ) );
+      }
+
+      [[nodiscard]] static std::uint32_t convert( const std::uint32_t n ) noexcept
+      {
+         return _byteswap_ulong( n );
+      }
+   };
+
+   template<>
+   struct to_and_from_be< 8 >
+   {
+      [[nodiscard]] static double convert( double n ) noexcept
+      {
+         std::uint64_t u;
+         std::memcpy( &u, &n, 8 );
+         u = convert( u );
+         std::memcpy( &n, &u, 8 );
+         return n;
+      }
+
+      [[nodiscard]] static std::int64_t convert( const std::int64_t n ) noexcept
+      {
+         return std::int64_t( _byteswap_uint64( std::uint64_t( n ) ) );
+      }
+
+      [[nodiscard]] static std::uint64_t convert( const std::uint64_t n ) noexcept
+      {
+         return _byteswap_uint64( n );
+      }
+   };
+
+}  // namespace tao::json::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/internal/errors.hpp b/3rdParty/taocpp-json/include/tao/json/internal/errors.hpp
new file mode 100644
index 000000000000..6071a91da363
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/internal/errors.hpp
@@ -0,0 +1,85 @@
+// Copyright (c) 2015-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_INTERNAL_ERRORS_HPP
+#define TAO_JSON_INTERNAL_ERRORS_HPP
+
+#include <string>
+
+#include "../external/pegtl/normal.hpp"
+#include "../external/pegtl/parse_error.hpp"
+
+#include "grammar.hpp"
+
+namespace tao::json::internal
+{
+   template< typename Rule >
+   struct errors
+      : pegtl::normal< Rule >
+   {
+      static const std::string error_message;
+
+      template< typename Input, typename... States >
+      static void raise( const Input& in, States&&... /*unused*/ )
+      {
+         throw pegtl::parse_error( error_message, in );
+      }
+
+      template< template< typename... > class Action, typename Iterator, typename Input, typename... States >
+      static auto apply( const Iterator& begin, const Input& in, States&&... st )
+         -> decltype( Action< Rule >::apply( std::declval< const typename Input::action_t& >(), st... ) )
+      {
+         try {
+            using action_t = typename Input::action_t;
+            const action_t action_input( begin, in );
+            return Action< Rule >::apply( action_input, st... );
+         }
+         catch( const pegtl::parse_error& ) {
+            throw;
+         }
+         catch( const std::exception& e ) {
+            throw pegtl::parse_error( e.what(), in );
+         }
+      }
+
+      template< template< typename... > class Action, typename Input, typename... States >
+      static auto apply0( const Input& in, States&&... st )
+         -> decltype( Action< Rule >::apply0( st... ) )
+      {
+         try {
+            return Action< Rule >::apply0( st... );
+         }
+         catch( const pegtl::parse_error& ) {
+            throw;
+         }
+         catch( const std::exception& e ) {
+            throw pegtl::parse_error( e.what(), in );
+         }
+      }
+   };
+
+   // clang-format off
+   template<> inline const std::string errors< rules::text >::error_message = "no valid JSON";
+
+   template<> inline const std::string errors< rules::end_array >::error_message = "incomplete array, expected ']'";
+   template<> inline const std::string errors< rules::end_object >::error_message = "incomplete object, expected '}'";
+   template<> inline const std::string errors< rules::member >::error_message = "expected member";
+   template<> inline const std::string errors< rules::name_separator >::error_message = "expected ':'";
+   template<> inline const std::string errors< rules::array_element >::error_message = "expected value";
+   template<> inline const std::string errors< rules::value >::error_message = "expected value";
+   template<> inline const std::string errors< rules::sor_value >::error_message = "expected value";
+
+   template<> inline const std::string errors< rules::edigits >::error_message = "expected at least one exponent digit";
+   template<> inline const std::string errors< rules::fdigits >::error_message = "expected at least one fraction digit";
+   template<> inline const std::string errors< rules::xdigit >::error_message = "incomplete universal character name";
+   template<> inline const std::string errors< rules::escaped >::error_message = "unknown escape sequence";
+   template<> inline const std::string errors< rules::unescaped >::error_message = "invalid unescaped character";
+   template<> inline const std::string errors< rules::string::content >::error_message = "unterminated string";
+   template<> inline const std::string errors< rules::key::content >::error_message = "unterminated key";
+
+   template<> inline const std::string errors< pegtl::eof >::error_message = "unexpected character after JSON value";
+   // clang-format on
+
+}  // namespace tao::json::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/internal/escape.hpp b/3rdParty/taocpp-json/include/tao/json/internal/escape.hpp
new file mode 100644
index 000000000000..a6e687295a51
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/internal/escape.hpp
@@ -0,0 +1,77 @@
+// Copyright (c) 2016-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_INTERNAL_ESCAPE_HPP
+#define TAO_JSON_INTERNAL_ESCAPE_HPP
+
+#include <ostream>
+#include <sstream>
+#include <string>
+#include <string_view>
+
+namespace tao::json::internal
+{
+   inline void escape( std::ostream& os, const std::string_view s )
+   {
+      static const char* h = "0123456789abcdef";
+
+      const char* p = s.data();
+      const char* l = p;
+      const char* const e = s.data() + s.size();
+      while( p != e ) {
+         const unsigned char c = *p;
+         if( c == '\\' ) {
+            os.write( l, p - l );
+            l = ++p;
+            os << "\\\\";
+         }
+         else if( c == '"' ) {
+            os.write( l, p - l );
+            l = ++p;
+            os << "\\\"";
+         }
+         else if( c < 32 ) {
+            os.write( l, p - l );
+            l = ++p;
+            switch( c ) {
+               case '\b':
+                  os << "\\b";
+                  break;
+               case '\f':
+                  os << "\\f";
+                  break;
+               case '\n':
+                  os << "\\n";
+                  break;
+               case '\r':
+                  os << "\\r";
+                  break;
+               case '\t':
+                  os << "\\t";
+                  break;
+               default:
+                  os << "\\u00" << h[ ( c & 0xf0 ) >> 4 ] << h[ c & 0x0f ];
+            }
+         }
+         else if( c == 127 ) {
+            os.write( l, p - l );
+            l = ++p;
+            os << "\\u007f";
+         }
+         else {
+            ++p;
+         }
+      }
+      os.write( l, p - l );
+   }
+
+   [[nodiscard]] inline std::string escape( const std::string_view s )
+   {
+      std::ostringstream o;
+      escape( o, s );
+      return o.str();
+   }
+
+}  // namespace tao::json::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/internal/format.hpp b/3rdParty/taocpp-json/include/tao/json/internal/format.hpp
new file mode 100644
index 000000000000..3bf727255ec8
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/internal/format.hpp
@@ -0,0 +1,59 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_INTERNAL_FORMAT_HPP
+#define TAO_JSON_INTERNAL_FORMAT_HPP
+
+#include <ostream>
+#include <sstream>
+#include <typeinfo>
+
+#include "escape.hpp"
+
+#include "../forward.hpp"
+#include "../message_extension.hpp"
+#include "../type.hpp"
+
+#include "../external/pegtl/internal/demangle.hpp"
+
+namespace tao::json::internal
+{
+   inline void to_stream( std::ostream& os, const bool v )
+   {
+      os << ( v ? "true" : "false" );
+   }
+
+   inline void to_stream( std::ostream& os, const type t )
+   {
+      os << to_string( t );
+   }
+
+   template< typename T >
+   void to_stream( std::ostream& os, const T& t )
+   {
+      os << t;
+   }
+
+   template< std::size_t N >
+   void to_stream( std::ostream& os, const char ( &t )[ N ] )
+   {
+      os.write( t, N - 1 );
+   }
+
+   template< typename... Ts >
+   void format_to( std::ostream& oss, const Ts&... ts )
+   {
+      ( internal::to_stream( oss, ts ), ... );
+   }
+
+   template< typename... Ts >
+   [[nodiscard]] std::string format( const Ts&... ts )
+   {
+      std::ostringstream oss;
+      format_to( oss, ts... );
+      return oss.str();
+   }
+
+}  // namespace tao::json::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/internal/grammar.hpp b/3rdParty/taocpp-json/include/tao/json/internal/grammar.hpp
new file mode 100644
index 000000000000..b5919ae6fcf3
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/internal/grammar.hpp
@@ -0,0 +1,229 @@
+// Copyright (c) 2015-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_INTERNAL_GRAMMAR_HPP
+#define TAO_JSON_INTERNAL_GRAMMAR_HPP
+
+#include "../external/pegtl.hpp"
+#include "../external/pegtl/contrib/abnf.hpp"
+
+namespace tao::json::internal
+{
+   // clang-format off
+   namespace rules
+   {
+      using namespace pegtl;
+
+      struct ws : one< ' ', '\t', '\n', '\r' > {};
+
+      template< typename R, typename P = ws >
+      using padr = pegtl::internal::seq< R, pegtl::internal::star< P > >;
+
+      struct begin_array : padr< one< '[' > > {};
+      struct begin_object : padr< one< '{' > > {};
+      struct end_array : one< ']' > {};
+      struct end_object : one< '}' > {};
+      struct name_separator : pad< one< ':' >, ws > {};
+      struct value_separator : padr< one< ',' > > {};
+      struct element_separator : padr< one< ',' > > {};
+
+      struct false_ : pegtl::string< 'f', 'a', 'l', 's', 'e' > {};
+      struct null : pegtl::string< 'n', 'u', 'l', 'l' > {};
+      struct true_ : pegtl::string< 't', 'r', 'u', 'e' > {};
+
+      struct digits : plus< abnf::DIGIT > {};
+
+      struct esign : one< '-', '+' > {};
+
+      struct edigits : digits {};
+      struct fdigits : digits {};
+      struct idigits : digits {};
+
+      struct exp : seq< one< 'e', 'E' >, opt< esign >, must< edigits > > {};
+      struct frac : if_must< one< '.' >, fdigits > {};
+
+      template< bool NEG >
+      struct number : seq< idigits, opt< frac >, opt< exp > > {};
+
+      struct xdigit : abnf::HEXDIG {};
+      struct escaped_unicode : list< seq< one< 'u' >, rep< 4, must< xdigit > > >, one< '\\' > > {};
+
+      struct escaped_char : one< '"', '\\', '/', 'b', 'f', 'n', 'r', 't' > {};
+      struct escaped : sor< escaped_char, escaped_unicode > {};
+
+      struct unescaped
+      {
+         using analyze_t = pegtl::analysis::generic< pegtl::analysis::rule_type::any >;
+
+         template< typename Input >
+         [[nodiscard]] static bool match( Input& in )
+         {
+            bool result = false;
+
+            while( const std::size_t s = in.size( 4 ) ) {
+               if( const auto t = pegtl::internal::peek_utf8::peek( in, s ) ) {
+                  if( ( 0x20 <= t.data ) && ( t.data != '\\' ) && ( t.data != '"' ) ) {
+                     in.bump_in_this_line( t.size );
+                     result = true;
+                     continue;
+                  }
+               }
+               break;
+            }
+            return result;
+         }
+      };
+
+      struct chars : if_must_else< one< '\\' >, escaped, unescaped > {};
+
+      struct string_content : until< at< one< '"' > >, chars > {};
+      struct string : seq< one< '"' >, must< string_content >, any >
+      {
+         using content = string_content;
+      };
+
+      struct key_content : string_content {};
+      struct key : seq< one< '"' >, must< key_content >, any >
+      {
+         using content = key_content;
+      };
+
+      struct value;
+
+      struct array_element;
+      struct array_content : opt< list_must< array_element, element_separator > > {};
+      struct array : seq< begin_array, array_content, must< end_array > >
+      {
+         using begin = begin_array;
+         using end = end_array;
+         using element = array_element;
+         using content = array_content;
+      };
+
+      struct member : if_must< key, name_separator, value > {};
+      struct object_content : opt< list_must< member, value_separator > > {};
+      struct object : seq< begin_object, object_content, must< end_object > >
+      {
+         using begin = begin_object;
+         using end = end_object;
+         using element = member;
+         using content = object_content;
+      };
+
+      template< bool NEG >
+      struct zero {};
+
+      struct sor_value
+      {
+         using analyze_t = pegtl::analysis::generic< pegtl::analysis::rule_type::sor, string, number< false >, object, array, false_, true_, null >;
+
+         template< bool NEG,
+                   apply_mode A,
+                   rewind_mode M,
+                   template< typename... > class Action,
+                   template< typename... > class Control,
+                   typename Input,
+                   typename... States >
+         [[nodiscard]] static bool match_zero( Input& in, States&&... st )
+         {
+            if( in.size( 2 ) > 1 ) {
+               switch( in.peek_char( 1 ) ) {
+               case '.':
+               case 'e':
+               case 'E':
+                  return Control< number< NEG > >::template match< A, M, Action, Control >( in, st... );
+
+               case '0':
+               case '1':
+               case '2':
+               case '3':
+               case '4':
+               case '5':
+               case '6':
+               case '7':
+               case '8':
+               case '9':
+                  throw pegtl::parse_error( "invalid leading zero", in );
+               }
+            }
+            in.bump_in_this_line();
+            Control< zero< NEG > >::template apply0< Action >( in, st... );
+            return true;
+         }
+
+         template< bool NEG,
+                   apply_mode A,
+                   rewind_mode M,
+                   template< typename... > class Action,
+                   template< typename... > class Control,
+                   typename Input,
+                   typename... States >
+         [[nodiscard]] static bool match_number( Input& in, States&&... st )
+         {
+            if( in.peek_char() == '0' ) {
+               if( !match_zero< NEG, A, rewind_mode::dontcare, Action, Control >( in, st... ) ) {
+                  throw pegtl::parse_error( "incomplete number", in );
+               }
+               return true;
+            }
+            return Control< number< NEG > >::template match< A, M, Action, Control >( in, st... );
+         }
+
+         template< apply_mode A,
+                   rewind_mode M,
+                   template< typename... > class Action,
+                   template< typename... > class Control,
+                   typename Input,
+                   typename... States >
+         [[nodiscard]] static bool match_impl( Input& in, States&&... st )
+         {
+            switch( in.peek_char() ) {
+            case '"': return Control< string >::template match< A, M, Action, Control >( in, st... );
+            case '{': return Control< object >::template match< A, M, Action, Control >( in, st... );
+            case '[': return Control< array >::template match< A, M, Action, Control >( in, st... );
+            case 'n': return Control< null >::template match< A, M, Action, Control >( in, st... );
+            case 't': return Control< true_ >::template match< A, M, Action, Control >( in, st... );
+            case 'f': return Control< false_ >::template match< A, M, Action, Control >( in, st... );
+
+            case '-':
+               in.bump_in_this_line();
+               if( in.empty() || !match_number< true, A, rewind_mode::dontcare, Action, Control >( in, st... ) ) {
+                  throw pegtl::parse_error( "incomplete number", in );
+               }
+               return true;
+
+            default:
+               return match_number< false, A, M, Action, Control >( in, st... );
+            }
+         }
+
+         template< apply_mode A,
+                   rewind_mode M,
+                   template< typename... > class Action,
+                   template< typename... > class Control,
+                   typename Input,
+                   typename... States >
+         [[nodiscard]] static bool match( Input& in, States&&... st )
+         {
+            if( in.size( 2 ) && match_impl< A, M, Action, Control >( in, st... ) ) {
+               in.discard();
+               return true;
+            }
+            return false;
+         }
+      };
+
+      struct value : padr< sor_value > {};
+      struct array_element : value {};
+
+      struct text : seq< star< ws >, value > {};
+
+   }  // namespace rules
+
+   struct grammar : pegtl::must< rules::text, pegtl::eof > {};
+   struct embedded : pegtl::must< rules::sor_value > {};
+   // clang-format on
+
+}  // namespace tao::json::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/internal/hexdump.hpp b/3rdParty/taocpp-json/include/tao/json/internal/hexdump.hpp
new file mode 100644
index 000000000000..5e87e76cb42d
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/internal/hexdump.hpp
@@ -0,0 +1,31 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_INTERNAL_HEXDUMP_HPP
+#define TAO_JSON_INTERNAL_HEXDUMP_HPP
+
+#include <sstream>
+
+namespace tao::json::internal
+{
+   template< typename T >
+   void hexdump( std::ostream& os, const T& v )
+   {
+      static const char h[] = "0123456789ABCDEF";
+      for( const auto b : v ) {
+         os.put( h[ static_cast< unsigned char >( b ) >> 4 ] );
+         os.put( h[ static_cast< unsigned char >( b ) & 0xF ] );
+      }
+   }
+
+   template< typename T >
+   [[nodiscard]] std::string hexdump( const T& v )
+   {
+      std::ostringstream os;
+      internal::hexdump( os, v );
+      return os.str();
+   }
+
+}  // namespace tao::json::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/internal/identity.hpp b/3rdParty/taocpp-json/include/tao/json/internal/identity.hpp
new file mode 100644
index 000000000000..2f470e75efd2
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/internal/identity.hpp
@@ -0,0 +1,22 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_INTERNAL_IDENTITY_HPP
+#define TAO_JSON_INTERNAL_IDENTITY_HPP
+
+#include <type_traits>
+
+namespace tao::internal
+{
+   template< typename T >
+   struct identity
+   {
+      using type = T;
+   };
+
+   template< typename T >
+   using identity_t = typename identity< T >::type;
+
+}  // namespace tao::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/internal/number_state.hpp b/3rdParty/taocpp-json/include/tao/json/internal/number_state.hpp
new file mode 100644
index 000000000000..07dfc829d91f
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/internal/number_state.hpp
@@ -0,0 +1,80 @@
+// Copyright (c) 2016-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_INTERNAL_NUMBER_STATE_HPP
+#define TAO_JSON_INTERNAL_NUMBER_STATE_HPP
+
+#include <cmath>
+#include <cstdint>
+#include <cstdlib>
+#include <stdexcept>
+
+#include "../external/double.hpp"
+
+namespace tao::json::internal
+{
+   static const std::size_t max_mantissa_digits = 772;
+
+   template< bool NEG >
+   struct number_state
+   {
+      using exponent10_t = std::int32_t;
+      using msize_t = std::uint16_t;
+
+      number_state() = default;
+
+      number_state( const number_state& ) = delete;
+      number_state( number_state&& ) = delete;
+
+      ~number_state() = default;
+
+      void operator=( const number_state& ) = delete;
+      void operator=( number_state&& ) = delete;
+
+      exponent10_t exponent10 = 0;
+      msize_t msize = 0;  // Excluding sign.
+      bool isfp = false;
+      bool eneg = false;
+      bool drop = false;
+      char mantissa[ max_mantissa_digits + 1 ];
+
+      template< typename Consumer >
+      void success( Consumer& consumer )
+      {
+         if( !isfp && msize <= 20 ) {
+            mantissa[ msize ] = 0;
+            char* p;
+            errno = 0;
+            const std::uint64_t ull = std::strtoull( mantissa, &p, 10 );
+            if( ( errno != ERANGE ) && ( p == mantissa + msize ) ) {
+               if constexpr( NEG ) {
+                  if( ull < 9223372036854775808ULL ) {
+                     consumer.number( -static_cast< std::int64_t >( ull ) );
+                     return;
+                  }
+                  if( ull == 9223372036854775808ULL ) {
+                     consumer.number( static_cast< std::int64_t >( -9223372036854775807LL - 1 ) );
+                     return;
+                  }
+               }
+               else {
+                  consumer.number( ull );
+                  return;
+               }
+            }
+         }
+         if( drop ) {
+            mantissa[ msize++ ] = '1';
+            --exponent10;
+         }
+         const auto d = double_conversion::Strtod( double_conversion::Vector< const char >( mantissa, msize ), exponent10 );
+         if( !std::isfinite( d ) ) {
+            throw std::runtime_error( "invalid double value" );
+         }
+         consumer.number( NEG ? -d : d );
+      }
+   };
+
+}  // namespace tao::json::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/internal/number_traits.hpp b/3rdParty/taocpp-json/include/tao/json/internal/number_traits.hpp
new file mode 100644
index 000000000000..4025386b4e57
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/internal/number_traits.hpp
@@ -0,0 +1,267 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_INTERNAL_NUMBER_TRAITS_HPP
+#define TAO_JSON_INTERNAL_NUMBER_TRAITS_HPP
+
+#include <cstdint>
+#include <stdexcept>
+
+#include "../forward.hpp"
+#include "../message_extension.hpp"
+#include "../type.hpp"
+
+#include "format.hpp"
+
+#ifdef _MSC_VER
+#pragma warning( push )
+#pragma warning( disable : 4702 )
+#endif
+
+namespace tao::json::internal
+{
+   template< typename T >
+   struct number_trait
+   {
+      template< template< typename... > class Traits >
+      [[nodiscard]] static T as( const basic_value< Traits >& v )
+      {
+         switch( v.type() ) {
+            case type::SIGNED:
+               return static_cast< T >( v.get_signed() );
+            case type::UNSIGNED:
+               return static_cast< T >( v.get_unsigned() );
+            case type::DOUBLE:
+               return static_cast< T >( v.get_double() );
+            default:
+               throw std::logic_error( internal::format( "invalid json type '", v.type(), "' for conversion to number", json::message_extension( v ) ) );
+         }
+      }
+   };
+
+   template< typename T >
+   struct signed_trait
+      : number_trait< T >
+   {
+      template< template< typename... > class, typename Parts >
+      [[nodiscard]] static T consume( Parts& parser )
+      {
+         return static_cast< T >( parser.number_signed() );
+      }
+
+      template< template< typename... > class Traits, typename Consumer >
+      static void produce( Consumer& c, const T i )
+      {
+         c.number( std::int64_t( i ) );
+      }
+
+      template< template< typename... > class Traits >
+      static void assign( basic_value< Traits >& v, const T i ) noexcept
+      {
+         v.set_signed( i );
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool equal( const basic_value< Traits >& lhs, const T rhs ) noexcept
+      {
+         const auto& p = lhs.skip_value_ptr();
+         switch( p.type() ) {
+            case type::SIGNED:
+               return p.get_signed() == rhs;
+            case type::UNSIGNED:
+               return ( rhs >= 0 ) && ( p.get_unsigned() == static_cast< std::uint64_t >( rhs ) );
+            case type::DOUBLE:
+               return p.get_double() == rhs;
+            default:
+               return false;
+         }
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool less_than( const basic_value< Traits >& lhs, const T rhs ) noexcept
+      {
+         const auto& p = lhs.skip_value_ptr();
+         switch( p.type() ) {
+            case type::SIGNED:
+               return p.get_signed() < rhs;
+            case type::UNSIGNED:
+               return ( rhs >= 0 ) && ( p.get_unsigned() < static_cast< std::uint64_t >( rhs ) );
+            case type::DOUBLE:
+               return p.get_double() < rhs;
+            default:
+               return p.type() < type::SIGNED;
+         }
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool greater_than( const basic_value< Traits >& lhs, const T rhs ) noexcept
+      {
+         const auto& p = lhs.skip_value_ptr();
+         switch( p.type() ) {
+            case type::SIGNED:
+               return p.get_signed() > rhs;
+            case type::UNSIGNED:
+               return ( rhs < 0 ) || ( p.get_unsigned() > static_cast< std::uint64_t >( rhs ) );
+            case type::DOUBLE:
+               return p.get_double() > rhs;
+            default:
+               return p.type() > type::SIGNED;
+         }
+      }
+   };
+
+   template< typename T >
+   struct unsigned_trait
+      : number_trait< T >
+   {
+      template< template< typename... > class, typename Parts >
+      [[nodiscard]] static T consume( Parts& parser )
+      {
+         return static_cast< T >( parser.number_unsigned() );
+      }
+
+      template< template< typename... > class Traits, typename Consumer >
+      static void produce( Consumer& c, const T i )
+      {
+         c.number( std::uint64_t( i ) );
+      }
+
+      template< template< typename... > class Traits >
+      static void assign( basic_value< Traits >& v, const T i ) noexcept
+      {
+         v.set_unsigned( i );
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool equal( const basic_value< Traits >& lhs, const T rhs ) noexcept
+      {
+         const auto& p = lhs.skip_value_ptr();
+         switch( p.type() ) {
+            case type::SIGNED: {
+               const auto v = p.get_signed();
+               return ( v >= 0 ) && ( static_cast< std::uint64_t >( v ) == rhs );
+            }
+            case type::UNSIGNED:
+               return p.get_unsigned() == rhs;
+            case type::DOUBLE:
+               return p.get_double() == rhs;
+            default:
+               return false;
+         }
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool less_than( const basic_value< Traits >& lhs, const T rhs ) noexcept
+      {
+         const auto& p = lhs.skip_value_ptr();
+         switch( p.type() ) {
+            case type::SIGNED: {
+               const auto v = p.get_signed();
+               return ( v < 0 ) || ( static_cast< std::uint64_t >( v ) < rhs );
+            }
+            case type::UNSIGNED:
+               return p.get_unsigned() < rhs;
+            case type::DOUBLE:
+               return p.get_double() < rhs;
+            default:
+               return p.type() < type::UNSIGNED;
+         }
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool greater_than( const basic_value< Traits >& lhs, const T rhs ) noexcept
+      {
+         const auto& p = lhs.skip_value_ptr();
+         switch( p.type() ) {
+            case type::SIGNED: {
+               const auto v = p.get_signed();
+               return ( v >= 0 ) && ( static_cast< std::uint64_t >( v ) > rhs );
+            }
+            case type::UNSIGNED:
+               return p.get_unsigned() > rhs;
+            case type::DOUBLE:
+               return p.get_double() > rhs;
+            default:
+               return p.type() > type::UNSIGNED;
+         }
+      }
+   };
+
+   template< typename T >
+   struct float_trait
+      : number_trait< T >
+   {
+      template< template< typename... > class, typename Parts >
+      [[nodiscard]] static T consume( Parts& parser )
+      {
+         return static_cast< T >( parser.number_double() );
+      }
+
+      template< template< typename... > class Traits, typename Consumer >
+      static void produce( Consumer& c, const T f )
+      {
+         c.number( double( f ) );
+      }
+
+      template< template< typename... > class Traits >
+      static void assign( basic_value< Traits >& v, const T f ) noexcept
+      {
+         v.set_double( f );
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool equal( const basic_value< Traits >& lhs, const T rhs ) noexcept
+      {
+         const auto& p = lhs.skip_value_ptr();
+         switch( p.type() ) {
+            case type::SIGNED:
+               return p.get_signed() == rhs;
+            case type::UNSIGNED:
+               return p.get_unsigned() == rhs;
+            case type::DOUBLE:
+               return p.get_double() == rhs;  // TODO: Is it ok for overall semantics that NaN != NaN?
+            default:
+               return false;
+         }
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool less_than( const basic_value< Traits >& lhs, const T rhs ) noexcept
+      {
+         const auto& p = lhs.skip_value_ptr();
+         switch( p.type() ) {
+            case type::SIGNED:
+               return p.get_signed() < rhs;
+            case type::UNSIGNED:
+               return p.get_unsigned() < rhs;
+            case type::DOUBLE:
+               return p.get_double() < rhs;
+            default:
+               return p.type() < type::DOUBLE;
+         }
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool greater_than( const basic_value< Traits >& lhs, const T rhs ) noexcept
+      {
+         const auto& p = lhs.skip_value_ptr();
+         switch( p.type() ) {
+            case type::SIGNED:
+               return p.get_signed() > rhs;
+            case type::UNSIGNED:
+               return p.get_unsigned() > rhs;
+            case type::DOUBLE:
+               return p.get_double() > rhs;
+            default:
+               return p.type() > type::DOUBLE;
+         }
+      }
+   };
+
+}  // namespace tao::json::internal
+
+#ifdef _MSC_VER
+#pragma warning( pop )
+#endif
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/internal/pair.hpp b/3rdParty/taocpp-json/include/tao/json/internal/pair.hpp
new file mode 100644
index 000000000000..1f15f8e2f460
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/internal/pair.hpp
@@ -0,0 +1,42 @@
+// Copyright (c) 2016-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_INTERNAL_PAIR_HPP
+#define TAO_JSON_INTERNAL_PAIR_HPP
+
+#include <string>
+#include <type_traits>
+#include <utility>
+
+#include "../forward.hpp"
+
+namespace tao::json::internal
+{
+   template< template< typename... > class Traits >
+   struct pair
+   {
+      mutable std::string key;
+      mutable basic_value< Traits > value;
+
+      template< typename U >
+      pair( U&& v )
+         : key( Traits< std::decay_t< U > >::template default_key< Traits >::as_string() ),
+           value( std::forward< U >( v ) )
+      {}
+
+      template< typename U >
+      pair( U&& k, basic_value< Traits >&& v )
+         : key( std::forward< U >( k ) ),
+           value( std::move( v ) )
+      {}
+
+      template< typename U >
+      pair( U&& k, const basic_value< Traits >& v )
+         : key( std::forward< U >( k ) ),
+           value( v )
+      {}
+   };
+
+}  // namespace tao::json::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/internal/parse_util.hpp b/3rdParty/taocpp-json/include/tao/json/internal/parse_util.hpp
new file mode 100644
index 000000000000..26961fe86586
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/internal/parse_util.hpp
@@ -0,0 +1,112 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_INTERNAL_PARSE_UTIL_HPP
+#define TAO_JSON_INTERNAL_PARSE_UTIL_HPP
+
+#include <cassert>
+
+#include "../external/pegtl/parse_error.hpp"
+#include "../utf8.hpp"
+
+#include "endian.hpp"
+#include "format.hpp"
+
+#ifdef _MSC_VER
+#pragma warning( push )
+#pragma warning( disable : 4702 )
+#endif
+
+namespace tao::json::internal
+{
+   template< typename Input >
+   void throw_on_empty( Input& in )
+   {
+      if( in.empty() ) {
+         throw pegtl::parse_error( format( "unexpected end of input" ), in );
+      }
+   }
+
+   template< typename Input >
+   void throw_on_empty( Input& in, const std::size_t required )
+   {
+      const auto available = in.size( required );
+      if( available < required ) {
+         throw pegtl::parse_error( format( "unexpected end of input -- required ", required, " available ", available ), in );
+      }
+   }
+
+   template< typename Input >
+   [[nodiscard]] std::uint8_t peek_uint8( Input& in )
+   {
+      throw_on_empty( in );
+      return in.peek_uint8();
+   }
+
+   template< typename Input >
+   [[nodiscard]] char peek_char( Input& in )
+   {
+      throw_on_empty( in );
+      return in.peek_char();
+   }
+
+   template< typename Input >
+   [[nodiscard]] char read_char_unsafe( Input& in )
+   {
+      const auto r = in.peek_char();
+      in.bump_in_this_line( 1 );
+      return r;
+   }
+
+   template< typename Input >
+   [[nodiscard]] char read_char( Input& in )
+   {
+      throw_on_empty( in );
+      return read_char_unsafe( in );
+   }
+
+   template< utf8_mode U, typename Result, typename Input >
+   [[nodiscard]] Result read_string( Input& in, const std::size_t size )
+   {
+      using value_t = typename Result::value_type;
+      json::internal::throw_on_empty( in, size );
+      const auto* pointer = reinterpret_cast< const value_t* >( in.current() );
+      const Result result( pointer, size );
+      json::internal::consume_utf8_throws< U >( in, size );
+      return result;
+   }
+
+   template< typename Result, typename Number = Result, typename Input >
+   [[nodiscard]] Result read_big_endian_number( Input& in, const std::size_t extra = 0 )
+   {
+      throw_on_empty( in, extra + sizeof( Number ) );
+      const auto result = static_cast< Result >( be_to_h< Number >( in.current() + extra ) );
+      in.bump_in_this_line( extra + sizeof( Number ) );
+      return result;
+   }
+
+   template< typename Integer >
+   [[nodiscard]] Integer hex_char_to_integer( const char c ) noexcept
+   {
+      if( ( '0' <= c ) && ( c <= '9' ) ) {
+         return static_cast< Integer >( c - '0' );
+      }
+      if( ( 'a' <= c ) && ( c <= 'f' ) ) {
+         return static_cast< Integer >( c - 'a' + 10 );
+      }
+      if( ( 'A' <= c ) && ( c <= 'F' ) ) {
+         return static_cast< Integer >( c - 'A' + 10 );
+      }
+      // LCOV_EXCL_START
+      assert( false );
+      return 0;
+      // LCOV_EXCL_STOP
+   }
+
+}  // namespace tao::json::internal
+
+#ifdef _MSC_VER
+#pragma warning( pop )
+#endif
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/internal/sha256.hpp b/3rdParty/taocpp-json/include/tao/json/internal/sha256.hpp
new file mode 100644
index 000000000000..03bcd467edab
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/internal/sha256.hpp
@@ -0,0 +1,218 @@
+// Copyright (c) 2016-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_INTERNAL_SHA256_HPP
+#define TAO_JSON_INTERNAL_SHA256_HPP
+
+// Implements RFC 6234, SHA-256
+
+#include <cstddef>
+#include <cstdint>
+#include <cstring>
+#include <string>
+
+// RFC 6234, 3.d; see also http://stackoverflow.com/a/4209604/2073257
+#define ROR( x, N ) ( ( ( x ) >> ( N ) ) | ( ( x ) << ( 32 - ( N ) ) ) )
+
+// RFC 6234, 5.1
+#define CH( x, y, z ) ( ( ( x ) & ( y ) ) ^ ( ~( x ) & ( z ) ) )
+#define MAJ( x, y, z ) ( ( ( x ) & ( y ) ) ^ ( ( x ) & ( z ) ) ^ ( ( y ) & ( z ) ) )
+#define BSIG0( x ) ( ROR( x, 2 ) ^ ROR( x, 13 ) ^ ROR( x, 22 ) )
+#define BSIG1( x ) ( ROR( x, 6 ) ^ ROR( x, 11 ) ^ ROR( x, 25 ) )
+#define SSIG0( x ) ( ROR( x, 7 ) ^ ROR( x, 18 ) ^ ( ( x ) >> 3 ) )
+#define SSIG1( x ) ( ROR( x, 17 ) ^ ROR( x, 19 ) ^ ( ( x ) >> 10 ) )
+
+namespace tao::json::internal
+{
+   // RFC 6234, 5.1
+   // clang-format off
+   static std::uint32_t K[ 64 ] = {
+      0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5,
+      0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
+      0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3,
+      0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
+      0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc,
+      0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
+      0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7,
+      0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
+      0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13,
+      0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
+      0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3,
+      0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
+      0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5,
+      0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
+      0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208,
+      0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2
+   };
+   // clang-format on
+
+   class sha256
+   {
+   private:
+      unsigned char M[ 64 ];
+      std::uint64_t size;
+
+      std::uint32_t H[ 8 ];
+
+      // RFC 6234, 6.2
+      void process() noexcept
+      {
+         std::uint32_t W[ 64 ];
+
+         // step 1
+         for( std::size_t t = 0, i = 0; t != 16; ++t, i += 4 ) {
+            W[ t ] = ( M[ i ] << 24 ) | ( M[ i + 1 ] << 16 ) | ( M[ i + 2 ] << 8 ) | ( M[ i + 3 ] );
+         }
+         for( std::size_t t = 16; t != 64; ++t ) {
+            W[ t ] = SSIG1( W[ t - 2 ] ) + W[ t - 7 ] + SSIG0( W[ t - 15 ] ) + W[ t - 16 ];
+         }
+
+         // step 2
+         std::uint32_t a, b, c, d, e, f, g, h;
+         a = H[ 0 ];
+         b = H[ 1 ];
+         c = H[ 2 ];
+         d = H[ 3 ];
+         e = H[ 4 ];
+         f = H[ 5 ];
+         g = H[ 6 ];
+         h = H[ 7 ];
+
+         // step 3
+         for( std::size_t t = 0; t != 64; ++t ) {
+            const std::uint32_t T1 = h + BSIG1( e ) + CH( e, f, g ) + K[ t ] + W[ t ];
+            const std::uint32_t T2 = BSIG0( a ) + MAJ( a, b, c );
+            h = g;
+            g = f;
+            f = e;
+            e = d + T1;
+            d = c;
+            c = b;
+            b = a;
+            a = T1 + T2;
+         }
+
+         // step 4
+         H[ 0 ] += a;
+         H[ 1 ] += b;
+         H[ 2 ] += c;
+         H[ 3 ] += d;
+         H[ 4 ] += e;
+         H[ 5 ] += f;
+         H[ 6 ] += g;
+         H[ 7 ] += h;
+      }
+
+   public:
+      sha256() noexcept
+      {
+         reset();
+      }
+
+      sha256( const sha256& ) = delete;
+      sha256( sha256&& ) = delete;
+
+      ~sha256() = default;
+
+      void operator=( const sha256& ) = delete;
+      void operator=( sha256&& ) = delete;
+
+      void reset() noexcept
+      {
+         size = 0;
+
+         // RFC 6234, 6.1
+         H[ 0 ] = 0x6a09e667;
+         H[ 1 ] = 0xbb67ae85;
+         H[ 2 ] = 0x3c6ef372;
+         H[ 3 ] = 0xa54ff53a;
+         H[ 4 ] = 0x510e527f;
+         H[ 5 ] = 0x9b05688c;
+         H[ 6 ] = 0x1f83d9ab;
+         H[ 7 ] = 0x5be0cd19;
+      }
+
+      void feed( const unsigned char c ) noexcept
+      {
+         M[ size++ % 64 ] = c;
+         if( ( size % 64 ) == 0 ) {
+            process();
+         }
+      }
+
+      void feed( const void* p, std::size_t s ) noexcept
+      {
+         auto* q = static_cast< const unsigned char* >( p );
+         while( s != 0 ) {
+            feed( *q++ );
+            --s;
+         }
+      }
+
+      void feed( const std::string_view v ) noexcept
+      {
+         feed( v.data(), v.size() );
+      }
+
+      // RFC 6234, 4.1
+      void store_unsafe( unsigned char* buffer ) noexcept
+      {
+         std::size_t i = size % 64;
+         if( i < 56 ) {
+            M[ i++ ] = 0x80;
+#if defined( __GNUC__ ) && ( __GNUC__ >= 9 )
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Waggressive-loop-optimizations"
+#endif
+            while( i < 56 ) {
+               M[ i++ ] = 0x00;
+            }
+#if defined( __GNUC__ ) && ( __GNUC__ >= 9 )
+#pragma GCC diagnostic pop
+#endif
+         }
+         else {
+            M[ i++ ] = 0x80;
+            while( i < 64 ) {
+               M[ i++ ] = 0x00;
+            }
+            process();
+            std::memset( M, 0, 56 );
+         }
+
+         size *= 8;
+
+         M[ 63 ] = static_cast< unsigned char >( size );
+         M[ 62 ] = static_cast< unsigned char >( size >> 8 );
+         M[ 61 ] = static_cast< unsigned char >( size >> 16 );
+         M[ 60 ] = static_cast< unsigned char >( size >> 24 );
+         M[ 59 ] = static_cast< unsigned char >( size >> 32 );
+         M[ 58 ] = static_cast< unsigned char >( size >> 40 );
+         M[ 57 ] = static_cast< unsigned char >( size >> 48 );
+         M[ 56 ] = static_cast< unsigned char >( size >> 56 );
+
+         process();
+
+         for( std::size_t j = 0; j < 4; ++j ) {
+            buffer[ j ] = ( H[ 0 ] >> ( 24 - j * 8 ) ) & 0xff;
+            buffer[ j + 4 ] = ( H[ 1 ] >> ( 24 - j * 8 ) ) & 0xff;
+            buffer[ j + 8 ] = ( H[ 2 ] >> ( 24 - j * 8 ) ) & 0xff;
+            buffer[ j + 12 ] = ( H[ 3 ] >> ( 24 - j * 8 ) ) & 0xff;
+            buffer[ j + 16 ] = ( H[ 4 ] >> ( 24 - j * 8 ) ) & 0xff;
+            buffer[ j + 20 ] = ( H[ 5 ] >> ( 24 - j * 8 ) ) & 0xff;
+            buffer[ j + 24 ] = ( H[ 6 ] >> ( 24 - j * 8 ) ) & 0xff;
+            buffer[ j + 28 ] = ( H[ 7 ] >> ( 24 - j * 8 ) ) & 0xff;
+         }
+      }
+
+      [[nodiscard]] std::string get()
+      {
+         std::string result( 32, '\0' );
+         store_unsafe( reinterpret_cast< unsigned char* >( result.data() ) );
+         return result;
+      }
+   };
+
+}  // namespace tao::json::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/internal/single.hpp b/3rdParty/taocpp-json/include/tao/json/internal/single.hpp
new file mode 100644
index 000000000000..f56818c69dae
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/internal/single.hpp
@@ -0,0 +1,40 @@
+// Copyright (c) 2016-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_INTERNAL_SINGLE_HPP
+#define TAO_JSON_INTERNAL_SINGLE_HPP
+
+#include <utility>
+
+#include "../forward.hpp"
+
+#include "pair.hpp"
+
+namespace tao::json::internal
+{
+   template< template< typename... > class Traits >
+   struct single
+   {
+      mutable basic_value< Traits > value;
+
+      template< typename U >
+      single( U&& v )
+         : value( std::forward< U >( v ) )
+      {}
+
+      single( std::initializer_list< pair< Traits > >&& l )
+         : value( std::move( l ) )
+      {}
+
+      single( const std::initializer_list< pair< Traits > >& l )
+         : value( l )
+      {}
+
+      single( std::initializer_list< pair< Traits > >& l )
+         : value( l )
+      {}
+   };
+
+}  // namespace tao::json::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/internal/string_t.hpp b/3rdParty/taocpp-json/include/tao/json/internal/string_t.hpp
new file mode 100644
index 000000000000..ba6c931c9873
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/internal/string_t.hpp
@@ -0,0 +1,35 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_INTERNAL_STRING_T_HPP
+#define TAO_JSON_INTERNAL_STRING_T_HPP
+
+#include <string>
+#include <string_view>
+
+#include "../external/pegtl/internal/pegtl_string.hpp"
+
+namespace tao::json::internal
+{
+   template< char... Cs >
+   struct string_t
+      : pegtl::string< Cs... >
+   {
+      static constexpr const char value[] = { Cs..., 0 };
+
+      [[nodiscard]] static constexpr std::string_view as_string_view() noexcept
+      {
+         return std::string_view( value, sizeof...( Cs ) );
+      }
+
+      [[nodiscard]] static std::string as_string()
+      {
+         return std::string( value, sizeof...( Cs ) );
+      }
+   };
+
+}  // namespace tao::json::internal
+
+#define TAO_JSON_STRING_T( VaLue ) TAO_JSON_PEGTL_INTERNAL_STRING( tao::json::internal::string_t, VaLue )
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/internal/type_traits.hpp b/3rdParty/taocpp-json/include/tao/json/internal/type_traits.hpp
new file mode 100644
index 000000000000..d34c9caa8e92
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/internal/type_traits.hpp
@@ -0,0 +1,113 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_INTERNAL_TYPE_TRAITS_HPP
+#define TAO_JSON_INTERNAL_TYPE_TRAITS_HPP
+
+#include <type_traits>
+#include <typeinfo>
+
+#include "../forward.hpp"
+
+namespace tao::json::internal
+{
+   template< typename... Ts >
+   struct type_list
+   {
+      static constexpr std::size_t size = sizeof...( Ts );
+   };
+
+   template< typename... >
+   struct merge_type_lists_t;
+
+   template< typename... Ts >
+   struct merge_type_lists_t< type_list< Ts... > >
+   {
+      using list = type_list< Ts... >;
+   };
+
+   template< typename... Vs, typename... Ws, typename... Rs >
+   struct merge_type_lists_t< type_list< Vs... >, type_list< Ws... >, Rs... >
+      : merge_type_lists_t< type_list< Vs..., Ws... >, Rs... >
+   {};
+
+   template< typename... Ts >
+   using merge_type_lists = typename merge_type_lists_t< Ts... >::list;
+
+   struct type_info_less
+   {
+      [[nodiscard]] bool operator()( const std::type_info* l, const std::type_info* r ) const
+      {
+         return l->before( *r );
+      }
+   };
+
+   template< typename... >
+   inline constexpr bool has_as_impl = false;
+
+   template< typename Trait, typename... Args >
+   inline constexpr bool has_as_impl< decltype( (void)Trait::as( std::declval< Args >()... ), void() ), Trait, Args... > = true;
+
+   template< typename Trait, typename Value, typename... With >
+   inline constexpr bool has_as = has_as_impl< void, Trait, const Value&, With&... >;
+
+   template< typename, template< typename... > typename, typename, typename... >
+   inline constexpr bool has_as_type_impl = false;
+
+   template< template< typename... > typename Traits, typename T, typename... Args >
+   inline constexpr bool has_as_type_impl< decltype( (void)Traits< T >::template as_type< Traits, T >( std::declval< Args >()... ), void() ), Traits, T, Args... > = true;
+
+   template< template< typename... > typename Traits, typename T, typename Value, typename... With >
+   inline constexpr bool has_as_type = has_as_type_impl< void, Traits, T, const Value&, With&... >;
+
+   template< typename... >
+   inline constexpr bool has_to_impl = false;
+
+   template< typename Trait, typename... Args >
+   inline constexpr bool has_to_impl< decltype( Trait::to( std::declval< Args >()... ), void() ), Trait, Args... > = true;
+
+   template< typename Trait, typename Value, typename... With >
+   inline constexpr bool has_to = has_to_impl< void, Trait, const Value&, With&... >;
+
+   template< template< typename... > class, typename, typename, typename = void >
+   inline constexpr bool has_consume_one = false;
+
+   template< template< typename... > class Traits, typename P, typename U >
+   inline constexpr bool has_consume_one< Traits, P, U, decltype( (void)Traits< U >::template consume< Traits >( std::declval< P& >() ), void() ) > = true;
+
+   template< template< typename... > class, typename, typename, typename = void >
+   inline constexpr bool has_consume_two = false;
+
+   template< template< typename... > class Traits, typename P, typename U >
+   inline constexpr bool has_consume_two< Traits, P, U, decltype( (void)Traits< U >::template consume< Traits >( std::declval< P& >(), std::declval< U& >() ), void() ) > = true;
+
+   template< template< typename... > class Traits, typename T, typename = void >
+   inline constexpr bool has_is_nothing = false;
+
+   template< template< typename... > class Traits, typename T >
+   inline constexpr bool has_is_nothing< Traits, T, decltype( (void)Traits< T >::template is_nothing< Traits >( std::declval< const T& >() ), void() ) > = true;
+
+   template< template< typename... > class Traits, typename T >
+   [[nodiscard]] std::enable_if_t< has_is_nothing< Traits, T >, bool > is_nothing( const T& t ) noexcept( noexcept( Traits< T >::template is_nothing< Traits >( t ) ) )
+   {
+      return Traits< T >::template is_nothing< Traits >( t );
+   }
+
+   template< template< typename... > class Traits, typename T >
+   [[nodiscard]] std::enable_if_t< !has_is_nothing< Traits, T >, bool > is_nothing( const T& /*unused*/ ) noexcept
+   {
+      return false;
+   }
+
+   template< template< typename... > class Traits, typename T, typename = void >
+   inline constexpr bool has_enable_implicit_constructor = false;
+
+   template< template< typename... > class Traits, typename T >
+   inline constexpr bool has_enable_implicit_constructor< Traits, T, decltype( Traits< T >::enable_implicit_constructor, void() ) > = true;
+
+   template< template< typename... > class Traits, typename T >
+   inline constexpr bool enable_implicit_constructor = Traits< std::conditional_t< has_enable_implicit_constructor< Traits, T >, T, void > >::enable_implicit_constructor;
+
+}  // namespace tao::json::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/internal/unescape_action.hpp b/3rdParty/taocpp-json/include/tao/json/internal/unescape_action.hpp
new file mode 100644
index 000000000000..b74fc30b1510
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/internal/unescape_action.hpp
@@ -0,0 +1,24 @@
+// Copyright (c) 2015-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_INTERNAL_UNESCAPE_ACTION_HPP
+#define TAO_JSON_INTERNAL_UNESCAPE_ACTION_HPP
+
+#include "../external/pegtl/contrib/unescape.hpp"
+#include "../external/pegtl/nothing.hpp"
+
+#include "grammar.hpp"
+
+namespace tao::json::internal
+{
+   // clang-format off
+   template< typename Rule > struct unescape_action : pegtl::nothing< Rule > {};
+
+   template<> struct unescape_action< rules::escaped_unicode > : pegtl::unescape::unescape_j {};
+   template<> struct unescape_action< rules::escaped_char > : pegtl::unescape::unescape_c< rules::escaped_char, '"', '\\', '/', '\b', '\f', '\n', '\r', '\t' > {};
+   template<> struct unescape_action< rules::unescaped > : pegtl::unescape::append_all {};
+   // clang-format on
+
+}  // namespace tao::json::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/internal/uri_fragment.hpp b/3rdParty/taocpp-json/include/tao/json/internal/uri_fragment.hpp
new file mode 100644
index 000000000000..acedcbba28d0
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/internal/uri_fragment.hpp
@@ -0,0 +1,182 @@
+// Copyright (c) 2016-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_INTERNAL_URI_FRAGMENT_HPP
+#define TAO_JSON_INTERNAL_URI_FRAGMENT_HPP
+
+#include <stdexcept>
+#include <string_view>
+
+#include "../pointer.hpp"
+
+namespace tao::json::internal
+{
+   // clang-format off
+   const bool allowed_uri_fragment_characters[] = {
+      false, false, false, false, false, false, false, false, // 0
+      false, false, false, false, false, false, false, false,
+      false, false, false, false, false, false, false, false, // 16
+      false, false, false, false, false, false, false, false,
+      false, true,  false, false, true,  false, true,  true,  // 32
+      true,  true,  true,  true,  true,  true,  true,  true,
+      true,  true,  true,  true,  true,  true,  true,  true,  // 48
+      true,  true,  true,  true,  false, true,  false, true,
+      true,  true,  true,  true,  true,  true,  true,  true,  // 64
+      true,  true,  true,  true,  true,  true,  true,  true,
+      true,  true,  true,  true,  true,  true,  true,  true,  // 80
+      true,  true,  true,  false, false, false, false, true,
+      false, true,  true,  true,  true,  true,  true,  true,  // 96
+      true,  true,  true,  true,  true,  true,  true,  true,
+      true,  true,  true,  true,  true,  true,  true,  true,  // 112
+      true,  true,  true,  false, false, false, true,  false,
+      false, false, false, false, false, false, false, false, // 128
+      false, false, false, false, false, false, false, false,
+      false, false, false, false, false, false, false, false,
+      false, false, false, false, false, false, false, false,
+      false, false, false, false, false, false, false, false,
+      false, false, false, false, false, false, false, false,
+      false, false, false, false, false, false, false, false,
+      false, false, false, false, false, false, false, false,
+      false, false, false, false, false, false, false, false,
+      false, false, false, false, false, false, false, false,
+      false, false, false, false, false, false, false, false,
+      false, false, false, false, false, false, false, false,
+      false, false, false, false, false, false, false, false,
+      false, false, false, false, false, false, false, false,
+      false, false, false, false, false, false, false, false,
+      false, false, false, false, false, false, false, false
+   };
+   // clang-format on
+
+   [[nodiscard]] inline char xdigit_value( const char c )
+   {
+      // clang-format off
+      switch ( c ) {
+      case '0': return 0;
+      case '1': return 1;
+      case '2': return 2;
+      case '3': return 3;
+      case '4': return 4;
+      case '5': return 5;
+      case '6': return 6;
+      case '7': return 7;
+      case '8': return 8;
+      case '9': return 9;
+      case 'a': case 'A': return 10;
+      case 'b': case 'B': return 11;
+      case 'c': case 'C': return 12;
+      case 'd': case 'D': return 13;
+      case 'e': case 'E': return 14;
+      case 'f': case 'F': return 15;
+      default:
+         throw std::invalid_argument( "invalid URI Fragment escape sequence, '%' must be followed by two hexadecimal digits" );
+      }
+      // clang-format on
+   }
+
+   [[nodiscard]] inline pointer uri_fragment_to_pointer( const std::string_view v )
+   {
+      pointer result;
+      if( v.empty() || v[ 0 ] != '#' ) {
+         throw std::invalid_argument( "invalid URI Fragment value, must begin with '#'" );
+      }
+      if( v.size() > 1 ) {
+         const char* p = v.data() + 1;
+         const char* const e = v.data() + v.size();
+         if( *p++ != '/' ) {
+            throw std::invalid_argument( "invalid JSON Pointer value, must be empty or begin with '/'" );
+         }
+         std::string token;
+         while( p != e ) {
+            const char c = *p++;
+            switch( c ) {
+                  // clang-format off
+            case '!': case '$': case '&': case '\'': case '(': case ')': case '*': case '+': case ',': case '-': case '.':
+            case '0': case '1': case '2': case '3': case '4': case '5': case '6': case '7': case '8': case '9':
+            case ':': case ';': case '=': case '?': case '@':
+            case 'A': case 'B': case 'C': case 'D': case 'E': case 'F': case 'G': case 'H': case 'I': case 'J': case 'K': case 'L': case 'M':
+            case 'N': case 'O': case 'P': case 'Q': case 'R': case 'S': case 'T': case 'U': case 'V': case 'W': case 'X': case 'Y': case 'Z':
+            case '_':
+            case 'a': case 'b': case 'c': case 'd': case 'e': case 'f': case 'g': case 'h': case 'i': case 'j': case 'k': case 'l': case 'm':
+            case 'n': case 'o': case 'p': case 'q': case 'r': case 's': case 't': case 'u': case 'v': case 'w': case 'x': case 'y': case 'z':
+                  // clang-format on
+                  token += c;
+                  continue;
+
+               case '%':
+                  if( p != e ) {
+                     const char h1 = xdigit_value( *p++ );
+                     if( p != e ) {
+                        const char h2 = xdigit_value( *p++ );
+                        token += static_cast< char >( h1 * 16 + h2 );
+                        continue;
+                     }
+                  }
+                  throw std::invalid_argument( "invalid URI Fragment escape sequence, '%' must be followed by two hexadecimal digits" );
+
+               case '~':
+                  if( p != e ) {
+                     switch( *p++ ) {
+                        case '0':
+                           token += '~';
+                           continue;
+                        case '1':
+                           token += '/';
+                           continue;
+                     }
+                  }
+                  throw std::invalid_argument( "invalid JSON Pointer escape sequence, '~' must be followed by '0' or '1'" );
+
+               case '/':
+                  result += std::move( token );
+                  token.clear();
+                  continue;
+
+               default:
+                  throw std::invalid_argument( "invalid URI Fragment character" );
+            }
+         }
+         result += std::move( token );
+      }
+      return result;
+   }
+
+   [[nodiscard]] inline std::string tokens_to_uri_fragment( std::vector< token >::const_iterator it, const std::vector< token >::const_iterator& end )
+   {
+      static const char* hex = "0123456789ABCDEF";
+
+      std::string result = "#";
+      while( it != end ) {
+         result += '/';
+         for( const unsigned char c : it->key() ) {
+            switch( c ) {
+               case '~':
+                  result += "~0";
+                  break;
+               case '/':
+                  result += "~1";
+                  break;
+               default:
+                  if( allowed_uri_fragment_characters[ c ] ) {
+                     result += c;
+                  }
+                  else {
+                     result += '%';
+                     result += hex[ c >> 4 ];
+                     result += hex[ c & 15 ];
+                  }
+            }
+         }
+         ++it;
+      }
+      return result;
+   }
+
+   [[nodiscard]] inline std::string to_uri_fragment( const pointer& p )
+   {
+      return tokens_to_uri_fragment( p.begin(), p.end() );
+   }
+
+}  // namespace tao::json::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/jaxn.hpp b/3rdParty/taocpp-json/include/tao/json/jaxn.hpp
new file mode 100644
index 000000000000..10f40034b5e0
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/jaxn.hpp
@@ -0,0 +1,19 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_JAXN_HPP
+#define TAO_JSON_JAXN_HPP
+
+#include "../json.hpp"
+
+#include "jaxn/consume_file.hpp"
+#include "jaxn/consume_string.hpp"
+#include "jaxn/from_file.hpp"
+#include "jaxn/from_input.hpp"
+#include "jaxn/from_stream.hpp"
+#include "jaxn/from_string.hpp"
+#include "jaxn/parts_parser.hpp"
+#include "jaxn/to_stream.hpp"
+#include "jaxn/to_string.hpp"
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/jaxn/consume_file.hpp b/3rdParty/taocpp-json/include/tao/json/jaxn/consume_file.hpp
new file mode 100644
index 000000000000..1bf9a5bd2385
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/jaxn/consume_file.hpp
@@ -0,0 +1,34 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_JAXN_CONSUME_FILE_HPP
+#define TAO_JSON_JAXN_CONSUME_FILE_HPP
+
+#include <utility>
+
+#include "../external/pegtl/file_input.hpp"
+
+#include "../consume.hpp"
+#include "../forward.hpp"
+
+#include "parts_parser.hpp"
+
+namespace tao::json::jaxn
+{
+   template< typename T, template< typename... > class Traits = traits, typename F >
+   [[nodiscard]] T consume_file( F&& filename )
+   {
+      jaxn::basic_parts_parser< pegtl::file_input< pegtl::tracking_mode::lazy > > pp( std::forward< F >( filename ) );
+      return json::consume< T, Traits >( pp );
+   }
+
+   template< template< typename... > class Traits = traits, typename F, typename T >
+   void consume_file( F&& filename, T& t )
+   {
+      jaxn::basic_parts_parser< pegtl::file_input< pegtl::tracking_mode::lazy > > pp( std::forward< F >( filename ) );
+      json::consume< Traits >( pp, t );
+   }
+
+}  // namespace tao::json::jaxn
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/jaxn/consume_string.hpp b/3rdParty/taocpp-json/include/tao/json/jaxn/consume_string.hpp
new file mode 100644
index 000000000000..3051d0ec506c
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/jaxn/consume_string.hpp
@@ -0,0 +1,32 @@
+// Copyright (c) 2019-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_JAXN_CONSUME_STRING_HPP
+#define TAO_JSON_JAXN_CONSUME_STRING_HPP
+
+#include "../external/pegtl/string_input.hpp"
+
+#include "../consume.hpp"
+#include "../forward.hpp"
+
+#include "parts_parser.hpp"
+
+namespace tao::json::jaxn
+{
+   template< typename T, template< typename... > class Traits = traits, typename F >
+   [[nodiscard]] T consume_string( F&& string )
+   {
+      jaxn::basic_parts_parser< pegtl::memory_input< pegtl::tracking_mode::lazy, pegtl::eol::lf_crlf, const char* > > pp( string, __FUNCTION__ );
+      return json::consume< T, Traits >( pp );
+   }
+
+   template< template< typename... > class Traits = traits, typename F, typename T >
+   void consume_string( F&& string, T& t )
+   {
+      jaxn::basic_parts_parser< pegtl::memory_input< pegtl::tracking_mode::lazy, pegtl::eol::lf_crlf, const char* > > pp( string, __FUNCTION__ );
+      json::consume< Traits >( pp, t );
+   }
+
+}  // namespace tao::json::jaxn
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/jaxn/events/from_file.hpp b/3rdParty/taocpp-json/include/tao/json/jaxn/events/from_file.hpp
new file mode 100644
index 000000000000..f645b59489cf
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/jaxn/events/from_file.hpp
@@ -0,0 +1,28 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_JAXN_EVENTS_FROM_FILE_HPP
+#define TAO_JSON_JAXN_EVENTS_FROM_FILE_HPP
+
+#include <utility>
+
+#include "../internal/action.hpp"
+#include "../internal/errors.hpp"
+#include "../internal/grammar.hpp"
+
+#include "../../external/pegtl/file_input.hpp"
+
+namespace tao::json::jaxn::events
+{
+   // Events producer to parse a file containing a JAXN string representation.
+
+   template< typename T, typename Consumer >
+   void from_file( Consumer& consumer, T&& filename )
+   {
+      pegtl::file_input< pegtl::tracking_mode::lazy > in( std::forward< T >( filename ) );
+      pegtl::parse< internal::grammar, internal::action, internal::errors >( in, consumer );
+   }
+
+}  // namespace tao::json::jaxn::events
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/jaxn/events/from_input.hpp b/3rdParty/taocpp-json/include/tao/json/jaxn/events/from_input.hpp
new file mode 100644
index 000000000000..bb27cedcc39a
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/jaxn/events/from_input.hpp
@@ -0,0 +1,45 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_JAXN_EVENTS_FROM_INPUT_HPP
+#define TAO_JSON_JAXN_EVENTS_FROM_INPUT_HPP
+
+#include <utility>
+
+#include "../../external/pegtl/parse.hpp"
+
+#include "../internal/action.hpp"
+#include "../internal/errors.hpp"
+#include "../internal/grammar.hpp"
+
+namespace tao::json::jaxn::events
+{
+   // Events producers that parse a JAXN string representation from a PEGTL input (or something compatible).
+
+   template< typename Consumer, typename Input >
+   void from_input( Consumer& consumer, Input&& in )
+   {
+      pegtl::parse< internal::grammar, internal::action, internal::errors >( std::forward< Input >( in ), consumer );
+   }
+
+   template< typename Consumer, typename Input >
+   void from_input_embedded( Consumer& consumer, Input&& in )
+   {
+      pegtl::parse< internal::embedded, internal::action, internal::errors >( std::forward< Input >( in ), consumer );
+   }
+
+   template< typename Consumer, typename Outer, typename Input >
+   void from_input_nested( Consumer& consumer, const Outer& oi, Input&& in )
+   {
+      pegtl::parse_nested< internal::grammar, internal::action, internal::errors >( oi, std::forward< Input >( in ), consumer );
+   }
+
+   template< typename Consumer, typename Outer, typename Input >
+   void from_input_embedded_nested( Consumer& consumer, const Outer& oi, Input&& in )
+   {
+      pegtl::parse_nested< internal::embedded, internal::action, internal::errors >( oi, std::forward< Input >( in ), consumer );
+   }
+
+}  // namespace tao::json::jaxn::events
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/jaxn/events/from_stream.hpp b/3rdParty/taocpp-json/include/tao/json/jaxn/events/from_stream.hpp
new file mode 100644
index 000000000000..2c5984dd985e
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/jaxn/events/from_stream.hpp
@@ -0,0 +1,33 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_JAXN_EVENTS_FROM_STREAM_HPP
+#define TAO_JSON_JAXN_EVENTS_FROM_STREAM_HPP
+
+#include <istream>
+
+#include "../../external/pegtl/internal/istream_reader.hpp"
+#include "../../external/pegtl/parse.hpp"
+
+#include "../internal/action.hpp"
+#include "../internal/errors.hpp"
+#include "../internal/grammar.hpp"
+
+namespace tao::json::jaxn::events
+{
+   template< typename Consumer >
+   void from_stream( Consumer& consumer, std::istream& stream, const char* source = nullptr, const std::size_t maximum_buffer_size = 4000 )
+   {
+      pegtl::istream_input in( stream, maximum_buffer_size, source ? source : "tao::json::events::jaxn::from_stream" );
+      pegtl::parse< internal::grammar, internal::action, internal::errors >( in, consumer );
+   }
+
+   template< typename Consumer >
+   void from_stream( Consumer& consumer, std::istream& stream, const std::string& source, const std::size_t maximum_buffer_size = 4000 )
+   {
+      from_stream( consumer, stream, source.c_str(), maximum_buffer_size );
+   }
+
+}  // namespace tao::json::jaxn::events
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/jaxn/events/from_string.hpp b/3rdParty/taocpp-json/include/tao/json/jaxn/events/from_string.hpp
new file mode 100644
index 000000000000..ee20ca7583ba
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/jaxn/events/from_string.hpp
@@ -0,0 +1,39 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_JAXN_EVENTS_FROM_STRING_HPP
+#define TAO_JSON_JAXN_EVENTS_FROM_STRING_HPP
+
+#include <string>
+#include <string_view>
+
+#include "../../external/pegtl/memory_input.hpp"
+
+#include "from_input.hpp"
+
+namespace tao::json::jaxn::events
+{
+   // Events producer to parse a JAXN string representation.
+
+   template< typename Consumer >
+   void from_string( Consumer& consumer, const char* data, const std::size_t size, const char* source = nullptr, const std::size_t byte = 0, const std::size_t line = 1, const std::size_t column = 0 )
+   {
+      pegtl::memory_input< pegtl::tracking_mode::lazy, pegtl::eol::lf_crlf, const char* > in( data, data + size, source ? source : "tao::json::jaxn::events::from_string", byte, line, column );
+      jaxn::events::from_input( consumer, std::move( in ) );
+   }
+
+   template< typename Consumer >
+   void from_string( Consumer& consumer, const char* data, const std::size_t size, const std::string& source, const std::size_t byte = 0, const std::size_t line = 1, const std::size_t column = 0 )
+   {
+      jaxn::events::from_string( consumer, data, size, source.c_str(), byte, line, column );
+   }
+
+   template< typename Consumer, typename... Ts >
+   void from_string( Consumer& consumer, const std::string_view data, Ts&&... ts )
+   {
+      jaxn::events::from_string( consumer, data.data(), data.size(), std::forward< Ts >( ts )... );
+   }
+
+}  // namespace tao::json::jaxn::events
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/jaxn/events/to_pretty_stream.hpp b/3rdParty/taocpp-json/include/tao/json/jaxn/events/to_pretty_stream.hpp
new file mode 100644
index 000000000000..cff8895d2dc8
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/jaxn/events/to_pretty_stream.hpp
@@ -0,0 +1,69 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_JAXN_EVENTS_TO_PRETTY_STREAM_HPP
+#define TAO_JSON_JAXN_EVENTS_TO_PRETTY_STREAM_HPP
+
+#include "../../internal/hexdump.hpp"
+
+#include "../../external/ryu.hpp"
+
+#include "../../events/to_pretty_stream.hpp"
+
+#include "../is_identifier.hpp"
+
+namespace tao::json::jaxn::events
+{
+   // Events consumer to build a JAXN string representation.
+
+   struct to_pretty_stream
+      : json::events::to_pretty_stream
+   {
+      using json::events::to_pretty_stream::to_pretty_stream;
+
+      using json::events::to_pretty_stream::number;
+
+      void number( const double v )
+      {
+         next();
+         if( !std::isfinite( v ) ) {
+            if( std::isnan( v ) ) {
+               os.write( "NaN", 3 );
+            }
+            else if( v < 0 ) {
+               os.write( "-Infinity", 9 );
+            }
+            else {
+               os.write( "Infinity", 8 );
+            }
+         }
+         else {
+            ryu::d2s_stream( os, v );
+         }
+      }
+
+      void binary( const tao::binary_view v )
+      {
+         next();
+         os.put( '$' );
+         json::internal::hexdump( os, v );
+      }
+
+      void key( const std::string_view v )
+      {
+         if( jaxn::is_identifier( v ) ) {
+            next();
+            os.write( v.data(), v.size() );
+         }
+         else {
+            string( v );
+         }
+         os.write( ": ", 2 );
+         first = true;
+         after_key = true;
+      }
+   };
+
+}  // namespace tao::json::jaxn::events
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/jaxn/events/to_stream.hpp b/3rdParty/taocpp-json/include/tao/json/jaxn/events/to_stream.hpp
new file mode 100644
index 000000000000..0fd96ff7c09f
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/jaxn/events/to_stream.hpp
@@ -0,0 +1,67 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_JAXN_EVENTS_TO_STREAM_HPP
+#define TAO_JSON_JAXN_EVENTS_TO_STREAM_HPP
+
+#include "../../events/to_stream.hpp"
+
+#include "../../external/ryu.hpp"
+
+#include "../../internal/hexdump.hpp"
+
+#include "../is_identifier.hpp"
+
+namespace tao::json::jaxn::events
+{
+   // Events consumer to build a JAXN string representation.
+
+   struct to_stream
+      : json::events::to_stream
+   {
+      using json::events::to_stream::number;
+      using json::events::to_stream::to_stream;
+
+      void number( const double v )
+      {
+         next();
+         if( !std::isfinite( v ) ) {
+            if( std::isnan( v ) ) {
+               os << "NaN";
+            }
+            else if( v < 0 ) {
+               os << "-Infinity";
+            }
+            else {
+               os << "Infinity";
+            }
+         }
+         else {
+            ryu::d2s_stream( os, v );
+         }
+      }
+
+      void key( const std::string_view v )
+      {
+         if( jaxn::is_identifier( v ) ) {
+            next();
+            os.write( v.data(), v.size() );
+         }
+         else {
+            string( v );
+         }
+         os.put( ':' );
+         first = true;
+      }
+
+      void binary( const tao::binary_view v )
+      {
+         next();
+         os.put( '$' );
+         json::internal::hexdump( os, v );
+      }
+   };
+
+}  // namespace tao::json::jaxn::events
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/jaxn/events/to_string.hpp b/3rdParty/taocpp-json/include/tao/json/jaxn/events/to_string.hpp
new file mode 100644
index 000000000000..124c57dae841
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/jaxn/events/to_string.hpp
@@ -0,0 +1,33 @@
+// Copyright (c) 2016-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_JAXN_EVENTS_TO_STRING_HPP
+#define TAO_JSON_JAXN_EVENTS_TO_STRING_HPP
+
+#include <sstream>
+#include <string>
+
+#include "to_stream.hpp"
+
+namespace tao::json::jaxn::events
+{
+   // Events consumer to build a JAXN string representation.
+
+   struct to_string
+      : to_stream
+   {
+      std::ostringstream oss;
+
+      to_string()
+         : to_stream( oss )
+      {}
+
+      [[nodiscard]] std::string value() const
+      {
+         return oss.str();
+      }
+   };
+
+}  // namespace tao::json::jaxn::events
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/jaxn/from_file.hpp b/3rdParty/taocpp-json/include/tao/json/jaxn/from_file.hpp
new file mode 100644
index 000000000000..1406244a2108
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/jaxn/from_file.hpp
@@ -0,0 +1,33 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_JAXN_FROM_FILE_HPP
+#define TAO_JSON_JAXN_FROM_FILE_HPP
+
+#include <string>
+#include <utility>
+
+#include "../events/to_value.hpp"
+#include "../events/transformer.hpp"
+
+#include "events/from_file.hpp"
+
+namespace tao::json::jaxn
+{
+   template< template< typename... > class Traits, template< typename... > class... Transformers >
+   [[nodiscard]] basic_value< Traits > basic_from_file( const std::string& filename )
+   {
+      json::events::transformer< json::events::to_basic_value< Traits >, Transformers... > consumer;
+      events::from_file( consumer, filename );
+      return std::move( consumer.value );
+   }
+
+   template< template< typename... > class... Transformers >
+   [[nodiscard]] value from_file( const std::string& filename )
+   {
+      return basic_from_file< traits, Transformers... >( filename );
+   }
+
+}  // namespace tao::json::jaxn
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/jaxn/from_input.hpp b/3rdParty/taocpp-json/include/tao/json/jaxn/from_input.hpp
new file mode 100644
index 000000000000..f17f2143d63e
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/jaxn/from_input.hpp
@@ -0,0 +1,33 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_JAXN_FROM_INPUT_HPP
+#define TAO_JSON_JAXN_FROM_INPUT_HPP
+
+#include <cstddef>
+#include <utility>
+
+#include "../events/to_value.hpp"
+#include "../events/transformer.hpp"
+
+#include "events/from_input.hpp"
+
+namespace tao::json::jaxn
+{
+   template< template< typename... > class Traits, template< typename... > class... Transformers, typename... Ts >
+   [[nodiscard]] basic_value< Traits > basic_from_input( Ts&&... ts )
+   {
+      json::events::transformer< json::events::to_basic_value< Traits >, Transformers... > consumer;
+      jaxn::events::from_input( consumer, std::forward< Ts >( ts )... );
+      return std::move( consumer.value );
+   }
+
+   template< template< typename... > class... Transformers, typename... Ts >
+   [[nodiscard]] value from_input( Ts&&... ts )
+   {
+      return basic_from_input< traits, Transformers... >( std::forward< Ts >( ts )... );
+   }
+
+}  // namespace tao::json::jaxn
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/jaxn/from_stream.hpp b/3rdParty/taocpp-json/include/tao/json/jaxn/from_stream.hpp
new file mode 100644
index 000000000000..615b657bde6d
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/jaxn/from_stream.hpp
@@ -0,0 +1,48 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_JAXN_FROM_STREAM_HPP
+#define TAO_JSON_JAXN_FROM_STREAM_HPP
+
+#include <cstddef>
+#include <string>
+#include <utility>
+
+#include "../value.hpp"
+
+#include "../events/to_value.hpp"
+#include "../events/transformer.hpp"
+
+#include "events/from_stream.hpp"
+
+namespace tao::json::jaxn
+{
+   template< template< typename... > class Traits, template< typename... > class... Transformers >
+   [[nodiscard]] basic_value< Traits > basic_from_stream( std::istream& stream, const char* source = nullptr, const std::size_t maximum_buffer_size = 4000 )
+   {
+      json::events::transformer< json::events::to_basic_value< Traits >, Transformers... > consumer;
+      events::from_stream( consumer, stream, source, maximum_buffer_size );
+      return std::move( consumer.value );
+   }
+
+   template< template< typename... > class Traits, template< typename... > class... Transformers >
+   [[nodiscard]] basic_value< Traits > basic_from_stream( std::istream& stream, const std::string& source, const std::size_t maximum_buffer_size = 4000 )
+   {
+      return basic_from_stream< Traits, Transformers... >( stream, source.c_str(), maximum_buffer_size );
+   }
+
+   template< template< typename... > class... Transformers >
+   [[nodiscard]] value from_stream( std::istream& stream, const char* source = nullptr, const std::size_t maximum_buffer_size = 4000 )
+   {
+      return basic_from_stream< traits, Transformers... >( stream, source, maximum_buffer_size );
+   }
+
+   template< template< typename... > class... Transformers >
+   [[nodiscard]] value from_stream( std::istream& stream, const std::string& source, const std::size_t maximum_buffer_size = 4000 )
+   {
+      return basic_from_stream< traits, Transformers... >( stream, source.c_str(), maximum_buffer_size );
+   }
+
+}  // namespace tao::json::jaxn
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/jaxn/from_string.hpp b/3rdParty/taocpp-json/include/tao/json/jaxn/from_string.hpp
new file mode 100644
index 000000000000..cfc08a811bf4
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/jaxn/from_string.hpp
@@ -0,0 +1,42 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_JAXN_FROM_STRING_HPP
+#define TAO_JSON_JAXN_FROM_STRING_HPP
+
+#include <cstddef>
+#include <utility>
+
+#include "../events/to_value.hpp"
+#include "../events/transformer.hpp"
+
+#include "events/from_string.hpp"
+
+namespace tao::json::jaxn
+{
+   template< template< typename... > class Traits, template< typename... > class... Transformers, typename... Ts >
+   [[nodiscard]] basic_value< Traits > basic_from_string( Ts&&... ts )
+   {
+      json::events::transformer< json::events::to_basic_value< Traits >, Transformers... > consumer;
+      events::from_string( consumer, std::forward< Ts >( ts )... );
+      return std::move( consumer.value );
+   }
+
+   template< template< typename... > class... Transformers, typename... Ts >
+   [[nodiscard]] value from_string( Ts&&... ts )
+   {
+      return basic_from_string< traits, Transformers... >( std::forward< Ts >( ts )... );
+   }
+
+   inline namespace literals
+   {
+      [[nodiscard]] inline value operator"" _jaxn( const char* data, const std::size_t size )
+      {
+         return jaxn::from_string( data, size, "literal" );
+      }
+
+   }  // namespace literals
+
+}  // namespace tao::json::jaxn
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/jaxn/internal/action.hpp b/3rdParty/taocpp-json/include/tao/json/jaxn/internal/action.hpp
new file mode 100644
index 000000000000..f4f9fea10b45
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/jaxn/internal/action.hpp
@@ -0,0 +1,355 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_JAXN_INTERNAL_ACTION_HPP
+#define TAO_JSON_JAXN_INTERNAL_ACTION_HPP
+
+#include <string>
+#include <string_view>
+#include <utility>
+#include <vector>
+
+#include "../../external/pegtl/nothing.hpp"
+
+#include "../../internal/number_state.hpp"
+#include "../../internal/parse_util.hpp"
+
+#include "bunescape_action.hpp"
+#include "grammar.hpp"
+#include "unescape_action.hpp"
+
+namespace tao::json::jaxn::internal
+{
+   template< typename Rule >
+   struct action
+      : pegtl::nothing< Rule >
+   {};
+
+   template<>
+   struct action< rules::null >
+   {
+      template< typename Consumer >
+      static void apply0( Consumer& consumer )
+      {
+         consumer.null();
+      }
+   };
+
+   template<>
+   struct action< rules::true_ >
+   {
+      template< typename Consumer >
+      static void apply0( Consumer& consumer )
+      {
+         consumer.boolean( true );
+      }
+   };
+
+   template<>
+   struct action< rules::false_ >
+   {
+      template< typename Consumer >
+      static void apply0( Consumer& consumer )
+      {
+         consumer.boolean( false );
+      }
+   };
+
+   template<>
+   struct action< rules::identifier >
+   {
+      template< typename Input, typename Consumer >
+      static void apply( const Input& in, Consumer& consumer )
+      {
+         consumer.key( std::string_view( in.begin(), in.size() ) );
+      }
+   };
+
+   template< bool NEG >
+   struct action< rules::hexnum< NEG > >
+   {
+      template< typename Input, typename Consumer >
+      static void apply( const Input& in, Consumer& consumer )
+      {
+         std::uint64_t value = 0;
+         for( char c : in ) {
+            if( value & 0xF000000000000000 ) {
+               throw pegtl::parse_error( "JAXN hexadecimal number too large", in );
+            }
+            value <<= 4;
+            value += json::internal::hex_char_to_integer< std::uint8_t >( c );
+         }
+         if constexpr( NEG ) {
+            if( value < 9223372036854775808ULL ) {
+               consumer.number( -static_cast< std::int64_t >( value ) );
+            }
+            else if( value == 9223372036854775808ULL ) {
+               consumer.number( static_cast< std::int64_t >( -9223372036854775807LL - 1 ) );
+            }
+            else {
+               throw pegtl::parse_error( "JAXN hexadecimal number too large to negate", in );
+            }
+         }
+         else {
+            consumer.number( value );
+         }
+      }
+   };
+
+   template<>
+   struct action< rules::array::begin >
+   {
+      template< typename Consumer >
+      static void apply0( Consumer& consumer )
+      {
+         consumer.begin_array();
+      }
+   };
+
+   template<>
+   struct action< rules::array::element >
+   {
+      template< typename Consumer >
+      static void apply0( Consumer& consumer )
+      {
+         consumer.element();
+      }
+   };
+
+   template<>
+   struct action< rules::array::end >
+   {
+      template< typename Consumer >
+      static void apply0( Consumer& consumer )
+      {
+         consumer.end_array();
+      }
+   };
+
+   template<>
+   struct action< rules::object::begin >
+   {
+      template< typename Consumer >
+      static void apply0( Consumer& consumer )
+      {
+         consumer.begin_object();
+      }
+   };
+
+   template<>
+   struct action< rules::object::element >
+   {
+      template< typename Consumer >
+      static void apply0( Consumer& consumer )
+      {
+         consumer.member();
+      }
+   };
+
+   template<>
+   struct action< rules::object::end >
+   {
+      template< typename Consumer >
+      static void apply0( Consumer& consumer )
+      {
+         consumer.end_object();
+      }
+   };
+
+   template<>
+   struct action< rules::zero< false > >
+   {
+      template< typename Consumer >
+      static void apply0( Consumer& consumer )
+      {
+         consumer.number( std::uint64_t( 0 ) );
+      }
+   };
+
+   template<>
+   struct action< rules::zero< true > >
+   {
+      template< typename Consumer >
+      static void apply0( Consumer& consumer )
+      {
+         consumer.number( std::int64_t( 0 ) );
+      }
+   };
+
+   template<>
+   struct action< rules::nan >
+   {
+      template< typename Consumer >
+      static void apply0( Consumer& consumer )
+      {
+         consumer.number( NAN );
+      }
+   };
+
+   template<>
+   struct action< rules::infinity< false > >
+   {
+      template< typename Consumer >
+      static void apply0( Consumer& consumer )
+      {
+         consumer.number( INFINITY );
+      }
+   };
+
+   template<>
+   struct action< rules::infinity< true > >
+   {
+      template< typename Consumer >
+      static void apply0( Consumer& consumer )
+      {
+         consumer.number( -INFINITY );
+      }
+   };
+
+   template<>
+   struct action< rules::esign >
+   {
+      template< typename Input, bool NEG >
+      static void apply( const Input& in, json::internal::number_state< NEG >& result )
+      {
+         result.eneg = ( in.peek_char() == '-' );
+      }
+   };
+
+   template<>
+   struct action< rules::idigits >
+   {
+      template< typename Input, bool NEG >
+      static void apply( const Input& in, json::internal::number_state< NEG >& result )
+      {
+         const auto s = in.size();
+
+         if( s == 1 && in.peek_char() == '0' ) {
+            return;
+         }
+
+         if( s > ( 1 << 20 ) ) {
+            throw pegtl::parse_error( "JSON number with 1 megabyte digits", in );
+         }
+
+         const auto c = ( std::min )( s, json::internal::max_mantissa_digits );
+         std::memcpy( result.mantissa, in.begin(), c );
+         result.exponent10 += static_cast< typename json::internal::number_state< NEG >::exponent10_t >( s - c );
+         result.msize = static_cast< typename json::internal::number_state< NEG >::msize_t >( c );
+
+         for( std::size_t i = c; i < s; ++i ) {
+            if( in.peek_char( i ) != '0' ) {
+               result.drop = true;
+               return;
+            }
+         }
+      }
+   };
+
+   template<>
+   struct action< rules::fdigits >
+   {
+      template< typename Input, bool NEG >
+      static void apply( const Input& in, json::internal::number_state< NEG >& result )
+      {
+         result.isfp = true;
+
+         const auto* b = in.begin();
+         const auto* e = in.end();
+
+         while( ( e > b ) && ( e[ -1 ] == '0' ) ) {
+            --e;
+         }
+         if( !result.msize ) {
+            while( ( b < e ) && ( b[ 0 ] == '0' ) ) {
+               ++b;
+               --result.exponent10;
+            }
+         }
+         const auto c = ( std::min )( std::size_t( e - b ), json::internal::max_mantissa_digits - result.msize );
+         std::memcpy( result.mantissa + result.msize, b, c );
+         result.exponent10 -= static_cast< typename json::internal::number_state< NEG >::exponent10_t >( c );
+         result.msize += static_cast< typename json::internal::number_state< NEG >::msize_t >( c );
+
+         for( const auto* r = b + c; r < e; ++r ) {
+            if( *r != '0' ) {
+               result.drop = true;
+               return;
+            }
+         }
+      }
+   };
+
+   template<>
+   struct action< rules::edigits >
+   {
+      template< typename Input, bool NEG >
+      static void apply( const Input& in, json::internal::number_state< NEG >& result )
+      {
+         result.isfp = true;
+
+         const char* b = in.begin();
+
+         while( ( b < in.end() ) && ( b[ 0 ] == '0' ) ) {
+            ++b;
+         }
+         if( ( in.end() - b ) > 9 ) {
+            throw pegtl::parse_error( "JSON exponent has more than 9 significant digits", in );
+         }
+         int exponent10 = 0;
+
+         while( b < in.end() ) {
+            exponent10 = ( exponent10 * 10 ) + ( b[ 0 ] - '0' );
+            ++b;
+         }
+         result.exponent10 += ( result.eneg ? -exponent10 : exponent10 );
+      }
+   };
+
+   template< bool NEG >
+   struct action< rules::number< NEG > >
+      : pegtl::change_states< tao::json::internal::number_state< NEG > >
+   {
+      template< typename Input, typename Consumer >
+      static void success( const Input& /*unused*/, tao::json::internal::number_state< NEG >& state, Consumer& consumer )
+      {
+         state.success( consumer );
+      }
+   };
+
+   template<>
+   struct action< rules::string >
+      : pegtl::change_action_and_states< unescape_action, std::string >
+   {
+      template< typename Input, typename Consumer >
+      static void success( const Input& /*unused*/, std::string& unescaped, Consumer& consumer )
+      {
+         consumer.string( std::move( unescaped ) );
+      }
+   };
+
+   template<>
+   struct action< rules::key >
+      : pegtl::change_action_and_states< unescape_action, std::string >
+   {
+      template< typename Input, typename Consumer >
+      static void success( const Input& /*unused*/, std::string& unescaped, Consumer& consumer )
+      {
+         consumer.key( std::move( unescaped ) );
+      }
+   };
+
+   template<>
+   struct action< rules::binary >
+      : pegtl::change_action_and_states< bunescape_action, std::vector< std::byte > >
+   {
+      template< typename Input, typename Consumer >
+      static void success( const Input& /*unused*/, std::vector< std::byte >& value, Consumer& consumer )
+      {
+         consumer.binary( std::move( value ) );
+      }
+   };
+
+}  // namespace tao::json::jaxn::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/jaxn/internal/bunescape_action.hpp b/3rdParty/taocpp-json/include/tao/json/jaxn/internal/bunescape_action.hpp
new file mode 100644
index 000000000000..1cf981a512a0
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/jaxn/internal/bunescape_action.hpp
@@ -0,0 +1,114 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_JAXN_INTERNAL_BUNESCAPE_ACTION_HPP
+#define TAO_JSON_JAXN_INTERNAL_BUNESCAPE_ACTION_HPP
+
+#include <cstddef>
+#include <vector>
+
+#include "../../external/pegtl/contrib/unescape.hpp"
+#include "../../external/pegtl/nothing.hpp"
+
+#include "grammar.hpp"
+
+namespace tao::json::jaxn::internal
+{
+   template< typename Rule >
+   struct bunescape_action
+      : pegtl::nothing< Rule >
+   {};
+
+   template<>
+   struct bunescape_action< rules::bescaped_char >
+   {
+      template< typename Input >
+      static void apply( const Input& in, std::vector< std::byte >& value )
+      {
+         switch( *in.begin() ) {
+            case '"':
+               value.push_back( std::byte( '"' ) );
+               break;
+
+            case '\'':
+               value.push_back( std::byte( '\'' ) );
+               break;
+
+            case '\\':
+               value.push_back( std::byte( '\\' ) );
+               break;
+
+            case '/':
+               value.push_back( std::byte( '/' ) );
+               break;
+
+            case 'b':
+               value.push_back( std::byte( '\b' ) );
+               break;
+
+            case 'f':
+               value.push_back( std::byte( '\f' ) );
+               break;
+
+            case 'n':
+               value.push_back( std::byte( '\n' ) );
+               break;
+
+            case 'r':
+               value.push_back( std::byte( '\r' ) );
+               break;
+
+            case 't':
+               value.push_back( std::byte( '\t' ) );
+               break;
+
+            case 'v':
+               value.push_back( std::byte( '\v' ) );
+               break;
+
+            case '0':
+               value.push_back( std::byte( '\0' ) );
+               break;
+
+            default:
+               throw pegtl::parse_error( "invalid character in unescape", in );  // LCOV_EXCL_LINE
+         }
+      }
+   };
+
+   template<>
+   struct bunescape_action< rules::bescaped_hexcode >
+   {
+      template< typename Input >
+      static void apply( const Input& in, std::vector< std::byte >& value )
+      {
+         assert( !in.empty() );  // First character MUST be present, usually 'x'.
+         value.push_back( static_cast< std::byte >( pegtl::unescape::unhex_string< char >( in.begin() + 1, in.end() ) ) );
+      }
+   };
+
+   template< char D >
+   struct bunescape_action< rules::bunescaped< D > >
+   {
+      template< typename Input >
+      static void apply( const Input& in, std::vector< std::byte >& value )
+      {
+         const auto begin = reinterpret_cast< const std::byte* >( in.begin() );
+         const auto end = begin + in.size();
+         value.insert( value.end(), begin, end );
+      }
+   };
+
+   template<>
+   struct bunescape_action< rules::bbyte >
+   {
+      template< typename Input >
+      static void apply( const Input& in, std::vector< std::byte >& value )
+      {
+         value.push_back( static_cast< std::byte >( pegtl::unescape::unhex_string< char >( in.begin(), in.end() ) ) );
+      }
+   };
+
+}  // namespace tao::json::jaxn::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/jaxn/internal/errors.hpp b/3rdParty/taocpp-json/include/tao/json/jaxn/internal/errors.hpp
new file mode 100644
index 000000000000..607a143e54fb
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/jaxn/internal/errors.hpp
@@ -0,0 +1,108 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_JAXN_INTERNAL_ERRORS_HPP
+#define TAO_JSON_JAXN_INTERNAL_ERRORS_HPP
+
+#include <string>
+
+#include "../../external/pegtl/normal.hpp"
+#include "../../external/pegtl/parse_error.hpp"
+
+#include "grammar.hpp"
+
+namespace tao::json::jaxn::internal
+{
+   template< typename Rule >
+   struct errors
+      : pegtl::normal< Rule >
+   {
+      static const std::string error_message;
+
+      template< typename Input, typename... States >
+      static void raise( const Input& in, States&&... /*unused*/ )
+      {
+         throw pegtl::parse_error( error_message, in );
+      }
+
+      template< template< typename... > class Action, typename Iterator, typename Input, typename... States >
+      static auto apply( const Iterator& begin, const Input& in, States&&... st )
+         -> decltype( Action< Rule >::apply( std::declval< const typename Input::action_t& >(), st... ) )
+      {
+         try {
+            using action_t = typename Input::action_t;
+            const action_t action_input( begin, in );
+            return Action< Rule >::apply( action_input, st... );
+         }
+         catch( const pegtl::parse_error& ) {
+            throw;
+         }
+         catch( const std::exception& e ) {
+            throw pegtl::parse_error( e.what(), in );
+         }
+      }
+
+      template< template< typename... > class Action, typename Input, typename... States >
+      static auto apply0( const Input& in, States&&... st )
+         -> decltype( Action< Rule >::apply0( st... ) )
+      {
+         try {
+            return Action< Rule >::apply0( st... );
+         }
+         catch( const pegtl::parse_error& ) {
+            throw;
+         }
+         catch( const std::exception& e ) {
+            throw pegtl::parse_error( e.what(), in );
+         }
+      }
+   };
+
+   // clang-format off
+   template<> inline const std::string errors< rules::text >::error_message = "no valid JAXN";
+
+   template<> inline const std::string errors< rules::comment >::error_message = "expected '*' or '/'";
+   template<> inline const std::string errors< rules::line_comment_char >::error_message = "invalid character in line comment";
+   template<> inline const std::string errors< rules::block_comment_char >::error_message = "invalid character in block comment";
+   template<> inline const std::string errors< rules::end_block_comment >::error_message = "unterminated multi-line comment";
+
+   template<> inline const std::string errors< rules::end_array >::error_message = "incomplete array, expected value or ']'";
+   template<> inline const std::string errors< rules::end_object >::error_message = "incomplete object, expected key or '}'";
+   template<> inline const std::string errors< rules::name_separator >::error_message = "expected ':'";
+   template<> inline const std::string errors< rules::value >::error_message = "expected value";
+   template<> inline const std::string errors< rules::sor_value >::error_message = "expected value";
+
+   template<> inline const std::string errors< rules::edigits >::error_message = "expected at least one exponent digit";
+   template<> inline const std::string errors< rules::fdigits >::error_message = "expected at least one fraction digit";
+   template<> inline const std::string errors< rules::nan >::error_message = "invalid numeric literal";
+   template<> inline const std::string errors< rules::infinity< false > >::error_message = "invalid numeric literal";
+   template<> inline const std::string errors< rules::infinity< true > >::error_message = "invalid numeric literal";
+   template<> inline const std::string errors< rules::hexnum< false > >::error_message = "expected at least one hexadecimal digit";
+   template<> inline const std::string errors< rules::hexnum< true > >::error_message = "expected at least one hexadecimal digit";
+
+   template<> inline const std::string errors< rules::xdigit >::error_message = "incomplete universal character name";
+   template<> inline const std::string errors< rules::escaped >::error_message = "unknown escape sequence in string";
+   template<> inline const std::string errors< rules::chars< '"' > >::error_message = "invalid character in string";
+   template<> inline const std::string errors< rules::chars< '\'' > >::error_message = "invalid character in string";
+   template<> inline const std::string errors< rules::qstring_content< '"' > >::error_message = "unterminated string";
+   template<> inline const std::string errors< rules::qstring_content< '\'' > >::error_message = "unterminated string";
+   template<> inline const std::string errors< rules::mchars< '"' > >::error_message = "invalid character in multiline string";
+   template<> inline const std::string errors< rules::mchars< '\'' > >::error_message = "invalid character in multiline string";
+   template<> inline const std::string errors< rules::mqstring_content< '"' > >::error_message = "unterminated multiline string";
+   template<> inline const std::string errors< rules::mqstring_content< '\'' > >::error_message = "unterminated multiline string";
+   template<> inline const std::string errors< rules::string_fragment >::error_message = "expected string";
+
+   template<> inline const std::string errors< rules::bescaped >::error_message = "unknown escape sequence in binary string";
+   template<> inline const std::string errors< rules::bchars< '"' > >::error_message = "invalid character in binary string";
+   template<> inline const std::string errors< rules::bchars< '\'' > >::error_message = "invalid character in binary string";
+   template<> inline const std::string errors< rules::bqstring_content< '"' > >::error_message = "unterminated binary string";
+   template<> inline const std::string errors< rules::bqstring_content< '\'' > >::error_message = "unterminated binary string";
+   template<> inline const std::string errors< rules::bvalue >::error_message = "expected binary";
+   template<> inline const std::string errors< rules::bpart >::error_message = "expected a pair of hexadecimal digits";
+
+   template<> inline const std::string errors< pegtl::eof >::error_message = "unexpected character after JAXN value";
+   // clang-format on
+
+}  // namespace tao::json::jaxn::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/jaxn/internal/grammar.hpp b/3rdParty/taocpp-json/include/tao/json/jaxn/internal/grammar.hpp
new file mode 100644
index 000000000000..d0d55b703e71
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/jaxn/internal/grammar.hpp
@@ -0,0 +1,375 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_JAXN_INTERNAL_GRAMMAR_HPP
+#define TAO_JSON_JAXN_INTERNAL_GRAMMAR_HPP
+
+#include <cctype>
+
+#include "../../external/pegtl.hpp"
+#include "../../external/pegtl/contrib/abnf.hpp"
+
+namespace tao::json::jaxn::internal
+{
+   // clang-format off
+   namespace rules
+   {
+      using namespace pegtl;
+
+      struct line_comment_char : sor< one< '\t' >, utf8::ranges< 0x20, 0x7E, 0x80, 0x10FFFF > > {};
+      struct line_comment : seq< one< '/' >, until< eolf, must< line_comment_char > > > {};
+
+      struct block_comment_char : sor< one< '\t' >, utf8::ranges< 0x20, 0x7E, 0x80, 0x10FFFF >, eol > {};
+      struct end_block_comment : until< pegtl::string< '*', '/' >, must< block_comment_char > > {};
+      struct block_comment : if_must< one< '*' >, end_block_comment > {};
+
+      struct comment : sor< line_comment, block_comment > {};
+
+      struct ws : sor< one< ' ', '\t', '\n', '\r' >, seq< one< '#' >, until< eolf > >, if_must< one< '/' >, comment > > {};
+
+      template< typename R, typename P = ws >
+      using padr = pegtl::internal::seq< R, pegtl::internal::star< P > >;
+
+      struct begin_array : padr< one< '[' > > {};
+      struct begin_object : padr< one< '{' > > {};
+      struct end_array : one< ']' > {};
+      struct end_object : one< '}' > {};
+      struct name_separator : pad< one< ':' >, ws > {};
+      struct value_separator : padr< one< ',' > > {};
+      struct element_separator : padr< one< ',' > > {};
+      struct value_concat : pad< one< '+' >, ws > {};
+
+      struct false_ : pegtl::string< 'f', 'a', 'l', 's', 'e' > {};
+      struct null : pegtl::string< 'n', 'u', 'l', 'l' > {};
+      struct true_ : pegtl::string< 't', 'r', 'u', 'e' > {};
+
+      struct nan : pegtl::string< 'N', 'a', 'N' > {};
+
+      template< bool NEG >
+      struct infinity : pegtl::string< 'I', 'n', 'f', 'i', 'n', 'i', 't', 'y' > {};
+
+      template< bool NEG >
+      struct hexnum : plus< abnf::HEXDIG > {};
+
+      struct digits : plus< abnf::DIGIT > {};
+
+      struct esign : one< '-', '+' > {};
+
+      struct edigits : digits {};
+      struct fdigits : digits {};
+      struct idigits : digits {};
+
+      struct exp : seq< one< 'e', 'E' >, opt< esign >, must< edigits > > {};
+      struct frac0 : seq< one< '.' >, opt< fdigits > > {};
+      struct frac1 : if_must< one< '.' >, fdigits > {};
+
+      template< bool NEG >
+      struct number : seq< sor< seq< idigits, opt< frac0 > >, frac1 >, opt< exp > > {};
+
+      struct xdigit : abnf::HEXDIG {};
+      struct escaped_unicode_code_point_content : seq< one< '{' >, plus< xdigit > > {};
+      struct escaped_unicode_code_point : seq< one< 'u' >, escaped_unicode_code_point_content, one< '}' > > {};
+      struct escaped_unicode : list< seq< one< 'u' >, rep< 4, xdigit > >, one< '\\' > > {};
+
+      struct escaped_char : one< '"', '\'', '\\', '/', 'b', 'f', 'n', 'r', 't', 'v', '0' > {};
+      struct escaped : sor< escaped_char, escaped_unicode_code_point, escaped_unicode > {};
+
+      template< char D >
+      struct unescaped
+      {
+         using analyze_t = pegtl::analysis::generic< pegtl::analysis::rule_type::any >;
+
+         template< typename Input >
+         [[nodiscard]] static bool match( Input& in )
+         {
+            bool result = false;
+
+            while( const std::size_t s = in.size( 4 ) ) {
+               if( const auto t = pegtl::internal::peek_utf8::peek( in, s ) ) {
+                  if( ( 0x20 <= t.data ) && ( t.data <= 0x10FFFF ) && ( t.data != '\\' ) && ( t.data != D ) && ( t.data != 0x7F ) ) {
+                     in.bump_in_this_line( t.size );
+                     result = true;
+                     continue;
+                  }
+               }
+               return result;
+            }
+            throw pegtl::parse_error( "invalid character in string", in );
+         }
+      };
+
+      template< char D >
+      struct chars : if_then_else< one< '\\' >, must< escaped >, unescaped< D > > {};
+
+      template< char D >
+      struct qstring_content : until< at< one< D > >, must< chars< D > > > {};
+
+      template< char D >
+      struct qstring : seq< one< D >, must< qstring_content< D > >, any > {};
+
+      template< char D >
+      struct mchars_non_eol
+      {
+         using analyze_t = pegtl::analysis::generic< pegtl::analysis::rule_type::any >;
+
+         template< typename Input >
+         [[nodiscard]] static bool match( Input& in )
+         {
+            bool result = false;
+
+            while( const std::size_t s = in.size( 4 ) ) {
+               if( const auto t = pegtl::internal::peek_utf8::peek( in, s ) ) {
+                  if( ( ( 0x20 <= t.data ) && ( t.data <= 0x10FFFF ) && ( t.data != D ) && ( t.data != 0x7F ) ) || ( t.data == '\t' ) ) {
+                     in.bump_in_this_line( t.size );
+                     result = true;
+                     continue;
+                  }
+               }
+               return result;
+            }
+            throw pegtl::parse_error( "invalid character in string", in );
+         }
+      };
+
+      template< char D >
+      struct mchars : sor< mchars_non_eol< D >, one< D >, eol > {};
+
+      template< char D >
+      struct mqstring_content : until< at< three< D > >, must< mchars< D > > > {};
+
+      template< char D >
+      struct mqstring : seq< three< D >, opt< eol >, must< mqstring_content< D > >, any, any, any > {};
+
+      struct string_fragment : sor< mqstring< '"' >, mqstring< '\'' >, qstring< '"' >, qstring< '\'' > > {};
+
+      struct string : list_must< string_fragment, value_concat > {};
+
+      struct binary_prefix : one< '$' > {};
+
+      struct bescaped_hexcode : seq< one< 'x' >, rep< 2, must< xdigit > > > {};
+
+      struct bescaped_char : one< '"', '\'', '\\', '/', 'b', 'f', 'n', 'r', 't', 'v', '0' > {};
+      struct bescaped : sor< bescaped_char, bescaped_hexcode > {};
+
+      template< char D >
+      struct bunescaped
+      {
+         using analyze_t = pegtl::analysis::generic< pegtl::analysis::rule_type::any >;
+
+         template< typename Input >
+         [[nodiscard]] static bool match( Input& in )
+         {
+            bool result = false;
+
+            while( !in.empty() ) {
+               const auto t = in.peek_char();
+               if( ( 0x20 <= t ) && ( t <= 0x7E ) && ( t != '\\' ) && ( t != D ) ) {
+                  in.bump_in_this_line( 1 );
+                  result = true;
+                  continue;
+               }
+               return result;
+            }
+            throw pegtl::parse_error( "invalid character in binary string", in );
+         }
+      };
+
+      template< char D >
+      struct bchars : if_then_else< one< '\\' >, must< bescaped >, bunescaped< D > > {};
+
+      template< char D >
+      struct bqstring_content : until< at< one< D > >, must< bchars< D > > > {};
+
+      template< char D >
+      struct bqstring : seq< one< D >, must< bqstring_content< D > >, any > {};
+
+      struct bstring : sor< bqstring< '"' >, bqstring< '\'' > > {};
+
+      struct bbyte : rep< 2, abnf::HEXDIG > {};
+
+      struct bpart : plus< bbyte > {};
+
+      struct bdirect : list_must< bpart, one< '.' > > {};
+
+      struct bvalue : seq< binary_prefix, opt< sor< bstring, bdirect > > > {};
+
+      struct binary : list_must< bvalue, value_concat > {};
+
+      struct value;
+
+      struct array_element;
+      struct array_content : opt< list_tail< array_element, element_separator > > {};
+      struct array : seq< begin_array, array_content, must< end_array > >
+      {
+         using begin = begin_array;
+         using end = end_array;
+         using element = array_element;
+         using content = array_content;
+      };
+
+      struct key : string {};
+
+      struct mkey : sor< key, identifier > {};
+      struct member : if_must< mkey, name_separator, value > {};
+      struct object_content : opt< list_tail< member, value_separator > > {};
+      struct object : seq< begin_object, object_content, must< end_object > >
+      {
+         using begin = begin_object;
+         using end = end_object;
+         using element = member;
+         using content = object_content;
+      };
+
+      template< bool NEG >
+      struct zero : one< '0' > {};
+
+      struct sor_value
+      {
+         using analyze_t = pegtl::analysis::generic< pegtl::analysis::rule_type::sor, string, number< false >, object, array, false_, true_, null >;
+
+         template< typename Rule,
+                   apply_mode A,
+                   template< typename... > class Action,
+                   template< typename... > class Control,
+                   typename Input,
+                   typename... States >
+         [[nodiscard]] static bool match_must( Input& in, States&&... st )
+         {
+            return Control< must< Rule > >::template match< A, rewind_mode::dontcare, Action, Control >( in, st... );
+         }
+
+         template< bool NEG,
+                   apply_mode A,
+                   rewind_mode M,
+                   template< typename... > class Action,
+                   template< typename... > class Control,
+                   typename Input,
+                   typename... States >
+         [[nodiscard]] static bool match_zero( Input& in, States&&... st )
+         {
+            if( in.size( 2 ) > 1 ) {
+               switch( in.peek_char( 1 ) ) {
+               case '.':
+               case 'e':
+               case 'E':
+                  return Control< number< NEG > >::template match< A, M, Action, Control >( in, st... );
+
+               case 'x':
+               case 'X':
+                  in.bump_in_this_line( 2 );
+                  return Control< must< hexnum< NEG > > >::template match< A, M, Action, Control >( in, st... );
+
+               case '0':
+               case '1':
+               case '2':
+               case '3':
+               case '4':
+               case '5':
+               case '6':
+               case '7':
+               case '8':
+               case '9':
+                  throw pegtl::parse_error( "invalid leading zero", in );
+               }
+            }
+            return Control< zero< NEG > >::template match< A, M, Action, Control >( in, st... );
+         }
+
+         template< bool NEG,
+                   apply_mode A,
+                   rewind_mode M,
+                   template< typename... > class Action,
+                   template< typename... > class Control,
+                   typename Input,
+                   typename... States >
+         [[nodiscard]] static bool match_number( Input& in, States&&... st )
+         {
+            switch( in.peek_char() ) {
+            case 'N':
+               return Control< must< nan > >::template match< A, M, Action, Control >( in, st... );
+
+            case 'I':
+               return Control< must< infinity< NEG > > >::template match< A, M, Action, Control >( in, st... );
+
+            case '0':
+               if( !match_zero< NEG, A, rewind_mode::dontcare, Action, Control >( in, st... ) ) {
+                  throw pegtl::parse_error( "incomplete number", in );
+               }
+               return true;
+
+            default:
+               return Control< number< NEG > >::template match< A, M, Action, Control >( in, st... );
+            }
+         }
+
+         template< apply_mode A,
+                   rewind_mode M,
+                   template< typename... > class Action,
+                   template< typename... > class Control,
+                   typename Input,
+                   typename... States >
+         [[nodiscard]] static bool match_impl( Input& in, States&&... st )
+         {
+            switch( in.peek_char() ) {
+            case '{': return Control< object >::template match< A, M, Action, Control >( in, st... );
+            case '[': return Control< array >::template match< A, M, Action, Control >( in, st... );
+            case 'n': return Control< null >::template match< A, M, Action, Control >( in, st... );
+            case 't': return Control< true_ >::template match< A, M, Action, Control >( in, st... );
+            case 'f': return Control< false_ >::template match< A, M, Action, Control >( in, st... );
+
+            case '"':
+            case '\'':
+               return Control< string >::template match< A, M, Action, Control >( in, st... );
+
+            case '$':
+               return Control< binary >::template match< A, M, Action, Control >( in, st... );
+
+            case '+':
+               in.bump_in_this_line();
+               if( in.empty() || !match_number< false, A, rewind_mode::dontcare, Action, Control >( in, st... ) ) {
+                  throw pegtl::parse_error( "incomplete number", in );
+               }
+               return true;
+
+            case '-':
+               in.bump_in_this_line();
+               if( in.empty() || !match_number< true, A, rewind_mode::dontcare, Action, Control >( in, st... ) ) {
+                  throw pegtl::parse_error( "incomplete number", in );
+               }
+               return true;
+
+            default:
+               return match_number< false, A, M, Action, Control >( in, st... );
+            }
+         }
+
+         template< apply_mode A,
+                   rewind_mode M,
+                   template< typename... > class Action,
+                   template< typename... > class Control,
+                   typename Input,
+                   typename... States >
+         [[nodiscard]] static bool match( Input& in, States&&... st )
+         {
+            if( in.size( 2 ) && match_impl< A, M, Action, Control >( in, st... ) ) {
+               in.discard();
+               return true;
+            }
+            return false;
+         }
+      };
+
+      struct value : padr< sor_value > {};
+      struct array_element : value {};
+
+      struct text : seq< star< ws >, value > {};
+
+   }  // namespace rules
+
+   struct grammar : pegtl::must< rules::text, pegtl::eof > {};
+   struct embedded : pegtl::must< rules::sor_value > {};
+   // clang-format on
+
+}  // namespace tao::json::jaxn::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/jaxn/internal/integer.hpp b/3rdParty/taocpp-json/include/tao/json/jaxn/internal/integer.hpp
new file mode 100644
index 000000000000..b4b72dbc65b3
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/jaxn/internal/integer.hpp
@@ -0,0 +1,256 @@
+// Copyright (c) 2019-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_JAXN_INTERNAL_INTEGER_HPP
+#define TAO_JSON_JAXN_INTERNAL_INTEGER_HPP
+
+#include <cassert>
+#include <cstdint>
+#include <cstdlib>
+
+#include <string_view>
+#include <type_traits>
+
+#include "../../external/pegtl.hpp"
+#include "../../external/pegtl/contrib/integer.hpp"
+
+#include "../../internal/parse_util.hpp"
+
+namespace tao::json::jaxn::internal::integer
+{
+   struct unsigned_rule
+      : pegtl::if_then_else< pegtl::one< '0' >, pegtl::if_then_else< pegtl::one< 'x' >, pegtl::plus< pegtl::xdigit >, pegtl::not_at< pegtl::digit > >, pegtl::plus< pegtl::digit > >
+   {
+      // Unsigned hex or dec integer, no leading zeros for dec.
+   };
+
+   struct signed_rule
+      : pegtl::seq< pegtl::opt< pegtl::one< '-', '+' > >, unsigned_rule >
+   {
+      // Signed hex or dec integer, no leading zeros for dec.
+   };
+
+   [[nodiscard]] constexpr bool is_hex_digit( const char c ) noexcept
+   {
+      // We don't use std::isxdigit() because it might
+      // return true for other values on MS platforms?
+
+      return ( ( '0' <= c ) && ( c <= '9' ) ) || ( ( 'a' <= c ) && ( c <= 'f' ) ) || ( ( 'A' <= c ) && ( c <= 'F' ) );
+   }
+
+   template< typename Integer, Integer Maximum = ( std::numeric_limits< Integer >::max )() >
+   [[nodiscard]] constexpr bool accumulate_hex_digit( Integer& result, const char xdigit ) noexcept
+   {
+      // Assumes that xdigit is an xdigit as per is_hex_digit(); returns false on overflow.
+
+      static_assert( std::is_integral_v< Integer > );
+
+      constexpr Integer cutoff = Maximum / 16;
+      constexpr Integer cutlim = Maximum % 16;
+
+      const Integer c = json::internal::hex_char_to_integer< Integer >( xdigit );
+
+      if( ( result > cutoff ) || ( ( result == cutoff ) && ( c > cutlim ) ) ) {
+         return false;
+      }
+      result *= 16;
+      result += c;
+      return true;
+   }
+
+   template< typename Integer, Integer Maximum = ( std::numeric_limits< Integer >::max )() >
+   [[nodiscard]] constexpr bool accumulate_hex_digits( Integer& result, const std::string_view input ) noexcept
+   {
+      // Assumes input is a non-empty sequence of hex-digits; returns false on overflow.
+
+      for( const auto c : input ) {
+         if( !accumulate_hex_digit< Integer, Maximum >( result, c ) ) {
+            return false;
+         }
+      }
+      return true;
+   }
+
+   template< typename Integer, Integer Maximum = ( std::numeric_limits< Integer >::max )() >
+   [[nodiscard]] constexpr bool convert_hex_positive( Integer& result, const std::string_view input ) noexcept
+   {
+      // Assumes result == 0 and that input is a non-empty sequence of hex-digits; returns false on overflow.
+
+      static_assert( std::is_integral_v< Integer > );
+      return accumulate_hex_digits< Integer, Maximum >( result, input );
+   }
+
+   template< typename Signed >
+   [[nodiscard]] constexpr bool convert_hex_negative( Signed& result, const std::string_view input ) noexcept
+   {
+      // Assumes result == 0 and that input is a non-empty sequence of hex-digits; returns false on overflow.
+
+      static_assert( std::is_signed_v< Signed > );
+      using Unsigned = std::make_unsigned_t< Signed >;
+      constexpr Unsigned maximum = static_cast< Unsigned >( ( std::numeric_limits< Signed >::max )() ) + 1;
+      Unsigned temporary = 0;
+      if( accumulate_hex_digits< Unsigned, maximum >( temporary, input ) ) {
+         result = static_cast< Signed >( ~temporary ) + 1;
+         return true;
+      }
+      return false;
+   }
+
+   template< typename Unsigned, Unsigned Maximum = ( std::numeric_limits< Unsigned >::max )() >
+   [[nodiscard]] constexpr bool convert_hex_unsigned( Unsigned& result, const std::string_view input ) noexcept
+   {
+      // Assumes result == 0 and that input is a non-empty sequence of hex-digits; returns false on overflow.
+
+      static_assert( std::is_unsigned_v< Unsigned > );
+      return accumulate_hex_digits< Unsigned, Maximum >( result, input );
+   }
+
+   template< typename Signed >
+   [[nodiscard]] constexpr bool convert_hex_signed( Signed& result, const std::string_view input ) noexcept
+   {
+      // Assumes result == 0 and that input is an optional sign followed by a "0x" and a non-empty sequence of hex-digits; returns false on overflow.
+
+      static_assert( std::is_signed_v< Signed > );
+      if( input[ 0 ] == '-' ) {
+         return convert_hex_negative< Signed >( result, std::string_view( input.data() + 3, input.size() - 3 ) );
+      }
+      const auto offset = unsigned( input[ 0 ] == '+' ) + 2;  // The "0x" prefix has length 2.
+      return convert_hex_positive< Signed >( result, std::string_view( input.data() + offset, input.size() - offset ) );
+   }
+
+   using unsigned_dec_action = pegtl::integer::unsigned_action;
+
+   struct unsigned_hex_action
+   {
+      // Assumes that 'in' contains a non-empty sequence of ASCII hex-digits with "0x" prefix.
+
+      template< typename Input >
+      static auto apply( const Input& in, std::uint64_t& st )
+      {
+         auto sv = in.string_view();
+         sv.remove_prefix( 2 );
+         if( !convert_hex_unsigned( st, sv ) ) {
+            throw pegtl::parse_error( "unsigned hex integer overflow", in );
+         }
+      }
+   };
+
+   template< typename Rule >
+   struct unsigned_action_action
+      : pegtl::nothing< Rule >
+   {
+   };
+
+   template<>
+   struct unsigned_action_action< pegtl::plus< pegtl::digit > >
+      : unsigned_dec_action
+   {
+   };
+
+   template<>
+   struct unsigned_action_action< pegtl::plus< pegtl::xdigit > >
+   {
+      template< typename Input, typename Unsigned >
+      static void apply( const Input& in, Unsigned& st )
+      {
+         if( !convert_hex_unsigned( st, in.string_view() ) ) {
+            throw pegtl::parse_error( "unsigned hex integer overflow", in );
+         }
+      }
+   };
+
+   struct unsigned_rule_with_action
+   {
+      using analyze_t = unsigned_rule::analyze_t;
+
+      template< pegtl::apply_mode,
+                pegtl::rewind_mode,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class Control,
+                typename Input >
+      [[nodiscard]] static auto match( Input& in, std::uint64_t& st )
+      {
+         return pegtl::parse< unsigned_rule, unsigned_action_action >( in, st );  // Throws on overflow.
+      }
+   };
+
+   using signed_dec_action = pegtl::integer::signed_action;
+
+   struct signed_hex_action
+   {
+      // Assumes that 'in' contains a non-empty sequence of ASCII hex-digits,
+      // with optional leading sign before the "0x" prefix; when there is a
+      // sign, in.size() must be >= 4.
+
+      template< typename Input >
+      static auto apply( const Input& in, std::int64_t& st )
+      {
+         if( !convert_hex_signed( st, in.string_view() ) ) {
+            throw pegtl::parse_error( "signed hex integer overflow", in );
+         }
+      }
+   };
+
+   template< typename Rule >
+   struct signed_action_action
+      : pegtl::nothing< Rule >
+   {
+   };
+
+   template<>
+   struct signed_action_action< pegtl::one< '-', '+' > >
+   {
+      template< typename Input, typename Signed >
+      static void apply( const Input& in, bool& negative, Signed& /*unused*/ )
+      {
+         negative = ( in.peek_char() == '-' );  // TODO: Optimise with custom rule to prevent building marker and action_input for single char?
+      }
+   };
+
+   template<>
+   struct signed_action_action< pegtl::plus< pegtl::digit > >
+   {
+      template< typename Input, typename Signed >
+      static void apply( const Input& in, const bool negative, Signed& st )
+      {
+         if( !( negative ? pegtl::integer::internal::convert_negative< Signed >( st, in.string_view() ) : pegtl::integer::internal::convert_positive< Signed >( st, in.string_view() ) ) ) {
+            throw pegtl::parse_error( "signed dec integer overflow", in );
+         }
+      }
+   };
+
+   template<>
+   struct signed_action_action< pegtl::plus< pegtl::xdigit > >
+   {
+      template< typename Input, typename Signed >
+      static void apply( const Input& in, const bool negative, Signed& st )
+      {
+         if( !( negative ? convert_hex_negative< Signed >( st, in.string_view() ) : convert_hex_positive< Signed >( st, in.string_view() ) ) ) {
+            throw pegtl::parse_error( "signed hex integer overflow", in );
+         }
+      }
+   };
+
+   struct signed_rule_with_action
+   {
+      using analyze_t = signed_rule::analyze_t;
+
+      template< pegtl::apply_mode,
+                pegtl::rewind_mode,
+                template< typename... >
+                class Action,
+                template< typename... >
+                class Control,
+                typename Input >
+      [[nodiscard]] static auto match( Input& in, std::int64_t& st )
+      {
+         bool negative = false;                                                         // Superfluous initialisation.
+         return pegtl::parse< signed_rule, signed_action_action >( in, negative, st );  // Throws on overflow.
+      }
+   };
+
+}  // namespace tao::json::jaxn::internal::integer
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/jaxn/internal/unescape_action.hpp b/3rdParty/taocpp-json/include/tao/json/jaxn/internal/unescape_action.hpp
new file mode 100644
index 000000000000..48b46bb5c59b
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/jaxn/internal/unescape_action.hpp
@@ -0,0 +1,28 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_JAXN_INTERNAL_UNESCAPE_ACTION_HPP
+#define TAO_JSON_JAXN_INTERNAL_UNESCAPE_ACTION_HPP
+
+#include "../../external/pegtl/contrib/unescape.hpp"
+#include "../../external/pegtl/nothing.hpp"
+
+#include "grammar.hpp"
+
+namespace tao::json::jaxn::internal
+{
+   // clang-format off
+   template< typename Rule > struct unescape_action : pegtl::nothing< Rule > {};
+
+   template<> struct unescape_action< rules::escaped_char > : pegtl::unescape::unescape_c< rules::escaped_char, '"', '\'', '\\', '/', '\b', '\f', '\n', '\r', '\t', '\v', '\0' > {};
+   template<> struct unescape_action< rules::escaped_unicode > : pegtl::unescape::unescape_j {};
+   template<> struct unescape_action< rules::escaped_unicode_code_point_content > : pegtl::unescape::unescape_u {};
+
+   template<> struct unescape_action< rules::identifier > : pegtl::unescape::append_all {};  // For parts_parser.
+   template< char D > struct unescape_action< rules::unescaped< D > > : pegtl::unescape::append_all {};
+   template< char D > struct unescape_action< rules::mchars< D > > : pegtl::unescape::append_all {};
+   // clang-format on
+
+}  // namespace tao::json::jaxn::internal
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/jaxn/is_identifier.hpp b/3rdParty/taocpp-json/include/tao/json/jaxn/is_identifier.hpp
new file mode 100644
index 000000000000..8268c5753fe2
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/jaxn/is_identifier.hpp
@@ -0,0 +1,27 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_JAXN_IS_IDENTIFIER_HPP
+#define TAO_JSON_JAXN_IS_IDENTIFIER_HPP
+
+#include <cctype>
+#include <string_view>
+
+namespace tao::json::jaxn
+{
+   [[nodiscard]] inline bool is_identifier( const std::string_view v ) noexcept
+   {
+      if( v.empty() || std::isdigit( v[ 0 ] ) ) {
+         return false;
+      }
+      for( const auto c : v ) {
+         if( !std::isalnum( c ) && c != '_' ) {
+            return false;
+         }
+      }
+      return true;
+   }
+
+}  // namespace tao::json::jaxn
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/jaxn/parts_parser.hpp b/3rdParty/taocpp-json/include/tao/json/jaxn/parts_parser.hpp
new file mode 100644
index 000000000000..61240c321dcc
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/jaxn/parts_parser.hpp
@@ -0,0 +1,263 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_JAXN_PARTS_PARSER_HPP
+#define TAO_JSON_JAXN_PARTS_PARSER_HPP
+
+#include "../parts_parser.hpp"
+
+#include "internal/action.hpp"
+#include "internal/bunescape_action.hpp"
+#include "internal/grammar.hpp"
+#include "internal/integer.hpp"
+#include "internal/unescape_action.hpp"
+
+namespace tao::json::jaxn
+{
+   namespace internal
+   {
+      namespace rules
+      {
+         struct double_rule
+         {
+            using analyze_t = pegtl::analysis::generic< pegtl::analysis::rule_type::any >;
+
+            template< apply_mode A,
+                      rewind_mode M,
+                      template< typename... >
+                      class Action,
+                      template< typename... >
+                      class Control,
+                      typename Input,
+                      typename... States >
+            [[nodiscard]] static bool match_impl( Input& in, States&&... st )
+            {
+               switch( in.peek_char() ) {
+                  case '+':
+                     in.bump_in_this_line();
+                     if( in.empty() || !sor_value::match_number< false, A, rewind_mode::dontcare, Action, Control >( in, st... ) ) {
+                        throw pegtl::parse_error( "incomplete number", in );
+                     }
+                     return true;
+
+                  case '-':
+                     in.bump_in_this_line();
+                     if( in.empty() || !sor_value::match_number< true, A, rewind_mode::dontcare, Action, Control >( in, st... ) ) {
+                        throw pegtl::parse_error( "incomplete number", in );
+                     }
+                     return true;
+
+                  default:
+                     return sor_value::match_number< false, A, M, Action, Control >( in, st... );
+               }
+            }
+
+            template< apply_mode A,
+                      rewind_mode M,
+                      template< typename... >
+                      class Action,
+                      template< typename... >
+                      class Control,
+                      typename Input,
+                      typename... States >
+            [[nodiscard]] static bool match( Input& in, States&&... st )
+            {
+               return in.size( 2 ) && match_impl< A, M, Action, Control >( in, st... );
+            }
+         };
+
+      }  // namespace rules
+
+      template< typename Rule >
+      struct double_action
+         : action< Rule >
+      {};
+
+      template< bool NEG >
+      struct double_action< rules::number< NEG > >
+         : pegtl::change_states< json::internal::number_state< NEG > >
+      {
+         template< typename Input, typename Consumer >
+         static void success( const Input& /*unused*/, json::internal::number_state< NEG >& state, Consumer& consumer )
+         {
+            state.success( consumer );
+         }
+      };
+
+   }  // namespace internal
+
+   // TODO: Optimise some of the simpler cases?
+
+   template< typename Input = pegtl::string_input< pegtl::tracking_mode::lazy, pegtl::eol::lf_crlf, std::string > >
+   class basic_parts_parser
+   {
+   public:
+      template< typename... Ts >
+      explicit basic_parts_parser( Ts&&... ts )
+         : m_input( std::forward< Ts >( ts )... )
+      {
+         pegtl::parse< json::internal::rules::wss >( m_input );
+      }
+
+      [[nodiscard]] bool empty()  // noexcept( noexcept( m_input.empty() ) )
+      {
+         return m_input.empty();
+      }
+
+      [[nodiscard]] bool null()
+      {
+         return pegtl::parse< pegtl::seq< json::internal::rules::null, json::internal::rules::wss > >( m_input );
+      }
+
+      [[nodiscard]] bool boolean()
+      {
+         bool r;
+         pegtl::parse< pegtl::must< json::internal::rules::boolean, json::internal::rules::wss > >( m_input, r );
+         return r;
+      }
+
+      [[nodiscard]] double number_double()
+      {
+         json::internal::double_state_and_consumer st;
+         pegtl::parse< pegtl::must< internal::rules::double_rule, json::internal::rules::wss >, internal::double_action >( m_input, st );
+         return st.converted;
+      }
+
+      [[nodiscard]] std::int64_t number_signed()
+      {
+         std::int64_t st = 0;
+         pegtl::parse< pegtl::must< internal::integer::signed_rule_with_action, json::internal::rules::wss > >( m_input, st );
+         return st;
+      }
+
+      [[nodiscard]] std::uint64_t number_unsigned()
+      {
+         std::uint64_t st = 0;
+         pegtl::parse< pegtl::must< internal::integer::unsigned_rule_with_action, json::internal::rules::wss > >( m_input, st );
+         return st;
+      }
+
+      [[nodiscard]] std::string string()
+      {
+         std::string unescaped;
+         pegtl::parse< pegtl::must< internal::rules::string, json::internal::rules::wss >, internal::unescape_action >( m_input, unescaped );
+         return unescaped;
+      }
+
+      // TODO: std::string_view string_view() that only works for strings without escape sequences?
+
+      [[nodiscard]] std::vector< std::byte > binary()
+      {
+         std::vector< std::byte > data;
+         pegtl::parse< pegtl::must< internal::rules::binary, json::internal::rules::wss >, internal::bunescape_action >( m_input, data );
+         return data;
+      }
+
+      [[nodiscard]] std::string key()
+      {
+         std::string unescaped;
+         pegtl::parse< pegtl::must< internal::rules::mkey, json::internal::rules::wss, pegtl::one< ':' >, json::internal::rules::wss >, internal::unescape_action >( m_input, unescaped );
+         return unescaped;
+      }
+
+      // TODO: std::string_view key_view() that only works for identifiers (and possibly strings without escape sequences)?
+
+   protected:
+      template< char C >
+      void parse_single_must()
+      {
+         pegtl::parse< pegtl::must< pegtl::one< C >, json::internal::rules::wss > >( m_input );
+      }
+
+      template< char C >
+      bool parse_single_test()
+      {
+         return pegtl::parse< pegtl::seq< pegtl::one< C >, json::internal::rules::wss > >( m_input );
+      }
+
+      struct state_t
+      {
+         std::size_t i = 0;
+         static constexpr std::size_t* size = nullptr;
+      };
+
+   public:
+      [[nodiscard]] state_t begin_array()
+      {
+         parse_single_must< '[' >();
+         return state_t();
+      }
+
+      void end_array( state_t& /*unused*/ )
+      {
+         parse_single_must< ']' >();
+      }
+
+      void element( state_t& p )
+      {
+         if( p.i++ ) {
+            parse_single_must< ',' >();
+         }
+      }
+
+      [[nodiscard]] bool element_or_end_array( state_t& p )
+      {
+         if( parse_single_test< ']' >() ) {
+            return false;
+         }
+         element( p );
+         return true;
+      }
+
+      [[nodiscard]] state_t begin_object()
+      {
+         parse_single_must< '{' >();
+         return state_t();
+      }
+
+      void end_object( state_t& /*unused*/ )
+      {
+         parse_single_must< '}' >();
+      }
+
+      void member( state_t& p )
+      {
+         if( p.i++ ) {
+            parse_single_must< ',' >();
+         }
+      }
+
+      [[nodiscard]] bool member_or_end_object( state_t& p )
+      {
+         if( parse_single_test< '}' >() ) {
+            return false;
+         }
+         member( p );
+         return true;
+      }
+
+      void skip_value()
+      {
+         pegtl::parse< pegtl::must< pegtl::json::value > >( m_input );  // Includes right-padding.
+      }
+
+      [[nodiscard]] auto mark()  // noexcept( noexcept( m_input.template mark< pegtl::rewind_mode::required >() ) )
+      {
+         return m_input.template mark< pegtl::rewind_mode::required >();
+      }
+
+      template< typename T >
+      void throw_parse_error( T&& t ) const
+      {
+         throw pegtl::parse_error( std::forward< T >( t ), m_input );
+      }
+
+   protected:
+      Input m_input;
+   };
+
+   using parts_parser = basic_parts_parser<>;
+
+}  // namespace tao::json::jaxn
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/jaxn/to_stream.hpp b/3rdParty/taocpp-json/include/tao/json/jaxn/to_stream.hpp
new file mode 100644
index 000000000000..ba0a6a0c5287
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/jaxn/to_stream.hpp
@@ -0,0 +1,36 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_JAXN_TO_STREAM_HPP
+#define TAO_JSON_JAXN_TO_STREAM_HPP
+
+#include <cstddef>
+#include <ostream>
+
+#include "../value.hpp"
+
+#include "../events/from_value.hpp"
+#include "../events/transformer.hpp"
+
+#include "events/to_pretty_stream.hpp"
+#include "events/to_stream.hpp"
+
+namespace tao::json::jaxn
+{
+   template< template< typename... > class... Transformers, template< typename... > class Traits >
+   void to_stream( std::ostream& os, const basic_value< Traits >& v )
+   {
+      json::events::transformer< events::to_stream, Transformers... > consumer( os );
+      json::events::from_value( consumer, v );
+   }
+
+   template< template< typename... > class... Transformers, template< typename... > class Traits >
+   void to_stream( std::ostream& os, const basic_value< Traits >& v, const std::size_t indent )
+   {
+      json::events::transformer< events::to_pretty_stream, Transformers... > consumer( os, indent );
+      json::events::from_value( consumer, v );
+   }
+
+}  // namespace tao::json::jaxn
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/jaxn/to_string.hpp b/3rdParty/taocpp-json/include/tao/json/jaxn/to_string.hpp
new file mode 100644
index 000000000000..5b64c8cd1fd4
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/jaxn/to_string.hpp
@@ -0,0 +1,33 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_JAXN_TO_STRING_HPP
+#define TAO_JSON_JAXN_TO_STRING_HPP
+
+#include <sstream>
+
+#include "../value.hpp"
+
+#include "to_stream.hpp"
+
+namespace tao::json::jaxn
+{
+   template< template< typename... > class... Transformers, template< typename... > class Traits >
+   [[nodiscard]] std::string to_string( const basic_value< Traits >& v )
+   {
+      std::ostringstream o;
+      jaxn::to_stream< Transformers... >( o, v );
+      return o.str();
+   }
+
+   template< template< typename... > class... Transformers, template< typename... > class Traits >
+   [[nodiscard]] std::string to_string( const basic_value< Traits >& v, const unsigned indent )
+   {
+      std::ostringstream o;
+      jaxn::to_stream< Transformers... >( o, v, indent );
+      return o.str();
+   }
+
+}  // namespace tao::json::jaxn
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/message_extension.hpp b/3rdParty/taocpp-json/include/tao/json/message_extension.hpp
new file mode 100644
index 000000000000..f524354b10c9
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/message_extension.hpp
@@ -0,0 +1,49 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_MESSAGE_EXTENSION_HPP
+#define TAO_JSON_MESSAGE_EXTENSION_HPP
+
+#include <ostream>
+#include <string>
+
+namespace tao::json
+{
+   template< typename T, typename = void >
+   struct message_extension
+   {
+      const T& m_v;
+
+      explicit message_extension( const T& v ) noexcept
+         : m_v( v )
+      {}
+
+      friend std::ostream& operator<<( std::ostream& os, const message_extension& /*unused*/ ) noexcept
+      {
+         return os;
+      }
+   };
+
+   template< typename T >
+   struct message_extension< T, decltype( std::declval< const T& >().public_base().append_message_extension( std::declval< std::ostream& >() ), void() ) >
+   {
+      const T& m_v;
+
+      explicit message_extension( const T& v ) noexcept
+         : m_v( v )
+      {}
+
+      friend std::ostream& operator<<( std::ostream& os, const message_extension& v )
+      {
+         os << ' ';
+         v.m_v.public_base().append_message_extension( os );
+         return os;
+      }
+   };
+
+   template< typename T >
+   message_extension( const T& )->message_extension< T >;
+
+}  // namespace tao::json
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/operators.hpp b/3rdParty/taocpp-json/include/tao/json/operators.hpp
new file mode 100644
index 000000000000..d09edbe70bd2
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/operators.hpp
@@ -0,0 +1,494 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_OPERATORS_HPP
+#define TAO_JSON_OPERATORS_HPP
+
+#include "basic_value.hpp"
+
+#include "internal/format.hpp"
+
+namespace tao::json
+{
+   template< template< typename... > class TraitsL, template< typename... > class TraitsR >
+   [[nodiscard]] bool operator==( const basic_value< TraitsL >& lhs, const basic_value< TraitsR >& rhs ) noexcept
+   {
+      if( rhs.is_value_ptr() ) {
+         return lhs == rhs.skip_value_ptr();
+      }
+      if( lhs.type() != rhs.type() ) {
+         switch( lhs.type() ) {
+            case type::VALUE_PTR:
+               return lhs.skip_value_ptr() == rhs;
+
+            case type::SIGNED:
+               if( rhs.type() == type::UNSIGNED ) {
+                  const auto v = lhs.get_signed();
+                  return ( v >= 0 ) && ( static_cast< std::uint64_t >( v ) == rhs.get_unsigned() );
+               }
+               if( rhs.type() == type::DOUBLE ) {
+                  return lhs.get_signed() == rhs.get_double();
+               }
+               break;
+
+            case type::UNSIGNED:
+               if( rhs.type() == type::SIGNED ) {
+                  const auto v = rhs.get_signed();
+                  return ( v >= 0 ) && ( lhs.get_unsigned() == static_cast< std::uint64_t >( v ) );
+               }
+               if( rhs.type() == type::DOUBLE ) {
+                  return lhs.get_unsigned() == rhs.get_double();
+               }
+               break;
+
+            case type::DOUBLE:
+               if( rhs.type() == type::SIGNED ) {
+                  return lhs.get_double() == rhs.get_signed();
+               }
+               if( rhs.type() == type::UNSIGNED ) {
+                  return lhs.get_double() == rhs.get_unsigned();
+               }
+               break;
+
+            case type::STRING:
+               if( rhs.type() == type::STRING_VIEW ) {
+                  return lhs.get_string() == rhs.get_string_view();
+               }
+               break;
+
+            case type::STRING_VIEW:
+               if( rhs.type() == type::STRING ) {
+                  return lhs.get_string_view() == rhs.get_string();
+               }
+               break;
+
+            case type::BINARY:
+               if( rhs.type() == type::BINARY_VIEW ) {
+                  return tao::internal::binary_equal( lhs.get_binary(), rhs.get_binary_view() );
+               }
+               break;
+
+            case type::BINARY_VIEW:
+               if( rhs.type() == type::BINARY ) {
+                  return tao::internal::binary_equal( lhs.get_binary_view(), rhs.get_binary() );
+               }
+               break;
+
+            case type::OPAQUE_PTR:
+               assert( lhs.type() != type::OPAQUE_PTR );
+               break;
+
+            default:
+               break;
+         }
+         assert( rhs.type() != type::OPAQUE_PTR );
+         return false;
+      }
+
+      switch( lhs.type() ) {
+         case type::UNINITIALIZED:
+            return true;
+
+         case type::NULL_:
+            return true;
+
+         case type::BOOLEAN:
+            return lhs.get_boolean() == rhs.get_boolean();
+
+         case type::SIGNED:
+            return lhs.get_signed() == rhs.get_signed();
+
+         case type::UNSIGNED:
+            return lhs.get_unsigned() == rhs.get_unsigned();
+
+         case type::DOUBLE:
+            return lhs.get_double() == rhs.get_double();
+
+         case type::STRING:
+            return lhs.get_string() == rhs.get_string();
+
+         case type::STRING_VIEW:
+            return lhs.get_string_view() == rhs.get_string_view();
+
+         case type::BINARY:
+            return lhs.get_binary() == rhs.get_binary();
+
+         case type::BINARY_VIEW:
+            return tao::internal::binary_equal( lhs.get_binary_view(), rhs.get_binary_view() );
+
+         case type::ARRAY:
+            return lhs.get_array() == rhs.get_array();
+
+         case type::OBJECT:
+            return lhs.get_object() == rhs.get_object();
+
+         case type::VALUE_PTR:
+            assert( lhs.type() != type::VALUE_PTR );
+            break;  // LCOV_EXCL_LINE
+
+         case type::OPAQUE_PTR:
+            assert( lhs.type() != type::OPAQUE_PTR );
+            break;  // LCOV_EXCL_LINE
+
+         case type::VALUELESS_BY_EXCEPTION:
+            assert( lhs.type() != type::VALUELESS_BY_EXCEPTION );
+            break;  // LCOV_EXCL_LINE
+      }
+      // LCOV_EXCL_START
+      assert( false );
+      return false;
+      // LCOV_EXCL_STOP
+   }
+
+   template< template< typename... > class Traits, int = 1 >  // work-around for Visual C++
+   [[nodiscard]] bool operator==( const basic_value< Traits >& lhs, tao::internal::identity_t< basic_value< Traits > > rhs ) noexcept
+   {
+      return lhs == rhs;
+   }
+
+   template< template< typename... > class Traits, int = 2 >  // work-around for Visual C++
+   [[nodiscard]] bool operator==( tao::internal::identity_t< basic_value< Traits > > lhs, const basic_value< Traits >& rhs ) noexcept
+   {
+      return lhs == rhs;
+   }
+
+   template< template< typename... > class Traits, typename T >
+   [[nodiscard]] bool operator==( const basic_value< Traits >& lhs, const std::optional< T >& rhs ) noexcept
+   {
+      static_assert( noexcept( Traits< std::optional< T > >::equal( lhs, rhs ) ), "equal must be noexcept" );
+      return Traits< std::optional< T > >::equal( lhs, rhs );
+   }
+
+   template< typename T, template< typename... > class Traits >
+   [[nodiscard]] bool operator==( const std::optional< T >& lhs, const basic_value< Traits >& rhs ) noexcept
+   {
+      return rhs == lhs;
+   }
+
+   template< template< typename... > class Traits, typename T >
+   [[nodiscard]] auto operator==( const basic_value< Traits >& lhs, const T& rhs ) noexcept -> decltype( Traits< std::decay_t< T > >::equal( lhs, rhs ) )
+   {
+      using D = std::decay_t< T >;
+      static_assert( noexcept( Traits< D >::equal( lhs, rhs ) ), "equal must be noexcept" );
+      return Traits< D >::equal( lhs, rhs );
+   }
+
+   template< typename T, template< typename... > class Traits >
+   [[nodiscard]] auto operator==( const T& lhs, const basic_value< Traits >& rhs ) noexcept -> decltype( Traits< std::decay_t< T > >::equal( rhs, lhs ) )
+   {
+      return rhs == lhs;
+   }
+
+   template< template< typename... > class TraitsL, template< typename... > class TraitsR >
+   [[nodiscard]] bool operator!=( const basic_value< TraitsL >& lhs, const basic_value< TraitsR >& rhs ) noexcept
+   {
+      return !( lhs == rhs );
+   }
+
+   template< template< typename... > class Traits, typename T >
+   [[nodiscard]] bool operator!=( const basic_value< Traits >& lhs, const std::optional< T >& rhs ) noexcept
+   {
+      return !( lhs == rhs );
+   }
+
+   template< typename T, template< typename... > class Traits >
+   [[nodiscard]] bool operator!=( const std::optional< T >& lhs, const basic_value< Traits >& rhs ) noexcept
+   {
+      return !( rhs == lhs );
+   }
+
+   template< template< typename... > class Traits, typename T >
+   [[nodiscard]] bool operator!=( const basic_value< Traits >& lhs, const T& rhs ) noexcept
+   {
+      return !( lhs == rhs );
+   }
+
+   template< typename T, template< typename... > class Traits >
+   [[nodiscard]] bool operator!=( const T& lhs, const basic_value< Traits >& rhs ) noexcept
+   {
+      return !( lhs == rhs );
+   }
+
+   template< template< typename... > class TraitsL, template< typename... > class TraitsR >
+   [[nodiscard]] bool operator<( const basic_value< TraitsL >& lhs, const basic_value< TraitsR >& rhs ) noexcept
+   {
+      if( rhs.is_value_ptr() ) {
+         return lhs < rhs.skip_value_ptr();
+      }
+      if( lhs.type() != rhs.type() ) {
+         switch( lhs.type() ) {
+            case type::VALUE_PTR:
+               return lhs.skip_value_ptr() < rhs;
+
+            case type::SIGNED:
+               if( rhs.type() == type::UNSIGNED ) {
+                  const auto v = lhs.get_signed();
+                  return ( v < 0 ) || ( static_cast< std::uint64_t >( v ) < rhs.get_unsigned() );
+               }
+               if( rhs.type() == type::DOUBLE ) {
+                  return lhs.get_signed() < rhs.get_double();
+               }
+               break;
+
+            case type::UNSIGNED:
+               if( rhs.type() == type::SIGNED ) {
+                  const auto v = rhs.get_signed();
+                  return ( v >= 0 ) && ( lhs.get_unsigned() < static_cast< std::uint64_t >( v ) );
+               }
+               if( rhs.type() == type::DOUBLE ) {
+                  return lhs.get_unsigned() < rhs.get_double();
+               }
+               break;
+
+            case type::DOUBLE:
+               if( rhs.type() == type::SIGNED ) {
+                  return lhs.get_double() < rhs.get_signed();
+               }
+               if( rhs.type() == type::UNSIGNED ) {
+                  return lhs.get_double() < rhs.get_unsigned();
+               }
+               break;
+
+            case type::STRING:
+               if( rhs.type() == type::STRING_VIEW ) {
+                  return lhs.get_string() < rhs.get_string_view();
+               }
+               break;
+
+            case type::STRING_VIEW:
+               if( rhs.type() == type::STRING ) {
+                  return lhs.get_string_view() < rhs.get_string();
+               }
+               break;
+
+            case type::BINARY:
+               if( rhs.type() == type::BINARY_VIEW ) {
+                  return tao::internal::binary_less( lhs.get_binary(), rhs.get_binary_view() );
+               }
+               break;
+
+            case type::BINARY_VIEW:
+               if( rhs.type() == type::BINARY ) {
+                  return tao::internal::binary_less( lhs.get_binary_view(), rhs.get_binary() );
+               }
+               break;
+
+            case type::OPAQUE_PTR:
+               assert( lhs.type() != type::OPAQUE_PTR );
+               break;
+
+            default:
+               break;
+         }
+         assert( rhs.type() != type::OPAQUE_PTR );
+         return lhs.type() < rhs.type();
+      }
+
+      switch( lhs.type() ) {
+         case type::UNINITIALIZED:
+            return false;
+
+         case type::NULL_:
+            return false;
+
+         case type::BOOLEAN:
+            return lhs.get_boolean() < rhs.get_boolean();
+
+         case type::SIGNED:
+            return lhs.get_signed() < rhs.get_signed();
+
+         case type::UNSIGNED:
+            return lhs.get_unsigned() < rhs.get_unsigned();
+
+         case type::DOUBLE:
+            return lhs.get_double() < rhs.get_double();
+
+         case type::STRING:
+            return lhs.get_string() < rhs.get_string();
+
+         case type::STRING_VIEW:
+            return lhs.get_string_view() < rhs.get_string_view();
+
+         case type::BINARY:
+            return lhs.get_binary() < rhs.get_binary();
+
+         case type::BINARY_VIEW:
+            return tao::internal::binary_less( lhs.get_binary_view(), rhs.get_binary_view() );
+
+         case type::ARRAY:
+            return lhs.get_array() < rhs.get_array();
+
+         case type::OBJECT:
+            return lhs.get_object() < rhs.get_object();
+
+         case type::VALUE_PTR:
+            assert( lhs.type() != type::VALUE_PTR );
+            break;  // LCOV_EXCL_LINE
+
+         case type::OPAQUE_PTR:
+            assert( lhs.type() != type::OPAQUE_PTR );
+            break;  // LCOV_EXCL_LINE
+
+         case type::VALUELESS_BY_EXCEPTION:
+            assert( lhs.type() != type::VALUELESS_BY_EXCEPTION );
+            break;  // LCOV_EXCL_LINE
+      }
+      // LCOV_EXCL_START
+      assert( false );
+      return false;
+      // LCOV_EXCL_STOP
+   }
+
+   template< template< typename... > class Traits, int = 1 >  // work-around for Visual C++
+   [[nodiscard]] bool operator<( const basic_value< Traits >& lhs, tao::internal::identity_t< basic_value< Traits > > rhs ) noexcept
+   {
+      return lhs < rhs;
+   }
+
+   template< template< typename... > class Traits, int = 2 >  // work-around for Visual C++
+   [[nodiscard]] bool operator<( const tao::internal::identity_t< basic_value< Traits > > lhs, const basic_value< Traits >& rhs ) noexcept
+   {
+      return lhs < rhs;
+   }
+
+   template< template< typename... > class Traits, typename T >
+   [[nodiscard]] bool operator<( const basic_value< Traits >& lhs, const std::optional< T >& rhs ) noexcept
+   {
+      static_assert( noexcept( Traits< std::optional< T > >::less_than( lhs, rhs ) ), "less_than must be noexcept" );
+      return Traits< std::optional< T > >::less_than( lhs, rhs );
+   }
+
+   template< typename T, template< typename... > class Traits >
+   [[nodiscard]] bool operator<( const std::optional< T >& lhs, const basic_value< Traits >& rhs ) noexcept
+   {
+      static_assert( noexcept( Traits< std::optional< T > >::greater_than( rhs, lhs ) ), "greater_than must be noexcept" );
+      return Traits< std::optional< T > >::greater_than( rhs, lhs );
+   }
+
+   template< template< typename... > class Traits, typename T >
+   [[nodiscard]] auto operator<( const basic_value< Traits >& lhs, const T& rhs ) noexcept -> decltype( Traits< std::decay_t< T > >::less_than( lhs, rhs ) )
+   {
+      using D = std::decay_t< T >;
+      static_assert( noexcept( Traits< D >::less_than( lhs, rhs ) ), "less_than must be noexcept" );
+      return Traits< D >::less_than( lhs, rhs );
+   }
+
+   template< typename T, template< typename... > class Traits >
+   [[nodiscard]] auto operator<( const T& lhs, const basic_value< Traits >& rhs ) noexcept -> decltype( Traits< std::decay_t< T > >::greater_than( rhs, lhs ) )
+   {
+      using D = std::decay_t< T >;
+      static_assert( noexcept( Traits< D >::greater_than( rhs, lhs ) ), "greater_than must be noexcept" );
+      return Traits< D >::greater_than( rhs, lhs );
+   }
+
+   template< template< typename... > class TraitsL, template< typename... > class TraitsR >
+   [[nodiscard]] bool operator>( const basic_value< TraitsL >& lhs, const basic_value< TraitsR >& rhs ) noexcept
+   {
+      return rhs < lhs;
+   }
+
+   template< template< typename... > class Traits >
+   [[nodiscard]] bool operator>( const basic_value< Traits >& lhs, tao::internal::identity_t< basic_value< Traits > > rhs ) noexcept
+   {
+      return rhs < lhs;
+   }
+
+   template< template< typename... > class Traits >
+   [[nodiscard]] bool operator>( tao::internal::identity_t< basic_value< Traits > > lhs, const basic_value< Traits >& rhs ) noexcept
+   {
+      return rhs < lhs;
+   }
+
+   template< template< typename... > class Traits, typename T >
+   [[nodiscard]] bool operator>( const basic_value< Traits >& lhs, const std::optional< T >& rhs ) noexcept
+   {
+      static_assert( noexcept( Traits< std::optional< T > >::greater_than( lhs, rhs ) ), "greater_than must be noexcept" );
+      return Traits< std::optional< T > >::greater_than( lhs, rhs );
+   }
+
+   template< typename T, template< typename... > class Traits >
+   [[nodiscard]] bool operator>( const std::optional< T >& lhs, const basic_value< Traits >& rhs ) noexcept
+   {
+      static_assert( noexcept( Traits< std::optional< T > >::less_than( rhs, lhs ) ), "less_than must be noexcept" );
+      return Traits< std::optional< T > >::less_than( rhs, lhs );
+   }
+
+   template< template< typename... > class Traits, typename T >
+   [[nodiscard]] auto operator>( const basic_value< Traits >& lhs, const T& rhs ) noexcept -> decltype( Traits< std::decay_t< T > >::greater_than( lhs, rhs ) )
+   {
+      using D = std::decay_t< T >;
+      static_assert( noexcept( Traits< D >::greater_than( lhs, rhs ) ), "greater_than must be noexcept" );
+      return Traits< D >::greater_than( lhs, rhs );
+   }
+
+   template< typename T, template< typename... > class Traits >
+   [[nodiscard]] auto operator>( const T& lhs, const basic_value< Traits >& rhs ) noexcept -> decltype( Traits< std::decay_t< T > >::less_than( rhs, lhs ) )
+   {
+      using D = std::decay_t< T >;
+      static_assert( noexcept( Traits< D >::less_than( rhs, lhs ) ), "less_than must be noexcept" );
+      return Traits< D >::less_than( rhs, lhs );
+   }
+
+   template< template< typename... > class TraitsL, template< typename... > class TraitsR >
+   [[nodiscard]] bool operator<=( const basic_value< TraitsL >& lhs, const basic_value< TraitsR >& rhs ) noexcept
+   {
+      return !( lhs > rhs );
+   }
+
+   template< template< typename... > class Traits, typename T >
+   [[nodiscard]] bool operator<=( const basic_value< Traits >& lhs, const std::optional< T >& rhs ) noexcept
+   {
+      return !( lhs > rhs );
+   }
+
+   template< typename T, template< typename... > class Traits >
+   [[nodiscard]] bool operator<=( const std::optional< T >& lhs, const basic_value< Traits >& rhs ) noexcept
+   {
+      return !( lhs > rhs );
+   }
+
+   template< template< typename... > class Traits, typename T >
+   [[nodiscard]] bool operator<=( const basic_value< Traits >& lhs, const T& rhs ) noexcept
+   {
+      return !( lhs > rhs );
+   }
+
+   template< typename T, template< typename... > class Traits >
+   [[nodiscard]] bool operator<=( const T& lhs, const basic_value< Traits >& rhs ) noexcept
+   {
+      return !( lhs > rhs );
+   }
+
+   template< template< typename... > class TraitsL, template< typename... > class TraitsR >
+   [[nodiscard]] bool operator>=( const basic_value< TraitsL >& lhs, const basic_value< TraitsR >& rhs ) noexcept
+   {
+      return !( lhs < rhs );
+   }
+
+   template< template< typename... > class Traits, typename T >
+   [[nodiscard]] bool operator>=( const basic_value< Traits >& lhs, const std::optional< T >& rhs ) noexcept
+   {
+      return !( lhs < rhs );
+   }
+
+   template< typename T, template< typename... > class Traits >
+   [[nodiscard]] bool operator>=( const std::optional< T >& lhs, const basic_value< Traits >& rhs ) noexcept
+   {
+      return !( lhs < rhs );
+   }
+
+   template< template< typename... > class Traits, typename T >
+   [[nodiscard]] bool operator>=( const basic_value< Traits >& lhs, const T& rhs ) noexcept
+   {
+      return !( lhs < rhs );
+   }
+
+   template< typename T, template< typename... > class Traits >
+   [[nodiscard]] bool operator>=( const T& lhs, const basic_value< Traits >& rhs ) noexcept
+   {
+      return !( lhs < rhs );
+   }
+
+}  // namespace tao::json
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/parts_parser.hpp b/3rdParty/taocpp-json/include/tao/json/parts_parser.hpp
new file mode 100644
index 000000000000..e6c37c8a9636
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/parts_parser.hpp
@@ -0,0 +1,306 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_PARTS_PARSER_HPP
+#define TAO_JSON_PARTS_PARSER_HPP
+
+#include "external/pegtl.hpp"
+#include "external/pegtl/contrib/integer.hpp"
+#include "external/pegtl/contrib/json.hpp"
+
+#include "internal/action.hpp"
+#include "internal/format.hpp"
+#include "internal/grammar.hpp"
+#include "internal/number_state.hpp"
+#include "internal/unescape_action.hpp"
+
+namespace tao::json
+{
+   namespace internal
+   {
+      namespace rules
+      {
+         struct wss
+            : pegtl::star< ws >
+         {};
+
+         struct boolean
+         {
+            using analyze_t = pegtl::analysis::generic< pegtl::analysis::rule_type::any >;
+
+            template< pegtl::apply_mode,
+                      pegtl::rewind_mode,
+                      template< typename... >
+                      class,
+                      template< typename... >
+                      class,
+                      typename Input >
+            [[nodiscard]] static bool match( Input& in, bool& st ) noexcept( noexcept( in.size( 5 ) ) )
+            {
+               const auto s = in.size( 5 );
+               if( s >= 5 ) {
+                  if( std::memcmp( in.current(), "false", 5 ) == 0 ) {
+                     in.bump_in_this_line( 5 );
+                     st = false;
+                     return true;
+                  }
+               }
+               if( s >= 4 ) {
+                  if( std::memcmp( in.current(), "true", 4 ) == 0 ) {
+                     in.bump_in_this_line( 4 );
+                     st = true;
+                     return true;
+                  }
+               }
+               return false;
+            }
+         };
+
+         struct double_rule
+         {
+            using analyze_t = pegtl::analysis::generic< pegtl::analysis::rule_type::any >;
+
+            template< apply_mode A,
+                      rewind_mode M,
+                      template< typename... >
+                      class Action,
+                      template< typename... >
+                      class Control,
+                      typename Input,
+                      typename... States >
+            [[nodiscard]] static bool match_impl( Input& in, States&&... st )
+            {
+               switch( in.peek_char() ) {
+                  case '-':
+                     in.bump_in_this_line();
+                     if( in.empty() || !sor_value::match_number< true, A, rewind_mode::dontcare, Action, Control >( in, st... ) ) {
+                        throw pegtl::parse_error( "incomplete number", in );
+                     }
+                     return true;
+
+                  default:
+                     return sor_value::match_number< false, A, M, Action, Control >( in, st... );
+               }
+            }
+
+            template< apply_mode A,
+                      rewind_mode M,
+                      template< typename... >
+                      class Action,
+                      template< typename... >
+                      class Control,
+                      typename Input,
+                      typename... States >
+            [[nodiscard]] static bool match( Input& in, States&&... st )
+            {
+               return in.size( 2 ) && match_impl< A, M, Action, Control >( in, st... );
+            }
+         };
+
+      }  // namespace rules
+
+      template< typename Rule >
+      struct double_action
+         : action< Rule >
+      {};
+
+      template< bool NEG >
+      struct double_action< rules::number< NEG > >
+         : pegtl::change_states< number_state< NEG > >
+      {
+         template< typename Input, typename Consumer >
+         static void success( const Input& /*unused*/, number_state< NEG >& state, Consumer& consumer )
+         {
+            state.success( consumer );
+         }
+      };
+
+      struct double_state_and_consumer
+      {
+         void number( const double d )
+         {
+            converted = d;
+         }
+
+         void number( const std::int64_t i )
+         {
+            converted = double( i );
+         }
+
+         void number( const std::uint64_t u )
+         {
+            converted = double( u );
+         }
+
+         double converted = 0.0;  // TODO: Remove superfluous initialisation when we manage to shup up the warnings on all compilers.
+      };
+
+   }  // namespace internal
+
+   // TODO: Optimise some of the simpler cases?
+
+   template< typename Input = pegtl::string_input< pegtl::tracking_mode::lazy, pegtl::eol::lf_crlf, std::string > >
+   class basic_parts_parser
+   {
+   public:
+      template< typename... Ts >
+      explicit basic_parts_parser( Ts&&... ts )
+         : m_input( std::forward< Ts >( ts )... )
+      {
+         pegtl::parse< internal::rules::wss >( m_input );
+      }
+
+      [[nodiscard]] bool empty()
+      {
+         return m_input.empty();
+      }
+
+      [[nodiscard]] bool null()
+      {
+         return pegtl::parse< pegtl::seq< internal::rules::null, internal::rules::wss > >( m_input );
+      }
+
+      [[nodiscard]] bool boolean()
+      {
+         bool r;
+         pegtl::parse< pegtl::must< internal::rules::boolean, internal::rules::wss > >( m_input, r );
+         return r;
+      }
+
+      [[nodiscard]] double number_double()
+      {
+         internal::double_state_and_consumer st;
+         pegtl::parse< pegtl::must< internal::rules::double_rule, internal::rules::wss >, internal::double_action >( m_input, st );
+         return st.converted;
+      }
+
+      [[nodiscard]] std::int64_t number_signed()
+      {
+         std::int64_t st = 0;  // TODO: Remove superfluous initialisation when we manage to shup up the warnings on all compilers.
+         pegtl::parse< pegtl::must< pegtl::integer::signed_rule_with_action, internal::rules::wss > >( m_input, st );
+         return st;
+      }
+
+      [[nodiscard]] std::uint64_t number_unsigned()
+      {
+         std::uint64_t st = 0;  // TODO: Remove superfluous initialisation when we manage to shup up the warnings on all compilers.
+         pegtl::parse< pegtl::must< pegtl::integer::unsigned_rule_with_action, internal::rules::wss > >( m_input, st );
+         return st;
+      }
+
+      [[nodiscard]] std::string string()
+      {
+         std::string unescaped;
+         pegtl::parse< pegtl::must< internal::rules::string, internal::rules::wss >, internal::unescape_action >( m_input, unescaped );
+         return unescaped;
+      }
+
+      [[nodiscard]] std::vector< std::byte > binary()
+      {
+         throw std::runtime_error( "json format does not support binary" );
+      }
+
+      [[nodiscard]] std::string key()
+      {
+         std::string unescaped;
+         pegtl::parse< pegtl::must< internal::rules::string, internal::rules::wss, pegtl::one< ':' >, internal::rules::wss >, internal::unescape_action >( m_input, unescaped );
+         return unescaped;
+      }
+
+      template< char C >
+      void parse_single_must()
+      {
+         pegtl::parse< pegtl::must< pegtl::one< C >, internal::rules::wss > >( m_input );
+      }
+
+      template< char C >
+      [[nodiscard]] bool parse_single_test()
+      {
+         return pegtl::parse< pegtl::seq< pegtl::one< C >, internal::rules::wss > >( m_input );
+      }
+
+      struct state_t
+      {
+         std::size_t i = 0;
+         static constexpr std::size_t* size = nullptr;
+      };
+
+      [[nodiscard]] state_t begin_array()
+      {
+         parse_single_must< '[' >();
+         return state_t();
+      }
+
+      void end_array( state_t& /*unused*/ )
+      {
+         parse_single_must< ']' >();
+      }
+
+      void element( state_t& p )
+      {
+         if( p.i++ ) {
+            parse_single_must< ',' >();
+         }
+      }
+
+      [[nodiscard]] bool element_or_end_array( state_t& p )
+      {
+         if( parse_single_test< ']' >() ) {
+            return false;
+         }
+         element( p );
+         return true;
+      }
+
+      [[nodiscard]] state_t begin_object()
+      {
+         parse_single_must< '{' >();
+         return state_t();
+      }
+
+      void end_object( state_t& /*unused*/ )
+      {
+         parse_single_must< '}' >();
+      }
+
+      void member( state_t& p )
+      {
+         if( p.i++ ) {
+            parse_single_must< ',' >();
+         }
+      }
+
+      [[nodiscard]] bool member_or_end_object( state_t& p )
+      {
+         if( parse_single_test< '}' >() ) {
+            return false;
+         }
+         member( p );
+         return true;
+      }
+
+      void skip_value()
+      {
+         pegtl::parse< pegtl::must< pegtl::json::value > >( m_input );  // Includes standard JSON right-padding.
+      }
+
+      [[nodiscard]] auto mark()
+      {
+         return m_input.template mark< pegtl::rewind_mode::required >();
+      }
+
+      template< typename T >
+      void throw_parse_error( T&& t ) const
+      {
+         throw pegtl::parse_error( std::forward< T >( t ), m_input );
+      }
+
+   protected:
+      Input m_input;
+   };
+
+   using parts_parser = basic_parts_parser<>;
+
+}  // namespace tao::json
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/pointer.hpp b/3rdParty/taocpp-json/include/tao/json/pointer.hpp
new file mode 100644
index 000000000000..38360a1338b2
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/pointer.hpp
@@ -0,0 +1,432 @@
+// Copyright (c) 2016-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_POINTER_HPP
+#define TAO_JSON_POINTER_HPP
+
+#include <algorithm>
+#include <cassert>
+#include <cstdint>
+#include <stdexcept>
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "type.hpp"
+
+#include "external/pegtl.hpp"
+#include "internal/format.hpp"
+
+namespace tao::json
+{
+   namespace internal
+   {
+      template< std::size_t = sizeof( std::size_t ) >
+      struct token_to_index;
+
+      template<>
+      struct token_to_index< 4 >
+      {
+         [[nodiscard]] static std::size_t convert( const std::string& key ) noexcept
+         {
+            if( !key.empty() && key.size() <= 10 ) {
+               if( key == "0" ) {
+                  return 0;
+               }
+               if( ( key[ 0 ] != '0' ) && ( key.find_first_not_of( "0123456789" ) == std::string::npos ) ) {
+                  if( key.size() < 10 || key < "4294967296" ) {
+                     return static_cast< std::size_t >( std::stoul( key ) );
+                  }
+               }
+            }
+            return std::string::npos;
+         }
+      };
+
+      template<>
+      struct token_to_index< 8 >
+      {
+         [[nodiscard]] static std::size_t convert( const std::string& key ) noexcept
+         {
+            if( !key.empty() && key.size() <= 20 ) {
+               if( key == "0" ) {
+                  return 0;
+               }
+               if( ( key[ 0 ] != '0' ) && ( key.find_first_not_of( "0123456789" ) == std::string::npos ) ) {
+                  if( key.size() < 20 || key < "18446744073709551616" ) {
+                     return static_cast< std::size_t >( std::stoull( key ) );
+                  }
+               }
+            }
+            return std::string::npos;
+         }
+      };
+
+   }  // namespace internal
+
+   // RFC 6901
+   class token
+   {
+   private:
+      std::size_t m_index;
+      std::string m_key;
+
+   public:
+      explicit token( const std::string& in_key )
+         : m_index( internal::token_to_index<>::convert( in_key ) ),
+           m_key( in_key )
+      {}
+
+      explicit token( std::string&& in_key ) noexcept
+         : m_index( internal::token_to_index<>::convert( in_key ) ),
+           m_key( std::move( in_key ) )
+      {}
+
+      explicit token( const std::size_t in_index )
+         : m_index( in_index ),
+           m_key( std::to_string( m_index ) )
+      {}
+
+      token( const token& ) = default;
+      token( token&& v ) noexcept
+         : m_index( v.m_index ),
+           m_key( std::move( v.m_key ) )
+      {}
+
+      ~token() = default;
+
+      token& operator=( const token& ) = default;
+      token& operator=( token&& v ) noexcept
+      {
+         m_index = v.m_index;
+         m_key = std::move( v.m_key );
+         return *this;
+      }
+
+      [[nodiscard]] bool has_index() const noexcept
+      {
+         return m_index != std::string::npos;
+      }
+
+      [[nodiscard]] const std::string& key() const noexcept
+      {
+         return m_key;
+      }
+
+      [[nodiscard]] std::size_t index() const
+      {
+         if( !has_index() ) {
+            throw std::invalid_argument( internal::format( "unable to resolve json pointer with array, token '", m_key, "' is not an index" ) );
+         }
+         return m_index;
+      }
+
+      [[nodiscard]] friend bool operator==( const token& lhs, const token& rhs ) noexcept
+      {
+         return lhs.m_key == rhs.m_key;
+      }
+
+      [[nodiscard]] friend bool operator<( const token& lhs, const token& rhs ) noexcept
+      {
+         return lhs.m_key < rhs.m_key;
+      }
+   };
+
+   namespace internal
+   {
+      // clang-format off
+      struct pointer_zero : pegtl::one< '0' > {};
+      struct pointer_one : pegtl::one< '1' > {};
+      struct pointer_tilde : pegtl::one< '~' > {};
+      struct pointer_escaped : pegtl::sor< pointer_zero, pointer_one > {};
+      struct pointer_slash : pegtl::one< '/' > {};
+      struct pointer_char : pegtl::utf8::not_one< '/' > {};
+      struct pointer_escape : pegtl::if_must< pointer_tilde, pointer_escaped > {};
+      struct pointer_token : pegtl::star< pegtl::sor< pointer_escape, pointer_char > > {};
+      struct pointer_rule : pegtl::until< pegtl::eof, pegtl::must< pointer_slash, pointer_token > > {};
+      struct pointer_grammar : pegtl::must< pointer_rule > {};
+      // clang-format on
+
+      template< typename Rule >
+      struct pointer_action
+         : pegtl::nothing< Rule >
+      {};
+
+      template<>
+      struct pointer_action< pointer_zero >
+      {
+         static void apply0( std::vector< token >& /*unused*/, std::string& t )
+         {
+            t += '~';
+         }
+      };
+
+      template<>
+      struct pointer_action< pointer_one >
+      {
+         static void apply0( std::vector< token >& /*unused*/, std::string& t )
+         {
+            t += '/';
+         }
+      };
+
+      template<>
+      struct pointer_action< pointer_char >
+      {
+         template< typename Input >
+         static void apply( const Input& in, std::vector< token >& /*unused*/, std::string& t )
+         {
+            t.append( in.begin(), in.size() );
+         }
+      };
+
+      template<>
+      struct pointer_action< pointer_token >
+      {
+         static void apply0( std::vector< token >& v, std::string& t )
+         {
+            v.emplace_back( std::move( t ) );
+            t.clear();
+         }
+      };
+
+   }  // namespace internal
+
+   class pointer
+      : public std::vector< token >
+   {
+   private:
+      void parse( const std::string& v )
+      {
+         std::string t;
+         pegtl::memory_input< pegtl::tracking_mode::lazy, pegtl::eol::lf_crlf, const char* > in( v, "parse()" );
+         pegtl::parse< internal::pointer_grammar, internal::pointer_action >( in, vector(), t );
+      }
+
+   public:
+      pointer() = default;
+      pointer( const pointer& ) = default;
+      pointer( pointer&& p ) = default;
+
+      explicit pointer( const std::string& v )
+      {
+         parse( v );
+      }
+
+      pointer( const std::initializer_list< token >& l )
+         : std::vector< token >( l )
+      {}
+
+      ~pointer() = default;
+
+      pointer& operator=( const pointer& ) = default;
+      pointer& operator=( pointer&& p ) = default;
+
+      pointer& operator=( const std::string& v )
+      {
+         clear();
+         parse( v );
+         return *this;
+      }
+
+      pointer& operator=( const std::initializer_list< token >& l )
+      {
+         vector() = l;
+         return *this;
+      }
+
+      [[nodiscard]] explicit operator bool() const noexcept
+      {
+         return !empty();
+      }
+
+      void push_back() = delete;
+
+      void pop_back()
+      {
+         assert( !empty() );
+         vector().pop_back();
+      }
+
+      [[nodiscard]] bool is_prefix_of( const pointer& other ) const noexcept
+      {
+         if( other.size() >= size() ) {
+            return std::equal( begin(), end(), other.begin() );
+         }
+         return false;
+      }
+
+      [[nodiscard]] std::vector< token >& vector() noexcept
+      {
+         return static_cast< std::vector< token >& >( *this );
+      }
+
+      [[nodiscard]] const std::vector< token >& vector() const noexcept
+      {
+         return static_cast< const std::vector< token >& >( *this );
+      }
+   };
+
+   [[nodiscard]] inline bool operator==( const pointer& lhs, const pointer& rhs ) noexcept
+   {
+      return lhs.vector() == rhs.vector();
+   }
+
+   [[nodiscard]] inline bool operator<( const pointer& lhs, const pointer& rhs ) noexcept
+   {
+      return lhs.vector() < rhs.vector();
+   }
+
+   [[nodiscard]] inline bool operator!=( const pointer& lhs, const pointer& rhs ) noexcept
+   {
+      return !( lhs == rhs );
+   }
+
+   [[nodiscard]] inline bool operator>( const pointer& lhs, const pointer& rhs ) noexcept
+   {
+      return rhs < lhs;
+   }
+
+   [[nodiscard]] inline bool operator<=( const pointer& lhs, const pointer& rhs ) noexcept
+   {
+      return !( rhs < lhs );
+   }
+
+   [[nodiscard]] inline bool operator>=( const pointer& lhs, const pointer& rhs ) noexcept
+   {
+      return !( lhs < rhs );
+   }
+
+   inline pointer& operator+=( pointer& lhs, const std::string& rhs )
+   {
+      lhs.emplace_back( rhs );
+      return lhs;
+   }
+
+   inline pointer& operator+=( pointer& lhs, std::string&& rhs )
+   {
+      lhs.emplace_back( std::move( rhs ) );
+      return lhs;
+   }
+
+   inline pointer& operator+=( pointer& lhs, const std::size_t rhs )
+   {
+      lhs.emplace_back( rhs );
+      return lhs;
+   }
+
+   [[nodiscard]] inline pointer operator+( const pointer& p, const std::string& v )
+   {
+      pointer nrv( p );
+      nrv += v;
+      return nrv;
+   }
+
+   [[nodiscard]] inline pointer operator+( const pointer& p, std::string&& v )
+   {
+      pointer nrv( p );
+      nrv += std::move( v );
+      return nrv;
+   }
+
+   [[nodiscard]] inline pointer operator+( const pointer& p, const std::size_t i )
+   {
+      pointer nrv( p );
+      nrv += i;
+      return nrv;
+   }
+
+   namespace internal
+   {
+      [[nodiscard]] inline std::string tokens_to_string( std::vector< token >::const_iterator it, const std::vector< token >::const_iterator& end )
+      {
+         std::string result;
+         while( it != end ) {
+            result += '/';
+            for( const char c : it->key() ) {
+               switch( c ) {
+                  case '~':
+                     result += "~0";
+                     break;
+                  case '/':
+                     result += "~1";
+                     break;
+                  default:
+                     result += c;
+               }
+            }
+            ++it;
+         }
+         return result;
+      }
+
+      [[nodiscard]] inline std::runtime_error invalid_type( const std::vector< token >::const_iterator& begin, const std::vector< token >::const_iterator& end )
+      {
+         return std::runtime_error( internal::format( "unable to resolve JSON Pointer '", tokens_to_string( begin, end ), "' -- value type is neither 'object' nor 'array'" ) );
+      }
+
+      template< typename T >
+      [[nodiscard]] T& pointer_at( T* v, const std::vector< token >::const_iterator& begin, const std::vector< token >::const_iterator& end )
+      {
+         for( auto it = begin; it != end; ++it ) {
+            switch( v->type() ) {
+               case type::ARRAY:
+                  v = &v->at( it->index() );
+                  break;
+               case type::OBJECT:
+                  v = &v->at( it->key() );
+                  break;
+               default:
+                  throw invalid_type( begin, std::next( it ) );
+            }
+         }
+         return *v;
+      }
+
+      template< typename T >
+      [[nodiscard]] T* pointer_find( T* v, const std::vector< token >::const_iterator& begin, const std::vector< token >::const_iterator& end )
+      {
+         for( auto it = begin; v && ( it != end ); ++it ) {
+            switch( v->type() ) {
+               case type::ARRAY:
+                  v = v->find( it->index() );
+                  break;
+               case type::OBJECT:
+                  v = v->find( it->key() );
+                  break;
+               default:
+                  throw invalid_type( begin, std::next( it ) );
+            }
+         }
+         return v;
+      }
+
+   }  // namespace internal
+
+   [[nodiscard]] inline std::string to_string( const pointer& p )
+   {
+      return internal::tokens_to_string( p.begin(), p.end() );
+   }
+
+   [[nodiscard]] inline std::string to_string( pointer& p )
+   {
+      return internal::tokens_to_string( p.begin(), p.end() );
+   }
+
+   [[nodiscard]] inline std::string to_string( pointer&& p )
+   {
+      return internal::tokens_to_string( p.begin(), p.end() );
+   }
+
+   inline namespace literals
+   {
+      [[nodiscard]] inline pointer operator"" _json_pointer( const char* data, const std::size_t size )
+      {
+         return pointer( { data, size } );
+      }
+
+   }  // namespace literals
+
+}  // namespace tao::json
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/produce.hpp b/3rdParty/taocpp-json/include/tao/json/produce.hpp
new file mode 100644
index 000000000000..d3713f92c171
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/produce.hpp
@@ -0,0 +1,61 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_PRODUCE_HPP
+#define TAO_JSON_PRODUCE_HPP
+
+#include <ostream>
+#include <sstream>
+#include <string>
+#include <utility>
+
+#include "forward.hpp"
+
+#include "events/produce.hpp"
+#include "events/to_pretty_stream.hpp"
+#include "events/to_stream.hpp"
+#include "events/to_string.hpp"
+#include "events/to_value.hpp"
+
+namespace tao::json::produce
+{
+   template< template< typename... > class Traits = traits, typename T >
+   [[nodiscard]] basic_value< Traits > to_value( T&& t )
+   {
+      events::to_basic_value< Traits > consumer;
+      events::produce< Traits >( consumer, std::forward< T >( t ) );
+      return std::move( consumer.value );
+   }
+
+   template< template< typename... > class Traits = traits, typename T >
+   void to_stream( std::ostream& os, const T& t )
+   {
+      events::to_stream consumer( os );
+      events::produce< Traits >( consumer, t );
+   }
+
+   template< template< typename... > class Traits = traits, typename T >
+   void to_stream( std::ostream& os, const T& t, const std::size_t indent )
+   {
+      events::to_pretty_stream consumer( os, indent );
+      events::produce< Traits >( consumer, t );
+   }
+
+   template< template< typename... > class Traits = traits, typename T, typename S >
+   void to_stream( std::ostream& os, const T& t, const std::size_t indent, S&& eol )
+   {
+      events::to_pretty_stream consumer( os, indent, std::forward< S >( eol ) );
+      events::produce< Traits >( consumer, t );
+   }
+
+   template< template< typename... > class Traits = traits, typename... Ts >
+   [[nodiscard]] std::string to_string( Ts&&... ts )
+   {
+      std::ostringstream oss;
+      to_stream< Traits >( oss, std::forward< Ts >( ts )... );
+      return oss.str();
+   }
+
+}  // namespace tao::json::produce
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/self_contained.hpp b/3rdParty/taocpp-json/include/tao/json/self_contained.hpp
new file mode 100644
index 000000000000..226738529de6
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/self_contained.hpp
@@ -0,0 +1,143 @@
+// Copyright (c) 2016-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_SELF_CONTAINED_HPP
+#define TAO_JSON_SELF_CONTAINED_HPP
+
+#include "events/to_value.hpp"
+#include "events/virtual_ref.hpp"
+
+#include "value.hpp"
+
+namespace tao::json
+{
+   // recursively checks for the existence
+   // of VALUE_PTR or OPAQUE_PTR nodes, STRING_VIEW or BINARY_VIEW,
+   // returns true is no such nodes were found.
+
+   template< template< typename... > class Traits >
+   [[nodiscard]] bool is_self_contained( const basic_value< Traits >& v ) noexcept
+   {
+      switch( v.type() ) {
+         case type::UNINITIALIZED:
+            return true;
+
+         case type::NULL_:
+         case type::BOOLEAN:
+         case type::SIGNED:
+         case type::UNSIGNED:
+         case type::DOUBLE:
+         case type::STRING:
+         case type::BINARY:
+            return true;
+
+         case type::STRING_VIEW:
+         case type::BINARY_VIEW:
+            return false;
+
+         case type::ARRAY:
+            for( auto& e : v.get_array() ) {
+               if( !is_self_contained( e ) ) {
+                  return false;
+               }
+            }
+            return true;
+
+         case type::OBJECT:
+            for( auto& e : v.get_object() ) {
+               if( !is_self_contained( e.second ) ) {
+                  return false;
+               }
+            }
+            return true;
+
+         case type::VALUE_PTR:
+            return false;
+
+         case type::OPAQUE_PTR:
+            return false;
+
+         case type::VALUELESS_BY_EXCEPTION:
+            return true;
+      }
+      // LCOV_EXCL_START
+      assert( false );
+      return false;
+      // LCOV_EXCL_STOP
+   }
+
+   // Removes all VALUE_PTR and OPAQUE_PTR nodes,
+   // recursively, by copying/generating their content;
+   // replaces STRING_VIEW and BINARY_VIEW with STRING
+   // and BINARY, respectively, with a copy of the data.
+
+   template< template< typename... > class Traits >
+   void make_self_contained( basic_value< Traits >& v )
+   {
+      switch( v.type() ) {
+         case type::UNINITIALIZED:
+            return;
+
+         case type::NULL_:
+         case type::BOOLEAN:
+         case type::SIGNED:
+         case type::UNSIGNED:
+         case type::DOUBLE:
+         case type::STRING:
+         case type::BINARY:
+            return;
+
+         case type::STRING_VIEW:
+            v.emplace_string( v.get_string_view() );
+            return;
+
+         case type::BINARY_VIEW: {
+            const auto xv = v.get_binary_view();
+            v.emplace_binary( xv.begin(), xv.end() );
+            return;
+         }
+
+         case type::ARRAY:
+            for( auto& e : v.get_array() ) {
+               make_self_contained( e );
+            }
+            return;
+
+         case type::OBJECT:
+            for( auto& e : v.get_object() ) {
+               make_self_contained( e.second );
+            }
+            return;
+
+         case type::VALUE_PTR:
+            v = *v.get_value_ptr();
+            make_self_contained( v );
+            return;
+
+         case type::OPAQUE_PTR: {
+            const auto& q = v.get_opaque_ptr();
+            events::to_basic_value< Traits > consumer;
+            events::virtual_ref< events::to_basic_value< Traits > > ref( consumer );
+            q.producer( ref, q.data );
+            consumer.value.public_base() = std::move( v.public_base() );
+            v = std::move( consumer.value );
+            return;
+         }
+
+         case type::VALUELESS_BY_EXCEPTION:
+            return;
+      }
+      throw std::logic_error( "invalid value for tao::json::type" );  // LCOV_EXCL_LINE
+   }
+
+   template< template< typename... > class Traits >
+   [[nodiscard]] basic_value< Traits > self_contained_copy( const basic_value< Traits >& v )
+   {
+      basic_value< Traits > r( &v );
+      make_self_contained( r );
+      return r;
+   }
+
+}  // namespace tao::json
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/span.hpp b/3rdParty/taocpp-json/include/tao/json/span.hpp
new file mode 100644
index 000000000000..bcdb61e23818
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/span.hpp
@@ -0,0 +1,568 @@
+// Copyright (c) 2019-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_SPAN_HPP
+#define TAO_JSON_SPAN_HPP
+
+#if !defined( TAO_JSON_USE_STD_SPAN ) && ( __cplusplus > 201703L ) && defined( __has_include )
+// clang-format off
+#if __has_include(<span>)
+// clang-format on
+#define TAO_JSON_USE_STD_SPAN
+#endif
+#endif
+
+#if defined( TAO_JSON_USE_STD_SPAN )
+
+#include <span>
+
+namespace tao
+{
+   using std::dynamic_extent;
+   using std::span;
+
+   using std::as_bytes;
+   using std::as_writable_bytes;
+
+}  // namespace tao
+
+#else
+
+#include <array>
+#include <cassert>
+#include <cstddef>
+#include <iterator>
+#include <limits>
+#include <tuple>
+#include <type_traits>
+
+namespace tao
+{
+   inline constexpr std::size_t dynamic_extent = std::numeric_limits< std::size_t >::max();
+
+   template< typename ElementType, std::size_t Extent = dynamic_extent >
+   class span;
+
+   namespace internal
+   {
+      template< typename >
+      struct is_span_impl
+         : std::false_type
+      {};
+
+      template< typename ElementType, std::size_t Extent >
+      struct is_span_impl< span< ElementType, Extent > >
+         : std::true_type
+      {};
+
+      template< typename T >
+      using is_span = is_span_impl< std::remove_cv_t< T > >;
+
+      template< typename >
+      struct is_std_array_impl
+         : std::false_type
+      {};
+
+      template< typename T, std::size_t N >
+      struct is_std_array_impl< std::array< T, N > >
+         : std::true_type
+      {};
+
+      template< typename T >
+      using is_std_array = is_std_array_impl< std::remove_cv_t< T > >;
+
+      template< typename T, typename ElementType >
+      using is_span_compatible_ptr = std::is_convertible< T ( * )[], ElementType ( * )[] >;
+
+      template< typename, typename, typename = void >
+      struct is_span_compatible_container
+         : std::false_type
+      {};
+
+      template< typename Container, typename ElementType >
+      struct is_span_compatible_container< Container,
+                                           ElementType,
+                                           std::void_t<
+                                              std::enable_if_t< !is_span< Container >::value >,
+                                              std::enable_if_t< !is_std_array< Container >::value >,
+                                              std::enable_if_t< !std::is_array_v< Container > >,
+                                              decltype( std::data( std::declval< Container >() ) ),
+                                              decltype( std::size( std::declval< Container >() ) ),
+                                              std::enable_if_t< is_span_compatible_ptr< std::remove_pointer_t< decltype( std::data( std::declval< Container& >() ) ) >, ElementType >::value > > >
+         : std::true_type
+      {};
+
+   }  // namespace internal
+
+   template< typename ElementType, std::size_t Extent >
+   class span
+   {
+   public:
+      static_assert( !std::is_abstract_v< ElementType > );
+
+      using element_type = ElementType;
+      using value_type = std::remove_cv_t< ElementType >;
+      using index_type = std::size_t;
+      using difference_type = std::ptrdiff_t;
+      using pointer = element_type*;
+      using const_pointer = const element_type*;
+      using reference = element_type&;
+      using const_reference = const element_type&;
+      using iterator = pointer;
+      using const_iterator = const_pointer;
+      using reverse_iterator = std::reverse_iterator< iterator >;
+      using const_reverse_iterator = std::reverse_iterator< const_iterator >;
+
+      static constexpr index_type extent = Extent;
+
+      template< typename T = void, typename = std::enable_if_t< Extent == 0, T > >
+      constexpr span() noexcept
+         : m_data( nullptr )
+      {}
+
+      constexpr span( pointer ptr, index_type count ) noexcept
+         : m_data( ptr )
+      {
+         assert( count == Extent );
+      }
+
+      constexpr span( pointer first, pointer last ) noexcept
+         : m_data( first )
+      {
+         assert( std::distance( first, last ) == Extent );
+      }
+
+      constexpr span( element_type ( &arr )[ Extent ] ) noexcept
+         : m_data( arr )
+      {}
+
+      template< std::size_t N, typename = std::enable_if_t< ( N == Extent ) && tao::internal::is_span_compatible_ptr< value_type, ElementType >::value > >
+      constexpr span( std::array< value_type, N >& arr ) noexcept
+         : m_data( arr.data() )
+      {}
+
+      template< std::size_t N, typename = std::enable_if_t< ( N == Extent ) && tao::internal::is_span_compatible_ptr< const value_type, ElementType >::value > >
+      constexpr span( const std::array< value_type, N >& arr ) noexcept
+         : m_data( arr.data() )
+      {}
+
+      constexpr span( const span& other ) = default;
+
+      template< typename OtherElementType, typename = std::enable_if_t< tao::internal::is_span_compatible_ptr< OtherElementType, ElementType >::value > >
+      constexpr span( const span< OtherElementType, Extent >& s ) noexcept
+         : m_data( s.data() )
+      {}
+
+      ~span() = default;
+
+      constexpr span& operator=( const span& ) = default;
+
+      constexpr index_type size() const noexcept
+      {
+         return Extent;
+      }
+
+      constexpr index_type size_bytes() const noexcept
+      {
+         return Extent * sizeof( element_type );
+      }
+
+      [[nodiscard]] constexpr bool empty() const noexcept
+      {
+         return Extent == 0;
+      }
+
+      constexpr reference operator[]( index_type idx ) const noexcept
+      {
+         assert( idx < Extent );
+         return *( data() + idx );
+      }
+
+      constexpr reference front() const noexcept
+      {
+         assert( Extent != 0 );
+         return *data();
+      }
+
+      constexpr reference back() const noexcept
+      {
+         assert( Extent != 0 );
+         return *( data() + ( Extent - 1 ) );
+      }
+
+      constexpr pointer data() const noexcept
+      {
+         return m_data;
+      }
+
+      constexpr iterator begin() const noexcept
+      {
+         return data();
+      }
+
+      constexpr const_iterator cbegin() const noexcept
+      {
+         return data();
+      }
+
+      constexpr iterator end() const noexcept
+      {
+         return data() + Extent;
+      }
+
+      constexpr const_iterator cend() const noexcept
+      {
+         return data() + Extent;
+      }
+
+      constexpr reverse_iterator rbegin() const noexcept
+      {
+         return reverse_iterator( end() );
+      }
+
+      constexpr reverse_iterator rend() const noexcept
+      {
+         return reverse_iterator( begin() );
+      }
+
+      constexpr const_reverse_iterator crbegin() const noexcept
+      {
+         return const_reverse_iterator( cend() );
+      }
+
+      constexpr const_reverse_iterator crend() const noexcept
+      {
+         return const_reverse_iterator( cbegin() );
+      }
+
+      friend constexpr iterator begin( span s ) noexcept
+      {
+         return s.begin();
+      }
+
+      friend constexpr iterator end( span s ) noexcept
+      {
+         return s.end();
+      }
+
+      template< std::size_t Count >
+      constexpr span< element_type, Count > first() const noexcept
+      {
+         static_assert( Count <= Extent );
+         return { data(), Count };
+      }
+
+      template< std::size_t Count >
+      constexpr span< element_type, Count > last() const noexcept
+      {
+         static_assert( Count <= Extent );
+         return { data() + ( Extent - Count ), Count };
+      }
+
+      template< std::size_t Offset, std::size_t Count = dynamic_extent >
+      constexpr auto subspan() const
+         -> span< element_type, ( ( Count != dynamic_extent ) ? Count : ( Extent - Offset ) ) >
+      {
+         static_assert( Offset <= Extent );
+         static_assert( ( Count == dynamic_extent ) || ( Count <= ( Extent - Offset ) ) );
+         return { data() + Offset, ( Count != dynamic_extent ) ? Count : ( Extent - Offset ) };
+      }
+
+      constexpr span< element_type, dynamic_extent > first( index_type count ) const
+      {
+         assert( count <= Extent );
+         return { data(), count };
+      }
+
+      constexpr span< element_type, dynamic_extent > last( index_type count ) const
+      {
+         assert( count <= Extent );
+         return { data() + Extent - count, count };
+      }
+
+      constexpr span< element_type, dynamic_extent > subspan( index_type offset, index_type count = dynamic_extent ) const
+      {
+         assert( offset <= Extent );
+         assert( ( count == dynamic_extent ) || ( count <= ( Extent - offset ) ) );
+         return { data() + offset, ( count != dynamic_extent ) ? count : ( Extent - offset ) };
+      }
+
+   private:
+      pointer m_data;
+   };
+
+   template< typename ElementType >
+   class span< ElementType, dynamic_extent >
+   {
+   public:
+      static_assert( !std::is_abstract_v< ElementType > );
+
+      using element_type = ElementType;
+      using value_type = std::remove_cv_t< ElementType >;
+      using index_type = std::size_t;
+      using difference_type = std::ptrdiff_t;
+      using pointer = element_type*;
+      using const_pointer = const element_type*;
+      using reference = element_type&;
+      using const_reference = const element_type&;
+      using iterator = pointer;
+      using const_iterator = const_pointer;
+      using reverse_iterator = std::reverse_iterator< iterator >;
+      using const_reverse_iterator = std::reverse_iterator< const_iterator >;
+
+      static constexpr index_type extent = dynamic_extent;
+
+      constexpr span() noexcept
+         : m_data( nullptr ), m_size( 0 )
+      {}
+
+      constexpr span( pointer ptr, index_type count ) noexcept
+         : m_data( ptr ), m_size( count )
+      {}
+
+      constexpr span( pointer first, pointer last ) noexcept
+         : m_data( first ), m_size( std::distance( first, last ) )
+      {}
+
+      template< std::size_t N >
+      constexpr span( element_type ( &arr )[ N ] ) noexcept
+         : m_data( arr ), m_size( N )
+      {}
+
+      template< std::size_t N, typename = std::enable_if_t< tao::internal::is_span_compatible_ptr< value_type, ElementType >::value > >
+      constexpr span( std::array< value_type, N >& arr ) noexcept
+         : m_data( arr.data() ), m_size( N )
+      {}
+
+      template< std::size_t N, typename = std::enable_if_t< tao::internal::is_span_compatible_ptr< const value_type, ElementType >::value > >
+      constexpr span( const std::array< value_type, N >& arr ) noexcept
+         : m_data( arr.data() ), m_size( N )
+      {}
+
+      template< typename Container, typename = std::enable_if_t< tao::internal::is_span_compatible_container< Container, ElementType >::value > >
+      constexpr span( Container& cont )
+         : m_data( std::data( cont ) ), m_size( std::size( cont ) )
+      {}
+
+      template< typename Container, typename = std::enable_if_t< tao::internal::is_span_compatible_container< const Container, ElementType >::value > >
+      constexpr span( const Container& cont )
+         : m_data( std::data( cont ) ), m_size( std::size( cont ) )
+      {}
+
+      constexpr span( const span& other ) = default;
+
+      template< typename OtherElementType, std::size_t OtherExtent, typename = std::enable_if_t< tao::internal::is_span_compatible_ptr< OtherElementType, ElementType >::value > >
+      constexpr span( const span< OtherElementType, OtherExtent >& s ) noexcept
+         : m_data( s.data() ), m_size( s.size() )
+      {}
+
+      ~span() = default;
+
+      constexpr span& operator=( const span& ) = default;
+
+      constexpr index_type size() const noexcept
+      {
+         return m_size;
+      }
+
+      constexpr index_type size_bytes() const noexcept
+      {
+         return size() * sizeof( element_type );
+      }
+
+      [[nodiscard]] constexpr bool empty() const noexcept
+      {
+         return size() == 0;
+      }
+
+      constexpr reference operator[]( index_type idx ) const noexcept
+      {
+         assert( idx < size() );
+         return *( data() + idx );
+      }
+
+      constexpr reference front() const noexcept
+      {
+         assert( !empty() );
+         return *data();
+      }
+
+      constexpr reference back() const noexcept
+      {
+         assert( !empty() );
+         return *( data() + ( size() - 1 ) );
+      }
+
+      constexpr pointer data() const noexcept
+      {
+         return m_data;
+      }
+
+      constexpr iterator begin() const noexcept
+      {
+         return data();
+      }
+
+      constexpr const_iterator cbegin() const noexcept
+      {
+         return data();
+      }
+
+      constexpr iterator end() const noexcept
+      {
+         return data() + size();
+      }
+
+      constexpr const_iterator cend() const noexcept
+      {
+         return data() + size();
+      }
+
+      constexpr reverse_iterator rbegin() const noexcept
+      {
+         return reverse_iterator( end() );
+      }
+
+      constexpr reverse_iterator rend() const noexcept
+      {
+         return reverse_iterator( begin() );
+      }
+
+      constexpr const_reverse_iterator crbegin() const noexcept
+      {
+         return const_reverse_iterator( cend() );
+      }
+
+      constexpr const_reverse_iterator crend() const noexcept
+      {
+         return const_reverse_iterator( cbegin() );
+      }
+
+      friend constexpr iterator begin( span s ) noexcept
+      {
+         return s.begin();
+      }
+
+      friend constexpr iterator end( span s ) noexcept
+      {
+         return s.end();
+      }
+
+      template< std::size_t Count >
+      constexpr span< element_type, Count > first() const noexcept
+      {
+         assert( Count <= size() );
+         return { data(), Count };
+      }
+
+      template< std::size_t Count >
+      constexpr span< element_type, Count > last() const noexcept
+      {
+         assert( Count <= size() );
+         return { data() + ( size() - Count ), Count };
+      }
+
+      template< std::size_t Offset, std::size_t Count = dynamic_extent >
+      constexpr auto subspan() const
+         -> span< element_type, ( ( Count != dynamic_extent ) ? Count : dynamic_extent ) >
+      {
+         assert( Offset <= size() );
+         assert( ( Count == dynamic_extent ) || ( Count <= ( size() - Offset ) ) );
+         return { data() + Offset, ( Count != dynamic_extent ) ? Count : ( size() - Offset ) };
+      }
+
+      constexpr span< element_type, dynamic_extent > first( index_type count ) const
+      {
+         assert( count <= size() );
+         return { data(), count };
+      }
+
+      constexpr span< element_type, dynamic_extent > last( index_type count ) const
+      {
+         assert( count <= size() );
+         return { data() + size() - count, count };
+      }
+
+      constexpr span< element_type, dynamic_extent > subspan( index_type offset, index_type count = dynamic_extent ) const
+      {
+         assert( offset <= size() );
+         assert( ( count == dynamic_extent ) || ( count <= ( size() - offset ) ) );
+         return { data() + offset, ( count != dynamic_extent ) ? count : ( size() - offset ) };
+      }
+
+   private:
+      pointer m_data;
+      index_type m_size;
+   };
+
+   template< typename ElementType, std::size_t Extent >
+   auto as_bytes( span< ElementType, Extent > s ) noexcept
+      -> span< const std::byte, ( ( Extent == dynamic_extent ) ? dynamic_extent : ( sizeof( ElementType ) * Extent ) ) >
+   {
+      return { reinterpret_cast< const std::byte* >( s.data() ), s.size_bytes() };
+   }
+
+   template< typename ElementType, std::size_t Extent, typename = std::enable_if_t< !std::is_const_v< ElementType > > >
+   auto as_writable_bytes( span< ElementType, Extent > s ) noexcept
+      -> span< std::byte, ( ( Extent == dynamic_extent ) ? dynamic_extent : ( sizeof( ElementType ) * Extent ) ) >
+   {
+      return { reinterpret_cast< std::byte* >( s.data() ), s.size_bytes() };
+   }
+
+   // deduction guides
+   template< typename T, std::size_t N >
+   span( T ( & )[ N ] )->span< T, N >;
+
+   template< typename T, std::size_t N >
+   span( std::array< T, N >& )->span< T, N >;
+
+   template< typename T, std::size_t N >
+   span( const std::array< T, N >& )->span< const T, N >;
+
+   template< typename Container >
+   span( Container& )->span< typename Container::value_type >;
+
+   template< typename Container >
+   span( const Container& )->span< const typename Container::value_type >;
+
+}  // namespace tao
+
+namespace std
+{
+#if defined( __clang__ )
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wmismatched-tags"
+#endif
+
+   template< typename ElementType, size_t Extent >
+   struct tuple_size< tao::span< ElementType, Extent > >
+      : integral_constant< size_t, Extent >
+   {};
+
+   template< typename ElementType >
+   struct tuple_size< tao::span< ElementType, tao::dynamic_extent > >;  // not defined
+
+   template< size_t I, typename ElementType, size_t Extent >
+   struct tuple_element< I, tao::span< ElementType, Extent > >
+   {
+      static_assert( ( Extent != tao::dynamic_extent ) && ( I < Extent ) );
+      using type = ElementType;
+   };
+
+#if defined( __clang__ )
+#pragma clang diagnostic pop
+#endif
+
+   // TODO: this is probably illegal. keep it?
+   template< size_t I, typename ElementType, size_t Extent >
+   constexpr ElementType& get( tao::span< ElementType, Extent > s ) noexcept
+   {
+      static_assert( ( Extent != tao::dynamic_extent ) && ( I < Extent ) );
+      return s[ I ];
+   }
+
+}  // namespace std
+
+#endif
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/stream.hpp b/3rdParty/taocpp-json/include/tao/json/stream.hpp
new file mode 100644
index 000000000000..13fda705567a
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/stream.hpp
@@ -0,0 +1,38 @@
+// Copyright (c) 2015-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_STREAM_HPP
+#define TAO_JSON_STREAM_HPP
+
+#include <iomanip>
+#include <iosfwd>
+#include <stdexcept>
+
+#include "to_stream.hpp"
+#include "value.hpp"
+
+#include "internal/format.hpp"
+
+namespace tao::json
+{
+   // Use ostream << std::setw( n ) for pretty-printing with indent n.
+
+   template< template< typename... > class Traits >
+   std::ostream& operator<<( std::ostream& o, const basic_value< Traits >& v )
+   {
+      const auto w = o.width( 0 );
+      if( w > 0 ) {
+         if( w >= 256 ) {
+            throw std::runtime_error( internal::format( "indentation ", w, " larger than 255" ) );
+         }
+         json::to_stream( o, v, static_cast< std::size_t >( w ) );
+      }
+      else {
+         json::to_stream( o, v );
+      }
+      return o;
+   }
+
+}  // namespace tao::json
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/to_stream.hpp b/3rdParty/taocpp-json/include/tao/json/to_stream.hpp
new file mode 100644
index 000000000000..62b2dae57dcc
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/to_stream.hpp
@@ -0,0 +1,42 @@
+// Copyright (c) 2015-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_TO_STREAM_HPP
+#define TAO_JSON_TO_STREAM_HPP
+
+#include <cstddef>
+#include <ostream>
+#include <utility>
+
+#include "events/from_value.hpp"
+#include "events/to_pretty_stream.hpp"
+#include "events/to_stream.hpp"
+#include "events/transformer.hpp"
+#include "value.hpp"
+
+namespace tao::json
+{
+   template< template< typename... > class... Transformers, template< typename... > class Traits >
+   void to_stream( std::ostream& os, const basic_value< Traits >& v )
+   {
+      events::transformer< events::to_stream, Transformers... > consumer( os );
+      events::from_value( consumer, v );
+   }
+
+   template< template< typename... > class... Transformers, template< typename... > class Traits >
+   void to_stream( std::ostream& os, const basic_value< Traits >& v, const std::size_t indent )
+   {
+      events::transformer< events::to_pretty_stream, Transformers... > consumer( os, indent );
+      events::from_value( consumer, v );
+   }
+
+   template< template< typename... > class... Transformers, template< typename... > class Traits, typename S >
+   void to_stream( std::ostream& os, const basic_value< Traits >& v, const std::size_t indent, S&& eol )
+   {
+      events::transformer< events::to_pretty_stream, Transformers... > consumer( os, indent, std::forward< S >( eol ) );
+      events::from_value( consumer, v );
+   }
+
+}  // namespace tao::json
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/to_string.hpp b/3rdParty/taocpp-json/include/tao/json/to_string.hpp
new file mode 100644
index 000000000000..9dd8f5cf1177
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/to_string.hpp
@@ -0,0 +1,23 @@
+// Copyright (c) 2015-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_TO_STRING_HPP
+#define TAO_JSON_TO_STRING_HPP
+
+#include <sstream>
+
+#include "to_stream.hpp"
+
+namespace tao::json
+{
+   template< template< typename... > class... Transformers, typename... Ts >
+   [[nodiscard]] std::string to_string( Ts&&... ts )
+   {
+      std::ostringstream o;
+      json::to_stream< Transformers... >( o, std::forward< Ts >( ts )... );
+      return o.str();
+   }
+
+}  // namespace tao::json
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/traits.hpp b/3rdParty/taocpp-json/include/tao/json/traits.hpp
new file mode 100644
index 000000000000..b19d6bb889e4
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/traits.hpp
@@ -0,0 +1,971 @@
+// Copyright (c) 2016-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_TRAITS_HPP
+#define TAO_JSON_TRAITS_HPP
+
+#include <cstddef>
+#include <cstdint>
+#include <cstdlib>
+
+#include <algorithm>
+#include <map>
+#include <optional>
+#include <string>
+#include <string_view>
+#include <vector>
+
+#include "binary_view.hpp"
+#include "consume.hpp"
+#include "forward.hpp"
+#include "type.hpp"
+
+#include "events/from_value.hpp"
+#include "events/produce.hpp"
+
+#include "internal/format.hpp"
+#include "internal/identity.hpp"
+#include "internal/number_traits.hpp"
+#include "internal/string_t.hpp"
+#include "internal/type_traits.hpp"
+
+#include "external/pegtl/internal/pegtl_string.hpp"
+
+#define TAO_JSON_DEFAULT_KEY( x )                   \
+   template< template< typename... > class Traits > \
+   using default_key = TAO_JSON_STRING_T( x )
+
+#ifdef _MSC_VER
+#pragma warning( push )
+#pragma warning( disable : 4702 )
+#endif
+
+namespace tao::json
+{
+   namespace internal
+   {
+      struct empty_base
+      {};
+
+   }  // namespace internal
+
+   // Traits< void > is special and configures the basic_value class template
+   template<>
+   struct traits< void >
+   {
+      static constexpr bool enable_implicit_constructor = true;
+
+      template< typename >
+      using public_base = internal::empty_base;
+   };
+
+   template<>
+   struct traits< uninitialized_t >
+   {
+      static constexpr bool enable_implicit_constructor = true;
+
+      template< template< typename... > class Traits >
+      static void assign( basic_value< Traits >& /*unused*/, uninitialized_t /*unused*/ ) noexcept
+      {}
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool equal( const basic_value< Traits >& lhs, uninitialized_t /*unused*/ ) noexcept
+      {
+         return lhs.skip_value_ptr().is_uninitialized();
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool less_than( const basic_value< Traits >& /*unused*/, uninitialized_t /*unused*/ ) noexcept
+      {
+         return false;  // Because std::underlying_type_t< tao::json::type > is unsigned and type::uninitialized is 0.
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool greater_than( const basic_value< Traits >& lhs, uninitialized_t /*unused*/ ) noexcept
+      {
+         return lhs.skip_value_ptr().type() > type::UNINITIALIZED;
+      }
+   };
+
+   template<>
+   struct traits< null_t >
+   {
+      static constexpr bool enable_implicit_constructor = true;
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static null_t as( const basic_value< Traits >& v )
+      {
+         return v.get_null();
+      }
+
+      template< template< typename... > class Traits >
+      static void assign( basic_value< Traits >& v, null_t /*unused*/ ) noexcept
+      {
+         v.set_null();
+      }
+
+      template< template< typename... > class Traits, typename Consumer >
+      static void produce( Consumer& c, const null_t /*unused*/ )
+      {
+         c.null();
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool equal( const basic_value< Traits >& lhs, null_t /*unused*/ ) noexcept
+      {
+         return lhs.skip_value_ptr().is_null();
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool less_than( const basic_value< Traits >& lhs, null_t /*unused*/ ) noexcept
+      {
+         return lhs.skip_value_ptr().type() < type::NULL_;
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool greater_than( const basic_value< Traits >& lhs, null_t /*unused*/ ) noexcept
+      {
+         return lhs.skip_value_ptr().type() > type::NULL_;
+      }
+   };
+
+   template<>
+   struct traits< bool >
+   {
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool as( const basic_value< Traits >& v )
+      {
+         return v.get_boolean();
+      }
+
+      template< template< typename... > class Traits >
+      static void assign( basic_value< Traits >& v, const bool b ) noexcept
+      {
+         v.set_boolean( b );
+      }
+
+      template< template< typename... > class, typename Producer >
+      [[nodiscard]] static bool consume( Producer& parser )
+      {
+         return parser.boolean();
+      }
+
+      template< template< typename... > class Traits, typename Consumer >
+      static void produce( Consumer& c, const bool b )
+      {
+         c.boolean( b );
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool equal( const basic_value< Traits >& lhs, const bool rhs ) noexcept
+      {
+         const auto& p = lhs.skip_value_ptr();
+         return p.is_boolean() && ( p.get_boolean() == rhs );
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool less_than( const basic_value< Traits >& lhs, const bool rhs ) noexcept
+      {
+         const auto& p = lhs.skip_value_ptr();
+         return ( p.type() < type::BOOLEAN ) || ( p.is_boolean() && ( p.get_boolean() < rhs ) );
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool greater_than( const basic_value< Traits >& lhs, const bool rhs ) noexcept
+      {
+         const auto& p = lhs.skip_value_ptr();
+         return ( p.type() > type::BOOLEAN ) || ( p.is_boolean() && ( p.get_boolean() > rhs ) );
+      }
+   };
+
+   // clang-format off
+   template<> struct traits< signed char > : internal::signed_trait< signed char > {};
+   template<> struct traits< signed short > : internal::signed_trait< signed short > {};
+   template<> struct traits< signed int > : internal::signed_trait< signed int > {};
+   template<> struct traits< signed long > : internal::signed_trait< signed long > {};
+   template<> struct traits< signed long long > : internal::signed_trait< signed long long > {};
+
+   template<> struct traits< unsigned char > : internal::unsigned_trait< unsigned char > {};
+   template<> struct traits< unsigned short > : internal::unsigned_trait< unsigned short > {};
+   template<> struct traits< unsigned int > : internal::unsigned_trait< unsigned int > {};
+   template<> struct traits< unsigned long > : internal::unsigned_trait< unsigned long > {};
+   template<> struct traits< unsigned long long > : internal::unsigned_trait< unsigned long long > {};
+
+   template<> struct traits< float > : internal::float_trait< float > {};
+   template<> struct traits< double > : internal::float_trait< double > {};
+   // clang-format on
+
+   template<>
+   struct traits< empty_string_t >
+   {
+      static constexpr bool enable_implicit_constructor = true;
+
+      template< template< typename... > class Traits >
+      static void assign( basic_value< Traits >& v, empty_string_t /*unused*/ ) noexcept
+      {
+         v.emplace_string();
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool equal( const basic_value< Traits >& lhs, empty_string_t /*unused*/ ) noexcept
+      {
+         const auto& p = lhs.skip_value_ptr();
+         switch( p.type() ) {
+            case type::STRING:
+               return p.get_string().empty();
+            case type::STRING_VIEW:
+               return p.get_string_view().empty();
+            default:
+               return false;
+         }
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool less_than( const basic_value< Traits >& lhs, empty_string_t /*unused*/ ) noexcept
+      {
+         const auto& p = lhs.skip_value_ptr();
+         switch( p.type() ) {
+            case type::STRING:
+            case type::STRING_VIEW:
+               return false;
+            default:
+               return p.type() < type::STRING;
+         }
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool greater_than( const basic_value< Traits >& lhs, empty_string_t /*unused*/ ) noexcept
+      {
+         const auto& p = lhs.skip_value_ptr();
+         switch( p.type() ) {
+            case type::STRING:
+               return !p.get_string().empty();
+            case type::STRING_VIEW:
+               return !p.get_string_view().empty();
+            default:
+               return p.type() > type::STRING;
+         }
+      }
+   };
+
+   template<>
+   struct traits< empty_binary_t >
+   {
+      static constexpr bool enable_implicit_constructor = true;
+
+      template< template< typename... > class Traits >
+      static void assign( basic_value< Traits >& v, empty_binary_t /*unused*/ ) noexcept
+      {
+         v.emplace_binary();
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool equal( const basic_value< Traits >& lhs, empty_binary_t /*unused*/ ) noexcept
+      {
+         const auto& p = lhs.skip_value_ptr();
+         switch( p.type() ) {
+            case type::BINARY:
+               return p.get_binary().empty();
+            case type::BINARY_VIEW:
+               return p.get_binary_view().empty();
+            default:
+               return false;
+         }
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool less_than( const basic_value< Traits >& lhs, empty_binary_t /*unused*/ ) noexcept
+      {
+         const auto& p = lhs.skip_value_ptr();
+         switch( p.type() ) {
+            case type::BINARY:
+            case type::BINARY_VIEW:
+               return false;
+            default:
+               return p.type() < type::BINARY;
+         }
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool greater_than( const basic_value< Traits >& lhs, empty_binary_t /*unused*/ ) noexcept
+      {
+         const auto& p = lhs.skip_value_ptr();
+         switch( p.type() ) {
+            case type::BINARY:
+               return !p.get_binary().empty();
+            case type::BINARY_VIEW:
+               return !p.get_binary_view().empty();
+            default:
+               return p.type() > type::BINARY;
+         }
+      }
+   };
+
+   template<>
+   struct traits< empty_array_t >
+   {
+      static constexpr bool enable_implicit_constructor = true;
+
+      template< template< typename... > class Traits >
+      static void assign( basic_value< Traits >& v, empty_array_t /*unused*/ ) noexcept
+      {
+         v.emplace_array();
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool equal( const basic_value< Traits >& lhs, empty_array_t /*unused*/ ) noexcept
+      {
+         const auto& p = lhs.skip_value_ptr();
+         return p.is_array() && p.get_array().empty();
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool less_than( const basic_value< Traits >& lhs, empty_array_t /*unused*/ ) noexcept
+      {
+         return lhs.skip_value_ptr().type() < type::ARRAY;
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool greater_than( const basic_value< Traits >& lhs, empty_array_t /*unused*/ ) noexcept
+      {
+         const auto& p = lhs.skip_value_ptr();
+         return ( p.type() > type::ARRAY ) || ( p.is_array() && !p.get_array().empty() );
+      }
+   };
+
+   template<>
+   struct traits< empty_object_t >
+   {
+      static constexpr bool enable_implicit_constructor = true;
+
+      template< template< typename... > class Traits >
+      static void assign( basic_value< Traits >& v, empty_object_t /*unused*/ ) noexcept
+      {
+         v.emplace_object();
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool equal( const basic_value< Traits >& lhs, empty_object_t /*unused*/ ) noexcept
+      {
+         const auto& p = lhs.skip_value_ptr();
+         return p.is_object() && p.get_object().empty();
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool less_than( const basic_value< Traits >& lhs, empty_object_t /*unused*/ ) noexcept
+      {
+         return lhs.skip_value_ptr().type() < type::OBJECT;
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool greater_than( const basic_value< Traits >& lhs, empty_object_t /*unused*/ ) noexcept
+      {
+         const auto& p = lhs.skip_value_ptr();
+         return ( p.type() > type::OBJECT ) || ( p.is_object() && !p.get_object().empty() );
+      }
+   };
+
+   template<>
+   struct traits< std::string >
+   {
+      template< template< typename... > class Traits >
+      [[nodiscard]] static std::string as( const basic_value< Traits >& v )
+      {
+         switch( v.type() ) {
+            case type::STRING:
+               return v.get_string();
+            case type::STRING_VIEW:
+               return std::string( v.get_string_view() );
+            default:
+               throw std::logic_error( internal::format( "invalid json type '", v.type(), "' for conversion to std::string", json::message_extension( v ) ) );
+         }
+      }
+
+      template< template< typename... > class Traits >
+      static void assign( basic_value< Traits >& v, const std::string& s )
+      {
+         v.set_string( s );
+      }
+
+      template< template< typename... > class Traits >
+      static void assign( basic_value< Traits >& v, std::string&& s ) noexcept
+      {
+         v.set_string( std::move( s ) );
+      }
+
+      template< template< typename... > class, typename Producer >
+      [[nodiscard]] static std::string consume( Producer& parser )
+      {
+         return parser.string();
+      }
+
+      template< template< typename... > class Traits, typename Consumer >
+      static void produce( Consumer& c, const std::string& s )
+      {
+         c.string( s );
+      }
+
+      template< template< typename... > class Traits, typename Consumer >
+      static void produce( Consumer& c, std::string&& s )
+      {
+         c.string( std::move( s ) );
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool equal( const basic_value< Traits >& lhs, const std::string& rhs ) noexcept
+      {
+         const auto& p = lhs.skip_value_ptr();
+         switch( p.type() ) {
+            case type::STRING:
+               return p.get_string() == rhs;
+            case type::STRING_VIEW:
+               return p.get_string_view() == rhs;
+            default:
+               return false;
+         }
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool less_than( const basic_value< Traits >& lhs, const std::string& rhs ) noexcept
+      {
+         const auto& p = lhs.skip_value_ptr();
+         switch( p.type() ) {
+            case type::STRING:
+               return p.get_string() < rhs;
+            case type::STRING_VIEW:
+               return p.get_string_view() < rhs;
+            default:
+               return p.type() < type::STRING;
+         }
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool greater_than( const basic_value< Traits >& lhs, const std::string& rhs ) noexcept
+      {
+         const auto& p = lhs.skip_value_ptr();
+         switch( p.type() ) {
+            case type::STRING:
+               return p.get_string() > rhs;
+            case type::STRING_VIEW:
+               return p.get_string_view() > rhs;
+            default:
+               return p.type() > type::STRING;
+         }
+      }
+   };
+
+   template<>
+   struct traits< std::string_view >
+   {
+      template< template< typename... > class Traits >
+      [[nodiscard]] static std::string_view as( const basic_value< Traits >& v )
+      {
+         switch( v.type() ) {
+            case type::STRING:
+               return v.get_string();
+            case type::STRING_VIEW:
+               return v.get_string_view();
+            default:
+               throw std::logic_error( internal::format( "invalid json type '", v.type(), "' for conversion to std::string_view", json::message_extension( v ) ) );
+         }
+      }
+
+      template< template< typename... > class Traits >
+      static void assign( basic_value< Traits >& v, const std::string_view sv )
+      {
+         v.emplace_string( sv );
+      }
+
+      template< template< typename... > class Traits, typename Consumer >
+      static void produce( Consumer& c, const std::string_view sv )
+      {
+         c.string( sv );
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool equal( const basic_value< Traits >& lhs, const std::string_view rhs ) noexcept
+      {
+         const auto& p = lhs.skip_value_ptr();
+         switch( p.type() ) {
+            case type::STRING:
+               return p.get_string() == rhs;
+            case type::STRING_VIEW:
+               return p.get_string_view() == rhs;
+            default:
+               return false;
+         }
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool less_than( const basic_value< Traits >& lhs, const std::string_view rhs ) noexcept
+      {
+         const auto& p = lhs.skip_value_ptr();
+         switch( p.type() ) {
+            case type::STRING:
+               return p.get_string() < rhs;
+            case type::STRING_VIEW:
+               return p.get_string_view() < rhs;
+            default:
+               return p.type() < type::STRING;
+         }
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool greater_than( const basic_value< Traits >& lhs, const std::string_view rhs ) noexcept
+      {
+         const auto& p = lhs.skip_value_ptr();
+         switch( p.type() ) {
+            case type::STRING:
+               return p.get_string() > rhs;
+            case type::STRING_VIEW:
+               return p.get_string_view() > rhs;
+            default:
+               return p.type() > type::STRING;
+         }
+      }
+   };
+
+   template<>
+   struct traits< const char* >
+   {
+      template< template< typename... > class Traits >
+      [[nodiscard]] static const char* as( const basic_value< Traits >& v )
+      {
+         return v.get_string().c_str();  // String views might not be '\0'-terminated.
+      }
+
+      template< template< typename... > class Traits >
+      static void assign( basic_value< Traits >& v, const char* s )
+      {
+         v.emplace_string( s );
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool equal( const basic_value< Traits >& lhs, const char* rhs ) noexcept
+      {
+         const auto& p = lhs.skip_value_ptr();
+         switch( p.type() ) {
+            case type::STRING:
+               return p.get_string() == rhs;
+            case type::STRING_VIEW:
+               return p.get_string_view() == rhs;
+            default:
+               return false;
+         }
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool less_than( const basic_value< Traits >& lhs, const char* rhs ) noexcept
+      {
+         const auto& p = lhs.skip_value_ptr();
+         switch( p.type() ) {
+            case type::STRING:
+               return p.get_string() < rhs;
+            case type::STRING_VIEW:
+               return p.get_string_view() < rhs;
+            default:
+               return p.type() < type::STRING;
+         }
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool greater_than( const basic_value< Traits >& lhs, const char* rhs ) noexcept
+      {
+         const auto& p = lhs.skip_value_ptr();
+         switch( p.type() ) {
+            case type::STRING:
+               return p.get_string() > rhs;
+            case type::STRING_VIEW:
+               return p.get_string_view() > rhs;
+            default:
+               return p.type() > type::STRING;
+         }
+      }
+   };
+
+   template<>
+   struct traits< const std::string& >
+   {
+      template< template< typename... > class Traits >
+      [[nodiscard]] static const std::string& as( const basic_value< Traits >& v )
+      {
+         return v.get_string();
+      }
+   };
+
+   template<>
+   struct traits< std::vector< std::byte > >
+   {
+      template< template< typename... > class Traits >
+      [[nodiscard]] static std::vector< std::byte > as( const basic_value< Traits >& v )
+      {
+         switch( v.type() ) {
+            case type::BINARY:
+               return v.get_binary();
+            case type::BINARY_VIEW: {
+               const auto xv = v.get_binary_view();
+               return std::vector< std::byte >( xv.begin(), xv.end() );
+            }
+            default:
+               throw std::logic_error( internal::format( "invalid json type '", v.type(), "' for conversion to std::vector< std::byte >", json::message_extension( v ) ) );
+         }
+      }
+
+      template< template< typename... > class Traits >
+      static void assign( basic_value< Traits >& v, const std::vector< std::byte >& x )
+      {
+         v.set_binary( x );
+      }
+
+      template< template< typename... > class Traits >
+      static void assign( basic_value< Traits >& v, std::vector< std::byte >&& x ) noexcept
+      {
+         v.set_binary( std::move( x ) );
+      }
+
+      template< template< typename... > class, typename Producer >
+      [[nodiscard]] static std::vector< std::byte > consume( Producer& parser )
+      {
+         return parser.binary();
+      }
+
+      template< template< typename... > class Traits, typename Consumer >
+      static void produce( Consumer& c, const std::vector< std::byte >& x )
+      {
+         c.binary( x );
+      }
+
+      template< template< typename... > class Traits, typename Consumer >
+      static void produce( Consumer& c, std::vector< std::byte >&& x )
+      {
+         c.binary( std::move( x ) );
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool equal( const basic_value< Traits >& lhs, const std::vector< std::byte >& rhs ) noexcept
+      {
+         const auto& p = lhs.skip_value_ptr();
+         switch( p.type() ) {
+            case type::BINARY:
+               return p.get_binary() == rhs;
+            case type::BINARY_VIEW:
+               return tao::internal::binary_equal( p.get_binary_view(), rhs );
+            default:
+               return false;
+         }
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool less_than( const basic_value< Traits >& lhs, const std::vector< std::byte >& rhs ) noexcept
+      {
+         const auto& p = lhs.skip_value_ptr();
+         switch( p.type() ) {
+            case type::BINARY:
+               return p.get_binary() < rhs;
+            case type::BINARY_VIEW:
+               return tao::internal::binary_less( p.get_binary_view(), rhs );
+            default:
+               return p.type() < type::BINARY;
+         }
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool greater_than( const basic_value< Traits >& lhs, const std::vector< std::byte >& rhs ) noexcept
+      {
+         const auto& p = lhs.skip_value_ptr();
+         switch( p.type() ) {
+            case type::BINARY:
+               return p.get_binary() > rhs;
+            case type::BINARY_VIEW:
+               return tao::internal::binary_less( rhs, p.get_binary_view() );
+            default:
+               return p.type() > type::BINARY;
+         }
+      }
+   };
+
+   template<>
+   struct traits< tao::binary_view >
+   {
+      template< template< typename... > class Traits >
+      [[nodiscard]] static tao::binary_view as( const basic_value< Traits >& v )
+      {
+         switch( v.type() ) {
+            case type::BINARY:
+               return v.get_binary();
+            case type::BINARY_VIEW:
+               return v.get_binary_view();
+            default:
+               throw std::logic_error( internal::format( "invalid json type '", v.type(), "' for conversion to tao::binary_view", json::message_extension( v ) ) );
+         }
+      }
+
+      template< template< typename... > class Traits >
+      static void assign( basic_value< Traits >& v, const tao::binary_view xv )
+      {
+         v.emplace_binary( xv.begin(), xv.end() );
+      }
+
+      template< template< typename... > class Traits, typename Consumer >
+      static void produce( Consumer& c, const tao::binary_view xv )
+      {
+         c.binary( xv );
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool equal( const basic_value< Traits >& lhs, const tao::binary_view rhs ) noexcept
+      {
+         const auto& p = lhs.skip_value_ptr();
+         switch( p.type() ) {
+            case type::BINARY:
+               return tao::internal::binary_equal( p.get_binary(), rhs );
+            case type::BINARY_VIEW:
+               return tao::internal::binary_equal( p.get_binary_view(), rhs );
+            default:
+               return false;
+         }
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool less_than( const basic_value< Traits >& lhs, const tao::binary_view rhs ) noexcept
+      {
+         const auto& p = lhs.skip_value_ptr();
+         switch( p.type() ) {
+            case type::BINARY:
+               return tao::internal::binary_less( p.get_binary(), rhs );
+            case type::BINARY_VIEW:
+               return tao::internal::binary_less( p.get_binary_view(), rhs );
+            default:
+               return p.type() < type::BINARY;
+         }
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool greater_than( const basic_value< Traits >& lhs, const tao::binary_view rhs ) noexcept
+      {
+         const auto& p = lhs.skip_value_ptr();
+         switch( p.type() ) {
+            case type::BINARY:
+               return tao::internal::binary_less( rhs, p.get_binary() );
+            case type::BINARY_VIEW:
+               return tao::internal::binary_less( rhs, p.get_binary_view() );
+            default:
+               return p.type() > type::BINARY;
+         }
+      }
+   };
+
+   template<>
+   struct traits< const std::vector< std::byte >& >
+   {
+      template< template< typename... > class Traits >
+      [[nodiscard]] static const std::vector< std::byte >& as( const basic_value< Traits >& v )
+      {
+         return v.get_binary();
+      }
+   };
+
+   template< template< typename... > class Traits >
+   struct traits< basic_value< Traits > >
+   {
+      template< template< typename... > class, typename Consumer >
+      static void produce( Consumer& c, const basic_value< Traits >& v )
+      {
+         events::from_value( c, v );
+      }
+
+      template< template< typename... > class, typename Consumer >
+      static void produce( Consumer& c, basic_value< Traits >&& v )
+      {
+         events::from_value( c, std::move( v ) );
+      }
+   };
+
+   template< template< typename... > class Traits >
+   struct traits< std::vector< basic_value< Traits > > >
+   {
+      static void assign( basic_value< Traits >& v, const std::vector< basic_value< Traits > >& a )
+      {
+         v.set_array( a );
+      }
+
+      static void assign( basic_value< Traits >& v, std::vector< basic_value< Traits > >&& a ) noexcept
+      {
+         v.set_array( std::move( a ) );
+      }
+
+      template< template< typename... > class, typename Consumer >
+      static void produce( Consumer& c, const std::vector< basic_value< Traits > >& a )
+      {
+         c.begin_array( a.size() );
+         for( const auto& i : a ) {
+            Traits< basic_value< Traits > >::produce( c, i );
+            c.element();
+         }
+         c.end_array( a.size() );
+      }
+
+      template< template< typename... > class, typename Consumer >
+      static void produce( Consumer& c, std::vector< basic_value< Traits > >&& a )
+      {
+         c.begin_array( a.size() );
+         for( auto&& i : a ) {
+            Traits< basic_value< Traits > >::produce( c, std::move( i ) );
+            c.element();
+         }
+         c.end_array( a.size() );
+      }
+   };
+
+   template< template< typename... > class Traits >
+   struct traits< std::map< std::string, basic_value< Traits >, std::less<> > >
+   {
+      static void assign( basic_value< Traits >& v, const std::map< std::string, basic_value< Traits >, std::less<> >& o )
+      {
+         v.set_object( std::move( o ) );
+      }
+
+      static void assign( basic_value< Traits >& v, std::map< std::string, basic_value< Traits >, std::less<> >&& o ) noexcept
+      {
+         v.set_object( std::move( o ) );
+      }
+
+      template< template< typename... > class, typename Consumer >
+      static void produce( Consumer& c, const std::map< std::string, basic_value< Traits >, std::less<> >& o )
+      {
+         c.begin_object( o.size() );
+         for( const auto& i : o ) {
+            c.key( i.first );
+            Traits< basic_value< Traits > >::produce( c, i.second );
+            c.member();
+         }
+         c.end_object( o.size() );
+      }
+
+      template< template< typename... > class, typename Consumer >
+      static void produce( Consumer& c, std::map< std::string, basic_value< Traits >, std::less<> >&& o )
+      {
+         c.begin_object( o.size() );
+         for( auto&& i : o ) {
+            c.key( std::move( i.first ) );
+            Traits< basic_value< Traits > >::produce( c, std::move( i.second ) );
+            c.member();
+         }
+         c.end_object( o.size() );
+      }
+   };
+
+   template< template< typename... > class Traits >
+   struct traits< const basic_value< Traits >* >
+   {
+      static void assign( basic_value< Traits >& v, const basic_value< Traits >* p ) noexcept
+      {
+         v.set_value_ptr( p );
+      }
+
+      template< template< typename... > class TraitsLL >
+      [[nodiscard]] static bool equal( const basic_value< TraitsLL >& lhs, const basic_value< Traits >* rhs ) noexcept
+      {
+         assert( rhs );
+         return lhs == *rhs;
+      }
+
+      template< template< typename... > class TraitsLL >
+      [[nodiscard]] static bool less_than( const basic_value< TraitsLL >& lhs, const basic_value< Traits >* rhs ) noexcept
+      {
+         assert( rhs );
+         return lhs < *rhs;
+      }
+
+      template< template< typename... > class TraitsLL >
+      [[nodiscard]] static bool greater_than( const basic_value< TraitsLL >& lhs, const basic_value< Traits >* rhs ) noexcept
+      {
+         assert( rhs );
+         return lhs > *rhs;
+      }
+   };
+
+   template< template< typename... > class Traits >
+   struct traits< basic_value< Traits >* >
+      : traits< const basic_value< Traits >* >
+   {
+   };
+
+   template< typename T >
+   struct traits< std::optional< T > >
+   {
+      template< template< typename... > class Traits >
+      using default_key = typename Traits< T >::template default_key< Traits >;
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool is_nothing( const std::optional< T >& o )
+      {
+         return ( !bool( o ) ) || internal::is_nothing< Traits >( *o );  // TODO: Only query o?
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static std::optional< T > as( const basic_value< Traits >& v )
+      {
+         if( v == null ) {
+            return std::nullopt;
+         }
+         return v.template as< T >();
+      }
+
+      template< template< typename... > class Traits >
+      static void assign( basic_value< Traits >& v, const std::optional< T >& o )
+      {
+         if( o ) {
+            v.assign( *o );
+         }
+         else {
+            v.set_null();
+         }
+      }
+
+      template< template< typename... > class Traits, typename Producer >
+      [[nodiscard]] static std::optional< T > consume( Producer& parser )
+      {
+         if( parser.null() ) {
+            return std::nullopt;
+         }
+         return json::consume< T, Traits >( parser );
+      }
+
+      template< template< typename... > class Traits, typename Consumer >
+      static void produce( Consumer& c, const std::optional< T >& o )
+      {
+         if( o ) {
+            json::events::produce< Traits >( c, *o );
+         }
+         else {
+            json::events::produce< Traits >( c, null );
+         }
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool equal( const basic_value< Traits >& lhs, const std::optional< T >& rhs ) noexcept
+      {
+         return rhs ? ( lhs == *rhs ) : ( lhs == null );
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool less_than( const basic_value< Traits >& lhs, const std::optional< T >& rhs ) noexcept
+      {
+         return rhs ? ( lhs < *rhs ) : ( lhs < null );
+      }
+
+      template< template< typename... > class Traits >
+      [[nodiscard]] static bool greater_than( const basic_value< Traits >& lhs, const std::optional< T >& rhs ) noexcept
+      {
+         return rhs ? ( lhs > *rhs ) : ( lhs > null );
+      }
+   };
+
+}  // namespace tao::json
+
+#ifdef _MSC_VER
+#pragma warning( pop )
+#endif
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/type.hpp b/3rdParty/taocpp-json/include/tao/json/type.hpp
new file mode 100644
index 000000000000..bb25d29c419b
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/type.hpp
@@ -0,0 +1,112 @@
+// Copyright (c) 2015-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_TYPE_HPP
+#define TAO_JSON_TYPE_HPP
+
+#include <cstdint>
+#include <string_view>
+#include <type_traits>
+#include <variant>
+
+#include "binary_view.hpp"
+
+namespace tao::json
+{
+   enum class type : std::size_t
+   {
+      UNINITIALIZED = 0,
+      NULL_,
+      BOOLEAN,
+      SIGNED,
+      UNSIGNED,
+      DOUBLE,
+      STRING,
+      STRING_VIEW,
+      BINARY,
+      BINARY_VIEW,
+      ARRAY,
+      OBJECT,
+      VALUE_PTR,
+      OPAQUE_PTR,
+
+      VALUELESS_BY_EXCEPTION = std::variant_npos
+   };
+
+   constexpr std::string_view to_string( const type t )
+   {
+      switch( t ) {
+         case type::UNINITIALIZED:
+            return "uninitialized";
+         case type::NULL_:
+            return "null";
+         case type::BOOLEAN:
+            return "boolean";
+         case type::SIGNED:
+            return "signed";
+         case type::UNSIGNED:
+            return "unsigned";
+         case type::DOUBLE:
+            return "double";
+         case type::STRING:
+            return "string";
+         case type::STRING_VIEW:
+            return "string_view";
+         case type::BINARY:
+            return "binary";
+         case type::BINARY_VIEW:
+            return "binary_view";
+         case type::ARRAY:
+            return "array";
+         case type::OBJECT:
+            return "object";
+         case type::VALUE_PTR:
+            return "value_ptr";
+         case type::OPAQUE_PTR:
+            return "opaque_ptr";
+         case type::VALUELESS_BY_EXCEPTION:
+            return "valueless_by_exception";
+      }
+      return "unknown";
+   }
+
+   struct null_t
+   {
+      explicit constexpr null_t( int /*unused*/ ) {}
+   };
+
+   struct empty_string_t
+   {
+      explicit constexpr empty_string_t( int /*unused*/ ) {}
+   };
+
+   struct empty_binary_t
+   {
+      explicit constexpr empty_binary_t( int /*unused*/ ) {}
+   };
+
+   struct empty_array_t
+   {
+      explicit constexpr empty_array_t( int /*unused*/ ) {}
+   };
+
+   struct empty_object_t
+   {
+      constexpr explicit empty_object_t( int /*unused*/ ) {}
+   };
+
+   struct uninitialized_t
+   {};
+
+   constexpr null_t null{ 0 };
+
+   constexpr empty_string_t empty_string{ 0 };
+   constexpr empty_binary_t empty_binary{ 0 };
+   constexpr empty_array_t empty_array{ 0 };
+   constexpr empty_object_t empty_object{ 0 };
+
+   constexpr uninitialized_t uninitialized;
+
+}  // namespace tao::json
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/utf8.hpp b/3rdParty/taocpp-json/include/tao/json/utf8.hpp
new file mode 100644
index 000000000000..18f139fe15a0
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/utf8.hpp
@@ -0,0 +1,57 @@
+// Copyright (c) 2018-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_UTF8_HPP
+#define TAO_JSON_UTF8_HPP
+
+#include "external/pegtl/memory_input.hpp"
+#include "external/pegtl/parse.hpp"
+#include "external/pegtl/rules.hpp"
+#include "external/pegtl/utf8.hpp"
+
+namespace tao::json
+{
+   enum class utf8_mode : bool
+   {
+      check,
+      trust
+   };
+
+   namespace internal
+   {
+      template< typename Input >
+      bool consume_utf8_impl( Input& in, const std::size_t todo )
+      {
+         std::size_t i = 0;
+         while( i < todo ) {
+            const auto p = pegtl::internal::peek_utf8::peek( in, pegtl::internal::peek_utf8::max_input_size ).size;
+            if( ( p == 0 ) || ( ( i += p ) > todo ) ) {
+               return false;
+            }
+            in.bump_in_this_line( p );
+         }
+         return true;
+      }
+
+      template< utf8_mode M, typename Input >
+      void consume_utf8_throws( Input& in, const std::size_t todo )
+      {
+         if constexpr( M == utf8_mode::trust ) {
+            in.bump_in_this_line( todo );
+         }
+         else if( !consume_utf8_impl( in, todo ) ) {
+            throw pegtl::parse_error( "invalid utf8", in );
+         }
+      }
+
+      inline bool validate_utf8_nothrow( const std::string_view sv ) noexcept
+      {
+         pegtl::memory_input in( sv, "validate_utf8" );
+         return consume_utf8_impl( in, sv.size() );
+      }
+
+   }  // namespace internal
+
+}  // namespace tao::json
+
+#endif
diff --git a/3rdParty/taocpp-json/include/tao/json/value.hpp b/3rdParty/taocpp-json/include/tao/json/value.hpp
new file mode 100644
index 000000000000..df8453ecb5bb
--- /dev/null
+++ b/3rdParty/taocpp-json/include/tao/json/value.hpp
@@ -0,0 +1,12 @@
+// Copyright (c) 2017-2020 Dr. Colin Hirsch and Daniel Frey
+// Please see LICENSE for license or visit https://github.com/taocpp/json/
+
+#ifndef TAO_JSON_VALUE_HPP
+#define TAO_JSON_VALUE_HPP
+
+#include "basic_value.hpp"
+#include "forward.hpp"
+#include "operators.hpp"
+#include "traits.hpp"
+
+#endif
diff --git a/3rdParty/velocypack/include/velocypack/Iterator.h b/3rdParty/velocypack/include/velocypack/Iterator.h
index 6eb6232754d4..6e6075db22b0 100644
--- a/3rdParty/velocypack/include/velocypack/Iterator.h
+++ b/3rdParty/velocypack/include/velocypack/Iterator.h
@@ -41,8 +41,14 @@ class ArrayIterator : public std::iterator<std::forward_iterator_tag, Slice> {
  public:
   using iterator_category = std::forward_iterator_tag;
 
+  struct Empty {};
+
   ArrayIterator() = delete;
 
+  // optimization for an empty array
+  explicit ArrayIterator(Empty) noexcept
+      : _slice(Slice::emptyArraySlice()), _size(0), _position(0), _current(nullptr), _first(nullptr) {}
+
   explicit ArrayIterator(Slice slice)
       : _slice(slice), _size(0), _position(0), _current(nullptr), _first(nullptr) {
     
diff --git a/CHANGELOG b/CHANGELOG
index 977e99471bb6..6b3b9fb07993 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,13 +1,105 @@
 devel
 -----
 
+* Supervision hot backup and supervision maintenance modes ttl fix.
+
+* Fix a bug that leads to graph traversals yielding empty output when none of the
+  output variables (vertex, edge, path) are used. This is relevant when a query 
+  is only interested in a COUNT of the outputs, for example.
+
+* MoveShard to check, if target is in sync follower before promotion
+  to leader.
+
+* Agency ttl bug fix
+
+* Added the SNI feature for TLS. This means that one can configure multiple
+  server keys and certificate chains and the system dynamically uses
+  the right one depending on the value of the TLS servername extension.
+  This allows to use different TLS setups for the same server which is
+  reachable behind different DNS names, for example (enterprise only).
+
+* Do not create a reboot tracker for empty serverId ubin sync repl.
+
+* Fix the usage of the AQL functions `CALL` and `APPLY` for calling user-defined
+  AQL functions when invoking an AQL query from the arangosh or a client application.
+  Previously, invoking an AQL query and using the `CALL` or `APPLY` AQL functions
+  to call user-defined AQL function caused undefined behavior.
+
+* Improved graph traversal performance via some internal code refactoring:
+
+  - Traversal cursors are reused instead of recreated from scratch, if possible.
+    This can save lots of calls to the memory management subsystem.
+  - Unnecessary checks have been removed from the cursors, by ensuring some
+    invariants.
+  - Each vertex lookup needs to perform slightly less work.
+
+  The traversal speedups observed by these changes alone were around 8 to 10% for
+  single-server traversals and traversals in OneShard setups. Cluster traversals
+  will also benefit from these changes, but to a lesser extent. This is because the
+  network roundtrips have a higher share of the total query execution times there.
+
+* Traversal performance can also be improved by not fetching the visited vertices
+  from the storage engine in case the traversal query does not refer to them.
+  For example, in the query
+
+      FOR v, e, p IN 1..3 OUTBOUND 'collection/startVertex' edges
+        RETURN e
+
+  the vertex variable (`v`) is never accessed, making it unnecessary to fetch the
+  vertices from storage. If this optimization is applied, the traversal node will be
+  marked with `/* vertex optimized away */` in the query's execution plan output.
+
+* The existing optimizer rule "move-calculations-down" is now able to also move
+  unrelated subqueries beyond SORT and LIMIT instructions, which can help avoid the
+  execution of subqueries for which the results are later discarded.
+  For example, in the query
+
+      FOR doc IN collection1
+        LET sub1 = FIRST(FOR sub IN collection2 FILTER sub.ref == doc._key RETURN sub)
+        LET sub2 = FIRST(FOR sub IN collection3 FILTER sub.ref == doc._key RETURN sub)
+        SORT sub1
+        LIMIT 10
+        RETURN { doc, sub1, sub2 }
+
+  the execution of the `sub2` subquery can be delayed to after the SORT and LIMIT,
+  turning it into
+
+      FOR doc IN collection1
+        LET sub1 = FIRST(FOR sub IN collection2 FILTER sub.ref == doc._key RETURN sub)
+        SORT sub1
+        LIMIT 10
+        LET sub2 = FIRST(FOR sub IN collection3 FILTER sub.ref == doc._key RETURN sub)
+        RETURN { doc, sub1, sub2 }
+
+* Added JSON-Schema (draft-4) document validation. The validation can be
+  specified by providing the new `validation` collection property when creating a
+  new collection or when updating the properties of an existing collection:
+
+      db.mycollection.properties({
+        validation: {
+          rule : { nums : { type : "array", items : { type : "number", maximum : 6 }}},
+          message : "Json-Schema validation failed"
+        }
+      });
+
+* Fix supervision mode detection when unlocking agency in hot backup.
+
+* Foxx Response#throw will no longer generate incomplete error objects when
+  passed invalid arguments.
+
+* Foxx will now always generate a numeric HTTP status code even if the response
+  status code has been set to a non-numeric value.
+
+* Make arangobench return a proper error message when its initial attempt to
+  create the test collection fails.
+
 * Added traversal options `vertexCollections` and `edgeCollections` to restrict
   traversal to certain vertex or edge collections.
 
   The use case for `vertexCollections` is to not follow any edges that will point
   to other than the specified vertex collections, e.g.
 
-      FOR v, e, p IN 1..3 OUTBOUND 'products/123' components 
+      FOR v, e, p IN 1..3 OUTBOUND 'products/123' components
         OPTIONS { vertexCollections: [ "bolts", "screws" ] }
 
   The traversal's start vertex is always considered valid, regardless of whether
@@ -15,8 +107,8 @@ devel
 
   The use case for `edgeCollections` is to not take into consideration any edges
   from edge collections other than the specified ones, e.g.
-      
-      FOR v, e, p IN 1..3 OUTBOUND 'products/123' GRAPH 'components' 
+
+      FOR v, e, p IN 1..3 OUTBOUND 'products/123' GRAPH 'components'
         OPTIONS { edgeCollections: [ "productsToBotls", "productsToScrews" ] }
 
   This is mostly useful in the context of named graphs, when the named graph
@@ -26,17 +118,20 @@ devel
   from the named graph are needed, the `edgeCollections` option can be a handy
   performance optimization.
 
+* Make arangobench return a proper error message when its initial attempt to
+  create the test collection fails.
+
 * In some cases with a COLLECT LIMIT situation on a small limit the collect
   does more calls to upstream than without a limit to provide the same
   result. We improved this situation and made sure that LIMIT does
   not cause the COLLECT to fetch too few input rows. There is a chance
   that queries with a very small amount of data might suffer from this
-  modification, most queries will benefit however.  
+  modification, most queries will benefit however.
 
 * Use OpenSSL's EVP interface for SHA256 instead of the deprecated low-level
   message digest APIs.
 
-* Prevent startup error "specifiy either '--server.jwt-secret-keyfile' or 
+* Prevent startup error "specifiy either '--server.jwt-secret-keyfile' or
   '--server.jwt-secret-folder' but not both." from occurring when specifying the
   JWT secret keyfile option.
 
@@ -75,8 +170,8 @@ devel
 
   Previously, document attributes named `geometry` were treated in a special
   way, assuming they were JSON objects. In case a document contained a
-	`geometry` attribute that had a non-object value (e.g. `null`) the web UI
-	threw a JavaScript exception and would not display AQL query results properly.
+  `geometry` attribute that had a non-object value (e.g. `null`) the web UI
+  threw a JavaScript exception and would not display AQL query results properly.
 
 * Disable "collect-in-cluster" AQL optimizer rule in case a LIMIT node is between
   the COLLECT and the source data. In this case it is not safe to apply the
@@ -85,10 +180,10 @@ devel
 * Fixed internal issue #4932: COLLECT WITH COUNT together with FILTER yields
   zero.
 
-  This bugfix fixes an issue when skipping over documents in an index scan 
+  This bugfix fixes an issue when skipping over documents in an index scan
   using a covering index and also at the same time using an early-pruning filter.
 
-  In this case wrong document data may have been injected into the filter 
+  In this case wrong document data may have been injected into the filter
   condition for filtering, with the filter wrongfully deciding which documents
   to filter out.
 
@@ -118,7 +213,7 @@ devel
   met and not allowing for inconsistency.
 
 * V8 version upgrade to 7.9.317; ICU version upgrade to 64.2.
-  - JSON parsing is roughly 60% faster than in V8 7.1; you should prefer 
+  - JSON parsing is roughly 60% faster than in V8 7.1; you should prefer
     JSON.parse(string) over deeply nested javascript variable declarations.
   - several new javascript language features
 
@@ -193,6 +288,7 @@ devel
   Like for the existing variant the `overwrite` flag has to be set to true.
   Then the update version can be selected by setting the `overwriteMode` to `"update"`.
 
+
 * Updated ArangoDB Starter to 0.14.13.
 
 * Added HotBackup events into auditing.
@@ -207,7 +303,7 @@ devel
 
 * Internal statistics API now uses integer timestamps instead of doubles. The
   old behaviour sometimes leads to failed requests because of parse errors
-	which occured in the internal used JavaScript joi library.
+  which occured in the internal used JavaScript joi library.
 
 * Support trailing commas in AQL object and array definitions as follows:
 
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 27629fd70bf6..abe5c608a133 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -520,8 +520,8 @@ endif ()
 
 if (WINDOWS)
   set(BASE_FLAGS     "/D WIN32 /D _WINDOWS /W3 /MP"      CACHE STRING "base flags")
-  set(BASE_C_FLAGS   ""                         	 CACHE STRING "base C flags")
-  set(BASE_CXX_FLAGS "/GR /EHsc"                	 CACHE STRING "base C++flags")
+  set(BASE_C_FLAGS   ""                                  CACHE STRING "base C flags")
+  set(BASE_CXX_FLAGS "/GR /EHsc /Zc:__cplusplus"         CACHE STRING "base C++flags")
 else ()
   set(BASE_FLAGS     ""                                  CACHE STRING "base flags")
   set(BASE_C_FLAGS   "${CMAKE_C_FLAGS}   $ENV{CFLAGS}"   CACHE STRING "base C flags")
diff --git a/Documentation/DocuBlocks/Rest/Administration/get_admin_server_tls.md b/Documentation/DocuBlocks/Rest/Administration/get_admin_server_tls.md
index 869008611434..800cdc85fb23 100644
--- a/Documentation/DocuBlocks/Rest/Administration/get_admin_server_tls.md
+++ b/Documentation/DocuBlocks/Rest/Administration/get_admin_server_tls.md
@@ -12,7 +12,12 @@ Return a summary of the TLS data. The JSON response will contain a field
   - `clientCA`: Information about the CA for client certificate
     verification.
 
-In both cases the value of the attribute will be a JSON object, which
+If server name indication (SNI) is used and multiple key files are
+configured for different server names, then there is an additional
+attribute `SNI`, which contains for each configured server name
+the corresponding information about the key file for that server name.
+
+In all cases the value of the attribute will be a JSON object, which
 has a subset of the following attributes (whatever is appropriate):
 
   - `SHA256`: The value is a string with the SHA256 of the whole input
diff --git a/Documentation/Scripts/codeBlockReader.py b/Documentation/Scripts/codeBlockReader.py
index 75dc7a1fa167..13fa6bc80056 100644
--- a/Documentation/Scripts/codeBlockReader.py
+++ b/Documentation/Scripts/codeBlockReader.py
@@ -1,9 +1,13 @@
+from __future__ import unicode_literals
 import os
 import sys
 import re
 import inspect
-import urllib
 import io
+try:
+  from urllib.parse import quote_plus
+except ImportError:
+  from urllib import quote_plus
 
 validExtensions = (".cpp", ".h", ".js", ".md")
 # specify the paths in which docublocks are searched. note that js/apps/* must not be included because it contains js/apps/system/
@@ -30,7 +34,7 @@ def file_content(filepath, forceDokuBlockContent):
   """ Fetches and formats file's content to perform the required operation.
   """
 
-  infile = io.open(filepath, 'r', encoding='utf-8', newline=None)
+  infile = io.open(filepath, encoding='utf-8', newline=None)
   filelines = tuple(infile)
   infile.close()
 
@@ -48,7 +52,7 @@ def file_content(filepath, forceDokuBlockContent):
           (not searchMDPaths[2] in filepath) and
           (not searchMDPaths[3] in filepath) and
           (not searchMDPaths[4] in filepath)):
-        print "next startDocuBlock found without endDocuBlock in between in file %s [%s]" %(filepath, line)
+        print("next startDocuBlock found without endDocuBlock in between in file %s [%s]" %(filepath, line))
         raise Exception
       _start = line[0]
     if "@endDocuBlock" in line[1]:
@@ -58,11 +62,11 @@ def file_content(filepath, forceDokuBlockContent):
         comment_indexes.append([_start, _end])
         _start = None
       except NameError:
-        print "endDocuBlock without previous startDocublock seen while analyzing file %s [%s]" %(filepath, line)
+        print("endDocuBlock without previous startDocublock seen while analyzing file %s [%s]" %(filepath, line))
         raise Exception
 
   if len(docublockname) != 0 and forceDokuBlockContent: 
-    print "no endDocuBlock found while analyzing file %s [%s]" %(filepath, docublockname)
+    print("no endDocuBlock found while analyzing file %s [%s]" %(filepath, docublockname))
     raise Exception
 
   for index in comment_indexes:
@@ -78,7 +82,7 @@ def example_content(filepath, fh, tag, blockType, placeIntoFilePath):
   first = True
   aqlResult = False
   lastline = None
-  longText = u""
+  longText = ""
   longLines = 0
   short = ""
   shortLines = 0
@@ -99,7 +103,7 @@ def example_content(filepath, fh, tag, blockType, placeIntoFilePath):
   blockCount = 0
 
   # read in the context, split into long and short
-  infile = io.open(filepath, 'r', encoding='utf-8', newline=None)
+  infile = io.open(filepath, encoding='utf-8', newline=None)
   for line in infile:
     stripped_line = re.sub('<[^<]+?>', '', line) # remove HTML tags
     if first:
@@ -196,70 +200,69 @@ def example_content(filepath, fh, tag, blockType, placeIntoFilePath):
   # python3: urllib.parse.quote_plus
 
   # write example
-  fh.write(unicode("\n"))
+  fh.write("\n")
 
-  utag = urllib.quote_plus(tag) + '_container'
-  ustr = u"\uE9CB"
-  #anchor = u"<a class=\"anchorjs-link \" href=\"#"+ utag + "\" aria-label=\"Anchor\" data-anchorjs-icon=\"" + ustr + "\"></a>"
+  utag = quote_plus(tag) + '_container'
+  ustr = "\uE9CB"
+  #anchor = "<a class=\"anchorjs-link \" href=\"#"+ utag + "\" aria-label=\"Anchor\" data-anchorjs-icon=\"" + ustr + "\"></a>"
 
   longTag = "%s_long" % tag
   shortTag = "%s_short" % tag
   shortToggle = "$('#%s').hide(); $('#%s').show();" % (shortTag, longTag)
   longToggle = "$('#%s').hide(); $('#%s').show(); window.location.hash='%s';" % (longTag, shortTag, utag)
 
-  fh.write(unicode("<div class=\"example-container\" id=\"%s\">\n" % utag))
-  #fh.write(unicode(anchor))
-
+  fh.write("<div class=\"example-container\" id=\"%s\">\n" % utag)
+  #fh.write(anchor)
 
   if shortable:
-    fh.write(unicode("<div id=\"%s\" style=\"display: none;\">\n" % longTag))
+    fh.write("<div id=\"%s\" style=\"display: none;\">\n" % longTag)
   else:
-    fh.write(unicode("<div id=\"%s\">\n" % longTag))
+    fh.write("<div id=\"%s\">\n" % longTag)
 
   if blockType != "AQL" and blockType != "EXPLAIN":
-    fh.write(unicode("<pre>\n"))
-  fh.write(unicode("%s" % longText))
-  fh.write(unicode("</pre>\n"))
+    fh.write("<pre>\n")
+  fh.write("%s" % longText)
+  fh.write("</pre>\n")
   if shortable:
     hideText=""
     if blockType == "arangosh":
-      hideText = u"Hide execution results"
+      hideText = "Hide execution results"
     elif blockType == "curl":
-      hideText = u"Hide response body"
+      hideText = "Hide response body"
     elif blockType == "AQL":
-      hideText = u"Hide query result"
+      hideText = "Hide query result"
     elif blockType == "EXPLAIN":
-        hideText = u"Hide explain output"
+        hideText = "Hide explain output"
     else:
-      hideText = u"Hide"
-    fh.write(unicode('<div id="%s_collapse" onclick="%s" class="example_show_button">%s</div>' % (
+      hideText = "Hide"
+    fh.write('<div id="%s_collapse" onclick="%s" class="example_show_button">%s</div>' % (
       utag,
       longToggle,
       hideText
-      )))
-  fh.write(unicode("</div>\n"))
+      ))
+  fh.write("</div>\n")
     
   if shortable:    
-    fh.write(unicode("<div id=\"%s\" onclick=\"%s\">\n" % (shortTag, shortToggle)))
+    fh.write("<div id=\"%s\" onclick=\"%s\">\n" % (shortTag, shortToggle))
     if blockType != "AQL" and blockType != "EXPLAIN":
-      fh.write(unicode("<pre>\n"))
-    fh.write(unicode("%s" % short))
+      fh.write("<pre>\n")
+    fh.write("%s" % short)
 
     if blockType == "arangosh":
-      fh.write(unicode("</pre><div class=\"example_show_button\">Show execution results</div>\n"))
+      fh.write("</pre><div class=\"example_show_button\">Show execution results</div>\n")
     elif blockType == "curl":
-      fh.write(unicode("</pre><div class=\"example_show_button\">Show response body</div>\n"))
+      fh.write("</pre><div class=\"example_show_button\">Show response body</div>\n")
     elif blockType == "AQL":
-      fh.write(unicode("</pre><div class=\"example_show_button\">Show query result</div>\n"))
+      fh.write("</pre><div class=\"example_show_button\">Show query result</div>\n")
     elif blockType == "EXPLAIN":
-      fh.write(unicode("</pre><div class=\"example_show_button\">Show explain output</div>\n"))
+      fh.write("</pre><div class=\"example_show_button\">Show explain output</div>\n")
     else:
-      fh.write(unicode("</pre><div class=\"example_show_button\">Show</div>\n"))
+      fh.write("</pre><div class=\"example_show_button\">Show</div>\n")
       
-    fh.write(unicode("</div>\n"))
+    fh.write("</div>\n")
 
-  fh.write(unicode("</div>\n"))
-  fh.write(unicode("\n"))
+  fh.write("</div>\n")
+  fh.write("\n")
 
 
 def fetch_comments(dirpath, forceDokuBlockContent):
@@ -278,7 +281,7 @@ def fetch_comments(dirpath, forceDokuBlockContent):
         filepath = os.path.join(root, filename)
         file_comments = file_content(filepath, forceDokuBlockContent)
         for comment in file_comments:
-          fh.write(unicode("\n<!-- filename: %s -->\n" % filepath))
+          fh.write("\n<!-- filename: %s -->\n" % filepath)
           explain = False
           for _com in comment:
             if "@EXPLAIN{TRUE}" in _com:
@@ -292,7 +295,7 @@ def fetch_comments(dirpath, forceDokuBlockContent):
               if not shouldIgnoreLine:
                 if ("@startDocuBlock" in _text) or \
                   ("@endDocuBlock" in _text):
-                  fh.write(unicode("%s\n\n" % _text))
+                  fh.write("%s\n\n" % _text)
                 elif ("@EXAMPLE_ARANGOSH_OUTPUT" in _text or \
                       "@EXAMPLE_ARANGOSH_RUN" in _text or \
                       "@EXAMPLE_AQL" in _text):
@@ -311,35 +314,35 @@ def fetch_comments(dirpath, forceDokuBlockContent):
                   try:
                     _filename = re.search("{(.*)}", _text).group(1)
                   except Exception as x:
-                    print "failed to match file name in  %s while parsing %s " % (_text, filepath)
+                    print("failed to match file name in  %s while parsing %s " % (_text, filepath))
                     raise x
                   dirpath = os.path.abspath(os.path.join(os.path.dirname( __file__ ), os.pardir, "Examples", _filename + ".generated"))
                   if os.path.isfile(dirpath):
                     example_content(dirpath, fh, _filename, blockType, filepath)
                   else:
                     fullSuccess = False
-                    print "Could not find the generated example for " + _filename + " found in " + filepath
+                    print("Could not find the generated example for " + _filename + " found in " + filepath)
                 else:
-                  fh.write(unicode("%s\n" % _text))
+                  fh.write("%s\n" % _text)
               elif ("@END_EXAMPLE_ARANGOSH_OUTPUT" in _text or \
                     "@END_EXAMPLE_ARANGOSH_RUN" in _text or \
                     "@END_EXAMPLE_AQL" in _text):
                 shouldIgnoreLine = False
             else:
-              fh.write(unicode("\n"))
+              fh.write("\n")
   fh.close()
 
 if __name__ == "__main__":
-  errorsFile = io.open("../../lib/Basics/errors.dat", "r", encoding="utf-8", newline=None)
-  commentsFile = io.open("allComments.txt", "w", encoding="utf-8", newline="")
-  commentsFile.write(unicode("@startDocuBlock errorCodes \n"))
+  errorsFile = io.open("../../lib/Basics/errors.dat", encoding="utf-8", newline=None)
+  commentsFile = io.open("allComments.txt", mode="w", encoding="utf-8", newline="")
+  commentsFile.write("@startDocuBlock errorCodes \n")
   for line in errorsFile:
-    commentsFile.write(unicode(line + "\n"))
-  commentsFile.write(unicode("@endDocuBlock \n"))
+    commentsFile.write(line + "\n")
+  commentsFile.write("@endDocuBlock \n")
   commentsFile.close()
   errorsFile.close()
   for i in searchPaths:
-    print "Searching for docublocks in " + i[0] + ": "
+    print("Searching for docublocks in " + i[0] + ": ")
     dirpath = os.path.abspath(os.path.join(os.path.dirname( __file__ ), os.pardir,"ArangoDB/../../"+i[0]))
     fetch_comments(dirpath, i[1])
     os.path.abspath(os.path.join(os.path.dirname( __file__ ), '..', 'templates'))
diff --git a/LICENSES-OTHER-COMPONENTS.md b/LICENSES-OTHER-COMPONENTS.md
index 3ff953db6965..3549e92c5b81 100644
--- a/LICENSES-OTHER-COMPONENTS.md
+++ b/LICENSES-OTHER-COMPONENTS.md
@@ -1869,6 +1869,15 @@ exception from the GPL license:
 * License Name: BSD 3-clause "New" or "Revised" License
 * License Id: BSD-3-Clause
 
+#### taocpp::json
+
+* Name: json
+* Version: master
+* Project Home: https://github.com/taocpp/json
+* License: https://github.com/taocpp/json/blob/master/LICENSE
+* License Name: MIT License
+* License Id: MIT
+
 #### text-table
 
 * Name: text-table
diff --git a/README.md b/README.md
index ec4bb770cbcd..d3e55b8d4d83 100644
--- a/README.md
+++ b/README.md
@@ -10,6 +10,9 @@ documents, graphs, and key-values. Build high performance applications using a
 convenient SQL-like query language or JavaScript extensions. Use ACID
 transactions if you require them. Scale horizontally with a few mouse clicks.
 
+ArangoDB runs everywhere: On-prem, in the cloud and also on
+[ArangoDBs Cloud Service Oasis](https://cloud.arangodb.com/home).
+
 The supported data models can be mixed in queries and allow ArangoDB to be the
 aggregation point for your data.
 
diff --git a/UnitTests/tls-ca.crt b/UnitTests/tls-ca.crt
new file mode 100644
index 000000000000..2452c535050b
--- /dev/null
+++ b/UnitTests/tls-ca.crt
@@ -0,0 +1,11 @@
+-----BEGIN CERTIFICATE-----
+MIIBiTCCAS+gAwIBAgIRAPjpM679uKG2EUMP49KjUeQwCgYIKoZIzj0EAwIwJjER
+MA8GA1UEChMIQXJhbmdvREIxETAPBgNVBAMTCEFyYW5nb0RCMB4XDTIwMDIxNzEy
+NTc0MloXDTM1MDIxMzEyNTc0MlowJjERMA8GA1UEChMIQXJhbmdvREIxETAPBgNV
+BAMTCEFyYW5nb0RCMFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEQmA2AzR/6SAH
+qlOrfUx0mCWHbFVaux3b42Nzqynb0poRzDbMPiJKFd3Hy0IVRfa2nNcGGYF/ekv1
+JW8C+ZXdpqM+MDwwDgYDVR0PAQH/BAQDAgKkMBkGA1UdJQQSMBAGBFUdJQAGCCsG
+AQUFBwMBMA8GA1UdEwEB/wQFMAMBAf8wCgYIKoZIzj0EAwIDSAAwRQIgW0EnfKLF
+rWlfBC2e4dJETZ1oeGiUsmYDTpg3byiG0GsCIQD5pNYAw+iMABgUEb4Vp/yj/ZlB
+E72mWZfsnTvTtJcw6w==
+-----END CERTIFICATE-----
diff --git a/UnitTests/tls-ca.key b/UnitTests/tls-ca.key
new file mode 100644
index 000000000000..7f251cffebc4
--- /dev/null
+++ b/UnitTests/tls-ca.key
@@ -0,0 +1,5 @@
+-----BEGIN EC PRIVATE KEY-----
+MHcCAQEEIJ8VLjNAdSGk40iM9X4C3Ken/VmIU1Lp390mes3e9MofoAoGCCqGSM49
+AwEHoUQDQgAEQmA2AzR/6SAHqlOrfUx0mCWHbFVaux3b42Nzqynb0poRzDbMPiJK
+Fd3Hy0IVRfa2nNcGGYF/ekv1JW8C+ZXdpg==
+-----END EC PRIVATE KEY-----
diff --git a/UnitTests/tls.keyfile b/UnitTests/tls.keyfile
new file mode 100644
index 000000000000..d22cd9622baa
--- /dev/null
+++ b/UnitTests/tls.keyfile
@@ -0,0 +1,28 @@
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----
+-----BEGIN EC PRIVATE KEY-----
+MHcCAQEEIJn82W+gXecn28BUIBjNseASBLp7zl31EPfmoul4H0uwoAoGCCqGSM49
+AwEHoUQDQgAEhTf30T85HKSBzkqJBeozMjHrWY4jN7617OE0AuHMPhfG9T8hMM7c
+cA+18VZqZXAUF5rc5CK02yI3xlV/kMDuWA==
+-----END EC PRIVATE KEY-----
\ No newline at end of file
diff --git a/arangod/Agency/AgencyCommon.h b/arangod/Agency/AgencyCommon.h
index 85ced37d38c8..89598328e05f 100644
--- a/arangod/Agency/AgencyCommon.h
+++ b/arangod/Agency/AgencyCommon.h
@@ -110,13 +110,13 @@ struct log_t {
   std::chrono::milliseconds timestamp;  // Timestamp
 
   log_t(index_t idx, term_t t, buffer_t const& e,
-        std::string const& clientId = std::string())
+        std::string const& clientId,
+        uint64_t const& m = 0)
       : index(idx),
         term(t),
         entry(std::make_shared<arangodb::velocypack::Buffer<uint8_t>>(*e.get())),
         clientId(clientId),
-        timestamp(std::chrono::duration_cast<std::chrono::milliseconds>(
-            std::chrono::system_clock::now().time_since_epoch())) {
+        timestamp(m) {
   }
 
   friend std::ostream& operator<<(std::ostream& o, log_t const& l) {
diff --git a/arangod/Agency/AgencyStrings.h b/arangod/Agency/AgencyStrings.h
index 6ce20a39c94b..18d70fc89427 100644
--- a/arangod/Agency/AgencyStrings.h
+++ b/arangod/Agency/AgencyStrings.h
@@ -44,7 +44,7 @@ constexpr char const* PLAN_VERSION = "Plan/Version";
 constexpr char const* PLAN_COLLECTIONS = "Plan/Collections/";
 constexpr char const* PLAN_DATABASES = "Plan/Databases/";
 
-constexpr char const* TARGET_HOTBACKUP = "Target/HotBackup";
+constexpr char const* HOTBACKUP_KEY = "/Target/HotBackup/Create";
 
 constexpr char const* PREC_IS_READ_LOCKED = "is-read-locked";
 constexpr char const* PREC_IS_WRITE_LOCKED = "is-write-locked";
diff --git a/arangod/Agency/Job.cpp b/arangod/Agency/Job.cpp
index 37a0edca156e..d5c090b11258 100644
--- a/arangod/Agency/Job.cpp
+++ b/arangod/Agency/Job.cpp
@@ -645,6 +645,20 @@ void Job::addPutJobIntoSomewhere(Builder& trx, std::string const& where,
   }
 }
 
+void Job::addPreconditionCurrentReplicaShardGroup(Builder& pre, std::string const& database,
+                                                  std::vector<shard_t> const& shardGroup,
+                                                  std::string const& serverId) {
+  for (auto const& sh : shardGroup) {
+    std::string const curPath =
+      curColPrefix + database + "/" + sh.collection + "/" + sh.shard + "/servers";
+    pre.add(VPackValue(curPath));
+    {
+      VPackObjectBuilder guard(&pre);
+      pre.add("in", VPackValue(serverId));
+    }
+  }
+}
+
 void Job::addPreconditionCollectionStillThere(Builder& pre, std::string const& database,
                                               std::string const& collection) {
   std::string planPath = planColPrefix + database + "/" + collection;
diff --git a/arangod/Agency/Job.h b/arangod/Agency/Job.h
index f01c18f88793..a3d1128b852f 100644
--- a/arangod/Agency/Job.h
+++ b/arangod/Agency/Job.h
@@ -199,6 +199,10 @@ struct Job {
   static void addReleaseShard(velocypack::Builder& trx, std::string const& shard);
   static void addPreconditionServerNotBlocked(velocypack::Builder& pre,
                                               std::string const& server);
+  static void addPreconditionCurrentReplicaShardGroup(VPackBuilder& pre,
+                                                      std::string const& database,
+                                                      std::vector<shard_t> const&,
+                                                      std::string const& server);
   static void addPreconditionServerHealth(velocypack::Builder& pre, std::string const& server,
                                           std::string const& health);
   static void addPreconditionShardNotBlocked(velocypack::Builder& pre,
diff --git a/arangod/Agency/MoveShard.cpp b/arangod/Agency/MoveShard.cpp
index 700baa6662aa..190e98565e1a 100644
--- a/arangod/Agency/MoveShard.cpp
+++ b/arangod/Agency/MoveShard.cpp
@@ -556,6 +556,29 @@ JOB_STATUS MoveShard::pendingLeader() {
 
     // We need to switch leaders:
     {
+      // Abort in to server no longer among replica for any shards like me
+      for (auto const& sh : shardsLikeMe) {
+        auto const shardPath = curColPrefix + _database + "/" + sh.collection + "/" + sh.shard;
+        auto const tmp = _snapshot.hasAsArray(shardPath + "/servers");
+        if (tmp.second) {
+          bool found = false;
+          for (auto const& server : VPackArrayIterator(tmp.first)) {
+            if (server.isEqualString(_to)) {
+              found = true;
+              break;
+            }
+          }
+          if (!found) {
+            // _to server no longer replica of this shard
+            abort(_to + " no longer holds a replica of " + shardPath);
+            return FAILED;
+          }
+        } else {
+          // this shard is either gone or worse
+          abort(shardPath + " no longer has replica");
+          return FAILED;
+        }
+      }
       VPackArrayBuilder trxArray(&trx);
       {
         VPackObjectBuilder trxObject(&trx);
@@ -586,6 +609,7 @@ JOB_STATUS MoveShard::pendingLeader() {
                          }
                        });
         addPreconditionCollectionStillThere(pre, _database, _collection);
+        addPreconditionCurrentReplicaShardGroup(pre, _database, shardsLikeMe, _to);
         addIncreasePlanVersion(trx);
       }
       // Add precondition to transaction:
diff --git a/arangod/Agency/Node.cpp b/arangod/Agency/Node.cpp
index 09597bc24a8b..dd2f44b57125 100644
--- a/arangod/Agency/Node.cpp
+++ b/arangod/Agency/Node.cpp
@@ -404,8 +404,7 @@ Store* Node::getStore() {
 ValueType Node::valueType() const { return slice().type(); }
 
 // file time to live entry for this node to now + millis
-bool Node::addTimeToLive(long millis) {
-  auto tkey = std::chrono::system_clock::now() + std::chrono::milliseconds(millis);
+bool Node::addTimeToLive(std::chrono::time_point<std::chrono::system_clock> const& tkey) {
   store().timeTable().insert(std::pair<TimePoint, std::string>(tkey, uri()));
   _ttl = tkey;
   return true;
@@ -440,6 +439,8 @@ namespace consensus {
 template <>
 ResultT<std::shared_ptr<Node>> Node::handle<SET>(VPackSlice const& slice) {
 
+  using namespace std::chrono;
+
   if (!slice.hasKey("new")) {
     return ResultT<std::shared_ptr<Node>>::error(
       TRI_ERROR_FAILED, std::string(
@@ -463,11 +464,22 @@ ResultT<std::shared_ptr<Node>> Node::handle<SET>(VPackSlice const& slice) {
   if (slice.hasKey("ttl")) {
     VPackSlice ttl_v = slice.get("ttl");
     if (ttl_v.isNumber()) {
+
+      // ttl in millisconds
       long ttl =
           1000l * ((ttl_v.isDouble())
-                       ? static_cast<long>(slice.get("ttl").getNumber<double>())
-                       : static_cast<long>(slice.get("ttl").getNumber<int>()));
-      addTimeToLive(ttl);
+                   ? static_cast<long>(slice.get("ttl").getNumber<double>())
+                   : static_cast<long>(slice.get("ttl").getNumber<int>()));
+
+      // calclate expiry time
+      auto const expires = slice.hasKey("epoch_millis") ?
+        time_point<system_clock>(
+          milliseconds(slice.get("epoch_millis").getNumber<uint64_t>() + ttl)) :
+        system_clock::now() + milliseconds(ttl);
+
+      // set ttl limit
+      addTimeToLive(expires);
+
     } else {
       LOG_TOPIC("66da2", WARN, Logger::AGENCY)
           << "Non-number value assigned to ttl: " << ttl_v.toJson();
diff --git a/arangod/Agency/Node.h b/arangod/Agency/Node.h
index a8885ba76185..5cbd7773de41 100644
--- a/arangod/Agency/Node.h
+++ b/arangod/Agency/Node.h
@@ -370,7 +370,8 @@ class Node {
 
  protected:
   /// @brief Add time to live entry
-  virtual bool addTimeToLive(long millis);
+  virtual bool addTimeToLive(
+    std::chrono::time_point<std::chrono::system_clock> const& tp);
 
   /// @brief Remove time to live entry
   virtual bool removeTimeToLive();
diff --git a/arangod/Agency/State.cpp b/arangod/Agency/State.cpp
index 5e043b91dfd0..2ca00a0032b5 100644
--- a/arangod/Agency/State.cpp
+++ b/arangod/Agency/State.cpp
@@ -75,14 +75,16 @@ State::~State() = default;
 
 inline static std::string timestamp(uint64_t m) {
 
+  TRI_ASSERT(m != 0);
+
   using namespace std::chrono;
 
   std::time_t t = (m == 0) ? std::time(nullptr) :
     system_clock::to_time_t(system_clock::time_point(milliseconds(m)));
   char mbstr[100];
-  return std::strftime(mbstr, sizeof(mbstr), "%Y-%m-%d %H:%M:%S %Z", std::localtime(&t))
-             ? std::string(mbstr)
-             : std::string();
+  return std::strftime(mbstr, sizeof(mbstr), "%Y-%m-%d %H:%M:%S %Z", std::gmtime(&t))
+    ? std::string(mbstr)
+    : std::string();
 }
 
 inline static std::string stringify(index_t index) {
@@ -106,6 +108,7 @@ bool State::persist(index_t index, term_t term, uint64_t millis,
     body.add("request", entry);
     body.add("clientId", Value(clientId));
     body.add("timestamp", Value(timestamp(millis)));
+    body.add("epoch_millis", Value(millis));
   }
 
   TRI_ASSERT(_vocbase != nullptr);
@@ -154,6 +157,7 @@ bool State::persistconf(index_t index, term_t term, uint64_t millis,
     log.add("request", entry);
     log.add("clientId", Value(clientId));
     log.add("timestamp", Value(timestamp(millis)));
+    log.add("epoch_millis", Value(millis));
   }
 
   // The new configuration to be persisted.-------------------------------------
@@ -228,6 +232,9 @@ bool State::persistconf(index_t index, term_t term, uint64_t millis,
 std::vector<index_t> State::logLeaderMulti(query_t const& transactions,
                                            std::vector<apply_ret_t> const& applicable,
                                            term_t term) {
+
+  using namespace std::chrono;
+
   std::vector<index_t> idx(applicable.size());
   size_t j = 0;
   auto const& slice = transactions->slice();
@@ -260,8 +267,10 @@ std::vector<index_t> State::logLeaderMulti(query_t const& transactions,
       TRI_ASSERT(transaction.length() > 0);
       size_t pos = transaction.keyAt(0).copyString().find(RECONFIGURE);
 
-      idx[j] = logNonBlocking(_log.back().index + 1, i[0], term, 0, clientId, true,
-                              pos == 0 || pos == 1);
+      idx[j] = logNonBlocking(
+        _log.back().index + 1, i[0], term,
+        duration_cast<milliseconds>(system_clock::now().time_since_epoch()).count(),
+        clientId, true, pos == 0 || pos == 1);
     }
     ++j;
   }
@@ -272,7 +281,10 @@ std::vector<index_t> State::logLeaderMulti(query_t const& transactions,
 index_t State::logLeaderSingle(velocypack::Slice const& slice, term_t term,
                                std::string const& clientId) {
   MUTEX_LOCKER(mutexLocker, _logLock);  // log entries must stay in order
-  return logNonBlocking(_log.back().index + 1, slice, term, 0, clientId, true);
+  using namespace std::chrono;
+  return logNonBlocking(
+    _log.back().index + 1, slice, term,
+    duration_cast<milliseconds>(system_clock::now().time_since_epoch()).count(), clientId, true);
 }
 
 /// Log transaction (leader)
@@ -293,7 +305,7 @@ index_t State::logNonBlocking(index_t idx, velocypack::Slice const& slice,
     FATAL_ERROR_EXIT();
   }
 
-  logEmplaceBackNoLock(log_t(idx, term, buf, clientId));
+  logEmplaceBackNoLock(log_t(idx, term, buf, clientId, millis));
 
   return _log.back().index;
 }
@@ -326,6 +338,7 @@ void State::logEmplaceBackNoLock(log_t&& l) {
 index_t State::logFollower(query_t const& transactions) {
   VPackSlice slices = transactions->slice();
   size_t nqs = slices.length();
+  using namespace std::chrono;
 
   while (!_ready && !_agent->isStopping()) {
     LOG_TOPIC("8dd4c", DEBUG, Logger::AGENCY) << "Waiting for state to get ready ...";
@@ -409,9 +422,14 @@ index_t State::logFollower(query_t const& transactions) {
       auto index = slice.get("index").getUInt();
 
       uint64_t tstamp = 0;
-      if (slice.hasKey("timestamp")) { // compatibility with older appendEntries protocol
+      if (slice.hasKey("timestamp")) {
+        // compatibility with older appendEntries protocol
         tstamp = slice.get("timestamp").getUInt();
       }
+      if (tstamp == 0) {
+        tstamp = duration_cast<milliseconds>(
+          system_clock::now().time_since_epoch()).count();
+      }
 
       bool reconfiguration = query.keyAt(0).isEqualString(RECONFIGURE);
 
@@ -666,8 +684,23 @@ VPackBuilder State::slices(index_t start, index_t end) const {
     }
 
     for (size_t i = start - _cur; i <= end - _cur; ++i) {
-      try {
-        slices.add(VPackSlice(_log.at(i).entry->data()));
+      try { //{ "a" : {"op":"set", "ttl":20, ...}}
+        auto slice = VPackSlice(_log.at(i).entry->data());
+        VPackObjectBuilder o(&slices);
+        for (auto const& oper : VPackObjectIterator(slice)) {
+          slices.add(VPackValue(oper.key.copyString()));
+
+          if (oper.value.isObject() && oper.value.hasKey("op") &&
+              oper.value.get("op").isEqualString("set") && oper.value.hasKey("ttl")) {
+            VPackObjectBuilder oo(&slices);
+            for (auto const& i : VPackObjectIterator(oper.value)) {
+              slices.add(i.key.copyString(), i.value);
+            }
+            slices.add("epoch_millis", VPackValue(_log.at(i).timestamp.count()));
+          } else {
+            slices.add(oper.value);
+          }
+        }
       } catch (std::exception const&) {
         break;
       }
@@ -675,9 +708,7 @@ VPackBuilder State::slices(index_t start, index_t end) const {
   }
 
   mutexLocker.unlock();
-
   slices.close();
-
   return slices;
 }
 
@@ -755,6 +786,11 @@ bool State::ready() const { return _ready; }
 /// Load collections
 bool State::loadCollections(TRI_vocbase_t* vocbase,
                             QueryRegistry* queryRegistry, bool waitForSync) {
+
+  using namespace std::chrono;
+  auto const epoch_millis =
+    duration_cast<milliseconds>(system_clock::now().time_since_epoch()).count();
+
   _vocbase = vocbase;
   _queryRegistry = queryRegistry;
 
@@ -769,8 +805,8 @@ bool State::loadCollections(TRI_vocbase_t* vocbase,
       std::shared_ptr<Buffer<uint8_t>> buf = std::make_shared<Buffer<uint8_t>>();
       VPackSlice value = arangodb::velocypack::Slice::emptyObjectSlice();
       buf->append(value.startAs<char const>(), value.byteSize());
-      _log.emplace_back(log_t(index_t(0), term_t(0), buf, std::string()));
-      persist(0, 0, 0, value, std::string());
+      _log.emplace_back(log_t(index_t(0), term_t(0), buf, std::string(), epoch_millis));
+      persist(0, 0, epoch_millis, value, std::string());
     }
     _ready = true;
     return true;
@@ -1027,7 +1063,7 @@ bool State::loadRemaining() {
   MUTEX_LOCKER(logLock, _logLock);
   if (result.isArray() && result.length() > 0) {
     TRI_ASSERT(_log.empty());  // was cleared in loadCompacted
-    std::string clientId;
+    std::string clientId, tstamp;
     // We know that _cur has been set in loadCompacted to the index of the
     // snapshot that was loaded or to 0 if there is no snapshot.
     index_t lastIndex = _cur;
@@ -1042,6 +1078,22 @@ bool State::loadRemaining() {
       clientId = req.hasKey("clientId") ? req.get("clientId").copyString()
                                         : std::string();
 
+      uint64_t millis = 0;
+      if (ii.hasKey("epoch_millis")) {
+        if (ii.get("epoch_millis").isInteger()) {
+          try {
+            millis = ii.get("epoch_millis").getNumber<uint64_t>();
+          } catch (std::exception const& e) {
+            LOG_TOPIC("2ee75", ERR, Logger::AGENCY)
+              << "Failed to parse integer value for epoch_millis " << e.what();
+            FATAL_ERROR_EXIT();
+          }
+        } else {
+          LOG_TOPIC("52ee7", ERR, Logger::AGENCY) << "epoch_millis is not an integer type";
+          FATAL_ERROR_EXIT();
+        }
+      }
+
       // Dummy fill missing entries (Not good at all.)
       index_t index(StringUtils::uint64(ii.get(StaticStrings::KeyString).copyString()));
 
@@ -1067,7 +1119,7 @@ bool State::loadRemaining() {
           // Real entries
           logEmplaceBackNoLock(
             log_t(StringUtils::uint64(ii.get(StaticStrings::KeyString).copyString()),
-                  ii.get("term").getNumber<uint64_t>(), tmp, clientId));
+                  ii.get("term").getNumber<uint64_t>(), tmp, clientId, millis));
           lastIndex = index;
         }
       }
@@ -1543,8 +1595,12 @@ std::shared_ptr<VPackBuilder> State::latestAgencyState(TRI_vocbase_t& vocbase,
         std::string clientId =
             req.hasKey("clientId") ? req.get("clientId").copyString() : std::string();
 
+        uint64_t epoch_millis =
+          (req.hasKey("epoch_millis") && req.get("epoch_millis").isInteger()) ?
+          req.get("epoch_millis").getNumber<uint64_t>() : 0;
+
         log_t entry(StringUtils::uint64(ii.get(StaticStrings::KeyString).copyString()),
-                    ii.get("term").getNumber<uint64_t>(), tmp, clientId);
+                    ii.get("term").getNumber<uint64_t>(), tmp, clientId, epoch_millis);
 
         if (entry.index <= index) {
           LOG_TOPIC("c8f91", WARN, Logger::AGENCY)
diff --git a/arangod/Agency/Supervision.cpp b/arangod/Agency/Supervision.cpp
index 63541ab43425..243c3cd1f078 100644
--- a/arangod/Agency/Supervision.cpp
+++ b/arangod/Agency/Supervision.cpp
@@ -184,6 +184,7 @@ Supervision::~Supervision() {
 
 static std::string const syncPrefix = "/Sync/ServerStates/";
 static std::string const supervisionPrefix = "/Supervision";
+static std::string const supervisionMaintenance = "/Supervision/Maintenance";
 static std::string const healthPrefix = "/Supervision/Health/";
 static std::string const targetShortID = "/Target/MapUniqueToShortID/";
 static std::string const currentServersRegisteredPrefix =
@@ -289,6 +290,8 @@ void Supervision::upgradeAgency() {
     fixPrototypeChain(builder);
     upgradeOne(builder);
     upgradeHealthRecords(builder);
+    upgradeMaintenance(builder);
+    upgradeBackupKey(builder);
   }
 
   LOG_TOPIC("f7315", DEBUG, Logger::AGENCY) << "Upgrading the agency:" << builder.toJson();
@@ -300,6 +303,69 @@ void Supervision::upgradeAgency() {
   _upgraded = true;
 }
 
+
+void Supervision::upgradeMaintenance(VPackBuilder& builder) {
+  _lock.assertLockedByCurrentThread();
+  if (_snapshot.has(supervisionMaintenance)) {
+
+    std::string maintenanceState;
+    try {
+      maintenanceState = _snapshot.get(supervisionMaintenance).getString();
+    } catch (std::exception const& e) {
+      LOG_TOPIC("cf235", ERR, Logger::SUPERVISION)
+        << "Supervision maintenance key in agency is not a string. This should never happen and will prevent hot backups. " << e.what();
+      return;
+    }
+
+    if (maintenanceState == "on") {
+      VPackArrayBuilder trx(&builder);
+      {
+        VPackObjectBuilder o(&builder);
+        builder.add(
+          supervisionMaintenance,
+          VPackValue(
+            timepointToString(
+              std::chrono::system_clock::now() + std::chrono::hours(1))));
+      }
+      {
+        VPackObjectBuilder o(&builder);
+        builder.add(supervisionMaintenance, VPackValue(maintenanceState));
+      }
+    }
+  }
+}
+
+
+void Supervision::upgradeBackupKey(VPackBuilder& builder) {
+
+  // Upgrade /arango/Target/HotBackup/Create from 0 to time out
+
+  _lock.assertLockedByCurrentThread();
+  if (_snapshot.has(HOTBACKUP_KEY)) {
+
+    Node const& tmp  = _snapshot(HOTBACKUP_KEY);
+    if (tmp.isNumber()) {
+      if (tmp.getInt() == 0) {
+
+        VPackArrayBuilder trx(&builder);
+        {
+          VPackObjectBuilder o(&builder);
+          builder.add(
+            HOTBACKUP_KEY,
+            VPackValue(
+              timepointToString(
+                std::chrono::system_clock::now() + std::chrono::hours(1))));
+        }
+        {
+          VPackObjectBuilder o(&builder);
+          builder.add(HOTBACKUP_KEY, VPackValue(0));
+        }
+      }
+    }
+  }
+}
+
+
 void handleOnStatusDBServer(Agent* agent, Node const& snapshot,
                             HealthRecord& persisted, HealthRecord& transisted,
                             std::string const& serverID, uint64_t const& jobId,
@@ -835,12 +901,37 @@ void Supervision::run() {
           updateSnapshot();
           LOG_TOPIC("aaabb", TRACE, Logger::SUPERVISION) << "Finished updateSnapshot";
 
-          if (!_snapshot.has("Supervision/Maintenance")) {
-            reportStatus("Normal");
 
-            if (!_upgraded) {
-              upgradeAgency();
+          if (!_upgraded) {
+            upgradeAgency();
+          }
+
+          bool maintenanceMode = false;
+          if (_snapshot.has(supervisionMaintenance)) {
+            try {
+              if (_snapshot.get(supervisionMaintenance).isString()) {
+                std::string tmp = _snapshot.get(supervisionMaintenance).getString();
+                if (tmp.size() < 18) { // legacy behaviour
+                  maintenanceMode = true;
+                } else {
+                  auto const maintenanceExpires = stringToTimepoint(tmp);
+                  if (maintenanceExpires >= std::chrono::system_clock::now()) {
+                    maintenanceMode = true;
+                  }
+                }
+              } else { // legacy behaviour
+                maintenanceMode = true;
+              }
+            } catch (std::exception const& e) {
+                LOG_TOPIC("cf236", ERR, Logger::SUPERVISION)
+                  << "Supervision maintenace key in agency is not a string. This should never happen and will prevent hot backups. " << e.what();
+              return;
             }
+          }
+
+          if (!maintenanceMode) {
+
+            reportStatus("Normal");
 
             _haveAborts = false;
 
@@ -1129,10 +1220,34 @@ void Supervision::cleanupLostCollections(Node const& snapshot, AgentInterface* a
   }
 }
 
+
+// Remove expired hot backup lock if exists
+void Supervision::unlockHotBackup() {
+  _lock.assertLockedByCurrentThread();
+  if (_snapshot.has(HOTBACKUP_KEY)) {
+    Node tmp = _snapshot(HOTBACKUP_KEY);
+    if (tmp.isString()) {
+      if (std::chrono::system_clock::now() > stringToTimepoint(tmp.getString())) {
+        VPackBuilder unlock;
+        { VPackArrayBuilder trxs(&unlock);
+          { VPackObjectBuilder u(&unlock);
+            unlock.add(VPackValue(HOTBACKUP_KEY));
+            { VPackObjectBuilder o(&unlock);
+              unlock.add("op", VPackValue("delete")); }}}
+        write_ret_t res = singleWriteTransaction(_agent, unlock, false);
+      }
+    }
+  }
+}
+
+
 // Guarded by caller
 bool Supervision::handleJobs() {
   _lock.assertLockedByCurrentThread();
   // Do supervision
+  LOG_TOPIC("67eef", TRACE, Logger::SUPERVISION) << "Begin unlockHotBackup";
+  unlockHotBackup();
+
   LOG_TOPIC("76ffe", TRACE, Logger::SUPERVISION) << "Begin shrinkCluster";
   shrinkCluster();
 
diff --git a/arangod/Agency/Supervision.h b/arangod/Agency/Supervision.h
index 6660dd08f2b9..aeea078e750c 100644
--- a/arangod/Agency/Supervision.h
+++ b/arangod/Agency/Supervision.h
@@ -110,6 +110,15 @@ class Supervision : public arangodb::CriticalThread {
   /// @brief Upgrade agency
   void upgradeAgency();
 
+  /// @brief Upgrade hot backup entry, if 0
+  void upgradeMaintenance(VPackBuilder& builder);
+
+  /// @brief Upgrade maintenance key, if "on"
+  void upgradeBackupKey(VPackBuilder& builder);
+
+  /// @brief remove hotbackup lock in agency, if expired
+  void unlockHotBackup();
+
   static constexpr char const* HEALTH_STATUS_GOOD = "GOOD";
   static constexpr char const* HEALTH_STATUS_BAD = "BAD";
   static constexpr char const* HEALTH_STATUS_FAILED = "FAILED";
diff --git a/arangod/Aql/AqlFunctionFeature.cpp b/arangod/Aql/AqlFunctionFeature.cpp
index 391f1ac70d9e..d2a9d6430e6c 100644
--- a/arangod/Aql/AqlFunctionFeature.cpp
+++ b/arangod/Aql/AqlFunctionFeature.cpp
@@ -24,6 +24,7 @@
 
 #include "Aql/AstNode.h"
 #include "Aql/Function.h"
+#include "Basics/StringUtils.h"
 #include "Cluster/ServerState.h"
 #include "FeaturePhases/V8FeaturePhase.h"
 #include "RestServer/AqlFeature.h"
@@ -82,6 +83,7 @@ Function const* AqlFunctionFeature::getFunctionByName(std::string const& name) {
 }
 
 void AqlFunctionFeature::add(Function const& func) {
+  TRI_ASSERT(func.name == basics::StringUtils::toupper(func.name));
   TRI_ASSERT(_functionNames.find(func.name) == _functionNames.end());
   // add function to the map
   _functionNames.try_emplace(func.name, func);
diff --git a/arangod/Aql/AqlItemBlock.cpp b/arangod/Aql/AqlItemBlock.cpp
index 79d7428910ae..88929d9cb925 100644
--- a/arangod/Aql/AqlItemBlock.cpp
+++ b/arangod/Aql/AqlItemBlock.cpp
@@ -111,13 +111,14 @@ void AqlItemBlock::initFromSlice(VPackSlice const slice) {
   VPackSlice data = slice.get("data");
   VPackSlice raw = slice.get("raw");
 
+  VPackArrayIterator rawIterator(raw);
+
   std::vector<AqlValue> madeHere;
-  madeHere.reserve(static_cast<size_t>(raw.length()));
+  madeHere.reserve(static_cast<size_t>(rawIterator.size()));
   madeHere.emplace_back();  // an empty AqlValue
   madeHere.emplace_back();  // another empty AqlValue, indices start w. 2
 
   VPackArrayIterator dataIterator(data);
-  VPackArrayIterator rawIterator(raw);
 
   auto storeSingleValue = [this](size_t row, RegisterId column, VPackArrayIterator& it,
                                  std::vector<AqlValue>& madeHere) {
@@ -302,7 +303,8 @@ void AqlItemBlock::destroy() noexcept {
       return;
     }
 
-    for (size_t i = 0; i < numEntries(); i++) {
+    size_t const n = numEntries();
+    for (size_t i = 0; i < n; i++) {
       auto& it = _data[i];
       if (it.requiresDestruction()) {
         auto it2 = _valueCount.find(it);
@@ -354,7 +356,8 @@ void AqlItemBlock::shrink(size_t nrItems) {
   // adjust the size of the block
   _nrItems = nrItems;
 
-  for (size_t i = numEntries(); i < _data.size(); ++i) {
+  size_t const n = numEntries();
+  for (size_t i = n; i < _data.size(); ++i) {
     AqlValue& a = _data[i];
     if (a.requiresDestruction()) {
       auto it = _valueCount.find(a);
diff --git a/arangod/Aql/Ast.cpp b/arangod/Aql/Ast.cpp
index fae24176ec29..5121906a6b47 100644
--- a/arangod/Aql/Ast.cpp
+++ b/arangod/Aql/Ast.cpp
@@ -1149,7 +1149,7 @@ AstNode* Ast::createNodeIntersectedArray(AstNode const* lhs, AstNode const* rhs)
     cache.try_emplace(slice, member);
   }
 
-  auto node = createNodeArray(cache.size() + nr);
+  auto node = createNodeArray(nl);
 
   for (size_t i = 0; i < nr; ++i) {
     auto member = rhs->getMemberUnchecked(i);
@@ -1157,8 +1157,12 @@ AstNode* Ast::createNodeIntersectedArray(AstNode const* lhs, AstNode const* rhs)
 
     auto it = cache.find(slice);
 
-    if (it != cache.end()) {
+    if (it != cache.end() &&
+        (*it).second != nullptr) {
+      // add to output
       node->addMember((*it).second);
+      // make sure we don't add the same value again
+      (*it).second = nullptr;
     }
   }
 
@@ -3736,13 +3740,7 @@ std::pair<std::string, bool> Ast::normalizeFunctionName(char const* name, size_t
   // convert name to upper case
   std::transform(functionName.begin(), functionName.end(), functionName.begin(), ::toupper);
 
-  if (functionName.find(':') == std::string::npos) {
-    // prepend default namespace for internal functions
-    return std::make_pair(std::move(functionName), true);
-  }
-
-  // user-defined function
-  return std::make_pair(std::move(functionName), false);
+  return std::make_pair(std::move(functionName), functionName.find(':') == std::string::npos);
 }
 
 /// @brief create a node of the specified type
diff --git a/arangod/Aql/AstNode.cpp b/arangod/Aql/AstNode.cpp
index 7f7f6b64c553..b4d8d927ae90 100644
--- a/arangod/Aql/AstNode.cpp
+++ b/arangod/Aql/AstNode.cpp
@@ -769,9 +769,7 @@ AstNode::AstNode(std::function<void(AstNode*)> const& registerNode,
 
 /// @brief destroy the node
 AstNode::~AstNode() {
-  if (computedValue != nullptr) {
-    delete[] computedValue;
-  }
+  freeComputedValue();
 }
 
 /// @brief return the string value of a node, as an std::string
@@ -1587,12 +1585,33 @@ bool AstNode::willUseV8() const {
     // check if the called function is one of them
     auto func = static_cast<Function*>(getData());
     TRI_ASSERT(func != nullptr);
-
+    
     if (func->implementation == nullptr) {
-      // a function without a V8 implementation
+      // a function without a C++ implementation
       setFlag(DETERMINED_V8, VALUE_V8);
       return true;
     }
+    
+    if (func->name == "CALL" || func->name == "APPLY") {
+      // CALL and APPLY can call arbitrary other functions...
+      if (numMembers() > 0 && getMemberUnchecked(0)->isStringValue()) {
+        auto s = getMemberUnchecked(0)->getStringRef();
+        if (s.find(':') != std::string::npos) {
+          // a user-defined function.
+          // this will use V8
+          setFlag(DETERMINED_V8, VALUE_V8);
+          return true;
+        }
+        // fallthrough intentional
+      } else {
+        // we are unsure about what function will be called by 
+        // CALL and APPLY. We cannot rule out user-defined functions,
+        // so we assume the worst case here
+        setFlag(DETERMINED_V8, VALUE_V8);
+        return true;
+      }
+    }
+
   }
 
   size_t const n = numMembers();
@@ -2590,14 +2609,6 @@ void AstNode::appendValue(arangodb::basics::StringBuffer* buffer) const {
   }
 }
 
-void AstNode::stealComputedValue() {
-  TRI_ASSERT(!hasFlag(AstNodeFlagType::FLAG_FINALIZED));
-  if (computedValue != nullptr) {
-    delete[] computedValue;
-    computedValue = nullptr;
-  }
-}
-
 void AstNode::markFinalized(AstNode* subtreeRoot) {
   if ((nullptr == subtreeRoot) || subtreeRoot->hasFlag(AstNodeFlagType::FLAG_FINALIZED)) {
     return;
@@ -2828,6 +2839,8 @@ void AstNode::setIntValue(int64_t v) {
 
 void AstNode::setDoubleValue(double v) {
   TRI_ASSERT(!hasFlag(AstNodeFlagType::FLAG_FINALIZED));
+  
+  freeComputedValue();
   value.value._double = v;
 }
 
@@ -2838,6 +2851,8 @@ size_t AstNode::getStringLength() const {
 
 void AstNode::setStringValue(char const* v, size_t length) {
   TRI_ASSERT(!hasFlag(AstNodeFlagType::FLAG_FINALIZED));
+
+  freeComputedValue();
   // note: v may contain the NUL byte and is not necessarily
   // null-terminated itself (if from VPack)
   value.type = VALUE_TYPE_STRING;
@@ -2875,6 +2890,13 @@ void AstNode::setData(void const* v) {
   value.value._data = const_cast<void*>(v);
 }
 
+void AstNode::freeComputedValue() {
+  if (computedValue != nullptr) {
+    delete[] computedValue;
+    computedValue = nullptr;
+  }
+}
+
 /// @brief append the AstNode to an output stream
 std::ostream& operator<<(std::ostream& stream, arangodb::aql::AstNode const* node) {
   if (node != nullptr) {
diff --git a/arangod/Aql/AstNode.h b/arangod/Aql/AstNode.h
index 9e5ee012aa46..51a37bd532a8 100644
--- a/arangod/Aql/AstNode.h
+++ b/arangod/Aql/AstNode.h
@@ -557,9 +557,6 @@ struct AstNode {
   /// this creates an equivalent to what JSON.stringify() would do
   void appendValue(arangodb::basics::StringBuffer*) const;
 
-  /// @brief Steals the computed value and frees it.
-  void stealComputedValue();
-
   /// @brief If the node has not been marked finalized, mark its subtree so.
   /// If it runs into a finalized node, it assumes the whole subtree beneath
   /// it is marked already and exits early; otherwise it will finalize the node
@@ -584,6 +581,8 @@ struct AstNode {
 
   static std::underlying_type<AstNodeFlagType>::type makeFlags();
 
+  void freeComputedValue();
+
  private:
   /// @brief precomputed VPack value (used when executing expressions)
   uint8_t mutable* computedValue;
diff --git a/arangod/Aql/BindParameters.cpp b/arangod/Aql/BindParameters.cpp
index 88d6f6cf4873..066b6d1b4176 100644
--- a/arangod/Aql/BindParameters.cpp
+++ b/arangod/Aql/BindParameters.cpp
@@ -107,9 +107,9 @@ void BindParameters::stripCollectionNames(VPackSlice const& keys,
 }
 
 BindParameters::BindParameters()
-    : _builder(nullptr), _parameters(), _processed(false) {}
+    : _parameters(), _processed(false) {}
 
-BindParameters::BindParameters(std::shared_ptr<arangodb::velocypack::Builder>  builder)
+BindParameters::BindParameters(std::shared_ptr<arangodb::velocypack::Builder> builder)
     : _builder(std::move(builder)), _parameters(), _processed(false) {}
 
 BindParametersType& BindParameters::get() {
diff --git a/arangod/Aql/DocumentProducingHelper.cpp b/arangod/Aql/DocumentProducingHelper.cpp
index 8c815474988d..14debde7e413 100644
--- a/arangod/Aql/DocumentProducingHelper.cpp
+++ b/arangod/Aql/DocumentProducingHelper.cpp
@@ -95,10 +95,6 @@ IndexIterator::DocumentCallback aql::getCallback(DocumentProducingCallbackVarian
       return true;
     }
 
-    InputAqlItemRow const& input = context.getInputRow();
-    OutputAqlItemRow& output = context.getOutputRow();
-    RegisterId registerId = context.getOutputRegister();
-
     transaction::BuilderLeaser b(context.getTrxPtr());
     b->openObject(true);
 
@@ -106,6 +102,10 @@ IndexIterator::DocumentCallback aql::getCallback(DocumentProducingCallbackVarian
                       *b.get(), context.getUseRawDocumentPointers());
 
     b->close();
+    
+    InputAqlItemRow const& input = context.getInputRow();
+    OutputAqlItemRow& output = context.getOutputRow();
+    RegisterId registerId = context.getOutputRegister();
 
     AqlValue v(b.get());
     AqlValueGuard guard{v, true};
@@ -423,9 +423,6 @@ IndexIterator::DocumentCallback aql::getCallback(DocumentProducingCallbackVarian
       checkFilter = false;
     }
 
-    InputAqlItemRow const& input = context.getInputRow();
-    OutputAqlItemRow& output = context.getOutputRow();
-
     transaction::BuilderLeaser b(context.getTrxPtr());
     b->openObject(true);
 
@@ -473,8 +470,10 @@ IndexIterator::DocumentCallback aql::getCallback(DocumentProducingCallbackVarian
       context.incrFiltered();
       return false;
     }
-
+    
     if constexpr (!skip) {
+      InputAqlItemRow const& input = context.getInputRow();
+      OutputAqlItemRow& output = context.getOutputRow();
       RegisterId registerId = context.getOutputRegister();
       AqlValue v(b.get());
       AqlValueGuard guard{v, true};
diff --git a/arangod/Aql/ExecutionPlan.cpp b/arangod/Aql/ExecutionPlan.cpp
index 3a419c6dd5f4..93166f2c0a73 100644
--- a/arangod/Aql/ExecutionPlan.cpp
+++ b/arangod/Aql/ExecutionPlan.cpp
@@ -197,7 +197,7 @@ std::unique_ptr<graph::BaseOptions> createTraversalOptions(aql::Query* query,
             THROW_ARANGO_EXCEPTION_MESSAGE(
                 TRI_ERROR_BAD_PARAMETER,
                 "uniqueEdges: 'global' is not supported, "
-                "due to unpredictable results. Use 'path' "
+                "due to otherwise unpredictable results. Use 'path' "
                 "or 'none' instead");
           }
         } else if (name == "edgeCollections") {
@@ -214,7 +214,7 @@ std::unique_ptr<graph::BaseOptions> createTraversalOptions(aql::Query* query,
     THROW_ARANGO_EXCEPTION_MESSAGE(TRI_ERROR_BAD_PARAMETER,
                                    "uniqueVertices: 'global' is only "
                                    "supported, with bfs: true due to "
-                                   "unpredictable results.");
+                                   "otherwise unpredictable results.");
   }
 
   return options;
diff --git a/arangod/Aql/Functions.cpp b/arangod/Aql/Functions.cpp
index fa1bb44143ab..c33b98ed3e2c 100644
--- a/arangod/Aql/Functions.cpp
+++ b/arangod/Aql/Functions.cpp
@@ -1486,7 +1486,7 @@ AqlValue Functions::ToBase64(ExpressionContext*, transaction::Methods* trx,
   ::appendAsString(trx, adapter, value);
 
   std::string encoded =
-      basics::StringUtils::encodeBase64(std::string(buffer->begin(), buffer->length()));
+      basics::StringUtils::encodeBase64(buffer->begin(), buffer->length());
 
   return AqlValue(encoded);
 }
diff --git a/arangod/Aql/IndexExecutor.cpp b/arangod/Aql/IndexExecutor.cpp
index 5b99e75fed48..54b9e0589151 100644
--- a/arangod/Aql/IndexExecutor.cpp
+++ b/arangod/Aql/IndexExecutor.cpp
@@ -426,19 +426,20 @@ void IndexExecutor::CursorReader::reset() {
   if (iterator != nullptr && iterator->canRearm()) {
     bool didRearm =
         iterator->rearm(_condition, _infos.getOutVariable(), _infos.getOptions());
-    if (!didRearm) {
+    if (didRearm) {
+      _cursor->reset();
+    } else {
       // iterator does not support the condition
       // It will not create any results
       _cursor->rearm(std::make_unique<EmptyIndexIterator>(iterator->collection(),
                                                           _infos.getTrxPtr()));
     }
-    _cursor->reset();
-    return;
+  } else {
+    // We need to build a fresh search and cannot go the rearm shortcut
+    _cursor->rearm(_infos.getTrxPtr()->indexScanForCondition(_index, _condition,
+                                                             _infos.getOutVariable(),
+                                                             _infos.getOptions()));
   }
-  // We need to build a fresh search and cannot go the rearm shortcut
-  _cursor->rearm(_infos.getTrxPtr()->indexScanForCondition(_index, _condition,
-                                                           _infos.getOutVariable(),
-                                                           _infos.getOptions()));
 }
 
 IndexExecutor::IndexExecutor(Fetcher& fetcher, Infos& infos)
diff --git a/arangod/Aql/OptimizerRules.cpp b/arangod/Aql/OptimizerRules.cpp
index 9cd9e7b83bd2..a095f95dd505 100644
--- a/arangod/Aql/OptimizerRules.cpp
+++ b/arangod/Aql/OptimizerRules.cpp
@@ -5779,6 +5779,7 @@ void arangodb::aql::optimizeTraversalsRule(Optimizer* opt,
   // variables from them
   for (auto const& n : tNodes) {
     TraversalNode* traversal = ExecutionNode::castTo<TraversalNode*>(n);
+    auto* options = static_cast<arangodb::traverser::TraverserOptions*>(traversal->options());
 
     std::vector<Variable const*> pruneVars;
     traversal->getPruneVariables(pruneVars);
@@ -5800,7 +5801,7 @@ void arangodb::aql::optimizeTraversalsRule(Optimizer* opt,
                                      std::find(pruneVars.begin(), pruneVars.end(),
                                                outVariable) == pruneVars.end())) {
         // both traversal vertex and path outVariables not used later
-        traversal->options()->setProduceVertices(false);
+        options->setProduceVertices(false);
         modified = true;
       }
     }
@@ -5820,6 +5821,23 @@ void arangodb::aql::optimizeTraversalsRule(Optimizer* opt,
       traversal->setPathOutput(nullptr);
       modified = true;
     }
+  
+    // check if we can make use of the optimized neighbors enumerator
+    if (!ServerState::instance()->isCoordinator()) {
+      if (traversal->vertexOutVariable() != nullptr &&
+          traversal->edgeOutVariable() == nullptr &&
+          traversal->pathOutVariable() == nullptr &&
+          options->useBreadthFirst &&
+          options->uniqueVertices == arangodb::traverser::TraverserOptions::GLOBAL &&
+          !options->usesPrune() &&
+          !options->hasDepthLookupInfo()) {
+        // this is possible in case *only* vertices are produced (no edges, no path),
+        // the traversal is breadth-first, the vertex uniqueness level is set to "global", 
+        // there is no pruning and there are no depth-specific filters
+        options->useNeighbors = true;
+        modified = true;
+      }
+    }
   }
 
   if (!tNodes.empty()) {
diff --git a/arangod/Aql/RegisterPlan.cpp b/arangod/Aql/RegisterPlan.cpp
index fe04381a8fb5..9c012cc1aefb 100644
--- a/arangod/Aql/RegisterPlan.cpp
+++ b/arangod/Aql/RegisterPlan.cpp
@@ -91,109 +91,84 @@ RegisterPlan* RegisterPlan::clone(ExecutionPlan* otherPlan, ExecutionPlan* plan)
   return other.release();
 }
 
+void RegisterPlan::increaseDepth() {
+  depth++;
+  nrRegsHere.emplace_back(0);
+  // create a copy of the last value here
+  // this is required because back returns a reference and emplace/push_back
+  // may invalidate all references
+  RegisterId registerId = nrRegs.back();
+  nrRegs.emplace_back(registerId);
+}
+
+void RegisterPlan::registerVariable(Variable const* v) {
+  nrRegsHere[depth]++;
+  nrRegs[depth]++;
+  varInfo.try_emplace(v->id, VarInfo(depth, totalNrRegs));
+  totalNrRegs++;
+}
+
 void RegisterPlan::after(ExecutionNode* en) {
+  TRI_ASSERT(en != nullptr);
+
   switch (en->getType()) {
     case ExecutionNode::ENUMERATE_COLLECTION: {
-      depth++;
-      nrRegsHere.emplace_back(1);
-      // create a copy of the last value here
-      // this is required because back returns a reference and emplace/push_back
-      // may invalidate all references
-      RegisterId registerId = 1 + nrRegs.back();
-      nrRegs.emplace_back(registerId);
-
+      increaseDepth();
       auto ep = dynamic_cast<DocumentProducingNode const*>(en);
       if (ep == nullptr) {
         THROW_ARANGO_EXCEPTION_MESSAGE(
             TRI_ERROR_INTERNAL,
             "unexpected cast result for DocumentProducingNode");
       }
-
-      varInfo.try_emplace(ep->outVariable()->id, VarInfo(depth, totalNrRegs));
-      totalNrRegs++;
+      registerVariable(ep->outVariable());
       break;
     }
 
     case ExecutionNode::INDEX: {
       auto ep = ExecutionNode::castTo<IndexNode const*>(en);
-      TRI_ASSERT(ep);
-
       ep->planNodeRegisters(nrRegsHere, nrRegs, varInfo, totalNrRegs, ++depth);
       break;
     }
 
     case ExecutionNode::ENUMERATE_LIST: {
-      depth++;
-      nrRegsHere.emplace_back(1);
-      // create a copy of the last value here
-      // this is required because back returns a reference and emplace/push_back
-      // may invalidate all references
-      RegisterId registerId = 1 + nrRegs.back();
-      nrRegs.emplace_back(registerId);
-
+      increaseDepth();
       auto ep = ExecutionNode::castTo<EnumerateListNode const*>(en);
-      TRI_ASSERT(ep != nullptr);
-      varInfo.try_emplace(ep->outVariable()->id, VarInfo(depth, totalNrRegs));
-      totalNrRegs++;
+      registerVariable(ep->outVariable());
       break;
     }
 
     case ExecutionNode::CALCULATION: {
-      nrRegsHere[depth]++;
-      nrRegs[depth]++;
       auto ep = ExecutionNode::castTo<CalculationNode const*>(en);
-      TRI_ASSERT(ep != nullptr);
-      varInfo.try_emplace(ep->outVariable()->id, VarInfo(depth, totalNrRegs));
-      totalNrRegs++;
+      registerVariable(ep->outVariable());
       break;
     }
 
     case ExecutionNode::SUBQUERY: {
-      nrRegsHere[depth]++;
-      nrRegs[depth]++;
       auto ep = ExecutionNode::castTo<SubqueryNode const*>(en);
-      TRI_ASSERT(ep != nullptr);
-      varInfo.try_emplace(ep->outVariable()->id, VarInfo(depth, totalNrRegs));
-      totalNrRegs++;
+      registerVariable(ep->outVariable());
       subQueryNodes.emplace_back(en);
       break;
     }
 
     case ExecutionNode::COLLECT: {
-      depth++;
-      nrRegsHere.emplace_back(0);
-      // create a copy of the last value here
-      // this is required because back returns a reference and emplace/push_back
-      // may invalidate all references
-      RegisterId registerId = nrRegs.back();
-      nrRegs.emplace_back(registerId);
-
+      increaseDepth();
       auto ep = ExecutionNode::castTo<CollectNode const*>(en);
       for (auto const& p : ep->groupVariables()) {
         // p is std::pair<Variable const*,Variable const*>
         // and the first is the to be assigned output variable
         // for which we need to create a register in the current
         // frame:
-        nrRegsHere[depth]++;
-        nrRegs[depth]++;
-        varInfo.try_emplace(p.first->id, VarInfo(depth, totalNrRegs));
-        totalNrRegs++;
+        registerVariable(p.first);
       }
       for (auto const& p : ep->aggregateVariables()) {
         // p is std::pair<Variable const*,Variable const*>
         // and the first is the to be assigned output variable
         // for which we need to create a register in the current
         // frame:
-        nrRegsHere[depth]++;
-        nrRegs[depth]++;
-        varInfo.try_emplace(p.first->id, VarInfo(depth, totalNrRegs));
-        totalNrRegs++;
+        registerVariable(p.first);
       }
       if (ep->hasOutVariable()) {
-        nrRegsHere[depth]++;
-        nrRegs[depth]++;
-        varInfo.try_emplace(ep->outVariable()->id, VarInfo(depth, totalNrRegs));
-        totalNrRegs++;
+        registerVariable(ep->outVariable());
       }
       break;
     }
@@ -203,13 +178,7 @@ void RegisterPlan::after(ExecutionNode* en) {
     case ExecutionNode::REPLACE:
     case ExecutionNode::REMOVE:
     case ExecutionNode::UPSERT: {
-      depth++;
-      nrRegsHere.emplace_back(0);
-      // create a copy of the last value here
-      // this is required because back returns a reference and emplace/push_back
-      // may invalidate all references
-      RegisterId registerId = nrRegs.back();
-      nrRegs.emplace_back(registerId);
+      increaseDepth();
 
       auto ep = dynamic_cast<ModificationNode const*>(en);
       if (ep == nullptr) {
@@ -217,18 +186,11 @@ void RegisterPlan::after(ExecutionNode* en) {
             TRI_ERROR_INTERNAL, "unexpected cast result for ModificationNode");
       }
       if (ep->getOutVariableOld() != nullptr) {
-        nrRegsHere[depth]++;
-        nrRegs[depth]++;
-        varInfo.try_emplace(ep->getOutVariableOld()->id, VarInfo(depth, totalNrRegs));
-        totalNrRegs++;
+        registerVariable(ep->getOutVariableOld());
       }
       if (ep->getOutVariableNew() != nullptr) {
-        nrRegsHere[depth]++;
-        nrRegs[depth]++;
-        varInfo.try_emplace(ep->getOutVariableNew()->id, VarInfo(depth, totalNrRegs));
-        totalNrRegs++;
+        registerVariable(ep->getOutVariableNew());
       }
-
       break;
     }
 
@@ -259,51 +221,30 @@ void RegisterPlan::after(ExecutionNode* en) {
     case ExecutionNode::TRAVERSAL:
     case ExecutionNode::SHORTEST_PATH:
     case ExecutionNode::K_SHORTEST_PATHS: {
-      depth++;
+      increaseDepth();
       auto ep = dynamic_cast<GraphNode const*>(en);
       if (ep == nullptr) {
         THROW_ARANGO_EXCEPTION_MESSAGE(TRI_ERROR_INTERNAL,
                                        "unexpected cast result for GraphNode");
       }
-      TRI_ASSERT(ep != nullptr);
-      auto vars = ep->getVariablesSetHere();
-      nrRegsHere.emplace_back(static_cast<RegisterId>(vars.size()));
-      // create a copy of the last value here
-      // this is requried because back returns a reference and emplace/push_back
-      // may invalidate all references
-      RegisterId registerId = static_cast<RegisterId>(vars.size() + nrRegs.back());
-      nrRegs.emplace_back(registerId);
-
-      for (auto& it : vars) {
-        varInfo.try_emplace(it->id, VarInfo(depth, totalNrRegs));
-        totalNrRegs++;
+
+      for (auto const& it : ep->getVariablesSetHere()) {
+        registerVariable(it);
       }
       break;
     }
 
     case ExecutionNode::REMOTESINGLE: {
-      depth++;
+      increaseDepth();
       auto ep = ExecutionNode::castTo<SingleRemoteOperationNode const*>(en);
-      TRI_ASSERT(ep != nullptr);
-      auto vars = ep->getVariablesSetHere();
-      nrRegsHere.emplace_back(static_cast<RegisterId>(vars.size()));
-      // create a copy of the last value here
-      // this is requried because back returns a reference and emplace/push_back
-      // may invalidate all references
-      RegisterId registerId = static_cast<RegisterId>(vars.size() + nrRegs.back());
-      nrRegs.emplace_back(registerId);
-
-      for (auto& it : vars) {
-        varInfo.try_emplace(it->id, VarInfo(depth, totalNrRegs));
-        totalNrRegs++;
+      for (auto const& it : ep->getVariablesSetHere()) {
+        registerVariable(it);
       }
       break;
     }
 
     case ExecutionNode::ENUMERATE_IRESEARCH_VIEW: {
       auto ep = ExecutionNode::castTo<iresearch::IResearchViewNode const*>(en);
-      TRI_ASSERT(ep);
-
       ep->planNodeRegisters(nrRegsHere, nrRegs, varInfo, totalNrRegs, ++depth);
       break;
     }
@@ -313,27 +254,16 @@ void RegisterPlan::after(ExecutionNode* en) {
     }
 
     case ExecutionNode::SUBQUERY_END: {
-      nrRegsHere[depth]++;
-      nrRegs[depth]++;
       auto ep = ExecutionNode::castTo<SubqueryEndNode const*>(en);
-      TRI_ASSERT(ep != nullptr);
-      varInfo.try_emplace(ep->outVariable()->id, VarInfo(depth, totalNrRegs));
-      totalNrRegs++;
+      registerVariable(ep->outVariable());
       subQueryNodes.emplace_back(en);
       break;
     }
+
     case ExecutionNode::MATERIALIZE: {
-      depth++;
-      nrRegsHere.emplace_back(1);
-      // create a copy of the last value here
-      // this is required because back returns a reference and emplace/push_back
-      // may invalidate all references
-      RegisterId registerId = nrRegs.back() + 1;
-      nrRegs.emplace_back(registerId);
+      increaseDepth();
       auto ep = ExecutionNode::castTo<materialize::MaterializeNode const*>(en);
-      TRI_ASSERT(ep != nullptr);
-      varInfo.try_emplace(ep->outVariable().id, VarInfo(depth, totalNrRegs));
-      totalNrRegs++;
+      registerVariable(&(ep->outVariable()));
       break;
     }
     default: {
diff --git a/arangod/Aql/RegisterPlan.h b/arangod/Aql/RegisterPlan.h
index abdb67bf0b2d..5e84752fb6f2 100644
--- a/arangod/Aql/RegisterPlan.h
+++ b/arangod/Aql/RegisterPlan.h
@@ -36,6 +36,7 @@ namespace aql {
 
 class ExecutionNode;
 class ExecutionPlan;
+struct Variable;
 
 /// @brief static analysis, walker class and information collector
 struct VarInfo {
@@ -80,14 +81,20 @@ struct RegisterPlan final : public WalkerWorker<ExecutionNode> {
     nrRegs.reserve(8);
     nrRegs.emplace_back(0);
   }
-
-  void clear();
-
-  void setSharedPtr(std::shared_ptr<RegisterPlan>* shared) { me = shared; }
-
+  
   // Copy constructor used for a subquery:
   RegisterPlan(RegisterPlan const& v, unsigned int newdepth);
   ~RegisterPlan() = default;
+  
+  void setSharedPtr(std::shared_ptr<RegisterPlan>* shared) { me = shared; }
+
+  void clear();
+  
+  RegisterPlan* clone(ExecutionPlan* otherPlan, ExecutionPlan* plan);
+
+  void registerVariable(Variable const* v);
+  
+  void increaseDepth();
 
   virtual bool enterSubquery(ExecutionNode*, ExecutionNode*) override final {
     return false;  // do not walk into subquery
@@ -95,8 +102,6 @@ struct RegisterPlan final : public WalkerWorker<ExecutionNode> {
 
   virtual void after(ExecutionNode* eb) override final;
 
-  RegisterPlan* clone(ExecutionPlan* otherPlan, ExecutionPlan* plan);
-
  public:
   /// @brief maximum register id that can be assigned, plus one.
   /// this is used for assertions
diff --git a/arangod/Aql/SimpleModifier.cpp b/arangod/Aql/SimpleModifier.cpp
index ff1df68ed5d3..efbd9b8248d1 100644
--- a/arangod/Aql/SimpleModifier.cpp
+++ b/arangod/Aql/SimpleModifier.cpp
@@ -200,7 +200,7 @@ VPackArrayIterator SimpleModifier<ModifierCompletion, Enable>::getResultsIterato
     TRI_ASSERT(_results.hasSlice() && _results.slice().isArray());
     return VPackArrayIterator{_results.slice()};
   }
-  return VPackArrayIterator{VPackSlice::emptyArraySlice()};
+  return VPackArrayIterator(VPackArrayIterator::Empty{});
 }
 
 template class ::arangodb::aql::SimpleModifier<InsertModifierCompletion>;
diff --git a/arangod/Aql/SimpleModifier.h b/arangod/Aql/SimpleModifier.h
index 221f4d248434..23d3465ab673 100644
--- a/arangod/Aql/SimpleModifier.h
+++ b/arangod/Aql/SimpleModifier.h
@@ -104,7 +104,7 @@ class SimpleModifier {
       : _infos(infos),
         _completion(infos),
         _accumulator(nullptr),
-        _resultsIterator(VPackSlice::emptyArraySlice()),
+        _resultsIterator(VPackArrayIterator::Empty{}),
         _batchSize(ExecutionBlock::DefaultBatchSize) {}
   ~SimpleModifier() = default;
 
diff --git a/arangod/Aql/SortedCollectExecutor.cpp b/arangod/Aql/SortedCollectExecutor.cpp
index 1e3ec9446d95..d23975c5f72c 100644
--- a/arangod/Aql/SortedCollectExecutor.cpp
+++ b/arangod/Aql/SortedCollectExecutor.cpp
@@ -51,14 +51,14 @@ static const AqlValue EmptyValue;
 SortedCollectExecutor::CollectGroup::CollectGroup(bool count, Infos& infos)
     : groupLength(0),
       count(count),
+      _shouldDeleteBuilderBuffer(true),
       infos(infos),
-      _lastInputRow(InputAqlItemRow{CreateInvalidInputRowHint{}}),
-      _shouldDeleteBuilderBuffer(true) {
+      _lastInputRow(InputAqlItemRow{CreateInvalidInputRowHint{}}) {
   for (auto const& aggName : infos.getAggregateTypes()) {
     aggregators.emplace_back(Aggregator::fromTypeString(infos.getTransaction(), aggName));
   }
   TRI_ASSERT(infos.getAggregatedRegisters().size() == aggregators.size());
-};
+}
 
 SortedCollectExecutor::CollectGroup::~CollectGroup() {
   for (auto& it : groupValues) {
diff --git a/arangod/Aql/SortedCollectExecutor.h b/arangod/Aql/SortedCollectExecutor.h
index 9145b991ad69..55e28d0585af 100644
--- a/arangod/Aql/SortedCollectExecutor.h
+++ b/arangod/Aql/SortedCollectExecutor.h
@@ -139,10 +139,10 @@ class SortedCollectExecutor {
     AggregateValuesType aggregators;
     size_t groupLength;
     bool const count;
+    bool _shouldDeleteBuilderBuffer;
     Infos& infos;
     InputAqlItemRow _lastInputRow;
     arangodb::velocypack::Builder _builder;
-    bool _shouldDeleteBuilderBuffer;
 
     CollectGroup() = delete;
     CollectGroup(CollectGroup&&) = default;
diff --git a/arangod/Aql/TraversalExecutor.cpp b/arangod/Aql/TraversalExecutor.cpp
index 92b6c7fc4048..58e917dde61f 100644
--- a/arangod/Aql/TraversalExecutor.cpp
+++ b/arangod/Aql/TraversalExecutor.cpp
@@ -54,7 +54,6 @@ TraversalExecutorInfos::TraversalExecutorInfos(
       _inputRegister(inputRegister),
       _filterConditionVariables(std::move(filterConditionVariables)) {
   TRI_ASSERT(_traverser != nullptr);
-  TRI_ASSERT(!_registerMapping.empty());
   // _fixedSource XOR _inputRegister
   // note: _fixedSource can be the empty string here
   TRI_ASSERT(_fixedSource.empty() ||
@@ -198,6 +197,13 @@ auto TraversalExecutor::doOutput(OutputAqlItemRow& output) -> void {
       AqlValueGuard guard{path, true};
       output.moveValueInto(_infos.pathRegister(), _inputRow, guard);
     }
+
+    // No output is requested from the register plan. We still need
+    // to copy the inputRow for the query to yield correct results.
+    if (!_infos.useVertexOutput() && !_infos.useEdgeOutput() && !_infos.usePathOutput()) {
+      output.copyRow(_inputRow);
+    }
+
     output.advanceRow();
   }
 }
diff --git a/arangod/Aql/UpsertModifier.cpp b/arangod/Aql/UpsertModifier.cpp
index c9bc009183e8..aa6e4105576c 100644
--- a/arangod/Aql/UpsertModifier.cpp
+++ b/arangod/Aql/UpsertModifier.cpp
@@ -205,14 +205,14 @@ VPackArrayIterator UpsertModifier::getUpdateResultsIterator() const {
   if (_updateResults.hasSlice() && _updateResults.slice().isArray()) {
     return VPackArrayIterator(_updateResults.slice());
   }
-  return VPackArrayIterator(VPackSlice::emptyArraySlice());
+  return VPackArrayIterator(VPackArrayIterator::Empty{});
 }
 
 VPackArrayIterator UpsertModifier::getInsertResultsIterator() const {
   if (_insertResults.hasSlice() && _insertResults.slice().isArray()) {
     return VPackArrayIterator(_insertResults.slice());
   }
-  return VPackArrayIterator(VPackSlice::emptyArraySlice());
+  return VPackArrayIterator(VPackArrayIterator::Empty{});
 }
 
 Result UpsertModifier::accumulate(InputAqlItemRow& row) {
diff --git a/arangod/CMakeLists.txt b/arangod/CMakeLists.txt
index 69ab26c764ef..5c2cd2aad906 100644
--- a/arangod/CMakeLists.txt
+++ b/arangod/CMakeLists.txt
@@ -426,6 +426,7 @@ set(LIB_ARANGO_STORAGE_ENGINE_SOURCES
 )
 
 set(LIB_ARANGO_STORAGE_ENGINE_COMMON_SOURCES
+  StorageEngine/ReplicationIterator.cpp
   StorageEngine/WalAccess.cpp
 )
 
@@ -859,6 +860,7 @@ target_link_libraries(arango_aql arango_network)
 
 target_link_libraries(arango_cache arango)
 target_link_libraries(arango_cache boost_system)
+target_link_libraries(arango_cache arango::validation)
 
 target_link_libraries(arango_cluster_engine arango_indexes)
 target_link_libraries(arango_cluster_engine boost_boost)
@@ -875,6 +877,7 @@ target_link_libraries(arango_graph boost_boost)
 
 target_link_libraries(arango_indexes arango_geo)
 target_link_libraries(arango_indexes boost_boost)
+target_link_libraries(arango_indexes arango::validation)
 
 target_link_libraries(arango_iresearch arango_indexes)
 target_link_libraries(arango_iresearch arango_cluster_engine)
@@ -893,6 +896,7 @@ target_link_libraries(arango_network boost_boost)
 target_link_libraries(arango_network fuerte)
 target_link_libraries(arango_network llhttp)
 target_link_libraries(arango_network nghttp2)
+target_link_libraries(arango_network arango::validation)
 
 target_link_libraries(arango_pregel arango_agency)
 target_link_libraries(arango_pregel boost_boost)
@@ -908,6 +912,8 @@ target_link_libraries(arango_rocksdb arango_geo)
 target_link_libraries(arango_rocksdb arango_indexes)
 target_link_libraries(arango_rocksdb arango_storage_engine_common)
 target_link_libraries(arango_rocksdb boost_boost)
+target_link_libraries(arango_rocksdb arango::validation)
+target_link_libraries(arango_storage_engine_common arango::validation)
 
 if (USE_ENTERPRISE)
   # this is required for hotbackup. Views need to be flushed.
@@ -920,8 +926,10 @@ target_link_libraries(arango_storage_engine arango_cluster_engine)
 target_link_libraries(arango_storage_engine arango_cluster_methods)
 target_link_libraries(arango_storage_engine arango_mmfiles)
 target_link_libraries(arango_storage_engine arango_rocksdb)
+target_link_libraries(arango_storage_engine arango::validation)
 
 target_link_libraries(arango_utils boost_boost)
+target_link_libraries(arango_utils arango::validation)
 
 target_link_libraries(arango_v8server arango_agency)
 target_link_libraries(arango_v8server arango_iresearch)
@@ -933,6 +941,7 @@ target_link_libraries(arango_vocbase arango_cluster_methods)
 target_link_libraries(arango_vocbase arango_indexes)
 target_link_libraries(arango_vocbase arango_replication)
 target_link_libraries(arango_vocbase boost_system)
+target_link_libraries(arango_vocbase arango::validation)
 
 target_link_libraries(arangoserver arango_agency)
 target_link_libraries(arangoserver arango_aql)
diff --git a/arangod/Cache/BucketState.cpp b/arangod/Cache/BucketState.cpp
index 87c4a2aa4d25..df27e3ce1423 100644
--- a/arangod/Cache/BucketState.cpp
+++ b/arangod/Cache/BucketState.cpp
@@ -18,19 +18,18 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 ////////////////////////////////////////////////////////////////////////////////
 
+#include <atomic>
+#include <cstdint>
+
 #include "Cache/BucketState.h"
 #include "Basics/Common.h"
 #include "Basics/cpu-relax.h"
 #include "Basics/debugging.h"
 
-#include <stdint.h>
-#include <atomic>
-
-using namespace arangodb::basics;
-using namespace arangodb::cache;
+namespace arangodb::cache {
 
 BucketState::BucketState() : _state(0) {}
 
@@ -46,17 +45,17 @@ BucketState& BucketState::operator=(BucketState const& other) {
 }
 
 bool BucketState::isLocked() const {
-  return ((_state.load() & static_cast<uint32_t>(Flag::locked)) > 0);
+  return ((_state.load() & static_cast<std::uint32_t>(Flag::locked)) > 0);
 }
 
-bool BucketState::lock(uint64_t maxTries, BucketState::CallbackType cb) {
+bool BucketState::lock(std::uint64_t maxTries, BucketState::CallbackType cb) {
   uint64_t attempt = 0;
   while (attempt < maxTries) {
     // expect unlocked, but need to preserve migrating status
-    uint32_t current = _state.load(std::memory_order_relaxed);
-    uint32_t expected = current & (~static_cast<uint32_t>(Flag::locked));
+    std::uint32_t current = _state.load(std::memory_order_relaxed);
+    std::uint32_t expected = current & (~static_cast<std::uint32_t>(Flag::locked));
     if (current == expected) {
-      uint32_t desired = expected | static_cast<uint32_t>(Flag::locked);
+      uint32_t desired = expected | static_cast<std::uint32_t>(Flag::locked);
       // try to lock
       bool success = _state.compare_exchange_strong(expected, desired, std::memory_order_acq_rel,
                                                     std::memory_order_relaxed);
@@ -66,7 +65,7 @@ bool BucketState::lock(uint64_t maxTries, BucketState::CallbackType cb) {
       }
     }
     attempt++;
-    cpu_relax();
+    basics::cpu_relax();
     // TODO: exponential back-off for failure?
   }
 
@@ -75,26 +74,27 @@ bool BucketState::lock(uint64_t maxTries, BucketState::CallbackType cb) {
 
 void BucketState::unlock() {
   TRI_ASSERT(isLocked());
-  _state.fetch_and(~static_cast<uint32_t>(Flag::locked), std::memory_order_release);
+  _state.fetch_and(~static_cast<std::uint32_t>(Flag::locked), std::memory_order_release);
 }
 
 bool BucketState::isSet(BucketState::Flag flag) const {
   TRI_ASSERT(isLocked());
-  return ((_state.load() & static_cast<uint32_t>(flag)) > 0);
+  return ((_state.load() & static_cast<std::uint32_t>(flag)) > 0);
 }
 
 bool BucketState::isSet(BucketState::Flag flag1, BucketState::Flag flag2) const {
   TRI_ASSERT(isLocked());
-  return ((_state.load() &
-           (static_cast<uint32_t>(flag1) | static_cast<uint32_t>(flag2))) > 0);
+  return ((_state.load() & (static_cast<std::uint32_t>(flag1) |
+                            static_cast<std::uint32_t>(flag2))) > 0);
 }
 
 void BucketState::toggleFlag(BucketState::Flag flag) {
   TRI_ASSERT(isLocked());
-  _state ^= static_cast<uint32_t>(flag);
+  _state ^= static_cast<std::uint32_t>(flag);
 }
 
 void BucketState::clear() {
   TRI_ASSERT(isLocked());
-  _state = static_cast<uint32_t>(Flag::locked);
+  _state = static_cast<std::uint32_t>(Flag::locked);
+}
 }
diff --git a/arangod/Cache/BucketState.h b/arangod/Cache/BucketState.h
index 3fc20a7701ab..2c5f4f3c714e 100644
--- a/arangod/Cache/BucketState.h
+++ b/arangod/Cache/BucketState.h
@@ -18,7 +18,7 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 ////////////////////////////////////////////////////////////////////////////////
 
 #ifndef ARANGODB_CACHE_BUCKET_STATE_H
@@ -27,8 +27,7 @@
 #include <atomic>
 #include <cstdint>
 #include <functional>
-
-#include "Basics/Common.h"
+#include <limits>
 
 namespace arangodb {
 namespace cache {
@@ -56,7 +55,7 @@ struct BucketState {
   /// and all flag values should be adjusted to keep bit-significance in
   /// ascending order.
   //////////////////////////////////////////////////////////////////////////////
-  enum class Flag : uint32_t {
+  enum class Flag : std::uint32_t {
     locked = 0x00000001,
     blacklisted = 0x00000002,
     disabled = 0x00000004,
@@ -98,7 +97,8 @@ struct BucketState {
   /// locked or not. The optional second parameter is a function which will be
   /// called upon successfully locking the state.
   //////////////////////////////////////////////////////////////////////////////
-  bool lock(uint64_t maxTries = UINT64_MAX, BucketState::CallbackType cb = []() -> void {});
+  bool lock(std::uint64_t maxTries = std::numeric_limits<std::uint64_t>::max(),
+            BucketState::CallbackType cb = []() -> void {});
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Unlocks the state. Requires state to be locked.
@@ -122,11 +122,11 @@ struct BucketState {
   void clear();
 
  private:
-  std::atomic<uint32_t> _state;
+  std::atomic<std::uint32_t> _state;
 };
 
 // ensure that state is exactly the size of uint32_t
-static_assert(sizeof(BucketState) == sizeof(uint32_t),
+static_assert(sizeof(BucketState) == sizeof(std::uint32_t),
               "Expected sizeof(BucketState) == sizeof(uint32_t).");
 
 };  // end namespace cache
diff --git a/arangod/Cache/Cache.cpp b/arangod/Cache/Cache.cpp
index d13748f485f1..bf3920d0f8fe 100644
--- a/arangod/Cache/Cache.cpp
+++ b/arangod/Cache/Cache.cpp
@@ -18,12 +18,22 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 ////////////////////////////////////////////////////////////////////////////////
 
+#include <algorithm>
+#include <chrono>
+#include <cmath>
+#include <cstdint>
+#include <limits>
+#include <list>
+#include <thread>
+
 #include "Cache/Cache.h"
 
 #include "Basics/SharedPRNG.h"
+#include "Basics/SpinLocker.h"
+#include "Basics/SpinUnlocker.h"
 #include "Basics/fasthash.h"
 #include "Cache/CachedValue.h"
 #include "Cache/Common.h"
@@ -32,23 +42,20 @@
 #include "Cache/Table.h"
 #include "Random/RandomGenerator.h"
 
-#include <algorithm>
-#include <chrono>
-#include <cmath>
-#include <cstdint>
-#include <list>
-#include <thread>
+namespace arangodb::cache {
 
-using namespace arangodb::cache;
+using SpinLocker = ::arangodb::basics::SpinLocker;
+using SpinUnlocker = ::arangodb::basics::SpinUnlocker;
 
-const uint64_t Cache::minSize = 16384;
-const uint64_t Cache::minLogSize = 14;
+const std::uint64_t Cache::minSize = 16384;
+const std::uint64_t Cache::minLogSize = 14;
 
-uint64_t Cache::_findStatsCapacity = 16384;
+std::uint64_t Cache::_findStatsCapacity = 16384;
 
-Cache::Cache(ConstructionGuard guard, Manager* manager, uint64_t id,
+Cache::Cache(ConstructionGuard guard, Manager* manager, std::uint64_t id,
              Metadata&& metadata, std::shared_ptr<Table> table, bool enableWindowedStats,
-             std::function<Table::BucketClearer(Metadata*)> bucketClearer, size_t slotsPerBucket)
+             std::function<Table::BucketClearer(Metadata*)> bucketClearer,
+             std::size_t slotsPerBucket)
     : _taskLock(),
       _shutdown(false),
       _enableWindowedStats(enableWindowedStats),
@@ -78,40 +85,31 @@ Cache::Cache(ConstructionGuard guard, Manager* manager, uint64_t id,
   }
 }
 
-uint64_t Cache::size() const {
+std::uint64_t Cache::size() const {
   if (isShutdown()) {
     return 0;
   }
 
-  _metadata.readLock();
-  uint64_t size = _metadata.allocatedSize;
-  _metadata.readUnlock();
-
-  return size;
+  SpinLocker metaGuard(SpinLocker::Mode::Read, _metadata.lock());
+  return _metadata.allocatedSize;
 }
 
-uint64_t Cache::usageLimit() const {
+std::uint64_t Cache::usageLimit() const {
   if (isShutdown()) {
     return 0;
   }
 
-  _metadata.readLock();
-  uint64_t limit = _metadata.softUsageLimit;
-  _metadata.readUnlock();
-
-  return limit;
+  SpinLocker metaGuard(SpinLocker::Mode::Read, _metadata.lock());
+  return _metadata.softUsageLimit;
 }
 
-uint64_t Cache::usage() const {
+std::uint64_t Cache::usage() const {
   if (isShutdown()) {
     return false;
   }
 
-  _metadata.readLock();
-  uint64_t usage = _metadata.usage;
-  _metadata.readUnlock();
-
-  return usage;
+  SpinLocker metaGuard(SpinLocker::Mode::Read, _metadata.lock());
+  return _metadata.usage;
 }
 
 void Cache::sizeHint(uint64_t numElements) {
@@ -119,11 +117,11 @@ void Cache::sizeHint(uint64_t numElements) {
     return;
   }
 
-  uint64_t numBuckets = static_cast<uint64_t>(
+  std::uint64_t numBuckets = static_cast<std::uint64_t>(
       static_cast<double>(numElements) /
       (static_cast<double>(_slotsPerBucket) * Table::idealUpperRatio));
-  uint32_t requestedLogSize = 0;
-  for (; (static_cast<uint64_t>(1) << requestedLogSize) < numBuckets; requestedLogSize++) {
+  std::uint32_t requestedLogSize = 0;
+  for (; (static_cast<std::uint64_t>(1) << requestedLogSize) < numBuckets; requestedLogSize++) {
   }
   requestMigrate(requestedLogSize);
 }
@@ -132,8 +130,8 @@ std::pair<double, double> Cache::hitRates() {
   double lifetimeRate = std::nan("");
   double windowedRate = std::nan("");
 
-  uint64_t currentMisses = _findMisses.value(std::memory_order_relaxed);
-  uint64_t currentHits = _findHits.value(std::memory_order_relaxed);
+  std::uint64_t currentMisses = _findMisses.value(std::memory_order_relaxed);
+  std::uint64_t currentHits = _findHits.value(std::memory_order_relaxed);
   if (currentMisses + currentHits > 0) {
     lifetimeRate = 100 * (static_cast<double>(currentHits) /
                           static_cast<double>(currentHits + currentMisses));
@@ -142,13 +140,13 @@ std::pair<double, double> Cache::hitRates() {
   if (_enableWindowedStats && _findStats) {
     auto stats = _findStats->getFrequencies();
     if (stats.size() == 1) {
-      if (stats[0].first == static_cast<uint8_t>(Stat::findHit)) {
+      if (stats[0].first == static_cast<std::uint8_t>(Stat::findHit)) {
         windowedRate = 100.0;
       } else {
         windowedRate = 0.0;
       }
     } else if (stats.size() == 2) {
-      if (stats[0].first == static_cast<uint8_t>(Stat::findHit)) {
+      if (stats[0].first == static_cast<std::uint8_t>(Stat::findHit)) {
         currentHits = stats[0].second;
         currentMisses = stats[1].second;
       } else {
@@ -170,11 +168,8 @@ bool Cache::isResizing() {
     return false;
   }
 
-  _metadata.readLock();
-  bool resizing = _metadata.isResizing();
-  _metadata.readUnlock();
-
-  return resizing;
+  SpinLocker metaGuard(SpinLocker::Mode::Read, _metadata.lock());
+  return _metadata.isResizing();
 }
 
 bool Cache::isMigrating() {
@@ -182,11 +177,8 @@ bool Cache::isMigrating() {
     return false;
   }
 
-  _metadata.readLock();
-  bool migrating = _metadata.isMigrating();
-  _metadata.readUnlock();
-
-  return migrating;
+  SpinLocker metaGuard(SpinLocker::Mode::Read, _metadata.lock());
+  return _metadata.isMigrating();
 }
 
 bool Cache::isBusy() {
@@ -194,11 +186,8 @@ bool Cache::isBusy() {
     return false;
   }
 
-  _metadata.readLock();
-  bool busy = _metadata.isResizing() || _metadata.isMigrating();
-  _metadata.readUnlock();
-
-  return busy;
+  SpinLocker metaGuard(SpinLocker::Mode::Read, _metadata.lock());
+  return _metadata.isResizing() || _metadata.isMigrating();
 }
 
 void Cache::destroy(std::shared_ptr<Cache> const& cache) {
@@ -214,43 +203,46 @@ void Cache::requestGrow() {
     return;
   }
 
-  if (_taskLock.writeLock(Cache::triesSlow)) {
+  SpinLocker taskGuard(SpinLocker::Mode::Write, _taskLock,
+                       static_cast<std::size_t>(Cache::triesSlow));
+  if (taskGuard.isLocked()) {
     if (std::chrono::steady_clock::now().time_since_epoch().count() >
         _resizeRequestTime.load()) {
-      _metadata.readLock();
-      bool ok = !_metadata.isResizing();
-      _metadata.readUnlock();
+      bool ok = false;
+      {
+        SpinLocker metaGuard(SpinLocker::Mode::Read, _metadata.lock());
+        ok = !_metadata.isResizing();
+      }
       if (ok) {
         auto result = _manager->requestGrow(this);
         _resizeRequestTime.store(result.second.time_since_epoch().count());
       }
     }
-    _taskLock.writeUnlock();
   }
 }
 
-void Cache::requestMigrate(uint32_t requestedLogSize) {
+void Cache::requestMigrate(std::uint32_t requestedLogSize) {
   // fail fast if inside banned window
   if (isShutdown() || std::chrono::steady_clock::now().time_since_epoch().count() <=
                           _migrateRequestTime.load()) {
     return;
   }
 
-  if (_taskLock.writeLock(Cache::triesGuarantee)) {
-    if (std::chrono::steady_clock::now().time_since_epoch().count() >
-        _migrateRequestTime.load()) {
-      cache::Table* table = _table.load(std::memory_order_relaxed);
-      TRI_ASSERT(table != nullptr);
+  SpinLocker taskGuard(SpinLocker::Mode::Write, _taskLock);
+  if (std::chrono::steady_clock::now().time_since_epoch().count() >
+      _migrateRequestTime.load()) {
+    cache::Table* table = _table.load(std::memory_order_relaxed);
+    TRI_ASSERT(table != nullptr);
 
-      _metadata.readLock();
-      bool ok = !_metadata.isMigrating() && (requestedLogSize != table->logSize());
-      _metadata.readUnlock();
-      if (ok) {
-        auto result = _manager->requestMigrate(this, requestedLogSize);
-        _migrateRequestTime.store(result.second.time_since_epoch().count());
-      }
+    bool ok = false;
+    {
+      SpinLocker metaGuard(SpinLocker::Mode::Read, _metadata.lock());
+      ok = !_metadata.isMigrating() && (requestedLogSize != table->logSize());
+    }
+    if (ok) {
+      auto result = _manager->requestMigrate(this, requestedLogSize);
+      _migrateRequestTime.store(result.second.time_since_epoch().count());
     }
-    _taskLock.writeUnlock();
   }
 }
 
@@ -262,17 +254,14 @@ void Cache::freeValue(CachedValue* value) {
   delete value;
 }
 
-bool Cache::reclaimMemory(uint64_t size) {
-  _metadata.readLock();
-  _metadata.adjustUsageIfAllowed(-static_cast<int64_t>(size));
-  bool underLimit = (_metadata.softUsageLimit >= _metadata.usage);
-  _metadata.readUnlock();
-
-  return underLimit;
+bool Cache::reclaimMemory(std::uint64_t size) {
+  SpinLocker metaGuard(SpinLocker::Mode::Read, _metadata.lock());
+  _metadata.adjustUsageIfAllowed(-static_cast<std::int64_t>(size));
+  return (_metadata.softUsageLimit >= _metadata.usage);
 }
 
-uint32_t Cache::hashKey(void const* key, size_t keySize) const {
-  return (std::max)(static_cast<uint32_t>(1), fasthash32(key, keySize, 0xdeadbeefUL));
+std::uint32_t Cache::hashKey(void const* key, std::size_t keySize) const {
+  return (std::max)(static_cast<std::uint32_t>(1), fasthash32(key, keySize, 0xdeadbeefUL));
 }
 
 void Cache::recordStat(Stat stat) {
@@ -284,7 +273,7 @@ void Cache::recordStat(Stat stat) {
     case Stat::findHit: {
       _findHits.add(1, std::memory_order_relaxed);
       if (_enableWindowedStats && _findStats) {
-        _findStats->insertRecord(static_cast<uint8_t>(Stat::findHit));
+        _findStats->insertRecord(static_cast<std::uint8_t>(Stat::findHit));
       }
       _manager->reportHitStat(Stat::findHit);
       break;
@@ -292,7 +281,7 @@ void Cache::recordStat(Stat stat) {
     case Stat::findMiss: {
       _findMisses.add(1, std::memory_order_relaxed);
       if (_enableWindowedStats && _findStats) {
-        _findStats->insertRecord(static_cast<uint8_t>(Stat::findMiss));
+        _findStats->insertRecord(static_cast<std::uint8_t>(Stat::findMiss));
       }
       _manager->reportHitStat(Stat::findMiss);
       break;
@@ -308,8 +297,8 @@ bool Cache::reportInsert(bool hadEviction) {
   }
   _insertsTotal.add(1, std::memory_order_relaxed);
   if ((basics::SharedPRNG::rand() & _evictionMask) == 0) {
-    uint64_t total = _insertsTotal.value(std::memory_order_relaxed);
-    uint64_t evictions = _insertEvictions.value(std::memory_order_relaxed);
+    std::uint64_t total = _insertsTotal.value(std::memory_order_relaxed);
+    std::uint64_t evictions = _insertEvictions.value(std::memory_order_relaxed);
     if ((static_cast<double>(evictions) / static_cast<double>(total)) > _evictionRateThreshold) {
       shouldMigrate = true;
       cache::Table* table = _table.load(std::memory_order_relaxed);
@@ -323,29 +312,29 @@ bool Cache::reportInsert(bool hadEviction) {
   return shouldMigrate;
 }
 
-Metadata* Cache::metadata() { return &_metadata; }
+Metadata& Cache::metadata() { return _metadata; }
 
 std::shared_ptr<Table> Cache::table() const {
   return std::atomic_load(&_tableShrdPtr);
 }
+
 void Cache::shutdown() {
-  _taskLock.writeLock();
+  SpinLocker taskGuard(SpinLocker::Mode::Write, _taskLock);
   auto handle = shared_from_this();  // hold onto self-reference to prevent
                                      // pre-mature shared_ptr destruction
   TRI_ASSERT(handle.get() == this);
   if (!_shutdown.exchange(true)) {
-    _metadata.readLock();
     while (true) {
-      if (!_metadata.isMigrating() && !_metadata.isResizing()) {
-        break;
+      {
+        SpinLocker metaGuard(SpinLocker::Mode::Read, _metadata.lock());
+        if (!_metadata.isMigrating() && !_metadata.isResizing()) {
+          break;
+        }
       }
-      _metadata.readUnlock();
-      _taskLock.writeUnlock();
+
+      SpinUnlocker taskUnguard(SpinUnlocker::Mode::Write, _taskLock);
       std::this_thread::sleep_for(std::chrono::microseconds(10));
-      _taskLock.writeLock();
-      _metadata.readLock();
     }
-    _metadata.readUnlock();
 
     cache::Table* table = _table.load(std::memory_order_relaxed);
     if (table != nullptr) {
@@ -358,14 +347,13 @@ void Cache::shutdown() {
     }
 
     _manager->reclaimTable(std::atomic_load(&_tableShrdPtr));
-    _metadata.writeLock();
-    _metadata.changeTable(0);
-    _metadata.writeUnlock();
+    {
+      SpinLocker metaGuard(SpinLocker::Mode::Write, _metadata.lock());
+      _metadata.changeTable(0);
+    }
     _manager->unregisterCache(_id);
     _table.store(nullptr, std::memory_order_relaxed);
   }
-
-  _taskLock.writeUnlock();
 }
 
 bool Cache::canResize() {
@@ -373,14 +361,8 @@ bool Cache::canResize() {
     return false;
   }
 
-  bool allowed = true;
-  _metadata.readLock();
-  if (_metadata.isResizing() || _metadata.isMigrating()) {
-    allowed = false;
-  }
-  _metadata.readUnlock();
-
-  return allowed;
+  SpinLocker metaGuard(SpinLocker::Mode::Read, _metadata.lock());
+  return !(_metadata.isResizing() || _metadata.isMigrating());
 }
 
 bool Cache::canMigrate() {
@@ -388,14 +370,8 @@ bool Cache::canMigrate() {
     return false;
   }
 
-  bool allowed = true;
-  _metadata.readLock();
-  if (_metadata.isMigrating()) {
-    allowed = false;
-  }
-  _metadata.readUnlock();
-
-  return allowed;
+  SpinLocker metaGuard(SpinLocker::Mode::Read, _metadata.lock());
+  return !_metadata.isMigrating();
 }
 
 bool Cache::freeMemory() {
@@ -404,11 +380,12 @@ bool Cache::freeMemory() {
   }
 
   bool underLimit = reclaimMemory(0ULL);
-  uint64_t failures = 0;
+  std::uint64_t failures = 0;
   while (!underLimit) {
     // pick a random bucket
-    uint32_t randomHash = RandomGenerator::interval(UINT32_MAX);
-    uint64_t reclaimed = freeMemoryFrom(randomHash);
+    std::uint32_t randomHash =
+        RandomGenerator::interval(std::numeric_limits<std::uint32_t>::max());
+    std::uint64_t reclaimed = freeMemoryFrom(randomHash);
 
     if (reclaimed > 0) {
       failures = 0;
@@ -441,27 +418,32 @@ bool Cache::migrate(std::shared_ptr<Table> newTable) {
   table->setAuxiliary(newTable);
 
   // do the actual migration
-  for (uint32_t i = 0; i < table->size(); i++) {
+  for (std::uint32_t i = 0; i < table->size(); i++) {
     migrateBucket(table->primaryBucket(i), table->auxiliaryBuckets(i), newTable);
   }
 
   // swap tables
-  _taskLock.writeLock();
-  _table.store(newTable.get(), std::memory_order_relaxed);
-  std::shared_ptr<Table> oldTable = std::atomic_exchange(&_tableShrdPtr, newTable);
-  std::shared_ptr<Table> confirm =
-      oldTable->setAuxiliary(std::shared_ptr<Table>(nullptr));
-  _taskLock.writeUnlock();
+  std::shared_ptr<Table> oldTable;
+  {
+    SpinLocker taskGuard(SpinLocker::Mode::Write, _taskLock);
+    _table.store(newTable.get(), std::memory_order_relaxed);
+    oldTable = std::atomic_exchange(&_tableShrdPtr, newTable);
+    std::shared_ptr<Table> confirm =
+        oldTable->setAuxiliary(std::shared_ptr<Table>(nullptr));
+  }
 
   // clear out old table and release it
   oldTable->clear();
   _manager->reclaimTable(oldTable);
 
   // unmarking migrating flag
-  _metadata.writeLock();
-  _metadata.changeTable(table->memoryUsage());
-  _metadata.toggleMigrating();
-  _metadata.writeUnlock();
+  {
+    SpinLocker metaGuard(SpinLocker::Mode::Write, _metadata.lock());
+    _metadata.changeTable(table->memoryUsage());
+    _metadata.toggleMigrating();
+  }
 
   return true;
 }
+
+}  // namespace arangodb::cache
\ No newline at end of file
diff --git a/arangod/Cache/Cache.h b/arangod/Cache/Cache.h
index f6bea5b0fee4..cd6f0bc79f1f 100644
--- a/arangod/Cache/Cache.h
+++ b/arangod/Cache/Cache.h
@@ -18,13 +18,12 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 ////////////////////////////////////////////////////////////////////////////////
 
 #ifndef ARANGODB_CACHE_CACHE_H
 #define ARANGODB_CACHE_CACHE_H
 
-#include "Basics/Common.h"
 #include "Basics/ReadWriteSpinLock.h"
 #include "Basics/Result.h"
 #include "Basics/SharedCounter.h"
@@ -38,6 +37,7 @@
 #include "Cache/Table.h"
 
 #include <cstdint>
+#include <limits>
 #include <list>
 #include <memory>
 
@@ -68,40 +68,44 @@ class Cache : public std::enable_shared_from_this<Cache> {
  public:
   typedef FrequencyBuffer<uint8_t> StatBuffer;
 
-  static const uint64_t minSize;
-  static const uint64_t minLogSize;
+  static const std::uint64_t minSize;
+  static const std::uint64_t minLogSize;
+
+  static constexpr std::uint64_t triesGuarantee =
+      std::numeric_limits<std::uint64_t>::max();
 
  public:
-  Cache(ConstructionGuard guard, Manager* manager, uint64_t id,
+  Cache(ConstructionGuard guard, Manager* manager, std::uint64_t id,
         Metadata&& metadata, std::shared_ptr<Table> table, bool enableWindowedStats,
-        std::function<Table::BucketClearer(Metadata*)> bucketClearer, size_t slotsPerBucket);
+        std::function<Table::BucketClearer(Metadata*)> bucketClearer,
+        std::size_t slotsPerBucket);
   virtual ~Cache() = default;
 
   // primary functionality; documented in derived classes
-  virtual Finding find(void const* key, uint32_t keySize) = 0;
+  virtual Finding find(void const* key, std::uint32_t keySize) = 0;
   virtual Result insert(CachedValue* value) = 0;
-  virtual Result remove(void const* key, uint32_t keySize) = 0;
-  virtual Result blacklist(void const* key, uint32_t keySize) = 0;
+  virtual Result remove(void const* key, std::uint32_t keySize) = 0;
+  virtual Result blacklist(void const* key, std::uint32_t keySize) = 0;
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Returns the ID for this cache.
   //////////////////////////////////////////////////////////////////////////////
-  uint64_t id() const { return _id; }
+  std::uint64_t id() const { return _id; }
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Returns the total memory usage for this cache in bytes.
   //////////////////////////////////////////////////////////////////////////////
-  uint64_t size() const;
+  std::uint64_t size() const;
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Returns the limit on data memory usage for this cache in bytes.
   //////////////////////////////////////////////////////////////////////////////
-  uint64_t usageLimit() const;
+  std::uint64_t usageLimit() const;
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Returns the current data memory usage for this cache in bytes.
   //////////////////////////////////////////////////////////////////////////////
-  uint64_t usage() const;
+  std::uint64_t usage() const;
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Gives hint to attempt to preallocate space for an incoming load.
@@ -109,7 +113,7 @@ class Cache : public std::enable_shared_from_this<Cache> {
   /// The parameter specifies an expected number of elements to be inserted.
   /// This allows for migration to an appropriately-sized table.
   //////////////////////////////////////////////////////////////////////////////
-  void sizeHint(uint64_t numElements);
+  void sizeHint(std::uint64_t numElements);
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Returns the cache hit-rates.
@@ -142,15 +146,14 @@ class Cache : public std::enable_shared_from_this<Cache> {
   inline bool isShutdown() const { return _shutdown.load(); }
 
  protected:
-  static constexpr uint64_t triesFast = 200;
-  static constexpr uint64_t triesSlow = 10000;
-  static constexpr uint64_t triesGuarantee = UINT64_MAX;
+  static constexpr std::uint64_t triesFast = 200;
+  static constexpr std::uint64_t triesSlow = 10000;
 
  protected:
   basics::ReadWriteSpinLock _taskLock;
   std::atomic<bool> _shutdown;
 
-  static uint64_t _findStatsCapacity;
+  static std::uint64_t _findStatsCapacity;
   bool _enableWindowedStats;
   std::unique_ptr<StatBuffer> _findStats;
   mutable basics::SharedCounter<64> _findHits;
@@ -158,7 +161,7 @@ class Cache : public std::enable_shared_from_this<Cache> {
 
   // allow communication with manager
   Manager* _manager;
-  uint64_t _id;
+  std::uint64_t _id;
   Metadata _metadata;
 
   // manage the actual table
@@ -167,12 +170,12 @@ class Cache : public std::enable_shared_from_this<Cache> {
   std::atomic<Table*> _table;
 
   Table::BucketClearer _bucketClearer;
-  size_t _slotsPerBucket;
+  std::size_t _slotsPerBucket;
 
   // manage eviction rate
   basics::SharedCounter<64> _insertsTotal;
   basics::SharedCounter<64> _insertEvictions;
-  static constexpr uint64_t _evictionMask = 4095;  // check roughly every 4096 insertions
+  static constexpr std::uint64_t _evictionMask = 4095;  // check roughly every 4096 insertions
   static constexpr double _evictionRateThreshold = 0.01;  // if more than 1%
                                                           // evictions in past 4096
                                                           // inserts, migrate
@@ -191,18 +194,18 @@ class Cache : public std::enable_shared_from_this<Cache> {
   static void destroy(std::shared_ptr<Cache> const& cache);
 
   void requestGrow();
-  void requestMigrate(uint32_t requestedLogSize = 0);
+  void requestMigrate(std::uint32_t requestedLogSize = 0);
 
   static void freeValue(CachedValue* value);
-  bool reclaimMemory(uint64_t size);
+  bool reclaimMemory(std::uint64_t size);
 
-  uint32_t hashKey(void const* key, size_t keySize) const;
+  std::uint32_t hashKey(void const* key, std::size_t keySize) const;
   void recordStat(Stat stat);
 
   bool reportInsert(bool hadEviction);
 
   // management
-  Metadata* metadata();
+  Metadata& metadata();
   std::shared_ptr<Table> table() const;
   void shutdown();
   bool canResize();
@@ -210,7 +213,7 @@ class Cache : public std::enable_shared_from_this<Cache> {
   bool freeMemory();
   bool migrate(std::shared_ptr<Table> newTable);
 
-  virtual uint64_t freeMemoryFrom(uint32_t hash) = 0;
+  virtual std::uint64_t freeMemoryFrom(std::uint32_t hash) = 0;
   virtual void migrateBucket(void* sourcePtr, std::unique_ptr<Table::Subtable> targets,
                              std::shared_ptr<Table> newTable) = 0;
 };
diff --git a/arangod/Cache/CacheManagerFeature.cpp b/arangod/Cache/CacheManagerFeature.cpp
index 6f30b27d3f09..1cdf2237e338 100644
--- a/arangod/Cache/CacheManagerFeature.cpp
+++ b/arangod/Cache/CacheManagerFeature.cpp
@@ -18,20 +18,16 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Dr. Frank Celler
+/// @author Dan Larkin-York
 ////////////////////////////////////////////////////////////////////////////////
 
 #include "CacheManagerFeature.h"
 
-#ifdef _WIN32
-#include <stdio.h>
-#include <windows.h>
-#endif
-
 #include "ApplicationFeatures/ApplicationServer.h"
 #include "Basics/ArangoGlobalContext.h"
 #include "Basics/PhysicalMemory.h"
 #include "Basics/application-exit.h"
+#include "Basics/operating-system.h"
 #include "Basics/process-utils.h"
 #include "Cache/CacheManagerFeatureThreads.h"
 #include "Cache/Manager.h"
@@ -59,11 +55,12 @@ CacheManagerFeature::CacheManagerFeature(application_features::ApplicationServer
     : ApplicationFeature(server, "CacheManager"),
       _manager(nullptr),
       _rebalancer(nullptr),
-      _cacheSize((PhysicalMemory::getValue() >= (static_cast<uint64_t>(4) << 30))
-                     ? static_cast<uint64_t>(
-                           (PhysicalMemory::getValue() - (static_cast<uint64_t>(2) << 30)) * 0.25)
-                     : (256 << 20)),
-      _rebalancingInterval(static_cast<uint64_t>(2 * 1000 * 1000)) {
+      _cacheSize(
+          (PhysicalMemory::getValue() >= (static_cast<std::uint64_t>(4) << 30))
+              ? static_cast<std::uint64_t>(
+                    (PhysicalMemory::getValue() - (static_cast<std::uint64_t>(2) << 30)) * 0.25)
+              : (256 << 20)),
+      _rebalancingInterval(static_cast<std::uint64_t>(2 * 1000 * 1000)) {
   setOptional(true);
   startsAfter<BasicFeaturePhaseServer>();
 }
diff --git a/arangod/Cache/CacheManagerFeature.h b/arangod/Cache/CacheManagerFeature.h
index d663cb175492..efec88f1aa3c 100644
--- a/arangod/Cache/CacheManagerFeature.h
+++ b/arangod/Cache/CacheManagerFeature.h
@@ -18,14 +18,13 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 ////////////////////////////////////////////////////////////////////////////////
 
 #ifndef ARANGOD_CACHE_CACHE_MANAGER_FEATURE_H
 #define ARANGOD_CACHE_CACHE_MANAGER_FEATURE_H 1
 
 #include "ApplicationFeatures/ApplicationFeature.h"
-
 #include "Cache/CacheManagerFeatureThreads.h"
 #include "Cache/Manager.h"
 
@@ -51,8 +50,8 @@ class CacheManagerFeature final : public application_features::ApplicationFeatur
 
   std::unique_ptr<cache::Manager> _manager;
   std::unique_ptr<CacheRebalancerThread> _rebalancer;
-  uint64_t _cacheSize;
-  uint64_t _rebalancingInterval;
+  std::uint64_t _cacheSize;
+  std::uint64_t _rebalancingInterval;
 };
 
 }  // namespace arangodb
diff --git a/arangod/Cache/CacheManagerFeatureThreads.cpp b/arangod/Cache/CacheManagerFeatureThreads.cpp
index 3a9dbbe475b8..c48c0dffd783 100644
--- a/arangod/Cache/CacheManagerFeatureThreads.cpp
+++ b/arangod/Cache/CacheManagerFeatureThreads.cpp
@@ -18,10 +18,10 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 ////////////////////////////////////////////////////////////////////////////////
 
-#include <stdint.h>
+#include <cstdint>
 
 #include "Basics/ConditionLocker.h"
 #include "Basics/ConditionVariable.h"
@@ -34,7 +34,7 @@
 using namespace arangodb;
 
 CacheRebalancerThread::CacheRebalancerThread(application_features::ApplicationServer& server,
-                                             cache::Manager* manager, uint64_t interval)
+                                             cache::Manager* manager, std::uint64_t interval)
     : Thread(server, "CacheRebalancerThread"),
       _manager(manager),
       _rebalancer(_manager),
@@ -53,7 +53,7 @@ void CacheRebalancerThread::beginShutdown() {
 void CacheRebalancerThread::run() {
   while (!isStopping()) {
     int result = _rebalancer.rebalance();
-    uint64_t interval = (result != TRI_ERROR_ARANGO_BUSY) ? _fullInterval : _shortInterval;
+    std::uint64_t interval = (result != TRI_ERROR_ARANGO_BUSY) ? _fullInterval : _shortInterval;
 
     CONDITION_LOCKER(guard, _condition);
     guard.wait(interval);
diff --git a/arangod/Cache/CacheManagerFeatureThreads.h b/arangod/Cache/CacheManagerFeatureThreads.h
index 6963282e36c9..dbf29f10b7a9 100644
--- a/arangod/Cache/CacheManagerFeatureThreads.h
+++ b/arangod/Cache/CacheManagerFeatureThreads.h
@@ -18,20 +18,19 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 ////////////////////////////////////////////////////////////////////////////////
 
 #ifndef ARANGODB_CACHE_MANAGER_FEATURE_THREADS_H
 #define ARANGODB_CACHE_MANAGER_FEATURE_THREADS_H
 
-#include "Basics/Common.h"
+#include <cstdint>
+
 #include "Basics/ConditionVariable.h"
 #include "Basics/Thread.h"
 #include "Cache/Manager.h"
 #include "Cache/Rebalancer.h"
 
-#include <stdint.h>
-
 namespace arangodb {
 namespace application_features {
 class ApplicationServer;
@@ -40,7 +39,7 @@ class ApplicationServer;
 class CacheRebalancerThread final : public Thread {
  public:
   CacheRebalancerThread(application_features::ApplicationServer& server,
-                        cache::Manager* manager, uint64_t interval);
+                        cache::Manager* manager, std::uint64_t interval);
   ~CacheRebalancerThread();
 
   void beginShutdown() override;
@@ -51,8 +50,8 @@ class CacheRebalancerThread final : public Thread {
  private:
   cache::Manager* _manager;
   cache::Rebalancer _rebalancer;
-  uint64_t _fullInterval;
-  uint64_t _shortInterval;
+  std::uint64_t _fullInterval;
+  std::uint64_t _shortInterval;
   basics::ConditionVariable _condition;
 };
 
diff --git a/arangod/Cache/CachedValue.cpp b/arangod/Cache/CachedValue.cpp
index 4c290ff96f42..308ae0660b5d 100644
--- a/arangod/Cache/CachedValue.cpp
+++ b/arangod/Cache/CachedValue.cpp
@@ -18,22 +18,22 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 ////////////////////////////////////////////////////////////////////////////////
 
-#include "Cache/CachedValue.h"
-
-#include <stdint.h>
+#include <cstdint>
 #include <cstring>
 
+#include "Cache/CachedValue.h"
+
 #include "Basics/debugging.h"
 
-using namespace arangodb::cache;
+namespace arangodb::cache {
 
-const size_t CachedValue::_headerAllocSize = sizeof(CachedValue) + CachedValue::_padding;
+const std::size_t CachedValue::_headerAllocSize = sizeof(CachedValue) + CachedValue::_padding;
 
 CachedValue* CachedValue::copy() const {
-  uint8_t* buf = new uint8_t[size()];
+  std::uint8_t* buf = new std::uint8_t[size()];
   CachedValue* value = nullptr;
   try {
     value = new (buf + offset()) CachedValue(*this);
@@ -45,39 +45,42 @@ CachedValue* CachedValue::copy() const {
   return value;
 }
 
-CachedValue* CachedValue::construct(void const* k, size_t kSize, void const* v, size_t vSize) {
+CachedValue* CachedValue::construct(void const* k, std::size_t kSize,
+                                    void const* v, std::size_t vSize) {
   if (kSize == 0 || k == nullptr || (vSize > 0 && v == nullptr) ||
       kSize > maxKeySize || vSize > maxValueSize) {
     return nullptr;
   }
 
-  uint8_t* buf = new uint8_t[_headerAllocSize + kSize + vSize];
-  uint8_t* aligned = reinterpret_cast<uint8_t*>(
-      (reinterpret_cast<size_t>(buf) + _headerAllocOffset) & _headerAllocMask);
-  size_t offset = buf - aligned;
+  std::uint8_t* buf = new std::uint8_t[_headerAllocSize + kSize + vSize];
+  std::uint8_t* aligned = reinterpret_cast<std::uint8_t*>(
+      (reinterpret_cast<std::size_t>(buf) + _headerAllocOffset) & _headerAllocMask);
+  std::size_t offset = buf - aligned;
   // ctor of CachedValue is noexcept
   return new (aligned) CachedValue(offset, k, kSize, v, vSize);
 }
 
 void CachedValue::operator delete(void* ptr) {
   CachedValue* cv = reinterpret_cast<CachedValue*>(ptr);
-  size_t offset = cv->offset();
+  std::size_t offset = cv->offset();
   cv->~CachedValue();
-  delete[](reinterpret_cast<uint8_t*>(ptr) - offset);
+  delete[](reinterpret_cast<std::uint8_t*>(ptr) - offset);
 }
 
-CachedValue::CachedValue(size_t off, void const* k, size_t kSize, void const* v,
-                         size_t vSize) noexcept
+CachedValue::CachedValue(std::size_t off, void const* k, std::size_t kSize,
+                         void const* v, std::size_t vSize) noexcept
     : _refCount(0),
-      _keySize(static_cast<uint32_t>(kSize + (off << _offsetShift))),
-      _valueSize(static_cast<uint32_t>(vSize)) {
-  std::memcpy(const_cast<uint8_t*>(key()), k, kSize);
+      _keySize(static_cast<std::uint32_t>(kSize + (off << _offsetShift))),
+      _valueSize(static_cast<std::uint32_t>(vSize)) {
+  std::memcpy(const_cast<std::uint8_t*>(key()), k, kSize);
   if (vSize > 0) {
-    std::memcpy(const_cast<uint8_t*>(value()), v, vSize);
+    std::memcpy(const_cast<std::uint8_t*>(value()), v, vSize);
   }
 }
 
 CachedValue::CachedValue(CachedValue const& other) noexcept
     : _refCount(0), _keySize(other._keySize), _valueSize(other._valueSize) {
-  std::memcpy(const_cast<uint8_t*>(key()), other.key(), keySize() + valueSize());
+  std::memcpy(const_cast<std::uint8_t*>(key()), other.key(), keySize() + valueSize());
 }
+
+}  // namespace arangodb::cache
\ No newline at end of file
diff --git a/arangod/Cache/CachedValue.h b/arangod/Cache/CachedValue.h
index dfb8fb571c1c..6365f9783a17 100644
--- a/arangod/Cache/CachedValue.h
+++ b/arangod/Cache/CachedValue.h
@@ -18,16 +18,14 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 ////////////////////////////////////////////////////////////////////////////////
 
 #ifndef ARANGODB_CACHE_CACHED_VALUE_H
 #define ARANGODB_CACHE_CACHED_VALUE_H
 
-#include "Basics/Common.h"
-
-#include <stdint.h>
 #include <atomic>
+#include <cstdint>
 #include <cstring>
 
 namespace arangodb {
@@ -43,56 +41,56 @@ namespace cache {
 ////////////////////////////////////////////////////////////////////////////////
 struct CachedValue {
   // key size must fit in 3 bytes
-  static constexpr size_t maxKeySize = 0x00FFFFFFULL;
+  static constexpr std::size_t maxKeySize = 0x00FFFFFFULL;
   // value size must fit in 4 bytes
-  static constexpr size_t maxValueSize = 0xFFFFFFFFULL;
+  static constexpr std::size_t maxValueSize = 0xFFFFFFFFULL;
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Reference count (to avoid premature deletion)
   //////////////////////////////////////////////////////////////////////////////
-  inline uint32_t refCount() const noexcept { return _refCount.load(); }
+  inline std::uint32_t refCount() const noexcept { return _refCount.load(); }
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Size of the key in bytes
   //////////////////////////////////////////////////////////////////////////////
-  inline size_t keySize() const noexcept {
-    return static_cast<size_t>(_keySize & _keyMask);
+  inline std::size_t keySize() const noexcept {
+    return static_cast<std::size_t>(_keySize & _keyMask);
   }
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Size of the value in bytes
   //////////////////////////////////////////////////////////////////////////////
-  inline size_t valueSize() const noexcept {
-    return static_cast<size_t>(_valueSize);
+  inline std::size_t valueSize() const noexcept {
+    return static_cast<std::size_t>(_valueSize);
   }
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Returns a pointer offset to the key
   //////////////////////////////////////////////////////////////////////////////
-  inline uint8_t const* key() const noexcept {
-    return (reinterpret_cast<uint8_t const*>(this) + sizeof(CachedValue));
+  inline std::uint8_t const* key() const noexcept {
+    return (reinterpret_cast<std::uint8_t const*>(this) + sizeof(CachedValue));
   }
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Returns a pointer offset to the value
   //////////////////////////////////////////////////////////////////////////////
-  inline uint8_t const* value() const noexcept {
+  inline std::uint8_t const* value() const noexcept {
     return (_valueSize == 0) ? nullptr
-                             : reinterpret_cast<uint8_t const*>(this) +
+                             : reinterpret_cast<std::uint8_t const*>(this) +
                                    sizeof(CachedValue) + keySize();
   }
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Returns the allocated size of bytes including the key and value
   //////////////////////////////////////////////////////////////////////////////
-  inline size_t size() const noexcept {
+  inline std::size_t size() const noexcept {
     return _headerAllocSize + keySize() + valueSize();
   }
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Utility method to compare underlying key to external key
   //////////////////////////////////////////////////////////////////////////////
-  inline bool sameKey(void const* k, size_t kSize) const noexcept {
+  inline bool sameKey(void const* k, std::size_t kSize) const noexcept {
     return (keySize() == kSize) && (0 == memcmp(key(), k, kSize));
   }
 
@@ -119,7 +117,8 @@ struct CachedValue {
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Construct a CachedValue object from a given key and value
   //////////////////////////////////////////////////////////////////////////////
-  static CachedValue* construct(void const* k, size_t kSize, void const* v, size_t vSize);
+  static CachedValue* construct(void const* k, std::size_t kSize, void const* v,
+                                std::size_t vSize);
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Custom deleter to handle casting issues
@@ -127,23 +126,24 @@ struct CachedValue {
   static void operator delete(void* ptr);
 
  private:
-  static constexpr size_t _padding = alignof(std::atomic<uint32_t>) - 1;
-  static const size_t _headerAllocSize;
-  static constexpr size_t _headerAllocMask = ~_padding;
-  static constexpr size_t _headerAllocOffset = _padding;
-  static constexpr uint32_t _keyMask = 0x00FFFFFF;
-  static constexpr uint32_t _offsetMask = 0xFF000000;
-  static constexpr size_t _offsetShift = 24;
-
-  std::atomic<uint32_t> _refCount;
-  uint32_t _keySize;
-  uint32_t _valueSize;
+  static constexpr std::size_t _padding = alignof(std::atomic<std::uint32_t>) - 1;
+  static const std::size_t _headerAllocSize;
+  static constexpr std::size_t _headerAllocMask = ~_padding;
+  static constexpr std::size_t _headerAllocOffset = _padding;
+  static constexpr std::uint32_t _keyMask = 0x00FFFFFF;
+  static constexpr std::uint32_t _offsetMask = 0xFF000000;
+  static constexpr std::size_t _offsetShift = 24;
+
+  std::atomic<std::uint32_t> _refCount;
+  std::uint32_t _keySize;
+  std::uint32_t _valueSize;
 
  private:
-  CachedValue(size_t off, void const* k, size_t kSize, void const* v, size_t vSize) noexcept;
+  CachedValue(std::size_t off, void const* k, std::size_t kSize, void const* v,
+              std::size_t vSize) noexcept;
   CachedValue(CachedValue const& other) noexcept;
 
-  inline size_t offset() const {
+  inline std::size_t offset() const {
     return ((_keySize & _offsetMask) >> _offsetShift);
   }
 };
diff --git a/arangod/Cache/Common.h b/arangod/Cache/Common.h
index abab46614ed9..4b7f03b69e83 100644
--- a/arangod/Cache/Common.h
+++ b/arangod/Cache/Common.h
@@ -18,7 +18,7 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 ////////////////////////////////////////////////////////////////////////////////
 
 #ifndef ARANGODB_CACHE_COMMON_H
@@ -27,15 +27,13 @@
 #include <cstdint>
 #include <cstdlib>
 
-#include "Basics/Common.h"
-
 namespace arangodb {
 namespace cache {
 
 ////////////////////////////////////////////////////////////////////////////////
 /// @brief Common size for all bucket types.
 ////////////////////////////////////////////////////////////////////////////////
-constexpr size_t BUCKET_SIZE = 128;
+constexpr std::size_t BUCKET_SIZE = 128;
 
 ////////////////////////////////////////////////////////////////////////////////
 /// @brief Enum to specify cache types.
@@ -45,7 +43,7 @@ enum CacheType { Plain, Transactional };
 ////////////////////////////////////////////////////////////////////////////////
 /// @brief Enum to allow easy statistic recording across classes.
 ////////////////////////////////////////////////////////////////////////////////
-enum class Stat : uint8_t { findHit = 1, findMiss = 2 };
+enum class Stat : std::uint8_t { findHit = 1, findMiss = 2 };
 
 };  // end namespace cache
 };  // end namespace arangodb
diff --git a/arangod/Cache/Finding.cpp b/arangod/Cache/Finding.cpp
index 6fd543a02637..60d37218f00d 100644
--- a/arangod/Cache/Finding.cpp
+++ b/arangod/Cache/Finding.cpp
@@ -18,7 +18,7 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 ////////////////////////////////////////////////////////////////////////////////
 
 #include "Cache/Finding.h"
@@ -27,8 +27,7 @@
 #include "Basics/voc-errors.h"
 #include "Cache/CachedValue.h"
 
-using namespace arangodb;
-using namespace arangodb::cache;
+namespace arangodb::cache {
 
 Finding::Finding() : _value(nullptr), _result(TRI_ERROR_NO_ERROR) {}
 
@@ -110,3 +109,5 @@ CachedValue* Finding::copy() const {
 }
 
 Result const& Finding::result() const { return _result; }
+
+}  // namespace arangodb::cache
diff --git a/arangod/Cache/Finding.h b/arangod/Cache/Finding.h
index d7c4da367cb2..e41acb1a2e66 100644
--- a/arangod/Cache/Finding.h
+++ b/arangod/Cache/Finding.h
@@ -18,13 +18,12 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 ////////////////////////////////////////////////////////////////////////////////
 
 #ifndef ARANGODB_CACHE_FINDING_H
 #define ARANGODB_CACHE_FINDING_H
 
-#include "Basics/Common.h"
 #include "Basics/Result.h"
 #include "Cache/CachedValue.h"
 
diff --git a/arangod/Cache/FrequencyBuffer.h b/arangod/Cache/FrequencyBuffer.h
index 6edc7ae8cc6a..32cd31048a1a 100644
--- a/arangod/Cache/FrequencyBuffer.h
+++ b/arangod/Cache/FrequencyBuffer.h
@@ -18,23 +18,22 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 ////////////////////////////////////////////////////////////////////////////////
 
 #ifndef ARANGODB_CACHE_FREQUENCY_BUFFER_H
 #define ARANGODB_CACHE_FREQUENCY_BUFFER_H
 
-#include "Basics/Common.h"
-#include "Basics/SharedPRNG.h"
-
-#include <stdint.h>
 #include <algorithm>
 #include <atomic>
+#include <cstdint>
 #include <memory>
 #include <unordered_map>
 #include <utility>
 #include <vector>
 
+#include "Basics/SharedPRNG.h"
+
 namespace arangodb {
 namespace cache {
 
@@ -54,17 +53,17 @@ class FrequencyBuffer {
   static_assert(sizeof(std::atomic<T>) == sizeof(T), "");
 
  private:
-  size_t _capacity;
-  size_t _mask;
+  std::size_t _capacity;
+  std::size_t _mask;
   std::vector<std::atomic<T>> _buffer;
   Comparator _cmp;
   T _empty;
 
  private:
-  static size_t powerOf2(size_t capacity) {
+  static std::size_t powerOf2(std::size_t capacity) {
     // TODO maybe use
     // https://graphics.stanford.edu/~seander/bithacks.html#RoundUpPowerOf2
-    size_t i = 0;
+    std::size_t i = 0;
     for (; (static_cast<size_t>(1) << i) < capacity; i++) {
     }
     return (static_cast<size_t>(1) << i);
@@ -74,7 +73,7 @@ class FrequencyBuffer {
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Initialize with the given capacity.
   //////////////////////////////////////////////////////////////////////////////
-  explicit FrequencyBuffer(size_t capacity)
+  explicit FrequencyBuffer(std::size_t capacity)
       : _capacity(powerOf2(capacity)),
         _mask(_capacity - 1),
         _buffer(_capacity),
@@ -87,12 +86,14 @@ class FrequencyBuffer {
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Reports the hidden allocation size (not captured by sizeof).
   //////////////////////////////////////////////////////////////////////////////
-  static size_t allocationSize(size_t capacity) { return capacity * sizeof(T); }
+  static std::size_t allocationSize(std::size_t capacity) {
+    return capacity * sizeof(T);
+  }
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Reports the memory usage in bytes.
   //////////////////////////////////////////////////////////////////////////////
-  size_t memoryUsage() const {
+  std::size_t memoryUsage() const {
     return ((_capacity * sizeof(T)) + sizeof(FrequencyBuffer<T>));
   }
 
@@ -108,7 +109,7 @@ class FrequencyBuffer {
   /// @brief Remove all occurrences of the specified event record.
   //////////////////////////////////////////////////////////////////////////////
   void purgeRecord(T record) {
-    for (size_t i = 0; i < _capacity; i++) {
+    for (std::size_t i = 0; i < _capacity; i++) {
       auto tmp = _buffer[i].load(std::memory_order_relaxed);
       if (_cmp(tmp, record)) {
         _buffer[i].compare_exchange_strong(tmp, _empty, std::memory_order_relaxed);
@@ -122,8 +123,8 @@ class FrequencyBuffer {
   //////////////////////////////////////////////////////////////////////////////
   typename FrequencyBuffer::stats_t getFrequencies() const {
     // calculate frequencies
-    std::unordered_map<T, uint64_t, Hasher, Comparator> frequencies;
-    for (size_t i = 0; i < _capacity; i++) {
+    std::unordered_map<T, std::size_t, Hasher, Comparator> frequencies;
+    for (std::size_t i = 0; i < _capacity; i++) {
       T const entry = _buffer[i].load(std::memory_order_relaxed);
       if (!_cmp(entry, _empty)) {
         frequencies[entry]++;
@@ -134,10 +135,10 @@ class FrequencyBuffer {
     stats_t data;
     data.reserve(frequencies.size());
     for (auto f : frequencies) {
-      data.emplace_back(std::pair<T, uint64_t>(f.first, f.second));
+      data.emplace_back(std::pair<T, std::size_t>(f.first, f.second));
     }
     std::sort(data.begin(), data.end(),
-              [](std::pair<T, uint64_t> const& left, std::pair<T, uint64_t> const& right) {
+              [](std::pair<T, std::uint64_t> const& left, std::pair<T, std::size_t> const& right) {
                 return left.second < right.second;
               });
 
@@ -148,7 +149,7 @@ class FrequencyBuffer {
   /// @brief Clear the buffer, removing all event records.
   //////////////////////////////////////////////////////////////////////////////
   void clear() {
-    for (size_t i = 0; i < _capacity; i++) {
+    for (std::size_t i = 0; i < _capacity; i++) {
       _buffer[i].store(T(), std::memory_order_relaxed);
     }
   }
diff --git a/arangod/Cache/Manager.cpp b/arangod/Cache/Manager.cpp
index 7c6f53a49418..75f151afa5a1 100644
--- a/arangod/Cache/Manager.cpp
+++ b/arangod/Cache/Manager.cpp
@@ -18,7 +18,7 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 ////////////////////////////////////////////////////////////////////////////////
 
 #include <algorithm>
@@ -33,6 +33,8 @@
 #include "Cache/Manager.h"
 
 #include "Basics/SharedPRNG.h"
+#include "Basics/SpinLocker.h"
+#include "Basics/SpinUnlocker.h"
 #include "Basics/voc-errors.h"
 #include "Cache/Cache.h"
 #include "Cache/CachedValue.h"
@@ -48,24 +50,27 @@
 #include "Logger/Logger.h"
 #include "Logger/LoggerStream.h"
 
-using namespace arangodb::cache;
+namespace arangodb::cache {
 
-const uint64_t Manager::minSize = 1024 * 1024;
-const uint64_t Manager::minCacheAllocation =
+using SpinLocker = ::arangodb::basics::SpinLocker;
+using SpinUnlocker = ::arangodb::basics::SpinUnlocker;
+
+const std::uint64_t Manager::minSize = 1024 * 1024;
+const std::uint64_t Manager::minCacheAllocation =
     Cache::minSize + Table::allocationSize(Table::minLogSize) +
     std::max(PlainCache::allocationSize(true), TransactionalCache::allocationSize(true)) +
     Manager::cacheRecordOverhead;
 const std::chrono::milliseconds Manager::rebalancingGracePeriod(10);
 
-Manager::Manager(PostFn schedulerPost, uint64_t globalLimit, bool enableWindowedStats)
+Manager::Manager(PostFn schedulerPost, std::uint64_t globalLimit, bool enableWindowedStats)
     : _lock(),
       _shutdown(false),
       _shuttingDown(false),
       _resizing(false),
       _rebalancing(false),
       _accessStats((globalLimit >= (1024 * 1024 * 1024))
-                       ? ((1024 * 1024) / sizeof(uint64_t))
-                       : (globalLimit / (1024 * sizeof(uint64_t)))),
+                       ? ((1024 * 1024) / sizeof(std::uint64_t))
+                       : (globalLimit / (1024 * sizeof(std::uint64_t)))),
       _enableWindowedStats(enableWindowedStats),
       _findStats(nullptr),
       _findHits(),
@@ -74,7 +79,7 @@ Manager::Manager(PostFn schedulerPost, uint64_t globalLimit, bool enableWindowed
       _nextCacheId(1),
       _globalSoftLimit(globalLimit),
       _globalHardLimit(globalLimit),
-      _globalHighwaterMark(static_cast<uint64_t>(
+      _globalHighwaterMark(static_cast<std::uint64_t>(
           Manager::highwaterMultiplier * static_cast<double>(_globalSoftLimit))),
       _fixedAllocation(sizeof(Manager) + Manager::tableListsOverhead +
                        _accessStats.memoryUsage()),
@@ -110,47 +115,48 @@ Manager::~Manager() {
 }
 
 std::shared_ptr<Cache> Manager::createCache(CacheType type, bool enableWindowedStats,
-                                            uint64_t maxSize) {
-  std::shared_ptr<Cache> result(nullptr);
-  _lock.writeLock();
-  bool allowed = isOperational();
-  Metadata metadata;
-  std::shared_ptr<Table> table(nullptr);
-  uint64_t id = _nextCacheId++;
-
-  if (allowed) {
-    uint64_t fixedSize = 0;
-    switch (type) {
-      case CacheType::Plain:
-        fixedSize = PlainCache::allocationSize(enableWindowedStats);
-        break;
-      case CacheType::Transactional:
-        fixedSize = TransactionalCache::allocationSize(enableWindowedStats);
-        break;
-      default:
-        break;
+                                            std::uint64_t maxSize) {
+  std::shared_ptr<Cache> result;
+  {
+    SpinLocker guard(SpinLocker::Mode::Write, _lock);
+    bool allowed = isOperational();
+    Metadata metadata;
+    std::shared_ptr<Table> table;
+    std::uint64_t id = _nextCacheId++;
+
+    if (allowed) {
+      std::uint64_t fixedSize = 0;
+      switch (type) {
+        case CacheType::Plain:
+          fixedSize = PlainCache::allocationSize(enableWindowedStats);
+          break;
+        case CacheType::Transactional:
+          fixedSize = TransactionalCache::allocationSize(enableWindowedStats);
+          break;
+        default:
+          break;
+      }
+      std::tie(allowed, metadata, table) = registerCache(fixedSize, maxSize);
     }
-    std::tie(allowed, metadata, table) = registerCache(fixedSize, maxSize);
-  }
 
-  if (allowed) {
-    switch (type) {
-      case CacheType::Plain:
-        result = PlainCache::create(this, id, std::move(metadata), table, enableWindowedStats);
-        break;
-      case CacheType::Transactional:
-        result = TransactionalCache::create(this, id, std::move(metadata),
-                                            table, enableWindowedStats);
-        break;
-      default:
-        break;
+    if (allowed) {
+      switch (type) {
+        case CacheType::Plain:
+          result = PlainCache::create(this, id, std::move(metadata), table, enableWindowedStats);
+          break;
+        case CacheType::Transactional:
+          result = TransactionalCache::create(this, id, std::move(metadata),
+                                              table, enableWindowedStats);
+          break;
+        default:
+          break;
+      }
     }
-  }
 
-  if (result.get() != nullptr) {
-    _caches.try_emplace(id, result);
+    if (result.get() != nullptr) {
+      _caches.try_emplace(id, result);
+    }
   }
-  _lock.writeUnlock();
 
   return result;
 }
@@ -160,40 +166,39 @@ void Manager::destroyCache(std::shared_ptr<Cache> const& cache) {
 }
 
 void Manager::beginShutdown() {
-  _lock.writeLock();
+  SpinLocker guard(SpinLocker::Mode::Write, _lock);
+
   if (!_shutdown) {
     _shuttingDown = true;
   }
-  _lock.writeUnlock();
 }
 
 void Manager::shutdown() {
-  _lock.writeLock();
+  SpinLocker guard(SpinLocker::Mode::Write, _lock);
+
   if (!_shutdown) {
     if (!_shuttingDown) {
       _shuttingDown = true;
     }
     while (!_caches.empty()) {
       std::shared_ptr<Cache> cache = _caches.begin()->second;
-      _lock.writeUnlock();
+      SpinUnlocker unguard(SpinUnlocker::Mode::Write, _lock);
       cache->shutdown();
-      _lock.writeLock();
     }
     freeUnusedTables();
     _shutdown = true;
   }
-  _lock.writeUnlock();
 }
 
 // change global cache limit
-bool Manager::resize(uint64_t newGlobalLimit) {
-  _lock.writeLock();
+bool Manager::resize(std::uint64_t newGlobalLimit) {
+  SpinLocker guard(SpinLocker::Mode::Write, _lock);
+
   if ((newGlobalLimit < Manager::minSize) ||
-      (static_cast<uint64_t>(0.5 * (1.0 - Manager::highwaterMultiplier) *
-                             static_cast<double>(newGlobalLimit)) < _fixedAllocation) ||
-      (static_cast<uint64_t>(Manager::highwaterMultiplier * static_cast<double>(newGlobalLimit)) <
+      (static_cast<std::uint64_t>(0.5 * (1.0 - Manager::highwaterMultiplier) *
+                                  static_cast<double>(newGlobalLimit)) < _fixedAllocation) ||
+      (static_cast<std::uint64_t>(Manager::highwaterMultiplier * static_cast<double>(newGlobalLimit)) <
        (_caches.size() * Manager::minCacheAllocation))) {
-    _lock.writeUnlock();
     return false;
   }
 
@@ -207,7 +212,7 @@ bool Manager::resize(uint64_t newGlobalLimit) {
       // otherwise we need to actually resize
       _resizing = true;
       _globalSoftLimit = newGlobalLimit;
-      _globalHighwaterMark = static_cast<uint64_t>(
+      _globalHighwaterMark = static_cast<std::uint64_t>(
           Manager::highwaterMultiplier * static_cast<double>(_globalSoftLimit));
       freeUnusedTables();
       done = adjustGlobalLimitsIfAllowed(newGlobalLimit);
@@ -218,32 +223,25 @@ bool Manager::resize(uint64_t newGlobalLimit) {
     }
   }
 
-  _lock.writeUnlock();
   return success;
 }
 
-uint64_t Manager::globalLimit() {
-  _lock.readLock();
-  uint64_t limit = _resizing ? _globalSoftLimit : _globalHardLimit;
-  _lock.readUnlock();
-
-  return limit;
+std::uint64_t Manager::globalLimit() {
+  SpinLocker guard(SpinLocker::Mode::Read, _lock);
+  return _resizing ? _globalSoftLimit : _globalHardLimit;
 }
 
-uint64_t Manager::globalAllocation() {
-  _lock.readLock();
-  uint64_t allocation = _globalAllocation;
-  _lock.readUnlock();
-
-  return allocation;
+std::uint64_t Manager::globalAllocation() {
+  SpinLocker guard(SpinLocker::Mode::Read, _lock);
+  return _globalAllocation;
 }
 
 std::pair<double, double> Manager::globalHitRates() {
   double lifetimeRate = std::nan("");
   double windowedRate = std::nan("");
 
-  uint64_t currentHits = _findHits.value(std::memory_order_relaxed);
-  uint64_t currentMisses = _findMisses.value(std::memory_order_relaxed);
+  std::uint64_t currentHits = _findHits.value(std::memory_order_relaxed);
+  std::uint64_t currentMisses = _findMisses.value(std::memory_order_relaxed);
   if (currentHits + currentMisses > 0) {
     lifetimeRate = 100.0 * (static_cast<double>(currentHits) /
                             static_cast<double>(currentHits + currentMisses));
@@ -252,13 +250,13 @@ std::pair<double, double> Manager::globalHitRates() {
   if (_enableWindowedStats && _findStats.get() != nullptr) {
     auto stats = _findStats->getFrequencies();
     if (stats.size() == 1) {
-      if (stats[0].first == static_cast<uint8_t>(Stat::findHit)) {
+      if (stats[0].first == static_cast<std::uint8_t>(Stat::findHit)) {
         windowedRate = 100.0;
       } else {
         windowedRate = 0.0;
       }
     } else if (stats.size() == 2) {
-      if (stats[0].first == static_cast<uint8_t>(Stat::findHit)) {
+      if (stats[0].first == static_cast<std::uint8_t>(Stat::findHit)) {
         currentHits = stats[0].second;
         currentMisses = stats[1].second;
       } else {
@@ -285,9 +283,9 @@ void Manager::endTransaction(Transaction* tx) noexcept {
 
 bool Manager::post(std::function<void()> fn) { return _schedulerPost(fn); }
 
-std::tuple<bool, Metadata, std::shared_ptr<Table>> Manager::registerCache(uint64_t fixedSize,
-                                                                          uint64_t maxSize) {
-  TRI_ASSERT(_lock.isWriteLocked());
+std::tuple<bool, Metadata, std::shared_ptr<Table>> Manager::registerCache(std::uint64_t fixedSize,
+                                                                          std::uint64_t maxSize) {
+  TRI_ASSERT(_lock.isLockedWrite());
   Metadata metadata;
   std::shared_ptr<Table> table;
   bool ok = true;
@@ -318,43 +316,42 @@ std::tuple<bool, Metadata, std::shared_ptr<Table>> Manager::registerCache(uint64
   return std::make_tuple(ok, std::move(metadata), std::move(table));
 }
 
-void Manager::unregisterCache(uint64_t id) {
-  _lock.writeLock();
+void Manager::unregisterCache(std::uint64_t id) {
+  SpinLocker guard(SpinLocker::Mode::Write, _lock);
   _accessStats.purgeRecord(id);
   auto it = _caches.find(id);
   if (it == _caches.end()) {
-    _lock.writeUnlock();
     return;
   }
   std::shared_ptr<Cache>& cache = it->second;
-  Metadata* metadata = cache->metadata();
-  metadata->readLock();
-  _globalAllocation -= metadata->allocatedSize;
-  TRI_ASSERT(_globalAllocation >= _fixedAllocation);
-  metadata->readUnlock();
+  Metadata& metadata = cache->metadata();
+  {
+    SpinLocker metaGuard(SpinLocker::Mode::Read, metadata.lock());
+    _globalAllocation -= metadata.allocatedSize;
+    TRI_ASSERT(_globalAllocation >= _fixedAllocation);
+  }
   _caches.erase(id);
-  _lock.writeUnlock();
 }
 
 std::pair<bool, Manager::time_point> Manager::requestGrow(Cache* cache) {
   Manager::time_point nextRequest = futureTime(100);
   bool allowed = false;
 
-  bool ok = _lock.writeLock(Manager::triesSlow);
-  if (ok) {
+  SpinLocker guard(SpinLocker::Mode::Write, _lock,
+                   static_cast<std::size_t>(Manager::triesSlow));
+  if (guard.isLocked()) {
     if (isOperational() && !globalProcessRunning()) {
-      Metadata* metadata = cache->metadata();
-      metadata->writeLock();
+      Metadata& metadata = cache->metadata();
+      SpinLocker metaGuard(SpinLocker::Mode::Write, metadata.lock());
 
-      allowed = !metadata->isResizing() && !metadata->isMigrating();
+      allowed = !metadata.isResizing() && !metadata.isMigrating();
       if (allowed) {
-        if (metadata->allocatedSize >= metadata->deservedSize &&
-            pastRebalancingGracePeriod()) {
-          uint64_t increase = std::min(metadata->hardUsageLimit / 2,
-                                       metadata->maxSize - metadata->allocatedSize);
+        if (metadata.allocatedSize >= metadata.deservedSize && pastRebalancingGracePeriod()) {
+          std::uint64_t increase = std::min(metadata.hardUsageLimit / 2,
+                                            metadata.maxSize - metadata.allocatedSize);
           if (increase > 0 && increaseAllowed(increase)) {
-            uint64_t newLimit = metadata->allocatedSize + increase;
-            metadata->adjustDeserved(newLimit);
+            std::uint64_t newLimit = metadata.allocatedSize + increase;
+            metadata.adjustDeserved(newLimit);
           } else {
             allowed = false;
           }
@@ -362,40 +359,37 @@ std::pair<bool, Manager::time_point> Manager::requestGrow(Cache* cache) {
 
         if (allowed) {
           nextRequest = std::chrono::steady_clock::now();
-          resizeCache(TaskEnvironment::none, cache,
-                      metadata->newLimit());  // unlocks metadata
+          resizeCache(TaskEnvironment::none, std::move(metaGuard), cache,
+                      metadata.newLimit());  // unlocks metadata
         }
       }
-
-      if (!allowed) {
-        metadata->writeUnlock();
-      }
     }
-    _lock.writeUnlock();
   }
 
   return std::make_pair(allowed, nextRequest);
 }
 
-std::pair<bool, Manager::time_point> Manager::requestMigrate(Cache* cache, uint32_t requestedLogSize) {
+std::pair<bool, Manager::time_point> Manager::requestMigrate(Cache* cache, std::uint32_t requestedLogSize) {
   Manager::time_point nextRequest = futureTime(100);
   bool allowed = false;
 
-  bool ok = _lock.writeLock(Manager::triesSlow);
-  if (ok) {
+  SpinLocker guard(SpinLocker::Mode::Write, _lock,
+                   static_cast<std::size_t>(Manager::triesSlow));
+  if (guard.isLocked()) {
     if (isOperational() && !globalProcessRunning()) {
-      Metadata* metadata = cache->metadata();
-      metadata->writeLock();
+      Metadata& metadata = cache->metadata();
+      SpinLocker metaGuard(SpinLocker::Mode::Write, metadata.lock());
 
-      allowed = !metadata->isMigrating();
+      allowed = !metadata.isMigrating();
       if (allowed) {
-        if (metadata->tableSize < Table::allocationSize(requestedLogSize)) {
-          uint64_t increase = Table::allocationSize(requestedLogSize) - metadata->tableSize;
-          if ((metadata->allocatedSize + increase >= metadata->deservedSize) &&
+        if (metadata.tableSize < Table::allocationSize(requestedLogSize)) {
+          std::uint64_t increase =
+              Table::allocationSize(requestedLogSize) - metadata.tableSize;
+          if ((metadata.allocatedSize + increase >= metadata.deservedSize) &&
               pastRebalancingGracePeriod()) {
             if (increaseAllowed(increase)) {
-              uint64_t newLimit = metadata->allocatedSize + increase;
-              uint64_t granted = metadata->adjustDeserved(newLimit);
+              std::uint64_t newLimit = metadata.allocatedSize + increase;
+              std::uint64_t granted = metadata.adjustDeserved(newLimit);
               if (granted < newLimit) {
                 allowed = false;
               }
@@ -408,7 +402,7 @@ std::pair<bool, Manager::time_point> Manager::requestMigrate(Cache* cache, uint3
 
       if (allowed) {
         // first find out if cache is allowed to migrate
-        allowed = metadata->migrationAllowed(Table::allocationSize(requestedLogSize));
+        allowed = metadata.migrationAllowed(Table::allocationSize(requestedLogSize));
       }
       if (allowed) {
         // now find out if we can lease the table
@@ -416,22 +410,16 @@ std::pair<bool, Manager::time_point> Manager::requestMigrate(Cache* cache, uint3
         allowed = (table != nullptr);
         if (allowed) {
           nextRequest = std::chrono::steady_clock::now();
-          migrateCache(TaskEnvironment::none, cache,
-                       table);  // unlocks metadata
+          migrateCache(TaskEnvironment::none, std::move(metaGuard), cache, table);  // unlocks metadata
         }
       }
-
-      if (!allowed) {
-        metadata->writeUnlock();
-      }
     }
-    _lock.writeUnlock();
   }
 
   return std::make_pair(allowed, nextRequest);
 }
 
-void Manager::reportAccess(uint64_t id) {
+void Manager::reportAccess(std::uint64_t id) {
   if ((basics::SharedPRNG::rand() & static_cast<unsigned long>(7)) == 0) {
     _accessStats.insertRecord(id);
   }
@@ -442,14 +430,14 @@ void Manager::reportHitStat(Stat stat) {
     case Stat::findHit: {
       _findHits.add(1, std::memory_order_relaxed);
       if (_enableWindowedStats && _findStats != nullptr) {
-        _findStats->insertRecord(static_cast<uint8_t>(Stat::findHit));
+        _findStats->insertRecord(static_cast<std::uint8_t>(Stat::findHit));
       }
       break;
     }
     case Stat::findMiss: {
       _findMisses.add(1, std::memory_order_relaxed);
       if (_enableWindowedStats && _findStats != nullptr) {
-        _findStats->insertRecord(static_cast<uint8_t>(Stat::findMiss));
+        _findStats->insertRecord(static_cast<std::uint8_t>(Stat::findMiss));
       }
       break;
     }
@@ -487,18 +475,16 @@ void Manager::unprepareTask(Manager::TaskEnvironment environment) {
   switch (environment) {
     case TaskEnvironment::rebalancing: {
       if ((--_rebalancingTasks) == 0) {
-        _lock.writeLock();
+        SpinLocker guard(SpinLocker::Mode::Write, _lock);
         _rebalancing = false;
         _rebalanceCompleted = std::chrono::steady_clock::now();
-        _lock.writeUnlock();
       };
       break;
     }
     case TaskEnvironment::resizing: {
       if ((--_resizingTasks) == 0) {
-        _lock.writeLock();
+        SpinLocker guard(SpinLocker::Mode::Write, _lock);
         _resizing = false;
-        _lock.writeUnlock();
       };
       break;
     }
@@ -510,18 +496,16 @@ void Manager::unprepareTask(Manager::TaskEnvironment environment) {
 }
 
 int Manager::rebalance(bool onlyCalculate) {
+  SpinLocker guard(SpinLocker::Mode::Write, _lock, !onlyCalculate);
+
   if (!onlyCalculate) {
-    _lock.writeLock();
     if (_caches.empty()) {
-      _lock.writeUnlock();
       return TRI_ERROR_NO_ERROR;
     }
     if (!isOperational()) {
-      _lock.writeUnlock();
       return TRI_ERROR_SHUTTING_DOWN;
     }
     if (globalProcessRunning()) {
-      _lock.writeUnlock();
       return TRI_ERROR_ARANGO_BUSY;
     }
 
@@ -534,7 +518,7 @@ int Manager::rebalance(bool onlyCalculate) {
   for (auto pair : (*cacheList)) {
     std::shared_ptr<Cache>& cache = pair.first;
     double weight = pair.second;
-    auto newDeserved = static_cast<uint64_t>(
+    auto newDeserved = static_cast<std::uint64_t>(
         std::ceil(weight * static_cast<double>(_globalHighwaterMark)));
 #ifdef ARANGODB_ENABLE_MAINTAINER_MODE
     if (newDeserved < Manager::minCacheAllocation) {
@@ -545,18 +529,17 @@ int Manager::rebalance(bool onlyCalculate) {
       TRI_ASSERT(newDeserved >= Manager::minCacheAllocation);
     }
 #endif
-    Metadata* metadata = cache->metadata();
-    metadata->writeLock();
+    Metadata& metadata = cache->metadata();
+    SpinLocker metaGuard(SpinLocker::Mode::Write, metadata.lock());
 #ifdef ARANGODB_ENABLE_MAINTAINER_MODE
-    uint64_t fixed = metadata->fixedSize + metadata->tableSize + Manager::cacheRecordOverhead;
+    std::uint64_t fixed = metadata.fixedSize + metadata.tableSize + Manager::cacheRecordOverhead;
     if (newDeserved < fixed) {
       LOG_TOPIC("e63e4", DEBUG, Logger::CACHE)
           << "Setting deserved cache size " << newDeserved
           << " below usage: " << fixed << " ; Using weight  " << weight;
     }
 #endif
-    metadata->adjustDeserved(newDeserved);
-    metadata->writeUnlock();
+    metadata.adjustDeserved(newDeserved);
   }
 
   if (!onlyCalculate) {
@@ -568,15 +551,13 @@ int Manager::rebalance(bool onlyCalculate) {
       _rebalanceCompleted = std::chrono::steady_clock::now();
       _rebalancing = false;
     }
-
-    _lock.writeUnlock();
   }
 
   return TRI_ERROR_NO_ERROR;
 }
 
 void Manager::shrinkOvergrownCaches(Manager::TaskEnvironment environment) {
-  TRI_ASSERT(_lock.isWriteLocked());
+  TRI_ASSERT(_lock.isLockedWrite());
   for (auto it : _caches) {
     std::shared_ptr<Cache>& cache = it.second;
     // skip this cache if it is already resizing or shutdown!
@@ -584,21 +565,19 @@ void Manager::shrinkOvergrownCaches(Manager::TaskEnvironment environment) {
       continue;
     }
 
-    Metadata* metadata = cache->metadata();
-    metadata->writeLock();
+    Metadata& metadata = cache->metadata();
+    SpinLocker metaGuard(SpinLocker::Mode::Write, metadata.lock());
 
-    if (metadata->allocatedSize > metadata->deservedSize) {
-      resizeCache(environment, cache.get(),
-                  metadata->newLimit());  // unlocks metadata
-    } else {
-      metadata->writeUnlock();
+    if (metadata.allocatedSize > metadata.deservedSize) {
+      resizeCache(environment, std::move(metaGuard), cache.get(),
+                  metadata.newLimit());  // unlocks metadata
     }
   }
 }
 
 void Manager::freeUnusedTables() {
-  TRI_ASSERT(_lock.isWriteLocked());
-  for (size_t i = 0; i < 32; i++) {
+  TRI_ASSERT(_lock.isLockedWrite());
+  for (std::size_t i = 0; i < 32; i++) {
     while (!_tables[i].empty()) {
       auto table = _tables[i].top();
       _globalAllocation -= table->memoryUsage();
@@ -608,13 +587,13 @@ void Manager::freeUnusedTables() {
   }
 }
 
-bool Manager::adjustGlobalLimitsIfAllowed(uint64_t newGlobalLimit) {
-  TRI_ASSERT(_lock.isWriteLocked());
+bool Manager::adjustGlobalLimitsIfAllowed(std::uint64_t newGlobalLimit) {
+  TRI_ASSERT(_lock.isLockedWrite());
   if (newGlobalLimit < _globalAllocation) {
     return false;
   }
 
-  _globalHighwaterMark = static_cast<uint64_t>(
+  _globalHighwaterMark = static_cast<std::uint64_t>(
       Manager::highwaterMultiplier * static_cast<double>(newGlobalLimit));
   _globalSoftLimit = newGlobalLimit;
   _globalHardLimit = newGlobalLimit;
@@ -622,63 +601,62 @@ bool Manager::adjustGlobalLimitsIfAllowed(uint64_t newGlobalLimit) {
   return true;
 }
 
-void Manager::resizeCache(Manager::TaskEnvironment environment, Cache* cache, uint64_t newLimit) {
-  TRI_ASSERT(_lock.isWriteLocked());
-  Metadata* metadata = cache->metadata();
-  TRI_ASSERT(metadata->isWriteLocked());
+void Manager::resizeCache(Manager::TaskEnvironment environment, SpinLocker&& metaGuard,
+                          Cache* cache, std::uint64_t newLimit) {
+  TRI_ASSERT(_lock.isLockedWrite());
+  TRI_ASSERT(metaGuard.isLocked());
+  Metadata& metadata = cache->metadata();
 
-  if (metadata->usage <= newLimit) {
-    uint64_t oldLimit = metadata->hardUsageLimit;
-    bool success = metadata->adjustLimits(newLimit, newLimit);
+  if (metadata.usage <= newLimit) {
+    std::uint64_t oldLimit = metadata.hardUsageLimit;
+    bool success = metadata.adjustLimits(newLimit, newLimit);
     TRI_ASSERT(success);
-    metadata->writeUnlock();
+    metaGuard.release();
     _globalAllocation -= oldLimit;
     _globalAllocation += newLimit;
     TRI_ASSERT(_globalAllocation >= _fixedAllocation);
     return;
   }
 
-  bool success = metadata->adjustLimits(newLimit, metadata->hardUsageLimit);
+  bool success = metadata.adjustLimits(newLimit, metadata.hardUsageLimit);
   TRI_ASSERT(success);
-  TRI_ASSERT(!metadata->isResizing());
-  metadata->toggleResizing();
-  metadata->writeUnlock();
+  TRI_ASSERT(!metadata.isResizing());
+  metadata.toggleResizing();
+  metaGuard.release();
 
-  auto task =
-      std::make_shared<FreeMemoryTask>(environment, this, cache->shared_from_this());
+  auto task = std::make_shared<FreeMemoryTask>(environment, *this,
+                                               cache->shared_from_this());
   bool dispatched = task->dispatch();
   if (!dispatched) {
     // TODO: decide what to do if we don't have an io_service
-    metadata->writeLock();
-    metadata->toggleResizing();
-    metadata->writeUnlock();
+    SpinLocker altMetaGuard(SpinLocker::Mode::Write, metadata.lock());
+    metadata.toggleResizing();
   }
 }
 
-void Manager::migrateCache(Manager::TaskEnvironment environment, Cache* cache,
-                           std::shared_ptr<Table>& table) {
-  TRI_ASSERT(_lock.isWriteLocked());
-  Metadata* metadata = cache->metadata();
-  TRI_ASSERT(metadata->isWriteLocked());
+void Manager::migrateCache(Manager::TaskEnvironment environment, SpinLocker&& metaGuard,
+                           Cache* cache, std::shared_ptr<Table>& table) {
+  TRI_ASSERT(_lock.isLockedWrite());
+  TRI_ASSERT(metaGuard.isLocked());
+  Metadata& metadata = cache->metadata();
 
-  TRI_ASSERT(!metadata->isMigrating());
-  metadata->toggleMigrating();
-  metadata->writeUnlock();
+  TRI_ASSERT(!metadata.isMigrating());
+  metadata.toggleMigrating();
+  metaGuard.release();
 
-  auto task = std::make_shared<MigrateTask>(environment, this,
+  auto task = std::make_shared<MigrateTask>(environment, *this,
                                             cache->shared_from_this(), table);
   bool dispatched = task->dispatch();
   if (!dispatched) {
     // TODO: decide what to do if we don't have an io_service
-    metadata->writeLock();
+    SpinLocker altMetaGuard(SpinLocker::Mode::Write, metadata.lock());
     reclaimTable(table, true);
-    metadata->toggleMigrating();
-    metadata->writeUnlock();
+    metadata.toggleMigrating();
   }
 }
 
-std::shared_ptr<Table> Manager::leaseTable(uint32_t logSize) {
-  TRI_ASSERT(_lock.isWriteLocked());
+std::shared_ptr<Table> Manager::leaseTable(std::uint32_t logSize) {
+  TRI_ASSERT(_lock.isLockedWrite());
 
   std::shared_ptr<Table> table;
   if (_tables[logSize].empty()) {
@@ -702,12 +680,11 @@ std::shared_ptr<Table> Manager::leaseTable(uint32_t logSize) {
 
 void Manager::reclaimTable(std::shared_ptr<Table> table, bool internal) {
   TRI_ASSERT(table.get() != nullptr);
-  if (!internal) {
-    _lock.writeLock();
-  }
+  SpinLocker guard(SpinLocker::Mode::Write, _lock, !internal);
 
-  uint32_t logSize = table->logSize();
-  size_t maxTables = (logSize < 18) ? (1u << (18 - logSize)) : 1;
+  std::uint32_t logSize = table->logSize();
+  std::size_t maxTables =
+      (logSize < 18) ? (static_cast<std::size_t>(1) << (18 - logSize)) : 1;
   if ((_tables[logSize].size() < maxTables) &&
       ((table->memoryUsage() + _spareTableAllocation) <
        ((_globalSoftLimit - _globalHighwaterMark) / 2))) {
@@ -718,13 +695,9 @@ void Manager::reclaimTable(std::shared_ptr<Table> table, bool internal) {
     TRI_ASSERT(_globalAllocation >= _fixedAllocation);
     table.reset();
   }
-
-  if (!internal) {
-    _lock.writeUnlock();
-  }
 }
 
-bool Manager::increaseAllowed(uint64_t increase, bool privileged) const {
+bool Manager::increaseAllowed(std::uint64_t increase, bool privileged) const {
   TRI_ASSERT(_lock.isLocked());
   if (privileged) {
     if (_resizing && (_globalAllocation <= _globalSoftLimit)) {
@@ -738,10 +711,11 @@ bool Manager::increaseAllowed(uint64_t increase, bool privileged) const {
 }
 
 std::shared_ptr<Manager::PriorityList> Manager::priorityList() {
-  TRI_ASSERT(_lock.isWriteLocked());
+  TRI_ASSERT(_lock.isLockedWrite());
   double minimumWeight = static_cast<double>(Manager::minCacheAllocation) /
                          static_cast<double>(_globalHighwaterMark);
-  while (static_cast<uint64_t>(std::ceil(minimumWeight * static_cast<double>(_globalHighwaterMark))) <
+  while (static_cast<std::uint64_t>(
+             std::ceil(minimumWeight * static_cast<double>(_globalHighwaterMark))) <
          Manager::minCacheAllocation) {
     minimumWeight *= 1.001;  // bump by 0.1% until we fix precision issues
   }
@@ -766,9 +740,9 @@ std::shared_ptr<Manager::PriorityList> Manager::priorityList() {
   // catalog accessed caches and count total accesses
   // to get basis for comparison
   typename AccessStatBuffer::stats_t stats = _accessStats.getFrequencies();
-  std::set<uint64_t> accessed;
-  uint64_t totalAccesses = 0;
-  uint64_t globalUsage = 0;
+  std::set<std::uint64_t> accessed;
+  std::uint64_t totalAccesses = 0;
+  std::uint64_t globalUsage = 0;
   for (auto const& s : stats) {
     auto c = _caches.find(s.first);
     if (c != _caches.end()) {
@@ -776,7 +750,7 @@ std::shared_ptr<Manager::PriorityList> Manager::priorityList() {
       accessed.emplace(c->second->id());
     }
   }
-  totalAccesses = std::max(static_cast<uint64_t>(1), totalAccesses);
+  totalAccesses = std::max(static_cast<std::uint64_t>(1), totalAccesses);
 
   double allocFrac = 0.8 * std::min(1.0, static_cast<double>(_globalAllocation) /
                                              static_cast<double>(_globalHighwaterMark));
@@ -784,7 +758,7 @@ std::shared_ptr<Manager::PriorityList> Manager::priorityList() {
   for (auto it = _caches.begin(); it != _caches.end(); it++) {
     globalUsage += it->second->usage();
   }
-  globalUsage = std::max(globalUsage, static_cast<uint64_t>(1));  // avoid div-by-zero
+  globalUsage = std::max(globalUsage, static_cast<std::uint64_t>(1));  // avoid div-by-zero
 
   // gather all unaccessed caches at beginning of list
   for (auto it = _caches.begin(); it != _caches.end(); it++) {
@@ -817,7 +791,7 @@ std::shared_ptr<Manager::PriorityList> Manager::priorityList() {
   return list;
 }
 
-Manager::time_point Manager::futureTime(uint64_t millisecondsFromNow) {
+Manager::time_point Manager::futureTime(std::uint64_t millisecondsFromNow) {
   return (std::chrono::steady_clock::now() + std::chrono::milliseconds(millisecondsFromNow));
 }
 
@@ -830,3 +804,5 @@ bool Manager::pastRebalancingGracePeriod() const {
 
   return ok;
 }
+
+}
diff --git a/arangod/Cache/Manager.h b/arangod/Cache/Manager.h
index 44894b3d0ad1..ea764bfc984d 100644
--- a/arangod/Cache/Manager.h
+++ b/arangod/Cache/Manager.h
@@ -18,16 +18,16 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 ////////////////////////////////////////////////////////////////////////////////
 
 #ifndef ARANGODB_CACHE_MANAGER_H
 #define ARANGODB_CACHE_MANAGER_H
 
-#include "Basics/Common.h"
 #include "Basics/ReadWriteSpinLock.h"
 #include "Basics/SharedAtomic.h"
 #include "Basics/SharedCounter.h"
+#include "Basics/SpinLocker.h"
 #include "Cache/CachedValue.h"
 #include "Cache/Common.h"
 #include "Cache/FrequencyBuffer.h"
@@ -40,6 +40,7 @@
 #include <atomic>
 #include <chrono>
 #include <cstdint>
+#include <limits>
 #include <map>
 #include <memory>
 #include <stack>
@@ -76,7 +77,7 @@ class Manager {
   typedef std::function<bool(std::function<void()>)> PostFn;
 
  public:
-  static const uint64_t minSize;
+  static const std::uint64_t minSize;
   typedef FrequencyBuffer<uint64_t> AccessStatBuffer;
   typedef FrequencyBuffer<uint8_t> FindStatBuffer;
   typedef std::vector<std::pair<std::shared_ptr<Cache>&, double>> PriorityList;
@@ -87,7 +88,7 @@ class Manager {
   /// @brief Initialize the manager with a scheduler post method and global
   /// usage limit.
   //////////////////////////////////////////////////////////////////////////////
-  Manager(PostFn schedulerPost, uint64_t globalLimit, bool enableWindowedStats = true);
+  Manager(PostFn schedulerPost, std::uint64_t globalLimit, bool enableWindowedStats = true);
   ~Manager();
 
   //////////////////////////////////////////////////////////////////////////////
@@ -103,8 +104,9 @@ class Manager {
   /// lifetime. It should likely only be set to a non-default value for
   /// infrequently accessed or short-lived caches.
   //////////////////////////////////////////////////////////////////////////////
-  std::shared_ptr<Cache> createCache(CacheType type, bool enableWindowedStats = false,
-                                     uint64_t maxSize = UINT64_MAX);
+  std::shared_ptr<Cache> createCache(
+      CacheType type, bool enableWindowedStats = false,
+      std::uint64_t maxSize = std::numeric_limits<std::uint64_t>::max());
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Destroy the given cache.
@@ -124,12 +126,12 @@ class Manager {
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Change the global usage limit.
   //////////////////////////////////////////////////////////////////////////////
-  bool resize(uint64_t newGlobalLimit);
+  bool resize(std::uint64_t newGlobalLimit);
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Report the current global usage limit.
   //////////////////////////////////////////////////////////////////////////////
-  uint64_t globalLimit();
+  std::uint64_t globalLimit();
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Report the current amoutn of memory allocated to all caches.
@@ -139,7 +141,7 @@ class Manager {
   /// additional synchronization between the caches and slow things down
   /// considerably.
   //////////////////////////////////////////////////////////////////////////////
-  uint64_t globalAllocation();
+  std::uint64_t globalAllocation();
 
   std::pair<double, double> globalHitRates();
 
@@ -166,11 +168,13 @@ class Manager {
   // use sizeof(uint64_t) + sizeof(std::shared_ptr<Cache>) + 64 for upper bound
   // on size of std::set<std::shared_ptr<Cache>> node -- should be valid for
   // most libraries
-  static constexpr uint64_t cacheRecordOverhead = sizeof(std::shared_ptr<Cache>) + 64;
+  static constexpr std::uint64_t cacheRecordOverhead =
+      sizeof(std::shared_ptr<Cache>) + 64;
   // assume at most 16 slots in each stack -- TODO: check validity
-  static constexpr uint64_t tableListsOverhead = 32 * 16 * sizeof(std::shared_ptr<Cache>);
-  static constexpr uint64_t triesFast = 100;
-  static constexpr uint64_t triesSlow = 1000;
+  static constexpr std::uint64_t tableListsOverhead =
+      32 * 16 * sizeof(std::shared_ptr<Cache>);
+  static constexpr std::uint64_t triesFast = 100;
+  static constexpr std::uint64_t triesSlow = 1000;
 
   // simple state variables
   basics::ReadWriteSpinLock _lock;
@@ -189,20 +193,20 @@ class Manager {
   basics::SharedCounter<64> _findMisses;
 
   // registry to keep track of registered caches
-  std::map<uint64_t, std::shared_ptr<Cache>> _caches;
-  uint64_t _nextCacheId;
+  std::map<std::uint64_t, std::shared_ptr<Cache>> _caches;
+  std::uint64_t _nextCacheId;
 
   // actual tables to lease out
 
   std::array<std::stack<std::shared_ptr<Table>>, 32> _tables;
 
   // global statistics
-  uint64_t _globalSoftLimit;
-  uint64_t _globalHardLimit;
-  uint64_t _globalHighwaterMark;
-  uint64_t _fixedAllocation;
-  uint64_t _spareTableAllocation;
-  uint64_t _globalAllocation;
+  std::uint64_t _globalSoftLimit;
+  std::uint64_t _globalHardLimit;
+  std::uint64_t _globalHighwaterMark;
+  std::uint64_t _fixedAllocation;
+  std::uint64_t _spareTableAllocation;
+  std::uint64_t _globalAllocation;
 
   // transaction management
   TransactionManager _transactions;
@@ -210,10 +214,10 @@ class Manager {
   // task management
   enum TaskEnvironment { none, rebalancing, resizing };
   PostFn _schedulerPost;
-  uint64_t _resizeAttempt;
-  basics::SharedAtomic<uint64_t> _outstandingTasks;
-  basics::SharedAtomic<uint64_t> _rebalancingTasks;
-  basics::SharedAtomic<uint64_t> _resizingTasks;
+  std::uint64_t _resizeAttempt;
+  basics::SharedAtomic<std::uint64_t> _outstandingTasks;
+  basics::SharedAtomic<std::uint64_t> _rebalancingTasks;
+  basics::SharedAtomic<std::uint64_t> _resizingTasks;
   Manager::time_point _rebalanceCompleted;
 
   // friend class tasks and caches to allow access
@@ -227,21 +231,21 @@ class Manager {
 
  private:  // used by caches
   // register and unregister individual caches
-  std::tuple<bool, Metadata, std::shared_ptr<Table>> registerCache(uint64_t fixedSize,
-                                                                   uint64_t maxSize);
-  void unregisterCache(uint64_t id);
+  std::tuple<bool, Metadata, std::shared_ptr<Table>> registerCache(std::uint64_t fixedSize,
+                                                                   std::uint64_t maxSize);
+  void unregisterCache(std::uint64_t id);
 
   // allow individual caches to request changes to their allocations
   std::pair<bool, Manager::time_point> requestGrow(Cache* cache);
   std::pair<bool, Manager::time_point> requestMigrate(Cache* cache, uint32_t requestedLogSize);
 
   // stat reporting
-  void reportAccess(uint64_t id);
+  void reportAccess(std::uint64_t id);
   void reportHitStat(Stat stat);
 
  private:  // used internally and by tasks
   static constexpr double highwaterMultiplier = 0.8;
-  static const uint64_t minCacheAllocation;
+  static const std::uint64_t minCacheAllocation;
   static const std::chrono::milliseconds rebalancingGracePeriod;
 
   // check if shutdown or shutting down
@@ -259,12 +263,14 @@ class Manager {
   // helpers for global resizing
   void shrinkOvergrownCaches(TaskEnvironment environment);
   void freeUnusedTables();
-  bool adjustGlobalLimitsIfAllowed(uint64_t newGlobalLimit);
+  bool adjustGlobalLimitsIfAllowed(std::uint64_t newGlobalLimit);
 
   // methods to adjust individual caches
-  void resizeCache(TaskEnvironment environment, Cache* cache, uint64_t newLimit);
-  void migrateCache(TaskEnvironment environment, Cache* cache, std::shared_ptr<Table>& table);
-  std::shared_ptr<Table> leaseTable(uint32_t logSize);
+  void resizeCache(TaskEnvironment environment, basics::SpinLocker&& metaGuard,
+                   Cache* cache, uint64_t newLimit);
+  void migrateCache(TaskEnvironment environment, basics::SpinLocker&& metaGuard,
+                    Cache* cache, std::shared_ptr<Table>& table);
+  std::shared_ptr<Table> leaseTable(std::uint32_t logSize);
   void reclaimTable(std::shared_ptr<Table> table, bool internal = false);
 
   // helpers for individual allocations
@@ -274,7 +280,7 @@ class Manager {
   std::shared_ptr<PriorityList> priorityList();
 
   // helper for wait times
-  [[nodiscard]] static Manager::time_point futureTime(uint64_t millisecondsFromNow);
+  [[nodiscard]] static Manager::time_point futureTime(std::uint64_t millisecondsFromNow);
   [[nodiscard]] bool pastRebalancingGracePeriod() const;
 };
 
diff --git a/arangod/Cache/ManagerTasks.cpp b/arangod/Cache/ManagerTasks.cpp
index 23ad29e6a163..41b8b644deb6 100644
--- a/arangod/Cache/ManagerTasks.cpp
+++ b/arangod/Cache/ManagerTasks.cpp
@@ -18,67 +18,75 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 ////////////////////////////////////////////////////////////////////////////////
 
 #include "Cache/ManagerTasks.h"
+#include "Basics/SpinLocker.h"
 #include "Cache/Cache.h"
 #include "Cache/Manager.h"
 #include "Cache/Metadata.h"
 
-using namespace arangodb::cache;
+namespace arangodb::cache {
 
 FreeMemoryTask::FreeMemoryTask(Manager::TaskEnvironment environment,
-                               Manager* manager, std::shared_ptr<Cache> cache)
+                               Manager& manager, std::shared_ptr<Cache> cache)
     : _environment(environment), _manager(manager), _cache(cache) {}
 
 FreeMemoryTask::~FreeMemoryTask() = default;
 
 bool FreeMemoryTask::dispatch() {
-  _manager->prepareTask(_environment);
-  return _manager->post([self = shared_from_this()]() -> void { self->run(); });
+  _manager.prepareTask(_environment);
+  return _manager.post([self = shared_from_this()]() -> void { self->run(); });
 }
 
 void FreeMemoryTask::run() {
+  using basics::SpinLocker;
+
   bool ran = _cache->freeMemory();
 
   if (ran) {
-    _manager->_lock.writeLock();
-    Metadata* metadata = _cache->metadata();
-    metadata->writeLock();
-    uint64_t reclaimed = metadata->hardUsageLimit - metadata->softUsageLimit;
-    metadata->adjustLimits(metadata->softUsageLimit, metadata->softUsageLimit);
-    metadata->toggleResizing();
-    metadata->writeUnlock();
-    _manager->_globalAllocation -= reclaimed;
-    _manager->_lock.writeUnlock();
+    std::uint64_t reclaimed = 0;
+    SpinLocker guard(SpinLocker::Mode::Write, _manager._lock);
+    Metadata& metadata = _cache->metadata();
+    {
+      SpinLocker metaGuard(SpinLocker::Mode::Write, metadata.lock());
+      reclaimed = metadata.hardUsageLimit - metadata.softUsageLimit;
+      metadata.adjustLimits(metadata.softUsageLimit, metadata.softUsageLimit);
+      metadata.toggleResizing();
+    }
+    _manager._globalAllocation -= reclaimed;
   }
 
-  _manager->unprepareTask(_environment);
+  _manager.unprepareTask(_environment);
 }
 
-MigrateTask::MigrateTask(Manager::TaskEnvironment environment, Manager* manager,
+MigrateTask::MigrateTask(Manager::TaskEnvironment environment, Manager& manager,
                          std::shared_ptr<Cache> cache, std::shared_ptr<Table> table)
     : _environment(environment), _manager(manager), _cache(cache), _table(table) {}
 
 MigrateTask::~MigrateTask() = default;
 
 bool MigrateTask::dispatch() {
-  _manager->prepareTask(_environment);
-  return _manager->post([self = shared_from_this()]() -> void { self->run(); });
+  _manager.prepareTask(_environment);
+  return _manager.post([self = shared_from_this()]() -> void { self->run(); });
 }
 
 void MigrateTask::run() {
+  using basics::SpinLocker;
+
   // do the actual migration
   bool ran = _cache->migrate(_table);
 
   if (!ran) {
-    Metadata* metadata = _cache->metadata();
-    metadata->writeLock();
-    metadata->toggleMigrating();
-    metadata->writeUnlock();
-    _manager->reclaimTable(_table);
+    Metadata& metadata = _cache->metadata();
+    {
+      SpinLocker metaGuard(SpinLocker::Mode::Write, metadata.lock());
+      metadata.toggleMigrating();
+    }
+    _manager.reclaimTable(_table);
   }
 
-  _manager->unprepareTask(_environment);
+  _manager.unprepareTask(_environment);
+}
 }
diff --git a/arangod/Cache/ManagerTasks.h b/arangod/Cache/ManagerTasks.h
index 9437ac66eeac..311fbc4f9f63 100644
--- a/arangod/Cache/ManagerTasks.h
+++ b/arangod/Cache/ManagerTasks.h
@@ -18,28 +18,28 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 ////////////////////////////////////////////////////////////////////////////////
 
 #ifndef ARANGODB_CACHE_MANAGER_TASKS_H
 #define ARANGODB_CACHE_MANAGER_TASKS_H
 
-#include "Basics/Common.h"
+#include <atomic>
+#include <cstdint>
+#include <memory>
+
+#include "Basics/SpinLocker.h"
 #include "Cache/Cache.h"
 #include "Cache/Manager.h"
 #include "Cache/Metadata.h"
 
-#include <stdint.h>
-#include <atomic>
-#include <memory>
-
 namespace arangodb {
 namespace cache {
 
 class FreeMemoryTask : public std::enable_shared_from_this<FreeMemoryTask> {
  private:
   Manager::TaskEnvironment _environment;
-  Manager* _manager;
+  Manager& _manager;
   std::shared_ptr<Cache> _cache;
 
  public:
@@ -47,7 +47,7 @@ class FreeMemoryTask : public std::enable_shared_from_this<FreeMemoryTask> {
   FreeMemoryTask(FreeMemoryTask const&) = delete;
   FreeMemoryTask& operator=(FreeMemoryTask const&) = delete;
 
-  FreeMemoryTask(Manager::TaskEnvironment environment, Manager* manager,
+  FreeMemoryTask(Manager::TaskEnvironment environment, Manager& manager,
                  std::shared_ptr<Cache>);
   ~FreeMemoryTask();
 
@@ -60,7 +60,7 @@ class FreeMemoryTask : public std::enable_shared_from_this<FreeMemoryTask> {
 class MigrateTask : public std::enable_shared_from_this<MigrateTask> {
  private:
   Manager::TaskEnvironment _environment;
-  Manager* _manager;
+  Manager& _manager;
   std::shared_ptr<Cache> _cache;
   std::shared_ptr<Table> _table;
 
@@ -69,7 +69,7 @@ class MigrateTask : public std::enable_shared_from_this<MigrateTask> {
   MigrateTask(MigrateTask const&) = delete;
   MigrateTask& operator=(MigrateTask const&) = delete;
 
-  MigrateTask(Manager::TaskEnvironment environment, Manager* manager,
+  MigrateTask(Manager::TaskEnvironment environment, Manager& manager,
               std::shared_ptr<Cache>, std::shared_ptr<Table>);
   ~MigrateTask();
 
diff --git a/arangod/Cache/Metadata.cpp b/arangod/Cache/Metadata.cpp
index 9f6a0b363e9c..9fffc746ea6b 100644
--- a/arangod/Cache/Metadata.cpp
+++ b/arangod/Cache/Metadata.cpp
@@ -18,7 +18,7 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 ////////////////////////////////////////////////////////////////////////////////
 
 #include "Cache/Metadata.h"
@@ -32,7 +32,7 @@
 #include <atomic>
 #include <cstdint>
 
-using namespace arangodb::cache;
+namespace arangodb::cache {
 
 Metadata::Metadata()
     : fixedSize(0),
@@ -47,7 +47,8 @@ Metadata::Metadata()
       _migrating(false),
       _resizing(false) {}
 
-Metadata::Metadata(uint64_t usageLimit, uint64_t fixed, uint64_t table, uint64_t max)
+Metadata::Metadata(uint64_t usageLimit, std::uint64_t fixed,
+                   std::uint64_t table, std::uint64_t max)
     : fixedSize(fixed),
       tableSize(table),
       maxSize(max),
@@ -93,38 +94,14 @@ Metadata& Metadata::operator=(Metadata&& other) noexcept {
   return *this;
 }
 
-void Metadata::readLock() const noexcept {
-  _lock.readLock();
-}
-
-void Metadata::writeLock() const noexcept {
-  _lock.writeLock();
-}
-
-void Metadata::readUnlock() const noexcept {
-  TRI_ASSERT(isLocked());
-  _lock.readUnlock();
-}
-
-void Metadata::writeUnlock() const noexcept {
-  TRI_ASSERT(isWriteLocked());
-  _lock.writeUnlock();
-}
-
-bool Metadata::isLocked() const noexcept {
-  return _lock.isLocked();
-}
+basics::ReadWriteSpinLock& Metadata::lock() const { return _lock; }
 
-bool Metadata::isWriteLocked() const noexcept {
-  return _lock.isWriteLocked();
-}
-
-bool Metadata::adjustUsageIfAllowed(int64_t usageChange) noexcept {
+bool Metadata::adjustUsageIfAllowed(std::int64_t usageChange) noexcept {
   while (true) {
-    uint64_t expected = usage.load(std::memory_order_acquire);
-    uint64_t desired = (usageChange < 0)
-                           ? expected - static_cast<uint64_t>(-usageChange)
-                           : expected + static_cast<uint64_t>(usageChange);
+    std::uint64_t expected = usage.load(std::memory_order_acquire);
+    std::uint64_t desired =
+        (usageChange < 0) ? expected - static_cast<std::uint64_t>(-usageChange)
+                          : expected + static_cast<std::uint64_t>(usageChange);
 
     if ((desired > hardUsageLimit) ||
         ((expected <= softUsageLimit) && (desired > softUsageLimit))) {
@@ -141,8 +118,8 @@ bool Metadata::adjustUsageIfAllowed(int64_t usageChange) noexcept {
   return true;
 }
 
-bool Metadata::adjustLimits(uint64_t softLimit, uint64_t hardLimit) noexcept {
-  TRI_ASSERT(isWriteLocked());
+bool Metadata::adjustLimits(std::uint64_t softLimit, std::uint64_t hardLimit) noexcept {
+  TRI_ASSERT(_lock.isLockedWrite());
   uint64_t fixed = tableSize + fixedSize + Manager::cacheRecordOverhead;
   auto approve = [&]() -> bool {
     softUsageLimit = softLimit;
@@ -183,28 +160,30 @@ bool Metadata::adjustLimits(uint64_t softLimit, uint64_t hardLimit) noexcept {
   return false;
 }
 
-uint64_t Metadata::adjustDeserved(uint64_t deserved) noexcept {
-  TRI_ASSERT(isWriteLocked());
+std::uint64_t Metadata::adjustDeserved(std::uint64_t deserved) noexcept {
+  TRI_ASSERT(_lock.isLockedWrite());
   deservedSize = std::min(deserved, maxSize);
   return deservedSize;
 }
 
-uint64_t Metadata::newLimit() const noexcept {
-  TRI_ASSERT(isLocked());
-  uint64_t fixed = fixedSize + tableSize + Manager::cacheRecordOverhead;
+std::uint64_t Metadata::newLimit() const noexcept {
+  TRI_ASSERT(_lock.isLocked());
+  std::uint64_t fixed = fixedSize + tableSize + Manager::cacheRecordOverhead;
   return ((Cache::minSize + fixed) >= deservedSize)
              ? Cache::minSize
              : std::min((deservedSize - fixed), 4 * hardUsageLimit);
 }
 
-bool Metadata::migrationAllowed(uint64_t newTableSize) noexcept {
-  TRI_ASSERT(isLocked());
+bool Metadata::migrationAllowed(std::uint64_t newTableSize) noexcept {
+  TRI_ASSERT(_lock.isLocked());
   return (hardUsageLimit + fixedSize + newTableSize + Manager::cacheRecordOverhead <=
           std::min(deservedSize, maxSize));
 }
 
-void Metadata::changeTable(uint64_t newTableSize) noexcept {
-  TRI_ASSERT(isWriteLocked());
+void Metadata::changeTable(std::uint64_t newTableSize) noexcept {
+  TRI_ASSERT(_lock.isLockedWrite());
   tableSize = newTableSize;
   allocatedSize = hardUsageLimit + fixedSize + tableSize + Manager::cacheRecordOverhead;
 }
+
+}  // namespace arangodb::cache
\ No newline at end of file
diff --git a/arangod/Cache/Metadata.h b/arangod/Cache/Metadata.h
index 31d09ad201cf..b2ec31d74864 100644
--- a/arangod/Cache/Metadata.h
+++ b/arangod/Cache/Metadata.h
@@ -18,7 +18,7 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 ////////////////////////////////////////////////////////////////////////////////
 
 #ifndef ARANGODB_CACHE_METADATA_H
@@ -40,16 +40,16 @@ class Cache;  // forward declaration
 ////////////////////////////////////////////////////////////////////////////////
 struct Metadata {
   // info about allocated memory
-  uint64_t fixedSize;
-  uint64_t tableSize;
-  uint64_t maxSize;
-  uint64_t allocatedSize;
-  uint64_t deservedSize;
+  std::uint64_t fixedSize;
+  std::uint64_t tableSize;
+  std::uint64_t maxSize;
+  std::uint64_t allocatedSize;
+  std::uint64_t deservedSize;
 
   // vital information about memory usage
-  std::atomic<uint64_t> usage;
-  uint64_t softUsageLimit;
-  uint64_t hardUsageLimit;
+  std::atomic<std::uint64_t> usage;
+  std::uint64_t softUsageLimit;
+  std::uint64_t hardUsageLimit;
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Default constructor for placeholder objects.
@@ -59,7 +59,7 @@ struct Metadata {
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Initializes record with given information.
   //////////////////////////////////////////////////////////////////////////////
-  Metadata(uint64_t usage, uint64_t fixed, uint64_t table, uint64_t max);
+  Metadata(std::uint64_t usage, std::uint64_t fixed, std::uint64_t table, std::uint64_t max);
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Initializes record from an existing record.
@@ -72,34 +72,9 @@ struct Metadata {
   Metadata& operator=(Metadata&& other) noexcept;
 
   //////////////////////////////////////////////////////////////////////////////
-  /// @brief Locks the record for reading
+  /// @brief Returns the lock for the metadata structure
   //////////////////////////////////////////////////////////////////////////////
-  void readLock() const noexcept;
-
-  //////////////////////////////////////////////////////////////////////////////
-  /// @brief Locks the record for writing
-  //////////////////////////////////////////////////////////////////////////////
-  void writeLock() const noexcept;
-
-  //////////////////////////////////////////////////////////////////////////////
-  /// @brief Unlocks the record. Requires record to be read-locked.
-  //////////////////////////////////////////////////////////////////////////////
-  void readUnlock() const noexcept;
-
-  //////////////////////////////////////////////////////////////////////////////
-  /// @brief Unlocks the record. Requires record to be write-locked.
-  //////////////////////////////////////////////////////////////////////////////
-  void writeUnlock() const noexcept;
-
-  //////////////////////////////////////////////////////////////////////////////
-  /// @brief Returns true if the record is locked, false otherwise.
-  //////////////////////////////////////////////////////////////////////////////
-  bool isLocked() const noexcept;
-
-  //////////////////////////////////////////////////////////////////////////////
-  /// @brief Returns true if the record is write-locked, false otherwise.
-  //////////////////////////////////////////////////////////////////////////////
-  bool isWriteLocked() const noexcept;
+  basics::ReadWriteSpinLock& lock() const;
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Adjusts usage by the specified amount if it will not violate
@@ -109,24 +84,24 @@ struct Metadata {
   /// in a single operation to determine whether they can afford to store a new
   /// value.
   //////////////////////////////////////////////////////////////////////////////
-  bool adjustUsageIfAllowed(int64_t usageChange) noexcept;
+  bool adjustUsageIfAllowed(std::int64_t usageChange) noexcept;
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Sets the soft and hard usage limits. Requires record to be
   /// write-locked.
   //////////////////////////////////////////////////////////////////////////////
-  bool adjustLimits(uint64_t softLimit, uint64_t hardLimit) noexcept;
+  bool adjustLimits(std::uint64_t softLimit, std::uint64_t hardLimit) noexcept;
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Sets the deserved size. Requires record to be write-locked.
   //////////////////////////////////////////////////////////////////////////////
-  uint64_t adjustDeserved(uint64_t deserved) noexcept;
+  std::uint64_t adjustDeserved(std::uint64_t deserved) noexcept;
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Calculates the new usage limit based on deserved size and other
   /// values. Requires record to be read-locked.
   //////////////////////////////////////////////////////////////////////////////
-  uint64_t newLimit() const noexcept;
+  std::uint64_t newLimit() const noexcept;
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Checks feasibility of new table size prior to migration. Requires
@@ -135,13 +110,13 @@ struct Metadata {
   /// If migrating to table of new size would exceed either deserved or maximum
   /// size, then returns false.
   //////////////////////////////////////////////////////////////////////////////
-  bool migrationAllowed(uint64_t newTableSize) noexcept;
+  bool migrationAllowed(std::uint64_t newTableSize) noexcept;
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Sets the table size after migration. Requires record to be
   /// write-locked.
   //////////////////////////////////////////////////////////////////////////////
-  void changeTable(uint64_t newTableSize) noexcept;
+  void changeTable(std::uint64_t newTableSize) noexcept;
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Checks if cache is migrating. Requires record to be read-locked.
diff --git a/arangod/Cache/PlainBucket.cpp b/arangod/Cache/PlainBucket.cpp
index 12105f58e9e6..a5a940422b05 100644
--- a/arangod/Cache/PlainBucket.cpp
+++ b/arangod/Cache/PlainBucket.cpp
@@ -18,26 +18,26 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 ////////////////////////////////////////////////////////////////////////////////
 
+#include <atomic>
+#include <cstdint>
+
 #include "Cache/PlainBucket.h"
 
 #include "Basics/Common.h"
 #include "Basics/debugging.h"
 #include "Cache/CachedValue.h"
 
-#include <stdint.h>
-#include <atomic>
-
-using namespace arangodb::cache;
+namespace arangodb::cache {
 
 PlainBucket::PlainBucket() {
   _state.lock();
   clear();
 }
 
-bool PlainBucket::lock(uint64_t maxTries) { return _state.lock(maxTries); }
+bool PlainBucket::lock(std::uint64_t maxTries) { return _state.lock(maxTries); }
 
 void PlainBucket::unlock() {
   TRI_ASSERT(_state.isLocked());
@@ -65,11 +65,12 @@ bool PlainBucket::isFull() const {
   return !hasEmptySlot;
 }
 
-CachedValue* PlainBucket::find(uint32_t hash, void const* key, size_t keySize, bool moveToFront) {
+CachedValue* PlainBucket::find(std::uint32_t hash, void const* key,
+                               std::size_t keySize, bool moveToFront) {
   TRI_ASSERT(isLocked());
   CachedValue* result = nullptr;
 
-  for (size_t i = 0; i < slotsData; i++) {
+  for (std::size_t i = 0; i < slotsData; i++) {
     if (_cachedHashes[i] == 0) {
       break;
     }
@@ -86,9 +87,9 @@ CachedValue* PlainBucket::find(uint32_t hash, void const* key, size_t keySize, b
 }
 
 // requires there to be an open slot, otherwise will not be inserted
-void PlainBucket::insert(uint32_t hash, CachedValue* value) {
+void PlainBucket::insert(std::uint32_t hash, CachedValue* value) {
   TRI_ASSERT(isLocked());
-  for (size_t i = 0; i < slotsData; i++) {
+  for (std::size_t i = 0; i < slotsData; i++) {
     if (_cachedHashes[i] == 0) {
       // found an empty slot
       _cachedHashes[i] = hash;
@@ -101,7 +102,7 @@ void PlainBucket::insert(uint32_t hash, CachedValue* value) {
   }
 }
 
-CachedValue* PlainBucket::remove(uint32_t hash, void const* key, size_t keySize) {
+CachedValue* PlainBucket::remove(std::uint32_t hash, void const* key, std::size_t keySize) {
   TRI_ASSERT(isLocked());
   CachedValue* value = find(hash, key, keySize, false);
   if (value != nullptr) {
@@ -113,8 +114,8 @@ CachedValue* PlainBucket::remove(uint32_t hash, void const* key, size_t keySize)
 
 CachedValue* PlainBucket::evictionCandidate(bool ignoreRefCount) const {
   TRI_ASSERT(isLocked());
-  for (size_t i = 0; i < slotsData; i++) {
-    size_t slot = slotsData - (i + 1);
+  for (std::size_t i = 0; i < slotsData; i++) {
+    std::size_t slot = slotsData - (i + 1);
     if (_cachedData[slot] == nullptr) {
       continue;
     }
@@ -128,8 +129,8 @@ CachedValue* PlainBucket::evictionCandidate(bool ignoreRefCount) const {
 
 void PlainBucket::evict(CachedValue* value, bool optimizeForInsertion) {
   TRI_ASSERT(isLocked());
-  for (size_t i = 0; i < slotsData; i++) {
-    size_t slot = slotsData - (i + 1);
+  for (std::size_t i = 0; i < slotsData; i++) {
+    std::size_t slot = slotsData - (i + 1);
     if (_cachedData[slot] == value) {
       // found a match
       _cachedHashes[slot] = 0;
@@ -144,7 +145,7 @@ void PlainBucket::clear() {
   TRI_ASSERT(isLocked());
   _state.clear();  // "clear" will keep the lock!
 
-  for (size_t i = 0; i < slotsData; ++i) {
+  for (std::size_t i = 0; i < slotsData; ++i) {
     _cachedHashes[i] = 0;
     _cachedData[i] = nullptr;
   }
@@ -152,11 +153,11 @@ void PlainBucket::clear() {
   _state.unlock();
 }
 
-void PlainBucket::moveSlot(size_t slot, bool moveToFront) {
+void PlainBucket::moveSlot(std::size_t slot, bool moveToFront) {
   TRI_ASSERT(isLocked());
-  uint32_t hash = _cachedHashes[slot];
+  std::uint32_t hash = _cachedHashes[slot];
   CachedValue* value = _cachedData[slot];
-  size_t i = slot;
+  std::size_t i = slot;
   if (moveToFront) {
     // move slot to front
     for (; i >= 1; i--) {
@@ -173,3 +174,5 @@ void PlainBucket::moveSlot(size_t slot, bool moveToFront) {
   _cachedHashes[i] = hash;
   _cachedData[i] = value;
 }
+
+}  // namespace arangodb::cache
\ No newline at end of file
diff --git a/arangod/Cache/PlainBucket.h b/arangod/Cache/PlainBucket.h
index 2dfbcf200ec7..b4a4bd640e57 100644
--- a/arangod/Cache/PlainBucket.h
+++ b/arangod/Cache/PlainBucket.h
@@ -18,20 +18,19 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 ////////////////////////////////////////////////////////////////////////////////
 
 #ifndef ARANGODB_CACHE_PLAIN_BUCKET_H
 #define ARANGODB_CACHE_PLAIN_BUCKET_H
 
-#include "Basics/Common.h"
+#include <atomic>
+#include <cstdint>
+
 #include "Cache/BucketState.h"
 #include "Cache/CachedValue.h"
 #include "Cache/Common.h"
 
-#include <stdint.h>
-#include <atomic>
-
 namespace arangodb {
 namespace cache {
 
@@ -47,11 +46,11 @@ namespace cache {
 struct PlainBucket {
   BucketState _state;
 
-  uint32_t _paddingExplicit;  // fill 4-byte gap for alignment purposes
+  std::uint32_t _paddingExplicit;  // fill 4-byte gap for alignment purposes
 
   // actual cached entries
-  static constexpr size_t slotsData = 10;
-  uint32_t _cachedHashes[slotsData];
+  static constexpr std::size_t slotsData = 10;
+  std::uint32_t _cachedHashes[slotsData];
   CachedValue* _cachedData[slotsData];
 
 // padding, if necessary?
@@ -67,7 +66,7 @@ struct PlainBucket {
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Attempt to lock bucket (failing after maxTries attempts).
   //////////////////////////////////////////////////////////////////////////////
-  bool lock(uint64_t maxTries);
+  bool lock(std::uint64_t maxTries);
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Unlock the bucket. Requires bucket to be locked.
@@ -100,7 +99,8 @@ struct PlainBucket {
   /// bucket to allow basic LRU semantics. If no matching entry is found,
   /// nothing will be changed and a nullptr will be returned.
   //////////////////////////////////////////////////////////////////////////////
-  CachedValue* find(uint32_t hash, void const* key, size_t keySize, bool moveToFront = true);
+  CachedValue* find(std::uint32_t hash, void const* key, std::size_t keySize,
+                    bool moveToFront = true);
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Inserts a given value. Requires state to be locked.
@@ -113,7 +113,7 @@ struct PlainBucket {
   /// the bucket is full, the user should evict an item and specify the
   /// optimizeForInsertion flag to be true.
   //////////////////////////////////////////////////////////////////////////////
-  void insert(uint32_t hash, CachedValue* value);
+  void insert(std::uint32_t hash, CachedValue* value);
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Removes an item with the given key if one exists. Requires state to
@@ -124,7 +124,7 @@ struct PlainBucket {
   /// to the value. Upon removal, the empty slot generated is moved to the back
   /// of the bucket (to remove the gap).
   //////////////////////////////////////////////////////////////////////////////
-  CachedValue* remove(uint32_t hash, void const* key, size_t keySize);
+  CachedValue* remove(std::uint32_t hash, void const* key, std::size_t keySize);
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Searches for the best candidate in the bucket to evict. Requires
@@ -154,7 +154,7 @@ struct PlainBucket {
   void clear();
 
  private:
-  void moveSlot(size_t slot, bool moveToFront);
+  void moveSlot(std::size_t slot, bool moveToFront);
 };
 
 // ensure that PlainBucket is exactly BUCKET_SIZE
diff --git a/arangod/Cache/PlainCache.cpp b/arangod/Cache/PlainCache.cpp
index 2467913d8ed4..bf6e59ac50e2 100644
--- a/arangod/Cache/PlainCache.cpp
+++ b/arangod/Cache/PlainCache.cpp
@@ -18,9 +18,14 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 ////////////////////////////////////////////////////////////////////////////////
 
+#include <atomic>
+#include <chrono>
+#include <cstdint>
+#include <list>
+
 #include "Cache/PlainCache.h"
 
 #include "Basics/Common.h"
@@ -34,29 +39,26 @@
 #include "Cache/PlainBucket.h"
 #include "Cache/Table.h"
 
-#include <stdint.h>
-#include <atomic>
-#include <chrono>
-#include <list>
+namespace arangodb::cache {
 
-using namespace arangodb;
-using namespace arangodb::cache;
+using SpinLocker = ::arangodb::basics::SpinLocker;
 
-Finding PlainCache::find(void const* key, uint32_t keySize) {
+Finding PlainCache::find(void const* key, std::uint32_t keySize) {
   TRI_ASSERT(key != nullptr);
   Finding result;
-  uint32_t hash = hashKey(key, keySize);
+  std::uint32_t hash = hashKey(key, keySize);
 
   Result status;
-  PlainBucket* bucket;
-  Table* source;
-  std::tie(status, bucket, source) = getBucket(hash, Cache::triesFast);
+  Table::BucketLocker guard;
+  std::tie(status, guard) = getBucket(hash, Cache::triesFast);
   if (status.fail()) {
     result.reportError(status);
     return result;
   }
 
-  result.set(bucket->find(hash, key, keySize));
+  PlainBucket& bucket = guard.bucket<PlainBucket>();
+  ;
+  result.set(bucket.find(hash, key, keySize));
   if (result.found()) {
     recordStat(Stat::findHit);
   } else {
@@ -64,66 +66,69 @@ Finding PlainCache::find(void const* key, uint32_t keySize) {
     status.reset(TRI_ERROR_ARANGO_DOCUMENT_NOT_FOUND);
     result.reportError(status);
   }
-  bucket->unlock();
 
   return result;
 }
 
 Result PlainCache::insert(CachedValue* value) {
   TRI_ASSERT(value != nullptr);
-  uint32_t hash = hashKey(value->key(), value->keySize());
+  bool maybeMigrate = false;
+  std::uint32_t hash = hashKey(value->key(), value->keySize());
 
-  Result status{TRI_ERROR_NO_ERROR};
-  PlainBucket* bucket;
+  Result status;
   Table* source;
-  std::tie(status, bucket, source) = getBucket(hash, Cache::triesFast);
-  if (status.fail()) {
-    return status;
-  }
-
-  bool allowed = true;
-  bool maybeMigrate = false;
-  int64_t change = static_cast<int64_t>(value->size());
-  CachedValue* candidate = bucket->find(hash, value->key(), value->keySize());
-
-  if (candidate == nullptr && bucket->isFull()) {
-    candidate = bucket->evictionCandidate();
-    if (candidate == nullptr) {
-      allowed = false;
-      status.reset(TRI_ERROR_ARANGO_BUSY);
+  {
+    Table::BucketLocker guard;
+    std::tie(status, guard) = getBucket(hash, Cache::triesFast);
+    if (status.fail()) {
+      return status;
     }
-  }
 
-  if (allowed) {
-    if (candidate != nullptr) {
-      change -= static_cast<int64_t>(candidate->size());
+    PlainBucket& bucket = guard.bucket<PlainBucket>();
+    source = guard.source();
+    bool allowed = true;
+    std::int64_t change = static_cast<std::int64_t>(value->size());
+    CachedValue* candidate = bucket.find(hash, value->key(), value->keySize());
+
+    if (candidate == nullptr && bucket.isFull()) {
+      candidate = bucket.evictionCandidate();
+      if (candidate == nullptr) {
+        allowed = false;
+        status.reset(TRI_ERROR_ARANGO_BUSY);
+      }
     }
 
-    _metadata.readLock();  // special case
-    allowed = _metadata.adjustUsageIfAllowed(change);
-    _metadata.readUnlock();
-
     if (allowed) {
-      bool eviction = false;
       if (candidate != nullptr) {
-        bucket->evict(candidate, true);
-        if (!candidate->sameKey(value->key(), value->keySize())) {
-          eviction = true;
-        }
-        freeValue(candidate);
+        change -= static_cast<std::int64_t>(candidate->size());
+      }
+
+      {
+        SpinLocker metaGuard(SpinLocker::Mode::Read, _metadata.lock());  // special case
+        allowed = _metadata.adjustUsageIfAllowed(change);
       }
-      bucket->insert(hash, value);
-      if (!eviction) {
-        maybeMigrate = source->slotFilled();
+
+      if (allowed) {
+        bool eviction = false;
+        if (candidate != nullptr) {
+          bucket.evict(candidate, true);
+          if (!candidate->sameKey(value->key(), value->keySize())) {
+            eviction = true;
+          }
+          freeValue(candidate);
+        }
+        bucket.insert(hash, value);
+        if (!eviction) {
+          maybeMigrate = source->slotFilled();
+        }
+        maybeMigrate |= reportInsert(eviction);
+      } else {
+        requestGrow();  // let function do the hard work
+        status.reset(TRI_ERROR_RESOURCE_LIMIT);
       }
-      maybeMigrate |= reportInsert(eviction);
-    } else {
-      requestGrow();  // let function do the hard work
-      status.reset(TRI_ERROR_RESOURCE_LIMIT);
     }
   }
 
-  bucket->unlock();
   if (maybeMigrate) {
     requestMigrate(source->idealSize());  // let function do the hard work
   }
@@ -131,34 +136,37 @@ Result PlainCache::insert(CachedValue* value) {
   return status;
 }
 
-Result PlainCache::remove(void const* key, uint32_t keySize) {
+Result PlainCache::remove(void const* key, std::uint32_t keySize) {
   TRI_ASSERT(key != nullptr);
-  uint32_t hash = hashKey(key, keySize);
+  bool maybeMigrate = false;
+  std::uint32_t hash = hashKey(key, keySize);
 
   Result status;
-  PlainBucket* bucket;
   Table* source;
-  std::tie(status, bucket, source) = getBucket(hash, Cache::triesSlow);
-  if (status.fail()) {
-    return status;
-  }
-
-  bool maybeMigrate = false;
-  CachedValue* candidate = bucket->remove(hash, key, keySize);
+  {
+    Table::BucketLocker guard;
+    std::tie(status, guard) = getBucket(hash, Cache::triesSlow);
+    if (status.fail()) {
+      return status;
+    }
+    PlainBucket& bucket = guard.bucket<PlainBucket>();
+    source = guard.source();
+    CachedValue* candidate = bucket.remove(hash, key, keySize);
 
-  if (candidate != nullptr) {
-    int64_t change = -static_cast<int64_t>(candidate->size());
+    if (candidate != nullptr) {
+      std::int64_t change = -static_cast<std::int64_t>(candidate->size());
 
-    _metadata.readLock();  // special case
-    bool allowed = _metadata.adjustUsageIfAllowed(change);
-    TRI_ASSERT(allowed);
-    _metadata.readUnlock();
+      {
+        SpinLocker metaGuard(SpinLocker::Mode::Read, _metadata.lock());  // special case
+        bool allowed = _metadata.adjustUsageIfAllowed(change);
+        TRI_ASSERT(allowed);
+      }
 
-    freeValue(candidate);
-    maybeMigrate = source->slotEmptied();
+      freeValue(candidate);
+      maybeMigrate = source->slotEmptied();
+    }
   }
 
-  bucket->unlock();
   if (maybeMigrate) {
     requestMigrate(source->idealSize());
   }
@@ -166,26 +174,26 @@ Result PlainCache::remove(void const* key, uint32_t keySize) {
   return status;
 }
 
-Result PlainCache::blacklist(void const* key, uint32_t keySize) {
+Result PlainCache::blacklist(void const* key, std::uint32_t keySize) {
   return {TRI_ERROR_NOT_IMPLEMENTED};
 }
 
-uint64_t PlainCache::allocationSize(bool enableWindowedStats) {
+std::uint64_t PlainCache::allocationSize(bool enableWindowedStats) {
   return sizeof(PlainCache) +
          (enableWindowedStats
               ? (sizeof(StatBuffer) + StatBuffer::allocationSize(_findStatsCapacity))
               : 0);
 }
 
-std::shared_ptr<Cache> PlainCache::create(Manager* manager, uint64_t id, Metadata&& metadata,
-                                          std::shared_ptr<Table> table,
+std::shared_ptr<Cache> PlainCache::create(Manager* manager, std::uint64_t id,
+                                          Metadata&& metadata, std::shared_ptr<Table> table,
                                           bool enableWindowedStats) {
   return std::make_shared<PlainCache>(Cache::ConstructionGuard(), manager, id,
                                       std::move(metadata), table, enableWindowedStats);
 }
 
 PlainCache::PlainCache(Cache::ConstructionGuard guard, Manager* manager,
-                       uint64_t id, Metadata&& metadata,
+                       std::uint64_t id, Metadata&& metadata,
                        std::shared_ptr<Table> table, bool enableWindowedStats)
     : Cache(guard, manager, id, std::move(metadata), table, enableWindowedStats,
             PlainCache::bucketClearer, PlainBucket::slotsData) {}
@@ -200,32 +208,32 @@ PlainCache::~PlainCache() {
   }
 }
 
-uint64_t PlainCache::freeMemoryFrom(uint32_t hash) {
-  uint64_t reclaimed = 0;
-  Result status;
+std::uint64_t PlainCache::freeMemoryFrom(std::uint32_t hash) {
+  std::uint64_t reclaimed = 0;
   bool maybeMigrate = false;
-  PlainBucket* bucket;
-  Table* source;
-  std::tie(status, bucket, source) = getBucket(hash, Cache::triesFast, false);
-  if (status.fail()) {
-    return 0;
-  }
+  Result status;
+  {
+    Table::BucketLocker guard;
+    std::tie(status, guard) = getBucket(hash, Cache::triesFast, false);
+    if (status.fail()) {
+      return 0;
+    }
 
-  // evict LRU freeable value if exists
-  CachedValue* candidate = bucket->evictionCandidate();
+    PlainBucket& bucket = guard.bucket<PlainBucket>();
+    // evict LRU freeable value if exists
+    CachedValue* candidate = bucket.evictionCandidate();
 
-  if (candidate != nullptr) {
-    reclaimed = candidate->size();
-    bucket->evict(candidate);
-    freeValue(candidate);
-    maybeMigrate = source->slotEmptied();
+    if (candidate != nullptr) {
+      reclaimed = candidate->size();
+      bucket.evict(candidate);
+      freeValue(candidate);
+      maybeMigrate = guard.source()->slotEmptied();
+    }
   }
 
-  bucket->unlock();
-
   cache::Table* table = _table.load(std::memory_order_relaxed);
   if (table) {
-    int32_t size = table->idealSize();
+    std::int32_t size = table->idealSize();
     if (maybeMigrate) {
       requestMigrate(size);
     }
@@ -237,101 +245,90 @@ uint64_t PlainCache::freeMemoryFrom(uint32_t hash) {
 void PlainCache::migrateBucket(void* sourcePtr, std::unique_ptr<Table::Subtable> targets,
                                std::shared_ptr<Table> newTable) {
   // lock current bucket
-  auto source = reinterpret_cast<PlainBucket*>(sourcePtr);
-  source->lock(Cache::triesGuarantee);
-
-  // lock target bucket(s)
-  targets->applyToAllBuckets([](void* ptr) -> bool {
-    auto targetBucket = reinterpret_cast<PlainBucket*>(ptr);
-    return targetBucket->lock(Cache::triesGuarantee);
-  });
-
-  for (size_t j = 0; j < PlainBucket::slotsData; j++) {
-    size_t k = PlainBucket::slotsData - (j + 1);
-    if (source->_cachedHashes[k] != 0) {
-      uint32_t hash = source->_cachedHashes[k];
-      CachedValue* value = source->_cachedData[k];
-
-      auto targetBucket = reinterpret_cast<PlainBucket*>(targets->fetchBucket(hash));
-      bool haveSpace = true;
-      if (targetBucket->isFull()) {
-        CachedValue* candidate = targetBucket->evictionCandidate();
-        if (candidate != nullptr) {
-          targetBucket->evict(candidate, true);
-          uint64_t size = candidate->size();
-          freeValue(candidate);
-          reclaimMemory(size);
-          newTable->slotEmptied();
+  Table::BucketLocker sourceGuard(sourcePtr, _table.load(), Cache::triesGuarantee);
+  PlainBucket& source = sourceGuard.bucket<PlainBucket>();
+
+  {
+    // lock target bucket(s)
+    std::vector<Table::BucketLocker> targetGuards = targets->lockAllBuckets();
+
+    for (std::size_t j = 0; j < PlainBucket::slotsData; j++) {
+      std::size_t k = PlainBucket::slotsData - (j + 1);
+      if (source._cachedHashes[k] != 0) {
+        std::uint32_t hash = source._cachedHashes[k];
+        CachedValue* value = source._cachedData[k];
+
+        auto targetBucket = reinterpret_cast<PlainBucket*>(targets->fetchBucket(hash));
+        bool haveSpace = true;
+        if (targetBucket->isFull()) {
+          CachedValue* candidate = targetBucket->evictionCandidate();
+          if (candidate != nullptr) {
+            targetBucket->evict(candidate, true);
+            std::uint64_t size = candidate->size();
+            freeValue(candidate);
+            reclaimMemory(size);
+            newTable->slotEmptied();
+          } else {
+            haveSpace = false;
+          }
+        }
+        if (haveSpace) {
+          targetBucket->insert(hash, value);
+          newTable->slotFilled();
         } else {
-          haveSpace = false;
+          std::uint64_t size = value->size();
+          freeValue(value);
+          reclaimMemory(size);
         }
-      }
-      if (haveSpace) {
-        targetBucket->insert(hash, value);
-        newTable->slotFilled();
-      } else {
-        uint64_t size = value->size();
-        freeValue(value);
-        reclaimMemory(size);
-      }
 
-      source->_cachedHashes[k] = 0;
-      source->_cachedData[k] = nullptr;
+        source._cachedHashes[k] = 0;
+        source._cachedData[k] = nullptr;
+      }
     }
   }
 
-  // unlock targets
-  targets->applyToAllBuckets([](void* ptr) -> bool {
-    auto targetBucket = reinterpret_cast<PlainBucket*>(ptr);
-    targetBucket->unlock();
-    return true;
-  });
-
   // finish up this bucket's migration
-  source->_state.toggleFlag(BucketState::Flag::migrated);
-  source->unlock();
+  source._state.toggleFlag(BucketState::Flag::migrated);
 }
 
-std::tuple<Result, PlainBucket*, Table*> PlainCache::getBucket(uint32_t hash, uint64_t maxTries,
-                                                               bool singleOperation) {
+std::pair<Result, Table::BucketLocker> PlainCache::getBucket(std::uint32_t hash,
+                                                             std::uint64_t maxTries,
+                                                             bool singleOperation) {
   Result status;
-  PlainBucket* bucket = nullptr;
-  Table* source = nullptr;
+  Table::BucketLocker guard;
 
   Table* table = _table.load(std::memory_order_relaxed);
   if (isShutdown() || table == nullptr) {
     status.reset(TRI_ERROR_SHUTTING_DOWN);
-    return std::make_tuple(std::move(status), bucket, source);
+    return std::make_pair(std::move(status), std::move(guard));
   }
 
   if (singleOperation) {
     _manager->reportAccess(_id);
   }
 
-  auto pair = table->fetchAndLockBucket(hash, maxTries);
-  bucket = reinterpret_cast<PlainBucket*>(pair.first);
-  source = pair.second;
-  bool ok = (bucket != nullptr);
-  if (!ok) {
+  guard = table->fetchAndLockBucket(hash, maxTries);
+  if (!guard.isLocked()) {
     status.reset(TRI_ERROR_LOCK_TIMEOUT);
   }
 
-  return std::make_tuple(std::move(status), bucket, source);
+  return std::make_pair(std::move(status), std::move(guard));
 }
 
 Table::BucketClearer PlainCache::bucketClearer(Metadata* metadata) {
   return [metadata](void* ptr) -> void {
     auto bucket = reinterpret_cast<PlainBucket*>(ptr);
     bucket->lock(Cache::triesGuarantee);
-    for (size_t j = 0; j < PlainBucket::slotsData; j++) {
+    for (std::size_t j = 0; j < PlainBucket::slotsData; j++) {
       if (bucket->_cachedData[j] != nullptr) {
-        uint64_t size = bucket->_cachedData[j]->size();
+        std::uint64_t size = bucket->_cachedData[j]->size();
         freeValue(bucket->_cachedData[j]);
-        metadata->readLock();  // special case
+        SpinLocker metaGuard(SpinLocker::Mode::Read, metadata->lock());  // special case
         metadata->adjustUsageIfAllowed(-static_cast<int64_t>(size));
-        metadata->readUnlock();
       }
     }
     bucket->clear();
   };
 }
+
+}  // namespace arangodb::cache
\ No newline at end of file
diff --git a/arangod/Cache/PlainCache.h b/arangod/Cache/PlainCache.h
index fa19c0095138..6ec84a320d99 100644
--- a/arangod/Cache/PlainCache.h
+++ b/arangod/Cache/PlainCache.h
@@ -18,13 +18,17 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 ////////////////////////////////////////////////////////////////////////////////
 
 #ifndef ARANGODB_CACHE_PLAIN_CACHE_H
 #define ARANGODB_CACHE_PLAIN_CACHE_H
 
-#include "Basics/Common.h"
+#include <atomic>
+#include <chrono>
+#include <cstdint>
+#include <list>
+
 #include "Cache/Cache.h"
 #include "Cache/CachedValue.h"
 #include "Cache/Common.h"
@@ -36,11 +40,6 @@
 #include "Cache/PlainBucket.h"
 #include "Cache/Table.h"
 
-#include <stdint.h>
-#include <atomic>
-#include <chrono>
-#include <list>
-
 namespace arangodb {
 namespace cache {
 
@@ -53,7 +52,7 @@ namespace cache {
 ////////////////////////////////////////////////////////////////////////////////
 class PlainCache final : public Cache {
  public:
-  PlainCache(Cache::ConstructionGuard guard, Manager* manager, uint64_t id,
+  PlainCache(Cache::ConstructionGuard guard, Manager* manager, std::uint64_t id,
              Metadata&& metadata, std::shared_ptr<Table> table, bool enableWindowedStats);
   ~PlainCache();
 
@@ -69,7 +68,7 @@ class PlainCache final : public Cache {
   /// fashion. The Result contained in the return value should report an error
   /// code in this case. Should not block for long.
   //////////////////////////////////////////////////////////////////////////////
-  Finding find(void const* key, uint32_t keySize) override;
+  Finding find(void const* key, std::uint32_t keySize) override;
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Attempts to insert the given value.
@@ -89,12 +88,12 @@ class PlainCache final : public Cache {
   /// acquire a lock in a timely fashion. Makes more attempts to acquire a lock
   /// before quitting, so may block for longer than find or insert.
   //////////////////////////////////////////////////////////////////////////////
-  Result remove(void const* key, uint32_t keySize) override;
+  Result remove(void const* key, std::uint32_t keySize) override;
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Does nothing; convenience method inheritance compliance
   //////////////////////////////////////////////////////////////////////////////
-  Result blacklist(void const* key, uint32_t keySize) override;
+  Result blacklist(void const* key, std::uint32_t keySize) override;
 
  private:
   // friend class manager and tasks
@@ -104,18 +103,18 @@ class PlainCache final : public Cache {
 
  private:
   static uint64_t allocationSize(bool enableWindowedStats);
-  static std::shared_ptr<Cache> create(Manager* manager, uint64_t id, Metadata&& metadata,
-                                       std::shared_ptr<Table> table,
+  static std::shared_ptr<Cache> create(Manager* manager, std::uint64_t id,
+                                       Metadata&& metadata, std::shared_ptr<Table> table,
                                        bool enableWindowedStats);
 
-  virtual uint64_t freeMemoryFrom(uint32_t hash) override;
+  virtual uint64_t freeMemoryFrom(std::uint32_t hash) override;
   virtual void migrateBucket(void* sourcePtr, std::unique_ptr<Table::Subtable> targets,
                              std::shared_ptr<Table> newTable) override;
 
   // helpers
-  std::tuple<Result, PlainBucket*, Table*> getBucket(uint32_t hash, uint64_t maxTries,
-                                                     bool singleOperation = true);
-  uint32_t getIndex(uint32_t hash, bool useAuxiliary) const;
+  std::pair<Result, Table::BucketLocker> getBucket(std::uint32_t hash, std::uint64_t maxTries,
+                                                   bool singleOperation = true);
+  uint32_t getIndex(std::uint32_t hash, bool useAuxiliary) const;
 
   static Table::BucketClearer bucketClearer(Metadata* metadata);
 };
diff --git a/arangod/Cache/Rebalancer.cpp b/arangod/Cache/Rebalancer.cpp
index 8f2e6e06d0e9..cbe54c3040eb 100644
--- a/arangod/Cache/Rebalancer.cpp
+++ b/arangod/Cache/Rebalancer.cpp
@@ -18,7 +18,7 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 ////////////////////////////////////////////////////////////////////////////////
 
 #include "Cache/Rebalancer.h"
@@ -26,7 +26,7 @@
 #include "Basics/voc-errors.h"
 #include "Cache/Manager.h"
 
-using namespace arangodb::cache;
+namespace arangodb::cache {
 
 Rebalancer::Rebalancer(Manager* manager) : _manager(manager) {}
 
@@ -36,3 +36,5 @@ int Rebalancer::rebalance() {
   }
   return TRI_ERROR_INTERNAL;
 }
+
+}  // namespace arangodb::cache
\ No newline at end of file
diff --git a/arangod/Cache/Rebalancer.h b/arangod/Cache/Rebalancer.h
index 943f55fae794..b4911be544f1 100644
--- a/arangod/Cache/Rebalancer.h
+++ b/arangod/Cache/Rebalancer.h
@@ -18,14 +18,12 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 ////////////////////////////////////////////////////////////////////////////////
 
 #ifndef ARANGODB_CACHE_REBALANCER_H
 #define ARANGODB_CACHE_REBALANCER_H
 
-#include "Basics/Common.h"
-
 #include "Manager.h"
 
 namespace arangodb {
diff --git a/arangod/Cache/Table.cpp b/arangod/Cache/Table.cpp
index d4dd3dc7f5df..82fbfb8af125 100644
--- a/arangod/Cache/Table.cpp
+++ b/arangod/Cache/Table.cpp
@@ -18,27 +18,36 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 ////////////////////////////////////////////////////////////////////////////////
 
+#include <algorithm>
+#include <cstdint>
+#include <limits>
+#include <memory>
+#include <stdexcept>
+
 #include "Cache/Table.h"
 
+#include "Basics/Exceptions.h"
+#include "Basics/SpinLocker.h"
 #include "Basics/debugging.h"
+#include "Basics/voc-errors.h"
+#include "Cache/Cache.h"
 #include "Cache/Common.h"
+#include "Cache/PlainBucket.h"
+#include "Cache/TransactionalBucket.h"
 
-#include <algorithm>
-#include <cstdint>
-#include <memory>
-#include <stdexcept>
+namespace arangodb::cache {
 
-using namespace arangodb::cache;
+using SpinLocker = ::arangodb::basics::SpinLocker;
 
-const uint32_t Table::minLogSize = 8;
-const uint32_t Table::maxLogSize = 32;
+const std::uint32_t Table::minLogSize = 8;
+const std::uint32_t Table::maxLogSize = 32;
 
 Table::GenericBucket::GenericBucket() : _state{}, _padding{} {}
 
-bool Table::GenericBucket::lock(uint64_t maxTries) {
+bool Table::GenericBucket::lock(std::uint64_t maxTries) {
   return _state.lock(maxTries);
 }
 
@@ -48,10 +57,10 @@ void Table::GenericBucket::unlock() {
 }
 
 void Table::GenericBucket::clear() {
-  _state.lock(UINT64_MAX, [this]() -> void {
+  _state.lock(std::numeric_limits<std::uint64_t>::max(), [this]() -> void {
     _state.clear();
     for (size_t i = 0; i < paddingSize; i++) {
-      _padding[i] = static_cast<uint8_t>(0);
+      _padding[i] = static_cast<std::uint8_t>(0);
     }
     _state.unlock();
   });
@@ -63,49 +72,127 @@ bool Table::GenericBucket::isMigrated() const {
 }
 
 Table::Subtable::Subtable(std::shared_ptr<Table> source, GenericBucket* buckets,
-                          uint64_t size, uint32_t mask, uint32_t shift)
+                          std::uint64_t size, std::uint32_t mask, std::uint32_t shift)
     : _source(source), _buckets(buckets), _size(size), _mask(mask), _shift(shift) {}
 
-void* Table::Subtable::fetchBucket(uint32_t hash) {
+void* Table::Subtable::fetchBucket(std::uint32_t hash) {
   return &(_buckets[(hash & _mask) >> _shift]);
 }
 
-bool Table::Subtable::applyToAllBuckets(std::function<bool(void*)> cb) {
+std::vector<Table::BucketLocker> Table::Subtable::lockAllBuckets() {
+  std::vector<Table::BucketLocker> guards;
+  for (std::uint64_t i = 0; i < _size; i++) {
+    guards.emplace_back(&(_buckets[i]), _source.get(), Cache::triesGuarantee);
+  }
+  return guards;
+}
+
+template <typename BucketType>
+bool Table::Subtable::applyToAllBuckets(std::function<bool(BucketType&)> cb) {
   bool ok = true;
-  for (uint64_t i = 0; i < _size; i++) {
+  for (std::uint64_t i = 0; i < _size; i++) {
     GenericBucket* bucket = &(_buckets[i]);
-    ok = cb(bucket);
+    TRI_ASSERT(bucket != nullptr);
+    ok = cb(*reinterpret_cast<BucketType*>(bucket));
     if (!ok) {
       break;
     }
   }
   return ok;
 }
+template bool Table::Subtable::applyToAllBuckets<PlainBucket>(std::function<bool(PlainBucket&)>);
+template bool Table::Subtable::applyToAllBuckets<TransactionalBucket>(
+    std::function<bool(TransactionalBucket&)>);
+
+Table::BucketLocker::BucketLocker()
+    : _bucket(nullptr), _source(nullptr), _locked(false) {}
+
+Table::BucketLocker::BucketLocker(void* bucket, Table* source, std::uint64_t maxAttempts)
+    : _bucket(reinterpret_cast<GenericBucket*>(bucket)),
+      _source(source),
+      _locked(this->bucket<Table::GenericBucket>().lock(maxAttempts)) {
+  if (!_locked) {
+    _bucket = nullptr;
+    _source = nullptr;
+  }
+}
+
+Table::BucketLocker::BucketLocker(BucketLocker&& other) noexcept {
+  steal(std::move(other));
+}
+
+Table::BucketLocker::~BucketLocker() { release(); }
+
+Table::BucketLocker& Table::BucketLocker::operator=(BucketLocker&& other) noexcept {
+  if (this != &other) {
+    release();
+    steal(std::move(other));
+  }
+  return *this;
+}
+
+bool Table::BucketLocker::isValid() const { return _bucket != nullptr; }
+
+bool Table::BucketLocker::isLocked() const {
+  TRI_ASSERT(!_locked || isValid());
+  return _locked;
+}
 
-Table::Table(uint32_t logSize)
+Table* Table::BucketLocker::source() const { return _source; }
+
+template <typename BucketType>
+BucketType& Table::BucketLocker::bucket() const {
+  if (!isValid()) {
+    THROW_ARANGO_EXCEPTION_MESSAGE(
+        TRI_ERROR_INTERNAL, "attempted to dereference invalid bucket pointer");
+  }
+  return *reinterpret_cast<BucketType*>(_bucket);
+}
+template PlainBucket& Table::BucketLocker::bucket<PlainBucket>() const;
+template TransactionalBucket& Table::BucketLocker::bucket<TransactionalBucket>() const;
+
+void Table::BucketLocker::release() {
+  if (isValid() && isLocked()) {
+    _bucket->unlock();
+    _locked = false;
+  }
+  _bucket = nullptr;
+  _source = nullptr;
+}
+
+void Table::BucketLocker::steal(Table::BucketLocker&& other) {
+  _bucket = other._bucket;
+  _source = other._source;
+  _locked = other._locked;
+  other._bucket = nullptr;
+  other._source = nullptr;
+  other._locked = false;
+}
+
+Table::Table(std::uint32_t logSize)
     : _lock(),
       _disabled(true),
       _evictions(false),
       _logSize(std::min(logSize, maxLogSize)),
-      _size(static_cast<uint64_t>(1) << _logSize),
+      _size(static_cast<std::uint64_t>(1) << _logSize),
       _shift(32 - _logSize),
-      _mask((uint32_t)((_size - 1) << _shift)),
-      _buffer(new uint8_t[(_size * BUCKET_SIZE) + Table::padding]),
+      _mask(static_cast<std::uint32_t>((_size - 1) << _shift)),
+      _buffer(new std::uint8_t[(_size * BUCKET_SIZE) + Table::padding]),
       _buckets(reinterpret_cast<GenericBucket*>(
-          reinterpret_cast<uint64_t>((_buffer.get() + (BUCKET_SIZE - 1))) &
-          ~(static_cast<uint64_t>(BUCKET_SIZE - 1)))),
+          reinterpret_cast<std::uint64_t>((_buffer.get() + (BUCKET_SIZE - 1))) &
+          ~(static_cast<std::uint64_t>(BUCKET_SIZE - 1)))),
       _auxiliary(nullptr),
       _bucketClearer(defaultClearer),
       _slotsTotal(_size),
-      _slotsUsed(static_cast<uint64_t>(0)) {
-  for (size_t i = 0; i < _size; i++) {
+      _slotsUsed(static_cast<std::uint64_t>(0)) {
+  for (std::size_t i = 0; i < _size; i++) {
     // use placement new in order to properly initialize the bucket
     new (_buckets + i) GenericBucket();
   }
 }
 
 Table::~Table() {
-  for (size_t i = 0; i < _size; i++) {
+  for (std::size_t i = 0; i < _size; i++) {
     // retrieve pointer to bucket
     GenericBucket* b = _buckets + i;
     // call dtor
@@ -113,52 +200,44 @@ Table::~Table() {
   }
 }
 
-uint64_t Table::allocationSize(uint32_t logSize) {
-  return sizeof(Table) + (BUCKET_SIZE * (static_cast<uint64_t>(1) << logSize)) + Table::padding;
+std::uint64_t Table::allocationSize(std::uint32_t logSize) {
+  return sizeof(Table) +
+         (BUCKET_SIZE * (static_cast<std::uint64_t>(1) << logSize)) + Table::padding;
 }
 
-uint64_t Table::memoryUsage() const { return Table::allocationSize(_logSize); }
-
-uint64_t Table::size() const { return _size; }
-
-uint32_t Table::logSize() const { return _logSize; }
-
-std::pair<void*, Table*> Table::fetchAndLockBucket(uint32_t hash, uint64_t maxTries) {
-  GenericBucket* bucket = nullptr;
-  Table* source = nullptr;
-  bool ok = _lock.readLock(maxTries);
-  if (ok) {
-    ok = !_disabled;
-    if (ok) {
-      bucket = &(_buckets[(hash & _mask) >> _shift]);
-      source = this;
-      ok = bucket->lock(maxTries);
-      if (ok) {
-        if (bucket->isMigrated()) {
-          bucket->unlock();
-          bucket = nullptr;
-          source = nullptr;
+std::uint64_t Table::memoryUsage() const {
+  return Table::allocationSize(_logSize);
+}
+
+std::uint64_t Table::size() const { return _size; }
+
+std::uint32_t Table::logSize() const { return _logSize; }
+
+Table::BucketLocker Table::fetchAndLockBucket(std::uint32_t hash, std::uint64_t maxTries) {
+  SpinLocker guard(SpinLocker::Mode::Read, _lock, static_cast<std::size_t>(maxTries));
+  BucketLocker bucketGuard;
+
+  if (guard.isLocked()) {
+    if (!_disabled) {
+      bucketGuard = BucketLocker(&(_buckets[(hash & _mask) >> _shift]), this, maxTries);
+      if (bucketGuard.isLocked()) {
+        if (bucketGuard.bucket<GenericBucket>().isMigrated()) {
+          bucketGuard.release();
           if (_auxiliary) {
-            auto pair = _auxiliary->fetchAndLockBucket(hash, maxTries);
-            bucket = reinterpret_cast<GenericBucket*>(pair.first);
-            source = pair.second;
+            bucketGuard = _auxiliary->fetchAndLockBucket(hash, maxTries);
           }
         }
-      } else {
-        bucket = nullptr;
-        source = nullptr;
       }
     }
-    _lock.readUnlock();
   }
 
-  return std::make_pair(bucket, source);
+  return bucketGuard;
 }
 
 std::shared_ptr<Table> Table::setAuxiliary(std::shared_ptr<Table> const& table) {
   std::shared_ptr<Table> result = table;
   if (table.get() != this) {
-    _lock.writeLock();
+    SpinLocker guard(SpinLocker::Mode::Write, _lock);
     if (table == nullptr) {
       result = _auxiliary;
       _auxiliary = table;
@@ -166,7 +245,6 @@ std::shared_ptr<Table> Table::setAuxiliary(std::shared_ptr<Table> const& table)
       _auxiliary = table;
       result.reset();
     }
-    _lock.writeUnlock();
   }
   return result;
 }
@@ -178,39 +256,41 @@ void* Table::primaryBucket(uint64_t index) {
   return &(_buckets[index]);
 }
 
-std::unique_ptr<Table::Subtable> Table::auxiliaryBuckets(uint32_t index) {
+std::unique_ptr<Table::Subtable> Table::auxiliaryBuckets(std::uint32_t index) {
   if (!isEnabled()) {
     return std::unique_ptr<Subtable>(nullptr);
   }
   GenericBucket* base;
-  uint64_t size;
-  uint32_t mask;
-  uint32_t shift;
-
-  _lock.readLock();
-  std::shared_ptr<Table> source = _auxiliary->shared_from_this();
-  TRI_ASSERT(_auxiliary.get() != nullptr);
-  if (_logSize > _auxiliary->_logSize) {
-    uint32_t diff = _logSize - _auxiliary->_logSize;
-    base = &(_auxiliary->_buckets[index >> diff]);
-    size = 1;
-    mask = 0;
-    shift = 0;
-  } else {
-    uint32_t diff = _auxiliary->_logSize - _logSize;
-    base = &(_auxiliary->_buckets[index << diff]);
-    size = static_cast<uint64_t>(1) << diff;
-    mask = (static_cast<uint32_t>(size - 1) << _auxiliary->_shift);
-    shift = _auxiliary->_shift;
+  std::uint64_t size;
+  std::uint32_t mask;
+  std::uint32_t shift;
+
+  std::shared_ptr<Table> source = nullptr;
+  {
+    SpinLocker guard(SpinLocker::Mode::Read, _lock);
+    source = _auxiliary->shared_from_this();
+    TRI_ASSERT(_auxiliary.get() != nullptr);
+    if (_logSize > _auxiliary->_logSize) {
+      std::uint32_t diff = _logSize - _auxiliary->_logSize;
+      base = &(_auxiliary->_buckets[index >> diff]);
+      size = 1;
+      mask = 0;
+      shift = 0;
+    } else {
+      std::uint32_t diff = _auxiliary->_logSize - _logSize;
+      base = &(_auxiliary->_buckets[index << diff]);
+      size = static_cast<std::uint64_t>(1) << diff;
+      mask = (static_cast<std::uint32_t>(size - 1) << _auxiliary->_shift);
+      shift = _auxiliary->_shift;
+    }
   }
-  _lock.readUnlock();
 
   return std::make_unique<Subtable>(source, base, size, mask, shift);
 }
 
-void Table::setTypeSpecifics(BucketClearer clearer, size_t slotsPerBucket) {
+void Table::setTypeSpecifics(BucketClearer clearer, std::size_t slotsPerBucket) {
   _bucketClearer = clearer;
-  _slotsTotal = _size * static_cast<uint64_t>(slotsPerBucket);
+  _slotsTotal = _size * static_cast<std::uint64_t>(slotsPerBucket);
 }
 
 void Table::clear() {
@@ -218,7 +298,7 @@ void Table::clear() {
   if (_auxiliary.get() != nullptr) {
     throw;
   }
-  for (uint64_t i = 0; i < _size; i++) {
+  for (std::uint64_t i = 0; i < _size; i++) {
     _bucketClearer(&(_buckets[i]));
   }
   _bucketClearer = Table::defaultClearer;
@@ -226,24 +306,18 @@ void Table::clear() {
 }
 
 void Table::disable() {
-  _lock.writeLock();
+  SpinLocker guard(SpinLocker::Mode::Write, _lock);
   _disabled = true;
-  _lock.writeUnlock();
 }
 
 void Table::enable() {
-  _lock.writeLock();
+  SpinLocker guard(SpinLocker::Mode::Write, _lock);
   _disabled = false;
-  _lock.writeUnlock();
 }
 
-bool Table::isEnabled(uint64_t maxTries) {
-  bool ok = _lock.readLock(maxTries);
-  if (ok) {
-    ok = !_disabled;
-    _lock.readUnlock();
-  }
-  return ok;
+bool Table::isEnabled(std::uint64_t maxTries) {
+  SpinLocker guard(SpinLocker::Mode::Read, _lock, static_cast<std::size_t>(maxTries));
+  return guard.isLocked() && !_disabled;
 }
 
 bool Table::slotFilled() {
@@ -258,34 +332,32 @@ bool Table::slotEmptied() {
 }
 
 void Table::signalEvictions() {
-  bool ok = _lock.writeLock(triesGuarantee);
-  if (ok) {
-    _evictions = true;
-    _lock.writeUnlock();
+  SpinLocker guard(SpinLocker::Mode::Write, _lock);
+  _evictions = true;
   }
-}
 
-uint32_t Table::idealSize() {
-  bool ok = _lock.writeLock(triesGuarantee);
-  bool forceGrowth = false;
-  if (ok) {
-    forceGrowth = _evictions;
-    _evictions = false;
-    _lock.writeUnlock();
-  }
-  if (forceGrowth) {
-    return logSize() + 1;
-  }
+  std::uint32_t Table::idealSize() {
+    bool forceGrowth = false;
+    {
+      SpinLocker guard(SpinLocker::Mode::Write, _lock);
+      forceGrowth = _evictions;
+      _evictions = false;
+    }
+    if (forceGrowth) {
+      return logSize() + 1;
+    }
 
-  return (((static_cast<double>(_slotsUsed.load()) / static_cast<double>(_slotsTotal)) >
-           Table::idealUpperRatio)
-              ? (logSize() + 1)
-              : (((static_cast<double>(_slotsUsed.load()) /
-                   static_cast<double>(_slotsTotal)) < Table::idealLowerRatio)
-                     ? (logSize() - 1)
-                     : logSize()));
+    return (((static_cast<double>(_slotsUsed.load()) /
+              static_cast<double>(_slotsTotal)) > Table::idealUpperRatio)
+                ? (logSize() + 1)
+                : (((static_cast<double>(_slotsUsed.load()) /
+                     static_cast<double>(_slotsTotal)) < Table::idealLowerRatio)
+                       ? (logSize() - 1)
+                       : logSize()));
 }
 
 void Table::defaultClearer(void* ptr) {
   throw std::invalid_argument("must register a clearer");
 }
+
+}  // namespace arangodb::cache
\ No newline at end of file
diff --git a/arangod/Cache/Table.h b/arangod/Cache/Table.h
index 687f03b08f62..a4db6168702a 100644
--- a/arangod/Cache/Table.h
+++ b/arangod/Cache/Table.h
@@ -18,18 +18,18 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 ////////////////////////////////////////////////////////////////////////////////
 
 #ifndef ARANGODB_CACHE_TABLE_H
 #define ARANGODB_CACHE_TABLE_H
 
-#include "Basics/Common.h"
 #include "Basics/ReadWriteSpinLock.h"
 #include "Cache/BucketState.h"
 #include "Cache/Common.h"
 
 #include <cstdint>
+#include <limits>
 #include <memory>
 
 namespace arangodb {
@@ -42,21 +42,22 @@ class Table : public std::enable_shared_from_this<Table> {
  public:
   static constexpr double idealLowerRatio = 0.04;
   static constexpr double idealUpperRatio = 0.25;
-  static const uint32_t minLogSize;
-  static const uint32_t maxLogSize;
-  static constexpr uint32_t standardLogSizeAdjustment = 6;
-  static constexpr uint64_t triesGuarantee = UINT64_MAX;
-  static constexpr uint64_t padding = BUCKET_SIZE;
+  static const std::uint32_t minLogSize;
+  static const std::uint32_t maxLogSize;
+  static constexpr std::uint32_t standardLogSizeAdjustment = 6;
+  static constexpr std::uint64_t triesGuarantee =
+      std::numeric_limits<std::uint64_t>::max();
+  static constexpr std::uint64_t padding = BUCKET_SIZE;
 
   typedef std::function<void(void*)> BucketClearer;
 
  private:
   struct GenericBucket {
     BucketState _state;
-    static constexpr size_t paddingSize = BUCKET_SIZE - sizeof(BucketState);
-    uint8_t _padding[paddingSize];
+    static constexpr std::size_t paddingSize = BUCKET_SIZE - sizeof(BucketState);
+    std::uint8_t _padding[paddingSize];
     GenericBucket();
-    bool lock(uint64_t maxTries);
+    bool lock(std::uint64_t maxTries);
     void unlock();
     void clear();
     bool isMigrated() const;
@@ -65,21 +66,57 @@ class Table : public std::enable_shared_from_this<Table> {
                 "Expected sizeof(GenericBucket) == BUCKET_SIZE.");
 
  public:
+  //////////////////////////////////////////////////////////////////////////////
+  /// @brief Helper class for RAII-style bucket locking
+  //////////////////////////////////////////////////////////////////////////////
+  struct BucketLocker {
+    BucketLocker();
+    BucketLocker(void* bucket, Table* source, std::uint64_t maxAttempts);
+    BucketLocker(BucketLocker&&) noexcept;
+    ~BucketLocker();
+    BucketLocker& operator=(BucketLocker&&) noexcept;
+
+    BucketLocker(BucketLocker const&) = delete;             // no copy
+    BucketLocker& operator=(BucketLocker const&) = delete;  // no copy
+
+    bool isValid() const;
+    bool isLocked() const;
+
+    Table* source() const;
+
+    template <typename BucketType>
+    BucketType& bucket() const;
+
+    void release();
+
+   private:
+    void steal(BucketLocker&&);
+
+   private:
+    GenericBucket* _bucket;
+    Table* _source;
+    bool _locked;
+  };
+
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Helper class for migration.
   //////////////////////////////////////////////////////////////////////////////
   struct Subtable {
     Subtable(std::shared_ptr<Table> source, GenericBucket* buckets,
-             uint64_t size, uint32_t mask, uint32_t shift);
-    void* fetchBucket(uint32_t hash);
-    bool applyToAllBuckets(std::function<bool(void*)> cb);
+             std::uint64_t size, std::uint32_t mask, std::uint32_t shift);
+    void* fetchBucket(std::uint32_t hash);
+
+    std::vector<BucketLocker> lockAllBuckets();
+
+    template <typename BucketType>
+    bool applyToAllBuckets(std::function<bool(BucketType&)> cb);
 
    private:
     std::shared_ptr<Table> _source;
     GenericBucket* _buckets;
-    uint64_t _size;
-    uint32_t _mask;
-    uint32_t _shift;
+    std::uint64_t _size;
+    std::uint32_t _mask;
+    std::uint32_t _shift;
   };
 
  public:
@@ -88,7 +125,7 @@ class Table : public std::enable_shared_from_this<Table> {
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Construct a new table of size 2^(logSize) in disabled state.
   //////////////////////////////////////////////////////////////////////////////
-  explicit Table(uint32_t logSize);
+  explicit Table(std::uint32_t logSize);
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Destroy the table
@@ -99,22 +136,22 @@ class Table : public std::enable_shared_from_this<Table> {
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Returns the memory usage for a table with specified logSize
   //////////////////////////////////////////////////////////////////////////////
-  static uint64_t allocationSize(uint32_t logSize);
+  static std::uint64_t allocationSize(std::uint32_t logSize);
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Returns the memory usage of the table.
   //////////////////////////////////////////////////////////////////////////////
-  uint64_t memoryUsage() const;
+  std::uint64_t memoryUsage() const;
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Returns the number of buckets in the table.
   //////////////////////////////////////////////////////////////////////////////
-  uint64_t size() const;
+  std::uint64_t size() const;
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Returns the logSize of the table. (2^(logSize()) == size())
   //////////////////////////////////////////////////////////////////////////////
-  uint32_t logSize() const;
+  std::uint32_t logSize() const;
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Fetches a pointer to the bucket mapped by the given hash, and locks
@@ -126,7 +163,8 @@ class Table : public std::enable_shared_from_this<Table> {
   /// the auxiliary table. The second member of the returned pair is the source
   /// table for the bucket returned as the first member.
   //////////////////////////////////////////////////////////////////////////////
-  std::pair<void*, Table*> fetchAndLockBucket(uint32_t hash, uint64_t maxTries = UINT64_MAX);
+  BucketLocker fetchAndLockBucket(std::uint32_t hash,
+                                  std::uint64_t maxTries = std::numeric_limits<std::uint64_t>::max());
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Sets the auxiliary table.
@@ -142,18 +180,18 @@ class Table : public std::enable_shared_from_this<Table> {
   /// @brief Returns a pointer to the specified bucket in the primary table,
   /// regardless of migration status.
   //////////////////////////////////////////////////////////////////////////////
-  void* primaryBucket(uint64_t index);
+  void* primaryBucket(std::uint64_t index);
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Returns a subtable in the auxiliary index which corresponds to the
   /// specified bucket in the primary table.
   //////////////////////////////////////////////////////////////////////////////
-  std::unique_ptr<Table::Subtable> auxiliaryBuckets(uint32_t index);
+  std::unique_ptr<Table::Subtable> auxiliaryBuckets(std::uint32_t index);
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Set cache-type-specific members.
   //////////////////////////////////////////////////////////////////////////////
-  void setTypeSpecifics(BucketClearer clearer, size_t slotsPerBucket);
+  void setTypeSpecifics(BucketClearer clearer, std::size_t slotsPerBucket);
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Reset table to fully empty state. Disables table.
@@ -200,11 +238,11 @@ class Table : public std::enable_shared_from_this<Table> {
   bool _disabled;
   bool _evictions;
 
-  uint32_t _logSize;
-  uint64_t _size;
-  uint32_t _shift;
-  uint32_t _mask;
-  std::unique_ptr<uint8_t[]> _buffer;
+  std::uint32_t _logSize;
+  std::uint64_t _size;
+  std::uint32_t _shift;
+  std::uint32_t _mask;
+  std::unique_ptr<std::uint8_t[]> _buffer;
   GenericBucket* _buckets;
 
   std::shared_ptr<Table> _auxiliary;
@@ -212,11 +250,11 @@ class Table : public std::enable_shared_from_this<Table> {
   BucketClearer _bucketClearer;
 
   uint64_t _slotsTotal;
-  std::atomic<uint64_t> _slotsUsed;
+  std::atomic<std::uint64_t> _slotsUsed;
 
  private:
   void disable();
-  bool isEnabled(uint64_t maxTries = triesGuarantee);
+  bool isEnabled(std::uint64_t maxTries = triesGuarantee);
   static void defaultClearer(void* ptr);
 };
 
diff --git a/arangod/Cache/Transaction.cpp b/arangod/Cache/Transaction.cpp
index 82d171de345a..c23b70fdab93 100644
--- a/arangod/Cache/Transaction.cpp
+++ b/arangod/Cache/Transaction.cpp
@@ -18,16 +18,18 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 ////////////////////////////////////////////////////////////////////////////////
 
-#include "Cache/Transaction.h"
+#include <cstdint>
 
-#include <stdint.h>
+#include "Cache/Transaction.h"
 
-using namespace arangodb::cache;
+namespace arangodb::cache {
 
 Transaction::Transaction() : term(0), readOnly(true), sensitive(false) {}
 
 Transaction::Transaction(bool ro)
     : term(0), readOnly(ro), sensitive(!readOnly) {}
+
+}  // namespace arangodb::cache
\ No newline at end of file
diff --git a/arangod/Cache/Transaction.h b/arangod/Cache/Transaction.h
index c9dd5796213a..d9f7beaafeac 100644
--- a/arangod/Cache/Transaction.h
+++ b/arangod/Cache/Transaction.h
@@ -18,22 +18,21 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 ////////////////////////////////////////////////////////////////////////////////
 
 #ifndef ARANGODB_CACHE_TRANSACTION_H
 #define ARANGODB_CACHE_TRANSACTION_H
 
-#include "Basics/Common.h"
+#include <cstdint>
 
-#include <stdint.h>
 namespace arangodb {
 namespace cache {
 
 ////////////////////////////////////////////////////////////////////////////////
 /// @brief Structure to maintain information about an individual transaction.
 struct Transaction {
-  uint64_t term;
+  std::uint64_t term;
   bool readOnly;
   bool sensitive;
 
diff --git a/arangod/Cache/TransactionManager.cpp b/arangod/Cache/TransactionManager.cpp
index 16cae196dcf3..47f45f107681 100644
--- a/arangod/Cache/TransactionManager.cpp
+++ b/arangod/Cache/TransactionManager.cpp
@@ -18,94 +18,82 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 ////////////////////////////////////////////////////////////////////////////////
 
+#include <atomic>
+#include <cstdint>
+
 #include "Cache/TransactionManager.h"
 
 #include "Basics/cpu-relax.h"
 #include "Basics/debugging.h"
 #include "Cache/Transaction.h"
 
-#include <stdint.h>
-#include <atomic>
-
-using namespace arangodb::cache;
+namespace arangodb::cache {
 
 TransactionManager::TransactionManager()
-    : _openReads(0), _openSensitive(0), _openWrites(0), _term(0), _lock(false) {}
+    : _state({{0,0,0}, 0}) {}
 
 Transaction* TransactionManager::begin(bool readOnly) {
   Transaction* tx = new Transaction(readOnly);
 
-  lock();
-
+  State newState;
   if (readOnly) {
-    _openReads++;
-    if (_openWrites.load() > 0) {
-      tx->sensitive = true;
-      _openSensitive++;
-    }
+    State state = _state.load(std::memory_order_relaxed);
+    do {
+      tx->sensitive = false;
+      newState = state;
+      newState.counters.openReads++;
+      if (newState.counters.openWrites > 0) {
+        tx->sensitive = true;
+        newState.counters.openSensitive++;
+      }
+    } while (!_state.compare_exchange_strong(state, newState, std::memory_order_acq_rel, std::memory_order_relaxed));
   } else {
     tx->sensitive = true;
-    if (_openSensitive.load() == 0) {
-      _term++;
-    }
-    if (_openWrites.load() == 0) {
-      _openSensitive = _openReads.load() + _openWrites.load();
-    }
-    _openWrites++;
-    _openSensitive++;
+    State state = _state.load(std::memory_order_relaxed);
+    do {
+      newState = state;
+      if (newState.counters.openSensitive == 0) {
+        newState.term++;
+      }
+      if (newState.counters.openWrites++ == 0) {
+        newState.counters.openSensitive = state.counters.openReads + 1;
+      } else {
+        newState.counters.openSensitive++;
+      }
+    } while (!_state.compare_exchange_strong(state, newState, std::memory_order_acq_rel, std::memory_order_relaxed));
   }
-
-  tx->term = _term.load();
-
-  unlock();
-
+  tx->term = newState.term;
   return tx;
 }
 
 void TransactionManager::end(Transaction* tx) noexcept {
   TRI_ASSERT(tx != nullptr);
-  lock();
-
-  // if currently in sensitive phase, and transaction term is old, it was
-  // upgraded to sensitive status
-  if (((_term & static_cast<uint64_t>(1)) > 0) && (_term > tx->term)) {
-    tx->sensitive = true;
-  }
 
-  if (tx->readOnly) {
-    _openReads--;
-  } else {
-    _openWrites--;
-  }
+  State state = _state.load(std::memory_order_relaxed);
+  State newState;
+  do {
+    if (((state.term & static_cast<uint64_t>(1)) > 0) && (state.term > tx->term)) {
+      tx->sensitive = true;
+    }
 
-  if (tx->sensitive && (--_openSensitive == 0)) {
-    _term++;
-  }
+    newState = state;
+    if (tx->readOnly) {
+      newState.counters.openReads--;
+    } else {
+      newState.counters.openWrites--;
+    }
 
-  unlock();
+    if (tx->sensitive && (--newState.counters.openSensitive == 0)) {
+      newState.term++;
+    }
+  } while (!_state.compare_exchange_strong(state, newState, std::memory_order_acq_rel, std::memory_order_relaxed));
 
   delete tx;
 }
 
-uint64_t TransactionManager::term() { return _term.load(); }
+uint64_t TransactionManager::term() { return _state.load(std::memory_order_acquire).term; }
 
-void TransactionManager::lock() {
-  while (true) {
-    while (_lock.load(std::memory_order_relaxed)) {
-      basics::cpu_relax();
-    }
-    bool expected = false;
-    if (_lock.compare_exchange_weak(expected, true, std::memory_order_acq_rel,
-                                    std::memory_order_relaxed)) {
-      return;
-    }
-    basics::cpu_relax();
-  }
-}
-
-void TransactionManager::unlock() {
-  _lock.store(false, std::memory_order_release);
-}
+}  // namespace arangodb::cache
diff --git a/arangod/Cache/TransactionManager.h b/arangod/Cache/TransactionManager.h
index 65c6d2626bc7..27774fa7c454 100644
--- a/arangod/Cache/TransactionManager.h
+++ b/arangod/Cache/TransactionManager.h
@@ -18,19 +18,18 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 ////////////////////////////////////////////////////////////////////////////////
 
 #ifndef ARANGODB_CACHE_TRANSACTION_WINDOW_H
 #define ARANGODB_CACHE_TRANSACTION_WINDOW_H
 
-#include "Basics/Common.h"
-#include "Basics/ReadWriteSpinLock.h"
-#include "Cache/Transaction.h"
-
 #include <atomic>
 #include <cstdint>
 
+#include "Basics/ReadWriteSpinLock.h"
+#include "Cache/Transaction.h"
+
 namespace arangodb {
 namespace cache {
 
@@ -68,17 +67,22 @@ class TransactionManager {
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Return the current window identifier.
   //////////////////////////////////////////////////////////////////////////////
-  uint64_t term();
+  std::uint64_t term();
 
  private:
-  std::atomic<uint64_t> _openReads;
-  std::atomic<uint64_t> _openSensitive;
-  std::atomic<uint64_t> _openWrites;
-  std::atomic<uint64_t> _term;
-  std::atomic<bool> _lock;
+  struct Counters {
+    uint64_t openReads : 21;
+    uint64_t openWrites : 21;
+    uint64_t openSensitive : 21;
+  };
+  static_assert(sizeof(Counters) == sizeof(uint64_t), "unexpected size");
+
+  struct alignas(16) State {
+    Counters counters;
+    uint64_t term;
+  };
 
-  void lock();
-  void unlock();
+  std::atomic<State> _state;
 };
 
 };  // end namespace cache
diff --git a/arangod/Cache/TransactionalBucket.cpp b/arangod/Cache/TransactionalBucket.cpp
index fc9610299ed3..0725df126131 100644
--- a/arangod/Cache/TransactionalBucket.cpp
+++ b/arangod/Cache/TransactionalBucket.cpp
@@ -18,26 +18,26 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 ////////////////////////////////////////////////////////////////////////////////
 
+#include <atomic>
+#include <cstdint>
+
 #include "Cache/TransactionalBucket.h"
 
 #include "Basics/Common.h"
 #include "Basics/debugging.h"
 #include "Cache/CachedValue.h"
 
-#include <stdint.h>
-#include <atomic>
-
-using namespace arangodb::cache;
+namespace arangodb::cache {
 
 TransactionalBucket::TransactionalBucket() {
   _state.lock();
   clear();
 }
 
-bool TransactionalBucket::lock(uint64_t maxTries) {
+bool TransactionalBucket::lock(std::uint64_t maxTries) {
   return _state.lock(maxTries);
 }
 
@@ -61,8 +61,8 @@ bool TransactionalBucket::isFullyBlacklisted() const {
 bool TransactionalBucket::isFull() const {
   TRI_ASSERT(isLocked());
   bool hasEmptySlot = false;
-  for (size_t i = 0; i < slotsData; i++) {
-    size_t slot = slotsData - (i + 1);
+  for (std::size_t i = 0; i < slotsData; i++) {
+    std::size_t slot = slotsData - (i + 1);
     if (_cachedData[slot] == nullptr) {
       hasEmptySlot = true;
       break;
@@ -72,12 +72,12 @@ bool TransactionalBucket::isFull() const {
   return !hasEmptySlot;
 }
 
-CachedValue* TransactionalBucket::find(uint32_t hash, void const* key,
-                                       size_t keySize, bool moveToFront) {
+CachedValue* TransactionalBucket::find(std::uint32_t hash, void const* key,
+                                       std::size_t keySize, bool moveToFront) {
   TRI_ASSERT(isLocked());
   CachedValue* result = nullptr;
 
-  for (size_t i = 0; i < slotsData; i++) {
+  for (std::size_t i = 0; i < slotsData; i++) {
     if (_cachedData[i] == nullptr) {
       break;
     }
@@ -93,11 +93,11 @@ CachedValue* TransactionalBucket::find(uint32_t hash, void const* key,
   return result;
 }
 
-void TransactionalBucket::insert(uint32_t hash, CachedValue* value) {
+void TransactionalBucket::insert(std::uint32_t hash, CachedValue* value) {
   TRI_ASSERT(isLocked());
   TRI_ASSERT(!isBlacklisted(hash));  // checks needs to be done outside
 
-  for (size_t i = 0; i < slotsData; i++) {
+  for (std::size_t i = 0; i < slotsData; i++) {
     if (_cachedData[i] == nullptr) {
       // found an empty slot
       _cachedHashes[i] = hash;
@@ -110,7 +110,8 @@ void TransactionalBucket::insert(uint32_t hash, CachedValue* value) {
   }
 }
 
-CachedValue* TransactionalBucket::remove(uint32_t hash, void const* key, size_t keySize) {
+CachedValue* TransactionalBucket::remove(std::uint32_t hash, void const* key,
+                                         std::size_t keySize) {
   TRI_ASSERT(isLocked());
   CachedValue* value = find(hash, key, keySize, false);
   if (value != nullptr) {
@@ -120,7 +121,8 @@ CachedValue* TransactionalBucket::remove(uint32_t hash, void const* key, size_t
   return value;
 }
 
-CachedValue* TransactionalBucket::blacklist(uint32_t hash, void const* key, size_t keySize) {
+CachedValue* TransactionalBucket::blacklist(std::uint32_t hash, void const* key,
+                                            std::size_t keySize) {
   TRI_ASSERT(isLocked());
   if (!haveOpenTransaction()) {
     return nullptr;
@@ -133,7 +135,7 @@ CachedValue* TransactionalBucket::blacklist(uint32_t hash, void const* key, size
     return value;
   }
 
-  for (size_t i = 0; i < slotsBlacklist; i++) {
+  for (std::size_t i = 0; i < slotsBlacklist; i++) {
     if (_blacklistHashes[i] == 0) {
       // found an empty slot
       _blacklistHashes[i] = hash;
@@ -146,7 +148,7 @@ CachedValue* TransactionalBucket::blacklist(uint32_t hash, void const* key, size
   return value;
 }
 
-bool TransactionalBucket::isBlacklisted(uint32_t hash) const {
+bool TransactionalBucket::isBlacklisted(std::uint32_t hash) const {
   TRI_ASSERT(isLocked());
   if (!haveOpenTransaction()) {
     return false;
@@ -157,7 +159,7 @@ bool TransactionalBucket::isBlacklisted(uint32_t hash) const {
   }
 
   bool blacklisted = false;
-  for (size_t i = 0; i < slotsBlacklist; i++) {
+  for (std::size_t i = 0; i < slotsBlacklist; i++) {
     if (_blacklistHashes[i] == hash) {
       blacklisted = true;
       break;
@@ -169,8 +171,8 @@ bool TransactionalBucket::isBlacklisted(uint32_t hash) const {
 
 CachedValue* TransactionalBucket::evictionCandidate(bool ignoreRefCount) const {
   TRI_ASSERT(isLocked());
-  for (size_t i = 0; i < slotsData; i++) {
-    size_t slot = slotsData - (i + 1);
+  for (std::size_t i = 0; i < slotsData; i++) {
+    std::size_t slot = slotsData - (i + 1);
     if (_cachedData[slot] == nullptr) {
       continue;
     }
@@ -184,8 +186,8 @@ CachedValue* TransactionalBucket::evictionCandidate(bool ignoreRefCount) const {
 
 void TransactionalBucket::evict(CachedValue* value, bool optimizeForInsertion) {
   TRI_ASSERT(isLocked());
-  for (size_t i = 0; i < slotsData; i++) {
-    size_t slot = slotsData - (i + 1);
+  for (std::size_t i = 0; i < slotsData; i++) {
+    std::size_t slot = slotsData - (i + 1);
     if (_cachedData[slot] == value) {
       // found a match
       _cachedHashes[slot] = 0;
@@ -199,18 +201,18 @@ void TransactionalBucket::evict(CachedValue* value, bool optimizeForInsertion) {
 void TransactionalBucket::clear() {
   TRI_ASSERT(isLocked());
   _state.clear();  // "clear" will keep the lock!
-  for (size_t i = 0; i < slotsBlacklist; ++i) {
+  for (std::size_t i = 0; i < slotsBlacklist; ++i) {
     _blacklistHashes[i] = 0;
   }
   _blacklistTerm = 0;
-  for (size_t i = 0; i < slotsData; ++i) {
+  for (std::size_t i = 0; i < slotsData; ++i) {
     _cachedHashes[i] = 0;
     _cachedData[i] = nullptr;
   }
   _state.unlock();
 }
 
-void TransactionalBucket::updateBlacklistTerm(uint64_t term) {
+void TransactionalBucket::updateBlacklistTerm(std::uint64_t term) {
   if (term > _blacklistTerm) {
     _blacklistTerm = term;
 
@@ -218,15 +220,15 @@ void TransactionalBucket::updateBlacklistTerm(uint64_t term) {
       _state.toggleFlag(BucketState::Flag::blacklisted);
     }
 
-    memset(_blacklistHashes, 0, (slotsBlacklist * sizeof(uint32_t)));
+    memset(_blacklistHashes, 0, (slotsBlacklist * sizeof(std::uint32_t)));
   }
 }
 
-void TransactionalBucket::moveSlot(size_t slot, bool moveToFront) {
+void TransactionalBucket::moveSlot(std::size_t slot, bool moveToFront) {
   TRI_ASSERT(isLocked());
-  uint32_t hash = _cachedHashes[slot];
+  std::uint32_t hash = _cachedHashes[slot];
   CachedValue* value = _cachedData[slot];
-  size_t i = slot;
+  std::size_t i = slot;
   if (moveToFront) {
     // move slot to front
     for (; i >= 1; i--) {
@@ -247,5 +249,6 @@ void TransactionalBucket::moveSlot(size_t slot, bool moveToFront) {
 bool TransactionalBucket::haveOpenTransaction() const {
   TRI_ASSERT(isLocked());
   // only have open transactions if term is odd
-  return ((_blacklistTerm & 1ULL) > 0);
+  return ((_blacklistTerm & static_cast<uint64_t>(1)) > 0);
+}
 }
diff --git a/arangod/Cache/TransactionalBucket.h b/arangod/Cache/TransactionalBucket.h
index f2125e1b3490..e9dd88c834d6 100644
--- a/arangod/Cache/TransactionalBucket.h
+++ b/arangod/Cache/TransactionalBucket.h
@@ -18,22 +18,20 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 ////////////////////////////////////////////////////////////////////////////////
 
 #ifndef ARANGODB_CACHE_TRANSACTIONAL_BUCKET_H
 #define ARANGODB_CACHE_TRANSACTIONAL_BUCKET_H
 
-#include "Basics/Common.h"
+#include <atomic>
+#include <cstddef>
+#include <cstdint>
+
 #include "Cache/BucketState.h"
 #include "Cache/CachedValue.h"
 #include "Cache/Common.h"
 
-#include <stddef.h>
-
-#include <stdint.h>
-#include <atomic>
-
 namespace arangodb {
 namespace cache {
 
@@ -51,13 +49,13 @@ struct TransactionalBucket {
   BucketState _state;
 
   // blacklist entries for transactional semantics
-  static constexpr size_t slotsBlacklist = 5;
-  uint32_t _blacklistHashes[slotsBlacklist];
-  uint64_t _blacklistTerm;
+  static constexpr std::size_t slotsBlacklist = 5;
+  std::uint32_t _blacklistHashes[slotsBlacklist];
+  std::uint64_t _blacklistTerm;
 
   // actual cached entries
-  static constexpr size_t slotsData = 8;
-  uint32_t _cachedHashes[slotsData];
+  static constexpr std::size_t slotsData = 8;
+  std::uint32_t _cachedHashes[slotsData];
   CachedValue* _cachedData[slotsData];
 
 // padding, if necessary?
@@ -73,7 +71,7 @@ struct TransactionalBucket {
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Attempt to lock bucket (failing after maxTries attempts).
   //////////////////////////////////////////////////////////////////////////////
-  bool lock(uint64_t maxTries);
+  bool lock(std::uint64_t maxTries);
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Unlock the bucket. Requires bucket to be locked.
@@ -112,7 +110,8 @@ struct TransactionalBucket {
   /// bucket to allow basic LRU semantics. If no matching entry is found,
   /// nothing will be changed and a nullptr will be returned.
   //////////////////////////////////////////////////////////////////////////////
-  CachedValue* find(uint32_t hash, void const* key, size_t keySize, bool moveToFront = true);
+  CachedValue* find(std::uint32_t hash, void const* key, std::size_t keySize,
+                    bool moveToFront = true);
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Inserts a given value if it is not blacklisted. Requires state to
@@ -128,7 +127,7 @@ struct TransactionalBucket {
   /// user should evict an item and specify the optimizeForInsertion flag to be
   /// true.
   //////////////////////////////////////////////////////////////////////////////
-  void insert(uint32_t hash, CachedValue* value);
+  void insert(std::uint32_t hash, CachedValue* value);
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Removes an item with the given key if one exists. Requires state to
@@ -139,7 +138,7 @@ struct TransactionalBucket {
   /// to the value. Upon removal, the empty slot generated is moved to the back
   /// of the bucket (to remove the gap).
   //////////////////////////////////////////////////////////////////////////////
-  CachedValue* remove(uint32_t hash, void const* key, size_t keySize);
+  CachedValue* remove(std::uint32_t hash, void const* key, std::size_t keySize);
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Blacklists a key and removes it if it exists. Requires state to
@@ -149,13 +148,13 @@ struct TransactionalBucket {
   /// hash associated with the key. If there are no empty blacklist slots, fully
   /// blacklist the bucket.
   //////////////////////////////////////////////////////////////////////////////
-  CachedValue* blacklist(uint32_t hash, void const* key, size_t keySize);
+  CachedValue* blacklist(std::uint32_t hash, void const* key, std::size_t keySize);
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Checks whether a given hash is blacklisted. Requires state to be
   /// locked.
   //////////////////////////////////////////////////////////////////////////////
-  bool isBlacklisted(uint32_t hash) const;
+  bool isBlacklisted(std::uint32_t hash) const;
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Searches for the best candidate in the bucket to evict. Requires
@@ -181,7 +180,7 @@ struct TransactionalBucket {
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Updates the bucket's blacklist term. Requires state to be locked.
   //////////////////////////////////////////////////////////////////////////////
-  void updateBlacklistTerm(uint64_t term);
+  void updateBlacklistTerm(std::uint64_t term);
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Reinitializes a bucket to be completely empty and unlocked.
@@ -190,7 +189,7 @@ struct TransactionalBucket {
   void clear();
 
  private:
-  void moveSlot(size_t slot, bool moveToFront);
+  void moveSlot(std::size_t slot, bool moveToFront);
   bool haveOpenTransaction() const;
 };
 
diff --git a/arangod/Cache/TransactionalCache.cpp b/arangod/Cache/TransactionalCache.cpp
index 736117864023..867f192ddfa2 100644
--- a/arangod/Cache/TransactionalCache.cpp
+++ b/arangod/Cache/TransactionalCache.cpp
@@ -18,12 +18,17 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 ////////////////////////////////////////////////////////////////////////////////
 
+#include <atomic>
+#include <chrono>
+#include <cstdint>
+#include <list>
+
 #include "Cache/TransactionalCache.h"
 
-#include "Basics/Common.h"
+#include "Basics/SpinLocker.h"
 #include "Basics/voc-errors.h"
 #include "Cache/Cache.h"
 #include "Cache/CachedValue.h"
@@ -35,29 +40,25 @@
 #include "Cache/TransactionalBucket.h"
 #include "Logger/Logger.h"
 
-#include <stdint.h>
-#include <atomic>
-#include <chrono>
-#include <list>
+namespace arangodb::cache {
 
-using namespace arangodb;
-using namespace arangodb::cache;
+using SpinLocker = ::arangodb::basics::SpinLocker;
 
-Finding TransactionalCache::find(void const* key, uint32_t keySize) {
+Finding TransactionalCache::find(void const* key, std::uint32_t keySize) {
   TRI_ASSERT(key != nullptr);
   Finding result;
-  uint32_t hash = hashKey(key, keySize);
+  std::uint32_t hash = hashKey(key, keySize);
 
   Result status;
-  TransactionalBucket* bucket;
-  Table* source;
-  std::tie(status, bucket, source) = getBucket(hash, Cache::triesFast);
+  Table::BucketLocker guard;
+  std::tie(status, guard) = getBucket(hash, Cache::triesFast, false);
   if (status.fail()) {
     result.reportError(status);
     return result;
   }
 
-  result.set(bucket->find(hash, key, keySize));
+  TransactionalBucket& bucket = guard.bucket<TransactionalBucket>();
+  result.set(bucket.find(hash, key, keySize));
   if (result.found()) {
     recordStat(Stat::findHit);
   } else {
@@ -66,70 +67,73 @@ Finding TransactionalCache::find(void const* key, uint32_t keySize) {
     result.reportError(status);
   }
   recordStat(result.found() ? Stat::findHit : Stat::findMiss);
-  bucket->unlock();
 
   return result;
 }
 
 Result TransactionalCache::insert(CachedValue* value) {
   TRI_ASSERT(value != nullptr);
-  uint32_t hash = hashKey(value->key(), value->keySize());
+  bool maybeMigrate = false;
+  std::uint32_t hash = hashKey(value->key(), value->keySize());
 
   Result status;
-  TransactionalBucket* bucket;
   Table* source;
-  std::tie(status, bucket, source) = getBucket(hash, Cache::triesFast);
-  if (status.fail()) {
-    return status;
-  }
-
-  bool maybeMigrate = false;
-  bool allowed = !bucket->isBlacklisted(hash);
-  if (allowed) {
-    int64_t change = static_cast<int64_t>(value->size());
-    CachedValue* candidate = bucket->find(hash, value->key(), value->keySize());
-
-    if (candidate == nullptr && bucket->isFull()) {
-      candidate = bucket->evictionCandidate();
-      if (candidate == nullptr) {
-        allowed = false;
-        status.reset(TRI_ERROR_ARANGO_BUSY);
-      }
+  {
+    Table::BucketLocker guard;
+    std::tie(status, guard) = getBucket(hash, Cache::triesFast, false);
+    if (status.fail()) {
+      return status;
     }
 
+    TransactionalBucket& bucket = guard.bucket<TransactionalBucket>();
+    source = guard.source();
+    bool allowed = !bucket.isBlacklisted(hash);
     if (allowed) {
-      if (candidate != nullptr) {
-        change -= static_cast<int64_t>(candidate->size());
+      std::int64_t change = static_cast<std::int64_t>(value->size());
+      CachedValue* candidate = bucket.find(hash, value->key(), value->keySize());
+
+      if (candidate == nullptr && bucket.isFull()) {
+        candidate = bucket.evictionCandidate();
+        if (candidate == nullptr) {
+          allowed = false;
+          status.reset(TRI_ERROR_ARANGO_BUSY);
+        }
       }
 
-      _metadata.readLock();
-      allowed = _metadata.adjustUsageIfAllowed(change);
-      _metadata.readUnlock();
-
       if (allowed) {
-        bool eviction = false;
         if (candidate != nullptr) {
-          bucket->evict(candidate, true);
-          if (!candidate->sameKey(value->key(), value->keySize())) {
-            eviction = true;
-          }
-          freeValue(candidate);
+          change -= static_cast<std::int64_t>(candidate->size());
+        }
+
+        {
+          SpinLocker metaGuard(SpinLocker::Mode::Read, _metadata.lock());
+          allowed = _metadata.adjustUsageIfAllowed(change);
         }
-        bucket->insert(hash, value);
-        if (!eviction) {
-          maybeMigrate = source->slotFilled();
+
+        if (allowed) {
+          bool eviction = false;
+          if (candidate != nullptr) {
+            bucket.evict(candidate, true);
+            if (!candidate->sameKey(value->key(), value->keySize())) {
+              eviction = true;
+            }
+            freeValue(candidate);
+          }
+          bucket.insert(hash, value);
+          if (!eviction) {
+            maybeMigrate = source->slotFilled();
+          }
+          maybeMigrate |= reportInsert(eviction);
+        } else {
+          requestGrow();  // let function do the hard work
+          status.reset(TRI_ERROR_RESOURCE_LIMIT);
         }
-        maybeMigrate |= reportInsert(eviction);
-      } else {
-        requestGrow();  // let function do the hard work
-        status.reset(TRI_ERROR_RESOURCE_LIMIT);
       }
+    } else {
+      status.reset(TRI_ERROR_ARANGO_CONFLICT);
     }
-  } else {
-    status.reset(TRI_ERROR_ARANGO_CONFLICT);
   }
 
-  bucket->unlock();
   if (maybeMigrate) {
     requestMigrate(source->idealSize());  // let function do the hard work
   }
@@ -137,33 +141,37 @@ Result TransactionalCache::insert(CachedValue* value) {
   return status;
 }
 
-Result TransactionalCache::remove(void const* key, uint32_t keySize) {
+Result TransactionalCache::remove(void const* key, std::uint32_t keySize) {
   TRI_ASSERT(key != nullptr);
-  uint32_t hash = hashKey(key, keySize);
+  bool maybeMigrate = false;
+  std::uint32_t hash = hashKey(key, keySize);
 
   Result status;
-  TransactionalBucket* bucket;
   Table* source;
-  std::tie(status, bucket, source) = getBucket(hash, Cache::triesSlow);
-  if (status.fail()) {
-    return status;
-  }
+  {
+    Table::BucketLocker guard;
+    std::tie(status, guard) = getBucket(hash, Cache::triesSlow, false);
+    if (status.fail()) {
+      return status;
+    }
 
-  bool maybeMigrate = false;
-  CachedValue* candidate = bucket->remove(hash, key, keySize);
+    TransactionalBucket& bucket = guard.bucket<TransactionalBucket>();
+    source = guard.source();
+    CachedValue* candidate = bucket.remove(hash, key, keySize);
 
-  if (candidate != nullptr) {
-    int64_t change = -static_cast<int64_t>(candidate->size());
-    _metadata.readLock();
-    bool allowed = _metadata.adjustUsageIfAllowed(change);
-    TRI_ASSERT(allowed);
-    _metadata.readUnlock();
+    if (candidate != nullptr) {
+      std::int64_t change = -static_cast<std::int64_t>(candidate->size());
+      {
+        SpinLocker metaGuard(SpinLocker::Mode::Read, _metadata.lock());
+        bool allowed = _metadata.adjustUsageIfAllowed(change);
+        TRI_ASSERT(allowed);
+      }
 
-    freeValue(candidate);
-    maybeMigrate = source->slotEmptied();
+      freeValue(candidate);
+      maybeMigrate = source->slotEmptied();
+    }
   }
 
-  bucket->unlock();
   if (maybeMigrate) {
     requestMigrate(source->idealSize());
   }
@@ -171,34 +179,38 @@ Result TransactionalCache::remove(void const* key, uint32_t keySize) {
   return status;
 }
 
-Result TransactionalCache::blacklist(void const* key, uint32_t keySize) {
+Result TransactionalCache::blacklist(void const* key, std::uint32_t keySize) {
   TRI_ASSERT(key != nullptr);
-  uint32_t hash = hashKey(key, keySize);
+  bool maybeMigrate = false;
+  std::uint32_t hash = hashKey(key, keySize);
 
   Result status;
-  TransactionalBucket* bucket;
   Table* source;
-  std::tie(status, bucket, source) = getBucket(hash, Cache::triesSlow);
-  if (status.fail()) {
-    return status;
-  }
+  {
+    Table::BucketLocker guard;
+    std::tie(status, guard) = getBucket(hash, Cache::triesSlow, false);
+    if (status.fail()) {
+      return status;
+    }
 
-  bool maybeMigrate = false;
-  CachedValue* candidate = bucket->blacklist(hash, key, keySize);
+    TransactionalBucket& bucket = guard.bucket<TransactionalBucket>();
+    source = guard.source();
+    CachedValue* candidate = bucket.blacklist(hash, key, keySize);
 
-  if (candidate != nullptr) {
-    int64_t change = -static_cast<int64_t>(candidate->size());
+    if (candidate != nullptr) {
+      std::int64_t change = -static_cast<std::int64_t>(candidate->size());
 
-    _metadata.readLock();
-    bool allowed = _metadata.adjustUsageIfAllowed(change);
-    TRI_ASSERT(allowed);
-    _metadata.readUnlock();
+      {
+        SpinLocker metaGuard(SpinLocker::Mode::Read, _metadata.lock());
+        bool allowed = _metadata.adjustUsageIfAllowed(change);
+        TRI_ASSERT(allowed);
+      }
 
-    freeValue(candidate);
-    maybeMigrate = source->slotEmptied();
+      freeValue(candidate);
+      maybeMigrate = source->slotEmptied();
+    }
   }
 
-  bucket->unlock();
   if (maybeMigrate) {
     requestMigrate(source->idealSize());
   }
@@ -213,7 +225,7 @@ uint64_t TransactionalCache::allocationSize(bool enableWindowedStats) {
               : 0);
 }
 
-std::shared_ptr<Cache> TransactionalCache::create(Manager* manager, uint64_t id,
+std::shared_ptr<Cache> TransactionalCache::create(Manager* manager, std::uint64_t id,
                                                   Metadata&& metadata,
                                                   std::shared_ptr<Table> table,
                                                   bool enableWindowedStats) {
@@ -223,7 +235,7 @@ std::shared_ptr<Cache> TransactionalCache::create(Manager* manager, uint64_t id,
 }
 
 TransactionalCache::TransactionalCache(Cache::ConstructionGuard guard, Manager* manager,
-                                       uint64_t id, Metadata&& metadata,
+                                       std::uint64_t id, Metadata&& metadata,
                                        std::shared_ptr<Table> table, bool enableWindowedStats)
     : Cache(guard, manager, id, std::move(metadata), table, enableWindowedStats,
             TransactionalCache::bucketClearer, TransactionalBucket::slotsData) {}
@@ -238,32 +250,33 @@ TransactionalCache::~TransactionalCache() {
   }
 }
 
-uint64_t TransactionalCache::freeMemoryFrom(uint32_t hash) {
-  uint64_t reclaimed = 0;
+uint64_t TransactionalCache::freeMemoryFrom(std::uint32_t hash) {
+  std::uint64_t reclaimed = 0;
+  bool maybeMigrate = false;
+
   Result status;
-  TransactionalBucket* bucket;
-  Table* source;
-  std::tie(status, bucket, source) = getBucket(hash, Cache::triesFast, false);
-  if (status.fail()) {
-    return 0;
-  }
+  {
+    Table::BucketLocker guard;
+    std::tie(status, guard) = getBucket(hash, Cache::triesFast, false);
+    if (status.fail()) {
+      return 0;
+    }
 
-  bool maybeMigrate = false;
-  // evict LRU freeable value if exists
-  CachedValue* candidate = bucket->evictionCandidate();
-
-  if (candidate != nullptr) {
-    reclaimed = candidate->size();
-    bucket->evict(candidate);
-    freeValue(candidate);
-    maybeMigrate = source->slotEmptied();
-  }
+    TransactionalBucket& bucket = guard.bucket<TransactionalBucket>();
+    // evict LRU freeable value if exists
+    CachedValue* candidate = bucket.evictionCandidate();
 
-  bucket->unlock();
+    if (candidate != nullptr) {
+      reclaimed = candidate->size();
+      bucket.evict(candidate);
+      freeValue(candidate);
+      maybeMigrate = guard.source()->slotEmptied();
+    }
+  }
 
   cache::Table* table = _table.load(std::memory_order_relaxed);
   if (table) {
-    int32_t size = table->idealSize();
+    std::int32_t size = table->idealSize();
     if (maybeMigrate) {
       requestMigrate(size);
     }
@@ -275,152 +288,142 @@ uint64_t TransactionalCache::freeMemoryFrom(uint32_t hash) {
 void TransactionalCache::migrateBucket(void* sourcePtr,
                                        std::unique_ptr<Table::Subtable> targets,
                                        std::shared_ptr<Table> newTable) {
-  uint64_t term = _manager->_transactions.term();
+  std::uint64_t term = _manager->_transactions.term();
 
   // lock current bucket
-  auto source = reinterpret_cast<TransactionalBucket*>(sourcePtr);
-  source->lock(Cache::triesGuarantee);
-  term = std::max(term, source->_blacklistTerm);
-
-  // lock target bucket(s)
-  targets->applyToAllBuckets([&term](void* ptr) -> bool {
-    auto targetBucket = reinterpret_cast<TransactionalBucket*>(ptr);
-    bool locked = targetBucket->lock(Cache::triesGuarantee);
-    term = std::max(term, targetBucket->_blacklistTerm);
-    return locked;
-  });
-
-  // update all buckets to maximum term found (guaranteed at most the current)
-  source->updateBlacklistTerm(term);
-  targets->applyToAllBuckets([&term](void* ptr) -> bool {
-    auto targetBucket = reinterpret_cast<TransactionalBucket*>(ptr);
-    targetBucket->updateBlacklistTerm(term);
-    return true;
-  });
-  // now actually migrate any relevant blacklist terms
-  if (source->isFullyBlacklisted()) {
-    targets->applyToAllBuckets([](void* ptr) -> bool {
-      auto targetBucket = reinterpret_cast<TransactionalBucket*>(ptr);
-      if (!targetBucket->isFullyBlacklisted()) {
-        targetBucket->_state.toggleFlag(BucketState::Flag::blacklisted);
-      }
+  Table::BucketLocker sourceGuard(sourcePtr, _table.load(), Cache::triesGuarantee);
+  TransactionalBucket& source = sourceGuard.bucket<TransactionalBucket>();
+  term = std::max(term, source._blacklistTerm);
+
+  {
+    // lock target bucket(s)
+    std::vector<Table::BucketLocker> targetGuards = targets->lockAllBuckets();
+
+    targets->applyToAllBuckets<TransactionalBucket>([&term](TransactionalBucket& bucket) -> bool {
+      term = std::max(term, bucket._blacklistTerm);
+      return true;
+    });
+
+    // update all buckets to maximum term found (guaranteed at most the current)
+    source.updateBlacklistTerm(term);
+    targets->applyToAllBuckets<TransactionalBucket>([&term](TransactionalBucket& bucket) -> bool {
+      bucket.updateBlacklistTerm(term);
       return true;
     });
-  } else {
-    for (size_t j = 0; j < TransactionalBucket::slotsBlacklist; j++) {
-      uint32_t hash = source->_blacklistHashes[j];
-      if (hash != 0) {
-        auto targetBucket =
-            reinterpret_cast<TransactionalBucket*>(targets->fetchBucket(hash));
-        CachedValue* candidate = targetBucket->blacklist(hash, nullptr, 0);
-        if (candidate != nullptr) {
-          uint64_t size = candidate->size();
-          freeValue(candidate);
-          reclaimMemory(size);
-          newTable->slotEmptied();
-        }
-        source->_blacklistHashes[j] = 0;
-      }
-    }
-  }
 
-  // migrate actual values
-  for (size_t j = 0; j < TransactionalBucket::slotsData; j++) {
-    size_t k = TransactionalBucket::slotsData - (j + 1);
-    if (source->_cachedData[k] != nullptr) {
-      uint32_t hash = source->_cachedHashes[k];
-      CachedValue* value = source->_cachedData[k];
-
-      auto targetBucket =
-          reinterpret_cast<TransactionalBucket*>(targets->fetchBucket(hash));
-      if (targetBucket->isBlacklisted(hash)) {
-        uint64_t size = value->size();
-        freeValue(value);
-        reclaimMemory(size);
-      } else {
-        bool haveSpace = true;
-        if (targetBucket->isFull()) {
-          CachedValue* candidate = targetBucket->evictionCandidate();
+    // now actually migrate any relevant blacklist terms
+    if (source.isFullyBlacklisted()) {
+      targets->applyToAllBuckets<TransactionalBucket>([](TransactionalBucket& bucket) -> bool {
+        if (!bucket.isFullyBlacklisted()) {
+          bucket._state.toggleFlag(BucketState::Flag::blacklisted);
+        }
+        return true;
+      });
+    } else {
+      for (std::size_t j = 0; j < TransactionalBucket::slotsBlacklist; j++) {
+        std::uint32_t hash = source._blacklistHashes[j];
+        if (hash != 0) {
+          auto targetBucket =
+              reinterpret_cast<TransactionalBucket*>(targets->fetchBucket(hash));
+          CachedValue* candidate = targetBucket->blacklist(hash, nullptr, 0);
           if (candidate != nullptr) {
-            targetBucket->evict(candidate, true);
-            uint64_t size = candidate->size();
+            std::uint64_t size = candidate->size();
             freeValue(candidate);
             reclaimMemory(size);
             newTable->slotEmptied();
-          } else {
-            haveSpace = false;
           }
+          source._blacklistHashes[j] = 0;
         }
-        if (haveSpace) {
-          targetBucket->insert(hash, value);
-          newTable->slotFilled();
-        } else {
-          uint64_t size = value->size();
+      }
+    }
+
+    // migrate actual values
+    for (std::size_t j = 0; j < TransactionalBucket::slotsData; j++) {
+      std::size_t k = TransactionalBucket::slotsData - (j + 1);
+      if (source._cachedData[k] != nullptr) {
+        std::uint32_t hash = source._cachedHashes[k];
+        CachedValue* value = source._cachedData[k];
+
+        auto targetBucket =
+            reinterpret_cast<TransactionalBucket*>(targets->fetchBucket(hash));
+        if (targetBucket->isBlacklisted(hash)) {
+          std::uint64_t size = value->size();
           freeValue(value);
           reclaimMemory(size);
+        } else {
+          bool haveSpace = true;
+          if (targetBucket->isFull()) {
+            CachedValue* candidate = targetBucket->evictionCandidate();
+            if (candidate != nullptr) {
+              targetBucket->evict(candidate, true);
+              std::uint64_t size = candidate->size();
+              freeValue(candidate);
+              reclaimMemory(size);
+              newTable->slotEmptied();
+            } else {
+              haveSpace = false;
+            }
+          }
+          if (haveSpace) {
+            targetBucket->insert(hash, value);
+            newTable->slotFilled();
+          } else {
+            std::uint64_t size = value->size();
+            freeValue(value);
+            reclaimMemory(size);
+          }
         }
-      }
 
-      source->_cachedHashes[k] = 0;
-      source->_cachedData[k] = nullptr;
+        source._cachedHashes[k] = 0;
+        source._cachedData[k] = nullptr;
+      }
     }
   }
 
-  // unlock targets
-  targets->applyToAllBuckets([](void* ptr) -> bool {
-    auto bucket = reinterpret_cast<TransactionalBucket*>(ptr);
-    bucket->unlock();
-    return true;
-  });
-
   // finish up this bucket's migration
-  source->_state.toggleFlag(BucketState::Flag::migrated);
-  source->unlock();
+  source._state.toggleFlag(BucketState::Flag::migrated);
 }
 
-std::tuple<Result, TransactionalBucket*, Table*> TransactionalCache::getBucket(
-    uint32_t hash, uint64_t maxTries, bool singleOperation) {
+std::tuple<Result, Table::BucketLocker> TransactionalCache::getBucket(
+    std::uint32_t hash, std::uint64_t maxTries, bool singleOperation) {
   Result status;
-  TransactionalBucket* bucket = nullptr;
-  Table* source = nullptr;
+  Table::BucketLocker guard;
 
   Table* table = _table.load(std::memory_order_relaxed);
   if (isShutdown() || table == nullptr) {
     status.reset(TRI_ERROR_SHUTTING_DOWN);
-    return std::make_tuple(std::move(status), bucket, source);
+    return std::make_tuple(std::move(status), std::move(guard));
   }
 
   if (singleOperation) {
     _manager->reportAccess(_id);
   }
 
-  uint64_t term = _manager->_transactions.term();
-  auto pair = table->fetchAndLockBucket(hash, maxTries);
-  bucket = reinterpret_cast<TransactionalBucket*>(pair.first);
-  source = pair.second;
-  bool ok = (bucket != nullptr);
-  if (ok) {
-    bucket->updateBlacklistTerm(term);
+  std::uint64_t term = _manager->_transactions.term();
+  guard = table->fetchAndLockBucket(hash, maxTries);
+  if (guard.isLocked()) {
+    guard.bucket<TransactionalBucket>().updateBlacklistTerm(term);
   } else {
     status.reset(TRI_ERROR_LOCK_TIMEOUT);
   }
 
-  return std::make_tuple(std::move(status), bucket, source);
+  return std::make_tuple(std::move(status), std::move(guard));
 }
 
 Table::BucketClearer TransactionalCache::bucketClearer(Metadata* metadata) {
   return [metadata](void* ptr) -> void {
     auto bucket = reinterpret_cast<TransactionalBucket*>(ptr);
     bucket->lock(Cache::triesGuarantee);
-    for (size_t j = 0; j < TransactionalBucket::slotsData; j++) {
+    for (std::size_t j = 0; j < TransactionalBucket::slotsData; j++) {
       if (bucket->_cachedData[j] != nullptr) {
-        uint64_t size = bucket->_cachedData[j]->size();
+        std::uint64_t size = bucket->_cachedData[j]->size();
         freeValue(bucket->_cachedData[j]);
-        metadata->readLock();
+        SpinLocker metaGuard(SpinLocker::Mode::Read, metadata->lock());
         metadata->adjustUsageIfAllowed(-static_cast<int64_t>(size));
-        metadata->readUnlock();
       }
     }
     bucket->clear();
   };
 }
+
+}  // namespace arangodb::cache
diff --git a/arangod/Cache/TransactionalCache.h b/arangod/Cache/TransactionalCache.h
index 8e9407e8e56f..a37dcb2ad505 100644
--- a/arangod/Cache/TransactionalCache.h
+++ b/arangod/Cache/TransactionalCache.h
@@ -18,13 +18,17 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 ////////////////////////////////////////////////////////////////////////////////
 
 #ifndef ARANGODB_CACHE_TRANSACTIONAL_CACHE_H
 #define ARANGODB_CACHE_TRANSACTIONAL_CACHE_H
 
-#include "Basics/Common.h"
+#include <atomic>
+#include <chrono>
+#include <cstdint>
+#include <list>
+
 #include "Cache/Cache.h"
 #include "Cache/CachedValue.h"
 #include "Cache/Common.h"
@@ -36,11 +40,6 @@
 #include "Cache/Table.h"
 #include "Cache/TransactionalBucket.h"
 
-#include <stdint.h>
-#include <atomic>
-#include <chrono>
-#include <list>
-
 namespace arangodb {
 namespace cache {
 
@@ -62,7 +61,7 @@ namespace cache {
 class TransactionalCache final : public Cache {
  public:
   TransactionalCache(Cache::ConstructionGuard guard, Manager* manager,
-                     uint64_t id, Metadata&& metadata,
+                     std::uint64_t id, Metadata&& metadata,
                      std::shared_ptr<Table> table, bool enableWindowedStats);
   ~TransactionalCache();
 
@@ -78,7 +77,7 @@ class TransactionalCache final : public Cache {
   /// fashion. The Result contained in the return value should report an error
   /// code in this case. Should not block for long.
   //////////////////////////////////////////////////////////////////////////////
-  Finding find(void const* key, uint32_t keySize) override;
+  Finding find(void const* key, std::uint32_t keySize) override;
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Attempts to insert the given value.
@@ -100,7 +99,7 @@ class TransactionalCache final : public Cache {
   /// before quitting, so may block for longer than find or insert. Client may
   /// re-try.
   //////////////////////////////////////////////////////////////////////////////
-  Result remove(void const* key, uint32_t keySize) override;
+  Result remove(void const* key, std::uint32_t keySize) override;
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Attempts to blacklist the given key.
@@ -111,7 +110,7 @@ class TransactionalCache final : public Cache {
   /// before quitting, so may block for longer than find or insert. Client
   /// should re-try.
   //////////////////////////////////////////////////////////////////////////////
-  Result blacklist(void const* key, uint32_t keySize) override;
+  Result blacklist(void const* key, std::uint32_t keySize) override;
 
  private:
   // friend class manager and tasks
@@ -121,18 +120,18 @@ class TransactionalCache final : public Cache {
 
  private:
   static uint64_t allocationSize(bool enableWindowedStats);
-  static std::shared_ptr<Cache> create(Manager* manager, uint64_t id, Metadata&& metadata,
-                                       std::shared_ptr<Table> table,
+  static std::shared_ptr<Cache> create(Manager* manager, std::uint64_t id,
+                                       Metadata&& metadata, std::shared_ptr<Table> table,
                                        bool enableWindowedStats);
 
-  virtual uint64_t freeMemoryFrom(uint32_t hash) override;
+  virtual uint64_t freeMemoryFrom(std::uint32_t hash) override;
   virtual void migrateBucket(void* sourcePtr, std::unique_ptr<Table::Subtable> targets,
                              std::shared_ptr<Table> newTable) override;
 
   // helpers
-  std::tuple<Result, TransactionalBucket*, Table*> getBucket(uint32_t hash, uint64_t maxTries,
-                                                             bool singleOperation = true);
-  uint32_t getIndex(uint32_t hash, bool useAuxiliary) const;
+  std::tuple<Result, Table::BucketLocker> getBucket(std::uint32_t hash, std::uint64_t maxTries,
+                                                    bool singleOperation = true);
+  std::uint32_t getIndex(uint32_t hash, bool useAuxiliary) const;
 
   static Table::BucketClearer bucketClearer(Metadata* metadata);
 };
diff --git a/arangod/Cluster/ClusterEdgeCursor.cpp b/arangod/Cluster/ClusterEdgeCursor.cpp
index 01717f43ea8a..1371a3e7f9c8 100644
--- a/arangod/Cluster/ClusterEdgeCursor.cpp
+++ b/arangod/Cluster/ClusterEdgeCursor.cpp
@@ -23,6 +23,7 @@
 
 #include "ClusterEdgeCursor.h"
 
+#include "Basics/Result.h"
 #include "Cluster/ClusterMethods.h"
 #include "Cluster/ClusterTraverser.h"
 #include "Graph/ClusterTraverserCache.h"
@@ -37,42 +38,17 @@ using namespace arangodb;
 using namespace arangodb::graph;
 using namespace arangodb::traverser;
 
-// Traverser variant
-ClusterEdgeCursor::ClusterEdgeCursor(arangodb::velocypack::StringRef vertexId, uint64_t depth,
-                                     graph::BaseOptions* opts)
+ClusterEdgeCursor::ClusterEdgeCursor(graph::BaseOptions const* opts) 
     : _position(0),
-      _resolver(opts->trx()->resolver()),
       _opts(opts),
       _cache(static_cast<ClusterTraverserCache*>(opts->cache())),
       _httpRequests(0) {
   TRI_ASSERT(_cache != nullptr);
-  auto trx = _opts->trx();
-  transaction::BuilderLeaser leased(trx);
-  transaction::BuilderLeaser b(trx);
-
-  b->add(VPackValuePair(vertexId.data(), vertexId.length(), VPackValueType::String));
-  fetchEdgesFromEngines(*trx, _cache->engines(), b->slice(), depth,
-                        _cache->cache(), _edgeList, _cache->datalake(),
-                        _cache->filteredDocuments(), _cache->insertedDocuments());
-  _httpRequests += _cache->engines()->size();
-}
-
-// ShortestPath variant
-ClusterEdgeCursor::ClusterEdgeCursor(arangodb::velocypack::StringRef vertexId, bool backward, graph::BaseOptions* opts)
-    : _position(0),
-      _resolver(opts->trx()->resolver()),
-      _opts(opts),
-      _cache(static_cast<ClusterTraverserCache*>(opts->cache())),
-      _httpRequests(0) {
-  TRI_ASSERT(_cache != nullptr);
-  auto trx = _opts->trx();
-  transaction::BuilderLeaser leased(trx);
-  transaction::BuilderLeaser b(trx);
 
-  b->add(VPackValuePair(vertexId.data(), vertexId.length(), VPackValueType::String));
-  fetchEdgesFromEngines(*trx, _cache->engines(), b->slice(), backward, _cache->cache(),
-                        _edgeList, _cache->datalake(), _cache->insertedDocuments());
-  _httpRequests += _cache->engines()->size();
+  if (_cache == nullptr) {
+    THROW_ARANGO_EXCEPTION_MESSAGE(
+        TRI_ERROR_INTERNAL, "no cache present for cluster edge cursor");
+  }
 }
 
 bool ClusterEdgeCursor::next(EdgeCursor::Callback const& callback) {
@@ -90,3 +66,45 @@ void ClusterEdgeCursor::readAll(EdgeCursor::Callback const& callback) {
     callback(EdgeDocumentToken(edge), edge, _position);
   }
 }
+  
+ClusterTraverserEdgeCursor::ClusterTraverserEdgeCursor(graph::BaseOptions const* opts)
+    : ClusterEdgeCursor(opts) {}
+
+void ClusterTraverserEdgeCursor::rearm(arangodb::velocypack::StringRef vertexId, uint64_t depth) {
+  _edgeList.clear();
+  _position = 0;
+
+  auto trx = _opts->trx();
+  transaction::BuilderLeaser leased(trx);
+  transaction::BuilderLeaser b(trx);
+
+  b->add(VPackValuePair(vertexId.data(), vertexId.length(), VPackValueType::String));
+  Result res = fetchEdgesFromEngines(*trx, _cache->engines(), b->slice(), depth,
+                                     _cache->cache(), _edgeList, _cache->datalake(),
+                                     _cache->filteredDocuments(), _cache->insertedDocuments());
+  if (res.fail()) {
+    THROW_ARANGO_EXCEPTION(res);
+  }
+  _httpRequests += _cache->engines()->size();
+}
+
+ClusterShortestPathEdgeCursor::ClusterShortestPathEdgeCursor(graph::BaseOptions const* opts, bool backward)
+    : ClusterEdgeCursor(opts),
+      _backward(backward) {}
+
+void ClusterShortestPathEdgeCursor::rearm(arangodb::velocypack::StringRef vertexId, uint64_t /*depth*/) {
+  _edgeList.clear();
+  _position = 0;
+
+  auto trx = _opts->trx();
+  transaction::BuilderLeaser leased(trx);
+  transaction::BuilderLeaser b(trx);
+
+  b->add(VPackValuePair(vertexId.data(), vertexId.length(), VPackValueType::String));
+  Result res = fetchEdgesFromEngines(*trx, _cache->engines(), b->slice(), _backward, _cache->cache(),
+                                     _edgeList, _cache->datalake(), _cache->insertedDocuments());
+  if (res.fail()) {
+    THROW_ARANGO_EXCEPTION(res);
+  }
+  _httpRequests += _cache->engines()->size();
+}
diff --git a/arangod/Cluster/ClusterEdgeCursor.h b/arangod/Cluster/ClusterEdgeCursor.h
index 2f1219df1580..a89b069d20f2 100644
--- a/arangod/Cluster/ClusterEdgeCursor.h
+++ b/arangod/Cluster/ClusterEdgeCursor.h
@@ -28,7 +28,6 @@
 #include "Graph/TraverserOptions.h"
 
 namespace arangodb {
-class CollectionNameResolver;
 
 namespace graph {
 struct BaseOptions;
@@ -41,10 +40,7 @@ class Traverser;
 
 class ClusterEdgeCursor : public graph::EdgeCursor {
  public:
-  // Traverser Variant
-  ClusterEdgeCursor(arangodb::velocypack::StringRef vid, uint64_t, graph::BaseOptions*);
-  // ShortestPath Variant
-  ClusterEdgeCursor(arangodb::velocypack::StringRef vid, bool isBackward, graph::BaseOptions*);
+  explicit ClusterEdgeCursor(graph::BaseOptions const* opts);
 
   ~ClusterEdgeCursor() = default;
 
@@ -55,15 +51,34 @@ class ClusterEdgeCursor : public graph::EdgeCursor {
   /// @brief number of HTTP requests performed.
   size_t httpRequests() const override { return _httpRequests; }
 
- private:
+ protected:
   std::vector<arangodb::velocypack::Slice> _edgeList;
 
   size_t _position;
-  CollectionNameResolver const* _resolver;
-  arangodb::graph::BaseOptions* _opts;
+  arangodb::graph::BaseOptions const* _opts;
   arangodb::graph::ClusterTraverserCache* _cache;
   size_t _httpRequests;
 };
+
+class ClusterTraverserEdgeCursor final : public ClusterEdgeCursor {
+ public:
+
+  explicit ClusterTraverserEdgeCursor(graph::BaseOptions const* opts);
+  
+  void rearm(arangodb::velocypack::StringRef vid, uint64_t depth) override;
+};
+
+class ClusterShortestPathEdgeCursor final : public ClusterEdgeCursor {
+ public:
+
+  explicit ClusterShortestPathEdgeCursor(graph::BaseOptions const* opts, bool backward);
+  
+  void rearm(arangodb::velocypack::StringRef vid, uint64_t depth) override;
+
+ private:
+  bool const _backward;
+};
+
 }  // namespace traverser
 }  // namespace arangodb
 
diff --git a/arangod/Cluster/ClusterInfo.cpp b/arangod/Cluster/ClusterInfo.cpp
index 0e89543dbf54..96337009d84f 100644
--- a/arangod/Cluster/ClusterInfo.cpp
+++ b/arangod/Cluster/ClusterInfo.cpp
@@ -25,6 +25,7 @@
 
 #include "ClusterInfo.h"
 
+#include "Agency/TimeString.h"
 #include "ApplicationFeatures/ApplicationServer.h"
 #include "Basics/ConditionLocker.h"
 #include "Basics/Exceptions.h"
@@ -2625,7 +2626,7 @@ Result ClusterInfo::setCollectionPropertiesCoordinator(std::string const& databa
   temp.add(StaticStrings::ReplicationFactor, VPackValue(info->replicationFactor()));
   temp.add(StaticStrings::MinReplicationFactor, VPackValue(info->writeConcern())); // deprecated in 3.6
   temp.add(StaticStrings::WriteConcern, VPackValue(info->writeConcern()));
-  temp.add(VPackValue(StaticStrings::Validators));
+  temp.add(VPackValue(StaticStrings::Validation));
   info->validatorsToVelocyPack(temp);
   info->getPhysical()->getPropertiesVPack(temp);
   temp.close();
@@ -4432,6 +4433,7 @@ arangodb::Result ClusterInfo::agencyReplan(VPackSlice const plan) {
 
 std::string const backupKey = "/arango/Target/HotBackup/Create/";
 std::string const maintenanceKey = "/arango/Supervision/Maintenance";
+std::string const supervisionMode = "/arango/Supervision/State/Mode";
 std::string const toDoKey = "/arango/Target/ToDo";
 std::string const pendingKey = "/arango/Target/Pending";
 std::string const writeURL = "_api/agency/write";
@@ -4449,6 +4451,8 @@ arangodb::Result ClusterInfo::agencyHotBackupLock(std::string const& backupId,
   LOG_TOPIC("e74e5", DEBUG, Logger::BACKUP)
       << "initiating agency lock for hot backup " << backupId;
 
+  auto const timeouti = static_cast<long>(std::ceil(timeout));
+
   VPackBuilder builder;
   {
     VPackArrayBuilder trxs(&builder);
@@ -4458,8 +4462,16 @@ arangodb::Result ClusterInfo::agencyHotBackupLock(std::string const& backupId,
       // Operations
       {
         VPackObjectBuilder o(&builder);
-        builder.add(backupKey + backupId, VPackValue(0));  // Hot backup key
-        builder.add(maintenanceKey, VPackValue("on"));  // Turn off supervision
+        builder.add(                                      // Backup lock
+          backupKey + backupId,
+          VPackValue(
+            timepointToString(
+              std::chrono::system_clock::now() + std::chrono::seconds(timeouti))));
+        builder.add(                                      // Turn off supervision
+          maintenanceKey,
+          VPackValue(
+            timepointToString(
+              std::chrono::system_clock::now() + std::chrono::seconds(timeouti))));
       }
 
       // Preconditions
@@ -4480,10 +4492,10 @@ arangodb::Result ClusterInfo::agencyHotBackupLock(std::string const& backupId,
           VPackObjectBuilder oe(&builder);
           builder.add("old", VPackSlice::emptyObjectSlice());
         }
-        builder.add(VPackValue(maintenanceKey));  // Supervision on
+        builder.add(VPackValue(supervisionMode));  // Supervision on
         {
           VPackObjectBuilder old(&builder);
-          builder.add("oldEmpty", VPackValue(true));
+          builder.add("old", VPackValue("Normal"));
         }
       }
     }
@@ -4494,8 +4506,16 @@ arangodb::Result ClusterInfo::agencyHotBackupLock(std::string const& backupId,
       // Operations
       {
         VPackObjectBuilder o(&builder);
-        builder.add(backupKey + backupId, VPackValue(0));  // Hot backup key
-        builder.add(maintenanceKey, VPackValue("on"));  // Turn off maintenance
+        builder.add(                                      // Backup lock
+          backupKey + backupId,
+          VPackValue(
+            timepointToString(
+              std::chrono::system_clock::now() + std::chrono::seconds(timeouti))));
+        builder.add(                                      // Turn off supervision
+          maintenanceKey,
+          VPackValue(
+            timepointToString(
+              std::chrono::system_clock::now() + std::chrono::seconds(timeouti))));
       }
 
       // Prevonditions
@@ -4516,10 +4536,10 @@ arangodb::Result ClusterInfo::agencyHotBackupLock(std::string const& backupId,
           VPackObjectBuilder oe(&builder);
           builder.add("old", VPackSlice::emptyObjectSlice());
         }
-        builder.add(VPackValue(maintenanceKey));  // Supervision off
+        builder.add(VPackValue(supervisionMode));  // Supervision off
         {
           VPackObjectBuilder old(&builder);
-          builder.add("old", VPackValue("on"));
+          builder.add("old", VPackValue("Maintenance"));
         }
       }
     }
@@ -4668,9 +4688,13 @@ arangodb::Result ClusterInfo::agencyHotBackupUnlock(std::string const& backupId,
         "invalid agency result while releasing backup lock");
   }
 
+  if (supervisionOff) {
+    return arangodb::Result();
+  }
+
   double wait = 0.1;
   while (!_server.isStopping() && std::chrono::steady_clock::now() < endTime) {
-    result = _agency.getValues("/arango/Supervision/State/Mode");
+    result = _agency.getValues("Supervision/State/Mode");
     if (result.successful()) {
       if (!result.slice().isArray() || result.slice().length() != 1 ||
           !result.slice()[0].hasKey(modepv) || !result.slice()[0].get(modepv).isString()) {
diff --git a/arangod/Cluster/ClusterMethods.cpp b/arangod/Cluster/ClusterMethods.cpp
index d3901d85432b..0254e7fd1939 100644
--- a/arangod/Cluster/ClusterMethods.cpp
+++ b/arangod/Cluster/ClusterMethods.cpp
@@ -1794,13 +1794,13 @@ Future<OperationResult> getDocumentOnCoordinator(transaction::Methods& trx,
 ///        only and do not run out of scope unless
 ///        the lake is cleared.
 
-int fetchEdgesFromEngines(transaction::Methods& trx,
-                          std::unordered_map<ServerID, traverser::TraverserEngineID> const* engines,
-                          VPackSlice const vertexId, size_t depth,
-                          std::unordered_map<arangodb::velocypack::StringRef, VPackSlice>& cache,
-                          std::vector<VPackSlice>& result,
-                          std::vector<std::shared_ptr<VPackBufferUInt8>>& datalake,
-                          size_t& filtered, size_t& read) {
+Result fetchEdgesFromEngines(transaction::Methods& trx,
+                             std::unordered_map<ServerID, traverser::TraverserEngineID> const* engines,
+                             VPackSlice const vertexId, size_t depth,
+                             std::unordered_map<arangodb::velocypack::StringRef, VPackSlice>& cache,
+                             std::vector<VPackSlice>& result,
+                             std::vector<std::shared_ptr<VPackBufferUInt8>>& datalake,
+                             size_t& filtered, size_t& read) {
   // TODO map id => ServerID if possible
   // And go fast-path
 
@@ -1837,16 +1837,21 @@ int fetchEdgesFromEngines(transaction::Methods& trx,
     if (r.fail()) {
       return network::fuerteToArangoErrorCode(r);
     }
-
+    
     auto payload = r.response->stealPayload();
     VPackSlice resSlice(payload->data());
     if (!resSlice.isObject()) {
       // Response has invalid format
       return TRI_ERROR_HTTP_CORRUPTED_JSON;
     }
+    
+    Result res = network::resultFromBody(resSlice, TRI_ERROR_NO_ERROR);
+    if (res.fail()) {
+      return res;
+    }
     filtered += Helper::getNumericValue<size_t>(resSlice, "filtered", 0);
     read += Helper::getNumericValue<size_t>(resSlice, "readIndex", 0);
-
+          
     VPackSlice edges = resSlice.get("edges");
     bool allCached = true;
 
@@ -1872,7 +1877,7 @@ int fetchEdgesFromEngines(transaction::Methods& trx,
       datalake.emplace_back(std::move(payload));
     }
   }
-  return TRI_ERROR_NO_ERROR;
+  return {};
 }
 
 /// @brief fetch edges from TraverserEngines
@@ -1886,13 +1891,12 @@ int fetchEdgesFromEngines(transaction::Methods& trx,
 ///        only and do not run out of scope unless
 ///        the lake is cleared.
 
-int fetchEdgesFromEngines(
-    transaction::Methods& trx,
-    std::unordered_map<ServerID, traverser::TraverserEngineID> const* engines,
-    VPackSlice const vertexId, bool backward,
-    std::unordered_map<arangodb::velocypack::StringRef, VPackSlice>& cache,
-    std::vector<VPackSlice>& result,
-    std::vector<std::shared_ptr<VPackBufferUInt8>>& datalake, size_t& read) {
+Result fetchEdgesFromEngines(transaction::Methods& trx,
+                             std::unordered_map<ServerID, traverser::TraverserEngineID> const* engines,
+                             VPackSlice const vertexId, bool backward,
+                             std::unordered_map<arangodb::velocypack::StringRef, VPackSlice>& cache,
+                             std::vector<VPackSlice>& result,
+                             std::vector<std::shared_ptr<VPackBufferUInt8>>& datalake, size_t& read) {
   // TODO map id => ServerID if possible
   // And go fast-path
 
@@ -1929,13 +1933,17 @@ int fetchEdgesFromEngines(
     if (r.fail()) {
       return network::fuerteToArangoErrorCode(r);
     }
-
+    
     auto payload = r.response->stealPayload();
     VPackSlice resSlice(payload->data());
     if (!resSlice.isObject()) {
       // Response has invalid format
       return TRI_ERROR_HTTP_CORRUPTED_JSON;
     }
+    Result res = network::resultFromBody(resSlice, TRI_ERROR_NO_ERROR);
+    if (res.fail()) {
+      return res;
+    }
     read += Helper::getNumericValue<size_t>(resSlice, "readIndex", 0);
 
     bool allCached = true;
@@ -1962,7 +1970,7 @@ int fetchEdgesFromEngines(
       datalake.emplace_back(std::move(payload));
     }
   }
-  return TRI_ERROR_NO_ERROR;
+  return {};
 }
 
 /// @brief fetch vertices from TraverserEngines
diff --git a/arangod/Cluster/ClusterMethods.h b/arangod/Cluster/ClusterMethods.h
index 1c12f3b8422f..4d68597ea538 100644
--- a/arangod/Cluster/ClusterMethods.h
+++ b/arangod/Cluster/ClusterMethods.h
@@ -149,13 +149,12 @@ futures::Future<OperationResult> getDocumentOnCoordinator(transaction::Methods&
 ///        the lake is cleared.
 ///        TraversalVariant
 
-int fetchEdgesFromEngines(
-    transaction::Methods& trx,
-    std::unordered_map<ServerID, traverser::TraverserEngineID> const*,
-    arangodb::velocypack::Slice vertexId, size_t depth,
-    std::unordered_map<arangodb::velocypack::StringRef, arangodb::velocypack::Slice>&,
-    std::vector<arangodb::velocypack::Slice>&,
-    std::vector<std::shared_ptr<arangodb::velocypack::UInt8Buffer>>&, size_t&, size_t&);
+Result fetchEdgesFromEngines(transaction::Methods& trx,
+                             std::unordered_map<ServerID, traverser::TraverserEngineID> const*,
+                             arangodb::velocypack::Slice vertexId, size_t depth,
+                             std::unordered_map<arangodb::velocypack::StringRef, arangodb::velocypack::Slice>&,
+                             std::vector<arangodb::velocypack::Slice>&,
+                             std::vector<std::shared_ptr<arangodb::velocypack::UInt8Buffer>>&, size_t&, size_t&);
 
 /// @brief fetch edges from TraverserEngines
 ///        Contacts all TraverserEngines placed
@@ -169,14 +168,14 @@ int fetchEdgesFromEngines(
 ///        the lake is cleared.
 ///        ShortestPathVariant
 
-int fetchEdgesFromEngines(
-    transaction::Methods& trx,
-    std::unordered_map<ServerID, traverser::TraverserEngineID> const* engines,
-    arangodb::velocypack::Slice vertexId, bool backward,
-    std::unordered_map<arangodb::velocypack::StringRef, arangodb::velocypack::Slice>& cache,
-    std::vector<arangodb::velocypack::Slice>& result,
-    std::vector<std::shared_ptr<arangodb::velocypack::UInt8Buffer>>& datalake,
-    size_t& read);
+Result fetchEdgesFromEngines(
+            transaction::Methods& trx,
+            std::unordered_map<ServerID, traverser::TraverserEngineID> const* engines,
+            arangodb::velocypack::Slice vertexId, bool backward,
+            std::unordered_map<arangodb::velocypack::StringRef, arangodb::velocypack::Slice>& cache,
+            std::vector<arangodb::velocypack::Slice>& result,
+            std::vector<std::shared_ptr<arangodb::velocypack::UInt8Buffer>>& datalake,
+            size_t& read);
 
 /// @brief fetch vertices from TraverserEngines
 ///        Contacts all TraverserEngines placed
diff --git a/arangod/Cluster/ClusterTraverser.cpp b/arangod/Cluster/ClusterTraverser.cpp
index 68c69ddc8deb..02f32582d979 100644
--- a/arangod/Cluster/ClusterTraverser.cpp
+++ b/arangod/Cluster/ClusterTraverser.cpp
@@ -32,6 +32,8 @@
 #include "Cluster/ClusterMethods.h"
 #include "Graph/BreadthFirstEnumerator.h"
 #include "Graph/ClusterTraverserCache.h"
+#include "Graph/EdgeCursor.h"
+#include "Graph/PathEnumerator.h"
 #include "Graph/TraverserCache.h"
 #include "Logger/LogMacros.h"
 #include "Network/Methods.h"
diff --git a/arangod/Cluster/Maintenance.cpp b/arangod/Cluster/Maintenance.cpp
index 18a2c80d4cde..4665430372a2 100644
--- a/arangod/Cluster/Maintenance.cpp
+++ b/arangod/Cluster/Maintenance.cpp
@@ -54,7 +54,7 @@ using namespace arangodb::maintenance;
 using namespace arangodb::methods;
 using namespace arangodb::basics::StringUtils;
 
-static std::vector<std::string> const cmp{JOURNAL_SIZE, WAIT_FOR_SYNC, DO_COMPACT, VALIDATORS, INDEX_BUCKETS, CACHE_ENABLED};
+static std::vector<std::string> const cmp{JOURNAL_SIZE, WAIT_FOR_SYNC, DO_COMPACT, VALIDATION, CACHE_ENABLED};
 
 static VPackValue const VP_DELETE("delete");
 static VPackValue const VP_SET("set");
@@ -1221,7 +1221,7 @@ arangodb::Result arangodb::maintenance::phaseTwo(VPackSlice const& plan,
       }
     }
 
-    // maintenace actions
+    // maintenance actions
     report.add(VPackValue("actions"));
     {
       VPackObjectBuilder agency(&report);
diff --git a/arangod/Cluster/MaintenanceFeature.h b/arangod/Cluster/MaintenanceFeature.h
index a6ad3fe64f62..6a6ebc521df5 100644
--- a/arangod/Cluster/MaintenanceFeature.h
+++ b/arangod/Cluster/MaintenanceFeature.h
@@ -280,7 +280,7 @@ class MaintenanceFeature : public application_features::ApplicationFeature {
   /**
    * @brief copy all error maps (shards, indexes and databases) for Maintenance
    *
-   * @param  errors  errors struct into which all maintenace feature error are copied
+   * @param  errors  errors struct into which all maintenance feature error are copied
    * @return         success
    */
   arangodb::Result copyAllErrors(errors_t& errors) const;
diff --git a/arangod/Cluster/MaintenanceStrings.h b/arangod/Cluster/MaintenanceStrings.h
index f0ef9e80a056..b2dc9268a0a0 100644
--- a/arangod/Cluster/MaintenanceStrings.h
+++ b/arangod/Cluster/MaintenanceStrings.h
@@ -69,7 +69,7 @@ constexpr char const* TAKEOVER_SHARD_LEADERSHIP = "TakeoverShardLeadership";
 constexpr char const* THE_LEADER = "theLeader";
 constexpr char const* UNDERSCORE = "_";
 constexpr char const* UPDATE_COLLECTION = "UpdateCollection";
-constexpr char const* VALIDATORS = "validators";
+constexpr char const* VALIDATION = "validation";
 constexpr char const* WAIT_FOR_SYNC = "waitForSync";
 constexpr char const* OLD_CURRENT_COUNTER = "oldCurrentCounter";
 
diff --git a/arangod/Cluster/TraverserEngine.cpp b/arangod/Cluster/TraverserEngine.cpp
index b1f452612cd6..0b7f006e289c 100644
--- a/arangod/Cluster/TraverserEngine.cpp
+++ b/arangod/Cluster/TraverserEngine.cpp
@@ -107,6 +107,7 @@ BaseEngine::BaseEngine(TRI_vocbase_t& vocbase,
   }
 
   // Add all Edge shards to the transaction
+  TRI_ASSERT(edgesSlice.isArray());
   for (VPackSlice const shardList : VPackArrayIterator(edgesSlice)) {
     TRI_ASSERT(shardList.isArray());
     for (VPackSlice const shard : VPackArrayIterator(shardList)) {
@@ -116,8 +117,10 @@ BaseEngine::BaseEngine(TRI_vocbase_t& vocbase,
   }
 
   // Add all Vertex shards to the transaction
+  TRI_ASSERT(vertexSlice.isObject());
   for (auto const& collection : VPackObjectIterator(vertexSlice)) {
     std::vector<std::string> shards;
+    TRI_ASSERT(collection.value.isArray());
     for (VPackSlice const shard : VPackArrayIterator(collection.value)) {
       TRI_ASSERT(shard.isString());
       std::string name = shard.copyString();
@@ -288,6 +291,15 @@ BaseTraverserEngine::BaseTraverserEngine(TRI_vocbase_t& vocbase,
 
 BaseTraverserEngine::~BaseTraverserEngine() = default;
 
+graph::EdgeCursor* BaseTraverserEngine::getCursor(arangodb::velocypack::StringRef nextVertex, uint64_t currentDepth) {
+  if (currentDepth >= _cursors.size()) {
+    _cursors.emplace_back(_opts->buildCursor(currentDepth));
+  }
+  graph::EdgeCursor* cursor = _cursors.at(currentDepth).get();
+  cursor->rearm(nextVertex, currentDepth);
+  return cursor;
+}
+
 void BaseTraverserEngine::getEdges(VPackSlice vertex, size_t depth, VPackBuilder& builder) {
   // We just hope someone has locked the shards properly. We have no clue...
   // Thanks locking
@@ -295,10 +307,9 @@ void BaseTraverserEngine::getEdges(VPackSlice vertex, size_t depth, VPackBuilder
   auto outputVertex = [this, depth](VPackBuilder& builder, VPackSlice vertex) {
     TRI_ASSERT(vertex.isString());
 
-    std::unique_ptr<arangodb::graph::EdgeCursor> edgeCursor(
-        _opts->nextCursor(arangodb::velocypack::StringRef(vertex), depth));
-      
-    edgeCursor->readAll([&](EdgeDocumentToken&& eid, VPackSlice edge, size_t cursorId) {
+    graph::EdgeCursor* cursor = getCursor(arangodb::velocypack::StringRef(vertex), depth);
+
+    cursor->readAll([&](EdgeDocumentToken&& eid, VPackSlice edge, size_t cursorId) {
       if (edge.isString()) {
         edge = _opts->cache()->lookupToken(eid);
       }
@@ -313,8 +324,7 @@ void BaseTraverserEngine::getEdges(VPackSlice vertex, size_t depth, VPackBuilder
 
   TRI_ASSERT(vertex.isString() || vertex.isArray());
   builder.openObject();
-  builder.add(VPackValue("edges"));
-  builder.openArray();
+  builder.add("edges", VPackValue(VPackValueType::Array));
   if (vertex.isArray()) {
     for (VPackSlice v : VPackArrayIterator(vertex)) {
       outputVertex(builder, v);
@@ -409,6 +419,7 @@ ShortestPathEngine::ShortestPathEngine(TRI_vocbase_t& vocbase,
                                        std::shared_ptr<transaction::Context> const& ctx,
                                        arangodb::velocypack::Slice info, bool needToLock)
     : BaseEngine(vocbase, ctx, info, needToLock) {
+
   VPackSlice optsSlice = info.get(OPTIONS);
   if (optsSlice.isNone() || !optsSlice.isObject()) {
     THROW_ARANGO_EXCEPTION_MESSAGE(TRI_ERROR_BAD_PARAMETER,
@@ -427,6 +438,9 @@ ShortestPathEngine::ShortestPathEngine(TRI_vocbase_t& vocbase,
   _opts.reset(new ShortestPathOptions(_query, optsSlice, edgesSlice));
   // We create the cache, but we do not need any engines.
   _opts->activateCache(false, nullptr);
+  
+  _forwardCursor = _opts->buildCursor(false);
+  _backwardCursor = _opts->buildCursor(true);
 }
 
 ShortestPathEngine::~ShortestPathEngine() = default;
@@ -436,52 +450,18 @@ void ShortestPathEngine::getEdges(VPackSlice vertex, bool backward, VPackBuilder
   // Thanks locking
   TRI_ASSERT(vertex.isString() || vertex.isArray());
 
-  std::unique_ptr<arangodb::graph::EdgeCursor> edgeCursor;
-
   builder.openObject();
-  builder.add(VPackValue("edges"));
-  builder.openArray();
+  builder.add("edges", VPackValue(VPackValueType::Array));
   if (vertex.isArray()) {
     for (VPackSlice v : VPackArrayIterator(vertex)) {
-      if (!vertex.isString()) {
+      if (!v.isString()) {
         continue;
       }
-      TRI_ASSERT(v.isString());
-      // result.clear();
-      arangodb::velocypack::StringRef vertexId(v);
-      if (backward) {
-        edgeCursor.reset(_opts->nextReverseCursor(vertexId));
-      } else {
-        edgeCursor.reset(_opts->nextCursor(vertexId));
-      }
-
-      edgeCursor->readAll([&](EdgeDocumentToken&& eid, VPackSlice edge, size_t cursorId) {
-        if (edge.isString()) {
-          edge = _opts->cache()->lookupToken(eid);
-        }
-        if (edge.isNull()) {
-          return;
-        }
-        builder.add(edge);
-      });
+      addEdgeData(builder, backward, arangodb::velocypack::StringRef(v));
       // Result now contains all valid edges, probably multiples.
     }
   } else if (vertex.isString()) {
-    arangodb::velocypack::StringRef vertexId(vertex);
-    if (backward) {
-      edgeCursor.reset(_opts->nextReverseCursor(vertexId));
-    } else {
-      edgeCursor.reset(_opts->nextCursor(vertexId));
-    }
-    edgeCursor->readAll([&](EdgeDocumentToken&& eid, VPackSlice edge, size_t cursorId) {
-      if (edge.isString()) {
-        edge = _opts->cache()->lookupToken(eid);
-      }
-      if (edge.isNull()) {
-        return;
-      }
-      builder.add(edge);
-    });
+    addEdgeData(builder, backward, arangodb::velocypack::StringRef(vertex));
     // Result now contains all valid edges, probably multiples.
   } else {
     THROW_ARANGO_EXCEPTION(TRI_ERROR_BAD_PARAMETER);
@@ -492,6 +472,21 @@ void ShortestPathEngine::getEdges(VPackSlice vertex, bool backward, VPackBuilder
   builder.close();
 }
 
+void ShortestPathEngine::addEdgeData(VPackBuilder& builder, bool backward, arangodb::velocypack::StringRef v) {
+  graph::EdgeCursor* cursor = backward ? _backwardCursor.get() : _forwardCursor.get();
+  cursor->rearm(v, 0);
+
+  cursor->readAll([&](EdgeDocumentToken&& eid, VPackSlice edge, size_t cursorId) {
+    if (edge.isString()) {
+      edge = _opts->cache()->lookupToken(eid);
+    }
+    if (edge.isNull()) {
+      return;
+    }
+    builder.add(edge);
+  });
+}
+
 TraverserEngine::TraverserEngine(TRI_vocbase_t& vocbase,
                                  std::shared_ptr<transaction::Context> const& ctx,
                                  arangodb::velocypack::Slice info, bool needToLock)
diff --git a/arangod/Cluster/TraverserEngine.h b/arangod/Cluster/TraverserEngine.h
index 084f82076936..d9657d3a3876 100644
--- a/arangod/Cluster/TraverserEngine.h
+++ b/arangod/Cluster/TraverserEngine.h
@@ -47,12 +47,14 @@ class Query;
 }  // namespace aql
 
 namespace graph {
+class EdgeCursor;
 struct ShortestPathOptions;
 }
 
 namespace velocypack {
 class Builder;
 class Slice;
+class StringRef;
 }  // namespace velocypack
 
 namespace traverser {
@@ -122,6 +124,8 @@ class BaseTraverserEngine : public BaseEngine {
 
   void getVertexData(arangodb::velocypack::Slice, size_t, arangodb::velocypack::Builder&);
 
+  graph::EdgeCursor* getCursor(arangodb::velocypack::StringRef nextVertex, uint64_t currentDepth);
+
   virtual void smartSearch(arangodb::velocypack::Slice, arangodb::velocypack::Builder&) = 0;
 
   virtual void smartSearchBFS(arangodb::velocypack::Slice,
@@ -133,6 +137,7 @@ class BaseTraverserEngine : public BaseEngine {
  
  protected:
   std::unique_ptr<traverser::TraverserOptions> _opts;
+  std::vector<std::unique_ptr<graph::EdgeCursor>> _cursors;
 };
 
 class ShortestPathEngine : public BaseEngine {
@@ -152,9 +157,15 @@ class ShortestPathEngine : public BaseEngine {
   void getEdges(arangodb::velocypack::Slice, bool backward, arangodb::velocypack::Builder&);
 
   EngineType getType() const override { return SHORTESTPATH; }
+
+ private:
+  void addEdgeData(arangodb::velocypack::Builder& builder, bool backward, arangodb::velocypack::StringRef v);
  
  protected:
   std::unique_ptr<graph::ShortestPathOptions> _opts;
+
+  std::unique_ptr<graph::EdgeCursor> _forwardCursor;
+  std::unique_ptr<graph::EdgeCursor> _backwardCursor;
 };
 
 class TraverserEngine : public BaseTraverserEngine {
diff --git a/arangod/ClusterEngine/ClusterCollection.cpp b/arangod/ClusterEngine/ClusterCollection.cpp
index 58cb6c1dc897..e18d255c6f4c 100644
--- a/arangod/ClusterEngine/ClusterCollection.cpp
+++ b/arangod/ClusterEngine/ClusterCollection.cpp
@@ -185,13 +185,13 @@ Result ClusterCollection::updateProperties(VPackSlice const& slice, bool doSync)
     merge.add("journalSize", VPackValue(journalSize));
 
   } else if (_engineType == ClusterEngineType::RocksDBEngine) {
-    bool def = Helper::getBooleanValue(_info.slice(), "cacheEnabled", false);
-    merge.add("cacheEnabled",
-              VPackValue(Helper::getBooleanValue(slice, "cacheEnabled", def)));
+    bool def = Helper::getBooleanValue(_info.slice(), StaticStrings::CacheEnabled, false);
+    merge.add(StaticStrings::CacheEnabled,
+              VPackValue(Helper::getBooleanValue(slice, StaticStrings::CacheEnabled, def)));
 
-    auto validators = slice.get(StaticStrings::Validators);
+    auto validators = slice.get(StaticStrings::Validation);
     if(!validators.isNone()) {
-      merge.add(StaticStrings::Validators, validators);
+      merge.add(StaticStrings::Validation, validators);
     }
   } else if (_engineType != ClusterEngineType::MockEngine) {
     TRI_ASSERT(false);
@@ -247,8 +247,8 @@ void ClusterCollection::getPropertiesVPack(velocypack::Builder& result) const {
                                                    TRI_JOURNAL_DEFAULT_SIZE)));
 
   } else if (_engineType == ClusterEngineType::RocksDBEngine) {
-    result.add("cacheEnabled",
-               VPackValue(Helper::getBooleanValue(_info.slice(), "cacheEnabled", false)));
+    result.add(StaticStrings::CacheEnabled,
+               VPackValue(Helper::getBooleanValue(_info.slice(), StaticStrings::CacheEnabled, false)));
 
   } else if (_engineType != ClusterEngineType::MockEngine) {
     TRI_ASSERT(false);
diff --git a/arangod/ClusterEngine/ClusterCollection.h b/arangod/ClusterEngine/ClusterCollection.h
index 3ecb93b0a8e0..20bb182520fc 100644
--- a/arangod/ClusterEngine/ClusterCollection.h
+++ b/arangod/ClusterEngine/ClusterCollection.h
@@ -111,6 +111,7 @@ class ClusterCollection final : public PhysicalCollection {
 
   std::unique_ptr<IndexIterator> getSortedAllIterator(transaction::Methods* trx) const;
 
+
   ////////////////////////////////////
   // -- SECTION DML Operations --
   ///////////////////////////////////
@@ -127,11 +128,6 @@ class ClusterCollection final : public PhysicalCollection {
   Result read(transaction::Methods*, arangodb::velocypack::StringRef const& key,
               ManagedDocumentResult& result, bool) override;
 
-  Result read(transaction::Methods* trx, arangodb::velocypack::Slice const& key,
-              ManagedDocumentResult& result, bool locked) override {
-    return this->read(trx, arangodb::velocypack::StringRef(key), result, locked);
-  }
-
   bool readDocument(transaction::Methods* trx, LocalDocumentId const& token,
                     ManagedDocumentResult& result) const override;
 
diff --git a/arangod/ClusterEngine/ClusterEngine.cpp b/arangod/ClusterEngine/ClusterEngine.cpp
index a8a3b8de2534..72708c830041 100644
--- a/arangod/ClusterEngine/ClusterEngine.cpp
+++ b/arangod/ClusterEngine/ClusterEngine.cpp
@@ -156,8 +156,8 @@ std::unique_ptr<TransactionCollection> ClusterEngine::createTransactionCollectio
 void ClusterEngine::addParametersForNewCollection(VPackBuilder& builder, VPackSlice info) {
   if (isRocksDB()) {
     // deliberately not add objectId
-    if (!info.hasKey("cacheEnabled") || !info.get("cacheEnabled").isBool()) {
-      builder.add("cacheEnabled", VPackValue(false));
+    if (!info.get(StaticStrings::CacheEnabled).isBool()) {
+      builder.add(StaticStrings::CacheEnabled, VPackValue(false));
     }
   }
 }
diff --git a/arangod/ClusterEngine/ClusterIndex.cpp b/arangod/ClusterEngine/ClusterIndex.cpp
index efdea39481c6..834a06a1c13f 100644
--- a/arangod/ClusterEngine/ClusterIndex.cpp
+++ b/arangod/ClusterEngine/ClusterIndex.cpp
@@ -184,8 +184,8 @@ void ClusterIndex::updateProperties(velocypack::Slice const& slice) {
   if (_engineType == ClusterEngineType::MMFilesEngine) {
     // nothing to update here
   } else if (_engineType == ClusterEngineType::RocksDBEngine) {
-    merge.add("cacheEnabled",
-              VPackValue(Helper::getBooleanValue(slice, "cacheEnabled", false)));
+    merge.add(StaticStrings::CacheEnabled,
+              VPackValue(Helper::getBooleanValue(slice, StaticStrings::CacheEnabled, false)));
 
   } else {
     TRI_ASSERT(false);
diff --git a/arangod/GeneralServer/AcceptorTcp.cpp b/arangod/GeneralServer/AcceptorTcp.cpp
index cdd0cf6cb3ee..929bdec1966a 100644
--- a/arangod/GeneralServer/AcceptorTcp.cpp
+++ b/arangod/GeneralServer/AcceptorTcp.cpp
@@ -264,7 +264,7 @@ void AcceptorTcp<SocketType::Ssl>::asyncAccept() {
   // select the io context for this socket
   auto& ctx = _server.selectIoContext();
 
-  _asioSocket = std::make_unique<AsioSocket<SocketType::Ssl>>(ctx, _server.sslContext());
+  _asioSocket = std::make_unique<AsioSocket<SocketType::Ssl>>(ctx, _server.sslContexts());
   auto handler = [this](asio_ns::error_code const& ec) {
     if (ec) {
       handleError(ec);
diff --git a/arangod/GeneralServer/AsioSocket.h b/arangod/GeneralServer/AsioSocket.h
index 5b74c11518d2..4e6be74b35d4 100644
--- a/arangod/GeneralServer/AsioSocket.h
+++ b/arangod/GeneralServer/AsioSocket.h
@@ -24,6 +24,7 @@
 #define ARANGOD_GENERAL_SERVER_ASIOSOCKET_H 1
 
 #include "GeneralServer/IoContext.h"
+#include "GeneralServer/SslServerFeature.h"
 
 namespace arangodb {
 namespace rest {
@@ -87,8 +88,8 @@ struct AsioSocket<SocketType::Tcp> {
 
 template <>
 struct AsioSocket<SocketType::Ssl> {
-  AsioSocket(arangodb::rest::IoContext& ctx, std::shared_ptr<asio_ns::ssl::context> sslContext)
-      : context(ctx), storedSslContext(std::move(sslContext)), socket(ctx.io_context, *storedSslContext), timer(ctx.io_context) {
+  AsioSocket(arangodb::rest::IoContext& ctx, SslServerFeature::SslContextList sslContexts)
+      : context(ctx), storedSslContexts(std::move(sslContexts)), socket(ctx.io_context, (*storedSslContexts)[0]), timer(ctx.io_context) {
     context.incClients();
   }
 
@@ -143,7 +144,7 @@ struct AsioSocket<SocketType::Ssl> {
   }
 
   arangodb::rest::IoContext& context;
-  std::shared_ptr<asio_ns::ssl::context> storedSslContext;
+  SslServerFeature::SslContextList storedSslContexts;
   asio_ns::ssl::stream<asio_ns::ip::tcp::socket> socket;
   asio_ns::ip::tcp::acceptor::endpoint_type peer;
   asio_ns::steady_timer timer;
diff --git a/arangod/GeneralServer/GeneralServer.cpp b/arangod/GeneralServer/GeneralServer.cpp
index 0dd36aa639b5..16a7a6020c95 100644
--- a/arangod/GeneralServer/GeneralServer.cpp
+++ b/arangod/GeneralServer/GeneralServer.cpp
@@ -33,7 +33,6 @@
 #include "GeneralServer/CommTask.h"
 #include "GeneralServer/GeneralDefinitions.h"
 #include "GeneralServer/GeneralServerFeature.h"
-#include "GeneralServer/SslServerFeature.h"
 #include "Logger/LogMacros.h"
 #include "Logger/Logger.h"
 #include "Logger/LoggerStream.h"
@@ -185,18 +184,41 @@ IoContext& GeneralServer::selectIoContext() {
   return _contexts[lowpos];
 }
 
-std::shared_ptr<asio_ns::ssl::context> GeneralServer::sslContext() {
+#ifdef USE_ENTERPRISE
+extern int clientHelloCallback(SSL* ssl, int* al, void* arg);
+#endif
+
+SslServerFeature::SslContextList GeneralServer::sslContexts() {
   std::lock_guard<std::mutex> guard(_sslContextMutex);
-  if (!_sslContext) {
-    _sslContext = SslServerFeature::SSL->createSslContext();
+  if (!_sslContexts) {
+    _sslContexts = SslServerFeature::SSL->createSslContexts();
+#ifdef USE_ENTERPRISE
+    if (_sslContexts->size() > 0) {
+      // Set a client hello callback such that we have a chance to change the SSL context:
+      SSL_CTX_set_client_hello_cb((*_sslContexts)[0].native_handle(), &clientHelloCallback, (void*) this);
+    }
+#endif
   }
-  return _sslContext;
+  return _sslContexts;
 }
 
-Result GeneralServer::reloadTLS() {
+SSL_CTX* GeneralServer::getSSL_CTX(size_t index) {
   std::lock_guard<std::mutex> guard(_sslContextMutex);
+  return (*_sslContexts)[index].native_handle();
+}
+
+Result GeneralServer::reloadTLS() {
   try {
-    _sslContext = SslServerFeature::SSL->createSslContext();
+    {
+      std::lock_guard<std::mutex> guard(_sslContextMutex);
+      _sslContexts = SslServerFeature::SSL->createSslContexts();
+#ifdef USE_ENTERPRISE
+      if (_sslContexts->size() > 0) {
+        // Set a client hello callback such that we have a chance to change the SSL context:
+        SSL_CTX_set_client_hello_cb((*_sslContexts)[0].native_handle(), &clientHelloCallback, (void*) this);
+      }
+#endif
+    }
     // Now cancel every acceptor once, such that a new AsioSocket is generated which will
     // use the new context. Otherwise, the first connection will still use the old certs:
     for (auto& a : _acceptors) {
diff --git a/arangod/GeneralServer/GeneralServer.h b/arangod/GeneralServer/GeneralServer.h
index 2a7a9e9aea0a..f89880472b7d 100644
--- a/arangod/GeneralServer/GeneralServer.h
+++ b/arangod/GeneralServer/GeneralServer.h
@@ -29,6 +29,7 @@
 #include "Basics/Result.h"
 #include "Basics/Thread.h"
 #include "GeneralServer/IoContext.h"
+#include "GeneralServer/SslServerFeature.h"
 
 #include <mutex>
 
@@ -62,7 +63,8 @@ class GeneralServer {
   void stopWorking();
 
   IoContext& selectIoContext();
-  std::shared_ptr<asio_ns::ssl::context> sslContext();
+  SslServerFeature::SslContextList sslContexts();
+  SSL_CTX* getSSL_CTX(size_t index);
 
   application_features::ApplicationServer& server() const;
 
@@ -83,7 +85,7 @@ class GeneralServer {
   /// protect ssl context creation
   std::mutex _sslContextMutex;
   /// global SSL context to use here
-  std::shared_ptr<asio_ns::ssl::context> _sslContext;
+  SslServerFeature::SslContextList _sslContexts;
 };
 }  // namespace rest
 }  // namespace arangodb
diff --git a/arangod/GeneralServer/H2CommTask.cpp b/arangod/GeneralServer/H2CommTask.cpp
index 2c9fad1bc3f3..389f0a93a8b7 100644
--- a/arangod/GeneralServer/H2CommTask.cpp
+++ b/arangod/GeneralServer/H2CommTask.cpp
@@ -576,45 +576,46 @@ void H2CommTask<T>::queueHttp2Responses() {
     }
 
     nghttp2_data_provider *prd_ptr = nullptr, prd;
-
-    std::string len;
-    if (res.generateBody() &&
-        ::expectResponseBody(static_cast<int>(res.responseCode()))) {
+    if (!res.generateBody() ||
+        ::expectResponseBody(static_cast<int>(res.responseCode()))
+      ) {
+      std::string len;
       len = std::to_string(res.bodySize());
       nva.push_back({(uint8_t*)"content-length", (uint8_t*)len.c_str(), 14,
                      len.length(), NGHTTP2_NV_FLAG_NO_COPY_NAME});
+    }
+    if ((res.bodySize() > 0) &&
+        res.generateBody() &&
+        ::expectResponseBody(static_cast<int>(res.responseCode()))
+      ) {
+      prd.source.ptr = strm;
+      prd.read_callback = [](nghttp2_session* session, int32_t stream_id,
+                             uint8_t* buf, size_t length, uint32_t* data_flags,
+                             nghttp2_data_source* source, void* user_data) -> ssize_t {
+        auto strm = static_cast<H2CommTask<T>::Stream*>(source->ptr);
+
+        basics::StringBuffer& body = strm->response->body();
+
+        // TODO do not copy the body if it is > 16kb
+        TRI_ASSERT(body.size() > strm->responseOffset);
+        size_t nread = std::min(length, body.size() - strm->responseOffset);
+        TRI_ASSERT(nread > 0);
+
+        const char* src = body.data() + strm->responseOffset;
+        std::copy_n(src, nread, buf);
+        strm->responseOffset += nread;
+
+        if (strm->responseOffset == body.size()) {
+          *data_flags |= NGHTTP2_DATA_FLAG_EOF;
+        }
 
-      if (res.bodySize() > 0) {
-        
-        prd.source.ptr = strm;
-        prd.read_callback = [](nghttp2_session* session, int32_t stream_id,
-                               uint8_t* buf, size_t length, uint32_t* data_flags,
-                               nghttp2_data_source* source, void* user_data) -> ssize_t {
-          auto strm = static_cast<H2CommTask<T>::Stream*>(source->ptr);
-
-          basics::StringBuffer& body = strm->response->body();
-
-          // TODO do not copy the body if it is > 16kb
-          TRI_ASSERT(body.size() > strm->responseOffset);
-          size_t nread = std::min(length, body.size() - strm->responseOffset);
-          TRI_ASSERT(nread > 0);
-            
-          const char* src = body.data() + strm->responseOffset;
-          std::copy_n(src, nread, buf);
-          strm->responseOffset += nread;
-          
-          if (strm->responseOffset == body.size()) {
-            *data_flags |= NGHTTP2_DATA_FLAG_EOF;
-          }
-          
-          // simon: might be needed if NGHTTP2_DATA_FLAG_NO_COPY is used
-//        if (nghttp2_session_get_stream_remote_close(session, stream_id) == 0) {
-//            nghttp2_submit_rst_stream(session, NGHTTP2_FLAG_NONE, stream_id, NGHTTP2_NO_ERROR);
-//        }
-          return static_cast<ssize_t>(nread);
-        };
-        prd_ptr = &prd;
-      }
+        // simon: might be needed if NGHTTP2_DATA_FLAG_NO_COPY is used
+//      if (nghttp2_session_get_stream_remote_close(session, stream_id) == 0) {
+//          nghttp2_submit_rst_stream(session, NGHTTP2_FLAG_NONE, stream_id, NGHTTP2_NO_ERROR);
+//      }
+        return static_cast<ssize_t>(nread);
+      };
+      prd_ptr = &prd;
     }
 
     int rv = nghttp2_submit_response(this->_session, streamId, nva.data(),
diff --git a/arangod/GeneralServer/SslServerFeature.cpp b/arangod/GeneralServer/SslServerFeature.cpp
index eb2ddc9f2b7e..7ae4c10e3963 100644
--- a/arangod/GeneralServer/SslServerFeature.cpp
+++ b/arangod/GeneralServer/SslServerFeature.cpp
@@ -176,8 +176,12 @@ void SslServerFeature::verifySslOptions() {
     FATAL_ERROR_EXIT();
   }
 
+  // Set up first _sniEntry:
+  _sniEntries.clear();
+  _sniEntries.emplace_back("", _keyfile);
+
   try {
-    createSslContext();
+    createSslContexts();   // just to test if everything works
   } catch (...) {
     LOG_TOPIC("997d2", FATAL, arangodb::Logger::SSL)
         << "cannot create SSL context";
@@ -209,15 +213,21 @@ static int alpn_select_proto_cb(SSL *ssl, const unsigned char **out,
   return SSL_TLSEXT_ERR_OK;
 }
 
-std::shared_ptr<asio_ns::ssl::context> SslServerFeature::createSslContext() {
+asio_ns::ssl::context SslServerFeature::createSslContextInternal(
+    std::string keyfilename, std::string& content) {
+  // This method creates an SSL context using the keyfile in `keyfilename`
+  // It is used internally if the public method `createSslContext`
+  // is called and if the hello callback happens and a non-default
+  // servername extension is detected, then with a non-empty servername.
+  // If all goes well, the string `content` is set to the content of the keyfile.
   try {
-    std::string keyfileContent = FileUtils::slurp(_keyfile);
+    std::string keyfileContent = FileUtils::slurp(keyfilename);
     // create context
-    std::shared_ptr<asio_ns::ssl::context> sslContext = ::sslContext(SslProtocol(_sslProtocol), _keyfile);
-    _keyfileContent = std::move(keyfileContent);
+    asio_ns::ssl::context sslContext = ::sslContext(SslProtocol(_sslProtocol), keyfilename);
+    content = std::move(keyfileContent);
 
     // and use this native handle
-    asio_ns::ssl::context::native_handle_type nativeContext = sslContext->native_handle();
+    asio_ns::ssl::context::native_handle_type nativeContext = sslContext.native_handle();
 
     // set cache mode
     SSL_CTX_set_session_cache_mode(nativeContext, _sessionCache ? SSL_SESS_CACHE_SERVER
@@ -229,7 +239,7 @@ std::shared_ptr<asio_ns::ssl::context> SslServerFeature::createSslContext() {
     }
 
     // set options
-    sslContext->set_options(static_cast<long>(_sslOptions));
+    sslContext.set_options(static_cast<long>(_sslOptions));
 
     if (!_cipherList.empty()) {
       if (SSL_CTX_set_cipher_list(nativeContext, _cipherList.c_str()) != 1) {
@@ -332,9 +342,9 @@ std::shared_ptr<asio_ns::ssl::context> SslServerFeature::createSslContext() {
       SSL_CTX_set_client_CA_list(nativeContext, certNames);
     }
 
-    sslContext->set_verify_mode(SSL_VERIFY_NONE);
+    sslContext.set_verify_mode(SSL_VERIFY_NONE);
 
-    SSL_CTX_set_alpn_select_cb(sslContext->native_handle(), alpn_select_proto_cb, NULL);
+    SSL_CTX_set_alpn_select_cb(sslContext.native_handle(), alpn_select_proto_cb, NULL);
 
     return sslContext;
   } catch (std::exception const& ex) {
@@ -348,6 +358,27 @@ std::shared_ptr<asio_ns::ssl::context> SslServerFeature::createSslContext() {
   }
 }
 
+SslServerFeature::SslContextList SslServerFeature::createSslContexts() {
+  auto result = std::make_shared<std::vector<asio_ns::ssl::context>>();
+  for (size_t i = 0; i < _sniEntries.size(); ++i) {
+    auto res = createSslContextInternal(_sniEntries[i].keyfileName, _sniEntries[i].keyfileContent);
+    result->emplace_back(std::move(res));
+  }
+  return result;
+}
+
+size_t SslServerFeature::chooseSslContext(std::string const& serverName) const {
+  // Note that the map _sniServerIndex is basically immutable after the
+  // startup phase, since the number of SNI entries cannot be changed
+  // at runtime. Therefore, we do not need any protection here.
+  auto it = _sniServerIndex.find(serverName);
+  if (it == _sniServerIndex.end()) {
+    return 0;
+  } else {
+    return it->second;
+  }
+}
+
 std::string SslServerFeature::stringifySslOptions(uint64_t opts) const {
   std::string result;
 
@@ -673,8 +704,15 @@ static void dumpPEM(std::string const& pem, VPackBuilder& builder, std::string a
 // are hashed.
 Result SslServerFeature::dumpTLSData(VPackBuilder& builder) const {
   { VPackObjectBuilder guard(&builder);
-    dumpPEM(_keyfileContent, builder, "keyfile");
+    dumpPEM(_sniEntries[0].keyfileContent, builder, "keyfile");
     dumpPEM(_cafileContent, builder, "clientCA");
+    if (_sniEntries.size() > 1) {
+      VPackObjectBuilder guard2(&builder, "SNI");
+      for (size_t i = 1; i < _sniEntries.size(); ++i) {
+        dumpPEM(_sniEntries[i].keyfileContent, builder, _sniEntries[i].serverName);
+      }
+    }
   }
   return Result(TRI_ERROR_NO_ERROR);
 }
+
diff --git a/arangod/GeneralServer/SslServerFeature.h b/arangod/GeneralServer/SslServerFeature.h
index 16a521255e24..b98ade440339 100644
--- a/arangod/GeneralServer/SslServerFeature.h
+++ b/arangod/GeneralServer/SslServerFeature.h
@@ -51,6 +51,8 @@ class SslServerFeature : public application_features::ApplicationFeature {
  public:
   static SslServerFeature* SSL;
 
+  typedef std::shared_ptr<std::vector<asio_ns::ssl::context>> SslContextList;
+
   explicit SslServerFeature(application_features::ApplicationServer& server);
 
   void collectOptions(std::shared_ptr<options::ProgramOptions>) override;
@@ -59,17 +61,30 @@ class SslServerFeature : public application_features::ApplicationFeature {
   void unprepare() override final;
   virtual void verifySslOptions();
 
-  virtual std::shared_ptr<asio_ns::ssl::context> createSslContext();
+  virtual SslContextList createSslContexts();
+  size_t chooseSslContext(std::string const& serverName) const;
 
   // Dump all SSL related data into a builder, private keys
   // are hashed.
   virtual Result dumpTLSData(VPackBuilder& builder) const;
 
  protected:
+
+  struct SNIEntry {
+    std::string serverName;      // empty for default
+    std::string keyfileName;     // name of key file
+    std::string keyfileContent;  // content of key file
+    SNIEntry(std::string name, std::string keyfileName)
+      : serverName(name), keyfileName(keyfileName) {}
+  };
+
   std::string _cafile;
   std::string _cafileContent;  // the actual cert file
-  std::string _keyfile;
-  std::string _keyfileContent; // the actual keyfile
+  std::string _keyfile;        // name of default keyfile
+  // For SNI, we have two maps, one mapping to the filename for a certain
+  // server, another, to keep the actual keyfile in memory.
+  std::vector<SNIEntry> _sniEntries;   // the first entry is the default server keyfile
+  std::unordered_map<std::string, size_t> _sniServerIndex;  // map server names to indices in _sniEntries
   bool _sessionCache;
   std::string _cipherList;
   uint64_t _sslProtocol;
@@ -77,6 +92,9 @@ class SslServerFeature : public application_features::ApplicationFeature {
   std::string _ecdhCurve;
 
  private:
+  asio_ns::ssl::context createSslContextInternal(std::string keyfileName,
+                                                 std::string& content);
+
   std::string stringifySslOptions(uint64_t opts) const;
 
   std::string _rctx;
diff --git a/arangod/Graph/AttributeWeightShortestPathFinder.cpp b/arangod/Graph/AttributeWeightShortestPathFinder.cpp
index f249afe331f0..9aa14317ae3e 100644
--- a/arangod/Graph/AttributeWeightShortestPathFinder.cpp
+++ b/arangod/Graph/AttributeWeightShortestPathFinder.cpp
@@ -46,12 +46,12 @@ AttributeWeightShortestPathFinder::Step::Step(arangodb::velocypack::StringRef co
 
 AttributeWeightShortestPathFinder::Searcher::Searcher(
     AttributeWeightShortestPathFinder* pathFinder, ThreadInfo& myInfo,
-    ThreadInfo& peerInfo, arangodb::velocypack::StringRef const& start, bool isBackward)
+    ThreadInfo& peerInfo, arangodb::velocypack::StringRef const& start, bool backward)
     : _pathFinder(pathFinder),
       _myInfo(myInfo),
       _peerInfo(peerInfo),
       _start(start),
-      _isBackward(isBackward) {}
+      _backward(backward) {}
 
 void AttributeWeightShortestPathFinder::Searcher::insertNeighbor(std::unique_ptr<Step>&& step,
                                                                  double newWeight) {
@@ -137,12 +137,11 @@ bool AttributeWeightShortestPathFinder::Searcher::oneStep() {
   TRI_ASSERT(s != nullptr);
 
   std::vector<std::unique_ptr<Step>> neighbors;
-  _pathFinder->expandVertex(_isBackward, v, neighbors);
+  _pathFinder->expandVertex(_backward, v, neighbors);
   for (std::unique_ptr<Step>& neighbor : neighbors) {
     insertNeighbor(std::move(neighbor), s->weight() + neighbor->weight());
   }
   // All neighbours are moved out.
-  neighbors.clear();
   lookupPeer(v, s->weight());
 
   Step* s2 = _myInfo._pq.find(v);
@@ -160,7 +159,10 @@ AttributeWeightShortestPathFinder::AttributeWeightShortestPathFinder(ShortestPat
       _bingo(false),
       _resultCode(TRI_ERROR_NO_ERROR),
       _intermediateSet(false),
-      _intermediate() {}
+      _intermediate() {
+  _forwardCursor = _options.buildCursor(false);
+  _backwardCursor = _options.buildCursor(true);
+}
 
 AttributeWeightShortestPathFinder::~AttributeWeightShortestPathFinder() = default;
 
@@ -299,17 +301,13 @@ void AttributeWeightShortestPathFinder::inserter(
 }
 
 void AttributeWeightShortestPathFinder::expandVertex(
-    bool isBackward, arangodb::velocypack::StringRef const& vertex,
+    bool backward, arangodb::velocypack::StringRef const& vertex,
     std::vector<std::unique_ptr<Step>>& result) {
-  std::unique_ptr<EdgeCursor> edgeCursor;
-  if (isBackward) {
-    edgeCursor.reset(_options.nextReverseCursor(vertex));
-  } else {
-    edgeCursor.reset(_options.nextCursor(vertex));
-  }
+  EdgeCursor* cursor = backward ? _backwardCursor.get() : _forwardCursor.get();
+  cursor->rearm(vertex, 0);
 
   std::unordered_map<arangodb::velocypack::StringRef, size_t> candidates;
-  auto callback = [&](EdgeDocumentToken&& eid, VPackSlice edge, size_t cursorIdx) -> void {
+  cursor->readAll([&](EdgeDocumentToken&& eid, VPackSlice edge, size_t cursorIdx) -> void {
     if (edge.isString()) {
       VPackSlice doc = _options.cache()->lookupToken(eid);
       double currentWeight = _options.weightEdge(doc);
@@ -333,9 +331,7 @@ void AttributeWeightShortestPathFinder::expandVertex(
         inserter(candidates, result, to, from, currentWeight, std::move(eid));
       }
     }
-  };
-
-  edgeCursor->readAll(callback);
+  });
 }
 
 /*
diff --git a/arangod/Graph/AttributeWeightShortestPathFinder.h b/arangod/Graph/AttributeWeightShortestPathFinder.h
index bd5face9ebec..ebb342f6790c 100644
--- a/arangod/Graph/AttributeWeightShortestPathFinder.h
+++ b/arangod/Graph/AttributeWeightShortestPathFinder.h
@@ -33,12 +33,13 @@
 
 #include <velocypack/StringRef.h>
 
+#include <memory>
 #include <thread>
 
 namespace arangodb {
 
 namespace graph {
-
+class EdgeCursor;
 struct EdgeDocumentToken;
 struct ShortestPathOptions;
 
@@ -154,7 +155,7 @@ class AttributeWeightShortestPathFinder : public ShortestPathFinder {
    public:
     Searcher(AttributeWeightShortestPathFinder* pathFinder, ThreadInfo& myInfo,
              ThreadInfo& peerInfo, arangodb::velocypack::StringRef const& start,
-             bool isBackward);
+             bool backward);
 
    public:
     //////////////////////////////////////////////////////////////////////////////
@@ -181,7 +182,7 @@ class AttributeWeightShortestPathFinder : public ShortestPathFinder {
     ThreadInfo& _myInfo;
     ThreadInfo& _peerInfo;
     arangodb::velocypack::StringRef _start;
-    bool _isBackward;
+    bool _backward;
   };
 
   // -----------------------------------------------------------------------------
@@ -218,7 +219,7 @@ class AttributeWeightShortestPathFinder : public ShortestPathFinder {
                 arangodb::velocypack::StringRef const& t, double currentWeight,
                 graph::EdgeDocumentToken&& edge);
 
-  void expandVertex(bool isBackward, arangodb::velocypack::StringRef const& source,
+  void expandVertex(bool backward, arangodb::velocypack::StringRef const& source,
                     std::vector<std::unique_ptr<Step>>& result);
 
   //////////////////////////////////////////////////////////////////////////////
@@ -275,6 +276,9 @@ class AttributeWeightShortestPathFinder : public ShortestPathFinder {
 
   bool _intermediateSet;
   arangodb::velocypack::StringRef _intermediate;
+
+  std::unique_ptr<EdgeCursor> _forwardCursor;
+  std::unique_ptr<EdgeCursor> _backwardCursor;
 };
 
 }  // namespace graph
diff --git a/arangod/Graph/BaseOptions.cpp b/arangod/Graph/BaseOptions.cpp
index a65e85c8c986..cda7ea40bd20 100644
--- a/arangod/Graph/BaseOptions.cpp
+++ b/arangod/Graph/BaseOptions.cpp
@@ -31,6 +31,7 @@
 #include "Aql/IndexNode.h"
 #include "Aql/Query.h"
 #include "Containers/HashSet.h"
+#include "Cluster/ClusterEdgeCursor.h"
 #include "Graph/ShortestPathOptions.h"
 #include "Graph/SingleServerEdgeCursor.h"
 #include "Graph/TraverserCache.h"
@@ -339,10 +340,6 @@ arangodb::transaction::Methods* BaseOptions::trx() const { return _trx; }
 
 arangodb::aql::Query* BaseOptions::query() const { return _query; }
 
-arangodb::graph::TraverserCache* BaseOptions::cache() const {
-  return _cache.get();
-}
-
 void BaseOptions::injectEngineInfo(VPackBuilder& result) const {
   TRI_ASSERT(result.isOpenObject());
   result.add(VPackValue("baseLookupInfos"));
@@ -397,40 +394,16 @@ double BaseOptions::costForLookupInfoList(std::vector<BaseOptions::LookupInfo> c
   return cost;
 }
 
-EdgeCursor* BaseOptions::nextCursorLocal(arangodb::velocypack::StringRef vid,
-                                         std::vector<LookupInfo> const& list) {
-  auto allCursor = std::make_unique<SingleServerEdgeCursor>(this, list.size());
-  auto& opCursors = allCursor->getCursors();
-  for (auto& info : list) {
-    auto& node = info.indexCondition;
-    TRI_ASSERT(node->numMembers() > 0);
-    if (info.conditionNeedUpdate) {
-      // We have to inject _from/_to iff the condition needs it
-      auto dirCmp = node->getMemberUnchecked(info.conditionMemberToUpdate);
-      TRI_ASSERT(dirCmp->type == aql::NODE_TYPE_OPERATOR_BINARY_EQ);
-      TRI_ASSERT(dirCmp->numMembers() == 2);
-
-      auto idNode = dirCmp->getMemberUnchecked(1);
-      TRI_ASSERT(idNode->type == aql::NODE_TYPE_VALUE);
-      TRI_ASSERT(idNode->isValueType(aql::VALUE_TYPE_STRING));
-      // must edit node in place; TODO replace node?
-      TEMPORARILY_UNLOCK_NODE(idNode);
-      idNode->setStringValue(vid.data(), vid.length());
-    }
-    std::vector<OperationCursor*> csrs;
-    csrs.reserve(info.idxHandles.size());
-    IndexIteratorOptions opts;
-    for (auto const& it : info.idxHandles) {
-      // the emplace_back cannot throw here, as we reserved enough space before
-      csrs.emplace_back(
-          new OperationCursor(_trx->indexScanForCondition(it, node, _tmpVar, opts)));
-    }
-    opCursors.emplace_back(std::move(csrs));
-  }
-  return allCursor.release();
+arangodb::graph::TraverserCache* BaseOptions::cache() const {
+  return _cache.get();
 }
 
 TraverserCache* BaseOptions::cache() {
+  ensureCache();
+  return _cache.get();
+}
+
+void BaseOptions::ensureCache() {
   if (_cache == nullptr) {
     // If the Coordinator does NOT activate the Cache
     // the datalake is not created and cluster data cannot
@@ -441,14 +414,13 @@ TraverserCache* BaseOptions::cache() {
     activateCache(false, nullptr);
   }
   TRI_ASSERT(_cache != nullptr);
-  return _cache.get();
 }
 
 void BaseOptions::activateCache(bool enableDocumentCache,
                                 std::unordered_map<ServerID, traverser::TraverserEngineID> const* engines) {
   // Do not call this twice.
   TRI_ASSERT(_cache == nullptr);
-  _cache.reset(cacheFactory::CreateCache(_query, enableDocumentCache, engines, this));
+  _cache.reset(CacheFactory::CreateCache(_query, enableDocumentCache, engines, this));
 }
 
 void BaseOptions::injectTestCache(std::unique_ptr<TraverserCache>&& testCache) {
diff --git a/arangod/Graph/BaseOptions.h b/arangod/Graph/BaseOptions.h
index d5aee02de847..2817ca86a834 100644
--- a/arangod/Graph/BaseOptions.h
+++ b/arangod/Graph/BaseOptions.h
@@ -31,6 +31,8 @@
 #include "Cluster/TraverserEngineRegistry.h"
 #include "Transaction/Methods.h"
 
+#include <memory>
+
 namespace arangodb {
 
 namespace aql {
@@ -49,10 +51,11 @@ class Slice;
 namespace graph {
 
 class EdgeCursor;
+class SingleServerEdgeCursor;
 class TraverserCache;
 
 struct BaseOptions {
- protected:
+  public:
   struct LookupInfo {
     // This struct does only take responsibility for the expression
     // NOTE: The expression can be nullptr!
@@ -120,8 +123,6 @@ struct BaseOptions {
 
   aql::Query* query() const;
 
-  TraverserCache* cache() const;
-
   /// @brief Build a velocypack for cloning in the plan.
   virtual void toVelocyPack(arangodb::velocypack::Builder&) const = 0;
 
@@ -137,6 +138,8 @@ struct BaseOptions {
   virtual bool shouldExcludeEdgeCollection(std::string const& name) const { return false; }
 
   TraverserCache* cache();
+  TraverserCache* cache() const;
+  void ensureCache();
 
   void activateCache(bool enableDocumentCache,
                      std::unordered_map<ServerID, traverser::TraverserEngineID> const* engines);
@@ -158,10 +161,7 @@ struct BaseOptions {
   void injectLookupInfoInList(std::vector<LookupInfo>&, aql::ExecutionPlan* plan,
                               std::string const& collectionName,
                               std::string const& attributeName, aql::AstNode* condition);
-
-  EdgeCursor* nextCursorLocal(arangodb::velocypack::StringRef vid,
-                              std::vector<LookupInfo> const&);
-
+  
   void injectTestCache(std::unique_ptr<TraverserCache>&& cache);
 
  protected:
diff --git a/arangod/Graph/BreadthFirstEnumerator.cpp b/arangod/Graph/BreadthFirstEnumerator.cpp
index 38eec4f61f56..50b0afacde6c 100644
--- a/arangod/Graph/BreadthFirstEnumerator.cpp
+++ b/arangod/Graph/BreadthFirstEnumerator.cpp
@@ -115,59 +115,55 @@ bool BreadthFirstEnumerator::next() {
     auto const nextIdx = _toSearch[_toSearchPos++].sourceIdx;
     auto const nextVertex = _schreier[nextIdx].vertex;
 
-    std::unique_ptr<EdgeCursor> cursor(
-        _opts->nextCursor(nextVertex, _currentDepth));
-    if (cursor != nullptr) {
-      incHttpRequests(cursor->httpRequests());
-      bool shouldReturnPath = _currentDepth + 1 >= _opts->minDepth;
-      bool didInsert = false;
-
-      auto callback = [&](graph::EdgeDocumentToken&& eid, VPackSlice e,
-                          size_t cursorIdx) -> void {
-        if (!keepEdge(eid, e, nextVertex, _currentDepth, cursorIdx)) {
+    EdgeCursor* cursor = getCursor(nextVertex, _currentDepth);
+    bool shouldReturnPath = _currentDepth + 1 >= _opts->minDepth;
+    bool didInsert = false;
+
+    cursor->readAll([&](graph::EdgeDocumentToken&& eid, VPackSlice e,
+                         size_t cursorIdx) -> void {
+      if (!keepEdge(eid, e, nextVertex, _currentDepth, cursorIdx)) {
+        return;
+      }
+
+      if (_opts->uniqueEdges == TraverserOptions::UniquenessLevel::PATH) {
+        if (pathContainsEdge(nextIdx, eid)) {
+          // This edge is on the path.
           return;
         }
+      }
+
+      arangodb::velocypack::StringRef vId;
 
-        if (_opts->uniqueEdges == TraverserOptions::UniquenessLevel::PATH) {
-          if (pathContainsEdge(nextIdx, eid)) {
-            // This edge is on the path.
+      if (_traverser->getSingleVertex(e, nextVertex, _currentDepth + 1, vId)) {
+        if (_opts->uniqueVertices == TraverserOptions::UniquenessLevel::PATH) {
+          if (pathContainsVertex(nextIdx, vId)) {
+            // This vertex is on the path.
             return;
           }
         }
 
-        arangodb::velocypack::StringRef vId;
-
-        if (_traverser->getSingleVertex(e, nextVertex, _currentDepth + 1, vId)) {
-          if (_opts->uniqueVertices == TraverserOptions::UniquenessLevel::PATH) {
-            if (pathContainsVertex(nextIdx, vId)) {
-              // This vertex is on the path.
-              return;
-            }
-          }
-
-          _schreier.emplace_back(nextIdx, std::move(eid), vId);
-          if (_currentDepth < _opts->maxDepth - 1) {
-            // Prune here
-            if (!shouldPrune()) {
-              _nextDepth.emplace_back(NextStep(_schreierIndex));
-            }
+        _schreier.emplace_back(nextIdx, std::move(eid), vId);
+        if (_currentDepth < _opts->maxDepth - 1) {
+          // Prune here
+          if (!shouldPrune()) {
+            _nextDepth.emplace_back(_schreierIndex);
           }
-          _schreierIndex++;
-          didInsert = true;
         }
-      };
-
-      cursor->readAll(callback);
-
-      if (!shouldReturnPath) {
-        _lastReturned = _schreierIndex;
-        didInsert = false;
-      }
-      if (didInsert) {
-        // We exit the loop here.
-        // _schreierIndex is moved forward
-        break;
+        _schreierIndex++;
+        didInsert = true;
       }
+    });
+    
+    incHttpRequests(cursor->httpRequests());
+
+    if (!shouldReturnPath) {
+      _lastReturned = _schreierIndex;
+      didInsert = false;
+    }
+    if (didInsert) {
+      // We exit the loop here.
+      // _schreierIndex is moved forward
+      break;
     }
     // Nothing found for this vertex.
     // _toSearchPos is increased so
@@ -206,27 +202,25 @@ arangodb::aql::AqlValue BreadthFirstEnumerator::edgeToAqlValue(size_t index) {
 }
 
 VPackSlice BreadthFirstEnumerator::pathToIndexToSlice(VPackBuilder& result, size_t index) {
-  std::vector<size_t> fullPath;
+  _tempPathHelper.clear();
   while (index != 0) {
     // Walk backwards through the path and push everything found on the local
     // stack
-    fullPath.emplace_back(index);
+    _tempPathHelper.emplace_back(index);
     index = _schreier[index].sourceIdx;
   }
 
   result.clear();
   result.openObject();
-  result.add(VPackValue("edges"));
-  result.openArray();
-  for (auto it = fullPath.rbegin(); it != fullPath.rend(); ++it) {
+  result.add(StaticStrings::GraphQueryEdges, VPackValue(VPackValueType::Array));
+  for (auto it = _tempPathHelper.rbegin(); it != _tempPathHelper.rend(); ++it) {
     _opts->cache()->insertEdgeIntoResult(_schreier[*it].edge, result);
   }
   result.close();  // edges
-  result.add(VPackValue("vertices"));
-  result.openArray();
+  result.add(StaticStrings::GraphQueryVertices, VPackValue(VPackValueType::Array));
   // Always add the start vertex
   _traverser->addVertexToVelocyPack(_schreier[0].vertex, result);
-  for (auto it = fullPath.rbegin(); it != fullPath.rend(); ++it) {
+  for (auto it = _tempPathHelper.rbegin(); it != _tempPathHelper.rend(); ++it) {
     _traverser->addVertexToVelocyPack(_schreier[*it].vertex, result);
   }
   result.close();  // vertices
@@ -255,7 +249,6 @@ bool BreadthFirstEnumerator::pathContainsVertex(size_t index,
     }
     index = step.sourceIdx;
   }
-  return false;
 }
 
 bool BreadthFirstEnumerator::pathContainsEdge(size_t index,
@@ -264,11 +257,12 @@ bool BreadthFirstEnumerator::pathContainsEdge(size_t index,
     TRI_ASSERT(index < _schreier.size());
     auto const& step = _schreier[index];
     if (step.edge.equals(edge)) {
-      // We have the given vertex on this path
+      // We have the given edge on this path
       return true;
     }
     index = step.sourceIdx;
   }
+  // We have checked the complete path
   return false;
 }
 
@@ -293,34 +287,36 @@ bool BreadthFirstEnumerator::prepareSearchOnNextDepth() {
 }
 
 bool BreadthFirstEnumerator::shouldPrune() {
-  if (_opts->usesPrune()) {
-    // evaluator->evaluate() might access these, so they have to live long enough.
-    // To make that perfectly clear, I added a scope.
-    transaction::BuilderLeaser pathBuilder(_opts->trx());
-    aql::AqlValue vertex, edge;
-    aql::AqlValueGuard vertexGuard{vertex, true}, edgeGuard{edge, true};
-    {
-      auto* evaluator = _opts->getPruneEvaluator();
-      if (evaluator->needsVertex()) {
-        // Note: vertexToAqlValue() copies the original vertex into the AqlValue.
-        // This could be avoided with a function that just returns the slice,
-        // as it will stay valid long enough.
-        vertex = vertexToAqlValue(_schreierIndex);
-        evaluator->injectVertex(vertex.slice());
-      }
-      if (evaluator->needsEdge()) {
-        // Note: edgeToAqlValue() copies the original edge into the AqlValue.
-        // This could be avoided with a function that just returns the slice,
-        // as it will stay valid long enough.
-        edge = edgeToAqlValue(_schreierIndex);
-        evaluator->injectEdge(edge.slice());
-      }
-      if (evaluator->needsPath()) {
-        VPackSlice path = pathToIndexToSlice(*pathBuilder.get(), _schreierIndex);
-        evaluator->injectPath(path);
-      }
-      return evaluator->evaluate();
-    }
+  if (!_opts->usesPrune()) {
+    return false;
   }
-  return false;
+  
+  transaction::BuilderLeaser pathBuilder(_opts->trx());
+
+  // evaluator->evaluate() might access these, so they have to live long enough.
+  aql::AqlValue vertex, edge;
+  aql::AqlValueGuard vertexGuard{vertex, true}, edgeGuard{edge, true};
+  
+  auto* evaluator = _opts->getPruneEvaluator();
+  TRI_ASSERT(evaluator != nullptr);
+
+  if (evaluator->needsVertex()) {
+    // Note: vertexToAqlValue() copies the original vertex into the AqlValue.
+    // This could be avoided with a function that just returns the slice,
+    // as it will stay valid long enough.
+    vertex = vertexToAqlValue(_schreierIndex);
+    evaluator->injectVertex(vertex.slice());
+  }
+  if (evaluator->needsEdge()) {
+    // Note: edgeToAqlValue() copies the original edge into the AqlValue.
+    // This could be avoided with a function that just returns the slice,
+    // as it will stay valid long enough.
+    edge = edgeToAqlValue(_schreierIndex);
+    evaluator->injectEdge(edge.slice());
+  }
+  if (evaluator->needsPath()) {
+    VPackSlice path = pathToIndexToSlice(*pathBuilder.get(), _schreierIndex);
+    evaluator->injectPath(path);
+  }
+  return evaluator->evaluate();
 }
diff --git a/arangod/Graph/BreadthFirstEnumerator.h b/arangod/Graph/BreadthFirstEnumerator.h
index 5ca780931a0c..45e3987c7181 100644
--- a/arangod/Graph/BreadthFirstEnumerator.h
+++ b/arangod/Graph/BreadthFirstEnumerator.h
@@ -27,6 +27,9 @@
 #include "Basics/Common.h"
 #include "Graph/PathEnumerator.h"
 
+#include <memory>
+#include <vector>
+
 namespace arangodb {
 
 namespace traverser {
@@ -35,6 +38,7 @@ struct TraverserOptions;
 }  // namespace traverser
 
 namespace graph {
+class EdgeCursor;
 
 class BreadthFirstEnumerator final : public arangodb::traverser::PathEnumerator {
  private:
@@ -90,6 +94,10 @@ class BreadthFirstEnumerator final : public arangodb::traverser::PathEnumerator
   ///        with this depth.
   size_t _toSearchPos;
 
+  /// @brief helper vector that is used temporarily when building the path
+  /// output
+  std::vector<size_t> _tempPathHelper;
+
  public:
   BreadthFirstEnumerator(arangodb::traverser::Traverser* traverser,
                          arangodb::traverser::TraverserOptions* opts);
@@ -108,15 +116,6 @@ class BreadthFirstEnumerator final : public arangodb::traverser::PathEnumerator
   aql::AqlValue pathToAqlValue(arangodb::velocypack::Builder& result) override;
 
  private:
-  inline size_t getDepth(size_t index) const {
-    size_t depth = 0;
-    while (index != 0) {
-      ++depth;
-      index = _schreier[index].sourceIdx;
-    }
-    return depth;
-  }
-
   /**
    * @brief Helper function to validate if the path contains the given
    *        vertex.
diff --git a/arangod/Graph/ConstantWeightShortestPathFinder.cpp b/arangod/Graph/ConstantWeightShortestPathFinder.cpp
index f519b86b9f5c..ffbc889899d1 100644
--- a/arangod/Graph/ConstantWeightShortestPathFinder.cpp
+++ b/arangod/Graph/ConstantWeightShortestPathFinder.cpp
@@ -47,7 +47,10 @@ ConstantWeightShortestPathFinder::PathSnippet::PathSnippet(arangodb::velocypack:
     : _pred(pred), _path(std::move(path)) {}
 
 ConstantWeightShortestPathFinder::ConstantWeightShortestPathFinder(ShortestPathOptions& options)
-    : ShortestPathFinder(options) {}
+    : ShortestPathFinder(options) {
+  _forwardCursor = _options.buildCursor(false);
+  _backwardCursor = _options.buildCursor(true);
+}
 
 ConstantWeightShortestPathFinder::~ConstantWeightShortestPathFinder() {
   clearVisited();
@@ -172,14 +175,10 @@ void ConstantWeightShortestPathFinder::fillResult(arangodb::velocypack::StringRe
 }
 
 void ConstantWeightShortestPathFinder::expandVertex(bool backward, arangodb::velocypack::StringRef vertex) {
-  std::unique_ptr<EdgeCursor> edgeCursor;
-  if (backward) {
-    edgeCursor.reset(_options.nextReverseCursor(vertex));
-  } else {
-    edgeCursor.reset(_options.nextCursor(vertex));
-  }
+  EdgeCursor* cursor = backward ? _backwardCursor.get() : _forwardCursor.get();
+  cursor->rearm(vertex, 0);
 
-  auto callback = [&](EdgeDocumentToken&& eid, VPackSlice edge, size_t cursorIdx) -> void {
+  cursor->readAll([&](EdgeDocumentToken&& eid, VPackSlice edge, size_t cursorIdx) -> void {
     if (edge.isString()) {
       if (edge.compareString(vertex.data(), vertex.length()) != 0) {
         arangodb::velocypack::StringRef id = _options.cache()->persistString(arangodb::velocypack::StringRef(edge));
@@ -197,8 +196,7 @@ void ConstantWeightShortestPathFinder::expandVertex(bool backward, arangodb::vel
         _neighbors.emplace_back(id);
       }
     }
-  };
-  edgeCursor->readAll(callback);
+  });
 }
 
 void ConstantWeightShortestPathFinder::clearVisited() {
diff --git a/arangod/Graph/ConstantWeightShortestPathFinder.h b/arangod/Graph/ConstantWeightShortestPathFinder.h
index cd8a6eb9c7c2..50027e56952b 100644
--- a/arangod/Graph/ConstantWeightShortestPathFinder.h
+++ b/arangod/Graph/ConstantWeightShortestPathFinder.h
@@ -30,6 +30,7 @@
 
 #include <velocypack/StringRef.h>
 #include <deque>
+#include <memory>
 
 namespace arangodb {
 
@@ -38,7 +39,7 @@ class Slice;
 }
 
 namespace graph {
-
+class EdgeCursor;
 struct ShortestPathOptions;
 
 class ConstantWeightShortestPathFinder : public ShortestPathFinder {
@@ -83,6 +84,9 @@ class ConstantWeightShortestPathFinder : public ShortestPathFinder {
 
   std::vector<arangodb::velocypack::StringRef> _neighbors;
   std::vector<graph::EdgeDocumentToken> _edges;
+
+  std::unique_ptr<EdgeCursor> _forwardCursor;
+  std::unique_ptr<EdgeCursor> _backwardCursor;
 };
 
 }  // namespace graph
diff --git a/arangod/Graph/EdgeCursor.h b/arangod/Graph/EdgeCursor.h
index 0d82265b68f7..88492b22ed77 100644
--- a/arangod/Graph/EdgeCursor.h
+++ b/arangod/Graph/EdgeCursor.h
@@ -32,6 +32,7 @@ namespace arangodb {
 
 namespace velocypack {
 class Slice;
+class StringRef;
 }
 
 namespace graph {
@@ -55,6 +56,8 @@ class EdgeCursor {
   virtual void readAll(std::function<void(EdgeDocumentToken&&, arangodb::velocypack::Slice, size_t)> const& callback) = 0;
 
   virtual size_t httpRequests() const = 0;
+
+  virtual void rearm(arangodb::velocypack::StringRef vid, uint64_t depth) = 0;
 };
 
 }  // namespace graph
diff --git a/arangod/Graph/KShortestPathsFinder.cpp b/arangod/Graph/KShortestPathsFinder.cpp
index 56371dc1e4f1..3af9a1fa2127 100644
--- a/arangod/Graph/KShortestPathsFinder.cpp
+++ b/arangod/Graph/KShortestPathsFinder.cpp
@@ -43,7 +43,10 @@ using namespace arangodb;
 using namespace arangodb::graph;
 
 KShortestPathsFinder::KShortestPathsFinder(ShortestPathOptions& options)
-    : ShortestPathFinder(options), _traversalDone(true) {}
+    : ShortestPathFinder(options) {
+  _forwardCursor = options.buildCursor(false);
+  _backwardCursor = options.buildCursor(true);
+}
 
 KShortestPathsFinder::~KShortestPathsFinder() = default;
 
@@ -129,22 +132,13 @@ void KShortestPathsFinder::computeNeighbourhoodOfVertexCache(VertexRef vertex,
 
 void KShortestPathsFinder::computeNeighbourhoodOfVertex(VertexRef vertex, Direction direction,
                                                         std::vector<Step>& steps) {
-  std::unique_ptr<EdgeCursor> edgeCursor;
-
-  switch (direction) {
-    case BACKWARD:
-      edgeCursor.reset(_options.nextReverseCursor(vertex));
-      break;
-    case FORWARD:
-      edgeCursor.reset(_options.nextCursor(vertex));
-      break;
-    default:
-      TRI_ASSERT(false);
-  }
+  EdgeCursor* cursor =
+      direction == BACKWARD ? _backwardCursor.get() : _forwardCursor.get();
+  cursor->rearm(vertex, 0);
 
   // TODO: This is a bit of a hack
   if (_options.useWeight()) {
-    auto callback = [&](EdgeDocumentToken&& eid, VPackSlice edge, size_t cursorIdx) -> void {
+    cursor->readAll([&](EdgeDocumentToken&& eid, VPackSlice edge, size_t cursorIdx) -> void {
       if (edge.isString()) {
         VPackSlice doc = _options.cache()->lookupToken(eid);
         double weight = _options.weightEdge(doc);
@@ -162,10 +156,9 @@ void KShortestPathsFinder::computeNeighbourhoodOfVertex(VertexRef vertex, Direct
           steps.emplace_back(std::move(eid), id, _options.weightEdge(edge));
         }
       }
-    };
-    edgeCursor->readAll(callback);
+    });
   } else {
-    auto callback = [&](EdgeDocumentToken&& eid, VPackSlice edge, size_t cursorIdx) -> void {
+    cursor->readAll([&](EdgeDocumentToken&& eid, VPackSlice edge, size_t cursorIdx) -> void {
       if (edge.isString()) {
         if (edge.compareString(vertex.data(), vertex.length()) != 0) {
           VertexRef id = _options.cache()->persistString(VertexRef(edge));
@@ -181,8 +174,7 @@ void KShortestPathsFinder::computeNeighbourhoodOfVertex(VertexRef vertex, Direct
           steps.emplace_back(std::move(eid), id, 1);
         }
       }
-    };
-    edgeCursor->readAll(callback);
+    });
   }
 }
 
diff --git a/arangod/Graph/KShortestPathsFinder.h b/arangod/Graph/KShortestPathsFinder.h
index 1d62cc863894..433da5312f38 100644
--- a/arangod/Graph/KShortestPathsFinder.h
+++ b/arangod/Graph/KShortestPathsFinder.h
@@ -33,6 +33,7 @@
 #include <velocypack/StringRef.h>
 
 #include <list>
+#include <memory>
 #include <optional>
 
 namespace arangodb {
@@ -42,7 +43,7 @@ class Slice;
 }
 
 namespace graph {
-
+class EdgeCursor;
 struct ShortestPathOptions;
 
 // Inherit from ShortestPathfinder to get destroyEngines and not copy it
@@ -268,6 +269,9 @@ class KShortestPathsFinder : public ShortestPathFinder {
   std::vector<Path> _shortestPaths;
 
   std::list<Path> _candidatePaths;
+
+  std::unique_ptr<EdgeCursor> _forwardCursor;
+  std::unique_ptr<EdgeCursor> _backwardCursor;
 };
 
 }  // namespace graph
diff --git a/arangod/Graph/NeighborsEnumerator.cpp b/arangod/Graph/NeighborsEnumerator.cpp
index c6447ca86607..c6ed9c3a9ff9 100644
--- a/arangod/Graph/NeighborsEnumerator.cpp
+++ b/arangod/Graph/NeighborsEnumerator.cpp
@@ -36,7 +36,12 @@ using namespace arangodb::traverser;
 
 NeighborsEnumerator::NeighborsEnumerator(Traverser* traverser, TraverserOptions* opts)
     : PathEnumerator(traverser, opts), 
-      _searchDepth(0) {}
+      _searchDepth(0) {
+      
+  TRI_ASSERT(opts->useBreadthFirst);
+  TRI_ASSERT(opts->uniqueVertices == arangodb::traverser::TraverserOptions::GLOBAL);
+  TRI_ASSERT(!opts->hasDepthLookupInfo());
+}
 
 void NeighborsEnumerator::setStartVertex(arangodb::velocypack::StringRef startVertex) {
   PathEnumerator::setStartVertex(startVertex);
@@ -74,26 +79,28 @@ bool NeighborsEnumerator::next() {
 
       swapLastAndCurrentDepth();
       for (auto const& nextVertex : _lastDepth) {
-        auto callback = [&](EdgeDocumentToken&& eid, VPackSlice other, size_t cursorId) {
-          if (!keepEdge(eid, other, nextVertex, _searchDepth, cursorId)) {
+        EdgeCursor* cursor = getCursor(nextVertex, _searchDepth);
+        cursor->readAll([&](EdgeDocumentToken&& eid, VPackSlice vertex, size_t cursorId) {
+          if (!keepEdge(eid, vertex, nextVertex, _searchDepth, cursorId)) {
             return;
           }
 
           // Counting should be done in readAll
-          arangodb::velocypack::StringRef v;
-          if (other.isString()) {
-            v = _opts->cache()->persistString(arangodb::velocypack::StringRef(other));
-          } else {
-            TRI_ASSERT(other.isObject());
-            VPackSlice tmp = transaction::helpers::extractFromFromDocument(other);
+          if (!vertex.isString()) {
+            TRI_ASSERT(vertex.isObject());
+            VPackSlice tmp = transaction::helpers::extractFromFromDocument(vertex);
             if (tmp.compareString(nextVertex.data(), nextVertex.length()) == 0) {
-              tmp = transaction::helpers::extractToFromDocument(other);
+              tmp = transaction::helpers::extractToFromDocument(vertex);
             }
             TRI_ASSERT(tmp.isString());
-            v = _opts->cache()->persistString(arangodb::velocypack::StringRef(tmp));
+            vertex = tmp;
           }
+          
+          arangodb::velocypack::StringRef v(vertex);
 
           if (_allFound.find(v) == _allFound.end()) {
+            v = _opts->cache()->persistString(v);
+            
             if (_traverser->vertexMatchesConditions(v, _searchDepth + 1)) {
               _allFound.emplace(v);
               if (shouldPrune(v)) {
@@ -104,14 +111,9 @@ bool NeighborsEnumerator::next() {
           } else {
             _opts->cache()->increaseFilterCounter();
           }
-        };
-
-        std::unique_ptr<arangodb::graph::EdgeCursor> cursor(
-            _opts->nextCursor(nextVertex, _searchDepth));
-        if (cursor != nullptr) {
-          incHttpRequests(cursor->httpRequests());
-          cursor->readAll(callback);
-        }
+        });
+
+        incHttpRequests(cursor->httpRequests());
       }
       if (_currentDepth.empty()) {
         // Nothing found. Cannot do anything more.
@@ -158,15 +160,20 @@ void NeighborsEnumerator::swapLastAndCurrentDepth() {
 
 bool NeighborsEnumerator::shouldPrune(arangodb::velocypack::StringRef v) {
   // Prune here
-  if (_opts->usesPrune()) {
-    auto* evaluator = _opts->getPruneEvaluator();
-    if (evaluator->needsVertex()) {
-      evaluator->injectVertex(_traverser->fetchVertexData(v).slice());
-    }
-    // We cannot support these two here
-    TRI_ASSERT(!evaluator->needsEdge());
-    TRI_ASSERT(!evaluator->needsPath());
-    return evaluator->evaluate();
+  if (!_opts->usesPrune()) {
+    return false;
+  }
+
+  auto* evaluator = _opts->getPruneEvaluator();
+  aql::AqlValue vertex;
+  aql::AqlValueGuard vertexGuard{vertex, true};
+  if (evaluator->needsVertex()) {
+    vertex = _traverser->fetchVertexData(v);
+    evaluator->injectVertex(vertex.slice());
   }
-  return false;
+  
+  // We cannot support these two here
+  TRI_ASSERT(!evaluator->needsEdge());
+  TRI_ASSERT(!evaluator->needsPath());
+  return evaluator->evaluate();
 }
diff --git a/arangod/Graph/PathEnumerator.cpp b/arangod/Graph/PathEnumerator.cpp
index 255d610a20eb..c1ce3543d934 100644
--- a/arangod/Graph/PathEnumerator.cpp
+++ b/arangod/Graph/PathEnumerator.cpp
@@ -30,6 +30,8 @@
 #include "Graph/TraverserCache.h"
 #include "Graph/TraverserOptions.h"
 
+using namespace arangodb;
+
 using PathEnumerator = arangodb::traverser::PathEnumerator;
 using DepthFirstEnumerator = arangodb::traverser::DepthFirstEnumerator;
 using Traverser = arangodb::traverser::Traverser;
@@ -41,6 +43,8 @@ PathEnumerator::PathEnumerator(Traverser* traverser, TraverserOptions* opts)
       _opts(opts),
       _httpRequests(0) {}
 
+PathEnumerator::~PathEnumerator() = default;
+
 void PathEnumerator::setStartVertex(arangodb::velocypack::StringRef startVertex) {
   _enumeratedPath.edges.clear();
   _enumeratedPath.vertices.clear();
@@ -69,8 +73,19 @@ bool PathEnumerator::keepEdge(arangodb::graph::EdgeDocumentToken& eid,
   return _opts->destinationCollectionAllowed(edge, sourceVertex);
 }
 
+graph::EdgeCursor* PathEnumerator::getCursor(arangodb::velocypack::StringRef nextVertex, uint64_t currentDepth) {
+  if (currentDepth >= _cursors.size()) {
+    _cursors.emplace_back(_opts->buildCursor(currentDepth));
+  }
+  graph::EdgeCursor* cursor = _cursors.at(currentDepth).get();
+  cursor->rearm(nextVertex, currentDepth);
+  return cursor;
+}
+
 DepthFirstEnumerator::DepthFirstEnumerator(Traverser* traverser, TraverserOptions* opts)
-    : PathEnumerator(traverser, opts), _pruneNext(false) {}
+    : PathEnumerator(traverser, opts), 
+      _activeCursors(0),
+      _pruneNext(false) {}
 
 DepthFirstEnumerator::~DepthFirstEnumerator() = default;
 
@@ -99,13 +114,9 @@ bool DepthFirstEnumerator::next() {
     if (_enumeratedPath.edges.size() < _opts->maxDepth && !_pruneNext) {
       // We are not done with this path, so
       // we reserve the cursor for next depth
-      auto cursor = _opts->nextCursor(arangodb::velocypack::StringRef(
-                                          _enumeratedPath.vertices.back()),
-                                      _enumeratedPath.edges.size());
-      if (cursor != nullptr) {
-        incHttpRequests(cursor->httpRequests());
-        _edgeCursors.emplace_back(cursor);
-      }
+      graph::EdgeCursor* cursor = getCursor(arangodb::velocypack::StringRef(_enumeratedPath.vertices.back()), _enumeratedPath.edges.size());
+      incHttpRequests(cursor->httpRequests());
+      ++_activeCursors;
     } else {
       if (!_enumeratedPath.edges.empty()) {
         // This path is at the end. cut the last step
@@ -167,14 +178,13 @@ bool DepthFirstEnumerator::next() {
 
         _enumeratedPath.edges.push_back(std::move(eid));
         foundPath = true;
-        return;
       }
       // Vertex Invalid. Do neither insert edge nor vertex
     };
 
-    while (!_edgeCursors.empty()) {
-      TRI_ASSERT(_edgeCursors.size() == _enumeratedPath.edges.size() + 1);
-      auto& cursor = _edgeCursors.back();
+    while (_activeCursors > 0) {
+      TRI_ASSERT(_activeCursors == _enumeratedPath.edges.size() + 1);
+      auto& cursor = _cursors[_activeCursors - 1];
 
       if (cursor->next(callback)) {
         if (foundPath) {
@@ -189,7 +199,8 @@ bool DepthFirstEnumerator::next() {
         }
       } else {
         // cursor is empty.
-        _edgeCursors.pop_back();
+        TRI_ASSERT(_activeCursors > 0);
+        --_activeCursors;
         if (!_enumeratedPath.edges.empty()) {
           _enumeratedPath.edges.pop_back();
           _enumeratedPath.vertices.pop_back();
@@ -197,7 +208,7 @@ bool DepthFirstEnumerator::next() {
       }
     }
 
-    if (_edgeCursors.empty()) {
+    if (_activeCursors == 0) {
       // If we get here all cursors are exhausted.
       _enumeratedPath.edges.clear();
       _enumeratedPath.vertices.clear();
@@ -215,23 +226,19 @@ arangodb::aql::AqlValue DepthFirstEnumerator::lastEdgeToAqlValue() {
   if (_enumeratedPath.edges.empty()) {
     return arangodb::aql::AqlValue(arangodb::aql::AqlValueHintNull());
   }
-  // FIXME: add some asserts back into this
-  // TRI_ASSERT(_enumeratedPath.edges.back() != nullptr);
   return _opts->cache()->fetchEdgeAqlResult(_enumeratedPath.edges.back());
 }
 
 VPackSlice DepthFirstEnumerator::pathToSlice(VPackBuilder& result) {
   result.clear();
   result.openObject();
-  result.add(VPackValue("edges"));
-  result.openArray();
+  result.add(StaticStrings::GraphQueryEdges, VPackValue(VPackValueType::Array));
   for (auto const& it : _enumeratedPath.edges) {
     // TRI_ASSERT(it != nullptr);
     _opts->cache()->insertEdgeIntoResult(it, result);
   }
   result.close();
-  result.add(VPackValue("vertices"));
-  result.openArray();
+  result.add(StaticStrings::GraphQueryVertices, VPackValue(VPackValueType::Array));
   for (auto const& it : _enumeratedPath.vertices) {
     _traverser->addVertexToVelocyPack(VPackStringRef(it), result);
   }
@@ -247,28 +254,31 @@ arangodb::aql::AqlValue DepthFirstEnumerator::pathToAqlValue(VPackBuilder& resul
 
 bool DepthFirstEnumerator::shouldPrune() {
   // We need to call prune here
-  if (_opts->usesPrune()) {
-    // evaluator->evaluate() might access these, so they have to live long
-    // enough. To make that perfectly clear, I added a scope.
-    transaction::BuilderLeaser pathBuilder(_opts->trx());
-    aql::AqlValue vertex, edge;
-    aql::AqlValueGuard vertexGuard{vertex, true}, edgeGuard{edge, true};
-    {
-      aql::PruneExpressionEvaluator* evaluator = _opts->getPruneEvaluator();
-      if (evaluator->needsVertex()) {
-        vertex = lastVertexToAqlValue();
-        evaluator->injectVertex(vertex.slice());
-      }
-      if (evaluator->needsEdge()) {
-        edge = lastEdgeToAqlValue();
-        evaluator->injectEdge(edge.slice());
-      }
-      if (evaluator->needsPath()) {
-        VPackSlice path = pathToSlice(*pathBuilder.get());
-        evaluator->injectPath(path);
-      }
-      return evaluator->evaluate();
-    }
+  if (!_opts->usesPrune()) {
+    return false;
   }
-  return false;
+  
+  transaction::BuilderLeaser pathBuilder(_opts->trx());
+  // evaluator->evaluate() might access these, so they have to live long
+  // enough
+  aql::AqlValue vertex, edge;
+  aql::AqlValueGuard vertexGuard{vertex, true}, edgeGuard{edge, true};
+  
+  aql::PruneExpressionEvaluator* evaluator = _opts->getPruneEvaluator();
+  TRI_ASSERT(evaluator != nullptr);
+
+  if (evaluator->needsVertex()) {
+    vertex = lastVertexToAqlValue();
+    evaluator->injectVertex(vertex.slice());
+  }
+  if (evaluator->needsEdge()) {
+    edge = lastEdgeToAqlValue();
+    evaluator->injectEdge(edge.slice());
+  }
+  if (evaluator->needsPath()) {
+    VPackSlice path = pathToSlice(*pathBuilder.get());
+    evaluator->injectPath(path);
+  }
+  return evaluator->evaluate();
 }
+
diff --git a/arangod/Graph/PathEnumerator.h b/arangod/Graph/PathEnumerator.h
index f072867e4fd6..09ae14d864f4 100644
--- a/arangod/Graph/PathEnumerator.h
+++ b/arangod/Graph/PathEnumerator.h
@@ -95,7 +95,7 @@ class PathEnumerator {
  public:
   PathEnumerator(Traverser* traverser, TraverserOptions* opts);
 
-  virtual ~PathEnumerator() = default;
+  virtual ~PathEnumerator();
   
   /// @brief set start vertex and reset
   /// note that the caller *must* guarantee that the string data pointed to by
@@ -122,16 +122,18 @@ class PathEnumerator {
   }
   
   void incHttpRequests(size_t requests) { _httpRequests += requests; }
+ 
+ protected:
+  graph::EdgeCursor* getCursor(arangodb::velocypack::StringRef nextVertex, uint64_t currentDepth);
+  
+  /// @brief The vector of EdgeCursors to walk through.
+  std::vector<std::unique_ptr<graph::EdgeCursor>> _cursors;
 };
 
 // cppcheck-suppress noConstructor
 class DepthFirstEnumerator final : public PathEnumerator {
  private:
-  //////////////////////////////////////////////////////////////////////////////
-  /// @brief The vector of EdgeCursors to walk through.
-  //////////////////////////////////////////////////////////////////////////////
-
-  std::vector<std::unique_ptr<graph::EdgeCursor>> _edgeCursors;
+  size_t _activeCursors;
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Flag if we need to prune the next path
@@ -157,7 +159,7 @@ class DepthFirstEnumerator final : public PathEnumerator {
 
  private:
   bool shouldPrune();
-
+  
   velocypack::Slice pathToSlice(arangodb::velocypack::Builder& result);
 };
 }  // namespace traverser
diff --git a/arangod/Graph/ShortestPathOptions.cpp b/arangod/Graph/ShortestPathOptions.cpp
index cfaaf8d40c7b..86d672d07ab0 100644
--- a/arangod/Graph/ShortestPathOptions.cpp
+++ b/arangod/Graph/ShortestPathOptions.cpp
@@ -28,6 +28,7 @@
 #include "Cluster/ClusterEdgeCursor.h"
 #include "Cluster/ClusterMethods.h"
 #include "Graph/ClusterTraverserCache.h"
+#include "Graph/SingleServerEdgeCursor.h"
 #include "Indexes/Index.h"
 #include "Transaction/Helpers.h"
 
@@ -174,30 +175,16 @@ double ShortestPathOptions::weightEdge(VPackSlice edge) const {
       edge, weightAttribute.c_str(), defaultWeight);
 }
 
-EdgeCursor* ShortestPathOptions::nextCursor(arangodb::velocypack::StringRef vid) {
-  if (_isCoordinator) {
-    return nextCursorCoordinator(vid);
-  }
-  return nextCursorLocal(vid, _baseLookupInfos);
-}
+std::unique_ptr<EdgeCursor> ShortestPathOptions::buildCursor(bool backward) {
+  ensureCache();
 
-EdgeCursor* ShortestPathOptions::nextReverseCursor(arangodb::velocypack::StringRef vid) {
   if (_isCoordinator) {
-    return nextReverseCursorCoordinator(vid);
+    return std::make_unique<ClusterShortestPathEdgeCursor>(this, backward);
   }
-  return nextCursorLocal(vid, _reverseLookupInfos);
-}
-
-EdgeCursor* ShortestPathOptions::nextCursorCoordinator(arangodb::velocypack::StringRef vid) {
-  auto cursor = std::make_unique<ClusterEdgeCursor>(vid, false, this);
-  return cursor.release();
-}
-
-EdgeCursor* ShortestPathOptions::nextReverseCursorCoordinator(arangodb::velocypack::StringRef vid) {
-  auto cursor = std::make_unique<ClusterEdgeCursor>(vid, true, this);
-  return cursor.release();
+  
+  return std::make_unique<SingleServerEdgeCursor>(this, _tmpVar, nullptr, backward ? _reverseLookupInfos : _baseLookupInfos);
 }
-
+  
 void ShortestPathOptions::fetchVerticesCoordinator(
     std::deque<arangodb::velocypack::StringRef> const& vertexIds) {
   // TRI_ASSERT(arangodb::ServerState::instance()->isCoordinator());
diff --git a/arangod/Graph/ShortestPathOptions.h b/arangod/Graph/ShortestPathOptions.h
index 3cd0c13fdb01..b8c4dbc391d7 100644
--- a/arangod/Graph/ShortestPathOptions.h
+++ b/arangod/Graph/ShortestPathOptions.h
@@ -25,6 +25,7 @@
 #define ARANGOD_GRAPH_SHORTEST_PATH_OPTIONS_H 1
 
 #include "Graph/BaseOptions.h"
+#include <memory>
 
 namespace arangodb {
 
@@ -38,6 +39,7 @@ class Builder;
 class Slice;
 }  // namespace velocypack
 namespace graph {
+class EdgeCursor;
 
 struct ShortestPathOptions : public BaseOptions {
  public:
@@ -69,7 +71,9 @@ struct ShortestPathOptions : public BaseOptions {
 
   arangodb::velocypack::Slice getStart() const;
   arangodb::velocypack::Slice getEnd() const;
-
+  
+  std::unique_ptr<EdgeCursor> buildCursor(bool backward);
+  
   /// @brief  Test if we have to use a weight attribute
   bool useWeight() const;
 
@@ -90,19 +94,11 @@ struct ShortestPathOptions : public BaseOptions {
 
   // Compute the weight of the given edge
   double weightEdge(arangodb::velocypack::Slice const) const;
-
-  EdgeCursor* nextCursor(arangodb::velocypack::StringRef vid);
-
-  EdgeCursor* nextReverseCursor(arangodb::velocypack::StringRef vid);
-
+  
   void fetchVerticesCoordinator(std::deque<arangodb::velocypack::StringRef> const& vertexIds);
 
   void isQueryKilledCallback() const;
 
- private:
-  EdgeCursor* nextCursorCoordinator(arangodb::velocypack::StringRef vid);
-  EdgeCursor* nextReverseCursorCoordinator(arangodb::velocypack::StringRef vid);
-
  private:
   /// @brief Lookup info to find all reverse edges.
   std::vector<LookupInfo> _reverseLookupInfos;
diff --git a/arangod/Graph/SingleServerEdgeCursor.cpp b/arangod/Graph/SingleServerEdgeCursor.cpp
index 614c7569bd45..75f45471555e 100644
--- a/arangod/Graph/SingleServerEdgeCursor.cpp
+++ b/arangod/Graph/SingleServerEdgeCursor.cpp
@@ -26,6 +26,7 @@
 #include "Graph/BaseOptions.h"
 #include "Graph/EdgeDocumentToken.h"
 #include "Graph/TraverserCache.h"
+#include "Indexes/IndexIterator.h"
 #include "StorageEngine/TransactionState.h"
 #include "Transaction/Helpers.h"
 #include "Transaction/Methods.h"
@@ -35,6 +36,10 @@
 using namespace arangodb;
 using namespace arangodb::graph;
 
+namespace {
+IndexIteratorOptions defaultIndexIteratorOptions;
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 /// @brief Get a document by it's ID. Also lazy locks the collection.
 ///        If DOCUMENT_NOT_FOUND this function will return normally
@@ -42,29 +47,28 @@ using namespace arangodb::graph;
 ///        On all other cases this function throws.
 ////////////////////////////////////////////////////////////////////////////////
 
-SingleServerEdgeCursor::SingleServerEdgeCursor(BaseOptions* opts, size_t nrCursors,
-                                               std::vector<size_t> const* mapping)
+SingleServerEdgeCursor::SingleServerEdgeCursor(BaseOptions const* opts,
+                                               aql::Variable const* tmpVar,
+                                               std::vector<size_t> const* mapping,
+                                               std::vector<BaseOptions::LookupInfo> const& lookupInfo)
     : _opts(opts),
       _trx(opts->trx()),
+      _tmpVar(tmpVar),
       _currentCursor(0),
       _currentSubCursor(0),
       _cachePos(0),
-      _internalCursorMapping(mapping) {
-  _cursors.reserve(nrCursors);
+      _internalCursorMapping(mapping),
+      _lookupInfo(lookupInfo) {
   _cache.reserve(1000);
+  TRI_ASSERT(_opts->cache() != nullptr);
+
   if (_opts->cache() == nullptr) {
     THROW_ARANGO_EXCEPTION_MESSAGE(
         TRI_ERROR_INTERNAL, "no cache present for single server edge cursor");
   }
 }
 
-SingleServerEdgeCursor::~SingleServerEdgeCursor() {
-  for (auto& it : _cursors) {
-    for (auto& it2 : it) {
-      delete it2;
-    }
-  }
-}
+SingleServerEdgeCursor::~SingleServerEdgeCursor() = default;
 
 #ifdef USE_ENTERPRISE
 static bool CheckInaccessible(transaction::Methods* trx, VPackSlice const& edge) {
@@ -80,9 +84,6 @@ static bool CheckInaccessible(transaction::Methods* trx, VPackSlice const& edge)
 
 void SingleServerEdgeCursor::getDocAndRunCallback(OperationCursor* cursor, EdgeCursor::Callback const& callback) {
   auto collection = cursor->collection();
-  if (collection == nullptr) {
-    return;
-  }
   EdgeDocumentToken etkn(collection->id(), _cache[_cachePos++]);
   collection->readDocumentWithCallback(
       _trx, etkn.localDocumentId(), [&](LocalDocumentId const&, VPackSlice edgeDoc) {
@@ -108,19 +109,20 @@ void SingleServerEdgeCursor::getDocAndRunCallback(OperationCursor* cursor, EdgeC
 }
 
 bool SingleServerEdgeCursor::advanceCursor(OperationCursor*& cursor,
-                                           std::vector<OperationCursor*>& cursorSet) {
+                                           std::vector<std::unique_ptr<OperationCursor>>*& cursorSet) {
+  TRI_ASSERT(!_cursors.empty());
   ++_currentSubCursor;
-  if (_currentSubCursor >= cursorSet.size()) {
+  if (_currentSubCursor >= cursorSet->size()) {
     ++_currentCursor;
     _currentSubCursor = 0;
     if (_currentCursor == _cursors.size()) {
       // We are done, all cursors exhausted.
       return false;
     }
-    cursorSet = _cursors[_currentCursor];
+    cursorSet = &_cursors[_currentCursor];
   }
 
-  cursor = cursorSet[_currentSubCursor];
+  cursor = (*cursorSet)[_currentSubCursor].get();
   // If we switch the cursor. We have to clear the cache.
   _cache.clear();
   return true;
@@ -130,6 +132,7 @@ bool SingleServerEdgeCursor::next(EdgeCursor::Callback const& callback) {
   // fills callback with next EdgeDocumentToken and Slice that contains the
   // ohter side of the edge (we are standing on a node and want to iterate all
   // connected edges
+  TRI_ASSERT(!_cursors.empty());
 
   if (_currentCursor == _cursors.size()) {
     return false;
@@ -138,22 +141,21 @@ bool SingleServerEdgeCursor::next(EdgeCursor::Callback const& callback) {
   // There is still something in the cache
   if (_cachePos < _cache.size()) {
     // get the collection
-    auto cur = _cursors[_currentCursor][_currentSubCursor];
-    getDocAndRunCallback(cur, callback);
+    getDocAndRunCallback(_cursors[_currentCursor][_currentSubCursor].get(), callback);
     return true;
   }
 
   // We need to refill the cache.
   _cachePos = 0;
-  auto cursorSet = _cursors[_currentCursor];
+  auto* cursorSet = &_cursors[_currentCursor];
 
   // get current cursor
-  auto cursor = cursorSet[_currentSubCursor];
+  auto cursor = (*cursorSet)[_currentSubCursor].get();
 
   // NOTE: We cannot clear the cache,
   // because the cursor expect's it to be filled.
   do {
-    if (cursorSet.empty() || !cursor->hasMore()) {
+    if (cursorSet->empty() || !cursor->hasMore()) {
       if (!advanceCursor(cursor, cursorSet)) {
         return false;
       }
@@ -168,9 +170,6 @@ bool SingleServerEdgeCursor::next(EdgeCursor::Callback const& callback) {
               return false;
             }
 #endif
-            if (cursor->collection() == nullptr) {
-              return false;
-            }
             operationSuccessful = true;
             auto etkn = EdgeDocumentToken(cursor->collection()->id(), token);
             if (_internalCursorMapping != nullptr) {
@@ -209,6 +208,7 @@ bool SingleServerEdgeCursor::next(EdgeCursor::Callback const& callback) {
 }
 
 void SingleServerEdgeCursor::readAll(EdgeCursor::Callback const& callback) {
+  TRI_ASSERT(!_cursors.empty());
   size_t cursorId = 0;
   for (_currentCursor = 0; _currentCursor < _cursors.size(); ++_currentCursor) {
     if (_internalCursorMapping != nullptr) {
@@ -220,9 +220,6 @@ void SingleServerEdgeCursor::readAll(EdgeCursor::Callback const& callback) {
     auto& cursorSet = _cursors[_currentCursor];
     for (auto& cursor : cursorSet) {
       LogicalCollection* collection = cursor->collection();
-      if (collection == nullptr) {
-        continue;
-      }
       auto cid = collection->id();
       if (cursor->hasExtra()) {
         auto cb = [&](LocalDocumentId const& token, VPackSlice edge) {
@@ -259,3 +256,96 @@ void SingleServerEdgeCursor::readAll(EdgeCursor::Callback const& callback) {
     }
   }
 }
+  
+void SingleServerEdgeCursor::rearm(arangodb::velocypack::StringRef vertex, uint64_t /*depth*/) {
+  _currentCursor = 0;
+  _currentSubCursor = 0;
+  _cache.clear();
+  _cachePos = 0;
+
+  if (_cursors.empty()) {
+    buildLookupInfo(vertex);
+    return;
+  }
+
+  size_t i = 0;
+  for (auto& info : _lookupInfo) {
+    auto& node = info.indexCondition;
+    TRI_ASSERT(node->numMembers() > 0);
+    if (info.conditionNeedUpdate) {
+      // We have to inject _from/_to iff the condition needs it
+      auto dirCmp = node->getMemberUnchecked(info.conditionMemberToUpdate);
+      TRI_ASSERT(dirCmp->type == aql::NODE_TYPE_OPERATOR_BINARY_EQ);
+      TRI_ASSERT(dirCmp->numMembers() == 2);
+
+      auto idNode = dirCmp->getMemberUnchecked(1);
+      TRI_ASSERT(idNode->type == aql::NODE_TYPE_VALUE);
+      TRI_ASSERT(idNode->isValueType(aql::VALUE_TYPE_STRING));
+      // must edit node in place; TODO replace node?
+      TEMPORARILY_UNLOCK_NODE(idNode);
+      idNode->setStringValue(vertex.data(), vertex.length());
+    }
+
+    auto& csrs = _cursors[i++];
+    size_t j = 0;
+    for (auto const& it : info.idxHandles) {
+      auto* cursor = csrs[j].get();
+      // check if the underlying index iterator supports rearming
+      IndexIterator* idxIterator = cursor->indexIterator();
+      if (idxIterator->canRearm()) {
+        // rearming supported
+        idxIterator->rearm(node, _tmpVar, ::defaultIndexIteratorOptions);
+        cursor->reset();
+      } else {
+        // rearming not supported - we need to throw away the index iterator
+        // and create a new one
+        csrs[j] = std::make_unique<OperationCursor>(_trx->indexScanForCondition(it, node, _tmpVar, ::defaultIndexIteratorOptions));
+      }
+      ++j;
+    }
+  }
+}
+
+void SingleServerEdgeCursor::buildLookupInfo(arangodb::velocypack::StringRef vertex) { 
+  TRI_ASSERT(_cursors.empty());
+  _cursors.reserve(_lookupInfo.size());
+    
+  if (_internalCursorMapping == nullptr) {
+    for (auto& info : _lookupInfo) {
+      addCursor(info, vertex);
+    }
+  } else {
+    for (auto& index : *_internalCursorMapping) {
+      TRI_ASSERT(index < _lookupInfo.size());
+      auto& info = _lookupInfo[index];
+      addCursor(info, vertex);
+    }
+  }
+  TRI_ASSERT(_internalCursorMapping == nullptr || _internalCursorMapping->size() == _cursors.size());
+}
+
+void SingleServerEdgeCursor::addCursor(BaseOptions::LookupInfo const& info, arangodb::velocypack::StringRef vertex) {
+  auto& node = info.indexCondition;
+  TRI_ASSERT(node->numMembers() > 0);
+  if (info.conditionNeedUpdate) {
+    // We have to inject _from/_to iff the condition needs it
+    auto dirCmp = node->getMemberUnchecked(info.conditionMemberToUpdate);
+    TRI_ASSERT(dirCmp->type == aql::NODE_TYPE_OPERATOR_BINARY_EQ);
+    TRI_ASSERT(dirCmp->numMembers() == 2);
+
+    auto idNode = dirCmp->getMemberUnchecked(1);
+    TRI_ASSERT(idNode->type == aql::NODE_TYPE_VALUE);
+    TRI_ASSERT(idNode->isValueType(aql::VALUE_TYPE_STRING));
+    // must edit node in place; TODO replace node?
+    TEMPORARILY_UNLOCK_NODE(idNode);
+    idNode->setStringValue(vertex.data(), vertex.length());
+  }
+  
+  _cursors.emplace_back();
+  auto& csrs = _cursors.back();
+  csrs.reserve(info.idxHandles.size());
+  for (auto const& it : info.idxHandles) {
+    csrs.emplace_back(
+        std::make_unique<OperationCursor>(_trx->indexScanForCondition(it, node, _tmpVar, ::defaultIndexIteratorOptions)));
+  }
+}
diff --git a/arangod/Graph/SingleServerEdgeCursor.h b/arangod/Graph/SingleServerEdgeCursor.h
index 270cdfecf4fd..122e979ea7f0 100644
--- a/arangod/Graph/SingleServerEdgeCursor.h
+++ b/arangod/Graph/SingleServerEdgeCursor.h
@@ -24,9 +24,11 @@
 #ifndef ARANGOD_GRAPH_SINGLE_SERVER_EDGE_CURSOR_H
 #define ARANGOD_GRAPH_SINGLE_SERVER_EDGE_CURSOR_H 1
 
+#include <memory>
 #include <vector>
 
 #include "Basics/Common.h"
+#include "BaseOptions.h"
 #include "Graph/EdgeCursor.h"
 
 #include <velocypack/StringRef.h>
@@ -37,6 +39,10 @@ class LocalDocumentId;
 struct OperationCursor;
 class LogicalCollection;
 
+namespace aql {
+struct Variable;
+}
+
 namespace transaction {
 class Methods;
 }
@@ -51,18 +57,23 @@ struct SingleServerEdgeDocumentToken;
 
 class SingleServerEdgeCursor final : public EdgeCursor {
  private:
-  BaseOptions* _opts;
+  BaseOptions const* _opts;
   transaction::Methods* _trx;
-  std::vector<std::vector<OperationCursor*>> _cursors;
+  aql::Variable const* _tmpVar;
+  // TODO: make this a flat vector
+  std::vector<std::vector<std::unique_ptr<OperationCursor>>> _cursors;
   size_t _currentCursor;
   size_t _currentSubCursor;
   std::vector<LocalDocumentId> _cache;
   size_t _cachePos;
   std::vector<size_t> const* _internalCursorMapping;
+  std::vector<BaseOptions::LookupInfo> const& _lookupInfo;
 
  public:
-  SingleServerEdgeCursor(BaseOptions* options, size_t,
-                         std::vector<size_t> const* mapping = nullptr);
+  explicit SingleServerEdgeCursor(BaseOptions const* options, 
+                                  aql::Variable const* tmpVar,
+                                  std::vector<size_t> const* mapping,
+                                  std::vector<BaseOptions::LookupInfo> const& lookupInfo);
 
   ~SingleServerEdgeCursor();
 
@@ -70,17 +81,22 @@ class SingleServerEdgeCursor final : public EdgeCursor {
 
   void readAll(EdgeCursor::Callback const& callback) override;
 
-  std::vector<std::vector<OperationCursor*>>& getCursors() { return _cursors; }
-  
   /// @brief number of HTTP requests performed. always 0 in single server
   size_t httpRequests() const override { return 0; }
-
+  
+  void rearm(arangodb::velocypack::StringRef vertex, uint64_t depth) override;
+  
  private:
   // returns false if cursor can not be further advanced
-  bool advanceCursor(OperationCursor*& cursor, std::vector<OperationCursor*>& cursorSet);
+  bool advanceCursor(OperationCursor*& cursor, std::vector<std::unique_ptr<OperationCursor>>*& cursorSet);
 
   void getDocAndRunCallback(OperationCursor*, EdgeCursor::Callback const& callback);
+
+  void buildLookupInfo(arangodb::velocypack::StringRef vertex); 
+
+  void addCursor(BaseOptions::LookupInfo const& info, arangodb::velocypack::StringRef vertex);
 };
+
 }  // namespace graph
 }  // namespace arangodb
 
diff --git a/arangod/Graph/SingleServerTraverser.cpp b/arangod/Graph/SingleServerTraverser.cpp
index 57111edacd18..1c8ab7c4f8c1 100644
--- a/arangod/Graph/SingleServerTraverser.cpp
+++ b/arangod/Graph/SingleServerTraverser.cpp
@@ -24,7 +24,9 @@
 #include "SingleServerTraverser.h"
 #include "Aql/AqlValue.h"
 #include "Graph/BreadthFirstEnumerator.h"
+#include "Graph/EdgeCursor.h"
 #include "Graph/NeighborsEnumerator.h"
+#include "Graph/PathEnumerator.h"
 #include "Graph/TraverserCache.h"
 #include "Graph/TraverserOptions.h"
 #include "Transaction/Methods.h"
@@ -81,12 +83,16 @@ void SingleServerTraverser::createEnumerator() {
   TRI_ASSERT(_enumerator == nullptr);
 
   if (_opts->useBreadthFirst) {
-    if (_canUseOptimizedNeighbors) {
+    // breadth-first enumerator
+    if (_opts->useNeighbors) {
+      // optimized neighbors enumerator
       _enumerator.reset(new NeighborsEnumerator(this, _opts));
     } else {
+      // default breadth-first enumerator
       _enumerator.reset(new BreadthFirstEnumerator(this, _opts));
     }
   } else {
+    // normal, depth-first enumerator
     _enumerator.reset(new DepthFirstEnumerator(this, _opts));
   }
 }
diff --git a/arangod/Graph/SingleServerTraverser.h b/arangod/Graph/SingleServerTraverser.h
index 579c8295bd2b..914e417a6a18 100644
--- a/arangod/Graph/SingleServerTraverser.h
+++ b/arangod/Graph/SingleServerTraverser.h
@@ -32,7 +32,6 @@ namespace arangodb {
 
 namespace graph {
 struct BaseOptions;
-class SingleServerEdgeCursor;
 }  // namespace graph
 
 namespace traverser {
diff --git a/arangod/Graph/Traverser.cpp b/arangod/Graph/Traverser.cpp
index 4c9e3c6e5b12..e826cf1eb17c 100644
--- a/arangod/Graph/Traverser.cpp
+++ b/arangod/Graph/Traverser.cpp
@@ -131,7 +131,6 @@ void Traverser::UniqueVertexGetter::reset(arangodb::velocypack::StringRef const&
 Traverser::Traverser(arangodb::traverser::TraverserOptions* opts, transaction::Methods* trx)
     : _trx(trx),
       _done(true),
-      _canUseOptimizedNeighbors(false),
       _opts(opts) {
   if (opts->uniqueVertices == TraverserOptions::UniquenessLevel::GLOBAL) {
     _vertexGetter = std::make_unique<UniqueVertexGetter>(this);
@@ -145,10 +144,7 @@ Traverser::~Traverser() = default;
 bool arangodb::traverser::Traverser::edgeMatchesConditions(VPackSlice e,
                                                            arangodb::velocypack::StringRef vid,
                                                            uint64_t depth, size_t cursorId) {
-  if (!_opts->evaluateEdgeExpression(e, vid, depth, cursorId)) {
-    return false;
-  }
-  return true;
+  return _opts->evaluateEdgeExpression(e, vid, depth, cursorId);
 }
 
 bool arangodb::traverser::Traverser::vertexMatchesConditions(arangodb::velocypack::StringRef v,
@@ -186,12 +182,5 @@ size_t arangodb::traverser::Traverser::getAndResetReadDocuments() {
 }
 
 size_t arangodb::traverser::Traverser::getAndResetHttpRequests() {
-  if (_enumerator != nullptr) {
-    return _enumerator->getAndResetHttpRequests();
-  }
-  return 0;
-}
-
-void arangodb::traverser::Traverser::allowOptimizedNeighbors() {
-  _canUseOptimizedNeighbors = true;
+  return _enumerator->getAndResetHttpRequests();
 }
diff --git a/arangod/Graph/Traverser.h b/arangod/Graph/Traverser.h
index 953b7b1d021b..0e056c04c362 100644
--- a/arangod/Graph/Traverser.h
+++ b/arangod/Graph/Traverser.h
@@ -292,8 +292,6 @@ class Traverser {
 
   bool vertexMatchesConditions(arangodb::velocypack::StringRef vid, uint64_t depth);
 
-  void allowOptimizedNeighbors();
-
   transaction::Methods* trx() const { return _trx; }
 
   //////////////////////////////////////////////////////////////////////////////
@@ -314,8 +312,6 @@ class Traverser {
 
   /// @brief indicator if this traversal is done
   bool _done;
-  
-  bool _canUseOptimizedNeighbors;
 
   /// @brief options for traversal
   TraverserOptions* _opts;
diff --git a/arangod/Graph/TraverserCache.h b/arangod/Graph/TraverserCache.h
index 642f1bd54531..dd8ddc247dfb 100644
--- a/arangod/Graph/TraverserCache.h
+++ b/arangod/Graph/TraverserCache.h
@@ -32,8 +32,6 @@
 #include <unordered_set>
 
 namespace arangodb {
-class ManagedDocumentResult;
-class StringHeap;
 
 namespace transaction {
 class Methods;
diff --git a/arangod/Graph/TraverserCacheFactory.cpp b/arangod/Graph/TraverserCacheFactory.cpp
index 614c9aaa79e6..b1417d60616e 100644
--- a/arangod/Graph/TraverserCacheFactory.cpp
+++ b/arangod/Graph/TraverserCacheFactory.cpp
@@ -32,9 +32,9 @@
 using namespace arangodb;
 using namespace arangodb::graph;
 using namespace arangodb::traverser;
-using namespace arangodb::graph::cacheFactory;
+using namespace arangodb::graph::CacheFactory;
 
-TraverserCache* cacheFactory::CreateCache(
+TraverserCache* CacheFactory::CreateCache(
     arangodb::aql::Query* query, bool activateDocumentCache,
     std::unordered_map<ServerID, traverser::TraverserEngineID> const* engines, BaseOptions const* opts) {
   if (ServerState::instance()->isCoordinator()) {
diff --git a/arangod/Graph/TraverserCacheFactory.h b/arangod/Graph/TraverserCacheFactory.h
index 08fb7d6af24f..5d84f539485c 100644
--- a/arangod/Graph/TraverserCacheFactory.h
+++ b/arangod/Graph/TraverserCacheFactory.h
@@ -35,7 +35,7 @@ namespace graph {
 class TraverserCache;
 struct BaseOptions;
 
-namespace cacheFactory {
+namespace CacheFactory {
 TraverserCache* CreateCache(arangodb::aql::Query* query, bool activateDocumentCache,
                             std::unordered_map<ServerID, traverser::TraverserEngineID> const* engines, BaseOptions const* opts);
 
diff --git a/arangod/Graph/TraverserOptions.cpp b/arangod/Graph/TraverserOptions.cpp
index 1439de1055bd..9a38d5060b12 100644
--- a/arangod/Graph/TraverserOptions.cpp
+++ b/arangod/Graph/TraverserOptions.cpp
@@ -31,6 +31,7 @@
 #include "Basics/tryEmplaceHelper.h"
 #include "Basics/VelocyPackHelper.h"
 #include "Cluster/ClusterEdgeCursor.h"
+#include "Graph/SingleServerEdgeCursor.h"
 #include "Graph/SingleServerTraverser.h"
 #include "Indexes/Index.h"
 
@@ -70,6 +71,7 @@ TraverserOptions::TraverserOptions(aql::Query* query)
       minDepth(1),
       maxDepth(1),
       useBreadthFirst(false),
+      useNeighbors(false),
       uniqueVertices(UniquenessLevel::NONE),
       uniqueEdges(UniquenessLevel::PATH) {}
 
@@ -80,6 +82,7 @@ TraverserOptions::TraverserOptions(aql::Query* query, VPackSlice const& obj)
       minDepth(1),
       maxDepth(1),
       useBreadthFirst(false),
+      useNeighbors(false),
       uniqueVertices(UniquenessLevel::NONE),
       uniqueEdges(UniquenessLevel::PATH) {
   TRI_ASSERT(obj.isObject());
@@ -94,6 +97,10 @@ TraverserOptions::TraverserOptions(aql::Query* query, VPackSlice const& obj)
   maxDepth = VPackHelper::getNumericValue<uint64_t>(obj, "maxDepth", 1);
   TRI_ASSERT(minDepth <= maxDepth);
   useBreadthFirst = VPackHelper::getBooleanValue(obj, "bfs", false);
+  useNeighbors = VPackHelper::getBooleanValue(obj, "neighbors", false);
+
+  TRI_ASSERT(!useNeighbors || useBreadthFirst);
+  
   std::string tmp = VPackHelper::getStringValue(obj, "uniqueVertices", "");
   if (tmp == "path") {
     uniqueVertices = TraverserOptions::UniquenessLevel::PATH;
@@ -102,7 +109,7 @@ TraverserOptions::TraverserOptions(aql::Query* query, VPackSlice const& obj)
       THROW_ARANGO_EXCEPTION_MESSAGE(TRI_ERROR_BAD_PARAMETER,
                                      "uniqueVertices: 'global' is only "
                                      "supported, with bfs: true due to "
-                                     "unpredictable results.");
+                                     "otherwise unpredictable results.");
     }
     uniqueVertices = TraverserOptions::UniquenessLevel::GLOBAL;
   } else {
@@ -115,7 +122,7 @@ TraverserOptions::TraverserOptions(aql::Query* query, VPackSlice const& obj)
   } else if (tmp == "global") {
     THROW_ARANGO_EXCEPTION_MESSAGE(TRI_ERROR_BAD_PARAMETER,
                                    "uniqueEdges: 'global' is not supported, "
-                                   "due to unpredictable results. Use 'path' "
+                                   "due to otherwise unpredictable results. Use 'path' "
                                    "or 'none' instead");
   } else {
     uniqueEdges = TraverserOptions::UniquenessLevel::PATH;
@@ -174,6 +181,7 @@ arangodb::traverser::TraverserOptions::TraverserOptions(arangodb::aql::Query* qu
       minDepth(1),
       maxDepth(1),
       useBreadthFirst(false),
+      useNeighbors(false),
       uniqueVertices(UniquenessLevel::NONE),
       uniqueEdges(UniquenessLevel::PATH) {
 #ifdef ARANGODB_ENABLE_MAINTAINER_MODE
@@ -203,6 +211,12 @@ arangodb::traverser::TraverserOptions::TraverserOptions(arangodb::aql::Query* qu
                                    "The options require a bfs");
   }
   useBreadthFirst = read.getBool();
+  
+  read = info.get("neighbors");
+  if (read.isBoolean()) {
+    useNeighbors = read.getBool();
+  }
+  TRI_ASSERT(!useNeighbors || useBreadthFirst);
 
   read = info.get("uniqueVertices");
   if (!read.isInteger()) {
@@ -357,6 +371,7 @@ arangodb::traverser::TraverserOptions::TraverserOptions(TraverserOptions const&
       minDepth(other.minDepth),
       maxDepth(other.maxDepth),
       useBreadthFirst(other.useBreadthFirst),
+      useNeighbors(other.useNeighbors),
       uniqueVertices(other.uniqueVertices),
       uniqueEdges(other.uniqueEdges),
       vertexCollections(other.vertexCollections),
@@ -385,6 +400,7 @@ void TraverserOptions::toVelocyPack(VPackBuilder& builder) const {
   builder.add("minDepth", VPackValue(minDepth));
   builder.add("maxDepth", VPackValue(maxDepth));
   builder.add("bfs", VPackValue(useBreadthFirst));
+  builder.add("neighbors", VPackValue(useNeighbors));
 
   switch (uniqueVertices) {
     case TraverserOptions::UniquenessLevel::NONE:
@@ -462,6 +478,7 @@ void TraverserOptions::buildEngineInfo(VPackBuilder& result) const {
   result.add("minDepth", VPackValue(minDepth));
   result.add("maxDepth", VPackValue(maxDepth));
   result.add("bfs", VPackValue(useBreadthFirst));
+  result.add("neighbors", VPackValue(useNeighbors));
 
   result.add(VPackValue("uniqueVertices"));
   switch (uniqueVertices) {
@@ -621,7 +638,6 @@ bool TraverserOptions::evaluateEdgeExpression(arangodb::velocypack::Slice edge,
     auto idNode = dirCmp->getMemberUnchecked(1);
     TRI_ASSERT(idNode->type == aql::NODE_TYPE_VALUE);
     TRI_ASSERT(idNode->isValueType(aql::VALUE_TYPE_STRING));
-    idNode->stealComputedValue();
     idNode->setStringValue(vertexId.data(), vertexId.length());
   }
   if (edge.isExternal()) {
@@ -664,23 +680,19 @@ bool TraverserOptions::destinationCollectionAllowed(VPackSlice edge,
   return true;
 }
 
-EdgeCursor* arangodb::traverser::TraverserOptions::nextCursor(
-    arangodb::velocypack::StringRef vid, uint64_t depth) {
+std::unique_ptr<EdgeCursor> arangodb::traverser::TraverserOptions::buildCursor(uint64_t depth) {
+  ensureCache();
+
   if (_isCoordinator) {
-    return nextCursorCoordinator(vid, depth);
+    return std::make_unique<ClusterTraverserEdgeCursor>(this);
   }
+  
   auto specific = _depthLookupInfo.find(depth);
   if (specific != _depthLookupInfo.end()) {
-    return nextCursorLocal(vid, specific->second);
+    return std::make_unique<graph::SingleServerEdgeCursor>(this, _tmpVar, nullptr, specific->second);
   }
-  return nextCursorLocal(vid, _baseLookupInfos);
-}
 
-EdgeCursor* TraverserOptions::nextCursorCoordinator(arangodb::velocypack::StringRef vid,
-                                                    uint64_t depth) {
-  TRI_ASSERT(_traverser != nullptr);
-  auto cursor = std::make_unique<ClusterEdgeCursor>(vid, depth, this);
-  return cursor.release();
+  return std::make_unique<graph::SingleServerEdgeCursor>(this, _tmpVar, nullptr, _baseLookupInfos);
 }
 
 void TraverserOptions::linkTraverser(ClusterTraverser* trav) {
diff --git a/arangod/Graph/TraverserOptions.h b/arangod/Graph/TraverserOptions.h
index be46c0bf2219..b9a5538c7224 100644
--- a/arangod/Graph/TraverserOptions.h
+++ b/arangod/Graph/TraverserOptions.h
@@ -32,6 +32,8 @@
 
 #include <velocypack/StringRef.h>
 
+#include <memory>
+
 namespace arangodb {
 
 namespace velocypack {
@@ -48,6 +50,10 @@ class TraversalNode;
 struct Variable;
 }  // namespace aql
 
+namespace graph {
+class EdgeCursor;
+}
+
 namespace traverser {
 
 class ClusterTraverser;
@@ -78,6 +84,8 @@ struct TraverserOptions : public graph::BaseOptions {
 
   bool useBreadthFirst;
 
+  bool useNeighbors;
+
   UniquenessLevel uniqueVertices;
 
   UniquenessLevel uniqueEdges;
@@ -117,6 +125,8 @@ struct TraverserOptions : public graph::BaseOptions {
   void addDepthLookupInfo(aql::ExecutionPlan* plan, std::string const& collectionName,
                           std::string const& attributeName,
                           aql::AstNode* condition, uint64_t depth);
+  
+  bool hasDepthLookupInfo() const { return !_depthLookupInfo.empty(); }
 
   bool vertexHasFilter(uint64_t) const;
 
@@ -132,9 +142,9 @@ struct TraverserOptions : public graph::BaseOptions {
 
   bool destinationCollectionAllowed(velocypack::Slice edge, velocypack::StringRef sourceVertex);
 
-  graph::EdgeCursor* nextCursor(arangodb::velocypack::StringRef vid, uint64_t);
-
   void linkTraverser(arangodb::traverser::ClusterTraverser*);
+  
+  std::unique_ptr<arangodb::graph::EdgeCursor> buildCursor(uint64_t depth);
 
   double estimateCost(size_t& nrItems) const override;
 
@@ -148,9 +158,6 @@ struct TraverserOptions : public graph::BaseOptions {
     TRI_ASSERT(usesPrune());
     return _pruneExpression.get();
   }
-
- private:
-  graph::EdgeCursor* nextCursorCoordinator(arangodb::velocypack::StringRef vid, uint64_t);
 };
 }  // namespace traverser
 }  // namespace arangodb
diff --git a/arangod/IResearch/ExpressionFilter.cpp b/arangod/IResearch/ExpressionFilter.cpp
index b0c0cfaeddf2..80b5fe7874d5 100644
--- a/arangod/IResearch/ExpressionFilter.cpp
+++ b/arangod/IResearch/ExpressionFilter.cpp
@@ -48,7 +48,7 @@ inline irs::filter::prepared::ptr compileQuery(
   irs::bstring stats(order.stats_size(), 0);
 
   // skip filed-level/term-level statistics because there are no fields/terms
-  order.prepare_collectors().finish(&stats[0], index);
+  order.fixed_prepare_collectors().finish(&stats[0], index);
 
   return irs::filter::prepared::make<type_t>(ctx, std::move(stats), boost);
 }
diff --git a/arangod/IResearch/IResearchAnalyzerFeature.cpp b/arangod/IResearch/IResearchAnalyzerFeature.cpp
index d727f9ed20f8..9f216ff9bcfd 100644
--- a/arangod/IResearch/IResearchAnalyzerFeature.cpp
+++ b/arangod/IResearch/IResearchAnalyzerFeature.cpp
@@ -74,7 +74,6 @@
 #include "VocBase/LocalDocumentId.h"
 #include "VocBase/LogicalCollection.h"
 #include "VocBase/LogicalView.h"
-#include "VocBase/ManagedDocumentResult.h"
 #include "VocBase/vocbase.h"
 #include "VocBase/Methods/Collections.h"
 
diff --git a/arangod/IResearch/IResearchFeature.cpp b/arangod/IResearch/IResearchFeature.cpp
index 0eb3a4537ae5..ba0696674723 100644
--- a/arangod/IResearch/IResearchFeature.cpp
+++ b/arangod/IResearch/IResearchFeature.cpp
@@ -96,7 +96,7 @@ arangodb::aql::AqlValue dummyFilterFunc(arangodb::aql::ExpressionContext*,
                                         arangodb::containers::SmallVector<arangodb::aql::AqlValue> const&) {
   THROW_ARANGO_EXCEPTION_MESSAGE(
       TRI_ERROR_NOT_IMPLEMENTED,
-      "ArangoSearch filter functions EXISTS, IN_RANGE, PHRASE "
+      "ArangoSearch filter functions EXISTS, IN_RANGE, PHRASE, NGRAM_MATCH "
       " are designed to be used only within a corresponding SEARCH statement "
       "of ArangoSearch view."
       " Please ensure function signature is correct.");
@@ -407,6 +407,7 @@ void registerFilters(arangodb::aql::AqlFunctionFeature& functions) {
   addFunction(functions, { "MIN_MATCH", ".,.|.+", flags, &minMatchFunc });  // (filter expression [, filter expression, ... ], min match count)
   addFunction(functions, { "BOOST", ".,.", flags, &contextFunc });  // (filter expression, boost)
   addFunction(functions, { "ANALYZER", ".,.", flags, &contextFunc });  // (filter expression, analyzer)
+  addFunction(functions, { "NGRAM_MATCH", ".,.|.,.", flags, &dummyFilterFunc }); // (attribute, target, threshold, [analyzer]) OR (attribute, target, [analyzer])
 }
 
 namespace {
diff --git a/arangod/IResearch/IResearchFilterFactory.cpp b/arangod/IResearch/IResearchFilterFactory.cpp
index 01bf8dbb69da..f83ca12f5e6a 100644
--- a/arangod/IResearch/IResearchFilterFactory.cpp
+++ b/arangod/IResearch/IResearchFilterFactory.cpp
@@ -37,6 +37,7 @@
 #include "search/range_filter.hpp"
 #include "search/term_filter.hpp"
 #include "search/wildcard_filter.hpp"
+#include "search/ngram_similarity_filter.hpp"
 
 #include "ApplicationFeatures/ApplicationServer.h"
 #include "Aql/Ast.h"
@@ -228,7 +229,7 @@ arangodb::Result evaluateArg(
     char const* funcName,
     arangodb::aql::AstNode const& args,
     size_t i,
-    irs::boolean_filter const* filter,
+    bool isFilter,
     QueryContext const& ctx) {
   static_assert(
     std::is_same<T, irs::string_ref>::value ||
@@ -250,7 +251,7 @@ arangodb::Result evaluateArg(
 
   value.reset(*arg);
 
-  if (filter || value.isConstant()) {
+  if (isFilter || value.isConstant()) {
     if (!value.execute(ctx)) {
       return error::failedToEvaluate(funcName, i + 1);
     }
@@ -286,22 +287,13 @@ arangodb::Result evaluateArg(
   return {};
 }
 
-arangodb::Result extractAnalyzerFromArg(
+arangodb::Result getAnalyzerByName(
     arangodb::iresearch::FieldMeta::Analyzer& out,
+    const irs::string_ref& analyzerId,
     char const* funcName,
-    irs::boolean_filter const* filter,
-    arangodb::aql::AstNode const& args,
-    size_t i,
     QueryContext const& ctx) {
-  auto const* analyzerArg = args.getMemberUnchecked(i);
-
-  if (!analyzerArg) {
-    return {
-      TRI_ERROR_BAD_PARAMETER,
-      "'"s.append(funcName).append("' AQL function: ")
-          .append(std::to_string(i + 1)).append(" argument is invalid analyzer")
-    };
-  }
+  auto& analyzer = out._pool;
+  auto& shortName = out._shortName;
 
   TRI_ASSERT(ctx.trx);
   auto& server = ctx.trx->vocbase().server();
@@ -315,31 +307,15 @@ arangodb::Result extractAnalyzerFromArg(
   }
   auto& analyzerFeature = server.getFeature<IResearchAnalyzerFeature>();
 
-  ScopedAqlValue analyzerValue(*analyzerArg);
-  irs::string_ref analyzerId;
-
-  auto rv = evaluateArg(analyzerId, analyzerValue, funcName, args, i, filter, ctx);
-
-  if (rv.fail()) {
-    return rv;
-  }
-
-  if (!filter && !analyzerValue.isConstant()) {
-    return {};
-  }
-
-  auto& analyzer = out._pool;
-  auto& shortName = out._shortName;
-
   auto sysVocbase = server.hasFeature<arangodb::SystemDatabaseFeature>()
-                        ? server.getFeature<arangodb::SystemDatabaseFeature>().use()
-                        : nullptr;
+    ? server.getFeature<arangodb::SystemDatabaseFeature>().use()
+    : nullptr;
 
   if (sysVocbase) {
     analyzer = analyzerFeature.get(analyzerId, ctx.trx->vocbase(), *sysVocbase);
 
     shortName = arangodb::iresearch::IResearchAnalyzerFeature::normalize(  // normalize
-        analyzerId, ctx.trx->vocbase(), *sysVocbase, false);  // args
+      analyzerId, ctx.trx->vocbase(), *sysVocbase, false);  // args
   }
 
   if (!analyzer) {
@@ -353,6 +329,39 @@ arangodb::Result extractAnalyzerFromArg(
   return {};
 }
 
+arangodb::Result extractAnalyzerFromArg(
+    arangodb::iresearch::FieldMeta::Analyzer& out,
+    char const* funcName,
+    irs::boolean_filter const* filter,
+    arangodb::aql::AstNode const& args,
+    size_t i,
+    QueryContext const& ctx) {
+  auto const* analyzerArg = args.getMemberUnchecked(i);
+
+  if (!analyzerArg) {
+    return {
+      TRI_ERROR_BAD_PARAMETER,
+      "'"s.append(funcName).append("' AQL function: ")
+          .append(std::to_string(i + 1)).append(" argument is invalid analyzer")
+    };
+  }
+
+  ScopedAqlValue analyzerValue(*analyzerArg);
+  irs::string_ref analyzerId;
+
+  auto rv = evaluateArg(analyzerId, analyzerValue, funcName, args, i, filter, ctx);
+
+  if (rv.fail()) {
+    return rv;
+  }
+
+  if (!filter && !analyzerValue.isConstant()) {
+    return {};
+  }
+
+  return getAnalyzerByName(out, analyzerId, funcName, ctx);
+}
+
 struct FilterContext {
   FilterContext( // constructor
       arangodb::iresearch::FieldMeta::Analyzer const& analyzer, // analyzer
@@ -396,7 +405,7 @@ void appendTerms(irs::by_phrase& filter, irs::string_ref const& value,
 
   // add tokens
   while (stream.next()) {
-    filter.push_back(token.value(), firstOffset);
+    filter.push_back(irs::by_phrase::simple_term{token.value()}, firstOffset);
     firstOffset = 0;
   }
 }
@@ -1723,7 +1732,7 @@ arangodb::Result fromFuncAnalyzer(
 
   auto rv = evaluateArg<decltype(analyzerId), true>(
         analyzerId, analyzerIdValue, funcName,
-        args, 1, filter, ctx);
+        args, 1, filter != nullptr, ctx);
 
   if (rv.fail()) {
     return rv;
@@ -1810,7 +1819,7 @@ arangodb::Result fromFuncBoost(
   // 2nd argument defines a boost
   double_t boostValue = 0;
   auto rv = evaluateArg<decltype(boostValue), true>(
-        boostValue, tmpValue, funcName, args, 1, filter, ctx);
+        boostValue, tmpValue, funcName, args, 1, filter != nullptr, ctx);
 
   if (rv.fail()) {
     return rv;
@@ -1868,7 +1877,7 @@ arangodb::Result fromFuncExists(
     // 2nd argument defines a type (if present)
     ScopedAqlValue argValue;
     irs::string_ref arg;
-    auto rv = evaluateArg(arg, argValue, funcName, args, 1, filter, ctx);
+    auto rv = evaluateArg(arg, argValue, funcName, args, 1, filter != nullptr, ctx);
 
     if (rv.fail()) {
       return rv;
@@ -1987,10 +1996,10 @@ arangodb::Result fromFuncMinMatch(
 
   auto const lastArg = argc - 1;
   ScopedAqlValue minMatchCountValue;
-  int64_t minMatchCount= 0;
+  int64_t minMatchCount = 0;
 
   auto rv = evaluateArg<decltype(minMatchCount), true>(
-        minMatchCount, minMatchCountValue, funcName, args, lastArg, filter, ctx);
+        minMatchCount, minMatchCountValue, funcName, args, lastArg, filter != nullptr, ctx);
 
   if (rv.fail()) {
     return rv;
@@ -2040,6 +2049,332 @@ arangodb::Result fromFuncMinMatch(
   return {};
 }
 
+typedef std::function<
+  arangodb::Result(char const*,
+                   size_t const,
+                   char const*,
+                   irs::by_phrase*,
+                   QueryContext const&,
+                   arangodb::aql::AstNode const&,
+                   size_t)
+> ConversionPhraseHandler;
+
+std::string getSubFuncErrorSuffix(char const* funcName, size_t const funcArgumentPosition) {
+  return " (in '"s.append(funcName).append("' AQL function at position '")
+      .append(std::to_string(funcArgumentPosition + 1)).append("')");
+}
+
+arangodb::Result oneArgumentfromFuncPhrase(char const* funcName,
+                                           size_t const funcArgumentPosition,
+                                           char const* subFuncName,
+                                           irs::by_phrase* filter,
+                                           QueryContext const& ctx,
+                                           arangodb::aql::AstNode const& elem,
+                                           irs::string_ref& term) {
+  if (!elem.isDeterministic()) {
+    auto res = error::nondeterministicArgs(subFuncName);
+    return {
+      res.errorNumber(),
+      res.errorMessage().append(getSubFuncErrorSuffix(funcName, funcArgumentPosition))
+    };
+  }
+
+  if (elem.numMembers() != 1) {
+    auto res = error::invalidArgsCount<error::ExactValue<1>>(subFuncName);
+    return {
+      res.errorNumber(),
+      res.errorMessage().append(getSubFuncErrorSuffix(funcName, funcArgumentPosition))
+    };
+  }
+
+  ScopedAqlValue termValue;
+  auto res = evaluateArg(term, termValue, subFuncName, elem, 0, filter != nullptr, ctx);
+
+  if (res.fail()) {
+    return {
+      res.errorNumber(),
+      res.errorMessage().append(getSubFuncErrorSuffix(funcName, funcArgumentPosition))
+    };
+  }
+  return {};
+}
+
+// {<STARTS_WITH>: [ '[' ] <term> [ ']' ] }
+arangodb::Result fromFuncPhraseStartsWith(char const* funcName,
+                                          size_t funcArgumentPosition,
+                                          char const* subFuncName,
+                                          irs::by_phrase* filter,
+                                          QueryContext const& ctx,
+                                          arangodb::aql::AstNode const& elem,
+                                          size_t firstOffset) {
+  irs::string_ref term;
+  auto res = oneArgumentfromFuncPhrase(funcName, funcArgumentPosition, subFuncName, filter, ctx, elem, term);
+  if (res.fail()) {
+    return res;
+  }
+  if (filter) {
+    // 128 - FIXME make configurable
+    filter->push_back(irs::by_phrase::prefix_term{128, irs::ref_cast<irs::byte_type>(term)}, firstOffset);
+  }
+  return {};
+}
+
+// {<WILDCARD>: [ '[' ] <term> [ ']' ] }
+arangodb::Result fromFuncPhraseLike(char const* funcName,
+                                    size_t const funcArgumentPosition,
+                                    char const* subFuncName,
+                                    irs::by_phrase* filter,
+                                    QueryContext const& ctx,
+                                    arangodb::aql::AstNode const& elem,
+                                    size_t firstOffset) {
+  irs::string_ref term;
+  auto res = oneArgumentfromFuncPhrase(funcName, funcArgumentPosition, subFuncName, filter, ctx, elem, term);
+  if (res.fail()) {
+    return res;
+  }
+  if (filter) {
+    // 128 - FIXME make configurable
+    filter->push_back(irs::by_phrase::wildcard_term{128, irs::ref_cast<irs::byte_type>(term)}, firstOffset);
+  }
+  return {};
+}
+
+template<size_t First>
+arangodb::Result getLevenshteinArguments(char const* funcName, bool isFilter,
+                                         QueryContext const& ctx,
+                                         arangodb::aql::AstNode const& args,
+                                         arangodb::aql::AstNode const** field,
+                                         ScopedAqlValue& targetValue,
+                                         irs::string_ref& target,
+                                         size_t& scoringLimit, int64_t& maxDistance,
+                                         bool& withTranspositions,
+                                         std::string const& errorSuffix = std::string()) {
+  if (!args.isDeterministic()) {
+    auto res = error::nondeterministicArgs(funcName);
+    return {
+      res.errorNumber(),
+      res.errorMessage().append(errorSuffix)
+    };
+  }
+  auto const argc = args.numMembers();
+  constexpr size_t min = 3 - First;
+  constexpr size_t max = 4 - First;
+  if (argc < min || argc > max) {
+    auto res = error::invalidArgsCount<error::Range<min, max>>(funcName);
+    return {
+      res.errorNumber(),
+      res.errorMessage().append(errorSuffix)
+    };
+  }
+
+  if constexpr (0 == First) {
+    TRI_ASSERT(field);
+    // (0 - First) argument defines a field
+    *field = arangodb::iresearch::checkAttributeAccess(args.getMemberUnchecked(0), *ctx.ref);
+
+    if (!*field) {
+      return error::invalidAttribute(funcName, 1);
+    }
+  }
+
+  // (1 - First) argument defines a target
+  auto res = evaluateArg(target, targetValue, funcName, args, 1 - First, isFilter, ctx);
+
+  if (res.fail()) {
+    return {
+      res.errorNumber(),
+      res.errorMessage().append(errorSuffix)
+    };
+  }
+
+  ScopedAqlValue tmpValue; // can reuse value for int64_t and bool
+
+  // (2 - First) argument defines a max distance
+  res = evaluateArg(maxDistance, tmpValue, funcName, args, 2 - First, isFilter, ctx);
+
+  if (res.fail()) {
+    return {
+      res.errorNumber(),
+      res.errorMessage().append(errorSuffix)
+    };
+  }
+
+  if (maxDistance < 0) {
+    return {
+      TRI_ERROR_BAD_PARAMETER, "'"s.append(funcName)
+          .append("' AQL function: max distance must be a non-negative number")
+          .append(errorSuffix)
+    };
+  }
+
+  // optional (3 - First) argument defines transpositions
+  if (4 - First == argc) {
+    res = evaluateArg(withTranspositions, tmpValue, funcName, args, 3 - First, isFilter, ctx);
+
+    if (res.fail()) {
+      return {
+        res.errorNumber(),
+        res.errorMessage().append(errorSuffix)
+      };
+    }
+  }
+
+  if (!withTranspositions && maxDistance > MAX_LEVENSHTEIN_DISTANCE) {
+    return {
+      TRI_ERROR_BAD_PARAMETER,
+      "'"s.append(funcName)
+          .append("' AQL function: max Levenshtein distance must be a number in range [0, ")
+          .append(std::to_string(MAX_LEVENSHTEIN_DISTANCE)).append("]")
+          .append(errorSuffix)
+    };
+  } else if (withTranspositions && maxDistance > MAX_DAMERAU_LEVENSHTEIN_DISTANCE) {
+    return {
+      TRI_ERROR_BAD_PARAMETER,
+      "'"s.append(funcName)
+          .append("' AQL function: max Damerau-Levenshtein distance must be a number in range [0, ")
+          .append(std::to_string(MAX_DAMERAU_LEVENSHTEIN_DISTANCE)).append("]")
+          .append(errorSuffix)
+    };
+  }
+
+  scoringLimit = 128; // FIXME make configurable
+
+  return {};
+}
+
+// {<LEVENSHTEIN_MATCH>: '[' <term>, <max_distance> [, <with_transpositions> ] ']'}
+arangodb::Result fromFuncPhraseLevenshteinMatch(char const* funcName,
+                                                size_t const funcArgumentPosition,
+                                                char const* subFuncName,
+                                                irs::by_phrase* filter,
+                                                QueryContext const& ctx,
+                                                arangodb::aql::AstNode const& array,
+                                                size_t firstOffset) {
+  if (!array.isArray()) {
+    return {
+      TRI_ERROR_BAD_PARAMETER,
+      "'"s.append(funcName).append("' AQL function: '")
+          .append(subFuncName)
+          .append("' arguments must be in an array at position '")
+          .append(std::to_string(funcArgumentPosition + 1)).append("'")
+    };
+  }
+
+  ScopedAqlValue targetValue;
+  irs::string_ref target;
+  size_t scoringLimit = 0;
+  int64_t maxDistance = 0;
+  auto withTranspositions = false;
+  auto res = getLevenshteinArguments<1>(subFuncName, filter != nullptr, ctx, array, nullptr,
+                                        targetValue, target, scoringLimit, maxDistance,
+                                        withTranspositions,
+                                        getSubFuncErrorSuffix(funcName, funcArgumentPosition));
+  if (res.fail()) {
+    return res;
+  }
+
+  if (filter) {
+    filter->push_back(
+          irs::by_phrase::levenshtein_term{withTranspositions, static_cast<irs::byte_type>(maxDistance),
+                                           scoringLimit, &arangodb::iresearch::getParametricDescription,
+                                           irs::ref_cast<irs::byte_type>(target)}, firstOffset);
+  }
+  return {};
+}
+
+// {<TERMS>: '[' <term0> [, <term1>, ...] ']'}
+arangodb::Result fromFuncPhraseTerms(char const* funcName,
+                                     size_t const funcArgumentPosition,
+                                     char const* subFuncName,
+                                     irs::by_phrase* filter,
+                                     QueryContext const& ctx,
+                                     arangodb::aql::AstNode const& array,
+                                     size_t firstOffset) {
+  if (!array.isArray()) {
+    return {
+      TRI_ERROR_BAD_PARAMETER,
+      "'"s.append(funcName).append("' AQL function: '")
+          .append(subFuncName)
+          .append("' arguments must be in an array at position '")
+          .append(std::to_string(funcArgumentPosition + 1)).append("'")
+    };
+  }
+
+  if (!array.isDeterministic()) {
+    auto res = error::nondeterministicArgs(subFuncName);
+    return {
+      res.errorNumber(),
+      res.errorMessage().append(getSubFuncErrorSuffix(funcName, funcArgumentPosition))
+    };
+  }
+
+  auto const argc = array.numMembers();
+  if (0 == argc) {
+    auto res = error::invalidArgsCount<error::OpenRange<false, 1>>(subFuncName);
+    return {
+      res.errorNumber(),
+      res.errorMessage().append(getSubFuncErrorSuffix(funcName, funcArgumentPosition))
+    };
+  }
+
+  std::vector<irs::bstring> terms;
+  terms.reserve(argc);
+  ScopedAqlValue termValue;
+  irs::string_ref term;
+  for (size_t i = 0; i < argc; ++i) {
+    auto res = evaluateArg(term, termValue, subFuncName, array, i, filter != nullptr, ctx);
+
+    if (res.fail()) {
+      return {
+        res.errorNumber(),
+        res.errorMessage().append(getSubFuncErrorSuffix(funcName, funcArgumentPosition))
+      };
+    }
+    terms.emplace_back(irs::ref_cast<irs::byte_type>(term));
+  }
+  if (filter) {
+    filter->push_back(irs::by_phrase::set_term{std::move(terms)}, firstOffset);
+  }
+  return {};
+}
+
+constexpr char const* termsFuncName = "TERMS";
+
+std::map<std::string, ConversionPhraseHandler> const FCallSystemConversionPhraseHandlers {
+  {"STARTS_WITH", fromFuncPhraseStartsWith},
+  {"WILDCARD", fromFuncPhraseLike}, // 'LIKE' is a key word
+  {"LEVENSHTEIN_MATCH", fromFuncPhraseLevenshteinMatch},
+  {termsFuncName, fromFuncPhraseTerms}
+};
+
+// {<STARTS_WITH>|<WILDCARD>|<LEVENSHTEIN_MATCH>|<TERMS>: '[' <term> [, ...] ']'}
+arangodb::Result processPhraseArgObjectType(char const* funcName,
+                                            size_t const funcArgumentPosition,
+                                            irs::by_phrase* filter,
+                                            QueryContext const& ctx,
+                                            arangodb::aql::AstNode const& object,
+                                            size_t firstOffset) {
+  TRI_ASSERT(object.isObject() && object.numMembers() == 1);
+  auto const* objectElem = object.getMember(0);
+  std::string name = objectElem->getStringValue();
+  arangodb::basics::StringUtils::toupperInPlace(name);
+  auto const entry = FCallSystemConversionPhraseHandlers.find(name);
+  if (FCallSystemConversionPhraseHandlers.cend() == entry) {
+    return {
+      TRI_ERROR_BAD_PARAMETER,
+      "'"s.append(funcName).append("' AQL function: Unknown '")
+          .append(objectElem->getStringValue()).append("' at position '")
+          .append(std::to_string(funcArgumentPosition + 1)).append("'")
+    };
+  }
+  TRI_ASSERT(objectElem->numMembers() == 1);
+  auto const* elem = objectElem->getMember(0);
+  if (!elem->isArray()) {
+    elem = objectElem;
+  }
+  return entry->second(funcName, funcArgumentPosition, entry->first.c_str(), filter, ctx, *elem, firstOffset);
+}
+
 arangodb::Result processPhraseArgs(
     char const* funcName,
     irs::by_phrase* phrase,
@@ -2050,7 +2385,7 @@ arangodb::Result processPhraseArgs(
     irs::analysis::analyzer::ptr& analyzer,
     size_t offset,
     bool allowDefaultOffset,
-    bool allowRecursion) {
+    bool isInArray) {
   irs::string_ref value;
   bool expectingOffset = false;
   for (size_t idx = valueArgsBegin; idx < valueArgsEnd; ++idx) {
@@ -2058,30 +2393,56 @@ arangodb::Result processPhraseArgs(
     if (!currentArg) {
       return error::invalidArgument(funcName, idx);
     }
-    if (currentArg->isArray() && (!expectingOffset || allowDefaultOffset)) {
-      if (0 == currentArg->numMembers()) {
-        expectingOffset = true;
-        // do not reset offset here as we should accumulate it
-        continue; // just skip empty arrays. This is not error anymore as this case may arise while working with autocomplete
-      }
-      // array arg is processed with possible default 0 offsets - to be easily compatible with TOKENS function
-      // No array recursion allowed. This could be allowed, but just looks tangled.
-      // Anyone interested coud use FLATTEN  to explicitly require processing all recurring arrays as one array
-      if (allowRecursion) {
-        auto subRes = processPhraseArgs(funcName, phrase, ctx, filterCtx, *currentArg, 0, currentArg->numMembers(), analyzer, offset, true, false);
-        if (subRes.fail()) {
-          return subRes;
+    if (currentArg->isArray()) {
+      // '[' <term0> [, <term1>, ...] ']'
+      if (isInArray) {
+        auto res = fromFuncPhraseTerms(funcName, idx, termsFuncName, phrase, ctx, *currentArg, offset);
+        if (res.fail()) {
+          return res;
         }
         expectingOffset = true;
         offset = 0;
         continue;
       }
+      if (!expectingOffset || allowDefaultOffset) {
+        if (0 == currentArg->numMembers()) {
+          expectingOffset = true;
+          // do not reset offset here as we should accumulate it
+          continue; // just skip empty arrays. This is not error anymore as this case may arise while working with autocomplete
+        }
+        // array arg is processed with possible default 0 offsets - to be easily compatible with TOKENS function
+        if (!isInArray) {
+          auto subRes = processPhraseArgs(funcName, phrase, ctx, filterCtx, *currentArg, 0, currentArg->numMembers(), analyzer, offset, true, true);
+          if (subRes.fail()) {
+            return subRes;
+          }
+          expectingOffset = true;
+          offset = 0;
+          continue;
+        }
 
-      return {
-        TRI_ERROR_BAD_PARAMETER,
-        "'"s.append(funcName).append("' AQL function: recursive arrays not allowed at position ")
-            .append(std::to_string(idx))
-      };
+        return {
+          TRI_ERROR_BAD_PARAMETER,
+          "'"s.append(funcName).append("' AQL function: recursive arrays not allowed at position ")
+              .append(std::to_string(idx))
+        };
+      }
+    }
+    if (currentArg->isObject()) {
+      if (currentArg->numMembers() != 1) {
+        return {
+          TRI_ERROR_BAD_PARAMETER,
+          "'"s.append(funcName).append("' AQL function: Invalid number of fields in an object (expected ")
+              .append(std::to_string(1)).append(") at position '").append(std::to_string(idx)).append("'")
+        };
+      }
+      auto res = processPhraseArgObjectType(funcName, idx, phrase, ctx, *currentArg, offset);
+      if (res.fail()) {
+        return res;
+      }
+      offset = 0;
+      expectingOffset = true;
+      continue;
     }
     ScopedAqlValue currentValue(*currentArg);
     if (phrase || currentValue.isConstant()) {
@@ -2223,7 +2584,153 @@ arangodb::Result fromFuncPhrase(
   }
   // on top level we require explicit offsets - to be backward compatible and be able to distinguish last argument as analyzer or value
   // Also we allow recursion inside array to support older syntax (one array arg) and add ability to pass several arrays as args
-  return processPhraseArgs(funcName, phrase, ctx, filterCtx, *valueArgs, valueArgsBegin, valueArgsEnd, analyzer, 0, false, true);
+  return processPhraseArgs(funcName, phrase, ctx, filterCtx, *valueArgs, valueArgsBegin, valueArgsEnd, analyzer, 0, false, false);
+}
+
+// NGRAM_MATCH (attribute, target, threshold [, analyzer])
+// NGRAM_MATCH (attribute, target [, analyzer]) // default threshold is set to 0.7
+arangodb::Result fromFuncNgramMatch(
+    char const* funcName,
+    irs::boolean_filter* filter, QueryContext const& ctx,
+    FilterContext const& filterCtx,
+    arangodb::aql::AstNode const& args) {
+
+  if (!args.isDeterministic()) {
+    return error::nondeterministicArgs(funcName);
+  }
+
+  auto const argc = args.numMembers();
+
+  if (argc < 2 || argc > 4) {
+    return error::invalidArgsCount<error::Range<2, 4>>(funcName);
+  }
+
+  // 1st argument defines a field
+  auto const* field =
+    arangodb::iresearch::checkAttributeAccess(args.getMemberUnchecked(0), *ctx.ref);
+
+  if (!field) {
+    return error::invalidAttribute(funcName, 1);
+  }
+
+  // 2nd argument defines a value
+  ScopedAqlValue matchAqlValue;
+  irs::string_ref matchValue;
+  {
+    auto res = evaluateArg(matchValue, matchAqlValue, funcName, args, 1, filter, ctx);
+    if (!res.ok()) {
+      return res;
+    }
+  }
+
+  double_t threshold = 0.7;
+  TRI_ASSERT(filterCtx.analyzer);
+  auto analyzerPool = filterCtx.analyzer;
+
+  if (argc > 3) {// 4 args given. 3rd is threshold
+    ScopedAqlValue tmpValue;
+    auto res = evaluateArg(threshold, tmpValue, funcName, args, 2, filter, ctx);
+
+    if (!res.ok()) {
+      return res;
+    }
+  } else if (argc > 2) {  //3 args given  -  3rd argument defines a threshold (if double) or analyzer (if string)
+    auto const* arg = args.getMemberUnchecked(2);
+
+    if (!arg) {
+      return error::invalidArgument(funcName, 3);
+    }
+
+    if (!arg->isDeterministic()) {
+      return error::nondeterministicArg(funcName, 3);
+    }
+    ScopedAqlValue tmpValue(*arg);
+    if (filter || tmpValue.isConstant()) {
+      if (!tmpValue.execute(ctx)) {
+        return error::failedToEvaluate(funcName, 3);
+      }
+      if (arangodb::iresearch::SCOPED_VALUE_TYPE_STRING == tmpValue.type()) { // this is analyzer
+        irs::string_ref analyzerId;
+        if (!tmpValue.getString(analyzerId)) {
+          return error::failedToParse(funcName, 3, arangodb::iresearch::SCOPED_VALUE_TYPE_STRING);
+        }
+        if (filter || tmpValue.isConstant()) {
+          auto analyzerRes = getAnalyzerByName(analyzerPool, analyzerId, funcName, ctx);
+          if (!analyzerRes.ok()) {
+            return analyzerRes;
+          }
+        }
+      } else if (arangodb::iresearch::SCOPED_VALUE_TYPE_DOUBLE == tmpValue.type()) {
+        if (!tmpValue.getDouble(threshold)) {
+          return error::failedToParse(funcName, 3, arangodb::iresearch::SCOPED_VALUE_TYPE_DOUBLE);
+        }
+      } else {
+        return {
+            TRI_ERROR_BAD_PARAMETER,
+            "'"s.append(funcName).append("' AQL function: argument at position '").append(std::to_string(3))
+           .append("' has invalid type '").append(ScopedAqlValue::typeString(tmpValue.type()).c_str())
+           .append("' ('").append(ScopedAqlValue::typeString(arangodb::iresearch::SCOPED_VALUE_TYPE_DOUBLE).c_str())
+           .append("' or '").append(ScopedAqlValue::typeString(arangodb::iresearch::SCOPED_VALUE_TYPE_STRING).c_str())
+           .append("' expected)")
+        };
+      }
+    }
+  }
+
+  if (threshold <= 0 || threshold > 1) {
+    return {
+      TRI_ERROR_BAD_PARAMETER,
+      "'"s.append(funcName)
+      .append("' AQL function: threshold must be between 0 and 1")
+    };
+  }
+
+  // 4th optional argument defines an analyzer
+  if (argc > 3) {
+      auto rv = extractAnalyzerFromArg(analyzerPool, funcName, filter, args, 3, ctx);
+
+      if (rv.fail()) {
+        return rv;
+      }
+      TRI_ASSERT(analyzerPool._pool);
+      if (!analyzerPool._pool) {
+        return { TRI_ERROR_BAD_PARAMETER };
+      }
+  }
+
+  if (filter) {
+    std::string name;
+
+    if (!nameFromAttributeAccess(name, *field, ctx)) {
+      auto message = "'"s.append(funcName).append("' AQL function: Failed to generate field name from the 1st argument");
+      LOG_TOPIC("91862", WARN, arangodb::iresearch::TOPIC) << message;
+      return { TRI_ERROR_BAD_PARAMETER, message };
+    }
+
+    TRI_ASSERT(analyzerPool._pool);
+    auto analyzer = analyzerPool._pool->get();
+
+    if (!analyzer) {
+      return {
+        TRI_ERROR_INTERNAL,
+        "'"s.append(funcName).append("' AQL function: Unable to instantiate analyzer '")
+            .append(analyzerPool._pool->name()).append("'")
+      };
+    }
+
+
+    kludge::mangleStringField(name, analyzerPool);
+
+    auto& ngramFilter = filter->add<irs::by_ngram_similarity>();
+    ngramFilter.field(std::move(name)).threshold(threshold).boost(filterCtx.boost);;
+
+    analyzer->reset(matchValue);
+    irs::term_attribute const& token = *analyzer->attributes().get<irs::term_attribute>();
+    while (analyzer->next()) {
+      ngramFilter.push_back(token.value());
+    }
+  }
+  return {};
 }
 
 // STARTS_WITH(<attribute>, <prefix>, [<scoring-limit>])
@@ -2256,7 +2763,7 @@ arangodb::Result fromFuncStartsWith(
   // 2nd argument defines a value
   ScopedAqlValue prefixValue;
   irs::string_ref prefix;
-  auto rv = evaluateArg(prefix, prefixValue, funcName, args, 1, filter, ctx);
+  auto rv = evaluateArg(prefix, prefixValue, funcName, args, 1, filter != nullptr, ctx);
 
   if (rv.fail()) {
     return rv;
@@ -2268,7 +2775,7 @@ arangodb::Result fromFuncStartsWith(
     // 3rd (optional) argument defines a number of scored terms
     ScopedAqlValue scoringLimitValueBuf;
     int64_t scoringLimitValue = static_cast<int64_t>(scoringLimit);
-    rv = evaluateArg(scoringLimitValue, scoringLimitValueBuf, funcName, args, 2, filter, ctx);
+    rv = evaluateArg(scoringLimitValue, scoringLimitValueBuf, funcName, args, 2, filter != nullptr, ctx);
 
     if (rv.fail()) {
       return rv;
@@ -2347,7 +2854,7 @@ arangodb::Result fromFuncInRange(
   // 4th argument defines inclusion of lower boundary
   bool lhsInclude = false;
 
-  auto rv = evaluateArg(lhsInclude, includeValue, funcName, args, 3, filter, ctx);
+  auto rv = evaluateArg(lhsInclude, includeValue, funcName, args, 3, filter != nullptr, ctx);
 
   if (rv.fail()) {
     return rv;
@@ -2356,7 +2863,7 @@ arangodb::Result fromFuncInRange(
   // 5th argument defines inclusion of upper boundary
   bool rhsInclude = false;
 
-  rv = evaluateArg(rhsInclude, includeValue, funcName, args, 4, filter, ctx);
+  rv = evaluateArg(rhsInclude, includeValue, funcName, args, 4, filter != nullptr, ctx);
 
   if (rv.fail()) {
     return rv;
@@ -2402,7 +2909,7 @@ arangodb::Result fromFuncLike(
   // 2nd argument defines a matching pattern
   ScopedAqlValue patternValue;
   irs::string_ref pattern;
-  arangodb::Result res = evaluateArg(pattern, patternValue, funcName, args, 1, filter, ctx);
+  arangodb::Result res = evaluateArg(pattern, patternValue, funcName, args, 1, filter != nullptr, ctx);
 
   if (!res.ok()) {
     return res;
@@ -2439,80 +2946,19 @@ arangodb::Result fromFuncLevenshteinMatch(
     arangodb::aql::AstNode const& args) {
   TRI_ASSERT(funcName);
 
-  if (!args.isDeterministic()) {
-    return error::nondeterministicArgs(funcName);
-  }
-
-  auto const argc = args.numMembers();
-
-  if (argc < 3 || argc > 4) {
-    return error::invalidArgsCount<error::Range<3, 4>>(funcName);
-  }
-
-  // 1st argument defines a field
-  auto const* field =
-      arangodb::iresearch::checkAttributeAccess(args.getMemberUnchecked(0), *ctx.ref);
-
-  if (!field) {
-    return error::invalidAttribute(funcName, 1);
-  }
-
-  // 2nd argument defines a target
+  arangodb::aql::AstNode const* field = nullptr;
   ScopedAqlValue targetValue;
   irs::string_ref target;
-  arangodb::Result res = evaluateArg(target, targetValue, funcName, args, 1, filter, ctx);
-
-  if (!res.ok()) {
-    return res;
-  }
-
-  ScopedAqlValue tmpValue; // can reuse value for int64_t and bool
-
-  // 3rd argument defines a max distance
+  size_t scoringLimit = 0;
   int64_t maxDistance = 0;
-  res = evaluateArg(maxDistance, tmpValue, funcName, args, 2, filter, ctx);
-
-  if (!res.ok()) {
+  auto withTranspositions = false;
+  auto res = getLevenshteinArguments<0>(funcName, filter != nullptr, ctx, args, &field,
+                                        targetValue, target, scoringLimit, maxDistance,
+                                        withTranspositions);
+  if (res.fail()) {
     return res;
   }
 
-  if (maxDistance < 0) {
-    return {
-      TRI_ERROR_BAD_PARAMETER,
-      "'"s.append(funcName)
-          .append("' AQL function: max distance must be a positive number")
-    };
-  }
-
-  // optional 4th argument defines transpositions
-  bool withTranspositions = false;
-
-  if (4 == argc) {
-    res = evaluateArg(withTranspositions, tmpValue, funcName, args, 3, filter, ctx);
-
-    if (!res.ok()) {
-      return res;
-    }
-  }
-
-  if (!withTranspositions && maxDistance > MAX_LEVENSHTEIN_DISTANCE) {
-    return {
-      TRI_ERROR_BAD_PARAMETER,
-      "'"s.append(funcName)
-          .append("' AQL function: max Levenshtein distance must be a number in range [0, ")
-          .append(std::to_string(MAX_LEVENSHTEIN_DISTANCE)).append("]")
-    };
-  } else if (withTranspositions && maxDistance > MAX_DAMERAU_LEVENSHTEIN_DISTANCE) {
-    return {
-      TRI_ERROR_BAD_PARAMETER,
-      "'"s.append(funcName)
-          .append("' AQL function: max Damerau-Levenshtein distance must be a number in range [0, ")
-          .append(std::to_string(MAX_DAMERAU_LEVENSHTEIN_DISTANCE)).append("]")
-    };
-  }
-
-  const size_t scoringLimit = 128;  // FIXME make configurable
-
   if (filter) {
     std::string name;
 
@@ -2589,6 +3035,7 @@ std::map<std::string, ConvertionHandler> const FCallSystemConvertionHandlers{
     {"IN_RANGE", fromFuncInRange},
     {"LIKE", fromFuncLike },
     {"LEVENSHTEIN_MATCH", fromFuncLevenshteinMatch},
+    {"NGRAM_MATCH", fromFuncNgramMatch},
     // context functions
     {"BOOST", fromFuncBoost},
     {"ANALYZER", fromFuncAnalyzer},
diff --git a/arangod/IResearch/IResearchLink.cpp b/arangod/IResearch/IResearchLink.cpp
index cc6bc3459870..ea70e3427bb1 100644
--- a/arangod/IResearch/IResearchLink.cpp
+++ b/arangod/IResearch/IResearchLink.cpp
@@ -61,7 +61,7 @@ namespace {
 ////////////////////////////////////////////////////////////////////////////////
 /// @brief the storage format used with IResearch writers
 ////////////////////////////////////////////////////////////////////////////////
-const irs::string_ref IRESEARCH_STORE_FORMAT("1_2");
+const irs::string_ref IRESEARCH_STORE_FORMAT("1_3simd");
 
 typedef irs::async_utils::read_write_mutex::read_mutex ReadMutex;
 typedef irs::async_utils::read_write_mutex::write_mutex WriteMutex;
diff --git a/arangod/IResearch/IResearchRocksDBLink.h b/arangod/IResearch/IResearchRocksDBLink.h
index 8f04c1b33ebf..9134c73ebcaf 100644
--- a/arangod/IResearch/IResearchRocksDBLink.h
+++ b/arangod/IResearch/IResearchRocksDBLink.h
@@ -59,8 +59,8 @@ class IResearchRocksDBLink final : public arangodb::RocksDBIndex, public IResear
                           arangodb::RocksDBMethods* methods,
                           arangodb::LocalDocumentId const& documentId,
                           arangodb::velocypack::Slice const& doc,
-                          arangodb::Index::OperationMode mode) override {
-    return IResearchLink::insert(trx, documentId, doc, mode);
+                          arangodb::OperationOptions& options) override {
+    return IResearchLink::insert(trx, documentId, doc, options.indexOperationMode);
   }
 
   bool isSorted() const override { return IResearchLink::isSorted(); }
diff --git a/arangod/Indexes/IndexIterator.cpp b/arangod/Indexes/IndexIterator.cpp
index 5b4b05e51ed4..f3589b2480e2 100644
--- a/arangod/Indexes/IndexIterator.cpp
+++ b/arangod/Indexes/IndexIterator.cpp
@@ -31,7 +31,7 @@ using namespace arangodb;
 
 IndexIterator::IndexIterator(LogicalCollection* collection, transaction::Methods* trx)
     : _collection(collection), _trx(trx) {
-  // note: collection may be a nullptr here, if we are dealing with the EmptyIndexIterator
+  TRI_ASSERT(_collection != nullptr);
   TRI_ASSERT(_trx != nullptr);
 }
 
diff --git a/arangod/Indexes/IndexIterator.h b/arangod/Indexes/IndexIterator.h
index 372c306a41df..adbc19bff4ca 100644
--- a/arangod/Indexes/IndexIterator.h
+++ b/arangod/Indexes/IndexIterator.h
@@ -84,7 +84,7 @@ class IndexIterator {
   virtual char const* typeName() const = 0;
 
   /// @brief return the underlying collection
-  /// note: this may return a nullptr in case we are dealing with the EmptyIndexIterator! 
+  /// this is guaranteed to be a non-nullptr
   LogicalCollection* collection() const { return _collection; }
 
   transaction::Methods* transaction() const { return _trx; }
diff --git a/arangod/MMFiles/MMFilesCollection.cpp b/arangod/MMFiles/MMFilesCollection.cpp
index 34244f793a8b..cd816ebb98bc 100644
--- a/arangod/MMFiles/MMFilesCollection.cpp
+++ b/arangod/MMFiles/MMFilesCollection.cpp
@@ -1590,22 +1590,22 @@ size_t MMFilesCollection::memory() const {
 }
 
 /// @brief disallow compaction of the collection
-void MMFilesCollection::preventCompaction() { _compactionLock.readLock(); }
+void MMFilesCollection::preventCompaction() { _compactionLock.lockRead(); }
 
 /// @brief try disallowing compaction of the collection
 bool MMFilesCollection::tryPreventCompaction() {
-  return _compactionLock.tryReadLock();
+  return _compactionLock.tryLockRead();
 }
 
 /// @brief re-allow compaction of the collection
 void MMFilesCollection::allowCompaction() { _compactionLock.unlock(); }
 
 /// @brief exclusively lock the collection for compaction
-void MMFilesCollection::lockForCompaction() { _compactionLock.writeLock(); }
+void MMFilesCollection::lockForCompaction() { _compactionLock.lockWrite(); }
 
 /// @brief try to exclusively lock the collection for compaction
 bool MMFilesCollection::tryLockForCompaction() {
-  return _compactionLock.tryWriteLock();
+  return _compactionLock.tryLockWrite();
 }
 
 /// @brief signal that compaction is finished
@@ -1993,8 +1993,13 @@ LocalDocumentId MMFilesCollection::lookupKey(transaction::Methods* trx,
   return element ? LocalDocumentId(element.localDocumentId()) : LocalDocumentId();
 }
 
-Result MMFilesCollection::read(transaction::Methods* trx, VPackSlice const& key,
+Result MMFilesCollection::read(transaction::Methods* trx, 
+                               arangodb::velocypack::StringRef const& key,
                                ManagedDocumentResult& result, bool lock) {
+  // copy string into a vpack string
+  transaction::BuilderLeaser builder(trx);
+  builder->add(VPackValuePair(key.data(), key.size(), VPackValueType::String));
+
   TRI_IF_FAILURE("ReadDocumentNoLock") {
     // test what happens if no lock can be acquired
     return Result(TRI_ERROR_DEBUG);
@@ -2015,7 +2020,7 @@ Result MMFilesCollection::read(transaction::Methods* trx, VPackSlice const& key,
   }
   TRI_DEFER(if (lock) { unlockRead(useDeadlockDetector, trx->state()); });
 
-  LocalDocumentId const documentId = lookupDocument(trx, key, result);
+  LocalDocumentId const documentId = lookupDocument(trx, builder->slice(), result);
   if (documentId.empty()) {
     return Result(TRI_ERROR_ARANGO_DOCUMENT_NOT_FOUND);
   }
@@ -2024,15 +2029,6 @@ Result MMFilesCollection::read(transaction::Methods* trx, VPackSlice const& key,
   return Result(TRI_ERROR_NO_ERROR);
 }
 
-Result MMFilesCollection::read(transaction::Methods* trx,
-                               arangodb::velocypack::StringRef const& key,
-                               ManagedDocumentResult& result, bool lock) {
-  // copy string into a vpack string
-  transaction::BuilderLeaser builder(trx);
-  builder->add(VPackValuePair(key.data(), key.size(), VPackValueType::String));
-  return read(trx, builder->slice(), result, lock);
-}
-
 bool MMFilesCollection::readDocument(transaction::Methods* trx,
                                      LocalDocumentId const& documentId,
                                      ManagedDocumentResult& result) const {
diff --git a/arangod/MMFiles/MMFilesCollection.h b/arangod/MMFiles/MMFilesCollection.h
index 791ef5e07a8d..1e542842f8b3 100644
--- a/arangod/MMFiles/MMFilesCollection.h
+++ b/arangod/MMFiles/MMFilesCollection.h
@@ -236,6 +236,7 @@ class MMFilesCollection final : public PhysicalCollection {
 
   std::unique_ptr<IndexIterator> getAllIterator(transaction::Methods* trx) const override;
   std::unique_ptr<IndexIterator> getAnyIterator(transaction::Methods* trx) const override;
+
   void invokeOnAllElements(transaction::Methods* trx,
                            std::function<bool(LocalDocumentId const&)> callback);
 
@@ -283,9 +284,6 @@ class MMFilesCollection final : public PhysicalCollection {
   Result read(transaction::Methods*, arangodb::velocypack::StringRef const& key,
               ManagedDocumentResult& result, bool) override;
 
-  Result read(transaction::Methods*, arangodb::velocypack::Slice const& key,
-              ManagedDocumentResult& result, bool) override;
-
   bool readDocument(transaction::Methods* trx, LocalDocumentId const& documentId,
                     ManagedDocumentResult& result) const override;
 
diff --git a/arangod/Pregel/GraphStore.h b/arangod/Pregel/GraphStore.h
index 81aa276f9ea5..55c9a2bc8268 100644
--- a/arangod/Pregel/GraphStore.h
+++ b/arangod/Pregel/GraphStore.h
@@ -23,7 +23,6 @@
 #ifndef ARANGODB_PREGEL_GRAPH_STORE_H
 #define ARANGODB_PREGEL_GRAPH_STORE_H 1
 
-#include "Basics/StringHeap.h"
 #include "Cluster/ClusterInfo.h"
 #include "Pregel/Graph.h"
 #include "Pregel/GraphFormat.h"
diff --git a/arangod/Pregel/IncomingCache.h b/arangod/Pregel/IncomingCache.h
index 7c3f8aeb6dc2..db7a9a1a2c2c 100644
--- a/arangod/Pregel/IncomingCache.h
+++ b/arangod/Pregel/IncomingCache.h
@@ -30,7 +30,6 @@
 #include <map>
 
 #include "Basics/Common.h"
-#include "Basics/StringHeap.h"
 
 #include "Pregel/GraphStore.h"
 #include "Pregel/Iterators.h"
diff --git a/arangod/Replication/DatabaseInitialSyncer.cpp b/arangod/Replication/DatabaseInitialSyncer.cpp
index 0b5acf44a899..a6fa0ddb20ee 100644
--- a/arangod/Replication/DatabaseInitialSyncer.cpp
+++ b/arangod/Replication/DatabaseInitialSyncer.cpp
@@ -25,6 +25,7 @@
 
 #include "ApplicationFeatures/ApplicationServer.h"
 #include "Basics/Exceptions.h"
+#include "Basics/HybridLogicalClock.h"
 #include "Basics/ReadLocker.h"
 #include "Basics/Result.h"
 #include "Basics/RocksDBUtils.h"
@@ -36,6 +37,8 @@
 #include "Logger/Logger.h"
 #include "Replication/DatabaseReplicationApplier.h"
 #include "Replication/utilities.h"
+#include "Rest/CommonDefines.h"
+#include "RestHandler/RestReplicationHandler.h"
 #include "SimpleHttpClient/SimpleHttpClient.h"
 #include "SimpleHttpClient/SimpleHttpResult.h"
 #include "StorageEngine/EngineSelectorFeature.h"
@@ -48,6 +51,7 @@
 #include "Utils/OperationOptions.h"
 #include "VocBase/LogicalCollection.h"
 #include "VocBase/LogicalView.h"
+#include "VocBase/ManagedDocumentResult.h"
 #include "VocBase/voc-types.h"
 #include "VocBase/vocbase.h"
 
@@ -87,6 +91,202 @@ std::chrono::milliseconds sleepTimeFromWaitTime(double waitTime) {
 std::string const kTypeString = "type";
 std::string const kDataString = "data";
 
+arangodb::Result removeRevisions(arangodb::transaction::Methods& trx,
+                                 arangodb::LogicalCollection& collection,
+                                 std::vector<std::size_t>& toRemove,
+                                 arangodb::InitialSyncerIncrementalSyncStats& stats) {
+  using arangodb::PhysicalCollection;
+  using arangodb::Result;
+
+  if (toRemove.empty()) {
+    // no need to do anything
+    return Result();
+  }
+
+  PhysicalCollection* physical = collection.getPhysical();
+
+  arangodb::ManagedDocumentResult mdr;
+  arangodb::OperationOptions options;
+  options.silent = true;
+  options.ignoreRevs = true;
+  options.isRestore = true;
+
+  for (std::size_t rid : toRemove) {
+    double t = TRI_microtime();
+    auto r = physical->remove(trx, arangodb::LocalDocumentId::create(rid), mdr, options,
+                              /*lock*/ false, nullptr, nullptr);
+    stats.waitedForRemovals += TRI_microtime() - t;
+    if (r.fail() && r.isNot(TRI_ERROR_ARANGO_DOCUMENT_NOT_FOUND)) {
+      // ignore not found, we remove conflicting docs ahead of time
+      return r;
+    }
+
+    if (r.ok()) {
+      ++stats.numDocsRemoved;
+    }
+  }
+
+  return Result();
+}
+
+arangodb::Result fetchRevisions(arangodb::transaction::Methods& trx,
+                                arangodb::DatabaseInitialSyncer::Configuration& config,
+                                arangodb::Syncer::SyncerState& state,
+                                arangodb::LogicalCollection& collection,
+                                std::string const& leader, std::vector<std::size_t>& toFetch,
+                                arangodb::InitialSyncerIncrementalSyncStats& stats) {
+  using arangodb::PhysicalCollection;
+  using arangodb::RestReplicationHandler;
+  using arangodb::Result;
+
+  if (toFetch.empty()) {
+    return Result();  // nothing to do
+  }
+
+  arangodb::transaction::BuilderLeaser keyBuilder(&trx);
+  arangodb::ManagedDocumentResult mdr, previous;
+  arangodb::OperationOptions options;
+  options.silent = true;
+  options.ignoreRevs = true;
+  options.isRestore = true;
+  options.indexOperationMode = arangodb::Index::OperationMode::internal;
+  options.ignoreUniqueConstraints = true;
+  if (!state.leaderId.empty()) {
+    options.isSynchronousReplicationFrom = state.leaderId;
+  }
+
+  PhysicalCollection* physical = collection.getPhysical();
+
+  std::string url =
+      arangodb::replutils::ReplicationUrl + "/" +
+      RestReplicationHandler::Revisions + "/" + RestReplicationHandler::Documents +
+      "?collection=" + arangodb::basics::StringUtils::urlEncode(leader) +
+      "&serverId=" + state.localServerIdString +
+      "&batchId=" + std::to_string(config.batch.id);
+  auto headers = arangodb::replutils::createHeaders();
+
+  std::string msg = "fetching documents by revision for collection '" +
+                    collection.name() + "' from " + url;
+  config.progress.set(msg);
+
+  auto removeConflict = [&](std::string const& conflictingKey) -> Result {
+    keyBuilder->clear();
+    keyBuilder->add(VPackValue(conflictingKey));
+
+    auto res = physical->remove(trx, keyBuilder->slice(), mdr, options,
+                                /*lock*/ false, nullptr, nullptr);
+
+    if (res.ok()) {
+      ++stats.numDocsRemoved;
+    }
+
+    return res;
+  };
+
+  std::size_t current = 0;
+  auto guard = arangodb::scopeGuard(
+      [&current, &stats]() -> void { stats.numDocsRequested += current; });
+  char ridBuffer[11];
+  std::unique_ptr<arangodb::httpclient::SimpleHttpResult> response;
+  while (current < toFetch.size()) {
+    arangodb::transaction::BuilderLeaser requestBuilder(&trx);
+    {
+      VPackArrayBuilder list(requestBuilder.get());
+      for (std::size_t i = 0; i < 5000 && current + i < toFetch.size(); ++i) {
+        requestBuilder->add(arangodb::basics::HybridLogicalClock::encodeTimeStampToValuePair(
+            toFetch[current + i], ridBuffer));
+      }
+    }
+    std::string request = requestBuilder->slice().toJson();
+
+    double t = TRI_microtime();
+    config.connection.lease([&](arangodb::httpclient::SimpleHttpClient* client) {
+      response.reset(client->retryRequest(arangodb::rest::RequestType::PUT, url,
+                                          request.data(), request.size(), headers));
+    });
+    stats.waitedForDocs += TRI_microtime() - t;
+    ++stats.numDocsRequests;
+
+    if (arangodb::replutils::hasFailed(response.get())) {
+      return arangodb::replutils::buildHttpError(response.get(), url, config.connection);
+    }
+
+    arangodb::transaction::BuilderLeaser responseBuilder(&trx);
+    Result r =
+        arangodb::replutils::parseResponse(*responseBuilder.get(), response.get());
+    if (r.fail()) {
+      return Result(TRI_ERROR_REPLICATION_INVALID_RESPONSE,
+                    std::string("got invalid response from master at ") +
+                        config.master.endpoint + url + ": " + r.errorMessage());
+    }
+
+    VPackSlice const docs = responseBuilder->slice();
+    if (!docs.isArray()) {
+      return Result(TRI_ERROR_REPLICATION_INVALID_RESPONSE,
+                    std::string("got invalid response from master at ") +
+                        config.master.endpoint + url +
+                        ": response is not an array");
+    }
+
+    for (VPackSlice masterDoc : VPackArrayIterator(docs)) {
+      if (!masterDoc.isObject()) {
+        return Result(TRI_ERROR_REPLICATION_INVALID_RESPONSE,
+                      std::string("got invalid response from master at ") +
+                          config.master.endpoint + url +
+                          ": response document entry is not an object");
+      }
+
+      VPackSlice const keySlice = masterDoc.get(arangodb::StaticStrings::KeyString);
+      if (!keySlice.isString()) {
+        return Result(TRI_ERROR_REPLICATION_INVALID_RESPONSE,
+                      std::string("got invalid response from master at ") +
+                          state.master.endpoint + ": document key is invalid");
+      }
+
+      VPackSlice const revSlice = masterDoc.get(arangodb::StaticStrings::RevString);
+      if (!revSlice.isString()) {
+        return Result(TRI_ERROR_REPLICATION_INVALID_RESPONSE,
+                      std::string("got invalid response from master at ") +
+                          state.master.endpoint +
+                          ": document revision is invalid");
+      }
+
+      TRI_ASSERT(options.indexOperationMode == arangodb::Index::OperationMode::internal);
+
+      Result res = physical->insert(&trx, masterDoc, mdr, options,
+                                    /*lock*/ false, nullptr, nullptr);
+      if (res.fail()) {
+        if (res.is(TRI_ERROR_ARANGO_UNIQUE_CONSTRAINT_VIOLATED) &&
+            res.errorMessage() > keySlice.copyString()) {
+          // remove conflict and retry
+          // errorMessage() is this case contains the conflicting key
+          auto inner = removeConflict(res.errorMessage());
+          if (inner.fail()) {
+            return res;
+          }
+          options.indexOperationMode = arangodb::Index::OperationMode::normal;
+          res = physical->insert(&trx, masterDoc, mdr, options,
+                                 /*lock*/ false, nullptr, nullptr);
+          options.indexOperationMode = arangodb::Index::OperationMode::internal;
+          if (res.fail()) {
+            return res;
+          }
+          // fall-through
+        } else {
+          int errorNumber = res.errorNumber();
+          res.reset(errorNumber, std::string(TRI_errno_string(errorNumber)) +
+                                     ": " + res.errorMessage());
+          return res;
+        }
+      }
+
+      ++stats.numDocsInserted;
+    }
+    current += docs.length();
+  }
+
+  return Result();
+}
 }  // namespace
 
 namespace arangodb {
@@ -827,6 +1027,23 @@ Result DatabaseInitialSyncer::fetchCollectionDump(arangodb::LogicalCollection* c
 Result DatabaseInitialSyncer::fetchCollectionSync(arangodb::LogicalCollection* coll,
                                                   std::string const& leaderColl,
                                                   TRI_voc_tick_t maxTick) {
+  if (coll->syncByRevision() &&
+      (_config.master.majorVersion > 3 ||
+       (_config.master.majorVersion = 3 && _config.master.minorVersion >= 6))) {
+    // local collection should support revisions, and master is at least aware
+    // of the revision-based protocol, so we can query it to find out if we
+    // can use the new protocol; will fall back to old one if master collection
+    // is an old variant
+    return fetchCollectionSyncByRevisions(coll, leaderColl, maxTick);
+  }
+  return fetchCollectionSyncByKeys(coll, leaderColl, maxTick);
+}
+
+/// @brief incrementally fetch data from a collection using keys as the primary
+/// document identifier
+Result DatabaseInitialSyncer::fetchCollectionSyncByKeys(arangodb::LogicalCollection* coll,
+                                                        std::string const& leaderColl,
+                                                        TRI_voc_tick_t maxTick) {
   using ::arangodb::basics::StringUtils::urlEncode;
 
   if (!_config.isChild()) {
@@ -1012,6 +1229,410 @@ Result DatabaseInitialSyncer::fetchCollectionSync(arangodb::LogicalCollection* c
   }
 }
 
+/// @brief incrementally fetch data from a collection using keys as the primary
+/// document identifier
+Result DatabaseInitialSyncer::fetchCollectionSyncByRevisions(arangodb::LogicalCollection* coll,
+                                                             std::string const& leaderColl,
+                                                             TRI_voc_tick_t maxTick) {
+  using ::arangodb::basics::StringUtils::urlEncode;
+  using ::arangodb::transaction::Hints;
+
+  InitialSyncerIncrementalSyncStats stats;
+  double const startTime = TRI_microtime();
+
+  if (!_config.isChild()) {
+    batchExtend();
+    _config.barrier.extend(_config.connection);
+  }
+
+  std::unique_ptr<containers::RevisionTree> treeMaster;
+  std::string const baseUrl =
+      replutils::ReplicationUrl + "/" + RestReplicationHandler::Revisions;
+
+  // get master tree
+  {
+    std::string url = baseUrl + "/" + RestReplicationHandler::Tree +
+                      "?collection=" + urlEncode(leaderColl) +
+                      "&to=" + std::to_string(maxTick) +
+                      "&serverId=" + _state.localServerIdString +
+                      "&batchId=" + std::to_string(_config.batch.id);
+
+    std::string msg = "fetching collection revision tree for collection '" +
+                      coll->name() + "' from " + url;
+    _config.progress.set(msg);
+
+    auto headers = replutils::createHeaders();
+    std::unique_ptr<httpclient::SimpleHttpResult> response;
+    double t = TRI_microtime();
+    _config.connection.lease([&](httpclient::SimpleHttpClient* client) {
+      response.reset(client->retryRequest(rest::RequestType::GET, url, nullptr, 0, headers));
+    });
+    stats.waitedForInitial += TRI_microtime() - t;
+
+    if (replutils::hasFailed(response.get())) {
+      if (response && response->getHttpReturnCode() ==
+                          static_cast<int>(rest::ResponseCode::NOT_IMPLEMENTED)) {
+        // collection on master doesn't support revisions-based protocol, fallback
+        return fetchCollectionSyncByKeys(coll, leaderColl, maxTick);
+      }
+      return replutils::buildHttpError(response.get(), url, _config.connection);
+    }
+
+    auto body = response->getBodyVelocyPack();
+    if (!body) {
+      return Result(
+          TRI_ERROR_INTERNAL,
+          "received improperly formed response when fetching revision tree");
+    }
+    treeMaster = containers::RevisionTree::deserialize(body->slice());
+    if (!treeMaster) {
+      return Result(TRI_ERROR_REPLICATION_INVALID_RESPONSE,
+                    std::string("got invalid response from master at ") +
+                        _config.master.endpoint + url +
+                        ": response does not contain a valid revision tree");
+    }
+
+    if (treeMaster->count() == 0) {
+      // remote collection has no documents. now truncate our local collection
+      SingleCollectionTransaction trx(transaction::StandaloneContext::Create(vocbase()),
+                                      *coll, AccessMode::Type::EXCLUSIVE);
+      trx.addHint(transaction::Hints::Hint::INTERMEDIATE_COMMITS);
+      trx.addHint(transaction::Hints::Hint::ALLOW_RANGE_DELETE);
+      Result res = trx.begin();
+
+      if (!res.ok()) {
+        return Result(res.errorNumber(),
+                      std::string("unable to start transaction (") + std::string(__FILE__) +
+                          std::string(":") + std::to_string(__LINE__) +
+                          std::string("): ") + res.errorMessage());
+      }
+
+      OperationOptions options;
+
+      if (!_state.leaderId.empty()) {
+        options.isSynchronousReplicationFrom = _state.leaderId;
+      }
+
+      OperationResult opRes = trx.truncate(coll->name(), options);
+
+      if (opRes.fail()) {
+        return Result(opRes.errorNumber(),
+                      std::string("unable to truncate collection '") + coll->name() +
+                          "': " + TRI_errno_string(opRes.errorNumber()));
+      }
+
+      return trx.finish(opRes.result);
+    }
+  }
+
+  if (isAborted()) {
+    return Result(TRI_ERROR_REPLICATION_APPLIER_STOPPED);
+  }
+
+  PhysicalCollection* physical = coll->getPhysical();
+  TRI_ASSERT(physical);
+  auto context = arangodb::transaction::StandaloneContext::Create(coll->vocbase());
+  TRI_voc_tid_t blockerId = context->generateId();
+  physical->placeRevisionTreeBlocker(blockerId);
+  std::unique_ptr<arangodb::SingleCollectionTransaction> trx;
+  try {
+    trx = std::make_unique<arangodb::SingleCollectionTransaction>(
+        context, *coll, arangodb::AccessMode::Type::EXCLUSIVE);
+  } catch (arangodb::basics::Exception const& ex) {
+    if (ex.code() == TRI_ERROR_ARANGO_DATA_SOURCE_NOT_FOUND) {
+      bool locked = false;
+      TRI_vocbase_col_status_e status = coll->tryFetchStatus(locked);
+      if (!locked) {
+        // fall back to unsafe method as last resort
+        status = coll->status();
+      }
+      if (status == TRI_vocbase_col_status_e::TRI_VOC_COL_STATUS_DELETED) {
+        // TODO handle
+        setAborted(true); // probably wrong?
+        return Result(TRI_ERROR_REPLICATION_APPLIER_STOPPED);
+      }
+    }
+    return Result(ex.code());
+  }
+  trx->addHint(Hints::Hint::RECOVERY);  // turn off waitForSync!
+  trx->addHint(Hints::Hint::NO_INDEXING);
+  // turn on intermediate commits as the number of keys to delete can be huge
+  // here
+  trx->addHint(Hints::Hint::INTERMEDIATE_COMMITS);
+  Result res = trx->begin();
+  if (!res.ok()) {
+    return Result(res.errorNumber(),
+                  std::string("unable to start transaction: ") + res.errorMessage());
+  }
+  auto guard = scopeGuard(
+      [trx = trx.get()]() -> void { 
+        if (trx->status() == transaction::Status::RUNNING) {
+          trx->abort();
+        }
+       });
+
+
+  // diff with local tree
+  //std::pair<std::size_t, std::size_t> fullRange = treeMaster->range();
+  std::unique_ptr<containers::RevisionTree> treeLocal =
+      physical->revisionTree(*trx);
+  physical->removeRevisionTreeBlocker(blockerId);
+  std::vector<std::pair<std::size_t, std::size_t>> ranges = treeMaster->diff(*treeLocal);
+  if (ranges.empty()) {
+    // no differences, done!
+    setProgress("no differences between two revision trees, ending");
+    return Result{};
+  }
+
+  // now lets get the actual ranges and handle the differences
+
+  {
+    VPackBuilder requestBuilder;
+    {
+      char ridBuffer[11];
+      VPackArrayBuilder list(&requestBuilder);
+      for (auto& pair : ranges) {
+        VPackArrayBuilder range(&requestBuilder);
+        requestBuilder.add(
+            basics::HybridLogicalClock::encodeTimeStampToValuePair(pair.first, ridBuffer));
+        requestBuilder.add(
+            basics::HybridLogicalClock::encodeTimeStampToValuePair(pair.second, ridBuffer));
+      }
+    }
+    std::string request = requestBuilder.slice().toJson();
+
+    std::string url = baseUrl + "/" + RestReplicationHandler::Ranges +
+                      "?collection=" + urlEncode(leaderColl) +
+                      "&serverId=" + _state.localServerIdString +
+                      "&batchId=" + std::to_string(_config.batch.id);
+    auto headers = replutils::createHeaders();
+    std::unique_ptr<httpclient::SimpleHttpResult> response;
+    TRI_voc_rid_t requestResume = ranges[0].first;  // start with beginning
+    TRI_ASSERT(requestResume);
+    TRI_voc_rid_t iterResume = static_cast<TRI_voc_rid_t>(requestResume);
+    std::size_t chunk = 0;
+    std::unique_ptr<ReplicationIterator> iter =
+        physical->getReplicationIterator(ReplicationIterator::Ordering::Revision, *trx);
+    if (!iter) {
+      return Result(TRI_ERROR_INTERNAL, "could not get replication iterator");
+    }
+
+    std::vector<std::size_t> toFetch;
+    std::vector<std::size_t> toRemove;
+    const uint64_t documentsFound = treeLocal->count();
+    RevisionReplicationIterator& local =
+        *static_cast<RevisionReplicationIterator*>(iter.get());
+
+    while (requestResume < std::numeric_limits<TRI_voc_rid_t>::max()) {
+      if (isAborted()) {
+        return Result(TRI_ERROR_REPLICATION_APPLIER_STOPPED);
+      }
+
+      if (!_config.isChild()) {
+        batchExtend();
+        _config.barrier.extend(_config.connection);
+      }
+
+      std::string batchUrl =
+          url + "&" + StaticStrings::RevisionTreeResume + "=" +
+          basics::HybridLogicalClock::encodeTimeStamp(requestResume);
+      std::string msg = "fetching collection revision ranges for collection '" +
+                        coll->name() + "' from " + batchUrl;
+      _config.progress.set(msg);
+      double t = TRI_microtime();
+      _config.connection.lease([&](httpclient::SimpleHttpClient* client) {
+        response.reset(client->retryRequest(rest::RequestType::PUT, batchUrl,
+                                            request.data(), request.size(), headers));
+      });
+      stats.waitedForKeys += TRI_microtime() - t;
+      ++stats.numKeysRequests;
+
+      if (replutils::hasFailed(response.get())) {
+        return replutils::buildHttpError(response.get(), batchUrl, _config.connection);
+      }
+
+      VPackBuilder responseBuilder;
+      Result r = replutils::parseResponse(responseBuilder, response.get());
+      if (r.fail()) {
+        return Result(TRI_ERROR_REPLICATION_INVALID_RESPONSE,
+                      std::string("got invalid response from master at ") +
+                          _config.master.endpoint + batchUrl + ": " + r.errorMessage());
+      }
+
+      VPackSlice const slice = responseBuilder.slice();
+      if (!slice.isObject()) {
+        return Result(TRI_ERROR_REPLICATION_INVALID_RESPONSE,
+                      std::string("got invalid response from master at ") +
+                          _config.master.endpoint + batchUrl +
+                          ": response is not an object");
+      }
+
+      VPackSlice const resumeSlice = slice.get("resume");
+      if (!resumeSlice.isNone() && !resumeSlice.isString()) {
+        return Result(TRI_ERROR_REPLICATION_INVALID_RESPONSE,
+                      std::string("got invalid response from master at ") +
+                          _config.master.endpoint + batchUrl +
+                          ": response field 'resume' is not a number");
+      }
+      requestResume = resumeSlice.isNone()
+                          ? std::numeric_limits<TRI_voc_rid_t>::max()
+                          : basics::HybridLogicalClock::decodeTimeStamp(resumeSlice);
+
+      VPackSlice const rangesSlice = slice.get("ranges");
+      if (!rangesSlice.isArray()) {
+        return Result(TRI_ERROR_REPLICATION_INVALID_RESPONSE,
+                      std::string("got invalid response from master at ") +
+                          _config.master.endpoint + batchUrl +
+                          ": response field 'ranges' is not an array");
+      }
+
+      for (VPackSlice masterSlice : VPackArrayIterator(rangesSlice)) {
+        if (!masterSlice.isArray()) {
+          return Result(
+              TRI_ERROR_REPLICATION_INVALID_RESPONSE,
+              std::string("got invalid response from master at ") +
+                  _config.master.endpoint + batchUrl +
+                  ": response field 'ranges' entry is not a revision range");
+        }
+        auto& currentRange = ranges[chunk];
+        if (!local.hasMore() ||
+            local.revision() < static_cast<TRI_voc_rid_t>(currentRange.first)) {
+          local.seek(std::max(iterResume,
+                              static_cast<TRI_voc_rid_t>(currentRange.first)));
+        }
+
+        TRI_voc_rid_t removalBound =
+            masterSlice.isEmptyArray()
+                ? currentRange.second + 1
+                : basics::HybridLogicalClock::decodeTimeStamp(masterSlice.at(0));
+        TRI_ASSERT(currentRange.first <= removalBound);
+        TRI_ASSERT(removalBound <= currentRange.second + 1);
+        std::size_t mixedBound = masterSlice.isEmptyArray()
+                                     ? currentRange.second
+                                     : basics::HybridLogicalClock::decodeTimeStamp(
+                                           masterSlice.at(masterSlice.length() - 1));
+        TRI_ASSERT(currentRange.first <= mixedBound);
+        TRI_ASSERT(mixedBound <= currentRange.second);
+
+        while (local.hasMore() && local.revision() < removalBound) {
+          toRemove.emplace_back(local.revision());
+          iterResume = std::max(iterResume, local.revision() + 1);
+          local.next();
+        }
+
+        std::size_t index = 0;
+        while (local.hasMore() && local.revision() <= mixedBound) {
+          TRI_voc_rid_t masterRev =
+              basics::HybridLogicalClock::decodeTimeStamp(masterSlice.at(index));
+
+          if (local.revision() < masterRev) {
+            toRemove.emplace_back(local.revision());
+            iterResume = std::max(iterResume, local.revision() + 1);
+            local.next();
+          } else if (masterRev < local.revision()) {
+            toFetch.emplace_back(masterRev);
+            ++index;
+            iterResume = std::max(iterResume, masterRev + 1);
+          } else {
+            TRI_ASSERT(local.revision() == masterRev);
+            // match, no need to remove local or fetch from master
+            ++index;
+            iterResume = std::max(iterResume, masterRev + 1);
+            local.next();
+          }
+        }
+        for (; index < masterSlice.length(); ++index) {
+          TRI_voc_rid_t masterRev =
+              basics::HybridLogicalClock::decodeTimeStamp(masterSlice.at(index));
+          // fetch any leftovers
+          toFetch.emplace_back(masterRev);
+          iterResume = std::max(iterResume, masterRev + 1);
+        }
+
+        while (local.hasMore() &&
+               local.revision() <= std::min(requestResume - 1, static_cast<TRI_voc_rid_t>(currentRange.second))) {
+          toRemove.emplace_back(local.revision());
+          iterResume = std::max(iterResume, local.revision() + 1);
+          local.next();
+        }
+
+        if (requestResume > currentRange.second) {
+          ++chunk;
+        }
+      }
+
+      Result res = ::removeRevisions(*trx, *coll, toRemove, stats);
+      if (res.fail()) {
+        return res;
+      }
+      toRemove.clear();
+
+      if (!_state.isChildSyncer) {
+        _state.barrier.extend(_state.connection);
+      }
+
+      res = ::fetchRevisions(*trx, _config, _state, *coll, leaderColl, toFetch,
+                             /*removed,*/ stats);
+      if (res.fail()) {
+        return res;
+      }
+      toFetch.clear();
+    }
+
+    // adjust counts
+    {
+      uint64_t numberDocumentsAfterSync =
+          documentsFound + stats.numDocsInserted - stats.numDocsRemoved;
+      uint64_t numberDocumentsDueToCounter =
+          coll->numberDocuments(trx.get(), transaction::CountType::Normal);
+
+      setProgress(std::string("number of remaining documents in collection '") +
+                  coll->name() + "': " + std::to_string(numberDocumentsAfterSync) +
+                  ", number of documents due to collection count: " +
+                  std::to_string(numberDocumentsDueToCounter));
+
+      if (numberDocumentsAfterSync != numberDocumentsDueToCounter) {
+        LOG_TOPIC("118bf", WARN, Logger::REPLICATION)
+            << "number of remaining documents in collection '" + coll->name() +
+                   "' is " + std::to_string(numberDocumentsAfterSync) +
+                   " and differs from number of documents returned by "
+                   "collection count " +
+                   std::to_string(numberDocumentsDueToCounter);
+
+        // patch the document counter of the collection and the transaction
+        int64_t diff = static_cast<int64_t>(numberDocumentsAfterSync) -
+                       static_cast<int64_t>(numberDocumentsDueToCounter);
+
+        trx->documentCollection()->getPhysical()->adjustNumberDocuments(*trx, diff);
+      }
+    }
+
+    res = trx->commit();
+    if (res.fail()) {
+      return res;
+    }
+    TRI_ASSERT(requestResume == std::numeric_limits<std::size_t>::max());
+  }
+
+  setProgress(
+      std::string("incremental sync statistics for collection '") + coll->name() +
+      "': " + "keys requests: " + std::to_string(stats.numKeysRequests) + ", " +
+      "docs requests: " + std::to_string(stats.numDocsRequests) + ", " +
+      "number of documents requested: " + std::to_string(stats.numDocsRequested) +
+      ", " + "number of documents inserted: " + std::to_string(stats.numDocsInserted) +
+      ", " + "number of documents removed: " + std::to_string(stats.numDocsRemoved) +
+      ", " + "waited for initial: " + std::to_string(stats.waitedForInitial) +
+      " s, " + "waited for keys: " + std::to_string(stats.waitedForKeys) +
+      " s, " + "waited for docs: " + std::to_string(stats.waitedForDocs) +
+      " s, " + "waited for insertions: " + std::to_string(stats.waitedForInsertions) +
+      " s, " + "waited for removals: " + std::to_string(stats.waitedForRemovals) +
+      " s, " + "waited for key lookups: " + std::to_string(stats.waitedForKeyLookups) +
+      " s, " + "total time: " + std::to_string(TRI_microtime() - startTime) +
+      " s");
+
+  return Result{};
+}
+
 /// @brief incrementally fetch data from a collection
 /// @brief changes the properties of a collection, based on the VelocyPack
 /// provided
diff --git a/arangod/Replication/DatabaseInitialSyncer.h b/arangod/Replication/DatabaseInitialSyncer.h
index 0359f6223f6c..9d8c08502c55 100644
--- a/arangod/Replication/DatabaseInitialSyncer.h
+++ b/arangod/Replication/DatabaseInitialSyncer.h
@@ -26,6 +26,7 @@
 
 #include "Basics/Result.h"
 #include "Cluster/ServerState.h"
+#include "Containers/MerkleTree.h"
 #include "Replication/InitialSyncer.h"
 #include "Replication/utilities.h"
 #include "Utils/SingleCollectionTransaction.h"
@@ -192,11 +193,24 @@ class DatabaseInitialSyncer final : public InitialSyncer {
   Result fetchCollectionDump(arangodb::LogicalCollection*,
                              std::string const& leaderColl, TRI_voc_tick_t);
 
-  /// @brief incrementally fetch data from a collection
+  /// @brief incrementally fetch data from a collection using keys as the
+  /// primary document identifier
   // TODO worker safety
   Result fetchCollectionSync(arangodb::LogicalCollection*,
                              std::string const& leaderColl, TRI_voc_tick_t);
 
+  /// @brief incrementally fetch data from a collection using keys as the
+  /// primary document identifier
+  // TODO worker safety
+  Result fetchCollectionSyncByKeys(arangodb::LogicalCollection*,
+                                   std::string const& leaderColl, TRI_voc_tick_t);
+
+  /// @brief incrementally fetch data from a collection using revisions as the
+  /// primary document identifier, not supported by all engines/collections
+  // TODO worker safety
+  Result fetchCollectionSyncByRevisions(arangodb::LogicalCollection*,
+                                        std::string const& leaderColl, TRI_voc_tick_t);
+
   /// @brief changes the properties of a collection, based on the VelocyPack
   /// provided
   Result changeCollection(arangodb::LogicalCollection*, arangodb::velocypack::Slice const&);
diff --git a/arangod/Replication/InitialSyncer.h b/arangod/Replication/InitialSyncer.h
index d1a04e13f579..04c209f9fbcc 100644
--- a/arangod/Replication/InitialSyncer.h
+++ b/arangod/Replication/InitialSyncer.h
@@ -64,6 +64,9 @@ struct InitialSyncerIncrementalSyncStats {
   double waitedForKeys = 0.0;
   // total time spent waiting for responses to /_api/replication/keys?type=docs
   double waitedForDocs = 0.0;
+  double waitedForInsertions = 0.0;
+  double waitedForRemovals = 0.0;
+  double waitedForKeyLookups = 0.0;
 };
 
 class InitialSyncer : public Syncer {
diff --git a/arangod/Replication/ReplicationFeature.cpp b/arangod/Replication/ReplicationFeature.cpp
index 9cecd502cebf..b638c626c5a7 100644
--- a/arangod/Replication/ReplicationFeature.cpp
+++ b/arangod/Replication/ReplicationFeature.cpp
@@ -56,6 +56,7 @@ ReplicationFeature::ReplicationFeature(ApplicationServer& server)
       _forceRequestTimeout(false),
       _replicationApplierAutoStart(true),
       _enableActiveFailover(false),
+      _syncByRevision(false),
       _parallelTailingInvocations(0),
       _maxParallelTailingInvocations(0) {
   setOptional(true);
@@ -101,6 +102,13 @@ void ReplicationFeature::collectOptions(std::shared_ptr<ProgramOptions> options)
                      "Default timeout value for replication requests (in seconds)",
                      new DoubleParameter(&_requestTimeout))
                      .setIntroducedIn(30409).setIntroducedIn(30504);
+
+  options
+      ->addOption(
+          "--replication.sync-by-revision",
+          "Whether to use the newer revision-based replication protocol",
+          new BooleanParameter(&_syncByRevision))
+      .setIntroducedIn(30700);
 }
 
 void ReplicationFeature::validateOptions(std::shared_ptr<options::ProgramOptions> options) {
@@ -216,6 +224,12 @@ double ReplicationFeature::checkRequestTimeout(double value) const {
   return value;
 }
 
+bool ReplicationFeature::isActiveFailoverEnabled() const {
+  return _enableActiveFailover;
+}
+
+bool ReplicationFeature::syncByRevision() const { return _syncByRevision; }
+
 // start the replication applier for a single database
 void ReplicationFeature::startApplier(TRI_vocbase_t* vocbase) {
   TRI_ASSERT(vocbase->type() == TRI_VOCBASE_TYPE_NORMAL);
@@ -242,6 +256,15 @@ void ReplicationFeature::startApplier(TRI_vocbase_t* vocbase) {
   }
 }
 
+GlobalReplicationApplier* ReplicationFeature::globalReplicationApplier() const {
+  TRI_ASSERT(_globalReplicationApplier != nullptr);
+  return _globalReplicationApplier.get();
+}
+
+void ReplicationFeature::disableReplicationApplier() {
+  _replicationApplierAutoStart = false;
+}
+
 // stop the replication applier for a single database
 void ReplicationFeature::stopApplier(TRI_vocbase_t* vocbase) {
   TRI_ASSERT(vocbase->type() == TRI_VOCBASE_TYPE_NORMAL);
@@ -251,6 +274,12 @@ void ReplicationFeature::stopApplier(TRI_vocbase_t* vocbase) {
   }
 }
 
+/// @brief returns the connect timeout for replication requests
+double ReplicationFeature::connectTimeout() const { return _connectTimeout; }
+
+/// @brief returns the request timeout for replication requests
+double ReplicationFeature::requestTimeout() const { return _requestTimeout; }
+
 // replace tcp:// with http://, and ssl:// with https://
 static std::string FixEndpointProto(std::string const& endpoint) {
   if (endpoint.compare(0, 6, "tcp://") == 0) {  //  find("tcp://", 0, 6)
diff --git a/arangod/Replication/ReplicationFeature.h b/arangod/Replication/ReplicationFeature.h
index a125e5b7f5a3..3fccd364922b 100644
--- a/arangod/Replication/ReplicationFeature.h
+++ b/arangod/Replication/ReplicationFeature.h
@@ -46,13 +46,10 @@ class ReplicationFeature final : public application_features::ApplicationFeature
   void unprepare() override final;
 
   /// @brief return a pointer to the global replication applier
-  GlobalReplicationApplier* globalReplicationApplier() const {
-    TRI_ASSERT(_globalReplicationApplier != nullptr);
-    return _globalReplicationApplier.get();
-  }
+  GlobalReplicationApplier* globalReplicationApplier() const;
 
   /// @brief disable replication appliers
-  void disableReplicationApplier() { _replicationApplierAutoStart = false; }
+  void disableReplicationApplier();
 
   /// @brief start the replication applier for a single database
   void startApplier(TRI_vocbase_t* vocbase);
@@ -61,11 +58,11 @@ class ReplicationFeature final : public application_features::ApplicationFeature
   void stopApplier(TRI_vocbase_t* vocbase);
 
   /// @brief returns the connect timeout for replication requests
-  double connectTimeout() const { return _connectTimeout; }
-  
+  double connectTimeout() const;
+
   /// @brief returns the request timeout for replication requests
-  double requestTimeout() const { return _requestTimeout; }
-  
+  double requestTimeout() const;
+
   /// @brief returns the connect timeout for replication requests
   /// this will return the provided value if the user has not adjusted the
   /// timeout via configuration. otherwise it will return the configured
@@ -79,7 +76,9 @@ class ReplicationFeature final : public application_features::ApplicationFeature
   double checkRequestTimeout(double value) const;
 
   /// @brief automatic failover of replication using the agency
-  bool isActiveFailoverEnabled() const { return _enableActiveFailover; }
+  bool isActiveFailoverEnabled() const;
+
+  bool syncByRevision() const;
 
   /// @brief track the number of (parallel) tailing operations
   /// will throw an exception if the number of concurrently running operations
@@ -117,7 +116,10 @@ class ReplicationFeature final : public application_features::ApplicationFeature
 
   /// Enable the active failover
   bool _enableActiveFailover;
-  
+
+  /// Use the revision-based replication protocol
+  bool _syncByRevision;
+
   /// @brief number of currently operating tailing operations
   std::atomic<uint64_t> _parallelTailingInvocations;
 
diff --git a/arangod/RestHandler/RestCollectionHandler.cpp b/arangod/RestHandler/RestCollectionHandler.cpp
index 549ce3331bcd..247ebe4e2a8c 100644
--- a/arangod/RestHandler/RestCollectionHandler.cpp
+++ b/arangod/RestHandler/RestCollectionHandler.cpp
@@ -132,14 +132,14 @@ RestStatus RestCollectionHandler::handleCommandGet() {
 
   std::string const& sub = suffixes[1];
   _builder.clear();
-  
+
   std::shared_ptr<LogicalCollection> coll;
   auto res = methods::Collections::lookup(_vocbase, name, coll);
   if (res.fail()) {
     generateError(res);
     return RestStatus::DONE;
   }
-  
+
   TRI_ASSERT(coll);
   if (sub == "checksum") {
     // /_api/collection/<identifier>/checksum
@@ -149,12 +149,12 @@ RestStatus RestCollectionHandler::handleCommandGet() {
 
     bool withRevisions = _request->parsedValue("withRevisions", false);
     bool withData = _request->parsedValue("withData", false);
-    
+
     uint64_t checksum;
     TRI_voc_rid_t revId;
     res = methods::Collections::checksum(*coll, withRevisions, withData,
                                          checksum, revId);
-    
+
     if (res.ok()) {
       {
         VPackObjectBuilder obj(&_builder, true);
@@ -176,7 +176,7 @@ RestStatus RestCollectionHandler::handleCommandGet() {
 
     generateError(res);
     return RestStatus::DONE;
-  
+
   } else if (sub == "figures") {
     // /_api/collection/<identifier>/figures
     _ctxt = std::make_unique<methods::Collections::Context>(_vocbase, *coll);
@@ -283,7 +283,7 @@ RestStatus RestCollectionHandler::handleCommandGet() {
     }
     return standardResponse();
   }
-  
+
   generateError(
       rest::ResponseCode::NOT_FOUND, TRI_ERROR_HTTP_NOT_FOUND,
       "expecting one of the resources 'checksum', 'count', "
@@ -355,7 +355,7 @@ void RestCollectionHandler::handleCommandPost() {
                                             StaticStrings::ReplicationFactor,
                                             StaticStrings::MinReplicationFactor, // deprecated
                                             StaticStrings::WriteConcern,
-                                            StaticStrings::Validators,
+                                            StaticStrings::Validation,
                                             "servers"
                                           });
   VPackSlice const parameters = filtered.slice();
@@ -381,7 +381,7 @@ void RestCollectionHandler::handleCommandPost() {
     /*showFigures*/ false,
     /*showCount*/ false,
     /*detailedCount*/ true);
-    
+
     generateOk(rest::ResponseCode::OK, _builder);
   } else {
     generateError(res);
@@ -416,7 +416,7 @@ RestStatus RestCollectionHandler::handleCommandPut() {
 
   std::shared_ptr<LogicalCollection> coll;
   Result res = methods::Collections::lookup(_vocbase, name, coll);
-  
+
   if (res.fail()) {
     generateError(res);
     return RestStatus::DONE;
@@ -455,7 +455,7 @@ RestStatus RestCollectionHandler::handleCommandPut() {
       generateError(res);
       return RestStatus::DONE;
     }
-    
+
   } else if (sub == "compact") {
     res = coll->compact();
 
@@ -470,7 +470,7 @@ RestStatus RestCollectionHandler::handleCommandPut() {
       generateError(res);
       return RestStatus::DONE;
     }
-    
+
     VPackBuilder temp;
     if (body.isString()) {
       temp.openObject();
@@ -499,7 +499,7 @@ RestStatus RestCollectionHandler::handleCommandPut() {
       generateError(res);
       return RestStatus::DONE;
     }
-    
+
   } else if (sub == "truncate") {
     OperationOptions opts;
 
@@ -516,7 +516,7 @@ RestStatus RestCollectionHandler::handleCommandPut() {
       _activeTrx.reset();
       return RestStatus::DONE;
     }
-    
+
     return waitForFuture(
         _activeTrx->truncateAsync(coll->name(), opts).thenValue([this, coll](OperationResult&& opres) {
           // Will commit if no error occured.
@@ -554,12 +554,12 @@ RestStatus RestCollectionHandler::handleCommandPut() {
                                    /*detailedCount*/ true);
           standardResponse();
         }));
-      
+
   } else if (sub == "properties") {
     std::vector<std::string> keep = {StaticStrings::DoCompact,
                                      StaticStrings::JournalSize,
                                      StaticStrings::WaitForSyncString,
-                                     StaticStrings::Validators,
+                                     StaticStrings::Validation,
                                      StaticStrings::IndexBuckets,
                                      StaticStrings::ReplicationFactor,
                                      StaticStrings::MinReplicationFactor,  // deprecated
@@ -572,14 +572,14 @@ RestStatus RestCollectionHandler::handleCommandPut() {
       generateError(res);
       return RestStatus::DONE;
     }
-    
+
     collectionRepresentation(name, /*showProperties*/ true,
                              /*showFigures*/ false, /*showCount*/ false,
                              /*detailedCount*/ true);
     return standardResponse();
 
   } else if (sub == "rename") {
-    
+
     VPackSlice const newNameSlice = body.get(StaticStrings::DataSourceName);
     if (!newNameSlice.isString()) {
       generateError(Result(TRI_ERROR_ARANGO_ILLEGAL_NAME, "name is empty"));
@@ -595,10 +595,10 @@ RestStatus RestCollectionHandler::handleCommandPut() {
                                /*detailedCount*/ true);
       return standardResponse();
     }
-    
+
     generateError(res);
     return RestStatus::DONE;
-    
+
   } else if (sub == "loadIndexesIntoMemory") {
 
     return waitForFuture(
@@ -615,9 +615,9 @@ RestStatus RestCollectionHandler::handleCommandPut() {
 
           standardResponse();
         }));
-    
+
   }
-  
+
   res = handleExtraCommandPut(*coll, sub, _builder);
   if (res.is(TRI_ERROR_NOT_IMPLEMENTED)) {
     res.reset(
@@ -630,7 +630,7 @@ RestStatus RestCollectionHandler::handleCommandPut() {
   } else {
     standardResponse();
   }
-  
+
   return RestStatus::DONE;
 }
 
diff --git a/arangod/RestHandler/RestReplicationHandler.cpp b/arangod/RestHandler/RestReplicationHandler.cpp
index c1d26b7985c6..8fb7ffe7d850 100644
--- a/arangod/RestHandler/RestReplicationHandler.cpp
+++ b/arangod/RestHandler/RestReplicationHandler.cpp
@@ -27,18 +27,22 @@
 #include "Aql/Query.h"
 #include "Aql/QueryRegistry.h"
 #include "Basics/ConditionLocker.h"
+#include "Basics/HybridLogicalClock.h"
 #include "Basics/ReadLocker.h"
 #include "Basics/Result.h"
 #include "Basics/RocksDBUtils.h"
 #include "Basics/StaticStrings.h"
+#include "Basics/VPackStringBufferAdapter.h"
 #include "Basics/VelocyPackHelper.h"
 #include "Basics/WriteLocker.h"
+#include "Basics/hashes.h"
 #include "Cluster/ClusterFeature.h"
 #include "Cluster/ClusterHelpers.h"
 #include "Cluster/ClusterMethods.h"
 #include "Cluster/FollowerInfo.h"
 #include "Cluster/RebootTracker.h"
 #include "Cluster/ResignShardLeadership.h"
+#include "Containers/MerkleTree.h"
 #include "GeneralServer/AuthenticationFeature.h"
 #include "Indexes/Index.h"
 #include "Network/NetworkFeature.h"
@@ -67,6 +71,7 @@
 
 #include <velocypack/Builder.h>
 #include <velocypack/Collection.h>
+#include <velocypack/Dumper.h>
 #include <velocypack/Iterator.h>
 #include <velocypack/Parser.h>
 #include <velocypack/Slice.h>
@@ -258,6 +263,10 @@ std::string const RestReplicationHandler::Batch = "batch";
 std::string const RestReplicationHandler::Barrier = "barrier";
 std::string const RestReplicationHandler::Inventory = "inventory";
 std::string const RestReplicationHandler::Keys = "keys";
+std::string const RestReplicationHandler::Revisions = "revisions";
+std::string const RestReplicationHandler::Tree = "tree";
+std::string const RestReplicationHandler::Ranges = "ranges";
+std::string const RestReplicationHandler::Documents = "documents";
 std::string const RestReplicationHandler::Dump = "dump";
 std::string const RestReplicationHandler::RestoreCollection =
     "restore-collection";
@@ -414,6 +423,25 @@ RestStatus RestReplicationHandler::execute() {
       } else if (type == rest::RequestType::DELETE_REQ) {
         handleCommandRemoveKeys();
       }
+    } else if (command == Revisions) {
+      if (isCoordinatorError()) {
+        return RestStatus::DONE;
+      }
+
+      if (len > 1) {
+        std::string const& subCommand = suffixes[1];
+        if (type == rest::RequestType::GET && subCommand == Tree) {
+          handleCommandRevisionTree();
+        } else if (type == rest::RequestType::POST && subCommand == Tree) {
+          handleCommandRebuildRevisionTree();
+        } else if (type == rest::RequestType::PUT && subCommand == Ranges) {
+          handleCommandRevisionRanges();
+        } else if (type == rest::RequestType::PUT && subCommand == Documents) {
+          handleCommandRevisionDocuments();
+        }
+      } else {
+        goto BAD_CALL;
+      }
     } else if (command == Dump) {
       // works on collections
       // example: curl --dump -
@@ -1397,6 +1425,9 @@ Result RestReplicationHandler::processRestoreData(std::string const& colName) {
   }
 #endif
 
+  bool generateNewRevisionIds =
+      !_request->parsedValue(StaticStrings::PreserveRevisionIds, false);
+
   ExecContextSuperuserScope escope(ExecContext::current().isAdminUser());
 
   if (colName == TRI_COL_NAME_USERS) {
@@ -1419,7 +1450,7 @@ Result RestReplicationHandler::processRestoreData(std::string const& colName) {
     return res;
   }
 
-  res = processRestoreDataBatch(trx, colName);
+  res = processRestoreDataBatch(trx, colName, generateNewRevisionIds);
   res = trx.finish(res);
 
   return res;
@@ -1573,7 +1604,8 @@ Result RestReplicationHandler::processRestoreUsersBatch(std::string const& colle
 ////////////////////////////////////////////////////////////////////////////////
 
 Result RestReplicationHandler::processRestoreDataBatch(transaction::Methods& trx,
-                                                       std::string const& collectionName) {
+                                                       std::string const& collectionName,
+                                                       bool generateNewRevisionIds) {
   std::unordered_map<std::string, VPackValueLength> latest;
   VPackBuilder allMarkers;
 
@@ -1651,6 +1683,16 @@ Result RestReplicationHandler::processRestoreDataBatch(transaction::Methods& trx
   bool const isUsersOnCoordinator = (ServerState::instance()->isCoordinator() &&
                                      collectionName == TRI_COL_NAME_USERS);
 
+  LogicalCollection* collection = trx.documentCollection(collectionName);
+  if (generateNewRevisionIds && !collection) {
+    return TRI_ERROR_ARANGO_DATA_SOURCE_NOT_FOUND;
+  }
+  PhysicalCollection* physical = collection->getPhysical();
+  if (!physical) {
+    return TRI_ERROR_ARANGO_DATA_SOURCE_NOT_FOUND;
+  }
+  char ridBuffer[11];
+
   // Now try to insert all keys for which the last marker was a document
   // marker, note that these could still be replace markers!
   VPackBuilder builder;
@@ -1672,19 +1714,24 @@ Result RestReplicationHandler::processRestoreDataBatch(transaction::Methods& trx
       if (type == REPLICATION_MARKER_DOCUMENT) {
         VPackSlice const doc = marker.get(::dataString);
         TRI_ASSERT(doc.isObject());
-        if (isUsersOnCoordinator) {
-          // In the _users case we silently remove the _key value.
-          builder.openObject();
-          for (auto it : VPackObjectIterator(doc)) {
-            if (arangodb::velocypack::StringRef(it.key) != StaticStrings::KeyString &&
-                arangodb::velocypack::StringRef(it.key) != StaticStrings::IdString) {
-              builder.add(it.key);
-              builder.add(it.value);
-            }
+        // In the _users case we silently remove the _key value.
+        VPackObjectBuilder guard(&builder);
+        for (auto it : VPackObjectIterator(doc)) {
+          if (isUsersOnCoordinator &&
+              (arangodb::velocypack::StringRef(it.key) == StaticStrings::KeyString ||
+               arangodb::velocypack::StringRef(it.key) == StaticStrings::IdString)) {
+            continue;
+          }
+
+          builder.add(it.key);
+
+          if (generateNewRevisionIds && arangodb::velocypack::StringRef(it.key) ==
+                                            StaticStrings::RevString) {
+            TRI_voc_rid_t newRid = physical->newRevisionId();
+            builder.add(TRI_RidToValuePair(newRid, ridBuffer));
+          } else {
+            builder.add(it.value);
           }
-          builder.close();
-        } else {
-          builder.add(doc);
         }
       }
     }
@@ -2893,6 +2940,341 @@ void RestReplicationHandler::handleCommandLoggerTickRanges() {
   }
 }
 
+bool RestReplicationHandler::prepareRevisionOperation(RevisionOperationContext& ctx) {
+  auto& selector = server().getFeature<EngineSelectorFeature>();
+  if (!selector.isRocksDB()) {
+    generateError(
+        rest::ResponseCode::NOT_IMPLEMENTED, TRI_ERROR_NOT_IMPLEMENTED,
+        "this storage engine does not support revision-based replication");
+    return false;
+  }
+
+  LOG_TOPIC("253e2", TRACE, arangodb::Logger::REPLICATION)
+      << "enter prepareRevisionOperation";
+
+  bool found = false;
+
+  // get collection Name
+  ctx.cname = _request->value("collection");
+  if (ctx.cname.empty()) {
+    generateError(rest::ResponseCode::BAD, TRI_ERROR_HTTP_BAD_PARAMETER,
+                  "invalid collection parameter");
+    return false;
+  }
+
+  // get batchId
+  std::string const& batchIdString = _request->value("batchId", found);
+  if (found) {
+    ctx.batchId = StringUtils::uint64(batchIdString);
+  } else {
+    generateError(rest::ResponseCode::NOT_FOUND, TRI_ERROR_HTTP_BAD_PARAMETER,
+                  "replication revision tree - request misses batchId");
+    return false;
+  }
+
+  // get resume
+  std::string const& resumeString = _request->value("resume", found);
+  if (found) {
+    ctx.resume = basics::HybridLogicalClock::decodeTimeStamp(resumeString);
+  }
+
+  // print request
+  LOG_TOPIC("2b70f", TRACE, arangodb::Logger::REPLICATION)
+      << "requested revision tree for collection '" << ctx.cname
+      << "' using contextId '" << ctx.batchId << "'";
+
+  ExecContextSuperuserScope escope(ExecContext::current().isAdminUser());
+
+  if (!ExecContext::current().canUseCollection(_vocbase.name(), ctx.cname, auth::Level::RO)) {
+    generateError(rest::ResponseCode::FORBIDDEN, TRI_ERROR_FORBIDDEN);
+    return false;
+  }
+
+  ctx.collection = _vocbase.lookupCollection(ctx.cname);
+  if (!ctx.collection) {
+    generateError(rest::ResponseCode::NOT_FOUND, TRI_ERROR_ARANGO_DATA_SOURCE_NOT_FOUND);
+    return false;
+  }
+  if (!ctx.collection->syncByRevision()) {
+    generateError(rest::ResponseCode::NOT_IMPLEMENTED, TRI_ERROR_NOT_IMPLEMENTED,
+                  "this collection doesn't support revision-based replication");
+    return false;
+  }
+
+  // determine end tick for dump
+  ctx.tickEnd = std::numeric_limits<TRI_voc_tick_t>::max();
+  std::string const& value2 = _request->value("to", found);
+  if (found) {
+    ctx.tickEnd = static_cast<TRI_voc_tick_t>(StringUtils::uint64(value2));
+  }
+
+  ctx.iter =
+      ctx.collection->getPhysical()->getReplicationIterator(ReplicationIterator::Ordering::Revision,
+                                                            ctx.batchId);
+  if (!ctx.iter) {
+    generateError(rest::ResponseCode::SERVER_ERROR, TRI_ERROR_INTERNAL,
+                  "could not get replication iterator for collection '" +
+                      ctx.cname + "'");
+    return false;
+  }
+
+  return true;
+}
+
+//////////////////////////////////////////////////////////////////////////////
+/// @brief return the revision tree for a given collection, if available
+/// @response serialized revision tree, binary
+//////////////////////////////////////////////////////////////////////////////
+
+void RestReplicationHandler::handleCommandRevisionTree() {
+  RevisionOperationContext ctx;
+  if (!prepareRevisionOperation(ctx)) {
+    return;
+  }
+
+  auto tree = ctx.collection->getPhysical()->revisionTree(ctx.batchId);
+  if (!tree) {
+    generateError(rest::ResponseCode::SERVER_ERROR, TRI_ERROR_INTERNAL,
+                  "could not generate revision tree");
+    return;
+  }
+  VPackBuffer<uint8_t> buffer;
+  VPackBuilder result(buffer);
+  tree->serialize(result);
+
+  generateResult(rest::ResponseCode::OK, std::move(buffer));
+}
+
+void RestReplicationHandler::handleCommandRebuildRevisionTree() {
+  RevisionOperationContext ctx;
+  if (!prepareRevisionOperation(ctx)) {
+    return;
+  }
+
+  if (!ctx.collection->syncByRevision()) {
+    generateError(Result(TRI_ERROR_BAD_PARAMETER,
+                         "collection does not support revision tree commands"));
+    return;
+  }
+
+  Result res = ctx.collection->getPhysical()->rebuildRevisionTree();
+  if (res.fail()) {
+    generateError(res);
+    return;
+  }
+
+  generateResult(rest::ResponseCode::NO_CONTENT, VPackSlice::nullSlice());
+}
+
+//////////////////////////////////////////////////////////////////////////////
+/// @brief return the requested revision ranges for a given collection, if
+///        available
+/// @response VPackObject, containing
+///           * ranges, VPackArray of VPackArray of revisions
+///           * resume, optional, if response is chunked; revision resume
+///                     point to specify on subsequent requests
+//////////////////////////////////////////////////////////////////////////////
+
+void RestReplicationHandler::handleCommandRevisionRanges() {
+  RevisionOperationContext ctx;
+  if (!prepareRevisionOperation(ctx)) {
+    return;
+  }
+
+  bool success = false;
+  std::size_t current = 0;
+  VPackSlice const body = this->parseVPackBody(success);
+  if (!success) {
+    // error already created
+    return;
+  }
+  bool badFormat = !body.isArray();
+  if (!badFormat) {
+    std::size_t i = 0;
+    std::uint64_t previousRight = 0;
+    for (VPackSlice entry : VPackArrayIterator(body)) {
+      if (!entry.isArray() || entry.length() != 2) {
+        badFormat = true;
+        break;
+      }
+      VPackSlice first = entry.at(0);
+      VPackSlice second = entry.at(1);
+      if (!first.isString() || !second.isString()) {
+        badFormat = true;
+        break;
+      }
+      TRI_voc_rid_t left = basics::HybridLogicalClock::decodeTimeStamp(first);
+      TRI_voc_rid_t right = basics::HybridLogicalClock::decodeTimeStamp(second);
+      if (left == std::numeric_limits<TRI_voc_rid_t>::max() ||
+          right == std::numeric_limits<TRI_voc_rid_t>::max() || left >= right ||
+          left < previousRight) {
+        badFormat = true;
+        break;
+      }
+      if (left <= ctx.resume || (i > 0 && previousRight < ctx.resume)) {
+        current = std::max(current, i);
+      }
+      previousRight = right;
+      ++i;
+    }
+  }
+  if (badFormat) {
+    generateError(rest::ResponseCode::BAD, TRI_ERROR_HTTP_BAD_PARAMETER,
+                  "body needs to be an array of pairs of revisions");
+    return;
+  }
+
+  RevisionReplicationIterator& it =
+      *static_cast<RevisionReplicationIterator*>(ctx.iter.get());
+  it.seek(ctx.resume);
+
+  std::size_t constexpr limit = 64 * 1024;  // ~2MB data
+  std::size_t total = 0;
+  VPackBuilder response;
+  {
+    VPackObjectBuilder obj(&response);
+    TRI_voc_rid_t resumeNext = ctx.resume;
+    VPackSlice range;
+    TRI_voc_rid_t left;
+    TRI_voc_rid_t right;
+    auto setRange = [&body, &range, &left, &right](std::size_t index) -> void {
+      range = body.at(index);
+      left = basics::HybridLogicalClock::decodeTimeStamp(range.at(0));
+      right = basics::HybridLogicalClock::decodeTimeStamp(range.at(1));
+    };
+    setRange(current);
+
+    char ridBuffer[11];
+    {
+      TRI_ASSERT(response.isOpenObject());
+      VPackArrayBuilder rangesGuard(&response, StaticStrings::RevisionTreeRanges);
+      TRI_ASSERT(response.isOpenArray());
+      bool subOpen = false;
+      while (total < limit && current < body.length()) {
+        if (!it.hasMore() || it.revision() <= left || it.revision() > right ||
+            (!subOpen && it.revision() <= right)) {
+          auto target = std::max(ctx.resume, left);
+          if (it.hasMore() && it.revision() < target) {
+            it.seek(target);
+          }
+          TRI_ASSERT(!subOpen);
+          response.openArray();
+          subOpen = true;
+          resumeNext = std::max(ctx.resume + 1, left);
+        }
+
+        if (it.hasMore() && it.revision() >= left && it.revision() <= right) {
+          response.add(basics::HybridLogicalClock::encodeTimeStampToValuePair(it.revision(), ridBuffer));
+          ++total;
+          resumeNext = it.revision() + 1;
+          it.next();
+        }
+
+        if (!it.hasMore() || it.revision() > right) {
+          TRI_ASSERT(response.isOpenArray());
+          TRI_ASSERT(subOpen);
+          subOpen = false;
+          response.close();
+          TRI_ASSERT(response.isOpenArray());
+          resumeNext = right + 1;
+          ++current;
+          if (current < body.length()) {
+            setRange(current);
+          }
+        }
+      }
+      if (subOpen) {
+        TRI_ASSERT(response.isOpenArray());
+        response.close();
+        subOpen = false;
+        TRI_ASSERT(response.isOpenArray());
+      }
+      TRI_ASSERT(!subOpen);
+      TRI_ASSERT(response.isOpenArray());
+      // exit scope closes "ranges"
+    }
+
+    TRI_ASSERT(response.isOpenObject());
+
+    if (body.length() >= 1) {
+      setRange(body.length() - 1);
+      if (body.length() > 0 && resumeNext <= right) {
+        response.add(StaticStrings::RevisionTreeResume,
+                     basics::HybridLogicalClock::encodeTimeStampToValuePair(resumeNext, ridBuffer));
+      }
+    }
+  }
+
+  generateResult(rest::ResponseCode::OK, response.slice());
+}
+
+//////////////////////////////////////////////////////////////////////////////
+/// @brief return the requested documents from a given collection, if
+///        available
+/// @response VPackArray, containing VPackObject documents or errors
+//////////////////////////////////////////////////////////////////////////////
+
+void RestReplicationHandler::handleCommandRevisionDocuments() {
+  RevisionOperationContext ctx;
+  if (!prepareRevisionOperation(ctx)) {
+    return;
+  }
+
+  bool success = false;
+  VPackSlice const body = this->parseVPackBody(success);
+  if (!success) {
+    // error already created
+    return;
+  }
+  bool badFormat = !body.isArray();
+  if (!badFormat) {
+    for (VPackSlice entry : VPackArrayIterator(body)) {
+      if (!entry.isString()) {
+        badFormat = true;
+        break;
+      }
+      std::uint64_t entryNum = basics::HybridLogicalClock::decodeTimeStamp(entry);
+      if (entryNum == std::numeric_limits<std::uint64_t>::max()) {
+        badFormat = true;
+        break;
+      }
+    }
+  }
+  if (badFormat) {
+    generateError(rest::ResponseCode::BAD, TRI_ERROR_HTTP_BAD_PARAMETER,
+                  "body needs to be an array of revisions");
+    return;
+  }
+
+  std::size_t constexpr sizeLimit = 16 * 1024 * 1024;
+  std::size_t size = 0;  // running total, approximation
+  RevisionReplicationIterator& it =
+      *static_cast<RevisionReplicationIterator*>(ctx.iter.get());
+
+  VPackBuffer<std::uint8_t> buffer;
+  VPackBuilder response(buffer);
+  {
+    VPackArrayBuilder docs(&response);
+
+    for (VPackSlice entry : VPackArrayIterator(body)) {
+      TRI_voc_rid_t rev = basics::HybridLogicalClock::decodeTimeStamp(entry);
+      if (it.hasMore() && it.revision() < rev) {
+        it.seek(rev);
+      }
+      VPackSlice res =
+          it.hasMore() ? it.document() : velocypack::Slice::emptyObjectSlice();
+      if (size + res.byteSize() > sizeLimit && !response.slice().isEmptyArray()) {
+        break;
+      }
+      response.add(res);
+      size += res.byteSize();
+    }
+  }
+
+  auto ctxt = transaction::StandaloneContext::Create(_vocbase);
+  generateResult(rest::ResponseCode::OK, std::move(buffer), ctxt);
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 /// @brief creates a collection, based on the VelocyPack provided
 ////////////////////////////////////////////////////////////////////////////////
@@ -3079,10 +3461,12 @@ Result RestReplicationHandler::createBlockingTransaction(
     std::string comment = std::string("SynchronizeShard from ") + serverId +
                           " for " + col.name() + " access mode " +
                           AccessMode::typeString(access);
-    auto rGuard = std::make_unique<CallbackGuard>(
+    std::unique_ptr<CallbackGuard> rGuard = nullptr;
+    if (!serverId.empty()) {
+      rGuard = std::make_unique<CallbackGuard>(
         ci.rebootTracker().callMeOnChange(RebootTracker::PeerState(serverId, rebootId),
                                           f, comment));
-
+    }
     queryRegistry->insert(id, query.get(), ttl, true, true, std::move(rGuard));
 
   } catch (...) {
diff --git a/arangod/RestHandler/RestReplicationHandler.h b/arangod/RestHandler/RestReplicationHandler.h
index 28367cecda9b..4c58be8ec3aa 100644
--- a/arangod/RestHandler/RestReplicationHandler.h
+++ b/arangod/RestHandler/RestReplicationHandler.h
@@ -33,6 +33,7 @@
 #include "Replication/Syncer.h"
 #include "Replication/common-defines.h"
 #include "RestHandler/RestVocbaseBaseHandler.h"
+#include "StorageEngine/ReplicationIterator.h"
 
 namespace arangodb {
 class ClusterInfo;
@@ -74,6 +75,12 @@ class RestReplicationHandler : public RestVocbaseBaseHandler {
                          GeneralRequest*, GeneralResponse*);
   ~RestReplicationHandler();
 
+ public:
+  static std::string const Revisions;
+  static std::string const Tree;
+  static std::string const Ranges;
+  static std::string const Documents;
+
  protected:
   //////////////////////////////////////////////////////////////////////////////
   /// @brief list of available commands
@@ -286,6 +293,39 @@ class RestReplicationHandler : public RestVocbaseBaseHandler {
 
   void handleCommandLoggerTickRanges();
 
+  //////////////////////////////////////////////////////////////////////////////
+  /// @brief return the revision tree for a given collection, if available
+  /// @response serialized revision tree, binary
+  //////////////////////////////////////////////////////////////////////////////
+
+  void handleCommandRevisionTree();
+
+  //////////////////////////////////////////////////////////////////////////////
+  /// @brief rebuild the revision tree for a given collection, if allowed
+  /// @response 204 No Content if all goes well
+  //////////////////////////////////////////////////////////////////////////////
+
+  void handleCommandRebuildRevisionTree();
+
+  //////////////////////////////////////////////////////////////////////////////
+  /// @brief return the requested revision ranges for a given collection, if
+  ///        available
+  /// @response VPackObject, containing
+  ///           * ranges, VPackArray of VPackArray of revisions
+  ///           * resume, optional, if response is chunked; revision resume
+  ///                     point to specify on subsequent requests
+  //////////////////////////////////////////////////////////////////////////////
+
+  void handleCommandRevisionRanges();
+
+  //////////////////////////////////////////////////////////////////////////////
+  /// @brief return the requested documents from a given collection, if
+  ///        available
+  /// @response VPackArray, containing VPackObject documents or errors
+  //////////////////////////////////////////////////////////////////////////////
+
+  void handleCommandRevisionDocuments();
+
   //////////////////////////////////////////////////////////////////////////////
   /// @brief determine chunk size from request
   ///        Reads chunkSize attribute from request
@@ -299,6 +339,17 @@ class RestReplicationHandler : public RestVocbaseBaseHandler {
   ReplicationApplier* getApplier(bool& global);
 
  private:
+  struct RevisionOperationContext {
+    uint64_t batchId;
+    TRI_voc_rid_t resume;
+    TRI_voc_tick_t tickEnd;
+    std::string cname;
+    std::shared_ptr<LogicalCollection> collection;
+    std::unique_ptr<ReplicationIterator> iter;
+  };
+
+  bool prepareRevisionOperation(RevisionOperationContext&);
+
   //////////////////////////////////////////////////////////////////////////////
   /// @brief restores the structure of a collection
   //////////////////////////////////////////////////////////////////////////////
@@ -323,7 +374,7 @@ class RestReplicationHandler : public RestVocbaseBaseHandler {
   /// @brief restores the data of a collection
   //////////////////////////////////////////////////////////////////////////////
 
-  Result processRestoreDataBatch(transaction::Methods& trx, std::string const& colName);
+  Result processRestoreDataBatch(transaction::Methods& trx, std::string const& colName, bool generateNewRevisionIds);
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief restores the indexes of a collection
diff --git a/arangod/RocksDBEngine/CMakeLists.txt b/arangod/RocksDBEngine/CMakeLists.txt
index d8b5ac0da7b2..295eb904b66b 100644
--- a/arangod/RocksDBEngine/CMakeLists.txt
+++ b/arangod/RocksDBEngine/CMakeLists.txt
@@ -66,6 +66,7 @@ set(ROCKSDB_SOURCES
   RocksDBEngine/RocksDBRecoveryManager.cpp
   RocksDBEngine/RocksDBReplicationCommon.cpp
   RocksDBEngine/RocksDBReplicationContext.cpp
+  RocksDBEngine/RocksDBReplicationIterator.cpp
   RocksDBEngine/RocksDBReplicationManager.cpp
   RocksDBEngine/RocksDBReplicationTailing.cpp
   RocksDBEngine/RocksDBRestCollectionHandler.cpp
diff --git a/arangod/RocksDBEngine/RocksDBBuilderIndex.cpp b/arangod/RocksDBEngine/RocksDBBuilderIndex.cpp
index 336c0a633b1d..71d7c98383f5 100644
--- a/arangod/RocksDBEngine/RocksDBBuilderIndex.cpp
+++ b/arangod/RocksDBEngine/RocksDBBuilderIndex.cpp
@@ -102,7 +102,7 @@ void RocksDBBuilderIndex::toVelocyPack(VPackBuilder& builder,
 Result RocksDBBuilderIndex::insert(transaction::Methods& trx, RocksDBMethods* mthd,
                                    LocalDocumentId const& documentId,
                                    arangodb::velocypack::Slice const& slice,
-                                   OperationMode mode) {
+                                   OperationOptions& options) {
 #ifdef ARANGODB_ENABLE_MAINTAINER_MODE
   auto* ctx = dynamic_cast<::BuilderCookie*>(trx.state()->cookie(this));
 #else
@@ -202,7 +202,7 @@ static arangodb::Result fillIndex(RocksDBIndex& ridx, WriteBatchType& batch,
     }
     batch.Clear();
 
-    auto ops = trxColl->stealTrackedOperations();
+    auto ops = trxColl->stealTrackedIndexOperations();
     if (!ops.empty()) {
       TRI_ASSERT(ridx.hasSelectivityEstimate() && ops.size() == 1);
       auto it = ops.begin();
@@ -224,6 +224,7 @@ static arangodb::Result fillIndex(RocksDBIndex& ridx, WriteBatchType& batch,
     }
   };
 
+  OperationOptions options;
   for (it->Seek(bounds.start()); it->Valid(); it->Next()) {
     TRI_ASSERT(it->key().compare(upper) < 0);
     if (ridx.collection().vocbase().server().isStopping()) {
@@ -232,7 +233,8 @@ static arangodb::Result fillIndex(RocksDBIndex& ridx, WriteBatchType& batch,
     }
 
     res = ridx.insert(trx, &batched, RocksDBKey::documentId(it->key()),
-                      VPackSlice(reinterpret_cast<uint8_t const*>(it->value().data())), Index::OperationMode::normal);
+                      VPackSlice(reinterpret_cast<uint8_t const*>(it->value().data())),
+                      options);
     if (res.fail()) {
       break;
     }
@@ -330,8 +332,8 @@ struct ReplayHandler final : public rocksdb::WriteBatch::Handler {
       case RocksDBLogType::TrackedDocumentInsert:
         if (_lastObjectID == _objectId) {
           auto pair = RocksDBLogValue::trackedDocument(blob);
-          tmpRes = _index.insert(_trx, _methods, pair.first, pair.second,
-                                 Index::OperationMode::normal);
+          OperationOptions options;
+          tmpRes = _index.insert(_trx, _methods, pair.first, pair.second, options);
           numInserted++;
         }
         break;
@@ -463,7 +465,7 @@ Result catchup(RocksDBIndex& ridx, WriteBatchType& wb, AccessMode::Type mode,
     }
     wb.Clear();
 
-    auto ops = trxColl->stealTrackedOperations();
+    auto ops = trxColl->stealTrackedIndexOperations();
     if (!ops.empty()) {
       TRI_ASSERT(ridx.hasSelectivityEstimate() && ops.size() == 1);
       auto it = ops.begin();
diff --git a/arangod/RocksDBEngine/RocksDBBuilderIndex.h b/arangod/RocksDBEngine/RocksDBBuilderIndex.h
index b31a4614b97e..472116b59ced 100644
--- a/arangod/RocksDBEngine/RocksDBBuilderIndex.h
+++ b/arangod/RocksDBEngine/RocksDBBuilderIndex.h
@@ -81,7 +81,7 @@ class RocksDBBuilderIndex final : public arangodb::RocksDBIndex {
 
   /// insert index elements into the specified write batch.
   Result insert(transaction::Methods& trx, RocksDBMethods*, LocalDocumentId const& documentId,
-                arangodb::velocypack::Slice const&, OperationMode mode) override;
+                arangodb::velocypack::Slice const&, OperationOptions& options) override;
 
   /// remove index elements and put it in the specified write batch.
   Result remove(transaction::Methods& trx, RocksDBMethods*, LocalDocumentId const& documentId,
diff --git a/arangod/RocksDBEngine/RocksDBCollection.cpp b/arangod/RocksDBEngine/RocksDBCollection.cpp
index df1a4be3f91f..6c453ffd3b54 100644
--- a/arangod/RocksDBEngine/RocksDBCollection.cpp
+++ b/arangod/RocksDBEngine/RocksDBCollection.cpp
@@ -22,11 +22,13 @@
 
 #include "RocksDBCollection.h"
 
+#include "ApplicationFeatures/ApplicationServer.h"
 #include "Aql/PlanCache.h"
 #include "Basics/Result.h"
 #include "Basics/StaticStrings.h"
 #include "Basics/StringUtils.h"
 #include "Basics/VelocyPackHelper.h"
+#include "Basics/hashes.h"
 #include "Cache/CacheManagerFeature.h"
 #include "Cache/Common.h"
 #include "Cache/Manager.h"
@@ -44,11 +46,14 @@
 #include "RocksDBEngine/RocksDBLogValue.h"
 #include "RocksDBEngine/RocksDBMethods.h"
 #include "RocksDBEngine/RocksDBPrimaryIndex.h"
+#include "RocksDBEngine/RocksDBReplicationIterator.h"
+#include "RocksDBEngine/RocksDBReplicationManager.h"
 #include "RocksDBEngine/RocksDBSettingsManager.h"
 #include "RocksDBEngine/RocksDBTransactionState.h"
 #include "StorageEngine/EngineSelectorFeature.h"
 #include "StorageEngine/StorageEngine.h"
 #include "Transaction/Helpers.h"
+#include "Transaction/Context.h"
 #include "Utils/CollectionNameResolver.h"
 #include "Utils/Events.h"
 #include "Utils/OperationOptions.h"
@@ -66,14 +71,21 @@
 
 using namespace arangodb;
 
+namespace {
+LocalDocumentId generateDocumentId(LogicalCollection const& collection,
+                                   TRI_voc_rid_t revisionId) {
+  bool useRev = collection.usesRevisionsAsDocumentIds();
+  return useRev ? LocalDocumentId::create(revisionId) : LocalDocumentId::create();
+}
+}  // namespace
+
 RocksDBCollection::RocksDBCollection(LogicalCollection& collection,
                                      arangodb::velocypack::Slice const& info)
     : RocksDBMetaCollection(collection, info),
       _primaryIndex(nullptr),
-      _cache(nullptr),
       _cacheEnabled(
           !collection.system() &&
-          basics::VelocyPackHelper::getBooleanValue(info, "cacheEnabled", false) &&
+          basics::VelocyPackHelper::getBooleanValue(info, StaticStrings::CacheEnabled, false) &&
           CacheManagerFeature::MANAGER != nullptr),
       _numIndexCreations(0) {
   TRI_ASSERT(_logicalCollection.isAStub() || _objectId != 0);
@@ -86,7 +98,6 @@ RocksDBCollection::RocksDBCollection(LogicalCollection& collection,
                                      PhysicalCollection const* physical)
     : RocksDBMetaCollection(collection, VPackSlice::emptyObjectSlice()),
       _primaryIndex(nullptr),
-      _cache(nullptr),
       _cacheEnabled(static_cast<RocksDBCollection const*>(physical)->_cacheEnabled &&
                     CacheManagerFeature::MANAGER != nullptr),
       _numIndexCreations(0) {
@@ -109,7 +120,7 @@ Result RocksDBCollection::updateProperties(VPackSlice const& slice, bool doSync)
 
   _cacheEnabled =
       !isSys &&
-      basics::VelocyPackHelper::getBooleanValue(slice, "cacheEnabled", _cacheEnabled) &&
+      basics::VelocyPackHelper::getBooleanValue(slice, StaticStrings::CacheEnabled, _cacheEnabled) &&
       CacheManagerFeature::MANAGER != nullptr;
   primaryIndex()->setCacheEnabled(_cacheEnabled);
 
@@ -124,7 +135,7 @@ Result RocksDBCollection::updateProperties(VPackSlice const& slice, bool doSync)
   }
 
   // nothing else to do
-  return TRI_ERROR_NO_ERROR;
+  return {};
 }
 
 PhysicalCollection* RocksDBCollection::clone(LogicalCollection& logical) const {
@@ -135,7 +146,7 @@ PhysicalCollection* RocksDBCollection::clone(LogicalCollection& logical) const {
 void RocksDBCollection::getPropertiesVPack(velocypack::Builder& result) const {
   TRI_ASSERT(result.isOpenObject());
   result.add("objectId", VPackValue(std::to_string(_objectId)));
-  result.add("cacheEnabled", VPackValue(_cacheEnabled));
+  result.add(StaticStrings::CacheEnabled, VPackValue(_cacheEnabled));
   TRI_ASSERT(result.isOpenObject());
 }
 
@@ -514,6 +525,38 @@ std::unique_ptr<IndexIterator> RocksDBCollection::getAnyIterator(transaction::Me
   return std::make_unique<RocksDBAnyIndexIterator>(&_logicalCollection, trx);
 }
 
+std::unique_ptr<ReplicationIterator> RocksDBCollection::getReplicationIterator(
+    ReplicationIterator::Ordering order, uint64_t batchId) {
+  if (order != ReplicationIterator::Ordering::Revision) {
+    // not supported
+    return nullptr;
+  }
+
+  EngineSelectorFeature& selector =
+      _logicalCollection.vocbase().server().getFeature<EngineSelectorFeature>();
+  RocksDBEngine& engine = selector.engine<RocksDBEngine>();
+  RocksDBReplicationManager* manager = engine.replicationManager();
+  RocksDBReplicationContext* ctx = batchId == 0 ? nullptr : manager->find(batchId);
+  auto guard = scopeGuard([manager, ctx]() -> void {
+    if (ctx) {
+      manager->release(ctx);
+    }
+  });
+  rocksdb::Snapshot const* snapshot = ctx ? ctx->snapshot() : nullptr;
+
+  return std::make_unique<RocksDBRevisionReplicationIterator>(_logicalCollection, snapshot);
+}
+
+std::unique_ptr<ReplicationIterator> RocksDBCollection::getReplicationIterator(
+    ReplicationIterator::Ordering order, transaction::Methods& trx) {
+  if (order != ReplicationIterator::Ordering::Revision) {
+    // not supported
+    return nullptr;
+  }
+
+  return std::make_unique<RocksDBRevisionReplicationIterator>(_logicalCollection, trx);
+}
+
 ////////////////////////////////////
 // -- SECTION DML Operations --
 ///////////////////////////////////
@@ -601,6 +644,7 @@ Result RocksDBCollection::truncate(transaction::Methods& trx, OperationOptions&
         idx->afterTruncate(seq);  // clears caches / clears links (if applicable)
       }
     }
+    bufferTruncate(seq);
 
     guard.fire();  // remove blocker
 
@@ -802,7 +846,8 @@ Result RocksDBCollection::insert(arangodb::transaction::Methods* trx,
 
   VPackSlice newSlice = builder->slice();
   if(options.validate) {
-    res = _logicalCollection.validate(newSlice);
+    res = _logicalCollection.validate(newSlice, trx->transactionContextPtr()->getVPackOptions());
+
     if (res.fail()) {
       return res;
     }
@@ -837,7 +882,7 @@ Result RocksDBCollection::insert(arangodb::transaction::Methods* trx,
     }
   }
 
-  LocalDocumentId const documentId = LocalDocumentId::create();
+  LocalDocumentId const documentId = ::generateDocumentId(_logicalCollection, revisionId);
 
   RocksDBSavePoint guard(trx, TRI_VOC_DOCUMENT_OPERATION_INSERT);
 
@@ -926,7 +971,6 @@ Result RocksDBCollection::update(arangodb::transaction::Methods* trx,
 
   // merge old and new values
   TRI_voc_rid_t revisionId;
-  LocalDocumentId const newDocumentId = LocalDocumentId::create();
   auto isEdgeCollection = (TRI_COL_TYPE_EDGE == _logicalCollection.type());
 
   transaction::BuilderLeaser builder(trx);
@@ -936,6 +980,7 @@ Result RocksDBCollection::update(arangodb::transaction::Methods* trx,
   if (res.fail()) {
     return res;
   }
+  LocalDocumentId const newDocumentId = ::generateDocumentId(_logicalCollection, revisionId);
 
 
   if (_isDBServer) {
@@ -949,7 +994,7 @@ Result RocksDBCollection::update(arangodb::transaction::Methods* trx,
   }
 
   if(options.validate) {
-    res = _logicalCollection.validate(builder->slice(), oldDoc);
+    res = _logicalCollection.validate(builder->slice(), oldDoc, trx->transactionContextPtr()->getVPackOptions());
     if (res.fail()) {
       return res;
     }
@@ -1035,7 +1080,6 @@ Result RocksDBCollection::replace(transaction::Methods* trx,
 
   // merge old and new values
   TRI_voc_rid_t revisionId;
-  LocalDocumentId const newDocumentId = LocalDocumentId::create();
   bool const isEdgeCollection = (TRI_COL_TYPE_EDGE == _logicalCollection.type());
 
   transaction::BuilderLeaser builder(trx);
@@ -1044,6 +1088,7 @@ Result RocksDBCollection::replace(transaction::Methods* trx,
   if (res.fail()) {
     return res;
   }
+  LocalDocumentId const newDocumentId = ::generateDocumentId(_logicalCollection, revisionId);
 
   if (_isDBServer) {
     // Need to check that no sharding keys have changed:
@@ -1058,7 +1103,7 @@ Result RocksDBCollection::replace(transaction::Methods* trx,
   VPackSlice const newDoc(builder->slice());
 
   if(options.validate) {
-    res = _logicalCollection.validate(newDoc, oldDoc);
+    res = _logicalCollection.validate(newDoc, oldDoc, trx->transactionContextPtr()->getVPackOptions());
     if (res.fail()) {
       return res;
     }
@@ -1105,10 +1150,9 @@ Result RocksDBCollection::replace(transaction::Methods* trx,
 }
 
 Result RocksDBCollection::remove(transaction::Methods& trx, velocypack::Slice slice,
-                                 ManagedDocumentResult& previousMdr, OperationOptions& options,
-                                 bool /*lock*/, KeyLockInfo* /*keyLockInfo*/,
+                                 ManagedDocumentResult& previousMdr,
+                                 OperationOptions& options, bool lock, KeyLockInfo* keyLockInfo,
                                  std::function<void()> const& cbDuringLock) {
-
   VPackSlice keySlice;
   if (slice.isString()) {
     keySlice = slice;
@@ -1124,11 +1168,35 @@ Result RocksDBCollection::remove(transaction::Methods& trx, velocypack::Slice sl
   if (!documentId.isSet()) {
     return TRI_ERROR_ARANGO_DOCUMENT_NOT_FOUND;
   }
+
+  // Check old revision:
+  LocalDocumentId expectedId;
+  if (!options.ignoreRevs && slice.isObject()) {
+    expectedId = LocalDocumentId::create(TRI_ExtractRevisionId(slice));
+  }
+
+  return remove(trx, documentId, expectedId, previousMdr, options, cbDuringLock);
+}
+
+Result RocksDBCollection::remove(transaction::Methods& trx, LocalDocumentId documentId,
+                                 ManagedDocumentResult& previousMdr,
+                                 OperationOptions& options, bool lock, KeyLockInfo* keyLockInfo,
+                                 std::function<void()> const& cbDuringLock) {
+  return remove(trx, documentId, LocalDocumentId(), previousMdr, options, cbDuringLock);
+}
+
+Result RocksDBCollection::remove(transaction::Methods& trx, LocalDocumentId documentId,
+                                 LocalDocumentId expectedId, ManagedDocumentResult& previousMdr,
+                                 OperationOptions& options,
+                                 std::function<void()> const& cbDuringLock) {
+  if (!documentId.isSet()) {
+    return TRI_ERROR_ARANGO_DOCUMENT_NOT_FOUND;
+  }
   std::string* prevBuffer = previousMdr.setManaged();
   // uses either prevBuffer or avoids memcpy (if read hits block cache)
   rocksdb::PinnableSlice previousPS(prevBuffer);
   Result res = lookupDocumentVPack(&trx, documentId, previousPS,
-                                   /*readCache*/true, /*fillCache*/false);
+                                   /*readCache*/ true, /*fillCache*/ false);
   if (res.fail()) {
     return res;
   }
@@ -1139,10 +1207,8 @@ Result RocksDBCollection::remove(transaction::Methods& trx, velocypack::Slice sl
   TRI_ASSERT(previousMdr.revisionId() != 0);
 
   // Check old revision:
-  if (!options.ignoreRevs && slice.isObject()) {
-    TRI_voc_rid_t expectedRevisionId = TRI_ExtractRevisionId(slice);
-    res = checkRevision(&trx, expectedRevisionId, previousMdr.revisionId());
-
+  if (!options.ignoreRevs && expectedId.isSet()) {
+    res = checkRevision(&trx, expectedId.id(), previousMdr.revisionId());
     if (res.fail()) {
       return res;
     }
@@ -1169,7 +1235,8 @@ Result RocksDBCollection::remove(transaction::Methods& trx, velocypack::Slice sl
     }
 
     bool hasPerformedIntermediateCommit = false;
-    res = state->addOperation(_logicalCollection.id(), newRevisionId(), TRI_VOC_DOCUMENT_OPERATION_REMOVE,
+    res = state->addOperation(_logicalCollection.id(), newRevisionId(),
+                              TRI_VOC_DOCUMENT_OPERATION_REMOVE,
                               hasPerformedIntermediateCommit);
 
     if (res.ok() && cbDuringLock != nullptr) {
@@ -1182,6 +1249,11 @@ Result RocksDBCollection::remove(transaction::Methods& trx, velocypack::Slice sl
   return res;
 }
 
+void RocksDBCollection::adjustNumberDocuments(transaction::Methods& trx, int64_t diff) {
+  auto seq = rocksutils::latestSequenceNumber();
+  meta().adjustNumberDocuments(seq, /*revId*/ 0, diff);
+}
+
 /// @brief return engine-specific figures
 void RocksDBCollection::figuresSpecific(arangodb::velocypack::Builder& builder) {
   rocksdb::TransactionDB* db = rocksutils::globalRocksDB();
@@ -1214,10 +1286,9 @@ void RocksDBCollection::figuresSpecific(arangodb::velocypack::Builder& builder)
 }
 
 namespace {
-template<typename F>
+template <typename F>
 void reverseIdxOps(PhysicalCollection::IndexContainerType const& indexes,
-                   PhysicalCollection::IndexContainerType::const_iterator& it,
-                   F&& op) {
+                   PhysicalCollection::IndexContainerType::const_iterator& it, F&& op) {
   while (it != indexes.begin()) {
     it--;
     auto* rIdx = static_cast<RocksDBIndex*>(it->get());
@@ -1225,12 +1296,13 @@ void reverseIdxOps(PhysicalCollection::IndexContainerType const& indexes,
       if (std::forward<F>(op)(rIdx).fail()) {
         // best effort for reverse failed. Let`s trigger full rollback
         // or we will end up with inconsistent storage and indexes
-        THROW_ARANGO_EXCEPTION_MESSAGE(TRI_ERROR_INTERNAL, "Failed to reverse index operation.");
+        THROW_ARANGO_EXCEPTION_MESSAGE(TRI_ERROR_INTERNAL,
+                                       "Failed to reverse index operation.");
       }
     }
   }
 }
-}
+}  // namespace
 
 Result RocksDBCollection::insertDocument(arangodb::transaction::Methods* trx,
                                          LocalDocumentId const& documentId,
@@ -1268,18 +1340,23 @@ Result RocksDBCollection::insertDocument(arangodb::transaction::Methods* trx,
   bool needReversal = false;
   for (auto it = _indexes.begin(); it != _indexes.end(); it++) {
     RocksDBIndex* rIdx = static_cast<RocksDBIndex*>(it->get());
-    res = rIdx->insert(*trx, mthds, documentId, doc, options.indexOperationMode);
+    res = rIdx->insert(*trx, mthds, documentId, doc, options);
     needReversal = needReversal || rIdx->needsReversal();
     if (res.fail()) {
       if (needReversal && !state->isSingleOperation()) {
         ::reverseIdxOps(_indexes, it, [mthds, trx, &documentId, &doc](RocksDBIndex* rid) {
-          return rid->remove(*trx, mthds, documentId, doc,  Index::OperationMode::rollback);
+          return rid->remove(*trx, mthds, documentId, doc, Index::OperationMode::rollback);
         });
       }
       break;
     }
   }
 
+  if (res.ok()) {
+    RocksDBTransactionState::toState(trx)->trackInsert(_logicalCollection.id(),
+                                                       documentId.id());
+  }
+
   return res;
 }
 
@@ -1322,13 +1399,20 @@ Result RocksDBCollection::removeDocument(arangodb::transaction::Methods* trx,
     if (res.fail()) {
       if (needReversal && !trx->isSingleOperationTransaction()) {
         ::reverseIdxOps(_indexes, it, [mthds, trx, &documentId, &doc](RocksDBIndex* rid) {
-          return rid->insert(*trx, mthds, documentId, doc, Index::OperationMode::rollback);
+          OperationOptions options;
+          options.indexOperationMode = Index::OperationMode::rollback;
+          return rid->insert(*trx, mthds, documentId, doc, options);
         });
       }
       break;
     }
   }
 
+  if (res.ok()) {
+    RocksDBTransactionState::toState(trx)->trackRemove(_logicalCollection.id(),
+                                                       documentId.id());
+  }
+
   return res;
 }
 
@@ -1383,7 +1467,8 @@ Result RocksDBCollection::updateDocument(transaction::Methods* trx,
     if (!res.ok()) {
       if (needReversal && !trx->isSingleOperationTransaction()) {
         ::reverseIdxOps(_indexes, it,
-                        [mthds, trx, &newDocumentId, &newDoc, &oldDocumentId, &oldDoc](RocksDBIndex* rid) {
+                        [mthds, trx, &newDocumentId, &newDoc, &oldDocumentId,
+                         &oldDoc](RocksDBIndex* rid) {
                           return rid->update(*trx, mthds, newDocumentId, newDoc, oldDocumentId,
                                              oldDoc, Index::OperationMode::rollback);
                         });
@@ -1391,6 +1476,14 @@ Result RocksDBCollection::updateDocument(transaction::Methods* trx,
       break;
     }
   }
+
+  if (res.ok()) {
+    RocksDBTransactionState::toState(trx)->trackRemove(_logicalCollection.id(),
+                                                       oldDocumentId.id());
+    RocksDBTransactionState::toState(trx)->trackInsert(_logicalCollection.id(),
+                                                       newDocumentId.id());
+  }
+
   return res;
 }
 
@@ -1400,8 +1493,7 @@ Result RocksDBCollection::updateDocument(transaction::Methods* trx,
 arangodb::Result RocksDBCollection::lookupDocumentVPack(transaction::Methods* trx,
                                                         LocalDocumentId const& documentId,
                                                         rocksdb::PinnableSlice& ps,
-                                                        bool readCache,
-                                                        bool fillCache) const {
+                                                        bool readCache, bool fillCache) const {
   TRI_ASSERT(trx->state()->isRunning());
   TRI_ASSERT(_objectId != 0);
   Result res;
@@ -1419,7 +1511,7 @@ arangodb::Result RocksDBCollection::lookupDocumentVPack(transaction::Methods* tr
       ps.PinSelf(rocksdb::Slice(reinterpret_cast<char const*>(f.value()->value()),
                                 f.value()->valueSize()));
       // TODO we could potentially use the PinSlice method ?!
-      return res; // all good
+      return res;  // all good
     }
     if (f.result().errorNumber() == TRI_ERROR_LOCK_TIMEOUT) {
       // assuming someone is currently holding a write lock, which
@@ -1433,8 +1525,8 @@ arangodb::Result RocksDBCollection::lookupDocumentVPack(transaction::Methods* tr
 
   if (!s.ok()) {
     LOG_TOPIC("f63dd", DEBUG, Logger::ENGINES)
-    << "NOT FOUND rev: " << documentId.id() << " trx: " << trx->state()->id()
-    << " objectID " << _objectId << " name: " << _logicalCollection.name();
+        << "NOT FOUND rev: " << documentId.id() << " trx: " << trx->state()->id()
+        << " objectID " << _objectId << " name: " << _logicalCollection.name();
     return res.reset(rocksutils::convertStatus(s, rocksutils::document));
   }
 
@@ -1465,10 +1557,13 @@ bool RocksDBCollection::lookupDocumentVPack(transaction::Methods* trx,
                                             LocalDocumentId const& documentId,
                                             IndexIterator::DocumentCallback const& cb,
                                             bool withCache) const {
+  TRI_ASSERT(trx->state()->isRunning());
+  TRI_ASSERT(_objectId != 0);
+
+  RocksDBKeyLeaser key(trx);
+  key->constructDocument(_objectId, documentId);
 
   if (withCache && useCache()) {
-    RocksDBKeyLeaser key(trx);
-    key->constructDocument(_objectId, documentId);
     TRI_ASSERT(_cache != nullptr);
     // check cache first for fast path
     auto f = _cache->find(key->string().data(),
@@ -1481,13 +1576,38 @@ bool RocksDBCollection::lookupDocumentVPack(transaction::Methods* trx,
 
   transaction::StringLeaser buffer(trx);
   rocksdb::PinnableSlice ps(buffer.get());
-  Result res = lookupDocumentVPack(trx, documentId, ps, /*readCache*/false, withCache);
-  if (res.ok()) {
-    TRI_ASSERT(ps.size() > 0);
-    cb(documentId, VPackSlice(reinterpret_cast<uint8_t const*>(ps.data())));
-    return true;
+  
+  RocksDBMethods* mthd = RocksDBTransactionState::toMethods(trx);
+  rocksdb::Status s = mthd->Get(RocksDBColumnFamily::documents(), key->string(), &ps);
+
+  if (!s.ok()) {
+    return false;
   }
-  return false;
+    
+  TRI_ASSERT(ps.size() > 0);
+  cb(documentId, VPackSlice(reinterpret_cast<uint8_t const*>(ps.data())));
+  
+  if (withCache && useCache()) {
+    TRI_ASSERT(_cache != nullptr);
+    // write entry back to cache
+    auto entry =
+        cache::CachedValue::construct(key->string().data(),
+                                      static_cast<uint32_t>(key->string().size()),
+                                      ps.data(), static_cast<uint64_t>(ps.size()));
+    if (entry) {
+      auto status = _cache->insert(entry);
+      if (status.errorNumber() == TRI_ERROR_LOCK_TIMEOUT) {
+        // the writeLock uses cpu_relax internally, so we can try yield
+        std::this_thread::yield();
+        status = _cache->insert(entry);
+      }
+      if (status.fail()) {
+        delete entry;
+      }
+    }
+  }
+  
+  return true;
 }
 
 void RocksDBCollection::createCache() const {
diff --git a/arangod/RocksDBEngine/RocksDBCollection.h b/arangod/RocksDBEngine/RocksDBCollection.h
index 3d689a931eb6..ae26a00c4e3a 100644
--- a/arangod/RocksDBEngine/RocksDBCollection.h
+++ b/arangod/RocksDBEngine/RocksDBCollection.h
@@ -83,6 +83,11 @@ class RocksDBCollection final : public RocksDBMetaCollection {
   std::unique_ptr<IndexIterator> getAllIterator(transaction::Methods* trx) const override;
   std::unique_ptr<IndexIterator> getAnyIterator(transaction::Methods* trx) const override;
 
+  std::unique_ptr<ReplicationIterator> getReplicationIterator(ReplicationIterator::Ordering,
+                                                              uint64_t batchId) override;
+  std::unique_ptr<ReplicationIterator> getReplicationIterator(ReplicationIterator::Ordering,
+                                                              transaction::Methods&) override;
+
   ////////////////////////////////////
   // -- SECTION DML Operations --
   ///////////////////////////////////
@@ -97,14 +102,6 @@ class RocksDBCollection final : public RocksDBMetaCollection {
   Result read(transaction::Methods*, arangodb::velocypack::StringRef const& key,
               ManagedDocumentResult& result, bool) override;
 
-  Result read(transaction::Methods* trx, arangodb::velocypack::Slice const& key,
-              ManagedDocumentResult& result, bool locked) override {
-    if (!key.isString()) {
-      return Result(TRI_ERROR_ARANGO_DOCUMENT_KEY_BAD);
-    }
-    return this->read(trx, arangodb::velocypack::StringRef(key), result, locked);
-  }
-
   bool readDocument(transaction::Methods* trx, LocalDocumentId const& token,
                     ManagedDocumentResult& result) const override;
 
@@ -130,8 +127,20 @@ class RocksDBCollection final : public RocksDBMetaCollection {
                 bool lock, KeyLockInfo* keyLockInfo,
                 std::function<void()> const& cbDuringLock) override;
 
+  Result remove(transaction::Methods& trx, LocalDocumentId documentId,
+                ManagedDocumentResult& previous, OperationOptions& options,
+                bool lock, KeyLockInfo* keyLockInfo,
+                std::function<void()> const& cbDuringLock) override;
+
   inline bool cacheEnabled() const { return _cacheEnabled; }
 
+  void adjustNumberDocuments(transaction::Methods&, int64_t) override;
+
+ protected:
+  Result remove(transaction::Methods& trx, LocalDocumentId documentId,
+                LocalDocumentId expectedId, ManagedDocumentResult& previous,
+                OperationOptions& options, std::function<void()> const& cbDuringLock);
+
  private:
   /// @brief return engine-specific figures
   void figuresSpecific(velocypack::Builder&) override;
diff --git a/arangod/RocksDBEngine/RocksDBEdgeIndex.cpp b/arangod/RocksDBEngine/RocksDBEdgeIndex.cpp
index a73180edc35a..8855af16e9f6 100644
--- a/arangod/RocksDBEngine/RocksDBEdgeIndex.cpp
+++ b/arangod/RocksDBEngine/RocksDBEdgeIndex.cpp
@@ -97,7 +97,7 @@ class RocksDBEdgeIndexLookupIterator final : public IndexIterator {
         _keys(std::move(keys)),
         _keysIterator(_keys->slice()),
         _bounds(RocksDBKeyBounds::EdgeIndex(0)),
-        _builderIterator(arangodb::velocypack::Slice::emptyArraySlice()),
+        _builderIterator(VPackArrayIterator::Empty{}),
         _lastKey(VPackSlice::nullSlice()) {
     TRI_ASSERT(_keys != nullptr);
     TRI_ASSERT(_keys->slice().isArray());
@@ -174,7 +174,7 @@ class RocksDBEdgeIndexLookupIterator final : public IndexIterator {
       if (_cache) {
         for (size_t attempts = 0; attempts < 10; ++attempts) {
           // Try to read from cache
-          auto finding = _cache->find(fromTo.data(), (uint32_t)fromTo.size());
+          auto finding = _cache->find(fromTo.data(), static_cast<uint32_t>(fromTo.size()));
           if (finding.found()) {
             needRocksLookup = false;
             // We got sth. in the cache
@@ -196,7 +196,7 @@ class RocksDBEdgeIndexLookupIterator final : public IndexIterator {
                 _builderIterator.next();
                 limit--;
               }
-              _builderIterator = VPackArrayIterator(VPackSlice::emptyArraySlice());
+              _builderIterator = VPackArrayIterator(VPackArrayIterator::Empty{});
             } else {
               // We need to copy it.
               // And then we just get back to beginning of the loop
@@ -261,8 +261,7 @@ class RocksDBEdgeIndexLookupIterator final : public IndexIterator {
     resetInplaceMemory();
     _keysIterator.reset();
     _lastKey = VPackSlice::nullSlice();
-    _builderIterator =
-        VPackArrayIterator(arangodb::velocypack::Slice::emptyArraySlice());
+    _builderIterator = VPackArrayIterator(VPackArrayIterator::Empty{});
   }
 
   /// @brief index supports rearming
@@ -450,7 +449,7 @@ void RocksDBEdgeIndex::toVelocyPack(VPackBuilder& builder,
 
 Result RocksDBEdgeIndex::insert(transaction::Methods& trx, RocksDBMethods* mthd,
                                 LocalDocumentId const& documentId,
-                                velocypack::Slice const& doc, Index::OperationMode mode) {
+                                velocypack::Slice const& doc, OperationOptions& options) {
   Result res;
   VPackSlice fromTo = doc.get(_directionAttr);
   TRI_ASSERT(fromTo.isString());
diff --git a/arangod/RocksDBEngine/RocksDBEdgeIndex.h b/arangod/RocksDBEngine/RocksDBEdgeIndex.h
index 35c0a0811d84..d8b8abe4fd7d 100644
--- a/arangod/RocksDBEngine/RocksDBEdgeIndex.h
+++ b/arangod/RocksDBEngine/RocksDBEdgeIndex.h
@@ -112,8 +112,8 @@ class RocksDBEdgeIndex final : public RocksDBIndex {
   void afterTruncate(TRI_voc_tick_t tick) override;
 
   Result insert(transaction::Methods& trx, RocksDBMethods* methods,
-                LocalDocumentId const& documentId,
-                velocypack::Slice const& doc, Index::OperationMode mode) override;
+                LocalDocumentId const& documentId, velocypack::Slice const& doc,
+                OperationOptions& options) override;
 
   Result remove(transaction::Methods& trx, RocksDBMethods* methods,
                 LocalDocumentId const& documentId,
diff --git a/arangod/RocksDBEngine/RocksDBEngine.cpp b/arangod/RocksDBEngine/RocksDBEngine.cpp
index 5bf6c387fd98..596d9d45c92c 100644
--- a/arangod/RocksDBEngine/RocksDBEngine.cpp
+++ b/arangod/RocksDBEngine/RocksDBEngine.cpp
@@ -141,7 +141,7 @@ std::vector<std::shared_ptr<RocksDBRecoveryHelper>> RocksDBEngine::_recoveryHelp
 RocksDBFilePurgePreventer::RocksDBFilePurgePreventer(RocksDBEngine* engine)
     : _engine(engine) {
   TRI_ASSERT(_engine != nullptr);
-  _engine->_purgeLock.readLock();
+  _engine->_purgeLock.lockRead();
 }
 
 RocksDBFilePurgePreventer::~RocksDBFilePurgePreventer() {
@@ -160,7 +160,7 @@ RocksDBFilePurgeEnabler::RocksDBFilePurgeEnabler(RocksDBEngine* engine)
     : _engine(nullptr) {
   TRI_ASSERT(engine != nullptr);
 
-  if (engine->_purgeLock.tryWriteLock()) {
+  if (engine->_purgeLock.tryLockWrite()) {
     // we got the lock
     _engine = engine;
   }
@@ -882,8 +882,8 @@ void RocksDBEngine::addParametersForNewCollection(VPackBuilder& builder, VPackSl
   if (!info.hasKey("objectId")) {
     builder.add("objectId", VPackValue(std::to_string(TRI_NewTickServer())));
   }
-  if (!info.hasKey("cacheEnabled") || !info.get("cacheEnabled").isBool()) {
-    builder.add("cacheEnabled", VPackValue(false));
+  if (!info.get(StaticStrings::CacheEnabled).isBool()) {
+    builder.add(StaticStrings::CacheEnabled, VPackValue(false));
   }
 }
 
diff --git a/arangod/RocksDBEngine/RocksDBFulltextIndex.cpp b/arangod/RocksDBEngine/RocksDBFulltextIndex.cpp
index f49f83cf1cb4..e64e6376fb4e 100644
--- a/arangod/RocksDBEngine/RocksDBFulltextIndex.cpp
+++ b/arangod/RocksDBEngine/RocksDBFulltextIndex.cpp
@@ -212,7 +212,7 @@ bool RocksDBFulltextIndex::matchesDefinition(VPackSlice const& info) const {
 Result RocksDBFulltextIndex::insert(transaction::Methods& trx, RocksDBMethods* mthd,
                                     LocalDocumentId const& documentId,
                                     velocypack::Slice const& doc,
-                                    Index::OperationMode mode) {
+                                    OperationOptions& options) {
   Result res;
   std::set<std::string> words = wordlist(doc);
 
diff --git a/arangod/RocksDBEngine/RocksDBFulltextIndex.h b/arangod/RocksDBEngine/RocksDBFulltextIndex.h
index fd167e7049de..55d25c79f7a2 100644
--- a/arangod/RocksDBEngine/RocksDBFulltextIndex.h
+++ b/arangod/RocksDBEngine/RocksDBFulltextIndex.h
@@ -94,8 +94,8 @@ class RocksDBFulltextIndex final : public RocksDBIndex {
  protected:
   /// insert index elements into the specified write batch.
   Result insert(transaction::Methods& trx, RocksDBMethods* methods,
-                LocalDocumentId const& documentId,
-                velocypack::Slice const& doc, Index::OperationMode mode) override;
+                LocalDocumentId const& documentId, velocypack::Slice const& doc,
+                OperationOptions& options) override;
 
   /// remove index elements and put it in the specified write batch.
   Result remove(transaction::Methods& trx, RocksDBMethods* methods,
diff --git a/arangod/RocksDBEngine/RocksDBGeoIndex.cpp b/arangod/RocksDBEngine/RocksDBGeoIndex.cpp
index 649538899f25..e16ecfd92a16 100644
--- a/arangod/RocksDBEngine/RocksDBGeoIndex.cpp
+++ b/arangod/RocksDBEngine/RocksDBGeoIndex.cpp
@@ -371,7 +371,7 @@ std::unique_ptr<IndexIterator> RocksDBGeoIndex::iteratorForCondition(
 Result RocksDBGeoIndex::insert(transaction::Methods& trx, RocksDBMethods* mthd,
                                LocalDocumentId const& documentId,
                                velocypack::Slice const& doc,
-                               arangodb::Index::OperationMode mode) {
+                               arangodb::OperationOptions& options) {
   // covering and centroid of coordinate / polygon / ...
   size_t reserve = _variant == Variant::GEOJSON ? 8 : 1;
   std::vector<S2CellId> cells;
diff --git a/arangod/RocksDBEngine/RocksDBGeoIndex.h b/arangod/RocksDBEngine/RocksDBGeoIndex.h
index d507b1aed794..f5292d37c82a 100644
--- a/arangod/RocksDBEngine/RocksDBGeoIndex.h
+++ b/arangod/RocksDBEngine/RocksDBGeoIndex.h
@@ -31,6 +31,7 @@
 #include <velocypack/Builder.h>
 
 namespace arangodb {
+
 class RocksDBGeoIndex final : public RocksDBIndex, public geo_index::Index {
   friend class RocksDBSphericalIndexIterator;
 
@@ -74,7 +75,7 @@ class RocksDBGeoIndex final : public RocksDBIndex, public geo_index::Index {
   /// insert index elements into the specified write batch.
   Result insert(transaction::Methods& trx, RocksDBMethods* methods,
                 LocalDocumentId const& documentId, velocypack::Slice const& doc,
-                arangodb::Index::OperationMode mode) override;
+                arangodb::OperationOptions& options) override;
 
   /// remove index elements and put it in the specified write batch.
   Result remove(transaction::Methods& trx, RocksDBMethods* methods,
diff --git a/arangod/RocksDBEngine/RocksDBIncrementalSync.cpp b/arangod/RocksDBEngine/RocksDBIncrementalSync.cpp
index 19af8a96c7ca..2aa2aa670644 100644
--- a/arangod/RocksDBEngine/RocksDBIncrementalSync.cpp
+++ b/arangod/RocksDBEngine/RocksDBIncrementalSync.cpp
@@ -439,6 +439,7 @@ Result syncChunkRocksDB(DatabaseInitialSyncer& syncer, SingleCollectionTransacti
 
     size_t foundLength = slice.length();
 
+    double t = TRI_microtime();
     for (VPackSlice it : VPackArrayIterator(slice)) {
       if (it.isNull()) {
         continue;
@@ -548,6 +549,7 @@ Result syncChunkRocksDB(DatabaseInitialSyncer& syncer, SingleCollectionTransacti
         }
       }
     }
+    stats.waitedForInsertions += TRI_microtime() - t;
 
     if (foundLength >= toFetch.size()) {
       break;
@@ -893,6 +895,7 @@ Result handleSyncKeysRocksDB(DatabaseInitialSyncer& syncer,
       ", " + "waited for initial: " + std::to_string(stats.waitedForInitial) +
       " s, " + "waited for keys: " + std::to_string(stats.waitedForKeys) +
       " s, " + "waited for docs: " + std::to_string(stats.waitedForDocs) +
+      " s, " + "waited for insertions: " + std::to_string(stats.waitedForInsertions) +
       " s, " + "total time: " + std::to_string(TRI_microtime() - startTime) +
       " s");
 
diff --git a/arangod/RocksDBEngine/RocksDBIndex.cpp b/arangod/RocksDBEngine/RocksDBIndex.cpp
index 11b858de222c..f76295fe98c1 100644
--- a/arangod/RocksDBEngine/RocksDBIndex.cpp
+++ b/arangod/RocksDBEngine/RocksDBIndex.cpp
@@ -251,7 +251,9 @@ Result RocksDBIndex::update(transaction::Methods& trx, RocksDBMethods* mthd,
   if (!res.ok()) {
     return res;
   }
-  return insert(trx, mthd, newDocumentId, newDoc, mode);
+  OperationOptions options;
+  options.indexOperationMode = mode;
+  return insert(trx, mthd, newDocumentId, newDoc, options);
 }
 
 /// @brief return the memory usage of the index
diff --git a/arangod/RocksDBEngine/RocksDBIndex.h b/arangod/RocksDBEngine/RocksDBIndex.h
index 8e15cd8b7b37..29d73f7fc0ff 100644
--- a/arangod/RocksDBEngine/RocksDBIndex.h
+++ b/arangod/RocksDBEngine/RocksDBIndex.h
@@ -43,6 +43,7 @@ class Cache;
 }
 class LogicalCollection;
 class RocksDBMethods;
+struct OperationOptions;
 
 class RocksDBIndex : public Index {
  protected:
@@ -91,7 +92,7 @@ class RocksDBIndex : public Index {
   virtual Result insert(transaction::Methods& trx, RocksDBMethods* methods,
                         LocalDocumentId const& documentId,
                         arangodb::velocypack::Slice const& doc,
-                        Index::OperationMode mode) = 0;
+                        OperationOptions& options) = 0;
 
   /// remove index elements and put it in the specified write batch.
   virtual Result remove(transaction::Methods& trx, RocksDBMethods* methods,
diff --git a/arangod/RocksDBEngine/RocksDBKey.cpp b/arangod/RocksDBEngine/RocksDBKey.cpp
index 01d61bcc0e2e..2c94c55efff3 100644
--- a/arangod/RocksDBEngine/RocksDBKey.cpp
+++ b/arangod/RocksDBEngine/RocksDBKey.cpp
@@ -266,6 +266,17 @@ void RocksDBKey::constructKeyGeneratorValue(uint64_t objectId) {
   TRI_ASSERT(_buffer->size() == keyLength);
 }
 
+void RocksDBKey::constructRevisionTreeValue(uint64_t collectionObjectId) {
+  TRI_ASSERT(collectionObjectId != 0);
+  _type = RocksDBEntryType::RevisionTreeValue;
+  size_t keyLength = sizeof(char) + sizeof(uint64_t);
+  _buffer->clear();
+  _buffer->reserve(keyLength);
+  _buffer->push_back(static_cast<char>(_type));
+  uint64ToPersistent(*_buffer, collectionObjectId);
+  TRI_ASSERT(_buffer->size() == keyLength);
+}
+
 // ========================= Member methods ===========================
 
 RocksDBEntryType RocksDBKey::type(RocksDBKey const& key) {
diff --git a/arangod/RocksDBEngine/RocksDBKey.h b/arangod/RocksDBEngine/RocksDBKey.h
index 4ba795bcffb3..8657cd27864d 100644
--- a/arangod/RocksDBEngine/RocksDBKey.h
+++ b/arangod/RocksDBEngine/RocksDBKey.h
@@ -157,6 +157,11 @@ class RocksDBKey {
   //////////////////////////////////////////////////////////////////////////////
   void constructKeyGeneratorValue(uint64_t objectId);
 
+  //////////////////////////////////////////////////////////////////////////////
+  /// @brief Create a fully-specified key for revision tree for a collection
+  //////////////////////////////////////////////////////////////////////////////
+  void constructRevisionTreeValue(uint64_t objectId);
+
  public:
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Extracts the type from a key
diff --git a/arangod/RocksDBEngine/RocksDBKeyBounds.cpp b/arangod/RocksDBEngine/RocksDBKeyBounds.cpp
index 78c570709907..b33c1a8349d3 100644
--- a/arangod/RocksDBEngine/RocksDBKeyBounds.cpp
+++ b/arangod/RocksDBEngine/RocksDBKeyBounds.cpp
@@ -52,6 +52,12 @@ RocksDBKeyBounds RocksDBKeyBounds::CollectionDocuments(uint64_t collectionObject
   return RocksDBKeyBounds(RocksDBEntryType::Document, collectionObjectId);
 }
 
+RocksDBKeyBounds RocksDBKeyBounds::CollectionDocumentRange(uint64_t collectionObjectId,
+                                                           std::size_t min,
+                                                           std::size_t max) {
+  return RocksDBKeyBounds(RocksDBEntryType::Document, collectionObjectId, min, max);
+}
+
 RocksDBKeyBounds RocksDBKeyBounds::PrimaryIndex(uint64_t indexId) {
   return RocksDBKeyBounds(RocksDBEntryType::PrimaryIndexValue, indexId);
 }
@@ -226,6 +232,7 @@ rocksdb::ColumnFamilyHandle* RocksDBKeyBounds::columnFamily() const {
     case RocksDBEntryType::ReplicationApplierConfig:
     case RocksDBEntryType::IndexEstimateValue:
     case RocksDBEntryType::KeyGeneratorValue:
+    case RocksDBEntryType::RevisionTreeValue:
     case RocksDBEntryType::View:
       return RocksDBColumnFamily::definitions();
   }
@@ -482,6 +489,17 @@ RocksDBKeyBounds::RocksDBKeyBounds(RocksDBEntryType type, uint64_t first,
                                    uint64_t second, uint64_t third)
     : _type(type) {
   switch (_type) {
+    case RocksDBEntryType::Document: {
+      // Documents are stored as follows:
+      // Key: 8-byte object ID of collection + 8-byte document revision ID
+      _internals.reserve(4 * sizeof(uint64_t));
+      uint64ToPersistent(_internals.buffer(), first);   // objectid
+      uint64ToPersistent(_internals.buffer(), second);  // min revision
+      _internals.separate();
+      uint64ToPersistent(_internals.buffer(), first);  // objectid
+      uint64ToPersistent(_internals.buffer(), third);  // max revision
+      break;
+    }
     case RocksDBEntryType::GeoIndexValue: {
       _internals.reserve(sizeof(uint64_t) * 3 * 2);
       uint64ToPersistent(_internals.buffer(), first);
diff --git a/arangod/RocksDBEngine/RocksDBKeyBounds.h b/arangod/RocksDBEngine/RocksDBKeyBounds.h
index 0b683a0f3707..a2454bd6bddf 100644
--- a/arangod/RocksDBEngine/RocksDBKeyBounds.h
+++ b/arangod/RocksDBEngine/RocksDBKeyBounds.h
@@ -64,6 +64,13 @@ class RocksDBKeyBounds {
   //////////////////////////////////////////////////////////////////////////////
   static RocksDBKeyBounds CollectionDocuments(uint64_t objectId);
 
+  //////////////////////////////////////////////////////////////////////////////
+  /// @brief Bounds for all documents belonging to a specified collection within
+  /// a certain range
+  //////////////////////////////////////////////////////////////////////////////
+  static RocksDBKeyBounds CollectionDocumentRange(uint64_t objectId,
+                                                  std::size_t min, std::size_t max);
+
   //////////////////////////////////////////////////////////////////////////////
   /// @brief Bounds for all index-entries- belonging to a specified primary
   /// index
diff --git a/arangod/RocksDBEngine/RocksDBMetaCollection.cpp b/arangod/RocksDBEngine/RocksDBMetaCollection.cpp
index 5faf2d49beef..2b90c2eb8bc5 100644
--- a/arangod/RocksDBEngine/RocksDBMetaCollection.cpp
+++ b/arangod/RocksDBEngine/RocksDBMetaCollection.cpp
@@ -23,19 +23,27 @@
 
 #include "RocksDBMetaCollection.h"
 
+#include "ApplicationFeatures/ApplicationServer.h"
 #include "Basics/ReadLocker.h"
 #include "Basics/VelocyPackHelper.h"
 #include "Basics/WriteLocker.h"
+#include "Basics/hashes.h"
 #include "Basics/system-functions.h"
 #include "Cluster/ServerState.h"
+#include "Random/RandomGenerator.h"
 #include "RocksDBEngine/RocksDBIndex.h"
 #include "RocksDBEngine/RocksDBLogValue.h"
 #include "RocksDBEngine/RocksDBMethods.h"
+#include "RocksDBEngine/RocksDBReplicationContext.h"
+#include "RocksDBEngine/RocksDBReplicationManager.h"
 #include "RocksDBEngine/RocksDBSettingsManager.h"
 #include "RocksDBEngine/RocksDBTransactionCollection.h"
 #include "RocksDBEngine/RocksDBTransactionState.h"
+#include "StorageEngine/EngineSelectorFeature.h"
 #include "Transaction/Methods.h"
+#include "Transaction/StandaloneContext.h"
 #include "Utils/OperationOptions.h"
+#include "Utils/SingleCollectionTransaction.h"
 
 #include <velocypack/velocypack-aliases.h>
 
@@ -43,8 +51,11 @@ using namespace arangodb;
 
 RocksDBMetaCollection::RocksDBMetaCollection(LogicalCollection& collection,
                                              VPackSlice const& info)
-: PhysicalCollection(collection, info),
-  _objectId(basics::VelocyPackHelper::stringUInt64(info, "objectId")) {
+    : PhysicalCollection(collection, info),
+      _objectId(basics::VelocyPackHelper::stringUInt64(info, "objectId")),
+      _revisionTreeApplied(0),
+      _revisionTreeSerializedSeq(0),
+      _revisionTreeSerializedTime(std::chrono::steady_clock::now()) {
   TRI_ASSERT(!ServerState::instance()->isCoordinator());
   VPackSlice s = info.get("isVolatile");
   if (s.isBoolean() && s.getBoolean()) {
@@ -55,20 +66,37 @@ RocksDBMetaCollection::RocksDBMetaCollection(LogicalCollection& collection,
   TRI_ASSERT(_logicalCollection.isAStub() || _objectId != 0);
   rocksutils::globalRocksEngine()->addCollectionMapping(_objectId, _logicalCollection.vocbase().id(),
                                                         _logicalCollection.id());
+
+  if (collection.syncByRevision()) {
+    _revisionTree =
+        std::make_unique<containers::RevisionTree>(6, collection.minRevision());
+  }
 }
 
 RocksDBMetaCollection::RocksDBMetaCollection(LogicalCollection& collection,
                                              PhysicalCollection const* physical)
-: PhysicalCollection(collection, VPackSlice::emptyObjectSlice()),
-  _objectId(static_cast<RocksDBMetaCollection const*>(physical)->_objectId) {
+    : PhysicalCollection(collection, VPackSlice::emptyObjectSlice()),
+      _objectId(static_cast<RocksDBMetaCollection const*>(physical)->_objectId),
+      _revisionTreeApplied(0) {
   TRI_ASSERT(!ServerState::instance()->isCoordinator());
   rocksutils::globalRocksEngine()->addCollectionMapping(_objectId, _logicalCollection.vocbase().id(), _logicalCollection.id());
+
+  if (collection.syncByRevision()) {
+    _revisionTree =
+        std::make_unique<containers::RevisionTree>(6, collection.minRevision());
+  }
 }
 
 std::string const& RocksDBMetaCollection::path() const {
   return StaticStrings::Empty;  // we do not have any path
 }
 
+void RocksDBMetaCollection::deferDropCollection(std::function<bool(LogicalCollection&)> const&) {
+  TRI_ASSERT(!_logicalCollection.syncByRevision());
+  std::unique_lock<std::mutex> guard(_revisionTreeLock);
+  _revisionTree.reset();
+}
+
 TRI_voc_rid_t RocksDBMetaCollection::revision(transaction::Methods* trx) const {
   auto* state = RocksDBTransactionState::toState(trx);
   auto trxCollection = static_cast<RocksDBTransactionCollection*>(
@@ -315,3 +343,452 @@ void RocksDBMetaCollection::estimateSize(velocypack::Builder& builder) {
   builder.add("total", VPackValue(total));
   builder.close();
 }
+
+void RocksDBMetaCollection::setRevisionTree(std::unique_ptr<containers::RevisionTree>&& tree,
+                                            uint64_t seq) {
+  TRI_ASSERT(_logicalCollection.syncByRevision());
+  TRI_ASSERT(tree);
+  std::unique_lock<std::mutex> guard(_revisionTreeLock);
+  _revisionTree = std::move(tree);
+  _revisionTreeApplied.store(seq);
+}
+
+std::unique_ptr<containers::RevisionTree> RocksDBMetaCollection::revisionTree(transaction::Methods& trx) {
+  if (!_logicalCollection.syncByRevision()) {
+    return nullptr;
+  }
+  TRI_ASSERT(_revisionTree);
+
+  // first apply any updates that can be safely applied
+  RocksDBEngine* engine = rocksutils::globalRocksEngine();
+  rocksdb::DB* db = engine->db()->GetRootDB();
+  rocksdb::SequenceNumber safeSeq = meta().committableSeq(db->GetLatestSequenceNumber());
+
+  std::unique_lock<std::mutex> guard(_revisionTreeLock);
+  applyUpdates(safeSeq);
+
+  // now clone the tree so we can apply all updates consistent with our ongoing trx
+  auto tree = _revisionTree->clone();
+  if (!tree) {
+    return nullptr;
+  }
+
+  {
+    // apply any which are buffered and older than our ongoing transaction start
+    rocksdb::SequenceNumber trxSeq = RocksDBTransactionState::toState(&trx)->beginSeq();
+    TRI_ASSERT(trxSeq != 0);
+    Result res = applyUpdatesForTransaction(*tree, trxSeq);
+    if (res.fail()) {
+      return nullptr;
+    }
+  }
+
+  {
+    // now peek at updates buffered inside transaction and apply those too
+    auto operations = RocksDBTransactionState::toState(&trx)->trackedOperations(
+        _logicalCollection.id());
+    tree->insert(operations.inserts);
+    tree->remove(operations.removals);
+  }
+
+  return tree;
+}
+
+std::unique_ptr<containers::RevisionTree> RocksDBMetaCollection::revisionTree(uint64_t batchId) {
+  if (!_logicalCollection.syncByRevision()) {
+    return nullptr;
+  }
+  TRI_ASSERT(_revisionTree);
+
+  EngineSelectorFeature& selector =
+      _logicalCollection.vocbase().server().getFeature<EngineSelectorFeature>();
+  // first apply any updates that can be safely applied
+  RocksDBEngine* engine = rocksutils::globalRocksEngine();
+  rocksdb::DB* db = engine->db()->GetRootDB();
+  rocksdb::SequenceNumber safeSeq = meta().committableSeq(db->GetLatestSequenceNumber());
+
+  std::unique_lock<std::mutex> guard(_revisionTreeLock);
+  applyUpdates(safeSeq);
+
+  // now clone the tree so we can apply all updates consistent with our ongoing trx
+  auto tree = _revisionTree->clone();
+  if (!tree) {
+    return nullptr;
+  }
+
+  {
+    // apply any which are buffered and older than our ongoing transaction start
+    RocksDBEngine& engine = selector.engine<RocksDBEngine>();
+    RocksDBReplicationManager* manager = engine.replicationManager();
+    RocksDBReplicationContext* ctx = batchId == 0 ? nullptr : manager->find(batchId);
+    if (!ctx) {
+      return nullptr;
+    }
+    auto guard = scopeGuard([manager, ctx]() -> void { manager->release(ctx); });
+    rocksdb::Snapshot const* snapshot = ctx->snapshot();
+    rocksdb::SequenceNumber trxSeq = snapshot->GetSequenceNumber();
+    TRI_ASSERT(trxSeq != 0);
+    Result res = applyUpdatesForTransaction(*tree, trxSeq);
+    if (res.fail()) {
+      return nullptr;
+    }
+  }
+
+  return tree;
+}
+
+bool RocksDBMetaCollection::needToPersistRevisionTree(rocksdb::SequenceNumber maxCommitSeq) const {
+  if (!_logicalCollection.syncByRevision()) {
+    return maxCommitSeq < _revisionTreeApplied.load();
+  }
+
+  std::unique_lock<std::mutex> guard(_revisionBufferLock);
+
+  if (!_revisionTruncateBuffer.empty() && *_revisionTruncateBuffer.begin() <= maxCommitSeq) {
+    return true;
+  }
+
+  if (!_revisionInsertBuffers.empty() && _revisionInsertBuffers.begin()->first <= maxCommitSeq) {
+    return true;
+  }
+
+  if (!_revisionRemovalBuffers.empty() && _revisionRemovalBuffers.begin()->first <= maxCommitSeq) {
+    return true;
+  }
+
+  return false;
+}
+
+rocksdb::SequenceNumber RocksDBMetaCollection::serializeRevisionTree(
+    std::string& output, rocksdb::SequenceNumber commitSeq) {
+  std::unique_lock<std::mutex> guard(_revisionTreeLock);
+  if (_logicalCollection.syncByRevision()) {
+    auto appliedSeq = applyUpdates(commitSeq);  // always apply updates...
+    bool neverDone = _revisionTreeSerializedSeq.load() == 0;
+    bool coinFlip = RandomGenerator::interval(static_cast<uint32_t>(5)) == 0;
+    bool beenTooLong = 30 < std::chrono::duration_cast<std::chrono::seconds>(
+                                std::chrono::steady_clock::now() - _revisionTreeSerializedTime)
+                                .count();
+    if (neverDone || coinFlip || beenTooLong) {  // ...but only write the tree out sometimes
+      _revisionTree->serializeBinary(output, true);
+      _revisionTreeSerializedSeq.store(appliedSeq);
+      _revisionTreeSerializedTime = std::chrono::steady_clock::now();
+    }
+    return _revisionTreeSerializedSeq.load();
+  }
+  // mark as don't persist again, tree should be deleted now
+  _revisionTreeApplied.store(std::numeric_limits<rocksdb::SequenceNumber>::max());
+  return commitSeq;
+}
+
+Result RocksDBMetaCollection::rebuildRevisionTree() {
+  std::unique_lock<std::mutex> guard(_revisionTreeLock);
+  _revisionTree =
+      std::make_unique<containers::RevisionTree>(6, _logicalCollection.minRevision());
+
+  Result res = basics::catchToResult([this]() -> Result {
+    auto ctxt = transaction::StandaloneContext::Create(_logicalCollection.vocbase());
+    SingleCollectionTransaction trx(ctxt, _logicalCollection, AccessMode::Type::READ);
+    auto* state = RocksDBTransactionState::toState(&trx);
+
+    std::vector<std::size_t> revisions;
+    auto iter = getReplicationIterator(ReplicationIterator::Ordering::Revision, trx);
+    if (!iter) {
+      LOG_TOPIC("d1e54", WARN, arangodb::Logger::ENGINES)
+          << "failed to retrieve replication iterator to rebuild revision tree "
+             "for collection '"
+          << _logicalCollection.id() << "'";
+      return Result(TRI_ERROR_INTERNAL);
+    }
+    RevisionReplicationIterator& it =
+        *static_cast<RevisionReplicationIterator*>(iter.get());
+    while (it.hasMore()) {
+      revisions.emplace_back(it.revision());
+      if (revisions.size() >= 5000) {  // arbitrary batch size
+        _revisionTree->insert(revisions);
+        revisions.clear();
+      }
+    }
+    if (!revisions.empty()) {
+      _revisionTree->insert(revisions);
+    }
+    _revisionTreeApplied.store(state->beginSeq());
+    return Result();
+  });
+
+  if (res.fail() && res.is(TRI_ERROR_ARANGO_DATA_SOURCE_NOT_FOUND)) {
+    res.reset();
+    // okay, we are in recovery and can't open a transaction, so we need to
+    // read the raw RocksDB data; on the plus side, we are in recovery, so we
+    // are single-threaded and don't need to worry about transactions anyway
+
+    RocksDBKeyBounds documentBounds = RocksDBKeyBounds::CollectionDocuments(_objectId);
+    rocksdb::Comparator const* cmp = RocksDBColumnFamily::documents()->GetComparator();
+    rocksdb::ReadOptions ro;
+    rocksdb::Slice const end = documentBounds.end();
+    ro.iterate_upper_bound = &end;
+    ro.fill_cache = false;
+
+    std::vector<std::size_t> revisions;
+    auto* db = rocksutils::globalRocksDB();
+    auto iter = db->NewIterator(ro, documentBounds.columnFamily());
+    for (iter->Seek(documentBounds.start());
+         iter->Valid() && cmp->Compare(iter->key(), end) < 0; iter->Next()) {
+      LocalDocumentId const docId = RocksDBKey::documentId(iter->key());
+      revisions.emplace_back(docId.id());
+      if (revisions.size() >= 5000) {  // arbitrary batch size
+        _revisionTree->insert(revisions);
+        revisions.clear();
+      }
+    }
+    if (!revisions.empty()) {
+      _revisionTree->insert(revisions);
+    }
+    _revisionTreeApplied.store(db->GetLatestSequenceNumber());
+  }
+
+  return res;
+}
+
+void RocksDBMetaCollection::revisionTreeSummary(VPackBuilder& builder) {
+  if (!_logicalCollection.syncByRevision()) {
+    return;
+  }
+  TRI_ASSERT(_revisionTree);
+
+  std::unique_lock<std::mutex> guard(_revisionTreeLock);
+  VPackObjectBuilder obj(&builder);
+  obj->add(StaticStrings::RevisionTreeCount, VPackValue(_revisionTree->count()));
+  obj->add(StaticStrings::RevisionTreeHash, VPackValue(_revisionTree->rootValue()));
+}
+
+void RocksDBMetaCollection::placeRevisionTreeBlocker(TRI_voc_tid_t transactionId) {
+  rocksdb::TransactionDB* db = rocksutils::globalRocksDB();
+  rocksdb::SequenceNumber preSeq = db->GetLatestSequenceNumber();
+  _meta.placeBlocker(transactionId, preSeq);
+}
+
+void RocksDBMetaCollection::removeRevisionTreeBlocker(TRI_voc_tid_t transactionId) {
+  _meta.removeBlocker(transactionId);
+}
+
+void RocksDBMetaCollection::bufferUpdates(rocksdb::SequenceNumber seq,
+                                          std::vector<std::size_t>&& inserts,
+                                          std::vector<std::size_t>&& removals) {
+  if (!_logicalCollection.syncByRevision()) {
+    return;
+  }
+
+  if (_revisionTreeApplied.load() > seq) {
+    TRI_ASSERT(_logicalCollection.vocbase()
+                   .server()
+                   .getFeature<EngineSelectorFeature>()
+                   .engine()
+                   .inRecovery());
+    return;
+  }
+
+  TRI_ASSERT(!inserts.empty() || !removals.empty());
+
+  std::unique_lock<std::mutex> guard(_revisionBufferLock);
+  if (!inserts.empty()) {
+    _revisionInsertBuffers.emplace(seq, std::move(inserts));
+  }
+  if (!removals.empty()) {
+    _revisionRemovalBuffers.emplace(seq, std::move(removals));
+  }
+}
+
+Result RocksDBMetaCollection::bufferTruncate(rocksdb::SequenceNumber seq) {
+  if (!_logicalCollection.syncByRevision()) {
+    return Result();
+  }
+
+  Result res = basics::catchVoidToResult([&]() -> void {
+    if (_revisionTreeApplied.load() > seq) {
+      return;
+    }
+    std::unique_lock<std::mutex> guard(_revisionBufferLock);
+    _revisionTruncateBuffer.emplace(seq);
+  });
+  return res;
+}
+
+rocksdb::SequenceNumber RocksDBMetaCollection::applyUpdates(rocksdb::SequenceNumber commitSeq) {
+  if (!_logicalCollection.syncByRevision()) {
+    return 0;
+  }
+  TRI_ASSERT(_revisionTree);
+
+  rocksdb::SequenceNumber appliedSeq = 0;
+  Result res = basics::catchVoidToResult([&]() -> void {
+    std::multimap<rocksdb::SequenceNumber, std::vector<std::size_t>>::const_iterator insertIt;
+    std::multimap<rocksdb::SequenceNumber, std::vector<std::size_t>>::const_iterator removeIt;
+    {
+      std::unique_lock<std::mutex> guard(_revisionBufferLock);
+      insertIt = _revisionInsertBuffers.begin();
+      removeIt = _revisionRemovalBuffers.begin();
+    }
+
+    {
+      rocksdb::SequenceNumber ignoreSeq = 0;  // truncate will increase this sequence
+      bool foundTruncate = false;
+      // check for a truncate marker
+      std::unique_lock<std::mutex> guard(_revisionBufferLock);
+      auto it = _revisionTruncateBuffer.begin();  // sorted ASC
+      while (it != _revisionTruncateBuffer.end() && *it <= commitSeq) {
+        ignoreSeq = *it;
+        TRI_ASSERT(ignoreSeq != 0);
+        foundTruncate = true;
+        appliedSeq = std::max(appliedSeq, ignoreSeq);
+        it = _revisionTruncateBuffer.erase(it);
+      }
+      if (foundTruncate) {
+        TRI_ASSERT(ignoreSeq <= commitSeq);
+        while (insertIt != _revisionInsertBuffers.end() && insertIt->first <= ignoreSeq) {
+          insertIt = _revisionInsertBuffers.erase(insertIt);
+        }
+        while (removeIt != _revisionRemovalBuffers.end() && removeIt->first <= ignoreSeq) {
+          removeIt = _revisionRemovalBuffers.erase(removeIt);
+        }
+        _revisionTree->clear();  // clear estimates
+      }
+    }
+
+    while (true) {
+      std::vector<std::size_t> inserts;
+      std::vector<std::size_t> removals;
+      // find out if we have buffers to apply
+      {
+        bool haveInserts = insertIt != _revisionInsertBuffers.end() &&
+                           insertIt->first <= commitSeq;
+        bool haveRemovals = removeIt != _revisionRemovalBuffers.end() &&
+                            removeIt->first <= commitSeq;
+
+        bool applyInserts =
+            haveInserts && (!haveRemovals || removeIt->first >= insertIt->first);
+        bool applyRemovals = haveRemovals && !applyInserts;
+
+        // check for inserts
+        if (applyInserts) {
+          std::unique_lock<std::mutex> guard(_revisionBufferLock);
+          inserts = std::move(insertIt->second);
+          appliedSeq = std::max(appliedSeq, insertIt->first);
+          insertIt = _revisionInsertBuffers.erase(insertIt);
+        }
+        // check for removals
+        if (applyRemovals) {
+          std::unique_lock<std::mutex> guard(_revisionBufferLock);
+          removals = std::move(removeIt->second);
+          appliedSeq = std::max(appliedSeq, removeIt->first);
+          removeIt = _revisionRemovalBuffers.erase(removeIt);
+        }
+      }
+
+      // no inserts or removals left to apply, drop out of loop
+      if (inserts.empty() && removals.empty()) {
+        break;
+      }
+
+      // apply inserts
+      if (!inserts.empty()) {
+        _revisionTree->insert(inserts);
+        inserts.clear();
+      }
+
+      // apply removals
+      if (!removals.empty()) {
+        _revisionTree->remove(removals);
+        removals.clear();
+      }
+    }  // </while(true)>
+  });
+  _revisionTreeApplied.store(appliedSeq);
+  return appliedSeq;
+}
+
+Result RocksDBMetaCollection::applyUpdatesForTransaction(containers::RevisionTree& tree,
+                                                         rocksdb::SequenceNumber commitSeq) const {
+  if (!_logicalCollection.syncByRevision()) {
+    return Result();
+  }
+
+  Result res = basics::catchVoidToResult([&]() -> void {
+    std::multimap<rocksdb::SequenceNumber, std::vector<std::size_t>>::const_iterator insertIt;
+    std::multimap<rocksdb::SequenceNumber, std::vector<std::size_t>>::const_iterator removeIt;
+    {
+      std::unique_lock<std::mutex> guard(_revisionBufferLock);
+      insertIt = _revisionInsertBuffers.begin();
+      removeIt = _revisionRemovalBuffers.begin();
+    }
+
+    {
+      rocksdb::SequenceNumber ignoreSeq = 0;  // truncate will increase this sequence
+      bool foundTruncate = false;
+      // check for a truncate marker
+      std::unique_lock<std::mutex> guard(_revisionBufferLock);
+      auto it = _revisionTruncateBuffer.begin();  // sorted ASC
+      while (it != _revisionTruncateBuffer.end() && *it <= commitSeq) {
+        ignoreSeq = *it;
+        TRI_ASSERT(ignoreSeq != 0);
+        foundTruncate = true;
+        ++it;
+      }
+      if (foundTruncate) {
+        TRI_ASSERT(ignoreSeq <= commitSeq);
+        while (insertIt != _revisionInsertBuffers.end() && insertIt->first <= ignoreSeq) {
+          ++insertIt;
+        }
+        while (removeIt != _revisionRemovalBuffers.end() && removeIt->first <= ignoreSeq) {
+          ++removeIt;
+        }
+        tree.clear();  // clear estimates
+      }
+    }
+
+    while (true) {
+      std::vector<std::size_t> const* inserts = nullptr;
+      std::vector<std::size_t> const* removals = nullptr;
+      // find out if we have buffers to apply
+      {
+        bool haveInserts = insertIt != _revisionInsertBuffers.end() &&
+                           insertIt->first <= commitSeq;
+        bool haveRemovals = removeIt != _revisionRemovalBuffers.end() &&
+                            removeIt->first <= commitSeq;
+
+        bool applyInserts =
+            haveInserts && (!haveRemovals || removeIt->first >= insertIt->first);
+        bool applyRemovals = haveRemovals && !applyInserts;
+
+        // check for inserts
+        if (applyInserts) {
+          std::unique_lock<std::mutex> guard(_revisionBufferLock);
+          inserts = &insertIt->second;
+          ++insertIt;
+        }
+        // check for removals
+        if (applyRemovals) {
+          std::unique_lock<std::mutex> guard(_revisionBufferLock);
+          removals = &removeIt->second;
+          ++removeIt;
+        }
+      }
+
+      // no inserts or removals left to apply, drop out of loop
+      if (!inserts && !removals) {
+        break;
+      }
+
+      // apply inserts
+      if (inserts) {
+        tree.insert(*inserts);
+      }
+
+      // apply removals
+      if (removals) {
+        tree.remove(*removals);
+      }
+    }  // </while(true)>
+  });
+  return res;
+}
diff --git a/arangod/RocksDBEngine/RocksDBMetaCollection.h b/arangod/RocksDBEngine/RocksDBMetaCollection.h
index 603c233dfc15..7f0fe1eebbe8 100644
--- a/arangod/RocksDBEngine/RocksDBMetaCollection.h
+++ b/arangod/RocksDBEngine/RocksDBMetaCollection.h
@@ -26,8 +26,9 @@
 
 #include "Basics/Common.h"
 #include "Basics/ReadWriteLock.h"
-#include "RocksDBEngine/RocksDBMetadata.h"
+#include "Containers/MerkleTree.h"
 #include "RocksDBEngine/RocksDBCommon.h"
+#include "RocksDBEngine/RocksDBMetadata.h"
 #include "StorageEngine/PhysicalCollection.h"
 #include "VocBase/LogicalCollection.h"
 
@@ -51,9 +52,9 @@ class RocksDBMetaCollection : public PhysicalCollection {
   void open(bool /*ignoreErrors*/) override final {
     TRI_ASSERT(_objectId != 0);
   }
-  
-  void deferDropCollection(std::function<bool(LogicalCollection&)> const&) override final  {}
-  
+
+  void deferDropCollection(std::function<bool(LogicalCollection&)> const&) override final;
+
   /// @brief report extra memory used by indexes etc.
   size_t memory() const override final { return 0; }
   uint64_t objectId() const { return _objectId; }
@@ -78,6 +79,37 @@ class RocksDBMetaCollection : public PhysicalCollection {
   /// estimate size of collection and indexes
   void estimateSize(velocypack::Builder& builder);
 
+  void setRevisionTree(std::unique_ptr<containers::RevisionTree>&& tree, uint64_t seq);
+  std::unique_ptr<containers::RevisionTree> revisionTree(transaction::Methods& trx) override;
+  std::unique_ptr<containers::RevisionTree> revisionTree(uint64_t batchId) override;
+
+  bool needToPersistRevisionTree(rocksdb::SequenceNumber maxCommitSeq) const;
+  rocksdb::SequenceNumber serializeRevisionTree(std::string& output,
+                                                rocksdb::SequenceNumber commitSeq);
+
+  Result rebuildRevisionTree() override;
+
+  void revisionTreeSummary(VPackBuilder& builder);
+
+  void placeRevisionTreeBlocker(TRI_voc_tid_t transactionId) override;
+  void removeRevisionTreeBlocker(TRI_voc_tid_t transactionId) override;
+
+  /**
+   * @brief Buffer updates to this collection to be applied when appropriate
+   *
+   * Buffers updates associated with a given commit seq/tick. Will hold updates
+   * until all previous blockers have been removed to ensure a consistent state
+   * for sync/recovery and avoid any missed updates.
+   *
+   * @param  seq      The seq/tick post-commit, prior to call
+   * @param  inserts  Vector of revisions to insert
+   * @param  removals Vector of revisions to remove
+   */
+  void bufferUpdates(rocksdb::SequenceNumber seq, std::vector<std::size_t>&& inserts,
+                     std::vector<std::size_t>&& removals);
+
+  Result bufferTruncate(rocksdb::SequenceNumber seq);
+
  public:
   
   /// return bounds for all documents
@@ -87,12 +119,28 @@ class RocksDBMetaCollection : public PhysicalCollection {
   
   /// @brief track the usage of waitForSync option in an operation
   void trackWaitForSync(arangodb::transaction::Methods* trx, OperationOptions& options);
-  
+
+  rocksdb::SequenceNumber applyUpdates(rocksdb::SequenceNumber commitSeq);
+
+  Result applyUpdatesForTransaction(containers::RevisionTree& tree,
+                                    rocksdb::SequenceNumber commitSeq) const;
+
  protected:
-  RocksDBMetadata _meta;  /// collection metadata
-  uint64_t const _objectId; /// rocksdb-specific object id for collection
+  RocksDBMetadata _meta;     /// collection metadata
+  uint64_t const _objectId;  /// rocksdb-specific object id for collection
   /// @brief collection lock used for write access
   mutable basics::ReadWriteLock _exclusiveLock;
+
+  /// @revision tree management for replication
+  std::unique_ptr<containers::RevisionTree> _revisionTree;
+  std::atomic<rocksdb::SequenceNumber> _revisionTreeApplied;
+  std::atomic<rocksdb::SequenceNumber> _revisionTreeSerializedSeq;
+  std::chrono::steady_clock::time_point _revisionTreeSerializedTime;
+  mutable std::mutex _revisionTreeLock;
+  std::multimap<rocksdb::SequenceNumber, std::vector<std::size_t>> _revisionInsertBuffers;
+  std::multimap<rocksdb::SequenceNumber, std::vector<std::size_t>> _revisionRemovalBuffers;
+  std::set<rocksdb::SequenceNumber> _revisionTruncateBuffer;
+  mutable std::mutex _revisionBufferLock;
 };
 
 } // namespace arangodb
diff --git a/arangod/RocksDBEngine/RocksDBMetadata.cpp b/arangod/RocksDBEngine/RocksDBMetadata.cpp
index ee8d312f797c..4b37d3be7270 100644
--- a/arangod/RocksDBEngine/RocksDBMetadata.cpp
+++ b/arangod/RocksDBEngine/RocksDBMetadata.cpp
@@ -78,9 +78,10 @@ RocksDBMetadata::RocksDBMetadata()
 /**
  * @brief Place a blocker to allow proper commit/serialize semantics
  *
- * Should be called immediately prior to internal RocksDB commit. If the
- * commit succeeds, any inserts/removals should be buffered, then the blocker
- * removed; otherwise simply remove the blocker.
+ * Should be called immediately prior to beginning an internal trx. If the
+ * trx commit succeeds, any inserts/removals should be buffered, then the
+ * blocker updated (intermediate) or removed (final); otherwise simply remove
+ * the blocker.
  *
  * @param  trxId The identifier for the active transaction
  * @param  seq   The sequence number immediately prior to call
@@ -103,6 +104,42 @@ Result RocksDBMetadata::placeBlocker(TRI_voc_tid_t trxId, rocksdb::SequenceNumbe
   });
 }
 
+/**
+ * @brief Update a blocker to allow proper commit/serialize semantics
+ *
+ * Should be called after initializing an internal trx.
+ *
+ * @param  trxId The identifier for the active transaction (should match input
+ *               to earlier `placeBlocker` call)
+ * @param  seq   The sequence number from the internal snapshot
+ * @return       May return error if we fail to allocate and place blocker
+ */
+Result RocksDBMetadata::updateBlocker(TRI_voc_tid_t trxId, rocksdb::SequenceNumber seq) {
+  return basics::catchToResult([&]() -> Result {
+    Result res;
+    WRITE_LOCKER(locker, _blockerLock);
+
+    auto previous = _blockers.find(trxId);
+    if (_blockers.end() == previous ||
+        _blockersBySeq.end() ==
+            _blockersBySeq.find(std::make_pair(previous->second, trxId))) {
+      res.reset(TRI_ERROR_INTERNAL);
+    }
+
+    auto removed = _blockersBySeq.erase(std::make_pair(previous->second, trxId));
+    if (!removed) {
+      return res.reset(TRI_ERROR_INTERNAL);
+    }
+
+    _blockers[trxId] = seq;
+    auto crosslist = _blockersBySeq.emplace(seq, trxId);
+    if (!crosslist.second) {
+      return res.reset(TRI_ERROR_INTERNAL);
+    }
+    return res;
+  });
+}
+
 /**
  * @brief Removes an existing transaction blocker
  *
@@ -192,19 +229,21 @@ void RocksDBMetadata::adjustNumberDocuments(rocksdb::SequenceNumber seq,
 /// @brief serialize the collection metadata
 Result RocksDBMetadata::serializeMeta(rocksdb::WriteBatch& batch,
                                       LogicalCollection& coll, bool force,
-                                      VPackBuilder& tmp,
-                                      rocksdb::SequenceNumber& appliedSeq) {
+                                      VPackBuilder& tmp, rocksdb::SequenceNumber& appliedSeq,
+                                      std::string& output) {
   TRI_ASSERT(appliedSeq != UINT64_MAX);
-  
+  TRI_ASSERT(appliedSeq > 0);
+
   Result res;
   if (coll.deleted()) {
     return res;
   }
 
   const rocksdb::SequenceNumber maxCommitSeq = committableSeq(appliedSeq);
-  bool didWork = applyAdjustments(maxCommitSeq);
   TRI_ASSERT(maxCommitSeq <= appliedSeq);
   TRI_ASSERT(maxCommitSeq != UINT64_MAX);
+  TRI_ASSERT(maxCommitSeq > 0);
+  bool didWork = applyAdjustments(maxCommitSeq);
   appliedSeq = maxCommitSeq;
 
   RocksDBKey key;
@@ -248,7 +287,6 @@ Result RocksDBMetadata::serializeMeta(rocksdb::WriteBatch& batch,
   }
 
   // Step 3. store the index estimates
-  std::string output;
   auto indexes = coll.getIndexes();
   for (std::shared_ptr<arangodb::Index>& index : indexes) {
     RocksDBIndex* idx = static_cast<RocksDBIndex*>(index.get());
@@ -284,6 +322,37 @@ Result RocksDBMetadata::serializeMeta(rocksdb::WriteBatch& batch,
     }
   }
 
+  // Step 4. store the revision tree
+  if (rcoll->needToPersistRevisionTree(maxCommitSeq)) {
+    if (coll.syncByRevision()) {
+      output.clear();
+      rocksdb::SequenceNumber seq = rcoll->serializeRevisionTree(output, maxCommitSeq);
+      appliedSeq = std::min(appliedSeq, seq);
+
+      if (!output.empty()) {
+        rocksutils::uint64ToPersistent(output, seq);
+
+        key.constructRevisionTreeValue(rcoll->objectId());
+        rocksdb::Slice value(output);
+
+        rocksdb::Status s = batch.Put(cf, key.string(), value);
+        if (!s.ok()) {
+          LOG_TOPIC("ff234", WARN, Logger::ENGINES)
+              << "writing revision tree failed";
+          return res.reset(rocksutils::convertStatus(s));
+        }
+      }
+    } else {
+      key.constructRevisionTreeValue(rcoll->objectId());
+      rocksdb::Status s = batch.Delete(cf, key.string());
+      if (!s.ok() && !s.IsNotFound()) {
+        LOG_TOPIC("ff235", WARN, Logger::ENGINES)
+            << "deleting revision tree failed";
+        return res.reset(rocksutils::convertStatus(s));
+      }
+    }
+  }
+
   return res;
 }
 
@@ -373,6 +442,41 @@ Result RocksDBMetadata::deserializeMeta(rocksdb::DB* db, LogicalCollection& coll
     }
   }
 
+  // Step 4. load the revision tree
+  if (coll.syncByRevision()) {
+    key.constructRevisionTreeValue(rcoll->objectId());
+    s = db->Get(ro, cf, key.string(), &value);
+    if (!s.ok() && !s.IsNotFound()) {
+      return rocksutils::convertStatus(s);
+    } else if (s.IsNotFound()) {
+      LOG_TOPIC("ecdbc", WARN, Logger::ENGINES)
+          << "no revision tree found for collection with id '" << coll.id()
+          << "', rebuilding";
+      Result res = rcoll->rebuildRevisionTree();
+      if (res.fail()) {
+        LOG_TOPIC("ecdbd", WARN, Logger::ENGINES)
+            << "failed to rebuild revision tree for collection '" << coll.id() << "'";
+      }
+    } else {
+      auto tree = containers::RevisionTree::fromBuffer(
+          std::string_view(value.data(), value.size() - sizeof(uint64_t)));
+      if (tree) {
+        uint64_t seq = rocksutils::uint64FromPersistent(
+            value.data() + value.size() - sizeof(uint64_t));
+        rcoll->setRevisionTree(std::move(tree), seq);
+      } else {
+        LOG_TOPIC("dcd99", ERR, Logger::ENGINES)
+            << "unsupported revision tree format in collection "
+            << "with id '" << coll.id() << "', rebuilding";
+        Result res = rcoll->rebuildRevisionTree();
+        if (res.fail()) {
+          LOG_TOPIC("ecdbf", WARN, Logger::ENGINES)
+              << "failed to rebuild revision tree for collection '" << coll.id() << "'";
+        }
+      }
+    }
+  }
+
   return Result();
 }
 
@@ -425,6 +529,14 @@ void RocksDBMetadata::loadInitialNumberDocuments() {
     return rocksutils::convertStatus(s);
   }
 
+  key.constructRevisionTreeValue(objectId);
+  s = db->Delete(wo, cf, key.string());
+  if (!s.ok() && !s.IsNotFound()) {
+    LOG_TOPIC("af3dd", ERR, Logger::ENGINES)
+        << "could not delete revision tree value: " << s.ToString();
+    return rocksutils::convertStatus(s);
+  }
+
   return Result();
 }
 
diff --git a/arangod/RocksDBEngine/RocksDBMetadata.h b/arangod/RocksDBEngine/RocksDBMetadata.h
index 1290b8679b67..20bae2ec9faf 100644
--- a/arangod/RocksDBEngine/RocksDBMetadata.h
+++ b/arangod/RocksDBEngine/RocksDBMetadata.h
@@ -71,9 +71,10 @@ struct RocksDBMetadata final {
   /**
    * @brief Place a blocker to allow proper commit/serialize semantics
    *
-   * Should be called immediately prior to internal RocksDB commit. If the
-   * commit succeeds, any inserts/removals should be buffered, then the blocker
-   * removed; otherwise simply remove the blocker.
+   * Should be called immediately prior to beginning an internal trx. If the
+   * trx commit succeeds, any inserts/removals should be buffered, then the
+   * blocker updated (intermediate) or removed (final); otherwise simply remove
+   * the blocker.
    *
    * @param  trxId The identifier for the active transaction
    * @param  seq   The sequence number immediately prior to call
@@ -81,6 +82,18 @@ struct RocksDBMetadata final {
    */
   Result placeBlocker(TRI_voc_tid_t trxId, rocksdb::SequenceNumber seq);
 
+  /**
+   * @brief Update a blocker to allow proper commit/serialize semantics
+   *
+   * Should be called after initializing an internal trx.
+   *
+   * @param  trxId The identifier for the active transaction (should match input
+   *               to earlier `placeBlocker` call)
+   * @param  seq   The sequence number from the internal snapshot
+   * @return       May return error if we fail to allocate and place blocker
+   */
+  Result updateBlocker(TRI_voc_tid_t trxId, rocksdb::SequenceNumber seq);
+
   /**
    * @brief Removes an existing transaction blocker
    *
@@ -105,7 +118,7 @@ struct RocksDBMetadata final {
   /// @brief serialize the collection metadata
   arangodb::Result serializeMeta(rocksdb::WriteBatch&, LogicalCollection&,
                                  bool force, arangodb::velocypack::Builder&,
-                                 rocksdb::SequenceNumber& appliedSeq);
+                                 rocksdb::SequenceNumber& appliedSeq, std::string& output);
 
   /// @brief deserialize collection metadata, only called on startup
   arangodb::Result deserializeMeta(rocksdb::DB*, LogicalCollection&);
diff --git a/arangod/RocksDBEngine/RocksDBPrimaryIndex.cpp b/arangod/RocksDBEngine/RocksDBPrimaryIndex.cpp
index 8e7146c65db9..c0bc920dd94d 100644
--- a/arangod/RocksDBEngine/RocksDBPrimaryIndex.cpp
+++ b/arangod/RocksDBEngine/RocksDBPrimaryIndex.cpp
@@ -21,6 +21,7 @@
 /// @author Jan Steemann
 ////////////////////////////////////////////////////////////////////////////////
 
+#include "RocksDBPrimaryIndex.h"
 #include "Aql/Ast.h"
 #include "Aql/AstNode.h"
 #include "Basics/Exceptions.h"
@@ -41,12 +42,12 @@
 #include "RocksDBEngine/RocksDBTransactionState.h"
 #include "RocksDBEngine/RocksDBTypes.h"
 #include "RocksDBEngine/RocksDBValue.h"
-#include "RocksDBPrimaryIndex.h"
 #include "StorageEngine/EngineSelectorFeature.h"
 #include "Transaction/Context.h"
 #include "Transaction/Helpers.h"
 #include "Transaction/Methods.h"
 #include "Utils/CollectionNameResolver.h"
+#include "Utils/OperationOptions.h"
 #include "VocBase/LogicalCollection.h"
 
 #include "RocksDBEngine/RocksDBPrefixExtractor.h"
@@ -572,7 +573,8 @@ bool RocksDBPrimaryIndex::lookupRevision(transaction::Methods* trx,
 Result RocksDBPrimaryIndex::insert(transaction::Methods& trx, RocksDBMethods* mthd,
                                    LocalDocumentId const& documentId,
                                    velocypack::Slice const& slice,
-                                   Index::OperationMode mode) {
+                                   OperationOptions& options) {
+  Index::OperationMode mode = options.indexOperationMode;
   VPackSlice keySlice;
   TRI_voc_rid_t revision;
   transaction::helpers::extractKeyAndRevFromDocument(slice, keySlice, revision);
@@ -583,21 +585,23 @@ Result RocksDBPrimaryIndex::insert(transaction::Methods& trx, RocksDBMethods* mt
 
   transaction::StringLeaser leased(&trx);
   rocksdb::PinnableSlice ps(leased.get());
-  rocksdb::Status s = mthd->GetForUpdate(_cf, key->string(), &ps);
-
   Result res;
-  if (s.ok()) {  // detected conflicting primary key
-    if (mode == OperationMode::internal) {
-      return res.reset(TRI_ERROR_ARANGO_UNIQUE_CONSTRAINT_VIOLATED, keySlice.copyString());
+  if (!options.ignoreUniqueConstraints) {
+    rocksdb::Status s = mthd->GetForUpdate(_cf, key->string(), &ps);
+
+    if (s.ok()) {  // detected conflicting primary key
+      if (mode == OperationMode::internal) {
+        return res.reset(TRI_ERROR_ARANGO_UNIQUE_CONSTRAINT_VIOLATED, keySlice.copyString());
+      }
+      res.reset(TRI_ERROR_ARANGO_UNIQUE_CONSTRAINT_VIOLATED);
+      return addErrorMsg(res, keySlice.copyString());
+    } else if (!s.IsNotFound()) {
+      // IsBusy(), IsTimedOut() etc... this indicates a conflict
+      return addErrorMsg(res.reset(rocksutils::convertStatus(s)));
     }
-    res.reset(TRI_ERROR_ARANGO_UNIQUE_CONSTRAINT_VIOLATED);
-    return addErrorMsg(res, keySlice.copyString());
-  } else if (!s.IsNotFound()) {
-    // IsBusy(), IsTimedOut() etc... this indicates a conflict
-    return addErrorMsg(res.reset(rocksutils::convertStatus(s)));
-  }
 
-  ps.Reset();  // clear used memory
+    ps.Reset();  // clear used memory
+  }
 
   if (trx.state()->hasHint(transaction::Hints::Hint::GLOBAL_MANAGED)) {
     // blacklist new index entry to avoid caching without committing first
@@ -606,7 +610,7 @@ Result RocksDBPrimaryIndex::insert(transaction::Methods& trx, RocksDBMethods* mt
 
   TRI_ASSERT(revision != 0);
   auto value = RocksDBValue::PrimaryIndexValue(documentId, revision);
-  s = mthd->Put(_cf, key.ref(), value.string(), /*assume_tracked*/true);
+  rocksdb::Status s = mthd->Put(_cf, key.ref(), value.string(), /*assume_tracked*/ true);
   if (!s.ok()) {
     res.reset(rocksutils::convertStatus(s, rocksutils::index));
     addErrorMsg(res);
diff --git a/arangod/RocksDBEngine/RocksDBPrimaryIndex.h b/arangod/RocksDBEngine/RocksDBPrimaryIndex.h
index 1ae813a9dc7e..8ca261ec1a1d 100644
--- a/arangod/RocksDBEngine/RocksDBPrimaryIndex.h
+++ b/arangod/RocksDBEngine/RocksDBPrimaryIndex.h
@@ -109,8 +109,8 @@ class RocksDBPrimaryIndex final : public RocksDBIndex {
 
   /// insert index elements into the specified write batch.
   Result insert(transaction::Methods& trx, RocksDBMethods* methods,
-                LocalDocumentId const& documentId,
-                velocypack::Slice const& doc, Index::OperationMode mode) override;
+                LocalDocumentId const& documentId, velocypack::Slice const& doc,
+                OperationOptions& options) override;
 
   /// remove index elements and put it in the specified write batch.
   Result remove(transaction::Methods& trx, RocksDBMethods* methods,
diff --git a/arangod/RocksDBEngine/RocksDBRecoveryManager.cpp b/arangod/RocksDBEngine/RocksDBRecoveryManager.cpp
index 91c77ef61d10..60a30722807b 100644
--- a/arangod/RocksDBEngine/RocksDBRecoveryManager.cpp
+++ b/arangod/RocksDBEngine/RocksDBRecoveryManager.cpp
@@ -317,7 +317,12 @@ class WBReader final : public rocksdb::WriteBatch::Handler {
             transaction::helpers::extractRevFromDocument(RocksDBValue::data(value));
         coll->meta().loadInitialNumberDocuments();
       }
-
+      if (coll) {
+        std::vector<std::size_t> inserts;
+        std::vector<std::size_t> removes;
+        inserts.emplace_back(RocksDBKey::documentId(key).id());
+        coll->bufferUpdates(_currentSequence, std::move(inserts), std::move(removes));
+      }
     } else {
       // We have to adjust the estimate with an insert
       uint64_t hashval = 0;
@@ -366,6 +371,12 @@ class WBReader final : public rocksdb::WriteBatch::Handler {
         }
         coll->meta().loadInitialNumberDocuments();
       }
+      if (coll) {
+        std::vector<std::size_t> inserts;
+        std::vector<std::size_t> removes;
+        removes.emplace_back(RocksDBKey::documentId(key).id());
+        coll->bufferUpdates(_currentSequence, std::move(inserts), std::move(removes));
+      }
       _lastRemovedDocRid = 0;  // reset in any case
 
     } else {
diff --git a/arangod/RocksDBEngine/RocksDBReplicationContext.cpp b/arangod/RocksDBEngine/RocksDBReplicationContext.cpp
index 523ce452a9e4..dd6dfa17554b 100644
--- a/arangod/RocksDBEngine/RocksDBReplicationContext.cpp
+++ b/arangod/RocksDBEngine/RocksDBReplicationContext.cpp
@@ -36,8 +36,9 @@
 #include "Replication/common-defines.h"
 #include "Replication/utilities.h"
 #include "RestServer/DatabaseFeature.h"
-#include "RocksDBEngine/RocksDBMetaCollection.h"
+#include "RocksDBEngine/RocksDBCollection.h"
 #include "RocksDBEngine/RocksDBCommon.h"
+#include "RocksDBEngine/RocksDBMetaCollection.h"
 #include "RocksDBEngine/RocksDBMethods.h"
 #include "RocksDBEngine/RocksDBPrimaryIndex.h"
 #include "Transaction/Context.h"
@@ -96,6 +97,10 @@ RocksDBReplicationContext::~RocksDBReplicationContext() {
 
 TRI_voc_tick_t RocksDBReplicationContext::id() const { return _id; }
 
+rocksdb::Snapshot const* RocksDBReplicationContext::snapshot() {
+  return _snapshot;
+}
+
 uint64_t RocksDBReplicationContext::snapshotTick() {
   MUTEX_LOCKER(locker, _contextLock);
   lazyCreateSnapshot();
@@ -153,6 +158,9 @@ std::tuple<Result, TRI_voc_cid_t, uint64_t> RocksDBReplicationContext::bindColle
   }
   TRI_voc_cid_t cid = logical->id();
 
+  LOG_TOPIC("71235", TRACE, Logger::REPLICATION)
+      << "binding replication context " << id() << " to collection '" << cname << "'";
+
   MUTEX_LOCKER(writeLocker, _contextLock);
 
   auto it = _iterators.find(cid);
@@ -821,11 +829,16 @@ RocksDBReplicationContext::CollectionIterator::CollectionIterator(
   if (res != TRI_ERROR_NO_ERROR) {  // collection was deleted
     THROW_ARANGO_EXCEPTION(TRI_ERROR_ARANGO_DATA_SOURCE_NOT_FOUND);
   }
+
+  LOG_TOPIC("71236", TRACE, Logger::REPLICATION)
+      << "replication created iterator for collection '" << coll->name() << "'";
 }
 
 RocksDBReplicationContext::CollectionIterator::~CollectionIterator() {
   TRI_ASSERT(!vocbase.isDangling());
   vocbase.releaseCollection(logical.get());
+  LOG_TOPIC("71237", TRACE, Logger::REPLICATION)
+      << "replication released iterator for collection '" << logical->name() << "'";
   logical.reset();
   vocbase.release();
 }
diff --git a/arangod/RocksDBEngine/RocksDBReplicationContext.h b/arangod/RocksDBEngine/RocksDBReplicationContext.h
index 672a4ce70647..5b595cc5c967 100644
--- a/arangod/RocksDBEngine/RocksDBReplicationContext.h
+++ b/arangod/RocksDBEngine/RocksDBReplicationContext.h
@@ -123,6 +123,7 @@ class RocksDBReplicationContext {
   ~RocksDBReplicationContext();
 
   TRI_voc_tick_t id() const;  // batchId
+  rocksdb::Snapshot const* snapshot();
   uint64_t snapshotTick();
 
   /// invalidate all iterators with that vocbase
diff --git a/arangod/RocksDBEngine/RocksDBReplicationIterator.cpp b/arangod/RocksDBEngine/RocksDBReplicationIterator.cpp
new file mode 100644
index 000000000000..ffe2923896c8
--- /dev/null
+++ b/arangod/RocksDBEngine/RocksDBReplicationIterator.cpp
@@ -0,0 +1,115 @@
+////////////////////////////////////////////////////////////////////////////////
+/// DISCLAIMER
+///
+/// Copyright 2014-2017 ArangoDB GmbH, Cologne, Germany
+/// Copyright 2004-2014 triAGENS GmbH, Cologne, Germany
+///
+/// Licensed under the Apache License, Version 2.0 (the "License");
+/// you may not use this file except in compliance with the License.
+/// You may obtain a copy of the License at
+///
+///     http://www.apache.org/licenses/LICENSE-2.0
+///
+/// Unless required by applicable law or agreed to in writing, software
+/// distributed under the License is distributed on an "AS IS" BASIS,
+/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+/// See the License for the specific language governing permissions and
+/// limitations under the License.
+///
+/// Copyright holder is ArangoDB GmbH, Cologne, Germany
+///
+/// @author Dan Larkin-York
+////////////////////////////////////////////////////////////////////////////////
+
+#include "RocksDBReplicationIterator.h"
+
+#include <rocksdb/utilities/transaction_db.h>
+
+#include "ApplicationFeatures/ApplicationServer.h"
+#include "RocksDBEngine/RocksDBCollection.h"
+#include "RocksDBEngine/RocksDBEngine.h"
+#include "RocksDBEngine/RocksDBKey.h"
+#include "RocksDBEngine/RocksDBMethods.h"
+#include "RocksDBEngine/RocksDBTransactionState.h"
+#include "RocksDBEngine/RocksDBValue.h"
+#include "StorageEngine/EngineSelectorFeature.h"
+
+namespace arangodb {
+
+RocksDBRevisionReplicationIterator::RocksDBRevisionReplicationIterator(
+    LogicalCollection& collection, rocksdb::Snapshot const* snapshot)
+    : RevisionReplicationIterator(collection),
+      _readOptions(),
+      _bounds(RocksDBKeyBounds::CollectionDocuments(
+          static_cast<RocksDBCollection*>(collection.getPhysical())->objectId())) {
+  auto& selector = collection.vocbase().server().getFeature<EngineSelectorFeature>();
+  RocksDBEngine& engine = *static_cast<RocksDBEngine*>(&selector.engine());
+  rocksdb::TransactionDB* db = engine.db();
+
+  if (snapshot) {
+    _readOptions.snapshot = snapshot;
+  }
+
+  _readOptions.verify_checksums = false;
+  _readOptions.fill_cache = false;
+  _readOptions.prefix_same_as_start = true;
+
+  rocksdb::ColumnFamilyHandle* cf = _bounds.columnFamily();
+  _cmp = cf->GetComparator();
+
+  _iter.reset(db->NewIterator(_readOptions, cf));
+  _iter->Seek(_bounds.start());
+}
+
+RocksDBRevisionReplicationIterator::RocksDBRevisionReplicationIterator(
+    LogicalCollection& collection, transaction::Methods& trx)
+    : RevisionReplicationIterator(collection),
+      _readOptions(),
+      _bounds(RocksDBKeyBounds::CollectionDocuments(
+          static_cast<RocksDBCollection*>(collection.getPhysical())->objectId())) {
+  RocksDBMethods* methods = RocksDBTransactionState::toMethods(&trx);
+  _readOptions = methods->iteratorReadOptions();
+
+  _readOptions.verify_checksums = false;
+  _readOptions.fill_cache = false;
+  _readOptions.prefix_same_as_start = true;
+
+  rocksdb::ColumnFamilyHandle* cf = _bounds.columnFamily();
+  _cmp = cf->GetComparator();
+
+  _iter = methods->NewIterator(_readOptions, cf);
+  _iter->Seek(_bounds.start());
+}
+
+bool RocksDBRevisionReplicationIterator::hasMore() const {
+  return _iter->Valid() && _cmp->Compare(_iter->key(), _bounds.end()) <= 0;
+}
+
+void RocksDBRevisionReplicationIterator::reset() {
+  _iter->Seek(_bounds.start());
+}
+
+TRI_voc_rid_t RocksDBRevisionReplicationIterator::revision() const {
+  TRI_ASSERT(hasMore());
+  return RocksDBKey::documentId(_iter->key()).id();
+}
+
+VPackSlice RocksDBRevisionReplicationIterator::document() const {
+  TRI_ASSERT(hasMore());
+  return RocksDBValue::data(_iter->value());
+}
+
+void RocksDBRevisionReplicationIterator::next() {
+  TRI_ASSERT(hasMore());
+  _iter->Next();
+}
+
+void RocksDBRevisionReplicationIterator::seek(TRI_voc_rid_t rid) {
+  uint64_t objectId =
+      static_cast<RocksDBCollection*>(_collection.getPhysical())->objectId();
+  RocksDBKey key;
+  key.constructDocument(objectId, LocalDocumentId::create(rid));
+  _iter->Seek(key.string());
+}
+
+}  // namespace arangodb
diff --git a/arangod/RocksDBEngine/RocksDBReplicationIterator.h b/arangod/RocksDBEngine/RocksDBReplicationIterator.h
new file mode 100644
index 000000000000..73016f29c6e6
--- /dev/null
+++ b/arangod/RocksDBEngine/RocksDBReplicationIterator.h
@@ -0,0 +1,59 @@
+////////////////////////////////////////////////////////////////////////////////
+/// DISCLAIMER
+///
+/// Copyright 2014-2017 ArangoDB GmbH, Cologne, Germany
+/// Copyright 2004-2014 triAGENS GmbH, Cologne, Germany
+///
+/// Licensed under the Apache License, Version 2.0 (the "License");
+/// you may not use this file except in compliance with the License.
+/// You may obtain a copy of the License at
+///
+///     http://www.apache.org/licenses/LICENSE-2.0
+///
+/// Unless required by applicable law or agreed to in writing, software
+/// distributed under the License is distributed on an "AS IS" BASIS,
+/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+/// See the License for the specific language governing permissions and
+/// limitations under the License.
+///
+/// Copyright holder is ArangoDB GmbH, Cologne, Germany
+///
+/// @author Dan Larkin-York
+////////////////////////////////////////////////////////////////////////////////
+
+#ifndef ARANGOD_ROCKSDB_ENGINE_ROCKSDB_REPLICATION_ITERATOR_H
+#define ARANGOD_ROCKSDB_ENGINE_ROCKSDB_REPLICATION_ITERATOR_H 1
+
+#include <rocksdb/iterator.h>
+#include <rocksdb/options.h>
+#include <rocksdb/snapshot.h>
+
+#include "RocksDBEngine/RocksDBKeyBounds.h"
+#include "StorageEngine/ReplicationIterator.h"
+
+namespace arangodb {
+class LogicalCollection;
+
+class RocksDBRevisionReplicationIterator : public RevisionReplicationIterator {
+ public:
+  RocksDBRevisionReplicationIterator(LogicalCollection&, rocksdb::Snapshot const*);
+  RocksDBRevisionReplicationIterator(LogicalCollection&, transaction::Methods&);
+
+  virtual bool hasMore() const override;
+  virtual void reset() override;
+
+  virtual TRI_voc_rid_t revision() const override;
+  virtual VPackSlice document() const override;
+
+  virtual void next() override;
+  virtual void seek(TRI_voc_rid_t) override;
+
+ private:
+  std::unique_ptr<rocksdb::Iterator> _iter;
+  rocksdb::ReadOptions _readOptions;
+  RocksDBKeyBounds _bounds;
+  rocksdb::Comparator const* _cmp;
+};
+
+}  // namespace arangodb
+#endif
diff --git a/arangod/RocksDBEngine/RocksDBReplicationManager.cpp b/arangod/RocksDBEngine/RocksDBReplicationManager.cpp
index 6c9cb6ec34d6..ba986aec8744 100644
--- a/arangod/RocksDBEngine/RocksDBReplicationManager.cpp
+++ b/arangod/RocksDBEngine/RocksDBReplicationManager.cpp
@@ -218,6 +218,9 @@ RocksDBReplicationManager::extendLifetime(RocksDBReplicationId id, double ttl) {
     return {TRI_ERROR_CURSOR_NOT_FOUND};
   }
 
+  LOG_TOPIC("71234", TRACE, Logger::REPLICATION)
+      << "extending lifetime of replication context " << id;
+
   RocksDBReplicationContext* context = it->second;
   TRI_ASSERT(context != nullptr);
 
diff --git a/arangod/RocksDBEngine/RocksDBSettingsManager.cpp b/arangod/RocksDBEngine/RocksDBSettingsManager.cpp
index c03e2f8441b8..c4a7f3bf7ede 100644
--- a/arangod/RocksDBEngine/RocksDBSettingsManager.cpp
+++ b/arangod/RocksDBEngine/RocksDBSettingsManager.cpp
@@ -168,6 +168,8 @@ Result RocksDBSettingsManager::sync(bool force) {
 
   bool didWork = false;
   auto mappings = engine->collectionMappings();
+  std::string scratch;
+  scratch.reserve(10485760);  // reserve 10MB of scratch space to work with
   for (auto const& pair : mappings) {
     TRI_voc_tick_t dbid = pair.first;
     TRI_voc_cid_t cid = pair.second;
@@ -185,12 +187,14 @@ Result RocksDBSettingsManager::sync(bool force) {
       continue;
     }
     TRI_DEFER(vocbase->releaseCollection(coll.get()));
-    
-    LOG_TOPIC("afb17", TRACE, Logger::ENGINES) << "syncing metadata for collection '" << coll->name() << "'";    
+
+    LOG_TOPIC("afb17", TRACE, Logger::ENGINES)
+        << "syncing metadata for collection '" << coll->name() << "'";
 
     auto* rcoll = static_cast<RocksDBCollection*>(coll->getPhysical());
     rocksdb::SequenceNumber appliedSeq = maxSeqNr;
-    Result res = rcoll->meta().serializeMeta(batch, *coll, force, _tmpBuilder, appliedSeq);
+    Result res = rcoll->meta().serializeMeta(batch, *coll, force, _tmpBuilder,
+                                             appliedSeq, scratch);
     minSeqNr = std::min(minSeqNr, appliedSeq);
 
     const std::string err = "could not sync metadata for collection '";
diff --git a/arangod/RocksDBEngine/RocksDBTransactionCollection.cpp b/arangod/RocksDBEngine/RocksDBTransactionCollection.cpp
index 14df2e882b5b..03cb25434482 100644
--- a/arangod/RocksDBEngine/RocksDBTransactionCollection.cpp
+++ b/arangod/RocksDBEngine/RocksDBTransactionCollection.cpp
@@ -195,17 +195,18 @@ void RocksDBTransactionCollection::addOperation(TRI_voc_document_operation_e ope
   }
 }
 
-void RocksDBTransactionCollection::prepareCommit(uint64_t trxId, uint64_t preCommitSeq) {
+void RocksDBTransactionCollection::prepareTransaction(uint64_t trxId, uint64_t beginSeq) {
   TRI_ASSERT(_collection != nullptr);
-  if (hasOperations() || !_trackedIndexOperations.empty()) {
+  if (hasOperations() || !_trackedOperations.empty() || !_trackedIndexOperations.empty()) {
     auto* coll = static_cast<RocksDBMetaCollection*>(_collection->getPhysical());
-    coll->meta().placeBlocker(trxId, preCommitSeq);
+    TRI_ASSERT(beginSeq > 0);
+    coll->meta().placeBlocker(trxId, beginSeq);
   }
 }
 
 void RocksDBTransactionCollection::abortCommit(uint64_t trxId) {
   TRI_ASSERT(_collection != nullptr);
-  if (hasOperations() || !_trackedIndexOperations.empty()) {
+  if (hasOperations() || !_trackedOperations.empty() || !_trackedIndexOperations.empty()) {
     auto* coll = static_cast<RocksDBMetaCollection*>(_collection->getPhysical());
     coll->meta().removeBlocker(trxId);
   }
@@ -222,6 +223,12 @@ void RocksDBTransactionCollection::commitCounts(TRI_voc_tid_t trxId, uint64_t co
     rcoll->meta().adjustNumberDocuments(commitSeq, _revision, adj);
   }
 
+  // update the revision tree
+  if (!_trackedOperations.empty()) {
+    rcoll->bufferUpdates(commitSeq, std::move(_trackedOperations.inserts),
+                         std::move(_trackedOperations.removals));
+  }
+
   // Update the index estimates.
   for (auto& pair : _trackedIndexOperations) {
     auto idx = _collection->lookupIndex(pair.first);
@@ -239,7 +246,7 @@ void RocksDBTransactionCollection::commitCounts(TRI_voc_tid_t trxId, uint64_t co
     }
   }
 
-  if (hasOperations() || !_trackedIndexOperations.empty()) {
+  if (hasOperations() || !_trackedOperations.empty() || !_trackedIndexOperations.empty()) {
     rcoll->meta().removeBlocker(trxId);
   }
 
@@ -247,16 +254,27 @@ void RocksDBTransactionCollection::commitCounts(TRI_voc_tid_t trxId, uint64_t co
   _numInserts = 0;
   _numUpdates = 0;
   _numRemoves = 0;
+  _trackedOperations.clear();
   _trackedIndexOperations.clear();
 }
 
+void RocksDBTransactionCollection::trackInsert(TRI_voc_rid_t rid) {
+  if (_collection->syncByRevision()) {
+    _trackedOperations.inserts.emplace_back(static_cast<std::size_t>(rid));
+  }
+}
+
+void RocksDBTransactionCollection::trackRemove(TRI_voc_rid_t rid) {
+  if (_collection->syncByRevision()) {
+    _trackedOperations.removals.emplace_back(static_cast<std::size_t>(rid));
+  }
+}
+
 void RocksDBTransactionCollection::trackIndexInsert(TRI_idx_iid_t iid, uint64_t hash) {
-  // First list is Inserts
   _trackedIndexOperations[iid].inserts.emplace_back(hash);
 }
 
 void RocksDBTransactionCollection::trackIndexRemove(TRI_idx_iid_t iid, uint64_t hash) {
-  // Second list is Removes
   _trackedIndexOperations[iid].removals.emplace_back(hash);
 }
 
diff --git a/arangod/RocksDBEngine/RocksDBTransactionCollection.h b/arangod/RocksDBEngine/RocksDBTransactionCollection.h
index 723a8e6b79ad..426e3a8f8fdb 100644
--- a/arangod/RocksDBEngine/RocksDBTransactionCollection.h
+++ b/arangod/RocksDBEngine/RocksDBTransactionCollection.h
@@ -65,11 +65,11 @@ class RocksDBTransactionCollection final : public TransactionCollection {
   void addOperation(TRI_voc_document_operation_e operationType, TRI_voc_rid_t revisionId);
 
   /**
-   * @brief Prepare collection for commit by placing index blockers
-   * @param trxId        Active transaction ID
-   * @param preCommitSeq Current seq/tick immediately before call
+   * @brief Prepare collection for commit by placing collection blockers
+   * @param trxId    Active transaction ID
+   * @param beginSeq Current seq/tick on transaction begin
    */
-  void prepareCommit(uint64_t trxId, uint64_t preCommitSeq);
+  void prepareTransaction(uint64_t trxId, uint64_t beginSeq);
 
   /**
    * @brief Signal upstream abort/rollback to clean up index blockers
@@ -84,6 +84,33 @@ class RocksDBTransactionCollection final : public TransactionCollection {
    */
   void commitCounts(TRI_voc_tid_t trxId, uint64_t commitSeq);
 
+  /// @brief Track documents inserted to the collection
+  ///        Used to update the revision tree for replication after commit
+  void trackInsert(TRI_voc_rid_t rid);
+
+  /// @brief Track documents removed from the collection
+  ///        Used to update the revision tree for replication after commit
+  void trackRemove(TRI_voc_rid_t rid);
+
+  struct TrackedOperations {
+    std::vector<std::size_t> inserts;
+    std::vector<std::size_t> removals;
+    bool empty() const { return inserts.empty() && removals.empty(); }
+    void clear() {
+      inserts.clear();
+      removals.clear();
+    }
+  };
+
+  TrackedOperations& trackedOperations() { return _trackedOperations; }
+
+  TrackedOperations stealTrackedOperations() {
+    TrackedOperations empty;
+    _trackedOperations.inserts.swap(empty.inserts);
+    _trackedOperations.removals.swap(empty.removals);
+    return empty;
+  }
+
   /// @brief Every index can track hashes inserted into this index
   ///        Used to update the estimate after the trx commited
   void trackIndexInsert(TRI_idx_iid_t iid, uint64_t hash);
@@ -93,15 +120,15 @@ class RocksDBTransactionCollection final : public TransactionCollection {
   void trackIndexRemove(TRI_idx_iid_t iid, uint64_t hash);
 
   /// @brief tracked index operations
-  struct IndexOperations {
+  struct TrackedIndexOperations {
     std::vector<uint64_t> inserts;
     std::vector<uint64_t> removals;
   };
-  typedef std::unordered_map<TRI_idx_iid_t, IndexOperations> OperationsMap;
+  using IndexOperationsMap = std::unordered_map<TRI_idx_iid_t, TrackedIndexOperations>;
 
   /// @brief steal the tracked operations from the map
-  OperationsMap stealTrackedOperations() {
-    OperationsMap empty;
+  IndexOperationsMap stealTrackedIndexOperations() {
+    IndexOperationsMap empty;
     _trackedIndexOperations.swap(empty);
     return empty;
   }
@@ -126,9 +153,13 @@ class RocksDBTransactionCollection final : public TransactionCollection {
   uint64_t _numUpdates;
   uint64_t _numRemoves;
 
+  /// @brief A list where collection can store its document operations
+  ///        Will be applied on commit and not applied on abort
+  TrackedOperations _trackedOperations;
+
   /// @brief A list where all indexes with estimates can store their operations
   ///        Will be applied to the inserter on commit and not applied on abort
-  OperationsMap _trackedIndexOperations;
+  IndexOperationsMap _trackedIndexOperations;
 };
 }  // namespace arangodb
 
diff --git a/arangod/RocksDBEngine/RocksDBTransactionState.cpp b/arangod/RocksDBEngine/RocksDBTransactionState.cpp
index c3044f9eaf9d..8c175d8d5a65 100644
--- a/arangod/RocksDBEngine/RocksDBTransactionState.cpp
+++ b/arangod/RocksDBEngine/RocksDBTransactionState.cpp
@@ -224,6 +224,33 @@ void RocksDBTransactionState::createTransaction() {
   }
 }
 
+void RocksDBTransactionState::prepareCollections() {
+  rocksdb::TransactionDB* db = rocksutils::globalRocksDB();
+  rocksdb::SequenceNumber preSeq = db->GetLatestSequenceNumber();
+  for (auto& trxColl : _collections) {
+    auto* coll = static_cast<RocksDBTransactionCollection*>(trxColl);
+    coll->prepareTransaction(id(), preSeq);
+  }
+}
+
+void RocksDBTransactionState::commitCollections(rocksdb::SequenceNumber lastWritten) {
+  TRI_ASSERT(lastWritten > 0);
+  for (auto& trxColl : _collections) {
+    auto* coll = static_cast<RocksDBTransactionCollection*>(trxColl);
+    // we need this in case of an intermediate commit. The number of
+    // initial documents is adjusted and numInserts / removes is set to 0
+    // index estimator updates are buffered
+    coll->commitCounts(id(), lastWritten);
+  }
+}
+
+void RocksDBTransactionState::cleanupCollections() {
+  for (auto& trxColl : _collections) {
+    auto* coll = static_cast<RocksDBTransactionCollection*>(trxColl);
+    coll->abortCommit(id());
+  }
+}
+
 void RocksDBTransactionState::cleanupTransaction() noexcept {
   delete _rocksTransaction;
   _rocksTransaction = nullptr;
@@ -251,10 +278,10 @@ arangodb::Result RocksDBTransactionState::internalCommit() {
     // this is most likely the fill index case
 #ifdef ARANGODB_ENABLE_MAINTAINER_MODE
     for (auto& trxColl : _collections) {
-      TRI_IF_FAILURE("RocksDBCommitCounts") { continue; }
       auto* rcoll = static_cast<RocksDBTransactionCollection*>(trxColl);
       TRI_ASSERT(!rcoll->hasOperations());
       TRI_ASSERT(rcoll->stealTrackedOperations().empty());
+      TRI_ASSERT(rcoll->stealTrackedIndexOperations().empty());
     }
     // don't write anything if the transaction is empty
 #endif
@@ -270,19 +297,7 @@ arangodb::Result RocksDBTransactionState::internalCommit() {
     }
   }
 
-  auto commitCounts = [this]() {
-    TRI_ASSERT(_lastWrittenOperationTick > 0);
-    for (auto& trxColl : _collections) {
-      auto* coll = static_cast<RocksDBTransactionCollection*>(trxColl);
-      // we need this in case of an intermediate commit. The number of
-      // initial documents is adjusted and numInserts / removes is set to 0
-      // index estimator updates are buffered
-      TRI_IF_FAILURE("RocksDBCommitCounts") {
-        continue;
-      }
-      coll->commitCounts(id(), _lastWrittenOperationTick);
-    }
-  };
+  auto commitCounts = [this]() { commitCollections(_lastWrittenOperationTick); };
 
   // we are actually going to attempt a commit
   if (!isSingleOperation()) {
@@ -314,21 +329,10 @@ arangodb::Result RocksDBTransactionState::internalCommit() {
   TRI_ASSERT(x > 0);
 #endif
 
-  // prepare for commit on each collection, e.g. place blockers for estimators
-  rocksdb::SequenceNumber preCommitSeq =
-      rocksutils::globalRocksDB()->GetLatestSequenceNumber();
-  for (auto& trxColl : _collections) {
-    auto* coll = static_cast<RocksDBTransactionCollection*>(trxColl);
-    coll->prepareCommit(id(), preCommitSeq);
-  }
+  prepareCollections();
 
   // if we fail during commit, make sure we remove blockers, etc.
-  auto cleanupCollTrx = scopeGuard([this]() {
-    for (auto& trxColl : _collections) {
-      auto* coll = static_cast<RocksDBTransactionCollection*>(trxColl);
-      coll->abortCommit(id());
-    }
-  });
+  auto cleanupCollTrx = scopeGuard([this]() { cleanupCollections(); });
 
 #ifdef _WIN32
   // set wait for sync flag if required
@@ -641,6 +645,30 @@ Result RocksDBTransactionState::checkIntermediateCommit(uint64_t newSize, bool&
   return TRI_ERROR_NO_ERROR;
 }
 
+RocksDBTransactionCollection::TrackedOperations& RocksDBTransactionState::trackedOperations(TRI_voc_cid_t cid) {
+  auto col = findCollection(cid);
+  TRI_ASSERT(col != nullptr);
+  return static_cast<RocksDBTransactionCollection*>(col)->trackedOperations();
+}
+
+void RocksDBTransactionState::trackInsert(TRI_voc_cid_t cid, TRI_voc_rid_t rid) {
+  auto col = findCollection(cid);
+  if (col != nullptr) {
+    static_cast<RocksDBTransactionCollection*>(col)->trackInsert(rid);
+  } else {
+    TRI_ASSERT(false);
+  }
+}
+
+void RocksDBTransactionState::trackRemove(TRI_voc_cid_t cid, TRI_voc_rid_t rid) {
+  auto col = findCollection(cid);
+  if (col != nullptr) {
+    static_cast<RocksDBTransactionCollection*>(col)->trackRemove(rid);
+  } else {
+    TRI_ASSERT(false);
+  }
+}
+
 void RocksDBTransactionState::trackIndexInsert(TRI_voc_cid_t cid,
                                                TRI_idx_iid_t idxId, uint64_t hash) {
   auto col = findCollection(cid);
@@ -673,6 +701,16 @@ bool RocksDBTransactionState::isOnlyExclusiveTransaction() const {
   return true;
 }
 
+rocksdb::SequenceNumber RocksDBTransactionState::beginSeq() const {
+  if (_rocksTransaction) {
+    return _rocksTransaction->GetSnapshot()->GetSequenceNumber();
+  } else if (_readSnapshot) {
+    return _readSnapshot->GetSequenceNumber();
+  }
+  rocksdb::TransactionDB* db = rocksutils::globalRocksDB();
+  return db->GetLatestSequenceNumber();
+}
+
 /// @brief constructor, leases a builder
 RocksDBKeyLeaser::RocksDBKeyLeaser(transaction::Methods* trx)
     : _ctx(trx->transactionContextPtr()),
diff --git a/arangod/RocksDBEngine/RocksDBTransactionState.h b/arangod/RocksDBEngine/RocksDBTransactionState.h
index 1b3191c36794..3f3d93f507ec 100644
--- a/arangod/RocksDBEngine/RocksDBTransactionState.h
+++ b/arangod/RocksDBEngine/RocksDBTransactionState.h
@@ -30,6 +30,7 @@
 #include "Basics/Common.h"
 #include "Containers/SmallVector.h"
 #include "RocksDBEngine/RocksDBKey.h"
+#include "RocksDBEngine/RocksDBTransactionCollection.h"
 #include "StorageEngine/TransactionState.h"
 #include "Transaction/Hints.h"
 #include "Transaction/Methods.h"
@@ -139,6 +140,16 @@ class RocksDBTransactionState final : public TransactionState {
   /// @brief in parallel mode. READ-ONLY transactions
   bool inParallelMode() const { return _parallel; }
 
+  RocksDBTransactionCollection::TrackedOperations& trackedOperations(TRI_voc_cid_t cid);
+
+  /// @brief Track documents inserted to the collection
+  ///        Used to update the revision tree for replication after commit
+  void trackInsert(TRI_voc_cid_t cid, TRI_voc_rid_t rid);
+
+  /// @brief Track documents removed from the collection
+  ///        Used to update the revision tree for replication after commit
+  void trackRemove(TRI_voc_cid_t cid, TRI_voc_rid_t rid);
+
   /// @brief Every index can track hashes inserted into this index
   ///        Used to update the estimate after the trx committed
   void trackIndexInsert(TRI_voc_cid_t cid, TRI_idx_iid_t idxObjectId, uint64_t hash);
@@ -149,9 +160,16 @@ class RocksDBTransactionState final : public TransactionState {
   
   bool isOnlyExclusiveTransaction() const;
 
+  rocksdb::SequenceNumber beginSeq() const;
+
  private:
   /// @brief create a new rocksdb transaction
   void createTransaction();
+
+  void prepareCollections();
+  void commitCollections(rocksdb::SequenceNumber lastWritten);
+  void cleanupCollections();
+
   /// @brief delete transaction, snapshot and cache trx
   void cleanupTransaction() noexcept;
   /// @brief internally commit a transaction
@@ -183,6 +201,8 @@ class RocksDBTransactionState final : public TransactionState {
   /// @brief wrapper to use outside this class to access rocksdb
   std::unique_ptr<RocksDBMethods> _rocksMethods;
 
+  bool _blockers = false;
+
 #ifdef ARANGODB_ENABLE_MAINTAINER_MODE
   /// store the number of log entries in WAL
   uint64_t _numLogdata = 0;
diff --git a/arangod/RocksDBEngine/RocksDBTtlIndex.cpp b/arangod/RocksDBEngine/RocksDBTtlIndex.cpp
index 865b57dacb7d..c457a22b9820 100644
--- a/arangod/RocksDBEngine/RocksDBTtlIndex.cpp
+++ b/arangod/RocksDBEngine/RocksDBTtlIndex.cpp
@@ -71,8 +71,7 @@ void RocksDBTtlIndex::toVelocyPack(arangodb::velocypack::Builder& builder,
 /// @brief inserts a document into the index
 Result RocksDBTtlIndex::insert(transaction::Methods& trx, RocksDBMethods* mthds,
                                LocalDocumentId const& documentId,
-                               velocypack::Slice const& doc,
-                               Index::OperationMode mode) {
+                               velocypack::Slice const& doc, OperationOptions& options) {
   double timestamp = getTimestamp(doc);
   if (timestamp < 0) {
     // index attribute not present or invalid. nothing to do 
@@ -81,8 +80,8 @@ Result RocksDBTtlIndex::insert(transaction::Methods& trx, RocksDBMethods* mthds,
   transaction::BuilderLeaser leased(&trx);
   leased->openObject();
   leased->add(getAttribute(), VPackValue(timestamp));
-  leased->close(); 
-  return RocksDBVPackIndex::insert(trx, mthds, documentId, leased->slice(), mode);
+  leased->close();
+  return RocksDBVPackIndex::insert(trx, mthds, documentId, leased->slice(), options);
 }
 
 /// @brief removes a document from the index
diff --git a/arangod/RocksDBEngine/RocksDBTtlIndex.h b/arangod/RocksDBEngine/RocksDBTtlIndex.h
index 158b5240f140..1732d657eac5 100644
--- a/arangod/RocksDBEngine/RocksDBTtlIndex.h
+++ b/arangod/RocksDBEngine/RocksDBTtlIndex.h
@@ -55,8 +55,8 @@ class RocksDBTtlIndex final : public RocksDBSkiplistIndex {
  protected:
   // special override method that extracts a timestamp value from the index attribute
   Result insert(transaction::Methods& trx, RocksDBMethods* methods,
-                LocalDocumentId const& documentId,
-                velocypack::Slice const& doc, Index::OperationMode mode) override;
+                LocalDocumentId const& documentId, velocypack::Slice const& doc,
+                OperationOptions& options) override;
 
   // special override method that extracts a timestamp value from the index attribute
   Result remove(transaction::Methods& trx, RocksDBMethods* methods,
diff --git a/arangod/RocksDBEngine/RocksDBTypes.cpp b/arangod/RocksDBEngine/RocksDBTypes.cpp
index 64602a4d741a..002465a22c9c 100644
--- a/arangod/RocksDBEngine/RocksDBTypes.cpp
+++ b/arangod/RocksDBEngine/RocksDBTypes.cpp
@@ -97,6 +97,10 @@ static rocksdb::Slice IndexEstimateValue(
 static RocksDBEntryType keyGeneratorValue = RocksDBEntryType::KeyGeneratorValue;
 static rocksdb::Slice KeyGeneratorValue(
     reinterpret_cast<std::underlying_type<RocksDBEntryType>::type*>(&keyGeneratorValue), 1);
+
+static RocksDBEntryType revisionTreeValue = RocksDBEntryType::RevisionTreeValue;
+static rocksdb::Slice RevisionTreeValue(
+    reinterpret_cast<std::underlying_type<RocksDBEntryType>::type*>(&revisionTreeValue), 1);
 }  // namespace
 
 char const* arangodb::rocksDBEntryTypeName(arangodb::RocksDBEntryType type) {
@@ -135,6 +139,8 @@ char const* arangodb::rocksDBEntryTypeName(arangodb::RocksDBEntryType type) {
       return "IndexEstimateValue";
     case arangodb::RocksDBEntryType::KeyGeneratorValue:
       return "KeyGeneratorValue";
+    case arangodb::RocksDBEntryType::RevisionTreeValue:
+      return "RevisionTreeValue";
   }
   return "Invalid";
 }
@@ -231,6 +237,8 @@ rocksdb::Slice const& arangodb::rocksDBSlice(RocksDBEntryType const& type) {
       return IndexEstimateValue;
     case RocksDBEntryType::KeyGeneratorValue:
       return KeyGeneratorValue;
+    case RocksDBEntryType::RevisionTreeValue:
+      return RevisionTreeValue;
   }
 
   return Placeholder;  // avoids warning - errorslice instead ?!
diff --git a/arangod/RocksDBEngine/RocksDBTypes.h b/arangod/RocksDBEngine/RocksDBTypes.h
index 9d9c0ee42f5f..435762d569d3 100644
--- a/arangod/RocksDBEngine/RocksDBTypes.h
+++ b/arangod/RocksDBEngine/RocksDBTypes.h
@@ -52,7 +52,8 @@ enum class RocksDBEntryType : char {
   IndexEstimateValue = '<',
   KeyGeneratorValue = '=',
   View = '>',
-  GeoIndexValue = '?'
+  GeoIndexValue = '?',
+  RevisionTreeValue = '@'
 };
 
 char const* rocksDBEntryTypeName(RocksDBEntryType);
diff --git a/arangod/RocksDBEngine/RocksDBV8Functions.cpp b/arangod/RocksDBEngine/RocksDBV8Functions.cpp
index c20013a44bf3..b2bdbd29a365 100644
--- a/arangod/RocksDBEngine/RocksDBV8Functions.cpp
+++ b/arangod/RocksDBEngine/RocksDBV8Functions.cpp
@@ -201,6 +201,25 @@ static void JS_WaitForEstimatorSync(v8::FunctionCallbackInfo<v8::Value> const& a
   TRI_V8_TRY_CATCH_END
 }
 
+static void JS_CollectionRevisionTreeSummary(v8::FunctionCallbackInfo<v8::Value> const& args) {
+  TRI_V8_TRY_CATCH_BEGIN(isolate);
+  v8::HandleScope scope(isolate);
+
+  auto* collection = UnwrapCollection(isolate, args.Holder());
+
+  if (!collection) {
+    TRI_V8_THROW_EXCEPTION_INTERNAL("cannot extract collection");
+  }
+
+  auto* physical = toRocksDBCollection(*collection);
+  VPackBuilder builder;
+  physical->revisionTreeSummary(builder);
+
+  v8::Handle<v8::Value> result = TRI_VPackToV8(isolate, builder.slice());
+  TRI_V8_RETURN(result);
+  TRI_V8_TRY_CATCH_END
+}
+
 void RocksDBV8Functions::registerResources() {
   ISOLATE;
   v8::HandleScope scope(isolate);
@@ -219,6 +238,9 @@ void RocksDBV8Functions::registerResources() {
   TRI_AddMethodVocbase(isolate, rt,
                        TRI_V8_ASCII_STRING(isolate, "estimatedSize"),
                        JS_EstimateCollectionSize);
+  TRI_AddMethodVocbase(isolate, rt,
+                       TRI_V8_ASCII_STRING(isolate, "_revisionTreeSummary"),
+                       JS_CollectionRevisionTreeSummary);
 
   // add global WAL handling functions
   TRI_AddGlobalFunctionVocbase(isolate,
diff --git a/arangod/RocksDBEngine/RocksDBVPackIndex.cpp b/arangod/RocksDBEngine/RocksDBVPackIndex.cpp
index 5da89c221070..19007050723f 100644
--- a/arangod/RocksDBEngine/RocksDBVPackIndex.cpp
+++ b/arangod/RocksDBEngine/RocksDBVPackIndex.cpp
@@ -653,8 +653,8 @@ void RocksDBVPackIndex::fillPaths(std::vector<std::vector<std::string>>& paths,
 /// @brief inserts a document into the index
 Result RocksDBVPackIndex::insert(transaction::Methods& trx, RocksDBMethods* mthds,
                                  LocalDocumentId const& documentId,
-                                 velocypack::Slice const& doc,
-                                 Index::OperationMode mode) {
+                                 velocypack::Slice const& doc, OperationOptions& options) {
+  Index::OperationMode mode = options.indexOperationMode;
   Result res;
   rocksdb::Status s;
   ::arangodb::containers::SmallVector<RocksDBKey>::allocator_type::arena_type elementsArena;
@@ -680,13 +680,15 @@ Result RocksDBVPackIndex::insert(transaction::Methods& trx, RocksDBMethods* mthd
     transaction::StringLeaser leased(&trx);
     rocksdb::PinnableSlice existing(leased.get());
     for (RocksDBKey& key : elements) {
-      s = mthds->GetForUpdate(_cf, key.string(), &existing);
-      if (s.ok()) {  // detected conflicting index entry
-        res.reset(TRI_ERROR_ARANGO_UNIQUE_CONSTRAINT_VIOLATED);
-        break;
-      } else if (!s.IsNotFound()) {
-        res.reset(rocksutils::convertStatus(s));
-        break;
+      if (!options.ignoreUniqueConstraints) {
+        s = mthds->GetForUpdate(_cf, key.string(), &existing);
+        if (s.ok()) {  // detected conflicting index entry
+          res.reset(TRI_ERROR_ARANGO_UNIQUE_CONSTRAINT_VIOLATED);
+          break;
+        } else if (!s.IsNotFound()) {
+          res.reset(rocksutils::convertStatus(s));
+          break;
+        }
       }
       s = mthds->Put(_cf, key, value.string(), /*assume_tracked*/true);
       if (!s.ok()) {
diff --git a/arangod/RocksDBEngine/RocksDBVPackIndex.h b/arangod/RocksDBEngine/RocksDBVPackIndex.h
index cad9d1b31d4a..dc6fd8b13161 100644
--- a/arangod/RocksDBEngine/RocksDBVPackIndex.h
+++ b/arangod/RocksDBEngine/RocksDBVPackIndex.h
@@ -119,8 +119,8 @@ class RocksDBVPackIndex : public RocksDBIndex {
 
  protected:
   Result insert(transaction::Methods& trx, RocksDBMethods* methods,
-                LocalDocumentId const& documentId,
-                velocypack::Slice const& doc, Index::OperationMode mode) override;
+                LocalDocumentId const& documentId, velocypack::Slice const& doc,
+                OperationOptions& options) override;
 
   Result remove(transaction::Methods& trx, RocksDBMethods* methods,
                 LocalDocumentId const& documentId,
diff --git a/arangod/StorageEngine/EngineSelectorFeature.cpp b/arangod/StorageEngine/EngineSelectorFeature.cpp
index 92c0c1b99aab..7ce19180615a 100644
--- a/arangod/StorageEngine/EngineSelectorFeature.cpp
+++ b/arangod/StorageEngine/EngineSelectorFeature.cpp
@@ -263,6 +263,14 @@ StorageEngine& EngineSelectorFeature::engine() {
   return *ENGINE;
 }
 
+template <typename As, typename std::enable_if<std::is_base_of<StorageEngine, As>::value, int>::type>
+As& EngineSelectorFeature::engine() {
+  return *static_cast<As*>(ENGINE);
+}
+template ClusterEngine& EngineSelectorFeature::engine<ClusterEngine>();
+template MMFilesEngine& EngineSelectorFeature::engine<MMFilesEngine>();
+template RocksDBEngine& EngineSelectorFeature::engine<RocksDBEngine>();
+
 std::string const& EngineSelectorFeature::engineName() {
   return ENGINE->typeName();
 }
diff --git a/arangod/StorageEngine/EngineSelectorFeature.h b/arangod/StorageEngine/EngineSelectorFeature.h
index fd295788ba7f..2293cc6d3dbc 100644
--- a/arangod/StorageEngine/EngineSelectorFeature.h
+++ b/arangod/StorageEngine/EngineSelectorFeature.h
@@ -47,6 +47,9 @@ class EngineSelectorFeature final : public application_features::ApplicationFeat
 
   StorageEngine& engine();
 
+  template <typename As, typename std::enable_if<std::is_base_of<StorageEngine, As>::value, int>::type = 0>
+  As& engine();
+
   static std::string const& engineName();
 
   static std::string const& defaultEngine();
diff --git a/arangod/StorageEngine/PhysicalCollection.cpp b/arangod/StorageEngine/PhysicalCollection.cpp
index 5c4db282979c..fd94e6f516d9 100644
--- a/arangod/StorageEngine/PhysicalCollection.cpp
+++ b/arangod/StorageEngine/PhysicalCollection.cpp
@@ -23,14 +23,18 @@
 
 #include "PhysicalCollection.h"
 
+#include "ApplicationFeatures/ApplicationServer.h"
 #include "Basics/Exceptions.h"
 #include "Basics/ReadLocker.h"
 #include "Basics/StaticStrings.h"
 #include "Basics/VelocyPackHelper.h"
 #include "Basics/WriteLocker.h"
 #include "Basics/encoding.h"
+#include "Cluster/ClusterFeature.h"
+#include "Cluster/ClusterInfo.h"
 #include "Futures/Utilities.h"
 #include "Indexes/Index.h"
+#include "Logger/LogMacros.h"
 #include "StorageEngine/TransactionState.h"
 #include "Transaction/Methods.h"
 #include "VocBase/KeyGenerator.h"
@@ -170,6 +174,13 @@ std::shared_ptr<Index> PhysicalCollection::lookupIndex(std::string const& idxNam
 }
 
 TRI_voc_rid_t PhysicalCollection::newRevisionId() const {
+  if (_logicalCollection.hasClusterWideUniqueRevs()) {
+    application_features::ApplicationServer& server =
+        _logicalCollection.vocbase().server();
+    ClusterFeature& cf = server.getFeature<ClusterFeature>();
+    ClusterInfo& ci = cf.clusterInfo();
+    return static_cast<TRI_voc_rid_t>(ci.uniqid());
+  }
   return TRI_HybridLogicalClock();
 }
 
@@ -517,6 +528,27 @@ Result PhysicalCollection::newObjectForReplace(transaction::Methods*,
   return Result();
 }
 
+std::unique_ptr<containers::RevisionTree> PhysicalCollection::revisionTree(
+    transaction::Methods& trx) {
+  return nullptr;
+}
+
+std::unique_ptr<containers::RevisionTree> PhysicalCollection::revisionTree(uint64_t batchId) {
+  return nullptr;
+}
+
+Result PhysicalCollection::rebuildRevisionTree() {
+  return Result(TRI_ERROR_NOT_IMPLEMENTED);
+}
+
+void PhysicalCollection::placeRevisionTreeBlocker(TRI_voc_tid_t) {
+  THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
+}
+
+void PhysicalCollection::removeRevisionTreeBlocker(TRI_voc_tid_t) {
+  THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
+}
+
 /// @brief checks the revision of a document
 int PhysicalCollection::checkRevision(transaction::Methods*, TRI_voc_rid_t expected,
                                       TRI_voc_rid_t found) const {
@@ -585,6 +617,24 @@ futures::Future<OperationResult> PhysicalCollection::figures() {
   return OperationResult(Result(), std::move(buffer));
 }
 
+std::unique_ptr<ReplicationIterator> PhysicalCollection::getReplicationIterator(
+    ReplicationIterator::Ordering, uint64_t batchId) {
+  return nullptr;
+}
+
+std::unique_ptr<ReplicationIterator> PhysicalCollection::getReplicationIterator(
+    ReplicationIterator::Ordering, transaction::Methods&) {
+  return nullptr;
+}
+
+void PhysicalCollection::adjustNumberDocuments(transaction::Methods&, int64_t) {}
+
+Result PhysicalCollection::remove(transaction::Methods& trx, LocalDocumentId documentId,
+                                  ManagedDocumentResult& previous, OperationOptions& options,
+                                  bool lock, KeyLockInfo* keyLockInfo,
+                                  std::function<void()> const& cbDuringLock) {
+  return Result(TRI_ERROR_NOT_IMPLEMENTED);
+}
 
 bool PhysicalCollection::IndexOrder::operator()(const std::shared_ptr<Index>& left,
                                                 const std::shared_ptr<Index>& right) const {
diff --git a/arangod/StorageEngine/PhysicalCollection.h b/arangod/StorageEngine/PhysicalCollection.h
index 448f9f42d595..137c02942fa1 100644
--- a/arangod/StorageEngine/PhysicalCollection.h
+++ b/arangod/StorageEngine/PhysicalCollection.h
@@ -30,9 +30,11 @@
 
 #include "Basics/Common.h"
 #include "Basics/ReadWriteLock.h"
+#include "Containers/MerkleTree.h"
 #include "Futures/Future.h"
 #include "Indexes/Index.h"
 #include "Indexes/IndexIterator.h"
+#include "StorageEngine/ReplicationIterator.h"
 #include "Utils/OperationResult.h"
 #include "VocBase/voc-types.h"
 
@@ -139,6 +141,16 @@ class PhysicalCollection {
   virtual std::unique_ptr<IndexIterator> getAllIterator(transaction::Methods* trx) const = 0;
   virtual std::unique_ptr<IndexIterator> getAnyIterator(transaction::Methods* trx) const = 0;
 
+  /// @brief Get an iterator associated with the specified replication batch
+  virtual std::unique_ptr<ReplicationIterator> getReplicationIterator(ReplicationIterator::Ordering,
+                                                                      uint64_t batchId);
+
+  /// @brief Get an iterator associated with the specified transaction
+  virtual std::unique_ptr<ReplicationIterator> getReplicationIterator(
+      ReplicationIterator::Ordering, transaction::Methods&);
+
+  virtual void adjustNumberDocuments(transaction::Methods&, int64_t);
+
   ////////////////////////////////////
   // -- SECTION DML Operations --
   ///////////////////////////////////
@@ -160,9 +172,6 @@ class PhysicalCollection {
   virtual Result read(transaction::Methods*, arangodb::velocypack::StringRef const& key,
                       ManagedDocumentResult& result, bool lock) = 0;
 
-  virtual Result read(transaction::Methods*, arangodb::velocypack::Slice const& key,
-                      ManagedDocumentResult& result, bool lock) = 0;
-
   /// @brief read a documument referenced by token (internal method)
   virtual bool readDocument(transaction::Methods* trx, LocalDocumentId const& token,
                             ManagedDocumentResult& result) const = 0;
@@ -205,11 +214,27 @@ class PhysicalCollection {
                         bool lock, KeyLockInfo* keyLockInfo,
                         std::function<void()> const& cbDuringLock) = 0;
 
+  virtual Result remove(transaction::Methods& trx, LocalDocumentId documentId,
+                        ManagedDocumentResult& previous, OperationOptions& options,
+                        bool lock, KeyLockInfo* keyLockInfo,
+                        std::function<void()> const& cbDuringLock);
+
   /// @brief new object for insert, value must have _key set correctly.
   Result newObjectForInsert(transaction::Methods* trx, velocypack::Slice const& value,
                             bool isEdgeCollection, velocypack::Builder& builder,
                             bool isRestore, TRI_voc_rid_t& revisionId) const;
 
+  virtual std::unique_ptr<containers::RevisionTree> revisionTree(
+      transaction::Methods& trx);
+  virtual std::unique_ptr<containers::RevisionTree> revisionTree(uint64_t batchId);
+
+  virtual Result rebuildRevisionTree();
+
+  virtual void placeRevisionTreeBlocker(TRI_voc_tid_t transactionId);
+  virtual void removeRevisionTreeBlocker(TRI_voc_tid_t transactionId);
+
+  TRI_voc_rid_t newRevisionId() const;
+
  protected:
   PhysicalCollection(LogicalCollection& collection, arangodb::velocypack::Slice const& info);
 
@@ -218,8 +243,6 @@ class PhysicalCollection {
 
   // SECTION: Document pre commit preperation
 
-  TRI_voc_rid_t newRevisionId() const;
-
   bool isValidEdgeAttribute(velocypack::Slice const& slice) const;
 
   /// @brief new object for remove, must have _key set
diff --git a/lib/SimpleHttpClient/Options.h b/arangod/StorageEngine/ReplicationIterator.cpp
similarity index 59%
rename from lib/SimpleHttpClient/Options.h
rename to arangod/StorageEngine/ReplicationIterator.cpp
index 032c92d19150..b37d6d275cae 100644
--- a/lib/SimpleHttpClient/Options.h
+++ b/arangod/StorageEngine/ReplicationIterator.cpp
@@ -1,7 +1,8 @@
 ////////////////////////////////////////////////////////////////////////////////
 /// DISCLAIMER
 ///
-/// Copyright 2016 ArangoDB GmbH, Cologne, Germany
+/// Copyright 2014-2017 ArangoDB GmbH, Cologne, Germany
+/// Copyright 2004-2014 triAGENS GmbH, Cologne, Germany
 ///
 /// Licensed under the Apache License, Version 2.0 (the "License");
 /// you may not use this file except in compliance with the License.
@@ -17,29 +18,25 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Andreas Streichardt
-/// @author Frank Celler
+/// @author Dan Larkin-York
 ////////////////////////////////////////////////////////////////////////////////
 
-#ifndef ARANGODB_SIMPLE_HTTP_CLIENT_OPTIONS_H
-#define ARANGODB_SIMPLE_HTTP_CLIENT_OPTIONS_H 1
+#include "ReplicationIterator.h"
 
-#include <functional>
-#include <memory>
+namespace arangodb {
 
-#include <curl/curl.h>
+ReplicationIterator::ReplicationIterator(LogicalCollection& collection)
+    : _collection(collection) {}
 
-namespace arangodb {
-namespace communicator {
-class Options {
- public:
-  double requestTimeout = 120.0;
-  double connectionTimeout = 2.0;
-#ifdef ARANGODB_USE_GOOGLE_TESTS
-  std::shared_ptr<std::function<void(CURLcode)>> _curlRcFn;
-#endif
-};
-}  // namespace communicator
-}  // namespace arangodb
+LogicalCollection& ReplicationIterator::collection() const {
+  return _collection;
+}
 
-#endif
+RevisionReplicationIterator::RevisionReplicationIterator(LogicalCollection& collection)
+    : ReplicationIterator(collection) {}
+
+ReplicationIterator::Ordering RevisionReplicationIterator::order() const {
+  return Ordering::Revision;
+}
+
+}  // namespace arangodb
diff --git a/arangod/StorageEngine/ReplicationIterator.h b/arangod/StorageEngine/ReplicationIterator.h
new file mode 100644
index 000000000000..e66f58bfb050
--- /dev/null
+++ b/arangod/StorageEngine/ReplicationIterator.h
@@ -0,0 +1,79 @@
+////////////////////////////////////////////////////////////////////////////////
+/// DISCLAIMER
+///
+/// Copyright 2014-2017 ArangoDB GmbH, Cologne, Germany
+/// Copyright 2004-2014 triAGENS GmbH, Cologne, Germany
+///
+/// Licensed under the Apache License, Version 2.0 (the "License");
+/// you may not use this file except in compliance with the License.
+/// You may obtain a copy of the License at
+///
+///     http://www.apache.org/licenses/LICENSE-2.0
+///
+/// Unless required by applicable law or agreed to in writing, software
+/// distributed under the License is distributed on an "AS IS" BASIS,
+/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+/// See the License for the specific language governing permissions and
+/// limitations under the License.
+///
+/// Copyright holder is ArangoDB GmbH, Cologne, Germany
+///
+/// @author Dan Larkin-York
+////////////////////////////////////////////////////////////////////////////////
+
+#ifndef ARANGOD_STORAGE_ENGINE_REPLICATION_ITERATOR_H
+#define ARANGOD_STORAGE_ENGINE_REPLICATION_ITERATOR_H 1
+
+#include "Basics/Common.h"
+#include "VocBase/LocalDocumentId.h"
+#include "VocBase/vocbase.h"
+
+namespace arangodb {
+class Index;
+class LogicalCollection;
+
+namespace transaction {
+class Methods;
+}
+
+/// @brief a base class to iterate over the collection. An iterator is requested
+/// at the collection itself
+class ReplicationIterator {
+ public:
+  enum Ordering { Key, Revision };
+
+  ReplicationIterator(ReplicationIterator const&) = delete;
+  ReplicationIterator& operator=(ReplicationIterator const&) = delete;
+  ReplicationIterator() = delete;
+
+  ReplicationIterator(LogicalCollection&);
+
+  virtual ~ReplicationIterator() = default;
+
+  virtual Ordering order() const = 0;
+
+  /// @brief return the underlying collection
+  LogicalCollection& collection() const;
+
+  virtual bool hasMore() const = 0;
+  virtual void reset() = 0;
+
+ protected:
+  LogicalCollection& _collection;
+};
+
+class RevisionReplicationIterator : public ReplicationIterator {
+ public:
+  RevisionReplicationIterator(LogicalCollection&);
+
+  Ordering order() const override;
+
+  virtual TRI_voc_rid_t revision() const = 0;
+  virtual VPackSlice document() const = 0;
+
+  virtual void next() = 0;
+  virtual void seek(TRI_voc_rid_t) = 0;
+};
+
+}  // namespace arangodb
+#endif
diff --git a/arangod/Transaction/Manager.cpp b/arangod/Transaction/Manager.cpp
index 2c254333e2e0..0714b232485f 100644
--- a/arangod/Transaction/Manager.cpp
+++ b/arangod/Transaction/Manager.cpp
@@ -116,7 +116,7 @@ void Manager::registerTransaction(TRI_voc_tid_t transactionId,
                                   std::unique_ptr<TransactionData> data,
                                   bool isReadOnlyTransaction) {
   if (!isReadOnlyTransaction) {
-    _rwLock.readLock();
+    _rwLock.lockRead();
   }
 
   _nrRunning.fetch_add(1, std::memory_order_relaxed);
@@ -297,7 +297,7 @@ void Manager::unregisterAQLTrx(TRI_voc_tid_t tid) noexcept {
   TRI_ASSERT(it->second.type == MetaType::StandaloneAQL);
 
   /// we need to make sure no-one else is still using the TransactionState
-  if (!it->second.rwlock.writeLock(/*maxAttempts*/ 256)) {
+  if (!it->second.rwlock.lockWrite(/*maxAttempts*/ 256)) {
     LOG_TOPIC("9f7d7", ERR, Logger::TRANSACTIONS)
         << "a transaction is still in use";
     TRI_ASSERT(false);
@@ -524,12 +524,12 @@ std::shared_ptr<transaction::Context> Manager::leaseManagedTrx(TRI_voc_tid_t tid
             TRI_ERROR_TRANSACTION_DISALLOWED_OPERATION,
             "not allowed to write lock an AQL transaction");
       }
-      if (mtrx.rwlock.tryWriteLock()) {
+      if (mtrx.rwlock.tryLockWrite()) {
         state = mtrx.state;
         break;
       }
     } else {
-      if (mtrx.rwlock.tryReadLock()) {
+      if (mtrx.rwlock.tryLockRead()) {
         state = mtrx.state;
         break;
       }
diff --git a/arangod/Transaction/Methods.cpp b/arangod/Transaction/Methods.cpp
index 1568ce2a9418..7a0c90753e13 100644
--- a/arangod/Transaction/Methods.cpp
+++ b/arangod/Transaction/Methods.cpp
@@ -1281,7 +1281,6 @@ Future<OperationResult> transaction::Methods::documentAsync(std::string const& c
     THROW_ARANGO_EXCEPTION(TRI_ERROR_ARANGO_DOCUMENT_TYPE_INVALID);
   }
 
-  OperationResult result;
   if (_state->isCoordinator()) {
     return addTracking(documentCoordinator(cname, value, options), value,
                        [=](OperationResult const& opRes, VPackSlice data) {
diff --git a/arangod/Utils/OperationOptions.h b/arangod/Utils/OperationOptions.h
index 1415c194d093..5bb542334907 100644
--- a/arangod/Utils/OperationOptions.h
+++ b/arangod/Utils/OperationOptions.h
@@ -43,6 +43,7 @@ struct OperationOptions {
         returnNew(false),
         isRestore(false),
         overwrite(false),
+        ignoreUniqueConstraints(false),
         overwriteModeUpdate(false)
         {}
 
@@ -109,6 +110,10 @@ struct OperationOptions {
   // for insert operations: do not fail if _key exists but replace the document
   bool overwrite;
 
+  // for replication; only set true if you an guarantee that any conflicts have
+  // already been removed, and are simply not reflected in the transaction read
+  bool ignoreUniqueConstraints;
+  
   // above replace becomes an update
   bool overwriteModeUpdate;
 
diff --git a/arangod/V8Server/v8-actions.cpp b/arangod/V8Server/v8-actions.cpp
index 613ced16ba01..eb9a6b10d149 100644
--- a/arangod/V8Server/v8-actions.cpp
+++ b/arangod/V8Server/v8-actions.cpp
@@ -517,6 +517,7 @@ v8::Handle<v8::Object> TRI_RequestCppToV8(v8::Isolate* isolate,
     case rest::RequestType::DELETE_REQ: {
       TRI_GET_GLOBAL_STRING(DeleteConstant);
       req->Set(context, RequestTypeKey, DeleteConstant).FromMaybe(false);
+      setRequestBodyJsonOrVPack();
       break;
     }
     case rest::RequestType::HEAD: {
@@ -629,19 +630,26 @@ static void ResponseV8ToCpp(v8::Isolate* isolate, TRI_v8_global_t const* v8g,
   v8::Local<v8::Context> context = isolate->GetCurrentContext();
   TRI_ASSERT(request != nullptr);
 
-  rest::ResponseCode code = rest::ResponseCode::OK;
-
   using arangodb::Endpoint;
 
   // set response code
   TRI_GET_GLOBAL_STRING(ResponseCodeKey);
   if (TRI_HasProperty(context, isolate, res, ResponseCodeKey)) {
-    code = (rest::ResponseCode)(TRI_ObjectToInt64(isolate,
-                                                  res->Get(context,
-                                                           ResponseCodeKey
-                                                    ).FromMaybe(v8::Local<v8::Value>())));
+    uint64_t foxxcode = TRI_ObjectToInt64(isolate,
+                                          res->Get(context,
+                                                   ResponseCodeKey
+                                                   ).FromMaybe(v8::Local<v8::Value>()));
+    if (GeneralResponse::isValidResponseCode(foxxcode)) {
+      response->setResponseCode(static_cast<rest::ResponseCode>(foxxcode));
+    } else {
+      response->setResponseCode(rest::ResponseCode::SERVER_ERROR);
+      LOG_TOPIC("37d37", ERR, Logger::V8)
+        << "invalid http status code specified " << foxxcode
+        << " diverting to 500";
+    }
+  } else {
+    response->setResponseCode(rest::ResponseCode::OK);
   }
-  response->setResponseCode(code);
 
   // string should not be used
   std::string contentType = StaticStrings::MimeTypeJsonNoEncoding;
@@ -724,6 +732,7 @@ static void ResponseV8ToCpp(v8::Isolate* isolate, TRI_v8_global_t const* v8g,
 
           // what type is out? always json?
           httpResponse->body().appendText(out);
+          httpResponse->sealBody();
         } else {
           TRI_GET_GLOBAL_STRING(BodyKey);
           v8::Handle<v8::Value> b = res->Get(context, BodyKey).FromMaybe(v8::Local<v8::Value>());
@@ -732,6 +741,7 @@ static void ResponseV8ToCpp(v8::Isolate* isolate, TRI_v8_global_t const* v8g,
             auto obj = b.As<v8::Object>();
             httpResponse->body().appendText(V8Buffer::data(isolate, obj),
                                             V8Buffer::length(isolate, obj));
+            httpResponse->sealBody();
           } else if (autoContent && request->contentTypeResponse() == rest::ContentType::VPACK) {
             // use velocypack
             try {
@@ -744,10 +754,12 @@ static void ResponseV8ToCpp(v8::Isolate* isolate, TRI_v8_global_t const* v8g,
               httpResponse->setPayload(std::move(buffer));
             } catch (...) {
               httpResponse->body().appendText(TRI_ObjectToString(isolate, res->Get(context, BodyKey).FromMaybe(v8::Local<v8::Value>())));
+              httpResponse->sealBody();
             }
           } else {
             // treat body as a string
             httpResponse->body().appendText(TRI_ObjectToString(isolate, res->Get(context, BodyKey).FromMaybe(v8::Local<v8::Value>())));
+            httpResponse->sealBody();
           }
         }
       } break;
@@ -853,6 +865,7 @@ static void ResponseV8ToCpp(v8::Isolate* isolate, TRI_v8_global_t const* v8g,
         HttpResponse* httpResponse = dynamic_cast<HttpResponse*>(response);
         httpResponse->body().appendText(content, length);
         TRI_FreeString(content);
+        httpResponse->sealBody();
       }
       break;
 
diff --git a/arangod/VocBase/LogicalCollection.cpp b/arangod/VocBase/LogicalCollection.cpp
index 5780adcbcf99..6a6d8a63203f 100644
--- a/arangod/VocBase/LogicalCollection.cpp
+++ b/arangod/VocBase/LogicalCollection.cpp
@@ -35,6 +35,7 @@
 #include "Cluster/ClusterMethods.h"
 #include "Cluster/FollowerInfo.h"
 #include "Cluster/ServerState.h"
+#include "Replication/ReplicationFeature.h"
 #include "RestServer/DatabaseFeature.h"
 #include "Sharding/ShardingInfo.h"
 #include "StorageEngine/EngineSelectorFeature.h"
@@ -134,32 +135,40 @@ LogicalCollection::LogicalCollection(TRI_vocbase_t& vocbase, VPackSlice const& i
     : LogicalDataSource(
           LogicalCollection::category(),
           ::readType(info, StaticStrings::DataSourceType, TRI_COL_TYPE_UNKNOWN),
-          vocbase, Helper::extractIdValue(info),
-          ::readGloballyUniqueId(info),
+          vocbase, Helper::extractIdValue(info), ::readGloballyUniqueId(info),
           Helper::stringUInt64(info.get(StaticStrings::DataSourcePlanId)),
           ::readStringValue(info, StaticStrings::DataSourceName, ""), planVersion,
           TRI_vocbase_t::IsSystemName(
               ::readStringValue(info, StaticStrings::DataSourceName, "")) &&
               Helper::getBooleanValue(info, StaticStrings::DataSourceSystem, false),
           Helper::getBooleanValue(info, StaticStrings::DataSourceDeleted, false)),
-      _version(static_cast<Version>(Helper::getNumericValue<uint32_t>(info, "version",
-                                                    static_cast<uint32_t>(currentVersion())))),
+      _version(static_cast<Version>(Helper::getNumericValue<uint32_t>(
+          info, "version", static_cast<uint32_t>(currentVersion())))),
       _v8CacheVersion(0),
       _type(Helper::getNumericValue<TRI_col_type_e, int>(info, StaticStrings::DataSourceType,
-                                                          TRI_COL_TYPE_UNKNOWN)),
+                                                         TRI_COL_TYPE_UNKNOWN)),
       _status(Helper::getNumericValue<TRI_vocbase_col_status_e, int>(
           info, "status", TRI_VOC_COL_STATUS_CORRUPTED)),
       _isAStub(isAStub),
 #ifdef USE_ENTERPRISE
       _isSmart(Helper::getBooleanValue(info, StaticStrings::IsSmart, false)),
+      _isSmartChild(Helper::getBooleanValue(info, StaticStrings::IsSmartChild, false)),
 #endif
+      _usesRevisionsAsDocumentIds(
+          Helper::getBooleanValue(info, StaticStrings::UsesRevisionsAsDocumentIds, false)),
+      _minRevision(isSmartChild()
+                       ? 0
+                       : Helper::getNumericValue<TRI_voc_rid_t>(info, StaticStrings::MinRevision,
+                                                                0)),
       _waitForSync(Helper::getBooleanValue(info, StaticStrings::WaitForSyncString, false)),
       _allowUserKeys(Helper::getBooleanValue(info, "allowUserKeys", true)),
+      _syncByRevision(determineSyncByRevision()),
 #ifdef USE_ENTERPRISE
       _smartJoinAttribute(
           ::readStringValue(info, StaticStrings::SmartJoinAttribute, "")),
 #endif
       _physical(EngineSelectorFeature::ENGINE->createPhysicalCollection(*this, info)) {
+
   TRI_ASSERT(info.isObject());
 
   if (!TRI_vocbase_t::IsAllowedName(info)) {
@@ -175,7 +184,7 @@ LogicalCollection::LogicalCollection(TRI_vocbase_t& vocbase, VPackSlice const& i
     THROW_ARANGO_EXCEPTION_MESSAGE(TRI_ERROR_FAILED, errorMsg);
   }
 
-  auto res = updateValidators(info.get(StaticStrings::Validators));
+  auto res = updateValidators(info.get(StaticStrings::Validation));
   if(res.fail()){
     THROW_ARANGO_EXCEPTION(res);
   }
@@ -260,43 +269,21 @@ LogicalCollection::LogicalCollection(TRI_vocbase_t& vocbase, VPackSlice const& i
   return category;
 }
 
-Result LogicalCollection::updateValidators(VPackSlice validatorArray) {
+Result LogicalCollection::updateValidators(VPackSlice validatorSlice) {
   using namespace std::literals::string_literals;
-  if(validatorArray.isNone()) {
+  if(validatorSlice.isNone() || validatorSlice.isNull()) {
     return { TRI_ERROR_NO_ERROR };
-  } else if (!validatorArray.isArray()) {
-    return { TRI_ERROR_VALIDATION_BAD_PARAMETER, "Validators are not given in an array."};
+  } else if (!validatorSlice.isObject()) {
+    return {TRI_ERROR_VALIDATION_BAD_PARAMETER, "Validator description is not an object."};
   }
 
   std::shared_ptr<ValidatorVec> newVec = std::make_shared<ValidatorVec>();
-  for(VPackSlice validatorSlice : VPackArrayIterator(validatorArray)) {
-    if(!validatorSlice.isObject()){
-      return {TRI_ERROR_VALIDATION_BAD_PARAMETER, "Validator description is not an object."};
-    }
-
-    try {
-      std::unique_ptr<ValidatorBase> validator;
-      auto typeSlice = validatorSlice.get(StaticStrings::ValidatorParameterType);
-      if(typeSlice.isNone()) {
-        validator = std::make_unique<ValidatorAQL>(validatorSlice);
-      } else if (typeSlice.isString()) {
-        auto type = typeSlice.copyString();
-        std::transform(type.begin(),type.end(),type.begin(),[](unsigned char c){ return std::tolower(c); });
-        if (type == StaticStrings::ValidatorTypeAQL) {
-          validator = std::make_unique<ValidatorAQL>(validatorSlice);
-        } else if (type == StaticStrings::ValidatorTypeBool) {
-          validator = std::make_unique<ValidatorBool>(validatorSlice);
-        } else {
-          return {TRI_ERROR_BAD_PARAMETER, "Validator type '" + typeSlice.copyString() + "' is not supported."};
-        }
-      } else {
-        return {TRI_ERROR_BAD_PARAMETER, "Validator type is not a string."};
-      }
 
-      newVec->push_back(std::move(validator));
-    } catch (std::exception const& ex) {
-      return { TRI_ERROR_VALIDATION_BAD_PARAMETER, "Error when building validator: "s + ex.what() };
-    }
+  try {
+    auto validator = std::make_unique<ValidatorJsonSchema>(validatorSlice);
+    newVec->push_back(std::move(validator));
+  } catch (std::exception const& ex) {
+    return { TRI_ERROR_VALIDATION_BAD_PARAMETER, "Error when building validator: "s + ex.what() };
   }
 
   std::atomic_store_explicit(&_validators, newVec, std::memory_order_relaxed);
@@ -427,6 +414,10 @@ uint64_t LogicalCollection::numberDocuments(transaction::Methods* trx,
   return documents;
 }
 
+bool LogicalCollection::hasClusterWideUniqueRevs() const {
+  return usesRevisionsAsDocumentIds() && isSmartChild();
+}
+
 uint32_t LogicalCollection::v8CacheVersion() const { return _v8CacheVersion; }
 
 TRI_col_type_e LogicalCollection::type() const { return _type; }
@@ -475,10 +466,33 @@ TRI_voc_rid_t LogicalCollection::revision(transaction::Methods* trx) const {
   return _physical->revision(trx);
 }
 
+bool LogicalCollection::usesRevisionsAsDocumentIds() const {
+  return _usesRevisionsAsDocumentIds;
+}
+
+TRI_voc_rid_t LogicalCollection::minRevision() const {
+  return _minRevision;
+}
+
 std::unique_ptr<FollowerInfo> const& LogicalCollection::followers() const {
   return _followers;
 }
 
+bool LogicalCollection::syncByRevision() const { return _syncByRevision; }
+
+bool LogicalCollection::determineSyncByRevision() const {
+  if (!system() && version() >= LogicalCollection::Version::v37) {
+    auto& server = vocbase().server();
+    if (server.hasFeature<EngineSelectorFeature>() &&
+        server.hasFeature<ReplicationFeature>()) {
+      auto& engine = server.getFeature<EngineSelectorFeature>();
+      auto& replication = server.getFeature<ReplicationFeature>();
+      return engine.isRocksDB() && replication.syncByRevision();
+    }
+  }
+  return false;
+}
+
 IndexEstMap LogicalCollection::clusterIndexEstimates(bool allowUpdating, TRI_voc_tid_t tid) {
   return getPhysical()->clusterIndexEstimates(allowUpdating, tid);
 }
@@ -718,13 +732,17 @@ arangodb::Result LogicalCollection::appendVelocyPack(arangodb::velocypack::Build
 
   // Validators
   {
-    result.add(VPackValue(StaticStrings::Validators));
+    result.add(VPackValue(StaticStrings::Validation));
     validatorsToVelocyPack(result);
   }
 
   // Cluster Specific
   result.add(StaticStrings::IsSmart, VPackValue(isSmart()));
-
+  result.add(StaticStrings::IsSmartChild, VPackValue(isSmartChild()));
+  result.add(StaticStrings::UsesRevisionsAsDocumentIds,
+             VPackValue(usesRevisionsAsDocumentIds()));
+  result.add(StaticStrings::MinRevision, VPackValue(minRevision()));
+             
   if (hasSmartJoinAttribute()) {
     result.add(StaticStrings::SmartJoinAttribute, VPackValue(_smartJoinAttribute));
   }
@@ -797,7 +815,7 @@ arangodb::Result LogicalCollection::properties(velocypack::Slice const& slice, b
 
   MUTEX_LOCKER(guard, _infoLock);  // prevent simultaneous updates
 
-  auto res = updateValidators(slice.get(StaticStrings::Validators));
+  auto res = updateValidators(slice.get(StaticStrings::Validation));
   if(res.fail()){
     THROW_ARANGO_EXCEPTION(res);
   }
@@ -1006,11 +1024,16 @@ void LogicalCollection::persistPhysicalCollection() {
   getPhysical()->setPath(path);
 }
 
+basics::ReadWriteLock& LogicalCollection::statusLock() {
+  return _statusLock;
+}
+
 /// @brief Defer a callback to be executed when the collection
 ///        can be dropped. The callback is supposed to drop
 ///        the collection and it is guaranteed that no one is using
 ///        it at that moment.
 void LogicalCollection::deferDropCollection(std::function<bool(LogicalCollection&)> const& callback) {
+  _syncByRevision = false;  // safety to make sure we can do physical cleanup
   _physical->deferDropCollection(callback);
 }
 
@@ -1022,13 +1045,6 @@ Result LogicalCollection::read(transaction::Methods* trx,
   return getPhysical()->read(trx, key, result, lock);
 }
 
-Result LogicalCollection::read(transaction::Methods* trx,
-                               arangodb::velocypack::Slice const& key,
-                               ManagedDocumentResult& result, bool lock) {
-  TRI_IF_FAILURE("LogicalCollection::read") { return Result(TRI_ERROR_DEBUG); }
-  return getPhysical()->read(trx, key, result, lock);
-}
-
 ////////////////////////////////////////////////////////////////////////////////
 /// @brief processes a truncate operation (note: currently this only clears
 /// the read-cache
@@ -1128,30 +1144,30 @@ VPackSlice LogicalCollection::keyOptions() const {
 }
 
 void LogicalCollection::validatorsToVelocyPack(VPackBuilder& b) const {
-  VPackArrayBuilder guard(&b);
   auto vals = std::atomic_load_explicit(&_validators, std::memory_order_relaxed);
-  if (vals == nullptr) { return ; }
-  for(auto const& validator : *vals) {
-    validator->toVelocyPack(b);
+  if(vals == nullptr || vals->empty()){
+    b.add(VPackSlice::nullSlice());
+    return;
   }
+  vals->front()->toVelocyPack(b);
 }
 
-Result LogicalCollection::validate(VPackSlice s) const {
+Result LogicalCollection::validate(VPackSlice s, VPackOptions const* options) const {
   auto vals = std::atomic_load_explicit(&_validators, std::memory_order_relaxed);
   if (vals == nullptr) { return {}; }
   for(auto const& validator : *vals) {
-    if(!validator->validate(s, VPackSlice::noneSlice(), true)) {
+    if(!validator->validate(s, VPackSlice::noneSlice(), true, options)) {
       return {TRI_ERROR_VALIDATION_FAILED, "validation failed: " + validator->message() };
     }
   }
   return {};
 }
 
-Result LogicalCollection::validate(VPackSlice modifiedDoc, VPackSlice oldDoc) const {
+Result LogicalCollection::validate(VPackSlice modifiedDoc, VPackSlice oldDoc, VPackOptions const* options) const {
   auto vals = std::atomic_load_explicit(&_validators, std::memory_order_relaxed);
   if (vals == nullptr) { return {}; }
   for(auto const& validator : *vals) {
-    if(!validator->validate(modifiedDoc, oldDoc, false)) {
+    if(!validator->validate(modifiedDoc, oldDoc, false, options)) {
       return {TRI_ERROR_VALIDATION_FAILED, "validation failed: " + validator->message() };
     }
   }
diff --git a/arangod/VocBase/LogicalCollection.h b/arangod/VocBase/LogicalCollection.h
index 79381e285aec..b3c5e2640958 100644
--- a/arangod/VocBase/LogicalCollection.h
+++ b/arangod/VocBase/LogicalCollection.h
@@ -28,6 +28,7 @@
 #include "Basics/Common.h"
 #include "Basics/Mutex.h"
 #include "Basics/ReadWriteLock.h"
+#include "Containers/MerkleTree.h"
 #include "Futures/Future.h"
 #include "Indexes/IndexIterator.h"
 #include "Transaction/CountCache.h"
@@ -84,12 +85,7 @@ class LogicalCollection : public LogicalDataSource {
   LogicalCollection& operator=(LogicalCollection const&) = delete;
   virtual ~LogicalCollection();
 
-  enum class Version {
-    v30 = 5,
-    v31 = 6,
-    v33 = 7,
-    v34 = 8
-  };
+  enum class Version { v30 = 5, v31 = 6, v33 = 7, v34 = 8, v37 = 9 };
 
   //////////////////////////////////////////////////////////////////////////////
   /// @brief the category representing a logical collection
@@ -144,9 +140,13 @@ class LogicalCollection : public LogicalDataSource {
   void waitForSync(bool value) { _waitForSync = value; }
 #ifdef USE_ENTERPRISE
   bool isSmart() const { return _isSmart; }
+  bool isSmartChild() const { return _isSmartChild; }
 #else
   bool isSmart() const { return false; }
+  bool isSmartChild() const { return false; }
 #endif
+  bool usesRevisionsAsDocumentIds() const;
+  TRI_voc_rid_t minRevision() const;
   /// @brief is this a cluster-wide Plan (ClusterInfo) collection
   bool isAStub() const { return _isAStub; }
   /// @brief is this a cluster-wide Plan (ClusterInfo) collection
@@ -154,6 +154,8 @@ class LogicalCollection : public LogicalDataSource {
 
   bool hasSmartJoinAttribute() const { return !smartJoinAttribute().empty(); }
 
+  bool hasClusterWideUniqueRevs() const;
+
   /// @brief return the name of the smart join attribute (empty string
   /// if no smart join attribute is present)
   std::string const& smartJoinAttribute() const { return _smartJoinAttribute; }
@@ -270,8 +272,6 @@ class LogicalCollection : public LogicalDataSource {
   /// @brief reads an element from the document collection
   Result read(transaction::Methods* trx, arangodb::velocypack::StringRef const& key,
               ManagedDocumentResult& mdr, bool lock);
-  Result read(transaction::Methods*, arangodb::velocypack::Slice const&,
-              ManagedDocumentResult& result, bool lock);
 
   /// @brief processes a truncate operation
   Result truncate(transaction::Methods& trx, OperationOptions& options);
@@ -318,7 +318,7 @@ class LogicalCollection : public LogicalDataSource {
   void persistPhysicalCollection();
 
   /// lock protecting the status and name
-  basics::ReadWriteLock& statusLock() { return _statusLock; }
+  basics::ReadWriteLock& statusLock();
 
   /// @brief Defer a callback to be executed when the collection
   ///        can be dropped. The callback is supposed to drop
@@ -329,8 +329,8 @@ class LogicalCollection : public LogicalDataSource {
   // SECTION: Key Options
   velocypack::Slice keyOptions() const;
   void validatorsToVelocyPack(VPackBuilder&) const;
-  Result validate(VPackSlice newDoc) const; // insert
-  Result validate(VPackSlice modifiedDoc, VPackSlice oldDoc) const; // update / replace
+  Result validate(VPackSlice newDoc, VPackOptions const*) const; // insert
+  Result validate(VPackSlice modifiedDoc, VPackSlice oldDoc, VPackOptions const*) const; // update / replace
 
   // Get a reference to this KeyGenerator.
   // Caller is not allowed to free it.
@@ -340,6 +340,8 @@ class LogicalCollection : public LogicalDataSource {
 
   std::unique_ptr<FollowerInfo> const& followers() const;
 
+  bool syncByRevision() const;
+
  protected:
   virtual arangodb::Result appendVelocyPack(arangodb::velocypack::Builder& builder,
                                            Serialization context) const override;
@@ -351,6 +353,8 @@ class LogicalCollection : public LogicalDataSource {
 
   void increaseV8Version();
 
+  bool determineSyncByRevision() const;
+
   transaction::CountCache _countCache;
 
  protected:
@@ -379,13 +383,21 @@ class LogicalCollection : public LogicalDataSource {
 #ifdef USE_ENTERPRISE
   // @brief Flag if this collection is a smart one. (Enterprise only)
   bool const _isSmart;
+  // @brief Flag if this collection is a child of a smart collection (Enterprise only)
+  bool const _isSmartChild;
 #endif
 
+  bool const _usesRevisionsAsDocumentIds;
+
+  TRI_voc_rid_t const _minRevision;
+
   // SECTION: Properties
   bool _waitForSync;
 
   bool const _allowUserKeys;
 
+  bool _syncByRevision;
+
   std::string _smartJoinAttribute;
 
   // SECTION: Key Options
diff --git a/arangod/VocBase/Methods/Collections.cpp b/arangod/VocBase/Methods/Collections.cpp
index 2181692783fd..6e21177232ca 100644
--- a/arangod/VocBase/Methods/Collections.cpp
+++ b/arangod/VocBase/Methods/Collections.cpp
@@ -46,6 +46,7 @@
 #include "Scheduler/SchedulerFeature.h"
 #include "Sharding/ShardingFeature.h"
 #include "Sharding/ShardingInfo.h"
+#include "StorageEngine/EngineSelectorFeature.h"
 #include "StorageEngine/PhysicalCollection.h"
 #include "Transaction/Helpers.h"
 #include "Transaction/V8Context.h"
@@ -256,6 +257,9 @@ Result Collections::create(TRI_vocbase_t& vocbase,
   TRI_ASSERT(!vocbase.isDangling());
   bool haveShardingFeature = ServerState::instance()->isCoordinator() &&
                              vocbase.server().hasFeature<ShardingFeature>();
+  bool addUseRevs = ServerState::instance()->isSingleServerOrCoordinator();
+  bool useRevs =
+      vocbase.server().getFeature<arangodb::EngineSelectorFeature>().isRocksDB();
   VPackBuilder builder;
   VPackBuilder helper;
   builder.openArray();
@@ -287,6 +291,15 @@ Result Collections::create(TRI_vocbase_t& vocbase,
     helper.add(arangodb::StaticStrings::DataSourceType, VPackValue(static_cast<int>(info.collectionType)));
     helper.add(arangodb::StaticStrings::DataSourceName, VPackValue(info.name));
 
+    if (addUseRevs) {
+      helper.add(arangodb::StaticStrings::UsesRevisionsAsDocumentIds,
+                 arangodb::velocypack::Value(useRevs));
+      bool isSmartChild =
+          Helper::getBooleanValue(info.properties, StaticStrings::IsSmartChild, false);
+      TRI_voc_rid_t minRev = isSmartChild ? 0 : TRI_HybridLogicalClock();
+      helper.add(arangodb::StaticStrings::MinRevision, arangodb::velocypack::Value(minRev));
+    }
+
     if (ServerState::instance()->isCoordinator()) {
       auto replicationFactorSlice = info.properties.get(StaticStrings::ReplicationFactor);
       if (replicationFactorSlice.isNone()) {
diff --git a/arangod/VocBase/Validators.cpp b/arangod/VocBase/Validators.cpp
index 096f13359162..19c8b6d92514 100644
--- a/arangod/VocBase/Validators.cpp
+++ b/arangod/VocBase/Validators.cpp
@@ -21,9 +21,15 @@
 /// @author Jan Christoph Uhde
 ////////////////////////////////////////////////////////////////////////////////
 
+
 #include "Validators.h"
 #include <Basics/Exceptions.h>
 #include <Basics/StaticStrings.h>
+#include <Logger/LogMacros.h>
+
+#include <tao/json/contrib/schema.hpp>
+#include <tao/json/jaxn/to_string.hpp>
+#include <validation/validation.hpp>
 
 namespace arangodb {
 
@@ -74,7 +80,7 @@ ValidatorBase::ValidatorBase(VPackSlice params)
   }
 }
 
-bool ValidatorBase::validate(VPackSlice newDoc, VPackSlice oldDoc, bool isInsert) const {
+bool ValidatorBase::validate(VPackSlice newDoc, VPackSlice oldDoc, bool isInsert, VPackOptions const* options) const {
   // This function performs the validation depending on operation (Insert /
   // Update / Replace) and requested validation level (None / Insert / New /
   // Strict / Moderate).
@@ -84,7 +90,7 @@ bool ValidatorBase::validate(VPackSlice newDoc, VPackSlice oldDoc, bool isInsert
   }
 
   if (isInsert) {
-    return this->validateDerived(newDoc);
+    return this->validateDerived(newDoc, options);
   }
 
   /* update replace case */
@@ -95,13 +101,13 @@ bool ValidatorBase::validate(VPackSlice newDoc, VPackSlice oldDoc, bool isInsert
 
   if (this->_level == ValidationLevel::Strict) {
     // Changed document must be good!
-    return validateDerived(newDoc);
+    return validateDerived(newDoc, options);
   }
 
   TRI_ASSERT(this->_level == ValidationLevel::Moderate);
   // Changed document must be good IIF the unmodified
   // document passed validation.
-  return (this->validateDerived(newDoc) || !this->validateDerived(oldDoc));
+  return (this->validateDerived(newDoc, options) || !this->validateDerived(oldDoc, options));
 }
 
 void ValidatorBase::toVelocyPack(VPackBuilder& b) const {
@@ -117,7 +123,7 @@ void ValidatorBase::toVelocyPack(VPackBuilder& b) const {
 ValidatorBool::ValidatorBool(VPackSlice params) : ValidatorBase(params) {
   _result = params.get(StaticStrings::ValidatorParameterRule).getBool();
 }
-bool ValidatorBool::validateDerived(VPackSlice slice) const { return _result; }
+bool ValidatorBool::validateDerived(VPackSlice slice, VPackOptions const* options) const { return _result; }
 void ValidatorBool::toVelocyPackDerived(VPackBuilder& b) const {
   b.add(StaticStrings::ValidatorParameterRule, VPackValue(_result));
 }
@@ -127,13 +133,21 @@ std::string const ValidatorBool::type() const {
 
 /////////////////////////////////////////////////////////////////////////////
 
-ValidatorAQL::ValidatorAQL(VPackSlice params) : ValidatorBase(params) {}
-bool ValidatorAQL::validateDerived(VPackSlice slice) const { return true; }
-void ValidatorAQL::toVelocyPackDerived(VPackBuilder& b) const {
-  b.add(StaticStrings::ValidatorParameterRule, VPackValue(std::string("test")));
+ValidatorJsonSchema::ValidatorJsonSchema(VPackSlice params) : ValidatorBase(params) {
+  auto rule = params.get(StaticStrings::ValidatorParameterRule);
+  auto taoRuleValue = validation::slice_to_value(rule);
+  LOG_TOPIC("aa245", TRACE, arangodb::Logger::VALIDATION) << "using schema: " << tao::json::jaxn::to_string(taoRuleValue,2);
+  _schema = std::make_shared<tao::json::schema>(taoRuleValue);
+  _builder.add(rule);
+}
+bool ValidatorJsonSchema::validateDerived(VPackSlice slice, VPackOptions const* options) const {
+  return validation::validate(slice, options, *_schema);
+}
+void ValidatorJsonSchema::toVelocyPackDerived(VPackBuilder& b) const {
+  b.add(StaticStrings::ValidatorParameterRule, _builder.slice());
 }
-std::string const ValidatorAQL::type() const {
-  return StaticStrings::ValidatorTypeAQL;
+std::string const ValidatorJsonSchema::type() const {
+  return StaticStrings::ValidatorTypeJsonSchema;
 }
 
 }  // namespace arangodb
diff --git a/arangod/VocBase/Validators.h b/arangod/VocBase/Validators.h
index 366a51c9b786..25c379f11401 100644
--- a/arangod/VocBase/Validators.h
+++ b/arangod/VocBase/Validators.h
@@ -28,9 +28,17 @@
 #include <velocypack/Builder.h>
 #include <velocypack/Slice.h>
 #include <velocypack/StringRef.h>
+#include <velocypack/Options.h>
 #include <velocypack/velocypack-aliases.h>
 #include <string>
 
+#include <tao/json/forward.hpp>
+
+namespace tao::json {
+   template< template< typename... > class Traits >
+   class basic_schema;
+}
+
 namespace arangodb {
 
 enum class ValidationLevel {
@@ -44,29 +52,32 @@ struct ValidatorBase {
   explicit ValidatorBase(VPackSlice params);
   virtual ~ValidatorBase() = default;
 
-  bool validate(VPackSlice new_, VPackSlice old_, bool isInsert) const;
+  bool validate(VPackSlice new_, VPackSlice old_, bool isInsert, VPackOptions const*) const;
   void toVelocyPack(VPackBuilder&) const;
   virtual std::string const type() const = 0;
   std::string const message() const { return this->_message; }
 
  protected:
-  virtual bool validateDerived(VPackSlice slice) const = 0;
+  virtual bool validateDerived(VPackSlice slice, VPackOptions const*) const = 0;
   virtual void toVelocyPackDerived(VPackBuilder&) const = 0;
 
   std::string _message;
   ValidationLevel _level;
 };
 
-struct ValidatorAQL : public ValidatorBase {
-  explicit ValidatorAQL(VPackSlice params);
-  bool validateDerived(VPackSlice slice) const override;
+struct ValidatorJsonSchema : public ValidatorBase {
+  explicit ValidatorJsonSchema(VPackSlice params);
+  bool validateDerived(VPackSlice slice, VPackOptions const*) const override;
   void toVelocyPackDerived(VPackBuilder& b) const override;
   std::string const type() const override;
+private:
+  std::shared_ptr<tao::json::basic_schema<tao::json::traits>> _schema;
+  VPackBuilder _builder;
 };
 
 struct ValidatorBool : public ValidatorBase {
   explicit ValidatorBool(VPackSlice params);
-  bool validateDerived(VPackSlice slice) const override;
+  bool validateDerived(VPackSlice slice, VPackOptions const*) const override;
   void toVelocyPackDerived(VPackBuilder& b) const override;
   std::string const type() const override;
 
diff --git a/arangosh/Benchmark/test-cases.h b/arangosh/Benchmark/test-cases.h
index b8b1ee500508..41452cff2660 100644
--- a/arangosh/Benchmark/test-cases.h
+++ b/arangosh/Benchmark/test-cases.h
@@ -22,7 +22,7 @@
 ////////////////////////////////////////////////////////////////////////////////
 
 #include "Basics/Common.h"
-
+#include "Basics/StringUtils.h"
 #include "Random/RandomGenerator.h"
 
 static bool DeleteCollection(SimpleHttpClient*, std::string const&);
@@ -1549,13 +1549,28 @@ static bool CreateCollection(SimpleHttpClient* client, std::string const& name,
   std::unique_ptr<SimpleHttpResult> result(client->request(rest::RequestType::POST, "/_api/collection",
                            payload.c_str(), payload.size(), headerFields));
 
-  bool failed = true;
-
-  if (result != nullptr) {
-    int statusCode = result->getHttpReturnCode();
-    if (statusCode == 200 || statusCode == 201 || statusCode == 202) {
-      failed = false;
+  if (result == nullptr) {
+    LOG_TOPIC("03767", FATAL, Logger::FIXME) << "got no response from server when trying to create collection";
+    FATAL_ERROR_EXIT();
+  } 
+  int statusCode = result->getHttpReturnCode();
+  if (statusCode >= 400) {
+    std::string errorMsg = result->getHttpReturnMessage();
+    std::shared_ptr<arangodb::velocypack::Builder> bodyBuilder(result->getBodyVelocyPack());
+    arangodb::velocypack::Slice error = bodyBuilder->slice();
+    if (!error.isNone() && error.hasKey(arangodb::StaticStrings::ErrorMessage)) {
+      errorMsg = error.get(arangodb::StaticStrings::ErrorMessage).copyString();
     }
+    LOG_TOPIC("44810", FATAL, Logger::FIXME) 
+      << "got error message when trying to create collection: " 
+      << "HTTP " << arangodb::basics::StringUtils::itoa(result->getHttpReturnCode()) << ": " 
+      << errorMsg;
+    FATAL_ERROR_EXIT();
+  }
+
+  bool failed = true;
+  if (statusCode == 200 || statusCode == 201 || statusCode == 202) {
+    failed = false;
   }
 
   return !failed;
diff --git a/arangosh/Restore/RestoreFeature.cpp b/arangosh/Restore/RestoreFeature.cpp
index 60c5b59de290..04ad37f76de9 100644
--- a/arangosh/Restore/RestoreFeature.cpp
+++ b/arangosh/Restore/RestoreFeature.cpp
@@ -583,9 +583,13 @@ arangodb::Result sendRestoreData(arangodb::httpclient::SimpleHttpClient& httpCli
     bufferSize = cleaned.length();
   }
 
-  std::string const url = "/_api/replication/restore-data?collection=" + urlEncode(cname) +
-                          "&force=" + (options.force ? "true" : "false");
-  
+  std::string const url =
+      "/_api/replication/restore-data?collection=" + urlEncode(cname) +
+      "&force=" + (options.force ? "true" : "false") +
+      (options.preserveRevisionIds
+           ? ("&" + arangodb::StaticStrings::PreserveRevisionIds + "=true")
+           : "");
+
   std::unordered_map<std::string, std::string> headers;
   headers.emplace(arangodb::StaticStrings::ContentTypeHeader,
                   arangodb::StaticStrings::MimeTypeDump);
@@ -1363,6 +1367,14 @@ void RestoreFeature::collectOptions(std::shared_ptr<options::ProgramOptions> opt
           arangodb::options::makeDefaultFlags(arangodb::options::Flags::Hidden))
       .setDeprecatedIn(30322)
       .setDeprecatedIn(30402);
+
+  options
+      ->addOption(
+          "--preserve-revision-ids",
+          "preserve `_rev` values for the documents (potentially unsafe)",
+          new BooleanParameter(&_options.preserveRevisionIds),
+          arangodb::options::makeDefaultFlags(options::Flags::Hidden))
+      .setIntroducedIn(30700);
 }
 
 void RestoreFeature::validateOptions(std::shared_ptr<options::ProgramOptions> options) {
diff --git a/arangosh/Restore/RestoreFeature.h b/arangosh/Restore/RestoreFeature.h
index e0591e37ab73..359ee30f043c 100644
--- a/arangosh/Restore/RestoreFeature.h
+++ b/arangosh/Restore/RestoreFeature.h
@@ -92,6 +92,7 @@ class RestoreFeature final : public application_features::ApplicationFeature {
     bool overwrite{true};
     bool cleanupDuplicateAttributes{false};
     bool progress{true};
+    bool preserveRevisionIds{false};
   };
 
   /// @brief Stores stats about the overall restore progress
diff --git a/arangosh/Shell/V8ClientConnection.cpp b/arangosh/Shell/V8ClientConnection.cpp
index 2794f8298dd4..116ca8fafc95 100644
--- a/arangosh/Shell/V8ClientConnection.cpp
+++ b/arangosh/Shell/V8ClientConnection.cpp
@@ -1757,7 +1757,6 @@ v8::Local<v8::Value> V8ClientConnection::requestDataRaw(
                                  "not connected");
     return v8::Undefined(isolate);
   }
-
   fu::Error rc = fu::Error::NoError;
   std::unique_ptr<fu::Response> response;
   try {
@@ -1817,25 +1816,53 @@ v8::Local<v8::Value> V8ClientConnection::requestDataRaw(
                 v8::Boolean::New(isolate, false)).FromMaybe(false);
   }
 
-  // got a body, copy it into the result
-  auto sb = response->payload();
-  if (sb.size() > 0) {
-    const char* str = reinterpret_cast<const char*>(sb.data());
-    v8::Local<v8::String> b = TRI_V8_PAIR_STRING(isolate, str, sb.size());
+  v8::Local<v8::Object> headers = v8::Object::New(isolate);
+  auto responseBody = response->payload();
+  if (response->contentType() != fuerte::ContentType::Custom) {
+    if ((responseBody.size() > 0) && response->isContentTypeVPack()) {
+      std::vector<VPackSlice> const& slices = response->slices();
+      if (!slices.empty()) {
+        result->Set(context,
+                    TRI_V8_ASCII_STRING(isolate, "parsedBody"),
+                    TRI_VPackToV8(isolate, slices[0])).FromMaybe(false);
+      }
+    }
+    if (responseBody.size() > 0) {
+      const char* bodyStr = reinterpret_cast<const char*>(responseBody.data());
+      v8::Local<v8::String> b = TRI_V8_PAIR_STRING(isolate, bodyStr, responseBody.size());
+      result->Set(context,
+                  TRI_V8_ASCII_STRING(isolate, "body"), b).FromMaybe(false);
+    }
+
+    auto contentType = TRI_V8_STD_STRING(isolate, fu::to_string(response->contentType()));
+    headers->Set(context,
+                 TRI_V8_STD_STRING(isolate, StaticStrings::ContentTypeHeader), contentType).FromMaybe(false);
+  } else {
+    V8Buffer* buffer = V8Buffer::New
+      (isolate,
+       static_cast<char const*>(responseBody.data()),
+       responseBody.size());
+    auto bufObj = v8::Local<v8::Object>::New(isolate, buffer->_handle);
     result->Set(context,
-                TRI_V8_ASCII_STRING(isolate, "body"), b).FromMaybe(false);
+                TRI_V8_ASCII_STRING(isolate, "body"),
+                bufObj).FromMaybe(false);
   }
-
-  // copy all headers
-  v8::Local<v8::Object> headers = v8::Object::New(isolate);
+  
   for (auto const& it : response->header.meta()) {
     headers->Set(context,
-                TRI_V8_STD_STRING(isolate, it.first),
+                 TRI_V8_STD_STRING(isolate, it.first),
                  TRI_V8_STD_STRING(isolate, it.second)).FromMaybe(false);
   }
-  auto content = TRI_V8_STD_STRING(isolate, fu::to_string(response->contentType()));
-  headers->Set(context,
-               TRI_V8_STD_STRING(isolate, StaticStrings::ContentTypeHeader), content).FromMaybe(false);
+
+  if ((_builder.protocolType() == fu::ProtocolType::Vst) &&
+      (method != fu::RestVerb::Head)) {
+    // VST only adds a content-length header in case of head, since else its
+    // part of the protocol.
+    headers->Set(context,
+                 TRI_V8_STD_STRING(isolate, StaticStrings::ContentLength),
+                 TRI_V8_STD_STRING(isolate, std::to_string(responseBody.size()))).FromMaybe(false);
+    
+  }
 
   result->Set(context,
               TRI_V8_ASCII_STRING(isolate, "headers"), headers).FromMaybe(false);
diff --git a/js/client/modules/@arangodb/arango-collection.js b/js/client/modules/@arangodb/arango-collection.js
index 3313710339ba..9ee12f93bb25 100644
--- a/js/client/modules/@arangodb/arango-collection.js
+++ b/js/client/modules/@arangodb/arango-collection.js
@@ -373,7 +373,8 @@ ArangoCollection.prototype.properties = function (properties) {
     'distributeShardsLike': false,
     'shardingStrategy': false,
     'cacheEnabled': true,
-    'validators' : [ ]
+    'usesRevisionsAsDocumentIds': false,
+    'validation' : null
   };
   var a;
 
@@ -387,7 +388,6 @@ ArangoCollection.prototype.properties = function (properties) {
 
     for (a in attributes) {
       if (attributes.hasOwnProperty(a) &&
-        attributes[a] &&
         properties.hasOwnProperty(a)) {
         body[a] = properties[a];
       }
diff --git a/js/client/modules/@arangodb/arango-database.js b/js/client/modules/@arangodb/arango-database.js
index 85606c32278a..10ad85fd63ed 100644
--- a/js/client/modules/@arangodb/arango-database.js
+++ b/js/client/modules/@arangodb/arango-database.js
@@ -331,7 +331,7 @@ ArangoDatabase.prototype._create = function (name, properties, type, options) {
       'doCompact', 'keyOptions', 'shardKeys', 'numberOfShards',
       'distributeShardsLike', 'indexBuckets', 'id', 'isSmart',
       'replicationFactor', 'minReplicationFactor', 'writeConcern', 'shardingStrategy', 'smartGraphAttribute',
-      'smartJoinAttribute', 'avoidServers', 'cacheEnabled', 'validators'].forEach(function (p) {
+      'smartJoinAttribute', 'avoidServers', 'cacheEnabled', 'validation'].forEach(function (p) {
       if (properties.hasOwnProperty(p)) {
         body[p] = properties[p];
       }
diff --git a/js/client/modules/@arangodb/crash-utils.js b/js/client/modules/@arangodb/crash-utils.js
index bffbb034020b..efe9866255e7 100755
--- a/js/client/modules/@arangodb/crash-utils.js
+++ b/js/client/modules/@arangodb/crash-utils.js
@@ -69,13 +69,13 @@ let GDB_OUTPUT = '';
 function analyzeCoreDump (instanceInfo, options, storeArangodPath, pid) {
   let gdbOutputFile = fs.getTempFile();
 
-  let command;
-  command = '(';
+  let command = 'ulimit -c 0; (';
   command += 'printf \'' +
     'set logging file ' + gdbOutputFile + '\\n' +
     'set logging on\\n' +
-    'bt full\\n' +
+    'bt\\n' +
     'thread apply all bt\\n'+
+    'bt full\\n' +
     '\';';
 
   command += 'sleep 10;';
diff --git a/js/client/modules/@arangodb/process-utils.js b/js/client/modules/@arangodb/process-utils.js
index de8a5abe339c..a4f132975180 100755
--- a/js/client/modules/@arangodb/process-utils.js
+++ b/js/client/modules/@arangodb/process-utils.js
@@ -568,17 +568,23 @@ function initProcessStats(instanceInfo) {
 }
 
 function getDeltaProcessStats(instanceInfo) {
-  let deltaStats = {};
-  instanceInfo.arangods.forEach((arangod) => {
-    let newStats = getProcessStats(arangod.pid);
-    let myDeltaStats = {};
-    for (let key in arangod.stats) {
-      myDeltaStats[key] = newStats[key] - arangod.stats[key];
-    }
-    deltaStats[arangod.pid + '_' + arangod.role] = myDeltaStats;
-    arangod.stats = newStats;
-  });
-  return deltaStats;
+  try {
+    let deltaStats = {};
+    instanceInfo.arangods.forEach((arangod) => {
+      let newStats = getProcessStats(arangod.pid);
+      let myDeltaStats = {};
+      for (let key in arangod.stats) {
+        myDeltaStats[key] = newStats[key] - arangod.stats[key];
+      }
+      deltaStats[arangod.pid + '_' + arangod.role] = myDeltaStats;
+      arangod.stats = newStats;
+    });
+    return deltaStats;
+  }
+  catch (x) {
+    print("aborting stats generation");
+    return {};
+  }
 }
 
 function summarizeStats(deltaStats) {
diff --git a/js/client/modules/@arangodb/replication.js b/js/client/modules/@arangodb/replication.js
index 8f90bb993182..c4d601720956 100644
--- a/js/client/modules/@arangodb/replication.js
+++ b/js/client/modules/@arangodb/replication.js
@@ -215,11 +215,13 @@ globalApplier.properties = function (config) { return applierProperties(true, co
 var waitForResult = function (config, id) {
   const db = internal.db;
 
+  let sleepTime = 0.05;
+
   if (!config.hasOwnProperty('progress')) {
     config.progress = true;
   }
 
-  internal.sleep(1);
+  internal.sleep(sleepTime);
   var iterations = 0;
 
   while (true) {
@@ -235,10 +237,10 @@ var waitForResult = function (config, id) {
     }
 
     ++iterations;
-    if (iterations < 6) {
-      internal.sleep(2);
+    if (iterations > 6) {
+      internal.sleep(sleepTime);
     } else {
-      internal.sleep(3);
+      internal.sleep(sleepTime);
     }
 
     if (config.progress && iterations % 3 === 0) {
diff --git a/js/client/modules/@arangodb/result-processing.js b/js/client/modules/@arangodb/result-processing.js
index 4613f271ca7d..d8254d23dc43 100644
--- a/js/client/modules/@arangodb/result-processing.js
+++ b/js/client/modules/@arangodb/result-processing.js
@@ -411,7 +411,6 @@ function unitTestPrettyPrintResults (options, results) {
           }
 
           let details = successCases[name];
-
           if (details.skipped) {
             SuccessMessages += YELLOW + '    [SKIPPED] ' + name + RESET + '\n';
           } else {
@@ -443,7 +442,11 @@ function unitTestPrettyPrintResults (options, results) {
             continue;
           }
 
-          m = '    [FAILED]  ' + name;
+          if (name === 'SKIPPED') {
+            m = '    [SKIPPED]  the following tests were skipped due to the server not being in a trustworthy state anymore.';
+          } else {
+            m = '    [FAILED]  ' + name;
+          }
           failedMessages += RED + m + RESET + '\n\n';
           onlyFailedMessages += m + '\n\n';
 
diff --git a/js/client/modules/@arangodb/test-utils.js b/js/client/modules/@arangodb/test-utils.js
index 7e8e473d040c..5a2999767ced 100755
--- a/js/client/modules/@arangodb/test-utils.js
+++ b/js/client/modules/@arangodb/test-utils.js
@@ -207,7 +207,7 @@ function performTests (options, testList, testname, runFn, serverOptions, startS
         if (!continueTesting) {
 
           if (!results.hasOwnProperty('SKIPPED')) {
-            print('oops! Skipping remaining tests, server is gone.');
+            print('oops! Skipping remaining tests, server is unavailable for testing.');
 
             results['SKIPPED'] = {
               status: false,
@@ -215,7 +215,7 @@ function performTests (options, testList, testname, runFn, serverOptions, startS
             };
             results[te] = {
               status: false,
-              message: 'server crashed'
+              message: 'server unavailable for testing: ' + results[te].message
             };
           } else {
             if (results['SKIPPED'].message !== '') {
@@ -233,6 +233,7 @@ function performTests (options, testList, testname, runFn, serverOptions, startS
         let reply = runFn(options, instanceInfo, te, env);
 
         if (reply.hasOwnProperty('forceTerminate')) {
+          results[te] = reply;
           continueTesting = false;
           forceTerminate = true;
           continue;
@@ -342,7 +343,7 @@ function performTests (options, testList, testname, runFn, serverOptions, startS
           continueTesting = false;
           results[te] = {
             status: false,
-            message: 'server is dead.'
+            message: 'server is dead: + ' + results[te].message
           };
         }
         
diff --git a/js/client/modules/@arangodb/testsuites/resilience.js b/js/client/modules/@arangodb/testsuites/resilience.js
index 207cb4b8cd05..bbdf740b9e22 100644
--- a/js/client/modules/@arangodb/testsuites/resilience.js
+++ b/js/client/modules/@arangodb/testsuites/resilience.js
@@ -25,8 +25,6 @@
 // @author Max Neunhoeffer
 // /////////////////////////////////////////////////////////////////////////////
 
-const _ = require("lodash");
-
 const functionsDocumentation = {
   'resilience_move': 'resilience "move" tests',
   'resilience_move_view': 'resilience "move view" tests',
@@ -43,6 +41,7 @@ const optionsDocumentation = [
 ];
 
 const tu = require('@arangodb/test-utils');
+const _ = require('lodash');
 
 const testPaths = {
   'resilience_move': [tu.pathForTesting('server/resilience/move')],
@@ -65,17 +64,19 @@ var _resilience = function(path) {
   this.func = function resilience (options) {
     let suiteName = path;
     let testCases = tu.scanTestPaths(testPaths[path], options);
-    options.cluster = true;
-    options.propagateInstanceInfo = true;
-    if (options.test !== undefined) {
+    let localOptions = _.clone(options);
+    localOptions.cluster = true;
+    localOptions.propagateInstanceInfo = true;
+    localOptions.oneTestTimeout = 1800;
+    if (localOptions.test !== undefined) {
       // remove non ascii characters from our working directory:
       //                                       < A                           > Z && < a                   > z
-      suiteName += '_' + options.test.replace(/[\x00-\x40]/g, "_").replace(/[\x5B-\x60]/g, "_").replace(/[\x7B-\xFF]/g, "_");
+      suiteName += '_' + localOptions.test.replace(/[\x00-\x40]/g, "_").replace(/[\x5B-\x60]/g, "_").replace(/[\x7B-\xFF]/g, "_");
     }
-    if (options.dbServers < 5) {
-      options.dbServers = 5;
+    if (localOptions.dbServers < 5) {
+      localOptions.dbServers = 5;
     }
-    return tu.performTests(options, testCases, suiteName, tu.runThere, {
+    return tu.performTests(localOptions, testCases, suiteName, tu.runThere, {
       'javascript.allow-external-process-control': 'true',
       'javascript.allow-port-testing': 'true',
     });
diff --git a/js/client/modules/@arangodb/testsuites/server_permissions.js b/js/client/modules/@arangodb/testsuites/server_permissions.js
index 866860d0f768..6e79519a489c 100644
--- a/js/client/modules/@arangodb/testsuites/server_permissions.js
+++ b/js/client/modules/@arangodb/testsuites/server_permissions.js
@@ -175,12 +175,18 @@ function server_secrets(options) {
   copyOptions['protocol'] = "ssl";
 
   const testCases = tu.scanTestPaths([tu.pathForTesting('client/server_secrets')], copyOptions);
-  return tu.performTests(copyOptions, testCases, 'server_secrets', tu.runInLocalArangosh, {
+  let additionalArguments = {
     'server.authentication': 'true',
     'server.jwt-secret-folder': secretsDir,
     'cluster.create-waits-for-sync-replication': false,
     'ssl.keyfile': keyfileName
-  });
+  };
+  let version = global.ARANGODB_CLIENT_VERSION(true);
+  if (version.hasOwnProperty('enterprise-version')) {
+    additionalArguments['ssl.server-name-indication']
+      = "hans.arangodb.com=./UnitTests/tls.keyfile";
+  }
+  return tu.performTests(copyOptions, testCases, 'server_secrets', tu.runInLocalArangosh, additionalArguments);
 }
 
 exports.setup = function (testFns, defaultFns, opts, fnDocs, optionsDoc, allTestPaths) {
diff --git a/js/common/bootstrap/errors.js b/js/common/bootstrap/errors.js
index f8ad0d8f2ffb..3b234dc633da 100644
--- a/js/common/bootstrap/errors.js
+++ b/js/common/bootstrap/errors.js
@@ -42,8 +42,6 @@
     "ERROR_CANNOT_READ_FILE"       : { "code" : 34, "message" : "cannot read file" },
     "ERROR_INCOMPATIBLE_VERSION"   : { "code" : 35, "message" : "incompatible server version" },
     "ERROR_DISABLED"               : { "code" : 36, "message" : "disabled" },
-    "ERROR_VALIDATION_FAILED"      : { "code" : 37, "message" : "validation failed" },
-    "ERROR_VALIDATION_BAD_PARAMETER" : { "code" : 38, "message" : "invalid validation parameter" },
     "ERROR_HTTP_BAD_PARAMETER"     : { "code" : 400, "message" : "bad parameter" },
     "ERROR_HTTP_UNAUTHORIZED"      : { "code" : 401, "message" : "unauthorized" },
     "ERROR_HTTP_FORBIDDEN"         : { "code" : 403, "message" : "forbidden" },
@@ -220,6 +218,8 @@
     "ERROR_QUERY_USER_WARN"        : { "code" : 1594, "message" : "%s" },
     "ERROR_CURSOR_NOT_FOUND"       : { "code" : 1600, "message" : "cursor not found" },
     "ERROR_CURSOR_BUSY"            : { "code" : 1601, "message" : "cursor is busy" },
+    "ERROR_VALIDATION_FAILED"      : { "code" : 1620, "message" : "validation failed" },
+    "ERROR_VALIDATION_BAD_PARAMETER" : { "code" : 1621, "message" : "invalid validation parameter" },
     "ERROR_TRANSACTION_INTERNAL"   : { "code" : 1650, "message" : "internal transaction error" },
     "ERROR_TRANSACTION_NESTED"     : { "code" : 1651, "message" : "nested transactions detected" },
     "ERROR_TRANSACTION_UNREGISTERED_COLLECTION" : { "code" : 1652, "message" : "unregistered collection used in transaction" },
diff --git a/js/common/modules/@arangodb/aql/explainer.js b/js/common/modules/@arangodb/aql/explainer.js
index 9944805bf66e..038406d999c8 100644
--- a/js/common/modules/@arangodb/aql/explainer.js
+++ b/js/common/modules/@arangodb/aql/explainer.js
@@ -502,7 +502,8 @@ function printTraversalDetails(traversals) {
 
   var optify = function (options, colorize) {
     var opts = {
-      bfs: options.bfs || undefined, /* only print if set to true to space room */
+      bfs: options.bfs || undefined, /* only print if set to true to save room */
+      neighbors: options.neighbors || undefined, /* only print if set to true to save room */
       uniqueVertices: options.uniqueVertices,
       uniqueEdges: options.uniqueEdges
     };
diff --git a/js/server/modules/@arangodb/foxx/router/response.js b/js/server/modules/@arangodb/foxx/router/response.js
index 777d9cd2b6b9..e25dd47a48a4 100644
--- a/js/server/modules/@arangodb/foxx/router/response.js
+++ b/js/server/modules/@arangodb/foxx/router/response.js
@@ -304,20 +304,26 @@ module.exports =
     }
 
     throw (status, reason, options) {
-      if (typeof status === 'string') {
+      if (typeof status !== "number") {
         status = statuses(status);
       }
-      if (reason instanceof Error) {
-        const err = reason;
-        reason = err.message;
-        options = Object.assign({
-          cause: err,
-          errorNum: err.errorNum
-        }, options);
-      }
-      if (reason && typeof reason === 'object') {
-        options = reason;
-        reason = undefined;
+      if (reason) {
+        if (reason instanceof Error) {
+          const err = reason;
+          reason = err.message;
+          options = Object.assign(
+            {
+              cause: err,
+              errorNum: err.errorNum
+            },
+            options
+          );
+        } else if (typeof reason === "object") {
+          options = reason;
+          reason = undefined;
+        } else if (typeof reason !== "string") {
+          reason = String(reason);
+        }
       }
       throw Object.assign(
         httperr(status, reason),
diff --git a/js/server/modules/@arangodb/foxx/service.js b/js/server/modules/@arangodb/foxx/service.js
index 60a902653291..55245d525b6d 100644
--- a/js/server/modules/@arangodb/foxx/service.js
+++ b/js/server/modules/@arangodb/foxx/service.js
@@ -410,12 +410,25 @@ module.exports =
                   body[key] = error.extra[key];
                 });
               }
-              res.responseCode = error.statusCode;
+              res.responseCode = error.statusCode || 500;
               res.contentType = 'application/json';
               res.body = JSON.stringify(body);
             }
 
             if (handled) {
+              if (!res.responseCode) {
+                res.responseCode = 200;
+              } else if (isNaN(res.responseCode)) {
+                console.warn(`Unexpected status code value: ${res.responseCode}`);
+                res.responseCode = 500;
+              } else {
+                res.responseCode = Number(res.responseCode);
+              }
+              if (!res.contentType) {
+                res.contentType = 'application/json';
+              } else {
+                res.contentType = String(res.contentType);
+              }
               // provide default CORS headers
               if (req.headers.origin) {
                 if (!res.headers) {
diff --git a/lib/Basics/ConditionLocker.cpp b/lib/Basics/ConditionLocker.cpp
index 1ab96b1ecca9..3e3fc3767353 100644
--- a/lib/Basics/ConditionLocker.cpp
+++ b/lib/Basics/ConditionLocker.cpp
@@ -28,7 +28,8 @@
 #include "Basics/debugging.h"
 
 #ifdef ARANGODB_SHOW_LOCK_TIME
-#include "Logger/Logger.h"
+#include "Basics/system-functions.h"
+#include "Logger/LogMacros.h"
 #endif
 
 using namespace arangodb::basics;
@@ -40,11 +41,12 @@ using namespace arangodb::basics;
 #ifdef ARANGODB_SHOW_LOCK_TIME
 
 ConditionLocker::ConditionLocker(ConditionVariable* conditionVariable,
-                                 char const* file, int line)
+                                 char const* file, int line, bool showLockTime)
     : _conditionVariable(conditionVariable),
       _isLocked(true),
       _file(file),
       _line(line),
+      _showLockTime(showLockTime),
       _time(0.0) {
   double t = TRI_microtime();
   _conditionVariable->lock();
@@ -67,9 +69,10 @@ ConditionLocker::~ConditionLocker() {
   }
 
 #ifdef ARANGODB_SHOW_LOCK_TIME
-  if (_time > TRI_SHOW_LOCK_THRESHOLD) {
-    LOG_TOPIC("89086", WARN, arangodb::Logger::FIXME)
-        << "ConditionLocker " << _file << ":" << _line << " took " << _time << " s";
+  if (_showLockTime && _time > TRI_SHOW_LOCK_THRESHOLD) {
+    LOG_TOPIC("89086", INFO, arangodb::Logger::PERFORMANCE)
+        << "ConditionLocker for condition [" << _conditionVariable << "]"
+        << _file << ":" << _line << " took " << _time << " s";
   }
 #endif
 }
diff --git a/lib/Basics/ConditionLocker.h b/lib/Basics/ConditionLocker.h
index d01c3747bec4..00f169f9181d 100644
--- a/lib/Basics/ConditionLocker.h
+++ b/lib/Basics/ConditionLocker.h
@@ -63,7 +63,8 @@ class ConditionLocker {
 /// the condition variable
 #ifdef ARANGODB_SHOW_LOCK_TIME
 
-  ConditionLocker(ConditionVariable* conditionVariable, char const* file, int line);
+  ConditionLocker(ConditionVariable* conditionVariable, char const* file,
+                  int line, bool showLockTime = true);
 
 #else
 
@@ -116,6 +117,8 @@ class ConditionLocker {
   /// @brief line number
   int _line;
 
+  bool _showLockTime;
+
   /// @brief lock time
   double _time;
 
diff --git a/lib/Basics/CrashHandler.cpp b/lib/Basics/CrashHandler.cpp
index fa682a1479dd..7e742d687fbd 100644
--- a/lib/Basics/CrashHandler.cpp
+++ b/lib/Basics/CrashHandler.cpp
@@ -29,6 +29,8 @@
 #include <unistd.h>
 #endif
 #include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
 
 #ifndef _WIN32
 #include <execinfo.h>
@@ -41,6 +43,8 @@
 #include "Basics/PhysicalMemory.h"
 #include "Basics/StringUtils.h"
 #include "Basics/Thread.h"
+#include "Basics/files.h"
+#include "Basics/operating-system.h"
 #include "Basics/process-utils.h"
 #include "Basics/signals.h"
 #include "Logger/LoggerFeature.h"
@@ -52,6 +56,9 @@
 #ifndef _WIN32
 namespace {
 
+/// @brief filename that we will use to write a backtrace into
+std::string crashFilename;
+
 /// @brief helper struct that is used to create an alternative stack for the
 /// signal handler on construction and to tear it down on destruction
 struct CrashHandlerStackInitializer {
@@ -116,7 +123,7 @@ void appendNullTerminatedString(char const* src, char*& dst) {
 /// in context of SIGSEGV, with a broken heap etc.
 /// Assumes that the buffer pointed to by s has enough space to
 /// hold the thread id, the thread name and the signal name
-/// (1024 bytes should be more than enough).
+/// (4096 bytes should be more than enough).
 size_t buildLogMessage(char* s, int signal, siginfo_t const* info, int stackSize) {
   // build a crash message
   char* p = s;
@@ -194,8 +201,8 @@ void crashHandler(int signal, siginfo_t* info, void*) {
 #endif
 
     try {
-      // buffer for constructing temporary log messages (to avoid malloc as much as possible)
-      char buffer[1024];
+      // buffer for constructing temporary log messages (to avoid malloc)
+      char buffer[4096];
       memset(&buffer[0], 0, sizeof(buffer));
 
       // acquire backtrace
@@ -210,26 +217,74 @@ void crashHandler(int signal, siginfo_t* info, void*) {
       LOG_TOPIC("a7902", FATAL, arangodb::Logger::CRASH) << arangodb::Logger::CHARS(&buffer[0], length);
       arangodb::Logger::flush();
 
-      if (numFrames > 0) {
-        // note: backtrace_symbols() will allocate memory
-        char** stack = backtrace_symbols(traces, numFrames); 
-        if (stack != nullptr) {
-          for (int i = skipFrames /* ignore first frames */; i < numFrames; ++i) {
-            char* p = &buffer[0];
-            appendNullTerminatedString("- frame #", p);
-            p += arangodb::basics::StringUtils::itoa(uint64_t(i), p);
-            appendNullTerminatedString(": ", p);
-            if (strlen(stack[i]) <= sizeof(buffer) / 2) {
-              // only append stack trace to buffer if it is safe (i.e. short enough to append it)
-              appendNullTerminatedString(stack[i], p);
-
-              // note: LOG_TOPIC() will allocate memory
-              LOG_TOPIC("308c2", INFO, arangodb::Logger::CRASH) << arangodb::Logger::CHARS(&buffer[0], p - &buffer[0]);
+      if (numFrames > 0 && !::crashFilename.empty()) {
+        // open crash file to write backtrace information into it
+        int fd = TRI_CREATE(::crashFilename.c_str(), O_CREAT | O_TRUNC | O_EXCL | O_RDWR | TRI_O_CLOEXEC, S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP);
+        
+        if (fd >= 0) {
+          // actually write backtrace information into file. this does not malloc!
+          backtrace_symbols_fd(traces, numFrames, fd);
+          TRI_CLOSE(fd);
+
+          // reopen the file for reading it
+          fd = TRI_OPEN(::crashFilename.c_str(), O_RDONLY | TRI_O_CLOEXEC);
+          if (fd >= 0) {
+            // fill buffer with \n bytes, so we can simplify the following logic
+            memset(&buffer[0], '\n', sizeof(buffer));
+            // also make sure it is always null-terminated
+            buffer[sizeof(buffer) - 1] = '\0';
+
+            p = &buffer[0];
+            size_t bytesLeft = sizeof(buffer) - 2;
+            while (bytesLeft > 0) {
+              TRI_read_return_t n = TRI_READ(fd, p, static_cast<TRI_read_t>(bytesLeft));
+              if (n <= 0) {
+                *p = '\0';
+                break;
+              }
+              TRI_ASSERT(bytesLeft >= static_cast<size_t>(n));
+              bytesLeft -= n;
+              p += n;
+            }
+
+            int frame = 0;
+            length = p - &buffer[0]; 
+            p = &buffer[0];
+            char* e = p + length;
+            while (p < e) {
+              char* split = strchr(p, '\n');
+              if (split != nullptr) {
+                length = split - p;
+              } else {
+                length = e - p;
+              }
+              if (length <= 1) {
+                break;
+              }
+              TRI_ASSERT(length > 0);
+
+              if (frame >= skipFrames) {
+                LOG_TOPIC("308c2", INFO, arangodb::Logger::CRASH) << arangodb::Logger::CHARS(p, length);
+              }
+              
+              ++frame;
+
+              if (frame >= numFrames) {
+                break;
+              }
+
+              if (split != nullptr) {
+                p = split + 1;
+              } else {
+                // reached the end
+                p = e;
+              }
             }
+            TRI_CLOSE(fd);
           }
-          free(stack);
-          arangodb::Logger::flush();
+
         }
+        arangodb::Logger::flush();
       }
      
       {
@@ -286,6 +341,14 @@ namespace arangodb {
 
 void CrashHandler::installCrashHandler() {
 #ifndef _WIN32
+  // create a temporary file. This will automatically be deleted at shutdown
+  long int unusedError;
+  std::string unusedMessage;
+  int res = TRI_GetTempName(nullptr, ::crashFilename, false, unusedError, unusedMessage);
+  if (res != TRI_ERROR_NO_ERROR) {
+    ::crashFilename.clear();
+  }
+
   // install signal handlers for the following signals
   struct sigaction act;
   sigemptyset(&act.sa_mask);
diff --git a/lib/Basics/HybridLogicalClock.h b/lib/Basics/HybridLogicalClock.h
index 220602dbcff1..4ff63e6d714c 100644
--- a/lib/Basics/HybridLogicalClock.h
+++ b/lib/Basics/HybridLogicalClock.h
@@ -29,6 +29,9 @@
 #include <chrono>
 #include <string>
 
+#include <velocypack/Slice.h>
+#include <velocypack/Value.h>
+
 #include "Basics/Common.h"
 
 namespace arangodb {
@@ -124,10 +127,24 @@ class HybridLogicalClock {
     return std::make_pair(pos, 11 - pos);
   }
 
+  static velocypack::ValuePair encodeTimeStampToValuePair(uint64_t t, char* r) {
+    auto p = encodeTimeStamp(t, r);
+    return velocypack::ValuePair(&r[0] + p.first, p.second, velocypack::ValueType::String);
+  }
+
   static uint64_t decodeTimeStamp(std::string const& s) {
     return decodeTimeStamp(s.data(), s.size());
   }
 
+  static uint64_t decodeTimeStamp(velocypack::Slice const& s) {
+    if (!s.isString()) {
+      return std::numeric_limits<std::uint64_t>::max();
+    }
+    velocypack::ValueLength l;
+    char const* p = s.getString(l);
+    return decodeTimeStamp(p, l);
+  }
+
   static uint64_t decodeTimeStamp(char const* p, size_t len) {
     // Returns UINT64_MAX if format is not valid
     if (len > 11) {
diff --git a/lib/Basics/MutexLocker.h b/lib/Basics/MutexLocker.h
index cfc4bba5529b..5a8b657959f6 100644
--- a/lib/Basics/MutexLocker.h
+++ b/lib/Basics/MutexLocker.h
@@ -30,7 +30,8 @@
 #include "Basics/debugging.h"
 
 #ifdef ARANGODB_SHOW_LOCK_TIME
-#include "Logger/Logger.h"
+#include "Basics/system-functions.h"
+#include "Logger/LogMacros.h"
 #endif
 
 #include <thread>
@@ -108,7 +109,8 @@ class MutexLocker {
 #ifdef ARANGODB_SHOW_LOCK_TIME
     if (_time > TRI_SHOW_LOCK_THRESHOLD) {
       LOG_TOPIC("bb435", INFO, arangodb::Logger::PERFORMANCE)
-          << "MutexLocker " << _file << ":" << _line << " took " << _time << " s";
+          << "MutexLocker for lock [" << _mutex << "]" << _file << ":" << _line
+          << " took " << _time << " s";
     }
 #endif
   }
diff --git a/lib/Basics/NumberUtils.h b/lib/Basics/NumberUtils.h
index 410500772f15..ea72858c77d9 100644
--- a/lib/Basics/NumberUtils.h
+++ b/lib/Basics/NumberUtils.h
@@ -251,6 +251,11 @@ inline T atoi_zero(char const* p, char const* e) noexcept {
   return valid ? result : 0;
 }
 
+template <typename T>
+constexpr std::enable_if_t<std::is_integral<T>::value, bool> isPowerOf2(T n) {
+  return n > 0 && (n & (n - 1)) == 0;
+}
+
 /// @brief calculate the integer log2 value for the given input
 /// the result is undefined when calling this with a value of 0!
 uint32_t log2(uint32_t value) noexcept;
diff --git a/lib/Basics/ReadLocker.h b/lib/Basics/ReadLocker.h
index 0fa00f9e015a..ff8f9f2058a7 100644
--- a/lib/Basics/ReadLocker.h
+++ b/lib/Basics/ReadLocker.h
@@ -31,7 +31,8 @@
 #include "Basics/debugging.h"
 
 #ifdef ARANGODB_SHOW_LOCK_TIME
-#include "Logger/Logger.h"
+#include "Basics/system-functions.h"
+#include "Logger/LogMacros.h"
 #endif
 
 #include <thread>
@@ -111,7 +112,8 @@ class ReadLocker {
 #ifdef ARANGODB_SHOW_LOCK_TIME
     if (_time > TRI_SHOW_LOCK_THRESHOLD) {
       LOG_TOPIC("8e47e", INFO, arangodb::Logger::PERFORMANCE)
-          << "ReadLocker " << _file << ":" << _line << " took " << _time << " s";
+          << "ReadLocker for lock [" << _readWriteLock << "] " << _file << ":"
+          << _line << " took " << _time << " s";
     }
 #endif
   }
@@ -129,7 +131,7 @@ class ReadLocker {
 
   bool tryLock() {
     TRI_ASSERT(!_isLocked);
-    if (_readWriteLock->tryReadLock()) {
+    if (_readWriteLock->tryLockRead()) {
       _isLocked = true;
     }
     return _isLocked;
@@ -138,7 +140,7 @@ class ReadLocker {
   /// @brief acquire the read lock, blocking
   void lock() {
     TRI_ASSERT(!_isLocked);
-    _readWriteLock->readLock();
+    _readWriteLock->lockRead();
     _isLocked = true;
   }
 
diff --git a/lib/Basics/ReadUnlocker.h b/lib/Basics/ReadUnlocker.h
index 1ba55febbb5e..3afde92fd571 100644
--- a/lib/Basics/ReadUnlocker.h
+++ b/lib/Basics/ReadUnlocker.h
@@ -36,17 +36,8 @@
 /// number.
 ////////////////////////////////////////////////////////////////////////////////
 
-#ifdef ARANGODB_SHOW_LOCK_TIME
-
-#define READ_UNLOCKER(obj, lock) \
-  arangodb::basics::ReadUnlocker obj(&lock, __FILE__, __LINE__)
-
-#else
-
 #define READ_UNLOCKER(obj, lock) arangodb::basics::ReadUnlocker obj(&lock)
 
-#endif
-
 namespace arangodb {
 namespace basics {
 
@@ -68,22 +59,11 @@ class ReadUnlocker {
   /// The constructor unlocks the lock, the destructors acquires a read-lock.
   //////////////////////////////////////////////////////////////////////////////
 
-#ifdef ARANGODB_SHOW_LOCK_TIME
-
-  ReadUnlocker(ReadWriteLock* readWriteLock, char const* file, int line)
-      : _readWriteLock(readWriteLock), _file(file), _line(line) {
-    _readWriteLock->unlockRead();
-  }
-
-#else
-
   explicit ReadUnlocker(ReadWriteLock* readWriteLock)
       : _readWriteLock(readWriteLock) {
     _readWriteLock->unlockRead();
   }
 
-#endif
-
   ////////////////////////////////////////////////////////////////////////////////
   /// @brief unlocks the lock
   ///
@@ -95,7 +75,7 @@ class ReadUnlocker {
   /// @brief acquires the read-lock
   ////////////////////////////////////////////////////////////////////////////////
 
-  ~ReadUnlocker() { _readWriteLock->readLock(); }
+  ~ReadUnlocker() { _readWriteLock->lockRead(); }
 
  private:
   ////////////////////////////////////////////////////////////////////////////////
@@ -104,21 +84,6 @@ class ReadUnlocker {
 
   ReadWriteLock* _readWriteLock;
 
-#ifdef ARANGODB_SHOW_LOCK_TIME
-
-  ////////////////////////////////////////////////////////////////////////////////
-  /// @brief file
-  ////////////////////////////////////////////////////////////////////////////////
-
-  char const* _file;
-
-  ////////////////////////////////////////////////////////////////////////////////
-  /// @brief line number
-  ////////////////////////////////////////////////////////////////////////////////
-
-  int _line;
-
-#endif
 };
 }  // namespace basics
 }  // namespace arangodb
diff --git a/lib/Basics/ReadWriteLock.cpp b/lib/Basics/ReadWriteLock.cpp
index 0dffc4fa4404..c5b1d056c980 100644
--- a/lib/Basics/ReadWriteLock.cpp
+++ b/lib/Basics/ReadWriteLock.cpp
@@ -28,8 +28,8 @@
 using namespace arangodb::basics;
 
 /// @brief locks for writing
-void ReadWriteLock::writeLock() {
-  if (tryWriteLock()) {
+void ReadWriteLock::lockWrite() {
+  if (tryLockWrite()) {
     return;
   }
 
@@ -54,7 +54,7 @@ void ReadWriteLock::writeLock() {
 
 /// @brief lock for writes with microsecond timeout
 bool ReadWriteLock::writeLock(std::chrono::microseconds timeout) {
-  if (tryWriteLock()) {
+  if (tryLockWrite()) {
     return true;
   }
 
@@ -93,7 +93,7 @@ bool ReadWriteLock::writeLock(std::chrono::microseconds timeout) {
 }
 
 /// @brief locks for writing, but only tries
-bool ReadWriteLock::tryWriteLock() {
+bool ReadWriteLock::tryLockWrite() {
   // order_relaxed is an optimization, cmpxchg will synchronize side-effects
   auto state = _state.load(std::memory_order_relaxed);
   // try to acquire write lock as long as no readers or writers are active,
@@ -107,14 +107,14 @@ bool ReadWriteLock::tryWriteLock() {
 }
 
 /// @brief locks for reading
-void ReadWriteLock::readLock() {
-  if (tryReadLock()) {
+void ReadWriteLock::lockRead() {
+  if (tryLockRead()) {
     return;
   }
 
   std::unique_lock<std::mutex> guard(_reader_mutex);
   while (true) {
-    if (tryReadLock()) {
+    if (tryLockRead()) {
       return;
     }
 
@@ -123,7 +123,7 @@ void ReadWriteLock::readLock() {
 }
 
 /// @brief locks for reading, tries only
-bool ReadWriteLock::tryReadLock() {
+bool ReadWriteLock::tryLockRead() {
   // order_relaxed is an optimization, cmpxchg will synchronize side-effects
   auto state = _state.load(std::memory_order_relaxed);
   // try to acquire read lock as long as no writers are active or queued
diff --git a/lib/Basics/ReadWriteLock.h b/lib/Basics/ReadWriteLock.h
index 13e05dc0b36c..8a5b655db515 100644
--- a/lib/Basics/ReadWriteLock.h
+++ b/lib/Basics/ReadWriteLock.h
@@ -51,7 +51,7 @@ class ReadWriteLock {
   ReadWriteLock() : _state(0) {}
 
   /// @brief locks for writing
-  void writeLock();
+  void lockWrite();
 
   /// @brief locks for writing within microsecond timeout
   [[nodiscard]] bool writeLock(uint64_t timeout) {
@@ -62,13 +62,13 @@ class ReadWriteLock {
   [[nodiscard]] bool writeLock(std::chrono::microseconds timeout);
 
   /// @brief locks for writing, but only tries
-  [[nodiscard]] bool tryWriteLock();
+  [[nodiscard]] bool tryLockWrite();
 
   /// @brief locks for reading
-  void readLock();
+  void lockRead();
 
   /// @brief locks for reading, tries only
-  [[nodiscard]] bool tryReadLock();
+  [[nodiscard]] bool tryLockRead();
 
   /// @brief releases the read-lock or write-lock
   void unlock() noexcept;
diff --git a/lib/Basics/ReadWriteSpinLock.cpp b/lib/Basics/ReadWriteSpinLock.cpp
index 3ca7bb3d03c4..30bb1306f494 100644
--- a/lib/Basics/ReadWriteSpinLock.cpp
+++ b/lib/Basics/ReadWriteSpinLock.cpp
@@ -17,7 +17,7 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 /// @author Manuel Pöter
 ////////////////////////////////////////////////////////////////////////////////
 
@@ -26,8 +26,30 @@
 #include "Basics/cpu-relax.h"
 #include "Basics/debugging.h"
 
-using namespace arangodb;
-using namespace arangodb::basics;
+namespace {
+static constexpr std::uint32_t WriteLock{1};
+
+static constexpr std::uint32_t ReaderIncrement{static_cast<std::uint32_t>(1) << 16};
+static constexpr std::uint32_t ReaderMask{~(::ReaderIncrement - 1)};
+
+static constexpr std::uint32_t QueuedWriterIncrement{static_cast<std::uint32_t>(1) << 1};
+static constexpr std::uint32_t QueuedWriterMask{(::ReaderIncrement - 1) & ~::WriteLock};
+
+static_assert((::ReaderMask & ::WriteLock) == 0,
+              "::ReaderMask and ::WriteLock conflict");
+static_assert((::ReaderMask & ::QueuedWriterMask) == 0,
+              "::ReaderMask and ::QueuedWriterMask conflict");
+static_assert((::QueuedWriterMask & ::WriteLock) == 0,
+              "::QueuedWriterMask and ::WriteLock conflict");
+
+static_assert((::ReaderMask & ::ReaderIncrement) != 0 && (::ReaderMask & (::ReaderIncrement >> 1)) == 0,
+              "::ReaderIncrement must be first bit in ::ReaderMask");
+static_assert((::QueuedWriterMask & ::QueuedWriterIncrement) != 0 &&
+                  (::QueuedWriterMask & (::QueuedWriterIncrement >> 1)) == 0,
+              "::QueuedWriterIncrement must be first bit in ::QueuedWriterMask");
+}
+
+namespace arangodb::basics {
 
 ReadWriteSpinLock::ReadWriteSpinLock(ReadWriteSpinLock&& other) noexcept {
   auto val = other._state.load(std::memory_order_relaxed);
@@ -43,31 +65,31 @@ ReadWriteSpinLock& ReadWriteSpinLock::operator=(ReadWriteSpinLock&& other) noexc
   return *this;
 }
 
-bool ReadWriteSpinLock::tryWriteLock() noexcept {
+bool ReadWriteSpinLock::tryLockWrite() noexcept {
   // order_relaxed is an optimization, cmpxchg will synchronize side-effects
   auto state = _state.load(std::memory_order_relaxed);
   // try to acquire write lock as long as no readers or writers are active,
   // we might "overtake" other queued writers though.
-  while ((state & ~QUEUED_WRITER_MASK) == 0) {
-    if (_state.compare_exchange_weak(state, state | WRITE_LOCK, std::memory_order_acquire)) {
+  while ((state & ~::QueuedWriterMask) == 0) {
+    if (_state.compare_exchange_weak(state, state | ::WriteLock, std::memory_order_acquire)) {
       return true;  // we successfully acquired the write lock!
     }
   }
   return false;
 }
 
-void ReadWriteSpinLock::writeLock() noexcept {
-  if (tryWriteLock()) {
+void ReadWriteSpinLock::lockWrite() noexcept {
+  if (tryLockWrite()) {
     return;
   }
 
   // the lock is either hold by another writer or we have active readers
   // -> announce that we want to write
-  auto state = _state.fetch_add(QUEUED_WRITER_INC, std::memory_order_relaxed);
+  auto state = _state.fetch_add(::QueuedWriterIncrement, std::memory_order_relaxed);
   for (;;) {
-    while ((state & ~QUEUED_WRITER_MASK) == 0) {
+    while ((state & ~::QueuedWriterMask) == 0) {
       // try to acquire lock and perform queued writer decrement in one step
-      if (_state.compare_exchange_weak(state, (state - QUEUED_WRITER_INC) | WRITE_LOCK,
+      if (_state.compare_exchange_weak(state, (state - ::QueuedWriterIncrement) | ::WriteLock,
                                        std::memory_order_acquire)) {
         return;
       }
@@ -77,8 +99,8 @@ void ReadWriteSpinLock::writeLock() noexcept {
   }
 }
 
-bool ReadWriteSpinLock::writeLock(uint64_t maxAttempts) noexcept {
-  if (tryWriteLock()) {
+bool ReadWriteSpinLock::lockWrite(std::size_t maxAttempts) noexcept {
+  if (tryLockWrite()) {
     return true;
   }
 
@@ -86,11 +108,11 @@ bool ReadWriteSpinLock::writeLock(uint64_t maxAttempts) noexcept {
 
   // the lock is either hold by another writer or we have active readers
   // -> announce that we want to write
-  auto state = _state.fetch_add(QUEUED_WRITER_INC, std::memory_order_relaxed);
+  auto state = _state.fetch_add(::QueuedWriterIncrement, std::memory_order_relaxed);
   while (++attempts < maxAttempts) {
-    while ((state & ~QUEUED_WRITER_MASK) == 0) {
+    while ((state & ~::QueuedWriterMask) == 0) {
       // try to acquire lock and perform queued writer decrement in one step
-      if (_state.compare_exchange_weak(state, (state - QUEUED_WRITER_INC) | WRITE_LOCK,
+      if (_state.compare_exchange_weak(state, (state - ::QueuedWriterIncrement) | ::WriteLock,
                                        std::memory_order_acquire)) {
         return true;
       }
@@ -104,31 +126,31 @@ bool ReadWriteSpinLock::writeLock(uint64_t maxAttempts) noexcept {
   return false;
 }
 
-bool ReadWriteSpinLock::tryReadLock() noexcept {
+bool ReadWriteSpinLock::tryLockRead() noexcept {
   // order_relaxed is an optimization, cmpxchg will synchronize side-effects
   auto state = _state.load(std::memory_order_relaxed);
   // try to acquire read lock as long as no writers are active or queued
-  while ((state & ~READER_MASK) == 0) {
-    if (_state.compare_exchange_weak(state, state + READER_INC, std::memory_order_acquire)) {
+  while ((state & ~::ReaderMask) == 0) {
+    if (_state.compare_exchange_weak(state, state + ::ReaderIncrement, std::memory_order_acquire)) {
       return true;
     }
   }
   return false;
 }
 
-void ReadWriteSpinLock::readLock() noexcept {
+void ReadWriteSpinLock::lockRead() noexcept {
   for (;;) {
-    if (tryReadLock()) {
+    if (tryLockRead()) {
       return;
     }
     cpu_relax();
   }
 }
 
-bool ReadWriteSpinLock::readLock(uint64_t maxAttempts) noexcept {
+bool ReadWriteSpinLock::lockRead(std::size_t maxAttempts) noexcept {
   uint64_t attempts = 0;
   while (attempts++ < maxAttempts) {
-    if (tryReadLock()) {
+    if (tryLockRead()) {
       return true;
     }
     cpu_relax();
@@ -136,26 +158,35 @@ bool ReadWriteSpinLock::readLock(uint64_t maxAttempts) noexcept {
   return false;
 }
 
-void ReadWriteSpinLock::readUnlock() noexcept { unlockRead(); }
+void ReadWriteSpinLock::unlock() noexcept {
+  if (isLockedWrite()) {
+    unlockWrite();
+  } else {
+    TRI_ASSERT(isLockedRead());
+    unlockRead();
+  }
+}
+
 void ReadWriteSpinLock::unlockRead() noexcept {
-  TRI_ASSERT(isReadLocked());
-  _state.fetch_sub(READER_INC, std::memory_order_release);
+  TRI_ASSERT(isLockedRead());
+  _state.fetch_sub(::ReaderIncrement, std::memory_order_release);
 }
 
-void ReadWriteSpinLock::writeUnlock() noexcept { unlockWrite(); }
 void ReadWriteSpinLock::unlockWrite() noexcept {
-  TRI_ASSERT(isWriteLocked());
-  _state.fetch_sub(WRITE_LOCK, std::memory_order_release);
+  TRI_ASSERT(isLockedWrite());
+  _state.fetch_sub(::WriteLock, std::memory_order_release);
 }
 
 bool ReadWriteSpinLock::isLocked() const noexcept {
-  return (_state.load(std::memory_order_relaxed) & ~QUEUED_WRITER_MASK) != 0;
+  return (_state.load(std::memory_order_relaxed) & ~::QueuedWriterMask) != 0;
+}
+
+bool ReadWriteSpinLock::isLockedRead() const noexcept {
+  return (_state.load(std::memory_order_relaxed) & ::ReaderMask) > 0;
 }
 
-bool ReadWriteSpinLock::isReadLocked() const noexcept {
-  return (_state.load(std::memory_order_relaxed) & READER_MASK) > 0;
+bool ReadWriteSpinLock::isLockedWrite() const noexcept {
+  return _state.load(std::memory_order_relaxed) & ::WriteLock;
 }
 
-bool ReadWriteSpinLock::isWriteLocked() const noexcept {
-  return _state.load(std::memory_order_relaxed) & WRITE_LOCK;
 }
diff --git a/lib/Basics/ReadWriteSpinLock.h b/lib/Basics/ReadWriteSpinLock.h
index 392fdd80a840..5c9301b29051 100644
--- a/lib/Basics/ReadWriteSpinLock.h
+++ b/lib/Basics/ReadWriteSpinLock.h
@@ -18,7 +18,7 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 /// @author Manuel Pöter
 ////////////////////////////////////////////////////////////////////////////////
 
@@ -26,6 +26,7 @@
 #define ARANGO_READ_WRITE_SPIN_LOCK_H 1
 
 #include <atomic>
+#include <cstdint>
 
 namespace arangodb::basics {
 
@@ -38,49 +39,26 @@ class ReadWriteSpinLock {
 
   ReadWriteSpinLock& operator=(ReadWriteSpinLock&& other) noexcept;
 
-  [[nodiscard]] bool tryWriteLock() noexcept;
-  void writeLock() noexcept;
-  [[nodiscard]] bool writeLock(uint64_t maxAttempts) noexcept;
+  [[nodiscard]] bool tryLockWrite() noexcept;
+  void lockWrite() noexcept;
+  [[nodiscard]] bool lockWrite(std::size_t maxAttempts) noexcept;
 
-  [[nodiscard]] bool tryReadLock() noexcept;
-  void readLock() noexcept;
-  [[nodiscard]] bool readLock(uint64_t maxAttempts) noexcept;
+  [[nodiscard]] bool tryLockRead() noexcept;
+  void lockRead() noexcept;
+  [[nodiscard]] bool lockRead(std::size_t maxAttempts) noexcept;
 
-  void readUnlock() noexcept;
+  void unlock() noexcept;
   void unlockRead() noexcept;
-
-  void writeUnlock() noexcept;
   void unlockWrite() noexcept;
 
   [[nodiscard]] bool isLocked() const noexcept;
-  [[nodiscard]] bool isReadLocked() const noexcept;
-  [[nodiscard]] bool isWriteLocked() const noexcept;
+  [[nodiscard]] bool isLockedRead() const noexcept;
+  [[nodiscard]] bool isLockedWrite() const noexcept;
 
  private:
   /// @brief _state, lowest bit is write_lock, the next 15 bits is the number of
   /// queued writers, the last 16 bits the number of active readers.
-  std::atomic<uint32_t> _state = 0;
-
-  static constexpr uint32_t WRITE_LOCK = 1;
-
-  static constexpr uint32_t READER_INC = 1 << 16;
-  static constexpr uint32_t READER_MASK = ~(READER_INC - 1);
-
-  static constexpr uint32_t QUEUED_WRITER_INC = 1 << 1;
-  static constexpr uint32_t QUEUED_WRITER_MASK = (READER_INC - 1) & ~WRITE_LOCK;
-
-  static_assert((READER_MASK & WRITE_LOCK) == 0,
-                "READER_MASK and WRITE_LOCK conflict");
-  static_assert((READER_MASK & QUEUED_WRITER_MASK) == 0,
-                "READER_MASK and QUEUED_WRITER_MASK conflict");
-  static_assert((QUEUED_WRITER_MASK & WRITE_LOCK) == 0,
-                "QUEUED_WRITER_MASK and WRITE_LOCK conflict");
-
-  static_assert((READER_MASK & READER_INC) != 0 && (READER_MASK & (READER_INC >> 1)) == 0,
-                "READER_INC must be first bit in READER_MASK");
-  static_assert((QUEUED_WRITER_MASK & QUEUED_WRITER_INC) != 0 &&
-                    (QUEUED_WRITER_MASK & (QUEUED_WRITER_INC >> 1)) == 0,
-                "QUEUED_WRITER_INC must be first bit in QUEUED_WRITER_MASK");
+  std::atomic<std::uint32_t> _state = 0;
 };
 
 }  // namespace arangodb::basics
diff --git a/lib/Basics/SpinLocker.h b/lib/Basics/SpinLocker.h
new file mode 100644
index 000000000000..808e6482c232
--- /dev/null
+++ b/lib/Basics/SpinLocker.h
@@ -0,0 +1,107 @@
+////////////////////////////////////////////////////////////////////////////////
+/// DISCLAIMER
+///
+/// Copyright 2014-2020 ArangoDB GmbH, Cologne, Germany
+/// Copyright 2004-2014 triAGENS GmbH, Cologne, Germany
+///
+/// Licensed under the Apache License, Version 2.0 (the "License");
+/// you may not use this file except in compliance with the License.
+/// You may obtain a copy of the License at
+///
+///     http://www.apache.org/licenses/LICENSE-2.0
+///
+/// Unless required by applicable law or agreed to in writing, software
+/// distributed under the License is distributed on an "AS IS" BASIS,
+/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+/// See the License for the specific language governing permissions and
+/// limitations under the License.
+///
+/// Copyright holder is ArangoDB GmbH, Cologne, Germany
+///
+/// @author Dan Larkin-York
+////////////////////////////////////////////////////////////////////////////////
+
+#ifndef ARANGO_SPIN_LOCKER_H
+#define ARANGO_SPIN_LOCKER_H 1
+
+#include <atomic>
+#include <cstdint>
+
+#include "Basics/ReadWriteSpinLock.h"
+
+namespace arangodb::basics {
+
+class SpinLocker {
+ public:
+  enum class Mode : std::uint8_t { Read, Write };
+  enum class Effort { Try, Succeed };
+
+ public:
+  SpinLocker(Mode mode, ReadWriteSpinLock& lock, bool doLock = true,
+             Effort effort = Effort::Succeed)
+      : _lock(lock), _mode(mode), _locked(false) {
+    if (doLock) {      
+      if (effort == Effort::Succeed) {
+        if (_mode == Mode::Read) {
+          _lock.lockRead();
+        } else {
+          _lock.lockWrite();
+        }
+        _locked = true;
+      } else {
+        if (_mode == Mode::Read) {
+          _locked = _lock.tryLockRead();
+        } else {
+          _locked = _lock.tryLockWrite();
+        }
+      }
+    }
+  }
+
+  SpinLocker(Mode mode, ReadWriteSpinLock& lock, std::size_t maxAttempts)
+      : _lock(lock), _mode(mode), _locked(false) {
+    if (_mode == Mode::Read) {
+      _locked = _lock.lockRead(maxAttempts);
+    } else {
+      _locked = _lock.lockWrite(maxAttempts);
+    }
+  }
+
+  ~SpinLocker() {
+    release();
+  }
+
+  SpinLocker(SpinLocker&& other)
+    : _lock(other._lock), _mode(other._mode), _locked(other._locked) {
+    other._locked = false;
+  }
+
+  // no move assignment (no reference assignment)
+  SpinLocker& operator=(SpinLocker&& other) = delete;
+
+  // no copy
+  SpinLocker(SpinLocker const&) = delete;
+  SpinLocker& operator=(SpinLocker const&) = delete;
+
+  bool isLocked() const { return _locked; }
+
+  void release() {
+    if (_locked) {
+      if (_mode == Mode::Read) {
+        _lock.unlockRead();
+      } else {
+        _lock.unlockWrite();
+      }
+      _locked = false;
+    }
+  }
+
+ private:
+  ReadWriteSpinLock& _lock;
+  Mode _mode;
+  bool _locked;
+};
+
+}  // namespace arangodb::basics
+
+#endif
diff --git a/lib/Basics/SpinUnlocker.h b/lib/Basics/SpinUnlocker.h
new file mode 100644
index 000000000000..31fe43fcff8c
--- /dev/null
+++ b/lib/Basics/SpinUnlocker.h
@@ -0,0 +1,81 @@
+////////////////////////////////////////////////////////////////////////////////
+/// DISCLAIMER
+///
+/// Copyright 2014-2020 ArangoDB GmbH, Cologne, Germany
+/// Copyright 2004-2014 triAGENS GmbH, Cologne, Germany
+///
+/// Licensed under the Apache License, Version 2.0 (the "License");
+/// you may not use this file except in compliance with the License.
+/// You may obtain a copy of the License at
+///
+///     http://www.apache.org/licenses/LICENSE-2.0
+///
+/// Unless required by applicable law or agreed to in writing, software
+/// distributed under the License is distributed on an "AS IS" BASIS,
+/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+/// See the License for the specific language governing permissions and
+/// limitations under the License.
+///
+/// Copyright holder is ArangoDB GmbH, Cologne, Germany
+///
+/// @author Dan Larkin-York
+////////////////////////////////////////////////////////////////////////////////
+
+#ifndef ARANGO_SPIN_UNLOCKER_H
+#define ARANGO_SPIN_UNLOCKER_H 1
+
+#include <atomic>
+#include <cstdint>
+
+#include "Basics/ReadWriteSpinLock.h"
+
+namespace arangodb::basics {
+
+class SpinUnlocker {
+ public:
+  enum class Mode : std::uint8_t { Read, Write };
+  enum class Effort { Try, Succeed };
+
+ public:
+  SpinUnlocker(Mode mode, ReadWriteSpinLock& lock)
+      : _lock(lock), _mode(mode), _locked(true) {
+    if (_mode == Mode::Read) {
+      _lock.unlockRead();
+    } else {
+      _lock.unlockWrite();
+    }
+    _locked = false;
+  }
+
+  ~SpinUnlocker() { acquire(); }
+
+  // no move
+  SpinUnlocker(SpinUnlocker&&) = delete;
+  SpinUnlocker& operator=(SpinUnlocker&&) = delete;
+
+  // no copy
+  SpinUnlocker(SpinUnlocker const&) = delete;
+  SpinUnlocker& operator=(SpinUnlocker const&) = delete;
+
+  bool isLocked() const { return _locked; }
+
+  void acquire() {
+    if (!_locked) {
+      if (_mode == Mode::Read) {
+        _lock.lockRead();
+      } else {
+        _lock.lockWrite();
+      }
+      _locked = true;
+    }
+  }
+
+ private:
+  ReadWriteSpinLock& _lock;
+  Mode _mode;
+  bool _locked;
+};
+
+}  // namespace arangodb::basics
+
+#endif
diff --git a/lib/Basics/StaticStrings.cpp b/lib/Basics/StaticStrings.cpp
index 4a36d9d71ce1..9cace46fc55c 100644
--- a/lib/Basics/StaticStrings.cpp
+++ b/lib/Basics/StaticStrings.cpp
@@ -66,6 +66,7 @@ std::string const StaticStrings::Prefix("prefix");
 std::string const StaticStrings::ReplaceExisting("replaceExisting");
 std::string const StaticStrings::OverWrite("overwrite");
 std::string const StaticStrings::OverWriteMode("overwriteMode");
+std::string const StaticStrings::PreserveRevisionIds("preserveRevisionIds");
 
 // replication headers
 std::string const StaticStrings::ReplicationHeaderCheckMore(
@@ -227,6 +228,7 @@ std::string const StaticStrings::EncodingDeflate("deflate");
 // collection attributes
 std::string const StaticStrings::DistributeShardsLike("distributeShardsLike");
 std::string const StaticStrings::IsSmart("isSmart");
+std::string const StaticStrings::IsSmartChild("isSmartChild");
 std::string const StaticStrings::NumberOfShards("numberOfShards");
 std::string const StaticStrings::CacheEnabled("cacheEnabled");
 std::string const StaticStrings::IndexBuckets("indexBuckets");
@@ -234,13 +236,16 @@ std::string const StaticStrings::JournalSize("journalSize");
 std::string const StaticStrings::DoCompact("doCompact");
 std::string const StaticStrings::ReplicationFactor("replicationFactor");
 std::string const StaticStrings::MinReplicationFactor("minReplicationFactor");
+std::string const StaticStrings::MinRevision("minRevision");
 std::string const StaticStrings::ShardKeys("shardKeys");
 std::string const StaticStrings::ShardingStrategy("shardingStrategy");
 std::string const StaticStrings::SmartJoinAttribute("smartJoinAttribute");
 std::string const StaticStrings::Sharding("sharding");
 std::string const StaticStrings::Satellite("satellite");
+std::string const StaticStrings::UsesRevisionsAsDocumentIds(
+    "usesRevisionsAsDocumentIds");
+std::string const StaticStrings::Validation("validation");
 std::string const StaticStrings::WriteConcern("writeConcern");
-std::string const StaticStrings::Validators("validators");
 
 // graph attribute names
 std::string const StaticStrings::GraphCollection("_graphs");
@@ -276,6 +281,15 @@ std::string const StaticStrings::GraphCreateCollection("createCollection");
 // Replication
 std::string const StaticStrings::ReplicationSoftLockOnly("doSoftLockOnly");
 std::string const StaticStrings::FailoverCandidates("failoverCandidates");
+std::string const StaticStrings::RevisionTreeCount("count");
+std::string const StaticStrings::RevisionTreeHash("hash");
+std::string const StaticStrings::RevisionTreeMaxDepth("maxDepth");
+std::string const StaticStrings::RevisionTreeNodes("nodes");
+std::string const StaticStrings::RevisionTreeRangeMax("rangeMax");
+std::string const StaticStrings::RevisionTreeRangeMin("rangeMin");
+std::string const StaticStrings::RevisionTreeRanges("ranges");
+std::string const StaticStrings::RevisionTreeResume("resume");
+std::string const StaticStrings::RevisionTreeVersion("version");
 
 // Generic attribute names
 std::string const StaticStrings::AttrCoordinator("coordinator");
@@ -327,4 +341,5 @@ std::string const StaticStrings::ValidatorParameterType("type");
 std::string const StaticStrings::ValidatorParameterRule("rule");
 
 std::string const StaticStrings::ValidatorTypeAQL("aql");
+std::string const StaticStrings::ValidatorTypeJsonSchema("json");
 std::string const StaticStrings::ValidatorTypeBool("bool");
diff --git a/lib/Basics/StaticStrings.h b/lib/Basics/StaticStrings.h
index b5e180ec1fd4..e1d317546170 100644
--- a/lib/Basics/StaticStrings.h
+++ b/lib/Basics/StaticStrings.h
@@ -70,6 +70,7 @@ class StaticStrings {
   static std::string const Prefix;
   static std::string const OverWrite;
   static std::string const OverWriteMode;
+  static std::string const PreserveRevisionIds;
 
   // replication headers
   static std::string const ReplicationHeaderCheckMore;
@@ -209,6 +210,7 @@ class StaticStrings {
   // collection attributes
   static std::string const NumberOfShards;
   static std::string const IsSmart;
+  static std::string const IsSmartChild;
   static std::string const DistributeShardsLike;
   static std::string const CacheEnabled;
   static std::string const IndexBuckets;
@@ -216,13 +218,15 @@ class StaticStrings {
   static std::string const DoCompact;
   static std::string const ReplicationFactor;
   static std::string const MinReplicationFactor;
+  static std::string const MinRevision;
   static std::string const ShardKeys;
   static std::string const ShardingStrategy;
   static std::string const SmartJoinAttribute;
   static std::string const Sharding;
   static std::string const Satellite;
+  static std::string const UsesRevisionsAsDocumentIds;
+  static std::string const Validation;
   static std::string const WriteConcern;
-  static std::string const Validators;
 
   // graph attribute names
   static std::string const GraphCollection;
@@ -255,6 +259,15 @@ class StaticStrings {
   // Replication
   static std::string const ReplicationSoftLockOnly;
   static std::string const FailoverCandidates;
+  static std::string const RevisionTreeCount;
+  static std::string const RevisionTreeHash;
+  static std::string const RevisionTreeMaxDepth;
+  static std::string const RevisionTreeNodes;
+  static std::string const RevisionTreeRangeMax;
+  static std::string const RevisionTreeRangeMin;
+  static std::string const RevisionTreeRanges;
+  static std::string const RevisionTreeResume;
+  static std::string const RevisionTreeVersion;
 
   // generic attribute names
   static std::string const AttrCoordinator;
@@ -301,6 +314,7 @@ class StaticStrings {
   static std::string const ValidatorParameterType;
   static std::string const ValidatorParameterRule;
 
+  static std::string const ValidatorTypeJsonSchema;
   static std::string const ValidatorTypeAQL;
   static std::string const ValidatorTypeBool;
 };
diff --git a/lib/Basics/StringUtils.cpp b/lib/Basics/StringUtils.cpp
index 454ca15c7ad2..b2b83173c34d 100644
--- a/lib/Basics/StringUtils.cpp
+++ b/lib/Basics/StringUtils.cpp
@@ -1494,24 +1494,6 @@ bool boolean(std::string const& str) {
   return false;
 }
 
-#ifndef ARANGODB_STRING_UTILS_USE_FROM_CHARS
-int64_t int64(std::string const& value) {
-  try {
-    return std::stoll(value, nullptr, 10);
-  } catch (...) {
-    return 0;
-  }
-}
-
-uint64_t uint64(std::string const& value) {
-  try {
-    return std::stoull(value, nullptr, 10);
-  } catch (...) {
-    return 0;
-  }
-}
-#endif
-
 uint64_t uint64_trusted(char const* value, size_t length) {
   uint64_t result = 0;
 
@@ -1580,88 +1562,6 @@ uint64_t uint64_trusted(char const* value, size_t length) {
   return result;
 }
 
-#ifndef ARANGODB_STRING_UTILS_USE_FROM_CHARS
-int32_t int32(std::string const& str) {
-#ifdef TRI_HAVE_STRTOL_R
-  struct reent buffer;
-  return strtol_r(&buffer, str.c_str(), 0, 10);
-#else
-#ifdef TRI_HAVE__STRTOL_R
-  struct reent buffer;
-  return _strtol_r(&buffer, str.c_str(), 0, 10);
-#else
-  return (int32_t)strtol(str.c_str(), nullptr, 10);
-#endif
-#endif
-}
-
-int32_t int32(char const* value, size_t size) {
-  char tmp[22];
-
-  if (value[size] != '\0') {
-    if (size >= sizeof(tmp)) {
-      size = sizeof(tmp) - 1;
-    }
-
-    memcpy(tmp, value, size);
-    tmp[size] = '\0';
-    value = tmp;
-  }
-
-#ifdef TRI_HAVE_STRTOL_R
-  struct reent buffer;
-  return strtol_r(&buffer, value, 0, 10);
-#else
-#ifdef TRI_HAVE__STRTOL_R
-  struct reent buffer;
-  return _strtol_r(&buffer, value, 0, 10);
-#else
-  return (int32_t)strtol(value, nullptr, 10);
-#endif
-#endif
-}
-
-uint32_t uint32(std::string const& str) {
-#ifdef TRI_HAVE_STRTOUL_R
-  struct reent buffer;
-  return strtoul_r(&buffer, str.c_str(), 0, 10);
-#else
-#ifdef TRI_HAVE__STRTOUL_R
-  struct reent buffer;
-  return _strtoul_r(&buffer, str.c_str(), 0, 10);
-#else
-  return (uint32_t)strtoul(str.c_str(), nullptr, 10);
-#endif
-#endif
-}
-
-uint32_t uint32(char const* value, size_t size) {
-  char tmp[22];
-
-  if (value[size] != '\0') {
-    if (size >= sizeof(tmp)) {
-      size = sizeof(tmp) - 1;
-    }
-
-    memcpy(tmp, value, size);
-    tmp[size] = '\0';
-    value = tmp;
-  }
-
-#ifdef TRI_HAVE_STRTOUL_R
-  struct reent buffer;
-  return strtoul_r(&buffer, value, 0, 10);
-#else
-#ifdef TRI_HAVE__STRTOUL_R
-  struct reent buffer;
-  return _strtoul_r(&buffer, value, 0, 10);
-#else
-  return (uint32_t)strtoul(value, nullptr, 10);
-#endif
-#endif
-}
-#endif
-
 double doubleDecimal(std::string const& str) {
   return doubleDecimal(str.c_str(), str.size());
 }
diff --git a/lib/Basics/StringUtils.h b/lib/Basics/StringUtils.h
index b28b3ac4ecb4..3d8bce8cd684 100644
--- a/lib/Basics/StringUtils.h
+++ b/lib/Basics/StringUtils.h
@@ -26,6 +26,7 @@
 #define ARANGODB_BASICS_STRING_UTILS_H 1
 
 #include <stddef.h>
+#include <charconv>
 #include <cstdint>
 #include <cstring>
 #include <functional>
@@ -35,14 +36,7 @@
 
 #include "Basics/Common.h"
 
-#if __cpp_lib_to_chars >= 201611
 // use non-throwing, non-allocating std::from_chars etc. from standard library
-#include <charconv>
-#define ARANGODB_STRING_UTILS_USE_FROM_CHARS 1
-#else
-// use own functionality
-#undef ARANGODB_STRING_UTILS_USE_FROM_CHARS
-#endif
 
 /// @brief helper macro for calculating strlens for static strings at
 /// a compile-time (unless compiled with fno-builtin-strlen etc.)
@@ -294,8 +288,6 @@ inline int hex2int(char ch, int errorValue = 0) {
 bool boolean(std::string const& str);
 
 /// @brief parses an integer
-#ifdef ARANGODB_STRING_UTILS_USE_FROM_CHARS
-// use functionality provided by c++17
 inline int64_t int64(char const* value, size_t size) noexcept {
   int64_t result = 0;
   std::from_chars(value, value + size, result, 10);
@@ -304,16 +296,8 @@ inline int64_t int64(char const* value, size_t size) noexcept {
 inline int64_t int64(std::string const& value) noexcept {
   return StringUtils::int64(value.data(), value.size());
 }
-#else
-int64_t int64(std::string const& value);
-inline int64_t int64(char const* value, size_t size) {
-  return StringUtils::int64(std::string(value, size));
-}
-#endif
 
 /// @brief parses an unsigned integer
-#ifdef ARANGODB_STRING_UTILS_USE_FROM_CHARS
-// use functionality provided by c++17
 inline uint64_t uint64(char const* value, size_t size) noexcept {
   uint64_t result = 0;
   std::from_chars(value, value + size, result, 10);
@@ -325,15 +309,6 @@ inline uint64_t uint64(std::string const& value) noexcept {
 inline uint64_t uint64(std::string_view const& value) noexcept {
   return StringUtils::uint64(value.data(), value.size());
 }
-#else
-uint64_t uint64(std::string const& value);
-inline uint64_t uint64(char const* value, size_t size) {
-  return StringUtils::uint64(std::string(value, size));
-}
-inline uint64_t uint64(std::string_view const& value) noexcept {
-  return StringUtils::uint64(value.data(), value.size());
-}
-#endif
 
 /// @brief parses an unsigned integer
 /// the caller must make sure that the input buffer only contains valid
@@ -346,8 +321,6 @@ inline uint64_t uint64_trusted(std::string const& value) {
 }
 
 /// @brief parses an integer
-#ifdef ARANGODB_STRING_UTILS_USE_FROM_CHARS
-// use functionality provided by c++17
 inline int32_t int32(char const* value, size_t size) noexcept {
   int32_t result = 0;
   std::from_chars(value, value + size, result, 10);
@@ -356,14 +329,8 @@ inline int32_t int32(char const* value, size_t size) noexcept {
 inline int32_t int32(std::string const& value) noexcept {
   return StringUtils::int32(value.data(), value.size());
 }
-#else
-int32_t int32(std::string const& value);
-int32_t int32(char const* value, size_t size);
-#endif
 
 /// @brief parses an unsigned integer
-#ifdef ARANGODB_STRING_UTILS_USE_FROM_CHARS
-// use functionality provided by c++17
 inline uint32_t uint32(char const* value, size_t size) noexcept {
   uint32_t result = 0;
   std::from_chars(value, value + size, result, 10);
@@ -372,10 +339,6 @@ inline uint32_t uint32(char const* value, size_t size) noexcept {
 inline uint32_t uint32(std::string const& value) noexcept {
   return StringUtils::uint32(value.data(), value.size());
 }
-#else
-uint32_t uint32(std::string const& value);
-uint32_t uint32(char const* value, size_t size);
-#endif
 
 /// @brief parses a decimal
 double doubleDecimal(std::string const& str);
diff --git a/lib/Basics/WriteLocker.h b/lib/Basics/WriteLocker.h
index 4f326c259658..53b3521ab496 100644
--- a/lib/Basics/WriteLocker.h
+++ b/lib/Basics/WriteLocker.h
@@ -31,7 +31,8 @@
 #include "Basics/debugging.h"
 
 #ifdef ARANGODB_SHOW_LOCK_TIME
-#include "Logger/Logger.h"
+#include "Basics/system-functions.h"
+#include "Logger/LogMacros.h"
 #endif
 
 #include <thread>
@@ -112,7 +113,8 @@ class WriteLocker {
 #ifdef ARANGODB_SHOW_LOCK_TIME
     if (_time > TRI_SHOW_LOCK_THRESHOLD) {
       LOG_TOPIC("95aa0", INFO, arangodb::Logger::PERFORMANCE)
-          << "WriteLocker " << _file << ":" << _line << " took " << _time << " s";
+          << "WriteLocker for lock [" << _readWriteLock << "] " << _file << ":"
+          << _line << " took " << _time << " s";
     }
 #endif
   }
@@ -130,7 +132,7 @@ class WriteLocker {
 
   [[nodiscard]] bool tryLock() {
     TRI_ASSERT(!_isLocked);
-    if (_readWriteLock->tryWriteLock()) {
+    if (_readWriteLock->tryLockWrite()) {
       _isLocked = true;
     }
     return _isLocked;
@@ -139,7 +141,7 @@ class WriteLocker {
   /// @brief acquire the write lock, blocking
   void lock() {
     TRI_ASSERT(!_isLocked);
-    _readWriteLock->writeLock();
+    _readWriteLock->lockWrite();
     _isLocked = true;
   }
 
diff --git a/lib/Basics/WriteUnlocker.h b/lib/Basics/WriteUnlocker.h
index f5c877cde9a6..63e0b59bc9dc 100644
--- a/lib/Basics/WriteUnlocker.h
+++ b/lib/Basics/WriteUnlocker.h
@@ -36,17 +36,8 @@
 /// number.
 ////////////////////////////////////////////////////////////////////////////////
 
-#ifdef ARANGODB_SHOW_LOCK_TIME
-
-#define WRITE_UNLOCKER(obj, lock) \
-  arangodb::basics::WriteUnlocker obj(&lock, __FILE__, __LINE__)
-
-#else
-
 #define WRITE_UNLOCKER(obj, lock) arangodb::basics::WriteUnlocker obj(&lock)
 
-#endif
-
 namespace arangodb {
 namespace basics {
 
@@ -68,33 +59,16 @@ class WriteUnlocker {
   /// The constructor unlocks the lock, the destructors acquires a write-lock.
   //////////////////////////////////////////////////////////////////////////////
 
-#ifdef ARANGODB_SHOW_LOCK_TIME
-
-  //////////////////////////////////////////////////////////////////////////////
-  /// @brief unlocks the lock
-  ///
-  /// The constructor unlocks the lock, the destructors acquires a write-lock.
-  //////////////////////////////////////////////////////////////////////////////
-
-  WriteUnlocker(ReadWriteLock* readWriteLock, char const* file, int line)
-      : _readWriteLock(readWriteLock), _file(file), _line(line) {
-    _readWriteLock->unlockWrite();
-  }
-
-#else
-
   explicit WriteUnlocker(ReadWriteLock* readWriteLock)
       : _readWriteLock(readWriteLock) {
     _readWriteLock->unlockWrite();
   }
 
-#endif
-
   ////////////////////////////////////////////////////////////////////////////////
   /// @brief acquires the write-lock
   ////////////////////////////////////////////////////////////////////////////////
 
-  ~WriteUnlocker() { _readWriteLock->writeLock(); }
+  ~WriteUnlocker() { _readWriteLock->lockWrite(); }
 
  private:
   ////////////////////////////////////////////////////////////////////////////////
@@ -103,21 +77,6 @@ class WriteUnlocker {
 
   basics::ReadWriteLock* _readWriteLock;
 
-#ifdef ARANGODB_SHOW_LOCK_TIME
-
-  ////////////////////////////////////////////////////////////////////////////////
-  /// @brief file
-  ////////////////////////////////////////////////////////////////////////////////
-
-  char const* _file;
-
-  ////////////////////////////////////////////////////////////////////////////////
-  /// @brief line number
-  ////////////////////////////////////////////////////////////////////////////////
-
-  int _line;
-
-#endif
 };
 }  // namespace basics
 }  // namespace arangodb
diff --git a/lib/Basics/debugging.h b/lib/Basics/debugging.h
index 560e38a29078..5e959bb5f617 100644
--- a/lib/Basics/debugging.h
+++ b/lib/Basics/debugging.h
@@ -102,7 +102,6 @@ void TRI_LogBacktrace();
 void TRI_FlushDebugging();
 void TRI_FlushDebugging(char const* file, int line, char const* message);
 
-
 ////////////////////////////////////////////////////////////////////////////////
 /// @brief container traits
 ////////////////////////////////////////////////////////////////////////////////
@@ -111,7 +110,8 @@ namespace container_traits {
 
 using tc = char[2];
 
-template<typename T> struct is_container {
+template <typename T>
+struct is_container {
   static tc& test(...);
 
   template <typename U>
@@ -119,15 +119,16 @@ template<typename T> struct is_container {
   static constexpr bool value = sizeof(test(std::declval<T>())) == 1;
 };
 
-template< class T >
+template <class T>
 inline constexpr bool is_container_v = is_container<T>::value;
 
-template < typename T > struct is_associative {
-  static tc& test(...) ;
-  
-  template < typename U >
-  static char test(U&&, typename U::key_type* = 0) ;
-  static constexpr bool value = sizeof( test( std::declval<T>() ) ) == 1 ;
+template <typename T>
+struct is_associative {
+  static tc& test(...);
+
+  template <typename U>
+  static char test(U&&, typename U::key_type* = 0);
+  static constexpr bool value = sizeof(test(std::declval<T>())) == 1;
 };
 
 }  // namespace container_traits
@@ -139,21 +140,21 @@ struct remove_cvref {
 template <class T>
 using remove_cvref_t = typename remove_cvref<T>::type;
 
-template < typename T > struct is_container :
-  std::conditional_t<(container_traits::is_container_v<T> || std::is_array_v<T>)
-                   && !std::is_same_v<char *, std::decay_t<T>>
-                   && !std::is_same_v<char const*, std::decay_t<T>>
-                   && !std::is_same_v<unsigned char *, std::decay_t<T>>
-                   && !std::is_same_v<unsigned char const*, std::decay_t<T>>
-                   && !std::is_same_v<std::string, std::decay_t<T>>
-                   && !std::is_same_v<std::string_view, std::decay_t<T>>,
-                   std::true_type, std::false_type > {};
-
-template < typename T > struct is_associative :
-  std::conditional< container_traits::is_container<T>::value && container_traits::is_associative<T>::value,
-                    std::true_type, std::false_type >::type {};
-
-
+template <typename T>
+struct is_container
+    : std::conditional<(container_traits::is_container<T>::value || std::is_array<T>::value) &&
+                           !std::is_same_v<char*, typename std::decay<T>::type> &&
+                           !std::is_same_v<char const*, typename std::decay<T>::type> &&
+                           !std::is_same_v<unsigned char*, typename std::decay<T>::type> &&
+                           !std::is_same_v<unsigned char const*, typename std::decay<T>::type> &&
+                           !std::is_same_v<T, std::string> && !std::is_same_v<T, std::string_view> &&
+                           !std::is_same_v<T, const std::string>,
+                       std::true_type, std::false_type>::type {};
+
+template <typename T>
+struct is_associative
+    : std::conditional<container_traits::is_container<T>::value && container_traits::is_associative<T>::value,
+                       std::true_type, std::false_type>::type {};
 
 ////////////////////////////////////////////////////////////////////////////////
 /// @brief no std::enable_if_t in c++11
@@ -161,8 +162,8 @@ template < typename T > struct is_associative :
 
 #if __cplusplus <= 201103L
 namespace std {
-template< bool B, class T = void >
-using enable_if_t = typename std::enable_if<B,T>::type;
+template <bool B, class T = void>
+using enable_if_t = typename std::enable_if<B, T>::type;
 }
 #endif
 
@@ -170,9 +171,9 @@ using enable_if_t = typename std::enable_if<B,T>::type;
 /// @brief forward declaration for pair output below
 ////////////////////////////////////////////////////////////////////////////////
 
-template<typename T>
-std::enable_if_t<is_container<T>::value, std::ostream&>
-operator<< (std::ostream& o, T const& t);
+template <typename T>
+std::enable_if_t<is_container<T>::value, std::ostream&> operator<<(std::ostream& o,
+                                                                   T const& t);
 
 ////////////////////////////////////////////////////////////////////////////////
 /// @brief dump pair contents to an ostream
@@ -188,20 +189,19 @@ std::ostream& operator<<(std::ostream& stream, std::pair<T1, T2> const& obj) {
 /// @brief dump vector contents to an ostream
 ////////////////////////////////////////////////////////////////////////////////
 
-template<bool b>
+template <bool b>
 struct conpar {
   static char const open;
   static char const close;
 };
 
-template< bool B, class T = void >
-using enable_if_t = typename std::enable_if<B,T>::type;
+template <bool B, class T = void>
+using enable_if_t = typename std::enable_if<B, T>::type;
 
-template<typename T>
-enable_if_t<is_container<T>::value, std::ostream&>
-operator<< (std::ostream& o, T const& t) {
+template <typename T>
+enable_if_t<is_container<T>::value, std::ostream&> operator<<(std::ostream& o, T const& t) {
   o << conpar<is_associative<T>::value>::open;
-  bool first = true;  
+  bool first = true;
   for (auto const& i : t) {
     if (first) {
       o << " ";
@@ -209,10 +209,10 @@ operator<< (std::ostream& o, T const& t) {
     } else {
       o << ", ";
     }
-    o << i ;
+    o << i;
   }
   o << " " << conpar<is_associative<T>::value>::close;
-  return o;  
+  return o;
 }
 
 /// @brief assert
diff --git a/lib/Basics/errors.dat b/lib/Basics/errors.dat
index 7cad8f9840c8..514a33157a6f 100755
--- a/lib/Basics/errors.dat
+++ b/lib/Basics/errors.dat
@@ -36,8 +36,6 @@ ERROR_ARANGO_ICU_ERROR,33,"icu error: %s","will be raised if icu operations fail
 ERROR_CANNOT_READ_FILE,34,"cannot read file","Will be raised when a file cannot be read."
 ERROR_INCOMPATIBLE_VERSION,35,"incompatible server version","Will be raised when a server is running an incompatible version of ArangoDB."
 ERROR_DISABLED,36,"disabled","Will be raised when a requested resource is not enabled."
-ERROR_VALIDATION_FAILED,37,"validation failed","Will be raised when document does not pass validation."
-ERROR_VALIDATION_BAD_PARAMETER,38,"invalid validation parameter","Will be raised when values in validator array are not valid."
 
 ################################################################################
 ## HTTP error status codes
@@ -280,6 +278,13 @@ ERROR_QUERY_USER_WARN,1594,"%s","Will be raised if and user provided expression
 ERROR_CURSOR_NOT_FOUND,1600,"cursor not found","Will be raised when a cursor is requested via its id but a cursor with that id cannot be found."
 ERROR_CURSOR_BUSY,1601,"cursor is busy","Will be raised when a cursor is requested via its id but a concurrent request is still using the cursor."
 
+################################################################################
+## ArangoDB validation errors
+################################################################################
+
+ERROR_VALIDATION_FAILED,1620,"validation failed","Will be raised when a document does not pass validation."
+ERROR_VALIDATION_BAD_PARAMETER,1621,"invalid validation parameter","Will be raised when the validator description is invalid."
+
 ################################################################################
 ## ArangoDB transaction errors
 ################################################################################
diff --git a/lib/Basics/hashes.h b/lib/Basics/hashes.h
index ad4ac4567fad..24db25be5083 100644
--- a/lib/Basics/hashes.h
+++ b/lib/Basics/hashes.h
@@ -26,6 +26,7 @@
 
 #include <cstdint>
 #include <cstdlib>
+#include <type_traits>
 
 #include "Basics/Common.h"
 
@@ -38,6 +39,12 @@ uint64_t TRI_FnvHashPointer(void const*, size_t);
 /// @brief computes a FNV hash for strings
 uint64_t TRI_FnvHashString(char const*);
 
+/// @brief computes a FNV hash for POD types
+template <typename T>
+std::enable_if_t<std::is_pod_v<T>, uint64_t> TRI_FnvHashPod(T input) {
+  return TRI_FnvHashPointer(&input, sizeof(T));
+}
+
 /// @brief computes a initial FNV for blocks
 static constexpr uint64_t TRI_FnvHashBlockInitial() {
   return 0xcbf29ce484222325ULL;
diff --git a/lib/Basics/voc-errors.cpp b/lib/Basics/voc-errors.cpp
index 2e131705a634..dd8dbb2ca497 100644
--- a/lib/Basics/voc-errors.cpp
+++ b/lib/Basics/voc-errors.cpp
@@ -42,8 +42,6 @@ void TRI_InitializeErrorMessages() {
   REG_ERROR(ERROR_CANNOT_READ_FILE, "cannot read file");
   REG_ERROR(ERROR_INCOMPATIBLE_VERSION, "incompatible server version");
   REG_ERROR(ERROR_DISABLED, "disabled");
-  REG_ERROR(ERROR_VALIDATION_FAILED, "validation failed");
-  REG_ERROR(ERROR_VALIDATION_BAD_PARAMETER, "invalid validation parameter");
   REG_ERROR(ERROR_HTTP_BAD_PARAMETER, "bad parameter");
   REG_ERROR(ERROR_HTTP_UNAUTHORIZED, "unauthorized");
   REG_ERROR(ERROR_HTTP_FORBIDDEN, "forbidden");
@@ -220,6 +218,8 @@ void TRI_InitializeErrorMessages() {
   REG_ERROR(ERROR_QUERY_USER_WARN, "%s");
   REG_ERROR(ERROR_CURSOR_NOT_FOUND, "cursor not found");
   REG_ERROR(ERROR_CURSOR_BUSY, "cursor is busy");
+  REG_ERROR(ERROR_VALIDATION_FAILED, "validation failed");
+  REG_ERROR(ERROR_VALIDATION_BAD_PARAMETER, "invalid validation parameter");
   REG_ERROR(ERROR_TRANSACTION_INTERNAL, "internal transaction error");
   REG_ERROR(ERROR_TRANSACTION_NESTED, "nested transactions detected");
   REG_ERROR(ERROR_TRANSACTION_UNREGISTERED_COLLECTION, "unregistered collection used in transaction");
diff --git a/lib/Basics/voc-errors.h b/lib/Basics/voc-errors.h
index ee239cca48fe..f069909fcbfc 100644
--- a/lib/Basics/voc-errors.h
+++ b/lib/Basics/voc-errors.h
@@ -178,16 +178,6 @@ constexpr int TRI_ERROR_INCOMPATIBLE_VERSION
 /// Will be raised when a requested resource is not enabled.
 constexpr int TRI_ERROR_DISABLED                                                = 36;
 
-/// 37: ERROR_VALIDATION_FAILED
-/// "validation failed"
-/// Will be raised when document does not pass validation.
-constexpr int TRI_ERROR_VALIDATION_FAILED                                       = 37;
-
-/// 38: ERROR_VALIDATION_BAD_PARAMETER
-/// "invalid validation parameter"
-/// Will be raised when values in validator array are not valid.
-constexpr int TRI_ERROR_VALIDATION_BAD_PARAMETER                                = 38;
-
 /// 400: ERROR_HTTP_BAD_PARAMETER
 /// "bad parameter"
 /// Will be raised when the HTTP request does not fulfill the requirements.
@@ -1169,6 +1159,16 @@ constexpr int TRI_ERROR_CURSOR_NOT_FOUND
 /// request is still using the cursor.
 constexpr int TRI_ERROR_CURSOR_BUSY                                             = 1601;
 
+/// 1620: ERROR_VALIDATION_FAILED
+/// "validation failed"
+/// Will be raised when a document does not pass validation.
+constexpr int TRI_ERROR_VALIDATION_FAILED                                       = 1620;
+
+/// 1621: ERROR_VALIDATION_BAD_PARAMETER
+/// "invalid validation parameter"
+/// Will be raised when the validator description is invalid.
+constexpr int TRI_ERROR_VALIDATION_BAD_PARAMETER                                = 1621;
+
 /// 1650: ERROR_TRANSACTION_INTERNAL
 /// "internal transaction error"
 /// Will be raised when a wrong usage of transactions is detected. this is an
diff --git a/lib/CMakeLists.txt b/lib/CMakeLists.txt
index d968a482f345..0e22f3093a11 100644
--- a/lib/CMakeLists.txt
+++ b/lib/CMakeLists.txt
@@ -167,6 +167,7 @@ add_library(arango STATIC
   Basics/voc-errors.cpp
   Basics/exitcodes.cpp
   Basics/xxhash.cpp
+  Containers/MerkleTree.cpp
   Endpoint/Endpoint.cpp
   Endpoint/EndpointIp.cpp
   Endpoint/EndpointIpV4.cpp
@@ -232,6 +233,11 @@ target_link_libraries(arango
   ${SYSTEM_LIBRARIES}
 )
 
+add_dependencies(arango snappy-static)
+
+set(SNAPPY_INCLUDE_DIR "${SNAPPY_SOURCE_DIR};${SNAPPY_BUILD_DIR}" CACHE PATH "relation to snappy")
+include_directories(${SNAPPY_INCLUDE_DIR})
+
 # Rebuild generated error files so they are up-to-date when all
 # dependent stuff is built
 if (USE_MAINTAINER_MODE)
diff --git a/lib/Containers/Enumerate.h b/lib/Containers/Enumerate.h
new file mode 100644
index 000000000000..6fcf458d00f9
--- /dev/null
+++ b/lib/Containers/Enumerate.h
@@ -0,0 +1,130 @@
+////////////////////////////////////////////////////////////////////////////////
+/// DISCLAIMER
+///
+/// Copyright 2014-2020 ArangoDB GmbH, Cologne, Germany
+/// Copyright 2004-2014 triAGENS GmbH, Cologne, Germany
+///
+/// Licensed under the Apache License, Version 2.0 (the "License");
+/// you may not use this file except in compliance with the License.
+/// You may obtain a copy of the License at
+///
+///     http://www.apache.org/licenses/LICENSE-2.0
+///
+/// Unless required by applicable law or agreed to in writing, software
+/// distributed under the License is distributed on an "AS IS" BASIS,
+/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+/// See the License for the specific language governing permissions and
+/// limitations under the License.
+///
+/// Copyright holder is ArangoDB GmbH, Cologne, Germany
+///
+/// @author Lars Maier
+////////////////////////////////////////////////////////////////////////////////
+#ifndef ARANGODB_CONTAINERS_ENUMERATE_H
+#define ARANGODB_CONTAINERS_ENUMERATE_H
+#include <functional>
+#include <iterator>
+
+namespace arangodb {
+
+template <typename T, typename C>
+struct enumerate_wrapper;
+
+/*
+ * enumerate function similar to pythons enumerate.
+ * Usage:
+ *  for (auto [idx, e] : enumerate(v)) {
+ *    // idx is incremented for each element
+ *    // e is the reference type of the iterator of the container v.
+ *  }
+ *
+ * Usable for std::vector, std::list, std::map and std::unordered_map. _should_
+ * work for other containers that provide a LegacyIterator as well.
+ */
+template <typename T, typename C = unsigned int>
+enumerate_wrapper<T, C> enumerate(T&& v, C c = C());
+
+template <typename T, typename C = unsigned int>
+struct enumerate_iterator;
+
+template <typename T, typename C>
+void swap(enumerate_iterator<T, C>& a, enumerate_iterator<T, C>& b);
+
+template <typename T, typename C>
+struct enumerate_iterator {
+  enumerate_iterator() : _iter(), _c(0) {}
+
+  explicit enumerate_iterator(T iter, C c = C()) : _iter(iter), _c(c) {}
+  enumerate_iterator(enumerate_iterator const&) = default;
+  enumerate_iterator(enumerate_iterator&&) noexcept = default;
+
+  enumerate_iterator& operator=(enumerate_iterator const&) = default;
+  enumerate_iterator& operator=(enumerate_iterator&&) noexcept = default;
+
+  ~enumerate_iterator() noexcept = default;
+
+  friend void swap<>(enumerate_iterator<T, C>& a, enumerate_iterator<T, C>& b);
+
+  using difference_type = typename std::iterator_traits<T>::difference_type;
+  using value_type = std::pair<C, typename std::iterator_traits<T>::value_type>;
+  using pointer = std::pair<C, typename std::iterator_traits<T>::pointer>;
+  using reference = std::pair<C, typename std::iterator_traits<T>::reference>;
+  using iterator_category = typename std::iterator_traits<T>::iterator_category;
+
+  reference operator*() const;
+
+  enumerate_iterator& operator++();
+
+  bool operator==(enumerate_iterator const& other) const;
+  bool operator!=(enumerate_iterator const& other) const;
+
+  T _iter;
+  C _c;
+};
+
+template <typename T, typename C>
+auto enumerate_iterator<T, C>::operator*() const -> reference {
+  return std::make_pair(_c, std::reference_wrapper(*_iter));
+}
+
+template <typename T, typename C>
+struct enumerate_wrapper {
+  using I = typename std::decay_t<T>::iterator;
+  T _t;
+  C _c;
+
+  auto begin() { return enumerate_iterator(_t.begin(), _c); }
+  auto end() { return enumerate_iterator(_t.end(), _c); }
+};
+
+template <typename T, typename C>
+void swap(enumerate_iterator<T, C>& a, enumerate_iterator<T, C>& b) {
+  using std::swap;
+  swap(a._iter, b._iter);
+  swap(a._c, b._c);
+}
+
+template <typename T, typename C>
+auto enumerate_iterator<T, C>::operator++() -> enumerate_iterator& {
+  ++_c;
+  ++_iter;
+  return *this;
+}
+
+template <typename T, typename C>
+bool enumerate_iterator<T, C>::operator==(enumerate_iterator const& other) const {
+  return _iter == other._iter;
+}
+
+template <typename T, typename C>
+bool enumerate_iterator<T, C>::operator!=(enumerate_iterator const& other) const {
+  return _iter != other._iter;
+}
+
+template <typename T, typename C>
+enumerate_wrapper<T, C> enumerate(T&& v, C c) {
+  return enumerate_wrapper<T, C>{std::forward<T>(v), c};
+}
+};  // namespace arangodb
+
+#endif
diff --git a/lib/Containers/MerkleTree.cpp b/lib/Containers/MerkleTree.cpp
new file mode 100644
index 000000000000..dbd78cd718a1
--- /dev/null
+++ b/lib/Containers/MerkleTree.cpp
@@ -0,0 +1,773 @@
+////////////////////////////////////////////////////////////////////////////////
+/// DISCLAIMER
+///
+/// Copyright 2019 ArangoDB GmbH, Cologne, Germany
+///
+/// Licensed under the Apache License, Version 2.0 (the "License");
+/// you may not use this file except in compliance with the License.
+/// You may obtain a copy of the License at
+///
+///     http://www.apache.org/licenses/LICENSE-2.0
+///
+/// Unless required by applicable law or agreed to in writing, software
+/// distributed under the License is distributed on an "AS IS" BASIS,
+/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+/// See the License for the specific language governing permissions and
+/// limitations under the License.
+///
+/// Copyright holder is ArangoDB GmbH, Cologne, Germany
+///
+/// @author Dan Larkin-York
+////////////////////////////////////////////////////////////////////////////////
+
+#include <algorithm>
+#include <cmath>
+#include <cstddef>
+#include <cstring>
+#include <functional>
+#include <limits>
+#include <memory>
+#include <mutex>
+#include <queue>
+#include <shared_mutex>
+#include <stdexcept>
+#include <string>
+#include <string_view>
+#include <type_traits>
+#include <utility>
+#include <vector>
+
+#include <snappy.h>
+
+#include <velocypack/Iterator.h>
+
+#include "MerkleTree.h"
+
+#include "Basics/HybridLogicalClock.h"
+#include "Basics/NumberUtils.h"
+#include "Basics/StaticStrings.h"
+#include "Basics/debugging.h"
+#include "Basics/hashes.h"
+
+namespace {
+static constexpr std::uint8_t CurrentVersion = 0x01;
+static constexpr char CompressedCurrent = '1';
+static constexpr char UncompressedCurrent = '2';
+}  // namespace
+
+namespace arangodb {
+namespace containers {
+
+template <std::size_t const BranchingBits, std::size_t const LockStripes>
+bool MerkleTree<BranchingBits, LockStripes>::Node::operator==(Node const& other) {
+  return ((this->count == other.count) && (this->hash == other.hash));
+}
+
+template <std::size_t const BranchingBits, std::size_t const LockStripes>
+constexpr std::size_t MerkleTree<BranchingBits, LockStripes>::nodeCountAtDepth(std::size_t maxDepth) {
+  return static_cast<std::size_t>(1) << (BranchingBits * maxDepth);
+}
+class TestNodeCountAtDepth : public MerkleTree<3, 64> {
+  static_assert(nodeCountAtDepth(0) == 1);
+  static_assert(nodeCountAtDepth(1) == 8);
+  static_assert(nodeCountAtDepth(2) == 64);
+  static_assert(nodeCountAtDepth(3) == 512);
+  // ...
+  static_assert(nodeCountAtDepth(10) == 1073741824);
+};
+
+template <std::size_t const BranchingBits, std::size_t const LockStripes>
+constexpr std::size_t MerkleTree<BranchingBits, LockStripes>::nodeCountUpToDepth(std::size_t maxDepth) {
+  return ((static_cast<std::size_t>(1) << (BranchingBits * (maxDepth + 1))) - 1) /
+         (BranchingFactor - 1);
+}
+class TestNodeCountUpToDepth : public MerkleTree<3, 64> {
+  static_assert(nodeCountUpToDepth(0) == 1);
+  static_assert(nodeCountUpToDepth(1) == 9);
+  static_assert(nodeCountUpToDepth(2) == 73);
+  static_assert(nodeCountUpToDepth(3) == 585);
+  // ...
+  static_assert(nodeCountUpToDepth(10) == 1227133513);
+};
+
+template <std::size_t const BranchingBits, std::size_t const LockStripes>
+constexpr std::size_t MerkleTree<BranchingBits, LockStripes>::allocationSize(std::size_t maxDepth) {
+  return MetaSize + (NodeSize * nodeCountUpToDepth(maxDepth));
+}
+
+template <std::size_t const BranchingBits, std::size_t const LockStripes>
+constexpr std::size_t MerkleTree<BranchingBits, LockStripes>::log2ceil(std::size_t n) {
+  if (n > (std::numeric_limits<std::size_t>::max() / 2)) {
+    return 8 * sizeof(std::size_t) - 1;
+  }
+  std::size_t i = 1;
+  for (; (static_cast<std::size_t>(1) << i) < n; ++i) {
+  }
+  return i;
+}
+class TestLog2Ceil : public MerkleTree<3, 64> {
+  static_assert(log2ceil(0) == 1);
+  static_assert(log2ceil(1) == 1);
+  static_assert(log2ceil(2) == 1);
+  static_assert(log2ceil(3) == 2);
+  static_assert(log2ceil(4) == 2);
+  static_assert(log2ceil(5) == 3);
+  static_assert(log2ceil(8) == 3);
+  static_assert(log2ceil(9) == 4);
+  static_assert(log2ceil(16) == 4);
+  static_assert(log2ceil(17) == 5);
+  // ...
+  static_assert(log2ceil((std::numeric_limits<std::size_t>::max() / 2) + 1) ==
+                8 * sizeof(std::size_t) - 1);
+};
+
+template <std::size_t const BranchingBits, std::size_t const LockStripes>
+constexpr std::size_t MerkleTree<BranchingBits, LockStripes>::minimumFactorFor(
+    std::size_t current, std::size_t target) {
+  if (target < current) {
+    throw std::invalid_argument("Was expecting target >= current.");
+  }
+
+  if (!NumberUtils::isPowerOf2(current)) {
+    throw std::invalid_argument("Was expecting current to be power of 2.");
+  }
+
+  // special fast case
+  if (target == current) {
+    return 2;
+  }
+
+  std::size_t rawFactor = target / current;
+  std::size_t correctedFactor = static_cast<std::size_t>(1)
+                                << log2ceil(rawFactor + 1);  // force power of 2
+  TRI_ASSERT(NumberUtils::isPowerOf2(correctedFactor));
+  TRI_ASSERT(target >= (current * correctedFactor / 2));
+  return correctedFactor;
+}
+class TestMinimumFactorFor : public MerkleTree<3, 64> {
+  static_assert(minimumFactorFor(1, 2) == 4);
+  static_assert(minimumFactorFor(1, 4) == 8);
+  static_assert(minimumFactorFor(1, 12) == 16);
+  static_assert(minimumFactorFor(1, 16) == 32);
+  static_assert(minimumFactorFor(2, 3) == 2);
+  static_assert(minimumFactorFor(2, 4) == 4);
+  static_assert(minimumFactorFor(2, 5) == 4);
+  static_assert(minimumFactorFor(2, 7) == 4);
+  static_assert(minimumFactorFor(2, 8) == 8);
+  static_assert(minimumFactorFor(2, 15) == 8);
+  static_assert(minimumFactorFor(2, 16) == 16);
+  static_assert(minimumFactorFor(2, 17) == 16);
+  static_assert(minimumFactorFor(2, 31) == 16);
+  static_assert(minimumFactorFor(2, 32) == 32);
+  static_assert(minimumFactorFor(65536, 90000) == 2);
+  static_assert(minimumFactorFor(8192, 2147483600) == 262144);
+};
+
+template <std::size_t const BranchingBits, std::size_t const LockStripes>
+std::size_t MerkleTree<BranchingBits, LockStripes>::defaultRange(std::size_t maxDepth) {
+  // start with 64 revisions per leaf; this is arbitrary, but the key is we want
+  // to start with a relatively fine-grained tree so we can differentiate well,
+  // but we don't want to go so small that we have to resize immediately
+  return nodeCountAtDepth(maxDepth) * 64;
+}
+
+template <std::size_t const BranchingBits, std::size_t const LockStripes>
+std::unique_ptr<MerkleTree<BranchingBits, LockStripes>>
+MerkleTree<BranchingBits, LockStripes>::fromBuffer(std::string_view buffer) {
+  bool compressed = false;
+  std::uint8_t version = static_cast<uint8_t>(buffer[buffer.size() - 1]);
+  if (version == 0x01) {
+    compressed = ::CompressedCurrent == buffer[buffer.size() - 2];
+  } else {
+    throw std::invalid_argument(
+        "Buffer does not contain a properly versioned tree.");
+  }
+
+  std::string scratch;
+  if (compressed) {
+    snappy::Uncompress(buffer.data(), buffer.size() - 2, &scratch);
+    buffer = std::string_view(scratch);
+  } else {
+    buffer = std::string_view(buffer.data(), buffer.size() - 2);
+  }
+
+  if (buffer.size() < MetaSize) {
+    // not enough space to even store the meta info, can't proceed
+    return nullptr;
+  }
+
+  Meta const& meta = *reinterpret_cast<Meta const*>(buffer.data());
+  if (buffer.size() != MetaSize + (NodeSize * nodeCountUpToDepth(meta.maxDepth))) {
+    // allocation size doesn't match meta data, can't proceed
+    return nullptr;
+  }
+
+  return std::unique_ptr<MerkleTree<BranchingBits, LockStripes>>(
+      new MerkleTree<BranchingBits, LockStripes>(buffer));
+}
+
+template <std::size_t const BranchingBits, std::size_t const LockStripes>
+std::unique_ptr<MerkleTree<BranchingBits, LockStripes>>
+MerkleTree<BranchingBits, LockStripes>::deserialize(velocypack::Slice slice) {
+  std::unique_ptr<MerkleTree<BranchingBits, LockStripes>> tree{nullptr};
+
+  if (!slice.isObject()) {
+    return tree;
+  }
+
+  velocypack::Slice read = slice.get(StaticStrings::RevisionTreeVersion);
+  if (!read.isNumber() || read.getNumber<std::uint8_t>() != ::CurrentVersion) {
+    return tree;
+  }
+
+  read = slice.get(StaticStrings::RevisionTreeMaxDepth);
+  if (!read.isNumber()) {
+    return tree;
+  }
+  std::size_t maxDepth = read.getNumber<std::size_t>();
+
+  read = slice.get(StaticStrings::RevisionTreeRangeMax);
+  if (!read.isString()) {
+    return tree;
+  }
+  velocypack::ValueLength l;
+  char const* p = read.getString(l);
+  std::size_t rangeMax = basics::HybridLogicalClock::decodeTimeStamp(p, l);
+  if (rangeMax == std::numeric_limits<std::size_t>::max()) {
+    return tree;
+  }
+
+  read = slice.get(StaticStrings::RevisionTreeRangeMin);
+  if (!read.isString()) {
+    return tree;
+  }
+  p = read.getString(l);
+  std::size_t rangeMin = basics::HybridLogicalClock::decodeTimeStamp(p, l);
+  if (rangeMin == std::numeric_limits<std::size_t>::max()) {
+    return tree;
+  }
+
+  velocypack::Slice nodes = slice.get(StaticStrings::RevisionTreeNodes);
+  if (!nodes.isArray() || nodes.length() < nodeCountUpToDepth(maxDepth)) {
+    return tree;
+  }
+
+  // allocate the tree
+  tree.reset(new MerkleTree<BranchingBits, LockStripes>(maxDepth, rangeMin, rangeMax));
+
+  std::size_t index = 0;
+  for (velocypack::Slice nodeSlice : velocypack::ArrayIterator(nodes)) {
+    read = nodeSlice.get(StaticStrings::RevisionTreeCount);
+    if (!read.isNumber()) {
+      tree.reset();
+      return tree;
+    }
+    std::size_t count = read.getNumber<std::size_t>();
+
+    read = nodeSlice.get(StaticStrings::RevisionTreeHash);
+    if (!read.isString()) {
+      tree.reset();
+      return tree;
+    }
+    p = nodeSlice.get(StaticStrings::RevisionTreeHash).getString(l);
+    std::size_t hash = basics::HybridLogicalClock::decodeTimeStamp(p, l);
+    if (hash == std::numeric_limits<std::size_t>::max()) {
+      tree.reset();
+      return tree;
+    }
+
+    std::unique_lock<std::mutex> guard(tree->lock(index));
+    Node& node = tree->node(index);
+    node.hash = hash;
+    node.count = count;
+
+    ++index;
+  }
+
+  return tree;
+}
+
+template <std::size_t const BranchingBits, std::size_t const LockStripes>
+MerkleTree<BranchingBits, LockStripes>::MerkleTree(std::size_t maxDepth, std::size_t rangeMin,
+                                                   std::size_t rangeMax) {
+  if (maxDepth < 2) {
+    throw std::invalid_argument("Must specify a maxDepth >= 2.");
+  }
+  _buffer.reset(new uint8_t[allocationSize(maxDepth)]);
+
+  if (rangeMax == 0) {
+    rangeMax = rangeMin + defaultRange(maxDepth);
+  }
+  TRI_ASSERT(((rangeMax - rangeMin) / nodeCountAtDepth(maxDepth)) * nodeCountAtDepth(maxDepth) ==
+             (rangeMax - rangeMin));
+  new (&meta()) Meta{rangeMin, rangeMax, maxDepth};
+
+  std::size_t const last = nodeCountUpToDepth(maxDepth);
+  for (std::size_t i = 0; i < last; ++i) {
+    new (&node(i)) Node{0, 0};
+  }
+}
+
+template <std::size_t const BranchingBits, std::size_t const LockStripes>
+MerkleTree<BranchingBits, LockStripes>::~MerkleTree() {
+  std::unique_lock<std::shared_mutex> guard(_bufferLock);
+
+  if (!_buffer) {
+    return;
+  }
+
+  std::size_t const last = nodeCountUpToDepth(meta().maxDepth);
+  for (std::size_t i = 0; i < last; ++i) {
+    node(i).~Node();
+  }
+
+  meta().~Meta();
+}
+
+template <std::size_t const BranchingBits, std::size_t const LockStripes>
+MerkleTree<BranchingBits, LockStripes>& MerkleTree<BranchingBits, LockStripes>::operator=(
+    std::unique_ptr<MerkleTree<BranchingBits, LockStripes>>&& other) {
+  if (!other) {
+    return *this;
+  }
+
+  std::unique_lock<std::shared_mutex> guard1(_bufferLock);
+  std::unique_lock<std::shared_mutex> guard2(other->_bufferLock);
+
+  TRI_ASSERT(this->meta().maxDepth == other->meta().maxDepth);
+  TRI_ASSERT(this->_buffer);
+  TRI_ASSERT(other->_buffer);
+
+  _buffer = std::move(other->_buffer);
+
+  TRI_ASSERT(this->_buffer);
+  TRI_ASSERT(!other->_buffer);
+
+  return *this;
+}
+
+template <std::size_t const BranchingBits, std::size_t const LockStripes>
+std::size_t MerkleTree<BranchingBits, LockStripes>::count() const {
+  std::shared_lock<std::shared_mutex> guard(_bufferLock);
+  std::unique_lock<std::mutex> lock(this->lock(0));
+  return node(0).count;
+}
+
+template <std::size_t const BranchingBits, std::size_t const LockStripes>
+std::size_t MerkleTree<BranchingBits, LockStripes>::rootValue() const {
+  std::shared_lock<std::shared_mutex> guard(_bufferLock);
+  std::unique_lock<std::mutex> lock(this->lock(0));
+  return node(0).hash;
+}
+
+template <std::size_t const BranchingBits, std::size_t const LockStripes>
+std::pair<std::size_t, std::size_t> MerkleTree<BranchingBits, LockStripes>::range() const {
+  std::shared_lock<std::shared_mutex> guard(_bufferLock);
+  return {meta().rangeMin, meta().rangeMax};
+}
+
+template <std::size_t const BranchingBits, std::size_t const LockStripes>
+std::size_t MerkleTree<BranchingBits, LockStripes>::maxDepth() const {
+  std::shared_lock<std::shared_mutex> guard(_bufferLock);
+  return meta().maxDepth;
+}
+
+template <std::size_t const BranchingBits, std::size_t const LockStripes>
+void MerkleTree<BranchingBits, LockStripes>::insert(std::size_t key, std::size_t value) {
+  std::shared_lock<std::shared_mutex> guard(_bufferLock);
+  if (key < meta().rangeMin) {
+    throw std::out_of_range("Cannot insert, key " + std::to_string(key) +
+                            " less than range minimum " +
+                            std::to_string(meta().rangeMin) + ".");
+  }
+
+  if (key >= meta().rangeMax) {
+    // unlock so we can get exclusive access to grow the range
+    guard.unlock();
+    grow(key);
+    guard.lock();
+  }
+
+  modify(key, value, /* isInsert */ true);
+}
+
+template <std::size_t const BranchingBits, std::size_t const LockStripes>
+void MerkleTree<BranchingBits, LockStripes>::insert(std::vector<std::size_t> const& keys) {
+  if (keys.empty()) {
+    return;
+  }
+
+  std::vector<std::size_t> sortedKeys = keys;
+  std::sort(sortedKeys.begin(), sortedKeys.end());
+
+  std::size_t minKey = sortedKeys[0];
+  std::size_t maxKey = sortedKeys[sortedKeys.size() - 1];
+
+  std::unique_lock<std::shared_mutex> guard(_bufferLock);
+
+  if (minKey < meta().rangeMin) {
+    throw std::out_of_range("Cannot insert, key " + std::to_string(minKey) +
+                            " less than range minimum " +
+                            std::to_string(meta().rangeMin) + ".");
+  }
+
+  if (maxKey >= meta().rangeMax) {
+    // unlock so we can get exclusive access to grow the range
+    guard.unlock();
+    grow(maxKey);
+    guard.lock();
+  }
+
+  modify(sortedKeys, true);
+}
+
+template <std::size_t const BranchingBits, std::size_t const LockStripes>
+void MerkleTree<BranchingBits, LockStripes>::remove(std::size_t key, std::size_t value) {
+  std::shared_lock<std::shared_mutex> guard(_bufferLock);
+  if (key < meta().rangeMin || key >= meta().rangeMax) {
+    throw std::out_of_range("Cannot remove, key out of current range.");
+  }
+
+  modify(key, value, /* isInsert */ false);
+}
+
+template <std::size_t const BranchingBits, std::size_t const LockStripes>
+void MerkleTree<BranchingBits, LockStripes>::remove(std::vector<std::size_t> const& keys) {
+  if (keys.empty()) {
+    return;
+  }
+
+  std::vector<std::size_t> sortedKeys = keys;
+  std::sort(sortedKeys.begin(), sortedKeys.end());
+
+  std::size_t minKey = sortedKeys[0];
+  std::size_t maxKey = sortedKeys[sortedKeys.size() - 1];
+
+  std::unique_lock<std::shared_mutex> guard(_bufferLock);
+
+  if (minKey < meta().rangeMin || maxKey >= meta().rangeMax) {
+    throw std::out_of_range("Cannot remove, key out of current range.");
+  }
+
+  modify(sortedKeys, false);
+}
+
+template <std::size_t const BranchingBits, std::size_t const LockStripes>
+void MerkleTree<BranchingBits, LockStripes>::clear() {
+  std::unique_lock<std::shared_mutex> guard(_bufferLock);
+  std::size_t const last = nodeCountUpToDepth(meta().maxDepth);
+  for (std::size_t i = 0; i < last; ++i) {
+    new (&node(i)) Node{0, 0};
+  }
+}
+
+template <std::size_t const BranchingBits, std::size_t const LockStripes>
+std::unique_ptr<MerkleTree<BranchingBits, LockStripes>> MerkleTree<BranchingBits, LockStripes>::clone() {
+  std::shared_lock<std::shared_mutex> guard(_bufferLock);
+  return std::unique_ptr<MerkleTree<BranchingBits, LockStripes>>(
+      new MerkleTree<BranchingBits, LockStripes>(*this));
+}
+
+template <std::size_t const BranchingBits, std::size_t const LockStripes>
+std::vector<std::pair<std::size_t, std::size_t>> MerkleTree<BranchingBits, LockStripes>::diff(
+    MerkleTree<BranchingBits, LockStripes>& other) {
+  std::shared_lock<std::shared_mutex> guard1(_bufferLock);
+  std::shared_lock<std::shared_mutex> guard2(other._bufferLock);
+
+  if (this->meta().maxDepth != other.meta().maxDepth) {
+    throw std::invalid_argument("Expecting two trees with same maxDepth.");
+  }
+
+  if (this->meta().rangeMin != other.meta().rangeMin) {
+    throw std::invalid_argument("Expecting two trees with same rangeMin.");
+  }
+
+  while (this->meta().rangeMax != other.meta().rangeMax) {
+    if (this->meta().rangeMax < other.meta().rangeMax) {
+      // grow this to match other range
+      guard1.unlock();
+      this->grow(other.meta().rangeMax - 1);
+      guard1.lock();
+    } else {
+      // grow other to match this range
+      guard2.unlock();
+      other.grow(this->meta().rangeMax - 1);
+      guard2.lock();
+    }
+    // loop to repeat check to make sure someone else didn't grow while we
+    // switched between shared/exclusive locks
+  }
+
+  std::vector<std::pair<std::size_t, std::size_t>> result;
+  std::queue<std::size_t> candidates;
+  candidates.emplace(0);
+
+  while (!candidates.empty()) {
+    std::size_t index = candidates.front();
+    candidates.pop();
+    if (!equalAtIndex(other, index)) {
+      bool leaves = childrenAreLeaves(index);
+      for (std::size_t child = (BranchingFactor * index) + 1;
+           child < (BranchingFactor * (index + 1) + 1); ++child) {
+        if (!leaves) {
+          // internal children, queue them all up for further investigation
+          candidates.emplace(child);
+        } else {
+          if (!equalAtIndex(other, child)) {
+            // actually work with key ranges now
+            std::size_t chunk = child - nodeCountUpToDepth(meta().maxDepth - 1);
+            std::pair<std::size_t, std::size_t> range = chunkRange(chunk, meta().maxDepth);
+            if (!result.empty() && result.back().second >= range.first - 1) {
+              // we are in a continuous range here, just extend it
+              result.back().second = range.second;
+            } else {
+              // discontinuous range, add a new entry
+              result.emplace_back(range);
+            }
+          }
+        }
+      }
+    }
+  }
+
+  return result;
+}
+
+template <std::size_t const BranchingBits, std::size_t const LockStripes>
+std::string MerkleTree<BranchingBits, LockStripes>::toString() const {
+  std::shared_lock<std::shared_mutex> guard(_bufferLock);
+  std::string output("{");
+  for (std::size_t depth = 0; depth <= meta().maxDepth; ++depth) {
+    output.append(std::to_string(depth));
+    output.append(": [");
+    for (std::size_t chunk = 0; chunk < nodeCountAtDepth(depth); ++chunk) {
+      std::size_t index = this->index(chunk, depth);
+      std::unique_lock<std::mutex> guard(this->lock(index));
+      Node& node = this->node(index);
+      output.append("[");
+      output.append(std::to_string(node.count));
+      output.append(",");
+      output.append(std::to_string(node.hash));
+      output.append("],");
+    }
+    output.append("],");
+  }
+  output.append("}");
+  return output;
+}
+
+template <std::size_t const BranchingBits, std::size_t const LockStripes>
+void MerkleTree<BranchingBits, LockStripes>::serialize(velocypack::Builder& output,
+                                                       std::size_t maxDepth) const {
+  std::unique_lock<std::shared_mutex> guard(_bufferLock);
+  TRI_ASSERT(output.isEmpty());
+  char ridBuffer[11];
+  std::size_t depth = std::min(maxDepth, meta().maxDepth);
+
+  velocypack::ObjectBuilder topLevelGuard(&output);
+  output.add(StaticStrings::RevisionTreeVersion, velocypack::Value(::CurrentVersion));
+  output.add(StaticStrings::RevisionTreeMaxDepth, velocypack::Value(depth));
+  output.add(StaticStrings::RevisionTreeRangeMax,
+             basics::HybridLogicalClock::encodeTimeStampToValuePair(meta().rangeMax, ridBuffer));
+  output.add(StaticStrings::RevisionTreeRangeMin,
+             basics::HybridLogicalClock::encodeTimeStampToValuePair(meta().rangeMin, ridBuffer));
+  velocypack::ArrayBuilder nodeArrayGuard(&output, StaticStrings::RevisionTreeNodes);
+  for (std::size_t index = 0; index < nodeCountUpToDepth(depth); ++index) {
+    velocypack::ObjectBuilder nodeGuard(&output);
+    std::unique_lock<std::mutex> guard(this->lock(index));
+    Node& node = this->node(index);
+    output.add(StaticStrings::RevisionTreeHash,
+               basics::HybridLogicalClock::encodeTimeStampToValuePair(node.hash, ridBuffer));
+    output.add(StaticStrings::RevisionTreeCount, velocypack::Value(node.count));
+  }
+}
+
+template <std::size_t const BranchingBits, std::size_t const LockStripes>
+void MerkleTree<BranchingBits, LockStripes>::serializeBinary(std::string& output,
+                                                             bool compress) const {
+  std::unique_lock<std::shared_mutex> guard(_bufferLock);
+  TRI_ASSERT(output.empty());
+  if (compress) {
+    snappy::Compress(reinterpret_cast<char*>(_buffer.get()),
+                     allocationSize(meta().maxDepth), &output);
+    output.push_back(::CompressedCurrent);
+  } else {
+    output.append(reinterpret_cast<char*>(_buffer.get()), allocationSize(meta().maxDepth));
+    output.push_back(::UncompressedCurrent);
+  }
+  output.push_back(static_cast<char>(::CurrentVersion));
+}
+
+template <std::size_t const BranchingBits, std::size_t const LockStripes>
+MerkleTree<BranchingBits, LockStripes>::MerkleTree(std::string_view buffer)
+    : _buffer(new uint8_t[buffer.size()]) {
+  std::memcpy(_buffer.get(), buffer.data(), buffer.size());
+}
+
+template <std::size_t const BranchingBits, std::size_t const LockStripes>
+MerkleTree<BranchingBits, LockStripes>::MerkleTree(MerkleTree<BranchingBits, LockStripes>& other)
+    : _buffer(new uint8_t[allocationSize(other.meta().maxDepth)]) {
+  new (&meta()) Meta{other.meta().rangeMin, other.meta().rangeMax, other.meta().maxDepth};
+
+  std::size_t const last = nodeCountUpToDepth(meta().maxDepth);
+  for (std::size_t i = 0; i < last; ++i) {
+    std::unique_lock<std::mutex> nodeGuard(other.lock(i));
+    new (&this->node(i)) Node{other.node(i).hash, other.node(i).count};
+  }
+}
+
+template <std::size_t const BranchingBits, std::size_t const LockStripes>
+typename MerkleTree<BranchingBits, LockStripes>::Meta& MerkleTree<BranchingBits, LockStripes>::meta() const {
+  // not thread-safe, lock buffer from outside
+  TRI_ASSERT(_buffer);
+  return *reinterpret_cast<Meta*>(_buffer.get());
+}
+
+template <std::size_t const BranchingBits, std::size_t const LockStripes>
+typename MerkleTree<BranchingBits, LockStripes>::Node&
+MerkleTree<BranchingBits, LockStripes>::node(std::size_t index) const {
+  // not thread-safe, lock buffer from outside
+  TRI_ASSERT(index < nodeCountUpToDepth(meta().maxDepth));
+  uint8_t* ptr = _buffer.get() + MetaSize + (NodeSize * index);
+  return *reinterpret_cast<Node*>(ptr);
+}
+
+template <std::size_t const BranchingBits, std::size_t const LockStripes>
+std::mutex& MerkleTree<BranchingBits, LockStripes>::lock(std::size_t index) const {
+  return _nodeLocks[TRI_FnvHashPod(index) % LockStripes];
+}
+
+template <std::size_t const BranchingBits, std::size_t const LockStripes>
+std::size_t MerkleTree<BranchingBits, LockStripes>::index(std::size_t key,
+                                                          std::size_t depth) const {
+  // not thread-safe, lock buffer from outside
+  TRI_ASSERT(depth <= meta().maxDepth);
+  TRI_ASSERT(key >= meta().rangeMin);
+  TRI_ASSERT(key < meta().rangeMax);
+
+  // special fast case
+  if (depth == 0) {
+    return 0;
+  }
+
+  std::size_t offset = key - meta().rangeMin;
+  std::size_t chunkSizeAtDepth = (meta().rangeMax - meta().rangeMin) /
+                                 (static_cast<std::size_t>(1) << (BranchingBits * depth));
+  std::size_t chunk = offset / chunkSizeAtDepth;
+
+  return chunk + nodeCountUpToDepth(depth - 1);
+}
+
+template <std::size_t const BranchingBits, std::size_t const LockStripes>
+void MerkleTree<BranchingBits, LockStripes>::modify(std::size_t key, std::size_t value,
+                                                    bool isInsert) {
+  // not thread-safe, shared-lock buffer from outside
+  for (std::size_t depth = 0; depth <= meta().maxDepth; ++depth) {
+    modifyLocal(depth, key, value, isInsert, true);
+  }
+}
+
+template <std::size_t const BranchingBits, std::size_t const LockStripes>
+void MerkleTree<BranchingBits, LockStripes>::modify(std::vector<std::size_t> const& keys,
+                                                    bool isInsert) {
+  // not thread-safe, unique-lock buffer from outside
+  for (std::size_t depth = 0; depth <= meta().maxDepth; ++depth) {
+    for (std::size_t key : keys) {
+      modifyLocal(depth, key, TRI_FnvHashPod(key), isInsert, false);
+    }
+  }
+}
+
+template <std::size_t const BranchingBits, std::size_t const LockStripes>
+void MerkleTree<BranchingBits, LockStripes>::modifyLocal(std::size_t depth,
+                                                         std::size_t key, std::size_t value,
+                                                         bool isInsert, bool doLock) {
+  // only use via modify
+  std::size_t index = this->index(key, depth);
+  Node& node = this->node(index);
+  std::unique_lock<std::mutex> lock(this->lock(index), std::defer_lock);
+  if (doLock) {
+    lock.lock();
+  }
+  if (isInsert) {
+    ++node.count;
+  } else {
+    if (node.count == 0) {
+      throw std::invalid_argument("Tried to remove key that is not present.");
+    }
+    --node.count;
+  }
+  node.hash ^= value;
+}
+
+template <std::size_t const BranchingBits, std::size_t const LockStripes>
+void MerkleTree<BranchingBits, LockStripes>::grow(std::size_t key) {
+  std::unique_lock<std::shared_mutex> guard(_bufferLock);
+  // no need to lock nodes as we have an exclusive lock on the buffer
+
+  std::size_t rangeMin = meta().rangeMin;
+  std::size_t rangeMax = meta().rangeMax;
+  if (key < rangeMax) {
+    // someone else resized already while we were waiting for the lock
+    return;
+  }
+
+  std::size_t factor = minimumFactorFor(rangeMax - rangeMin, key - rangeMin);
+
+  for (std::size_t depth = 1; depth <= meta().maxDepth; ++depth) {
+    // iterate over all nodes and left-combine, (skipping the first, identity)
+    std::size_t offset = nodeCountUpToDepth(depth - 1);
+    for (std::size_t index = 1; index < nodeCountAtDepth(depth); ++index) {
+      Node& src = this->node(offset + index);
+      Node& dst = this->node(offset + (index / factor));
+      dst.count += src.count;
+      dst.hash ^= src.hash;
+      src = Node{0, 0};
+    }
+  }
+
+  meta().rangeMax = rangeMin + ((rangeMax - rangeMin) * factor);
+  TRI_ASSERT(key < meta().rangeMax);
+}
+
+template <std::size_t const BranchingBits, std::size_t const LockStripes>
+bool MerkleTree<BranchingBits, LockStripes>::equalAtIndex(
+    MerkleTree<BranchingBits, LockStripes> const& other, std::size_t index) const {
+  // not fully thread-safe, lock buffer from outside
+  std::unique_lock<std::mutex> lock1(this->lock(index));
+  std::unique_lock<std::mutex> lock2(other.lock(index));
+  return (this->node(index) == other.node(index));
+}
+
+template <std::size_t const BranchingBits, std::size_t const LockStripes>
+bool MerkleTree<BranchingBits, LockStripes>::childrenAreLeaves(std::size_t index) {
+  // not thread-safe, lock buffer from outside
+  std::size_t maxDepth = meta().maxDepth;
+  return index >= nodeCountUpToDepth(maxDepth - 2) &&
+         index < nodeCountUpToDepth(maxDepth - 1);
+}
+
+template <std::size_t const BranchingBits, std::size_t const LockStripes>
+std::pair<std::size_t, std::size_t> MerkleTree<BranchingBits, LockStripes>::chunkRange(
+    std::size_t chunk, std::size_t depth) {
+  // not thread-safe, lock buffer from outside
+  std::size_t rangeMin = meta().rangeMin;
+  std::size_t rangeMax = meta().rangeMax;
+  std::size_t chunkSizeAtDepth =
+      (rangeMax - rangeMin) / (static_cast<std::size_t>(1) << (BranchingBits * depth));
+  return std::make_pair(rangeMin + (chunkSizeAtDepth * chunk),
+                        rangeMin + (chunkSizeAtDepth * (chunk + 1)) - 1);
+}
+
+template <std::size_t const BranchingBits, std::size_t const LockStripes>
+std::ostream& operator<<(std::ostream& stream,
+                         MerkleTree<BranchingBits, LockStripes> const& tree) {
+  return stream << tree.toString();
+}
+
+/// INSTANTIATIONS
+template class MerkleTree<3, 64>;
+template std::ostream& operator<<(std::ostream& stream, MerkleTree<3, 64> const&);
+
+}  // namespace containers
+}  // namespace arangodb
diff --git a/lib/Containers/MerkleTree.h b/lib/Containers/MerkleTree.h
new file mode 100644
index 000000000000..2cca2d1ac259
--- /dev/null
+++ b/lib/Containers/MerkleTree.h
@@ -0,0 +1,276 @@
+////////////////////////////////////////////////////////////////////////////////
+/// DISCLAIMER
+///
+/// Copyright 2019 ArangoDB GmbH, Cologne, Germany
+///
+/// Licensed under the Apache License, Version 2.0 (the "License");
+/// you may not use this file except in compliance with the License.
+/// You may obtain a copy of the License at
+///
+///     http://www.apache.org/licenses/LICENSE-2.0
+///
+/// Unless required by applicable law or agreed to in writing, software
+/// distributed under the License is distributed on an "AS IS" BASIS,
+/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+/// See the License for the specific language governing permissions and
+/// limitations under the License.
+///
+/// Copyright holder is ArangoDB GmbH, Cologne, Germany
+///
+/// @author Dan Larkin-York
+////////////////////////////////////////////////////////////////////////////////
+
+#ifndef ARANGODB_CONTAINERS_MERKLE_TREE_H
+#define ARANGODB_CONTAINERS_MERKLE_TREE_H 1
+
+#include <cstddef>
+#include <cstdint>
+#include <cstring>
+#include <memory>
+#include <mutex>
+#include <shared_mutex>
+#include <string>
+#include <string_view>
+#include <vector>
+
+#include <velocypack/Builder.h>
+
+namespace arangodb {
+namespace containers {
+
+template <std::size_t const BranchingBits = 3,  // 8 children per internal node,
+          std::size_t const LockStripes = 64  // number number of buckets that can be accessed simultaneously
+          >
+class MerkleTree {
+ protected:
+  static constexpr std::size_t CacheLineSize =
+      64;  // TODO replace with std::hardware_constructive_interference_size
+           // once supported by all necessary compilers
+  static constexpr std::size_t BranchingFactor = static_cast<std::size_t>(1) << BranchingBits;
+
+  struct Node {
+    std::size_t hash;
+    std::size_t count;
+
+    bool operator==(Node const& other);
+  };
+  static_assert(sizeof(Node) == 16, "Node size assumptions invalid.");
+  static_assert(CacheLineSize % sizeof(Node) == 0,
+                "Node size assumptions invalid.");
+  static constexpr std::size_t NodeSize = sizeof(Node);
+
+  struct Meta {
+    std::size_t rangeMin;
+    std::size_t rangeMax;
+    std::size_t maxDepth;
+  };
+  static_assert(sizeof(Meta) == 24, "Meta size assumptions invalid.");
+  static constexpr std::size_t MetaSize =
+      (CacheLineSize * ((sizeof(Meta) + (CacheLineSize - 1)) / CacheLineSize));
+
+  static constexpr std::size_t nodeCountAtDepth(std::size_t maxDepth);
+  static constexpr std::size_t nodeCountUpToDepth(std::size_t maxDepth);
+  static constexpr std::size_t allocationSize(std::size_t maxDepth);
+  static constexpr std::size_t log2ceil(std::size_t n);
+  static constexpr std::size_t minimumFactorFor(std::size_t current, std::size_t target);
+
+ public:
+  /**
+   * @brief Chooses the default range width for a tree of a given depth.
+   *
+   * Most applications should use either this value or some power-of-two
+   * mulitple of this value. The default is chosen so that each leaf bucket
+   * initially covers a range of 64 keys.
+   *
+   * @param maxDepth The same depth value passed to the constructor
+   */
+  static std::size_t defaultRange(std::size_t maxDepth);
+
+  /**
+   * @brief Construct a tree from a buffer containing a serialized tree
+   *
+   * @param buffer      A buffer containing a serialized tree
+   * @return A newly allocated tree constructed from the input
+   */
+  static std::unique_ptr<MerkleTree<BranchingBits, LockStripes>> fromBuffer(std::string_view buffer);
+
+  /**
+   * @brief Construct a tree from a portable serialized tree
+   *
+   * @param slice A slice containing a serialized tree
+   * @return A newly allocated tree constructed from the input
+   */
+  static std::unique_ptr<MerkleTree<BranchingBits, LockStripes>> deserialize(velocypack::Slice slice);
+
+  /**
+   * @brief Construct a Merkle tree of a given depth with a given minimum key
+   *
+   * @param maxDepth The depth of the tree. This determines how much memory The
+   *                 tree will consume, and how fine-grained the hash is.
+   *                 Constructor will throw if a value less than 2 is specified.
+   * @param rangeMin The minimum key that can be stored in the tree over its
+   *                 lifetime. An attempt to insert a smaller key will result
+   *                 in an exception.
+   * @param rangeMax Must be an offset from rangeMin of a multiple of the number
+   *                 of leaf nodes. If 0, it will be  chosen using the
+   *                 defaultRange method. This is just an initial value to
+   *                 prevent immediate resizing; if a key larger than rangeMax
+   *                 is inserted into the tree, it will be dynamically resized
+   *                 so that a larger rangeMax is chosen, and adjacent nodes
+   *                 merged as necessary.
+   * @throws std::invalid_argument  If maxDepth is less than 2
+   */
+  MerkleTree(std::size_t maxDepth, std::size_t rangeMin, std::size_t rangeMax = 0);
+
+  ~MerkleTree();
+
+  /**
+   * @brief Move assignment operator from pointer
+   *
+   * @param other Input tree, intended assignment
+   */
+  MerkleTree& operator=(std::unique_ptr<MerkleTree<BranchingBits, LockStripes>>&& other);
+
+  /**
+   * @brief Returns the number of hashed keys contained in the tree
+   */
+  std::size_t count() const;
+
+  /**
+   * @brief Returns the hash of all values in the tree, equivalently the root
+   *        value
+   */
+  std::size_t rootValue() const;
+
+  /**
+   * @brief Returns the current range of the tree
+   */
+  std::pair<std::size_t, std::size_t> range() const;
+
+  /**
+   * @brief Returns the maximum depth of the tree
+   */
+  std::size_t maxDepth() const;
+
+  /**
+   * @brief Insert a value into the tree. May trigger a resize.
+   *
+   * @param key   The key for the item. If it is less than the minimum specified
+   *              at construction, then it will trigger an exception. If it is
+   *              greater than the current max, it will trigger a (potentially
+   *              expensive) growth operation to ensure the key can be inserted.
+   * @param value The hashed value associated with the key
+   * @throws std::out_of_range  If key is less than rangeMin
+   */
+  void insert(std::size_t key, std::size_t value);
+
+  /**
+   * @brief Insert a batch of keys (as values) into the tree. May trigger a
+   * resize.
+   *
+   * @param keys  The keys to be inserted. Each key will be hashed to generate
+   *              a value, then inserted as if by the basic single insertion
+   *              method. This batch method is considerably more efficient.
+   * @throws std::out_of_range  If key is less than rangeMin
+   */
+  void insert(std::vector<std::size_t> const& keys);
+
+  /**
+   * @brief Remove a value from the tree.
+   *
+   * @param key   The key for the item. If it is outside the current tree range,
+   *              then it will trigger an exception.
+   * @param value The hashed value associated with the key
+   * @throws std::out_of_range  If key is outside current range
+   * @throws std::invalid_argument  If remove hits a node with 0 count
+   */
+  void remove(std::size_t key, std::size_t value);
+
+  /**
+   * @brief Remove a batch of keys (as values) from the tree.
+   *
+   * @param keys  The keys to be removed. Each key will be hashed to generate
+   *              a value, then removed as if by the basic single removal
+   *              method. This batch method is considerably more efficient.
+   * @throws std::out_of_range  If key is less than rangeMin
+   */
+  void remove(std::vector<std::size_t> const& keys);
+
+  /**
+   * @brief Remove all values from the tree.
+   */
+  void clear();
+
+  /**
+   * @brief Clone the tree.
+   */
+  std::unique_ptr<MerkleTree<BranchingBits, LockStripes>> clone();
+
+  /**
+   * @brief Find the ranges of keys over which two trees differ.
+   *
+   * @param other The other tree to compare
+   * @return  Vector of (inclusive) ranges of keys over which trees differ
+   * @throws std::invalid_argument  If trees do not have different depth or
+   *                                rangeMin
+   */
+  std::vector<std::pair<std::size_t, std::size_t>> diff(MerkleTree<BranchingBits, LockStripes>& other);
+
+  /**
+   * @brief Convert to a human-readable string for printing
+   *
+   * @return String representing the tree
+   */
+  std::string toString() const;
+
+  /**
+   * @brief Serialize the tree for transport or storage in portable format
+   *
+   * @param output    VPackBuilder for output
+   * @param depth     Maximum depth to serialize
+   */
+  void serialize(velocypack::Builder& output,
+                 std::size_t maxDepth = std::numeric_limits<std::size_t>::max()) const;
+
+  /**
+   * @brief Serialize the tree for transport or storage in binary format
+   *
+   * @param output    String for output
+   * @param compress  Whether or not to compress the output
+   */
+  void serializeBinary(std::string& output, bool compress) const;
+
+ protected:
+  explicit MerkleTree(std::string_view buffer);
+  explicit MerkleTree(MerkleTree<BranchingBits, LockStripes>& other);
+
+  Meta& meta() const;
+  Node& node(std::size_t index) const;
+  std::mutex& lock(std::size_t index) const;
+  std::size_t index(std::size_t key, std::size_t depth) const;
+  void modify(std::size_t key, std::size_t value, bool isInsert);
+  void modify(std::vector<std::size_t> const& keys, bool isInsert);
+  void modifyLocal(std::size_t depth, std::size_t key, std::size_t value,
+                   bool isInsert, bool doLock);
+  void grow(std::size_t key);
+  bool equalAtIndex(MerkleTree<BranchingBits, LockStripes> const& other,
+                    std::size_t index) const;
+  bool childrenAreLeaves(std::size_t index);
+  std::pair<std::size_t, std::size_t> chunkRange(std::size_t chunk, std::size_t depth);
+
+ private:
+  std::unique_ptr<std::uint8_t[]> _buffer;
+  mutable std::shared_mutex _bufferLock;
+  mutable std::mutex _nodeLocks[LockStripes];
+};
+
+template <std::size_t const BranchingBits, std::size_t const LockStripes>
+std::ostream& operator<<(std::ostream& stream,
+                         MerkleTree<BranchingBits, LockStripes> const& tree);
+
+using RevisionTree = MerkleTree<3, 64>;
+
+}  // namespace containers
+}  // namespace arangodb
+
+#endif
diff --git a/lib/Logger/LogThread.cpp b/lib/Logger/LogThread.cpp
index 5aee753b3fe9..f0a8411c886d 100644
--- a/lib/Logger/LogThread.cpp
+++ b/lib/Logger/LogThread.cpp
@@ -67,8 +67,13 @@ void LogThread::flush() noexcept {
 }
 
 void LogThread::wakeup() noexcept {
+#ifdef ARANGODB_SHOW_LOCK_TIME
+  // cppcheck-suppress redundantPointerOp
+  basics::ConditionLocker guard(_condition, __FILE__, __LINE__, false);
+#else
   // cppcheck-suppress redundantPointerOp
   CONDITION_LOCKER(guard, _condition);
+#endif
   guard.signal();
 }
 
diff --git a/lib/Logger/LogTopic.cpp b/lib/Logger/LogTopic.cpp
index c8b762ea4eec..c32e9d7d0b08 100644
--- a/lib/Logger/LogTopic.cpp
+++ b/lib/Logger/LogTopic.cpp
@@ -150,6 +150,7 @@ LogTopic Logger::SYSCALL("syscall", LogLevel::INFO);
 LogTopic Logger::THREADS("threads", LogLevel::WARN);
 LogTopic Logger::TRANSACTIONS("trx", LogLevel::WARN);
 LogTopic Logger::TTL("ttl", LogLevel::WARN);
+LogTopic Logger::VALIDATION("validation", LogLevel::INFO);
 LogTopic Logger::V8("v8", LogLevel::WARN);
 LogTopic Logger::VIEWS("views", LogLevel::FATAL);
 
diff --git a/lib/Logger/Logger.h b/lib/Logger/Logger.h
index 12dbc89f019e..8286066fccb6 100644
--- a/lib/Logger/Logger.h
+++ b/lib/Logger/Logger.h
@@ -87,14 +87,14 @@ struct LogMessage {
   LogMessage(LogMessage const&) = delete;
   LogMessage& operator=(LogMessage const&) = delete;
 
-  LogMessage(char const* function, char const* file, int line, 
+  LogMessage(char const* function, char const* file, int line,
              LogLevel level, size_t topicId, std::string&& message, size_t offset)
       : _function(function),
         _file(file),
         _line(line),
-        _level(level), 
-        _topicId(topicId), 
-        _message(std::move(message)), 
+        _level(level),
+        _topicId(topicId),
+        _message(std::move(message)),
         _offset(offset) {}
 
   char const* _function;
@@ -184,6 +184,7 @@ class Logger {
   static LogTopic THREADS;
   static LogTopic TRANSACTIONS;
   static LogTopic TTL;
+  static LogTopic VALIDATION;
   static LogTopic V8;
   static LogTopic VIEWS;
 
diff --git a/lib/Rest/GeneralResponse.cpp b/lib/Rest/GeneralResponse.cpp
index b4acc6ca7b90..ed9fc278bf34 100644
--- a/lib/Rest/GeneralResponse.cpp
+++ b/lib/Rest/GeneralResponse.cpp
@@ -31,6 +31,10 @@
 using namespace arangodb;
 using namespace arangodb::basics;
 
+bool GeneralResponse::isValidResponseCode(uint64_t code) {
+  return ((code >= 100) && (code < 600));
+}
+
 std::string GeneralResponse::responseString(ResponseCode code) {
   switch (code) {
     //  Informational 1xx
@@ -152,13 +156,18 @@ std::string GeneralResponse::responseString(ResponseCode code) {
           return StringUtils::itoa((int)code) + " Client error";
         case 5:
           return StringUtils::itoa((int)code) + " Server error";
+        case 0:
+          if (static_cast<int>(code) != 0) {
+            return StringUtils::itoa(500) + " Internal Server error";
+          }
+          break;
         default:
           break;
       }
     }
   }
 
-  return StringUtils::itoa((int)code) + " Unknown";
+  return StringUtils::itoa(500) + " Internal Server error - Unknown";
 }
 
 rest::ResponseCode GeneralResponse::responseCode(std::string const& str) {
diff --git a/lib/Rest/GeneralResponse.h b/lib/Rest/GeneralResponse.h
index e68a898dfd52..6855de043b29 100644
--- a/lib/Rest/GeneralResponse.h
+++ b/lib/Rest/GeneralResponse.h
@@ -56,6 +56,9 @@ class GeneralResponse {
   // converts the response code to a string for delivering to a http client.
   static std::string responseString(ResponseCode);
 
+  // returns true if code will become a valid http response.
+  static bool isValidResponseCode(uint64_t code);
+
   // converts the response code string to the internal code
   static ResponseCode responseCode(std::string const& str);
 
diff --git a/lib/Rest/HttpResponse.h b/lib/Rest/HttpResponse.h
index 40e7d7f3bcad..8a711d8e51a3 100644
--- a/lib/Rest/HttpResponse.h
+++ b/lib/Rest/HttpResponse.h
@@ -67,6 +67,10 @@ class HttpResponse : public GeneralResponse {
   }
   size_t bodySize() const;
 
+  void sealBody() {
+    _bodySize = _body->length();
+  }
+
   // you should call writeHeader only after the body has been created
   void writeHeader(basics::StringBuffer*);  // override;
 
diff --git a/lib/Rest/VstResponse.cpp b/lib/Rest/VstResponse.cpp
index c40bb623a47b..8a6429e9d965 100644
--- a/lib/Rest/VstResponse.cpp
+++ b/lib/Rest/VstResponse.cpp
@@ -216,6 +216,10 @@ void VstResponse::writeMessageHeader(VPackBuffer<uint8_t>& buffer) const {
     fixCase(currentHeader);
     builder.add(currentHeader, VPackValue(item.second));
   }
+  if (!generateBody()) {
+    std::string len = std::to_string(_payload.size());
+    builder.add(StaticStrings::ContentLength, VPackValue(len));
+  }
   if (_contentType != ContentType::VPACK &&
       _contentType != ContentType::CUSTOM) { // fuerte uses VPack as default
     currentHeader = StaticStrings::ContentTypeHeader;
diff --git a/lib/Ssl/SslInterface.cpp b/lib/Ssl/SslInterface.cpp
index 8cc7dff1d777..5f103b5e4dc1 100644
--- a/lib/Ssl/SslInterface.cpp
+++ b/lib/Ssl/SslInterface.cpp
@@ -195,21 +195,6 @@ void sslHEX(char const* inputStr, char*& outputStr, size_t& outputLen) {
   sslHEX(inputStr, strlen(inputStr), outputStr, outputLen);
 }
 
-void sslBASE64(char const* inputStr, size_t length, char*& outputStr, size_t& outputLen) {
-  std::string b = StringUtils::encodeBase64(std::string(inputStr, length));
-
-  if (outputStr == nullptr) {
-    outputStr = new char[b.size() + 1];
-    outputLen = length * 2;
-  }
-
-  memcpy(outputStr, b.c_str(), outputLen);
-}
-
-void sslBASE64(char const* inputStr, char*& outputStr, size_t& outputLen) {
-  sslBASE64(inputStr, strlen(inputStr), outputStr, outputLen);
-}
-
 std::string sslPBKDF2HS1(char const* salt, size_t saltLength, char const* pass,
                          size_t passLength, int iter, int keyLength) {
   unsigned char* dk = (unsigned char*)TRI_Allocate(keyLength + 1);
diff --git a/lib/Ssl/SslInterface.h b/lib/Ssl/SslInterface.h
index bda9ba947abf..dfabf0ae4c9b 100644
--- a/lib/Ssl/SslInterface.h
+++ b/lib/Ssl/SslInterface.h
@@ -139,18 +139,6 @@ void sslHEX(char const* inputStr, size_t const length, char*& outputStr, size_t&
 
 void sslHEX(char const* inputStr, char*& outputStr, size_t& outputLen);
 
-//////////////////////////////////////////////////////////////////////////
-/// @brief BASE64
-//////////////////////////////////////////////////////////////////////////
-
-void sslBASE64(char const* inputStr, size_t const length, char*& outputStr, size_t& outputLen);
-
-//////////////////////////////////////////////////////////////////////////
-/// @brief BASE64
-//////////////////////////////////////////////////////////////////////////
-
-void sslBASE64(char const* inputStr, char*& outputStr, size_t& outputLen);
-
 //////////////////////////////////////////////////////////////////////////
 /// @brief PBKDF2HS1
 //////////////////////////////////////////////////////////////////////////
diff --git a/lib/Ssl/ssl-helper.cpp b/lib/Ssl/ssl-helper.cpp
index 387232e40a1a..7e660d39bda0 100644
--- a/lib/Ssl/ssl-helper.cpp
+++ b/lib/Ssl/ssl-helper.cpp
@@ -50,7 +50,7 @@ extern "C" const SSL_METHOD* SSLv3_method(void);
 /// @brief creates an SSL context
 ////////////////////////////////////////////////////////////////////////////////
 
-std::shared_ptr<asio_ns::ssl::context> arangodb::sslContext(SslProtocol protocol, std::string const& keyfile) {
+asio_ns::ssl::context arangodb::sslContext(SslProtocol protocol, std::string const& keyfile) {
   // create our context
 
   asio_ns::ssl::context::method meth;
@@ -95,9 +95,9 @@ std::shared_ptr<asio_ns::ssl::context> arangodb::sslContext(SslProtocol protocol
                                      "unknown SSL protocol method");
   }
 
-  auto sslctx = std::make_shared<asio_ns::ssl::context>(meth);
+  asio_ns::ssl::context sslctx(meth);
 
-  if (sslctx->native_handle() == nullptr) {
+  if (sslctx.native_handle() == nullptr) {
     // could not create SSL context - this is mostly due to the OpenSSL
     // library not having been initialized
     THROW_ARANGO_EXCEPTION_MESSAGE(TRI_ERROR_INTERNAL,
@@ -106,7 +106,7 @@ std::shared_ptr<asio_ns::ssl::context> arangodb::sslContext(SslProtocol protocol
 
   // load our keys and certificates
   boost::system::error_code ec;
-  sslctx->use_certificate_chain_file(keyfile, ec);
+  sslctx.use_certificate_chain_file(keyfile, ec);
   if (ec) {
     LOG_TOPIC("c6a00", ERR, arangodb::Logger::SSL)
     << "cannot read certificate from '" << keyfile << "': " << ec;
@@ -114,7 +114,7 @@ std::shared_ptr<asio_ns::ssl::context> arangodb::sslContext(SslProtocol protocol
                                    "unable to read certificate from file");
   }
   
-  sslctx->use_private_key_file(keyfile, asio_ns::ssl::context::file_format::pem, ec);
+  sslctx.use_private_key_file(keyfile, asio_ns::ssl::context::file_format::pem, ec);
   if (ec) {
     LOG_TOPIC("98712", ERR, arangodb::Logger::FIXME)
     << "cannot read key from '" << keyfile << "': " << ec;
@@ -122,7 +122,7 @@ std::shared_ptr<asio_ns::ssl::context> arangodb::sslContext(SslProtocol protocol
                                    "unable to read key from keyfile");
   }
 #if (OPENSSL_VERSION_NUMBER < 0x00905100L)
-  sslctx->set_verify_depth(1);
+  sslctx.set_verify_depth(1);
 #endif
 
   return sslctx;
diff --git a/lib/Ssl/ssl-helper.h b/lib/Ssl/ssl-helper.h
index cab4bc8a22d7..d063d2e54959 100644
--- a/lib/Ssl/ssl-helper.h
+++ b/lib/Ssl/ssl-helper.h
@@ -70,7 +70,7 @@ std::unordered_set<uint64_t> availableSslProtocols();
 /// @brief returns a string description the available SSL protocols
 std::string availableSslProtocolsDescription();
 
-std::shared_ptr<asio_ns::ssl::context> sslContext(SslProtocol, std::string const& keyfile);
+asio_ns::ssl::context sslContext(SslProtocol, std::string const& keyfile);
 
 std::string protocolName(SslProtocol protocol);
 
diff --git a/scripts/build-bundle.sh b/scripts/build-bundle.sh
deleted file mode 100755
index c3d7f198e18f..000000000000
--- a/scripts/build-bundle.sh
+++ /dev/null
@@ -1,31 +0,0 @@
-#!/usr/bin/env bash
-
-set -e
-
-DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
-
-cd "${DIR}/.."
-EP=""
-for i in "$@"; do
-    if test "$i" == "--enterprise"; then
-        EP="EP"
-    fi
-done
-
-if ! test -d 3rdParty/arangodb-starter; then
-    MOREOPTS+=("--downloadStarter")
-fi
-
-./Installation/Jenkins/build.sh \
-    standard \
-    --parallel 8 \
-    --package Bundle \
-    --buildDir build-${EP}bundle \
-    --targetDir /var/tmp/ \
-    --prefix "/opt/arangodb" \
-    --clang \
-    --staticOpenSSL \
-    "${MOREOPTS[@]}" \
-    "$@"
-
-cd "${DIR}/.."
diff --git a/scripts/build-dbg-deb.sh b/scripts/build-dbg-deb.sh
deleted file mode 100755
index ea8dfd72c745..000000000000
--- a/scripts/build-dbg-deb.sh
+++ /dev/null
@@ -1,37 +0,0 @@
-#!/usr/bin/env bash
-# To install the build libraries needed by this script run:
-# `sudo apt-get install cmake libjemalloc-dev libssl-dev libreadline-dev`
-# After the packages are built you will find them in /var/tmp
-
-set -e
-
-DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
-
-cd ${DIR}/..
-
-EP=""
-for i in $@; do
-    if test "$i" == "--enterprise"; then
-        EP="EP"
-    fi
-done
-
-export CPU_CORES=$(grep -c ^processor /proc/cpuinfo)
-
-if ! test -d 3rdParty/arangodb-starter; then
-    MOREOPTS="${MOREOPTS} --downloadStarter"
-fi
-
-./Installation/Jenkins/build.sh \
-    debug \
-    --failure-tests \
-    --rpath \
-    --parallel ${CPU_CORES} \
-    --package DEB \
-    --buildDir build-${EP}deb-dbg \
-    --targetDir /var/tmp/ \
-    --noopt \
-    ${MOREOPTS} \
-    $@
-
-cd ${DIR}/..
diff --git a/scripts/build-deb.sh b/scripts/build-deb.sh
deleted file mode 100755
index 4eb02b1dba2a..000000000000
--- a/scripts/build-deb.sh
+++ /dev/null
@@ -1,41 +0,0 @@
-#!/usr/bin/env bash
-# To install the build libraries needed by this script run:
-# `sudo apt-get install cmake libjemalloc-dev libssl-dev libreadline-dev`
-# After the packages are built you will find them in /var/tmp
-
-set -e
-
-DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
-
-cd ${DIR}/..
-
-BUILD_CONFIGURATION="standard"
-
-EP=""
-for i in $@; do
-    if test "$i" == "--enterprise"; then
-        EP="EP"
-    fi
-    if test "$i" == "--maintainer"; then
-        BUILD_CONFIGURATION="maintainer"
-    fi
-done
-
-if ! test -d 3rdParty/arangodb-starter; then
-    MOREOPTS="${MOREOPTS} --downloadStarter"
-fi
-
-export CPU_CORES=$(grep -c ^processor /proc/cpuinfo)
-
-./Installation/Jenkins/build.sh \
-    ${BUILD_CONFIGURATION} \
-    --rpath \
-    --parallel ${CPU_CORES} \
-    --package DEB \
-    --buildDir build-${EP}deb \
-    --targetDir /var/tmp/ \
-    --jemalloc \
-    ${MOREOPTS} \
-    $@
-
-cd ${DIR}/..
diff --git a/scripts/build-docker.sh b/scripts/build-docker.sh
deleted file mode 100755
index 66da0678f98a..000000000000
--- a/scripts/build-docker.sh
+++ /dev/null
@@ -1,76 +0,0 @@
-#!/usr/bin/env bash
-
-set -e
-
-DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
-ROOTDIR=${DIR}/..
-BUILDDIR=${ROOTDIR}/build 
-mkdir -p ${BUILDDIR}
-mkdir -p ${ROOTDIR}/build-tmp
-
-VERSION=$(cat ${ROOTDIR}/VERSION)
-export DEBVERSION=${VERSION}-1
-DOCKERTAG=${DOCKERTAG:=${VERSION}-local}
-DEBIMAGE_NAME="arangodb3-${DEBVERSION}_amd64"
-BUILDDEB_ARGS="--gcc6"
-BUILDDEB_DOCKER_ARGS=""
-
-DOCKERFILENAME=Dockerfile$(echo ${VERSION} | cut -d '.' -f 1,2 --output-delimiter=).local
-
-for i in $@; do
-    if test "$i" == "--enterprise"; then
-        DEBIMAGE_NAME="arangodb3e-${DEBVERSION}_amd64"
-        BUILDDEB_ARGS+=" --enterprise git@github.com:arangodb/enterprise.git "
-    fi
-    if test "$i" == "--maintainer"; then
-        BUILDDEB_ARGS+=" --maintainer"
-    fi
-done
-
-if [ ! -z "${SSH_AUTH_SOCK}" ]; then
-    BUILDDEB_DOCKER_ARGS="${BUILDDEB_DOCKER_ARGS} -v ${SSH_AUTH_SOCK}:/.ssh-agent -e SSH_AUTH_SOCK=/.ssh-agent"
-fi
-
-# Create debian-stretch-builder
-if [ ! -e ${BUILDDIR}/.build-docker-containers ]; then
-    cd ${BUILDDIR} 
-    git clone https://github.com/arangodb-helper/build-docker-containers ${BUILDDIR}/.build-docker-containers
-else
-    (cd ${BUILDDIR}/.build-docker-containers && git pull)
-fi
-
-docker build -t arangodb/debian-stretch-builder ${BUILDDIR}/.build-docker-containers/distros/debian/stretch/build/
-
-# Ensure arangodb/arangodb-docker exists 
-if [ ! -e ${BUILDDIR}/.arangodb-docker ]; then
-    cd ${BUILDDIR}
-    git clone https://github.com/arangodb/arangodb-docker ${BUILDDIR}/.arangodb-docker
-else
-    (cd ${BUILDDIR}/.arangodb-docker && git pull)
-fi 
-
-# Clean build tag
-(
-    cd ${BUILDDIR}/.arangodb-docker
-    rm -f .docker-tag
-)
-
-# Build stretch package
-docker run -i \
-    -e GIT_SSH_COMMAND="ssh -o UserKnownHostsFile=/dev/null -o StrictHostKeyChecking=no" \
-    -v ${ROOTDIR}:/arangodb \
-    -v ${ROOTDIR}/build-tmp:/var/tmp \
-    -w /arangodb \
-    ${BUILDDEB_DOCKER_ARGS} \
-    arangodb/debian-stretch-builder \
-    /arangodb/scripts/build-deb.sh $BUILDDEB_ARGS
-
-# Copy deb image to docker build root
-cp -a ${ROOTDIR}/build-tmp/${DEBIMAGE_NAME}.deb ${BUILDDIR}/.arangodb-docker/arangodb.deb
-
-# Build docker image
-(
-    cd ${BUILDDIR}/.arangodb-docker
-    docker build -f ${DOCKERFILENAME} -t arangodb:${DOCKERTAG} .
-    echo "${DOCKERTAG}" > .docker-tag
-)
diff --git a/scripts/build-nsis.sh b/scripts/build-nsis.sh
deleted file mode 100644
index b39b59bdee57..000000000000
--- a/scripts/build-nsis.sh
+++ /dev/null
@@ -1,28 +0,0 @@
-#!/usr/bin/env bash
-
-set -e
-
-DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
-
-cd ${DIR}/..
-EP="y"
-for i in $@; do
-    if test "$i" == "--enterprise"; then
-        EP="e"
-    fi
-done
-
-if ! test -d 3rdParty/arangodb-starter; then
-    MOREOPTS="${MOREOPTS} --downloadStarter"
-fi
-
-./Installation/Jenkins/build.sh \
-    standard \
-    --msvc \
-    --buildDir /cygdrive/c/b/${EP}/ \
-    --package NSIS \
-    --targetDir /var/tmp/ \
-    ${MOREOPTS} \
-    $@
-
-cd ${DIR}/..
diff --git a/scripts/build-rpm.sh b/scripts/build-rpm.sh
deleted file mode 100755
index 9d75a4e0db1f..000000000000
--- a/scripts/build-rpm.sh
+++ /dev/null
@@ -1,31 +0,0 @@
-#!/usr/bin/env bash
-
-set -e
-
-DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
-
-cd ${DIR}/..
-
-EP=""
-for i in $@; do
-    if test "$i" == "--enterprise"; then
-        EP="EP"
-    fi
-done
-
-if ! test -d 3rdParty/arangodb-starter; then
-    MOREOPTS="${MOREOPTS} --downloadStarter"
-fi
-
-./Installation/Jenkins/build.sh \
-    standard \
-    --rpath \
-    --package RPM \
-    --buildDir build-${EP}rpm \
-    --targetDir /var/tmp/ \
-    --jemalloc \
-    --noopt \
-    ${MOREOPTS} \
-    $@
-
-cd ${DIR}/..
diff --git a/scripts/build-snap.sh b/scripts/build-snap.sh
deleted file mode 100755
index 022dd80043db..000000000000
--- a/scripts/build-snap.sh
+++ /dev/null
@@ -1,40 +0,0 @@
-
-#!/usr/bin/env bash
-
-set -e
-
-if test -z ${CXX}; then
-  export CC=gcc
-  export CXX=g++
-fi
-
-EP=""
-for i in $@; do
-    if test "$i" == "--enterprise"; then
-        EP="EP"
-    fi
-done
-
-export CPU_CORES=$(grep -c ^processor /proc/cpuinfo)
-
-DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
-
-cd ${DIR}/..
-
-if ! test -d 3rdParty/arangodb-starter; then
-    MOREOPTS="${MOREOPTS} --downloadStarter"
-fi
-
-./Installation/Jenkins/build.sh \
-    standard \
-    --rpath \
-    --parallel ${CPU_CORES} \
-    --package TGZ \
-    --snap \
-    --buildDir build-${EP}snap \
-    --targetDir /var/tmp/ \
-    --noopt \
-    ${MOREOPTS} \
-    $@
-
-cd ${DIR}/..
diff --git a/scripts/build-xc-deb.sh b/scripts/build-xc-deb.sh
deleted file mode 100755
index e0b8c9999b45..000000000000
--- a/scripts/build-xc-deb.sh
+++ /dev/null
@@ -1,28 +0,0 @@
-#!/usr/bin/env bash
-
-set -e
-
-DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
-
-cd ${DIR}/..
-
-EP=""
-for i in $@; do
-    if test "$i" == "--enterprise"; then
-        EP="EP"
-    fi
-done
-
-
-./Installation/Jenkins/build.sh \
-    standard \
-    --parallel 25 \
-    --package DEB \
-    $SNAP \
-    --xcArm /usr/bin/arm-linux-gnueabihf \
-    --buildDir build-${EP}deb \
-    --targetDir /var/tmp/ \
-    --noopt \
-    $@
-
-cd ${DIR}/..
diff --git a/scripts/build-xc64-deb.sh b/scripts/build-xc64-deb.sh
deleted file mode 100755
index 6ab866412b18..000000000000
--- a/scripts/build-xc64-deb.sh
+++ /dev/null
@@ -1,31 +0,0 @@
-
-#!/usr/bin/env bash
-
-set -e
-
-DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
-export CPU_CORES=$(grep -c ^processor /proc/cpuinfo)
-
-
-cd ${DIR}/..
-
-EP=""
-for i in $@; do
-    if test "$i" == "--enterprise"; then
-        EP="EP"
-    fi
-done
-
-
-./Installation/Jenkins/build.sh \
-    standard \
-    --parallel ${CPU_CORES} \
-    --package DEB \
-    $SNAP \
-    --xcArm /usr/bin/aarch64-linux-gnu \
-    --buildDir build-${EP}deb \
-    --targetDir /var/tmp/ \
-    --noopt \
-    $@
-
-cd ${DIR}/..
diff --git a/scripts/encryptionTest.sh b/scripts/encryptionTest.sh
deleted file mode 100755
index 24577f825dc2..000000000000
--- a/scripts/encryptionTest.sh
+++ /dev/null
@@ -1,37 +0,0 @@
-#!/usr/bin/env bash
-#
-# This script runs the go-driver tests against an ArangoDB enterprise 
-# docker image that has encryption turned on.
-#
-# The ArangoDB docker image is typically created by `build-docker.sh`.
-#
-set -e
-
-DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
-ROOTDIR=${DIR}/..
-BUILDDIR=${ROOTDIR}/build 
-mkdir -p ${BUILDDIR}
-ENCRYPTION_KEYFILE=${BUILDDIR}/.encryption-keyfile
-
-VERSION=$(cat ${ROOTDIR}/VERSION)
-DOCKERTAG=${VERSION}-local
-
-# Fetch go driver
-if [ ! -e ${BUILDDIR}/.go-driver ]; then
-    cd ${BUILDDIR} 
-    git clone git@github.com:arangodb/go-driver.git ${BUILDDIR}/.go-driver
-fi
-
-# Create debian-jessie-builder
-if [ ! -e ${BUILDDIR}/.build-docker-containers ]; then
-    cd ${BUILDDIR} 
-    git clone git@github.com:arangodb-helper/build-docker-containers.git ${BUILDDIR}/.build-docker-containers
-fi
-docker build -t arangodb/debian-jessie-builder ${BUILDDIR}/.build-docker-containers/distros/debian/jessie/build/
-
-# Start test 
-if [ ! -e ${ENCRYPTION_KEYFILE} ]; then
-    dd if=/dev/random bs=1 count=32 of=${ENCRYPTION_KEYFILE}
-fi
-export ARANGODB="-v ${ENCRYPTION_KEYFILE}:/encryption-keyfile:ro -e ARANGO_ENCRYPTION_KEYFILE=/encryption-keyfile arangodb:${DOCKERTAG} --log.level=startup=DEBUG"
-make -C ${BUILDDIR}/.go-driver run-tests-single
diff --git a/scripts/generateDocumentation.sh b/scripts/generateDocumentation.sh
deleted file mode 100755
index bf4513274661..000000000000
--- a/scripts/generateDocumentation.sh
+++ /dev/null
@@ -1,118 +0,0 @@
-#!/usr/bin/env bash
-
-##python-setuptools
-##
-##python setup.py install
-##
-##node npm
-##
-##https://github.com/GitbookIO/gitbook
-## npm install gitbook-cli -g
-##
-##  http://calibre-ebook.com/download
-
-test_tools(){
-    if ! type easy_install >> /dev/null; then
-        echo "you are missing setuptools"
-        echo "apt-get install python-setuptools"
-        exit 1
-    fi
-
-    if ! type node >> /dev/null; then
-        echo "you are missing node"
-        echo "apt-get install nodejs nodejs-legacy"
-        exit 1
-    fi
-
-    if ! type npm >> /dev/null; then
-        echo "you are missing node"
-        echo "apt-get install npm"
-        exit 1
-    fi
-
-    if ! type calibre >> /dev/null; then
-        echo "you are missing node"
-        echo "apt-get install calibre-bin"
-        exit 1
-    fi
-    ARANGODB_VERSION_MAJOR=`grep 'set(ARANGODB_VERSION_MAJOR' CMakeLists.txt | sed 's;.*"\(.*\)".*;\1;'`
-    ARANGODB_VERSION_MINOR=`grep 'set(ARANGODB_VERSION_MINOR' CMakeLists.txt | sed 's;.*"\(.*\)".*;\1;'`
-    ARANGODB_VERSION_PATCH=`grep 'set(ARANGODB_VERSION_PATCH' CMakeLists.txt | sed 's;.*"\(.*\)".*;\1;'`
-
-    if test "${ARANGODB_VERSION_PATCH}" == "devel"; then
-        export NODE_MODULES_DIR="/tmp/devel/node_modules"
-    else
-        export NODE_MODULES_DIR="/tmp/${ARANGODB_VERSION_MAJOR}.${ARANGODB_VERSION_MINOR}/node_modules"
-    fi
-
-    if test ! -d ${NODE_MODULES_DIR}; then
-        echo "Your docker container doesn't contain the needed modules to build the documentation: ${NODE_MODULES_DIR}"
-        echo "Please delete the old arangodb/documentation-builder container, and re-run this script so it will pull "
-        echo "the latest version."
-        exit 1
-    fi
-    if test $(whoami) != "root"; then
-        cp -a /root/.gitbook/ ~/
-        cp -a /root/.npm/ ~/
-    fi
-}
-
-main(){
-    #test for basic tools
-    test_tools
-
-    TARGET=$1
-    shift
-    if test -z "$TARGET"; then
-        if test -d enterprise; then
-            ENTERPRISE="--enterprise true"
-        fi
-        ./scripts/build-deb.sh --buildDir build-docu --parallel $(nproc) ${ENTERPRISE} ||exit 1
-
-        # we expect this to be a symlink, so no -r ;-)
-        echo "#############################################"
-        echo "RELINKING BUILD DIRECTORY !!!!!!!!!!!!!!!!!!!"
-        echo "#############################################"
-        rm -f build
-        ln -s build-docu build
-
-        ./utils/generateExamples.sh
-    fi
-    ./utils/generateSwagger.sh
-
-    INSTALLED_GITBOOK_VERSION=$(gitbook ls |grep '*'|sed "s;.*\* ;;")
-    if test -z "${INSTALLED_GITBOOK_VERSION}"; then
-        echo "your container doesn't come with a preloaded version of gitbook, please update it."
-        exit 1
-    fi
-    export GITBOOK_ARGS="--gitbook ${INSTALLED_GITBOOK_VERSION}"
-
-    cd Documentation/Books
-
-    if test -z "$TARGET"; then
-        ./build.sh build-dist-books --outputDir /build/build-docu --nodeModulesDir "${NODE_MODULES_DIR}"
-    else
-        ./build.sh build-book --name "$TARGET" --outputDir /build/build-docu  --nodeModulesDir "${NODE_MODULES_DIR}" $@
-    fi
-}
-
-if test "$1" != "docker"; then
-
-    cd "$(dirname "${BASH_SOURCE[0]}")/.."
-    pwd
-
-    N=`basename $0`
-    if test "$N" != generateDocumentation.sh; then
-        DOCTarget=`echo $N | sed "s;.sh;;"`
-        cd ..
-    fi
-    WD=`pwd`
-
-    docker pull arangodb/documentation-builder 
-    docker run -it --volume ${WD}:/build arangodb/documentation-builder /bin/bash /build/scripts/generateDocumentation.sh docker $DOCTarget $@ 
-
-else
-    cd /build
-    shift
-    main "$@"
-fi
diff --git a/tests/Agency/MoveShardTest.cpp b/tests/Agency/MoveShardTest.cpp
index 0b7160ba49d9..b897eabc4333 100644
--- a/tests/Agency/MoveShardTest.cpp
+++ b/tests/Agency/MoveShardTest.cpp
@@ -48,6 +48,7 @@ const std::string COLLECTION = "collection";
 const std::string SHARD = "s99";
 const std::string SHARD_LEADER = "leader";
 const std::string SHARD_FOLLOWER1 = "follower1";
+const std::string SHARD_FOLLOWER2 = "follower2";
 const std::string FREE_SERVER = "free";
 const std::string FREE_SERVER2 = "free2";
 
@@ -996,6 +997,71 @@ TEST_F(MoveShardTest, if_the_job_is_too_old_it_should_be_aborted_to_prevent_a_de
   Verify(Method(spy, abort));
 }
 
+TEST_F(MoveShardTest, if_the_to_server_no_longer_replica_we_should_abort) {
+  std::function<std::unique_ptr<VPackBuilder>(VPackSlice const&, std::string const&)> createTestStructure =
+      [&](VPackSlice const& s, std::string const& path) {
+        std::unique_ptr<VPackBuilder> builder;
+        builder.reset(new VPackBuilder());
+        if (s.isObject()) {
+          builder->add(VPackValue(VPackValueType::Object));
+          for (auto it : VPackObjectIterator(s)) {
+            auto childBuilder =
+                createTestStructure(it.value, path + "/" + it.key.copyString());
+            if (childBuilder) {
+              builder->add(it.key.copyString(), childBuilder->slice());
+            }
+          }
+
+          if (path == "/arango/Target/Pending") {
+            VPackBuilder pendingJob;
+            {
+              VPackObjectBuilder b(&pendingJob);
+              auto plainJob = createJob(COLLECTION, SHARD_LEADER, SHARD_FOLLOWER1);
+              for (auto it : VPackObjectIterator(plainJob.slice())) {
+                pendingJob.add(it.key.copyString(), it.value);
+              }
+              pendingJob.add("timeCreated", VPackValue("2015-01-03T20:00:00Z"));
+            }
+            builder->add(jobId, pendingJob.slice());
+          }
+          builder->close();
+        } else {
+          if (path == "/arango/Plan/Collections/" + DATABASE + "/" +
+                          COLLECTION + "/shards/" + SHARD) {
+            builder->add(VPackValue(VPackValueType::Array));
+            builder->add(VPackValue("_" + SHARD_LEADER));
+            builder->add(VPackValue(SHARD_FOLLOWER1));
+            builder->add(VPackValue(SHARD_FOLLOWER2));
+            builder->close();
+          } else if (path == "/arango/Plan/Collections/" + DATABASE + "/" +
+                          COLLECTION + "/" + SHARD + "/servers") {
+            builder->add(VPackValue(VPackValueType::Array));
+            builder->add(VPackValue("_" + SHARD_LEADER));
+            builder->add(VPackValue(SHARD_FOLLOWER2));
+            builder->close();
+          } else {
+            builder->add(s);
+          }
+        }
+        return builder;
+      };
+
+  auto builder = createTestStructure(baseStructure.toBuilder().slice(), "");
+  Node agency = createAgencyFromBuilder(*builder);
+
+  Mock<AgentInterface> mockAgent;
+  AgentInterface& agent = mockAgent.get();
+
+  auto moveShard = MoveShard(agency, &agent, PENDING, jobId);
+  Mock<Job> spy(moveShard);
+  Fake(Method(spy, abort));
+
+  Job& spyMoveShard = spy.get();
+  spyMoveShard.run(aborts);
+
+  Verify(Method(spy, abort));
+}
+
 TEST_F(MoveShardTest, if_the_job_is_too_old_leader_case_it_should_be_aborted_to_prevent_deadloop) {
   std::function<std::unique_ptr<VPackBuilder>(VPackSlice const&, std::string const&)> createTestStructure =
       [&](VPackSlice const& s, std::string const& path) {
diff --git a/tests/Aql/TraversalExecutorTest.cpp b/tests/Aql/TraversalExecutorTest.cpp
index f219a3cb1c27..6d41a5f9b3e9 100644
--- a/tests/Aql/TraversalExecutorTest.cpp
+++ b/tests/Aql/TraversalExecutorTest.cpp
@@ -195,11 +195,12 @@ class GraphEnumerator : public PathEnumerator {
 class TraverserHelper : public Traverser {
  public:
   TraverserHelper(TraverserOptions* opts, transaction::Methods* trx, TestGraph const& g)
-      : Traverser(opts, trx), _graph(g) {}
+      : Traverser(opts, trx), _graph(g) {
+    _enumerator.reset(new GraphEnumerator(this, _opts, _graph));
+  }
 
   void setStartVertex(std::string const& value) override {
     _usedVertexAt.push_back(value);
-    _enumerator.reset(new GraphEnumerator(this, _opts, _graph));
     _enumerator->setStartVertex(arangodb::velocypack::StringRef(_usedVertexAt.back()));
     _done = false;
   }
diff --git a/tests/Basics/StringUtilsTest.cpp b/tests/Basics/StringUtilsTest.cpp
index 85b4571f3e16..9b06f4376eaf 100644
--- a/tests/Basics/StringUtilsTest.cpp
+++ b/tests/Basics/StringUtilsTest.cpp
@@ -181,13 +181,8 @@ TEST_F(StringUtilsTest, test_uint64) {
   EXPECT_EQ(12ULL,  StringUtils::uint64("00012"s));
   EXPECT_EQ(1234ULL,  StringUtils::uint64("1234"s));
   EXPECT_EQ(1234ULL,  StringUtils::uint64("1234a"s));
-#ifdef ARANGODB_STRING_UTILS_USE_FROM_CHARS
   EXPECT_EQ(0ULL,  StringUtils::uint64("-1"s));
   EXPECT_EQ(0ULL,  StringUtils::uint64("-12345"s));
-#else
-  EXPECT_EQ(18446744073709551615ULL,  StringUtils::uint64("-1"s));
-  EXPECT_EQ(18446744073709539271ULL,  StringUtils::uint64("-12345"s));
-#endif
   EXPECT_EQ(1234ULL,  StringUtils::uint64("1234.56"s));
   EXPECT_EQ(0ULL,  StringUtils::uint64("1234567890123456789012345678901234567890"s));
   EXPECT_EQ(0ULL,  StringUtils::uint64("@"s));
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 4c8d6934d0dd..4c041d369ab3 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -131,7 +131,9 @@ set(ARANGODB_TESTS_SOURCES
   Cluster/RebootTrackerTest.cpp
   Containers/associative-multi-pointer-test.cpp
   Containers/associative-multi-pointer-nohashcache-test.cpp
+  Containers/EnumerateTest.cpp
   Containers/HashSetTest.cpp
+  Containers/MerkleTreeTest.cpp
   Containers/skiplist-test.cpp
   Futures/Future-test.cpp
   Futures/Promise-test.cpp
@@ -179,6 +181,7 @@ set(ARANGODB_TESTS_SOURCES
   IResearch/IResearchQueryJoin-test.cpp
   IResearch/IResearchQueryLateMaterialization-test.cpp
   IResearch/IResearchQueryMinMatch-test.cpp
+  IResearch/IResearchQueryNGramMatch-test.cpp
   IResearch/IResearchQueryNoMaterialization-test.cpp
   IResearch/IResearchQueryNullTerm-test.cpp
   IResearch/IResearchQueryNumericTerm-test.cpp
@@ -240,8 +243,7 @@ set(ARANGODB_TESTS_SOURCES
   VocBase/vocbase-test.cpp
   VocBase/LogicalDataSource-test.cpp
   VocBase/LogicalView-test.cpp
-  VocBase/VersionTest.cpp
-)
+  VocBase/VersionTest.cpp)
 
 if (LINUX)
   # add "-fno-var-tracking" to the compiler flags
diff --git a/tests/Cache/BucketState.cpp b/tests/Cache/BucketState.cpp
index fa3b46209700..720032dd7f5e 100644
--- a/tests/Cache/BucketState.cpp
+++ b/tests/Cache/BucketState.cpp
@@ -21,16 +21,15 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 /// @author Copyright 2017, ArangoDB GmbH, Cologne, Germany
 ////////////////////////////////////////////////////////////////////////////////
 
-#include "Basics/Common.h"
-#include "Cache/BucketState.h"
-
 #include "gtest/gtest.h"
 
-#include <stdint.h>
+#include <cstdint>
+
+#include "Cache/BucketState.h"
 
 using namespace arangodb::cache;
 
@@ -38,7 +37,7 @@ TEST(CacheBucketStateTest, test_lock_methods) {
   BucketState state;
   bool success;
 
-  uint32_t outsideBucketState = 0;
+  std::uint32_t outsideBucketState = 0;
 
   auto cb1 = [&outsideBucketState]() -> void { outsideBucketState = 1; };
 
diff --git a/tests/Cache/CachedValue.cpp b/tests/Cache/CachedValue.cpp
index 0c9ce58f3f8a..1811c9bd0b91 100644
--- a/tests/Cache/CachedValue.cpp
+++ b/tests/Cache/CachedValue.cpp
@@ -21,61 +21,60 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 /// @author Copyright 2017, ArangoDB GmbH, Cologne, Germany
 ////////////////////////////////////////////////////////////////////////////////
 
-#include "Basics/Common.h"
-#include "Cache/CachedValue.h"
-
 #include "gtest/gtest.h"
 
-#include <stdint.h>
+#include <cstdint>
 #include <string>
 
+#include "Cache/CachedValue.h"
+
 using namespace arangodb::cache;
 
-const size_t padding = alignof(std::atomic<uint32_t>) - 1;
+const std::size_t padding = alignof(std::atomic<std::uint32_t>) - 1;
 
 TEST(CacheCachedValueTest, test_constructor_with_valid_input) {
-  uint64_t k = 1;
+  std::uint64_t k = 1;
   std::string v("test");
   CachedValue* cv;
 
   // fixed key, variable value
-  cv = CachedValue::construct(&k, sizeof(uint64_t), v.data(), v.size());
+  cv = CachedValue::construct(&k, sizeof(std::uint64_t), v.data(), v.size());
   ASSERT_NE(nullptr, cv);
-  ASSERT_EQ(sizeof(uint64_t), cv->keySize());
+  ASSERT_EQ(sizeof(std::uint64_t), cv->keySize());
   ASSERT_EQ(v.size(), cv->valueSize());
-  ASSERT_EQ(sizeof(CachedValue) + padding + sizeof(uint64_t) + v.size(), cv->size());
-  ASSERT_EQ(k, *reinterpret_cast<uint64_t const*>(cv->key()));
+  ASSERT_EQ(sizeof(CachedValue) + padding + sizeof(std::uint64_t) + v.size(), cv->size());
+  ASSERT_EQ(k, *reinterpret_cast<std::uint64_t const*>(cv->key()));
   ASSERT_EQ(0, memcmp(v.data(), cv->value(), v.size()));
   delete cv;
 
   // variable key, fixed value
-  cv = CachedValue::construct(v.data(), static_cast<uint32_t>(v.size()), &k,
-                              sizeof(uint64_t));
+  cv = CachedValue::construct(v.data(), static_cast<std::uint32_t>(v.size()),
+                              &k, sizeof(std::uint64_t));
   ASSERT_NE(nullptr, cv);
   ASSERT_EQ(v.size(), cv->keySize());
-  ASSERT_EQ(sizeof(uint64_t), cv->valueSize());
-  ASSERT_EQ(sizeof(CachedValue) + padding + sizeof(uint64_t) + v.size(), cv->size());
+  ASSERT_EQ(sizeof(std::uint64_t), cv->valueSize());
+  ASSERT_EQ(sizeof(CachedValue) + padding + sizeof(std::uint64_t) + v.size(), cv->size());
   ASSERT_EQ(0, memcmp(v.data(), cv->key(), v.size()));
-  ASSERT_EQ(k, *reinterpret_cast<uint64_t const*>(cv->value()));
+  ASSERT_EQ(k, *reinterpret_cast<std::uint64_t const*>(cv->value()));
   delete cv;
 
   // fixed key, zero length value
-  cv = CachedValue::construct(&k, sizeof(uint64_t), nullptr, 0);
+  cv = CachedValue::construct(&k, sizeof(std::uint64_t), nullptr, 0);
   ASSERT_NE(nullptr, cv);
-  ASSERT_EQ(sizeof(uint64_t), cv->keySize());
+  ASSERT_EQ(sizeof(std::uint64_t), cv->keySize());
   ASSERT_EQ(0ULL, cv->valueSize());
-  ASSERT_EQ(sizeof(CachedValue) + padding + sizeof(uint64_t), cv->size());
-  ASSERT_EQ(k, *reinterpret_cast<uint64_t const*>(cv->key()));
+  ASSERT_EQ(sizeof(CachedValue) + padding + sizeof(std::uint64_t), cv->size());
+  ASSERT_EQ(k, *reinterpret_cast<std::uint64_t const*>(cv->key()));
   ASSERT_EQ(nullptr, cv->value());
   delete cv;
 }
 
 TEST(CacheCachedValueTest, test_that_constructor_rejects_invalid_data) {
-  uint64_t k = 1;
+  std::uint64_t k = 1;
   std::string v("test");
   CachedValue* cv;
 
@@ -88,11 +87,11 @@ TEST(CacheCachedValueTest, test_that_constructor_rejects_invalid_data) {
   ASSERT_EQ(nullptr, cv);
 
   // nullptr key, non-zero size
-  cv = CachedValue::construct(nullptr, sizeof(uint64_t), v.data(), v.size());
+  cv = CachedValue::construct(nullptr, sizeof(std::uint64_t), v.data(), v.size());
   ASSERT_EQ(nullptr, cv);
 
   // nullptr value, non-zero length
-  cv = CachedValue::construct(&k, sizeof(uint64_t), nullptr, v.size());
+  cv = CachedValue::construct(&k, sizeof(std::uint64_t), nullptr, v.size());
   ASSERT_EQ(nullptr, cv);
 
   // too large key size
@@ -100,24 +99,24 @@ TEST(CacheCachedValueTest, test_that_constructor_rejects_invalid_data) {
   ASSERT_EQ(nullptr, cv);
 
   // too large value size
-  cv = CachedValue::construct(&k, sizeof(uint64_t), v.data(), 0x100000000ULL);
+  cv = CachedValue::construct(&k, sizeof(std::uint64_t), v.data(), 0x100000000ULL);
   ASSERT_EQ(nullptr, cv);
 }
 
 TEST(CacheCachedValueTest, copy_should_produce_a_correct_copy) {
-  uint64_t k = 1;
+  std::uint64_t k = 1;
   std::string v("test");
 
   // fixed key, variable value
-  auto original = CachedValue::construct(&k, sizeof(uint64_t), v.data(), v.size());
+  auto original = CachedValue::construct(&k, sizeof(std::uint64_t), v.data(), v.size());
   ASSERT_NE(nullptr, original);
   auto copy = original->copy();
   ASSERT_NE(nullptr, copy);
   ASSERT_NE(copy, original);
-  ASSERT_EQ(sizeof(uint64_t), copy->keySize());
+  ASSERT_EQ(sizeof(std::uint64_t), copy->keySize());
   ASSERT_EQ(v.size(), copy->valueSize());
-  ASSERT_EQ(sizeof(CachedValue) + padding + sizeof(uint64_t) + v.size(), copy->size());
-  ASSERT_EQ(k, *reinterpret_cast<uint64_t const*>(copy->key()));
+  ASSERT_EQ(sizeof(CachedValue) + padding + sizeof(std::uint64_t) + v.size(), copy->size());
+  ASSERT_EQ(k, *reinterpret_cast<std::uint64_t const*>(copy->key()));
   ASSERT_EQ(0, memcmp(v.data(), copy->value(), v.size()));
   delete original;
   delete copy;
@@ -127,20 +126,20 @@ TEST(CacheCachedValueTest, samekey_method_for_key_comparison_works) {
   std::string k1("test");
   std::string k2("testing");
   std::string k3("TEST");
-  uint64_t v = 1;
+  std::uint64_t v = 1;
 
-  auto cv = CachedValue::construct(k1.data(), static_cast<uint32_t>(k1.size()),
-                                   &v, sizeof(uint64_t));
+  auto cv = CachedValue::construct(k1.data(), static_cast<std::uint32_t>(k1.size()),
+                                   &v, sizeof(std::uint64_t));
   ASSERT_NE(nullptr, cv);
 
   // same key
-  ASSERT_TRUE(cv->sameKey(k1.data(), static_cast<uint32_t>(k1.size())));
+  ASSERT_TRUE(cv->sameKey(k1.data(), static_cast<std::uint32_t>(k1.size())));
 
   // different length, matching prefix
-  ASSERT_FALSE(cv->sameKey(k2.data(), static_cast<uint32_t>(k2.size())));
+  ASSERT_FALSE(cv->sameKey(k2.data(), static_cast<std::uint32_t>(k2.size())));
 
   // same length, different key
-  ASSERT_FALSE(cv->sameKey(k3.data(), static_cast<uint32_t>(k3.size())));
+  ASSERT_FALSE(cv->sameKey(k3.data(), static_cast<std::uint32_t>(k3.size())));
 
   delete cv;
 }
diff --git a/tests/Cache/FrequencyBuffer.cpp b/tests/Cache/FrequencyBuffer.cpp
index e6f4a879a8e0..c347f9452e3d 100644
--- a/tests/Cache/FrequencyBuffer.cpp
+++ b/tests/Cache/FrequencyBuffer.cpp
@@ -21,61 +21,60 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 /// @author Copyright 2017, ArangoDB GmbH, Cologne, Germany
 ////////////////////////////////////////////////////////////////////////////////
 
-#include "Basics/Common.h"
-#include "Cache/FrequencyBuffer.h"
-
 #include "gtest/gtest.h"
 
-#include <stdint.h>
+#include <cstdint>
 #include <memory>
 
+#include "Cache/FrequencyBuffer.h"
+
 using namespace arangodb::cache;
 
 TEST(CacheFrequencyBufferTest, test_buffer_with_uint8_entries) {
-  uint8_t zero = 0;
-  uint8_t one = 1;
-  uint8_t two = 2;
+  std::uint8_t zero = 0;
+  std::uint8_t one = 1;
+  std::uint8_t two = 2;
 
   // check that default construction is as expected
-  ASSERT_EQ(uint8_t(), zero);
+  ASSERT_EQ(std::uint8_t(), zero);
 
-  FrequencyBuffer<uint8_t> buffer(1024);
-  ASSERT_EQ(buffer.memoryUsage(), sizeof(FrequencyBuffer<uint8_t>) + 1024);
+  FrequencyBuffer<std::uint8_t> buffer(1024);
+  ASSERT_EQ(buffer.memoryUsage(), sizeof(FrequencyBuffer<std::uint8_t>) + 1024);
 
-  for (size_t i = 0; i < 512; i++) {
+  for (std::size_t i = 0; i < 512; i++) {
     buffer.insertRecord(two);
   }
-  for (size_t i = 0; i < 256; i++) {
+  for (std::size_t i = 0; i < 256; i++) {
     buffer.insertRecord(one);
   }
 
   auto frequencies = buffer.getFrequencies();
-  ASSERT_EQ(static_cast<uint64_t>(2), frequencies.size());
+  ASSERT_EQ(static_cast<std::uint64_t>(2), frequencies.size());
   ASSERT_EQ(one, frequencies[0].first);
-  ASSERT_TRUE(static_cast<uint64_t>(150) <= frequencies[0].second);
-  ASSERT_TRUE(static_cast<uint64_t>(256) >= frequencies[0].second);
+  ASSERT_TRUE(static_cast<std::uint64_t>(150) <= frequencies[0].second);
+  ASSERT_TRUE(static_cast<std::uint64_t>(256) >= frequencies[0].second);
   ASSERT_EQ(two, frequencies[1].first);
-  ASSERT_TRUE(static_cast<uint64_t>(300) <= frequencies[1].second);
-  ASSERT_TRUE(static_cast<uint64_t>(512) >= frequencies[1].second);
+  ASSERT_TRUE(static_cast<std::uint64_t>(300) <= frequencies[1].second);
+  ASSERT_TRUE(static_cast<std::uint64_t>(512) >= frequencies[1].second);
 
-  for (size_t i = 0; i < 8192; i++) {
+  for (std::size_t i = 0; i < 8192; i++) {
     buffer.insertRecord(one);
   }
 
   frequencies = buffer.getFrequencies();
   if (frequencies.size() == 1) {
-    ASSERT_EQ(static_cast<size_t>(1), frequencies.size());
+    ASSERT_EQ(static_cast<std::size_t>(1), frequencies.size());
     ASSERT_EQ(one, frequencies[0].first);
-    ASSERT_TRUE(static_cast<uint64_t>(800) <= frequencies[0].second);
+    ASSERT_TRUE(static_cast<std::uint64_t>(800) <= frequencies[0].second);
   } else {
-    ASSERT_EQ(static_cast<uint64_t>(2), frequencies.size());
+    ASSERT_EQ(static_cast<std::uint64_t>(2), frequencies.size());
     ASSERT_EQ(two, frequencies[0].first);
-    ASSERT_TRUE(static_cast<uint64_t>(100) >= frequencies[0].second);
+    ASSERT_TRUE(static_cast<std::uint64_t>(100) >= frequencies[0].second);
     ASSERT_EQ(one, frequencies[1].first);
-    ASSERT_TRUE(static_cast<uint64_t>(800) <= frequencies[1].second);
+    ASSERT_TRUE(static_cast<std::uint64_t>(800) <= frequencies[1].second);
   }
 }
diff --git a/tests/Cache/LockStressTest.cpp b/tests/Cache/LockStressTest.cpp
index 9bb663736230..27f85048321c 100644
--- a/tests/Cache/LockStressTest.cpp
+++ b/tests/Cache/LockStressTest.cpp
@@ -21,25 +21,25 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 /// @author Copyright 2017, ArangoDB GmbH, Cologne, Germany
 ////////////////////////////////////////////////////////////////////////////////
 
-#include "Basics/Common.h"
-#include "Cache/Manager.h"
-#include "Cache/Rebalancer.h"
-#include "Random/RandomGenerator.h"
-
-#include "MockScheduler.h"
-#include "TransactionalStore.h"
 #include "gtest/gtest.h"
 
-#include <stdint.h>
 #include <chrono>
+#include <cstdint>
 #include <iostream>
 #include <thread>
 #include <vector>
 
+#include "Cache/Manager.h"
+#include "Cache/Rebalancer.h"
+#include "Random/RandomGenerator.h"
+
+#include "MockScheduler.h"
+#include "TransactionalStore.h"
+
 using namespace arangodb;
 using namespace arangodb::cache;
 
@@ -50,21 +50,21 @@ TEST(CacheLockStressTest, test_transactionality_for_mixed_load) {
   MockScheduler scheduler(4);
   Manager manager(scheduler.ioService(), 32 * 1024 * 1024);
   TransactionalStore store(&manager);
-  uint64_t totalDocuments = 1000000;
-  uint64_t readBatchSize = 10000;
-  uint64_t numBatches = 250;
-  size_t readerCount = 24;
+  std::uint64_t totalDocuments = 1000000;
+  std::uint64_t readBatchSize = 10000;
+  std::uint64_t numBatches = 250;
+  std::size_t readerCount = 24;
 
   // initial fill
-  for (uint64_t i = 1; i <= totalDocuments; i++) {
+  for (std::uint64_t i = 1; i <= totalDocuments; i++) {
     store.insert(nullptr, TransactionalStore::Document(i));
   }
 
   auto readWorker = [&store, totalDocuments, readBatchSize, numBatches]() -> void {
-    for (uint64_t batch = 0; batch < numBatches; batch++) {
+    for (std::uint64_t batch = 0; batch < numBatches; batch++) {
       auto tx = store.beginTransaction(true);
-      for (uint64_t i = 0; i < readBatchSize; i++) {
-        uint64_t choice = RandomGenerator::interval(totalDocuments);
+      for (std::uint64_t i = 0; i < readBatchSize; i++) {
+        std::uint64_t choice = RandomGenerator::interval(totalDocuments);
         if (choice == 0) {
           choice = 1;
         }
@@ -81,7 +81,7 @@ TEST(CacheLockStressTest, test_transactionality_for_mixed_load) {
 
   std::vector<std::thread*> threads;
   // dispatch reader threads
-  for (size_t i = 0; i < readerCount; i++) {
+  for (std::size_t i = 0; i < readerCount; i++) {
     threads.push_back(new std::thread(readWorker));
   }
 
diff --git a/tests/Cache/Manager.cpp b/tests/Cache/Manager.cpp
index 59e541f95bea..049a10f5eafd 100644
--- a/tests/Cache/Manager.cpp
+++ b/tests/Cache/Manager.cpp
@@ -21,11 +21,18 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 /// @author Copyright 2017, ArangoDB GmbH, Cologne, Germany
 ////////////////////////////////////////////////////////////////////////////////
 
-#include "Basics/Common.h"
+#include "gtest/gtest.h"
+
+#include <cstdint>
+#include <queue>
+#include <string>
+#include <thread>
+#include <vector>
+
 #include "Cache/CacheManagerFeatureThreads.h"
 #include "Cache/Common.h"
 #include "Cache/Manager.h"
@@ -33,13 +40,6 @@
 #include "Random/RandomGenerator.h"
 
 #include "MockScheduler.h"
-#include "gtest/gtest.h"
-
-#include <stdint.h>
-#include <queue>
-#include <string>
-#include <thread>
-#include <vector>
 
 using namespace arangodb;
 using namespace arangodb::cache;
@@ -47,7 +47,7 @@ using namespace arangodb::cache;
 // long-running
 
 TEST(CacheManagerTest, test_basic_constructor_function) {
-  uint64_t requestLimit = 1024 * 1024;
+  std::uint64_t requestLimit = 1024 * 1024;
   auto postFn = [](std::function<void()>) -> bool { return false; };
   Manager manager(postFn, requestLimit);
 
@@ -56,7 +56,7 @@ TEST(CacheManagerTest, test_basic_constructor_function) {
   ASSERT_TRUE(0ULL < manager.globalAllocation());
   ASSERT_TRUE(requestLimit > manager.globalAllocation());
 
-  uint64_t bigRequestLimit = 4ULL * 1024ULL * 1024ULL * 1024ULL;
+  std::uint64_t bigRequestLimit = 4ULL * 1024ULL * 1024ULL * 1024ULL;
   Manager bigManager(nullptr, bigRequestLimit);
 
   ASSERT_EQ(bigRequestLimit, bigManager.globalLimit());
@@ -73,28 +73,28 @@ TEST(CacheManagerTest, test_mixed_cache_types_under_mixed_load_LongRunning) {
     return true;
   };
   Manager manager(postFn, 1024ULL * 1024ULL * 1024ULL);
-  size_t cacheCount = 4;
-  size_t threadCount = 4;
+  std::size_t cacheCount = 4;
+  std::size_t threadCount = 4;
   std::vector<std::shared_ptr<Cache>> caches;
-  for (size_t i = 0; i < cacheCount; i++) {
+  for (std::size_t i = 0; i < cacheCount; i++) {
     auto res = manager.createCache(((i % 2 == 0) ? CacheType::Plain : CacheType::Transactional));
     TRI_ASSERT(res);
     caches.emplace_back(res);
   }
 
-  uint64_t chunkSize = 4 * 1024 * 1024;
-  uint64_t initialInserts = 1 * 1024 * 1024;
-  uint64_t operationCount = 4 * 1024 * 1024;
-  std::atomic<uint64_t> hitCount(0);
-  std::atomic<uint64_t> missCount(0);
+  std::uint64_t chunkSize = 4 * 1024 * 1024;
+  std::uint64_t initialInserts = 1 * 1024 * 1024;
+  std::uint64_t operationCount = 4 * 1024 * 1024;
+  std::atomic<std::uint64_t> hitCount(0);
+  std::atomic<std::uint64_t> missCount(0);
   auto worker = [&caches, cacheCount, initialInserts, operationCount, &hitCount,
-                 &missCount](uint64_t lower, uint64_t upper) -> void {
+                 &missCount](std::uint64_t lower, std::uint64_t upper) -> void {
     // fill with some initial data
-    for (uint64_t i = 0; i < initialInserts; i++) {
-      uint64_t item = lower + i;
-      size_t cacheIndex = item % cacheCount;
-      CachedValue* value =
-          CachedValue::construct(&item, sizeof(uint64_t), &item, sizeof(uint64_t));
+    for (std::uint64_t i = 0; i < initialInserts; i++) {
+      std::uint64_t item = lower + i;
+      std::size_t cacheIndex = item % cacheCount;
+      CachedValue* value = CachedValue::construct(&item, sizeof(std::uint64_t),
+                                                  &item, sizeof(std::uint64_t));
       TRI_ASSERT(value != nullptr);
       auto status = caches[cacheIndex]->insert(value);
       if (status.fail()) {
@@ -103,46 +103,47 @@ TEST(CacheManagerTest, test_mixed_cache_types_under_mixed_load_LongRunning) {
     }
 
     // initialize valid range for keys that *might* be in cache
-    uint64_t validLower = lower;
-    uint64_t validUpper = lower + initialInserts - 1;
+    std::uint64_t validLower = lower;
+    std::uint64_t validUpper = lower + initialInserts - 1;
 
     // commence mixed workload
-    for (uint64_t i = 0; i < operationCount; i++) {
-      uint32_t r = RandomGenerator::interval(static_cast<uint32_t>(99));
+    for (std::uint64_t i = 0; i < operationCount; i++) {
+      std::uint32_t r = RandomGenerator::interval(static_cast<std::uint32_t>(99));
 
       if (r >= 99) {  // remove something
         if (validLower == validUpper) {
           continue;  // removed too much
         }
 
-        uint64_t item = validLower++;
-        size_t cacheIndex = item % cacheCount;
+        std::uint64_t item = validLower++;
+        std::size_t cacheIndex = item % cacheCount;
 
-        caches[cacheIndex]->remove(&item, sizeof(uint64_t));
+        caches[cacheIndex]->remove(&item, sizeof(std::uint64_t));
       } else if (r >= 95) {  // insert something
         if (validUpper == upper) {
           continue;  // already maxed out range
         }
 
-        uint64_t item = ++validUpper;
-        size_t cacheIndex = item % cacheCount;
-        CachedValue* value =
-            CachedValue::construct(&item, sizeof(uint64_t), &item, sizeof(uint64_t));
+        std::uint64_t item = ++validUpper;
+        std::size_t cacheIndex = item % cacheCount;
+        CachedValue* value = CachedValue::construct(&item, sizeof(std::uint64_t),
+                                                    &item, sizeof(std::uint64_t));
         TRI_ASSERT(value != nullptr);
         auto status = caches[cacheIndex]->insert(value);
         if (status.fail()) {
           delete value;
         }
       } else {  // lookup something
-        uint64_t item = RandomGenerator::interval(static_cast<int64_t>(validLower),
-                                                  static_cast<int64_t>(validUpper));
-        size_t cacheIndex = item % cacheCount;
+        std::uint64_t item =
+            RandomGenerator::interval(static_cast<int64_t>(validLower),
+                                      static_cast<int64_t>(validUpper));
+        std::size_t cacheIndex = item % cacheCount;
 
-        auto f = caches[cacheIndex]->find(&item, sizeof(uint64_t));
+        auto f = caches[cacheIndex]->find(&item, sizeof(std::uint64_t));
         if (f.found()) {
           hitCount++;
           TRI_ASSERT(f.value() != nullptr);
-          TRI_ASSERT(f.value()->sameKey(&item, sizeof(uint64_t)));
+          TRI_ASSERT(f.value()->sameKey(&item, sizeof(std::uint64_t)));
         } else {
           missCount++;
           TRI_ASSERT(f.value() == nullptr);
@@ -153,9 +154,9 @@ TEST(CacheManagerTest, test_mixed_cache_types_under_mixed_load_LongRunning) {
 
   std::vector<std::thread*> threads;
   // dispatch threads
-  for (size_t i = 0; i < threadCount; i++) {
-    uint64_t lower = i * chunkSize;
-    uint64_t upper = ((i + 1) * chunkSize) - 1;
+  for (std::size_t i = 0; i < threadCount; i++) {
+    std::uint64_t lower = i * chunkSize;
+    std::uint64_t upper = ((i + 1) * chunkSize) - 1;
     threads.push_back(new std::thread(worker, lower, upper));
   }
 
@@ -180,14 +181,14 @@ TEST(CacheManagerTest, test_manager_under_cache_lifecycle_chaos_LongRunning) {
     return true;
   };
   Manager manager(postFn, 1024ULL * 1024ULL * 1024ULL);
-  size_t threadCount = 4;
-  uint64_t operationCount = 4ULL * 1024ULL;
+  std::size_t threadCount = 4;
+  std::uint64_t operationCount = 4ULL * 1024ULL;
 
   auto worker = [&manager, operationCount]() -> void {
     std::queue<std::shared_ptr<Cache>> caches;
 
-    for (uint64_t i = 0; i < operationCount; i++) {
-      uint32_t r = RandomGenerator::interval(static_cast<uint32_t>(1));
+    for (std::uint64_t i = 0; i < operationCount; i++) {
+      std::uint32_t r = RandomGenerator::interval(static_cast<std::uint32_t>(1));
       switch (r) {
         case 0: {
           auto res = manager.createCache((i % 2 == 0) ? CacheType::Plain
@@ -211,7 +212,7 @@ TEST(CacheManagerTest, test_manager_under_cache_lifecycle_chaos_LongRunning) {
 
   std::vector<std::thread*> threads;
   // dispatch threads
-  for (size_t i = 0; i < threadCount; i++) {
+  for (std::size_t i = 0; i < threadCount; i++) {
     threads.push_back(new std::thread(worker));
   }
 
diff --git a/tests/Cache/Metadata.cpp b/tests/Cache/Metadata.cpp
index 40e3057a5740..d22ad4c74796 100644
--- a/tests/Cache/Metadata.cpp
+++ b/tests/Cache/Metadata.cpp
@@ -21,27 +21,28 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 /// @author Copyright 2017, ArangoDB GmbH, Cologne, Germany
 ////////////////////////////////////////////////////////////////////////////////
 
-#include "Basics/Common.h"
-#include "Cache/Metadata.h"
-#include "Cache/PlainCache.h"
-#include "Cache/Table.h"
-
 #include "gtest/gtest.h"
 
 #include <stdint.h>
 #include <memory>
 
+#include "Basics/SpinLocker.h"
+#include "Cache/Metadata.h"
+#include "Cache/PlainCache.h"
+#include "Cache/Table.h"
+
 using namespace arangodb::cache;
+using SpinLocker = ::arangodb::basics::SpinLocker;
 
 TEST(CacheMetadataTest, test_basic_constructor) {
-  uint64_t usageLimit = 1024;
-  uint64_t fixed = 128;
-  uint64_t table = Table::allocationSize(Table::minLogSize);
-  uint64_t max = UINT64_MAX;
+  std::uint64_t usageLimit = 1024;
+  std::uint64_t fixed = 128;
+  std::uint64_t table = Table::allocationSize(Table::minLogSize);
+  std::uint64_t max = UINT64_MAX;
   Metadata metadata(usageLimit, fixed, table, max);
 
   ASSERT_EQ(metadata.fixedSize, fixed);
@@ -56,10 +57,10 @@ TEST(CacheMetadataTest, test_basic_constructor) {
 }
 
 TEST(CacheMetadataTest, verify_usage_limits_are_adjusted_and_enforced_correctly) {
-  uint64_t overhead = 80;
+  std::uint64_t overhead = 80;
   Metadata metadata(1024, 0, 0, 2048 + overhead);
 
-  metadata.writeLock();
+  SpinLocker guard(SpinLocker::Mode::Write, metadata.lock());
 
   ASSERT_TRUE(metadata.adjustUsageIfAllowed(512));
   ASSERT_TRUE(metadata.adjustUsageIfAllowed(512));
@@ -88,15 +89,13 @@ TEST(CacheMetadataTest, verify_usage_limits_are_adjusted_and_enforced_correctly)
 
   ASSERT_FALSE(metadata.adjustLimits(2049, 2049));
   ASSERT_EQ(metadata.allocatedSize, 1024 + overhead);
-
-  metadata.writeUnlock();
 }
 
 TEST(CacheMetadataTest, verify_table_methods_work_correctly) {
-  uint64_t overhead = 80;
+  std::uint64_t overhead = 80;
   Metadata metadata(1024, 0, 512, 2048 + overhead);
 
-  metadata.writeLock();
+  SpinLocker guard(SpinLocker::Mode::Write, metadata.lock());
 
   ASSERT_FALSE(metadata.migrationAllowed(1024));
   ASSERT_EQ(2048 + overhead, metadata.adjustDeserved(2048 + overhead));
@@ -111,6 +110,4 @@ TEST(CacheMetadataTest, verify_table_methods_work_correctly) {
   metadata.changeTable(512);
   ASSERT_EQ(metadata.tableSize, 512);
   ASSERT_EQ(metadata.allocatedSize, 1536 + overhead);
-
-  metadata.writeUnlock();
 }
diff --git a/tests/Cache/MockScheduler.cpp b/tests/Cache/MockScheduler.cpp
index feb25df5f4ca..c65bcb2c0654 100644
--- a/tests/Cache/MockScheduler.cpp
+++ b/tests/Cache/MockScheduler.cpp
@@ -21,12 +21,11 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 /// @author Copyright 2017, ArangoDB GmbH, Cologne, Germany
 ////////////////////////////////////////////////////////////////////////////////
 
-#include "MockScheduler.h"
-#include "Basics/Common.h"
+#include <memory>
 
 #include <boost/asio/io_service.hpp>
 #include <boost/bind.hpp>
@@ -34,14 +33,14 @@
 #undef sleep
 #include <boost/thread/thread.hpp>
 
-#include <memory>
+#include "MockScheduler.h"
 
 using namespace arangodb::cache;
 
-MockScheduler::MockScheduler(size_t threads)
+MockScheduler::MockScheduler(std::size_t threads)
     : _ioService(new asio_ns::io_context()),
       _serviceGuard(new asio_ns::io_context::work(*_ioService)) {
-  for (size_t i = 0; i < threads; i++) {
+  for (std::size_t i = 0; i < threads; i++) {
     auto worker = std::bind(static_cast<size_t (asio_ns::io_context::*)()>(
                                 &asio_ns::io_context::run),
                             _ioService.get());
diff --git a/tests/Cache/MockScheduler.h b/tests/Cache/MockScheduler.h
index ea4b484304b7..3bc6f6b70312 100644
--- a/tests/Cache/MockScheduler.h
+++ b/tests/Cache/MockScheduler.h
@@ -21,21 +21,21 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 /// @author Copyright 2017, ArangoDB GmbH, Cologne, Germany
 ////////////////////////////////////////////////////////////////////////////////
 
 #ifndef UNITTESTS_CACHE_MOCK_SCHEDULER_H
 #define UNITTESTS_CACHE_MOCK_SCHEDULER_H
 
-#include "Basics/Common.h"
-#include "Basics/asio_ns.h"
-
-#include <boost/asio/io_service.hpp>
 #include <memory>
 #include <thread>
 #include <vector>
 
+#include <boost/asio/io_service.hpp>
+
+#include "Basics/asio_ns.h"
+
 namespace arangodb {
 namespace cache {
 
@@ -46,7 +46,7 @@ class MockScheduler {
   std::vector<std::thread*> _group;
 
  public:
-  MockScheduler(size_t threads);
+  MockScheduler(std::size_t threads);
   ~MockScheduler();
   void post(std::function<void()> fn);
 };
diff --git a/tests/Cache/PlainBucket.cpp b/tests/Cache/PlainBucket.cpp
index 9dea882f4a44..83765767ac0b 100644
--- a/tests/Cache/PlainBucket.cpp
+++ b/tests/Cache/PlainBucket.cpp
@@ -21,33 +21,32 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 /// @author Copyright 2017, ArangoDB GmbH, Cologne, Germany
 ////////////////////////////////////////////////////////////////////////////////
 
-#include "Cache/PlainBucket.h"
-#include "Basics/Common.h"
-#include "Basics/debugging.h"
-
 #include "gtest/gtest.h"
 
-#include <stdint.h>
+#include <cstdint>
 #include <string>
 
+#include "Basics/debugging.h"
+#include "Cache/PlainBucket.h"
+
 using namespace arangodb::cache;
 
 TEST(CachePlainBucketTest, verify_that_insertion_works_correctly) {
   auto bucket = std::make_unique<PlainBucket>();
   bool success;
 
-  uint32_t hashes[11] = {1, 2, 3, 4,  5, 6,
-                         7, 8, 9, 10, 11};  // don't have to be real, but should be unique and non-zero
-  uint64_t keys[11] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
-  uint64_t values[11] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
+  std::uint32_t hashes[11] = {1, 2, 3, 4,  5, 6,
+                              7, 8, 9, 10, 11};  // don't have to be real, but should be unique and non-zero
+  std::uint64_t keys[11] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
+  std::uint64_t values[11] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
   CachedValue* ptrs[11];
-  for (size_t i = 0; i < 11; i++) {
-    ptrs[i] = CachedValue::construct(&(keys[i]), sizeof(uint64_t), &(values[i]),
-                                     sizeof(uint64_t));
+  for (std::size_t i = 0; i < 11; i++) {
+    ptrs[i] = CachedValue::construct(&(keys[i]), sizeof(std::uint64_t),
+                                     &(values[i]), sizeof(std::uint64_t));
     TRI_ASSERT(ptrs[i] != nullptr);
   }
 
@@ -56,7 +55,7 @@ TEST(CachePlainBucketTest, verify_that_insertion_works_correctly) {
 
   // insert ten to fill
   ASSERT_FALSE(bucket->isFull());
-  for (size_t i = 0; i < 10; i++) {
+  for (std::size_t i = 0; i < 10; i++) {
     bucket->insert(hashes[i], ptrs[i]);
     if (i < 9) {
       ASSERT_FALSE(bucket->isFull());
@@ -64,7 +63,7 @@ TEST(CachePlainBucketTest, verify_that_insertion_works_correctly) {
       ASSERT_TRUE(bucket->isFull());
     }
   }
-  for (size_t i = 0; i < 10; i++) {
+  for (std::size_t i = 0; i < 10; i++) {
     CachedValue* res = bucket->find(hashes[i], ptrs[i]->key(), ptrs[i]->keySize());
     ASSERT_EQ(res, ptrs[i]);
   }
@@ -77,7 +76,7 @@ TEST(CachePlainBucketTest, verify_that_insertion_works_correctly) {
   bucket->unlock();
 
   // cleanup
-  for (size_t i = 0; i < 11; i++) {
+  for (std::size_t i = 0; i < 11; i++) {
     delete ptrs[i];
   }
 }
@@ -86,23 +85,23 @@ TEST(CachePlainBucketTest, verify_removal_works_correctly) {
   auto bucket = std::make_unique<PlainBucket>();
   bool success;
 
-  uint32_t hashes[3] = {1, 2, 3};  // don't have to be real, but should be unique and non-zero
-  uint64_t keys[3] = {0, 1, 2};
-  uint64_t values[3] = {0, 1, 2};
+  std::uint32_t hashes[3] = {1, 2, 3};  // don't have to be real, but should be unique and non-zero
+  std::uint64_t keys[3] = {0, 1, 2};
+  std::uint64_t values[3] = {0, 1, 2};
   CachedValue* ptrs[3];
-  for (size_t i = 0; i < 3; i++) {
-    ptrs[i] = CachedValue::construct(&(keys[i]), sizeof(uint64_t), &(values[i]),
-                                     sizeof(uint64_t));
+  for (std::size_t i = 0; i < 3; i++) {
+    ptrs[i] = CachedValue::construct(&(keys[i]), sizeof(std::uint64_t),
+                                     &(values[i]), sizeof(std::uint64_t));
     TRI_ASSERT(ptrs[i] != nullptr);
   }
 
   success = bucket->lock(-1LL);
   ASSERT_TRUE(success);
 
-  for (size_t i = 0; i < 3; i++) {
+  for (std::size_t i = 0; i < 3; i++) {
     bucket->insert(hashes[i], ptrs[i]);
   }
-  for (size_t i = 0; i < 3; i++) {
+  for (std::size_t i = 0; i < 3; i++) {
     CachedValue* res = bucket->find(hashes[i], ptrs[i]->key(), ptrs[i]->keySize());
     ASSERT_EQ(res, ptrs[i]);
   }
@@ -124,7 +123,7 @@ TEST(CachePlainBucketTest, verify_removal_works_correctly) {
   bucket->unlock();
 
   // cleanup
-  for (size_t i = 0; i < 3; i++) {
+  for (std::size_t i = 0; i < 3; i++) {
     delete ptrs[i];
   }
 }
@@ -133,14 +132,14 @@ TEST(CachePlainBucketTest, verify_eviction_works_correctly) {
   auto bucket = std::make_unique<PlainBucket>();
   bool success;
 
-  uint32_t hashes[11] = {1, 2, 3, 4,  5, 6,
-                         7, 8, 9, 10, 11};  // don't have to be real, but should be unique and non-zero
-  uint64_t keys[11] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
-  uint64_t values[11] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
+  std::uint32_t hashes[11] = {1, 2, 3, 4,  5, 6,
+                              7, 8, 9, 10, 11};  // don't have to be real, but should be unique and non-zero
+  std::uint64_t keys[11] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
+  std::uint64_t values[11] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
   CachedValue* ptrs[11];
-  for (size_t i = 0; i < 11; i++) {
-    ptrs[i] = CachedValue::construct(&(keys[i]), sizeof(uint64_t), &(values[i]),
-                                     sizeof(uint64_t));
+  for (std::size_t i = 0; i < 11; i++) {
+    ptrs[i] = CachedValue::construct(&(keys[i]), sizeof(std::uint64_t),
+                                     &(values[i]), sizeof(std::uint64_t));
     TRI_ASSERT(ptrs[i] != nullptr);
   }
 
@@ -149,7 +148,7 @@ TEST(CachePlainBucketTest, verify_eviction_works_correctly) {
 
   // insert five to fill
   ASSERT_FALSE(bucket->isFull());
-  for (size_t i = 0; i < 10; i++) {
+  for (std::size_t i = 0; i < 10; i++) {
     bucket->insert(hashes[i], ptrs[i]);
     if (i < 9) {
       ASSERT_FALSE(bucket->isFull());
@@ -157,7 +156,7 @@ TEST(CachePlainBucketTest, verify_eviction_works_correctly) {
       ASSERT_TRUE(bucket->isFull());
     }
   }
-  for (size_t i = 0; i < 10; i++) {
+  for (std::size_t i = 0; i < 10; i++) {
     CachedValue* res = bucket->find(hashes[i], ptrs[i]->key(), ptrs[i]->keySize());
     ASSERT_EQ(res, ptrs[i]);
   }
@@ -186,7 +185,7 @@ TEST(CachePlainBucketTest, verify_eviction_works_correctly) {
   bucket->unlock();
 
   // cleanup
-  for (size_t i = 0; i < 11; i++) {
+  for (std::size_t i = 0; i < 11; i++) {
     delete ptrs[i];
   }
 }
diff --git a/tests/Cache/PlainCache.cpp b/tests/Cache/PlainCache.cpp
index afed28971907..ea5db57be2e2 100644
--- a/tests/Cache/PlainCache.cpp
+++ b/tests/Cache/PlainCache.cpp
@@ -21,11 +21,17 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 /// @author Copyright 2017, ArangoDB GmbH, Cologne, Germany
 ////////////////////////////////////////////////////////////////////////////////
 
-#include "Basics/Common.h"
+#include "gtest/gtest.h"
+
+#include <stdint.h>
+#include <string>
+#include <thread>
+#include <vector>
+
 #include "Basics/xoroshiro128plus.h"
 #include "Cache/Common.h"
 #include "Cache/Manager.h"
@@ -33,12 +39,6 @@
 #include "Random/RandomGenerator.h"
 
 #include "MockScheduler.h"
-#include "gtest/gtest.h"
-
-#include <stdint.h>
-#include <string>
-#include <thread>
-#include <vector>
 
 using namespace arangodb;
 using namespace arangodb::cache;
@@ -62,46 +62,46 @@ TEST(CachePlainCacheTest, test_basic_cache_creation) {
 }
 
 TEST(CachePlainCacheTest, check_that_insertion_works_as_expected) {
-  uint64_t cacheLimit = 128 * 1024;
+  std::uint64_t cacheLimit = 128 * 1024;
   auto postFn = [](std::function<void()>) -> bool { return false; };
   Manager manager(postFn, 4 * cacheLimit);
   auto cache = manager.createCache(CacheType::Plain, false, cacheLimit);
 
-  for (uint64_t i = 0; i < 1024; i++) {
+  for (std::uint64_t i = 0; i < 1024; i++) {
     CachedValue* value =
-        CachedValue::construct(&i, sizeof(uint64_t), &i, sizeof(uint64_t));
+        CachedValue::construct(&i, sizeof(std::uint64_t), &i, sizeof(std::uint64_t));
     TRI_ASSERT(value != nullptr);
     auto status = cache->insert(value);
     if (status.ok()) {
-      auto f = cache->find(&i, sizeof(uint64_t));
+      auto f = cache->find(&i, sizeof(std::uint64_t));
       ASSERT_TRUE(f.found());
     } else {
       delete value;
     }
   }
 
-  for (uint64_t i = 0; i < 1024; i++) {
-    uint64_t j = 2 * i;
+  for (std::uint64_t i = 0; i < 1024; i++) {
+    std::uint64_t j = 2 * i;
     CachedValue* value =
-        CachedValue::construct(&i, sizeof(uint64_t), &j, sizeof(uint64_t));
+        CachedValue::construct(&i, sizeof(std::uint64_t), &j, sizeof(std::uint64_t));
     TRI_ASSERT(value != nullptr);
     auto status = cache->insert(value);
     if (status.ok()) {
-      auto f = cache->find(&i, sizeof(uint64_t));
+      auto f = cache->find(&i, sizeof(std::uint64_t));
       ASSERT_TRUE(f.found());
-      ASSERT_EQ(0, memcmp(f.value()->value(), &j, sizeof(uint64_t)));
+      ASSERT_EQ(0, memcmp(f.value()->value(), &j, sizeof(std::uint64_t)));
     } else {
       delete value;
     }
   }
 
-  for (uint64_t i = 1024; i < 128 * 1024; i++) {
+  for (std::uint64_t i = 1024; i < 128 * 1024; i++) {
     CachedValue* value =
-        CachedValue::construct(&i, sizeof(uint64_t), &i, sizeof(uint64_t));
+        CachedValue::construct(&i, sizeof(std::uint64_t), &i, sizeof(std::uint64_t));
     TRI_ASSERT(value != nullptr);
     auto status = cache->insert(value);
     if (status.ok()) {
-      auto f = cache->find(&i, sizeof(uint64_t));
+      auto f = cache->find(&i, sizeof(std::uint64_t));
       ASSERT_TRUE(f.found());
     } else {
       delete value;
@@ -113,57 +113,57 @@ TEST(CachePlainCacheTest, check_that_insertion_works_as_expected) {
 }
 
 TEST(CachePlainCacheTest, test_that_removal_works_as_expected) {
-  uint64_t cacheLimit = 128 * 1024;
+  std::uint64_t cacheLimit = 128 * 1024;
   auto postFn = [](std::function<void()>) -> bool { return false; };
   Manager manager(postFn, 4 * cacheLimit);
   auto cache = manager.createCache(CacheType::Plain, false, cacheLimit);
 
-  for (uint64_t i = 0; i < 1024; i++) {
+  for (std::uint64_t i = 0; i < 1024; i++) {
     CachedValue* value =
-        CachedValue::construct(&i, sizeof(uint64_t), &i, sizeof(uint64_t));
+        CachedValue::construct(&i, sizeof(std::uint64_t), &i, sizeof(std::uint64_t));
     TRI_ASSERT(value != nullptr);
     auto status = cache->insert(value);
     if (status.ok()) {
-      auto f = cache->find(&i, sizeof(uint64_t));
+      auto f = cache->find(&i, sizeof(std::uint64_t));
       ASSERT_TRUE(f.found());
       ASSERT_NE(f.value(), nullptr);
-      ASSERT_TRUE(f.value()->sameKey(&i, sizeof(uint64_t)));
+      ASSERT_TRUE(f.value()->sameKey(&i, sizeof(std::uint64_t)));
     } else {
       delete value;
     }
   }
-  uint64_t inserted = 0;
-  for (uint64_t j = 0; j < 1024; j++) {
-    auto f = cache->find(&j, sizeof(uint64_t));
+  std::uint64_t inserted = 0;
+  for (std::uint64_t j = 0; j < 1024; j++) {
+    auto f = cache->find(&j, sizeof(std::uint64_t));
     if (f.found()) {
       inserted++;
       ASSERT_NE(f.value(), nullptr);
-      ASSERT_TRUE(f.value()->sameKey(&j, sizeof(uint64_t)));
+      ASSERT_TRUE(f.value()->sameKey(&j, sizeof(std::uint64_t)));
     }
   }
 
   // test removal of bogus keys
-  for (uint64_t i = 1024; i < 1088; i++) {
-    auto status = cache->remove(&i, sizeof(uint64_t));
+  for (std::uint64_t i = 1024; i < 1088; i++) {
+    auto status = cache->remove(&i, sizeof(std::uint64_t));
     ASSERT_TRUE(status.ok());
     // ensure existing keys not removed
-    uint64_t found = 0;
-    for (uint64_t j = 0; j < 1024; j++) {
-      auto f = cache->find(&j, sizeof(uint64_t));
+    std::uint64_t found = 0;
+    for (std::uint64_t j = 0; j < 1024; j++) {
+      auto f = cache->find(&j, sizeof(std::uint64_t));
       if (f.found()) {
         found++;
         ASSERT_NE(f.value(), nullptr);
-        ASSERT_TRUE(f.value()->sameKey(&j, sizeof(uint64_t)));
+        ASSERT_TRUE(f.value()->sameKey(&j, sizeof(std::uint64_t)));
       }
     }
     ASSERT_EQ(inserted, found);
   }
 
   // remove actual keys
-  for (uint64_t i = 0; i < 1024; i++) {
-    auto status = cache->remove(&i, sizeof(uint64_t));
+  for (std::uint64_t i = 0; i < 1024; i++) {
+    auto status = cache->remove(&i, sizeof(std::uint64_t));
     ASSERT_TRUE(status.ok());
-    auto f = cache->find(&i, sizeof(uint64_t));
+    auto f = cache->find(&i, sizeof(std::uint64_t));
     ASSERT_FALSE(f.found());
   }
 
@@ -178,11 +178,11 @@ TEST(CachePlainCacheTest, verify_that_cache_can_indeed_grow_when_it_runs_out_of_
   };
   Manager manager(postFn, 1024 * 1024 * 1024);
   auto cache = manager.createCache(CacheType::Plain);
-  uint64_t minimumUsage = cache->usageLimit() * 2;
+  std::uint64_t minimumUsage = cache->usageLimit() * 2;
 
-  for (uint64_t i = 0; i < 4 * 1024 * 1024; i++) {
+  for (std::uint64_t i = 0; i < 4 * 1024 * 1024; i++) {
     CachedValue* value =
-        CachedValue::construct(&i, sizeof(uint64_t), &i, sizeof(uint64_t));
+        CachedValue::construct(&i, sizeof(std::uint64_t), &i, sizeof(std::uint64_t));
     TRI_ASSERT(value != nullptr);
     auto status = cache->insert(value);
     if (status.fail()) {
@@ -204,21 +204,21 @@ TEST(CachePlainCacheTest, test_behavior_under_mixed_load_LongRunning) {
     return true;
   };
   Manager manager(postFn, 1024 * 1024 * 1024);
-  size_t threadCount = 4;
+  std::size_t threadCount = 4;
   std::shared_ptr<Cache> cache = manager.createCache(CacheType::Plain);
 
-  uint64_t chunkSize = 16 * 1024 * 1024;
-  uint64_t initialInserts = 4 * 1024 * 1024;
-  uint64_t operationCount = 16 * 1024 * 1024;
-  std::atomic<uint64_t> hitCount(0);
-  std::atomic<uint64_t> missCount(0);
+  std::uint64_t chunkSize = 16 * 1024 * 1024;
+  std::uint64_t initialInserts = 4 * 1024 * 1024;
+  std::uint64_t operationCount = 16 * 1024 * 1024;
+  std::atomic<std::uint64_t> hitCount(0);
+  std::atomic<std::uint64_t> missCount(0);
   auto worker = [&cache, initialInserts, operationCount, &hitCount,
-                 &missCount](uint64_t lower, uint64_t upper) -> void {
+                 &missCount](std::uint64_t lower, std::uint64_t upper) -> void {
     // fill with some initial data
-    for (uint64_t i = 0; i < initialInserts; i++) {
-      uint64_t item = lower + i;
-      CachedValue* value =
-          CachedValue::construct(&item, sizeof(uint64_t), &item, sizeof(uint64_t));
+    for (std::uint64_t i = 0; i < initialInserts; i++) {
+      std::uint64_t item = lower + i;
+      CachedValue* value = CachedValue::construct(&item, sizeof(std::uint64_t),
+                                                  &item, sizeof(std::uint64_t));
       TRI_ASSERT(value != nullptr);
       auto status = cache->insert(value);
       if (status.fail()) {
@@ -227,45 +227,45 @@ TEST(CachePlainCacheTest, test_behavior_under_mixed_load_LongRunning) {
     }
 
     // initialize valid range for keys that *might* be in cache
-    uint64_t validLower = lower;
-    uint64_t validUpper = lower + initialInserts - 1;
+    std::uint64_t validLower = lower;
+    std::uint64_t validUpper = lower + initialInserts - 1;
 
     basics::xoroshiro128plus prng;
     prng.seed(RandomGenerator::interval(UINT64_MAX), RandomGenerator::interval(UINT64_MAX));
 
     // commence mixed workload
-    for (uint64_t i = 0; i < operationCount; i++) {
-      uint64_t r = prng.next() % 99;
+    for (std::uint64_t i = 0; i < operationCount; i++) {
+      std::uint64_t r = prng.next() % 99;
 
       if (r >= 99) {  // remove something
         if (validLower == validUpper) {
           continue;  // removed too much
         }
 
-        uint64_t item = validLower++;
+        std::uint64_t item = validLower++;
 
-        cache->remove(&item, sizeof(uint64_t));
+        cache->remove(&item, sizeof(std::uint64_t));
       } else if (r >= 95) {  // insert something
         if (validUpper == upper) {
           continue;  // already maxed out range
         }
 
-        uint64_t item = ++validUpper;
-        CachedValue* value =
-            CachedValue::construct(&item, sizeof(uint64_t), &item, sizeof(uint64_t));
+        std::uint64_t item = ++validUpper;
+        CachedValue* value = CachedValue::construct(&item, sizeof(std::uint64_t),
+                                                    &item, sizeof(std::uint64_t));
         TRI_ASSERT(value != nullptr);
         auto status = cache->insert(value);
         if (status.fail()) {
           delete value;
         }
       } else {  // lookup something
-        uint64_t item = (prng.next() % (validUpper + 1 - validLower)) + validLower;
+        std::uint64_t item = (prng.next() % (validUpper + 1 - validLower)) + validLower;
 
-        Finding f = cache->find(&item, sizeof(uint64_t));
+        Finding f = cache->find(&item, sizeof(std::uint64_t));
         if (f.found()) {
           hitCount++;
           TRI_ASSERT(f.value() != nullptr);
-          TRI_ASSERT(f.value()->sameKey(&item, sizeof(uint64_t)));
+          TRI_ASSERT(f.value()->sameKey(&item, sizeof(std::uint64_t)));
         } else {
           missCount++;
           TRI_ASSERT(f.value() == nullptr);
@@ -276,9 +276,9 @@ TEST(CachePlainCacheTest, test_behavior_under_mixed_load_LongRunning) {
 
   std::vector<std::thread*> threads;
   // dispatch threads
-  for (size_t i = 0; i < threadCount; i++) {
-    uint64_t lower = i * chunkSize;
-    uint64_t upper = ((i + 1) * chunkSize) - 1;
+  for (std::size_t i = 0; i < threadCount; i++) {
+    std::uint64_t lower = i * chunkSize;
+    std::uint64_t upper = ((i + 1) * chunkSize) - 1;
     threads.push_back(new std::thread(worker, lower, upper));
   }
 
@@ -293,30 +293,30 @@ TEST(CachePlainCacheTest, test_behavior_under_mixed_load_LongRunning) {
 }
 
 TEST(CachePlainCacheTest, test_hit_rate_statistics_reporting) {
-  uint64_t cacheLimit = 256 * 1024;
+  std::uint64_t cacheLimit = 256 * 1024;
   auto postFn = [](std::function<void()>) -> bool { return false; };
   Manager manager(postFn, 4 * cacheLimit);
   auto cacheMiss = manager.createCache(CacheType::Plain, true, cacheLimit);
   auto cacheHit = manager.createCache(CacheType::Plain, true, cacheLimit);
   auto cacheMixed = manager.createCache(CacheType::Plain, true, cacheLimit);
 
-  for (uint64_t i = 0; i < 1024; i++) {
+  for (std::uint64_t i = 0; i < 1024; i++) {
     CachedValue* value =
-        CachedValue::construct(&i, sizeof(uint64_t), &i, sizeof(uint64_t));
+        CachedValue::construct(&i, sizeof(std::uint64_t), &i, sizeof(std::uint64_t));
     TRI_ASSERT(value != nullptr);
     auto status = cacheHit->insert(value);
     if (status.fail()) {
       delete value;
     }
 
-    value = CachedValue::construct(&i, sizeof(uint64_t), &i, sizeof(uint64_t));
+    value = CachedValue::construct(&i, sizeof(std::uint64_t), &i, sizeof(std::uint64_t));
     TRI_ASSERT(value != nullptr);
     status = cacheMiss->insert(value);
     if (status.fail()) {
       delete value;
     }
 
-    value = CachedValue::construct(&i, sizeof(uint64_t), &i, sizeof(uint64_t));
+    value = CachedValue::construct(&i, sizeof(std::uint64_t), &i, sizeof(std::uint64_t));
     TRI_ASSERT(value != nullptr);
     status = cacheMixed->insert(value);
     if (status.fail()) {
@@ -324,8 +324,8 @@ TEST(CachePlainCacheTest, test_hit_rate_statistics_reporting) {
     }
   }
 
-  for (uint64_t i = 0; i < 1024; i++) {
-    auto f = cacheHit->find(&i, sizeof(uint64_t));
+  for (std::uint64_t i = 0; i < 1024; i++) {
+    auto f = cacheHit->find(&i, sizeof(std::uint64_t));
   }
   {
     auto cacheStats = cacheHit->hitRates();
@@ -336,8 +336,8 @@ TEST(CachePlainCacheTest, test_hit_rate_statistics_reporting) {
     ASSERT_TRUE(managerStats.second >= 40.0);
   }
 
-  for (uint64_t i = 1024; i < 2048; i++) {
-    auto f = cacheMiss->find(&i, sizeof(uint64_t));
+  for (std::uint64_t i = 1024; i < 2048; i++) {
+    auto f = cacheMiss->find(&i, sizeof(std::uint64_t));
   }
   {
     auto cacheStats = cacheMiss->hitRates();
@@ -350,11 +350,11 @@ TEST(CachePlainCacheTest, test_hit_rate_statistics_reporting) {
     ASSERT_TRUE(managerStats.second < 60.0);
   }
 
-  for (uint64_t i = 0; i < 1024; i++) {
-    auto f = cacheMixed->find(&i, sizeof(uint64_t));
+  for (std::uint64_t i = 0; i < 1024; i++) {
+    auto f = cacheMixed->find(&i, sizeof(std::uint64_t));
   }
-  for (uint64_t i = 1024; i < 2048; i++) {
-    auto f = cacheMixed->find(&i, sizeof(uint64_t));
+  for (std::uint64_t i = 1024; i < 2048; i++) {
+    auto f = cacheMixed->find(&i, sizeof(std::uint64_t));
   }
   {
     auto cacheStats = cacheMixed->hitRates();
diff --git a/tests/Cache/Rebalancer.cpp b/tests/Cache/Rebalancer.cpp
index 1a2990b9bc40..bf4926e2b179 100644
--- a/tests/Cache/Rebalancer.cpp
+++ b/tests/Cache/Rebalancer.cpp
@@ -21,29 +21,28 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 /// @author Copyright 2017, ArangoDB GmbH, Cologne, Germany
 ////////////////////////////////////////////////////////////////////////////////
 
-#include "Cache/Rebalancer.h"
-#include "Basics/Common.h"
+#include "gtest/gtest.h"
+
+#include <cstdint>
+#include <memory>
+#include <string>
+#include <thread>
+#include <vector>
+
 #include "Basics/voc-errors.h"
 #include "Cache/Common.h"
 #include "Cache/Manager.h"
 #include "Cache/PlainCache.h"
+#include "Cache/Rebalancer.h"
 #include "Cache/Transaction.h"
 #include "Cache/TransactionalCache.h"
 #include "Random/RandomGenerator.h"
 
 #include "MockScheduler.h"
-#include "gtest/gtest.h"
-
-#include <cstdint>
-#include <memory>
-#include <string>
-#include <thread>
-#include <vector>
-
 using namespace arangodb;
 using namespace arangodb::cache;
 
@@ -79,10 +78,10 @@ TEST(CacheRebalancerTest, test_rebalancing_with_plaincache_LongRunning) {
   Manager manager(postFn, 128 * 1024 * 1024);
   Rebalancer rebalancer(&manager);
 
-  size_t cacheCount = 4;
-  size_t threadCount = 4;
+  std::size_t cacheCount = 4;
+  std::size_t threadCount = 4;
   std::vector<std::shared_ptr<Cache>> caches;
-  for (size_t i = 0; i < cacheCount; i++) {
+  for (std::size_t i = 0; i < cacheCount; i++) {
     caches.emplace_back(manager.createCache(CacheType::Plain));
   }
 
@@ -100,19 +99,19 @@ TEST(CacheRebalancerTest, test_rebalancing_with_plaincache_LongRunning) {
 
   ThreadGuard rebalancerThread(std::make_unique<std::thread>(rebalanceWorker));
 
-  uint64_t chunkSize = 4 * 1024 * 1024;
-  uint64_t initialInserts = 1 * 1024 * 1024;
-  uint64_t operationCount = 4 * 1024 * 1024;
-  std::atomic<uint64_t> hitCount(0);
-  std::atomic<uint64_t> missCount(0);
+  std::uint64_t chunkSize = 4 * 1024 * 1024;
+  std::uint64_t initialInserts = 1 * 1024 * 1024;
+  std::uint64_t operationCount = 4 * 1024 * 1024;
+  std::atomic<std::uint64_t> hitCount(0);
+  std::atomic<std::uint64_t> missCount(0);
   auto worker = [&caches, cacheCount, initialInserts, operationCount, &hitCount,
-                 &missCount](uint64_t lower, uint64_t upper) -> void {
+                 &missCount](std::uint64_t lower, std::uint64_t upper) -> void {
     // fill with some initial data
-    for (uint64_t i = 0; i < initialInserts; i++) {
-      uint64_t item = lower + i;
-      size_t cacheIndex = item % cacheCount;
-      CachedValue* value =
-          CachedValue::construct(&item, sizeof(uint64_t), &item, sizeof(uint64_t));
+    for (std::uint64_t i = 0; i < initialInserts; i++) {
+      std::uint64_t item = lower + i;
+      std::size_t cacheIndex = item % cacheCount;
+      CachedValue* value = CachedValue::construct(&item, sizeof(std::uint64_t),
+                                                  &item, sizeof(std::uint64_t));
       TRI_ASSERT(value != nullptr);
       auto status = caches[cacheIndex]->insert(value);
       if (status.fail()) {
@@ -121,46 +120,47 @@ TEST(CacheRebalancerTest, test_rebalancing_with_plaincache_LongRunning) {
     }
 
     // initialize valid range for keys that *might* be in cache
-    uint64_t validLower = lower;
-    uint64_t validUpper = lower + initialInserts - 1;
+    std::uint64_t validLower = lower;
+    std::uint64_t validUpper = lower + initialInserts - 1;
 
     // commence mixed workload
-    for (uint64_t i = 0; i < operationCount; i++) {
-      uint32_t r = RandomGenerator::interval(static_cast<uint32_t>(99UL));
+    for (std::uint64_t i = 0; i < operationCount; i++) {
+      std::uint32_t r = RandomGenerator::interval(static_cast<std::uint32_t>(99UL));
 
       if (r >= 99) {  // remove something
         if (validLower == validUpper) {
           continue;  // removed too much
         }
 
-        uint64_t item = validLower++;
-        size_t cacheIndex = item % cacheCount;
+        std::uint64_t item = validLower++;
+        std::size_t cacheIndex = item % cacheCount;
 
-        caches[cacheIndex]->remove(&item, sizeof(uint64_t));
+        caches[cacheIndex]->remove(&item, sizeof(std::uint64_t));
       } else if (r >= 95) {  // insert something
         if (validUpper == upper) {
           continue;  // already maxed out range
         }
 
-        uint64_t item = ++validUpper;
-        size_t cacheIndex = item % cacheCount;
-        CachedValue* value =
-            CachedValue::construct(&item, sizeof(uint64_t), &item, sizeof(uint64_t));
+        std::uint64_t item = ++validUpper;
+        std::size_t cacheIndex = item % cacheCount;
+        CachedValue* value = CachedValue::construct(&item, sizeof(std::uint64_t),
+                                                    &item, sizeof(std::uint64_t));
         TRI_ASSERT(value != nullptr);
         auto status = caches[cacheIndex]->insert(value);
         if (status.fail()) {
           delete value;
         }
       } else {  // lookup something
-        uint64_t item = RandomGenerator::interval(static_cast<int64_t>(validLower),
-                                                  static_cast<int64_t>(validUpper));
-        size_t cacheIndex = item % cacheCount;
+        std::uint64_t item =
+            RandomGenerator::interval(static_cast<int64_t>(validLower),
+                                      static_cast<int64_t>(validUpper));
+        std::size_t cacheIndex = item % cacheCount;
 
-        Finding f = caches[cacheIndex]->find(&item, sizeof(uint64_t));
+        Finding f = caches[cacheIndex]->find(&item, sizeof(std::uint64_t));
         if (f.found()) {
           hitCount++;
           TRI_ASSERT(f.value() != nullptr);
-          TRI_ASSERT(f.value()->sameKey(&item, sizeof(uint64_t)));
+          TRI_ASSERT(f.value()->sameKey(&item, sizeof(std::uint64_t)));
         } else {
           missCount++;
           TRI_ASSERT(f.value() == nullptr);
@@ -171,9 +171,9 @@ TEST(CacheRebalancerTest, test_rebalancing_with_plaincache_LongRunning) {
 
   std::vector<ThreadGuard> threads;
   // dispatch threads
-  for (size_t i = 0; i < threadCount; i++) {
-    uint64_t lower = i * chunkSize;
-    uint64_t upper = ((i + 1) * chunkSize) - 1;
+  for (std::size_t i = 0; i < threadCount; i++) {
+    std::uint64_t lower = i * chunkSize;
+    std::uint64_t upper = ((i + 1) * chunkSize) - 1;
     threads.emplace_back(std::make_unique<std::thread>(worker, lower, upper));
   }
 
@@ -200,10 +200,10 @@ TEST(CacheRebalancerTest, test_rebalancing_with_transactionalcache_LongRunning)
   Manager manager(postFn, 128 * 1024 * 1024);
   Rebalancer rebalancer(&manager);
 
-  size_t cacheCount = 4;
-  size_t threadCount = 4;
+  std::size_t cacheCount = 4;
+  std::size_t threadCount = 4;
   std::vector<std::shared_ptr<Cache>> caches;
-  for (size_t i = 0; i < cacheCount; i++) {
+  for (std::size_t i = 0; i < cacheCount; i++) {
     caches.emplace_back(manager.createCache(CacheType::Transactional));
   }
 
@@ -221,20 +221,20 @@ TEST(CacheRebalancerTest, test_rebalancing_with_transactionalcache_LongRunning)
   
   ThreadGuard rebalancerThread(std::make_unique<std::thread>(rebalanceWorker));
 
-  uint64_t chunkSize = 4 * 1024 * 1024;
-  uint64_t initialInserts = 1 * 1024 * 1024;
-  uint64_t operationCount = 4 * 1024 * 1024;
-  std::atomic<uint64_t> hitCount(0);
-  std::atomic<uint64_t> missCount(0);
-  auto worker = [&manager, &caches, cacheCount, initialInserts, operationCount,
-                 &hitCount, &missCount](uint64_t lower, uint64_t upper) -> void {
+  std::uint64_t chunkSize = 4 * 1024 * 1024;
+  std::uint64_t initialInserts = 1 * 1024 * 1024;
+  std::uint64_t operationCount = 4 * 1024 * 1024;
+  std::atomic<std::uint64_t> hitCount(0);
+  std::atomic<std::uint64_t> missCount(0);
+  auto worker = [&manager, &caches, cacheCount, initialInserts, operationCount, &hitCount,
+                 &missCount](std::uint64_t lower, std::uint64_t upper) -> void {
     Transaction* tx = manager.beginTransaction(false);
     // fill with some initial data
-    for (uint64_t i = 0; i < initialInserts; i++) {
-      uint64_t item = lower + i;
-      size_t cacheIndex = item % cacheCount;
-      CachedValue* value =
-          CachedValue::construct(&item, sizeof(uint64_t), &item, sizeof(uint64_t));
+    for (std::uint64_t i = 0; i < initialInserts; i++) {
+      std::uint64_t item = lower + i;
+      std::size_t cacheIndex = item % cacheCount;
+      CachedValue* value = CachedValue::construct(&item, sizeof(std::uint64_t),
+                                                  &item, sizeof(std::uint64_t));
       TRI_ASSERT(value != nullptr);
       auto status = caches[cacheIndex]->insert(value);
       if (status.fail()) {
@@ -243,35 +243,35 @@ TEST(CacheRebalancerTest, test_rebalancing_with_transactionalcache_LongRunning)
     }
 
     // initialize valid range for keys that *might* be in cache
-    uint64_t validLower = lower;
-    uint64_t validUpper = lower + initialInserts - 1;
-    uint64_t blacklistUpper = validUpper;
+    std::uint64_t validLower = lower;
+    std::uint64_t validUpper = lower + initialInserts - 1;
+    std::uint64_t blacklistUpper = validUpper;
 
     // commence mixed workload
-    for (uint64_t i = 0; i < operationCount; i++) {
-      uint32_t r = RandomGenerator::interval(static_cast<uint32_t>(99UL));
+    for (std::uint64_t i = 0; i < operationCount; i++) {
+      std::uint32_t r = RandomGenerator::interval(static_cast<std::uint32_t>(99UL));
 
       if (r >= 99) {  // remove something
         if (validLower == validUpper) {
           continue;  // removed too much
         }
 
-        uint64_t item = validLower++;
-        size_t cacheIndex = item % cacheCount;
+        std::uint64_t item = validLower++;
+        std::size_t cacheIndex = item % cacheCount;
 
-        caches[cacheIndex]->remove(&item, sizeof(uint64_t));
+        caches[cacheIndex]->remove(&item, sizeof(std::uint64_t));
       } else if (r >= 90) {  // insert something
         if (validUpper == upper) {
           continue;  // already maxed out range
         }
 
-        uint64_t item = ++validUpper;
+        std::uint64_t item = ++validUpper;
         if (validUpper > blacklistUpper) {
           blacklistUpper = validUpper;
         }
-        size_t cacheIndex = item % cacheCount;
-        CachedValue* value =
-            CachedValue::construct(&item, sizeof(uint64_t), &item, sizeof(uint64_t));
+        std::size_t cacheIndex = item % cacheCount;
+        CachedValue* value = CachedValue::construct(&item, sizeof(std::uint64_t),
+                                                    &item, sizeof(std::uint64_t));
         TRI_ASSERT(value != nullptr);
         auto status = caches[cacheIndex]->insert(value);
         if (status.fail()) {
@@ -282,19 +282,20 @@ TEST(CacheRebalancerTest, test_rebalancing_with_transactionalcache_LongRunning)
           continue;  // already maxed out range
         }
 
-        uint64_t item = ++blacklistUpper;
-        size_t cacheIndex = item % cacheCount;
-        caches[cacheIndex]->blacklist(&item, sizeof(uint64_t));
+        std::uint64_t item = ++blacklistUpper;
+        std::size_t cacheIndex = item % cacheCount;
+        caches[cacheIndex]->blacklist(&item, sizeof(std::uint64_t));
       } else {  // lookup something
-        uint64_t item = RandomGenerator::interval(static_cast<int64_t>(validLower),
-                                                  static_cast<int64_t>(validUpper));
-        size_t cacheIndex = item % cacheCount;
+        std::uint64_t item =
+            RandomGenerator::interval(static_cast<int64_t>(validLower),
+                                      static_cast<int64_t>(validUpper));
+        std::size_t cacheIndex = item % cacheCount;
 
-        Finding f = caches[cacheIndex]->find(&item, sizeof(uint64_t));
+        Finding f = caches[cacheIndex]->find(&item, sizeof(std::uint64_t));
         if (f.found()) {
           hitCount++;
           TRI_ASSERT(f.value() != nullptr);
-          TRI_ASSERT(f.value()->sameKey(&item, sizeof(uint64_t)));
+          TRI_ASSERT(f.value()->sameKey(&item, sizeof(std::uint64_t)));
         } else {
           missCount++;
           TRI_ASSERT(f.value() == nullptr);
@@ -303,12 +304,12 @@ TEST(CacheRebalancerTest, test_rebalancing_with_transactionalcache_LongRunning)
     }
     manager.endTransaction(tx);
   };
-  
+
   std::vector<ThreadGuard> threads;
   // dispatch threads
-  for (size_t i = 0; i < threadCount; i++) {
-    uint64_t lower = i * chunkSize;
-    uint64_t upper = ((i + 1) * chunkSize) - 1;
+  for (std::size_t i = 0; i < threadCount; i++) {
+    std::uint64_t lower = i * chunkSize;
+    std::uint64_t upper = ((i + 1) * chunkSize) - 1;
     threads.emplace_back(std::make_unique<std::thread>(worker, lower, upper));
   }
 
diff --git a/tests/Cache/Table.cpp b/tests/Cache/Table.cpp
index 5f74bc1d7021..ca963e7987da 100644
--- a/tests/Cache/Table.cpp
+++ b/tests/Cache/Table.cpp
@@ -21,36 +21,35 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 /// @author Copyright 2017, ArangoDB GmbH, Cologne, Germany
 ////////////////////////////////////////////////////////////////////////////////
 
-#include "Basics/Common.h"
-#include "Cache/Common.h"
-#include "Cache/PlainBucket.h"
-#include "Cache/Table.h"
-
 #include "gtest/gtest.h"
 
-#include <stdint.h>
+#include <cstdint>
 #include <memory>
 
+#include "Cache/Common.h"
+#include "Cache/PlainBucket.h"
+#include "Cache/Table.h"
+
 using namespace arangodb::cache;
 
 TEST(CacheTableTest, test_static_allocation_size_method) {
-  for (uint32_t i = Table::minLogSize; i <= Table::maxLogSize; i++) {
+  for (std::uint32_t i = Table::minLogSize; i <= Table::maxLogSize; i++) {
     ASSERT_TRUE(Table::allocationSize(i) ==
                 (sizeof(Table) + (BUCKET_SIZE << i) + Table::padding));
   }
 }
 
 TEST(CacheTableTest, test_basic_constructor_behavior) {
-  for (uint32_t i = Table::minLogSize; i <= 20; i++) {
+  for (std::uint32_t i = Table::minLogSize; i <= 20; i++) {
     auto table = std::make_shared<Table>(i);
     ASSERT_NE(table.get(), nullptr);
     ASSERT_EQ(table->memoryUsage(), (sizeof(Table) + (BUCKET_SIZE << i) + Table::padding));
     ASSERT_EQ(table->logSize(), i);
-    ASSERT_EQ(table->size(), (static_cast<uint64_t>(1) << i));
+    ASSERT_EQ(table->size(), (static_cast<std::uint64_t>(1) << i));
   }
 }
 
@@ -58,26 +57,21 @@ TEST(CacheTableTest, test_basic_bucket_fetching_behavior) {
   auto table = std::make_shared<Table>(Table::minLogSize);
   ASSERT_NE(table.get(), nullptr);
   table->enable();
-  for (uint64_t i = 0; i < table->size(); i++) {
-    uint32_t hash = static_cast<uint32_t>(i << (32 - Table::minLogSize));
-    auto pair = table->fetchAndLockBucket(hash, -1);
-    auto bucket = reinterpret_cast<PlainBucket*>(pair.first);
-    auto source = pair.second;
-    ASSERT_NE(bucket, nullptr);
-    ASSERT_TRUE(bucket->isLocked());
-    ASSERT_NE(source, nullptr);
-    ASSERT_EQ(source, table.get());
+  for (std::uint64_t i = 0; i < table->size(); i++) {
+    std::uint32_t hash = static_cast<std::uint32_t>(i << (32 - Table::minLogSize));
+    Table::BucketLocker guard = table->fetchAndLockBucket(hash, -1);
+    ASSERT_TRUE(guard.isValid());
+    ASSERT_TRUE(guard.isLocked());
+    ASSERT_TRUE(guard.bucket<PlainBucket>().isLocked());
+    ASSERT_NE(guard.source(), nullptr);
+    ASSERT_EQ(guard.source(), table.get());
 
     auto rawBucket = reinterpret_cast<PlainBucket*>(table->primaryBucket(i));
-    ASSERT_EQ(bucket, rawBucket);
+    ASSERT_EQ(&guard.bucket<PlainBucket>(), rawBucket);
 
-    auto badPair = table->fetchAndLockBucket(hash, 10);
-    auto badBucket = reinterpret_cast<PlainBucket*>(badPair.first);
-    auto badSource = badPair.second;
-    ASSERT_EQ(badBucket, nullptr);
-    ASSERT_EQ(badSource, nullptr);
-
-    bucket->unlock();
+    Table::BucketLocker badGuard = table->fetchAndLockBucket(hash, 10);
+    ASSERT_FALSE(badGuard.isValid());
+    ASSERT_EQ(badGuard.source(), nullptr);
   }
 }
 
@@ -110,36 +104,34 @@ TEST_F(CacheTableMigrationTest, check_that_bucket_locking_falls_through_appropri
   auto res = small->setAuxiliary(large);
   ASSERT_EQ(res.get(), nullptr);
 
-  uint32_t indexSmall = 17;  // picked something at "random"
-  uint32_t indexLarge = indexSmall << 2;
-  uint32_t hash = indexSmall << (32 - small->logSize());
-
-  auto pair = small->fetchAndLockBucket(hash, -1);
-  auto bucket = reinterpret_cast<PlainBucket*>(pair.first);
-  auto source = pair.second;
-  ASSERT_EQ(bucket, reinterpret_cast<PlainBucket*>(small->primaryBucket(indexSmall)));
-  bucket->_state.toggleFlag(BucketState::Flag::migrated);
-  bucket->unlock();
-  ASSERT_EQ(source, small.get());
-
-  pair = small->fetchAndLockBucket(hash, -1);
-  bucket = reinterpret_cast<PlainBucket*>(pair.first);
-  source = pair.second;
-  ASSERT_EQ(bucket, reinterpret_cast<PlainBucket*>(large->primaryBucket(indexLarge)));
-  ASSERT_EQ(source, large.get());
-  pair = small->fetchAndLockBucket(hash, 10);
-  ASSERT_EQ(pair.first, nullptr);
-  ASSERT_EQ(pair.second, nullptr);
-  bucket->unlock();
+  std::uint32_t indexSmall = 17;  // picked something at "random"
+  std::uint32_t indexLarge = indexSmall << 2;
+  std::uint32_t hash = indexSmall << (32 - small->logSize());
+
+  {
+    Table::BucketLocker guard = small->fetchAndLockBucket(hash, -1);
+    ASSERT_EQ(&guard.bucket<PlainBucket>(),
+              reinterpret_cast<PlainBucket*>(small->primaryBucket(indexSmall)));
+    guard.bucket<PlainBucket>()._state.toggleFlag(BucketState::Flag::migrated);
+    ASSERT_EQ(guard.source(), small.get());
+  }
+
+  Table::BucketLocker guard = small->fetchAndLockBucket(hash, -1);
+  ASSERT_EQ(&guard.bucket<PlainBucket>(),
+            reinterpret_cast<PlainBucket*>(large->primaryBucket(indexLarge)));
+  ASSERT_EQ(guard.source(), large.get());
+  Table::BucketLocker busyGuard = small->fetchAndLockBucket(hash, 10);
+  ASSERT_FALSE(busyGuard.isValid());
+  ASSERT_EQ(busyGuard.source(), nullptr);
 }
 
 TEST_F(CacheTableMigrationTest, check_subtable_fetching_for_moving_to_a_smaller_table) {
   auto res = large->setAuxiliary(small);
   ASSERT_EQ(res.get(), nullptr);
 
-  uint32_t indexLarge = 822;  // picked something at "random"
-  uint32_t indexSmall = indexLarge >> 2;
-  uint32_t hash = indexLarge << (32 - large->logSize());
+  std::uint32_t indexLarge = 822;  // picked something at "random"
+  std::uint32_t indexSmall = indexLarge >> 2;
+  std::uint32_t hash = indexLarge << (32 - large->logSize());
 
   auto subtable = large->auxiliaryBuckets(indexLarge);
   ASSERT_NE(subtable.get(), nullptr);
@@ -151,14 +143,14 @@ TEST_F(CacheTableMigrationTest, check_subtable_fetching_for_moving_to_a_larger_t
   auto res = small->setAuxiliary(large);
   ASSERT_EQ(res.get(), nullptr);
 
-  uint32_t indexSmall = 217;  // picked something at "random"
-  uint32_t indexLargeBase = indexSmall << 2;
+  std::uint32_t indexSmall = 217;  // picked something at "random"
+  std::uint32_t indexLargeBase = indexSmall << 2;
 
   auto subtable = small->auxiliaryBuckets(indexSmall);
   ASSERT_NE(subtable.get(), nullptr);
-  for (uint32_t i = 0; i < 4; i++) {
-    uint32_t indexLarge = indexLargeBase + i;
-    uint32_t hash = indexLarge << (32 - large->logSize());
+  for (std::uint32_t i = 0; i < 4; i++) {
+    std::uint32_t indexLarge = indexLargeBase + i;
+    std::uint32_t hash = indexLarge << (32 - large->logSize());
     ASSERT_EQ(subtable->fetchBucket(hash), large->primaryBucket(indexLarge));
   }
 }
@@ -167,30 +159,27 @@ TEST_F(CacheTableMigrationTest, check_subtable_apply_all_works) {
   auto res = small->setAuxiliary(large);
   ASSERT_EQ(res.get(), nullptr);
 
-  uint32_t indexSmall = 172;  // picked something at "random"
-  uint32_t indexLargeBase = indexSmall << 2;
+  std::uint32_t indexSmall = 172;  // picked something at "random"
+  std::uint32_t indexLargeBase = indexSmall << 2;
 
   auto subtable = small->auxiliaryBuckets(indexSmall);
   ASSERT_NE(subtable.get(), nullptr);
-  subtable->applyToAllBuckets([](void* ptr) -> bool {
-    PlainBucket* bucket = reinterpret_cast<PlainBucket*>(ptr);
-    return bucket->lock(-1);
-  });
-  for (uint32_t i = 0; i < 4; i++) {
-    uint32_t indexLarge = indexLargeBase + i;
-    uint32_t hash = indexLarge << (32 - large->logSize());
+  subtable->applyToAllBuckets<PlainBucket>(
+      [](PlainBucket& bucket) -> bool { return bucket.lock(-1); });
+  for (std::uint32_t i = 0; i < 4; i++) {
+    std::uint32_t indexLarge = indexLargeBase + i;
+    std::uint32_t hash = indexLarge << (32 - large->logSize());
     auto bucket = reinterpret_cast<PlainBucket*>(subtable->fetchBucket(hash));
     ASSERT_TRUE(bucket->isLocked());
   }
-  subtable->applyToAllBuckets([](void* ptr) -> bool {
-    PlainBucket* bucket = reinterpret_cast<PlainBucket*>(ptr);
-    bucket->unlock();
+  subtable->applyToAllBuckets<PlainBucket>([](PlainBucket& bucket) -> bool {
+    bucket.unlock();
     return true;
   });
 }
 
 TEST_F(CacheTableMigrationTest, test_fill_ratio_methods) {
-  for (uint64_t i = 0; i < large->size(); i++) {
+  for (std::uint64_t i = 0; i < large->size(); i++) {
     bool res = large->slotFilled();
     if (static_cast<double>(i + 1) < 0.04 * static_cast<double>(large->size())) {
       ASSERT_EQ(large->idealSize(), large->logSize() - 1);
@@ -203,7 +192,7 @@ TEST_F(CacheTableMigrationTest, test_fill_ratio_methods) {
       ASSERT_FALSE(res);
     }
   }
-  for (uint64_t i = large->size(); i > 0; i--) {
+  for (std::uint64_t i = large->size(); i > 0; i--) {
     bool res = large->slotEmptied();
     if (static_cast<double>(i - 1) < 0.04 * static_cast<double>(large->size())) {
       ASSERT_EQ(large->idealSize(), large->logSize() - 1);
diff --git a/tests/Cache/TransactionManager.cpp b/tests/Cache/TransactionManager.cpp
index d0b05c0634d9..ca29961819c1 100644
--- a/tests/Cache/TransactionManager.cpp
+++ b/tests/Cache/TransactionManager.cpp
@@ -21,17 +21,16 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 /// @author Copyright 2017, ArangoDB GmbH, Cologne, Germany
 ////////////////////////////////////////////////////////////////////////////////
 
-#include "Basics/Common.h"
-#include "Cache/Transaction.h"
-#include "Cache/TransactionManager.h"
-
 #include "gtest/gtest.h"
 
-#include <stdint.h>
+#include <cstdint>
+
+#include "Cache/Transaction.h"
+#include "Cache/TransactionManager.h"
 
 using namespace arangodb::cache;
 
diff --git a/tests/Cache/TransactionalBucket.cpp b/tests/Cache/TransactionalBucket.cpp
index e5fa1e08318d..5c05aa138539 100644
--- a/tests/Cache/TransactionalBucket.cpp
+++ b/tests/Cache/TransactionalBucket.cpp
@@ -21,19 +21,18 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 /// @author Copyright 2017, ArangoDB GmbH, Cologne, Germany
 ////////////////////////////////////////////////////////////////////////////////
 
-#include "Cache/TransactionalBucket.h"
-#include "Basics/Common.h"
-#include "Basics/debugging.h"
-
 #include "gtest/gtest.h"
 
-#include <stdint.h>
+#include <cstdint>
 #include <string>
 
+#include "Basics/debugging.h"
+#include "Cache/TransactionalBucket.h"
+
 using namespace arangodb::cache;
 
 TEST(CacheTransactionalBucketTest, test_locking_behavior) {
@@ -68,14 +67,14 @@ TEST(CacheTransactionalBucketTest, verify_that_insertion_works_as_expected) {
   auto bucket = std::make_unique<TransactionalBucket>();
   bool success;
 
-  uint32_t hashes[9] = {1, 2, 3, 4, 5,
-                        6, 7, 8, 9};  // don't have to be real, but should be unique and non-zero
-  uint64_t keys[9] = {0, 1, 2, 3, 4, 5, 6, 7, 8};
-  uint64_t values[9] = {0, 1, 2, 3, 4, 5, 6, 7, 8};
+  std::uint32_t hashes[9] = {1, 2, 3, 4, 5,
+                             6, 7, 8, 9};  // don't have to be real, but should be unique and non-zero
+  std::uint64_t keys[9] = {0, 1, 2, 3, 4, 5, 6, 7, 8};
+  std::uint64_t values[9] = {0, 1, 2, 3, 4, 5, 6, 7, 8};
   CachedValue* ptrs[9];
-  for (size_t i = 0; i < 9; i++) {
-    ptrs[i] = CachedValue::construct(&(keys[i]), sizeof(uint64_t), &(values[i]),
-                                     sizeof(uint64_t));
+  for (std::size_t i = 0; i < 9; i++) {
+    ptrs[i] = CachedValue::construct(&(keys[i]), sizeof(std::uint64_t),
+                                     &(values[i]), sizeof(std::uint64_t));
     TRI_ASSERT(ptrs[i] != nullptr);
   }
 
@@ -84,7 +83,7 @@ TEST(CacheTransactionalBucketTest, verify_that_insertion_works_as_expected) {
 
   // insert three to fill
   ASSERT_FALSE(bucket->isFull());
-  for (size_t i = 0; i < 8; i++) {
+  for (std::size_t i = 0; i < 8; i++) {
     bucket->insert(hashes[i], ptrs[i]);
     if (i < 7) {
       ASSERT_FALSE(bucket->isFull());
@@ -92,7 +91,7 @@ TEST(CacheTransactionalBucketTest, verify_that_insertion_works_as_expected) {
       ASSERT_TRUE(bucket->isFull());
     }
   }
-  for (size_t i = 0; i < 7; i++) {
+  for (std::size_t i = 0; i < 7; i++) {
     CachedValue* res = bucket->find(hashes[i], ptrs[i]->key(), ptrs[i]->keySize());
     ASSERT_EQ(res, ptrs[i]);
   }
@@ -105,7 +104,7 @@ TEST(CacheTransactionalBucketTest, verify_that_insertion_works_as_expected) {
   bucket->unlock();
 
   // cleanup
-  for (size_t i = 0; i < 9; i++) {
+  for (std::size_t i = 0; i < 9; i++) {
     delete ptrs[i];
   }
 }
@@ -114,23 +113,23 @@ TEST(CacheTransactionalBucketTest, verify_that_removal_works_as_expected) {
   auto bucket = std::make_unique<TransactionalBucket>();
   bool success;
 
-  uint32_t hashes[3] = {1, 2, 3};  // don't have to be real, but should be unique and non-zero
-  uint64_t keys[3] = {0, 1, 2};
-  uint64_t values[3] = {0, 1, 2};
+  std::uint32_t hashes[3] = {1, 2, 3};  // don't have to be real, but should be unique and non-zero
+  std::uint64_t keys[3] = {0, 1, 2};
+  std::uint64_t values[3] = {0, 1, 2};
   CachedValue* ptrs[3];
-  for (size_t i = 0; i < 3; i++) {
-    ptrs[i] = CachedValue::construct(&(keys[i]), sizeof(uint64_t), &(values[i]),
-                                     sizeof(uint64_t));
+  for (std::size_t i = 0; i < 3; i++) {
+    ptrs[i] = CachedValue::construct(&(keys[i]), sizeof(std::uint64_t),
+                                     &(values[i]), sizeof(std::uint64_t));
     TRI_ASSERT(ptrs[i] != nullptr);
   }
 
   success = bucket->lock(-1LL);
   ASSERT_TRUE(success);
 
-  for (size_t i = 0; i < 3; i++) {
+  for (std::size_t i = 0; i < 3; i++) {
     bucket->insert(hashes[i], ptrs[i]);
   }
-  for (size_t i = 0; i < 3; i++) {
+  for (std::size_t i = 0; i < 3; i++) {
     CachedValue* res = bucket->find(hashes[i], ptrs[i]->key(), ptrs[i]->keySize());
     ASSERT_EQ(res, ptrs[i]);
   }
@@ -152,7 +151,7 @@ TEST(CacheTransactionalBucketTest, verify_that_removal_works_as_expected) {
   bucket->unlock();
 
   // cleanup
-  for (size_t i = 0; i < 3; i++) {
+  for (std::size_t i = 0; i < 3; i++) {
     delete ptrs[i];
   }
 }
@@ -161,14 +160,14 @@ TEST(CacheTransactionalBucketTest, verify_that_eviction_works_as_expected) {
   auto bucket = std::make_unique<TransactionalBucket>();
   bool success;
 
-  uint32_t hashes[9] = {1, 2, 3, 4, 5,
-                        6, 7, 8, 9};  // don't have to be real, but should be unique and non-zero
-  uint64_t keys[9] = {0, 1, 2, 3, 4, 5, 6, 7, 8};
-  uint64_t values[9] = {0, 1, 2, 3, 4, 5, 6, 7, 8};
+  std::uint32_t hashes[9] = {1, 2, 3, 4, 5,
+                             6, 7, 8, 9};  // don't have to be real, but should be unique and non-zero
+  std::uint64_t keys[9] = {0, 1, 2, 3, 4, 5, 6, 7, 8};
+  std::uint64_t values[9] = {0, 1, 2, 3, 4, 5, 6, 7, 8};
   CachedValue* ptrs[9];
-  for (size_t i = 0; i < 9; i++) {
-    ptrs[i] = CachedValue::construct(&(keys[i]), sizeof(uint64_t), &(values[i]),
-                                     sizeof(uint64_t));
+  for (std::size_t i = 0; i < 9; i++) {
+    ptrs[i] = CachedValue::construct(&(keys[i]), sizeof(std::uint64_t),
+                                     &(values[i]), sizeof(std::uint64_t));
     TRI_ASSERT(ptrs[i] != nullptr);
   }
 
@@ -177,7 +176,7 @@ TEST(CacheTransactionalBucketTest, verify_that_eviction_works_as_expected) {
 
   // insert three to fill
   ASSERT_FALSE(bucket->isFull());
-  for (size_t i = 0; i < 8; i++) {
+  for (std::size_t i = 0; i < 8; i++) {
     bucket->insert(hashes[i], ptrs[i]);
     if (i < 7) {
       ASSERT_FALSE(bucket->isFull());
@@ -185,7 +184,7 @@ TEST(CacheTransactionalBucketTest, verify_that_eviction_works_as_expected) {
       ASSERT_TRUE(bucket->isFull());
     }
   }
-  for (size_t i = 0; i < 8; i++) {
+  for (std::size_t i = 0; i < 8; i++) {
     CachedValue* res = bucket->find(hashes[i], ptrs[i]->key(), ptrs[i]->keySize());
     ASSERT_EQ(res, ptrs[i]);
   }
@@ -214,7 +213,7 @@ TEST(CacheTransactionalBucketTest, verify_that_eviction_works_as_expected) {
   bucket->unlock();
 
   // cleanup
-  for (size_t i = 0; i < 9; i++) {
+  for (std::size_t i = 0; i < 9; i++) {
     delete ptrs[i];
   }
 }
@@ -224,14 +223,14 @@ TEST(CacheTransactionalBucketTest, verify_that_blacklisting_works_as_expected) {
   bool success;
   CachedValue* res;
 
-  uint32_t hashes[8] = {1, 1, 2, 3, 4,
-                        5, 6, 7};  // don't have to be real, want some overlap
-  uint64_t keys[8] = {0, 1, 2, 3, 4, 5, 6, 7};
-  uint64_t values[8] = {0, 1, 2, 3, 4, 5, 6, 7};
+  std::uint32_t hashes[8] = {1, 1, 2, 3, 4,
+                             5, 6, 7};  // don't have to be real, want some overlap
+  std::uint64_t keys[8] = {0, 1, 2, 3, 4, 5, 6, 7};
+  std::uint64_t values[8] = {0, 1, 2, 3, 4, 5, 6, 7};
   CachedValue* ptrs[8];
-  for (size_t i = 0; i < 8; i++) {
-    ptrs[i] = CachedValue::construct(&(keys[i]), sizeof(uint64_t), &(values[i]),
-                                     sizeof(uint64_t));
+  for (std::size_t i = 0; i < 8; i++) {
+    ptrs[i] = CachedValue::construct(&(keys[i]), sizeof(std::uint64_t),
+                                     &(values[i]), sizeof(std::uint64_t));
     TRI_ASSERT(ptrs[i] != nullptr);
   }
 
@@ -241,7 +240,7 @@ TEST(CacheTransactionalBucketTest, verify_that_blacklisting_works_as_expected) {
 
   // insert eight to fill
   ASSERT_FALSE(bucket->isFull());
-  for (size_t i = 0; i < 8; i++) {
+  for (std::size_t i = 0; i < 8; i++) {
     bucket->insert(hashes[i], ptrs[i]);
     if (i < 7) {
       ASSERT_FALSE(bucket->isFull());
@@ -249,16 +248,16 @@ TEST(CacheTransactionalBucketTest, verify_that_blacklisting_works_as_expected) {
       ASSERT_TRUE(bucket->isFull());
     }
   }
-  for (size_t i = 0; i < 8; i++) {
+  for (std::size_t i = 0; i < 8; i++) {
     res = bucket->find(hashes[i], ptrs[i]->key(), ptrs[i]->keySize());
     ASSERT_EQ(res, ptrs[i]);
   }
 
   // blacklist 1-5 to fill blacklist
-  for (size_t i = 1; i < 6; i++) {
+  for (std::size_t i = 1; i < 6; i++) {
     bucket->blacklist(hashes[i], ptrs[i]->key(), ptrs[i]->keySize());
   }
-  for (size_t i = 1; i < 6; i++) {
+  for (std::size_t i = 1; i < 6; i++) {
     ASSERT_TRUE(bucket->isBlacklisted(hashes[i]));
     res = bucket->find(hashes[i], ptrs[i]->key(), ptrs[i]->keySize());
     ASSERT_EQ(nullptr, res);
@@ -288,13 +287,13 @@ TEST(CacheTransactionalBucketTest, verify_that_blacklisting_works_as_expected) {
   bucket->lock(-1LL);
   bucket->updateBlacklistTerm(2ULL);
   ASSERT_FALSE(bucket->isFullyBlacklisted());
-  for (size_t i = 0; i < 7; i++) {
+  for (std::size_t i = 0; i < 7; i++) {
     ASSERT_FALSE(bucket->isBlacklisted(hashes[i]));
   }
   bucket->unlock();
 
   // cleanup
-  for (size_t i = 0; i < 8; i++) {
+  for (std::size_t i = 0; i < 8; i++) {
     delete ptrs[i];
   }
 }
diff --git a/tests/Cache/TransactionalCache.cpp b/tests/Cache/TransactionalCache.cpp
index ed9222a8931f..794be833fbc1 100644
--- a/tests/Cache/TransactionalCache.cpp
+++ b/tests/Cache/TransactionalCache.cpp
@@ -21,11 +21,17 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 /// @author Copyright 2017, ArangoDB GmbH, Cologne, Germany
 ////////////////////////////////////////////////////////////////////////////////
 
-#include "Basics/Common.h"
+#include "gtest/gtest.h"
+
+#include <cstdint>
+#include <string>
+#include <thread>
+#include <vector>
+
 #include "Cache/Common.h"
 #include "Cache/Manager.h"
 #include "Cache/Transaction.h"
@@ -33,12 +39,6 @@
 #include "Random/RandomGenerator.h"
 
 #include "MockScheduler.h"
-#include "gtest/gtest.h"
-
-#include <stdint.h>
-#include <string>
-#include <thread>
-#include <vector>
 
 using namespace arangodb;
 using namespace arangodb::cache;
@@ -61,46 +61,46 @@ TEST(CacheTransactionalCacheTest, test_basic_cache_construction) {
 }
 
 TEST(CacheTransactionalCacheTest, verify_that_insertion_works_as_expected) {
-  uint64_t cacheLimit = 128 * 1024;
+  std::uint64_t cacheLimit = 128 * 1024;
   auto postFn = [](std::function<void()>) -> bool { return false; };
   Manager manager(postFn, 4 * cacheLimit);
   auto cache = manager.createCache(CacheType::Transactional, false, cacheLimit);
 
-  for (uint64_t i = 0; i < 1024; i++) {
+  for (std::uint64_t i = 0; i < 1024; i++) {
     CachedValue* value =
-        CachedValue::construct(&i, sizeof(uint64_t), &i, sizeof(uint64_t));
+        CachedValue::construct(&i, sizeof(std::uint64_t), &i, sizeof(std::uint64_t));
     TRI_ASSERT(value != nullptr);
     auto status = cache->insert(value);
     if (status.ok()) {
-      auto f = cache->find(&i, sizeof(uint64_t));
+      auto f = cache->find(&i, sizeof(std::uint64_t));
       ASSERT_TRUE(f.found());
     } else {
       delete value;
     }
   }
 
-  for (uint64_t i = 0; i < 1024; i++) {
-    uint64_t j = 2 * i;
+  for (std::uint64_t i = 0; i < 1024; i++) {
+    std::uint64_t j = 2 * i;
     CachedValue* value =
-        CachedValue::construct(&i, sizeof(uint64_t), &j, sizeof(uint64_t));
+        CachedValue::construct(&i, sizeof(std::uint64_t), &j, sizeof(std::uint64_t));
     TRI_ASSERT(value != nullptr);
     auto status = cache->insert(value);
     if (status.ok()) {
-      auto f = cache->find(&i, sizeof(uint64_t));
+      auto f = cache->find(&i, sizeof(std::uint64_t));
       ASSERT_TRUE(f.found());
-      ASSERT_EQ(0, memcmp(f.value()->value(), &j, sizeof(uint64_t)));
+      ASSERT_EQ(0, memcmp(f.value()->value(), &j, sizeof(std::uint64_t)));
     } else {
       delete value;
     }
   }
 
-  for (uint64_t i = 1024; i < 128 * 1024; i++) {
+  for (std::uint64_t i = 1024; i < 128 * 1024; i++) {
     CachedValue* value =
-        CachedValue::construct(&i, sizeof(uint64_t), &i, sizeof(uint64_t));
+        CachedValue::construct(&i, sizeof(std::uint64_t), &i, sizeof(std::uint64_t));
     TRI_ASSERT(value != nullptr);
     auto status = cache->insert(value);
     if (status.ok()) {
-      auto f = cache->find(&i, sizeof(uint64_t));
+      auto f = cache->find(&i, sizeof(std::uint64_t));
       ASSERT_TRUE(f.found());
     } else {
       delete value;
@@ -112,57 +112,57 @@ TEST(CacheTransactionalCacheTest, verify_that_insertion_works_as_expected) {
 }
 
 TEST(CacheTransactionalCacheTest, verify_removal_works_as_expected) {
-  uint64_t cacheLimit = 128 * 1024;
+  std::uint64_t cacheLimit = 128 * 1024;
   auto postFn = [](std::function<void()>) -> bool { return false; };
   Manager manager(postFn, 4 * cacheLimit);
   auto cache = manager.createCache(CacheType::Transactional, false, cacheLimit);
 
-  for (uint64_t i = 0; i < 1024; i++) {
+  for (std::uint64_t i = 0; i < 1024; i++) {
     CachedValue* value =
-        CachedValue::construct(&i, sizeof(uint64_t), &i, sizeof(uint64_t));
+        CachedValue::construct(&i, sizeof(std::uint64_t), &i, sizeof(std::uint64_t));
     TRI_ASSERT(value != nullptr);
     auto status = cache->insert(value);
     if (status.ok()) {
-      auto f = cache->find(&i, sizeof(uint64_t));
+      auto f = cache->find(&i, sizeof(std::uint64_t));
       ASSERT_TRUE(f.found());
       ASSERT_NE(f.value(), nullptr);
-      ASSERT_TRUE(f.value()->sameKey(&i, sizeof(uint64_t)));
+      ASSERT_TRUE(f.value()->sameKey(&i, sizeof(std::uint64_t)));
     } else {
       delete value;
     }
   }
-  uint64_t inserted = 0;
-  for (uint64_t j = 0; j < 1024; j++) {
-    auto f = cache->find(&j, sizeof(uint64_t));
+  std::uint64_t inserted = 0;
+  for (std::uint64_t j = 0; j < 1024; j++) {
+    auto f = cache->find(&j, sizeof(std::uint64_t));
     if (f.found()) {
       inserted++;
       ASSERT_NE(f.value(), nullptr);
-      ASSERT_TRUE(f.value()->sameKey(&j, sizeof(uint64_t)));
+      ASSERT_TRUE(f.value()->sameKey(&j, sizeof(std::uint64_t)));
     }
   }
 
   // test removal of bogus keys
-  for (uint64_t i = 1024; i < 1088; i++) {
-    auto status = cache->remove(&i, sizeof(uint64_t));
+  for (std::uint64_t i = 1024; i < 1088; i++) {
+    auto status = cache->remove(&i, sizeof(std::uint64_t));
     ASSERT_TRUE(status.ok());
     // ensure existing keys not removed
-    uint64_t found = 0;
-    for (uint64_t j = 0; j < 1024; j++) {
-      auto f = cache->find(&j, sizeof(uint64_t));
+    std::uint64_t found = 0;
+    for (std::uint64_t j = 0; j < 1024; j++) {
+      auto f = cache->find(&j, sizeof(std::uint64_t));
       if (f.found()) {
         found++;
         ASSERT_NE(f.value(), nullptr);
-        ASSERT_TRUE(f.value()->sameKey(&j, sizeof(uint64_t)));
+        ASSERT_TRUE(f.value()->sameKey(&j, sizeof(std::uint64_t)));
       }
     }
     ASSERT_EQ(inserted, found);
   }
 
   // remove actual keys
-  for (uint64_t i = 0; i < 1024; i++) {
-    auto status = cache->remove(&i, sizeof(uint64_t));
+  for (std::uint64_t i = 0; i < 1024; i++) {
+    auto status = cache->remove(&i, sizeof(std::uint64_t));
     ASSERT_TRUE(status.ok());
-    auto f = cache->find(&i, sizeof(uint64_t));
+    auto f = cache->find(&i, sizeof(std::uint64_t));
     ASSERT_FALSE(f.found());
   }
 
@@ -170,58 +170,58 @@ TEST(CacheTransactionalCacheTest, verify_removal_works_as_expected) {
 }
 
 TEST(CacheTransactionalCacheTest, verify_blacklisting_works_as_expected) {
-  uint64_t cacheLimit = 128 * 1024;
+  std::uint64_t cacheLimit = 128 * 1024;
   auto postFn = [](std::function<void()>) -> bool { return false; };
   Manager manager(postFn, 4 * cacheLimit);
   auto cache = manager.createCache(CacheType::Transactional, false, cacheLimit);
 
   Transaction* tx = manager.beginTransaction(false);
 
-  for (uint64_t i = 0; i < 1024; i++) {
+  for (std::uint64_t i = 0; i < 1024; i++) {
     CachedValue* value =
-        CachedValue::construct(&i, sizeof(uint64_t), &i, sizeof(uint64_t));
+        CachedValue::construct(&i, sizeof(std::uint64_t), &i, sizeof(std::uint64_t));
     TRI_ASSERT(value != nullptr);
     auto status = cache->insert(value);
     if (status.ok()) {
-      auto f = cache->find(&i, sizeof(uint64_t));
+      auto f = cache->find(&i, sizeof(std::uint64_t));
       ASSERT_TRUE(f.found());
       ASSERT_NE(f.value(), nullptr);
-      ASSERT_TRUE(f.value()->sameKey(&i, sizeof(uint64_t)));
+      ASSERT_TRUE(f.value()->sameKey(&i, sizeof(std::uint64_t)));
     } else {
       delete value;
     }
   }
 
-  for (uint64_t i = 512; i < 1024; i++) {
-    auto status = cache->blacklist(&i, sizeof(uint64_t));
+  for (std::uint64_t i = 512; i < 1024; i++) {
+    auto status = cache->blacklist(&i, sizeof(std::uint64_t));
     ASSERT_TRUE(status.ok());
-    auto f = cache->find(&i, sizeof(uint64_t));
+    auto f = cache->find(&i, sizeof(std::uint64_t));
     ASSERT_FALSE(f.found());
   }
 
-  for (uint64_t i = 512; i < 1024; i++) {
+  for (std::uint64_t i = 512; i < 1024; i++) {
     CachedValue* value =
-        CachedValue::construct(&i, sizeof(uint64_t), &i, sizeof(uint64_t));
+        CachedValue::construct(&i, sizeof(std::uint64_t), &i, sizeof(std::uint64_t));
     TRI_ASSERT(value != nullptr);
     auto status = cache->insert(value);
     ASSERT_TRUE(status.fail());
     delete value;
-    auto f = cache->find(&i, sizeof(uint64_t));
+    auto f = cache->find(&i, sizeof(std::uint64_t));
     ASSERT_FALSE(f.found());
   }
 
   manager.endTransaction(tx);
   tx = manager.beginTransaction(false);
 
-  uint64_t reinserted = 0;
-  for (uint64_t i = 512; i < 1024; i++) {
+  std::uint64_t reinserted = 0;
+  for (std::uint64_t i = 512; i < 1024; i++) {
     CachedValue* value =
-        CachedValue::construct(&i, sizeof(uint64_t), &i, sizeof(uint64_t));
+        CachedValue::construct(&i, sizeof(std::uint64_t), &i, sizeof(std::uint64_t));
     TRI_ASSERT(value != nullptr);
     auto status = cache->insert(value);
     if (status.ok()) {
       reinserted++;
-      auto f = cache->find(&i, sizeof(uint64_t));
+      auto f = cache->find(&i, sizeof(std::uint64_t));
       ASSERT_TRUE(f.found());
     } else {
       delete value;
@@ -241,11 +241,11 @@ TEST(CacheTransactionalCacheTest, verify_cache_can_grow_correctly_when_it_runs_o
   };
   Manager manager(postFn, 1024 * 1024 * 1024);
   auto cache = manager.createCache(CacheType::Transactional);
-  uint64_t minimumUsage = cache->usageLimit() * 2;
+  std::uint64_t minimumUsage = cache->usageLimit() * 2;
 
-  for (uint64_t i = 0; i < 4 * 1024 * 1024; i++) {
+  for (std::uint64_t i = 0; i < 4 * 1024 * 1024; i++) {
     CachedValue* value =
-        CachedValue::construct(&i, sizeof(uint64_t), &i, sizeof(uint64_t));
+        CachedValue::construct(&i, sizeof(std::uint64_t), &i, sizeof(std::uint64_t));
     TRI_ASSERT(value != nullptr);
     auto status = cache->insert(value);
     if (status.fail()) {
@@ -267,22 +267,22 @@ TEST(CacheTransactionalCacheTest, test_behavior_under_mixed_load_LongRunning) {
     return true;
   };
   Manager manager(postFn, 1024 * 1024 * 1024);
-  size_t threadCount = 4;
+  std::size_t threadCount = 4;
   std::shared_ptr<Cache> cache = manager.createCache(CacheType::Transactional);
 
-  uint64_t chunkSize = 16 * 1024 * 1024;
-  uint64_t initialInserts = 4 * 1024 * 1024;
-  uint64_t operationCount = 16 * 1024 * 1024;
-  std::atomic<uint64_t> hitCount(0);
-  std::atomic<uint64_t> missCount(0);
+  std::uint64_t chunkSize = 16 * 1024 * 1024;
+  std::uint64_t initialInserts = 4 * 1024 * 1024;
+  std::uint64_t operationCount = 16 * 1024 * 1024;
+  std::atomic<std::uint64_t> hitCount(0);
+  std::atomic<std::uint64_t> missCount(0);
   auto worker = [&manager, &cache, initialInserts, operationCount, &hitCount,
-                 &missCount](uint64_t lower, uint64_t upper) -> void {
+                 &missCount](std::uint64_t lower, std::uint64_t upper) -> void {
     Transaction* tx = manager.beginTransaction(false);
     // fill with some initial data
-    for (uint64_t i = 0; i < initialInserts; i++) {
-      uint64_t item = lower + i;
-      CachedValue* value =
-          CachedValue::construct(&item, sizeof(uint64_t), &item, sizeof(uint64_t));
+    for (std::uint64_t i = 0; i < initialInserts; i++) {
+      std::uint64_t item = lower + i;
+      CachedValue* value = CachedValue::construct(&item, sizeof(std::uint64_t),
+                                                  &item, sizeof(std::uint64_t));
       TRI_ASSERT(value != nullptr);
       auto status = cache->insert(value);
       if (status.fail()) {
@@ -291,33 +291,33 @@ TEST(CacheTransactionalCacheTest, test_behavior_under_mixed_load_LongRunning) {
     }
 
     // initialize valid range for keys that *might* be in cache
-    uint64_t validLower = lower;
-    uint64_t validUpper = lower + initialInserts - 1;
-    uint64_t blacklistUpper = validUpper;
+    std::uint64_t validLower = lower;
+    std::uint64_t validUpper = lower + initialInserts - 1;
+    std::uint64_t blacklistUpper = validUpper;
 
     // commence mixed workload
-    for (uint64_t i = 0; i < operationCount; i++) {
-      uint32_t r = RandomGenerator::interval(static_cast<uint32_t>(99UL));
+    for (std::uint64_t i = 0; i < operationCount; i++) {
+      std::uint32_t r = RandomGenerator::interval(static_cast<std::uint32_t>(99UL));
 
       if (r >= 99) {  // remove something
         if (validLower == validUpper) {
           continue;  // removed too much
         }
 
-        uint64_t item = validLower++;
+        std::uint64_t item = validLower++;
 
-        cache->remove(&item, sizeof(uint64_t));
+        cache->remove(&item, sizeof(std::uint64_t));
       } else if (r >= 90) {  // insert something
         if (validUpper == upper) {
           continue;  // already maxed out range
         }
 
-        uint64_t item = ++validUpper;
+        std::uint64_t item = ++validUpper;
         if (validUpper > blacklistUpper) {
           blacklistUpper = validUpper;
         }
-        CachedValue* value =
-            CachedValue::construct(&item, sizeof(uint64_t), &item, sizeof(uint64_t));
+        CachedValue* value = CachedValue::construct(&item, sizeof(std::uint64_t),
+                                                    &item, sizeof(std::uint64_t));
         TRI_ASSERT(value != nullptr);
         auto status = cache->insert(value);
         if (status.fail()) {
@@ -328,17 +328,18 @@ TEST(CacheTransactionalCacheTest, test_behavior_under_mixed_load_LongRunning) {
           continue;  // already maxed out range
         }
 
-        uint64_t item = ++blacklistUpper;
-        cache->blacklist(&item, sizeof(uint64_t));
+        std::uint64_t item = ++blacklistUpper;
+        cache->blacklist(&item, sizeof(std::uint64_t));
       } else {  // lookup something
-        uint64_t item = RandomGenerator::interval(static_cast<int64_t>(validLower),
-                                                  static_cast<int64_t>(validUpper));
+        std::uint64_t item =
+            RandomGenerator::interval(static_cast<int64_t>(validLower),
+                                      static_cast<int64_t>(validUpper));
 
-        Finding f = cache->find(&item, sizeof(uint64_t));
+        Finding f = cache->find(&item, sizeof(std::uint64_t));
         if (f.found()) {
           hitCount++;
           TRI_ASSERT(f.value() != nullptr);
-          TRI_ASSERT(f.value()->sameKey(&item, sizeof(uint64_t)));
+          TRI_ASSERT(f.value()->sameKey(&item, sizeof(std::uint64_t)));
         } else {
           missCount++;
           TRI_ASSERT(f.value() == nullptr);
@@ -350,9 +351,9 @@ TEST(CacheTransactionalCacheTest, test_behavior_under_mixed_load_LongRunning) {
 
   std::vector<std::thread*> threads;
   // dispatch threads
-  for (size_t i = 0; i < threadCount; i++) {
-    uint64_t lower = i * chunkSize;
-    uint64_t upper = ((i + 1) * chunkSize) - 1;
+  for (std::size_t i = 0; i < threadCount; i++) {
+    std::uint64_t lower = i * chunkSize;
+    std::uint64_t upper = ((i + 1) * chunkSize) - 1;
     threads.push_back(new std::thread(worker, lower, upper));
   }
 
diff --git a/tests/Cache/TransactionalStore.cpp b/tests/Cache/TransactionalStore.cpp
index 2c0a04b4404a..a3ab15d895e0 100644
--- a/tests/Cache/TransactionalStore.cpp
+++ b/tests/Cache/TransactionalStore.cpp
@@ -21,39 +21,39 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 /// @author Copyright 2017, ArangoDB GmbH, Cologne, Germany
 ////////////////////////////////////////////////////////////////////////////////
 
-#include "TransactionalStore.h"
-#include "Basics/Common.h"
-#include "Basics/StringBuffer.h"
-#include "Basics/files.h"
-#include "Cache/Common.h"
-#include "Cache/Manager.h"
-#include "Cache/TransactionalCache.h"
+#include <chrono>
 
 #include <rocksdb/db.h>
 #include <rocksdb/options.h>
 #include <rocksdb/utilities/transaction.h>
 #include <rocksdb/utilities/transaction_db.h>
 
-#include <chrono>
+#include "Basics/StringBuffer.h"
+#include "Basics/files.h"
+#include "Cache/Common.h"
+#include "Cache/Manager.h"
+#include "Cache/TransactionalCache.h"
+
+#include "TransactionalStore.h"
 
 using namespace arangodb::cache;
 
-std::atomic<uint32_t> TransactionalStore::_sequence(0);
+std::atomic<std::uint32_t> TransactionalStore::_sequence(0);
 
 TransactionalStore::Document::Document() : Document(0) {}
 
-TransactionalStore::Document::Document(uint64_t k)
+TransactionalStore::Document::Document(std::uint64_t k)
     : key(k),
-      timestamp(static_cast<uint64_t>(
+      timestamp(static_cast<std::uint64_t>(
           std::chrono::steady_clock::now().time_since_epoch().count())),
       sequence(0) {}
 
 void TransactionalStore::Document::advance() {
-  timestamp = static_cast<uint64_t>(
+  timestamp = static_cast<std::uint64_t>(
       std::chrono::steady_clock::now().time_since_epoch().count());
   sequence++;
 }
@@ -148,11 +148,11 @@ bool TransactionalStore::insert(TransactionalStore::Transaction* tx,
   Document d = lookup(tx, document.key);
   if (d.empty()) {  // ensure document with this key does not exist
     // blacklist in cache first
-    _cache->blacklist(&(document.key), sizeof(uint64_t));
+    _cache->blacklist(&(document.key), sizeof(std::uint64_t));
 
     // now write to rocksdb
     rocksdb::Slice kSlice(reinterpret_cast<char const*>(&(document.key)),
-                          sizeof(uint64_t));
+                          sizeof(std::uint64_t));
     rocksdb::Slice vSlice(reinterpret_cast<char const*>(&document),
                           sizeof(Document));
     auto status = tx->rocks->Put(kSlice, vSlice);
@@ -181,11 +181,11 @@ bool TransactionalStore::update(TransactionalStore::Transaction* tx,
   Document d = lookup(tx, document.key);
   if (!d.empty()) {  // ensure document with this key exists
     // blacklist in cache first
-    _cache->blacklist(&(document.key), sizeof(uint64_t));
+    _cache->blacklist(&(document.key), sizeof(std::uint64_t));
 
     // now write to rocksdb
     rocksdb::Slice kSlice(reinterpret_cast<char const*>(&(document.key)),
-                          sizeof(uint64_t));
+                          sizeof(std::uint64_t));
     rocksdb::Slice vSlice(reinterpret_cast<char const*>(&document),
                           sizeof(Document));
     auto status = tx->rocks->Put(kSlice, vSlice);
@@ -203,8 +203,7 @@ bool TransactionalStore::update(TransactionalStore::Transaction* tx,
   return updated;
 }
 
-bool TransactionalStore::remove(TransactionalStore::Transaction* tx,
-                                uint64_t key) {
+bool TransactionalStore::remove(TransactionalStore::Transaction* tx, std::uint64_t key) {
   bool useInternalTransaction = (tx == nullptr);
   if (useInternalTransaction) {
     tx = beginTransaction(false);
@@ -214,10 +213,10 @@ bool TransactionalStore::remove(TransactionalStore::Transaction* tx,
   Document d = lookup(tx, key);
   if (!d.empty()) {  // ensure document with this key exists
     // blacklist in cache first
-    _cache->blacklist(&key, sizeof(uint64_t));
+    _cache->blacklist(&key, sizeof(std::uint64_t));
 
     // now write to rocksdb
-    rocksdb::Slice kSlice(reinterpret_cast<char*>(&key), sizeof(uint64_t));
+    rocksdb::Slice kSlice(reinterpret_cast<char*>(&key), sizeof(std::uint64_t));
     auto status = tx->rocks->Delete(kSlice);
     removed = status.ok();
   }
@@ -233,8 +232,8 @@ bool TransactionalStore::remove(TransactionalStore::Transaction* tx,
   return removed;
 }
 
-TransactionalStore::Document TransactionalStore::lookup(
-    TransactionalStore::Transaction* tx, uint64_t key) {
+TransactionalStore::Document TransactionalStore::lookup(TransactionalStore::Transaction* tx,
+                                                        std::uint64_t key) {
   bool useInternalTransaction = (tx == nullptr);
   if (useInternalTransaction) {
     tx = beginTransaction(true);
@@ -242,7 +241,7 @@ TransactionalStore::Document TransactionalStore::lookup(
 
   Document result;
   {
-    Finding f = _cache->find(&key, sizeof(uint64_t));
+    Finding f = _cache->find(&key, sizeof(std::uint64_t));
     if (f.found()) {
       CachedValue const* cv = f.value();
       memcpy(&result, cv->value(), sizeof(Document));
@@ -251,12 +250,12 @@ TransactionalStore::Document TransactionalStore::lookup(
   if (result.empty()) {
     auto readOptions = rocksdb::ReadOptions();
     readOptions.snapshot = tx->rocks->GetSnapshot();
-    rocksdb::Slice kSlice(reinterpret_cast<char*>(&key), sizeof(uint64_t));
+    rocksdb::Slice kSlice(reinterpret_cast<char*>(&key), sizeof(std::uint64_t));
     std::string buffer;
     auto status = tx->rocks->Get(readOptions, kSlice, &buffer);
     if (status.ok()) {
       memcpy(&result, buffer.data(), sizeof(Document));
-      CachedValue* value = CachedValue::construct(&key, sizeof(uint64_t),
+      CachedValue* value = CachedValue::construct(&key, sizeof(std::uint64_t),
                                                   &result, sizeof(Document));
       if (value) {
         auto status = _cache->insert(value);
diff --git a/tests/Cache/TransactionalStore.h b/tests/Cache/TransactionalStore.h
index d03052f8d6b3..e335589436ef 100644
--- a/tests/Cache/TransactionalStore.h
+++ b/tests/Cache/TransactionalStore.h
@@ -21,24 +21,23 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 /// @author Copyright 2017, ArangoDB GmbH, Cologne, Germany
 ////////////////////////////////////////////////////////////////////////////////
 
 #ifndef UNITTESTS_CACHE_TRANSACTIONAL_STORE_H
 #define UNITTESTS_CACHE_TRANSACTIONAL_STORE_H
 
-#include "Basics/Common.h"
-#include "Basics/StringBuffer.h"
-#include "Cache/Manager.h"
-#include "Cache/TransactionalCache.h"
+#include <chrono>
 
 #include <rocksdb/db.h>
 #include <rocksdb/options.h>
 #include <rocksdb/utilities/transaction.h>
 #include <rocksdb/utilities/transaction_db.h>
 
-#include <chrono>
+#include "Basics/StringBuffer.h"
+#include "Cache/Manager.h"
+#include "Cache/TransactionalCache.h"
 
 namespace arangodb {
 namespace cache {
@@ -46,12 +45,12 @@ namespace cache {
 class TransactionalStore {
  public:
   struct Document {
-    uint64_t key;
-    uint64_t timestamp;
-    uint64_t sequence;
+    std::uint64_t key;
+    std::uint64_t timestamp;
+    std::uint64_t sequence;
 
     Document();
-    Document(uint64_t k);
+    Document(std::uint64_t k);
     void advance();
     void clear();
     bool empty() const;
@@ -76,16 +75,16 @@ class TransactionalStore {
 
   bool insert(TransactionalStore::Transaction* tx, Document const& document);
   bool update(TransactionalStore::Transaction* tx, Document const& document);
-  bool remove(TransactionalStore::Transaction* tx, uint64_t key);
-  Document lookup(TransactionalStore::Transaction* tx, uint64_t key);
+  bool remove(TransactionalStore::Transaction* tx, std::uint64_t key);
+  Document lookup(TransactionalStore::Transaction* tx, std::uint64_t key);
 
  private:
-  static std::atomic<uint32_t> _sequence;
+  static std::atomic<std::uint32_t> _sequence;
   Manager* _manager;
   std::shared_ptr<Cache> _cache;
 
   arangodb::basics::StringBuffer _directory;
-  uint32_t _id;
+  std::uint32_t _id;
   rocksdb::TransactionDB* _db;
   rocksdb::ReadOptions _readOptions;
   rocksdb::WriteOptions _writeOptions;
diff --git a/tests/Cache/TransactionsWithBackingStore.cpp b/tests/Cache/TransactionsWithBackingStore.cpp
index f6daa90b3857..2581a28233dc 100644
--- a/tests/Cache/TransactionsWithBackingStore.cpp
+++ b/tests/Cache/TransactionsWithBackingStore.cpp
@@ -21,17 +21,10 @@
 ///
 /// Copyright holder is ArangoDB GmbH, Cologne, Germany
 ///
-/// @author Daniel H. Larkin
+/// @author Dan Larkin-York
 /// @author Copyright 2017, ArangoDB GmbH, Cologne, Germany
 ////////////////////////////////////////////////////////////////////////////////
 
-#include "Basics/Common.h"
-#include "Cache/Manager.h"
-#include "Cache/Rebalancer.h"
-#include "Random/RandomGenerator.h"
-
-#include "MockScheduler.h"
-#include "TransactionalStore.h"
 #include "gtest/gtest.h"
 
 #include <chrono>
@@ -40,6 +33,13 @@
 #include <thread>
 #include <vector>
 
+#include "Cache/Manager.h"
+#include "Cache/Rebalancer.h"
+#include "Random/RandomGenerator.h"
+
+#include "MockScheduler.h"
+#include "TransactionalStore.h"
+
 using namespace arangodb;
 using namespace arangodb::cache;
 
@@ -103,21 +103,21 @@ TEST(CacheWithBackingStoreTest, test_hit_rate_for_readonly_hotset_workload_LongR
   };
   Manager manager(postFn, 16 * 1024 * 1024);
   TransactionalStore store(&manager);
-  uint64_t totalDocuments = 1000000;
-  uint64_t hotsetSize = 50000;
-  size_t threadCount = 4;
-  uint64_t lookupsPerThread = 1000000;
+  std::uint64_t totalDocuments = 1000000;
+  std::uint64_t hotsetSize = 50000;
+  std::size_t threadCount = 4;
+  std::uint64_t lookupsPerThread = 1000000;
 
   // initial fill
-  for (uint64_t i = 1; i <= totalDocuments; i++) {
+  for (std::uint64_t i = 1; i <= totalDocuments; i++) {
     store.insert(nullptr, TransactionalStore::Document(i));
   }
 
   auto worker = [&store, hotsetSize, totalDocuments, lookupsPerThread]() -> void {
-    for (uint64_t i = 0; i < lookupsPerThread; i++) {
-      uint32_t r = RandomGenerator::interval(static_cast<uint32_t>(99));
-      uint64_t choice = (r >= 90) ? RandomGenerator::interval(totalDocuments)
-                                  : RandomGenerator::interval(hotsetSize);
+    for (std::uint64_t i = 0; i < lookupsPerThread; i++) {
+      std::uint32_t r = RandomGenerator::interval(static_cast<std::uint32_t>(99));
+      std::uint64_t choice = (r >= 90) ? RandomGenerator::interval(totalDocuments)
+                                       : RandomGenerator::interval(hotsetSize);
       if (choice == 0) {
         choice = 1;
       }
@@ -129,7 +129,7 @@ TEST(CacheWithBackingStoreTest, test_hit_rate_for_readonly_hotset_workload_LongR
 
   std::vector<ThreadGuard> threads;
   // dispatch threads
-  for (size_t i = 0; i < threadCount; i++) {
+  for (std::size_t i = 0; i < threadCount; i++) {
     threads.emplace_back(std::make_unique<std::thread>(worker));
   }
 
@@ -152,21 +152,21 @@ TEST(CacheWithBackingStoreTest, test_hit_rate_for_mixed_workload_LongRunning) {
   };
   Manager manager(postFn, 256 * 1024 * 1024);
   TransactionalStore store(&manager);
-  uint64_t totalDocuments = 1000000;
-  uint64_t batchSize = 1000;
-  size_t readerCount = 4;
-  size_t writerCount = 2;
-  std::atomic<size_t> writersDone(0);
+  std::uint64_t totalDocuments = 1000000;
+  std::uint64_t batchSize = 1000;
+  std::size_t readerCount = 4;
+  std::size_t writerCount = 2;
+  std::atomic<std::size_t> writersDone(0);
   auto writeWaitInterval = std::chrono::milliseconds(10);
 
   // initial fill
-  for (uint64_t i = 1; i <= totalDocuments; i++) {
+  for (std::uint64_t i = 1; i <= totalDocuments; i++) {
     store.insert(nullptr, TransactionalStore::Document(i));
   }
 
   auto readWorker = [&store, &writersDone, writerCount, totalDocuments]() -> void {
     while (writersDone.load() < writerCount) {
-      uint64_t choice = RandomGenerator::interval(totalDocuments);
+      std::uint64_t choice = RandomGenerator::interval(totalDocuments);
       if (choice == 0) {
         choice = 1;
       }
@@ -177,12 +177,12 @@ TEST(CacheWithBackingStoreTest, test_hit_rate_for_mixed_workload_LongRunning) {
   };
 
   auto writeWorker = [&store, &writersDone, batchSize,
-                      &writeWaitInterval](uint64_t lower, uint64_t upper) -> void {
-    uint64_t batches = (upper + 1 - lower) / batchSize;
-    uint64_t choice = lower;
-    for (uint64_t batch = 0; batch < batches; batch++) {
+                      &writeWaitInterval](std::uint64_t lower, std::uint64_t upper) -> void {
+    std::uint64_t batches = (upper + 1 - lower) / batchSize;
+    std::uint64_t choice = lower;
+    for (std::uint64_t batch = 0; batch < batches; batch++) {
       auto tx = store.beginTransaction(false);
-      for (uint64_t i = 0; i < batchSize; i++) {
+      for (std::uint64_t i = 0; i < batchSize; i++) {
         auto d = store.lookup(tx, choice);
         TRI_ASSERT(!d.empty());
         d.advance();
@@ -199,14 +199,14 @@ TEST(CacheWithBackingStoreTest, test_hit_rate_for_mixed_workload_LongRunning) {
 
   std::vector<ThreadGuard> threads;
   // dispatch reader threads
-  for (size_t i = 0; i < readerCount; i++) {
+  for (std::size_t i = 0; i < readerCount; i++) {
     threads.emplace_back(std::make_unique<std::thread>(readWorker));
   }
   // dispatch writer threads
-  uint64_t chunkSize = totalDocuments / writerCount;
-  for (size_t i = 0; i < writerCount; i++) {
-    uint64_t lower = (i * chunkSize) + 1;
-    uint64_t upper = ((i + 1) * chunkSize);
+  std::uint64_t chunkSize = totalDocuments / writerCount;
+  for (std::size_t i = 0; i < writerCount; i++) {
+    std::uint64_t lower = (i * chunkSize) + 1;
+    std::uint64_t upper = ((i + 1) * chunkSize);
     threads.emplace_back(std::make_unique<std::thread>(writeWorker, lower, upper));
   }
 
@@ -229,16 +229,16 @@ TEST(CacheWithBackingStoreTest, test_transactionality_for_mixed_workload_LongRun
   };
   Manager manager(postFn, 256 * 1024 * 1024);
   TransactionalStore store(&manager);
-  uint64_t totalDocuments = 1000000;
-  uint64_t writeBatchSize = 1000;
-  uint64_t readBatchSize = 10000;
-  size_t readerCount = 4;
-  size_t writerCount = 2;
-  std::atomic<size_t> writersDone(0);
+  std::uint64_t totalDocuments = 1000000;
+  std::uint64_t writeBatchSize = 1000;
+  std::uint64_t readBatchSize = 10000;
+  std::size_t readerCount = 4;
+  std::size_t writerCount = 2;
+  std::atomic<std::size_t> writersDone(0);
   auto writeWaitInterval = std::chrono::milliseconds(10);
 
   // initial fill
-  for (uint64_t i = 1; i <= totalDocuments; i++) {
+  for (std::uint64_t i = 1; i <= totalDocuments; i++) {
     store.insert(nullptr, TransactionalStore::Document(i));
   }
 
@@ -246,10 +246,10 @@ TEST(CacheWithBackingStoreTest, test_transactionality_for_mixed_workload_LongRun
                      readBatchSize]() -> void {
     while (writersDone.load() < writerCount) {
       auto tx = store.beginTransaction(true);
-      uint64_t start = static_cast<uint64_t>(
+      std::uint64_t start = static_cast<std::uint64_t>(
           std::chrono::steady_clock::now().time_since_epoch().count());
-      for (uint64_t i = 0; i < readBatchSize; i++) {
-        uint64_t choice = RandomGenerator::interval(totalDocuments);
+      for (std::uint64_t i = 0; i < readBatchSize; i++) {
+        std::uint64_t choice = RandomGenerator::interval(totalDocuments);
         if (choice == 0) {
           choice = 1;
         }
@@ -264,12 +264,12 @@ TEST(CacheWithBackingStoreTest, test_transactionality_for_mixed_workload_LongRun
   };
 
   auto writeWorker = [&store, &writersDone, writeBatchSize,
-                      &writeWaitInterval](uint64_t lower, uint64_t upper) -> void {
-    uint64_t batches = (upper + 1 - lower) / writeBatchSize;
-    uint64_t choice = lower;
-    for (uint64_t batch = 0; batch < batches; batch++) {
+                      &writeWaitInterval](std::uint64_t lower, std::uint64_t upper) -> void {
+    std::uint64_t batches = (upper + 1 - lower) / writeBatchSize;
+    std::uint64_t choice = lower;
+    for (std::uint64_t batch = 0; batch < batches; batch++) {
       auto tx = store.beginTransaction(false);
-      for (uint64_t i = 0; i < writeBatchSize; i++) {
+      for (std::uint64_t i = 0; i < writeBatchSize; i++) {
         auto d = store.lookup(tx, choice);
         TRI_ASSERT(!d.empty());
         d.advance();
@@ -286,14 +286,14 @@ TEST(CacheWithBackingStoreTest, test_transactionality_for_mixed_workload_LongRun
 
   std::vector<ThreadGuard> threads;
   // dispatch reader threads
-  for (size_t i = 0; i < readerCount; i++) {
+  for (std::size_t i = 0; i < readerCount; i++) {
     threads.emplace_back(std::make_unique<std::thread>(readWorker));
   }
   // dispatch writer threads
-  uint64_t chunkSize = totalDocuments / writerCount;
-  for (size_t i = 0; i < writerCount; i++) {
-    uint64_t lower = (i * chunkSize) + 1;
-    uint64_t upper = ((i + 1) * chunkSize);
+  std::uint64_t chunkSize = totalDocuments / writerCount;
+  for (std::size_t i = 0; i < writerCount; i++) {
+    std::uint64_t lower = (i * chunkSize) + 1;
+    std::uint64_t upper = ((i + 1) * chunkSize);
     threads.emplace_back(std::make_unique<std::thread>(writeWorker, lower, upper));
   }
 
@@ -314,14 +314,14 @@ TEST(CacheWithBackingStoreTest, test_rebalancing_in_the_wild_LongRunning) {
   Rebalancer rebalancer(&manager);
   TransactionalStore store1(&manager);
   TransactionalStore store2(&manager);
-  uint64_t totalDocuments = 1000000;
-  uint64_t writeBatchSize = 1000;
-  uint64_t readBatchSize = 100;
-  size_t readerCount = 4;
-  size_t writerCount = 2;
-  std::atomic<size_t> writersDone(0);
+  std::uint64_t totalDocuments = 1000000;
+  std::uint64_t writeBatchSize = 1000;
+  std::uint64_t readBatchSize = 100;
+  std::size_t readerCount = 4;
+  std::size_t writerCount = 2;
+  std::atomic<std::size_t> writersDone(0);
   auto writeWaitInterval = std::chrono::milliseconds(50);
-  uint32_t storeBias;
+  std::uint32_t storeBias;
 
   bool doneRebalancing = false;
   auto rebalanceWorker = [&rebalancer, &doneRebalancing]() -> void {
@@ -338,7 +338,7 @@ TEST(CacheWithBackingStoreTest, test_rebalancing_in_the_wild_LongRunning) {
   ThreadGuard rebalancerThread(std::make_unique<std::thread>(rebalanceWorker));
 
   // initial fill
-  for (uint64_t i = 1; i <= totalDocuments; i++) {
+  for (std::uint64_t i = 1; i <= totalDocuments; i++) {
     store1.insert(nullptr, TransactionalStore::Document(i));
     store2.insert(nullptr, TransactionalStore::Document(i));
   }
@@ -346,13 +346,13 @@ TEST(CacheWithBackingStoreTest, test_rebalancing_in_the_wild_LongRunning) {
   auto readWorker = [&store1, &store2, &storeBias, &writersDone, writerCount,
                      totalDocuments, readBatchSize]() -> void {
     while (writersDone.load() < writerCount) {
-      uint32_t r = RandomGenerator::interval(static_cast<uint32_t>(99UL));
+      std::uint32_t r = RandomGenerator::interval(static_cast<std::uint32_t>(99UL));
       TransactionalStore* store = (r <= storeBias) ? &store1 : &store2;
       auto tx = store->beginTransaction(true);
-      uint64_t start = static_cast<uint64_t>(
+      std::uint64_t start = static_cast<std::uint64_t>(
           std::chrono::steady_clock::now().time_since_epoch().count());
-      for (uint64_t i = 0; i < readBatchSize; i++) {
-        uint64_t choice = RandomGenerator::interval(totalDocuments);
+      for (std::uint64_t i = 0; i < readBatchSize; i++) {
+        std::uint64_t choice = RandomGenerator::interval(totalDocuments);
         if (choice == 0) {
           choice = 1;
         }
@@ -367,14 +367,14 @@ TEST(CacheWithBackingStoreTest, test_rebalancing_in_the_wild_LongRunning) {
   };
 
   auto writeWorker = [&store1, &store2, &storeBias, &writersDone, writeBatchSize,
-                      &writeWaitInterval](uint64_t lower, uint64_t upper) -> void {
-    uint64_t batches = (upper + 1 - lower) / writeBatchSize;
-    uint64_t choice = lower;
-    for (uint64_t batch = 0; batch < batches; batch++) {
-      uint32_t r = RandomGenerator::interval(static_cast<uint32_t>(99UL));
+                      &writeWaitInterval](std::uint64_t lower, std::uint64_t upper) -> void {
+    std::uint64_t batches = (upper + 1 - lower) / writeBatchSize;
+    std::uint64_t choice = lower;
+    for (std::uint64_t batch = 0; batch < batches; batch++) {
+      std::uint32_t r = RandomGenerator::interval(static_cast<std::uint32_t>(99UL));
       TransactionalStore* store = (r <= storeBias) ? &store1 : &store2;
       auto tx = store->beginTransaction(false);
-      for (uint64_t i = 0; i < writeBatchSize; i++) {
+      for (std::uint64_t i = 0; i < writeBatchSize; i++) {
         auto d = store->lookup(tx, choice);
         TRI_ASSERT(!d.empty());
         d.advance();
@@ -389,20 +389,19 @@ TEST(CacheWithBackingStoreTest, test_rebalancing_in_the_wild_LongRunning) {
     writersDone++;
   };
 
-
   // bias toward first store
   storeBias = 80;
 
   // dispatch reader threads
   std::vector<ThreadGuard> threads;
-  for (size_t i = 0; i < readerCount; i++) {
+  for (std::size_t i = 0; i < readerCount; i++) {
     threads.emplace_back(std::make_unique<std::thread>(readWorker));
   }
   // dispatch writer threads
-  uint64_t chunkSize = totalDocuments / writerCount;
-  for (size_t i = 0; i < writerCount; i++) {
-    uint64_t lower = (i * chunkSize) + 1;
-    uint64_t upper = ((i + 1) * chunkSize);
+  std::uint64_t chunkSize = totalDocuments / writerCount;
+  for (std::size_t i = 0; i < writerCount; i++) {
+    std::uint64_t lower = (i * chunkSize) + 1;
+    std::uint64_t upper = ((i + 1) * chunkSize);
     threads.emplace_back(std::make_unique<std::thread>(writeWorker, lower, upper));
   }
 
@@ -417,13 +416,13 @@ TEST(CacheWithBackingStoreTest, test_rebalancing_in_the_wild_LongRunning) {
   storeBias = 20;
 
   // dispatch reader threads
-  for (size_t i = 0; i < readerCount; i++) {
+  for (std::size_t i = 0; i < readerCount; i++) {
     threads.emplace_back(std::make_unique<std::thread>(readWorker));
   }
   // dispatch writer threads
-  for (size_t i = 0; i < writerCount; i++) {
-    uint64_t lower = (i * chunkSize) + 1;
-    uint64_t upper = ((i + 1) * chunkSize);
+  for (std::size_t i = 0; i < writerCount; i++) {
+    std::uint64_t lower = (i * chunkSize) + 1;
+    std::uint64_t upper = ((i + 1) * chunkSize);
     threads.emplace_back(std::make_unique<std::thread>(writeWorker, lower, upper));
   }
 
diff --git a/tests/Containers/EnumerateTest.cpp b/tests/Containers/EnumerateTest.cpp
new file mode 100644
index 000000000000..a1d76f899b79
--- /dev/null
+++ b/tests/Containers/EnumerateTest.cpp
@@ -0,0 +1,105 @@
+////////////////////////////////////////////////////////////////////////////////
+/// DISCLAIMER
+///
+/// Copyright 2014-2020 ArangoDB GmbH, Cologne, Germany
+/// Copyright 2004-2014 triAGENS GmbH, Cologne, Germany
+///
+/// Licensed under the Apache License, Version 2.0 (the "License");
+/// you may not use this file except in compliance with the License.
+/// You may obtain a copy of the License at
+///
+///     http://www.apache.org/licenses/LICENSE-2.0
+///
+/// Unless required by applicable law or agreed to in writing, software
+/// distributed under the License is distributed on an "AS IS" BASIS,
+/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+/// See the License for the specific language governing permissions and
+/// limitations under the License.
+///
+/// Copyright holder is ArangoDB GmbH, Cologne, Germany
+///
+/// @author Lars Maier
+////////////////////////////////////////////////////////////////////////////////
+#include <list>
+#include <vector>
+#include <deque>
+
+#include "gtest/gtest.h"
+
+#include "Containers/Enumerate.h"
+#if GTEST_HAS_TYPED_TEST_P
+
+using namespace arangodb;
+
+template<typename T>
+struct NonCopyableType {
+  explicit NonCopyableType(T t) : t(std::move(t)) {}
+  NonCopyableType(NonCopyableType const&) = delete;
+  NonCopyableType(NonCopyableType &&) noexcept = default;
+
+  NonCopyableType& operator=(NonCopyableType const&) = delete;
+  NonCopyableType& operator=(NonCopyableType&&) noexcept = default;
+
+  T t;
+};
+
+template<template <typename...> typename C>
+struct TemplateTemplateType {
+  template<typename... T>
+  using type = C<T...>;
+};
+
+template<typename TT, typename... T>
+using template_template_type_t = typename TT::template type<T...>;
+
+template<typename TT>
+class EnumerateVectorLikeTest : public ::testing::Test {};
+TYPED_TEST_CASE_P(EnumerateVectorLikeTest);
+
+TYPED_TEST_P(EnumerateVectorLikeTest, test_vector_iterate) {
+  template_template_type_t<TypeParam, unsigned> v = { 3, 5, 4, 1, 6, 8, 7};
+
+  unsigned i = 0;
+  auto iter = v.begin();
+  for (auto [idx, e] : enumerate(v)) {
+    EXPECT_EQ(idx, i);
+    EXPECT_EQ(e, *iter);
+    ++i;
+    ++iter;
+  }
+
+  EXPECT_EQ(i, v.size());
+}
+
+TYPED_TEST_P(EnumerateVectorLikeTest, test_vector_modify) {
+  template_template_type_t<TypeParam, unsigned> v = { 3, 5, 4, 1, 6, 8, 7};
+  for (auto [idx, e] : enumerate(v)) {
+    e = idx;
+  }
+
+  unsigned i = 0;
+  for (auto const& e : v) {
+    EXPECT_EQ(i, e);
+    i++;
+  }
+}
+
+TYPED_TEST_P(EnumerateVectorLikeTest, test_vector_no_copy) {
+  template_template_type_t<TypeParam, NonCopyableType<unsigned>> v;
+  v.emplace_back(1);
+
+  unsigned i = 0;
+  auto iter = v.begin();
+  for (auto const [idx, e] : enumerate(v)) {
+    EXPECT_EQ(idx, i);
+    EXPECT_EQ(e.t, iter->t);
+    ++i;
+    ++iter;
+  }
+}
+
+REGISTER_TYPED_TEST_CASE_P(EnumerateVectorLikeTest, test_vector_iterate, test_vector_modify, test_vector_no_copy);
+
+using VectorLikeTypes = ::testing::Types<TemplateTemplateType<std::vector>, TemplateTemplateType<std::list>, TemplateTemplateType<std::deque>>;
+INSTANTIATE_TYPED_TEST_CASE_P(EnumerateVectorLikeTestInstant, EnumerateVectorLikeTest, VectorLikeTypes);
+#endif
diff --git a/tests/Containers/MerkleTreeTest.cpp b/tests/Containers/MerkleTreeTest.cpp
new file mode 100644
index 000000000000..5161bad04d4e
--- /dev/null
+++ b/tests/Containers/MerkleTreeTest.cpp
@@ -0,0 +1,464 @@
+////////////////////////////////////////////////////////////////////////////////
+/// DISCLAIMER
+///
+/// Copyright 2019 ArangoDB GmbH, Cologne, Germany
+///
+/// Licensed under the Apache License, Version 2.0 (the "License");
+/// you may not use this file except in compliance with the License.
+/// You may obtain a copy of the License at
+///
+///     http://www.apache.org/licenses/LICENSE-2.0
+///
+/// Unless required by applicable law or agreed to in writing, software
+/// distributed under the License is distributed on an "AS IS" BASIS,
+/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+/// See the License for the specific language governing permissions and
+/// limitations under the License.
+///
+/// Copyright holder is ArangoDB GmbH, Cologne, Germany
+///
+/// @author Dan Larkin-York
+////////////////////////////////////////////////////////////////////////////////
+
+#include <algorithm>
+#include <random>
+#include <vector>
+
+#include "gtest/gtest.h"
+
+#include "Basics/hashes.h"
+#include "Containers/MerkleTree.h"
+#include "Logger/LogMacros.h"
+
+namespace {
+std::vector<std::size_t> permutation(std::size_t n) {
+  std::vector<std::size_t> v;
+
+  v.reserve(n);
+  for (std::size_t i = 0; i < n; ++i) {
+    v.emplace_back(i);
+  }
+
+  std::random_device rd;
+  std::mt19937_64 g(rd());
+  std::shuffle(v.begin(), v.end(), g);
+
+  return v;
+}
+
+bool diffAsExpected(arangodb::containers::MerkleTree<3, 64>& t1,
+                    arangodb::containers::MerkleTree<3, 64>& t2,
+                    std::vector<std::pair<std::size_t, std::size_t>>& expected) {
+  std::vector<std::pair<std::size_t, std::size_t>> d1 = t1.diff(t2);
+  std::vector<std::pair<std::size_t, std::size_t>> d2 = t2.diff(t1);
+
+  auto printTrees = [&t1, &t2]() -> void {
+    LOG_DEVEL << "T1:";
+    LOG_DEVEL << t1;
+    LOG_DEVEL << "T2:";
+    LOG_DEVEL << t2;
+  };
+
+  if (d1.size() != expected.size() || d2.size() != expected.size()) {
+    printTrees();
+    return false;
+  }
+  for (std::size_t i = 0; i < expected.size(); ++i) {
+    if (d1[i].first != expected[i].first || d1[i].second != expected[i].second ||
+        d2[i].first != expected[i].first || d2[i].second != expected[i].second) {
+      printTrees();
+      return false;
+    }
+  }
+  return true;
+}
+}  // namespace
+
+class InternalMerkleTreeTest : public ::arangodb::containers::MerkleTree<3, 64>,
+                               public ::testing::Test {
+ public:
+  InternalMerkleTreeTest() : MerkleTree<3, 64>(2, 0, 64) {}
+};
+
+TEST_F(InternalMerkleTreeTest, test_childrenAreLeaves) {
+  ASSERT_FALSE(childrenAreLeaves(0));
+  for (std::size_t index = 1; index < 9; ++index) {
+    ASSERT_TRUE(childrenAreLeaves(index));
+  }
+  for (std::size_t index = 9; index < 73; ++index) {
+    ASSERT_FALSE(childrenAreLeaves(index));
+  }
+}
+
+TEST_F(InternalMerkleTreeTest, test_chunkRange) {
+  auto r = chunkRange(0, 0);
+  ASSERT_EQ(r.first, 0);
+  ASSERT_EQ(r.second, 63);
+
+  for (std::size_t chunk = 0; chunk < 8; ++chunk) {
+    auto r = chunkRange(chunk, 1);
+    ASSERT_EQ(r.first, chunk * 8);
+    ASSERT_EQ(r.second, ((chunk + 1) * 8) - 1);
+  }
+
+  for (std::size_t chunk = 0; chunk < 64; ++chunk) {
+    auto r = chunkRange(chunk, 2);
+    ASSERT_EQ(r.first, chunk);
+    ASSERT_EQ(r.second, chunk);
+  }
+}
+
+TEST_F(InternalMerkleTreeTest, test_index) {
+  std::pair<std::size_t, std::size_t> range = this->range();
+  ASSERT_EQ(range.first, 0);
+  ASSERT_EQ(range.second, 64);
+
+  // make sure depth 0 always gets us 0
+  ASSERT_EQ(index(0, 0), 0);
+  ASSERT_EQ(index(63, 0), 0);
+
+  // check boundaries at level 1
+  for (std::size_t chunk = 0; chunk < 8; ++chunk) {
+    std::size_t left = chunk * 8;
+    std::size_t right = ((chunk + 1) * 8) - 1;
+    ASSERT_EQ(index(left, 1), chunk + 1);
+    ASSERT_EQ(index(right, 1), chunk + 1);
+  }
+
+  // check boundaries at level 2
+  for (std::size_t chunk = 0; chunk < 64; ++chunk) {
+    std::size_t left = chunk;  // only one value per chunk
+    ASSERT_EQ(index(left, 2), chunk + 9);
+  }
+}
+
+TEST_F(InternalMerkleTreeTest, test_modify) {
+  std::pair<std::size_t, std::size_t> range = this->range();
+  ASSERT_EQ(range.first, 0);
+  ASSERT_EQ(range.second, 64);
+
+  ASSERT_EQ(count(), 0);
+  // check that an attempt to remove will fail if it's empty
+  ASSERT_THROW(modify(0, TRI_FnvHashPod(0), false), std::invalid_argument);
+  ASSERT_EQ(count(), 0);
+
+  // insert a single value
+  modify(0, TRI_FnvHashPod(0), true);
+  ASSERT_EQ(count(), 1);
+
+  // build set of indexes that should be touched
+  std::set<std::size_t> indices0;
+  for (std::size_t depth = 0; depth <= meta().maxDepth; ++depth) {
+    indices0.emplace(this->index(0, depth));
+  }
+
+  // check that it sets everything it should, and nothing it shouldn't
+  for (std::size_t index = 0; index < 73; ++index) {
+    bool inSet0 = indices0.find(index) != indices0.end();
+    std::size_t expectedCount = inSet0 ? 1 : 0;
+    std::size_t expectedHash = inSet0 ? TRI_FnvHashPod(0) : 0;
+
+    InternalMerkleTreeTest::Node& node = this->node(index);
+    ASSERT_EQ(node.count, expectedCount);
+    ASSERT_EQ(node.hash, expectedHash);
+  }
+
+  // insert another value, minimal overlap
+  modify(63, TRI_FnvHashPod(63), true);
+  ASSERT_EQ(count(), 2);
+
+  // build set of indexes that should be touched
+  std::set<std::size_t> indices63;
+  for (std::size_t depth = 0; depth <= meta().maxDepth; ++depth) {
+    indices63.emplace(this->index(63, depth));
+  }
+
+  // check that it sets everything it should, and nothing it shouldn't
+  for (std::size_t index = 0; index < 73; ++index) {
+    bool inSet0 = indices0.find(index) != indices0.end();
+    std::size_t expectedCount = inSet0 ? 1 : 0;
+    std::size_t expectedHash = inSet0 ? TRI_FnvHashPod(0) : 0;
+    if (indices63.find(index) != indices63.end()) {
+      ++expectedCount;
+      expectedHash ^= TRI_FnvHashPod(63);
+    }
+
+    InternalMerkleTreeTest::Node& node = this->node(index);
+    ASSERT_EQ(node.count, expectedCount);
+    ASSERT_EQ(node.hash, expectedHash);
+  }
+
+  // insert another value, more overlap
+  modify(1, TRI_FnvHashPod(1), true);
+  ASSERT_EQ(count(), 3);
+
+  // build set of indexes that should be touched
+  std::set<std::size_t> indices1;
+  for (std::size_t depth = 0; depth <= meta().maxDepth; ++depth) {
+    indices1.emplace(this->index(1, depth));
+  }
+
+  // check that it sets everything it should, and nothing it shouldn't
+  for (std::size_t index = 0; index < 73; ++index) {
+    bool inSet0 = indices0.find(index) != indices0.end();
+    std::size_t expectedCount = inSet0 ? 1 : 0;
+    std::size_t expectedHash = inSet0 ? TRI_FnvHashPod(0) : 0;
+    if (indices1.find(index) != indices1.end()) {
+      ++expectedCount;
+      expectedHash ^= TRI_FnvHashPod(1);
+    }
+    if (indices63.find(index) != indices63.end()) {
+      ++expectedCount;
+      expectedHash ^= TRI_FnvHashPod(63);
+    }
+
+    InternalMerkleTreeTest::Node& node = this->node(index);
+    ASSERT_EQ(node.count, expectedCount);
+    ASSERT_EQ(node.hash, expectedHash);
+  }
+
+  // remove a value, minimal overlap
+  modify(63, TRI_FnvHashPod(63), false);
+  ASSERT_EQ(count(), 2);
+
+  // check that it sets everything it should, and nothing it shouldn't
+  for (std::size_t index = 0; index < 73; ++index) {
+    bool inSet0 = indices0.find(index) != indices0.end();
+    std::size_t expectedCount = inSet0 ? 1 : 0;
+    std::size_t expectedHash = inSet0 ? TRI_FnvHashPod(0) : 0;
+    if (indices1.find(index) != indices1.end()) {
+      ++expectedCount;
+      expectedHash ^= TRI_FnvHashPod(1);
+    }
+
+    InternalMerkleTreeTest::Node& node = this->node(index);
+    ASSERT_EQ(node.count, expectedCount);
+    ASSERT_EQ(node.hash, expectedHash);
+  }
+
+  // remove a value, maximal overlap
+  modify(1, TRI_FnvHashPod(1), false);
+  ASSERT_EQ(count(), 1);
+
+  // check that it sets everything it should, and nothing it shouldn't
+  for (std::size_t index = 0; index < 73; ++index) {
+    bool inSet0 = indices0.find(index) != indices0.end();
+    std::size_t expectedCount = inSet0 ? 1 : 0;
+    std::size_t expectedHash = inSet0 ? TRI_FnvHashPod(0) : 0;
+
+    InternalMerkleTreeTest::Node& node = this->node(index);
+    ASSERT_EQ(node.count, expectedCount);
+    ASSERT_EQ(node.hash, expectedHash);
+  }
+
+  // remove a value, maximal overlap
+  modify(0, TRI_FnvHashPod(0), false);
+  ASSERT_EQ(count(), 0);
+
+  // check that it sets everything it should, and nothing it shouldn't
+  for (std::size_t index = 0; index < 73; ++index) {
+    InternalMerkleTreeTest::Node& node = this->node(index);
+    ASSERT_EQ(node.count, 0);
+    ASSERT_EQ(node.hash, 0);
+  }
+}
+
+TEST_F(InternalMerkleTreeTest, test_grow) {
+  std::pair<std::size_t, std::size_t> range = this->range();
+  ASSERT_EQ(range.first, 0);
+  ASSERT_EQ(range.second, 64);
+
+  // fill the tree, but not enough that it grows
+  for (std::size_t i = 0; i < 64; ++i) {
+    insert(i, TRI_FnvHashPod(i));
+  }
+  range = this->range();
+  ASSERT_EQ(range.first, 0);
+  ASSERT_EQ(range.second, 64);
+
+  // check that tree state is as expected prior to growing
+  {
+    std::size_t hash0 = 0;
+    std::size_t hash1[8] = {0};
+    std::size_t hash2[64] = {0};
+    for (std::size_t i = 0; i < 64; ++i) {
+      hash0 ^= TRI_FnvHashPod(i);
+      hash1[i / 8] ^= TRI_FnvHashPod(i);
+      hash2[i] ^= TRI_FnvHashPod(i);
+    }
+    for (std::size_t i = 0; i < 64; ++i) {
+      Node& node = this->node(this->index(i, 2));
+      ASSERT_EQ(node.count, 1);
+      ASSERT_EQ(node.hash, hash2[i]);
+    }
+    for (std::size_t i = 0; i < 8; ++i) {
+      Node& node = this->node(i + 1);
+      ASSERT_EQ(node.count, 8);
+      ASSERT_EQ(node.hash, hash1[i]);
+    }
+    {
+      Node& node = this->node(0);
+      ASSERT_EQ(node.count, 64);
+      ASSERT_EQ(node.hash, hash0);
+    }
+  }
+
+  // insert some more and cause it to grow
+  for (std::size_t i = 64; i < 128; ++i) {
+    insert(i, TRI_FnvHashPod(i));
+  }
+  range = this->range();
+  ASSERT_EQ(range.first, 0);
+  ASSERT_EQ(range.second, 128);
+
+  // check that tree state is as expected after growing
+  {
+    std::size_t hash0 = 0;
+    std::size_t hash1[8] = {0};
+    std::size_t hash2[64] = {0};
+    for (std::size_t i = 0; i < 128; ++i) {
+      hash0 ^= TRI_FnvHashPod(i);
+      hash1[i / 16] ^= TRI_FnvHashPod(i);
+      hash2[i / 2] ^= TRI_FnvHashPod(i);
+    }
+    for (std::size_t i = 0; i < 64; ++i) {
+      Node& node = this->node(i + 9);
+      ASSERT_EQ(node.count, 2);
+      if (node.hash != hash2[i]) {
+      }
+      ASSERT_EQ(node.hash, hash2[i]);
+    }
+    for (std::size_t i = 0; i < 8; ++i) {
+      Node& node = this->node(i + 1);
+      ASSERT_EQ(node.count, 16);
+      ASSERT_EQ(node.hash, hash1[i]);
+    }
+    {
+      Node& node = this->node(0);
+      ASSERT_EQ(node.count, 128);
+      ASSERT_EQ(node.hash, hash0);
+    }
+  }
+}
+
+TEST(MerkleTreeTest, test_diff_equal) {
+  ::arangodb::containers::MerkleTree<3, 64> t1(2, 0, 64);
+  ::arangodb::containers::MerkleTree<3, 64> t2(2, 0, 64);
+
+  std::vector<std::pair<std::size_t, std::size_t>> expected;  // empty
+  ASSERT_TRUE(::diffAsExpected(t1, t2, expected));
+
+  std::vector<std::size_t> order = ::permutation(64);
+  for (std::size_t i : order) {
+    t1.insert(i, TRI_FnvHashPod(i));
+    t2.insert(i, TRI_FnvHashPod(i));
+    ASSERT_TRUE(::diffAsExpected(t1, t2, expected));
+  }
+
+  order = ::permutation(64);
+  for (std::size_t i : order) {
+    t1.remove(i, TRI_FnvHashPod(i));
+    t2.remove(i, TRI_FnvHashPod(i));
+    ASSERT_TRUE(::diffAsExpected(t1, t2, expected));
+  }
+}
+
+TEST(MerkleTreeTest, test_diff_one_empty) {
+  ::arangodb::containers::MerkleTree<3, 64> t1(2, 0, 64);
+  ::arangodb::containers::MerkleTree<3, 64> t2(2, 0, 64);
+
+  std::vector<std::pair<std::size_t, std::size_t>> expected;
+  ASSERT_TRUE(::diffAsExpected(t1, t2, expected));
+
+  for (std::size_t i = 0; i < 8; ++i) {
+    t1.insert(8 * i, TRI_FnvHashPod(8 * i));
+    expected.emplace_back(std::make_pair(8 * i, 8 * i));
+    ASSERT_TRUE(::diffAsExpected(t1, t2, expected));
+  }
+
+  expected.clear();
+  for (std::size_t i = 0; i < 8; ++i) {
+    t1.insert((8 * i) + 1, TRI_FnvHashPod((8 * i) + 1));
+    expected.emplace_back(std::make_pair(8 * i, (8 * i) + 1));
+  }
+  ASSERT_TRUE(::diffAsExpected(t1, t2, expected));
+
+  expected.clear();
+  for (std::size_t i = 0; i < 8; ++i) {
+    t1.insert((8 * i) + 2, TRI_FnvHashPod((8 * i) + 2));
+    t1.insert((8 * i) + 3, TRI_FnvHashPod((8 * i) + 3));
+    expected.emplace_back(std::make_pair(8 * i, (8 * i) + 3));
+  }
+  ASSERT_TRUE(::diffAsExpected(t1, t2, expected));
+
+  expected.clear();
+  for (std::size_t i = 0; i < 8; ++i) {
+    t1.insert((8 * i) + 4, TRI_FnvHashPod((8 * i) + 4));
+    t1.insert((8 * i) + 5, TRI_FnvHashPod((8 * i) + 5));
+    t1.insert((8 * i) + 6, TRI_FnvHashPod((8 * i) + 6));
+    t1.insert((8 * i) + 7, TRI_FnvHashPod((8 * i) + 7));
+  }
+  expected.emplace_back(std::make_pair(0, 63));
+  ASSERT_TRUE(::diffAsExpected(t1, t2, expected));
+}
+
+TEST(MerkleTreeTest, test_diff_misc) {
+  ::arangodb::containers::MerkleTree<3, 64> t1(2, 0, 64);
+  ::arangodb::containers::MerkleTree<3, 64> t2(2, 0, 64);
+
+  std::vector<std::pair<std::size_t, std::size_t>> expected;
+  ASSERT_TRUE(::diffAsExpected(t1, t2, expected));
+
+  for (std::size_t i = 0; i < 32; ++i) {
+    t1.insert(2 * i, TRI_FnvHashPod(2 * i));
+    expected.emplace_back(std::make_pair(2 * i, 2 * i));
+  }
+  ASSERT_TRUE(::diffAsExpected(t1, t2, expected));
+
+  expected.clear();
+  for (std::size_t i = 0; i < 32; ++i) {
+    t2.insert((2 * i) + 1, TRI_FnvHashPod((2 * i) + 1));
+  }
+  expected.emplace_back(std::make_pair(0, 63));
+  ASSERT_TRUE(::diffAsExpected(t1, t2, expected));
+
+  expected.clear();
+  for (std::size_t i = 0; i < 16; ++i) {
+    t1.insert((2 * i) + 1, TRI_FnvHashPod((2 * i) + 1));
+    expected.emplace_back(std::make_pair(2 * i, 2 * i));
+  }
+  expected.emplace_back(std::make_pair(32, 63));
+  ASSERT_TRUE(::diffAsExpected(t1, t2, expected));
+}
+
+TEST(MerkleTreeTest, test_serializeBinary) {
+  ::arangodb::containers::MerkleTree<3, 64> t1(2, 0, 64);
+
+  for (std::size_t i = 0; i < 32; ++i) {
+    t1.insert(2 * i, TRI_FnvHashPod(2 * i));
+  }
+
+  std::string t1s;
+  t1.serializeBinary(t1s, true);
+  std::unique_ptr<::arangodb::containers::MerkleTree<3, 64>> t2 =
+      ::arangodb::containers::MerkleTree<3, 64>::fromBuffer(t1s);
+  ASSERT_NE(t2, nullptr);
+  ASSERT_TRUE(t1.diff(*t2).empty());
+  ASSERT_TRUE(t2->diff(t1).empty());
+}
+
+TEST(MerkleTreeTest, test_serializePortable) {
+  ::arangodb::containers::MerkleTree<3, 64> t1(2, 0, 64);
+
+  for (std::size_t i = 0; i < 32; ++i) {
+    t1.insert(2 * i, TRI_FnvHashPod(2 * i));
+  }
+
+  ::arangodb::velocypack::Builder t1s;
+  t1.serialize(t1s);
+  std::unique_ptr<::arangodb::containers::MerkleTree<3, 64>> t2 =
+      ::arangodb::containers::MerkleTree<3, 64>::deserialize(t1s.slice());
+  ASSERT_NE(t2, nullptr);
+  ASSERT_TRUE(t1.diff(*t2).empty());
+  ASSERT_TRUE(t2->diff(t1).empty());
+}
diff --git a/tests/IResearch/IResearchAnalyzerFeature-test.cpp b/tests/IResearch/IResearchAnalyzerFeature-test.cpp
index 03110f99371d..780bae14748b 100644
--- a/tests/IResearch/IResearchAnalyzerFeature-test.cpp
+++ b/tests/IResearch/IResearchAnalyzerFeature-test.cpp
@@ -374,7 +374,7 @@ static const VPackSlice   systemDatabaseArgs = systemDatabaseBuilder.slice();
 class IResearchAnalyzerFeatureTest
     : public ::testing::Test,
       public arangodb::tests::LogSuppressor<arangodb::Logger::AUTHENTICATION, arangodb::LogLevel::ERR>,
-      public arangodb::tests::LogSuppressor<arangodb::Logger::CLUSTER, arangodb::LogLevel::WARN> {
+      public arangodb::tests::LogSuppressor<arangodb::Logger::CLUSTER, arangodb::LogLevel::FATAL> {
  protected:
         
   arangodb::tests::mocks::MockV8Server server;
@@ -2340,6 +2340,7 @@ TEST_F(IResearchAnalyzerFeatureTest, test_tokens) {
   auto& sharding = newServer.addFeature<arangodb::ShardingFeature>();
   auto& systemdb = newServer.addFeature<arangodb::SystemDatabaseFeature>();
   newServer.addFeature<arangodb::V8DealerFeature>();  // required for DatabaseFeature::createDatabase>(std::make_unique<arangodb::V8DealerFeature(server)); // required for DatabaseFeature::createDatabase>(...)
+  newServer.addFeature<arangodb::EngineSelectorFeature>();
 
   auto cleanup = arangodb::scopeGuard([&dbfeature]() { dbfeature.unprepare(); });
 
@@ -3227,6 +3228,7 @@ TEST_F(IResearchAnalyzerFeatureTest, test_visit) {
   newServer.addFeature<arangodb::QueryRegistryFeature>();  // required for constructing TRI_vocbase_t
   auto& sysDatabase = newServer.addFeature<arangodb::SystemDatabaseFeature>();  // required for IResearchAnalyzerFeature::start()
   newServer.addFeature<arangodb::V8DealerFeature>();  // required for DatabaseFeature::createDatabase>(std::make_unique<arangodb::V8DealerFeature(server)); // required for DatabaseFeature::createDatabase>(...)
+  newServer.addFeature<arangodb::EngineSelectorFeature>();
 
   // create system vocbase (before feature start)
   {
@@ -3495,6 +3497,7 @@ TEST_F(IResearchAnalyzerFeatureTest, custom_analyzers_toVelocyPack) {
   newServer.addFeature<arangodb::QueryRegistryFeature>();  // required for constructing TRI_vocbase_t
   auto& sysDatabase = newServer.addFeature<arangodb::SystemDatabaseFeature>();  // required for IResearchAnalyzerFeature::start()
   newServer.addFeature<arangodb::V8DealerFeature>();  // required for DatabaseFeature::createDatabase>(std::make_unique<arangodb::V8DealerFeature(server)); // required for DatabaseFeature::createDatabase>(...)
+  newServer.addFeature<arangodb::EngineSelectorFeature>();
   auto cleanup = arangodb::scopeGuard([&dbFeature]() { dbFeature.unprepare(); });
 
   // create system vocbase (before feature start)
@@ -3597,6 +3600,7 @@ TEST_F(IResearchAnalyzerFeatureTest, custom_analyzers_vpack_create) {
   newServer.addFeature<arangodb::QueryRegistryFeature>();  // required for constructing TRI_vocbase_t
   auto& sysDatabase = newServer.addFeature<arangodb::SystemDatabaseFeature>();  // required for IResearchAnalyzerFeature::start()
   newServer.addFeature<arangodb::V8DealerFeature>();  // required for DatabaseFeature::createDatabase>(std::make_unique<arangodb::V8DealerFeature(server)); // required for DatabaseFeature::createDatabase>(...)
+  newServer.addFeature<arangodb::EngineSelectorFeature>();
   auto cleanup = arangodb::scopeGuard([&dbFeature]() { dbFeature.unprepare(); });
 
   // create system vocbase (before feature start)
diff --git a/tests/IResearch/IResearchFilterFunction-test.cpp b/tests/IResearch/IResearchFilterFunction-test.cpp
index c26c69ce7dd3..41eafc5fd9c3 100644
--- a/tests/IResearch/IResearchFilterFunction-test.cpp
+++ b/tests/IResearch/IResearchFilterFunction-test.cpp
@@ -36,6 +36,7 @@
 #include "search/term_filter.hpp"
 #include "search/wildcard_filter.hpp"
 #include "search/levenshtein_filter.hpp"
+#include "search/ngram_similarity_filter.hpp"
 
 #include "IResearch/ExpressionContextMock.h"
 #include "IResearch/common.h"
@@ -1965,7 +1966,7 @@ TEST_F(IResearchFilterFunctionTest, Phrase) {
     irs::Or expected;
     auto& phrase = expected.add<irs::by_phrase>();
     phrase.field(mangleStringIdentity("name"));
-    phrase.push_back("quick");
+    phrase.push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("quick"))});
 
     // implicit (by default)
     assertFilterSuccess(
@@ -2046,8 +2047,11 @@ TEST_F(IResearchFilterFunctionTest, Phrase) {
     irs::Or expected;
     auto& phrase = expected.add<irs::by_phrase>();
     phrase.field(mangleString("name", "test_analyzer"));
-    phrase.push_back("q").push_back("u").push_back("i").push_back("c").push_back(
-        "k");
+    phrase.push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("q"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("u"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("i"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("c"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("k"))});
 
     assertFilterSuccess(
         vocbase(),
@@ -2143,8 +2147,11 @@ TEST_F(IResearchFilterFunctionTest, Phrase) {
     irs::Or expectedAccumulated;
     auto& phraseAccumulated = expectedAccumulated.add<irs::by_phrase>();
     phraseAccumulated.field(mangleString("name", "test_analyzer"));
-    phraseAccumulated.push_back("q").push_back("u", 7).push_back("i", 3).push_back("c", 4).push_back(
-      "k",5);
+    phraseAccumulated.push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("q"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("u"))}, 7)
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("i"))}, 3)
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("c"))}, 4)
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("k"))}, 5);
     assertFilterSuccess(
       vocbase(),
       "FOR d IN myView FILTER ANALYZER(phrase(d.name, "
@@ -2204,8 +2211,11 @@ TEST_F(IResearchFilterFunctionTest, Phrase) {
     irs::Or expected;
     auto& phrase = expected.add<irs::by_phrase>();
     phrase.field(mangleString("a.b.c.e[4].f[5].g[3].g.a", "test_analyzer"));
-    phrase.push_back("q").push_back("u").push_back("i").push_back("c").push_back(
-        "k");
+    phrase.push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("q"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("u"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("i"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("c"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("k"))});
 
     assertFilterSuccess(
         vocbase(),
@@ -2306,8 +2316,11 @@ TEST_F(IResearchFilterFunctionTest, Phrase) {
     irs::Or expected;
     auto& phrase = expected.add<irs::by_phrase>();
     phrase.field(mangleString("[42]", "test_analyzer"));
-    phrase.push_back("q").push_back("u").push_back("i").push_back("c").push_back(
-        "k");
+    phrase.push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("q"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("u"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("i"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("c"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("k"))});
 
     assertFilterSuccess(
         vocbase(),
@@ -2341,8 +2354,11 @@ TEST_F(IResearchFilterFunctionTest, Phrase) {
     irs::Or expected;
     auto& phrase = expected.add<irs::by_phrase>();
     phrase.field(mangleString("name", "test_analyzer"));
-    phrase.push_back("q").push_back("u").push_back("i").push_back("c").push_back(
-        "k");
+    phrase.push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("q"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("u"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("i"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("c"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("k"))});
 
     assertFilterSuccess(
         vocbase(),
@@ -2546,10 +2562,16 @@ TEST_F(IResearchFilterFunctionTest, Phrase) {
     irs::Or expected;
     auto& phrase = expected.add<irs::by_phrase>();
     phrase.field(mangleString("name", "test_analyzer"));
-    phrase.push_back("q").push_back("u").push_back("i").push_back("c").push_back(
-        "k");
-    phrase.push_back("b").push_back("r").push_back("o").push_back("w").push_back(
-        "n");
+    phrase.push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("q"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("u"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("i"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("c"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("k"))});
+    phrase.push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("b"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("r"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("o"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("w"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("n"))});
 
     assertFilterSuccess(
         vocbase(),
@@ -2657,10 +2679,17 @@ TEST_F(IResearchFilterFunctionTest, Phrase) {
     irs::Or expected;
     auto& phrase = expected.add<irs::by_phrase>();
     phrase.field(mangleString("name", "test_analyzer"));
-    phrase.push_back("q").push_back("u").push_back("i").push_back("c").push_back(
-      "k").push_back("0");
-    phrase.push_back("b").push_back("r").push_back("o").push_back("w").push_back(
-      "n");
+    phrase.push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("q"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("u"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("i"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("c"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("k"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("0"))});
+    phrase.push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("b"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("r"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("o"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("w"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("n"))});
     assertFilterSuccess(
         vocbase(),
         "FOR d IN myView FILTER AnaLYZER(phrase(d.name, [ 'quick', '0', "
@@ -2677,10 +2706,16 @@ TEST_F(IResearchFilterFunctionTest, Phrase) {
     irs::Or expected;
     auto& phrase = expected.add<irs::by_phrase>();
     phrase.field(mangleString("obj.name", "test_analyzer"));
-    phrase.push_back("q").push_back("u").push_back("i").push_back("c").push_back(
-        "k");
-    phrase.push_back("b", 5).push_back("r").push_back("o").push_back("w").push_back(
-        "n");
+    phrase.push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("q"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("u"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("i"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("c"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("k"))});
+    phrase.push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("b"))}, 5)
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("r"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("o"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("w"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("n"))});
 
     assertFilterSuccess(
         vocbase(),
@@ -2810,10 +2845,16 @@ TEST_F(IResearchFilterFunctionTest, Phrase) {
     irs::Or expected;
     auto& phrase = expected.add<irs::by_phrase>();
     phrase.field(mangleString("obj.name", "test_analyzer")).boost(3.0f);
-    phrase.push_back("q").push_back("u").push_back("i").push_back("c").push_back(
-        "k");
-    phrase.push_back("b", 5).push_back("r").push_back("o").push_back("w").push_back(
-        "n");
+    phrase.push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("q"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("u"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("i"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("c"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("k"))});
+    phrase.push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("b"))}, 5)
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("r"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("o"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("w"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("n"))});
 
     assertFilterSuccess(
         vocbase(),
@@ -2853,10 +2894,16 @@ TEST_F(IResearchFilterFunctionTest, Phrase) {
     irs::Or expected;
     auto& phrase = expected.add<irs::by_phrase>();
     phrase.field(mangleString("obj[3].name[1]", "test_analyzer"));
-    phrase.push_back("q").push_back("u").push_back("i").push_back("c").push_back(
-        "k");
-    phrase.push_back("b", 5).push_back("r").push_back("o").push_back("w").push_back(
-        "n");
+    phrase.push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("q"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("u"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("i"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("c"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("k"))});
+    phrase.push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("b"))}, 5)
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("r"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("o"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("w"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("n"))});
 
     assertFilterSuccess(
         vocbase(),
@@ -2986,10 +3033,16 @@ TEST_F(IResearchFilterFunctionTest, Phrase) {
     irs::Or expected;
     auto& phrase = expected.add<irs::by_phrase>();
     phrase.field(mangleString("[5].obj.name[100]", "test_analyzer"));
-    phrase.push_back("q").push_back("u").push_back("i").push_back("c").push_back(
-        "k");
-    phrase.push_back("b", 5).push_back("r").push_back("o").push_back("w").push_back(
-        "n");
+    phrase.push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("q"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("u"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("i"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("c"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("k"))});
+    phrase.push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("b"))}, 5)
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("r"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("o"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("w"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("n"))});
 
     assertFilterSuccess(
         vocbase(),
@@ -3119,13 +3172,24 @@ TEST_F(IResearchFilterFunctionTest, Phrase) {
     irs::Or expected;
     auto& phrase = expected.add<irs::by_phrase>();
     phrase.field(mangleString("obj.properties.id.name", "test_analyzer"));
-    phrase.push_back("q").push_back("u").push_back("i").push_back("c").push_back(
-        "k");
-    phrase.push_back("b", 3).push_back("r").push_back("o").push_back("w").push_back(
-        "n");
-    phrase.push_back("f", 2).push_back("o").push_back("x");
-    phrase.push_back("j").push_back("u").push_back("m").push_back("p").push_back(
-        "s");
+    phrase.push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("q"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("u"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("i"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("c"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("k"))});
+    phrase.push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("b"))}, 3)
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("r"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("o"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("w"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("n"))});
+    phrase.push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("f"))}, 2)
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("o"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("x"))});
+    phrase.push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("j"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("u"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("m"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("p"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("s"))});
 
     assertFilterSuccess(
         vocbase(),
@@ -3435,13 +3499,24 @@ TEST_F(IResearchFilterFunctionTest, Phrase) {
     irs::Or expected;
     auto& phrase = expected.add<irs::by_phrase>();
     phrase.field(mangleString("obj.properties.id.name", "test_analyzer"));
-    phrase.push_back("q").push_back("u").push_back("i").push_back("c").push_back(
-        "k");
-    phrase.push_back("b", 3).push_back("r").push_back("o").push_back("w").push_back(
-        "n");
-    phrase.push_back("f", 2).push_back("o").push_back("x");
-    phrase.push_back("j").push_back("u").push_back("m").push_back("p").push_back(
-        "s");
+    phrase.push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("q"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("u"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("i"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("c"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("k"))});
+    phrase.push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("b"))}, 3)
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("r"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("o"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("w"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("n"))});
+    phrase.push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("f"))}, 2)
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("o"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("x"))});
+    phrase.push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("j"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("u"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("m"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("p"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("s"))});
 
     ExpressionContextMock ctx;
     ctx.vars.emplace("offset", arangodb::aql::AqlValue(arangodb::aql::AqlValueHintInt(2)));
@@ -3599,13 +3674,24 @@ TEST_F(IResearchFilterFunctionTest, Phrase) {
     irs::Or expected;
     auto& phrase = expected.add<irs::by_phrase>();
     phrase.field(mangleString("obj.properties.id.name", "test_analyzer"));
-    phrase.push_back("q").push_back("u").push_back("i").push_back("c").push_back(
-      "k");
-    phrase.push_back("b", 3).push_back("r").push_back("o").push_back("w").push_back(
-      "n");
-    phrase.push_back("f").push_back("o").push_back("x");
-    phrase.push_back("j").push_back("u").push_back("m").push_back("p").push_back(
-      "s");
+    phrase.push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("q"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("u"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("i"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("c"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("k"))});
+    phrase.push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("b"))}, 3)
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("r"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("o"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("w"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("n"))});
+    phrase.push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("f"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("o"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("x"))});
+    phrase.push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("j"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("u"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("m"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("p"))})
+        .push_back(irs::by_phrase::simple_term{irs::ref_cast<irs::byte_type>(irs::string_ref("s"))});
 
     ExpressionContextMock ctx;
     ctx.vars.emplace("offset", arangodb::aql::AqlValue(arangodb::aql::AqlValueHintInt(2)));
@@ -3634,14 +3720,14 @@ TEST_F(IResearchFilterFunctionTest, Phrase) {
       vocbase(),
       "FOR d IN myView FILTER "
       "analyzer(phrase(d.obj.properties.id.name, ['quick'], 3, "
-      "'123', 'wn', 0, ['f', 'o', 'x'], 0, ['j', ['u'], 'mps']), 'test_analyzer') "
+      "'123', 'wn', 0, ['f', 'o', 'x'], 0, [['j', ['u'], 'mps']]), 'test_analyzer') "
       "RETURN d", &ctx);
 
     assertFilterFail(
       vocbase(),
       "FOR d IN myView FILTER "
       "analyzer(phrase(d.obj.properties.id.name, ['quick', 3, "
-      "'123', 'wn', 0, 'f', 'o', 'x', 0, ['j'], 'u', 'mps']), 'test_analyzer') "
+      "'123', 'wn', 0, 'f', 'o', 'x', 0, [['j']], 'u', 'mps']), 'test_analyzer') "
       "RETURN d", &ctx);
   }
 
@@ -5557,3 +5643,387 @@ TEST_F(IResearchFilterFunctionTest, inRange) {
       "FOR d IN myView FILTER in_range(d.name, 'abc', true, 'z', false, false) "
       "RETURN d");
 }
+
+TEST_F(IResearchFilterFunctionTest, ngramMatch) {
+  // NGRAM_MATCH with default analyzer default threshold
+  {
+    irs::Or expected;
+    expected.add<irs::by_ngram_similarity>().field(mangleStringIdentity("name"))
+      .threshold(0.7f)
+      .push_back("foo");
+
+    assertFilterSuccess(
+      vocbase(),
+      "FOR d IN myView FILTER NGRAM_MATCH(d.name, 'foo') RETURN d",
+      expected);
+    assertFilterSuccess(
+      vocbase(),
+      "FOR d IN myView FILTER NGRAM_match(d['name'], 'foo') RETURN d",
+      expected);
+  }
+
+  // NGRAM_MATCH with default analyzer default threshold value by var 
+  {
+    ExpressionContextMock ctx;
+    ctx.vars.emplace("strVal", arangodb::aql::AqlValue("foo"));
+
+    irs::Or expected;
+    expected.add<irs::by_ngram_similarity>().field(mangleStringIdentity("name"))
+      .threshold(0.7f)
+      .push_back("foo");
+
+    assertFilterSuccess(
+      vocbase(),
+      "LET strVal = 'foo' FOR d IN myView FILTER NGRAM_MATCH(d.name, strVal) RETURN d",
+      expected, &ctx);
+    assertFilterSuccess(
+      vocbase(),
+      "LET strVal = 'foo' FOR d IN myView FILTER NGRAM_match(d['name'], strVal) RETURN d",
+      expected, &ctx);
+  }
+
+  // NGRAM_MATCH with boost
+  {
+    irs::Or expected;
+    expected.add<irs::by_ngram_similarity>().field(mangleStringIdentity("name"))
+      .threshold(0.7f)
+      .push_back("foo").boost(1.5);
+
+    assertFilterSuccess(
+      vocbase(),
+      "FOR d IN myView FILTER BOOST(NGRAM_MATCH(d.name, 'foo'), 1.5) RETURN d",
+      expected);
+    assertFilterSuccess(
+      vocbase(),
+      "FOR d IN myView FILTER BOOST(NGRAM_match(d['name'], 'foo'), 1.5) RETURN d",
+      expected);
+  }
+
+  // NGRAM_MATCH with default analyzer explicit threshold
+  {
+    irs::Or expected;
+    expected.add<irs::by_ngram_similarity>().field(mangleStringIdentity("name"))
+      .threshold(0.8f)
+      .push_back("foo");
+
+    assertFilterSuccess(
+      vocbase(),
+      "FOR d IN myView FILTER NGRAM_MATCH(d.name, 'foo', 0.8) RETURN d",
+      expected);
+    assertFilterSuccess(
+      vocbase(),
+      "FOR d IN myView FILTER NGRAM_match(d['name'], 'foo', 0.8) RETURN d",
+      expected);
+  }
+
+  // NGRAM_MATCH with default analyzer explicit threshold via variable
+  {
+    ExpressionContextMock ctx;
+    ctx.vars.emplace("numVal", arangodb::aql::AqlValue(arangodb::aql::AqlValueHintDouble(0.8)));
+
+    irs::Or expected;
+    expected.add<irs::by_ngram_similarity>().field(mangleStringIdentity("name"))
+      .threshold(0.8f)
+      .push_back("foo");
+
+    assertFilterSuccess(
+      vocbase(),
+      "LET numVal = 0.8 FOR d IN myView FILTER NGRAM_MATCH(d.name, 'foo', numVal) RETURN d",
+      expected, &ctx);
+    assertFilterSuccess(
+      vocbase(),
+      "LET numVal = 0.8 FOR d IN myView FILTER NGRAM_match(d['name'], 'foo', numVal) RETURN d",
+      expected, &ctx);
+  }
+  // variables + function calls
+  {
+    irs::Or expected;
+    expected.add<irs::by_ngram_similarity>().field(mangleString("name.foo", "test_analyzer"))
+      .threshold(0.5)
+      .push_back("f").push_back("o").push_back("o").push_back("o");
+
+    ExpressionContextMock ctx;
+    ctx.vars.emplace("x", arangodb::aql::AqlValue(arangodb::aql::AqlValueHintDouble{ 0.5 }));
+    ctx.vars.emplace("y", arangodb::aql::AqlValue(arangodb::aql::AqlValue{ "o" }));
+    ctx.vars.emplace("idx", arangodb::aql::AqlValue("foo"));
+
+    assertFilterSuccess(
+      vocbase(),
+      "FOR d IN myView FILTER ANALYZER(NGRAM_MATCH(d.name[_FORWARD_('foo')], 'fooo', 0.5), 'test_analyzer') RETURN d",
+      expected, &ctx);
+    assertFilterSuccess(
+      vocbase(),
+      "LET y='o' LET idx='foo' LET x=0.5 FOR d IN myView FILTER ANALYZER(NGRAM_MATCH(d.name[idx], CONCAT('foo', y), x), 'test_analyzer') RETURN d",
+      expected,
+      &ctx);
+  }
+
+
+  // NGRAM_MATCH with explicit analyzer default threshold
+  {
+    irs::Or expected;
+    expected.add<irs::by_ngram_similarity>().field(mangleString("name", "test_analyzer"))
+      .threshold(0.7f)
+      .push_back("f").push_back("o").push_back("o");
+
+    assertFilterSuccess(
+      vocbase(),
+      "FOR d IN myView FILTER NGRAM_MATCH(d.name, 'foo', 'test_analyzer') RETURN d",
+      expected);
+    assertFilterSuccess(
+      vocbase(),
+      "FOR d IN myView FILTER NGRAM_match(d['name'], 'foo', 'test_analyzer') RETURN d",
+      expected);
+  }
+
+  // NGRAM_MATCH with explicit analyzer via ANALYZER default threshold
+  {
+    irs::Or expected;
+    expected.add<irs::by_ngram_similarity>().field(mangleString("name", "test_analyzer"))
+      .threshold(0.7f)
+      .push_back("f").push_back("o").push_back("o");
+
+    assertFilterSuccess(
+      vocbase(),
+      "FOR d IN myView FILTER ANALYZER(NGRAM_MATCH(d.name, 'foo'), 'test_analyzer') RETURN d",
+      expected);
+    assertFilterSuccess(
+      vocbase(),
+      "FOR d IN myView FILTER ANALYZER(NGRAM_match(d['name'], 'foo'), 'test_analyzer') RETURN d",
+      expected);
+  }
+
+  // NGRAM_MATCH with explicit analyzer explicit threshold
+  {
+    irs::Or expected;
+    expected.add<irs::by_ngram_similarity>().field(mangleString("name", "test_analyzer"))
+      .threshold(0.25f)
+      .push_back("f").push_back("o").push_back("o");
+
+    assertFilterSuccess(
+      vocbase(),
+      "FOR d IN myView FILTER NGRAM_MATCH(d.name, 'foo', 0.25, 'test_analyzer') RETURN d",
+      expected);
+    assertFilterSuccess(
+      vocbase(),
+      "FOR d IN myView FILTER NGRAM_match(d['name'], 'foo', 0.25, 'test_analyzer') RETURN d",
+      expected);
+  }
+
+  // NGRAM_MATCH with explicit analyzer via ANALYZER explicit threshold
+  {
+    irs::Or expected;
+    expected.add<irs::by_ngram_similarity>().field(mangleString("name", "test_analyzer"))
+      .threshold(0.25f)
+      .push_back("f").push_back("o").push_back("o");
+
+    assertFilterSuccess(
+      vocbase(),
+      "FOR d IN myView FILTER ANALYZER(NGRAM_MATCH(d.name, 'foo', 0.25), 'test_analyzer') RETURN d",
+      expected);
+    assertFilterSuccess(
+      vocbase(),
+      "FOR d IN myView FILTER ANALYZER(NGRAM_match(d['name'], 'foo', 0.25), 'test_analyzer') RETURN d",
+      expected);
+  }
+
+  // wrong number of arguments
+  assertFilterParseFail(
+    vocbase(),
+    "FOR d IN myView FILTER NGRAM_MATCH(d.name) RETURN d");
+  assertFilterParseFail(
+    vocbase(),
+    "FOR d IN myView FILTER NGRAM_MATCH(d['name']) RETURN d");
+  assertFilterParseFail(
+    vocbase(),
+    "FOR d IN myView FILTER NGRAM_MATCH(d['name'], 1, 2, 3, 4) RETURN d");
+
+  // invalid parameter order (overload with default analyzer)
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER NGRAM_MATCH(d.name, 0.5, 'foo') RETURN d");
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER NGRAM_MATCH(d['name'], 0.5, 'foo') RETURN d");
+
+  // invalid parameter order (overload with default threshold)
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER NGRAM_MATCH('foo', d.name, 'test_analyzer') RETURN d");
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER NGRAM_MATCH('foo', d['name'], 'test_analyzer') RETURN d");
+
+  // wrong first arg type
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER ANALYZER(NGRAM_MATCH(d[*], 'foo', 0.25), 'test_analyzer') RETURN d");
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER ANALYZER(NGRAM_MATCH('a', 'foo', 0.25), 'test_analyzer') RETURN d");
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER ANALYZER(NGRAM_match('a', 'foo', 0.25), 'test_analyzer') RETURN d");
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER ANALYZER(NGRAM_MATCH(1, 'foo', 0.25), 'test_analyzer') RETURN d");
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER ANALYZER(NGRAM_match(1, 'foo', 0.25), 'test_analyzer') RETURN d");
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER ANALYZER(NGRAM_MATCH(null, 'foo', 0.25), 'test_analyzer') RETURN d");
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER ANALYZER(NGRAM_match(null, 'foo', 0.25), 'test_analyzer') RETURN d");
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER ANALYZER(NGRAM_MATCH(['a'], 'foo', 0.25), 'test_analyzer') RETURN d");
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER ANALYZER(NGRAM_match(['a'], 'foo', 0.25), 'test_analyzer') RETURN d");
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER ANALYZER(NGRAM_MATCH({a:1}, 'foo', 0.25), 'test_analyzer') RETURN d");
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER ANALYZER(NGRAM_match({a:1}, 'foo', 0.25), 'test_analyzer') RETURN d");
+
+  // wrong second arg type
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER NGRAM_MATCH(d.name, 0.5) RETURN d");
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER NGRAM_MATCH(d['name'], 0.5) RETURN d");
+
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER NGRAM_MATCH(d.name, [1, 2]) RETURN d");
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER NGRAM_MATCH(d['name'], [1, 2]) RETURN d");
+
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER NGRAM_MATCH(d.name, {a: 1 }) RETURN d");
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER NGRAM_MATCH(d['name'], {a: 1 }) RETURN d");
+
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER NGRAM_MATCH(d.name, true) RETURN d");
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER NGRAM_MATCH(d['name'], true) RETURN d");
+
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER NGRAM_MATCH(d.name, null) RETURN d");
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER NGRAM_MATCH(d['name'], null) RETURN d");
+
+  // wrong third argument type (may be only string or double)
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER NGRAM_MATCH(d.name, 'abc', null) RETURN d");
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER NGRAM_MATCH(d['name'], 'abc', null) RETURN d");
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER NGRAM_MATCH(d.name, 'abc', true) RETURN d");
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER NGRAM_MATCH(d['name'], 'abc', true) RETURN d");
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER NGRAM_MATCH(d.name, 'abc', [1, 2]) RETURN d");
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER NGRAM_MATCH(d['name'], 'abc', [1, 2]) RETURN d");
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER NGRAM_MATCH(d.name, 'abc', {a:1}) RETURN d");
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER NGRAM_MATCH(d['name'], 'abc', {a:1}) RETURN d");
+
+  // invalid threshold value
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER NGRAM_MATCH(d.name, 'abc', 1.1) RETURN d");
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER NGRAM_MATCH(d['name'], 'abc', 1.1) RETURN d");
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER NGRAM_MATCH(d.name, 'abc', 0) RETURN d");
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER NGRAM_MATCH(d['name'], 'abc', 0) RETURN d");
+
+  // invalid analyzer arg type
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER NGRAM_MATCH(d.name, 'abc', 0.5, true) RETURN d");
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER NGRAM_MATCH(d['name'], 'abc', 0.5, true) RETURN d");
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER NGRAM_MATCH(d.name, 'abc', 0.5, null) RETURN d");
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER NGRAM_MATCH(d['name'], 'abc', 0.5, null) RETURN d");
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER NGRAM_MATCH(d.name, 'abc', 0.5, 0.5) RETURN d");
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER NGRAM_MATCH(d['name'], 'abc', 0.5, 0.5) RETURN d");
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER NGRAM_MATCH(d.name, 'abc', 0.5, [1, 2]) RETURN d");
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER NGRAM_MATCH(d['name'], 'abc', 0.5, [1,2]) RETURN d");
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER NGRAM_MATCH(d.name, 'abc', 0.5, {a:1}) RETURN d");
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER NGRAM_MATCH(d['name'], 'abc', 0.5, {a:1}) RETURN d");
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER NGRAM_MATCH(d['name'], 'abc', 'test_analyzer', 'test_analyzer') RETURN d");
+
+  // non-deterministic arg
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER NGRAM_MATCH(RAND() ? d.pui : d.name, 'def') RETURN d");
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER NGRAM_MATCH(RAND() ? d['pui'] : d['name'], 'def') RETURN d");
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER NGRAM_MATCH(d.name, RAND() ? 'abc' : 'def') RETURN d");
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER NGRAM_MATCH(d['name'], RAND() ? 'abc' : 'def') RETURN d");
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER NGRAM_MATCH(d.name, 'abc',  RAND() ? 0.5 : 0.6) RETURN d");
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER NGRAM_MATCH(d['name'], 'abc',  RAND() ? 0.5 : 0.6) RETURN d");
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER NGRAM_MATCH(d.name, 'abc', 0.5,  RAND() ? 'identity' : 'test_analyzer') RETURN d");
+  assertFilterFail(
+    vocbase(),
+    "FOR d IN myView FILTER NGRAM_MATCH(d['name'], 'abc', 0.5, RAND() ? 'identity' : 'test_analyzer') RETURN d");
+  
+}
diff --git a/tests/IResearch/IResearchQueryNGramMatch-test.cpp b/tests/IResearch/IResearchQueryNGramMatch-test.cpp
new file mode 100644
index 000000000000..9aea757b2e31
--- /dev/null
+++ b/tests/IResearch/IResearchQueryNGramMatch-test.cpp
@@ -0,0 +1,1160 @@
+////////////////////////////////////////////////////////////////////////////////
+/// DISCLAIMER
+///
+/// Copyright 2020 ArangoDB GmbH, Cologne, Germany
+///
+/// Licensed under the Apache License, Version 2.0 (the "License");
+/// you may not use this file except in compliance with the License.
+/// You may obtain a copy of the License at
+///
+///     http://www.apache.org/licenses/LICENSE-2.0
+///
+/// Unless required by applicable law or agreed to in writing, software
+/// distributed under the License is distributed on an "AS IS" BASIS,
+/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+/// See the License for the specific language governing permissions and
+/// limitations under the License.
+///
+/// Copyright holder is ArangoDB GmbH, Cologne, Germany
+///
+/// @author Andrei Lobov
+////////////////////////////////////////////////////////////////////////////////
+
+#include "IResearchQueryCommon.h"
+
+#include "IResearch/IResearchView.h"
+#include "Transaction/StandaloneContext.h"
+#include "Utils/OperationOptions.h"
+#include "Utils/SingleCollectionTransaction.h"
+#include "VocBase/LogicalCollection.h"
+
+#include <velocypack/Iterator.h>
+
+extern const char* ARGV0;  // defined in main.cpp
+
+namespace {
+
+static const VPackBuilder systemDatabaseBuilder = dbArgsBuilder();
+static const VPackSlice   systemDatabaseArgs = systemDatabaseBuilder.slice();
+// -----------------------------------------------------------------------------
+// --SECTION--                                                 setup / tear-down
+// -----------------------------------------------------------------------------
+
+class IResearchQueryNGramMatchTest : public IResearchQueryTest {};
+
+}  // namespace
+
+// -----------------------------------------------------------------------------
+// --SECTION--                                                        test suite
+// -----------------------------------------------------------------------------
+
+TEST_F(IResearchQueryNGramMatchTest, SysVocbase) {
+  std::vector<arangodb::velocypack::Builder> insertedDocs;
+  arangodb::LogicalView* view;
+
+  auto& sysVocBaseFeature = server.getFeature<arangodb::SystemDatabaseFeature>();
+
+  auto sysVocBasePtr = sysVocBaseFeature.use();
+  auto& vocbase = *sysVocBasePtr;
+
+  // 2-gram analyzer
+  {
+
+    auto& analyzers = server.getFeature<arangodb::iresearch::IResearchAnalyzerFeature>();
+    arangodb::iresearch::IResearchAnalyzerFeature::EmplaceResult result;
+
+    auto res =
+      analyzers.emplace(result, "_system::myngram", "ngram",
+        VPackParser::fromJson("{\"min\":2, \"max\":2, \"streamType\":\"utf8\", \"preserveOriginal\":false}")->slice(),
+        irs::flags{ irs::frequency::type(), irs::position::type() }  // required for PHRASE
+    );  // cache analyzer
+    EXPECT_TRUE(res.ok());
+  }
+
+  // create collection0
+  {
+    auto createJson = arangodb::velocypack::Parser::fromJson(
+        "{ \"name\": \"testCollection0\" }");
+    auto collection = vocbase.createCollection(createJson->slice());
+    ASSERT_NE(nullptr, collection);
+
+    std::vector<std::shared_ptr<arangodb::velocypack::Builder>> docs{
+        arangodb::velocypack::Parser::fromJson(
+            "{ \"seq\": -6, \"value\": \"Jack Daniels\" }"),
+        arangodb::velocypack::Parser::fromJson(
+            "{ \"seq\": -5, \"value\": \"Jack Sparrow\" }"),
+        arangodb::velocypack::Parser::fromJson(
+            "{ \"seq\": -4, \"value\": \"Daniel Sorano\" }"),
+        arangodb::velocypack::Parser::fromJson(
+            "{ \"seq\": -3, \"value\": \"Sinderella\" }"),
+        arangodb::velocypack::Parser::fromJson(
+            "{ \"seq\": -2, \"value\": \"Jack the Ripper\" }"),
+        arangodb::velocypack::Parser::fromJson(
+            "{ \"seq\": -1, \"value\": \"Jack Rabbit\" }"),
+    };
+
+    arangodb::OperationOptions options;
+    options.returnNew = true;
+    arangodb::SingleCollectionTransaction trx(arangodb::transaction::StandaloneContext::Create(vocbase),
+                                              *collection,
+                                              arangodb::AccessMode::Type::WRITE);
+    EXPECT_TRUE(trx.begin().ok());
+
+    for (auto& entry : docs) {
+      auto res = trx.insert(collection->name(), entry->slice(), options);
+      EXPECT_TRUE(res.ok());
+      insertedDocs.emplace_back(res.slice().get("new"));
+    }
+
+    EXPECT_TRUE(trx.commit().ok());
+  }
+
+  // create view
+  {
+    auto createJson = arangodb::velocypack::Parser::fromJson(
+        "{ \"name\": \"testView\", \"type\": \"arangosearch\" }");
+    auto logicalView = vocbase.createView(createJson->slice());
+    ASSERT_FALSE(!logicalView);
+
+    view = logicalView.get();
+    auto* impl = dynamic_cast<arangodb::iresearch::IResearchView*>(view);
+    ASSERT_FALSE(!impl);
+
+    auto updateJson = arangodb::velocypack::Parser::fromJson(
+        "{ \"links\": {"
+        "\"testCollection0\": { \"analyzers\": [ \"::myngram\", "
+        "\"identity\" ], \"includeAllFields\": true, \"trackListPositions\": "
+        "true }}}");
+    EXPECT_TRUE(impl->properties(updateJson->slice(), true).ok());
+    std::set<TRI_voc_cid_t> cids;
+    impl->visitCollections([&cids](TRI_voc_cid_t cid) -> bool {
+      cids.emplace(cid);
+      return true;
+    });
+    EXPECT_EQ(1, cids.size());
+    EXPECT_TRUE(
+        (arangodb::tests::executeQuery(vocbase,
+                                       "FOR d IN testView SEARCH 1 ==1 OPTIONS "
+                                       "{ waitForSync: true } RETURN d")
+             .result.ok()));  // commit
+  }
+
+  // test missing field
+  {
+    std::vector<arangodb::velocypack::Slice> expected = {};
+    auto result = arangodb::tests::executeQuery(
+        vocbase,
+        "FOR d IN testView SEARCH NGRAM_MATCH(d.missing, 'abc', 0.5, 'myngram') SORT BM25(d) ASC, "
+        "TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.ok());
+    auto slice = result.data->slice();
+    EXPECT_TRUE(slice.isArray());
+    size_t i = 0;
+
+    for (arangodb::velocypack::ArrayIterator itr(slice); itr.valid(); ++itr) {
+      auto const resolved = itr.value().resolveExternals();
+      EXPECT_TRUE(i < expected.size());
+      EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
+                                                                    resolved, true)));
+    }
+
+    EXPECT_EQ(i, expected.size());
+  }
+
+  // test missing field via []
+  {
+    std::vector<arangodb::velocypack::Slice> expected = {};
+    auto result = arangodb::tests::executeQuery(
+        vocbase,
+        "FOR d IN testView SEARCH NGRAM_MATCH(d['missing'], 'abc', 0.5, 'myngram') SORT BM25(d) "
+        "ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.ok());
+    auto slice = result.data->slice();
+    EXPECT_TRUE(slice.isArray());
+    size_t i = 0;
+
+    for (arangodb::velocypack::ArrayIterator itr(slice); itr.valid(); ++itr) {
+      auto const resolved = itr.value().resolveExternals();
+      EXPECT_TRUE(i < expected.size());
+      EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
+                                                                    resolved, true)));
+    }
+
+    EXPECT_EQ(i, expected.size());
+  }
+
+  // test invalid column type
+  {
+    std::vector<arangodb::velocypack::Slice> expected = {};
+    auto result = arangodb::tests::executeQuery(
+        vocbase,
+        "FOR d IN testView SEARCH NGRAM_MATCH(d.seq, '0', 0.5, 'myngram') SORT BM25(d) ASC, "
+        "TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.ok());
+    auto slice = result.data->slice();
+    EXPECT_TRUE(slice.isArray());
+    size_t i = 0;
+
+    for (arangodb::velocypack::ArrayIterator itr(slice); itr.valid(); ++itr) {
+      auto const resolved = itr.value().resolveExternals();
+      EXPECT_TRUE(i < expected.size());
+      EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
+                                                                    resolved, true)));
+    }
+
+    EXPECT_EQ(i, expected.size());
+  }
+
+  // test invalid column type via []
+  {
+    std::vector<arangodb::velocypack::Slice> expected = {};
+    auto result = arangodb::tests::executeQuery(
+        vocbase,
+        "FOR d IN testView SEARCH NGRAM_MATCH(d['seq'], '0', 0.5, 'myngram') SORT BM25(d) ASC, "
+        "TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.ok());
+    auto slice = result.data->slice();
+    EXPECT_TRUE(slice.isArray());
+    size_t i = 0;
+
+    for (arangodb::velocypack::ArrayIterator itr(slice); itr.valid(); ++itr) {
+      auto const resolved = itr.value().resolveExternals();
+      EXPECT_TRUE(i < expected.size());
+      EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
+                                                                    resolved, true)));
+    }
+
+    EXPECT_EQ(i, expected.size());
+  }
+
+  // test invalid input type (array)
+  {
+    auto result = arangodb::tests::executeQuery(
+        vocbase,
+        "FOR d IN testView SEARCH NGRAM_MATCH(d.value, [ 1, \"abc\" ], 0.5, 'myngram') SORT BM25(d) "
+        "ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid input type (array) via []
+  {
+    auto result = arangodb::tests::executeQuery(
+        vocbase,
+        "FOR d IN testView SEARCH NGRAM_MATCH(d['value'], [ 1, \"abc\" ], 0.5, 'myngram') SORT "
+        "BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid input type (boolean)
+  {
+    auto result = arangodb::tests::executeQuery(
+        vocbase,
+        "FOR d IN testView SEARCH NGRAM_MATCH(d.value, true, 0.5, 'myngram') SORT BM25(d) ASC, "
+        "TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid input type (boolean) via []
+  {
+    auto result = arangodb::tests::executeQuery(
+        vocbase,
+        "FOR d IN testView SEARCH NGRAM_MATCH(d['value'], false, 0.5, 'myngram') SORT BM25(d) ASC, "
+        "TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid input type (null)
+  {
+    auto result = arangodb::tests::executeQuery(
+        vocbase,
+        "FOR d IN testView SEARCH NGRAM_MATCH(d.value, null, 0.5, 'myngram') SORT BM25(d) ASC, "
+        "TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid input type (null) via []
+  {
+    auto result = arangodb::tests::executeQuery(
+        vocbase,
+        "FOR d IN testView SEARCH NGRAM_MATCH(d['value'], null, 0.5, 'myngram') SORT BM25(d) ASC, "
+        "TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid input type (numeric)
+  {
+    auto result = arangodb::tests::executeQuery(
+        vocbase,
+        "FOR d IN testView SEARCH NGRAM_MATCH(d.value, 3.14, 0.5, 'myngram') SORT BM25(d) ASC, "
+        "TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid input type (numeric) via []
+  {
+    auto result = arangodb::tests::executeQuery(
+        vocbase,
+        "FOR d IN testView SEARCH NGRAM_MATCH(d['value'], 1234, 0.5, 'myngram') SORT BM25(d) ASC, "
+        "TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid input type (object)
+  {
+    auto result = arangodb::tests::executeQuery(
+        vocbase,
+        "FOR d IN testView SEARCH NGRAM_MATCH(d.value, { \"a\": 7, \"b\": \"c\" }, 0.5, 'myngram') "
+        "SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid input type (object) via []
+  {
+    auto result = arangodb::tests::executeQuery(
+        vocbase,
+        "FOR d IN testView SEARCH NGRAM_MATCH(d['value'], { \"a\": 7, \"b\": \"c\" "
+        "}, 0.5, 'myngram') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test missing value
+  {
+    auto result = arangodb::tests::executeQuery(
+        vocbase,
+        "FOR d IN testView SEARCH NGRAM_MATCH(d.value) SORT BM25(d) ASC, TFIDF(d) "
+        "DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_QUERY_FUNCTION_ARGUMENT_NUMBER_MISMATCH));
+  }
+
+  // test too much args
+  {
+    auto result = arangodb::tests::executeQuery(
+        vocbase,
+        "FOR d IN testView SEARCH NGRAM_MATCH(d['value'], 'test', 0.5, 'analyzer', 'too much') SORT BM25(d) ASC, "
+        "TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_QUERY_FUNCTION_ARGUMENT_NUMBER_MISMATCH));
+  }
+
+  // test invalid threshold type (array)
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH NGRAM_MATCH(d.duplicated, 'z', [ 1, "
+      "\"abc\" ]) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid threshold type (string)
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH NGRAM_MATCH(d.duplicated, 'z', '123') "
+      " SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid threshold type (object)
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH NGRAM_MATCH(d.duplicated, 'z', { \"a\": "
+      "7, \"b\": \"c\" }) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid threshold type (null)
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH NGRAM_MATCH(d.duplicated, 'z', null) "
+      " SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+
+  // test invalid threshold value (> 1)
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH NGRAM_MATCH(d.duplicated, 'z', 1.1) "
+      " SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid threshold value (0)
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH NGRAM_MATCH(d.duplicated, 'z', 0) "
+      " SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid analyzer type (array)
+  {
+    auto result = arangodb::tests::executeQuery(
+        vocbase,
+        "FOR d IN testView SEARCH NGRAM_MATCH(d.duplicated, 'z', 0.5, [ 1, "
+        "\"abc\" ]) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid analyzer type (boolean)
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH NGRAM_MATCH(d.duplicated, 'z', 0.5, true) "
+      " SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid analyzer type (null)
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH NGRAM_MATCH(d.duplicated, 'z', 0.5, null) "
+      " SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid analyzer type (numeric)
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH NGRAM_MATCH(d.duplicated, 'z', 0.5, 5) "
+      " SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid analyzer type (object)
+  {
+    auto result = arangodb::tests::executeQuery(
+        vocbase,
+        "FOR d IN testView SEARCH NGRAM_MATCH(d.duplicated, 'z', 0.5, { \"a\": "
+        "7, \"b\": \"c\" }) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test undefined analyzer
+  {
+    auto result = arangodb::tests::executeQuery(
+        vocbase,
+        "FOR d IN testView SEARCH NGRAM_MATCH(d.duplicated, 'z', "
+        "'invalid_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // can't access to local analyzer in other database
+  {
+    auto result = arangodb::tests::executeQuery(
+        vocbase,
+        "FOR d IN testView SEARCH NGRAM_MATCH(d.duplicated, 'z', "
+        "'testVocbase::test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq "
+        "RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test via ANALYZER function
+  {
+    std::vector<arangodb::velocypack::Slice> expected = {
+        insertedDocs[0].slice()
+    };
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH ANALYZER(NGRAM_mATCH(d.value, 'Jack Daniels', 0.7), "
+      "'myngram') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.ok());
+    auto slice = result.data->slice();
+    EXPECT_TRUE(slice.isArray());
+    size_t i = 0;
+
+    for (arangodb::velocypack::ArrayIterator itr(slice); itr.valid(); ++itr) {
+      auto const resolved = itr.value().resolveExternals();
+      EXPECT_TRUE(i < expected.size());
+      EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
+        resolved, true)));
+    }
+    EXPECT_EQ(i, expected.size());
+  }
+
+
+  // test via analyzer parameter
+  {
+    std::vector<arangodb::velocypack::Slice> expected = {
+        insertedDocs[0].slice()
+    };
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH nGrAm_MaTcH(d.value, 'Jack Daniels', 0.7, "
+      "'myngram') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.ok());
+    auto slice = result.data->slice();
+    EXPECT_TRUE(slice.isArray());
+    size_t i = 0;
+
+    for (arangodb::velocypack::ArrayIterator itr(slice); itr.valid(); ++itr) {
+      auto const resolved = itr.value().resolveExternals();
+      EXPECT_TRUE(i < expected.size());
+      EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
+        resolved, true)));
+    }
+    EXPECT_EQ(i, expected.size());
+  }
+
+
+  // test via analyzer parameter
+  {
+    std::vector<arangodb::velocypack::Slice> expected = {
+        insertedDocs[1].slice()
+    };
+    // Searching for Jack Arrow and we have Jack Sparrow which will be matched
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH nGrAm_MaTcH(d.value, 'Jack Arrow', 0.5, "
+      "'myngram') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.ok());
+    auto slice = result.data->slice();
+    EXPECT_TRUE(slice.isArray());
+    size_t i = 0;
+
+    for (arangodb::velocypack::ArrayIterator itr(slice); itr.valid(); ++itr) {
+      auto const resolved = itr.value().resolveExternals();
+      EXPECT_TRUE(i < expected.size());
+      EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
+        resolved, true)));
+    }
+    EXPECT_EQ(i, expected.size());
+  }
+
+  // test via analyzer parameter
+  {
+    std::vector<arangodb::velocypack::Slice> expected = {
+        insertedDocs[0].slice(),
+        insertedDocs[4].slice(),
+        insertedDocs[5].slice(),
+        insertedDocs[1].slice()
+    };
+    // Searching for Jack Arrow and set low threshold to match all Jack`s
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH nGrAm_MaTcH(d.value, 'Jack Arrow', 0.2, "
+      "'myngram') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.ok());
+    auto slice = result.data->slice();
+    EXPECT_TRUE(slice.isArray());
+    size_t i = 0;
+
+    for (arangodb::velocypack::ArrayIterator itr(slice); itr.valid(); ++itr) {
+      auto const resolved = itr.value().resolveExternals();
+      EXPECT_TRUE(i < expected.size());
+      EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
+        resolved, true)));
+    }
+    EXPECT_EQ(i, expected.size());
+  }
+
+  // test via default analyzer
+  {
+    std::vector<arangodb::velocypack::Slice> expected = {
+      // no results  will be found as identity analyzer has no positions        
+    };
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH nGrAm_MaTcH(d.value, 'Jack Daniels', 1) "
+      "SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.ok());
+    auto slice = result.data->slice();
+    EXPECT_TRUE(slice.isArray());
+    size_t i = 0;
+
+    for (arangodb::velocypack::ArrayIterator itr(slice); itr.valid(); ++itr) {
+      auto const resolved = itr.value().resolveExternals();
+      EXPECT_TRUE(i < expected.size());
+      EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
+        resolved, true)));
+    }
+    EXPECT_EQ(i, expected.size());
+  }
+
+}
+
+TEST_F(IResearchQueryNGramMatchTest, test) {
+  TRI_vocbase_t vocbase(TRI_vocbase_type_e::TRI_VOCBASE_TYPE_NORMAL, testDBInfo(server.server()));
+  std::vector<arangodb::velocypack::Builder> insertedDocs;
+  arangodb::LogicalView* view;
+
+  // 2-gram analyzer
+  {
+
+    auto& analyzers = server.getFeature<arangodb::iresearch::IResearchAnalyzerFeature>();
+    arangodb::iresearch::IResearchAnalyzerFeature::EmplaceResult result;
+
+    auto res =
+      analyzers.emplace(result, "testVocbase::myngram", "ngram",
+        VPackParser::fromJson("{\"min\":2, \"max\":2, \"streamType\":\"utf8\", \"preserveOriginal\":false}")->slice(),
+        irs::flags{ irs::frequency::type(), irs::position::type() }  // required for PHRASE
+    );  // cache analyzer
+    EXPECT_TRUE(res.ok());
+  }
+  {
+    // 2-gram analyzer in another DB
+    {
+
+      auto& analyzers = server.getFeature<arangodb::iresearch::IResearchAnalyzerFeature>();
+      arangodb::iresearch::IResearchAnalyzerFeature::EmplaceResult result;
+
+      TRI_vocbase_t* vocbase2;
+      auto& dbFeature = server.getFeature<arangodb::DatabaseFeature>();
+      dbFeature.createDatabase(testDBInfo(server.server(), "testVocbase2"), vocbase2); 
+      std::shared_ptr<arangodb::LogicalCollection> unused;
+      ASSERT_NE(nullptr, vocbase2);
+      arangodb::methods::Collections::createSystem(*vocbase2, arangodb::tests::AnalyzerCollectionName,
+        false, unused);
+
+      auto res =
+        analyzers.emplace(result, "testVocbase2::myngram", "ngram",
+          VPackParser::fromJson("{\"min\":2, \"max\":2, \"streamType\":\"utf8\", \"preserveOriginal\":false}")->slice(),
+          irs::flags{ irs::frequency::type(), irs::position::type() } 
+      );  // cache analyzer
+      EXPECT_TRUE(res.ok());
+    }
+  }
+
+  // create collection0
+  {
+    auto createJson = arangodb::velocypack::Parser::fromJson(
+      "{ \"name\": \"testCollection0\" }");
+    auto collection = vocbase.createCollection(createJson->slice());
+    ASSERT_NE(nullptr, collection);
+
+    std::vector<std::shared_ptr<arangodb::velocypack::Builder>> docs{
+        arangodb::velocypack::Parser::fromJson(
+            "{ \"seq\": -6, \"value\": \"Jack Daniels\" }"),
+        arangodb::velocypack::Parser::fromJson(
+            "{ \"seq\": -5, \"value\": \"Jack Sparrow\" }"),
+        arangodb::velocypack::Parser::fromJson(
+            "{ \"seq\": -4, \"value\": \"Daniel Sorano\" }"),
+        arangodb::velocypack::Parser::fromJson(
+            "{ \"seq\": -3, \"value\": \"Sinderella\" }"),
+        arangodb::velocypack::Parser::fromJson(
+            "{ \"seq\": -2, \"value\": \"Jack the Ripper\" }"),
+        arangodb::velocypack::Parser::fromJson(
+            "{ \"seq\": -1, \"value\": \"Jack Rabbit\" }"),
+    };
+
+    arangodb::OperationOptions options;
+    options.returnNew = true;
+    arangodb::SingleCollectionTransaction trx(arangodb::transaction::StandaloneContext::Create(vocbase),
+      *collection,
+      arangodb::AccessMode::Type::WRITE);
+    EXPECT_TRUE(trx.begin().ok());
+
+    for (auto& entry : docs) {
+      auto res = trx.insert(collection->name(), entry->slice(), options);
+      EXPECT_TRUE(res.ok());
+      insertedDocs.emplace_back(res.slice().get("new"));
+    }
+
+    EXPECT_TRUE(trx.commit().ok());
+  }
+
+  // create view
+  {
+    auto createJson = arangodb::velocypack::Parser::fromJson(
+      "{ \"name\": \"testView\", \"type\": \"arangosearch\" }");
+    auto logicalView = vocbase.createView(createJson->slice());
+    ASSERT_FALSE(!logicalView);
+
+    view = logicalView.get();
+    auto* impl = dynamic_cast<arangodb::iresearch::IResearchView*>(view);
+    ASSERT_FALSE(!impl);
+
+    auto updateJson = arangodb::velocypack::Parser::fromJson(
+      "{ \"links\": {"
+      "\"testCollection0\": { \"analyzers\": [ \"myngram\", "
+      "\"identity\" ], \"includeAllFields\": true, \"trackListPositions\": "
+      "true }}}");
+    EXPECT_TRUE(impl->properties(updateJson->slice(), true).ok());
+    std::set<TRI_voc_cid_t> cids;
+    impl->visitCollections([&cids](TRI_voc_cid_t cid) -> bool {
+      cids.emplace(cid);
+      return true;
+      });
+    EXPECT_EQ(1, cids.size());
+    EXPECT_TRUE(
+      (arangodb::tests::executeQuery(vocbase,
+        "FOR d IN testView SEARCH 1 ==1 OPTIONS "
+        "{ waitForSync: true } RETURN d")
+        .result.ok()));  // commit
+  }
+
+  // test missing field
+  {
+    std::vector<arangodb::velocypack::Slice> expected = {};
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH NGRAM_MATCH(d.missing, 'abc', 0.5, 'myngram') SORT BM25(d) ASC, "
+      "TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.ok());
+    auto slice = result.data->slice();
+    EXPECT_TRUE(slice.isArray());
+    size_t i = 0;
+
+    for (arangodb::velocypack::ArrayIterator itr(slice); itr.valid(); ++itr) {
+      auto const resolved = itr.value().resolveExternals();
+      EXPECT_TRUE(i < expected.size());
+      EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
+        resolved, true)));
+    }
+
+    EXPECT_EQ(i, expected.size());
+  }
+
+  // test missing field via []
+  {
+    std::vector<arangodb::velocypack::Slice> expected = {};
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH NGRAM_MATCH(d['missing'], 'abc', 0.5, 'myngram') SORT BM25(d) "
+      "ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.ok());
+    auto slice = result.data->slice();
+    EXPECT_TRUE(slice.isArray());
+    size_t i = 0;
+
+    for (arangodb::velocypack::ArrayIterator itr(slice); itr.valid(); ++itr) {
+      auto const resolved = itr.value().resolveExternals();
+      EXPECT_TRUE(i < expected.size());
+      EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
+        resolved, true)));
+    }
+
+    EXPECT_EQ(i, expected.size());
+  }
+
+  // test invalid column type
+  {
+    std::vector<arangodb::velocypack::Slice> expected = {};
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH NGRAM_MATCH(d.seq, '0', 0.5, 'myngram') SORT BM25(d) ASC, "
+      "TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.ok());
+    auto slice = result.data->slice();
+    EXPECT_TRUE(slice.isArray());
+    size_t i = 0;
+
+    for (arangodb::velocypack::ArrayIterator itr(slice); itr.valid(); ++itr) {
+      auto const resolved = itr.value().resolveExternals();
+      EXPECT_TRUE(i < expected.size());
+      EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
+        resolved, true)));
+    }
+
+    EXPECT_EQ(i, expected.size());
+  }
+
+  // test invalid column type via []
+  {
+    std::vector<arangodb::velocypack::Slice> expected = {};
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH NGRAM_MATCH(d['seq'], '0', 0.5, 'myngram') SORT BM25(d) ASC, "
+      "TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.ok());
+    auto slice = result.data->slice();
+    EXPECT_TRUE(slice.isArray());
+    size_t i = 0;
+
+    for (arangodb::velocypack::ArrayIterator itr(slice); itr.valid(); ++itr) {
+      auto const resolved = itr.value().resolveExternals();
+      EXPECT_TRUE(i < expected.size());
+      EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
+        resolved, true)));
+    }
+
+    EXPECT_EQ(i, expected.size());
+  }
+
+  // test invalid input type (array)
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH NGRAM_MATCH(d.value, [ 1, \"abc\" ], 0.5, 'myngram') SORT BM25(d) "
+      "ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid input type (array) via []
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH NGRAM_MATCH(d['value'], [ 1, \"abc\" ], 0.5, 'myngram') SORT "
+      "BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid input type (boolean)
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH NGRAM_MATCH(d.value, true, 0.5, 'myngram') SORT BM25(d) ASC, "
+      "TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid input type (boolean) via []
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH NGRAM_MATCH(d['value'], false, 0.5, 'myngram') SORT BM25(d) ASC, "
+      "TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid input type (null)
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH NGRAM_MATCH(d.value, null, 0.5, 'myngram') SORT BM25(d) ASC, "
+      "TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid input type (null) via []
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH NGRAM_MATCH(d['value'], null, 0.5, 'myngram') SORT BM25(d) ASC, "
+      "TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid input type (numeric)
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH NGRAM_MATCH(d.value, 3.14, 0.5, 'myngram') SORT BM25(d) ASC, "
+      "TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid input type (numeric) via []
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH NGRAM_MATCH(d['value'], 1234, 0.5, 'myngram') SORT BM25(d) ASC, "
+      "TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid input type (object)
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH NGRAM_MATCH(d.value, { \"a\": 7, \"b\": \"c\" }, 0.5, 'myngram') "
+      "SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid input type (object) via []
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH NGRAM_MATCH(d['value'], { \"a\": 7, \"b\": \"c\" "
+      "}, 0.5, 'myngram') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test missing value
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH NGRAM_MATCH(d.value) SORT BM25(d) ASC, TFIDF(d) "
+      "DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_QUERY_FUNCTION_ARGUMENT_NUMBER_MISMATCH));
+  }
+
+  // test missing value via []
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH NGRAM_MATCH(d['value']) SORT BM25(d) ASC, "
+      "TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_QUERY_FUNCTION_ARGUMENT_NUMBER_MISMATCH));
+  }
+
+  // test too much args
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH NGRAM_MATCH(d.value, 'abs', 0.5, 'identity', 'too much') SORT BM25(d) ASC, TFIDF(d) "
+      "DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_QUERY_FUNCTION_ARGUMENT_NUMBER_MISMATCH));
+  }
+
+  // test invalid threshold type (array)
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH NGRAM_MATCH(d.duplicated, 'z', [ 1, "
+      "\"abc\" ]) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid threshold type (string)
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH NGRAM_MATCH(d.duplicated, 'z', '123') "
+      " SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid threshold type (object)
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH NGRAM_MATCH(d.duplicated, 'z', { \"a\": "
+      "7, \"b\": \"c\" }) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid threshold type (null)
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH NGRAM_MATCH(d.duplicated, 'z', null) "
+      " SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+
+  // test invalid threshold value (> 1)
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH NGRAM_MATCH(d.duplicated, 'z', 1.1) "
+      " SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid threshold value (0)
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH NGRAM_MATCH(d.duplicated, 'z', 0) "
+      " SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid analyzer type (array)
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH NGRAM_MATCH(d.duplicated, 'z', 0.5, [ 1, "
+      "\"abc\" ]) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid analyzer type (boolean)
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH NGRAM_MATCH(d.duplicated, 'z', 0.5, true) "
+      " SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid analyzer type (null)
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH NGRAM_MATCH(d.duplicated, 'z', 0.5, null) "
+      " SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid analyzer type (numeric)
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH NGRAM_MATCH(d.duplicated, 'z', 0.5, 5) "
+      " SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid analyzer type (object)
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH NGRAM_MATCH(d.duplicated, 'z', 0.5, { \"a\": "
+      "7, \"b\": \"c\" }) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test undefined analyzer
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH NGRAM_MATCH(d.duplicated, 'z', "
+      "'invalid_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // can't access to local analyzer in other database
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH NGRAM_MATCH(d.duplicated, 'z', "
+      "'testVocbase2::test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq "
+      "RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test via ANALYZER function
+  {
+    std::vector<arangodb::velocypack::Slice> expected = {
+        insertedDocs[0].slice()
+    };
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH ANALYZER(NGRAM_mATCH(d.value, 'Jack Daniels', 0.7), "
+      "'myngram') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.ok());
+    auto slice = result.data->slice();
+    EXPECT_TRUE(slice.isArray());
+    size_t i = 0;
+
+    for (arangodb::velocypack::ArrayIterator itr(slice); itr.valid(); ++itr) {
+      auto const resolved = itr.value().resolveExternals();
+      EXPECT_TRUE(i < expected.size());
+      EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
+        resolved, true)));
+    }
+    EXPECT_EQ(i, expected.size());
+  }
+
+
+  // test via analyzer parameter
+  {
+    std::vector<arangodb::velocypack::Slice> expected = {
+        insertedDocs[0].slice()
+    };
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH nGrAm_MaTcH(d.value, 'Jack Daniels', 0.7, "
+      "'myngram') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.ok());
+    auto slice = result.data->slice();
+    EXPECT_TRUE(slice.isArray());
+    size_t i = 0;
+
+    for (arangodb::velocypack::ArrayIterator itr(slice); itr.valid(); ++itr) {
+      auto const resolved = itr.value().resolveExternals();
+      EXPECT_TRUE(i < expected.size());
+      EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
+        resolved, true)));
+    }
+    EXPECT_EQ(i, expected.size());
+  }
+
+  // test via analyzer parameter with default threshold
+  {
+    std::vector<arangodb::velocypack::Slice> expected = {
+        insertedDocs[0].slice()
+    };
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH nGrAm_MaTcH(d.value, 'Jack Daniels', "
+      "'myngram') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.ok());
+    auto slice = result.data->slice();
+    EXPECT_TRUE(slice.isArray());
+    size_t i = 0;
+
+    for (arangodb::velocypack::ArrayIterator itr(slice); itr.valid(); ++itr) {
+      auto const resolved = itr.value().resolveExternals();
+      EXPECT_TRUE(i < expected.size());
+      EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
+        resolved, true)));
+    }
+    EXPECT_EQ(i, expected.size());
+  }
+
+
+  // test via analyzer parameter
+  {
+    std::vector<arangodb::velocypack::Slice> expected = {
+        insertedDocs[1].slice()
+    };
+    // Searching for Jack Arrow and we have Jack Sparrow which will be matched
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH nGrAm_MaTcH(d.value, 'Jack Arrow', 0.5, "
+      "'myngram') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.ok());
+    auto slice = result.data->slice();
+    EXPECT_TRUE(slice.isArray());
+    size_t i = 0;
+
+    for (arangodb::velocypack::ArrayIterator itr(slice); itr.valid(); ++itr) {
+      auto const resolved = itr.value().resolveExternals();
+      EXPECT_TRUE(i < expected.size());
+      EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
+        resolved, true)));
+    }
+    EXPECT_EQ(i, expected.size());
+  }
+
+  // test via analyzer parameter
+  {
+    std::vector<arangodb::velocypack::Slice> expected = {
+        insertedDocs[0].slice(),
+        insertedDocs[4].slice(),
+        insertedDocs[5].slice(),
+        insertedDocs[1].slice()
+    };
+    // Searching for Jack Arrow and set low threshold to match all Jack`s
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH nGrAm_MaTcH(d.value, 'Jack Arrow', 0.2, "
+      "'myngram') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.ok());
+    auto slice = result.data->slice();
+    EXPECT_TRUE(slice.isArray());
+    size_t i = 0;
+
+    for (arangodb::velocypack::ArrayIterator itr(slice); itr.valid(); ++itr) {
+      auto const resolved = itr.value().resolveExternals();
+      EXPECT_TRUE(i < expected.size());
+      EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
+        resolved, true)));
+    }
+    EXPECT_EQ(i, expected.size());
+  }
+
+  // test via default analyzer
+  {
+    std::vector<arangodb::velocypack::Slice> expected = {
+      // no results  will be found as identity analyzer has no positions        
+    };
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH nGrAm_MaTcH(d.value, 'Jack Daniels', 1) "
+      "SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.ok());
+    auto slice = result.data->slice();
+    EXPECT_TRUE(slice.isArray());
+    size_t i = 0;
+
+    for (arangodb::velocypack::ArrayIterator itr(slice); itr.valid(); ++itr) {
+      auto const resolved = itr.value().resolveExternals();
+      EXPECT_TRUE(i < expected.size());
+      EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
+        resolved, true)));
+    }
+    EXPECT_EQ(i, expected.size());
+  }
+
+}
diff --git a/tests/IResearch/IResearchQueryPhrase-test.cpp b/tests/IResearch/IResearchQueryPhrase-test.cpp
index 9edf19ee48da..33c126596067 100644
--- a/tests/IResearch/IResearchQueryPhrase-test.cpp
+++ b/tests/IResearch/IResearchQueryPhrase-test.cpp
@@ -1337,145 +1337,1012 @@ TEST_F(IResearchQueryPhraseTest, test) {
     ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
   }
 
+  // test invalid input for starts_with (object)
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d['value'], {starts_with: {a: '1'}}) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
 
-  // test missing value
+  // test invalid input for starts_with (object) via []
   {
     auto result = arangodb::tests::executeQuery(
-        vocbase,
-        "FOR d IN testView SEARCH PHRASE(d.value) SORT BM25(d) ASC, TFIDF(d) "
-        "DESC, d.seq RETURN d");
-    ASSERT_TRUE(result.result.is(TRI_ERROR_QUERY_FUNCTION_ARGUMENT_NUMBER_MISMATCH));
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d['value'], [{starts_with: {a: '1'}}]) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
   }
 
-  // test missing value via []
+  // test invalid input for wildcard (object)
   {
     auto result = arangodb::tests::executeQuery(
-        vocbase,
-        "FOR d IN testView SEARCH PHRASE(d['value']) SORT BM25(d) ASC, "
-        "TFIDF(d) DESC, d.seq RETURN d");
-    ASSERT_TRUE(result.result.is(TRI_ERROR_QUERY_FUNCTION_ARGUMENT_NUMBER_MISMATCH));
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d['value'], {wildcard: {a: '1'}}) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
   }
 
-  // test invalid analyzer type (array)
+  // test invalid input for wildcard (object) via []
   {
     auto result = arangodb::tests::executeQuery(
-        vocbase,
-        "FOR d IN testView SEARCH ANALYZER(PHRASE(d.duplicated, 'z'), [ 1, "
-        "\"abc\" ]) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d['value'], [{wildcard: {a: '1'}}]) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
     ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
   }
 
-  // test invalid analyzer type (array) via []
+  // test invalid input for levenshtein_match (no array)
   {
     auto result = arangodb::tests::executeQuery(
-        vocbase,
-        "FOR d IN testView SEARCH ANALYZER(PHRASE(d['duplicated'], 'z'), [ 1, "
-        "\"abc\" ]) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d['value'], {levenshtein_match: '1'}) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
     ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
   }
 
-  // test invalid analyzer type (boolean)
+  // test invalid input for levenshtein_match (no array) via []
   {
     auto result = arangodb::tests::executeQuery(
-        vocbase,
-        "FOR d IN testView SEARCH ANALYZER(PHRASE(d.duplicated, 'z'), true) "
-        "SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d['value'], [{levenshtein_match: '1'}]) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
     ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
   }
 
-  // test invalid analyzer type (boolean) via []
+  // test invalid input for levenshtein_match (object)
   {
     auto result = arangodb::tests::executeQuery(
-        vocbase,
-        "FOR d IN testView SEARCH analyzer(PHRASE(d['duplicated'], 'z'), "
-        "false) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d['value'], {levenshtein_match: {a: '1'}}) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
     ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
   }
 
-  // test invalid analyzer type (null)
+  // test invalid input for levenshtein_match (object) via []
   {
     auto result = arangodb::tests::executeQuery(
-        vocbase,
-        "FOR d IN testView SEARCH analyzer(PHRASE(d.duplicated, 'z'), null) "
-        "SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d['value'], [{levenshtein_match: {a: '1'}}]) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
     ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
   }
 
-  // test invalid analyzer type (null) via []
+  // test invalid input for terms (no array)
   {
     auto result = arangodb::tests::executeQuery(
-        vocbase,
-        "FOR d IN testView SEARCH analyzer(PHRASE(d['duplicated'], 'z'), null) "
-        "SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d['value'], {terms: '1'}) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
     ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
   }
 
-  // test invalid analyzer type (numeric)
+  // test invalid input for terms (no array) via []
   {
     auto result = arangodb::tests::executeQuery(
-        vocbase,
-        "FOR d IN testView SEARCH analyzer(PHRASE(d.duplicated, 'z'), 3.14) "
-        "SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d['value'], [{terms: '1'}]) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
     ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
   }
 
-  // test invalid analyzer type (numeric) via []
+  // test invalid input for terms (object)
   {
     auto result = arangodb::tests::executeQuery(
-        vocbase,
-        "FOR d IN testView SEARCH analyzer(PHRASE(d['duplicated'], 'z'), 1234) "
-        "SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d['value'], {terms: {a: '1'}}) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
     ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
   }
 
-  // test invalid analyzer type (object)
+  // test invalid input for terms (object) via []
   {
     auto result = arangodb::tests::executeQuery(
-        vocbase,
-        "FOR d IN testView SEARCH analyzer(PHRASE(d.duplicated, 'z'), { \"a\": "
-        "7, \"b\": \"c\" }) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d['value'], [{terms: {a: '1'}}]) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
     ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
   }
 
-  // test invalid analyzer type (object) via []
+  // test invalid input for starts_with (empty array)
   {
     auto result = arangodb::tests::executeQuery(
-        vocbase,
-        "FOR d IN testView SEARCH analyzer(PHRASE(d['duplicated'], 'z'), { "
-        "\"a\": 7, \"b\": \"c\" }) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq "
-        "RETURN d");
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d['value'], {starts_with: []}) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
     ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
   }
 
-  // test undefined analyzer
+  // test invalid input for starts_with (empty array) via []
   {
     auto result = arangodb::tests::executeQuery(
-        vocbase,
-        "FOR d IN testView SEARCH analyzer(PHRASE(d.duplicated, 'z'), "
-        "'invalid_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d['value'], [{starts_with: []}]) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
     ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
   }
 
-  // test undefined analyzer via []
+  // test invalid input for wildcard (empty array)
   {
     auto result = arangodb::tests::executeQuery(
-        vocbase,
-        "FOR d IN testView SEARCH ANALYZER(PHRASE(d['duplicated'], 'z'), "
-        "'invalid_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d['value'], {wildcard: []}) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid input for wildcard (empty array) via []
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d['value'], [{wildcard: []}]) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid input for levenshtein_match (empty array)
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d['value'], {levenshtein_match: []}) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid input for levenshtein_match (empty array) via []
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d['value'], [{levenshtein_match: []}]) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid input for terms (empty array)
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d['value'], {terms: []}) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid input for terms (empty array) via []
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d['value'], [{terms: []}]) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid input for starts_with (wrong type)
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d['value'], {starts_with: 1}) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid input for starts_with (wrong type in an array)
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d['value'], {starts_with: [1]}) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid input for starts_with (wrong type) via []
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d['value'], [{starts_with: 1}]) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
     ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
   }
 
-  // test custom analyzer (local)
+  // test invalid input for starts_with (wrong type in an array) via []
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d['value'], [{starts_with: [1]}]) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid input for wildcard (wrong type)
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d['value'], {wildcard: 1}) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid input for wildcard (wrong type in an array)
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d['value'], {wildcard: [1]}) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid input for wildcard (wrong type) via []
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d['value'], [{wildcard: 1}]) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid input for wildcard (wrong type in an array) via []
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d['value'], [{wildcard: [1]}]) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid input for levenshtein_match (wrong type 1)
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d['value'], {levenshtein_match: [1, 2]}) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid input for levenshtein_match (wrong type 1) via []
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d['value'], [{levenshtein_match: [1, 2]}]) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid input for levenshtein_match (wrong type '2')
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d['value'], {levenshtein_match: ['1', '2']}) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid input for levenshtein_match (wrong type '2') via []
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d['value'], [{levenshtein_match: ['1', '2']}]) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid input for levenshtein_match (wrong type 3)
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d['value'], {levenshtein_match: ['1', 2, 3]}) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid input for levenshtein_match (wrong type 3) via []
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d['value'], [{levenshtein_match: ['1', 2, 3]}]) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid input for terms (wrong type)
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d['value'], {terms: [1]}) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid input for terms (wrong type) via []
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d['value'], [{terms: [1]}]) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid input for terms (wrong type) via [[]]
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d['value'], [[1]]) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid input for terms (many nested arrays)
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d['value'], [[['1']]]) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid input for starts_with (wrong number of arguments)
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d['value'], {starts_with: ['1', 1]}) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid input for starts_with (wrong number of arguments) via []
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d['value'], [{starts_with: ['1', 1]}]) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid input for wildcard (wrong number of arguments)
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d['value'], {wildcard: ['1', 1]}) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid input for wildcard (wrong number of arguments) via []
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d['value'], [{wildcard: ['1', 1]}]) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid input for levenshtein_match (wrong number of arguments)
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d['value'], {levenshtein_match: ['1']}) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid input for levenshtein_match (wrong number of arguments) via []
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d['value'], [{levenshtein_match: ['1']}]) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid input for levenshtein_match (wrong number of arguments)
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d['value'], {levenshtein_match: ['1', 2, true, 3]}) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid input for levenshtein_match (wrong number of arguments) via []
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d['value'], [{levenshtein_match: ['1', 2, true, 3]}]) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid input for levenshtein_match (negative max distance)
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d['value'], {levenshtein_match: ['1', -1, true]}) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid input for levenshtein_match (negative max distance) via []
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d['value'], [{levenshtein_match: ['1', -1, true]}]) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid input for levenshtein_match (out of range max distance)
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d['value'], {levenshtein_match: ['1', 10, true]}) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid input for levenshtein_match (out of range max distance) via []
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d['value'], [{levenshtein_match: ['1', 10, true]}]) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test missing value
+  {
+    auto result = arangodb::tests::executeQuery(
+        vocbase,
+        "FOR d IN testView SEARCH PHRASE(d.value) SORT BM25(d) ASC, TFIDF(d) "
+        "DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_QUERY_FUNCTION_ARGUMENT_NUMBER_MISMATCH));
+  }
+
+  // test missing value via []
+  {
+    auto result = arangodb::tests::executeQuery(
+        vocbase,
+        "FOR d IN testView SEARCH PHRASE(d['value']) SORT BM25(d) ASC, "
+        "TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_QUERY_FUNCTION_ARGUMENT_NUMBER_MISMATCH));
+  }
+
+  // test invalid analyzer type (array)
+  {
+    auto result = arangodb::tests::executeQuery(
+        vocbase,
+        "FOR d IN testView SEARCH ANALYZER(PHRASE(d.duplicated, 'z'), [ 1, "
+        "\"abc\" ]) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid analyzer type (array) via []
+  {
+    auto result = arangodb::tests::executeQuery(
+        vocbase,
+        "FOR d IN testView SEARCH ANALYZER(PHRASE(d['duplicated'], 'z'), [ 1, "
+        "\"abc\" ]) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid analyzer type (boolean)
+  {
+    auto result = arangodb::tests::executeQuery(
+        vocbase,
+        "FOR d IN testView SEARCH ANALYZER(PHRASE(d.duplicated, 'z'), true) "
+        "SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid analyzer type (boolean) via []
+  {
+    auto result = arangodb::tests::executeQuery(
+        vocbase,
+        "FOR d IN testView SEARCH analyzer(PHRASE(d['duplicated'], 'z'), "
+        "false) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid analyzer type (null)
+  {
+    auto result = arangodb::tests::executeQuery(
+        vocbase,
+        "FOR d IN testView SEARCH analyzer(PHRASE(d.duplicated, 'z'), null) "
+        "SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid analyzer type (null) via []
+  {
+    auto result = arangodb::tests::executeQuery(
+        vocbase,
+        "FOR d IN testView SEARCH analyzer(PHRASE(d['duplicated'], 'z'), null) "
+        "SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid analyzer type (numeric)
+  {
+    auto result = arangodb::tests::executeQuery(
+        vocbase,
+        "FOR d IN testView SEARCH analyzer(PHRASE(d.duplicated, 'z'), 3.14) "
+        "SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid analyzer type (numeric) via []
+  {
+    auto result = arangodb::tests::executeQuery(
+        vocbase,
+        "FOR d IN testView SEARCH analyzer(PHRASE(d['duplicated'], 'z'), 1234) "
+        "SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid analyzer type (object)
+  {
+    auto result = arangodb::tests::executeQuery(
+        vocbase,
+        "FOR d IN testView SEARCH analyzer(PHRASE(d.duplicated, 'z'), { \"a\": "
+        "7, \"b\": \"c\" }) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test invalid analyzer type (object) via []
+  {
+    auto result = arangodb::tests::executeQuery(
+        vocbase,
+        "FOR d IN testView SEARCH analyzer(PHRASE(d['duplicated'], 'z'), { "
+        "\"a\": 7, \"b\": \"c\" }) SORT BM25(d) ASC, TFIDF(d) DESC, d.seq "
+        "RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test undefined analyzer
+  {
+    auto result = arangodb::tests::executeQuery(
+        vocbase,
+        "FOR d IN testView SEARCH analyzer(PHRASE(d.duplicated, 'z'), "
+        "'invalid_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test undefined analyzer via []
+  {
+    auto result = arangodb::tests::executeQuery(
+        vocbase,
+        "FOR d IN testView SEARCH ANALYZER(PHRASE(d['duplicated'], 'z'), "
+        "'invalid_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+
+  // test custom analyzer (local)
+  {
+    std::vector<arangodb::velocypack::Slice> expected = {
+        insertedDocs[7].slice(),  insertedDocs[8].slice(),
+        insertedDocs[13].slice(), insertedDocs[19].slice(),
+        insertedDocs[22].slice(), insertedDocs[24].slice(),
+        insertedDocs[29].slice(),
+    };
+    auto result = arangodb::tests::executeQuery(
+        vocbase,
+        "FOR d IN testView SEARCH ANALYZER(PHRASE(d.duplicated, 'z'), "
+        "'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.ok());
+    auto slice = result.data->slice();
+    EXPECT_TRUE(slice.isArray());
+    size_t i = 0;
+
+    for (arangodb::velocypack::ArrayIterator itr(slice); itr.valid(); ++itr) {
+      auto const resolved = itr.value().resolveExternals();
+      EXPECT_TRUE(i < expected.size());
+      EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
+                                                                    resolved, true)));
+    }
+
+    EXPECT_EQ(i, expected.size());
+  }
+
+  // test custom analyzer (local)
+  {
+    std::vector<arangodb::velocypack::Slice> expected = {
+        insertedDocs[7].slice(),  insertedDocs[8].slice(),
+        insertedDocs[13].slice(), insertedDocs[19].slice(),
+        insertedDocs[22].slice(), insertedDocs[24].slice(),
+        insertedDocs[29].slice(),
+    };
+    auto result = arangodb::tests::executeQuery(
+        vocbase,
+        "FOR d IN testView SEARCH ANALYZER(PHRASE(d.duplicated, 'z'), "
+        "'testVocbase::test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq "
+        "RETURN d");
+    ASSERT_TRUE(result.result.ok());
+    auto slice = result.data->slice();
+    EXPECT_TRUE(slice.isArray());
+    size_t i = 0;
+
+    for (arangodb::velocypack::ArrayIterator itr(slice); itr.valid(); ++itr) {
+      auto const resolved = itr.value().resolveExternals();
+      EXPECT_TRUE(i < expected.size());
+      EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
+                                                                    resolved, true)));
+    }
+
+    EXPECT_EQ(i, expected.size());
+  }
+
+  // test custom analyzer (system)
+  {
+    std::vector<arangodb::velocypack::Slice> expected = {
+        insertedDocs[7].slice(),  insertedDocs[8].slice(),
+        insertedDocs[13].slice(), insertedDocs[19].slice(),
+        insertedDocs[22].slice(), insertedDocs[24].slice(),
+        insertedDocs[29].slice(),
+    };
+    auto result = arangodb::tests::executeQuery(
+        vocbase,
+        "FOR d IN testView SEARCH ANALYZER(PHRASE(d.duplicated, 'z'), "
+        "'::test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.ok());
+    auto slice = result.data->slice();
+    EXPECT_TRUE(slice.isArray());
+    size_t i = 0;
+
+    for (arangodb::velocypack::ArrayIterator itr(slice); itr.valid(); ++itr) {
+      auto const resolved = itr.value().resolveExternals();
+      EXPECT_TRUE(i < expected.size());
+      EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
+                                                                    resolved, true)));
+    }
+
+    EXPECT_EQ(i, expected.size());
+  }
+
+  // test custom analyzer (system)
+  {
+    std::vector<arangodb::velocypack::Slice> expected = {
+        insertedDocs[7].slice(),  insertedDocs[8].slice(),
+        insertedDocs[13].slice(), insertedDocs[19].slice(),
+        insertedDocs[22].slice(), insertedDocs[24].slice(),
+        insertedDocs[29].slice(),
+    };
+    auto result = arangodb::tests::executeQuery(
+        vocbase,
+        "FOR d IN testView SEARCH ANALYZER(PHRASE(d.duplicated, 'z'), "
+        "'_system::test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq "
+        "RETURN d");
+    ASSERT_TRUE(result.result.ok());
+    auto slice = result.data->slice();
+    EXPECT_TRUE(slice.isArray());
+    size_t i = 0;
+
+    for (arangodb::velocypack::ArrayIterator itr(slice); itr.valid(); ++itr) {
+      auto const resolved = itr.value().resolveExternals();
+      EXPECT_TRUE(i < expected.size());
+      EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
+                                                                    resolved, true)));
+    }
+
+    EXPECT_EQ(i, expected.size());
+  }
+
+  // test custom analyzer
+  {
+    std::vector<arangodb::velocypack::Slice> expected = {
+        insertedDocs[7].slice(),  insertedDocs[8].slice(),
+        insertedDocs[13].slice(), insertedDocs[19].slice(),
+        insertedDocs[22].slice(), insertedDocs[24].slice(),
+        insertedDocs[29].slice(),
+    };
+    auto result = arangodb::tests::executeQuery(
+        vocbase,
+        "FOR d IN testView SEARCH PHRASE(d.duplicated, 'z', 'test_analyzer') "
+        "SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.ok());
+    auto slice = result.data->slice();
+    EXPECT_TRUE(slice.isArray());
+    size_t i = 0;
+
+    for (arangodb::velocypack::ArrayIterator itr(slice); itr.valid(); ++itr) {
+      auto const resolved = itr.value().resolveExternals();
+      EXPECT_TRUE(i < expected.size());
+      EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
+                                                                    resolved, true)));
+    }
+
+    EXPECT_EQ(i, expected.size());
+  }
+
+  // test custom analyzer via []
+  {
+    std::vector<arangodb::velocypack::Slice> expected = {
+        insertedDocs[7].slice(),  insertedDocs[8].slice(),
+        insertedDocs[13].slice(), insertedDocs[19].slice(),
+        insertedDocs[22].slice(), insertedDocs[24].slice(),
+        insertedDocs[29].slice(),
+    };
+    auto result = arangodb::tests::executeQuery(
+        vocbase,
+        "FOR d IN testView SEARCH analyzer(PHRASE(d['duplicated'], 'z'), "
+        "'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.ok());
+    auto slice = result.data->slice();
+    EXPECT_TRUE(slice.isArray());
+    size_t i = 0;
+
+    for (arangodb::velocypack::ArrayIterator itr(slice); itr.valid(); ++itr) {
+      auto const resolved = itr.value().resolveExternals();
+      EXPECT_TRUE(i < expected.size());
+      EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
+                                                                    resolved, true)));
+    }
+
+    EXPECT_EQ(i, expected.size());
+  }
+
+  // test custom analyzer with offsets
+  {
+    std::vector<arangodb::velocypack::Slice> expected = {
+        insertedDocs[7].slice(),  insertedDocs[8].slice(),
+        insertedDocs[13].slice(), insertedDocs[19].slice(),
+        insertedDocs[22].slice(), insertedDocs[24].slice(),
+        insertedDocs[29].slice(),
+    };
+    auto result = arangodb::tests::executeQuery(
+        vocbase,
+        "FOR d IN testView SEARCH ANALYZER(PHRASE(d.duplicated, 'v', 1, 'z'), "
+        "'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.ok());
+    auto slice = result.data->slice();
+    EXPECT_TRUE(slice.isArray());
+    size_t i = 0;
+
+    for (arangodb::velocypack::ArrayIterator itr(slice); itr.valid(); ++itr) {
+      auto const resolved = itr.value().resolveExternals();
+      EXPECT_TRUE(i < expected.size());
+      EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
+                                                                    resolved, true)));
+    }
+
+    EXPECT_EQ(i, expected.size());
+  }
+
+  // test custom analyzer with offsets
+  {
+    std::vector<arangodb::velocypack::Slice> expected = {
+        insertedDocs[7].slice(),  insertedDocs[8].slice(),
+        insertedDocs[13].slice(), insertedDocs[19].slice(),
+        insertedDocs[22].slice(), insertedDocs[24].slice(),
+        insertedDocs[29].slice(),
+    };
+    auto result = arangodb::tests::executeQuery(
+        vocbase,
+        "FOR d IN testView SEARCH PHRASE(d.duplicated, 'v', 1, 'z', "
+        "'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.ok());
+    auto slice = result.data->slice();
+    EXPECT_TRUE(slice.isArray());
+    size_t i = 0;
+
+    for (arangodb::velocypack::ArrayIterator itr(slice); itr.valid(); ++itr) {
+      auto const resolved = itr.value().resolveExternals();
+      EXPECT_TRUE(i < expected.size());
+      EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
+                                                                    resolved, true)));
+    }
+
+    EXPECT_EQ(i, expected.size());
+  }
+
+  // test custom analyzer with offsets via []
+  {
+    std::vector<arangodb::velocypack::Slice> expected = {
+        insertedDocs[7].slice(),  insertedDocs[8].slice(),
+        insertedDocs[13].slice(), insertedDocs[19].slice(),
+        insertedDocs[22].slice(), insertedDocs[24].slice(),
+        insertedDocs[29].slice(),
+    };
+    auto result = arangodb::tests::executeQuery(
+        vocbase,
+        "FOR d IN testView SEARCH ANALYZER(PHRASE(d['duplicated'], 'v', 2, "
+        "'c'), 'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN "
+        "d");
+    ASSERT_TRUE(result.result.ok());
+    auto slice = result.data->slice();
+    EXPECT_TRUE(slice.isArray());
+    size_t i = 0;
+
+    for (arangodb::velocypack::ArrayIterator itr(slice); itr.valid(); ++itr) {
+      auto const resolved = itr.value().resolveExternals();
+      EXPECT_TRUE(i < expected.size());
+      EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
+                                                                    resolved, true)));
+    }
+
+    EXPECT_EQ(i, expected.size());
+  }
+
+  // test custom analyzer with offsets via []
+  {
+    std::vector<arangodb::velocypack::Slice> expected = {
+        insertedDocs[7].slice(),  insertedDocs[8].slice(),
+        insertedDocs[13].slice(), insertedDocs[19].slice(),
+        insertedDocs[22].slice(), insertedDocs[24].slice(),
+        insertedDocs[29].slice(),
+    };
+    auto result = arangodb::tests::executeQuery(
+        vocbase,
+        "FOR d IN testView SEARCH ANALYZER(PHRASE(d['duplicated'], 'v', 2, "
+        "'c', 'test_analyzer'), 'identity') SORT BM25(d) ASC, TFIDF(d) DESC, "
+        "d.seq RETURN d");
+    ASSERT_TRUE(result.result.ok());
+    auto slice = result.data->slice();
+    EXPECT_TRUE(slice.isArray());
+    size_t i = 0;
+
+    for (arangodb::velocypack::ArrayIterator itr(slice); itr.valid(); ++itr) {
+      auto const resolved = itr.value().resolveExternals();
+      EXPECT_TRUE(i < expected.size());
+      EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
+                                                                    resolved, true)));
+    }
+
+    EXPECT_EQ(i, expected.size());
+  }
+
+  // test custom analyzer with offsets (no match)
+  {
+    std::vector<arangodb::velocypack::Slice> expected = {};
+    auto result = arangodb::tests::executeQuery(
+        vocbase,
+        "FOR d IN testView SEARCH ANALYZER(PHRASE(d.duplicated, 'v', 0, 'z'), "
+        "'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.ok());
+    auto slice = result.data->slice();
+    EXPECT_TRUE(slice.isArray());
+    size_t i = 0;
+
+    for (arangodb::velocypack::ArrayIterator itr(slice); itr.valid(); ++itr) {
+      auto const resolved = itr.value().resolveExternals();
+      EXPECT_TRUE(i < expected.size());
+      EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
+                                                                    resolved, true)));
+    }
+
+    EXPECT_EQ(i, expected.size());
+  }
+
+  // test custom analyzer with offsets (no match) via []
+  {
+    std::vector<arangodb::velocypack::Slice> expected = {};
+    auto result = arangodb::tests::executeQuery(
+        vocbase,
+        "FOR d IN testView SEARCH ANALYZER(PHRASE(d['duplicated'], 'v', 1, "
+        "'c'), 'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN "
+        "d");
+    ASSERT_TRUE(result.result.ok());
+    auto slice = result.data->slice();
+    EXPECT_TRUE(slice.isArray());
+    size_t i = 0;
+
+    for (arangodb::velocypack::ArrayIterator itr(slice); itr.valid(); ++itr) {
+      auto const resolved = itr.value().resolveExternals();
+      EXPECT_TRUE(i < expected.size());
+      EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
+                                                                    resolved, true)));
+    }
+
+    EXPECT_EQ(i, expected.size());
+  }
+
+  // test custom analyzer with [ phrase ] arg
+  {
+    std::vector<arangodb::velocypack::Slice> expected = {
+        insertedDocs[7].slice(),  insertedDocs[8].slice(),
+        insertedDocs[13].slice(), insertedDocs[19].slice(),
+        insertedDocs[22].slice(), insertedDocs[24].slice(),
+        insertedDocs[29].slice(),
+    };
+    auto result = arangodb::tests::executeQuery(
+        vocbase,
+        "FOR d IN testView SEARCH ANALYZER(PHRASE(d.duplicated, [ 'z' ]), "
+        "'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.ok());
+    auto slice = result.data->slice();
+    EXPECT_TRUE(slice.isArray());
+    size_t i = 0;
+
+    for (arangodb::velocypack::ArrayIterator itr(slice); itr.valid(); ++itr) {
+      auto const resolved = itr.value().resolveExternals();
+      EXPECT_TRUE(i < expected.size());
+      EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
+                                                                    resolved, true)));
+    }
+
+    EXPECT_EQ(i, expected.size());
+  }
+
+  // test custom analyzer via [] with [ phrase ] arg
+  {
+    std::vector<arangodb::velocypack::Slice> expected = {
+        insertedDocs[7].slice(),  insertedDocs[8].slice(),
+        insertedDocs[13].slice(), insertedDocs[19].slice(),
+        insertedDocs[22].slice(), insertedDocs[24].slice(),
+        insertedDocs[29].slice(),
+    };
+    auto result = arangodb::tests::executeQuery(
+        vocbase,
+        "FOR d IN testView SEARCH ANALYZER(PHRASE(d['duplicated'], [ 'z' ]), "
+        "'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.ok());
+    auto slice = result.data->slice();
+    EXPECT_TRUE(slice.isArray());
+    size_t i = 0;
+
+    for (arangodb::velocypack::ArrayIterator itr(slice); itr.valid(); ++itr) {
+      auto const resolved = itr.value().resolveExternals();
+      EXPECT_TRUE(i < expected.size());
+      EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
+                                                                    resolved, true)));
+    }
+
+    EXPECT_EQ(i, expected.size());
+  }
+
+  // test custom analyzer with offsets with [ phrase ] arg
+  {
+    std::vector<arangodb::velocypack::Slice> expected = {
+        insertedDocs[7].slice(),  insertedDocs[8].slice(),
+        insertedDocs[13].slice(), insertedDocs[19].slice(),
+        insertedDocs[22].slice(), insertedDocs[24].slice(),
+        insertedDocs[29].slice(),
+    };
+    auto result = arangodb::tests::executeQuery(
+        vocbase,
+        "FOR d IN testView SEARCH ANALYZER(PHRASE(d.duplicated, [ 'v', 1, 'z' "
+        "]), 'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.ok());
+    auto slice = result.data->slice();
+    EXPECT_TRUE(slice.isArray());
+    size_t i = 0;
+
+    for (arangodb::velocypack::ArrayIterator itr(slice); itr.valid(); ++itr) {
+      auto const resolved = itr.value().resolveExternals();
+      EXPECT_TRUE(i < expected.size());
+      EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
+                                                                    resolved, true)));
+    }
+
+    EXPECT_EQ(i, expected.size());
+  }
+
+  // test custom analyzer with offsets via [] with [ phrase ] arg
+  {
+    std::vector<arangodb::velocypack::Slice> expected = {
+        insertedDocs[7].slice(),  insertedDocs[8].slice(),
+        insertedDocs[13].slice(), insertedDocs[19].slice(),
+        insertedDocs[22].slice(), insertedDocs[24].slice(),
+        insertedDocs[29].slice(),
+    };
+    auto result = arangodb::tests::executeQuery(
+        vocbase,
+        "FOR d IN testView SEARCH ANALYZER(PHRASE(d['duplicated'], [ 'v', 2, "
+        "'c' ]), 'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq "
+        "RETURN d");
+    ASSERT_TRUE(result.result.ok());
+    auto slice = result.data->slice();
+    EXPECT_TRUE(slice.isArray());
+    size_t i = 0;
+
+    for (arangodb::velocypack::ArrayIterator itr(slice); itr.valid(); ++itr) {
+      auto const resolved = itr.value().resolveExternals();
+      EXPECT_TRUE(i < expected.size());
+      EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
+                                                                    resolved, true)));
+    }
+
+    EXPECT_EQ(i, expected.size());
+  }
+
+  // test custom analyzer with offsets (no match) with [ phrase ] arg
+  {
+    std::vector<arangodb::velocypack::Slice> expected = {};
+    auto result = arangodb::tests::executeQuery(
+        vocbase,
+        "FOR d IN testView SEARCH ANALYZER(PHRASE(d.duplicated, [ 'v', 0, 'z' "
+        "]), 'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.ok());
+    auto slice = result.data->slice();
+    EXPECT_TRUE(slice.isArray());
+    size_t i = 0;
+
+    for (arangodb::velocypack::ArrayIterator itr(slice); itr.valid(); ++itr) {
+      auto const resolved = itr.value().resolveExternals();
+      EXPECT_TRUE(i < expected.size());
+      EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
+                                                                    resolved, true)));
+    }
+
+    EXPECT_EQ(i, expected.size());
+  }
+
+  // test custom analyzer with offsets (no match) via [] with [ phrase ] arg
+  {
+    std::vector<arangodb::velocypack::Slice> expected = {};
+    auto result = arangodb::tests::executeQuery(
+        vocbase,
+        "FOR d IN testView SEARCH ANALYZER(PHRASE(d['duplicated'], [ 'v', 1, "
+        "'c' ]), 'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq "
+        "RETURN d");
+    ASSERT_TRUE(result.result.ok());
+    auto slice = result.data->slice();
+    EXPECT_TRUE(slice.isArray());
+    size_t i = 0;
+
+    for (arangodb::velocypack::ArrayIterator itr(slice); itr.valid(); ++itr) {
+      auto const resolved = itr.value().resolveExternals();
+      EXPECT_TRUE(i < expected.size());
+      EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
+                                                                    resolved, true)));
+    }
+
+    EXPECT_EQ(i, expected.size());
+  }
+
+  // test custom analyzer with offsets (no match) via [] with [ phrase ] arg
   {
-    std::vector<arangodb::velocypack::Slice> expected = {
-        insertedDocs[7].slice(),  insertedDocs[8].slice(),
-        insertedDocs[13].slice(), insertedDocs[19].slice(),
-        insertedDocs[22].slice(), insertedDocs[24].slice(),
-        insertedDocs[29].slice(),
-    };
+    std::vector<arangodb::velocypack::Slice> expected = {};
     auto result = arangodb::tests::executeQuery(
         vocbase,
-        "FOR d IN testView SEARCH ANALYZER(PHRASE(d.duplicated, 'z'), "
+        "FOR d IN testView SEARCH PHRASE(d['duplicated'], [ 'v', 1, 'c' ], "
         "'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
     ASSERT_TRUE(result.result.ok());
     auto slice = result.data->slice();
@@ -1492,19 +2359,14 @@ TEST_F(IResearchQueryPhraseTest, test) {
     EXPECT_EQ(i, expected.size());
   }
 
-  // test custom analyzer (local)
+  // test custom analyzer with offsets (no match) via [] with [ phrase ] arg
   {
-    std::vector<arangodb::velocypack::Slice> expected = {
-        insertedDocs[7].slice(),  insertedDocs[8].slice(),
-        insertedDocs[13].slice(), insertedDocs[19].slice(),
-        insertedDocs[22].slice(), insertedDocs[24].slice(),
-        insertedDocs[29].slice(),
-    };
+    std::vector<arangodb::velocypack::Slice> expected = {};
     auto result = arangodb::tests::executeQuery(
         vocbase,
-        "FOR d IN testView SEARCH ANALYZER(PHRASE(d.duplicated, 'z'), "
-        "'testVocbase::test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq "
-        "RETURN d");
+        "FOR d IN testView SEARCH PHRASE(d['duplicated'], [ 'v', 1, "
+        "'c' ], 'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, "
+        "d.seq RETURN d");
     ASSERT_TRUE(result.result.ok());
     auto slice = result.data->slice();
     EXPECT_TRUE(slice.isArray());
@@ -1519,19 +2381,17 @@ TEST_F(IResearchQueryPhraseTest, test) {
 
     EXPECT_EQ(i, expected.size());
   }
-
-  // test custom analyzer (system)
+  // test custom analyzer with multiple mixed offsets
   {
     std::vector<arangodb::velocypack::Slice> expected = {
-        insertedDocs[7].slice(),  insertedDocs[8].slice(),
-        insertedDocs[13].slice(), insertedDocs[19].slice(),
-        insertedDocs[22].slice(), insertedDocs[24].slice(),
-        insertedDocs[29].slice(),
+        insertedDocs[6].slice(),  insertedDocs[10].slice(),
+        insertedDocs[16].slice(), insertedDocs[26].slice(),
+        insertedDocs[32].slice(), insertedDocs[36].slice()
     };
     auto result = arangodb::tests::executeQuery(
-        vocbase,
-        "FOR d IN testView SEARCH ANALYZER(PHRASE(d.duplicated, 'z'), "
-        "'::test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d.duplicated, ['a', 'b'], 1, ['d'], "
+      "'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
     ASSERT_TRUE(result.result.ok());
     auto slice = result.data->slice();
     EXPECT_TRUE(slice.isArray());
@@ -1541,25 +2401,22 @@ TEST_F(IResearchQueryPhraseTest, test) {
       auto const resolved = itr.value().resolveExternals();
       EXPECT_TRUE(i < expected.size());
       EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
-                                                                    resolved, true)));
+        resolved, true)));
     }
 
     EXPECT_EQ(i, expected.size());
   }
-
-  // test custom analyzer (system)
+  // test custom analyzer with multiple mixed offsets via []
   {
     std::vector<arangodb::velocypack::Slice> expected = {
-        insertedDocs[7].slice(),  insertedDocs[8].slice(),
-        insertedDocs[13].slice(), insertedDocs[19].slice(),
-        insertedDocs[22].slice(), insertedDocs[24].slice(),
-        insertedDocs[29].slice(),
+        insertedDocs[6].slice(),  insertedDocs[10].slice(),
+        insertedDocs[16].slice(), insertedDocs[26].slice(),
+        insertedDocs[32].slice(), insertedDocs[36].slice()
     };
     auto result = arangodb::tests::executeQuery(
-        vocbase,
-        "FOR d IN testView SEARCH ANALYZER(PHRASE(d.duplicated, 'z'), "
-        "'_system::test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq "
-        "RETURN d");
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d.duplicated, ['a', 'b', 1, 'd'], "
+      "'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
     ASSERT_TRUE(result.result.ok());
     auto slice = result.data->slice();
     EXPECT_TRUE(slice.isArray());
@@ -1569,24 +2426,22 @@ TEST_F(IResearchQueryPhraseTest, test) {
       auto const resolved = itr.value().resolveExternals();
       EXPECT_TRUE(i < expected.size());
       EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
-                                                                    resolved, true)));
+        resolved, true)));
     }
 
     EXPECT_EQ(i, expected.size());
   }
-
-  // test custom analyzer
+  // test custom analyzer with multiple mixed offsets
   {
     std::vector<arangodb::velocypack::Slice> expected = {
-        insertedDocs[7].slice(),  insertedDocs[8].slice(),
-        insertedDocs[13].slice(), insertedDocs[19].slice(),
-        insertedDocs[22].slice(), insertedDocs[24].slice(),
-        insertedDocs[29].slice(),
+        insertedDocs[6].slice(),  insertedDocs[10].slice(),
+        insertedDocs[16].slice(), insertedDocs[26].slice(),
+        insertedDocs[32].slice(), insertedDocs[36].slice()
     };
     auto result = arangodb::tests::executeQuery(
-        vocbase,
-        "FOR d IN testView SEARCH PHRASE(d.duplicated, 'z', 'test_analyzer') "
-        "SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d.duplicated, ['a', 1, 'c'], 0, 'd', "
+      "'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
     ASSERT_TRUE(result.result.ok());
     auto slice = result.data->slice();
     EXPECT_TRUE(slice.isArray());
@@ -1596,24 +2451,22 @@ TEST_F(IResearchQueryPhraseTest, test) {
       auto const resolved = itr.value().resolveExternals();
       EXPECT_TRUE(i < expected.size());
       EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
-                                                                    resolved, true)));
+        resolved, true)));
     }
 
     EXPECT_EQ(i, expected.size());
   }
-
-  // test custom analyzer via []
+  // test custom analyzer with multiple mixed offsets
   {
     std::vector<arangodb::velocypack::Slice> expected = {
-        insertedDocs[7].slice(),  insertedDocs[8].slice(),
-        insertedDocs[13].slice(), insertedDocs[19].slice(),
-        insertedDocs[22].slice(), insertedDocs[24].slice(),
-        insertedDocs[29].slice(),
+        insertedDocs[6].slice(),  insertedDocs[10].slice(),
+        insertedDocs[16].slice(), insertedDocs[26].slice(),
+        insertedDocs[32].slice(), insertedDocs[36].slice()
     };
     auto result = arangodb::tests::executeQuery(
-        vocbase,
-        "FOR d IN testView SEARCH analyzer(PHRASE(d['duplicated'], 'z'), "
-        "'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d.duplicated, ['a', 'b', 'c'], 0, 'd', "
+      "'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
     ASSERT_TRUE(result.result.ok());
     auto slice = result.data->slice();
     EXPECT_TRUE(slice.isArray());
@@ -1623,24 +2476,22 @@ TEST_F(IResearchQueryPhraseTest, test) {
       auto const resolved = itr.value().resolveExternals();
       EXPECT_TRUE(i < expected.size());
       EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
-                                                                    resolved, true)));
+        resolved, true)));
     }
 
     EXPECT_EQ(i, expected.size());
   }
-
-  // test custom analyzer with offsets
+  // test custom analyzer with multiple mixed offsets via []
   {
     std::vector<arangodb::velocypack::Slice> expected = {
-        insertedDocs[7].slice(),  insertedDocs[8].slice(),
-        insertedDocs[13].slice(), insertedDocs[19].slice(),
-        insertedDocs[22].slice(), insertedDocs[24].slice(),
-        insertedDocs[29].slice(),
+        insertedDocs[6].slice(),  insertedDocs[10].slice(),
+        insertedDocs[16].slice(), insertedDocs[26].slice(),
+        insertedDocs[32].slice(), insertedDocs[36].slice()
     };
     auto result = arangodb::tests::executeQuery(
-        vocbase,
-        "FOR d IN testView SEARCH ANALYZER(PHRASE(d.duplicated, 'v', 1, 'z'), "
-        "'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+      vocbase,
+      "FOR d IN testView SEARCH ANALYZER(PHRASE(d.duplicated, ['a', 1, 'c', 'd']), "
+      "'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
     ASSERT_TRUE(result.result.ok());
     auto slice = result.data->slice();
     EXPECT_TRUE(slice.isArray());
@@ -1650,24 +2501,22 @@ TEST_F(IResearchQueryPhraseTest, test) {
       auto const resolved = itr.value().resolveExternals();
       EXPECT_TRUE(i < expected.size());
       EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
-                                                                    resolved, true)));
+        resolved, true)));
     }
 
     EXPECT_EQ(i, expected.size());
   }
-
-  // test custom analyzer with offsets
+  // testarray at first arg
   {
     std::vector<arangodb::velocypack::Slice> expected = {
-        insertedDocs[7].slice(),  insertedDocs[8].slice(),
-        insertedDocs[13].slice(), insertedDocs[19].slice(),
-        insertedDocs[22].slice(), insertedDocs[24].slice(),
-        insertedDocs[29].slice(),
+        insertedDocs[6].slice(),  insertedDocs[10].slice(),
+        insertedDocs[16].slice(), insertedDocs[26].slice(),
+        insertedDocs[32].slice(), insertedDocs[36].slice()
     };
     auto result = arangodb::tests::executeQuery(
-        vocbase,
-        "FOR d IN testView SEARCH PHRASE(d.duplicated, 'v', 1, 'z', "
-        "'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+      vocbase,
+      "FOR d IN testView SEARCH ANALYZER(PHRASE(d.duplicated, ['a', 1, 'c', 'd']), "
+      "'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
     ASSERT_TRUE(result.result.ok());
     auto slice = result.data->slice();
     EXPECT_TRUE(slice.isArray());
@@ -1677,25 +2526,61 @@ TEST_F(IResearchQueryPhraseTest, test) {
       auto const resolved = itr.value().resolveExternals();
       EXPECT_TRUE(i < expected.size());
       EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
-                                                                    resolved, true)));
+        resolved, true)));
     }
 
     EXPECT_EQ(i, expected.size());
   }
-
-  // test custom analyzer with offsets via []
+  // test empty array at first arg
   {
     std::vector<arangodb::velocypack::Slice> expected = {
-        insertedDocs[7].slice(),  insertedDocs[8].slice(),
-        insertedDocs[13].slice(), insertedDocs[19].slice(),
-        insertedDocs[22].slice(), insertedDocs[24].slice(),
-        insertedDocs[29].slice(),
     };
     auto result = arangodb::tests::executeQuery(
-        vocbase,
-        "FOR d IN testView SEARCH ANALYZER(PHRASE(d['duplicated'], 'v', 2, "
-        "'c'), 'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN "
-        "d");
+      vocbase,
+      "FOR d IN testView SEARCH ANALYZER(PHRASE(d.duplicated, []), "
+      "'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.ok());
+    auto slice = result.data->slice();
+    EXPECT_TRUE(slice.isArray());
+    EXPECT_EQ(0, slice.length());
+  }
+  // test array with empty string
+  {
+    std::vector<arangodb::velocypack::Slice> expected = {
+    };
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH ANALYZER(PHRASE(d.duplicated, ['']), "
+      "'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.ok());
+    auto slice = result.data->slice();
+    EXPECT_TRUE(slice.isArray());
+    EXPECT_EQ(0, slice.length());
+  }
+  // test with empty string
+  {
+    std::vector<arangodb::velocypack::Slice> expected = {
+    };
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH ANALYZER(PHRASE(d.duplicated, ''), "
+      "'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.ok());
+    auto slice = result.data->slice();
+    EXPECT_TRUE(slice.isArray());
+    EXPECT_EQ(0, slice.length());
+  }
+  // test custom analyzer with multiple mixed offsets with empty array
+  {
+    std::vector<arangodb::velocypack::Slice> expected = {
+        insertedDocs[6].slice(),  insertedDocs[10].slice(),
+        insertedDocs[16].slice(), insertedDocs[26].slice(),
+        insertedDocs[32].slice(), insertedDocs[36].slice()
+    };
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d.duplicated, 'a', 0, 'b', 0, 'c', 0, [], 0, 'd', "
+      "'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
     ASSERT_TRUE(result.result.ok());
     auto slice = result.data->slice();
     EXPECT_TRUE(slice.isArray());
@@ -1705,47 +2590,43 @@ TEST_F(IResearchQueryPhraseTest, test) {
       auto const resolved = itr.value().resolveExternals();
       EXPECT_TRUE(i < expected.size());
       EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
-                                                                    resolved, true)));
+        resolved, true)));
     }
 
     EXPECT_EQ(i, expected.size());
   }
-
-  // test custom analyzer with offsets via []
+  // test custom analyzer with multiple mixed offsets with empty array check accumulating offset
   {
     std::vector<arangodb::velocypack::Slice> expected = {
-        insertedDocs[7].slice(),  insertedDocs[8].slice(),
-        insertedDocs[13].slice(), insertedDocs[19].slice(),
-        insertedDocs[22].slice(), insertedDocs[24].slice(),
-        insertedDocs[29].slice(),
+        insertedDocs[29].slice()
     };
     auto result = arangodb::tests::executeQuery(
-        vocbase,
-        "FOR d IN testView SEARCH ANALYZER(PHRASE(d['duplicated'], 'v', 2, "
-        "'c', 'test_analyzer'), 'identity') SORT BM25(d) ASC, TFIDF(d) DESC, "
-        "d.seq RETURN d");
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d.prefix, 'b', 1, [], 2, 'r', " // bateradsfsfasdf
+      "'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
     ASSERT_TRUE(result.result.ok());
     auto slice = result.data->slice();
     EXPECT_TRUE(slice.isArray());
     size_t i = 0;
-
     for (arangodb::velocypack::ArrayIterator itr(slice); itr.valid(); ++itr) {
       auto const resolved = itr.value().resolveExternals();
       EXPECT_TRUE(i < expected.size());
       EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
-                                                                    resolved, true)));
+        resolved, true)));
     }
-
     EXPECT_EQ(i, expected.size());
   }
-
-  // test custom analyzer with offsets (no match)
+  // testarray at first arg with analyzer
   {
-    std::vector<arangodb::velocypack::Slice> expected = {};
+    std::vector<arangodb::velocypack::Slice> expected = {
+        insertedDocs[6].slice(),  insertedDocs[10].slice(),
+        insertedDocs[16].slice(), insertedDocs[26].slice(),
+        insertedDocs[32].slice(), insertedDocs[36].slice()
+    };
     auto result = arangodb::tests::executeQuery(
-        vocbase,
-        "FOR d IN testView SEARCH ANALYZER(PHRASE(d.duplicated, 'v', 0, 'z'), "
-        "'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d.duplicated, ['a', 1, 'c', 'd'], "
+      "'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
     ASSERT_TRUE(result.result.ok());
     auto slice = result.data->slice();
     EXPECT_TRUE(slice.isArray());
@@ -1755,20 +2636,63 @@ TEST_F(IResearchQueryPhraseTest, test) {
       auto const resolved = itr.value().resolveExternals();
       EXPECT_TRUE(i < expected.size());
       EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
-                                                                    resolved, true)));
+        resolved, true)));
     }
 
     EXPECT_EQ(i, expected.size());
   }
+  // array recursion simple
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d.prefix, ['b', 1, ['t', 'e', 1, 'a']], "
+      "'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+  // array recursion
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d.prefix, ['b', 1, ['t', 'e', 1, 'a']], 0, ['d'], 0, ['s', 0, 'f', 's'], 1, [[['a', 1, 'd']]], 0, 'f', "
+      "'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+  // array recursion via []
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d.prefix, [['b', 1, ['t', 'e', 1, 'a']], 0, ['d'], 0, ['s', 0, 'f', 's'], 1, [[['a', 1, 'd']]], 0, 'f'], "
+      "'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+  // array recursion without analyzer
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH ANALYZER(PHRASE(d.prefix, ['b', 1, ['t', 'e', 1, 'a']], 0, ['d'], 0, ['s', 0, 'f', 's'], 1, [[['a', 1, 'd']]], 0, 'f'), "
+      "'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
+  // array recursion without analyzer via []
+  {
+    auto result = arangodb::tests::executeQuery(
+      vocbase,
+      "FOR d IN testView SEARCH ANALYZER(PHRASE(d.prefix, [['b', 1, ['t', 'e', 1, 'a']], 0, ['d'], 0, ['s', 0, 'f', 's'], 1, [[['a', 1, 'd']]], 0, 'f']), "
+      "'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
+  }
 
-  // test custom analyzer with offsets (no match) via []
+  // test custom analyzer with starts_with
   {
-    std::vector<arangodb::velocypack::Slice> expected = {};
+    std::vector<arangodb::velocypack::Slice> expected = {
+      insertedDocs[6].slice(), insertedDocs[10].slice(),
+      insertedDocs[16].slice(), insertedDocs[26].slice(),
+      insertedDocs[32].slice(), insertedDocs[36].slice()
+    };
     auto result = arangodb::tests::executeQuery(
-        vocbase,
-        "FOR d IN testView SEARCH ANALYZER(PHRASE(d['duplicated'], 'v', 1, "
-        "'c'), 'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN "
-        "d");
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d.duplicated, {starts_with: 'a'}, 0, 'b', 0, 'c', 0, 'd', "
+      "'test_analyzer') SORT d.seq RETURN d");
     ASSERT_TRUE(result.result.ok());
     auto slice = result.data->slice();
     EXPECT_TRUE(slice.isArray());
@@ -1778,24 +2702,23 @@ TEST_F(IResearchQueryPhraseTest, test) {
       auto const resolved = itr.value().resolveExternals();
       EXPECT_TRUE(i < expected.size());
       EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
-                                                                    resolved, true)));
+        resolved, true)));
     }
 
     EXPECT_EQ(i, expected.size());
   }
 
-  // test custom analyzer with [ phrase ] arg
+  // test custom analyzer with starts_with (in an array)
   {
     std::vector<arangodb::velocypack::Slice> expected = {
-        insertedDocs[7].slice(),  insertedDocs[8].slice(),
-        insertedDocs[13].slice(), insertedDocs[19].slice(),
-        insertedDocs[22].slice(), insertedDocs[24].slice(),
-        insertedDocs[29].slice(),
+      insertedDocs[6].slice(), insertedDocs[10].slice(),
+      insertedDocs[16].slice(), insertedDocs[26].slice(),
+      insertedDocs[32].slice(), insertedDocs[36].slice()
     };
     auto result = arangodb::tests::executeQuery(
-        vocbase,
-        "FOR d IN testView SEARCH ANALYZER(PHRASE(d.duplicated, [ 'z' ]), "
-        "'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d.duplicated, {starts_with: ['a']}, 0, 'b', 0, 'c', 0, 'd', "
+      "'test_analyzer') SORT d.seq RETURN d");
     ASSERT_TRUE(result.result.ok());
     auto slice = result.data->slice();
     EXPECT_TRUE(slice.isArray());
@@ -1805,24 +2728,23 @@ TEST_F(IResearchQueryPhraseTest, test) {
       auto const resolved = itr.value().resolveExternals();
       EXPECT_TRUE(i < expected.size());
       EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
-                                                                    resolved, true)));
+        resolved, true)));
     }
 
     EXPECT_EQ(i, expected.size());
   }
 
-  // test custom analyzer via [] with [ phrase ] arg
+  // test custom analyzer with starts_with via []
   {
     std::vector<arangodb::velocypack::Slice> expected = {
-        insertedDocs[7].slice(),  insertedDocs[8].slice(),
-        insertedDocs[13].slice(), insertedDocs[19].slice(),
-        insertedDocs[22].slice(), insertedDocs[24].slice(),
-        insertedDocs[29].slice(),
+      insertedDocs[6].slice(), insertedDocs[10].slice(),
+      insertedDocs[16].slice(), insertedDocs[26].slice(),
+      insertedDocs[32].slice(), insertedDocs[36].slice()
     };
     auto result = arangodb::tests::executeQuery(
-        vocbase,
-        "FOR d IN testView SEARCH ANALYZER(PHRASE(d['duplicated'], [ 'z' ]), "
-        "'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d.duplicated, [{starts_with: 'a'}, 'b', 'c', 'd'], "
+      "'test_analyzer') SORT d.seq RETURN d");
     ASSERT_TRUE(result.result.ok());
     auto slice = result.data->slice();
     EXPECT_TRUE(slice.isArray());
@@ -1832,24 +2754,23 @@ TEST_F(IResearchQueryPhraseTest, test) {
       auto const resolved = itr.value().resolveExternals();
       EXPECT_TRUE(i < expected.size());
       EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
-                                                                    resolved, true)));
+        resolved, true)));
     }
 
     EXPECT_EQ(i, expected.size());
   }
 
-  // test custom analyzer with offsets with [ phrase ] arg
+  // test custom analyzer with starts_with (in an array) via []
   {
     std::vector<arangodb::velocypack::Slice> expected = {
-        insertedDocs[7].slice(),  insertedDocs[8].slice(),
-        insertedDocs[13].slice(), insertedDocs[19].slice(),
-        insertedDocs[22].slice(), insertedDocs[24].slice(),
-        insertedDocs[29].slice(),
+      insertedDocs[6].slice(), insertedDocs[10].slice(),
+      insertedDocs[16].slice(), insertedDocs[26].slice(),
+      insertedDocs[32].slice(), insertedDocs[36].slice()
     };
     auto result = arangodb::tests::executeQuery(
-        vocbase,
-        "FOR d IN testView SEARCH ANALYZER(PHRASE(d.duplicated, [ 'v', 1, 'z' "
-        "]), 'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d.duplicated, [{starts_with: ['a']}, 'b', 'c', 'd'], "
+      "'test_analyzer') SORT d.seq RETURN d");
     ASSERT_TRUE(result.result.ok());
     auto slice = result.data->slice();
     EXPECT_TRUE(slice.isArray());
@@ -1859,25 +2780,23 @@ TEST_F(IResearchQueryPhraseTest, test) {
       auto const resolved = itr.value().resolveExternals();
       EXPECT_TRUE(i < expected.size());
       EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
-                                                                    resolved, true)));
+        resolved, true)));
     }
 
     EXPECT_EQ(i, expected.size());
   }
 
-  // test custom analyzer with offsets via [] with [ phrase ] arg
+  // test custom analyzer with wildcard
   {
     std::vector<arangodb::velocypack::Slice> expected = {
-        insertedDocs[7].slice(),  insertedDocs[8].slice(),
-        insertedDocs[13].slice(), insertedDocs[19].slice(),
-        insertedDocs[22].slice(), insertedDocs[24].slice(),
-        insertedDocs[29].slice(),
+      insertedDocs[6].slice(), insertedDocs[10].slice(),
+      insertedDocs[16].slice(), insertedDocs[26].slice(),
+      insertedDocs[32].slice(), insertedDocs[36].slice()
     };
     auto result = arangodb::tests::executeQuery(
-        vocbase,
-        "FOR d IN testView SEARCH ANALYZER(PHRASE(d['duplicated'], [ 'v', 2, "
-        "'c' ]), 'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq "
-        "RETURN d");
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d.duplicated, {wildcard: '_'}, 0, 'b', 0, 'c', 0, 'd', "
+      "'test_analyzer') SORT d.seq RETURN d");
     ASSERT_TRUE(result.result.ok());
     auto slice = result.data->slice();
     EXPECT_TRUE(slice.isArray());
@@ -1887,19 +2806,23 @@ TEST_F(IResearchQueryPhraseTest, test) {
       auto const resolved = itr.value().resolveExternals();
       EXPECT_TRUE(i < expected.size());
       EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
-                                                                    resolved, true)));
+        resolved, true)));
     }
 
     EXPECT_EQ(i, expected.size());
   }
 
-  // test custom analyzer with offsets (no match) with [ phrase ] arg
+  // test custom analyzer with wildcard (in an array)
   {
-    std::vector<arangodb::velocypack::Slice> expected = {};
+    std::vector<arangodb::velocypack::Slice> expected = {
+      insertedDocs[6].slice(), insertedDocs[10].slice(),
+      insertedDocs[16].slice(), insertedDocs[26].slice(),
+      insertedDocs[32].slice(), insertedDocs[36].slice()
+    };
     auto result = arangodb::tests::executeQuery(
-        vocbase,
-        "FOR d IN testView SEARCH ANALYZER(PHRASE(d.duplicated, [ 'v', 0, 'z' "
-        "]), 'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d.duplicated, {wildcard: ['_']}, 0, 'b', 0, 'c', 0, 'd', "
+      "'test_analyzer') SORT d.seq RETURN d");
     ASSERT_TRUE(result.result.ok());
     auto slice = result.data->slice();
     EXPECT_TRUE(slice.isArray());
@@ -1909,20 +2832,23 @@ TEST_F(IResearchQueryPhraseTest, test) {
       auto const resolved = itr.value().resolveExternals();
       EXPECT_TRUE(i < expected.size());
       EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
-                                                                    resolved, true)));
+        resolved, true)));
     }
 
     EXPECT_EQ(i, expected.size());
   }
 
-  // test custom analyzer with offsets (no match) via [] with [ phrase ] arg
+  // test custom analyzer with wildcard via []
   {
-    std::vector<arangodb::velocypack::Slice> expected = {};
+    std::vector<arangodb::velocypack::Slice> expected = {
+      insertedDocs[6].slice(), insertedDocs[10].slice(),
+      insertedDocs[16].slice(), insertedDocs[26].slice(),
+      insertedDocs[32].slice(), insertedDocs[36].slice()
+    };
     auto result = arangodb::tests::executeQuery(
-        vocbase,
-        "FOR d IN testView SEARCH ANALYZER(PHRASE(d['duplicated'], [ 'v', 1, "
-        "'c' ]), 'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq "
-        "RETURN d");
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d.duplicated, [{wildcard: '_'}, 'b', 'c', 'd'], "
+      "'test_analyzer') SORT d.seq RETURN d");
     ASSERT_TRUE(result.result.ok());
     auto slice = result.data->slice();
     EXPECT_TRUE(slice.isArray());
@@ -1932,19 +2858,23 @@ TEST_F(IResearchQueryPhraseTest, test) {
       auto const resolved = itr.value().resolveExternals();
       EXPECT_TRUE(i < expected.size());
       EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
-                                                                    resolved, true)));
+        resolved, true)));
     }
 
     EXPECT_EQ(i, expected.size());
   }
 
-  // test custom analyzer with offsets (no match) via [] with [ phrase ] arg
+  // test custom analyzer with wildcard (in an array) via []
   {
-    std::vector<arangodb::velocypack::Slice> expected = {};
+    std::vector<arangodb::velocypack::Slice> expected = {
+      insertedDocs[6].slice(), insertedDocs[10].slice(),
+      insertedDocs[16].slice(), insertedDocs[26].slice(),
+      insertedDocs[32].slice(), insertedDocs[36].slice()
+    };
     auto result = arangodb::tests::executeQuery(
-        vocbase,
-        "FOR d IN testView SEARCH PHRASE(d['duplicated'], [ 'v', 1, 'c' ], "
-        "'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d.duplicated, [{wildcard: ['_']}, 'b', 'c', 'd'], "
+      "'test_analyzer') SORT d.seq RETURN d");
     ASSERT_TRUE(result.result.ok());
     auto slice = result.data->slice();
     EXPECT_TRUE(slice.isArray());
@@ -1954,20 +2884,23 @@ TEST_F(IResearchQueryPhraseTest, test) {
       auto const resolved = itr.value().resolveExternals();
       EXPECT_TRUE(i < expected.size());
       EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
-                                                                    resolved, true)));
+        resolved, true)));
     }
 
     EXPECT_EQ(i, expected.size());
   }
 
-  // test custom analyzer with offsets (no match) via [] with [ phrase ] arg
+  // test custom analyzer with levenshtein_match
   {
-    std::vector<arangodb::velocypack::Slice> expected = {};
+    std::vector<arangodb::velocypack::Slice> expected = {
+      insertedDocs[6].slice(), insertedDocs[10].slice(),
+      insertedDocs[16].slice(), insertedDocs[26].slice(),
+      insertedDocs[32].slice(), insertedDocs[36].slice()
+    };
     auto result = arangodb::tests::executeQuery(
-        vocbase,
-        "FOR d IN testView SEARCH PHRASE(d['duplicated'], [ 'v', 1, "
-        "'c' ], 'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, "
-        "d.seq RETURN d");
+      vocbase,
+      "FOR d IN testView SEARCH PHRASE(d.duplicated, {levenshtein_match: ['f', 1]}, 0, 'b', 0, 'c', 0, 'd', "
+      "'test_analyzer') SORT d.seq RETURN d");
     ASSERT_TRUE(result.result.ok());
     auto slice = result.data->slice();
     EXPECT_TRUE(slice.isArray());
@@ -1977,22 +2910,23 @@ TEST_F(IResearchQueryPhraseTest, test) {
       auto const resolved = itr.value().resolveExternals();
       EXPECT_TRUE(i < expected.size());
       EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
-                                                                    resolved, true)));
+        resolved, true)));
     }
 
     EXPECT_EQ(i, expected.size());
   }
-  // test custom analyzer with multiple mixed offsets
+
+  // test custom analyzer with levenshtein_match via []
   {
     std::vector<arangodb::velocypack::Slice> expected = {
-        insertedDocs[6].slice(),  insertedDocs[10].slice(),
-        insertedDocs[16].slice(), insertedDocs[26].slice(),
-        insertedDocs[32].slice(), insertedDocs[36].slice()
+      insertedDocs[6].slice(), insertedDocs[10].slice(),
+      insertedDocs[16].slice(), insertedDocs[26].slice(),
+      insertedDocs[32].slice(), insertedDocs[36].slice()
     };
     auto result = arangodb::tests::executeQuery(
       vocbase,
-      "FOR d IN testView SEARCH PHRASE(d.duplicated, ['a', 'b'], 1, ['d'], "
-      "'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+      "FOR d IN testView SEARCH PHRASE(d.duplicated, [{levenshtein_match: ['f', 1]}, 'b', 'c', 'd'], "
+      "'test_analyzer') SORT d.seq RETURN d");
     ASSERT_TRUE(result.result.ok());
     auto slice = result.data->slice();
     EXPECT_TRUE(slice.isArray());
@@ -2007,17 +2941,18 @@ TEST_F(IResearchQueryPhraseTest, test) {
 
     EXPECT_EQ(i, expected.size());
   }
-  // test custom analyzer with multiple mixed offsets via []
+
+  // test custom analyzer with levenshtein_match (not Damerau-Levenshtein)
   {
     std::vector<arangodb::velocypack::Slice> expected = {
-        insertedDocs[6].slice(),  insertedDocs[10].slice(),
-        insertedDocs[16].slice(), insertedDocs[26].slice(),
-        insertedDocs[32].slice(), insertedDocs[36].slice()
+      insertedDocs[6].slice(), insertedDocs[10].slice(),
+      insertedDocs[16].slice(), insertedDocs[26].slice(),
+      insertedDocs[32].slice(), insertedDocs[36].slice()
     };
     auto result = arangodb::tests::executeQuery(
       vocbase,
-      "FOR d IN testView SEARCH PHRASE(d.duplicated, ['a', 'b', 1, 'd'], "
-      "'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+      "FOR d IN testView SEARCH PHRASE(d.duplicated, {levenshtein_match: ['f', 1, false]}, 0, 'b', 0, 'c', 0, 'd', "
+      "'test_analyzer') SORT d.seq RETURN d");
     ASSERT_TRUE(result.result.ok());
     auto slice = result.data->slice();
     EXPECT_TRUE(slice.isArray());
@@ -2032,17 +2967,18 @@ TEST_F(IResearchQueryPhraseTest, test) {
 
     EXPECT_EQ(i, expected.size());
   }
-  // test custom analyzer with multiple mixed offsets
+
+  // test custom analyzer with levenshtein_match via [] (not Damerau-Levenshtein)
   {
     std::vector<arangodb::velocypack::Slice> expected = {
-        insertedDocs[6].slice(),  insertedDocs[10].slice(),
-        insertedDocs[16].slice(), insertedDocs[26].slice(),
-        insertedDocs[32].slice(), insertedDocs[36].slice()
+      insertedDocs[6].slice(), insertedDocs[10].slice(),
+      insertedDocs[16].slice(), insertedDocs[26].slice(),
+      insertedDocs[32].slice(), insertedDocs[36].slice()
     };
     auto result = arangodb::tests::executeQuery(
       vocbase,
-      "FOR d IN testView SEARCH PHRASE(d.duplicated, ['a', 1, 'c'], 0, 'd', "
-      "'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+      "FOR d IN testView SEARCH PHRASE(d.duplicated, [{levenshtein_match: ['f', 1, false]}, 'b', 'c', 'd'], "
+      "'test_analyzer') SORT d.seq RETURN d");
     ASSERT_TRUE(result.result.ok());
     auto slice = result.data->slice();
     EXPECT_TRUE(slice.isArray());
@@ -2057,17 +2993,18 @@ TEST_F(IResearchQueryPhraseTest, test) {
 
     EXPECT_EQ(i, expected.size());
   }
-  // test custom analyzer with multiple mixed offsets
+
+  // test custom analyzer with levenshtein_match (Damerau-Levenshtein)
   {
     std::vector<arangodb::velocypack::Slice> expected = {
-        insertedDocs[6].slice(),  insertedDocs[10].slice(),
-        insertedDocs[16].slice(), insertedDocs[26].slice(),
-        insertedDocs[32].slice(), insertedDocs[36].slice()
+      insertedDocs[6].slice(), insertedDocs[10].slice(),
+      insertedDocs[16].slice(), insertedDocs[26].slice(),
+      insertedDocs[32].slice(), insertedDocs[36].slice()
     };
     auto result = arangodb::tests::executeQuery(
       vocbase,
-      "FOR d IN testView SEARCH PHRASE(d.duplicated, ['a', 'b', 'c'], 0, 'd', "
-      "'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+      "FOR d IN testView SEARCH PHRASE(d.duplicated, {levenshtein_match: ['f', 1, true]}, 0, 'b', 0, 'c', 0, 'd', "
+      "'test_analyzer') SORT d.seq RETURN d");
     ASSERT_TRUE(result.result.ok());
     auto slice = result.data->slice();
     EXPECT_TRUE(slice.isArray());
@@ -2082,17 +3019,18 @@ TEST_F(IResearchQueryPhraseTest, test) {
 
     EXPECT_EQ(i, expected.size());
   }
-  // test custom analyzer with multiple mixed offsets via []
+
+  // test custom analyzer with levenshtein_match via [] (Damerau-Levenshtein)
   {
     std::vector<arangodb::velocypack::Slice> expected = {
-        insertedDocs[6].slice(),  insertedDocs[10].slice(),
-        insertedDocs[16].slice(), insertedDocs[26].slice(),
-        insertedDocs[32].slice(), insertedDocs[36].slice()
+      insertedDocs[6].slice(), insertedDocs[10].slice(),
+      insertedDocs[16].slice(), insertedDocs[26].slice(),
+      insertedDocs[32].slice(), insertedDocs[36].slice()
     };
     auto result = arangodb::tests::executeQuery(
       vocbase,
-      "FOR d IN testView SEARCH ANALYZER(PHRASE(d.duplicated, ['a', 1, 'c', 'd']), "
-      "'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+      "FOR d IN testView SEARCH PHRASE(d.duplicated, [{levenshtein_match: ['f', 1, true]}, 'b', 'c', 'd'], "
+      "'test_analyzer') SORT d.seq RETURN d");
     ASSERT_TRUE(result.result.ok());
     auto slice = result.data->slice();
     EXPECT_TRUE(slice.isArray());
@@ -2107,17 +3045,18 @@ TEST_F(IResearchQueryPhraseTest, test) {
 
     EXPECT_EQ(i, expected.size());
   }
-  // testarray at first arg
+
+  // test custom analyzer with terms
   {
     std::vector<arangodb::velocypack::Slice> expected = {
-        insertedDocs[6].slice(),  insertedDocs[10].slice(),
-        insertedDocs[16].slice(), insertedDocs[26].slice(),
-        insertedDocs[32].slice(), insertedDocs[36].slice()
+      insertedDocs[6].slice(), insertedDocs[10].slice(),
+      insertedDocs[16].slice(), insertedDocs[26].slice(),
+      insertedDocs[32].slice(), insertedDocs[36].slice()
     };
     auto result = arangodb::tests::executeQuery(
       vocbase,
-      "FOR d IN testView SEARCH ANALYZER(PHRASE(d.duplicated, ['a', 1, 'c', 'd']), "
-      "'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+      "FOR d IN testView SEARCH PHRASE(d.duplicated, {terms: ['a', 'b']}, 0, 'b', 0, 'c', 0, 'd', "
+      "'test_analyzer') SORT d.seq RETURN d");
     ASSERT_TRUE(result.result.ok());
     auto slice = result.data->slice();
     EXPECT_TRUE(slice.isArray());
@@ -2132,56 +3071,18 @@ TEST_F(IResearchQueryPhraseTest, test) {
 
     EXPECT_EQ(i, expected.size());
   }
-  // test empty array at first arg
-  {
-    std::vector<arangodb::velocypack::Slice> expected = {
-    };
-    auto result = arangodb::tests::executeQuery(
-      vocbase,
-      "FOR d IN testView SEARCH ANALYZER(PHRASE(d.duplicated, []), "
-      "'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
-    ASSERT_TRUE(result.result.ok());
-    auto slice = result.data->slice();
-    EXPECT_TRUE(slice.isArray());
-    EXPECT_EQ(0, slice.length());
-  }
-  // test array with empty string
-  {
-    std::vector<arangodb::velocypack::Slice> expected = {
-    };
-    auto result = arangodb::tests::executeQuery(
-      vocbase,
-      "FOR d IN testView SEARCH ANALYZER(PHRASE(d.duplicated, ['']), "
-      "'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
-    ASSERT_TRUE(result.result.ok());
-    auto slice = result.data->slice();
-    EXPECT_TRUE(slice.isArray());
-    EXPECT_EQ(0, slice.length());
-  }
-  // test with empty string
-  {
-    std::vector<arangodb::velocypack::Slice> expected = {
-    };
-    auto result = arangodb::tests::executeQuery(
-      vocbase,
-      "FOR d IN testView SEARCH ANALYZER(PHRASE(d.duplicated, ''), "
-      "'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
-    ASSERT_TRUE(result.result.ok());
-    auto slice = result.data->slice();
-    EXPECT_TRUE(slice.isArray());
-    EXPECT_EQ(0, slice.length());
-  }
-  // test custom analyzer with multiple mixed offsets with empty array
+
+  // test custom analyzer with terms via []
   {
     std::vector<arangodb::velocypack::Slice> expected = {
-        insertedDocs[6].slice(),  insertedDocs[10].slice(),
-        insertedDocs[16].slice(), insertedDocs[26].slice(),
-        insertedDocs[32].slice(), insertedDocs[36].slice()
+      insertedDocs[6].slice(), insertedDocs[10].slice(),
+      insertedDocs[16].slice(), insertedDocs[26].slice(),
+      insertedDocs[32].slice(), insertedDocs[36].slice()
     };
     auto result = arangodb::tests::executeQuery(
       vocbase,
-      "FOR d IN testView SEARCH PHRASE(d.duplicated, 'a', 0, 'b', 0, 'c', 0, [], 0, 'd', "
-      "'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+      "FOR d IN testView SEARCH PHRASE(d.duplicated, [{terms: ['a', 'b']}, 'b', 'c', 'd'], "
+      "'test_analyzer') SORT d.seq RETURN d");
     ASSERT_TRUE(result.result.ok());
     auto slice = result.data->slice();
     EXPECT_TRUE(slice.isArray());
@@ -2196,38 +3097,44 @@ TEST_F(IResearchQueryPhraseTest, test) {
 
     EXPECT_EQ(i, expected.size());
   }
-  // test custom analyzer with multiple mixed offsets with empty array check accumulating offset
+
+  // test custom analyzer with terms via [[]]
   {
     std::vector<arangodb::velocypack::Slice> expected = {
-        insertedDocs[29].slice()
+      insertedDocs[6].slice(), insertedDocs[10].slice(),
+      insertedDocs[16].slice(), insertedDocs[26].slice(),
+      insertedDocs[32].slice(), insertedDocs[36].slice()
     };
     auto result = arangodb::tests::executeQuery(
       vocbase,
-      "FOR d IN testView SEARCH PHRASE(d.prefix, 'b', 1, [], 2, 'r', " // bateradsfsfasdf
-      "'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+      "FOR d IN testView SEARCH PHRASE(d.duplicated, [['a', 'b'], 'b', 'c', 'd'], "
+      "'test_analyzer') SORT d.seq RETURN d");
     ASSERT_TRUE(result.result.ok());
     auto slice = result.data->slice();
     EXPECT_TRUE(slice.isArray());
     size_t i = 0;
+
     for (arangodb::velocypack::ArrayIterator itr(slice); itr.valid(); ++itr) {
       auto const resolved = itr.value().resolveExternals();
       EXPECT_TRUE(i < expected.size());
       EXPECT_TRUE((0 == arangodb::basics::VelocyPackHelper::compare(expected[i++],
         resolved, true)));
     }
+
     EXPECT_EQ(i, expected.size());
   }
-  // testarray at first arg with analyzer
+
+  // test custom analyzer with mixed terms, starts_with, wildcard, levenshtein_match
   {
     std::vector<arangodb::velocypack::Slice> expected = {
-        insertedDocs[6].slice(),  insertedDocs[10].slice(),
-        insertedDocs[16].slice(), insertedDocs[26].slice(),
-        insertedDocs[32].slice(), insertedDocs[36].slice()
+      insertedDocs[6].slice(), insertedDocs[10].slice(),
+      insertedDocs[16].slice(), insertedDocs[26].slice(),
+      insertedDocs[32].slice(), insertedDocs[36].slice()
     };
     auto result = arangodb::tests::executeQuery(
       vocbase,
-      "FOR d IN testView SEARCH PHRASE(d.duplicated, ['a', 1, 'c', 'd'], "
-      "'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
+      "FOR d IN testView SEARCH PHRASE(d.duplicated, [['a', 'b'], {starts_with: ['b']}, 0, {wildcard: '%'}, {levenshtein_match: ['f', 1, true]}], "
+      "'test_analyzer') SORT d.seq RETURN d");
     ASSERT_TRUE(result.result.ok());
     auto slice = result.data->slice();
     EXPECT_TRUE(slice.isArray());
@@ -2242,44 +3149,4 @@ TEST_F(IResearchQueryPhraseTest, test) {
 
     EXPECT_EQ(i, expected.size());
   }
-  // array recursion simple
-  {
-    auto result = arangodb::tests::executeQuery(
-      vocbase,
-      "FOR d IN testView SEARCH PHRASE(d.prefix, ['b', 1, ['t', 'e', 1, 'a']], "
-      "'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
-    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
-  }
-  // array recursion
-  {
-    auto result = arangodb::tests::executeQuery(
-      vocbase,
-      "FOR d IN testView SEARCH PHRASE(d.prefix, ['b', 1, ['t', 'e', 1, 'a']], 0, ['d'], 0, ['s', 0, 'f', 's'], 1, [[['a', 1, 'd']]], 0, 'f', "
-      "'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
-    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
-  }
-  // array recursion via []
-  {
-    auto result = arangodb::tests::executeQuery(
-      vocbase,
-      "FOR d IN testView SEARCH PHRASE(d.prefix, [['b', 1, ['t', 'e', 1, 'a']], 0, ['d'], 0, ['s', 0, 'f', 's'], 1, [[['a', 1, 'd']]], 0, 'f'], "
-      "'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
-    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
-  }
-  // array recursion without analyzer
-  {
-    auto result = arangodb::tests::executeQuery(
-      vocbase,
-      "FOR d IN testView SEARCH ANALYZER(PHRASE(d.prefix, ['b', 1, ['t', 'e', 1, 'a']], 0, ['d'], 0, ['s', 0, 'f', 's'], 1, [[['a', 1, 'd']]], 0, 'f'), "
-      "'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
-    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
-  }
-  // array recursion without analyzer via []
-  {
-    auto result = arangodb::tests::executeQuery(
-      vocbase,
-      "FOR d IN testView SEARCH ANALYZER(PHRASE(d.prefix, [['b', 1, ['t', 'e', 1, 'a']], 0, ['d'], 0, ['s', 0, 'f', 's'], 1, [[['a', 1, 'd']]], 0, 'f']), "
-      "'test_analyzer') SORT BM25(d) ASC, TFIDF(d) DESC, d.seq RETURN d");
-    ASSERT_TRUE(result.result.is(TRI_ERROR_BAD_PARAMETER));
-  }
 }
diff --git a/tests/IResearch/common.cpp b/tests/IResearch/common.cpp
index 18964020ecf4..6070b791ade8 100644
--- a/tests/IResearch/common.cpp
+++ b/tests/IResearch/common.cpp
@@ -894,6 +894,7 @@ void assertFilterExecutionFail(TRI_vocbase_t& vocbase, std::string const& queryS
 void assertFilterParseFail(TRI_vocbase_t& vocbase, std::string const& queryString,
                            std::shared_ptr<arangodb::velocypack::Builder> bindVars /*= nullptr*/
 ) {
+  SCOPED_TRACE(testing::Message("assertFilterParseFail failed for query:<") << queryString << ">");
   arangodb::aql::Query query(false, vocbase, arangodb::aql::QueryString(queryString),
                              bindVars, nullptr, arangodb::aql::PART_MAIN);
 
diff --git a/tests/Metrics/MetricsTest.cpp b/tests/Metrics/MetricsTest.cpp
index 2d234bd2c3ec..31814a6a2099 100644
--- a/tests/Metrics/MetricsTest.cpp
+++ b/tests/Metrics/MetricsTest.cpp
@@ -55,10 +55,9 @@ TEST_F(MetricsTest, test_counter) {
   c.store(0);
   ASSERT_EQ(c.load(),  0);
 
-  std::string s;
-  c.toPrometheus(s);
-  LOG_DEVEL << s;
-
+  //std::string s;
+  //c.toPrometheus(s);
+  //LOG_DEVEL << s;
 }
 
 template<typename T> void gauge_test() {
@@ -79,10 +78,9 @@ template<typename T> void gauge_test() {
   g -= g.load();
   ASSERT_DOUBLE_EQ(g.load(),  zero);
 
-  std::string s;
-  g.toPrometheus(s);
-  LOG_DEVEL << s;
-
+  //std::string s;
+  //g.toPrometheus(s);
+  //LOG_DEVEL << s;
 }
 
 TEST_F(MetricsTest, long_double) {
@@ -132,10 +130,9 @@ template<typename T> void histogram_test(
   ASSERT_DOUBLE_EQ(h.load(buckets-1), 5);
 
   // dump
-  std::string s;
-  h.toPrometheus(s);
-  LOG_DEVEL << s;
-
+  //std::string s;
+  //h.toPrometheus(s);
+  //LOG_DEVEL << s;
 }
 
 
diff --git a/tests/Mocks/StorageEngineMock.cpp b/tests/Mocks/StorageEngineMock.cpp
index 27b695975895..f29f8cc55427 100644
--- a/tests/Mocks/StorageEngineMock.cpp
+++ b/tests/Mocks/StorageEngineMock.cpp
@@ -1076,6 +1076,11 @@ std::unique_ptr<arangodb::IndexIterator> PhysicalCollectionMock::getAnyIterator(
   return std::make_unique<AllIteratorMock>(_documents, this->_logicalCollection, trx);
 }
 
+std::unique_ptr<arangodb::ReplicationIterator> PhysicalCollectionMock::getReplicationIterator(
+    arangodb::ReplicationIterator::Ordering, uint64_t) {
+  return nullptr;
+}
+
 void PhysicalCollectionMock::getPropertiesVPack(arangodb::velocypack::Builder&) const {
   before();
 }
@@ -1253,13 +1258,6 @@ arangodb::Result PhysicalCollectionMock::read(arangodb::transaction::Methods*,
   return arangodb::Result(TRI_ERROR_ARANGO_DOCUMENT_NOT_FOUND);
 }
 
-arangodb::Result PhysicalCollectionMock::read(arangodb::transaction::Methods* trx,
-                                              arangodb::velocypack::Slice const& key,
-                                              arangodb::ManagedDocumentResult& result,
-                                              bool unusedFlag) {
-  return read(trx, arangodb::velocypack::StringRef(key), result, unusedFlag);
-}
-
 bool PhysicalCollectionMock::readDocument(arangodb::transaction::Methods* trx,
                                           arangodb::LocalDocumentId const& token,
                                           arangodb::ManagedDocumentResult& result) const {
diff --git a/tests/Mocks/StorageEngineMock.h b/tests/Mocks/StorageEngineMock.h
index 240b1ac6e297..61120406afa7 100644
--- a/tests/Mocks/StorageEngineMock.h
+++ b/tests/Mocks/StorageEngineMock.h
@@ -81,6 +81,8 @@ class PhysicalCollectionMock : public arangodb::PhysicalCollection {
       arangodb::transaction::Methods* trx) const override;
   virtual std::unique_ptr<arangodb::IndexIterator> getAnyIterator(
       arangodb::transaction::Methods* trx) const override;
+  virtual std::unique_ptr<arangodb::ReplicationIterator> getReplicationIterator(
+      arangodb::ReplicationIterator::Ordering, uint64_t) override;
   virtual void getPropertiesVPack(arangodb::velocypack::Builder&) const override;
   virtual arangodb::Result insert(arangodb::transaction::Methods* trx,
                                   arangodb::velocypack::Slice const newSlice,
@@ -100,9 +102,6 @@ class PhysicalCollectionMock : public arangodb::PhysicalCollection {
   virtual arangodb::Result read(arangodb::transaction::Methods*,
                                 arangodb::velocypack::StringRef const& key,
                                 arangodb::ManagedDocumentResult& result, bool) override;
-  virtual arangodb::Result read(arangodb::transaction::Methods*,
-                                arangodb::velocypack::Slice const& key,
-                                arangodb::ManagedDocumentResult& result, bool) override;
   virtual bool readDocument(arangodb::transaction::Methods* trx,
                             arangodb::LocalDocumentId const& token,
                             arangodb::ManagedDocumentResult& result) const override;
diff --git a/tests/js/client/shell/shell-aql-v8.js b/tests/js/client/shell/shell-aql-v8.js
new file mode 100644
index 000000000000..6a60e7789ee2
--- /dev/null
+++ b/tests/js/client/shell/shell-aql-v8.js
@@ -0,0 +1,118 @@
+/*jshint globalstrict:false, strict:false, maxlen:1000*/
+/*global assertEqual, assertTrue, assertFalse, fail, more */
+
+////////////////////////////////////////////////////////////////////////////////
+/// @brief test V8 invocation from AQL
+///
+/// @file
+///
+/// DISCLAIMER
+///
+/// Copyright 2010-2012 triagens GmbH, Cologne, Germany
+///
+/// Licensed under the Apache License, Version 2.0 (the "License");
+/// you may not use this file except in compliance with the License.
+/// You may obtain a copy of the License at
+///
+///     http://www.apache.org/licenses/LICENSE-2.0
+///
+/// Unless required by applicable law or agreed to in writing, software
+/// distributed under the License is distributed on an "AS IS" BASIS,
+/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+/// See the License for the specific language governing permissions and
+/// limitations under the License.
+///
+/// Copyright holder is triAGENS GmbH, Cologne, Germany
+///
+/// @author Jan Steemann
+/// @author Copyright 2012, triAGENS GmbH, Cologne, Germany
+////////////////////////////////////////////////////////////////////////////////
+
+const jsunity = require("jsunity");
+
+const arangodb = require("@arangodb");
+const functions = require('@arangodb/aql/functions');
+const db = arangodb.db;
+
+function V8QuerySuite () {
+  'use strict';
+  return {
+    setUpAll : function () {
+      try {
+        functions.unregister('test::testudf');
+      } catch (err) {}
+      
+      functions.register('test::testudf', function() { return 42; });
+    },
+    
+    tearDownAll : function () {
+      try {
+        functions.unregister('test::testudf');
+      } catch (err) {}
+    },
+
+    testCallV8 : function () {
+      let results = db._query({ query: "RETURN CALL('V8', 'abcde')" }).toArray();
+      assertEqual('abcde', results[0]);
+    },
+    
+    testCallV8Hidden : function () {
+      let results = db._query({ query: "RETURN CALL(NOOPT('V8'), 'abcde')" }).toArray();
+      assertEqual('abcde', results[0]);
+    },
+    
+    testApplyV8 : function () {
+      let results = db._query({ query: "RETURN APPLY('V8', [ 'abcde' ])" }).toArray();
+      assertEqual('abcde', results[0]);
+    },
+    
+    testApplyV8Hidden : function () {
+      let results = db._query({ query: "RETURN APPLY(NOOPT('V8'), [ 'abcde' ])" }).toArray();
+      assertEqual('abcde', results[0]);
+    },
+
+    testCallNonV8 : function () {
+      let results = db._query({ query: "RETURN CALL('SUBSTRING', 'abcde', 1, 2)" }).toArray();
+      assertEqual('bc', results[0]);
+    },
+    
+    testCallNonV8Hidden : function () {
+      let results = db._query({ query: "RETURN CALL(NOOPT('SUBSTRING'), 'abcde', 1, 2)" }).toArray();
+      assertEqual('bc', results[0]);
+    },
+    
+    testApplyNonV8 : function () {
+      let results = db._query({ query: "RETURN APPLY('SUBSTRING', ['abcde', 1, 2])" }).toArray();
+      assertEqual('bc', results[0]);
+    },
+    
+    testApplyNonV8Hidden : function () {
+      let results = db._query({ query: "RETURN APPLY(NOOPT('SUBSTRING'), ['abcde', 1, 2])" }).toArray();
+      assertEqual('bc', results[0]);
+    },
+    
+    testCallUserDefined : function () {
+      let results = db._query({ query: "RETURN CALL('test::testudf')" }).toArray();
+      assertEqual(42, results[0]);
+    },
+    
+    testCallUserDefinedHidden : function () {
+      let results = db._query({ query: "RETURN CALL(NOOPT('test::testudf'))" }).toArray();
+      assertEqual(42, results[0]);
+    },
+    
+    testApplyUserDefined : function () {
+      let results = db._query({ query: "RETURN APPLY('test::testudf', [])" }).toArray();
+      assertEqual(42, results[0]);
+    },
+    
+    testApplyUserDefinedHidden : function () {
+      let results = db._query({ query: "RETURN APPLY(NOOPT('test::testudf'), [])" }).toArray();
+      assertEqual(42, results[0]);
+    },
+
+  };
+}
+
+jsunity.run(V8QuerySuite);
+return jsunity.done();
diff --git a/tests/js/client/shell/shell-foxx-interface.js b/tests/js/client/shell/shell-foxx-interface.js
new file mode 100644
index 000000000000..b1249940d3ed
--- /dev/null
+++ b/tests/js/client/shell/shell-foxx-interface.js
@@ -0,0 +1,225 @@
+/* jshint globalstrict:false, strict:false, maxlen: 200 */
+/* global assertTrue, assertEqual, assertUndefined, arango, Buffer */
+
+// //////////////////////////////////////////////////////////////////////////////
+// / @brief ArangoTransaction sTests
+// /
+// /
+// / DISCLAIMER
+// /
+// / Copyright 2020 ArangoDB GmbH, Cologne, Germany
+// /
+// / Licensed under the Apache License, Version 2.0 (the "License")
+// / you may not use this file except in compliance with the License.
+// / You may obtain a copy of the License at
+// /
+// /     http://www.apache.org/licenses/LICENSE-2.0
+// /
+// / Unless required by applicable law or agreed to in writing, software
+// / distributed under the License is distributed on an "AS IS" BASIS,
+// / WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// / See the License for the specific language governing permissions and
+// / limitations under the License.
+// /
+// / Copyright holder is ArangoDB Inc, Cologne, Germany
+// /
+// / @author Wilfried Goesgens
+// //////////////////////////////////////////////////////////////////////////////
+
+var jsunity = require('jsunity');
+var internal = require('internal');
+var arangodb = require('@arangodb');
+const path = require('path');
+var db = arangodb.db;
+var origin = arango.getEndpoint().replace(/\+vpp/, '').replace(/^tcp:/, 'http:').replace(/^ssl:/, 'https:').replace(/^vst:/, 'http:').replace(/^h2:/, 'http:');
+const FoxxManager = require('@arangodb/foxx/manager');
+const basePath = path.resolve(internal.pathForTesting('common'), 'test-data', 'apps', 'interface');
+
+const jsonMime = 'application/json';
+const vpackMime = "application/x-velocypack";
+const binaryMime = 'image/gif';
+const textMime = 'text/plain';
+const pixelStr = 'R0lGODlhAQABAIAAAP///wAAACH5BAEAAAAALAAAAAABAAEAAAICRAEAOw==';
+const pixelGif = new Buffer(pixelStr, 'base64');
+const vpackObjectSize = 73;
+
+const cmpBuffer = function(a, b) {
+  if (a.length !== b.length) {
+    return false;
+  }
+  if (typeof b === 'string') {
+    for (let i = 0; i < a.length; ++i) {
+      if (a[i] !== b.charCodeAt(i)) {
+        return false;
+      }
+    }
+  } else {
+    for (let i = 0; i < a.length; ++i) {
+      if (a[i] !== b[i]) {
+        return false;
+      }
+    }
+  }
+  return true;
+};
+
+// //////////////////////////////////////////////////////////////////////////////
+// / @brief test suite
+// //////////////////////////////////////////////////////////////////////////////
+
+function foxxInterfaceSuite () {
+  'use strict';
+  const cn = "UnitTestsCollection";
+  const mount = '/test-interface';
+  const url = `/_db/${db._name()}${mount}/interface-echo`;
+  const binUrl = `${url}-bin`;
+  const txtUrl = `${url}-str`;
+  return {
+
+    setUpAll: function () {
+      FoxxManager.install(basePath, mount);
+    },
+
+    tearDownAll: function () {
+      FoxxManager.uninstall(mount, {force: true});
+    },
+    
+    testFoxxInterfacePostBody: function () {
+      [
+        'POST_RAW',
+        'PUT_RAW',
+        'PATCH_RAW',
+        'DELETE_RAW'
+      ].forEach((reqMethod) => {
+        let res = arango[reqMethod](url,
+                                    {
+                                      pixelStr
+                                    },
+                                    {
+                                      'content-type': jsonMime
+                                    });
+        assertEqual(res.code, 200, { meth: reqMethod, replyBody: res.parsedBody });
+        assertTrue(typeof res.parsedBody === 'object');
+        
+        assertEqual(JSON.stringify(res.parsedBody), JSON.stringify({ pixelStr }));
+        assertEqual(res.headers['content-length'], vpackObjectSize);
+        assertEqual(res.headers['content-type'], vpackMime);
+        assertEqual(res.headers['test'], 'header');
+        assertEqual(res.headers['request-type'], reqMethod);
+      });
+    },
+    testFoxxInterfaceGet: function () {
+      let res = arango.GET_RAW(url);
+      assertEqual(res.code, 200, res.parsedBody);
+      assertTrue(typeof res.parsedBody === 'object');
+      
+      assertEqual(JSON.stringify(res.parsedBody), JSON.stringify({ pixelStr }));
+      assertEqual(res.headers['content-length'], vpackObjectSize);
+      assertEqual(res.headers['content-type'], vpackMime);
+      assertEqual(res.headers['test'], 'header');
+      assertEqual(res.headers['request-type'], 'GET_RAW');
+    },
+    testFoxxInterfaceHead: function () {
+      let res = arango.HEAD_RAW(url);
+      assertEqual(res.code, 200, res.parsedBody);
+      assertUndefined(res.body);
+      assertEqual(res.headers['content-length'], vpackObjectSize);
+      assertEqual(res.headers['content-type'], vpackMime);
+      assertEqual(res.headers['test'], 'header');
+      assertEqual(res.headers['request-type'], 'HEAD_RAW');
+    },
+    testFoxxInterfacePostBodyBinary: function () {
+      [
+        'POST_RAW',
+        'PUT_RAW',
+        'PATCH_RAW',
+        'DELETE_RAW'
+      ].forEach((reqMethod) => {
+        let res = arango[reqMethod](binUrl,
+                                    pixelGif,
+                                    {
+                                      'content-type': binaryMime
+                                    });
+        assertEqual(res.code, 200, { meth: reqMethod, replyBody: res.parsedBody });
+        assertTrue(res.body instanceof Buffer);
+        
+        let respBody = new Buffer(res.body);
+        assertTrue(cmpBuffer(respBody, pixelGif), "whether the server sent us a proper one pixel gif");
+        assertEqual(res.headers['content-length'], pixelGif.length);
+        assertEqual(res.headers['content-type'], binaryMime);
+        assertEqual(res.headers['test'], 'header');
+        assertEqual(res.headers['request-type'], reqMethod);
+      });
+    },
+    testFoxxInterfaceGetBinary: function () {
+      let res = arango.GET_RAW(binUrl);
+      assertEqual(res.code, 200, res.parsedBody);
+      assertTrue(res.body instanceof Buffer);
+      
+      let respBody = new Buffer(res.body);
+      assertTrue(cmpBuffer(respBody, pixelGif), "whether the server sent us a proper one pixel gif");
+      assertEqual(res.headers['content-length'], pixelGif.length);
+      assertEqual(res.headers['content-type'], binaryMime);
+      assertEqual(res.headers['test'], 'header');
+      assertEqual(res.headers['request-type'], 'GET_RAW');
+    },
+    testFoxxInterfaceHeadBinary: function () {
+      let res = arango.HEAD_RAW(binUrl);
+      assertEqual(res.code, 200, res.parsedBody);
+      assertTrue(res.body instanceof Buffer);
+      assertEqual(res.body.length, 0);
+      
+      assertEqual(res.headers['content-length'], pixelGif.length);
+      assertEqual(res.headers['content-type'], binaryMime);
+      assertEqual(res.headers['test'], 'header');
+      assertEqual(res.headers['request-type'], 'HEAD_RAW');
+    },
+
+    testFoxxInterfacePostBodyText: function () {
+      [
+        'POST_RAW',
+        'PUT_RAW',
+        'PATCH_RAW',
+        'DELETE_RAW'
+      ].forEach((reqMethod) => {
+        let res = arango[reqMethod](txtUrl,
+                                    pixelStr,
+                                    {
+                                      'content-type': textMime
+                                    });
+        assertEqual(res.code, 200, { meth: reqMethod, replyBody: res.parsedBody });
+        assertTrue(typeof res.body === 'string');
+
+        assertEqual(res.body, pixelStr, "whether the server sent us a proper one pixel gif");
+        assertEqual(res.headers['content-length'], pixelStr.length);
+        assertEqual(res.headers['content-type'], textMime);
+        assertEqual(res.headers['test'], 'header');
+        assertEqual(res.headers['request-type'], reqMethod);
+      });
+    },
+    testFoxxInterfaceGetText: function () {
+      let res = arango.GET_RAW(txtUrl);
+      assertEqual(res.code, 200, res.parsedBody);
+      assertTrue(typeof res.body === 'string');
+
+      assertEqual(res.body, pixelStr, "whether the server sent us a proper one pixel gif");
+      assertEqual(res.headers['content-length'], pixelStr.length);
+      assertEqual(res.headers['content-type'], textMime);
+      assertEqual(res.headers['test'], 'header');
+      assertEqual(res.headers['request-type'], 'GET_RAW');
+    },
+    testFoxxInterfaceHeadText: function () {
+      let res = arango.HEAD_RAW(txtUrl);
+      assertEqual(res.code, 200, res.parsedBody);
+      assertUndefined(res.body);
+      assertEqual(res.headers['content-length'], pixelStr.length);
+      assertEqual(res.headers['content-type'], textMime);
+      assertEqual(res.headers['test'], 'header');
+      assertEqual(res.headers['request-type'], 'HEAD_RAW');
+    }
+  };
+}
+
+jsunity.run(foxxInterfaceSuite);
+
+return jsunity.done();
diff --git a/tests/js/client/shell/shell-statement.js b/tests/js/client/shell/shell-statement.js
index 349a782edcae..0148103929bf 100644
--- a/tests/js/client/shell/shell-statement.js
+++ b/tests/js/client/shell/shell-statement.js
@@ -42,20 +42,6 @@ function StatementSuite () {
   'use strict';
   return {
 
-////////////////////////////////////////////////////////////////////////////////
-/// @brief set up
-////////////////////////////////////////////////////////////////////////////////
-
-    setUp : function () {
-    },
-
-////////////////////////////////////////////////////////////////////////////////
-/// @brief tear down
-////////////////////////////////////////////////////////////////////////////////
-
-    tearDown : function () {
-    },
-
 ////////////////////////////////////////////////////////////////////////////////
 /// @brief test cursor
 ////////////////////////////////////////////////////////////////////////////////
@@ -165,20 +151,6 @@ function StatementStreamSuite () {
 
   return {
 
-////////////////////////////////////////////////////////////////////////////////
-/// @brief set up
-////////////////////////////////////////////////////////////////////////////////
-
-    setUp : function () {
-    },
-
-////////////////////////////////////////////////////////////////////////////////
-/// @brief tear down
-////////////////////////////////////////////////////////////////////////////////
-
-    tearDown : function () {
-    },
-
 ////////////////////////////////////////////////////////////////////////////////
 /// @brief test cursor
 ////////////////////////////////////////////////////////////////////////////////
diff --git a/tests/js/common/aql/aql-view-arangosearch-cluster.inc b/tests/js/common/aql/aql-view-arangosearch-cluster.inc
index 08357b40b4cc..e8e1eb0964df 100644
--- a/tests/js/common/aql/aql-view-arangosearch-cluster.inc
+++ b/tests/js/common/aql/aql-view-arangosearch-cluster.inc
@@ -1669,6 +1669,85 @@
           db._dropView(queryOptView);
         }
       },
+      testNGramMatch : function() {
+        let queryColl = "NgramMatchCol";
+        let queryView = "NgramMatchView";
+        let queryAnalyzer = "ngram_match_myngram";
+        try {
+          db._drop(queryColl);
+          db._dropView(queryView);
+          analyzers.save(queryAnalyzer, 
+                         "ngram", 
+                         {
+                           "min":2, 
+                           "max":2, 
+                           "streamType":"utf8", 
+                           "preserveOriginal":false
+                         },
+                         ["frequency", "position", "norm"]);
+          let coll = db._create(queryColl);
+          let view = db._createView(queryView,
+                                    "arangosearch",
+                                    { 
+                                      links: { 
+                                              NgramMatchCol : { analyzers: [ queryAnalyzer],
+                                                                includeAllFields: true, 
+                                                                trackListPositions: true} 
+                                              }
+                                    });
+          coll.save({ value1: "1", value2: "Jack Daniels"}); 
+          coll.save({ value1: "2", value2: "Jack Sparrow"}); 
+          coll.save({ value1: "3", value2: "Jack The Reaper"}); 
+          coll.save({ value1: "4", value2: "Jackhammer"}); 
+          coll.save({ value1: "5", value2: "Jacky Chan"}); 
+          {
+            let res = db._query("FOR d IN " + queryView  + 
+              " SEARCH NGRAM_MATCH(d.value2, 'Jack Sparrow', 0.7, '" + queryAnalyzer + "') " + 
+              " OPTIONS { waitForSync : true} SORT BM25(d) DESC RETURN d").toArray();
+            assertEqual(1, res.length);  
+            assertEqual('2', res[0].value1);
+          }
+          // same but with default threshold (0.7 also)
+          {
+            let res = db._query("FOR d IN " + queryView  + 
+              " SEARCH NGRAM_MATCH(d.value2, 'Jack Sparrow', '" + queryAnalyzer + "') " + 
+              " OPTIONS { waitForSync : true} SORT BM25(d) DESC RETURN d").toArray();
+            assertEqual(1, res.length);  
+            assertEqual('2', res[0].value1);
+          }
+          // same but with default threshold (0.7 also) and analyzer via ANALYZER func
+          {
+            let res = db._query("FOR d IN " + queryView  + 
+              " SEARCH ANALYZER(NGRAM_MATCH(d.value2, 'Jack Sparrow'), '" + queryAnalyzer + "') " + 
+              " OPTIONS { waitForSync : true} SORT BM25(d) DESC RETURN d").toArray();
+            assertEqual(1, res.length);  
+            assertEqual('2', res[0].value1);
+          }
+          {
+            let res = db._query("FOR d IN " + queryView  + 
+              " SEARCH NGRAM_MATCH(d.value2, 'Jack Doniels', 0.3, '" + queryAnalyzer + "') " + 
+              " OPTIONS { waitForSync : true} SORT BM25(d) DESC RETURN d").toArray();
+            assertEqual(3, res.length);  
+            assertEqual('1', res[0].value1);
+            assertEqual('3', res[1].value1);
+            assertEqual('2', res[2].value1);
+          }
+          {
+            let res = db._query("FOR d IN " + queryView  + 
+              " SEARCH NGRAM_MATCH(d.value2, 'Jack Doniels', 0.3, '" + queryAnalyzer + "') " + 
+              " OPTIONS { waitForSync : true} SORT TFIDF(d) DESC RETURN d").toArray();
+            assertEqual(3, res.length);  
+            assertEqual('1', res[0].value1);
+            assertEqual('2', res[1].value1);
+            assertEqual('3', res[2].value1);
+          }
+        } 
+        finally {
+          db._drop(queryColl);
+          db._dropView(queryView);
+          analyzers.remove(queryAnalyzer, true);
+        }
+      }
     };
   };
 }());
diff --git a/tests/js/common/aql/aql-view-arangosearch-noncluster.js b/tests/js/common/aql/aql-view-arangosearch-noncluster.js
index 78d86c379db5..39f3a7a03f76 100644
--- a/tests/js/common/aql/aql-view-arangosearch-noncluster.js
+++ b/tests/js/common/aql/aql-view-arangosearch-noncluster.js
@@ -1714,6 +1714,85 @@ function iResearchAqlTestSuite () {
         db._dropView(queryOptView);
       }
     },
+    testNGramMatch : function() {
+      let queryColl = "NgramMatchCol";
+      let queryView = "NgramMatchView";
+      let queryAnalyzer = "ngram_match_myngram";
+      try {
+        db._drop(queryColl);
+        db._dropView(queryView);
+        analyzers.save(queryAnalyzer, 
+                       "ngram", 
+                       {
+                         "min":2, 
+                         "max":2, 
+                         "streamType":"utf8", 
+                         "preserveOriginal":false
+                       },
+                       ["frequency", "position", "norm"]);
+        let coll = db._create(queryColl);
+        let view = db._createView(queryView,
+                                  "arangosearch",
+                                  { 
+                                    links: { 
+                                            NgramMatchCol : { analyzers: [ queryAnalyzer],
+                                                              includeAllFields: true, 
+                                                              trackListPositions: true} 
+                                            }
+                                  });
+        coll.save({ value1: "1", value2: "Jack Daniels"}); 
+        coll.save({ value1: "2", value2: "Jack Sparrow"}); 
+        coll.save({ value1: "3", value2: "Jack The Reaper"}); 
+        coll.save({ value1: "4", value2: "Jackhammer"}); 
+        coll.save({ value1: "5", value2: "Jacky Chan"}); 
+        {
+          let res = db._query("FOR d IN " + queryView  + 
+            " SEARCH NGRAM_MATCH(d.value2, 'Jack Sparrow', 0.7, '" + queryAnalyzer + "') " + 
+            " OPTIONS { waitForSync : true} SORT BM25(d) DESC RETURN d").toArray();
+          assertEqual(1, res.length);  
+          assertEqual('2', res[0].value1);
+        }
+        // same but with default threshold (0.7 also)
+        {
+          let res = db._query("FOR d IN " + queryView  + 
+            " SEARCH NGRAM_MATCH(d.value2, 'Jack Sparrow', '" + queryAnalyzer + "') " + 
+            " OPTIONS { waitForSync : true} SORT BM25(d) DESC RETURN d").toArray();
+          assertEqual(1, res.length);  
+          assertEqual('2', res[0].value1);
+        }
+        // same but with default threshold (0.7 also) and analyzer via ANALYZER func
+        {
+          let res = db._query("FOR d IN " + queryView  + 
+            " SEARCH ANALYZER(NGRAM_MATCH(d.value2, 'Jack Sparrow'), '" + queryAnalyzer + "') " + 
+            " OPTIONS { waitForSync : true} SORT BM25(d) DESC RETURN d").toArray();
+          assertEqual(1, res.length);  
+          assertEqual('2', res[0].value1);
+        }
+        {
+          let res = db._query("FOR d IN " + queryView  + 
+            " SEARCH NGRAM_MATCH(d.value2, 'Jack Doniels', 0.3, '" + queryAnalyzer + "') " + 
+            " OPTIONS { waitForSync : true} SORT BM25(d) DESC RETURN d").toArray();
+          assertEqual(3, res.length);  
+          assertEqual('1', res[0].value1);
+          assertEqual('3', res[1].value1);
+          assertEqual('2', res[2].value1);
+        }
+        {
+          let res = db._query("FOR d IN " + queryView  + 
+            " SEARCH NGRAM_MATCH(d.value2, 'Jack Doniels', 0.3, '" + queryAnalyzer + "') " + 
+            " OPTIONS { waitForSync : true} SORT TFIDF(d) DESC RETURN d").toArray();
+          assertEqual(3, res.length);  
+          assertEqual('1', res[0].value1);
+          assertEqual('2', res[1].value1);
+          assertEqual('3', res[2].value1);
+        }
+      } 
+      finally {
+        db._drop(queryColl);
+        db._dropView(queryView);
+        analyzers.remove(queryAnalyzer, true);
+      }
+    },
   };
 }
 
diff --git a/tests/js/common/shell/shell-collection.js b/tests/js/common/shell/shell-collection.js
index b1a088c2228e..f188847bfa41 100644
--- a/tests/js/common/shell/shell-collection.js
+++ b/tests/js/common/shell/shell-collection.js
@@ -533,6 +533,31 @@ function CollectionSuite () {
       db._drop(cn);
     },
 
+////////////////////////////////////////////////////////////////////////////////
+/// @brief check that properties include usesRevisionsAsDocumentIds
+////////////////////////////////////////////////////////////////////////////////
+
+    testUsesRevisionsAsDocumentIds: function () {
+      var cn = "example";
+
+      db._drop(cn);
+      var c1 = db._create(cn);
+
+      assertTypeOf("string", c1._id);
+      assertEqual(cn, c1.name());
+      assertTypeOf("number", c1.status());
+      assertEqual(ArangoCollection.TYPE_DOCUMENT, c1.type());
+      assertTypeOf("number", c1.type());
+
+      var p = c1.properties();
+
+      var isRocksDB = db._engine().name === "rocksdb";
+      assertEqual(true, p.hasOwnProperty("usesRevisionsAsDocumentIds"));
+      assertEqual(isRocksDB, p.usesRevisionsAsDocumentIds);
+
+      db._drop(cn);
+    },
+
 ////////////////////////////////////////////////////////////////////////////////
 /// @brief drop new-born
 ////////////////////////////////////////////////////////////////////////////////
diff --git a/tests/js/common/shell/shell-validation-rocksdb.js b/tests/js/common/shell/shell-validation-rocksdb.js
index c801cbaa68b5..1e4e9f52cf0c 100644
--- a/tests/js/common/shell/shell-validation-rocksdb.js
+++ b/tests/js/common/shell/shell-validation-rocksdb.js
@@ -31,7 +31,6 @@ var jsunity = require("jsunity");
 
 const internal = require("internal");
 const db = internal.db;
-const print = internal.print;
 const arangodb = require("@arangodb");
 const ERRORS = arangodb.errors;
 
@@ -43,35 +42,15 @@ let sleepInCluster = () => {
   }
 };
 
-function ValidationBasicsSuite () {
-  const validatorsStart=[
-    {
-        type : "bool",
-        rule : true,
-        message : "Hit tautology rule.",
-        //description : "This rule is always successful"
-    },
-    {
-        type : "bool",
-        rule : false,
-        message : "Hit always-fail rule.",
-        //description : "This rule always fails"
-    },
-    {
-        type : "aql",
-        level : "new",
-        rule : "RETURN TRUE",
-        message : "Another tautology rule!",
-    }
-  ];
-
+const goodDoc = { "zahlen" : [1, 2, 3, 4] };
+const badDoc = { "zahlen" : "1, 2, 3, 4" };
 
+function ValidationBasicsSuite () {
   const skipOptions = { skipDocumentValidation : true };
 
   const testCollectionName = "TestValidationCollection";
   var testCollection;
-  var validatorsTrueOnly;
-  var validatorsFalseOnly;
+  var validatorJson;
 
   return {
 
@@ -79,19 +58,13 @@ function ValidationBasicsSuite () {
       try {
         db._drop(testCollectionName);
       } catch (ex) {}
-      testCollection = db._create(testCollectionName, { "validators" :  validatorsStart });
-      validatorsTrueOnly = [ {
-        type : "bool",
-        level : "new",
-        rule : true,
-        message : "First rule of the tautology club is the first rule of the tautology club.",
-      } ];
-      validatorsFalseOnly = [ {
-        type : "bool",
-        level : "moderate",
-        rule : false,
-        message : "Oh no what a nightmare!",
-      } ];
+      validatorJson = {
+        level : "strict",
+        rule : { properties: { zahlen : { type : "array", items : { type : "number", maximum : 6 }}}},
+        message : "Json-Schema validation failed",
+        type : "json"
+      };
+      testCollection = db._create(testCollectionName, { "validation" :  validatorJson });
     },
 
     tearDown : () => {
@@ -102,36 +75,33 @@ function ValidationBasicsSuite () {
 
     // properties ////////////////////////////////////////////////////////////////////////////////////////
     testProperties : () => {
-      const v = validatorsStart;
+      const v = validatorJson;
       var props = testCollection.properties();
       assertTrue(props !== undefined);
-      assertEqual(props.validators.length, 3);
-      assertEqual(props.validators[0].type, v[0].type);
-      assertEqual(props.validators[0].rule, v[0].rule);
-      assertEqual(props.validators[0].message, v[0].message);
-      assertEqual(props.validators[0].level, "strict");
-
-      assertEqual(props.validators[2].type, v[2].type);
-      assertEqual(props.validators[2].level, v[2].level);
+      assertEqual(props.validation.type, v.type);
+      assertEqual(props.validation.rule, v.rule);
+      assertEqual(props.validation.message, v.message);
+      assertEqual(props.validation.level, v.level);
     },
 
     testPropertiesUpdate : () => {
-      const v =  validatorsTrueOnly;
-      testCollection.properties({"validators" : v});
+      let v =  validatorJson;
+      v.level = "none";
+
+      testCollection.properties({"validation" : v});
 
       var props = testCollection.properties();
+      assertEqual(props.validation.type, v.type);
+      assertEqual(props.validation.rule, v.rule);
+      assertEqual(props.validation.message, v.message);
+      assertEqual(props.validation.level, v.level);
       assertTrue(props !== undefined);
-      assertEqual(props.validators.length, 1);
-      assertEqual(props.validators[0].type, "bool");
-      assertEqual(props.validators[0].rule, true);
-      assertEqual(props.validators[0].message, v[0].message);
-      assertEqual(props.validators[0].level, v[0].level);
     },
 
-    testPropertiesUpdateNoArray : () => {
-      const v =  validatorsTrueOnly[0];
+    testPropertiesUpdateNoObject : () => {
+      const v =  "hund";
       try {
-        testCollection.properties({"validators" : v});
+        testCollection.properties({"validation" : v});
         fail();
       } catch (err) {
         assertEqual(ERRORS.ERROR_VALIDATION_BAD_PARAMETER.code, err.errorNum);
@@ -141,7 +111,7 @@ function ValidationBasicsSuite () {
     // insert ////////////////////////////////////////////////////////////////////////////////////////////
     testDocumentsShellInsert : () => {
       try {
-        testCollection.insert({"foo" : "bar"});
+        testCollection.insert(badDoc);
         fail();
       } catch (err) {
         assertEqual(ERRORS.ERROR_VALIDATION_FAILED.code, err.errorNum);
@@ -149,13 +119,13 @@ function ValidationBasicsSuite () {
     },
 
     testDocumentsShellInsertSkip : () => {
-      testCollection.insert({"foo" : "bar"}, skipOptions);
+      testCollection.insert(badDoc, skipOptions);
       assertEqual(testCollection.toArray().length, 1);
     },
 
     testAQLInsert : () => {
       try {
-        db._query(`INSERT {"foo" : "bar"} INTO ${testCollectionName}`);
+        db._query(`INSERT {"zahlen" : "1, 2, 3, 4"} INTO ${testCollectionName}`);
         fail();
       } catch (err) {
         assertEqual(ERRORS.ERROR_VALIDATION_FAILED.code, err.errorNum);
@@ -163,16 +133,16 @@ function ValidationBasicsSuite () {
     },
 
     testAQLInsertSkip : () => {
-      db._query(`INSERT {"foo" : "bar"} INTO ${testCollectionName} OPTIONS { "skipDocumentValidation" : true }`);
+      db._query(`INSERT {"zahlen" : "1, 2, 3, 4"} INTO ${testCollectionName} OPTIONS { "skipDocumentValidation" : true }`);
       assertEqual(testCollection.toArray().length, 1);
     },
 
     testDocumentsShellUpdate : () => {
-      let doc = testCollection.insert({"foo" : "bar"}, skipOptions);
+      let doc = testCollection.insert(badDoc, skipOptions);
       assertEqual(testCollection.toArray().length, 1);
 
       try {
-        testCollection.update(doc._key, {"foo" : "baz"});
+        testCollection.update(doc._key, badDoc);
         fail();
       } catch (err) {
         assertEqual(ERRORS.ERROR_VALIDATION_FAILED.code, err.errorNum);
@@ -181,19 +151,19 @@ function ValidationBasicsSuite () {
 
     // update ////////////////////////////////////////////////////////////////////////////////////////////
     testDocumentsShellUpdateSkip : () => {
-      let doc = testCollection.insert({"foo" : "bar"}, skipOptions);
+      let doc = testCollection.insert(badDoc, skipOptions);
       assertEqual(testCollection.toArray().length, 1);
 
-      testCollection.update(doc._key, {"foo" : "baz"}, skipOptions);
+      testCollection.update(doc._key, badDoc, skipOptions);
       assertEqual(testCollection.toArray().length, 1);
     },
 
     testAQLUpdate : () => {
-      let doc = testCollection.insert({"foo" : "bar"}, skipOptions);
+      let doc = testCollection.insert(badDoc, skipOptions);
       assertEqual(testCollection.toArray().length, 1);
 
       try {
-        db._query(`UPDATE "${doc._key}" WITH {"foo" : "baz"} INTO ${testCollectionName}`);
+        db._query(`UPDATE "${doc._key}" WITH {"zahlen" : "baz"} INTO ${testCollectionName}`);
         fail();
       } catch (err) {
         assertEqual(ERRORS.ERROR_VALIDATION_FAILED.code, err.errorNum);
@@ -201,28 +171,28 @@ function ValidationBasicsSuite () {
     },
 
     testAQLUpdateSkip : () => {
-      let doc = testCollection.insert({"foo" : "bar"}, skipOptions);
+      let doc = testCollection.insert(badDoc, skipOptions);
       assertEqual(testCollection.toArray().length, 1);
 
-      db._query(`UPDATE "${doc._key}" WITH {"foo" : "baz"} INTO ${testCollectionName} OPTIONS { "skipDocumentValidation" : true }`);
+      db._query(`UPDATE "${doc._key}" WITH {"zahlen" : "baz"} INTO ${testCollectionName} OPTIONS { "skipDocumentValidation" : true }`);
       assertEqual(testCollection.toArray().length, 1);
     },
 
     // replace ///////////////////////////////////////////////////////////////////////////////////////////
     testDocumentsShellReplaceSkip : () => {
-      let doc = testCollection.insert({"foo" : "bar"}, skipOptions);
+      let doc = testCollection.insert(badDoc, skipOptions);
       assertEqual(testCollection.toArray().length, 1);
 
-      testCollection.replace(doc._key, {"foo" : "baz"}, skipOptions);
+      testCollection.replace(doc._key, badDoc, skipOptions);
       assertEqual(testCollection.toArray().length, 1);
     },
 
     testAQLReplace : () => {
-      let doc = testCollection.insert({"foo" : "bar"}, skipOptions);
+      let doc = testCollection.insert(badDoc, skipOptions);
       assertEqual(testCollection.toArray().length, 1);
 
       try {
-        db._query(`REPLACE "${doc._key}" WITH {"foo" : "baz"} INTO ${testCollectionName}`);
+        db._query(`REPLACE "${doc._key}" WITH {"zahlen" : "baz"} INTO ${testCollectionName}`);
         fail();
       } catch (err) {
         assertEqual(ERRORS.ERROR_VALIDATION_FAILED.code, err.errorNum);
@@ -230,95 +200,106 @@ function ValidationBasicsSuite () {
     },
 
     testAQLReplaceSkip : () => {
-      let doc = testCollection.insert({"foo" : "bar"}, skipOptions);
+      let doc = testCollection.insert(badDoc, skipOptions);
       assertEqual(testCollection.toArray().length, 1);
 
-      db._query(`REPLACE "${doc._key}" WITH {"foo" : "baz"} INTO ${testCollectionName} OPTIONS { "skipDocumentValidation" : true }`);
+      db._query(`REPLACE "${doc._key}" WITH {"zahlen" : "baz"} INTO ${testCollectionName} OPTIONS { "skipDocumentValidation" : true }`);
       assertEqual(testCollection.toArray().length, 1);
     },
 
     // levels ////////////////////////////////////////////////////////////////////////////////////////////
     testLevelNone : () => {
-      const v =  validatorsFalseOnly;
-      const v0 =  v[0];
-      v0.level = "none";
-      testCollection.properties({"validators" : v });
+      const v =  validatorJson;
+      v.level = "none";
+      testCollection.properties({"validation" : v });
       sleepInCluster();
-      assertEqual(testCollection.properties().validators[0].level, v0.level);
-      let  doc = testCollection.insert({"foo" : "bar"});
+      assertEqual(testCollection.properties().validation.level, v.level);
+      let  doc = testCollection.insert(badDoc);
     },
 
     testLevelNew : () => {
-      const v =  validatorsFalseOnly;
-      const v0 =  v[0];
-      v0.level = "new";
-      testCollection.properties({"validators" : v });
+      const v =  validatorJson;
+      v.level = "new";
+      testCollection.properties({"validation" : v });
       sleepInCluster();
-      assertEqual(testCollection.properties().validators[0].level, v0.level);
+      assertEqual(testCollection.properties().validation.level, v.level);
 
-      let  doc = testCollection.insert({"foo" : "bar"}, skipOptions);
+      let  doc = testCollection.insert(badDoc, skipOptions);
       try {
-        testCollection.insert({"foo" : "bar"});
+        testCollection.insert(badDoc);
         fail();
       } catch (err) {
         assertEqual(ERRORS.ERROR_VALIDATION_FAILED.code, err.errorNum);
       }
-      testCollection.replace(doc._key, {"foo" : "baz"});
-      testCollection.update(doc._key, {"foo" : "poo"});
+      testCollection.replace(doc._key, badDoc);
+      testCollection.update(doc._key, badDoc);
     },
 
     testLevelModerate : () => {
-      const v =  validatorsFalseOnly;
-      const v0 =  v[0];
-      v0.level = "moderate";
-      testCollection.properties({"validators" : v });
+      const v =  validatorJson;
+      v.level = "moderate";
+      testCollection.properties({"validation" : v });
       sleepInCluster();
-      assertEqual(testCollection.properties().validators[0].level, v0.level);
+      assertEqual(testCollection.properties().validation.level, v.level);
 
-      let  doc = testCollection.insert({"foo" : "bar"}, skipOptions);
+      let  doc = testCollection.insert(badDoc, skipOptions);
       try {
-        testCollection.insert({"foo" : "bar"});
+        testCollection.insert(badDoc);
         fail();
       } catch (err) {
         assertEqual(ERRORS.ERROR_VALIDATION_FAILED.code, err.errorNum);
       }
 
-      testCollection.replace(doc._key, {"foo" : "baz"});
-      testCollection.update(doc._key, {"foo" : "poo"});
+      testCollection.replace(doc._key, badDoc);
+      testCollection.update(doc._key, badDoc);
     },
 
     testLevelStict : () => {
-      const v =  validatorsFalseOnly;
-      const v0 =  v[0];
-      v0.level = "strict";
-      testCollection.properties({"validators" : v });
+      const v =  validatorJson;
+      v.level = "strict";
+      testCollection.properties({"validation" : v });
       sleepInCluster();
-      assertEqual(testCollection.properties().validators[0].level, v0.level);
+      assertEqual(testCollection.properties().validation.level, v.level);
 
-      let  doc = testCollection.insert({"foo" : "bar"}, skipOptions);
+      let  doc = testCollection.insert(badDoc, skipOptions);
 
       try {
-        testCollection.insert({"foo" : "bar"});
+        testCollection.insert(badDoc);
         fail();
       } catch (err) {
         assertEqual(ERRORS.ERROR_VALIDATION_FAILED.code, err.errorNum);
       }
 
       try {
-        testCollection.replace(doc._key, {"foo" : "baz"});
+        testCollection.replace(doc._key, badDoc);
         fail();
       } catch (err) {
         assertEqual(ERRORS.ERROR_VALIDATION_FAILED.code, err.errorNum);
       }
 
       try {
-        testCollection.update(doc._key, {"foo" : "poo"});
+        testCollection.update(doc._key, badDoc);
         fail();
       } catch (err) {
         assertEqual(ERRORS.ERROR_VALIDATION_FAILED.code, err.errorNum);
       }
 
     },
+    // json  ////////////////////////////////////////////////////////////////////////////////////////////
+    testJson : () => {
+      const v =  validatorJson;
+      v.level = "strict";
+      testCollection.properties({"validation" : v });
+      sleepInCluster();
+
+      let  doc = testCollection.insert(goodDoc, skipOptions);
+      try {
+        testCollection.insert(badDoc);
+        fail();
+      } catch (err) {
+        assertEqual(ERRORS.ERROR_VALIDATION_FAILED.code, err.errorNum);
+      }
+    },
 ////////////////////////////////////////////////////////////////////////////////
   }; // return
 } // END - ValidationBasicsSuite
diff --git a/tests/js/common/test-data/apps/interface/index.js b/tests/js/common/test-data/apps/interface/index.js
new file mode 100644
index 000000000000..8ef5dcf83fc8
--- /dev/null
+++ b/tests/js/common/test-data/apps/interface/index.js
@@ -0,0 +1,412 @@
+
+const pixelStr = 'R0lGODlhAQABAIAAAP///wAAACH5BAEAAAAALAAAAAABAAEAAAICRAEAOw==';
+const pixelGif = new Buffer(pixelStr, 'base64');
+const binaryMime = 'image/gif';
+const textMime = 'text/plain';
+const jsonMime = 'application/json; charset=utf-8';
+const createRouter = require('@arangodb/foxx/router');
+const ArangoError = require('@arangodb').ArangoError;
+const errors = require('internal').errors;
+const router = createRouter();
+
+const cmpBuffer = function(a, b) {
+  if (a.length !== b.length) {
+    return false;
+  }
+  if (typeof b === 'string') {
+    for (let i = 0; i < a.length; ++i) {
+      if (a[i] !== b.charCodeAt(i)) {
+        return false;
+      }
+    }
+  } else {
+    for (let i = 0; i < a.length; ++i) {
+      if (a[i] !== b[i]) {
+        return false;
+      }
+    }
+  }
+  return true;
+};
+
+router.post('/interface-echo', function (req, res) {
+  let postBuffer = req._raw.requestBody;
+  if (postBuffer !== JSON.stringify({pixelStr}) ) {
+    res.throw(500, {
+      errorNum: errors.ERROR_VALIDATION_FAILED.code,
+      errorMessage: "pixel gifs don't match"
+    });
+  }
+  if (req._raw.headers['content-type'] !== jsonMime) {
+    res.throw(500, {
+      errorNum: errors.ERROR_VALIDATION_FAILED.code,
+      errorMessage: `mimetypes don't match - ${jsonMime} !== ${req._raw.headers.content-type}`
+    });
+  }
+  let bufLen = postBuffer.length;
+  let headerLen = parseInt(req._raw.headers['content-length']);
+  if (headerLen !== bufLen) {
+    res.throw(500, {
+      errorNum: errors.ERROR_VALIDATION_FAILED.code,
+      errorMessage: `content-length header doesn't match - ${bufLen} !== ${headerLen}`
+    });
+  }
+  res.write({pixelStr});
+  res.set('test', 'header');
+  res.set('request-type', 'POST_RAW');
+});
+
+router.put('/interface-echo', function (req, res) {
+  let postBuffer = req._raw.requestBody;
+  if (postBuffer !== JSON.stringify({pixelStr}) ) {
+    res.throw(500, {
+      errorNum: errors.ERROR_VALIDATION_FAILED.code,
+      errorMessage: "pixel gifs don't match"
+    });
+  }
+  if (req._raw.headers['content-type'] !== jsonMime) {
+    res.throw(500, {
+      errorNum: errors.ERROR_VALIDATION_FAILED.code,
+      errorMessage: `mimetypes don't match - ${jsonMime} !== ${req._raw.headers.content-type}`
+    });
+  }
+  let bufLen = postBuffer.length;
+  let headerLen = parseInt(req._raw.headers['content-length']);
+  if (headerLen !== bufLen) {
+    res.throw(500, {
+      errorNum: errors.ERROR_VALIDATION_FAILED.code,
+      errorMessage: `content-length header doesn't match - ${bufLen} !== ${headerLen}`
+    });
+  }
+  res.write({pixelStr});
+  res.set('test', 'header');
+  res.set('request-type', 'PUT_RAW');
+});
+
+router.delete('/interface-echo', function (req, res){
+  let postBuffer = req._raw.requestBody;
+  if (postBuffer !== JSON.stringify({pixelStr}) ) {
+    res.throw(500, {
+      errorNum: errors.ERROR_VALIDATION_FAILED.code,
+      errorMessage: "pixel gifs don't match"
+    });
+  }
+  if (req._raw.headers['content-type'] !== jsonMime) {
+    res.throw(500, {
+      errorNum: errors.ERROR_VALIDATION_FAILED.code,
+      errorMessage: `mimetypes don't match - ${jsonMime} !== ${req._raw.headers.content-type}`
+    });
+  }
+  let bufLen = postBuffer.length;
+  let headerLen = parseInt(req._raw.headers['content-length']);
+  if (headerLen !== bufLen) {
+    res.throw(500, {
+      errorNum: errors.ERROR_VALIDATION_FAILED.code,
+      errorMessage: `content-length header doesn't match - ${bufLen} !== ${headerLen}`
+    });
+  }
+  res.write({pixelStr});
+  res.set('test', 'header');
+  res.set('request-type', 'DELETE_RAW');
+}).body("I can haz body");
+
+router.patch('/interface-echo', function (req, res) {
+  let postBuffer = req._raw.requestBody;
+  if (postBuffer !== JSON.stringify({pixelStr}) ) {
+    res.throw(500, {
+      errorNum: errors.ERROR_VALIDATION_FAILED.code,
+      errorMessage: "pixel gifs don't match"
+    });
+  }
+  if (req._raw.headers['content-type'] !== jsonMime) {
+    res.throw(500, {
+      errorNum: errors.ERROR_VALIDATION_FAILED.code,
+      errorMessage: `mimetypes don't match - ${jsonMime} !== ${req._raw.headers.content-type}`
+    });
+  }
+  let bufLen = postBuffer.length;
+  let headerLen = parseInt(req._raw.headers['content-length']);
+  if (headerLen !== bufLen) {
+    res.throw(500, {
+      errorNum: errors.ERROR_VALIDATION_FAILED.code,
+      errorMessage: `content-length header doesn't match - ${bufLen} !== ${headerLen}`
+    });
+  }
+  res.write({pixelStr});
+  res.set('test', 'header');
+  res.set('request-type', 'PATCH_RAW');
+});
+
+router.head('/interface-echo', function (req, res) {
+  res.write({pixelStr});
+  res.set('test', 'header');
+  res.set('request-type', 'HEAD_RAW');
+});
+
+router.get('/interface-echo', function (req, res) {
+  res.write({pixelStr});
+  res.set('test', 'header');
+  res.set('request-type', 'GET_RAW');
+});
+
+////////////////////////////////////////////////////////////////////////////////
+//            Binary post body + reply
+////////////////////////////////////////////////////////////////////////////////
+router.post('/interface-echo-bin', function (req, res) {
+  // convert SlowBuffer->Buffer
+  let postBuffer = new Buffer(req._raw.rawRequestBody);
+  if (!cmpBuffer(postBuffer, pixelGif)) {
+    res.throw(500, {
+      errorNum: errors.ERROR_VALIDATION_FAILED.code,
+      errorMessage: "pixel gifs don't match"
+    });
+  }
+  if (req._raw.headers['content-type'] !== binaryMime) {
+    res.throw(500, {
+      errorNum: errors.ERROR_VALIDATION_FAILED.code,
+      errorMessage: `mimetypes don't match - ${binaryMime} !== ${req._raw.headers.content-type}`
+    });
+  }
+  let bufLen = postBuffer.length;
+  let headerLen = parseInt(req._raw.headers['content-length']);
+  if (headerLen !== bufLen) {
+    res.throw(500, {
+      errorNum: errors.ERROR_VALIDATION_FAILED.code,
+      errorMessage: `content-length header doesn't match - ${bufLen} !== ${headerLen}`
+    });
+  }
+  res.write(pixelGif);
+  res.set('content-type', binaryMime);
+  res.set('test', 'header');
+  res.set('request-type', 'POST_RAW');
+});
+router.put('/interface-echo-bin', function (req, res) {
+  let postBuffer = new Buffer(req._raw.rawRequestBody);
+  if (!cmpBuffer(postBuffer, pixelGif)) {
+    res.throw(500, {
+      errorNum: errors.ERROR_VALIDATION_FAILED.code,
+      errorMessage: "pixel gifs don't match"
+    });
+  }
+  if (req._raw.headers['content-type'] !== binaryMime) {
+    res.throw(500, {
+      errorNum: errors.ERROR_VALIDATION_FAILED.code,
+      errorMessage: `mimetypes don't match - ${binaryMime} !== ${req._raw.headers['content-type']}`
+    });
+  }
+
+  let bufLen = postBuffer.length;
+  let headerLen = parseInt(req._raw.headers['content-length']);
+  if (headerLen !== bufLen) {
+    res.throw(500, {
+      errorNum: errors.ERROR_VALIDATION_FAILED.code,
+      errorMessage: `content-length header doesn't match - ${bufLen} !== ${headerLen}`
+    });
+  }
+  res.write(pixelGif);
+  res.set('content-type', binaryMime);
+  res.set('test', 'header');
+  res.set('request-type', 'PUT_RAW');
+});
+
+router.delete('/interface-echo-bin', function (req, res) {
+  let postBuffer = new Buffer(req._raw.rawRequestBody);
+  if (!cmpBuffer(postBuffer, pixelGif)) {
+    res.throw({
+      errorNum: errors.ERROR_VALIDATION_FAILED.code,
+      errorMessage: "pixel gifs don't match"
+    });
+  }
+  if (req._raw.headers['content-type'] !== binaryMime) {
+    res.throw(500, {
+      errorNum: errors.ERROR_VALIDATION_FAILED.code,
+      errorMessage: `mimetypes don't match - ${binaryMime} !== ${req._raw.headers.content-type}`
+    });
+  }
+  let bufLen = postBuffer.length;
+  let headerLen = parseInt(req._raw.headers['content-length']);
+  if (headerLen !== bufLen) {
+    res.throw(500, {
+      errorNum: errors.ERROR_VALIDATION_FAILED.code,
+      errorMessage: `content-length header doesn't match - ${bufLen} !== ${headerLen}`
+    });
+  }
+  res.write(pixelGif);
+  res.set('content-type', binaryMime);
+  res.set('test', 'header');
+  res.set('request-type', 'DELETE_RAW');
+}).body("I can haz body");
+
+router.patch('/interface-echo-bin', function (req, res) {
+  let postBuffer = new Buffer(req._raw.rawRequestBody);
+  if (!cmpBuffer(postBuffer, pixelGif)) {
+    res.throw(500, {
+      errorNum: errors.ERROR_VALIDATION_FAILED.code,
+      errorMessage: "pixel gifs don't match"
+    });
+  }
+  if (req._raw.headers['content-type'] !== binaryMime) {
+    res.throw(500, {
+      errorNum: errors.ERROR_VALIDATION_FAILED.code,
+      errorMessage: `mimetypes don't match - ${binaryMime} !== ${req._raw.headers.content-type}`
+    });
+  }
+  let bufLen = postBuffer.length;
+  let headerLen = parseInt(req._raw.headers['content-length']);
+  if (headerLen !== bufLen) {
+    res.throw(500, {
+      errorNum: errors.ERROR_VALIDATION_FAILED.code,
+      errorMessage: `content-length header doesn't match - ${bufLen} !== ${headerLen}`
+    });
+  }
+  res.write(pixelGif);
+  res.set('content-type', binaryMime);
+  res.set('test', 'header');
+  res.set('request-type', 'PATCH_RAW');
+});
+
+router.head('/interface-echo-bin', function (req, res) {
+  res.write(pixelGif);
+  res.set('content-type', binaryMime);
+  res.set('test', 'header');
+  res.set('request-type', 'HEAD_RAW');
+});
+
+router.get('/interface-echo-bin', function (req, res) {
+  res.write(pixelGif);
+  res.set('content-type', binaryMime);
+  res.set('test', 'header');
+  res.set('request-type', 'GET_RAW');
+});
+
+////////////////////////////////////////////////////////////////////////////////
+//            text post body + reply
+////////////////////////////////////////////////////////////////////////////////
+
+router.post('/interface-echo-str', function (req, res) {
+  let postBuffer = new Buffer(req._raw.rawRequestBody);
+  if (!cmpBuffer(postBuffer, pixelStr)) {
+    res.throw(500, {
+      errorNum: errors.ERROR_VALIDATION_FAILED.code,
+      errorMessage: "pixel gifs don't match"
+    });
+  }
+  if (req._raw.headers['content-type'] !== textMime) {
+    res.throw(500, {
+      errorNum: errors.ERROR_VALIDATION_FAILED.code,
+      errorMessage: `mimetypes don't match - ${textMime} !== ${req._raw.headers.content-type}`
+    });
+  }
+  let bufLen = postBuffer.length;
+  let headerLen = parseInt(req._raw.headers['content-length']);
+  if (headerLen !== bufLen) {
+    res.throw(500, {
+      errorNum: errors.ERROR_VALIDATION_FAILED.code,
+      errorMessage: `content-length header doesn't match - ${bufLen} !== ${headerLen}`
+    });
+  }
+  res.write(pixelStr);
+  res.set('content-type', textMime);
+  res.set('test', 'header');
+  res.set('request-type', 'POST_RAW');
+});
+
+router.put('/interface-echo-str', function (req, res) {
+  let postBuffer = new Buffer(req._raw.rawRequestBody);
+  if (!cmpBuffer(postBuffer, pixelStr)) {
+    res.throw(500, {
+      errorNum: errors.ERROR_VALIDATION_FAILED.code,
+      errorMessage: "pixel gifs don't match"
+    });
+  }
+  if (req._raw.headers['content-type'] !== textMime) {
+    res.throw(500, {
+      errorNum: errors.ERROR_VALIDATION_FAILED.code,
+      errorMessage: `mimetypes don't match - ${textMime} !== ${req._raw.headers.content-type}`
+    });
+  }
+  let bufLen = postBuffer.length;
+  let headerLen = parseInt(req._raw.headers['content-length']);
+  if (headerLen !== bufLen) {
+    res.throw(500, {
+      errorNum: errors.ERROR_VALIDATION_FAILED.code,
+      errorMessage: `content-length header doesn't match - ${bufLen} !== ${headerLen}`
+    });
+  }
+  res.write(pixelStr);
+  res.set('content-type', textMime);
+  res.set('test', 'header');
+  res.set('request-type', 'PUT_RAW');
+});
+
+router.delete('/interface-echo-str', function (req, res) {
+  let postBuffer = new Buffer(req._raw.rawRequestBody);
+  if (!cmpBuffer(postBuffer, pixelStr)) {
+    res.throw(500, {
+      errorNum: errors.ERROR_VALIDATION_FAILED.code,
+      errorMessage: "pixel gifs don't match"
+    });
+  }
+  if (req._raw.headers['content-type'] !== textMime) {
+    res.throw(500, {
+      errorNum: errors.ERROR_VALIDATION_FAILED.code,
+      errorMessage: `mimetypes don't match - ${textMime} !== ${req._raw.headers.content-type}`
+    });
+  }
+  let bufLen = postBuffer.length;
+  let headerLen = parseInt(req._raw.headers['content-length']);
+  if (headerLen !== bufLen) {
+    res.throw(500, {
+      errorNum: errors.ERROR_VALIDATION_FAILED.code,
+      errorMessage: `content-length header doesn't match - ${bufLen} !== ${headerLen}`
+    });
+  }
+  res.write(pixelStr);
+  res.set('content-type', textMime);
+  res.set('test', 'header');
+  res.set('request-type', 'DELETE_RAW');
+}).body("I can haz body");
+
+router.patch('/interface-echo-str', function (req, res) {
+  let postBuffer = new Buffer(req._raw.rawRequestBody);
+  if (!cmpBuffer(postBuffer, pixelStr)) {
+    res.throw(500, {
+      errorNum: errors.ERROR_VALIDATION_FAILED.code,
+      errorMessage: "pixel gifs don't match"
+    });
+  }
+  if (req._raw.headers['content-type'] !== textMime) {
+    res.throw(500, {
+      errorNum: errors.ERROR_VALIDATION_FAILED.code,
+      errorMessage: `mimetypes don't match - ${textMime} !== ${req._raw.headers.content-type}`
+    });
+  }
+  let bufLen = postBuffer.length;
+  let headerLen = parseInt(req._raw.headers['content-length']);
+  if (headerLen !== bufLen) {
+    res.throw(500, {
+      errorNum: errors.ERROR_VALIDATION_FAILED.code,
+      errorMessage: `content-length header doesn't match - ${bufLen} !== ${headerLen}`
+    });
+  }
+  res.write(pixelStr);
+  res.set('content-type', textMime);
+  res.set('test', 'header');
+  res.set('request-type', 'PATCH_RAW');
+});
+
+router.head('/interface-echo-str', function (req, res) {
+  res.write(pixelStr);
+  res.set('content-type', textMime);
+  res.set('test', 'header');
+  res.set('request-type', 'HEAD_RAW');
+});
+
+router.get('/interface-echo-str', function (req, res) {
+  res.write(pixelStr);
+  res.set('content-type', textMime);
+  res.set('test', 'header');
+  res.set('request-type', 'GET_RAW');
+});
+
+module.context.use(router);
diff --git a/tests/js/common/test-data/apps/interface/manifest.json b/tests/js/common/test-data/apps/interface/manifest.json
new file mode 100644
index 000000000000..4c9f408c8a29
--- /dev/null
+++ b/tests/js/common/test-data/apps/interface/manifest.json
@@ -0,0 +1,7 @@
+{
+  "name": "interface",
+  "version": "0.0.1",
+  "author": "arangodb",
+  "description": "revalidating all possible ways to foxx from outside in.",
+  "main": "index.js"
+}
diff --git a/tests/js/server/aql/aql-graph-traverser.js b/tests/js/server/aql/aql-graph-traverser.js
index 7fc72b47820a..d8805a955d2f 100644
--- a/tests/js/server/aql/aql-graph-traverser.js
+++ b/tests/js/server/aql/aql-graph-traverser.js
@@ -4550,6 +4550,86 @@ function pruneTraversalSuite() {
 
   return testObj;
 }
+
+function unusedVariableSuite() {
+  const gn = 'UnitTestGraph';
+
+  return {
+
+    setUpAll: function () {
+      db._drop(gn + 'v');
+      db._drop(gn + 'e');
+
+      var i;
+
+      var c = db._create(gn + 'v');
+      for (i = 0; i < 10000; ++i) {
+        c.insert({_key: 'test' + i});
+      }
+
+      c = db._createEdgeCollection(gn + 'e');
+      for (i = 0; i < 10000; ++i) {
+        c.insert({_from: gn + 'v/test' + i, _to: gn + 'v/test' + (i+1)});
+      }
+    },
+
+    tearDownAll: function () {
+      db._drop(gn + 'v');
+      db._drop(gn + 'e');
+    },
+
+    testCount: function () {
+      const queries = [
+        [ 'WITH @@vertices,@@edges FOR v IN 1..1 OUTBOUND @start @@edges RETURN 1', 1],
+        [ 'WITH @@vertices,@@edges FOR v IN 1..100 OUTBOUND @start @@edges RETURN 1', 100],
+        [ 'WITH @@vertices,@@edges FOR v IN 1..1000 OUTBOUND @start @@edges RETURN 1', 1000],
+        [ 'WITH @@vertices,@@edges FOR v,e IN 1..1 OUTBOUND @start @@edges RETURN 1', 1],
+        [ 'WITH @@vertices,@@edges FOR v,e IN 1..100 OUTBOUND @start @@edges RETURN 1', 100],
+        [ 'WITH @@vertices,@@edges FOR v,e IN 1..1000 OUTBOUND @start @@edges RETURN 1', 1000],
+        [ 'WITH @@vertices,@@edges FOR v,e,p IN 1..1 OUTBOUND @start @@edges RETURN 1', 1],
+        [ 'WITH @@vertices,@@edges FOR v,e,p IN 1..100 OUTBOUND @start @@edges RETURN 1', 100],
+        [ 'WITH @@vertices,@@edges FOR v,e,p IN 1..1000 OUTBOUND @start @@edges RETURN 1', 1000],
+        [ 'WITH @@vertices,@@edges FOR v,e,p IN 1..1 OUTBOUND @start @@edges RETURN v', 1],
+        [ 'WITH @@vertices,@@edges FOR v,e,p IN 1..100 OUTBOUND @start @@edges RETURN v', 100],
+        [ 'WITH @@vertices,@@edges FOR v,e,p IN 1..1000 OUTBOUND @start @@edges RETURN v', 1000],
+      ];
+
+      queries.forEach(function (query) {
+        const r = db._query(query[0], {"start": gn + 'v/test0', "@vertices": gn+'v', "@edges": gn+'e'});
+        const resultArray = r.toArray();
+        assertEqual(query[1], resultArray.length, query);
+      });
+
+    },
+
+    testCountSubquery: function () {
+      const queries = [
+        [ 'RETURN COUNT(FOR v IN 1..1 OUTBOUND @start @@edges RETURN 1)', 1],
+        [ 'RETURN COUNT(FOR v IN 1..100 OUTBOUND @start @@edges RETURN 1)', 100],
+        [ 'RETURN COUNT(FOR v IN 1..1000 OUTBOUND @start @@edges RETURN 1)', 1000],
+        [ 'RETURN COUNT(FOR v,e IN 1..1 OUTBOUND @start @@edges RETURN 1)', 1],
+        [ 'RETURN COUNT(FOR v,e IN 1..100 OUTBOUND @start @@edges RETURN 1)', 100],
+        [ 'RETURN COUNT(FOR v,e IN 1..1000 OUTBOUND @start @@edges RETURN 1)', 1000],
+        [ 'RETURN COUNT(FOR v,e,p IN 1..1 OUTBOUND @start @@edges RETURN 1)', 1],
+        [ 'RETURN COUNT(FOR v,e,p IN 1..100 OUTBOUND @start @@edges RETURN 1)', 100],
+        [ 'RETURN COUNT(FOR v,e,p IN 1..1000 OUTBOUND @start @@edges RETURN 1)', 1000],
+        [ 'RETURN COUNT(FOR v,e,p IN 1..1 OUTBOUND @start @@edges RETURN v)', 1],
+        [ 'RETURN COUNT(FOR v,e,p IN 1..100 OUTBOUND @start @@edges RETURN v)', 100],
+        [ 'RETURN COUNT(FOR v,e,p IN 1..1000 OUTBOUND @start @@edges RETURN v)', 1000],
+      ];
+
+      queries.forEach(function (query) {
+        const r = db._query(query[0], {"start": gn + 'v/test0', "@edges": gn+'e'});
+        const resultArray = r.toArray();
+        assertEqual(resultArray.length, 1);
+        assertEqual(query[1], resultArray[0], query);
+      });
+    },
+  };
+}
+
+
+
 jsunity.run(invalidStartVertexSuite);
 jsunity.run(simpleInboundOutboundSuite);
 jsunity.run(limitSuite);
@@ -4572,4 +4652,5 @@ if (!isCluster) {
   jsunity.run(optimizeNonVertexCentricIndexesSuite);
 }
 jsunity.run(pruneTraversalSuite);
+jsunity.run(unusedVariableSuite);
 return jsunity.done();
diff --git a/tests/js/server/aql/aql-traversal-empty-register-mapping-regression.js b/tests/js/server/aql/aql-traversal-empty-register-mapping-regression.js
new file mode 100644
index 000000000000..26b4812c2e55
--- /dev/null
+++ b/tests/js/server/aql/aql-traversal-empty-register-mapping-regression.js
@@ -0,0 +1,93 @@
+/*jshint globalstrict:false, strict:false, maxlen: 500 */
+/*global assertEqual, AQL_EXECUTE, assertTrue, fail */
+
+////////////////////////////////////////////////////////////////////////////////
+/// @brief tests for regression returning blocks to the manager
+///
+/// @file
+///
+/// DISCLAIMER
+///
+/// Copyright 2010-2014 triagens GmbH, Cologne, Germany
+///
+/// Licensed under the Apache License, Version 2.0 (the "License");
+/// you may not use this file except in compliance with the License.
+/// You may obtain a copy of the License at
+///
+///     http://www.apache.org/licenses/LICENSE-2.0
+///
+/// Unless required by applicable law or agreed to in writing, software
+/// distributed under the License is distributed on an "AS IS" BASIS,
+/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+/// See the License for the specific language governing permissions and
+/// limitations under the License.
+///
+/// Copyright holder is triAGENS GmbH, Cologne, Germany
+///
+/// @author Markus Pfeiffer
+/// @author Copyright 2020, triAGENS GmbH, Cologne, Germany
+////////////////////////////////////////////////////////////////////////////////
+
+var jsunity = require("jsunity");
+var internal = require("internal");
+var errors = internal.errors;
+var db = require("@arangodb").db, indexId;
+
+const vertexCollectionName = "RegressionGraphVertex";
+const edgeCollectionName = "RegressionGraphEdges";
+
+var cleanup = function() {
+  db._drop(vertexCollectionName);
+  db._drop(edgeCollectionName);
+};
+
+var createBaseGraph = function () {
+  const vc = db._create(vertexCollectionName);
+  const ec = db._createEdgeCollection(edgeCollectionName);
+};
+
+
+////////////////////////////////////////////////////////////////////////////////
+/// @brief test suite
+////////////////////////////////////////////////////////////////////////////////
+
+function traversalEmptyRegisterMappingSuite() {
+  return {
+
+////////////////////////////////////////////////////////////////////////////////
+/// @brief set up
+////////////////////////////////////////////////////////////////////////////////
+
+    setUpAll : function () {
+      cleanup();
+      createBaseGraph();
+    },
+
+////////////////////////////////////////////////////////////////////////////////
+/// @brief tear down
+////////////////////////////////////////////////////////////////////////////////
+
+    tearDownAll : function () {
+      cleanup();
+    },
+
+////////////////////////////////////////////////////////////////////////////////
+/// @brief test object access for path object
+////////////////////////////////////////////////////////////////////////////////
+
+    testEmptyRegisterMappingCrashes : function () {
+      const query = `RETURN COUNT(FOR v, e, p IN 1..1 INBOUND "a" @@edges RETURN 1)`;
+      var actual = db._query(query, { "@edges": edgeCollectionName });
+    },
+
+  };
+}
+
+////////////////////////////////////////////////////////////////////////////////
+/// @brief executes the test suite
+////////////////////////////////////////////////////////////////////////////////
+
+jsunity.run(traversalEmptyRegisterMappingSuite);
+
+return jsunity.done();
+
diff --git a/tests/js/server/recovery/revision-trees-no-sync-rocksdb-disabled.js b/tests/js/server/recovery/revision-trees-no-sync-rocksdb-disabled.js
new file mode 100644
index 000000000000..5c4e32bcbdb4
--- /dev/null
+++ b/tests/js/server/recovery/revision-trees-no-sync-rocksdb-disabled.js
@@ -0,0 +1,126 @@
+/* jshint globalstrict:false, strict:false, unused : false */
+/* global assertEqual, assertFalse, assertTrue */
+
+// //////////////////////////////////////////////////////////////////////////////
+// / @brief tests for dump/reload
+// /
+// / @file
+// /
+// / DISCLAIMER
+// /
+// / Copyright 2010-2012 triagens GmbH, Cologne, Germany
+// /
+// / Licensed under the Apache License, Version 2.0 (the "License")
+// / you may not use this file except in compliance with the License.
+// / You may obtain a copy of the License at
+// /
+// /     http://www.apache.org/licenses/LICENSE-2.0
+// /
+// / Unless required by applicable law or agreed to in writing, software
+// / distributed under the License is distributed on an "AS IS" BASIS,
+// / WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// / See the License for the specific language governing permissions and
+// / limitations under the License.
+// /
+// / Copyright holder is triAGENS GmbH, Cologne, Germany
+// /
+// / @author Jan Steemann
+// / @author Copyright 2012, triAGENS GmbH, Cologne, Germany
+// //////////////////////////////////////////////////////////////////////////////
+
+const db = require('@arangodb').db;
+const internal = require('internal');
+const jsunity = require('jsunity');
+
+const colName1 = 'UnitTestsRecovery1';
+const colName2 = 'UnitTestsRecovery2';
+const colName3 = 'UnitTestsRecovery3';
+
+function runSetup () {
+  'use strict';
+  internal.debugClearFailAt();
+
+  internal.debugSetFailAt("RocksDBSettingsManagerSync"); 
+
+  db._drop(colName1);
+  var c = db._create(colName1), i;
+  c.ensureHashIndex('value');
+
+  for (i = 0; i < 1000; ++i) {
+    c.save({ _key: "test_" + i });
+  }
+
+  db._drop(colName2);
+  c = db._create(colName2);
+
+  for (i = 0; i < 1000; ++i) {
+    c.save({ _key: "test_" + i });
+  }
+  for (i = 0; i < 500; ++i) {
+    c.remove({ _key: "test_" + i });
+  }
+
+  db._drop(colName3);
+  c = db._create(colName3);
+
+  for (i = 0; i < 1000; ++i) {
+    c.save({ _key: "test_" + i });
+  }
+  c.truncate();
+
+  db._drop('test');
+  c = db._create('test');
+  c.save({ _key: 'crashme' }, true);
+
+  internal.debugTerminate('crashing server');
+}
+
+// //////////////////////////////////////////////////////////////////////////////
+// / @brief test suite
+// //////////////////////////////////////////////////////////////////////////////
+
+function recoverySuite () {
+  'use strict';
+  jsunity.jsUnity.attachAssertions();
+
+  return {
+    setUp: function () {
+      internal.waitForEstimatorSync(); // make sure estimates are consistent
+    },
+    tearDown: function () {},
+
+    // //////////////////////////////////////////////////////////////////////////////
+    // / @brief test whether we can restore the trx data
+    // //////////////////////////////////////////////////////////////////////////////
+
+    testRevisionTreeCounts: function() {
+      const c1 = db._collection(colName1);
+      assertEqual(c1._revisionTreeSummary().count, c1.count());
+      assertEqual(c1._revisionTreeSummary().count, 1000);
+
+      const c2 = db._collection(colName2);
+      assertEqual(c2._revisionTreeSummary().count, c2.count());
+      assertEqual(c2._revisionTreeSummary().count, 500);
+
+      const c3 = db._collection(colName3);
+      assertEqual(c3._revisionTreeSummary().count, c3.count());
+      assertEqual(c3._revisionTreeSummary().count, 0);
+    },
+
+  };
+}
+
+// //////////////////////////////////////////////////////////////////////////////
+// / @brief executes the test suite
+// //////////////////////////////////////////////////////////////////////////////
+
+function main (argv) {
+  'use strict';
+  if (argv[1] === 'setup') {
+    runSetup();
+    return 0;
+  } else {
+    jsunity.run(recoverySuite);
+    return jsunity.writeDone().status ? 0 : 1;
+  }
+}
diff --git a/tests/js/server/recovery/revision-trees-partial-sync-rocksdb-disabled.js b/tests/js/server/recovery/revision-trees-partial-sync-rocksdb-disabled.js
new file mode 100644
index 000000000000..9434eee34c8d
--- /dev/null
+++ b/tests/js/server/recovery/revision-trees-partial-sync-rocksdb-disabled.js
@@ -0,0 +1,130 @@
+/* jshint globalstrict:false, strict:false, unused : false */
+/* global assertEqual, assertFalse, assertTrue */
+
+// //////////////////////////////////////////////////////////////////////////////
+// / @brief tests for dump/reload
+// /
+// / @file
+// /
+// / DISCLAIMER
+// /
+// / Copyright 2010-2012 triagens GmbH, Cologne, Germany
+// /
+// / Licensed under the Apache License, Version 2.0 (the "License")
+// / you may not use this file except in compliance with the License.
+// / You may obtain a copy of the License at
+// /
+// /     http://www.apache.org/licenses/LICENSE-2.0
+// /
+// / Unless required by applicable law or agreed to in writing, software
+// / distributed under the License is distributed on an "AS IS" BASIS,
+// / WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// / See the License for the specific language governing permissions and
+// / limitations under the License.
+// /
+// / Copyright holder is triAGENS GmbH, Cologne, Germany
+// /
+// / @author Jan Steemann
+// / @author Copyright 2012, triAGENS GmbH, Cologne, Germany
+// //////////////////////////////////////////////////////////////////////////////
+
+const db = require('@arangodb').db;
+const internal = require('internal');
+const jsunity = require('jsunity');
+
+const colName1 = 'UnitTestsRecovery1';
+const colName2 = 'UnitTestsRecovery2';
+const colName3 = 'UnitTestsRecovery3';
+
+function runSetup () {
+  'use strict';
+  internal.debugClearFailAt();
+
+  db._drop(colName1);
+  var c = db._create(colName1), i;
+  c.ensureHashIndex('value');
+
+  for (i = 0; i < 1000; ++i) {
+    c.save({ _key: "test_" + i });
+  }
+
+  db._drop(colName2);
+  c = db._create(colName2);
+
+  for (i = 0; i < 1000; ++i) {
+    c.save({ _key: "test_" + i });
+  }
+
+  db._drop(colName3);
+  c = db._create(colName3);
+
+  for (i = 0; i < 1000; ++i) {
+    c.save({ _key: "test_" + i });
+  }
+
+  internal.debugSetFailAt("RocksDBSettingsManagerSync");
+
+  c = db._collection(colName2);
+  for (i = 0; i < 500; ++i) {
+    c.remove({ _key: "test_" + i });
+  }
+
+  c = db._collection(colName3);
+  c.truncate();
+
+  db._drop('test');
+  c = db._create('test');
+  c.save({ _key: 'crashme' }, true);
+
+  internal.debugTerminate('crashing server');
+}
+
+// //////////////////////////////////////////////////////////////////////////////
+// / @brief test suite
+// //////////////////////////////////////////////////////////////////////////////
+
+function recoverySuite () {
+  'use strict';
+  jsunity.jsUnity.attachAssertions();
+
+  return {
+    setUp: function () {
+      internal.waitForEstimatorSync(); // make sure estimates are consistent
+    },
+    tearDown: function () {},
+
+    // //////////////////////////////////////////////////////////////////////////////
+    // / @brief test whether we can restore the trx data
+    // //////////////////////////////////////////////////////////////////////////////
+
+    testRevisionTreeCounts: function() {
+      const c1 = db._collection(colName1);
+      assertEqual(c1._revisionTreeSummary().count, c1.count());
+      assertEqual(c1._revisionTreeSummary().count, 1000);
+
+      const c2 = db._collection(colName2);
+      assertEqual(c2._revisionTreeSummary().count, c2.count());
+      assertEqual(c2._revisionTreeSummary().count, 500);
+
+      const c3 = db._collection(colName3);
+      assertEqual(c3._revisionTreeSummary().count, c3.count());
+      assertEqual(c3._revisionTreeSummary().count, 0);
+    },
+
+  };
+}
+
+// //////////////////////////////////////////////////////////////////////////////
+// / @brief executes the test suite
+// //////////////////////////////////////////////////////////////////////////////
+
+function main (argv) {
+  'use strict';
+  if (argv[1] === 'setup') {
+    runSetup();
+    return 0;
+  } else {
+    jsunity.run(recoverySuite);
+    return jsunity.writeDone().status ? 0 : 1;
+  }
+}
diff --git a/tests/js/server/recovery/revision-trees-rocksdb-disabled.js b/tests/js/server/recovery/revision-trees-rocksdb-disabled.js
new file mode 100644
index 000000000000..e74205b09eb4
--- /dev/null
+++ b/tests/js/server/recovery/revision-trees-rocksdb-disabled.js
@@ -0,0 +1,124 @@
+/* jshint globalstrict:false, strict:false, unused : false */
+/* global assertEqual, assertFalse, assertTrue */
+
+// //////////////////////////////////////////////////////////////////////////////
+// / @brief tests for dump/reload
+// /
+// / @file
+// /
+// / DISCLAIMER
+// /
+// / Copyright 2010-2012 triagens GmbH, Cologne, Germany
+// /
+// / Licensed under the Apache License, Version 2.0 (the "License")
+// / you may not use this file except in compliance with the License.
+// / You may obtain a copy of the License at
+// /
+// /     http://www.apache.org/licenses/LICENSE-2.0
+// /
+// / Unless required by applicable law or agreed to in writing, software
+// / distributed under the License is distributed on an "AS IS" BASIS,
+// / WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// / See the License for the specific language governing permissions and
+// / limitations under the License.
+// /
+// / Copyright holder is triAGENS GmbH, Cologne, Germany
+// /
+// / @author Jan Steemann
+// / @author Copyright 2012, triAGENS GmbH, Cologne, Germany
+// //////////////////////////////////////////////////////////////////////////////
+
+const db = require('@arangodb').db;
+const internal = require('internal');
+const jsunity = require('jsunity');
+
+const colName1 = 'UnitTestsRecovery1';
+const colName2 = 'UnitTestsRecovery2';
+const colName3 = 'UnitTestsRecovery3';
+
+function runSetup () {
+  'use strict';
+  internal.debugClearFailAt();
+
+  db._drop(colName1);
+  var c = db._create(colName1), i;
+  c.ensureHashIndex('value');
+
+  for (i = 0; i < 1000; ++i) {
+    c.save({ _key: "test_" + i });
+  }
+
+  db._drop(colName2);
+  c = db._create(colName2);
+
+  for (i = 0; i < 1000; ++i) {
+    c.save({ _key: "test_" + i });
+  }
+  for (i = 0; i < 500; ++i) {
+    c.remove({ _key: "test_" + i });
+  }
+
+  db._drop(colName3);
+  c = db._create(colName3);
+
+  for (i = 0; i < 1000; ++i) {
+    c.save({ _key: "test_" + i });
+  }
+  c.truncate();
+
+  db._drop('test');
+  c = db._create('test');
+  c.save({ _key: 'crashme' }, true);
+
+  internal.debugTerminate('crashing server');
+}
+
+// //////////////////////////////////////////////////////////////////////////////
+// / @brief test suite
+// //////////////////////////////////////////////////////////////////////////////
+
+function recoverySuite () {
+  'use strict';
+  jsunity.jsUnity.attachAssertions();
+
+  return {
+    setUp: function () {
+      internal.waitForEstimatorSync(); // make sure estimates are consistent
+    },
+    tearDown: function () {},
+
+    // //////////////////////////////////////////////////////////////////////////////
+    // / @brief test whether we can restore the trx data
+    // //////////////////////////////////////////////////////////////////////////////
+
+    testRevisionTreeCounts: function() {
+      const c1 = db._collection(colName1);
+      assertEqual(c1._revisionTreeSummary().count, c1.count());
+      assertEqual(c1._revisionTreeSummary().count, 1000);
+
+      const c2 = db._collection(colName2);
+      assertEqual(c2._revisionTreeSummary().count, c2.count());
+      assertEqual(c2._revisionTreeSummary().count, 500);
+
+      const c3 = db._collection(colName3);
+      assertEqual(c3._revisionTreeSummary().count, c3.count());
+      assertEqual(c3._revisionTreeSummary().count, 0);
+    },
+
+  };
+}
+
+// //////////////////////////////////////////////////////////////////////////////
+// / @brief executes the test suite
+// //////////////////////////////////////////////////////////////////////////////
+
+function main (argv) {
+  'use strict';
+  if (argv[1] === 'setup') {
+    runSetup();
+    return 0;
+  } else {
+    jsunity.run(recoverySuite);
+    return jsunity.writeDone().status ? 0 : 1;
+  }
+}
diff --git a/tests/js/server/replication/sync/replication-sync.js b/tests/js/server/replication/sync/replication-sync.js
index 3930d0e7ab94..ba57708b7964 100644
--- a/tests/js/server/replication/sync/replication-sync.js
+++ b/tests/js/server/replication/sync/replication-sync.js
@@ -143,7 +143,7 @@ function BaseTestConfig () {
           arango.PUT_RAW("/_admin/debug/failat/RocksDBCommitCounts", "");
           c.insert({});
           arango.DELETE_RAW("/_admin/debug/failat", "");
-          assertEqual(5000, c.count());
+          assertEqual(5001, c.count());
           assertEqual(5001, c.toArray().length);
         },
         function (state) {
@@ -204,7 +204,7 @@ function BaseTestConfig () {
             c.insert({ _key: "testmann" + i });
           }
           arango.DELETE_RAW("/_admin/debug/failat", "");
-          assertEqual(9000, c.count());
+          assertEqual(9100, c.count());
           assertEqual(9100, c.toArray().length);
         },
         function (state) {
diff --git a/tests/js/server/shell/shell-index-rocksdb.js b/tests/js/server/shell/shell-index-rocksdb.js
index f088aa42a6db..b0f08759fa8d 100644
--- a/tests/js/server/shell/shell-index-rocksdb.js
+++ b/tests/js/server/shell/shell-index-rocksdb.js
@@ -311,7 +311,7 @@ function backgroundIndexSuite() {
         } 
         c.save(docs);
       }
-      
+
       assertEqual(c.count(), 100000);
 
       // lets remove half via tasks
@@ -347,18 +347,23 @@ function backgroundIndexSuite() {
       // sanity checks
       assertEqual(c.count(), 50000);
       for (let i = 0; i < 10; i++) { // check for remaining docs via index
+        let invalues = [];
         for (let x = i * 10000 + 5000; x < (i + 1) * 10000; x++) {
-          const cursor = db._query("FOR doc IN @@coll FILTER doc.value == @val RETURN 1", 
-                                   {'@coll': cn, 'val': x}, {count:true});
-          assertEqual(cursor.count(), 1);
+          invalues.push(x);
         }
+        const cursor = db._query("FOR doc IN @@coll FILTER doc.value in @val RETURN 1", 
+                                   {'@coll': cn, 'val': invalues }, {count:true});
+        assertEqual(cursor.count(), 5000);
       }
+
       for (let i = 0; i < 10; i++) { // check for removed docs via index
+        let invalues = [];
         for (let x = i * 10000; x < i * 10000 + 5000; x++) {
-          const cursor = db._query("FOR doc IN @@coll FILTER doc.value == @val RETURN 1", 
-                                   {'@coll': cn, 'val': x}, {count:true});
-          assertEqual(cursor.count(), 0, [i, x]);
+          invalues.push(x);
         }
+        const cursor = db._query("FOR doc IN @@coll FILTER doc.value in @val RETURN 1", 
+                                 {'@coll': cn, 'val': invalues }, {count:true});
+        assertEqual(cursor.count(), 0, [i, invalues]);
       }
 
       internal.waitForEstimatorSync(); // make sure estimates are consistent
@@ -427,6 +432,7 @@ function backgroundIndexSuite() {
       const newCursor = db._query("FOR doc IN @@coll FILTER doc.value >= @val RETURN 1", 
                                   {'@coll': cn, 'val': 100000}, {count:true});
       assertEqual(newCursor.count(), 100000);
+
       // check for old entries via index
       const oldCursor = db._query("FOR doc IN @@coll FILTER doc.value < @val RETURN 1", 
                                   {'@coll': cn, 'val': 100000}, {count:true});
diff --git a/utils/checkLogIds.py b/utils/checkLogIds.py
index 39ae106f85b4..63b70e98e584 100755
--- a/utils/checkLogIds.py
+++ b/utils/checkLogIds.py
@@ -204,4 +204,4 @@ def generate_ids_main(check_only, project_root, directories_to_include, director
             ,[".", "lib/Logger/LogMacros.h",
               "arangod/StorageEngine/TransactionState.h"]    #dirs and files to exclude (does not purge the dir)
             , dict()                                         #database
-            ));
+            ))
diff --git a/utils/generateErrorfile.py b/utils/generateErrorfile.py
index dc607ee4ace6..319a4747ddc0 100755
--- a/utils/generateErrorfile.py
+++ b/utils/generateErrorfile.py
@@ -1,6 +1,6 @@
 #!/usr/bin/env python3
 from __future__ import print_function
-import csv, sys, os.path, re
+import csv, sys, os.path, re, io
 
 # wrap text after x characters
 def wrap(string, width=80, ind1=0, ind2=0, prefix=''):
@@ -130,8 +130,8 @@ def genCHeaderFile(errors):
 # read input file
 
 erros = []
-with open(source) as source_fh:
-    errors = csv.reader(open(source, "r"))
+with io.open(source, encoding="utf-8", newline=None) as source_fh:
+    errors = csv.reader(io.open(source, encoding="utf-8", newline=None))
 
     errorsList = []
 
@@ -168,5 +168,5 @@ def genCHeaderFile(errors):
   print("usage: {} <sourcefile> <outfile>".format(sys.argv[0]), file=sys.stderr)
   sys.exit(1)
 
-with open(outfile, "w") as out_fh:
+with io.open(outfile, mode="w", encoding="utf-8", newline="") as out_fh:
     out_fh.write(out)
diff --git a/utils/generateExamples.py b/utils/generateExamples.py
index 7f857af55722..864202217144 100644
--- a/utils/generateExamples.py
+++ b/utils/generateExamples.py
@@ -31,7 +31,8 @@
 ### @author Copyright 2011-2014, triagens GmbH, Cologne, Germany
 ################################################################################
 
-import re, sys, string, os, re
+from __future__ import print_function # py2 compat
+import re, sys, string, os, re, io
 from pprint import pprint
 
 ################################################################################
@@ -145,8 +146,8 @@
 ################################################################################
 
 def generateArangoshHeader():
-    headerF = open("./Documentation/Scripts/exampleHeader.js", "r")
-    print headerF.read()
+    headerF = io.open("./Documentation/Scripts/exampleHeader.js", encoding="utf-8", newline=None)
+    print(headerF.read())
     headerF.close()
 
 ################################################################################
@@ -172,12 +173,12 @@ def matchStartLine(line, filename):
         name = m.group(2)
 
         if name in ArangoshFiles:
-            print >> sys.stderr, "%s\nduplicate test name '%s' in file %s!\n%s\n" % ('#' * 80, name, filename, '#' * 80)
+            print("%s\nduplicate test name '%s' in file %s!\n%s\n" % ('#' * 80, name, filename, '#' * 80), file=sys.stderr)
             sys.exit(1)
 
         # if we match for filters, only output these!
         if ((FilterForTestcase != None) and not FilterForTestcase.match(name)):
-            print >> sys.stderr, "Arangosh: filtering out testcase '%s'" %name
+            print("Arangosh: filtering out testcase '%s'" %name, file=sys.stderr)
             filterTestList.append(name)
             return("", STATE_BEGIN)
 
@@ -190,13 +191,13 @@ def matchStartLine(line, filename):
         name = m.group(2)
 
         if name in ArangoshFiles:
-            print >> sys.stderr, "%s\nduplicate test name '%s' in file %s!\n%s\n" % ('#' * 80, name, filename, '#' * 80)
+            print("%s\nduplicate test name '%s' in file %s!\n%s\n" % ('#' * 80, name, filename, '#' * 80), file=sys.stderr)
             sys.exit(1)
 
         # if we match for filters, only output these!
         if ((FilterForTestcase != None) and not FilterForTestcase.match(name)):
             filterTestList.append(name)
-            print >> sys.stderr, "CuRL: filtering out testcase '%s'" %name
+            print("CuRL: filtering out testcase '%s'" %name, file=sys.stderr)
             return("", STATE_BEGIN)
 
         ArangoshFiles[name] = True
@@ -208,12 +209,12 @@ def matchStartLine(line, filename):
         name = m.group(2)
 
         if name in AQLFiles:
-            print >> sys.stderr, "%s\nduplicate test name '%s' in file %s!\n%s\n" % ('#' * 80, name, filename, '#' * 80)
+            print("%s\nduplicate test name '%s' in file %s!\n%s\n" % ('#' * 80, name, filename, '#' * 80), file=sys.stderr)
             sys.exit(1)
 
         # if we match for filters, only output these!
         if ((FilterForTestcase != None) and not FilterForTestcase.match(name)):
-            print >> sys.stderr, "AQL: filtering out testcase '%s'" %name
+            print("AQL: filtering out testcase '%s'" %name, file=sys.stderr)
             filterTestList.append(name)
             return("", STATE_BEGIN)
 
@@ -384,9 +385,7 @@ def analyzeFile(f, filename):
 
 
 def generateSetupFunction():
-    print
-    print "(function () {\n%s}());" % ArangoshSetup
-    print
+    print("\n(function () {\n%s}());\n" % ArangoshSetup)
 
 ################################################################################
 ### @brief generate arangosh example
@@ -402,10 +401,10 @@ def generateArangoshOutput(testName):
     #print value[TESTLINES][0][2]
     #print type(value[TESTLINES][0][2])
     if (len(value[TESTLINES]) == 0) or (len(value[TESTLINES][0]) < 3):
-        print >> sys.stderr, "syntax error in %s - its empty! Maybe you've used too many pipes?" %(testName)
+        print("syntax error in %s - its empty! Maybe you've used too many pipes?" %(testName), file=sys.stderr)
         raise Exception
     try:
-        print '''
+        print('''
 %s
 /// %s
 (function() {
@@ -424,11 +423,11 @@ def generateArangoshOutput(testName):
         value[TESTLINES][0][2],
         escapeBS.sub(doubleBS, OutputDir),
         escapeBS.sub(doubleBS, MapSourceFiles[testName])
-        )
+        ))
     except Exception as x:
-        print  >> sys.stderr,x
-        print  >> sys.stderr,testName
-        print  >> sys.stderr,value
+        print(x, file=sys.stderr)
+        print(testName, file=sys.stderr)
+        print(value, file=sys.stderr)
         raise
 
     for l in value[TESTLINES]:
@@ -443,26 +442,26 @@ def generateArangoshOutput(testName):
         fakeVar = 'false'
         if m and l[0][0:3] == 'var':
             count = l[0].find('=')
-            print  "  " + l[0][0:count].rstrip(' ') + ";"
+            print("  " + l[0][0:count].rstrip(' ') + ";")
             l[0] = l[0][4:]
             fakeVar = 'true'
 
-        print "  runTestLine('%s', testName, sourceFile, %s, lineCount++, %s, %s, %s, %s);" % (
+        print("  runTestLine('%s', testName, sourceFile, %s, lineCount++, %s, %s, %s, %s);" % (
             l[0],                         # the test string
             l[2],                         # line in the source file
             'true' if l[1] else 'false',  # Is it visible in the documentation?
             expectError,                  # will it throw? if the errorcode else undefined.
             'true' if m    else 'false',  # is it a loop construct? (will be evaluated different)
             fakeVar                       # 'var ' should be printed
-            )
-    print '''  var output = internal.stopCaptureMode();
+            ))
+    print('''  var output = internal.stopCaptureMode();
 
   print("[" + (time () - startTime) + "s] done with  " + testName);
   output = highlight("js", output);
   fs.write(outputDir + fs.pathSeparator + testName + '.generated', output);
   checkForOrphanTestCollections('not all collections were cleaned up after ' + sourceFile + ' Line[' + startLineCount + '] [' + testName + ']:');
 }());
-'''
+''')
 
 ################################################################################
 ### @brief generate arangosh run
@@ -471,13 +470,13 @@ def generateArangoshOutput(testName):
 def generateArangoshRun(testName):
 
     if JS_DEBUG:
-        print "internal.output('%s\\n');" % ('=' * 80)
-        print "internal.output('ARANGOSH RUN\\n');"
-        print "internal.output('%s\\n');" % ('=' * 80)
+        print("internal.output('%s\\n');" % ('=' * 80))
+        print("internal.output('ARANGOSH RUN\\n');")
+        print("internal.output('%s\\n');" % ('=' * 80))
 
     value = RunTests[testName]
     startLineNo = RunTests[testName][LINE_NO]
-    print '''
+    print('''
 %s
 /// %s
 (function() {
@@ -501,14 +500,14 @@ def generateArangoshRun(testName):
         startLineNo,
         escapeBS.sub(doubleBS, OutputDir),
         escapeBS.sub(doubleBS, MapSourceFiles[testName]),
-        value[STRING].lstrip().rstrip())
+        value[STRING].lstrip().rstrip()))
 
     if testName in ArangoshExpect:
-        print "  rc = runTestFuncCatch(testFunc, testName, errors.%s);" % (ArangoshExpect[key])
+        print("  rc = runTestFuncCatch(testFunc, testName, errors.%s);" % (ArangoshExpect[key]))
     else:
-        print "  rc = runTestFunc(testFunc, testName, sourceFile);"
+        print("  rc = runTestFunc(testFunc, testName, sourceFile);")
 
-    print '''
+    print('''
   if (rc === undefined || rc === '' ) {
     rc = " FAILED in " + testName;
   }
@@ -517,7 +516,7 @@ def generateArangoshRun(testName):
   fs.write(outputDir + fs.pathSeparator + testName + '.generated', output);
   checkForOrphanTestCollections('not all collections were cleaned up after ' + sourceFile + ' Line[' + startLineCount + '] [' + testName + ']:');
 }());
-'''
+''')
 
 ################################################################################
 ### @brief generate arangosh run
@@ -535,7 +534,7 @@ def generateAQL(testName):
     if not AQLEXPLAIN in value:
         value[AQLEXPLAIN] = 'false'
 
-    print '''
+    print('''
 %s
 /// %s
 (() => {
@@ -555,12 +554,12 @@ def generateAQL(testName):
         startLineNo,
         escapeBS.sub(doubleBS, OutputDir),
         escapeBS.sub(doubleBS, MapSourceFiles[testName])
-    )
-    print "  const query = `" + value[AQL] + "`;"
-    print "  const bv = " + value[AQLBV] + ";"
-    print "  const ds = '" + value[AQLDS] + "';"
-    print "  const explainAql = " + value[AQLEXPLAIN].lower() + ";"
-    print '''
+    ))
+    print("  const query = `" + value[AQL] + "`;")
+    print("  const bv = " + value[AQLBV] + ";")
+    print("  const ds = '" + value[AQLDS] + "';")
+    print("  const explainAql = " + value[AQLEXPLAIN].lower() + ";")
+    print('''
   if (ds !== '') {
     exds[ds].removeDS();
     exds[ds].createDS();
@@ -590,19 +589,19 @@ def generateAQL(testName):
   checkForOrphanTestCollections('not all collections were cleaned up after ' + sourceFile + ' Line[' + startLineCount + '] [' + testName + ']:');
 })();
 
-'''
+''')
 
 ################################################################################
 ### @brief generate arangosh run
 ################################################################################
 
 def generateArangoshShutdown():
-    print '''
+    print('''
 if (allErrors.length > 0) {
     print(allErrors);
     throw new Error('trouble during generating documentation data; see above.');
 }
-'''
+''')
 
 ################################################################################
 ### @brief get file names
@@ -660,7 +659,7 @@ def loopDirectories():
 
         elif fstate == OPTION_ARANGOSH_SETUP:
             fstate = OPTION_NORMAL
-            f = open(filename, "r")
+            f = io.open(filename, encoding="utf-8", newline=None)
 
             for line in f:
                 line = line.rstrip('\n')
@@ -674,7 +673,7 @@ def loopDirectories():
 
         elif fstate == OPTION_OUTPUT_FILE:
             fstate = OPTION_NORMAL
-            sys.stdout = open(filename, 'w')
+            sys.stdout = io.open(filename, mode='w', encoding='utf-8', newline='')
 
         elif fstate == OPTION_OUTPUT_ENGINE:
             fstate = OPTION_NORMAL
@@ -694,35 +693,34 @@ def loopDirectories():
 
     for filename in filenames:
         if (filename.find("#") < 0):
-            f = open(filename, "r")
+            f = io.open(filename, encoding="utf-8", newline=None)
             analyzeFile(f, filename)
 
             f.close()
         else:
-            print >> sys.stderr, "skipping %s\n" % (filename)
+            print("skipping %s\n" % (filename), file=sys.stderr)
 
 
 def generateTestCases():
     global TESTLINES, TYPE, LINE_NO, STRING, RunTests, storageEngineAgnostic, cluster, engine, otherEngine
     testNames = RunTests.keys()
-    testNames.sort()
 
-    for thisTest in testNames:
+    for thisTest in sorted(testNames):
         if thisTest.endswith(otherEngine):
-            print >> sys.stderr, "skipping " + thisTest
+            print("skipping " + thisTest, file=sys.stderr)
             continue
 
         # skip agnostic examples if storage engine is mmfiles to not generate them twice
         if not storageEngineAgnostic and not thisTest.endswith(engine):
-            print >> sys.stderr, "skipping " + thisTest
+            print("skipping " + thisTest, file=sys.stderr)
             continue
 
         if cluster and not thisTest.endswith('_cluster'):
-            print >> sys.stderr, "skipping " + thisTest
+            print("skipping " + thisTest, file=sys.stderr)
             continue
 
         if not cluster and thisTest.endswith('_cluster'):
-            print >> sys.stderr, "skipping " + thisTest
+            print("skipping " + thisTest, file=sys.stderr)
             continue
 
         if RunTests[thisTest][TYPE] == STATE_ARANGOSH_OUTPUT:
@@ -739,9 +737,9 @@ def generateTestCases():
 
 loopDirectories()
 if len(RunTests) == 0:
-    print >> sys.stderr, "no testcases generated - bailing out"
+    print("no testcases generated - bailing out", file=sys.stderr)
     raise Exception("no Testcases")
-print >> sys.stderr, "filtering test %d cases" %(len(filterTestList))
+print("filtering test %d cases" %(len(filterTestList)), file=sys.stderr)
 
 generateArangoshHeader()
 generateSetupFunction()
diff --git a/utils/generateExitCodesFiles.py b/utils/generateExitCodesFiles.py
index 839df4d320d9..03a89bf655a7 100755
--- a/utils/generateExitCodesFiles.py
+++ b/utils/generateExitCodesFiles.py
@@ -1,6 +1,6 @@
 #!/usr/bin/env python3
 from __future__ import print_function
-import csv, sys, os.path, re
+import csv, sys, os.path, re, io
 
 # wrap text after x characters
 def wrap(string, width=80, ind1=0, ind2=0, prefix=''):
@@ -178,7 +178,7 @@ def genCHeaderFile(errors):
 # read input file
 errors=None
 errorsList = []
-with open(source, "r") as source_fh:
+with io.open(source, encoding="utf-8", newline=None) as source_fh:
     errors = csv.reader(source_fh)
 
     r1 = re.compile(r'^#.*')
@@ -216,5 +216,5 @@ def genCHeaderFile(errors):
   print("usage: {} <sourcefile> <outfile>".format(sys.argv[0]), file=sys.stderr)
   sys.exit(1)
 
-with open(outfile, "w") as out_fh:
-    out_fh.write(out);
+with io.open(outfile, mode="w", encoding="utf-8", newline="") as out_fh:
+    out_fh.write(out)
diff --git a/utils/generateSwagger.py b/utils/generateSwagger.py
index 5a2a80571463..cd6ce31a87d2 100755
--- a/utils/generateSwagger.py
+++ b/utils/generateSwagger.py
@@ -34,12 +34,15 @@
 ### @author Copyright 2014, triAGENS GmbH, Cologne, Germany
 ################################################################################
 
+from __future__ import print_function # py2 compat
+from __future__ import unicode_literals
 import sys
 import re
 import json
 import operator
 import os
 import os.path
+import io
 #string,
 #from pygments import highlight
 #from pygments.lexers import YamlLexer
@@ -58,7 +61,7 @@
     "swagger": "2.0",
     "info": {
         "description": "ArangoDB REST API Interface",
-        "version": "1.0",
+        "version": "1.0", # placeholder
         "title": "ArangoDB",
         "license": {
             "name": "Apache License, Version 2.0"
@@ -211,7 +214,7 @@ def brTrim(text):
 reqOpt = ["required", "optional"]
 def CheckReqOpt(token):
     if token not in reqOpt:
-        print >> sys.stderr, "This is supposed to be required or optional!"
+        print("This is supposed to be required or optional!", file=sys.stderr)
         raise Exception("invalid value '%s'" % token)
 
 ################################################################################
@@ -396,8 +399,8 @@ def run(self, cargo=None):
                 else:
                     handler = newState
         except Exception as x:
-            print >> sys.stderr, "while parsing '" + self.fn + "'"
-            print >> sys.stderr, "trying to use handler '"  + handler.__name__ + "'"
+            print("while parsing '" + self.fn + "'", file=sys.stderr)
+            print("trying to use handler '"  + handler.__name__ + "'", file=sys.stderr)
             raise x
 
 ################################################################################
@@ -503,7 +506,7 @@ def generic_handler(cargo, r, message):
     global DEBUG
 
     if DEBUG:
-        print >> sys.stderr, message
+        print(message, file=sys.stderr)
     (fp, last) = cargo
     last
     while 1:
@@ -526,7 +529,7 @@ def generic_handler_desc(cargo, r, message, op, para, name):
     global DEBUG, operation
 
     if DEBUG:
-        print >> sys.stderr, message
+        print(message, file=sys.stderr)
     (fp, dummy) = cargo
 
     while 1:
@@ -540,7 +543,7 @@ def generic_handler_desc(cargo, r, message, op, para, name):
                 try:
                     operation[op].append(para)
                 except AttributeError as x:
-                    print >> sys.stderr, "trying to set '%s' on operations - failed. '%s'" % (op, para)
+                    print("trying to set '%s' on operations - failed. '%s'" % (op, para), file=sys.stderr)
                     raise x
             return next, c
 
@@ -557,7 +560,7 @@ def start_docublock(cargo, r=Regexen()):
         else:
             currentDocuBlock = last.split(' ')[1].rstrip()
     except Exception as x:
-        print >> sys.stderr, "failed to fetch docublock in '" + last + "': " + str(x)
+        print("failed to fetch docublock in '" + last + "': " + str(x), file=sys.stderr)
         raise x
 
     return generic_handler(cargo, r, 'start_docublock')
@@ -573,12 +576,12 @@ def setRequired(where, which):
 ################################################################################
 def restparam(cargo, r=Regexen()):
     global swagger, operation, httpPath, method, restBodyParam, fn, currentExample, currentReturnCode, currentDocuBlock, lastDocuBlock, restReplyBodyParam
-    print >> sys.stderr, "deprecated RESTPARAM declaration detected:"
-    print >> sys.stderr, json.dumps(
+    print("deprecated RESTPARAM declaration detected:", file=sys.stderr)
+    print(json.dumps(
         swagger['paths'][httpPath],
         indent=4,
         separators=(', ', ': '),
-        sort_keys=True)
+        sort_keys=True), file=sys.stderr)
     raise Exception("RESTPARAM not supported anymore.")
 
 ################################################################################
@@ -586,12 +589,12 @@ def restparam(cargo, r=Regexen()):
 ################################################################################
 def restqueryparams(cargo, r=Regexen()):
     global swagger, operation, httpPath, method, restBodyParam, fn, currentExample, currentReturnCode, currentDocuBlock, lastDocuBlock, restReplyBodyParam
-    print >> sys.stderr, "deprecated RESTQUERYPARAMS declaration detected:"
-    print >> sys.stderr, json.dumps(
+    print("deprecated RESTQUERYPARAMS declaration detected:", file=sys.stderr)
+    print(json.dumps(
         swagger['paths'][httpPath],
         indent=4,
         separators=(', ', ': '),
-        sort_keys=True)
+        sort_keys=True), file=sys.stderr)
     raise Exception("RESTQUERYPARAMS not supported anymore. Use RESTQUERYPARAMETERS instead.")
 
 ################################################################################
@@ -624,13 +627,13 @@ def restheader(cargo, r=Regexen()):
     if not httpPath in swagger['paths']:
         swagger['paths'][httpPath] = {}
     if method in swagger['paths'][httpPath]:
-        print >> sys.stderr, "duplicate route detected:"
-        print >> sys.stderr, "There already is a route [" + ucmethod + " " + httpPath + "]: "
-        print >> sys.stderr, json.dumps(
+        print("duplicate route detected:", file=sys.stderr)
+        print("There already is a route [" + ucmethod + " " + httpPath + "]: ", file=sys.stderr)
+        print(json.dumps(
             swagger['paths'][httpPath],
             indent=4,
             separators=(', ', ': '),
-            sort_keys=True)
+            sort_keys=True), file=sys.stderr)
         raise Exception("Duplicate route")
 
     if currentDocuBlock == None:
@@ -643,7 +646,7 @@ def restheader(cargo, r=Regexen()):
     if len(temp) > 2:
         operationId = temp[2]
     if operationId in operationIDs:
-        print operationIDs
+        print(operationIDs)
         raise Exception("duplicate operation ID! " + operationId)
     lastDocuBlock = currentDocuBlock
 
@@ -682,11 +685,11 @@ def resturlparam(cargo, r=Regexen()):
     try:
         (name, pformat, required) = parameters(last).split(',')
     except Exception:
-        print >> sys.stderr, "RESTURLPARAM: 3 arguments required. You gave me: " + parameters(last)
+        print("RESTURLPARAM: 3 arguments required. You gave me: " + parameters(last), file=sys.stderr)
         raise x
 
     if required.strip() != 'required':
-        print >> sys.stderr, "only required is supported in RESTURLPARAM"
+        print("only required is supported in RESTURLPARAM", file=sys.stderr)
         raise Exception("invalid url parameter")
 
     para = {
@@ -746,8 +749,8 @@ def restbodyparam(cargo, r=Regexen()):
     try:
         (name, ptype, required, ptype2) = parameters(last).split(',')
     except Exception:
-        print >> sys.stderr, "RESTBODYPARAM: 4 arguments required. You gave me: " + parameters(last)
-        print >> sys.stderr, "In this docublock: " + currentDocuBlock
+        print("RESTBODYPARAM: 4 arguments required. You gave me: " + parameters(last), file=sys.stderr)
+        print("In this docublock: " + currentDocuBlock, file=sys.stderr)
         raise Exception("Argument count error")
 
     CheckReqOpt(required)
@@ -818,7 +821,7 @@ def restbodyparam(cargo, r=Regexen()):
         swagger['definitions'][currentDocuBlock]['properties'][name]['additionalProperties'] = {}
     elif ptype != 'string':
         if ptype in swaggerFormats and ptype2 not in swaggerFormats[ptype]:
-            print >> sys.stderr, "RESTSTRUCT: ptype2 (format)[" + ptype2 + "]  not valid: " + parameters(last)
+            print("RESTSTRUCT: ptype2 (format)[" + ptype2 + "]  not valid: " + parameters(last), file=sys.stderr)
             raise Exception("'%s' is not one of %s!" % (ptype2, str(swaggerFormats)))
         swagger['definitions'][currentDocuBlock]['properties'][name]['format'] = ptype2
 
@@ -841,7 +844,7 @@ def restallbodyparam(cargo, r=Regexen()):
     try:
         (_name, _ptype, required) = parameters(last).split(',')
     except Exception:
-        print >> sys.stderr, "RESTALLBODYPARAM: 3 arguments required. You gave me: " + parameters(last)
+        print("RESTALLBODYPARAM: 3 arguments required. You gave me: " + parameters(last), file=sys.stderr)
 
     CheckReqOpt(required)
     if required == 'required':
@@ -879,7 +882,7 @@ def reststruct(cargo, r=Regexen()):
     try:
         (name, className, ptype, required, ptype2) = parameters(last).split(',')
     except Exception:
-        print >> sys.stderr, "RESTSTRUCT: 5 arguments required (name, className, ptype, required, ptype2). You gave me: " + parameters(last)
+        print("RESTSTRUCT: 5 arguments required (name, className, ptype, required, ptype2). You gave me: " + parameters(last), file=sys.stderr)
         raise Exception("Argument count error")
 
     CheckReqOpt(required)
@@ -931,7 +934,7 @@ def reststruct(cargo, r=Regexen()):
 
     elif ptype != 'string' and ptype != 'boolean':
         if ptype in swaggerFormats and ptype2 not in swaggerFormats[ptype]:
-            print >> sys.stderr, "RESTSTRUCT: ptype2 (format)[" + ptype2 + "]  not valid: " + parameters(last)
+            print("RESTSTRUCT: ptype2 (format)[" + ptype2 + "]  not valid: " + parameters(last), file=sys.stderr)
             raise Exception("'%s' is not one of %s!" % (ptype2, str(swaggerFormats)))
         swagger['definitions'][className]['properties'][name]['format'] = ptype2
 
@@ -957,7 +960,7 @@ def restqueryparam(cargo, r=Regexen()):
     swaggerType = parametersList[1].lower()
     
     if swaggerType not in swaggerBaseTypes:
-        print >> sys.stderr, "RESTQUERYPARAM is supposed to be a swagger type."
+        print("RESTQUERYPARAM is supposed to be a swagger type.", file=sys.stderr)
         raise Exception("'%s' is not one of %s!" % (swaggerType, str(swaggerBaseTypes)))
 
     para = {
@@ -983,7 +986,7 @@ def hints(cargo, r=Regexen()):
 
     if r.TRIPLENEWLINEATSTART.match(swagger['paths'][httpPath][method]['x-hints']):
         (fp, dummy) = cargo
-        print >> sys.stderr, 'remove newline after @HINTS in file %s' % (fp.name)
+        print('remove newline after @HINTS in file %s' % (fp.name), file=sys.stderr)
         exit(1)
 
     return ret
@@ -1002,7 +1005,7 @@ def restdescription(cargo, r=Regexen()):
 
     if r.TRIPLENEWLINEATSTART.match(swagger['paths'][httpPath][method]['description']):
         (fp, dummy) = cargo
-        print >> sys.stderr, 'remove newline after @RESTDESCRIPTION in file %s' % (fp.name)
+        print('remove newline after @RESTDESCRIPTION in file %s' % (fp.name), file=sys.stderr)
         exit(1)
 
     return ret
@@ -1018,7 +1021,7 @@ def restreplybody(cargo, r=Regexen()):
     try:
         (name, ptype, required, ptype2) = parameters(last).split(',')
     except Exception:
-        print >> sys.stderr, "RESTREPLYBODY: 4 arguments required. You gave me: " + parameters(last)
+        print("RESTREPLYBODY: 4 arguments required. You gave me: " + parameters(last), file=sys.stderr)
         raise x
 
     CheckReqOpt(required)
@@ -1185,7 +1188,7 @@ def example_arangosh_run(cargo, r=Regexen()):
     global currentExample, DEBUG
 
     if DEBUG:
-        print >> sys.stderr, "example_arangosh_run"
+        print("example_arangosh_run", file=sys.stderr)
     (fp, last) = cargo
 
     exampleHeader = brTrim(operation['x-examples'][currentExample]).strip()
@@ -1193,14 +1196,15 @@ def example_arangosh_run(cargo, r=Regexen()):
     # new examples code TODO should include for each example own object in json file
     fn = os.path.join(os.path.dirname(__file__), '../Documentation/Examples/' + parameters(last) + '.generated')
     try:
-        examplefile = open(fn)
+        examplefile = io.open(fn, encoding='utf-8', newline=None)
     except:
-        print >> sys.stderr, "Failed to open example file:\n  '%s'" % fn
+        print("Failed to open example file:\n  '%s'" % fn, file=sys.stderr)
         raise Exception("failed to open example file:" + fn)
     operation['x-examples'][currentExample] = '\n\n**Example:**\n ' + exampleHeader.strip('\n ') + '\n\n<pre>'
 
     for line in examplefile.readlines():
         operation['x-examples'][currentExample] += '<code>' + line + '</code>'
+    examplefile.close()
 
     operation['x-examples'][currentExample] += '</pre>\n\n\n'
 
@@ -1223,7 +1227,7 @@ def example_arangosh_run(cargo, r=Regexen()):
 def eof(cargo):
     global DEBUG
     if DEBUG:
-        print >> sys.stderr, "eof"
+        print("eof", file=sys.stderr)
 
 ################################################################################
 ### @brief error
@@ -1232,7 +1236,7 @@ def eof(cargo):
 def error(cargo):
     global DEBUG
     if DEBUG:
-        print >> sys.stderr, "error"
+        print("error", file=sys.stderr)
 
     sys.stderr.write('Unidentifiable line:\n' + cargo)
 
@@ -1244,7 +1248,7 @@ def comment(cargo, r=Regexen()):
     global DEBUG
 
     if DEBUG:
-        print >> sys.stderr, "comment"
+        print("comment", file=sys.stderr)
     (fp, dummy) = cargo
 
     while 1:
@@ -1267,7 +1271,7 @@ def skip_code(cargo, r=Regexen()):
     global DEBUG
 
     if DEBUG:
-        print >> sys.stderr, "skip_code"
+        print("skip_code", file=sys.stderr)
     (fp, last) = cargo
 
     return comment((fp, last), r)
@@ -1317,8 +1321,8 @@ def getReference(name, source, verb):
     try:
         ref = name['$ref'][defLen:]
     except Exception:
-        print >>sys.stderr, "No reference in: "
-        print >>sys.stderr, name
+        print("No reference in: ", file=sys.stderr)
+        print(name, file=sys.stderr)
         raise Exception("No reference in: " + name)
     if not ref in swagger['definitions']:
         fn = ''
@@ -1326,11 +1330,11 @@ def getReference(name, source, verb):
             fn = swagger['paths'][route][verb]['x-filename']
         else:
             fn = swagger['definitions'][source]['x-filename']
-        print >> sys.stderr, json.dumps(
+        print(json.dumps(
             swagger['definitions'],
             indent=4,
             separators=(', ', ': '),
-            sort_keys=True)
+            sort_keys=True), file=sys.stderr)
         raise Exception("invalid reference: " + ref + " in " + fn)
     return ref
 
@@ -1395,13 +1399,13 @@ def unwrapPostJson(reference, layer):
                     try:
                         subStructRef = getReference(thisParam['items'], reference, None)
                     except:
-                        print >>sys.stderr, "while analyzing: " + param
-                        print >>sys.stderr, thisParam
+                        print("while analyzing: " + param, file=sys.stderr)
+                        print(thisParam, file=sys.stderr)
                     rc += "\n" + unwrapPostJson(subStructRef, layer + 1)
             else:
                 if thisParam['type'] not in swaggerDataTypes:
-                    print >>sys.stderr, "while analyzing: " + param
-                    print >>sys.stderr, thisParam['type'] + " is not a valid swagger datatype; supported ones: " + str(swaggerDataTypes)
+                    print("while analyzing: " + param, file=sys.stderr)
+                    print(thisParam['type'] + " is not a valid swagger datatype; supported ones: " + str(swaggerDataTypes), file=sys.stderr)
                     raise Exception("invalid swagger type")
                 rc += '  ' * layer + "- **" + param + "**: " + TrimThisParam(thisParam['description'], layer) + '\n'
     return rc
@@ -1410,7 +1414,7 @@ def unwrapPostJson(reference, layer):
 
 
 if len(sys.argv) < 4:
-    print >> sys.stderr, "usage: " + sys.argv[0] + " <scriptDir> <outDir> <relDir> <docublockdir> <optional: filter>"
+    print("usage: " + sys.argv[0] + " <scriptDir> <outDir> <relDir> <docublockdir> <optional: filter>", file=sys.stderr)
     sys.exit(1)
 
 scriptDir = sys.argv[1]
@@ -1428,13 +1432,13 @@ def unwrapPostJson(reference, layer):
 fileFilter = ""
 if len(sys.argv) > 5:
     fileFilter = sys.argv[5]
-    print >> sys.stderr, "Filtering for: [" + fileFilter + "]"
-# read ArangoDB version
-f = open(scriptDir + "VERSION", "r")
-for version in f:
-    version = version.strip('\n')
-f.close()
+    print("Filtering for: [" + fileFilter + "]", file=sys.stderr)
 
+# read ArangoDB version and use it as API version
+f = io.open(scriptDir + "VERSION", encoding="utf-8", newline=None)
+version = f.read().strip()
+f.close()
+swagger['info']['version'] = version
 
 paths = {}
 
@@ -1448,7 +1452,7 @@ def unwrapPostJson(reference, layer):
     curPath = os.path.join(topdir, chapter)
     for oneFile in os.listdir(curPath):
         if fileFilter != "" and oneFile != fileFilter:
-            print >> sys.stderr, "Skipping: [" + oneFile + "]"
+            print("Skipping: [" + oneFile + "]", file=sys.stderr)
             continue
         curPath2 = os.path.join(curPath, oneFile)
         if os.path.isfile(curPath2) and oneFile[0] != "." and oneFile.endswith(".md"):
@@ -1458,11 +1462,11 @@ def unwrapPostJson(reference, layer):
     currentTag = name
     for fn in filenames:
         thisfn = fn
-        infile = open(fn)
+        infile = io.open(fn, encoding='utf-8', newline=None)
         try:
             getOneApi(infile, name + " - " + ', '.join(filenames), fn)
         except Exception as x:
-            print >> sys.stderr, "\nwhile parsing file: '%s' error: %s" % (thisfn, x)
+            print("\nwhile parsing file: '%s' error: %s" % (thisfn, x), file=sys.stderr)
             raise Exception("while parsing file '%s' error: %s" %(thisfn, x))
         infile.close()
         currentDocuBlock = None
@@ -1477,8 +1481,8 @@ def descOffsetGet(value):
         offsetPlus = 0
         thisVerb = swagger['paths'][route][verb]
         if not thisVerb['description']:
-            print >> sys.stderr, "Description of Route empty; @RESTDESCRIPTION missing?"
-            print >> sys.stderr, "in :" + verb + " " + route
+            print("Description of Route empty; @RESTDESCRIPTION missing?", file=sys.stderr)
+            print("in :" + verb + " " + route, file=sys.stderr)
             #raise TODO
         # insert the post json description into the place we extracted it:
         # Collect the blocks we want to work on, sort them by replacement place:
@@ -1573,7 +1577,7 @@ def descOffsetGet(value):
 
 #print highlight(yaml.dump(swagger, Dumper=yaml.RoundTripDumper), YamlLexer(), TerminalFormatter())
 #print yaml.dump(swagger, Dumper=yaml.RoundTripDumper)
-print json.dumps(swagger, indent=4, separators=(', ', ': '), sort_keys=True)
+print(json.dumps(swagger, indent=4, separators=(', ', ': '), sort_keys=True))
 #print json.dumps(swagger['paths'], indent=4, separators=(', ',': '), sort_keys=True)
 #print highlight(yaml.dump(swagger, Dumper=yaml.RoundTripDumper), YamlLexer(), TerminalFormatter())
 

From 4b09567540fd386e5e0e17459d23a9809fa14d1a Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Fri, 13 Mar 2020 08:36:31 +0100
Subject: [PATCH 103/122] Fixed assertion in SubqueryStart. On initial call it
 can be called with a non-allocated block

---
 arangod/Aql/SubqueryStartExecutor.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arangod/Aql/SubqueryStartExecutor.cpp b/arangod/Aql/SubqueryStartExecutor.cpp
index f854d404496d..208afb2fc6b9 100644
--- a/arangod/Aql/SubqueryStartExecutor.cpp
+++ b/arangod/Aql/SubqueryStartExecutor.cpp
@@ -47,8 +47,8 @@ auto SubqueryStartExecutor::produceRows(AqlItemBlockInputRange& input, OutputAql
     return {ExecutorState::DONE, NoStats{}, AqlCall{}};
   }
   TRI_ASSERT(!_inputRow.isInitialized());
-  TRI_ASSERT(!output.isFull());
   if (input.hasDataRow()) {
+    TRI_ASSERT(!output.isFull());
     std::tie(_upstreamState, _inputRow) = input.peekDataRow();
     output.copyRow(_inputRow);
     output.advanceRow();

From ace0317a0945c9b50e56b18cc9fd3dd827bdebd2 Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Fri, 13 Mar 2020 08:36:56 +0100
Subject: [PATCH 104/122] Added methods to count available rows in
 AqlItemBlockInputRange

---
 arangod/Aql/AqlItemBlockInputRange.cpp | 10 ++++++++++
 arangod/Aql/AqlItemBlockInputRange.h   | 14 ++++++++++++++
 2 files changed, 24 insertions(+)

diff --git a/arangod/Aql/AqlItemBlockInputRange.cpp b/arangod/Aql/AqlItemBlockInputRange.cpp
index b0329dfd94d7..dafbb43ffde1 100644
--- a/arangod/Aql/AqlItemBlockInputRange.cpp
+++ b/arangod/Aql/AqlItemBlockInputRange.cpp
@@ -181,3 +181,13 @@ auto AqlItemBlockInputRange::skipAll() noexcept -> std::size_t {
   _skipped = 0;
   return skipped;
 }
+
+auto AqlItemBlockInputRange::countDataRows() const noexcept -> std::size_t {
+  auto const& block = getBlock();
+  return block->size() - block->getShadowRowIndexes().size();
+}
+
+auto AqlItemBlockInputRange::countShadowRows() const noexcept -> std::size_t {
+  auto const& block = getBlock();
+  return block->getShadowRowIndexes().size();
+}
\ No newline at end of file
diff --git a/arangod/Aql/AqlItemBlockInputRange.h b/arangod/Aql/AqlItemBlockInputRange.h
index ef2bfd6b70e6..8af13379acde 100644
--- a/arangod/Aql/AqlItemBlockInputRange.h
+++ b/arangod/Aql/AqlItemBlockInputRange.h
@@ -72,6 +72,20 @@ class AqlItemBlockInputRange {
 
   [[nodiscard]] auto skippedInFlight() const noexcept -> std::size_t;
 
+  /**
+   * @brief Count how many datarows are expected in this range
+   *        Used to estimate amount of produced rows
+   * @return std::size_t
+   */
+  [[nodiscard]] auto countDataRows() const noexcept -> std::size_t;
+
+  /**
+   * @brief Count how many shadowRows are expected in this range
+   *        Used to estimate amount of produced rows
+   * @return std::size_t
+   */
+  [[nodiscard]] auto countShadowRows() const noexcept -> std::size_t;
+
  private:
   bool isIndexValid(std::size_t index) const noexcept;
 

From b8d4b48cd99cda002ac8c6d98334f235f7f266e3 Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Fri, 13 Mar 2020 08:37:46 +0100
Subject: [PATCH 105/122] Allow a path to Ask the Executor how many rows are
 going to be produced for allocation.

---
 arangod/Aql/ExecutionBlockImpl.cpp | 30 +++++++++++++++++++++++-------
 arangod/Aql/ExecutionBlockImpl.h   |  6 +++---
 2 files changed, 26 insertions(+), 10 deletions(-)

diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index 133df32b4677..736ba0ac0a2b 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -114,6 +114,7 @@ CREATE_HAS_MEMBER_CHECK(skipRows, hasSkipRows);
 CREATE_HAS_MEMBER_CHECK(fetchBlockForPassthrough, hasFetchBlockForPassthrough);
 CREATE_HAS_MEMBER_CHECK(expectedNumberOfRows, hasExpectedNumberOfRows);
 CREATE_HAS_MEMBER_CHECK(skipRowsRange, hasSkipRowsRange);
+CREATE_HAS_MEMBER_CHECK(expectedNumberOfRowsNew, hasExpectedNumberOfRowsNew);
 
 #ifdef ARANGODB_USE_GOOGLE_TESTS
 // Forward declaration of Test Executors.
@@ -1032,7 +1033,7 @@ std::pair<ExecutionState, SharedAqlItemBlockPtr> ExecutionBlockImpl<Executor>::r
 
 // TODO: We need to define the size of this block based on Input / Executor / Subquery depth
 template <class Executor>
-auto ExecutionBlockImpl<Executor>::allocateOutputBlock(AqlCall&& call)
+auto ExecutionBlockImpl<Executor>::allocateOutputBlock(AqlCall&& call, DataRange const& inputRange)
     -> std::unique_ptr<OutputAqlItemRow> {
   if constexpr (Executor::Properties::allowsBlockPassthrough == BlockPassthrough::Enable) {
     SharedAqlItemBlockPtr newBlock{nullptr};
@@ -1047,8 +1048,22 @@ auto ExecutionBlockImpl<Executor>::allocateOutputBlock(AqlCall&& call)
 
     return createOutputRow(newBlock, std::move(call));
   } else {
+    if (!inputRange.hasShadowRow() && !inputRange.hasDataRow()) {
+      // On empty input do not yet create output.
+      SharedAqlItemBlockPtr newBlock{nullptr};
+      return createOutputRow(newBlock, std::move(call));
+    }
     // Non-Passthrough variant, we need to allocate the block ourselfs
     size_t blockSize = ExecutionBlock::DefaultBatchSize;
+    if constexpr (hasExpectedNumberOfRowsNew<Executor>::value) {
+      blockSize = _executor.expectedNumberOfRowsNew(inputRange, call);
+      // The executor cannot expect to produce more then the limit!
+      TRI_ASSERT(blockSize <= call.getLimit());
+
+      blockSize += inputRange.countShadowRows();
+      // We have an upper bound by DefaultBatchSize;
+      blockSize = std::min(ExecutionBlock::DefaultBatchSize, blockSize);
+    }
     SharedAqlItemBlockPtr newBlock =
         _engine->itemBlockManager().requestBlock(blockSize, _infos.numberOfOutputRegisters());
     return createOutputRow(newBlock, std::move(call));
@@ -1056,9 +1071,10 @@ auto ExecutionBlockImpl<Executor>::allocateOutputBlock(AqlCall&& call)
 }
 
 template <class Executor>
-void ExecutionBlockImpl<Executor>::ensureOutputBlock(AqlCall&& call) {
+void ExecutionBlockImpl<Executor>::ensureOutputBlock(AqlCall&& call,
+                                                     DataRange const& inputRange) {
   if (_outputItemRow == nullptr || !_outputItemRow->isInitialized()) {
-    _outputItemRow = allocateOutputBlock(std::move(call));
+    _outputItemRow = allocateOutputBlock(std::move(call), inputRange);
   } else {
     _outputItemRow->setCall(std::move(call));
   }
@@ -1939,9 +1955,9 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
             TRI_ASSERT(!stack.empty());
             AqlCall const& subqueryCall = stack.peek();
             AqlCall copyCall = subqueryCall;
-            ensureOutputBlock(std::move(copyCall));
+            ensureOutputBlock(std::move(copyCall), _lastRange);
           } else {
-            ensureOutputBlock(std::move(clientCall));
+            ensureOutputBlock(std::move(clientCall), _lastRange);
           }
           TRI_ASSERT(_outputItemRow);
           TRI_ASSERT(!_executorReturnedDone);
@@ -2133,9 +2149,9 @@ ExecutionBlockImpl<Executor>::executeWithoutTrace(AqlCallStack stack) {
             TRI_ASSERT(!stack.empty());
             AqlCall const& subqueryCall = stack.peek();
             AqlCall copyCall = subqueryCall;
-            ensureOutputBlock(std::move(copyCall));
+            ensureOutputBlock(std::move(copyCall), _lastRange);
           } else {
-            ensureOutputBlock(std::move(clientCall));
+            ensureOutputBlock(std::move(clientCall), _lastRange);
           }
 
           TRI_ASSERT(!_outputItemRow->allRowsUsed());
diff --git a/arangod/Aql/ExecutionBlockImpl.h b/arangod/Aql/ExecutionBlockImpl.h
index 1b4365c78c40..ff6b7f63cf0c 100644
--- a/arangod/Aql/ExecutionBlockImpl.h
+++ b/arangod/Aql/ExecutionBlockImpl.h
@@ -309,12 +309,12 @@ class ExecutionBlockImpl final : public ExecutionBlock {
   [[nodiscard]] ExecutionState fetchShadowRowInternal();
 
   // Allocate an output block and install a call in it
-  [[nodiscard]] auto allocateOutputBlock(AqlCall&& call)
+  [[nodiscard]] auto allocateOutputBlock(AqlCall&& call, DataRange const& inputRange)
       -> std::unique_ptr<OutputAqlItemRow>;
 
-  // Ensure that we have an output block of the desired dimenstions
+  // Ensure that we have an output block of the desired dimensions
   // Will as a side effect modify _outputItemRow
-  void ensureOutputBlock(AqlCall&& call);
+  void ensureOutputBlock(AqlCall&& call, DataRange const& inputRange);
 
   // Compute the next state based on the given call.
   // Can only be one of Skip/Produce/FullCount/FastForward/Done

From 94d7729338ff073fd54644888f17fdad19487126 Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Fri, 13 Mar 2020 08:38:22 +0100
Subject: [PATCH 106/122] Let Return and SubqueryExecutors present how many
 data rows are to be expected.

---
 arangod/Aql/ReturnExecutor.cpp   |  6 ++++++
 arangod/Aql/ReturnExecutor.h     |  3 +++
 arangod/Aql/SubqueryExecutor.cpp | 10 ++++++++++
 arangod/Aql/SubqueryExecutor.h   |  3 +++
 4 files changed, 22 insertions(+)

diff --git a/arangod/Aql/ReturnExecutor.cpp b/arangod/Aql/ReturnExecutor.cpp
index 52a03761d39d..d72fab851036 100644
--- a/arangod/Aql/ReturnExecutor.cpp
+++ b/arangod/Aql/ReturnExecutor.cpp
@@ -131,3 +131,9 @@ auto ReturnExecutor::produceRows(AqlItemBlockInputRange& inputRange, OutputAqlIt
 
   return {inputRange.upstreamState(), stats, output.getClientCall()};
 }
+
+[[nodiscard]] auto ReturnExecutor::expectedNumberOfRowsNew(AqlItemBlockInputRange const& input,
+                                                           AqlCall const& call) const
+    noexcept -> size_t {
+  return input.countDataRows();
+}
\ No newline at end of file
diff --git a/arangod/Aql/ReturnExecutor.h b/arangod/Aql/ReturnExecutor.h
index c2d46ae638c1..69d03fa7accd 100644
--- a/arangod/Aql/ReturnExecutor.h
+++ b/arangod/Aql/ReturnExecutor.h
@@ -115,6 +115,9 @@ class ReturnExecutor {
   [[nodiscard]] auto expectedNumberOfRows(size_t atMost) const
       -> std::pair<ExecutionState, size_t>;
 
+  [[nodiscard]] auto expectedNumberOfRowsNew(AqlItemBlockInputRange const& input,
+                                             AqlCall const& call) const noexcept -> size_t;
+
  private:
   ReturnExecutorInfos& _infos;
   Fetcher& _fetcher;
diff --git a/arangod/Aql/SubqueryExecutor.cpp b/arangod/Aql/SubqueryExecutor.cpp
index 76be9ef6c6cc..a48d517ad51a 100644
--- a/arangod/Aql/SubqueryExecutor.cpp
+++ b/arangod/Aql/SubqueryExecutor.cpp
@@ -341,6 +341,16 @@ auto SubqueryExecutor<true>::skipRowsRange<>(AqlItemBlockInputRange& inputRange,
   _skipped = 0;
   return {translatedReturnType(), NoStats{}, call.getSkipCount(), getUpstreamCall()};
 }
+template <bool isModificationSubquery>
+[[nodiscard]] auto SubqueryExecutor<isModificationSubquery>::expectedNumberOfRowsNew(
+    AqlItemBlockInputRange const& input, AqlCall const& call) const noexcept -> size_t {
+  if constexpr (isModificationSubquery) {
+    // This executor might skip data.
+    // It could overfetch it before.
+    return std::min(call.getLimit(), input.countDataRows());
+  }
+  return input.countDataRows();
+}
 
 template class ::arangodb::aql::SubqueryExecutor<true>;
 template class ::arangodb::aql::SubqueryExecutor<false>;
diff --git a/arangod/Aql/SubqueryExecutor.h b/arangod/Aql/SubqueryExecutor.h
index b28823180849..b9659b5a2178 100644
--- a/arangod/Aql/SubqueryExecutor.h
+++ b/arangod/Aql/SubqueryExecutor.h
@@ -133,6 +133,9 @@ class SubqueryExecutor {
   auto initializeSubquery(AqlItemBlockInputRange& input)
       -> std::tuple<ExecutionState, bool>;
 
+  [[nodiscard]] auto expectedNumberOfRowsNew(AqlItemBlockInputRange const& input,
+                                             AqlCall const& call) const noexcept -> size_t;
+
  private:
   Fetcher& _fetcher;
   SubqueryExecutorInfos& _infos;

From db8a7753e2b035e37c8e9477e17c41225c9cab3e Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Fri, 13 Mar 2020 12:23:53 +0100
Subject: [PATCH 107/122] Implement a fast forwarding of Rows in IdExecutor

---
 arangod/Aql/IdExecutor.cpp       | 18 ++++++++----------
 arangod/Aql/OutputAqlItemRow.cpp | 24 ++++++++++++++++++++++++
 arangod/Aql/OutputAqlItemRow.h   | 13 +++++++++++++
 3 files changed, 45 insertions(+), 10 deletions(-)

diff --git a/arangod/Aql/IdExecutor.cpp b/arangod/Aql/IdExecutor.cpp
index 1350038678e0..adddd943f4a9 100644
--- a/arangod/Aql/IdExecutor.cpp
+++ b/arangod/Aql/IdExecutor.cpp
@@ -88,25 +88,23 @@ auto IdExecutor<UsedFetcher>::produceRows(AqlItemBlockInputRange& inputRange,
     -> std::tuple<ExecutorState, CountStats, AqlCall> {
   CountStats stats;
   TRI_ASSERT(output.numRowsWritten() == 0);
-  // TODO: We can implement a fastForward copy here.
-  // We know that all rows we have will fit into the output
-  while (!output.isFull() && inputRange.hasDataRow()) {
-    auto const& [state, inputRow] = inputRange.nextDataRow();
-    TRI_ASSERT(inputRow);
-
+  if (inputRange.hasDataRow()) {
+    TRI_ASSERT(!output.isFull());
     TRI_IF_FAILURE("SingletonBlock::getOrSkipSome") {
       THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
     }
+    auto const& [state, inputRow] = inputRange.peekDataRow();
+
+    output.fastForwardAllRows(inputRow, inputRange.countDataRows());
 
-    /*Second parameter are to ignore registers that should be kept but are missing in the input row*/
-    output.copyRow(inputRow, std::is_same_v<UsedFetcher, ConstFetcher>);
-    TRI_ASSERT(output.produced());
-    output.advanceRow();
+    std::ignore = inputRange.skipAllRemainingDataRows();
 
     TRI_IF_FAILURE("SingletonBlock::getOrSkipSomeSet") {
       THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
     }
   }
+
+  TRI_ASSERT(!inputRange.hasDataRow());
   if (_infos.doCount()) {
     stats.addCounted(output.numRowsWritten());
   }
diff --git a/arangod/Aql/OutputAqlItemRow.cpp b/arangod/Aql/OutputAqlItemRow.cpp
index 9eddbcf13a1a..b7d933018c25 100644
--- a/arangod/Aql/OutputAqlItemRow.cpp
+++ b/arangod/Aql/OutputAqlItemRow.cpp
@@ -166,6 +166,30 @@ void OutputAqlItemRow::copyRow(ItemRowType const& sourceRow, bool ignoreMissing)
   doCopyRow(sourceRow, ignoreMissing);
 }
 
+auto OutputAqlItemRow::fastForwardAllRows(InputAqlItemRow const& sourceRow, size_t rows)
+    -> void {
+#ifdef ARANGODB_ENABLE_MAINTAINER_MODE
+  TRI_ASSERT(sourceRow.internalBlockIs(_block));
+#endif
+  TRI_ASSERT(_doNotCopyInputRow);
+  TRI_ASSERT(_call.getLimit() >= rows);
+  TRI_ASSERT(rows > 0);
+  // We have the guarantee that we have all data in our block.
+  // We only need to adjust internal indexes.
+#ifdef ARANGODB_ENABLE_MAINTAINER_MODE
+  // Safely assert that the API is not missused.
+  TRI_ASSERT(_baseIndex + rows <= _block->size());
+  for (size_t i = _baseIndex; i < _baseIndex + rows; ++i) {
+    TRI_ASSERT(!_block->isShadowRow(i));
+  }
+#endif
+  _baseIndex += rows;
+  TRI_ASSERT(_baseIndex > 0);
+  _lastBaseIndex = _baseIndex - 1;
+  _lastSourceRow = InputAqlItemRow{_block, _lastBaseIndex};
+  _call.didProduce(rows);
+}
+
 void OutputAqlItemRow::copyBlockInternalRegister(InputAqlItemRow const& sourceRow,
                                                  RegisterId input, RegisterId output) {
   // This method is only allowed if the block of the input row is the same as
diff --git a/arangod/Aql/OutputAqlItemRow.h b/arangod/Aql/OutputAqlItemRow.h
index 29b9e26017bf..baee6f7d44bf 100644
--- a/arangod/Aql/OutputAqlItemRow.h
+++ b/arangod/Aql/OutputAqlItemRow.h
@@ -99,6 +99,19 @@ class OutputAqlItemRow {
   void copyBlockInternalRegister(InputAqlItemRow const& sourceRow,
                                  RegisterId input, RegisterId output);
 
+  /**
+   * @brief This function will only work if input and output
+   *        have the same block.
+   *        We will "copy" all rows in the input block into the output.
+   *        No Registers will be modified.
+   *
+   * @param sourceRow The input source row.
+   *                  Requirements:
+   *                    - Input and Output blocks are the same
+   *                    - Input and Output row position are identical
+   */
+  auto fastForwardAllRows(InputAqlItemRow const& sourceRow, size_t rows) -> void;
+
   [[nodiscard]] std::size_t getNrRegisters() const {
     return block().getNrRegs();
   }

From e431ccf35da8027a1d2ac7d1afe0d9e9ec603677 Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Fri, 13 Mar 2020 14:03:17 +0100
Subject: [PATCH 108/122] Initialize all the bools

---
 arangod/Graph/KShortestPathsFinder.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arangod/Graph/KShortestPathsFinder.h b/arangod/Graph/KShortestPathsFinder.h
index 433da5312f38..bb621f83e8bf 100644
--- a/arangod/Graph/KShortestPathsFinder.h
+++ b/arangod/Graph/KShortestPathsFinder.h
@@ -259,7 +259,7 @@ class KShortestPathsFinder : public ShortestPathFinder {
                        VertexRef& join, std::optional<double>& currentBest);
 
  private:
-  bool _traversalDone;
+  bool _traversalDone{true};
 
   VertexRef _start;
   VertexRef _end;

From 7c1069ccf364075f914e482358704e828412a782 Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Fri, 13 Mar 2020 14:03:33 +0100
Subject: [PATCH 109/122] Fixed ASAN warning

---
 arangod/Aql/KShortestPathsExecutor.cpp | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arangod/Aql/KShortestPathsExecutor.cpp b/arangod/Aql/KShortestPathsExecutor.cpp
index 30ac99e57eb1..de049943c252 100644
--- a/arangod/Aql/KShortestPathsExecutor.cpp
+++ b/arangod/Aql/KShortestPathsExecutor.cpp
@@ -232,7 +232,9 @@ auto KShortestPathsExecutor::doOutputPath(OutputAqlItemRow& output) -> void {
   tmp->clear();
 
   if (_finder.getNextPathAql(*tmp.builder())) {
-    output.cloneValueInto(_infos.getOutputRegister(), _inputRow, AqlValue(*tmp.builder()));
+    AqlValue path{*tmp.builder()};
+    AqlValueGuard guard{path, true};
+    output.moveValueInto(_infos.getOutputRegister(), _inputRow, guard);
     output.advanceRow();
   }
 }

From bc40f0254c1e277ccb9ed9e3a1ce96fed48cabfa Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Fri, 13 Mar 2020 14:14:23 +0100
Subject: [PATCH 110/122] Fixed ASAN warning in ShortestPathExecutor

---
 arangod/Aql/ShortestPathExecutor.cpp | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/arangod/Aql/ShortestPathExecutor.cpp b/arangod/Aql/ShortestPathExecutor.cpp
index e8d1a3336b92..d6e21d5e5b3e 100644
--- a/arangod/Aql/ShortestPathExecutor.cpp
+++ b/arangod/Aql/ShortestPathExecutor.cpp
@@ -168,13 +168,15 @@ auto ShortestPathExecutor::doOutputPath(OutputAqlItemRow& output) -> void {
   while (!output.isFull() && _posInPath < _path->length()) {
     if (_infos.usesOutputRegister(ShortestPathExecutorInfos::VERTEX)) {
       AqlValue vertex = _path->vertexToAqlValue(_infos.cache(), _posInPath);
-      output.cloneValueInto(_infos.getOutputRegister(ShortestPathExecutorInfos::VERTEX),
-                            _inputRow, vertex);
+      AqlValueGuard guard{vertex, true};
+      output.moveValueInto(_infos.getOutputRegister(ShortestPathExecutorInfos::VERTEX),
+                           _inputRow, guard);
     }
     if (_infos.usesOutputRegister(ShortestPathExecutorInfos::EDGE)) {
       AqlValue edge = _path->edgeToAqlValue(_infos.cache(), _posInPath);
-      output.cloneValueInto(_infos.getOutputRegister(ShortestPathExecutorInfos::EDGE),
-                            _inputRow, edge);
+      AqlValueGuard guard{edge, true};
+      output.moveValueInto(_infos.getOutputRegister(ShortestPathExecutorInfos::EDGE),
+                           _inputRow, guard);
     }
     output.advanceRow();
     _posInPath++;

From 350f6d05b8a6737ea84ddcc05775effa25023db0 Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Fri, 13 Mar 2020 15:25:09 +0100
Subject: [PATCH 111/122] Fixed invalid access in block allocation if input is
 empty

---
 arangod/Aql/AqlItemBlockInputRange.cpp |  6 ++++++
 arangod/Aql/CountCollectExecutor.cpp   |  6 ++++++
 arangod/Aql/CountCollectExecutor.h     |  3 +++
 arangod/Aql/ExecutionBlockImpl.cpp     | 22 ++++++++++++++++++----
 4 files changed, 33 insertions(+), 4 deletions(-)

diff --git a/arangod/Aql/AqlItemBlockInputRange.cpp b/arangod/Aql/AqlItemBlockInputRange.cpp
index dafbb43ffde1..96be2d02c41f 100644
--- a/arangod/Aql/AqlItemBlockInputRange.cpp
+++ b/arangod/Aql/AqlItemBlockInputRange.cpp
@@ -183,11 +183,17 @@ auto AqlItemBlockInputRange::skipAll() noexcept -> std::size_t {
 }
 
 auto AqlItemBlockInputRange::countDataRows() const noexcept -> std::size_t {
+  if (_block == nullptr) {
+    return 0;
+  }
   auto const& block = getBlock();
   return block->size() - block->getShadowRowIndexes().size();
 }
 
 auto AqlItemBlockInputRange::countShadowRows() const noexcept -> std::size_t {
+  if (_block == nullptr) {
+    return 0;
+  }
   auto const& block = getBlock();
   return block->getShadowRowIndexes().size();
 }
\ No newline at end of file
diff --git a/arangod/Aql/CountCollectExecutor.cpp b/arangod/Aql/CountCollectExecutor.cpp
index ff6bb3ad4130..b66ce1e61662 100644
--- a/arangod/Aql/CountCollectExecutor.cpp
+++ b/arangod/Aql/CountCollectExecutor.cpp
@@ -108,6 +108,12 @@ std::pair<ExecutionState, size_t> CountCollectExecutor::expectedNumberOfRows(siz
   return {ExecutionState::HASMORE, 1};
 }
 
+auto CountCollectExecutor::expectedNumberOfRowsNew(AqlItemBlockInputRange const& input,
+                                                   AqlCall const& call) const
+    noexcept -> size_t {
+  return std::min<size_t>(1, call.getLimit());
+}
+
 const CountCollectExecutor::Infos& CountCollectExecutor::infos() const noexcept {
   return _infos;
 }
diff --git a/arangod/Aql/CountCollectExecutor.h b/arangod/Aql/CountCollectExecutor.h
index 2fad185c917c..21e51a9e29f8 100644
--- a/arangod/Aql/CountCollectExecutor.h
+++ b/arangod/Aql/CountCollectExecutor.h
@@ -105,6 +105,9 @@ class CountCollectExecutor {
 
   std::pair<ExecutionState, size_t> expectedNumberOfRows(size_t atMost) const;
 
+  [[nodiscard]] auto expectedNumberOfRowsNew(AqlItemBlockInputRange const& input,
+                                             AqlCall const& call) const noexcept -> size_t;
+
  private:
   Infos const& infos() const noexcept;
 
diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index 736ba0ac0a2b..13c2468ad446 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -1048,11 +1048,25 @@ auto ExecutionBlockImpl<Executor>::allocateOutputBlock(AqlCall&& call, DataRange
 
     return createOutputRow(newBlock, std::move(call));
   } else {
-    if (!inputRange.hasShadowRow() && !inputRange.hasDataRow()) {
-      // On empty input do not yet create output.
-      SharedAqlItemBlockPtr newBlock{nullptr};
-      return createOutputRow(newBlock, std::move(call));
+    if constexpr (isMultiDepExecutor<Executor>) {
+      // MultiDepExecutor wpuld require dependency handling.
+      // We do not have it here.
+      if (!inputRange.hasShadowRow() && !inputRange.hasDataRow()) {
+        // On empty input do not yet create output.
+        // We are going to ask again later
+        SharedAqlItemBlockPtr newBlock{nullptr};
+        return createOutputRow(newBlock, std::move(call));
+      }
+    } else {
+      if (!inputRange.hasShadowRow() && !inputRange.hasDataRow() &&
+          inputRange.upstreamState() == ExecutorState::HASMORE) {
+        // On empty input do not yet create output.
+        // We are going to ask again later
+        SharedAqlItemBlockPtr newBlock{nullptr};
+        return createOutputRow(newBlock, std::move(call));
+      }
     }
+
     // Non-Passthrough variant, we need to allocate the block ourselfs
     size_t blockSize = ExecutionBlock::DefaultBatchSize;
     if constexpr (hasExpectedNumberOfRowsNew<Executor>::value) {

From 014d1a4c90ed863e7b5035b979d2a72b18be703e Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Sun, 15 Mar 2020 10:45:48 +0100
Subject: [PATCH 112/122] Reactivated expectedNumberOfRows on all
 SingleRowFetcher executors

---
 arangod/Aql/DistinctCollectExecutor.cpp |  8 ++++++++
 arangod/Aql/DistinctCollectExecutor.h   |  3 +++
 arangod/Aql/FilterExecutor.cpp          |  6 ++++++
 arangod/Aql/FilterExecutor.h            |  3 +++
 arangod/Aql/HashedCollectExecutor.cpp   | 13 +++++++++++++
 arangod/Aql/HashedCollectExecutor.h     | 11 ++++++++++-
 arangod/Aql/NoResultsExecutor.cpp       |  9 ++++++++-
 arangod/Aql/NoResultsExecutor.h         |  3 +++
 arangod/Aql/SortedCollectExecutor.cpp   | 10 ++++++++++
 arangod/Aql/SortedCollectExecutor.h     |  3 +++
 arangod/Aql/SubqueryEndExecutor.cpp     |  7 +++++++
 arangod/Aql/SubqueryEndExecutor.h       |  3 +++
 arangod/Aql/SubqueryStartExecutor.cpp   |  5 +++++
 arangod/Aql/SubqueryStartExecutor.h     |  4 +++-
 14 files changed, 85 insertions(+), 3 deletions(-)

diff --git a/arangod/Aql/DistinctCollectExecutor.cpp b/arangod/Aql/DistinctCollectExecutor.cpp
index bb6dc923baf1..046cec1c4940 100644
--- a/arangod/Aql/DistinctCollectExecutor.cpp
+++ b/arangod/Aql/DistinctCollectExecutor.cpp
@@ -85,6 +85,14 @@ std::pair<ExecutionState, size_t> DistinctCollectExecutor::expectedNumberOfRows(
   return _fetcher.preFetchNumberOfRows(atMost);
 }
 
+[[nodiscard]] auto DistinctCollectExecutor::expectedNumberOfRowsNew(
+    AqlItemBlockInputRange const& input, AqlCall const& call) const noexcept -> size_t {
+  // Worst case assumption:
+  // For every input row we have a new group.
+  // We will never produce more then asked for
+  return std::min(call.getLimit(), input.countDataRows());
+}
+
 void DistinctCollectExecutor::destroyValues() {
   // destroy all AqlValues captured
   for (auto& value : _seen) {
diff --git a/arangod/Aql/DistinctCollectExecutor.h b/arangod/Aql/DistinctCollectExecutor.h
index def1af36cf13..00197b40d4b6 100644
--- a/arangod/Aql/DistinctCollectExecutor.h
+++ b/arangod/Aql/DistinctCollectExecutor.h
@@ -120,6 +120,9 @@ class DistinctCollectExecutor {
 
   std::pair<ExecutionState, size_t> expectedNumberOfRows(size_t atMost) const;
 
+  [[nodiscard]] auto expectedNumberOfRowsNew(AqlItemBlockInputRange const& input,
+                                             AqlCall const& call) const noexcept -> size_t;
+
  private:
   Infos const& infos() const noexcept;
   void destroyValues();
diff --git a/arangod/Aql/FilterExecutor.cpp b/arangod/Aql/FilterExecutor.cpp
index 516c2ea4678a..63882d26a00b 100644
--- a/arangod/Aql/FilterExecutor.cpp
+++ b/arangod/Aql/FilterExecutor.cpp
@@ -153,3 +153,9 @@ auto FilterExecutor::produceRows(AqlItemBlockInputRange& inputRange, OutputAqlIt
                            (std::min)(clientCall.softLimit, clientCall.hardLimit);
   return {inputRange.upstreamState(), stats, upstreamCall};
 }
+
+[[nodiscard]] auto FilterExecutor::expectedNumberOfRowsNew(AqlItemBlockInputRange const& input,
+                                                           AqlCall const& call) const
+    noexcept -> size_t {
+  return std::min(call.getLimit(), input.countDataRows());
+}
diff --git a/arangod/Aql/FilterExecutor.h b/arangod/Aql/FilterExecutor.h
index 4b7350088180..8c443b69c5c3 100644
--- a/arangod/Aql/FilterExecutor.h
+++ b/arangod/Aql/FilterExecutor.h
@@ -108,6 +108,9 @@ class FilterExecutor {
 
   [[nodiscard]] std::pair<ExecutionState, size_t> expectedNumberOfRows(size_t atMost) const;
 
+  [[nodiscard]] auto expectedNumberOfRowsNew(AqlItemBlockInputRange const& input,
+                                             AqlCall const& call) const noexcept -> size_t;
+
  private:
   Infos& _infos;
   Fetcher& _fetcher;
diff --git a/arangod/Aql/HashedCollectExecutor.cpp b/arangod/Aql/HashedCollectExecutor.cpp
index 6f8e086fb6f6..4fd098d01279 100644
--- a/arangod/Aql/HashedCollectExecutor.cpp
+++ b/arangod/Aql/HashedCollectExecutor.cpp
@@ -360,6 +360,19 @@ std::pair<ExecutionState, size_t> HashedCollectExecutor::expectedNumberOfRows(si
   THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
 }
 
+[[nodiscard]] auto HashedCollectExecutor::expectedNumberOfRowsNew(
+    AqlItemBlockInputRange const& input, AqlCall const& call) const noexcept -> size_t {
+  if (!_isInitialized) {
+    // Worst case assumption:
+    // For every input row we have a new group.
+    // We will never produce more then asked for
+    return std::min(call.getLimit(), input.countDataRows());
+  }
+  // We know how many groups we have left
+  return std::min<size_t>(call.getLimit(),
+                          std::distance(_currentGroup, _allGroups.end()));
+}
+
 const HashedCollectExecutor::Infos& HashedCollectExecutor::infos() const noexcept {
   return _infos;
 }
diff --git a/arangod/Aql/HashedCollectExecutor.h b/arangod/Aql/HashedCollectExecutor.h
index 1ff7767d1f74..49cd7a047910 100644
--- a/arangod/Aql/HashedCollectExecutor.h
+++ b/arangod/Aql/HashedCollectExecutor.h
@@ -168,6 +168,15 @@ class HashedCollectExecutor {
    */
   std::pair<ExecutionState, size_t> expectedNumberOfRows(size_t atMost) const;
 
+  /**
+   * @brief This Executor does not know how many distinct rows will be fetched
+   * from upstream, it can only report how many it has found by itself, plus
+   * it knows that it can only create as many new rows as pulled from upstream.
+   * So it will overestimate.
+   */
+  [[nodiscard]] auto expectedNumberOfRowsNew(AqlItemBlockInputRange const& input,
+                                             AqlCall const& call) const noexcept -> size_t;
+
  private:
   using AggregateValuesType = std::vector<std::unique_ptr<Aggregator>>;
   using GroupKeyType = std::vector<AqlValue>;
@@ -215,7 +224,7 @@ class HashedCollectExecutor {
 
   /// @brief hashmap of all encountered groups
   GroupMapType _allGroups;
-  GroupMapType::iterator _currentGroup;
+  GroupMapType::const_iterator _currentGroup;
 
   bool _isInitialized;  // init() was called successfully (e.g. it returned DONE)
 
diff --git a/arangod/Aql/NoResultsExecutor.cpp b/arangod/Aql/NoResultsExecutor.cpp
index 0291a889bd31..a7620d3d843f 100644
--- a/arangod/Aql/NoResultsExecutor.cpp
+++ b/arangod/Aql/NoResultsExecutor.cpp
@@ -42,4 +42,11 @@ auto NoResultsExecutor::skipRowsRange(AqlItemBlockInputRange& inputRange, AqlCal
     noexcept -> std::tuple<ExecutorState, Stats, size_t, AqlCall> {
   return {inputRange.upstreamState(), NoStats{}, 0,
           AqlCall{0, false, 0, AqlCall::LimitType::HARD}};
-};
\ No newline at end of file
+};
+
+[[nodiscard]] auto NoResultsExecutor::expectedNumberOfRowsNew(AqlItemBlockInputRange const& input,
+                                                              AqlCall const& call) const
+    noexcept -> size_t {
+  // Well nevermind the input, but we will always return 0 rows here.
+  return 0;
+}
\ No newline at end of file
diff --git a/arangod/Aql/NoResultsExecutor.h b/arangod/Aql/NoResultsExecutor.h
index db5f7ed91059..c12bd06842a2 100644
--- a/arangod/Aql/NoResultsExecutor.h
+++ b/arangod/Aql/NoResultsExecutor.h
@@ -76,6 +76,9 @@ class NoResultsExecutor {
     // Well nevermind the input, but we will always return 0 rows here.
     return {ExecutionState::DONE, 0};
   }
+
+  [[nodiscard]] auto expectedNumberOfRowsNew(AqlItemBlockInputRange const& input,
+                                             AqlCall const& call) const noexcept -> size_t;
 };
 }  // namespace aql
 }  // namespace arangodb
diff --git a/arangod/Aql/SortedCollectExecutor.cpp b/arangod/Aql/SortedCollectExecutor.cpp
index d23975c5f72c..54a633e1310b 100644
--- a/arangod/Aql/SortedCollectExecutor.cpp
+++ b/arangod/Aql/SortedCollectExecutor.cpp
@@ -299,6 +299,16 @@ std::pair<ExecutionState, size_t> SortedCollectExecutor::expectedNumberOfRows(si
   THROW_ARANGO_EXCEPTION(TRI_ERROR_NOT_IMPLEMENTED);
 }
 
+[[nodiscard]] auto SortedCollectExecutor::expectedNumberOfRowsNew(
+    AqlItemBlockInputRange const& input, AqlCall const& call) const noexcept -> size_t {
+  // Worst case assumption:
+  // For every input row we have a new group.
+  // If we have an open group right now, we need to add 1 to this estimate.
+  // We will never produce more then asked for
+  return std::min(call.getLimit(),
+                  input.countDataRows() + (_currentGroup.isValid() ? 1 : 0));
+}
+
 auto SortedCollectExecutor::produceRows(AqlItemBlockInputRange& inputRange,
                                         OutputAqlItemRow& output)
     -> std::tuple<ExecutorState, Stats, AqlCall> {
diff --git a/arangod/Aql/SortedCollectExecutor.h b/arangod/Aql/SortedCollectExecutor.h
index 55e28d0585af..21c633176d55 100644
--- a/arangod/Aql/SortedCollectExecutor.h
+++ b/arangod/Aql/SortedCollectExecutor.h
@@ -209,6 +209,9 @@ class SortedCollectExecutor {
   [[nodiscard]] auto expectedNumberOfRows(size_t atMost) const
       -> std::pair<ExecutionState, size_t>;
 
+  [[nodiscard]] auto expectedNumberOfRowsNew(AqlItemBlockInputRange const& input,
+                                             AqlCall const& call) const noexcept -> size_t;
+
  private:
   Infos const& infos() const noexcept { return _infos; };
 
diff --git a/arangod/Aql/SubqueryEndExecutor.cpp b/arangod/Aql/SubqueryEndExecutor.cpp
index 6973ac216de4..7d5c7023ad1f 100644
--- a/arangod/Aql/SubqueryEndExecutor.cpp
+++ b/arangod/Aql/SubqueryEndExecutor.cpp
@@ -199,3 +199,10 @@ std::pair<ExecutionState, size_t> SubqueryEndExecutor::expectedNumberOfRows(size
   std::tie(state, expected) = _fetcher.preFetchNumberOfRows(atMost);
   return {state, expected};
 }
+
+[[nodiscard]] auto SubqueryEndExecutor::expectedNumberOfRowsNew(
+    AqlItemBlockInputRange const& input, AqlCall const& call) const noexcept -> size_t {
+  // This executor will not produce any more rows based on it's inbound data rows
+  // It will produce 1 row per ShadowRow, this is handled outside of this block.
+  return 0;
+}
diff --git a/arangod/Aql/SubqueryEndExecutor.h b/arangod/Aql/SubqueryEndExecutor.h
index 19b684f03b9e..5bc2a6dcdc41 100644
--- a/arangod/Aql/SubqueryEndExecutor.h
+++ b/arangod/Aql/SubqueryEndExecutor.h
@@ -88,6 +88,9 @@ class SubqueryEndExecutor {
   [[deprecated]] std::pair<ExecutionState, Stats> produceRows(OutputAqlItemRow& output);
   std::pair<ExecutionState, size_t> expectedNumberOfRows(size_t atMost) const;
 
+  [[nodiscard]] auto expectedNumberOfRowsNew(AqlItemBlockInputRange const& input,
+                                             AqlCall const& call) const noexcept -> size_t;
+
   // produceRows accumulates all input rows it can get into _accumulator, which
   // will then be read out by ExecutionBlockImpl
   // TODO: can the production of output be moved to produceRows again?
diff --git a/arangod/Aql/SubqueryStartExecutor.cpp b/arangod/Aql/SubqueryStartExecutor.cpp
index 208afb2fc6b9..2ce99adc4a53 100644
--- a/arangod/Aql/SubqueryStartExecutor.cpp
+++ b/arangod/Aql/SubqueryStartExecutor.cpp
@@ -100,3 +100,8 @@ auto SubqueryStartExecutor::expectedNumberOfRows(size_t atMost) const
   TRI_ASSERT(false);
   return {ExecutionState::DONE, 0};
 }
+
+[[nodiscard]] auto SubqueryStartExecutor::expectedNumberOfRowsNew(
+    AqlItemBlockInputRange const& input, AqlCall const& call) const noexcept -> size_t {
+  return std::min<size_t>({1, call.getLimit(), input.countDataRows()});
+}
diff --git a/arangod/Aql/SubqueryStartExecutor.h b/arangod/Aql/SubqueryStartExecutor.h
index 1cdd6f6fbeb0..0182e3153514 100644
--- a/arangod/Aql/SubqueryStartExecutor.h
+++ b/arangod/Aql/SubqueryStartExecutor.h
@@ -73,7 +73,9 @@ class SubqueryStartExecutor {
 
   std::pair<ExecutionState, size_t> expectedNumberOfRows(size_t atMost) const;
 
- private:
+  [[nodiscard]] auto expectedNumberOfRowsNew(AqlItemBlockInputRange const& input,
+                                             AqlCall const& call) const noexcept -> size_t;
+
  private:
   // Upstream state, used to determine if we are done with all subqueries
   ExecutorState _upstreamState{ExecutorState::HASMORE};

From dafce76d5d02d2c86c3672d72d02ff598a39c275 Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Sun, 15 Mar 2020 10:47:42 +0100
Subject: [PATCH 113/122] Deactivated Debug Logging in Enumerate Collection
 Executor test

---
 tests/Aql/EnumerateCollectionExecutorTest.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/Aql/EnumerateCollectionExecutorTest.cpp b/tests/Aql/EnumerateCollectionExecutorTest.cpp
index 8e94dfba206b..b1936d169a46 100644
--- a/tests/Aql/EnumerateCollectionExecutorTest.cpp
+++ b/tests/Aql/EnumerateCollectionExecutorTest.cpp
@@ -68,7 +68,7 @@ static const std::string GetAllDocs =
 
 using CursorType = arangodb::transaction::Methods::CursorType;
 
-class EnumerateCollectionExecutorTest : public AqlExecutorTestCase<true> {
+class EnumerateCollectionExecutorTest : public AqlExecutorTestCase<false> {
  protected:
   ExecutionState state;
   AqlItemBlockManager itemBlockManager;

From 920521ba5ef39acf77b5123e03ce4fbb4e896d6a Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Sun, 15 Mar 2020 11:13:33 +0100
Subject: [PATCH 114/122] Fixed SubqueryStartExecutor produceRows estimate

---
 arangod/Aql/SubqueryStartExecutor.cpp | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/arangod/Aql/SubqueryStartExecutor.cpp b/arangod/Aql/SubqueryStartExecutor.cpp
index 2ce99adc4a53..1af0c2fe806f 100644
--- a/arangod/Aql/SubqueryStartExecutor.cpp
+++ b/arangod/Aql/SubqueryStartExecutor.cpp
@@ -103,5 +103,17 @@ auto SubqueryStartExecutor::expectedNumberOfRows(size_t atMost) const
 
 [[nodiscard]] auto SubqueryStartExecutor::expectedNumberOfRowsNew(
     AqlItemBlockInputRange const& input, AqlCall const& call) const noexcept -> size_t {
-  return std::min<size_t>({1, call.getLimit(), input.countDataRows()});
+  // NOTE:
+  // As soon as we can overfetch data, this needs to be modified to
+  // returnVlaue * countDataRows();
+  if (input.countDataRows() > 0) {
+    // We will write one ShadowRow
+    if (call.getLimit() > 0) {
+      // We will write one DataRow
+      return 2;
+    }
+    return 1;
+  }
+  // Nothing to create here.
+  return 0;
 }

From 33b9d943fd5675fb9cc1a79efd3a8b9f68d1e5a3 Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Sun, 15 Mar 2020 11:28:11 +0100
Subject: [PATCH 115/122] For now SubqueryEndExecutor cannot define expected
 number of rows. We end at the shadowRow with input, but EndExecutor will loop
 here, so it needs more space for output.

---
 arangod/Aql/SubqueryEndExecutor.cpp | 7 -------
 arangod/Aql/SubqueryEndExecutor.h   | 3 ---
 2 files changed, 10 deletions(-)

diff --git a/arangod/Aql/SubqueryEndExecutor.cpp b/arangod/Aql/SubqueryEndExecutor.cpp
index 7d5c7023ad1f..6973ac216de4 100644
--- a/arangod/Aql/SubqueryEndExecutor.cpp
+++ b/arangod/Aql/SubqueryEndExecutor.cpp
@@ -199,10 +199,3 @@ std::pair<ExecutionState, size_t> SubqueryEndExecutor::expectedNumberOfRows(size
   std::tie(state, expected) = _fetcher.preFetchNumberOfRows(atMost);
   return {state, expected};
 }
-
-[[nodiscard]] auto SubqueryEndExecutor::expectedNumberOfRowsNew(
-    AqlItemBlockInputRange const& input, AqlCall const& call) const noexcept -> size_t {
-  // This executor will not produce any more rows based on it's inbound data rows
-  // It will produce 1 row per ShadowRow, this is handled outside of this block.
-  return 0;
-}
diff --git a/arangod/Aql/SubqueryEndExecutor.h b/arangod/Aql/SubqueryEndExecutor.h
index 5bc2a6dcdc41..19b684f03b9e 100644
--- a/arangod/Aql/SubqueryEndExecutor.h
+++ b/arangod/Aql/SubqueryEndExecutor.h
@@ -88,9 +88,6 @@ class SubqueryEndExecutor {
   [[deprecated]] std::pair<ExecutionState, Stats> produceRows(OutputAqlItemRow& output);
   std::pair<ExecutionState, size_t> expectedNumberOfRows(size_t atMost) const;
 
-  [[nodiscard]] auto expectedNumberOfRowsNew(AqlItemBlockInputRange const& input,
-                                             AqlCall const& call) const noexcept -> size_t;
-
   // produceRows accumulates all input rows it can get into _accumulator, which
   // will then be read out by ExecutionBlockImpl
   // TODO: can the production of output be moved to produceRows again?

From 9f618e4f960e467af1e943cbc8c289fabc3d51dd Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Sun, 15 Mar 2020 11:28:35 +0100
Subject: [PATCH 116/122] SubqueryStart will have more output then limit
 defines (ShadowRow)

---
 arangod/Aql/ExecutionBlockImpl.cpp | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index 5782147dab4e..65327a8323cd 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -1072,7 +1072,11 @@ auto ExecutionBlockImpl<Executor>::allocateOutputBlock(AqlCall&& call, DataRange
     if constexpr (hasExpectedNumberOfRowsNew<Executor>::value) {
       blockSize = _executor.expectedNumberOfRowsNew(inputRange, call);
       // The executor cannot expect to produce more then the limit!
-      TRI_ASSERT(blockSize <= call.getLimit());
+      if constexpr (!std::is_same_v<Executor, SubqueryStartExecutor>) {
+        // Except the subqueryStartExecutor, it's limit differs
+        // from it's output (it needs to count the new ShadowRows in addition)
+        TRI_ASSERT(blockSize <= call.getLimit());
+      }
 
       blockSize += inputRange.countShadowRows();
       // We have an upper bound by DefaultBatchSize;

From b00eff8bead4f469e70ac4a144eedf2663b25353 Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Sun, 15 Mar 2020 11:51:42 +0100
Subject: [PATCH 117/122] Fixed Filter numberOfExpectedRows

---
 arangod/Aql/AqlItemBlockInputRange.cpp | 4 ++++
 arangod/Aql/AqlItemBlockInputRange.h   | 2 ++
 arangod/Aql/ExecutionBlockImpl.cpp     | 5 +++++
 arangod/Aql/FilterExecutor.cpp         | 7 ++++++-
 4 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/arangod/Aql/AqlItemBlockInputRange.cpp b/arangod/Aql/AqlItemBlockInputRange.cpp
index f2e8dc5d1e63..6e90698e2bc0 100644
--- a/arangod/Aql/AqlItemBlockInputRange.cpp
+++ b/arangod/Aql/AqlItemBlockInputRange.cpp
@@ -197,3 +197,7 @@ auto AqlItemBlockInputRange::countShadowRows() const noexcept -> std::size_t {
   auto const& block = getBlock();
   return block->getShadowRowIndexes().size();
 }
+
+[[nodiscard]] auto AqlItemBlockInputRange::finalState() const noexcept -> ExecutorState {
+  return _finalState;
+}
diff --git a/arangod/Aql/AqlItemBlockInputRange.h b/arangod/Aql/AqlItemBlockInputRange.h
index 8af13379acde..6a03bb1e6942 100644
--- a/arangod/Aql/AqlItemBlockInputRange.h
+++ b/arangod/Aql/AqlItemBlockInputRange.h
@@ -86,6 +86,8 @@ class AqlItemBlockInputRange {
    */
   [[nodiscard]] auto countShadowRows() const noexcept -> std::size_t;
 
+  [[nodiscard]] auto finalState() const noexcept -> ExecutorState;
+
  private:
   bool isIndexValid(std::size_t index) const noexcept;
 
diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index 65327a8323cd..c86f2a27d61b 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -1082,6 +1082,11 @@ auto ExecutionBlockImpl<Executor>::allocateOutputBlock(AqlCall&& call, DataRange
       // We have an upper bound by DefaultBatchSize;
       blockSize = std::min(ExecutionBlock::DefaultBatchSize, blockSize);
     }
+    if (blockSize == 0) {
+      // There is no data to be produced
+      SharedAqlItemBlockPtr newBlock{nullptr};
+      return createOutputRow(newBlock, std::move(call));
+    }
     SharedAqlItemBlockPtr newBlock =
         _engine->itemBlockManager().requestBlock(blockSize, _infos.numberOfOutputRegisters());
     return createOutputRow(newBlock, std::move(call));
diff --git a/arangod/Aql/FilterExecutor.cpp b/arangod/Aql/FilterExecutor.cpp
index 63882d26a00b..f151119acfde 100644
--- a/arangod/Aql/FilterExecutor.cpp
+++ b/arangod/Aql/FilterExecutor.cpp
@@ -157,5 +157,10 @@ auto FilterExecutor::produceRows(AqlItemBlockInputRange& inputRange, OutputAqlIt
 [[nodiscard]] auto FilterExecutor::expectedNumberOfRowsNew(AqlItemBlockInputRange const& input,
                                                            AqlCall const& call) const
     noexcept -> size_t {
-  return std::min(call.getLimit(), input.countDataRows());
+  if (input.finalState() == ExecutorState::DONE) {
+    return std::min(call.getLimit(), input.countDataRows());
+  }
+  // We do not know how many more rows will be returned from upstream.
+  // So we can only overestimate
+  return call.getLimit();
 }

From a6fd85ceee63fcf65a638bc6f0b8a1f7dde161a1 Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Sun, 15 Mar 2020 14:55:50 +0100
Subject: [PATCH 118/122] Removed do-copy row test from ID executor. It now
 uses a fast-forward variant that only works on non-copy

---
 tests/Aql/IdExecutorTest.cpp | 37 ++++++++++--------------------------
 1 file changed, 10 insertions(+), 27 deletions(-)

diff --git a/tests/Aql/IdExecutorTest.cpp b/tests/Aql/IdExecutorTest.cpp
index 4ec6f1b94df8..e7b86ac4a0bc 100644
--- a/tests/Aql/IdExecutorTest.cpp
+++ b/tests/Aql/IdExecutorTest.cpp
@@ -50,8 +50,7 @@ namespace arangodb::tests::aql {
 using TestParam = std::tuple<size_t,         // The input data 0 -> number
                              ExecutorState,  // The upstream state
                              AqlCall,        // The client Call,
-                             bool,  // flag to decide if we need to do couting
-                             OutputAqlItemRow::CopyRowBehavior  // How the data is handled within outputRow
+                             bool  // flag to decide if we need to do couting
                              >;
 
 class IdExecutorTestCombiner : public AqlExecutorTestCaseWithParam<TestParam> {
@@ -72,7 +71,7 @@ class IdExecutorTestCombiner : public AqlExecutorTestCaseWithParam<TestParam> {
   }
 
   auto doCount() -> bool {
-    auto const& [a, b, c, doCount, d] = GetParam();
+    auto const& [a, b, c, doCount] = GetParam();
     return doCount;
   }
 
@@ -81,17 +80,17 @@ class IdExecutorTestCombiner : public AqlExecutorTestCaseWithParam<TestParam> {
   }
 
   auto getInput() -> size_t {
-    auto const& [input, a, b, c, d] = GetParam();
+    auto const& [input, a, b, c] = GetParam();
     return input;
   }
 
   auto getCall() -> AqlCall {
-    auto const& [a, b, call, c, d] = GetParam();
+    auto const& [a, b, call, c] = GetParam();
     return call;
   }
 
   auto getUpstreamState() -> ExecutorState {
-    auto const& [a, state, b, c, d] = GetParam();
+    auto const& [a, state, b, c] = GetParam();
     return state;
   }
 
@@ -153,23 +152,11 @@ class IdExecutorTestCombiner : public AqlExecutorTestCaseWithParam<TestParam> {
     auto toWrite = make_shared_unordered_set({});
     auto toKeep = make_shared_unordered_set({0});
     auto toClear = make_shared_unordered_set();
-    auto const& [unused, upstreamState, clientCall, unused2, copyBehaviour] = GetParam();
+    auto const& [unused, upstreamState, clientCall, unused2] = GetParam();
     AqlCall callCopy = clientCall;
-    if (copyBehaviour == OutputAqlItemRow::CopyRowBehavior::DoNotCopyInputRows) {
-      // For passthrough we reuse the block
-      return OutputAqlItemRow(input, toWrite, toKeep, toClear,
-                              std::move(callCopy), copyBehaviour);
-    }
-    // Otherwise we need to create a fresh block (or forward nullptr)
-    if (input == nullptr) {
-      SharedAqlItemBlockPtr outBlock{nullptr};
-      return OutputAqlItemRow(outBlock, toWrite, toKeep, toClear,
-                              std::move(callCopy), copyBehaviour);
-    }
-    SharedAqlItemBlockPtr outBlock{
-        new AqlItemBlock(manager(), input->size(), input->getNrRegs())};
-    return OutputAqlItemRow(outBlock, toWrite, toKeep, toClear,
-                            std::move(callCopy), copyBehaviour);
+    // For passthrough we reuse the block
+    return OutputAqlItemRow(input, toWrite, toKeep, toClear, std::move(callCopy),
+                            OutputAqlItemRow::CopyRowBehavior::DoNotCopyInputRows);
   }
 };
 
@@ -270,13 +257,9 @@ auto clientCalls = testing::Values(AqlCall{},  // unlimited call
                                    AqlCall{0, AqlCall::Infinity{}, 7, true}  // hardlimit call (note this is larger than length of input data), with fullcount
 );
 
-auto copyBehaviours = testing::Values(OutputAqlItemRow::CopyRowBehavior::CopyInputRows,  // Create a new row and write the data
-                                      OutputAqlItemRow::CopyRowBehavior::DoNotCopyInputRows  // Just passthrough (production)
-);
-
 INSTANTIATE_TEST_CASE_P(IdExecutorTest, IdExecutorTestCombiner,
                         ::testing::Combine(inputs, upstreamStates, clientCalls,
-                                           ::testing::Bool(), copyBehaviours));
+                                           ::testing::Bool()));
 
 class IdExecutionBlockTest : public AqlExecutorTestCase<> {};
 

From 31f0b2e56316a2073a169089dc7b4a590b523ea3 Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Sun, 15 Mar 2020 15:16:56 +0100
Subject: [PATCH 119/122] Only estimate the number of Rows if the range is
 complete.

---
 arangod/Aql/DistinctCollectExecutor.cpp | 12 ++++++++----
 arangod/Aql/HashedCollectExecutor.cpp   | 12 ++++++++----
 arangod/Aql/ReturnExecutor.cpp          |  6 +++++-
 arangod/Aql/SortedCollectExecutor.cpp   | 16 ++++++++++------
 tests/Aql/ExecutionBlockImplTest.cpp    |  6 +++---
 5 files changed, 34 insertions(+), 18 deletions(-)

diff --git a/arangod/Aql/DistinctCollectExecutor.cpp b/arangod/Aql/DistinctCollectExecutor.cpp
index 046cec1c4940..30cffcd2e3f6 100644
--- a/arangod/Aql/DistinctCollectExecutor.cpp
+++ b/arangod/Aql/DistinctCollectExecutor.cpp
@@ -87,10 +87,14 @@ std::pair<ExecutionState, size_t> DistinctCollectExecutor::expectedNumberOfRows(
 
 [[nodiscard]] auto DistinctCollectExecutor::expectedNumberOfRowsNew(
     AqlItemBlockInputRange const& input, AqlCall const& call) const noexcept -> size_t {
-  // Worst case assumption:
-  // For every input row we have a new group.
-  // We will never produce more then asked for
-  return std::min(call.getLimit(), input.countDataRows());
+  if (input.finalState() == ExecutorState::DONE) {
+    // Worst case assumption:
+    // For every input row we have a new group.
+    // We will never produce more then asked for
+    return std::min(call.getLimit(), input.countDataRows());
+  }
+  // Otherwise we do not know.
+  return call.getLimit();
 }
 
 void DistinctCollectExecutor::destroyValues() {
diff --git a/arangod/Aql/HashedCollectExecutor.cpp b/arangod/Aql/HashedCollectExecutor.cpp
index 4fd098d01279..178639fc53a0 100644
--- a/arangod/Aql/HashedCollectExecutor.cpp
+++ b/arangod/Aql/HashedCollectExecutor.cpp
@@ -363,10 +363,14 @@ std::pair<ExecutionState, size_t> HashedCollectExecutor::expectedNumberOfRows(si
 [[nodiscard]] auto HashedCollectExecutor::expectedNumberOfRowsNew(
     AqlItemBlockInputRange const& input, AqlCall const& call) const noexcept -> size_t {
   if (!_isInitialized) {
-    // Worst case assumption:
-    // For every input row we have a new group.
-    // We will never produce more then asked for
-    return std::min(call.getLimit(), input.countDataRows());
+    if (input.finalState() == ExecutorState::DONE) {
+      // Worst case assumption:
+      // For every input row we have a new group.
+      // We will never produce more then asked for
+      return std::min(call.getLimit(), input.countDataRows());
+    }
+    // Otherwise we do not know.
+    return call.getLimit();
   }
   // We know how many groups we have left
   return std::min<size_t>(call.getLimit(),
diff --git a/arangod/Aql/ReturnExecutor.cpp b/arangod/Aql/ReturnExecutor.cpp
index 315d784e678c..7a5fc4344cde 100644
--- a/arangod/Aql/ReturnExecutor.cpp
+++ b/arangod/Aql/ReturnExecutor.cpp
@@ -135,5 +135,9 @@ auto ReturnExecutor::produceRows(AqlItemBlockInputRange& inputRange, OutputAqlIt
 [[nodiscard]] auto ReturnExecutor::expectedNumberOfRowsNew(AqlItemBlockInputRange const& input,
                                                            AqlCall const& call) const
     noexcept -> size_t {
-  return input.countDataRows();
+  if (input.finalState() == ExecutorState::DONE) {
+    return input.countDataRows();
+  }
+  // Otherwise we do not know.
+  return call.getLimit();
 }
diff --git a/arangod/Aql/SortedCollectExecutor.cpp b/arangod/Aql/SortedCollectExecutor.cpp
index 54a633e1310b..f2e22479b1a0 100644
--- a/arangod/Aql/SortedCollectExecutor.cpp
+++ b/arangod/Aql/SortedCollectExecutor.cpp
@@ -301,12 +301,16 @@ std::pair<ExecutionState, size_t> SortedCollectExecutor::expectedNumberOfRows(si
 
 [[nodiscard]] auto SortedCollectExecutor::expectedNumberOfRowsNew(
     AqlItemBlockInputRange const& input, AqlCall const& call) const noexcept -> size_t {
-  // Worst case assumption:
-  // For every input row we have a new group.
-  // If we have an open group right now, we need to add 1 to this estimate.
-  // We will never produce more then asked for
-  return std::min(call.getLimit(),
-                  input.countDataRows() + (_currentGroup.isValid() ? 1 : 0));
+  if (input.finalState() == ExecutorState::DONE) {
+    // Worst case assumption:
+    // For every input row we have a new group.
+    // If we have an open group right now, we need to add 1 to this estimate.
+    // We will never produce more then asked for
+    return std::min(call.getLimit(),
+                    input.countDataRows() + (_currentGroup.isValid() ? 1 : 0));
+  }
+  // Otherwise we do not know.
+  return call.getLimit();
 }
 
 auto SortedCollectExecutor::produceRows(AqlItemBlockInputRange& inputRange,
diff --git a/tests/Aql/ExecutionBlockImplTest.cpp b/tests/Aql/ExecutionBlockImplTest.cpp
index 97bf70ad6ec8..b99a66db3b5c 100644
--- a/tests/Aql/ExecutionBlockImplTest.cpp
+++ b/tests/Aql/ExecutionBlockImplTest.cpp
@@ -549,7 +549,7 @@ class SharedExecutionBlockImplTest {
    * @return ProduceCall The call ready to hand over to the LambdaExecutorInfos
    */
   static auto generateProduceCall(size_t& nrCalls, AqlCall expectedCall,
-                                  size_t numRowsLeftNoInput = ExecutionBlock::DefaultBatchSize,
+                                  size_t numRowsLeftNoInput = 0,
                                   size_t numRowsLeftWithInput = ExecutionBlock::DefaultBatchSize)
       -> ProduceCall {
     return [&nrCalls, numRowsLeftNoInput, numRowsLeftWithInput,
@@ -793,7 +793,7 @@ TEST_P(ExecutionBlockImplExecuteSpecificTest, test_toplevel_softlimit_call) {
   // in the executor.
   // Non passthrough the available lines (visible to executor) are only the given soft limit.
   ProduceCall execImpl = GetParam() ? generateProduceCall(nrCalls, fullCall, 0, 1)
-                                    : generateProduceCall(nrCalls, fullCall, 20, 20);
+                                    : generateProduceCall(nrCalls, fullCall, 0, 20);
   SkipCall skipCall = generateNeverSkipCall();
   auto [state, skipped, block] = runTest(execImpl, skipCall, fullCall);
 
@@ -815,7 +815,7 @@ TEST_P(ExecutionBlockImplExecuteSpecificTest, test_toplevel_hardlimit_call) {
   // in the executor.
   // Non passthrough the available lines (visible to executor) are only the given soft limit.
   ProduceCall execImpl = GetParam() ? generateProduceCall(nrCalls, fullCall, 0, 1)
-                                    : generateProduceCall(nrCalls, fullCall, 20, 20);
+                                    : generateProduceCall(nrCalls, fullCall, 0, 20);
   SkipCall skipCall = generateNeverSkipCall();
   auto [state, skipped, block] = runTest(execImpl, skipCall, fullCall);
 

From a6003ea4a93ec1952929bb1a1f75b7824b769f36 Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Sun, 15 Mar 2020 15:35:54 +0100
Subject: [PATCH 120/122] On Collect nodes we sometimes produce an additional
 empty row

---
 arangod/Aql/HashedCollectExecutor.cpp |  7 ++++++-
 arangod/Aql/SortedCollectExecutor.cpp | 13 +++++++++++--
 2 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/arangod/Aql/HashedCollectExecutor.cpp b/arangod/Aql/HashedCollectExecutor.cpp
index 178639fc53a0..4efd9f0f50f1 100644
--- a/arangod/Aql/HashedCollectExecutor.cpp
+++ b/arangod/Aql/HashedCollectExecutor.cpp
@@ -367,7 +367,12 @@ std::pair<ExecutionState, size_t> HashedCollectExecutor::expectedNumberOfRows(si
       // Worst case assumption:
       // For every input row we have a new group.
       // We will never produce more then asked for
-      return std::min(call.getLimit(), input.countDataRows());
+      auto estOnInput = input.countDataRows();
+      if (estOnInput == 0 && _infos.getGroupRegisters().empty()) {
+        // Special case, on empty input we will produce 1 output
+        estOnInput = 1;
+      }
+      return std::min(call.getLimit(), estOnInput);
     }
     // Otherwise we do not know.
     return call.getLimit();
diff --git a/arangod/Aql/SortedCollectExecutor.cpp b/arangod/Aql/SortedCollectExecutor.cpp
index f2e22479b1a0..cc12029222a0 100644
--- a/arangod/Aql/SortedCollectExecutor.cpp
+++ b/arangod/Aql/SortedCollectExecutor.cpp
@@ -306,8 +306,17 @@ std::pair<ExecutionState, size_t> SortedCollectExecutor::expectedNumberOfRows(si
     // For every input row we have a new group.
     // If we have an open group right now, we need to add 1 to this estimate.
     // We will never produce more then asked for
-    return std::min(call.getLimit(),
-                    input.countDataRows() + (_currentGroup.isValid() ? 1 : 0));
+    auto estOnInput = input.countDataRows();
+    if (_currentGroup.isValid()) {
+      // Have one group still to write,
+      // that is not part of this input.
+      estOnInput += 1;
+    }
+    if (estOnInput == 0 && _infos.getGroupRegisters().empty()) {
+      // Special case, on empty input we will produce 1 output
+      estOnInput = 1;
+    }
+    return std::min(call.getLimit(), estOnInput);
   }
   // Otherwise we do not know.
   return call.getLimit();

From 37f5e1f53e5085ffbf2a8134bb674f18f936b2f6 Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Sun, 15 Mar 2020 21:09:31 +0100
Subject: [PATCH 121/122] Fixed endles loop in ParallelUnsortedGather, if the
 initial input is empty.

---
 .../Aql/ParallelUnsortedGatherExecutor.cpp    | 23 ++++++++-----------
 1 file changed, 10 insertions(+), 13 deletions(-)

diff --git a/arangod/Aql/ParallelUnsortedGatherExecutor.cpp b/arangod/Aql/ParallelUnsortedGatherExecutor.cpp
index 457d6daa61c1..8f9130034b70 100644
--- a/arangod/Aql/ParallelUnsortedGatherExecutor.cpp
+++ b/arangod/Aql/ParallelUnsortedGatherExecutor.cpp
@@ -91,19 +91,16 @@ auto ParallelUnsortedGatherExecutor::produceRows(typename Fetcher::DataRange& in
   auto callSet = AqlCallSet{};
 
   for (size_t dep = 0; dep < input.numberDependencies(); ++dep) {
-    while (!output.isFull()) {
-      auto [state, row] = input.nextDataRow(dep);
-      if (row) {
-        output.copyRow(row);
-        output.advanceRow();
-      } else {
-        // This output did not produce anything
-        if (state == ExecutorState::HASMORE) {
-          callSet.calls.emplace_back(
-              AqlCallSet::DepCallPair{dep, upstreamCallProduce(clientCall)});
-        }
-        break;
-      }
+    auto& range = input.rangeForDependency(dep);
+    while (!output.isFull() && range.hasDataRow()) {
+      auto [state, row] = range.nextDataRow();
+      TRI_ASSERT(row);
+      output.copyRow(row);
+      output.advanceRow();
+    }
+    // Produce a new call if necessary (we consumed all, and the state is still HASMORE)
+    if (!range.hasDataRow() && range.upstreamState() == ExecutorState::HASMORE) {
+      callSet.calls.emplace_back(AqlCallSet::DepCallPair{dep, upstreamCallProduce(clientCall)});
     }
   }
 

From f4cbf4aa9da484d305deab797e4f80f424969a2c Mon Sep 17 00:00:00 2001
From: Michael Hackstein <michael@arangodb.com>
Date: Fri, 20 Mar 2020 13:41:38 +0100
Subject: [PATCH 122/122] Apply suggestions from code review

Thanks a lot!

Co-Authored-By: Markus Pfeiffer <markuspf@users.noreply.github.com>
---
 arangod/Aql/ExecutionBlockImpl.cpp | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arangod/Aql/ExecutionBlockImpl.cpp b/arangod/Aql/ExecutionBlockImpl.cpp
index c86f2a27d61b..e8e8e68d60bf 100644
--- a/arangod/Aql/ExecutionBlockImpl.cpp
+++ b/arangod/Aql/ExecutionBlockImpl.cpp
@@ -1049,7 +1049,7 @@ auto ExecutionBlockImpl<Executor>::allocateOutputBlock(AqlCall&& call, DataRange
     return createOutputRow(newBlock, std::move(call));
   } else {
     if constexpr (isMultiDepExecutor<Executor>) {
-      // MultiDepExecutor wpuld require dependency handling.
+      // MultiDepExecutor would require dependency handling.
       // We do not have it here.
       if (!inputRange.hasShadowRow() && !inputRange.hasDataRow()) {
         // On empty input do not yet create output.
@@ -1288,7 +1288,6 @@ auto ExecutionBlockImpl<Executor>::executeFetcher(AqlCallStack& stack, AqlCallTy
         _lastRange.setDependency(dependency, range);
       }
       return {state, skipped, _lastRange};
-
     } else if constexpr (executorHasSideEffects<Executor>) {
       // If the executor has side effects, we cannot bypass any subqueries
       // by skipping them. So we need to fetch all shadow rows in order to